US3472675A - Pressure-sensitive capsule-containing foraminated sheet material - Google Patents

Description

Oct. 14, 1969 r. r. GORDON ETAL 3,472,675

PRESSURE-SENSITIVE CAPSULE-CONTAINING FORAMINATED SHEET MATERIAL Filed Dec. 25, 1966 FIGJ Hes

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mvsmoas THOMAS T. GORDON RENE K HIMMEL I THEIR ATTORNEY United States Patent 3,472,675 PRESSURE-SENSITIVE CAPSULE-CONTAINING FORAMINATED SHEET MATERIAL Thomas T. Gordon, Dayton, Ohio, and Rene K. Himmel,

Kilchberg, Zurich, Switzerland, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Dec. 23, 1966, Ser. No. 604,332 Claims priority, application Great Britain, Jan. 27, 1966,

Int. Cl. B41m 5/22 US. Cl. 117-369 9 Claims ABSTRACT OF THE DISCLOSURE Self-wetting sheet material having perforations through the sheet thickness filled with minute liquid-containing capsules. Such a sheet material is intended for use, among other uses, as a source or reservoir for encapsulated liquid materials, of any desired kind, which liquid materials are released upon rupture of the capsules. Typical sheets are perforated paper or film material provided with such liquids as may be desired, distributed in a pattern controlled by the perforation distribution in which the capsules nest.

This invention relates to a pressureor heat-sensitive liquid-loaded sheet material which is normally dry to the touch but which yields a liquid when and where the sheet material is subjected to external pressure and/or heat. Such liquids, for example, may consist of agents for cleaning and/or grease spot removal, antiseptic applications, solvents such as for dissolving polymers, adhesive materials, furniture-polishing or shoe-shining materials; vegetable and other oils for greasing, perfumes, low-vapor-pressure inhalants for nasal or oral applications, marking materials, and materials for many other purposes.

According to its main feature, the invention consists in a liquid-loaded sheet material which has a pattern of closely spaced perforated structure and which has its perforate foramina extending through the sheet thickness filled with confined small droplets of a liquid, preferably each entrapped within an enveloping film coating or film binder material which is rupturable under applied pressure or on being heated, or both, for releasing the liquid in selected areas of applied pressure and/or heat.

The perforate sheet material may inherently be micro porous in itself to partly or entirely absorb the released liquid. For example, the sheet may be fibrous, such as paper or other cellulosic fabric which may be rendered macro porous by the deliberate provision of perforate minute cavities between the fibers. On the other hand, the sheet may consist of a thin perforate film of a plastic polymeric material which is substantially a non-absorbent of the contained liquid, so that, on rupture of the entrapping material, all of the there-released liquid is available for external usage.

The droplets of the liquid may be contained as a dispersed phase in a continuous liquid phase of polymeric film material to make an emulsion with which the perforations are filled, and then the emulsion is dried, or alternatively the droplets may be enveloped in a wall of the polymeric film material as microscopic to macroscopic capsules which are held within the perforations either by their inherent adhesiveness or by a binder material different from the film material.

The various ways in which the invention may be carried out and used in practice are described by way of ice example in the following description, which should be read in conjunction with the accompanying drawing, in which:

FIG. 1 shows a gross face view of a filled sheet material in accordance with the invention,

FIG. 2 shows, on a larger scale than FIG. 1, a sectional view of the sheet material taken along the broken sectional line indicated in FIG. 1,

FIG. 3 shows a gross view of a section of the sheet material to illustrate the filling of the perforations.

FIG. 4 shows a gross sectional view of the sheet material which either carries a coating or operates in a complete system with another sheet or sheets in superficial contact therewith,

FIG. 5 shows in plan view a gross representation of a perforation in sheet material filled with an intermixture of encapsulated droplets of the liquid and particles of another material, and

FIG. 6 is a gross representation of minute capsules having a liquid content.

In FIGS. 1, 2, and 3, a perforated sheet is illustrated at 1, and its perforations at 2. The perforations may have a shape dependent upon whether the sheet is required to resist stretching in either direction, or to give it elasticity along either its length or its breadth. For example, elastcity across the width of a machine-made paper may be imparted by the substantially elliptical foramina, as shown, while it will be substantially inelastic along the length. This would also occur with diamondshaped foramina with the two axes of different lengths. Infiexibility in both directions can be imparted if the perforations are made circular or of equal dimensions along both axes. In a particular example, a perforation may have a major dimension of the order of one sixteenth of one inch (approximately 1.5 millimeters) and a minor dimension of one sixty-fourth of one inch (approximately O.4 millimeter).

The perforations 2 contain droplets 3 (FIGS. 2 and 3) of a liquid which may be free-flowing or viscous. These droplets may be contained as a dispersion in a continuous phase 4 of a binder material such as gelatin or casein, or, alternatively, the droplets may be contained as the fillings within enclosing walls 5 of discrete minute capsules, as represented in FIG. 6.

