Abstract:
The invention relates to a method for manufacturing a sealable and peelable polymer blend, in which method polystyrene and an ethylene copolymer are first melt blended and the obtained blend is further mixed with the same ethylene copolymer either by melt blending or dry blending so that the final polymer blend contains 1-50% by weight polystyrene and 99-50% by weight ethylene copolymer. Ethylene copolymer is preferably ethylene/methyl(meth)acrylate, ethylene/ethyl(meth)acrylate, ethylenelbutyl(meth)acrylate or ethylene/vinylacetate copolymer.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation of co-pending application Ser. No. 09/557,097 filed on Apr. 21, 2000, which is a continuation-in-part of application Ser. No. 08/817,918 filed Jul. 10, 1997, which is a national phase filing of PCT international application No. PCT/FI94/00479 which has an International filing date of Oct. 245, 1994 which designated the United States, the entire contents of which are hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention concerns a polyolefin based thermoplastic elastomer which can be prepared without a separate vulcanization stage and which has polyacrylate as a dispersed phase and which has been achieved by polymerization of acrylate into the polyolefin matrix.  
           [0003]    Thermoplastic elastomers are polymers which have the desirable processing properties of thermoplastics but have the same physical properties a vulcanized rubbers. This combination of properties generates materials having segments that are soft and elastic with low glass transition temperature (tK) and a rigid, eventually crystalline, segment with a high glass transition temperature or a high melting point. The rigid and soft segments must be thermodynamically incompatible so that they form separate phases. Unlike conventional rubber, thermoplastic elastomers do not need a separate vulcanizing stage and can be processed using methods normally used with thermoplastics, such as extrusion, injection molding and blow molding. In addition, thermoplastic elastomers can also be reprocessed, for example when recycling material from the processing stage.  
           [0004]    Thermoplastic elastomers can be divided into two main groups, block copolymers and thermoplastic/elastomer blends. A well-known example of block copolymers, which are thermoplastic elastomers, is the anionically polymerized block copolymer of styrene and butadiene (SBS) and the hydrogenized form of the same (SEBS). When these polymers are at room temperature, the soft and elastic phase is the continuous phase and the rigid phase, polypropylene, is dispersed. Here, the rigid polystyrene gives the material its strength, but during processing the temperature is raised over the glass transition temperature of polystyrene when it melts and the material can flow. The SBS thermoplastic elastomer, however, has poor weather resistance because of the butadiene double bonds. In SBS and SEBS polybutadiene and its hydrogenated form is the continuous phase, consequently they both have low oil resistance. Additionally, SEBS is expensive and requires a complicated preparation method.  
           [0005]    Examples of materials that belong to the group of thermoplastic/elastomer blends are blends of polypropylene and ethylene/polypropylene rubber or ethylene/polypropylene/diene rubber. In these blends the rigid polypropylene phase is the continuous phase and the soft phase is dispersed, giving the material good oil resistance properties. These blends are made by blending the two main components and various additives in an extruder. Stabile phase separation results from curing the dispersed rubber phase (see, for example, U.S. Pat. No. 4,594,390 .  
           [0006]    The current invention describes a method to produce a thermoplastic elastomer with a polyolefin as a continuous phase and a rubber-like polyacrylate as a dispersed phase. This product is made in a reactor where crosslinking, if needed, can occur during polymerization. Thus, no separate vulcanization stage is needed. The resulting product has very good weather and oil resistance properties because the polyolefin is the continuous phase and because the elastomer is a polyacrylate. Hence, the current invention provides a method to produce a polyolefin based thermoplastic elastomer with a dispersed polyacrylate phase and without requiring a separate vulcanization stage.  
         SUMMARY OF THE INVENTION  
         [0007]    The object of the current invention is to provide a new thermoplastic elastomer comprising a polyloefin/polyacrylate blend that has the polyolefin as the continuous phase and the polyacrylate as a dispersed phase.  
           [0008]    A further object of the invention is to provide a new thermoplastic elastomer which maintains its dispersed polyacrylate structure during processing due to crosslinking of the dispersed elastic polyacrylate phase to the continuous polyolefin phase during polymerization.  
           [0009]    Another object of the current invention is to provide a method for preparation of the new thermoplastic elastomer without employing a separate vulcanization stage.  
