Concrete admixture
The present invention relates to concrete admixture for incorporation in cementing composition, for example, concrete mix, mortar, cement paste and the like. 
     More particularly, it relates to concrete admixture which comprises polyethyleneimine compounds mentioned below, which improve the flow properties of the cementing composition, especially facilitating high flow rates of the cementing composition when they are being pumped to its desired location during the cementing operation and which prevent the change of the consistency to a stiffer one with time, such as slump loss in concrete. 
     Said polyethyleneimine compounds are those having polysubstituents in which said substituents are selected from the group consisting of 
     (1) acidic group, acidic group(s) substituted-alkyl or acidic group(s) substituted-acyl and 
     (2) acidic group(s) substituted-alkyl and a group selected from the group consisting of carbamoylalkyl and hydroxyalkyl, namely, polyethyleneimine compounds of the invention are selected from the compound consisting of 
     (1) poly[acidic group(s) and/or acidic group(s) substituted-alkyl group(s) and/or acidic group(s) substituted-acyl group(s)]polyethyleneimine and 
     (2) poly[acidic group(s) substituted-alkyl and a group selected from the group consisting of carbamoylalkyl and hydroxyalkyl]polyethyleneimine. 
     More particularly, polyethyleneimine compounds are those having polysubstituents in which said substituents are selected from the group consisting of 
     (1) acidic group, 
     (2) acidic group(s) substituted-alkyl, 
     (3) acidic group(s) substituted-acyl, 
     (4) acidic group(s) substituted-alkyl and hydroxyalkyl and 
     (5) acidic group(s) substituted-alkyl and carbamoylalkyl, namely, polyethyleneimine compounds of the present invention are selected from the compound consisting of 
     (1) poly(acidic group)polyethyleneimine, 
     (2) poly[acidic group(s) substituted-alkyl group(s)]polyethyleneimine, 
     (3) poly[acidic group(s) substituted-acyl]polyethyleneimine, 
     (4) poly[acidic group(s) substituted-alkyl and hydroxyalkyl]polyethyleneimine and 
     (5) poly[acidic group(s) substituted-alkyl and carbamoylalkyl]polyethyleneimine. 
     These compounds (1) to (5) are hereinafter referred to as &#34;polyethyleneimine compounds&#34;. 
     The alkyl group in the term &#34;acidic group(s) substituted-alkyl&#34; in the above polyethyleneimine compounds may be further substituted with suitable substituent(s). 
     In addition to the characteristics as mentioned above, since the polyethyleneimine compounds of the present invention reduce apparently the viscosity of a cementing composition to which they are added, it is possible to reduce the unit water content of cementing composition, thus obtaining greater compressive strengths in the concrete as obtained. 
     Up to now, although various kinds of concrete admixture are known in the art, they are insufficient in improvement of the flow properties of the cementing composition and in prevention of the change of the consistency with time. 
     The inventors of the present invention conducted the research work to find out more preferable concrete admixture which possesses the improved characteristics in the flow properties and prevention of the change of the consistency of cementing composition, and have completed the present invention. 
     In the above and subsequent descriptions of the present specification, the various definitions which the present invention intends to include within the scope thereof are explained in detail as follows. 
     The term &#34;lower&#34; is used to intend a group having 1 to 6 carbon atom(s), unless otherwise provided. 
     Suitable acidic group and acidic group moiety in the terms &#34;acidic group(s) substituted-alkyl&#34; and &#34;acidic group(s) substituted-acyl&#34; may include carboxy, salt thereof, cyano, and the like. 
     The acidic group as substituent on alkyl or acyl group may be more than one, wherein the acidic groups may be the same or different. 
     Suitable salt of carboxy may include salt with base, for example, inorganic salt such as alkali metal salt (e.g., sodium salt, potassium salt, etc.), alkaline earth metal salt (e.g., calcium salt, magnesium salt, etc.) or the like. 
     Suitable alkyl moiety in the terms &#34;acidic group(s) substituted-alkyl&#34;, &#34;carbamoylalkyl&#34; and &#34;hydroxyalkyl&#34; may include lower alkyl and higher alkyl. 
     Suitable lower alkyl may be the ones having 1 to 6 carbon atom(s), which may be branched and may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl and the like. 
     Suitable higher alkyl may be the ones having 7 to 16 carbon atoms, which may be branched and may include heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl and the like. 
     Suitable acyl moiety in the term &#34;acidic group(s) substituted-acyl&#34; may be aliphatic acyl, aromatic acyl and the like and may include lower alkanoyl (e.g., formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, pivaloyl, etc.), aroyl (e.g., benzoyl, toluoyl, etc.) and the like. 
