Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-10-19
2003-05-27
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S423000, C525S481000, C525S485000, C525S486000, C525S488000, C525S510000, C525S524000, C525S526000, C525S528000, C525S533000, C525S934000
Reexamination Certificate
active
06569959
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a modified resin composition containing phenolic hydroxyl group and a curable resin composition thereof. The invention further relates to the epoxy resin composition which is obtained by epoxidation of said modified resin composition containing phenolic hydroxyl group by epihalohydrin and a curable resin composition of said epoxy resin.
BACK GROUND OF THE INVENTION
In general, an epoxy resin weight components is broadly applied as a component of paint or adhesive and for various uses such as electric fields or civil engineering because of the excellent chemical and physical properties which an epoxy resin composition originally has. However, the required level for the features of epoxy resin composition are becoming higher and higher along with the progress of each field of application. Especially, in the uses of powder coating, molding materials or paints for inside surface coating of a can, the development of a resin whose contents of lower molecular weight is low is expected. For instance, since an epoxy resin powder coating has a good durability for corrosion and has a strong resistance to chemicals, it is practically used as the paint for an inner and an outer surface coating of a steel tube or as the paint for a steel frame coating.
Generally, as an epoxy resin composition, bisphenol A type solid epoxy resin is used and as a hardener, dicyandiamide, acid anhydride aromatic amine, dihydrazide or phenol resin is used. As a phenol resin which is used as the hardener, a novolac type phenol resin, preferably the modified resin which has a phenolic hydroxyl group at both ends can be used. For instance, the composition obtained by a chemical reaction between a bisphenol type epoxy resin composition obtained by reacting bisphenol such as bisphenol A or bisphenol F with epichlorohydrin under the presence of hydroxide of alkali metal and excess bisphenol. As the modified resin which contains phenolic hydroxyl group, “TH-4100” produced by THOTO KASEI, EPICURE 171 and 172″ produced by YUKA SHELL EPOXY and XD-8062″ of DOW CHMICAL are currently in the market. The powder coating which uses above mentioned modified resin as a hardener is disclosed, for instance, in Japanese Patent Laid-open publication 54-7473, Japanese Patent Laid-open publication 58-79011, Japanese Patent Laid-open publication 58-113267 and Japanese Patent Laid-open publication 61-12762, and these powder coating are remarkably improved so as to be applied to outer surface of a pipe. However, in these conventional modified resins which contains phenolic hydroxyl group, since from 5 to 20 wt % of bisphenol A used for the reacted remains, and vaporizes at a baking procedure, following two phenomena are pointed out as serious problems. That is, accompanied with the vaporization of bisphenol A, many tiny pin holes are formed on the surface of coated film and the physical properties of coated film is deteriorated, further the inside of a furnace for baking is polluted. Further, there is another problem that, by the vaporization of bisphenol A, the anticipated mixing ratio with epoxy resin is changed and deteriorates the physical properties of a coated film.
In the fields of powder coating and molding materials, conventional bisphenol type solid epoxy resins have a problem of blocking and deteriorate the stability of quality for storing, when a low epoxy equivalent resin is used. To solve the above mentioned problems, an epoxy resin not containing a low molecular component which causes a blocking problem, whose viscosity at molten state is low and has good fluidity has been expected.
As a method to remove low molecular weight component in solid type epoxy resin, for instance, the method to remove low molecular weight component by a molecular distillation is well known. However, even by this method, it is difficult to remove the low molecular weight component whose degree of polymerization (hereafter shortened to n) is bigger than 0, further the problem that the solid epoxy resin is thermally decomposed by high temperature at the procedure of distillation has been pointed out. Furthermore, since it is necessary to repeat a distillation for several times to remove n=0 component completely, this method is not useful for the industrial utilization. In the document of Japanese laid open publication of 61-231018, the method to remove the low molecular weight component by contact with a hydrocarbon solvent such as xylene is reported, however by this method it is difficult to remove n=0 component selectively and components bigger than n=0 are also removed and also the removing effect of n=0 component is not sufficient. In Japanese patent laid open publication 1-230678, the refined bisphenol type epoxy resin from which low molecular weight component i.e., lower than 800, is reduced or removed by contacting high molecular weight epoxy resin having 2000 to 6000 number-average molecular weight with lower alcohol in an affinity solvent is disclosed. This method is suited to a high molecule epoxy resin containing smaller than 2% of n=0 or n=1 lower molecule components, and the removing effect is not complete. The removing of these lower molecule components is not complete, even after 5 times repetition of rinsing procedure by alcohol, and is not a useful method as an industrial use.
From the view point of sanitation, an epoxy resin composition which does not contain low molecular weight composition is expected. In general, for the use of inside surface coating of a can for beverage, an epoxy/phenol type coating, an epoxy/amino resin coating and an epoxy/urea resin coating are used.
However, recently, kinds of beverage to be packed in a can have become more diverse. Green tea, oolong tea and black tea are becoming more popular as a beverage to be packed in a can. Since these kinds of beverage are heat treated by high temperature (retort treatment) after being packed into cans, components of coating are partially dissolved at this procedure and the lasting of flavor of contents is spoiled. As a coating which has good durability to bending at the can production, a polyvinyl-chloride organosol coating is usually used, however this coating has a problem of sanitation caused by monomer and plasticizer residue, and also has an environmental problem caused by chlorine gas generated when the wasted cans are burned. Therefore, a development of epoxy resin coating which has good durability to bending and an excellent feature for lasting of flavor is desired.
The objects of this invention are to provide a modified resin containing phenolic hydroxyl group [A] which does not contain a vaporizing component at a baking procedure and a curable resin composition thereof; a solid epoxy resin [B] which does not contain a low molecular weight component and has a good fluidity and a curable resin composition thereof; and a low molecular weight component free epoxy resin [C] which forms a coating having good durability to bending and an excellent feature for lasting of flavor and a curable resin composition thereof.
DISCLOSURE OF THE INVENTION
The important points of this invention include, a modified phenolic hydroxyl group containing resin having a low free difunctional phenol content comprising a resin [A] of formula (1), said resin having a phenolic hydroxyl group equivalent of from 300 to 1,200 g/eq; and, wherein residues of unreacted difunctional phenol is less than 5% by weight of resin, and a curable composition (a) comprising the modified phenolic hydroxyl group containing resin and an epoxy resin as the necessary components, [a] an epoxy resin which is solid at room temperature [B] and which comprises the product of epoxidizing the modified resin with epihalohydrin, said epoxy resin having an epoxy equivalent in the range of from 450 to 2,500 g/eq and a curable resin composition (b) comprising the solid epoxy resin and a hardener; an epoxy resin [C] which is solid at room temperat
Hanafusa Masayoshi
Nozawa Hidenori
Saitoh Nobuhisa
Shinohara Shuya
Takeda Yasuyuki
Sellers Robert E. L.
Sherman & Shalloway
Tohto Kasei Co., Ltd.
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