CN107351354B

CN107351354B - Tube extruding machine head of three-layer plastic composite tube with middle layer fiber oriented along circumferential direction

Info

Publication number: CN107351354B
Application number: CN201710557555.XA
Authority: CN
Inventors: 申开智; 李白千; 张�杰; 彭晓翊; 王军; 金季靖
Original assignee: Sichuan University; Rifeng Enterprise Group Co Ltd
Current assignee: Sichuan University; Rifeng Enterprise Group Co Ltd
Priority date: 2017-07-10
Filing date: 2017-07-10
Publication date: 2023-07-04
Anticipated expiration: 2037-07-10
Also published as: CN107351354A

Abstract

The invention discloses a pipe extruding machine head of a three-layer plastic composite pipe with middle layer fibers oriented along the circumferential direction, which comprises a machine head neck, a core rod bracket, a material distributing ring, a rear machine head body, a front machine head body, a mouth die, a pressing block, a core rod, a rotary sleeve, a transmission mechanism and a motor, wherein one end of the core rod is connected with the core rod bracket for supporting, and the rotary sleeve is movably fixed in the cavities of the rear machine head body and the front machine head body by a bearing and is coaxially positioned outside the core rod. Because the rotating sleeve with adjustable rotating speed is arranged in the pipe extruding machine head, the pipe blank formed by compounding the fiber reinforced middle layer and the pure material inner layer is subjected to strong shearing along the circumferential direction, and the reinforced fiber and part of macromolecular chains are gradually changed from the original axial orientation to the orientation along the circumferential direction, so that the circumferential strength of the pipe is obviously improved, and the blank of the processing equipment which is not provided with the fiber reinforced three-layer coextrusion structure pipe capable of being extruded and processed along the circumferential orientation at present is filled.

Description

Tube extruding machine head of three-layer plastic composite tube with middle layer fiber oriented along circumferential direction

The invention belongs to the technical field of high polymer material processing devices, relates to a special multilayer composite pipe extrusion die in a pipe extrusion forming die, and particularly relates to a pipe extrusion machine head for preparing a three-layer plastic composite pipe with middle layer fibers oriented along the circumferential direction. The extruder head is characterized in that the inner layer and the outer layer of the extruded three-layer composite tube are made of pure plastics, the middle layer is made of fiber reinforced plastics, and the reinforced fibers of the middle layer can be distributed and oriented along the circumferential direction. The machine head can improve the pressure-bearing strength and the service life of the extruded pipe under the condition that the raw materials are unchanged, or reduce the wall thickness of the pipe and save the raw materials on the premise of maintaining the strength and the service life unchanged.

Background

The existing single-layer glass fiber reinforced pipe is easy to expose glass fibers and hair on the surface, so that the surface quality is poor, and larger resistance is brought to fluid transportation. In order to solve the problems of single-layer glass fiber reinforced pipes, the urban construction industry standard of the people's republic of China is issued by the construction department: a fiber reinforced random copolymer polypropylene composite pipe (CJ/T258-2007) is defined as a composite pipe with a three-layer coextrusion structure, wherein the inner layer and the outer layer are made of random copolymer polypropylene (PP-R) materials, and the middle layer is made of glass fiber reinforced PP-R composite materials. Because the inner surface and the outer surface of the fiber reinforced plastic interlayer of the pipe are covered by the pure material layer, the phenomenon that glass fibers on the inner surface and the outer surface of the pipe are exposed and the surface is not smooth can be avoided. However, the glass fiber reinforcement effect of the middle layer of the pipe is poor, and the aim of obviously improving the bearing strength of the pipe is not achieved. The reason is that the reinforced glass fibers and the polymer chains are axially oriented along the extrusion flow direction, namely the pipe, in the extrusion molding process, so that the axial strength of the pipe wall is improved, but the circumferential strength of the pipe wall is not obviously improved. According to the stress analysis of the internal pressure thin-wall pipe, the circumferential stress of the pipe wall is about twice of the axial stress, namely the direction of the worst strength of the pipe wall is exactly the direction of the greatest stress. Therefore, the fiber reinforcement effect of the existing three-layer co-extrusion structure composite pipe made of the glass fiber reinforced PP-R composite material can not be fully exerted in the practical use.

