AU569469B2 - High impact, high modulus fiber reinforced polymers - Google Patents

Description

HIGH IMPACT, HIGH MODULUS FIBER REINFORCED POLYMERS This invention is directed to an improved polycarbonate composition of an aromatic carbonate polymer and a linear polyester 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 roc wool fibers, into polycarbon¬ ate 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 deteriora- tion 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 im¬ pact modifiers, such as selectively hydrogenated styrene-butadiene-styrene block copolymers, then there is a detrimental effect 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 rein¬ forcing 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.

SUBSTITUTE SHEET

OfflPI The ductility of the compositions mention¬ ed above decreases even further when linear poly¬ esters are blended in the fiber-reinforced polycar¬ bonates in order to establish outstanding chemical resistance. Polycarbonates are known to have a very limited resistance against environmental stress crack conditions.

It has now been discovered that the addi¬ tion of poly C,-C,₀ alkyl (or phenyl) hydrogen sil- oxanes to compositions comprising "pristine" (or sizing-free) fibrous reinforcements and polycarbon¬ ates-polyester admixtures, '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. 4,147,707, who des- cribe glass fiber reinforced polycarbonates with im¬ proved 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 ductiie impact with such specific hydrogen polysiloxanes is, as will be illustrated later, more than ten times greater than TUTE SHEET "BU E- with the dimethyl-polysiloxanes used in Alewelt et al. Bialous et al., U.S. 3,971,756 is also relevant to the present invention, but only insofar as it shows that from 0.01 to about 5 weight per- cent of a polysiloxane having silicon-bonded hy¬ drogens can be used to prevent dripping in flame retardant polycarbonate compositions. Although the amounts and types of hydrogen siloxanes sug¬ gested in the '756 patent are within the limits employed herein, and the inclusion of fibrous glass is suggested, the need for sizing-free fi¬ bers to enhance ductile impact is not at all evi¬ dent.

It is believed that the following conditions are essential herein:

(i) sizing agents (on the fibrous reinforce¬ ment or separately added) must be absent because these either evoke adhesive bonds between the matrix and fiber, or they prevent reactions between the hy- drogen 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 hydro¬ gen silicon bonds.

Following the use, especially, of short glass fibers, additional advantages in improved isotropy and high surface quality are obtained. It is again reempha- sized, 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-

SUBSTITUTE SHEET

O PI 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 20% short glass fiber-reinforced polycarbonate polyester blend can be increased from

<5J to 60G, while the unnotched impact bar increased from about 400 to about 800 J/m. 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, there are provided high impact strength, high modulus thermoplastic compositions comprising per 100 parts by weight (a) , (b) , (c) and (d) , an intimate admixture of:

(a) an aromatic carbonate polymer or copolymer;

(b) a linear polyester, the combined amount of (a) and (b) consisting of from about 35 to 95 parts by weight of the total composition;

(c) from about 5 to about 65 parts by weight of a fibrous reinforcing agent essentially free of any sizing agent; and (d) from about 0.05 to about 4 parts by weight of a hyd

wherein e of any of the foregoing, and n plus m is at least 4, and, for example, up to about 200.

