CN220373881U

CN220373881U - Water-cooled thermoplastic extrusion device for producing thermoplastic granules

Info

Publication number: CN220373881U
Application number: CN202321706615.7U
Authority: CN
Inventors: 金闪; 吴超; 王智生
Original assignee: Wiggs High Performance Materials Trading Shanghai Co ltd
Current assignee: Wiggs High Performance Materials Trading Shanghai Co ltd
Priority date: 2023-06-30
Filing date: 2023-06-30
Publication date: 2024-01-23
Anticipated expiration: 2033-06-30

Abstract

The utility model relates to a water-cooled thermoplastic extrusion device for producing thermoplastic pellets, comprising: an extruder provided with an extrusion die having a plurality of die holes configured to produce strands of thermoplastic extrudate; a conveyor belt disposed in front of the extruder and configured to convey the thermoplastic extrudate strands away from the extruder; a first water outlet arm and a second water outlet arm disposed on a surface of the conveyor belt, each water outlet arm being configured with at least one spray nozzle for generating a respective at least one spray water; a pelletizer disposed toward the end of the conveyor belt remote from the extruder and configured to comminute the cooled thermoplastic extrudate strands into pellets, the lateral spacing between the outlet of the extrusion die and the first water outlet arm being from about 50cm to about 65cm; and at least one spray nozzle of each of the first and second water outlet arms are each independently oriented in the direction of travel of the conveyor belt at an oblique angle of about 40 degrees to about 80 degrees relative to the plane of the conveyor belt.

Description

Water-cooled thermoplastic extrusion device for producing thermoplastic granules

Technical Field

The present utility model relates to a water-cooled thermoplastic extrusion device, in particular for producing pellets of polyetheretherketone polymer (PEEK polymer), more particularly wherein the device comprises an extruder, a water-jet cooling device and a granulator.

Background

For many years, the process for producing thermoplastic compositions has involved three main steps, namely extrusion, cooling and pellet formation. The use and production of polymer pellets is common because the pellets represent a convenient form of material for handling and dispensing of the polymer product. In addition, pellets are convenient starting materials for a variety of downstream applications, such as injection molding.

Advanced thermoplastic materials have many high performance applications, for example, in the automotive and aerospace industries, where example products include mechanical gears. Further uses are found in the medical industry, where example products include medical implants and devices. Thus, one of the main factors in designing an extrusion device is to produce high quality pellets that are free or substantially free of surface defects, have consistent and repeatable crystallinity, and wherein the different batches have consistent characteristics. Furthermore, given that thermoplastics used in the high performance industry tend to be expensive, it is desirable that pellet production be substantially error free, which can be accomplished to some extent by ensuring that pellet production can run continuously (e.g., 3 to 6 hours or more) without having to pause production or perform maintenance.

Consistent and high levels of productivity in the pellet production process can be achieved by ensuring that the extrusion apparatus contains equipment that cools the extrudate in an efficient and repeatable manner. Furthermore, it is desirable to configure the cooling apparatus to cool the extrudate that will yield pellets that have a consistent and narrow size distribution and that are completely free of significant surface defects and substantially or completely free of small surface defects. Thus, accurate and repeatable control of extrudate cooling is a desirable quality for extrusion and cooling equipment.

The object of the present utility model is to seek to reduce the above-mentioned problems.

Disclosure of Invention

According to a first aspect, there is provided a water-cooled thermoplastic extrusion apparatus for producing thermoplastic pellets, the apparatus comprising:

an extruder provided with an extrusion die having a plurality of die holes configured to produce thermoplastic extrudate strands;

a conveyor belt disposed in front of the extruder and configured to convey the thermoplastic extrudate strands away from the extruder;

a first water outlet arm and a second water outlet arm disposed on a surface of the conveyor belt, each water outlet arm being configured with at least one spray nozzle for generating a respective at least one spray water;

a pelletizer disposed toward the end of the conveyor belt remote from the extruder, configured to comminute the cooled thermoplastic extrudate strands into pellets,

wherein the apparatus is configured such that:

the lateral spacing between the outlet of the extrusion die and the first water outlet arm is in the range of about 50cm to about 65cm; and at least one spray nozzle of each of the first and second water outlet arms are each independently oriented in the direction of travel of the conveyor belt at an oblique angle of about 40 degrees to about 80 degrees relative to the plane of the conveyor belt.

Drawings

FIG. 1 is a schematic diagram illustrating a side view of a water-cooled thermoplastic extrusion device according to aspects of the present disclosure.

