CA1131837A - Composition of a polycarbonate resin and a selectively hydrogenated block copolymer of a vinyl aromatic compound and an olefinic elastomer - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
There are provided compositions comprising (a) an aromatic polycarbonate resin and (b) selectively hydrogenated elastomeric block copolymer. The use of component (b) provides remarkable improvements in the melt flow characteristics, in resistance to brittle failure, and in the resistance to environmental stress crazing and cracking of the polycarbonate resin component (a). The polycarbonates of the present invention are particularly useful in the manufacture of molded automobile parts.

Description

~ 8CH-~705 This invention relates to novel resin compositions and more particularly, to polymer compositions comprising an aromatic polycarbonate resin and a selectively hydrogenated elastomeric block copolymer of a vinyl aromatic compound and an olefinic elastomer, alone, or in fuxther combination with a reinforcing agent, a foaming agent and/or pigments~
flame retardants and the like.
C 1~
Aromatic carbonate polymers ~ well known, commercially available materials having a variety of applications in the plastics art. Such carbonate polymers may be prepared by reaching a dihydric phenol, such as ~,2-bis(~-hydroxyphenyl) propane, with a carbonate precursor, such as phosgene, in the presence of an acid binding agent. See the Encyclopedia of Polymer Science and Technology, Vol. 10, pp. 710-764, Interscience, New Yor]s, 1969. Generally speaking, aromatic polycarbonate resins offer a high resistance to attack by mineral acids, and they are physiologically harmless as well as stain resistant. In addition, articles molded - from such polymers have a high tensile strength and a hlgh impact strength, except in thick sections, a high heat resistance and a dimensional stability far surpassing that of most other thermoplastic material. However, in certaln applications~ the use of aromatic polycarbonate resins is limited because (i) they have a high viscosity in the melt, making molding of complex, large, and especially foamed parts difficult; (ii) they exhibit brittleness under sharp impact conditions in thick sections and regardless of thickness when small amounts of reinforcements, e.g., glass or pigments, e.g., titanium dioxide, are added for con-~entional purposes; and (iii) they exhibit severe environ-mental stress crazing and cracking. The term "environmental stress crazing and cracking" refers to the type of failure ~ 3t~ ~CH~2705 which is hastened by the presence of organic solvents, e.g., acetone, heptane and carbon -tetrachloride when such solvents are in contact with stressed parts fabricated from aromatic polycarbonate reslns. Such contacts may occur, for example, when the solvents are used to clean or degrease stressed parts fabricated from polycarbonates, or when such parts are used in automobiles, especially under the hood.
The relatively high melt viscosities and softening points of aromatic polycarbonates make them difficult to melt process and several approaches have been suggested for improving melt flow, but theyhave disadvantages. For example, plasticizers can be added but other important properties are lost, the parts becoming brittle and losing a substan-tial amount of their ability to resist distortion by heat. On the other hand, as is suggested in Goldblum IJ.S. Patent No.
3,431,22~ dated March 4, 1969, sma]] amounts of polyethy-lene can be added, and, while -this markedly enhances re-sistance to environmental stress cracking, low levels of polyethylene are not too effective to enhance melt flow and an increase into effective ranges tends to result in molded articles which delaminate.

