A polypropylene material with good weather resistance, a hollow board using the material and a manufacturing process

Abstract

The invention discloses a polypropylene material with good weather resistance, a hollow board using the material and a manufacturing process. The polypropylene material with good weather resistance comprises the following raw materials: a dispersant, an antioxidant and modified polypropylene. The invention firstly crosslinks and polymerizes polypropylene, a modifier, a grafting agent, a synergist and an inorganic filler to obtain modified polypropylene, then melt-blends the modified polypropylene with other substances, and extrudes to obtain a hollow board. Compared with the prior art, the hollow board prepared by the invention has the advantages of good flame retardancy and excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of hollow plates, and in particular to a polypropylene material with good weather resistance, a hollow plate using the material and a manufacturing process. Background Art

[0002] Polypropylene is a lightweight, chemically resistant thermoplastic with good mechanical properties, electrical insulation and heat resistance. In outdoor applications, polypropylene has poor weather resistance and is easily affected by ultraviolet radiation and oxidation, which causes the material to become brittle, discolored and have reduced mechanical properties. In order to solve this problem, weather-resistant polypropylene materials came into being. Weather-resistant polypropylene materials are made by adding additives such as ultraviolet absorbers, light stabilizers and antioxidants to polypropylene raw materials to increase their service life in outdoor environments. These additives can effectively absorb or reflect ultraviolet rays, slow down the degradation rate of polymer molecules, and thus maintain the original properties of the material. In addition, weather-resistant polypropylene materials also have excellent chemical resistance, wear resistance and impact resistance, which enables them to show high performance stability in various outdoor environments.

[0003] Hollow board is a lightweight, environmentally friendly, reusable board consisting of two panels and an air layer in the middle. This structure gives the hollow board excellent thermal insulation, sound insulation and impact resistance. In outdoor construction, advertising, transportation, agriculture and other fields, the hollow board made of weather-resistant polypropylene material has many excellent performance characteristics.

[0004] CN108359178A discloses a composition for flame-retardant hollow boards, a preparation method, flame-retardant hollow boards and applications thereof. The invention comprises the following components in parts by weight: 88-94 parts of polypropylene particles, 5-10 parts of fillers, 0.8-1.5 parts of flame retardants, 0.3-1.1 parts of dispersants, and 0.05-0.11 parts of antioxidants. Although the hollow boards prepared by the method have flame-retardant effects, the hollow boards prepared by the method have poor mechanical properties and are prone to breakage, which affects their service life.

[0005] CN111218067B discloses a PP hollow board and a preparation method thereof, comprising the following steps: S1, 18-25 parts by weight of random copolymer PP material, 16-22 parts by weight of drawing grade PP material, 18-25 parts by weight of homopolymer PP material, 18-25 parts by weight of high-transparency copolymer PP material; and 16-25 parts by weight of drawing grade PE material are mixed uniformly; S2, the above mixture is extruded and formed at a temperature of 193-198°C to form the novel PP hollow board. Although the hollow board prepared by this method can improve the toughness and tensile strength of the hollow board, and improve the surface smoothness and flatness, the hollow board prepared by this method is extremely flammable and easily causes problems such as fire. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to improve the flame retardant properties and mechanical properties of the hollow board and extend the service life of the hollow board.

[0007] To achieve the above object, the present invention provides a polypropylene material with good weather resistance, comprising the following components in parts by weight: 0.5-2 parts of a dispersant, 0.1-0.5 parts of an antioxidant, and 80-100 parts of modified polypropylene, wherein the modified polypropylene is prepared from polypropylene, a modifier, a grafting agent, a synergist and an inorganic filler.

[0008] Preferably, the method for preparing the modified polypropylene comprises the following steps:

[0009] A1. Dry the polypropylene and the modifier in an oven at 60-85°C for 10-30 min, respectively, then add dicumyl peroxide, the modifier, the inorganic filler and the synergist to the polypropylene and mix at 200-350 rpm for 20-50 min to obtain a mixture, then add the mixture, the grafting agent and styrene to an internal mixer, and melt-blend at 190-225°C and 50-150 rpm for 5-15 min to obtain a molten mixture;

[0010] A2. Add the molten mixture in A1 into xylene, stir at 200-300 rpm at 120-140°C for 1-3 hours, then add 150-250 mL of acetone for sedimentation to remove ungrafted small molecules, filter and dry in an oven at 80-100°C for 10 minutes to obtain modified polypropylene.