SUBSTITUTE SHEET DETAILED DESCRIPTION OF THE INVENTION The term "aromatic carbonate polymer or co- polymer" is used in its broadest aspects. Suitable are those described in the above-mentioned U.S. 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 re¬ acting a dihydric phenol with a carbonote precursor. Suitable dihydric phenols are bis(4-hydroxyphenyl)methane; 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenbl-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) ropane; 2,2-bis (4-hydroxy-3,5-dimethyl- phenyl)propane,^* and the like; dihydric phenol ethers such as bis(4-hydroxy-ρhenyl)ether, and the like; dihydroxy- diphenyls, such as p,p'-dihydroxydiρhenyl; 3,3'-dichloro- 4,4'-dihydroxydiphenyl, and the like, dihydroxyaryl sul- fones, such as bis(4-hydroxy-phenyl) sulfone; bis(3,5- methyl-4-hydroxyphenyl)sulfone, and the like; dihydroxy- benzenes; resorcinol hydroquinone, halo- and alkyl- substituted dihydroxybenzenes, such as 1,4-dihydroxy- 2,5-dichlorobenzene; l,4-dihydroxy-3-methyl-benzene, and the like; and dihydroxy diphenyl sufloxides, such as bis(3,5-dibromo-4-hydroxy-phenyl) sulfoxide, and the like. A variety of additional dihydric phenols are also avail¬ able to provide carbonate polymers and are disclosed in U.S. 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 copolymerize with halogen-containing•dihydric phenols, such as 2,2- bis(3,5-dichloro-4-hydroxyphenyl)propane; 2,2-bis(3,5- dibromo-4-hydroxyphenyl) ropane, and the like. It is contemplated to employ two or more different dihydric phenols or a copolymers of a dihydric phenol with a glycol

E SHEET OMPI or with hydroxy or acid terminated polyester, or with a dibasic acid in the eventthat a carbonate copolymer 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 poly¬ mers. Especially preferred dihydric phenols are bis- phenol-A and 2,2-bis(4-hydroxy-3,5-dimethylphenyl) ropane.

The carbonate precursor may be either a car- bonyl halide, a carbonyl ester or a haloformate. The carbonyl halides which may be employed include carbonyl bromide, carbonyl chloride and mixtures thereof. Typi¬ cal of the carbonate esters are diphenyl carbonate, di- (halophenyl)-carbonate such as di(chlorophenyl)carbonate, di(bromophenyl)-carbonate, di (trichlorophenyl) car- bonate, 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 di¬ hydric phenols are (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. 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. Suit¬ able 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

SUBSTITUTE SHEET 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.

The linear polyesters (b) used in the practice of the present invention are polymeric glycol esters of terephthalic and isophthalic acids. They are available commercially or can be prepared by known techniques such as by the alcoholysis of esters of the phthalic acid with a glycol and subsequent polymerization, by heating glycols with the free acids or with^' halide derivatives thereof, and similar processes. These are described in U.S. 2,465,319 and 3,047,539. Although the glycol portion of the polyester can contain from two to ten carbon atoms, it is preferred that it contain from two to four carbon atoms in the form of linear methylene chains.

Preferred polyesters will be of the family con- sisting of high molecular weight, polymeric glycol tere- phthalates or isophthalates having repeat general formula:

wherein n is a whole number from two to four, and mixtures of such esters, including copolyester of terephthalic and isophthalic acids.

Especially preferred polyesters are poly(ethylene terephthalate) and poly(1,4-butylene terephthalate) .

The amounts of components (a) , (b) - (c) , (d) and, optionally, (e) to be used have been broadly set forth above. Preferably, 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

SUBSTITUTE SHEET 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 (d) combined. Mixing temperatures and molding tem¬ peratures will be illustrated in the following examples but, in any event, they will correspond entirely to those well known to those skilled in the art of resin technology. DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples illustrate the composi¬ tions of the present invention. They are not to be con¬ strued as limiting the claims in any manner whatsoever.

EXAMPLES 1-6 Resin compositions are prepared by extruding a mixture of a homopolymer of 2,2-bis(4-hydroxyphenyl) propane (Bisphenol-A) and phosgene (LEXA _-^125) , a linear polyester, short milled glass fibers, essentially free of any sizing agent, and, where indicated, a poly- methyl hydrogen siloxane fluid (DF 1040, General Electric Company) . Extrusion is carried out at 265°C. and the extrudate is comminuted into pellets.

The pellets are then injection molded at about 300°C. (cylinder) for Examples A and B and 270°C. for Examples C, D, E and F into standard physical test speci- mens 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 disk according to standard test methods; elastic modulus and tensile yield strength and elongation at yield and at break can be measured by standard test methods.

The compositions used and the properties observed are set forth in Table 1.

