EvoH-coated modified composite wood pulp fibers, modification method, composite reinforcing material and method of making

Abstract

The application provides a kind of EVOH coated modified composite wood pulp fiber, modification method, composite reinforcing material and preparation method thereof, and the modification method comprises: ethylene-vinyl alcohol copolymer is added to organic aqueous solution and mixed and heated to obtain coating solution;Wood pulp fiber is added to the coating solution and mixed and stirred, and after filtration, washing and drying, composite wood pulp fiber is obtained.The preparation method comprises: composite wood pulp fiber, poly-L-lactic acid and polyglycolic acid are mixed and then injected into a first twin-screw extruder, melt granulation to obtain filler master batch;Filler master batch, polybutylene adipate terephthalate, poly-D-lactic acid, antioxidant, lubricant and plasticizer are mixed and then injected into a second twin-screw extruder, melt granulation to obtain composite reinforcing material.The application uses impregnation process to make EVOH uniformly cover on the surface of wood pulp fiber, and EVOH can be used as an interfacial compatibilizer to improve the interfacial compatibility between wood pulp fiber and resin matrix.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite reinforcing materials, and relates to EVOH-coated modified composite wood pulp fibers, a modification method, a composite reinforcing material and a preparation method thereof. BACKGROUND

[0002] Due to the increasingly serious white pollution caused by the development and use of traditional non-biodegradable high molecular materials, the difficulty in treating waste plastics, the great harm to biology and many other problems, the development and application of biodegradable high molecular materials not only meet the concept of green environmental protection but also comply with the trend of sustainable development, so biodegradable high molecular materials are paid more and more attention by people.

[0003] Although aliphatic polyesters are more common in biodegradable high molecular materials, the aliphatic polyesters are difficult to meet the application requirements of materials in many aspects due to factors such as poor mechanical properties, low melting point, poor thermal stability, poor processability and high production cost, so the wide application of the aliphatic polyesters is greatly limited. Traditional thermoplastic aromatic polyesters such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) not only have excellent mechanical properties, good heat resistance, good thermal processing and dimensional stability, but also have low production cost, but they do not have biodegradability and cannot be used as green and environmentally friendly biodegradable materials. Therefore, researchers try to combine the segments of aliphatic polyesters with certain flexibility and the segments of aromatic polyesters with excellent mechanical properties, processing properties and thermal properties by copolymerization to obtain polybutylene terephthalate-co-polybutylene adipate (PBAT).

[0004] As a fatty-aromatic high molecular material, PBAT has many advantages such as good flexibility, complete biodegradability, excellent thermal stability, high resilience, excellent tear resistance and good biocompatibility, so PBAT is very suitable for application in film materials and toughening modification of hard and brittle materials such as polylactic acid. However, the poor gas barrier property, high price, low crystallinity, poor rheological property, low strength and modulus, and small melt strength of PBAT greatly limit the application of PBAT in the above two fields. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide EVOH-coated modified composite wood pulp fibers, a modification method, a composite reinforcing material and a preparation method thereof. In the present application, wood pulp fibers are mixed with a coating solution containing ethylene-vinyl alcohol copolymer (EVOH) by impregnation modification process, so that EVOH uniformly covers the surface of the wood pulp fibers. EVOH can be used as an interfacial compatibilizer to improve the interfacial compatibility between wood pulp fibers and resin matrix in the wood-plastic composite reinforcing material.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a modified method for modifying EVOH-coated modified composite wood pulp fibers, the modified method comprising:

[0008] adding ethylene-vinyl alcohol copolymer into an organic aqueous solution and mixing and heating until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution; adding wood pulp fibers into the coating solution and mixing and stirring to allow the ethylene-vinyl alcohol copolymer to uniformly coat the surface of the composite wood pulp fibers to form an organic coating layer, and after filtering, washing and drying, the composite wood pulp fibers are obtained.

[0009] In the present application, the wood pulp fibers are mixed with the coating solution containing ethylene-vinyl alcohol copolymer (EVOH) by impregnation modification process, so that the EVOH uniformly covers the surface of the wood pulp fibers. The EVOH can act as an interfacial compatibilizer to improve the interfacial compatibility between the wood pulp fibers and the resin matrix in the wood-plastic composite reinforcing material. On the one hand, the EVOH can reduce the surface polarity of the wood pulp fibers, thereby improving the wettability between the wood pulp fibers and the resin melt, so as to improve the interfacial compatibility between the composite wood pulp fibers and the resin matrix, thereby reducing the pore size and quantity between the composite wood pulp fibers and the resin matrix, and improving the mechanical engagement between the composite wood pulp fibers and the resin matrix. On the other hand, since the EVOH molecular chain structure contains both hydroxyl groups and ethylene structural units, the hydroxyl groups can be combined with the wood pulp fibers in the form of hydrogen bonds, and the ethylene structural units can form molecular chain entanglement with the resin matrix, thereby forming a bridge between the polar wood pulp fibers and the non-polar or weakly polar resin matrix, and achieving the purpose of interfacial chemical modification.

