CN111844671A - Special process method for producing PBT plastic rod - Google Patents

Abstract

The invention provides a process method specially used for producing PBT plastic rods. The process includes: drying, removing moisture, plasticizing and extruding, using a specific temperature to heat a barrel in three zones, using a PBT barrel screw with a specific structure, and Specific extrusion speed; homogenization and splitting, the main mold is divided into four zones to further homogenize the melt; forming/setting, the melt flowing in a straight line is uniformly flowed into the guide plate through the main mold outlet, and the flow is divided through the guide plate, respectively. Entering the forming tube of the multi-rod forming die, the melt is formed in the compression forming zone within the forming tube; cutting. The invention overcomes the shrinkage deformation or cracking and scrapping caused by excessive internal stress of the bar, and the bar has better impact resistance, smooth surface and almost no welding seam.

Description

Process method dedicated to the production of PBT plastic rods

technical field

The invention relates to a process method specially used for producing PBT plastic rods.

Background technique

PBT (polybutyleneterephthalate, polybutylene phthalate) molding is to add granular materials from a hopper into the barrel of the extruder. The function is forward conveying and compacting, and is melted and plasticized under high temperature and high pressure conditions through the heating device and frictional preheating outside the barrel. Then, the continuously rotating screw pushes the molten material into the die, and the molten material extruded from the die is cooled and shaped into the desired PBT product.

The PBT rod forming process includes: feeding - drying - plasticizing extrusion - forming and shaping - cutting/stacking, etc.

At present, in the process of preparing PBT rods, the barrel is heated in three zones during plasticization and extrusion:

The temperature of the feeding section in the first zone is 260-270 °C;

The temperature of the melting and compression section of the second zone is 260-270 °C;

The temperature of the three-zone homogenization section is 270-280℃;

The temperature of the joint is 250-260℃;

The screw length-diameter ratio is 30:1, the compression ratio is 3, and the extrusion speed is 25-30r/min.

In the process of forming and setting, it enters the head body (the temperature of the head body is 250-260 ℃) under the action of screw rotation and shearing, and then enters the single-bar mold for direct molding. After molding, under the action of cooling water, the temperature continues to decrease. Solidification, crystallization, and shape are extruded from a single-rod die.

The subsequent heat treatment is divided into eleven sections:

The first stage: heating temperature 45 ℃, heating time 100 minutes;

The second stage: the constant temperature is 50°C, and the constant temperature time is thickness * 3 * 70 minutes;

The third stage: heating temperature 75 ℃, heating time 20 minutes;

The fourth stage: constant temperature of 90°C and constant temperature of 200 minutes;

The fifth stage: heating temperature 100 ℃, heating time 30 minutes;

Section 6: constant temperature of 130°C and constant temperature of 150 minutes;

The seventh stage: heating temperature 100 ℃, heating time 10 minutes;

Section 8: constant temperature of 60°C and constant temperature of 180 minutes;

The ninth paragraph: heating temperature 60 ℃, heating time 60 minutes;

Section 10: constant temperature of 60°C and constant temperature of 180 minutes;

The eleventh stage: the cooling temperature is 60°C, and the cooling time is 20 minutes.

The problems existing in the above process are: 1. The impact resistance of the bar is low; 2. The surface is not bright, but there are melted seams; 3. The internal stress of the bar is large; 4. It is easy to crack during processing.

SUMMARY OF THE INVENTION

In view of this, it is necessary to provide a special process method for producing PBT plastic rods to solve the above technical problems.

