Preparation method of BOPP (Biaxially-oriented Polypropylene) composite film with oxygen-barrier modified preparation

Abstract

The invention discloses a preparation method of a BOPP (Biaxially-oriented Polypropylene) composite film with an oxygen-barrier modified preparation. The preparation method comprises the following specific steps: S1, mixing raw materials: adding 15-25% of EVOH (Ethylene Vinyl Alcohol), 4-8% of PP-g-MAH (Polypropylene-g-MAH), 3-5% of organic montmorillonite, 0.3-0.5% of magnesium stearate and the balance of PP matrix in proportion, and mixing in an extruder; s2, injecting a dispersion liquid: injecting an ethanol dispersion liquid in the mixing process, and controlling the vacuum devolatilization pressure to be-0.08 MPa; s3, master batch preparation: performing melt extrusion granulation to obtain composite master batch; s4, three-layer co-extrusion casting: feeding materials independently by the three extruders respectively to realize three-layer co-extrusion casting; s5, carrying out two-way stretching treatment; s6, carrying out post-treatment; s7, surface treatment; and S8, rolling is conducted. According to the preparation method of the BOPP composite film with the oxygen-barrier modified preparation, disclosed by the invention, the barrier property, the mechanical property and the processability are synchronously increased.

Description

Technical Field

[0001] This invention relates to the field of plastic film materials technology, and in particular to a method for preparing a BOPP composite film with an oxygen-barrier modifier. Background Technology

[0002] Currently, food and pharmaceutical preservation requires packaging materials with excellent oxygen barrier properties to prevent the destruction of physiologically active substances by oxygen in the air. Biaxially oriented polypropylene (BOPP) film is widely used in food and pharmaceutical packaging. Compared with traditional plastic packaging films, it has good mechanical properties and a certain degree of oxygen barrier properties. However, due to the non-polar nature of polypropylene, the oxygen permeability (OTR) of traditional BOPP film is typically as high as 800-1200 cm³ / (m²·24h·0.1MPa). Its oxygen barrier properties are currently far from meeting the packaging needs of foods and pharmaceuticals where contact with air would degrade the quality of the active ingredients. Therefore, it is difficult to meet the high-barrier packaging requirements of the food and pharmaceutical industries.

[0003] The current improvement scheme mainly faces the following bottlenecks: the limitations of single modification. Although the oxygen permeability of EVOH can be as low as 50-80 cm³ / (m²·24h·0.1MPa), its barrier performance is significantly affected by humidity and requires secondary processing, which increases costs. Summary of the Invention

[0004] This invention discloses a method for preparing a BOPP composite film with an oxygen-barrier modifier, aiming to solve the technical problem of how to overcome the limitations of single modification.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a BOPP composite film with an oxygen-barrier modifier includes the following specific steps:

[0007] S1: Raw material mixing: Add 15-25% EVOH, 4-8% PP-g-MAH, 3-5% organo-modified montmorillonite, 0.3-0.5% magnesium stearate and the balance PP matrix in proportion, and mix in an extruder;

[0008] S2: Injection of dispersion: During the mixing process, inject the ethanol dispersion and control the vacuum devolatilization pressure at -0.08 MPa;

[0009] S3: Masterbatch preparation: melt extrusion granulation to obtain composite masterbatch;

[0010] S4: Three-layer co-extrusion casting: Three extruders are fed independently to achieve three-layer co-extrusion casting;

[0011] S5: Biaxial stretching treatment: Biaxial stretching is performed using a synchronous stretching device;

[0012] S6: Post-treatment: Heat setting treatment, processed for 25 seconds under hot air circulation at 160℃;

[0013] S7: Surface treatment: Dielectric barrier discharge plasma treatment;

[0014] S8: Roll up.

[0015] The quaternary system of this invention achieves stable OTR output for the first time under industrial extrusion conditions through the synergistic effect of EVOH / PP-g-MAH chemical crosslinking and OMMT physical barrier, combined with the directional lubrication of magnesium stearate. Simultaneously, it achieves breakthroughs in barrier performance, interface strengthening and dispersion optimization, and reduction of melt viscosity by magnesium stearate. Thus, this formulation achieves a simultaneous leap in barrier properties, mechanical properties, and processability through a three-level synergy of EVOH / PP-g-MAH chemical crosslinking-led barrier, OMMT nanosheet physical assistance, and magnesium stearate processing lubrication.

