A method for continuously and efficiently preparing a spaced water-permeable rubber-plastic blended microporous permeation irrigation pipe by using multiple extruders

Abstract

A method for the continuous and efficient production of intermittently permeable rubber-plastic blend microporous irrigation pipes using multiple extruders belongs to the field of waste rubber recycling. This method utilizes a single-screw extruder for rubber-plastic blend masterbatch, a plastic-coated screw-plastic extruder or a single-screw extruder, a co-extrusion die head, a cooling water tank, a traction machine, and a winding machine. The rubber-plastic blend masterbatch is extruded into the co-extrusion die head through the single-screw extruder, while the plastic-coated screw-plastic extruder or the single-screw extruder extrudes the molten plastic into the co-extrusion die head. After forming in the co-extrusion die head, intermittently permeable rubber-plastic blend microporous irrigation pipes are formed. These pipes are then cooled and shaped in the cooling water tank and finally packaged by the traction machine and winding machine. This method solves the need for localized permeable irrigation during tree planting. This method has advantages such as continuous operation, high efficiency, low cost, good uniformity of permeable water in the intermittent permeable sections, enhanced mechanical properties, low odor, and anti-clogging properties.

Description

Technical fields:

[0001] This invention relates to a novel method for preparing intermittently permeable rubber-plastic blend microporous irrigation pipes, and more particularly to a method for preparing intermittently permeable rubber-plastic blend microporous irrigation pipes using multiple extruders, belonging to the fields of waste rubber recycling and water-saving agricultural irrigation. Background technology:

[0002] my country faces the dual challenges of being the world's largest producer of waste tires annually and having extremely limited per capita freshwater resources. Agricultural irrigation accounts for 50% of total water consumption, but the effective utilization coefficient of farmland irrigation water in my country is only 0.50. Therefore, the efficient and environmentally friendly utilization of waste tire rubber to solve the problem of water conservation in agricultural irrigation is of great significance. Rubber-plastic blended microporous drip irrigation pipes can be buried 20 to 60 centimeters underground. Compared with other irrigation facilities such as plastic drip irrigation pipes, they have advantages such as lower surface evaporation loss, better water-saving effect, and increased yield, showing promising development and application prospects.

[0003] In the cultivation and planting of fruit trees and forest trees, the spacing between trees generally ranges from 2 to 4 meters, depending on the canopy coverage of different types of mature trees. When irrigating these trees, water needs to be concentrated at the base of each tree, while areas away from the roots do not require watering. Currently, the main water-saving irrigation method for trees is the use of ground-level plastic drip irrigation pipes. The distance between two adjacent drippers can be customized according to the distance between two adjacent trees. However, this drip irrigation technology results in significant water loss through evaporation from the ground, and the plastic drip irrigation pipes are susceptible to aging due to ultraviolet radiation from sunlight, requiring frequent replacement. They are also easily damaged during mechanized farming.

[0004] The rubber-plastic blend microporous drip irrigation pipes produced by Ren Dongyun et al. (ZL201810798121.3) and all current methods for preparing rubber-plastic blend drip irrigation pipes have the characteristic of uniformly seeping water outward along the length of the pipe. However, these rubber-plastic blend microporous drip irrigation pipes cannot achieve the goal of irrigating only the roots of each tree while eliminating the need for water seepage in other areas. Therefore, using these pipes to irrigate trees results in a significant waste of water, and the tree roots do not receive sufficient water. The method for producing intermittent drip irrigation pipes by Sun Zhaojun et al. (CN108859050A, A Processing Technology for Intermittent Drip Irrigation Pipes with Water Outlet and Non-Water Outlet) presents two major challenges compared to the method of producing intermittent drip irrigation pipes in this invention: First, the continuous extrusion of different rubber-plastic composite melts of this type of drip irrigation pipe in the co-extrusion die head is intermittent, as they are extruded from two extruders respectively. This makes it difficult to ensure the reliability of the connection between the transition zones of the two rubber-plastic composite melts. Second, the two extruders continuously pause and circulate extrusion, which increases the difficulty of production operation.

