US2000528A - Laminated composite paper - Google Patents

Description

y 1935- G. B. LINDERMAN, JR 2,000,528

LAMINATED COMPOSITE PAPER Filed Dec. 27, 1952 Game)! EZ/mrmaw/k:

Patented May 7, 1935 UNITED STATES 2,000,528 LAMINATED oomosrra PAPER Garrett B. Linderman, Jr., Pittsburgh, Pa assignor to Pittsburgh Equitable Meter Company, Pittsburgh, Pa., a corporation of Pennsylvania Application December 27, 1932, Serial No. 649,082

2 Claims.

This invention relates to laminated composite paper, or a paper substitute, and more particularly to laminated material composed of a layer or layers of fibrous material, or material manufactured from fibrous material, and a sheet or sheets of metallic foil all intimately united by adhesion.

The invention resides further in the provision of a high grade paper substitute made up of laminations, only some of which are made of materials heretofore used in the production of paper of high grade character; and in a uniting of the layers so as to form a structure that to ordinary inspection appears merely paper of excellent quality.

Papers for general use where durability is of special importance, for example, paper prepared with ruled markings for business records including ledger and index paper and blank forms, may be manufactured in accordance with my invention disclosed herein to meet the need of a paper possessing superior durability and improved quality without appreciably increased thickness over that or ordinary paper. Paper used for stationery and general correspondence manufactured according to this invention will have the appearance of fine quality relatively heavy stock, but nlay consist of materials which are relatively cheap.

Heretofore the application of paper to special uses has been hampered by the lack of necessary and desired properties in the ordinary papers of commerce. By my invention special stationery papers may be provided having essential properties dictated by the use to which the paper is to be put. While ordinary paper of commerce may be made from different sources of fibrous material, with widely differing fillers and many styles of surface texture and calendering, it has been impossible to produce a paper impervious to moisture. The paper of my invention may be manufactured with any desired finish or texture combined with opaqueness and moisture resisting qualities.

It is therefore a primary object of my invention to provide a laminated composite paper, or paper substitute composed of alternate layers of fibrous material and metallic foil intimately and uniformly united at all points by an adhesive, so that the resulting composite paper is in effect a pliable homogenous sheet which may, if desidered, be provided with a calendered surface or any other typical paper finish.

It is a further object of my invention to produce laminated composite paper having properties desirable and necessary for a wide variety of special uses that are not possessed by papers heretofore used, though in appearance, upon ordinary inspection, the composite material seems to be paper.

A further object of this invention is to provide a paper substitute that may be used for special purposes to which the ordinary papers of commerce known heretofore were either wholly inapplicable or gave indifierent or unsatisfactory results, to provide a paper substitute that is impervious to moisture and has the characteristic thata given area thereof will not change appreciably in extent with changes from extremely dry to extremely moist conditions, to the end that the paper substitute may be used where distances and areas are to be measured accurately on its surface because it does not expand or contract appreciably when subjected to conditions that vary from extremely moist to extremely dry, to provide a paper substitute for materials used for maps, charts, accurate drawing paper, and particularly military maps and navigation charts, which are exposed to widely varying conditions of relative humidity and even under these conditions must be relied on to represent geographical distances to scale so that the location of a ship may be plotted or ordnance trained by measuring distances to scale on the chart or map.

The paper of this invention in addition to being substantially waterproof and free from. expansion on wetting has a resistant quality because of the metallic layer in the laminated structure, which minimizes danger of tearing. For these reasons, the paper of my invention is especially applicable to uses where combined nonexpansibility and resistance to tearing are important such as for templates where an edge of the paper is cut to an outline which is to be reproduced by scribing or by other meansfor transferring a facsimile of the outline to the metal or other inaterial to be shaped or where the outline of the template is to be followed by a stylus or pointer to control a reproducing machine. For pattern sheets and rolls provided with perforations used in controlling machines such as looms and spacing tables for multiple punches, the resistance to tearing and non-expansible qualities provide a perforated sheet, the perforations of which will not tear or fray and which will maintain their proper relative location in the sheet. Paper stock for color printing where close and accurate register of successive superimposed printings is necessary must, in conjunction with other requirements, be substantially free from distortion. The composite paper of my invention admirably fulfills this condition.