[0010] As a preferred technical solution of the present application, the organic aqueous solution is an isopropyl alcohol aqueous solution.

[0011] In some optional examples, the volume ratio of isopropyl alcohol to water in the isopropyl alcohol aqueous solution is (6-8):(2-4), for example, it can be 6.0:4.0, 6.2:3.8, 6.4:3.6, 6.6:3.4, 6.8:3.2, 7.0:3.0, 7.2:2.8, 7.4:2.6, 7.6:2.4, 7.8:2.2 or 8.0:2.0, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0012] In some optional examples, the ratio of ethylene-vinyl alcohol copolymer to organic aqueous solution is (40-50) g:1 L, for example, it can be 40 g:1 L, 41 g:1 L, 42 g:1 L, 43 g:1 L, 44 g:1 L, 45 g:1 L, 46 g:1 L, 47 g:1 L, 48 g:1 L, 49 g:1 L or 50 g:1 L, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0013] In some optional examples, the heating temperature is 70-80℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃, but not only limited to the listed values, other values in the range of the values are also applicable.

[0014] In some optional examples, the heating time is 10-30min, for example, it can be 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min or 30min, but not only limited to the listed values, other values in the range of the values are also applicable.

[0015] As a preferred technical solution of the present application, the mass ratio of the wood pulp fiber to the ethylene-vinyl alcohol copolymer in the coating solution is (5-7):1, for example, it can be 5.0:1, 5.2:1, 5.4:1, 5.6:1, 5.8:1, 6.0:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1 or 7.0:1, but not only limited to the listed values, other values in the range of the values are also applicable.

[0016] In some optional examples, the mixing and stirring time of the composite wood pulp fiber in the coating solution is 1-3h, for example, it can be 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h or 3.0h, but not only limited to the listed values, other values in the range of the values are also applicable.

[0017] In the second aspect, the present application provides an EVOH-coated modified composite wood pulp fiber prepared by the modification method of the first aspect.

[0018] In the third aspect, the present application provides a composite reinforcing material comprising the composite wood pulp fiber of the second aspect, which comprises the composite wood pulp fiber, poly-L-polylactic acid, polyglycolic acid, polybutylene terephthalate adipate, poly-D-lactic acid, antioxidant, lubricant and plasticizer.

[0019] As a preferred technical solution of the present application, the composite reinforcing material comprises the following components by weight:

[0020] Composite wood pulp fiber 10-20 parts;

[0021] Poly-L-lactic acid 40-50 parts;

[0022] Polyglycolic acid 5-10 parts;

[0023] Polybutylene adipate terephthalate 50-60 parts;

[0024] Poly D-lactic acid 2-5 parts;

[0025] Antioxidant 0.1-0.5 parts;

[0026] Lubricant 0.5-1 parts;

[0027] Plasticizer 1-2 parts.

[0028] The weight parts of the composite wood pulp fiber can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts; the weight parts of the poly-L-lactic acid can be 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 parts, 49 parts, or 50 parts; the weight parts of the polyglycolic acid can be 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, 8.0 parts, 8.5 parts, 9.0 parts, 9.5 parts, or 10.0 parts; the weight parts of the polybutylene adipate terephthalate can be 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, or 60 parts; the weight parts of the poly D-lactic acid can be 2.0 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3.0 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4.0 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, or 5.0 parts; the weight parts of the antioxidant can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts; the weight parts of the lubricant can be 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.7 parts, 0.75 parts, 0.8 parts, 0.85 parts, 0.9 parts, 0.95 parts, or 1 parts; the weight parts of the plasticizer can be 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2.0 parts, but not limited to the listed values, other values not listed in the range are also applicable.

