High impact, high modulus fiber reinforced aromatic carbonate polymers

High impact, high modulus thermoplastic molding compositions comprise PA1 (a) an aromatic carbonate polymer; PA1 (b) a fibrous reinforcing agent essentially free of any sizing agent; and PA1 (c) a small amount of a polysiloxane having a substantial content of Si-H bonds.

This invention is directed to an improved polycarbonate composition of an 
aromatic carbonate polymer in intimate admixture with an unsized fibrous 
reinforcing agent and a small amount of a hydrogen siloxane. 
BACKGROUND OF THE INVENTION 
Incorporating fibrous reinforcements, such as glass fibers and rock wool 
fiber, into polycarbonate resins is known to improve dimensional 
stability, heat distortion temperature, creep resistance, tensile strength 
and, most dramatically, elastic modulus. However, this always results in a 
serious deterioration in overall ductility, manifested in poor notched and 
unnotched impact strength as well as a decreased falling ball impact 
strength. Even small amounts of fibrous reinforcements have a serious 
effect on the ductility of polycarbonate. If it is sought to improve 
impact performance by adding conventional impact modifiers, such as 
selectively hydrogenated styrene-butadiene-styrene block copolymers, then 
there is a detrimental affect on stiffness (modulus) and only a minor 
improvement in impact strength, in any event. It has been found that 
elimination of the adhesive bond between polycarbonate and fibrous 
reinforcing agents can be accomplished by burning off or otherwise using 
fibers free of conventional sizing or coupling agents. This does improve 
ductility, but only for relatively small fiber contents, e.g., up to less 
than about 10% by weight of sizing-free glass fibers in the 
polycarbonate--this is usually below the optimum amount. 
It has now been discovered that the addition of poly C.sub.1 -C.sub.10 
alkyl (or phenyl) hydrogen siloxanes to compositions comprising "pristine" 
(or sizing-free) fibrous reinforcements and polycarbonates, in which the 
fiber content exceeds even 30%, results in a tremendous improvement in 
falling ball (ductile) impact strength, and notched impact and unnotched 
impact strengths, too. These can be improved by several hundred percent 
with almost full retention of the elastic modulus. 
The foregoing is altogether surprising in light of Alewelt et al., U.S. 
Pat. No. 4,147,707, who describe glass fiber reinforced polycarbonates 
with improved mechanical properties containing 0.5 to 5.0% of 
organopolysiloxane. While the '707 patent states that both long and short 
glass fibers can be used, Col. 3, lines 22-50, it is specified that they 
must be "provided with a polycarbonate-compatible finish by means of 
suitable sizes" (Col. 3, lines 25-27). The patent makes no distinction 
between conventional silicones, like polydimethyl siloxanes, and those 
containing silicone-hydrogen bonding. Applicant finds superior results 
with unsized glass fibers, if a hydrogen-siloxane is selected, and then 
used in amounts below 1.0%, and especially below the 0.5% lower limit of 
Alewelt et al. The falling ball ductile impact with such specific hydrogen 
polysiloxanes is, as will be illustrated later, more than ten times 
greater than the dimethylpolysiloxanes used in Alewelt et al. Bialous et 
al., U.S. Pat. No. 3,971,756 is also relevent to the present invention, 
but only insofar as it shows that from 0.01 to about 5 weight % of a 
polysiloxane having silicon-bonded hydrogens can be used to prevent 
dripping in flame retardant polycarbonate compositions. Although the 
amounts and types of hydrogen siloxanes suggested in the '756 patent are 
within the limits employed herein, and the inclusion of fibrous glass is 
suggested, the need for sizing-free fibers to enhance ductile impact is 
not at all evident. 
