Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-05-08
2001-07-31
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
Reexamination Certificate
active
06268462
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a branched polycarbonate resin and a method for producing it, and precisely to a branched polycarbonate resin of which the branching agent content is low and the melt tension is high and which therefore has improved moldability in blow molding, extrusion, vacuum forming and so on, and also to a method for producing the resin.
BACKGROUND OF THE INVENTION
Generally having good transparency, good heat resistance and good mechanical properties, polycarbonate resins to be produced from bisphenol A and others have many applications in various fields. However, the polycarbonate resins generally have low melt tension. Therefore, when molded through blow molding, extrusion, vacuum forming and so on, they are often defective in that their moldings could not all the time have even thickness. In addition, as they often draw down while being molded, they could not be formed into satisfactory moldings.
For overcoming the defects, Japanese Patent Laid-Open No. 47228/1984 discloses a method of adding from 0.1 to 2.0 mol % or so of a branching agent having three functional groups to a polymerization system to give a branched polycarbonate resin. The melt tension of the branched polycarbonate resin as produced according to that method could surely be increased in some degree, but is not still on a satisfactory level. On the other hand, in order to produce a branched polycarbonate resin having a satisfactory level of melt tension according to the method, a large amount of the branching agent must be used. In that case, however, increasing the amount of the branching agent added will lead to an unfavorable situation where crosslinked polycarbonate resins are readily produced. This is problematic in that the resins are often gelled. In addition, it is said that, with the increase in the branching agent added, the impact resistance of the polycarbonates produced is to lower. For these reasons, the acceptable amount of the branching agent is limited, and it is desired to reduce as much as possible the amount of the branching agent to be added.
On the other hand, U.S. Pat. No. 4,415,725 discloses a branched polycarbonate resin for which a tetrahydric phenol is used as the branching agent. However, the branched polycarbonate resin has low melt tension, and its moldability in blow molding, extrusion, vacuum forming and so on is not still satisfactory.
The object of the present invention is to provide a branched polycarbonate resin of which the branching agent content is controlled low and which has high melt tension and good melt characteristics and can be stably produced and molded through blow molding, extrusion, vacuum forming and so on.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied so as to attain the object noted above, and, as a result, have found that the above-mentioned object can be attained by a specific polymerization method of producing a branched polycarbonate resin in which is used a tetrahydric phenol having a specific structure as the branching agent. On the basis of this finding, we have completed the present invention.
Specifically, the invention is to provide a branched polycarbonate resin and a method for producing it, which are mentioned below.
(1) A branched polycarbonate resin for which is used a tetrahydric phenol having a structure of the following general formula and serving as a branching agent, and which has a branching agent content x:(branching agent/(dihydric phenol+terminating agent+branching agent)×100) x, of from 0.05 to 0.5 mol % and satisfies a relationship of y≧11x+0.5 where x indicates the branching agent content of the resin and y indicates the melt tension (g) of the resin at 280° C.:
wherein A, R
1
, R
2
and p are as follows:
A represents a single bond, an alkylene or alkylidene group having from 1 to 20 carbon atoms, a polymethylene group having from 3 to 20 carbon atoms, a cycloalkylene or cycloalkylidene group having from 5 to 20 carbon atoms, an arylene or arylalkylene group having from 6 to 20 carbon atoms, —O—, —CO—, —S—, —SO—, or —SO
2
—;
R
1
represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkyl group having from 7 to 20 carbon atoms;
R
2
represents a halogen atom, an alkyl group having from 1 to 8 carbon atoms, an aryl group having from 6 to 20 carbon atoms, or an arylalkyl group having from 7 to 20 carbon atoms;
p represents an integer of from 0 to 4.
(2) A method for producing a branched polycarbonate resin of (1) from a dihydric phenol, phosgene or a carbonate compound, a branching agent and a terminating agent, wherein an oligocarbonate is first prepared without adding the terminating agent thereto, and thereafter the resulting oligocarbonate is reacted with the dihydric phenol and the terminating agent.
(3) A method for producing a branched polycarbonate resin of (1) from a dihydric phenol, phosgene, a branching agent and a terminating agent, wherein an oligocarbonate having chloroformate groups is first prepared without adding the terminating agent thereto, and thereafter the resulting oligocarbonate is reacted with the dihydric phenol and the terminating agent.
BEST MODE FOR CARRYING OUT THE INVENTION
The invention is described in detail hereinunder.
1. Branched polycarbonate resin:
The branched polycarbonate resin of the invention is characterized by the following characteristics:
(1) Characteristics:
{circle around (1)} Branching agent content:
The branching agent content of the resin indicates the mol % of the branching agent in the resin, relative to the number of all mols of (dihydric phenol+terminating agent+branching agent) therein, and falls between 0.05 and 0.5 mol %, but preferably between 0.07 and 0.45 mol %. If the content is smaller than 0.05 mol %, the melt tension of the resin will be low, and blow molding of the resin will be difficult. If, on the other hand, the content is larger than 0.5 mol %, the resin will be crosslinked and gelled whereby the impact resistance of the moldings of the resin will be low.
{circle around (2)} Relationship between the branching agent content, x, and the melt tension, y (g), at 280° C.:
The resin must satisfy a relationship of y≧11x+0.5, preferably y≧13x+0.5, more preferably y≧14x+0.5, where x indicates the branching agent content of the resin and y indicates the melt tension of the resin at 280° C. The melt tension of the resin increases with the increase in the amount of the branching agent added to the resin. However, the polycarbonate resin will be crosslinked and gelled, if the amount of the branching agent added thereto increases too much. Therefore, it is necessary to control low the amount of the branching agent to be added to the resin while realizing high melt tension of the resin.
{circle around (3)} Viscosity-average molecular weight (Mv):
Preferably, the viscosity-average molecular weight (Mv) of the resin falls between 19000 and 37000, more preferably between 20000 and 30000. If Mv is smaller than 19000, the melt tension of the resin will be low, and blow molding of the resin will be difficult. If larger than 37000, however, the fluidity of the resin will be lowered and the moldability thereof will be poor.
(2) Method for production:
The method for producing the branched polycarbonate resin of the invention is not specifically defined. Starting materials to be mentioned hereinunder may be used for producing the resin. Concretely, for example, a dihydric phenol, phosgene or a carbonate compound, and a specific branching agent are reacted optionally along with any other components necessary for the reaction, but without adding a terminating agent thereto, to prepare an oligocarbonate, and thereafter the resulting oligocarbonate is reacted with a dihydric phenol and a terminating agent. This is one preferred embodiment for producing the resin of the invention. In the step of adding the terminating agent to the oligocarbonate in the embodiment, it is desirable th
Ishikawa Yasuhiro
Okamoto Masaya
Boykin Terressa M.
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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