Stable polypropylene cooking cast film additive and preparation method thereof

Abstract

The invention discloses a stable polypropylene cooking cast film additive and a preparation method thereof. The stable polypropylene cooking cast film additive is prepared from the following components in percentage by mass: 50-60% of a COF-ANT carrier; the functional effects are that an antioxidant is loaded, active components are fixed through pi-pi accumulation and hydrogen bonds, and migration is inhibited; 25%-30% of a bipolar dynamic antioxidant (DA-362); double active sites of phosphite ester (P = O) and thioether (-S-) are contained, and free radicals are captured in a molten phase and a solid phase respectively; 10%-15% of a rare earth coordination lubricant (RE-LUB); the lanthanide stearic acid coordination compound reduces the melt viscosity (the reduction amplitude is greater than or equal to 40%) and reduces shear heat generation; 5 to 10% of an interface compatibilizer (IC-7); the compatibility of COF and PP matrix is improved (the contact angle is less than or equal to 15 degrees), and the light transmittance is maintained (the haze is less than or equal to 3%); according to the invention, by virtue of multi-stage structural design and process synergy, the DA-362 antioxidant is fixed by a COF-ANT carrier through a topological confinement effect, and the bipolar structure of the DA-362 antioxidant dynamically responds in a molten state and a solid state, so that a free radical chain reaction is synchronously blocked.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene cooking cast film, and particularly relates to a stable polypropylene cooking cast film additive and a preparation method thereof. Background Art

[0002] Polypropylene retort cast film is usually used for high-temperature retort packaging, so the additives need to be resistant to high temperatures and oxidation, while also maintaining the transparency and mechanical properties of the film.

[0003] The existing polypropylene cast film additives are prone to the following problems during high temperature (120-140°C) cooking and processing: Dynamic thermal-oxidative synergistic degradation: High-temperature shearing causes molecular chain breakage, while oxygen penetration triggers a free radical chain reaction, which cannot be simultaneously inhibited by traditional single antioxidant systems; Interfacial migration failure: small molecule additives migrate to the film surface during cooking, resulting in insufficient long-term stability; Transmittance loss: The difference in refractive index between the inorganic filler and the matrix causes the haze to increase. Summary of the Invention

[0004] The purpose of the present invention is to provide a stable polypropylene cooking cast film additive and a preparation method to solve the problems raised in the above background technology that polypropylene cooking cast film is prone to dynamic thermal-oxidative synergistic degradation, interface migration failure, and transmittance loss at high temperatures.

[0005] To achieve the above object, the present invention provides the following technical solution: a stable polypropylene steam-cast film additive, comprising the following components in percentage by mass: COF-ANT carrier 50-60%; its function is to load antioxidants, fix active ingredients through π-π stacking and hydrogen bonding, and inhibit migration; Bipolar dynamic antioxidant (DA-362) 25-30%; contains phosphite (P=O) and thioether (-S-) dual active sites, which capture free radicals in the melt and solid phases respectively; Rare earth complex lubricant (RE-LUB) 10-15%; lanthanide stearic acid complex, reduces melt viscosity (reduction ≥ 40%) and reduces shear heating; Interfacial compatibilizer (IC-7) 5-10%; improves the compatibility between COF and PP matrix (contact angle ≤15°) and maintains light transmittance (haze ≤3%).

[0006] As a preferred technical solution of the present invention, the chemical formula of the rare earth coordinated lubricant is La(C17H35COO)3·2H2O, and the chemical formula of the bipolar dynamic antioxidant is C32H48O6P2S2.

