MXPA05013158A - Nonwoven fabric printing medium and method of production - Google Patents

Abstract

A nonwoven fabric printing medium comprises a first nonwoven fabric layer formed of thermoplastic polymer continuous filaments and at least one additional nonwoven fabric layer bonded to the first nonwoven fabric layer to form an integral unitary composite sheet material. The first nonwoven fabric layer has an outer surface adapted to receive printingink, and the nonwoven fabric printing medium has a porosity of no more than 75 CFM pursuant to ASTM D-737-80, and in a preferred embodiment no more than 25 CFM. The first nonwoven fabric layer includes a thermoplastic polymer binder bonding together the thermoplastic polymer continuous filaments and also bonding the first nonwoven fabric layer to the one or more additional nonwoven fabric layers.

Description

PRINTING MEDIA FOR NON-WOVEN FABRICS AND PRODUCTION METHOD FIELD OF THE INVENTION The present invention relates to non-woven fabrics suitable for use as a means for printing. More specifically, the present invention relates to non-woven fabrics suitable for printing with inkjet printers or by other conventional printing processes.

BACKGROUND OF THE INVENTION Although paper is possibly the most used medium for printing, there are many applications where paper can not be used due to its lack of strength, impermeability, resistance to inclement weather, lasting quality or other physical properties. For example, outdoor signage or banners should be able to withstand weather elements such as wind, rain, cold and exposure to ultraviolet light. For these applications, different alternative printing media have been developed, such as woven fabrics, films and nonwoven fabrics coated with vinyl. For example, DuPont markets its Tyvek non-woven fabric for graphic design and printing applications. Tyvek is a non-woven flash spun fabric made from very thin high density polyethylene fibers bonded by heat and pressure. Because polyethylene has a relatively low melting point, Tyvek is not recommended for printing processes involving temperatures of more than about 79.4 ° C. The use of non-woven fabrics as a printing medium has been proposed in different prior patent documents, such as, for example, the patents of E.U.A. No. 5,240,767 and 5,853,861. However, little attention is paid to the structural and physical properties of the non-woven fabric required to convert the fabric into a commercially acceptable printing substrate. One of the problems inherent in the manufacture of non-woven fabrics by conventional manufacturing methods is that the deposition of fibers can be irregular or variable, producing thick and thin spots or other variations of the base weight that make the material unattractive or inappropriate to be used as a printing medium. As a result, very few non-woven fabrics have had commercial acceptance as a printing medium. The present invention addresses the problem of providing a non-woven fabric with a sufficiently uniform thickness and basis weight and sufficient structural properties to be suitable for use in various commercial printing operations, such as, for example, inkjet printing and laser printing, as well as as the more traditional printing technologies such as flexography, lithography, printing typography, gravure and offset.

