POLYMERIC BLENDS BASED ON POLYOLEFINS AND POLYAMIDE RESINS

Abstract: A polymer composition consisting of a compatibilized blend of a polyolefin being grafted with a copolymerized allyl epoxy compound and a styrenic compound, and a polyamide. This composition is obtained by grafting the polyolefin with an allyl epoxy compound and styrene in the presence of a peroxide in a single step reactive extrusion process. This composition may be used in packages for food packaging and other products requiring an improved oxygen barrier.

Description: POLYMERIC BLENDS BASED ON POLYOLEFINS AND POLYAMIDE RESINS FIELD OF INVENTION The present invention relates to compatibilized blends of polyolefin and polyamide resins, a process for producing such blends, and the use thereof. More particularly, the invention relates to a continuous single step reactive extrusion process comprising a simultaneous grafting of allyl epoxy and styrenic monomers onto the polyolefin resin and then blending therewith a polyamide resin. BACKGROUND OF THE INVENTION Polyolefins ( PO) , such as polyethylenes ( PE ) and poly- propylenes (PP) , are very versatile resins used in numerous fields, also being converted into sheets or films for packaging and other purposes. Polyolefins have a very low water vapour transmission and a high gas permeability. To reduce the latter, they are often combined with a polyamide (PA), for instance by combining film layers of PO and PA in a laminate. Attempts have also been made to blend polyolefins and polyamides to obtain a composition having both low water vapour and gas permeabilities. However, polyolefins and polyamides are highly incompatible, and to obtain homogenous blends thereof a compatibilizer is required to improve the miscibility of them through a stabilization of the polymer-polymer interfaces. A commonly used compatibilizing agent is a separately synthesized copolymer, which necessarily will be fairly expensive. Moreover, when a separate compatibilizing agent is used a part thereof will be located away from the polymer- polymer interfaces, i.e. in the bulk regions of the polymer composition, where it is of no use. Another procedure is to graft one or more of the resins to be blended with an appropriate compatibilizing compound. All prior art processes for the production of compatibilized PO/PA blends are two-step processes: a first step com- prising a separate preparation of a compatibilizing agent, or the grafting of specific compounds onto one or both of the resins to be blended, and a second step of blending the components. EP 0 363 479 discloses blends of polypropylene with polyamide produced by a two-step method. In a first step poly- propylene homopolymer (70%) and PA6 (30%) with added maleic anhydride (0.3%) and a peroxide (0.3%) are mixed in a Henschel mixer at room temperature, and in a second step the obtained blend is extruded in a twin-screw extruder at 220 °C to obtain a masterbatch. The final composition is manufactured by mixing 20 parts of this masterbatch with 30 parts of PA6, 50 parts of PP homopolymer and 10 parts of a styrene rubber (SEBS), where all parts are based on weight, in a Henschel mixer at room temperature, followed by extrusion in a twin-screw extruder at 250 °C. GB 1403797 discloses a composition prepared by grafting maleic anhydride onto a polypropylene, mixing the obtained material with another amount of the polypropylene, and subsequently mixing the obtained material with a polyamide. US 4 814 379 relates to blends obtained by combining a polyamide with a mixture comprising a maleic anhydride grafted high density polyethylene, a linear low density polyethylene and an EPDM rubber. US 5162422 relates to a PP/PA composition prepared by a two-step process. In a first step, a polypropylene and an un- saturated carboxylic acid and a peroxide are mixed in a highspeed mixer, and in a second step the obtained mixture is extruded in a twin-screw extruder through a reaction zone. The polyamide and an impact-modifying rubber are extruded in another extruder, and the melt streams from the two extruders are combined. International Application WO 96/06871, included herein by reference, discloses compatibilized blends of polypropylene and polybutylene terephthalate obtained by utilizing reactive extrusion. In a first section of an extruder polypropylene is melted and mixed with a peroxide, glycidyl methacrylate and a styrenic compound to obtain a grafted polypropylene resin, and in a second section of the same extruder polybutylene terephthalate is