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
  • C09D11/52—Electrically conductive inks
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24893—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including particulate material

Definitions

• the invention relates to an ink for producing conductive printed images, based on carbon nanotubes and at least one polymeric dispersing aid in an aqueous formulation and a process for their preparation.
• RFID tags Radio Frequency Identification tags
• US 2006/124028 A1 discloses an ink using carbon nanotubes for use in ink jet printers.
• the ink is characterized herein by a O- ber lakeschreib of 0.02-0.07 N / m and a viscosity of 0.001-0.03 Pa 's at 25 ° C.
• the content of carbon nanotubes is disclosed within wide limits to 0.1-30% by weight.
• the inks are not suitable for screen printing with a viscosity of up to 0.03 Pa * s.
• a viscosity in the order of 1 Pa * s would be necessary.
• US 2005/284232 A1 discloses an electrically conductive coating which contains carbon halofibres. The coating should be applied by brushing, rolling, or spraying a corresponding ink.
• the ink has a content of carbon nanofibers of 4-12% by weight in a matrix similar to the substrate, here for example urethanes, polyimides, cyanate esters and other organics.
• a disclosure regarding screen printing relevant parameters such as surface tension on a particular substrate or viscosity is not given. It is disclosed that the viscosity can be reduced by dissolving the matrix.
• WO 2005/119772 A2 discloses an ink comprising carbon nanotubes, wherein the carbon nanotubes used have an outer diameter of not more than 20 nm and are used in a concentration of ⁇ 10% by weight.
• the after-treatment temperature is disclosed as greater than 75 ° C, which should be at least 10 minutes.
• compositions of an ink for use e.g. in screen printing using, inter alia, derivatives of cellulose to achieve or obtain dispersion in the resulting formulation.
• the resulting surface resistance of the inks according to the present invention is at most 10 k ⁇ / m.
• WO 2005/029528 A1 discloses inks or pastes comprising carbon nanotubes which are applied by means of various printing techniques (eg screen printing) for the purpose of producing electrodes on surfaces.
• the disclosed inks are either aqueous formulations comprising carbon nanotubes with inorganic auxiliaries, or organic solvent formulations comprising carbon nanotubes with organic polymeric auxiliaries.
• the carbon nanotubes used are the types well known to those skilled in the art.
• the physical properties of the inks in terms of viscosity, surface tension and conductivity are not disclosed.
• the disclosed inks are disadvantageous in that they are either present in organic solvents and thus potentially hazardous to the environment, or include inorganic adjuvants such as Al 2 O 3 , SiO 2 which are nonconductive and Also in the course of a Nachbehandelns can not be easily removed. Thus, it can be assumed that the conductivity of the printed image, compared to an ink without such aids is disadvantageous.
• cylinder type carbon nanotubes are always used to prepare inks.
• These carbon nanotubes are either single wall carbon nanotubes (SWNTs) or multiwalled (so called “multi walled carbon nanotubes” - MWNTs) carbon nanotubes, as described, for example, in the publication by Ijima (Publication: p Ijima, Nature 354, 56-58, 1991).
• SWNTs single wall carbon nanotubes
• multiwalled carbon nanotubes - MWNTs
• Such known carbon nanotubes are characterized in that they are structures of carbon tubes, in which one or more self-contained concentrically arranged graphene layers are the basis for the construction of the nanotube.
• an ink comprising special carbon nanotubes which are suitable for large-scale printing processes such as printing. Screen printing is well suited and has over the prior art improved conductivities and environmentally harmless. It has surprisingly been found that an ink for producing conductive printed images can achieve this object, which has a specific proportion of special carbon nanotubes which have an internal structure, which has not been described so far, consisting of several graphene layers which are combined into a stack and rolled up (multi-scroll type). , and having a proportion of at least one polymeric dispersing aid in an aqueous formulation.
• the invention relates to a printable composition for producing electrically conductive coatings based on carbon nanotubes and at least one polymeric dispersing aid in an aqueous formulation, characterized in that the carbon nanotubes consist of at least one fifth of carbon nanotubes having a molecular structure with multiple graphene layers, which are combined into a stack and rolled up (MultiScroll type).
• printed images refers to structures on surfaces which have been applied to the surface by means of a generally known printing technique.
• Printed images thus also include printed conductors which are applied to surfaces by means of a printing technique. The term should not be understood as limiting in terms of its creative aspect.
• Special carbon nanotubes of the multi-scroll type denote carbon nanotubes and their agglomerates, as they are, for example, the subject of the still unpublished German patent application with the official file reference 102007044031.8. Their content is hereby incorporated with respect to the carbon nanotubes and their preparation to the disclosure content of this application.
• the special carbon nanotubes of the multiscroll type can be used in Mixed with other types of carbon nanotubes known per se, single wall CNTs and / or multiwall CNT carbon nanotubes can be used.
• the individual graphene or graphite layers in these special carbon nanotubes run continuously from the center of the carbon nanotubes to the outer edge without interruption. This can e.g. allow for improved and faster intercalation of other materials in the tube framework, as more open edges are available than the entry zone of the intercalates, as compared to known carbon nanotubes.
• These properties surprisingly achieve the good dispersibility and homogeneity of the resulting ink in interaction with the polymeric dispersing assistant.
• the term ink is also used in the following to simplify the term printable composition.
