CN111716672A

CN111716672A - Special process method for producing PBT plastic plate

Info

Publication number: CN111716672A
Application number: CN202010636391.1A
Authority: CN
Inventors: 刘福华
Original assignee: Dongguan Enxinlong Special Material Co ltd
Current assignee: Dongguan Enxinlong Special Material Co ltd
Priority date: 2020-07-04
Filing date: 2020-07-04
Publication date: 2020-09-29

Abstract

The invention provides a special process method for producing a PBT plastic plate, which comprises the following steps: feeding; drying and removing water: plasticizing and extruding, namely heating a barrel in three zones at a specific temperature, and adopting a PBT barrel screw with a specific structure and a specific extrusion speed; molding/shaping, namely dividing the compression molding area into four areas for constant temperature, continuously cooling the molten material in the shaping area, and finally solidifying, crystallizing and shaping to be extruded; heat preservation heat treatment, three-stage heat treatment; and (5) cutting the plate. The invention can reduce the internal stress of the product, avoid shrinkage or cracking and scrap, and the product has few air hole impurities inside.

Description

Special process method for producing PBT plastic plate

Technical Field

The invention relates to a special process method for producing a PBT plastic plate.

Background

PBT (polybutylene terephthalate) molding is that granular materials are added into a machine barrel of an extruder from a hopper, the materials are conveyed forward and compacted under the extrusion pushing action of the rotation of a screw rod through the friction action of the inner wall of the machine barrel and the surface of the screw rod, and are melted and plasticized under the conditions of high temperature and high pressure through a heating device and friction preheating outside the machine barrel. Then, the continuously rotating screw pushes the molten material into a head die, and the molten material extruded from the head die is cooled and shaped into the required PBT product.

The PBT plate forming process comprises the following steps: feeding, drying, plasticizing extrusion, molding and shaping, cutting into plates, chamfering and the like, wherein in the plasticizing extrusion process, a machine barrel needs to be heated, and in the molding and shaping process, the constant temperature needs to be kept.

At present, in the process of preparing the PBT plate, the plasticizing extrusion is divided into three zones to heat a machine barrel:

the temperature of the feeding section in the first area is 260 ℃ and 270 ℃;

the temperature of the second-zone melting compression section is 260-270 ℃;

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

the joint temperature is 250 ℃ and 260 ℃;

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

And (3) keeping constant temperature in four zones during compression molding:

temperature of the former zone: 270 ℃ and 280 ℃;

temperature in the first two zones: 275 ℃ and 290 ℃;

temperature in the latter zone: 275 ℃ and 290 ℃;

temperature in the second zone: 275 ℃ to 290 ℃.

The heat treatment is divided into eleven sections:

a first stage: the heating temperature is 45 ℃ and the heating time is 100 minutes;

and a second stage: the constant temperature is 50 ℃ and the constant temperature time is 3 x 70 minutes in thickness;

a third stage: the heating temperature is 75 ℃, and the heating time is 20 minutes;

a fourth stage: keeping the temperature at 90 ℃ for 200 minutes;

a fifth stage: the heating temperature is 100 ℃, and the heating time is 30 minutes;

a sixth stage: keeping the temperature at 130 ℃ for 150 minutes;

a seventh stage: the heating temperature is 100 ℃, and the heating time is 10 minutes;

an eighth stage: keeping the temperature at 60 ℃ for 180 minutes;

a ninth stage: the heating temperature is 60 ℃, and the heating time is 60 minutes;

a tenth stage: keeping the temperature at 60 ℃ for 180 minutes;

an eleventh stage: the temperature is reduced to 60 ℃ for 20 minutes.

The PBT plate prepared by the process is easy to crack, deform, have pores, have white cores and white lines, so that the mechanical property does not reach the standard, and the like, which is a very serious problem and can influence the use or even cannot use.

Disclosure of Invention

In view of the above, there is a need to provide a special process for producing PBT plastic plate, which can reduce the internal stress of the product, avoid shrinkage or cracking and scrap, and have few pore impurities inside the product.

