Plastic blank pipe production process and special device

Abstract

The invention discloses a production process of a plastic blank pipe. The production process comprises the following steps: 1, preparing a raw material mixture; 2, putting the raw material mixture obtained in the step 1 into a plastic extruding machine for plastic extruding to obtain a melt, injecting the melt into a blank mold to obtain a bottle blank, and cooling the bottle blank to room temperature; 3, putting the bottle preform obtained in the step 2 into a forming mold, heating to 95-120 DEG C, carrying out extension blow molding on the bottle preform to form a preset shape, and putting the forming mold into a cooling chamber for cooling to room temperature; and fourthly, the forming mold cooled to the room temperature is subjected to demolding treatment, and a product is obtained. And fifthly, burrs and sprues of the product obtained in the fourth step are cut off, and the cut-off position is polished. The invention aims to provide the plastic blank pipe production process and the special device which can give consideration to both the product quality and the production efficiency.

Description

Technical Field

[0001] The invention relates to a plastic embryo tube, in particular to a production process and a special device for the plastic embryo tube. Background Art

[0002] Plastic embryo tube, also known as plastic bottle embryo, is an unformed plastic bottle product, mainly obtained by pre-processing plastic raw materials before molding. It is widely used in many industries, such as packaging industry, construction industry, and agriculture.

[0003] According to the material classification, plastic embryo tubes can be divided into PVC (polyvinyl chloride) embryo tubes, PET (polyethylene terephthalate) embryo tubes, PE (polyethylene) embryo tubes, PP (polypropylene) embryo tubes, ABS (acrylonitrile-butadiene-styrene tube) embryo tubes, etc. Among them, PET (polyethylene terephthalate) is widely used in the production of various bottles and containers due to its high transparency, excellent mechanical properties and recyclability. It is used as a container for beverages, food, cosmetics and other items, and common packaging materials such as mineral water, fruit juice, tea drinks, condiments, cooking oil, etc.

[0004] The existing PET embryo tube production has the following problems: 1. If the screw speed is too fast during production, the friction between the screw and the plastic will increase, which may cause the temperature of the PET material melt to be too high, thereby aggravating the degradation of the PET material, aggravating the oxidation of the PET material, discoloring the PET material and reducing the crystallization rate. The aggravated degradation and oxidation of the PET material will lead to a decrease in the mechanical properties of the PET material (such as strength, toughness, etc.). The discoloration of the PET material will affect the transparency of the product, and the crystallization rate of the PET material will increase the difficulty of subsequent molding; 2. If the temperature of the PET material is too high, it will also increase the difficulty of cooling to obtain the bottle embryo. If the cooling effect of the bottle embryo is not good, it may cause the product to warp or deform or produce surface defects, easy to break and other problems, affecting the product quality; 3. If the screw speed is reduced, the production efficiency of the enterprise is low, which makes the market competitiveness of the enterprise insufficient. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a plastic embryo tube production process and a special device that can take into account both product quality and production efficiency.

[0006] Technical solution: The production process of the plastic embryo tube of the present invention comprises the following steps:

[0007] Step 1: prepare the raw material mixture;

[0008] Step 2: Put the raw material mixture obtained after the first step into an extruder to extrude a melt, inject the melt into an embryo mold to obtain a bottle embryo, and cool the bottle embryo to room temperature;

[0009] Step 3: Place the preform obtained after the second step into a forming mold, heat it to 95° C. to 120° C., stretch blow mold the preform (stretch blow mold means to achieve the forming effect by stretching, blowing, etc. the preform) into a preset shape, and place the forming mold into a cooling chamber to cool to room temperature;

[0010] Step 4: demoulding the molding mold cooled to room temperature to obtain the product;

[0011] Step 5: Cut off the burrs and gates of the product obtained after the fourth step, and polish the cut parts.

[0012] Further, the screw speed of the extruder in the second step is constrained by the following formula:

[0013] Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the screw surface to the inner surface of the barrel, and V q The range is 5.6s -1 (Second -1 )~17.4s -1 (Second -1 ).

[0014] Furthermore, the temperature of the inner cavity of the extruder is 258°C to 280°C.

[0015] Furthermore, the compression ratio of the screw in the extruder is ε=S i / S e , wherein the S i is the volume of the first screw groove of the screw feeding section, and S e It is the volume of the last screw groove in the screw material balancing section, and the range of ε is 1.9:1~2.3:1.

