Nonwoven webs with enhanced loft and process for forming such webs

Abstract

The present invention relates to a process of forming a soft bulky nonwoven web from a batt using thermobonding and to a soft bulky nonwoven web with a bond impression pattern and shape. The process comprises several steps including feeding a batt to a nip between first and second surface of first and second roller, where at least the first of the surfaces comprises spaced apart bonding protrusions surrounded by recessed areas. The bonding protrusions and the bond impression shape in the web exhibit a ratio of the greatest measurable width to the greatest measurable length of at least 1:2.5 and the perimeters thereof comprise a convex portion. The bonding protrusions are symmetric and / or have a certain angle to the machine direction.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method of producing a nonwoven web material exhibiting improved properties as well as to such a nonwoven material. Such a material may be useful for a number of applications, such as cleaning articles, like wipes or dusters, or in particular for disposable articles, such as disposable absorbent articles.BACKGROUND OF THE INVENTION[0002]It is well known in the industry that the final properties of thermally bonded nonwoven webs can be significantly influenced by an appropriate pattern of bonding points or bonding impressions expressed particularly by the shape and the size of the bond impression as well as the total bond area, and their arrangement in the plane such as in a certain pattern. By selecting appropriate parameters for the pattern, it is possible with the use of the same input material to, for example, produce both a strong compact web resistant against rubbing, as well as a lofty web with an increased softness...

AI Technical Summary

Benefits of technology

The present invention is about a process for making a soft and loose nonwoven material. The process involves using a special tool to compress and bond a heat-bondable fiber batt into a regular pattern of bonded areas. The resultant nonwoven material has improved softness and loft and can be used for various applications.

Problems solved by technology

The achieved thickness and structure of the resulting material are, however, not suitable for all applications.

In this way it is possible to produce a soft lofty material, however at the cost of a significant loss in strength.

The resulting material achieves a higher loft than with the use of a standard pyramid pattern, the bonding points of which, are similar to a regular rhombus, however softness as measured by the HandleOMeter does not achieve the values achieved in the described solution.

As a result of the complexity of the mix of the above-described characteristics, to the extent softness is considered an attribute of a nonwoven web material, it may elude precise measurement or quantification.

Although several methods for measuring and evaluating material features that are believed to affect softness signals have been developed, there are no standard, universally accepted units or methods of measurement for softness.

It is a subjective, relative concept, difficult to characterize in an objective way.

Because softness is difficult to characterize, it can also be difficult to affect in a predictable way, through changes or adjustments to specifications in materials or manufacturing processes.

However, among the costs involved in producing nonwoven web material formed of polymer fibers is the cost of the polymer resin(s) from which the fibers are spun.

Higher basis weight nonwovens require more resin to produce, and therefore, cost more per unit.

Thus, attempting to enhance loft and / or perceived softness by increasing nonwoven basis weight is incompatible with the ever-present objective of controlling or reducing costs.

Additionally, many current methods for enhancing softness signals in a nonwoven web have the undesirable effect of decreasing desirable mechanical properties such as tensile strength, and may also add cost to the web manufacturing process in the form of additional materials or additional equipment and energy required for processing steps.

The challenge to improve loft and / or softness becomes more difficult as nonwoven web basis weight is reduced, because, as basis weight is reduced, fewer fibers per unit surface area are available to contribute to loft and opacity of the web.

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