Double-screw kneading machine for polyformaldehyde production

Abstract

The utility model discloses a double-screw kneading machine for producing polyformaldehyde, which comprises a barrel body, a screw rod, a screw rod, a screw rod, a screw rod, a screw rod, a screw rod, a screw rod, a screw rod and a screw rod, wherein the barrel body extends along the horizontal direction; a feeding hole is formed above one end of the barrel body, and a plurality of vacuumizing holes are formed in the top; the end covers respectively cover two ports of the cylinder body; each screw rotor comprises a rotor shaft, each rotor shaft is sequentially provided with a spiral rolling propelling section impeller, a crushing propelling section impeller, a complete crushing section impeller and a reverse-rotation crushing discharging section impeller from the feeding end to the discharging end, the phase difference of the impellers on the two rotor shafts is 90 degrees, the impellers are matched with each other, and the impellers are matched with the inner wall of the cavity of the barrel; the shaft ends of the two rotor shafts penetrate out of center holes of the end covers respectively, and rotor shaft center cooling hole channels are formed in the shaft ends of the two rotor shafts respectively along the axes. And the heating jacket covers the periphery of the cylinder body and is arranged in sections, and each section is provided with a heating medium inlet and a heating medium outlet. The equipment is high in devolatilization efficiency, low in energy consumption and capable of continuously running for a long time, and the obtained polyformaldehyde product is good in quality.

Description

Technical Field

[0001] The utility model relates to a mixing reaction device for high-viscosity materials, a twin-screw kneader for polyformaldehyde production, and belongs to the technical field of polyformaldehyde manufacturing equipment. Background Art

[0002] Polyoxymethylene (POM) is one of the five general-purpose engineering plastics, commonly known as "Saigang, Duogang, Chaogang", and has the reputation of "metal in plastics". Its usage ranks third after polyamide (PA) and polycarbonate (PC). Polyoxymethylene has metal-like hardness, strength and rigidity. It is the product with the mechanical properties closest to metal materials among engineering plastics. At the same time, polyoxymethylene has outstanding advantages such as good fatigue resistance and self-lubrication, low friction coefficient, resistance to organic solvents, and simple molding and processing. It is widely used in the manufacture of key components of various industrial products.

[0003] Producing high-quality polyoxymethylene products is also an urgent problem that polyoxymethylene companies need to solve.

[0004] Since polyoxymethylene is a highly crystalline polymer with a special molecular structure, it is prone to thermal degradation under the action of heat, oxygen, etc., and its thermal stability is the worst among existing polymer materials. This is a global problem that has long existed in its synthesis, processing and application and seriously affects its performance. The main problems are as follows: 1. The melt index and volatility of polyoxymethylene products are high, and the product toughness is poor; 2. The overall energy consumption of the polyoxymethylene system is high, and the utilization rate of low calorific value media is low; 3. The operation cycle of the polyoxymethylene device is short, and it needs to be stopped for maintenance and cleaning once a month; 4. The quality of high-end modified polyoxymethylene products is unstable.

[0005] DuPont in the United States uses a catalytic synthesis process with formaldehyde as the monomer. This process first removes water, methanol and other impurities from formaldehyde, and then purifies it to obtain high-purity formaldehyde; then it is polymerized into homopolymerized formaldehyde by passing it into an inert solution containing a cationic catalyst; then, in the presence of an acylating agent, acetic anhydride, the terminal hydroxyl groups are esterified and capped to obtain a heat-stable POM, and then antioxidants and other additives are added, and granulation is performed to obtain a homopolymerized formaldehyde product. The homopolymerization process has very high requirements on the purity of the raw material formaldehyde, and high-purity formaldehyde must be used. The content of impurities such as water and methanol in the monomer formaldehyde must be strictly controlled; in addition, the end-capping treatment after polymerization is difficult, the process flow is long, the equipment is large, and the corrosion is serious.

[0006] The invention patent of DuPont Company of the United States with publication number CN1976966B protects the polymerization of formaldehyde with aliphatic anhydride and quaternary ammonium salt polymerization initiator, which has poor thermal stability.

[0007] In its invention patent with publication number CN100362033C, Basford AG of Germany disclosed a method for preparing polyoxymethylene, which is polymerized in the presence of a cationic initiator. During the polymerization process, both the monomer and the polymer exist in a molten form, and then the polymer is inactivated, the melt is discharged, cooled and pressurized for granulation. The method includes discharging, cooling and granulating the polymer under elevated pressure and in the presence of a liquid. The disadvantage is that in order to reduce the foaming phenomenon of the product during the degassing and melting process, a liquid medium (water or oil) should be present during the granulation process. Utility Model Content

[0008] The purpose of this section is to summarize some aspects of the embodiments of the utility model and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and utility model name of this application to avoid blurring the purpose of this section, specification abstract and utility model name, and such simplifications or omissions cannot be used to limit the scope of the utility model.

