Injection molding method of semi-dry paper pulp packaging product

Abstract

The invention discloses an injection molding method of a semi-dry paper pulp packaging product, which is characterized in that the used raw material is a dough block-shaped semi-dry paper pulp, and the semi-dry paper pulp is injected into a molding mold by a horizontal injection molding machine under high pressure and is heated and cured to form the semi-dry paper pulp packaging product. The three-dimensional packaging box has the effects of forming complex three-dimensional packaging products, saving water and electricity and reducing waste of paper fibers. And the label can be combined with the packaging product, the image-text surface can be realized through the label, the inner cavity can be sprayed, and the packaging product with waterproof and oil-proof performance can be formed. In addition, the produced packaging product has better dimensional precision and mechanical performance, is a new good way of replacing plastic with paper, and is energy-saving and environment-friendly.

Description

Technical Field

[0001] The invention belongs to a pulp molding process, and in particular relates to an injection molding method for a semi-dry pulp packaging product. Background Art

[0002] The main technological trends in reducing plastic use are plastic molding processes using bioplastics and molding processes using paper-based materials, exemplified by pulp molding. The former has the disadvantage of the high cost of bioplastics, while the latter requires large amounts of fresh water, consumes significant energy, and has low molding precision. Existing pulp molding technology primarily utilizes two methods to produce pulp molded packaging products with varying quality and performance. One is the wet process, which involves preparing a pulp solution, applying it to a mold on a molding machine through adsorption, filtration, trimming, and drying to shape it, thereby producing pulp molded products of a specific shape and size. However, due to the low specific gravity of fibers in the slurry, the adsorption, filtration, and trimming processes in the existing wet pulp molding process can easily lead to waste of pulp and water, low efficiency, high energy consumption, and a rough surface, making it unsuitable for printing or waterproof and oil-proof containers. The other is the dry process, which involves preparing a semi-solid pulp (also known as semi-dry pulp) in the form of a dough or block, weighing it, and loading it into a press mold cavity. The press then squeezes and heats the semi-dry pulp to dry and solidify it into shape. The dry forming process significantly reduces pulp moisture, saving water and electricity, and improving production efficiency to a certain extent. However, the press is a vertical motion mechanism, and its movement speed is slower than that of a horizontal forming machine. The products formed by extrusion and stretching are limited by the pulp's fluidity, resulting in a low flow length ratio. This makes it impossible to form complex, three-dimensional packaging products, and the dimensional accuracy and mechanical properties of the formed products are relatively poor. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an injection molding method for semi-dry pulp packaging products, which can produce three-dimensional packaging products with complex shapes.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A method for injection molding a semi-dry pulp packaging product employs a horizontal injection molding machine and a mold capable of opening and heating. The horizontal injection molding machine comprises an extrusion mechanism and an ejection mechanism. The mold is provided with a pulp flow channel and a valve group controlling the flow channel and connecting it to the mold cavity. The ejection mechanism comprises a horizontally arranged barrel with a front end capable of communicating with the mold, and an ejection screw disposed within the barrel capable of rotating to store material and translating to eject material. The extrusion mechanism comprises a hopper disposed vertically on the barrel, an extrusion screw disposed within the hopper capable of rotating to eject material toward the barrel, and a spiral ribbon disposed on the extrusion screw.

[0006] The injection molding method comprises the following steps:

[0007] A. Extrusion: The semi-dry pulp is squeezed into the barrel of the injection mechanism through the extrusion screw of the extrusion mechanism;

[0008] B. Matured storage: The injection screw rotates to fully mix the semi-dry pulp at 40-90°C and delivers it to the screw head and pulp flow channel for storage.

[0009] C. Mold closing, the mold closes to form the cavity;

[0010] D. Injection, the valve group opens, the injection screw moves forward linearly, and the semi-dry pulp is injected into the mold cavity through the pulp flow channel, and the valve group closes;

[0011] E. Heating and curing: the mold is heated to make the temperature of the slurry in the cavity reach 150-200℃, so that it can be cured quickly;

[0012] F. Open mold;

[0013] G. Take out the product.