It is believed that the following conditions are essential herein: 
(i) sizing agents (on the fibrous reinforcement or separately added) must 
be absent because these either evoke adhesive bonds between the matrix and 
fiber, or they prevent reactions between the hydrogen polysiloxane and the 
fiber, or both; 
(ii) a very good dispersion of the fibers in the matrix is required; 
(iii) for best combination of high modulus and creep performance, the 
addition of polysiloxane is preferably kept below 1.0% and, especially 
preferably, below 0.5%; and 
(iv) the polysiloxane used must contain hydrogen silicon bonds. 
Following the use, especially, of short glass fibers, additional advantages 
in improved isotropy and high surface quality are obtained. It is again 
re-emphasized, that sizing agents must not be present to contribute to 
adhesive bonds between matrix and fibers, nor should they prevent 
reactions between the silicon-hydrogen bond-containing polysiloxane and 
the fibers. In practical terms this means that pristine fibers should be 
used. Using the factors mentioned above, the falling dart impact strength 
of a 30% short glass fiber-reinforced polycarbonate can be increased from 
0.1 kgm to 6 kgm, while the unnotched impact bar does not even break. The 
new composition has a desirable high modulus. These results are evident at 
surprisingly low levels of hydrogen polysiloxane. Substantially the same 
results are also obtained with other fibrous fillers, pristine or virgin, 
including rockwool-mineral fibers, carbon fibers, and the like. 
SUMMARY OF THE INVENTION 
According to the present invention, these are provided high impact 
strength, high modulus thermoplastic compositions comprising per 100 parts 
by weight (a), (b) and (c), an intimate admixture of: 
(a) from about 95 to about 35 parts by weight of an aromatic carbonate 
polymer or copolymer; 
(b) from about 5 to about 65 parts by weight of a fibrous reinforcing agent 
essentially free of any sizing agent; and 
(c) from about 0.05 to about 4 parts by weight of a hydrogen siloxane 
comprising units of the formula 
##STR1## 
wherein R is hydrogen, C.sub.1 -C.sub.10 alkyl, phenyl or a mixture of 
any of the foregoing, and n plus m is at least 4, and, for example, up to 
about 200. 
DETAILED DESCRIPTION OF THE INVENTION 
The term "aromatic carbonate polymer or copolymer" is used in its broader 
aspects. Suitable are those described in the above-mentioned U.S. Pat. 
Nos. 3,971,756 and 4,147,707, the disclosures of which are incorporated 
herein by reference. The aromatic carbonate polymers are homopolymers and 
copolymers that are prepared by reacting a dihydric phenol with a 
carbonate precursor. Suitable dihydric phenols are 
bis(4-hydroxyphenol)methane; 2,2-bis(4-hydroxyphenyl)propane (hereinafter 
referred to as bisphenol-A); 2,2-bis(4-hydroxy-3-methylphenyl)propane; 
4,4-bis(4-hydroxyphenyl)heptane; 
2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane; 
2,2-bis(4-hydroxy-3,5-dibromophenyl)propane; 
2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, and the like; dihydric 
phenol ethers usch as bis(4-hydroxyphenyl)ether, and the like; 
dihydroxydiphenyls, such as p,p'-dihydroxydiphenyl; 
3,3'-dichloro-4,4'-dihydroxydiphenyl, and the like; dihydroxyaryl 
sulfones, such as bis(4-hydroxyphenyl)sulfone; 
bis(3,5-methyl-4-hydroxyphenyl)sulfone, and the like; dihydroxybenzenes; 
resorcinol; hydroquinone, halo- and alkyl-substituted dihydroxybenzenes, 
such as 1,4-dihydroxy-2,5-dichlorobenzene; 1,4-dihydroxy-3-methylbenzene, 
and the like; and dihydroxy diphenyl sulfoxides, such as 
bis(3,5-dibromo-4-hydroxyphenyl)sulforide, and the like. A variety of 
additional dihydric phenols arealso available to provide carbonate 
polymers and are disclosed in U.S. Pat. Nos. 2,999,835; 3,028,365; and 
3,153,008. Also suitable for use as the aromatic carbonate polymer 
component (a) are copolymers prepared from any of the above copolymerized 
with halogen-containing dihydric phenols, such as 
2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane; 
2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, and the like. It is 
contemplated to employ two or more different dihydric phenols or a 
copolymer of a dihydric phenol with a glycol or with hydroxy or acid 
terminated polyester, or with a dibasic acid in the event that a carbonate 
coplymer or interpolymer rather than a homopolymer is desired for use as 
component (a). Also contemplated for use are blends of any of the above 
aromatic carbonate polymers. Especially preferred dihydric phenols are 
bisphenol-A and 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane. 
