Plant fiber reinforced polypropylene composite and method for producing the same

Abstract

The present application relates to a kind of plant fiber reinforced polypropylene composite material and its preparation method.The plant fiber reinforced polypropylene composite material component includes by weight ratio: polypropylene 50-80 parts;Plant fiber 20-50 parts;Pillar-like attapulgite 0.05-2 parts;Aluminum-titanium composite coupling agent 0.2-2 parts;Carboxylic acid sodium salt alpha nucleating agent 0.05-0.2 parts.The composite material has good moisture absorption resistance, and lower smell and warping.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer material modification, and particularly relates to a plant fiber reinforced polypropylene composite material and a preparation method thereof. BACKGROUND

[0002] Due to the increasing shortage of petrochemical resources, people are constantly looking for new energy and new materials to replace coal and oil chemical products to alleviate or solve the energy and resource crisis. Glass fiber and carbon fiber composites have brought convenience to human life, but also brought new problems such as resource shortage, recycling and environmental impact. The development of environmentally friendly green composite materials using biomass renewable resources has become one of the hotspots of attention and research in the world.

[0003] Natural plant fiber is one of the most abundant natural polymer materials in nature. The total amount of cellulose grown in nature every year is hundreds of billions of tons, far exceeding the total oil reserves on earth. Natural plant fibers include flax, jute, bamboo fiber, coconut fiber, straw, etc., which can provide a wide range of raw material sources for polypropylene composites. Compared with inorganic powders, carbon fibers and glass fibers used in modified polypropylene composites, natural plant fibers have the advantages of abundant source, low price, renewable, degradable, light weight, etc. Plant fiber reinforced polypropylene composite material is a new type of composite material composed of natural renewable plant fiber and polypropylene matrix. By blending with different types of plant fibers, different appearance effects and different performance specifications of the composite material can be prepared. In order to solve the problem of resource shortage and take advantage of low carbon and environmental protection, plant fiber materials are actively promoted at home and abroad and can be applied to automobile parts, household appliances and daily consumer goods. By fully utilizing the potential of natural plant fibers and taking advantage of their unique functions and characteristics, new application fields can be developed, which has very broad industrial value.

[0004] The chemical composition of natural plant fiber is very complex, most of its components are polymers with large relative molecular mass, mainly including cellulose, hemicellulose and lignin, and resin, fat, wax, starch, pectin, pigment, etc. These polymers contain a large number of hydroxyl and phenolic hydroxyl groups, and have strong polarity and hydrophilicity, while polypropylene is non-polar and has hydrophobicity. This leads to poor interfacial wettability and small adhesion between the fiber and the polypropylene matrix, thus affecting the mechanical properties. In order to improve the compatibility between the fiber and the plastic matrix, it is necessary to modify it. There are three methods for modification: the first method is to modify the wood fiber raw material, the purpose is to reduce the polarity and increase the roughness of the material surface, including heat treatment, steam explosion treatment, alkali treatment, esterification or etherification, graft modification, surface physical processing, etc.; the second method is to modify the plastic matrix, the purpose is to improve the polarity of the plastic matrix, including chemical modification, photochemical modification, mechanochemical modification, radiation modification, etc.; the third method is to add a suitable coupling agent (or called compatibilizer) during blending. Among them, adding coupling agent is the most commonly used modification method in the current blending modification process. At present, the research on the preparation of natural plant fiber reinforced polypropylene composite mainly focuses on the improvement of the mechanical properties of the material and the influence of the size of the plant fiber on the performance of the material.

[0005] Akhalil et al. studied the effect of different sizes of fillers on the water absorption and mechanical properties of PP / wood powder composites. The results showed that the mechanical strength of the composite material after adding wood powder was lower than that of pure PP. The tensile properties of the composite material with wood powder size of 100 μm were better than those of 212 μm and 300 μm.

