CN103419349A - Polymer melt shear vibration extrusion molding device - Google Patents

Abstract

The polymer melt shear vibration extrusion molding device provided by the present invention includes an extruder 13, an extruder head 1 connected to the extruder through a flange, a die 12, a setting die 14, a cooling water tank 15, The traction device 16 and the cutting device 17 are characterized in that they also include a crank connecting rod shearing vibration system 18 arranged above the extruder head 1 and a vibrating chamber 2 of the melt channel in the extruder head 1, wherein the crank connecting rod shears The cutting vibration system is composed of a crank-link mechanism and a reciprocating vibrating rod 3 . The reciprocating vibrating rod 3 is located in the through hole 9 opened on the extruder head 1 , and the through hole 9 communicates with the vibrating cavity 2 of the melt channel. The device can not only promote the orientation of polymer molecular chains, the generation of string crystal structure and the refinement of polymer crystal grains at the same time, improve the mechanical properties of products, but also reduce extrusion resistance and improve production efficiency.

Description

Polymer melt shear vibration extrusion molding device

technical field

The invention belongs to the technical field of polymer extrusion molding processing devices, in particular to a crank-connecting rod type polymer melt shear vibration extrusion molding device.

Background technique

Polymer melt vibration molding processing technology refers to the technology of applying a vibration field during the molding process to affect the rheological properties and condensed state structure of polymer melt. This technology can not only effectively promote the disentanglement of polymer molecules, reduce the viscosity of the polymer melt, improve the fluidity of the melt, thereby improving the melt breakage during extrusion and the degree of polymer extrusion swelling, and improving the extrusion process. It can improve the yield and quality, and at the same time, it can refine the grain size of the extrudate and improve the thermal stability.

At present, there have been some reports on the research on the processing instruments and devices of polymer melt vibration extrusion molding, such as Peng Xiangfang and Qu Jinping developed a capillary dynamic rheometer ("China Plastics", Polymer Dynamic Extrusion Rheology Behavioral Research, 2000, 14(1): 42). The capillary dynamic rheometer is based on the conventional capillary rheometer, through the vibration pressurization system to act on the pressure plunger to superimpose a sinusoidal vibration field on the melt in the barrel, the vibration frequency is 0-80Hz, the amplitude It is 0-0.3mm, but the rheometer is only a simple simulation of the processing process, not a real molding processing device. Another example is that Guo Shaoyun, Li Huilin, etc. reported an ultrasonic extrusion device for polymer melts ("Chemical Bulletin", Research on the Rheological Properties of Polyethylene Melt Extrusion under Ultrasonic Irradiation, 2001, 1: 40). The vibration field of the device is generated by an ultrasonic generator and an ultrasonic probe. The ultrasonic frequency can reach 20kHz, and the power can be continuously adjusted from 0 to 300W. The diameter of the ultrasonic probe is 15mm. The direction of ultrasonic vibration is parallel to the direction of melt flow. It is a variable-section capillary extrusion die, and is equipped with a high-temperature melt pressure sensor to continuously measure the extrusion die pressure. Compared with capillary dynamic rheometer, the vibration of this device belongs to ultra-high frequency vibration. In addition, Isayev et al. (A.I. Isayev, Rishi Kumar, Todd M.Lewis, Ultrasound assisted twin screw extrusion of polymer–nanocomposites containing carbon nanotubes, Polymer, 2009, 50: 250) also conducted ultrasonic vibration extrusion research and found that ultrasonic vibration is The rheological behavior of the polymer melt can be significantly improved. After the ultrasonic vibration field is applied, the extrusion pressure, extrusion swelling and melt viscosity of the polymer are all reduced, which can refine the crystallization and make the blend Enhanced compatibility. However, ultrasonic vibration is not ideal in improving the mechanical properties of products, and even in some cases, the mechanical properties of long-term ultrasonic treatment will decline (Fridman M L Peshkovsky S L Vinogradov G V. The rheology of thermoplastics under conditions of spiral flow and vibrations on extrusion. Polym. Eng. Sci. 1981 21( 12): 755.).

Contents of the invention

The purpose of the present invention is to address the deficiencies of the prior art, to provide a polymer melt shear vibration extrusion molding device, which can not only avoid the mechanical degradation of the product caused by too high frequency, but also promote the orientation of polymer molecular chains, The generation of string crystal structure and the refinement of polymer grains can improve the mechanical properties of products.

