Polycarbonate blends

Details Polycarbonate blends Polycarbonate blends

2002-07-17

2004-05-25

Buttner, David J. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S462000, C528S204000

Reexamination Certificate

active

06740714

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to thermoplastic molding compositions and in particular to compositions containing polycarbonate resins.
SUMMARY OF THE INVENTION
A thermoplastic molding composition suitable for making articles having good combination of properties is disclosed. The composition contains
(A) a copolycarbonate derived from compounds of formula (I)
wherein R
1
to R
4
independently of one another represent H, C
1
-C
4
-alkyl, phenyl, substituted phenyl or halogen, and compounds of formula (II)
wherein R
5
to R
8
independently of the others denote 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, and (B) a homopolycarbonate derived from bisphenol A. The composition that features resistance to stress cracking and good low-temperature properties is suitable for automotive construction and exterior applications.
BACKGROUND OF THE INVENTION
For automotive construction and other exterior applications, polycarbonates have long been sought that are as resistant as possible to chemicals and are preferably transparent and that are both resistant to low temperatures and are thermally stable. Transparent polycarbonates are therefore required that exhibit improved low-temperature strength compared with polycarbonate of pure 2,2-bis(4-hydroxyphenyl)propane, and have increased thermal stability, while having improved stress cracking behavior.
Copolycarbonates based on 4,4′-dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)propane are already known from JP-A 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 resistant to chemicals, resistant to heat and flame retardant, while having the same mechanical properties and transparency as commercially available polycarbonate of pure bisphenol.
German Patent Application DE 10047483.7 describes copolycarbonates of 4,4′-dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) that exhibit particularly good low-temperature properties. However, it is also described that the good low-temperature properties diminish as the content of 4,4′-dihydroxydiphenyl falls. Since 4,4′-dihydroxydiphenyl is an expensive component in comparison with 2,2-bis(4-hydroxyphenyl)propane, it is desirable for reasons of cost to keep the 4,4′-dihydroxydiphenyl content as low as possible, without losing the desired improvement in the low-temperature strength.
The object was, therefore, to reduce the amount of 4,4′-dihydroxydiphenyl (DOD), or compounds of formula (I), necessary to prepare a particular amount of the polycarbonate, without thereby losing the desired properties of the polycarbonate.
Surprisingly, it has now been found that it is possible to produce blends of copolycarbonates containing DOD, or compounds of formula (I), and polycarbonate of pure bisphenol A that exhibit the desired properties of the copolycarbonate (A) unchanged, while the amount of DOD or compounds of formula (I), based on the amount of end product, is reduced.
That is particularly astonishing given that it is generally not possible when producing blends to predict what properties a blend will ultimately have. The properties of the starting polymers may be enhanced, eliminated, may change (in either direction), and in some cases the starting polymers may not even be miscible homogeneously, etc. In short, no prediction is possible and a result like the present result is in no way obvious but, on the contrary, is highly surprising.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a thermoplastic molding composition containing (A)1 to 99 wt. % of copolycarbonate derived from 0.1 mol % to 46 mol %, preferably from 11 mol % to 34 mol % and especially from 26 mol % to 34 mol %, of compounds of formula (I)
wherein R
1
, R
2
, R
3
and R
4
independently of one another represents H, C
1
-C
4
-alkyl, phenyl, substituted phenyl or halogen, preferably H, C
1
-C
4
-alkyl or halogen, and particularly preferably all represent the same radical, especially H or tert-butyl, and complementary amounts, that is from 99.9 mol % to 54 mol %, preferably from 89 mol % to 66 mol % and especially from 74 mol % to 66 mol %, of compounds of formula (II)
wherein R
5
, R
6
, R
7
and R
8
independently one of the others denote 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 bisphenol monomers, and
(B) 1 to 99 wt. % of a bisphenol A-derived homopolycarbonate.
The molding composition is suitable for use in fields in which particularly good low-temperature properties are sought. Preferred mixtures of the copolymer (A) with polycarbonate (B) are from 30 to 95 wt. % of (A), very particularly preferably from 40 to 95 wt. % of (A), with correspondingly complementary amounts of polycarbonate (B).
Mixtures of polycarbonate (B) with copolycarbonates (A) in which the copolycarbonates (A) is present in amounts of 34 to 26 mol %, especially from 33 to 27 mol %, more especially from 32 to 28 mol %, very especially from 31 to 29 mol % and most especially 30 mol % of bisphenol monomer of formula (I), in each case supplemented by a complementary content of bisphenol monomer of formula (II), are very particularly preferred, and the invention relates thereto.
The indicated percentages of the bisphenol monomers relate to the total content of bisphenols in the polycarbonates, defined on the basis of 100%. Component B is a homopolycarbonate derived from bisphenol A.
Blends that have the compositions mentioned as being preferred, particularly preferred or very particularly preferred are preferred, particularly preferred or very particularly preferred.
The definitions, relative proportions and explanations given above in general or within the scope of preferences may, however, also be combined with one another as desired, that is to say between the respective ranges and preferred ranges. They apply correspondingly to end products as well as to preliminary and intermediate products.
Surprisingly, it has now been found that the polycarbonate blends according to the invention have good low-temperature properties. That is especially surprising because blends derived from only a small amount of bisphenol monomer (I) exhibit better low-temperature properties than the corresponding pure copolycarbonates (A) derived from the same amount of (I).
The blends may therefore be used to make molded articles wherever the properties profile of the polycarbonates known hitherto is inadequate, especially, for example, in the electrical sector and in the construction sector, for coverings or glazing, especially in the automotive sector as films, sheets, fittings or housing parts, but also in the optical field as lenses and data storage means, and also as commodity goods, and when increased dimensional stability under heat or chemical resistance are required at the same time as good low-temperature properties. In addition, they may also replace other materials in applications in which conventional polycarbonates could hitherto not be used because their low-temperature properties were not adequate therefor.
According to the invention, good low-temperature properties are to be understood as meaning, for example, without being limited thereto, good low-temperature strength, since conventional polycarbonates become brittle at low temperatures and thus tend to break and tear.
According to the invention, low temperatures are to be understood as being temperatures below 0° C., particularly preferably below −10° C., particularly preferably below −20° C., very particularly preferably below −30° C., especially below −40° C. and very especially below −50° C.
Preferred compounds of 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′-dihydro

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