CN103819801A - Polyolefin wood-plastic composite and preparation method thereof - Google Patents

Abstract

The invention discloses a polyolefin-based wood-plastic composite material and a preparation method thereof. Plant fibers modified by polyolefin and ethylene-vinyl alcohol copolymer (EVOH) are used as main raw materials, and plasticizers, stabilizers and lubricants are added. prepared wood-plastic composites with good mechanical properties and environmental friendliness through the common melt blending method in plastic processing. The wood-plastic composite material of the present invention can be used in conventional fields such as building materials, decorative materials, foaming materials, boards, packaging materials, toys, auto parts, etc., which broadens the application range of the ethylene-vinyl alcohol copolymer.

Description

A kind of polyolefin-based wood-plastic composite material and preparation method thereof

technical field

The invention belongs to the technical field of polymer processing, and in particular relates to a polyolefin-based wood-plastic composite material and a preparation method thereof. the

Background technique

Wood-plastic composite material is a new type of material formed by compounding plant fiber as the main component and thermoplastic plastic through certain molding and processing methods. It has the dual characteristics of natural fiber and plastic, and can make up for the shortcomings of both and overcome wood It has low strength and large variability and other limitations in use. It has the characteristics of low price, good mechanical properties, acid and alkali corrosion resistance, and recyclability. It can be used instead of wood in many occasions. Its development and promotion will effectively relieve my country's petroleum Contradictions with the shortage of forest resource supply, reduce environmental pollution caused by plastic and agricultural waste incineration. the

However, although the development of wood-plastic composite materials is of great significance, its development and application are also facing many problems. Since the surface of plant fibers contains a large number of alcoholic and phenolic hydroxyl groups, these hydroxyl groups are easy to form intermolecular or intramolecular hydrogen bonds, which have strong polarity and water absorption; while the surface of thermoplastic polymers is generally non-polar or weakly polar, when the two When compounding, the dispersion of plant fibers in the polymer matrix is not good, agglomeration is easy to occur, the compatibility between the two is poor, and the interfacial occlusal force is weak. When the material is subjected to external force, the stress cannot be effectively transmitted at the interface, and the interface debonding is prone to occur and the material will be damaged. Therefore, improving the interfacial compatibility between plant fibers and polymers is a key issue to be solved in the preparation of wood-plastic composites. the

Many domestic scholars have done a lot of research on how to improve the compatibility between plant fibers and polymer matrix. Generally, physical or chemical means are used to treat plant fibers or add compatibilizers to improve the compatibility between fibers and the matrix. Such as using alkali treatment, acylation, etherification of plant fibers or adding silane coupling agents, isocyanate coupling agents, maleic anhydride grafted polymers, etc. as compatibilizers, in order to improve the compatibility between plant fibers and polymer matrix, But these methods have some shortcomings. For example, the treatment of plant fibers with alkali mainly dissolves pectin and lignin in plant fibers to increase the contact surface between plant fibers and polymer matrix to improve interfacial occlusal force, which belongs to physical and mechanical occlusion, and has limited improvement in product performance; Moreover, the process of the alkali treatment method is cumbersome, and the treated waste liquid will cause serious pollution to the environment, so it is generally seldom used. Coupling agent is a kind of compatibilizer with better treatment effect, but its application in industry is limited due to the high price of coupling agent. Graft polymers are the most researched class of compatibilizers, among which maleic anhydride graft polymers are the most common. However, the production of maleic anhydride grafted polymers requires another process, and the volatilization of small molecule grafted monomers such as maleic anhydride during the production process will cause serious irritation to the respiratory tract and eyes of operators, endangering the environment and the health of operators . Although the principle of using the maleic anhydride grafted polymer as a compatibilizer is based on the esterification reaction between the maleic anhydride grafted polymer and the phenolic hydroxyl group on the plant fiber, but due to the interaction between the maleic anhydride grafted polymer and the plant fiber The esterification reaction is a reaction between macromolecules, and the reaction is relatively difficult. There are no clear and sufficient experimental facts to prove that the acid anhydride group has a chemical interaction with the plant fiber, so the interaction between them is physical hydrogen bonding or chemical combination. Further scientific exploration is still needed; and because the grafting rate of maleic anhydride grafted polymers is low, generally only 0.4% to 1%, so to achieve the purpose of treatment, the amount of maleic anhydride grafted polymers required is relatively large . Therefore, the use of graft polymer as a compatibilizer must first solve the problem of low grafting rate of the compatibilizer, but there is no better solution at present. In recent years, many scholars have been committed to the research of polyolefin multi-graft copolymers (such as Chinese patent application No. 02118793, 200510035486.3), in order to increase the grafting rate of polar groups in the compatibilizer, but this method is similar to Production of maleic anhydride grafted polymers. The preparation method and operation process are relatively complicated, the cost is high, and there are also hazards to the health of operators and the environment caused by the small-molecule grafted monomer. the

