CA2282128C - Stainless steel anode for electrocoagulation printing - Google Patents
Stainless steel anode for electrocoagulation printing Download PDFInfo
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- CA2282128C CA2282128C CA 2282128 CA2282128A CA2282128C CA 2282128 C CA2282128 C CA 2282128C CA 2282128 CA2282128 CA 2282128 CA 2282128 A CA2282128 A CA 2282128A CA 2282128 C CA2282128 C CA 2282128C
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- Prior art keywords
- colloid
- iron
- positive electrode
- iron alloy
- balance
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
- B41C1/00—Forme preparation
- B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
- B41C1/105—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by electrocoagulation, by electro-adhesion or by electro-releasing of material, e.g. a liquid from a gel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Inks, Pencil-Leads, Or Crayons (AREA)
- Printing Plates And Materials Therefor (AREA)
Abstract
An anode having a passive oxide film thereon and made of an iron alloy consisting essentially of at least 20 wt.% Cr, 5 to 15 wt.% Ni, 1 to 2 wt.% Si, 0.9 to 1.5 wt.% Mn and 0.1 to 0.3 wt.% C with the balance consisting of iron and unavoidable impurities is used for reproducing an image by electrocoagulation of a colloid.
Such an anode can be thoroughly cleaned without undergoing abrasion and/or pitting during cleaning. The alloy composition does not adversely affect passivation.
Such an anode can be thoroughly cleaned without undergoing abrasion and/or pitting during cleaning. The alloy composition does not adversely affect passivation.
Description
STAINLESS STEEL ANODE FOR
ELECTROCOAGULATION PRINTING
The present invention pertains to improvements s in the field of electrocoagulation printing. More particularly, the invention relates to an improved anode for use in an electrocoagulation printing method and apparatus.
~o In US Patent N° 4,895,629 of January 23, 1990, Applicant has described a high-speed electrocoagulation printing method and apparatus in which use is made of a positive electrode in the form of a revolving cylinder having a passivated surface onto which dots of colored, coagulated colloid representative of an image are produced. These dots of colored, coagulated colloid are thereafter contacted with a substrate such as paper to cause transfer of the colored, coagulated colloid onto the substrate and thereby imprint the substrate with the zo image. As explained in this patent, the positive electrode is coated with a dispersion containing an olefinic substance and a metal oxide prior to electrical energization of the negative electrodes in order to weaken the adherence of the dots of coagulated colloid to z5 the positive electrode and also to prevent an uncontrolled corrosion of the positive electrode. In addition, gas generated as a result of electrolysis upon energizing the negative electrodes is consumed by reaction with the olefinic substance so that there is no 3o gas accumulation between the negative and positive electrodes.
The electrocoagulation printing ink which is injected into the gap defined between the positive and 3s negative electrodes consists essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent. Where the coloring agent used is a pigment, a dispersing agent is added for uniformly dispersing the pigment into the ink. After coagulation of the colloid, any remaining non-coagulated s colloid is removed from the surface of the positive electrode, for example, by scraping the surface with a soft rubber squeegee, so as to fully uncover the colored, coagulated colloid which is thereafter transferred onto the substrate. The surface of the positive electrode is ~o thereafter cleaned by means of a plurality of rotating brushes and a cleaning liquid to remove any residual coagulated colloid adhered to the surface of the positive electrode.
15 When a polychromic image is desired, the negative and positive electrodes, the positive electrode coating device, ink injector, rubber squeegee and positive electrode cleaning device are arranged to define a printing unit and several printing units each using a zo coloring agent of different color are disposed in tandem relation to produce several differently colored images of coagulated colloid which are transferred at respective transfer stations onto the substrate in superimposed relation to provide the desired polychromic image. Alter-25 natively, the printing units can be arranged around a single roller adapted to bring the substrate into contact with the dots of colored, coagulated colloid produced by each printing unit, and the substrate which is in the form of a continuous web is partially wrapped around the 3o roller and passed through the respective transfer stations for being imprinted with the differently colored images in superimposed relation.
The positive electrode which is used for 35 electrocoagulation printing must be made of an electrolytically inert metal capable of releasing trivalent ions so that upon electrical energization of the negative electrodes, dissolution of the passive oxide film on such an electrode generates trivalent ions which then initiate coagulation of the colloid. Examples of suitable electrolytically inert metals include stainless steels, aluminium and tin.
As explained in Applicant s Canadian patent No.
2,138,190 of October 13, 1998, a breakdown of passive oxide films occurs in the presence of electrolyte anions, ~o such as C1-, Br- and I-, there being a gradual oxygen displacement from the passive film by the halide anions and a displacement of adsorbed oxygen from the metal surface by the halide anions. The velocity of passive film breakdown, once started, increases explosively in the presence of an applied electric field. There is thus formation of a soluble metal halide at the metal surface.
In other words, a local dissolution of the passive oxide film occurs at the breakdown sites, which releases metal ions into the electrolyte solution. Where a positive zo electrode made of stainless steel or aluminium is utilized in Applicant s electrocoagulation printing method, dissolution of the passive oxide film on such an electrode generates Fe3+ or A13+ ions. These trivalent ions then initiate coagulation of the colloid.
Stainless steels are preferred due to their low cost and availability. These are iron alloys containing a minimum of approximately 11 wt.% chromium. This amount of chromium prevents the formation of rust in unpoluted 3o atmospheres. Their corrosion resistance is provided by the aforesaid passive oxide film which is self-healing in a wide variety of environments.
The stainless steels hitherto used by the Applicant consisted of 12 to 20 wt.% Cr, 3 to 10 wt.% Ni, 0.5 to 2.5 wt.% Mo and 0.03 to 0.09 wt.% C, with the balance consisting of iron and unavoidable impurities.
Although such alloys give satisfactory results in respect of electrocoagulation, Applicant has observed that they do not have a hardness sufficient to withstand the harsh s conditions encountered during cleaning of the positive electrode, resulting in abrasion and pitting of such an electrode. It is therefore necessary to regrind the surface of the electrode after every forty hours of printing. This, of course, requires shutdown of the ~o printing apparatus and removal of the electrode.
As it is known, many elements other than chromium are added to iron to provide specific properties or ease of fabrication. For example, nickel, nitrogen and ~5 molybdenum are added for corrosion resistance; carbon, nitrogen and titanium for strength; sulfur and selenium for machinability and nickel for formability and toughness. Applicant has observed that a stainless steel with a high carbon content adversely affects passivation.
2o A stainless steel with a high nickel content, on the other hand, is difficult to clean so that a residual film of ink containing non-coagulated colloid is left on the surface of the positive electrode and is transferred with the colored, coagulated colloid onto the substrate during 2s contacting same. Thus, when black, cyan, magenta and yellow coloring agents are used to provide a polychromic image, the residual films containing these coloring agents upon being transferred onto the substrate in superimposed relation create on the printed image an 3o undesirable colored background.
It is therefore an object of the present invention to overcome the above drawbacks and to provide an improved stainless steel anode for use in an 35 electrocoagulation printing method and apparatus, that can be thoroughly cleaned without undergoing abrasion and/or pitting during cleaning and has an alloy composition which does not adversely affect passivation.
According to one aspect of the invention, there s is provided an improved electrocoagulation printing method comprising the steps of:
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving ~o at substantially constant speed along a predetermined path, the passivated surface defining a positive electrode active surface;
b) forming on the positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the 2o electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of Zs the colored, coagulated colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image;
the improvement wherein the positive electrode is made of 3o an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
35 Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
ELECTROCOAGULATION PRINTING
The present invention pertains to improvements s in the field of electrocoagulation printing. More particularly, the invention relates to an improved anode for use in an electrocoagulation printing method and apparatus.
~o In US Patent N° 4,895,629 of January 23, 1990, Applicant has described a high-speed electrocoagulation printing method and apparatus in which use is made of a positive electrode in the form of a revolving cylinder having a passivated surface onto which dots of colored, coagulated colloid representative of an image are produced. These dots of colored, coagulated colloid are thereafter contacted with a substrate such as paper to cause transfer of the colored, coagulated colloid onto the substrate and thereby imprint the substrate with the zo image. As explained in this patent, the positive electrode is coated with a dispersion containing an olefinic substance and a metal oxide prior to electrical energization of the negative electrodes in order to weaken the adherence of the dots of coagulated colloid to z5 the positive electrode and also to prevent an uncontrolled corrosion of the positive electrode. In addition, gas generated as a result of electrolysis upon energizing the negative electrodes is consumed by reaction with the olefinic substance so that there is no 3o gas accumulation between the negative and positive electrodes.
