Dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting modified polyolefin material and preparation method thereof

Abstract

The invention discloses a polyolefin material modified by dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting and a preparation method of the polyolefin material. The preparation method of the polyolefin material comprises the following steps: (1) injecting dipentene and maleic anhydride into a single-screw or double-screw extruder for reaction to obtain a dipentene-maleic anhydride addition product; and (2) carrying out co-melting reaction on a polyolefin matrix, the dipentene-maleic anhydride addition product obtained in the step (1), styrene and maleic anhydride, and carrying out synergistic grafting under the initiation of a peroxide initiator to obtain the polyolefin material. The preparation method provided by the invention not only can realize coexistence of high grafting efficiency and low residual monomers, but also can introduce a sustainable carbon source by utilizing the bio-based property of dipentene, thereby providing a brand new technical path for a polyolefin compatilizer and a binding material.

Description

Technical Field

[0001] This invention relates to the field of polyolefin materials technology, and in particular to a polyolefin material modified by dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting and its preparation method. Background Technology

[0002] Polyolefins such as polypropylene (PP) and polyethylene (PE) are widely used in packaging, automotive, home appliance, electronics, and building materials due to their low price, high specific strength, excellent chemical resistance, and good processing performance. However, the molecular chains of polyolefins are almost entirely composed of carbon-hydrogen bonds, resulting in extremely low polarity. This leads to insufficient interfacial bonding when they are compounded with polar polymers (such as polyamide, polyethylene terephthalate, and ethylene-vinyl alcohol copolymer) and inorganic fillers (such as glass fiber, talc, and calcium carbonate). This manifests as delamination, brittleness, and low peel strength, severely limiting their application in high-performance composite materials and multilayer co-extruded films.

[0003] To improve interfacial compatibility, maleic anhydride-grafted polyolefins (PO-g-MAH) are commonly used as compatibilizers or adhesive layers. This type of material can introduce anhydride polarity, improving adhesion to polar substrates. However, it suffers from several drawbacks, including limited grafting efficiency (maleic anhydride readily self-polymerizes or volatilizes under high-temperature free radical conditions, resulting in generally low actual grafting rates; large amounts of monomer are required to achieve limited polarity, increasing material costs and making stable control difficult), high levels of residual monomers and VOCs (due to unreacted MAH residues in the system during melting, the finished product contains high levels of residual monomers, which are easily released during processing and use, causing noticeable odors and excessive volatile organic compound emissions), and severe main chain degradation (under peroxide-induced conditions, free radicals not only induce grafting but also easily trigger β-cleavage of the polyolefin main chain, leading to a decrease in molecular weight, abnormally high melt flow rate, and decreased mechanical properties, especially toughness, limiting the material's impact resistance and reliability).

[0004] To address the aforementioned issues, attempts have been made to introduce styrene as an auxiliary monomer during the grafting process. For example, in the "polyolefin grafted styrene-maleic anhydride (PO-g-(St-co-MAH))" system, styrene can act as a "free radical buffer," improving the grafting rate and slowing down main chain degradation to some extent. However, these materials still have the following shortcomings:

[0005] 1. Insufficient grafting efficiency: In traditional processes, maleic anhydride is prone to self-polymerization, side reactions, or volatilization loss under free radical conditions, resulting in a low effective grafting rate. Usually, a higher feed amount is required to achieve a limited polarity content, resulting in low raw material utilization and increased costs.

[0006] 2. Residual substances and VOCs are prominent issues: Free maleic anhydride and styrene residues are difficult to completely remove, and volatile substances are easily released during processing and use, which not only causes odor and safety hazards, but also limits its application in areas sensitive to odor and hygiene, such as automotive interiors and food packaging.

[0007] 3. Main chain degradation and performance decline: Under high-temperature peroxide-induced conditions, the polyolefin main chain is prone to β-cracks, which leads to a significant increase in melt flow rate, a decrease in molecular weight, and ultimately a reduction in material toughness or even embrittlement.

[0008] 4. Simple structure and difficult performance control: Traditional grafting systems mainly form isolated anhydride groups or simple short SMA segments, with a simple distribution of polar units, making it difficult to achieve a comprehensive balance between "grafting polarity - toughness maintenance - VOC control".

