Production method of low-moisture-absorption high-barrier BOPA (Biaxially Oriented Polyamide) film

Abstract

The invention discloses a production method of a low-moisture-absorption high-barrier BOPA film. The BOPA film comprises a surface layer, a middle layer and an inner layer, the surface layer is composed of PA6, BC and an inorganic powder surface treating agent; the middle layer is prepared from low-water-absorption copolyamide resin, MXD6, silane coupling agent modified glass fibers, POE-g-MAH, talcum powder, an antioxidant and a lubricating agent; and the inner layer is composed of 11-aminoundecanoic acid modified PA6, phenolic resin, glass fibers, an antioxidant and a lubricant. The BOPA film has the advantages of low moisture absorption and high barrier.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of BOPA, in particular to a production method of high-transparency and high-toughness BOPA film. BACKGROUND

[0002] Polyamide (PA) is a thermoplastic resin containing repeating amide group structure in the molecular chain, which has excellent mechanical properties, self-lubricating properties, processing properties and many other excellent characteristics. For example, PA6, PA66 and the like are widely used in the field of engineering plastics. However, due to the strong polar amide group on the main chain of the polyamide resin, it is easy to form hydrogen bonds with water molecules, so the polyamide resin is easy to absorb water during use, has high hygroscopicity, and causes the products to have poor dimensional stability, decreased mechanical properties, and short service life. SUMMARY

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a production method of low-hygroscopic and high-barrier BOPA film.

[0004] The technical solution of the present application is: a production method of low-hygroscopic and high-barrier BOPA film, the BOPA film comprising a surface layer, an intermediate layer and an inner layer. The surface layer is composed of PA6, BC and inorganic powder surface treatment agent. The intermediate layer is composed of low-water-absorption copolyamide resin, MXD6, silane coupling agent modified glass fiber, POE-g-MAH, talcum powder, antioxidant and lubricant. The inner layer is composed of 11-aminoundecanoic acid modified PA6, phenolic resin, glass fiber, antioxidant and lubricant. The production method comprises the following steps: (1) The surface layer raw materials are blended; the intermediate layer is prepared by PACM-6 nylon salt, caprolactam, benzoic acid and deionized water to prepare low-water-absorption copolyamide resin, and the prepared low-water-absorption copolyamide resin is blended with silane coupling agent modified glass fiber, POE-g-MAH, talcum powder, antioxidant and lubricant; 11-aminoundecanoic acid modified PA6 is prepared, and the prepared 11-aminoundecanoic acid modified PA6 is blended with phenolic resin, glass fiber, antioxidant and lubricant; (2) The surface layer, intermediate layer and inner layer raw materials are fed into respective extruders for plasticizing and mixing; (3) The molten melt is respectively fed into the die head, and the melt is combined in the die head to form a molten sheet through the flat die head opening; (4) The sheet is attached to the chill roller by the air knife for quenching to form an unformed sheet, and then the sheet is shaped into a cast sheet after water bath cooling; (5) The cast sheet is stretched to form a film; (6) The film is wound up.

[0005] Further, the preparation method of the water-absorbing copolyamide resin in the intermediate layer is as follows: Adipic acid is placed in deionized water at 90℃, stirred at a uniform speed, and 4,4'-diaminodicyclohexylmethane is slowly added dropwise to obtain PACM-6 nylon salt. PACM-6 nylon salt and caprolactam are added to a polymerization reactor, along with benzoic acid and deionized water. The reactor is evacuated to a vacuum degree of 0.1 MPa, then high-purity nitrogen is introduced to 0.2 MPa. The air inside the reactor is replaced three times to balance the pressure inside the reactor to atmospheric pressure. The polymerization reactor is gradually heated to 210℃, maintaining an internal pressure of 2.0 MPa for 1.5 h. The temperature is then further increased to 250℃, and the vent valve is opened to begin venting. During the heating and venting process, the internal pressure is maintained at 2.0 MPa. The temperature is increased to 250℃. Afterwards, close the exhaust valve and maintain pressure for 1 hour, release the gas to normal pressure, drain the water from the system, and then gradually evacuate the system to reduce the pressure to -0.05 MPa. Discharge the material, granulate and extract to obtain the low water absorption copolyamide resin.

[0006] Furthermore, the components of PACM-6 nylon salt, caprolactam, benzoic acid, and deionized water in the polymerization reactor are in the following mass ratio: PACM-6 nylon salt 33%, caprolactam 50%, benzoic acid 0.2%, and deionized water 16.8%.