The electrocoagulation printing ink which is injected into the gap defined between the positive and 3s negative electrodes consists essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent. Where the coloring agent used is a pigment, a dispersing agent is added for uniformly dispersing the pigment into the ink. After coagulation of the colloid, any remaining non-coagulated s colloid is removed from the surface of the positive electrode, for example, by scraping the surface with a soft rubber squeegee, so as to fully uncover the colored, coagulated colloid which is thereafter transferred onto the substrate. The surface of the positive electrode is ~o thereafter cleaned by means of a plurality of rotating brushes and a cleaning liquid to remove any residual coagulated colloid adhered to the surface of the positive electrode.
15 When a polychromic image is desired, the negative and positive electrodes, the positive electrode coating device, ink injector, rubber squeegee and positive electrode cleaning device are arranged to define a printing unit and several printing units each using a zo coloring agent of different color are disposed in tandem relation to produce several differently colored images of coagulated colloid which are transferred at respective transfer stations onto the substrate in superimposed relation to provide the desired polychromic image. Alter-25 natively, the printing units can be arranged around a single roller adapted to bring the substrate into contact with the dots of colored, coagulated colloid produced by each printing unit, and the substrate which is in the form of a continuous web is partially wrapped around the 3o roller and passed through the respective transfer stations for being imprinted with the differently colored images in superimposed relation.
The positive electrode which is used for 35 electrocoagulation printing must be made of an electrolytically inert metal capable of releasing trivalent ions so that upon electrical energization of the negative electrodes, dissolution of the passive oxide film on such an electrode generates trivalent ions which then initiate coagulation of the colloid. Examples of suitable electrolytically inert metals include stainless steels, aluminium and tin.
As explained in Applicant s Canadian patent No.
2,138,190 of October 13, 1998, a breakdown of passive oxide films occurs in the presence of electrolyte anions, ~o such as C1-, Br- and I-, there being a gradual oxygen displacement from the passive film by the halide anions and a displacement of adsorbed oxygen from the metal surface by the halide anions. The velocity of passive film breakdown, once started, increases explosively in the presence of an applied electric field. There is thus formation of a soluble metal halide at the metal surface.
In other words, a local dissolution of the passive oxide film occurs at the breakdown sites, which releases metal ions into the electrolyte solution. Where a positive zo electrode made of stainless steel or aluminium is utilized in Applicant s electrocoagulation printing method, dissolution of the passive oxide film on such an electrode generates Fe3+ or A13+ ions. These trivalent ions then initiate coagulation of the colloid.
Stainless steels are preferred due to their low cost and availability. These are iron alloys containing a minimum of approximately 11 wt.% chromium. This amount of chromium prevents the formation of rust in unpoluted 3o atmospheres. Their corrosion resistance is provided by the aforesaid passive oxide film which is self-healing in a wide variety of environments.
The stainless steels hitherto used by the Applicant consisted of 12 to 20 wt.% Cr, 3 to 10 wt.% Ni, 0.5 to 2.5 wt.% Mo and 0.03 to 0.09 wt.% C, with the balance consisting of iron and unavoidable impurities.
Although such alloys give satisfactory results in respect of electrocoagulation, Applicant has observed that they do not have a hardness sufficient to withstand the harsh s conditions encountered during cleaning of the positive electrode, resulting in abrasion and pitting of such an electrode. It is therefore necessary to regrind the surface of the electrode after every forty hours of printing. This, of course, requires shutdown of the ~o printing apparatus and removal of the electrode.
As it is known, many elements other than chromium are added to iron to provide specific properties or ease of fabrication. For example, nickel, nitrogen and ~5 molybdenum are added for corrosion resistance; carbon, nitrogen and titanium for strength; sulfur and selenium for machinability and nickel for formability and toughness. Applicant has observed that a stainless steel with a high carbon content adversely affects passivation.
2o A stainless steel with a high nickel content, on the other hand, is difficult to clean so that a residual film of ink containing non-coagulated colloid is left on the surface of the positive electrode and is transferred with the colored, coagulated colloid onto the substrate during 2s contacting same. Thus, when black, cyan, magenta and yellow coloring agents are used to provide a polychromic image, the residual films containing these coloring agents upon being transferred onto the substrate in superimposed relation create on the printed image an 3o undesirable colored background.
It is therefore an object of the present invention to overcome the above drawbacks and to provide an improved stainless steel anode for use in an 35 electrocoagulation printing method and apparatus, that can be thoroughly cleaned without undergoing abrasion and/or pitting during cleaning and has an alloy composition which does not adversely affect passivation.
According to one aspect of the invention, there s is provided an improved electrocoagulation printing method comprising the steps of:
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving ~o at substantially constant speed along a predetermined path, the passivated surface defining a positive electrode active surface;
b) forming on the positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the 2o electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of Zs the colored, coagulated colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image;
the improvement wherein the positive electrode is made of 3o an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
35 Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
According to another aspect of the invention, there is also provided an improved electrocoagulation printing apparatus comprising:
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
~o - means for moving the positive electrode active surface at a substantially constant speed along a predetermined path;
- means for forming on the positive electrode ~5 active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the zo electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and - means for bringing a substrate into contact with the dots of colored, coagulated colloid to cause z5 transfer of the colored, coagulated colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image;
the improvement wherein the positive electrode is made of 3o an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
35 Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
~o - means for moving the positive electrode active surface at a substantially constant speed along a predetermined path;
- means for forming on the positive electrode ~5 active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the zo electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and - means for bringing a substrate into contact with the dots of colored, coagulated colloid to cause z5 transfer of the colored, coagulated colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image;
the improvement wherein the positive electrode is made of 3o an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
35 Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
App7_icant has found quite unexpectedly that a stainless steel anode with the above alloy composition is sufficiently hard so that it can be thoroughly cleaned s without undergoing abrasion and/or pitting during cleaning and that such an alloy composition does not adversely affect passivation. The stainless steel must have a chromium content of at least 20 wt.o since, when the chromium content is lower than 20 wt. o, the passive ~o oxide film does not have sufficiently rapid self-healing properties and there is a release of undesirable Fe+2 ions. A chromium content ranging between 20 and 30 wt.o is preferred. The stainless steel must also have a nickel content within the range of 5 to 15 wt . % since, when the ~s nickel content. is higher than 15 wt.%, the anode cannot be thoroughly cleaned so that a residual film of ink containing non-coagulated colloid is left on the surface of the anode, leading to the formation of undesirable background on the printed image. On the other hand, when 2o the nickel content is lower than 5 wt.%, the steel is not sufficiently ductile and corrosion-resistant. A carbon content within. the range of 0.1 to 0.3 wt. o is essential since, when tine carbon content is higher than 0.3 wt.%, passivation is adversely affected and, when the carbon z5 content is lower than 0.1 wt.%, the steel is not sufficiently hard. Manganese is an alloying agent added for providing depassivation initiation sites, whereas silicon is an alloying agent added for increasing the resistance to chloride corrosion.
Where a pc>lychromic image is desired, steps (b) and (c) of the above electrocoagulation printing method are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along the aforesaid path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated colloid which are transferred at: tYu_e ~especti.ve transfer positions onto the subst rate in uperi;nposed relation to provide a polyc:-.hrc>rriic image. 1t: is also possible to repeat several t:imes steps (a), b) and (c) to define a s corresponding number o_ pri.nt~irug stages arranged in tandem relation and each using a coloring agent of different color, and to l:h~-~:ceba produce several differently colored images of_ c~c:m~gulated colloid which are transferred at respective transfer positions onto the ~o substrate in superimposed. r_e'':ata..on t:o provide a polychromic image, the wubst~rate being in the form of a continuous web which i:; passed thxwugh the respective transfer positions for Joez.ng impr~:inted with the colored images at the printing stagfas. Alternatively, the 15 printing stages defined by r_epeat:ing several times steps (a) , (b) and (c) c,aru be arranged ar:_~und a single roller adapted to bring the substrate ins:c> c:ontact with the dots of colored, coagulated colloid of each printing stage and the substrate which i_s ii: t:he forr~u of a continuous web is zo partially wr<~pped around the roller and passed through the respective transfer ~:>ositiorjs for being imprinted with the colored images at t:rne print W g stages. The last two arrangements; arE: de.>cribed irn A~>plicant' s US Patent No. 4,895,629.
zs When a polychromic image oø~ high definition is desired, it is preferable to bring an endless non-extensible belt moving av: substantv:i_a:JLy the same speed as the positive electrode active: st~r:face and having on one 3o side thereof a cc>.l l o:id reta.~.n:lng surface adapted to releasably retain dots o:~ electrocoagulated colloid, into contact with the positive e:Lect:rocJe active surface to cause transfer of t:he d:ifferentl,r cc>>lored images at the respective transfer positions onto tine colloid retaining 35 surface of such a belt i.n st.rpez:i.mposed relation to provide a polychromic image, arc:~ thereafter bring the substrate into c.ont<~c-~t with tJ-.e colloid retaining surface _ g _ of the belt to cause transfer of the polychromic image from the colloid regaining surface onto the substrate and to thereby imprint the substrate with the polychromic image. As explained in Applicant's c:opend:i_ng Canadian s patent application No. 2,214,300 filed August 29, 1997, by utilizing are. endless non-extens~ ble belt having a colloid retaining tsurface such as a porous surface on which dots of cc~l.orecl, coagulated colloid can be transferred and by moving such a belt independently of ~o the positive electrode, from cane printing unit to another, so that the colloid retaining surface of the belt contacts the colored, coag~rlated colloid in sequence, it is pc;ssible to sic~ni_fi.cantly improve the registration of the differently colored images upon their 15 transfer onto the c~~..i..l.oicl ret.aini.ro~ ,urface of the belt, thereby providing a polychromic i.rnage of high definition which can thereafter be t: ran:>fer_r~~d onto the paper web or other substrate. For example, use can be made of a belt comprising a plastic: rrratr~ri.a1 havu.ng a porous coating of zo silica.
