CA1192695A - High impact, high modulus fiber reinforced aromatic carbonate polymers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

.

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

Description

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HIGH IMPACT, HIGH MODULUS FIBER
REINFORC~D AROM~TIC CA~BONATE POLYMERS
BACKGROUND OF THE INVENTION
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 oE a hydrogen siloxane.
Incorporating fibrous reinforcements, such as glass fibers and rock wool fibers, 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 deteriration 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 Eound 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.y., up to less than about 10% by weight of sizing-free glass fibers in the polycarbonate --this is usually below the optimum amount.

- 2 - gCH-3396 It has now been discovered that -the addition of poly Cl-C10 alkyl (or phenyl) hydrogen siloxanes to compositions comprising "pristine" (or sizing-Cree) fibrous reinforcements and polycarbona-tes, in which -the fiber con-tent exceeds even 306, results in a tremendous improvement in falling ball (ductile) impact strength, and notched impact and unnotched impact s-trengths 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. Patent No. 4,147,707 issued on April 3, 1979, who described glass fiber reinforced poly-carbonates 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 poly-dimethyl 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 polysilozanes is, as will be illustrated later, more than ten times greater than with the dimethylpolysiloxanes used in Alewelt et al.
Bialous et al, U.S. Patent No. 3,971,756 issued July 27, 1976 is also relevant to the present invention, but only in-sofar as it shows that from 0.01 to about 5 wei~ht % of apolysiloxane having silicon bonded hydrogens can be used to prevent dripping in flame xetardant 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.

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- 3 - 8C~-3396 It is belleved that the following conditions are essential herein:
1. sizing agents (on the fibrous reinEorcement 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;
2. a very good dispersion of the fibers in the matrix is required;
3. for the best combination of high modulus and creep performance, the addition of polysiloxane is pre-ferably kept below 1.0% and, especially preferably, below 0.5%; and

4. 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 reemphasized, 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, che falling dart impact strength of a 30% short glass fiber-reinforced polycarbonate can be increased from 0.1 kgm to 6kgm, 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 INV~NTION
_ According to the presen-t invention, these are provided high impact strength, high modulus thermoplastic compositions comprising per 100 parts by weight (a), (b~ and (c~ an intima-te admixture of:
(a) from about 95 to 35 parts by wei~ht of an aromatic carbonate polymer or copolymer;
(b) from about 5 to about 65 parts by weight of a flbrous 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 ~i -~Si - ~
n R m wherein R is hydrogen, Cl-C10 alkyl, phenyl or a mixture of any of the foregoing, and _ plus m is at least 4, and, for example, up to about 200.
DETAILED DESCRIPTION OF THE INVENTION
r--The term "aromatic carbonate polymer ~copolymer" is used in its broadest aspects. Suitable are those described in the above-mentioned U.S. Patent No. 3,971,756 and 4,147,707.
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-hydroxyphenyl)methane; 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred tp 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-dimethyl-phenyl)propane, and the like; dihydric phenol ethers such as bis(4-hydroxyphenyl)ether, and the like; dihydroxydiphenyls, such as p,p'-dihydroxydiphenyl; 3,3'--dichloro-4,4'-dihydroxy-diphenyl, and the like; dihydroxyaryl sulfones, such as bis~4-hydroxyphenyl~sulfone; bis(3,5-methyl-4-hydroxyphenyl2 sulfone, and the like; dihydroxybenzenes; resorcinol;
hydroquinone, halo-and alkyl-substituted dihydroxybenzenes, such as 1,4-dihydroxy-2,5-dichlorobenzene; 1,4-dihydroxy-3-methyl-benzene, and the like; and dihydroxy diphenyl sulfoxides such as bis(3,5-dibromo-4-hydroxyphenyl)sulforide, 6~35

- 5 - ~CH-3396 and the like. A variety of additional dihydric phenols are also available to provide carbonate polymers and are disclosed in ~.S. Paten-t Nos. 2,999,835 to ~ugene P. Goldberg, issued September 12, 1961; 3,028,365 to Hermann Schnell et al, issued April 3, 1962; and 3,153,008 to Daniel W. Fox, issued October 13, 1964. 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-hydroxy-phenyl)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 copolymer or interpolymer rather than a homo-polymer is desired fro 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, di(chloronaphthyl) carbonate, and the like, or mixtures thereof. The halo-formates of dihydric phenols are (bischlorofo~mates of hydroquinone, etc.l or glycols (bis haloformates of ethylene glycol, neopentyl glycol, polyethylene glycol, etc.).
While othex 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

