CN109049616B - Production method of polypropylene composite material - Google Patents
Production method of polypropylene composite material Download PDFInfo
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- CN109049616B CN109049616B CN201811016460.8A CN201811016460A CN109049616B CN 109049616 B CN109049616 B CN 109049616B CN 201811016460 A CN201811016460 A CN 201811016460A CN 109049616 B CN109049616 B CN 109049616B
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Abstract
The invention discloses a production method of a polypropylene composite material, and belongs to the technical field of production of polypropylene composite materials. According to the invention, the mixture is added to the feeding end of the extrusion unit through the obliquely arranged feeding screw rod in the hopper, the mixture entering the extrusion unit is conveyed, extruded, melted and reacted in the extrusion unit and then moves to the vacuum exhaust section, the mixture in the vacuum exhaust section is subjected to two-stage vacuum pumping treatment through the vacuum pumping unit, and the mixture enters the extrusion section after the vacuum pumping is finished to be molded and extrude the strip-shaped polypropylene composite material; the drawing unit draws the long-strip polypropylene composite material to the granulating unit for granulating. The invention can smoothly feed the polypropylene mixture and effectively reduce the VOC content in the polypropylene composite material.
Description
Technical Field
The invention relates to the technical field of polypropylene composite material production, in particular to a production method of a polypropylene composite material.
Background
In the production process of plastics such as polypropylene, air, adsorbed moisture, residual monomers, low-boiling point plasticizers and oligomers which can be volatilized at the molding temperature are often entrained in the plastics. The existing extruder can not completely discharge the components under the condition of only a single group of vacuum pumping device, so that the surface of the product is dim, the phenomena of pores, bubbles, stripes and the like appear on the surface and inside of the product, and the appearance and the product quality of the product are influenced, and potential hidden dangers such as volatile matters, odor and the like are caused. With the wide application of plastics in the automobile industry, the requirements of customers on plastic products are stricter and stricter, and the VOC and the odor of the plastic products are also paid more and more attention. In the production process, the processing process control needs to control the technological parameters such as temperature, rotating speed, feeding speed and the like, so that the degradation or decomposition of the mixture in the process of producing the polypropylene composite material is reduced as much as possible, but the implementation in actual operation is difficult, and the optimal control technological parameters are difficult to find; in addition, the exhaust and vacuum capacity can be improved in the processing process, low-molecular volatile matters are reduced, but the exhaust is insufficient due to too low vacuum degree, but the higher vacuum degree cannot be effectively realized, and the production cost is increased due to too high vacuum degree.
Through retrieval, the name of the invention is: a double-screw plastic extruder (application No. 201120292362.4, application date: 2011.08.12) is disclosed in the application, and comprises a feeding device, a driving mechanism, a charging barrel and a vacuumizing device, wherein the vacuumizing device comprises an exhaust port on the charging barrel, a pressure gauge, an air flow regulating valve and a vacuum pump. The application can guarantee that the vacuumizing is smooth to a certain extent, and the impurities are discharged from the VOC in the polypropylene production mixture, but the impurities are not sufficiently discharged. Through retrieval, the name of the invention is: a low-odor and low-emission glass fiber reinforced polypropylene composition and a preparation method thereof (application No. 201511016683.0, application date: 2015.12.29) disclose a low-odor and low-emission glass fiber reinforced polypropylene composition and a preparation method thereof, wherein a plurality of vacuum ports are arranged at the tail end of an extruder for extraction. This application has strengthened the miscellaneous intensity of row of VOC in the polypropylene production mixture to a certain extent for more VOC can get rid of, but this application only carries out row miscellaneous through the quantity that increases the vacuum port, and use cost is higher, can't realize VOC's high efficiency row miscellaneous. Therefore, a production mode capable of realizing efficient VOC removal in the mixture in the production process of the polypropylene composite material is needed.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to provide a production method of a polypropylene composite material and a use method thereof, aiming at the problems of difficult blanking of a polypropylene mixture and low VOC removal efficiency in the polypropylene composite material in the prior art. The mixture is fed through the obliquely arranged feeding screw, so that the problem of difficult blanking is solved; the mixture is subjected to two-stage vacuum VOC removal in different temperature environments, so that the VOC content in the polypropylene composite material is effectively reduced.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention relates to a production method of a polypropylene composite material, wherein a mixture is added to a feeding end of an extrusion unit through an obliquely arranged feeding screw rod in a hopper, the mixture entering the extrusion unit is conveyed in the extrusion unit for extrusion, melting and reaction and then moves to a vacuum exhaust section, the mixture in the vacuum exhaust section is subjected to two-stage vacuum pumping treatment through a vacuum pumping unit, and the mixture enters the extrusion section after the vacuum pumping is finished to be molded and extrude a strip-shaped polypropylene composite material; the drawing unit draws the long-strip polypropylene composite material to the granulating unit for granulating.
Preferably, the specific steps are as follows:
step of charging
The stirrer is used for stirring the mixture in the hopper, and the mixture at the bottom of the hopper is fed by the obliquely arranged feeding screw;
step of extrusion
Adding the mixture into an extrusion unit of a double-screw extruder from a feeding hole of the double-screw extruder, conveying, extruding, melting and reacting the mixture in the extrusion unit, moving the mixture to a vacuum exhaust section, firstly carrying out primary vacuum pumping on the reacted mixture in a primary vacuum section, carrying out transition in a buffer section after the primary vacuum pumping, and carrying out secondary vacuum pumping on the mixture in a secondary vacuum section after the transition; after the mixture is vacuumized, the mixture enters an extrusion section, and a long-strip-shaped polypropylene composite material is molded and extruded at the extrusion section of a double-screw extruder;
traction and grain-sized dicing step
And (3) cooling, drying, drawing and granulating the strip-shaped polypropylene composite material obtained by extrusion molding to obtain the granular polypropylene composite material.