It has now been discovered that the addition of a minor amount of a hydrogenated block copolymer to aromatic polycarbonates, causes the melt viscosity to go way down, but the heat distortion temperature is substantially unaffected. In practical terms, the melt flow length of parts molded under standard conditions is significan-tly increased with 2, 5, 10 and 20% added block copolymer, and large foamed parts which are especially dif~icult to produce with unmodified polycarbonate are easily produced.
The results are surprising because aromatic polycarbonates by themselves have high viscosities which are not too de-3.~ 3~i33~7 pendent on shear rate; block copolymers by themselves are also high in melt viscosity but are very shear rate dependent, while after mixing the two there is now obtained a very substantial reduction in melt viscosity, below that of either component. As has been mentioned, hydrogenated block co-polymers of the type to be defined appear to be uniquely suited for this application because while 4% of polyethylene improves the flow of aromatic polycarbonates to the extent of 13% at 300C., 5% of a hydrogenated block copolymer im-proves flow to the e~tent of 45%, and much smaller amountsare therefore useful.
The second major advantage ln adding hydrogenated block copolymers to polycarbonates is the improvement in impact resistance in thick-walled molded articles. Normally, thick walled workpieces formed from aromatic polycarbonates are brittle, even if made from a resin which is entirely satisfactory in thin walls, For example, an Izod impact of 14 ft. lbs./in. notch on a 1/8" thick specimen drops to 2.5 ft. lbs as the thickness is only doubled, to 1/4".
Polyolefins, such as are described in U.S. patent No.
3,431,224 dated March 4, 1969 mentioned abov~, improve the situation somewhat, but their use is limited above 3% because of a tendency to delaminate, and in any event, the impact ; strength can be raised only to about 6 ft. lbs./inch of notch in 1/4" sections, with polyethylene. Surprisingly, now it has been found that only 3% by weight of a hydrogenated block copolymer is ef~ective to raise the 2.5 ft. lbs./inch impact of a 1/4" thick specimen all the way up to about 11 ft.
lbs./in. notch, which is seen to approach the value for a 30, thin walled, unmodified polycarbonate.
The third major advantages in adding hydrogenated block copolymers to polycarbonates is to improve their environment . 8CII-2705 3~
resistance. Thus, the molded parts can be subjected to more strain before cracking starts, without appreciably affecting any other of their desirable properties. Althouyh the above-mentioned U.S. patent No r 3,431,224 discloses that polyolefins and other resins are useful for this purpose~ and German Patent Publication 2,329,585 dated January 2, 1975 ~iscloses the addition of rubbery random polymers ancL copolymers to enhance certain properties of aromatic polycarbonates, hydro-genated block copolymers have now been found to be excellent and uniquely suitable for measurably lengthening the time required for stress cracking of parts under stain, e.g., by immersion in aggressive solvents, such as gasoline and carbon tetrachloride. .
The new compositions may also be reinforced, e.g, with fibrous glass, and rendered flame retardant either by using a halogenated aromatic polycarbonate as all or part of component (a), and/or by using flame retardant additives, : or they may be pigmented, and/or foamed by known procedures to extend their field of use in melt processed products~
In comparision with the compositions of prior art, they will in generalt also have hiyh stiffness and strength, excellent surface appearance, and excellent resistance to discoloration by heat~
According to the present invention, there are provided hiyh impact strength thermoplastic compositions comprising an intimate blend of:
(a) an aromatic polycarbonate resin with ~b) a selectively hydrogenated linear, sequential or radial teleblock copolymer of a vinyl aromatic compound (A)n and (A)n and an olefinic elastomer (s)~ of the A-s-A , A-(B-A-B)n -A; A(BA)n B; (A)4; or B](AB) B]4 type, wherein n is an integer of 1 -to 10.

. 8CH-2705 i337 Preerred compositions will be those :in which component (a) comprises from 99.5 to 50 parts by weight and component (b) comprises from 0.5 to 50 parts by weight of the total weight of components (a) and (b)n In particularly preferred compositions, component (a) comprises from 99.5 to 90 parts by weight and component (b) from 0.5 to 10 parts by weight of the total weight of (a) and (b).
In preferred compositions, the aromatic polycarbonate component (a) will be an aromatic polycarbonate of a dihydric phenol and a carbonate precursor such as phosgene, a halo-formate or a carbonate ester. Generally speakin~, such carbonate polymers may be typified as possessing recurring structural units of the formula O

- ~ 0 - A- - 0 ~- C t -wherein A is a divalent aromatic radical of the dihydric phenol employed in the polymer producing reaction. Pre-ferably, the carbonate polymers used to provide the resinous component (a) have an intrinsic viscosity (as measured in p dioxane in deciliters per gram at 3~C.) ranging from about 0.35 to about 0.75. The dihydric phenols which may be employed to provide such aromatic pol.ycarbonate polymers are mononuclear and polynuclear aromatic compounds, containing as ~unctional groups, 2 hydroxyl radicals, each of which is attached directly to a carbon atom of an aromatic nucleus.
Illustrative dihydric phenols are 2,2-bis (4-hydroxyphenyl) propane (Bisphenol-A); hydroquinone; resorcional; 2,2-bis-(4-hydroxyphenyl) pentane, 2,4'-dihydroxydiphenyl methane;
bis-(2-hydroxyphenyl)methane; bis (4-hydroxyphenyl) methane;
bis-(4-hydroxy-5-nilrophenyl)methane; 1;1-bis-(4-hy~roxy-phenyl)ethane, 3,3-bis(4-hydroxyphenyl)pentane; 2,2'-dihy-~ 7~ 8CH-2705 droxy-diphenyl; 2,6-clihydroxy naphthalene; bls-(4-hydroxy-phenyl 5ul fone); 2,4'-di-hydroxy-diphenyl)sulfone; 5'-chloro-

