Paper making and fiber liberation – Processes and products – With coating after drying
Reexamination Certificate
2002-02-12
2004-03-30
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
With coating after drying
C162S145000, C162S146000, C162S158000, C162S181100, C428S141000, C428S143000, C428S144000, C428S156000, C428S220000, C428S323000, C428S332000
Reexamination Certificate
active
06712932
ABSTRACT:
DESCRIPTION
The present invention relates a method of producing self-cleaning and non-adhesive or paper-like material.
Numerous methods are described in literature to achieve water-repelling, oil-repelling, and dirt-repelling qualities, which allows self-cleaning as well among other things. Common in these methods is the fact that a highly smooth surface is finished in most cases in a highly hydrophobic manner. However, it has been shown that the effect is either only temporarily or developed inadequately strong for industrial use.
EP-A-0 772 514 discloses that aside from a highly hydrophobic finish, an additional microstructure contributes to the distinct support for the qualities described above. The phenomenon has been observed and described in nature for plants like nasturtium or more highly developed in lotus plants. Accordingly, the creation of artificial surface structures consisting of elevations and depressions with distances between the elevations ranging from 5-200 microns, preferably 10-100 microns, and the height of the elevation ranging from 50-100 microns, preferably 110-50 microns, whereby the elevations are made of hydrophobic polymers, which contributes additionally that items having such artificial surfaces may be given qualities of this type.
However, paper or paper-like material has in general a rather random and disorderly structure that is typically not smooth but has a specific macrostructure, which has as a consequence that a specific development of the above-mentioned microstructure will be impossible.
In particular, the inventors of the present invention have discovered during an attempt to use the method described in EP-A-0 772 514 for the development of a hydrophobic surface structure on paper that the achievable effect is inadequate for commercial application. In particular, fiber swelling occurs in paper that is treated according to the method described in EP-A-0 772 514 upon contact with water, which causes a change in the microstructure. In addition, the inventors of the present invention have observed penetration of water through paper that has been treated in such a manner, which causes the dirt dissolved in water to enter into the paper or even travel completely through the paper thereby.
It was therefore that much more surprising that the inventors of the present invention were from the start successful to produce paper or paper-like material having a non-adhesive and/or self-cleaning effect whereby non-adhesive and/or self-cleaning qualities are durable.
The object of the first aspect of the present invention is thereby a micro-structured paper or paper-like material having a self-cleaning and/or non-adhesive effect whereby the paper or paper-like material is hydrophobic through the entire cross-section of the material and which is micro-structured in such a way that the surface is provided with elevations and depressions whereby the distance between the elevations ranges from 0.04 to 100 microns and the height of the elevations ranges from 0.04 to 100 microns, and whereby the paper or paper-like material is characterized in that it contains particles having the size of 0.04 to 50 microns that are bound to the paper or paper-like material by means of a binder.
With paper and paper-like materials there are understood, according to the invention, materials such as paper, metallized paper, paperboard, cardboard, boxboard and non-wovens, but not textiles.
In a preferred embodiment of the first aspect of the present invention, the distance between the elevations on the surface of a thusly micro-structured paper or paper-like material ranges from 0.04 to 50 microns, particularly preferred in a range of 0.04 to 20 microns. In an additional preferred embodiment, the height of the elevations on the surface of a thusly micro-structured paper or paper-like material ranges from 0.04 to 50 microns, particularly preferred in a range of 0.04 to 20 microns.
It is further preferred according to the invention that the paper or paper-like material is additionally oil repellant. The paper or the paper-like material is thereby, in a preferred manner, oil repellant as well as water repellant [hydrophobic].
According to a preferred embodiment of the first aspect of the present invention, the inventive paper or paper-like material is additionally characterized in that drops of water do not adhere to the surface of the paper or paper-like material but that they roll off durably. This may be determined according to the invention in that a water droplet measuring 20 micro-liters rolls off the surface of the novel paper or paper-like material tilted by 40°, preferably by 10° from the horizontal position, and whereby said water droplet does not adhere to the surface.
Furthermore, the paper or paper-like material in an additional preferred embodiment of the first aspect of the present invention is characterized in that is has a resistance to moisture penetration of more than 10 minutes, preferably more than 30 minutes. This resistance to moisture penetration was determined according to the invention in that the tested paper or paper-like material was placed on top of a sheet of blotting paper whereby a stained water droplet measuring 20 micro-liters was deposited on the surface of the material to be tested and it was left in place on the surface. The underlying blotting paper was visually examined after 10 minutes or correspondingly later. Should there be no staining of the blotting paper be visible, then one can considers the paper to be resistant to moisture penetration for the time tested according to the invention.
Furthermore, the paper or paper-like material is preferably characterized by a resistance to the swelling of fibers. This can be determined according to the invention in that the surface of the paper or paper-like material is visually examined for any swelling of fibers after removing the droplets after 30 minutes from the tested paper surface according to the method described for testing the resistance to moisture penetration. Swelling of fibers may be recognized hereby, for example, by undulations [washboard marks] on the paper or paper-like material. Should these undulations not occur, then the paper is considered to be resistant against swelling of fibers.
In a preferred embodiment of the first aspect of the present invention, the paper or paper-like material has a contact angle with the water greater than 120°, preferably greater than 140°. According to the invention, a water droplet in the amount of 20 micro-liters was placed on the paper or paper-like material to measure the contact angle at room temperature and the contact angle was measured with the aid of a contact measuring device commonly used in the trade, e.g. one from the Kruss Company (Firma Kruss).
Additional properties of the paper or paper-like material, such as basis weight, strength or thickness may be adjusted without difficulties, depending on the desired application, in a traditional manner by those skilled in the art in the appropriate technical field.
The object of an additional aspect of the present invention is a method to manufacture a micro-structured paper or paper-like material that is water-repellant over the entire cross section of the material and having a self-cleaning and/or non-adhesive effect, which is provided with elevations and depressions whereby the distance between the elevations ranges from 0.04 to 100 microns and the height of the elevations ranges from 0.04 to 100 microns as well and whereby the method is characterized in that particles of a size of 0.04 to 50 microns are added to the fibers of the paper or paper-like material and said particles are fixed to the fibers by means of a binder together with the use of a water-repelling agent in the scope of a wet-laying method.
It is basically insignificant for the method in the invention as to which one of the available wet-laying methods is used. Thereby, it could be a method using a papermaking machine having an endless [Fourdrinier] wire, a forming vat, or an oblique wire. The
Büchsel Martin
Kaussen Manfred
Schroft Sabine
Chin Peter
Papierfabrik Schoeller & Hoesch GmbH & Co. KG
Pennie & Edmonds LLP
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