BRIEF DESCRIPTION OF THE INVENTION The nonwoven fabric printing medium of the present invention comprises a first nonwoven fabric layer formed of continuous filaments of thermoplastic polymer and at least one additional layer of nonwoven fabric bonded to the first nonwoven fabric layer to form a nonwoven fabric layer. Laminar material integral unitary compound. The first non-woven fabric layer has a calendered surface adapted to receive printing ink, and a non-woven fabric printing medium has a porosity of not more than 75 CFM in accordance with ASTM D-737-80, and in a preferred no more than 25 CFM. The first layer of non-woven fabric includes a binder of thermoplastic polymer joining the continuous filaments of thermoplastic polymer and also the first layer of non-woven fabric with one or more additional layers of non-woven fabric. In an advantageous embodiment, the continuous filaments of the first layer have a cross section of three lobes and formed from polyester. In a specific embodiment, the first layer of non-woven fabric comprises a continuous fiber nonwoven formed from continuous polyester homopolymer matrix filaments of a three-lobed cross section, and a fibrous binder of a low melt polyester copolymer joining the continuous matrix filaments, and at least one additional nonwoven fabric layer of the composite comprises a second continuous fiber nonwoven fabric bonded to said fabric, being formed this second continuous fiber web from continuous polyester homopolymer matrix filaments of a three-lobed cross section, and a fibrous binder of a low melt polyester copolymer joining the continuous matrix filaments.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description of the invention and the drawings in which: Figure 1 is a schematic illustration of an enlarged cross-sectional view of an example of a means of printing formed in accordance with the invention and Figure 2 is a schematic illustration of an example of a method for manufacturing printing means of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in greater detail with reference to the accompanying drawings in which some but not all embodiments of the invention are shown. In fact, the invention can be realized in several different forms and should not be understood as limited to the modalities described therein; rather, these modalities are provided in such a way that this description complies with the applicable legal requirements. Equal numbers refer to the same elements throughout the document. An example of a printing medium in accordance with the present invention is shown in Figure 1. The medium 10 comprises a composite nonwoven fabric that includes at least two layers of non-woven fabric that have been bonded together in a non-woven fabric. opposite face to face relationship. Although it refers to the composite medium as including "layers", this term is used only to facilitate the description with respect to the different compositions and / or constructions that may be present in various regions within the printing medium. The medium, although referred to as being formed from such "layers", provides a unitary structure exhibiting cohesive properties throughout its thickness. Preferably, the first layer 16 of the non-woven fabric is a non-woven filament fabric formed from a plurality of continuous thermoplastic polymer filaments. More particularly, the filament fabric typically includes from about 80 to 100% by weight of continuous thermoplastic polymer filaments. As used herein, the terms "filament" and "continuous filament" are used in a generic sense to refer to fibrous materials of an indefinite or extreme length, such as a length of several tens of centimeters or more. As is well known, non-woven filament fabrics are manufactured by extruding a thermoplastic fiber-forming polymer through a spinner having a large number of orifices to form filaments, pulling or attenuating polymer filaments extruded mechanically or with a jet. of high speed air, depositing the filaments randomly on a collection surface to form a network, and joining the filaments to form a strong coherent fabric. The title of the filaments within the first layer 16, expressed in denier per filament ("dpf), typically ranges from about 1 to 10 dpf, such as about 4 to 6 dpf.In certain preferred embodiments, the thermowelded filaments within the first layer 16 has a fineness of about 4 dpf, particularly 4 dpf fibers with a three-lobed cross-sectional shape In alternative embodiments, the thermowelded filaments may have a denier combination The continuous filaments within the first heat-sealed layer 16 may formed from any thermoplastic fiber-forming polymer that provides acceptable mechanical properties and chemical resistance For example, continuous polymeric filaments can be formed from polyester homopolymers and / or copolymers, or from polyamide homopolymers and / or copolymers or mixtures of them An example of polyester is polyethylene terephthalate. Examples of polyamides include nylon 6 and nylon 6,6. In specific advantageous embodiments of the invention, the continuous filaments within the first layer 16 are formed from polyethylene terephthalate. The filaments may additionally include conventional additives as stabilizers, UV inhibitors, pigments, bleaches, delustrants, optical brighteners and the like. The first layer 16 can be formed from thermowelded continuous filaments of various cross sections, including three, four, five lobes, circular shape, elliptical and dumbbell shape. Either a single cross section or a mixture of filaments of different cross sections may be included within the first layer 16. In the preferred embodiments of the invention, the first layer 16 is formed from heat-sealed filaments having a cross-section of three lobes. The three-lobed cross section of the filaments increases the definition of the print by providing a base of material that appears to absorb the light instead of reflecting it to produce a shiny appearance. The three-lobed filament also increases the capture of inks and receptive coatings to ink. The Applicant has found that thermowelded layers having fairly uniform structures can provide an unexpectedly smooth surface for a synthetic printing medium, especially when calendering by heated calender rolls. The fabric can be provided with a completely smooth surface using smooth calender rolls, or with a uniform textured surface that simulates canvas or other fabric using stamped calender rolls. Examples of bulk densities for the first layer 16 before calendering generally range from about 0.100 g / cc to 0.250 g / cc, such as bulk densities ranging from about 0.100 g / cc to 0.150 g / cc. In order to provide adequate intralaminar resistance within the first layer 16, the continuous filaments within the first heat-sealed layer 16 are joined together at contact points. Although the continuous filaments within the first heat-sealed layer 16 are joined, the non-woven structure remains flexible and sufficiently porous to provide beneficial properties of the ink transport. The junction within the first layer 16 can be achieved thermally or by ultrasonic energy, as for example by melting thermoplastic binder filaments, joining thermoplastic resins, etc. The joint may extend throughout the structure of the non-woven fabric (known as "area bonding") which is preferred when a uniformly smooth outer printing surface is desired, or the bonding may be performed in discrete areas (typically referred to as "bonding"). points ") that can provide a beneficial textured appearance for the printing surface. In specific advantageous embodiments, the first layer 16 is bound by a fibrous binder. The fibrous binder may be included within the first layer 16 during the manufacturing process as continuous filaments of binder in an amount effective to induce a suitable level of binding.