• the carbon nanotubes may be treated or untreated in the ink of the present invention. When treated, they have preferably been previously treated with an oxidizing agent.
• the oxidizing agent is preferably nitric acid and / or hydrogen peroxide, more preferably the oxidizing agent is hydrogen peroxide.
• the carbon nanotubes used here preferably have an average outside diameter of 3 to 100 nm, more preferably of 5 to 80 nm, most preferably of 6 to 60 nm.
• the special carbon nanotubes in the ink according to the invention are present at least partially in agglomerates.
• the carbon nanotubes are present in agglomerates in the ink, they preferably have a diameter of essentially ⁇ 5 ⁇ m, more preferably ⁇ 3 ⁇ m. Very particularly preferred is the agglomerate diameter ⁇ 2 microns.
• a small proportion of the smallest possible agglomerates is advantageous because it improves the physical properties of viscosity and conductivity of the ink, as well as their processability in their use according to the invention. Coarse and many agglomerates may cause clogging of the printing devices during printing. In addition, coarse and many agglomerates can lead to areas of the print image that have high conductivity while other areas have no or only very low conductivity.
• the resistance of an electrical track results from a series connection of its individual resistances, the resistance of the overall track is unfavorably high if such an inhomogeneous resistance distribution is produced by too many and too coarse agglomerates.
• the preferred length to outer diameter ratio and the average outer diameter of the carbon nanotubes ensure the high specific conductivity of the resulting ink, as this, together with the close contact in the existing agglomerates, a good percolation of the conductive layer is achieved.
• the content of the carbon nanotubes on the ink is usually from 0.1% by weight to 15% by weight.
• the proportion of carbon nanotubes in the ink is preferably from 5% by weight to 10% by weight.
• a smaller proportion of carbon nanotubes results in the resultant ink being too thin and thus possibly unsuitable for high throughput printing processes such as screen printing.
• a higher proportion of carbon nanotubes also increases the viscosity beyond the level that would still appear reasonable for use of the ink in printing processes.
• Aqueous formulation in the context of the present invention refers to a composition in which the solvent consists predominantly of water which preferably contains ink above 50% by weight. Most preferably, the ink contains at least 80% by weight of water.
• the high content of water as a solvent is advantageous because it makes the ink harmless to working hygiene in the printing process as well as after use with respect to the solvent.
• the at least one polymeric dispersing aid is usually selected from at least one of water-soluble homopolymers, water-soluble random copolymers, water-soluble block copolymers, water-soluble graft polymers, especially polyvinyl alcohols, copolymers of polyvinyl alcohols and polyvinyl acetates, polyvinyl pyrrolidones, cellulose derivatives such as carboxymethyl cellulose, carboxypropyl cellulose, carboxymethylpropyl cellulose, hydro xyethylcellulose, starch, gelatin, gelatin derivatives, amino acid polymers, polylysine, polyaspartic acid, polyacrylates, polyethylene sulfonates, polystyrenesulfonates, polymethacrylates, polysulfonic acids, condensation products of aromatic sulfonic acids with formaldehyde, naphthalenesulfonates, ligninsulfonates, copolymers of acrylic monomers, polyethyleneimines, polyvinylamine
• the at least one polymeric dispersing aid is preferably at least one agent selected from the series: polyvinylpyrrolidone, block copolyether and block copolyether with polystyrene blocks, Carboxymethylcellulose, carboxypropylcellulose, carboxymethylpropylcellulose, gelatin, gelatin derivatives and polysulfonic acids.
• polymeric dispersants polyvinylpyrrolidone and / or
• Block copolyether used with polystyrene blocks Particularly suitable polyvinylpyrrolidone has a molecular weight M n in the range of 5000 to 400,000.
• Fluka (poppy about 10000 amu) or PVP K90 from Fluka (molecular weight of about 360000 amu) or block copolyether with polystyrene blocks, with 62% by weight C 2 polyether, 23% by weight C 3 -
• Ratio of the block lengths C 2 polyether to C 3 polyether of 7 2 units (eg Disperbyk 190 from BYK-Chemie, Wesel).
• the at least one polymeric dispersing aid is advantageously present in a proportion of from 0.01% by weight to 10% by weight, preferably in a proportion of from 0.1% by weight to 7% by weight, more preferably in a proportion of From 0.5% to 5% by weight in the ink.
• the commonly used and preferred polymeric dispersants are particularly advantageous in the specified proportions, because in addition to supporting a suitable dispersion of the carbon nanotubes and an adjustment of the viscosity of the ink of the invention, as well as an adjustment of surface tension and film formation and adhesion to the respective substrate Allow ink.
• Inventive inks usually have a dynamic viscosity of at least 0.5 Pa * s, preferably from 1 to 200 Pa * s.
• Such a viscosity of the ink makes them particularly well suited for use in high throughput printing processes such as screen printing.
• Far lower viscosity compositions generally result in the aqueous ink formulations bleeding the ink on the surfaces to which it is applied, thus resulting in a poor print image. This is of particular importance in the printing of printed circuits for circuits.
• the ink may also comprise at least one conductive salt.
• the at least one conductive salt is hereby preferably selected from the list of salts with the cations: tetraalkylammonium, pyridinium, imidazolium, tetraalkylphosphonium, and as anions are different ions of simple halide on more complex inorganic ions such as tetrafluoroborates up to large organic ions such as trifluoromethanesulfonimide used.
• the addition of at least one conductive salt to the ink of the invention is advantageous because such salts have negligible vapor pressure and are conductive.
• the salt as a film former and conductive agent is also available at higher temperatures and under reduced pressure. addition.