Accordingly, the present invention also provides, in a further aspect thereof, an improved multicolor electrocoagulation pr~.nt;i.ng method comprising 2s the steps of:
a) providing a positive electrolytically inert electrode having a c:ontp nuous pa.::,sivated surface moving at substantially constant speed along a predetermined 3o path, the pas sivated si.zrface dev-ining a positive electrode active surface;
b) forming on thue pos:i.,tivn electrode active surface a plurality of dots of colored, coagulated 35 colloid representative of; a desired image, by electrocoagulation of an electrolytically coagulable collo:i.d present in an electrocos3gLrlation printing ink _ c~ _ comprising a liquid colloidal dispersion containing the electrolytically coagu_La>r~le c~ol~oid, a dispex:sing medium, a soluble electrolyte and a c;olori_ng cogent;
c) bringing an endless non-extensible belt moving at substantial:Ly the Name sptaed as the positive electrode acting surface and having on one side thereof a colloid retaining 4~urface adapted t,o releasably retain dots of electrocoagulatec~ colloid, iruto contact with the ~o positive electrode active surface to cause transfer of the dots of colored, coagulated cr>llo:~d from the positive electrode active surface onto the colloid retaining surface of the belt: and to thereby imprint the colloid retaining surface with the image;
d) repeating steps (b) and c) several times to define a corresponding member o.f pr.in :ing stages arranged at predetermined locations along the path and each using a coloring agent of dift::erent_ colcor, to thereby produce 2'o several differently colored image::, <o coagulated colloid which are transferred at respective transfer positions onto the colloid retafining s~zrfacie in superimposed relation to provide a polychromi.c :image; and ~5 e) bringing a sukastrate int=o contact with the colloid retaining surface of the belt to cause transfer of the polychromic image from the colloid retaining surface onto the substrate and t::o thereby imprint the substrate with the polychromic image;
the improvement wherein the positive c:>_lectrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.s Ni: 5 to 15 wt.
Si: 1 to 2 wt °-Mn : 0 . ~3 to 1 . 5 wt . °~s - 1.0 -C: 0.1 t0 0.3 wt.'s balance: iron and unavc>i.dak:>le impurities.
According too yet. another aspect of the invention, there is prc_~vu ded an improved electrocoagulation printing apparatus comprising:
- a positive electro.Lyti.cal_Ly inert: elect=rode having a continuous pass>ivated surface defining a positive 'o electrode active surface;
- means for moving the positive electrode active surface at a substantial..ly constant speed along a predetermined path;
- an endless non-extensible be:Lr having on one side thereof a colloid retaining surface adapted to releasably retain dots of elect=rocoagu.Lated col__:Lc id;
a:o - means for moving the belts at sub standal7_y the same speed as the positive electrode active surface;
- a plurality of printinct units arranged at predetermined locations along the path, each print~_ng unit comprising:
c.5 - means for forming on the positive electrode active surface a pl;_rrality of dots of colored, coagulated colloid representative of: a dc.:sired image, by elect r:ocoagulation of an elect:ro:Lytically coagulable ~o colloid present in an electroco.~gulation painting ink comprising a liquid colloidal. di:>persion containing the electrolytically coagulable colloid, ~-~ dispersion medium, a soluble electrolyte and a colc~ri.rng agent, and 35 - mE=ans fc~r bringing the be:l_t into contact with the positive electrode active si..irface at a respective transfer station to cause transferv of the dots of colored, coagulated colloid from the positive electrode active surface onto the coll.o id r.~eta:i._ning surface of the belt and to imprint t:he~ cool. ioid retaining :>urface with the image, whereby to produce several c~i.ffex~ent ~ y colored images of coagulated colloid which are transferred at the respective transfer stations onto t:rce colloid retaining surface in superimposed relation to provide a polychromic ~o image; and - means for bringing a substrate inr_o contact with the colloid retaining surface of. the belt to cause transfer of the polychromic: image f rom tr~e~ colloid retaining t5 surface onto the substrate and to thereby imprint the substrate with tine polycrromic image the improvement wherein said electrode is made of an iron alloy consisting es~~enti~,lly of:
zo Cr : at least 20 wt . o Ni : 5 to 15 wt .
Si: 1. to 2 wt:. o Mn: 0.9 to 1.5 wt.o z5 C: 0.1 to 0.3 wt.'s balance: iron and unavoida~>le impurities.
Use is preferably m~~de of an iron alloy consisting essentially of== ~'.5 to 28 wt.o Cr, 8 to 11 wt.~
o Ni, lto2wt.° Si, (7.9t.o1..5wt.'<:Mnand0.1to0.2 wt.o C, the balance consisting of iron and unavoidable impurities. A particularly preferred iron alloy consists essentially of 26. 4 wt . o Cr, 9. 7 wt . '~ Ni, 1 . 08 wt . o Si, 0. 95 wt. o Mn and 0. 1.2 wt:. °, C, the k~alance consisting of iron and unavoidab.Le impurities. Such an alloy has a Brinell hardness of about 225. :Its is possible to increase the Brinell hardness of this ~a.l.:loy up to about 325, without adversely affect:irug passivation, by subjecting the alloy after c:ast.ing to a teat treatment at a temperature of abou ~ 1120 °C ( 205() ° F') and to a subsequent water quenching. The alloy t.hu.s treatE:d has an s austenitic-ferritic structure.
The positive e:Lectrode used can be in the form of a moving endless belt as c~esc:Y-ibed in Applicant's US
Patent No. 4,661,222, or in the form of a revolving ~o cylinder as described in Appl.i.cant's US Patent Nos. 4,895,629 and 5,533,Fi01.. In the later case, the printing stages or ur~,its are arrar;ged around t:.he positive cylindrical electrode. Prefer.abl_y, th~a positive electrode active surface and the ink are maintained at a tem-perature of about ..5-60°C, preferably 40°C, to increase the viscosity of tree coagulated ~::~olloid in step (b) so that the dots of <~o.l.orec:l, coagulated colloid remain coherent during their transfer in step (c), thereby enhancing transfer of t: he col..ored, coag=alated colloid a:o onto the substrate or belt. For example, the positive electrode active surface cyan be heated at the desired temperature and the ink applied on the heated electrode surface to cause a transfer_ of heat: t:r~nerefrom to the ink.
When use i.s m;~de of a po;>itive electrode of cylindrical configuration rotating at substantially constant speed about: its central Longitudinal axis, step (b) of the above electrocoa.gulation printing method is carried out by:
i) providing a pluralit:.;r of negative electro-lytically inert electrodes elec~ric~:~lly insulated from one another and arranged in rectilinear alignment to define a series of cc~rrespondi.rlg negative electrode active surfaces disposed in a plarue parallel to the longitudinal axis c;f thc> positive electrode and spaced from the positive e:Lectrode active surface by a constant predetermined gap, the ruegatzve ~~lec°trodes being spaced from one another by a distance at least equal to the electrode gap;
s ii) co<~tir7g tine positive electrode active surface with an olef.inic sub:>tance to form on the surface micro-droplets of olefinic substance;
iii) filling the electrode gap with the afore-~o said electrocoagulat:ion printing ~_rlk;
iv) electrically energi;_:ing selected ones of the negative electrr_ades to cause point:-by-point selective coagulation and adherenca~ of t:he col_l.o.id Into the olefin coated positive e_Lect.rode active surface opposite the electrode active ;=,urfaces of the energized negative electrodes while, the p.;~si_t:ive t~ Lectrode i_s rotating, thereby forming the c.~ots of c-.ol.o.re~d, coagulated colloid;
and zo v) removing any rerria:irn ng non-coagulated colloid from the positive electrode active surface.