It will be appreciated that, when the sheet is subjected to pressure sufiicient to rupture the material entrapping the liquid droplets, the liquid is released and flows to the exterior of the paper or film for use to its intended purpose.

Alternatively, the sheet material, if of film material, may be made porous, as indicated at 6 (FIG. 2), to assist the penetration of the liquid into the structure of, and thus to wet or dampen, the sheet material itself.

The sheet material may have a coating of material on one or both sides thereof, as indicated at 7 (FIG. 4), which may be applied either to serve as a mechanical pro.- tection or for some other purpose. For example, the coating may consist of a dry adhesive substance (for example, nitrile rubber), and the liquid droplets may contain a solvent for the adhesive substance (for example, toluene), so that, on the rupture of the entrapping material, the solvent is released to wet the coating and render it adhesive. Alternatively, the liquid droplets may be a dryable adhesive in itself, so that, on the placing of a sheet material on one or both sides thereof (see broken lines adjacent the right-hand side of FIG. 4), the adhesive is released onto the applied sheets to cause them to adhere. Obviously, such a sheet may be used for the joining of two solid objects together.

As an alternative, the droplets may comprise a colorless dyestuft, such as crystal violet lactone, in a solvent there for, and the separate sheets 7 may be provided with a coating of a substance, such as a clay, which is acid relative to the dyestulf, which sheets are collated with the coated sides against the novel sheet material 1. On application of pressure to this collated set, the entrapping walls burst to release the dyestuff, which flows onto the clay surfaces to cause the dyestuif to assume a color over an area corresponding in shape to the site of the pressure. For the true image to be visible on the uncoated side of the sheet 7, the sheet 7 must be transparent or absorbent to allow the colored dyestuff to penetrate through at least a part of the thickness of the sheet to be visible from the uncoated side.

FIG. illustrates a perforation filled with two reacting agents which are normally maintained separated by the walls of the capsules 3 containing one of the ingredients. The capsules are indicated'as circles 3 and the coating material by dots 9. The walls of the capsules are burst when pressure is applied to release the encapsulated material into coacting relationship with the material of the dots 9. For example, the capsules could contain an epoxy resin, and the catalyst could be contained as separate droplet or solid entities, as the dots 9 represent, in a binder material. When the capsules and the binder material are ruptured, the two reactants intermixed are expressed for transfer to another body as an active adhesive, or for the adhesion of some said body thereto. To permit expression of the activated adhesive from one side of the material only, the other side may be insulated by an impervious coating or an applied layer.

' Alternatively, for a self-contained or autogenous copy material, a dissolved chemically basic colorless chromogenic dyestuff may be encapsulated, and particles of an acid reactant substance, such as a clay, may b included adjacent thereto in a binder material, so that, when the capsules are ruptured under pressure, the dyestuif is released into contact with the acid reactant, thereby to form a color. As before, one side of the sheet material could be insulated to prevent expression of the liquid by a coating or an applied layer of an impervious substance, and the uninsulated side of the sheet material could be coated, as with gelatin, to provide a smooth writing surface. As an alternative to including the reactant substance in the filling of the perforations, it may be dispersed throughout the above-mentioned gelatin coating.

Although reference has hereinbefore been made to the rupture of the binder material or the capsule walls by the application of pressure, it is to be understood that the material of the binder or of the capsule walls can be such that it will melt to release the liquid content at elevated temperatures.

A perforated paper stock material suitable for the application of the present invention is known which, it is believed, is produced on a paper-making machinesay, a Fourdrinier machine-by providing the Wire with an arrangement of vertical pins. arranged in a perforate pattern to be produced in the paper sheet, the length of the pins being equal to or just exceeding the thickness of the final paper web, whereby the layer of extruded pulp from the stuff box flows around the pins, so that th perforations remain formed when the web passes from the wire in a sufficiently solid state to the dry end of the paper machine.

Obviously, the perforations may be formed in a finished paper web by a mechanical perforating machine.

It is required that the paper shall be given a patterned porosity in excess of the natural porosity given by the interlacing of its felted fibers. Openings in paper can be produced in the structure by the inclusion of particles of a material insoluble in the pulp slurry which, after the web has been formed, can be leached out by the webs being passed through a bath of a solvent, inert as far as the paper is concerned, to produce in the paper an interconnected cellular foraminal structure-or a heat-sublimable filler can be used.

In regard to the use of a polymer film as the stock sheet, owing to the difficulties of producing such a film in perforated form, a continuous sheet of the film can be passed through a perforating machine of any suitable form to puncture the sheet in any desired pattern.