[0029] The application particularly limits the weight of poly-D-lactic acid to 2-5 parts. After adding poly-D-lactic acid into the resin melt, the poly-lactic acid stereocomplex crystalline phase is formed in situ on the surface of the filler master batch. The poly-lactic acid stereocomplex crystalline phase can act as a nucleating agent for the crystallization of poly-L-poly-lactic acid, significantly accelerating the crystallization process of the polymer. The generated poly-lactic acid stereocomplex crystalline phase forms a network structure, which can effectively improve the mechanical properties of the composite reinforcing material. When the addition amount of poly-D-lactic acid is less than 2 parts, the poly-L-poly-lactic acid is a continuous amorphous phase. Due to the low addition amount of poly-D-lactic acid, the amount of the generated poly-lactic acid stereocomplex crystalline phase is small, and the poly-lactic acid stereocomplex crystalline phase is discontinuous in the resin melt. Therefore, the poly-lactic acid stereocomplex crystalline phase region has no significant effect on the toughness of the resin melt. When the addition amount of poly-D-lactic acid is more than 5 parts, the amount of the generated poly-lactic acid stereocomplex crystalline phase is too large. The continuous poly-lactic acid stereocomplex crystalline phase restricts the movement of the molecular chain, which limits the plastic deformation of the resin matrix caused by interfacial peeling under tension, and finally reduces the toughness of the composite reinforcing material.

[0030] The application particularly limits the addition amount of poly-L-lactic acid to 40-50 parts and the addition amount of PGA to 5-10 parts. The poly-L-poly-lactic acid molecule has a methyl group on the side chain, and the intermolecular force is large, so it has a stable chain packing structure and is more likely to form a network structure, making the molecular chain and the intermolecular chain less likely to slip, which is beneficial to improve the tensile strength of the composite reinforcing material. PGA is a linear macromolecule with small steric hindrance, and the molecular chain is more likely to slip, which is limited in improving the tensile strength of the composite reinforcing material, but is beneficial to improve the elongation at break of the composite reinforcing material. Therefore, when the addition amount of poly-L-lactic acid and PGA is within the weight range defined in the application, the tensile strength and elongation at break can be considered at the same time, so as to obtain a composite reinforcing material with excellent mechanical properties.

[0031] As a preferred technical solution of the application, the lubricant includes any one or a combination of at least two of paraffin wax, zinc stearate, calcium stearate, polyethylene wax, glycerol monostearate, or glycerol distearate.

[0032] In some optional examples, the antioxidant includes any one or a combination of at least two of antioxidant 1010, antioxidant 1076, antioxidant 300, antioxidant 1790, antioxidant DSTBP, antioxidant 1098, antioxidant 168, or antioxidant 691.

[0033] In some optional examples, the plasticizer includes any one or a combination of at least two of polypropylene glycol, phthalic acid diester, diethyl phthalate, dibutyl phthalate, or dicyclohexyl phthalate.

[0034] In a fourth aspect, the present application provides a preparation method of the composite reinforcing material of the third aspect, and the preparation method comprises:

[0035] (I) mixing the composite wood pulp fiber, the poly-L-lactic acid and the polyglycolic acid, and then stirring at high speed to obtain a reinforcing filler mixture, injecting the reinforcing filler mixture into a first double screw extruder, and then melt granulating to obtain a filler master batch;

[0036] (II) mixing the filler master batch obtained in step (I), the polybutylene adipate terephthalate, the poly-D-lactic acid, the antioxidant, the lubricant and the plasticizer, and then stirring at high speed to obtain a reinforcing material mixture, injecting the reinforcing material mixture into a second double screw extruder, and then melt granulating to obtain the composite reinforcing material.

[0037] As a preferred technical solution of the present application, in step (I), the stirring speed is 10-30 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0038] In some optional examples, the stirring speed is 800-1000 rpm, for example, it can be 800 rpm, 820 rpm, 840 rpm, 860 rpm, 880 rpm, 900 rpm, 920 rpm, 940 rpm, 960 rpm, 980 rpm or 1000 rpm, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0039] In some optional examples, the extrusion temperature of the first double screw extruder is 230-250°C, for example, it can be 230°C, 232°C, 234°C, 236°C, 238°C, 240°C, 242°C, 244°C, 246°C, 248°C or 250°C, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0040] In some optional examples, the screw speed of the first double screw extruder is 100-200 rpm, for example, it can be 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm or 200 rpm, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0041] As a preferred technical solution of the present application, in step (II), the time for high-speed stirring is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but not only limited to the listed values, other values not listed in this range are also applicable.

[0042] In some optional examples, the rotation speed of high-speed stirring is 1000-1200 rpm, for example, it can be 1000 rpm, 1020 rpm, 1040 rpm, 1060 rpm, 1080 rpm, 1100 rpm, 1120 rpm, 1140 rpm, 1160 rpm, 1180 rpm or 1200 rpm, but not only limited to the listed values, other values not listed in this range are also applicable.

