CN2334574Y

CN2334574Y - Four-section type reaction extrusion screw bolt

Info

Publication number: CN2334574Y
Application number: CN98241516U
Authority: CN
Inventors: 吴大鸣; 龙文保; 王伟明; 丁玉梅; 刘颖
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 1998-10-15
Filing date: 1998-10-15
Publication date: 1999-08-25
Anticipated expiration: 2008-10-15

Abstract

The utility model provides a four-section type reactive extrusion screw bolt, relating to a screw bolt which is used on a single-screw extruder. The utility model is divided into a material feeding section, a melting section, a homogenizing section and a reacting section. The length of the reacting section is 20 percent to 45 percent of the total length of the four-section type reaction and extrusion screw bolt. The depth of a screw groove of the reacting section is 10 percent to 50 percent larger than the depth of the homogenizing section. The melting section is provided with a mixing and smelting element. When used in extrusion processing of silane crosslinking polyethylene, the utility model can obviously raise the graft reaction efficiency, increase the productivity, and improve the process quality. The utility model not only can be used in extrusion processing of silane crosslinking polyethylene pipes, cables, plate and special-shaped material, but also can be used in reactive extrusion or foaming extrusion of other polyolefin.

Description

A kind of four-part form reaction extrusion screw rod

The utility model relates to a kind of screw rod that is used for single screw extrusion machine, is applicable to that plastics reactions extrudes processing, and particularly the organosilane crosslinked polyethylene graft reaction is extruded processing.

The general traditional single screw extrusion machine that is adopted in plastic processing mostly is syllogic greatly, and screw rod is divided into feeding section, melt zone and homogenizing zone.Particle or powdered plastic are extruded continuously through plasticizing, homogenizing in extruder, and plastics have experienced different physical states in extrusion, but its chemical constitution does not change.Extrude in the processing in the plastics reaction, for example in the organosilane crosslinked polyethylene extrusion, raw material except the experience physical process, also will be finished the silane graft reaction, than general plastics extrusion process complexity in extruder.Time of staying of common three-stage screw extruder distributes wide, and the complete melting zone of material is shorter relatively, and obviously the adaptive response requirement of extruding fully only increases spiro rod length and can not improve reaction efficiency effectively.To the common screw rod that equidistantly deepens, plastic grain could melt fully at screw rod total length about five/everywhere, though adopt mixed milling type screw rod and divergence type screw rod that the complete melting zone relative length of material is increased, but still there is a melt residence time wide problem that distributes, this is very disadvantageous to improving graft reaction efficient, and therefore common single screw extrusion machine is not suitable for reaction and extrudes processing.

The purpose of this utility model provides and a kind ofly can be used for plastics reactions and extrude the screw rod of processing, and this screw rod can be used for organosilane crosslinked polyethylene and extrudes processing, can obviously improve graft reaction efficient, and can improve output and improve crudy.

A kind of four-part form reaction of the utility model extrusion screw rod is to be provided with conversion zone after the homogenizing zone of common three-stage screw, and the spiral groove depth of conversion zone is greater than the spiral groove depth of homogenizing zone; Be provided with mixing elements at melt zone.The length of conversion zone is the 20%-45% of screw rod total length; Spiral groove depth is than the dark 10%-50% of the spiral groove depth of homogenizing zone.Mixing elements is separate type or barrier-type structure.

Fig. 1 is the structural representation of the utility model four-part form reaction extrusion screw rod.

