Method of making embossing rolls

Abstract: An embossing roll (32) is formed by a process which includes moulding a seamless embossing roll (32) within a seamless sleeve (16). The sleeve has indicia disposed about the inner circumference and which is the reverse moulded into the roll. The sleeve (16) is unprinted on the outside, hardened and turned inside out, or moulded from an imprinted roller (8).

Description: This invention relates to the art of embossing and particularly to the formation of embossing cylinders (embossing rolls). Films are frequently provided with decorative indicia by an embossing process in which the film is passed between a pressure roll and an embossing roll to receive the indicia. These films may be of any of numerous polymeric materials including, for example, polyolefins, linear polyesters, polyamides and poly(vinyl chloride). Additionally the films may optionally be provided with a suitable backing such as, for example, a reinforcing mesh backing of glass fibers or polymeric fibers such as poly(ethylene terephthlate). The backing may be of the woven or the non-woven type. Methods of manufacturing such films are well known in the art. One specific field where such embossed films are produced is the manufacture of wallcoverings. There is a need in the art to provide a process for manufacturing embossing cylinders (rolls) in a more economical manner. There is also a need in the art for manufacturing rolls which are capable of providing embossed, more aesthetically pleasing ornamentation on films without the occurrence of seams. Additionally, in providing a process for manufacturing embossing rolls, there is a need to involve the skilled artist into the manufacturing process to provide the decorative indicia for the rolls, and thereby, provide the opportunity for the innovative creation of a wide variety of ornamental patterns and designs. Presently, one technique for manufacturing embossing rolls is an electroforming process in which a segmented sleeve is formed. This segmented sleeve provides for the occurrence of seams which is aesthetically undesirable. This is also an expensive and time consuming process and it removes the artist from the process of forming the embossing cylinder. US-A-4,634,484 is directed to embossing rollers and forms a sleeve which is positioned around a core and used as the embossing medium. This sleeve is made by a time consuming multi-step process which is costly. In accordance with this process, a design on a roller is coated with a silicone rubber to form an annular member having indicia disposed internally. This sleeve is then turned inside-out and used as an embossing medium to emboss the external surface of a tube of thermoplastic film. The tube of embossed thermoplastic film is then in turn coated with a silicone rubber to form another annular or cylindrical sleeve member which is then vulcanized and turned inside-out. After being turned inside-out the sleeve is drawn over a core roller coated with an adhesion promoter and a silicone adhesive. The adhesive is then hardened and the composite roller is used as an embossing roller in a device for the continuous embossing of a thermoplastic rectilinear film. Obviously, this is a labor and capital intensive process. Moreover, since the embossing roll is a composite, as opposed to a unitary roll in which the embossing indicia is integral and unitary with the external surface of roll, there is a danger of slippage of the sleeve along the underlying surface which can seriously adversely impact production quality and efficiency. US-A-4,551,297 also discloses the formation of a composite embossing or decorating cylinder which includes a silicone sleeve member which bears indicia to be embossed onto a film and is adhered to the surface of a cylindrical core. Both of the above specific patents, furthermore, are essentially directed at duplicating a leather grain. WO-A-91/01225 (on which the two-part form of present claim 1 is based) describes making an embossing cylinder by forming an initial pattern on a master roller having a soft metal (Al or Sn) drum surface which is patterned by indentation using hard metal imprinting elements. A hollow, internally-patterned sleeve is made by casting around the master roller, and then used as an intermediate mould to pattern the surface of a relatively soft resilient material on a mandrel to give the desired embossing cylinder. Our general aim herein is to provide new and useful ways of making embossing cylinders with the particular goal of facilitating design freedom for the artist creating the pattern. A preferred aim is to provide indicia integrally on the surface of an embossing cylinder without the need for adhering a patterned