High-polarity polypropylene composite material and preparation method thereof

Abstract

The application discloses a high-polarity polypropylene composite material which is prepared from the following components in parts by weight: polypropylene resin 65-75 parts; polar monomer composition 4-7 parts; hydroxylated nano-silicon dioxide 20-30 parts; initiator 0.2-0.4 parts; compatibilizer 2-4 parts; and antioxidant 0.5-0.8 parts. The application realizes high-strength and long-acting bonding with polyurethane water-based glue by introducing stable amino / hydroxyl polar sites into a polypropylene matrix through an in-situ polymerization-surface grafting-nano synergistic composite modification strategy and optimizing interface reaction conditions.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically a highly polar polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene (PP) is widely used in the automotive, home appliance, and building materials industries due to its low density, low cost, and excellent processing performance. However, the non-polar molecular chains and extremely low surface energy of polypropylene result in very poor interfacial bonding with polar materials (especially polyurethane water-based adhesives), making it prone to delamination or peeling after bonding. This severely limits its application in scenarios requiring high-strength bonding.

[0003] To address the aforementioned issues, existing technologies typically employ physical surface treatments (such as flame, plasma, or corona treatment) or chemical grafting modifications (such as using PP-g-MAH) to enhance the surface polarity of polypropylene. However, physical treatment methods suffer from drawbacks such as short-lived effects, uneven treatment of complex-shaped products, and high energy consumption. On the other hand, single chemical grafting modification faces challenges such as uneven distribution of polarity sites, unstable grafting rates, and difficulty in forming stable and uniform chemical bonds with polyurethane water-based adhesives, resulting in bond strength that still cannot meet the requirements of high-end applications.

[0004] Therefore, developing a polypropylene modified material that requires no complex post-processing, has a uniform distribution of polar sites, can form long-lasting and high-strength chemical bonds with polyurethane waterborne adhesives, and has a simple process and excellent comprehensive performance has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a high-polarity polypropylene composite material and its preparation method. Through an in-situ polymerization-surface grafting-nanosynergistic composite modification strategy, stable amino / hydroxyl polar sites are introduced into the polypropylene matrix, while simultaneously optimizing interfacial reaction conditions to achieve high-strength, long-lasting adhesion with polyurethane waterborne adhesives. To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention discloses a highly polar polypropylene composite material, which is prepared from the following components in parts by weight: 65-75 parts of polypropylene resin; 4-7 parts of polar monomer composition; 20-30 parts of hydroxylated nano-silica; Initiator 0.2~0.4 parts; 2-4 parts compatibilizer; Antioxidant 0.5~0.8 parts.

[0006] Furthermore, the hydroxyl and amino-containing olefinic unsaturated monomer is a compound of hydroxyethyl methacrylate (HEMA) and methacrylamide (MAM) in a mass ratio of 1:(0.3~0.5). Hydroxyethyl methacrylate provides hydroxyl groups (-OH), and methacrylamide provides amino groups (-NH2). Their synergistic effect allows them to undergo an addition reaction with the isocyanate groups (-NCO) in the polyurethane waterborne adhesive, forming stable chemical bonds. This specific compounding ratio avoids the problems of uneven polar site distribution or insufficient reactivity caused by a single monomer.

[0007] Furthermore, the polypropylene resin is a copolymer polypropylene, which has a melt flow rate of 15~40g / 10min, preferably 20~30g / 10min, under conditions of 230℃ and 2.16kg load. It has both good processing fluidity and mechanical stability, and is suitable for in-situ polymerization modification and subsequent molding processes.

[0008] Furthermore, the hydroxylated nano-silica has a particle size of 20-80 nm and a surface hydroxyl content of 1.2-2.0 mmol / g. Its pretreatment process involves dispersing the hydroxylated nano-silica in anhydrous ethanol, adding silane coupling agent KH-560 (3-5% of the nano-silica mass), stirring and reacting at 60-80°C for 2-3 hours, filtering, and drying for later use. The pretreated nano-silica forms epoxy groups on its surface, which can react with the amino / hydroxyl groups of the bifunctional monomers, simultaneously improving the surface roughness of polypropylene and enhancing the interface through a dual effect of physical anchoring and chemical bonding.

