Abstract:
A two-step process for production of thermoplastic elastomer, which comprises dynamically vulcanizing polypropylene and olefinic rubber in the presence of peroxide (1st step), and dynamically vulcanizing the vulcanized mixture, polypropylene and halogenated butyl rubber in the presence of zinc oxide (2nd step). In another method (a) polyolefin and olefin rubber are dynamically cross-linked in the presence of an organic peroxide and (b) in a separate second operation a dynamically vulcanized blend comprising polyolefin and halogenated butyl rubber is prepared and mixed with (a) to disperse (a) and (b) in one another. The thermoplastic elastomer composition is useful in materials for parts of automobiles. 
     In an example, pp 9 wt. % parts, EPDM 21 wt. % parts, peroxide 0.3 wt. % part and divinylbenzene 0.5 wt. % part were blended and supplied to the first hopper (1) of biaxial extruder as shown in a figure. In the first blending zone (2), temperature and residence time are 200° C. and 60 seconds respectively. And then, to the second hopper (3) of the extruder, pp 50 parts and the vulcanized product (EPDM+chlorinated butyl rubber) 20 parts were supplied and extruded in the heat blending zone (4) above mentioned mixture for 30 seconds of residence time. The physical properties of the composition are MFR: 18, Flex. Mod.: 3,300 (23° C.) and 1,150 (80° C.), Tens. at break: 105, Elong.: 420%, Izod.: No break (room temperature) and 25 (-40° C.) Shore-D: 58, Flow marks: good and paintability: 100/100.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method for preparation of a thermoplastic resin composition with good impact-resistance and, in particular, to a method for preparation of a thermoplastic resin composition containing two different crosslinked rubbers uniformly dispersed in a polyolefin phase, preferably polypropylene. 
     A thermoplastic elastomeric composition comprising a polyolefin and a partially crosslinked rubber component has excellent properties, such as heat-resistance, mechanical strength, softness and elasticity, and such compositions are being widely utilized for formation of large-sized shaped articles such as bumpers for cars. 
     Regarding thermoplastic elastomers of this type, JP-B-No. 53-34210 (the term &#34;JP-B&#34; as used herein means an &#34;examined Japanese patent publication&#34;) illustrates a thermoplastic blend formed by dynamically partially curing from 60 to 80 parts by weight of a monoolefin copolymer rubber and from 40 to 20 parts by weight of a polyolefin plastic. The thermoplastic blend may be obtained by mixing the said components together with a curing agent and dynamically mixing them at the curing temperature to cure the same. 
     In addition, there were proposed, for example, a partially crosslinked composition comprising a polyolefin and two kinds of rubber compositions (JP-B-No. 54-23702), a partially crosslinked composition obtained by incorporating a polyolefin into a composition formed by processing a polyolefin and a rubber component in the presence of an organic peroxide (JP-B-No. 56-15743), and a method for preparation of the said composition (JP-B No. 56-15740). 
     However, organic peroxides to be used in the preparation of the above-mentioned partially crosslinked thermoplastic elastomer composition as a crosslinking agent are too strongly reactive so that it is difficult to control the crosslinking degree in the composition. Moreover, there are still other problems that the physical properties of the crosslinked composition would be reduced because of the cleavage of molecular chains following crosslinking in the composition. The resulting low molecular weight substances would have a bad influence on the coatability of the composition, and additionally the shaped article from the composition would have a rough surface because of the partial gelation in the composition. In addition, free radicals may be present in the shaped article because of the organic peroxide used so that the heat stability of the article would lower. This is still another problem. 
     In order to overcome these problems, JP-A-No. 62-50354 (the term &#34;JP-A&#34; as used herein means an &#34;unexamined published Japanese patent application&#34;) illustrates an olefin soft resin composition obtained by hot-melting and mixing a mixture comprising (A) from 10 to 90 parts by weight of a polypropylene, (B) from 90 to 10 parts by weight of a halogenated butyl rubber (provided that (A)+(B)=100 parts by weight), (C) from 10 to 120 parts by weight of an olefin rubber and (D) from 5 to 120 parts by weight of a mineral oil softening agent in the presence of (E) a metal oxide and/or a metal chloride and then uniformly incorporating (F) a polyolefin into the said blend. 
     However, it has been found that the composition of JP-A-No. 62-5054 is still insufficient with regard to properties which are required for bumpers or the like parts of cars, though the composition has fairly good shapeability, impact-strength, coatability, softness and mechanical strength. 
     Accordingly, the object of the present invention is to provide a method of preparing a thermoplastic resin composition having more improved physical properties with respect to the above-mentioned points. 