sleeve on a support mandrel. Accordingly we provide a method of making an embossing cylinder having decorative surface indicia for embossing onto film material, comprising forming a seamless sleeve having said indicia patterned in reverse on its internal surface, and moulding the embossing cylinder within said seamless sleeve so as to form the desired indicia on the embossing cylinder's circumference; characterised in that the seamless sleeve is formed by (a) modelling corresponding indicia into the outer surface of a seamless cylinder of hardenable or settable imprintable material which is then hardened or set, and then (b) turning the modelled cylinder inside-out to constitute the seamless sleeve, or (c) forming the seamless sleeve by moulding it against the outer surface of the modelled cylinder of imprintable material. Optional/preferred features are set out in the sub-claims. The indicia may be positive (raised or impastoed as in a letter press) or negative (recessed as for a gravure printing surface). For example, modelling of recessed indicia into the imprintable material creates impastoed indicia on the seamless sleeve. The imprintable material may be hardened or set by heating. The embossing cylinder may be moulded by putting curable liquid organic resin into the sleeve, curing the resin and then removing the sleeve. The embossing cylinder can be used to emboss the indicia onto a polymeric film. Furthermore, a film so embossed may itself serve as a master film for the modelling of corresponding indicia into imprintable material for making further embossing cylinders. Examples and preferred features are now described. Referring to the drawings: Figure 1 schematically illustrates one step in a process embodying the invention; Figure 2 schematically illustrates another step in which indicia are modelled into a cylinder; Figure 3 represents another step in the process showing the formation of a sleeve; Figure 4 represents another step in the process showing the molding of an embossing roll within the formed sleeve; Figure 5 schematically illustrates the use of an embossing roll embodying this invention; Figure 6 illustrates a step in an alternate and preferred embodiment of this invention; Figure 7 represents a further step in a preferred embodiment of this invention; Figure 8 shows a decorating cylinder produced in accordance with this invention. The drawings illustrate various steps in the present method for forming decorating cylinders, or embossing rolls, having indicia which are to be embossed onto a film. Any of a wide variety of films may be so embossed, especially polymeric films like poly(vinyl chloride) and the polyolefins Importantly, the method comprises molding a seamless decorating cylinder within a seamless sleeve which sleeve carries a design along the internal circumference thereof, and hence the reverse form of the design is molded into the external surface of the decorating cylinder. This decorating cylinder is then used in a conventional manner as the embossing medium or roll. Referring now to Figures 1-4, a metal core cylinder 2 carrying a central shaft 4 and opposed flanges 6 is first provided with a sleeve 8 of a hardenable and imprintable material. This imprintable material is in the nature of what is commonly referred to as modelling clay but more accurately is a plastic molding compound. The plastic molding material is formed into a sleeve, or seamless cylinder, 8 within the flanges 6 around core 2 and, by means of a leveling roller 10, is smoothed into a uniform surface. An especially preferred imprintable material for this purpose is a plasticized poly(vinyl chloride) . One such material is the material available from Polyform Products Company as their Super Sculpey product line. The next step in the process, as seen in Figure 2, is to form or model indicia in the outer surface of the imprintable cylindrical member 8. In Figure 2, indicia or pattern 12 is schematically shown to be formed into the imprintable sleeve 8 using a device 14 which is in the form of a roller carrying raised indicia 15. Depending on the nature of the pattern to be formed in the sleeve 8 of modelling material, the indicia 12 may either be recessed or it may be raised, or impastoed. Preferably, the plastic modelling material with the pattern formed in its circumferential externally disposed surface is then heat-hardened. These modelling compounds are preferably of a plasticized poly(vinyl chloride) and have heat-hardening cycles of about 121°C to 163°C (250° to 325°F) for about 5 to about 15 minutes. After the heat-hardening of the hardenable plastic modelling material, a continuous elastic seamless sleeve 16 is formed about the cylindrical sleeve 8 in such a