Method of making functionalized styrene butadiene type latex binders
This invention relates to vinyl aryl-conjugated diene copolymers desirably containing functional comonomers as binders for paper, nonwovens, and textiles. 
     An object of this invention is to provide a latex binder providing improved properties for paper, nonwovens, and textiles. 
     This and other objects and advantages will become more apparent from the following detailed description and examples. 
     BRIEF STATEMENT OF THE INVENTION 
     It has been found that styrene-butadiene type latexes polymerized at low temperature and desirably containing small amounts of selected functional monomers provide excellent performance as binders for polyester and cellulosic substrates. The performance of these low temperature polymerized binders significantly exceeds those of the similar optimized binders prepared by the so-called hot polymerization process. 
     DISCUSSION OF DETAILS AND PREFERRED EMBODIMENTS 
     The latexes are prepared in anionic aqueous emulsion at 5° C. using a redox initiator. 
     Redox polymerization is known as shown by Whitby et al, &#34;Synthetic Rubber,&#34; John Wiley &amp; Sons, Inc. New York, 1954. 
     The latexes comprise: 
     a. a mixture of 35 to 60% by weight of at least one conjugated diene monomer having from 4 to 8 carbon atoms and from about 30 to 65% by weight of at least one vinyl aromatic monomer having from 8 to 12 carbon atoms, 
     b. a mixture according to a. containing additionally from about 1 to 3% by weight of at least one copolymerizable monomer selected from the group consisting of acrylic acid and methacrylic acid, 
     c. a mixture according to a. containing additionally from about 0.5 to 3.5% by weight of iraconic acid, 
     d. a mixture according to a. containing additionally from about 1 to 15% by weight at least one functional monomer having an activatable methyl, ethyl, propyl or butyl ester group and a vinyl group and 
     e. a mixture according to a. containing additionally from about 1 to 15% by weight of at least one functional monomer having an activatable methyl, ethyl, propyl or butyl ester group and a vinyl group and from about 1 to 0.5 to 3.5% by weight of iraconic acid. 
     The conjugated diene monomer is selected from the group consisting of butadiene - 1,3, (preferred), piperylene, isoprene, and 2,3-dimethyl-1, 3-butadiene. 
     The vinyl aromatic monomer is selected from the group consisting of styrene (preferred), alpha methyl styrene, p-tertiary butyl styrene, methyl vinyl toluene, p-vinyl toluene and 3-ethyl styrene. 
     The functional monomer is at least one monomer selected from the group consisting of: 
     methyl acrylamoidoglycolate (MAG), 
     ethyl acrylamidoglycolate (EAG), 
     butyl acrylamidoglycolate (BAG), 
     methyl acrylamidoglycolate methyl ether (MAGME) (Preferred), 
     butyl acrylamidoglycolate butyl ether (BAGBE), 
     methyl methacryloxyacetate, 
     ethyl acrylamido-N-oxalate (N-ethyloxalyl acrylamide), 
     N,N&#39;-Bis(ethyloxalyl)acrylamide, 
     N-isopropyl, N-ethyloxalyl-3 propylamino methacrylamide, 
     N-ethyloxalyl-N&#39;-methyleneaminoacrylamide, 
     ethyl N-2-ethyloxamatoacrylate, 
     ethyl 3-pyruvylacrylate, 
     ethyl methylenepyruvate, 
     methyl acrylthiocarbonyloxyacetate (Methylthiacryloxyacetate), 
     methyl thiacrylthioglycolate 
     methyl acryl-2-thiogylcolate, 
     methyl thiacrylamidoacetate, 
     methyl acrylamidoglycolate thioether, 
     methyl acrylamido-N-methylenethioglycolate and 
     p-ethyl oxalyl styrene. 
     These latexes contain the usual polymerization additives such as emulsifiers, chelating agents and chain transfer agents. The solids content of the latexes can vary from about 35 to 55%. The degree of polymerization can vary from about 90 to 100%. The latexes of the present invention can be used in paper, nonwovens, flooring felts, carpet backing adhesives, and so forth. 
     It has been found that when styrene butadiene (SB) latexes are prepared using a low temperature (5° C.) (41° F.) polymerization process, the resulting polymers have significantly improved bonding properties for polyester nonwovens compared to the polymers obtained under &#34;hot polymerization&#34; conditions (˜65° C.) (149° F.). In some applications, this improvement in performance is so large that the low temperature polymerized SB binders (no functional monomers added) perform even better than the hot polymerized binders which contain some functional monomers (e.g. acrylic acid, iraconic acid, MAGME). The addition of functional monomers during low temperature polymerization further improves the performance of these binders relative to those not containing the functional monomers. Also, it has been found that the low temperature polymerized SB latexes containing MAGME perform significantly better than the corresponding hot polymerized latexes as binders for cellulosic substrates. 
     The following example will serve to illustrate the present invention with more particularity to those skilled in the art. 
    