[0005] The distance between adjacent seepage sections and the length of the seepage sections in the intermittent seepage rubber-plastic blend microporous irrigation pipe of this invention can be designed and manufactured according to different tree species, different spacing between two adjacent trees, and the required seepage volume. After the intermittent seepage rubber-plastic blend microporous irrigation pipe is buried 20 cm to 60 cm underground, the irrigation water required for each tree can be provided by the seepage section of this irrigation pipe near the tree roots. This irrigation pipe is buried underground and irrigates upwards, eliminating the water evaporation caused by surface drip irrigation; it does not age due to sunlight ultraviolet rays and can be used continuously for more than 10 years before replacement; mechanized cultivation can be carried out between trees without damaging the irrigation pipe; the soil moisture retention time after one irrigation is about three times that of surface drip irrigation, which is beneficial to the increase of fruit yield; through the monitoring and control of soil temperature and humidity sensors, the orchard ground can be kept dry all year round, reducing weed growth and thus reducing the labor costs of orchard management. Therefore, the drip irrigation pipe of this invention can be used for tree planting and cultivation, and has advantages such as better water saving, increased yield, facilitating mechanized farming, and reducing labor costs, and has good prospects for development and application.

[0006] This invention, based on the continuous extrusion of uniformly permeable rubber-plastic blend microporous injection pipes using a single-screw extruder of rubber-plastic blend masterbatch, adds a co-extrusion die head. A key technology of this invention involves using either a plastic-coated screw-plastic plunger extruder equipped with a melt storage tank and a plastic melt plunger, or a single-screw extruder equipped with a melt storage area and a reciprocating screw, to intermittently coat the surface of the rubber-plastic blend microporous injection pipe with a plastic film. Common single-screw extruders are used for continuous extrusion of plastic products. Plastic plunger extruders are typically used for intermittently injecting molten plastic into a mold, which is then cooled and shaped into a plastic product; the injection time is short, and the residence time is long. When producing intermittently permeable rubber-plastic blend microporous irrigation pipes using the equipment described in this invention, a single-screw extruder continuously extrudes uniformly permeable rubber-plastic blend microporous irrigation pipes from the rubber-plastic blend masterbatch. Then, one of the following extrusion techniques—a plastic-coated screw-plastic extruder or a single-screw extruder—extrudes a plastic film onto the surface of the uniformly permeable rubber-plastic blend microporous irrigation pipe through a co-extrusion die head. The extrusion coating time on the irrigation pipe surface is long, with short intermittent residence times; for example, after coating a length of 3.8 meters, the uncoated permeable section is 0.2 meters. The continuous extrusion of the rubber-plastic blend masterbatch by the single-screw extruder, followed by the sequential intermittent extrusion of the plastic-coated screw-plastic extruder or a single-screw extruder, allows for the production of intermittently permeable rubber-plastic blend microporous irrigation pipes. Therefore, it is necessary to technically modify the general-purpose single-screw extruder and plunger extruder by adapting their equipment structure and processing technology. For example, a single-screw extruder and a plunger extruder are connected in series. The single-screw extruder plasticizes and melts the plastic, continuously extruding it into the melt storage tank within the plunger extruder. When a plastic layer needs to be coated on the surface of the rubber-plastic permeation tube, a hydraulic drive unit drives the plastic melt plunger in the plunger extruder to force the melt from the storage tank into the co-extrusion head, coating the surface of the rubber-plastic blend microporous permeation tube within the co-extrusion tube die head. The hydraulic cylinder is adjusted to move the plunger in the melt storage tank, advancing, retracting, or pausing, based on the extrusion speed of the rubber-plastic permeation tube and the interval between plastic coating layers. Another example is a single-screw extruder with its barrel extended to 2 to 4 times its diameter, with the front cavity near the extruder die head serving as a plastic melt storage area. Driven by a hydraulic cylinder, the screw moves axially within the barrel; therefore, the screw not only plasticizes and melts the plastic and conveys it but also acts as a plunger. Plastic granules are fed into the inlet and plasticized and melted within a heated barrel by a rotating single screw. Simultaneously, the screw moves backward under the drive of a hydraulic cylinder, forming a melt storage zone within the barrel at the screw's tip. When a thin plastic layer needs to be coated onto the surface of the continuously extruded rubber-plastic permeable tube, the hydraulic cylinder drives the reciprocating single screw to extrude the molten plastic from the storage zone into the co-extrusion die head, where it is coated onto the surface of the rubber-plastic permeable tube. Depending on the amount of plastic required for the coating, the plasticizing process can be continuous or intermittent.The reciprocating motion of the hydraulic cylinder-driven screw is adjusted according to the extrusion speed of the rubber-plastic permeable pipe and the interval distance of the plastic coating layer. Through these corresponding technical modifications, this production equipment can fully meet the needs of producing intermittent permeable rubber-plastic blend microporous permeable irrigation pipes. Summary of the Invention:

[0007] The purpose of this invention is to overcome the limitations of current methods for preparing microporous drip irrigation pipes made from rubber and plastic blends, which cannot meet the needs of localized irrigation of trees.

