CA1339040C - Grafted block copolymers and process for the preparation thereof - Google Patents

Abstract

A selectively hydrogenated block copolymer Bn(AB)oAp in which A is a monoalkenyl aromatic hydrocarbon block, B is a hydrogenated conjugated diene hydrocarbon block, n = 0 or 1, o is 1 to 100 and p = 0 or 1, grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin, and impact resistant compositions containing a polyamide, a polyolefin and said block copolymer, and processes for the preparation thereof by melt-mixing the components in question.

Description

13390~0 GRAFTED BLOCK COPOLYMERS
AND PROCESS FOR THE PREPARATION THEREOF
The invention relates to a grafted block copolymer, to a process for the preparation thereof, to an impact resistant compo-sition containing said grafted block copolymer and to a process for the preparation of said impact resistant composition.
The present application is related to Canadian patent application Serial No. 545,952, filed on September 2, 1987 and to Canadian patent application Serial No. 545,946 filed on September 2, 1987.
It is known that a block copolymer can be obtained by an anionic copolymerization of a conjugated diene compound and an aromatic vinyl compound by using an organic alkali metal initiator. These types of block copolymers are diversified in characteristics, ranging from rubber-like characteristics to resin-like characteristics, depending on the content of the aromatic vinyl compound.
When the content of the aromatic vinyl compound is small, the produced block copolymer is a so-called thermoplastic rubber. It is a very useful polymer which shows rubber elasticity in the unvulcanized state and is applicable for various uses such as mouldings of shoe sole, impact modifiers for polystyrene resins, adhesives, and binders.
The block copolymers with a high aromatic vinyl compound content, such as more than 70% by weight, provide a resin posses-sing both excellent impact resistance and transparency, and such a resin is widely used in the field of packaging. Many proposals have been made *

on processes for the preparation of these types of block copolymers, for example as described in US patent specification 3,639,517.
The elastomeric properties of certain aromatic vinyl polymers also appear to be due in part to their degree of branching. While the aromatic vinyl polymers have a basic straight carbon chain backbone, those with elastomeric properties always have dependent alkyl radicals. For example, EPR (ethylene-propylene rubber) has a structure of dependent methyl radicals which appears to provide elasticity and other elastomeric properties. When an essentially unbranched straight chain polymer is formed, such as some polyethylenes, the resulting polymer is essentially non-elastomeric or in the other words relatively rigid, and behaves like a typical thermoplastic without possessing rubber-like resilience or high elongation, tensile strength without yield, low set or other properties characteristic of desirable elastomers.
Block copolymers have been produced, see U.S.
Patent Re 27,145 which comprise primarily those having a general structure A--B--A
wherein the two terminal polymer blocks A comprise thermoplastic polymer blocks of aromatic vinyl compounds such as polystyrene, while block B is a polymer block of a selectively hydrogenated conjugated diene. The proportion of the thermoplastic terminal blocks to the center elastomeric polymer block and the relative molecular weights of each of these blocks is balanced to obtain a rubber having an optimum combination of properties such that it behaves as a vulcanized rubber without requiring the actual step of vulcanization.
Moreover, these block copolymers can be designed not only with this important advantage but also so as to be handled in thermoplastic forming equipment and are soluble in a variety of relatively low cost solvents.