    
     EXAMPLE I 
     Preparation of Latexes 
     All polymerizations were carried out at 5° C. in quart size glass bottles using the general recipe (based on 150 parts of total monomer charge) and the procedures given below (Table I). 
     
                       TABLE I                                                     
______________________________________                                    
       LATEX                                                              
       A     B       C       D     E     F                                
______________________________________                                    
INGREDI-                                                                  
ENTS                                                                      
Solution A                                                                
         220.5   220.5   220.5 220.5 --    --                             
Solution B                                                                
         --      --      --    --    167.3 --                             
Solution C                                                                
         --      --                  --    167.3                          
Acrylic Acid                                                              
         --      1.5     3.0   --    --    --                             
Itaconic Acid                                                             
         --      --      --    1.5   0.43  --                             
Solution D                                                                
         --      --      --    --    57.7  57.7                           
Deionized                                                                 
         --      --      --    --    3.0   3.0                            
Water                                                                     
Solution E                                                                
         79.5    79.5    79.5  79.5  78.0  79.5                           
Styrene  11.25   9.75    8.25  9.75  3.0   3.75                           
Butadiene                                                                 
         60.0    60.0    60.0  60.0  60.0  60.0                           
Solution F.sup.(1)                                                        
         15.0    15.0    15.0  15.0  15.0  15.0                           
______________________________________                                    
 .sup.(1) Added after cooling the reactants to 5° C.               
 
    
     
         Solution A                                                                
         2.2 gm Na.sub.3 PO.sub.4.12 H.sub.2 O + 73.5 gm Dowfax           
         2Al (45% by weight) + 3157.9 gm                                  
         deionized water.                                                 
Solution B                                                                
         1.1 gm Na.sub.3 PO.sub.4.12 H.sub.2 O + 36.8 gm Dowfax           
         2Al (45% by weight) + 13.5 gm itaconic                           
         acid + 1188.9 gm deionized water.                                
Solution C                                                                
         1.1 gm Na.sub.3 PO.sub.4.12H.sub.2 O + 36.8 gm Dowfax 2Al        
         (45% by weight) + 1188.9 gm deionized                            
         water.                                                           
Solution D                                                                
         13% (by weight) MAGME in deionized water                         
Solution E                                                                
         1075 gm styrene + 8.0 gm Sulfole 120 +                           
         2.0 gm p-menthane hydroperoxide (50% by                          
         weight).                                                         
Solution F                                                                
         1.06 gm Sequestrene AA + 1.34 gm sodium                          
         formaldehyde sulfoxylate + 0.54 gm                               
         FeSO.sub.4.7 H.sub.2 O + 5.4 gm NaOH (10% by                     
         weight) + 261.4 gm deionized water                               
______________________________________                                    
 
    
     Procedure 
     The ingredients were added in the order listed and mixed well after each addition using a magnetic stirrer. Before the addition of butadiene-1,3, the bottles were sparged with N 2  for 10 minutes. The required amount of butadiene was then added, the bottles were capped and placed in the 5° C. bath for 1 hour. Solution F was then added through the cap using a syringe All bottles were reacted to vacuum at 5° C. Table II gives the weight percent of monomers charged for each latex and some of the properties of the resulting latexes. 
     
