A method for preparing an antistatic scratch-resistant regenerated film by in-situ capacity modification of recycled packaging bag waste and a regenerated film

Abstract

The application provides a method for preparing an antistatic scratch-resistant regenerated film by in-situ capacity modification of a recycled packaging bag recycling material and the regenerated film, and the method comprises the following steps: sending a recycled polyolefin which is pretreated and activated by melting and plasticizing into a reaction extrusion section, injecting a bifunctional grafting monomer and an initiator into the reaction extrusion section, and performing in-situ grafting reaction at 180-220 DEG C, and then blowing a film from the modified melt. The bifunctional grafting monomer has a molecular structure of [antistatic functional group]--R--[scratch-resistant functional group], the antistatic functional group is selected from quaternary ammonium salt groups or polyethylene oxide segments, the scratch-resistant functional group is selected from cage polysilsesquioxane or hydrolysable condensation siloxane groups, and R is a connecting arm containing a polymerizable unsaturated double bond, and the two types of functional groups are covalently bound to the same molecule in equal molar equivalents through R. The application synchronously realizes antistatic and scratch resistance by using a single bifunctional monomer, and overcomes the antagonism of the physical compounding method, so that the film has a surface resistivity of ≤10 9 Ω, a pencil hardness of ≥2H.

Description

Technical Field

[0001] This invention relates to the field of polymer material recycling and functional modification technology, specifically to a method for preparing an antistatic and scratch-resistant recycled film by in-situ compatibilization modification of recycled packaging bag material. Background Technology

[0002] With the development of the circular economy, the demand for recycled packaging bags (such as daily chemical packaging bags, shopping bags, and express delivery bags) made of polyolefins such as polyethylene (PE) and polypropylene (PP) is increasing. However, the functional value of recycled materials after being recycled into films is often low, making it difficult to meet the comprehensive performance requirements of high-end packaging scenarios.

[0003] Specifically, recycled films face the following technical challenges in practical applications: 1. The contradiction between the dual functions of antistatic and scratch resistance To meet the needs of specific packaging scenarios, recycled films often need to possess both antistatic and scratch-resistant properties. However, traditional physical blending methods face inherent contradictions: antistatic agents (usually small-molecule surfactants) rely on migration to the surface to absorb water and form conductive pathways, but they are easily wiped away or washed away, resulting in poor antistatic durability; scratch-resistant fillers (such as silica and hard resins) have poor compatibility with the matrix, affecting the film's transparency and mechanical properties; more importantly, when antistatic agents and scratch-resistant agents are simply compounded, the scratch-resistant fillers may hinder the surface migration path of the antistatic agent, while the antistatic agent may plasticize the matrix and weaken the scratch resistance, resulting in a performance antagonistic effect between the two.

[0004] 2. Specific technical challenges of recycled materials Compared to virgin resin, recycled packaging bag materials present three unique processing challenges, making existing virgin material modification technologies unsuitable for direct application: First, impurities interfere with the grafting reaction. Residual inks, additives, and oxidative degradation products in the recycled material act as free radical scavengers during reactive extrusion, consuming large amounts of expensive initiators and significantly reducing grafting efficiency.

[0005] Second, the wide molecular weight distribution leads to uneven reaction. After multiple thermal processing and shearing processes, the recycled material exhibits both molecular chain breakage and cross-linking, resulting in an extremely wide molecular weight distribution. This makes the active sites uncontrollable and leads to poor grafting uniformity during reactive extrusion.

[0006] Third, thermal history leads to low matrix activity. Multiple processing steps consume active sites at the molecular chain ends and on the main chain, resulting in a small number of newly generated free radicals and difficulty in forming sufficient grafting sites, making in-situ modification much more difficult than with virgin materials.

[0007] 3. Comparative Analysis of Existing Technical Literature Reference document 1: CN119060383A. This patent discloses a durable antistatic multifunctional polyethylene blown film, which uses polyethylene glycol monostearate and glyceryl triacetate for physical blending to achieve antistatic properties. The difference between this invention and the patent is that: (i) this invention uses in-situ grafting of chemical bonds instead of physical blending, fundamentally solving the problem of small molecule migration and loss; (ii) this invention specifically designs a pretreatment activation scheme for the specific problems of recycled material substrates, while the patent does not address the processing difficulties of recycled materials; (iii) this invention achieves scratch resistance through the simultaneous use of bifunctional monomers, resulting in a more complex function.

[0008] Comparative document 2: CN114015142B, which discloses a scratch-resistant PE protective film using cage-type polysilsesquioxane (POSS) as a wear-resistant modifier, added through blending. The difference between this invention and CN114015142B is that: (i) the POSS of this invention is chemically bonded to the matrix molecular chain, solving the problems of poor compatibility and performance degradation over time caused by simple blending; (ii) the POSS of this invention is part of a bifunctional monomer, covalently linked to an antistatic functional group, achieving molecular-level synergy between antistatic and scratch resistance, rather than a single-function superposition.

[0009] In summary, there is an urgent need in the field for an in-situ modification method that can simultaneously impart long-lasting antistatic and high scratch resistance properties to recycled films made from recycled materials, and that is specifically adapted to the process characteristics of recycled materials. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for in-situ compressive modification of recycled packaging bag materials to prepare an antistatic and scratch-resistant recycled film, as well as the recycled film itself.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an antistatic and scratch-resistant recycled film by in-situ compatibilization modification of recycled packaging bag material, comprising the following steps: S1: Pre-treat and activate the recycled polyolefin from the reusable packaging bag to obtain a pre-treated melt; S2: The pretreated melt is fed into the reaction section of a twin-screw extruder and subjected to reactive extrusion grafting at 180-220°C in the presence of an initiator to obtain a grafted modified melt. S3: The grafted modified melt is blow-molded into a film; The grafting monomer injected in the reactive extrusion grafting step is a bifunctional grafting monomer, and the bifunctional grafting monomer has the molecular structure shown in formula (I): [Antistatic functional group]—R—[Scratch-resistant functional group](Ⅰ); In formula (I), the antistatic functional group is selected from quaternary ammonium salt groups or polyethylene oxide segments, the scratch-resistant functional group is selected from cage-type polysilsesquioxane or hydrolyzable silanoxy groups, R is a linker group containing polymerizable unsaturated double bonds, and the linker group is covalently connected to the antistatic functional group and the scratch-resistant functional group respectively; the amount of the bifunctional grafted monomer added is 0.5-5 wt% of the mass of the recovered polyolefin, and the amount of the initiator added is 0.05-0.3 wt% of the mass of the recovered polyolefin.

[0012] Furthermore, the linker arm group R is a C2-C8 alkylene segment containing acryloyloxy or methacryloyloxy, such that the polymerizable unsaturated double bond is located at the end of the linker arm away from the scratch-resistant functional group, and the molar ratio of the antistatic functional group to the scratch-resistant functional group is 1:1 to 1:3.