While these block copolymers have a number of outstAn~ing technical advantages, one of their principal limitations lies in their sensitivity to oxidation.
This was due to their unsaturated character which can be minimized by hydrogenating the copolymer, especially in the center section comprising the polymeric diene block. Hydrogenation may be effected selectively as disclosed in U.S. Patent Re 27,145. These polymers are hydrogenated block copolymers having a configuration, prior to hydrogenation, of A-B-A wherein each of the A's is an alkenyl- substituted aromatic hydrocarbon polymer block and B is a butadiene polymer block wherein 35-55 mol per cent of the condensed butadiene units in the butadiene polymer block have 1,2 configuration.
These selectively hydrogenated ABA block copolymers are deficient in many applications in which adhesion is required due to its hydrocarbon nature. Examples include the toughening and compatibilization of polar polymers such as the engineering thermoplastics, the adhesion to high energy substrates of hydrogenated block copolymer elastomer based adhesives, sealants and coatings, and the use of hydrogenated elastomer in reinforced polymer systems. However, the placement onto the block copolymer of functional groups which can provide interactions not possible with hydrocarbon polymers solves the adhesion problem and extends the range of applicability of this material.
Functionalized S-EB-S polymer can be described as basically commercially produced S-EB-S polymers which are produced by hydrogenation of S-B-S polymer to which is chemically attached to either the styrene or the ethylene-butylene block, chemically functional moieties.
Many attempts have been made for the purpose of improving adhesiveness, green strength and other properties by modifying block copolymers with acid moieties and various methods have been proposed for modifying synthetic conjugated diene rubbers with acid moieties.
U.S. patent specification 4,292,414 concerns a method for the production of monovinyl aryl/conjugated diene block copolymer having low 1,2 content grafted with maleic acid compounds. U.S. patent specification 4,427,828 concerns a process for producing an acid functionalized high 1,2 content block copolymer.
However, both processes involve "ENE" type reaction which rely on residual unsaturation in the block copolymer for the addition of functional groups. It is not possible to produce functionalized block polymers which contain low residual unsaturation along with reasonable functionalization using the 'ENE' process.
Thermoplastic polyamides, such as nylon 66, are a class of materials which possess a good balance of properties comprising strength and stiffness which make them useful as structural materials. However, for a particular application, a thermoplastic polyamide may not offer the combination of properties desired, and therefore, means to correct this deficiency are of interest.
One major deficiency of thermoplastic polyamides is their poor resistance to impact, especially when dry. A particularly appealing route to achieving improved impact resistance in a thermoplastic is by blending it with another polymer. It is well known that stiff plastics can often be impact modified by addition of an immiscible low modulus elastomer.
However, in general, physical blending of polymers has not been a successful route to toughen thermoplastic polyamides. This is due to the poor adhesion immiscible polymers typically exhibit with each other. As a result, interfaces between blend component domains -represent areas of severe weaknesses, providing natural flows which result in facile mech~nical failure.
It is well known to those skilled in the art that hydrogenated block copolymers of styrene and butadiene possess many of the properties which are required for impact modification of plastics. They have a low glass transition, low modulus rubber phase which is required for toughening. Because they contain little unsaturation, they can be blended with high temperature processing temperature plastics without degrading. In addition, they are unique compared to other rubbers in that they contain blocks which are microphase separated over the range of application and processing conditions. This microphase separation results in physical crosslinking, causing elasticity in the solid and molten stages. Such an internal strength mechanism is often required to achieve toughness in the application of plastic impact modification.
Proof that hydrogenated block copolymers of styrene and butadiene are useful plastic impact modifiers can be seen in their widespread use for modifying polyolefins and polystyrene. For these blends, interfacial adhesion is great enough to achieve toughening.
Although the hydrogenated block copolymers do have many of the characteristics required for plastic impact modification, they are deficient in modifying many materials which are dissimilar in structure to styrene or hydrogenated butadiene. Blends of the hydrogenated block copolymer with dissimilar plastics are often not tough due to a lack of interfacial adhesion.
A route to achieve interfacial adhesion between dissimilar materials is by chemically attaching to one or more of the materials functional moieties which enhance their interaction. Such interactions include chemical reaction, hydrogen bonding, and dipole-dipole interactions.

U.S. patent specification 4,174,358 concerns a broad range of low modulus polyamide modifiers. However, this patent specification does not disclose or suggest the use of modified block copolymers of styrene and butadiene.
It is an object of the present invention to provide functionalized block copolymers which contain low residual unsaturation and high functionality.
Another object is to provide impact resistant compositions containing said functionalized block copolymers.
Accordingly the invention provides a grafted block copolymer comprising a selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which formula each A is predominantly a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight in the range of from 2,000 to 115,000, each B
prior to hydrogenation is predominantly a polymerized conjugated diene hydrocarbon block having an average molecular weight in the range of from 20,000 to 450,000, n = 0 or 1, o is in the range of from 1 to 100 and p = 0 or 1, the blocks A constitute in the range of from 5 to 95 per cent by weight of the copolymer, the unsaturation of block B is less than 20% of the original unsaturation and the unsaturation of the blocks A is above 50% of the original unsaturation, which block copolymer is grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin.
The invention also provides an impact resistant composition which comprises:-(a) in the range of from 3 to 95% by weight of a polyamide having a number average molecular weight of at least 5,000;
(b) in the range of from 1 to 50% by weight of a pOlyolefin;

133904~
-~ 7 ~ 63293-2848 (c) in the range of from 1 to 50% by weight of a graftçd selectively hydrogenated block copolymer as defined above; and (d) in the range of from 0 to 50% by weight of a functionalized selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which A, B, n, o and p have the meaning stated above, which block copolymer is grafted with an acid moiety or a derivative thereof.
The impact resistant composition according to the present invention preferably comprises (a) in the range of from 60 to 85% by weight of said polyamide;
(b) in the range of from 5 to 30% by weight of a polyolefin;
(c) in the range of from 5 to 30% by weight of said selectively hydrogenated block copolymer grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin; and (d) in the range of from 5 to 30% by weight of said functionalized selectively hydrogenated block copolymer grafted with an acid moiety or a derivative thereof.
The polyolefins employed in the instant invention are cyrstalline or crystallizable poly(alpha-olefins) and their copolymers. The alpha-olefin or l-olefin monomers employed in the instant invention, both have 2 to 5 carbon atoms per molecule. Examples of particular useful polyoleflns, both plastic and elastomeric, include low or high density polyethylene, polypropylene, poly(l-butene), poly-3-methyl-1-butene, poly-(4-methyl-l-pentene), copolymers of monoolefins with other olefins (mono- or diolefins) or vinyl monomers such as ethylene-propylene copolymers or with one or more additional monomers, i.e., EPDM, ethylene/butylene copolymer, B