Typically, the binder is present in the first layer 16 in an amount ranging from 2 to 20 weight percent, as an amount of about 10 weight percent. In alternative aspects of the invention, the thermowelded filaments within the first layer 16 can be multi-constituent fibers including a thermoplastic binder polymer as a component. For example, in such alternative embodiments, the thermowelded filaments may have a layer / core configuration wherein the layer is formed from a binder polymer. The binder filaments used in the first layer 16 are generally formed from a polymer that exhibits a melting or softening temperature of at least about 10 ° C less than the continuous filaments. All binder filaments may be formed from the same polymer or may include a mixture of lower or higher melt binder filaments. For example, the binder filaments may include a mixture of filaments, a first portion of which may have a lower melting temperature, such as about 107.2 ° C, and a second portion of which has a higher melting temperature, as approximately 190.5 ° C. Examples of binder filaments can be formed from one or more lower melt polymers or copolymers, such as polyester copolymers. In an advantageous embodiment of the invention, the thermowelded layer is produced by extruding polyester homopolymer matrix (polyethylene terephthalate) matrix filaments interspersed with binder filaments formed from a lower melting polyester copolymer, such as polyethylene isophthalate. It will be understood that during the manufacturing process, when the higher melting continuous matrix filaments of the first layer 16 join to form a coherent layer, the lower melting binder filaments typically soften and flow to join the matrix filaments in crossed points, and subsequently may not necessarily be easily identifiable as continuous binder filaments. To provide a greater uniformity of basis weight and thickness, the first layer 16 is laminated to at least one additional non-woven layer thereof or a different construction. The lamination of two or more layers reduces the non-uniformity effect of the basis weight in the individual layers. In the embodiment shown in Figure 1, a second non-woven layer 17 joins the first layer 16, with the second layer forming the rear surface of the composite medium 10. In the embodiment illustrated in Figure 1, both the first layer 16 as the second layer 17 are the non-woven fabrics of filaments formed from continuous filaments. In other embodiments, the composite support 10 may include three, four or more heat-welded non-woven layers laminated with one another. In still other embodiments, one or more intermediate non-woven layers of another non-woven construction, such as an air-laid non-woven, a carded non-woven, a non-woven or a wet-laid non-woven fabric may be incorporated into the composite. For embodiments that include at least two thermowelded layers, the fibers and materials comprising the respective thermowelded layers may be the same or different. For example, the thermowelded layers may have different composition, denier, basis weight or cross section of the fiber. In the embodiment shown, the second layer 18 is also a non-woven filament fabric formed from a plurality of substantially continuous thermoplastic polyester filaments including higher melting matrix filaments and a lower melt binder. The binder filaments provided in the second layer 18 are generally formed from a polymer that exhibits a melting or softening temperature of at least about 10 ° C lower than the matrix filaments. All binder filaments may be formed from the same polymer or may include a mixture of lower and higher melt binder filament compositions. For example, the binder filaments may include a mixture of filaments, a first portion of which has a lower melting temperature, such as about 107.2 ° C, and a second portion of which has a higher melting temperature, such as 190.5. ° C. Examples of binder filaments can be formed from one or more low melt polyolefin polymers or copolymers, one or more low melt polyester polymers or copolymers or mixtures thereof. In an advantageous embodiment of the invention, the binder filaments are formed from a low melt polyester copolymer, particularly a polyethylene isophthalate copolymer, and the matrix filaments are formed from a polyethylene terephthalate homopolymer.