The valuable feature of maintaining constant area also makes possible the use of paper according to this invention as chart paper for recording meters arid gauges. Recording meters and gauges are generally installed where wide variations in relative humidity are encountered. The records on the charts are traced over a period of time during which the quantity of moisture may vary erratically and it would be impossible, therefore, to correct the readings taken from the chart without a simultaneous record of the relative humidity affecting the. chart at the time of recording. Obtaining such a record would be almost impossible and the endless labor involved and uncertainty of the results would make them practically worthless. With the composite paper of my invention the need for correction for expansion in any direction is eliminated and the record obtained may be taken as indicate of the variable recorded.

In the preferred embodiments of the invention a valuable feature lies in the selection of adhesives to adapt the laminated paper to specialized uses, the laminations of the composite paper being joined by the selected adhesive which may include solvents and plasticizers depending on the contemplated use. .The selection of the adhesive will be governed by the properties desired among which are thermo-plasticity, resistance to heat and insolubility in liquids. These properties may be varied by the inclusion of solvents and plasticizers.

Still another object of this invention therefore is to produce a laminated composite paper, the laminations of which are joined uniformly and at all points by adhesives incorporating solvents and plasticizers, the selection of the adhesive being governed by its properties to suit the use contemplated.

Documents written on the paper substitute of this invention are immune to alteration or tampering to a'degree heretofore unattainable as the opaqueness thereof precludes any possibility of tracing signatures or other writing from a copy by means of transmitted light. An adhesive which is non-water soluble and unaffected by heat may be selected in which solvents may be incorporated if desired to enable the adhesive to penetrate the fibrous layers over the foil to make them moisture resistant and prevent alteration of the fibrous layer bearing the printing and writing. It is further contemplated in this phase of my invention to use inks sensitive to heat and/or moisture which will change in appearance when subjected to heat or concentrated water vapor and also to impregnate the fibrous layer or layers with coloring matter sensitive to heat and/or moisture by direct impregnation of the fibrous layer or by including it in the adhesive as a solvent and permitting it to penetrate the fibrous layer during manufacture. i

It is therefore a further object of the invention to provide an opaque laminated composite paper the fibrous laminations of which are impregnated with a heat sensitive element and the laminated body 'of which is joined uniformly and at all points by a heat resistant binder.

A still further object of this invention is to provide an opaque laminated composite paper the laminations of which are joined uniformly and at all points by an adhesive heat resistant binder embodying solvents to condition it to initially r penetrate the laminations.

It is desi able that'paper stock for close and accurate or printing be free from distortion so that superimposed successive printings will be in perfect register. Ordinary paper of whatever grade or quality will expand and contract with changes in moisture content of the air in the press room, and where the paper stock has been stored prior to use in a moist place contraction of the paper will occur when heat is applied after the initial printing to dry the ink in preparation for successive printings. This general contraction of the paper is aggravated by local distortion caused by the wet ink which is applied to the sum face of the paper at each successive printing an. H

dried by the application of heat.

'In the preferred embodiments of the invention I have provided a paper immume from general expansion and contraction caused by change in moisture content and local distortion due to the application and drying of moist ink. Adhesives may be selected in accordance with the ink drying process used. Where the ink is dried rapidly by application of intense heat for very short intervals it is obvious that the adhesive selected must have heat resistant properties. If moderate drying temperatures are used, any adhesive suitable for use in the manufacture of laminated paper, in accordance with the invention, will be suitable.

A still further object of this invention therefore is to produce a laminated composite paper for color printing stock, free from expansion and contraction, the laminations of which are joined uniformly at all points by a binder unaflected by ink and ink solvents, and which will remain unchanged at ink drying temperatures.

