Patent Publication Number: US-4550130-A

Title: Composite material with improved properties

Description:
CROSS REFERENCE TO THE RELATED APPLICATION 
     This is a continuation-in-part application of application Ser. No. 450,378 filed on Dec. 16, 1982, now pending. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a composite material with improved properties which can provide a molded product having excellent various properties. 
     BACKGROUND OF THE INVENTION 
     Thermoplastic composite materials have excellent mechanical and electrical properties, and investigations for use as industrial materials have recently been developed rapidly. Of polymers constituting the composite materials, polyolefins such as polyethylene, polypropylene, and so forth have characteristics such as small specific gravity, good moldability and processability, excellent chemical resistance, and so forth, and applications of the thermoplastic composite materials comprising polyolefins as a matrix will now increase. 
     However, since polyolefins constituting the thermoplastic composite materials are nonpolar polymers, they do not have a satisfactory affinity for glass fibers, carbon fibers, carbon black, mica, talc, alumina fibers, silicon carbide fibers, aromatic polyamide fibers, and so forth which are used as a reinforcement. Therefore, a thermoplastic composite material having a further improved reinforcing effect has been demanded. 
     Many investigations have been made to develop a thermoplastic composite material satisfying the above requirement. 
     For example, Japanese Patent Application (OPI) No. 74649/1977 (the term &#34;OPI&#34; as used herein refers to a &#34;published unexamined Japanese patent application&#34;) describes a material prepared by adding 0.2 to 2 wt% of polyacrylic acid to a composite material composed of 50 to 95 parts by weight of a polyolefin and 5 to 50 parts by weight of an inorganic filler. However, this composite material cannot be said to possess sufficiently improved properties because the affinity of the matrix polymer for the filler has not yet been improved. Japanese Patent Application (OPI) No. 50041/1980 and U.S. Pat. No. 3,862,265 describe a composite material composed of a graft polyolefin and an inorganic filler which is obtained by blending an unsaturated carboxylic acid, a polyolefin, and an inorganic filler, followed by subjecting the blend to a reaction under heating and mixing in an extruder. This composite material has good affinity of the graft polyolefin for the inorganic filler but has not a sufficient flowability since it contains inorganic fibers. Therefore, a molded product prepared from this composite material has not a sufficient impact strength. Thus, composite materials having improved properties are strongly desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a thermoplastic composite material which can provide a molded product having excellent mechanical properties (particularly, impact strength), a high flexial modulus a small specific gravity and a good water repllency. 
     Another object of the present invention is to provide a composite material having a good moldability due to its excellent flowability. 
     The composite material of the present invention comprises a modified polyolefin (i.e., a polyolefin modified with an unsaturated carboxylic acid), a reinforcement, and at least one polyfunctional compound selected from the group consisting of a polyfunctional epoxide, a polyfunctional amino compound, and a polyfunctional polyisocyanate compound. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The modified polyolefin used in the present invention can be obtained by graft-polymerizing an unsaturated carboxylic acid onto a polyolefin and has an excellent affinity for reinforcements as compared with unmodified polyolefins. 
     Examples of polyolefins used for preparation of the modified polyolefin include polyethylene, polypropylene, poly(4-methylpentene-1), ethylene/vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, ethylene/propylene/diene copolymer, and so forth. When polypropylene is used, a composite material having particularly various excellent characteristics can be prepared. 
     The modifier used for preparations of the modified polyolefin is unsaturated carboxylic acids and examples thereof include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and anhydrides of these acids. The amount of these modifiers used is 0.05 to 0.8 part by weight, preferably 0.1 to 0.6 part by weight, per 100 parts by weight of the polyolefin. 
     A modified polyolefin prepared using a small amount of the modifier has not a sufficient affinity for the reinforcement, making it difficult to prepare a composite material having excellent properties. On the other hand, when a modified polyolefin is prepared using a large amount of the modifier, modification of the polyolefin does not proceed sufficiently, and a modified polyolefin contains a large amount of unreacted modifier. Such a product tends to deteriorate with the passage of time. 
     The modified polyolefin can be prepared by mixing a polyolefin, a modifier, and a catalyst in predetermined proportions and reacting the resulting mixture at 150° to 280° C. for 1 to 20 minutes. When the reaction temperature and/or the reaction time exceed(s) the abovedescribed range(s), the modified polyolefin obtained shows unfavorable coloring or unnecessary thermal decomposition. 