The binder filaments used in the production of the second layer 18 can have any cross section that is known in the art. In the preferred embodiments, the binder filaments of the second layer 18 have a circular cross section as initially formed. The binder filaments may have a denier or denier combination consistent with that known in the art for bonding non-woven fabrics. An important property of the printing medium 10 is its basis weight. For the desirable operation in automatic feeding printers, the printing medium must have a basis weight of at least about 102 grams per square meter. Preferably, the printing medium has a basis weight of 102 to 407 grams per square meter. Particularly suitable are fabrics with a basis weight of 102 to 136 grams per square meter. The higher weights can be used successfully in applications where a more rigid sheet material is desired. The composite printing medium 10 is quite strong and resistant to traction. The printing medium is characterized by having a resistance to grip both in machine direction (MD) and cross direction (XD, for its acronym in English) of at least 45.4 kilograms, preferably by at least 54.4 kilograms, and for heavier base weights more than 90 kilograms. The tensile properties representative of two different weights of the uncoated printing medium according to the present invention are given in Table 1.

TABLE 1 Grip resistance is the force required to lengthen and break a sample previously cut on a tensile testing machine, such as an Instron® machine. Samples are analyzed from machine direction (MD) and cross direction (XD) in accordance with ASTM standard test method 4632-96. The basis weight is measured in accordance with ASTM D2776-96. Another important property that affects the suitability of the substrate is represented by the ink transport properties. It is desirable that the ink penetrate a part of the medium, but not too much so that the ink does not migrate to the interior of the network producing dull colors. Therefore, a certain degree of porosity is required in the medium. The porosity of the medium can be measured by standard air permeability measurements that determine the air flow through a given area of the network at a given pressure. The ASTMD-737-80 standard test method can be used for this purpose. Preferably, the medium has an air porosity of not more than 75 CFM as measured by ASTM D-737-80, and most preferably not more than 50 CFM. The preferred air permeability is between 5 and 25 CFM. The composite printing medium 10 of the present invention has particularly advantageous durability properties since it can be formed completely from relatively inert polymers and without the presence of wood pulp or other reactive or degradable materials. The printing medium is light and flexible and, in comparison with the paper, it resists wrinkling even after folding. It can also withstand repeated folding and unfolding without wrinkling, tearing or losing tensile strength. In addition, it can be entirely composed of inherently hydrophobic synthetic polymers so that the printing medium is not sensitive to exposure to water or high humidity environments. The unit structure with continuous filaments of the printing medium guarantees a clean, lint-free material that can be used in applications such as clean rooms where particles transported by air must be avoided. The printing medium resists curling and wrinkling and forms clean edges without tangling and fraying. It can be stuck, sewn, punched, stapled or nailed without losing strength. Figure 2 illustrates a suitable method and apparatus for producing the composite printing medium 10 of the present invention. Two thermo-welded non-woven networks 1618 are unwound from respective rolls 84 and 86 are joined in an opposite relation superimposed face to face. The superposed layers 88 are subsequently driven longitudinally through a first inlet 90. Within the first inlet 90, the low melt copolymer binder present in the first thermowelded fabric layer 16 and the copolymer binder present in the second one are heated. layer at the point at which the binder begins to soften and melt to adhere one layer to the other without the need for any additional adhesive or binder. The first inlet 90 is constructed in a conventional manner as is known to the person skilled in the art. In the embodiment illustrated in FIG. 2, the first inlet 90 is defined by a pair of coordinated calender rolls 94 and 96 which are preferably smooth and conveniently formed of steel. The coordinated calender rolls 94 and 96 preferably provide a fixed space entry. The fixed space entry ensures that the superimposed layers 88 do not exit the first inlet 90 with a thickness less than the thickness of the target space, independently of an excessive pressure that may be applied. In the advantageous embodiment illustrated in 2, the pressure is applied to the first inlet 90 using the upper roller 97. The bonding conditions, including the temperature and pressure of the first inlet 90, are known in the art for different polymers. For composite printing media comprising thermo-welded polyethylene isophthalate nonwoven filaments and also including