[0016] In a preferred embodiment, the extruder in S1 includes: an extruder body; a premixing mechanism fixedly connected to the feed inlet of the extruder body; and a cleaning mechanism installed on one side of the premixing mechanism.

[0017] The premixing mechanism includes: a premixing chamber, a top plate fixedly connected to the inner wall of its top, and two feed inlets fixedly connected to the inner wall of the top of the top plate; and two support shafts symmetrically rotatably connected to the inner walls of opposite sides of the premixing chamber.

[0018] The premixing mechanism further includes: four sets of tapping plates, each set of tapping plates including the same number of tapping plates, two sets of tapping plates are fixedly connected to the outer circumference of each support shaft, and the two sets of tapping plates are staggered, and the two sets of tapping plates facing each other on the two support shafts are also staggered; a motor, fixedly connected to one side of the outer wall of the premixing chamber, and its output end passes through the premixing chamber and is fixedly connected to one of the support shafts;

[0019] The premixing mechanism further includes: two gears, which are fixedly connected to the same end of two support shafts and mesh with each other; two sleeves, which are rotatably connected to the middle section of two support shafts, and each sleeve has a vertical rod fixedly connected to the outer wall of its bottom end, and each vertical rod has an inclined support fixedly connected to its outer side.

[0020] The premixing mechanism further includes: a guide ramp, symmetrically arranged on the bottom inner wall of the premixing chamber, with the bottom ends of the vertical rod and the ramp support fixedly connected to the guide ramp; two curved partitions, symmetrically fixedly connected to the inner walls of opposite sides of the two vertical rods; and a slot located between the curved partitions and the guide ramp.

[0021] The premixing mechanism further includes: a perforation that extends through the premixing chamber, the vertical rod, and the curved partition; multiple suction bends that are symmetrically and fixedly connected within the perforation; multiple negative pressure units that are fixedly connected to the outer wall of the premixing chamber and are fixedly connected to the suction bends; and multiple suction hoses that are fixedly connected to the input end of the negative pressure units.

[0022] With a premixing mechanism, different granular base materials enter the premixing chamber through the feed inlet and fall diagonally above the two support shafts. Multiple beaters rotate rapidly, continuously beating the falling base materials, causing them to fall between two curved partitions for premixing. Under the action of the beaters, uniform premixing can be achieved before the base materials enter the extruder body. At the same time, the base materials that are stuck together are broken up to optimize the uniformity of mixing. Based on the setting of the negative pressure machine, powdered additives can be extracted and enter the base material mixing position. The powdered additives are sprayed out and directly mixed with the base materials. This can simultaneously achieve preferential mixing of different base materials, provide beating force to disperse the sticky base materials, and spray the powdered additives for mixing, thereby improving plasticizing efficiency.

[0023] In a preferred embodiment, the cleaning mechanism includes: an irregularly shaped scraper, movably fitted to the inner wall of two curved partitions, with a slide rod fixedly connected to one outer wall of the scraper, the slide rod being movably and tightly inserted into one side of the premixing chamber, and a carriage fixedly connected to the outer end of the slide rod; an electric guide rail, fixedly connected to one outer wall of the premixing chamber, with the carriage movably connected to the electric guide rail; and a square through slot, penetrating the inner wall of the premixing chamber on the same side.

[0024] The cleaning mechanism further includes: a support cover, which is fixedly connected to the outer wall of the premixing chamber on the same side, and the inner wall of the support cover is fixedly connected to multiple springs; and a collision plate, which is movably embedded in a square through slot, and one side of the plate is fixedly connected to multiple springs.

[0025] By incorporating a cleaning mechanism, the carriage moves via an electric guide rail, simultaneously propelling the shaped scraper forward. This causes the powder adhering to the inner wall of the curved partition to detach and fall, then smoothly enter the extruder body. Subsequently, the shaped scraper returns to its original position and impacts the protruding collision plate, generating high-frequency vibration and completing the self-cleaning process. Thus, this structure prevents the waste of powder additives and further ensures the accuracy of the formulation.