[0014] The mold is provided with a gate sleeve connected to the cavity, the gate sleeve is connected to the pulp flow channel, and the outside of the mold is also provided with a heat insulation plate and a cold runner plate with cooling water inside. The valve group is a valve needle driven by a piston, and the valve needle is arranged in the pulp flow channel. In step D, the valve group is opened to withdraw the pulp flow channel backward through the valve needle so that the pulp flow channel is connected to the gate sleeve and the cavity; the valve group is closed to close the pulp flow channel forward through the valve needle and push the slurry in the gate sleeve into the cavity.

[0015] The front end of the barrel is provided with a nozzle that can be connected to and against the pulp flow channel, and the rear end of the nozzle is a conical inner cavity; the front end of the shooting screw is sequentially provided with a stop boss and a conical screw head that matches the nozzle, and a discharge slot hole is provided on the screw head. A non-return ring is also sleeved on the shooting screw between the screw head and the stop boss. There is a radial gap between the inner hole of the non-return ring and the shooting screw, and the non-return ring can move between the screw head and the boss. The front end of the non-return ring is provided with a first convex block that is locked with the discharge slot hole and can rotate with the shooting screw. The front end of the non-return ring is also provided with a The rear end of the screw head abuts against each other to form a second protrusion with an axial gap, and the radial gap, the axial gap and the discharge slot are connected to form a storage channel; in step B, when the shooting screw rotates to store material, the check ring and the screw head are locked and rotate together, and the check ring and the stop boss are pushed forward by the pulp to form an axial gap, opening the storage channel, and the pulp enters the pulp flow channel, and the shooting screw moves linearly backward due to the storage reaction force at the front end of the screw head; in step D, when the shooting screw moves linearly forward, the check ring and the stop boss abut against each other to close the storage channel.

[0016] In step E, the mold is heated to a temperature in the range of 150-200°C.

[0017] Before the extrusion in step A, there is also an in-mold labeling step, in which a robot is used to place the prefabricated label paper into the mold cavity and position it; and in step G, the product is taken out; the base material, printing ink and varnish of the label paper can withstand a maximum temperature of not less than 220°C.

[0018] The process also includes step H. spraying, spraying or coating the inner cavity or working surface of the removed product with a water-based paint with a spraying or coating amount of 4-5g / m 2 .

[0019] The method further comprises the step I. hot-air drying or air-drying the sprayed product to form a film.

[0020] The semi-dry pulp material comprises paper fiber, starch, PVA, water and additives, wherein the solid content is 50-70% and the total moisture content is 30-50%.

[0021] The injection molding method of the semi-dry pulp packaging product of the present invention is adopted, and high-pressure molding is performed on a horizontal injection molding machine, which not only saves water, saves fiber, and reduces energy consumption, but also can form complex three-dimensional packaging shapes with precise dimensions, uniform quality, and excellent mechanical and usage performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Figure 1 It is a schematic structural diagram of the semi-dry pulp injection molding equipment used in the present invention;

[0024] Figure 2 It is a structural schematic diagram of the mold of the present invention;

[0025] Figure 3 is a schematic cross-sectional view of the pulp flow channel and valve needle of the present invention;

[0026] Figure 4 It is a structural schematic diagram of the horizontal injection molding machine of the present invention;

[0027] Figure 5 It is a structural schematic diagram of the injection screw of the present invention;

[0028] Figure 6 、 Figure 7 They are schematic diagrams of the screw head and the check ring of the present invention from different perspectives;

[0029] Figure 8 This is a flowchart of the injection molding method of the semi-dry pulp packaging product of the present invention;

[0030] Figure 9 A square lunch box made by the method of the present invention;

[0031] Figure 10 A square paper cover is produced by the method of the present invention;

[0032] Figure 11 A paper bottle made by the method of the present invention;

[0033] Figure 12 A paper bottle cap manufactured by the method of the present invention;

[0034] Figure 13 The invention discloses an egg tray manufactured by the method of the invention. DETAILED DESCRIPTION

[0035] The injection molding method of the semi-dry pulp packaging product of the present invention adopts the following method: Figure 1 The semi-dry pulp injection molding equipment shown mainly includes a horizontal injection molding machine and a clamping mechanism 3. The horizontal injection molding machine includes an extrusion mechanism 1 and an injection mechanism 2. The extrusion mechanism 1 is connected to the injection mechanism 2 and is used to extrude pulp into the injection mechanism 2; the injection mechanism 2 is connected to the clamping mechanism 3 and is arranged together on a frame 101. The injection mechanism 2 is used to inject pulp into the mold cavity of the clamping mechanism 3.

