Patterning on SMS product

A method and apparatus for the production of nonwovens. The nonwovens including a spunbonding apparatus for forming a first web of nonwoven material on a first belt, and a meltblowing apparatus for forming a second web of nonwoven material on a second belt. The second belt moves in a direction opposite the first belt and after formation, the second web is deposited on said first web to form a composite spunbond and meltblown web.

FIELD OF THE INVENTION

The present invention is directed towards a method and apparatus for applying a pattern to a nonwoven web and particularly to a nonwoven web formed by spunbonding and spunbond-meltblown-spunbond (“SMS”) processes.

BACKGROUND OF THE INVENTION

There presently exists apparatus for the production of spunbond webs or fabrics formed from filaments or fibers typically made from a thermoplastic resin. Such an apparatus is disclosed in U.S. Pat. No. 5,814,349 issued Sep. 29, 1998, the disclosure of which is incorporated herein by reference. Typically, such apparatus includes a spinneret for producing a curtain of strands and a process-air blower for blowing process air onto the curtain of strands for cooling same to form thermoplastic filaments. The thermoplastic filaments are then typically, aerodynamically entrained by the process air for aerodynamic stretching of the thermoplastic filaments which are then, after passing through a diffuser, deposited upon a continuously circulating sieve belt for collecting the interentangled filaments and forming a web thereon. The web or fabric, so formed, is then subject to further processing.

In the spunbonding process for manufacturing nonwoven materials, thermoplastic fiber forming polymer is placed in an extruder and passed through a linear or circular spinneret. The extruded polymer streams are rapidly cooled and attenuated by air and/or mechanical drafting rollers to form desired diameter solidifying filaments. The solidifying filaments are then laid down on a conveyor belt to form a web. The web is then bonded by rollers to form a spunbonded web.

In the meltblown process for manufacturing nonwoven materials, thermoplastic forming polymer is placed in an extruder and is then passed through a linear die containing about twenty to forty small orifices per inch of die width. Convergent streams of hot air rapidly attenuate the extruded polymer steams to form solidifying filaments. The solidifying filaments are subsequently blown by high velocity air onto a take-up screen or another layer of woven or nonwoven material thus forming a meltblown web.

The spunbonding and meltblowing process can be combined in applications such as SMS shown inFIG. 1. In SMS a first layer of spunbonded material is formed on a belt or conveyor10by the spunbond beam12. The belt10typically has a uniform surface and air permeability to reach the right formation during spunbond process. The spunbonded material is deposited on the belt10at a point between the upstream and downstream press rolls16and16′ to form the web. The press rolls16and16′ function to eliminate any air leakage between the belt10and the web to enhance pre-bonding caused by the pressure and temperature of the top heated press roll. In order to assist in drawing the thermoplastic fibers onto the belt10, a vacuum box14is located beneath the belt10and which applies a suction to the belt. The airflow needed for the spunbond process is sucked from the system by a vacuum box14.

Next, in the meltblown beam18small fibers are blown onto the spunbond web layer. During the meltblowing process there is typically no need for precompaction press rolls.

Finally, a second spunbond beam20with press rolls22applies a second spunbond layer onto the web formed of the meltblown layer and the first spunbond layer. The composite spunbond-meltblown-spunbond material is then consolidated through a calender or a dryer mechanism (not shown).

While, initially it may appear that to form a pattern on an SMS or spunbond product all that would be necessary is a conveyor or forming belt having the desired topographical features, it is intuitive that the combination of the press rolls and the thermoplastic materials could be combined to create a spunbond material having a mirror image of the pattern of the conveyor. However, as described in U.S. Patent Application No. 2003/0164199, incorporated herein by reference, the competing factors of speed, avoidance of undesirable marking, air permeability, and reduced bounce make the use of a topographical pattern belt as the conveyor very difficult in practice.