manner that the newly formed sleeve is provided on its internal surface with a reversed form of the indicia 12, initially formed as set forth in Figure 2. These steps are generally best appreciated by reference to Figure 3. Opposed flanges 14 are applied over core 2 outwardly of flanges 6. They have diameters larger than the diameter of the hardened modelling compound of sleeve 8. Within the confines of flanges 14 and around the cylindrical surface of the hardened sleeve 8, an annular or sleeve member 16 is then formed generally in the same manner as was seamless cylinder 8. Seamless sleeve 16 is of a moldable material which likewise can be hardened such as, for example, by heat. This material is resilient and flexible after heating. Silicone rubbers generally are most suitable for this purpose. One such material is Thixotropic POR-A-MOLD (trade mark) prepolymer and S-333TA curative commercially available from the Synair Corp. The materials are used in a ratio of 1:1 (by volume). The mixture hardens and cures at room temperature in 12 to 24 hours. In order to maintain rigidity and stability for molding and during heating of sleeve 16, an outer circumscribing and reinforcing mold 18 such as, for example, plaster of Paris is formed around seamless cylinder sleeve 8. Because of the moldable nature of the material of seamless sleeve 16, the internal surface molds and conforms to the indicia 12. Thus, the indicia formed on the internal surface of sleeve 16 is the reverse form of the indicia in the hardened modelling material of sleeve 8. In Figure 4, this reversed indicia is shown as inwardly extending protuberances 20. After solidifying and hardening the material of sleeve 16, for example by curing at room temperature the elastic sleeve 16 is separated from the assembly illustrated in Figure 3. It is then used to mold the decorating cylinder as generally illustrated in Figure 4. Referring now to Figure 4, it will be seen that seamless sleeve 16 is sealingly supported on opposed step flanges 22 and, again for rigidity and support, disposed about sleeve 16 is a reinforcing and supporting mold structure 24, formed of plaster of Paris. Core rod 26 extends between and through step flanges 22 and includes outer rods 28 which can be used to secure the final embossing roll in a conventional embossing mechanism. Upper step flange 22 has an opening 30 through which the moldable and hardenable material used to form decorating cylinder or embossing roll 32 is added inside sleeve 16. Especially suitable materials for the final embossing roll 32 are cured polyurethanes and cured epoxies with an especially preferred formulation being EPON® 828 epoxy 100 parts manufactured by Shell along with an amine curative (100 parts) sold under the designation Ancamide 260A by Pacific Anchor Chemical Corporation. After the material used to form decoration cylinder 32 is added within the internal confines of sleeve 16 and sufficient time is allowed for the material to mold against the internal surface of sleeve 16, the material is cured. This can be done by heating, for example, at a temperature of 60°C (140°F) for two hours and then at 100°C (212°F) for one hour. The curing also binds the material to core rod 26. External supporting structure 24 and flexible sleeve 16 are then separated from the cured embossing cylinder 32. Figure 5 generally shows the use of embossing roll 32 to provide the embossing indicia 12' onto a polymeric film 36. The embossing is done by passing film 36 through the nip provided by embossing roll 32 and a compression roll 38. Figure 5 also schematically illustrates another embodiment of the invention wherein at least a portion of the film 36 is later employed as a master. In this embodiment, film 36 with indicia 12' is used later to provide the indicia 12 onto the imprintable material of sleeve 8 as set forth in Figure 2. In other words, the material 36 with the indicia 12' is used as a substitute for the device 14 schematically illustrated in Figure 2. As will be apparent from the foregoing, one of the advantages of the present technique is that in providing the indicia 12 into the moldable material, as set forth in Figure 2, an artist is now free to create any ornamental and original pattern as such artist desires. This can be done by the use of a any positive device, or jig, to form recessed indicia of the desired pattern in the surface of sleeve 8 . Figures 6-8 along with Figures 2 & 4 generally schematically illustrate a different embodiment of this invention. In accordance with this embodiment, the molding step generally set forth in Figure 3 is eliminated. In this embodiment, a pattern is first formed on the external portion of the moldable, hardenable, seamless sleeve