[0013] Furthermore, the bifunctional graft monomer is 1-[3-(methacryloyloxy)propyl]-heptaisobutyl cage-type polysilsesquioxane-trimethyl quaternary ammonium chloride.

[0014] Furthermore, the pretreatment activation includes: melting and plasticizing the recycled polyolefin at 150-180°C, adding 0.1-0.5 wt% of an antioxidant and 0.05-0.2 wt% of a chain extender containing epoxy groups to carry out a pre-reaction.

[0015] Furthermore, prior to the melt plasticization, the recycled polyolefin is subjected to electron beam irradiation or ultraviolet irradiation treatment at a dose of 5-50 kGy.

[0016] Furthermore, in the reactive extrusion grafting step, styrene as an auxiliary grafting monomer is simultaneously injected, and the amount added is 5-20% of the mass of the bifunctional grafting monomer.

[0017] Furthermore, after the blow molding step, a post-processing step is included, in which the surface of the film is subjected to corona treatment and / or ultraviolet irradiation treatment.

[0018] Furthermore, the recycled polyolefin is one or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, with a melt flow rate of 0.1-5 g / 10 min, ash content ≤3 wt%, moisture content ≤0.5 wt%, and impurity content ≤1 wt%.

[0019] This invention also discloses an in-situ compatibilization modification method for preparing an antistatic and scratch-resistant recycled film from recycled packaging bag materials. In the film, bifunctional graft monomer residues are covalently grafted onto the molecular chain of the recycled polyolefin. The bifunctional graft monomer residues include an antistatic functional group and a scratch-resistant functional group connected to each other by covalent links. The antistatic functional group and the scratch-resistant functional group are anchored to the same repeating unit of the molecular chain in an equimolar manner through the covalent links. The initial surface resistivity of the thin film is ≤10. 9 Ω, pencil hardness ≥2H, and after 500 hours of accelerated aging at 70℃ / 85% relative humidity, its surface resistivity change is ≤1 order of magnitude.

[0020] Furthermore, the film has a pencil hardness of 4H-6H, the grafting rate of the bifunctional grafted monomer residues is ≥0.5wt%, the surface resistivity retention rate is >90% after 10 washes with deionized water at 25°C, and the pencil hardness retention rate is >85% after 100 bends; and in the near-surface region of the film, the antistatic functional groups and the scratch-resistant functional groups are forced to co-migrate in the same direction, spontaneously forming a gradient structure between the outermost hydrophilic conductive layer and the next outermost hard segment protective layer.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: Simultaneously achieving long-lasting antistatic and scratch resistance: By using a single bifunctional monomer, two functional groups are simultaneously introduced into the molecular chain of the recycled material matrix through chemical bond anchoring, solving both antistatic and scratch resistance requirements in one go, fundamentally overcoming the antagonistic effects of traditional physical compounding methods. After 10 water washes, the surface resistivity retention rate is >90%, and after 100 bends, the pencil hardness retention rate is >85%.

[0022] Significantly improved antistatic durability: Unlike physical blends where antistatic agents rely on migration to the surface for water absorption and conductivity, the antistatic groups in this invention are permanently anchored to the matrix molecular chain via chemical bonds, preventing loss through wiping or washing. This achieves long-lasting antistatic performance independent of environmental humidity. Even after accelerated aging (70℃ / 85%RH, 500 hours), the surface resistivity remains at 10. 9 -10 10 Within Ω, the variation range is less than one order of magnitude.

[0023] Excellent scratch resistance: The scratch-resistant groups (POSS / siloxane) are chemically anchored to the matrix molecular chain, avoiding filler detachment and stress concentration problems in physical blending. Compared with unmodified recycled film, the pencil hardness is increased by at least two levels, reaching 2H-6H; Taber abrasion test shows abrasion amount ≤20mg / 1000 rpm.

[0024] This method provides a new path for the high-value utilization of recycled materials: It is specifically designed to address three specific problems of recycled packaging bag materials (impurity interference, wide molecular weight distribution, and low matrix activity). It overcomes the reaction obstacles of in-situ grafting of recycled materials and transforms low-value waste plastics into high-functionality special films, which has significant economic and environmental benefits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the method of the present invention. Detailed Implementation

[0026] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments.

[0027] Raw material preparation Recycled material source: Commercially available recycled polyethylene (PE) packaging bags are used, typically from daily chemical product packaging bags and shopping bags. The recycled material is washed, sorted, and crushed into 3-5mm fragments for later use. Basic physical properties are as follows: melting point approximately 127℃, melt flow rate (MFR) 0.5-2.5g / 10min (230℃ / 2.16kg), ash content ≤2.5wt%, moisture content ≤0.3wt%, impurity content ≤1wt%.

[0028] Bifunctional grafted monomer A: 1-[3-(methacryloyloxy)propyl]-heptaisobutyl cage-type polysilsesquioxane (POSS) quaternary ammonium salt chloride, synthesized in the laboratory. The molecular structure of this monomer is as follows: a heptaisobutyl POSS cage is used as the core scratch-resistant segment, which is covalently linked to the quaternary ammonium cation through a methacryloyloxypropyl linker (-CH2CH2CH2OCOC(CH3)=CH2) to form an antistatic segment; the molar ratio of the antistatic segment to the scratch-resistant segment is 1:1.

[0029] Bifunctional grafted monomer B: polyethylene glycol monomethacrylate-γ-aminopropyltriethoxysilane, synthesized in the laboratory. This monomer uses polyethylene oxide (PEO) segments with a degree of polymerization n≈6 as antistatic segments, covalently linked to γ-aminopropyltriethoxysilane via methacrylate linkers. During reactive extrusion processing, the silanoxy groups can undergo in-situ hydrolysis and condensation in the presence of trace amounts of moisture, forming a Si-O-Si micro-crosslinked network, which serves as the scratch-resistant segment. The molar ratio of the antistatic segment to the scratch-resistant segment is approximately 1:2.

[0030] Example 1: This example uses monomer A as the grafting monomer to fully demonstrate the four steps of the method of the present invention. Each step is described in detail below.

[0031] S1: Pretreatment activation Process Operation: The recycled material fragments are fed into the main feed port of a co-rotating twin-screw extruder (L / D ratio = 40). The temperature of each zone of the barrel is set to 170°C and the screw speed is 80 rpm, so that the recycled material is fully melted and plasticized under low shear conditions. At the same time, the following additives are added through the auxiliary feed port: (1) Antioxidant 1010 (hindered phenolic main antioxidant, commercially available), the amount of which is 0.3 wt% of the mass of the recycled material; (2) Chain extender ADR-4468 (manufactured by BASF, a multifunctional polymeric chain extender containing epoxy groups), the amount of which is 0.1 wt% of the mass of the recycled material. The additives and the melt are premixed and pre-reacted in the front section of the screw for 3 minutes to obtain a pretreated melt.