The polymer melt shear vibration extrusion molding device provided by the present invention includes an extruder, an extruder head connected to the extruder through a flange, a die, a setting die, a cooling water tank, a traction device and a cutting device , which is characterized in that it also includes a crank connecting rod shear vibration system arranged above the extruder head and a melt channel vibration chamber in the extruder head, wherein the crank connecting rod shear vibration system is composed of a crank connecting rod mechanism and The reciprocating vibrating rod is composed of a reciprocating vibrating rod located in a through hole opened on the extruder head, and the through hole is connected with the vibrating cavity of the melt channel.

When the above device is working, when the polymer melt enters the vibrating chamber of the melt channel, the reciprocating vibrating rod will continuously reciprocate up and down in the through hole under the drive of the crank linkage mechanism, and the rod head will not move. Squeeze up and down the polymer melt in the vibrating cavity of the melt flow channel without stopping, so that the melt in the melting cavity is subjected to strong shear force, which promotes the orientation of polymer molecular chains, the generation of string crystal structure and the polymerization grain refinement.

The crank connecting rod mechanism in the above device is characterized in that the crank connecting rod mechanism is composed of a continuously variable speed motor, a shaft coupling, a crank, a connecting rod and a piston, the continuously variable speed motor is connected with the crank through a shaft coupling, and one end of the connecting rod is It is connected to the crank through the connecting rod cover, and the other end is connected to the piston.

In order to make the polymer melt flowing through the vibrating chamber of the melt flow path be subject to a stronger shearing action, there are 2 to 6 reciprocating vibrating rods in the above device, and each reciprocating vibrating rod is respectively connected to the corresponding one in the crank connecting rod mechanism. The piston is connected, and its end passes through the through hole on the extruder head and extends into the melt vibration cavity in the extruder head. In addition, the distance between the reciprocating vibrating rod and the die is as short as possible, so as to avoid too much recovery of the orientation and disentanglement of polymer molecular chains caused by vibration shearing in this distance.

In the above device, a one-way valve is set between the melt channel of the extruder and the melt vibration cavity in the extruder head, and the one-way valve is located in the one-way valve sleeve that is interference fit with the extruder head. middle. The setting of the one-way valve can prevent the vibration of the head part from affecting the flow of the melt in the screw part of the single-screw extruder, so as to ensure that the flow state of the polymer melt in it is more stable.

In the above-mentioned device, powder metallurgy bearings are installed in the through holes on the upper part of the extruder head. The powder metallurgy bearings form an interference fit with the through holes and a gap fit with the reciprocating vibrating rod to reduce the friction between the reciprocating vibrating rod and the through hole. .

The die and extruder head in the above device can be detachably connected to ensure that various sizes of dies are designed and manufactured, including capillary dies used to study the rheological properties of polymers, and to study the mechanical properties of products in both vertical and horizontal directions. The thick and thin sheet dies can be easily installed on it, so as to facilitate the research on the rheological properties of polymers and the structural properties of products. The length of the die should be as short as possible, and the mold should be shaped as soon as possible after the die is exported, so as to facilitate the retention of the polymer melt orientation structure.

For the above polymer melt shear vibration extrusion molding device, the calibrating mold used is a vacuum calibrating mold or a compressed air calibrating mold or other sliding calibrating molds.

In the above polymer melt shear vibration extrusion molding device, the extruder head is covered with a heating ring, and the head is provided with a pressure sensor hole, a thermometer and a thermocouple socket to measure the pressure and temperature of the head.

Compared with the prior art, the present invention has the following beneficial effects:

1. Since the extrusion molding device provided by the present invention adds a crank connecting rod shear vibration system, the reciprocating vibration rod reciprocates in the through hole of the extruder head, which can make the melt in the melting cavity during the extrusion process Under the strong shear force, it is not only beneficial to the orientation of polymer molecular chains and the generation of string crystal structure, but also conducive to the uniform dispersion and orientation of fillers in polymer composite materials, changing the rheological properties and The condensed state structure can improve the molding and processing performance of polymer melt, improve the mechanical properties of products, and at the same time reduce extrusion resistance and improve production efficiency.

2. In the crank connecting rod shear vibration system of the extrusion molding device provided by the present invention, the vibration frequency and amplitude of the reciprocating vibration rod can be adjusted and controlled by adjusting the rotation speed of the motor, thus avoiding the excessive frequency causing the product Mechanical degradation, and polymer products with different orientation degrees and string crystal structures can be obtained through adjustment to meet different use requirements.