ethylene/vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, propylene/4-methyl-1-pentene copolymer, ethylene/methacrylic acid, ethylene/acrylic acid and their ionomers and the like. The number average molecular weight of the polyolefins is preferably above about 10,000, more preferably above about 50,000. In addition, it is preferred that the apparent crystalline melting point be above about 100C, preferably between about 100C and about 250C, and more preferably between about 140C and about 250C. The preparation of these various polyolefins is well known. See generally "Olefin Polymers," Volume 14, Kirk-Othmer Encyclopedia of Chemical Technology, pages 217-335 (1967).
The high density polyethylene employed has an approximate crystallinity of over about 75% and a density in grams per cubic centimetre (g/cm3) of between about 0.94 and 1.0 while the low density polyethylene employed has an approximate crystallinity of over about 35% and a density of between about 0.90 g/cm3 and 0.94 g/cm3. Most commercial polyethylenes have a number average molecular weight of about 50,000 to about 500,000.
The polypropylene employed is the so-called isotactic polypropylene as opposed to atactic polypropylene.
This polypropylene is described in the above Kirk-Othmer reference and in U.S. patent specification No. 3,112,300.
The number average molecular weight of the polypropylene employed is typically in excess of about 100,000. The polypropylene suitable for this invention may be prepared using methods of the prior art. Depending on the specific catalyst and polymerization conditions employed, the polymer produced may contain atactic as well as isotactic, syndiotactic or so-called stereo-block molecules. These may be separated, if desired, by selective solvent extraction to yield products of low I3390~0 atactic content that crystallize more completely. The preferred commercial polypropylenes are generally prepared using a solid, crystalline, hydrocarbon-insoluble catalyst made from a titanium trichloride composition and an aluminium-alkyl compound, e.g., triethylaluminium or diethylaluminium chloride. If desired, the poly-propylene employed may be a copolymer containing minor (1 to 20 per cent by weight) amounts of ethylene or other alpha-olefin comonomers.
The poly(l-butene) preferably has an isotactic structure. The catalysts used in preparing the poly(1-butene) are typically organometallic compounds commonly referred to as Ziegler-Natta catalysts. A typical catalyst is the interacted product resulting from mixing equimolar quantities of titanium tetrachloride and triethylaluminum. The manufacturing process is normally carried out in an inert diluent such as hexane.
Manufacturing operation, in all phases of polymer formation, is conducted in such a manner as to guarantee rigorous exclusion of water, even in trace amounts.
One very suitable polyolefin is poly(4-methyl-1-pentene). Poly(4-methyl-1-pentene) typically has an apparent crystalline melting point of between about 240 and 250C and a relative density of between about 0.80 and 0.85. Monomeric 4-methyl-1-pentene is commer-cially manufactured by the alkali-metal catalyst dimer-ization of propylene. The homopolymerization of 4-methyl-l-pentene with Ziegler-Natta catalysts is described in the Kirk-Othmer Encyclopedia of Chemical Technology, Supplement volume, pages 789-792 (second edition, 1971). However, the isotactic homopolymer of 4-methyl-1-pentene has certain technical defects, such as brittleness and inadequate transparency. Therefore, commercially available poly(4-methyl-1-pentene) is actually a copolymer with minor proportions of other alpha-olefins, together with the addition of suitable oxidation and melt stabilizer systems. These copolymers are described in the Kirk-Othmer Encyclopedia of Chemical Technology, Supplement volume, pages 792-907 (second edition, 1971), and are available from Mitsui Chemical Company under the tradename TPX resin. Typical alpha-olefins are linear alpha-olefins having from 4 to 18 carbon atoms per molecule. Suitable resins are copolymers of 4-methyl-1-pentene with from about 0.5 to about 30%
by weight of a linear alpha-olefin.
If desired, the polyolefin may be a mixture of various polyolefins. However, the much preferred polyolefin is isotactic polypropylene.
Block copolymers of conjugated dienes and vinyl aromatic hydrocarbons which may be utilized include any of those which exhibit elastomeric properties and those which have 1,2-microstructure contents prior to hydro-genation of from about 7% to about 100%, preferably in the range of from 35 to 55%, more preferably 35 to 50%
and in particular from 40 to 50%. Such block copolymers may be multiblock copolymers of varying structures containing various ratios of conjugated dienes to vinyl aromatic hydrocarbons including those containing up to about 60 per cent by weight of vinyl aromatic hydrocarbon.
Thus, multiblock copolymers may be utilized which are linear or radial, symmetric or asymmetric and which have structures represented by the formulae A-B, A-B-A, A-B-A-B, B-A-B, (AB)o 1 2 BA and the like wherein A
is a polymer block of a vinyl aromatic hydrocarbon or a conjugated diene/vinyl aromatic hydrocarbon tapered copolymer block and B is a polymer block of a conjugated diene.
The block copolymers may be produced by any well known block polymerization or copolymerization procedures including the well known sequential addition of monomer -techniques, incremental addition of monomer technique or coupling technique as illustrated in, for example, U.S. patent specifica-tions 3,251,905; 3,390,207; 3,598,887 and 4,219,627. As is well known in the block copolymer art, tapered copolymer blocks can be incorporated in the multiblock copolymer by copolymerizing a mixture of conjugated diene and vinyl aromatic hydrocarbon monomers utilizing the difference in their copolymerization re-activity rates. Various patent specifications describe the preparation of multiblock copolymers containing tapered copolymer blocks including U.S. patent specifications, 3,251,905; 3,265,765;
3,639,521 and 4,208,356.
Conjugated dienes which may be utilized to prepare the polymers and copolymers are those having from 4 to 8 carbon atoms per molecule and include for example 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Mixtures of such conjugated dienes may also be used. The preferred conjugated diene is 1,3-butadiene.
Vinyl aromatic hydrocarbons which may be utilized to prepare copolymers include for example styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene and vinylanthracene. The pre-ferred vinyl aromatic hydrocarbon is styrene.
It should be observed that the above-described polymers and copolymers may, if desired, be readily prepared by the methods set forth hereinbefore. However, since many of these polymers and copolymers are commercially available, it is usually preferred to ~A -~