[0036] like Figure 2 、 Figure 3 As shown, the mold clamping mechanism 3 mainly includes a mold with heaters 204 and 208 (which can be resistors, microwaves, or electromagnetic heaters) and a cavity, a sprue bushing 209 provided on the mold and connected to the cavity, and a pulp flow channel connecting the sprue bushing 209 to the injection mechanism 2. A front heat insulation board 210 and a rear heat insulation board 202 are respectively provided on the front and rear outer sides of the mold. The heat insulation boards can be made of ceramic material or high-temperature resistant bakelite. A cold runner plate 211 with cooling water passing through it is also provided on the outside of the front heat insulation plate 210. One end of the pulp flow channel is passed through the cold runner plate 211 and is connected to the gate sleeve 209. A valve needle 214 driven by a piston 215 is also provided in the pulp flow channel. By withdrawing the pulp flow channel backward through the valve needle 214, the pulp flow channel can be connected to the gate sleeve 209 and the cavity, and by moving the valve needle 214 forward, the pulp flow channel can be closed and the pulp material in the gate sleeve 209 can be pushed into the cavity.

[0037] The mold specifically comprises a front template 207 and a rear template 203, which have at least one cavity. Figure 2 Two independent upper and lower cavities are provided in the mold. Each cavity has a sprue bushing 209, one end of which is connected to a guide bushing 212. The pulp flow path includes a main flow tube 218 and branch flow tubes 221. One end of the main flow tube 218 is connected to each guide bushing 212 through two branch flow tubes 221. The number of valve pins 214 matches the number of cavities, and the corresponding valve pins 214 can be inserted into the sprue bushing 209 through the guide bushing 212. Figure 2-3The mold comprises a pair of upper and lower hydraulic or pneumatic cylinders, each having a cylinder head 213 provided with a flow channel diversion hole 224 connected to a branch channel pipe 221 and a guide sleeve 212. The cylinder head 213 is connected to the front mold base plate 217 by a cylinder barrel 216. A piston 215 is mounted in the cylinder barrel 216. A valve needle 214 is mounted on the piston 215. The valve needle 214 passes through the cylinder head 213 and is concentric with the guide sleeve 212 and the gate sleeve 209. Before and during injection, piston 215 retracts to its limit, and valve needle 214 retracts into cylinder head 213. Main flow channel 218 connects to the mold cavity through branch flow channel 221, the flow channel reversing hole in cylinder head 213, guide sleeve 212, and sprue sleeve 209, allowing the pulp to be smoothly injected into the mold cavity. At the end of injection, piston 215 advances, and valve needle 214 passes through guide sleeve 212 and into sprue sleeve 209, flush with the cavity surface. It pushes the pulp in sprue sleeve 209 into the mold cavity, completing cavity filling and sealing the sprue. The product is molded without a sprue. The purpose of needle valve 214 sealing sprue sleeve 209 is to isolate the slurry in the mold cavity from the slurry in the pulp flow channel. This keeps the slurry in the pulp flow channel at a lower temperature while the slurry in the mold cavity is heated and solidified, preserving the pulp's flow properties.

[0038] The main channel pipe 218 and the branch channel pipe 221 both adopt a through structure, and their open ends are respectively blocked by a first screw plug 220 and a second screw plug 219. These screw plugs can be removed from the outside of the mold, so that the residual material in the flow channel can be cleared and the mold can be maintained without removing the mold.

[0039] A large water trough 222 is provided on the cold runner plate 211, surrounding the diverter pipe 221. By cooperating with an external mold temperature controller, the mold temperature can be isolated from the outside during operation, and the diverter pipe 221 outside the cold runner plate 211 can be accurately temperature controlled to prevent the solidification of the stored material in the pipe.

[0040] Guide pins and guide sleeves are usually provided between the front and rear templates 207 and 203 for positioning; an ejection mechanism can be provided in the rear template 203 for conveniently removing the product after the mold is opened; for larger or multi-cavity (group) molds, an integral mold frame is used for installation and support, etc., which is existing technology and will not be described in detail here.