[0008] The technical route of the equipment composition of this invention is as follows: a single-screw extruder is connected to the first inlet of the co-extrusion die head; another plastic-coated screw-plastic plunger extruder with a built-in storage cylinder and plastic melt plunger, or a single-screw plastic extruder with a built-in device for reciprocating screw movement and a front-end storage area, is connected to the second inlet of the co-extrusion die head. The outlet of the co-extrusion die head is connected to the drip irrigation pipe shaping device. The shaping device consists of a cooling water tank, a traction machine, and a packaging and winding machine. The plastic-coated screw-plastic plunger extruder consists of a plastic plasticizing single-screw extruder, a plastic melt storage cylinder, and a plastic melt plunger driven by a hydraulic drive device, wherein the hydraulic drive device is equipped with a reciprocating plastic melt plunger. The single-screw plastic extruder has a built-in melt storage area, a reciprocating single screw, and a hydraulic cylinder.

[0009] The objective of this invention is achieved through the following process: Rubber-plastic blend masterbatch is fed into a single-screw extruder, and uniformly permeable rubber-plastic blend microporous irrigation pipes are continuously extruded from the co-extrusion die head. Another plastic-coated screw-plastic piston extruder or a single-screw plastic extruder is connected to the co-extrusion die head, intermittently extruding the plasticized molten plastic into the co-extrusion die head, coating the surface of the uniformly permeable rubber-plastic blend microporous irrigation pipe inside the co-extrusion die head. The rubber-plastic blend microporous irrigation pipe extruded from the co-extrusion die head forms an intermittently permeable rubber-plastic blend microporous irrigation pipe. The barrel and co-extrusion die head temperatures of both extruders are between 120°C and 200°C. The material is extruded into pipes from the co-extrusion die head through both extruders, cooled to below 40°C in a cooling water tank for setting, and then passed through a traction machine and a packaging and winding machine to obtain the packaged intermittently permeable rubber-plastic blend microporous irrigation pipe.

[0010] The waste rubber powder used in the rubber-plastic blend masterbatch is one or more of the tread, sidewall, crown, and skin rubber powder of heavy-duty radial tires or passenger car tire rubber powder, with a weight ratio of 70% to 85%.

[0011] The plastic used in the rubber-plastic blend masterbatch is one or a mixture of polyethylene, high-density polyethylene, polypropylene, and high-density polypropylene, with a weight ratio of 10% to 25%.

[0012] The compatibilizer used in the rubber-plastic blend masterbatch is one or a mixture of ethylene-vinyl acetate copolymer, maleic anhydride grafted, saturated thermoplastic styrene-butadiene rubber, and glycidyl methacrylate grafted polypropylene, with a weight ratio of 5% to 15%.

[0013] The plastic used to coat the surface of the rubber-plastic blend microporous irrigation pipe is one of polyethylene, high-density polyethylene, polypropylene, high-density polypropylene, or ethylene-vinyl acetate copolymer.

[0014] The diameter of the single-screw extruder used should be 25mm to 90mm, and the length-to-diameter ratio should be 8:1 to 36:1.

[0015] The plastic-coated screw-plasticor extruder used is equipped with a melt storage cylinder and a hydraulically driven plastic melt plunger. The screw extruder plasticizes the plastic into a melt and extrudes it into the storage cylinder. The hydraulically driven plastic melt plunger intermittently drives the melt in the storage cylinder to extrude the melt into the co-extrusion die head.

[0016] The single-screw extruder used is equipped with a melt storage zone at the front end of the barrel and a hydraulic cylinder that drives the screw to reciprocate. The screw extruder plasticizes the plastic into a melt and extrudes it into the melt storage zone. The hydraulic drive intermittently pushes the screw to extrude the melt in the melt storage zone into the co-extrusion die head. The co-extrusion die head extrudes a shaped, intermittently permeable rubber-plastic blend microporous irrigation pipe.

[0017] This invention breaks with existing processes for preparing rubber-plastic blend microporous irrigation pipes. By combining two extruders and a co-extrusion die head, and controlling the temperature of each barrel and the co-extrusion die head, a method for preparing intermittently permeable rubber-plastic blend microporous irrigation pipes through continuous mixing and extrusion is achieved, solving the need for localized water seepage irrigation of trees.

[0018] This invention realizes a method for preparing intermittently permeable rubber-plastic blended microporous irrigation pipes by adjusting the direction, speed and time interval of the axial movement of the hydraulic cylinder-driven plunger or screw according to the extrusion speed of the rubber-plastic permeable pipe and the interval distance of the plastic coating layer.