The carbonate precursor may be either a carbonyl halide, a carbonyl ester 
or a haloformate. The carbonyl halides which may be employed include 
carbonyl bromide, carbonyl chloride and mixtures thereof. Typical of the 
carbonate esters are diphenyl carbonate, di(halophenyl)carbonates such as 
di(chlorophenyl)carbonate, di(bromophenyl)carbonate, 
di(trichlorophenyl)carbonate, di(tribromophenyl)carbonate, and the like; 
di(alkylphenyl)carbonate, such as di(tolyl)carbonate, 
di(naphthyl)carbonate, di(chloronaphthyl)carbonate, and the like, or 
mixtures thereof. The haloformates of dihydric phenols are 
(bischloroformates of hydroquinone, etc.), or glycols (bis haloformates of 
ethylene glycol, neopentyl glycol, polyethylene glycol, etc.). While other 
carbonate precursors will occur to those skilled in the art, carbonyl 
chloride, also known as phosgene, is preferred. 
Also contemplated are polymeric components (a) comprising units of a 
dihydric phenol, a dicarboxylic acid and carbonic acid, such as disclosed 
in U.S. Pat. No. 3,169,121, incorporated herein by reference. 
The aromatic carbonate polymers used as component (a) herein are prepared 
preferably by employing a molecular weight regulator, an acid acceptor and 
a catalyst. Suitable molecular weight regulators are phenol, cyclohexanol, 
methanol, p-t-butylphenol, p-bromophenol, and the like. 
A suitable acid acceptor may be either organic or inorganic. Illustrative 
of the former are tertiary amines, such as pyridine, triethylamine, 
dimethylaniline, tributylamine, and the like. Inorganic acid acceptors can 
comprise a hydroxide, a carbonate, a bicarbonate, a phosphate, or the 
like, of an alkali- or an alkaline earth metal. 
Conventional additives, such as anti-static agents, pigments, mold release 
agents, thermal stabilizers, and the like can be present in component (a). 
The fibrous reinforcing agent (b) can vary widely in nature and type, so 
long as it is "pristine", that is, essentially free of any sizing 
materials, as mentioned above. There can be used glass fibers, mineral 
fibers, such as rockwool, asbestos, and the like, carbon fibers, and 
others. Preferred are glass fibers and rockwool fibers. 
Like the above mentioned U.S. Pat. No. 4,147,707, suitable fibers, e.g., 
glass fibers, are all the commercially available kinds and types, such as 
cut glass filaments (long glass fiber and short glass fiber), rovings and 
staple fibers. 
The length of the filaments, whether or not they have been bundled to form 
fibers, should be between about 60 mm and 6 mm, for long fibers and 
between about 5 mm and 0.05 mm in the case of short fibers. Alkali-free 
aluminum-boron-silicate glass ("E" glass) or alkali containing glass ("C" 
glass) can be used, as well as others. Preferred is a ground short glass 
fiber. 
Any of the hydrogen polysiloxanes known in the art can serve as component 
(c). Especially useful are those set forth by formula in the 
above-mentioned U.S. Pat. No. 3,971,756. The patent also cites U.S. Pat. 
Nos. 2,445,794; 2,448,756; 2,484,595 and 3,514,424 as showing ways of 
making such siloxanes. To save unnecessarily detailed description, these 
are all incorporated herein by reference. Most important members of the 
family are those in which R is methyl, or phenyl, or a mixture thereof. 
