FIELD: process for producing bristles of thermoplastic polymers by injection casting and apparatus for performing the same.
SUBSTANCE: method for producing bristle of thermoplastic polymer by injection casting comprises steps of injecting melt polymer under pressure into bristle shaping duct having predetermined length and predetermined contour of cross section along the whole length of duct and blown through at injection casting process. It provides creation of shear flow of high speed in mean zone of melt polymer with high shear effect due to friction of melt polymer and wall at strictly defined longitudinal orientation of polymer molecules at least in zone of melt polymer near wall. Simultaneously said duct is blown through along its length. Injection pressure acting upon melt polymer is set depending upon cross section contour of duct for shaping bristle, preferably it is no less than 500 bars (0.5 x 105 kPa). Relation of maximum width of bristle shaping duct to length of said duct is selected in range ≤1 : 10 in order to sustain longitudinal orientation of molecules of polymer along length of duct. According to invention it is possible to make bristle of high flexibility by regulating injection pressure depending upon cross section of shaping duct for creating shear flow of high speed in mean zone of melt polymer with large shear force due to friction of polymer and wall of ducts. Such flow has strictly defined longitudinal orientation of polymer molecules at least in region near wall and it is sustained by simultaneously flowing through the whole length of duct. Apparatus for performing the method includes unit for creating injection pressure and injection mold having at least one duct for feeding melt polymer and at least one cavity in the form of shaping duct whose contour corresponds to length and shape of produced bristle. Shaping duct is provided with blow through unit for removing air displaced at injection process. Blow through unit includes blow cross section zones distributed along length of shaping duct. Unit for creating injection pressure provides pressure at least 500 bars ( 0.5 x 105 kPa). Relation of maximum width of cross section of shaping duct to length of duct is in range < 1 : 10. It allows create shear flow of high speed in mean zone of melt polymer and with high shear effect near wall of shaping duct.
EFFECT: possibility for making high-quality bristles with bending properties and recovery characteristics after bending deformation exceeding those of extruded bristles due to achieving their elasticity modulus and tensile strength almost equal to theoretical ones.
74 cl, 36 dwg
