Abstract:
A process for applying relatively volatile or heat sensitive ingredients, such as perfume, to fabric dryer sheets minimizes the loss of the ingredients to the atmosphere or through degradation.

Description:
PRIORITY 
     This is a continuation of Ser. No. 09/850,989 filed May 8, 2001, now allowed U.S. Pat. No. 6,352,969 which is a continuation of application Ser. No. 09/504,098, now U.S. Pat. No. 6,297,210 filed Feb. 15,2000, which claims benefit of No. 60/130,773, filed Apr. 23, 1999. 
    
    
     BACKGROUND 
     A well known commercial product in the laundry care industry is the fabric dryer sheet. In use, the consumer typically uses at least one sheet in the drying cycle of the laundering process. The sheets generally include a substrate material, such as a web, wherein the substrate carries one or more ingredients to impart desired benefits to the clothing. These ingredients can include, for example, perfumes, anti-static agents, dye transfer inhibitors, whitening agents, enzymes, stain repellents and wrinkle reducing agents. 
     Processes for fabricating these dryer sheets are also well known. In a typical process, a large role of the web material is guided at high speeds through various coating, smoothing and drying/cooling steps wherein one or more ingredients are applied to the web. An example of this process is shown in FIG.  1 . 
     With reference to FIG. 1, web  5  is preferably a polyester material and provided in rolls  2 . Rolls  2  are typically about 37 inches to about 85 inches in width and have a length between about 8,000 and about 13,000 yards. Web  5  passes through various rollers and rods wherein ingredients are applied to the web. As shown, web  5  is passed over guide roll  12  and onto applicator roll  14 . Applicator roll  14  transfers ingredients  17  from coating pan  15  onto the web. A holding tank (not shown) can be used to supply the ingredients to coating pan  15 . Preferably, automatic controls are used to ensure a proper level and temperature of ingredients  17  in pan  15 . 
     As known in the art, ingredients  17  can include perfume material in addition to other fabric treatment agents, particularly those that provide anti-static and fabric softening benefits. These fabric treatment agents can include, for example: cationic compounds, such as quaternary ammonium compounds; nonionic surfactants, such as ethoxylated alcohols; fatty alcohols; fatty acids; alkali metal soaps of fatty acids; carboxylic acids and salts thereof; fatty acid esters; glycerides; waxes; anionic surfactants; water; optical brighteners; fluorescent agents; antioxidants; colorants; germacides; perfumes; bacteriocides; enzymes; dye transfer inhibitors; soil release polymers; skin care benefit agents; perfume carriers (e.g. starch, clyclodextrins); wrinkle reducing agents; and the like. Various preferred non-cationic formulations are disclosed in U.S. patent application Ser. No. 08/832,887, filed Apr. 4, 1997, the contents of which is incorporated by reference. In prior art processes, perfume has been present from about 2 wt % to about 6 wt % based on total ingredients  17 . 
     In a preferred embodiment, the ingredients are maintained at approximately 140-190° F. in both the holding tank and coating pan  15 . At this temperature, one or more ingredients can be lost to the atmosphere due to their volatility or be adversely affected by means of thermal degradation. When the perfume is present, it is estimated that there is a loss of approximately 15 wt. % of the perfume to the atmosphere at this coating step. 
     Further on in the process of FIG. 1, after coated in the coating pan, coated web  5 ′ passes over smoothing rod  18  to guide roll  20 . From guide roll  20 , the web passes to heating drum  22 , travels to cooling drums  24  and  26 , which are preferably cooled to below about 100° F. by chilled water. Cooled web  5 ′ then passes to trimming station  28 , wherein the web is rolled and preferably cut into roles  2 ′. Roles  2 ′ are preferably about 12 inches in width. At this point in the process, the roles can be stored for later cutting and packaging. During the process shown in FIG.  1 . the web can travel as fast as 1,000 feet per minute. It is estimated that the additional perfume lost after the step of coating can be in the range of approximately 20 wt. % to 30 wt. % from that which was originally present in pan  15 . 
     Turning to FIG. 2, final processing of coated web  5 ′ is carried out by passing one or more of the coated roles  2 ′ through a series of guide rollers  32 . The web is then folded by folders  34 , passed to conveyor  36  and cut by knife  38 . After cutting, the folded sheets are tamped down, stacked and accumulated for packaging. 
     During the above-described processes, it has been found that a significant amount of volatile agents can be lost prior to final packaging, particularly perfumes. This is generally due to the relatively high volatility of most perfume agents. For example, it has been found that up to 45% of the perfume added in a typical process can be lost by the time the dryer sheet is folded and packaged. 
     Therefore, there is a need for an improved fabric dryer sheet manufacturing process wherein the loss of volatile agents during the process of making the fabric sheets is minimized. 
     Perfume agents can be classified by their relative volatility. High volatile perfumes are known as “high notes” while relatively unvolatile perfumes are known as “low notes”. Due to their high volatility, high note perfumes are typically more perceptible by humans than low note perfumes. High note perfumes also have a wider range of odors and, therefore, allow for greater flexibility when selecting perfume agents. Unfortunately, when manufacturing dryer sheets, it is the desired high notes that can be lost during processing. This has resulted in a decreased amount of high note perfumes making it into the packaged product and alteration of the perfume profile. Use of high note perfumes have also been reduced or eliminated from perfume formulations due to the above-described process conditions. 
     Therefore, there is also a need for fabric sheet manufacturing techniques that would allow for increased usage of high note perfumes, wherein the highly volatile perfumes are retained on the fabric sheet so as to reach the consumer. 
     SUMMARY 
     For simplicity, “perfume” will be used herein to describe a fabric treatment agent that can volatilize or degrade from heat in an undesirable manner. It is within the scope of the present disclosure, however, that other volatile agents or heat sensitive agents can be advantageously applied by the presently disclosed process. 
     The present disclosure relates to a process that minimizes the loss of perfume and other volatile agents during the fabrication of dryer sheets. It has been found that it is possible to de-couple the addition of volatile or heat sensitive agents from one or more of the manufacturing process steps, particularly those portions that run at a high speed and/or high temperature. 
     In one preferred embodiment, the a selected agent or agents are applied during high speed web movement after high temperature application of other ingredients. In a second preferred embodiment, the selected agent or agents can be applied just prior to folding and packaging. 
