Apparatus and method for manufacturing a multi-layer web product

An apparatus and method for manufacturing a multi-layer web product. A long fiber stream is directed around a rotating carding cylinder. Two combing cylinders are disposed adjacent the carding cylinder to comb a first web of long fiber and a second web of long fiber, respectively, from the carding cylinder. A first conveyor receives the first web from the first combing cylinder and transports the first web toward a layering point. Similarly, a second conveyor receives the second web from the second combing cylinder and transports the second web toward the layering point. A short fiber deposition unit is disposed adjacent the second conveyor and deposits short fibers onto the second web. At the layering point, the first conveyor deposits the first web onto the second web, with the short fibers sandwiched therebetween, to form a layered web product.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the present invention is the manufacture of multi-layer web products, particularly web products made from nonwoven fibers.

Consumers tend to prefer nonwoven web products made from long fibers because of their superior hand feel as compared to short fibers such as wood pulp. Unfortunately, long fiber web products are generally more expensive than short fiber web products. Therefore, in order to meet the demands of consumers by providing a web product having a superior hand feel and meet the needs of manufacturers by reducing costs of materials and production, web products that include a combination of long and short fibers have been developed.

FIG. 1schematically illustrates a prior art apparatus for manufacturing wet laid fibrous web products using in-line hydroentanglement. The fibers are opened, treated, blended, diluted, and refined as necessary at the pre-treatment stage50of the apparatus to form the furnish. To provide a product having a hand feel that is superior to short fiber products, the furnish is formed from a combination of short and long fibers mixed together (throughout this description of the background and the description of the preferred embodiment of the invention, short fibers are typically natural fibers, but may also be or include synthetic fibers, while long fibers are typically synthetic fibers, but may also be or include natural fibers). From the pre-treatment stage50, the furnish is directed into the head box51, from which the fibers are deposited as a web onto the forming wire52. Once on the forming wire52, the web is conveyed to the hydroentanglement unit53, which directs high pressure water streams at the web to entangle the fibers. Depending upon the final web properties desired, the web may be transported under the hydroentanglement unit multiple times or under a hydroentanglement unit with multiple hydroentangling heads, or the web may be turned over to direct the high pressure water at the other side of the web. Following hydroentanglement, a drying unit54dries the web using any number of conventional drying processes, such as steam heated can dryers, TAD (through air drying), or Radiant Heat (such as Infra-Red). After drying, the web is wound into a roll55for storage or subsequent processing.

The combination web products produced using the apparatus ofFIG. 1exhibit cost savings over all long fiber products. At the same time, such products come closer to providing, but do not reach, the superior hand feel associated with all long fiber products.

Two-layer web products have also been developed. Such web products have a first layer of short fibers and a second layer of long fibers.FIGS. 2-4schematically illustrate prior art apparatuses for manufacturing two-layer web products. The apparatus ofFIG. 2is employed to manufacture a single layer wet laid short fiber web product. Such a short fiber web product is used as the first layer of a two-layer web product in a downstream process. In brief, the short fibers are separated, treated, blended, diluted and refined as necessary at the pre-treatment stage60of the apparatus to form the furnish. From the pre-treatment stage60, the furnish is directed into the head box61, from which the fibers are deposited onto the forming wire62. A drying unit63dries the web and the dried web is wound into a roll64pending subsequent processing.

The apparatus ofFIG. 3is employed to manufacture a single layer long fiber web product. Such a long fiber product is used as the second layer of a two-layer web product in a downstream process. The web formed with this apparatus typically uses longer fibers (generally 25 to 45 mm, or longer such as 45 to 100 mm). The long fibers are pre-opened in the bale opener70and transported to the fine opener71. Once the fibers are sufficiently separated and declumped for final processing and forming, they are transported to the chute feed72which meters them at a uniform rate and volume onto the feed roll73and then the lickerin roll74. The lickerin roll74transfers fibers in a separated, uniform, and controlled manner to the main carding cylinder75. The fibers are repeatedly combed and stripped from the main carding cylinder75by the worker and stripper rolls76. A combing cylinder77is positioned to comb the web from the main carding cylinder75and transfer the web to the doffer cylinder78(which also serves to comb the web). The web is transferred from the doffer cylinder78onto the forming wire82. Once on the forming wire82, the web is passed under a hydroentanglement unit79and through the drying unit80. The dried web is wound into a roll81pending subsequent processing.

The long fiber web product created by the process ofFIG. 3may be substituted with a two-layer long fiber web product through implementation of the carding apparatus disclosed in European Patent Application EP 1046731 A1, the disclosure of which is incorporated herein by reference. With such a carding apparatus, two webs are combed from the main carding cylinder, recombined, and joined either through entanglement or light adhesive bonding. Subsequent processing of both one- and two-layer long fiber webs may be performed in the same manner.

