High-rigidity anti-warping talc reinforced polypropylene hollow plate special material and preparation method thereof

Abstract

The application discloses a high-rigidity anti-warping talcum reinforced polypropylene hollow plate special material and a preparation method thereof. The material is prepared from raw materials including polypropylene, calcium carbonate, talcum powder, a coupling agent, stearic acid, zinc stearate, a vinyl-containing ionic liquid monomer, a free radical initiator and an antioxidant. The calcium carbonate and the talcum powder are subjected to surface modification through the coupling agent, the stearic acid and the zinc stearate, and then are mixed with the remaining raw materials under the condition that the temperature is reduced to below 50 DEG C, and then are sent into a double-screw extruder to be melt blended under the condition that the temperature is 160-220 DEG C, so that the vinyl-containing ionic liquid monomer is subjected to in-situ free radical polymerization under the action of the initiator to form a polyionic liquid network. The network is anchored on the surface of the talcum powder and is physically entangled with polypropylene molecular chains, so that the rigidity and impact toughness of the material can be improved, meanwhile, the sheet layer directional arrangement of the talcum powder is inhibited, the shrinkage anisotropy of the plate is reduced, and the warping is improved; and the imidazole cation in the polyionic liquid endows the material with antistatic properties.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and more specifically to a high-rigidity, anti-warping talc-reinforced polypropylene hollow board material and its preparation method. Background Technology

[0002] Polypropylene (PP) hollow sheets are widely used in packaging, logistics, and construction formwork due to their advantages such as light weight, environmental friendliness, corrosion resistance, and recyclability. To improve the rigidity of PP hollow sheets, talc is often used industrially as an inorganic filler for stiffening modification. However, the interfacial compatibility between talc and the PP matrix is ​​poor, and high filler content easily leads to agglomeration, resulting in a significant decrease in the material's impact toughness and elongation at break, i.e., a "rigidity-toughness contradiction." Simultaneously, talc flakes tend to align oriented along the flow direction during extrusion, causing different shrinkage rates in the longitudinal and transverse directions of the sheet. This can lead to warping and deformation after cooling, affecting the product's dimensional stability.

[0003] To address the aforementioned issues, existing technologies primarily employ two types of methods for modifying talc. One method involves surface treatment of talc with coupling agents, such as silane coupling agents or titanate coupling agents, to improve the dispersibility of talc in polypropylene. However, coupling agents only improve dispersion and cannot effectively enhance the material's toughness. The other method involves coating talc with elastomers. While this can improve toughness to some extent, it often leads to a significant reduction in material rigidity. Furthermore, the coating process typically requires organic solvents or grafting reactions, making it complex and unsuitable for industrial production.

[0004] In recent years, ionic liquids have been attempted for compatibilization and modification of polymer blends. However, existing reports mostly involve physical blending of small-molecule ionic liquids, which exhibit weak interfacial interactions within the polymer matrix and are prone to migration and precipitation, making it difficult to form stable network structures. Although published patent documents (such as CN120944138B) involve the modification of lignin with carboxyl-functionalized ionic liquids, their reaction mechanism is esterification grafting, applied to wood-plastic composite systems, and do not involve the free radical polymerization of vinyl-containing ionic liquid monomers, nor do they involve talc / polypropylene hollow board systems.

[0005] In summary, current technologies lack a modification scheme that can effectively balance the high rigidity of polypropylene hollow sheets with good toughness and anti-warping properties. Therefore, developing a special material for polypropylene hollow sheets that combines high rigidity, high toughness, and good dimensional stability has significant industrial application value. Summary of the Invention

[0006] In view of this, the present invention provides a special material for high-rigidity, anti-warping, talc-reinforced polypropylene hollow boards and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution, comprising the following components by weight: 30-50 parts of polypropylene; 40-55 parts calcium carbonate; 8-20 parts talcum powder; 0.3-0.8 parts of coupling agent; Stearic acid 0.3~0.8 parts; 0.2-0.6 parts of zinc stearate; 2-10 parts of vinyl-containing ionic liquid monomer; 0.04~0.2 parts of free radical initiator; Antioxidant 0.1~0.5 parts; The vinyl-containing ionic liquid monomer undergoes in-situ free radical polymerization during melt blending under the action of the free radical initiator, forming a polyionic liquid network.

