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
2001-02-28
2004-08-24
Seidleck, James J. (Department: 1711)
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, C524S443000, C524S445000
Reexamination Certificate
active
06780917
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to an aromatic polycarbonate resin composition. More specifically, it relates to an aromatic polycarbonate resin composition which has high stiffness, high impact resistance, a good surface appearance and excellent recyclability.
2. Prior Art
Aromatic polycarbonate resins and resin compositions obtained by blending thermoplastic polyesters such as a polyethylene terephthalate resin and a polybuthylene terephthalate resin or ABS resin with an aromatic polycarbonate resin are widely used in a variety of fields such as automobiles and OA equipment as a thermoplastic resin which has excellent mechanical properties such as impact strength and a material which retains excellent characteristic properties of aromatic polycarbonate resins and improves chemical resistance and moldability which are defects of aromatic polycarbonate resins, respectively.
As means of improving the stiffness and the like of aromatic polycarbonate resins and resin compositions comprising an aromatic polycarbonate resin as the main ingredient, there are proposed a method of blending a fibrous filler such as glass fiber (JP-A 54-94556, JP-A 6-49344) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and a method of blending a scaly or platy inorganic filler such as talc or mica (JP-A 55-129444, U.S. Pat. No. 4,280,949, JP-A 5-222283).
An aromatic polycarbonate resin reinforced with a fibrous filler such as glass fiber or carbon fiber and a resin composition comprising this aromatic polycarbonate as the main ingredient have excellent mechanical strength such as stiffness. However, they have such problems that a coating film must be made extremely thick to obtain a good coating appearance because the floating of the fibrous filler such as glass fiber or carbon fiber is observed markedly in the appearances of the molded products obtained by a general molding method and that dimensional stability is not satisfactory that the molded products are readily warped because anisotropy in molding shrinkage and the like is large.
Meanwhile, an aromatic polycarbonate resin obtained by blending a scaly or platy inorganic filler such as talc or mica and a resin composition comprising this aromatic polycarbonate resin as the main ingredient are superior in the appearances of their molded products and dimensional stability to an aromatic polycarbonate resin reinforced with a fibrous filler such as glass fiber or carbon fiber and a resin composition comprising this aromatic polycarbonate resin as the main ingredient. However, their application ranges are limited due to their small reinforcing effect.
Wollastonite particles are an inorganic filler which has excellent properties of the above two. The wollastonite particles have a fibrous form when they are finely ground because of the crystal structure. Therefore, they can provide characteristic properties different from those of the above fibrous and platy fillers to a resin composition.
For example, JP-A 7-90118 discloses a resin composition which comprises wollastonite including trace components (Fe
2
O
3
, Al
2
O
3
) in a specific proportion and a thermoplastic resin. The publication teaches that the wollastonite easily gets a fibrous form and is hardly broken. It further discloses that the obtained resin composition has high strength and elastic modulus and excellent surface smoothness and dimensional accuracy.
JP-A7-149948, EP639613A1 and U.S. Pat. No. 5,965,655 disclose resin compositions which comprise wollastonite needle-like particles having a number average fiber length of 1 to 50 &mgr;m and a number average fiber diameter of 0.1 to 10 &mgr;m and a thermoplastic resin such as an aromatic polycarbonate resin. They teach that the wollastonite needle-like particles are preferably particles which include particles having a fiber length of 5 to 25 &mgr;m in a proportion of at least 50% of the total. They further disclose that the resin compositions disclosed by the above publications satisfy requirements such as a coating appearance with high distinctness of image and a low linear expansion coefficient.
JP-A 9-12846 discloses a resin composition which comprises an aromatic polycarbonate resin, aromatic polyester resin and wollastonite having an aspect ratio of 3 to 50 in a specific ratio. The publication teaches that the resin composition has high stiffness, excellent impact resistance and provides a coated molded product having excellent surface smoothness.
JP-A 10-60251 discloses a resin composition which comprises an aromatic polycarbonate resin having a specific molecular weight, aromatic polyester resin, wollastonite having an aspect ratio of 3 to 50 and carboxyl group modified olefin wax and which has excellent blow moldability. The publication teaches that the resin composition has excellent drawdown properties required for blow molding and high chemical resistance and provides a coated molded product having excellent surface smoothness.
JP-A 10-324789 discloses a resin composition which comprises an aromatic polycarbonate resin having a specific molecular weight, thermoplastic graft copolymer such as ABS resin, wollastonite having an aspect ratio of 3 to 50 and carboxyl group modified olefin wax and which has excellent blow moldability. It teaches that the resin composition has excellent drawdown properties required for blow molding and high impact resistance and provides a coated molded product having excellent surface smoothness.
JP-A 2000-256505 discloses a resin composition which comprises wollastonite including trace components (Fe
2
O
3
, Al
2
O
3
) in a specific proportion and a thermoplastic resin. It teaches that the wollastonite preferably has an average fiber length of 20 to 50 &mgr;m, an average fiber diameter of 0.5 to 5 &mgr;m and an average aspect ratio of 7 to 100 and that the resin composition gives a molded product having high stiffness and heat resistance, excellent surface smoothness, high tinting properties and a good appearance.
As described above, a resin composition having high rigidity and an excellent surface appearance can be obtained from wollastonite. Wollastonite is particularly preferred as an inorganic filler for a thermoplastic resin mainly composed of an aromatic polycarbonate resin. In the case of a thermoplastic resin mainly composed of an aromatic polycarbonate resin, as the base resin has high impact resistance, a resin composition having high stiffness and high impact resistance can be obtained. Further, in the case of a thermoplastic resin mainly composed of an aromatic polycarbonate resin, the appearance of a molded product of a resin composition containing an inorganic filler is apt to worsen.
However, the above prior art is still unsatisfactory in some points. The first point is that deterioration in the appearance of a coated molded product occurs not a little. The occurrence of a deteriorated appearance affects product yield and production efficiency. The above resin composition containing wollastonite particles is used in a molded product which must have a great coating appearance based on its excellent surface smoothness. However, projecting foreign matter may be slightly formed on the surface of the molded product. The projecting foreign matter becomes extremely conspicuous when the entire surface is flat. Therefore, the suppression of the formation of the projecting foreign matter may be required of the resin composition which comprises an aromatic polycarbonate resin and wollastonite particles.
The second point is the recycling of a molded product. Since the wollastonite particles are a filler which is easily broken, when melt kneading is repeated for recycling, mechanical properties such as stiffness are liable to deteriorate. Deterioration in characteristic properties is marked in the case of a resin composition mainly composed of an aromatic polycarbonate resin having a high melt viscosity. Therefore, a reduction in the change of characteristic properties caused by repeating recyc
Aibara Tetsuya
Hashimoto Yoshihide
Onizawa Tomomitsu
Rajguru U. K.
Seidleck James J.
Teijin Chemicals Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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