Preferably, the device used by the method comprises a feeding unit, wherein the feeding unit comprises a hopper, a blanking groove is arranged below the hopper, a feeding screw rod is obliquely arranged in the blanking groove, and a feeding port is connected below the blanking groove; the extruding unit is used for melting, reacting and extruding the strip-shaped polypropylene composite material, and comprises a feeding screw rod and a charging barrel, wherein the feeding screw rod is arranged in the charging barrel; the feeding unit is connected with the feeding end of the charging barrel through a feeding port, an air exhaust hole is formed in a vacuum exhaust section of the charging barrel, a feeding screw in the vacuum exhaust section comprises an exhaust promoting section, and the lead of the exhaust promoting section is greater than or equal to the lead of other areas of the feeding screw; the vacuumizing unit is communicated with the vacuum exhaust section through a pipeline and is used for vacuumizing the charging barrel; the inlet of the traction unit is arranged corresponding to the extrusion end of the extrusion unit, and the traction unit is used for providing traction force for the long-strip-shaped polypropylene composite material; cut the grain unit, cut the grain unit and set up in the exit position of traction unit, cut the grain unit and be used for cutting the grain to rectangular form polypropylene composite.
Preferably, an extrusion end of the extrusion unit and an inlet of the traction unit are sequentially provided with: the cooling inlet of the cooling unit is arranged at the discharge end of the extrusion unit and is used for cooling the long-strip polypropylene composite material extruded by the extrusion unit; the drying unit is arranged at a cooling outlet of the cooling unit and is used for drying the long-strip-shaped polypropylene composite material; and the wire take-up unit is arranged in front of an inlet of the traction unit and is used for tidying and guiding the long-strip-shaped polypropylene composite material.
Preferably, a stirrer is arranged in a hopper of the feeding unit, and an included angle a between a feeding screw and the horizontal direction is 15-45 degrees.
Preferably, the feeding end of the feeding screw is a solid conveying section, the solid conveying section comprises a feeding screw section and a solid compression screw section along the movement direction of the mixture, the lead of the feeding screw section is the same as that of the solid compression screw section, and the cross section area of a screw groove of the feeding screw section is S1The cross-sectional area of the screw groove of the solid compression screw section is S2，S1＞S2。
Preferably, the evacuation unit comprises a primary evacuation device and a secondary evacuation device; the vacuum exhaust section comprises a one-level vacuum section, a buffer section and a second-level vacuum section in sequence along the motion direction of the mixture, a one-level air exhaust hole is formed in a charging barrel of the one-level vacuum section and connected with a one-level vacuum extractor through a pipeline, a second-level air exhaust hole is formed in a charging barrel of the second-level vacuum section and connected with a second-level vacuum extractor through a pipeline.
Preferably, the axial cross-section of the flights of the charging screw section is fluted and the axial cross-section of the flights of the solid compression screw section is arcuate.
Preferably, the heating temperature of the charging barrel on the first-stage vacuum section is 225-230 ℃, the heating temperature of the charging barrel on the buffer section is 190-210 ℃, and the heating temperature of the charging barrel on the second-stage vacuum section is 195-200 ℃.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:
(1) according to the production method of the polypropylene composite material, the mixture is added to the feeding end of the extrusion unit through the obliquely arranged feeding screw rod in the hopper, so that the smooth feeding of the polypropylene mixture is realized; the mixture entering the extrusion unit is conveyed in the extrusion unit to be extruded, melted and reacted and then moves to a vacuum exhaust section, the mixture in the vacuum exhaust section is subjected to two-stage vacuumizing treatment through a vacuumizing unit, and the mixture enters the extrusion section after vacuumizing is finished to be molded and extruded into a strip-shaped polypropylene composite material; the drawing unit draws the long-strip polypropylene composite material to the granulating unit for granulating. The method vacuumizes the mixture to realize effective removal of VOC in the mixture; the traction unit and the granulating unit are mainly used for traction and granulation of the long-strip polypropylene composite material.
(2) The invention relates to a production method of a polypropylene composite material, wherein a vacuumizing unit used in the method is arranged at a vacuum exhaust section of an extrusion unit, and the vacuumizing unit comprises a primary vacuumizing device and a secondary vacuumizing device; the vacuum exhaust section comprises a first-stage vacuum section, a buffer section and a second-stage vacuum section in sequence along the material movement direction, the lead of the feeding screw in the vacuum exhaust section is increased, the air exhaust area of the feeding screw can be enlarged, the VOC generation characteristic of the polypropylene composite material in the production process is combined, and the VOC content in the polypropylene composite material is effectively reduced through temperature matching two-stage vacuum pumping.
(3) According to the production method of the polypropylene composite material, the feeding screw comprises the feeding screw section and the solid compression screw section at the solid conveying section along the movement direction of the mixture, the lead of the feeding screw section is the same as that of the solid compression screw section, the screw groove sectional area of the feeding screw section is larger than that of the solid compression screw section, and the feeding amount in the feeding process is increased by the arrangement, so that the processing efficiency of an extrusion device is improved; in addition, the screw channel sectional area of the feeding screw section is S1, the screw channel sectional area of the solid compression screw section is S2, and S1 is more than S2, so that the mixture is extruded when entering the solid compression screw section from the feeding screw section of the feeding screw so as to be exhausted; the shape of the shaft section of the screw groove of the charging screw section is groove-shaped, and the shape of the shaft section of the screw groove of the solid compression screw section is arc-shaped, so that the device is favorable for fully exhausting mixed materials, and the mixed materials are prevented from being entrained with excessive gas to enter a subsequent melting process.