[0006] M. Naushad et al. prepared sisal reinforced PP bio-composites by melt mixing technology, and the bio-composites prepared by adding compatibilizer MAPP had significant improvement in tensile strength and bending strength. The impact fracture morphology of the bio-composite revealed that the interfacial adhesion of sisal fiber, MAPP and PP matrix was better.

[0007] Hong Jun et al. modified ramie fiber with silane coupling agent KH550, and studied the effect of coupling agent treatment concentration and ramie content on the mechanical properties of polypropylene / ramie reinforced composite materials. The results showed that with the increase of ramie fiber content, the tensile strength and bending strength of the composite material increased, and the mechanical properties of the composite material treated with coupling agent improved more; when the coupling agent treatment concentration was 1%, the tensile strength of the material was the highest. SEM observation found that the surface of untreated ramie fiber was smooth, while the surface of ramie fiber treated with coupling agent was rough and adhered to the polypropylene matrix, indicating that the addition of coupling agent improved the interfacial compatibility of the composite system and increased the interfacial bonding force.

[0008] Plant fibers are derived from nature, and the main component is cellulose. The odor properties of cellulose are very distinctive. For example, jute, wheat straw, pine, etc. will be uniformly dispersed in the PP base material during the high-temperature processing and shearing process of preparing composites, resulting in the modified composite material continuously emitting a large amount of odor of the filling fiber, which cannot meet the application requirements of low-emission parts such as automotive interiors.

[0009] At the same time, due to the orientation behavior of plant fibers during melt flow, the composite material exhibits anisotropic characteristics, resulting in a large difference in the shrinkage ratio of the composite material in the horizontal and vertical directions, and the behavior of warping deformation occurs during the preparation of parts, especially large-sized parts, which causes great disturbance and challenge to the molding process.

[0010] In addition, due to the presence of a large number of active groups such as hydroxyl groups in the cellulose molecular chain, the natural plant fiber exhibits strong polarity and hydrophilicity. The composite material prepared by pretreating the plant fiber and polypropylene has strong moisture absorption. After one week of conventional packaging and storage, the composite material cannot meet the use requirements. SUMMARY

[0011] The technical problem to be solved by the present application is to provide a plant fiber reinforced polypropylene composite material and a preparation method thereof to overcome the defects of strong odor, high warping and strong moisture absorption of the plant fiber modified polypropylene material in the prior art.

[0012] The present application provides a plant fiber reinforced polypropylene composite material, and the components of the plant fiber reinforced polypropylene composite material comprise, by weight fraction:

[0013]

[0014]

[0015] Preferably, the components of the plant fiber reinforced polypropylene composite material comprise, by weight fraction:

[0016]

[0017] Preferably, the melt index of the polypropylene under the condition of 230℃ and 2.16kg is 20-110g / 10min, and more preferably, the melt index of the polypropylene under the condition of 230℃ and 2.16kg is 25-100g / 10min. The test standard of the melt index is ISO 1133:2005.

[0018] Preferably, the plant fiber comprises one or more of jute, sisal, and bamboo fiber.

[0019] Preferably, the plant fiber reinforced polypropylene composite material further comprises a compatibilizer 0.01-2 parts, more preferably, the compatibilizer is 0.05-1.5 parts by weight.

[0020] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0021] Preferably, the weight fraction of the effective component hydrated magnesium aluminum silicate in the attapulgite is 88-99.9%, further preferably, the weight fraction of the effective component hydrated magnesium aluminum silicate in the attapulgite is 95-99.7%. The test standard of the weight fraction is DB32 / T1220:2008.

