Calendering film-making process based on direct molding of polymer matrix particles

Abstract

The invention relates to the technical field of high polymer material processing, and discloses a calendering film preparation process based on direct molding of polymer matrix particles. Polymer matrix particles, filler and auxiliaries are directly subjected to melt blending granulation to prepare composite particles, and the composite particles are directly put into a roller of a calender after being subjected to magnetic separation screening, so that one-step continuous plasticizing film formation is realized. Compared with a traditional process, 3-4 procedures are reduced, the dust concentration is reduced to be smaller than 5 mg / m < 3 >, calendering energy consumption is reduced to 0.8-1.2 kW.h / kg, and the method is suitable for material systems such as polyester, such as low-melting-point PET, PLA and PMMA, and polyolefin, such as PP and PE.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material processing, and discloses a grinding-free, short-process calendering film-making process, in particular a calendering film-making process based on direct molding of polymer matrix particles. Background Art

[0002] The traditional PVC calendering process requires multiple steps such as mixer-planetary mixer-rolling mill-filter, resulting in a lengthy production process. Furthermore, the PVC plasticizing process releases irritating gases such as HCl (at concentrations up to 50-80ppm), requiring an additional waste gas treatment system. Furthermore, a large amount of dust is generated during the feeding and mixing process, which not only pollutes the environment but also poses a threat to the health of operators. Currently, some new polymer materials (such as PP and PE) are being used in calendering film-making processes. Although the release of harmful gases during the processing is significantly reduced, the current process involves pre-processing the raw materials by grinding them, then mixing the ground polymer powder with inorganic fillers and functional additives at high speed, and feeding it to the high-speed kneading machine of the calendering plant. The powder is then passed through a planetary mixer or internal mixer, rolling mill, and filter, and then fed to the calendering roller for further shearing and plasticization. The production process is complex and lengthy, with serious dust pollution in key links, with dust concentrations as high as 80-120mg / m 3 (Exceeding the occupational exposure limit of 10mg / m 3 Therefore, it is of great practical significance to develop a calendering film-making process method that does not require grinding and has a short process. Summary of the Invention

[0003] In view of this, the present invention discloses a calendering film-making process based on direct molding of polymer matrix particles.

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

[0005] A calendering film-making process based on direct molding of polymer matrix particles, which directly melt-blends and granulates polymer matrix particles with a particle size of 2-5 mm with fillers and additives to prepare particles with a size of 3-6 mm and a bulk density of 0.55-0.65 g / cm 3 The composite particles are directly put into the roller of the calender after magnetic separation and screening, realizing one-step continuous plasticization and film formation;

[0006] The roller temperature is 165-195°C and the line speed is 15-25m / min.

[0007] Furthermore, the process specifically includes the following steps:

[0008] (1) putting polymer matrix particles, inorganic fillers, and functional additives into a twin-screw extruder, melt-blending and granulating at 160-195° C. to obtain composite particles;

[0009] (2) After being processed by a vibrating screen and a permanent magnetic iron remover, the composite particles are directly fed into the rollers of a calender; the screen mesh size is 6-9 mm, and the magnetic field strength is ≥8000 Gs;

[0010] (3) The temperature gradient of the four rollers of the calender is set to 182±5℃ for roller I, 187±5℃ for roller II, 175±5℃ for roller III, and 170±5℃ for roller IV, with a roller gap spacing of 0.1-0.5mm and a line speed of 15-25m / min, and finally continuous film formation is completed.

[0011] Furthermore, the raw materials of the polymer matrix particles, the inorganic fillers, and the functional additives include, by weight percentage:

[0012] Low melting point PET / HDPE 60-80%, lightweight nano calcium carbonate 10-25%, calcium stearate 1-5%, needle-shaped wollastonite 5%, nano-TiO2 3-8%, PE-g-MAH 2-5%, GMA-polyester 2-5%.

[0013] Furthermore, a co-rotating twin-screw extruder is used, the temperature is set to 160-170°C in zone I, 180-190°C in zone II, and 185-195°C in zone III, and the screw speed is 200-250 rpm.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This method eliminates the need for milling pretreatment. Instead, polymer particles are extruded and granulated together with fillers and additives. The granulated composite particles can be directly passed through a screen and magnet before being fed directly to a calender roller for rapid plasticization to form a continuous sheet or film. This method eliminates milling, produces low dust, shortens the process, and eliminates the need for raw material pretreatment. Furthermore, the granulated composite particles require a short plasticization process and consume less energy during calendering.