[0008] Preferably, in the above-mentioned high-rigidity, anti-warping, talc-reinforced polypropylene hollow board special material and its preparation method, the polypropylene is a mixture of polypropylene PPHT03 and polypropylene K8003, wherein the polypropylene PPHT03 is 25-40 parts and the polypropylene K8003 is 5-10 parts.

[0009] Preferably, in the above-mentioned high-rigidity, anti-warping, talc-reinforced polypropylene hollow board special material and its preparation method, the vinyl-containing ionic liquid monomer is selected from one or more of 1-vinyl-3-ethylimidazole bromide, 1-vinyl-3-ethylimidazole chloride, 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-vinyl-3-ethylimidazole hexafluorophosphate, bis(trifluoromethanesulfonyl)imide 1-vinyl-3-ethylimidazole, 1-vinyl-3-butylimidazole bromide, and 1-allyl-3-methylimidazole chloride.

[0010] Preferably, in the above-mentioned high-rigidity anti-warping talc-strengthened polypropylene hollow board special material and its preparation method, the free radical initiator is selected from one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and benzoyl peroxide.

[0011] Preferably, in the above-mentioned high-rigidity, anti-warping, talc-reinforced polypropylene hollow board special material and its preparation method, the coupling agent is an aluminate coupling agent; the antioxidant is antioxidant 1010.

[0012] Preferably, the above-mentioned high-rigidity, anti-warping, talc-reinforced polypropylene hollow board special material and its preparation method include the following steps: S1. Powder modification: Calcium carbonate and talc are added to a high-speed mixer and heated to 110~120℃. After premixing, the coupling agent is added and reacted for 5 minutes. Then stearic acid and zinc stearate are added and reacted for another 5 minutes to obtain modified mixed powder. S2. Premixing: Cool the modified mixed powder to below 50°C, add polypropylene, vinyl-containing ionic liquid monomer, free radical initiator and antioxidant, mix at room temperature for 5-10 minutes to obtain premix; S3. Extrusion granulation: The premixed material is fed into a twin-screw extruder and melt-blended and extruded at 160~220℃; during the melt blending process, the free radical initiator initiates the in-situ free radical polymerization of the vinyl-containing ionic liquid monomer to form a polyionic liquid network.

[0013] Preferably, in the above-mentioned high-rigidity anti-warping talc-reinforced polypropylene hollow board special material and its preparation method, the screw speed of the twin-screw extruder is 150~300 rpm, and the residence time of the material in the screw is 1~5 min.

