Polypropylene modified material prepared based on grafting blending method and preparation process thereof

Abstract

The invention relates to the technical field of high polymer material modification, and discloses a polypropylene modified material prepared based on a grafting blending method and a preparation process thereof, and the polypropylene modified material comprises the following materials in parts by weight: 100 parts of polypropylene used as a base resin and with the selected model of PP-H-1250; maleic anhydride is selected as a grafting monomer, and the use amount is 2-5 parts; the initiator comprises dicumyl peroxide, di-tert-butyl peroxide and tert-butylperoxy, and the total amount of the initiator and the di-tert-butyl peroxide is 0.61-1.25 parts. According to the polypropylene modified material prepared based on the grafting blending method and the preparation process thereof, by accurately controlling the raw material ratio and then adopting the grafting blending method, the polarity of polypropylene is effectively improved, so that the polypropylene can be better bonded with a polar material and blended with an inorganic material and a polar polymer, the application range is widened, the melt strength of the polypropylene is improved, and the mechanical property of the polypropylene is improved. The processing properties of foaming, extrusion molding, blow molding and the like of the material are improved, and the properties of the polyethylene material are further obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material modification, in particular to a polypropylene modified material prepared based on a graft blending method and a preparation process thereof. Background Art

[0002] Polypropylene is a thermoplastic polymer formed by the polymerization of propylene monomers. It has the advantages of abundant synthetic raw materials and low prices, and at the same time has high-strength mechanical properties, including high tensile strength, rigidity, etc., and has good chemical resistance. It can remain stable in many chemical environments. Based on the above advantages, polyethylene is widely used in many fields. Due to the low melt strength of polypropylene and the lack of strain hardening, it is difficult to maintain the stability of the pores during the foaming process, resulting in the pores being easily broken and merged, affecting the foaming quality. In extrusion molding, melt fracture and other phenomena are prone to occur, affecting the surface quality and dimensional accuracy of the product. In order to avoid the above shortcomings, the original polypropylene material needs to be modified, but there are some defects in the existing modification process, such as: Existing methods of cross-linking polypropylene with radiation or chemical methods are used to improve the melt strength, but the degree of cross-linking is difficult to control, which can easily lead to excessive or insufficient cross-linking and affect the material properties. Among them, simple blending modification can improve certain properties of polypropylene to a certain extent, but there is insufficient interfacial bonding strength and the overall performance improvement is limited. The melt method in the grafting modification is prone to side reactions, which makes the solution method have solvent recovery and high cost.

[0003] In view of the above problems, it is urgently necessary to carry out innovative design based on the original polyethylene modification preparation process. Summary of the invention

[0004] The object of the present invention is to provide a polypropylene modified material prepared by a graft blending method and a preparation process thereof, so as to solve the problems mentioned in the above background technology that the existing cross-linking treatment of polypropylene by radiation or chemical methods is difficult to control, which easily leads to excessive or insufficient cross-linking and affects the material properties, and that simple blending modification improves certain properties of polypropylene to a certain extent, but has insufficient interfacial bonding strength, and that the melting method in the graft modification is prone to produce side reactions, resulting in the problems of solvent recovery and high cost in the solution method.

[0005] To achieve the above object, the present invention provides the following technical solution: a polypropylene modified material prepared by graft blending method and its preparation process, comprising the following materials, calculated by weight: Polypropylene, as the base resin, selected model PP-H-1250, the dosage is 100 parts; The grafting monomer is maleic anhydride, and the amount is 2-5 parts; Initiators, including dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide, with a total amount of 0.61-1.25 parts; The blended polymer is ethylene-vinyl acetate copolymer with 18% VA content and polycarbonate, with a total amount of 8-12 parts; Additives include antioxidants, lubricants, and toughening agents, with a total amount of 5.4-10.9 parts.

[0006] By adopting the above technical solution, further adjustments can be made by adjusting the material ratio in the formula to facilitate modification of polypropylene.