[0009] In view of the above problems and / or the problems existing in the prior art, the present utility model is proposed.

[0010] The utility model aims to overcome the problems existing in the prior art and provide a twin-screw kneading machine for polyoxymethylene production, which has high devolatilization efficiency, low energy consumption, can be operated continuously for a long time, has few by-products, and has good quality of the obtained polyoxymethylene product.

[0011] In order to solve the above technical problems, the utility model of a twin-screw kneading machine for polyoxymethylene production comprises:

[0012] The cylinder extends in the horizontal direction, has a feed port at the top of one end, a discharge port at the bottom of the other end, and multiple vacuum ports distributed along the axial direction at the top;

[0013] End covers, respectively covering the two ends of the cylinder;

[0014] The screw rotor is provided with a pair of rotor shafts, each of which includes a rotor shaft. The two rotor shafts are respectively provided with a spiral rolling propulsion section impeller, a crushing propulsion section impeller, a complete crushing section impeller and a reverse rotation crushing discharge section impeller from the feed end to the discharge end. The phases of the impellers on the two rotor shafts are 90° apart and matched with each other and matched with the inner wall of the cavity of the cylinder; the shaft ends of the two rotor shafts are respectively passed through the center hole of the end cover, and the rotor shaft center cooling holes are respectively provided along the axis;

[0015] The heating jacket is covered on the outer circumference of the cylinder and is arranged in sections, and each section is respectively provided with a heat medium inlet and a heat medium outlet.

[0016] As an improvement of the present utility model, the spiral rolling propulsion section impeller and the crushing propulsion section impeller are respectively provided with a positive spiral angle for propelling the material toward the discharge end, and the spiral angle of the spiral rolling propulsion section impeller is greater than the spiral angle of the crushing propulsion section impeller.

[0017] As a further improvement of the utility model, the phase angles of adjacent complete crushing section impellers are staggered.

[0018] As a further improvement of the utility model, the impeller of the counter-rotating crushing discharge section is provided with a reverse helical angle for propelling the material toward the feed end.

[0019] As a further improvement of the utility model, the top of each of the complete crushing stage impellers is respectively provided with a sawtooth structure for cleaning the inner wall of the cylinder.

[0020] As a further improvement of the utility model, a weight-reducing cavity is symmetrically provided in each of the complete crushing stage impellers.

[0021] As a further improvement of the utility model, each of the lightening-type cavities is respectively provided with a partition to divide the lightening-type cavity into connected left and right cavities, the root of each of the partitions is respectively connected to the middle of the inner wall of the cavity close to the axis of the rotor shaft, the free end of each of the partitions points to the top direction of the impeller and leaves a flow gap between the inner wall of the other side of the lightening-type cavity; the bottom of the left and right cavities are respectively connected to the central cooling channel of the rotor shaft through radial cooling channels.

[0022] As a further improvement of the present invention, the outer walls of the end covers are respectively provided with hot water flow channels, and the hot water flow channels surround the outer circumference of the center seat of the end cover.

[0023] As a further improvement of the utility model, a stuffing box is provided between the center seat of the end cover and the corresponding rotor shaft, and a plurality of fillers are filled in the stuffing box. There are gas rings in the middle of the fillers, and the gas rings are provided with radial holes communicating with the inner and outer ring grooves, and the outer ring groove of the gas ring is upwardly connected to the nitrogen inlet, and the outer ring groove of the gas ring is downwardly connected to the nitrogen outlet.

[0024] As a further improvement of the present invention, the shaft ends of the rotor shaft are respectively supported in bearing seats, overflow collection cavities are respectively provided between the bearing seats and the corresponding end cover center seats, and overflow collection ports are respectively provided at the bottom of each overflow collection cavity.

[0025] As a further improvement of the utility model, a central cooling water pipe is inserted into the central cooling channel of the rotor shaft from the discharge end and extends toward the feed end.

[0026] Compared with the prior art, the utility model has achieved the following beneficial effects: 1. It has the functions of mixing, conveying, self-cleaning, etc., has good material crushing and propulsion performance, no dead angle, and good product quality. It is an ideal mixing reaction equipment for continuous production of high-viscosity materials;

[0027] 2. The temperature is controlled in sections along the length of the cylinder, and the end cover is individually temperature controlled through the hot water flow channel. The temperature control effect is good. The temperature is increased or decreased according to the process requirements of different parts to meet the inlet heating requirements and the outlet heat removal requirements. It avoids thermal degradation of high-viscosity materials at the outlet due to overheating, or causes the product to turn yellow and gray, thereby improving the material quality.