employ the commercially available polymer as this serves to reduce the number of processing steps involved in the overall process.
The hydrogenation of these polymers and copolymers may be carried out by a variety of well established processes including hydro-genation in the presence of such catalysts as Raney Nickel, noble metals, for example platinum and palladium and soluble transition metal catalysts. Suitable hydrogenation processes which can be used are ones wherein the diene-containing polymer or copolymer is dissolved in an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the presence of a soluble hydrogenation catalyst. Such processes are disclosed in U.S. patent specifications 3,113,986 and 4,226,952. The polymers and copolymers are hydrogenated in such a manner as to produce hydrogenated polymers and copolymers having a residual unsatura-tion content in the polydiene block B of from 0.5 to 20 per cent preferably less than 10 and in particular less than 5 per cent of their original unsaturation content prior to hydrogenation. It is preferred that an average of less than 10% of the monoalkenyl aromatic hydrocarbon units in block A are hydrogenated. It is, however, not excluded that an average from 25% to 50% of the mono-alkenyl aromatic hydrocarbon units are hydrogenated. The average unsaturation of the hydrogenated block copolymer is preferably reduced to less than 20% of its original value.
Block A preferably has an average molecular weight in the range of from 4,000 to 60,000 and block B preferably has an average molecular weight in the range of from 35,000 to 150,000.

The polyamide matrix resin of the toughened compositions of this invention is well known in the art and embraces those semi-crystalline and amorphous resins having a molecular weight of at least 5000 and commonly referred to as nylons. Suitable poly-amides include those described in U.S. patent specifications Nos.
2,071,250; 2,071,251; 2,130,523; 2,130,948; 2,241,322; 2,312,966;
2,512,606; and 3,393,210. The polyamide resin can be produced by condensation of equimolar amounts of a saturated dicarboxylic acid containing from 4 to 12 carbon atoms per molecule with a diamine, in which the diamine contains from 4 to 14 carbon atoms per mole-cule. Excess diamine can be employed to provide an excess of amine end groups over carboxyl end groups in the polyamide.
Examples of polyamides include polyhexamethylene adipamide (nylon 66), polyhexamethylene azelaamide (nylon 69), polyhexamethylene sebacamide (nylon 610), polyhexamethylene isophthalamide, poly-hexamethylene tere-co-isophthalamide, and polyhexamethylene dodecanoamide (nylon 612), the polyamide produced by ring opening of lactams, i.e., polycaprolactam, polylauric lactam, poly-ll-aminoundecanoic acid, bis(paraaminocyclohexyl) methane dodecano-amide. It is also possible to use in this invention polyamidesprepared by the copolymerization of two of the above polymers of terpolymerization of the above polymers or their components, for example, an adipic isophthalic acid hexamethylene diamine copolymer. Preferably the polyamides are linear with a melting point in excess of 200 C. Preferred compositions contain from 60 to 95 per cent, more narrowly 60 to 85 per cent, and in particular from 80 to 85 per cent by weight of polyamide.
In general, any materials having the ability to react with the block copolymer in question, in free radical initiated reactions as described in U.S. patent specification 4,578,429, or thermal addition reactions are operable for the purposes of the invention.
Monomers may be polymerizable or nonpolymerizable, how-ever, preferred monomers are nonpolymerizable or slowly polymeri-zing. U.S. patent specification 4,427,828 concerns block copoly-mers made by the thermal addition reaction. Free radicallyproduced block copolymers and free radical methods are disclosed in Canadian patent applications Nos. 488,172 and 488,156 both filed on August 6 1985.
In free radical reactions the monomers must be ethyleni-cally unsaturated in order to be graftable. It has been found that by grafting unsaturated monomers which have a slow polymeri-zation rate the resulting graft copolymers contain little or no homopolymer of the unsaturated monomer and contain only short grafted monomer chains which do not phase separate into separate domains.
The class of preferred monomers which will form graft polymers within the scope of the present invention have one or more functional groups or their derivatives such as carboxylic acid groups and their salts, anhydrides, esters, imide groups, amide groups, acid chlorides and the like in addition to at least A

-- 14a - 63293-2848 one point of unsaturation.
These functionalities can be subsequently reacted with other modifying materials to produce new functional groups. For example a graft of an acid-containing monomer could be suitably modified by esterifying the resulting acid groups in the graft with appropriate reaction with hydroxy-containing compounds of varying carbon atoms lengths. The reaction could take place simultaneously with the grafting or in a subsequent post modifica-tion reaction.
The grafted polymer will usually contain from 0.02 to 20, preferably 0.1 to 10, and most preferably 0.2 to 5 weight per cent of grafted portion.