[0019] The present invention, through the above preparation method, adds rubber-plastic blend masterbatch and plastic to the feeding devices of two extruders respectively, and continuously extrudes intermittently permeable rubber-plastic blend microporous infusion tubes in the co-extrusion die head. The product is cooled, shaped and packaged in the intermittently permeable rubber-plastic blend microporous infusion tube shaping device. No other operations are required, realizing the continuous and efficient operation of the whole process, which is fully applicable to large-scale continuous production. Attached image description:

[0020] Figure 1This is a schematic diagram of process route 1 of the present invention. Wherein, 1-a single-screw extruder for rubber-plastic blend masterbatch; 2-co-extrusion die head; 3-plastic-coated screw-plastic plunger extruder; 4-a shaping device for intermittently permeable rubber-plastic blend microporous irrigation pipes.

[0021] Figure 2 This is a schematic diagram of the plastic-coated screw-plasticor extruder 3 in this invention. Wherein, 5 is a plasticizing single-screw extruder; 6 is the interface with the co-extrusion die head; 7 is a plastic melt storage cylinder; and 8 is a hydraulic drive device.

[0022] Figure 3 This is a schematic diagram of process route 2 of the present invention. Wherein, 9 - a plastic single-screw extruder.

[0023] Figure 4 This is a schematic diagram of the connection structure between the plastic melt storage cylinder 7 and the hydraulic drive device 8 in the screw-plastic piston extruder 3. 10 represents the reciprocating plastic melt plunger.

[0024] Figure 5 This is a schematic diagram of the internal structure of a plastic single-screw extruder 9. 11 - melt storage area; 12 - reciprocating single screw; 13 - hydraulic cylinder. Detailed implementation method:

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] Example 1: A single-screw extruder 1 for rubber-plastic blend masterbatch uses a length-to-diameter ratio of 20:1 and a screw diameter of 50 mm; the die head is a co-extrusion tube die head 2. The barrel temperatures of the single-screw extruder 1 are 120℃, 150℃, 170℃, 180℃, and the die head temperature is 180℃. After the temperature reaches the set temperature and stabilizes, the rubber-plastic blend masterbatch is added to the feed port of the single-screw extruder 1. A plastic-coated screw-plastic piston extruder 3 uses a length-to-diameter ratio of 16:1 and a screw diameter of 25 mm; the melt storage cylinder 7 has a diameter of 50 mm and a length of 100 mm; the die head is a co-extrusion tube die head 2. The barrel temperatures of the plastic-coated screw-plastic piston extruder 3 are 120℃, 150℃, 180℃, and the die head temperature is 180℃. After the temperature reaches the set temperature and stabilizes, plastic is added to the feeding port of the plastic plasticizing single-screw extruder 5 in the plastic-coated screw-plasticor extruder 3, continuously plasticizing and pushing the plastic melt into the melt storage cylinder 7. The single-screw extruder 1 continuously extrudes uniformly permeable rubber-plastic blend microporous irrigation pipes at a speed of 5 meters per minute. The melt in the melt storage cylinder 7 of the plastic-coated screw-plasticor extruder 3 is pushed forward by the reciprocating plastic melt plunger 10 in the hydraulic drive device 8, and is extruded from the interface 6 with the co-extrusion pipe head into the co-extrusion pipe head 2. After extruding 1.9 meters of pipe (22.8 seconds), the reciprocating plastic melt plunger 10 is pushed forward and paused for 2.4 seconds, so that there is no plastic melt coating on the 20 cm length of the rubber-plastic blend microporous irrigation pipe. The rubber-plastic blend masterbatch is continuously extruded using a single-screw extruder 1. The melt in the melt storage cylinder 7 of the plastic-coated screw-plastic plunger extruder 3 is intermittently extruded under the push of the reciprocating plastic melt plunger 10. The molten material is then shaped and extruded through a co-extrusion die head 2, and finally formed, wound, and packaged as a finished product using an intermittently permeable rubber-plastic blend microporous irrigation pipe shaping device 4. This intermittently permeable rubber-plastic blend microporous irrigation pipe has a 20-centimeter permeable section every 2 meters, allowing for underground drip irrigation of each tree at 2-meter intervals.

[0027] The prepared intermittent seepage rubber-plastic blend microporous drip irrigation pipe has an outer diameter of 16mm, a wall thickness of 2.5mm, a tensile strength of 5.0MPa, a seepage rate of approximately 15L / (m×h) under a ground inlet water pressure of 0.05MPa, and a seepage uniformity of over 80% between each seepage section.