2,4'-dihydroxydiphenyl sulfone; bis (4-hydroxyphenyl) dip-henyl sulEone; 4,4'-dihydroxydiphenyl ether; 4,4'-dihy-droxy-3,3'-dichlorodiphenyl e-ther; 4,4'-dihydroxy-2,5-diethoxydiphenyl ether; ~,2-bis-(3,5-dichloro-4-hydroxyphenyl) propane; 2,2~bis-(3,5-dibromo-4-hydroxyphenyl) propane; 2,2-bis-(3,5-dimethyl-4-hydroxy phenyl)propane; and the li~e.
A variety of additional dihydric phenols which may be employed to provide such carbonate polymers are disclosed in Goldberg, U.S. 2,999,835 dated September 12, 1961. It ls, of course, known to employ t~o or more different dihydric ; phenols or a dihydric phenol in combination with a glycol, a hydroxy terminated polyester, or a dibasic acid ln the event that a carbonate copolymer rather that a homopolymer, e.g~, bisphenol A and tetrabromobisphenol A with flame retardant properties, i5 desired for use as component (a) in the compositions of this invention.
When a carbonate ester is used as the carbonate precursor in the polymer forming reaction, the materials are reacted at temperatures of from 100C. or higher for times varying from 1 to 1~ hours. Under such conditions, ester inter-change occurs between the carbonate ester and the dihydric phenol used. The ester interchange is advantageously con-summated at reduced pressures of the order of from about 10 to about 100 mm. of mercury, preferably in an inert atmosphere, such as nitrogen or argon, for example.
- Although the polymer forming reaction may be conducted in the absence of a catalyst, one may, if desired, employ the usual ester exchange catalysts, such as, for example, metallic lithium, potassium, calcium and magneslum. Additional cat-alysts and ~ariations in the exchange methods are discussed ~ 3~3~ 8CH-2705 in Groggins, "Unit Processes in Organic Synthesis" (4th edition, McGraw-Hill Book Company, 1952) pages 616 to 620.
The amount of such catalyst, if used, is usually small, ranging from about 0.001 to about 0.1~, based on the moles of the dihydric phenol employed.
The carbonate ester useful in this connection may be aliphatic or aromatic in nature, although aromatic esters, such as diphenyl carbonate, are preferred. Additional examples of carbonate esters which may be used are dimethyl carbonate, diethyl carbonate, phenylmethyl carbonate, pheny-ltolyl carbonate and di(tolyl) carbonate.
A preferred method for preparing the carbonate poly-mers suitable for use in providing the compositions of the present invention involves the use of a carbonyl halide, such as phosgene, as the carbonate precursor. This method involves passing phosgene gas into a reaction mixture con-taining the dihydric phenol and an acid acceptor such as -a tertiary amine (e.g., pyridine, dimethylaniline, quinoline etc.). The acid acceptor may be used undiluted or diluted with inert organic solvents as, for example, methylene chloride, chlorobenzene, or 1, 2-dichloroethane. Tertiary amines are advantageous since they are good solvents as well as acid acceptors during the reaction.
The temperature at which the carbonyl halide reaction proceeds may vary from below 0C. to above 100C. The reaction proceeds satisfactorily at temperatures from room temperature (25 Cn ) to 50C. Since the reaction is exothermic, the rate of phosgene addition may be used to control the reaction temperature. The amount of phosgene required will generally depend upon the amount of dihydric phenol present.