These are commercially available. At the present time, it is preferred to 
use poly(methyl hydrogen)siloxane, a fluid which is available commercially 
from General Electric Company under the trade designation DF-1040. 
In some embodiments, it is contemplated to use a small amount, e.g., up to 
10 parts by weight per 100 parts by weight of (a), (b) and (c) combined, 
of an impact modifier. This can comprise a polyacrylate, or a copolymer of 
a diene and acrylonitrile and/or vinyl aromatic compound. A preferred such 
modifier is a block copolymer, of the linear or radial type, comprising 
diene rubber center blocks and vinyl aromatic terminal blocks. 
Illustrative dienes are butadiene or isoprene, and illustrative vinyl 
aromatics are styrene, vinyl toluene, and the like. Especially suitable 
are selectively hydrogenated such compounds. Particularly valuable are the 
selectively hydrogenated linear ABA types, made from styrene (A) and 
butadiene (B), and sold by Shell Chemical under the tradename Kraton G, 
and the corresponding radial teleblocks sold by Phillips Chemical under 
the tradename Solprene. 
Any conventional method can be used to formulate the present thermoplastic 
compositions, and to mold them. The important factor is to insure intimate 
admixture. The amounts of components (a), (b) and (c) and, optionally (d) 
to be used have been broadly set forth above. Preferably, however, the 
siloxane will be present in an amount of from about 0.05 to less than 0.5, 
and especially preferably, about 0.4 parts, by weight per 100 parts by 
weight of (a), (b) and (c) combined. Especially preferably the fibrous 
reinforcing agent will be present in an amount of from about 15 to about 
40 parts by weight per 100 parts by weight of (a), (b) and (c) combined. 
Mixing temperatures and molding temperature will be illustrated in the 
following examples, but, in any event, will be entirely in harmony with 
those well known to those skilled in the art of polycarbonate resin 
technology.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following examples illustrate the compositions of the present 
invention. They are not to be construed to limit the claims in any manner 
whatsoever. 
EXAMPLES 1-3 
Polycarbonate compositions are prepared by extruding a homopolymer of 
2,2-bis(4-hydroxyphenyl) propane (bisphenol-A) and phosgene (LEXAN.RTM. 
125), either short milled glass fibers or short milled rockwoolmineral 
fibers, both essentially free of any sizing agent, and, where indicated, a 
polymethyl hydrogen siloxane fluid (DF1040, General Electric Company). For 
comparison purposes, a polydimethyl siloxane fluid (SF-18, General 
Electric Company) is also employed. Extrusion is carried out at 
265.degree. C., and the extrudate is comminuted into pellets. 
The pellets are then injection molded at about 315.degree. C. (cylinder), 
into standard physical test specimens, so that heat distortion temperature 
(HDT) can be measured according to standard test methods; Izod impact 
strength, notched and unnotched can be measured on 1/8" bars according to 
standard test methods; falling ball impact strength can be measured on a 
10 cm round disc according to standard test methods elastic modulus and 
tensile yield strength and elongation at yield and at break can be 
measured according to standard test methods. 
The compositions used, and the properties observed are set forth in Table 
1: 
TABLE 1 
______________________________________ 
Short Fiber Reinforced Polycarbonate Compositions 
Example 
1 1A* 1B* 2 2A* 3 3A* 
______________________________________ 
Composition(parts by weight) 
poly(bisphenol-A 
carbonate.sup.a 
70 70 70 80 80 80 80 
short unsized glass 
fibers.sup.b 
30 30 30 20 20 -- -- 
short unsized rock- 
wool fibers.sup.c 
-- -- -- -- -- 20 20 
poly(methyl hydro- 
gen)siloxane.sup.d 
0.4 -- -- 0.4 -- 0.4 -- 
poly(dimethyl) 
siloxane.sup.e 
-- -- 0.4 -- -- -- -- 
Properties 
heat distortion 
temp., .degree.C. at 
1.82 N/mm.sup.2 
143 143 143 142 142 141 142 
Izod impact, 
notched,J/m. 
