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
  • B41M5/1243—Inert particulate additives, e.g. protective stilt materials

Definitions

• ABSTRACT A capsule-carrying sheet or web such, for example, as is used in pressure-sensitive copying systems is produced by coating a surface of a base sheet or web with an aqueous coating mix which includes a rewettable binder material and a protective material. This coating is dried and then rewetted and a composite coating is formed by applying to the rewetted coating a coating of capsules. The composite coating is then dried.
• This invention relates to capsule-carrying sheets or webs and methods of producing such sheets or webs, and is particularly but not exclusively concerned with capsule-carrying sheets or webs for use in pressuresensitive copying systems.
• encapsulate for example, dyes, inks, chemical reagents, pharmaceuticals, flavourings, pesticides, herbicides and in fact any material which can be dissolved, suspended-or otherwise constituted in or as a liquid internal phase enclosed within a capsule wall.
• the capsule serves to maintain the internal phase in its liquid, or some other converted form, at least until the internal phase is released by rupture, melting, dissolving or other removal of the capsule wall, or until the internal phase is caused to diffuse out through the capsule wall.
• a disadvantage of capsules produced by known methods is that they are not sufficiently inherently strong to prevent accidental rupture thereof, this being a particular disadvantage, in pressure-sensitive copying systems where accidental rupture of capsules can result in undesirable marking of the copy sheet.
• a capsule-carrying sheet or web also carrying cellulose fibres as protective material for the capsules
• the capsules and cellulose fibres are coated together onto a base sheet or web in admixture with a gelatinised starch solution which is to serve as a binder between the capsules and cellulose fibre, and the base sheet or web.
• the sheet or web produced thus carries a coating including capsules, a protective material for protecting the capsules, i.e. the cellulose fibres, and a binder for the capsules and the protective material i.e. the gelatinised starch solution.
• a further disadvantage of such known methods is that the binder material gives the single coating mix used a relatively high viscosity, and thus the coating mix must be coated at a relatively low solids concentration, the sheet or web thus having a relatively high moisture content after coating.
• a method of producing a capsule-carrying sheet or web comprising a base sheet or web having on a surface thereof a coating containing capsules, protective material for protecting the capsules against accidental rupture, and a binder material serving to bind the capsules and protective material to the base sheet or web, comprises the steps of:
• steps 0 and d are carried out simultaneously by applying to the dried first coating an aqueous emulsion of capsules. Otherwise, steps 0 and d can be carried out consecutively, the capsules being applied in dry form, for example by spraying.
• the mechanism by which the method of the invention operates is simple.
• the binder material applied at step a is rewetted at step c and then after drying at step e serves to bind the capsules and protective material to the base sheet or web.
• Any suitable rewettable binder material can be used,
• binder material examples include dextrine, polyvinyl alcohol, or a mixture of dextrine and polyvinyl alcohol.
• the protective material can be the commonly used cellulose fibres, or otherwise can be a granular polymeric material or, preferably, starch granules, as described above.
• the base sheet or web is calendered between steps b and c of the method of the invention.
• Calendering considerably reduces the roughness of the coated sheet or web produced at step a, but rewetting of the coated surface at step 0 causes the coated surface to regenerate, but not completely, towards that existing prior to calendering.
• the method of the invention in addition to overcoming the disadvantages of known methods described above, has the advantage that the binder material/protective material coating can easily be applied using a size press on the machine on which the base sheet or web (which will normally be paper) is made. Further, a relatively high solids concentration can be used for the aqueous dispersion of capsules, if used, and thus drying of th sheet or web after application of the emulsion is simplified, and since less water is applied to the sheet or web during application of the dispersion appearance defects such as cockle, ribbing, curl, etc., all off which are related to the moisture content of the sheet or web, are reduced.
• aqueous dispersion of capsules can be applied by any means known for applying capsule coatings, for example by means of an air-knife coater.
• the suspension thus formed was applied as a surface size by means of a Meyer rod to one side of a 49 g/m base paper to give a coating weight of approximately 1.3 to 2.2 g/m
• the sized base paper was then dried, and calendered on a laboratory calender.
• Raw capsule dispersion i.e. dispersion containing only capsules
• microcapsules can be carried on one surface of a transfer sheet, known as a CB sheet, and the coreactant material carried on one surface of a separate record sheet, known as a CF sheet, and the invention will be described in relation to such a system.
• a coreactant material such as attapulgite EXAMPLE II clay, acid treated montmorillonite clay, or particles of an oil-soluble, acidic, phenolic, polymeric material
• microcapsules and the co-reactant material can be carried together on the same surface of a single sheet.
• the capsules used were approximately 12 pm in size, and had walls of gelatin and gum arabic enclosing an internal phase comprising the dye substances crystal violet lactone and benzoyl leuco methylene blue dissolved in a dibenzylbenzenes admixture, and diluted with kerosene.
• the dye substances crystal violet lactone and benzoyl leuco methylene blue dissolved in a dibenzylbenzenes admixture, and diluted with kerosene.
• many different kinds of capsules are known which could otherwise be used.
• EXAMPLE 1 A solution was formed by adding 5 g. of dextrine to 150 mls. of hot water. The solution was left to cool to A solution was formed by slowly adding 5 g. of Elvanol 52-22 (Registered Trade Mark) polyvinyl alcohol to mls. of cold water and then heating the dispersion formed to increase the rate of solution. The solution was left to cool to below 30C and 5 g. of unburst arrowroot starch granules approximately 25 pm in size were then dispersed in the solution.
• Elvanol 52-22 Registered Trade Mark