Generally speaking, one mole of phosgene will react with one mole of the dihydric phenol used to provide the polymer ~3~33~
and two moles of HCl. Two moles of HCl are i.n turn "attached"
by the acid acceptor present. The foregoing are herein referred to as stoichiometric or theoretical arnounts.
Another method for preparing the caxbonate polymers which may be used to provide the polycarbonate resin com-positions of the invention comprises adding phosgene to an alkaline aqueous suspension of the dihydric phenol. used.
This is preferably done in the presence o:E inert solvents such as methylene chloride, 1,2-dichloroethane and the like.
l~ Quaternary ammonium compounds may be employed to catalyze the reaction.
A fourth method for preparing such carbonate polymers involves the phosgenation o~ an agitated suspension of the anhydrous alkali salts of the dihydric phenol used in a nonaqueous medium such as benzene, chloroben~ene, and toluene.
This reaction is illustrated by the addition of phosgene to a slurry of the sodium salt of 2,2-bis-(4-hydroxyphenyl) -propane in an inert polymer solvent such as chlorobenzene.
The organic solvent should preferably by a polymer solvent but need not necessarily be a good solvent for the reactants.
Generally speaking, a haloformate such as the bishalo-formate of 2,2-bis-(4-hydroxyphenyl)-propane may be sub-stituted for phosgene as the carbonate precursor in any of the methods described above.
In each o~ the above solution methods of preparation, ~he carbonate polymer emerges ~rom the reaction in either a true or pseudo solution whether aqueous base or pyridine is used as an acid acceptor. The polymer may be precipitated from the solution by adding a polymer non-solvent, such as heptane or isopropanol. Alternatively, the polymer solution may be heated to evaporate the solvent.
~ith respect to component (b), the hydrogenated block ~ 83~ 8CH-2705 copolymers are made by mea~s known in the art and they are commercially available.
Prior to hydrogenation, the end blocks of these copolymers comprise homopolymers or copolymers preferably prepared from alkenyl aromatic hydrocarbons and particularly vinyl aromakic hydrocarbons wherein the aromatlc moiety may be either monocyclic or polycycllc. Typical monomers include styrene, alpha methyl styrene, vinyl xylene, ethyl vinyl xylene, vinyl naphthalene, and the like, or mixtures thereof. The end blocks (A) and (Al), may be the same or different7 They are preferably selected from styrene, ~-methyl styrene, vinyl toluene, vinyl xylene, vinyl naphthalene, especially styrene.
The center block (B) may be derived from, for example, but-adiene, isoprene, 1-3-pentadiene, 2,3, dimethyl butadiene, and the like, and it may have a linear, sequential or telera-dial structure.
The selectively hydroge~ated linear block copolymers are described by Haefele et al, U.S. patent No. 3,333,024 dated July/25/1967.
The ratio of the copolymers and the average molecular weights can vary broadly although the molecular weight of centex block should be greater than that of the combined terminal blocks. It is preferred to form terminal blocks A having average molecular weights of 2,000 to 100,000 and center block B, e.g., a hydrogenated polybutadiene block with an average molecular weight of 25 r 000 to l,OOQ,000.
Still ~ore preferably, the terminal blocks have average molecular weights of 8,000 to 60jO00 while the hydrogenated polybutadiene polymer blocks has an average molecular weight between 5Q,000 and 300,000. The terminal blocks will pre--ferably comprise 2 to 60% by weight, or more, preferably, 15 to 40% by weight, of the total block polymer. The preferred g _ ~. 3 ~337 copolymers will be those Eormed from a copolymer having a hydrogenated/saturated polybu-tadiene center block wherein 5 to 55~, or more, preEerably, 30 -to 50% of the butadiene carbon atoms, are vinyl side chains.
The hydroyenated copolymers will have the average unsaturation reduced to less than 20% of the original value. It is preferred to have the unsaturation of the center block B reduced to 10%, or less, preferablyJ 5~ o:~ its original value.
The block copolymers are formed by techniques well known to those skilled in the art. Hydrogenation may be conducted utilizing a variety of hydrogenation catalysts such as nickel or kieselguhr, Raney nickel, copper chroma~e, molybdenum sulfide and finely divided platinum or other noble matels on a low surface area carrier.
Hydrogenation may be conducted at any desired tem-perature or pressure, from atmospheric to 300 psig, the usual range being between 100 and 1,000 psig at ~emperatures from 75F. to 600~. for times between 0.1 and 24 hours, pre-ferably, from 0.2 to 8 ho~rs.
Hydrogenated block copolymers such as Kraton G - 6500, Kraton G - 6521, Kraton G 1650 and ~raton G - 1652 from Shell Chemical Company, Polymers Division, have heen found useable according to the present invention. Kraton G - 1650 is preferred. Also useable are the so-called hydroyenated Solprenes of Phillips, especially the product designated Solprene - 512.
The radical teleblock copolymers of which the Solprenes are typical examples can be characterized as having at least three polymer branches with each branch of the radial block pol~mer comprising terminal non-elastomeric seyments, e.g.
(A) and ~Al) as defined hereinabove. The branches of the o~