As explained in US Patent No. 4,895,629, 2s spacing of the negative e=lectrodes from one another by a distance which is equal. to or greater than the electrode gap prevents the negative electrodes 1-rom undergoing edge corrosion. On the ether hand, coating of the positive electrode with an o.l.efin:ic substaruc;e prior to electrical 3o energ:i.zation of tre negative elect.rcdes weakens the adherence of the dots of coagulated colloid to the positive elec;trc>de and also proven=s an uncontrolled corrosion of the positive a ec.trode. Tn addition, gas generated as a resu_Lt of electrolysis upon energizing the 35 negative elec:trcdes i s con:>umed by reaction with the olefinic substance so that there is no gas accumulation between the negative and positive. electrodes. Applicant has found that it is no longer necessary to admix a metal oxide with the olefin subst~anc~:e; it l s believed that the passive oxide f:ilno on ci.zrrentl~; available electrodes contains sufficient metal oxide to act as catalyst for s the desired reaction.
Examples of suitable ele~,trolytically inert metals from which =he positive and negative electrodes can be made are stainless steel, platinum, chromium, ~o nickel and aluminum. The gap which is defined between the posit.i_ve and negat i.ve eler_trode~~ can range from about 50 um to about 100 tern, the smaller true electrode gap the sharper are the dots of coagu.ated colloid produced.
Where the electrode gap i.s cof t~°ie c::~rder of 50 um, the ~s negative electrodes are the preferably spaced from one another by a distance of about 75 E.irn.
Examples of su__tab.le olefinic substances which may be used to coat the :.urface oI thca positive electrode zo in step (b)(ii) include unsaturated Latty acids such as arachidonic acid, linoleic acid, linolenic acid, oleic acid and palmitoleic: acid and un;~~.-3tuxated vegetable oils such as corn of l, l inseed c:~i:l, c:oli.ve oi7_, peanut oil, soybean oil and sunflower oil.. Oleic acid is particularly zs preferred. The micro-droplets of olefinic substance formed on the surface o:~ the positiT~e electrode active surface generally have a size ranging from about 1 to about 5 um.
so The olefin-coat::ed positive active surface is preferably polished to increase true adherence of the micro-droplets onto the positive electrode active surface, prior to step (z~) (:ii) . F~'or example, use can be made of a rotating brush provided with a plurality of 35 radially extending bristles made of horsehair and having extremities cont:act~ing the surface of the positive electrode. The fi:ict=ion caused by the bri_st.les contacting the surface upon rotation of the brush has been found to increase the adherence of the mi.cr,:>-droplets onto the positive electrode active surface.
s Where the positive cylindrical electrode extends vertically, step (b)(ii) of the above electro-coagulation printinc metr~.od is advantageously carried out by continuously discharging the ink onto the positive electrode active surface: from a f Lr.zid discharge means ~o disposed adjacent the e:,_ectrode chap at a predetermined height relative to the positive ele~~trode and allowing the ink to f.Low downwarc:lly a 1 ong the positive electrode active surface, the ink being thus carried by the positive electrode upon rotation t hereof to the electrode ~5 gap to fill same. Preferably, excess ink flowing downwardly off the positive electrode active surface is collected and the c:oll.ected i.nk i..s recirculated back to the fluid discharge means.
zo The co:Llo_i.d generally used is a linear colloid of high molecular weight, that is, one having a weight average molecular weight between about 10,000 and about 1,000,000, preferably between 100,000 and 600,000.
Examples of su.ii~able co:Llc>ids incluc:le natural polymers z5 such as albumin, ge:Latin, casein <:jnd agar, and synthetic polymers such as ~>olyacrylic acid, polyacrylamide and polyvinyl alcohol. P. part::icul.arly preferred colloid is an anionic copolymer of acrylamide and acrylic acid having a weight average molecular weight of. abe>ut 250,000 and sold 3o by Cyanamid lnc . under i.he t: r_ ade ma r_ k ACCOSTRENGTH 8 6 .
Water is preferably used as t:he medium for dispersing the colloid to provicie the desired co:l.:~oidal dispersion.
The ink also ccntai.ns a soluble electrolyte and 3s a coloring agent. Preferred electrol.~tes include alkali metal halides and alkaline earth metal halides, such as lithium chloride, sodium chloride, potassium chloride and calcium chloride. Potassium ~hlc>ri~:~e is particularly preferred. The col.or__ng <-~gemt can be a dye or a pigment.
Examples of suitable dye;: which may ke used t.o color the colloid are the water soluble dyes avai7_ab.le from HOECHST
s such a Duasyn Acid E37_ack for coloring in black and Duasyn Acid Blue for coloring in cyan, car those available from RIEDEL-DEHAEN such a.s P,nti-Halo Dye B7_ue T. Pina for coloring in cyan, Anti-Halo Dye AC Magenta Extra VO1 Pina for coloring in magenta and ~?,nti.-Halo Dye Oxonol Yellow ~o N. Pina for coloring in yellow. When ~zsing a pigment as a coloring agent, use ca:l li>e made of the pigments which are avail,~ible f rom CABOT CORf . such as O:arbon Black Monarch~
120 for coloring in black, ox tho:~e available from HOECHST such as Hostaperm E3:Lue Es~G or B3G for coloring in cyan, Permanent. Rubine ~:~6B ca.r_ L6B for coloring in magenta and Permanent. Yellow DGR or D1-iG for coloring in yellow. A dispersung cogent :i~> c~eided for uniformly dispersing the p=figment into t:he ink. l~,xamples of suitable dispersing agents i.nc:lude the aniani.c dispersing agent zo sold by Boehme fi7_atex Canada Tnc. under the trade mark CLOSPERSE 25000.
After coagulation of the co::l.loid, any remaining non-coagulated collo:i.d is removed from the positive z5 electrode active surface, for ex<ample, by scraping the surface with a soft rubber_ squeegee, so as to fully uncover the colored, coagu7_ated <~0:17_oid. Preferably, the non-coagulated c:ol7.oid ',thus rernc>ved is collected and mixed with the collected ink, and t:ze col:lec:ted non-3o coagulated colloid in admixture with t:he collected ink is recirculated back to the aforesaid fluid discharge means.
The optic<~l density of the dots of colored, coagulated colloid may be varied by varying the voltage 35 and/or pulse duration of the pulse-modulated signals applied to the negative electrodes.
After step (c), the po:;itive electrode active surface is generally cleaned t:o remove therefrom any remaining coagulated colloid. _~<.cording too a preferred embodiment, 1=he pos it:.ivc~ e:lE~ctr,~~de is rotatable in a predetermined direca:ion anc~ any remaining coagulated colloid is removed from t:he ~:~ositi~~re electrode active surface by providing an ~~lori<~ated rotatable brush extending parallel to the lonr~it=ac~inal axis of the positive electrode, the brush k>ei.ng provided with a plura7_ity o:fv radi ally E~xtE.mdi ruc~~ bristles made of horsehair and having extremities :=ont.acting the positive electrode active surface, rotating the brush in a direction opposite to tkue direct::i.on of rotation of the positive electrode so as to cJausfe the bristles to 15 frictionally engage the posit.i_ve electrode active surface, and directing jets of c~_E:~aning liquid under pressure against the po~~itive eiec:trode active surface, from either side of the k.~rush. In such an embodiment, the positive electrode act::i_ve surface and the ink are zo preferably maintained at a temperature of about 35-60°C
by heating the cleanin:~ liquid to thereby heat the posit.i_ve electrode active surface upon contacting same and applying the ink on the heated electrode surface to cause a transfer of heat therefrom t.o the ink.
Pre:Eerably, the elec:trocoagulation printing ink contains water as the dispersing med~rum and the dots of differently colored, coagulated colio::°._d representative of the polychromic image are rru~ist:ened between the 3o aforementioned steps (d) arid (e) so that the polychromic image is substanti~l:Ly :ornpletel~~- trvansferred onto the substrate in step (e).
According to another prc~~fe~rred embodiment, the substrate is in the form o.f a continucous web and step (e) is carried out by providing a su~~port roller and a pressure roller extending parallel. t.c the sub>port roller and pressed thereaga:inst to farm <_~ n i p through which the belt is passed, the support roller and pressure roller being driven by the belt: capon movement thereof, and guiding the web sa as to pass through the nip between the s pressure roller and the porous s4arv=ace of the belt for imprinting the web wi~~h the palychromic image.