(4) The invention relates to a production method of a polypropylene composite material, wherein the heating temperature of a charging barrel on a primary vacuum section in a vacuum exhaust section is T7, the heating temperature of a charging barrel on a buffer section is T8, the heating temperature of a charging barrel on a secondary vacuum section is T9, T7 is more than T8, and T7 is more than T9, a production mixture is firstly vacuumized in a high-temperature environment through a primary vacuumizer to remove VOC in the mixture, then the mixture is subjected to low-temperature transition through the buffer section, and finally the production mixture is vacuumized in a low-temperature environment through a secondary vacuumizer to remove the VOC in the mixture and inhibit the continuous degradation of the production mixture.
Drawings
FIG. 1 is a schematic flow chart of a process for producing a polypropylene composite according to the present invention;
FIG. 2 is a schematic diagram of a production system used in the production method of polypropylene composite material according to the present invention;
FIG. 3 is a schematic diagram showing the structure of a feeding unit in a production system used in the production method of a polypropylene composite material according to the present invention;
FIG. 4 is a schematic diagram showing the structure of an extrusion unit in a production system used in a production method of a polypropylene composite according to the present invention;
FIG. 5 is an enlarged view of a solid conveying section of an extrusion unit in a production system used in a production method of a polypropylene composite material according to the present invention.
The reference numerals in the schematic drawings illustrate:
100. a feeding unit;
110. a hopper; 111. a stirrer; 112. a stirring motor; 120. a discharging groove; 121. a feed screw; 122. a feeding motor; 130. a feed inlet;
200. an extrusion unit;
201. a feed screw; 202. a charging barrel; 203. a screw motor; 204. a feed aperture; 205. an exhaust hole; 206. a first-stage air extraction hole; 207. a secondary air exhaust hole;
210. a solids conveying section; 211. a charging screw section; 212. a solid compression screw section; 213. a screw groove; 220. a melting section; 230. a reaction section;
240. a vacuum exhaust section; 241. a first-stage vacuum section; 242. a buffer section; 243. a secondary vacuum section; 244. an exhaust promotion section; 250. an extrusion section;
300. a vacuum pumping unit; 310. a first-stage vacuum extractor; 320. a secondary vacuum extractor;
400. a cooling unit; 500. a drying unit; 600. a wire take-up unit; 700. a traction unit; 800. and a pelletizing unit.
Detailed Description
The detailed description and exemplary embodiments of the invention will be better understood when read in conjunction with the appended drawings, where the elements and features of the invention are identified by reference numerals.
Example 1
With reference to fig. 1 to 5, in the method for producing a polypropylene composite material according to the embodiment, a mixture passes through an obliquely arranged feeding screw 121 in a hopper 110 and is added to a feeding end of an extrusion unit 200, the mixture entering the extrusion unit 200 is transported, extruded, melted, reacted in the extrusion unit 200 and then moves to a vacuum exhaust section 240, the mixture in the vacuum exhaust section 240 is subjected to two-stage vacuum pumping by a vacuum pumping unit 300, and the mixture enters the extrusion section 250 after vacuum pumping is finished to be molded and extruded into a strip-shaped polypropylene composite material; the elongated polypropylene composite is pulled by the pulling unit 700, and the pulling unit 700 pulls the elongated polypropylene composite to the dicing unit 800 for dicing.
The method comprises the following specific steps:
step of charging
The stirrer 111 stirs the mixture in the hopper 110, and the mixture at the bottom of the hopper 110 is fed by the obliquely arranged feeding screw 121;
step of extrusion
The mixture is added into an extrusion unit 200 in the double-screw extruder from a feeding hole 204 of the double-screw extruder, the mixture is conveyed, extruded, melted and reacted in the extrusion unit 200 and then moves to a vacuum exhaust section 240, the reacted mixture is firstly subjected to primary vacuum pumping in a primary vacuum section 241, the mixture enters a buffer section 242 for transition after the primary vacuum pumping, and the mixture enters a secondary vacuum section 243 for secondary vacuum pumping after the transition; after the mixture is vacuumized, the mixture enters an extrusion section 250, and a strip-shaped polypropylene composite material is molded and extruded in the extrusion section 250 of the double-screw extruder;
traction and grain-sized dicing step
And (3) cooling, drying, drawing and granulating the strip-shaped polypropylene composite material obtained by extrusion molding to obtain the granular polypropylene composite material.
The production system used in the production method of the polypropylene composite material of the embodiment comprises a feeding unit 100, an extrusion unit 200, a vacuum pumping unit 300, a drawing unit 700 and a dicing unit 800.
The feeding unit 100 comprises a hopper 110, a feeding groove 120 is arranged below the hopper 110, a feeding screw 121 is obliquely arranged in the feeding groove 120, and a feeding port 130 is connected below the feeding groove 120; the feeding screw 121 passes through the drive of feeding motor 122, feeding screw 121 is 15 ~ 45 with the contained angle a of horizontal direction, contained angle a equals 30 in this embodiment, the inclination of setting can effectively avoid the light mixture of the quality in the hopper 110 or high filling mixture to appear not unloading, unloading difficulty and bridging phenomenon, and the feeding screw 121 that the slope set up does not have the dead angle, avoid causing the mixture to pile up, feeding screw 121 can force the mixture to see off simultaneously, and then avoid appearing the mixture and skid not unloading. In addition, a stirrer 111 is arranged in the hopper 110 of the feeding unit 100, and the stirrer 111 is driven by a stirring motor 112, and the stirring of the stirrer can enable the mixture to be more uniformly fed, and meanwhile, the stability of feeding can be ensured.