[0026] As can be seen from the above, a method for preparing a BOPP composite film with an oxygen-barrier modified agent includes the following specific steps: S1: Raw material mixing: 15-25% EVOH, 4-8% PP-g-MAH, 3-5% organo-modified montmorillonite, 0.3-0.5% magnesium stearate, and the balance PP matrix are added in proportion and mixed in an extruder; S2: Injection of dispersion: Ethanol dispersion is injected during the mixing process, and the vacuum devolatilization pressure is controlled at -0.08MPa; S3: Masterbatch preparation: Melt extrusion granulation is performed to obtain composite masterbatch; S4: Three-layer co-extrusion casting: Three extruders are fed independently to achieve three-layer co-extrusion casting; S5: Biaxial stretching treatment: Biaxial stretching is performed using a synchronous stretching device; S6: Post-treatment: Heat setting treatment is performed under hot air circulation at 160℃ for 25 seconds; S7: Surface treatment: Dielectric barrier discharge plasma treatment; S8: Winding. The method for preparing BOPP composite films with oxygen-barrier modified agents provided by this invention achieves a simultaneous leap in barrier properties, mechanical properties, and processability. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation method of a BOPP composite film with an oxygen-barrier modified agent proposed in this invention.

[0028] Figure 2 This is a schematic diagram of the overall structure of an extruder for a method of preparing a BOPP composite film with an oxygen-barrier modified agent proposed in this invention.

[0029] Figure 3 This is a schematic diagram of the internal structure of the premixing mechanism in the preparation method of BOPP composite film with oxygen-barrier modified agent proposed in this invention.

[0030] Figure 4 This is a schematic diagram showing the premixing mechanism of a method for preparing a BOPP composite film with an oxygen-barrier modified agent, as proposed in this invention.

[0031] Figure 5 This is a schematic diagram showing the cleaning mechanism of a method for preparing a BOPP composite film with an oxygen-barrier modified agent, as proposed in this invention.

[0032] In the diagram: 1. Premixing mechanism; 2. Cleaning mechanism; 3. Extruder body; 101. Feed inlet; 102. Top plate; 103. Gear; 104. Premixing chamber; 105. Guide slope; 106. Curved partition; 107. Groove; 108. Suction hose; 109. Negative pressure unit; 110. Suction bend; 111. Motor; 112. Beating plate; 113. Support shaft; 114. Sleeve; 115. Vertical rod; 116. Perforation; 117. Inclined support; 201. Support cover; 202. Spring; 203. Collision plate; 204. Square groove; 205. Irregular scraper; 206. Slide rod; 207. Slide carriage; 208. Electric guide rail. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] The method for preparing a BOPP composite film with an oxygen-barrier modified agent disclosed in this invention is mainly applied to the preparation of BOPP composite films.

[0035] Reference Figure 1 A method for preparing a BOPP composite film with an oxygen-barrier modifier includes the following specific steps:

[0036] S1: Raw material mixing: Add 15-25% EVOH, 4-8% PP-g-MAH, 3-5% organo-modified montmorillonite, 0.3-0.5% magnesium stearate and the balance PP matrix in proportion, and mix in an extruder;

[0037] S2: Injection of dispersion: During the mixing process, inject the ethanol dispersion and control the vacuum devolatilization pressure at -0.08 MPa;

[0038] S3: Masterbatch preparation: melt extrusion granulation to obtain composite masterbatch;

[0039] S4: Three-layer co-extrusion casting: Three extruders are fed independently to achieve three-layer co-extrusion casting;

[0040] S5: Biaxial stretching treatment: Biaxial stretching is performed using a synchronous stretching device;

[0041] S6: Post-treatment: Heat setting treatment, processed for 25 seconds under hot air circulation at 160℃;

[0042] S7: Surface treatment: Dielectric barrier discharge plasma treatment;

