Flame retardant composition
This application is a continuation-in-part of copending application Ser. No. 619,722, filed Oct. 6, 1975, now abandoned, which is a continuation of Ser. No. 232,189, filed Mar. 6, 1972, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to plasticized polyolefin compositions and, more particularly to plasticized, flame retardant olefin polymer compositions. Specifically, the invention is directed to a composition consisting essentially of an olefin polymer containing, as a preferred embodiment, a compatible plasticizer and antimony oxide. 
     It is well known that conventional plasticizers are normally incompatible with olefin polymers. Thus, attempts to incorporate conventional plasticizers result in a product wherein the plasticizer &#34;blooms&#34;, i.e., separates and migrates to the surface, to such an extent that the product is unusable. 
     Although the use of plasticizers with olefin polymers would increase the olefin polymer characteristics, such as flexibility, and would improve low temperature properties and decrease processing temperatures, olefin polymers are not ordinarily plasticized at the present time in view of the problem discussed above. 
     Similarly, flame retardance has been difficult to build into olefin polymers since almost all additives appear to suffer from incompatibility with olefin polymers. 
     U.S. Pat. No. 2,525,961 provides certain chlorobutyl and chlorobutoxybutyl esters of phthalic acid as plasticizers for cellulose derivatives, vinyl chloride polymers and alkyd resins. The compounds disclosed, however, are not taught to be compatible with resins other than the named resins and there is no indication that similar esters could be used as compatible plasticizers for olefin polymers. 
     Accordingly, the main objective of the present invention is to provide compatible plasticizers for olefin polymers. 
     SUMMARY OF THE INVENTION 
     It has been unexpectedly discovered that certain halogenated organic acid esters are highly compatible with olefin polymers and may be incorporated therein as plasticizers. It has further been found that such halogenated acid esters increase the flame retardance of olefin polymers containing antimony trioxide. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In accordance with the present invention, it has been found that esters of organic acids of the general formula: ##STR3## wherein R represents alkyl, aryl, ##STR4## X represents halogen; and n represents the integers 4 or 5 
     are highly compatible plasticizers for olefin polymers. 
     The esters of the above formula are easily prepared by reacting the appropriate acid halide with a five or six membered cyclic ether. 
     Typical acid halides which are utilized in accordance with the present invention are the halides of aliphatic and aromatic acids, including saturated aliphatic monocarboxylic acids of from 2 to 18 carbon atoms, e.g., acetic, pentanoic, capric, lauric and stearic acids; saturated aliphatic dicarboxylic acids of from 4 to 10 carbon atoms, e.g., succinic, adipic and sebacic acids; unsaturated aliphatic dicarboxylic acids of 4 to 10 carbon atoms such as fumaric and maleic acid; aromatic dicarboxylic acids, e.g. phthalic acid and aromatic tricarboxylic acids, e.g., trimellitic acid. 
     It is understood that, as used herein, the terms &#34;alkyl&#34;, &#34;aliphatic&#34;, &#34;aryl&#34; and &#34;aromatic&#34; also include substituted structures such as alkyl, aryl and polar group substitution. 
     Illustrative cyclic ethers which are used in accordance with this invention include tetrahydrofuran, tetrahydro-2-methylfuran and tetrahydropyran. 
     Illustrative esters, which are utilized as flame retardant plasticizers in accordance with this invention, include 
     bis(4-chlorobutyl) phthalate, 
     4-chlorobutylbenzyl tetrachlorophthalate, 
     bis(4-chlorobutyl) adipate, 
     bis(4-chlorobutyl) tetrachlorophthalate, 
     bis(4-bromobutyl) adipate, 
     bis(4-bromobutyl) phthalate, 
     tris(4-bromobutyl) trimellitate, 
     bis(4-chlorobutyl) maleate, 
     4-chlorobutyl acetate, 
     4-bromobutyl stearate, 
     bis(5-chloropentyl) phthalate, and 
     5-bromopentyl butyrate. 
     The olefin polymers which are plasticized in accordance with this invention include polymonoolefins such as polyethylene, polypropylene, polybutylene, e.g. poly-n-butylene and polyisobutylene; polydiolefins such as polybutadiene, polyisoprene and polychloroprene; interpolymers of at least one monoolefin and a diolefin, e.g., ethylene/butadiene, propylene/iosprene, isobutylene/butadiene, ethylene/propylene/butadiene; interpolymers of at least one monoolefin and a comonomer selected from the group consisting of acrylonitrile, vinyl acetate and another monoolefin, e.g., ethylene/styrene, ethylene/acrylonitrile, ethylene/vinyl acetate, ethylene/propylene, ethylene/isobutylene; and polyblends of monoolefins with vinyl acetate and diolefins, e.g. polyethylene/polyvinyl acetate, ethylene/propylene interpolymer polyblended with polybutadiene. 
     The plasticizers of the present invention are incorporated in the olefin polymers by conventional milling or extrusion methods. 
     The plasticizers are generally added in plasticizing amounts of from about 1 to at least about 50 parts per hundred parts resin (i.e., phr) or more, but preferably are added in amounts of from about 5 to about 20 phr. 
     In addition to the plasticizers of the present invention, the olefin polymer compositions may contain other processing ingredients such as fillers, extenders, colorants, stabilizers and similar conventional processing additives. 
    