member as set forth in Figure 2. The sleeve is then hardened as previously described but the material used in this embodiment needs to be more flexible and resilient than the material which can be used in the previous embodiment. After hardening, the sleeve is then turned inside-out and the inside-out sleeve is then used as a mold member into which a moldable, hardenable material which is to be used to form the embossing roll is dispensed and allowed to flow and mold against the inner portion of the sleeve. This molded material is then hardened to produce the embossing roll, namely a seamless cylindrical member having a pattern which is the reverse of the pattern initially formed in the external portion of the moldable, hardenable seamless sleeve member before its hardening and being turned inside-out. More specifically, in this embodiment, the moldable material is formed as a smooth, seamless sleeve 8 about core 2 in the manner described above with regard to Figures 1 & 2. Here, however, as indicated a material is needed which is flexible and resilient after hardening. One preferred material for this embodiment of the invention is a plastic molding material sold under the designation Super Elasticlay by the Polyform Products Co. The next step is to form a pattern in sleeve 8 as by imprinting indicia 12 into at least a portion of the external circumference of the seamless cylindrical sleeve member 8 to provide indicia, in this example, in the form of a recessed pattern. The indicia-bearing, moldable material in the form of the endless, seamless sleeve 8 is then hardened by heating at about 149°C (300°F) for 15 to 30 minutes. As seen in Figure 6, sleeve 8 of the now hardened resilient material bearing recessed indicia 12 is turned inside-out so that the indicia 12 is now disposed on the internal portion of the sleeve. The turned inside-out sleeve is designated 40 in Figure 7. The final embossing roll is formed in the manner explained above with regard to Figure 4 and as generally illustrated in Figure 7. The curable moldable epoxy resin is placed within sleeve 40 outwardly of a core cylinder 26 and extending rods 28. As in the case with the previous embodiment, an outer supporting mold 24 is also provided. The epoxy is allowed to flow into the recesses of indicia 12 to form outwardly extending protuberances 44 on the embossing roll 42. Thereafter the roll is cured as above and the roll used in the manner of Figure 5 to emboss film 36.

Claims: A method of making an embossing cylinder (32) having decorative surface indicia (12) for embossing onto film material, comprising forming a seamless sleeve (16,8) having said indicia (20,12) patterned in reverse on its internal surface, and moulding the embossing cylinder (32) within said seamless sleeve (16,8) so as to form the desired indicia on the embossing cylinder's circumference; characterised in that the seamless sleeve (16,8) is formed by (a) modelling corresponding indicia (12) into the outer surface of a seamless cylinder of hardenable or settable imprintable material (8) which is then hardened or set, and then (b) turning the modelled cylinder inside-out to constitute the seamless sleeve (8), or (c) forming the seamless sleeve (16) by moulding it against the outer surface of the modelled cylinder of imprintable material (8). A process according to claim 1 wherein said modelling of the indicia (12) into the imprintable material's outer surface comprises contacting said outer surface with an object (14) so that the indicia are recessed in said surface, and the resulting indicia on the seamless sleeve (16,8) comprises impastoed indicia. A process of claim 1 or claim 2 wherein the moulding comprises putting a mouldable, liquid curable organic resin in the sleeve (16,8) and in contact with the reversed indicia, curing the resin and removing the sleeve A process according to any one of the preceding claims in which the imprintable material is a heat hardenable or settable material and said hardening or setting thereof is by heating. A process according to any one of the preceding claims further comprising embossing the indicia onto a polymeric film (36) by contacting the film with the embossing cylinder. A process according to any one of the preceding claims, further comprising embossing a film (36) with the indicia by contacting the film with the embossing cylinder (32), and using said embossed film (36) as a master film for the modelling of indicia in step (a) for further embossing cylinders by using the master film (36) as a modelling tool.

Inventors: KILDUNE JOSEPH S, KILDUNE, JOSEPH S.
Applicants: GENCORP INC, GENCORP INC.
Application year: 1993
Main classification: B29D31
IPC codes: B29C59, B29L7, B29C39, B29C67, B29D99