[0014] Preferably, in the above-mentioned high-rigidity anti-warping talc-reinforced polypropylene hollow board special material and its preparation method, the stirring speed of the high-speed mixer is 500~1500 rpm.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a high-rigidity, anti-warping talc-enhanced polypropylene hollow board special material and its preparation method. By adding vinyl-containing ionic liquid monomers and polymerizing them in situ under the action of free radical initiators, a three-dimensional physical cross-linking network of polyionic liquid is formed between talc powder and polypropylene matrix. This network is anchored to the surface of talc powder through ion-dipole interactions and hydrogen bonds, and physically entangles with polypropylene molecular chains, so that talc powder plays an energy dissipation role as a physical cross-linking point. At the same time, it can suppress the excessive orientation of talc powder sheets during extrusion processing, reduce the anisotropy during product cooling and shrinkage, and thus improve the warping deformation of hollow boards. Comparative data from the examples and comparative examples show that, while maintaining the flexural modulus at 3980 MPa or higher, the notched impact strength can be increased from 4.61 kJ / m² to 10.24 kJ / m² or higher. Furthermore, the imidazole cations in the polyionic liquid impart antistatic properties to the material, eliminating the need for additional antistatic agents. Moreover, the preparation method does not require the use of organic solvents, and the process is compatible with existing polypropylene hollow board extrusion production lines. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] All raw materials involved in this invention are commercially available, and their specific specifications are as follows (this is only an example to ensure sufficient disclosure): Polypropylene PPHT03: Melt flow rate (MFR, 230℃, 2.16kg) is 2.5~3.5 g / 10min, purchased from a branch of Sinopec; Polypropylene K8003: Melt flow rate (MFR, 230℃, 2.16kg) is 1.5~2.5 g / 10min, impact copolymer polypropylene, purchased from a branch of Sinopec; Calcium carbonate: 1250 mesh particle size, untreated surface, purchased from a mining company; Talc powder: 1250 mesh particle size, untreated surface, purchased from a mining company; Aluminate coupling agent JF041: Commercially available industrial grade, purchased from a chemical additives company; Stearic acid and zinc stearate: both are industrial grade and were purchased from a chemical raw material company. Vinyl-containing ionic liquid monomers: 1-vinyl-3-ethylimidazole bromide ([VEIm]Br), purity ≥98%, purchased from an ionic liquid technology company; others such as 1-vinyl-3-ethylimidazole chloride, 1-vinyl-3-ethylimidazole tetrafluoroborate, etc. are similar; Free radical initiator: dicumyl peroxide (DCP), purity ≥99%, commercially available industrial grade; Antioxidant 1010: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], commercially available industrial grade.

[0018] The present invention provides a method for preparing a high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material, comprising the following steps (the dosage of each component in each step is shown in the specific embodiments): S1. Powder Modification: Add calcium carbonate and talc to a high-speed mixer according to the formula. Turn on the heating and heat until the material temperature reaches 110-120℃. Then stir and premix at 800-1200 rpm for 5 minutes. Then add aluminate coupling agent JF041 and continue the high-speed reaction for 5 minutes. Then add stearic acid and zinc stearate and continue the high-speed reaction for 5 minutes to obtain surface-modified mixed powder. After discharge, cool naturally or by forced cooling for later use.

[0019] S2. Premixing: Cool the modified mixed powder obtained in step S1 to below 50°C, place it in a high-speed mixer, and add the formulated amounts of polypropylene PPHT03, polypropylene K8003, vinyl-containing ionic liquid monomer, free radical initiator, and antioxidant 1010. Mix at room temperature (20-30°C) at a low speed of 400-600 rpm for 5-10 minutes to obtain the premix. Because the temperature in this step is lower than the decomposition temperature of the initiator and the polymerization temperature of the ionic liquid monomer, premature polymerization will not occur.

[0020] S3. Extrusion Granulation: The premix obtained in step S2 is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: Zone 1 160–170℃, Zone 2 180–190℃, Zone 3 190–200℃, Zone 4 200–210℃, and Die Head 200–220℃; the screw speed is 150–300 rpm; and the residence time of the material in the screw is 1–5 minutes. Under high-temperature shear conditions, the free radical initiator decomposes to generate free radicals, which initiate in-situ free radical polymerization of vinyl-containing ionic liquid monomers, forming a polyionic liquid network. The extruded melt is then water-cooled, stretched, and pelletized to obtain high-rigidity, anti-warping, talc-reinforced polypropylene hollow board granules.

[0021] S4. Standard specimen molding: The granules obtained in step S3 are dried at 80-100℃ for 2-4 hours, and then injection molded by an injection molding machine at an injection temperature of 180-220℃ and a mold temperature of 40-60℃ to obtain standard specimens for performance testing.

[0022] Example 1 By weight, the raw material composition is as follows: Polypropylene PPHT03 33.2 parts, polypropylene K8003 6.64 parts, calcium carbonate 46.87 parts, talc 11.72 parts, aluminate coupling agent JF041 0.59 parts, stearic acid 0.59 parts, zinc stearate 0.40 parts, 1-vinyl-3-ethylimidazolium bromide ([VEIm]Br) 2.0 parts, dicumyl peroxide (DCP) 0.04 parts, antioxidant 1010 0.2 parts.