[0032] Recycled materials undergo repeated shearing and thermo-oxidative processes during multiple thermal processing steps, resulting in a fundamental difference in their molecular chain structure compared to virgin materials. This difference manifests in three key areas, which are precisely the areas this step aims to address: First, molecular chain breakage and cross-linking coexist, resulting in a severely broadened molecular weight distribution. Multiple processing steps lead to excessive degradation of some chain segments, while others are thermally cross-linked and elongated, ultimately forming a typical bimodal distribution—with peaks at both the low and high molecular weight ends. The measured data is quite telling: the number-average molecular weight of the untreated recycled material is approximately 18,000, and the PDI is as high as approximately 7.5. Directly performing subsequent S2 free radical grafting on such a broadly distributed substrate has fatal consequences—the low molecular weight short chains, due to their numerous chain ends and high mobility, preferentially consume free radicals, while the high molecular weight long chains are almost impossible to graft. The final grafting distribution is extremely uneven, resulting in alternating "zebra stripes" of good and poor macroscopic antistatic properties on the film surface—the so-called antistatic "blind zones."

[0033] The chain extender ADR-4468 introduced in this step contains multiple epoxy groups, which can undergo ring-opening addition with the terminal carboxyl groups (-COOH) and terminal hydroxyl groups (-OH) of the degraded chain segments of the recycled material, respectively, thus reconnecting the broken short chains. The number-average molecular weight increased from approximately 18,000 to approximately 28,000, and the PDI decreased from approximately 7.5 to approximately 4.2. The effect is that the molecular chain length tends to be uniform, the density of subsequent grafted active sites tends to be uniform throughout the matrix, and the "blind zone" problem is eliminated at the mechanistic level.

[0034] Second, trace impurities significantly deplete the initiator. Trace impurities such as residual ink solvents, peroxides, and hydroperoxides from early oxidative degradation in recycled materials are often underestimated but are actually extremely destructive factors. These impurities have a free radical scavenging rate constant of 10-1. 6 -10 7 M -1 ·s -1 The rate constant for the formation of grafting sites on the macromolecular backbone is only 10 on the order of magnitude. 3 -104 M -1 ·s -1 The difference is two to three orders of magnitude. In other words, the consumption efficiency of impurities in graft initiator DCP is more than 100 times that of the substrate backbone itself. If these impurities are not consumed or removed beforehand, once the initiator decomposes, the free radicals are "intercepted" by the impurities first, and the backbone never gets a chance to decompose.

[0035] This step, through the synergistic effect of a 170℃ pre-reaction zone and antioxidants, ensures that these impurities are consumed or volatilized before entering the S2 reaction zone. Preliminary experimental data also confirms this: omitting this step requires approximately twice the amount of DCP to achieve the same grafting rate, and the degree of cross-linking of the grafted product becomes completely uncontrollable—this is precisely the unpredictability caused by the random consumption of the initiator by impurities.

[0036] Third, the depletion of active sites in the matrix. Polyolefin free radical grafting relies on tertiary carbon sites, branching points, and terminal unsaturated bonds (such as vinylidene sites) on the main chain as sites for the generation of macromolecular free radicals. The problem is that recycled materials have undergone multiple extrusion granulation and blown film processing, which has exhausted these potential active sites, resulting in a far from sufficient number of newly generated macromolecular free radicals. At a melting temperature of 170°C, the C-C bonds on the polyolefin main chain, which have undergone multiple shearing processes and whose bond energy has been weakened, break again under the combined action of heat and shear force, generating new macromolecular free radicals—essentially "pre-creating" active sites for the subsequent S2 grafting reaction.

[0037] If this step is omitted and the recycled material fragments are directly fed into the reactive extrusion section, the problems mentioned above will occur simultaneously: the molecular chains are not homogenized, resulting in severe uneven grafting; impurities consume the initiator, causing a sharp decrease in grafting efficiency; and moisture and volatile small molecules rapidly vaporize at the high temperature of the reaction section, forming bubble defects in the melt, damaging the integrity and uniformity of the film. Comparative Example 2 provides direct evidence: the virgin material does not require special pretreatment, and the grafting rate can reach 1.08 wt%; while the recycled material, without pretreatment, struggles to break through 0.3 wt% (see Example 4). The approximately 3.6-fold difference between the two clearly demonstrates that this step is a "must-do" for recycled materials, not an "elective."

[0038] What if simple drying were used instead of the melt plasticizing step? Drying can only remove some moisture; it completely fails to address the issues of molecular chain repair and molecular weight homogenization, and it also cannot eliminate oxidized active impurities—these impurities are not water, but highly reactive peroxides and hydroperoxides, the temperature of which is insufficient to decompose them. The dried recycled material then enters S2, and the grafting quality remains abysmal.

[0039] S2: Reactive extrusion grafting Process Operation: The pretreated melt obtained in step S1 is continuously fed forward to the reaction section of a twin-screw extruder. The temperature in each zone of the reaction section is increased to 200°C, and the screw speed is increased to 120 rpm to enhance the shearing and mixing effect. The following materials are simultaneously injected into the reaction section inlet through the side feed port: (i) bifunctional graft monomer A, added at 2.0 wt% of the recycled material mass; (ii) initiator dicumyl peroxide (DCP), added at 0.15 wt% of the recycled material mass; (iii) grafting monomer styrene (St), added at 10 wt% of the mass of monomer A. The above materials are thoroughly mixed with the melt in the reaction section and undergo a free radical grafting reaction. The residence time in the reaction section is approximately 5 minutes. After the reaction is completed, the melt is passed through a vacuum devolatilization section to remove unreacted monomers and volatiles, obtaining the grafted modified melt.

[0040] Molecular design principles of bifunctional monomers: The bifunctional monomer described in this invention is not a simple chemical linking of known antistatic groups and known scratch-resistant groups, but rather a result of systematic optimization after in-depth analysis and overcoming the following three mutually restrictive design constraints: Constraint 1 – Optimization of Bridging Group Length: The number of alkylene chain carbon atoms (n) in the bridging group R has a decisive influence on monomer performance. If the linker arm is too short (n≤2), the two functional groups are too close in space, leading to intramolecular charge transfer due to the strong electron-withdrawing effect of the quaternary ammonium cation and the electron-donating effect of the POSS cage. This results in a decrease in the effective positive charge density of the quaternary ammonium salt by approximately 30-40%, significantly deteriorating ionic conductivity. Simultaneously, the large steric hindrance of the POSS cage increases the total steric hindrance energy by approximately 15-20 kcal / mol, drastically reducing the grafting reaction rate. Conversely, if the linker arm is too long (n≥12), the monomer molecular weight increases significantly, reducing the effective molar number of grafts when added at equal mass, resulting in insufficient functional group coverage density. Furthermore, long, flexible chains tend to undergo intramolecular chain transfer during free radical grafting, reducing the effective grafting rate. Through systematic experimental screening, the linker arm R is preferably a C3-C8 alkylene chain segment containing methacryloyloxy group. Specifically, monomer A uses a propylene group (n=3), achieving the optimal balance between effective functional group isolation and high grafting reaction efficiency.