The extrusion unit 200 is used for melting, reacting and extruding the strip-shaped polypropylene composite material, the extrusion unit 200 comprises a feeding screw 201 and a material barrel 202, and the feeding screw 201 is arranged in the material barrel 202; the feeding unit 100 is connected with the feeding end of the cylinder 202 through the feeding port 130, the vacuum exhaust section 240 of the cylinder 202 is provided with an air exhaust hole, and the lead of the feeding screw 201 corresponding to the vacuum exhaust section 240 is greater than or equal to the lead of the feeding screw 201 in other areas; in addition, the vacuumizing unit 300 is used for vacuumizing the charging barrel 202, and the vacuumizing unit 300 is communicated with the vacuum exhaust section 240 through a pipeline; the specific structure, embodiment and function of the extrusion unit 200 and the vacuum unit 300 are described in detail in example 2.
The inlet of the traction unit 700 is arranged corresponding to the extrusion end of the extrusion unit 200, and when the extrusion end of the extrusion unit 200 extrudes the long-strip polypropylene composite material, the inlet of the traction unit 700 receives the long-strip polypropylene composite material and provides traction force for the long-strip polypropylene composite material through the traction rollers, so that the long-strip polypropylene composite material can continuously move forwards, and the continuous production process is realized.
The dicing unit 800 is disposed at an outlet of the drawing unit 700, and the dicing unit 800 performs dicing on the long-strip polypropylene composite material through a cutting roller, thereby obtaining a final granular polypropylene composite material.
It is worth mentioning that between the extrusion end of the extrusion unit 200 and the inlet of the traction unit 700 are sequentially disposed:
the cooling inlet of the cooling unit 400 is arranged at the extrusion end of the extrusion unit 200, and is used for cooling the long-strip polypropylene composite material extruded by the extrusion unit 200; the cooling unit 400 is cooled by cooling water, the cooling water is perpendicular to the motion direction of the long-strip-shaped polypropylene composite material, a water inlet of the cooling water is formed in one side of the motion direction of the long-strip-shaped polypropylene composite material, a water outlet of the cooling water is formed in the other side of the relative water inlet, when the long-strip-shaped polypropylene composite material passes through the cooling tank of the cooling unit 400, the cooling water flows through the surface of the long-strip-shaped polypropylene composite material from the side of the long-strip-shaped polypropylene composite material, the heat of the composite material is taken away, and the cooling strength of the cooling water to the composite material can be increased by flowing through.
The drying unit 500 is arranged at the cooling outlet of the cooling unit 400, and is used for drying the long-strip-shaped polypropylene composite material, the drying unit 500 is used for drying the long-strip-shaped polypropylene composite material through blowing, and the blowing outlet is arranged above the long-strip-shaped polypropylene composite material;
and the wire take-up unit 600 is arranged in front of an inlet of the traction unit 700, and is used for tidying and guiding the long-strip polypropylene composite material.
Example 2
With reference to fig. 2 to 5, the system for producing a polypropylene composite material for automotive interiors according to the present embodiment includes a feeding unit 100, an extruding unit 200, and a vacuum-pumping unit 300; the extrusion unit 200 comprises a feeding screw 201 and a barrel 202, wherein the feeding screw 201 is arranged in the barrel 202; the extrusion unit 200 comprises a solid conveying section 210, a melting section 220, a reaction section 230 and a vacuum exhaust section 240 along the movement direction of the mixture, in addition, 10 heating zones are sequentially arranged outside a barrel 202 of the extrusion unit 200 along the movement direction of the mixture, wherein the heating zones are respectively the 1 st to 10 th heating zones, and it should be noted that, because the mixture is in a gradual transition process between the processing stages in the extrusion unit 200, the corresponding relation between each section of the extrusion unit 200 and each heating zone is a rough correspondence, not an absolute correspondence in spatial position; wherein the mixture is a raw material for producing the polypropylene composite material and comprises polypropylene, a polyolefin elastomer, talcum powder and an antioxidant; the movement direction of the mixture is the movement direction of the mixture driven by the feed screw 201 after the mixture is added into the charging barrel 202.
The specification set of the screw elements of the feed screw 201 in the mix movement direction is shown in table 1:
TABLE 1 Specification Table for screw elements of feeding screw
| Serial number | 1# | 2# | 3# | 4# | 5# | 6# | 7# | 8# | 9# |
| Specification of | 56/56 | 96/96 | 96/96 | 96/96 | 72/72 | 72/72 | 56/56 | K45°/56 | K45°/56 |
| Serial number | 10# | 11# | 12# | 13# | 14# | 15# | 16# | 17# | 18# |
| Specification of | K60°/56 | 56/56 | 44/44 | K45°/56 | K60°/56 | K90°/56 | 56/56 | K45°/56 | K60°/56 |
| Serial number | 19# | 20# | 21# | 22# | 23# | 24# | 25# | 26# | 27# |
| Specification of | 28/28 | 72/72 | 72/72 | 56/56 | 56/56 | K45°/56 | K60°/56 | K90°/56 | 28/28 |
| Serial number | 28# | 29# | 30# | 31# | 32# | 33# | 34# | 35# | 36# |
| Specification of | 96/96 | 96/96 | 96/96 | 96/96 | 96/96 | 96/96 | 72/72 | 72/72 | 72/72 |
| Serial number | 37# | 38# | 39# | ||||||
| Specification of | 56/56 | 56/56 | 56/56 |
It should be noted that the screw element includes a delivery block and a shear block, and in the specification of the delivery block, "/" is a lead value before and a length value after, "/" is a length value, for example, 2# is a delivery block with a lead of 96mm and a length of 96 mm; in the specification of the cutout, "/" is preceded by an angle value of the staggered disks in the cutout, and "/" is followed by a length value, for example, 8# is a cutout, the angle value of the staggered disks is 45 degrees, and the length is 56 mm.
