Patent Publication Number: US-5298556-A

Title: Mold release composition and method coating a mold core

Description:
PRIOR APPLICATION 
     This application is a divisional continuation-in-part from my application Ser. No. 07/917,772, filed Jul., 21, 1992, now U.S. Pat. No. 5,219,925. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to organopolysiloxane mold release compositions. More particularly, it refers to such mold release compositions also containing a methyl trimethoxy or triethoxy silane in an aqueous solution and methods for employing the composition in a mold. 
     2. Description of the Prior Art 
     In the process of preparing molded products such as urethanes, natural rubber, silicones, neoprene, and other synthetic elastomers, it is necessary to coat the core surfaces of molds to prevent the molded product from sticking to the mold. Coatings used to prevent such molded products from sticking to molds are called mold release agents. Some of the mold release agents previously used are solvent based, and some are water based. Polydimethylsiloxanes have been used as one of the ingredients in prior art mold release compositions, as well as methyl triethoxy silanes together with surfactants, and in many instances with a catalyst. U.S. Pat. Re. No. 32,318 describes an aqueous lubricating composition for time curing bladders containing polydimethylsiloxane, methyl hydrogen or methyl trimethoxy silane, a surfactant and a metal salt of an organic acid. Organic solvents were specifically excluded from the composition because they degraded the rubber surfaces and required frequency of recoat. U.S. Pat. No. 3,894,881 describes coating compositions applied to a plastic substrate for providing improved scratch resistance. These scratch resistant compositions contain a hydrolyzed silicon tetraalkoxide, a methyl trimethoxy silane, and a metal salt. U.S. Pat. No. 4,534,928 describes mold release compositions containing a polydimethylsiloxane, an alkoxysilane such as methyl trimethoxy silane, a metal alkoxide, and a non reactive volatile organic solvent which is substantially water-free. 
     Although these prior art mold release compositions have the ability to release molded products, they suffer from the need to recoat the molds frequently, have odor problems, or are toxic. A mold release composition is needed that is environmentally friendly and will permit greater than twenty releases of molded urethane, natural rubber, neoprene, and other synthetic elastomer for transfer, compression, and injection molding. 
     SUMMARY OF THE INVENTION 
     I have discovered a unique mold release composition which is non-toxic, environmentally friendly, and will allow greater than twenty releases of a molded urethane, silicone, natural rubber, neoprene, or other synthetic elastomer during compression or injection molding procedures. 
     My composition is an aqueous reaction mixture of a multifunctional polydimethyl siloxane emulsified polymer, a methyl triethoxy silane, substituted nonyl or octyl phenol derivative surfactants, fluoroalkyd non-ionic surfactant, and synthetic ethoxylated amines, silanol terminated siloxane, ethanol, acetic acid and water. This reaction mixture can be coated on a mold core surface and cured with heat to form a semi-permanent mold release surface. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Composition I of this invention is a reaction mixture of a multi-functional organo-silane crosslinker, and multi-functional polydimethyl siloxane emulsified polymer in a solution of water and ethanol. This reaction mixture produces a reactive silane in a mixture of emulsified poly organo siloxanes forming an interpenetrating network on a mold core surface upon application of heat. 
     Composition II contains the ingredients as a percent by weight in the following ranges: 
     