Preferably, the belt with t:he ~orc.:us surface thereof imprinted with the pol.ychromic~ image is guided so as to travel along a path extending in a plane intersecting the ~o longit:udinal axis of the pc~sit:i_ve electrode at right angles, thereby expasinct the par:aus surface to permit contacting thereof by the web. Where the longitudinal axis of the posit:ivE~ electrade e>xtenc'.s vertically, the belt is preaerably guided so s~s to gravel along a 15 horizantal path wi th the pc:~z-aus surface facing downwardly, the suppc>rt nolle:r an<~ pressure roller having rotation axes dispotsed in a plane extending perpendicular to the horizantal path. Such an <~rrarigement i_s described in the aforementioned Canadian app!:ication No. 2,214,300.
ao After step (e) , the porous surface of the belt is generally cleaned to remove trierefrom any remaining coagulated colloid. Acco~cdi.ng to ~ p~~eferred embodiment, any remaining coagu3_ated colloids u::; removed from the 25 porous surface of the belt by providing at. least one elongated rotatable brush disposed on the one side of the belt and at. Least one sl.rpport roller extending parallel to the brush and disposed on t~hc~ o~:~posite side of the belt, the brush and sups.>ort r:ol:lfer t,aving rotation axes 3o disposed in a plane extending perpendicular to the belt, the brush being provident wvwth a pl~..aralit~y of radially extending bristles mace of har~~ehair and having extremities contacting the porous surface, rotating the brush in a di:rect:ion opposite to the direction of 35 movement of the belt so a:~ to cause the bristles to fricti_onally engage the porous surface while supporting the belt with the support rol_:l_er, di_rect:ing jets of cleaning liquid under pressure against the porous surface from either side of the brush and rE:moving the cleaning liquid with any dislodged coagulated colloid from the porous surface.
- 2a -
Where a pc>lychromic image is desired, steps (b) and (c) of the above electrocoagulation printing method are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along the aforesaid path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated colloid which are transferred at: tYu_e ~especti.ve transfer positions onto the subst rate in uperi;nposed relation to provide a polyc:-.hrc>rriic image. 1t: is also possible to repeat several t:imes steps (a), b) and (c) to define a s corresponding number o_ pri.nt~irug stages arranged in tandem relation and each using a coloring agent of different color, and to l:h~-~:ceba produce several differently colored images of_ c~c:m~gulated colloid which are transferred at respective transfer positions onto the ~o substrate in superimposed. r_e'':ata..on t:o provide a polychromic image, the wubst~rate being in the form of a continuous web which i:; passed thxwugh the respective transfer positions for Joez.ng impr~:inted with the colored images at the printing stagfas. Alternatively, the 15 printing stages defined by r_epeat:ing several times steps (a) , (b) and (c) c,aru be arranged ar:_~und a single roller adapted to bring the substrate ins:c> c:ontact with the dots of colored, coagulated colloid of each printing stage and the substrate which i_s ii: t:he forr~u of a continuous web is zo partially wr<~pped around the roller and passed through the respective transfer ~:>ositiorjs for being imprinted with the colored images at t:rne print W g stages. The last two arrangements; arE: de.>cribed irn A~>plicant' s US Patent No. 4,895,629.
zs When a polychromic image oø~ high definition is desired, it is preferable to bring an endless non-extensible belt moving av: substantv:i_a:JLy the same speed as the positive electrode active: st~r:face and having on one 3o side thereof a cc>.l l o:id reta.~.n:lng surface adapted to releasably retain dots o:~ electrocoagulated colloid, into contact with the positive e:Lect:rocJe active surface to cause transfer of t:he d:ifferentl,r cc>>lored images at the respective transfer positions onto tine colloid retaining 35 surface of such a belt i.n st.rpez:i.mposed relation to provide a polychromic image, arc:~ thereafter bring the substrate into c.ont<~c-~t with tJ-.e colloid retaining surface _ g _ of the belt to cause transfer of the polychromic image from the colloid regaining surface onto the substrate and to thereby imprint the substrate with the polychromic image. As explained in Applicant's c:opend:i_ng Canadian s patent application No. 2,214,300 filed August 29, 1997, by utilizing are. endless non-extens~ ble belt having a colloid retaining tsurface such as a porous surface on which dots of cc~l.orecl, coagulated colloid can be transferred and by moving such a belt independently of ~o the positive electrode, from cane printing unit to another, so that the colloid retaining surface of the belt contacts the colored, coag~rlated colloid in sequence, it is pc;ssible to sic~ni_fi.cantly improve the registration of the differently colored images upon their 15 transfer onto the c~~..i..l.oicl ret.aini.ro~ ,urface of the belt, thereby providing a polychromic i.rnage of high definition which can thereafter be t: ran:>fer_r~~d onto the paper web or other substrate. For example, use can be made of a belt comprising a plastic: rrratr~ri.a1 havu.ng a porous coating of zo silica.
Accordingly, the present invention also provides, in a further aspect thereof, an improved multicolor electrocoagulation pr~.nt;i.ng method comprising 2s the steps of:
a) providing a positive electrolytically inert electrode having a c:ontp nuous pa.::,sivated surface moving at substantially constant speed along a predetermined 3o path, the pas sivated si.zrface dev-ining a positive electrode active surface;
b) forming on thue pos:i.,tivn electrode active surface a plurality of dots of colored, coagulated 35 colloid representative of; a desired image, by electrocoagulation of an electrolytically coagulable collo:i.d present in an electrocos3gLrlation printing ink _ c~ _ comprising a liquid colloidal dispersion containing the electrolytically coagu_La>r~le c~ol~oid, a dispex:sing medium, a soluble electrolyte and a c;olori_ng cogent;
c) bringing an endless non-extensible belt moving at substantial:Ly the Name sptaed as the positive electrode acting surface and having on one side thereof a colloid retaining 4~urface adapted t,o releasably retain dots of electrocoagulatec~ colloid, iruto contact with the ~o positive electrode active surface to cause transfer of the dots of colored, coagulated cr>llo:~d from the positive electrode active surface onto the colloid retaining surface of the belt: and to thereby imprint the colloid retaining surface with the image;
d) repeating steps (b) and c) several times to define a corresponding member o.f pr.in :ing stages arranged at predetermined locations along the path and each using a coloring agent of dift::erent_ colcor, to thereby produce 2'o several differently colored image::, <o coagulated colloid which are transferred at respective transfer positions onto the colloid retafining s~zrfacie in superimposed relation to provide a polychromi.c :image; and ~5 e) bringing a sukastrate int=o contact with the colloid retaining surface of the belt to cause transfer of the polychromic image from the colloid retaining surface onto the substrate and t::o thereby imprint the substrate with the polychromic image;
the improvement wherein the positive c:>_lectrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.s Ni: 5 to 15 wt.
Si: 1 to 2 wt °-Mn : 0 . ~3 to 1 . 5 wt . °~s - 1.0 -C: 0.1 t0 0.3 wt.'s balance: iron and unavc>i.dak:>le impurities.
According too yet. another aspect of the invention, there is prc_~vu ded an improved electrocoagulation printing apparatus comprising:
- a positive electro.Lyti.cal_Ly inert: elect=rode having a continuous pass>ivated surface defining a positive 'o electrode active surface;
- means for moving the positive electrode active surface at a substantial..ly constant speed along a predetermined path;
- an endless non-extensible be:Lr having on one side thereof a colloid retaining surface adapted to releasably retain dots of elect=rocoagu.Lated col__:Lc id;
a:o - means for moving the belts at sub standal7_y the same speed as the positive electrode active surface;
- a plurality of printinct units arranged at predetermined locations along the path, each print~_ng unit comprising:
c.5 - means for forming on the positive electrode active surface a pl;_rrality of dots of colored, coagulated colloid representative of: a dc.:sired image, by elect r:ocoagulation of an elect:ro:Lytically coagulable ~o colloid present in an electroco.~gulation painting ink comprising a liquid colloidal. di:>persion containing the electrolytically coagulable colloid, ~-~ dispersion medium, a soluble electrolyte and a colc~ri.rng agent, and 35 - mE=ans fc~r bringing the be:l_t into contact with the positive electrode active si..irface at a respective transfer station to cause transferv of the dots of colored, coagulated colloid from the positive electrode active surface onto the coll.o id r.~eta:i._ning surface of the belt and to imprint t:he~ cool. ioid retaining :>urface with the image, whereby to produce several c~i.ffex~ent ~ y colored images of coagulated colloid which are transferred at the respective transfer stations onto t:rce colloid retaining surface in superimposed relation to provide a polychromic ~o image; and - means for bringing a substrate inr_o contact with the colloid retaining surface of. the belt to cause transfer of the polychromic: image f rom tr~e~ colloid retaining t5 surface onto the substrate and to thereby imprint the substrate with tine polycrromic image the improvement wherein said electrode is made of an iron alloy consisting es~~enti~,lly of:
zo Cr : at least 20 wt . o Ni : 5 to 15 wt .
Si: 1. to 2 wt:. o Mn: 0.9 to 1.5 wt.o z5 C: 0.1 to 0.3 wt.'s balance: iron and unavoida~>le impurities.
