Pressure sensitive cohesive

Abstract

A pressure sensitive adhesive/cohesive exhibits excellent cohesive body properties, and other desirable features, even when exposed to heat and polysiloxane based lubricants, such as in a laser printer. The formulation comprises 100 parts by weight natural rubber (e.g. electrosterically stabilized natural rubber graft and block terpolymer), and expressed as percentages by weight of the rubber the following components: about 5-35% (e.g. about 28%) acrylate monomer or monomers (such as methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and/or isobornyl methacrylate); about 0.5-8% acrylic acid and/or about 1-10% 4-acetoxystyrene; about 0-20% ethyl hexyl acrylate; about 1-50% (e.g. about 10-30%) finely divided hard particulate material (such as silica gel); 0-50% (preferably about 10-30%) starch; and 0-40% (preferably at least about 5%) carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or a styrene-acrylate-acrylonitrile latex, or vinyl-pyridine styrene-butadiene latex, or pre-crosslinked natural rubber latex, or a tackifier, or combinations thereof. The cohesive is coated onto paper and seals to like cohesive upon the application of a force of at least 100 lbs per lineal inch.

What is claimed is:  
     
         1 . A pressure sensitive adhesive/cohesive comprising: 
 100 parts by weight natural rubber;    about 5-35% by weight of the rubber at least one acrylate monomer;    about 0-8% by weight of the rubber acrylic acid and/or about 0-10% by weight of rubber 4-acetoxystyrene;    about 0-20% by weight of the rubber ethyl hexyl acrylate;    1-50% by weight of the rubber a finely divided hard particulate material having substantially no thermoplasticity;    0-50% by weight of the rubber starch; and    0-40% by weight of the rubber carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or vinyl-pyridine styrene-butadiene latex, or styrene-acrylate-acrylonitrile latex, or pre-crosslinked natural rubber latex, or a tackifier, or combinations thereof.    
     
     
         2 . A pressure sensitive adhesive/cohesive as recited in  claim 1  wherein the natural rubber is electrosterically stabilized latex of natural rubber graft and block terpolymer, and wherein the adhesive/cohesive is coated on a piece of paper.  
     
     
         3 . A pressure sensitive adhesive/cohesive as recited in  claim 2  coated on two portions of a piece of paper, said cohesive portions in contact with each other as a result of folding the paper, and pressure sealed together, so as to cause paper fiber tear if attempted to be pulled apart.  
     
     
         4 . A pressure sensitive adhesive/cohesive as recited in  claim 2  having a built-in antioxidant in the electrosterically stabilized latex of natural rubber graft and block terpolymer when 4-acetoxystyrene is used as a comonomer in grafting which gives an oxidative stability to the pressure sensitive adhesive/cohesive.  
     
     
         5 . A pressure sensitive adhesive/cohesive as recited in  claim 1  comprising at least 1% ethyl hexyl acrylate.  
     
     
         6 . A pressure sensitive adhesive/cohesive as recited in  claim 1  comprising at least 1% starch, and wherein the natural rubber comprises an electrosterically stabilized natural graft and block terpolymer.  
     
     
         7 . A pressure sensitive adhesive/cohesive as recited in  claim 1  comprising about 10-30% starch having an average particle size of about 5-25 microns.  
     
     
         8 . A pressure sensitive adhesive/cohesive as recited in  claim 7  wherein the hard particulate material comprises about 10-30% silica gel having an average particle size of about 1-20 microns.  
     
     
         9 . A pressure sensitive adhesive/cohesive as recited in  claim 1  comprising at least 5% carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or vinyl-pyridine styrene-butadiene latex, or pre-crosslinked natural rubber latex, or a styrene-acrylate-acrylonitrile latex, or a tackifier, or combinations thereof.  
     
     
         10 . A pressure sensitive adhesive/cohesive as recited in  claim 1  comprising about 1.5-4% acrylic acid, and wherein the acrylic monomer comprises about 15-35% methyl methacrylate.  
     
     
         11 . A pressure sensitive adhesive/cohesive as recited in  claim 8  wherein the acrylic monomer comprises methyl methacrylate.  
     
     
         12 . A pressure sensitive adhesive/cohesive as recited in  claim 3  comprising at least 1% starch, and wherein the natural rubber comprises an electrosterically stabilized natural graft and block terpolymer.  
     
     
         13 . A pressure sensitive adhesive/cohesive as recited in  claim 3  comprising about 10-30% starch having an average particle size of about 5-25 microns.  
     
     
         14 . A pressure sensitive adhesive/cohesive as recited in  claim 3  wherein the hard particulate material comprises about 10-30% silica gel having an average particle size of about 0.3-0.4 microns.  
     
     
         15 . A pressure sensitive adhesive/cohesive as recited in  claim 3  comprising at least 5% carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or vinyl-pyridine styrene-butadiene latex, or pre-crosslinked natural rubber latex, or a styrene-acrylate-acrylonitrile latex, or a tackifier, or combinations thereof.  
     
     
         16 . A pressure sensitive adhesive/cohesive as recited in  claim 3  comprising about 1.5-4% acrylic acid, and wherein the acrylic monomer comprises about 5-30% methyl methacrylate.  
     
     
         17 . A pressure sensitive adhesive/cohesive as recited in  claim 2  comprising at least 1% starch.  
     
     
         18 . A pressure sensitive adhesive/cohesive as recited in  claim 17  comprising at least 1% ethyl hexyl acrylate, and wherein the natural rubber comprises an electrosterically stabilized natural graft and block terpolymer.  
     
     
         19 . A pressure sensitive adhesive/cohesive as recited in  claim 16  comprising at least 5% carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or vinyl-pyridine styrene-butadiene latex, or pre-crosslinked natural rubber latex, or a styrene-acrylate-acrylonitrile latex, or a tackifier, or combinations thereof.  
     
     
         20 . A method of making a mailer type business form, comprising: 
 (a) applying cohesive as cooperating patterns to a sheet of paper so that when the sheet is folded or moved into contact with a like coated sheet, the patterns move into contact with each other, the cohesive comprising a pressure sensitive cohesive including: 100 parts by weight natural rubber; about 5-35% by weight of the rubber at least one acrylate monomer; about 0.5-8% by weight of the rubber acrylic acid and/or about 1 -1 0% by weight of the rubber 4-acetoxystyrene; about 0-20% by weight of the rubber ethyl hexyl acrylate; 1-50% by weight of the rubber a finely divided hard particulate material having substantially no thermoplasticity; 0-50% by weight of the rubber starch; and 0-40% by weight of the rubber carboxylated styrene-butadiene latex, or carboxylated polychloroprene latex, or vinyl-pyridine styrene-butadiene latex, or styrene-acrylate-acrylonitrile latex, or pre-crosslinked natural rubber latex, or a tackifier, or combinations thereof.    
     
     
         21 . A method as recited in  claim 20  further comprising: (b) folding the paper to move the cohesive patterns into contact with each other, and (c) applying a sealing pressure of at least about 100 lbs/lineal inch to the patterns to seal the cohesive together so as to cause fiber tear if attempted to be pulled apart.