[0009] Furthermore, the initiator is dicumyl peroxide (DCP), whose decomposition temperature matches the polypropylene processing temperature, and can efficiently initiate the in-situ polymerization reaction between the bifunctional monomer and polypropylene.

[0010] Furthermore, the compatibilizer is PP grafted maleic anhydride (PP-g-MAH) with a grafting rate of 0.8-3%, preferably 1.2-1.5%, which can improve the interfacial compatibility between the bifunctional monomer, nano-silica and the polypropylene matrix and reduce phase separation.

[0011] Furthermore, the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:(1~2), which can effectively inhibit the thermo-oxidative aging of polypropylene during high-temperature processing and subsequent use, and extend the service life of the material.

[0012] On the other hand, the present invention discloses a method for preparing the above-described high-polarity polypropylene composite material, comprising the following steps: Premixing: Weigh out polypropylene resin, amino / hydroxyl bifunctional monomer, pretreated hydroxylated nano silica, initiator, compatibilizer and antioxidant according to the weight parts, put them into a high-speed mixer, and mix for 8-15 minutes at 80~100℃ and 800~1200r / min to obtain a uniform premix. Melt extrusion granulation: The premixed material is fed into a twin-screw extruder for melt extrusion and granulation. The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 170~180℃, Zone 2 185~195℃, Zone 3 200~210℃, Zone 4 205~215℃, and the die head temperature is 210~220℃. The screw speed is 350~500 r / min, the residence time is 1.5~3 min, and the vacuum degree is -0.07~-0.09 MPa. Drying: The extruded granulated particles are dried in a forced-air drying oven at 70~90℃ for 3~5 hours to remove moisture and obtain a high-polarity polypropylene composite material.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a triple mechanism of matrix polarity modification, interfacial activity enhancement, and nano-synergistic anchoring: First, matrix polarity modification: through in-situ polymerization of amino / hydroxyl bifunctional monomers with polypropylene, polar groups such as hydroxyl and amino groups are stably embedded into the polypropylene molecular chain, fundamentally improving the surface energy of the polypropylene matrix and solving the interfacial incompatibility problem between non-polar and polar materials; Second, interfacial activity enhancement: the amino / hydroxyl groups of the bifunctional monomers can specifically react with the isocyanate groups in the polyurethane waterborne adhesive to form stable chemical bonds such as urea bonds and urethane bonds, constructing a chemical bridge between polypropylene, modifier, and polyurethane, significantly improving the bonding strength; Third, nano-synergistic anchoring: the pretreated hydroxylated nano-silica can not only form hydrogen bonds with the polar groups of the polypropylene matrix, but also improve the surface roughness of the material, increase the contact area with the adhesive, and at the same time, the epoxy groups on its surface can participate in the interfacial reaction, further strengthening the interfacial bonding and avoiding the limitations of single chemical modification or physical filling.

[0014] The composite material prepared by this invention exhibits significantly enhanced surface polarity, resulting in a bond strength with polyurethane water-based adhesives that is far superior to single grafting modification or physical treatment methods. More importantly, this modification effect achieves stable embedding of polar groups into the polypropylene matrix through chemical bonding, overcoming the shortcomings of poor aging properties of traditional flame or plasma treatments, and maintaining good surface polarity and bond strength even after long-term storage.

[0015] The composite material of this invention improves bonding performance while maintaining good levels of tensile strength and impact toughness, without exhibiting brittle deterioration due to excessive filler. Furthermore, this solution employs an integrated process of melt extrusion in-situ polymerization, eliminating the need for complex post-processing steps and avoiding the high energy consumption, safety hazards, and environmental problems associated with physical processing, making it suitable for large-scale industrial production. Attached Figure Description