     Examples of the catalysts used for the preparation of the modified polyolefin include benzoyl peroxide, lauroyl peroxide, and ketal or dialkyl peroxides which have a decomposition temperature necessary for attaining the half life of 10 hours of at least 80° C. Specific examples of the ketal or dialkyl peroxide catalysts include 1,1-bis(t-butylperoxy)cyclohexane, n-butyl 4,4-bis(t-butylperoxy)valerate, 1,1-bis-(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, dicumyl peroxide, t-butylcumyl peroxide, α,α&#39;-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3. 
     When the modified polyolefin is prepared using ketal peroxides or dialkyl peroxides having a decomposition temperature necessary for attaining the half life of 10 hours of at least 80° C., it exhibits a more effective molecular weight-lowering effect as compared with the modified polyolefin prepared using other catalysts. Accordingly, the composite material of the present invention prepared using the modified polyolefin has excellent moldability. Further, in crystallization of the polymer in the process for molding of the composite material of the present invention, the modified polyolefin prepared by using the specified ketal peroxides or dialkyl peroxides and benzoyl peroxide in a weight ratio of 10/1 to 1/10, preferably 1/6 to 6/1, exhibits an effect of inhibiting the growth of spherulites and, as a result, a composite material having good characteristics (a spherulite size of 50μ or less, preferably 5 to 30μ) can be obtained. 
     The amount of the catalyst used is 0.03 to 3 parts by weight, preferably 0.05 to 1 part by weight, per 100 parts by weight of the polyolefin. 
     As a modification reaction of the polyolefins, a solution reaction process using a solvent as a reaction medium or a method in which the reaction is conducted in a heat-melting state can be employed. From the standpoint of prevention of unnecessary coloring of the modified polyolefin obtained, prevention of unnecessary lowering of the molecular weight of the polyolefin, and the choice of an appropriate reaction time, it is preferred to employ a heat-melting reaction using an extruder as a reactor. 
     Polyfunctional epoxy compounds used in the present invention are compounds having two or more epoxy groups in the molecule. Examples thereof include a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, an aliphatic ether type epoxy compound, a novolak type epoxide, an isocyanurate type epoxide and so forth. Specific examples thereof include condensates between bisphenol A and epichlorohydrin; polyglycidyl ethers of polyols such as ethylene glycol, propylene glycol, polyethylene glycol, glycerol, neopentyl glycol, trimethylolpropane, and sorbitol; triglycidyl isocyanurate, N-methyl-N&#39;,N&#34;-diglycidyl isocyanurate, and triglycidyl cyanurate. The molecular weight of these polyfunctional epoxides is, though not particularly limited, about 4,000 or less. 
     Polyfunctional amines used in the present invention are compounds having two or more amino groups in the molecule. Specific examples thereof include hexamethylenediamine, tetramethylenediamine, methaxylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, 3,3&#39;-diaminobenzidine, isophthalic acid hydrazide, diaminodiphenyl ether, nanomethylenediamine, and diethylenetetramine. 
     Polyfunctional isocyanates are compounds having two or more isocyanate groups in the molecule. Examples thereof include tetramethylene diisocyanate, toluidine diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and their polyisocyanates obtained by extending them with a chain-extending agent. Of these polyfunctional compounds, polyepoxides having a cyanuric or isocyanuric ring have high reactivity toward the modified polyolefin in the process of preparing the composite material of the present invention and a molding product prepared from the composite material thus-obtained has more excellent impact strength as compared with other molded products. 
     Polyfunctional epoxides, polyfunctional amines, and polyfunctional isocyanates can be used alone or in combination, the amount thereof is each 0.03 to 5 wt% per the weight of the modified polyolefin but the total amount does not exceed 10 wt% per the weight of the modified polyolefin. 
     Molded products prepared from the composite material containing at least one of those polyfunctional amines, polyfunctional isocyanates, and polyfunctional epoxides of the present invention have an excellent strength characteristic as compared with molded products prepared from composite materials containing no those polyfunctional compounds. 
