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
2000-11-21
2002-09-17
Dawson, Robert (Department: 1712)
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...
C524S442000, C524S500000, C524S537000, C524S464000, C525S461000, C525S462000, C525S474000
Reexamination Certificate
active
06451906
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flame-retardant resin composition that contains a polycarbonate type resin. More specifically, the present invention relates to a flame-retardant resin composition that is useful in applications in which superior flame-retarding properties are required, e. g., housing materials and parts for household electrical appliances or OA equipment such as television sets, monitors, printers, copying machines, facsimile machines and personal computers, etc., battery packs, liquid crystal reflective panels, automotive materials and construction materials, etc.
BACKGROUND OF THE INVENTION
Polycarbonate resins are widely used in a broad range of fields including electrical devices, electronics and OA as engineering plastics that are superior in terms of transparency, impact resistance, heat resistance and electrical characteristics. In these fields of electrical devices, electronics and OA, superior flame-retarding properties (UL 94V) and impact resistance are required (as in the case of external parts of personal computers).
Polycarbonate resins are highly flame-retardant plastic materials that possess self-extinguishing properties; however, in order to satisfy further safety requirements in the fields of electrical devices, electronics and OA, there is a need for an even higher degree of flame-retarding properties corresponding to UL 94V-0 or 94V-1.
Conventionally, in order to improve the flame-retarding properties of polycarbonate resins, a method has been employed in which an oligomer or polymer of a carbonate derivative of brominated bisphenol A is added in large quantities to the polycarbonate. However, in cases where such oligomers or polymers of carbonate derivatives of brominated bisphenol A are added in large quantities as flame-retarding agents, although the flame-retarding properties of the polycarbonate resin are certainly improved, the impact resistance drops, and cracking occurs in molded articles that are molded from the resin. Furthermore, since a halogen type compound containing a large amount of bromine is added, there is a possibility that gases containing this halogen will be generated in the case of combustion. Accordingly, from an environmental standpoint as well, there is a demand for the use of flame-retarding agents that do not contain halogens such as chlorine or bromine, etc.
Phosphoric acid esters and silicone resins are known as flame-retarding agents that do not contain halogens. For example, in Japanese Examined Patent Application (Kokoku) No. Sho 62-25706, the addition of phosphoric acid esters for the purpose of improving the flame-retarding properties of polycarbonate type resins is proposed. However, in cases where phosphoric acid esters are added to polycarbonate type resins, the heat resistance and impact resistance drop when molded articles are manufactured.
On the other hand, in the case of silicone resins, the heat resistance is high, no harmful gases are generated during combustion, and silicone resins themselves are very safe; accordingly, such resins have come to be used as flame-retarding agents for polycarbonate type resins.
Silicone compounds used as flame-retarding agents are polymers that are formed by polymerizing at least some of the four types of siloxane units shown below (M units, D units, T units and Q units).
For example, a flame-retardant resin composition formed by adding a silicone resin containing 80 wt % or more T units of a thermoplastic resin is disclosed in Japanese Examined Patent Application (Kokoku) No. Sho 62-60421. Furthermore, a flame-retardant resin composition formed by adding a silicone resin containing 30 to 99 mol % T units, 0 to 80 mol % D units, 1 to 70 mol % M units and 0 to 50 mol % Q units to a synthetic resin such as a polycarbonate, etc., is disclosed in Japanese Unexamined Patent Application (Kokai) No. Hei 5-86295.
However, the addition of the silicone resins described in the abovementioned patent applications alone rarely produces a large flame-retarding effect. Furthermore, in order to satisfy the strict flame-retardant standards involved in the case of electrical and electronic equipment, silicone resins must be added in large amounts; as a result, this may have a deleterious effect on the moldability, kneadability and other necessary characteristics of the plastic. In addition, this is also disadvantageous from the standpoint of cost, so that such methods are not practical.
Accordingly, methods have also been proposed in which silicone compounds and metal salts are used in combination in an attempt to improve the flame-retarding effect of the silicone compounds themselves, and also to reduce the amount of silicone compounds added. For example, a flame-retardant resin composition formed by adding silicones consisting of D units and group IIa metal salts of carboxylic acids with 14 to 20 carbon atoms to polymers such as polycarbonates, etc., is disclosed in Japanese Unexamined Patent Application (Kokai) No. Sho 56-100853, and a flame-retardant composition formed by mixing a silicone resin constructed from M units and Q units with other silicone resins and group IIa metal salts of carboxylic acids is disclosed in Japanese Examined Patent Application (Kokoku) No. Hei 3-48947. However, even if silicone compounds and metal salts are used in combination, the resulting effect is inferior from the standpoint of flame-retarding characteristics; accordingly, in order to obtain a sufficient flame-retarding effect, it is necessary to increase the amount of silicone resin used, or to use an inorganic flame-retardant filler such as aluminum hydroxide, etc., or a halogen or phosphorus compound, in combination.
Thus, in cases where silicone resins are added as flame-retarding agents, a sufficient flame-retarding effect cannot be obtained unless the amount added is large. Furthermore, if the amount added is increased, various properties of the resulting molded articles such as external appearance and mechanical strength, etc., show a great deterioration, and since silicone resins themselves are expensive, material costs are increased when such resins are added to polycarbonate type resins. Consequently, there has been a demand for the development of silicone resin additives with a greater flame-retarding effect, or additives that improve the [flame-retarding] effect when used in combination with silicone resins.
A flame-retardant resin composition which is formed by adding an organopolysiloxane containing epoxy groups and an alkali metal salt of an organic sulfonic acid is described in Japanese Unexamined Patent Application (Kokai) No. Hei 8-176425, and a flame-retardant resin composition formed by adding a polycarbonate modified by an organopolysiloxane containing phenolic hydroxy groups, and an organic alkali metal salt, is described in Japanese Unexamined Patent Application (Kokai) No. Hei 8-176427. Furthermore, a composition whose flame-retarding effect is improved by the use of petroleum type heavy oils or pitches in combination with silicone compounds is described in Japanese Unexamined Patent Application (Kokai) No. Hei 9-169914. In the case of these compositions, however, it is necessary to use expensive silicone resins of the types described in Japanese Unexamined Patent Application (Kokai) No. Hei 8-176425 and Japanese Unexamined Patent Application (Kokai) No. Hei 8-176427, and a flame-retarding effect sufficient to justify the increased cost that results from the complication of the manufacturing process is not obtained. Thus, further improvement is desired.
Furthermore, none of the abovementioned conventional silicone resins shows sufficient dispersibility or compatibility with polycarbonate resins.
Moreover, a flame-retardant resin composition formed by mixing a silicone resin which has a molecular weight (weight average molecular weight) in the range of 10,000 to 270,000, and which contains D units and T units expressed by the formula shown below, with an aromatic polycarbonate has been proposed in Japanese Unexamined Patent Application (
Horie Yutaka
Ishida Hiromi
Kitamura Takuro
Saito Akihiro
Takezawa Yoshiaki
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