US3898123A

US3898123A - Method for wet print-bonding light-weight wet-formed fibrous webs

Info

Publication number: US3898123A
Application number: US394896A
Authority: US
Inventors: Charles H Phillips; Jay S Shultz; John A Toms
Original assignee: Johnson and Johnson
Current assignee: Johnson and Johnson
Priority date: 1973-09-06
Filing date: 1973-09-06
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05

Abstract

A method of making a light-weight, wet-formed, print-bonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials; (2) transferring the aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet, flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard; (3) removing water from the wet, flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of the wet, flat fibrous sheet; (4) transferring the wet, flat fibrous sheet to nonwoven fabric print-bonding rolls by passage through an open draw wherein the wet, flat fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to the wet, flat fibrous sheet by printbonding rolls employing an etched or engraved printing surface, the aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in the wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring the wet, flat fibrous sheet with the aqueous resin binder applied thereto to a carrier by passage through an open draw wherein the wet, flat fibrous sheet with resin binder applied thereto is conveyed unsupported through an open air gap; and (7) carrying the wet, flat fibrous sheet with resin binder applied thereto through a heated zone having an elevated temperature, whereby the resin binder is dried to bond the fibrous web into a self-sustaining, bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric; and apparatus for carrying out such a method.

Description

United States Patent 1191 Phillips et al.

[ Aug. 5, 1975 1 METHOD FOR WET PRINT-BONDING LIGHT-WEIGHT WET-FORMED FIBROUS WEBS [75] Inventors: Charles H. Phillips; Jay S. Shultz;

John A. Toms, all of Little Rock, Ark.

[73] Assignee: Johnson & Johnson, New

Brunswick, NJ.

22 Filed: Sept. 6, 1973 21 Appl. No.2 394,896

[52] US. Cl. 162/134; 162/164; 162/184; 162/206 [51] Int. Cl. D2lf 11/00; D21h 1/28 [58] Field of Search 162/205, 206, 207, 184, 162/265, 109, 117, 134, 362, 164

[56] References Cited UNITED STATES PATENTS 2,320,883 6/1943 Parkinson 162/265 X 3,009,822 1l/1961 Drelich et al. 162/184 X Primary Examiner-S. Leon Bashore Assistant E.\'uminerRichard V. Fisher [57] ABSTRACT A method of making a light-weight, wet-formed, printbonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials; (2) transferring the aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet, flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard; (3) removing water from the wet, flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of the wet, flat fibrous sheet; (4) transferring the wet, fiat fibrous sheet to nonwoven fabric print-bonding rolls by passage through an open draw wherein the wet, flat fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to the wet, flat fibrous sheet by print-bonding rolls employing an etched or engraved printing surface, the aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in the wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring the wet, flat fibrous sheet with the aqueous resin binder applied thereto to a carrier by passage through an open draw wherein the wet, flat fibrous sheet with resin binder applied thereto is conveyed unsupported through an open air gap; and (7) carrying the wet, flat fibrous sheet with resin binder applied thereto through a heated zone having an elevated temperature, whereby the resin binder is dried to bond the fibrous web into a self-sustaining, bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric; and apparatus for carrying out such a method.

3 Claims, 2 Drawing Figures PATENTED AUG .75

SHEET SHEET PATENTED AUG 51975 METHOD FOR WET PRINT-BONDING LIGHT-WEIGHT WET-FORMED FIBROUS WEBS BACKGROUND OF THE INVENTION The present invention relates to methods and apparatus for making light-weight, wet-formed, print-bonded nonwoven fabrics.

Nonwoven fabrics, i.e., fabrics produced from fibers without the use of conventional spinning and weaving, knitting, or like fabricating processes, have been made for many years. Such nowoven fabrics have been made primarily by two basic techniques: (1) dry processes involving the use of textile carding machines for making fibrous webs, followed by either printbonding or overall saturation bonding of the fibrous web; and (2) wet processes involving the use of conventional or modified high speed papermaking techniques utilizing stock chest bonding or other forms of pre-bonding of the fibrous sheet to supply the strength required to make the resulting fibrous sheet self-sustaining during subsequent fabricating processes.

Efforts to combine 1 the print-bonding techniques of the dry-forming processes which provides excellent softness. drape. and hand to the resulting nonwoven fabric with (2) the high productive rate of the wetforming processes have thus far not been commercially successful. This is particularly true for light-weight, wet-formed fibrous products which, without stock chest bonding or other forms of pre-bonding, simply do not have the strength to withstand subsequent fabricating processes. Excessive breakage of the light-weight, wet-formed fibrous web is noted during processing before bonding and particularly after application of the binder. Such breakage is even more severe when printbonding techniques are employed wherein the fibrous web passes through an open draw wherein it is conveyed unsupported through an open air gap. Additionally, it is also noted that light-weight, wet-formed printbonded fibrous webs tend to pick excessively on the print roll and on the drying cans and cause undesirable fiber and binder buildup thereon thus requiring periodic shut-downs for cleaning. As a result, such combined processes have not been commercially acceptable.