[0009] 5. Main chain degradation and performance decline: Under high-temperature peroxide-induced conditions, the polyolefin main chain is prone to β-cracks, which leads to a significant increase in melt flow rate, a decrease in molecular weight, and ultimately a reduction in material toughness or even embrittlement.

[0010] In summary, existing technologies struggle to simultaneously achieve high grafting rates, low residual number, low VOCs, maintained toughness, and structural controllability. These issues urgently need to be addressed. Summary of the Invention

[0011] To address the problems of low grafting efficiency, high residual monomer content, high VOC release, and insufficient toughness retention in existing polyolefin grafting materials, this invention proposes a modified polyolefin material and its preparation method based on bispentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting. The method involves a hydrogen-allyl addition reaction between bispentene and maleic anhydride (MAH) to generate a low-volatility, stable bispentene-maleic anhydride adduct (LM-MA adduct), significantly reducing residual monomer and VOC issues caused by free MAH. Furthermore, the bispentene-maleic anhydride adduct is synergistically grafted onto polyolefins with styrene-maleic anhydride (St / MAH) to construct a bipolar microstructure of "dot-like anhydride groups + short SMA segments." This modification method not only achieves high grafting efficiency and low residual monomer content but also utilizes the bio-based properties of bispentene to introduce a sustainable carbon source, thus providing a novel technological pathway for polyolefin compatibilizers and binders.

[0012] The first objective of this invention is to provide a method for modifying polyolefins to improve grafting efficiency. This method involves reacting dipentene with maleic anhydride via an alphaene reaction (hydro-allyl addition) to obtain a dipentene-maleic anhydride adduct. The dipentene-maleic anhydride adduct is then synergistically grafted onto the main chain of the polyolefin with styrene / maleic anhydride under the initiation of a peroxide, thereby obtaining a polyolefin material (grafted polymer) with high grafting efficiency.

[0013] The structural formula of this polyolefin (grafted polymer) is shown in Formula 1:

[0014] Formula 1

[0015] Where x = 2 - 10.

[0016] The polyolefin modification method proposed in this invention avoids self-polymerization and volatilization loss of MAH during the grafting process; by using LM-MA as a low-volatility anhydride source, the residual monomer content and VOC release are significantly reduced, and the odor is improved; through a two-stage process and segmented injection strategy, the main chain degradation is inhibited, ensuring the stability and toughness of MFR are maintained; a controllable bipolar microstructure of "anhydride group + SMA short segment" is constructed, which comprehensively improves the material's compatibility, adhesion, and impact performance; by utilizing the renewability of dipentene raw materials, bio-based carbon content (≥5%) is introduced into the material system, taking into account sustainable development.

[0017] A second objective of this invention is to provide the application of the aforementioned polyolefin modification method in the preparation of modified polyolefin materials. The modified polyolefin materials proposed in this invention possess low VOC, low residual monomer, high grafting rate, maintained toughness, and bio-based properties (bio-based carbon content not less than 1%).

[0018] The third objective of this invention is a method for preparing a dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting modified polyolefin material, comprising the following steps:

[0019] (1) Dipentene and maleic anhydride are injected into a single-screw or twin-screw extruder to react and obtain a dipentene-maleic anhydride adduct;

[0020] (2) The polyolefin matrix, the dipentene-maleic anhydride adduct obtained in step (1), styrene and maleic anhydride are melted together and synergistically grafted under the initiation of a peroxide initiator to obtain the polyolefin material.

[0021] The reaction formulas for steps (1) and (2) in the preparation method proposed in this invention are as follows: Formula 2. This invention constructs a controllable bipolar grafted microstructure by pre-addition fixing of anhydride groups and combining styrene / maleic anhydride synergistic grafting.

[0022]

[0023] Formula 2

[0024] The two-stage reactive extrusion process in the preparation method proposed in this invention is as follows:

[0025] The first paragraph describes the ene addition of dipentene to maleic anhydride in a single-screw or twin-screw extruder to obtain a low-volatility, structurally stable dipentene-maleic anhydride adduct (LM-MA). This intermediate effectively immobilizes the anhydride group, reducing odor and VOC issues caused by free MAH, while also introducing a bio-based carbon source to increase the sustainability of the material.