           [0010]    The current invention provides for a polyolefin based thermoplastic elastomer with a dispersed polyacrylate phase that is polymerized into the polyolefin matrix. The invention fuirther provides for a method for its preparation without a separate vulcanization stage. The acrylate used in the current invention has elastic properties and a glass transition temperature that is below room temperature. The acrylate forms a dispersed phase in the polyolefin matrix and, because polymerization occurs by the free radical technique, part of the acrylate chains are crosslinked to adjacent polyolefin chains. This provides good adhesion between the continuous polyolefin phase and the dispersed polyacrylate phase. Crosslinking can be controlled using varying ratios of diacrylate and acrylate. This crosslinking is especially important in cases where low adhesion between the polyolefin matrix and the polyacrylate is expected, for example when homopolyethylene or polypropylene is used. Here, because of the crosslinking, the soft dispersed polyacrylate is maintained in its dispersed form during processing when the polyolefin melts and becomes fluid.  
           [0011]    The material could be produced by some of the methods given in the patent literature in which monomers are polymerized by free radical polymerization techniques into polyolefin matrix, e.g. by the Finnish patent 88170. In principal the acrylate monomer, and optionally diacrylate monomer, and the initiator are absorbed into polyolefin particles. The impregnation temperature is low enough so that no decomposition of the initiator occurs, yet high enough so that the monomer and the initiator can penetrate into the polyolefin particles. When all of the monomer and initiator have been absorbed, the temperature is elevated and the initiator decomposes and initiates the polymerization of the acrylate. The polyolefin particles swell to some extent (depending on the amount of monomer added) during the impregnation, but maintain their particle structure. The polyolefin particle structure is also maintained during polymerization.  
         DETAILED DESCRIPTION OF THE INVENTION  
       Polyolefin  
         [0012]    Useful polyolefins include high density polyethylene, low density polyethylene and linear low density polyethylene. The polyethylene can be a homopolymer or a copolymer. The co- monomer of ethylene can be vinyl acetate, vinyl chloride, propylene or some other α-olefin, C 1 -C 7 -alkylacrylate and -methacrylate, glycidylacrylate and -methacrylate, dienes such as hexadiene-1,4, hexadiene-1,5, heptadiene-1,6,2-methylpentadiene-1,4,octadiene-1,7,6-methylheptadiene-1,5 and polyenes such as octatriene and dicyclopentadiene. Also ethylene-α-olefin-polyene-terpolymeres are useful. Useful α-olefins include propylene, butene, pentene, isoprene, hexene or their mixtures and useful polyenes include hexadiene-1,4, hexadiene-1,5, heptadiene-1,6,2-methylpentadiene-1,4, octadiene-1,7,6-methyl-heptadiene-1,5, octatriene, dicyclopentadiene. In cases where an ethylene copolymer is used, at least 50% by weight must be ethylene.  
           [0013]    The polyolefin can also be comprised of polypropylene and its copolymers. Propylene copolymers must consist of over 50% by weight propylene and can be random- or block copolymers of propylene and ethylene. Also, other α-olefins can be used as co-monomers and also dienes such as hexadiene-1,4, hexadiene-1,5, heptadiene-1,6,2-methylpentadiene-1,4, octadiene-1,7,6-methylheptadiene-1,5 and polyenes such as octatriene and dicyclo-pentadiene.  
           [0014]    The polyolefin can be in any form, but preferably in the form of pellets with a diameter of 0.5-10 mm. Particle forms of the polyolefin facilitate after treatment washing and drying.  
         Acrylate Monomer  
         [0015]    Suitable monomers are acrylates and methacrylates whose polymers have low glass temperatures, that is, they are rubber-like at and below room temperature, preferably at temperatures below −20° C. The glass temperature of the polyacrylate specifies the lower operating temperature of the material; below the glass temperature the polyacrylate is rigid and inelastic and the elastomeric properties of the material are lost. Suitable acrylates are alkylacrylates having 1 or preferably 2 or more carbon atoms in the alkyl chain. Methacrylates having a glass temperature low enough are alkylmethacrylates having 4 or more, preferably 8 or more, carbon atoms in the alkyl chain. These monomers can be used alone or in mixtures of two or more monomers. The glass temperature of the final product can be tailored by adding small amounts of monomers having fewer carbon atoms in the carbon chain to the above mentioned monomers. One can further use acrylates and methacrylates as co-monomers, which in addition to an ester bond have other polar groups such as alkeoxy or hydroxy groups. Examples of these are methoxy- and ethoxy-acrylate, hydroxyethyl- and hydroxypropyl-methacrylate. By using these co-monomers the oil resistance of the product can be improved. Also, small amounts of other non-acrylate monomers that are polymerizable by free radical polymerization techniques can be co-polymerized with the above mentioned acrylates and methacrylates.  