PURPOSE AND OBJECT OF THE INVENTION It is therefore a principal purpose and object of the present invention to provide methods and apparatus for making light-weight, wet-formed print-bonded nonwoven fabrics in which breakage of the fibrous web is substantially eliminated and picking of fibers and binder on the print roll and on the drying cans is minimized to commercially acceptable levels.

STATEMENT OF THE INVENTION It has been found that this principal purpose and object, and other purposes and other objects which will become clear from a further reading of this specification, will be accomplished by: (l) forming an aqueous slurry of fibrous materials wherein the fiber concentration is in the range of from about 0.005% to about 0.5% by weight, based on the weight of the aqueous slurry; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving forming surface in the form of a wet, flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard and wherein the fibers comprise from about to about 15% by weight of the total weight of the wet, flat fibrous sheet; (3) removing water from said wet, flat fibrous sheet to bring the fiber weigt into the range of from about 20% to about 35% by weight of the total weight of the wet, flat fibrous sheet; (4) transferring said wet flat fibrous sheet to nonwoven fabric printbonding means by passage through an open draw wherein the wet, flat fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to the wet, flat fibrous sheet by printbonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about 30% to about of the weight of the fibers in the wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring said wet flat fibrous sheet with said aqueous resin binder applied thereto to carrying means by passage through an open draw wherein the wet, flat fibrous sheet with resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet, flat fibrous sheet with resin binder applied thereto through a heated zone having an elevated temperature of from about 200F. to about 300F. whereby the resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.

In the following specification and accompanying drawings, there are described and illustrated preferred emobdiments of the invention but it is to be understood that the inventive concept is not to be considered limited to the embodiments disclosed, except as determined by the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the accompanying drawings,

FIG. 1 is a fragmentary, schematic view in elevation showing a preferred embodiment of wet-forming apparatus capable of producing the light-weight printbonded nonwoven fabrics of the present invention; and

FIG. 2 is a fragmentary, schematic view in elevation of another preferred embodiment of other wet-forming apparatus also capable of producing the lightweight print-bonded nonwoven fabrics of the present invention.

GENERAL DESCRIPTION OF THE INVENTION FIG. I

Referring to FIG. 1 of the drawings, there is shown a head box 10 containing a substantially uniform aqueous slurry l2 offibrous materials. It is to be appreciated that the aqueous slurry 12 is not initially prepared or mixed in the head box 10 but is prepared in other mixing and holding or storage tanks (not shown) prior to delivery to the head box 10. This is particularly true in those cases where the fibrous materials comprise two or more different kinds of fibers. In such cases, two or more different sets of mixing and holding or storage tanks are provided, along with a mixing and blending tank and holding or storage tanks, as required, prior to delivery in substantially uniformly blended state to the head box 10.

Immediately adjacent the head box 10 and in contact with the aqueous slurry 12 therein is a cylindrical. rotating, forming drum or roll 14 provided with a wire mesh cylindrical forming surface 16 on its periphery upon which is deposited the aqueous slurry of fibrous materials in the form of a wet, fiat fibrous sheet S. This type of modified papermaking machine is a fairly recent development in this form or related forms and is generally classified as a former, of which the Stevens Former, the Papriformer, the Periformers and the Rotoformer are typical commercial examples. As will be pointed out hereinafter, other papermaking machines such as the inclined wire, or flatwire Fourdrinier, the Vertiformer, or cylinder machines may be used.

THE AQUEOUS SLURRY OF FIBROUS MATERIALS The aqueous slurry 12 of fibrous materials is prepared, as described previously herein, in mixing tanks or equivalent apparatus (not shown) and normally has a fiber consistency in the head box of from about 0.005% to about 0.5% by weight, and preferably from about 0.05% to about 0.2% by weight, based on the weight of the aqueous slurry.

Cellulosic fibers are the preferred fibers used in the formation of the aqueous slurry and may be either natural, synthetic, or man-made fibers, such as wood pulp, cotton, cotton linters, flax, hemp, ramie, viscose rayon, cuprammonium rayon, etc. The natural, synthetic, or man-made cellulosic fibers may be used alone in various proportions or in various combinations with other natural, synthetic, or man-made fibers such as nylon polyamide 6 and 6/6, polyesters such as Dacron and Kodel, polyolefins such as polypropylene and polyethylene, etc.

The wood pulp and other natural fibers are used in lengths and thicknesses as they exist naturally or are subsequently processed; rayon and the other synthetic or man-made fibers are used in deniers from about 1 to about 20 and in lengths of from about 3/16 inch to about 1 inch or more.

