Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/132—Chemical colour-forming components; Additives or binders therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/165—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components characterised by the use of microcapsules; Special solvents for incorporating the ingredients

Definitions

• the invention relates to paper for carbonless copy paper sets and to copy paper sets made up using it.
• Carbonless copy paper sets consist of a top sheet known as the CB (coated back) sheet, a back sheet known as the CF (coated front) sheet, and optionally one or more intermediate sheets known as CFB (coated front and back) sheets.
• the coatings of the back of the CB sheet, of the front and back of the CFB sheets if any, and of the front of the CF sheet contain materials that when brought into association with each other develop a coloured image.
• the present invention has arisen from a requirement, in the highest grade products, for a pigment-containing coating on the front face of CB sheets, improving them in appearance and in printability.
• the invention provides record material comprising a paper sheet having on its front a printable pigment coating and on its back isolated droplets of colour former solution each confined within a pressure rupturable barrier, wherein the pigment coating comprises a binder for the pigment together-with a synthetic reactive sizing agent or a coating structure agent or both, the sizing agent being an alkyl ketene dimer, alkenyl succinic anhydride, polyurethane, or other synthetic reactive size, and the coating structure agent being a carboxy methyl cellulose, a soya or other protein, an alginate, or other hydrophilic polymer.
• the relative amounts of components in the coating are desirably by weight 0.5 - 10 parts (advantageously 0.5 or 1 up to 5 parts) size and 0.5 - 5 parts coating structure agent, together with 60 - 95 parts pigment and 5 - 30 parts, preferably 10 - 30 parts and advantageously 16 - 22 parts binder or, where the coating structure agent is present without size, 75 - 82 parts (less desirably up to 85 parts) pigment, and 15 - 22 parts (less desirably down to 12 parts) binder.
• the binder is present to hold the pigment in a non- dusting, printable coating, and to enable enough binder to be used for that purpose it must be a material that when tested at 40 weight % in water gives a fluid preparation mixable with pigment to give a coatable dispersion. Normally it will be a latex binder but for example hydroxyalkyl ether derivatives of starches are suitable. Auxiliary binder materials may also be included.
• the size is used to hold off latex-based or other edge-padding adhesives to allow form sets to be fanned.
• the coating structure agent is a hydrophilic polymer that provides a Bendtsen porosity of the finished i.e. CB coated sheet of not less than 25 ml/min, preferably more. Such porosities reflect porosities before CB coating of around 30 ml/min or more allowing economic application of the CB coating. Suitable materials are believed to act by gelling the pigment coating in the course of drying, preventing it from compacting into an impermeable layer, and all are materials that when tested in water at 25 weight % or more give a gel-like preparation not mixable with pigment to give a coatable dispersion.
• a well known use of copy paper sets is in the production of multiple sets or "form sets".
• CB repeats of the sequence of sheets, CB, optionally one or more CFB and CF, that constitute an individual set are made up as a stack.
• An adhesive known as an edge padding adhesive, is applied down one side of the stack, its characteristic being that it is attracted to the coating of the back of the CB (and any CFB) sheets, or to the coating of the front of the CF (and any CFB) sheets, or to both, to a greater extent than to what are, conventionally, uncoated faces of the sheets in the stack, which are the fronts of the CB sheets and the backs of the CF sheets.
• edge padding adhesive is applied down one side of the stack, its characteristic being that it is attracted to the coating of the back of the CB (and any CFB) sheets, or to the coating of the front of the CF (and any CFB) sheets, or to both, to a greater extent than to what are, conventionally, uncoated faces of the
• CB front face pigment coating would be thought of as incompatible with edge padding, the coating attracting the edge padding adhesive in the same way as the coatings within the sets.
• the invention in the aspect in which a size is present, overcomes such problems. While of course the use of sizes in paper generally is known, and so is pigment coating and the use of binders to retain the pigment on the paper, there has been no reason to size a pigment coating as such. Indeed a pigment would normally be thought of as incompatible with size, using a lot of it to no purpose, and the success of the combination is surprising.
• the pigment coating is typically highly consolidated to give a smooth surface.