FIG. 2 is a schematic diagram illustrating a plan view of the water-cooled thermoplastic extrusion device shown in FIG. 1 and in accordance with aspects of the present disclosure.

Fig. 3 shows the same apparatus and schematic as in fig. 2 in plan view, but without extrudate and water spray.

Fig. 4 is a schematic view of a water spraying device used as a part of the cooling apparatus shown in fig. 1 to 3.

Detailed Description

In a first aspect, there is provided a water-cooled thermoplastic extrusion apparatus for producing thermoplastic pellets, the apparatus comprising:

wherein the apparatus is configured such that:

In use, the cooling conditions imparted by the apparatus to the extrudate prior to processing into pellets can have a significant impact on the efficiency of production and the quality of the resulting pellets. The apparatus according to the first aspect can reliably produce thermoplastic pellets that are completely or substantially free of defects. The device provides a more time-efficient cooling than the known devices comprising only air cooling means, because contact with water from the water spray results in an increased cooling rate compared to air alone. This makes the conveyor belt of the device shorter than that of an air-cooling device. Furthermore, the use of water jets for cooling gives better control than the use of a water bath which cools the extrudate rapidly and indiscriminately. There are other advantages to using sprayed water compared to water baths: that is, the design and operation of an unsubmerged conveyor belt is logically more straightforward and is easier to handle manually in production errors, such as conveyor belt breakage. The water bath also tends to supercool the extrudate, which can lead to brittle extrudate breakage on the conveyor belt and reduced production efficiency. Furthermore, hard and/or brittle extrudates do not granulate uniformly and impose more wear on the granulator/slitter blades.

Thus, the use of water jets gives an advantageous control of the extrudate cooling, which helps to prevent conveyor breakage (which can clog the granulator and cause processing delays). The inventors have determined that a device containing two water jets produces an extrudate with a degree of structural integrity, but does not impose a rapid cooling rate that can embrittle the extrudate and be prone to breakage.

It would be advantageous to have the first water outlet arm positioned about 50cm to about 65cm from the extrusion die outlet. The gap defines the distance that the air initially cools the extrudate when the device is in use. The first water outlet arm provides high-speed cooling that can be achieved with relatively little water, as the extrudate is still relatively hot at the point where the water from the first water outlet arm contacts the extrudate. In addition, the water spray is not too close to the extruder outlet to prevent the extrudate from becoming too brittle by water impingement. The location of about 50cm to about 65cm provides a good balance between cooling rate (improving production efficiency and reducing water usage) and extrudate stability (since the extrudate cooling rate is not too fast to become brittle).

The inventors have determined that a device configured with a lateral spacing within this range provides: in use, the extrudate is allowed to dry for a period of time after being sprayed by the first water outlet arm (where the drying mechanism between the water sprays is primarily by evaporation and/or boiling of the water contacting the extrudate, as the surface of the extrudate is almost defined above the boiling point of water). Furthermore, providing water cooling near the extrusion die outlet while leaving sufficient drying time between the first and second water streams provides more efficient cooling and advantageously produces pellets of good size and quality, e.g., pellets of consistent size and shape and free of surface defects.

Further advantageously, the use of two outflow arms enables accurate control of the temperature of the extrudate as it reaches the granulator when in use. Thus, when reaching the granulator, the temperature of the extrudate is within the desired range. It would be advantageous to provide a device that can accurately and reliably provide cooling of extrudates within a narrow range. For example, it is preferable not to overcooling the extrudate, as this ensures that the life of the pelletizer blades will be lost faster when pelletizing the overcooled thermoplastic material. Extrudates well below the glass transition temperature will be stiffer and thus blunt the pelletizer blades and reduce overall production efficiency. It is also advantageous to ensure that the extrudate temperature is not overheated, as this makes the granulator, which may be disadvantageous for overheated extrudate when in use, as the hot extrudate may be too soft to be consistently cut by the granulator.

It would be beneficial to configure the device to provide water cooling no more than about 65cm from the extruder outlet, as this helps provide the most efficient cooling effect; i.e. closer to the extruder outlet, the hotter the extrudate, which means that the water has a greater cooling effect. Furthermore, cooling of the extrudate is balanced using as fast a flow of water as possible, but without too aggressive cooling (which may result in internal stress and/or brittleness and/or breakage of the extrudate), which advantageously enables the pellets to be cut uniformly and minimizes defects.

