Paint composition
This invention relates to a novel paint composition. More specifically, it relates to a paint composition having improved adhesion, flexibility, impact strength and alkali resistance which is prepared by incorporating a cyclopentadiene resin into an air drying paint comprising a chlorinated polyolefin rubber or a chlorinated polyolefin as at least one ingredient of a binder. 
     Chlorinated low-molecular-weight polyisoprene rubber, chlorinated low-molecular-weight polybutadiene rubber, chlorinated polyethylene and chlorinated polypropylene have been used widely as binders for air drying paints. These chlorinated polymers are obtained by chlorinating masticated natural rubber, masticated synthetic cis-1,4-polyisoprene rubber, masticated polybutadiene rubber, polyethylene resin or polypropylene resin. They are chemically stable with little susceptibility to attack by acids and alkalies. Films of these polymers have low permeability to water or a water vapor. These chlorinated polymers are rapid drying, and give very hard coated films. However, when these chlorinated polymers are used alone, they have the defect of being brittle and having poor adhesion to the substrate. The use of plasticizers is widespread in order to take advantage of the desirable characteristics of the chlorinated polymers. Examples of the plasticizers are phthalate esters or chlorinated paraffin. Use of the plasticizers can bring about an improvement of flexibility and adhesion to the substrate, but adversely affects the rapid drying property, hardness and chemical stability of the resulting coating. 
     Chlorinated polymers are also used as improvers for alkyd resin paints or oil varnish paints in order to take advantage of their superior properties such as rapid drying property, hardness, chemical resistance and low water permeability. Addition of a large quantity of such a chlorinated polymer causes an increase in the cost of production and in the viscosity of the resulting paint, and incompatibility with zinc-containing and aluminum-containing pigments. 
     One object of this invention is to improve the adhesion strength, flexibility and impact strength of coated films without impairing the characteristic water resistance, corrosion resistance and impact strength of paints having a chlorinated polymer as a binder (vehicle). 
     Another object of the invention is to provide an air drying paint composition having improved adhesion, flexibility, impact strength and alkali resistance and containing a chlorinated polymer as at least one ingredient of a binder. 
     Still another object of this invention is to provide a paint composition having superior water resistance, corrosion resistance, acid resistance and hardness and containing a chlorinated polymer as one ingredient of a binder. 
     These objects of the invention can be achieved by incorporating 5 to 100 parts by weight, per 100 parts by weight of the chlorinated polymer, of a cyclopentadiene resin having a softening point of 50° to 160° C. obtained by heat polymerization into an air drying paint containing as at least one ingredient of a binder a chlorinated polymer selected from the group consisting of chlorinated polydiolefin rubbers and chlorinated polyolefins, and if desired adding conventional compounding agents such as pigments, plasticizers, solvents, stabilizers and dispersants. 
     The cyclopentadiene resin used in this invention, is prepared by polymerizing 50 to 100% by weight, preferably 60 to 100% by weight, of a cyclopentadiene monomer and 50 to 0% by weight, preferably 40 to 0% by weight, of a comonomer copolymerizable with the aforesaid monomer, such as a diolefinic monomer, a monolefinic monomer or a polar vinyl monomer in the absence of a non-radical catalyst such as a cationic catalyst with or without an inert hydrocarbon solvent such as benzene, toluene or xylene at 200° to 300° C., preferably 250° to 280° C., for a period of 0.5 to 20 hours, preferably 1 to 10 hours, in an autoclave, and removing low-boiling products such as the unreacted materials by distillation or other usual means of polymer purification. The cyclopentadiene resin has a softening point of 50° to 160° C., preferably 80° to 140° C., and a Gardner color number of preferably not more than 10. A product obtained by hydrogenating the cyclopentadiene resin in a customary manner to reduce its color and improve its weatherability, and a product obtained by modifying the cyclopentadiene resin with an ethylenically unsaturated carboxylic compound typified by maleic anhydride can also be used as the cyclopentadiene resin in this invention. 