[0016] Furthermore, the present invention realizes direct calendering of polymer particles for the first time, eliminating the grinding process and adopting a twin-screw extrusion granulation-calendering integrated production line, which shortens the process by more than 40% and controls the dust concentration of the whole process within the occupational exposure limit (10mg / m 3 ) is less than 50%.

[0017] In addition, compared with the existing technology, the dust emission of the present invention is reduced by 90%, and the emission of harmful gases is close to zero; the unit energy consumption is reduced by 30%, and the equipment investment is reduced by 25%; the uniformity of film thickness is improved by 20%, and the mechanical properties are improved by 15%.

[0018] Furthermore, the dust concentration is compared with the traditional process: 80-120mg / m 3 →The present invention is less than 5mg / m 3(GBZ / T192.1-2007 test); VOC emissions are reduced: HCl concentration is reduced from 50-80 ppm to undetectable (GB 31572-2015 standard); and the present invention has passed pilot testing. Industrial production equipment can choose Coperion (Nanjing) Machinery Co., Ltd.'s ZSK series twin-screw extruder and φ450×1200 four-roll calender combination. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0021] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0022] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0023] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0024] The invention discloses a calendering film-making process based on direct molding of polymer matrix particles.

[0025] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0026] Example 1

[0027] Raw materials: 66kg low melting point PET / HDPE, 15kg light nano calcium carbonate, 3kg calcium stearate, 5kg needle-shaped wollastonite, 5kg nano TiO2, 2kg PE-g-MAH, 4kg GMA-polyester;

[0028] Matrix resin: Low melting point PET (melt index 20g / 10min) and HDPE (density 0.94g / cm 3 ) blended to achieve melt processing below 160°C; nano-reinforced phase: light calcium carbonate (particle size D50 = 30nm) and needle-shaped wollastonite (diameter 1μm, length 15μm) form a three-dimensional network structure; interface modification: PE-g-MAH and GMA-polyester synergistically improve the compatibility of inorganic fillers and resins (interface binding energy ≥50mJ / m 2 ).

[0029] Granulation process: twin-screw extruder (Coperion ZSK-58), barrel temperature 165 / 180 / 185°C, die temperature 190°C, pellet size 3 mm;

[0030] Calendering parameters: four-roll temperature 182 / 187 / 175 / 170℃, III-IV roller spacing 0.15mm, line speed 18m / min, cooling roller temperature 30-50℃, winding tension 50-80N.

[0031] Specifically, the operating steps revolve around a calendering film-making process based on direct molding of polymer matrix particles. First, the raw materials are prepared, followed by granulation through a twin-screw extruder, and then the composite particles are processed through a vibrating screen and a permanent magnetic iron remover, and then a calender is used to form a film, and finally the film is cooled and rolled up.

[0032] 1. Raw material preparation: According to the raw material ratio of Example 1, accurately weigh low melting point PET / HDPE, lightweight nano calcium carbonate, calcium stearate, needle-shaped wollastonite, nano TiO2, PE-g-MAH, GMA-polyester and other raw materials to ensure that the proportion of each component is accurate.

[0033] 2. Granulation: Start the Coperion ZSK-58 twin-screw extruder and set the barrel temperatures to 165°C, 180°C, and 185°C, respectively, and the die temperature to 190°C. After the temperatures stabilize, place the prepared raw materials into the twin-screw extruder hopper. Driven by the screws, the raw materials gradually melt and blend in different temperature zones. After being fully plasticized, they are extruded from the die and cut into 3mm composite pellets by a pelletizer. During the pelletization process, closely monitor the extruder's operation to ensure uniform extrusion of the raw materials and consistent pellet size.

[0034] 3. Composite Particle Pretreatment: After granulation, the composite particles are conveyed to a vibrating screen with a mesh size of 6-9mm to screen the composite particles and remove particles that do not meet the size requirements. The composite particles then pass through a permanent magnetic iron remover with a magnetic field strength of ≥8000Gs to absorb and remove magnetic impurities from the particles, ensuring the purity of the composite particles fed into the calender and ensuring the safe operation of the calendering equipment.

[0035] 4. Calendering: The pre-treated composite particles are directly fed into the calender rollers. The temperature of the four rollers is adjusted according to a set gradient: Roller I at 182°C, Roller II at 187°C, Roller III at 175°C, and Roller IV at 170°C, ensuring stable roller temperatures. The gap between rollers III and IV is adjusted to 0.15mm, and the calender line speed is set to 18m / min. Under the action of the calender rollers, the composite particles are gradually plasticized and stretched to form a continuous film. During the calendering process, the film's formation is monitored in real time to ensure uniform thickness and the absence of obvious defects.