     It has been found, for example, that by adding the perfume or other volatile agents closer to the step of packaging, i.e. after application of other ingredients in coating pan  15 , there is less loss of ingredients to the atmosphere during the dryer sheet process. In the case of perfumes, this new process has less affect on the perfume profile and, therefore, a wider variety of perfumes can be used. In addition, because ingredients are no longer lost or lost to a lesser extent, less of the ingredient is needed when practicing the present disclosure, resulting in raw material cost savings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a fabric sheet coating process that is known in the art; 
     FIG. 2 illustrates a fabric sheet cutting and folding process that is known in the art; 
     FIG. 3 illustrates a fabric sheet coating process that generally shows a preferred location of applying fabric treatment agents, subsequent to the main coating operation; 
     FIG. 4 illustrates a fabric sheet cutting and folding process that generally shows preferred locations of applying fabric treatment agents, subsequent to the main coating operation; 
     FIG. 5, illustrates a preferred method and apparatus for applying fabric treatment agents to a substrate material that can be used in the processes shown in FIGS. 3 and 4; 
     FIG. 6 illustrates an alternate, preferred method and apparatus for applying fabric treatment agents to a substrate material that can be used in the processes shown in FIGS. 3 and 4; 
     FIG. 7 illustrates a preferred method of transferring liquid agents to the apparatus of FIG. 6; and 
     FIG. 8 illustrates a fabric sheet cutting and folding process that shows the apparatus of FIG. 6 at preferred locations. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 3 and 4, processes in accordance with the present disclosure are shown. FIG. 3 shows preferred fabric treatment agent application zone A, wherein ingredients can be added to web  5 ′ subsequent to the coating of ingredients  17 . Zone A is located after cooling drums  24  and  26  before cutting station  28 . By applying perfumes and/or other fabric treatment agents at or near zone A, the high temperatures associated with the upstream coating operation are avoided. In addition, because web  5 ′ is rolled-up at trimming station  28  shortly after application zone A, the fabric treatment ingredients become trapped as web  5 ′ winds about itself. 
     FIG. 4 shows an alternate, preferred application zones B. In this embodiment, the fabric treatment agents are applied in prior to final folding and cutting of the substrate. Several zones are shown because the preferred process performs several cutting and folding operations simultaneously. An advantage of waiting to apply certain fabric treatment agents just prior to cutting and folding is that roles  2 ′ can be generic across several brands. More specifically, for example, if the only difference between two or more brands of product is the type or quantity of perfume, rolled stock  2 ′ can be used for each brand as needed. 
     Turning to FIG. 5, a preferred apparatus for applying fabric treatment agents to web  5 ′ is shown. Spray assemblies  80  have controllers  81  and air flow modules  82  for controlling the flow and spray pattern of liquid spray  83  emitted from nozzles N. Spray assemblies  80  can be pressure spray assemblies or, more preferably, ultrasonic sprayers as shown. Preferred ultrasonic spray assemblies are available from Sono-Tek Corporation, Milton, N.Y. The Sono-Tek sprayers use ultrasonic power to atomize liquids. The flow of liquid from nozzles N and the flow of air from modules  82  are regulated by controllers  81 . Controllers  81  can be programmed to apply more or less liquid agent and can be coupled to web speed information so as to apply predetermined, uniform quantities of fabric treatment agent. While three spray assemblies or shown, one or more can be used, depending on the width of web  5 ′ and on the width of the spray. Spray assemblies can be used in zones A or B of FIGS. 3 and 4, respectively. 
     With reference to FIGS. 6 and 7, an alternate preferred apparatus for applying fabric treatment agents web  5 ′ is shown. In FIG. 6, the perfume applicator generally includes tubular member  50  having a plurality of micro holes  52 . Web  5 ′ is directed past the applicator by one or more guide rolls  54 . The number and configuration of guide rolls  54  is not critical and could even be eliminated. 
     Liquid fabric treatment agent is preferable pumped into applicator  50  by means of a metering pump  60  associated with tank  70 . As shown, the liquid passes through tube  58 , into one end of applicators  50 . Most preferably, the liquid is pumped into applicators  50  through a manifold (not shown) that directs the liquid into each end of the applicators  50 . Such a system can provide a more uniform pressure profile within applicator  50 . Applicators  50  are preferably fabricated from a low friction material that can apply the fabric treatment agents to the web as it contacts tubular member/applicator  50  and passes over the micro holes. While two rows of micro holes are shown, various combinations of holes, slits or other orifice that allow the liquid to exit the applicator can be used. Applicators  50  can be used in zones A or B of FIGS. 3 and 4, respectively. FIG. 8 shows several applicators similar to FIG. 6 in use prior to the steps of cutting and folding. 
     In a preferred process where one or more of the fabric treatment applicators are used to apply perfume, at least between about 50% to about 75% by weight of the total perfume in the final product is added after the high temperature coating operation. In a most preferred process about 95% to about 100% by weight of the total perfume in the final product is added after the high temperature coating operation. 
     By applying certain fabric treatment agents at either or both zone A and zone B, the need for changing and cleaning ingredients  17  in coat pan  15  can be eliminated, allowing for manufacturing efficiencies. 
     In practice it was unexpectedly found that the post-added perfume could absorb into the dryer sheet material that was processed as shown in FIG.  1 . By absorbing, the sheet remained “non-tacky”, and processing, such as cutting and packaging, were not hindered. See example 2, below. 
     EXAMPLE 1 
     An 11 inch by 6.75 inch polyester substrate was first coated with 1.392 grams of anti-static/softening agent on a bench-top coater. Subsequently, 0.058 grams of perfume (4% by weight, excluding the weight of the substrate) was sprayed onto the coated sheet. This sheet and a typical production sheet were analysed by a HeadSpace GC. The production sheet was produced using the process shown in FIGS. 1 and 2, i.e., without de-coupling the perfume from the coating step. The perfume level in ingredients  17  dosed into coat pan  15  was also initially 4% by weight. The analysis data is shown in the following table. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Perfume added, 
                 Perfume remaining, 
                   