introduced and melt blended with the already grafted polypropylene. A homogenous blend is obtained, which is useful as an engineering resin. The need still exists for a suitable process for the production of an improved polyolefin/polyamide blend having useful mechanical and physical properties. Applicant has now surprisingly found that it is possible to produce homogeneous compatibilized blends of polyolefins and polyamides by an industrially applicable and cost efficient single step reactive extrusion process. SUMMARY OF THE INVENTION The present invention provides a compatibilized polymer blend comprising a polyolefin and a polyamide, wherein said polyolefin being copolymerised with allyl epoxy and styrenic compounds. The present invention also provides a process of producing an in situ compatibilized blend of polyolefin and polyamide resins by a continuous single step extrusion process performed in an extruder, by introducing into a first feed zone of the extruder a polyolefin resin; an allylepoxy compound having the formula wherein R is H or a C^ alkyl; R x is -(CH 2 ) n -, -C(O)O-(CH 2 ) n - or -(CH 2 ) n -O-, and n is an integer of 1 to 4; a styrenic compound having the formula: wherein R 2 is H, OH, CH 3 or allyl; and a peroxide being a free radical initiator, and subjecting these components to a continuous blending while heating to a temperature which is higher than the melting point of the polyolefin resin and the decomposition temperature of said peroxide, introducing the polyamide resin into the extruder barrel in a second feed zone located downstream the first one at a position along the extruder barrel where said polyolefin resin is in a molten state, and blending said polyamide resin with the molten polyolefin resin while heating until a homogeneous blend is achieved, and extruding the obtained blend. The obtained polymer compositions may be converted into packaging materials intended for the packaging of goods that require a low water vapour transmission rate and low gas and flavour permeabilities. DETAILED DESCRIPTION OF THE INVENTION The compatibilized blends of the present invention, comprising a polyolefin resin and a polyamide resin, are obtained by an extrusion process performed at such conditions that there will be substantially no degradation of the polyolefin and polyamide resins by chain scissions. In principle, all extrudable polyolefins may be used in the in situ grafting and blending process of the present inven- tion. Preferred polyolefins are those belonging to the group comprising polyethylene and polypropylene homopolymers, random copolymers of propylene or ethylene with comonomers, and block copolymers of propylene or ethylene with comonomers. More preferred are polypropylene homopolymers; copolymers of propylene with preferably not more then 20 % by weight of ethylene; copolymers of propylene with butadiene and optionally ethylene; copolymers of propylene with other α-olefins; low density polyethylene; and high density polyethylene. Most preferably the polyolefin resin is selected from the group comprising the polypropylene and low density polyethylene copolymers mentioned above. The polyolefin resins may be used in the form of granules or powder, preferably as a flowable powder. The polypropylene resins used in the present invention may comprise a single grade of polypropylene, or a mixture of two or more of the above mentioned polypropylenes. Preferred poly- propylenes are those having a molecular weight from 150,000 to 500,000 g/mole, and a melt flow rate from 0.2 to 100 g/10 min. , more preferably from 0.2 to 50 g/10 min. (determined according to ASTM D 1238 at the conditions of 230 °C and 2.16 kg load). Preferred polyethylenes are those having a density from 0.880 to 0.950 g/cm 3 , and a melt flow rate from 0.5 to 50 g/10 min, more preferably from 1 to 30 g/10 min (determined according to ASTM D 1238 at the conditions of 190 °C and 2.16 kg load). All commercially available types of polyamides may be used. Examples of particularly useful polyamides are poly- caprolactam (PA6), polyhexamethylene adipamide (PA66), poly- hexamethylene azaleamide (PA69), polyhexamethylene sebacamide (PA610), polyhexamethylene dodecandiamide (PA612), and poly- (ω-aminoundecanoic acid) (PA11). Also other types of polyamides may be used. Particularly preferred polyamides are the polycapro- lactams (PA6) of suitable viscosities. The monomeric allylepoxy compound to be grafted onto the polymer chains must contain polar or functional substituents. Such monomers