As a currently reported co-extrusion machine head design (Zhang Youxin, mould industry 1996, no.10. Total 188) capable of preparing the three-layer plastic pipe, a mould design for co-extruding the three-layer plastic pipe machine head through two extruders is introduced, the machine head considers the advantages and disadvantages of a straight-through type and right-angle type pipe extrusion machine head, and the main parts comprise a herringbone runner connector, a split sleeve with a separation layer, a bracket with a damping splitter and a core rod. The machine head can convey the same or different types of resin which are plasticized and extruded by the two extruders into the runners distributed by the machine head respectively, and the three layers of plastic pipes are obtained by compounding the resin in front of the inner die of the machine head after the resin is uniformly distributed along the circumference of the runner. However, the extruder head is limited in design structure, and when the extruder head is used for extrusion preparation of the fiber reinforced random copolymer polypropylene three-layer composite pipe, the flow direction of the middle layer reinforced fiber and the polymer macromolecular chain cannot be changed, so that only the pipe oriented along the extrusion flow direction, namely the axial direction, can be prepared.

Disclosure of Invention

The invention aims at overcoming the defects and shortcomings in the prior art, and provides a pipe extruding machine head for preparing a three-layer plastic composite pipe with middle layer fibers oriented along the circumferential direction.

The invention provides a pipe extruding machine head for preparing a three-layer plastic composite pipe with middle layer fibers oriented along the circumferential direction, which is characterized by comprising a machine head and neck, a core rod bracket, a material distributing ring, a rear machine head body, a front machine head body, a mouth die, a pressing block, a core rod, a rotating sleeve, a transmission mechanism and a motor, wherein the machine head and neck, the core rod bracket, the material distributing ring, the rear machine head body, the front machine head body, the mouth die and the pressing block are horizontally connected into a whole by connecting pieces in sequence; one end of the core rod is connected with the core rod bracket and supported, and the cantilever is positioned in a cavity formed by the material distributing ring, the rear machine head body, the front machine head body and the mouth die which are connected in sequence; the rotary sleeve is movably and fixedly arranged in the cavity of the connecting section of the rear machine head body and the front machine head body by a bearing, and keeps a certain gap to be coaxially arranged outside the core rod; the transmission mechanism consists of two chain wheels and two chains, one chain wheel is fixedly connected outside the rotary sleeve of the pipe extruding machine head, the other chain wheel is fixedly connected to the output shaft of the motor, and the chain passes through a hole groove formed in one side of the machine head body II at the joint of the machine head body I and is connected with the two chain wheels.

The inner wall of the rotary sleeve in the pipe extruding machine head can be provided with raised ribs, and the raised ribs can be not arranged, but at least 2 raised ribs are preferably arranged, and are uniformly distributed along the circumferential direction of the rotary sleeve so as to increase the circumferential shearing effect applied to the plastic melt when the rotary sleeve rotates. The length of the raised ribs can be equal to the length of the rotary sleeve or can be slightly shorter, if the length is slightly shorter, the raised ribs are biased towards the inlet end of the rotary sleeve.

The motor in the pipe extruding machine head is a speed regulating motor, and the rotating speed of the motor can be steplessly regulated between 0 and 150 revolutions per minute so as to change the orientation direction and the orientation degree of the reinforced fiber and macromolecules of the pipe.

The pipe extruding machine head further comprises two guiding joints, one guiding joint is connected to the feeding hole of the material distributing ring, and the other guiding joint is connected to the feeding hole on one side of the machine head body II.