     The substituent(s) on the alkyl group in the term &#34;acidic group(s) substituted-alkyl&#34; may be hydroxy or the like. 
     Preferred examples of the polyethyleneimine compounds of this invention may be 
     (1) poly[dialkali metal dicarboxylatoalkyl(more preferably disodium dicarboxylato(lower)alkyl]-polyethyleneimine, 
     (2) poly[dicarboxyalkyl(more preferably dicarboxy(lower)alkyl)]polyethyleneimine, 
     (3) poly[alkali metal or alkaline earth metal carboxylatoalkyl(more preferably sodium or calcium carboxylato(lower)alkyl, or sodium carboxylato(higher)alkyl)]polyethyleneimine, 
     (4) poly[alkali metal carboxylatoalkyl(more preferably sodium carboxylato(lower)alkyl)]-poly[cyanoalkyl(more preferably cyano(lower)alkyl)]polyethyleneimine, 
     (5) poly[carboxyalkyl(more preferably carboxy(lower)alkyl)]polyethyleneimine, 
     (6) poly[dialkali metal dicarboxylatohydroxyalkyl(more preferably disodium dicarboxylatohydroxy(lower)alkyl)]polyethyleneimine, 
     (7) poly[alkali metal carboxylatoaroyl(more preferably sodium carboxylatobenzoyl)]polyethyleneimine, 
     (8) poly[carboxyalkyl(more preferably carboxy(lower)alkyl)]-poly[hydroxyalkyl(more preferably hydroxy(lower)alkyl)]polyethyleneimine, 
     (9) poly[carboxyalkyl(more preferably carboxy(lower)alkyl)]-poly[cyanoalkyl(more preferably cyano(lower)alkyl)]polyethyleneimine, 
     (10) poly[carboxyalkyl(more preferably carboxy(lower)alkyl) or dicarboxyalkyl(more preferably dicarboxy(lower)alkyl)]-poly[carbamoylalkyl(more preferably carbamoyl(lower)alkyl)]polyethyleneimine and 
     (11) poly[alkali metal carboxylatoalkyl(more preferably sodium carboxylato(lower)alkyl)]-poly[hydroxyalkyl(more preferably hydroxy(lower)alkyl)]polyethyleneimine. 
     The introduction rate of the said substituents on polyethyleneimine is not critical and preferable rate may vary depending on some factors, e.g., kind of the substituent, molecular weight of the starting polyethyleneimine, etc. 
     Molecular weight of the polyethyleneimine used as starting compound for the preparation of the object polyethyleneimine compounds is not critical and may be 200 to 100,000, preferablely 5,000 to 20,000. 
     The starting polyethyleneimine are known compounds and it is well known to a person skilled in the art that they include primary, secondary and tertiary amines. 
     The object polyethyleneimine compounds can be prepared by reacting polyethyleneimine with conventional introducing agents of the desired substituents in a conventional manner, and if necessary by subjecting the resultant to hydrolysis, etc. 
     Now, in order to show the utility of the polyethyleneimine compounds of the present invention, with regard to some representative compounds of this invention, the test data on mortar flow and concrete are shown in the following. 
     Test 1 Mortar flow test 
     (1) Test Method 
     Consistency was measured by mortar flow test, and flow values of the mortars containing the test compounds were compared with that of the same mortar containing no additive. 
     The procedure utilized in the mortar flow test was the basic procedure described in the Japan Industrial Standard (JIS) R 5201, which includes similar sections to ASTM C 109-83, C 230-83 and C 305-83. 
     Materials and the mortar composition utilized in the test are 520 g of ordinary Portland cement specified in JIS R 5210, 1040 g of graded Toyoura standard sand and 364 ml of water or the aqueous solution containing 1.1 g of the test compound. 
     The mortars were made by mechanical mixing of ingredients, and flow values were determined in accordance with JIS R 5201. A flow cone (ASTM C 230-83) on a flow table was packed with the fresh mortar prepared in a mixing bowl. After the flow cone was lifted off vertically, diameter of the extended mortar mass on the table was measured four times at approximately equispaced intervals. The flow value of the fresh mortar was expressed as an average diameter (mm) of the mortar mass. 
     After measurement of the flow, the mortar was recovered from the flow table to the mixing bowl, allowed to stand for 60 minutes and then remixed for 60  seconds in the bowl. The flow value was measured again for the determination of flow loss, as described above. 
     (2) Test Results 
     The test results are given in Table 1. 