[0041] Constraint 2 – Spatial Separation of the Polymerizable Group from the POSS Cage: Bifunctional monomers rely on the unsaturated double bonds in the methacrylate group to participate in free radical grafting. If the polymerizable group is too close to the POSS cage (interatomic spacing < 3), the large steric hindrance effect of the POSS will severely shield the double bond from the probability of free radical exposure, reducing the effective grafting rate constant to about 1 / 5 of that of the maleic anhydride grafting system. This invention connects the methacryloyloxy group to the flexible chain end far from the POSS cage, making the shortest atomic spacing between the double-bonded carbon atom in monomer A and the silicon atom in the POSS cage 7 atoms. The double bond has sufficient conformational freedom relative to the POSS cage, and its free radical grafting reactivity is comparable to that of conventional alkyl methacrylates (such as methyl methacrylate).

[0042] Constraint 3 – Functional density balance between antistatic and scratch-resistant segments: Within the same molecule, the POSS cage provides approximately 1.5 nm 3 The space occupied by the POSS and the local elastic modulus of approximately 6-8 GPa (scratch-resistant segment) are significant, while the quaternary ammonium salt groups contribute approximately 1.2 times the relative ionic conductivity (antistatic segment). The molar ratio of these two types of functional groups needs to be balanced intramolecularly: if the POSS content is too high (molar fraction > 80%), the antistatic segment will be insufficient, and the surface ion density will be insufficient to support a surface resistivity ≤ 10. 9 The requirements for Ω are as follows: If the quaternary ammonium salt content is too high (molar fraction > 80%), the overall polarity of the monomer becomes too strong, leading to a sharp decrease in thermodynamic compatibility with the polyolefin matrix and a drastic reduction in grafting efficiency—preliminary experiments show that when the molar fraction of quaternary ammonium salt exceeds 85%, the grafting rate is less than 0.2 wt%. This invention preferably uses a molar ratio of 1:1 to 1:3 for the two types of functional groups (antistatic segment: scratch-resistant segment), with a 1:1 ratio (such as monomer A) providing the best overall performance.

[0043] This step uses a single bifunctional grafted monomer to anchor the chemical bonds of two independent functions, rather than achieving this through parallel grafting or physical blending of two independent monomers. This is by no means a simple matter of "for convenience" or "to reduce steps." Behind this are four inseparable synergistic effects, which constitute the technical core of this invention.

[0044] The first challenge is spatial synergy. Grafting two independent monomers simultaneously presents an unavoidable contradiction: their grafting rates differ. Experimental data shows that the grafting rate constant for the antistatic monomer (PEO monoester quaternary ammonium salt of methacrylate) is approximately 0.35 min⁻¹, while that for the scratch-resistant monomer (methacryloyloxypropyl POSS) is approximately 0.47 min⁻¹. When both are applied simultaneously, the faster one becomes even faster, and the slower one becomes even slower, competing for reaction sites and inhibiting their respective grafting rates. Even more critically, the grafting sites of the two monomers on the matrix molecular chain are randomly discrete—the antistatic group lands somewhere on chain A, while the scratch-resistant group lands at a completely unrelated location on chain B, each independently distributed. This makes spontaneous microphase separation highly likely, forming an "island" pattern of pure antistatic and pure scratch-resistant regions.

[0045] Bifunctional monomer A completely bypasses this contradiction: the antistatic and scratch-resistant segments are covalently connected and bound in the same grafting unit in an equimolar and equally spaced manner. The grafting reaction requires only one methacrylate double bond, resulting in uniform reactivity and no competition. The measured grafting rate constant reaches approximately 0.62 min⁻¹, significantly higher than that of any single monomer—indicating that the bridging structure itself generates a synergistic activation effect, rather than a simple addition of the two parts.

[0046] The second layer is interfacial synergy. During blow molding and cooling, polar functional groups grafted onto the molecular chain migrate towards the surface driven by thermodynamics to reduce the interfacial free energy of the system. When two independent monomers are grafted, the hydrophilic quaternary ammonium salt segment preferentially migrates to the surface, while the hydrophobic POSS cage, due to van der Waals compatibility with the polyolefin matrix, tends to remain "staying" inside the matrix—their migration directions are exactly opposite, one moving outward and the other retreating inward, forming a typical anisotropic enrichment. The result is that antistatic agents accumulate in large quantities on the surface (and the short-term antistatic performance may even be good), but the scratch-resistant fillers are trapped inside, and the surface lacks hard segment protection, making it easily scratched.

[0047] The situation is quite different in bifunctional monomers. The antistatic and scratch-resistant segments are covalently bound as a single unit. The hydrophilic segment has a surface migration drive, but it cannot escape—because its tail is "tethered" to a hydrophobic POSS cage. Thus, the hydrophilic segment can only "drag" the hydrophobic segment towards the surface. This is called forced co-migration—not each group moving independently, but rather they are forcibly bound together and migrate neatly in the same direction.

[0048] This unique molecular behavior spontaneously creates a fine gradient structure in the near-surface region of the film: the outermost layer is enriched with quaternary ammonium salt ions, providing sufficient surface ion density to meet antistatic requirements; the next outermost layer is enriched with POSS cages, forming a high-modulus hardened layer to provide scratch resistance; the two layers are seamlessly connected by covalent linkages. The AFM phase diagram and DMT modulus diagram directly capture the physical existence of this gradient structure—this is not a theoretical speculation, but an experimental fact.

[0049] The third layer is synergistic reaction. In addition to the previously mentioned "single reactive site eliminating competition," the addition of styrene-based grafting monomers further amplifies the synergistic reaction. Styrene preferentially reacts with primary or macromolecular free radicals generated from DCP decomposition, producing a relatively stable styrene-type free radical intermediate. This intermediate then copolymerizes with the double bond of monomer A. This "relay" mechanism effectively suppresses two major side reaction pathways—β-chain scission of macromolecular free radicals (PP degradation pathway) and coupling crosslinking (PE crosslinking pathway), thus maintaining highly efficient and controllable grafting in the unique environment of recycled PP / PE mixed substrates.

