CA1195027A - Polyphenylene ether resin compositions containing siloxane block copolymers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Novel compositions are disclosed which include a polyphenylene ether resin and a block copolymer of styrene and siloxane or a block copolymer of polyphenylene ether and a siloxane. Such compositions exhibit improved Izod impact strength and resistance to aging with no significant loss in tensile and elongation properties.

Also included within the scope of this inven-tion are methods for preparing the novel compositions, as well as methods for molding the compositions and the resulting molded products.

Description

2~7 .. . .. . . ...
SI-LOXANE BLOCK COPOLYMERS
.. . .... _ .
B~CKG~OU~ OF THE ;INVEN~ION
The polyphenylene ether resins are a famlly vf engineering thermoplastics that are well known to the polymer art. These polymers may be made by a ~ariety of catalytic and non-catalytic processe from the corres-ponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos~ 3,306,874 and

3,306,875 and in Stamatoff, U.S~ Pat. Nos. 3,257,357 and 3,257,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solu tion of a phenol and a metal-amine complex catalystO
Other disclosures relating to processes for preparing polyphenylene ether resins, including graft ccpolymexs of polyphenylene ethers with styrene type compounds, are found in Fox, ~.S. Pa~. No. 3,356,761, Sumitomo, IJ.K. Pat. NoO 1,291,609i Bussink et al., U.S. Pat. NosO
3~337,499; Blanchard et al., 3,219,626; Laakso et al., 3,~42,892, Borman, 3,344,116; Hori et al-.5- 3,384/619;
Faurote et alO, 3,440,217; and disclosuxes relating to metal based catalysts which do not include amines, are known from U.S. Pat~ Nos. such as Wieden et al.~ 3,442,885 (copper-amidines); Nakashio et al~, 3,573,257 (metal-alcoholate or -phenolate); Kobavashi et al., 3,455,880 (cobalt chelates~; and the like. In the S.am~tof~ paten~s, ~, , =, . . .
.. .. .... . . .... ............. . ...

the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite, and the like, in -the presence of a complexing agent. Dis-closures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide, etc. are described in U.S. Patent No. 3,382,212, issued May 7, 1968 to Price et al. U.S. Patent No. 3,383,435, issued May 14, 1968 to Cizek, discloses polyphenylene ether-styrene resin compositions.
In the prior art, rubber modified styrene resins have been admixed with polyphenylene ether resins to ~orrn compositions that have modi.fied properties.
The Cizek patent, U.S. Patent No. 3,383,435, discloses rubber-modified styrene resin-polyphenylene ether resin compositions wherein the rubber component is of the un-saturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers is improved.
U.S. Patent No. 3,65~,945, issued April. 25, 1972 to Nakashio et al, discloses that from 0.5 to 15~ by weight o:E an EPDM rubber modified by grafting with styrene may be used to upgrade the .impact strength of polyphenylene ether resins. In U.S. Patent No. 3,9~3,191, issued March 9, 1976 to Cooper et al it is disclosed that when the highly unsaturated rubber used in compositions of the type disclosed by Cizek is replaced with EP~M rubber that has a low degree of residual unsaturation~ -the thermal oxidative stability and color stability are improved.

~ ~ u~ 8C~ 6 It is disclosed in ~aaf, U.S. Pat. No.
3,737,47g that molding resins comprised of polyphenylene ether resins and polysiloxanes are useful. T~ese com-positions are prepared by m~chanical mixing and, while S the compositions are useful for many purposes, they .
have low notched Izod impac~ strength.

In Cooper et al., U.S. Patent No. 4,226,761 there are disclosed compositions of a polyphenylene ether resin and an alkenyl resin that is modiied with a polysiloxane in the form of small rubber like particles.

It has now been found that a composi~ion of a polyphenylene ether resin, which is also known as a poly~
phenylene oxide ~PPO) resin, and a block copolymer of polyphenylene ether and siloxane or a block copolymer of styrene and siloxane is a ~ery useful ~hermoplastic molding composition possessing improved impact strength and resistance to aging with no significant loss in tensile and elongation properties, or appreciabl~ stress whitening at the fracture surface of the impact bars.
' 2n It is, therefore, a pximary object of this in vention to provide improved ccmpositions that axe based on polyphenylene ethex resin and such block copolymers.

