Cleaning and liquid contact with solids – Processes – Miscellaneous
Reexamination Certificate
1998-10-30
2001-07-17
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Miscellaneous
C428S140000, C428S220000, C428S366000, C428S413000, C428S423100, C428S480000
Reexamination Certificate
active
06261380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of reusing a coated substrate having an easily removable coating which is fixed to the surface of material from which the deposit is easily removed with water, such that the coated material can be repeatedly cleaned easily.
2. Description of Related Art
Hitherto it was difficult to remove a water-insoluble deposit from a material surface. For example, liquid oil should be cleaned by water containing a surfactant with considerable labor, or by an organic solvent which is harmful to both the human body and the environment.
Since a waxy or solid deposit is difficult to remove using the surfactant, it should be removed by the organic solvent or mechanically scraped off, which requires heavy work. But such deposit may not be completely removed, or the material to which the deposit is adhered may be damaged. In many cases, the waxy or solid deposit may not be removed.
It is possible to remove the deposit by forming a releasable or soluble coating on the material and removing the deposit together with the coating. However, whenever the coating is removed, a fresh coating must be reformed, or the removed coating generates an additional waste. Therefore, this technique does not provide a viable solution.
As a coating from which the deposit can be repeatedly removed, a coating of polyterafluoroethylene (hereinafter referred to as “PTFE”, (for example, TEFLON™ of DuPont) is known. However, it is not widely used since it is expensive, and the kind of surface on which the PTFE coating can be formed is limited, or it has poor transparency.
It is highly desired to develop a coating such that a deposit can be repeatedly removed from the material surface and which solves the above problems.
As explained above, to remove the deposit from the material is surface, a large amount of work is required, or some other methods applied which use an organic solvent which is harmful to the human body and the environment. In the case of overhead projector (OHP) films or office automation papers such as copying papers, they are used and wasted on a large scale to cause an environmental problem, since ink cannot be removed from their surfaces. This is because there is no coating from which the deposit, such as the ink, is repeatedly removed with ease and which is cheap and has good flexibility in use.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of depositing a coating which is formed on the surface of a material and from which a deposit can be easily removed using water, whereby the material's surface can be easily cleaned.
This and other objects are achieved by providing a coating fixed to the surface of a material, the coating comprising a hydrophilic resin which swells with water but is not washed away by the water so as to disappear, and is solid in air at ambient temperature.
When the coating of the present invention is fixed on the surface of the material, a deposit adhering to the surface can be easily removed with water.
The coating of the present invention does not prevent but in fact allows adhesion of the deposit. The coating of the present invention is characterized in that the adhered deposit can be removed from the coating only with water.
From the coating of the present invention, mostly water-insoluble or hardly soluble deposits, such as an oily material, can be removed. Therefore, the present invention is particularly effective with these deposits.
DETAILED DESCRIPTION OF THE INVENTION
The coating of the present invention should be swellable with water. To effectively remove a deposit on the coating, a volume of the coating swells preferably at least 1.5 times the original volume. The volume swell herein used is obtained by dipping a sample having a length of about 1 cm, a width of about 1 cm and a thickness of about several ten &mgr;m in water for 5 minutes, calculating a ratio of the size (length or width) after dipping to that before dipping, and cubing the calculated ratio.
To repeatedly use the coating, it should not be washed away so as to disappear. To form such coating, preferably the resin has a gel content corresponding to a ratio of the resin portion, which is not dissolved in water and washed away of at least 50%, more preferably at least 70%. The resin having such gel content can provide scratch resistance, water resistance and the like to the coating.
To this end, it is effective to crosslink the resin. Examples of crosslinkable functional groups are an epoxy group, an isocyanate group, a double bond, and the like. The functional group can be present in a crosslinking agent and/or in the resin molecule. As a crosslinking source, a chemical crosslinking agent, such as an epoxy crosslinking agent, and isocyanate crosslinking agent etc., or irradiation can be used.
To suppress the washing away or peeling off of the coating, the coating should have adhesion or release resistance to prevent the removal of the coating from the surface of the material. To this end, it is advantageous to treat the material surface or form a layer of material on the surface which is different from the material to be coated.
For example, to improve the adhesion, treatment with or a surface layer of parachlorophenol, trifluoroacetic acid, a silane coupling agent, a titanium coupling agent, an azide compound or a polymer can be employed. When the degrees of swelling of the coating and the material to be coated are different, a surface layer having an intermediate degree of swelling between them can be formed to absorb strain generated therebetween.
The coating of the present invention which is fixed to the surface of the material should contain a resin swellable with water. Such resin has, for example, a polar functional group or a hydrophilic chain. Specific examples of the polar functional group or the hydrophilic chain are a carboxylic acid group, a hydroxyl group, a sulfonic acid group, an amide group, an amino group, a phosphoric acid group or their salts, and a polyethylene glycol chain.
Examples of a resin having the above functional group or the hydrophilic chain are homo- or copolymers of acrylic acid, methacrylic acid, vinyl alcohol, hydroxyethyl methacrylate, dihydroxy-propyl methacrylate, acrylamido-2-methylpropanesulfonic acid, acrylamide, methacrylamide, N,N-dimethylacrylamide, N-acryl-glycinamide, N-isopropylacrylamide, N,N-dimethylaminopropylacryl-amide, vinylpyrrolidone, N,N-dimethyaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, allylamine or their salts, quaternary amino compounds, polyethylene glycol, or copolymers of one or more of these monomers with other monomer.
The hydrophilicity of the resin can be evaluated by a receding water contact angle. In the present invention, the resin having a receding water contact angle of 40 degrees or less, preferably 20 degrees or less, more preferable 10 degrees or less, in particular, about 0 degree is used advantageously used. The receding water contact angle is measured by forming a water drop on the resin film, sucking water with a syringe, and measuring an angle between the water drop and the resin surface with, for example, a protractor, when the edge of water drop starts to move inwardly.
When the coating is treated with the specific aqueous solution and the hydrophilicity is changed by such treatment, the water contact angle should be measured after the resin is dipped in the aqueous solution and dried.
To improve various properties of the coating, it is possible to use components in combination with the hydrophilic resin. For example, the coating composition may optionally contain inorganic powder, a plasticizer, an antistatic agent, a lubricant, a dye or a pigment, a dispersant, a hydrophobic resin and the like.
The present invention makes it possible to use water to remove the deposit from the material surface. Therefore, when the deposit is removed by cleaning with water, the present invention is effectively practiced. When the resin is not sufficiently swelled by the water so that the re
Kohno Kenji
Mitsuhashi Hiroyuki
Miyata Kazushi
Saibara Shoji
Birch & Stewart Kolasch & Birch, LLP
Gulakowski Randy
Hitachi Maxell Ltd.
Wilkins Yolanda E.
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