polyethylene isophthalate filaments and / or binder fibers, the first inlet 90 is preferably heated to a temperature between about 120 ° C and 230 ° C, preferably from about 200 to 225 ° C. The first inlet 90 is typically operated at pressures between about 714.31 kg / m to 6250.26 kg / m (kilogram / meter), such as about 1428.63 to 3571.58 kg / m. In an alternative embodiment, which is shown by dashed lines, the two superposed layers 88 may be placed around an additional roller, v. g. passing over the upper roller 97 and then through the inlet defined between the rollers 97 and 94 which is subsequently heated to a temperature of about 200 ° C before passing through the inlet 90 between the rollers 94,96. Passing the superimposed networks 88 on the additional heated roller 97 before the calender rollers 94.96 preheats the superposed layers 88 before they enter the inlet 90. This preheating facilitates higher joining speeds. Now returning to Figure 2, the superposed layers coming out of the first inlet 90 subsequently enter a second inlet 98. The second inlet 98 is formed by a top roll 96 and a bottom roll 104. The rolls 96 and 104 are, preference, steel. The pressure within the second inlet 98 is typically higher than the pressure in the first inlet 90, further compressing the superposed layers exiting the first inlet 90. Accordingly, the space formed by the second inlet 98 is narrower than the space provided by the first inlet 90. The pressure in the second inlet 98 is typically from about 2142.94 to 19643.69 kg / m, such as from about 3214.42 to 5714.52 kg / m. The second inlet 98 can be further heated, for example to a temperature of about 120 to 230 ° C, preferably of about 200 ° C to 225 ° C. Due to the presence of the thermoplastic copolymer binder in the layers, the two layers 16, 18 are joined together to form a coherent, unitary, integral composite nonwoven without requiring additional adhesive compositions. The resulting joined composite support 14 exiting the second inlet 98 can be transported through a cooling roller 106 and Rolled with conventional means on a roller 112. The composite printing medium 10 can be used in a calendered uncoated state or it can be provided with an ink receptive coating on one or both surfaces. The coating can be applied before or after calendering or in both situations. Suitable coatings include the types of coating compositions that are conventionally used in the production of coated paper. Such coating compositions have, typically, an aqueous or otherwise solvent-based binder and may include pigments and fillers such as silica, calcium carbonate, kaolin, calcined kaolin, clay, titanium oxide, aluminum silicate, magnesium silicate, magnesium carbonate, oxide magnesium, zinc oxides, tin oxides, zinc hydroxide, aluminum oxide, aluminum hydroxide, talc, barium sulfate and calcium silicate, boehmite, pseudo-boehmite, diatomaceous earth, styrene plastic pigments, plastic pigments of urea resin and benzoguanamine plastic pigments. Examples of binders include polyvinyl alcohol, styrene-butadiene polymers, acrylic polymers, styrene-acrylic polymers and polymers of vinylacetate and ethylene vinyl acetate. Commercially available examples of such binders include acrylic polymers such as RHOPLEX B-15 and RHOPLEX P-376, and vinyl acetate / acrylic polymers such as Polyco 2152 and Polyco 3250, all manufactured by Rohm and Haas Company, and styrene / butadiene polymers such as CP 620 manufactured by the Dow Chemical Company. The coating composition may further include additives, such as flame retardants, optical brighteners, water resistant agents, antimicrobials, stabilizers and UV absorbers and the like. The coating composition can be tailored to the particular printing technology that is intended to be used in the printing operation. Therefore, a printing medium intended for inkjet printing can, for example, be provided with a coating responsive to dyes or pigments based on solvent or water used in the ink jet process, while a means for the laser print would have a coating receptive to the toner used in laser printing. Suitable coating compositions of this type are commercially available from a variety of dispensers and an appropriate coating formulation for a specific end-use printing application can be obtained easily. When the printing medium is intended for high resolution images, such as photographs, the surface is preferably calendered with a smooth calender roller to obtain a surface roughness Rz of not more than 10 μm, and preferably no more than 5 μm. As is well known, the surface roughness parameter Rz represents the average of 5 Rmax values, where Rmax represents the highest peak-to-valley height at any of the 5 sampling lengths. The surface roughness parameter Rz can be easily measured with commercially available surface roughness testers, such as those available from Qualitest International Inc. or Edmund Optics, for example. The following examples are provided for purposes of further illustrating the specific embodiments of the invention. However, it should be understood that the invention is not limited to the specific details that are provided in the examples.