In this embodiment, the barrel 202 corresponding to the solid conveying section 210 is connected to the charging opening of the charging unit 100 through the charging hole 204, and during production, the mixture in the charging unit 100 passes through the charging hole 204 from the charging opening and then enters the barrel 202 for processing. In addition, the solid conveying section 210 corresponds to the 1 st to 2 nd heating zones of the charging barrel 202, wherein the temperature of the 1 st heating zone is 180 ℃, the temperature of the 2 nd heating zone is 200 ℃, and the heating zones heat the mixture, so that further melting and reaction of subsequent mixture are facilitated.
In the solid conveying section 210, the feeding screw 201 comprises a feeding screw section 211 and a solid compression screw section 212 in the solid conveying section 210 along the movement direction of the mixture, the feeding screw section 211 is arranged at the position of the feeding hole 204, the solid compression screw section 212 is arranged behind the solid conveying section 210 along the movement direction of the mixture, and the lead of the feeding screw section 211 is the same as that of the solid compression screw section 212; in this embodiment, the screw specification of the charging screw section 211 corresponds to the specification of 2# to 3# in the feed screw specification table, and the screw specification of the solid compression screw section 212 corresponds to the specification of 4# in the feed screw specification table.
It is noted that the cross-sectional area of the flight 213 of the charging screw section 211 is S1, and the cross-sectional area of the flight 213 of the solid compression screw section 212 is S2, S1 > S2. During transportation, the feeding screw 201 mainly conveys the mixture through the screw groove 213, the feeding screw 201 is driven by the screw motor 203 to rotate, the mixture moves along the screw groove 213 along the movement direction of the mixture, therefore, the larger the sectional area of the screw groove 213 is, the larger the volume of the screw groove 213 is, and further, the more mixture can be stored in the feeding screw section 211 with the large sectional area of the screw groove 213. And reinforced screw section 211 sets up in charge-in hole 204 department, and reinforced screw section 211 stores the material loading volume that more mixture just can increase reinforced process, and then improves extrusion device's machining efficiency, and the volume that increases initial mixture to a certain extent moreover also plays the promotion effect to the extrusion of follow-up mixture.
After the mixture is added into the charging screw section 211 through the charging hole 204, the mixture is mainly in a particle powder shape, gaps exist among particles, the gaps are inevitably filled with air, if the air in the gaps is not removed, the mixture is subjected to oxidative degradation by oxygen in the air in the subsequent melting reaction process, and a large amount of small molecular impurities are formed after the mixture is subjected to oxidative degradation, so that the VOC content in the polypropylene composite material is increased.
In this embodiment, the specification of the threaded element of the solid conveying section 210 corresponds to the specification of 1# to 7# in the specification table of the threaded element of the feeding screw, and the lead of the conveying block of the section is continuously reduced, so that the volume of the screw groove 213 is also continuously reduced, and the mixture is extruded due to the reduction of the volume of the screw groove 213, thereby promoting the removal of air in the mixture.
However, if the air in the mix is removed by merely reducing the volume of the screw grooves 213, the effect is very limited because: for the mixture in the bottom area of the screw groove 213, especially for the mixture in the corner of the bottom area, the migration distance of the air contained in the mixture is long and the obstruction is large during the removing process, so that the removing effect of the air in the mixture in the area is poor.
Here, it is necessary to explain the shape of the axial cross section of the screw grooves 213, the shape of the axial cross section of the screw grooves 213 of the charging screw section 211 is a groove shape, the shape of the axial cross section of the screw grooves 213 of the solid compression screw section 212 is an arc shape, and the area of the axial cross section of the screw grooves 213 of the charging screw section 211 is larger than the area of the axial cross section of the screw grooves 213. The axial section of the spiral groove 213 of the solid compression screw section 212 is arc-shaped, so that a large corner at the bottom of the spiral groove 213 can be avoided, and the discharge process of air in the mixture is less obstructed; in addition, the shape of the axial section of the spiral groove 213 of the solid compression screw section 212 is arc-shaped, so that the mixture can be evenly distributed in the spiral groove 213 of the solid compression screw section 212 to a certain extent, the migration distance of the air of the mixture in each area in the spiral groove 213 in the removal process can be reduced, the contact area of the mixture and the outside is increased, the exhaust area of the mixture is increased, and the removal of the air in the mixture is facilitated in both aspects.
