Patent Application
20100032867
1. Technical Field
The present invention relates to embossing of non-woven webs and more particularly, to the permanent post-embossing of air-laid or double recrepe (DRC) fabrics. The method utilizes a hard, durable, raised emboss pattern roller and a soft, smooth, rubber backup emboss roller. The present invention further relates to an apparatus and method for embossing non-woven web material.
2. Background Art
Air-laid and DRC sheets are well known in the art. The following is a description of some illustrative patents.
1. U.S. Pat. No. 7,208,064 (Schmidt et. al.) describes a method for embossing air-laid webs using laser engraved, heated embossing rolls. The preferred use of these rolls is on the production line to thereby reduce cost and shorten emboss pattern development time.
2. U.S. Pat. No. 5,759,473 (Minke et. al). describes a process for producing a silicone coated embossing roll used for embossing a thermo-plastic film. A laser beam is used to cut a pattern in the smooth silicone rubber roll.
3. U.S. Pat. No. 5,529,563 (Veith et. al.) describes a method of embossing between unmatched male and female embossing elements wherein one of the rolls could be made of rubber.
4. U.S. Pat. No. 5,269,983 (Shultz) describes a method of embossing using a mated pair of emboss rolls whereby a laser can be used to make recesses in a resilient roll which, in turn, receives the protuberances of a rigid male embossing roll when nipped together.
5. U.S. Pat. No. 4,476,078 (Tao) describes conventional embossing either before or after binder is applied and cured. As described, each method has its advantages and disadvantages, with pre-embossing reducing production line speed, and post-embossing lacking good emboss clarity.
As is seen in the foregoing, rubber rolls have been used for embossing in pre and post production or binder in application. However, each known application has shortcomings. Typically, post emboss application methods produce results which suffer from lack of emboss definition or lack of emboss permanence, particularly on non-woven webs, such as air-laid web. To date, there has been no progress in the clear and permanent post embossing of non-woven air-laid or DRC webs.
The method of present invention ameliorates the shortcomings of known methods by providing clearly defined, permanent emboss patterns during post production handling of air-laid or DRC web. The present method produces a deeper emboss impression than that of previous methods, with the deeper impression maintaining itself over time, rather than flattening and losing definition. Further, the present method reduces costs through the use of rubber male and smooth rubber backup emboss rollers. In addition, pattern development time and emboss roller engraving is both less costly and less time consuming.
There is provided in accordance with the present invention, a method for permanent embossing non-woven, air-laid and DRC substrates in a continuous inline process. The inventive process includes: A) selecting a predetermined air-laid or DRC web for post embossing; B) providing a hard engraved emboss roller having a continuous, circumferential, hard embossing surface; C) providing the embossing surface with a predetermined pattern engraved thereon, the pattern having a height of 0.010 inches to about 0.040 inches; D) biasing the hard embossing surface toward a second, smooth backup roller; E) providing the smooth backup roller with a continuous surface composed of a soft rubber compound, the compound having a durometer hardness of 20 to about 60; and F) nipping a web of predetermined substrate between the two rolls at pressures of 50 to 500 pli to thereby emboss the web.
It is to be understood that the emboss pattern selection is critical to thereby minimize the amount of emboss area on the web and to maintain the original overall packaged product thickness. Further, the predetermined emboss pattern selected for emboss use should preferably have a raised emboss surface of about 0.5 percent to 35 percent of the emboss roller total surface area.
This process may also be adapted for use in discontinuous processes without departing from the spirit of the invention. Other modifications to this invention could also be readily acknowledged by experts in this field, however they should be considered within the scope of this invention.
Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
The present invention is directed to a method of post-embossing non-woven, air-laid or DRC web. The present method does not significantly affect the overall bulk and strength of the base fabric web, thereby maintaining the original overall packaged product thickness. The method further enhances separation and dispensing of the finished product.