[0016] Figure 1 The image shows the water contact angle test results of the high-polarity polypropylene composite material prepared in Example 1 of this invention after 7 days of storage. It indicates that the surface still maintains a low contact angle, demonstrating that the material has long-term stable surface polarity. The testing instrument used was a KRUSS DCAT21. The sample was placed on the contact angle testing platform, and water droplets of 2 μL volume were added vertically. The morphology and size of the water contact angle between the water droplets and the material were observed. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0020] The reagents used in this embodiment and comparative example, along with their suppliers, are as follows: Polypropylene resin: Homopolymer polypropylene PPH-MN90B, produced by Luoyang Petrochemical, with a melt flow rate of 97g / 10min at 230℃ and 2.16kg load; Bifunctional monomers: hydroxyethyl methacrylate (HEMA, industrial grade), methacrylamide (MAM, industrial grade); Hydroxylated nano-silica: particle size 50nm, surface hydroxyl content 1.5mmol / g, Nanjing Epuri Nanomaterials Co., Ltd. Silane coupling agent KH-560: Industrial grade, Hangzhou Jessica Chemical Co., Ltd.; Initiator: Dicumyl peroxide (DCP), industrial grade, Shanghai Yuanye Biotechnology Co., Ltd.; Compatibilizer: PP grafted with maleic anhydride, Huawen Chemical Co., Ltd.; Antioxidants: Antioxidant 1010, Antioxidant 168, manufactured by BASF; Polyurethane water-based adhesive: 40% solids content, brand name TOTAASEAL 6023, manufactured by Total.

[0021] The reagents described above are only for illustrating the source and composition of the reagents used in the experiments of this invention, so as to provide full disclosure, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0022] The pretreatment of hydroxylated nano-silica is as follows: 100 parts of hydroxylated nano-SiO2 were dispersed in 500 mL of anhydrous ethanol, and 4 parts of silane coupling agent KH-560 were added. The mixture was stirred at 70 °C for 2.5 h. After filtration, the filter cake was dried in a vacuum drying oven at 80 °C for 4 h for later use.

[0023] Example 1 Weigh out 75 parts of polypropylene resin, 4 parts of HEMA, 1.5 parts of MAM, 20 parts of pretreated hydroxylated nano silica, 0.3 parts of DCP, 3 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.4 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0024] Example 2 Weigh out 70 parts of polypropylene resin, 5 parts of HEMA, 2 parts of MAM, 25 parts of pretreated hydroxylated nano silica, 0.4 parts of DCP, 4 parts of compatibilizer, 0.3 parts of antioxidant 1010, and 0.5 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0025] Example 3 Weigh out 65 parts of polypropylene resin, 3 parts of HEMA, 1 part of MAM, 30 parts of pretreated hydroxylated nano silica, 0.2 parts of DCP, 2 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.3 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0026] Comparative Example 1 Weigh out 75 parts of polypropylene resin, 20 parts of pretreated hydroxylated nano silica, 3 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.4 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0027] Comparative Example 2 Weigh out 75 parts of polypropylene resin, 5.5 parts of HEMA, 20 parts of pretreated hydroxylated nano silica, 0.3 parts of DCP, 3 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.4 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0028] Comparative Example 3 Weigh out 75 parts of polypropylene resin, 5.5 parts of MAM, 20 parts of pretreated hydroxylated nano silica, 0.3 parts of DCP, 3 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.4 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0029] Comparative Example 4 Weigh out 75 parts of polypropylene resin, 20 parts of untreated hydroxylated nano silica, 3 parts of compatibilizer, 0.2 parts of antioxidant 1010, and 0.4 parts of antioxidant 168. Put all the above raw materials into a high-speed mixer and mix for 10 minutes at 25°C and 1000 r / min to obtain a premix. The premixed material was fed into a twin-screw extruder with the following zone temperatures: Zone 1 175℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, and Die head 210℃; Screw speed 400 r / min, residence time 2 min, vacuum degree -0.08 MPa, and extrusion granulation. The granulated particles were dried in an 80℃ forced-air oven for 4 hours to obtain a high-polarity polypropylene composite material.

[0030] The composite materials obtained in Examples 1-3 and Comparative Examples 1-4 were respectively prepared into 80×80×2.5mm high-gloss plates for performance testing. The high-gloss plate of Comparative Example 4 underwent plasma treatment (100W power, 3min) before testing. The specific testing method is as follows: (1) Surface dyne value: Tested using a dyne pen according to GB / T 14216-2008 standard; (2) T-peel strength: According to GB / T 2791-1995 standard, the bonding strength of the composite material was tested after being combined with polyurethane water-based adhesive. The composite curing conditions were 70℃, 50% humidity, and 1.5h curing time. (3) Mechanical properties: tensile strength was tested according to ISO 527 standard, and notched impact strength (23℃) was tested according to ISO 179 standard.