     SUMMARY OF THE INVENTION 
     A method for preparation of a thermoplastic resin composition comprising from 80 to 60% by weight of polyolefin and from 20 to 40% by weight of crosslinked olefin rubber and further comprising halogenated butyl rubber in an amount of from 5 to 30 parts by weight to 100 parts by weight of the total of said polyolefin and said crosslinked olefin rubber, characterized in that 
     (a) a first blend of polyolefin and crosslinkable olefin rubber are dynamically heat-treated in the presence of an organic peroxide to form a dynamically vulcanized composition, and 
     (b) polyolefin and halogenated butyl rubber and a crosslinking agent for said halogenated butyl are added to said first blend and dynamically heat-treated so as to crosslink said halogenated butyl rubber. 
     Alternatively, the first and second blend components can be independently prepared and blended with one another. Preferably, the halogenated butyl is chlorobutyl or bromobutyl and the crosslinking agent therefor is a metal oxide such as zinc oxide. The resulting composition has improved physical properties and is particularly useful as automotive parts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows an outline of a biaxial extruder useful for performance of the method of the present invention, in which (1) is a first hopper, (2) is a first mixing zone, (3) is a second hopper and (4) is a second mixing zone. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present inventors earnestly studied the above-mentioned problems and as a result have found that a thermoplastic resin composition which is excellent in the above-mentioned properties may be obtained by first crosslinking a mixture of a polyolefin such as polypropylene and a crosslinking olefin rubber in the presence of an organic peroxide and then blending a halogenated butyl rubber and polypropylene into the resulting mixture and crosslinking the halogenated butyl rubber in the presence of a metal oxide and/or a metal halide, or blending a mixture of cross-linked halogenated butyl rubber and polypropylene into the first mixture. Accordingly, the present inventors have achieved the present invention. 
     Precisely, the first method of the present invention for preparation of a thermoplastic resin composition is characterized in that (a) polypropylene and crosslinkable olefin rubber are dynamically heat-treated in the presence of an organic peroxide to form a mixed blend, and (b) polypropylene and halogenated butyl rubber and a crosslinking agent for the halogenated butyl rubber, e.g., metal oxide and/or metal chloride, are added to the blend from (a) and dynamically heat-treated so as to crosslink the halogenated butyl rubber. 
     The second method of the present invention for preparation of a thermoplastic resin composition is characterized in that (a) polypropylene and a cross-linking olefin rubber are dynamically heat-treated in the presence of an organic peroxide to form a first mixed blend, and (b) a second blend comprising polypropylene and halogenated butyl rubber crosslinked with e.g., a metal oxide and/or metal chloride is added to the first blend and mixed. 
     The materials to be used in the method of the present invention for preparation of a thermoplastic resin composition are described below. 
     (A) Polyolefin 
     The polyolefin, preferably polypropylene, for use in the present invention is a homopolymer of propylene or a random or block copolymer consisting essentially of a propylene copolymer copolymerized with an alpha-olefin such as ethylene, 1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene. The melt flow rate (MFR) is from 0.3 to 80 g/10 min, preferably from 3 to 70 g/10 min, more preferably from 15 to 70 g/10 min. 
     The polyolefin component, in particular poly-propylene, has a function for improving the heat-resistance and the mechanical strength of the thermoplastic resin composition. 
     (B) Crosslinkable Olefin Rubber 
     This includes copolymer rubbers made of two or more monoolefins such as ethylene, propylene, 1-butene, 1-hexene and/or 4-methyl-1-pentene (typically, ethylenepropylene copolymer rubber), as well as copolymer rubbers made of two of the above-mentioned monoolefins (ethylene and propylene are preferred) and a non-conjugated diolefin such as dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene or ethylidene- norbornene or a conjugated diolefin such as butadiene or isoprene. This further includes polyisoprene and nitrile rubber. The olefin rubber preferably has a Mooney viscosity ML1+8 (127° C.) of from 5 to 300, an iodine value of 30 or less and an ethylene content of from 35 to 85% by weight. 
     The crosslinked olefin rubber component exists in the composition as a partially crosslinked rubber and improves the heat-resistance properties, the mechanical strength, the impact-strength and the softness of the composition. 
     (C) Halogenated Butyl Rubber 
     This means a halogenated isobutylene-isoprene copolymer rubber. The proportion (molar ratio) of iso-butylene to isoprene in the copolymer is generally 99.5/0.5 to 96/4. 
     Halogens useful in the present invention include chlorine and bromine, and the halogen content is generally from about 0.5 to about 4.0% by weight. The halogenated butyl rubber preferably has a Mooney viscosity ML1+8 (100° C.) of from 30 to 100, and unsaturation preferably from about 0.5 to about 4.0 mol %. 