Aiming at the problems existing in the prior art, the present invention adopts commercialized ethylene-vinyl alcohol copolymer (EVOH) to modify plant fibers. Since the vinyl alcohol structural unit in the ethylene-vinyl alcohol copolymer has a molar content of up to 70-30%, it can generate hydrogen bonds with a large number of alcoholic and phenolic hydroxyl groups on the surface of plant fibers, naturally making it have a good phase with plant fibers. Capacitance; and the ethylene structural unit with a molar content of up to 30-70% in the ethylene-vinyl alcohol copolymer has good affinity with the matrix polymer, which can produce macromolecular chain entanglement between the two, so the ethylene-vinyl alcohol copolymer As an alternative to the common compatibilizers and coupling agents mentioned above, it can well improve the compatibility between plant fibers and polymer matrix, thus endowing polyolefin-based wood-plastic composites with good mechanical properties . There are no relevant literature and patent reports on this modification method at present. the

Searching a large number of patent documents and published related research papers only found that Zhang Yujun and others published "EVOH/montmorillonite intercalation composite Preparation and structural characterization of materials", the study used polyvinylpyrrolidone modified montmorillonite (MMT) as the inorganic phase, ethylene-vinyl alcohol copolymer as the matrix resin, and prepared EVOH/montmorillonite composite by melt intercalation materials, reducing the moisture absorption of composites and improving cost performance. Tang Zhongzhu and others published "Preparation and Properties of Thermoplastic Starch/Ethylene-Vinyl Alcohol Copolymer Composite Materials" in "Journal of Functional Polymers" (2005, 18 (3): 368-372). The study used ethylene-vinyl alcohol The copolymer and thermoplastic starch are blended to prepare starch-based biodegradable materials. The degradation performance of the composite system is controlled by controlling the ratio of ethylene-vinyl alcohol copolymer and thermoplastic starch in the composite system. The amount of ethylene-vinyl alcohol copolymer added is 10 Between -40%, similar studies include "Preparation and Performance Research of TPS/EVOH Blends" published by Zhang Meijie et al. in "Plastic Industry" (2003, 31(1): 27-29). In the above-mentioned papers, only the ethylene-vinyl alcohol copolymer is used as a blending material with thermoplastic starch to improve the degradation performance of the starch/ethylene-vinyl alcohol copolymer composite material, and the expensive ethylene-vinyl alcohol copolymer is used in a large amount in the formula. There is also no clear indication that ethylene-vinyl alcohol copolymer is used as a surface modifier for thermoplastic starch. At the same time, 1 authorized patent (ZL 201110189511.9) related to ethylene-vinyl alcohol copolymer-based composite materials was retrieved. This patent provides a method for manufacturing ethylene-vinyl alcohol copolymer-based composite materials using calcium sulfate and corn starch and its preparation process. Its purpose is to reduce the cost of ethylene-vinyl alcohol copolymer-based composite materials and endow the composite materials with certain degradability. This patent activates the surface of calcium sulfate by adding stearic acid to improve the compatibility of calcium sulfate, corn starch and ethylene-vinyl alcohol copolymer, and at the same time improve the fluidity of the melt and the surface smoothness of the composite material. It can be seen that the patentee did not realize the compatibility effect of ethylene-vinyl alcohol copolymer on calcium sulfate and corn starch, and the additives involved in patent ZL 201110189511.9 and the plant fiber in the scientific classification belong to two completely different substances, that is, the patent has no enlightening effect on the present invention. The present invention directly uses ethylene-vinyl alcohol copolymer to improve the compatibility between the polymer matrix and plant fibers in the wood-plastic composite material. This modification principle and modification method are proposed by the applicant for the first time. the