EXAMPLE 1 A printing medium was prepared by combining three times 33.9 grams per square meter of thermo-welded non-woven fabric produced by BBA Nonwovens under the name Reemay Elite, each consisting of extruded polyethylene terephthalate homopolymer filaments with polyethylene isophthalate copolymer binder filaments and subsequently thermally bonded. The three layers were thermally laminated with one another as they were passed through a heated calender. The polyethylene isophthalate copolymer present in the layers was activated by the heated calender and used to bond the layers in a coherent unitary fabric. The resulting composite was so uniform that it was previewed as a possible printing medium for inkjet printers. The experiments were performed with a HP high-resolution inkjet printer that was used in connection with a personal computer. When the calendered thermal lamination was fed through the printer with a high resolution configuration, the results were very surprising. The sharpness of the print was comparable to photo paper for HP Premium Plus inkjet printers, but the calendered nature of the non-woven web provided a pleasing look similar to canvas or textured fabrics to the printed page. The added benefit was that the resulting printed image on the calendered heat-sealed printing medium was a very flexible sheet compared to HP photo paper that was very rigid.

EXAMPLE 2 Although the impression on the calendered polyester thermowelded fabric of Example 1 is quite acceptable and shows good color and detail, the long-term receptivity and stability of the polyester to the conventional inkjet coating can be increased by applying a coating receptive to the ink injection in the middle. These coating compositions are typically pigment dispersions in a polymeric binder comprising polyvinyl alcohol, vinylacetate copolymers or other polymers and copolymers. To verify that the inkjet receptive coatings were compatible and usable, several levels of sheet coating of the calendered nonwoven fabric of Example 1 were applied. Two coatings were evaluated: Bezel 2006 and 2007 manufactured by Bercen Inc., 1381 Cranston Street, Cranston, Rhode Island. The coating compounds were applied at levels between 3.3 kg / ream (306.6 m2) and 7.9 kg / ream (~ 25 gsm / square meter). Also, another coating composition was evaluated from Sun Process Converting Inc., 1660 Kenneth Drive, Mt. Prospect, IL. When the coated media was passed through an HP CP 1160 and HP 7150 printer configured for the best print quality, image quality, color definition and vividness of color was comparable or better than the best photographic paper in the world. HP, Premium Plus Photo Paper. No dripping or color migration was observed. The printing medium has wide application as a printing medium for a variety of printing applications including small format inkjet printing, large format commercial inkjet printing; consumer inkjet printing (typically linked to personal printers), screen printing; flexographic printing, lithography, offset printing, typography and gravure printing. Due to its excellent resistance to high temperatures, it can be used as a printing medium in black and white and color laser printers using high temperature melting rollers. The printing medium is excellent for photographic prints and other applications where high resolution is required. The printing medium is suitable for the type of printing made by sterile packaging manufacturers where high resolution printing is required in a high strength flexible packaging material. Tests comparing the uncoated calendered product of the present invention with uncoated Tyvek show further refinement on the Tyvek. Typical Tyvek inkjet printing shows a shadow around the images when the color migrated, whereas this does not occur with the printing medium of the present invention.

Claims (21)

NOVELTY OF THE INVENTION CLAIMS

1. - A nonwoven fabric printing medium comprising a first layer of heat-welded nonwoven fabric comprising continuous filaments of thermoplastic polymer matrix with a cross section of three lobes and a binder of a lower melting thermoplastic polymer joining the filaments continuous of matrix, said first layer of non-woven fabric has an outer surface adapted to receive printing ink and at least one additional layer of non-woven fabric bonded with said first layer of non-woven fabric to form an integral unitary composite laminar material, wherein said non-woven fabric layer, at least one, comprises a second heat-welded non-woven fabric bonded with said first fabric, said second heat-sealed fabric comprises continuous filaments of thermoplastic polymer matrix with a cross-section of three lobes and a binder of a lower melting thermoplastic polymer that bonds the continuous filaments of matri z, and wherein the same thermoplastic binder also attaches said first layer of non-woven fabric with the additional polymeric binder, at least one, the non-woven fabric printing medium has a porosity of not more than 75 CFM in accordance with ASTM. D-737-80.

2. - The printing medium according to claim 1, further characterized in that the porosity of the printing medium is not more than 25 CFM in accordance with ASTM D-737-80.

3. The printing medium according to claim 1, further characterized in that said binder of thermoplastic polymer initially has fibrous form.

4. The printing medium according to claim 1, further characterized in that the continuous filaments of thermoplastic polymer are formed from polyester.

5. The printing medium according to claim 4, further characterized in that said thermoplastic polymer binder comprises a polyester copolymer with a lower melting temperature than the polyester polymer of said continuous filaments.

