Abstract:
A carbon paper ink is described which includes a 2200-3000 heavy oil. The ink also includes Montan wax, paraffin slack wax, carbon black, a lubricant, and a filler. The heavy oil acts as a dispersant to provide for more even pigmentation and darker printing of the ink.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improved carbon paper ink and method for making the same. 
     Prior art carbon paper ink has several disadvantages. Often the ink&#39;s pigmentation is not always evenly distributed, which results in lower print quality. Also, to achieve the requisite darkness of print, the manufacturer must often use large quantities of ink, which results in higher manufacturing costs. 
     In seeking to resolve these difficulties, Applicants have found that certain heavy oils and polybutenes when added to carbon paper ink impart favorable qualities. These substances, which have traditionally been used as industrial lubricants, provide the surprising results of producing an ink that is not only darker, but also has more uniform pigmentation than inks currently available. 
     Therefore, a primary object of the present invention is the provision of an improved carbon paper ink, and a method for making the same. 
     A further object of the present invention is the provision of an improved carbon paper ink which has even distribution of pigmentation throughout. 
     A further object of the present invention is the provision of an improved carbon paper ink for use on carbon paper which prints darker than ink presently available in the art. 
     A still further object of the present invention is a provision of an improved carbon paper ink and method for making the same which is economical in manufacture, and efficient in use. 
     SUMMARY OF THE INVENTION 
     The present invention disclosure involves the use of a 2200 to 3000 seconds heavy oil at 60° C. as a dispersant. Alternatively, polybutenes of the same viscosity and in the same amounts will produce the same quality of carbon paper. 
     The ink also contains the following ingredients: 1.) montan wax--an ester wax with melt point of 160° to 190° F.; 2.) paraffin slack wax--a semi-refined wax with melt point of 120°-140° F. and an oil content of 1-30%; 3.) carbon black--a 600 or 700 series rubber grade black. 
     In preparation, montan wax, heavy oil, and paraffin wax are first melted together, then mixed. The carbon black and filler are then slowly added then mixed in at maximum speed. The mixture is then ground. Following grinding, the speed of the mixer is slowed, mineral seal oil is added, then all ingredients are mixed again. These steps can be accomplished by use of a shot mill, ball mill, or roller mill, with the shot mill being preferred. The heavy oil or polybutene acts as an improved dispersing agent. Its effect on the ink when used in combination with the other listed ingredients, is to impart more even pigmentation and a darker color when used in printing. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The minimum ingredients necessary for the present invention are montan wax, a 2200-3000 seconds heavy oil at 60° F. or polybutene, paraffin slack wax, and carbon black. A lubricant such as mineral seal oil, and/or a filler, such as kaolin clay, may be added as well. The lubricant preferably has a flash point of between 150° to 180° F. The preferred heavy oils have viscosities within the range as set forth above. They are typically paraffinic or naphthenic heavy oils. 
     Some of the preferred heavy oils which may be used include: HF Bright Stock (trade name) produced by Magie Bros., 150 Solvent Bright by Mobil, by Witco-Golden Bear, Bright Stock by ARCO, and Bright Stock by Exxon. Likewise, the preferred polybutenes also have viscosities within the above-stated range. Some of the preferred polybutenes are: L-100 produced by Amoco, and H-50 by Amoco. 
    
    
     Below are examples of preferred combinations of materials for use in the present invention: 
     
         ______________________________________Material               % by Weight______________________________________EXAMPLE 1Montan Wax              32200-3000 Seconds Heavy Oil at 60° F.                   3Paraffin Slack Wax     75Carbon Black           15Mineral Seal Oil        1Kaolin Clay             3EXAMPLE 2Montan Wax              52200-3000 Seconds Heavy Oil at 60° F.                   5Paraffin Slack Wax     68Carbon Black           16Mineral Seal Oil        2Kaolin Clay             40EXAMPLE 3Montan Wax              72200-3000 Seconds Heavy Oil at 60° F.                   7Paraffin Slack Wax     61Carbon Black           17Mineral Seal Oil        3Kaolin Clay             5EXAMPLE 4Montan Wax             102200-3000 Seconds Heavy Oil at 60° F.                  10Paraffin Slack Wax     52Carbon Black           18Mineral Seal Oil        4Kaolin Clay             6EXAMPLE 5Montan Wax             152200-3000 Seconds Heavy Oil at 60° F.                  15Paraffin Slack Wax     39Carbon Black           19Mineral Seal Oil        5Kaolin Clay             7EXAMPLE 6Montan Wax             202200- 3000 Seconds Heavy Oil at 60° F.                  20Paraffin Slack Wax     26Carbon Black           20Mineral Seal Oil        6Kaolin Clay             8EXAMPLE 7Montan Wax             252200-3000 Seconds Heavy Oil at 60° F.                  25Paraffin Slack Wax      7Carbon Black           25Mineral Seal Oil        8Kaolin Clay            10______________________________________ 
    
     The above percentages may be varied without detracting from the invention. Below is a list of the various permissible ranges of percent by weight of each of the above materials: 
     
         ______________________________________Materials           % by Weight______________________________________Montan Wax          3-25%2200-3000 Seconds Heavy Oil               3-25%Paraffin Slack Wax  7-75%Carbon Black        15-25%Mineral Seal Oil    0-8%Kaolin Clay         0-10%______________________________________ 
    
     The montan wax is a dispersing agent and imparts hardness to the ink. Similarly, the 2200-3000 seconds heavy oil at 60° F. is a dispersing agent and serves to control the hardness of the ink: the more oil used, the softer the ink. The paraffin slack wax is a carrier and the carbon black is used for coloration purposes. The mineral seal oil is used as a lubricant and the kaolin clay as a filler. 
     The ink is preferably prepared in a shot mill at a temperature of 180°-210° F. The montan wax, heavy oil, and paraffin wax are first melted together, then mixed for at least 5 minutes, preferably for 15 minutes. 
     Next, the carbon black and kaolin clay is slowly added to the mix with slow agitation. After the required amounts are added, the speed of the mixer is increased to maximum. Next, the mix is ground for 15 minutes or longer, preferably 45 minutes. The fineness of the grind is 6 on the gauge. 
     Next, the mixer speed is slowed down and the mineral seal oil is added. All the ingredients are then mixed together for at least 1 minute, preferably 5 minutes. 
     The ink can be applied by a rotary roller method, whether a plain cylinder, rubber plate wrap cylinder, or gravure roll. 
     The weight of ink applied on a tissue is 1.20-2.0 lbs per 20×30×500 ream size. 
     For cleanness and legibility, the ideal ink weight is 1.80 lbs. for handwriting and mechanical applications. The coating temperature is 180°-230° F. and the chilling temperature is 30°-50° F. 
     In the specification, there has been set forth a preferred embodiment of the invention, and all those specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalence or contemplated as circumstances may suggest or render expedient without departing from the spirit and scope of the invention as further defined in the following claims.