[0026] The second stage involves a reactive extrusion process where LM-MA adducts and styrene / maleic anhydride are synergistically grafted onto the polyolefin backbone under peroxide initiation. This combination of "dotted anhydride groups + short polar segments" creates a bipolar microstructure, achieving high compatibility, maintained toughness, and low residual monomer content.

[0027] Preferably, the reaction conditions in step (1) are: reaction temperature 100 ℃-160 ℃, screw speed 200-400 rpm, and reaction time 60-240 s.

[0028] Further preferred, the reaction conditions in step (1) are: reaction temperature 130 ℃-150 ℃, screw speed 200-250 rpm, and reaction time 120-150 s.

[0029] Preferably, the molar ratio of dipentene to maleic anhydride in step (1) is 1:1.0-3.0.

[0030] Further preferred, the molar ratio of dipentene to maleic anhydride in step (1) is 1:1.1-1.3.

[0031] Preferably, in step (1), an inhibitor, p-hydroxyanisole, is added. The amount of p-hydroxyanisole added is 0.01%-0.05% of the sum of the molar amounts of dipentene and maleic anhydride. The purpose of using p-hydroxyanisole as an inhibitor is to avoid side reactions.

[0032] Further preferred, the amount of p-hydroxyanisole added is 0.02% of the sum of the molar amounts of dipentene and maleic anhydride.

[0033] In step (1), a vacuum exhaust system (below -0.08 MPa) and a condensation recovery system are set up to remove unreacted dipentene and MAH in a timely manner, ensuring the stability of the adduct and reducing VOC. The resulting LM-MA adduct masterbatch (which can be loaded onto an inert support or PP powder) or low-volatility liquid adduct can be used as a precursor for subsequent grafting.

[0034] Step (1) introduces anhydride groups in a stable form through pre-addition, reducing the self-polymerization and volatilization of MAH under high-temperature grafting conditions, improving monomer utilization, and providing a stable anhydride source for two-stage grafting.

[0035] Preferably, in step (2), the components are, by mass, 100 parts of polyolefin, 0.5-10 parts of dipentene-maleic anhydride adduct, 0.5-5 parts of styrene, 0.2-2.5 parts of maleic anhydride, 0.05-0.4 parts of peroxide initiator and 0.3-0.5 parts of antioxidant.

[0036] Further preferred, in step (2), each component by mass is: 100 parts polyolefin, 1 part dipentene-maleic anhydride adduct, 1-1.5 parts styrene, 0.15-0.8 parts maleic anhydride, 0.15-0.2 parts peroxide initiator and 0.4 parts antioxidant.

[0037] Peroxide initiators include, but are not limited to, dicumyl peroxide (DCP), tert-butyl peroxide (TBPB), tert-butyl peroxylaurate (TBLC), and di-tert-butyl peroxide (DTBP). The peroxides can be used alone or in combination of two or more to achieve hierarchical control of the free radical generation rate.

[0038] Preferably, the melting reaction conditions in step (2) are: reaction temperature 185 ℃-205 ℃, reaction time 30-90 s, and vacuum degree -0.09 MPa. The extruder screw speed in step (2) is 280-300 rpm.

[0039] Further preferred, the melting reaction conditions in step (2) are: reaction temperature 185 ℃-200 ℃, reaction time 60 s.

[0040] Preferably, the polyolefin matrix in step (2) is selected from one or more of polyethylene, polypropylene and polyethylene-polypropylene copolymer.

[0041] Step (2) employs segmented injection. Taking a twin-screw extruder as an example, peroxide is injected in zone Z2, LM-MA adduct is side-fed in zone Z3, and styrene / MAH is injected in zone Z4, achieving precise control over free radical distribution and reaction pathways. Subsequently, an antioxidant is added in zone Z5 to terminate residual free radicals and stabilize the grafted structure. LM-MA contributes "dotted anhydride groups," and styrene / MAH generates "short SMA segments." Both are grafted onto the polyolefin backbone to construct a bipolar grafted microstructure, while simultaneously improving interfacial adhesion and toughness retention.

[0042] The present invention also protects the use of the modified polyolefin material obtained by the preparation method described herein as a compatibilizer or binder in the preparation of high-performance composite materials and / or multilayer co-extruded films.