[0016] Furthermore, the raw material mixture described in the first step is prepared according to the following components: PET (polyethylene terephthalate) raw material, stabilizer, and lubricant are mixed in a mass ratio of 90-100:2-5:2-3, and the water content of the PET (polyethylene terephthalate) raw material is 0.015% to 0.04%.

[0017] Furthermore, the stabilizer is one of triphenyl phosphite, phosphorous acid, and trimethyl phosphate, or any mixture thereof.

[0018] Furthermore, the lubricant is one of zinc stearate, calcium stearate and fatty amide.

[0019] A special device for plastic embryo tubes includes an extruder, the extruder includes a cylindrical shell, a feed port is arranged on the shell, a screw is built in the shell, a motor is arranged outside the shell, the output end of the motor is connected to one end of the screw, and the screw speed is constrained according to the following formula:

[0020] Where n is the screw speed, D is the screw diameter, V q The shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the screw surface to the inner surface of the barrel, and V q The range is 5.6s -1 (Second -1 )~17.4s -1 (Second -1 ).

[0021] Furthermore, the screw includes a feed section and a material distribution section, the position of the feed section corresponds to the position of the feed port of the shell, and the compression ratio of the screw is ε=S i / S e , wherein the S i is the volume of the first screw groove of the screw feeding section, and S e It is the volume of the last screw groove in the screw material balancing section, and the range of ε is 1.9:1~2.3:1.

[0022] Furthermore, a heating device is arranged in the inner cavity of the shell of the extruder, and the heating device controls the temperature of the inner cavity of the shell to be 255°C to 280°C.

[0023] Furthermore, it also includes several water cooling systems, each of which includes a water cooling box, a cold water pipe, a preheating pipe and a return water pipe; a preheating device is arranged outside the feed section of the screw, and a plurality of preheating channels are arranged in the outer shell of the preheating device; a plurality of temperature measuring sensors for detecting the melt temperature on the screw are arranged on the inner wall of the heating device, and a plurality of cooling channels are arranged in the outer shell of the heating device; one end of the cold water pipe is connected to the outlet of the water cooling box, and the other end of the cold water pipe is connected to the inlet of the cooling channel, one end of the preheating pipe is connected to the outlet of the cooling channel, and the other end of the preheating pipe is connected to the inlet of the preheating channel, one end of the return water pipe is connected to the outlet of the preheating channel, and the other end of the return water pipe is connected to the inlet of the water cooling box.

[0024] Furthermore, a die head and an embryo body mold are sequentially arranged at the outlet end of the extruder.

[0025] Furthermore, the screw sleeve is arranged in a temperature increasing device.

[0026] Furthermore, the extruder is provided with a feed hopper, and the outlet of the feed hopper corresponds to the position of the feed inlet of the shell.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The present invention constrains the screw speed by the melt shear rate and controls the temperature of the inner cavity of the extruder, so that during the extrusion process, the temperature of the melt is controlled between 270 and 300°C. Within this temperature range, the mechanical properties of the product after molding will not decrease due to the excessively high melt temperature, and the production efficiency can be taken into account. Therefore, the present invention can take into account both product quality and production efficiency; 2. The compression ratio ε of the screw in the present invention is in the range of 1.9:1 to 2.3:1, which enables the screw to reduce the screw's influence on P The shear heat of ET materials can prevent the melt temperature from being too high, and can also improve the uniform melting and mixing of PET materials in the screw, improve the plasticizing quality, and thus improve the product quality. 3. The present invention is equipped with several water cooling systems. When it is found that the melt temperature on the screw is too high, the water cooling system is started. After the cold water enters the heating device, the local temperature in the heating device is reduced through heat exchange. The warm water after heat exchange enters the preheating device along the preheating pipe to heat the plastic that has just entered the extruder. This can not only efficiently utilize thermal energy, but also reduce the energy consumption during subsequent extrusion, reduce the operating costs of the enterprise, and improve the competitiveness of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the present invention.

[0029] Figure 2 A three-dimensional view of an extruder according to the present invention from one angle.

[0030] Figure 3 A three-dimensional view of the extruder of the present invention from another angle.

[0031] Figure 4 A cross-sectional view of an extruder in one direction of the present invention.