[0041] The rear heat insulation plate 202 isolates the high-temperature rear mold plate 203 from the room-temperature mounting base plate 201 to reduce energy consumption and protect the machine. The mounting base plate 201 and the front mold base plate 217 are respectively installed on the two movable plates 223 of the clamping mechanism 3. The movable plates 223 are connected to the opening and closing drive mechanism 5 of the clamping mechanism 3, and the opening and closing drive mechanism 5 drives the entire mold to open and close to meet the needs of injection filling and product removal.

[0042] like Figure 4-Figure 7As shown, the injection mechanism 2 comprises a barrel 102, an injection screw 103, an injection screw drive 115, an injection displacement bracket 116, and a injection platform pull rod assembly 118. A barrel temperature control device 109 is mounted on the outside of the barrel 102. This is a common technology and typically includes a heater, thermocouple, cooling loop, PID temperature controller, and solenoid valve, which will not be described in detail here. The barrel 102 is provided with a discharge port 119. A nozzle 104 is located at the front end, capable of interfacing with and communicating with the pulp flow path. The rear end of the nozzle 104 has a tapered inner cavity. The shooting screw 103 is horizontally arranged in the barrel 102, and a stop boss 120 and a conical screw head 105 matching the nozzle 104 are provided at the front end in sequence from back to front. The screw head 105 is provided with an axial discharge slot hole 121, and a (loosely fitted) check ring 106 is also sleeved on the shooting screw 103 between the screw head 105 and the stop boss 120. There is a radial gap 122 between the inner hole of the check ring 106 and the shooting screw 103 at the corresponding position, and the check ring 106 can move relative to the screw head 105 and the boss 120, and form a front axial gap between the front end face of the check ring 106 and the rear end face of the screw head 105, and a rear axial gap between the rear end face of the check ring 106 and the front end face of the stop boss 120 respectively. The above-mentioned radial gap, front and rear axial gaps and the connection of the discharge slot hole 121 form a storage channel. The shift bracket 116 is provided with a slide rail, and the barrel 102 is slidably arranged on the shot shift bracket 116 through the barrel support 117, and is connected to the clamping mechanism 3 through the shooting platform pull rod assembly 118. The barrel 102 is pulled forward by the shooting platform pull rod assembly 118, so that the nozzle 104 is tightly connected with the inlet of the main channel pipe 218 of the clamping mechanism 3. Similarly, the barrel 102 can also be pulled backward to disengage the clamping mechanism 3 from the shooting screw 103. The driving device 115 is also slidably arranged on the shot shift bracket 116 and is used to drive the shooting screw 103 to rotate and move back and forth.

[0043] The front end of the check ring 106 is also provided with a first protrusion 123 which is engaged with the discharge slot 121 and can rotate with the injection screw 103. The discharge slot 121 is relatively deep, and there is a space between the bottom of the first protrusion 123 and the bottom of the discharge slot 121. When storing materials, the check ring 106 is connected to the screw head 105 and rotates together to prevent the front end surface of the check ring 106 and the screw head 105 from wearing, and also to prevent the slurry from being deposited between the check ring 106 and the inner wall of the barrel 102 (if the check ring 106 does not rotate, there is no relative movement between the inner wall of the barrel 102 and the check ring 106, and the slurry will be deposited therebetween), and to realize the control of the storage channel, that is, when storing materials, when the injection screw 103 rotates, the pulp in the barrel 102 can be pushed forward, and the pulp pushes the check ring 106 to move forward, and the rear end surface of the check ring 106 and the stop boss 1 The rear axial gap between the front faces of the screw head 105 and the front end faces of the screw head 105 is opened, allowing the pulp to enter the main channel 218 through the storage channel (i.e., through the rear axial gap, radial gap, front axial gap, and discharge slot 121 of the screw head 105). Simultaneously, under the reaction of the storage, the injection screw 103 rotates counter-helically and retreats during storage. During injection, the injection screw 103 stops rotating and rapidly moves forward in a straight line, pushing the conical screw head 105 to sequentially pass the pulp through the nozzle 104, the main channel 218, the branch channel 221, the sprue bushing 209, and finally into the mold cavity 207, thus completing the injection of the pulp. During this process, the stop boss 120 of the injection screw 103 first contacts the check ring 106, closing the axial gap therebetween, thereby closing the storage channel and preventing further storage. Repeating this action allows for a continuous storage and injection process.