The invention provides a special process method for producing a PBT plastic plate, which comprises the following steps:

feeding;

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 230 ℃ and 250 ℃;

the temperature of the second-zone melting compression section is 240-250 ℃;

the temperature of the three-zone homogenizing section is 240-250 ℃;

the joint temperature is 245-250 ℃;

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 20-30 r/min;

molding/shaping: under the rotary extrusion of the extrusion screw, the fluid uniform melt enters a machine head through a porous plate, is molded and shaped according to a parison with a certain shape and is extruded out of a die; wherein

The compression molding area of the die is divided into four areas for constant temperature:

the temperature of the former zone is 230-260 ℃;

the temperature of the first two areas is 240 ℃ and 260 ℃;

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

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

the shaping area of the mould continuously cools the melting material, and finally the melting material is solidified, crystallized and shaped and is extruded out of the mould;

heat preservation and heat treatment: carrying out three-stage heat treatment on the product, wherein the first zone is 140 ℃, the second zone is 130 ℃, and the third zone is 120 ℃;

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

Further, the method also comprises a post heat treatment step after the plate cutting:

carrying out heat treatment on the stacked PBT plates, and dividing the heat treatment into eleven sections:

further, after the forming/shaping, the method further comprises the following steps:

braking: the plate forms certain resistance through braking, so that the thickness and the eccentricity of the plate are adjusted.

Further, after the heat-preserving heat treatment, the method further comprises the following steps:

traction: and drawing the plate subjected to heat preservation and heat treatment by using a drawing mechanism so as to enable the melt to form certain pressure in the compression molding area, so that the structural compactness of the plate is improved, and the thickness of the plate is adjusted to achieve eccentricity.

By selecting the process steps and setting the process parameters, the invention overcomes the shrinkage deformation or cracking scrap caused by overlarge internal stress of the plate, avoids the defect of serious waste, ensures the quality of the product because the product has few air-hole impurities inside, and greatly improves the yield of qualified products.

Drawings

Fig. 1 is a schematic structural view of a production apparatus according to an embodiment of the present invention.

Detailed Description

The special process method for producing the PBT plastic plate provided by the invention is produced by the special PBT production equipment shown in FIG. 1. As shown in figure 1, the equipment comprises a motor 1, a reduction gearbox 2, a hopper 3, a dryer 4, a control cabinet 5, a PBT special barrel screw 6, a flange joint 8, a mould 9, a mould frame 12, a middle plate 10, a brake seat 11, a heat preservation device 13, a tractor 14, a cutter 15, an oven and the like.

The motor 1, the reduction gearbox 2, the hopper 3, the dryer 4, the control cabinet 5, the PBT special gun barrel screw 6 and the like can form a main machine part of the equipment, and the mould 9, the middle plate 10, the brake seat 11, the mould frame 12, the heat preservation device 13, the tractor 14, the cutting machine 15, the oven and the like can form an auxiliary machine part of the equipment.

The motor 1 and the reduction gearbox 2 form a rotating system, the motor 1 runs and drives the reduction gearbox 2 through belt transmission, and therefore the special barrel screw 6 for the PBT keeps a certain shearing rate. The special parameters of the PBT special gun barrel screw 6 are as follows: the length-diameter ratio is 25: 1, compression ratio of 3.3.

The machine cabinet can be internally provided with a control system which specifically comprises an electrical instrument and an actuating mechanism and is mainly used for controlling the main machine, so that the rotating speed and the power of the operation of the main machine are normal, the temperature, the pressure, the flow and the quality of products of the main machine and the auxiliary machine are ensured, and the automatic control of the whole machine set is realized.