Preferably, the vertical separation between the conveyor belt surface and the first water outlet arm is about 18cm to about 25cm, preferably about 20cm to about 22cm, more preferably about 22cm. Preferably, the vertical separation between the conveyor belt surface and the second water outlet arm is about 18cm to about 25cm, preferably about 20cm to about 22cm, more preferably about 22cm. The height provides an advantageous tradeoff between: close enough to the conveyor belt that less water may be needed to impart the same cooling effect, but far enough from the conveyor belt that only one or two spray nozzles can provide water coverage of the entire extrudate.

Preferably, the lateral spacing between the extrusion die and the pelletizer inlet is from about 10m to about 14m, more preferably from about 11m to about 12m. Preferably, the lateral spacing between the second water outlet arm and the granulator inlet is from about 9m to about 13m, preferably from about 10m to about 12m.

By means of water cooling, the overall footprint (footprint) of the conveyor belt can be reduced, thus taking up less space. Furthermore, the shorter conveyor reduces the likelihood of extrudate breakage on its way to the pelletizer, which may lead to production delays and stops (e.g., because broken extrudate strands cannot be effectively cut by and/or clog the pelletizer, which means that production may have to be manually stopped and breakage removed and/or the pelletizer cleaned). Due to this reduced possibility of breakage caused by the water cooling stage, the productivity of the pellet production process can be improved.

Preferably, the at least one spray nozzle of each of the first and second water outlet arms is each independently oriented in the direction of travel of the conveyor belt at an oblique angle of about 50 degrees to about 70 degrees relative to the plane of the conveyor belt. Preferably, at least one spray nozzle of each of the first and second water outlet arms is oriented in the direction of travel of the conveyor belt at an oblique angle of about 60 degrees relative to the plane of the conveyor belt.

The angle of the spray nozzle is defined as: i) An acute angle formed between the direction of water flow from the water outlet arm and ii) the plane of the conveyor belt surface, wherein the spray nozzles are oriented in the direction of travel of the conveyor belt. In other words, the direction of the jet of water at an oblique angle is the same as the direction of travel of the conveyor belt. It will be appreciated that the plane of the conveyor belt relates to the surface defined by the upper (substantially flat) surface of the conveyor belt configured to convey the extrudate.

The extrudate strands do not readily rotate and are not ejected from under the conveyor belt. Advantageously, however, an embodiment of the device according to the first aspect contains a nozzle that jets the extrudate strands at an angle such that water from the jetting nozzle can be transported along at least some of the exposed surfaces of the extrudate. Thus, water contact from the jet of water (than would be possible if the water stream intersected the extrudate at right angles) results in a greater extrudate surface area and thus more uniform water coverage. In addition, in use, the spray nozzles arranged at an oblique angle allow an increase in the contact time between water and extrudate: this not only provides a greater cooling effect, but also provides a more efficient use of water.

An additional advantage of the orientation of the water jet is that it prevents water from being directed back into the extrusion die, which must remain hot enough to effectively extrude the thermoplastic material when in use. It would therefore be advantageous to orient the water nozzle in such a way as to ensure that the water does not contact and thus cool the extrusion die.

Preferably, the lateral spacing between the extrusion die outlet and the point at which the water produced in use from the at least one spray nozzle of the first water outlet arm first contacts the thermoplastic extrudate strands is in the range of from about 60cm to about 75 cm.

Preferably, the lateral spacing between the first and second water outlet arms is in the range of about 20cm to about 80cm, preferably about 30cm to about 50cm. More preferably, the lateral spacing between the first and second water outlet arms is about 40cm. It will be appreciated that in use, when the extrudate strands are conveyed along the conveyor belt, the extrudate strands will pass under the two water streams provided by the two water outlet arms. The preferred spacing between the two water outlet arms thus provides a gap between the two stages of water cooling during which point water can be evaporated, which is advantageous because evaporation provides effective cooling, a mechanism other than the cooling mechanism by heat transfer to the injected water.

Preferably, each of the at least one spray nozzles comprises an elongated aperture oriented along the width of the conveyor belt, such that, in use of the spray nozzles, the spray nozzles are configured to produce a substantially fan-shaped spray of water, preferably wherein the fan-shaped spray of water contacts substantially the entire width of the conveyor belt. Advantageously, in use, the elongated holes produce water jets having a shape that extends the width of the conveyor belt. Thus, the water ejected from the ejection nozzles may contact all of the extrudate strands configured to be produced by extrusion dies in parallel formation.