[0011] More preferably, the method for preparing the modified polypropylene comprises the following steps, in parts by weight:

[0012] A1. Dry 30-100 parts of polypropylene and modifier in an oven at 60-85°C for 10-30 min, respectively, then add 0.1-1 parts of dicumyl peroxide, 1-5 parts of modifier, 0.1-4 parts of inorganic filler and 0.5-2 parts of synergist to polypropylene and mix at 200-350 rpm for 20-50 min to obtain a mixture, then add the mixture, 1-5 parts of grafting agent and 1-7 parts of styrene to an internal mixer, and melt blend at 190-225°C and 50-150 rpm for 5-15 min to obtain a molten mixture;

[0013] A2. Add the molten mixture in A1 into 150-250 mL of xylene, stir at 200-300 rpm at 120-140° C. for 1-3 h, then add 150-250 mL of acetone for sedimentation to remove ungrafted small molecules, filter and dry in an oven at 80-100° C. for 10 min to obtain modified polypropylene.

[0014] Preferably, the modifier is any one of catechin, taxifolin, and tetrabromobisphenol A.

[0015] More preferably, the modifier is tetrabromobisphenol A.

[0016] Preferably, the grafting agent is any one of poly(tert-butyl methacrylate-co-glycidyl methacrylate) and 2-[3-(2-oxirane-1-yl)-2-acryloyloxypropoxy]carbonylcyclohexane-1-carboxylate.

[0017] Preferably, the inorganic filler is any one of calcium carbonate, talc, diatomaceous earth, glass fiber, carbon black, aluminum hydroxide and magnesium hydroxide.

[0018] Preferably, the synergist is any one of antimony trioxide and zinc borate.

[0019] A process for making a hollow plate using polypropylene material with good weather resistance comprises the following steps, measured in parts by weight:

[0020] Step 1: Evenly stir 0.5-2 parts of a dispersant, 0.1-0.5 parts of an antioxidant, and 80-100 parts of modified polypropylene to prepare a premix;

[0021] Step 2: heating, melting, extruding and processing the premixed material in step 1 to obtain a hollow board.

[0022] The present invention also provides a hollow plate made by the above process.

[0023] In this recipe, the ingredients and their functions are as follows:

[0024] Dispersant: The main function of the dispersant is to ensure that the various components in the entire polypropylene material system can be evenly dispersed. In addition, the dispersant can also reduce the surface tension of the components in the system, help reduce the formation of bubbles and pores, and further improve the density and mechanical properties of the material.

[0025] Antioxidant: The main function of antioxidant is to improve the weather resistance and oxidation resistance of polypropylene materials. During the processing and use of polypropylene materials, due to the influence of heat, light, oxygen and other factors, oxidation reactions are prone to occur, resulting in the degradation of material properties, such as yellowing, aging, and reduced mechanical properties. Therefore, adding an appropriate amount of antioxidant can effectively inhibit or slow down the oxidation reaction and extend the service life of polypropylene materials and hollow boards prepared from them.

[0026] Polypropylene: Polypropylene is the base resin for preparing polypropylene materials with good weather resistance. First, polypropylene provides the material with good mechanical properties, such as tensile strength, flexural strength and impact resistance, which are necessary for hollow boards as structural materials. Secondly, polypropylene has good chemical stability and can resist the erosion of various chemical substances, which ensures that the hollow board can remain stable under various environmental conditions.

[0027] Modifier: The modifier contains multiple phenolic hydroxyl functional groups. Similar to phenol in structure, it has strong hydrogen supply capacity and is expected to play the role of quenching free radicals. In addition, the electron-rich structure of the modifier is also expected to stabilize the tertiary carbon free radicals of polypropylene, inhibiting degradation during the grafting process, thereby improving the mechanical properties of modified polypropylene.

[0028] Grafting agent: Grafting agent contains epoxy functional groups and double bonds, which can react chemically with a variety of functional groups, and the monomer has a high boiling point, which is close to the temperature of melt grafting reaction. The epoxy functional groups contained in the grafting agent can react with the phenolic hydroxyl groups in the modifier, thereby linking the modifier to the polypropylene chain segment, and the double bonds contained in the grafting agent can also be directly grafted to the polypropylene.

[0029] Synergist: When zinc borate is used as a synergist, it can work synergistically with tetrabromobisphenol A to establish a synergistic system with better flame retardant effect, which works through the gas phase and / or condensed phase to improve the flame retardant properties of the material.