THE WET FLAT FIBROUS SHEET The aqueous slurry 12 is uniformly deposited on the cylindrical rotating fluid-permeable forming surface 16 of the forming roll 14 in the form of a very wet, flat fibrous sheet S and is transferred adheringly to the underside of a water-permeable moving carrier or top felt 18 as it passes around a rotating press roll or pick-up roll 20. At this point, the wet flat fibrous sheet S contains from about to about by weight of solids (fibers). The wet flat fibrous sheet S is then carried forwardly by the top felt l8 and is placed on a bottom felt 22 trained over a rotatable bottom press roll 24 and guide rolls 23, 25, thereby forming a sandwich with the wet flat fibrous sheet S positioned and pressed between the top felt l8 and the bottom felt 22. This sandwich passes between the bottom press roll 24 and a top press roll 26 which applies pressure to and squeezes water out of the wet flat fibrous sheet S. A suction or vacuum box 28 may be positioned adjacent the top felt l8 and draws additional water from the wet flat fibrous sheet S.

The wet flat fibrous sheet S passes between a bottom transfer press roll 30 and a top transfer press roll 32 and then passes through an open-draw OD-l wherein the wet, flat fibrous sheet S is conveyed unsupported through an open air gap extending from the bottom transfer press roll 30 to a rotating backing roll 33 forming a part of print-bonding apparatus 35. At this point, the wet flat fibrous sheet S contains from about 20% to about 35% by weight of solids (fibers).

It is to be appreciated that, regardless of how close it is desired to have the bottom transfer press roll 30 approach the closely adjacent backing roll 33, there will always be an open-draw or open air gap through which the wet, flat fibrous sheet must be conveyed in unsupported fashion. Naturally, this air gap is kept to a minimum so as to lessen breakage possibilities but it still exists in all circumstances with print bonding by the rotating print roll process.

It has been established that the wet, flat fibrous sheet must contain from about 20% to about 35% by weight of fiber solids during this time in order that it possess sufficient strength and cohesiveness so as to be capable of unsupported passage through the open air gap of the open draw OD-l and be suitable for further processing.

The wet fiat fibrous sheet is advanced around the ro tating backing roll 33 and enters the nip formed between the backing roll 33 and a rotating printing roll 34 having an etched or engraved peripheral printing surface. The printing roll 34 is partially immersed in a resin binder composition 36 contained in a binder receptacle or trough 38, picks up resin binder therefrom, and transfers the resin binder to the wet, fiat fibrous sheet in the intermittent print pattern desired. A doctor blade 37 controls the amount of binder 36 on the surface of the print roll and in the etched or engraved grooves thereof. Examples of typical intermittent print patterns such as used herein are noted in US. Pat. Nos. 2,705,498, 2,705,687, 2,705,688 and 3,009,822.

The most popular of such intermittent print patterns are the spiral line patterns, such as illustrated in FIG. 3 of US. Pat. No. 3,009,822 having from about 7 to about 23 lines per inch, and the diamond patterns, such as illustrated in FIG. 3 of US. Pat. No. 2,705,498. Other patterns are also of use, however. Surface coverages of such patterns range from about 10% to about of the total surface of the bonded nonwoven fab- The synthetic resin may be selected from a relatively large group of synthetic resins well known in the industry for bonding purposes and may be of a selfcrosslinking type, externally cross-linking type, or not crosslinked. Specific examples of such synthetic resins include: polymers and copolymers of vinyl ethers; vinyl halides such as plasticized and unplasticized polyvinyl chloride, polyvinyl chloride-polyvinyl acetate, ethylene-vinyl chloride, etc.; polymers and copolymers of vinyl esters such as plasticized and unplasticized polyvinyl acetate, ethylenevinyl acetate, acrylicvinyl acetate, etc.; polymers and copolymers of the polyacrylic resins such as ethyl acrylate, methyl acrylate, butyl acrylate, ethylbutyl acrylate, ethylhexyl acrylate, hydroxyethyl acrylate, dimethyl amino ethyl acrylate, etc; polymers and copolymers of the polymethacrylic resins such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, etc; polymers and copolymers of acrylonitrile, methacrylonitrile, acrylamide, N-isopropyl acrylamide, N-methylol acrylamide, methacrylamide, etcx, vinylidene polymers and copolymers, such as polyvinylidene chloride, polyvinylidene chloride-vinyl chloride, polyvinylidene chlorideethyl acrylate, polyvinylidene chloride-vinyl chlorideacrylonitrile, etc.; polymers and copolymers of polyole finic resins including polyethylene, polypropylene, ethylene-vinyl chloride and ethylene-vinyl acetate which have been listed previously; the synthetic rubbers such as 1,2-butadiene, l,3-butadiene, 2-ethyl-l ,3- butadiene, high, medium and carboxylated butadieneacrylonitrile, butadiene-styrene, chlorinated rubber, etc., natural latex; the polyurethanes; the polyamides; the polyesters; the polymers and copolymers of the styrenes including styrene, Z-methyl styrene, 3-methyl styrene, 4-methyl styrene, 4-ethyl styrene, 4-butyl styrene; natural latex; phenolic emulsions; polyvinyl alcohol;

etc.

These resins may be used either as homopolymers comprising a single repeating monomer unit, or they may be used as copolymers comprising two, three, or more different monomer units which are arranged in random fashion, or in a definite ordered alternating fashion, within the polymer chain. Also included within the inventive concept are the block polymers comprising relatively long blocks of different monomer units in a polymer chain and graft polymers comprising chains of one monomer attached to the backbone of another polymer chain.

The wet, flat fibrous sheet with the resin binder applied thcreto then is conveyed through a second open air gap or open draw OD-2 extending between the rotogravure print roll 34 and a closely adjacent directional rotatable guide roll 40.

Again, it is to be appreciated that, regardless of how close the directional guide roll is placed with respect to the rotogravure print-roll, that an open draw or open air gap will exist through which the wet flat fibrous sheet must be conveyed in unsupported fashion. Naturally, this open air-gap is kept to a minimum in order to reduce breakage possibilities but it still exists in all circumstances with print bonding by the print roll process.

Again, it is observed that the wet flat fibrous sheet must possess sufficient strength and cohesiveness that it is capable of unsupported passage through the open air gap of the open draw.

In order to maintain the required strength and cohesiveness in the wet flat fibrous sheet, the concentration of the resin binder solids in the resin binder composition 36 and the amount of resin binder applied to the wet flat fibrous sheet S must be carefully controlled so that the wet fiat fibrous sheet is capable of passing through the second open draw OD-2 extending from the rotogravure printing roll 34 to a rotating guide roll 40.

The concentration of the resin binder solids in the resin binder composition must be maintained between about and about 60% and preferably from about 40% to about 50%, based on the weight of the resin binder composition. And, the amount of the resin binder composition which is applied to the wet, flat fibrous sheet must be maintained between 30% and about 160%, and preferably from about 40% to about 90%, based on the weight of the fibers in the wet flat fibrous sheet.

The wet flat fibrous sheet with the resin binder applied thereto is carried around the directional guide roll 40 and is then deposited on and carried by a moving belt 44 trained over rotating roll 46 and 48 to be transferred to a series of heated drying cylinders 50 rotating in conventional speed-adjustable relationship. The temperatures of the heated drying cylinders is normally in the range of from about 200F. to about 300F,, or higher, if desired or required.

A dryer hood 52 for collecting steam and other vapors coming from the sheet S extends over the series of heated drying cylinders which may number from about 10 to about 30 or more, as desired or required, in number, as desired or required, so that the sheet being delivered by the last heated drying cylinder is down to the desired degree of dryness. The sheet is then passed over a rotating guide roll 54 to a rotatable wind-up roll 58 which is driven at substantially constant speed by contacting drive roll 56.

The dried bonded nonwoven fabric, upon being examined, is found to contain from about 5% to about 45% by weight of resin binder, based on the weight of the bonded nonwoven fabric.

FIG. 2

With reference to FIG. 2 of the drawings, there is shown other modified papermaking apparatus capable of applying the principles of the present inventive concept. In FIG. 2, there is shown basically a flat-wire Fourdrinier type of papermaking machine comprising a head box 60 containing a substantially uniform aqueous slurry 62 of fibrous materials. Immediately adjacent the head box 60 and in a position to receive the flow of the aqueous slurry from the head box is a fluidpermeable, moving Fourdrinier wire 64 which is a wire mesh belt which is trained over a rotating cylindrical roll 66 and is supported by a series of conventional intermediate rotating rolls (not shown) and conventional drainage control devices 68.

The aqueous slurry of fibrous materials is delivered from the head box 60 and is deposited on the Fourdrinier wire 64 in the form of a very wet, flat fibrous sheet S. This general type of papermaking machine is very known in the industry and exists in a great variety of modified forms.

THE AQUEOUS SLURRY OF FIBROUS MATERIALS The aqueous slurry 62 of fibrous materials is prepared in mixing and holding or storage tanks (not shown) and normally has a fiber consistency up to 2% or 3% or even more. This fiber consistency, however, is decreased to a head box fiber consistency of from about 0.005% to about 0.5% by weight, and preferably from about 0.05% to about 0.2% by weight, based on the weight of the aqueous slurry.

Cellulosic fibers are the preferred fibers used in the formation of the aqueous slurry and may be either natural, synthetic, or man-made fibers, such as wood pulp, cotton, cotton linters, flax, hemp, ramie, viscose rayon, cuprammonium rayon, etc. The cellulosic fibers may be used alone in various proportions or in various combinations with other natural, synthetic, or man-made fibers such as nylon polyamide 6 and 6/6, polyesters such as Dacron and Kodel, polyolefins such as polypropylene and polyethylene, etc.

The wood pulp and other natural fibers are used in lengths and thicknesses as they exist or are processed; rayon and the other synthetic or man-made fibers are used in deniers from about I to about 20 and in lengths of from about 3/16 inch to about 1 inch or more.

THE WET FLAT FIBROUS SHEET The aqueous slurry 62 is uniformly deposited on the Fourdrinier forming wire 64 and is carried onwardly or to the right, as viewed in FIG. 2. At this point, the wet flat fibrous sheet S contains from about 10% to about by weight of solids (fibers). A rotating top press roll 69 and a rotating bottom press roll 67 press the wet flat fibrous sheet and remove water therefrom. A vacuum or suction box 65 or other water removal or drainage means is positioned directly under the Fourdrinier wire and draws additional water from the wet flat fibrous sheet S.

A water-permeable, moving carrier or top felt 68 trained around the rotating top press roll 69 contacts the wet flat fibrous sheet S and carries it forwardly in adhering fashion on its underside and the remainder of the operation is very similar to the operation described with reference to FIG. 1.

The wet flat fibrous sheet S is then carried forwardly by the top felt 68 and is placed on a bottom felt 72 trained over a rotatable bottom press roll 74 and guide rolls 73, 75, thereby forming a sandwich with the wet flat fibrous sheet S positioned and pressed between the top felt 68 and the bottom felt 72. This sandwich passes between the bottom press roll 74 and a top press roll 76 which applies pressure to and squeezes water out of the wet flat fibrous sheet S. A suction or vacuum box 78 may be positioned adjacent the top felt 68 and draws additional water from the wet flat fibrous sheet S.

The wet flat fibrous sheet S passes between a bottom transfer press roll 80 and a top transfer press roll 82 and then passes through an open-draw OD-3 wherein the wet, flat fibrous sheet S is conveyed unsupported through an open air gap extending from the bottom transfer press roll 80 to a rotating backing roll 83 forming a part of print-bonding apparatus 85. At this point, the wet flat fibrous sheet S contains from about to about by weight of solids (fibers).

It is to be appreciated that, regardless of how close it is desired to have the bottom transfer press roll 80 approach the closely adjacent backing roll 83, there will always be an opendraw or open air gap through which the wet, flat fibrous sheet must be conveyed in unsupported fashion. Naturally, this air gap is kept to a minimum so as to lessen breakage possibilities but it still exists in all circumstances with print bonding by the rotating print roll process.

It has been established that the wet, flat fibrous sheet must contain from about 20% to about 35% by weight of fiber solids during this time in order that it possess sufficient strength and cohesiveness so as to be capable of unsupported passage through the open air gap of the open draw OD3 and be suitable for further processing.

The wet flat fibrous sheet is advanced around the rotating backing roll 83 and enters the nip formed between the backing roll 83 and a rotating printing roll 84 having an etched or engraved peripheral printing surface. The printing roll 84 is partially immersed in a resin binder composition 86 contained in a binder receptacle or trough 88, picks up resin binder therefrom and transfers the resin binder to the wet, flat fibrous sheet in the intermittent print pattern desired. A doctor blade 87 controls the amount of binder 86 on the surface of the print roll and in the etched or engraved grooves thereof. Examples of typical intermittent print patterns such as used herein are noted in US. Pat. Nos. 2,705,498, 2,705,687, 2,705,688, and 3,009,822 as described previously herein.

The synthetic resin may be selected from a relatively large group of synthetic resins well known in the industry for bonding purposes and may be of a selfcrosslinking type, externally cross-linking type, or not crosslinked. Specific examples of such synthetic resins have been set forth previously.

The wet, flat fibrous sheet with the resin binder applied thereto then is conveyed through a second open air gap or open draw OD4 extending between the rotogravure print roll 84 and closely adjacent directional rotatable guide roll 90.

Again, it is to be appreciated that, regardless of-how close the directinal guide roll is placed directional respect to the rotogravure print-roll, that an open draw or open air gap will exist through-which the wet flat fibrous sheet must be conveyed in unsupported fashion. Naturally, this open air gap is kept to a minimum in order to reduce breakage possibilities but it still exists in all cicumstances with print bonding by the print roll process.

In order to maintain the required strength and cohe siveness in the wet flat fibrous sheet, the concentration of the resin binder solids in the resin binder composition 86 and the amount of resin binder applied to the wet flat fibrous sheet S must be carefully controlled so that the wet flat fibrous sheet is capable of passing through the second open draw OD-4 extending from the rotogravure printing roll 84 to a rotating guide roll 90.

The concentration of the resin binder solids in the resin binder composition must be maintained between about 30% and about and preferably from about 40% to about 50%, based on the weight of the resin binder composition. And, the amount of the resin binder composition which is applied to the wet, flat fibrous sheet must be maintained between 30% and about 160%, and preferably from about 40% to about 90%, based on the weight of the fibers in the wet flat fibrous sheet.

The wet flat fibrous sheet with the resin binder applied thereto is carried around the directional guide roll 90 and is then deposited on and carried by a moving belt 94 trained over rotating rolls 96 and 98 to be transferred to a series of heated drying cylinders 100 rotating in conventional speed-adjustable relationship. The temperatures of the heated drying cylinders is normally in the range of from about 200F. to about 300F., or higher, if desired or required.

A dryer hood 102 for collecting steam and other vapors coming from the sheet S extends over the series of heated drying cylinders which may number from about 10 to about 30 or more, as desired or required, in number, as desired or required, so that the sheet being delivered by the last heated drying cylinder is down to the desired degree of dryness. The sheet is then passed over a rotating guide roll 104 to a rotatable wind-up roll 108 which is driven at substantially constant speed by contacting drive roll 106.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the invention. they are given primarily for purposes of illustration and the invention In its broader aspects is not to be construed as limited thereto.

EXAMPLE I The apparatus illustrated in FIG. 1 of the drawings is used. The fiber mixture is: 50% by weight hardwood wood pulp fibers, not refined or hydrated, 11.5 mm. in length; and 50% by weight bleached viscose rayon fibers. A inch length and 1.5 denier. The fiber consistency is 0.1% by weight in the aqueous slurry in the head box. The fiber consistency in the very wet, fiat fibrous sheet first positioned on the carrier top felt is 12% by weight. The fiber weight is 300 grains per square yard. A press section of press rolls and a suction box are used to remove water from the fibrous web. The fiber consistency in the wet, flat fibrous sheet at the first open draw before the print backing roll is 27% by weight. No excessive fibrous sheet breakage is noted at the first open draw. The resin binder composition used in the rotogravure print bonding apparatus is Rohm and Haas Rhoplex HA-8, essentially a polyethylacrylate self-cross linkable resin binder. It comprises approximately 46% by weight of resin solids (dry basis). Approximately 150% by weight of the resin binder composition, based on the fiber weight in the fibrous web, is applied to the fibrous web by the rotogravure print bonding apparatus. The binder pattern is 23 lines per inch with the total binder coverage 65% of the total nonwoven fabric area. The add-on of resin solids (dry) is 207 grains per yard. No excessive fibrous sheet breakage is noted after the application of the binder by the rotogravure printing roll. No picking of the fibers or of the resin is noted on the rotogravure printing roll. The drying takes place on heated drying cylinders at an elevated temperature of 225F. No excessive picking of the fibers or of the resin is noted on the surfaces of the drying cylinders. The total weight of the dried, bonded nonwoven fabric is 507 grains per square yard, which is broken down into 300 grains fibers and 207 grains resin binder per square yard. The dry tensile strength of the dry bonded nonwoven fabric is 6.2 pounds per inch in the machine direction. The Mullen burst results for the dried, bonded nonwoven fabric show 13 pounds per square inch (gauge). The dried bonded nonwoven fabric is useful and is commercially acceptable as a backing material for tape.

EXAMPLE II The procedures of Example I are followed substantially as set forth with the exception that the fiber mix is changed to: 50% by weight of hardwood wood pulp fibers; 40% by weight of bleached viscose rayon, 1.5 denier and A inch length; and by weight of nylon polyamide 6/6 fibers, 6 denier, inch length. The fabric weight is changed to 550 grains per square yard with 70% of the weight being due to fiber and 30% of the weight being due to binder. The results are generally comparable to those obtained in Example I. The fiber consistencies at both open draws are the same as indicated in Example I. No excessive fibrous web breakage is noted and no picking of fibers or of binder is noted on the rotogravure printing roll or on the heated drying cylinders. The dried bonded nonwoven fabric is useful and is commercially acceptable as a utility fabric.

EXAMPLE m The procedures of Example I are followed substantially as set forth therein except that the total weight of the dried bonded nonwoven fabric is 250 grains per square yard with approximately of the weight due to fibers. The results are generally comparable to those obtained in Example I. The fiber consistencies at both open draws are the same as indicated in Example I. No excessive fibrous web breakage is noted and there is no picking of fibers or of binder noted on the rotogravure printing roll or on the heated drying cylinders. The dried bonded nonwoven fabric is of light weight and is suitable as a facing material.

EXAMPLE IV The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web is increased to 42% by weight at the first open draw. The fibrous web picks excessively on the rotogravure printing roll and the operation must be repeatedly halted to clean away the excessive build-up of undesirable fiber and binder on the rotogravure printing roll. The method is not economically feasible.

EXAMPLE V The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web is decreased to 17% by weight at the first open draw. There is excessive fibrous web breakage at the first and second open draws. The method is not commercially feasible.

EXAMPLE VI The apparatus illustrated in FIG. 2 of the drawings is used. The fiber mixture is: 50% by weight hardwood wood pulp fibers, not refined or hydrated, 11.5 mm; in length; and 50% by weight bleached viscose rayon fibers, A inch length and 1.5 denier. The fiber consistency is 0.1% by weight in the aqueous slurry in the head box. The fiber consistency in the very wet flat fibrous sheet first positioned on the Fourdrinier carrier wire is 12% by weight. The fiber weight is 300 grains per square yard. A press section of press rolls and a suction box are used to remove water from the fibrous web. The fiber consistency in the wet, flat fibrous sheet at the first open draw before the print backing roll is 27% by weight. No excessive fibrous sheet breakage is noted at the first open draw. The resin binder composition used in the rotogravure print bonding apparatus is Rohm and Haas Rhoplex HA8, essentially a polyethylacrylate self-cross-linkable resin binder. It comprises approximately 46% by weight of resin solids (dry basis). Approximately by weight of the resin binder composition, based on the fiber weight in the fi brous web, is applied to the fibrous web by the rotogravure print bonding apparatus. The binder pattern is 23 lines per inch with the total binder coverage 65% of the total nonwoven fabric area. No excessive fibrous sheet breakage is noted after the application of the binder by the rotogravure printing roll. No picking of the fibers or of the resin is noted on the rotogravure printing roll. The drying takes place on heated drying cylinders at an elevated temperature of 225F. No excessive picking of the fibers or of the resin is noted on the surfaces'of the drying cylinders. The total weight of the dried, bonded nonwoven fabric is 507 grains per square yard. which is broken down into 300 grains fibers and 207 grains resin binder per square yard. The dry tensile strength of the dry bonded nonwoven fabric is 6.2 punds per inch in the machine direction. The Mullen burst results for the dried, bonded nonwoven fabric show 13 pounds per square inch (gauge). The dried bonded nonwoven fabric is useful and is commercially acceptable as a backing material for tape.

EXAMPLE VII The procedures of Example VI are followed substantially as set forth with the exception that the fiber mix is changed to: 50% by weight of hardwood wood pulp fibers; 40% by weight of bleached viscose rayon, 1.5 denier and A inch length; and by weight of nylon polyamide 6/6 fibers, 6 denier, inch length. The fabric weight is changed to 550 grains per square yard with 70% of the weight being due to fiber and 30% of the weight being due to binder. The results are generally comparable to those obtained in Example VI. The fiber consistencies at both open draws are the same as indicated in Example I. No excessive fibrous web breakage is noted and no picking of fibers or of binder is noted on the rotogravure printing roll or on the heated drying cylinders. The dried bonded nonwoven fabric is useful and is commercially acceptable as a utility fabric.

EXAMPLE VIII The procedures of Example VI are followed substantially as set forth therein except that the total weight of the dried bonded nonwoven fabric is 250 grains per square yard with approximately 80% of the weight due to fibers. The results are generally comparable to those obtained in Example VI. The fiber consistencies at both open draws are the same as indicated in Example I. No excessive fibrous web breakage is noted and there is no picking of fibers or of binder noted on the rotogravure printing roll or on the heated drying cylinders. The dried bonded nonwoven fabric is of light weight and is suitable as a facing material.

EXAMPLE IX The procedures of Example VI are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web is increased to 42% by weight at the first open draw. The fibrous web picks excessively on the rotogravure printing roll and the op eration must be repeatedly halted to clean away the excessive buildup of undesirable fiber and binder on the rotogravure printing roll. The method is not economically feasible.

EXAMPLE X The procedures of Example VI are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web is decreased to 17% by weight at the first open draw. There is excessive fibrous web breakage at the first and second open draws. The method is not commercially feasible.

EXAMPLE XI The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 22% by weight. The results are generally comparable to those obtained in Example I. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

EXAMPLE XII The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 30% by weight. The results are generally comparable to those obtained in Example I. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

EXAMPLE XIII The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 34% by weight. The results are generally comparable to those obtained in Example I. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

EXAMPLE XIV The procedures of Example VI are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 22% by weight. The results are generally comparable to those obtained in Example VI. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

EXAMPLE XV The procedures of Example VI are followed substantially as sest forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 30% by weight. The results are generally comparable to those obtained in Example VI. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

EXAMPLE XVI The procedures of Example VI are followed substantially as set forth therein with the exception that the fiber consistency of the fibrous web at the first open draw is changed from 27% by weight to 34% by weight. The results are generally comparable to those obtained in Example VI. There is no excessive breakage or rupture of the fibrous web during processing. The method is commercially acceptable.

Although the present invention has been described and illustrated with reference to preferred embodiments thereof, it is to be appreciated that such is merely for the purpose of disclosing the invention and is not to be construed as limitative of the broader aspects of the inventive concept. except as defined by the appended claims.

We claim:

1. A method of making a light-weight, wet-formed, print-bonded nonwoven fabric which comprises: (l) forming an aqueous slurry of fibrous materials; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet, flat fibrous sheet; (3) removing water from said wet, flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of said wet, flat fibrous sheet; (4) transferring said wet, flat fibrous sheet to nonwoven fabric print-bonding means by passage through an open draw wherein said wet, fiat fibrous sheet is conveyed unsupported through an open air gap; applying an aqueous resin binder to said wet, flat fibrous sheet by print-bonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in said wet, flat fibrous sheet and having a resin solids content of from about to about 60% by weight; (6) transferring said wet flat fibrous sheet with said aqueous resin binder applied thereto to carrying means by passage through an open draw wherein said wet, flat fibrous sheet with said resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet, flat fibrous sheet with said resin binder applied thereto through a heated zone having an elevated temperature whereby said resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.

2. A method of making a light-weight, wetformed, print-bonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard; (3) removing water from said wet, flat fibrous sheet to bring the fiber weight into the range of from about to about 35% by weight of the total weight of said wet, flat fibrous sheet; (4) transferring said wet, flat fibrous sheet to nonwoven fabric print-bonding means by passage through an open draw wherein said wet flat fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to said wet, flat fibrous sheet by print-bonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about to about 160% of the weight of the fibers in said wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring said wet, flat fibrous sheet with said aqueous resin binder applied thereto to carrying means by passage through an open draw wherein said wet, flat fibrous sheet with said resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet, flat fibrous sheet with said resin binder applied thereto through a heated zone having an elevated temperature of from about 200F. to about 300F. whereby said resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.

3. A method of making a light-weight, wet-formed, print-bonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials wherein the fiber concentration is in the range of from about 0.005% to about 0.1% by weight, based on the weight of the aqueous slurry; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet flat fibrous sheet having a fiber weight of from about to about 800 grains per square yard and wherein the fibers comprise from about 10% to about 15% by weight of the total weight of said wet, flat fibrous sheet; (3) removing water from said wet flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of said wet, flat fibrous sheet; (4) transferring said wet, flat fibrous sheet to nonwoven fabric print-bonding means by passage through an open draw wherein said wet, fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to said wet, flat fibrous sheet by print-bonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in said wet, fiat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring said wet, flat fibrous sheet with said aqueous resin binder applied thereto to carrying means by passage through an open draw wherein said wet, flat fibrous sheet with said resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet flat fibrous sheet with said resin binder applied thereto through a heated zone having an elevated temperature of from about 200F. to about 300F. whereby said resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.

Claims

1. A METHOD OF MAKING A LIGHT-WEIGHT WET-FORMED PRINTBONDED NONWOVEN FABRIC WHICH COMPRISES-(1) FORMING AN AQUEOUS SLURRY OF FIBROUS MATERIAL (2) TRANSFERRING SAID AQUEOUS SLURRY OF FIBROUS MATERIALS TO A FLUID-PERMEABLE MOVING FORMING SURFACE IN THE FORM OF A WET FLAT FIBROUS SHEET (3) REMOVING WATER FROM SAID WET FLAT FIBROUS SHEET TO BRING THE FIBER WEIGHT INTO THE RANGE OF FROM ABOUT 20% TO ABOUT 35% BY WEIGHT OF THE TOTAL WEIGHT OF SAID WET FLAT FIBROUS SHEET (J) TRANSFERRING SAID WET FLAT FIBROUS SHEET TO NONWOVEN FABRIC PRINT BONDING MEANS BY PASSAGE THROUGH AN OPEN DRAW WHEREIN SAID WET, FLAT FIBROUS SHEET IS CONVEYED UNSUPPORTED THROUGH AN OPEN AIR GAP, (5) APPLYING AN AQUEOUS RESIN BINDER TO SAID WET FLAT FIBROUS SHEET BY PRINT BONDING MEANS EMPLOYING AN ETCHED OR ENGRAVED PRINTING SURFACE SAID AQUEOUS RESIN BINDER BEING APPLIED IN AN AMOUNT EQUAL TO FROM ABOUT 30% TO ABOUT 160% OF THE WEIGHT OF THE FIBERS IN SAID WET FLAT

2. A method of making a light-weight, wet-formed, print-bonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard; (3) removing water from said wet, flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of said wet, flat fibrous sheet; (4) transferring said wet, flat fibrous sheet to nonwoven fabric print-bonding means by passage through an open draw wherein said wet flat fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to said wet, flat fibrous sheet by print-bonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in said wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring said wet, flat fibrous sheet with said aqueous resin binder applied thereto to carrying means by passage through an open draw wherein said wet, flat fibrous sheet with said resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet, flat fibrous sheet with said resin binder applied thereto through a heated zone having an elevated temperature of from about 200*F. to about 300*F. whereby said resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.

3. A method of making a light-weight, wet-formed, print-bonded nonwoven fabric which comprises: (1) forming an aqueous slurry of fibrous materials wherein the fiber concentration is in the range of from about 0.005% to about 0.1% by weight, based on the weight of the aqueous slurry; (2) transferring said aqueous slurry of fibrous materials to a fluid-permeable, moving, forming surface in the form of a wet flat fibrous sheet having a fiber weight of from about 160 to about 800 grains per square yard and wherein the fibers comprise from about 10% to about 15% by weight of the total weight of said wet, flat fibrous sheet; (3) removing water from said wet flat fibrous sheet to bring the fiber weight into the range of from about 20% to about 35% by weight of the total weight of said wet, flat fibrous sheet; (4) transferring said wet, flat fibrous sheet to nonwoven fabric print-bonding means by passage through an open draw wherein said wet, fibrous sheet is conveyed unsupported through an open air gap; (5) applying an aqueous resin binder to said wet, flat fibrous sheet by print-bonding means employing an etched or engraved printing surface, said aqueous resin binder being applied in an amount equal to from about 30% to about 160% of the weight of the fibers in said wet, flat fibrous sheet and having a resin solids content of from about 15% to about 60% by weight; (6) transferring said wet, flat fibrous sheet with said aqueous resin binder applied thEreto to carrying means by passage through an open draw wherein said wet, flat fibrous sheet with said resin binder applied thereto is conveyed unsupported through an open air gap; (7) and carrying said wet flat fibrous sheet with said resin binder applied thereto through a heated zone having an elevated temperature of from about 200*F. to about 300*F. whereby said resin binder is dried to bond the fibrous web into a self-sustaining bonded nonwoven fabric wherein the resin binder content is in the range of from about 5% to about 45% of the weight of the bonded nonwoven fabric.