Another object of this invention is to provide molding compositions and molded aTticles that are based on a polyphenylene ether resin and the aforemen~ioned block copolymers that have improved impact strength, resistance to aginy, and no appreciable stxess whitening at the fracture surface of the impact bars.

, ~ ~9 5~ ~ 8CN-1926 DESCRIPTION OF THE INVENTION

The above-mentioned advantages and objects and others will be readily apparen~ ~o those skilled in the art by the following compositions.

The compositions of this invention are thermo-plastic compositions which comprise:

(a) a polyphenylene ether resin; and (b) a block copolymer of polyphen~len~
ether and siloxane or a block co-polymer of styrene and siloxaneO

The preferred polyphenylene ether homopolymers and copolymexs are of the formula "' Q' _ ~-0-~ _.

: Q" Q n wherein Q, Ql, Q~ and Q"' axe independently selected .l5 from the ~roup consistins of hydrogen, hydrocarbon radicals, halohydrocarbon radicals havi.ng at least two carbon atoms between the halogen atom and the phenol nucleus, hyarocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atoms and the phenol nucleus, and Q', Q" and Q"' in addition may be halogen with the proviso tha~
Q and Q' are preferably free of a tertiary caxbon atom;
and n represents the total number of monomer residues and is an integer of at least 50.

.... _ .. _ ., .. ~

~ 5 ~2 7 8CN-1926 Examples of polyphenylene ethers correspondin~, to the above formula can be found in the above~referenced patents of Hay and Stamatoff. Especially preferred i5 poly(2,6-dimethyl-1,4-phenylene~ether.

The block .copolymer ~ styrene and siloxane should have its styrene units derived from an alkenyl aromatic monomer of the ormula:
CRl=CR2 ~`,f . wherein R and R are selec~ed from the group consis~ing of hydrogen and lower alkyl or alkenyl groups of from - 1 to 6 carbon atoms; R3 and R4 are selected from the group consisting of chloro, bromo, hydrogen, and lower alkyl groups of from 1 to 6 carbon atoms; and R5 and R6 are selected from the group consisting of hydrogen and lower alkyl and alkenyl groups o from 1 to 6 carbon atoms or R5 and R6 may be concatenated toge~her with hydrocarbyl groups to form a naphthyl grollp.

Specific examples of alkenyl aroma~ie monomers include styrene, bromostyrene, chlorostyrene, alpha-methylstyrene, para-methyl styrene, vinylxylene, divinyl-benzeIIe, vinyl slaphthalene, and vinyl-~oluene.

The polyphenyl ether units in the copolymer are of the formula of the preferred polyphenylene e~hers described above, the especially preferred units being of poly(2,6-dimethyl~1,4-phenylene~ether.

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119 5~7 8CN-1926 The block copolymers of polyphenylene ether and siloxane and of styrene and siloxane can be pre pared by the procedures set forth in the Examples bPlow .

Components (a) and (b) are combinable in a fairly wide range of proportions. Preferably, the compositions of this invention comprise for every 100 parts by weight of (a) and (b) together, rom about 75 to about 95 parts by weight of (a) the poly-ph~nylene ether to about 25 to about 5 parts by weight of ~b) the siloxane block copolymer~

The compositions of the invention may be formed by conventional techniques, that is, by dry mixing or dry ~lending the components to form a pre-mix, and then passing the premix through an extruder atan ele~ated temperature, for example at about 550FD
to a~out 625F. The extrudate is molded in a 3 oz.
Newbury injection molding machine at temperature of 550F.

DESCRIPTION OF THE PREFERR~D EMBODIMENTS

The following examples are set foxth as furthex illu~tratlons of the invention and are not to be construed 2S limitlng the invention thereto.