[0030] Inorganic fillers: First, the addition of inorganic fillers can significantly increase the modulus and strength of the material, improve its mechanical properties, and make it more suitable for structural applications such as hollow boards. Secondly, inorganic fillers can improve the thermal stability of the material, allowing it to withstand higher processing and use temperatures, thereby broadening the application range of the material. On the other hand, the use of aluminum hydroxide as a filler can make the hollow board made of polypropylene material have good flame retardant properties.

[0031] Dicumyl peroxide: The main function of dicumyl peroxide is to decompose and generate free radicals. These free radicals can react with polypropylene and styrene, thereby triggering a series of chain reactions.

[0032] Styrene: Styrene is usually added to the polypropylene melt grafting process to increase the grafting rate of the grafting monomer and inhibit degradation during the grafting process. The electron cloud of the styrene monomer is richer. When styrene is added to the grafting system, the styrene monomer will be preferentially grafted onto the polypropylene macromolecular free radical. At the same time, the π electron conjugated structure in styrene can stabilize the polypropylene macromolecular free radical, thereby reducing the β-chain scission reaction and inhibiting degradation during the grafting process.

[0033] Xylene: Xylene is used to dissolve or dilute certain raw materials that are difficult to mix directly, such as modified polypropylene and other substances.

[0034] Acetone: Acetone has certain compatibility differences with xylene and certain components in the molten mixture. Therefore, when acetone is added, it can effectively separate these ungrafted small molecules or impurities from the mixture and make them settle to the bottom of the solution. Acetone helps to purify the mixture, making the modified polypropylene higher in quality and more stable in performance.

[0035] Beneficial effects of the present invention:

[0036] 1. Compared with the prior art, the modified polypropylene is prepared by reacting the epoxy functional group in the grafting agent with the phenolic hydroxyl functional group in the modifier, adding styrene in the grafting reaction, and connecting the modifier to the polypropylene chain segment, which is beneficial to reducing the degradation of polypropylene macromolecular free radicals. The modified polypropylene is then used to prepare a hollow board, which is beneficial to improving the mechanical properties of the hollow board.

[0037] 2. Compared with the existing technology, the modifier tetrabromobisphenol A and zinc borate can synergistically establish a good flame retardant system, and then the two are used to prepare modified polypropylene, and finally aluminum hydroxide with flame retardant effect is added as filler to prepare hollow boards, which is beneficial to improve the flame retardant properties of hollow boards. DETAILED DESCRIPTION

[0038] Parameters for specific chemical substances used, sources.

[0039] Poly(tert-butyl methacrylate-co-glycidyl methacrylate), CAS number: 70939-77-4.

[0040] 2-[3-(Oxiran-2-yl)-2-prop-2-enoyloxypropoxy]carbonylcyclohexane-1-carboxylate, CAS No.: 63232-57-5.

[0041] Polypropylene, brand: K8303, Ningbo Zhongao Shenzhou Chemical Co., Ltd.

[0042] Aluminum hydroxide, 800 mesh.

[0043] Styrene, brand: GPPS-123, Zhejiang Jinbeiguang New Materials Co., Ltd.

[0044] Polypropylene wax, model: CS-52NC, Shanghai Hongzhuang Chemical Technology Co., Ltd.

[0045] Propyl gallate, model: CP2020, Xi'an Tianzheng Pharmaceutical Excipients Co., Ltd.

[0046] Example 1

[0047] A process for manufacturing a hollow plate using polypropylene material with good weather resistance, comprising the following steps:

[0048] Step 1: Add 1 kg of polypropylene wax, 0.5 kg of propyl gallate and 100 kg of modified polypropylene into a high-speed mixer and stir at 2000 rpm for 30 min to prepare a premix;

[0049] Step 2: Add the premixed material in step 1 to a twin-screw extruder at 200° C. and a screw speed of 350 rpm for heating, melt extrusion, and shaping to obtain a hollow board.