     If the resin has a cyclopentadiene monomer content of less than 50% by weight, it does not have sufficient compatibility with the chlorinated polymer, but has inferior ability to improve the drying property of the paint, and the hardness, flexibility and water resistance of the coated film. Thus, it is unsuitable as an additive for paints. Cyclopentadiene resins having a softening point of more than 160° C. have poor compatibility with chlorinated polymers. 
     The term &#34;cyclopentadiene monomer&#34;, as used in the present invention denote cyclopentadiene and its derivatives. It includes cyclopentadiene, cyclopentadienes substituted with a lower alkyl group such as methyl or ethyl, and lower Diels-Alder adducts of cyclopentadiene and its derivatives such as dimers, trimers or codimers. Since, cyclopentadiene is present as dicyclopentadiene stably at room temperature, cyclopentadiene and dicyclopentadiene are usually handled in quite the same manner. 
     The diolefinic monomer means not only conjugated diene compounds such as 1,3-butadiene, isoprene and 1,3-pentadiene, but also non-conjugated diene compounds such as 1,4-pentadiene and 1,5-hexadiene. 
     Examples of the monolefinic monomer are styrene, α-methylstyrene, ethylene, propylene, butene, and pentene. 
     The polar monolefinic monomer means a vinyl monomer having a polar group, and includes, for example, organic unsaturated cyano compounds such as acrylonitrile and methacrylonitrile; lower fatty acid esters of unsaturated alcohols such as vinyl acetate, vinyl propionate, allyl acetate, methallyl acetate, allyl propionate and methallyl propionate; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; esters formed between the aforesaid carboxylic acids and lower alcohols such as methyl alcohol, ethyl alcohol, butyl alcohol, glycide and ethylene glycol; unsaturated aldehydes such as acrolein and methacrolein; monohydric or polyhydric unsaturated alcohols such as allyl alcohol, crotyl alcohol, 1,4-butenediol and 3-hexane-2,5-diol; and unsaturated ethers such as allyl glycidyl ether. 
     The chlorinated polymer used in this invention is generally used as a binder for air drying paint compositions, and is obtained by chlorinating in a customary manner masticated natural rubber, masticated synthetic cis-1,4-polyisoprene rubber, low-molecular-weight synthetic cis-1,4-polyisoprene rubber, masticated polybutadiene rubber, polyethylene, or polypropylene, for example. These chlorinated polymers have a chlorine content of at least 55% by weight, preferably at least 60% by weight, and are soluble in toluene. They should have a viscosity, determined for its toluene solution at 25° C. in a concentration of 40% by weight, of 20 to 10,000 centipoises. One chlorinated polymer which meets these requirements is chlorinated masticated natural rubber having a molecular weight of 500 to 100,000. 
     It is essential in this invention that the aforesaid chlorinated polymer be contained as at least one ingredient of a binder. Usually, the amount of the chlorinated polymer is at least 20% by weight, preferably at least 30% by weight, based on the entire binder. A natural drying oil or an alkyd resin is, for example, used as another ingredient of the binder. 
     The cyclopentadiene resin should be added in an amount of 5 to 100 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of the chlorinated polymer. When the amount of the cyclopentadiene resin is too small, the improvement of the adhesion, flexibility, impact strength and alkali resistance of the coated film is not appreciably achieved. If it is too large, the drying speed of the coated film or its hardness are reduced. 
     The paint composition of this invention is prepared by dissolving the chlorinated polymer and cyclopentadiene resin in a paint-forming solvent such as toluene, xylene and solvent naphtha, and if desired, further adding another binder ingredient such as an alkyd resin, natural drying oil, amino resin or acrylic resin, a pigment such as titanium oxide, red lead, red iron oxide, zinc powder, calcium carbonate, or talc, a plasticizer such as dioctyl phthalate, dioctyl sebacate or chlorinated paraffin, and a stabilizer such as phenyl glycidyl ether or epoxidized soybean oil. 
     The composition is coated on the adherend by ordinary methods such as brush coating or spray coating, and allowed to stand at room temperature. If it is necessary to shorten the drying time, the coating is cured by forcible drying at a temperature of up to 100° C. Thus, a coated film can be formed which has superior hardness, adhesion, flexibility, impact strength, gloss, water resistance, corrosion resistance and chemical resistance. 