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0.5 to 12%                                                                
         a silane selected from the group consisting of                   
         methyl triethoxy silane, methyl trimethoxy silane,               
         vinyl triethoxy silane, vinyl trimethoxy silane,                 
         Gamma-ureidopropyltrialkoxy silane, where the                    
         alkoxy group has one to three carbon atoms,                      
         Gamma-glycidoxypropyltrimethoxy silane, octyl-                   
         triethoxy silane, Gamma-aminopropyltriethoxy                     
         silane, Gamma-isocyanatopropyltriethoxy silane,                  
         tetraethoxysilane, Gamma-methacryloxypropyl                      
         trimethoxysilane, Beta- (3,4-epoxycyclohexyl)                    
         ethyltrimethoxy silane, Gamma-mercaptopropyl-                    
         trimethoxy silane, and vinyl-tris (2-methoxyethoxy)              
         silane,                                                          
1 to 8%  a multi functional polydimethyl siloxane emulsified              
         polymer,                                                         
0.1 to 2.5%                                                               
         substituted nonyl or octyl phenol derivative                     
         surfactant,                                                      
0.05 to 4.0%                                                              
         fluoroalkyd non-ionic surfactant,                                
0.1 to 2.5%                                                               
         synthetic ethoxylated amine surfactant,                          
0.1 to 12.5%                                                              
         silanol terminated polydimethyl siloxane having a                
         molecular weight from 400 to 310,000,                            
0.5 to 8%                                                                 
         lower alkyl alcohol, wherein the alkyl has 1-3                   
         carbon atoms,                                                    
70 to 97%                                                                 
         water, and                                                       
0.5 to 1%                                                                 
         a weak acid to maintain the pH between 4.5 to 5.5.               
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     Three to five grams of the composition is applied to each square foot of a mold core surface and then heated to about 320 degrees F to form the interpenetrating network. 
     The two preferred compositions are prepared by mixing the following ingredients (% by weight) in water: 
     COMPOSITION I 
     3% methyl triethoxy silane, 
     1.8% deca methyl cyclopenta siloxane, 
     1.6% octo methyl cyclotetra siloxane, 
     0.6% dodeca methyl cyclo hexa siloxane, 
     1.5% surfactants which are a substituted nonyl and octyl phenol derivative and synthetic ethoxylated amines, 
     3.0% ethanol, and 
     88.5% water. 
     The methyl triethoxy silane reacts with the water to produce additional ethanol. The mixture is sprayed on a clean mold core surface and heated to 320 degrees F. to vaporize the water and coat the mold core. 
     The methyl triethoxy silane can be substituted with methyl trimethoxy silane, vinyl triethoxy silane or vinyl trimethoxy silane to achieve substantially the same results in the mixture and on spraying the resulting mixture on a mold core. 
     COMPOSITION II 
     3.4% methyl triethoxy silane, 
     1.8% deca methyl cyclopenta siloxane, 
     1.6% octo methyl cyclotetra siloxane, 
     0.6% dodeca methyl cyclo hexa siloxane, 
     1.5% non-ionic fluorinated alkyl esters surfactant, 
     0.5% substituted nonyl and octyl phenol surfactant, 
     0.3% synthetic ethoxylated amine surfactant, 
     2.6.% ethanol, 
     3.0% silanol terminated polydimethyl siloxane having a molecular weight between 400 and 310,000, 
     1% acetic acid, and 
     83.7 water. 
    
    
     The following examples exemplify methods of preparing the compositions of this invention and applying them to mold core surfaces. 
     EXAMPLE I 
     197 grams of distilled water was mixed with 23 grams of the mixture of siloxanes set forth above in the preferred composition I, together with substituted nonyl and octyl phenol derivative and synthetic ethoxylated amine surfactant mixtures and 9.4 grams of methyl triethoxy silane. 120 grams of ethanol was mixed with 2725 grams of tap water, 30 grams of methyl triethoxy silane and 300 grams of the aforementioned siloxane and surfactant mixture. The two mixtures were then blended and sprayed on a four inch mold. Both sides of the mold were preheated to 320 degrees F. and cured for five minutes. 
     A polyether millable urethane compound was applied and cured in the mold and released twenty times with no noticeable sticking on the mold. 
     Additional mold release compositions were prepared in the manner of EXAMPLE I with the ingredients indicated by weight percent in the following EXAMPLES II-V. 
     EXAMPLE II 
     1% methyl triethoxy silane, 
     0.9% deca methyl cyclopenta siloxane, 
     0.8% octo methyl cyclotetra siloxane, 
     0.6% dodeca methyl cyclo hexa siloxane, 
     0.75% surfactants, 
     1.0% ethanol and 
     96.0% water. 
     EXAMPLE III 
     6% methyl triethoxy silane, 
     1.8% deca methyl cyclopenta siloxane, 
     1.6% octo methyl cyclotetra siloxane, 
     0.6% dodeca methyl cyclo hexa siloxane, 
     1.5% surfactants, 
     3.0% ethanol and 
     85.5% water. 
     EXAMPLE IV 
     8% methyl triethoxy silane, 
     3.6% deca methyl cyclopenta siloxane, 
     3.2% octo methyl cyclotetra siloxane, 
     1.2% dodeca methyl cyclo hexa siloxane, 
     3.0% surfactants, 
     6.0% ethanol and 
     75% water. 
     EXAMPLE V 
     12% methyl triethoxy silane, 
     3.6% deca methyl cyclopenta siloxane, 
     3.2% octo methyl cyclotetra siloxane, 
     1.2% dodeca methyl cyclo hexa siloxane, 
     3.0% surfactants, 
     6.0% ethanol and 
     71% water. 
     EXAMPLE VI 
     A mold was used that had an undercut and a difficult configuration to mold. In a mold such as this, molding compounds will easily stick and tear. The mold was first degreased and then sandblasted. Thereafter, the mold release composition of EXAMPLE I above, was sprayed on the mold in a thin coating heated to molding temperature. Each of the following fluoroelastomer molding compositions was separately applied to the mold and released from the mold after curing thirty times without tearing. 
     