Preferably, each of the first and second water outlet arms comprises two spray nozzles. Advantageously, in use, the two spray nozzles produce a flow of water extending across the width of the conveyor belt, and preferably across the entire width of the conveyor belt, so that in use, all of the extrudate strands to be conveyed contact the sprayed water. Providing exactly two nozzles provides an advantageous compromise: i.e. complete coverage or substantially complete coverage of the conveyor belt surface can be achieved with less water than is used for more than two nozzles. Thus, two nozzles reduce waste of water when in use.

Preferably, the distance between the two spray nozzles on each water outlet arm is from about 10cm to about 25cm, preferably from about 15m to about 20cm. This distance is such that all extrudate strands to be conveyed are in contact with the sprayed water.

Preferably, the extruder is a twin screw extruder, preferably a twin screw co-rotating intermeshing compounding extruder.

It is further preferred that the conveyor belt comprises a grid configured to be completely or substantially permeable to water. The conveyor belt is preferably a grid, for example a perforated grid, preferably a solid grid or screen, preferably made of metal. This provides a wide space for water sprayed from the spray nozzles to easily pass (under gravity) through the conveyor belt. Thus, when the device is in use, contact between the sprayed water and the extrudate strands preferably represents contact between the water sprayed through the water outlet arms (rather than converging water) because there is substantially no water convergence or accumulation on the conveyor belt surface. It should also be appreciated that during air cooling, because the conveyor belt has a large number of air gaps within its surface, air is able to reach the extrudate underside via holes in the conveyor belt, thereby providing uniform and even air cooling.

Preferably, the conveyor belt comprises more than one conveyor belt, preferably about 2 to about 4 conveyor belts, preferably about 2 conveyor belts. It will be appreciated that more than one conveyor belt may be used due to the distance the extrudate is to be conveyed.

Furthermore, the device of the utility model is particularly suitable for use with polymers having high thermal stability, such as polyetheretherketone polymers (PEEK polymers). This is because water cooling can be applied later than is typically possible in known systems (i.e., where water cooling is sometimes applied immediately to prevent thermal degradation) because polymers, such as PEEK, have high thermal stability even at temperatures significantly above the glass transition temperature of the polymer. Thus, unlike known devices, which are often configured to apply rapid cooling to the hot extrudate as early as possible in an attempt to inhibit thermal degradation, the devices of the present utility model are formulated. It is advantageous to allow a milder air cooling of the PEEK as a first cooling stage, which produces a stable extrudate with a more uniform crystal structure prior to the more rapid water cooling stage.

Preferably, the PEEK polymer has a repeat unit of formula I:

-O-Ph-O-Ph-CO-Ph-

wherein Ph represents a phenylene moiety. In this embodiment, all phenylene groups are 1, 3-and/or 1, 4-substituted to the adjacent ether and/or carbonyl groups.

It will be appreciated that the water sprayed from the device according to the first aspect preferably contacts the entire upper surface of the extrudate and also contacts the sides and part of the bottom side of the extrudate.

The arrangement of the first and second water outlet arms on the device of the present utility model provides further cooling efficiency because three different cooling mechanisms are established when the device is in use: i) Rapid cooling by contact with water, ii) cooling provided by evaporation of water, and iii) cooling by contact with air alone. Furthermore, the combination of cooling mechanisms provides an accurately controllable cooling rate that allows for consistent (and long periods of time, e.g., about 3 hours to about 6 hours) control of the temperature of the extrudate.

Preferably, the water cooling stage comprises a first intermediate air cooling stage located between the first water jet and the second water jet. This provides greater control over cooling and enhances cooling via evaporation.

Examples

FIG. 1 is a schematic diagram illustrating a side view of a water-cooled thermoplastic extrusion device 100 according to aspects of the present disclosure.

The apparatus 100: an extruder 102 comprising an extruder 104 producing the illustrated extrudate; an extrusion die 103 through which an extrudate is formed; a conveyor 106 for transporting the extrudate 104 and configured to be driven by the conveyor rotor 105; two outlet arms 108a, 108b; and a granulator 110. The individual spray nozzles on the water arms 108a, 108b are not shown here. Also shown are first and second water sprays 107a, 107b, the first and second water sprays 107a, 107b will spray the surface of the conveyor belt when the apparatus is in use. The apparatus is configured such that the extrudate travels in a direction from the extruder 102 to the pelletizer 110. Preferably, the speed at which the extrudate exits the extruder matches or substantially matches the speed at which the conveyor belt conveys the extrudate.