[0032] Figure 5 It is a cross-sectional view from another direction of the extruder of the present invention.

[0033] Figure 6 It is a schematic diagram of the screw in the present invention.

[0034] Among them: 1. Motor; 2. Shell; 3. Feed hopper; 4. First water cooling box; 401. First cold water pipe; 402. First preheating pipe; 403. First return water pipe; 5. Machine head; 6. Embryo mold; 7. Second water cooling box; 701. Second cold water pipe; 702. Second preheating pipe; 703. Second return water pipe; 8. Preheating device; 9. Heating device; 10. Screw; 1001. Feed section; 1002. Material equalization section. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0036] See attached Figure 1 to Figure 6 The steps of the plastic embryo tube production process shown in the present invention are as follows:

[0037] The first step: preparing a raw material mixture according to the following composition: PET (polyethylene terephthalate) raw material, stabilizer, and lubricant are mixed in a mass ratio of 90-100:2-5:2-3, the water content of the PET (polyethylene terephthalate) raw material is 0.015%-0.04%, the stabilizer is one of triphenyl phosphite, phosphorous acid, and trimethyl phosphate or any mixture thereof, and the lubricant is one of zinc stearate, calcium stearate, and fatty amide;

[0038] Step 2: Put the raw material mixture obtained after the first step into an extruder for extrusion, and constrain the speed of the screw 4 in the extruder according to the following formula:

[0039] Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the surface of the screw 10 to the inner surface of the barrel, V q The range is 5.6s -1 (Second -1 )~17.4s -1 (Second -1 ), the compression ratio of the screw 10 in the extruder ε = S i / S e , where S i is the volume of the first screw groove of the feed section 1001 of the screw 10, S e The last screw groove volume of the material averaging section 1002 of the screw 10, the range of ε is 1.9:1-2.3:1, the temperature of the inner cavity of the extruder is 258°C-280°C, and the melt is obtained after extrusion. After the melt is injected into the embryo mold 6, a bottle embryo is obtained, and the bottle embryo is cooled to room temperature;

[0040] Step 3: Place the preform obtained after the second step into the forming mold, heat it to 95°C to 120°C, stretch and blow mold the preform into a preset shape, and place the forming mold into a cooling chamber to cool it to room temperature;

[0041] Step 4: demoulding the molding mold cooled to room temperature to obtain the product;

[0042] Step 5: Cut off the burrs and gates of the product obtained after step 4, and polish the cut parts.

[0043] Example 1

[0044] The production process of plastic embryo tubes is as follows:

[0045] The first step: preparing a raw material mixture as follows: PET (polyethylene terephthalate) raw material, stabilizer, and lubricant are mixed in a mass ratio of 90:2.5:2.5, the water content of the PET (polyethylene terephthalate) raw material is 0.02%, the stabilizer is triphenyl phosphite, and the lubricant is zinc stearate;

[0046] Step 2: Put the raw material mixture obtained after the first step into an extruder for extrusion, and constrain the screw speed of the extruder according to the following formula:

[0047] Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the surface of the screw 10 to the inner surface of the barrel, V q The range is 10.4s -1 (Second -1 ), the compression ratio of the screw 10 in the extruder ε = S i / S e , where S i is the volume of the first screw groove of the feed section 1001 of the screw 10, S e The last screw groove volume of the material averaging section 1002 of the screw 10, the range of ε is 2:1, the temperature of the inner cavity of the extruder is 265°C, and the melt is obtained after extrusion. After the melt is injected into the embryo mold 6, a bottle embryo is obtained, and the bottle embryo is cooled to room temperature;

[0048] Step 3: Place the preform obtained after the second step into the forming mold, heat it to 110°C, stretch and blow mold the preform into a preset shape, and place the forming mold into a cooling chamber to cool it to room temperature;

[0049] Step 4: demoulding the molding mold cooled to room temperature to obtain the product;

[0050] Step 5: Cut off the burrs and gates of the product obtained after step 4, and polish the cut parts.