[0043] In some optional examples, the second double screw extruder is divided into five temperature zones in the barrel along the material flow direction, which are first zone, second zone, third zone, fourth zone and fifth zone in turn.

[0044] In some optional examples, the temperature of the first zone is 170-180℃, for example, it can be 170℃, 171℃, 172℃, 173℃, 174℃, 175℃, 176℃, 177℃, 178℃, 179℃ or 180℃, but not only limited to the listed values, other values not listed in this range are also applicable.

[0045] In some optional examples, the temperature of the second zone is 190-200℃, for example, it can be 190℃, 191℃, 192℃, 193℃, 194℃, 195℃, 196℃, 197℃, 198℃, 199℃ or 200℃, but not only limited to the listed values, other values not listed in this range are also applicable.

[0046] In some optional examples, the temperature of the third zone is 220-230℃, for example, it can be 220℃, 221℃, 222℃, 223℃, 224℃, 225℃, 226℃, 227℃, 228℃, 229℃ or 230℃, but not only limited to the listed values, other values not listed in this range are also applicable.

[0047] In some optional examples, the temperature of the fourth zone is 240-250℃, for example, it can be 240℃, 241℃, 242℃, 243℃, 244℃, 245℃, 246℃, 247℃, 248℃, 249℃ or 250℃, but not only limited to the listed values, other values in the range of the values are also applicable.

[0048] In some optional examples, the temperature of the fifth zone is 230-240℃, for example, it can be 230℃, 231℃, 232℃, 233℃, 234℃, 235℃, 236℃, 237℃, 238℃, 239℃ or 240℃, but not only limited to the listed values, other values in the range of the values are also applicable.

[0049] In some optional examples, the screw rotation speed of the second twin-screw extruder is 80-100 rpm, for example, it can be 80 rpm, 82 rpm, 84 rpm, 86 rpm, 88 rpm, 90 rpm, 92 rpm, 94 rpm, 96 rpm, 98 rpm or 100 rpm, but not only limited to the listed values, other values in the range of the values are also applicable.

[0050] Exemplarily, the present application provides a modification method of EVOH-coated modified composite wood pulp fibers, which specifically comprises the following steps:

[0051] The ethylene-vinyl alcohol copolymer is added into the isopropyl alcohol aqueous solution (the volume ratio of isopropyl alcohol and water is (6-8):(2-4)), heated to 70-80℃ and kept for 10-30 min until the ethylene-vinyl alcohol copolymer is completely melted, to obtain a coating solution, wherein the ratio of ethylene-vinyl alcohol copolymer to organic aqueous solution is (40-50) g:1 L;

[0052] The wood pulp fibers are added into the coating solution, and the mass ratio of wood pulp fibers to ethylene-vinyl alcohol copolymer in the coating solution is (5-7):1, mixed and stirred for 1-3 h to make the ethylene-vinyl alcohol copolymer uniformly coated on the surface of the composite wood pulp fibers to form an organic coating layer, and after filtration, washing and drying, the composite wood pulp fibers are obtained.

[0053] Exemplarily, the present application also provides a preparation method of a composite reinforcing material, which specifically comprises the following steps:

[0054] (1) 10-20 parts of the composite wood pulp fiber prepared above, 40-50 parts of poly-L-lactic acid and 5-10 parts of polyglycolic acid are mixed and stirred at a speed of 800-1000 rpm for 10-30 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first double screw extruder, the extrusion temperature of the first double screw extruder is set to 230-250 DEG C, the screw speed is set to 100-200 rpm, and the filler master batch is obtained after melt granulation;

[0055] (2) The filler master batch obtained in step (1), 50-60 parts of polybutylene adipate terephthalate, 2-5 parts of poly-D-lactic acid, 0.1-0.5 parts of an antioxidant, 0.5-1 parts of a lubricant and 1-2 parts of a plasticizer are mixed and stirred at a speed of 1000-1200 rpm for 20-30 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second double screw extruder, the first zone temperature of the second double screw extruder is set to 170-180 DEG C, the second zone temperature is set to 190-200 DEG C, the third zone temperature is set to 220-230 DEG C, the fourth zone temperature is set to 240-250 DEG C, and the fifth zone temperature is set to 230-240 DEG C, the screw speed of the second double screw extruder is 80-100 rpm, and the composite reinforcing material is obtained after melt granulation.