Also shown is the angle 109 at which the water spray is directed towards the conveyor belt surface. The angle of inclination between the first and preferably the second water outlet arms is between about 40 and about 80 degrees, preferably between about 50 and about 70 degrees, more preferably about 60 degrees. It can be seen that the water spray is directed in the direction of travel of the conveyor belt, i.e. away from the extruder. As described above, the angle 109 is defined between i) the direction of water flow exiting the outlet arm and ii) the plane of the belt surface.

Fig. 1 also shows distances D1 to D4, which represent the following:

-D1: a horizontal distance between the extrusion die outlet and the position of the first water outlet arm 108 a;

-D2: a horizontal distance between the first water outlet arm and the second water outlet arm;

-D3: the horizontal distance between the second water outlet arm and the inlet of the granulator;

-D4: the vertical distance between the conveyor belt surface and the positions of the first and second water outlet arms. Thus, preferably, both the first and second water outlet arms are positioned at the same height above the conveyor belt.

It will be understood that the term "horizontal" or "transverse" means horizontal in the frame of reference of the figure and, more generally, aligned with the plane of the surface of the conveyor belt, e.g., the direction of travel of the conveyor belt. It will be appreciated that horizontal and transverse are generally used interchangeably and both represent the directions shown as D1, D2 and D3 in fig. 1.

D _{Conveyor belt} Represents the horizontal length of the conveyor belt, which is substantially equal to the sum of the distances D1 to D3.

In some embodiments, D1 is between about 50 to about 65cm. In the results illustrated in Table 1 below, D1 is 50cm.

D2 may vary between about 20cm, 40cm, 60cm or 80cm. D3 is preferably between about 9m to about 13m, preferably between about 10m to about 12m.

D _{Conveyor belt} Preferably between about 10m and about 14m, more preferably about 11m to 13m. In the results illustrated in Table 1 below, D _{Conveyor belt} 12.5m. In some embodiments, there is a small gap between the end of the conveyor belt (i.e., the right hand side in fig. 1) and the pelletizer inlet. However, the lateral spacing between the extrusion die and the pelletizer inlet is still typically about 10m to about 14m.

The height of the outlet arms 108a, 108b is preferably between about 18cm to about 25cm, preferably 20cm to about 25cm, preferably about 20cm to about 22cm, more preferably about 22cm. The angle 109 of the water flow produced by the outlet arm may vary between about 40 degrees and about 80 degrees, but is preferably about 60 degrees.

Although not explicitly labeled in fig. 1, it is preferred that the lateral spacing between the extrusion die outlet and the point at which the water 107a ejected from the first water outlet arm 108a first contacts the extrudate strands in use is in the range of about 60 to about 75 cm. In other words, the point at which the water is configured to contact the extrudate is preferably about 10cm farther in the direction of belt travel than D1 (the position of the first outlet 108a relative to the extrusion die 103).

The extrusion die preferably has about 4 to about 10 holes, i.e. the holes are configured to produce respective 4 to 10 strands of extrudate. Preferably, the die orifice is in the range of about 2mm to about 7mm, and preferably about 4mm.

In some embodiments, the output of extrudate from the extruder is from about 50 kg/hour to about 150 kg/hour, or more preferably from about 75 kg/hour to about 125 kg/hour. In the results illustrated in table 1 below, 10 strands of extrudate were produced from a die having 10 holes. In this example, the extrudate throughput was about 110 kg/hr. The die holes in the examples of table 1 had a diameter of about 4mm, resulting in extrudate strands having a diameter of about 4mm immediately after extrusion.

The speed of the conveyor belt 106 may vary between about 10 m/min to about 40 m/min (consistent with the rate at which the extruder extrudes the extrudate) when the apparatus is in use. Preferably, the speed of the conveyor belt is about 20 m/min to 30 m/min. In the results illustrated in Table 1 below, the conveyor belt speed was about 24 m/min.

FIG. 2 illustrates a schematic diagram of a plan view of the water-cooled thermoplastic extrusion device shown in FIG. 1 and in accordance with aspects of the present disclosure. In the illustrated embodiment, the extruder die has 10 holes, thus producing 10 strands of extrudate 104. Fig. 2 further illustrates a water feed 200 configured to provide water to both of the water outlet arms 108a, 108 b.

Each water outlet arm in the device is arranged on the surface of the conveyor belt. Thus, preferably, each water outlet arm is configured to extend in a direction substantially perpendicular to the direction of travel of the conveyor belt across the width of the conveyor belt, as shown in fig. 2. Each water outlet arm preferably contains 2 to 6 spray nozzles, wherein each spray nozzle produces its own respective water flow. It will be appreciated that in this disclosure, any reference to "first/second water jet" or "water jet" means the overall water output from each of the water outlet arms. For example, the first water jet represents the total water output from 2 to 4 nozzles contained on the first water outlet arm.