are preferably chosen from the group comprising the allylepoxy compounds having the formula: in which R is H or a C^ alkyl; R x is -(CH 2 ) n -, -C(O)O-(CH 2 ) n -, or -(CH 2 ) n -O-, and n is an integer of 1 to 4. Preferably R is H or CH 3 , more preferably CH 3 . R x is preferably -C(O)O-(CH 2 ) n -. Thus, the most preferred compound is glycidyl methacrylate (GMA). Each of these monomer species are suitably used alone, but also mixtures thereof may be used. The degree of conversion during the grafting reactions can be improved by the use of an appropriate comonomer, such as a styrenic compound. Suitable styrenic compounds are those having the formula: wherein R 2 is H, OH, CH 3 or allyl. Preferably R 2 is H, making styrene the preferred styrenic compound. The styrenic compound is also assumed to stabilize by delocalization the free radical species that are present during the blending process. Compounds other than those mentioned above, having conjugated unsaturated double bonds, such as quinone, may give similar results. The allylepoxy and styrenic compounds are used in about equal molar quantities. Based on weight, the amounts used of each of the two types of grafting monomers are in the range from 1 % to 10 %, preferably from 1 % to 7 %, more preferably from 1 % to 5 % by weight, based on the weight of the polypropylene resin. To initiate the grafting reactions any peroxide compound generating free radicals upon heating to a suitable decomposition temperature may be used. In particular, the following alkyl peroxide initiators have been found to give acceptable results: 2, 5-dimethyl-2, 5-bis( t-butylperoxy)hexane (DHBP); 2,5-dimethyl-2,5-bis(t-butylperoxy)-3-hexyne; α, -bis- (t-butylperoxy)diisopropylbenzene and dicumylperoxide (DCUP). These initiators are used in amounts from 0.10 % to 5 %, prefer- 5 ably from 0.20 % to 1 %, more preferably from 0.2 to 0.3 %, most preferably about 0.25 % by weight of the polypropylene resin.- The process according to the present invention is most suitably performed by the use of an extruder, preferably a double screw extruder having co-rotating intermeshing screws of suffici- o ent length, for example a length/diameter ratio, L/D, of 42. The extruder is provided with two feed hoppers, a first feed hopper located at the main feeding point of the extruder, and a second feed hopper located in a distance of approximately 0.4«L downstream of the first one. By this, the extruder barrel becomes s divided into two main zones, a first zone between the two feed inlets, and a second zone between the second feed inlet and the die. Each of the two feed hoppers are connected with a feeding device, from which the starting material is continuously fed at a controlled rate into the extruder. o The first hopper contains the polyolefin resin in admixture with the styrenic compound, optionally also the allylepoxy compound and the initiator. Optionally, these components may be premixed before being conveyed to the first feed hopper. In embodiments of the present invention the used allyl epoxy 5 monomers are maleic anhydride (MAH) or glycidylalkyl acrylate (GMA), and the styrenic compound is styrene. It is convenient first to mix the MAH or GMA with styrene and then dissolve the peroxide initiator in this mixture, which subsequently is mixed into the polypropylene powder. Accordingly, in the first main o extruder zone the polyolefin melt should have a level of MAH or GMA of 1 to 10 % by weight, preferably 2 to 5 % by weight, and a corresponding level of styrene, based on the neat polyolefin resin. The second hopper, in a position 0.4 L downstream of 5 the first hopper, contains the polyamide resin which is therefrom introduced into the extruder. To obtain an optimal mixing of the polypropylene and polyamide resins during the extrusion process, they should in their melted states have approximately equal melt viscosities at the actual processing temperature. In general, a practical melt processing temperature for polypropylenes is in the range from about 180 °C and upwards, and for polyamides in the range from about 220 °C and upwards. However, the processing temperatures s must not be so high that any substantial degree of degradation of the polymer resins will take place. The temperature of the melt should therefore not exceed about 300 °C. One problem that may be encountered in the present grafting and blending process is a possible contamination of the o reagents with oxygen from the surrounding air. Therefore, the present extrusion process is preferably