POLYMER COMPOSITION COMPRISING A MIXTURE OF A CRYSTALLINE OR SEMI-CRYSTALLINE POLYOLEFIN AND A POLYMER BASED ON VINYLAROMATIC AND DICARBOXYLIC ACID ANHYDRIDE MONOMER UNITS

Abstract: A polymer composition comprising a mixture of a crystalline or semi-crystalline polyolefin A and a polymer B based on vinyl-aromatic and dicarboxylic acid anhydride monomer units. The polymer B is chemically crosslinked with a compound which contains at least two functional groups which are able to react with the dicarboxylic acid anhydride group of the polymer B; polymer B can also be physically crosslinked.

Description: POLYMER COMPOSITION COMPRISING A MIXTURE OF A CRYSTALLINE OR SEMI- CRYSTALLINE POLYOLEFIN AND A POLYMER BASED ON VINYLAROMATIC AND DICARBOXYLIC ACID ANHYDRIDE MONOMER UNITS The invention relates to a polymer composition comprising a mixture of a crystalline or semi-crystalline polyolefin (A) and a polymer (B) based on vinyl-aromatic an dicarboxylic acid anhydride monomer units. A polymer composition of this type is known from WO-A-9005759. In WO-A-9005759 a polymer mixture of a crystalline or semi-crystalline polyolefin and a second polymer, such as a copolymer of styrene and maleic anhydride, is described. Since the polyolefin and the secon polymer are not miscible, the polymer mixture contains a compatibiliser. According to this publication, the compatibiliser is a block copolymer of a vinyl-aromatic compound and a conjugated diene or partially hydrogenated derivatives thereof. Here and hereafter a compatibiliser is understood to be a compound which improves the compatibilit of A and B and is primarily located at the interface of the polyolefin A and the polymer B. It is known from JP-A-63.205.341 to use styrene- containing rubber-like copolymers as compatibilisers in polymer compositions consisting of polypropene and styrene/maleic anhydride copolymers. A drawback of these polymer compositions is, however, that the impact strength/rigidity combination (Izod vs. modulus of elas¬ ticity) is poor, as a result of which the polymer com¬ positions are unsuitable for structural moulded components which are used in, for example, cars and furniture. The aim of the invention is to provide a polymer composition of a polyolefin A and a polymer B based on vinyl-aromatic monomer units and dicarboxylic acid anhydrid monomer units, which has a good impact strength/rigidity combination. The invention is characterised in that the polymer B is crosslinked. The crosslinking of the polymer B can be either of the chemical or the physical type. Physical crosslinking is effected under the influence of Van der aals forces, dipole-dipole interactions and ionogenic interactions. Polymer B can be chemically crosslinked by a reaction with a compound which contains at least two functional groups which are able to react with the dicarboxylic acid anhydride group of the polymer. A further advantage of the polymer composition according to the invention is that the elongation at break of the polymer composition increases. Another advantage of the polymer composition according to the invention is that the said composition also has good scratch resistance and paintability. Compounds containing two or more alcohol or thiol functional groups form a first group of possible compounds suitable for crosslinking the polymer B. The combination of alcohol and thiol functional groups in a compound is also possible. Compounds containing two or more alcohol functional groups, such as 1,4-butanediol, 1,6-hexanediol, pentaerythritol, ethylene glycol and propylene glycol and polymers thereof are preferred. Polyhydroxy ethers can also be used, for example polyhydroxy ethers based on bisphenol A. Compounds containing two or more primary or secondary amine functional groups, preferably primary amine groups, form a second group of compounds suitable for crosslinking the polymer B. The following may be mentioned as examples of these compounds containing amine functional groups: alkane diamines containing a C 4 -C 20 alkylene group, such as 1,4-diaminobutane and 1,6-diaminohexane, polyoxy- ethylene diamine, polyoxypropylene diamine, polyoxypropylen triamine, diphenyl sulphone diamine, 1,3-phenylene-diamine and 1,4-phenylene diamine. The combination of one or more primary amine groups with one or more secondary amine group in a compound is possible. Polyamides can also be used. The compound suitable for crosslinking the polymer B can also contain at least one alcohol or thiol group and also at least one amine group. Diethanolamine and monoethanolamine are examples of this type of compound. Compounds containing