     
                       TABLE 1                                                     
______________________________________                                    
Test compounds   Flow (mm)                                                
(Example Nos.)   0 min.  60 min.                                          
______________________________________                                    
 1               209     172                                              
 2               205     197                                              
 3               220     212                                              
 4               191     187                                              
 5               221     213                                              
 6               229     179                                              
 7               223     215                                              
 8               195     167                                              
 9               194     185                                              
10               196     182                                              
11               211     147                                              
12               208     197                                              
13               192     208                                              
14               224     175                                              
15               222     196                                              
16               211     195                                              
17               220     201                                              
18               200     193                                              
19               224     205                                              
20               222     215                                              
21               207     210                                              
22               228     170                                              
23               218     199                                              
24               209     196                                              
25               202     183                                              
26               216     198                                              
27               229     222                                              
28               215     182                                              
29               200     190                                              
30               209     203                                              
31               214     216                                              
32               218     193                                              
33               205     209                                              
34               218     204                                              
35               219     199                                              
36               214     227                                              
37               232     185                                              
38               213     222                                              
39               219     181                                              
40               223     225                                              
41               216     173                                              
42               208     195                                              
43               219     180                                              
44               204     185                                              
45               224     214                                              
46               208     170                                              
47               221     184                                              
48               206     204                                              
49               214     203                                              
50               216     197                                              
51               209     176                                              
Reference        169     144                                              
(non-additive)                                                            
______________________________________                                    
 
    
     Test 2 Concrete test 
     (1) Test Method 
     Consistency of the concrete containing test compounds were compared with that of the plain concrete (non-additive), and slump loss (the time-dependent change of consistency) of the concrete was compared with that of the reference concrete adjusted to the same initial slump by increasing unit water. The method utilized in the test was the basic procedure described in the Japan Industrial Standard (JIS) A 6204 for chemical admixtures for concrete and Guidelines of Architectural Institute of Japan for the use of superplasticizers in concrete. 
     Materials utilized in the test were as follows: 
     Cement: a mixture of ordinary Portland cements specified in JIS R 5210 from three different manufacturers. 
     Aggregates: sand from Fuji river and crushed stone from Kasama. Both were graded by following the standard specification in JIS A 6204. 
     Mix proportion of concrete is shown in Table 2. 
     The concrete was prepared by mixing cement, aggregates and water or water containing a test compound in a tilting mixer for 3 minutes on a scale of 30 liters, and was allowed to stand in a mixing pan. 
     Initial slump and the time-dependent change of slump (at every 20 minutes intervals to 1 hour) were measured after remixing in the mixing pan. 
     (2) Test Results 
     The results are given in Table 3. 
     
                       TABLE 2                                                     
______________________________________                                    
Mix proportion of concrete                                                
        Water-cement                                                      
        ratio    s/a    Unit weight (kg/m.sup.3)                          
Concrete  (%)        (%)    W    C    S    G                              
______________________________________                                    
Plain and 56.9       49     182  320  911  962                            
test concrete                                                             
Reference 63.8       49     204  320  882  932                            
concrete                                                                  
______________________________________                                    
 W: water, C: cement, S: sand, G: gravel                                  
 s/a: ratio of sand to aggregates (aggregates contain sand and gravel)    
 
    
     
                                           TABLE 3                                 
__________________________________________________________________________
             Dosage of                                                    
             the test                                                     
             compounds                                                    
                    Air                                                   
             [% (w/w) of                                                  
                    content                                               
                        Slump (cm)                                        
Concrete     cement]                                                      
                    (%) 0  20 40 60 minutes                               
__________________________________________________________________________
Plain concrete                                                            
             --     1.8  8.0                                              
                            7.0                                           
                               6.5                                        
                                  5.0                                     
Test concrete containing                                                  
a compound of Example 2                                                   
             0.52   1.5 20.5                                              
                           21.0                                           
                              19.5                                        
                                 19.0                                     
a compound of Example 3                                                   
             0.52   1.6 19.5                                              
                           21.0                                           
                              19.5                                        
                                 19.0                                     
a compound of Example 7                                                   
             0.52   2.0 16.5                                              
                           18.0                                           
                              17.5                                        
                                 18.5                                     
a compound of Example 17                                                  
             0.52   0.7 20.5                                              
                           19.0                                           
                              19.5                                        
                                 19.0                                     
a compound of Example 26                                                  
             0.52   2.4 19.5                                              
                           19.5                                           
                              19.0                                        
                                 19.0                                     
a compound of Example 27                                                  
             0.52   4.0 20.0                                              
                           20.0                                           
                              19.5                                        
                                 19.5                                     
a compound of Example 40                                                  
             0.52   2.6 17.0                                              
                           16.5                                           
                              16.0                                        
                                 17.0                                     
a compound of Example 50                                                  
             0.52   2.4 16.0                                              
                           15.5                                           
                              15.5                                        
                                 17.0                                     
Reference concrete                                                        
             --     1.6 17.0                                              
                           16.0                                           
                              15.0                                        
                                 13.5                                     
__________________________________________________________________________
 
    
     As clear from the test results as stated above, the polyethyleneimine compounds of the present invention improve the flow properties of the cementing composition (cf. high initial flow value) and prevent the slump loss in concrete as compared with the reference (non-additive). 