The die 9 comprises an upper die, a middle plate 10 and a lower die. In this embodiment, the upper and lower dies are 400 × 800 × 100 steel plates, and a molding cavity having a fan-shaped lower cross section and an angle of 135 degrees is provided in the middle. The first third of mould 9 is the compression molding district, adopts the heating tube to heat, control mould 9 temperature. Two thirds of the back of the die 9 is a shaping area, and is connected with circulating cooling water to cool the die 9, so that the product is shaped and extruded out of the die 9. The mould 9 and the host are connected together through the flange joint 8, and the molten material enters the mould 9 through the flange joint 8.

The water temperature machine for providing the circulating cooling water is arranged at the upper and lower die shaping sections, and the shaping water temperature is controlled by circulating hot water, so that the products in the shaping area are shaped at a constant and balanced temperature and are smoothly extruded out of the die 9.

The heat preservation device 13 mainly comprises an upper steel plate, a lower steel plate and a support thereof, the upper steel plate and the lower steel plate are heated by using a heating plate, a product passes through the upper steel plate and the lower steel plate, the product is subjected to heat treatment at a certain temperature, partial internal stress of the plate is eliminated, the flatness of the product is ensured, and the warping phenomenon is greatly improved.

The tractor 14 mainly comprises a transmission device, a roller pressing device and a brake device, is arranged behind the heat preservation device 13, fixes the die 9 and the tractor 14 together through a connecting rod, pneumatically controls the tractor 14 to press plates by 4 pairs of rollers up and down, and a speed reducer drags the rollers to enable products to keep a certain pressure in a compression area and move forward at a constant speed.

The cutting machine 15 is a plate cutting device and is arranged behind the outlet of the die 9, the extruded product passes through the plate cutting supporting surface of the plate cutting machine, and the plate is cut into products with required lengths through the high-speed rotation of the saw blade.

The oven is of a sealed box body structure, different temperatures are set through a temperature controller, heat treatment is carried out on the product at different time and in different sections, residual internal stress of the product is eliminated, and product quality and stability are guaranteed.

The special process method for producing the PBT plastic plate mainly comprises the following steps: feeding, drying, plasticizing and extruding, molding/shaping, braking, heat preservation and heat treatment, traction, plate cutting, stacking, heat treatment and edge chamfering.

The following focuses on the specific process steps of one embodiment of the present invention.

1. Feeding: when feeding, the materials should be fed in time to ensure that the hopper 3 is not empty. Different materials can not be used in a mixed mode, the grade of the clear materials and the type of the materials are noticed, and sundries are prevented from entering the hopper 3 to cause the blockage of the feed opening.

2. Drying: because the PBT resin has larger temperature absorption, the PBT resin needs to be dried before extrusion molding to remove moisture, otherwise, the moisture content exceeds a certain limit, and the moisture can be volatilized into gas in an extruder barrel, so that air holes are contained in the product, and the strength of the product is reduced.

In the step, aiming at the characteristics of the PBT plastic granules, the PBT plastic granules are dried by 100 ℃ circulating hot air for 2-4H, so that the moisture content in the product is lower than 0.2%, and the preheating effect of the PBT plastic granules is realized while the PBT plastic granules are dried by 100 ℃ circulating hot air.

3. Plasticizing and extruding: the PBT plastic granules are converted into a uniform continuous melt with certain fluidity by the action of the temperature of a cylinder and an extrusion screw and are extruded.

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, compression ratio of 3.3.

Wherein the barrel is heated in three zones, the temperature of the feeding section in one zone is 230-, 25r/min, 26r/min, 27r/min, 28r/min, 29 r/min).

By selecting a specific screw length-diameter ratio, a specific compression ratio, a specific three-zone heating temperature, a specific joint temperature and a specific extrusion speed, PBT plastic granules can be more completely plasticized, melted and extruded to form a product, and the setting of each parameter influences the stress, air holes, mechanical properties and the like of a plate product.

4. Molding/shaping: under the rotary extrusion of the extrusion screw, the fluid uniform melt enters the machine head through the porous plate, is molded and shaped according to a parison with a certain shape, and is extruded out of the die 9.

The die 9 is divided into a compression molding area and a shaping area, the first third of the die 9 is the compression molding area, and the second third of the back of the die 9 is the shaping area.