     Reinforcements used in the present invention are fibrous materials such as glass fibers, carbon fibers, graphite fibers, aromatic polyamide fibers, silicon carbide fibers, polysulfone type fibers, polyether ketone fibers, alumina fibers, potassium titanate fibers, asbestos fibers, boron fibers, metal fibers, and so forth. Fibers having the length of 5 mm or less, preferably 0.01 to 3 mm, are preferred. 
     As other reinforcements, powdery or flaky materials such as glass flakes, talc, mica, kaolin, clay, diatomaceous earth, calcium carbonate, calcium sulfate, magnesium oxide, carbon black, titanium oxide, metal powders, alumina, graphite, white carbon, wollastonite, molybdenum disulfide, and tungsten disulfide can be used. Those reinforcements are incorporated in the modified polyolefin alone or in combination thereof in an amount of 5 to 400 wt% per the weight of the modified polyolefin. If the amount of the reinforcement is too small, a sufficient reinforcing effect, high flexial modulus and high strength cannot be obtained. On the other hand, if the amount of the reinforcement is too large, moldability of the composite material is remarkable reduced and the mechanical properties of a molded product prepared from the composite material tend to deteriorate. 
     Other thermoplastic plastics, for example, engineering plastics such as polyamides, unmodified polyolefins, polyesters, polycarbonates, polyacetals, and polysulfones can be incorporated into the composite material of the present invention, if desired. 
     The composite material of the present invention is prepared by blending a modified polyolefin, at least one compound selected from the group consisting of polyfunctional epoxides, polyfunctional amines, and polyfunctional isocyanates, and a reinforcement in the predetermined proportions. This composite material can be molded into the desired molded product by an injection molding method or the like. 
     Moldability of the composite material of the present invention is superior to that of similar kinds of conventional composite materials. Thus, it is believed that a molded product prepared from the composite material of the present invention has sufficiently improved impact strength as compared with that prepared from similar kinds of conventional composite materials. 
    
    
     The present invention will now be explained in detail by reference to the following non-limiting examples. Unless otherwise indicated, all percents, parts, ratios and the like are by weight. 
     EXAMPLE 1 
     To 100 parts by weight of polypropylene powders having an inherent viscosity of 1.5 (measured in a tetralin solution at 135° C.) were added modifiers and peroxides with the amounts as shown in Table 1, and the mixture was blended in the Henschel mixer. The mixture was then fed into an extruder reactor of 30 φ and L/D=25, and modified in a mixed state under heat-melting at a reaction temperature of 230° C. for a reaction time of 7 minutes. The unreacted modifier was removed by reducing the pressure of the vent portion of the extruder, and then the reaction mixture was extruded into pellets to give modified polyolefins. 
     To 100 parts by weight of the resulting modified polyolefin pellets were each added prescribed amounts of reinforcements and polyfunctional compounds as shown in Table 1. The mixture was blended in a tumbler and melt mixed in an extruder, and extruded therefrom to give pellets of composite materials. 
     These composite materials were formed into 3 kinds of molded products, viz., plates of No. 1 dumbbell, 125×12.5×3.2 (mm), and 125×12.5×6.4 (mm) using a screw on-line type injection machine under molding conditions of a cylinder temperature of 220° C. and a mold temperature of 60° C. 
     The results obtained by measuring fabrication properties of the composite materials and mechanical properties of the molded products therefrom under the following conditions are shown in Table 1. 
     Melt Flow Index (molding flow index): ASTM-D-1238, load 2.16 kg, temperature 230° C. 
     Izod Impact Strength: ASTM-D-256. 