[0044] The axial length of the first projection 123 is greater than the axial travel of the check ring 106. That is, when the first projection 123 moves forward and backward with the check ring 106, the first projection 123 can always be locked with the discharge slot 121. The front end of the check ring 106 is also provided with a second projection 124 that abuts against the rear end of the screw head 105. This structure ensures that there is always an axial gap between the screw head 105 and the check ring 106 when the check ring 106 and the screw head 105 are locked and rotate synchronously, so that the storage channel is unobstructed.

[0045] like Figure 5As shown, the groove depth of the injection screw 103 gradually decreases from 50% to 15% of the screw's outer diameter from back to front. It is designed to be divided into a discharge section, an extrusion section, and a homogenization section. Since low-water pulp is doughy and difficult to flow through in the discharge section, an appropriate groove depth ensures efficient conveying. When pulp from the forced extrusion hopper is filled into the barrel 102, the rotation of the injection screw 103 generates a forward axial thrust on the inclined surface of the helical teeth. This thrust gradually increases as it moves toward the screw head 105. In the extrusion section, the gradually decreasing groove depth compresses the pulp, and the cumulative pressure gradually increases, creating conditions for the pulp to pass steadily through the narrow gap of the check ring 106. In the homogenization section, the pulp is rubbed and sheared by the inner wall of the barrel 102 and the bottom surface of the screw groove, producing a good mixing action, resulting in a uniform pulp texture and promoting product quality and stability.

[0046] The discharge port 119 is a waist-shaped hole with a width not less than the diameter of the injection screw 103 and a length L not less than twice the diameter of the injection screw 103. This can greatly increase the amount of pulp initially entering the groove of the discharge section of the injection screw 103, increase the internal pressure of the discharge section, and store the material smoothly.

[0047] Please refer to Figure 4 As shown, the extrusion mechanism 1 includes a hopper 114 vertically mounted on a discharge port 119, an extrusion screw 112 disposed within the hopper 114, a spiral ribbon 113 disposed on the extrusion screw 112, and an extrusion screw drive 110 connected to the extrusion screw 112 via a bearing seat 111 and vertically mounted on the upper end of the hopper 114. The spiral ribbon 113 is a variable diameter helical wire whose shape matches the inner cavity of the hopper 114. The extrusion screw drive 110 drives the extrusion screw 112 to rotate counter-helically with the spiral ribbon 113 fixed thereto. The spiral ribbon 113 continuously stirs the pulp in the hopper 114 and gathers it toward the center and downward, where it is then fed downward by the extrusion screw 112.

[0048] The injection molding method for semi-dry pulp packaging products further includes a control system 4 for controlling the opening and closing of the mold, the extrusion and injection of materials, and the corresponding temperatures.

[0049] The molding device of the present invention further comprises a manipulator 6, which can be a side-taking manipulator equipped with a suction cup palm for placing label paper into the mold and taking out the product from the mold. Preferably, the manipulator is provided with a label bin for storing label paper.

[0050] The molding process of the injection molding method of the semi-dry pulp packaging product of the present invention is as follows:

[0051] like Figure 8 As shown, the injection molding method of the present invention specifically includes the following steps:

[0052] A. Extrusion: The extrusion screw of the extrusion mechanism 1 extrudes semi-dry paper pulp into the barrel 102 of the injection mechanism 2. Before extrusion, a robotic arm can be used to place and secure label paper 206 in the mold cavity for in-mold labeling, as needed. The semi-dry paper pulp can be, but is not limited to, a mixture primarily consisting of paper fiber, starch, PVA, water, and additives, with a solids content of 50-70% and a total moisture content of 30-50%. The base material, printing ink, and varnish of the label paper 206 must withstand a maximum temperature of no less than 220°C.