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MOLDING COMPOUND A                                                        
INGREDIENTS             PHR                                               
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Viton E-60-C Dupont Fluoroelastomer                                       
                        100.0                                             
VPA No 3 Proprietary Viton Process Aid                                    
                        1.0                                               
Mag-D Magnesium Oxide   3.0                                               
Calcium Hydroxide       6.0                                               
N-990 Carbon black filler MT type                                         
                        30.0                                              
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MOLDING COMPOUND B                                                        
INGREDIENTS             PHR                                               
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Viton A401C Dupont Fluoroelastomer                                        
                        100.0                                             
Maglite D Magnesium Oxide                                                 
                        3.0                                               
Calcium Hydroxide       6.0                                               
Carnauba Wax            1.0                                               
N-990 Carbon black filler MT type                                         
                        20.0                                              
Powdered Teflon MP-1500 10.0                                              
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MOLDING COMPOUND C                                                        
INGREDIENTS             PHR                                               
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Viton A401C Dupont Fluoroelastomer                                        
                        100.0                                             
Maglite D Magnesium Oxide                                                 
                        3.0                                               
Calcium Hydroxide       6.0                                               
Carnauba Wax            1.0                                               
N-990 Carbon black filler MT type                                         
                        35.0                                              
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     EXAMPLE VII 
     A steel mold designed with a difficult undercut was employed. Any sticking at the undercut will result in a tear. The mold was first degreased and then sandblasted. The mold was heated to the molding temperature and the mold release composition of EXAMPLE I above was sprayed in the mold. Each of the following two silicone elastomer molding compositions were separately applied to the mold and released from the mold after curing. Thirty moldings were performed and no sticking or tearing occurred. 
     
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MOLDING COMPOUND D                                                        
INGREDIENTS              PHR                                              
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General Electric Silicone SE-4404U                                        
                         100.0                                            
Titanium Dioxide         1.0                                              
2,5-Dimethyl-2,5-Di (t-butyl-peroxy) hexane                               
                         1.0                                              
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MOLDING COMPOUND E                                                        
INGREDIENTS              PHR                                              
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General Electric Silicone SE-88U                                          
                         100.0                                            
Titanium Dioxide         1.0                                              
2,5-Dimethyl-2,5-Di (t-butyl-peroxy) hexane                               
                         1.0                                              
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     EXAMPLE VIII 
     A steel mold designed with a difficult undercut was employed. Any sticking at the undercut will result in a tear. The mold was first degreased and then sandblasted. The mold was heated to the molding temperature and the mold release composition of EXAMPLE I above, was sprayed on the mold in a thin coat. Each of the following two urethane gum molding compositions was separately applied to the mold and released from the mold after curing. Thirty moldings were performed and no sticking or tearing occurred. 
     