two or more epoxide functiona groups having the general formula: (CH CHR) n 0 in which n>2 and R is a hydrocarbon radical or a hydrogen atom form a third group of compounds suitable for cross- linking the polymer B. Examples of such compounds are: polyglycidyl ethers of polyhydroxyl-substituted compounds. These compounds can be subdivided into polyepoxide compound of the aromatic type, such as can be obtained from bispheno A, and polyepoxide compounds of the aliphatic type, such as polyglycidyl ethers of polyalcohols. The following may be mentioned as examples of the latter type of polyepoxide compounds: diglycidyl ethers of α-ω diols, such as butanediol diglycidyl ether, hexanediol diglycidyl ether, paracyclohexyldimethanol diglycidyl ether, neopentyl glycol diglycidyl ether and bisphenol A diglycidyl ether. Preferably, compounds are used which are the result of the epoxidation of olefins, such as epoxidised soya oil. When crosslinking with an epoxide compound it is usually desirable to use an activator, such as an imidazole a quaternary ammonium salt or a tertiary amine. Compounds containing 2 or more oxazoline groups form a fourth group of compounds suitable for crosslinking the polymer B. 1,3-phenylenebisoxazoline may be mentioned a an example of these compounds. Compounds containing 2 or more isocyanate groups form a fifth group of compounds suitable for crosslinking the polymer B. Examples of these compounds are toluene 2,4-diisocyanate, benzene 1,3,5-triisocyanate and methanediphenyl diisocyanate. Salts of metal atoms from groups 2-10 of the Periodic System of the Elements (Handbook of Chemistry and Physics, 70th Edition, CRC Press, 1989-1990) form a sixth group of compounds suitable for crosslinking the polymer B. Preferably, metal alkoxides and salts of divalent positive ions are used, such as tetrabutoxytitanium, zinc oxide and zinc acetate. A compound containing two or more functional groups, chosen from the abovementioned groups, is also suitable for crosslinking the polymer B. A mixture of compounds suitable for crosslinking the polymer B, chosen from one or more of the abovementioned groups of compounds, can also be used. The compound suitable for crosslinking the polymer B is present in an amount of 0.1-20 mol% with respect to the amount of dicarboxylic acid anhydride groups present in polymer B. Crystalline or semi-crystalline polyolefins A which can be used in a polymer composition according to the invention are homopolymers, copolymers or terpolymers or mixtures thereof. Polymers of α-olefins are preferably used and these α-olefins generally have 2 to 20 carbon atoms. The use of polymers of α-olefins having 2-6 carbon atoms is particularly preferred. The crystalline or semi-crystalline polyolefins are derived from olefins, such as ethylene, propylene, 1-butene, 1-pentene, 4-methyl-l-pentene, 1-octene, 1-decene, 4-ethyl- 1-hexene, etc. Examples of particularly suitable polyolefins are: low density polyethylene, high density polyethylene, linear low density polyethylene, ultra-low density poly¬ ethylene, polypropylene, (high and low density) poly(l- butene), pol (4-methyl-l-pentene) , ethylene/propylene copolymers and copolymers of ethylene and/or propylene with other copolymerisable monomers, such as ethylene/1-butene copolymer, ethylene/vinyl acrylate copolymer or ethylene/- vinyl acetate. Polymers and copolymers of halogenated olefins can also be used. An amount of 30-95 parts by weight of polyolefin A is present in the polymer composition, based on the sum of polyolefin A and polymer B. The amount of polyolefin is preferably 60-80 parts by weight. The amount of polyolefin in the polymer composition can proportionally be lowered when a functionalised polyolefin A is used as compatibiliser (see below). Polymer B comprises vinyl-aromatic monomer units and dicarboxylic acid anhydride monomer units. Suitable vinyl-aromatic monomers for use in the polymer B are, for example, styrene, alpha-methyl-styrene, para-methylstyrene and mixtures thereof. Styrene is preferably used. Suitable dicarboxylic acid anhydrides are, for example, maleic anhydride, chloromaleic anhydride, citraco- nic anhydride, cyclohexylmaleic anhydride, benzyl maleic anhydride, phenyl maleic anhydride, aconitic anhydride, propyl maleic anhydride and mixtures thereof. Maleic anhy¬ dride (MA) is preferably used. Polymer B preferably consists of styrene and malei anhydride and can contain 5-40 mol of maleic anhydride. In particular, polymer B contains 22-32 mol% of maleic anhydride. Polymer B can also contain imide monomer units or spirodilactone units. Imide monomer units which