SUBSTITUTE SHEET TABLE 1 Short Fiber Reinforced Polycarbonate-Polyester Compositions

Composition(pts. by wt.) B

Poly(bisphenol-A carbonate) 45 45 45 45 30 30

Poly(ethylene tere¬ phthalate) 35 35

Poly(1,4-butylene tere¬ phthalate) 35 35 45 45

Short unsized glass fibers 20 20 20 20 20 20

Poly(methyl hydrogen siloxane)^c 0.5 — 0.5 — 0.5

Kraton G 1651 —_ 5 5

Properties

Vicat B (120/50N) 147 146 135 124 131 131

Melt Viscosity, 300°C. Pa-s. 380 370

Melt Viscosity, 260°C. Pa-s. 430 430 360 360

Heat Distortion Temper¬ ature, °C. 131 130 117 113 —

2

Tensile Modulus, N/mm 4200 4120 4170 3960 3410 3300

2

Tensile Strength, N/mm 64 52 62 51 60 39.8

Elongation at break, % 5.6 20 4.5 30 4.5 16 Time to failure in gasoline at 1% strain No failure in twenty-four hours Whitening in gasoline No No No No No No Izod Impact: notched: J/m 90 130 90 135 48 105 unnotched: J/m 430 800 400 800 450 1150 Falling ball impact, <5 80 < 5 60 <5 85

, 10 KG; h=var.; Φ10 cm disc; w=3.2 mm; φ9♦5 cm support rjng

LEXAN ^"-*^: 125, General Electric Company b EC 10W, Gevetex Company c DF 1040, General Electric Company

SUBSTITUTE SHEET Obviously, many variations are possible in the 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, i.e., 5% by weight, of a selectively hydrogenated block copolymer of styrene- butadiene-styrene, such as Shell's Kraton G, can be in¬ cluded in the composition. For the polycarbonate, there can be substituted polyester^' carbonate, polycarbonate siloxane copolymers and blends thereof. All such ob¬ vious variations are within the full intended scope of the appended claims.

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 (c) 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 rock- wool fibers.

Like the above-mentioned U.S. 4,147,707, suitable fibers, e.g., glass fibers, are all the commercially avail¬ able 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 con-

'^■gUREA taining 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 (d) . Especially useful are those set forth by formula in the above-mentioned U.S. 3,971,756. The patent also cites U.S. 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 ref- erence. 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) , (c) and (d) combined, of an impact modifier (e) . 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 illus- trative 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 trade- name 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.

SUBSTITUTE SHEET

Claims (6)

1. CLAIMS 1. A high impact strength, high modulus thermoplastic composition comprising an intimate ad¬ mixture of: (a) an aromatic carbonate polymer or co¬ polymer;

   (b) a linear polyester, the total weight of (a) plus (b) being from about 35 to about 95 parts of the composition; (c) from about 5 to about 65 parts by weight of a fibrous reinforcing agent essentially free of any sizing agent; and

   ^"(d) from about 0.05 to about 4 parts by weight of a hydrogen siloxane comprising units of the formula

   wherein R is hydrogen,^" C-J-C,_Q alkyl, phenyl or a mixture thereof, and n plus m is at least about 4.
2. 2. The composition of claim 1 wherein the siloxane is present in an amount of from about 0.5 to less than 0.05 part by weight per 100 parts by weight of the total composition.
3. 3. The composition of claim 1 wherein the aromatic carbonate polymer is the reaction product of

   2,2-bis(4-hydroxyphenyl)propane and phosgene.
4. 4. The composition of claim 1 wherein the aromatic carbonate is the reaction product of 2,2- bis(4-hydroxy-3,5-dimethylphenyl)propane and phosgene.
5. 5. The composition of claim 1 wherein the linear polyester is poly(ethylene terphthalate) , poly- (1,4-butylene terephthalate) or mixtures thereof.
6. 6. The composition of claim 1 wherein the fibrous reinforcing agent comprises glass fibers or rock- . wool fibers.

   _SUBSTITUTE SHEET ^