When the extruder head is used, a part of molten plastic pure material enters the outer surface of a core rod through a material guiding joint connected with a material distributing ring, is uniformly distributed to serve as an inner layer melt of an extruded pipe through an annular flow passage of the material distributing ring, meanwhile, molten glass fiber reinforced material enters the head and neck of the extruder and is split by a split cone of a core rod bracket, and sequentially passes through the core rod bracket, the material distributing ring and an annular flow passage arranged in a rear extruder head body to be coated outside the melt of the inner layer plastic pure material; when the double-layer tube blank runs to the second half section of the machine head body II under the pushing of extrusion pressure, molten plastic pure material entering from a material guiding joint at one side of the machine head body II overflows gradually along the axial direction when flowing in a spiral groove of a spiral distributor, uniformly distributes on the circumference, coats the oriented tube blank to form an outer-layer tube blank, and is compounded with the oriented tube blank under the pressure to form a three-layer tube blank, and then the three-layer tube blank is extruded after the tube wall thickness is regulated by a mouth die. The extruded tube blank is cooled and shaped by a vacuum sizing cooling water tank under the powerful traction of a tube tractor, and is cut into finished tubes with certain length by a tube cutting machine.

Compared with the prior art, the invention has the following positive effects:

1. because the rotating sleeve with adjustable rotating speed is arranged in the pipe extruding machine head, the rotating sleeve is coaxial with the machine head core rod, when the pipe blank compounded by the fiber reinforced middle layer and the pure material inner layer enters between the core rod and the rotating sleeve, the pipe blank is subjected to strong shearing along the circumferential direction, thus the original axial orientation of reinforcing fibers and part of macromolecular chains in the extruded pipe is changed, and the pipe blank is gradually changed into the orientation along the circumferential direction along with the increase of the rotating speed, so that the circumferential strength of the obtained pipe with the maximum stress is obviously improved when the pipe is subjected to internal pressure.

2. The invention further provides the raised ribs which are uniformly distributed along the axial direction of the rotary sleeve on the inner wall of the rotary sleeve in the pipe extruding machine head, so that the circumferential shearing effect applied to the fiber and the plastic melt during the rotation of the rotary sleeve can be further enhanced, and the circumferential strength of the obtained pipe is ensured to be greatly improved.

3. The design of the pipe extruding machine head provided by the invention adopts a mode of gradually compounding three layers of molten materials, namely, a middle layer fiber reinforced plastic melt and an inner layer pure plastic melt are compounded in a first section of a post machine head body to form a double-layer pipe blank, then fiber and partial macromolecules are oriented to form a double-layer oriented pipe blank in a second section, and the outer layer pure plastic melt and the oriented pipe blank are compounded in a third section to form a final three-layer pipe blank, and the compounding process is carried out under high pressure in the machine head, so that the bonding fastness between layers is ensured.

4. The pipe extruding machine head provided by the invention can extrude and process the pipe with the three-layer co-extrusion structure of the fiber reinforced composite material with the fiber and the plastic capable of being oriented along the circumferential direction, so that the defect of the existing three-layer composite pipe oriented along the axial direction is overcome, and the blank that no processing equipment capable of extruding and processing the pipe with the fiber reinforced three-layer co-extrusion structure capable of being oriented along the circumferential direction exists at present is filled.

5. Because the motor adopted in the pipe extruding machine head is an stepless speed regulating motor, the rotating speed of the rotary sleeve can be regulated between 0 and 150 revolutions per minute, and thus, three-layer composite pipes with different circumferential orientation degrees and orientation directions can be processed and prepared.

Drawings

Fig. 1 is a schematic cross-sectional view of a front view of a tube extruding machine head provided by the invention.

Fig. 2 is a schematic cross-sectional view of a front view of a rotary sleeve in a tube extruder head according to the present invention.

FIG. 3 is a schematic cross-sectional side view of a rotating sleeve in a tube extruder head according to the present invention.

In the figure, the head and neck of the machine, the core rod support, the 3-guiding joint, the 4-distributing ring, the 5-rear machine head body, the 6-bearing, the 7-rotating sleeve, the 8-chain wheel, the 9-screw, the 10-front machine head body, the 11-pressing block, the 12-screw, the 13-die, the 14-adjusting screw, the 15-core rod, the 16-guiding joint, the 17-pin, the 18-screw, the 19-chain, the 20-motor and the 21-raised rib are arranged.