     It might be clear from the test results shown in Table 3 that the polyethyleneimine compounds much reduced unit water content without air-entraining. 
     Suitable dosage of the polyethyleneimine compounds of this invention to cementing composition may amount to 0.01-1.0% of cement, more preferably 0.1-0.6% of cement. 
     The following Examples are given for the purpose of illustrating the preparation of the polyethyleneimine compounds of the present invention. 
     The starting polyethyleneimine used in the following Examples are commercially available. 
    
    
     EXAMPLE 1 
     To a solution of polyethyleneimine (hereinafter referred to as &#34;PEI&#34;[average molecular weight (hereinafter referred to as &#34;molecular weight&#34;): 10,000] (43.0 g) in water (130 ml) was added dropwise maleic acid [Prepared from maleic anhydride (24.5 g) and water (29.0 g) (1/4 molar equivalent, a molar equivalent corresponds to one unit molecule of PEI) in water (37.5 ml)] at 25°-40° C. with stirring and the mixture was stirred for 2 hours at room temperature. Sodium hydroxide (20.0 g) in water (100 ml) was added to the aqueous solution with stirring, and the mixture was stirred for 18 hours under reflux to give an aqueous solution of poly(disodium 1,2-dicarboxylatoethyl)polyethyleneimine (83.0 g). The introduction rate of the acidic substituent (disodium 1,2-dicarboxylatoethyl) was calculated from amine and acid normalities determined by colloidal titration method described in &#34;Colloidal Titaration Method&#34; (published by Nankodo, 1969) and Kobunshi Ronbunshu 33, No. 6, 309-316(1976) to show 11.2%. (Hereinafter, the same colloidal titration method was applied to determine the introduction rate of the acidic substituent as introduced.). 
     EXAMPLE 2 
     To a solution of polyethyleneimine (molecular weight: 10,000) (32.1 g) in water (28 ml) was added dropwise maleic acid (7.2 g) (1/12 molar equivalent) in water (10.9 ml) [prepared from maleic anhydride (6.1 g) and water] at 30°-50° C. with stirring. The mixture was stirred for 10 hours under reflux to give an aqueous solution of poly(1,2-dicarboxyethyl)polyethyleneimine (39.3 g). The introduction rate of the acidic substituent was 7.2%. 
     EXAMPLE 3 
     To a solution of PEI (molecular weight: 10,000) (57.2 g) in water (78.8 ml) was added portionwise itaconic acid (21.6 g) (1/8 molar equivalent) at 25° to 40° C. with stirring. The mixture was stirred for 11 hours under reflux to give an aqueous solution of poly(2,3-dicarboxypropyl)polyethyleneimine (78.8 g). The introduction rate of the acidic substituent was 8.2%. 
     EXAMPLE 4 
     Poly(2,3-dicarboxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/16 molar equivalent of itaconic acid according to a similar manner to that of Example 3. 
     EXAMPLE 5 
     To a solution of PEI (molecular weight: 10,000) (62.0 g) in water (139 ml) was added dropwise acrylonitrile (19.1 g) (1/4 molar equivalent) at 28°-40° C. with stirring. The mixture was stirred for 1.25 hours at room temperature. Sodium hydroxide (14.4 g) in water (139 ml) was added to the reaction product, and the mixture was refluxed for 1 hour with stirring followed by removal of ammonia under reduced pressure at 45°-50° C. to give an aqueous solution of poly(sodium 2-carboxylatoethyl)-polyethyleneimine(95.9 g). The introduction rate of the acidic substituent was 22.1%. 
     EXAMPLE 6 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/3 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 33.1%. 
     EXAMPLE 7 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/5 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 18.7%. 
     EXAMPLE 8 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 600) with 1/4 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. 
     EXAMPLE 9 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight 1,800) with 1/2 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 46.1%. 
     EXAMPLE 10 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight 1,800) with 1/3 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 30.0%. 