• a bleeding of the printed image can be prevented.
• the ink may additionally comprise a proportion of carbon black.
• Carbon black in the context of the present invention refers to finely divided particles of elemental carbon in graphitic or amorphous form. Finely divided particles in this context are particles having an average diameter of less than or equal to 1 ⁇ m.
• carbon black is added to the ink according to the invention, this is preferably carbon black, as can be obtained from the company EVONIC under the name Printex® PE. Adding a portion of carbon black to the ink is advantageous because, with little further increase in viscosity, the conductivity of the printed image to be obtained from the ink can be further increased by filling potential voids between the carbon nanotubes with carbon black, thereby forming the conductive interconnection between the carbon nanotubes and thus the conductive cross section of the printed image is increased.
• Another object of the present invention is a process for preparing a printable composition for producing conductive coatings based on carbon nanotubes and at least one polymeric dispersing aid in an aqueous formulation, in particular a printable composition according to the invention, characterized in that it comprises at least the steps: a If appropriate, oxidative pretreatment of the carbon nanotubes, b) preparation of an aqueous predispersion, by dissolving the polymeric dispersing aid in an aqueous solvent, introduction and distribution of carbon nanotubes in the resulting solution, c) introduction of a volume-related energy density, preferably in the form of shear energy, of at least 10 4 J / m 3 , preferably of at least 10 5 J / m 3 , more preferably 10 7 to 10 9 J / m 3 in the predispersion until the agglomerate diameter of the carbon nanotube agglomerates substantially ⁇ 5 microns, preferably ⁇ 3 microns, more preferably ⁇ 2 microns comprises.
• the pretreatment is usually carried out by treatment with an oxidizing agent.
• the pretreatment with an oxidizing agent is advantageously carried out by dispersing the carbon nanotubes in a 5 to 10% by weight aqueous solution of the oxidizing agent, subsequently separating the carbon nanotubes from the oxidizing agent and thereafter drying them.
• the dispersion in an oxidizing agent is usually carried out for a period of one to 12 hours.
• the carbon nanotubes are dispersed in the oxidizing agent for a period of 2 hours to 6 hours, more preferably for about 4 hours.
• the separation of carbon nanotubes from the oxidizing agent is usually carried out by sedimentation.
• the separation is carried out by sedimentation in the gravitational field of the earth, or by sedimentation in a centrifuge. Drying the carbon nanotubes is carried out normally adjacent to the room air and at temperatures of 60 0 C to 140 0 C, preferably at temperatures from 80 0 C to 100 0 C.
• the oxidizing agent is usually nitric acid and / or hydrogen peroxide, preferably the oxidizing agent is hydrogen peroxide.
• the preparation of the aqueous predispersion according to step b) of the new process is advantageously carried out by adding water and dissolving the at least one polymeric dispersing aid and then adding carbon nanotubes.
• organic solvents preferably selected from the series: C r to C 5 -alcohol, in particular C r to C 3 -alcohol, ethers, in particular dioxalane, ketones, in particular acetone, may additionally be added to the water. It is also possible according to a preferred development of the new ink soot and / or conductive salts in the context of step b) of the new process are added.
• the addition of carbon nanotubes may be done together with the at least one polymeric dispersing aid, or one after the other.
• the at least one polymeric dispersing aid is added first and then the carbon nanotubes are added batchwise.
• Particular preference is given to adding the at least one polymeric dispersing aid and then adding the carbon nanotubes in portions using stirring and / or by treatment with ultrasound.
• this ink comprises conductive salts and / or carbon black
• the carbon black is preferably added together with the carbon nanotubes in the same way and / or the conductive salts are added in the same way together with the at least one polymeric dispersing aid.
• the sequential and batchwise addition of carbon nanotubes with stirring and / or ultrasound to prepare the predispersion is particularly advantageous because it can be used to improve the dispersion of the carbon nanotubes to the finished ink, in which Kohlenstoffiianorschreibchen stable to sedimentation and thus the necessary entry of energy in the predispersion, according to the inventive step c) of the method can be reduced.
• step b) of the process according to the invention at least one conductive salt is added after the addition of at least one polymeric dispersing assistant and the addition of carbon dioxide tubes.
• the entry of the volume-related energy density, for example in the form of shear energy, into the predispersion according to step c) of the novel process is particularly preferably carried out by passing the predispersion through a homogenizer at least once.
• the volume-related energy density can be introduced into the predispersion in the region of the nozzle opening, for example.
• Suitable homogenizers are all embodiments known to those skilled in the art, such as high-pressure homogenizers.
• Particularly suitable high-pressure homogenizers are basically known, for example, from the publication Chemie Ingenieurtechnik, Volume 77, Issue 3 (pp. 258-262).
• Particularly preferred homogenizers are high-pressure homogenizers, high pressure homogenizers are especially preferred dispersers jet, slot homogenizers and high pressure homogenizer type Microfluidizer ®.
• the predispersion is passed at least twice through a homogenizer, preferably a high pressure homogenizer.
• the predispersion is passed at least three times through a homogenizer, preferably a high-pressure homogenizer. Passing through a homogenizer, preferably a high-pressure homogenizer, is advantageous because it breaks down any remaining coarse agglomerates of the carbon nanotubes, thereby improving the ink's physical properties, such as viscosity and conductivity.