The specification of the thread element of the melting section 220 corresponds to the specification of 8# to 13# in the specification table of the thread element of the feeding screw, the specification corresponds to the 3 rd to 4 th heating areas of the charging barrel 202, and the heating temperature of the melting section 220 in the embodiment is 220 ℃; it should be noted here that when the mixture moves to the end of the melting section 220 after being heated and melted in the melting section 220, the mixture is in a substantially molten state, most of the air in the gaps between the granular mixture has been separated from the mixture, if the separated air is not discharged in time, the air enters the reaction section 230 with a strong shearing action along with the mixture, and the oxygen in the air is liable to cause the mixture to be oxidized and degraded, so that a large amount of small molecular impurities are generated, and the VOC content in the polypropylene composite product is increased. Therefore, in this embodiment, the vent hole 205 is disposed on the barrel 202, i.e. the 4 th heating zone, at the end of the melting section 220 close to the reaction section 230, and when the mixture moves to this position, the gas exhausted in the previous process is exhausted through the vent hole 205, so that the mixture can be prevented from being oxidized and degraded in the subsequent reaction process of the mixture, and the content of VOC in the polypropylene composite material can be reduced.
The specification of the threaded element of the reaction section 230 corresponds to the specification of 14# to 26# in the specification table of the threaded element of the feeding screw, and corresponds to the 5 th to 6 th heating zones of the charging barrel 202, wherein the heating temperature of the 5 th heating zone is 200 ℃, the heating temperature of the 6 th heating zone is 230 ℃, and the temperature of the 6 th heating zone reaches the highest temperature, so that the mixture is more fully reacted.
The vacuum exhaust section 240 sequentially comprises a primary vacuum section 241, a buffer section 242 and a secondary vacuum section 243 along the movement direction of the mixture, a vacuumizing unit 300 is arranged outside the vacuum exhaust section 240, and the vacuumizing unit 300 comprises a primary vacuumizing device 310 and a secondary vacuumizing device 320; the charging barrel 202 of the first-stage vacuum section 241 is provided with a first-stage suction hole 206, the first-stage suction hole 206 is connected with the first-stage vacuum extractor 310 through a pipeline, the charging barrel 202 of the second-stage vacuum section 243 is provided with a second-stage suction hole 207, and the second-stage suction hole 207 is connected with the second-stage vacuum extractor 320 through a pipeline.
The material feeding screw 201 in the vacuum exhaust section 240 comprises an exhaust promoting section 244, the lead of the exhaust promoting section 244 is greater than or equal to the lead of other areas of the material feeding screw 201, the specification of the thread element corresponds to the specification of 27# -37 # in the specification table of the thread element of the material feeding screw, wherein, the exhaust promoting section 244, which is positioned on the middle part of the material feeding screw 201 in the vacuum exhaust section 240 and mainly plays a role of promoting exhaust, is provided with an area with the lead of the thread element greater than or equal to the lead of other areas of the material feeding screw 201, the specification is 96/96, the front end and the rear end of the material feeding screw 201 in the exhaust promoting section 244 are also provided with thread elements with the lead smaller than the large lead, and the function is that the material feeding screw 201 with the large lead in the exhaust promoting section 244 can be better matched with the front and rear material feeding screws 201. In addition, the axial cross-section of the screw channel 213 of the feeding screw 201 in the vacuum exhaust section 240 is similar to that of the screw channel 213 of the solid compression screw section 212, so as to increase the exhaust area of the mixture, so that the vacuum unit 300 can more fully extract the gas containing the small molecular substances in the mixture.
It is worth to be noted that the primary vacuum section 241, the buffer section 242 and the secondary vacuum section 243 of the vacuum exhaust section 240 respectively correspond to 7 th to 9 th heating zones, the heating temperature of the 7 th heating zone of the charging barrel 202 on the primary vacuum section 241 is T7, the heating temperature of the 8 th heating zone of the charging barrel 202 on the buffer section 242 is T8, the heating temperature of the 9 th heating zone of the charging barrel 202 on the secondary vacuum section 243 is T9, T7 is greater than T8, and T7 is greater than T9; more specifically, the heating temperature of the cylinder 202 on the first-stage vacuum section 241 is 225-230 ℃, the heating temperature of the cylinder 202 on the buffer section 242 is 190-210 ℃, and the heating temperature of the cylinder 202 on the second-stage vacuum section 243 is 195-200 ℃. In this example, the temperature of the 7 th heating zone was 225 ℃, the temperature of the 8 th heating zone was 205 ℃, and the temperature of the 9 th heating zone was 200 ℃. An extrusion section 250 is arranged at the tail end of the vacuum exhaust section 240, wherein the extrusion section 250 corresponds to a 10 th heating zone, and the temperature of the 10 th heating zone is 210 ℃; the head temperature was 205 ℃.
In the one-level vacuum section 241 that the mixture got into vacuum exhaust section 240, one-level vacuum section 241 carries out high temperature heating to the mixture, make VOC and the gas in the mixture fully volatilize under the high temperature effect, the vacuum pumping effect of rethread one-level vacuum extractor 310, impurity such as VOC and gas that volatilize in with the high temperature environment is fully taken out, but the mixture also can decompose the production a certain amount of little molecular impurity under the high temperature environment of one-level vacuum section 241, and then be unfavorable for reducing VOC's content in the polypropylene composite product.
The mixture enters the buffer section 242 after being subjected to high-temperature vacuum pumping of the primary vacuum section 241, the temperature of the buffer section 242 is lower than that of the primary vacuum section 241, and the buffer section 242 can cool and buffer the mixture to a certain degree. The temperature of the mixed material is reduced after the mixed material is buffered by the buffer section 242, the mixed material enters the second-stage vacuum section 243, the temperature of the second-stage vacuum section 243 is lower than that of the first-stage vacuum section 241, the mixed material is vacuumized by the second-stage vacuumizing device 320, the second-stage vacuum section 243 has the function of inhibiting the mixed material from being continuously decomposed to generate small molecular impurities, and the mixed material is secondarily vacuumized by the second-stage vacuumizing device 320, so that residual VOC and gas in the mixed material and the small molecular impurities decomposed at high temperature in the first-stage vacuum section 241 are continuously pumped out, and the VOC in the mixed material is fully removed.