can be present in polymer B are N-phenylmaleimide, maleimide, citraconimide, itaconimide, aconimide, N-methylmaleimide or mixtures thereof. The spirodilactone units can be formed b heating the polymer B. The dicarboxylic acid anhydride content of polymer B must remain at least 5 mol%. Polymer B can be prepared by copolymerising the vinyl- aromatic monomer units and the dicarboxylic acid anhydride monomer units and/or the imide monomer units in a known manner. Imide units can also be obtained by reacting some of the dicarboxylic acid anhydride units in the polymer B with a primary amine or ammonia. Examples of amines which can be used are: aniline and methylamine. Polymer B is present in the polymer composition in an amount of 5-70 parts by weight based on the sum of polyolefin A and polymer B, preferably 20-40 parts by weight. The amount of polymer B in the polymer composition can proportionally be lowered when a functionalised polymer B is used as compatibiliser (see below). A functionalised polyolefin A and/or a functiona- lised polymer B can be added to the polymer composition in order to obtain an even better compatibility. To this end, a portion of the amount of polyolefin A or the amount of polymer B present in the polymer mixture can be replaced by, respectively, the functionalised polyolefin A or the functionalised polymer B. The portion which can be replaced is 0-100%, with a preference for 50-100% for the replacement of polymer B and a preference for 0.5-30% for the replacement of polyolefin A. Combinations of the functionalised polyolefins A and functionalised polymers B can also be used. A functionalised polyolefin A or a functionalised polymer B is understood to be: a polyolefin A or a polymer B which contains groups which are compatible or reactive with, respectively, the polymer B or the polyolefin A. The functionalised polyolefin A contains one or more functional groups, such as: - a hydroxyl group, - a thiol group, - an amine group, - an amide group, - an epoxide group, - an oxazoline group, - an isocyanate group or - an alkoxide group. Preferably, the functional polyolefin A contains one or more isocyanate groups, one or more oxazoline groups or one or more amine groups. The functionalised polymer B contains one or more linear or branched alkyl groups with 10-200 carbon atoms. The functionalised polyolefin A is, for example, prepared starting from a polyolefin grafted with a dicarboxylic acid or anhydride, like maleic anhydride or acrylic acid. Such a grafted polyolefin preferably contains 0.01-10 parts by weight of anhydride groups or acid groups. Preferably, the polyolefin is grafted with maleic anhydride or acrylic acid and contains 0.1-7% by weight of maleic anhydride groups or acrylic acid groups. The polyolefin grafted with an anhydride or with a acid can hereafter be reacted with one or more of the compounds listed below, or combinations of these compounds, in order to obtain the functionalised polyolefin A. The compound to be used contains 2 or more: - hydroxyl-groups, - thiol-groups, - amine-yroups, - amide-groups, - epoxide-groups, - oxazoline groups, - isocyanate groups. The compound can also be an alkoxide of a metal from group 4-13 of the Periodic System of the Elements (Handbook of Chemistry and Physics, 70th Edition, CRC Press, 1989-1990). Examples of such compounds are: 1,3-phenylene- bisoxazoline, 1,4-phenylene diamine, 1,3-phenylene diamine, methane-diphenyl diisocyanate, tetrabutyl titanate and ethanolamine. During these reactions preferably at least 70% of the anhydride groups or acid groups are reacted. Crosslinking of the functionalised polyolefin should be avoided. Particularly prefered, 100% of the anhydride or acid groups are converted. The functionalised polyolefin A can also be prepared by grafting non-functionalised polyolefin A with for example hydroxyethyl methacrylate, glycidyl methacrylate, acryla ide, isopropenyloxazoline and dimethyl ethaisopropenyl benzyl . isocyanate. The functionalised polymer B is, for example, synthesised by grafting the polymer B with a compound which contains a linear or branched alkylgroup with 10-200 carbon atoms and having a terminal functional group which is able to react with the dicarboxylic acid anhydride groups in the polymer B. Preferably, 20-90% of the dicarboxylic acid anhydride units are converted. The functionalised polymer B can be grafted with a linear or branched alkyl compound containing as the termina functional group: - a primary or secondary amine group, - a primary alcohol group, - a primary thiol group, - an oxazoline group, - an epoxide group and/or - an isocyanate