    
    
     The following Examples further illustrate the present invention. In these examples, all parts and percentages are by weight unless otherwise specified. 
     EXAMPLE 1 
     A monomeric mixture consisting of 70 parts of dicyclopentadiene and 30 parts of isoprene was heat polymerized at 260° C. for 3 hours in the presence of xylene to afford a cyclopentadiene resin having a softening point of 125° C. In accordance with the following compounding recipe, the resin was compounded with chlorinated rubber (chlorinated masticated natural rubber having a chlorine content of 65% by weight and a viscosity, determined for a toluene solution in a concentration of 40% at 25° C., of 300 centipoises) and other ingredients indicated to prepare a paint composition. 
     The composition was kneaded thoroughly in a ball mill, and coated on a degreased mild steel plate by a bar coater including piano wires having a diameter of 1 mm. The coating was dried for one week in an atmosphere kept at 25° C. and RH 60% to form a cured coating. The properties of the cured coating were measured in accordance with JIS K-5400. The results are shown in Table 1. 
     
         ______________________________________                                    
Compounding recipe                                                        
______________________________________                                    
Cyclopentadiene resin                                                     
                     0-55 parts)                                          
Chlorinated rubber                                                        
(CR-20, a product of                                                      
                    100-45                                                
Asahi Denka Co., Ltd.)                                                    
Chlorinated paraffin                                                      
(Chlorinated paraffin-40,                                                 
                    One-half of the                                       
a product of Ajinomoto                                                    
                    amount of the                                         
Co., Ltd.)          chlorinated rubber                                    
Titanium oxide (Tipaque                                                   
R-630, a product of 100                                                   
Ishihara Sangyo Co., Ltd.)                                                
Epoxidized soybean oil                                                    
(Adeka Cizer 0-120, a                                                     
product of Asahi Denka                                                    
                     10                                                   
Co., Ltd.)                                                                
Xylene              110                                                   
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                                           Table 1                                 
__________________________________________________________________________
              Compa-               Compa-                                 
              rison                                                       
                   Invention      rison                                   
Run No.       1    2    3    4    5                                       
__________________________________________________________________________
Cyclopentadiene resin (parts)                                             
              0    10   20   30   55                                      
Chlorinated rubber                                                        
              100  90   80   70   45                                      
Chlorinated Paraffin                                                      
              50   45   40   35   22.5                                    
Drying time (min.)                                                        
              45   45   55   45   120                                     
Pencil hardness                                                           
              H    H    F    HB   3B                                      
Flexural resistance (mm φ)                                            
              &gt;10  6    4    4    4                                       
Adhesion (crosscut test)                                                  
              62/100                                                      
                   100/100                                                
                        100/100                                           
                             100/100                                      
                                  100/100                                 
Erichsen test (mm)                                                        
              4    8    8    &gt;8   &gt;8                                      
DuPont impact test                                                        
              &lt;10  15   20   20   20                                      
(1/2&#34; × 300 g × cm)                                           
Water resistance                                                          
              no   no   no   no   no                                      
(dipped for 15 days at 40° C.)                                     
              change                                                      
                   change                                                 
                        change                                            
                             change                                       
                                  change                                  
Corrosion resistance                                                      
(salt spray at 35° C. for                                          
              &lt;1   &lt;1   &lt;1   &lt;1   &lt;1                                      
10 days; rust width, mm)                                                  
Acid resistance                                                           
(dipped for 14 days in 20%                                                
              no   no   no   no   no                                      
sulfuric acid)                                                            
              change                                                      
                   change                                                 
                        change                                            
                             change                                       
                                  change                                  
Alkali resistance                                                         
(the time which elapsed                                                   
until a swelling occurred                                                 
              1    5    5    15   15                                      
in 5% sodium hydroxide;                                                   
hours)                                                                    
Gloss (reflectance at 60°                                          
              84.6 91.5 91.0 91.2 90.4                                    
on the mirror surface)                                                    
__________________________________________________________________________
 
    
     These results demonstrate that the compositions of this invention have improved flexural strength, adhesion, Erichsen value, impact strength, alkali resistance and gloss over the composition not containing the cyclopentadiene resin (Run No. 1), but that when the cyclopentadiene is included in an amount larger than chlorinated rubber (Run No. 5), the drying time, hardness and water resistance are unsatisfactory. 