                       TABLE II                                                    
______________________________________                                    
        A     B       C       D     E    F                                
______________________________________                                    
MONOMERS                                                                  
Styrene   60      59      58    59    53.5 55                             
Butadiene 40      40      40    40    40   40                             
Acrylic Acid                                                              
          --       1       2    --    --   --                             
MAGME     --      --      --    --    5     5                             
Itaconic Acid                                                             
          --      --      --     1    1.5  --                             
Total Solids, %                                                           
          38.23   39.35   39.59 39.45 37.13                               
                                           39.54                          
pH        10.14   4.77    4.31  4.72  3.09 4.24                           
Brookfield                                                                
          2800    610     1110  1140  40.5 225                            
Viscosity, cps                                                            
______________________________________                                    
 
    
     The effectiveness of the above latexes as binders for polyester and cellulosic substrates was evaluated as follows. 
     Cellulosic Substrate 
     Whatman #4 chromatographic paper die-cut to 8&#34;×10&#34; was used. The sheets were saturated with the latex using a laboratory padder. The targeted binder add-on was 21.0±1% by weight. The saturated sheets were air dried at room temperature and then cured on a steam heated dryer at 315° F. for 15, 30, 180, and 240 seconds. All sheets were conditioned in accordance with TAPPI test method T402. The tensile strength was determined using 1&#34; wide strips cut from the sheets in the machine direction (MD) and the cross direction (CD). For wet tensiles, the samples were immersed in distilled water and completely wetted before testing. All reported tensile values represent wet total (MD+CD) tensile normalized to the average basis weight and average binder add-on of 74.6#/3000 ft. 2  ream and 21.0%, respectively. 
     Polyester Substrate 
     A carded web consisting of 1.5 dpf×1.5&#34; polyester was used. Die-cut 8&#34;×10&#34;sheets were saturated with the latex using a laboratory padder. Saturation was conducted by placing the web between two thicknesses of fiberglass window screen, immersing in the latex and removing the excess liquid by passing between pressure-controlled rubber and stainless steel rolls. Targeted binder add-on was 35±2% by weight (based on final total dry weight). 
     The saturated polyester sheets were first dried in a hot air oven at 250° F. for 5 minutes and then cured in a hot air oven at 320° F. for 30 seconds. 
     The tensile strengths were determined on the 1&#34; wide strips cut in the MD and CD directions. For wet tensile determination, the strips were immersed in distilled water until completely wetted and then tested. The reported values represent the average of 12 samples each. 
     The polyester application results for the latexes of this invention are given in Table III. For comparative purposes, two hot polymerized latexes, X and Y, which are not part of this invention but contain some of the monomers contained in latexes A-F were also included in this evaluation. The data in Table III clearly show the following: 
     (1) Low temparature polymerized Latex A which contains only styrene and butadiene performs significantly better than comparative Latex X which contains functional monomers MAGME, IA, and AAD in wet tensile strength. Also the wet tensile strength with Latex A is more than double that of the corresponding value obtained with comparative Latex Y which contains functional monomers IA and methacrylic acid. 
     (2) The addition of 1-2 parts of AA (Latexes B and C), 1 part of IA (Latex D), or 5 parts of MAGME (Latex F) during the low temperature polymerization further improves the performance of these binders. Wet tensile strengths exceeding double of that obtained with Latex X are achievable even without MAGME (Latexes, B, C, and D). 
     (3) A further increase in wet and dry tensiles is possible when both MAGME and IA are present (Latex E). 
     Another observation is that in addition to an increase in the dry and wet tensile observed with the low temperature polymerized latexes relative to that of the hot polymerized latexes, the binders of this invention retain a higher percentage of their dry strength under wet conditions (74.9-90.3%) than that for the hot polymerized binders (47.9-56.7%) (bottom row, Table III). 
     