[0007] Preferably, the amount of dicumyl peroxide in the initiator is 0.3-0.6 parts; Di-tert-butyl peroxide, dosage 0.3-0.6 parts; Tert-butyl peroxide, dosage 0.01-0.05 parts.

[0008] By adopting the above technical solution, the reaction efficiency in the modification process can be accelerated by adjusting the amount of the initiator.

[0009] Preferably, the antioxidant in the auxiliary agent is 1010, and the dosage is 0.1-0.3 parts; The lubricant is calcium stearate, the dosage is 0.3-0.6 parts; The toughening agent is a polyolefin elastomer, and the dosage is 5-10 parts.

[0010] By adopting the above technical solution and adding additives, the mechanical properties, processing properties, hydrophilicity and dyeability of the modified polypropylene material are significantly improved.

[0011] A polypropylene modified material prepared based on a graft blending method and a preparation process thereof, which is used to prepare the above-mentioned polypropylene modified material, comprises the following preparation steps: S1: Weigh various raw materials according to the formula, add the weighed polypropylene, grafting monomer and initiator into a high-speed mixer, wherein the speed is set to 600-800r / min and the mixing time is 8-10min; S2: Add the mixture in S1 into a twin-screw extruder, set the extruder temperature to 160-180°C, and the screw speed to 280-300r / min to carry out grafting reaction; S3: The grafted polyethylene in S2 is added into a high-speed mixer together with the blended polymer, antioxidant, lubricant and toughening agent, and the speed is set to 600 r / min and the mixing time is 6-8 min; S4: Add the mixed materials in S3 into the twin-screw extruder again, and adjust the temperature of the twin-screw extruder to 150-170°C and the screw speed to 180-250r / min; S5: The blended extruded material is extruded from the die of the twin-screw extruder in the form of continuous long strips, and then the extruded material is fed into a pelletizer to cut the long strips into pellets of uniform size according to certain specifications.

[0012] The above technical solutions and rigorous preparation process ensure product quality and production efficiency.

[0013] Preferably, before the step S1, all selected raw materials are pretreated, including drying the polypropylene to remove moisture, the drying temperature is 80-120° C., and the drying time is 2-4 hours.

[0014] The above technical solution is adopted to facilitate pretreatment of raw materials before modification and production, thereby increasing the effect of the modification work.

[0015] Preferably, the grafted monomer, initiator, polymer blend and auxiliary agent are weighed in S1 for purity detection and impurity screening.

[0016] The above technical solution is adopted to effectively improve the processing during polyethylene modification and provide a stable straight beam environment.

[0017] Preferably, during the S2 grafting reaction, the torque and temperature changes of the reaction system are monitored in real time by online monitoring equipment, and the temperature and screw speed of the extruder are adjusted in time according to the monitoring data.

[0018] The adoption of the technical solution makes it easier to supervise product quality during the grafting reaction and improve product quality.

[0019] Preferably, the high-speed mixer in S1 and the high-speed mixer in S3 are two devices.

[0020] The above technical solution is adopted to facilitate the production line preparation in the process of preparing the polypropylene modified material.

[0021] Preferably, a conveying device is provided between the twin-screw extruder and the pelletizer in S5.

[0022] By adopting the above technical solution, continuous production is facilitated by arranging a conveying device between the twin-screw extruder and the pelletizer.

[0023] Preferably, after the grafted polyethylene is pelletized, the pelletizer uses a screen to separate unqualified products from the pelletization, and the unqualified products are heated and then put into the twin-screw extruder in S5 for re-extrusion.

[0024] By adopting the above technical solution, defective products in production can be fully utilized and materials can be fully utilized for production.

