Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1998-06-11
2002-03-19
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S317100, C428S343000, C428S354000, C428S35500R, C442S156000
Reexamination Certificate
active
06358600
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a sheet for protecting a paint film which is difficult to deteriorate or discolor the paint film and thus is suitable for the surface protection of body, parts and the like of automobiles.
BACKGROUND OF THE INVENTION
As a method for protecting automobiles and their parts which have been painted against the attack by various suspended matters such as dust and rainwater or other harmful matters that can damage, dull or discolor the paint film during shipping on truck or ship to overseas or other remote places, there has been heretofore known a method of applying a coating material mainly comprised of wax in a thickness of from 5 to 40 &mgr;m. However, this method has some disadvantages. For example, it is difficult to form a wax coat with a uniform thickness, making it impossible to provide a uniform protection. Further, a wax coat is easily stained. Moreover, a wax coat is easily affected by acidic rainwater. Further, wax or other matters penetrate through the coated paint film to cause discoloration thereof. It takes much time and labor to apply and remove the wax coat. Further, this method requires the use of a solvent and the disposal of a waste liquid, causing environmental pollution.
On the other hand, various surface protective sheets comprising a support and a pressure-sensitive adhesive layer provided thereon have been known. A sheet comprising a support and a radiation-curing pressure-sensitive adhesive layer having a lowered glass transition point or a rubber pressure-sensitive adhesive layer made of a polyisobutylene or the like formed thereon has been proposed as a surface protective sheet for an adherend having a paint film, as disclosed in, for example, JP-A-2-199184 and JP-A-6-73352 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”). This sheet can overcome the above-described problems.
However, this proposal is disadvantageous in that a detergent from window washer or the like penetrates into the paint film through wrinkle portions unavoidably developed during covering the adherend with the surface protective sheet and then remains in bubble portions unavoidably developed during covering the adherend to cause the paint film to swell and hence discolor or deteriorate, giving stains that are not easily removed. Such stains are remarkable particularly when those are attributable to wrinkle portions which have been developed in the direction of gravitational force.
As a result of extensive studies to overcome the above-described problems, it was found that the deterioration or discoloration of a paint film is attributed to the evaporation and the concentration of water from acidic water or detergent which has unavoidably penetrated into the paint film during or after adhering the protective sheet to the paint film.
SUMMARY OF THE INVENTION
In the light of the fact that the penetration of acidic rainwater or detergent is unavoidable, an object of the present invention is to provide a sheet for protecting a paint film, which does not deteriorate or discolor the paint film even if the protective sheet is adhered to protect the paint film under the condition containing acidic rainwater or detergent and thus can maintain the adhered state to the paint film over a long period of time without peeling off the protective sheet.
The sheet for protecting a paint film according to the present invention comprises a porous substrate and a pressure-sensitive adhesive layer formed on one surface of the porous substrate, wherein the sheet has an air permeability in a direction of sheet thickness of 20,000 sec/100 cc or less and a moisture permeability in a direction of sheet thickness of 2,000 g/m
2
·24 hr or more, and also the porous substrate may have an ultraviolet transmission of 10% or less at a wavelength of 190 to 370 nm.
Even if acidic rainwater, detergent or the like penetrates into the interface between the sheet for protecting a paint film of the present invention and the paint film through wrinkle portions on the sheet, the water can evaporate away from a large area of the protective sheet due to the air permeability and moisture permeability of the porous substrate. Thus, evaporation or concentration of water is difficult to occur in local portions such as entrapped bubble portions.
As a result, even if the protective sheet is maintained to adhere to automobiles or other painted materials, the deterioration or discoloration of the paint film covered with the sheet can be prevented. Further, even if the protective sheet is adhered to painted materials under the condition containing acidic rainwater, detergent or the like, it is not necessary for the sheet to be peeled off and re-adhered. Thus, the sheet for protecting a paint film of the present invention can be applied to painted bodies having a vertical face.
Further, if the sheet of the present invention comprises a porous substrate which cuts ultraviolet rays, it is difficult to cause deterioration of substrate or adhesive layer even if the sheet is allowed to stand over an extended period of time under high ultraviolet intensity conditions such as outdoor. In other words, the sheet of the present invention can fairly maintain the initial strength and exhibits an excellent peelability. Thus, the sheet of the present invention is difficult to cause breakage of substrate or adhesive remaining and can be easily peeled off the painted material.
DETAILED DESCRIPTION OF THE INVENTION
The sheet for protecting a paint film of the present invention comprises a porous substrate and a pressure-sensitive adhesive layer formed on one surface of the porous substrate. The sheet has an air permeability in a direction of sheet thickness of 20,000 sec/100 cc or less and a moisture permeability in a direction of sheet thickness of 2,000 g/m
2
·24 hr or more. From the standpoint of the evaporatability of entrapped water in a large area, the air permeability of the sheet is preferably 10,000 sec/100 cc or less, and more preferably 5,000 sec/100 cc or less, and the moisture permeability of the sheet is preferably 3,000 g/m
2
·24 hr or more, and more preferably 5,000 g/m
2
·24 hr or more.
Another embodiment of the sheet for protecting a paint film of the present invention comprises a porous substrate and a pressure-sensitive adhesive layer formed on one surface of the porous substrate, wherein the porous substrate has an ultraviolet transmission of 10% or less at a wavelength of 190 to 370 nm. From the standpoint of prolonged maintenance of high peelability free from breakage of the sheet or adhesive remaining by preventing deterioration of the substrate or pressure-sensitive adhesive layer, the ultraviolet transmission of the porous substrate at a wavelength of from 190 to 370 nm is preferably 8% or less, more preferably 5% or less, and most preferably 1% or less.
Accordingly, the porous substrate which can be used is any appropriate porous material which at least has the air permeability and the moisture permeability fallen within the above defined range or the ultraviolet transmission fallen within the above defined range. In general, a sheet of processed fiber, such as nonwoven fabrics, woven fabrics or papers, can be used. From the standpoint of the simultaneous accomplishment of the prevention of deterioration or discoloration of the paint film and the good peelability of the sheet after accomplishment of protection, a sheet showing the air permeability and moisture permeability fallen within the above defined ranges and also the ultraviolet transmission falling within the above defined range is preferably used.
The fiber used to constitute the sheet of processed fiber can be any appropriate fiber. A fiber having excellent water resistance, etc. is preferable. Examples of such a fiber include fiber made of thermoplastic resins such as polyolefins (e.g., polyethylene, polypropylene, etc., which may be used alone or as mixtures thereof), polyesters and polyamides, regenerated or semisynthetic fibers such as rayon and cuprammonium rayon si
Eda Takeshi
Hayashi Keiji
Horada Mitsuru
Inoue Tsuyoshi
Matsui Komaharu
Copenheaver Blaine
Nitto Denko Corporation
Paulraj Christopher
Sughrue Mion Zinn Macpeak & Seas, PLLC
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