carried out in an inert atmosphere, such as a nitrogen atmosphere, which readily can be accomplished by flushing the feed hoppers with nitrogen. The polymer chain scissions and hence the molecular s weights of the present blends can be controlled by the use of the comonomer system described herein. It is believed that the styrenic compound will function as a chain transfer agent in the grafting reactions. Compared to traditional grafting and blending processes where no chain transfer agent is used, the present o process can be performed with less degradation of the polypropylene resin. The styrenic compound also functions as a comonomer and will react with the allylepoxy monomer, which results in a random copolymer. Thus, the side chains grafted onto the polypropylene 5 backbone will be random copolymers of these two species. The simultaneous grafting reactions of the two monomers provide a synergistic effect resulting in a higher grafting efficiency and a higher amount of monomers being grafted onto the polypropylene resin compared to other grafting processes. Consequently, the 0 number of polar groups in the final, grafted polypropylene resin will increase. It is assumed that said polar groups will react with the functional groups of the polyamide at the interfaces between the polypropylene and polyamide fractions. Hence, there will be a minor amount of more or less weak crosslinking bonds 5 between the polypropylene and polyamide resins with the allylepoxy compound as bridging species. The final blend will consist of a continuous matrix and a dispersed phase. In principle, either of the polypropylene and the polyamide resin may constitute the matrix with the other resin constituting the dispersed phase. However, in view of practical use, it is preferred that the polypropylene constitutes the matrix with the polyamide as the dispersed phase. Thus, a blend obtained by the process of the present invention will 5 preferably contain more than 50 % by weight of the polypropylene and less than 50 % by weight of the polyamide resin. When the composition contains about equal amounts of the polypropylene and polyamide resins, i.e. when the weight ratio between polypropylene and polyamide is in the range from about 50:50 to about o 60:40, respectively, problems may be encountered due to phase inversions, and consequently this range of composition should be avoided. Therefore, blends obtained by the present invention preferably contain less than about 40 % by weight of the polyamide component, based on the total weight of the final composition. s Blends having improved properties may contain 30 % by weight or less of the polyamide component, for instance 20 % by weight, or 15 % by weight. Even compositions containing only 1 % by weight of polyamide will have improved, useful properties. All common additives used in thermoplastic processing o may also be added to the composition, for instance colouring agents, UV absorbers, heat-stabilizers, antistatics, etc., which are well known to any person skilled in the art. The composition of the present invention may also be blended with any fillers suitable for use with polyolefins and 5 polyamides. Examples of such fillers are talc, mica, and barium sulphate. Also reinforcing fibres, in particular glass fibres, may be incorporated. The purpose of using fillers or fibres is to improve the modulus of elasticity and the heat deformation resistance. The use of such fillers or fibres is also well known 0 to any skilled person. Articles made from the in situ compatibilized blends of polypropylenes (PP) and polyamides (PA) according to the present invention are endowed with favourable properties from both the polypropylene and polyamide components of the composition. Com- 5 pared to common polypropylene materials the compositions of the invention will have a better oxygen barrier, improved print- ability, higher impact strength and higher modulus of elasticity. The composition is particularly suited for conversion to extrusion blown or cast films and sheets, and for injection moulding. Because of the favourable properties, the compositions of the present invention may be used in packages intended for the packaging of products that require a low water vapour transmission rate and low gas and flavour permeabilities. Thus, the s compositions of the present invention are well suited for use in food packaging and in the packaging of technical products that require a high to medium barrier against gases, such as oxygen, and against flavour components, such