Fig. 4 is a polarized light microscopic photograph of a longitudinal and transverse section slice of a composite pipe prepared by extrusion at a rotation speed of 30 rpm of a rotating sleeve in a pipe extruder head (namely application example 2), wherein the photograph is taken in the circumferential direction on the left side and the photograph is taken in the axial direction on the right side. It is clear from the photograph that the middle layer glass fiber of the pipe is obviously oriented along the circumferential direction.

Fig. 5 is a polarized light microscopic photograph of a cross section slice of a common composite pipe prepared by extrusion in the pipe extruder head provided by the invention, wherein the rotating speed of the rotating sleeve is 0 rpm (namely, comparative example 1 is applied), the left side is a photograph in the circumferential direction, and the right side is a photograph in the axial direction. It is clear from the photograph that the glass fibers of the tubing are oriented in the axial direction.

FIG. 6 is a photograph of wide angle X-ray diffraction of the circumferential direction of a composite pipe prepared by extrusion at a rotational speed of 30 rpm of a rotating sleeve in a pipe extruder head (i.e., application example 2). It is clear from the photograph that the Debye ring appears as an arc, indicating that in the spin extruded tube the PPR crystals and macromolecular chains are significantly oriented in the circumferential direction.

FIG. 7 is a photograph of wide angle X-ray diffraction of the circumferential direction of a composite pipe prepared by extrusion (i.e., comparative example 1) at a rotational speed of 0 rpm of a rotating sleeve in a pipe extruder head according to the present invention. From the photographs, a series of complete Debye rings are clearly observed, indicating that in conventional extruded tubing, the PPR crystals and macromolecular chains are not oriented in the circumferential direction.

Description of the embodiments

The extrusion apparatus provided by the present invention will be further described below by way of examples with reference to the accompanying drawings, but the examples given are not to be construed as limiting the scope of the present invention, and non-essential modifications and adaptations of the present invention based on the above-described teachings and design considerations should and are within the scope of the present invention.

Examples

As shown in fig. 1, the pipe extruding machine head provided by the embodiment is composed of a machine head and neck 1, a core rod bracket 2, a material distributing ring 4, a rear machine head body 5, a front machine head body 10, a mouth die 13, a pressing block 11, a core rod 15, a rotary sleeve 7, a transmission mechanism and a motor 20.

Wherein the head and neck 1, the core rod bracket 2, the material distributing ring 4, the rear machine head body 5, the front machine head body 10, the mouth die 13 and the pressing block 11 are horizontally connected into a whole by connecting pieces, namely

screws

9, 12 and 18 and pins 17. One end of the core rod 15 is tightly connected with the core rod bracket 2 by screw threads to support and cantilever the core rod in a cavity formed by the sequentially connected material distributing ring 4, the rear machine head body 5, the front machine head body 10 and the mouth die 13. The rotary sleeve 7 is movably fixed in the cavity of the connecting section of the rear machine head body 5 and the front machine head body 10 by the bearing 6, and keeps a certain gap to be coaxially positioned outside the core rod 15. In order to increase the circumferential shearing effect applied to the plastic melt when the rotating sleeve rotates, at least 2 raised ribs 21 are arranged on the inner wall of the rotating sleeve 7, and the 8 raised ribs 21 are uniformly distributed along the circumferential direction of the rotating sleeve 7, and the length of the raised ribs can be the same as or slightly shorter than that of the rotating sleeve, and all raised ribs are biased to the inlet end of the rotating sleeve, as shown in fig. 2 and 3. The eccentricity of the extruded tube is adjusted by adjusting the circumferential position of the die 13 by adjusting screws 14 located outside the press block 11. The pipe extruding machine head also comprises two guiding

connectors

3 and 16, wherein one guiding connector 3 is connected to the feeding port of the material distributing ring 4, and the other guiding connector 16 is connected to the feeding port on one side of the machine head body II 10. The transmission mechanism is composed of two chain wheels 8 and a chain 19, wherein one chain wheel 8 is fixedly connected with the outside of a rotary sleeve 7 of the pipe extruding machine head, the other chain wheel 8 is fixedly connected with an output shaft of a motor 20, the chain 19 penetrates through a hole groove formed in one side of a machine head body II 10 at the joint of the machine head body I5 to be connected with the two chain wheels 8, the motor of the embodiment adopts a stepless speed regulating motor, and the motor can be subjected to stepless regulation between 0-150 revolutions per minute.