group. These compounds are, for example: 1-dodecylamine, 1-octa- decylamine, 1-nonadecyl alcohol, epoxydodecane, OLOA 1200 R from Chevron (an amine-terminated polybutene having about 7 carbon atoms) . When grafting polymer B with an epoxide compound i is usually necessary to use an activator, such as an imida- zole, a quaternary ammonium salt or a tertiary amine. Preferably, a compound which contains a linear or branched alkylgroup with 10-200 carbon atoms and a primary amine functional group is used as the compound for grafting polymer B. The grafting reactions are performed by known methods for a person skilled in the art. A polymer composition according to the invention can also contain an elastomer or an elastomer-containing composition as an impact modifier. Examples of suitable elastomers or elastomer-containing compositions are: polybutadiene, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM) , functionalised EPDM acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-ethylene-styrene copolymer (AES) and silicone elastomer. 0-50% by weight of the elastomer or of the elastomer-containing composition can be added to the polyme composition. Preferably, 0-30 parts by weight are added. The polymer composition can be obtained by mixing all components in arbitrary sequence. The polymer composi¬ tion can preferably be obtained by dynamic crosslinking, that is to say, the composition is mixed and/or kneaded, with heating, in equipment customary for this purpose, for example in a Brabender mixer or on rollers or in an extruder. The polyolefin A, the polymer B and, where appropriate, the compatibiliser are mixed at a temperature at which all three of the materials flow readily. This temperature is higher than the glass transition temperature of the polymer B and higher than the glass transition temperature or the melting point of the polyolefin A, depending on the polyolefin A used and the polymer B used. It is preferred that the crosslinking compound is added after the polyolefin A and the polymer B have been mixed well. The time which is needed to carry out the crosslinking reaction varies with the compounding condition (such as temperature and shear rate) and the type of polyme and crosslinking agent used. Suitable temperatures are between the melting point of the polyolefin (175°C for polypropylene) and 300°C, while specifically the limits are 180-260°C. The polymer composition according to the invention can also contain the customary additives, such as fibres, fillers, plasticisers, flame retardants and stabilisers. The invention is further illustrated with the aid of the following examples, without being restricted thereto The Izod is determined in accordance with ISO R180/4A (23°C; measured parallel to the direction of injection-moulding) . The modulus of elasticity is determined in accordance with ISO 178 (23°C; measured parallel to the direction of injection-moulding). The elongation at break is determined in accordance with ISO 37-2 (23°C). Example 1 Mixtures of polypropylene (PP), styrene maleic acid anhydride copolymer (SMA) and crosslinking agent were prepared in a Berstorff twin-screw extruder. Blending conditions: cylinder temperature 215-240°C; screw Be 07; speed of rotation 150 rpm; yield: 5 kg/h. As reference, the same amounts of polypropylene and SMA were mixed without crosslinking agent being added. The polypropylene which was used is Stamylan P 83E00 R . The SMA which was used is Stapron 28110 R (both products of DSM). The crosslinking agents used were 1.3 mol% of 1,3-phenylene- bisoxazoline (PBO) from Takeda Chemicals and 1.5 mol% of pentaeryth itol (PTA) from Aldrich Chemie. The amount of crosslinking agent which is added is related to the amount of anhydride groups present in polymer B. Sheets were prepared from these mixtures by means of injection-moulding. Properties were determined on these sheets. The results are shown in Table 1. TABLE 1 Without crosslinking agent PP/SMA Izod Modulus of Elongation at elasticity break (parts by weight) (kJ/m 2 ) (N/mm 2 ) (%) 5.3 48.4 70/30 9.3 1750 53.3 It can clearly be seen that over a broad range of compositions the impact strength is increased by adding the crosslinking agent to the mixture of polypropylene and SMA, whilst the rigidity is largely retained in comparison with the mixture of polypropylene and SMA without crosslinking agent. The elongation at break also increases by adding the crosslinking agent. Comparative Experiment A On the basis of JP-A-63.205.341 mixtures of polypropylene, SMA and a compatibiliser were prepared. The polypropylene and SMA types are the same as were