Process for recycling rubber

Abstract

A process for manufacturing an article using a predetermined amount of crumb rubber comprising the steps of selecting an article to be manufactured, determining a maximum amount of recycled rubber which can be used in manufacturing the article selected. A particle size for recycled rubber to be used is determined and a binder for binding the recycled rubber is selected. The amount of binder required to be added is determined. Curing agents to be used in the process are selected and their weight determined. The components are mixed in a mixer and heated to a predetermined temperature. The mixture is removed and a mold is filled with the mixture. The mixture is then molded at a predetermined temperature and a predetermined pressure being at least sufficient to cure the mixture so as to form the article previously selected and then the molded product is removed from the mold.

We claim:  
     
         1 . A process for manufacturing an article using a predetermined amount of recycled rubber, said process comprising the steps of: 
 (a) selecting an article to be manufactured;    (b) determining a maximum amount by weight of recycled rubber to be used in manufacturing said article selected in step (a);    (c) determining a particle size for said recycled rubber which is used in manufacturing said article in step (a);    (d) selecting a binder for binding said recycled rubber determined in step (b);    (e) determining an amount by weight of said binder selected in step (d) required to be added to said recycled rubber determined in step (b) for molding said article determined in step (a);    (f) selecting curing agents to be used;    (g) determining an amount by weight of said curing agents selected in step (f);    (h) mixing said recycled rubber determined in step (b), said binder determined in step (e) and said curing agents selected in step (g);    (i) heating said recycled rubber, said binder and said curing agents mixed in step (h) to a predetermined temperature;    (j) removing a mixture of said recycled rubber, said binder and said curing agents mixed in step (h) and heated in step (i);    (k) filling a mold with said mixture from step (j);    (l) molding said mixture at a predetermined temperature and a predetermined pressure which is at least sufficient to cure said article selected in step (a) during molding; and    (m) removing molded product from such mold.    
     
     
         2 . The process, according to  claim 1 , wherein said binder selected in step (d) is one of natural rubber, styrene butadiene rubber and a mixture thereof.  
     
     
         3 . The process, according to  claim 2 , wherein said binder selected in step (d) is natural rubber.  
     
     
         4 . The process, according to  claim 1 , wherein said binder selected in step (d) is generally present in a concentration of between about 2.0% and about 95.0%.  
     
     
         5 . The process, according to  claim 1 , wherein said recycled rubber is at least one of crumb rubber and a mixture of crumb rubber and rubber buffings.  
     
     
         6 . The process, according to  claim 5 , wherein said recycled rubber is crumb rubber.  
     
     
         7 . The process, according to  claim 6 , wherein said maximum amount of crumb rubber determined in step (b) is generally between about 5.0% and about 98.0% by weight.  
     
     
         8 . The process, according to  claim 7 , wherein said maximum amount of crumb rubber determined in step (b) is generally between about 25.0% and about 98.0% by weight.  
     
     
         9 . The process, according to  claim 5 , wherein said tire buffings are present in said recycled rubber in a concentration of between about 25 and about 50% while crumb rubber is present in a concentration of between about 50 and about 75%.  
     
     
         10 . The process, according to  claim 1 , wherein said particle size of said recycled rubber determined in step (c) is substantially greater than 30 mesh.  
     
     
         11 . The process, according to  claim 10 , wherein said particle size of said recycled rubber determined in step (c) is substantially greater than 20 mesh.  
     
     
         12 . The process, according to  claim 11 , wherein said particle size of said recycled rubber determined in step (c) is substantially between about 5 and about 20 mesh.  
     
     
         13 . The process, according to  claim 1 , wherein said curing agents selected in step (f) are sulfur and trimethylthiuram disulfide.  
     
     
         14 . The process, according to  claim 13 , wherein said curing agents selected in step (f) further include N-t-butyl benzothiazole sulfenamide and 2-mercaptobenzothiazole as additional additives.  
     
     
         15 . The process, according to  claim 1 , wherein said recycled rubber, said binder and said curing agents mixed in step (h) are heated in step (i) until said mixture reaches about 220F.  
     
     
         16 . The process, according to  claim 1 , wherein said predetermined temperature of such molding of said mixture in step (l) is between about 300 and 390F.  
     
     
         17 . The process, according to  claim 1 , wherein said process further includes a step of cooling said mixture removed from such mixer in step (j).  
     
     
         18 . The process, according to  claim 17 , wherein said mixture is cooled to a temperature of 90F or less.  
     
     
         19 . The process, according to  claim 1 , wherein said process further includes a step of preheating said mixture prior to step (k).  
     
     
         20 . The process, according to  claim 10 , wherein said mixing in step (h) is shear mixing.  
     