     EXAMPLE 2 
     A mixture of 75 parts of dicyclopentadiene and 25 parts of vinyl acetate was heat polymerized in the presence of xylene at 260° C. for 3 hours to form a cyclopentadiene resin having a softening point of 125° C. The resin was compounded with chlorinated rubber and other ingredients in accordance with the compounding recipe shown below to form a paint composition. 
     The paint composition was coated, and the properties of the coating were measured in the same way as in Example 1. The results are shown in Table 2. 
     
         ______________________________________                                    
Compounding recipe                                                        
______________________________________                                    
Cyclopentadiene resin                                                     
                     0-55 (parts)                                         
Chlorinated rubber                                                        
(CR-20, a product of                                                      
                    100-45                                                
Asahi Denka Co., Ltd.)                                                    
Alkyd resin (Beckosol                                                     
J-535, a product of  50                                                   
Dainippon Ink and                                                         
Chemicals, Inc.)                                                          
Chlorinated paraffin                                                      
(chlorinated Paraffin-40,                                                 
                    One-half of the                                       
a product of Ajinomoto                                                    
                    amount of the                                         
Co., Ltd.)          chlorinated rubber                                    
Titanium oxide (Tipaque                                                   
R-630, a product of 130                                                   
Ishihara Sangyo Co., Ltd.)                                                
Epoxidized soybean oil                                                    
(Adeka Cizer 0-120, a                                                     
product of Asahi Denka                                                    
                     10                                                   
Co., Ltd.)                                                                
Xylene              150                                                   
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                                           Table 2                                 
__________________________________________________________________________
              Compa-              Compa-                                  
              rison                                                       
                   Invention      rison                                   
Run No.       6    7    8    9    10                                      
__________________________________________________________________________
Cyclopentadiene resin (parts)                                             
              0    10   20   30   55                                      
Chlorinated rubber                                                        
              100  90   80   70   45                                      
Chlorinated paraffin                                                      
              50   45   40   35   22.5                                    
Drying time (min.)                                                        
              60   75   60   70   180                                     
Pencil hardness                                                           
              H    F    H    HB   3B                                      
Flexural strength (mm φ)                                              
              8    2    2    2    2                                       
Adhesion (crosscut test)                                                  
              70/100                                                      
                   100/100                                                
                        100/100                                           
                             100/100                                      
                                  100/100                                 
Erichsen test (mm)                                                        
              5    8    8    &gt;8   &gt;8                                      
Du Pont impact test                                                       
              10   50   35   45   70                                      
(1/2&#34; × 300 g × cm)                                           
Water resistance                                                          
              no   no   no   no   no                                      
(dipped at 40 ° C. for 15                                          
              change                                                      
                   change                                                 
                        change                                            
                             change                                       
                                  change                                  
days)                                                                     
Corrosion     resistance                                                  
(salt spray at 35° C. for                                          
              1.3  1.4  1.0  1.3  1.6                                     
10 days; rust width, mm)                                                  
Acid resistance                                                           
(dipped for 5 days in 20%                                                 
              no   no   no   no   no                                      
sulfuric acid)                                                            
              change                                                      
                   change                                                 
                        change                                            
                             change                                       
                                  change                                  
Alkali resistance                                                         
(the time which elapsed                                                   
until a swelling occurred                                                 
              &lt;1   2    2    2    10                                      
in 5% sodium hydroxide;                                                   
hours)                                                                    
Gloss (reflectance at 60°                                          
              83   88.7 89.4 90.2 92.6                                    
on the mirror surface)                                                    
Weatherability (the rate                                                  
of retention of gloss                                                     
after exposure for 300                                                    
              54.1 58.4 55.0 54.2 33.6                                    
hours to a weather-                                                       
ometer; %)                                                                
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     It is seen from these results that in the case of a paint comprising an alkyd resin-chlorinated rubber system as a binder, the compositions of this invention have improved flexural strength, adhesion, Erichsen value, impact strength, alkali resistance and gloss over the composition not containing the cyclopentadiene resin, but that when the amount of the cyclopentadiene resin is larger than the chlorinated rubber (Run NO. 10), the drying time, hardness and water resistance are unsatisfactory. 