         Amount of Acrylate  
         [0016]    In order to produce a material that is a thermoplastic elastomer the acrylate must be in the majority although the exact amount to be polymerized into the polyolefin depends on the exact polyolefin used and whether or not oil is added. Here, majority means at least 50%; preferably greater than 50%, more preferably at least 60%, yet more preferably at least 64%, and still more preferably at least 69%. According to this invention, a polypropylene based material needs 50-90% by weight acrylate when no oil or filler are added. Thus, the polypropylene represents 50-10% by weight. Without oil and filler addition the amount of acrylate can vary from 50-90% by weight for homopolyethylene, down to 20-90% by weight for polyethylene qualities which contain up to 30% by weight co-monomers. The Examples indicate the effect of the amount of acrylate on the softness of the final product.  
         Addition of Oil  
         [0017]    Adding oil also softens the final product, thus reducing the amount of acrylate needed to obtain a particular softness. The amount of added oil can be 0-40% by weight in the final product and can be added with the acrylate and initiator, allowing penetration of the oil into the polyolefin-polyacrylate particles during the impregnation and/or polymerization. Alternatively, oil can be added to the reactor after the finalized polymerization and can be impregnated into the polyolefin-polyacrylate particles at an elevated temperature. Yet another way to introduce oil into the polyolefin-polyacrylate particles is in an extruder. Suitable oils are those normally used to soften rubber, e.g. paraffinic, naphthenic, aromatic and synthetic oils as well as plasticizers for thermoplastics such as dioctylphthalat.  
         Addition of Fillers  
         [0018]    Fillers can be added to modify the final product&#39;s properties. For example, fillers can raise the operating temperature and rigidity. The filler can be added to the polyolefin- polyacrylate blend in the extruder or can be included with the polyolefin used as raw material for the polymerization. Conventional fillers such as talc, caolin, CaCO 3  and silica can be used and can be 0-70% by weight in the end product.  
         Composition of the End Product  
         [0019]    The end product can also contain oil and fillers besides polyolefin and polyacrylate. Consequently, the amount of polyolefin and polyacrlate in the end product can vary within wide margins depending on the amount of oil and fillers used and also on the chosen polyolefin.; If the polyolefin is polypropylene, the ratio of polypropylene/polyacrylate can be 0.1 to 2. If the polyolefin is polyethylene, the ratio can vary from from 0.1 to 5.  
         Crosslinking the Polyacrylate  
         [0020]    Some acrylates spontaneously form gels without any diacrylate use, for example butylacrylate, and may eliminate the need to use diacrylate for crosslinking. The need for diacrylate also depends on the degree of adhesion between the discrete dispersed polyacrylate phase and the continuous polyolefin phase. As the adhesion between the phases increases the tendency of the dispersed polyacrylate to agglomerate and build bigger phase structures decreases. For example, if polyethylene, which contains polar groups, is used the adhesion can be so good that only small amounts or no diacrylate at all is needed. On the other hand, if a homopolyethylene or polypropylene is used, the adhesion between the phases is low and the polyacrylate must be crosslinked with diacrylate in order to enable processing of the dispersed polyacrylate without agglomeration and forming large polyacrlyate blocks. Low adhesion can also lead to phase invasion where the polyacrylate becomes a continuous or at least a co-continuous phase with the polyolefin. Crosslinking is preferably done in the reactor with an acrylate having two or more double bonds that can interact with different polyacrylate chains. Examples of suitable crosslinking agents are hexanediol diacrylate or dimethylacrylate. Generally the crosslinking agent is 0-15% by weight, based on the amount of acrylate. Other monomers having two or more double bonds, such as divinylbenezene, can also be used.  
         Initiator  
         [0021]    Initiators conventionally used in free radical polymerization of vinyl monomers, such as organic peroxides are suitable for the acrylate polymerization. Examples include benzoylperoxide,lauroylperoxide, t-butylperbenzoate, t-butyl-peroxy-2-ethylhexanate, t-butylperoxide, dicumylperoxide, di-t-butylperoxide, bis(t-butylperoxyisopropyl)benzene, t-butylperoxyisopropylcarbonate, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, and azo compounds like azobisisobutyronitrile and azobisdimethylvaleronitrile.  