[0043] S8: Rewinding. The quaternary system of this invention achieves stable OTR output for the first time under industrial extrusion conditions through the synergistic effect of EVOH / PP-g-MAH chemical crosslinking and OMMT physical barrier, combined with the directional lubrication of magnesium stearate. First, breakthrough in barrier performance: the hydroxyl groups (-OH) of EVOH react with the anhydride groups of PP-g-MAH to form a dense crosslinked network, reducing the free volume of the polymer and significantly lowering the oxygen permeability (OTR). Second, interface strengthening and dispersion optimization: the anhydride groups of PP-g-MAH react with the -OH of EVOH and the silanol groups of OMMT, improving interfacial bonding strength and tensile strength. Third, magnesium stearate reduces melt viscosity, promoting the peeling and dispersion of OMMT in the matrix, improving dispersion uniformity. Thus, this formulation achieves a simultaneous leap in barrier properties, mechanical properties, and processability through a three-level synergy of EVOH / PP-g-MAH chemical crosslinking as the primary barrier, OMMT nanosheets as the physical aid, and magnesium stearate as the processing lubricant.

[0044] Reference Figure 2 and Figure 3 In a preferred embodiment, the extruder in S1 includes:

[0045] Extruder body 3;

[0046] The premixing mechanism 1 is fixedly connected to the feed inlet of the extruder body 3;

[0047] Cleaning mechanism 2 is installed on one side of premixing mechanism 1;

[0048] Premixing mechanism 1 includes:

[0049] The premixing bin 104 has a top plate 102 fixedly connected to its top inner wall, and two feed inlets 101 are fixedly connected to the top inner wall of the top plate 102.

[0050] Two pivot shafts 113 are symmetrically rotated and connected to the inner walls of opposite sides of the premixing chamber 104.

[0051] Reference Figure 3 and Figure 4 In a preferred embodiment, the premixing mechanism 1 further includes:

[0052] Four sets of striking plates 112, each set of striking plates 112 includes the same number of striking plates 112, and two sets of striking plates 112 are fixedly connected to the outer circumference of each support shaft 113, and the two sets of striking plates 112 are staggered. The two sets of striking plates 112 facing each other on the two support shafts 113 are also staggered.

[0053] Motor 111 is fixedly connected to one side of the outer wall of premix chamber 104, and its output end passes through premix chamber 104 and is fixedly connected to one of the support shafts 113.

[0054] Reference Figure 3 and Figure 4 In a preferred embodiment, the premixing mechanism 1 further includes:

[0055] Two gears 103 are fixedly connected to the same end of two support shafts 113, and the two gears 103 mesh with each other. Different granular base materials enter the premixing chamber 104 through the feed port 101 and fall just above the two support shafts 113. At this time, under the action of the motor 111, the meshing of the two gears 103 drives the two support shafts 113 to rotate inward simultaneously, driving multiple beaters 112 to rotate rapidly, continuously beating the base material falling above and guiding it towards the center position. The base material falls down along the top of the two curved partitions 106 and falls between the two curved partitions 106 for premixing. Since the two sets of beaters 112 are arranged in an alternating manner, different granular base materials can fall between the two curved partitions 106 in an alternating manner.

[0056] Two sleeves 114 are rotatably connected to the middle sections of two support shafts 113, and each sleeve 114 has a vertical rod 115 fixedly connected to the outer wall of its bottom end, and each vertical rod 115 has an inclined bracket 117 fixedly connected to its outer side.

[0057] Reference Figure 3 and Figure 4 In a preferred embodiment, the premixing mechanism 1 further includes:

[0058] The guide slope 105 is symmetrically arranged on the bottom inner wall of the premixing chamber 104, and the bottom ends of the vertical rod 115 and the slope support 117 are fixedly connected to the guide slope 105. The base material that falls to the sides falls onto the guide slope 105 and is guided to fall into the extruder body 3 through the slot 107. Thus, under the action of the beater plate 112, uniform premixing can be achieved before the base material enters the extruder body 3. At the same time, the beater force is provided to break up the base material that is stuck together, so as to optimize the uniformity of mixing while ensuring the dispersion of the base material.

[0059] Two curved partitions 106 are symmetrically fixed to the inner walls of opposite sides of two vertical rods 115;

[0060] The slot 107 is located between the curved partition 106 and the guide slope 105.

[0061] Reference Figure 3 and Figure 4 In a preferred embodiment, the premixing mechanism 1 further includes:

[0062] Perforation 116 extends through the premixing chamber 104, the vertical rod 115, and the curved partition 106.