The compression molding zone of the mold 9 is thermostated in four zones, the temperature of the former zone is 230-260 ℃ (such as 231 ℃, 232 ℃, 234 ℃, 235 ℃, 239 ℃, 240 ℃, 243 ℃, 244 ℃, 247 ℃, 248 ℃, 253 ℃, 255 ℃, 258 ℃ and 259 ℃), the temperature of the former zone is 240-260 ℃ (such as 241 ℃, 242 ℃, 243 ℃, 244 ℃, 245 ℃, 246 ℃, 247 ℃, 248 ℃, 249 ℃, 250 ℃, 251 ℃, 252 ℃, 253 ℃, 254 ℃, 255 ℃, 256 ℃, 257 ℃, 258 ℃ and 259 ℃), the temperature of the latter zone is 250-260 ℃ (such as 251 ℃, 252 ℃, 253 ℃, 254 ℃, 255 ℃, 256 ℃, 257 ℃, 258 ℃ and 259 ℃), and the temperature of the latter zone is 250-260 ℃ (such as 251 ℃, 252 ℃, 253 ℃, 254 ℃, 255 ℃, 256 ℃, 257 ℃, 258 ℃, 259 ℃).

The shaping area of the mould 9 continuously cools the melting material and finally solidifies, crystallizes and shapes the melting material and is extruded out of the mould 9. The two ends of the shaping area of the mould 9 are both connected with cooling circulating water, and the temperature of the melting materials is continuously reduced through the continuous circulation of cold water.

5. Braking: the plate is clamped to form certain resistance by adjusting the tightness of the brake strip of the brake seat 11, and the thickness and the eccentricity of the plate can be adjusted by adjusting the tightness of the brake.

6. Heat preservation and heat treatment: the product was subjected to three stages of heat treatment, the first zone being 140 ℃, the second zone being 130 ℃ and the third zone being 120 ℃.

7. Traction: the outlet position of the heat preservation device 13 is provided with another brake seat 11, the brake seat 11 is used for adjusting the tightness of the brake strip to clamp the plate product, and the traction mechanism 14 is used for drawing the heat-preserved and heat-treated plate to enable the melt to form certain pressure in the compression molding area, so that the structural compactness of the plate is improved, and the thickness of the plate is adjusted to achieve eccentricity.

8. Cutting a plate: 1000MM length is measured by a measuring tape, and a plate cutting machine is started to cut out the required length.

9. Stacking: hoisting the plate by using a sucker to hoist the block, and neatly stacking the plate on a specific stacking frame; three stainless square steels are placed between the plates, the square steels between layers appearing preferably on top and bottom in a straight line.

10. And (3) post heat treatment: carrying out heat treatment on the stacked PBT plate by an oven, wherein the heat treatment is divided into eleven sections:

through the specific later-stage heat treatment steps, the PBT plate product is subjected to specific-temperature heat treatment in specific time and multiple sections, so that the residual internal stress of the PBT plate product can be effectively eliminated, and the quality and the stability of the PBT plate are ensured.

11. Chamfering: each edge of the plate is chamfered, so that the product is more attractive, and fingers can be prevented from being cut by the diamond edge of the plate in the carrying process.

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

item	Standard of merit	Unit of	Numerical value
				Density of	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	D	90
				Impact strength	ASTMD256	J/M	70
Thermal conductivity	DIN52612-1	W/(K-M)	0.24

The specific parameters are finally determined by the inventor of the invention through repeated large amount of specific experiments and time-consuming years and are suitable for producing the PBT plastic plate, the parameters are interdependent but not isolated, the selection of the parameters is very important, the parameters are matched together to finally obtain the expected PBT plastic plate, through the steps of the specific process method, the prepared PBT plastic plate overcomes the defects of shrinkage deformation or cracking scrapping caused by overlarge internal stress, the defect of serious waste is avoided, few air holes are generated in the product, the quality of the product is ensured, and the yield of qualified products is greatly improved.

Claims

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