     The halogenated butyl rubber component is a rubber which may be crosslinked with a metal oxide or metal chloride. After crosslinking, it is dispersed in the composition as a crosslinked rubber, which functions to improve the abrasion-resistance and scratch-resistance, the heat-resistance, the oil-resistance, the rubber elasticity, the gas-impermeability and the slipping resistance. 
     (D) Organic Peroxide 
     Organic peroxides to be used for crosslinking olefin rubbers are those having a half-life temperature of from about 160° to about 220° C., which include, for example, di-tert-butylperoxide, dicumylperoxide, benzoylperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane, etc. 
     For partial crosslinking of the olefin rubber with the above-mentioned peroxide, it is desired that a cross-linking aid such as p,p&#39;-dibenzoylquinone-dioxime or divinylbenzene is used. 
     The organic peroxide acts to partially crosslink the crosslinking olefin rubber thereby to improve the high temperature strength of the composition. The crosslinking aid acts to uniformly and mildly conduct the crosslinking reaction. 
     (E) Metal Oxide, Metal Chloride 
     The metal oxide for use in the present invention, includes zinc oxide, magnesium oxide, lead oxide and calcium oxide, and zinc oxide is preferred. 
     The metal chloride for use in the present invention, includes zinc chloride and tin chloride. In order to prevent the mould and other devices from being corroded by a free halogen during the process, it is desired to use magnesium oxide as a halogen-inactivating agent. 
     In addition, the following components are preferably incorporated into the composition of the present invention. 
     (F) Mineral Oil Softening Agent 
     This is a high boiling point petroleum fraction which is to be used for the purpose of lowering the hardness of the vulcanized rubber and of increasing the softness and elasticity. As examples, there are paraffinic, naphthenic and aromatic mineral oils. In particular, paraffinic and naphthenic mineral oil softening agents are preferred for use in coating compositions, since these do not have a negative influence on the coatability of the compositions. 
     (G) Others 
     In addition to the above-mentioned components, the composition of the present invention may further contain stabilizers such as antioxidants; ultraviolet absorbents and rust inhibitors for metals; additives such as lubricants, antistatic agents; electrical characteristic-improving agents; flame-retardants; processibility-improving agents and pigments; as well as inorganic fillers such as talc, calcium carbonate, barium sulfate and calcium silicate. 
     The manufacturing process of the thermoplastic resin composition of the present invention is as follows: 
     (1) First Step 
     Polyolefin, preferably polypropylene, and a cross-linkable olefin rubber are dynamically heat-treated in the presence of an organic peroxide and optionally a cross-linking aid to crosslink the olefin rubber. The dynamic heat-treatment is preferably conducted by mixing the components in an extruder or the like at 170° to 220° C. The mixing time (residence time) is from 30 to 120 seconds, preferably from 60 to 120 seconds. 
     When the subsequent second step is carried out continuously, an extruder having two feed ports (hoppers) is used. The extruder has, as shown in FIG. 1, a first hopper (1), a first mixing zone (2), a second hopper (3), and a second mixing zone (4). The above-mentioned materials as fed from the first hopper (1) are mixed in the first mixing zone, whereupon the condition is to be so defined that almost all the organic peroxide is to be consumed in the said first mixing zone (2) in order that any remaining organic peroxide would not act to decompose the halogenated butyl rubber to be fed from the second hopper (3). 
     The polypropylene to be used in the first step is from 3 to 15% by weight on the basis of the final thermoplastic resin composition (hereinafter referred to as &#34;final product&#34;), and the crosslinking olefin rubber is from 5 to 30% by weight on the basis of the final product. The organic peroxide is added in a proportion of from 1 to 4 parts by weigh to 100 parts by weight of the crosslinkable olefin rubber. As a preferred range of the respective components, the polypropylene is from 3 to 10% by weight, the crosslinking olefin rubber is from 5 to 20% by weight, and the organic peroxide is from 1.5 to 4 parts by weight to 100 parts by weight of the crosslinking olefin rubber. 
     (2) Second Step 
     Polyolefin, preferably polypropylene, halogenated butyl rubber and metal oxide or metal chloride are fed into the extruder of FIG. 1 from the second hopper (3) so that these are mixed together with the blend from the first mixing zone (2). In this step, the halogenated butyl rubber is crosslinked with the metal oxide and/or metal chloride, since almost all the organic peroxide as fed from the first hopper (1) was consumed in the first step. Regarding the dynamic heat-treatment in the second step, the heating temperature is generally from 170° to 220° C. and the residence time is from 30 to 120 seconds. Preferably, the heating temperature is from 180° to 200° C., and the residence time is from 30 to 60 seconds. 