3. Since a check valve is installed between the extruder and the extruder head of the polymer melt shear vibration extrusion molding device provided by the present invention, not only the vibration of the head part will not affect the single-screw extruder The flow of the melt in the screw part makes the flow state more stable, and the polymer melt will not flow back due to the vibration extrusion of the reciprocating vibrating rod, which will affect the extrusion efficiency.

4. Since the extruder head and the die of the extrusion molding device provided by the present invention are connected in a detachable manner, and the shearing direction of the melt is parallel to the flow direction of the melt, it is not only convenient to replace the die, but also vibration The effect is good, and the vibration extrusion technology can be applied to extruded products of different sizes and types only by changing the die.

5. Since the reciprocating motion of the reciprocating vibrating rod driven by the crank-link mechanism in the extrusion molding device provided by the present invention generates little vibration noise, the device operates smoothly and has little noise pollution.

6. The extrusion molding device provided by the present invention can not only be used as a new device for studying the influence of low-frequency shear vibration on the rheological behavior of polymer melts in the actual processing process, but also can be used as a highly practical processing of high polymer products equipment.

Description of drawings

Fig. 1 is a structural schematic diagram of a polymer melt shear vibration extrusion molding device provided by the present invention.

Fig. 2 is a structural schematic diagram of the crank connecting rod shear vibration system in the polymer melt shear vibration extrusion molding device provided by the present invention.

Figure 3 is the variation curve of apparent viscosity of HDPE 5000S melt with vibration frequency at different screw speeds.

It can be seen from Figure 3 that the apparent viscosity of the HDPE 5000S melt decreases significantly after shear vibration, and the lower the screw speed, the greater the impact of the vibration field on the apparent viscosity of the melt. When the rotational speed is 4r/min, the apparent viscosity decreases from 2994.1Pa.S to 1963.4Pa.S, with a maximum decrease of 34.42%.

Figure 4 is the variation curve of apparent viscosity of HDPE 5000S melt with vibration frequency at different die temperatures.

It can be seen from Figure 4 that when the die temperature is 180 °C, 190 °C and 200 °C, the maximum decrease in apparent viscosity of HDPE5000S melt is 19.83%, 15.86% and 16.85%, respectively.

Fig. 5 is the variation curve of apparent viscosity of PPF401 melt with vibration frequency at different screw speeds.

It can be seen from Figure 5 that the apparent viscosity of the PPF401 melt decreases significantly after shear vibration. As the vibration frequency increases, the apparent viscosity decreases rapidly at first, and after 1.0Hz, the decreasing speed tends to be gentle. The lower the screw speed, the greater the impact of the vibration field on the apparent viscosity of the melt. When the speed is 4r/min, the apparent viscosity decreases from 2179.5Pa.S to 1459.0Pa.S, with a maximum drop of 33.06%.

Figure 6 is the variation curve of apparent viscosity of PPF401 melt with frequency at different die temperatures.

It can be seen from Figure 6 that when the die temperature is 180 °C, 190 °C and 200 °C, the maximum decrease in apparent viscosity of PPF401 melt is 22.96%, 20.46% and 24.37%, respectively.

From Figures 3 to 6, it can be seen that the apparent viscosity change of the polymer melt in the shear vibration field is related to the vibration frequency, the die temperature and the screw speed of the extruder. After the shear vibration is applied, the melt surface of HDPE and PP The apparent viscosity is significantly reduced, which is beneficial to the disentanglement and orientation of molecular chains and the uniform dispersion of fillers in polymer composites. In addition, the apparent viscosity is reduced, the melt flow resistance is reduced, and the extrusion pressure Reduced; when the melt reaches the same apparent viscosity, the required extrusion temperature is also reduced.

Fig. 7 is the change curve of tensile strength before and after vibration extrusion of PP T30S through the polymer melt shear vibration extrusion molding device of the present invention.

Fig. 8 is the change curve of elongation at break before and after vibration extrusion of PP T30S through the polymer melt shear vibration extrusion molding device of the present invention.

It can be seen from Figure 7 and Figure 8 that the maximum elongation at break of the PP T30S sample after shear vibration extrusion is 837%, which is 51.6% higher than that of the conventional PP T30S sample (552%). The strength increased from 39.17MPa of the conventional sample to 41.53MPa, and it can be seen that the mechanical properties, especially the elongation at break, have been significantly improved.