Use is preferably m~~de of an iron alloy consisting essentially of== ~'.5 to 28 wt.o Cr, 8 to 11 wt.~
o Ni, lto2wt.° Si, (7.9t.o1..5wt.'<:Mnand0.1to0.2 wt.o C, the balance consisting of iron and unavoidable impurities. A particularly preferred iron alloy consists essentially of 26. 4 wt . o Cr, 9. 7 wt . '~ Ni, 1 . 08 wt . o Si, 0. 95 wt. o Mn and 0. 1.2 wt:. °, C, the k~alance consisting of iron and unavoidab.Le impurities. Such an alloy has a Brinell hardness of about 225. :Its is possible to increase the Brinell hardness of this ~a.l.:loy up to about 325, without adversely affect:irug passivation, by subjecting the alloy after c:ast.ing to a teat treatment at a temperature of abou ~ 1120 °C ( 205() ° F') and to a subsequent water quenching. The alloy t.hu.s treatE:d has an s austenitic-ferritic structure.
The positive e:Lectrode used can be in the form of a moving endless belt as c~esc:Y-ibed in Applicant's US
Patent No. 4,661,222, or in the form of a revolving ~o cylinder as described in Appl.i.cant's US Patent Nos. 4,895,629 and 5,533,Fi01.. In the later case, the printing stages or ur~,its are arrar;ged around t:.he positive cylindrical electrode. Prefer.abl_y, th~a positive electrode active surface and the ink are maintained at a tem-perature of about ..5-60°C, preferably 40°C, to increase the viscosity of tree coagulated ~::~olloid in step (b) so that the dots of <~o.l.orec:l, coagulated colloid remain coherent during their transfer in step (c), thereby enhancing transfer of t: he col..ored, coag=alated colloid a:o onto the substrate or belt. For example, the positive electrode active surface cyan be heated at the desired temperature and the ink applied on the heated electrode surface to cause a transfer_ of heat: t:r~nerefrom to the ink.
When use i.s m;~de of a po;>itive electrode of cylindrical configuration rotating at substantially constant speed about: its central Longitudinal axis, step (b) of the above electrocoa.gulation printing method is carried out by:
i) providing a pluralit:.;r of negative electro-lytically inert electrodes elec~ric~:~lly insulated from one another and arranged in rectilinear alignment to define a series of cc~rrespondi.rlg negative electrode active surfaces disposed in a plarue parallel to the longitudinal axis c;f thc> positive electrode and spaced from the positive e:Lectrode active surface by a constant predetermined gap, the ruegatzve ~~lec°trodes being spaced from one another by a distance at least equal to the electrode gap;
s ii) co<~tir7g tine positive electrode active surface with an olef.inic sub:>tance to form on the surface micro-droplets of olefinic substance;
iii) filling the electrode gap with the afore-~o said electrocoagulat:ion printing ~_rlk;
iv) electrically energi;_:ing selected ones of the negative electrr_ades to cause point:-by-point selective coagulation and adherenca~ of t:he col_l.o.id Into the olefin coated positive e_Lect.rode active surface opposite the electrode active ;=,urfaces of the energized negative electrodes while, the p.;~si_t:ive t~ Lectrode i_s rotating, thereby forming the c.~ots of c-.ol.o.re~d, coagulated colloid;
and zo v) removing any rerria:irn ng non-coagulated colloid from the positive electrode active surface.
As explained in US Patent No. 4,895,629, 2s spacing of the negative e=lectrodes from one another by a distance which is equal. to or greater than the electrode gap prevents the negative electrodes 1-rom undergoing edge corrosion. On the ether hand, coating of the positive electrode with an o.l.efin:ic substaruc;e prior to electrical 3o energ:i.zation of tre negative elect.rcdes weakens the adherence of the dots of coagulated colloid to the positive elec;trc>de and also proven=s an uncontrolled corrosion of the positive a ec.trode. Tn addition, gas generated as a resu_Lt of electrolysis upon energizing the 35 negative elec:trcdes i s con:>umed by reaction with the olefinic substance so that there is no gas accumulation between the negative and positive. electrodes. Applicant has found that it is no longer necessary to admix a metal oxide with the olefin subst~anc~:e; it l s believed that the passive oxide f:ilno on ci.zrrentl~; available electrodes contains sufficient metal oxide to act as catalyst for s the desired reaction.
Examples of suitable ele~,trolytically inert metals from which =he positive and negative electrodes can be made are stainless steel, platinum, chromium, ~o nickel and aluminum. The gap which is defined between the posit.i_ve and negat i.ve eler_trode~~ can range from about 50 um to about 100 tern, the smaller true electrode gap the sharper are the dots of coagu.ated colloid produced.
Where the electrode gap i.s cof t~°ie c::~rder of 50 um, the ~s negative electrodes are the preferably spaced from one another by a distance of about 75 E.irn.
Examples of su__tab.le olefinic substances which may be used to coat the :.urface oI thca positive electrode zo in step (b)(ii) include unsaturated Latty acids such as arachidonic acid, linoleic acid, linolenic acid, oleic acid and palmitoleic: acid and un;~~.-3tuxated vegetable oils such as corn of l, l inseed c:~i:l, c:oli.ve oi7_, peanut oil, soybean oil and sunflower oil.. Oleic acid is particularly zs preferred. The micro-droplets of olefinic substance formed on the surface o:~ the positiT~e electrode active surface generally have a size ranging from about 1 to about 5 um.
so The olefin-coat::ed positive active surface is preferably polished to increase true adherence of the micro-droplets onto the positive electrode active surface, prior to step (z~) (:ii) . F~'or example, use can be made of a rotating brush provided with a plurality of 35 radially extending bristles made of horsehair and having extremities cont:act~ing the surface of the positive electrode. The fi:ict=ion caused by the bri_st.les contacting the surface upon rotation of the brush has been found to increase the adherence of the mi.cr,:>-droplets onto the positive electrode active surface.
s Where the positive cylindrical electrode extends vertically, step (b)(ii) of the above electro-coagulation printinc metr~.od is advantageously carried out by continuously discharging the ink onto the positive electrode active surface: from a f Lr.zid discharge means ~o disposed adjacent the e:,_ectrode chap at a predetermined height relative to the positive ele~~trode and allowing the ink to f.Low downwarc:lly a 1 ong the positive electrode active surface, the ink being thus carried by the positive electrode upon rotation t hereof to the electrode ~5 gap to fill same. Preferably, excess ink flowing downwardly off the positive electrode active surface is collected and the c:oll.ected i.nk i..s recirculated back to the fluid discharge means.
zo The co:Llo_i.d generally used is a linear colloid of high molecular weight, that is, one having a weight average molecular weight between about 10,000 and about 1,000,000, preferably between 100,000 and 600,000.
Examples of su.ii~able co:Llc>ids incluc:le natural polymers z5 such as albumin, ge:Latin, casein <:jnd agar, and synthetic polymers such as ~>olyacrylic acid, polyacrylamide and polyvinyl alcohol. P. part::icul.arly preferred colloid is an anionic copolymer of acrylamide and acrylic acid having a weight average molecular weight of. abe>ut 250,000 and sold 3o by Cyanamid lnc . under i.he t: r_ ade ma r_ k ACCOSTRENGTH 8 6 .
Water is preferably used as t:he medium for dispersing the colloid to provicie the desired co:l.:~oidal dispersion.
The ink also ccntai.ns a soluble electrolyte and 3s a coloring agent. Preferred electrol.~tes include alkali metal halides and alkaline earth metal halides, such as lithium chloride, sodium chloride, potassium chloride and calcium chloride. Potassium ~hlc>ri~:~e is particularly preferred. The col.or__ng <-~gemt can be a dye or a pigment.
Examples of suitable dye;: which may ke used t.o color the colloid are the water soluble dyes avai7_ab.le from HOECHST
s such a Duasyn Acid E37_ack for coloring in black and Duasyn Acid Blue for coloring in cyan, car those available from RIEDEL-DEHAEN such a.s P,nti-Halo Dye B7_ue T. Pina for coloring in cyan, Anti-Halo Dye AC Magenta Extra VO1 Pina for coloring in magenta and ~?,nti.-Halo Dye Oxonol Yellow ~o N. Pina for coloring in yellow. When ~zsing a pigment as a coloring agent, use ca:l li>e made of the pigments which are avail,~ible f rom CABOT CORf . such as O:arbon Black Monarch~
120 for coloring in black, ox tho:~e available from HOECHST such as Hostaperm E3:Lue Es~G or B3G for coloring in cyan, Permanent. Rubine ~:~6B ca.r_ L6B for coloring in magenta and Permanent. Yellow DGR or D1-iG for coloring in yellow. A dispersung cogent :i~> c~eided for uniformly dispersing the p=figment into t:he ink. l~,xamples of suitable dispersing agents i.nc:lude the aniani.c dispersing agent zo sold by Boehme fi7_atex Canada Tnc. under the trade mark CLOSPERSE 25000.