[0023] The preparation process was carried out according to the general preparation method S1 to S4 described above, and finally the special material standard sample of Example 1 was obtained.

[0024] Example 2 The procedure is essentially the same as in Example 1, except that the amount of [VEIm]Br is 5.0 parts and the amount of DCP is 0.1 parts. All other components and preparation steps remain unchanged.

[0025] Example 3 The procedure is essentially the same as in Example 1, except that the amount of [VEIm]Br is 8.0 parts and the amount of DCP is 0.16 parts. All other components and preparation steps remain unchanged.

[0026] Comparative Example 1 By weight, the raw material composition is as follows: Polypropylene PPHT03 33.2 parts, polypropylene K8003 6.64 parts, calcium carbonate 46.87 parts, talc 11.72 parts, aluminate coupling agent JF041 0.59 parts, stearic acid 0.59 parts, zinc stearate 0.40 parts. No vinyl-containing ionic liquid monomers or free radical initiators are added.

[0027] Preparation process: S1 powder modification and S2 premixing (without monomers and initiators) were carried out, followed by S3 extrusion granulation (only conventional melt blending occurred, without in-situ polymerization reaction) and S4 injection molding to obtain the sample of Comparative Example 1.

[0028] Comparative Example 2 By weight, the raw material composition is as follows: Calcium carbonate 50.62 parts, aluminate coupling agent 0.67 parts, polyethylene wax 1.15 parts, zinc stearate 0.47 parts, polypropylene TO3 7.09 parts, polypropylene 1102K 30.00 parts, polypropylene K8003 10.00 parts.

[0029] This is a typical calcium carbonate-strengthened PP hollow board formulation in the existing technology. The preparation process is carried out in accordance with conventional blending, granulation, and injection molding.

[0030] Comparative Example 3 By weight, the raw material composition is as follows: Calcium carbonate 60.00 parts, aluminate coupling agent 0.70 parts, stearic acid 0.75 parts, polyethylene wax 0.43 parts, zinc stearate 0.40 parts, polypropylene TO3 7.72 parts, polypropylene 1102K 20.00 parts, polypropylene K8003 10.00 parts.

[0031] This is the existing formula for high-filled calcium carbonate stiffened PP hollow board.

[0032] Comparative Example 4 The mixture was essentially the same as Comparative Example 1, except that 5.0 parts of 1-ethyl-3-methylimidazole bromide ([EMIm]Br) were added, but no free radical initiator was added. Since [EMIm]Br does not contain vinyl double bonds, it cannot undergo polymerization during extrusion and exists only as a small-molecule physical blend.

[0033] The standard samples prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance testing according to the following national standards: Tensile properties: Tested according to GB / T 1040.2-2006, tensile rate 50 mm / min; Bending performance: Tested according to GB / T 9341-2008, bending rate 2 mm / min; Impact performance: Cantilever beam notched impact strength tested according to GB / T 1843-2008.

[0034] The test results are shown in Table 1: Table 1 Performance test results of each embodiment and comparative example The test data in Table 1 shows that: Comparative Example 1 (without ionized liquid network) has a flexural modulus of 4170 MPa and a notched impact strength of only 4.61 kJ / m². In contrast, Examples 1-3, while maintaining a flexural modulus of approximately 3980-4155 MPa (comparable to Comparative Example 1), show notched impact strengths of 10.24, 16.75, and 22.40 kJ / m², respectively, achieving a synergistic improvement in rigidity without brittleness. This significantly resolves the "rigidity-toughness contradiction" in traditional talc-enhanced PP.

[0035] Comparative Example 4, which added a vinyl-free small molecule ionic liquid [EMIm]Br (without initiator), had an impact strength of only 3.98 kJ / m², even lower than that of Comparative Example 1. This indicates that physically blended small molecule ionic liquids cannot form a cross-linked network and cannot play a role in interface compatibilization and energy dissipation. On the contrary, they may weaken the interface bonding due to migration, which proves the indispensability of the "in-situ free radical polymerization to form a polyionic liquid network" of the present invention.