[0043] The modified polyolefin material obtained by this invention has an anhydride content of 0.3-3.0 wt% and is uniformly distributed; the MFR changes by -20% to +20% compared with the matrix, avoiding severe degradation of the main chain; the residual monomer content is less than 280 ppm, which is significantly lower than that of the material PP-g-(St-co-MAH) disclosed in the prior art; the notched impact strength is increased by more than 15%, achieving a balance between grafting efficiency and toughness maintenance; and the peeling / compatibility with polar polymers (PA6, PET, EVOH) and inorganic fillers is significantly improved.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. This invention pre-adds dipentene to MAH to obtain a low-volatile anhydride source, effectively solving the problems of residual monomers and VOCs in direct MAH grafting.

[0046] 2. Unlike traditional single-stage grafting, this invention proposes a two-stage reactive extrusion process. This invention separates "anhydride immobilization" from "synergistic grafting," achieving process control and suppressing side reactions. The preparation method proposed in this invention can be used with either a single-machine integrated process or a dual-machine series process, making it suitable for industrial scale-up.

[0047] 3. This invention provides isolated anhydride groups through LM–MA and short polar segments through St / MAH, enabling the material to simultaneously possess high compatibility and maintain toughness.

[0048] 4. This invention utilizes dipentene, a renewable resource, to increase the bio-based carbon content of the material (above 0.5%), which aligns with the trend of low carbon and environmental protection.

[0049] 5. The modified polyolefin material proposed in this invention has the following advantages: (1) Improved grafting efficiency: The LM-MA pre-addition stabilizes the anhydride group, reduces MAH self-polymerization, and improves the grafting rate; (2) Low VOC and low residual monomer: LM-MA has low volatility under extrusion conditions, and the residual monomer is controlled to <300 ppm with vacuum exhaust; (3) Excellent toughness: St / MAH synergistic grafting alleviates chain cracking, MFR remains stable, and the impact strength is significantly improved; (4) Bipolar structure: LM-MA provides anhydride sites, and St / MAH provides short polar segments. The combination of the two improves compatibility and interfacial adhesion. (5) Green and sustainable: The introduction of dipentene gives the material a bio-based carbon content of more than 5%, which is in line with the direction of sustainable development. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of a two-stage extrusion process (A: first stage LM-MA preparation; B: second stage grafting modification).

[0051] Figure 2The infrared spectra (containing additives) of the dipentene-maleic anhydride pre-addition / styrene-maleic anhydride co-grafted polypropylene obtained in Example 1, the styrene-maleic anhydride co-grafted polypropylene obtained in Comparative Example 1 (without dipentene pre-addition), and the dipentene-maleic anhydride pre-addition polypropylene obtained in Comparative Example 2 (without styrene-maleic anhydride co-grafting). Detailed Implementation

[0052] The present invention will be further described in detail below with reference to the embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are considered to be commercially available materials and reagents that can be obtained through conventional markets and other commercial channels.

[0053] The reactants used in the following examples and comparative examples are as follows:

[0054] Polypropylene (PP): homopolymer, MFR=12 g / 10min (230 ℃ / 2.16 kg); Dipentene: industrial grade, purity ≥98%, dried by molecular sieve; Maleic anhydride (MAH): analytical grade, melting point 52 ℃; Styrene (St): chemically pure; Peroxide initiator: dicumyl peroxide (DCP), purity ≥98%; Antioxidant system: antioxidant 1010 and antioxidant 168 in a mass ratio of 1:3.

[0055] The following examples and comparative examples demonstrate the performance testing methods for polyolefin materials:

[0056] Anhydride content: determined by acid value titration according to GB / T 1677; MFR: GB / T 3682; residual value: determined by headspace GC-MS; notched impact: ASTM D256; peel strength: ASTM D903, tested after hot pressing with PA6 sheet at 180℃; odor index tested according to VDA 270 for automotive interior materials.

[0057] Example 1

[0058] like Figure 1-2 As shown, a method for preparing a polyolefin material modified by dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting includes the following steps:

[0059] (1) Preparation of LM–MA adduct: The process was carried out on a co-rotating twin-screw extruder with L / D=40. Dipentene was injected into the feed end (Z1 zone), and MAH and p-hydroxyanisole (molar ratio of dipentene to MAH 1:1.1) were side-fed in Z2 zone. The amount of p-hydroxyanisole added was 0.02% of the sum of the molar amounts of dipentene and maleic anhydride. The temperature distribution was 110 ℃-135 ℃, the rotation speed was 250 rpm, and the reaction time was about 120 s. A vacuum of -0.08 MPa was set in Z4 zone to remove unreacted monomers. The residual LM and MAH monomers were condensed and recovered. The acid value of the obtained LM–MA adduct was about 250 mg KOH / g, and the residual monomers were less than 0.3 wt%.

