Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-10-18
2002-07-23
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C264S176100, C525S132000, C525S461000, C528S198000
Reexamination Certificate
active
06423813
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a branched aromatic polycarbonate and production method and blow-molded article thereof.
BACKGROUND ART
An aromatic polycarbonate resin (to be sometimes referred to simply as “polycarbonate” hereinafter) is a high-performance engineering plastic having a number of excellent physical properties such as high optical transparency, toughness, dimensional stability, and excellent impact strength over a wide range of temperatures and used in a wide variety of fields.
However, when the polycarbonate is blow-molded, extruded or vacuum-molded, it may cause a nonuniform thickness or a drawdown in a molded article since it has a low structural viscosity index when molten. Therefore, a satisfactory molded article may not be obtained.
Particularly, a polycarbonate which is different from an ordinary polycarbonate and which has specific viscosity-average molecular weight and structural viscosity index is considered to be preferable for blow-molding a large-capacity hollow article or a large-size panel.
The melt properties of a polycarbonate can be expressed by an expression: Q=K·P
N
(wherein Q is a flow rate (mL/sec) of a molten resin, K is a constant, P is pressure (kg/cm
2
) and N is a structural viscosity index). In the above expression, it represents Newtonian flowability when N is 1, and non-Newtonian flowability increases as the value of N increases. In other words, the flow properties of a molten resin are evaluated based on the value of N.
Heretofore, it has been attempted and practiced to incorporate an appropriate amount of a branch structure into the molecules of the polycarbonate as a means for increasing the value of the above N appropriately to attain suitable structural viscosity.
A thermoplastic branchd polycarbonate having the high structural viscosity and suitable for blow molding, such as a bisphenol A-type polycarbonate having a branch structure, is produced by an interfacial polymerization method or a melt polymerization method based on transesterification.
U.S. Pat. No. 3,799,953 discloses a technique for producing a polycarbonate having high structural viscosity and suitable for blow molding by carrying out an interfacial polymerization method using, as a branching agent, a polyhydric phenol having at least three hydroxyl groups in a molecule such as 1,1,1-tris(4-hydroxyphenyl)ethane (THPE for short), 1,3,5-tris(4-hydroxyphenyl)benzene or 1,4-bis(4′,4″-dihydroxytriphenylmethyl)benzene.
In addition, as a method for producing a thermoplastic branched polycarbonate, a method using cyanuric chloride as a branching agent (refer to U.S. Pat. No. 3,541,049), a method using a branched dihydric phenol as a branching agent (refer to U.S. Pat. No. 4,469,861) and a method using 3,3-bis (4-hydroxyaryl)oxyindole as a branching agent (refer to U.S. Pat. No. 4,185,009) have been proposed. Further, U.S. Pat. No. 4,431,793 discloses a polycarbonate which is terminal-capped with a branched alkylacyl halide and/or acid and which has improved properties.
Japanese Patent Laid-Open Publication No. 7-70304 discloses a method for producing a branched polycarbonate containing boric acid or a boric acid ester as a thermal stabilizer by mixing a dihydric phenol with a carbonic acid ester, adding a small amount of a multifunctional organic compound having at least three functional groups as a branching agent to the mixture and subjecting the resulting mixture to melt transesterification in the presence of a catalyst and boric acid or a boric acid ester.
Japanese Patent Laid-Open Publication No. 7-90074 discloses a method for producing a polycarbonate by adding a bi- or higher-valent active diester, acid halide or acid anhydride when or after the conversion ratio of transesterification exceeds 70%. It also discloses in the Examples therein as a specific example in case that an active diester or acid halide was added when the conversion ratio was 92%.
Japanese Patent Laid-Open Publication No. 11-209469 discloses a method in which a polyfunctional phenolic or carboxylic branching agent and a basic transesterification catalyst are caused to react with each other and the obtained reaction product is melt-mixed with a linear polycarbonate to branch and cross-link the polycarbonate.
As described above, to produce a thermoplastic branched polycarbonate having a specific structural viscosity index, a branching agent must be incorporated into a molecule structure. Therefore, the branching agent must be added to a reaction system as a copolymerizable component at the time of polymerization.
Thus, since the production of the branched polycarbonate requires use of a branching agent, it requires. different monomers as raw materials from those used in the production of a typical linear polycarbonate. As a matter of course, the inclusion of a branching agent in a linear polycarbonate modifies the physical properties of the linear polycarbonate significantly. Thus, to avoid the inclusion of a branching agent, the branched polycarbonate must be produced by using a plant which is different from that for producing a linear polycarbonate or using a production plant for the linear polycarbonate after the plant is temporarily halted and its contents are washed out. Therefore, the production of a special product by use of different monomers from those used in a general-purpose product, particularly the production of a branched polycarbonate, causes a decrease in the efficiency (productivity) of a production plant and an increase in production costs.
As a method for solving the problems, there has been proposed a method in which a branched polycarbonate suitable for blow molding is produced by using a branching agent not as a comonomer at the time of polycondensing the polycarbonate but for modifying the pre-prepared liner polymer of the polycarbonate (refer to Japanese Patent Publication No. 7-116285). This method tries to solve the above problems by causing a polyhydric phenol to react with a linear polycarbonate in an extruder or the like in the presence of a catalyst.
However, in the above method in which the polyhydric phenol is caused to react with the linear polycarbonate, as is easily understood from its reaction mechanism, the phenolic OH groups of the polyhydric phenol as a branching agent cut the molecular chain of the polycarbonate, whereby the molecular weight of the polycarbonate decreases and the amount of free dihydric phenols in the polycarbonate increases. In addition, since a decrease in the amount of dihydric phenols in a polycarbonate resin has been widely desired from the viewpoint of environmental safety, such a method which eventually increases the amount of the free dihydric phenols cannot be said to be a preferable method.
That is, in a conventionally known method in which a polyvalent hydroxy compound is caused to react with a linear polycarbonate to produce a branched polycarbonate, as described in Japanese Patent Publication No. 7-116285, a phenoxide produced from the reaction of a polyhydric phenol as a branching agent and an equilibration catalyst reacts with linear polycarbonate molecules, cuts the molecular chain of the polycarbonate and produces low-molecular-weight fragments and branched polycarbonate molecules, and the reaction further proceeds to achieve equilibration. Therefore, the molecular weight of the branched polycarbonate becomes lower than the molecular weight of the starting linear polycarbonate according to the amount of the branching agent added. This is also clear from Examples 9 and 10 of Japanese Patent Publication No. 7-116285 which show that an increase from 0.5 mol % to 1.0 mol % in the amount of 1,1,1-tris(4-hydroxyphenyl)ethane to be applied decreases the intrinsic viscosity of “Lexan 130” from 0.541 to 0.493 significantly. Such a decrease in molecular weight is not a negligible problem since it also causes deterioration in mechanical properties of a molded article, particularly high impact resistance which is a characteristic of a polycarbonate.
Further, since the OH groups of a polyhydric pheno
Funakoshi Wataru
Kageyama Yuichi
Kaneko Hiroaki
Sasaki Katsushi
Boykin Terressa M.
Sughrue & Mion, PLLC
Teijin Limited
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