US 3442755 A
Description (OCR text may contain errors)
May 6, 1969 H. A. WALTERS ET AL 3,442,755
ORNAMENTAL PAPER INCORPORATING PLASTIC ELEMENTS Fild March 29, 1955 INVENTORS. Hero/0'14. Wa/fens RO/b M 6006/) H TTOR/VE Y United States Patent US. Cl. 162168 6 Claims ABSTRACT OF THE DISCLOSURE Attractive paper is prepared by incorporating iridescent plastic film particles in a paper, the plastic film particles being composed of .a plurality of transparent layers.
This aplication is a continuation-in-part of my copending application Ser. No. 431,423, filed Feb. 9, 1965, and now abandoned.
This invention relates to paper. It more particularly relates to paper having a unique and attractive appearance.
Decorative and eye-catching papers have been prepared for many years utilizing various additives other than a paper pulp. Planchettes, fibers, filaments and the like have been incorporated into paper to provide an attractive appearance. Some of such additives are set forth in United States Letters 'Patents 3,055,797, 2,949,398, 342,- 315 and 447,336 and British Patent 2,649 (1802). Although many attractive and decorative papers exist which include various additives such as foil, fibers, sequins and the like, it would be beneficial if there existed a paper which had iridescent materials incorporated therein. It would be further advantageous if there existed a paper incorporating iridescent elements wherein the iridescent elements had a thickness approximating that of the paper. It would be further advantageous if a paper existed which had iridescent elements incorporated therein which were flexible and would adapt themselves readily to inclusion in papers of various thicknesses and not tend to loosen or be removed from the paper by bending or flexing.
These benefits and other advantages in accordance with the invention are achieved by providing a paper having intimately incorporated therein a plurality of thermoplastic resinous elements, the resinous elements each comprising a transparent thermoplastic resinous body com-' posed of a plurality of generally parallel layers of transparent thermoplastic resinous material wherein at least about 20 percent of the layers have a thickness of between about 0.05 micron and about microns and preferably 0.05 to 1 micron for maximum iridescent effects, and
differ in refractive index from adjacent layers by at least about 0.03.
Further features and advantages of the present invention will become more apparent from the following specification taken in connection with the drawing wherem:
FIGURE 1 depicts a view of a sheet of paper containing iridescent elements;
FIGURES 2, 3 and 4 illustrate various configurations of iridescent elements which may be employed in the paper in accordance with the invention;
FIGURE 5 is a schematic representation of an edge view of an iridescent element for incorporation in paper.
In FIGURE 1 there is illustrated a paper in accordance with the invention generally designated by the reference numeral 10. The paper comprises a fibrous paper body 11 having incorporated therein a plurality of iridescent thermoplastic resinous elements 12 randomly distributed on a surface 13 of the paper 10.
In FIGURES 2, 3 and 4, iridescent elements 15, 16 and 17 depict shapes such as rectangles, filaments and circles, respectively, which may be employed either alone or in combination in papers in accordance with the invention.
In FIGURE 5 there is illustrated a schematic enlarged edge view of an iridescent thermoplastic resinous element generally designated by the reference numeral 20. The element 20 comprises opposed surface layers 22 and 23 and a plurality of interdigitated or alternating layers 25 and 26. At least 10 percent of the layers have a thickness of from about 0.05 micron to about 5 microns and preferably 0.05 to 1 micron for maximum iridescent effects, and the refractive index of the adjacent layers differs by 0.03 and beneficially by 0.1. I
Paper in accordance with the present invention is readily prepared utilizing conventional paper processes wherein the paper is prepared by the deposition of fibers from a fluid suspension on a porous support to give essentially the felted sheet of the fibers. Conventional cellulose fiber pulp or synthetic fiber pulp slurries or mixtures thereof are readily employed.
The iridescent synthetic thermoplastic resinous elements are readily prepared in the form of thin sheets or films beneficially having thicknesses from about 0.25 to about 10 mils by the simultaneous extrusion of a plurality of layers of diverse thermoplastic resinous materials and subsequently stretching the extrude at a thermoplastic temperature until the thickness of the composite sheet and the layers therein are reduced to the desired level. Beneficially, such a composite sheet can be obtained by the simultaneous extrusion of a plurality of layers from a single die or by preparing a composite sheet by hot lamination of film or extrude to provide the desired number of layers, heating the composite sheet to a thermoplastic temperature and reducing its thickness by stretching. Alternately, such a sheet is prepared by a coating or casting technique wherein thin layers of diverse thermoplastic resinous materials are deposited on a substrate and subsequently stretched from the substrate. In order to achieve a satisfactory iridescent effect, the layers of material must be deposited in such a manner that a relatively sharp interface is maintained. Such an interface can be maintained by the use of synthetic resinous materials in solvents which are solvents only for one of the materials. Thus, distinct layers are obtained having a sharp interface and as successive layers are deposited, the iridescent effect increases. About 10 layers are satisfactory for minimal iridescent effect. However, beneficially about 50 is usually the number of minimum layers suitable for a relatively intense iridescent effect and desirably, composite structures having -500 layers are employed for maximum iridescent effect.