    
     The following non-limiting examples serve to illustrate certain specific embodiments of the present invention. 
     EXAMPLE 1 
     The following resin formulations are prepared: 
     
         ______________________________________                                    
                 Parts by Weight                                          
Ingredient         1     2     3   4   5   6                              
______________________________________                                    
Polyethylene       40    40    40  40  --  --                             
Polypropylene      --    --    --  --  20  20                             
Bis(4-chlorobutyl adipate)                                                
                   20    --    --  10  20  --                             
Bis(4-chlorobutyl phthalate)                                              
                   --    20    10  --  --  20                             
SANTOWHITE Powder.sup.1                                                   
                    1     1     1   1   1   1                             
______________________________________                                    
 .sup.1 4, 4&#39;-butylidenebis(6-tert-butyl-m-cresol)                        
 
    
     In all formulations, the adipate and phthalate plasticizers are compatible when added on a 2-roll mill as the polyethylene or polypropylene sheet is being worked. The material is slightly flexible. 
     EXAMPLE 2 
     A paste is prepared from 50 grams 4-chlorobutylbenzyl tetrachlorophthalate and 0.25 gram carbon black. 
     A polyethylene sheet is formed and 10 phr of the paste is milled into the resin at 150° C. 
     Similar results may be obtained by substituting ethylene/propylene, ethylene/vinyl acetate, ethylene/acrylonitrile, polyisobutylene, polybutadiene, polyisoprene, polychloroprene, poly-n-butylene, ethylene/butadiene, isobutylene/butadiene or ethylene/styrene polymers for the polyethylene of this example. 
     EXAMPLE 3 
     The following samples are prepared: 
     
         ______________________________________                                    
                 Parts by Weight                                          
Ingredient         Sample 1 Sample 2                                      
______________________________________                                    
Polyethylene       32       27.5                                          
SANTOWHITE Powder.sup.1                                                   
                   0.5      0.75                                          
Carbon Black       2        2                                             
Paste.sup.2        8        12                                            
______________________________________                                    
 .sup.1 4, 4&#39;-butylidenebis(6-tert-butyl-m-cresol)                        
 .sup.2 Paste = 50 parts 4-chlorobutylbenzyl tetrachlorophthalate and 0.25
 part carbon black                                                        
 
    
     The paste is compatible in both samples. 
     Similar results may be obtained by substituting polypropylene, ethylene/acrylonitrile, ethylene/vinyl acetate, ethylene/isobutylene polymers, polyethylene/polyvinylacetate and ethylene/propylene/polybutadiene for the polyethylene of this example. 
     EXAMPLE 4 
     The following samples are prepared: 
     
         __________________________________________________________________________
                    Parts by Weight                                       
Ingredients         1   2   3   4   5   6   7   8                         
Polypropylene       100 100 100 100 100 100 100 100                       
Antimony trioxide   --  5   5   5   5   5   5   5                         
Carbon black        --  3   3   3   3   3   3   3                         
Bis(4-chlorobutyl)tetrachlorophthalate                                    
                    --  --  --  --  --  10  --  --                        
Bis(4-bromobutyl)adipate                                                  
                    --  --  --  10  --  --  --  --                        
Bis(4-chlorobutyl)adipate                                                 
                    --  --  --  --  10  --  --  --                        
Bis(4-bromobutyl)phthalate                                                
                    --  --  --  --  --  --  10  --                        
Tris(4-bromobutyl)trimellitate                                            
                    --  --  --  --  --  --  --  10                        
4-Chlorobutylbenzyl tetrachlorophthalate                                  
                    --  --  --  --  --  --  --  --                        
Bis(4-chlorobutyl)phthalate                                               
                    --  --  10  --  --  --  --  --                        
Oxygen Index        18.1                                                  
                        18.8                                              
                            19.1                                          
                                19.9                                      
                                    19.1                                  
                                        19.6                              
                                            19.9                          
                                                19.6                      
Increase over differential of                                             
Samples 1 and 2     --  --  0.3 1.1 0.3 0.8 1.1 0.8                       
                    Parts by Weight                                       
Ingredients         9   10  11  12  13  14  15  16                        
Polypropylene       100 100 100 100 100 100 100 100                       
Antimony trioxide   5   5   5   5   5   5   5   5                         
Carbon black        3   3   3   3   3   3   3   3                         
Bis(4-chlorobutyl)tetrachlorophthalate                                    
                    --  20  --  --  --  --  --  --                        
Bis(4-bromobutyl)adipate                                                  
                    --  --  20  --  --  --  --  --                        
Bis(4-chlorobutyl)adipate                                                 
                    --  --  --  20  --  --  --  --                        
Bis(4-bromobutyl)phthalate                                                
                    --  --  --  --  --  20  --  --                        
Tris(4-bromobutyl)trimellitate                                            
                    --  --  --  --  --  --  20  --                        
4-Chlorobutylbenzyl tetrachlorophthalate                                  
                    10  --  --  --  --  --  --  20                        
Bis(4-chlorobutyl)phthalate                                               
                    --  --  --  --  20  --  --  --                        
0xygen Index        19.6                                                  
                        19.6                                              
                            20.6                                          
                                19.4                                      
                                    19.6                                  
                                        20.6                              
                                            20.9                          
                                                19.6                      
Increase over differential of                                             
Samples 1 and 2     0.8 0.8 1.8 0.6 0.8 1.8 2.1 0.8                       
__________________________________________________________________________
 