Contents of the invention

The purpose of the present invention is to provide a polyolefin-based wood-plastic composite material and its preparation method, which has simple process, convenient operation, high production efficiency, low product production cost, and the obtained wood-plastic composite material is cheap, non-toxic, environmentally friendly, Good mechanical properties and recyclable materials can be used in fields such as food packaging, toys, building materials, decorative materials, foam materials, plates, auto parts, etc., expanding the application range of ethylene-vinyl alcohol copolymers,

To achieve the above object, the present invention adopts the following technical solutions:

The formula of raw materials in parts by weight is:

The said polyolefin is said plastic including the following thermoplastics: polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyethylene-vinyl acetate, or a mixture thereof.

The plant fiber raw material includes wood powder, bamboo powder and any kind of pulverized fiber such as stems, leaves, stalks and shells of other woody plants or a mixture thereof. The average particle size of the fibers is preferably above 20 mesh, and the water content is preferably below 5%. the

The ethylene molar content of the ethylene-vinyl alcohol copolymer is 30-70%. the

The plasticizer is octyl tridecyl phthalate, octyl tetradecyl phthalate, diethyl phthalate, acetyl tributyl citrate, chlorinated paraffin, dimaleic acid Butyl esters, stearic acid, zinc stearate, calcium stearate, barium stearate, dioctyl adipate or polyurethane plasticizers, or mixtures thereof. the

Described antioxidant is antioxidant 330, antioxidant 3114, antioxidant 1076, antioxidant 1010, antioxidant CA, antioxidant DLTP, antioxidant 2246, antioxidant 2246-S or antioxidant Oxygen 300, or a mixture of them. the

Described lubricant means that described lubricant is polyethylene wax, hydroxystearic acid, n-butyl stearate, monoglyceride stearate, oleamide, silicone oil, silicone, organosilane, liquid paraffin, glycerin Trihydroxystearate, N,N-ethylene bisstearic acid amide or polar group modified ethylene bis fatty acid amide, or a mixture of them. the

Described filler is calcium carbonate, wollastonite, kaolin, clay, mica, silicon dioxide, glass microspheres, graphite, carbon black, talcum powder, titanium dioxide, magnesium hydroxide, aluminum hydroxide, magnesium oxide, aluminum oxide, Barium sulfate, zinc oxide, or a mixture thereof. the

The above-mentioned components, including plastics, plant fibers, plasticizers, stabilizers, lubricants and fillers, etc., are prepared by the general melt blending method in plastic processing to prepare the wood-plastic composite material. the

The specific method is to first remove impurities from the plant fiber raw material, crush it, sieve it, and dry it under vacuum for 2 hours at a temperature of 80-100°C. The ethylene-vinyl alcohol copolymer was crushed into powder and dried in a vacuum oven at 90-92°C for 8 h. the

The above-mentioned components are pre-mixed according to the ratio, and the equipment used is the mixing equipment commonly used in plastic processing, such as high-speed mixers, kneaders, etc. When premixing, it can be heated appropriately according to the material condition, and the mixing temperature should generally be lower than 100°C. The pre-mixed materials are melt-blended using general-purpose rubber-plastic blending equipment, and then subjected to steps such as extrusion and granulation to obtain the wood-plastic composite material of the present invention. The blending equipment is a general blending equipment in the rubber and plastic processing industry, which can be a twin-screw extruder, a single-screw extruder, an internal mixer, etc., and the speed is 30-60 r/min. the