[0036] 5. Film Cooling and Winding: The film exiting the calender enters the chill roller area, where the temperature is controlled at 30-50°C. The chill roller cools the film and solidifies it into its final shape. During the cooling process, uniform cooling is ensured to prevent deformation caused by uneven cooling. The cooled film is then wound on a winding device with a tension controlled at 50-80N to ensure a neat and tight roll, facilitating subsequent storage and transportation.

[0037] Finished product indicators: thickness 0.08mm, tensile strength 45MPa.

[0038] Dust concentration comparison: traditional process 110mg / m 3 , Example 1 of the present invention is only 3mg / m 3 (GBZ / T192.1-2007 test); VOC emissions reduced: HCl concentration dropped from 65ppm to undetectable (GB 31572-2015 standard).

[0039] Example 2

[0040] 1. Raw material ratio: low melting point PET / HDPE 70kg, light nano calcium carbonate 12kg, calcium stearate 2kg, needle-shaped wollastonite 5kg, nano TiO2 6kg, PE-g-MAH 3kg, GMA-polyester 2kg.

[0041] Low melting point PET (melt index 22g / 10min) and HDPE (density 0.935g / cm 3) blended, light calcium carbonate (particle size D50 = 25nm) and needle-shaped wollastonite (diameter 0.8μm, length 12μm) formed a three-dimensional network structure, PE-g-MAH and GMA-polyester synergistically improved the compatibility of inorganic fillers and resins (interface binding energy ≥ 52mJ / m 2 ).

[0042] 2. Granulation process: twin-screw extruder (Coperion ZSK-58), barrel temperature 162 / 182 / 188°C, die temperature 192°C, pellet size 4 mm.

[0043] 3. Calendering parameters: four-roll temperature 180 / 185 / 173 / 168℃, III-IV roller spacing 0.2mm, line speed 20m / min, cooling roller temperature 35-50℃, winding tension 60-90N.

[0044] The specific operation steps are as described in Example 1.

[0045] 4. Finished product indicators: thickness 0.1mm, tensile strength 48MPa.

[0046] Example 3

[0047] 1. Raw material ratio: low melting point PET / HDPE 62kg, light nano calcium carbonate 20kg, calcium stearate 4kg, needle-shaped wollastonite 5kg, nano TiO2 4kg, PE-g-MAH 4kg, GMA-polyester 1kg.

[0048] Low melting point PET (melt index 18g / 10min) and HDPE (density 0.945g / cm 3 ) blended, light calcium carbonate (particle size D50 = 35nm) and needle-shaped wollastonite (diameter 1.2μm, length 18μm) formed a three-dimensional network structure, PE-g-MAH and GMA-polyester synergistically improved the compatibility of inorganic fillers and resins (interface binding energy ≥48mJ / m 2 ).

[0049] 2. Granulation process: twin-screw extruder (Coperion ZSK-58), barrel temperature 168 / 185 / 190°C, die temperature 195°C, pellet size 5 mm.

[0050] 3. Calendering parameters: four-roll temperature 185 / 190 / 178 / 173℃, III-IV roller spacing 0.3mm, line speed 22m / min, cooling roller temperature 40-55℃, winding tension 70-100N.

[0051] The specific operation steps are as described in Example 1.

[0052] 4. Finished product indicators: thickness 0.12mm, tensile strength 42MPa.

[0053] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are provided to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention without inventive work are also considered to fall within the scope of protection of the present invention.

[0054] Comparative Example 1

[0055] 1. Raw Material Processing and Processing: Using conventional processes, low-melting-point PET and HDPE were first ground into powder. The powder was then mixed with lightweight nano-calcium carbonate, calcium stearate, acicular wollastonite, nano-TiO2, PE-g-MAH, and GMA-polyester in the proportions described in Example 1 in a high-speed mixer. The mixture then passed through a planetary mill, a roller mill, and a filter before being fed into a calender. The four rollers in the calender were set at 182 / 187 / 175 / 170°C, with a gap of 0.15 mm between the III and IV rollers, and a line speed of 18 m / min.

[0056] 2. Finished product indicators: thickness 0.08mm, tensile strength 38MPa, dust concentration 85mg / m 3 , the HCl concentration during the production process is 55ppm.