EXAMPLE .l A polyphenylene ether-siloxane-polyphenylene ether block copolymer is prepared as follows :
Charge 90 grams o~ poly(2,6-dimethyl-1,4-phenylene ether resin (PPO~-O~o~ r~i~-:`

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s~

950 millileters of benzyl chloride and S0 milliliters of benzene, heat under nitrogen-at 145-150DC. for 13-14 hours while distilling off benzene, and let stand overnight. Then add a solu~ion of 21.6 grams of dimethyl siloxane in 90 ml of benzyl chloride to the reaction mixture, with stixring, followed by 250 ml of benzyl chloride. Heat gently until the mixture is clear. Add further small amounts of benzyl ehloride as necessary to obtain clarity~ Heat the reaction mixture at 145-150C. for 10 houxs. Collect the pro-duct and wash and/or re-slurry to purity.

The product has an intrinsic viscosity of about OA8 dl/gm in solution in chloroform at 25 C.

A siloxane-styrene-siloxane block copolymer is prepared as follows:

(1) A c~talyst solution is prepared from

4.85 ml (0.03 moles) of phenylcyclohexene-l and 0.21 grams of freshly distilled lithium (freshly di.stilled from Li2Np) in approximately 75 ml of tetrahydrofuran.
allow to cool to room te~perature, e.g., about 25C.

Charge 250 ml of a 50/50 toluene/tetrahydro-~uran mixture into a clean 1 liter resin kettle~ Add 10 moles ~35 ml) of the above catalyst solution.
Chill with an ice bath. Add 14 ml of styrene to the kettle. The addition is accompanied by a noticeable production of heat, but no particular color change.
Stir for 3~ minutes while chilling with an ice bath~
Then add 100 ml of styrene in S ml portions at 5 minute intervals (should take about 1 1/2 hours total)O Each .

addition produces a noticeable solution o heat.
After ~he additions are completed, there is obtained a moderately viscous syrup which i5 very dark red in color.

Another solution is in ~he meantime prepared by dissolving 74 g of hexamethyltrisiloxane in 250 ml of a 50/50 t~trahydrofuran/toluene solvent mixture.
Add 75 ml of this solution to the first (~he red syrup)~
Begin warming to 50-60~C., then after 15 minutes add another 50 ml of the hexamethyltrisiloxane solution A small decrease in the viscosity of ~he red syrup due to the dilution is noted, together with a slight lightening of the eolor. The mix~ure is heated at 55-60C. for one hour and the rest of the hexa~ethyl-trisiloxane solution is added. After 2 hours the colorhas diminished to a moderate red. Heating is continued for another hour (total heating 4 hours) and the mixture has become yellowish and much more viscous. At this point 69 ml of a 0.145 M solution of diphenylsiloxydi-acetate is added during about 5 minutes, the~ heatedat 60~C. with stirring for 3 hours more. Aftex hea~ing, the mixture is left at room temperature under a nitrogen blanket for 24-48 hours.

ThP resulting siloxane-styrene-siloxane block copolymer is precipitated in methanol. After drying, 169.6 g. of a dusty white powder are obtained (theoretical.
180.9 g. incIuding diphenylsiloxydiacetate). The ~ield is 93 ~%-The polymer has an intrlnsic viscosity of about 0.4 dl/~m as ~easured ln toluene at 25C. It containsabout 48 mole ~ of siloxane.

~ ~ 5~ 7 8CN 1926 (2) To a 1 liter resin kettle partially immersed in a water bath are added 350 ml of te-tra-hydrofuran and 31 ml of a catalyst solu~ion prepared as described above. A ~otal of 101 ml o styrene is set aside. 24 ml of the s~yrene are chilled for 1/2 hour with an ice ba~h and added to the ket~le. A
second portion consisting of 77 ml of styrene is then ~dded gradually during the next hour. The mixture is chilled for one hour.

In a separate vessel, a solution of 65.5 g of hexamethylcyclotrisiloxane în 150 ml of tetrahydro-furan is prepared 2nd degassed. 70 ml of ~his solu-tion is added to the above mix~ure, which promptly gells. The rernainder of the hexamethylcyclo~risiloxane is added, in three separate portions, during the next hour with the temperature of the bath surroundîng ~he ket~le being raised to 50C. The resulting mixture is very stiff, but plastic. Heating is continued for hours, while mi~.ing with a paddle blade type mixer.
17 ml of a 1.045 M solution of diphenylsiloxydiace~ate are added and the mixture is hea~ed to 50-55C. and sti.rred for 4 additional hours.