     In the second step, a crosslinking olefin rubber may be added in addition to the above-mentioned components, and a mineral oil softening agent may also be added so as to improve the softness of the resulting composition. In addition, a rubber which may be decomposed by an organic peroxide, such as polyisoprene rubber, may also be added, and if desired, a halogen-inactivating agent, an anti-oxidant and other additives may also be added. 
     Regarding the amounts of the respective components in the second step, the polypropylene is from 10 to 70% by weight on the basis of the final product, the halogenated butyl rubber is from 2 to 30% by weight; and preferably, the polypropylene is from 30 to 50% by weight, and the halogenated butyl rubber is from 3 to 15% by weight. When a crosslinking olefin rubber is added, this is from 5 to 30% by weight, preferably from 5 to 15% by weight, on the basis of the final product. The mineral oil softening agent, if added, is from 2 to 15% by weight, preferably from 2 to 8% by weight, on the basis of the final product. 
     The metal oxide and/or metal chloride is from 20 to 40 parts by weight, preferably from 20 to 25 parts by weight, in all to 100 parts by weight of the halogenated butyl rubber. 
     In the second step, the polyolefin, halogenated butyl rubber and metal oxide and/or metal chloride and other additives are fed from the second hopper (3) so that these may directly be mixed together with the blend from the first mixing zone (2). Alternatively, the components for the second step are previously blended and then the resulting blend may be fed from the second hopper (3). In the latter case of previous blending the components, the respective components are weighed as indicated above and are blended in a separate extruder or Banbury® mixer. 
     As still another process, a part of the polypropylene to be added and the halogenated butyl rubber are melted and mixed in the presence of a metal oxide and/or metal chloride so that the halogenated butyl rubber is crosslinked, and the resulting blend is fed into the second hopper (3) together with the balance of the polypropylene (and optionally together with a crosslinkable olefin rubber and other components, if necessary), whereby the mixture is mixed together with the first blend from the first mixing zone (2). 
     EXAMPLES 
     The present invention will be explained in greater detail with reference to the following examples. 
     In the examples and comparative examples, the physical properties of products were measured as mentioned below. 
     (1) MFR: JIS K 7210 (load 2.16 kg, 230° C.) 
     (2) Tensile breaking strength and tensile breaking elongation: JIS K 6301 
     (3) Flexural Modulus: JIS K 7203 
     (4) Izod Impact Strength: JIS K 7110 
     (5) Shore Hardness: JIS K 7215 (D method) 
     (6) Mouldability: 
     (i) Molding Condition: 
     Injection Moulding Machine (manufactured by Mitsubishi Natoco Co.), 350 MV×L 40 
     Injection Moulding Temperature: 230° C. 
     Injection Pressure: 
     Primary pressure 800 kg/cm 2   
     Secondary pressure 500 kg/cm 2   
     Injection Time: 13 seconds 
     Moulding Cycle: 38 seconds 
     Gate: Side gate 
     Moulded Body: 3 mm×100 mm×350 mm plate 
     (ii) Evaluation: 
     O: No flow mark. 
     :Slight flow marks. 
     X: Extreme flow marks. 
     (7) Coatability 
     Coating Step 
     A test sample was washed with a trichloroethane vapour for one minute, and then this was coated with a primer (RB-291, manufactured by Nippon Bee Chemical Co.) and baked at 100° C. for 30  minutes. Next, this was further coated with urethane paints (R-257, manufactured by Nippon Bee Chemical Co.) and baked at 100° C. for 30 minutes. 
     Evaluation 
     The thus coated sample was tested by cross-cut tape-peeling test in accordance with JIS K 5400. 
     Materials used in the following Manufacture Examples, Examples and Comparative Examples were as follows: 
     Polypropylene: 
     Block polypropylene having MI of 70 g/10 min and ethylene content of 7% by weight. 
     Ethylene-propylene-diene Copolymer (EPDM): 
     V-5630 manufactured by Exxon Chemical Co., having ethylene content of 65% by weight, oil content of 30 phr and Mooney viscosity of ML1+8 (127° C.) of 35. 
     Ethylene-propylene Rubber (EPR): 
     MD 806 manufactured by Exxon Chemical Co., having ethylene content of 60% by weight and Mooney viscosity ML1+8 (127° C.) of 30. 
     Chlorinated Butyl Rubber (CIIR): 
     Chlorobutyl-1066 manufactured by Exxon Chemical Co., having Mooney viscosity ML1+8 (125°) of 55. 
     Organic Peroxide: 
     Perhexyne-2,5B (2,5-dimethyl-2,5-di(t-butylperoxy) hexyne). 
     Crosslinking Aid: 
     Divinylbenzene. 
     Styrene-ethylene-butylene-styrene Block Copolymer (SEBS): 
     Kraton G 1657 manufactured by Shell Chemical Co. 