           [0022]    More than one initiator can be used simultaneously so that the polymerization starts at a low temperature with a “low temperature initiator” and continues with a “high tempeature:. initiator” at a higher temperature. The amount of the intiator can be between 0.001 and 2% by weight, preferably between 0.1 and 1% by weight, based on 100 weight parts of monomer.  
         Production, Including Impregnation and Polymerization  
         [0023]    In principal, the production of this polyolefin-polyacrylate material can be made by the methods presented in the patent literature in which the acrylate and the initiator are first initiated into polyolefin particles and the acrylate is thereafter polymerized by elevating the temperature. The impregnation of the acrylate and the initiator can thus be made in the total absence of water, by adding some water, by adding water when more than half of the acrylate has been impregnated (these three methods are in principal described in the Finnish patents F185496, F186642 and F188170) or in the presence of the total amount of water (as in U.S. Pat. No. 4,412,938). Impregnation and polymerization can also be conducted simultaneously by slowly adding the acrylate and initiator to a water suspension containing polyolefin particles over the course of several hours and at an elevated temperature. (see German patent DE 2,907,662).  
           [0024]    Finnish patent F188170 presents an advantageous method whereby a maximum of about 65% by weight of acrylate is impregnated and polymerized into polyolefin in the polymerization stage. For softer elastomer, additional polyacrylate can be impregnated into the product obtained from the first polymerization stage, followed by a second polymerization. Using this approach the polyacrylate content can gradually be raised close to 100%. It is not necessary, however, to use totally independent or separate polymerizations. For example, near the end of the first polymerization, the temperature can be lowered to the impregnation temperature and the desired amount of acrylate and initiator can be pumped in. After these have been absorbed into the particles, the temperature is raised and the acrylate polymerized.  
           [0025]    When polymerization is conducted in two or more stages and crosslinked polyacrylate is desired, the first polymerization is conducted without diacrylate. Here, the polyacrylate forms a discrete dispersed phase during the polymerization stage. During the other polymerization stage the added acrylate and diacrylate tend to migrate to the polyacrylate particles already formed in the polyolefin matrix, and crosslinking occurs there. This crosslinking is mainly between the added acrylate and diacrylate, but since this reaction occurs during polymerization in the presence of the existing polyacrylate particles, entanglements between the polymerizing strands and these preexisting particles are formed, creating physical crosslinks.  
         Properties of the Polvmerization Product  
         [0026]    The final product is a thermoplastic elastomer with a continuous phase of polyolefin crosslinked to a discrete dispersed phase of a rubber-like polyacrylate. The polyacrylate phase is in the majority. This final product maintains its two discrete phases during melt-processing. Other properties include: a Shore A hardness value greater than 50, preferably greater than 60, even more preferably greater than 70, 80 or 90 (test method is ISO 48), a modulus 100% of at least 0 Mpa, preferably greater than 1 Mpa, more preferably greater than 2 Mpa, even more preferably greater than 3 Mpa (test method is 37/1 mm/min), tensile strength of at least 1.9 MPa, preferably at least 3.2 MPa, more preferably at least 5.1 MPa, even more preferably at least 6.3, 7.1 or 8.4 MPa (test method is ISO 37), an elongation at break of at least 75%, preferably at least 107%, more preferably at least 209%, even more preferably at least 354%, 449% or 528% (test method is ISO 37), and a tear strength of at least 0 kN/m, preferably 2 kN/m, more preferably at least 8 kN/m, even more preferably at least 8 kN/m, 16 kN/m or 20 kN/m (test method is ISO 37).  
           [0027]    The polymerization product has especially good oil resistance, weather resistance and ageing resistance due to the polyacrylate elastomer. The properties of the thermoplastic elastomers produced according to this patent depend on the polyolefin used: homo, block or random polypropylene, homopolyethylene or polyethylene containing co-monomers. The choice of polyeolefin especially influences temperature resistance, chemical resistance and adhesion properties. The acrylate type, amount and crosslinking density affect the hardness, toughness and elasticity of the final product. Ethylene based products are characterized by good heat and oil resistance. Fillers, which can be added to the starting polyolefin, allow tailoring of the product&#39;s properties.  