[0031] The test results are shown in Table 1.

[0032] Table 1

[0033] The composite materials of Examples 1-3 all had surface dynes values ​​≥45 mN / m and T-peel strengths ≥300 N / m, exhibiting stable mechanical properties. This indicates that the composite modification strategy of the present invention can effectively improve the surface polarity of polypropylene and its adhesion strength to polyurethane waterborne adhesives. Comparative Example 1 (without bifunctional monomers) had extremely low surface dynes values ​​and peel strengths, indicating that the introduction of polar sites is key to enhanced adhesion. The peel strengths of Comparative Example 2 (containing only hydroxyl monomers) and Comparative Example 3 (containing only amino monomers) were lower than those of the examples, with Comparative Example 3 showing better performance than Comparative Example 2. This indicates that the synergistic use of amino and hydroxyl groups yields the best reactivity, and a single functional group is insufficient to achieve the desired adhesion effect. Comparative Example 4 (plasma treatment) showed acceptable initial performance, but its surface dynes values ​​and peel strengths decreased significantly after 7 days, indicating that the chemical modification of the present invention has superior long-term stability.

[0034] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0035] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A highly polar polypropylene composite material, characterized in that, It is prepared from the following components in parts by weight: 65-75 parts of polypropylene resin; 4-7 parts of polar monomer composition; 20-30 parts of hydroxylated nano-silica; Initiator 0.2~0.4 parts; 2-4 parts compatibilizer; Antioxidant 0.5~0.8 parts.

2. The high polarity polypropylene composite material according to claim 1, characterized in that, The polar monomer composition is prepared by compounding hydroxyethyl methacrylate and methacrylamide in a mass ratio of 1:(0.3~0.5).

3. The high polarity polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is homopolymer polypropylene, and its melt flow rate is 15~40g / 10min under conditions of 230℃ and 2.16kg load.

4. The high polarity polypropylene composite material according to claim 1, characterized in that, The hydroxylated nano-silica has a particle size of 20-80 nm and a surface hydroxyl content of 1.2-2.0 mmol / g.

5. The high polarity polypropylene composite material according to claim 1, characterized in that, The hydroxylated nano-silica undergoes the following pretreatment: Hydroxylated nano-silica was dispersed in anhydrous ethanol, a silane coupling agent was added, and the mixture was stirred at 60-80°C for 2-3 hours. After filtration and drying, it was ready for use. The mass ratio of the hydroxylated nano-silica to the silane coupling agent is 100:(3-5).

6. The high polarity polypropylene composite material according to claim 1, characterized in that, The initiator is dicumyl peroxide.

7. The high polarity polypropylene composite material according to claim 1, characterized in that, The compatibilizer is PP grafted with maleic anhydride, with a grafting rate of 0.8-3%.

8. The high polarity polypropylene composite material according to claim 1, characterized in that, The antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:(1~2).

9. A method for preparing a high-polarity polypropylene composite material as described in claims 1-8, characterized in that, Includes the following steps: Polypropylene resin, olefinic unsaturated monomers containing hydroxyl and amino groups, pretreated hydroxylated nano-silica, initiator, compatibilizer and oxidant are mixed at 20-30℃ and 800-1200 r / min for 8-15 min to obtain a uniform premix. The premixed material is fed into a twin-screw extruder for melt extrusion and granulation. The granulated particles are dried at 70-90℃ for 3-5 hours to obtain a high-polarity polypropylene composite material.

10. The preparation method according to claim 9, characterized in that, The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 170~180℃, Zone 2 185~195℃, Zone 3 200~210℃, Zone 4 205~215℃, and the die head temperature 210~220℃; the screw speed is 350~500 r / min, the residence time is 1.5~3 min, and the vacuum degree is -0.07~-0.09 MPa.

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