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Analysis of Applicable Blades for BMC Materials
The author:admin 来源:High Pu kneading machinery   date: 2017/5/9 Popularity:67

Abstract: In this paper, the mixing principle of BMC molding compound is briefly introduced. The structure and form of three kinds of stirring blades of double-arm kneading machine are introduced. It is recommended to use 180 ° single-screw and Banbury type Can be adapted to the high strength of the dispersion, high efficiency of mixing, the least fiberglass damage BMC molding compound preparation requirements. Key words: BMC molding compound kneading machine Sigma blade. The composition of BMC double arm mixer for domestics BMC Boming Kuang (Wuxi Xinhongtai Electrical Apparatus Co., Ltd.) Abstract: This article describes the mix principle of Bulk Molding Compound-three types of agitators construction and pattern used in the double arm mixer . The 180 ° spiral agitator and the Banbury agitator are recommended for its high dispensations, effective mix-up with less damage of the glass fiber to the BMC material, which are the concerns in the BMC manufacturing key word: BMC; Sigma agitator with unsaturated polyester resin as the matrix of fiber reinforced mass molding molding products since its inception, has been nearly 60 years of history, which is typically used in automotive headlamps of the mirror, the low voltage electrical device insulation shell Frame, household electrical appliances in the transmission of micro-motor stator coating, etc., short-term temporary can not find a substitute for this thermosetting plastic material. This depends mainly on the BMC cured products have a high working temperature, good apparent quality, light and low cost, superior electrical properties and flame retardant and so on. The uncured BMC can be easily pressed, conveyed or molded. BMC products manufacturing steps are: A. BMC components of the raw materials in the purchase, storage, quality control and formulation design; B. BMC molding compound preparation, that is, BMC molding compound kneading and kneading; C. BMC Molding, transportation and molding; D. BMC molding compound molding, including compression, transfer molding and injection molding; E. BMC products, finishing, secondary processing or surface coating. This paper only discusses some problems of mixing blades in BMC blended high-strength kneaders, so as to find the homogeneous BMC molding compounds with high mixing efficiency, glass fiber damage and minimal degradation. 1) BMC molding compound mixing principle BMC molding compound contains UP resin, mineral filler, low shrinkage additive, initiator, pigment, release agent, and chopped glass fiber. High solids / low liquid mixed {1}, its high solids not only contain a variety of different particle size of the powder, but also different lengths of glass fiber sheet. Leaving aside the molding process technology does not say that the performance of molded products depends on the quality of raw materials, reasonable formula design, of course, also depends on the nearly 10 kinds of components of the full mixing and dispersion. The preparation of the BMC molding compound requires a good dispersion of the mixture, the powdery filler mass is completely broken up, and is sufficiently wetted and coated with the liquid resin. While the dry glass fiber surface to be thick paste to impregnate, out of the glass interface of the air and evenly dispersed in the thick paste paste. In the kneader, the following physical mixing occurs: First, the physical shear of the liquid and solid surfaces is separated from the surface of the agglomerated particles by direct friction with the liquid. Second: solid-phase internal dynamic shear, from the particles ~ particles of contact, making the caking separation, and hope to have a certain crushing effect. Third: glass fiber sheet material is high viscosity paste extrusion, sliding, friction and thus get wet and dispersed. Other factors that affect mixing and dispersion are the degree of material agitation, the gravitational attraction between particles, the viscosity and specific gravity of the liquid, and the natural affinity of the solid particles. In general, the kneader is classified according to the designed output capacity: low strength (60 ~ 120Kg mixed material per Kw), medium strength (5 ~ 10Kg per Kw), high strength (1 ~ 1.8Kg per Kw) , The domestic early BMC kneading machine is to follow the pen industry lead core kneading machine, most of the preparation of a small motor, a 500-liter kneading machine configuration 7.5Kw motor, mixed strength was significantly lower, filling the lumps can not play Broken, and must be the internal power of the shear can not happen, adding fiberglass often produce boring car, glass fiber can not be quickly impregnated, only to extend the time, causing glass break. In recent years, many domestic BMC manufacturers newly added kneading machine, the standard configuration is 500 liters with 30Kw motor, to meet the strength of the mixer configuration, with foreign similar 500-liter machine configuration 25 ~ 40Kw motor quite. The operation of this new batch of kneading machine not only shortens the kneading time, but also greatly improves the dispersion quality and the mixing efficiency. 