     Heat Distortion Temperature (hereinafter referred to as HDT): ASTM-D-648. ##EQU1## 
     
                                           TABLE 1                                 
__________________________________________________________________________
              Experiment No.                                              
              1       2      3      4      5      6     7                 
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100    100    100    100    100   100               
Parts by weight                                                           
Peroxide                                                                  
Kind          --      Benzoyl                                             
                             --     Benzoyl                               
                                           Benzoyl                        
                                                  Benzoyl                 
                                                        Benzoyl           
                      peroxide      peroxide                              
                                           peroxide                       
                                                  peroxide                
                                                        peroxide          
Parts by weight                                                           
              --      0.3    --     0.3    0.3    0.3   0.3               
Modifier                                                                  
Kind          --      Maleic --     Maleic Maleic Maleic                  
                                                        Acrylic           
                      anhydride     anhydride                             
                                           anhydride                      
                                                  anhydride               
                                                        acid              
Parts by weight                                                           
              --      0.3    --     0.3    0.3    0.3   0.3               
Polyfunctional compound                                                   
Kind          --      --     Hexa-  Hexa-  Hexa-  --    --                
                             methylene                                    
                                    methylene                             
                                           methylene                      
                                                  diamino                 
                             diamine                                      
                                    diamine                               
                                           diamine                        
                                                  diphenyl                
                                                  ether                   
Parts by weight                                                           
              --      --     0.3    0.3    0.3    0.5   --                
Reinforcement                                                             
Kind          Carbon  Carbon Carbon Carbon Carbon Carbon                  
                                                        Carbon            
              fiber   fiber  fiber  fiber  fiber  fiber fiber             
Parts by weight                                                           
              25      25     25     25     25     25    25                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              770     1,140  820    1,470  1,540  1,460 1,160             
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              8.8     8.8    8.8    8.8    8.7    8.7   8.6               
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              15      18     16     31     33     28    17                
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              145     148    145    147    143    145   148               
Ratio of improvement in                                                   
              1.0     1.5    1.1    1.9    2.0    1.9   1.5               
strength (ratio)                                                          
Remark        Comparative                                                 
                      &#34;      &#34;      Invention                             
                                           Invention                      
                                                  Invention               
                                                        Comparative       
              Example                                   Example           
__________________________________________________________________________
              Experiment No.                                              
              8      9      10     11     12     13     15                
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100    100    100    100    100    100    100               
Parts by weight                                                           
Peroxide                                                                  
Kind          Benzoyl                                                     
                     Benzoyl                                              
                            Benzoyl                                       
                                   Benzoyl                                
                                          Benzoyl                         
                                                 Benzoyl                  
                                                        Benzoyl           
              peroxide                                                    
                     peroxide                                             
                            peroxide                                      
                                   peroxide                               
                                          peroxide                        
                                                 peroxide                 
                                                        peroxide          
Parts by weight                                                           
              1.0    0.3    1.0    0.3    0.3    0.3    0.3               
Modifier                                                                  
Kind          Acrylic                                                     
                     Acrylic                                              
                            Acrylic                                       
                                   Maleic Maleic Maleic Maleic            
              acid   acid   acid   anhydride                              
                                          anhydride                       
                                                 anhydride                
                                                        anhydride         
Parts by weight                                                           
              0.7    0.3    0.7    0.3    0.3    0.3    0.3               
Polyfunctional compound                                                   
Kind          --     Hexa-  Hexa-  2,4-   4,4&#39;-  Triglycidyl              
                                                        Bisphenol A       
                     methylene                                            
                            methylene                                     
                                   Toluilene                              
                                          Diphenyl-                       
                                                 isocyanurate             
                                                        diglycidyl        
                     diamine                                              
                            diamine                                       
                                   diisocyanate                           
                                          methane       ether             
                                          diisocyanate                    
Parts by weight                                                           
              --     0.3    0.3    0.3    0.3    0.3    0.3               
Reinforcement                                                             
Kind          Carbon Carbon Carbon Carbon fiber                           
                                          Carbon fiber                    
                                                 Carbon                   
                                                        Carbon            
              fiber  fiber  fiber                       fiber             
Parts by weight                                                           
              25     25     25     25     25     25     25                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              1,230  1,460  1,570  1,530  1,550  1,580  1,460             
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              8.6    8.7    8.8    8.4    8.6    8.9    8.6               
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              19     29     27     34     33     32     28                