Fig. 9 is a polarizing microscope photo of the PP T30S sample before and after vibration extrusion by the polymer melt shear vibration extrusion molding device of the present invention, wherein a is a conventional sample without shear vibration, and b is the vibration frequency F=2.0 Hz is the PP T30S sample formed by shear vibration extrusion molding, and c is the PP T30S sample formed by shear vibration extrusion molding when the vibration frequency F=2.5Hz.

It can be seen from Figure 9 that the grain size of the sample after vibration becomes significantly smaller, which shows that extrusion molding under the shear vibration field is conducive to the refinement of polymer grains, which is conducive to the improvement of the elongation at break of the sample .

Fig. 10 is a comparison curve of DSC between conventional extrusion of PLA and vibratory extrusion through the polymer melt shear vibration extrusion molding device of the present invention at a rotational speed of 2 rpm.

It can be seen from Figure 10 that when PLA (polylactic acid) is extruded at a vibration frequency of 2.0Hz and a screw speed of 2rpm, the cold crystallization peak disappears, and the crystallinity of the vibrating sample is significantly improved, from 2.69% of the conventional sample to the vibrating sample. 38.03%, which shows that shear vibration can accelerate the crystallization of polylactic acid, so that the polylactic acid material exhibits good mechanical properties, thermal properties and low shrinkage properties, and the heat distortion temperature is increased.

Detailed ways

Examples are given below with reference to the accompanying drawings and the polymer melt shear vibration extrusion molding device provided by the present invention is described in detail. It is necessary to point out that the following examples are only used to further illustrate the present invention, and can not be interpreted as limiting the protection scope of the present invention, some non-essential improvements and improvements made by those skilled in the art based on the content of the present invention above. Adjustment still belongs to the protection scope of the present invention.

Example

As shown in Figures 1 and 2, the polymer melt shear vibration extrusion molding device provided in this embodiment includes an extruder 13, an extruder head 1 connected to the extruder through a flange, and a die 12 , calibrating die 14, cooling water tank 15, traction device 16, cutting device 17 and the melt channel vibration cavity 2 in the crank connecting rod shear vibration system 18 that is arranged on extruder head 1 top and extruder head 1, Wherein the crank connecting rod shear vibration system is composed of a crank connecting rod mechanism and a reciprocating vibrating rod 3 .

The crank-link mechanism is composed of a continuously variable speed motor 4, a shaft coupling 5, a crank 6, a connecting rod 7 and a piston 8. The continuously variable speed motor 4 is connected with the crank 6 through a shaft coupling 5, and one end of the connecting rod 7 is connected through a connecting rod 7. The rod cover and the bolt are connected with the crank 6, the connecting rod bush is placed on the contact surface between the connecting rod 7 and the crank 6 and the connecting rod cover and the crank 6, and the other end is connected with the piston 8 through the piston pin.

There are two reciprocating vibrating rods 3 in this embodiment, and each reciprocating vibrating rod 3 is respectively connected with the corresponding piston 8 in the crank linkage mechanism, and its end passes through the through hole 9 on the extruder head to extend into the extruder. Inside the melt vibration cavity 2 in the machine head. Powder metallurgy bearings 20 are arranged in the through holes 9 on the upper part of the extruder head, and the powder metallurgy bearings 20 form an interference fit with the through holes 9 and form a clearance fit with the reciprocating vibrating rod 3 . In this embodiment, the through hole 9 on the extruder head is vertically connected with the vibrating cavity 2 of the melt channel, and the cross-sectional shape of the vibrating cavity 2 of the melt channel is circular.

A one-way valve 10 is arranged between the melt channel 19 of the extruder and the melt vibration cavity 2 in the extruder head, and the one-way valve 10 is located in the one-way valve sleeve which is an interference fit with the extruder head. In barrel 11.

The die 12 before the extruder head is made up of an upper die and a lower die, and is fixedly connected with the extruder head with screws.

During the polymer melt extrusion molding process, the molten polymer conveyed by the screw in the barrel of the extruder passes through the grid plate and enters the check valve in the check valve sleeve which is an interference fit with the extruder head. It flows into the vibrating chamber of the melt channel in the extruder head. The infinitely variable speed motor drives the crank to rotate, and the rotation of the crank drives the connecting rod to make linear reciprocating motion, and the connecting rod takes the reciprocating vibration rod connected to the piston to make linear reciprocating motion in the melt vibration chamber of the extruder head. The reciprocating motion of the vibrating rod causes the polymer melt in the flow channel of the extruder to be subjected to strong shear force, which makes the polymer molecular chain orientate or the filler in the polymer composite material is uniformly dispersed and oriented, followed by shearing The vibrating polymer melt flows into the slit die composed of the upper die and the lower die, and then flows out from the slit die. After shaping, cooling, pulling and cutting, it becomes a polymer sheet.