[0007] Further, the preparation method of 11-aminoundecanoic acid modified PA6 is as follows: 11-aminoundecanoic acid and caprolactam are mixed and added to a reactor, then adipic acid end-capping agent and deionized water are added as catalysts. Then, nitrogen is used to purge the oxygen in the reactor, and the ring-opening reaction is carried out under normal pressure and sealed. The polymerization temperature is controlled at 230 ℃, the polymerization pressure is controlled at 0.3 MPa, the rotation speed is 400 r / min, and the total duration of the ring-opening reaction is 2 h. After the ring-opening reaction is completed, the reactor is depressurized and polycondensation reaction is carried out for a total depressurization time of 1 h. After completion, nitrogen is continuously purged for protection, the temperature is controlled at 250 ℃, and the polycondensation reaction is carried out for 5 h before the material is discharged to obtain 11-aminoundecanoic acid modified PA6.

[0008] Furthermore, the surface layer consists of the following components by mass ratio: PA6 69%, BC 30%, and inorganic powder surface treatment agent 1%.

[0009] Furthermore, the components of the intermediate layer are as follows by mass ratio: 38% low water absorption copolyamide resin, 30% MXD6, 15% silane coupling agent modified glass fiber, 10% POE-g-MAH, 6% talc, 0.5% antioxidant, and 0.5% lubricant.

[0010] Furthermore, the components of the inner layer are as follows by mass ratio: 49% modified PA6 with 11-aminoundecanoic acid, 15% phenolic resin, 35% glass fiber, 0.5% antioxidant, and 0.5% lubricant.

[0011] Furthermore, BC consists of small-diameter BC and large-diameter BC, with the small-diameter BC having a particle size of 200 nm and the large-diameter BC having a particle size of 25 μm.

[0012] Furthermore, the carbonization temperature of BC is 1100℃.

[0013] The beneficial effects of this invention are as follows: PA6 on the surface is the matrix, and BC is the reinforcement. The addition of BC improves the water resistance and thermal stability of PA6. When the content of BC is 30wt%, it is beneficial to improve the processing fluidity of PA6. BC has a heterogeneous nucleation effect in the PA6 / BC composite system, which is beneficial to the formation of a stable α crystal form of PA6, and improves the crystallization temperature and crystallinity of the composite material. BC particles have good dispersion and wettability in the PA6 matrix, and generate van der Waals forces and mechanical interlocking effects with the PA6 matrix, thereby increasing the interfacial bonding strength and mechanical properties. The low-absorbency copolyamide resin in the middle layer uses PACM-6 nylon salt. PACM-6 nylon salt can significantly reduce the water absorption rate of the material, mainly due to the introduction of a large number of alicyclic structures, which can significantly reduce the amide group content on the nylon molecular backbone, thus showing a significant reduction in water absorption rate. The addition of MXD6 improves the barrier properties of the material. The addition of silane coupling agent modified glass fiber, POE-g-MAH, and talc improves the mechanical properties of the material. The addition of 11-aminoundecanoic acid to the inner layer reduces the moisture regain and saturated water absorption of the fiber, thus decreasing the hygroscopicity of the modified PA fiber. Phenolic resin can improve the mechanical properties and moisture resistance of the composite material. Detailed Implementation

[0014] To provide a more intuitive and complete understanding of the technical solution of this invention, the following non-limiting features are described: A method for producing a low-moisture-absorbing, high-barrier BOPA film, wherein the BOPA film comprises a surface layer, a middle layer, and an inner layer. The surface layer consists of PA6, BC, and inorganic powder surface treatment agent, where BC is bamboo charcoal; The intermediate layer is composed of low water absorption copolyamide resin, MXD6, silane coupling agent modified glass fiber, POE-g-MAH, talc, antioxidant, and lubricant; The inner layer is composed of 11-aminoundecanoic acid modified PA6, phenolic resin, glass fiber, antioxidant, and lubricant; The production method includes the following steps: (1) Surface raw material blending; the middle layer is prepared by using PACM-6 nylon salt, caprolactam, benzoic acid and deionized water to prepare low water-absorbing copolyamide resin, and the obtained low water-absorbing copolyamide resin is blended with silane coupling agent modified glass fiber, POE-g-MAH, talc, antioxidant and lubricant; 11-aminoundecanoic acid modified PA6 is prepared, and the obtained 11-aminoundecanoic acid modified PA6 is blended with phenolic resin, glass fiber, antioxidant and lubricant; (2) The surface, intermediate, and inner layer raw materials are fed into their respective extruders for mixing and plasticizing; (3) The molten melt is fed into the die head respectively. After the melt merges in the die head, it forms a molten sheet through the flat die head opening; (4) Use an air knife to attach the sheet to the cooling roller and cool it rapidly to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (5) The cast sheet is stretched to form a thin film; (6) Wind up the film.