[0007] The present invention also discloses a method for preparing a stable polypropylene steam-cooked cast film additive, comprising the cast film additive, and specifically comprising the following steps: Step 1: Preparation of COF-ANT carrier a. Dissolve triformylbenzene and diaminobenzenesulfonic acid in DMF / mesitylene; b. Add 0.05 mol of boric acid as a catalyst and react at 120°C for 72 h to produce a sulfonic acid-functionalized COF with a pore size of 2.8 nm; c. Vacuum activation at 200°C for 12 hours resulted in a surface area of ​​1800 m² / g. The porous COF-ANT synthesized in step 1 possesses a high surface area (1800 m² / g) and dual sulfonic acid / amino active sites, providing both physical adsorption (pore filling) and chemical anchoring (amino group coordination with the P=O of DA-362) for the DA-362 loading in step 2. Step 2: DA-362 in-situ loading; Ⅰ. Vacuum impregnation: Mix COF-ANT and DA-362 in a ratio of 3:1 and dissolve in supercritical CO2. Maintain the pressure for 6 hours and then slowly release the pressure. DA-362 will be embedded in the COF pores, with a loading rate of ≥92%. Ⅱ. Surface cross-linking: Immersed in a toluene solution containing 0.5% divinylbenzene, free radical crosslinking was initiated at 80°C, forming a surface crosslinked network. During high-temperature processing, the DA-362 surface crosslinked network (crosslinking degree 15-20%) released some free volume, forming a "lubricating-antioxidant synergistic interface" with the RE-LUB nanoparticles (D50 = 80nm), increasing the melt flow rate from 4.2g / 10min to 6.8g / 10min while suppressing local overheating caused by screw shear (temperature fluctuation ≤±2°C). Step 3: RE-LUB nano-processing High-energy ball milling: La(C17H35COO)3·2H2O was mixed with zinc stearate and ball milled at 300 rpm for 8 h under argon protection to obtain a composite powder with a particle size of D50 = 80 nm. Surface coating: Atomic layer deposition is used to deposit a 2nm thick Al2O3 layer on the powder surface to prevent agglomeration; Step 4: Compounding and granulation.

[0008] As a preferred technical solution in the present invention, in the step a, the concentration of trimacylbenzene is 0.1 mol, and the concentration of diaminobenzenesulfonic acid is 0.15 mol, and the volume ratio of the total volume of the trimacylbenzene and diaminobenzenesulfonic acid to the DMF / mesitylene is 3:7, wherein the volumes of the trimacylbenzene and diaminobenzenesulfonic acid are equal.

[0009] As a preferred technical solution of the present invention, in step three, the mass ratio of La(C17H35COO)3·2H2O to zinc stearate is 4:1.

[0010] As a preferred technical solution of the present invention, in step II, the cross-linking degree of the surface cross-linked network is 15-20%.

[0011] As a preferred technical solution of the present invention, in step I, the pressure is 15 MPa and the temperature is 50°C.

[0012] As a preferred technical solution of the present invention, the step 4 specifically includes the following steps: High-speed blending: Pre-mix COF-ANT@DA-362, RE-LUB, IC-7, and PP base materials; use a twin-screw extruder with temperature settings of 180 / 200 / 210 / 205°C; screw speed 400 rpm, residence time 90 s, vacuum degassing (-0.08 MPa) Underwater pelletizing: pelletizing water temperature is 25℃, particle size is controlled to be φ2×3mm, moisture content ≤0.2%.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention achieves a multi-level structural design and process synergy. The COF-ANT carrier fixes the DA-362 antioxidant through a topological confinement effect. Its bipolar structure dynamically responds in the molten and solid states, synchronously blocking the free radical chain reaction. At the same time, the DA-362 surface cross-linked network and the COF channel hydrogen bonds form a "double-lock" structure. After 100 steaming cycles, the additive residue rate is still ≥89%, and the yellowing index ΔYI is controlled within 1.2. In addition, the nano-lubrication of RE-LUB and the synergistic effect of IC-7 interface volume expansion reduce the melt viscosity by 40%. At the same time, the transmittance is increased to 92.7% through refractive index matching, and the haze is ≤3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0016] Example 1 See also Figure 1The present invention provides a technical solution: a stable polypropylene cooking cast film additive, comprising the following components in percentage by mass: COF-ANT carrier 50%; its function is to load antioxidants, fix the active ingredients through π-π stacking and hydrogen bonding, and inhibit migration; Bipolar dynamic antioxidant (DA-362) 25%; contains phosphite (P=O) and thioether (-S-) dual active sites, which capture free radicals in the melt and solid phases respectively; Rare earth complex lubricant (RE-LUB) 15%; lanthanide stearic acid complex, reduces melt viscosity (reduction ≥ 40%) and reduces shear heating; Interfacial compatibilizer (IC-7) 10%; improves the compatibility between COF and PP matrix (contact angle ≤15°) and maintains light transmittance (haze ≤3%).