[0022] Preferably, the specific surface area of the attapulgite is 146-185㎡ / g, further preferably, the specific surface area of the attapulgite is 150-180㎡ / g. The test method of the specific surface area is nitrogen adsorption BET method. Due to the treatment of the aluminum-titanium complex coupling agent on the non-polar surface of the attapulgite, the water absorption of the attapulgite is reduced, the adsorption selectivity of the attapulgite is changed, and water is no longer the first adsorption substance. More adsorption surface area is released for aldehyde, ketone, normal alkene, aromatic hydrocarbon, naphthenes, and alkane. If the specific surface area is too low, the adsorption capacity is low, and the odor intensity is not good. With the increase of the specific surface area, the adsorption capacity also increases, and the ability to reduce odor intensity also increases. However, with the continuous increase of the specific surface area, the adsorption capacity will decrease, and the ability to reduce odor intensity will decrease. This is because the pore size of the adsorbable molecular sieve channel becomes smaller and smaller with the increase of the specific surface area. When the pore size is smaller than the molecular chain size of the adsorbable substance, the large molecule substance cannot enter the porous inside of the attapulgite through the small pore size molecular sieve channel, thereby reducing the adsorption capacity.

[0023] Preferably, the aluminum-titanium complex coupling agent comprises titanium ester and aluminate complex; the titanium ester comprises one or more of mono-alkoxy fatty acid titanium ester, triisostearyl titanate isopropyl, isopropyl trioleate acyloxy titanate, tetraisopropyl di(dioctyl phosphite acyloxy) titanate; the aluminate comprises diisopropoxy aluminum isopropoxy diacetylacetone aluminate.

[0024] Preferably, the plant fiber reinforced polypropylene composite material further comprises other auxiliary agents 0.05-2 parts.

[0025] More preferably, the weight fraction of the other auxiliary agent is 0.2-1 part.

[0026] Preferably, the other auxiliary agent comprises an antioxidant and / or a lubricant.

[0027] Preferably, the antioxidant comprises one or more of hindered phenolic antioxidants, amine antioxidants, phosphite antioxidants.

[0028] Preferably, the lubricant comprises one or more of stearate, stearate salt, amide.

[0029] The application also provides a preparation method of the above-mentioned plant fiber reinforced polypropylene composite material, comprising:

[0030] The plant fiber, aluminum-titanium composite coupling agent and palygorskite are mixed, other components are added and mixed to obtain a mixture, the mixture is extruded and granulated, and baked to obtain the plant fiber reinforced polypropylene composite material.

[0031] Preferably, the processing temperature of the extrusion granulation is 70-90 DEG C in the first zone, 170-190 DEG C in the second to ninth zones, and 190-220 DEG C in the tenth zone.

[0032] Preferably, the screw rotation speed used in the extrusion granulation is 400-600 r / min.

[0033] Preferably, the baking temperature is greater than or equal to 120 DEG C, and the baking time is greater than or equal to 6 h.

[0034] The application also provides an application of the above-mentioned plant fiber reinforced polypropylene composite material in automobile interior parts, such as door panels, seats and glove boxes.

[0035] The porous structure of the palygorskite has very strong adsorption capacity, can adsorb small molecular gas substances released by the plant fiber in the heating process, and plays a prominent role in improving the odor of the composite material, and can effectively reduce the odor intensity of the composite material. Due to the extremely strong odor adsorption effect of the palygorskite, the hygroscopicity of the composite material is also enhanced, which is not conducive to the anti-hygroscopicity of the plant fiber. The added aluminum-titanium composite coupling agent can form a stable chemical bond with the surface of the plant fiber, change the hydrophilic group into a hydrophobic group, reduce the hygroscopicity of the material, and match the non-polarity of polypropylene, increase the compatibility and binding force of the plant fiber and polypropylene, reduce the gap between the two phases of the molecular, and reduce the channel of the water molecules into the composite material. Compared with the silane coupling agent and the single coupling agent of aluminate, the water absorption rate of the composite material is lower.

[0036] The crystal lattice structure initiated by the carboxylic acid sodium salt alpha nucleating agent and the crystal lattice structure initiated by the palygorskite can be complementary matched, the defects of the heterogeneous nucleation crystal structure are reduced, the crystal structure of the two synergistic nucleation is more uniform, and thus the warping deformation amount of the material is reduced.