- 6 - 8CH-3396 and carbonic acid, such as disclosed in U.S. Patent No.
3,169,121 to Eugene P. Goldberg, issued Fehruary 9, 1965.
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, _-bromophenol, and the like.
A suitable acid acceptor may be ei-ther organic or inorganic. Illustrative of the former are tertiary amines, such as pyridine, triethylamine, dimethylaniline, tri-butylamine, 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, essentia]ly 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 rockwoGl fibers.
Like the above mentioned U.S. 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 bet~een 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 aluminium - boron -silicate glass ("E" glass~ or alkali containin~ glass l''C'' glass) can be used, as well as others. Preferred is a ground short glass fiber.

- 7 - 8CH-3396 Any of the hydrogen polysiloxanes known in the ar-t can serve as component (c). Especially useful are -those set forth by formula in -the above-mentioned U.S. Patent No.
3,971,756. The paten-t also ci-tes U.S. Patent Nos. 2,445,794;
2,448,756; 2,434,595 and 3,514,424 to Maynard G. Noble, e-t al, issued May 26, 1970 as showing ways of making such siloxanes.
Most important members of the family are those in which R
is methyl, or phenyl or a mixture thereo-f. These are commercially available. A-t the present time, it is preferred to use poly(methyl hydrogen)siloxane, a fluid whlch is available commercially from General ElectricCompany under the trade designation DF-1040 In some embodiments, i-t 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 radical type, comprising diene rubber center blocks and vinyl 2Q aromatic terminal blocks. Illustrative dienes are buta-diene 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 trademark Kraton G, and the corresponding radical teleblocks sold by Phillips Chemical under the trademark 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 35 amount of from about 0.05 to less than 0.5, and especially preferably, about 0.4 parts, by weight per 100 parts by ~2~i9~

- 8 - 8CH-3396 weight of (a), (b) and (c) combined. Especially preferably the fibrous reinforcing agent will be present in an amount of from abou-t 15 to about 40 part.s by weight per 100 parts by weight of (a), (b) and (c) combined. Mixing temperatures and molding tempera-ture 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 inventlon. They are not to be construed to li~it the claims in any manner whatsoever.

Polycarbonate compositions are prepared by extruding a homopolymer of 2,2-bisl4-hydroxyphenyl~propane (bisphenol-A) and phosgene (LEX ~ 125), either short milled glass fibers or short milled rockwool-mineral 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 ou-t at 265C, and the extrudate is comminuted into pellets.
The pellets are then injection molded at about 315C.
(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 composition used, and the properties obser~ed are set forth in Table 1:

8C~-3396 _.., g O .
Table 1 Short ~iber Reinforced PolYcarbonz.e CO~POSitiOnS
~ . _ , .. _, Exz~ple 1 lA* lB~ 2 ~A~ 3 3A*
Com~osition(pa_ts by wei~ht) poly(bisphenol-A
carbonatea 70 70 70 8C 80 80 30 ¦ short unsized glass j fibe-sb 30 30 30 20 20 short unsized rock- .
wool fibersC ~ 20 20 10 poly(methyl hydro-gen)siloxaned 0.4 -- - O.4 -- 0.4 --poly(d~methyl) siloxanee -- -- 0.4 P-o~er~ies heat distortion temp., C~ at 1.82 ~ 2 143 143 1~3 142 142 141 142 Izod impact, notched,J/m.152 53 74 180- 70 150 60 Izod impact, uImotched,J/m.NB*~ 350 340 2~B 520 N~ 600 FallirLg ball impact, J lOkg.
dart, 10~ cm 55 <5 <5 110 c~ 55 <5 E modulus, ~/~25100 5250 5300 3600 32503950 4000 Tensi' e s .rength at yiel d 7 N/~2 0.5 c~/~in.43 . 5 66.0 63.0 4a . ~ 6~ . 055 . 0 68 . O
Elongation at yield, % 7 - - 7. 5 - 7. 0 break~ 7O _ 18~3.5 3. 5 25 5. 0 28 4.0 ControL
*~ id not break a LE,~AI~ 125 General Electric Co.
- b EC 10~ ~ M- from Gevetex Co .
: c Fix SpinrockT~ from Rockwool Kapi~us Co.
d D~1040, General Electric Company 35 e SF18, General Electric Com~&~y ' 6~