[0050] Wherein, the preparation method of the modified polypropylene comprises the following steps:

[0051] A1. 80 kg of polypropylene and 5 kg of tetrabromobisphenol A were dried in an oven at 80° C. for 25 min, and then 0.2 kg of dicumyl peroxide, 5 kg of tetrabromobisphenol A, 4 kg of aluminum hydroxide and 0.5 kg of zinc borate were added to the polypropylene and mixed at 300 rpm for 40 min to obtain a mixture. The mixture, 5 kg of 2-[3-(oxirane-2-yl)-2-acryloxypropoxy]carbonylcyclohexane-1-carboxylate and 5 kg of styrene were added to an internal mixer and melt-blended at 200° C. and 100 rpm for 10 min to obtain a molten mixture.

[0052] A2. Add the molten mixture in A1 into 200 mL of xylene, stir at 250 rpm for 1 h at 135 °C, then add 200 mL of acetone for sedimentation to remove ungrafted small molecules, filter and dry in an oven at 90 °C for 10 min to obtain modified polypropylene.

[0053] Example 2

[0054] The difference between Example 2 of the present application and Example 1 is that tetrabromobisphenol A in Example 1 is replaced by catechin.

[0055] Example 3

[0056] The difference between Example 3 of the present application and Example 1 is that the tetrabromobisphenol A in Example 1 is replaced by taxifolin.

[0057] Example 4

[0058] The difference between Example 4 of the present application and Example 1 is that the 2-[3-(ethylene oxide-2-yl)-2-acryloxypropoxy]carbonylcyclohexane-1-carboxylate in Example 1 is replaced by poly(tert-butyl methacrylate-co-methacrylic acid glycidyl ester).

[0059] Comparative Example 1

[0060] The difference between Comparative Example 1 of the present application and Example 1 is that the tetrabromobisphenol A in Example 1 is replaced by tea polyphenols.

[0061] Comparative Example 2

[0062] The difference between Comparative Example 2 of the present application and Example 1 is that the 2-[3-(oxiran-2-yl)-2-acryloxypropoxy]carbonylcyclohexane-1-carboxylate in Example 1 is replaced by glycidyl methacrylate.

[0063] Test Case

[0064] Simple supported beam notched impact strength: tested according to GB / T1043.1-2008 "Determination of impact properties of plastics simple supported beam Part 1: Non-instrumented impact test".

[0065] Tensile strength: tested according to GB / T1040.2-2022 "Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics".

[0066] Flame retardant grade: According to ANSL-UL94-2009 standard, tested with CZF-5 vertical combustion instrument.

[0067] The test results are shown in Table 1:

[0068] Table 1 Mechanical properties and flame retardant properties of hollow board

[0069]

[0070]

[0071] By comparing the tensile strength, simply supported beam notched impact strength, and flame retardancy data in Table 1, it can be found that the hollow board prepared in Example 1 has better mechanical properties and flame retardancy, thereby extending the service life of the hollow board.

[0072] Compared with the data in the table of Examples 1-3 and Comparative Example 1, it is found that the data are uniformly different, and the reason for these differences may be that different modifiers are used. The role of the modifier is that the phenolic hydroxyl group in the modifier can react with the epoxy functional group on the grafting agent to open the ring, so that the modifier can react with the grafting agent that has been grafted on the polypropylene segment and fixed on the polypropylene segment, thereby modifying the polypropylene, thereby affecting the tensile strength and impact strength of the polypropylene. Compared with the modifiers used in Examples 1-3 and Comparative Example 1, the modifier in Example 1 has the same phenolic hydroxyl functional group that can participate in the reaction as the modifiers in Examples 2-3 and Comparative Example 1, and the modifier used in Example 1 also contains bromine. The modifier used in Example 1 is tetrabromobisphenol A, and tetrabromobisphenol A belongs to a bromine-based flame retardant with excellent flame retardant effect. Tetrabromobisphenol A will decompose into hydrogen bromide during combustion, and hydrogen bromide reacts with the highly active free radicals of the polymer to reduce or prevent the chain decomposition of polypropylene. In addition, during the combustion process, tetrabromobisphenol A can produce water vapor, which can dilute the combustible gas while covering the substrate surface to play a barrier role, reduce the concentration of combustible gas, thereby inhibiting the continuous combustion of polypropylene. However, tetrabromobisphenol A has high requirements for the temperature range of releasing hydrogen bromide, and can only release limited hydrogen bromide in a narrow temperature range. Therefore, its flame retardant effect is enhanced by adding a synergist zinc borate. The addition of zinc borate can affect the early stage of the polypropylene combustion process, and can promote the decomposition of tetrabromobisphenol A to release hydrogen bromide in a narrow temperature range, thereby further improving the flame retardant efficiency of tetrabromobisphenol A. The modifier used in Examples 2-3 and Comparative Example 1 does not carry substances or functional groups such as brominated flame retardants, but is grafted onto polypropylene through the reaction of phenolic hydroxyl groups with the epoxy groups of grafting agents, which only changes the molecular weight of polypropylene polymers. Therefore, the flame retardant effect of the hollow plate prepared with polypropylene material in Example 1 is the best.