The present invention provides a kind of process method specially used for producing PBT plastic rod, and described process comprises the following steps:

Drying: drying the PBT plastic pellets by circulating hot air at 100°C so that the moisture content of the PBT plastic pellets is lower than 0.2%;

Plasticizing extrusion: The PBT plastic pellets are transformed into a uniform continuous melt with a certain fluidity through the action of the temperature of the barrel and the extrusion screw and extruded; temperature:

The temperature of the feeding section in the first zone is 240-250 °C;

The temperature of the melting and compression section of the second zone is 250-260 °C;

The temperature of the three-zone homogenization section is 250-270℃;

The temperature of the joint is 260-270℃;

The extrusion screw is a special equidistant gradient type PBT barrel screw, the screw length-diameter ratio is 25:1, the compression ratio is 3.3, and the extrusion speed is 30-35r/min;

Homogenization and shunting: under the rotary extrusion of the extrusion screw, the melt enters the main mold through the material nozzle, and the melt is further homogenized in the main mold, and the melt is converted from a spiral motion to a linear motion; The main mold is divided into four zones to set the constant temperature:

The temperature of the previous zone is 260-270℃;

The temperature of the first two zones is 250-260℃;

The temperature of the latter zone is 250-260℃;

The temperature of the second zone is 240-250℃;

Forming/Shaping: The melt flowing in a straight line is uniformly flowed into the deflector through the outlet of the main die, and is divided by the deflector, and then enters the forming tube of the multi-rod forming die respectively, and the melt is compressed in the forming tube. forming zone forming; wherein

The homogenization temperature of the guide plate is 250-260°C;

The shaping temperature of the shaping zone of the shaping tube is 140-160°C;

Cutting: Cut the formed bar into a predetermined length.

Further, after cutting, it also includes a post-heat treatment step:

The stacked PBT bars are heat treated and divided into eleven sections:

The heating temperature of the first stage is 40°C and the heating time: 120 minutes;

The second section of constant temperature is 70°C constant temperature time: thickness * 3 * 60 minutes;

The third stage heating temperature 70 ℃ heating time: 20 minutes;

The fourth section of constant temperature 100 ℃ constant temperature time: 180 minutes;

The fifth stage heating temperature 120 ℃ heating time: 20 minutes;

The sixth section constant temperature 100 ℃ constant temperature time: 180 minutes;

The seventh stage heating temperature 70 ℃ heating time: 20 minutes;

The eighth section constant temperature 40 ℃ constant temperature time: 180 minutes;

The ninth stage heating temperature 40 ℃ heating time: 40 minutes;

The tenth section constant temperature 40 ℃ constant temperature time: 180 minutes;

The eleventh section cooling temperature 40 ℃ cooling time: 150 minutes.

Further, after the forming/setting, it also includes:

Traction: The shaped bar is pulled by the traction mechanism, so that the melt forms a certain pressure in the compression molding area, so as to improve the compact structure of the bar.

Through the selection of the above process steps and the setting of process parameters, the invention overcomes the shrinkage deformation or cracking and scrapping caused by excessive internal stress of the bar, and the bar has better impact resistance, smooth surface and almost no welding seam.

Description of drawings

FIG. 1 is a schematic structural diagram of a production equipment according to an embodiment of the present invention.

Detailed ways

A process method specially used for producing PBT plastic rods provided by the present invention is produced by the special production equipment for PBT shown in FIG. 1 . As shown in Figure 1, the equipment includes a motor 1, a reduction box 2, a hopper 4, a dryer 3, a control cabinet 5, a special barrel screw 6 for PBT, a flange joint 7, a connecting square plate 8, a feeding port 9, The main mold 10, the mold frame 12, the deflector 11, the forming tube 13, the tractor 14, the cutting machine 15, and the oven, etc.

The motor 1, the reduction box 2, the hopper 4, the dryer 3, the control cabinet 5, the PBT-specific barrel screw 6, etc. can constitute the main part of the equipment. 10. The mold frame 12, the deflector 11, the heat insulation ring 14, the forming tube 13, the tractor 14, the cutting machine 15, and the oven can constitute the equipment the auxiliary part.