[0057] Comparative Example 2

[0058] 1. Raw Material Preparation and Processing: The polymer matrix particles, fillers, and additives were mixed according to the proportions in Example 1, but were not melt-blended and pelletized. The mixture was directly fed into a calender. The four-roller temperatures of the calender were 182 / 187 / 175 / 170°C, the gap between the III-IV rollers was 0.15 mm, and the line speed was 18 m / min.

[0059] 2. Finished product indicators: The film cannot be continuously formed, multiple holes and defects appear, the tensile strength cannot be effectively measured, the dust concentration is high, and there is obvious material agglomeration during the production process.

[0060] Test Example 1: Test on the influence of different screw speeds on finished product performance

[0061] 1. Raw materials and granulation process: The raw material ratio of Example 1 was adopted, a twin-screw extruder (Coperion ZSK-58), barrel temperatures of 165 / 180 / 185°C, a die temperature of 190°C, a pelletizing size of 3 mm, and screw speeds of 180 rpm, 200 rpm, 220 rpm, and 250 rpm were set for granulation, respectively.

[0062] 2. Calendering parameters: four-roll temperature 182 / 187 / 175 / 170℃, III-IV roller spacing 0.15mm, line speed 18m / min, cooling roller temperature 30-50℃, winding tension 50-80N.

[0063] 3. Test results: When the screw speed is 180rpm, the tensile strength of the finished film is 42MPa, and the thickness uniformity is general; when it is 200rpm, the tensile strength is 45MPa, and the thickness uniformity is good; when it is 220rpm, the tensile strength is 46MPa, and the thickness uniformity is good; when it is 250rpm, the tensile strength is 44MPa, slight melt fracture occurs, and the thickness uniformity decreases slightly.

[0064] Test Example 2: Effect of different calendering line speeds on finished product performance

[0065] 1. Raw materials and granulation process: The raw material ratio and granulation process of Example 1 were adopted.

[0066] 2. Calendering parameters: four-roll temperature 182 / 187 / 175 / 170℃, III-IV roller spacing 0.15mm, set line speeds to 12m / min, 15m / min, 18m / min, 22m / min, 25m / min for calendering respectively, cooling roller temperature 30-50℃, winding tension 50-80N.

[0067] 3. Test results: When the line speed is 12m / min, the production efficiency is low, the film surface is smooth, and the tensile strength is 46MPa; when the line speed is 15m / min, the production efficiency is improved, and the tensile strength is 45MPa; when the line speed is 18m / min, the overall performance is good, and the tensile strength is 45MPa; when the line speed is 22m / min, slight wrinkles appear on the film surface, and the tensile strength is 43MPa; when the line speed is 25m / min, the wrinkling phenomenon is aggravated, and the tensile strength is 40MPa.

[0068] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A calendering film-making process based on direct molding of polymer matrix particles, characterized in that: The polymer matrix particles with a particle size of 2-5 mm are directly melt-blended with fillers and additives to produce particles with a particle size of 3-6 mm and a bulk density of 0.55-0.65 g / cm 3 The composite particles are directly put into the roller of the calender after magnetic separation and screening, realizing one-step continuous plasticization and film formation; Among them, the roller temperature is 165-195℃ and the line speed is 15-25m / min.

2. The process according to claim 1, characterized in that The specific steps include: (1) putting polymer matrix particles, inorganic fillers, and functional additives into a twin-screw extruder, melt-blending and granulating at 160-195° C. to obtain composite particles; (2) After being processed by a vibrating screen and a permanent magnetic iron remover, the composite particles are directly fed into the rollers of a calender; the screen mesh size is 6-9 mm, and the magnetic field strength is ≥8000 Gs; (3) The temperature gradient of the four rollers of the calender is set to 182±5℃ for roller I, 187±5℃ for roller II, 175±5℃ for roller III, and 170±5℃ for roller IV, with a roller gap spacing of 0.1-0.5mm and a line speed of 15-25m / min, and finally continuous film formation is completed.

3. The process according to claim 1 or 2, characterized in that The raw materials of polymer matrix particles, inorganic fillers and functional additives, calculated by weight percentage, include: Low melting point PET / HDPE 60-80%, lightweight nano calcium carbonate 10-25%, calcium stearate 1-5%, needle-shaped wollastonite 5%, nano-TiO2 3-8%, PE-g-MAH 2-5%, GMA-polyester 2-5%.

4. The process according to claim 2, characterized in that A co-rotating twin-screw extruder was used, with the temperatures set at 160-170°C in zone I, 180-190°C in zone II, and 185-195°C in zone III, and the screw speed was 200-250 rpm.