2) Basic arrangement of the double-arm kneading machine The basic arrangement of the double-arm kneading machine shown in Fig. 1 is composed of a stirring blade, a mixing chamber and a driving device. The mixing chamber is a W-shaped bottom of the steel tank {2} Figure 1, the basic arrangement of the arm kneading machine {3} mixing blades in the mixing chamber in the form of installation there are two, see Figure 2 tangential installation of the mixing effect of two The speed of the blade is different, generally about 3: 2, when the paste, the two blades are tangent to the strong shear extrusion pulling and stirring effect. There are two dispersed zones: the area between the tangential region between the rotor and the outer edge of the rotor and the area between the mixing chamber walls. Suitable for high viscosity pastes, especially for the mixing of sheet materials. The two blades can only rotate at the same speed, the shear effect of the material occurs in the small gap between the outer edge of the rotor and the mixing chamber wall, the material of the two parts of the rotor form a cross flow, More homogeneous mix is very effective. Applicable to the lower viscosity of the powder-based material mixing. Figure 2, the different installation of the blade in the mixing chamber {4} 3) The type of paddle of the arm kneading machine 3.1 Sigma-type paddle, see Figure 3 This is very common in the food industry, pen chemical and rubber applications , The domestic early BMC kneading machine mostly use this blade, the design and production of more standardized and stereotypes. Suitable for strong mixing and precise dispersion of the occasion. Disadvantages are dead ends, the manufacture of paddles are not easy to all polished very smooth, it is easy to make in the local sticky material, clean up more difficult. 3.2 180 ° single screw type blade see Figure 4 This is a relatively new type of paddle, the factory has been modeled on the British company's prototype design and manufacture of BMC kneading machine, the domestic US factory selected this blade, and easy The overall casting into stainless steel blade, a substantial increase in rigidity. From the mixing effect, it is more suitable for the mixing and dispersion of the sheet chopped yarn, and the breakage and damage of the glass are the smallest. 3.3 Banbury-type blades see Figure 1 structure, the shape is relatively simple, but with the highest mixing strength, the most effective shear dispersion, because of this, when the high-intensity mixing caused by excessive temperature rise of material, this structure The central axis of the paddle shaft has a central hole, which can cool water and reduce the temperature rise of the material. Domestic BMC plant using such a structure, Figure 1 in the name of the kneading machine nominal volume of 600L, mixed out of each pot up to 300Kg, equipped with a 75Kw drive motor, the expected strength of 4Kg / Kw, beyond the strength of the mixer range. A mixing cycle is roughly 15 to 18 minutes. 4 The actual kneading effect of various blade types, see Table 1: Table 1: Comparison of the operating conditions of three different blade kneading machines Blade type 180 ° Single-screw type Banbury type Sigma new machine Sigma old machine Nominal volume (Liters) 1000 500 500 500 Full load per kilogram (kg) 450 250 250 250 Main motor power (kW) 37 30 32 7.5 Total mixing time per minute (min) 55 38 45 220 Output per kilowatt Kg / kw) 12.2 8.3 7.8 33.3 Hourly discharge (kg / h) 490 395 330 68 Note: 1, the liquid components before the first high-speed mixing machine after mixing. 2, with the BMC formula changes, the total work time slightly changed. Summary: The domestic BMC kneading machine, from the original old configuration, to enhance the main motor power, the Sigma blade of the kneading efficiency, significantly improved, coupled with the introduction of two new blade type, to further enhance the mix of operating results, To enhance the quality of BMC to promote a certain role in promoting. The 180 ° single helix type and Banbury type blades are more suitable for the preparation of BMC molding compounds for high strength dispersion, high efficiency mixing and minimal glass fiber damage. REFERENCES [1] Thomass A. Resing: "Mixing Glass Reinforced Polyester Bulk Molding Compounds" 43th Annual SP1-RP Conference, Session 13-A. [2] Geng Xiaozheng Zhang Pei: "plastic mixing and equipment" China Light Industry Press, 1992. [3] Japan Moriyama Company LTD. product sample. [4] US Littleford Day product samples. [5] Raymond W. Meyer: "Handbook of Polyester Molding Compounds and Molding Technology" 1987. Solid

 
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