• the inlet pressure and thus automatically adjusting the gap width of the homogenizer the maximum size of any remaining agglomerates can be selectively influenced.
• the homogenizer preferably high-pressure homogenizer, is usually a jet disperser or a gap homogenizer, which is operated with an inlet pressure of at least 50 bar and a gap width set automatically on it.
• the homogenizer preferably high-pressure homogenizer, is preferably operated with an inlet pressure of 1000 bar and a gap width automatically set thereon. Very particular preference is given to high-pressure homogenizers of the Micronlab type.
• the alternative also preferred embodiment of steps b) and c) of the new method involves the treatment of predispersion in a three-roll mill.
• the preferred process is characterized in that the preparation of the predispersion b) and the introduction of shear energy c) is effected by treating the predispersion in a rotating mill with rotating rollers, the process comprising at least steps bl) introducing the solution of the polymeric dispersing aid in aqueous Solvent together with the carbon nanotubes in a first gap between a first and a second roller at different rotational speeds, whereby the carbon nanotubes are predispersed in the solution and coarse agglomerates are comminuted; b2) transporting the predispersion from step bl) to a second gap between the second roller and a third roller at a different rotational speed, the predispersion at least partially adhering to the roller surface during transport; cl) introducing the predispersion into the second gap, the agglomerates of the carbon nanotubes in the dispersion being comminuted to a diameter of essentially ⁇ 5 ⁇ m, preferably ⁇ 3 ⁇ m, particularly
• the alternative embodiment of the method according to the invention is operated so that the ratio of the rotational speed of the first roller and the second roller and the ratio of the rotational speed of the second roller and the third roller independently of one another at least 1: 2, preferably at least 1: 3.
• the width of the gap between the first and second rolls, and between the second and third rolls may be the same or different.
• the width of the column is the same.
• the width of the column is equal to and less than 10 microns, preferably less than 5 microns, more preferably less than 3 microns.
• step c) inks with low agglomerate contents and small agglomerate sizes can be obtained.
• the adjustment of the gap in the homogenizer preferably high-pressure homogenizer
• Passing the Both columns in the three-roll mill can in preferred embodiments correspond to approximately twice the pass in the homogenizer, preferably high-pressure homogenizer.
• inks of the present invention obtained according to the process of this invention, as well as its preferred and alternative embodiments, are particularly suitable for use in screen printing, offset printing, or similar well-known high throughput printing processes for the production of conductive print images.
• Another object of the invention is an electrically conductive coating obtainable by printing, in particular by screen printing or offset printing, the composition of the invention on a surface and removing the solvent or solvents.
• the invention also relates to an article having surfaces of non or poorly electrically conductive material (surface resistance of less than 10 4 ohm * m) comprising a coating obtainable from the composition according to the invention.
• the conductive print image of the ink can be thermally post-treated.
• the thermal aftertreatment of the printed ink is carried out in the context of their use preferably by drying at a temperature of from room temperature (23 ° C) to 150 0 C, preferably 30 0 C to 140 0 C, particularly preferably 40 0 C to 80 0 C.
• a thermal aftertreatment is advantageous if the adhesion of the ink according to the invention to the substrate can be improved thereby and the printed ink can thus be secured against blurring.
• the new inks also have other properties that may be advantageous for other uses.
• the substance group of the carbon nanotubes and also the special carbon nanotubes used according to the invention have a particularly high strength.
• carbon nanotubes as obtained, for example, according to the disclosure of the still unpublished German patent application with the official file reference 102007044031.8, are characterized by special ratios of length to diameter (so-called aspect ratios).
• aspect ratios are characterized by special ratios of length to diameter.
• the pH of the template was maintained at about 10 by controlling the sodium hydroxide addition.
• the precipitated solid was separated from the suspension and washed several times.
• the washed solid was then dried in a paddle dryer over 16 hours, with the temperature of the dryer increasing from room temperature to 160 ° C. within the first eight hours.
• the solid was milled in a laboratory mill to an average particle size of 50 microns and the average fraction in the range of 30 .mu.m to 100 .mu.m particle size taken to facilitate the subsequent calcination, especially to improve the fluidization in the fluidized bed and a high yield to achieve product.
• the solid was calcined for 12 hours in an oven of 500 0 C under air access and then cooled for 24 hours.
• the catalyst material was then allowed to stand at room temperature for a further 7 days for post-oxidation. A total of 121.3 g of catalyst material were isolated.
• Example 2 (Production of the CNT in a fluidized bed)
• the catalyst prepared in Example 1 was tested in a laboratory scale fluid bed apparatus. For this purpose, a defined amount of catalyst was placed in a heated from the outside by a heat transfer steel reactor with an inner diameter of 100 mm. The temperature of the fluidized bed was controlled by a PID control of the electrically heated heat carrier. The temperature of the fluidized bed was determined by a thermocouple. Feed gases and inert diluent gases were fed into the reactor via electronically controlled mass flow controllers.
• the resulting paste was applied through a sieve (Heinen, Cologne-Pulheim) on polycarbonate (Macro-Ion, Bayer Material Science AG) and dried at RT. Subsequently, the conductivity of the printed images obtained is determined. It is 3 * 10 3 S / m.