6. The printing medium according to claim 1, further characterized in that said outer surface is a smooth calendered surface with a surface roughness Rz of not more than 10 / μm.

7. The printing medium according to claim 1, further characterized in that the filaments of said heat-sealed layer are from about 1 to 10 denier per filament.

8. The printing medium according to claim 1, further characterized in that the general basis weight is at least 102 grams per square meter.

9. - The printing medium according to claim 1, further characterized in that it comprises a coating of an ink-receptive composition on said outer surface.

10. The printing medium according to claim 1, further characterized in that it has a resistance to grip on both CD and XD of at least 54.36 kg.

11. A nonwoven fabric printing medium comprising: a first layer of non-woven fabric having a calendered outer surface adapted to receive printing ink, and continuous filaments of polyester homopolymer matrix with a cross section of three lobes and a fibrous binder of a lower melting polyester copolymer bonding the continuous matrix filaments, and a second nonwoven fabric layer bonded with said first nonwoven fabric layer and comprising a thermowelded nonwoven formed from filaments of a polyester homopolymer matrix with a three-lobe cross section and a fibrous binder of a lower melting polyester copolymer joining the continuous filaments of a nonwoven fabric second layer matrix, and characterized in that the copolymer binder present in the first and second layers it also joins the first layer with the second, and said printing means has a to porosity of not more than 25 CFM in accordance with ASTM D-737-80.

12. - The printing medium according to claim 11, further characterized in that the layers of non-woven fabric thereof are formed entirely of polyester.

13. The printing medium according to claim 11, further characterized in that it includes a coating of an ink-receptive composition on said calendered outer surface.

14. The printing medium according to claim 11, further characterized in that the first and second layers of non-woven fabric are bonded directly to one another by said binder filaments of the lower melting polyester copolymer.

15. The printing medium according to claim 11, further characterized in that it additionally includes at least one intermediate layer of non-woven fabric disposed between said first and second non-woven fabric layers and bonded thereto.

16. A non-woven fabric printing medium comprising: a first layer of non-woven fabric with an outer surface with a surface roughness Rz of not more than 10 μm, said first layer of non-woven fabric being formed from filaments continuous polyethylene terephthalate homopolymer matrix of about 1 to 10 denier per filament and a fibrous binder of a lower melt polyethylene isophthalate copolymer bonding the continuous matrix filaments, a second nonwoven fabric layer bonded to said first layer of non-woven fabric and formed from continuous filaments of polyethylene terephthalate homopolymer matrix and a fibrous binder of a lower melt polyethylene isophthalate copolymer joining the continuous matrix filaments of the second non-woven fabric layer woven, and characterized in that the polyethylene isophthalate copolymer binder present in the first and second layers also bonds the first and second with each other, and the printing medium has a basis weight of 105 to 420 grams per square meter and a porosity of not more than 25 CFM in accordance with ASTM D-737-80.

17. A method of producing a printing medium comprising the formation of a first layer of non-woven fabric of continuous filaments of thermoplastic polymer matrix with a cross section of three lobes and a binder of lower melting polymer joining the continuous filaments of matrix; the formation of a second non-woven fabric layer of continuous filaments of thermoplastic polymer matrix with a three-lobe cross section and a lower melting polymer binder that joins the continuous matrix filaments; driving said first and second nonwoven fabric layers in a superposed relationship with respect to each other; the joining of said first and second layers in an opposite face-to-face relationship to form a composite non-woven fabric by heating the respective fabric layers so that the polymer binder present in the first and second layers softens to melt and bond the layers each; and the calendering of the exposed outer surface of said first layer of non-woven fabric to form a calendered outer surface adapted to receive printing ink, the printing medium having a porosity of not more than 75 CFM in accordance with ASTM D-737- 80

18. The method according to claim 17, further characterized in that said joining step comprises transporting the printing medium through an entrance between a pair of coordinated calendar rolls.

19. The method according to claim 18, further characterized in that said joint further comprises the transport of the printing medium through a second entry between a second pair of coordinated calendar rolls, said second entry exerts a greater pressure than the first entry.

20. The method according to claim 19, further characterized in that the space within the second entry is narrower than the space within the first entry.

21. The method according to claim 17, further characterized in that it includes the step of applying an ink-receptive coating on the outer surface of said first layer of non-woven fabric.