The beneficial effects of the present invention are: (1) The vinyl alcohol structural unit in the ethylene-vinyl alcohol copolymer can form a good interface bond with the alcoholic hydroxyl group and the phenolic hydroxyl group on the plant fiber, without additional interfacial compatibilizer. If this technology is popularized and applied on a large scale, it can replace the commonly used modification method of wood-plastic composite materials, thereby reducing the environmental pollution caused by the production of conventional compatibilizers. Because commercial ethylene-vinyl alcohol copolymers are produced by modern large-scale chemical companies with strict environmental protection measures, compared with the production of maleic anhydride graft polymers in general plastic processing plants, the environmental pollution is small and it is convenient for centralized management. (2) There are many kinds of ethylene-vinyl alcohol copolymers, the molar content of vinyl alcohol is 30-70%, and there is a large choice of modifiers. The proportion of ethylene and vinyl alcohol structural units in the molecular structure of ethylene-vinyl alcohol copolymer can be adjusted, which provides a wide range of options for the preparation of a wide variety of polymer-based plant fiber composites with different fillings. (3) Plant fibers can be directly processed, with convenient operation, simple process, high production efficiency and low product production cost. (4) Ethylene-vinyl alcohol copolymer itself is non-toxic, and it has no pollution to the environment during the process of treating plant fibers. Ethylene-vinyl alcohol copolymer is a macromolecular modifier, and there are no pollution and failure problems such as precipitation and migration during the use of the product. the

Detailed ways

Example 1

The raw material components are by weight: 100 parts of high-density polyethylene, 0.1 part of ethylene-vinyl alcohol copolymer (the molar content of ethylene is 70%), 0.5 parts of glycerin, 10 parts of wood flour, 1 part of antioxidant 1076, 1 part of antioxidant 2 parts of agent 330, 1 part of polyethylene wax, 2 parts of liquid paraffin, 20 parts of calcium carbonate.

The wood flour was cleaned of impurities, crushed, sieved, and dried in vacuum at 80 °C for 2 h. At the same time, the ethylene-vinyl alcohol copolymer was pulverized and dried in a vacuum oven at 92 °C for 8 h. After mixing the dried ethylene-vinyl alcohol copolymer powder and glycerin evenly, the dried wood powder was activated in a high mixer at 150°C at 3000 r/min for 5 min to obtain surface-modified wood powder. pink. Then add high-density polyethylene, antioxidant 1076, antioxidant 330, polyethylene wax, liquid paraffin, modified wood powder and calcium carbonate into another high-mixer and mix for another 5 minutes. Take out the compound, put it into the twin-screw extruder, adjust the screw speed of the twin-screw extruder to 30 r/min, and the temperature from the feeding port to the die of the machine head is 160, 180, 183, 188, 192, 198, 202 ℃, extrude the strands after screw mixing, water cooling, drying, and pelletizing to obtain polyolefin-based wood-plastic composite materials. The wood-plastic composite tray is made in the injection molding machine (the temperature in the first to the third zone is: 180, 190, 200 ℃), which can be used for food-grade fast food boxes or trays. the

The mechanical properties of the obtained composites were tested by a universal testing machine, the tensile strength was 31.79 MPa, and the flexural modulus was 3629 MPa. the

Example 2

The raw material components are by weight: 100 parts of polyvinyl chloride, 3.6 parts of ethylene-vinyl alcohol copolymer (the molar content of ethylene is 30%), 18 parts of glycerin, 60 parts of bamboo powder, 5 parts of composite heat stabilizer, phthalate 5 parts of octyl tridecyl formate, 5 parts of acetyl tributyl citrate, 3 parts of antioxidant 1010, 4 parts of antioxidant 300, 9 parts of n-butyl stearate, 6 parts of oleamide, 10 parts of silicon dioxide .

Bamboo powder was cleaned of impurities, crushed, sieved, and vacuum-dried at 100 °C for 2 h. At the same time, the ethylene-vinyl alcohol copolymer was crushed and dried in a vacuum oven at 90 °C for 8 h. After mixing the dried ethylene-vinyl alcohol copolymer powder and glycerin evenly, the dried bamboo powder was activated in a high mixer at 190 °C at 6000 r/min for 10 min to obtain surface-modified bamboo powder. pink. Then add polyvinyl chloride, composite heat stabilizer, octyl tridecyl phthalate, acetyl tributyl citrate, antioxidant 1010, antioxidant 300, n-butyl stearate in another high mixer , oleamide, modified bamboo powder and silicon dioxide were mixed at 4000 r/min for another 10 min. Pour the mixture into an internal mixer at 190°C and mix at 60 r/min for 10 minutes, and finally hot press at 10 MPa on a flat vulcanizer at 190°C for 10 minutes and then cold press at room temperature for 15 minutes to obtain a wood-plastic composite. Panels, available for ceiling or floor. the