[0063] Multiple suction bends 110 are symmetrically and fixedly connected within the perforation 116;

[0064] Multiple negative pressure units 109 are fixedly connected to the outer wall of the premixing chamber 104 and are fixedly connected to the suction bend 110;

[0065] Multiple suction hoses 108 are fixedly connected to the input end of the negative pressure machine 109. Based on the configuration of the negative pressure machine 109, powdered additives can be extracted and discharged along the suction bend 110, directly entering the space between the two curved partitions 106, i.e., the base material mixing position. The powdered additives are directly mixed with the base material through the jet discharge, and the powdered additives are blocked by the bend at the top of the curved partition 106 to prevent them from moving upward. Under this structure, different base materials can be mixed preferentially at the same time, the base material can be dispersed and bound by the patting force, and the powdered additives can be mixed by jet discharge, thereby improving plasticizing efficiency.

[0066] Reference Figure 5 In a preferred embodiment, the cleaning mechanism 2 includes:

[0067] The irregular scraper 205 is movably fitted to the inner wall of the two curved partitions 106, and a slide rod 206 is fixedly connected to one side of its outer wall. The slide rod 206 is movably and tightly inserted into one side of the premixing chamber 104, and a slide frame 207 is fixedly connected to the outer end of the slide rod 206.

[0068] The electric guide rail 208 is fixedly connected to one side of the outer wall of the premixing chamber 104, and the carriage 207 is movably connected to the electric guide rail 208.

[0069] A square through-groove 204 is installed on the inner wall of the premixing chamber 104 on the same side. Since the powder is concentrated between the two curved partitions 106 for mixing, after feeding, some powder will adhere to the inner side of the curved partitions 106. At this time, the electric guide rail 208 drives the slide 207 to move, and simultaneously drives the slide rod 206 to pass through the premixing chamber 104 and push the shaped scraper 205 forward, which moves horizontally along the inner wall of the two curved partitions 106, so that the powder adhering to the inner wall of the curved partitions 106 will fall off and enter the extruder body 3.

[0070] Reference Figure 5 In a preferred embodiment, the cleaning mechanism 2 further includes:

[0071] The support cover 201 is fixedly connected to the outer wall of the premixing chamber 104 on the same side, and multiple springs 202 are fixedly connected to the inner wall of the support cover 201.

[0072] The collision plate 203 is movably embedded in the square through slot 204, and one side of it is fixedly connected to multiple springs 202. Then, the electric guide rail 208 drives the irregular scraper 205 to return to its position and impact the protruding collision plate 203. During the impact, the springs 202 generate high-frequency vibration, causing the dust adhering to the irregular scraper 205 to fall off and complete the self-cleaning. Then, with continuous pull back, the springs 202 are squeezed, and the irregular scraper 205 fits into the premixing chamber 104, sealing the position of the square through slot 204. Thus, this structure can prevent the waste of powder additives and further ensure the accuracy of the proportion.

[0073] Working Principle: The quaternary system of this invention achieves stable OTR output for the first time under industrial extrusion conditions through the synergistic effect of EVOH / PP-g-MAH chemical crosslinking and OMMT physical barrier, combined with the directional lubrication of magnesium stearate. First, breakthrough in barrier performance: the hydroxyl groups (-OH) of EVOH react with the anhydride groups of PP-g-MAH through esterification, forming a dense crosslinked network, reducing the free volume of the polymer, and significantly reducing the oxygen permeability (OTR). Second, interface strengthening and dispersion optimization: the anhydride groups of PP-g-MAH react with the -OH of EVOH and the silanol groups of OMMT, improving interfacial bonding strength and tensile strength. Third, magnesium stearate reduces melt viscosity, promoting the exfoliation and dispersion of OMMT in the matrix, improving dispersion uniformity. Thus, this formulation achieves a simultaneous leap in barrier properties, mechanical properties, and processability through a three-level synergy of EVOH / PP-g-MAH chemical crosslinking as the primary barrier, OMMT nanosheets as the physical aid, and magnesium stearate as the processing lubricant.