[0017] In this embodiment, the chemical formula of the rare earth coordinated lubricant is La(C17H35COO)3·2H2O, and the chemical formula of the bipolar dynamic antioxidant is C32H48O6P2S2.

[0018] The present invention also discloses a method for preparing a stable polypropylene steam-cooked cast film additive, comprising the cast film additive, and specifically comprising the following steps: Step 1: Preparation of COF-ANT carrier a. Dissolve triformylbenzene and diaminobenzenesulfonic acid in DMF / mesitylene; b. Add 0.05 mol of boric acid as a catalyst and react at 120°C for 72 h to produce a sulfonic acid-functionalized COF with a pore size of 2.8 nm; c. Vacuum activation at 200°C for 12 hours resulted in a surface area of ​​1800 m² / g. The porous COF-ANT synthesized in step 1 possesses a high surface area (1800 m² / g) and dual sulfonic acid / amino active sites, providing both physical adsorption (pore filling) and chemical anchoring (amino group coordination with the P=O of DA-362) for the DA-362 loading in step 2. Step 2: DA-362 in-situ loading; Ⅰ. Vacuum impregnation: Mix COF-ANT and DA-362 in a ratio of 3:1 and dissolve in supercritical CO2. Maintain the pressure for 6 hours and then slowly release the pressure. DA-362 will be embedded in the COF pores, with a loading rate of ≥92%. Ⅱ. Surface cross-linking: Immersed in a toluene solution containing 0.5% divinylbenzene, free radical crosslinking was initiated at 80°C, forming a surface crosslinked network. During high-temperature processing, the DA-362 surface crosslinked network (crosslinking degree 15-20%) released some free volume, forming a "lubricating-antioxidant synergistic interface" with the RE-LUB nanoparticles (D50 = 80nm), increasing the melt flow rate from 4.2g / 10min to 6.8g / 10min while suppressing local overheating caused by screw shear (temperature fluctuation ≤±2°C). Step 3: RE-LUB nano-processing High-energy ball milling: La(C17H35COO)3·2H2O was mixed with zinc stearate and ball milled at 300 rpm for 8 h under argon protection to obtain a composite powder with a particle size of D50 = 80 nm. Surface coating: Atomic layer deposition is used to deposit a 2nm thick Al2O3 layer on the powder surface to prevent agglomeration; Step 4: Compounding and granulation.

[0019] In the present embodiment, in step a, the concentration of trimacylbenzene is 0.1 mol, and the concentration of diaminobenzenesulfonic acid is 0.15 mol. The volume ratio of the total volume of trimacylbenzene and diaminobenzenesulfonic acid to DMF / mesitylene is 3:7, wherein the volumes of trimacylbenzene and diaminobenzenesulfonic acid are equal.

[0020] In this embodiment, in step 3, the mass ratio of La(C17H35COO)3·2H2O to zinc stearate is 4:1.

[0021] In this embodiment, in step II, the cross-linking degree of the surface cross-linked network is 20%.

[0022] In this embodiment, in step I, the pressure is 15 MPa and the temperature is 50°C.

[0023] In this embodiment, step 4 specifically includes the following steps: High-speed blending: Pre-mix COF-ANT@DA-362, RE-LUB, IC-7, and PP base materials; use a twin-screw extruder with temperature settings of 180 / 200 / 210 / 205°C; screw speed 400 rpm, residence time 90 s, vacuum degassing (-0.08 MPa) Underwater pelletizing: pelletizing water temperature is 25℃, particle size is controlled to be φ2×3mm, moisture content ≤0.2%.

[0024] Example 2 The difference from Example 1 is that the invention provides a technical solution: a stable polypropylene steam-cast film additive, comprising the following components in percentage by mass: COF-ANT carrier 60%; Bipolar dynamic antioxidant (DA-362) 25%; Rare earth complex lubricant (RE-LUB) 10%; Interfacial compatibilizer (IC-7) 5%.