After coagulation of the co::l.loid, any remaining non-coagulated collo:i.d is removed from the positive z5 electrode active surface, for ex<ample, by scraping the surface with a soft rubber_ squeegee, so as to fully uncover the colored, coagu7_ated <~0:17_oid. Preferably, the non-coagulated c:ol7.oid ',thus rernc>ved is collected and mixed with the collected ink, and t:ze col:lec:ted non-3o coagulated colloid in admixture with t:he collected ink is recirculated back to the aforesaid fluid discharge means.
The optic<~l density of the dots of colored, coagulated colloid may be varied by varying the voltage 35 and/or pulse duration of the pulse-modulated signals applied to the negative electrodes.
After step (c), the po:;itive electrode active surface is generally cleaned t:o remove therefrom any remaining coagulated colloid. _~<.cording too a preferred embodiment, 1=he pos it:.ivc~ e:lE~ctr,~~de is rotatable in a predetermined direca:ion anc~ any remaining coagulated colloid is removed from t:he ~:~ositi~~re electrode active surface by providing an ~~lori<~ated rotatable brush extending parallel to the lonr~it=ac~inal axis of the positive electrode, the brush k>ei.ng provided with a plura7_ity o:fv radi ally E~xtE.mdi ruc~~ bristles made of horsehair and having extremities :=ont.acting the positive electrode active surface, rotating the brush in a direction opposite to tkue direct::i.on of rotation of the positive electrode so as to cJausfe the bristles to 15 frictionally engage the posit.i_ve electrode active surface, and directing jets of c~_E:~aning liquid under pressure against the po~~itive eiec:trode active surface, from either side of the k.~rush. In such an embodiment, the positive electrode act::i_ve surface and the ink are zo preferably maintained at a temperature of about 35-60°C
by heating the cleanin:~ liquid to thereby heat the posit.i_ve electrode active surface upon contacting same and applying the ink on the heated electrode surface to cause a transfer of heat therefrom t.o the ink.
Pre:Eerably, the elec:trocoagulation printing ink contains water as the dispersing med~rum and the dots of differently colored, coagulated colio::°._d representative of the polychromic image are rru~ist:ened between the 3o aforementioned steps (d) arid (e) so that the polychromic image is substanti~l:Ly :ornpletel~~- trvansferred onto the substrate in step (e).
According to another prc~~fe~rred embodiment, the substrate is in the form o.f a continucous web and step (e) is carried out by providing a su~~port roller and a pressure roller extending parallel. t.c the sub>port roller and pressed thereaga:inst to farm <_~ n i p through which the belt is passed, the support roller and pressure roller being driven by the belt: capon movement thereof, and guiding the web sa as to pass through the nip between the s pressure roller and the porous s4arv=ace of the belt for imprinting the web wi~~h the palychromic image.
Preferably, the belt with t:he ~orc.:us surface thereof imprinted with the pol.ychromic~ image is guided so as to travel along a path extending in a plane intersecting the ~o longit:udinal axis of the pc~sit:i_ve electrode at right angles, thereby expasinct the par:aus surface to permit contacting thereof by the web. Where the longitudinal axis of the posit:ivE~ electrade e>xtenc'.s vertically, the belt is preaerably guided so s~s to gravel along a 15 horizantal path wi th the pc:~z-aus surface facing downwardly, the suppc>rt nolle:r an<~ pressure roller having rotation axes dispotsed in a plane extending perpendicular to the horizantal path. Such an <~rrarigement i_s described in the aforementioned Canadian app!:ication No. 2,214,300.
ao After step (e) , the porous surface of the belt is generally cleaned to remove trierefrom any remaining coagulated colloid. Acco~cdi.ng to ~ p~~eferred embodiment, any remaining coagu3_ated colloids u::; removed from the 25 porous surface of the belt by providing at. least one elongated rotatable brush disposed on the one side of the belt and at. Least one sl.rpport roller extending parallel to the brush and disposed on t~hc~ o~:~posite side of the belt, the brush and sups.>ort r:ol:lfer t,aving rotation axes 3o disposed in a plane extending perpendicular to the belt, the brush being provident wvwth a pl~..aralit~y of radially extending bristles mace of har~~ehair and having extremities contacting the porous surface, rotating the brush in a di:rect:ion opposite to the direction of 35 movement of the belt so a:~ to cause the bristles to fricti_onally engage the porous surface while supporting the belt with the support rol_:l_er, di_rect:ing jets of cleaning liquid under pressure against the porous surface from either side of the brush and rE:moving the cleaning liquid with any dislodged coagulated colloid from the porous surface.
- 2a -
Claims (50)
1. In an electrocoagulation printing method comprising the steps of:
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, said passivated surface defining a positive electrode active surface;
b) forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto said substrate and thereby imprint said substrate with said image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, said passivated surface defining a positive electrode active surface;
b) forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto said substrate and thereby imprint said substrate with said image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
2. A method as claimed in claim 1, wherein said iron alloy contains 20 to 30 wt.% of chromium.
3. A method as claimed in claim 2, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
4. A method as claimed in claim 3, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
5. A method as claimed in claim 4, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1120°C and to a subsequent water quenching.
6. A method as claimed in claim 5, wherein said cast alloy has an austenitic-ferritic structure.
7. A method as claimed in claim 1, wherein steps (b) and (c) are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along said path and each using a coloring agent of different color, to thereby produce several differently colored images of coagulated colloid which are transferred at respective transfer positions onto said substrate in superimposed relation to provide a polychromic image.
8. A method as claimed in claim 7, wherein said positive electrode is a cylindrical electrode having a central longitudinal axis and rotating at substantially constant speed about said longitudinal axis, and wherein said printing stages are arranged around said positive cylindrical electrode.
9. A method as claimed in claim 8, wherein said iron alloy contains 20 to 30 wt.% of chromium.
10. A method as claimed in claim 9, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
11. A method as claimed in claim 10, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
12. A method as claimed in claim 11, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1120°C and to a subsequent water quenching.
13. A method as claimed in claim 12, wherein said cast alloy has an austenitic-ferritic structure.
14. In a multicolor electrocoagulation printing method comprising the steps of:
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, said passivated surface defining a positive electrode active surface;
b) forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an a electrolytically coagulable colloid present in an electrocoagulation painting ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent;
c) bringing an endless non-extensible belt moving at substantially the same speed as said positive electrode active surface and having on one side thereof a colloid retaining surface adapted releasably retain dots of electrocoagulated colloid, into contact with said positive electrode active surface to cause transfer of the dots of colored, coagulated colloid from the positive electrode active surface onto the colloid retaining surface of said belt and to thereby imprint said colloid retaining surface with the image;
d) repeating steps (b) and (c) several times to define a corresponding number of printing stages arranged at predetermined locations along said path and each using a coloring agent of different color, to thereby produce several differently colored images of coagulated colloid which are transferred at respective transfer positions onto said colloid retaining surface in superimposed relation to provide a polychromic image; and e) bringing a substrate into contact with the colloid retaining surface of said belt to cause transfer of the polychromic image from said colloid retaining surface onto said substrate and to thereby imprint said substrate with said polychromic image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, said passivated surface defining a positive electrode active surface;
b) forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an a electrolytically coagulable colloid present in an electrocoagulation painting ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent;
c) bringing an endless non-extensible belt moving at substantially the same speed as said positive electrode active surface and having on one side thereof a colloid retaining surface adapted releasably retain dots of electrocoagulated colloid, into contact with said positive electrode active surface to cause transfer of the dots of colored, coagulated colloid from the positive electrode active surface onto the colloid retaining surface of said belt and to thereby imprint said colloid retaining surface with the image;
d) repeating steps (b) and (c) several times to define a corresponding number of printing stages arranged at predetermined locations along said path and each using a coloring agent of different color, to thereby produce several differently colored images of coagulated colloid which are transferred at respective transfer positions onto said colloid retaining surface in superimposed relation to provide a polychromic image; and e) bringing a substrate into contact with the colloid retaining surface of said belt to cause transfer of the polychromic image from said colloid retaining surface onto said substrate and to thereby imprint said substrate with said polychromic image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
15. A method as claimed in claim 14, wherein said iron alloy contains 20 to 30 wt% of chromium.
16. A method as claimed in claim 15, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1, to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1, to 0.2 wt.%
balance: iron and unavoidable impurities.
17. A method as claimed in claim 16, wherein said iron alloy consists essentially of:
Cr: 26. 4 wt%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26. 4 wt%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
18. A method as claimed in claim 17, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1122°C: and to a subsequent water quenching.
19. A method as claimed in claim 18, wherein said cast alloy has an austenitic-ferritic structure.
20. A method as claimed in claim 15, wherein said positive electrode is a cylindrical electrode having a central longitudinal axis and rotating at substantially constant speed about said longitudinal axis, and wherein said printing stages are arranged around said positive cylindrical electrode.