In all cases, ductile impact strength was enormously increased upon the addition of the siloxane fluid, excep-t when the siloxane fluid did not c~ntain silicon-hydrogen bonds (Control lB). There i5 no significant loss in tensile modulus, and also no loss in heat distortion temperature.
EXAMPLE ~
The general procedure of Examples 1-3 is repeated, increasing the amount of hydrogen siloxane fluid, and deter-mining, 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.

~ 8CH-339~

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Table 2: Short Fiber Relnfo-ced Polvca_30ncte Co~osi~ions Exa~le 4 4A^
Compositlon(parts by weight) 5 poly(bisphenol-A)carbonatea 80 80 short unsized glass fibersb 20 20 poly(methyl hydrogen siloxane)d 0.5 _~
Properties Vicat 3(120/SON) 148 14~
Mel.t viscosity, 300C 450 400 Hea~ dis~ortion te~perature, C. 143 142 T~nsile dulus, N/~m2 3600 375~
Tensile strength, N/mm2 48.5 ~.O
Elongation a~ break, % . 30 5 15 Ti~e to failure in gasoline at 1% strain 17 mir..... DO min.
Whitening in gasoline yes ~es Izod ~pact, notched, J/m. 220 70 , unnotched, J/m. NB** 520 20 Falling ball Lmpact, J, 10 kg; h=var.; ~10 cm dis~, w=3.2 ~m ~9.~ 05 1~0 <5 * Control ** ~ did not break a see footnote to Table l b see iootnote to Table 1 d see footnote to Table 1 - 12 - 8CH-339~

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 he substituted with a polycarbonate fromtetramethylbisphenol-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 selec~ively 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 ~he appended claims.

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A high impact strength, high modulus thermoplas-tic composition consisting essentially of 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 fibrous reinforcing agent essentially free of any sizing agent; and (c) from about 0.05 to about 4 parts by weight of hydrogen siloxane comprising units of the formula wherein R is hydrogen, Cl-C10 alkyl, phenyl or a mixture of any of the foregoing, and n plus m is at least about 4.

2. A composition as defined in claim 1 wherein the siloxane is present in an amount of from about 0.05 to less than 0.5 parts by weight per 100 parts by weight of (a), (b) and (c), combined.

3. A composition as defined in claim 1 wherein the siloxane is present in an amount of about 0.4 parts by weight per 100 parts by weight of (a), (b) and (c) combined.

4. A composition as defined in claim 1 wherein the aromatic carbonate polymer is the reaction product of 2,2-bis(4-hydroxyphenyl)propane and phosgene.

5. A composition as defined in claim 1 wherein the aromatic carbonate polymer is the reaction product of 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane and phosgene.

6. A composition as defined in claim 1 wherein the fibrous reinforcing agent comprises glass fibers or rock wool fibers.

7. A composition as defined in claim 6 wherein the fibrous reinforcing agent comprises glass fibers.

8. A composition as defined in claim 7 wherein the glass fibers are short glass fibers of from about 0.05 mm. to about 5 mm. in length.

9. A composition as defined in claim 1 wherein the fibrous reinforcing agent is 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.

10. A composition as defined in claim 1 which also includes (d) from a small effective amount up to about 10 parts by weight of an impact strength improving modifying agent per 100 parts by weight of (a), (b) and (c), combined.

11. A composition as defined in claim 10 wherein impact modifying agent (d) comprises a selectively hydrogenated block copolymer of the A-B-A type wherein units A are polymerized vinyl aromatic units and center-block units B comprise polymerized diene units.

12. A composition as defined in claim 11 wherein the A units are polymerized styrene units and the B units are polymerized butadiene units.