[0025] Example 3 The difference from the above embodiment is that the invention provides a technical solution: a stable polypropylene steam-cast film additive, comprising the following components in percentage by mass: COF-ANT carrier 55%; Bipolar dynamic antioxidant (DA-362) 25%; Rare earth complex lubricant (RE-LUB) 10%; Interfacial compatibilizer (IC-7) 10%.

[0026] Although the embodiments of the present invention have been shown and described (see the above detailed description for details), it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, and the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A stable polypropylene cooking cast film additive, characterized in that: It is prepared by including the following components in percentage by mass: COF-ANT carrier 50-60%; Bipolar dynamic antioxidant (DA-362) 25-30%; Rare earth complex lubricant (RE-LUB) 10-15%; Interface compatibilizer (IC-7) 5~10%.

2. The stable polypropylene cooking cast film additive according to claim 1, characterized in that: The chemical formula of the rare earth coordinated lubricant is La(C17H35COO)3·2H2O, and the chemical formula of the bipolar dynamic antioxidant is C32H48O6P2S2.

3. A method for preparing a stable polypropylene steam-cooked cast film additive, comprising the cast film additive according to any one of claims 1 to 2, characterized in that: The specific steps include: Step 1: Preparation of COF-ANT carrier a. Dissolve triformylbenzene and diaminobenzenesulfonic acid in DMF / mesitylene; b. Add 0.05 mol of boric acid as a catalyst and react at 120°C for 72 h to produce a sulfonic acid-functionalized COF with a pore size of 2.8 nm; c. Vacuum activation at 200℃ for 12h, the specific surface area reaches 1800m² / g; Step 2: DA-362 in-situ loading; Ⅰ. Vacuum impregnation: Mix COF-ANT and DA-362 in a ratio of 3:1 and dissolve in supercritical CO2. Maintain the pressure for 6 hours and then slowly release the pressure. DA-362 will be embedded in the COF pores, with a loading rate of ≥92%. Ⅱ. Surface cross-linking: Immersed in a toluene solution containing 0.5% divinylbenzene at 80°C, free radical crosslinking was initiated to form a surface crosslinked network; Step 3: RE-LUB nano-processing High-energy ball milling: La(C17H35COO)3·2H2O was mixed with zinc stearate and ball milled at 300 rpm for 8 h under argon protection to obtain a composite powder with a particle size of D50 = 80 nm. Surface coating: Atomic layer deposition is used to deposit a 2nm thick Al2O3 layer on the powder surface to prevent agglomeration; Step 4: Compounding and granulation.

4. The method for preparing a stable polypropylene steam-cast film additive according to claim 3, characterized in that: In the step a, the concentration of trimacylbenzene is 0.1 mol, and the concentration of diaminobenzenesulfonic acid is 0.15 mol. The volume ratio of the total volume of the trimacylbenzene and diaminobenzenesulfonic acid to the DMF / mesitylene is 3:7, wherein the volumes of the trimacylbenzene and diaminobenzenesulfonic acid are equal.

5. The method for preparing a stable polypropylene steam-cast film additive according to claim 3, characterized in that: In the step 3, the mass ratio of La(C17H35COO)3·2H2O to zinc stearate is 4:

1.

6. The method for preparing a stable polypropylene steam-cast film additive according to claim 3, characterized in that: In the step II, the cross-linking degree of the surface cross-linked network is 15-20%.

7. The method for preparing a stable polypropylene steam-cast film additive according to claim 3, characterized in that: In step I, the pressure is 15 MPa and the temperature is 50°C.

8. The method for preparing a stable polypropylene steam-cast film additive according to claim 3, characterized in that: The step 4 specifically includes the following steps: High-speed blending: Pre-mix COF-ANT@DA-362, RE-LUB, IC-7, and PP base materials; use a twin-screw extruder with temperature settings of 180 / 200 / 210 / 205°C; screw speed 400 rpm, residence time 90 s, vacuum degassing (-0.08 MPa) Underwater pelletizing: pelletizing water temperature is 25℃, particle size is controlled to be φ2×3mm, moisture content ≤0.2%.

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