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              147    147    149    146    145    151    150               
Ratio of improvement in                                                   
              1.6    1.9    2.0    2.0    2.0    2.1    1.9               
strength (ratio)                                                          
Remark        Comparative                                                 
                     Invention                                            
                            Invention                                     
                                   Invention                              
                                          Invention                       
                                                 Invention                
                                                        Invention         
              Example                                                     
__________________________________________________________________________
             Experiment No.                                               
             16    17     18     19      20      21     22                
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene                                                             
             100   100    100    100     100     100    100               
Parts by weight                                                           
Peroxide                                                                  
Kind         Benzoyl                                                      
                   Benzoyl                                                
                          Benzoyl                                         
                                 Benzoyl Benzoyl Benzoyl                  
                                                        --                
             peroxide                                                     
                   peroxide                                               
                          peroxide                                        
                                 peroxide                                 
                                         peroxide                         
                                                 peroxide                 
Parts by weight                                                           
             0.3   0.3    0.3    0.3     0.3     0.3    --                
Modifier                                                                  
Kind         Maleic                                                       
                   Maleic Maleic Maleic  Acrylic Acrylic                  
                                                        --                
             anhydride                                                    
                   anhydride                                              
                          anhydride                                       
                                 anhydride                                
                                         acid    acid                     
Parts by weight                                                           
             0.3   0.3    0.3    0.3     0.3     0.3    --                
Polyfunctional compound                                                   
Kind         Neopentyl-                                                   
                   --     Triglycidyl                                     
                                 Hexamethylene                            
                                         Hexamethylene                    
                                                 Triglycidyl              
                                                        --                
             glycol di-   isocyanurate                                    
                                 diamine diamine isocyanurate             
             glycidyl                                                     
             ether                                                        
Parts by weight                                                           
             0.3   --     0.3    0.3     0.3     0.3    --                
Reinforcement                                                             
Kind         Carbon                                                       
                   Glass  Glass fiber                                     
                                 Glass fiber                              
                                         Glass fiber                      
                                                 Carbon Talc              
             fiber fiber                         fiber                    
Parts by weight                                                           
             25    25     25     25      25      25     25                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
             1,500 1,080  1,330  1,280   1,250   1,600  430               
(kg/cm.sup.2 )                                                            
Flexial modulus                                                           
             8.7   5.3    5.5    5.4     5.3     8.5    4.3               
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
             30    20     25     27      28      30     10                
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
             151   145    144    145     148     149    80                
Ratio of improvement in                                                   
             1.9   1.2    1.5    1.5     1.4     2.1    1.0               
strength (ratio)                                                          
Remark       Invention                                                    
                   Comparative                                            
                          Invention                                       
                                 Invention                                
                                         Invention                        
                                                 Invention                
                                                        Comparative       
                   Example                              Example           
__________________________________________________________________________
              Experiment No.                                              
              23      24          25     26     27      28                
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100         100    100    100     100               
Parts by weight                                                           
Peroxide                                                                  
Kind          Benzoyl Benzoyl peroxide                                    
                                  Benzoyl                                 
                                         Benzoyl                          
                                                Benzoyl Benzoyl           
              peroxide            peroxide                                
                                         peroxide                         
                                                peroxide                  
                                                        peroxide          
Parts by weight                                                           
              0.3     0.3         0.3    0.3    0.3     0.7               
Modifier                                                                  
Kind          Maleic  Maleic anhydride                                    
                                  Maleic Maleic Maleic  Maleic            
              anhydride           anhydride                               
                                         anhydride                        
                                                anhydride                 
                                                        anhydride         
Parts by weight                                                           
              0.3     0.3         0.3    0.3    0.3     0.7               
Polyfunctional compound                                                   
Kind          --      4,4-Diphenylmethylene                               
                                  Triglycidyl                             
                                         Triglycidyl                      
                                                Triglycidyl               
                                                        Triglycidyl       
                      diisocyanate                                        
                                  isocyanurate                            
                                         isocyanurate                     
                                                isocyanurate              
                                                        isocyanurate      
Parts by weight                                                           
              --      0.5         0.3    0.3    0.3     0.3               
Reinforcement                                                             
Kind          Talc    Talc        Talc   Glass fiber                      