The apparatus ofFIG. 4is employed to combine a short fiber web with a long fiber web into a two-layer web product. A long fiber web, such as one made by the apparatus ofFIG. 3, is unwound from a roll81onto a carrier wire82. A short fiber web, such as one made by the apparatus ofFIG. 2, is unwound from a roll64and laid upon the long fiber web. The two webs are passed under a hydroentanglement unit90, through a dryer unit92, and wound into a roll93.

The two-layer web products produced using the apparatuses ofFIGS. 2-4also exhibit cost savings over all long fiber products. However, because only one side of such web products exhibits the superior hand feel of long fibers, while the other side exhibits the less desired hand feel of short fibers, such a product does not meet with the same consumer demand as does an all long fiber web product.

FIGS. 2-4illustrate an off-line process of manufacturing the two-layer web product. In practice, however, the apparatuses ofFIGS. 2-4are combinable for in-line formation of the two-layer web product.

U.S. Pat. No. 6,110,848, the disclosure of which is incorporated herein by reference, teaches a three-layer web product and the production thereof. This three-layer web product goes further toward meeting the demands of consumers and the cost needs of manufacturers, as it includes two outer layers of long fiber and a middle layer sandwiched therebetween of short fiber. The apparatus ofFIG. 5is employed to manufacture such a three-layer web product. A first long fiber web is unwound from a roll81onto a carrier wire91. A short fiber web is unwound from a second roll69and laid upon of the first long fiber web. A second long fiber web is unwound from a roll81and laid upon the short fiber web, thereby sandwiching the short fiber web between two layers of long fiber. This three-layer structure conveyed under a hydroentanglement unit90and through a drying unit92. As with other prior art, hydroentanglement of the three-layer web may be done with multiple passes, multiple heads, or on both sides of the web. The dried web is wound into a roll104pending further processing.

The three-layer web product is superior to other prior art web products that combine long and short fibers because it has the superior hand feel on both sides of the product and the product may be bulked up with short fiber as the middle layer without effecting the hand feel on either side of the product.

The apparatus ofFIG. 6illustrates the process ofFIG. 5as an in-line process. The long fiber forming equipment, labeled as C1and C2, respectively, up to the doffer cylinder78, is the same as described in connection withFIG. 3. A first long fiber web from the first forming equipment C1is laid upon the forming wire125. Short fiber deposition equipment S1deposits short fiber upon the first long fiber web. The short fiber, whether from a roll or otherwise, is fed into a hammermill121which separates the fibers. A transport fan122sends the separated short fibers to the forming heads123, where the short fibers are blown onto the first long fiber web. Vacuum suction units124on the opposite side of the forming wire125from the forming heads123assist in forming the layer of short fibers on the first long fiber web. The second long fiber web from the second forming equipment C2is laid on top of the short fibers. The three-layer structure is passed under the hydroentanglement unit79, through the drying unit80, and wound into a roll105pending subsequent processing.

Such an in-line process has the additional cost benefit of reducing or eliminating the need to store intermediary rolls. However, even with these advances in the production of nonwoven web products where 1) the products better meet the demands of consumers and 2) the manufacturing costs have been reduced, the costs of producing such web products remains high and would significantly benefit from apparatuses and processes which serve to further reduce production costs.

SUMMARY OF THE INVENTION

The present invention is directed towards an apparatus and method for manufacturing a multi-layer web product. A carding cylinder is rotated to transport long fiber. Two combing cylinders comb the long fiber from the carding cylinder to form first and second webs of long fiber. Both webs are deposited upon conveyors and conveyed toward a layering point. A short fiber deposition unit is disposed adjacent the conveyor carrying the second web and deposits short fiber upon the second web. The conveyor carrying the first web deposits the first web upon the second web at the layering point, thereby creating a layered web having outside layers formed of long fiber and an inner layer formed of short fiber. The layered web may thereafter be subjected to entanglement to better bind the layers together.

Accordingly, the present invention provides an improved apparatus and method for manufacturing a multi-layer web product. Other objects and advantages will appear hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning in detail to the drawings,FIGS. 1-6illustrate the state of the prior art as previously described. InFIG. 7, long fibers are pre-opened in the bale opener170and transported to the fine opener171. Once the fibers are sufficiently separated and declumped for final processing and forming, they are transported to the chute feed172which meters them at a uniform rate and volume onto the feed roll173and then the lickerin roll174. The lickerin roll174transfers fibers in a separated, uniform, and controlled manner to the main carding cylinder175. The fibers are repeatedly combed and stripped from the main carding cylinder175by the worker and stripper rolls176. The number or worker and stripper rolls may vary as desired.

