BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to methods for manufacturing cleaning wipes, more particularly to pre-moistened cleaning wipes that are formed from multi-layer substrates.

2. Description of Related Art

Numerous cleaning wipes are available, e.g., such as CLOROX DISINFECTING WIPES. While such wipes provide good overall cleaning and disinfection characteristics, versatility, and convenience, there is a continuing need for improved cleaning wipes, as well as methods for their manufacture.

BRIEF SUMMARY

The present invention relates methods of manufacturing wipes that may typically be pre-moistened during manufacture or use, where the wipe includes a multi-layer substrate comprising at least three layers, where the wipe as a whole may include a significant fraction of pulp fibers, and where such can be achieved in a relatively simple, high speed (350 meter per minute (mpm) or more), low capital investment process, where the process does not employ loose pulp fibers within the process, does not require use of process water to aid in maneuvering fibers (pulp or otherwise present in any of the layers) along the plane of the wipe or through the thickness of the wipe, does not require a drying step to remove such process water, does not require use of chemical binders to achieve bonding between the three layers, and which facilitates use of synthetic fibers (e.g., staple or continuous synthetic fibers) having particular properties, for the middle layer of the multi-layer substrate without the fibers of the middle layer protruding through the external surface of either the top or bottom layers.

An embodiment may be directed to a method for manufacturing a multi-layer substrate, including providing both top and bottom surface layers, e.g., both comprised of pulp fibers, providing a thermoplastic material that comprises polyethylene and/or has a tan delta value of 0.2 to 0.4 within the temperature range of 100° F. to 350° F., positioning the thermoplastic material so as to be sandwiched between the top and bottom surface layers, and heating the thermoplastic material to a temperature at which the thermoplastic material heat softens. During such heating there may also be application of pressure to the sandwich structure. In any case, such heating results in bonding of the thermoplastic material to groups of fiber in the top and bottom surface layers that are in contact with the sandwiched thermoplastic layer as it softens, such that no chemical adhesives are used to adhere the top and bottom surface layers to the thermoplastic material.

In addition, after heat softening, the thermoplastic material includes pores therethrough, providing a fluid pathway therethrough such that any liquid loaded into the top surface layer is able to pass through the pathway, into the bottom surface layer. Such is the case, even where the thermoplastic layer may initially have been an initially liquid impervious film layer, prior to the heating and bonding portion of the process. Once so formed, the multi-layer substrate can be loaded with a cleaning composition, e.g., by applying the cleaning composition to the top and/or bottom surface layer(s). Because of the fluid pathway, fluid communication is possible from one surface layer to the other, through the fluid pathway in the thermoplastic film layer. The multi-layer substrate may be void of any chemical adhesives for holding the plurality of layers together. Binders may technically be present in tissue paper or other pulp layers (e.g., in relatively small amounts) because such binders are frequently used as processing aids in processing pulp material layers, although the purpose of such included materials, like kymene, is to impart strength to the pulp fiber structures (better holding such fibers together, in the fixed web), rather than for any purpose of actually adhering a layer of pulp material to a thermoplastic material layer. Instead, the melted thermoplastic material bonds to groups of fibers (e.g., pulp fibers) in the top and bottom layers that were in contact with the thermoplastic material as it melted.

The referenced tan delta value is defined as the ratio of viscous modulus divided by elastic modulus. It therefore provides information relative to the ratio of a material's viscous liquid phase stiffness or flow characteristics relative to the material's solid phase stiffness characteristics. Different polymeric materials exhibit different tan delta characteristics, and this ratio also varies for a given material with temperature. Polyethylene is an exemplary material that exhibits a tan delta value in a range of 0.2 to 0.4 within the temperature range of 100° F. to 350° F. Other polymeric materials (e.g., polypropylene) do not necessarily exhibit such characteristics. Applicant has found that tan delta is a good indicator of whether a given polymeric material will result in a melted thermoplastic “sandwich” layer that effectively bonds to the exterior nonwoven layers both above and below the thermoplastic inner “sandwich” layer, while at the same time opening up fluid pathways through the thermoplastic layer, allowing liquids (e.g., a cleaning composition) to flow between the top and bottom layers, through the thermoplastic layer.

Another embodiment is directed to a method of manufacturing a multi-layer substrate, comprising providing top and bottom surface layers in which fibers of each surface layer comprise at least 95% by weight pulp fibers, providing a thermoplastic material that comprises polyethylene or has a tan delta value of 0.2 to 0.4 within the temperature range of 100° F. to 350° F., positioning the thermoplastic material so as to be sandwiched between the top and bottom surface layers, creating a sandwich structure having at least 3 layers, and applying a calendaring process to the sandwich structure by heating the sandwich structure to a temperature at which the thermoplastic material melt softens, while applying pressure during such heating. This results in bonding of the thermoplastic material to pulp fibers in the top and bottom surface layers that are in contact with the thermoplastic material as it softens, such that no chemical adhesives are used to adhere the top and bottom surface layers to the thermoplastic material. After calendaring, the thermoplastic material includes open pores through the thermoplastic material, providing a fluid pathway therethrough such that any liquid loaded into the top surface layer is able to pass through the pathway to the bottom surface layer. Once formed, the 3-layer multi-layer substrate is loaded with a cleaning composition.

Further features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the detailed description of preferred embodiments below.