[0025] Compared with the prior art, the invention has the following beneficial effects: the polypropylene modified material prepared by the graft blending method and its preparation process: 1. By precisely controlling the raw material ratio and then using the graft blending method, the polarity of polypropylene is effectively improved, so that it can better bond with polar materials, blend with inorganic materials and polar polymers, broaden the scope of application, improve the melt strength of polypropylene, improve the processing properties such as foaming, extrusion molding and blow molding, and improve the quality and dimensional accuracy of products. At the same time, after polyethylene modification, the dyeability, antistatic property, hydrophilicity and low-temperature brittleness of polyethylene materials are also significantly improved, further meeting the use requirements of more special fields, and thus the overall reaction conditions are mild, easy to realize industrial production, and the production cost is low; 2. At the same time, in the raw material pretreatment stage, polypropylene is dried and pretreated, and the grafted monomers, initiators, blended polymers and additives are tested for purity and impurities, providing a high-quality raw material basis for subsequent reactions; During the grafting reaction and blending process, the torque and temperature changes of the reaction system are monitored in real time through online monitoring equipment, and the temperature and screw speed of the extruder are adjusted in time to ensure the stability of the reaction and the grafting rate, and improve the consistency of product performance; Two high-speed mixers are used to mix the raw materials before grafting and the blended raw materials after grafting, respectively, to avoid cross contamination of raw materials mixed at different stages and optimize the mixing effect. A conveying device is set between the twin-screw extruder and the pelletizer to ensure the continuity of material transmission and improve production efficiency. The pelletizer separates the unqualified products through a sieve, and after heating, they are put into the twin-screw extruder for re-extrusion, thus realizing the recycling of materials and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a schematic diagram of the preparation process of the polypropylene modified material of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1 , the present invention provides a technical solution: a polypropylene modified material prepared based on a graft blending method and a preparation process thereof; Example 1: This example discloses the following contents, including: Raw material formula: Polypropylene, i.e. PP-H-1250: 100 parts, maleic anhydride: 3 parts, dicumyl peroxide: 0.6 parts, di-tert-butyl peroxide: 0.3 parts, tert-butyl peroxide: 0.02 parts, ethylene-vinyl acetate copolymer with VA content of 18%: 6 parts, polycarbonate: 4 parts, antioxidant 1010: 0.2 parts, lubricant calcium stearate: 0.4 parts, toughening agent polyolefin elastomer: 7 parts; Preparation process: Pretreatment: Dry the polypropylene at 100 °C for 3 h, and perform purity testing and impurity screening on the grafted monomer, initiator, blended polymer and additives; S1: Add weighed polypropylene, 3 parts of maleic anhydride, 0.4 parts of dicumyl peroxide, 0.4 parts of di-tert-butyl peroxide and 0.02 parts of tert-butyl peroxide into a high-speed mixer, set the speed to 700 r / min, and mix for 9 minutes; S2: Add the mixture in S1 into a twin-screw extruder, set the temperature to 170°C, and the screw speed to 290 r / min to carry out grafting reaction; S3: Add grafted polypropylene, 6 parts of ethylene-vinyl acetate copolymer, 4 parts of polycarbonate, 0.2 parts of antioxidant 1010, 0.4 parts of lubricant calcium stearate and 7 parts of toughening agent polyolefin elastomer into another high-speed mixer at a speed of 600 r / min and mix for 7 minutes; S4: Add the mixed materials in S3 into the twin-screw extruder again, adjust the temperature to 160°C, and the screw speed to 220r / min; S5: The materials after blending and extrusion enter the pelletizer through the conveying equipment, are cut into standard size particles, and unqualified products are separated by a screen. After heating, they are put into the twin-screw extruder for re-extrusion; Example 2: This example discloses the following contents, including: Raw material formula: Polypropylene, i.e. PP-H-1250: 100 parts, maleic anhydride: 4 parts, dicumyl peroxide: 0.5 parts, di-tert-butyl peroxide: 0.5 parts, tert-butyl peroxide: 0.03 parts, ethylene-vinyl acetate copolymer with VA content of 18%: 7 parts, polycarbonate: 5 parts, antioxidant 1010: 0.25 parts, lubricant calcium stearate: 0.5 parts, toughening agent polyolefin elastomer: 8 parts; Preparation process: Pretreatment: Polypropylene was dried at 110 °C for 2.5 h, and the remaining raw materials were tested for purity and impurities; S1: Add the raw materials into a high-speed mixer at a speed of 800 r / min and mix for 8 minutes; S2: twin-screw extruder temperature 175 °C, screw speed 300 r / min for grafting reaction; S3: another high-speed mixer, rotating at 600 r / min, mixing for 6 min; S4: twin-screw extruder temperature 165°C, screw speed 230r / min; S5: the same pelletizing and defective product treatment as in Example 1; Example 3: This example discloses the following contents, including: Raw material formula: Polypropylene, i.e. PP-H-1250: 100 parts, maleic anhydride: 2 parts, dicumyl peroxide: 0.3 parts, di-tert-butyl peroxide: 0.6 parts, ethylene-vinyl acetate copolymer with VA content of 18%: 7 parts, polycarbonate: 5 parts, antioxidant 1010: 0.25 parts; Lubricant calcium stearate: 0.5 parts, toughening agent polyolefin elastomer: 8 parts; Preparation process: Pretreatment: Polypropylene was dried at 110 °C for 2.5 h, and the remaining raw materials were tested for purity and impurities; S1: Add the raw materials into a high-speed mixer at a speed of 800 r / min and mix for 8 minutes; S2: twin-screw extruder temperature 175 °C, screw speed 300 r / min for grafting reaction; S3: another high-speed mixer, rotating at 600 r / min, mixing for 6 min; S4: twin-screw extruder temperature 165°C, screw speed 230r / min; S5: the same pelletizing and defective product treatment as in Example 1; Example 4: This example discloses the following contents, including: Raw material formula: Polypropylene, i.e. PP-H-1250: 100 parts, maleic anhydride: 5 parts, dicumyl peroxide: 0.5 parts, di-tert-butyl peroxide: 0.5 parts, ethylene-vinyl acetate copolymer with VA content of 18%: 8 parts, polycarbonate: 4 parts, antioxidant 1010: 0.2 parts, lubricant calcium stearate: 0.4 parts, toughening agent polyolefin elastomer: 6 parts; Preparation process: Pretreatment: Polypropylene was dried at 110 °C for 2.5 h, and the remaining raw materials were tested for purity and impurities; S1: Add the raw materials into a high-speed mixer at a speed of 800 r / min and mix for 8 minutes; S2: twin-screw extruder temperature 175 °C, screw speed 300 r / min for grafting reaction; S3: another high-speed mixer, rotating at 600 r / min, mixing for 6 min; S4: twin-screw extruder temperature 165°C, screw speed 230r / min; S5: the same pelletizing and defective product treatment as in Example 1;