Ordinary photographically' sensitized papers which are subjected to the action of chemicals in solution and to fixing and washing liquids are difficult to handle when wet and frequently tear at some stage of the process. The laminated composite paper, or paper substitute of this invention with a non-water soluble binder may be provided with a photographically sensitized surface and is capable of being handled while wet without tearing or curling. The distortion-free characteristic enables it to be used. for bearing photographic reproductions which may be scaled with the assurance that distances measured thereon will represent the scale the same distances as measured on the original from which the photographic image is taken. Blueprints and other reproductions made by contact printing methods or by the photostat process will be a true reproduction of the orignal. With a proper selection of lenses in accordance with known practice, maps made by aerial photography and reproduced photographically will be more accurate if my com- 1rtiosite paper is used than has been possible heretoore.

Still another object of this invention therefore is to produce anon-curling laminated composite paper free from expansion and contraction and bearing a photographically sensitized surface, the laminations of which are joined uniformly and at all points by a binder unaffected by immersion in sensitizing and developing liquids and resistant to temperatures within the range used for drying.

Many industrial processes may be greatly simplified by the use of my composite paper and this is particulary true where, during the initial steps, the paper is subjected to widely .varying temperatures and immersed in water and solutions of chemicals. Certain specialized processes inthefinalstepsrequireathinpaper. Inthia instance the paper of my inventiom-is of great utility as during the initial steps of the process, it will resist treatment by heat and liquids and may be prepared for the final process by removing all but the desired lamination, the adhesive being selected to resist separation under conditions imposed by the initial steps of the process, but to permit separation at the desired stage, for example, by the application of heat.

Still another object of my invention therefore is to produce a laminated composite paper for use in industrial processes, the laminations of which are joined uniformly and at all points by a binder resistant to intermediate steps of the particular process, but which will permit certain of the laminations to be separated from the main body thereof. at will, without destruction of the paper substitute.

Further objects of my invention will appear in the following disclosure of the preferred methods of manufacture. and embodiments of my invention and are defined by the terms of the appended claims.

Figure 1 is a conventional perspective view of one embodiment of my composite laminated paper, a portion of the laminated structure being shown is separated for cleamess of illustration.

Figure 2 is an enlarged fragmentary section through the embodiment of Figure 1.

Figure 3 is a view similar to Figure 1 illustrating a further embodiment.

Figure 4 is an enlarged fragmentary section through the embodiment of Figure 3.

This application is, in part, a continuation of application Serial No. 570,216, in which the invention is disclosed specifically as a substantially inexpansible recording chart'in combination with a recording meter.

In the preferred forms of my invention, a laminated sheet is produced having the pliability and texture of paper. Referring to the drawing there is shown in each of the severalfigures a portion of a composite sheet, representing by way of specific example, preferred embodiments of my invention.

A metallic sheet of the degree of thinness, known as foil, is represented by reference character 2. A layer or sheet of paper 3 covers foil! and is secured thereto in superposed relationship by an adhesive or binder 4, the thickness of which on the drawing is considerably exaggerated for the sake of clearness of illustration.

There will hereinafter be described more in detail in connection with a disclosure of the several specific embodiments, binders and adhesives combined with solvents and plasticizers to make the invention disclosed herein applicable to specific conditions of use.

The adhesive or binder 4, which preferably is one of those disclosed in connection with the description of the several specific embodiments to follow, unites a paper layer or layers 3 to foil 2 at all points and with uniform adhesive power, so that the laminated structure is pliable in all directions and when handled feels like a sheet of ordinary paper of a thickness equivalent to that of the combined thickness of the foil and paper layers. The laminated structure, incorporating the foil is opaque. The foil layer is unaifected by moisture and, therefore, the laminated structure will not expand or contract with changes of proof and does not lose its toughness on immer-v sion in liquids not solvents of the adhesives.

The modification shown on Figures 1 and 2 of the accompanying drawing is composed of two layers or laminations, foil layer 2 and paper sheet 3 united in the manner described above by an adhesive 4.

Figures 3 and 4 illustrate the preferred modification in which the laminated structure has the appearance and feel of paper, and is, in effect, a paper substitute that may be used to replace ordinary paper.