The motor 1 and the reduction box 2 constitute a rotating system. The motor 1 operates and drives the reduction box 2 through a belt drive, so that the PBT special barrel screw 6 maintains a certain shear rate. The special parameters of the PBT special barrel screw 6: the length-diameter ratio is 25:1, and the compression ratio is 3.3.

The control cabinet 5 can be provided with a control system, which can specifically include electrical instruments and actuators. Its main function is to control the main engine, so that the speed and power of its operation are normal, and to ensure the temperature, pressure, flow and power of the main engine and auxiliary machines. The quality of the products is realized, and the automatic control of the whole unit is realized.

The main mold 10 is set on the mold frame 12 . The melt enters the main mold 10 through the feed port 9 . The flow splitting is performed on both sides of the flow splitting block of the inflow channel, and the split melt enters the eight bell mouths of the deflector 11 and the forming tube 13 under a certain pressure, and is in the state of constant pressure and oil temperature. The forming tube 13 is internally formed and shaped.

The forming tube 13 includes a compression forming area and a setting area. The oil temperature machine is installed in the setting area of the forming tube 13, and through the continuous circulation of hot oil, the products in the setting area are shaped at a constant and balanced temperature and smoothly extruded from the mold.

The tractor 14 is mainly composed of a transmission device, a roller pressing device and a braking device. The main mold 13 and the tractor 14 are fixed together by connecting rods. The pneumatic control tractor 14 is connected with the square plate 8 up and down, and the reducer Drag the roller to make the product keep a certain pressure in the compression zone and move forward at a constant speed.

The cutting machine 15 is a bar cutting device, which is installed at the back. The extruded products pass through the cutting support surface of the cutting machine 15, and the bars are cut by the high-speed rotation of the saw blade to cut products of required lengths.

The oven is a sealed box structure, and different temperatures are set through a temperature controller, and the products are heat-treated in multiple stages at different times.

The process method specially used for producing PBT plastic rods provided by the present invention mainly includes the following steps: feeding, drying, plasticizing and extruding, homogenizing and shunting, forming/setting, pulling, cutting, stacking, and heat treatment.

The specific process steps of a specific embodiment of the present invention are emphatically described below.

1. Feeding: When feeding, it should be fed in time to ensure that the hopper 4 is not empty. Different materials can not be mixed, pay attention to distinguish the grades and types of materials, to prevent sundries and sundries from entering the hopper 4, causing the discharge port to be blocked.

2. Drying: Due to the high temperature absorption of PBT resin, it must be dried before extrusion to remove water, otherwise its water content exceeds a certain limit, and the water will volatilize into gas in the extruder barrel, causing The product contains pores, which reduces the strength of the product.

In this step, according to the characteristics of PBT plastic pellets, 100°C circulating hot air is used to dry the PBT plastic pellets, and the drying time is 2-4H, so that the moisture content in the product is less than 0.2%, and 100°C circulating hot air is used to dry the PBT plastic pellets. The plastic pellets are dried and the preheating effect of the PBT plastic pellets is achieved.

3. Plasticizing extrusion: The PBT plastic pellets are transformed into a uniform continuous melt with a certain fluidity and extruded through the action of the temperature of the barrel and the extrusion screw.

The extrusion screw is a special equidistant gradient type PBT barrel screw, the screw length-diameter ratio is 25:1, and the compression ratio is 3.3.

Wherein, the front and back are divided into three zones to heat the barrel, and the temperature of the feeding section in one zone is 240-250°C (for example, 241°C, 242°C, 243°C, 244°C, 245°C, 246°C, 247°C, 248°C) , 249°C); the temperature of the melting and compression section of the second zone is 250-260°C (for example, 251°C, 252°C, 253°C, 254°C, 255°C, 256°C, 257°C, 258°C, 259°C); The temperature of the melting section is 250-270°C (for example, 251°C, 252°C, 253°C, 254°C, 255°C, 256°C, 257°C, 258°C, 259°C, 260°C, 261°C, 262°C, 263°C, 264°C °C, 265 °C, 266 °C, 267 °C, 268 °C, 269 °C); joint temperature is 260-270 °C (eg 261 °C, 262 °C, 263 °C, 264 °C, 265 °C, 266 °C, 267 °C, 268 °C , 269°C); the extrusion speed is 30-35r/min (eg 31r/min, 32r/min, 33r/min, 34r/min).