                                                Talc/carbon               
                                                        Carbon fiber      
                                                fiber = 1/1               
Parts by weight                                                           
              25      25          25     25     50      25                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              500     560         540    1,320  1,530   1,640             
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              4.3     4.3         4.5    5.4    10.1    8.2               
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              10      19          17     27     29      32                
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              80      82          80     148    149     149               
Ratio of improvement in                                                   
              1.0     1.3         1.3    1.5    2.0     2.1               
strength (ratio)                                                          
Remark        Comparative                                                 
                      Invention   Invention                               
                                         Invention                        
                                                Invention                 
                                                        Invention         
              Example                                                     
__________________________________________________________________________
              Experiment No.                                              
              29      30      31       32      33      34                 
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100     100      100     100     100                
Parts by weight                                                           
Peroxide                                                                  
Kind          1,1-Bis(t-                                                  
                      2,5-Dimethyl-                                       
                              Benzoyl  *1      *2      *2                 
              butylperoxy)-                                               
                      2,5-di(t-                                           
                              peroxide                                    
              3,3,5-  butylperoxy)-                                       
              trimethyl-                                                  
                      hexyne-3                                            
              cyclohexane                                                 
Parts by weight                                                           
              0.2     0.2     0.       0.2     0.2     0.2                
Modifier                                                                  
Kind          Maleic  Maleic  Maleic   Maleic  Maleic  Maleic             
              anhydride                                                   
                      anhydride                                           
                              anhydride                                   
                                       anhydride                          
                                               anhydride                  
                                                       anhydride          
Parts by weight                                                           
              0.3     0.3     0.3      0.3     0.3     0.3                
Polyfunctional compound                                                   
Kind          Triglycidyl                                                 
                      Triglycidyl                                         
                              Triglycidyl                                 
                                       Triglycidyl                        
                                               Triglycidyl                
                                                       Triglycidyl        
              isocyanurate                                                
                      isocyanurate                                        
                              isocyanurate                                
                                       isocyanurate                       
                                               isocyanurate               
                                                       isocyanurate       
Parts by weight                                                           
              0.3     0.3     0.3      0.3     0.3     0.3                
Reinforcement                                                             
Kind          Carbon fiber                                                
                      Carbon fiber                                        
                              Carbon fiber                                
                                       Carbon fiber                       
                                               Carbon fiber               
                                                       Carbon fiber       
Parts by weight                                                           
              25      25      25       25      25      25                 
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              1,480   1,450   770      1,500   1,560   1,470              
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              8.7     8.7     8.4      8.6     8.7     8.6                
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              29      20      11       35      33      17                 
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              144     146     141      148     149     145                
Ratio of improvement in                                                   
              1.9     1.4     1.0      1.9     2.0     1.9                
strength (ratio)                                                          
Remark        Invention                                                   
                      Invention                                           
                              Comparative                                 
                                       Invention                          
                                               Invention                  
                                                       Invention          
                              Example                                     
MFI (g/10 min)        39.9    6.1                                         
Spherical size (μ)                                                     
              100     100     100      10      10      100                
Moldability into flat                                                     
              Better  Best    Bad      Better  Better  Better             
plate 1 mm thick                                                          
__________________________________________________________________________
              Experiment No.                                              
              35      36       37     38      39      40                  
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100      100    100     100     100                 
Parts by weight                                                           
Peroxide                                                                  
Kind          --      Benzoyl  Benzoyl                                    
                                      Benzoyl *1      *1                  
                      peroxide peroxide                                   
                                      peroxide                            
Parts by weight                                                           
              --      0.2      0.2    0.2     0.2     0.2                 
Modifier                                                                  
Kind          --      Maleic   Maleic Maleic  Maleic  Maleic              
                      anhydride                                           
                               anhydride                                  
                                      anhydride                           
                                              anhydride                   
                                                      anhydride           
Parts by weight                                                           
              --      0.3      0.3    0.3     0.3     0.3                 
Polyfunctional compound                                                   
Kind          Triglycidyl                                                 
                      Triglycidyl                                         
                               Hexa-  Bisphenol A                         
                                              Triglycidyl                 
                                                      Hexamethylene       
              isocyanurate                                                
                      isocyanurate                                        