[0053] B. Maturation and storage: The shot screw 103 rotates, thoroughly mixing the semi-dry pulp in the barrel 102 at a temperature of 40-90°C, and then delivers it to the screw head and pulp flow channel for storage until use. As the shot screw 103 rotates to store the pulp, the check ring 106 engages and rotates with the screw head 105. The reaction force from the stored material at the front end of the screw head 105 causes the shot screw 103 to move linearly backward. During this process, the valve block closes, isolating the pulp in the pulp flow channel from the mold cavity 207.

[0054] C. Mold closing, the mold closes to form the cavity;

[0055] D. Injection: The valve block opens, and the injection screw 103 rapidly moves forward in a straight line, injecting the semi-dry pulp through the pulp flow channel into the mold cavity. The valve block then closes. At this point, the check ring 106 abuts against the stop boss 120, sealing the material storage channel. The valve block opens by withdrawing the valve needle 214 backward from the pulp flow channel, establishing communication between the pulp flow channel and the sprue bushing 209 and the mold cavity. The valve block closes by moving the valve needle 214 forward, closing the pulp flow channel and pushing the slurry in the sprue bushing 209 into the mold cavity.

[0056] E. Heating and curing: The mold is heated to make the temperature of the slurry in the cavity reach 150-200℃, so that it can quickly lose moisture and solidify.

[0057] F. Mold opening: The mold opens and the molded product (such as a packaged product) is ejected. The ejection device used can be the same as the ejection mechanism of a general plastic injection molding machine.

[0058] G. Take out the product: The product is taken out by the robot. In addition, label paper 206 can be prepared for the next work cycle.

[0059] H. According to product requirements, spraying can also be performed. The inner cavity or working surface of the removed product can be sprayed or coated with a waterproof and oil-proof water-based paint. The spraying or coating amount is 4-5g / m 2 .

[0060] I. The sprayed product is then hot-air dried or air-dried to form a film. This can be done in an oven or on an assembly line using hot air or air drying to create a waterproof and oil-resistant product. Alternatively, the product can be left unsprayed for use in dry goods or industrial cushioning packaging.

[0061] Products manufactured using the injection molding method of the present invention include: packaging boxes (especially take-out boxes), box lids, paper bottles, paper bottle lids, and external buffering brackets such as cup holders and egg trays. For example:

[0062] like Figure 9 The picture shows a semi-dry pulp injection-molded square lunch box with a uniform wall thickness of 1-1.5 mm. A flange is provided along the edge to form a seal with the lid. A logo label is affixed to the outside, and a water-based coating is applied inside to provide a water and oil barrier. This lunch box, when used with the lid, can be used for takeout packaging, including rice, vegetables, soup, and more.

[0063] like Figure 10 The image shows a square paper lid made by injection molding using semi-dry pulp. Its wall thickness is uniformly distributed, ranging from 1 to 1.5 mm. The lid features vertical edges and internal snaps for secure fastening to the edge of the lunch box. The top surface features a label, and the inside is coated with a water-based paint that resists water and oil. This lid can be used with the lunch box as takeout packaging for rice, vegetables, soup, and more.

[0064] like Figure 11 The picture shows a paper bottle made by injection molding semi-dry pulp, with a wall thickness of 1.5-2.5 mm. The bottle's mouth is threaded for compatibility with a bottle cap, and the bottom has a load-bearing lip for stability. The cylindrical surface is affixed with a label pattern, and the interior is sprayed with a water-based paint that blocks water and oil. This paper bottle can hold liquids such as water and oil.

[0065] like Figure 12 The figure shows a paper bottle cap made by injection molding semi-dry pulp, with a wall thickness of 1-2 mm. The inner side of the paper bottle cap is threaded, allowing it to screw onto the mouth of a paper bottle. The top surface of the paper bottle cap is affixed with a label, and the inside is sprayed with a water-based paint to block water and oil. This paper bottle cap can be used with paper bottles to hold liquids such as water and oil.

[0066] like Figure 13 The following figure shows an egg tray made of semi-dry pulp injection molding. This egg tray has no label or painting.

[0067] In summary, the injection molding method of the present invention, compared to existing pulp molding technology, saves water and electricity, and reduces paper fiber waste. Furthermore, it allows for the integration of labels with packaging products, creating graphic and text surfaces through the label, and also allows for internal spray coating to create packaging products with waterproof and oil-proof properties. Furthermore, the resulting packaging products exhibit improved dimensional accuracy and mechanical properties.