The preferred modifying monomers are unsaturated mono- and polycarboxylic-containing acids (C3-C10) with preferably at least one olefinic unsaturation, and anhydrides, salts, esters, ethers, amides, nitriles, thiols, thioacids, glycidyl, cyano, hydroxy, glycol, and other substituted derivatives from said acids.
Examples of such acids, anhydrides and derivatives thereof include maleic acid, fumaric acid, itaconic acid, citraconic acid, acrylic acid, glycidyl acrylate, cyanoacrylates, hydroxy Cl-C20 alkyl methacrylates, acrylic polyethers, acrylic anhydride, methacrylic acid, crotonic acid, isocrotonic acid, mesaconic acid, angelic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, acrylonitrile, methacrylonitrile, sodium acrylate, calcium acrylate, and magnesium acrylate.
Other monomers which can be used either by themselves or in combination with one or more of the carboxylic acids or derivatives thereof include C2-C50 vinyl monomers such as acrylamide, acrylonitrile and monovinyl aromatic compounds, for example styrene, chlorostyrenes, bromostyrenes, ~-methylstyrene and vinylpyridines.
Other monomers which can be used are C4 to C50 vinyl esters, vinyl ethers and allyl esters, such as vinyl butyrate, vinyl laurate, vinyl stearate and vinyl adipate, and monomers having two or more vinyl groups, such as divinylbenzene, ethylene dimethacrylate, triallyl phosphite, dialkylcyanurate and triallyl cyanurate.
The preferred monomers to be grafted to the block copolymers according to the present invention are maleic anhydride, maleic acid, fumaric acid and their derivatives. It is well known in the art that these monomers do not polymerize easily.
The block copolymer may also be grafted with a sulphonic acid or a derivative thereof.

Of course, mixtures of monomer can be also added so as to achieve graft copolymers in which the graft chains originate from at least two different monomers therein (in addition to the base polymer monomers).
The grafted block copolymer according to the present invention may be prepared by any means known in the art. A preferred method for the preparation of the grafted block copolymer comprises melt-mixing the following components:-component (a): a selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which formula each A is predominantly a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight in the range of from 2,000 to 115,000, each B prior to hydrogenation is predominantly a poly-merized conjugated diene hydrocarbon block having an average molecular weight in the range of from 20,000 to 450,000, n = 0 or 1, o is in the range of from 1 to 100 and p = 0 or 1, the blocks A
constitute in the range of from 5 to 95 per cent by weight of the copolymer, the unsaturation of block B is less than 20%
of the original unsaturation and the unsaturation of the block A is above 50 of the original unsaturation;
component (b): an acid moiety or a derivative thereof;
and component (c): a polyolefin, adding a free radical initiator, graft-reacting under free radical conditions and recovering grafted block copolymer product.

13390~0 The grafting reaction is initiated by a free-radical initiator which is preferably an organic peroxygen compound. Especially preferred peroxides are 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne (known under the trade mark Lupersol 130), ~,~'-bis(tert-butylperoxy)diisopropylbenzene (known under the trade mark VulCup R), or any free radical initiator having a short half-life under the base polymer processing conditions; see Modern Plastics, November 1971, pages 66 and 67, for more initiators.
The concentration of the initiator used to prepare the polymer may also vary between wide limits and is determined by the desired degree of functionality and degradation allowable. Typical concentrations range from about 0.001 weight per cent to about 5.0 weight per cent, more preferably between 0.01 and 1.0 weight per cent.
Reaction temperatures and pressures should be sufficient to melt the reactants and also sufficient to thermally decompose the free radical initiator to form the free radical. Reaction temperatures would depend on the base polymer being used and the free radical initiator being used. Typical reaction conditions can be obtained by using a screw type extruder to mix and melt the reactants and to heat the reactant mixture to the desired reaction temperature.
The temperatures useful in the reaction of the process of the present invention may vary between wide limits such as from +75ac to 450C, preferably from about 200C to about 300C.
The process according to the invention is highly flexible and a great many modifications such as those proposed hereinbefore are available to carry out any particular purposes desired.