[0073] Comparing the data in the tables of Example 1, Example 4 and Comparative Example 2, it is found that the data are different, and the reason for these differences is that different grafting agents are used. The role of the grafting agent is that diisopropylbenzene peroxide decomposes under heat to form free radicals, and then the primary free radicals capture the hydrogen atoms on the polymer to form macromolecular free radicals. Styrene can quickly react with polypropylene macromolecular free radicals to form stable polypropylene styrene free radicals, and then the polypropylene styrene free radicals react with the grafting agent, and the grafting agent reacts with the modifier, so that the modifier is grafted on the polypropylene segment through the grafting agent. Compared with the grafting agents in Example 1, Example 4 and Comparative Example 2, the grafting agent in Example 1 contains ester bond functional groups in addition to double bonds and epoxy groups. Double bonds can be grafted onto polypropylene molecules through addition reactions, and epoxy groups can react with phenolic hydroxyl functional groups contained in the modifier, thereby affecting the content of the modifier grafted onto the polypropylene chain segment. Since the content of the modifier is indirectly controlled, and the modifier has a strong hydrogen supply capacity, it can quench free radicals and stabilize polypropylene tertiary carbon free radicals. Therefore, when the content of the modifier is increased, the degradation of the modified polypropylene is inhibited, thereby making the mechanical properties of the modified polypropylene better, thereby making the tensile strength and simply supported beam notched impact strength of the hollow plate prepared in Example 1 better.

Claims

1. A polypropylene material with good weather resistance, characterized in that: The invention comprises the following components in parts by weight: 0.5-2 parts of a dispersant, 0.1-0.5 parts of an antioxidant, and 80-100 parts of modified polypropylene; The preparation method of the modified polypropylene comprises the following steps, measured in parts by weight: A1. Dry 30-100 parts of polypropylene and modifier in an oven at 60-85°C for 10-30 min, respectively, then add 0.1-1 parts of dicumyl peroxide, 1-5 parts of modifier, 0.1-4 parts of inorganic filler and 0.5-2 parts of synergist to polypropylene and mix at 200-350 rpm for 20-50 min to obtain a mixture, then add the mixture, 1-5 parts of grafting agent and 1-7 parts of styrene to an internal mixer, and melt blend at 190-225°C and 50-150 rpm for 5-15 min to obtain a molten mixture; A2, adding the molten mixture in A1 into 150-250 mL of xylene, stirring at 200-300 rpm at 120-140°C for 1-3 h, then adding 150-250 mL of acetone for sedimentation to remove ungrafted small molecules, filtering and drying in an oven at 80-100°C for 10 min to obtain modified polypropylene; The modifier is any one of catechin, taxifolin, and tetrabromobisphenol A; The grafting agent is any one of poly(tert-butyl methacrylate-co-glycidyl methacrylate) and 2-[3-(2-oxirane-1-yl)-2-acryloyloxypropoxy]carbonylcyclohexane-1-carboxylate.

2. The polypropylene material with good weather resistance as claimed in claim 1, characterized in that: The modifier is tetrabromobisphenol A.

3. The polypropylene material with good weather resistance as claimed in claim 1, characterized in that: The inorganic filler is any one of calcium carbonate, talc, diatomaceous earth, glass fiber, carbon black, aluminum hydroxide and magnesium hydroxide.

4. The polypropylene material with good weather resistance as claimed in claim 1, characterized in that: The synergist is any one of antimony trioxide and zinc borate.

5. A process for producing a hollow plate using the polypropylene material with good weather resistance as claimed in any one of claims 1 to 4, characterized in that: The method comprises the following steps, in parts by weight: Step 1: Evenly stir 0.5-2 parts of a dispersant, 0.1-0.5 parts of an antioxidant, and 80-100 parts of modified polypropylene to prepare a premix; Step 2: heating, melting, extruding and processing the premixed material in step 1 to obtain a hollow board.

6. A hollow plate, characterized in that: Made by the process described in claim 5.

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