[0015] The intermediate layer uses antioxidant 1098 as the antioxidant and polyethylene wax H110 as the lubricant. The inner layer uses antioxidant 1098 as the antioxidant and silicone as the lubricant.

[0016] The preparation method of the water-absorbing copolyamide resin in the intermediate layer is as follows: Adipic acid is placed in deionized water at 90℃ and stirred at a uniform speed. 4,4'-Diaminodicyclohexylmethane (PCAM) is slowly added dropwise to obtain PACM-6 nylon salt. PACM-6 nylon salt and caprolactam are added to a polymerization reactor, along with benzoic acid and deionized water. The reactor is evacuated to a vacuum degree of 0.1 MPa, and then high-purity nitrogen is introduced to 0.2 MPa. The air inside the reactor is replaced three times to balance the pressure inside the reactor to atmospheric pressure. The polymerization reactor is gradually heated to 210℃, and the pressure inside the reactor is maintained at 2.0 MPa for 1.5 h. The temperature is then increased to 250℃, and the vent valve is opened to start venting. During the heating and venting process, the pressure inside the reactor is maintained at 2.0 MPa. The temperature is increased to 250℃. Afterwards, close the exhaust valve and maintain pressure for 1 hour, release the gas to normal pressure, drain the water from the system, and then gradually evacuate the system to reduce the pressure to -0.05 MPa. Discharge the material, granulate and extract to obtain the low water absorption copolyamide resin.

[0017] The components of PACM-6 nylon salt, caprolactam, benzoic acid, and deionized water in the polymerization reactor are in the following mass ratio: PACM-6 nylon salt 33%, caprolactam 50%, benzoic acid 0.2%, and deionized water 16.8%.

[0018] The preparation method of 11-aminoundecanoic acid modified PA6 is as follows: 11-aminoundecanoic acid and caprolactam are mixed and added to a reactor, then adipic acid end-capping agent and deionized water are added as catalysts. After that, the oxygen in the reactor is discharged with nitrogen gas, and the ring-opening reaction is carried out under normal pressure and sealed. The polymerization temperature is controlled at 230 ℃, the polymerization pressure is controlled at 0.3 MPa, the rotation speed is 400 r / min, and the total time of the ring-opening reaction is 2h. After the ring-opening reaction is completed, the reactor is depressurized and polycondensation reaction is carried out. The total depressurization time is 1h. After completion, nitrogen gas is continuously introduced for protection, the temperature is controlled at 250 ℃, and the polycondensation reaction time is 5h before the material is discharged to obtain 11-aminoundecanoic acid modified PA6.

[0019] The surface layer consists of the following components by mass ratio: PA6 69%, BC 30%, and inorganic powder surface treatment agent 1%. The inorganic powder surface treatment agent is WOT-108. This agent improves the dispersibility and wettability of BC particles, increases the interfacial compatibility and interfacial bonding strength of the PA6 / BC composite system, and also enhances the PA6 / BC composite system's toughness, water resistance, and dimensional stability.

[0020] The components of the intermediate layer by mass ratio are: 38% low water absorption copolyamide resin, 30% MXD6, 15% silane coupling agent modified glass fiber, 10% POE-g-MAH, 6% talc, 0.5% antioxidant, and 0.5% lubricant.

[0021] The inner layer consists of the following components by mass ratio: 49% modified PA6 with 11-aminoundecanoic acid, 15% phenolic resin, 35% glass fiber, 0.5% antioxidant, and 0.5% lubricant.

[0022] BC is composed of small-diameter and large-diameter BC particles, with the small-diameter BC having a particle size of 200 nm and the large-diameter BC having a particle size of 25 μm. The small-diameter BC particles exhibit better dispersibility and wettability, easily embedding into the PA6 matrix to form a relatively stable binary structure; the PA6 melt readily flows into the pores of the large-diameter BC particles, forming a strong mechanical interlock. The large-diameter BC particles provide better reinforcement, while the small-diameter BC particles have a smaller negative effect on toughness. Appropriately sized and hybridized BC particles exhibit a good gradation effect, achieving both reinforcement and toughening effects.