• the use of these highly consolidated coatings means that the sheet porosity of the paper is very low.
• the adverse effects of this high content of binder are overcome by the presence in the coating mix of the coating structure agent, sufficient permeability for successful subsequent application of CB coatings being obtained.
• the coating structure agent in the coating mix promotes the generation of a relatively porous coating. We believe that this arises because as the coating mix dries, the coating structure agent helps the mix to set or gel before all the water is removed, and that the set or gelled structure is, at least in part, preserved through drying to give a relatively bulky and thus porous coating. That this effect generates a porous coating even at the high binder levels typically used in this invention is very surprising as such binder levels would ordinarily be expected to "blind" the coating.
• the pigments are, generally, conventional paper coating pigments, in particular inorganic or miner al -derived particulate materials.
• Calcium carbonate especially is economic and suitable, giving good whiteness and purity and having good printing characteristics. It may be supplemented with coating clays such as china clay (kaolin), although with large amounts of clay care will be necessary in formulation to achieve satisfactory rheology and stability for successful coating, as will be appreciated by those skilled in the art.
• Suitable pigments besides china clay include calcined clays, titanium dioxide, finely divided silica and talc.
• Calcium carbonate contributes good whiteness and brightness, and high print definition, but on its own tends to give dusting on the surface and may not give good ink receptivity.
• Clay or talc contribute to a good surface finish and give good ink receptivity without dusting but give a less white appearance.
• Ground calcite as the calcium carbonate has high purity (to give whiteness etc. as compared with ground limestone or chalk) without the very high surface of precipitated carbonates, which can be used but are not preferred because of high binder demand arising from small particle size.
• the pigment in the coatings is not such as to have colour developing properties.
• specific colour developer materials such as the clays that are used as the active constituents of many CF coatings.
• Kaolin has been mentioned in the literature as a colour developer but in unmodified form is not so used or suitable, and papercoating grades are essentially non-colour developing. The use of high levels of binder reduces even further or eliminates any minor residual colour developing activity of the raw material.
• the particle size of the pigment is important. The finer the particles are the more effective the pigment is in terms of brightness but, equally, the more the coating is consolidated (thus reducing porosity) and also the more difficult any required sizing is. Particularly in a sizing context, a balance is desirable and the range of 1 to 10 microns, advantageously 2 to 5 microns, is preferred.
• Such particle sizes are as measured by a laser particle sizer such as the standard Malvern 3600 E Type. For particles of broadly the same dimensions in any direction, such as those of calcium carbonate, such sizes approximate actual sizes; for flat or elongated particles such as those of coating clays the particle sizes as measured are nominal.
• the laser instrument assesses particle size by measuring the interference pattern arising from diffraction of the laser light illuminating a sample suspension e.g. in water, of the particles. The pattern is manipulated by a computer to give results as particle size by volume, e.g. the volume itself or the diameter of spheres of equal volume.
• Amounts of pigment are given earlier, but a particularly convenient range when size is not being used is
• the binder may be selected from among those conventional in themselves in paper coating technology.
• it may be a synthetic rubber latex such as styrene butadiene latex (normally a carboxylated grade to give good dispersibility and stability in water) or styrene acrylic latex.
• styrene butadiene latex normally a carboxylated grade to give good dispersibility and stability in water
• styrene acrylic latex styrene acrylic latex.
• it is also howe er possible for it to be example a ether derivative of starch, as already mentioned, and these are not conventional in the sense of being in wide use.
• the size will typically be a neutral reactive size such as an alkyl ketene dimer or alkenyl succinic anhydride with the alkyl or alkenyl groups from Cg upwards, generally from C- j _2 upwards, with C ] _5 ⁇ c i8 typical and the upper limit determined, for example C24. by mix workability and suitability of the final coating for printing.
• Such sizes in which "neutral” connotes effectiveness as sizes at neutral coating mix pH, are effective in small quantities and readily provide acceptable rheology in the coating process, for example blade, roll or slot (extrusion) coating as known per se.