[0029] In the auxiliary agent ratio of the above embodiment, after comparing the data of different embodiments, it is determined that the compounding ratio of dicumyl peroxide and di-tert-butyl peroxide is adjusted to 2:1. Since the reaction temperature range of dicumyl peroxide and di-tert-butyl peroxide is relatively wide when used alone, it is difficult to accurately determine the reaction process. By adding tert-butyl peroxyl group, a new initiation temperature point can be formed between or outside the decomposition temperature of dicumyl peroxide and di-tert-butyl peroxide, thereby widening the temperature range of the initiation reaction and allowing the reaction to proceed smoothly within a wider temperature range. Since the decomposition temperature of dicumyl peroxide in the additive is relatively low, it begins to decompose significantly at around 120-130°C; The decomposition temperature of di-tert-butyl peroxide is relatively high, usually decomposing significantly at around 150°C; If the reaction needs to be initiated quickly at a lower temperature, the proportion of diisopropylbenzene peroxide can be appropriately increased; if stable initiation is required at a higher temperature, the proportion of di-tert-butyl peroxide can be increased; In Example 3, there is a lack of tert-butyl peroxy group, which results in that the interfacial bonding force of the blending system is not as good as that of other examples containing tert-butyl peroxy group, thereby affecting the tensile strength, impact strength and other mechanical properties of the material; By adding peroxides containing tert-butyl peroxide to act together with diisopropylbenzene peroxide and di-tert-butyl peroxide, a more uniform and reasonable cross-linked network structure can be formed. In the cross-linking modification of polypropylene, the appropriate free radical generation mode and cross-linking structure can improve the tensile strength, heat deformation temperature and other properties of polypropylene. In addition, the by-products generated during the reaction of adding tert-butyl peroxide are relatively few, or the by-products have little effect on the product performance, which reduces the occurrence of side reactions to a certain extent and improves the purity and performance stability of the product. By properly matching the peroxide containing tert-butyl peroxide with diisopropylbenzene peroxide and di-tert-butyl peroxide, the initiator can play a more full role in the reaction system, improve the initiation efficiency, and reduce the amount of initiator used; Wherein, in the grafting reaction step S2 under the same conditions, the twin-screw extruder is operated at a temperature of 175° C. and a screw speed of 300 r / min; In Examples 1, 2, and 4 containing tert-butyl peroxy groups, the three initiators acted synergistically to make the reaction more stable and the grafting reaction more complete; However, in Example 3, there are only two initiators, which may cause fluctuations in reaction activity, and the uniformity and grafting rate of the grafting reaction are affected; Through the comparison of the above data and experiments, under the premise of meeting the reaction requirements and product performance, it is possible to reduce the cost of the entire initiator system and improve the economic efficiency of production by selecting some relatively low-cost peroxides containing tert-butyl peroxide and compounding them with diisopropylbenzene peroxide and di-tert-butyl peroxide; Comparative Example 1: This comparative example discloses the following contents, including: Raw material formula: Polypropylene (PP-H-1250): 100 parts, dicumyl peroxide: 0.4 parts, di-tert-butyl peroxide: 0.4 parts, tert-butyl peroxide: 0.02 parts, ethylene-vinyl acetate copolymer with 18% VA content: 6 parts, polycarbonate: 4 parts, antioxidant 1010: 0.2 parts, lubricant calcium stearate: 0.4 parts, toughening agent polyolefin elastomer: 7 parts; Preparation process: The same as Example 1, since there is no grafting monomer, no adjustment of the grafting reaction is involved; Comparative Example 2: This comparative example discloses the following contents, including: Raw material formula: same as Example 1.