Examples

As shown in fig. 1, the pipe extruding machine head provided by the embodiment is composed of a machine head and neck 1, a core rod bracket 2, a material distributing ring 4, a rear machine head body 5, a front machine head body 10, a mouth die 13, a pressing block 11, a core rod 15, a rotary sleeve, a 7 transmission mechanism and a motor 20. This embodiment is different from embodiment 1 in that the number of ribs 21 of the protrusions provided on the inner wall of the rotating sleeve is 2, and the rest is the same as embodiment 1, so that the description thereof will be omitted.

Application example 1

The tube extruding machine head provided by the embodiment 1 of the application is adopted, and the tube extruding machine head is processed and prepared under the condition that the rotating speed of a machine head rotating sleeve is 15 revolutions per minute, namely, the three-layer composite tube based on the random copolymerization polypropylene with the middle layer being glass fiber oriented along the circumferential direction, namely, the inner layer being a pure random copolymerization polypropylene layer, the middle layer being a glass fiber reinforced random copolymerization polypropylene layer, and the outer layer being a pure random copolymerization polypropylene layer. The outer diameter of the pipe is phi 75mm, the total thickness of the pipe wall is 6.8mm, the thickness of the inner layer pure random copolymer polypropylene layer is 2.3mm, the thickness of the middle layer glass fiber reinforced random copolymer polypropylene layer is 2.5mm, and the thickness of the outer layer pure random copolymer polypropylene layer is 2mm. The circumferential strength of the obtained three-layer composite pipe is 35.4MPa, the bursting pressure is 6.27 MPa, and the bursting pressure is respectively improved by 41.6 percent and 62.4 percent compared with the pipe of the application comparative example 1.

Application example 2

The application example is that the pipe extruding machine head provided by the embodiment 1 is adopted, and the random copolymerization polypropylene three-layer composite pipe based on the glass fiber orientation along the circumferential direction is processed and prepared under the condition that the rotating speed of the machine head rotating sleeve is 30 revolutions per minute, and the structure, the outer diameter, the total pipe wall thickness and the thickness of each layer are the same as those of the application example 1, so that the description is omitted. The circumferential strength of the obtained three-layer composite pipe is 36.3MPa, the bursting pressure is 6.73MPa, and the bursting pressure is respectively improved by 45.2 percent and 74.4 percent compared with the pipe of the application comparative example 1.

Application example 3

The application example is that the pipe extruding machine head provided by the embodiment 1 is adopted, and the random copolymerization polypropylene three-layer composite pipe based on the glass fiber orientation along the circumferential direction is processed and prepared under the condition that the rotating speed of the machine head rotating sleeve is 60 revolutions per minute, and the structure, the outer diameter, the total pipe wall thickness and the thickness of each layer are the same as those of the application example 1, so that the description is omitted. The obtained three-layer composite pipe has the tested circumferential strength of 39.44MPa and the bursting pressure of 7.4MPa, which are respectively improved by 57.8 percent and 91.7 percent compared with the pipe of the application comparative example 1.

Application example 4

The application example is a random copolymerization polypropylene three-layer composite pipe which is prepared by adopting the pipe extruding machine head provided by the invention example 1 and is based on the fact that the middle layer is glass fiber oriented along the circumferential direction under the condition that the rotating speed of the machine head rotating sleeve is 60 revolutions per minute. Unlike application example 1, the composite pipe of the application example has the outer diameter of phi 63 and the total thickness of the pipe wall of 5.8mm, wherein the thickness of the inner layer of pure random copolymer polypropylene layer is 2mm, the thickness of the middle layer of glass fiber reinforced random copolymer polypropylene layer is 2.1mm, and the thickness of the outer layer of pure random copolymer polypropylene layer is 1.7mm. The circumferential strength of the obtained three-layer composite pipe is 35.5MPa, the bursting pressure is 6.96MPa, and the bursting pressure is respectively improved by 46.6 percent and 86.1 percent compared with the pipe of the application comparative example 2.