                                           TABLE III                               
__________________________________________________________________________
POLYESTER APPLICATION RESULTS                                             
          LATEX                                                           
          A   B   C   D   E   F   X(1)                                    
                                      -Y(2)                               
__________________________________________________________________________
Basis Weight                                                              
          21.1                                                            
              22.3                                                        
                  21.5                                                    
                      22.1                                                
                          21.6                                            
                              21.6                                        
                                  21.0                                    
                                      22.0                                
Add-On, % 35.4                                                            
              36.1                                                        
                  36.7                                                    
                      35.1                                                
                          35.1                                            
                              35.6                                        
                                  33.8                                    
                                      37.3                                
Wet Tensile.sup.(3)                                                       
MD        2520                                                            
              3585                                                        
                  3321                                                    
                      3656                                                
                          3844                                            
                              3460                                        
                                  1755                                    
                                      1099                                
CD        372 547 523 690 776 687 239 125                                 
Total     2892                                                            
              4132                                                        
                  3844                                                    
                      4346                                                
                          4620                                            
                              4147                                        
                                  1994                                    
                                      1224                                
Dry Tensile.sup.(3)                                                       
MD        3326                                                            
              3831                                                        
                  3795                                                    
                      4069                                                
                          4495                                            
                              4178                                        
                                  3038                                    
                                      2259                                
CD        533 745 713 768 961 871 480 294                                 
Total     3859                                                            
              4576                                                        
                  4508                                                    
                      4837                                                
                          5456                                            
                              5049                                        
                                  3518                                    
                                      2553                                
 ##STR1## 74.9                                                            
              90.3                                                        
                  85.3                                                    
                      89.8                                                
                          84.7                                            
                              82.1                                        
                                  56.7                                    
                                      47.9                                
__________________________________________________________________________
 .sup.(1) Not part of this invention. A hot polymerized (65° C.)   
 latex, containing 5 parts MAGME, 1.5 parts itaconic acid, 2.0 parts      
 acrylamide (AAD), 40 parts butadiene, and 51.5 parts styrene as per U.S. 
 Pat. No. 4,808,660.                                                      
 .sup.(2) Not part of this invention. A hot polymerized (65° C.)   
 latex containing 1.5 parts itaconic acid, 0.25 parts methacrylic acid,   
 46.1 parts styrene, and 51.7 parts butadiene.                            
 .sup.(3) All tensile values are in gm/inch.                              
 
    
     Table IV gives the Normalized Wet Total Tensile (NWTT) data for the application of low temperature polymerized latexes as binders for a cellulosic substrate (Whatman #4). Also shown in Table IV is the corresponding data for a comparative latex (Latex X) according to the teachings of U.S. Pat. No. 4,808,660. From the data in Table IV, it is seen that Latexes E and F of this invention perform significantly better than the corresponding comparative Latex X. Specifically, Latexes E and F provide a 16-22% increase in maximum NWTT and a 33-38% increase in NWTT at 15 seconds cure time as compared to the corresponding values for Latex X. Latexes E and F are, therefore, faster curing than Latex X and provide a higher ultimate NWTT than that for Latex X. This is particularly significant because Latexes E and F provide this improved performance without the use of AAD which is contained in Latex X and which, according to the teachings of U.S. Pat. 4,808,660, provides a synergistic effect when used together with MAGME. 
     
                       TABLE IV                                                    
______________________________________                                    
CELLULOSIC (WHATMAN #4) APPLICATION RESULTS                               
       LATEX                                                              
       A    B     C      D     E     F     X.sup.(1)                      
______________________________________                                    
Cure Time.sup.(2)                                                         
(seconds)                                                                 
 15      7.7    4.4   4.9  12.1  31.6  30.5  22.9                         
 30      7.9    5.0   5.1  19.4  32.5  34.8  25.9                         
180      9.7    9.0   9.3  29.3  35.1  36.8  30.2                         
240      10.2   9.4   10.1 28.1  34.9  35.2  29.9                         
______________________________________                                    
 .sup.(1) Not part of this invention. A hot polymerized (65° C.)   
 latex containing 5 parts MAGME, 1.5 parts itaconic acid, 2.0 parts       
 acrylamide, 40 parts butadiene, and 51.5 parts styrene as per U.S. Pat.  
 No. 4,808,660.                                                           
 .sup.(2) At 315° F.                                               
 .sup.(3) All tensile values are in lbs./inch.                            
 
