Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-28
2001-09-18
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S414000, C524S424000, C524S436000, C523S205000
Reexamination Certificate
active
06291570
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat deterioration resistant flame retardant comprising hydrotalcite compound particles having specific properties and to a substantially halogen-free synthetic resin composition comprising the same in a specific proportion and having heat deterioration resistance and flame retardancy. More specifically, it relates to a heat deterioration resistant flame retardant which comprises hydrotalcite compound particles having specific properties, is almost free from heat deterioration during the thermal molding of a synthetic resin and can provide distinguished heat deterioration resistance and flame retardancy to a resin, and to a substantially halogen-free resin composition comprising the same in a specific proportion.
Stated more specifically, the present invention relates to a substantially halogen-free resin composition which, though it contains a heat deterioration resistant flame retardant in relatively large quantities, rarely undergoes a reduction in physical strength caused by the heat deterioration of a resin at the time of molding or use, and to a molded article thereof which is rarely whitened by heat deterioration. The present invention also relates to a substantially halogen-free resin composition which is excellent in the dispersibility of particles, non-cohesiveness, moldability and physical properties such as impact strength, and to a molded articles thereof.
Prior Art
Flame retardancy has been being required of synthetic resins more increasingly and more strictly each year. To meet this, a flame retarding technology utilizing a halogen-containing resin such as PVC and a flame retarding technology utilizing an organic halide and antimony trioxide in combination have been proposed and widely used. However, as the halogen-containing resin and organic halide flame retardants used in these technologies partly decompose and generate halogen gas during the molding process, they have various problems that they corrode a processing machine and a molding machine, they are toxic for workers, they exert a bad influence upon the heat resistance or weatherability of a resin or rubber, and they generate a large amount of smoke including harmful gas and dioxin at the time of combustion of used molded article.
Therefore, there arises a strong demand for a non-halogen flame retardant having none of the above problems, and attention is now being paid to aluminum hydroxide particles, magnesium hydroxide particles and the like.
However, since aluminum hydroxide particles begin to be dehydrated at a temperature of about 190° C. and cause a foaming trouble in a molded article, the molding temperature must be kept below 190° C. Therefore, the aluminum hydroxide particles have such a problem that the types of usable resins are limited.
As magnesium hydroxide particles have a dehydration start temperature of about 340° C., it has an advantage in that it can be used with almost all types of resins. However, when a synthetic resin molded article containing magnesium hydroxide at a high concentration as a flame retardant is exposed to carbonic acid-containing water, acidic rain or the like for a long time, there occurs a problem that magnesium hydroxide dissolved in an acid separates out on the surface of the article in the form of magnesium carbonate, basic magnesium sulfate or the like to whiten the surface, thereby impairing the appearance of the molded article, and in addition, magnesium hydroxide contained in the resin migrates to the surface of the article gradually, thereby reducing its proper flame retardancy.
On the other hand, hydrotalcite compound particles have been developed as a flame retardant because they have excellent acid resistance (see JP-A 52-90192).
However, the hydrotalcite compound particles have properties suitable for use as a flame retardant molded article when it is filled in a resin, but it has been revealed that the particles have still problems to be solved along with recent growing requirements for properties of the particles.
That is, to fill hydrotalcite compound particles in a synthetic resin and acquire level V-0 in a UL-94 flame retardancy standard with a thickness of ⅛ inch to {fraction (1/16)} inch, about 150 to 250 parts by weight of the hydrotalcite compound particles must be filled based on 100 parts by weight of the resin. Filling such a relatively large amount of the hydrotalcite compound particles in the synthetic resin promotes the deterioration of a molded article by heating at the time of molding or use and reduces the inherent physical properties, especially such as Izod impact strength, elongation, tensile strength and the like, of the molded article.
It is an object of the present invention, therefore, to provide a novel heat deterioration resistant flame retardant comprising hydrotalcite compound particles, a heat deterioration flame retardant resin composition comprising the same and a synthetic resin, and a molded article thereof.
The inventors of the present invention have conducted studies on the purity and physical properties of hydrotalcite compound particles to attain the above object.
As a result, they have found that the amounts of specific metal compounds as impurities contained in the hydrotalcite compound particles and the value of average secondary particle diameter of the hydrotalcite compound particles have an influence upon the heat deterioration of the resin and that a flame retardant having excellent heat deterioration resistance can be obtained by controlling these values to specific values. The present invention has been accomplished based on these findings.
The hydrotalcite compound particles contains various impurities derived mainly from their source materials during their production process and these impurities are contained in the hydrotalcite compound particles as a solid solution or admixture.
That is, the hydrotalcite compound particles are industrially produced from a magnesium source material, aluminum source material and alkali source material as main source materials, and these source materials mostly rely on natural resources or processed products thereof. Therefore, these source materials contain many kinds of metal compounds and non-metal compounds, and are refined and used in limits that costs permit. However, it is impossible to avoid the inclusion of many kinds of impurities.
During the production process thereof, the elution and inclusion of metals derived from the materials of various apparatuses such as a reactor, container, transport pipes, crystallizer, grinder and the like occur in an unnegligible amount.
The present inventors have conducted studies on components and amounts thereof concerning many kinds of impurities which are derived from its source materials and generate from its production process and contained in the hydrotalcite compound and which have an influence upon heat deterioration and reductions in physical properties when a resin is molded or heat deterioration when a molded article is used. As a result, they have found that when an iron compound and a manganese compound out of the various impurities are contained in trace amounts as an admixture or even as a solid solution, they have an influence upon the heat deterioration of the resin.
They have also found that not only the contents of these specific impurities contained in the hydrotalcite compound particles but also the particle diameter of the hydrotalcite compound particles have a district influence upon heat deterioration. Therefore, it has been found that, to obtain a composition that is filled in a resin and rarely causes deterioration by heat, (i) the amounts of specific metal compounds contained in the hydrotalcite compound particles should be reduced to values smaller than predetermined values and (ii) the average secondary particle diameter of the hydrotalcite compound particles should be reduced to a value smaller than a predetermined value (that is, most of the particles do not agglomerate secondarily).
Thus, according to studies conducted by t
Imahashi Takeshi
Katsuki Keiko
Okada Akira
Kyowa Chemical Industry Co Ltd
Sanders Kriellion
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