The resulting siloxane-styrene-siloxane block copolymer is precipitated in methanol, separated and dried to produce a dusty white powder. Yield: 146.8 g (theoretical 170.3 g including diphenylsiloxydiacetate couplin~ agent) = 86%.

T~e polymer has an intrinsic viscosi~y of about 0.5 dl/gm as measured in soluti~n in toluene at 25 c I~ con~ains about 48 mole % of siloxane. The molecular weigh~ is o~er 100,000.

3~t~
8CN-lg26 The composi~ions and the proper~ies are summarized in Table I. The parts are by weigh~ in the PPO/copolymer ra~ios shown.

In the tabie PPO m~ans poly(2,6-dimethyl-1,4-phenylene) ether which is also ~nown as poly(2,6-dimethyl-1,4-phenylene) oxide having an intrinsic viscosity of abou~ 0.48 dl/g measured in chloroform at 30 C. Copolymer A stands for the polyphenylene-ether-siloxane-polyphenylene ether block copolymer described in Example l. Copolymer B stands for the siloxane-styrene-siloxane block copolym~r described in Example 2~1) and Copolymer C for tha~ described in Example ~(2).

The PPO and ~he copolymers in fine powder form are dry blended and coextruded in a 3/4" ~ayne extruder at a temperature of 625 F. The extrudate was molded into standard test pieces in a 3 oz. Newbury injection molding machine at molding temperatures of about 525 F. to about 550 F.

In Table I, Example 3 is a control, containing no block copolymer. It wil.l be seen that the Examples c.ontaining the block copolymers have an improved notched Izod impact ~trength with, in general, no significant lcss ~'n tensile and elongation properties. It was also observed that nvne of the blends of the Examples gave any appreciable whitening at the fracture surface of ~he impaet test bars as is commonly observed for rubber mod-ified polystyrene~PPO compositions, which suggest that the mechanism for reinforcement of PPO by the block co-polymers of ~he ins~ant invention may be differen~ from ~ha~ in a high impae~ pQlystyrene (HIPS).

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The compositions of the invention can also include other ingredients such as filler pigments, fire retardants and the like, as, for example, those disclosed in U.S~ Patent No. 4,336,761, issued October 7, 1980 to Cooper et al.
The compositions can be molde~ into any desired shapes, as for example, by injec-tion molding in, for example, a Newbury molding machine. Thus, the compositions can be used to make molded parts such as spur, helical, worm or bevel gears, ratchets, cams impactedparts and gaskets~
Obviously, other modifications and varlations of the invention are possible in the light of the above teachings. It is, thereforP, to be understood -that changes may be made in the particular embodiments of the invention described which are within the full in-tended scope of the invention as defined by the appended claims.

Claims (8)

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

1. A thermoplastic molding composition which, after molding, has improved impact resistance, said composition comprising:
(a) a poly(2,6-dimethyl-1,4-phenylene) ether resin; and (b) a block copolymer selected from the group consisting of block copolymers of polyphenylene ether and siloxane and block copolymers of styrene and siloxane.

2. The molding composition of claim 1, wherein the styrene unit in the copolymer is selected from the group consisting of styrene, alpha-methylstyrene, p-methylstyrene bromostyrene, chlorostyrene, divinyl-benzene, and vinyltoluene.

3. The composition as described in claim 1, in which the block copolymer is of styrene and siloxane.

4. The composition as described in claim 1, in which the block copolymer is of polyphenylene ether and siloxane.

5. The composition as described in claim 1, in which (a) comprises from about 75 to about 95 parts by weight for every 100 parts of (a) and (b) combined.

6. A molded composition having improved impact strength, resistance to aging and no appreciable stress whitening at the fracture surface of impact bars, said molded composition being obtained by molding the composition described in claim 1.

7. A process for preparing the composition described in claim 1 which comprises dry blending and coextruding components (a) and (b) at an elevated temperature.

8. A process as defined in claim 7 wherein the blended product is molded into any desired shape.