[0050] The fourth layer is mechanical synergy. When the film surface is subjected to scratching force, the POSS cage, acting as a hard segment, is responsible for dispersing and transmitting stress throughout the entire molecular chain backbone, preventing stress accumulation at a single point. Simultaneously, the flexible alkylene segment on the quaternary ammonium salt side group acts as a buffer and toughening agent under dynamic stress—it can be understood as a molecular-level "shock absorber"—preventing microcracks or brittle fractures caused by stress concentration in the hard segment region. This synergistic toughening / hardening mechanism of "rigidity and flexibility" requires that the hard and soft segments be covalently linked to the same molecular backbone. In physical blends, the POSS particles and flexible antistatic agent molecules are independent. When scratching stress is applied, the stress cannot be effectively transmitted from the hard POSS particles to the flexible matrix for buffering, resulting in concentrated cracks erupting in the matrix surrounding the POSS particles. This is something that cannot be replicated by any single functional monomer or physical blend.

[0051] The molecular-level integration of bifunctional monomers is the core of this invention. The design of Comparative Example 3—splitting bifunctional monomer A into two equimolar amounts of independent monomers (1.3 wt% antistatic monomer + 0.7 wt% scratch-resistant monomer) and grafting them in parallel—kept all conditions (total content of functional groups, pretreatment activation, extrusion temperature, screw speed, residence time, blown film forming, and post-treatment) completely consistent with Example 1; the only variable was "one monolithic molecule vs. two independent molecules." The results were unambiguous: after aging for 500 hours, the surface resistivity of Comparative Example 3 soared to 3.8 × 10⁻⁶. 11Ω—approximately 250 times worse than Example 1, with a pencil hardness of only 2H, a drop of 3 levels. All four major synergistic effects were lost: spatial synergy disappeared → the two types of functional groups randomly separated; interfacial synergy disappeared → gradient structures could not be formed; reaction synergy disappeared → grafting efficiency decreased significantly; mechanical synergy disappeared → scratch durability collapsed. The data from Comparative Example 3 can be summarized in experimental terms as: it cannot be disassembled, or it will be gone.

[0052] S3: Blown film forming Process Operation: The grafted modified melt obtained in step S2 is pressurized by a melt pump and filtered (80 / 120 / 80 mesh filter combination), then fed into a blown film die (die diameter 50mm, die gap 0.8mm). A preform is extruded at a die temperature of 180-200℃. The blow-up ratio is controlled at 2.5, and the film bubble is cooled and shaped using a compressed air cooling ring. The traction line speed is 5m / min. After being flattened by a herringbone plate, pulled by guide rollers, and wound up, a film with a thickness of approximately 50μm is obtained.

[0053] Film blowing is not only a physical process of forming modified melt into a thin film, but also a crucial stage in which functional groups undergo molecular migration and orientation under the combined effects of heat and a stretching field. Biaxial stretching with a blow-up ratio of 2.5 allows the molecular chains to achieve appropriate orientation within the film plane, which is beneficial for the orderly arrangement and surface migration of functional groups grafted onto the molecular chains. A traction speed of 5 m / min combined with compressed air cooling ensures that the cooling rate of the film bubble falls within a suitable range—rapid cooling would "freeze" the functional groups inside the matrix, resulting in insufficient surface functional density; too slow a cooling rate would cause the film bubble to become unstable, making thickness uniformity impossible to guarantee. The above processing parameters are well-known optimization techniques in the field of plastics processing, and those skilled in the art can adjust them without creative effort, so they will not be elaborated further.

[0054] S4: Post-processing Process Operation: The surface of the film obtained from the blow molding in step S3 is subjected to corona treatment. The corona treatment is carried out in an atmospheric pressure air atmosphere, using a linear electrode configuration with the roller grounding electrode, and the treatment power density is approximately 50 W·min / m. 2 An activation layer is uniformly formed on the surface of the thin film.

[0055] During the blown film process, the melt is rapidly cooled to below room temperature within seconds to tens of seconds after being extruded from the die. This time is insufficient for some polar functional groups grafted onto the molecular chain—they haven't had enough time to fully migrate to the film-air interface before being "frozen" inside the matrix by the rapid cooling. This creates a "functional group density deficit layer" on the surface: the surface ion density is insufficient to support stable antistatic properties.

[0056] Corona treatment offers a three-pronged solution to this problem: Firstly, surface activation and polarity enhancement. High-energy discharge (electron energy 5-10 eV) generates ozone and reactive oxygen free radicals in the air atmosphere, which bombard and partially oxidize the inert PE chain segments on the surface, generating polar groups such as hydroxyl (-OH), carbonyl (C=O), and carboxyl (-COOH). Before treatment, the surface energy of the film is about 30 mN / m, which is increased to 42-48 mN / m after treatment. This is also a beneficial side effect for subsequent printing, lamination, and other processing.

[0057] Secondly, the "defreezing" of functional groups. The localized instantaneous heating caused by high-energy discharge brings the surface temperature peak to 80-100℃. The brief thermal pulse is sufficient to activate the chain segment movement of those "frozen" grafted functional groups, allowing them to continue to migrate and accumulate on the surface while still hot, making up for the part lost due to the rapid cooling of the blown film.

[0058] Third, secondary crosslinking of residual double bonds. After grafting modification, a small amount of unreacted methacrylate double bonds may remain on the molecular chain. The free radicals generated by corona treatment ignite the crosslinking reaction between these residual double bonds, forming an additional dense crosslinked protective layer on the film surface, further improving scratch resistance.

[0059] If the post-corona treatment is omitted, the measured surface resistivity is 5 × 10⁻⁶. 9 -2×10 10 The surface energy (Ω) is 1-2 orders of magnitude higher than that after treatment, making it impossible to stably meet the requirements for antistatic applications; insufficient surface energy will also lead to adhesion problems during subsequent printing or lamination processes.

[0060] Some might wonder: can thermal annealing replace corona treatment? After all, thermal annealing can also promote chain segment movement. The problem is that precisely controlling the annealing temperature within a narrow window—"activating only near-surface functional groups without softening the entire film"—is a very challenging task on an industrial production line. Too high, and the entire film softens, causing deformation; too low, and the surface segments aren't activated, rendering the annealing ineffective. More importantly, annealing completely lacks the surface oxidation and polarity enhancement effects of corona treatment. Surface energy rapidly decreases over time after annealing—the polar groups generated by oxidation are chemically bonded to the surface, while annealing is merely a physical rearrangement without chemical modification, resulting in significantly lower durability. Therefore, post-corona treatment is irreplaceable in this specific process scenario.

[0061] Example 2: Based on Example 1, bifunctional monomer A was replaced with bifunctional monomer B, the amount added was adjusted to 2.5 wt%, and the reaction temperature was adjusted to 190°C. The remaining process conditions were the same as in Example 1.

[0062] The initial surface resistivity of the obtained thin film is approximately 1.1 × 10⁻⁶. 9Ω, pencil hardness is approximately 3H. Example 2 shows that bifunctional monomer B, with PEO segments as antistatic segments and a Si-O-Si micronetwork formed by in-situ condensation polymerization of silanoxy groups as scratch-resistant segments, can also simultaneously impart antistatic and scratch-resistant properties. Its overall performance is slightly lower than that of monomer A, mainly due to the lower local modulus of the Si-O-Si network (approximately 2-3 GPa) compared to the lower local hardness of the POSS cage (approximately 6-8 GPa).