~ 3~ ~ ~ ~

radial block polymer contain a terminal non-elastomeric segment attached to an elastomeric polymer segment, e.g.
(B) as defined above. These are described in ~arrs, in U.S. patent No. 3,753,936 dated Augus~ 21, 1973 and in Zelinski, and U.S. 3,281,383 dated October 25, 1966, and they are selectively hydrogenated by procedures known per se. In any event, the term "selective hydxogenation" is used herein to contemplate polymers in which the elastomeric blocks (B) have been hydrogenated, but the non-elastomeric blocks (A) and (A ) have been left unhydrogenated, i.e., aromatic.
As is mentioned above, other additive may be present in the compositions, such as pi~ments, e.g., titanium dioxide, flame retardants, foaming agents, e.y., 5-phenyltetrazole, etc., and the like, in amounts varying between about 0.1 and 100 parts by weight of the total resinous components (a) and (b) in the composition.
Among the preferred features of this invention are reinforced compositions containing reinforcing amounts of reinforcements, such as powders, whiskers, fibers or plate-lets of metals, e.g., aluminum, bronze, iron or nickel, and non-metals, e.g., carbon filaments, acicular CaSiO3, asbestos, TiO2, titanate whiskers, glass flakes, and the like. Such reinforcements will be present in an amount of e.g., 2 to 60~ by weight, preferably 5 to 4~ by weight. Especially preferred as a reinforcement is fibrous glass.
The method of forming the polymer composition is not critical. ~ny prior art blending technique is generally suit-able. The preferred method comprises blending the polymers and additives, such as reinforcements in powder, granular and filamentous form - - as the case may be - - extruding the blend and chopping into pellets suitable for molding to ~ 3~ 8CH-2705 shape by means conventionally used to mold normally solid -thermoplastlc composltions.
The advantages obtained by providing compositions of an aromatic polycarbonate resin, and a selectively hydrogenated elastomeric vinyl aromatic olefinic A-B-A block copolymer are illustrated in the following examples which are set for-th as further description of the invention, but are not to be construde as limiting the invention t:hereto.
The following formulations are produced by a general procedure comprising mechanically blending the components then predrying for 4 hours at 125C., then extruding in a twin screw Werner Pfleiderer (WP) extruder at 300C. After extrusion the materials were dried for 4 hours at 125 C, before molding into test pieces in a reciprocating screw injection molding machine at 260 to 320C. ~cylinder) and 20C to 115C. (mold)O To make foamable compositions, the pelletized extrudate is dr~ blended with 5-phenyl tetrazole, 0.25 parts per hundred of (a) and (b). And foam molding is carried out in a Siemag unit with a plasticizer/accumulator.
All conditions are standard for polycarbonate per se. All of the polycarbonate components contained a small amount, e.g., 0.1~ of a stabilizer combination, i.e., conventional phosphite/hindered phenol. The physical tests are carried out by the following procedures: notched Izod impact streng-th on 1/4" and 1/8" specimens; falling dart impact tests on ~ -1/8" disc speciments; tensile strength and modulus, flexural strength and modulus; heat distortion temperature; and apparent melt viscosity at 1500 sec. and 300C., and in the case of foams, Gardner impact and Charpy impact. Formulations made and physical properties on molded pieces are as follows:
A composition is prepared, molded and compared,

3~33~

A composition is prepared, molded and compared, _xample 1 lA*
~) (a) poly-(2 2-diphenylpropane) carhonatea 97 100 (b) hydrogenated styrene-bu~adiene-styrene block copolymer 3 --Properties Intrinsic viscosity, dl. /g. 0.62 0.56 Izod impact 1/8", ft.lbs./in.notch 13 14 1/4",ft.1bs./in.notch 11 2.5 Falling dart impact, kg./m. > 20 > 20 Tensile strength, kgf./cm2 580 630 Tensile modulus, kgf./cm2 23~600 24,300 Flexural strength, kgf./cm 910 950 Flexural modulus, kgf./cm2 22,700 23,900 Heat distor~tion temp. at 18.5 kg./cm , C. 139 140 Melt viscosity, poise 29Q0 3900 .
*Control a General Electric Co., Lexan 160, mol. wt. about b Shell Chemical Co., Kraton G1650 It is seen that the melt viscosity is significantly lowered and the thick part impact strength is substantially improved without loss in other properties in the composition of Example 1.
_XAMPLE _ A composition is prepared with a highex molecular weight aromatic polycarbonate~

~7 ~ ~3~ ~3~7 8 CH- 2 7 0 5 Example 2* 2A*
_ ition (parts by weigh-t) (a) poly-(2,2-diphenylpropane) carbonatea 95 lO0 (b) hydrogenated styrene-hutadi~ne-styrene block copolymer 5 --Properties Intrinsic viscosity, dl./g. 0.59 0.59 Izod impact l/8", ft. lbs./in.notch 13 14 1/4".ft.lbs./in.notch ll 2.5 Fallingdart impact, kg./m. >20 ~ 20 Tensile strength, kgf./cm2 560 630 Tensile modulus, kgf./cm2 22,500 24,300 Flexural strength~ kgf./cm 900 950 Flexural modulus, kgf./cm2 22,000 23,900 Heat disto~tion temp. at 185 kg./cm , IC. 138 140 Melt viscosity, poise 2,200 5,000 * Control a General Electric Co., Lexan 100, mol. wt. about b Shell Chemical Co., Kraton G1650 Again, there is seen a remarkable reduction in melt viscosity and increase in lmpact resistance of thicker parts.