[0037] Advantages

[0038] The application can significantly improve the moisture absorption resistance of the composite material and reduce the odor intensity of the composite material by using attapulgite, aluminum-titanium composite coupling agent and plant fiber. DETAILED DESCRIPTION

[0039] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope of the appended claims.

[0040] Reagent source:

[0041] Copolymerized polypropylene 1: the melt index under the condition of 230 DEG C and 2.16 kg is 28 g / 10 min, PP EP5074X, Zhongsha Petrochemical;

[0042] Copolymerized polypropylene 2: the melt index under the condition of 230 DEG C and 2.16 kg is 96 g / 10 min, PP M100RHC, Zhenhai Refinery;

[0043] Copolymerized polypropylene 3: the melt index under the condition of 230 DEG C and 2.16 kg is 21 g / 10 min, PP K7116, Guangzhou Petrochemical;

[0044] Copolymerized polypropylene 4: the melt index under the condition of 230 DEG C and 2.16 kg is 109 g / 10 min, PP K7100, Yanshan Petrochemical;

[0045] Homopolymerized polypropylene: the melt index under the condition of 230 DEG C and 2.16 kg is 60 g / 10 min, PP M60T, Zhenhai Refinery;

[0046] Plant fiber 1: jute, JF, Hengtai Leemaking Product Co., Ltd.;

[0047] Plant fiber 2: sisal, SF, Guangdong Dongfang Sisal Group;

[0048] Plant fiber 3: bamboo fiber, BF, Sichuan Dehong Bamboo Fiber Technology;

[0049] Attapulgite 1: the weight fraction of active ingredient hydrated magnesium aluminum silicate is 96%, and the specific surface area is 160 m2 / g, AT300, Zhejiang Chijing Chemical;

[0050] Attapulgite 2: the weight fraction of active ingredient hydrated magnesium aluminum silicate is 95.5%, and the specific surface area is 185 m2 / g, B4380, Hebei Qingdian Chemical;

[0051] Attapulgite 3: active ingredient hydrated magnesium aluminum silicate weight fraction 96.4%, specific surface area 146 m2 / g, LL55, Huai'an Jinggong Material;

[0052] Attapulgite 4: active ingredient hydrated magnesium aluminum silicate weight fraction 99.7%, specific surface area 163 m2 / g, 11-8A, Anhui Zhongshan Mineral Powder;

[0053] Attapulgite 5: active ingredient hydrated magnesium aluminum silicate weight fraction 88%, specific surface area 153 m2 / g, 26M, Hebei Zhonghe Mineral Resources;

[0054] Diatomite: INFILM, IMERYS;

[0055] Compatibility agent: maleic anhydride grafted polypropylene, CA100, Arkema;

[0056] Aluminum-titanium composite coupling agent 1: single alkoxy fatty acid titanate and distearyl oxyl isopropoxy aluminic acid ester complex,

[0057] JTW-1618, through Tianwei Chemical;

[0058] Aluminum-titanium composite coupling agent 2: triisostearyl titanate isopropyl and distearyl oxyl isopropoxy aluminic acid ester complex, HY-133, Ningbo Changfeng Chemical;

[0059] Aluminum-titanium composite coupling agent 3: isopropyl trioleic acid oxyl titanate and distearyl oxyl isopropoxy aluminic acid ester complex, LD, Lida Chemical;

[0060] Aluminum-titanium composite coupling agent 4: tetraisopropyl di(dioctyl phosphinic acid oxyl) titanate and diisopropyl di(acetylacetone) aluminic acid ester complex, TL-42, Jiangsu Lianjiang Chemical;

[0061] Aluminum coupling agent: distearyl oxyl isopropoxy aluminic acid ester, UP-802, Nanjing Youpu Chemical;

