Patent Application
20080051503
The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein:
Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting the same,
With continuing reference to
Still referring to
As explained above, conventional methods of mixing fiber loaded rubbers have proven ineffective in cases where compounds with high fiber loadings are needed. The inventors, however, have discovered that by using a “Y-mix” non-productive cycle in place of the single stage and two stage mixing cycles known in the art, large amounts of fibers can be mixed into the compound with surprisingly improved fiber dispersion characteristics. The Y-mix cycle includes the following three non-productive mixes: (1) creating a first blend by mixing a first portion of a polymer with a first component mix that includes the required fillers; (2) creating a second blend by mixing a second portion of the same polymer (or a portion of different polymer) with a second component mix that includes the required fibers; and, (3) creating the polymer compound by mixing the first blend with the second blend.
The particular polymer and fillers used with this invention can vary according to the required characteristics of the polymer compound. Similarly, this invention will work with any known fiber material including fibers formed of cotton, carbon, wood cellulose and related fibers, as well as fibers made of a suitable synthetic material including aramid, acrylic, nylon, rayon, polyester, carbon, polytetrafluoroethylene (PTFE), polybenzoxazole (PBO), fiberglass and the like. Each fiber may have a diameter ranging between 0.0004 inch to 0.050 inch (0.01 mm to 1.3 mm) and length ranging between 0.001 inch to 0.5 inch (0.025 mm to 12.5 mm). Preferably, the length of the fiber exceeds the diameter. The fibers may be used in an amount ranging from 1 to 100 parts per hundred crosslinkable elastomer, usually referred to as “parts per hundred rubber” or “phr”. Preferably, the fibers are used in an amount ranging from 20 phr to 70 phr and have a total fiber content of between 1% to 50% by weight. The fiber materials, dimensions, and quantities are exemplary only and those provided in previously mentioned U.S. Pat. No. 6,695,734 titled Power Transmission Belt are also contemplated. The orientation of the fibers in the rubber compound is achieved by means known to those skilled in the art in order to achieve the desired compound properties.
It is well known to employ a mixer and mixing process in the formulation of compounds necessary to the manufacture of polymeric based goods, including power transmission belts and tires. The mixer may be either continuous or discontinuous. A discontinuous, or “batch” process, mixes the material either relatively openly or within an enclosed chamber by operation of one or more mixing rotors. A well known device that provides an enclosed chamber for batch mixing is known as a Banbury™ mixer. Such a mixer 58, as illustrated in
The following two production trials are presented for the purposes of illustrating and not limiting this invention. Note that the fiber orientation was assessed by the ratio of the physical properties in the “with” direction (machine direction) to the physical properties in the “against” direction (perpendicular to the machine direction).
For this trial, a SBR elastomer was mixed with a fiber blend containing 4 mm polyester fiber and 1 mm Conex with a total fiber content of 17.7%. Four different mix cycles were proven to be feasible in the lab, and they were then mixed in production. The mix cycles are shown in
The test results for the polymer compounds made with the various mix cycles as well as the control and control with 100% WA are shown in Charts 1 through 7. A visual indication of the fiber dispersion is shown in
As shown in Chart 1, the following mixes show a decrease in Mooney Viscosity (at 100° C.) from the control; Y-mix, Remill Pass and Control With 100% Work Away.
As shown in Chart 2, flexibility of the vulcanizates, determined by an in-house procedure, was increased from the Control for all the different mixes except Mix Variation 1B. Note that the Y-mix had the second best flexibility.
As shown in Chart 3, the tensile strength “with” direction was increased from the Control for all of the different mix cycles. The highest tensile strength was the Y-mix.
As indicated in Chart 4, the 10% Modulus “with” direction was increased from the Control for all of the different mix cycles. The highest 10% Modulus was the Y-mix.
As indicated in Chart 3, the tensile % Coefficient of Variance (CV) “with” direction was improved from the Control for only mix Variation 1B. (As known by those of skill in the art, % CV=standard deviation/mean*100). Chart 4 shows that the % CV “with” direction for 10% Modulus was improved from the Control for the Remill Pass, Mix Variation 1A and Mix Variation 1B.
As shown in Chart 5, the orientation determined by the ratio of the “with” direction to “against” direction using tensile strength indicates that all the mixes are better oriented than the control. Using the 10% modulus, it is apparent that all mixes except the remill were better oriented than the control. The best orientation for tensile and 10% modulus was the Y-mix cycle. Chart 6, shows the dynamic stiffness data.
As shown in Chart 7, the average belt life data shows the belt made from Y-mixed compound had significantly more belt life that the one from control compound. The Remill Pass provided very good belt life. The inventors believe that this result can be explained by the additional mastication of natural rubber achieved with the extra mixing during the Remill Pass.
In conclusion, the fiber distribution and dispersion was improved from the Control using the Y-mix procedure. Overall, the Y-mix cycle showed the most overall improvements from this production trial. The average energy per batch used for the Y-mix is approximately the same for the Control. The highest average peak energy usage, however, for the Y-mix was 852 kilowatts (kw) versus 783 kw for the Control.
For this trial, a neoprene rubber polymer was mixed with a fiber blend containing cotton flock and ⅜ inch chopped polyester tire cord with a total fiber content of 17.0%. Four different mix cycles were proven to be feasible in the lab, and were then mixed in production. The mix cycles are shown in
The test results for the compounds made with the various mix cycles as well as the control are shown in Charts 8 through 14. A visual indication of the fiber dispersion is shown in
As shown in Chart 8, the following mixes showed a decrease in Mooney viscosity (at 100° C,) from the control; Y-mix, remill pass. As shown in Chart 9, flexibility was increased from the control for all the different mixes except the remill pass. The best flexibility was mix variation 1A followed by the Y. As shown in Chart 10, tensile strength “with” direction was increased from the control for three of the four different mix cycles. The highest tensile strength was the Y-mix.
The 10% modulus “with” direction was increased from the control for three of the four different mix cycles. The highest 10% modulus was the fiber master batch followed by the mix variation 1A and the Y-mix. As indicated in Chart 10, the tensile % CV “with” direction was improved from the control for only the fiber master batch. Chart 11, also indicates that the 10% modulus % CV “with” direction was similar to the control for fiber master batch and Y-mix, but worse than the control for the other mix cycles.
As shown in Chart 12, the orientation determined by the ratio of the “with” direction to “against” direction using tensile strength had all the mixes better oriented than the control. Using the 10% modulus, all mixes were better oriented than the control except for the remill pass. The best orientation for tensile and 10% modulus was the Y-mix cycle. Chart 13, shows the dynamic stiffness/Frequency data. Y-mix and fiber master batch had similar dynamic stiffness profiles, less than control and remill pass but well above mix variation 1A.
As shown in Chart 14, the average belt life data shows the Y-mix with more than twice the life of the control.
In conclusion, once again the Y-mix cycle showed the most significant overall improvement. The average energy used per batch was slightly higher for the Y-mix (32.6 kwh\batch) than the control (28.5 kwh\batch). The highest average peak power usage for control was 489 kw and for the Y-mix 405 kw. The peak power usage is slightly lower for the Y-mix.
The preferred embodiments have been described, hereinabove. It will be apparent to those skilled in the art that the above methods may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.
Having thus described the invention, it is now claimed:
