EXTRUSION OF PLASTICS Russian patent published in 2014 - IPC B29C47/40 

FIELD: chemistry.

SUBSTANCE: invention relates to extrusion of plastic mass using a multi-shaft extruder with special geometric parameters of augers. The result is achieved through a method of extruding plastic mass using auger elements for multi-shaft screw extruders, with auger shafts which rotate in pairs in the same direction and clean each other in pairs and have two or more auger pitches. The auger profiles can be presented on the entire cross-section in the form of a continuously differentiable profile curve, and between the auger elements and the housing and/or between adjacent auger elements, there are gaps measuring 0.1-0.001 times the diameter of the auger profile, and the auger profile on the entire cross-section consists of four or more circular arcs. In their initial and end points, the circular arcs transition into each other at a tangent. The forming and formed auger profiles are located at a centre-to-centre distance, a, from each other. The number of circular arcs of the formed auger profile is equal to n. The external radius ra of the forming auger profile is greater than 0 (ra>0) and less than the centre-to-centre distance (ra<a). The internal radius ri of the forming auger profile is greater than 0 (ri>0) and less than or equal to the centre-to-centre distance (ri≤ra). The circular arcs form a closed auger profile. Each circular arc of the formed auger profile is located within or on the boundary of a ring having an external radius ra and an internal radius ri, the centre of which lies at the centre of rotation of the forming auger profile. One of the circular arcs of the forming auger profile touches the external radius ra of the forming auger profile at a point P_A. One of the circular arcs of the forming auger profile touches the internal radius ri of the forming auger profile at a point P_I. The number of circular arcs of the formed auger profile n׳ is equal to the number of circular arcs of the forming auger profile n. The external radius of the formed auger profile ra׳ is equal to the difference when subtracting the internal radius ri of the forming auger profile from the centre-to-centre distance (ra׳=a-ri). The angle a_j׳ of the j׳-th circular arc of the formed auger profile is equal to the angle a_j of the j-th circular arc of the forming auger profile, wherein j and j׳ are integers which together assume all values in the range from 1 to the number of circular arcs n and n׳, respectively. The sum of the radius r_j׳ of the j׳-th circular arc of the formed auger profile and the radius r_j of the j׳-th circular arc of the forming auger profile is equal to the centre-to-centre distance a. The centre of the j׳-th circular arc of the formed auger profile is located from the centre of the j-th circular arc of the forming auger profile at a distance which is equal to centre-to-centre distance a. The line which connects the centre of the j׳-th circular arc of the formed auger profile and the centre of the j-th circular arc of the forming auger profile passes in parallel to the line which connects the centres of rotation. The initial point of the j׳-th circular arc of the formed auger profile is located relative to the centre of the j׳-th circular arc of the formed auger profile in a direction opposite to that in which the initial point of the j-th circular arch of the forming profile lies relative to the centre of the j-th circular arc of the forming auger profile.

EFFECT: reducing average and maximum temperature rise to avoid damage to the polymer.

14 cl, 37 dwg, 2 ex