In this modification, a layer of foil 2 is concealed between two layers or sheets 3 of paper. The adhesive indicated by reference character 4 unites layer 3 uniformly and at all points to foil 2. The laminated structure just described, because of the flexible character of adhesive 4, which is present in an amount just sufficient to intimately unite layer 3 to foil 2 without forming a perceptible body or layer of adhesive, is pliable in all directions, and constitutes a unitary structure.

The layer of foil concealed by the paper imparts aquality which presents to the sense of touch the feel of a fine paper of the heavier and more expensive grades.

The composite structure of Figures 1 and 2 is pliable and may be used where a paper substitute is desired, having one side which presents the appearance of metallic foil.

For the fibrous portion of my laminated composite structure, paper of any kind or quality may be used. Preferably the quality and surface finish of the paper will be selected in accordance with the use which is contemplated in each instance for the laminated paper. In producing paper which is to form a part of my laminated paper substitute, in event that a special surface finish of the paper is desired, it is necessary to treat one side only of each layer which is to enter the finished product.

Any desired weight or thickness of paper may be used but paper of from one one-thousandth of an inch to four one-thousandths of an inch thickness is preferable, and if paper is selected within these limits of thickness, the resulting composite structure will present the appearance of paper and will be applicable as a substitute for ordinary paper.

For the impervious moisture resisting component of my paper substitute, I prefer to use aluminum foil. I have discovered that aluminum foil when united with paper according to the invention disclosed herein, gives as a result a laminated structure which is tough, pliable and but slightly heavier than ordinary paper, which it resembles. It is to be understood that aluminum foil of any desired thickness may compose the opaque andimpervious component of the laminated paper of this invention,'but I have discovered that foil of the thickness between the limits of three and one-half ten-thousandths of an inch to one one-thousandth of an inch is best suited to the production of my laminated paper substitute.

The adhesive material for joining the paper to the foil layer is preferably a special thermoplastic adhesive which I have found to be especially suitable where high adhesive properties are desirable. This thermoplastic adhesive permits the laminations to be separated at a given time, as, for example, when in the course of an industrial process, it is necessary to use an embodiment of the paper-like material of this invention, which may be separated into its component laminations' during an intermediate or final step in the process. Rubber latex also has high adhesive properties and permits separation upon heating.

Where heat-resistant properties of the adhesive are desirable. the adhesive bond between the fibrous material and the foil may be effected by using a formaldehyde urea resin reacted in the recent resin stage, or a stage B glyptal resin combined with plasticizers and solvents to produce a glue. These resins when used as a binder to unite the laminations. produce a paper substitute, the structural unity of which will not be disturbed by the later application of heat.

The paper-llkequalities of the laminated paper substitute of this invention make it applicable to general paper uses, the quality of durability and imperviousness to moisture impartedto it by the metallic foil component enables it to replace papers generally and its special qualities open up new fields of use to which ordinary paper was imperfectly suited.

The adhesives disclosed herein, which are insoluble in water when used to join the component layers of my paper, give, as a result, a paper which is completely waterproof.

It will be understood by those skilled in the art that all of the commercially available adhesives including, organic and inorganic cements, natural and artificial latex, animal and vegetable glues, even those that develop their adhesive properties by evaporation of volatile solvents may be employed where the adhesive has the desired properties to adapt it to the particular use, as for example for uses wherein the evaporation and absorption of the solvent is of little consequence or is beneficial to the resulting composite structure.

The preferred thermo-plastic cement is not dependent upon solvent evaporation for developing adhesion between two surfaces. The intimate bond between the component layers of the composite structure provided by the cement is secured by means of heat and pressure alone, the volatile solvents serving only to lay a film on the surface and are preferably entirely volatilized prior to joining the surfaces. This adhesive when in solution is light in .color and deposits a clear, nearly colorless film. It is waterproof and has excellent flexibility and adhesion over a wide range of temperatures. A suitable thermoplastic cement suitable for the purposes of the present invention is sold commercially by the E. I. du Pont de Nemours & Company, known as Thermoplastic Cement #4620.