~ 3~ 8CH-2705 Glass reinforced composi-tion is prepared and co~pared:

Fxample 3 3A*

_mpositi ~ arts by weight) (a) poly-(2,2-diphenylpxopane) Carbonatea 90 95 (b) hydrogenated styrene-bu~adiene-s~yrene block copolymer 5 --(c) fibrous glass reinforcement 5 5 10~~
Intrinsic viscosity, dl. /g/ 0.57 0.57 Izod impact l/8", ft. lbs./in.notch 6.8 2.5 1/4",ft.1bs./in.notch 4.1 2.5 Falling dart impactt kg./m. 20 l9 Tensile strength, kgf./cm 610 635 Tensile modulus, kgf./cm 28,000 29,000 Flexural strength, kgf./cm 940 990 Flexural modulus, kgf./cm2 25,000 27,000 Heat distor~ionO temp. at 18.5 kg./cm , C. 140 140 Melt viscosity, poise 2,000 4,800 * Control a General Electric Co., Lexan lO0 b Shell Chemical Co., Kraton Gl650 Not only are the flow properties markedly improved, but also the serious embrittling effect of glass on both thick and thin walls is reversed~

_AMPLE 4 A pigmented composition is prepared ancl comparecl:
Example 4 4A*
.__ Composltion (parts by weight) , (a) poly(2,2-diphenylpropane) carbonatea 95 98 (b) hydrogenated styrene-bu~adiene-styrene block copolymer 3 --(c) pigment, titanium dioxide 2 2 Properties Intrinsic viscosity, dl./g. 0.57 0.57 Izod impact 1/8", ft.lbs./in.notch 13.5 2.5 1/4", ft.lbs./in.notch 3.5 2.5 Falling dart impact, kg./m. 20 20 Tensile strength, kgf./cm2 615 635 Tensile modulus, kgf./cm2 23,800 24,500 Heat distor~ion temp. at 18.5 kg./cm , C. 138 140 Melt viscosity, poise 2,900 4,500 . . . ~
* Control a General Electric Co., Lexan 100 b Shell Chemical Co., Kraton G1650 The flow properties and the impact strenyth are improved with no loss in other important properties.

~ 3~q~7 8CH-2705 _ A reinforced, flame retardant, foamed eomposition is prepared, molded and eompare:
Example 5 5A*
__ _ _ Composition (parts by weight) (a) poly(2,2-aiphenylpropane) earbonate 90 95 (b) hydrogenated styrene-bubadiene-styrene bloek eopolymer 5 (e) glass fiber reinforcement 5 5 (d) triehlorobenznesulfonic acid, sodium salt, flame retardant 0.8 0.8 (e) 5-phenyltetrazole foaming ~gent 0.25 0.25 Properties Intrinsic viscosity, dl./g. 0.59 0.59 Tensile strength, kgf./em 316 320 Tensile modulus, kgf./cm 14,700 17,00 Flexural strength, kgf./cm2 570 610 Flexural modulus, kgf./em2 17,900 20,000 Heat disto~tion temperature, 18. 5kg/em , C. 126 126 Melt viseosity, poise 3,000 4,000 Gardner impact, in. lbs. 200 105 Charpy impaet, kgfem./sm2 no break no break * Control a General Eleetrie Co., Lexan 100 b Shell Chemical Co., Kra-ton G1650 Beeause of the improved proeessability, large par-ts, e.g., of 3-4 kilos in weightf having optimum density, 0.7 to 0.9 g/ee are foamed from the composition of this invention and they have superior glossy surfaces. Typieal characteristies ~3~33~ 8C~I-2705 for structural foam molding are long dwell times and high temperatures which are necessary for flowa~ility requirements.
This consequently leads to severe technical problems, caused by polymer breakdown when chemical blowing agents are present.
The example according to this invention overcomes these problems in all respec~s.