• the suspension thus formed was applied as a surface size by means of a Meyer rod to one side of a 49 g/m base paper to give a coating weight of approximately 1.8 to 2.2 glm
• the sized base paper was then dried, and calendered on a laboratory calender.
• Example II The same tests as in Example I were than applied to samples of the base paper, and the sized base paper before and after calendering.
• Raw capsule dispersion was then coated onto the coated side of samples of the calendered sized base paper, as in Example I, and the capsule-carrying samples thus produced were, after drying, subjected to some of the tests detailed in Example I.
• a second solution was formed by adding 4.5 g. of dextrine to 100 mls. of hot water.
• the first and second solutions were then mixed and the resulting solution left to cool to below 30C. 5 g. of unburst arrowroot starch granules approximately um in size were than dispersed in the solution.
• the suspension thus formed was applied as a surface size by means of a Meyer rod to one side of a 49 g/m base paper to give a coating weight of approximately 1.2 to 2.3 g/m
• the sized base paper was then dried and calendered on a laboratory calender.
• the same tests an in Example I and 11 were then applied to samples of the base paper, and the sized base paper before and after calendering.
• Raw capsule dispersion was then coated onto the coated side of samples of the calendered sized base paper, as in Examples 1 and I1, and the capsule-carrying samples thus produced were, after drying, subjected to the same tests as the similar samples of Example 11.
• Calender Intensity Test A capsule-carrying sample and a sta' dard CF sheet (as described above) are superposed with their coated surfaces in contact and a strip of the two sheets then passed between two rollers. After a waiting period the reflectance of the coloured mark thus formed on the CF sheet and the reflectance of the background around the coloured mark are measured with an opacimeter. The Calender Intensity or Cl value of the capsule carrying sample is then determined from the equation:
• Frictional Smudge Intensity Test Adhesion Test A standard piece of black cloth is laid on the coated surface of a capsule-carrying sample; a weight is placed on the cloth and the cloth is then dragged across the coated surface of the capsule-carrying sample. The pattern thus produced on the cloth is then visually compared with a set of number standards, a value of 60 or above indicating acceptable adhesion of the coating on the capsule-carrying sample to the base paper.
• a method of producing a capsule-carrying sheet or web comprising a base sheet or web having on a surface thereof a composite coating containing capsules, protective material for protecting the capsules against accidental rupture, and a binder material serving to bind the capsules and protective material to the base sheet or web, comprising the steps of:
• steps (c) and (d) are carried out simultaneously by applying to the dried first coating an aqueous dispersion of capsules.
• binder material is selected from the group consisting of dextrine, polyvinyl alcohol, or a mixture of dextrine and polyvinyl alcohol.
• the protective material is selected from the group consisting of cellulose fibres, granular polymeric material, or starch granules.
• the aqueous coating mix applied thereto consists of a suspension formed by preparing a solution of 5g of dextrine in 150 mls of hot water, cooling the solution to below 30C, dispersing in the cooled solution 5g of unburst arrowrrot starch granules having a size of approximately 25 um and the suspension is applied to the paper to provide thereon a coating weight of approximately 1.3 to 2.2 glm 9.
• the aqueous coating mix applied thereto consists of a suspension formed by slowly adding 5g of polyvinyl alcohol to 150 mls of cold water, accelerating the rate of solution by heating the dispersion so formed, cooling the solution to below 30C, dispersing in the cooled solution 5g of unburst arrowroot starch granules having a size of approximately 25 um, and the suspension is applied to the paper to provide thereon a coating weight of approximately 1.8 to 2.2 g/m 10.
• the aqueous coating mix applied thereto consists of a suspension formed by preparing a first solution by slowly adding 0.5g of polyvinyl alcohol to 50 mls of cold water, accelerating the rate of solution by heating the dispersion so formed, preparing a second solution by adding 4.5g of dextrine to mls of hot water, mixing the first and second solutions, cooling the resulting solution to below 30C, dispersing in the cooled solution 5g of unburst arrow root starch granules having a size of approximately 25 pm, and the suspension is applied to the paper to provide thereon a coating weight of approximately 1.2 to 2.3 g/m 11.
• a method of producing a capsule-carrying sheet or web comprising a base sheet or web having on a surface thereof a composite coating containing (a) a binder material, (b) protective material, and (0) capsules, said protective material protecting said capsules against accidental rupture, and said binder material serving to bind said capsules and said protective material to said base sheet or web, which method consists essentially of the steps of:
• aqueous coating mix consisting essentially of (a) said binder material, said binder material being rewettable and se lected from the group consisting of dextrin, polyvinyl alcohol, and a mixture of dextrin and polyvinyl alcohol, and (b) said protective material, said protective material being selected from the group consisting of cellulose fibers, granular polymeric material and starch granules;
• Wiggins Teape Research & Development should read Wiggins Teape Research & Development Limited Signed and Sealed this eighteenth Day of May 1976 a ⁇ SEALI A nest:

Landscapes

• Color Printing (AREA)
• Paper (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Manufacturing Of Micro-Capsules (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9777826

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (5)

Citations (2)

• 1972
  • 1972-01-31 GB GB447272A patent/GB1370081A/en not_active Expired
• 1973
  • 1973-01-26 AU AU51531/73A patent/AU476079B2/en not_active Expired
  • 1973-01-29 US US327790A patent/US3914470A/en not_active Expired - Lifetime
  • 1973-01-29 FR FR7302985A patent/FR2170687A5/fr not_active Expired
  • 1973-01-30 ES ES411102A patent/ES411102A1/es not_active Expired
  • 1973-01-31 JP JP1208273A patent/JPS557398B2/ja not_active Expired
  • 1973-01-31 BE BE794831D patent/BE794831A/xx not_active IP Right Cessation
  • 1973-01-31 BR BR73734A patent/BR7300734D0/pt unknown

Patent Citations (2)

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