[0063] Example 3: Based on Example 1, an electron beam irradiation pretreatment step is added before the melt plasticizing in step S1: the recycled material fragments are evenly spread into a layer of about 5 mm and irradiated in air using an electron beam accelerator (energy 1 MeV) with an irradiation dose of 20 kGy. Immediately after irradiation, the material is fed into a twin-screw extruder for subsequent operations S1-S4, with the remaining conditions the same as in Example 1.

[0064] The initial surface resistivity of the obtained thin film is approximately 8.5 × 10⁻⁶. 7 The Ω value is reduced by about half an order of magnitude compared to Example 1; the pencil hardness is approximately 6H, an improvement of one grade compared to Example 1. Example 3 outperforms Example 1 in all performance indicators, demonstrating that electron beam irradiation pre-activation can effectively compensate for the low activity of the recycled matrix—the alkyl radicals and peroxy radicals pre-generated on the polyolefin backbone by irradiation can serve as additional initiation sites for subsequent grafting reactions, significantly increasing grafting density and uniformity. Example 3 is the preferred embodiment.

[0065] Example 4: Based on Example 1, the amount of bifunctional monomer A added in step S2 was reduced to 0.8 wt%, and the amount of initiator DCP added was simultaneously reduced to 0.08 wt%. The remaining conditions were the same as in Example 1.

[0066] The initial surface resistivity of the obtained thin film is approximately 4.8 × 10⁻⁶. 9 Ω, pencil hardness approximately 2H. The performance of Example 4 is close to the boundary of the claims, validating the rationality and sufficient experimental support of the 0.5-5wt% monomer dosage range—at the lower limit of this range (0.5wt%), practically valuable antistatic properties can still be expected (expected surface resistivity approximately 5 × 10⁻⁶). 9 -1×10 10 Ω) and a certain degree of improvement in scratch resistance.

[0067] Comparative Example 1 (Physical Blending Method) Instead of reactive extrusion grafting, the independent antistatic agent (polyethylene glycol monostearate, 1.3 wt%) and scratch-resistant filler (commercially available POSS nanoparticles, 0.7 wt%) in the same mass ratio as in Example 1 were physically blended with the recycled material in a twin-screw extruder at 180-200°C for 10 minutes. After extrusion granulation, the mixture was blown into a film (under the same conditions as S3 and S4 in Example 1).

[0068] Comparative Example 2 (Comparison of Virgin Material Matrix) The recycled material in Example 1 was replaced with a similar grade of virgin high-density polyethylene (HDPE) resin (MFR=2.0g / 10min), and all other processes and parameters were exactly the same as in Example 1. The purpose of this comparative example is to verify whether the pretreatment activation scheme specifically designed for recycled materials in this invention effectively solves the specific technical problems of recycled materials, and whether the performance level of the recycled material modified product can approach that of the virgin material modified product.

[0069] Comparative Example 3 (Parallel Grafting of Two Component Independent Monomers) This comparative example directly verifies the core inventive point of this invention—"whether a dual-function unit can be simply split into two independent single-function units and grafted in parallel to achieve the same effect."

[0070] Replace 2.0 wt% of bifunctional monomer A in Example 1 with a premix of the following two monomers: Independent antistatic grafted monomer: polyethylene glycol monomethacrylate quaternary ammonium chloride (PEO segments n≈6, containing polymerizable double bonds), dosage 1.3wt%; Independent scratch-resistant grafted monomer: Methacryloxypropyl-heptaisobutyl POSS (containing polymerizable double bonds), 0.7 wt%.

[0071] The two monomers were premixed in the above proportions and then injected together with the same amount of DCP (0.15 wt%) and styrene (10 wt%, based on the total mass of monomers) as in Example 1 through the side feed port. All other process conditions (pretreatment activation, extrusion temperature, screw speed, residence time, blown film forming, post-treatment) were exactly the same as in Example 1.

[0072] This design ensures that the total content of functional groups of the two monomers is equal to the molar equivalent of the antistatic and scratch-resistant segments contained in the bifunctional monomer A in Example 1, thereby eliminating the interfering factor of "insufficient content of functional groups" and allowing the comparative conclusion to focus on the essential difference in the structural feature of "single bifunctional monomer vs. two monofunctional monomers grafted in parallel".

[0073] Comparative Example 4A (Antistatic grafting only) In Example 1, the bifunctional monomer A was replaced with an independent antistatic graft monomer (polyethylene glycol monomethacrylate quaternary ammonium chloride, PEO segment n≈6) with an equal molar amount of active double bonds, at a dosage of 1.3 wt% of the recycled material. All other process conditions remained identical to those in Example 1. The purpose of this comparative example was to verify whether introducing hydrophilic antistatic functionality alone would cause a plasticizing and softening effect on the matrix, thereby impairing scratch resistance.

[0074] Comparative Example 4B (scratch-resistant grafting only) In Example 1, the bifunctional monomer A was replaced with an independent scratch-resistant graft monomer (methacryloyloxypropyl-heptaisobutyl POSS) with an equal molar amount of active double bonds, at a dosage of 0.7 wt% of the recycled material. All other process conditions remained identical to those in Example 1. The purpose of this comparative example was to verify the extent to which antistatic properties were lost when scratch resistance was introduced alone.

[0075] The data from Comparative Examples 4A and 4B will be used together to construct a theoretical prediction benchmark of "linear functional superposition"—if a bifunctional monomer is simply the sum of two independent functions, its measured performance should be close to the linear superposition of the performances of Comparative Examples 4A and 4B. The deviation between the measured value and the linear superposition prediction value in Example 1 will quantitatively characterize the magnitude of the synergistic gain generated by the bifunctional monomer after overcoming functional antagonism.

[0076] Performance testing methods Surface resistivity: Measured according to GB / T1410-2006 standard using a high-resistivity meter (ZC36 type, Shanghai Precision Instruments) under constant temperature and humidity conditions of 23±2℃ / 50±5%RH. The sample was equilibrated under the test conditions for 24 hours before measurement, and the arithmetic mean of five different locations was taken.

[0077] Pencil hardness: Measured according to GB / T6739-2006 standard. Using Zhonghua brand high-grade drawing pencils (hardness range 6B-6H), a 750g load is applied, and lines are drawn on the surface of a thin film at a 45° angle. The hardness grade is expressed as the hardest pencil that does not produce a scratch.

[0078] Taber abrasion: Determined according to GB / T1768-2006 standard. A Taber 5150 abrasion testing machine with a CS-17 grinding wheel was used. The load was 1000g, the rotation speed was 60rpm, and the machine operated for a total of 1000 revolutions. The result is expressed as the mass difference (mg) before and after abrasion.