• Other synthetic sizes such as polyurethane sizes may however be used. Amounts within the ranges given earlier are typically 1 to 5% dry weight of the coating but more usually 1 to 2% will be used.
• the water repellency of the coating is defined in terms of the contact angle taken up by a water droplet on the surface of the coated paper, measured within the drop, which for a size to be suitable is above 70° and advantageously above 90° or 100°.
• a convenient method of determining the contact angle depends on measurement of the observed height and contact width of a droplet of known volume applied to the paper, in particular in a Lorentze & Wettre No. 28 surface wettability tester. The method is as follows:-
• the coating structure agents that are suitable include in particular carboxy methyl cellulose such as is used in coating technology as a dewatering control.
• Other suitable materials are proteins, such as soya protein, and alginates such as sodium alginate, their essential characteristic being to provide the desired porous coating structure at the low amounts specified.
• the amounts used, within the overall range, depend on the nature of the material, enough to be effective but not so much as to increase viscosity or modify the rheology to make the mix uncoatable.
• Amounts are typically, weight % on coating:- Carboxy methyl cellulose high mol.wt. 0.5 - 1.5% medium mol.wt. 1 - 2 %
• agents for example sodium hydroxide or other alkalis such as potassium hydroxide or ammonia for pH adjustment, and further components of the final coating such as optical brightening agents, dispersants for the pigments, lubricants (e.g. calcium stearate) or antifoams.
• optical brightening agents for example sodium hydroxide or other alkalis such as potassium hydroxide or ammonia for pH adjustment
• dispersants for the pigments e.g. calcium stearate
• lubricants e.g. calcium stearate
• antifoams e.g. calcium stearate
• Coat weights may conveniently be 2 to 20 g/m , advantageously 3 to 15 g/m . Papers of reduced substance compared to normal , in terms of fibre weight per square metre, may be used compensating in part for the extra cost of the coatings. POROSITY
• CB coating the Bendtsen porosity of the final product is not less than 25 ml/min and preferably not less than 30 ml/min with (for this product) a typical range of 35 - 50 ml/min.
• "High speed" is ca.500 m/min or above and a preferred lower limit 400/450 m / _.in.
• a typical range is ca. 600 - 900 m/min and higher speeds e.g. up to 1500 m/min are oossible.
• the invention is described broadly above, but in the edge padding context most desirably provides a CB sheet with a printable front coat at 2 - 20g/m comprising an inorganic or mineral derived pigment and a latex-derived binder together with a sizing agent, the sizing agent being an alkyl ketene dimer or alkenyl succinic anhydride or other reactive neutral size giving a contact angle of 90° or more.
• a sizing agent being an alkyl ketene dimer or alkenyl succinic anhydride or other reactive neutral size giving a contact angle of 90° or more.
• Preferred proportions of components by weight are pigment 60
• binder 5 - 30 advantageously 16 - 22 and size 0.5 - 10 parts.
• the invention most desirably provides a CB sheet for carbonless copy paper sets carrying in addition to a CB coating a front coating at 3 - 15 g/m comprising pigment 75
• a coating material was prepared from the following components 48.2% solids in water, final pH 9.5.
• the coating structure agent is a medium molecular weight carboxymethyl cellulose.
• the calcium carbonate pigment is a ground calcite, desirable as high-white material economic in cost. Its median particle size is 2.8 microns.
• the china clay is a fine, white, commercially available coating clay, median particle size 3.3 microns. It acts as a white pigment accordingly, while preserving the advantages of clay coatings generally in terms of coat adhesion and printing characteristics. It gives no unacceptable reduction in the brightness of coating given by the calcium carbonate.
• the binder is a conventional carboxylated styrene- butadiene synthetic latex giving the coating the necessary- adhesion as a whole.
• the coating mix so prepared was applied using trailing blade metering to standard base paper of 48 g/ substance for 'Idem' (Trade Mark) CB sheet to give coat weights of 3 to 7 g/m .
• the coated paper was then calendered and its porosity checked and found to be at a suitable figure. It was CB coated at 800 m/min using a 3 roll coater head, solids of the coating mix ca. 24%, constitution of solids :—
• capsules conventional gelatin-based capsules, black-copy colour former formulation in solvent, formed by coacervation encapsulation
• the resulting CB sheets had excellent printing characteristics and improved visual appeal and feel in terms of formation and rouqhness.