[0060] (2) Grafting reaction: PP matrix, LM-MA adduct, St, MAH, and antioxidants in a mass ratio of 100:2:1.5:0.8:0.4 are grafted together. Figure 1 As shown in Figure B, the feed mixture (PP to DCP mass ratio of 100:0.18) is dissolved in a small amount of styrene and subjected to a melt reaction via liquid injection in zones Z1-Z2. The reaction zone temperature is 185 ℃-200 ℃, the die head temperature is 200 ℃, the rotation speed is 300 rpm, the reaction time is approximately 60 s, and the vacuum is -0.09 MPa, resulting in a modified polypropylene material (dipentene-maleic anhydride pre-addition / styrene-maleic anhydride co-grafted polypropylene). The final grafted polymer has a molecular weight of 1000-1500 g / mol (x=3-6), and the PDI of the resulting modified PP monolithic material is 4.6-5.1.

[0061] The modified polypropylene material was subjected to performance testing: To ensure the repeatability of the experimental results, all samples were prepared and tested under the same conditions. The modified polypropylene material was granulated by twin-screw extrusion and then dried in a hot air drying oven at 80 °C for 6 h to remove moisture and residual volatiles. The dried granules were then injection molded into standard test specimens using an injection molding machine. The injection temperature was 190 °C-200 °C, the mold temperature was 40 °C-50 °C, the injection pressure was 60-80 MPa, the holding time was 10 s, and the cooling time was 30 s. The resulting specimens were then placed in an environment of 25 °C and 50% relative humidity for 24 h before performance testing. All test results were taken as the average of three parallel experiments, with a deviation of less than 5%.

[0062] The test results are as follows: the anhydride content is 0.9 wt%, the MFR is 5% higher than that of the PP matrix, the residual monomer content is approximately 250 ppm, the notched impact strength is 20% higher than that of the PP matrix, and the peel strength with PA6 is 25% higher than that of the PP matrix. Compared with the control sample PP-g-(St-co-MAH), this embodiment adopts a dual-path design of LM–MA pre-addition + St / MAH synergistic grafting, combined with -0.09 MPa vacuum devolatilization, to control the residual monomer content to approximately 250 ppm, effectively suppressing processing odor and improving thermal stability while ensuring grafting efficiency. The "dot-like anhydride groups" provided by LM–MA work synergistically with the short SMA segments, resulting in a more complete interfacial polarity match with PA6, a 25% increase in peel strength compared to the PP matrix, and a 20% increase in notched impact strength, achieving a balance between enhanced interfacial adhesion and maintained toughness.

[0063] Comparative Example 1 (no LM–MA pre-addition, only St / MAH co-grafting)

[0064] Formula: PP: St: MAH: DCP: Antioxidant = 100: 1.5: 0.8: 0.18: 0.4.

[0065] Results: The acid anhydride content was approximately 0.5 wt%, the residual residue was >400 ppm, the odor was strong, and the peel strength only increased by 10%.

[0066] Comparative Example 2 (LM–MA pre-addition only, without St / MAH co-grafting)

[0067] Ratio: PP:LM-MA adduct:DCP:antioxidant = 100:4.3:0.18:0.4.

[0068] Results: The anhydride content was 0.6–0.7 wt%, the residual strength was low, but the peel strength only improved by 8%, and the impact improvement was not significant.

[0069] As can be seen from Comparative Examples 1 and 2, the grafting efficiency or interfacial enhancement effect is limited when using St / MAH or LM-MA adducts alone. However, combining LM-MA pre-addition with St / MAH co-grafting forms a bipolar grafting structure of "dot-like anhydride groups + short SMA segments," which simultaneously improves anhydride content, interfacial adhesion, and mechanical properties, while significantly reducing residual monomers, demonstrating a significant synergistic effect and achieving a technical effect of 1+1>2. Furthermore, compared to Example 1, this example appropriately extends the reaction time and increases the terminal temperature in the LM-MA addition reaction, resulting in a slight increase in the acid value of the adduct (approximately 260 mg KOH / g). Simultaneously, the ratio of MAH to St and the amount of DCP feed are moderately reduced in the grafting step to optimize grafting efficiency and residual monomer control. The results show that even under lower monomer feed conditions, the anhydride content and interfacial adhesion are still significantly improved, verifying the synergistic effect of LM-MA pre-addition and St / MAH co-grafting.