To further clarify the requirements for a film showing iridescence, it must have at least two pairs of adjacent discontinuities in refractive index, each member of the pair being separated by a distance of from about 0.05 to about 5 microns and preferably 0.05 to 1 micron for maximum iridescent effects. That is, the iridescent film shall have within the body of the film two layers having a thickness of about 0.05 micron to about 5 microns and preferably 0.05 to 1 micron for maximum iridescent effects, and differing from the adjacent portions of the body in refractive index by at least 0.03. Thus, the layers within the film which are responsible for the iridescence are restricted in thickness between the foregoing limits and may be bonded to each other by other layers in the body which are transparent and may be thicker, thinner, or equal to the thickness of the layers, giving rise to iridescence.
Maximum iridescence is achievedgenerally when two'or more materials are interlayered which have a maximum difference in refractive index and all of the layers lie within the range of 0.05 micron to 5 microns and preferably 0.05 to 1 micron for maximum iridescent effects. Thicker iridescent films, that is, those approaching mils in thickness, may have many layers thicker than 5 microns while the thinner films having an equal degree of iridescence have layers less than 0.05 micron. Multilayer film having all layers less than about 0.05 micron or having no layers within the range of about 0.05 micron to about 5 microns do not exhibit the desirable iridescent characteristic.
Beneficially once the composite iridescent film is prepared, it is then cut or processed into the desirable shapes such as elongated strips, rectangles, circles, and even chopped into random shapes, depending upon the desired effect. Oftentimes, particularly attractive effects are obtained by using film having layers of various thicknesses so that the iridescent colors obtained are varied.
Advantageously, attractive iridescent films are prepared from a wide variety of synthetic resinous thermoplastic materials including the materials hereinafter tabulated with their refractive index.
TABLE I Refractive Polymer name: index Polytetrafluoroethylene 1.35
FEP (fiuorinated ethylene-propylene copolymer 1.34 Polyvinylidenefluoride 1.42 Polychlorotrifluoroethylene 1.42 Polybutyl acrylate 1.46 Polyvinyl acetate 1.47 Ethyl cellulose 1.47 Polyformaldehyde 1.48 Polyisobutylmethacrylate 1.48 Polybutylmethacrylate 1.48 Polymethylacrylate 1.48 Polypropyl methacrylate 1.48 Polyethylene methacrylate 1.48 Polymethyl methacrylate 1.49 Cellulose acetate 1.49 Cellulose propionate 1.49 Cellulose acetate-butyrate 1.49 Cellulose nitrate 1.49 Polyvinyl butyral 1.49 Polypropylene 1.49 Low density polyethylene (branched) 1.51 Polyisobutylene 1.51 Natural rubber 1.52 Perbunan 1.52 Polybutadiene 1.52
Nylon (condensation copolymer of hexamethylene-diamine and adipic acid) 1.53 Polyvinyl chloroacetate 1.54 Polyvinylchloride 1.54 Polyethylene (high density linear) 1.54 A copolymer of 67 parts by weight methyl methacrylate and 33 parts by weight styrene n--- 1.54 A copolymer of 85 parts by weight vinyl chloride and parts by weight vinylidene chloride 1.55 Poly-a-methylstyrene 1.56 A copolymer of 60 parts by weight styrene and 40 parts by weight butadiene 1.56 Neoprene 1.56 A copolymer of 70 parts by weight styrene and parts by weight acrylonitrile 1.57 Polycarbonate resin 1.59 Polystyrene 1.60
A copolymer of 85 parts by weight vinylidene chloride and 15 parts by weight vinyl chloride 1.61 Polydichlorostyrene 1.62
By selecting combinations which have a difference in refractive index of at least 0.03, an iridescent film resullts. However, for maximum iridescence, beneficially the difference is about 0.1. When multilayer films are prepared using 3 or more components, iridescence is obtained when at least some of the adjacent layers exhibit the desired difference in refractive index.
Papers in accordance with the present invention are readily prepared by admixing the film with a pulp slurry in a conventional paper-making procedure and subsequently depositing the pulp on a screen or similar support. The iridescent elements are deposited in the plane of the resultant paper and on drying, are generally parallel to the surface of the paper, but many deviate sufficiently from a precise parallel relationship to each other that the iridescent elements appear and disappear as the paper is viewed from varying angles. Beneficially, the iridescent elements are incorporated in the paper in a proportion varying from about 2 weight percent to about 50 weight percent based on the dry weight of the pulp depending upon the particularly iridescent film employed and the results desired.
Generally in selecting a desired proportion of iridescent film to be employed, a visual inspection of the film prior to comminuting is helpful and the resultant visual effect will be about 10 times the iridescent effect of the uncomminuted film. Generally, the greater the degree of division or uncomminution of the film, the greater will be the iridescent effect of the resultant paper. The paper may be white, colored or black, the colors beneficially being imparted to the pulp fibers prior to the incorporation of the iridescent material. The precise visual effect is somewhat difficult to predict and will vary considerably with the color of the pulp employed.