By selecting specific screw aspect ratio, compression ratio, three-zone heating temperature, joint temperature and extrusion speed, the PBT plastic pellets can be more completely plasticized, melted and extruded. The settings of each parameter affect the Stress, porosity and mechanical properties of bar products.

4. Homogenization and diversion: Under the rotary extrusion of the extrusion screw, the melt enters the main mold through the material nozzle, and the melt is further homogenized in the main mold, and the melt is converted from a spiral motion to a linear motion.

The main mold is divided into four zones to set a constant temperature, and the temperature of the previous zone is 260-270°C (for example, 261°C, 262°C, 263°C, 264°C, 265°C, 266°C, 267°C, 268°C, 269°C); The temperature of the first two zones is 250-260°C (eg 251°C, 252°C, 253°C, 254°C, 255°C, 256°C, 257°C, 258°C, 259°C); the temperature of the latter zone is 250-260°C (eg 251°C, 252°C, 253°C, 254°C, 255°C, 256°C, 257°C, 258°C, 259°C); , 245°C, 246°C, 247°C, 248°C, 249°C).

5. Forming/Shaping: The melt flowing in a straight line is uniformly flowed into the deflector 11 through the outlet of the main mold 10, and is divided by the deflector 11, and then enters the forming tubes of the multi-rod forming mold respectively. The compression molding zone within the forming tube is formed. The homogenization temperature of the baffle is 250-260°C (for example, 251°C, 252°C, 253°C, 254°C, 255°C, 256°C, 257°C, 258°C, 259°C); The setting temperature of the zone is 140-160°C (for example, 141°C, 142°C, 143°C, 144°C, 145°C, 146°C, 147°C, 148°C, 149°C, 150°C, 151°C, 152°C, 153°C, 154°C, 155°C, 156°C, 157°C, 158°C, 159°C).

Combined with step 4, the main mold is kept at a constant temperature in four zones, the flow is divided through the baffle plate, and the specific baffle plate temperature and forming tube setting temperature are used to obtain the mutual matching of melt fluidity and shaping requirements, so as to ensure the bar product. It can be extruded smoothly, and the obtained bar has a high surface finish.

6. Traction: A brake seat is installed at the outlet of the main mold 10 of the heat preservation device. The brake seat is used to adjust the tightness of the brake strip to clamp the bar product, and the shaped bar is pulled by the tractor 14 to make the melt in The compression molding zone forms a certain pressure to improve the structural compactness of the bar and adjust the thickness of the bar to eccentricity.

7. Cutting: measure the length of 1000MM with a tape measure, start the cutting machine, and cut out the required length.

8. Stacking: Use suction cup hoist to lift the board and stack it neatly on a specific stacker; place stainless square steel between the rod layer and the rod layer, and the square steel between the layers looks up and down It's best to be in a straight line.

9. Post-heat treatment: heat treatment of the stacked PBT bars through the oven, which is divided into eleven sections:

The first section heating temperature 40 ℃ heating time: 120 minutes;

The second section constant temperature temperature 70 ℃ constant temperature time: thickness * 3 * 60 minutes;

The third stage heating temperature 70 ℃ heating time: 20 minutes;

The fourth section constant temperature 100 ℃ constant temperature time: 180 minutes;

The fifth section heating temperature 120 ℃ heating time: 20 minutes;

Section 6 Constant temperature 100℃ Constant temperature time: 180 minutes;

The seventh paragraph heating temperature 70 ℃ heating time: 20 minutes;

The eighth section constant temperature 40 ℃ constant temperature time: 180 minutes;

The ninth paragraph heating temperature 40 ℃ heating time: 40 minutes;

Section 10 Constant temperature 40℃ Constant temperature time: 180 minutes;

Section 11 Cooling temperature 40℃ Cooling time: 150 minutes.