     EXAMPLE 11 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/2 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 50.2%. 
     EXAMPLE 12 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: from 60,000 to 80,000) with 1/4 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 24.1%. 
     EXAMPLE 13 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: from 60,000 to 80,000) with 1/5 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 20.5%. 
     EXAMPLE 14 
     Poly(sodium 2-carboxylatoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: from 60,000 to 80,000) with 1/3 molar equivalent of acrylonitrile according to a similar manner to that of Example 5. The introduction rate of the acidic substituent was 33.0%. 
     EXAMPLE 15 
     To a solution of PEI(molecular weight: 10,000) (50.0 g) in water (112 ml) was added dropwise (61.7 g) acrylonitrile (1 molar equivalent) at 30°-40° C. with stirring. The mixture was stirred for 1 hour at room temperature and for 2 hours at 80° C. To the reaction product was added sodium hydroxide (1/4 molar equivalent) (11.2 g) in water (112 ml) and the mixture was refluxed for 42 hours with stirring to give an aqueous solution of poly(sodium 2-carboxylatoethyl)poly(2-cyanoethyl)polyethyleneimine (123.5 g). The introduction rate of the acidic substituent was 30.1%. 
     EXAMPLE 16 
     Poly(sodium 2-carboxylatoethyl)poly(2-cyanoethyl)polyethyleneimine was prepared by reacting PEI (molecular weight: 10,000) with 1 molar equivalent of acrylonitrile and 1/3 molar equivalent sodium hydroxide according to a similar manner to that of Example 15. The introduction rate of the acidic substituent was 22.3%. 
     EXAMPLE 17 
     To a solution of polyethyleneimine(molecular weight: 10,000) (82.5 g) in water (270 ml) was dropped acrylic acid (34.6 g) at 30°-40° C. under stirring, which was continued for 3 hours at 80° C. to give an aqueous solution of poly(2-carboxyethyl)polyethyleneimine (117.1 g). The introduction rate of the acidic substituent was 22.4%. 
     EXAMPLE 18 
     Poly(2-carboxyethyl)polyethyleneimine was prepared starting from PEI(molecular weight: 10,000) with 1/10 molar equivalent of acrylic acid according to a similar manner to that of Example 17. The introduction rate of the acidic substituent was 10.6%. 
     EXAMPLE 19 
     To a solution of PEI(molecular weight: 10,000) (32.5 g) in water (84.5 ml) was added dropwise methacrylic acid (13.0 g) (1/5 molar equivalent) at 25°-40° C. with stirring. The mixture was stirred for 3 days under reflux to give an aqueous solution of poly(2-carboxypropyl)polyethyleneimine (45.5 g). The introduction rate of the acidic substituent was 17.7%. 
     EXAMPLE 20 
     Poly(2-carboxyethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/5 molar equivalent acrylic acid according to a similar manner to that of Example 17. The introduction rate of the acidic substituent was 17.9%. 
     EXAMPLE 21 
     Poly(2-carboxyethyl)polyethyleneimine was prepared by reacting PEI (molecular weight: 5,000) with 2/9 molar equivalent of acrylic acid according to a similar manner to that of Example 17. The introduction rate of the acidic substituent was 22.2%. 
     EXAMPLE 22 
     To a solution of PEI(molecular weight: 10,000) (60.6 g) in water (85 ml) was added portionwise disodium epoxysuccinate (13.5 g) (1/16 molar equivalent) at room temperature with stirring, and the mixture was stirred for 3 hours at room temperature and for 5 hours at 50° C. to give an aqueous solution of poly(disodium 1,2-dicarboxylato-2-hydroxyethyl)-polyethyleneimine (74.1 g). The introduction rate of the acidic substituent was 5.5%. 
     EXAMPLE 23 
     To a solution of PEI(molecular weight: 10,000) (43.1 g) in water (70 ml) was added dropwise acrylamide (17.8 g) (1/4 molar equivalent) in water (80 ml) at 20°-45° C. with stirring. The mixture was stirred for 1 hour at room temperature. Calcium hydroxide (9.3 g) was added to the aqueous solution and the mixture was refluxed for 21 hours with stirring followed by removal of ammonia under reduced pressure to give an aqueous solution of poly(calcium 2-carboxylatoethyl)-polyethyleneimine (65.9 g). The introduction rate of the acidic substituent was 23.6%. 