     COMPARATIVE EXAMPLE 1 
     A paint composition was prepared in accordance with the same compounding recipe as in Run No. 8 (Example 2) except that a commercially available petroleum resin, Neopolymer 120 (a product of Nippon oil Chemical Co., Ltd.), was used instead of the cyclopentadiene resin. The properties of the coating from the paint composition were measured. It was found that a period of 11 hours was required for drying the coated film. 
     COMPARATIVE EXAMPLE 2 
     A paint composition was prepared in the same way as in Run No. 8 (Example 2) except that a commercially available coumarone resin, V-120 (a product of Nittetsu Chemical Industry Co., Ltd.), was used instead of the cyclopentadiene resin. The properties of the coating from the paint composition were measured. It was found that a period of 5 hours and 45 minutes was required for drying the coated film, and the Erichsen value was only 1.2 mm. 
     EXAMPLE 3 
     A monomeric mixture consisting of 70 parts of dicyclopentadiene and 30 parts of isoprene was heat polymerized in the presence of xylene at 260° C. for 3 hours to form a cyclopentadiene resin having a softening point of 125° C. 
     The resulting cyclopentadiene resin was compounded with chlorinated polyethylene (having a chlorine content of 63% by weight and a viscosity, determined for a toluene solution in a concentration of 40% by weight at 25° C., of 100 centipoises) and other ingredients indicated in accordance with the following compounding recipe. 
     The paint composition obtained was coated, and the properties of the coating were measured in the same way as in Example 1. The results are shown in Table 3. 
     
         ______________________________________                                    
Compounding recipe                                                        
______________________________________                                    
Cyclopentadiene resin  0-55 (parts)                                       
Chlorinated polyethylene                                                  
(Adekaprene CE-505, a 100-45                                              
product of Asahi Denka                                                    
Co., Ltd.)                                                                
Chlorinated paraffin                                                      
(Chlorinated paraffin-65,                                                 
                      75                                                  
a product of Ajinomoto                                                    
Co., Ltd.)                                                                
Titanium oxide (Tipaque                                                   
R-550, a product of   120                                                 
Ishihara Sangyo Co., Ltd.)                                                
Epoxidized soybean oil                                                    
(Adeka Cizer 0-120, a 5.5                                                 
product of Asahi Denka                                                    
Co., Ltd.)                                                                
Xylene                150                                                 
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                                           Table 3                                 
__________________________________________________________________________
              Compa-            Compa-                                    
              rison Invention   rison                                     
Run No.       11    12    13    14                                        
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Cyclopentadiene resin (parts)                                             
              0     10    30    55                                        
Chlorinated polyethylene                                                  
              100   90    70    45                                        
Thickness of the coated film                                              
              49    50    47    51                                        
(μm)                                                                   
Pencil hardness                                                           
              4B    4B    4B    6B                                        
Adhesion (crosscut test)                                                  
              55/100                                                      
                    90/100                                                
                          90/100                                          
                                100/100                                   
Erichsen test (mm)                                                        
              6     &gt;8    &gt;8    6                                         
Flexural strength (mm φ)                                              
              2     2     2     4                                         
Du Pont impact strength                                                   
              10    25    35    30                                        
(1/2&#34; × 300 g × cm)                                           
Water resistance                                                          
(dipped at 40° C. for 15                                           
              no change                                                   
                    no change                                             
                          no change                                       
                                no change                                 
days                                                                      
Alkali resistance                                                         
(the number of days which                                                 
elapsed until a swelling                                                  
              2     11    15    &gt;15                                       
occurred in 5% sodium                                                     
hydroxide)                                                                
Acid resistance                                                           
(the number of days which                                                 
elapsed until a swelling                                                  
              8     8     8     8                                         
occurred in 20% sulfuric                                                  
acid)                                                                     
Corrosion resistance                                                      
(salt spray at 35° C. for                                          
              1     1     1     1                                         
500 hours; rust width, mm)                                                
Weatherability                                                            
(the ratio of retention of                                                
gloss after exposure for                                                  
              75    77    80    76                                        
300 hours to a weather-                                                   
ometer)                                                                   
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     The results demonstrate that the compositions of this invention had improved adhesion, Erichsen value, impact strength and alkali resistance over the composition not containing the cyclopentadiene resin (Run No. 11), but that when the amount of the cyclopentadiene resin was larger than the chlorinated polyethylene (Run No. 14), the hardness, Erichsen value and flexural strength were unsatisfactory. 