In the manufacture of a sheet material filled according to the invention, the liquid droplets, as aforesaid, may be carried as a dispersed phase in a continuous phase of a binder material to which, as is obvious, the liquid droplets must be chemically and physically inert.

In this case, a paper-coating material such as gelatin, gum arabic, casein, polyvinyl alcohol, paper-coating starch, or clay, or any admixture thereof, is dissolved or mixed in a liquid manufacturing vehicle at an elevated temperature above the gel point of the gellable coating materials to assist in the solubilization of non-gellable materials. Into this system is mixed a quantity of the insoluble liquid filling material in an amount dependent upon the concentration of droplets required to be present in the finished sheet material. The liquid filling material must be immiscible with and chemically inert to the coating material and also to the manufacturing vehicle. The liquid filling material is then emulsified in the solution or mixture of the coating material, as in a colloid mill, to the required drop size.

This filling mixture, or emulsion, is applied by any ordinary paper-coating technique to a perforated paper web either on or off the machine when the web is sufficiently dry so as not to absorb the coating mixture, the web being carried over a bed to prevent egress of the mixture from the under side of the sheet, while a doctor blade is set close to the upper side of the sheet, so that the coating mixture is confined to the perforations, and to a predetermined thinness of coating if this is also required, or, alternatively, the blade may be set so closely as to substantially remove all of the mixture from the surface of the paper.

The web, so filled, is then dried, as by being passed through a drying tunnel, or by any other method, such as being festooned in a drying chamber.

In material prepared in this manner, the liquid droplets are contained in the binder material within the confines of the perforations, which gives protection against release of the droplets during normal handling, sheeting, or reeling. However, the droplets are released when sufficent pressure is applied to rupture the binder material.

In the construction wherein the liquid droplets form the internal phase of small capsule units, the units are preferably produced by a method employing a polymeric wall-forming material which, when in solution, can be caused to separate out in the solvent as a liquid phase rich in polymeric material, leaving the solvent poor in polymeric material. If the liquid droplets, immiscible in the solvent, are present in the system, as by emulsification therein either before or after the phase separation has been effected, and the system is maintained agitated, the entities of the polymer-rich phase will deposit upon and encompass the liquid droplets to form embryo capsules. The embryonic capsule walls may then be hardened if desired. Such methods, for example, are described in United States Patents Nos. 2,800,457, which issued July 23, 1957, on the application of Barrett K. Green and Lowell Schleicher; 2,800,458, which issued July 23, 1957, on the application of Barrett K. Green; 2,969,330, which issued Jan. 24, 1961, on the application of Carl Brynko; and 3,190,837, which issued June 22, 1965, on the application of Carl Brynko and Joseph A. Scarpelli. According to United States Patents Nos. 2,800,457 and 2,800,458, separation of a gelatin-rich liquid phase can be induced in a gelation sol, at a temperature above the gel point of the gelatin, by the addition of salt, or in a complex sol of gelatin and gum arabic by the addition of an organic acid, such as acetic acid. If droplets of a liquid immiscible in and inert as to the solvent, and generally referred to as an oil, are mixed in the sol before or after phase separation is induced, and while the mixture is agitated, the integers or conglomerate aggregates of the colloid-material-rich phase will deposit onto the liquid droplets to encompass them, after which the temperature is lowered below the gel point to solidify the preformed walls. The walls may subsequently be hardened by the introduction of a hardening agent such as formaldehyde, or glutaraldehyde. Particles of solid substances immiscible in the solvent may be similarly encapsulated.

A similar method for the encapsulation of materials is described in United States Patent No. 3,190,837, with the addition that the colloid-material-rich entities which have not deposited from the manufacturing vehicle onto the droplets are redissolved by elevation of the pH; a further quantity of one of the polymeric materials is introduced, and phase separation is again induced, so that entities of a new colloid-material-rich phase deposit onto the exterior of the already-formed capsules to increase the thicknesses of the walls, which may thereafter be hardened, as previously mentioned.

United States Patent No. 2,969,330 employs a polymerizable material as the wall-forming polymeric material; for example, styrene monomer, which is dissolved in the oil to be encapsulated. The introduction of a catalyst to the system causes the monomer to be withdrawn from the oil droplets to form polymerized capsule walls therearound. Any other method of encapsulation involving the phenomena of phase separation may be employed.

In the case of filling the perforations of a paper with an encapsulated emulsion produced in accordance with the method of United States Patents Nos. 2,800,457 or 3,190,837, the emulsion itself may form the filling mixture. That is, the emulsion itself, or with the addition of a. material to give it more body (for example, casein, polyvinyl alcohol, starch, or paper-coating clay), can be applied, by any suitable paper-coating process, to the perforated paper web, whereby the perforations are filled with the emulsion with or without a thin coating layer. The paper can then be dried in a drying tunnel or chamber. In such a paper, the capsules are held in the perforations either by the solidified material in the continuous phase of the coating emulsion, or by reason of the capsules adhering together.