As shown in fig. 2, each of the water outlet arms 108a, 108b produces two respective streams 107a and 107b of water. Thus, each of the water outlet arms 108a, 108b in fig. 2 contains two spray nozzles. For each of the water outlet arms, the two water streams are substantially fan-shaped, wherein the fan-shaped orientation is such that the water spray extends across the width of the conveyor belt. Thus, the two spray nozzles are configured so that they produce a spray of water that completely covers the conveyor belt bandwidth range, thereby providing cooling water to all extrudate strands. Preferably, two spray nozzles are provided on each water outlet arm so that the two water streams meet and/or overlap each other partway along the width of the conveyor belt. As shown in fig. 2, each of the two water sprays 107a generated by the first water outlet arm 108a provides coverage of 5 strands of extrudate, respectively. The same is true for the two streams 107b generated by the second outlet arm 108 b.

Furthermore, fig. 2 shows the result of the inclination angle of the spray nozzle orientation; i.e. they are oriented in the direction of travel of the conveyor belt so that, in use, the water sprayed from the nozzles contacts the extrudate at a position further along the direction of travel of the conveyor belt than the position of the water outlet arms 108a, 108 b.

Fig. 3 shows the same apparatus and schematic as in fig. 2 in plan view, but without extrudate and water spray. Thus, fig. 3 shows an apparatus according to the first aspect of the present disclosure when not in use.

Fig. 4 is a schematic view of a water spraying device used as a part of the cooling apparatus shown in fig. 1 to 3. Thus, fig. 4 illustrates the embodiment of the water outlet arms 108a and 108 shown in fig. 1 and 2, and a water feed 200 configured to provide water to the water outlet arms 108a, 108 b. The embodiment of fig. 4 also shows that each of the outlet arms 108a, 108b contains 6 spray nozzles 300, 302. In accordance with fig. 2, only two spray nozzles 300 are "on", i.e. configured such that they produce respective sprays of water. The remaining spray nozzles are closed spray nozzles 302. However, in an embodiment, 2 to 6 spray nozzles may be opened on each water outlet arm.

The injection nozzle is preferably a hydraulic/pressure operated nozzle. Water outlet arms each nozzle of each water outlet arm is configured to output about 3L/hr to about 12L/hr of water, more preferably about 4L/hr to about 8L/hr of water. The nozzles are each configured to output a generally fan-shaped stream of water, with the plane of the fan extending across the width of the conveyor belt, so that the stream of water ejected from each nozzle is arranged to cover all of the strands evenly. Thus, the fan-shaped water flow from the combined two nozzles covered all 10 strands of extrudate evenly across the width of the conveyor belt. The flow produced by the nozzle may be substantially continuous, i.e. have a laminar flow, or may be a dense mist/spray formed from droplets.

Although not shown, each spray nozzle 300, 302 preferably contains an elongated orifice oriented along the width of the conveyor belt. Thus, in use, the elongated apertures are configured to provide a fan-shaped water flow (as shown in fig. 2) generated through each nozzle.

Examples 1 to 3

The following experiments were performed only to illustrate the advantages of the device according to the first aspect.

As provided in Table 1 below, the following referencesExamples 1 to 3 were prepared: the conveyor belt speed was 24m/min, and the three water outlet arms were positioned 40cm to 80cm apart, wherein the spacing corresponds to D2. Conveyor belt length (D) _{Conveyor belt} ) About 12.5m. The extruder die diameter was 4mm and 10 die holes were used to produce 10 strands of extrudate. Each water outlet arm is equipped with two spray nozzles, each of which produces a water flow (in a conventional fan) at a rate of 6L/hour (equivalent to 100 mL/min). The height of the jet outlet above the surface of the conveyor belt was 22cm. The angle of the nozzles (as defined above) relative to the plane of the conveyor belt is about 60 degrees, with the water jet directed in/at an angle to the direction of travel of the conveyor belt (i.e. towards the granulator).

The polymer type used in examples 1 to 3 was PEEK 450G903, which contains a carbon black additive. The glass transition temperature of this PEEK is about 143 ℃. No other fillers or additives are used. The extruder is a twin-screw co-rotating meshing mixing extruder.

The variables in the three examples of table 1 are the spacing between the outlet arms (D2) and the spacing between the extrusion die outlet and the first outlet arm position (D1).