[0030] Preparation process: Pretreatment: Same as Example 1.

[0031] S1: Add all raw materials into a high-speed mixer at once, rotate at 700r / min, and mix for 15 minutes.

[0032] S2: directly added into the twin-screw extruder, the temperature was 165 °C, the screw speed was 250 r / min, and the grafting and blending stages were not distinguished.

[0033] S3: Pelletizing after blending and extrusion, without screening and recycling of unqualified products; By performing performance tests on the products of the embodiments and comparative examples and comparing the tensile strength, flexural strength, impact strength, melt flow rate, contact angle, dyeability and other indicators, the advantages of the present invention in terms of raw material formulation and preparation process can be intuitively reflected, as shown in the following table:

[0034] Among them, the mechanical properties of the product of the embodiment are obviously better than those of the comparative example 1, because the comparative example 1 lacks a grafting monomer, the performance improvement is not obvious; In terms of performance stability and production efficiency, the embodiment is also superior to comparative example 2, because the simplified process in comparative example 2 leads to performance fluctuations and material waste; By comparing the experimental data of the examples and comparative examples, it can be found that as the amount of maleic anhydride, initiator, etc. increases, the material performance tends to improve, and reasonable process steps are also crucial. Based on the experimental data, I will analyze the effects of various raw materials and process parameters on the performance, and thus infer the best combination.