The utility model as shown in Figure 1, this screw rod is divided into feeding section 1, melt zone 2, homogenizing zone 3 and conversion zone 4.The structure of first three section is similar to traditional three-stage screw, can adopt the known equidistant gradual change version such as dark of deeply, equidistantly suddenling change, and conversion zone 4 is located at after the homogenizing zone 3, and its length is the 20%-45% of screw rod total length.The screw channel of conversion zone 4 is than the dark 10%-50% of the screw channel of homogenizing zone 3, and the compression ratio of screw rod is got 1.4-4.5.Can make melt also can increase melt residence time like this in conversion zone 4 decompressions, be provided with mixing elements at melt zone 2, mixing elements is to adopt known structure, its structure can also adopt the barrier-type mixing elements except that the separate type mixing elements that adopts as shown in fig. 1, mixing elements can quicken the thawing of material.According to the screw rod design principle of routine, spiral groove depth is from depth to shallow, the screw channel that does not allow homogenizing zone from light to dark, in case major structure becomes to extrude instability.But extrude for reaction, the viscosity of material, density etc. are along with the carrying out of chemical reaction will change, the stable factor of extruding of influence also can change, for reaction extrusions such as grafting, crosslinked, foaming, might after homogenizing zone, adopt screw channel to deepen to carry out reduced pressure treatment fully, in the requirement of guaranteeing that realization response is extruded under the stable condition of extruding.Melt is through reducing pressure in conversion zone behind the homogenizing zone and finishing reaction and be fed forward equably.The utility model is used for organosilane crosslinked polyethylene to be extruded and adds man-hour, polyethylene-silane systems is along with the raising of percent grafting, and the viscosity of melt obviously increases, and reduces pressure at conversion zone, help to reduce the shear rate of melt, prevent the living thermal conductance pyrogenicity degraded of melt excessive shear.

Extrude in the processing at silane cross-linked polyethylene pipe, adopt four-part form screw extruder of the present utility model, used screw rod 1# is of a size of: directly through 65mm, draw ratio 30: 1, compression ratio 2.0, feeding section groove depth 9.6mm, melt zone separate type mixing elements, homogenizing zone groove depth 4.46mm, conversion zone are the dark screw rod such as equidistant grade of groove depth 5.8mm.The common syllogic single screw extrusion machine (size of used screw rod 2#: diameter 65mm of this extruder and equidistant gradual change, draw ratio 30: 1, compression ratio 1.88, feeding section groove depth 7.5mm) and equidistantly deepen the common syllogic single screw extrusion machine (size of used screw rod 3#: of band barrier-type mixing elements directly through 65mm, draw ratio 30: 1, compression ratio 3.5, feeding section groove depth 9.1) comparative test result shows, when the fused materials time of staying is 1 minute, the output of screw rod 3# is 28kg/h, the output of screw rod 2# is 37.5kg/h, and the output of screw rod 1# is 46.5kg/h; When the fused materials time of staying was 2 minutes, the output of screw rod 3# was 18.5kg/h, and the output of screw rod 2# is 25.5kg/h, and the output of screw rod 1# is 31.8kg/h.By experimental result as can be known, the utility model can obviously prolong the time of staying of fused materials, under identical prescription and reaction condition, extrude with extruder of the present utility model that two kinds of common syllogic single screw extrusion machines improve about 60% and about 25% respectively on the PR.Four-part form list spiro rod reaction extruder also has the characteristics of residence time of material narrowly distributing, for improving graft reaction efficient is very favourable, under, the condition that the degree of cross linking is constant constant, can increase substantially and extrude output, the uniformity and the presentation quality of goods all increased at prescription.

The utility model four-part form reaction extrusion screw rod not only can be used for the processing of extruding of silane cross-linked polyethylene pipe, cable, sheet material and profile shapes, can also be used for other polyolefin graft crosslinking reaction and extrude, foams and extrude and processing is extruded in other reaction.

Claims

1, a kind of four-part form reaction extrusion screw rod includes feeding section, melt zone, homogenizing zone, and it is characterized in that: be provided with conversion zone after homogenizing zone, the spiral groove depth of conversion zone is greater than the spiral groove depth of homogenizing zone; Be provided with mixing elements at melt zone.

2, four-part form reaction extrusion screw rod according to claim 1, it is characterized in that: the length of conversion zone is the 20%-45% of screw rod total length; Spiral groove depth is than the dark 10%-50% of the spiral groove depth of homogenizing zone.

3, four-part form reaction extrusion screw rod according to claim 1, it is characterized in that: mixing elements is separate type or barrier-type.