    
     The samples are milled at 177° C. for five minutes and molded at 150° C. for five minutes. All of the plasticizers are compatible with the polypropylene and complement the flame retardant characteristics imparted by antimony trioxide. 
     Oxygen index data is obtained by subjecting the samples to ASTM D2863-70 which is used to determine the relative flammability of plastics by measuring the minimum concentration of oxygen in a slowly rising mixture of O 2  /N 2  that will just support combustion. The &#34;oxygen index&#34; is defined as the minimum concentration of oxygen, expressed as volume percent, in a mixture of O 2  /N 2  that will just support combustion of the plastic material. 
     Similar results may be obtained if ethylene/propylene, ethylene/vinyl acetate, ethylene/propylene/butadiene interpolymer or ethylene/butadiene polymers are substituted for the polypropylene of this example. 
     EXAMPLE 5 
     The following samples are prepared: 
     
         __________________________________________________________________________
             Parts by Weight                                              
Ingredients  1   2   3   4   5   6   7   8   9   10                       
__________________________________________________________________________
Polypropylene                                                             
             100 100 100 100 100 100 100 100 100 100                      
Antimony trioxide                                                         
             --  5   5   5   5   5   10  10  10  10                       
Carbon black --  3   3   3   3   3   6   6   6   6                        
Bis(4-bromobutyl) adipate                                                 
             --  --  30  --  --  --  40  --  --  --                       
Tris(4-bromobutyl)                                                        
             --  --  --  30  --  --  --  40  --  --                       
 trimellitate                                                             
4-Chlorobutylbenzyl                                                       
 tetrachlorophthalate                                                     
             --  --  --  --  30  --  --  --  40  --                       
Bis(4-chlorobutyl)                                                        
 tetrachlorophthalate                                                     
             --  --  --  --  --  30  --  --  --  40                       
Oxygen Index 18.1                                                         
                 18.8                                                     
                     --.sup.1                                             
                         --.sup.1                                         
                             19.4                                         
                                 19.7                                     
                                     21.8                                 
                                         22  20.8                         
                                                 20.8                     
Increase over differential                                                
of Samples 1 and 2                                                        
             --  --  --  --  0.6 0.9 3.0 3.2 2.0 2.0                      
__________________________________________________________________________
  .sup.1 Samples not tested                                               
 
    
     The samples are milled at 177° C. and molded at 150° C. for five minutes. All of the plasticizers are compatible and those samples tested for oxygen indices show that the plasticizers also complement the flame retardant characteristics of antimony trioxide and thus impart a degree of flame retardance to the polymer. 
     EXAMPLE 6 
     The following samples are prepared: 
     
         ______________________________________                                    
            Parts by Weight                                               
Ingredients   1      2      3    4    5    6                              
______________________________________                                    
Polypropylene 100    100    100  100  100  100                            
Antimony trioxide                                                         
              --     5      5    10   7    5                              
Carbon black  --     3      3    --   4    3                              
Polyvinyl chloride                                                        
              --     --     10   20   7    3                              
Ba/Cd Stabilizer                                                          
              --     --     --   1    0.25 0.5                            
Tris(4-bromobutyl)                                                        
              --     --     40   40   10   --                             
trimellitate                                                              
4-Chlorobutylbenzyl                                                       
              --     --     --   --   --   15                             
tetrachloro-                                                              
phthalate                                                                 
Oxygen index  18.1   18.8   24.5 27.5 20.5 19.7                           
Increase over dif-                                                        
              --     --     5.7  8.7  1.7  0.9                            
ferential of Samples                                                      
1 and 2                                                                   
______________________________________                                    
 
    
     The samples are milled and molded as in Example 5 and subjected to oxygen index tests. 
     Samples 3 through 6 illustrate a preferred total plasticizer/flame retardant system for polyolefins. The samples contain a small amount of Ba/Cd stabilizer and a small amount of polyvinyl chloride resin which has been added to increase the chlorine concentration in the polypropylene. The plasticizers are compatible, and the oxygen index data for Samples 4 and 5 are outstanding. 
     Similar results may be obtained by substituting polyisobutylene or polyethylene polymers for the polypropylene of this example. 
     While the invention has been described hereinabove with regard to certain illustrative specific embodiments, it is not so limited since many modifications and variations are possible in light of the above teachings. It is understood therefore that the invention may be practiced otherwise than as specifically described without departing from the spirit and scope of the invention.