Of course, any of the standard additives can be used with these modified polymers. They include, for example, conventional heat stabilizers, slip-agents, antioxidants, antistatic agents, colorants, flame retardants, heat stabilizers, plasticizers, preservatives and processing aids. Flow promoters such as oils, low molecular weight resins, or other polymers can be included in the reaction mixture during the functional-ization step.
It is to be emphasized that in the definition of the base polymer, substituted polymers are also included;
thus, the backbone of the polymer before functionalization can be substituted with functional groups, for example chlorine, hydroxy, carboxy, nitrile, ester and amine.
Furthermore, polymers which have been functionalized, particularly those with functional carboxylic acid groups, can be additionally crosslinked in a conventional manner or by using metallic salts to obtain ionomeric crosslinking.
The toughened compositions of this invention can be prepared by melt blending, in a closed system, a polyamide, and a mixture of a polyolefin and at least one modified block copolymer into a uniform mixture in a multi-screw extruder such as a Werner Pfleiderer extruder having generally 2-5 kneading blocks and at least one reverse pitch to generate high shear, or other conventional plasticating devices such a a Brabender, Banbury mill, or the like. The polyolefin/ modified block copolymer mixture may be prepared by simultaneously subjecting both components to the grafting reaction previously described or alterantively by post blending polyolefin and a modified block copolymer.
The modified polyamide resin may be prepared by melt-blending from 3 per cent to 99 per cent by weight, preferably from 60 per cent to 95 per cent, more preferably from 70 per cent to 95 per cent and in particular from 80 per cent to 95 per cent, for example 85 percent to 95 per cent of a polyamide having a number average molecular weight of at least 5,000, from 1 per cent to 50 per cent by weight, preferably from 5 to 30 per cent or more preferably from 10 to 25 per cent of a polyolefin, from 1 per cent to 50 per cent by weight, preferably from 5 per cent to 30 per cent or more preferably 10 per cent to 25 per cent of said block copolymer grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin, and from 0 to 50 per cent by weight, preferably from 5-30 per cent or more preferably from 10-25 per cent by weight of a functionalized block copolymer having the general formula Bn(AB)oAp in which A, B, n, o and p have the meaning stated hereinbefore, which block copolymer is grafted with an acid moiety or a derivative thereof.
The compositions of the invention may be modified by one or more conventional additives such as stabilizers and inhibitors of oxidative, thermal, and ultraviolet light degradation; lubricants and mould release agents, colorants including dyes and pigments, fibrous and particulate fillers and reinforcements, nucleating agents, plasticizers, etc.
The stabilizers can be incorporated into the composition at any stage in the preparation of the thermoplastic composition. Preferably the stabilizers are included early to preclude the initiation of degra-dation before the composition can be protected. Such stabilizers must be compatible with the composition.
The oxidative and thermal stabilizers useful in the materials of the present invention include those used in addition polymers generally. They include, for example, up to 1 per cent by weight, based on the weight of polyamide, of halides of Group 1 of the 13~9040 Periodic Table of the Elements, for example sodium, potassium, lithium and copper (I), for example chloride, bromide, iodide, and, further of sterically hindered phenols, hydroquinones, and varieties of substituted members of those groups and combinations thereof.
The ultraviolet light stabilizers, e.g., up to 2.0 per cent, based on the weight of polyamide, can also be those used in addition to polymers generally. Examples of ultraviolet light stabilizers include various sub-stituted resorcinols, salicylates, benzotriazoles,benzophenones, and the like.
Suitable lubricants and mould release agents, e.g., up to 1.0 per cent, based on the weight of the composition, are stearic acid, stearic alcohol, stear-amides, organic dyes such as nigrosine, pigments, e.g.,titanium dioxide, cadmium sulfide, cadmium sulfide selenide, phthalocyamines, ultramarine blue, carbon black, etc. up to S0 per cent, based on the weight of the composition, of fibrous and particulate fillers and reinforcements, e.g., carbon fibres, glass fibres, amorphous silica, asbestos, calcium silicate, aluminium silicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, feldspar, etc.; nucleating agent, e.g., talc, calcium fluoride, sodium phenyl phosphinate, alumina, and finely divided polytetrafluoroethylene, etc.; plasticizers, up to about 20 per cent, based on the weight of the composition, e.g., dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils, N-normal butyl benzene sulfonamide, ortho and para toluene ethyl sulfonamide, etc. The colorants (dyes and pigments) can be present in an amount of up to about 5.0 per cent by weight, based on the weight of the composition.
It is to be understood that in the specification and claims herein, unless otherwise indicated, when in connection with melt-blending, the amount of reactants is expressed in terms of per cent by weight it is meant per cent by weight based on the total amount of these materials which is employed in the melt-blending.
The following Examples further illustrate the invention, parts and percentages being by weight unless otherwise specifically noted. The Examples are according to the present invention, the Comparative Experiments are not. The moulded bars were tested using the following test procedures in the dry-as-moulded state:
Notched Izod toughness: at each end ASTM D-256-56 Flexural Modulus: ASTM D-790-58T
Examples 1 and 2 and Comparative Experiments A-C
Preparation of Modified Block Copolymer bY Solution 15 ProceSS
The block copolymer used was a styrene-ethylene/
butylene-styrene block copolymer containing 29 weight %
styrene with a molecular weight of 54,000. This polymer was modified with maleic anhydride in a solution free radical initiated reaction, because it cannot be melt-processed in the pure form. Polymer (3.5 kg), maleic anhydride (104.5 g) and benzoyl peroxide initator (104.5 g) were dissolved in 32 kg of cyclohexane. This mixture was transferred to a 57 1 stainless steel stirred pressure reactor with an oil jacket heater.
The reactor contents were heated from ambient temperature to the boiling point of cyclohexane (81C) over a two hour time period. The heaters were turned off and the reactor contents were allowed to cool to about 40-C.
Water (0.95 1) and 10 g of antioxidant Ethyl 330 were then added to the vessel. The mixture was then trans-ferred to a Binks vessel and coagulated by steam stripping.
Colorometric titration with potassium methoxide and phenolphthalein indicator was used to determine the maleic anhydride content of the polymer. This modified copolymer was found to contain 0.5% by weight of grafted maleic anhydride.
Blending of N66 and Solution Modified Block Copolymer Prior to blending, the modified block copolymer was dried at 100C at sub-atmospheric pressure with a nitrogen purge for four hours. The thermoplastic polyamide used in this example was a commercial nylon 66 moulding grade having the trade name Zytel 101 and obtained from E. I. DuPont Company. Prior to all processing steps, the nylon 66 and its blends were dried at 120C for four hours at sub-atmospheric pressure with a nitrogen purge.
81ends of nylon 66 with both unmodified and modified block copolymer were prepared in a 30 mm diameter corotating twin screw extruder. The blend components were premixed by tumbling in polyethylene bags. A
stabilizer package, 0.5wt% of the total material, made up of a 3:1 ratio of a phosphite and sterically hindered phenol antioxidant was included in the composition.
The extruder melt temperature profile varied from 270C
in the feed zone to 285C at the die. The screw rotated at 300 revolutions per minute (rpm). The extrudate was pelletized and injection moulded into test specimens.
The formulations and physical properties are shown in Table 1.