[0068] However, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for injection molding a semi-dry pulp packaging product, characterized in that: A horizontal injection molding machine and a mold that can be opened and heated are used. The horizontal injection molding machine includes an extrusion mechanism and an ejection mechanism. The mold is provided with a pulp flow channel and a valve group that controls the flow channel and connects to the mold cavity. The ejection mechanism includes a barrel arranged horizontally and with a front end that can communicate with the mold, and an ejection screw arranged in the barrel that can rotate forward to store material and translate forward to eject material. The extrusion mechanism includes a hopper arranged vertically on the barrel, an extrusion screw arranged in the hopper that can rotate to extrude material into the barrel, and a spiral ribbon arranged on the extrusion screw. The injection molding method comprises the following steps: A. Extrusion: The semi-dry pulp is squeezed into the barrel of the injection mechanism through the extrusion screw of the extrusion mechanism; B. Matured storage: The injection screw rotates to fully mix the semi-dry pulp at 40-90°C and delivers it to the screw head and pulp flow channel for storage. C. Mold closing, the mold closes to form the cavity; D. Injection, the valve group opens, the injection screw moves forward linearly, and the semi-dry pulp is injected into the mold cavity through the pulp flow channel, and the valve group closes; E. Heating and curing: heating the mold to make the temperature of the slurry in the cavity reach 150-200℃, so that it can be quickly dried and cured; F. Open mold; G. Take out the product.

2. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: The mold is provided with a gate sleeve connected to the cavity, the gate sleeve is connected to the pulp flow channel, and the outside of the mold is also provided with a heat insulation plate and a cold runner plate with cooling water inside. The valve group is a valve needle driven by a piston, and the valve needle is arranged in the pulp flow channel. In step D, the valve group is opened to withdraw the pulp flow channel backward through the valve needle so that the pulp flow channel is connected to the gate sleeve and the cavity; the valve group is closed to close the pulp flow channel forward through the valve needle and push the slurry in the gate sleeve into the cavity.

3. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: The front end of the barrel is provided with a nozzle that can be connected to and against the pulp flow channel, and the rear end of the nozzle is a conical inner cavity; the front end of the shooting screw is sequentially provided with a stop boss and a conical screw head that matches the nozzle, and a discharge slot hole is provided on the screw head. A non-return ring is also sleeved on the shooting screw between the screw head and the stop boss. There is a radial gap between the inner hole of the non-return ring and the shooting screw, and the non-return ring can move between the screw head and the boss. The front end of the non-return ring is provided with a first convex block that is locked with the discharge slot hole and can rotate with the shooting screw. The front end of the non-return ring is also provided with a The rear end of the screw head abuts against each other to form a second protrusion with an axial gap, and the radial gap, the axial gap and the discharge slot are connected to form a storage channel; in step B, when the shooting screw rotates to store material, the check ring and the screw head are locked and rotate together, and the check ring and the stop boss are pushed forward by the pulp to form an axial gap, opening the storage channel, and the pulp enters the pulp flow channel, and the shooting screw moves linearly backward due to the storage reaction force at the front end of the screw head; in step D, when the shooting screw moves linearly forward, the check ring and the stop boss abut against each other to close the storage channel.

4. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: In step E, the mold is heated to a temperature in the range of 150-200°C.

5. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: Before the extrusion in step A, there is also an in-mold labeling step, in which the prefabricated label paper is placed into the mold cavity and positioned by a robot, and the product is taken out in step G; the substrate, printing ink and varnish of the label paper can withstand a maximum temperature of not less than 220°C.

6. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: The method further includes step H. spraying, spraying or coating the inner cavity or working surface of the removed product with a waterproof and oil-proof water-based coating at a spraying or coating amount of 4-5 g / m2.

7. The injection molding method of a semi-dry pulp packaging product according to claim 8, characterized in that: The method further comprises the step I. drying the sprayed product with hot air or air-drying it to form a film.

8. The injection molding method of a semi-dry pulp packaging product according to claim 1, characterized in that: The semi-dry pulp material comprises paper fiber, starch, PVA, water and additives, wherein the solid content is 50-70% and the total moisture content is 30-50%.

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