[0070] Example 2

[0071] This embodiment is basically the same as embodiment 1, except that the proportion and feeding position in step (2) are different.

[0072] In step (2), a raw material system with a mass ratio of PP:LM-MA adduct:St:MAH:DCP:antioxidant = 100:3:2:1.2:0.20:0.4 was used. During the reaction, DCP was dissolved in a small amount of styrene and injected into the liquid in zone Z2; LM-MA adduct was side-fed in zone Z3; the St / MAH mixture was injected in zone Z4; and the antioxidant was added in zone Z5. A vacuum of -0.095 MPa was set to remove unreacted monomers and low molecular weight substances. The temperature of the reaction zone was controlled at 190–205 ℃, the die head temperature at 200 ℃, the screw speed at 300 rpm, and the reaction time at approximately 60 s. After cooling and granulation, a polypropylene material modified by pre-addition of dipentene and maleic anhydride / co-grafting of styrene and maleic anhydride was obtained (the molecular weight of the final grafted polymer was 1600-2400 g / mol (x=6-10); PDI was 5.2-5.8). The prepared polypropylene materials were subjected to performance tests, and all samples were prepared and tested under the same conditions. All test results were averaged from three parallel experiments. The test results are as follows: the anhydride content was 1.6 wt%, the MFR decreased by 10% compared to the PP matrix, and the residual monomer was approximately 280 ppm; the peel strength with PET was 40% higher than that with the PP matrix, and the notched impact strength was 10% higher than that with the PP matrix.

[0073] Example 3

[0074] This embodiment is basically the same as embodiment 1, except that no free MAH was added in step (2), and the system ratio and feeding sequence were adjusted.

[0075] In step (2), a raw material system with a mass ratio of PP:LM-MA adduct:St:DCP:antioxidant = 100:2.8:1.5:0.18:0.4 was used. During the reaction, DCP was injected into zone Z3, LM-MA adduct was fed into zone Z4, and St was injected into zone Z5. The reaction zone temperature was controlled at 185 ℃–195 ℃, the screw speed was 280 rpm, the vacuum degree was -0.09 MPa, and the reaction time was about 60 s. After cooling and granulation, a dipentene-maleic anhydride pre-addition / styrene co-grafted modified polypropylene material without free MAH was obtained. The molecular weight of the final grafted polymer was 550-960 g / mol (x=2-4), and the PDI of the modified PP material was 4.9-5.3.

[0076] Under the same preparation and testing conditions, the average of three parallel tests on the sample was taken. The results were as follows: anhydride content of 0.7 wt%, MFR increased by 1% compared with PP matrix, and residual monomer content was approximately 230 ppm; compared with PP matrix, peel strength increased by approximately 10–20%, while notched impact strength showed no significant improvement. Due to the absence of free MAH, the system relied solely on the dotted anhydride groups of LM–MA, resulting in a lower anhydride group density and shorter graft chains; therefore, the effects on interfacial polarity matching and energy dissipation were limited, and the overall adhesion enhancement and toughness improvement were not as good as in Example 1.

[0077] Example 4

[0078] This embodiment is basically the same as embodiment 1, except that:

[0079] In step (1), the LM–MA addition reaction temperature is 110 ℃–140 ℃, the rotation speed is 200 rpm, the reaction time is 150 s, the vacuum is –0.08 MPa, and the acid value of the resulting adduct is about 260 mg KOH / g.

[0080] In step (2), the mass ratio of PP, LM-MA adduct, St, MAH, DCP, and antioxidant was 100:2:1:0.5:0.15:0.4. The reaction temperature was 185–200 ℃, the die head temperature was 200 ℃, the rotation speed was 300 rpm, the vacuum was -0.09 MPa, and the reaction time was approximately 60 s. Performance tests were conducted on the polypropylene material, and the results were: anhydride content of 1.2 wt%, MFR increased by 2% compared to the PP matrix, residual monomer content was approximately 200 ppm, peel strength with PA6 increased by 35%, and notched impact strength increased by 18%.