as hydrocarbons. While the foregoing discussion has been restricted to ιo specific polyolefins, the same principles will also apply to related polyolefins. The word "comprising" and other forms of the word "comprising" used in this description and in the claims does not limit the claimed invention to exclude any variations or addi- i5 tions which are obvious to the person skilled in the art and which do not have a material effect upon the invention. The invention will now be illustrated with the following examples, which are not to be construed as limiting the scope of the present invention. In the examples all weights are given 20 in percent by weight based on the combined weight of the polymeric resins, unless stated otherwise. EXAMPLES General procedure 25 The extruder used in the examples was a ZSK30 Werner & Pfleiderer double screw extruder with co-rotating intermeshing screws of length L = 1230 mm and L/D = 42. The extruder was provided with two feed hoppers, a first feed hopper defining a first feeding point; and at a distance of L x = 0.378L downstream 30 therefrom a second feed hopper defining a second feeding point. The temperatures of the extruder were set at about 200 °C in the zone between the two feed hoppers, and at about 250 °C downstream of the second feed hopper. The temperature profile was adjusted to obtain at the extruder die a melt temperature of about 250 °C. 35 The extruder was run wit a screw rotation speed of about 100 rpm, giving a output of about 5 kg/h. The polymer melt was extruded as strands which were cooled and continuously pelletized in a water bath in an expedient manner. The polyolefin resin admixed with styrene, maleic anhydride (MAH) or glycidyl methacrylate (GMA) , and peroxide was conveyed to the first feed hopper and then introduced into the extruder in the first feeding point. The polyamide resin was conveyed to the second feed hopper and introduced into the extruder in the second feeding point. Testing The obtained compositions were tested for the following critical properties. The modulus of elasticity (E-modulus) was determined according to ISO 527, based on the stress-strain curves recorded by tensile testing. Impact strengths were determined as the total energy of break by the method of a falling dart according to ISO 6603/1. s Moulded disks of thickness 3 mm and testing temperatures of 23 °C and -20 °C, respectively, were used. Oxygen permeabilities were measured in 1 mm thick injection moulded disks at 23 °C by the use of a common "Oxtrans" apparatus. 0 Water vapour transmission rates (WVTR) in sheets injection moulded from the obtained polymer blends were determined at 23 °C according to the procedure of ASTM D 3985. Heat distortion temperatures (HDT) were determined according to the procedure of ISO 75. 5 The obtained values are presented in tables 1 to 3. Example 1 The general procedure described above was followed. As the polyolefin was used a polypropylene (PP) block copolymer o ("Borealis P 401H", commercially available from Borealis AS, Norway), an as the polyamide (PA) was used a PA6 low viscosity grade ( "Ultramid B3", commercially available from BASF GmbH, Germany). The amounts of polypropylene and polyamide comprised 85 % and 15 %, respectively, by weight of the combined amount of the 5 polymer resins. The peroxide used was tert-butyl-peroxybenzoate, added in an amount of 0.25 % by weight of the polymer resins. The allyl epoxy compound was glycidyl methacrylate (GMA) added in an amount of 3 % by weight of the polymer resins. The styrene was introduced in an amount corresponding to a molar ratio between GMA and styrene of 1:1. Example 2 Example 1 was repeated, except that the amount of polyamide was 20 %. Example 3 Example 1 was repeated, except that instead of GMA it was used maleic anhydride (MAH) in an amount of 2 % by weight. Example 4 Comparative Example The polypropylene and polyamide grades of Example 1 were combined in the same amounts used in Example 1, i.e. 85 % and 15 % by weight, respectively, and admixed with 2 % by weight of a compatibilizing agent consisting of a polypropylene grafted with maleic anhydride (PP-g-MAH), which had been prepared in advance in accordance with the disclosure of International Patent Application WO 94/15981. This compatibilizing agent is also commercially available under the trade name of "Epolene E-43" from Eastman Chemicals, USA. The polypropylene, the compatibilizing agent and the polyamide were combined and fed into the extruder in the first feeding point. The