In adhesively joining the component laminations of the composite laminated paper. the heat necessary to secure a firm union need be applied only momentarily, thus permitting a rapid and continuous production of the laminated paper. The time of application of the heat may vary, depending on the heat conductivity of the laminated\ structure. Temperatures of from 100 to 150 C. and low pressures may be employed to secure perfect union, although pressures of from 200 to 300 pounds per square inch are preferred.

Latex, preferably artificially prepared, gives an intimate bond between the paper and the foil, which is not aifected by moisture and is firmly adherent. Preferably, the latex adhesive used contains about thirty-eight percent solids. but the invention is not limited to this composition of latex. Preferably also the latex is applied to the paper or foil, which then are brought together and pressed between rolls. no heat being employed for this purpose. although heat may be used in some cases. In this way an excellent bond is obtained.

The paper substitute of my invention with the laminations thereof united by rubber latex or the thermo-plastic adhesive is suitable for any paper use. Because of its wholly new qualities of opaqueness, imperviousness to moisture, and its further desirable property. of being undistorted in the presence of water vapor in concentrated amounts, it may be used for many special purposes. Stationery; wrapping paper, and accurate photographic, drawing and chart papers are exemplary of uses in a wide field of applicability to which the paper of my invention furnishes a new product.

The paper substitute of the foregoing disclosure is, because of special properties inherent in the structure thereof, a safety paper. Its inability to transmit light prevents tracing of signature or other inscription by transmitted illumination, which is a common method of forging or tracing documents. To detect attempts to falsify inscriptions on the surface of the laminated paper by separating the layers so that light may be passed through one component thereof, it is contemplated to use heat sensitive ink in preparing the original and genuine inscription so that if heat be "applied to separate the layers, this fact will be shown by alteration in the appearance of the ink of the genuine inscription.

Genuine documents written on the safety paper provided by this invention will preclude the copying of the signature or any part of the inscription on ordinary paper by transmitted light. A double safeguard is thus provided since if the original is inscribed on the safety paper of this invention, a falsified copy thereof must be attempted on a like sheet so that two layers of foil intervene to frustrate any production of a copy. Clear evidence of tampering would appear on both copies.

The light excluding properties of aluminum are such that it is opaque to radiant energy, which is perceptible to the sense of sight. Special rays are therefore ineffectual to transmit sufilcient illumination to make possible the copying of an inscription to or from my safety paper.

To make tampering impossible and, therefore. enhance the safety paper value of the invention, I preferably Join the foil and paper layers with a synthetic resin, as previously described, incorporating solvents and plasticizers .which when used as an adhesive will resist separation of the layers at any temperature which may be applied to the laminated structure without destroying it. This further inherent property of the paper substitute of this invention makes tampering impossible, and therefore an additional means. such as colored ink, to detect an attempted alteration is unnecessary. In this latter embodiment of the paper substitute wherein a synthetic resin is used, heating will more firmly unite the components of the laminated sheet.

In the manufacture of the novel product herein disclosed, it is produced continuously when joined with the preferred thermoplastic cement. The cement may be applied to either the paper or the metallic layer indiii'erently. The paper is then rolled in contact with the aluminum foil between two polished steel rollers which are heated by any suitable means to approximately 180 F. or between rubber rollers. The pressure applied to the rollers may vary within wide limits. If heavy pressures are used, lower temperatures may be maintained at the rollers, and conversely if lighter pressures are used, the rollers should be kept at a higher temperature. The thermoplastic adhesive referred to above, when used for uniting the layers if preferably applied to the surfaces of the foil, allowing sumcient time to elapse to permit evaporation of all of the solvent, after which it is joined by heat and pressure applied within the limits previously disclosed. These operations may be formed continuously, the foil layer receiving the adhesive coating as itis movedtowardtheheated rolls. The time and/or distance of passage from the point of application of the adhesive to the rolls may be regulated to allow time for evaporation of the solvents.

The invention maybe embodied inother specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are there-.

2. A laminated composite stationery papersuitable for taking an inscription consisting of a layer of metallic foil adhesively secured by unvulcanized latex to external sheets of paper of writing paper quality.

GARRETT B. LmDERMAN, Jr.

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