Apparatus for impregnating strands, webs, fabrics and the like

Abstract

Abstract A preferred embodiment of the invention is illustrated in an apparatus for impregnating a glass fiber strand. Particulate impregnant material is provided in a gaseous suspension. The particles of impregnant material are electrically charged with charges having a first polarity. The individual glass fibers are treated to render the surfaces thereof at least semi-conductive electrically. The glass fiber strand is opened and the individual glass fibers are separated from each other by electrostatically charging the semi-conductive surface of each of the fibers with charges having a second polarity, thereby causing the fibers to repel each other. The strand of separated glass fibers is passed through the gaseous suspension to enable the attraction of particles with a charge of the first polarity and adherence to the surface of the individual fibers having charges of the second polarity. The individual glass fibers in the strand may be treated by controllably moistening the strand to provide the fibers with a surface layer of moisture, as by passing the strand of glass fibers through a steam bath which penetrates the strand and, if the strand has sizing thereon, softens the binding components of the size. The individual glass fibers may be also treated by applying a sizing which includes an electrolytic material to the fibers before gathering the fibers together into the strand form, the electrolytic material having ions which are opposite in polarity to the electrostatic charges on the particles. The step of opening the strand may include generating an electrostatic field to provide the particles with charges on the first polarity, and locating a grounded electrode within the influence of the first polarity electrostatic field. The strand passing in contact with or within the range of influence of the electrode and also in the influence of the first electrostatic field enables the induction of electrostatic charges of the second polarity on the surfaces of the fibers in the strand. Alternately, the strand may be grounded before it enters the first electrostatic field, and then passed through the first electrostatic field in a fluidized bed of particulate impregnant and within the range of influence of an electrode disposed within the first electrostatic field. As a still further alternative, a second electrostatic field may be generated to charge the surfaces of the fibers with the charges of the second polarity. After adherence to the strand the particles may be coalesced to substantially coat each one of the fibers, and the fibers may be gathered together to provide a unitary, substantially impregnated multi-fiber strand. The invention is also applicable to webs, fabrics, and the like, made from multi-filament strands.

Inventors

• 👤 A Brown
• 👤 R Moran

Bibliographic Details