A series of compositions are prepared and molded, and the environmental stress cracking is determined under flexural load with 0.25% strain after immersion in carbon tetrachloride by procedures known per se.
Example _* 6 7 8A* 8 9_ _ _ _ (a) poly(2,2~~iphenylpropane) carbonateC 100 98 95 (b) poly(2,2-Ddiphenylpropane) carbonate ~ -- 100 98 95 (e) hydrogenated styrene buta-diene-styrene block co-polymerC -- 2 5 -- 2 4 Properties Crack initiation after: 31 45 2 45 12 12 sec. sec.min. sec. min. min Catastrophic crack after: 1 10 10 50 12 12 * Control a General Electric Co., Lexan 121 b General Electric Co., Lexan 101 e Shell Chemical Co., Kraton G1650 The compositions of this invention are seen to show a significant improvement of stress crack resistance.

In another test DIN tensile bars molded from each of compositions 6 and 6A are put under constant tensile de-dormation of 2.8% for 2~ hours. The sample 6A shows many crazes, whereas no crazes are shown by Example 1 showing superior resistance -to stress relaxa-tion in environmental air.

A composition according to Example 1 (97 parts of poly-(2,2-diphenylpropane) carbonate and 3~ hydrogenated (styrene~
butadiene-styrene block copolymer) is moldecl into 1/8" discs and subjected to a falling dart impact test. The discs are then tested for environmental stress crack resistance with the following results:
Immersion in Effect Carbon tetrachloride no break, only small crazes after long immersion times.

Gasoline (Super Petrol) no break, almost no crazes even after very long immersion times.

A flame retardant, foamed, glass reinforced composi-tion, according to Example 5, is molded into test bars, immersed in gasoline (Super Petrol), and the maximum flexural strength is determined as a function of time out to 50 minutes, and compared with that of bars molded from foamed polycarbonate controls. Initially, both bars have a maximum flexural strength of 560 kgf./cm2. The control decreases to 100 within 2 minutes and stabilizes. The composition according to this invention decreases to 250 kgf./cm 510wly, during 20 minutes, and does not fall below -this value, even out to S0 minutes immersion time.
From the foregoing data, it can be seen that the addi-tion of block copolymers to aromatic polycarbonates promotes ductile instead of brittle deformation in high wall thick-ness.

:

~ 1.3~8~7 8CH-2705 The same type of bene:Ficial ductile deEormation made is achieved also with -the pigmented and glass relnforcements, whlch are notorious for their embrittlement of aromatic polycarbonates.
Flame retardant modifications which also are not brittle have been produced and are superior when foamed.
The environmental stress crack resistance is drasti-cally improved for solids as well as for foams.
Obviously, other modifications and variations of the present invention are possible in the light of the above teachingsO It is, therefore, to be understood that changes may be made in particular embodiments of the invention de-scribed which are within the full intended scope of the invention as defined by the appended claims.

Claims (36)

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

1. A thermoplastic composition comprising an intimate blend of:
(a) an aromatic polycarbonate resin with (b) a selectively hydrogenated linear, sequential or radical teleblock copolymer of a vinyl aromatic compound (A)n and (A)n and an olefinic elastomer (B), of the A-B-A 1;
A-(B-A-B)n -A; A(BA)nB; (A)4B; B(A)4; or B[(AB)nB]4 type, wherein n is an integer of from 1 to 10.

2. A composition as defined in Claim 1 wherein componet (a) comprises from 99.5 to 50 parts by weight and component (b) comprises from 0.5 to 50 parts by weight of the total weight of components (a) and (b).

3. A composition as defined in Claim 2 wherein com-ponent (a) comprises from 99.5 to 90 parts by weight and component (b) from 0.5 to 10 parts by weight of the total weight of (a) and (b).

4. A composition as defined in Claim 1 wherein com-ponent (a) is an aromatic polycarbonate of a dihydric phenol and a carbonate precursor.

5. A composition as defined in Claim 4 wherein said aromatic polycarbonate is a polycarbonate of bisphenol-A.

6. A composition as defined in Claim 1 wherein, in component (b), (A) and (A) are selected from styrene, .alpha.- methyl styrene, vinyl tolune, vinyl xylene and vinyl naphthalene and (B) is selected from butadiene, isoprene, 1,3-pentadiene or 2,3- dimethylbutadiene.

7. A composition as defined in Claim 6 wherein, in component (b), (A) is a styrene block, (B) is an olefin block, and (A)1 is a styrene block.

8. A composition as defined in Claim 7 wherein, in component (b), terminal blocks (A) and (A)l have molecular weights of 2,000 to 100,000, respectively, and center block (B) has a molecular weight of from 25,000 to 1,000,000.