By way of further illustration, a paper is prepared employing an iridescent film which is 1 mil thick comprising 125 layers of polystyrene and polymethyl methacrylate alternately disposed with respect to each other wherein the thickness of the polymethyl methacrylate layers was about 3 microns. The film was placed in water and shredded by means of a high speed mixer to provide a slurry of about 0.5 percent by weight solids. A bleached kraft pulp was beaten to a Canadian Standard Freeness of 397 milliliters. Ten parts by weight of pulp based on the dry weight and 1 part of the shredded foil were mixed and added to the deckel box of an apparatus adapted to prepare a hand sheet. The water drained through an mesh screen from the deckel box and the pulp and foil were retained on the screen. The resulting hand sheet and screen are removed from the deckel box, the sheet pressed against and transferred to a sheet of blotting paper and the hand sheet then placed against a polished chromium-plated sheet under a pressure of about 60 pounds per square inch for a sufiicient length of time to remove by capillary action the majority of the Water available to the blotting paper. The sheet of blotting paper is removed and replaced with /2 inch thick felt. The feltpaper-plated sheet sandwich is placed in a platen press between closed platens for a period of 4 minutes and heated to reduce the water content of the sheet to about an equilibrium value at room temperature. The resultant sheet showed a plurality of fibers dispersed on and about the surface which had an attractive iridescent appearance and on movement of the sheet, the fibers appeared to change color and appear and disappear. Flexing of the sheet would not dislodge the iridescent film particles and the attractive appearance was maintained.
In a manner generally similar to the foregoing procedure, a hand sheet was prepared employing equal parts of pulp and iridescent film with the exception that a portion of the pulp was deposited on the screen before the addition of the iridescent film particles to the deckel box. This resulted in a sheet having iridescent film deposited on one side rather than on both sides as in the previously-described procedure. The paper showed a considerably greater iridescent effect. A hand sheet was prepared employing a black pulp employing weight percent iridescent film and a startlingly attractive iridescent sheet was obtained.
Repetition of the foregoing procedures utilizing iridescent film in the form of filaments about of an inch in width and about 1 inch in length, film in squares of about 1 of an inch per side and discs of about /8 inch in diameter also result in attractive and eye-catching iridescent paper. Similar beneficial results are obtained when a pulp is replaced with cotton fibers, fur, asbestos, glass and the like. Excellent iridescence is also achieved when laminates are prepared of such materials as polyvinylchloride-polystyrene, polystyrene-polyethylene, polypropylene-polystyrene, ethyl cellulose-styrene, polychlorotrifluoroethylene polypropylene, polyvinylidenefluoridepoly-u-methylstyrene, polybutyl acrylate-polydichlorostyrene, polybutyl acrylate-polyvinylchloride, polymethyl methacrylate-polycarbonate, cellulose acetate- -butyrate-copolymer of 70 parts by Weight styrene and 30 parts by weight acrylonitrile, polyformaldehyde-high density polyethylene, polyisobutyl methacrylate-copolymer of 85 parts by weight vinyl chloride and parts by weight vinylidene chloride, cellulose nitrate-polystyrene, cellulose acetate-copolymer of 85 parts by weight vinylidene chloride and 15 parts by weight vinyl chloride, polytetrafluoroethylene-polyisobutylene, polyvinyl chloroacetatepolyvinyl acetate, propyl methacrylate-neoprene, perbunan-fiuorinated ethylenepropylene copolymer, nylonpolyvinylidenefiuoride and the like are employed to form the iridescent film.
As is apparent from the foregoing specification, the article of the present invention is susceptible of being embodied with various modifications and alterations which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto appended claims.
What is claimed is:
1. A paper having intimately incorporated therein a plurality of thermoplastic resinous elements, the resinous elements comprising a thermoplastic resinous body composed of a plurality of generally parallel layers of transparent thermoplastic resinous material wherein at least about 20 percent of the layers have a thickness of between about 0.05 micron and about 5 microns and adjacent layers differ in refractive index from each other by at least 0.03, the body exhibiting an iridescent character.
2. The paper of claim 1 wherein the thermoplastic resinous elements have a thickness of up to about 10 mils and contain at least 10 layers.
3. The paper of claim 1 wherein the thermoplastic resinous body has at least layers and a thickness of up to about 2 mils.
4. The paper of claim 1 wherein the bodies are elongated fibers.
5. The paper of claim 1 wherein the paper is black.
6. The paper of claim 1 wherein the paper is white.
References Cited UNITED STATES PATENTS 1,675,642 7/1928 CleWell. 2,480,751 8/ 1949 Marks. 2,949,398 8/1960 Bolyard 162*l8l DONALL H. SYLVESTER, Primary Examiner. A. C. HODGSON, Assistant Examiner.
US. Cl. X.R.