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MOLDING COMPOUND F                                                        
INGREDIENTS                   PHR                                         
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Polyether/TDI Millable Urethane Gum                                       
                              50.0                                        
Butadine Acrylonitrile Copolymer                                          
                              35.0                                        
Styrene Butadiene Copolymer   15.0                                        
Stearic Acid                  1.0                                         
Zinc Stearate                 0.5                                         
N-550 FEF Carbon Black        25.0                                        
N-770 SRF Carbon Black        15.0                                        
Kaolin (hard) Clay (hydrated aluminum silicate)                           
                              50.0                                        
Dioctyl Phthalate             14.0                                        
Petroleum Hydrocarbon         2.0                                         
Polymerized 1,2-Dihydro-2,2,4-Trimethylquinoline                          
                              3.0                                         
Benzothiazyl Disulfide        4.0                                         
2-Mercaptobenzothiazole       2.0                                         
Partial complex of Zinc Chloride &amp; Benzothiazyl Disulfide                 
                              1.0                                         
99% Pure Sulfur Powder        2.0                                         
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MOLDING COMPOUND G                                                        
INGREDIENTS                PHR                                            
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Polyether/TDI Millable Urethane Gum                                       
                           100.0                                          
Low Molecular Weight Polyethylene Powder                                  
                           2.0                                            
Zinc Stearate              0.5                                            
Precipitated Hydrated Amorphous Silica                                    
                           35.0                                           
Coumarone-indene Resin     10.0                                           
Teflon Powder MP-1500      1.0                                            
Naphthenic Oil             1.0                                            
Blue Pigment in an EPDM binder 80%                                        
                           1.5                                            
Titanium Dioxide           0.7                                            
Benzothiazyl Disulfide     4.0                                            
2-Mercaptobenzothiazole    2.0                                            
Partial complex of Zinc Chloride &amp; Benzothiazyl                           
                           1.5                                            
Disulfide                                                                 
99% Pure Sulfur Powder     1.5                                            
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     EXAMPLE IX 
     1720 grams of distilled water was mixed with 111 grams of the siloxanes, substituted vinyl and octyl phenol surfactant and synthetic ethoxylated amine surfactant in the proportion set forth in Composition II, above. To this aqueous mixture was added 34 of ethanol and 68 grams of methyl triethoxy silane. A second mixture was prepared containing 31 grams of a silanol terminated polydimethyl siloxane having a molecular weight of about 1000, 10 grams of a non-ionic fluorinated alkyl ester surfactant and 14  grams of 1 Normal acetic acid. 
     The two mixtures were blended and sprayed on a four inch mold at ambient temperature. Both sides of the mold were heated to the molding temperature of 320 degrees F. A polyether millable urethane compound is applied repeatedly and cured in the mold and released twenty times with no noticeable sticking on the mold. 
     EXAMPLE X 
     A steel mold designed with a difficult undercut was employed. Any sticking at the undercut will result in a tear. The mold was first degreased and then sandblasted. The mold was heated to the molding temperature and the mold release composition of EXAMPLE IX above, was sprayed on the mold in a thin coat. Each of the following five elastomer molding compositions was separately applied to the mold and released from the mold after curing. Thirty moldings were performed and no sticking or tearing occurred. 
     
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MOLDING COMPOUND H                                                        
                         PHR                                              
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Ethylene/acrylic elastomer silica (DuPont)                                
                           123.0                                          
2,2-methylene-bis (4-methyl-6- butyl phenol)                              
                           2.0                                            
oxidation inhibitor (American Cyanamid)                                   
Fatty acid process aid (Harwick)                                          
                           0.5                                            
Foamed silica (Degussa)    5.0                                            
Calcium carbonate (E.C.E. AMERICA)                                        
                           100.0                                          
N, N-di-phenylene dimaleimide peroxide vulcanizing                        
                           2.0                                            
coagent (DuPont)                                                          
Dicumyl peroxide vulcanizing agent (Hercules)                             
                           7.0                                            
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MOLDING COMPOUND I                                                        
                 PHR                                                      
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AFLAS ISOP         100                                                    
TAIC (75% dispersion)                                                     
                   7.5                                                    
Vul-Cuip 401SE     2.5                                                    
Sodium stearate    2.0                                                    
Medium Thermal Black                                                      
                   28                                                     
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MOLDING COMPOUND J                                                        
                          PHR                                             
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Fluoroelastomer (3M)        100.0                                         
Medium thermal carbon black (Phillips Petroleum)                          
                            30.0                                          
Magnesium oxide acid acceptor (Calgon)                                    
                            3.0                                           
Calcium hydroxide cure activator (Henley)                                 
                            6.0                                           
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MOLDING COMPOUND K                                                        
                       PHR                                                
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Morton International ST polysulfide rubber                                
                         100                                              
Carbon black             60                                               
Stearic acid             1.0                                              
Zinc peroxide            5.0                                              
Calcium hydroxide        1.0                                              
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MOLDING COMPOUND L                                                        
                           PHR                                            
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Ethylene propylene diene terpolymer (Royalene 512                         
                             100.0                                        
by Uniroyal)                                                              
Zinc diacrylate (Sartomer SR-633)                                         
                             4.0                                          
Silicon dioxide (Summit Chemical)                                         
                             100.0                                        
Calcined and surface modified Kaolin clay (Engelhard)                     
                             100.0                                        
Paraffinic oil (R. E. Carroll)                                            
                             40.0                                         
Silane Coupling Agent vinyl-tris (2-methoxyethoxy silane                  
                             1.0                                          
(Union Carbide)                                                           
Dicumyl peroxide vulcanizing agent                                        
                             8.0                                          
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