     EXAMPLE 4 
     A monomeric mixture consisting of 75 parts of dicyclopentadiene and 25 parts of vinyl acetate was heat polymerized in the presence of xylene at 260° C. for 3 hours to form a cyclopentadiene resin having a softening point of 125° C. 
     The resulting cyclopentadiene resin was compounded with chlorinated polypropylene (having a chlorine content of 63% by weight, and a viscosity, determined for a toluene solution in a concentration of 40% by weight at 25° C., of 40 centipoises) and other ingredients indicated in accordance with the following compounding recipe. The resulting paint composition was coated, and the properties of the coated film were measured in the same way as in Example 1. The results are shown in Table 4. 
     
         ______________________________________                                    
Compounding recipe                                                        
______________________________________                                    
Cyclopentadiene resin  0-55 (parts)                                       
Chlorinated polypropylene                                                 
(Adekaprene CP-100, a 100-45                                              
product of Asahi Denka                                                    
Co., Ltd.)                                                                
Chlorinated paraffin                                                      
(Chlorinated Paraffin-65,                                                 
                      75                                                  
a product of Ajinomoto                                                    
Co., Ltd.)                                                                
Titanium oxide (Tipaque                                                   
                      120                                                 
R-550, a product of                                                       
Ishihara Sangyo Co., Ltd.)                                                
Epoxidized soybean oil                                                    
(Adeka Cizer 0-120, a                                                     
product of Asahi Denka                                                    
                      5.5                                                 
Co., Ltd.)                                                                
Xylene                150                                                 
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                                           Table 4                                 
__________________________________________________________________________
               Compa-            Compa                                    
               rison Invention   rison                                    
Run No.        15    16    17    18                                       
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Cyclopentadiene resin (parts)                                             
               0     15    30    55                                       
Chlorinated polypropylene                                                 
               100   85    70    45                                       
Thickness of the coated film                                              
(μm)        45    44    49    47                                       
Pencil hardness                                                           
               4B    4B    4B    6B                                       
Adhesion (crosscut test)                                                  
               80/100                                                     
                     100/100                                              
                           100/100                                        
                                 50/100                                   
Erichsen test (mm)                                                        
               6     &gt;8    &gt;8    2                                        
Flexural strength (mm φ)                                              
               2     2     2     2                                        
Du Pont impact strength                                                   
(1/2&#34; × 300 g × cm)                                           
               15    30    30    15                                       
Water resistance                                                          
(dipped at 40° C. for 1 month)                                     
               no change                                                  
                     no change                                            
                           no change                                      
                                 no change                                
Alkali resistance                                                         
(the number of days which                                                 
elapsed until a swelling                                                  
               1     3     3     3                                        
occurred in 5% sodium                                                     
hydroxide)                                                                
Acid resistance                                                           
(the number of days which                                                 
elapsed until a swelling                                                  
               3     3     3     3                                        
occurred in 20% sulfuric                                                  
acid)                                                                     
Corrosion resistance                                                      
(salt spray at 35° C. for 500                                      
hours; rust width, mm)                                                    
               1.5   1.5   1.5   1.5                                      
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     These results demonstrate that the compositions of this invention had improved adhesion, Erichsen value, impact strength and alkali resistance over the composition not containing the cyclopentadiene resin (Run No. 15), but that when the amount of the cyclopentadiene resin was larger than that of the chlorinated polypropylene (Run No. 18), the hardness, adhesion, Erichsen value and impact strength were unsatisfactory.