Composition (parts by weight) Comparative Experiment A B C
Example 1 2 Nylon 66 100 80 70 80 70 Unmodified Block Copolymer -- 20 30 -- --Modified Block Copolymer -- -- -- 20 30 0.32 cm Dry as Moulded Room 43 80 80 1050 1430 Temperature Notched Izod (J/m) 13390q o Comparison of Experiments A, B and C with Examples 1 and 2 shows that blends of modified block copolymer and Nylon 66 have a considerably higher impact strength than the Nylon 66 alone or blends of Nylon 66 with unmodified block copolymer.
Examples 3-8 and Comparative Experiments D-G
Preparation of Modified Block Copolymer by Melt Process The block copolymer used in the following example was KRAT0 ~G-1652 Rubber, a commercial S-EB-S material, which can be melt processed neat. This polymer was melt reacted with maleic anhydride and Lupersol~101 in a 30mm diameter corotating twin screw extruder. "Lupersol 101" is a trade name for 2,5-dimethyl-2,5-di(t-butyl-peroxy)hexane.
The reactants were premixed by tumbling in poly-ethylene bags, and then fed into the extruder. All extrusion conditions except for reactant concentrations were kept constant. The melt temperature was varied from 150C in the feed zone to 260C at the die. A
screw speed of 350 rpm was used.
Samples prepared in the above manner were analyzed for bound maleic by extracting the soluble fraction in refluxing tetrahydrofuran, recovering the soluble fraction by precipitation of the extractant into isopropyl alcohol, and titrating the dried precipitate using the method described in Example 1. Table 2 shows the reactant concentrations examined, as well as analytical results for the material prepared.

Wt% Maleic Wt% Maleic Anhydride Anhydride Wt% Lupersol grafted onto Polymer added 101 added THF Solubles X 3 0.01 0.2 Y 3 0.10 1.6 ~ Tr~t~

1339d40 Blending of Nylon 66 and Modified Block Copolymers Prepared bY Melt Process Blends of Nylon 66 with both modified and unmodified KRATON G-1652 Rubber, were prepared in the manner described in Examples 1-2. The formulations and physical properties are shown in Table 3. The physical properties are for dry as moulded material.

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13390~0 Comparison of Experiments D-G with Examples 3-8 shows that blends of modified block copolymer used have a considerably higher impact strength than the Nylon 66 or blends of Nylon 66 and unmodified block copolymer.

The process can also be carried in the melt by the addition of a polyolefin flow promotor such as poly-propylene. In addition, polymers or blends which are melt processable will benefit from the addition of a polyolefin flow promoter. The Examples 9-16 show that such a modified block copolymer processed with a poly-olefin also toughens thermoplastic polyamides.
In one example a 3:1 ratio of a high molecular weight S-EB-S block copolymer which cannot be processed neat and homopolypropylene were simultaneously subjected to free radical grafting reaction conditions in an extruder as described in Examples 4-8. The resulting product was subjected to extraction with tetrahydrofuran and the fractions were analyzed by gel permeation chromatography, maleic anhydride titration and by infrared spectroscopy. The product was found to contain block copolymer to which had been grafted maleic anhydride and homopolypropylene, block copolymer to which has been grafted maleic anhydride, homopolypropylene grafted with maleic anhydride along with minor amounts of scission products and crosslinked products.
The block copolymer used in the following was Kraton G 1651, a high molecular weight commercial SEBS
copolymer. This polymer cannot be melt processed in the pure form. Various ratios of this polymer with various polyolefins were simultaneously put through the maleic anhydride melt modification process described in Examples 3-8. For these examples 0.2wt% Lupersol 101 initiator was used. Once again, all reactants were simply premixed by tumbling prior to feeding into the extruder. Table 4 gives a description of the polyolefins used.

Manufacturer/
Polyolefin Supplier Description PP5520 Shell Injection Moulding Grade Propylene Homopolymer PP5225 Shell Extrusion Grade Propylene Homopolymer PP7522 Shell Impact Grade Propylene Copolymer PB8010 Shell Developmental Polybutylene Copolymer PB0200 Shell Polybutylene Homopolymer Petrothene U.S. Industries Injection Moulding Grade LB861 High Density Polyethylene Petrothene U.S. Industries Injection Moulding Grade NA202 Low Density Polyethylene Alathon 3445 DuPont Extrusion Grade EVA
Copolymer Blends of Nylon 66 with the melt modified Kraton G-1651 block copolymers described above were prepared in the manner described in Example 1. Dry as moulded physical properties of these blends are given in Tables 5 and 6.
The examples show that blends of a thermoplastic polyamide with modified block copolymers in which polyolefins are added retain impact strength and show an increase in flexural modulus over the corresponding blends without polyolefins.