The conveyor belt comprises a solid metal mesh with large gaps, providing sufficient space (under the force of gravity) for the sprayed water to pass through the conveyor belt. In other words, the conveyor belt is a moving grid with coarse gaps. Thus, contact with water means contact with water sprayed from the outlet, as there is substantially no water pooling or collecting on the surface of the conveyor belt.

TABLE 1

The extrudate temperature in the fourth column of table 1 represents the temperature measured immediately prior to pelletization. This range represents the highest and lowest temperatures recorded throughout the experiment.

References to "off-spec" batches mean that any batch of pellets contains more than three "too long" and/or "undersized" pellets. A batch of 250g pellets, one of which had a mass of about 0.03g. Individual pellets may also be "off-spec", where off-spec pellets are either "too long" or "undersized". For each example, the number of "too long" and "undersize" pellets was calculated, and therefore, for any count greater than three, the batch was considered to be unacceptable. "too long" can be obtained from a batch by sieving. The size of an "excessively long" off-spec pellet is defined as any pellet having a length greater than 2.0 mm. The size of an "undersized" off-spec pellet is defined as any pellet having a width of less than 1.0 mm.

Surface defects refer to visual defects. Slight defects are those which have little effect on the quality of the pellets. Serious defects mean any defect that significantly alters the cylindrical appearance of the pellet or that represents a gouge or macro dent on the surface and/or any defect that results in a significant (e.g., more than 2%) reduction relative to the average mass of the pellet.

Based on the above table, the inventors determined that it would be advantageous to turn on 2 water spraying devices, wherein D1 should be at least 50cm and from about 50cm to about 65cm. As shown, all examples produced a compliant batch (i.e., no off-specification pellets were produced at all). The cooling conditions imparted by having two water outlet arms thus result in extrudates that can be cut horizontally by the pelletizer with very high consistency and thus result in pellets of high quality (i.e., very few defects) and uniform size. In particular, it is advantageous that the two water sprays provide that the extrudate temperature be kept below 130 ℃, so that extrudates too close to the glass transition temperature (i.e., within about 5 degrees to about 10 degrees of the glass transition temperature) are soft and therefore prone to producing long pellets when cut by a pelletizer.

The results in table 1 show that for the first outflow arm it would be further advantageous to be about 50cm from the extrusion die, i.e. d1=50 cm. For example, comparative examples 2 and 3 both used the same total volume of water and therefore both use resulted in the same total contact time between the sprayed water and the extrudate. However, in example 3, water cooling was started at a subsequent point (90 cm from the die outlet), which resulted in an extrudate with a temperature range 3 degrees (115 to 130 ℃) higher than that in example 2 (112 to 127 ℃). Accordingly, the present inventors determined that the water cooling was started earlier (e.g., using the water spraying device 1, as in example 2) had a better cooling effect, which was not only more water-saving and more energy-saving, but also resulted in fewer surface defects. As shown in table 1, example 2 (which had a first water flow 50cm from the die outlet) resulted in 12 severe defects, as compared to 17 severe defects in example 3.

Test 1 produced the best quality pellets with two water outlet arms positioned 50cm and 90cm from the die outlet, respectively (i.e., d1=50 cm and d2=40 cm). This example resulted in the creation of minimal defects (zero severe defects and 8 minor defects) and an extrudate with a temperature in the range of 115 to 125 ℃. This range is advantageous because it is sufficiently lower than the glass transition temperature so that the extrudate hardens slightly and can effectively cut the extrudate without scarring the pellets, but not too lower than the glass transition temperature so that the pelletizer blades become worn and the extrudate is too brittle causing it to crumble and produce undersized or long pellets.

Thus, surprisingly, good results are obtained when d1=50 cm and d2=40 cm. In other words, when d1=50 cm, d2=40 cm is preferable instead of 80cm. This is observed by comparing examples 1 and 2: the pellets produced by example 1 had zero severe defects (and only 8 minor defects), whereas the pellets in example 2 contained 12 severe defects. The temperature range of example 1 is advantageously narrower (115-125 ℃) than the broader range of example 2 (112-127 ℃). Thus, the extrudate temperature is preferably maintained within a narrow range, for example, 28 degrees to 18 degrees below the glass transition temperature of the PEEK polymer, and even more preferably 21 to 25 degrees below the glass transition temperature of the PEEK polymer.

Thus, the results indicate that the most advantageous device configuration uses exactly two water outlet arms, with the water outlet arm locations selected (e.g., relatively close to the extruder to provide greater cooling effect and without overcooling the extrudate) to produce pellets with high quality and consistency. Other PEEK types and compositions, i.e., PEEK other than PEEK 450G903 containing carbon black used in examples 1-3, may be applied in a manner corresponding to the cooling conditions described above, thereby producing high quality pellets in the same manner.