                               methylene                                  
                                      diglycidyl                          
                                              isocyanurate                
                                                      diamine             
                               diamine                                    
                                      ether                               
Parts by weight                                                           
              0.3     0.6      0.6    0.6     0.6     0.6                 
Reinforcement                                                             
Kind          Carbon fiber                                                
                      Carbon fiber                                        
                               Carbon Carbon  Carbon fiber                
                                                      Carbon fiber        
                               fiber  fiber                               
Parts by weight                                                           
              25      25       25     25      25      25                  
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              750     1,750    1,520  1,510   1,700   1,480               
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              8.3     8.6      8.5    8.7     8.7     8.6                 
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              13      40       33     30      38      30                  
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              141     145      144    146     146     145                 
Ratio of improvement in                                                   
              1.0     2.3      2.0    2.0     2.2     1.9                 
strength (ratio)                                                          
Remark        Comparative                                                 
                      Invention                                           
                               Invention                                  
                                      Invention                           
                                              Invention                   
                                                      Invention           
              Example                                                     
MFI (g/10 min)                                                            
              5.6                                                         
Spherical size (μ)                                                     
              100     10       10     10      10      10                  
Moldability into flat                                                     
              Bad     Good     Good   Good    Best    Best                
plate 1 mm thick                                                          
__________________________________________________________________________
              Experiment No.                                              
              41      42      43      44      45       46                 
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100     100     100     100      100                
Parts by weight                                                           
Peroxide                                                                  
Kind          *1      --      Benzoyl --      Benzoyl  Benzoyl            
                              peroxide        peroxide peroxide           
Parts by weight                                                           
              0.2     --      0.3     --      0.3      0.3                
Modifier                                                                  
Kind          Maleic  --      Maleic  --      Maleic   Maleic             
              anhydride       anhydride       anhydride                   
                                                       anhydride          
Parts by weight                                                           
              0.3     --      0.3     --      0.3      0.3                
Polyfunctional compound                                                   
Kind          Bisphenol A                                                 
                      --      --      Triglycidyl                         
                                              Triglycidyl                 
                                                       Triglycidyl        
              diglycidyl              isocyanurate                        
                                              isocyanurate                
                                                       isocyanurate       
              ether                                                       
Parts by weight                                                           
              0.6     --      --      0.3     0.3      3.0                
Reinforcement                                                             
Kind          Carbon  Carbon  Carbon  Carbon  Carbon   Carbon             
              fiber   fiber   fiber   fiber   fiber    fiber              
Parts by weight                                                           
              25      100     100     100     100      100                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              1,470   990     1,450   950     1,950    2,110              
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              8.6     21.5    22.0    21.8    22.2     27.3               
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              29      10      17      11      28       25                 
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              146     149     148     148     148      149                
Ratio of improvement in                                                   
              1.9     1.0     1.5     1.0     2.0      --                 
strength (ratio)                                                          
Remark        Invention                                                   
                      Comparative                                         
                              &#34;       &#34;       Invention                   
                                                       Invention          
                      Example                                             
MFI (g/10 min)                                                            
              10      3       6       3       5                           
Spherical size (μ)                                                     
              10                                                          
Moldability into flat                                                     
              Best                                                        
plate 1 mm thick                                                          
__________________________________________________________________________
              Experiment No.                                              
              47     48      49      50       51       52                 
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100    100     100     100      100     100                 
Parts by weight                                                           
Peroxide                                                                  
Kind          Benzoyl                                                     
                     Benzoyl Benzoyl --       --      --                  
              peroxide                                                    
                     peroxide                                             
                             peroxide                                     
Parts by weight                                                           
              0.3    0.3     0.3     --       --      --                  
Modifier                                                                  
Kind          Acrylic                                                     
                     Maleic  Maleic  --       Maleic  --                  
              acid   anhydride                                            
                             anhydride        anhydride                   
Parts by weight                                                           
              0.3    0.3     0.3     --       0.3     --                  
Polyfunctional compound                                                   
Kind          Triglycidyl                                                 
                     Hexameth-                                            
                             4,4&#39;-diphenyl                                
                                     --       --      Triglycidyl         
              isocyanu-                                                   
                     ylene   methane                  isocyanurate        
              rate   diamine diisocya-                                    
                             nate                                         
Parts by weight                                                           
              0.3    0.3     0.3     --       --      0.3                 
Reinforcement                                                             