     Linear Low-density Polyethylene (LLDPE): 
     GS-381 manufactured by Nippon Unicar Co., having density of 0.92 and MI of 20 g/10 min. 
     MANUFACTURE EXAMPLE 1 
     Preparation of Crosslinked Product (1) 
     38 parts by weight of ethylene-propylene-diene copolymer rubber (EPDM), 14 parts by weight of chlorinated butyl rubber and 30 parts by weight of paraffinic oil (as mineral oil softening agent) were put in a Banbury mixer and melted and mixed at 130° to 140° C. for 3 minutes. Next, 18 parts by weight of polypropylene was put thereinto and continuously mixed at the same temperature. Further, 0.2 part by weight of ZnO, 0.8 part by weight of ZnCl 2  and 0.5 part by weight of MgO as a crosslinking agent and 0.1 part by weight of Irganox®-1010 as an antioxidant were added to conduct the crosslinking reaction at 140° C. for 6 minutes. 
     The Crosslinked Product (1) thus obtained was taken out from the mixer and pelletized in a conventional manner. 
     MANUFACTURE EXAMPLE 2 
     Preparation of Crosslinked Product (2) 
     In the same manner as in Manufacture Example 1, Crosslinked Product (2) was prepared from the following components: 
     
         ______________________________________Polypropylene       18 parts by weightEPDM                14 parts by weightChlorinated Butyl Rubber               38 parts by weightMineral Oil Softening Agent               30 parts by weightZnO                  6 parts by weightZnCl.sub.2           3 parts by weightMgO                  1.5 parts by weightIrganox-1010         0.1 parts by weight______________________________________ 
    
     EXAMPLE 1 
     Nine parts by weight of polypropylene, 21 parts by weight of EPDM, 0.3 part by weight of organic peroxide (Perhexyne-2,5B) and 0.5 part by weight of crosslinking aid (divinylbenzene) were previously fully mixed in a rotary mixer, and the resulting blend was fed into the biaxial extruder having the structure as shown in FIG. 1, from the first hopper (1) into the first mixing zone (2). The mixing temperature in the first mixing zone was 200° C., and the residence time was kept to be 60 seconds. Subsequently, a mixture comprising 50 parts by weight of polypropylene and 20 parts by weight of Crosslinked Product (1) previously prepared from halogenated butyl rubber was fed into the second mixing zone (4). The residence time in the second mixing zone (4) was 30 seconds. 
     The MFR, flexural modulus, tensile breaking strength, tensile breaking elongation, Izod impact strength, Shore hardness, mouldability and coatability of the thermoplastic resin composition thus obtained were measured and examined. The results obtained are shown in Table 1 below. 
     EXAMPLES 2 TO 5 
     In the same manner as Example 1, except that the weight ratio of polypropylene/EPDM to be fed into the first mixing zone (2), the weight ratio of polypropylene/Crosslinked Product (1) to be fed into the second mixing zone (4) and the ratio of the resin weight in the first mixing zone to that in the second mixing zone were varied as indicated in Table 1, thermoplastic resin compositions were prepared. These were tested in the same manner as Example 1 and the results obtained are shown in Table 1. 
     EXAMPLES 6 AND 7 
     In the same manner as Examples 1 and 2, except that EPDM in the resin to be fed into the first mixing zone was replaced by EPR, thermoplastic resin compositions were prepared. These were tested in the same manner as Example 1 and the results obtained are shown in Table 1. 
     EXAMPLES 8 AND 12 
     In the same manner as Example 1, except that the Chlorobutyl Crosslinked Product (1) to be fed into the second mixing zone was replaced by the Crosslinked Product (2) having a higher chlorobutyl content, thermoplastic resin compositions were prepared. These were tested in the same manner as Example 1 and the results obtained are shown in Table 1. 
     EXAMPLE 13 AND 14 
     The proportion of the resins in the first mixing zone and the second mixing zone was varied to obtain various thermoplastic resin composition having a high rubber content. The thermoplastic resin compositions thus prepared were tested in the same manner as above, and the results obtained are shown in Table 1. 
     EXAMPLE 15 
     In the same manner as Example 1, except that a part of the polypropylene and the Crosslinked Product (2) to be fed into the second mixing zone was reduced and styrene-ethylene-butylene-styrene block copolymer (SEBS) was added in place of the reduced amount, a thermoplastic resin composition was obtained. This was tested in the same manner as above, and the results obtained are shown in Table 1. 