               
               
                 Sample 
                 g 
                 g 
                 Perfume Loss, % 
               
               
                   
               
             
             
               
                 Lab Sample 
                  0.058 
                   0.055 
                  5.0 
               
               
                 Production 
                 0.058 
                 0.033 
                 42.5 
               
               
                 sheet 
               
               
                   
               
             
          
         
       
     
     The data indicates that the new process has improved the perfume retention. Therefore, for example, if the final product sold to the consumer only needs 0.033 g of perfume to deliver the expected perfume benefit, the methods disclosed herein allow for the addition of only 0.0347 g of perfume per sheet to deliver the same/expected amount—more than 40% reduction in perfume use. 
     EXAMPLE 2 
     An 11-inch wide dryer sheet roll was coated with anti-static/softening agent and perfume via the production process of FIG.  1 . The role was mounted on a pilot scale coater. An applicator device as shown in FIG. 6 was set to contact the web of dryer sheet between unwind and rewind rolls. The roll was unwound and rewound at the speed of 10 ft/min while a pump was pumping perfume with the flow rate of 1.03 g/min onto the coated web. The addition of perfume is equal to extra 4% of perfume added to the sheet. The sheets with the extra 4% perfume made by this method showed a minimal increase of tackiness. Thus, the process was demonstrated.