         Product Usage  
         [0028]    The material produced of the current invention can be used in applications which other thermoplastic elastomers or conventional rubber is used, for example in the construction industry (sealing lists and packages), in the motor industry (protection bellow at power transmission points and interior material for instrument panels) and in the electrical industry (material for cables, contacts and different cases). This material can also be used for diverse mechanical articles like handles, wheels and sheaths.  
           [0029]    The material can be processed by conventional processing methods used for thermoplastics, such as extrusion, injection molding and blow molding. Since polyolefin is the continuous phase, the material is well suited for co-extrusion with polyolefins. In processing, conventional additives like antioxidants, filler and oil can be added. 
       
    
    
     EXAMPLES  
       [0030]    Polyolefin pellets, acrylate, initiator and, in some cases 1,6-hexanediole diacrylate, were added to the reactor. The reactor was filled and emptied three times with 7-8 bar nitrogen in order to remove oxygen from the reactor. After that, the temperature was raised to the impregnation temperature and kept there, stirring continuously, until the mojor port of the acrylate and the initiators were impregnated. The impregnation time was 1-3 hours depending on the polyolefin quality. Thereafter, the suspension water, also rinsed with nitrogen, was added. The suspension water contained tricalsiumphosphate and sodiumdodecylbenzenesulphonate as a suspension agent. The temperature of the suspension water was the same as the impregnation temperature. After the water addition the temperature was raised so much that the initiator started to decompose and initiate the polymerization. The polymerization took 7-12 hours depending on the polyolefin quality. After polymerization, the product was washed and dried. Several different polyolefin-polyacrylate materials were made according to this model, see Table 1. All polypropylene based materials having more than 50% by weight acrylate were made in two stages so that the product from the first stage contained 50% by weight acrylate. Experiment 9 was also made in two stages and experiment 10 was made in three stages. The structure with the dispersed polyacrylate domains can be seen from FIG. 1, where the product from the first polymerization stage of experiment 15 has been photographed by a transmission electron microscope. In the picture, the dark dispersed phase is polyacrylate and the light continuous se is polypropylene. The diameter of the polyacrylate particles is about 0.5 μm.  
                                                                                                   TABLE 1                           Experiments 1-16.                                Diacry-                       Exp   Polyolefine 1         Acrylate   Weight   late 6     Initiator   Impreg.   Polym.   Gel 2         Nr   quality   MI 3     type 4     %   w-%   type 5     |C   |C   %                    1   EVA28   5   EHA   40   —   AIBN, BPO   37   55-100   62       2   EVA28   5   EHA   50   —   AIBN, BPO   41   55-100   56       3   EVA18   10   EHA   50   —   BPO, BPIC   51   75-115   61       4   EVA9   8   EHA   50   —   BPIC   69   90-120   54       5   EBA27   4   EHA   50   —   AIBN, BPO   44   55-100   77       6   EBA17   7   EHA   50   —   BPO   72   70-100   70       7   EBA17   7   BA   50   —   BPIC   61   85-115   55       8   EBA17   7   BA   50   1.0   BPIC   69   85-115   60       9   EBA7   1   BA   64   0.5   t-BPB   86   90-120   83       10   LLDPE   65   BA   69   1.6   DHBP   101   110-135    53       11   Random PP   20   BA   50   0.1   DYBP   116   125-150    53       12   Random PP   20   BA   68.5   1.6   DYBP   112   130-150    74       13   Random PP   20   BA   67   3.1   DYBP   108   130-150    67       14   Random PP   20   BA   74   1.5   DYBP   117   130-150    74       15   Random PP   20   EHA   68.4   1.6   DYBP   116   130-150    64       16   Block PP   40   BA   67   3.0   DYBP   120   135-150    76                                                                  
 
         [0031]    The polymer materials made according to Table 1 were injection moulded to sheets having the size of 80×80 mm and the thickness of 2 mm, at 165-205 | C, depending on the polyolefine used. The necessary test bars were punched from the sheets. The mechanical properties are in Table 2. Elongation at break and tensile strength have been measured from test rods which are punched transverse to the flow direction of the injection moulding.  