The mechanical properties of the obtained composite materials were tested by a universal testing machine, the tensile strength was 34.86 MPa, and the flexural modulus was 4562 MPa. the

Example 3

The raw material components are by weight: 100 parts of polypropylene, 2.4 parts of ethylene-vinyl alcohol copolymer (the molar content of ethylene is 44%), 12 parts of glycerin, 40 parts of wheat straw, 3 parts of antioxidant CA, and 2246 parts of antioxidant 2 parts, 3 parts of monoglyceride stearate, 6 parts of organosilane, 10 parts of wollastonite.

The wheat straw was cleaned of impurities, crushed, sieved, and vacuum-dried at 80 °C for 2 h. At the same time, the ethylene-vinyl alcohol copolymer was pulverized and dried in a vacuum oven at 91° C. for 8 hours. After mixing the dried ethylene-vinyl alcohol copolymer powder with glycerol evenly, the dried wheat straw was activated in a high-mixer at 175°C at 4500 r/min for 7 minutes to obtain the surface-modified wheat straw. stalk. Then add polypropylene, antioxidant CA, antioxidant 2246, monoglyceride stearate, organosilane, modified wheat straw and wollastonite to another high mixer and mix for another 5 minutes. Take out the compound, put it into the twin-screw extruder, adjust the screw speed of the twin-screw extruder to 40 r/min, and the temperature from the feeding port to the die of the machine head is 163, 183, 186, 191, 195, 200, 204 ℃, extrude and pelletize after screw mixing to obtain modified wood flour. Extrude the compounded material on a single-screw extruder (the temperatures of zones 1 to 7 are: 165, 185, 188, 192, 196, 201, 205°C) to prepare wood-plastic composite pipes. the

The mechanical properties of the obtained composite materials were tested by a universal testing machine, the tensile strength was 33.15 MPa, and the flexural modulus was 4321 MPa. the

Example 4

The raw material components are by weight: 100 parts of ethylene-vinyl acetate copolymer, 2.0 parts of ethylene-vinyl alcohol copolymer (the molar content of ethylene is 58%), 8 parts of glycerin, 50 parts of chaff powder, and 3 parts of antioxidant 3114, 3 parts of antioxidant 300, 10 parts of mica, 12 parts of glycerol trihydroxystearate.

The chaff powder was cleaned of impurities, crushed, sieved, and dried in vacuum at 80°C for 2 h. At the same time, the ethylene-vinyl alcohol copolymer was pulverized and dried in a vacuum oven at 92° C. for 8 hours. After mixing the dried ethylene-vinyl alcohol copolymer powder and glycerin evenly, the dried bran shell powder was activated in a high mixer at 170°C at 5000 r/min for 8 minutes to obtain surface-modified Chaff powder. Then add polypropylene, antioxidant 3114, antioxidant 300, glycerol trihydroxystearate, mica and modified chaff powder into another high mixer and mix for another 5 minutes. Pour the mixture into an internal mixer at 170°C and mix it at 40 r/min for 10 minutes, and finally heat press the mixture on a flat vulcanizer at 175°C at 10 MPa for 10 minutes and then cold press it at room temperature for 15 minutes to obtain wood-plastic Composite panels. the

The mechanical properties of the obtained composite materials were tested by a universal testing machine, the tensile strength was 32.85 MPa, and the flexural modulus was 4812 MPa. the

Comparative example 1

The raw material components are by weight: 100 parts of ethylene-vinyl acetate copolymer, 8 parts of glycerin, 50 parts of chaff powder, 3 parts of antioxidant 3114, 3 parts of antioxidant 300, 10 parts of mica, trihydroxyhard glycerin 12 parts of fatty acid ester.