Comparative example 1 was used

The comparative application example is also a pipe extruding machine head provided by the embodiment 1, but the middle layer is a random copolymerization polypropylene three-layer composite pipe which is prepared by processing under the condition that the rotating speed of a machine head rotating sleeve is 0 r/min and is based on the axial orientation of glass fiber, and the outer diameter, the total pipe wall thickness and the thickness of each layer of the glass fiber reinforced random copolymerization polypropylene three-layer composite pipe are the same as those of the application example 1, so that the description is omitted. The random copolymer polypropylene macromolecules and the reinforced glass fibers of the inner layer and the middle layer of the obtained three-layer composite pipe are not oriented along the circumferential direction; the test shows that the circumferential strength is 25MPa and the bursting pressure is 3.86MPa.

Comparative example 2 was used

The comparative application example is also a pipe extruding machine head provided in the embodiment 1 of the invention, but the middle layer is a random copolymerization polypropylene three-layer composite pipe which is prepared by processing under the condition that the rotating speed of a machine head rotating sleeve is 0 r/min and is based on the axial orientation of glass fiber, and the outer diameter, the total pipe wall thickness and the thickness of each layer of the glass fiber reinforced random copolymerization polypropylene three-layer composite pipe are the same as those of the application example 3, so that the description is omitted. The random copolymer polypropylene macromolecules and the reinforced glass fibers of the inner layer and the middle layer of the obtained three-layer composite pipe are not oriented along the circumferential direction; the test shows that the circumferential strength is 24.3MPa and the bursting pressure is 3.74MPa.

Claims

1. The pipe extruding machine head of the three-layer plastic composite pipe with the middle layer fiber oriented along the circumferential direction is characterized by comprising a machine head and neck (1), a core rod bracket (2), a distributing ring (4), a rear machine head body (5), a front machine head body (10), a mouth die (13), a pressing block (11), a core rod (15), a rotating sleeve (7), a transmission mechanism and a motor (20), wherein the machine head neck (1), the core rod bracket (2), the distributing ring (4), the rear machine head body (5), the front machine head body (10), the mouth die (13) and the pressing block (11) are horizontally connected into a whole by connecting pieces in sequence; one end of the core rod (15) is connected with the core rod bracket (2) to be supported and the cantilever is positioned in a cavity formed by the material distributing ring (4), the rear machine head body (5), the front machine head body (10) and the mouth die (13) which are connected in sequence; the rotary sleeve (7) is movably and fixedly arranged in the cavity of the connecting section of the rear machine head body (5) and the front machine head body (10) by the bearing (6), and is coaxially arranged outside the core rod (15) with a certain gap; the transmission mechanism consists of two chain wheels (8) and a chain (19), one chain wheel (8) is fixedly connected outside a rotary sleeve (7) of the pipe extruding machine head, the other chain wheel is fixedly connected on an output shaft of a motor (20), the chain (19) passes through a hole groove arranged on one side of a front machine head body (10) at the joint of the rear machine head body (5) to be connected with the two chain wheels (8),

at least 2 raised ribs (21) are arranged on the inner wall of the rotary sleeve (7), and the raised ribs (21) are uniformly distributed along the circumferential direction of the rotary sleeve (7).

2. The extrusion head of the three-layer plastic composite pipe with the middle layer fiber oriented along the circumferential direction according to claim 1, wherein the motor in the extrusion head is a speed regulating motor, and the rotating speed of the motor can be adjusted steplessly between 0 and 150 revolutions per minute.

3. Tube extrusion head of a three-layer plastic composite tube with middle layer fibers oriented along the circumferential direction according to claim 1 or 2, characterized in that the tube extrusion head further comprises two guiding joints (3, 16), wherein one guiding joint (3) is connected to the feed inlet of the distributing ring (4), and the other guiding joint (16) is connected to the feed inlet at one side of the front head body (10).