                                                                                                           TABLE 2                           Mechanical properties of the materials of the experiments 1-16.                                    elong.   tensile                                   Di-       at   stre-           Exp.   Polyolefine   Acrylate       Acr.   Gel   break 1     ngth 2         compr.   tension       Nr   quality   type   %   w-%   %   %   MPa   IRHD 3     set 4  %   set 5  %                    1   EVA28   EHA   40   —   62   158   5.5   65   —   24       2   EVA28   EHA   50   —   56   177   3.2   52   —   17       3   EVA18   EHA   50   —   61   107   2.7   61   —   20       4   EVA9   EHA   50   —   54   90   3.2   75   —   23       5   EBA27   EHA   50   —   77   75   1.9   56   —   16       6   EHA17   EHA   50   —   70   449   5.4   67   —   16       7   EBA17   BA   50   —   55   528   6.1   75   30   33       8   EBA17   BA   50   1.0   60   354   7.1   76   20   25       9   EBA7   BA   64   0.5   83   209   6.3   75   22   16       10   LLDPE   BA   69   1.6   73   175   5.1   82   38   37       11   Random PP   BA   50   0.1   53   198   8.4   97   —   66       12   Random PP   BA   68.5   1.6   74   169   7.3   90   43   40       13   Random PP   BA   67   3.1   67   142   8.9   92   31   32       14   Random PP   BA   74   1.5   74   128   5.6   81   26   16       15   Random PP   EHA   68.4   1.6   64   127   5.9   88   43   43       16   Block PP   EHA   72.5   3.5                                                          
 
         [0032]    The amount of polyacrylate has the biggest effect to the hardness of the product, the higher amount of polyacrylate the softer product, see experiments I and 2 and experiments 11-15. To the mechanical properties, the polyolefine quality also effects most to the hardness, compare 2, 3 and 4 as well as 5 and 6. The amount of diacrylate affects all mechanical properties. The higher amount of diacrylate improves strength, compression set and tension set but decreases the elongation at break, compare 7 and 8 as well as 12 and 13.  
         [0033]    In table 3 the product from the experiment 7 is compared with commercial SBS-quality, Dexcos Vektor-241 ID, at 55 | C. These both have about the same hardness and the same highest operating temperature, 60-70 | C. From the table it can be seen that SBS has considerably lower oil resistance than the product from the experiment 7. Also, in table 3 is compared the product from the experiment 13 with the thermoplastic elastomer Santopren 201-80 at 100 | C. The product from the experiment 13 has polypropylene as a polyolefine and a continuous phase and it can therefor regarding to the temperature resistance, be compared with Santopren which also had polypropylene as a continuous phase. Santopren has ethylene-propylene-diene rubber as an elastomeric phase. The both have same hardness. From the table it can be seen that the product from the experiment 13 has considerably better oils resistance than Santopren in ASTM 1—and ASTM2-oils. In ASTM3-oil Santopren is a little better.  
                                                                                   TABLE 3                           Oil resistance, measured as swelling, of the material made according to this invention       compared with commercial thermpolastic elastomers, by ISO 1817. For experiment 7 and SBS       was used 55 | C and for experiment 13 and Santopren was used 100 | C.                ASTM1   ASTM2   ASTM3            Exp       Hardness   1 day   3 days   7 days   1 day   3 days   7 days   1 day   3 days   7 days       Nr   Material   IRHD   %   %   %   %   %   %   %   %   %                7   EBA17-PBA   75    8   14   16   14   28   34   51   89   —           SBS, Vektor-2411D   82   35   50   52   98   127    —   —   —   —       13   PP-PBA   92   —    8   10   —   22   24   —   58   58           Santopren 201-80   91   —   18   19   —   31   31   —   52   54                  
 
         [0034]    The aging resistance of the material at high temperature was tested by aging the material at 70 | C during 168 hours. The elongation at break and tensile strength were measured for unaged and aged materials from test bars punched in flow direction. The material from experiment 7 was compared with a commercial SBS-quality, Enichem Europrene SOL T166, and with a commerical SEBS-quality, Neste polymer Compounds 6503. These three materials are comparable by hardness and operating temperature. From table 5 it can be seen that the material from experiment 7 has considerably better aging resistance at an elevated temperature. Apart from the fact that the material from experiment 7 was not stabilized with antioxidants. In the table there is also compared a polypropylene based material made according to example 13 with Santopren-quality 201-80.  