21. A method as claimed in claim 20, wherein said iron alloy contains 20 to 30 wt.% of chromium.
22. A method as claimed in claim 21, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1. to 0.2. wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1. to 0.2. wt.%
balance: iron and unavoidable impurities.
23. A method as claimed in claim 22, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.4 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.4 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
24. A method as claimed ire claim 23, wherein said iron alloy is a cash allay which has been subjected after casting to a heat treatment at a temperature of about 1122°C: and to a subsequent water quenching.
25. A method as claimed in claim 24, wherein said cast alloy has an austenitic-ferritic structure.
26. In an electrocoagulation printing apparatus comprising:
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
- means for moving said positive electrode active surface at a substantially constant speed along a predetermined path;
- means for forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and - means for bringing a suxostrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto said substrate and thereby imprint said substrate with said image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5wt.%
C: 0.1 to 0.3wt.%
balance: iron and unavoidable impurities.
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
- means for moving said positive electrode active surface at a substantially constant speed along a predetermined path;
- means for forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and - means for bringing a suxostrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto said substrate and thereby imprint said substrate with said image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5wt.%
C: 0.1 to 0.3wt.%
balance: iron and unavoidable impurities.
27. An apparatus as claimed in claim 26, wherein said iron alloy contains 20 to 30 wt.% of chromium.
28. An apparatus as claimed in claim 27, wherein said iron alloy consists essentially of Cr: 25 to 28 wt.%
Ni: 1 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Ni: 1 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
29. An apparatus as claimed in claim 28, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
30. An apparatus as claimed in claim 29, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1122°C and to a subsequent water quenching.
31. An apparatus as claimed in claim 30, wherein said cast alloy has an austenitic-ferritic structure.
32. An apparatus as claimed in claim 26, wherein said means for forming said dots of colored, coagulated colloid and said means for bringing said substrate into contact with said dots of colored, coagulated colloid are arranged to define a printing unit, and wherein there are several printing units positioned at predetermined locations along said path and each using a coloring agent of different colored for producing several differently colored images of coagulated colloid which are transferred at respective transfer stations onto said substrate in superimposed relation to provide a polychromic image.
33. An apparatus as claimed in claim 32, wherein said positive electrode is a cylindrical electrode having a central longitudinal axis and rotating at substantially constant speed about said longitudinal axis, and wherein said printing units are arranged around said positive cylindrical electrode.
34. An apparatus as claimed in claim 33, wherein said iron alloy contains 20 to 30 wt.% of chromium.
35. An apparatus as claimed in claim 34, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
36. An apparatus as claimed in claim 35, wherein said iron alloy consists essentially of:
Cr: 26.9 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.9 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
37. An apparatus as claimed in claim 36, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1122°C and to a subsequent water quenching.
38. An apparatus as claimed in claim 37, wherein said cast alloy has an austenitic-ferritic structure.
39. In a multicolor electrocoagulation printing apparatus comprising:
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
- means for moving said positive electrode active surface at a substantially constant speed along a predetermined path;
- an endless non-extensible belt having on one side thereof a colloid retaining surface adapted to releasably retain dots of electrocoagulated colloid;
- means for moving said belt at substantially the same speed as said positive electrode active surface;
- a plurality of printing units arranged at predetermined locations along said path, each printing unit comprising:
- means, for forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulated of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersion medium, a soluble electrolyte and a coloring agent, and - means for bringing said belt into contact with said positive electrode active surface at a respective transfer station to cause transfer of the dots of colored, coagulated colloid from the positive electrode active surface onto the colloid retaining surface of said belt and to imprint said colloid retaining surface with the image, whereby to produce several differently colored images of coagulated colloid which are transferred at said respective transfer stations onto said colloid retaining surface in superimposed relation to provide a polychromic image; and - means for bringing a substrate into contact with the colloid retaining surfaced of said belt to cause transfer of the polychromic image from said colloid retaining surface onto said substrate and to thereby imprint said substrate with said polychromic image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C : 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
- a positive electrolytically inert electrode having a continuous passivated surface defining a positive electrode active surface;
- means for moving said positive electrode active surface at a substantially constant speed along a predetermined path;
- an endless non-extensible belt having on one side thereof a colloid retaining surface adapted to releasably retain dots of electrocoagulated colloid;
- means for moving said belt at substantially the same speed as said positive electrode active surface;
- a plurality of printing units arranged at predetermined locations along said path, each printing unit comprising:
- means, for forming on said positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulated of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing said electrolytically coagulable colloid, a dispersion medium, a soluble electrolyte and a coloring agent, and - means for bringing said belt into contact with said positive electrode active surface at a respective transfer station to cause transfer of the dots of colored, coagulated colloid from the positive electrode active surface onto the colloid retaining surface of said belt and to imprint said colloid retaining surface with the image, whereby to produce several differently colored images of coagulated colloid which are transferred at said respective transfer stations onto said colloid retaining surface in superimposed relation to provide a polychromic image; and - means for bringing a substrate into contact with the colloid retaining surfaced of said belt to cause transfer of the polychromic image from said colloid retaining surface onto said substrate and to thereby imprint said substrate with said polychromic image;
the improvement wherein said positive electrode is made of an iron alloy consisting essentially of:
Cr: at least 20 wt.%
Ni: 5 to 15 wt.%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C : 0.1 to 0.3 wt.%
balance: iron and unavoidable impurities.
40. An apparatus as claimed in claim 39, wherein said iron alloy contains 20 to 30 wt.% of chromium.
41.. An apparatus as claimed in claim 40, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt%
Si: 1 to 2 wt.%
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
42. An apparatus as claimed in claim 41, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
43. An apparatus as claimed in claim 42, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1122°C and to a subsequent water quenching.
44. An apparatus as claimed in claim 43, wherein said cast alloy has an austenitic-ferritic structure.
45. An apparatus as claimed in claim 39, wherein said positive electrode is a cylindrical electrode having a central longitudinal axis and wherein said means for moving said positive electrode active surface includes means for rotating said positive cylindrical electrode about said longitudinal axis, said printing units being arranged around said positive cylindrical electrode.
46. An apparatus as claimed in claim 45, wherein said iron alloy contains 2.0 to 30 wt.% of chromium.
47. An apparatus as claimed in claim 46, wherein said iron alloy consists essentially of:
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.% ~
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
Cr: 25 to 28 wt.%
Ni: 8 to 11 wt.%
Si: 1 to 2 wt.% ~
Mn: 0.9 to 1.5 wt.%
C: 0.1 to 0.2 wt.%
balance: iron and unavoidable impurities.
48. An apparatus as claimed in claim 47, wherein said iron alloy consists essentially of:
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
Cr: 26.4 wt.%
Ni: 9.7 wt.%
Si: 1.08 wt.%
Mn: 0.95 wt.%
C: 0.12 wt.%
balance: iron and unavoidable impurities.
49. An apparatus as claimed in claim 48, wherein said iron alloy is a cast alloy which has been subjected after casting to a heat treatment at a temperature of about 1122°C and to a subsequent water quenching.
50. An apparatus as claimed in claim 49, wherein said cast alloy has an austenitic-ferritic structure.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2282128 CA2282128C (en) | 1999-09-14 | 1999-09-14 | Stainless steel anode for electrocoagulation printing |
| EP00120005A EP1084827A3 (en) | 1999-09-14 | 2000-09-14 | Positive electrode for electrocoagulation printing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2282128 CA2282128C (en) | 1999-09-14 | 1999-09-14 | Stainless steel anode for electrocoagulation printing |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2282128A1 CA2282128A1 (en) | 2001-03-14 |
| CA2282128C true CA2282128C (en) | 2004-03-02 |
Family
ID=4164124
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2282128 Expired - Fee Related CA2282128C (en) | 1999-09-14 | 1999-09-14 | Stainless steel anode for electrocoagulation printing |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP1084827A3 (en) |
| CA (1) | CA2282128C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110772718B (en) * | 2019-12-09 | 2022-02-08 | 哈尔滨海鸿基业科技发展有限公司 | Corona discharge therapeutic instrument |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB297045A (en) * | 1927-06-09 | 1928-09-10 | Electro Metallurg Co | Wrought articles of iron-chromium-nickel alloy |
| CA2214300C (en) * | 1997-08-29 | 2002-11-19 | Elcorsy Technology Inc. | Multicolor electrocoagulation printing method and apparatus |
-
1999
- 1999-09-14 CA CA 2282128 patent/CA2282128C/en not_active Expired - Fee Related
-
2000
- 2000-09-14 EP EP00120005A patent/EP1084827A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| CA2282128A1 (en) | 2001-03-14 |
| EP1084827A2 (en) | 2001-03-21 |
| EP1084827A3 (en) | 2001-03-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |