Abstract:
A method and apparatus for making an absorbent composite from continuous tow is disclosed. The method and apparatus includes the steps of or means for spreading a crimped tow; de-registering the crimped tow; shaping the de-registered tow to a substantially rectangular cross-section; and distributing a particulate onto the shaped tow. The method and apparatus also include the step of or means for introducing a crimped tow from a bale, wherein the tow&#39;s travel through de-registering, shaping, and particulate distribution, defines a vertical plane and the bale is located off the vertical plane.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention is directed to a method and apparatus for making an absorbent composite from a continuous tow.  
       BACKGROUND OF THE INVENTION  
       [0002]     An absorbent composite is a component of a disposable absorbent garment. Such garments include, but are not limited to, infant diapers or training pants, adult incontinence products, and feminine hygiene products. Typically, the absorbent composite comprises mixtures of fibrous material (e.g., wood pulp or fluff) and a superabsorbent polymer (SAP) that are sandwiched between strata, such as tissues, nonwovens, and permeable and impermeable films.  
         [0003]     It is known to use continuous tow in the manufacture of absorbent composites. See Japanese Kokoku 60-26537, US SIR H1565, and U.S. Pat. Nos. 6,068,620; 6,253,431; and 6,543,106. Each is discussed below.  
         [0004]     Japanese Kokoku 60-26537 discloses an absorbent structure made of crimped acetate tow and pulverized pulp but no SAP. Referring to  FIG. 4 , the process for making the absorbent structure is shown. Tow is removed from a bale and is spread by an air banding jet  14 . The tow is then de-registered between roller pairs  16 ,  17 . The de-registered tow is further spread and given a uniform density by a second air jet  18 . Pulverized pulp  21  is spread on to opened tow after it leaves the second air jet. Thereafter, absorbent sheets are added and the absorbent pad is folded into its final form.  
         [0005]     U.S. Statutory Invention Registration H1565 discloses an absorbent structure made of crimped acetate tow and SAP that is preferably adhered to the opened tow by a binder. The tow is opened with a Korber &amp; Co. Model AF2 machine (a common machine used in the manufacture of cigarette filters) and subsequently a mixture of binder and SAP or binder then SAP is added to the tow.  
         [0006]     U.S. Pat. No. 6,068,620 discloses an absorbent core made of fibrous crimped acetate tow and SAP between an upper and lower layer. Referring to  FIG. 7 , SAP is added to the tow via a mixing chamber.  
         [0007]     U.S. Pat. Nos. 6,253,431 and 6,543,106 disclose a method of making an absorbent structure from crimped acetate tow and SAP. Referring to  FIG. 1 , tow from a bale is spread by a banding jet  130 . The tow is then partially de-registered (or opened) through the roller assemblies  40 ,  64 ,  70 . Each roller assembly has a metal roller  42 ,  62 ,  72  and a rubber roller  44 ,  64 ,  74 . Optimally, a liquid is applied to the opened tow by liquid additive assembly  80 . The tow is then further opened, shaped in air jet  240 . Solid substances, such as SAP, are added after the fully opened and shaped tow emerges from jet  240 . Solid substances are added via a vibratory feeder.  
         [0008]     There is, however, a need for more practical processes and apparatus to make an absorbent composite.  
       SUMMARY OF THE INVENTION  
       [0009]     A method and apparatus for making an absorbent composite from continuous tow is disclosed. The method and apparatus includes the steps of or means for spreading a crimped tow; de-registering the crimped tow; shaping the de-registered tow; and distributing a particulate onto the shaped tow. The method and apparatus also include the step of or means for introducing a crimped tow from a bale, wherein the tow&#39;s travel through de-registering, shaping, and particulate distribution, defines a vertical plane and the bale is located off the vertical plane. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]     For the purpose of illustrating the invention, there is shown in the drawings a form that is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.  
         [0011]      FIGS. 1, 1   a , and  1   b  are schematic views of the present invention.  
         [0012]      FIG. 2  is an elevational view of the present invention.  
         [0013]      FIG. 3  is an elevational view of the de-registration mechanism of the present invention.  
         [0014]      FIG. 4  is an elevational view of the shaping and particulate distribution mechanisms of the present invention.  
         [0015]      FIG. 5  is an isometric view of the particulate distribution mechanism of the present invention.  
         [0016]      FIGS. 6   a ,  6   b ,  6   c , and  6   d  are elevational views of a portion of the particulate distribution mechanism of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     Referring to the drawings wherein like numerals indicate like elements, there is shown in  FIG. 1  an apparatus  10  for making an absorbent composite from a continuous tow.  
         [0018]     The absorbent composite discussed herein is for use in manufacture of absorbent garments. Absorbent garments include, for example, diapers or training pants, adult incontinence products, and feminine hygiene products. The absorbent composites disclosed herein are particularly useful in the absorbent cores and garments disclosed in U.S. Patent Publications Nos. 2003/0105442; 2003/0114814; 2003/0135177; and 2003/0135178, each is incorporated herein by reference.  
         [0019]     Tow is a large strand of continuous manufactured fiber filaments without definite twist, collected in a loose, band- or rope-like form, usually held together by crimp. Suitable tows materials include, but are not limited to, polyolefins, polyesters, polyamides, cellulosics, and mixtures thereof. Of these, cellulosic fibers are preferred. Cellulosic fibers include rayon, acetate (cellulose acetate), and triacetate (cellulose triacetate) fibers. Acetate tow is most preferred. For example, an acetate tow may consist of about 2,500 to about 25,000 fibers having an individual denier of from about 1 to about 15, preferably from 2 to 10, and most preferably 3 to 8. The total denier of a single acetate tow band may range from about 2,500 to about 125,000, preferably 15,000 to 75,000, and most preferably 20,000 to 40,000. The tow is preferably crimped, with about 5 to about 40 crimps per inch (2 to 16 crimps per cm), preferably, 25 to 30 crimps per inch (10 to 12 crimps per cm). The fibers of the tow may have any cross-sectional shape, including ‘y,’ ‘x,’ round, crenulated, dog bone or combinations thereof. The tow may include a finish, the finish comprising about 0.3% to about 5% by weight of the tow, preferably, 0.5 to 2.0%. The tow&#39;s cross-sectional dimensions may range from about 25 mm to 100 mm in width, preferably, 40 to 60 mm, and about 1 to 10 mm in height, preferably 2 to 5 mm. Tows are commercially available and are delivered in compressed bales.  
         [0020]     In  FIGS. 1 and 2 , there is shown an apparatus  10  for making absorbent composites from a continuous tow. Apparatus  10  generally comprises: apparatus  13  for spreading the tow, i.e., increasing its width from its compressed state in the bale; a de-registering apparatus  40  for de-registering the crimped fibers of the tow; a tow shaping apparatus  54  for forming the tow into its desired cross-sectional shape; a particle distribution apparatus  56  whereby particulate matter, e.g., SAP, may be delivered to the shaped tow, and a wind-up station  60  where the particulate laden, shaped tow is sandwiched between strata and then wound-up. Wind-up may be eliminated and the absorbent composite may be run directly into a subsequent machine for formation into the ultimate absorbent garment (for example, see: U.S. Patent Publications Nos. 2003/0105442; 2003/0114814; 2003/0134559; 2003/0135177; 2003/0135178; 2003/0150551, each is incorporated herein by reference).  
         [0021]     Bale  12  is preferably located at a right angle to the travel of the tow through the de-registering apparatus  40 , tow shaping apparatus  54 , and particulate distribution apparatus  56 . The bale may be located at any location, including a position inline with the foregoing apparatus. However, location at the right angle is preferred to allow easy access to the bale for changing out depleted bales and to allow easier visual inspection of the tow by an operator.  
         [0022]     Tow  14  is delivered to spreading apparatus  13  from bale  12 . Apparatus  13  guides between two locations and spreads the tow. Spreading apparatus  13  preferably has at least two banding jets. These banding jets work to spread and stabilize the tow as it moves through the rest of apparatus  10 . Tow  14  is drawn from bale  12  and guided through rings  16  to a first banding jet  18 . Banding jet  18  is a device that is used to spread (i.e., increase the width) and stabilize the tow  14 . Banding jet  18 , see  FIG. 1   a , generally comprises a plate  20  having a channel  22  with an air nozzle  24  located within channel  22 . Any conventional banding jet may be used, for example see U.S. Pat. No. 3,226,773 or U.S. patent application Ser. No. 09/219,818 filed Dec. 23, 1998, both are incorporated herein by reference. Air nozzle  24  is shown as a chevron, however, other shapes or patterns are permissible, for example, slots can be replaced by holes. The chevron may have a width of 50-140 mm. Compressed air is blown through air nozzle  24  and partially spreads the tow. The pressure of the compressed air may range from 0.5 to 5.0 psig, preferably, 2.5-3.0 psig. The width of channel  22  is referred to as W 1 .  
         [0023]     Tow carrier structure  26  carries tow  14  leaving banding jet  18  over the distance from jet  18  to the rest of apparatus  10 . Guide roller  28 , located at the distal end of carrier  26 , re-orients the tow for entry into the rest of the apparatus  10 .  
         [0024]     Second banding jet  30  receives tow  14  from guide roller  28 . The second banding jet  30 ,  FIG. 1   b , comprises a plate  32  having a channel  34  with an air nozzle  36 . Any conventional banding jet may be used, for example see U.S. Pat. No. 3,226,773 or U.S. patent application Ser. No. 09/219,818 filed Dec. 23, 1998, both are incorporated herein by reference. Air nozzle  36  is shown as a chevron, however, other shapes or patterns are permissible, for example, slots can be replaced by holes. The chevron may have a width of 70-155 mm. Compressed air is blown through air nozzle  36  and partially spreads the tow. The pressure of the compressed air may range from 0.5 to 5.0 psig, preferably, 3.0-3.5 psig. Channel  34  has a width W 2 . Preferably, W 1  is less than W 2 .  
         [0025]     Cabinet  38  (shown in phantom) contains de-registering apparatus  40  that receives tow  14  from spreading apparatus  13 . Cabinet  38  acts as a shielding device to prevent contaminates such as adhesives from gumming up or fouling the roll surfaces of the de-registering apparatus  40  and as a safety device. While cabinet  38  is preferred, other means can be used to accomplish the shielding function, such as, for example, curtains, air curtains, wire cages. Cabinet  38  will be discussed in greater detail below.  
         [0026]     De-registering apparatus  40 , which is preferably contained within cabinet  38 , has at least two pairs of rollers  42  and  48 . In de-registration, the individual crimped filaments of the tow are de-registered (or opened) and prepared for shaping. Roller pair  42  has a metal-faced roller  44  and a rubber-faced roller  46  (rubber-faced refers to any elastic polymer). Roller pair  48  also has a metal-faced roller  50  and a rubber-faced roller  52  (rubber-faced refers to any elastic polymer). The metal-faced rollers are driven and have diameters of 160 mm. The rubber-faced rollers have diameters of 250 mm. The pair of rollers  42  and  48  may be vertically oriented (as shown), horizontally oriented, or at some angle therebetween. Metal-faced rollers  48  and  50  may be smooth, grooved, threaded, textured, or combinations thereof. When grooved or threaded, the ratio of open surface to flat surface may nominally range from 90:10 to 10:90, preferably with 25:75; 50:50; and 75:25, and most preferred, 75:25. The rubber-faced rollers are preferably placed opposite one another in the pairing as shown, but they may be disposed on the same side, preferably on the side closest to apparatus  54 , so that fibers in the tow do not foul in the open surface of the metal rollers. The nip pressure between each roller pairs  42  and  48  is two (2) bars with a 70 mm diameter pressure cylinder. The roller pair  48  has greater surface speed than roller pair  42 . When cellulose acetate tow is used, the ratio of roller speed for pair  48  (S 48 ) to pair  42  (S 42 ) may range from 1≦S 48 /S 42 ≦2, and S 48 /S 42  is preferably 1.1-1.7, and most preferred 1.3-1.4.  
         [0027]     Optionally, a liquid application station  53  located after de-registration apparatus  40  may be used. Such liquids may be used to, for example, facilitate binding of fibers in the tow or particulate to the tow, or deodorize or scent the absorbent composite, or add an anti-microbial agent to the composite, or alter the hydrophilicity of the tow. Such liquids include water, hydrophilic liquids (such as alcohols, glycols, dimethyl sulfide, ketones, ethers and the like), plasticizers (such as triacetin), surfactants, and solutions containing plasticizers, surfactants and the like. Liquid application station  53  may include spray nozzles, disk applicators, rotating brush applicators, wick contact rolls, and the like, as is known in the art.  
         [0028]     Tow shaping apparatus  54  receives the tow  14  from de-registering apparatus  40 . Tow shaping apparatus  54  is used to shape the opened tow into a predetermined cross-sectional shape, preferably a generally rectangular cross-section, for use in the absorbent garment. Other cross-sectional shapes are also possible, they include: circular, oval, square, channeled, and grooved. A preferred tow shaping apparatus  54  is illustrated in, for example, U.S. Pat. No. 6,253,431, incorporated herein by reference. Another tow shaping apparatus  54  is illustrated in U.S. Pat. No. 5,331,976, incorporated herein by reference. When tow-shaping apparatus  54  has a 70 mm width, banding jet  18  has a width (W 1 ) of 62.5 mm and banding jet  30  has a width (W 2 ) of 65 mm. When apparatus  54  has a width of 110, W 1  is 82.5 mm and W 2  is 108 mm. When apparatus  54  has a width of 120, W 1  is 102.5 mm and W 2  is 118 mm. Additionally, apparatus  54  includes a dancer (not shown) that controls the thickness of the shaped tow as it exits apparatus  54 . The dancer is preferably a plate pivotally mounted within apparatus  54  and adapted to have bearing engagement with the tow along the tow&#39;s width. The dancer controls the thickness of the tow to ensure uniform thickness of the tow and to enable the line speeds disclosed hereinafter. The dancer is also illustrated in U.S. Patent Publications 2003/0130638; 2003/0135176; 2003/0143324, each is incorporated herein by reference.  
         [0029]     Particulate distribution apparatus  56  is located at the distal end of tow shaping apparatus  54 . Particulate distribution apparatus  56  is used to distribute particulate in a predetermined manner onto and/or into the opened, shaped tow and will be discussed in greater detail below. Particulate particularly includes SAP, but also includes other solid materials, such as adhesives, fragrances, wood pulp, deodorizers, anti-microbial agents, and the like. Particulate distribution apparatus  56  is further described in U.S. Patent Publications Nos. 2003/0130638; 2003/0132762; 2003/0135176; and 2003/0143324, each is incorporated herein by reference.  
         [0030]     Wind-up apparatus  60  is used to sandwich the particulate laden, shaped tow between strata (for example, tissues, nonwovens, and permeable and non permeable films). Apparatus  60  is conventional and driven. Strata  100  from unwind apparatus  62  is fed through a plurality of guide rollers  106  and passed by an adhesive applicator  64  to a vacuum apparatus  58 . Adhesive applicator  64  may be any adhesive applicator, but preferably is a hot melt adhesive applicator. Vacuum applicator  58  is coupled to a vacuum source  104  (see  FIG. 4 ) and may be any suitable vacuum apparatus, such as a vacuum drum or vacuum table (also see: U.S. Patent Publication No. 2003/0134559, incorporated herein by reference). Vacuum pressures range from 3-6 inches of water, preferably 5 inches of water. The vacuum drum or vacuum table is, preferably, driven. Strata  102  from unwind apparatus  66  is fed through a plurality of guide rollers  108  and passed by another adhesive applicator  64  to vacuum apparatus  58 . At vacuum apparatus  58 , stratum  100  and  102  sandwich the particulate laden, shaped tow. Strata  102  is pressed into the other layers by a lay on roller  110 . Lay on roller  110  may include a cavity of channel  114  (see  FIG. 5 ) to shape the absorbent composite  112  into a predetermined shape (e.g., hour glass, rectangular, etc.) and/or press stratum together for sealing. Thereafter, absorbent composite  112  may be wound-up on wind-up apparatus  60  or fed directly to a machine for making an absorbent garment.  
         [0031]     The line speed, as measured at the vacuum drum  58 , is preferably greater than 190 m/min, preferably greater than 225 m/min, and most preferably greater than 250 m/min. The maximum line speed is about 300 m/min. The ratio of tow speed exiting from cabinet  38  to the line speed at the vacuum drum  58  is greater than 1 and less than 3, preferably between 1.8 to 3.0, and most preferably about 2.4. This allows accumulation of the tow in the tow shaping apparatus  54 . Additionally, line speed can be used to control particulate distribution apparatus  56 . Coupling line speed to apparatus  56  minimizes particulate (e.g., SAP) loss during ramp up and ramp down of apparatus  10 .  
         [0032]     Additionally, static elimination devices (not shown) may be placed in apparatus  10  adjacent the tow band to decrease static charges that may accumulate on the tow band. Placement of those devices is within the skill of the art. Further, the driven rollers are preferably coupled or controlled (not shown) in a conventional manner to facilitate start-up, shutdown, and vary line speeds during operation.  
         [0033]     In  FIG. 3 , cabinet  38  is shown in greater detail. Tow  14  prior to entering cabinet  38  engages guide rollers  76 . Guide rollers  76  may be opened and closed via an opening mechanism  78 . Guide rollers  76  have a diameter of 50 mm and exert a nip pressure ranging from 0.5-5 bar, preferably 2-2.5 bar (using a 1.0625 inch cylinder). Cabinet  38  includes a door  70  that is fastened to the rest of the cabinet via hinges  72  and may be fastened shut by latch  74 . Cabinet  38  encloses de-registering apparatus  40  and prevents contaminants, such as adhesives from adhesive applicator  64  from fouling the surface of the rollers. Fouling of the surfaces can cause adhesion of the tow to the rolls. Cabinet  38  is supplied with an air nozzle  80  that is used to provide positive pressure within cabinet  38  so that contaminants cannot enter. The positive pressure may range from 0.1-1.0 psig, preferably 0.25-0.5 psig.  
         [0034]     Referring to  FIGS. 4, 5 , and  6 , the operation of the particulate distribution apparatus  56  is illustrated in greater detail. Particulate distribution apparatus  56  is preferably a vibratory feeder. At the bottom of a hopper is a clean out valve  90  and a motor  92  drives the feeder. Particulate is vibrated through an orifice defined, in part, by a trough  94  where it is deposited onto opened tow  98 . Particulate, when SAP, may be fed at rates of 1-25 Kg/min, preferably 5-13.5 Kg/min, assuming garment formation of 500-900/min with 10-15 g/garment. Particulate  96  and shaped tow  98  are held in place by the vacuum apparatus  58  (a rotary vacuum drum is shown), while stratum  100  and  102  are applied thereto. Stratum  100  and  102  are guided to vacuum apparatus  58  by rollers  106  and  108 , respectively. Adhesive from applicators  64  is preferably applied to the stratum prior to arrival at the vacuum apparatus  58 . When the stratum sandwich the particulate laden, shaped tow, on vacuum apparatus  58 , the lay on roller  110  squeezes the composite to seal it shut, preferably with the lateral edges of the stratum being sealed together. Thereafter, absorbent composite  112  is wound-up or directed on into a subsequent absorbent garment making operation.  
         [0035]     The distribution of the particulate is controlled, in part, by an orifice  118 ,  FIG. 6 . Orifice  118  is defined by trough  94  and plate  116  that may be moved to open and close the orifice. In  FIG. 6 , four possible configurations of orifice  118  are illustrated. Orifice  118 ′,  FIG. 6   a , illustrates a rectangular shaped orifice. Orifice  118 ″,  FIG. 6   b , illustrates a triangularly shaped orifice. Orifice  118 ′″,  FIG. 6   c , illustrates an arcuate shaped orifice. Orifice  118 ″″,  FIG. 6   d , illustrates a serrated or toothed shaped orifice. Of course, other configurations for the orifice would be obvious to those of ordinary skill in the art.  
         [0036]     The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicated the scope of the invention.