Landscapes

• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Conductive Materials (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Manufacturing Of Electric Cables (AREA)
• Carbon And Carbon Compounds (AREA)
• Non-Insulated Conductors (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=40551457

Family Applications (1)

Country Status (13)

Cited By (1)

Families Citing this family (37)

Family Cites Families (11)

• 2008
  • 2008-02-13 DE DE102008008837A patent/DE102008008837A1/de not_active Withdrawn
• 2009
  • 2009-02-07 JP JP2010546252A patent/JP2011517009A/ja not_active Withdrawn
  • 2009-02-07 RU RU2010137629/05A patent/RU2010137629A/ru not_active Application Discontinuation
  • 2009-02-07 CN CN200980105131.3A patent/CN101945959A/zh active Pending
  • 2009-02-07 BR BRPI0908234-4A patent/BRPI0908234A2/pt not_active IP Right Cessation
  • 2009-02-07 EP EP09711154A patent/EP2242809A1/de not_active Withdrawn
  • 2009-02-07 KR KR1020107017867A patent/KR20100112621A/ko not_active Application Discontinuation
  • 2009-02-07 WO PCT/EP2009/000870 patent/WO2009100865A1/de active Application Filing
  • 2009-02-07 AU AU2009214392A patent/AU2009214392A1/en not_active Abandoned
  • 2009-02-07 CA CA2714659A patent/CA2714659A1/en not_active Abandoned
  • 2009-02-12 TW TW098104402A patent/TW200951994A/zh unknown
  • 2009-02-13 US US12/370,643 patent/US20090226684A1/en not_active Abandoned
• 2010
  • 2010-07-05 IL IL206805A patent/IL206805A0/en unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events