There have also been described in the art other methods of providing patterns onto a nonwoven web or preform. For example, reference is made to U.S. Pat. No. 5,115,544, the disclosure of which is incorporated herein by reference. In the '544 patent, there is described a spunlacing method and apparatus for imprinting a pattern on a nonwoven material. In particular, the '544 patent describes a method and apparatus for imprinting a pattern on nonwovens formed by a spunlacing technique. As described therein, a nonwoven material is formed and transported on a wire screen having a pattern. The nonwoven material is then treated by a series of water jets, which cause the nonwoven to assume the shape of the wire screen. In this way the pattern from the wire screen is imparted on the nonwoven resulting in a patterned nonwoven.

While this method has proven to be very satisfactory in a spunlace application, the present invention is directed towards a spunbond apparatus and process. Accordingly, there is a need for an apparatus and method for the production of patterned spunbond nonwovens, and particularly an apparatus and method for the production of patterned SMS nonwoven.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for the formation of nonwovens having patterns in a spunbonding process.

It is another object of the present invention to provide a method and apparatus for the formation of spunbond and meltblown composite nonwovens having patterns formed thereon.

The objects of the invention will be generally achieved by providing an apparatus for the production of nonwovens including at least one spunbonding apparatus for forming a first web of nonwoven material on a first belt and at least one meltblowing apparatus for forming a second web of nonwoven material on a second belt. After formation, the second web is deposited on the first web by the second belt to form a composite spunbond and meltblown web.

Another aspect of the invention is directed to a method of forming a patterned nonwoven, including the steps of forming a first web of nonwoven material in a spunbonding process on a first belt, and forming a second web of nonwoven material in a meltblowing process on a second belt. The first and second webs of nonwoven material are then combined to form a composite nonwoven web.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now toFIG. 2, a spunbond-meltblown-spunbond nonwoven forming line according to one aspect of the present invention is shown. In this embodiment of the present invention, there is substantially no change in the spunbond beams12and20fromFIG. 1. As with the example shown inFIG. 1, a spunbond web24is formed by the spunbond beam12and the press rolls16. Again the vacuum box14operates to draw the thermoplastic fibers onto the belt10and remove the air used in the spunbond process to prevent disturbances in the formation of the web24.

Progressing down the SMS line, to the meltblown section, there is a patterning belt26supported by two rollers28, which in this example runs opposite to the direction of travel of belt10. This belt26is installed below the meltblown beam18and preferably is a patterning fabric. Meltblown fibers are laid down on the belt26and then transferred onto the belt10so that a meltblown web32that is formed on the belt26is deposited onto the spunbond web24.

The patterning fabric26provides a patterned surface onto which the meltblown fibers are deposited. Due to the heat and air pressure applied to the fibers by the meltblown process, a web formed by this process adopts the pattern of the belt26. In this fashion, by combining the meltblown web32with the spunbond web24it is possible to create a patterned SMS nonwoven. Alternatively, a drum covered with a patterning sleeve can be used instead of the belt26. In such an arrangement the drum would be placed downstream of the area where the meltblown fiber is deposited, and close enough so that such fibers have not yet cooled and may be impressed with the pattern on the drum.

As with the known SMS processes, air distribution and removal are important factors to consider. Due to the high pressure air applied to the meltblown fibers and the belt26during the meltblowing process, and in order to avoid air turbulence between the upper and lower portions of the patterning belt26, a diffuser30is installed to drive the airflow into the vacuum box14. The diffuser works to reduce the force of the air pressure which works on the backside of the belt26, the composite webs, and belt10and to eliminate turbulence between portions of the belt26. The vacuum box14is used to remove air from the system to prevent disruption of the web.

After combining the meltblown web32with the spunbond web24to form a combined web34, the combined web34may be directed through a second spunbond beam20. The second spunbond process is similar to the first in that it includes press rolls22and a means for applying a spunbond web to the combined web34to form a final SMS web36.

It has thus be shown that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, because certain changes may be made in carrying out the above method and in the construction(s) set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.