Use of copolycarbonates

Details Use of copolycarbonates Use of copolycarbonates

2002-11-08

2003-11-11

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

C528S198000, C359S107000, C359S361000, C296S037100, C428S412000

Reexamination Certificate

active

06646101

ABSTRACT:

The present invention provides the use of impact resistant, stress cracking resistant copolycarbonates with particularly good low temperature properties for applications in which particularly good low temperature properties and good impact behavior after heat aging are required, e.g., for automobile construction or external applications, and new copolycarbonates themselves.
For automobile construction and other external applications there has long been a search for polycarbonates which are as resistant as possible to chemicals and preferably transparent and which, on the one hand, are resistant to low temperatures and on the other hand have good aging stability. The object was, therefore, to find a transparent polycarbonate which, on the one hand, exhibits improved low temperature impact strength compared with polycarbonate composed of pure 2,2-bis(4-hydroxyphenyl)propane and, on the other hand, has increased aging stability, with improved stress cracking behaviour.
Polycarbonates typically loose their notched impact strength and become brittle at low temperatures. Additionally polycarbonates display, after storage at temperatures below the glass transition temperature, an ageing effect which is dependent on the period of storage and the temperature and as a result of which the high energy level of the notched impact strength is considerably decreased (Bottenbruch et al., Engineering Thermoplastics Polycarbonates, Polyacetals, Polyesters, Cellulose Esters, Carl Hanser Verlag, Munich, Vienna, N.Y., 1996, p. 183 et seq.).
Copolycarbonates based on 4,4′-dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)propane are already known from JP 5117382 and have been described in EP-A1 0 544 407, U.S. Pat. No. 5,470,938, U.S. Pat. No. 5,532,324 and U.S. Pat. No. 5,401,826 as being particularly chemical resistant, heat resistant and flame resistant whilst having, compared with commercial polycarbonate of pure bisphenol, the same mechanical properties and transparency. There is no indication whatsoever in the prior art, however, that these copolycarbonates have particularly good low temperature properties or a particularly good impact behavior after heat aging.
The problem therefore consisted in obtaining an polycarbonate with high transparency which on the one hand possesses improved low temperature properties, i.e. good notched impact strength even at low temperatures, especially compared to usual polycarbonate made of 2,2-bis(4-hydroxyphenyl)propane, and on the other hand shows an improved ageing behaviour when tempered below glass temperature besides enhanced environmental stress cracking.
It has now surprisingly been found that the copolycarbonate according to the invention does not exhibit any ageing effects upon storage at temperatures below the glass transition temperature, so that the high energy level of the notched impact strength is maintained.
These unexpected ageing properties of the copolycarbonate according to the invention are of major importance for practical use. Many uses are subject to continuously changing thermal conditions. The copolycarbonate according to the invention thus represents a material which has very high notched impact strength at low temperatures and which does not however lose this property as a result of storage at high temperatures due to ageing effects.
The present invention relates, therefore, to the use of copolycarbonates which are composed of 0.1 mole % to 46 mole %, preferably 11 mole % to 34 mole % and particularly 26 mole % to 34 mole % of compounds corresponding to formula (I)
wherein
R
1
to R
4
independently of one another, stand for H, C
1
-C
4
-alkyl, phenyl, substituted phenyl or halogen, preferably for H, C
1
-C
4
-alkyl or halogen and particularly preferably all stand for the same radical, particularly for H or tert.-butyl,
and complementary amounts, that is, 99.9 mole % to 54 mole %, preferably 89 mole % to 66 mole % and particularly 74 mole % to 66 mole % of compounds corresponding to formula (II)
wherein
R
5
to R
8
independently of one another, are H, CH
3
, Cl or Br, and
X is C
1
-C
5
-alkylene, C
2
-C
5
-alkylidene, C
5
-C
6
-cycloalkylene, C
5
-C
10
-cycloalkylidene, as monomers, as materials in areas in which particularly good low temperature properties and good aging stability are required.
More particularly preferred copolycarbonates and themselves the subject of the invention are those composed of 34-26 mole %, especially 33-27 mole %, particularly 32-28 mole %, more especially 31-29 mole %, and particularly preferably 30 mole % of monomer corresponding to formula (I), in each case supplemented by a complementary proportion of monomer corresponding to formula (II).
The percentage of monomers is defined based on 100 mole % representing the whole content of Bisphenols in the polycarbonate. A pure Bisphenol A Polycarbonate would therefore be defined as 100 mole % of Bisphenol A. The carbonate Part of derived from carbonic acid esters or halides is not taken into account.
Copolycarbonates which are preferred, particularly preferred or most preferred are those containing the compositions defined under preferred, particularly preferred or most preferred.
The general definitions, quantitative ratios or connotations stated above or those stated in preferred ranges, can however also be combined with each other in any desired manner, i.e. from among the respective ranges and preferred ranges. They apply correspondingly to the end products and to the precursors and intermediates.
Surprisingly, it has now become apparent that these copolycarbonates have particularly good low temperature properties and good impact behaviour after heat ageing. They may therefore be used as moulded articles in all applications where the polycarbonates known hitherto are inadequate in terms of their range of properties, particularly, e.g., in the electrical sector and in the construction sector, for coverings or glazing, particularly in the automotive sector as films, sheets, fittings parts or housing parts, and in the optical sector as lenses and data stores, and as consumer goods, namely in cases where increased heat resistance or chemical resistance is required at the same time as good low temperature properties. In addition, they may also replace other materials in which conventional polycarbonates could not be used hitherto because of their inadequate low temperature properties for said purpose.
According to the invention, the term good low temperature properties means, by way of example but not in a restrictive manner, good low temperature notched impact strength, since conventional polycarbonates become brittle at low temperatures and thus have a tendency to fracture and crack.
According to the invention, the term low temperatures means temperatures below 0° C., preferably below −10° C., particularly preferably below −20° C., more particularly preferably below −30° C., particularly below −40° C. and preferably below −50° C.
According to the invention high thermal stability is understood to be, by way of example and not limitation, high notched impact strength after tempering, since commonly available polycarbonates become brittle after tempering and thus tend to fracture and tear.
According to the invention tempering is understood to be storage at temperatures below the glass transition temperature of about 155° C., preferably between 40 and 140° C., particularly preferably 60-140° C., most particularly preferably 80-140° C.
Preferred compounds corresponding to formula (I) are 4,4′-dihydroxydiphenyl (DOD) and 4,4′-dihydroxy-3,3′,5,5′-tetra(tert.-butyl)diphenyl, 4,4′-Dihydroxy-3,3′,5,5′tetra(n-butyl)diphenyl and 4,4′-dihydroxy-3,3′,5,5′tetra(methyl)diphenyl, particularly 4,4′-dihydroxydiphenyl.
Preferred compounds corresponding to formula (II) are 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphen

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