[0081] Example 5

[0082] This embodiment is basically the same as Example 1, except that the preparation of LM-MA adduct and the grafting reaction conditions are optimized and adjusted to study the grafting reaction characteristics at lower addition ratios and initiator contents.

[0083] (1) Preparation of LM–MA adduct: The reaction was carried out on a co-rotating twin-screw extruder with an L / D ratio of 40. Dipentene was injected into the feed end, and maleic anhydride (LM:MAH molar ratio of 1:1.0) was fed into the Z2 zone side. The inhibitor p-hydroxyanisole was added at a rate of 0.01% of the sum of the molar amounts of dipentene and maleic anhydride. The reaction temperature was controlled at 100 ℃-140 ℃, the screw speed was 200 rpm, and the reaction time was 240 s. A vacuum (-0.08 MPa) was set in the Z4 zone to remove unreacted monomers and condense and recover them. The acid value of the obtained LM–MA adduct was approximately 245 mg KOH / g, and the residual monomer content was less than 0.3 wt%.

[0084] (2) Grafting reaction: 100 parts of polypropylene, 0.5 parts of LM-MA adduct, 0.5 parts of styrene, 0.2 parts of maleic anhydride, 0.05 parts of peroxide initiator (DCP), and 0.3 parts of antioxidant were mixed. The melt reaction was carried out in a co-rotating twin-screw extruder at a reaction temperature of 185 ℃-205 ℃, a screw speed of 280 rpm, a vacuum degree of -0.09 MPa, and a reaction time of about 90 s. After cooling and granulation, a dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafted modified polypropylene material with low anhydride content was obtained. The molecular weight of the final grafted polymer was 650-1050 g / mol, and the PDI of the obtained modified PP material was 4.4-5.0.

[0085] The performance of the prepared polypropylene material was tested. Under the same preparation and testing conditions, three parallel tests were performed on the samples, and the average was taken. The results showed that the anhydride content was only 0.5 wt%, the MFR increased by about 3% compared to the PP matrix, and the residual monomer was about 220 ppm. Compared to the PP matrix, the notched impact strength increased by only about 10%, and the peel strength with PA6 increased by only about 15%. Because this example used lower LM-MA and St / MAH feed amounts and a smaller initiator ratio, the grafting reaction was milder, the grafted segments were shorter, and the anhydride density was insufficient. Therefore, the interfacial polarity matching and stress transfer effects were limited, and the overall adhesion and toughening effects were weaker than in Example 1. The residual monomer and odor of the material were well controlled, but the performance improvement was limited. It is more suitable for scenarios with high requirements for low volatility / odor and thermal stability, but lower requirements for adhesion and toughness improvement.

[0086] Example 6

[0087] This embodiment is basically the same as Example 1, except that the preparation of LM-MA adduct and the grafting reaction conditions are both strengthened to verify the reaction stability and performance upper limit under high anhydride feeding and strong initiation conditions.

[0088] (1) Preparation of LM–MA adduct: The reaction was carried out on a co-rotating twin-screw extruder with an L / D ratio of 40. Dipentene was injected into the feed end, and maleic anhydride (LM:MAH molar ratio of 1:1.5) was fed into the Z2 zone side. The inhibitor p-hydroxyanisole was added at a rate of 0.03% of the sum of the molar amounts of dipentene and maleic anhydride. The reaction temperature was controlled at 110 ℃-160 ℃, the screw speed was 400 rpm, and the reaction time was 60 s. A vacuum (-0.08 MPa) was set in the Z4 zone to remove unreacted monomers and condense and recover them. The acid value of the obtained LM–MA adduct was approximately 280 mg KOH / g, and the residual monomer content was less than 0.4 wt%, indicating a high degree of addition and reaction efficiency.

[0089] (2) Grafting reaction: 100 parts of polypropylene (PP), 10 parts of LM-MA adduct, 5 parts of styrene, 2.5 parts of maleic anhydride, 0.4 parts of peroxide initiator (DCP), and 0.5 parts of antioxidant were mixed. The reaction temperature was 185–195 ℃, the screw speed was 300 rpm, the vacuum degree was -0.09 MPa, and the reaction time was about 90 s. After cooling and granulation, a dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafted modified polypropylene material with high anhydride content was obtained. The molecular weight of the final grafted polymer was 2250-3260 g / mol, and the PDI of the modified PP material was 5.8-6.6.