[0028] 3. Cooling hot water is injected into the deep of the central cooling channel of the rotor shaft along the central cooling water pipe, and then flows to the discharge end along the annular space around the central cooling water pipe, which can not only cool each section of the impeller, but also remove the heat of the rotor shaft in time to ensure that the thermal expansion of the rotor shaft is within the allowable range;

[0029] 4. The material removes small molecules under vacuum conditions and undergoes phase change. The inner wall of the cylinder and the discharge end have self-cleaning functions, and there are no dead corners, which prevents the material from being carbonized by long-term heat to produce black spots. The equipment can run continuously for a long time without forced shutdown for cleaning;

[0030] 5. The impellers on the two rotor shafts mesh with each other to crush the materials. At the same time, different impellers are set at different positions according to the production conditions of the project to ensure the crushing and crushing of the materials and the smoothness of the transportation; increase the propulsion effect of the impeller and improve the fluidity of the materials in the equipment;

[0031] 6. Reduce the weight and disturbance of the rotor shaft, reduce the vibration of the equipment, facilitate large-scale, effectively reduce the investment cost and maintenance cost of the polyoxymethylene equipment, increase the profit of the equipment, and strengthen the market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. The drawings are only provided for reference and explanation, not for limiting the present utility model. Among them:

[0033] Figure 1 This is a front view of a twin-screw kneading machine for producing polyoxymethylene according to the utility model;

[0034] Figure 2 for Figure 1 A top view of

[0035] Figure 3 for Figure 1 A cross-sectional view of

[0036] Figure 4 for Figure 3 Left view of

[0037] Figure 5 for Figure 3 Impeller direction diagram at each section position;

[0038] Figure 6 It is a structural schematic diagram of the screw rotor in the utility model;

[0039] Figure 7 for Figure 6 Sectional view along EE;

[0040] Figure 8 for Figure 6 Sectional view along the middle line FF;

[0041] Fig. 9 for Figure 6 Sectional view along GG;

[0042] Fig.10 for Figure 6 Sectional view along HH;

[0043] Fig.11 It is the cross-sectional view of the impeller in the complete crushing section;

[0044] Fig.12 It is the longitudinal cross-section of the impeller in the complete crushing section;

[0045] In the figure: 1. Cylinder; 1a. Feed inlet; 1b. Vacuuming port; 1c. Discharge port; 1d. Temperature measuring port; 1e. Low discharge port; 2. End cover; 2a. Hot water flow channel; 2b. Filler; 2c. Nitrogen inlet; 2d. Nitrogen outlet; 3. Screw rotor; 3a. Rotor shaft; 3b. Spiral rolling propulsion section impeller; 3c. Crushing propulsion section impeller; 3d. Complete crushing section impeller; 3d1. Sawtooth structure; 3d2. Lightening cavity; 3d3. Partition; 3d4. Radial cooling channel; 3e. Counter-rotation crushing discharge section impeller; 3f. Rotor shaft central cooling channel; 3g. Central cooling water pipe; 4. Heating jacket; 4a. Heat medium inlet; 4b. Heat medium outlet; 5. Bearing seat; 6. Overflow collection cavity; 6a. Overflow collection port. DETAILED DESCRIPTION

[0046] In the following description of the utility model, the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the utility model and simplifying the description, and do not mean that the device must have a specific direction.

[0047] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below with reference to specific figures. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0049] like Figures 1 to 5 As shown, the twin-screw kneading machine for polyoxymethylene production of the utility model comprises a barrel 1, an end cover 2, a screw rotor 3 and a heating jacket 4. The barrel 1 extends in a horizontal direction, a feed port 1a is provided above one end, a discharge port 1c is provided below the other end, and a plurality of vacuum ports 1b are distributed axially on the top to facilitate maintaining negative pressure in the inner cavity of the barrel during the production process.

[0050] The end covers 2 cover the two ports of the barrel 1, and the centers of the outer end surfaces of the two end covers 2 protrude outward to form the end cover center seat. The screw rotors 3 are arranged in pairs, and the two screw rotors 3 are meshed with each other. The shaft ends of the two rotor shafts 3a pass through the center holes of the end covers 2 and their center seats, and the rotor shaft center cooling holes 3f are respectively provided along the axis.

