Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Reexamination Certificate
1999-12-03
2002-07-23
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
C134S003000, C134S028000, C134S038000, C430S281100
Reexamination Certificate
active
06423150
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a removal of resin solid matter. More particularly, the present invention is concerned with recycling of materials, wherein resin solid matter stuck on a base material is removed, so that not only the base material but also the removed resin solid matter can be recycled.
BACKGROUND OF THE INVENTION
Recently, recycling of materials is the most important task to be achieved internationally. The presence of solid matter stuck on materials, such as paint, print, an adhesive material and the like, mainly causes obstruction of realizing the material recycling.
The present inventor has previously conducted studies with a view toward developing a method for removing such solid matter stuck on a base material and recycling the base material, and found that the solid matter can be easily removed by a method in which paint, print, an adhesive material or like is made from a resin having a chemical structure of formula (1), and then, solid matter made of the above resin is contacted with mixture (A) which contains acidic compound (a) and water (b) as essential components and optionally solvent (c).
SUMMARY OF THE INVENTION
However, the above method poses new problems in that the generated waste liquid causes environmental pollution.
The present inventor has conducted studies with a view toward, for minimizing or eliminating the above pollution problems, developing a method for extending the period of time when the mixture (A) can be used as long as possible or semipermanently, and further, a method for recycling the removed resin solid matter per se. As a result, it has been found that the problem is solved by dissolving and removing the resin solid matter having a chemical structure of formula (1) in two steps described below, and the present invention has been completed.
Specifically, the resin solid matter having a chemical structure of formula (1) is first contacted with mixtures (A), to thereby break the bonds in the chemical structure of formula (1), wherein the resin does not dissolve in mixture (A). Then, the resin solid matter in which the bonds are broken is contacted with a solvent, to thereby dissolve and remove the resin solid matter, wherein the resin dissolves in the solvent.
By the method of the present invention, mixture (A) used for the breaking the chemical bonds in the chemical structure of formula (1) is not contaminated with the resin, so that it is possible to remarkably extend the period of time that mixture (A) can be used. Further, the resin solution resulting form dissolution of the resin solid matter in the solvent also contains only a little contamination, such as an acid. Therefore, the disposal of this solution is easy.
When the resin solid matter is a resin cured by a cross-linking agent, in the first step of contacting with mixture (A), the cross-linking agent can be solely dissolved in mixture (A) simultaneously with breaking the crosslinkage in the resin. In this case, the resin solution resulting form dissolution of the resin solid matter in a solvent in the second step does not contain the cross-linking agent. Therefore, the resin can be reused simply by removing the solvent from the resin solution.
When the above cross-linking agent is hydrophilic, mixture (A) can be used in the form of a solution containing a major component of water. Therefore, this case is advantageous from the viewpoint of the safety.
When the above cross-linking agent is carbohydrazide, the cross-linking agent dissolved in mixture (A) undergoes decomposition by oxygen in the air or an oxidant. Therefore, in this case, mixture (A) can be used semipermanently.
The present invention is directed to a method for removing a resin solid matter having a chemical structure represented by the following chemical formula (1):
by having the resin solid matter contacted with a solvant after breaking the structure in the chemical formula (1) by having the resin solid matter contacted with a mixture (A), which contains an acidic compound (a) and water (b) as essential components, wherein the resin solid matter does not dissolve in mixture (A). In this case, the method according to the present invention, the mixture (A) may further contain an organic solvent (c).
The resin solid matter having a chemical structure represented by the above chemical formula (1) may be a substance obtained by a reaction between a carbonyl group-containing compound and a hydrazide group- or semicarbazide group-containing compound. In addition, the resin solid matter having a chemical structure represented by the above chemical formula (1) may be a substance obtained by a reaction between a carbonyl group-containing resin and a cross-linking agent which contains two or more hydrazide groups or semicarbazide groups.
PREFERRED EMBODIMENT OF THE INVENTION
With respect to the resin solid matter which can be used in the method of the present invention, there is no particular limitation as long as a resin constituting the resin solid matter has a chemical structure represented by the above formula (1). As specific examples of resin solid matter, there has been known a resin solid matter having a chemical structure represented by the above formula (1); a cured resin obtained by a reaction between a carbonyl group-containing resin and a hydrazide group- or semicarbazide group-containing resin; a cured resin obtained by cross-linking a carbonyl group-containing resin with a polyhydrazide compound or polysemicarbazide compound; or a cured resin obtained by cross-linking a hydrazide group- or semicarbazide group-containing resin with a polycarbonyl compound. These reactions are reported in a number of literatures (for example, see “The Chemistry of Amides” PAR[T] TWO (INTERSIENCE PUBLISHERS), issued in 1970, Chapter 10, pp. 515-600). Uses of these resins can be paint, print, adhesive material, resin treatment, an unsupported shaped article and the like. Further, in accordance with the uses, a pigment, an extender pigment, other resins, a plasticizer, a thickener and the like may be added.
Preferred resin solid matter is a resin cured by a cross-linking agent. In this case, when the resin solid matter is contacted with mixture (A) in the first step, the cross-linking agent can be solely dissolved in mixture (A) simultaneously with breaking the crosslinkage in the resin. In addition, the resin solution resulting from dissolution of the resin solid matter in a solvent in the subsequent second step does not contain the cross-linking agent. Therefore, the resin can be reused simply by removing the solvent from the resin solution.
More preferred resin solid matter is a cured resin in which the above cross-linking agent is hydrophilic. In this case, mixture (A) can be used in the form of a solution containing a major component of water. Therefore, this case is advantageous from the viewpoint of the safety.
Most preferred resin solid matter is a cured resin in which the above cross-linking agent is carbohydrazide. In this case, the cross-linking agent dissolved in mixture (A) can be decomposed by oxygen in the air or an oxidant, and therefore, mixture (A) can be used semipermanently.
Acidic compound (a) used in mixture (A) in the method of the present invention is used as a catalyst in the decomposition reaction of the chemical structure of the above formula (1). With respect to the acidic compound (a), there is no particular limitation, and either an inorganic acid or an organic acid can be used. The acidic compound having a high acidity can remarkably promote the decomposition reaction. Specific examples of acidic compounds (a) can be those described below.
Monobasic acids may include, for example: aromatic monobasic acids, such as benzenesulfonic acid, dodecylbenzenesulfonic acid, toluenesulfonic acid, benzoic acid, methylbenzoic acid or p-t-butylbenzoic acid; saturated or unsaturated fatty acids having 1 through 24 carbon atoms, such as formic acid, acetic acid, lactic acid, propionic acid, acrylic acid, butylic acid, caproic acid, caprylic acid, pelargonic acid, cap
Gulakowski Randy
Kansai Paint Co. Ltd.
Rader & Fishman & Grauer, PLLC
Winter Gentle E.
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