extrusion conditions were as in the preceding examples. Example 5 Example 3 was repeated, except that the amount of polyamide was 30 %. Example 6 Example 1 was repeated, except that the polyamide PA6 was of a high viscosity grade ( "Ultramide B4", commercially available from BASF) and that the allyl epoxy compound was maleic anhydride (MAH) added in an amount of 2 % by weight. The styrene was introduced in an amount corresponding to a molar ratio between MAH and styrene of 1:1. Example 7 Example 6 was repeated, except that the amount of polyamide was increased to 20 % by weight. Example 8 Example 6 was repeated, except that the amount of polyamide was increased to 30 % by weight. Example 9 Comparative Example The polypropylene copolymer used in Example 1 was blended mechanically with 20 % by weight of the polyamide PA6 low viscosity grade used in Example 1. This mixture was then introduced into the extruder in the first feeding point. The extrusion conditions were as in the preceding examples. No grafting monomers or peroxide were present. Example 10 Comparative Example The polypropylene grade used in examples 1 to 9 was extruded alone at the extrusion conditions of the preceding examples. The results obtained in examples 1 to 10 are presented in table 1. The results indicate that the present in situ method is performing equally well to the conventional, more expensive two-step route. MAH was observed to be a more efficient grafting monomer than GMA, as indicated by the results obtained in Examples 2 and 3, presented in Table 1. When comparing the results obtained in Example 3 according to the present invention with the results obtained in Example 4 representing the two-step route of the prior art, it is seen that the present one-step process provides a polymer composition having properties essentially equal to those of the corresponding compositions produced by the more expensive two-step processes of the prior art. The obtained results also reveals that the present composition will have a good impact strength. The modulus of elasticity and oxygen permeability depend more on the total content of polyamide and less on the compatibility of the constituents. The obtained results indicate that the novel one-step technology provides an efficient compatibilization starting with the pure polymers, a suitable peroxide and grafting monomers. TABLE 1 1) Two-step process Example 11 Example 6 was repeated, except that the polypropylene was replaced by a low-density polyethylene (LDPE) ("Borealis LE 0422", commercially available from Borealis AS, Norway) having a density of 0.922 g/cm 3 and a melt flow rate of 2.1 g/10 min (190 °C/2.16 kg) and the polyamide was replaced by a very high viscosity grade PA6 ( "Ultramide B5", commercially available from BASF, Germany). Example 12 Comparative Example The LDPE and PA grades and amounts of Example 11 were used. A compatibilizing agent consisting of PP grafted with MAH (PP-g-MAH) ("Epolene E-43" commercially available from Eastman Chemicals, USA) was added in an amount of 7.5 % by weight of the combined weight of the polymer resins. The LDPE and PA resins, as well as the compatibilizing agent were together introduced into the extruder in the first feeding point. The extrusion conditions of the preceding examples were used. Example 13 Comparative Example Example 12 was repeated, except that the amount of PA was 7.5 % and the amount of compatibilizing agent was 2.5 % by weight. Example 14 Comparative Example The LDPE grade of example 12 was extruded alone at the extrusion conditions of the preceding examples. The results obtained in Examples 11 to 14 are presented in Table 3. The results show that the composition of the present invention (Example 11) has an improved oxygen barrier, i.e. a reduced oxygen permeability, while the water vapour transmission rate is kept at the favourable level of pure low density polyethylene ( Example 14) . TABLE 2 1) Two-step process Reinforcing fibres Examples 15 to 18 below demonstrates the effect of adding glass fibres to the composition of the invention. Example 15 relates to a composition without reinforcing glass fibres, s while Examples 16 and 17 relate to a composition containing glass fibres. Examples 15 to 17 are according to the invention, while Example 18 is a comparative example. Experimental details and obtained results are presented in Table 3. o Example 15 The general procedure described above was followed. A polypropylene homopolymer having a melt flow rate of 12 (230 °C, 2.16 kg) ("Borealis "HE 