Compositions – Magnetic – With wax – bitumen – resin – or gum
Reexamination Certificate
2000-04-10
2002-01-08
Koslow, C. Melissa (Department: 1755)
Compositions
Magnetic
With wax, bitumen, resin, or gum
C252S062550, C252S609000, C355S117000, C355S117000, C355S117000, C355S117000
Reexamination Certificate
active
06337031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to flame-retardant resin magnet material that can be used in electrical appliances, building materials, and various other fields, and more particularly to a flame-retardant resin magnet material suitable for use in electrical appliances operated for extended periods of time in high-temperature environments, and to an electron beam adjustment apparatus obtained using this flame-retardant resin magnet material.
2. Description of the Related Art
A wide variety of synthetic resin materials have by now been introduced into our daily lives on a large scale and in a variety of forms. With electrical products, for example, large numbers of components made of synthetic resin materials are used as the constituent parts of such products, both large and small. Most of the synthetic resin materials for such synthetic resin components are organic materials, and are thus flammable and have high calorific value, so when these synthetic resin components are heated more than necessary, they ignite and burn, creating a possibility of major fires.
Television receivers, for example, are equipped with electron beam adjustment apparatus obtained by incorporating a plurality of annular magnets into the neck portion of a color picture tube. These annular magnets are molded from resin magnet materials obtained by adding magnetic powders to resin compositions. Because the electron beam adjustment apparatus are disposed adjacent to power generation units that generated considerable amounts of heat, these annular magnets are sometimes heated beyond the allowable limit, in which case the contained resin may ignite and burn, creating a danger that a fire or the like will occur. It is therefore imperative that flame retardancy be conferred on resin magnet materials, which serve as the molding materials for the annular magnets used in electron beam adjustment apparatus.
As typified by such electron beam adjustment apparatus, the resin magnet materials used in electrical products often must be flame retardant, and this requirement has tended to become progressively more stringent in recent years, with the issue of rendering currently flammable resin magnet materials flame retardant gradually becoming a very important element in terms of designing commercial products. Because various standards (for example, the UL standard in the USA) have been instituted concerning the flame retardancy of resin compositions, resin magnet materials also need to satisfy these standards, and continued efforts aimed at satisfying these standards are being made to achieve flame retardancy in resin magnet materials.
Well-known methods for achieving flame retardancy in flammable synthetic resin materials include (1) adding flame retardants to synthetic resin materials, (2) admixing inorganic fillers into synthetic resin materials, (3) compounding synthetic resin materials and flame-retardant polymers, (4) copolymerizing flame-retardant polymers with synthetic resin materials, and other methods. Bromine- or chlorine-based halogen substances have commonly been selected and used as such flame-retardants, inorganic fillers, flame-retardant polymers, flame-retardant monomers, or the like. Halogen-based substances, while possessing excellent flame retardancy, are also known to produce dioxins and other toxic substances during burning. The environmental impact of the toxic substances produced during burning have recently become a concern, and techniques aimed at enhancing flame retardancy without the use of halogen-based flame retardants are being developed. Such techniques are described, for example, in Unexamined Patent Application (Kokai) 1-201347 (Japanese Unexamined Patent Gazette).
This application discloses a polyolefin-based resin composition whose flame retardancy is enhanced by the addition of a nonhalogen-based flame retardant to ethylene, vinyl acetate, or the like. It is also disclosed that combinations of antimony trioxide with aluminum hydroxide, magnesium hydroxide, and other metal oxide hydrates can be used as such nonhalogen-based flame retardants. According to this technique, resin compositions exhibiting excellent flame retardancy can be obtained without the use of halogen-based substances.
This technique, however, still poses problems when applied to an electron beam adjustment apparatus, which is a typical application for the flame-retardant resin magnet material of the claimed invention.
The first problem is that no study has yet been conducted concerning the effect of a magnetic powder on flame retardancy when this powder is added to the resin composition in question, and that no proof has yet been obtained as to whether a magnetic powder is capable of preserving its stable magnetic characteristics in the presence of such flame retardants.
The second problem is that voids form inside the resin composition or that warping or deformation occurs. Aluminum hydroxide or magnesium hydroxide afford flame retardancy by releasing water (H
2
O) when heated, but when released at the heating temperature at which annular magnets are molded, this water (H
2
O) is trapped inside the molding, creating voids, warping, or deformation in the molding.
The issue that can be cited as a third problem is that it is completely unclear whether polyamide resins can be used as base resins, not to mention the fact that no information is yet available concerning the mixing ratios of various flame retardants in cases in which such polyamide resins are used as base resins. Polyamide resins are often used in electrical appliances because of considerations related to wear resistance, machining precision, heat resistance, mechanical strength, and the like, but the aforementioned techniques still cannot be used as reference because of the absence of any mention of the mixing ratios of various flame retardants in cases in which polyamide resins are used as base resins. In these conditions, a need existed for a resin magnet material that would be obtained by employing a polyamide resin as the base resin and that would have excellent flame retardancy and produce moldings devoid of voids, warping, deformation, or the like.
SUMMARY OF THE INVENTION
As a result of painstaking research aimed at overcoming the aforementioned problems, the inventors have succeeded in defining the specific aspects that should be adopted when polyamide resins are used as base resins in resin magnet materials obtained using halogen-based flame retardants. As used herein, the term “specific aspects” primarily refer to the types and mixing ratios of the flame retardants used.
The present invention can be broadly divided into the following three groups.
The inventions belonging to the first group reside in a flame-retardant resin magnet material obtained by adding
(Z) an alnico-based magnetic powder or a ferrite-based magnetic powder to a flame-retardant resin composition that is itself obtained by adding heat-resistant aluminum hydroxide and antimony trioxide to a polyamide resin in the following amounts:
(A) per 100 weight parts polyamide resin,
(B) X
1
weight parts heat-resistant aluminum hydroxide with a decomposition temperature of 280° C. or higher (where 10 weight parts<X
1
<70 weight parts), and
(C) X
2
weight parts antimony trioxide (where 40 weight parts<X
2
<270 weight parts).
The alnico-based magnetic powder is beneficial because of its less pronounced heat demagnetization, which is a phenomenon in which magnetic characteristics are adversely affected when the temperature rises, whereas the ferrite-based magnetic powder is beneficial because is it inexpensive and readily available.
The inventions belonging to the second group reside in a flame-retardant resin magnet material obtained by adding
(Z) an alnico-based magnetic powder or a ferrite-based magnetic powder to a flame-retardant resin composition that is itself obtained by adding heat-resistant aluminum hydroxide, antimony trioxide, and zinc borate to a polyamide resin in the following amounts:
(A) per 100 weight parts
Aoishi Eiji
Aoishi Tsutomu
Ida Takeshi
Marutani Naoshi
Aoishi Tsutomu
Kaneka Corporation
Koslow C. Melissa
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