     EXAMPLE 24 
     To a mixture of polyethyleneimine(molecular weight: 10,000) (41 g) and sodium hydroxide (9.5 g) in water (165 ml) was added chloroacetic acid (22.5 g) under cooling in an ice bath and the mixture was stirred at 75° C. for 2 hours to give an aqueous solution of poly(carboxymethyl)polyethyleneimine (57.7 g). The introduction rate of the acidic substituent was 17.2%. 
     EXAMPLE 25 
     To a solution of PEI(molecular weight: 10,000) (40.0 g) in water (210 ml) was added portionwise phthalic anhydride (34.4 g) (1/4 molar equivalent) over 1 hour with stirring at room temperature. The mixture was stirred for 61.5 hours at room temperature and sodium hydroxide (9.3 g) in water (30 ml) was added thereto to give an aqueous solution of poly(sodium 2-carboxylatobenzoyl)polyethyleneimine (79.5 g). The introduction rate of the acidic substituent was 20.0%. 
     EXAMPLE 26 
     To a solution of polyethyleneimine(molecular weight: 10,000) (46.9 g) in water (62.5 ml) was added dropwise acrylic acid (15.7 g) (1/5 molar equivalent) at 30°-40° C. with stirring. The mixture was stirred for 3 hours at 80° C. After cooling to room temperature the aqueous solution was diluted with water (31.2 ml). And ethylene oxide (31.2 g) (1/1.54 molar equivalent) was bubbled to the aqueous solution with stirring, keeping the temperature below 40 ° C. by occasional cooling, and the mixture was stirred for 2 hours at room temperature to give an aqueous solution of poly(2-carboxyethyl)-poly(2-hydroxyethyl)polyethyleneimine (93.8 g). The introduction rate of the acidic substituent was 15.4%. 
     EXAMPLE 27 
     To a solution of PEI(molecular weight: 10,000) (22.5 g) in water (63 ml) was added dropwise methacrylic acid (11.3 g) (1/4 molar equivalent) at 25°-40° C. with stirring. The mixture was stirred for 3 days under reflux. After cooling to room temperature propylene oxide (18.2 g) (1/1.67 molar equivalent) was added dropwise to the aqueous solution with stirring, and the mixture was stirred for 5 hours to give an aqueous solution of poly(2-carboxypropyl)-poly(2-hydroxypropyl)polyethyleneimine (52.0 g). The introduction rate of the acidic substituent was 23.1%. 
     EXAMPLE 28 
     Poly(2-carboxypropyl)-poly(2-cyanoethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/4 molar equivalent of methacrylic acid and 1/1.67 molar equivalent of acrylonitrile according to a similar manner to that of Example 27. The introduction rate of the acidic substituent was 31.3%. 
     EXAMPLE 29 
     Poly(2-carboxypropyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/6 molar equivalent of methacrylic acid and 1/1.46 molar equivalent of propylene oxide according to a similar manner to that of Example 27. 
     EXAMPLE 30 
     Poly(2-carboxypropyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/5 molar equivalent of methacrylic acid and 1/1.54 molar equivalent of propylene oxide according to a similar manner to that of Example 27. 
     EXAMPLE 31 
     Poly(2-carboxyethyl)-poly(2-hydroxypropyl)polyethyleneimine (95.6 g) was prepared by reacting PEI(molecular weight: 10,000) (43.1 g) with 2/9 molar equivalent of acrylic acid (16.0 g) and 1/1.59 molar equivalent of propylene oxide (36.5 g) according to a similar manner to that of Example 26. The introduction rate of the acidic substituent was 21.9%. 
     EXAMPLE 32 
     Poly(2-carboxyethyl)-poly(2-hydroxyethyl)polyethyleneimine was prepared by reacting PEI(molecular weight 10,000) with 2/9 molar equivalent of acrylic acid and 1/1.59 molar equivalent of ethylene oxide according to a similar manner to that of Example 26. The introduction rate of the acidic substituent was 18.7%. 
     EXAMPLE 33 
     Poly(2-carboxyethyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/5 molar equivalent of acrylic acid and 1/1.54 molar equivalent of propylene oxide according to a similar manner to that of Example 26. 
     EXAMPLE 34 
     To a solution of PEI(molecular weight: 10,000) (49.4 g) in water (100 ml) was bubbled ethylene oxide (32.9 g) (1/1.54 molar equivalent) with stirring keeping the temperature 20°-40° C. by occasional cooling, and the mixture was stirred for 2 hours at room temperature. Acrylic acid (16.5 g) (1/5 molar equivalent) was added dropwise to the aqueous solution at 30°-40° C. with stirring, and the mixture was stirred for 3 hours at 80° C. to give an aqueous solution of poly(2-carboxyethyl)-poly(2-hydroxyethyl)polyethyleneimine (98.8 g). The introduction rate of the acidic substituent was 17.8%. 