9. A reinforced composition as defined in claim 1 including a reinforcing amount of a reinforcing filler.

10. A composition as defined in claim 9 wherein said reinforcing agent comprises glass fibers.

11. A composition as defined in claim 1 which contains a flame retardant.

12. A composition as defined in claim 9 which contains a flame retardant.

13. A composition as defined in claim 1 which also includes a minor, effective amount of a foaming agent.

14. A composition as defined in claim 9 which also includes a minor, effective amount of a foaming agent.

15. A composition as defined in claim 1 which also includes a small, effective amount of a pigment.

16. A composition as defined in claim 15 wherein said pigment is titanium dioxide.

17. A thermoplastic composition having superior resistance to impact fracture in thick-walled molded articles and improved environmental solvent resistance comprising an intimate blend of (a) an aromatic polycarbonate resin; and (b) not substantially greater than up to about 3.5 parts by weight of a selectively hydrogenated linear, sequential, or radial teleblock copolymer of a vinyl aromatic compound (A)n and (Al)n and an olefinic elastomer (B), of the type A-B-A ; A-(B-A-B)n-A; A(BA)nB; (A)4B; B(A)4; or B[(AB)nB]4, wherein n is an integer from 1 to 10.

18. A composition as defined in claim 17, wherein component (a) comprises from 99.5 to not substantially less than about 96.5 parts by weight and component (b) comprises from 0.5 to not substantially greater than about 3.5 parts by weight, based on the total weight of components (a) and (b).

19. A composition as defined in claim 17, wherein component (a) comprises from 99.5 to not substantially less than about 97 parts by weight and component (b) comprises from 0.5 to not substantially greater than about 3 parts by weight, based on the total weight of components (a) and (b).

20. A composition as defined in claim 17, wherein component (a) is an aromatic polycarbonate of a dihydric phenol and a carbonate precursor.

21. A component as defined in claim 20, wherein said aromatic polycarbonate is a polycarbonate of bisphenol-A.

22. A composition as defined in claim 17, wherein, in component (b), (A) and (Al) are selected from the group consisting of styrene, .alpha.-methyl styrene, vinyl toluene, vinyl xylene, and vinyl naphthalene and (B) is selected from the group consisting of butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethylbutadiene.

23. A composition as defined in claim 22, wherein, in component (b), (A) is a styrene block, (B) is an olefin block, and (Al) is a styrene block.

24. A composition as defined in claim 23, wherein in component (b), terminal blocks (A) and (A) have molecular weights of 2,000 to 100,000, respectively, and center block (B) has a molecular weight of from 25,000 to 1,000,000.

25. A reinforced composition as defined in claim 17 including a reinforcing amount of a reinforcing filler.

26. A composition as defined in claim 25, wherein said reinforcing agent comprises glass fibers.

27. A composition as defined in claim 25 which contains a flame retardant.

28. A composition as defined in claim 17 which contains a flame retardant.

29. A composition as defined in claim 17 which also includes a minor, effective amount of a foaming agent.

30. A composition as defined in claim 25 which also includes a minor, effective amount of a foaming agent.

31. A composition as defined in claim 17 which also includes a small, effective amount of a pigment.

32. A composition as defined in claim 31, wherein said pigment is titanium dioxide.

33. A thermoplastic composition comprising an intimate blend of:
(a) 97 parts by weight of poly-(2,2-diphenylpropane carbonate); and (b) 3 parts by weight of hydrogenated styrene-butadiene-styrene block copolymer.

34. A thermoplastic composition comprising an intimate blend of:
(a) 95 parts by weight of poly-(2,2-diphenylpropane carbonate);
(b) 3 parts by weight of hydrogenated styrene-butadiene-styrene block copolymer, and (c) titanium dioxide pigment.

35. A thermoplastic composition having superior resistance to impact fracture in thick-walled molded articles and improved environmental solvent resistance comprising an intimate blend of:
(a) an aromatic polycarbonate resin; and (b) not substantially greater than up to about 3.0 parts by weight of a selectively hydrogenated linear, sequential, or radial teleblock copolymer of a vinyl aromatic compound (A)n and (A1)n and an olefinic elastomer (B), of the type A-B-A1;

A- (B-A-B) n-A; A (BA) nB; (A) 4B; B (A) 4; or B[(AB)nB]4, wherein n is an integer from 1 to 10.

36. A composition as defined in claim 35, wherein component (a) comprises from 99.5 to not substantially less than about 97 parts by weight and component (b) comprises from 0.5 to not substantially greater than about 3 parts by weight, based on the total weight of components (a) and (b).