The temperature in the first-stage vacuum-pumping device 310 is higher, so that the VOC and gas in the mixture have stronger volatility, the vacuum-pumping negative pressure of the first-stage vacuum-pumping device 310 does not need to be too large, and the vacuum-pumping negative pressure of the first-stage vacuum-pumping device 310 can be-0.04 to-0.05 MPa, so that the production cost can be reduced. In the embodiment, the vacuum-pumping negative pressure of the first-stage vacuum-pumping device 310 is-0.04 MPa; the temperature in the secondary vacuum-pumping device 320 is low, and the volatility of the VOC and the gas in the mixture is weak, so the vacuum-pumping negative pressure of the secondary vacuum-pumping device 320 needs to be properly increased, the vacuum-pumping negative pressure of the secondary vacuum-pumping device 320 can be-0.07 to-0.08 MPa, and the vacuum-pumping negative pressure of the secondary vacuum-pumping device 320 in this embodiment is-0.07 MPa.
In the embodiment, the vacuum exhaust section 240 fully and effectively reduces the VOC content in the produced polypropylene composite material, effectively reduces the VOC content in the polypropylene composite material product and improves the quality of the polypropylene composite material product by matching the temperature with two-stage vacuum pumping according to the VOC generation and elimination characteristics of the polypropylene composite material in the production process.
The invention relates to a using method of a polypropylene composite material extrusion device, wherein a mixture is added into an extrusion unit 200 in a double-screw extruder from a feeding hole 204 of the double-screw extruder, the mixture is conveyed, extruded, melted and reacted in the extrusion unit 200 and then moves to a vacuum exhaust section 240, the reacted mixture is firstly subjected to primary vacuum pumping in a primary vacuum section 241, the mixture enters a buffer section 242 for transition after the primary vacuum pumping, and the mixture enters a secondary vacuum section 243 for secondary vacuum pumping after the transition; and after the mixture is vacuumized, feeding the mixture into an extrusion section 250, extruding and molding the mixture in the extrusion section 250 of a double-screw extruder, namely an extrusion unit 200, wherein the rotating speed of a main machine is 400-450 r/min, the feeding rotating speed is 50-100 r/min, and extruding, granulating, drying and granulating.
Example 3
This embodiment is basically the same as embodiment 1, except that: in the vacuum exhaust section 240, the temperature of the 7 th heating zone is 227 ℃, the temperature of the 8 th heating zone is 197 ℃, and the temperature of the 9 th heating zone is 197 ℃, that is, the temperature of the 8 th heating zone is the same as that of the 9 th heating zone, so that the temperature of the mixture passing through the buffer section 242 can be rapidly and stably reduced to the temperature the same as that of the 9 th heating zone, and the subsequent secondary vacuum extractor 320 is more stable in the VOC removal process.
Example 4
This embodiment is basically the same as embodiment 1, except that: in the vacuum exhaust section 240, the temperature of the 7 th heating zone in this embodiment is 230 ℃, the temperature of the 8 th heating zone is 195 ℃, and the temperature of the 9 th heating zone is 195 ℃, that is, the temperatures of the 8 th heating zone and the 9 th heating zone are the same, so that the temperature of the mixture passing through the buffer section 242 can be rapidly reduced, the mixture is rapidly inhibited from being decomposed into small molecules due to high temperature, and the content of VOC in the polypropylene composite product is effectively reduced. The invention has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.
Claims (9)
1. A production method of a polypropylene composite material is characterized by comprising the following steps: the mixture is added to the feeding end of an extrusion unit (200) through an obliquely arranged feeding screw (121) in a hopper (110), the mixture entering the extrusion unit (200) is conveyed, extruded, melted and reacted in the extrusion unit (200) and then moves to a vacuum exhaust section (240), the mixture in the vacuum exhaust section (240) is subjected to two-stage vacuum pumping treatment through a vacuum pumping unit (300), and the mixture enters an extrusion section (250) after the vacuum pumping is finished to be molded and extruded into a strip-shaped polypropylene composite material; the drawing unit (700) provides drawing force for the long strip polypropylene composite material, and the drawing unit (700) draws the long strip polypropylene composite material to the granulating unit (800) for granulating; the vacuum unit (300) comprises a primary vacuum extractor (310) and a secondary vacuum extractor (320); the vacuum exhaust section (240) sequentially comprises a first-stage vacuum section (241), a buffer section (242) and a second-stage vacuum section (243) along the movement direction of the mixture, a first-stage air extraction hole (206) is formed in a charging barrel (202) of the first-stage vacuum section (241), the first-stage air extraction hole (206) is connected with a first-stage vacuum extractor (310) through a pipeline, a second-stage air extraction hole (270) is formed in the charging barrel (202) of the second-stage vacuum section (243), and the second-stage air extraction hole (270) is connected with a second-stage vacuum extractor (320) through a pipeline; the vacuum-pumping negative pressure of the primary vacuum-pumping device (310) is-0.04 to-0.05 MPa, and the vacuum-pumping negative pressure of the secondary vacuum-pumping device (320) is-0.07 to-0.08 MPa; the heating temperature of the material barrel (202) on the primary vacuum section (241) is T7, the heating temperature of the material barrel (202) on the buffer section (242) is T8, the heating temperature of the material barrel (202) on the secondary vacuum section (243) is T9, T7 is more than T8, and T7 is more than T9.