[0062] Titanium coupling agent: single alkoxy fatty acid titanate, TC-130, Chenglong City Hongsheng Fine Chemical Factory;

[0063] Silane coupling agent: γ-aminopropyl triethoxysilane, KH-550, Qingdao Hengda New Material;

[0064] Aluminum-zirconium coupling agent: long carbon chain single unit carboxylic acid base aluminum-zirconium complex, LD-139, Lida Chemical;

[0065] Carboxylic acid sodium salt α nucleating agent 1: HPN-68L, Milliken Company;

[0066] Carboxylic acid sodium salt α nucleating agent 2: NA-18, Japan Asahi Chemical;

[0067] Substituted aryl carboxylic acid aluminum salt type α nucleating agent: WNA-108, Guangdong Weilin;

[0068] Other auxiliary agents:

[0069] Antioxidant: tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester and tri[2,4-di-tert-butylphenyl]phosphite compounded at a weight ratio of 1:1, commercially available;

[0070] Lubricant: zinc stearate, commercially available;

[0071] Unless otherwise specified, the same commercially available product is used for a certain component (such as antioxidant, lubricant) in the parallel examples and comparative examples of the present application.

[0072] The preparation method of the plant fiber reinforced polypropylene composite material comprises the following steps: according to the proportions in Table 1 and Table 2, plant fibers, aluminum-titanium composite coupling agents and attapulgite are poured into a high-speed mixer and mixed for 180 s at a speed of 800 r / min, and other components are continuously mixed for 60 s to obtain a mixture, and the mixture is poured into a double-screw extruder for extrusion and granulation, and the granules are then subjected to a baking treatment in a high-efficiency drying tank at 120 ℃ for 6 h to obtain the product. The processing temperature of each section of the double-screw extruder is as follows: 80 ℃ for the first section, 180 ℃ for the second to ninth sections, and 200 ℃ for the tenth section, and the screw rotation speed of the double-screw extruder is 500 r / min.

[0073] Performance test:

[0074] (1) Water absorption rate: an infrared method is used to dry the sample to be tested at 120 ℃ for 4 h to remove the initial moisture in the material, then 10 g of the dried material is taken to test the moisture content of the material using an infrared moisture meter, and the result is recorded as m0 (m0 needs to be ≤0.05%, if m0 > 0.05%, the material needs to be continuously dried until the moisture content of the sample to be tested is m0 ≤0.05%), the sample to be tested is placed in a constant temperature and humidity environment of 23 ℃ and 50% RH for 24 h*7 days for static adjustment, then 10 g of the sample to be tested is taken again, the water content of the sample to be tested is tested using an infrared moisture meter, and the result is recorded as m1, (m1-m0) is the water absorption rate of the material.

[0075] (2) Odor: the test standard is performed according to the Volkswagen PV3900 standard, after the sample is placed in a 1L odor bottle, the odor bottle is placed in an 80 ℃ oven for baking, the time is 2 h, the odor test bottle is taken out of the oven and placed to cool to 60 ℃, then the cap is opened for odor evaluation, the evaluators are 5 professional evaluators with qualification, and the evaluation standard is according to the Volkswagen odor six-level system: 1st level, no odor; 2nd level, slight odor but no interference; 3rd level, obvious odor but no interference; 4th level, strong odor; 5th level, very strong odor; and 6th level, unbearable odor.

[0076] (3) warpage height: the test standard is GB / T 25257-2010, the sample is prepared using a 100*100*1mm square plate mold, the sample is placed in a constant temperature and humidity environment of 23℃, 50%RH for 48h, one corner of the square plate is taken as a base point, the base point corner is pressed on a flat support table, the height distance H1, H2, H3, H4 between the opposite corners and the support plane is measured, and the maximum H value among the four corners is taken as the warpage height.