[0023] The carbonization temperature of BC is 1100℃. Increasing the carbonization temperature of BC helps improve the processing fluidity of the PA6 / BC composite material, reduces its water absorption, and improves its water resistance and dimensional stability. At 1100℃, BC exhibits enhanced heterogeneous nucleation ability in the PA6 / BC composite system, increasing the crystallinity, mechanical strength, and toughness of the composite. The increased carbonization temperature lowers the melting temperature and linear thermal expansion coefficient of the PA6 / BC composite system while increasing its crystallization temperature and glass transition temperature, significantly improving the storage modulus and dimensional stability under thermal conditions. Furthermore, the increased carbonization temperature increases the specific surface area, surface roughness, and porosity of BC particles, enhancing surface wetting and diffusion. PA6 melt readily flows into the pore structure of BC, forming a robust interfacial interlocking structure, increasing the interfacial bonding strength of the PA6 / BC composite system, and improving the overall performance of the composite.

[0024] In this invention, PA6 is used as the matrix and BC is used as the reinforcement. The addition of BC improves the water resistance and thermal stability of PA6. When the content of BC is 30wt%, it is beneficial to improve the processing fluidity of PA6. BC has a heterogeneous nucleation effect in the PA6 / BC composite system, which is conducive to the formation of a stable α crystal form of PA6, and improves the crystallization temperature and crystallinity of the composite material. BC particles have good dispersion and wettability in the PA6 matrix, and generate van der Waals forces and mechanical interlocking effects with the PA6 matrix, thereby increasing the interfacial bonding strength and mechanical properties. The low-absorbency copolyamide resin in the middle layer of this invention uses PACM-6 nylon salt. PACM-6 nylon salt can significantly reduce the water absorption rate of the material, mainly due to the introduction of a large number of alicyclic structures, which can significantly reduce the amide group content on the nylon molecular backbone, thus showing a significant reduction in water absorption rate. The addition of MXD6 improves the barrier properties of the material. The addition of silane coupling agent modified glass fiber, POE-g-MAH, and talc improves the mechanical properties of the material. Talc has a layered structure, with the distance between layers generally a few nanometers and planar orientation. When liquid and gas molecules diffuse in the layered material, they must bypass the layers and diffuse in the gaps between the layers, which significantly increases the diffusion path and diffusion time of gas and liquid molecules. Maleic anhydride in POE-g-MAH reacts with the amide groups, and the carboxyl and carbonyl groups of maleic anhydride are highly polar and can form hydrogen bonds with the amide groups, preventing the amide groups from forming hydrogen bonds with water. With the synergistic effect of silane coupling agent pretreatment and POE-g-MAH chemical grafting, the bonding effect between glass fiber and the matrix interface is good, mitigating the increase in water absorption caused by gaps at the glass fiber and polyamide interface. Furthermore, the glass fiber has extremely low water absorption, does not easily absorb water and become damp, and provides excellent barrier properties against gases and liquids.

[0025] The addition of 11-aminoundecanoic acid to the inner layer of this invention reduces the moisture regain and saturated water absorption rate of the fiber, thus decreasing the hygroscopicity of the modified PA fiber. This is because the polar amide group —CONH— is a water-absorbing group, while the non-polar methylene group —CH2— is a hydrophobic group. As the content of 11-aminoundecanoic acid increases, the content of the hydrophobic group —CH2— increases, while the content of the water-absorbing group —CONH— decreases relatively. Therefore, the water absorption rate of the modified PA6 continuously decreases. Phenolic resin can improve the mechanical properties and moisture resistance of the composite material. The phenolic hydroxyl groups of the phenolic resin form strong hydrogen bonds with the amide groups of PA6, and the sterically hindered benzene ring structure of the phenolic resin inhibits the hydrogen bonding between water molecules and the amide groups, thereby reducing the penetration of water molecules into the interior of PA66.

