Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-10-01
2004-05-11
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S094000, C524S431000, C524S904000, C523S202000, C523S212000, C428S424600
Reexamination Certificate
active
06734236
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fluorine-containing resin powder coating composition which gives a fluorine-containing resin coating film having a high whiteness and to various articles having the fluorine-containing resin coating film.
BACKGROUND ART
Fluorine-containing resin coatings have been used widely for coating of an outer surface of chemical equipment and parts of a plant of chemical industry such as a reaction tank, reservoir tank, reaction tower, inner lining of piping, agitator and processing roll by making the best use of excellent properties of a fluorine-containing resin such as solvent resistance, heat resistance, non-sticking property, chemical resistance and electrically insulating property.
The fluorine-containing resin powder coating composition is subjected to baking at high temperature, particularly at 300° C. or more after the coating, and therefore foaming arises easily due to thermal deterioration of the fluorine-containing resin, and addition of a thermal stabilizer is essential.
The addition of a thermal stabilizer can inhibit the deterioration of the fluorine-containing resin considerably. However since the thermal stabilizer is deteriorated, there is a problem that the fluorine-containing resin coating film which is originally transparent and white is subject to a change in color into brown or black or non-uniformity of color after the baking due to a residue of the deteriorated stabilizer. Thermal deterioration of the fluorine-containing resin is also considered as a cause for the color change.
On the other hand, in the fields of medicines, foods and medical hygiene, from a point that staining of tanks for synthesis and storage of chemical substances is difficult to recognize when a dark coating is used and also from the viewpoint of appearance and cleanliness, a coating color is demanded to be as approximate to white as possible.
A usual method of making a color of coating film white is a method of incorporating a white pigment for coating. Examples of known white pigment are titanium oxide, calcium carbonate, zinc oxide, barium sulfate, and the like. The inventors of the present invention have made experiments and as a result in case of general-purpose white pigments for coating, non-uniformity of color arose and a satisfactory coating film could not be formed.
An another approach is a method of changing a thermal stabilizer. However even in this approach, a color change could not be inhibited only by changing the thermal stabilizer. Moreover the addition of the white pigment for coating still causes non-uniformity of color.
An object of the present invention is to provide a fluorine-containing resin powder coating composition which gives a fluorine-containing resin coating film having a high whiteness.
Another object of the present invention is to provide various articles having on an outer surface thereof a coating film which has a high whiteness and is obtained by applying the fluorine-containing resin powder coating composition.
DISCLOSURE OF INVENTION
Namely the present invention relates to the fluorine-containing resin powder coating composition to be subjected to baking at 300° C. or more, in which the fluorine-containing resin composition for forming a coating film contains surface-treated rutile titanium oxide particles as a whitening agent.
In the present invention it is preferable that the fluorine-containing resin composition for forming a coating film comprises a fluorine-containing resin, a thermal stabilizer and surface-treated rutile titanium oxide particles and that the fluorine-containing resin is a perfluoro resin, particularly a melt-moldable perfluoro resin and the thermal stabilizer has a melting point of not less than 70° C.
Further the present invention relates to the coating film which is obtained by applying the above-mentioned coating composition of the present invention and baking at 300° C. or more and has a whiteness of 60 or more and relates to the articles having the coating film on a surface thereof.
BEST MODE FOR CARRYING OUT THE INVENTION
The fluorine-containing resin to be used for the fluorine-containing resin composition for forming a coating film of the present invention is one which can stand baking at 300° C. The fluorine-containing resin may be a perfluoro resin or a non-perfluoro resin such as vinylidene fluoride copolymer, ethylene-tetrafluoroethylene copolymer or ethylene-chlorotrifluoroethylene copolymer. From the viewpoint of excellent heat resistance, solvent resistance, non-sticking property, chemical resistance and electrically insulating property, the perfluoro resin is preferable. Also among the perfluoro resins, melt-moldable perfluoro resins are preferred to polytetrafluoroethylene (PTFE) which is difficult to be melt-molded, from the point that a film forming property thereof is excellent and pin hole is difficult to arise.
Examples of the preferred melt-moldable perfluoro resin are tetrafluoroethylene (TFE) copolymers, for instance, copolymers of TFE with at least one of perfluoro(alkyl vinyl ethers) (PAVE) and hexafluoropropylene (HFP). Particularly TFE, PAVE and/or HFP copolymers, concretely TFE/PAVE copolymer (PFA), TFE/HFP copolymer (FEP) and TFE/PAVE/HFP copolymer are preferred.
Examples of PAVE are one or more of perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), and the like. Particularly PPVE is preferable.
One of the features of the present invention is that the fluorine-containing resin composition for forming a coating film comprises surface-treated rutile titanium oxide particles as a whitening agent in addition to the fluorine-containing resin.
It is necessary that titanium oxide to be used in the present invention is surface-treated and a crystalline form thereof is of rutile type. As shown in Comparative Examples mentioned hereinbelow, in case of un-treated titanium oxide which is a general-purpose white pigment for coating, non-uniformity of color arises, and also even in case of anatase titanium-oxide which is titanium oxide having another crystalline form, non-uniformity of color occurs.
It is preferable that a surface-treating agent for rutile titanium oxide is one comprising aluminum oxide and/or silicon oxide, more preferably one containing silicon oxide in a larger amount.
An average particle size of titanium oxide is not limited particularly, and is, for example, from about 0.1 &mgr;m to about 1.0 &mgr;m which is a size of commercially available titanium oxide.
Examples of the surface-treated rutile titanium oxide to be used preferably in the present invention are, for instance, Tipaque (registered trademark) CR-90), CR-95 and CR-97 available from Ishihara Sangyo Kaisha, Limited; Titanix (registered trademark) R-805 available from TAYCA CORPORATION; Ti-Pure (registered trademark) R-960 and R-902 available from Du Pont de Nemour E.I. & Co. Inc.; and the like. Also rutile titanium oxides surface-treated to the same extent as in those surface-treated rutile titanium oxides can be used preferably.
An amount of the surface-treated rutile titanium oxide is from 0.1 to 10 parts by weight (hereinafter referred to as “apart”), preferably 0.5 to 10 parts, further preferably 1 to 5 parts based on 100 parts of the fluorine-containing resin. When less than 0.1 part, a desired whiteness cannot be given to a coating film, and when more than 20 parts, non-sticking property and corrosion resistance of the fluorine-containing resin coating film are lowered.
To the fluorine-containing resin powder coating composition of the present invention is blended a thermal stabilizer. While various known thermal stabilizers can be used, when dry-blending each component for preparing a powder coating composition, since a temperature of the mixture becomes 60° C. or more, usually 70° C. or more, thermal stabilizers having a melting point of 70° C. or more, preferably. 80° C. or more are used. This is a characteristic point of the powder coating composition with respect to the thermal stabilizer.
Examples of the prefera
Miyatani Toshio
Ogita Koichiro
Tomihashi Nobuyuki
Daikin Industries Ltd.
Yoon Tae H.
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