[0051] The heating jacket 4 is wrapped around the outer circumference of the cylinder 1 and is arranged in sections. Each section of the heating jacket 4 is provided with a heat medium inlet 4a and a heat medium outlet 4b. The heat medium at the feed end has a high temperature and is used for heating; the heat medium is cooled by the cooler and enters the heating jacket 4 at the discharge end to cool the material. The outer wall of the end cover 2 is provided with a hot water flow channel 2a, which surrounds the outer circumference of the center seat of the end cover and is used to pass hot water to control the temperature of the end cover. Each section is provided with multiple temperature measuring ports 1d, and the lowest point of each section of the heating jacket 4 is provided with a low discharge port 1e.

[0052] like Figures 6 to 10 As shown, the rotor shaft 3a of the screw rotor 3 is provided with a spiral rolling propulsion section impeller 3b, a crushing propulsion section impeller 3c, a complete crushing section impeller 3d and a counter-rotation crushing discharge section impeller 3e in sequence from the feed end to the discharge end. The phases of the impellers on the two rotor shafts 3a are 90° apart and match each other and match the inner wall of the cavity of the barrel 1.

[0053] The impeller 3b of the spiral rolling propulsion section and the impeller 3c of the crushing propulsion section are respectively provided with a positive helix angle, and the helix angle of the impeller 3b of the spiral rolling propulsion section is greater than the helix angle of the impeller 3c of the crushing propulsion section. For example, the positive helix angle of the impeller 3b of the spiral rolling propulsion section is 90°, which is used to accelerate the propulsion of materials to the discharge end, so that the block materials entering the feed port 1a can be quickly and initially crushed and enter the inner cavity of the cylinder. The positive helix angle of the impeller 3c of the crushing propulsion section is 18-20°, which is convenient for continuing to crush while propulsion to the discharge end.

[0054] The complete crushing section impeller 3d has no helix angle and is provided with a plurality of impellers along the length direction of the rotor shaft 3a. The phase angles of adjacent complete crushing section impellers 3d are staggered with each other. After being squeezed by a plurality of pairs of complete crushing section impellers 3d, the material is completely crushed.

[0055] like Fig.10 As shown, due to the gap between the discharge port 1c and the right end cover, a dead angle of flow is formed, and the material is easily carbonized. The impeller 3e of the counter-rotation crushing discharge section of this equipment is provided with a reverse spiral angle, and the material is pushed back to the discharge port 1c when it reaches the gap position between the discharge port 1c and the end, avoiding the formation of a dead angle of the material.

[0056] like Fig. 9 As shown, the top of each complete crushing section impeller 3d is provided with a sawtooth structure 3d1 for cleaning the inner wall of the cylinder, which can be square teeth, trapezoidal teeth, triangular teeth or sawtooth of other shapes, to scrape the inner wall of the cylinder and reduce the residue on the cylinder wall.

[0057] Each complete crushing section impeller 3d is symmetrically provided with a weight-reducing cavity 3d2, which can effectively reduce the mass to 75% of the solid impeller mass, that is, it can reduce a quarter of the weight. After the weight-reducing design, the disturbance of the rotor shaft 3a is significantly reduced.

[0058] like Fig.11 , Fig.12 As shown, the lightening cavity 3d2 of the complete crushing section impeller 3d is provided with partitions 3d3 to separate the lightening cavity 3d2 into connected left and right cavities. The root of each partition 3d3 is connected to the middle of the cavity inner wall close to the axis of the rotor shaft. The free end of each partition 3d3 points to the top of the impeller and has a flow gap between the other inner wall of the lightening cavity 3d2. The bottom of the left and right cavities is connected to the central cooling channel 3f of the rotor shaft through the radial cooling channel 3d4. The central cooling water pipe 3g is inserted into the central cooling channel 3f of the rotor shaft from the discharge end and extends to the feed end.

[0059] Since the rotor shaft 3a is relatively long, the change in length caused by thermal expansion and contraction has a relatively large impact. This equipment injects hot water at about 70°C into the deep of the central cooling channel 3f of the rotor shaft through the central cooling water pipe 3g, while flowing from the feed end to the discharge end, and enters half of the weight-reducing cavity through the radial cooling channel 3d4 on one side, bypasses the flow gap at the end of the partition and enters the other half of the weight-reducing cavity, and then returns to the central cooling channel 3f of the rotor shaft through the radial cooling channel 3d4 on the other side and continues to flow downstream, so as to remove the heat of the rotor shaft 3a in time and ensure that the thermal expansion of the rotor shaft 3a is within the allowable range.