As mentioned hereinbefore, if it is required that particles of a solid material such as a clay shall be included in the coating emulsion in intermixture with the capsules, these particles, which must be insoluble in the manufacturing vehicle, are mixed in the emulsion after manufacture of the capsules. Thus, in the final dried coating, the perforations will be filled with capsules and particles in intermixed contiguity.

The use of the capsular structure also permits the inclusion of droplets of another liquid in close contiguity with the capsules. That is, after manufacture of the capsules, another liquid insoluble in the solvent may be emulsified into the system, such other liquid being reduced to the size of fine droplets to exist as neighbors to the capsules. An example of such further liquid consists of a co-reactant with the liquid of the capsules, as in a color-forming system; or the capsules may carry one polymeric adhesive, and the further liquid may be a hardener or a catalyst for the adhesive. The forces applied in emulsion of the additional liquid, as in a colloid mill, must not be so great as to risk bringing about rupture of the capsules.

In the case of capsules having polymerized walls, it is necessary to include in the filling mix a binder material as aforementioned, such as gelatin, casein, polyvinyl alcohol, paper-coating clay, or starch, so that in the finished coating the capsules with or without intermixed particles are held together by the binder material. This also applies in the case where capsules having walls of a hydrophilic polymeric material, such as gelatine alone or with some other polymeric material, are separated from the sol and dried. These dried capsules are mixed into a binding-filling mixture and coated onto the perforated material to -fill the foramina with or without a thin overlying coating.

The diameter of the capsules may vary from microscopic to macroscopic but preferably lies in the region between 200 and 500 microns. The liquid content of the capsules can vary between percent, by weight, to 99 percent, by weight, of the total mass. Where a maximum liquid loading is required, it is preferable that the capsules be as large as possible, and they may have a diameter of up to nearly the thickness of the sheet material.

A further modification of such a filled fibrous material is to provide a finely particulated polymerizable material as a dry filling dispersed throughout the fibers of the material and contain within the capsules a hardener or catalyst for the polymer. Thus, a sheet so made would normally be flexible, but on the rupture of the capsules the hardener or catalyst would flow to the polymerizable material to cause it to polymerize to its hard condition, thus to cause the material to assume a rigid form.

What is claimed is:

1. A liquid-loaded apparently dry sheet material having a perforated structure and containing within its perforations a filler, preferably made from a binder material, having entrapped therein and dispersed therethroughout droplets of a loading liquid, said binder material being rupturable to release the entrapped liquid, the perforations having dimensions of A of an inch as an upper limit and of an inch as a lower limit and arranged in a geometric pattern whose interperforation spacing is substantially between said upper and lower limits, in which the liquid droplets are taken from the class consisting of (a) washing and solvent fluids,

(b) liquid solutions and dispersions of marking materials and marking material reactants,

(c) polishing and coating solutions and dispersions,

(d) lubricants and liquid dispersions of lubricants,

and

(e) vapor inhalant producing materials of fragrance and pharmaceutical properties, and the droplets being of small size, so that many capsules are accommodated in a perforation.

2. The liquid-loaded sheet material of claim 1 in which a cover of a paper-coating material having dispersed therethroughout particles of a substance which is chemically reactive with the loading liquid is applied to one side of the sheet material.

3. The sheet material of claim 1 wherein the loading liquid includes a colorless dyestulf of the kind which is caused to assume a colored form when brought into contact with a coreactant substance.

4. The sheet material of claim 1 wherein the loading liquid includes an adhesive material.

5. The liquid-loaded sheet material of claim 1 in which the droplets of the loading liquid are contained as the contents of minute capsule entities each having a wall of a polymeric material.

6. The liquid-loaded sheet material of claim 5 in which particles of a substance which is reactive with the loading liquid on contact therewith are interspersed with the capsule entities in the binder material.

7. The liquid-loaded sheet material of claim 5 wherein a cover of a paper-coating material having dispersed therethroughout particles of a substance which is chemically reactive with the loading liquid is applied to one side of the sheet material.

8. The sheet material of claim 5 wherein the loading liquid includes a colorless dyestuff of the kind which is caused to assume a colored form when brought into contact with a co-reactant substance.

9. The sheet material of claim 5 wherein the loading 3,041,288 6/1962 Anthony 11736.2

liquid includes an adhesive material. 3,384,536 5/1968 Sandberg et a1. 117-362 References Cited MURRAY KATZ, Primary Examiner 2 730 456 S$2 6 G t a l TENTS 117 36 1 5 1 reen e 2 90 453 7 1957 Green 117 3 1 15-40493; 3,016,308 1/1962 Macaulay 117--36.3 401-132 3,020,171 2/1962 Bakan ct al. 117-362

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