Reinforced polyester resins having increased toughness and crack resistance

Abstract

A molding compound contains a reinforcing fiber, a non-fibrous filler, and an unsaturated polyester resin. The unsaturated polyester resin contains an unsaturated monomer as well as a polyester polymer. The polymer is a unsaturated polyester made from a hydroxyl component and a carboxylic component. The hydroxyl component contains both a monomeric diol or triol, and a polymeric polyol. The polymeric polyol is a hydroxyl-terminated polymer such as polyether or polyester diols or triols. The carboxylic component can be provided by an unsaturated carboxylic diacid, an unsaturated carboxylic anhydride, an unsaturated carboxylic diester or mixtures thereof. Molded articles are provided by compression or extrusion molding of a molding compound as described above. The articles are characterized by improved crack resistance, toughness, and surface appearance.

1 . A molding compound comprising: 
 a reinforcing fiber having average fiber length of 6 mm or greater present from 10 to 65 total weight percent;    a non-fibrous filler present up to 70 total weight percent; and    an unsaturated polyester resin comprising styrene as an unsaturated monomer and a polymer, the polymer comprising a hydroxyl component and a carboxylic component,    wherein the hydroxyl component comprises a monomeric diol or triol and a polymeric polyol, wherein the polymeric polyol has a number average molecular weight of 200 to 4000, and is selected from the group consisting of polyether diols, polyether triols, polyester polyols and combinations thereof, and the carboxylic component comprises at least one compound selected from the group consisting of unsaturated carboxylic diacids, unsaturated carboxylic anhydrides, unsaturated carboxylic diesters, and mixtures thereof,    wherein the polymeric polyol is present at a level of 1 to 30 weight percent, based on the total weight of the hydroxyl component and the carboxylic component.    
     
     
         2 . A molding compound according to  claim 1 , further comprising a second unsaturated monomer.  
     
     
         3 . A molding compound according to  claim 2 , wherein the second unsaturated monomer is methylmethacrylate.  
     
     
         4 . A molding compound according to  claim 1 , further comprising a thermoplastic polymer.  
     
     
         5 . A molding composition according to  claim 4 , wherein the thermoplastic polymer is selected from the group consisting of polyurethane, homopolymers of ethylene, styrene, vinyl toluene, vinyl acetate, alkyl methacrylates and alkyl acrylates and copolymers of vinyl chloride and vinyl acetate; vinyl acetate and acrylic or methacrylic acid; styrene and acrylonitrile; methyl methacrylate and alkyl esters of acrylic acid; methyl methacrylate and styrene; and methyl methacrylate and acrylamide.  
     
     
         6 . A molding compound according to  claim 1 , wherein the polymeric polyol is present at a level of 1 to 20 weight percent, based on the total weight of the hydroxyl component and the carboxylic component.  
     
     
         7 . A molding compound according to  claim 1 , wherein the monomeric diol comprises one or more compounds selected from the group consisting of propylene glycol, ethylene glycol, 1,2-butane diol, 1,4-butane diol, and combinations thereof.  
     
     
         8 . A molding compound according to  claim 1 , wherein the polymeric polyol is present from 10 to 20 weight percent, based on the total weight of the hydroxyl component and the carboxylic component.  
     
     
         9 . A molding compound according to  claim 1 , wherein the reinforcing fiber comprises glass fibers.  
     
     
         10 . A molding compound according to  claim 1 , wherein the non-fibrous filler is selected from the group consisting of calcium carbonate, alumina, clay, mica, wollastonite, silicate, wood flour, and mixtures thereof.  
     
     
         11 . A molding compound according to  claim 10 , wherein the non-fibrous filler comprises calcium carbonate.  
     
     
         12 . A molding compound according to  claim 1 , further comprising up to 7% by weight based on the weight of the entire molding compound, of a second fiber having fibers of average length less than or equal to 4 millimeters.  
     
     
         13 . A molding compound according to  claim 12 , wherein the second fiber is selected from the group consisting of glass fibers, carbon fibers, cellulose fibers, aramid fibers, textile fibers, SMC regrind, and nylon fibers.  
     
     
         14 . A molding compound according to  claim 12 , wherein the second fiber comprises carbon fibers.  
     
     
         15 . A molding compound according to  claim 12 , wherein the second fiber comprises SMC regrind.  
     
     
         16 . A molding compound according to  claim 12 , wherein the second fiber comprises glass fibers.  
     
     
         17 . A molding compound according to  claim 1 , wherein the reinforcing fiber comprises glass fibers having an average length of greater than 10 millimeters.  
     
     
         18 . A molded article prepared by compression molding a molding compound according to  claim 1 .  
     
     
         19 . A process for producing an unsaturated polyester resin comprising the steps of: 
 reacting in a vessel with heat an unsaturated monomer with a polymer, the polymer comprising a hydroxyl component and a carboxylic component, wherein the hydroxyl component comprises a monomeric diol or triol and a polymeric polyol, wherein the polymeric polyol has a number average molecular weight of 200 to 4000, and is selected from the group consisting of polyether, polyester polyols and combinations thereof, the carboxylic component comprises at least one compound selected from the group consisting of unsaturated carboxylic diacids, unsaturated carboxylic anhydrides, unsaturated carboxylic diesters, and mixtures thereof, and wherein the polymeric polyol is present at a level of 1 to 30 weight percent, based on the total weight of the hydroxyl component and the carboxylic component.    
     
     
         20 . A process according to  claim 19  wherein the unsaturated monomer is styrene.  
     
     
         21 . A process according to  claim 19  wherein heat is provided to react at between 120° and 200° C.  
     
     
         22 . A process according to  claim 19  wherein the unsaturated monomer, the hydroxyl component and the carboxylic component are delivered to the vessel in a single charge.  
     
     
         23 . The process according to  claim 19  wherein the unsaturated monomers, the hydroxyl component and the carboxylic component are fed into the vessel at a constant ratio relative to one another.  
     
     
         24 . The process according to  claim 19  wherein one of the unsaturated monomer component, the hydroxyl component, and the carboxylic component is added in a stage subsequent to delivery of the other components.  
     
     
         25 . The process according to  claim 19  wherein the polymeric polyol is a polyester polyol produced by homopolymerization of lactones.  
     
     
         26 . The process according to  claim 19  wherein the polymeric polyol is a polyester polyol produced by homopolymerization or copolymerization of a lower chain alkylene oxide or oxides.  
     
     
         27 . The process according to  claim 19  wherein the polymeric polyol comprises a polyether diol or polyether triol, or a mixture thereof.  
     
     
         28 . A fiber layered with the unsaturated polyester resin produced by a process according to  claim 19 .  
     
     
         29 . A mold having a mold release agent coating in contact with a uniform layer of the unsaturated polyester resin produced by a process according to  claim 19.