    
     The data in Table IV also show that even for Latex D of this invention which contains only 1.5 pphm itaconic acid as the functional monomer, the highest NWTT attained (29.3 lbs./inch) approaches that for Latex X (30.2 lbs./inch). Latex D does not contain MAGME. Thus, Latex D may be desirable for cellulosic applications that do not require fast curing. 
     As may be seen in Table IV, Latexes A, B, and C may not be as suitable as binders for cellulosics even though these latexes make excellent binders for polyester substrates (Table III). 
     EXAMPLE II 
     In another set of statistically designed experiments, the effect of varying the levels of MAGME, itaconic acid, butadiene, Sulfole 120, and Dowfax 2A1 on the performance of the resulting latexes was studied. Latexes were prepared according to the procedure described in Example I. Table V shows the amount of MAGME, itaconic acid, butadiene, styrene, Sulfole 120, and Dowfax 2A1 added per hundred parts of the total monomers charged. 
     The polyester application results for these latexes are given in Table VI. These results clearly demonstrate that the latexes of this invention provide excellent binding properties over the entire range of compositions studied (Table V). 
     Table VII gives the Normalized Wet Total Tensile (NWTT) data for the application of the latexes of Table V as binders for the cellulosic substrate (Whatman #4). These data show that an increase in the MAGME level increases both the cure rate (NWTT at 15 seconds) and the maximum NWTT attainable. An increase in the itaconic acid level has a similar, though a somewhat smaller, effect on the cure rate and the maximum NWTT. An increase in the butadiene level decreases the maximum NWTT but the cure rate is not affected signifcantly. Thus, a significant latitutde in butadiene content of these latexes is available by adjusting the MAGME and itaconic acid levels. 
     The data in Tables VI and vII also show that the variations in the Sulfole 120 and Dowfax 2A1 levels have no adverse effect on the properties of these binders. 
     
                                           TABLE V                                 
__________________________________________________________________________
Ingredients\                                                    
Latex  G  H  J  K  L  M  N  O  P  Q  R  S  T  U  V  W                     
__________________________________________________________________________
Styrene                                                                   
       63.5                                                               
          59.5                                                            
             61.5                                                         
                57.5                                                      
                   53.5                                                   
                      49.5                                                
                         51.5                                             
                            47.5                                          
                               63.5                                       
                                  59.5                                    
                                     61.5                                 
                                        57.5                              
                                           53.5                           
                                              49.5                        
                                                 51.5                     
                                                    47.5                  
Butadiene                                                                 
       35 35 35 35 45 45 45 45 35 35 35 35 45 45 45 45                    
MAGME  1  5  1  5  1  5  1  5  1  5  1  5  1  5  1  5                     
Itaconic                                                                  
       0.5                                                                
          0.5                                                             
             2.5                                                          
                2.5                                                       
                   0.5                                                    
                      0.5                                                 
                         2.5                                              
                            2.5                                           
                               0.5                                        
                                  0.5                                     
                                     2.5                                  
                                        2.5                               
                                           0.5                            
                                              0.5                         
                                                 2.5                      
                                                    2.5                   
Acid                                                                      
Sulfole 120                                                               
       0.3                                                                
          0.3                                                             
             0.3                                                          
                0.3                                                       
                   0.3                                                    
                      0.3                                                 
                         0.3                                              
                            0.3                                           
                               0.5                                        
                                  0.5                                     
                                     0.5                                  
                                        0.5                               
                                           0.5                            
                                              0.5                         
                                                 0.5                      
                                                    0.5                   
Dowfax 2Al                                                                
       1.5                                                                
          1.0                                                             
             1.0                                                          
                1.5                                                       
                   1.0                                                    
                      1.5                                                 
                         1.5                                              
                            1.0                                           
                               1.0                                        
                                  1.5                                     
                                     1.5                                  
                                        1.0                               
                                           1.5                            
                                              1.0                         
                                                 1.0                      
                                                    1.5                   
__________________________________________________________________________
 
    
     