[0028] Example 2: A single-screw extruder 1 for rubber-plastic blend masterbatch uses a length-to-diameter ratio of 20:1 and a screw diameter of 50mm; the die head is a co-extrusion tube die head 2. The barrel temperatures of the single-screw extruder 1 are sequentially 120℃, 150℃, 170℃, 180℃, and the die head temperature is 180℃. After the temperature reaches the set temperature and stabilizes, the rubber-plastic blend masterbatch is added to the feed port of the single-screw extruder 1. A single-screw extruder 9 for plastics uses a length-to-diameter ratio of 20:1 and a screw diameter of 35mm, wherein the melt storage zone 11 has a diameter of 35mm and a length of 70mm; the die head is a co-extrusion tube die head 2. The barrel temperatures of the single-screw extruder 9 for plastics are sequentially 120℃, 150℃, 180℃, and the die head temperature is 180℃. After the temperature reaches the set temperature and stabilizes, plastic is added to the feed port of the plastic single-screw extruder 9, continuously plasticizing and pushing the plastic melt into the melt storage area 11. The rubber-plastic blend masterbatch single-screw extruder 1 continuously extrudes uniformly permeable rubber-plastic blend microporous injection pipes at a speed of 5 meters per minute. Driven by the hydraulic cylinder 13, the reciprocating single screw 12 intermittently extrudes the plastic melt from the melt storage area 11 into the co-extrusion die head 2. After extruding 3.9 meters of pipe (46.8 seconds), the hydraulic cylinder 13 pauses for 2.4 seconds to ensure that there is no plastic melt coating on the 20-centimeter length of the rubber-plastic blend microporous injection pipe. The rubber-plastic blend masterbatch single-screw extruder 1 continuously extrudes, while the plastic single-screw extruder 9 intermittently extrudes. After being shaped and extruded through the co-extrusion die head 2, the finished product is formed, wound, and packaged by the intermittently permeable rubber-plastic blend microporous injection pipe shaping device 4. This type of intermittently permeable rubber-plastic blend microporous drip irrigation pipe has a 20-centimeter permeable section every 4 meters, which can provide underground drip irrigation for each tree at 4-meter intervals.

[0029] The prepared intermittent seepage rubber-plastic blend microporous drip irrigation pipe has an outer diameter of 16mm, a wall thickness of 2.5mm, a tensile strength of 5.0MPa, a seepage rate of approximately 15L / (m×h) under a ground inlet water pressure of 0.05MPa, and a seepage uniformity of over 80% between each seepage section.

Claims

1. A method for continuously and efficiently preparing intermittently permeable rubber-plastic blend microporous irrigation pipes using multiple extruders, comprising: A single-screw extruder for rubber-plastic blend masterbatch is connected to a co-extrusion die head; a plastic-coated screw-plastic piston extruder or a single-screw plastic extruder is connected to the aforementioned co-extrusion die head; the plastic-coated screw-plastic piston extruder is equipped with a storage cylinder; the single-screw plastic extruder is equipped with a device for pushing the screw to reciprocate inside the barrel; Rubber-plastic blend masterbatch enters the rubber-plastic blend masterbatch single-screw extruder through the feed port, while plastic enters the plastic-coated screw-plastic extruder or plastic single-screw extruder through the feed port. The plasticized rubber-plastic blend masterbatch material and plastic melt enter the co-extrusion die head. The temperature of the co-extrusion die head is 120℃~200℃. The material is extruded into tubes through two extruders from the co-extrusion die head. After being cooled to below 40℃ in a cooling water tank for shaping, it passes through a traction machine and a packaging and winding machine to obtain the finished rubber-plastic blend microporous irrigation pipe. Its characteristics are: the rubber-plastic blend masterbatch is continuously extruded in the co-extrusion die head by a single screw extruder to form a rubber-plastic blend microporous irrigation tube, and the plastic melt is intermittently extruded by a plastic coating screw-plastic piston extruder or a single plastic screw extruder, and an intermittent melt film is coated on the surface of the rubber-plastic blend microporous irrigation tube in the co-extrusion die head.

2. The method according to claim 1, characterized in that: The plastic single-screw extruder used has a storage area at the front end of the barrel, the length of which is 2 to 4 times the diameter of the barrel. The reciprocating single screw is driven intermittently by a hydraulic cylinder to extrude the plastic melt in the storage area into the co-extrusion tube head.

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