     EXAMPLE 35 
     Poly(2-carboxyethyl)-poly(2-hydroxyethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/1.59 molar equivalent of ethylene oxide and 2/9 molar equivalent of acrylic acid according to a similar manner to that of Example 34. The introduction rate of the acidic substituent was 20.0%. 
     EXAMPLE 36 
     Poly(2-carboxyethyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/1.54 molar equivalent of propylene oxide and 1/5 molar equivalent of acrylic acid according to a similar manner to that of Example 34. The introduction rate of the acidic substituent was 19.2%. 
     EXAMPLE 37 
     Poly(2-carboxyethyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/1.93 molar equivalent of propylene oxide and 1/3 molar equivalent of acrylic acid according to a similar manner to that of Example 34. 
     EXAMPLE 38 
     To a solution of PEI(molecular weight: 10,000) (42.9 g) in water (50 ml) was added dropwise acrylamide (46.0 g) (1/1.54 molar equivalent) in water (53 ml) at 20°-45° C. with stirring. The mixture was stirred for 1 hour at room temperature to give an aqueous solution of poly(2-carbamoylethyl)polyethyleneimine. Acrylic acid (14.3 g) (1/5 molar equivalent) was added dropwise to the aqueous solution with stirring and the mixture was stirred for 3 hours at 80° C. to give an aqueous solution of poly(2-carboxyethyl)-poly(2-carbamoylethyl)polyethyleneimine (103.2 g). The introduction rate of the acidic substituent was 23.4%. 
     EXAMPLE 39 
     Poly(2-carboxyethyl)-poly(2-carbamoylethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/1.93 molar equivalent of acrylamide and 1/3 molar equivalent of acrylic acid according to a similar manner to that of Example 38. The introduction rate of the acidic substituent was 37.7%. 
     EXAMPLE 40 
     Poly(2-carboxyethyl)-poly(2-carbamoylethyl)polyethyleneimine (103.0 g) was prepared by reacting PEI(molecular weight: 10,000) (42.7 g) with 1/1.59 molar equivalent of acrylamide (44.3 g) and 2/9 molar equivalent of acrylic acid (16.0 g) according to a similar manner to that of Example 38. The introduction rate of the acidic substituent was 25.6%. 
     EXAMPLE 41 
     To a solution of PEI(molecular weight: 10,000) (45.2 g) in water (60.3 g) was added dropwise acrylic acid (15.1 g) (1/5 molar equivalent) at 30°-40° C. with stirring. The mixture was stirred for 3 hours at 80° C. After cooling to room temperature, the aqueous solution was diluted with water (36 ml). Acrylonitrile (36.2 g) (1/1.54 molar equivalent) was added dropwise to the aqueous solution with stirring and the mixture was stirred for 2 hours at room temperature to give an aqueous solution of poly(2-carboxyethyl)-poly(2-cyanoethyl)polyethyleneimine (96.5 g). The introduction rate of the acidic substituent was 32.4%. 
     EXAMPLE 42 
     To a solution of PEI(molecular weight: 10,000) (50.0 g) in water (100 ml) was added dropwise acrylonitrile (15.4 g) (1/4 molar equivalent) at 30°-40° C. with stirring. The mixture was stirred for 1 hour at room temperature. Ethylene oxide (1/1.67 molar equivalent) (30.7 g) was bubbled to the reaction product with stirring, keeping the temperature below 40° C. by occasional cooling, and the mixture was stirred for 1 hour at room temperature. To the reaction product was added sodium hydroxide (11.6 g) in water (140 ml) and the mixture was refluxed for 3 hours with stirring to give an aqueous solution of poly(sodium -carboxylatoethyl)-poly(2-hydroxyethyl)polyethyleneimine (108.0 g). The introduction rate of the acidic substituent was 15.6%. 
     EXAMPLE 43 
     Poly(sodium 2-carboxylatoethyl)poly(2-hydroxyethyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/3 molar equivalent of acrylonitrile and 1/1.93 molar equivalent of ethylene oxide, successively, according to a similar manner to that of Example 42. The introduction rate of the acidic substituent was 24.9%. 
     EXAMPLE 44 
     Poly(sodium 2-carboxylatoethyl)poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/3 molar equivalent of acrylonitrile and 1/1.93 molar equivalent of propylene oxide, successively according to a similar manner to that of Example 42. The introduction rate of the acidic substituent was 26.5%. 