2. The method for producing a polypropylene composite material according to claim 1, wherein: the method comprises the following specific steps:
step of charging
The stirrer (111) stirs the mixed materials in the hopper (110), and the mixed materials at the bottom of the hopper (110) are fed through the obliquely arranged feeding screw (121);
step of extrusion
The mixture is added into an extrusion unit (200) in the double-screw extruder from a feeding hole (204) of the double-screw extruder, the mixture is conveyed, extruded, melted and reacted in the extrusion unit (200) and then moves to a vacuum exhaust section (240), the reacted mixture is firstly subjected to primary vacuum pumping in a primary vacuum section (241), the mixture enters a buffer section (242) for transition after the primary vacuum pumping, and the mixture enters a secondary vacuum section (243) for secondary vacuum pumping after the transition; after the mixture is vacuumized, the mixture enters an extrusion section (250), and a strip-shaped polypropylene composite material is molded and extruded in the extrusion section (250) of the double-screw extruder;
traction and grain-sized dicing step
And (3) cooling, drying, drawing and granulating the strip-shaped polypropylene composite material obtained by extrusion molding to obtain the granular polypropylene composite material.
3. The method for producing a polypropylene composite material according to claim 1, wherein: the method uses a device comprising
The feeding unit (100) comprises a hopper (110), a discharging groove (120) is arranged below the hopper (110), a feeding screw rod (121) is obliquely arranged in the discharging groove (120), and a feeding port (130) is connected below the discharging groove (120);
the extrusion unit (200), the extrusion unit (200) is used for melting, reacting and extruding the long-strip-shaped polypropylene composite material, the extrusion unit (200) comprises a feeding screw rod (201) and a charging barrel (202), and the feeding screw rod (201) is arranged in the charging barrel (202); the feeding unit (100) is connected with the feeding end of the charging barrel (202) through a feeding port (130), and a vacuum exhaust section (240) of the charging barrel (202) is provided with an air suction hole;
the vacuumizing unit (300), the vacuumizing unit (300) is communicated with the vacuum exhaust section (240) through a pipeline, and the vacuumizing unit (300) is used for vacuumizing the interior of the charging barrel (202);
the inlet of the traction unit (700) is arranged corresponding to the extrusion end of the extrusion unit (200), and the traction unit (700) is used for providing traction force for the long-strip-shaped polypropylene composite material;
and the granulating unit (800), the granulating unit (800) is arranged at the outlet position of the traction unit (700), and the granulating unit (800) is used for granulating the long-strip polypropylene composite material.
4. A method for producing a polypropylene composite according to claim 3, wherein: an extrusion end of the extrusion unit (200) and an inlet of the traction unit (700) are sequentially provided with:
the cooling inlet of the cooling unit (400) is arranged at the discharge end of the extrusion unit (200) and is used for cooling the long-strip-shaped polypropylene composite material extruded by the extrusion unit (200);
the drying unit (500), the drying unit (500) is arranged at the cooling outlet of the cooling unit (400), and dries the long-strip polypropylene composite material;
and the wire take-up unit (600) is arranged in front of an inlet of the traction unit (700) and is used for tidying and guiding the long-strip polypropylene composite material.
5. A method for producing a polypropylene composite according to claim 3, wherein: a stirrer (111) is arranged in a hopper (110) of the feeding unit (100), and an included angle a between a feeding screw (121) and the horizontal direction is 15-45 degrees.
6. A method for producing a polypropylene composite according to claim 3, wherein: the feeding end of the feeding screw (201) is a solid conveying section (210), the solid conveying section (210) comprises a feeding screw section (211) and a solid compression screw section (212) along the movement direction of the mixture, the screw leads of the feeding screw section (211) and the solid compression screw section (212) are the same, the sectional area of a screw groove (213) of the feeding screw section (211) is S1, the sectional area of a screw groove (213) of the solid compression screw section (212) is S2, and S1 is more than S2.
7. A method for producing a polypropylene composite according to claim 3, wherein: the vacuum unit (300) comprises a primary vacuum extractor (310) and a secondary vacuum extractor (320); the vacuum exhaust section (240) sequentially comprises a first-stage vacuum section (241), a buffer section (242) and a second-stage vacuum section (243) along the movement direction of the mixture, a first-stage air extraction hole (206) is formed in a charging barrel (202) of the first-stage vacuum section (241), the first-stage air extraction hole (206) is connected with a first-stage vacuum extractor (310) through a pipeline, a second-stage air extraction hole (270) is formed in the charging barrel (202) of the second-stage vacuum section (243), and the second-stage air extraction hole (270) is connected with a second-stage vacuum extractor (320) through a pipeline.
8. A method for producing a polypropylene composite according to claim 3, wherein: the axial section of the screw groove (213) of the charging screw section (211) is groove-shaped, and the axial section of the screw groove (213) of the solid compression screw section (212) is arc-shaped.
9. A method for producing a polypropylene composite material according to any one of claims 3 to 7, wherein: the heating temperature of the charging barrel (202) on the primary vacuum section (241) is 225-230 ℃, the heating temperature of the charging barrel (202) on the buffer section (242) is 190-210 ℃, and the heating temperature of the charging barrel (202) on the secondary vacuum section (243) is 195-200 ℃.
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