In order to investigate the processing effect of the polymer melt shear vibration extrusion molding device provided by the present invention, the present invention uses polymer systems such as HDPE5000S, HDPE5000S/CF, PLA (polylactic acid), PLA/OMMT (organic montmorillonite) The device is extruded at different screw speeds, different die temperatures and different vibration frequencies, and then the change of the apparent viscosity of the melt with the vibration frequency, tensile strength before and after extrusion, elongation at break, Changes in grain size and crystallinity, the results are shown in Figure 3-10. It is found that the PLA/OMMT (5%) system has the most significant improvement in mechanical properties. The data of the mechanical properties of this system are shown in the table below. From the table below, it can be known that the tensile strength and elongation at break of the sample after shear vibration extrusion by the device of the present invention Both elongation and elastic modulus are improved.

surface

Vibration frequency (Hz) Tensile strength (MPa) Elongation at break (%) Elastic modulus (MPa) 0 69.47 15.02 1503.34 0.7 77.02 20.28 1788.82 1.0 75.62 20.14 1752.26 1.5 76.66 20.27 1850.83 2.0 78.54 17.39 1897.51

Claims (8)

1. A polymer melt shear vibration extrusion molding device, including an extruder (13), an extruder head (1) connected to the extruder through a flange, a die (12), a setting die (14), cooling water tank (15), traction device (16) and cutting device (17), characterized in that it also includes a crank connecting rod shear vibration system (18) and extrusion The vibrating cavity (2) of the melt channel in the discharge head (1), in which the crank connecting rod shear vibration system is composed of a crank connecting rod mechanism and a reciprocating vibrating rod (3), and the reciprocating vibrating rod (3) is located in the extrusion In the through hole (9) opened on the machine head (1), the through hole (9) is connected with the vibrating cavity (2) of the melt channel. 2. The polymer melt shear vibration extrusion molding device according to claim 1, characterized in that the crank linkage mechanism is composed of a continuously variable speed motor (4), a coupling (5), a crank (6), and a Rod (7) and piston (8), the continuously variable speed motor (4) is connected to the crank (6) through the coupling (5), one end of the connecting rod (7) is connected to the crank (6) through the connecting rod cover, and the other One end is connected with the piston (8). 3. The polymer melt shear vibration extrusion molding device according to claim 1 or 2, characterized in that there are 2 to 6 reciprocating vibrating rods (3), and each reciprocating vibrating rod (3) is connected to the crank connecting rod The corresponding piston (8) in the mechanism is connected, and its end passes through the through hole (9) on the extruder head and extends into the melt channel vibration chamber (2) in the extruder head. 4. The polymer melt shear vibration extrusion molding device according to claim 1 or 2, characterized in that the melt flow path (19) of the extruder and the melt flow path vibration cavity ( 2) There is a one-way valve (10) between them, and the one-way valve (10) is located in the one-way valve sleeve (11) which is in interference fit with the extruder head. 5. The polymer melt shear vibration extrusion molding device according to claim 3, characterized in that the melt channel (19) of the extruder and the melt channel vibration cavity (2) in the extruder head A one-way valve (10) is arranged between them, and the one-way valve (10) is located in a one-way valve sleeve (11) which is in interference fit with the extruder head. 6. The polymer melt shear vibration extrusion molding device according to claim 1 or 2, characterized in that powder metallurgy bearings (20) are arranged in the through holes (9) on the upper part of the extruder head, and the powder metallurgy The bearing (20) forms an interference fit with the through hole (9), and forms a clearance fit with the reciprocating vibrating rod (3). 7. The polymer melt shear vibration extrusion molding device according to claim 3, characterized in that powder metallurgy bearings (20) are arranged in the through holes (9) on the upper part of the extruder head, and the powder metallurgy bearings ( 20) It is an interference fit with the through hole (9), and it is a clearance fit with the reciprocating vibrating rod (3). 8. The polymer melt shear vibration extrusion molding device according to claim 5, characterized in that powder metallurgy bearings (20) are arranged in the through holes (9) on the upper part of the extruder head, and the powder metallurgy bearings ( 20) It is an interference fit with the through hole (9), and it is a clearance fit with the reciprocating vibrating rod (3).

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