[0036] The flexural modulus of Comparative Examples 2 and 3 (existing formulations) were generally low (2507–3141 MPa), and the impact toughness was not significantly improved, indicating that traditional inorganic filler stiffening technology cannot simultaneously achieve rigidity, toughness, and anti-warping performance. The embodiments of this invention, with the same or lower filler dosage, suppress the directional alignment of talc flakes through a polyionic liquid network (thereby reducing warping) and utilize physical entanglement to absorb impact energy, resulting in comprehensive performance superior to existing technologies.

[0037] In summary, this invention constructs a three-dimensional physical cross-linked network of polyionic liquid at the talc / PP interface through in-situ free radical polymerization of vinyl ionic liquid monomers, achieving a synergistic effect of high rigidity (flexural modulus ≥3980 MPa), high toughness (notched impact strength ≥10 kJ / m²), and anti-warping. Moreover, the preparation process is simple, solvent-free, and has good industrial applicability.

[0038] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A special material for high-rigidity, anti-warping, talc-reinforced polypropylene hollow boards, characterized in that, By weight, it includes the following components: 30-50 parts of polypropylene; 40-55 parts calcium carbonate; 8-20 parts talcum powder; 0.3~0.8 parts of coupling agent; Stearic acid 0.3~0.8 parts; 0.2-0.6 parts of zinc stearate; 2-10 parts of vinyl-containing ionic liquid monomers; 0.04~0.2 parts of free radical initiator; Antioxidant 0.1~0.5 parts; The vinyl-containing ionic liquid monomer undergoes in-situ free radical polymerization during melt blending under the action of the free radical initiator, forming a polyionic liquid network.

2. The high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material as described in claim 1, characterized in that, The polypropylene is a mixture of polypropylene PPHT03 and polypropylene K8003, wherein the amount of polypropylene PPHT03 is 25-40 parts and the amount of polypropylene K8003 is 5-10 parts.

3. The high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material as described in claim 1, characterized in that, The vinyl-containing ionic liquid monomer is selected from one or more of 1-vinyl-3-ethylimidazole bromide, 1-vinyl-3-ethylimidazole chloride, 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-vinyl-3-ethylimidazole hexafluorophosphate, 1-vinyl-3-ethylimidazole bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-butylimidazole bromide, and 1-allyl-3-methylimidazole chloride.

4. The high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material as described in claim 1, characterized in that, The free radical initiator is selected from one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and benzoyl peroxide.

5. The high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material as described in claim 1, characterized in that, The coupling agent is an aluminate coupling agent; the antioxidant is antioxidant 1010.

6. A method for preparing a high-rigidity, anti-warping, talc-reinforced polypropylene hollow board material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Powder modification: Calcium carbonate and talc are added to a high-speed mixer and heated to 110~120℃. After premixing, the coupling agent is added and reacted for 5 minutes. Then stearic acid and zinc stearate are added and reacted for another 5 minutes to obtain modified mixed powder. S2. Premixing: Cool the modified mixed powder to below 50°C, add polypropylene, vinyl-containing ionic liquid monomer, free radical initiator and antioxidant, mix at room temperature for 5-10 minutes to obtain premix; S3. Extrusion granulation: The premixed material is fed into a twin-screw extruder and melt-blended and extruded at 160~220℃; during the melt blending process, the free radical initiator initiates the in-situ free radical polymerization of the vinyl-containing ionic liquid monomer to form a polyionic liquid network.

7. The preparation method according to claim 6, characterized in that, In step S3, the screw speed of the twin-screw extruder is 150~300 rpm, and the residence time of the material in the screw is 1~5 min.

8. The preparation method according to claim 6, characterized in that, In step S1, the stirring speed of the high-speed mixer is 500~1500 rpm.

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