Through the above specific post-heat treatment steps, the PBT bar products are heat treated at a specific temperature for a specific time and multiple stages, which can effectively eliminate the residual internal stress of the PBT bar products and ensure the quality and stability of the PBT bar products.

The PBT bar is tested, and the test items and results are as follows:

project standard unit Numerical value density ASTMD792 g/cm3 1.31 Tensile strength at yield ASTMD638 Mpa 80 Elongation at break ASTMD638 % 4 Bending strength ASTM790 Mpa 100 Flexural modulus ASTM790 Mpa 2400 Shore hardness ASTMD2240 Mpa 90 Impact strength ASTMD256 J/M 70 Thermal conductivity DIN52612-1 W/(K-M) 0.24

The above specific parameters are the parameters suitable for the production of PBT plastic rods finally determined by the inventor of the present invention after repeated a large number of specific experiments and taking several years to produce. These parameters are interdependent rather than isolated, and the selection of parameters is crucial It is important that these parameters are matched together to finally obtain the desired PBT plastic rod. Through the above specific process steps, the obtained PBT plastic rod overcomes the defects of shrinkage deformation or cracking and scrapping caused by excessive internal stress, and avoids serious problems. Waste defects, there are almost no pores and impurities in the product, which ensures the quality of the product, and the yield of qualified products is greatly improved.

Claims (3)

1. A special process method for producing PBT plastic rods is characterized by comprising the following steps:

drying: drying the PBT plastic granules by circulating hot air at 100 ℃ to ensure that the water content of the PBT plastic granules is lower than 0.2%;

plasticizing and extruding: the PBT plastic granules are converted into uniform continuous melt with certain fluidity by the action of the temperature of a machine barrel and an extrusion screw rod and are extruded; wherein, divide into three district and heat to the barrel around:

the temperature of the feeding section in the first area is 240 ℃ and 250 ℃;

the temperature of the second-zone melting compression section is 250-260 ℃;

The temperature of the three-zone homogenizing section is 250-270 ℃;

the joint temperature is 260 ℃ and 270 ℃;

the extrusion screw is a special PBT gun barrel screw with the equidistant gradual change type, the length-diameter ratio of the screw is 25: 1, the compression ratio is 3.3, and the extrusion speed is 30-35 r/min;

homogenizing and shunting: under the rotary extrusion of the extrusion screw, the melt enters a main die through a material nozzle, is further homogenized in the main die, and is converted into linear motion from spiral motion; the master mold is divided into four regions to set constant temperature:

the temperature of the former zone is 260 ℃ and 270 ℃;

the temperature of the first two areas is 250-260 ℃;

the temperature of the latter zone is 250-260 ℃;

the temperature of the second zone is 240 ℃ and 250 ℃;

molding/shaping: the melt flowing in a straight line uniformly flows into a guide plate through the outlet of the main die, is shunted by the guide plate and respectively enters a forming pipe of a multi-rod forming die, and the melt is formed in a compression forming area in the forming pipe; wherein

The homogenization temperature of the guide plate is 250-260 ℃;

the shaping temperature of the shaping area of the shaping pipe is 140-160 ℃;

cutting: and cutting the formed bar into a preset length.

2. The process method special for producing the PBT plastic rod according to claim 1, which further comprises a post heat treatment step after cutting:

Carrying out heat treatment on the stacked PBT bars, and dividing the heat treatment into eleven sections:

3. the process for producing PBT plastic rod according to claim 2, wherein after the shaping/fixing, further comprising:

traction: the shaped bar is drawn by the drawing mechanism, so that the melt is in the compression molding area to form certain pressure, and the structural compactness of the bar is improved.

Images