• Example 2 Similarly to Example 1, a coating material was prepared from the following components, made up to 3308 Kg with water
• Revinex 98 F10 latex is a carboxy lated SBR latex ex Doverstrand Limited. 'Dispex' , 'Hydrocarb' , 'Alphatex' , 'Revinex' and 'Nopcote' are trade marks.
• Examples 1 and 2 were repeated with respectively 2 parts by weight and 24 Kg of 'Aguapel' (Trade Mark) 360 X 3 neutral Cig alkyl ketene dimer size (the level used being such as to give a final coating contact angle of 110°. Papers of excellent printability and, further, edge paddable with 100% fanning were obtained.
• Example 7 The following is again of the use of a coating structure agent and size together, and is in effect six examples in one (three mixes each coated at two levels).
• Example l The formulations were made and coated as in Example l r the calcium carbonate being of 4 microns median particle size, at 3 and 6 g/m ,on the rougher side of 'Idem' base paper as used in Example 1.
• Coating structure agent 1 55% solids
• Optical brightener 1 The pairs of samples, all of which showed satisfactory porosities, were subjected to physical testing, in comparison to the uncoated base itself , on a number of criteria significant to CB sheet performance. a) Roughness
• Example 8-2 Mistron Vapour 3 P (Trade Mark) talc as pigment replacing the kaolin clay
• Example 8-5 Solfarex A 55 (Trade Mark) starch hydroxyalkyl ether as binder replacing latex
• Example 8-7 Cyclopal A (Trade Mark ) anionic modified polyurethane as size replacing the 'Aquapel'
• Example 8-10 CMC coating structure agent omitted
• Example 8-11 Procote 400 (Trade Mark) soy protein as coating structure agent replacing the CMC
• Finfix 5 Carboxy methyl cellulose coating 1.2 structure agent
• edge padding trials were carried out as before, with bond strengths found normal or slightly low (but still within-specif ication) CB-CFB and CFB-CF and 100% fan apart.
• Printing trials again carried out as before , gave good results , the ink on this occasion being Bon ⁇ fiel d Constat B lack 30862 ( Trade Mark ) .
• Ink density was good ( slightly light in the absence of the coating s compture a gent ) , pi l ing was absent , dus ting acceptable throughout and in the mix with starch ether binder exceptional ly low.
• a coat mix was made up as an Example 8-C but with the Aquapel 360X replaced by 3.6 parts by weight of 'Fibran 71' (Trade Mark) from National Starch & Chemical Co. , which is an alkenyl succinic anhydride size, the other components being in relative parts by weight as shown there, and coated as before.
• 'Fibran 71' Trade Mark
• a satisfactory coating was given, the measured contact angle in particular being 104°, well suited to edge padding.

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• 1987
  • 1987-12-16 CA CA000554742A patent/CA1316957C/en not_active Expired - Lifetime
  • 1987-12-17 EP EP87311138A patent/EP0274886B2/de not_active Expired - Lifetime
  • 1987-12-17 ES ES87311138T patent/ES2015062T5/es not_active Expired - Lifetime
  • 1987-12-17 AT AT87311138T patent/ATE51586T1/de active
  • 1987-12-17 AU AU10507/88A patent/AU613336B2/en not_active Expired
  • 1987-12-17 DE DE198787311138T patent/DE274886T1/de active Pending
  • 1987-12-17 JP JP63500586A patent/JP2583118B2/ja not_active Expired - Lifetime
  • 1987-12-17 DE DE8787311138T patent/DE3762106D1/de not_active Expired - Lifetime
  • 1987-12-17 DE DE19873790830 patent/DE3790830T1/de not_active Ceased
  • 1987-12-17 WO PCT/GB1987/000910 patent/WO1988004614A1/en active Application Filing
• 1988
  • 1988-10-31 GB GB8825451A patent/GB2209355B/en not_active Expired - Fee Related
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