[0074] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a BOPP composite film with an oxygen-barrier modifier, characterized in that, The specific steps include the following: S1: Raw material mixing: Add 15-25% EVOH, 4-8% PP-g-MAH, 3-5% organo-modified montmorillonite, 0.3-0.5% magnesium stearate and the balance PP matrix in proportion, and mix in an extruder; S2: Injection of dispersion: During the mixing process, inject the ethanol dispersion and control the vacuum devolatilization pressure at -0.08 MPa; S3: Masterbatch preparation: melt extrusion granulation to obtain composite masterbatch; S4: Three-layer co-extrusion casting: Three extruders are fed independently to achieve three-layer co-extrusion casting; S5: Biaxial stretching treatment: Biaxial stretching is performed using a synchronous stretching device; S6: Post-treatment: Heat setting treatment, processed for 25 seconds under hot air circulation at 160℃; S7: Surface treatment: Dielectric barrier discharge plasma treatment; S8: Roll up.

2. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 1, characterized in that, The extruder in S1 includes: Extruder body (3); The premixing mechanism (1) is fixedly connected to the feed port of the extruder body (3); The cleaning mechanism (2) is installed on one side of the premixing mechanism (1); The premixing mechanism (1) includes: The premixing bin (104) has a top plate (102) fixedly connected to its top inner wall, and the top inner wall of the top plate (102) has two feed inlets (101) fixedly connected to it. Two pivot shafts (113) are symmetrically rotated and connected to the inner walls of opposite sides of the premixing chamber (104).

3. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 2, characterized in that, The premixing mechanism (1) further includes: Four sets of striking plates (112), each set of striking plates (112) includes the same number of striking plates (112), and two sets of striking plates (112) are fixedly connected to the outer circumference of each support shaft (113), and the two sets of striking plates (112) are staggered. The two sets of striking plates (112) arranged opposite each other on the two support shafts (113) are also staggered. The motor (111) is fixedly connected to one side of the outer wall of the premix chamber (104), and its output end passes through the premix chamber (104) and is fixedly connected to one of the support shafts (113).

4. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 3, characterized in that, The premixing mechanism (1) further includes: Two gears (103) are fixedly connected to the same end of two support shafts (113), and the two gears (103) mesh with each other; Two sleeves (114) are rotatably connected to the middle sections of two support shafts (113), and each sleeve (114) has a vertical rod (115) fixedly connected to the bottom outer wall, and each vertical rod (115) has an inclined bracket (117) fixedly connected to the outside.

5. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 4, characterized in that, The premixing mechanism (1) further includes: A guide ramp (105) is symmetrically arranged on the bottom inner wall of the premix bin (104), and the bottom ends of the vertical rod (115) and the ramp support (117) are fixedly connected to the guide ramp (105); Two curved partitions (106) are symmetrically fixed to the inner walls of the opposite sides of the two vertical rods (115); The slot (107) is located between the curved partition (106) and the guide slope (105).

6. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 5, characterized in that, The premixing mechanism (1) further includes: The perforation (116) extends through the premixing chamber (104), the vertical bar (115), and the curved partition (106). Multiple suction bends (110) are symmetrically fixedly connected inside the perforation (116); Multiple negative pressure units (109) are fixedly connected to the outer wall of the premixing chamber (104) and are fixedly connected to the suction bend (110); Multiple suction hoses (108) are fixedly connected to the input end of the negative pressure machine (109).

7. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 5, characterized in that, The cleaning mechanism (2) includes: The irregular scraper (205) is movably attached to the inner wall of the two curved partitions (106), and a slide rod (206) is fixedly connected to one side of its outer wall. The slide rod (206) is movably and tightly inserted into one side of the premixing chamber (104), and a slide frame (207) is fixedly connected to the outer end of the slide rod (206). The electric guide rail (208) is fixedly connected to one side of the outer wall of the premixing chamber (104), and the carriage (207) is movably connected to the electric guide rail (208); A square through-hole (204) is provided through the inner wall of the premixing chamber (104) on the same side.

8. The method for preparing a BOPP composite film with an oxygen-barrier modified agent according to claim 7, characterized in that, The cleaning mechanism (2) also includes: The support cover (201) is fixedly connected to the outer wall of the premixing chamber (104) on the same side, and multiple springs (202) are fixedly connected to the inner wall of the support cover (201). The collision plate (203) is movably embedded in the square through slot (204), and one side of it is fixedly connected to multiple springs (202).

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