An apparatus which may be used to practice the present method may be viewed in
As may be further viewed in
As may be seen in
As may be observed in
Alternative embodiments of a hard raised embossing roller 32 for use in the present method may be viewed in
As viewed particularly in
An alternative hard raised emboss roller 32 may be viewed in
In a preferred method according to the present invention, the hard emboss roller 32 may be traditionally engraved by tooling and acid etching. Alternatively, the engraving may be made by laser. The depth (H) of the engraved pattern roll may be from about 0.010 inches to about 0.090 inches, about 0.015 inches to about 0.050 inches, or about 0.020 to about 0.040 inches.
With further reference to
It is to be understood that it is also possible to heat the raised hard emboss roller 32, the smooth soft rubber backup roller 36, or both, without departing from the spirit of the invention. Heating the rollers 32 or 36 allows for lower pounds per linear inch on the emboss rolls or faster throughput, with comparative emboss definition. Further, it is also possible to utilize the disclosed apparatus and method in an inline process.
While the inventive method of the present invention may be applied to any air-laid or DRC substrate, it is understood that most typically these substrates have basis weight from about 25 to about 200 pounds per 3000 square foot ream. Most preferably the basis weight of the substrate is approximately 28 pounds to 60 pounds per 3000 square foot ream. Further, the process described can be applied to webs made using other non woven technologies or materials, including, but not limited to, McAirlaid, Brettings point to point emboss product, and hydroentangled fabrics. Further, it is to be understood that post emboss handling of the substrate may include sheet folding and cutoff prior to discharge and packaging, such as that shown in
A method according to the present invention includes the steps of: A) selecting a predetermined air-laid or DRC web roll for post embossing; B) providing a hard, raised emboss roller 32 having a continuous, circumferential, hard embossing surface 34; C) providing the embossing surface 34 with a predetermined pattern 42 engraved thereon, the pattern 42 having a depth of 0.010 inches to about 0.040 inches; D) biasing the hard embossing surface 34 toward a second, smooth soft rubber backup roller 36 to thereby provide a nip 44; E) providing the second smooth soft rubber backup roller 36 with a continuous surface 38 composed of a soft rubber coating 46, the coating having a durometer hardness of 20 to about 60; and F) nipping a web 16 of predetermined substrate between the two rolls 32, 36 at pressures of 50 to 500 pli to thereby emboss the web 16. The method may further include the step of providing the hard, raised emboss roller 32 with a repeatable, predetermined pattern 42 which is arranged and employed in a manner to not significantly affect the overall substrate 16 thickness or strength.
Another method of embossing air-laid sheet product according to the present invention may comprise the steps of:
a) providing a base sheet 16 of pre-formed air-laid composed of binder and pulp; and
b) embossing said sheet 16 by nipping it between a hard, raised emboss roller 32, and a smooth soft rubber backup roller 36.
The process results in minimal change in overall sheet performance and physical properties due to the emboss depth and coverage.
A binder used in a preferred method may be composed of any one or combination of the following:
a) liquid polymer emulsions, ethylene vinyl acetate, vinyl acetate, acrylic, styrene butadiene, etc.
b) thermal bondable fiber or powders such as polyethylene, polypropylene, or mixtures thereof, by way of example.
Pulps used in a preferred method may be composed of any one or combination of the following: wood pulp, synthetic fibers including polyethylene, polypropylene, nylon, rayon, acrylic, by way of non-limiting example.
As mentioned previously, the present invention may also define a preferred method of embossing double recrepe (DRC) sheet product. A preferred method may comprise the steps of:
a) providing a base sheet 16 of pre-formed DRC;
b) embossing said sheet 16 by nipping it between a hard, raised emboss roller 32, and a smooth soft rubber backup roller 36.
The process results in minimal change in overall sheet performance and physical properties due to emboss depth and coverage.
The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/133,262, filed 27 Jun. 2008, and entitled “Method for Permanent Embossing of Non-Woven Webs.”
| Number | Date | Country | |
|---|---|---|---|
| 61133262 | Jun 2008 | US |