     
                                           TABLE 1__________________________________________________________________________              Example No.Ingredients (wt. pts.)              1    2     3    4     5    6     7    8__________________________________________________________________________First Mixing ZonePP                 9    6     3    9     3    9     6    9EPDM               21   14    7    21    7    --    --   21EPR                --   --    --   --    --   21    14   --Organic Peroxide   0.3  0.3   0.3  0.3   0.3  0.3   0.3  0.3Crosslinking Aid   0.5  0.5   0.5  0.5   0.5  0.5   0.5  0.5Second Mixing ZonePP                 50   50    50   30    70   50    50   50Crosslinked Product (1)              20   30    40   40    20   20    30   --Crosslinked Product (2)              --   --    --   --    --   --    --   20SEBS               --   --    --   --    --   --    --   --Physical PropertiesMFR (g/10 min)     13   14    14   9     16   12    13   10Flexural Modulus23° C. (kg/cm.sup.2)              3250 3200  3300 2700  8050 3300  3280 305080° C. (kg/cm.sup.2)              1200 1350  1500 900   4800 1020  1060 1280Tensile Breaking Strength (kg/cm.sup.2)              145  165   170  105   255  125   120  140Tensile Breaking Elongation (%)              630  650   640  680   330  635   620  640Izod Impact Strength room temperature              NB.sup.(1)                   NB    NB   NB    NB   NB    NB   NB(kg-cm/cm)-40° C.     NB   NB    NB   NB    PB.sup.(2)                                         NB    NB   NBShore Hardness (Shore-D)              58   59    59   54    80   57    59   55Mouldability (Flow Marks)              O    O     O    O     O    O     O    OCoatability        100/100                   100/100                         100/100                              100/100                                    100/100                                         100/100                                               100/100                                                    100/100(cross-cut tape-peeling test)__________________________________________________________________________                Example No.Ingredients (wt. pts.)                9     10    11    12    13    14    15__________________________________________________________________________First Mixing ZonePP                   6     3     9     3     12    3     9EPDM                 14    7     21    7     28    7     21EPR                  --    --    --    --    --    --    --Organic Peroxide     0.3   0.3   0.3   0.3   0.3   0.3   0.3Crosslinking Aid     0.5   0.5   0.5   0.5   0.5   0.5   0.5Second Mixing ZonePP                   50    50    30    70    20    10    40Crosslinked Product (1)                --    --    --    --    --    --    --Crosslinked Product (2)                30    40    40    20    40    80    10SEBS                             --    --    --    --    20Physical PropertiesMFR (g/10 min)       9     9     7     12    7     7     11Flexural Modulus23° C. (kg/cm.sup.2)                3030  3050  2800  7800  2400  2400  300080° C. (kg/cm.sup.2)                1250  1650  920   4600  760   880   1050Tensile Breaking Strength (kg/cm.sup.2)                142   145   95    260   83    88    110Tensile Breaking Elongation (%)                640   620   670   310   680   670   710Izod Impact Strength room temperature                NB    NB    PB    NB    NB    NB    NB(kg-cm/cm)-40° C.       NB    PB    NB    PB    NB    NB    NBShore Hardness (Shore-D)                55    55    54    78    52    52    56Mouldability (Flow Marks)                O     O     O     O     Δ                                              Δ                                                    OCoatability          100/100                      100/100                            100/100                                  100/100                                        100/100                                              100/100                                                    100/100(cross-cut tape-peeling test)__________________________________________________________________________ Notes: .sup.(1) Not Broken. .sup.(2) Partly Broken. 
    
     EXAMPLE 16 
     In the same manner as Example 15, except that butyl rubber (IIR) was added to the second mixing zone, a thermoplastic resin composition was prepared. This was tested in the same manner as above, and the results obtained were shown in Table 2 below. 
     EXAMPLE 17 
     In the same manner as Example 15, except that linear low-density polyethylene (LLDPE) was added to the second mixing zone, a thermoplastic resin composition was prepared. This was tested in the same manner as above, and the results obtained are shown in Table 2 below. 
     
                       TABLE 2______________________________________                Example No.Ingredients (wt. pts.) 16       17______________________________________First Mixing ZonePP                     9        9EPDM                   21       21Organic Peroxide       0.3      0.3Crosslinking Aid       0.5      0.5Second Mixing ZonePP                     40       40Crosslinked Product (2)                  10       10IIR                    20       --LLDPE                  --       20Physical PropertiesMFR (g/10 min)         10       10Flexural Modulus 23° C. (kg/cm.sup.2)                  2,900    3,200Flexural Modulus 80° C. (kg/cm.sup.2)                  1,000    1,100Tensile Breaking Strength (kg/cm.sup.2)                  105      125Tensile Breaking Elongation (%)                  620      610Izod Impact Strength Room Temperature                  NB       NB(kg-cm/cm)-40° C.         NB       NBShore Hardness (Shore-A)                  65       60Mouldability (Flow Marks)                  0        0Coatability            100/100  100/100(cross-cut tape-peeling test)______________________________________ 
    
     EXAMPLE 18 
     0.3 part by weight of organic peroxide (Perhexyne-2,5B) and 0.5 part by weight of crosslinking aid (divinylbenzene) were added to 9 parts by weight of polypropylene and 21 parts by weight of EPDM and well blended in a rotary mixer, and the resulting blend was fed into the first mixing zone of the extruder of FIG. 1. The reaction condition was the same as that in Example 1. 