152 53 74 180 70 150 60 
Izod impact, 
unnotched,J/m. 
NB** 350 340 NB 520 NB 600 
Falling ball 
impact, J 10kg. 
dart, 10.phi. cm 
55 &lt;5 &lt;5 110 &lt;5 55 &lt;5 
E modulus, N/mm.sup.2 
5100 5250 5300 3600 3250 3950 4000 
Tensile strength 
at yield,N/mm.sup.2 
0.5 cm/min. 43.5 66.0 63.0 48.5 63.0 55.0 68.0 
Elongation at 
yield, % 7 -- -- 7.5 -- 7.0 -- 
break, % 18 3.5 3.5 25 5.0 28 4.0 
______________________________________ 
*Control 
**NB did not break 
.sup.a LEXAN.RTM. 125 General Electric Co. 
.sup.b EC 10W from Gevetex Co. 
.sup.c Fix Spinrock from Rockwool Kapinus Co. 
.sup.d DF1040, General Electric Company 
.sup.e SF18, General Electric Company 
In all cases, ductile impact strength was enormously increased upon the 
addition of the siloxane fluid, except when the siloxane fluid did not 
contain silicon-hydrogen bonds (Control 1B). There is no significant loss 
in tensile modulus, and also no loss in heat distortion temperature. 
EXAMPLE 4 
The general procedure of Examples 1-3 is repeated, increasing the amount of 
hydrogen siloxane fluid, and determining, in addition, Vicat softening 
temperature, melt viscosity, and gasoline resistance. For comparison 
purposes, a composition is also made omitting the siloxane fluid. The 
compositions used and the results obtained are set forth in Table 2. 
TABLE 2 
______________________________________ 
Short Fiber Reinforced Polycarbonate Compositions 
Example 
4 4A* 
______________________________________ 
Composition(parts by weight) 
poly(bisphenol-A)carbonate.sup.a 
80 80 
short unsized glass fibers.sup.b 
20 20 
poly(methyl hydrogen siloxane).sup.d 
0.5 -- 
Properties 
Vicat B(120/50N) 148 148 
Melt viscosity, 300.degree. C. 
450 400 
Heat distortion temperature, .degree.C. 
143 142 
Tensile modulus, N/mm.sup.2 
3600 3750 
Tensile strength, N/mm.sup.2 
48.5 63.0 
Elongation at break, % 
30 5 
Time to failure in gasoline 
at 1% strain 17 min. 60 min. 
Whitening in gasoline 
yes yes 
Izod impact, notched, J/m. 
220 70 
Izod impact, unnotched, J/m. 
NB** 520 
Falling ball impact, J, 
10 kg; h = var.; .phi.10 cm 
disc, w = 3.2 mm 
.phi.9.5 cm support ring 
120 &lt;5 
______________________________________ 
*Control 
**NB -- did not break 
.sup.a see footnote to Table 1 
.sup.b see footnote to Table 1 
.sup.d see footnote to Table 1 
The ductile impact strength is again seen to be markedly increased. 
Obviously many variations are possible in light of the above, detailed 
description. For example, the bisphenol-A polycarbonate can be substituted 
with a polycarbonate from tetramethylbisphenol-A. The poly(methyl 
hydrogen) siloxane can be substituted with a poly(phenyl 
hydrogen)siloxane. Instead of short glass fibers, unsized long glass 
fibers can be substituted. An impact improving amount, e.g., 5% by weight, 
of a selectively hydrogenated block copolymer of 
styrene-butadiene-styrene, e.g., Shell's Kraton G, can be included in the 
composition. For the polycarbonate, there can be substituted polyester 
carbonate, polycarbonate siloxane copolymers and blends thereof. All such 
obvious variations are within the full intended scope of the appended 
claims.