[0077] Table 1 ratio of examples 1-10 (parts by weight)

[0078]

[0079] Table 2 ratio of examples 11-19

[0080]

[0081] Table 3 ratio of comparative examples (parts by weight)

[0082]

[0083]

[0084] From Tables 1-3, the water absorption of the polypropylene composite material of the present application is 0.15-0.31%, the odor is 3.7-3.9 grade, and the warpage height is 0.5-2.5mm. Comparative example 1 does not add attapulgite, comparative example 2 does not add aluminum-titanium composite coupling agent, and comparative example 3 does not add carboxylic acid sodium salt alpha nucleating agent. The water absorption, odor grade, and warpage height of comparative examples 1-3 are greater than those of example 1. Comparative example 4 uses an aluminum coupling agent, comparative example 5 uses a titanium coupling agent, comparative example 6 uses a silane coupling agent, comparative example 7 uses an aluminum-zirconium coupling agent, and comparative example 8 uses a substituted aryl carboxylic acid aluminum salt alpha nucleating agent. The water absorption, odor grade, and warpage height of comparative examples 4-8 are greater than those of example 1. Comparative example 9 uses diatomite, and the water absorption, odor grade, and warpage height are greater than those of example 1. As can be seen, the present application uses attapulgite, aluminum-titanium composite coupling agent, and plant fiber to compound, which can significantly improve the moisture resistance of the composite material, and at the same time reduce the odor intensity of the composite material. The carboxylic acid sodium salt alpha nucleating agent added in the present application has a synergistic effect with attapulgite, which can improve the warpage problem of the composite material.

Claims

1. A plant fiber reinforced polypropylene composite material, characterized by, The plant fiber reinforced polypropylene composite material components comprise, by weight fraction: The aluminum-titanium composite coupling agent comprises titanium ester and aluminate compound; the titanium ester comprises one or more of monoalkoxy fatty acid titanium ester, triisostearyl titanium isopropyl ester, isopropyl trioleic acyloxy titanium ester, and tetraisopropyl di(dioctyl phosphite acyloxy) titanium ester; the aluminate comprises diisopropoxy aluminum isopropoxy aluminate and / or diisopropyl diacetylacetone aluminate.

2. The plant fiber reinforced polypropylene composite according to claim 1, characterized in that, The plant fiber reinforced polypropylene composite material components comprise, by weight fraction:

3. The plant fiber reinforced polypropylene composite according to claim 1, characterized in that, The polypropylene has a melt index of 20-110 g / 10 min at 230℃ and 2.16 kg.

4. The plant fiber reinforced polypropylene composite according to claim 1, characterized in that, The plant fiber comprises one or more of jute, sisal, and bamboo fiber; the effective hydrated magnesium aluminum silicate content of the attapulgite is 88-99.9% by weight fraction; The specific surface area of the attapulgite is 146-185 m2 / g.

5. The plant fiber reinforced polypropylene composite according to claim 1, characterized in that, The plant fiber reinforced polypropylene composite material further comprises 0.01-2 parts of a compatibilizer; the compatibilizer is maleic anhydride grafted polypropylene.

6. The plant fiber reinforced polypropylene composite according to claim 1, characterized in that, The plant fiber reinforced polypropylene composite material further comprises 0.05-2 parts of other additives; the other additives comprise antioxidants and / or lubricants.

7. A method for preparing the plant fiber reinforced polypropylene composite material according to any one of claims 1-6, comprising: Mixing the plant fiber, aluminum-titanium composite coupling agent, and attapulgite, adding other components and continuing to mix to obtain a mixture, extruding and granulating the mixture, baking to obtain the plant fiber reinforced polypropylene composite material.

8. The preparation method according to claim 7, characterized in that, The processing temperature for the extruding and granulating is: zone 1, 70-90℃; zone 2 to zone 9, 170-190℃; and zone 10, 190-220℃.

9. Use of the plant fiber reinforced polypropylene composite material according to any one of claims 1-8 in automotive interior parts.

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