     Subsequently, 54 parts by weight of polypropylene, 3 parts by weight of chlorinated butyl rubber, 8 parts by weight of EPDM, 5 parts by weight of mineral oil softening agent and additionally, as a crosslinking agent for the chlorinated butyl rubber, a mixture comprising 0.4 part by weight of ZnO, 0.2 part by weight of ZnCl 2  and 0.1 part by weight of MgO were fed into the second mixing zone, and the chlorinated butyl rubber was crosslinked in the zone. The thermoplastic resin composition thus obtained was tested in the same manner as Example 1. The results obtained are shown in Table 3. 
     EXAMPLE 19 
     In the same manner as Example 18, chlorinated butyl rubber was crosslinked in the second mixing zone. The same process as Example 18 was repeated except that the resin composition in the second mixing zone was varied to polypropylene/chlorinated butyl rubber/EPDM=54/8/3 (parts by weight) and the crosslinking agent was varied to ZnO/ZnCl 2  /MgO=1.2/0.6/0.3 (parts by weight). The thermoplastic resin composition thus obtained was tested in the same manner as Example 1, and the results obtained are shown in Table 3. 
     
                       TABLE 3______________________________________              Example No.Ingredients (wt. pts.)                18            19______________________________________First Mixing ZonePP                   9             9EPDM                 21            21Organic Peroxide     0.3           0.3Crosslinking Aid     0.5           0.5Second Mixing ZonePP                   54            54CIIR                 3             8EPDM                 8             3Mineral Oil Softening Agent                5             5ZnO                  0.4           1.2ZnCl.sub.2           0.2           0.6MgO                  0.1           0.3Physical PropertiesMFR (g/10 min)       12            11Flexural Modulus 23° C. (kg/cm.sup.2)                3,200         3,250Flexural Modulus 80° C. (kg/cm.sup.2)                1,180         1,250Tensile Breaking Strength (kg/cm.sup.3)                140           140Tensile Breaking Elongation (%)                620           640Izod Impact Strength Room                NB            NBTemperature (kg-cm/cm)                NB            NB-40° C.Shore Hardness (Shore-D)                58            55Mouldability (Flow Marks)                0             0Coatability          100/100       100/100(cross-cut tape-peeling test)______________________________________ 
    
     COMPARATIVE EXAMPLE 1 
     Polypropylene, EPDM and Crosslinked Product (1) were blended so that the composition could be the same as the thermoplastic resin composition obtained in Example 1, and 0.3 part by weight of organic peroxide (Perhexyne-2,5B) and 0.5 part by weight of crosslinking aid (divinylbenzene) were added thereto and uniformly dispersed. Then the resulting dispersion was fed into the first mixing zone of the extruder. The residence time in the extruder was 60 seconds. 
     COMPARATIVE EXAMPLE 2 
     The same process as Comparative Example 1 was repeated except that the crosslinking agent was reduced to 0.1 part by weight and the crosslinking aid to 0.17 part by weight. The proportion of the resin components and the reaction condition were the same as those in Comparative Example 1. 
     COMPARATIVE EXAMPLE 3 
     Resin components were blended so that the final composition could be the same as that in Example 2, and 0.3 part by weight of crosslinking agent and 0.5 part by weight of crosslinking aid were uniformly dispersed therein. The resulting dispersion was mixed in accordance with the process of Comparative Example 1. 
     COMPARATIVE EXAMPLE 4 
     The same process as Comparative Example 1 was repeated except that the Crosslinked Product (1) was replaced by Crosslinked Product (2). 
     COMPARATIVE EXAMPLE 5 
     The resin components were the same as those in Comparative Example 4, but the crosslinking agent was reduced to 0.1 part by weight and the crosslinking aid to 0.17 part by weight. The mixture was mixed in the same manner as in Comparative Example 4. 
     COMPARATIVE EXAMPLE 6 
     The resin mixture as fed into the second mixing zone did not contain crosslinked product of chlorinated butyl rubber. The composition thus obtained was tested with respect to the properties thereof. 
     COMPARATIVE EXAMPLE 7 
     The resin components of polypropylene/EPDM=55/45 (by weight) were crosslinked with only organic peroxide. 