                                                                           TABLE 5                           Changing of the elongation at break and tensile strength during aging at 70 | C for       168 hours. The chance is given as per cent chance between the unaged and aged       materials.                                Chance,   %       Expr       Hardness   Elongation   Tensile   Elongation   Tensile       Nr   Material   IRHD   at break %   strength MPa   at break   strength                     7   EBA17-PBA   75   129   5.7   +4.9   +7.5           SBS 166   75   540   11.3   −15.2   −36.2           SEBS 6503   75   305   5.8   −21.0   −4.9       13   PP-BPA   91   126   10.3   −15.4   +5.1           Santopren 201-80                  
 
       Experiments 17-20  
       [0035]    A material made according to experiment 7 but with a diacrylate amount 0.5 % by weight, was filled with three different fillers, 23-41% by weight in the end product, in a screw extruder at 200 | C. From table 4 can be seen that hardness is rising together with a rising filler content. Other mechanical properties remain unchanged when compared with the unfilled material of experiment 17.  
                                                             TABLE 4                           Influence of fillers on the mechanical properties of the product of experiment 17.                                    Elong.                                       Diacr.       at           Compres-   Tension       Exp   Polyolefine   Acrylate       Weight   Gel   break 1     Tensile       sion set 4     set 5         Nr   quality   type   %   %   %   %   str. 2  MPa   IRHD 3     %   %               17   EBA17   Ba   50   0.5   63   360   6.6   78   28   32       18 4     EBA17   BA   50   0.5   —   270   6.2   84   24   32       19 7     EBA17   BA   50   0.5   —   238   6.0   87   30   39       20 4     EBA17   BA   50   0.5   —   322   7.1   87   27   41                                                                                  
 
       Experiments 21, 22 and 23  
       [0036]    To a material which is made exactly according experiment 13 was added 10 % by weight oil and 0.3% by weight antioxidant, Irganox 1520, in a single-screw extruder at 205 | C. A paraffin oil, Nypar 40 (Neste-Alfa Oy), and a naphthenic oil, Nytex 840 (Nyn Petroleum) were used as oils. The composition of the end product is thus 10% by weight oil, 63% by weight polybutylacrylate and 27% by weight polypropylene. The material was injection moulded to sheets from which test bars were punched at flow direction. From the results in table 6 can be seen that by oil addition the material has become softer without the loss of other mechanically good properties, compression set and tension set have even improved.  
                                                 TABLE 6                           Addition of 10% by weight oil to a polypropylene-polyacrylate material.                            Tensile                           % by   Elongation at   strength 2         Compression       Exp.   oil quality   weight   break 1  %   MPa   IRHD 3     set 4  %   Tension set 5  %               21   —   —   138   9.3   93   37   32       22   Nytex 840   10   131   8.0   88   33   27       23   Nypar 40   10   142   8.5   89   33   25                                                          
 
       Experiments 24 and 25  
       [0037]    These experiments were made in the same way as experiment 13 with the difference that to the reactor it was charged 6% by weight oil together with the acrylate in the second polymerisation stage. The whole anount of oil was absorbed into the pellets and the end product*s composition is thus 6% by weight oil, 70% by weight polybutylacrylate and 24 % by weight polypropylene. From the test results in table 7 down can be seen that the material, compared to experiment 13 becomes considerably softer and compression set becomes a little better. Elongation at break and tensile strength decrease a little.  
       Experiment 26  
       [0038]    This experiment was made in the same way as experiments 24 and 25 with the difference that oil was added in the both polymerisation stages, 6% by weight in the first and 11% by weight in the second polymerisation stage. This gives the final composition: 14% by weight oil, 30% by weight polypropylene and 56% by weight butylacrylate (inclusive 2.2 % by weight diacrylate). Oil was Nytex 940. Test results can be seen in table 7 down.  
       Experiments 27 and 28  
       [0039]    As starting material for oil and filler experiments was used a polypropylene based material which was made according to experiment 13, with the difference that the amount of butylacrylate in the first polymerisation stage was 37 % by weight and in the second polymerisation stage 34 % by weight (+3 % by weight). This gives an end composition of 60 % by weight polybutylacrylate and 40, including 3% by weight diacrylate.  
                                                             TABLE 7                           Influence of oil and fillers to the properties.                                        Tensile                               PP   PBA   Filler   Elong. at   str. 2         Compression   Tension set 5         Exp.   Oil quality   w-%   w-%   w-%   w-%   break 1  %   MPa   IRHD   set 4  %   %               24   Nypar 40    6   24   70   —   118   6.9   84   31   31       25   Nytex 840    6   24   70   —   126   7.5   85   27   29       26   Nytex 840   14   30   46   —       27   Nypar 40   20       28   Nypar 40   20