The data in Table 6 shows that the concentration of block copolymer can be reduced to 5% by weight of the total blend while still retaining a good balance of stiffness and toughness.

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Claims (15)

1. A grafted block copolymer comprising a selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which formula each A is predominantly a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight in the range of from

2,000 to 115,000, each B prior to hydrogenation is predominantly a polymerized conjugated diene hydrocarbon block having an average molecular weight in the range of from 20,000 to 450,000, n = 0 or 1, o is in the range of from 1 to 100 and p = 0 or 1, the blocks A
constitute in the range of from 5 to 95 per cent by weight of the copolymer, the unsaturation of block B is less than 20% of the original unsaturation and the unsaturation of the blocks A is above 50% of the original unsaturation, which block copolymer is grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin.
2. An impact resistant composition which comprises:-(a) in the range of from 3 to 95% by weight of a polyamide having a number average molecular weight of at least 5,000;
(b) in the range of from 1 to 50% by weight of a polyolefin;
(c) in the range of from 1 to 50% by weight of a grafted selectively hydrogenated block copolymer as claimed in claim 1; and (d) in the range of from 0 to 50% by weight of a functionalized selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which A, B, n, o and p have the meaning stated in claim 1, which block copolymer is grafted with an acid moiety or a derivative thereof.

3. A composition as claimed in claim 2 which comprises:-(a) in the range of from 60 to 85% by weight of said polyamide;
(b) in the range of from 5 to 30% by weight of a polyolefin;
(c) in the range of from 5 to 30% by weight of said selectively hydrogenated block copolymer grafted with (a) an acid moiety or a derivative thereof, and (b) a polyolefin; and (d) in the range of from 5 to 30% by weight of said functionalized selectively hydrogenated block copolymer grafted with an acid moiety or a derivative thereof.

4. A composition as claimed in claim 2 in which the selectively hydrogenated block copolymer is a selectively hydrogenated styrene-butadiene-styrene block copolymer.

5. A composition as claimed in any one of claims 2 to 4 in which block B has an unsaturation which is less than 5% of its original value and an average of less than 10% of the monoalkenyl aromatic hydrocarbon units in block A are hydrogenated.

6. A composition as claimed in any one of claims 2 to 4 in which block A has an average molecular weight in the range of from 4,000 to 60,000 and block B has an average molecular weight in the range of from 35,000 to 150,000 and in the range of from 35% to 50% of the condensed butadiene units have 1,2-configuration.

7. A composition as claimed in any one of claims 1 to 3 in which the block copolymer is grafted with a carboxylic acid or a derivative thereof.

8. A composition as claimed in any one of claims 1 to 3 in which the block copolymer is grafted with maleic acid or a derivative thereof.

9. A composition as claimed in any one of claims 1 to 3 in which the block copolymer is grafted with a sulphonic acid or a derivative thereof.

10. A composition as claimed in any one of claims 1 to 3 in which the acid moiety or the derivative thereof is present in the composition in an amount in the range of from 0.02 to 20% by weight, calculated on functionalized block copolymer.

11. A composition as claimed in any one of claims 2 to 4 in which the polyolefin is polypropylene, polybutylene, high density polyethylene, low density polyethylene or ethylene vinyl acetate copolymer.

12. A composition as claimed in any one of claims 2 to 4 in which the polyamide is polyhexamethylene adipamide.

13. A composition as claimed in any one of claims 2 to 4 in which the polyamide is polyhexamethylene sebacamide, polycaprolactam, polyhexamethylene isophthalamide, polyhexamethylene tere-co-isophthalamide or a mixture or a copolymer thereof.

14. A process for the preparation of a grafted block copolymer as claimed in claim 1 which process comprises melt-mixing the following components:-component (a): a selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which formula each A is predominantly a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight in the range of from 2,000 to 115,000, each B prior to hydrogenation is predominantly a poly-merized conjugated diene hydrocarbon block having an average molecular weight in the range of from 20,000 to 450,000, n = 0 or 1, o is in the range of from 1 to 100 and p = 0 or 1, the blocks A
constitute in the range of from 5 to 95 per cent by weight of the copolymer, the unsaturation of block B is less than 20%

of the original unsaturation and the unsaturation of the block A is above 50%
of the original unsaturation;
component (b): an acid moiety or a derivative thereof;
and component (c): a polyolefin, adding a free radical initiator, graft-reacting under free radical conditions and recovering grafted block copolymer product.

15. A process for the preparation of an impact resistant composition as claimed in claim 2 which process comprises melt-mixing in the range of from 3 to 99% by weight of a polyamide having a number average molecular weight of at least 5,000;
in the range of from 1 to 50% by weight of a polyolefin;
in the range of from 1 to 50% by weight of a grafted selectively hydrogenated block copolymer as claimed in claim 1; and in the range of from 0 to 50% by weight of a functionalized selectively hydrogenated block copolymer having the general formula Bn(AB)oAp in which A, B, n, o and p have the meaning stated in claim 1, which block copolymer is grafted with an acid moiety or a derivative thereof.