In this specification, embodiments have been described in a manner that enables a clear and concise description to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the utility model. For example, it should be understood that all of the preferred features described herein apply to all aspects of the utility model described herein and vice versa. For example, all preferred features of the composite are applicable to all aspects of the present utility model.

Reference to glass transition temperature in this disclosure refers to glass transition temperature measured according to ISO 11357 test standard.

In this specification, unless explicitly stated otherwise, the term "about" means plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%. For example, a distance of "about 50cm" should be understood to include a distance between 45cm and 55 cm.

In the present specification, the term "substantially" means a deviation of plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%.

In this specification, reference to "substantially" includes reference to "completely" and/or "exactly". That is, where the term substantially is included, it should be understood that this also includes references to specific sentences that do not contain the term "substantially".

In this specification, reference to an event "immediately before" or "immediately after" includes the meaning of "at the instant when the event" begins "or" at the instant when it "ends". References to "immediately" also include times before or after an event, e.g., up to 1 second after or before an event. Reference to "next to" in terms of distance and location includes reference to a distance from an object or location that is within 5cm or even within 1 cm.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present utility model and without diminishing its attendant advantages. It is therefore intended that the following claims cover such changes and modifications.

Claims

1. A water-cooled thermoplastic extrusion apparatus for producing thermoplastic pellets, said apparatus comprising:

wherein the apparatus is configured such that:

a lateral spacing between the outlet of the extrusion die and the first water outlet arm is in the range of about 50cm to about 65cm; and

the at least one spray nozzle of each of the first and second water outlet arms is each independently oriented in the direction of travel of the conveyor belt at an oblique angle of about 40 degrees to about 80 degrees relative to the plane of the conveyor belt.

2. The water-cooled thermoplastic extrusion apparatus of claim 1, wherein a vertical separation between the surface of the conveyor belt and the first water outlet arm is between about 18cm and about 25 cm; and/or a vertical spacing between a surface of the conveyor belt and the second water outlet arm is between about 18cm and about 25 cm.

3. The water-cooled thermoplastic extrusion apparatus of claim 1, wherein the lateral spacing between the extrusion die and the pelletizer inlet is from about 10m to about 14m.

4. The water-cooled thermoplastic extrusion device of claim 1, wherein the at least one spray nozzle of each of the first and second water outlet arms are each independently oriented in the direction of travel of the conveyor belt at an oblique angle of about 50 degrees to about 70 degrees relative to the plane of the conveyor belt.

5. The water-cooled thermoplastic extrusion apparatus of claim 1, wherein the at least one spray nozzle of each of the first and second water outlet arms is oriented in the direction of travel of the conveyor belt at an oblique angle of about 60 degrees relative to the plane of the conveyor belt.

6. The water-cooled thermoplastic extrusion device of claim 1, wherein a lateral spacing between the outlet of the extrusion die and a point at which water generated from the at least one spray nozzle of the first water outlet arm, in use, first contacts the thermoplastic extrudate strands is in a range of about 60cm to about 75 cm.

7. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein a lateral spacing between the first and second water outlet arms is in a range of about 20cm to about 80cm.

8. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein a lateral spacing between the first and second water outlet arms is in a range of about 30cm to about 50cm.

9. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein the lateral spacing between the second water outlet arm and the pelletizer inlet is about 9m to about 13m.

10. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein the lateral spacing between the second water outlet arm and the pelletizer inlet is about 10m to about 12m.

11. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein each of the at least one spray nozzle comprises an elongated aperture oriented along the width of the conveyor belt such that, in use, the spray nozzles are configured to produce a substantially fan-shaped spray of water.

12. The water-cooled thermoplastic extrusion apparatus of claim 11, wherein the fan-shaped water spray contacts substantially the entire width of the conveyor belt.

13. The water-cooled thermoplastic extrusion apparatus of any one of claims 1 to 6, wherein the extruder is a twin screw extruder.

14. The water-cooled thermoplastic extrusion apparatus of any one of claims 1 to 6, wherein the extruder is a twin screw co-rotating intermeshing compounding extruder.

15. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein each of the first and second water outlet arms comprises two spray nozzles.

16. The water-cooled thermoplastic extrusion apparatus of any of claims 1 to 6, wherein the conveyor belt comprises a grid configured to be completely permeable to water.