Claims

1. A method for producing a low-moisture-absorbing, high-barrier BOPA film, the BOPA film comprising a surface layer, a middle layer, and an inner layer, characterized in that: The surface layer is composed of PA6, BC, and inorganic powder surface treatment agent; The intermediate layer is composed of low water absorption copolyamide resin, MXD6, silane coupling agent modified glass fiber, POE-g-MAH, talc, antioxidant, and lubricant; The inner layer is composed of 11-aminoundecanoic acid modified PA6, phenolic resin, glass fiber, antioxidant, and lubricant; The production method includes the following steps: (1) Surface raw material blending; the middle layer is prepared by using PACM-6 nylon salt, caprolactam, benzoic acid and deionized water to prepare low water-absorbing copolyamide resin, and the obtained low water-absorbing copolyamide resin is blended with silane coupling agent modified glass fiber, POE-g-MAH, talc, antioxidant and lubricant; 11-aminoundecanoic acid modified PA6 is prepared, and the obtained 11-aminoundecanoic acid modified PA6 is blended with phenolic resin, glass fiber, antioxidant and lubricant; (2) The surface, intermediate, and inner layer raw materials are fed into their respective extruders for mixing and plasticizing; (3) The molten melt is fed into the die head separately. After the melt merges in the die head, it forms a molten sheet through the flat die head opening. (4) The sheet is attached to the cooling roller with an air knife and cooled rapidly to form an unshaped sheet. Then, the sheet is shaped into a cast sheet after being cooled in a water bath. (5) The cast sheet is stretched to form a thin film; (6) Wind up the film.

2. The method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The preparation method of the water-absorbing copolyamide resin in the intermediate layer is as follows: Adipic acid is placed in deionized water at 90℃ and stirred at a uniform speed. 4,4'-Diaminodicyclohexylmethane is slowly added dropwise to obtain PACM-6 nylon salt. PACM-6 nylon salt and caprolactam are added to a polymerization reactor, along with benzoic acid and deionized water. The reactor is evacuated to a vacuum degree of 0.1 MPa, and then high-purity nitrogen is introduced to 0.2 MPa. The air inside the reactor is replaced three times to balance the pressure inside the reactor to atmospheric pressure. The polymerization reactor is gradually heated to 210℃, and the pressure inside the reactor is maintained at 2.0 MPa for 1.5 h. The temperature is then increased to 250℃, and the vent valve is opened to start venting. During the heating and venting process, the pressure inside the reactor is maintained at 2.0 MPa. The temperature is increased to 250℃. Afterwards, close the exhaust valve and maintain pressure for 1 hour, release the gas to normal pressure, drain the water from the system, and then gradually evacuate the system to reduce the pressure to -0.05 MPa. Discharge the material, granulate and extract to obtain the low water absorption copolyamide resin.

3. The method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 2, characterized in that: The components of PACM-6 nylon salt, caprolactam, benzoic acid, and deionized water in the polymerization reactor are in the following mass ratio: PACM-6 nylon salt 33%, caprolactam 50%, benzoic acid 0.2%, and deionized water 16.8%.

4. A method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The preparation method of 11-aminoundecanoic acid modified PA6 is as follows: 11-aminoundecanoic acid and caprolactam are mixed and added to a reactor, then adipic acid end-capping agent and deionized water are added as catalysts. After that, the oxygen in the reactor is discharged with nitrogen gas, and the ring-opening reaction is carried out under normal pressure and sealed. The polymerization temperature is controlled at 230 ℃, the polymerization pressure is controlled at 0.3 MPa, the rotation speed is 400 r / min, and the total time of the ring-opening reaction is 2h. After the ring-opening reaction is completed, the reactor is depressurized and polycondensation reaction is carried out. The total depressurization time is 1h. After completion, nitrogen gas is continuously introduced for protection, the temperature is controlled at 250 ℃, and the polycondensation reaction time is 5h before the material is discharged to obtain 11-aminoundecanoic acid modified PA6.

5. A method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The surface layer consists of the following components by mass ratio: PA6 69%, BC 30%, and inorganic powder surface treatment agent 1%.

6. A method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The components of the intermediate layer by mass ratio are: 38% low water absorption copolyamide resin, 30% MXD6, 15% silane coupling agent modified glass fiber, 10% POE-g-MAH, 6% talc, 0.5% antioxidant, and 0.5% lubricant.

7. A method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The components of the inner layer are as follows by mass ratio: 49% modified PA6 with 11-aminoundecanoic acid, 15% phenolic resin, 35% glass fiber, 0.5% antioxidant, and 0.5% lubricant.

8. The method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: BC consists of small-diameter BC and large-diameter BC. The small-diameter BC has a particle size of 200 nm, and the large-diameter BC has a particle size of 25 μm.

9. The method for producing a low-moisture-absorbing, high-barrier BOPA film according to claim 1, characterized in that: The carbonization temperature of BC is 1100℃.