     COMPARATIVE EXAMPLE 8 
     Polypropylene and EPDM were put in the first mixing zone in the proportion as indicated in Table 4 below and mixed for 60 seconds (residence time) at 200° C. Then polypropylene and Crosslinked Product (1) were incorporated into the blend in the proportion as indicated in Table 4 in the second mixing zone. In the same manner as Example 1, a thermoplastic resin composition was obtained. 
     COMPARATIVE EXAMPLE 9 
     The same process as in Comparative Example 8 was repeated except that 0.3 part by weight of organic peroxide and 0.5 part by weight of crosslinking aid were added to the second mixing zone, and a thermoplastic resin composition was obtained. 
     COMPARATIVE EXAMPLE 10 
     The resin components as indicated in Table 4 were mixed in the first mixing zone, and polypropylene, EPDM, organic peroxide and crosslinking aid were added to the resulting blend in the proportion as indicated in Table 4 in the second mixing zone. These were mixed therein to obtain a thermoplastic resin composition. 
     The thermoplastic resin compositions thus obtained in the above-mentioned Comparative Examples 1 to 10 were tested with respect to the physical properties as well as the mouldability and the coatability thereof. The results obtained are shown in Table 4. 
     
                                           TABLE 4__________________________________________________________________________            Comparative Example No.Ingredients (wt. pts.)            1  2  3  4  5  6  7  8  9  10__________________________________________________________________________First Mixing ZonePP               59 59 56 59 59 9  55 9  9  50EPDM             21 21 14 21 21 21 45 21 21 --Crosslinked Product (1)            20 20 30 -- -- -- -- -- -- 20Crosslinked Product (2)            -- -- -- 20 20 -- -- -- -- --Organic Peroxide 0.3               0.1                  0.3                     0.3                        0.1                           0.3                              0.3                                 -- -- --Crosslinking Aid 0.5               0.17                  0.5                     0.5                        0.17                           0.5                              0.5                                 -- -- --Second Mixing ZonePP               -- -- -- -- -- 54 -- 50 50 9EPDM             -- -- -- -- -- 11 -- -- -- 21Mineral Oil Softening Agent            -- -- -- -- -- 5  -- -- -- --Crosslinked Product (1)            -- -- -- -- -- -- -- 20 20 --Organic Peroxide -- -- -- -- -- -- -- -- 0.3                                       0.3Crosslinking Aid -- -- -- -- -- -- -- -- 0.5                                       0.5Physical PropertiesMFR (g/10 min)   18 16 26 25 19 16 10 20 18 18Flexural Modulus23° C. (kg/cm.sup.2)            3300               3280                  3210                     3030                        3090                           2800                              2000                                 2700                                    2900                                       295080° C. (kg/cm.sup.2)            1150               1180                  1400                     1020                        1040                           750                              550                                 910                                    1600                                       1650Tensile Breaking Streangth (kg/cm.sup.2)            105               120                  115                     96 110                           110                              85 90 102                                       98Tensile Breaking Elongation (%)            420               510                  410                     320                        490                           660                              650                                 650                                    630                                       620Izod Impact Strength room temp.            NB NB NB NB NB NB NB NB NB NB(kg-cm/cm)-40° C.   25 38 22 18 40 NB NB NB NB NBShore Hardness (Shore-D)            58 57 57 54 54 52 48 45 48 48Mouldability (Flow Marks)            O  O  O  O  O  O     O  O  OCoatability      100/               100/                  100/                     100/                        100/                           100/                              100/                                 100/                                    100/                                       100/(cross-cut take-peeling test)            100               100                  100                     100                        100                           100                              100                                 100                                    100                                       100__________________________________________________________________________ 
    
     In accordance with the method for preparation of a thermoplastic resin composition of the present invention, as explained in detail above, a mixture containing a crosslinking olefin rubber is first crosslinked with an organic peroxide and then a mixture containing a halogenated butyl rubber is added thereto and is crosslinked with a metal oxide and/or metal chloride, or alternatively, the halogenated butyl rubber is crosslinked before being added. Accordingly, the crosslinkable olefin rubber may sufficiently be crosslinked while the halogenated butyl rubber may be crosslinked with the metal oxide and/or metal chloride without being decomposed by the organic peroxide. Thus a thermoplastic resin composition which is excellent in the mechanical strength, heat-resistance, impact-resistance, softness, mouldability and coatability may be obtained by the present invention. 
     As the thermoplastic resin composition obtained by the present invention is excellent in the above-mentioned properties, it is suitable for use in preparation of large-sized injection moulded articles, such as bumpers, air duct, door protector and the like car parts, as a substitute for polyurethane or polyester elastomers.