[0051] Example 2

[0052] The production process of plastic embryo tubes is as follows:

[0053] The first step: preparing a raw material mixture according to the following composition: PET (polyethylene terephthalate) raw material, stabilizer, and lubricant are mixed in a mass ratio of 99:4:2.3, the water content of the PET (polyethylene terephthalate) raw material is 0.035%, the stabilizer is a mixture of phosphorous acid and trimethyl phosphate, and the lubricant is calcium stearate;

[0054] Step 2: Put the raw material mixture obtained after the first step into an extruder for extrusion, and constrain the screw speed of the extruder according to the following formula:

[0055] Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the screw surface to the inner surface of the barrel, V q The range is 8.9s -1 (Second -1 ), the compression ratio of the screw in the extruder ε = S i / S e , where S i is the volume of the first screw groove of the feed section 1001 of the screw 10, S e is the last screw groove volume of the material averaging section 1002 of the screw 10, the range of ε is 2.2:1, the temperature of the inner cavity of the extruder is 260°C, and the melt is obtained after extrusion. After the melt is injected into the embryo mold 6, a bottle embryo is obtained, and the bottle embryo is cooled to room temperature;

[0056] Step 3: Place the preform obtained after the second step into the forming mold, heat it to 100°C, stretch and blow mold the preform into a preset shape, and place the forming mold into a cooling chamber to cool it to room temperature;

[0057] Step 4: demoulding the molding mold cooled to room temperature to obtain the product;

[0058] Step 5: Cut off the burrs and gates of the product obtained after step 4, and polish the cut parts.

[0059] See attached Figure 2 to Figure 6 The special device for plastic embryo tube shown in the present invention includes an extruder, which includes a cylindrical shell 2, a feed port is arranged on the shell 2, a screw 10 is built in the shell 2, and a motor 1 is arranged outside the shell 2. The output end of the motor 1 is connected to one end of the screw 10, and the speed of the screw 10 is constrained according to the following formula:

[0060] Where n is the speed of screw 10, D is the diameter of screw 10, Vq is the shear rate allowed by the material (the material refers to the melt after the raw material mixture is melted), h is the thickness of the material from the surface of screw 10 to the inner surface of the barrel, and the range of Vq is 5.6s -1 (Second -1 )~17.4s -1 (Second -1 ).

[0061] The screw 10 includes a feed section 1001 and a material balancing section 1002. The position of the feed section 1001 corresponds to the position of the feed port of the shell 2. The compression ratio ε of the screw 10 is Si / Se, wherein Si is the first screw groove volume of the feed section 1001 of the screw 10, Se is the last screw groove volume of the material balancing section 1002 of the screw 10, and the range of ε is 1.9:1 to 2.3:1.

[0062] It also includes a first water cooling system and a second water cooling system, the first water cooling system includes a first water cooling box 4, a first cold water pipe 401, a first preheating pipe 402 and a first return water pipe 403, and the second water cooling system includes a second water cooling box 7, a second cold water pipe 701, a second preheating pipe 702 and a second return water pipe 703; a preheating device 8 is arranged outside the feed section 1001 on the screw 10, and a first preheating channel and a second preheating channel (not drawn) are arranged in the outer shell of the preheating device 8; a plurality of temperature measuring sensors for detecting the melt temperature on the screw 10 are arranged on the inner wall of the heating device 9, and a first cooling channel and a second cooling channel (not drawn) are arranged in the outer shell of the heating device 9.

[0063] One end of the first cold water pipe 401 is connected to the outlet of the first water cooling box 4, the other end of the first cold water pipe 401 is connected to the inlet of the first cooling channel, one end of the first preheating pipe 402 is connected to the outlet of the first cooling channel, the other end of the first preheating pipe 402 is connected to the inlet of the first preheating channel, one end of the first return water pipe 403 is connected to the outlet of the first preheating channel, and the other end of the first return water pipe 403 is connected to the inlet of the first water cooling box 4; one end of the second cold water pipe 701 is connected to the outlet of the second water cooling box 7, the other end of the second cold water pipe 701 is connected to the inlet of the second cooling channel, one end of the second preheating pipe 702 is connected to the outlet of the second cooling channel, the other end of the second preheating pipe 702 is connected to the inlet of the second preheating channel, one end of the second return water pipe 703 is connected to the outlet of the second preheating channel, and the other end of the second return water pipe 703 is connected to the inlet of the second water cooling box 7.

[0064] The outlet end of the extruder is provided with a die head 5 and an embryo mold 6 in sequence, a heating device 9 is provided in the inner cavity of the shell 2 of the extruder, the heating device 9 controls the temperature of the inner cavity of the shell 2 to be 255°C to 280°C, and a screw 10 is sleeved in the heating device 9. The extruder is provided with a feed hopper 3, and the outlet of the feed hopper 3 corresponds to the feed port position of the shell 2.