[0035] From the perspective of raw material usage, the performance indicators of the product produced by the material ratio in Example 1 are relatively better; In terms of mechanical properties, the tensile strength, bending strength and impact strength all reach high values; the hydrophilicity and dyeability also perform well; Combining the data of the embodiments and comparative examples, within a certain range, appropriately increasing the amount of the grafted monomer maleic anhydride can more effectively introduce polar groups, improve the compatibility of the material with other components, and further enhance the mechanical properties and improve the hydrophilicity, dyeability, etc. Appropriately increasing the ratio of ethylene-vinyl acetate copolymer and polycarbonate in the blended polymer helps to synergistically improve the comprehensive performance of the material.

[0036] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A polypropylene modified material prepared by a graft blending method, characterized in that: Including the following materials, by weight: Polypropylene, as the base resin, selected model PP-H-1250, the dosage is 100 parts; The grafting monomer is maleic anhydride, and the amount is 2-5 parts; Initiators, including dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide, with a total amount of 0.61-1.25 parts; The blended polymer is ethylene-vinyl acetate copolymer with 18% VA content and polycarbonate, with a total amount of 8-12 parts; Additives include antioxidants, lubricants, and toughening agents, with a total amount of 5.4-10.9 parts.

2. The polypropylene modified material prepared by graft blending method according to claim 1, characterized in that: The dicumyl peroxide in the initiator is used in an amount of 0.3-0.6 parts; Di-tert-butyl peroxide, dosage 0.3-0.6 parts; Tert-butyl peroxide, dosage 0.01-0.05 parts.

3. The polypropylene modified material prepared by graft blending method according to claim 1, characterized in that: The antioxidant in the auxiliary agent is 1010, and the dosage is 0.1-0.3 parts; The lubricant is calcium stearate, the dosage is 0.3-0.6 parts; The toughening agent is a polyolefin elastomer, and the dosage is 5-10 parts.

4. A process for preparing a polypropylene modified material based on a graft blending method, used for preparing the polypropylene modified material in claim 1, characterized in that: The method comprises the following preparation steps: S1: Weigh various raw materials according to the formula, add the weighed polypropylene, grafting monomer and initiator into a high-speed mixer, wherein the speed is set to 600-800r / min and the mixing time is 8-10min; S2: Add the mixture in S1 into a twin-screw extruder, set the extruder temperature to 160-180°C, and the screw speed to 280-300r / min to carry out grafting reaction; S3: The grafted polyethylene in S2 is added into a high-speed mixer together with the blended polymer, antioxidant, lubricant and toughening agent, and the speed is set to 600 r / min and the mixing time is 6-8 min; S4: Add the mixed materials in S3 into the twin-screw extruder again, and adjust the temperature of the twin-screw extruder to 150-170°C and the screw speed to 180-250r / min; S5: The blended extruded material is extruded from the die of the twin-screw extruder in the form of continuous long strips, and then the extruded material is fed into a pelletizer to cut the long strips into pellets of uniform size according to certain specifications.

5. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: Before the step S1, all selected raw materials are pretreated, including drying the polypropylene to remove moisture, the drying temperature is 80-120° C., and the drying time is 2-4 hours.

6. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: In S1, the completed grafting monomer, initiator, blended polymer and auxiliary agent are weighed to perform purity testing and impurity screening.

7. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: During the S2 grafting reaction, the torque and temperature changes of the reaction system are monitored in real time by online monitoring equipment, and the temperature and screw speed of the extruder are adjusted in time according to the monitoring data.

8. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: The high-speed mixer in S1 and the high-speed mixer in S3 are two devices.

9. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: A conveying device is provided between the twin-screw extruder and the pelletizer in S5.

10. The process for preparing a polypropylene modified material based on a graft blending method according to claim 4, characterized in that: After the grafted polyethylene is pelletized, the pelletizer uses a screen to separate unqualified products from the pellets, heats the unqualified products, and then feeds them into the twin-screw extruder in S5 for re-extrusion.

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