Kind          Carbon Carbon  Carbon  Glass    Glass   Glass fiber         
              fiber  fiber   fiber   fiber    fiber                       
Parts by weight                                                           
              100    100     100     100      100     100                 
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              1,900  1,870   1,810   1,000    1,240   970                 
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              22.0   21.6    22.3    15.0     15.2    15.1                
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              27     26      28      12       19      13                  
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              149    148     147     148      149     148                 
Ratio of improvement in                                                   
              1.9    1.9     1.8     1.0      1.2     1.0                 
Remark        Invention                                                   
                     Invention                                            
                             Invention                                    
                                     Comparative                          
                                              Comparative                 
                                                      Comparative         
                                     Example  Example Example             
__________________________________________________________________________
              Experiment No.                                              
              53      54      55      56       57      58                 
__________________________________________________________________________
Composition of composite                                                  
material                                                                  
Polypropylene 100     100     100     100      100     100                
Parts by weight                                                           
Peroxide                                                                  
Kind          Benzoyl 1,1-Bis(t-                                          
                              *1      --       Benzoyl Benzoyl            
              peroxide                                                    
                      butylperoxy)-            peroxide                   
                                                       peroxide           
                      3,3,5-                                              
                      trimethyl-                                          
                      cyclohexane                                         
Parts by weight                                                           
              0.3     0.3     0.3     --       0.3     0.3                
Modifier                                                                  
Kind          Maleic  Maleic  Maleic  --       Maleic  Maleic             
              anhydride                                                   
                      anhydride                                           
                              anhydride        anhydride                  
                                                       anhydride          
Parts by weight                                                           
              0.3     0.3     0.3     --       0.3     0.3                
Polyfunctional compound                                                   
Kind          Triglycidyl                                                 
                      Triglycidyl                                         
                              Triglycidyl                                 
                                      --       --      Triglycidyl        
              isocyanurate                                                
                      isocyanurate                                        
                              isocyanurate             isocyanurate       
Parts by weight                                                           
              0.3     0.3     0.3     --       --      0.3                
Reinforcement                                                             
Kind          Glass fiber                                                 
                      Carbon fiber                                        
                              Carbon fiber                                
                                      Calcium  Calcium Calcium            
                                      carbonate                           
                                               carbonate                  
                                                       carbonate          
Parts by weight                                                           
              100     100     100     100      100     100                
Mechanical property of                                                    
molded product                                                            
Flexial strength                                                          
              1,590   1,850   1,920   390      510     600                
(kg/cm.sup.2)                                                             
Flexial modulus                                                           
              15.0    22.0    22.1    5.4      5.4     5.3                
(× 10.sup.4 kg/cm.sup.2)                                            
Izod impact strength                                                      
              24      22      27      8        9       16                 
(kg-cm/cm.sup.2)                                                          
HDT (°C.)                                                          
              149     148     149     80       80      80                 
Ratio of improvement in                                                   
              1.6     1.9     1.9     1.0      1.3     1.5                
strength (ratio)                                                          
Remark        Invention                                                   
                      Invention                                           
                              Invention                                   
                                      Comparative                         
                                               Comparative                
                                                       Invention          
                                      Example  Example                    
MFI (g/10 min)        14      12                                          
__________________________________________________________________________
 Notes                                                                    
 *1: A mixture of benzoyl peroxide and                                    
 1,1bis(t-butylperoxy)-3,3,5-trimethylcyclohexane (1:1)                   
 *2: A mixture of benzoyl peroxide and                                    
 2,5dimethyl-2,5-di(t-butylperoxy)hexyne-3 (1:1)                          
 
    
     EXAMPLE 2 
     To 100 parts by weight of polypropylene powders having an inherent viscosity of 2.0 (measured in a tetralin solution of 135° C.) were each added peroxides as shown in Table 2 and 0.3 part of maleic anhydride as a modifier, and the mixture was blended uniformly in the Henschel mixer. The mixture was then subjected to a heat-melting reaction under conditions of a reaction temperature of 250° C. and a reaction time period of 7 minutes. 
     The results obtained by measuring the inherent viscosity of modified polypropylenes thus-obtained are shown in Table 2 below. 
     
                       TABLE 2                                                     
______________________________________                                    
             Inherent Viscosity                                           
             Amount of Peroxide Added (parts)                             
Peroxide       0      0.05   0.1  0.3  0.4  0.8                           
______________________________________                                    
Benzoyl peroxide                                                          
               1.75   1.73   1.70 1.62 1.6  1.56                          
1,1-Bis(t-butylperoxy)-                                                   
               1.75   1.45   1.3  1.00 0.95 --                            
3,3,5-trimethyl cyclo-                                                    
hexane                                                                    
Dicumyl peroxide                                                          
               1.75   1.08   1.32 1.08 0.98 --                            
Benzoyl peroxide/1,1-                                                     
               1.75   --     1.31 1.09 --   --                            
Bis(t-butylperoxy)-3,3,5-                                                 
trimethyl cyclohexane (1:1                                                
weight ratio mixture)                                                     
______________________________________                                    
 
    
     While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.