[0060] like Figure 3 As shown, a stuffing box is provided between the center seat of the end cover and the corresponding rotor shaft 3a, and a plurality of packings 2b are filled in the stuffing box. The middle of the packing 2b is respectively provided with a gas ring, and the gas ring is provided with a radial hole communicating the inner and outer ring grooves, and the outer ring groove of the gas ring is upwardly communicated with the nitrogen inlet 2c, and the outer ring groove of the gas ring is downwardly communicated with the nitrogen outlet 2d. In this way, a packing seal plus a nitrogen seal is formed at the shaft end of the rotor shaft 3a, thereby improving the sealing effect.

[0061] The axial ends of the rotor shaft 3a are respectively supported in the bearing seats 5. Overflow collecting chambers 6 are respectively provided between the bearing seats 5 and the corresponding end cover center seats. The bottom of each overflow collecting chamber 6 is respectively provided with an overflow collecting port 6a. A small amount of medium that passes through the sealing section enters the overflow collecting chamber 6 and flows out from the overflow collecting port 6a, thereby preventing the medium from entering the bearing and causing damage.

[0062] The above description is only the preferred feasible embodiment of the utility model, which shows and describes the basic principle, main features and advantages of the utility model, but does not limit the scope of patent protection of the utility model. The technicians in this industry should understand that the utility model is not limited by the above embodiments. In addition to the above embodiments, the utility model can also have other implementation modes without departing from the spirit and scope of the utility model. The utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the utility model. The scope of protection required by the utility model is defined by the attached claims and their equivalents. The technical features not described in the utility model can be achieved by or using existing technologies, which will not be repeated here.

Claims

1. A twin-screw kneader for polyoxymethylene production, characterized in that: include: The cylinder extends in the horizontal direction, has a feed port at the top of one end, a discharge port at the bottom of the other end, and multiple vacuum ports distributed along the axial direction at the top; End covers, respectively covering the two ends of the cylinder; The screw rotor is provided with a pair of rotor shafts, each of which includes a rotor shaft. The two rotor shafts are respectively provided with a spiral rolling propulsion section impeller, a crushing propulsion section impeller, a complete crushing section impeller and a reverse rotation crushing discharge section impeller from the feed end to the discharge end. The phases of the impellers on the two rotor shafts are 90° apart and matched with each other and matched with the inner wall of the cavity of the cylinder; the shaft ends of the two rotor shafts are respectively passed through the center hole of the end cover, and the rotor shaft center cooling holes are respectively provided along the axis; The heating jacket is covered on the outer circumference of the cylinder and is arranged in sections, and each section is respectively provided with a heat medium inlet and a heat medium outlet.

2. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The spiral rolling propulsion section impeller and the crushing propulsion section impeller are respectively provided with a positive spiral angle for propulsing the material toward the discharge end, and the spiral angle of the spiral rolling propulsion section impeller is greater than the spiral angle of the crushing propulsion section impeller.

3. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The phase angles of adjacent complete crushing section impellers are staggered, and the counter-rotating crushing discharge section impeller is provided with a reverse spiral angle for propelling the material toward the feed end.

4. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The top of each complete crushing section impeller is respectively provided with a sawtooth structure for cleaning the inner wall of the cylinder.

5. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: Each of the complete crushing stage impellers is symmetrically provided with a weight-reducing cavity.

6. The twin-screw kneader for polyoxymethylene production according to claim 5, characterized in that: A partition is provided in each of the lightening-type cavities to separate the lightening-type cavity into connected left and right cavities, the root of each of the partitions is respectively connected to the middle of the inner wall of the cavity close to the axis of the rotor shaft, the free end of each of the partitions points to the top direction of the impeller and leaves a flow gap between the inner wall of the other side of the lightening-type cavity; the bottom of the left and right cavities are respectively connected to the central cooling channel of the rotor shaft through radial cooling channels.

7. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The outer walls of the end covers are respectively provided with hot water flow channels, and the hot water flow channels surround the outer circumference of the center seat of the end cover.

8. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: A stuffing box is provided between the center seat of the end cover and the corresponding rotor shaft. The stuffing box is filled with multiple fillers. There are gas rings in the middle of the fillers. The gas rings are provided with radial holes communicating with the inner and outer ring grooves. The outer ring groove of the gas ring is upwardly connected to the nitrogen inlet, and the outer ring groove of the gas ring is downwardly connected to the nitrogen outlet.

9. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The shaft ends of the rotor shafts are supported in bearing seats respectively, and overflow collecting cavities are respectively arranged between the bearing seats and the corresponding end cover center seats, and overflow collecting ports are respectively arranged at the bottom of each overflow collecting cavity.

10. The twin-screw kneader for polyoxymethylene production according to claim 1, characterized in that: The central cooling water pipe is inserted into the central cooling channel of the rotor shaft from the discharge end and extends toward the feed end.

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