used in Example 1. The mixtures were prepared using the same process as in Example 1. The sheets were injection-moulded. The compatibilisers used were: A. Kraton G 1652 R (a styrene/ethylene/butene/styrene block copolymer? product from Mitsui Petrochemical). B. Kraton G 1702 X R (a styrene/ethylene/propene block copolymer; product from Mitsui Petrochemical). C. Kraton FG 1901 X R (a maleic anhydride-modified styrene/α-olefin block copolymer; product from Mitsui Petrochemical) . The mixtures consist of PP/SMA/Kraton 63/27/10 TABLE 2 Kraton Izod Modulus of elasticity type kJ/m 2 N/mm 2 A B C Compared with a crosslinked polypropylene/SMA mixture containing 70% by weight of polypropylene and 30% by weight of SMA according to Example 1, the mixtures containing Kraton as compatibiliser show both a poorer impact strength and a poorer rigidity. Example II Process for the preparation of an α-octadecylamine- modified styrene/maleic anhydride copolymer. 150.0 g of Stapron 28110 R (SMA) were dissolved in 1 dm 3 of methyl ethyl ketone (MEK), with stirring and heating under a N 2 atmosphere. 28.6 g of α-octadecylamine were then added to the solution. The.mixture was then heated to 67°C, with stirring. After the amine had dissolved, the reaction mixture was stirred for a further 5 hours at 67°C under N 2 . 2.4 g of sodium acetate and 24 ml of acetic anhydride were then added to the pale yellow, clear reaction mixture, aft which the mixture was stirred for 5 hours at 80°C under N 2 After cooling to room temperature, the mixture was coagulated in methanol. The precipitated SMA-g-Ci 8 H 37 NH 2 w filtered off, washed with methanol and dried under vacuum 60°C. 25% of the original amount of MA groups in the SMA h been converted to imide groups (determined by FTIR and elementary analysis). 30 parts by weight of the so obtained SMA-g- C 18 H 37 NH 2 by the process described above were mixed with 7 parts by weight of Stamylan P 83E10 R (PP) under the conditions indicated in Example 1. The crosslinking agent used was 1.3 mol% of PBO. TABLE 3 P/SMA-g-Ci 8 H 37 NH 2 Izod Modulus of elasticity (parts by weight) (kJ/m 2 ) (N/mm 2 ) 70/30 13.1 1650 Compared with a mixture of 70 parts by weight of polypropylene with 30 parts by weight of non-modified SMA which has been crosslinked using PBO, as described in Example 1, the impact strength is even further improved.

Claims: C L A I M S 1. A polymer composition comprising a mixture of a crystalline or semi—crystalline polyolefin A and a polymer B based on vinyl-aromatic and dicarboxylic acid anhydride monomer units, characterised in that polymer B is crosslinked. 2. A polymer composition according to claim 1, characterised in that polymer B is crosslinked with a crosslinking agent being a compound which contains at least two functional groups which are able to react with the dicarboxylic acid anhydride group of polymer B. 3. A polymer composition according to claim 2, characterised in that the functional groups are selected from alcohol, thiol, amine, amide, epoxide, oxazoline isocyanate or mixtures thereof. 4. A polymer composition according to claim 2, characterised in that polymer B is crosslinked with a salt of a metal atom from group 4-13 of the Periodic System of the Elements. 5. A polymer composition according to anyone of claims 1-4, characterised in that 0.1-20 parts by weight of the crosslinking agent is present with respect to the amount of dicarboxylic acid anhydride monomers present in polymer B. 6. A polymer composition according to anyone of claims 1-5, characterised in that a compatibiliser consisting of a functionalised polyolefin A and/or a functionalised polymer B is also present. 7. Process for obtaining a polymer composition according to anyone of claims 1-6, characterized in that polyolefin A, polymer B, the crosslinking compound and, where appropriate, the compatibilizer are added to a mixing equipment and are mixed and/or kneaded with heating, so that dynamic crosslinking takes place. 8. Products entirely or partially formed from a polymer composition as described in anyone of claims 1-6 or produced by a process of claim 7. 9. Polymer composition, process and products as essentiall described and/or illustrated in more detail in the examples.

Inventors: BORGGREVE REINOLDUS JOZEF MARI, GRIMBERG JOHANNES HERMANUS, KONING CORNELIS EME, BORGGREVE, REINOLDUS, JOZEF, MARIA, GRIMBERG, JOHANNES, HERMANUS, KONING, CORNELIS, EME
Applicants: BORGGREVE REINOLDUS JOZEF MARI, DSM NV, GRIMBERG JOHANNES HERMANUS, KONING CORNELIS EME, DSM N.V.
Application year: 1993
Main classification: C08L35
IPC codes: C08K5, C08L23, C08L25, C08L35