     
         21 . A substantially dry, particulate molding material comprising a mixture of: 
 (a) recycled rubber particles, said recycled rubber particles being present in a predetermined concentration by weight;    (b) a binder being present in a concentration at least sufficient to provide predetermined properties of said substantially dry, particulate molding material after molding;    (c) sulfur being present in a concentration of between about 0.4 and about 0.6 percent by weight; and    (d) trimethylthiuram disulfide being present in a concentration of between about 0.7 and about 0.12 percent by weight.    
     
     
         22 . A substantially dry, particulate molding material, according to  claim 21 , wherein said recycled rubber is present in a concentration of up to 98 weight percent.  
     
     
         23 . A substantially dry, particulate molding material, according to  claim 21 , wherein said binder is present in a concentration of between about 2 and about 95 weight percent.  
     
     
         24 . A substantially dry, particulate molding material, according to  claim 21 , wherein said binder is one of natural rubber, styrene butadiene rubber and mixtures thereof.  
     
     
         25 . A substantially dry, particulate molding material, according to  claim 24 , wherein said binder is natural rubber.  
     
     
         26 . A substantially dry, particulate molding material, according to  claim 21 , wherein said recycled rubber is at least one of crumb rubber and a mixture of crumb rubber and rubber buffings.  
     
     
         27 . A process for forming a substantially dry, particulate material using a predetermined amount of recycled rubber, said process comprising the steps of: 
 (a) determining a maximum amount by weight of recycled rubber to be used to form said substantially dry, particulate material;    (b) determining a particle size for said recycled rubber;    (c) selecting a binder for binding said recycled rubber;    (d) determining an amount by weight of binder selected in step (c) required to be added to said maximum amount by weight of recycled rubber determined in step (a);    (e) selecting curing agents to be used;    (f) determining an amount by weight of said curing agents selected in step (e);    (g) mixing said maximum amount by weight of recycled rubber determined in step (a), said binder determined in step (d) and said curing agents determined in step (f);    (h) heating said recycled rubber, said binder and said curing agents mixed in step (g) to a predetermined temperature;    (i) removing a mixture of said recycled rubber, said binder and said curing agents mixed in step (g) and heated in step (h).    
     
     
         28 . The process, according to  claim 27 , wherein said mixing in step (g) involves shear mixing.  
     
     
         29 . The process, according to  claim 28 , wherein said shear mixing is carried out in a Banbury type mixer.  
     
     
         30 . The process, according to  claim 27 , wherein said binder selected in step (c) is one of natural rubber, styrene butadiene rubber and a mixture thereof.  
     
     
         31 . The process, according to  claim 30 , wherein said binder selected in step (c) is natural rubber.  
     
     
         32 . The process, according to  claim 27 , wherein said binder selected in step (c) is generally present in a concentration of between about 2.0% and about 95.0%.  
     
     
         33 . The process, according to  claim 26 , wherein said recycled rubber is at least one of crumb rubber and a mixture of crumb rubber and rubber buffings.  
     
     
         34 . The process, according to  claim 33 , wherein said tire buffings are present in said mixture of crumb rubber and tire buffings in a concentration of between about 25 and about 50% while crumb rubber is present in a concentration of between about 50 and about 75%.  
     
     
         35 . The process, according to  claim 33 , wherein said recycled rubber is crumb rubber.  
     
     
         36 . The process, according to  claim 35 , wherein said maximum amount of crumb rubber determined in step (a) is generally between about 5.0% and about 98.0% by weight.  
     
     
         37 . The process, according to  claim 36 , wherein said maximum amount of crumb rubber determined in step (a) is generally between about 25.0% and about 98.0% by weight.  
     
     
         38 . The process, according to  claim 27 , wherein said particle size of said recycled rubber determined in step (b) is substantially greater than 30 mesh.  
     
     
         39 . The process, according to  claim 38 , wherein said particle size of said recycled rubber determined in step (b) is substantially greater than 20 mesh.  
     
     
         40 . The process, according to  claim 39 , wherein said particle size of said recycled rubber determined in step (b) is substantially between about 5 and about 20 mesh.  
     
     
         41 . The process, according to  claim 27 , wherein said curing agents selected in step (e) are sulfur and trimethylthiuram disulfide.  
     
     
         42 . The process, according to  claim 41 , wherein said curing agents selected in step (e) further include N-t-butyl benzothiazole sulfenamide and 2-mercaptobenzothiazole as additional additives.  
     
     
         43 . The process, according to  claim 27 , wherein said recycled rubber, said binder and said curing agents mixed in step (g) are heated in step (h) until said mixture reaches about 220F.  
     
     
         44 . The process, according to  claim 27 , wherein said process further includes the additional step of cooling said substantially dry, particulate material.  
     
     
         45 . The process, according to  claim 44 , wherein said mixture is cooled to a temperature of 90F or less.