     EXAMPLE 45 
     To a solution of PEI(molecular weight: 10,000) (22.5 g) in water (63 ml) was added dropwise methacrylic acid (11.3 g) (1/4 molar equivalent) at 25°-40° C. with stirring. The mixture was stirred for 3 days under reflux. After cooling to room temperature, acrylamide (22.3 g) (1/1.67 molar equivalent) was added portionwise to the aqueous solution with stirring, and the mixture was stirred for 1 week at room temperature to give an aqueous solution of poly(2-carboxypropyl)poly(2-carbamoylethyl)polyethyleneimine (56.1 g). The introduction rate of the acidic substituent was 26.0%. 
     EXAMPLE 46 
     To a solution of polyethyleneimine (molecular weight: 10,000) (27.8 g) in water (24 ml) was added dropwise maleic acid (7.5 g) (1/10 molar equivalent) in water (11.1 ml) [prepared from maleic anhydride (6.3 g) and water] at 30°-50° C. with stirring. The mixture was stirred for 10 hours under reflux. After cooling to room temperature, the aqueous solution was diluted with water (35.2 ml). And acrylamide (34.5 g) (1/1.33 molar equivalent) was added portionwise to the aqueous solution with stirring, and the mixture was stirred 25 hours at room temperature to give an aqueous solution of poly(1,2-dicarboxyethyl)-poly(2-carbamoylethyl)-polyethyleneimine (69.8 g). The introduction rate of the acidic substituent was 8.6%. 
     EXAMPLE 47 
     To a solution of PEI(molecular weight: 10,000) (55.0 g) in water (100 ml) was bubbled ethylene oxide (29.1 g) (1/1.93 molar equivalent) with stirring keeping the temperature 30°-40° C. by occasional cooling, and the mixture was stirred for 1 hour at room temperature. Acrylonitrile (22.6 g) (1/3 molar equivalent) was added dropwise to the aqueous solution with stirring at 33°-39° C. and the mixture was stirred for 1 hour at room temperature. To the reaction product was added sodium hydroxide (17.1 g) in water (100 ml) and the mixture was refluxed for 3 hours with stirring to give an aqueous solution of poly(sodium 2-carboxylatoethyl)-poly(2-hydroxyethyl)-polyethyleneimine (124.1 g). The introduction rate of the acidic substituent was 26.1%. 
     EXAMPLE 48 
     Poly(sodium 2-carboxylatoethyl)-poly(2-hydroxypropyl)polyethyleneimine was prepared by reacting PEI(molecular weight: 10,000) with 1/1.93 molar equivalent of propylene oxide and 1/3 molar equivalent of acrylonitrile, successively, according to a similar manner to that of Example 47. The introduction rate of the acidic substituent was 21.5%. 
     EXAMPLE 49 
     Poly(2-carboxypropyl)-poly(2-carbamoylethyl)-polyethyleneimine (47.9 g) was prepared by reacting PEI(molecular weight: 10,000) (19.4 g) with 2/11 molar equivalent of methacrylic acid (7.1 g) and 1/1.5 molar equivalent of acrylamide (21.4 g) according to a similar manner to that of Example 45. The introduction rate of the acidic substituent was 15.6%. 
     EXAMPLE 50 
     To a solution of PEI (molecular weight: 10,000) (17.8 g) in water (24.5 ml) was added portionwise itaconic acid (6.7 g) (1/8 molar equivalent) at 25°-40° C. with stirring. The mixture was stirred for 11 hours under reflux. After cooling to room temperature, the aqueous solution was diluted with water (20.3 ml). And acrylamide (21.3 g) (1/1.38 molar equivalent) was added portionwise to the aqueous solution with stirring, and the mixture was stirred for 1 week at room temperature to give an aqueous solution of poly(2,3-dicarboxypropyl)-poly(2-carbamoylethyl)polyethyleneimine (45.8 g). The introduction rate of the acidic substituent was 9.0%. 
     EXAMPLE 51 
     To a solution of PEI(molecular weight: 10,000) (43.6 g) in water (80 ml) was added dropwise acrylonitrile (34.9 g) (1/1.54 molar equivalent) at 30°-40° C. with stirring. The mixture was stirred for 1 hour at room temperature. After diluted with water (13 ml), acrylic acid (14.6 g) (1/5 molar equivalent) was added dropwise to the reaction product with stirring, and the mixture was stirred for 3 hours at 80° C. to give an aqueous solution of poly(2-carboxyethyl)-poly(2-cyanoethyl)polyethyleneimine (93.1 g). The introduction rate of the acidic substituent was 31.1%.