Claims

1. The production process of plastic embryo tube, the steps are as follows: Step 1: prepare the raw material mixture; Step 2: Put the raw material mixture obtained after the first step into an extruder to extrude a melt, inject the melt into an embryo mold to obtain a bottle embryo, and cool the bottle embryo to room temperature; Step 3: placing the preform obtained after the second step into a forming mold, heating it to 95° C. to 120° C., stretching and blow-molding the preform into a preset shape, and placing the forming mold into a cooling chamber to cool it to room temperature; Step 4: demoulding the molding mold cooled to room temperature to obtain the product; Step 5: Cut off the burrs and gates of the product obtained after the fourth step, and polish the cut parts.

2. The process for producing a plastic embryo tube according to claim 1, characterized in that: The screw speed of the extruder described in the second step is constrained by the following formula: Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material, h is the thickness of the material from the screw surface to the inner surface of the barrel, and V q The range is 5.6s -1 ~17.4s -1 .

3. The process for producing a plastic embryo tube according to claim 1 or 2, characterized in that: The temperature of the inner cavity of the extruder is 258°C to 280°C.

4. The process for producing a plastic embryo tube according to claim 1, characterized in that: The compression ratio of the screw in the extruder is ε=S i / S e , wherein the S i is the volume of the first screw groove of the screw feeding section, and S e It is the volume of the last screw groove in the screw material balancing section, and the range of ε is 1.9:1~2.3:

1.

5. The process for producing a plastic embryo tube according to claim 1, characterized in that: The raw material mixture described in the first step is prepared according to the following components: polyethylene terephthalate raw material, stabilizer, and lubricant are mixed in a mass ratio of 90-100:2-5:2-3, and the water content of the polyethylene terephthalate raw material is 0.015%-0.04%.

6. The process for producing a plastic embryo tube according to claim 5, characterized in that: The stabilizer is one of triphenyl phosphite, phosphorous acid, and trimethyl phosphate, or any mixture thereof.

7. The process for producing a plastic embryo tube according to claim 5, characterized in that: The lubricant is one of zinc stearate, calcium stearate and fatty amide.

8. A special device for plastic embryo tubes, including an extruder, characterized in that: The extruder comprises a cylindrical shell, one end of which is provided with a feed port, a screw rod is built into the shell, a motor is arranged outside the shell, an output end of the motor is connected to one end of the screw rod, and the screw rod speed is constrained according to the following formula: Where n is the screw speed, D is the screw diameter, V q is the shear rate allowed by the material, h is the thickness of the material from the screw surface to the inner surface of the barrel, and V q The range is 5.6s -1 ~17.4s -1 .

9. The special device for plastic embryo tube according to claim 8, characterized in that: The screw includes a feed section and a material distribution section. The position of the feed section corresponds to the position of the feed port of the shell. The compression ratio of the screw ε=S i / S e , wherein the S i is the volume of the first screw groove of the screw feeding section, and S e It is the volume of the last screw groove in the screw material balancing section, and the range of ε is 1.9:1~2.3:

1.

10. The special device for plastic embryo tube according to claim 9, characterized in that: A heating device is arranged in the inner cavity of the shell of the extruder, and the heating device controls the temperature of the inner cavity of the shell to 255°C ~ 280°C. The screw is arranged in the heating device, and also includes several water cooling systems, each of which includes a water cooling box, a cold water pipe, a preheating pipe and a return water pipe. A preheating device is arranged outside the feed section of the screw, and several sections of preheating channels are arranged in the shell of the preheating device; a plurality of temperature measuring sensors for detecting the melt temperature on the screw are arranged on the inner wall of the heating device, and several sections of cooling channels are arranged in the shell of the heating device; one end of the cold water pipe is connected to the outlet of the water cooling box, and the other end of the cold water pipe is connected to the inlet of the cooling channel, one end of the preheating pipe is connected to the outlet of the cooling channel, and the other end of the preheating pipe is connected to the inlet of the preheating channel, one end of the return water pipe is connected to the outlet of the preheating channel, and the other end of the return water pipe is connected to the inlet of the water cooling box.

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