The chaff powder was cleaned of impurities, crushed, sieved, and dried in vacuum at 80°C for 2 h. At the same time, the ethylene-vinyl alcohol copolymer was pulverized and dried in a vacuum oven at 92° C. for 8 hours. Put chaff powder and glycerin into a high-speed mixer at 170°C in turn, mix at 5000 r/min for 10 min, and then discharge to obtain modified chaff powder. Then add polypropylene, antioxidant 3114, antioxidant 300, glycerol trihydroxystearate, mica and modified chaff powder into another high mixer and mix for another 5 minutes. Pour the mixture into an internal mixer at 170°C and mix it at 40 r/min for 10 minutes, and finally heat press the mixture at 10 MPa on a flat vulcanizer at 175°C for 10 minutes and then cold press it at room temperature for 15 minutes to obtain wood. Plastic composite panels. the

The mechanical properties of the obtained composite materials were tested by a universal testing machine, the tensile strength was 16.35 MPa, and the flexural modulus was 1328 MPa. the

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention. the

Claims (9)

1. a polyolefin-based wood plastic composite, is characterized in that: described matrix material is prepared from by the raw material of following parts by weight: 100 parts of polyolefine, ethylene-vinyl alcohol copolymer 0.1-3.6 part, glycerine 0.5-18 part, vegetable fibre 10-60 part, softening agent 0-10 part, oxidation inhibitor 3-7 part, lubricant 3-15 part, filler 10-20 part.

2. polyolefin-based wood plastic composite according to claim 1, is characterized in that: described polyolefine is one or more the mixture in polyethylene, polypropylene, polyvinyl chloride, polystyrene, EVA.

3. polyolefin-based wood plastic composite according to claim 1, it is characterized in that: described vegetable fibre is one or more in timber, bamboo, rattan, stalk, rice husk, fiber crops, reed, coconut husk, Pericarppium arachidis hypogaeae, the median size of its fiber is that more than 20 orders water content is below 5%.

4. polyolefin-based wood plastic composite according to claim 1, is characterized in that: the ethene molar content of described ethylene-vinyl alcohol copolymer is 30-70%.

5. polyolefin-based wood plastic composite according to claim 1, is characterized in that: described softening agent is one or more the mixture in misery 13 esters of O-phthalic, misery 14 esters of O-phthalic, diethyl phthalate, tributyl acetylcitrate, clorafin, dibutyl maleate, stearic acid, Zinic stearas, calcium stearate, barium stearate, Octyl adipate, polyurethane plasticizer.

6. polyolefin-based wood plastic composite according to claim 1, is characterized in that: described oxidation inhibitor is one or more the mixture in antioxidant 330, antioxidant 3114, antioxidant 1076, antioxidant 1010, antioxidant CA, anti-oxidant DLTP, antioxidant 2246, antioxidant 2246-S, antioxidant 300.

7. polyolefin-based wood plastic composite according to claim 1, it is characterized in that: described lubricant is polyethylene wax, oxystearic acid, n-butyl stearate, glyceryl monostearate, oleylamide, silicone oil, silicone, organosilane, whiteruss, glycerine three hydroxy stearic acid esters, N, the mixture of one or more in the ethylene bis-fatty acid amides of N-ethylene bis stearic acid amide, modified with polar.

8. polyolefin-based wood plastic composite according to claim 1, is characterized in that: described filler is one or more the mixture in calcium carbonate, wollastonite, kaolin, clay, mica, silicon-dioxide, glass microballon, graphite, carbon black, talcum powder, titanium dioxide, magnesium hydroxide, aluminium hydroxide, magnesium oxide, aluminum oxide, barium sulfate, zinc oxide.

9. a method of preparing polyolefin-based wood plastic composite as claimed in claim 1, is characterized in that: comprise the following steps:

(1) by vegetable fibre removal of contamination, pulverize, sieve, 80-100 ℃ of vacuum-drying 2 h;

(2) by ethylene-vinyl alcohol copolymer dry 8 h in 90-92 ℃ of vacuum drying oven;

(3) after dried ethylene-vinyl alcohol copolymer powder is mixed with glycerine, at 150-190 ℃, dried vegetable fibre is carried out to activation treatment 5-10 min, obtain the vegetable fibre of surface modification;

(4) vegetable fibre of polyolefine, surface modification, softening agent, oxidation inhibitor, lubricant and filler are mixed, by mixing, extrude, granulation obtains the described polyolefin-based wood plastic composite through ethylene-vinyl alcohol copolymer modification.