125E", commercially available from Borealis AS, Norway) was introduced into the extruder in the s first feeding point. The amount of PP homopolymer comprised 60 % by weight. A polyamide PA66 grade ( "Ultramide A45", commercially available from BASF, Germany) was introduced into the extruder in the second feeding point. The amount of PA66 comprised 40 % by weight. The peroxide used was tert-butyl- 0 peroxybenzoate in an amount of 2.5 % by weight of the total amount of the polymeric resins ( as in the preceding examples ) . As a compatibilizing agent maleic anhydride (MAH) was added in an amount of 3 % by weight. The styrene was introduced in an amount corresponding to a molar ratio between MAH and styrene of 5 1:1. The extrusion conditions were as specified above. Example 16 Example 15 was repeated, except that the polyamide had in advance been thoroughly mixed with short glass fibres having 0 a length of 4.5 mm and a sizing of amino silane in an amount of 0.7 % by weight. This mixture of polyamide and glass fibres was introduced into the extruder in the second feeding point. The final product comprised 40 % by weight of PP, 40 % by weight of PA66 and 20 % by weight of glass fibres, where all percentages 5 are based on the combined weight of the polymeric resins and glass fibres. Example 17 Example 16 was repeated, except that the amount of PP was 30 %, the amount of PA66 was 40 %, and the amount of glass was 30 % by weight. Example 18 Comparative Example Example 17 was repeated, except that no allyl epoxy compound or styrene were added. The results obtained in examples 15 to 18, presented in Table 3 below, show that the modulus of elasticity (E-modulus) and the heat distortion temperature (HDT/A) increased with an increasing content of glass fibres. In Example 18 where no grafting took place, the obtained composition had inferior properties compared to the composition of Example 17. This clearly demonstrates that compatibilization is obtained also in glass fibre reinforced compositions of the invention, and that the compatibilization has a positive influence on the mechanical properties of the composition. TABLE 3 oo

Claims: 5 6. The composition of claim 1, char terized in that the polyamide is PA6. extrusion process performed in an extruder by introducing into a first feed zone of the extruder: a polyolefin resin; an allylepoxy compound having the formula wherein R is H or a C^ alkyl; R x is -(CH 2 ) n -, -C(O)O-(CH 2 ) n -, or -(CH 2 ) n -O-, and n is an integer of 1 to 4; a styrenic compound having the formula: wherein R 2 is H, OH, CH 3 or allyl; and a peroxide being a free radical initiator, and subjecting these components to a continuous blending while heating to a temperature which is higher than the melting point of the polyolefin resin and the decomposition temperature of said peroxide, characterised by introducing the polyamide resin into the extruder barrel in a second feed zone located downstream the first one at a position along the extruder barrel where said polyolefin resin is in a molten state, and blending said polyamide resin with the molten polyolefin resin while heating until a homogeneous blend is achieved, and extruding the obtained blend. 11. The process of claim 10, characterized in that the poly- olefin is fed to the extruder in the form of a powder being premixed with the allylepoxy compound, the styrenic compound and the peroxide. 12. The process of claims 10 or 11, characterized in that the allylepoxy compound is selected from the group comprising maleic anhydride or glycidyl methacrylate. 13. The process of claims 10 to 11, characterized in that the styrenic compound is styrene. 14. The process of claims 10 to 13, characterized in that the peroxide initiator is bis(tert-butylperoxyisopropyl )benzene and that the concentration of said peroxide in the polyolefin melt mixture in the first extruder zone is in the range of 0.2 to 0.3 s % by weight, calculated on the polyolefin polymer. 15. A use of a polymer composition according to any of claims 1 to 9, in packages intended for the packaging of goods requiring a low water vapour transmission rate and low gas and flavour o permeabilities. 5 0 5 0 5

Inventors: BOERVE KJETIL LARSEN, CARTIER HERVE, HU GUO-HUA, BOERVE, KJETIL, LARSEN, CARTIER, HERVE, HU, GUO-HUA
Applicants: BOERVE KJETIL LARSEN, BOREALIS AS, CARTIER HERVE, HU GUO HUA, BOERVE, KJETIL, LARSEN, BOREALIS A/S, CARTIER, HERVE, HU, GUO-HUA
Application year: 1998
Main classification: C08L51
IPC codes: C08F255, C08F287, C08J3, C08L23, C08L51, C08L77