[0090] The performance of the prepared polypropylene material was tested. All samples were prepared and tested under the same conditions, and the results were the average of three parallel experiments. The results showed that the anhydride content was 2.3 wt%; the MFR was reduced by about 15% compared to the PP matrix; the residual monomer content was about 350 ppm; the notched impact strength was increased by about 8% compared to the PP matrix; and the peel strength with PA6 was increased by about 45%. In this example, under the conditions of high monomer ratio and high initiator, the LM-MA adduct provided a large number of "point-like anhydride groups", and St / MAH formed dense short SMA segments, significantly increasing the grafting density of the system (anhydride content reached 2.3 wt%). Due to the high concentration of initiator and polar monomer, the main chain partially broke, and the MFR decreased slightly (-15%), but the polarity and interfacial reactivity of the material were significantly enhanced. The 45% increase in peel strength with PA6 indicates that the high anhydride system can still maintain good structural stability under extreme conditions. This embodiment demonstrates that by increasing the degree of addition, monomer ratio, and initiator concentration, grafting efficiency and polar compatibility can be further improved, achieving higher interfacial adhesion strength. As can be seen from Examples 1–5, the system of the present invention exhibits controllable reaction behavior and significant interfacial enhancement effects under low, medium, and high reaction intensities, proving that the method has good versatility and process adjustability.

[0091] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for modifying polyolefins to improve grafting efficiency, characterized in that, Dipentene-maleic anhydride adduct is obtained by reacting dipentene with maleic anhydride in an alphaene reaction. Then, the dipentene-maleic anhydride adduct and styrene / maleic anhydride are synergistically grafted onto the main chain of polyolefin under the initiation of peroxide, thereby obtaining a polyolefin material with high grafting efficiency.

2. The application of the polyolefin modification method according to claim 1 in the preparation of modified polyolefin materials.

3. A method for preparing a polyolefin material modified by dipentene-maleic anhydride pre-addition / styrene-maleic anhydride synergistic grafting, characterized in that, Includes the following steps: (1) Dipentene and maleic anhydride are injected into a single-screw or twin-screw extruder to react and obtain a dipentene-maleic anhydride adduct; (2) The polyolefin matrix, the dipentene-maleic anhydride adduct obtained in step (1), styrene and maleic anhydride are melted together and synergistically grafted under the initiation of a peroxide initiator to obtain the polyolefin material.

4. The preparation method according to claim 3, characterized in that, The reaction conditions described in step (1) are: reaction temperature 100 ℃-160 ℃, screw speed 200-400 rpm, and reaction time 60-240 s.

5. The preparation method according to claim 3 or 4, characterized in that, The molar ratio of dipentene to maleic anhydride in step (1) is 1:1.0-3.

0.

6. The preparation method according to claim 3 or 4, characterized in that, In step (1), the inhibitor p-hydroxyanisole is also added. The amount of p-hydroxyanisole added is 0.01%-0.05% of the sum of the molar amounts of dipentene and maleic anhydride.

7. The preparation method according to claim 3, characterized in that, In step (2), the components are in the following proportions by mass: 100 parts of polyolefin, 0.5-10 parts of dipentene-maleic anhydride adduct, 0.5-5 parts of styrene, 0.2-2.5 parts of maleic anhydride, 0.05-0.4 parts of peroxide initiator, and 0.3-0.5 parts of antioxidant.

8. The preparation method according to claim 3 or 7, characterized in that, The melting reaction conditions described in step (2) are: reaction temperature 185 ℃-205 ℃, reaction time 30-90 s, and vacuum degree -0.09 MPa.

9. The preparation method according to claim 3, characterized in that, The polyolefin matrix mentioned in step (2) is selected from one or more of polyethylene, polypropylene and polyethylene-polypropylene copolymer.

10. The use of the modified polyolefin material obtained by the preparation method according to any one of claims 3-9 as a compatibilizer or binder in the preparation of high-performance composite materials and / or multilayer co-extruded films.

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