Patent Application
20090025872
The present invention relates to a method of making and using retroreflective fibers and especially to the making of retroreflective fibers from finely cut strips of a thin sheet of material having a corner cube array formed on one side thereof.
Reflective fibers for fabrics have generally been made attaching glass beads or parabolic reflectors to natural or synthetic fibers using a binder. This fiber thus has the retroreflective material exposed on the surface of the fiber, providing little protection against abrasion and degradation of the retroreflective elements. The fabric and materials made from these fibers tend to have low levels of retroreflectivity and do not have longevity in regard to retroreflection.
In addition, there exists today one generally practiced form of roadway marking for traffic that of applying roadway paint and then spreading glass beads on the wet paint surface to achieve a level of retroreflection. This practice achieves a very low level of retroreflection, and one in which the glass beads degrade, are eroded off the roadway by traffic, or as is well known with glass beads, lose their retroreflection properties when wet, such as in rainy weather when roadway illumination is most critical. A retroreflective coating is needed to ensure motorists that roadway markings illuminate and provide safe passage in darkness and during wet weather conditions.
A method of making retroreflective fibers includes selecting a sheet of retroreflective material which has a corner cube array on one side thereof. A polymer sheet of material is laminated to the retroreflective material and a coating applied over the retroreflective material. The sheet of material is cut into thin strips or threads for forming retroreflective fibers for use in making retroreflective materials. The process can include chopping the retroreflective thread into smaller retroreflective fibers for adding to a coating material such as paint. The process may include metalizing the corner cube side of the sheet of retroreflective material and optionally laminating a second sheet of retroreflective material to the either side of the selected sheet of retroreflective material. The method of making and using the retroreflective fibers includes weaving a retroreflective thread made of retroreflective fibers and polymers to form a retroreflective fabric and optionally using the retroreflective fibers for feeding into an injection molding machine to form a retroreflective polymer. The retroreflective fibers may also be mixed with a coating material, such as paint, and applied to a roadway or any other area requiring a reflective paint. Retroreflective fibers may also be included in a polymer film or a reflective tape or retrorefelctive strands may be applied through a fiberglass gun.
It is an object of this invention to provide an improved method of marking roadways, one which provides improved retroreflection and wet weather properties.
It is another object of the present invention to provide a method of roadway marking which does not degrade or erode from the surface with the rapidity of glass beads.
It is another object of the present invention to provide a system with superior retroreflection properties, including but not limited to, brightness, entrance angles and durability.
It is also possible to produce lengths of thin retroreflective thread or retroreflective fibers, which can be clad using an extrusion machine and coated with various materials, such as polyurethane or other materials to achieve wavelength selectivity, color, phosphorescence and other application specific properties to produce reflective thread for garments and patches with both decorative and safety features.
Other objects, features, and advantages of the present invention will be apparent from the written description and the drawings in which:
This invention relates to a method of making retroreflective thread for use in making retroreflective cloth or patches, and to the use of the same fibers, cut into smaller lengths, for making a retroreflective material.
The invention is accomplished using retroreflective sheeting made of arrays of corner cubes, typically from 0.002 to 0.010 inches on center. This sheeting is metalized, typically with aluminum, but many other metals can be used, and may be top coated to provide a retroreflected color. Two layers of retroreflective sheeting may also be joined together with an adhesive with the tips of the metalized corner cubes embedded in the adhesive, creating a two sided retroreflector. This film of corner cubes is then slit to a width of between 0.003 and 0.020 inches and then wound up on a spool. The wound material is then fed, singularly or multiple stands together, into a chopping machine. These thin threads are now cut into a uniform length, from 0.004 to several inches and are now individual fibers. These fibers are can now be processed by mixing with paint, applied on top of wet paint, or spread onto a carrier sheet and covered with a topcoat or film and slit into roadway products, or other retroreflective or decorative products.
Referring to
This metalized retroreflective sheeting 10 can then be laminated as shown in
This laminated sheeting 17 in
In another application, as shown in
At this stage, the resulting fibers 21 can be mixed into a coating 22, such as roadway paint, commonly specified by DOT offices, and applied by spray or other means to produce a retroreflective surface 23. In the case of a roadway, the fibers 21 can be applied by hand or by a machine to the top surface of freshly painted surfaces to add a retroreflective coating to the roadway.
In another application, the slit retroreflective material 19 is fed, preferably using several strands at one time through the nozzle of a fiberglass application gun, and chopped and mixed with fiberglass resin to form a molded material with a high level of retroreflection. This molded material can be used for marine, highway, personal safety or any other number of retroreflective uses.
In another application the slit retroreflective material 19 or retroreflective fibers 21 can be fed, preferably using several strands at one time through a chopping nozzle and mixed with a resin mixture of polyurea, a two part system and allowed to cure. The weathering of polyurea and its ability to adhere to metals and concrete, when mixed with the retroreflective strands will enhance the nighttime visibility of bridges and concrete roadway barriers.
In another application of the present invention, the slit retroreflective material 19 or retroreflective fibers 21 can be fed through a die 25 in an injection molding machine 24 and a cladding formed from a polymer, such as polyurethane or many other commonly used materials. This cladding can be applied to give the fiber 26 or fibers 21 special optical or color characteristics, while also providing added tensile strength to the fiber. This injection molded product may contain an internal wire or polymer string to provide increased tensile strength.
In another application as shown in
In another application, the slit retroreflective material 19, or the slit and clad retroreflective material 26, can be woven into a fabric 28 consisting of other materials, or woven using only slit retroreflective material 19 or 26 to produce a retroreflective cloth 28 or patch 28 of material. This material can be suitable for inclusion in garments such as turnout coats, sportswear, emergency personal garments and the like, where retroreflection is important for nighttime safety. The slit or slit and clad retroreflective material in fiber form may also be used to form non-woven sheeting by laying the fibers such that they overlap and then locally fusing the thermoplastic component of the fibers together under heat and pressure.
In another application, as shown in