                                           TABLE VI                                
__________________________________________________________________________
POLYESTER APPLICATION RESULTS                                             
LATEX                                                                     
      G   H   J   K   L   M   N   O   P                                   
__________________________________________________________________________
Basis Wt.                                                                 
      20.4                                                                
          21.6                                                            
              21.3                                                        
                  23.1                                                    
                      22.7                                                
                          21.7                                            
                              21.8                                        
                                  22.0                                    
                                      21.1                                
Add-On, %                                                                 
      34.1                                                                
          37.7                                                            
              36.4                                                        
                  38.7                                                    
                      37.7                                                
                          37.6                                            
                              36.4                                        
                                  38.6                                    
                                      36.7                                
Total Dry                                                                 
      3621                                                                
          3776                                                            
              3863                                                        
                  4792                                                    
                      3194                                                
                          3742                                            
                              3954                                        
                                  4144                                    
                                      3371                                
Tensile (1)                                                               
Total Wet                                                                 
      3690                                                                
          4449                                                            
              4572                                                        
                  4244                                                    
                      3528                                                
                          3296                                            
                              2929                                        
                                  4037                                    
                                      2869                                
Tensile (1)                                                               
              Q   R   S   T   U   V   W                                   
__________________________________________________________________________
        Basis Wt.                                                         
              21.7                                                        
                  21.8                                                    
                      22.2                                                
                          21.2                                            
                              21.7                                        
                                  22.1                                    
                                      21.5                                
        Add-On, %                                                         
              38.4                                                        
                  36.9                                                    
                      38.1                                                
                          36.6                                            
                              37.6                                        
                                  36.6                                    
                                      34.0                                
        Total Dry                                                         
              4533                                                        
                  4334                                                    
                      4440                                                
                          3541                                            
                              3891                                        
                                  4268                                    
                                      4291                                
        Tensile (1)                                                       
        Total Wet                                                         
              3575                                                        
                  3953                                                    
                      4237                                                
                          3186                                            
                              3832                                        
                                  3473                                    
                                      3841                                
        Tensile (1)                                                       
__________________________________________________________________________
 (1) All tensile values are in gm\inch                          
 
    
     
                                           TABLE VII                               
__________________________________________________________________________
CELLULOSIC (WHATMAN #4) APPLICATION RESULTS                               
       LATEX                                                              
       G  H  J  K  L  M  N  O  P  Q  R  S  T  U  V  W                     
__________________________________________________________________________
Curing                                                                    
Time (1)                                                                  
(Seconds) (2)                                                             
 15    14.9                                                               
          23.9                                                            
             22.2                                                         
                26.1                                                      
                   14.7                                                   
                      23.5                                                
                         20.3                                             
                            25.0                                          
                               16.8                                       
                                  25.2                                    
                                     22.6                                 
                                        26.9                              
                                           13.3                           
                                              21.8                        
                                                 18.7                     
                                                    24.8                  
 30    17.1                                                               
          24.6                                                            
             22.3                                                         
                26.1                                                      
                   15.3                                                   
                      23.3                                                
                         20.6                                             
                            27.3                                          
                               17.6                                       
                                  25.3                                    
                                     22.6                                 
                                        27.0                              
                                           14.5                           
                                              22.6                        
                                                 20.0                     
                                                    24.4                  
180    26.1                                                               
          27.3                                                            
             26.6                                                         
                29.0                                                      
                   21.6                                                   
                      25.8                                                
                         25.3                                             
                            29.1                                          
                               24.4                                       
                                  28.0                                    
                                     26.9                                 
                                        27.2                              
                                           21.5                           
                                              25.4                        
                                                 23.2                     
                                                    25.6                  
240    25.9                                                               
          27.4                                                            
             27.1                                                         
                28.8                                                      
                   22.1                                                   
                      25.5                                                
                         24.9                                             
                            28.9                                          
                               24.7                                       
                                  28.5                                    
                                     27.4                                 
                                        26.6                              
                                           22.1                           
                                              25.0                        
                                                 23.6                     
                                                    25.5                  
__________________________________________________________________________
 (1) At 315° F.                                                    
 (2) All tensile values are lbs/inch                                      
 
    
     Notes 
     &#34;Dowfax&#34;2A1--alkylated disulfonate diphenyloxide 
     Sulfole 120--t-dodecyl mercaptan, avg. mol, wt. 198, calc purity wt. 96.8% 
     Sequestrene AA--ethylene diamine tetraacctic acid