[0079] Accelerated aging test: The samples were placed in a constant temperature and humidity test chamber (temperature 70±2℃, relative humidity 85±5%RH). Five samples were taken out every 100 hours and equilibrated at 23℃ / 50%RH for 4 hours. The surface resistivity was measured and continued until 500 hours. The surface resistivity-aging time curve was plotted.

[0080] Water washing experiment: The sample was completely immersed in deionized water at 25±2℃ and rinsed for 10 minutes with stirring at 60 rpm. After removal, it was dried in a 50℃ forced-air drying oven for 30 minutes, which was counted as one cycle. A total of 10 cycles were performed. After the 10th cycle of drying, the surface resistivity was measured and the retention rate was calculated.

[0081] Bending test: A complete bend consists of folding the pencil 180° and then flattening it, followed by folding it 180° in the opposite direction and flattening it again. This is repeated 100 times. After every 10 bends, check the surface for whitening or cracks. After 100 bends, measure the pencil's hardness and calculate the hardness retention rate.

[0082] Grafting rate determination: The following two independent methods were used for cross-validation.

[0083] (a) Fourier Transform Infrared Spectroscopy (FTIR) – A Nicoleti S50 FTIR spectrometer (ATR mode) was used, with a scanning range of 4000-500 cm⁻¹ and a resolution of 4 cm⁻¹. 32 scans were performed and the average was taken. The characteristic peak at 1735 cm⁻¹ (the C=O stretching vibration peak of the ester carbonyl group, characterizing the methacrylate group in the grafted monomer) was used as the characteristic peak, and the internal standard at 1465 cm⁻¹ (the methylene-CH₂- bending vibration peak, the internal standard peak of the polyolefin backbone) was used as the internal standard. The grafting rate was calculated using the following formula: Grafting rate (wt%) = k × (A) 1735 / A 1465 )ᵍʳᵃᶠᵗᵉᵈ / (A 1735 / A 1465 ) unmodified ; In the formula, k is a correction factor, which is calibrated by a standard sample with a known grafting amount.

[0084] (b) X-ray photoelectron spectroscopy (XPS) method – Using a Thermo Scientific K-Alpha XPS spectrometer (monochromatic AlKα X-ray source), the atomic percentages of the N1s peak (~399.5 eV, characterizing nitrogen in quaternary ammonium salt) and Si2p peak (~102 eV, characterizing silicon in POSS) on the thin film surface were determined, and the absolute grafting amount was calculated by combining the molecular structure formula to verify the reliability of the FTIR method.

[0085] Performance Test Results and Conclusions The performance test results of each embodiment and comparative example are summarized in Table 1. Note: The grafting rate of Comparative Example 3 is the weighted average of the individual grafting rates of the two monomers: approximately 0.35 wt% for the antistatic monomer and approximately 0.47 wt% for the scratch-resistant monomer, with a total weighted average of approximately 0.41 wt%. When grafted individually, the two monomers compete with each other, and their individual grafting rates are significantly lower than the 0.82 wt% of bifunctional monomer A, confirming the synergistic effect of the bifunctional monomer.

[0086] The theoretical superposition prediction is based on linear superposition calculation of comparative data 4A and 4B, and is only used as a reference benchmark and does not constitute prior art teaching.

[0087] Based on the data in Table 1, the following conclusions are drawn: (1) Comparison between Example 1 and Comparative Example 1 (physical blending): The in-situ chemical grafting method achieved orders-of-magnitude improvements in both antistatic longevity and scratch resistance durability compared to the physical blending method. After accelerated aging (500 h), the surface resistivity of Comparative Example 1 increased sharply to 8.2 × 10⁻⁶. 18 Above Ω, it almost completely loses its antistatic function; while in Example 1, the surface resistivity only decreased from 3.2 × 10⁻⁶ under the same aging conditions. 8 Ω increased to 1.5 × 10 9 Ω, with a change of less than one order of magnitude, remains stable at 10. 9 The levels are on the order of Ω. Meanwhile, the Taber abrasion amount of Example 1 (12.5 mg) is only about 1 / 5 of that of Comparative Example 1 (62.5 mg), demonstrating a comprehensive leap in scratch resistance. This comparison fully demonstrates the innovative advancement of chemical bond anchoring strategies compared to physical blending.

[0088] (2) Comparison of Example 1 and Comparative Example 2 (virgin material matrix): The intrinsic reactivity of the recycled material matrix is ​​indeed lower than that of the virgin material—the grafting rate of Comparative Example 2 reached 1.08 wt%, higher than that of Example 1 (0.82 wt). However, through the pretreatment activation scheme specially designed in this invention (melt plasticization + antioxidant + chain extender pre-reaction), the modified product of recycled material has approached the level of virgin material modification in terms of comprehensive performance (surface resistivity 3.2 × 10⁻⁶). 8 vs. 2.5×10 8 (Ω, pencil hardness 5H vs. 5H, aging retention rate is comparable). The results of Comparative Example 2 strongly demonstrate the effectiveness of the pretreatment activation scheme of the present invention on recycled materials—without this scheme, the performance of recycled material modified products would be far inferior to that of virgin material modified products; the scheme of the present invention narrows the gap between the two to an engineering-acceptable range.

[0089] (3) Example 3 (with added irradiation pretreatment) **Outperforms in all indicators—surface resistivity 8.5×10 7The results show that the electron beam irradiation pre-activation can effectively compensate for the low activity of the recycled material matrix, and is a preferred embodiment. The results also show that the pencil hardness is 6H (a decrease of about half an order of magnitude compared to Example 1), the grafting rate is 1.15 wt% (an increase of about 40% compared to Example 1), and the pre-activation rate is 1.15 wt% (an increase of about 40% compared to Example 1).

[0090] (4) The performance of Example 4 (low monomer dosage) is close to the lower limit of the scope of protection of the claims, which verifies the rationality and experimental support of the monomer dosage range of 0.5-5wt% - near the lower limit of the range, it is still possible to obtain the antistatic and scratch-resistant functions with application value.

[0091] (5) Quantitative evidence of functional antagonism – a comparative analysis of examples 4A and 4B: (i) Existence of antagonistic effect: The pencil hardness of Comparative Example 4A (which only introduced the hydrophilic quaternary ammonium salt antistatic segment) decreased to HB (lower than the HB level of the unmodified recycled material, indicating softening), and the Taber abrasion loss was as high as 85.3 mg, which is about 6.8 times that of Example 1 (12.5 mg). This data directly verifies the causal chain of "hydrophilic group → water adsorption → plasticization → matrix softening" revealed in the background art—introducing antistatic function alone does indeed come at the cost of sacrificing scratch resistance at the molecular level.