A first combing cylinder177acombs a first web from the main carding cylinder175. The first web is transferred to the first doffer cylinder178aand from the first doffer cylinder onto the first conveyor183a. The first conveyor183amay be of any appropriate design known to those skilled in the art. The first conveyor183atransports the first web to the layering point196, which is the point at which the first and second conveyors recombine the respective webs being transported.

At the same time the first web is combed from the main carding cylinder175, a second combing cylinder177bcombs a second web from the main carding cylinder175. The second web is transferred to the second doffer cylinder178b, and from the second doffer cylinder the web is transferred onto the second conveyor183b. As with the first conveyor183a, the second conveyor183bmay be of any appropriate design known to those skilled in the art. The second conveyor183btransports the second web to the layering point196. While the second web is on the second conveyor183b, but before the layering point196, the second web passes by the short fiber deposition unit195, which deposits short fibers upon the second web. This short fiber deposition unit may be of the design described in connection withFIG. 6, which separates short fibers and uses air to lay the fibers evenly upon the second web, or it may be of any other appropriate design known to those skilled in the art, such as depositing a web of short fiber upon the second web. It is worth noting again that the short fibers may be synthetic, but use of natural fibers as the short fibers generally makes the process more economical. Similarly, the long fibers may be natural, but use of synthetic fibers as the long fibers generally makes the process more economical.

At the layering point, a layered web is formed by depositing the first web upon the second web, the short fibers being sandwiched therebetween. The layered web is received by a third conveyor184which passes the layered web under an entanglement unit179which directs jets of high pressure water at the web. The entanglement unit may be of any design known to those skilled in the art, such as drum or flatbed hydroentanglers. Thereafter, the web is passed through a drying unit180and wound into a roll194pending subsequent processing. However, if desired, subsequent processing may be performed in-line, thereby negating the need to wind the layered web into the roll.

InFIG. 8, three webs are combed from the main carding cylinder. As before, the first combing cylinder177acombs and transfers the first web to the first conveyor183avia a first doffer cylinder178a. The first conveyor183atransports the first web to the layering point196. The second combing cylinder177bcombs and transfers the second web onto a second conveyor183bvia a second doffer cylinder178b, and the third combing cylinder177ccombs and transfers the third web onto the third conveyor183cvia a third doffer cylinder178c. The second conveyor183bdeposits the second web onto the third web before the third web is transported under the short fiber deposition unit. After the second web is deposited upon the third web, the combined second and third webs pass under the short fiber deposition unit195, which deposits short fibers upon the combined second and third webs. The first web is thereafter deposited upon the combined second and third webs at the layering point196, with the short fibers sandwiched therebetween. Hydroentanglement and drying proceed as previously described.

In general, it has been found that when more than one web is combed from the carding cylinder, thinner webs are produced which are more easily manipulated to achieve desired properties of the web. Two generally desired qualities of web products are a low ratio between the machine direction strength and the cross direction strength of the web (“MD:CD ratio”) and a consistent basis weight. Older carding apparatuses which combed only one web from the carding cylinder were often lucky to achieve a 10:1 MD:CD ratio. Some carding apparatuses have reduced the MD:CD ratio within the range of 5:1 to 3:1. Carding apparatuses, such as the one depicted inFIG. 8which comb three thinner webs from the carding cylinder and which implement appropriate control features, are capable of reducing the MD:CD ratio within the range of 3:1 to 1:1. One such carding apparatus that has implemented control features to obtain a low MD:CD ratio is manufactured by F.O.R. of Biella, Italy, a division of FINCARDE S.p.H. Strade Campagne, also of Biella, Italy, as model number 06803/D153C1. An additional important capability of the F.O.R. carding apparatus is that the webs combed from the carding cylinder tend to have an approximately uniform basis weight. Variation in the basis weight for each of three webs has been found to be minimal. The F.O.R. carding apparatus is thus capable of generating the different web layers in the most preferred manner, and may be modified to make the apparatus and perform the method of producing the multi-layer web product as described herein.

A benefit of the present invention is the ability to reduce production costs by converting an older carding apparatus into a carding apparatus according to the present invention. Whereas prior to the present invention, multiple carding apparatuses and other equipment, such as that previously described, were necessary to form a multi-layer web product, now a single carding apparatus may be adapted to comb two or more webs from the carding cylinder, thereby enabling a multi-layer web product to be produced from a single carding apparatus. Reducing the amount of equipment necessary to manufacture a multi-layer web product will reduce the monetary and space requirements of manufacturing multi-layer web products.

Another benefit of the present invention is that existing dry-form pulp machines, which are losing utility within the industry as stand-alone units, may be retrofitted with a single carding apparatus of the type described herein to produce web products that are desirable to consumers. Investment costs for new equipment may thus be reduced while the useful life of existing equipment may be extended, thereby providing additional cost benefits.