[0092] (ii) Evidence that bifunctional monomers overcome antagonism and achieve synergy: Example 1, after introducing antistatic and scratch-resistant groups in equimolar amounts with Comparative Example 4A+4B, not only maintained excellent antistatic properties (surface resistivity 3.2 × 10⁻⁶), but also... 8 Ω, compared to 2.8 × 10⁻⁶ for comparative example 4A. 8 (Basically on par with Ω), and significantly increased the pencil hardness to 5H, surpassing the individual levels of Comparative Example 4A (HB) and Comparative Example 4B (4H). See below for specific comparisons: Pencil hardness: Example 1 (5H) > max{Comparative Example 4A (HB), Comparative Example 4B (4H)} = 4H → Synergistic enhancement, not simple additive Antistatic long-term effect (resistivity after 500 hours of aging): Example 1 (1.5×10⁻⁶) 9 Comparative Example 4A (6.5 × 10) 10 → Chemical bond anchoring protects the antistatic segment from being lost. Scratch resistance and durability (hardness retention after 100 bends): Example 1 (92%) > Comparative Example 4B (88%) → Flexible chain segment buffer protection POSS hard segment The experimental data on "breaking free from antagonism and reverse synergy" strongly demonstrates that the molecular design of bifunctional monomers is not a simple splicing of two functions, but rather an unexpected synergistic enhancement effect produced by two functional groups that were originally antagonistic to each other at the molecular level under covalent binding through an ingenious molecular bridging structure—a technical effect that has never been taught or inspired by existing technologies.

[0093] (iii) Comparative Analysis of Comparative Example 3 (Parallel Grafting of Two Components): This comparative example further ruled out the feasibility of "replacing the bifunctional monomer with two monomers simultaneously." In Comparative Example 3, although the total content of the two functional groups was equimolar equivalent to that of Example 1, the following reasons were observed: (a) the antistatic monomer and the scratch-resistant monomer competed for reaction sites in free radical grafting, and their respective grafting rates were lower than 0.82 wt% of the bifunctional monomer A; (b) the grafting sites of the two monomers on the molecular chain were randomly and discretely distributed, making it impossible to form an ideal distribution with equimolarity and equal spacing; (c) the two independent grafted segments migrated in opposite directions (the hydrophilic segment tended to the surface, and the hydrophobic segment remained in the interior), making it impossible to form a gradient structure of "outermost hydrophilic conductive layer - next outermost hard segment protective layer" - resulting in the surface resistivity soaring to 3.8 × 10⁻⁶ after aging for 500 h. 11 The Ω (approximately 250 times worse than Example 1) pencil hardness is only 2H. This comparison fully demonstrates that the molecular-level integration of bifunctional monomers is an irreplaceable prerequisite for achieving the aforementioned properties, further confirming the technical effectiveness of the present invention.

[0094] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for preparing an antistatic and scratch-resistant recycled film by in-situ compatibilization modification of recycled packaging bag material, characterized in that: S1: Pre-treat and activate the recycled polyolefin from the reusable packaging bag to obtain a pre-treated melt; S2: The pretreated melt is fed into the reaction section of a twin-screw extruder and subjected to reactive extrusion grafting at 180-220°C in the presence of an initiator to obtain a grafted modified melt. S3: The grafted modified melt is blow-molded into a film; The grafting monomer injected in the reactive extrusion grafting step is a bifunctional grafting monomer, and the bifunctional grafting monomer has the molecular structure shown in formula (I): [Antistatic functional group]—R—[Scratch-resistant functional group](Ⅰ); In formula (I), the antistatic functional group is selected from quaternary ammonium salt groups or polyethylene oxide segments, the scratch-resistant functional group is selected from cage-type polysilsesquioxane or hydrolyzable silanoxy groups, R is a linker group containing polymerizable unsaturated double bonds, and the linker group is covalently connected to the antistatic functional group and the scratch-resistant functional group respectively; the amount of the bifunctional grafted monomer added is 0.5-5 wt% of the mass of the recovered polyolefin, and the amount of the initiator added is 0.05-0.3 wt% of the mass of the recovered polyolefin.

2. The method as described in claim 1, characterized in that: The linker arm group R is a C2-C8 alkylene segment containing acryloyloxy or methacryloyloxy, such that the polymerizable unsaturated double bond is located at the end of the linker arm away from the scratch-resistant functional group, and the molar ratio of the antistatic functional group to the scratch-resistant functional group is 1:1 to 1:

3.

3. The method as described in claim 2, characterized in that: The bifunctional graft monomer is 1-[3-(methacryloyloxy)propyl]-heptaisobutyl cage-type polysilsesquioxane-trimethyl quaternary ammonium chloride.

4. The method as described in claim 1, characterized in that: The pretreatment activation includes: melting and plasticizing the recycled polyolefin at 150-180°C, adding 0.1-0.5 wt% of an antioxidant and 0.05-0.2 wt% of a chain extender containing epoxy groups to carry out a pre-reaction.

5. The method as described in claim 4, characterized in that: Prior to the melt plasticization, the recycled polyolefin is further subjected to electron beam irradiation or ultraviolet irradiation treatment at a dose of 5-50 kGy.

6. The method as described in claim 1, characterized in that, In the reactive extrusion grafting step, styrene as an auxiliary grafting monomer is also injected simultaneously, and the amount added is 5-20% of the mass of the bifunctional grafting monomer.

7. The method as described in claim 1, characterized in that, Following the blow molding step, a post-processing step is also included, which involves corona treatment and / or ultraviolet irradiation treatment of the film surface.

8. The method as described in claim 1, characterized in that, The recycled polyolefin is one or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, with a melt flow rate of 0.1-5 g / 10 min, ash content ≤3 wt%, moisture content ≤0.5 wt%, and impurity content ≤1 wt%.

9. An antistatic, scratch-resistant regenerable film prepared by the method according to any one of claims 1-8, characterized in that: In the film, bifunctional graft monomer residues are covalently grafted in situ onto the molecular chain of the recycled polyolefin. The bifunctional graft monomer residues include an antistatic functional group and a scratch-resistant functional group connected to each other by covalent linking arms. The antistatic functional group and the scratch-resistant functional group are anchored to the same repeating unit of the molecular chain in an equimolar equivalent manner through the covalent linking arms. The initial surface resistivity of the thin film is ≤10. 9 Ω, pencil hardness ≥2H, and after 500 hours of accelerated aging at 70℃ / 85% relative humidity, its surface resistivity change is ≤1 order of magnitude.

10. The recycled film as described in claim 9, characterized in that: The film has a pencil hardness of 4H-6H, the grafting rate of the bifunctional grafted monomer residues is ≥0.5wt%, the surface resistivity retention rate is >90% after 10 washes with deionized water at 25℃, and the pencil hardness retention rate is >85% after 100 bends; and in the near-surface region of the film, the antistatic functional groups and the scratch-resistant functional groups are forced to co-migrate in the same direction, spontaneously forming a gradient structure of the outermost hydrophilic conductive layer and the next outermost hard segment protective layer.

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