[0056] Compared with the prior art, the beneficial effects of the present application are:

[0057] In the present application, wood pulp fiber is mixed with a coating solution containing ethylene-vinyl alcohol copolymer (EVOH) by impregnation modification process, so that EVOH uniformly covers the surface of wood pulp fiber. EVOH can be used as an interfacial compatibilizer to improve the interfacial compatibility between wood pulp fiber and resin matrix in wood-plastic composite reinforcing material. On the one hand, EVOH can reduce the surface polarity of wood pulp fiber, thereby improving the wettability between wood pulp fiber and resin melt, so as to improve the interfacial compatibility between composite wood pulp fiber and resin matrix, thereby reducing the pore size and number between composite wood pulp fiber and resin matrix, and improving the mechanical interlocking action between composite wood pulp fiber and resin matrix; on the other hand, since the molecular chain structure of EVOH contains both hydroxyl groups and ethylene structural units, the hydroxyl groups can be combined with wood pulp fiber in the form of hydrogen bond, and the ethylene structural units can form molecular chain entanglement with the resin matrix, thereby forming a bridge between the polar wood pulp fiber and the non-polar or weakly polar resin matrix, and achieving the purpose of interfacial chemical modification. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The preparation process flow chart of the composite reinforcing material provided for embodiments 1-13 of the present application;

[0059] Figure 2A cross-section scanning electron microscope image of the composite reinforcing material prepared in Example 1 of the present application;

[0060] Figure 3 A cross-section scanning electron microscope image of the composite reinforcing material prepared in Comparative Example of the present application. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be described in detail below with reference to specific embodiments and the accompanying drawings. The embodiments described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; all the descriptions are explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the embodiments described herein, those skilled in the art can also employ other technical solutions that are obvious based on the disclosure of the claims and the specification of the present application, which include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0062] Example 1

[0063] The present embodiment provides a modification method of EVOH-coated modified composite wood pulp fibers, as shown in the following scheme: Figure 1 The modification method specifically includes the following steps:

[0064] The ethylene-vinyl alcohol copolymer is added to an isopropanol aqueous solution (the volume ratio of isopropanol to water is 6:4), mixed and heated to 70℃ and kept for 30 min until the ethylene-vinyl alcohol copolymer is completely melted, to obtain a coating solution, wherein the ratio of ethylene-vinyl alcohol copolymer to organic aqueous solution is 40g:1L;

[0065] Wood pulp fibers are added to the coating solution, and the mass ratio of wood pulp fibers to ethylene-vinyl alcohol copolymer in the coating solution is 5:1, mixed and stirred for 1h to make the ethylene-vinyl alcohol copolymer uniformly coated on the surface of the composite wood pulp fibers to form an organic coating layer, and the composite wood pulp fibers are obtained after filtration, washing and drying.

[0066] The present embodiment also provides a preparation method of a composite reinforcing material, as shown in the following scheme: Figure 1 The preparation method specifically includes the following steps:

[0067] (1) 10 parts of the composite wood pulp fibers prepared above, 40 parts of poly-L-lactic acid and 5 parts of polyglycolic acid are mixed and stirred at a speed of 800 rpm for 30 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first twin-screw extruder, the extrusion temperature of the first twin-screw extruder is set to 230℃, and the screw speed is set to 100 rpm, and the filler master batch is obtained after melt granulation;

[0068] (2) The filler master batch obtained in step (1), 50 parts of polybutylene adipate terephthalate, 2 parts of poly-D-lactic acid, 0.1 part of antioxidant 1010, 0.5 part of zinc stearate and 1 part of polypropylene glycol are mixed and stirred at a speed of 1000 rpm for 20 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second twin-screw extruder, the first zone temperature of the second twin-screw extruder is set to 170°C, the second zone temperature is set to 190°C, the third zone temperature is set to 220°C, the fourth zone temperature is set to 240°C, and the fifth zone temperature is set to 230°C, the screw speed of the second twin-screw extruder is 80 rpm, and the composite reinforcing material is obtained after melt granulation.

[0069] Example 2

[0070] The embodiment provides a modification method of EVOH-coated modified composite wood pulp fibers, as shown in the following scheme: Figure 1 The modification method specifically comprises the following steps:

[0071] The ethylene-vinyl alcohol copolymer is added into an isopropanol aqueous solution (the volume ratio of isopropanol to water is 6.5:3.5), mixed and heated to 72°C and kept for 25 min until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution, wherein the ratio of the ethylene-vinyl alcohol copolymer to the organic aqueous solution is 42 g:1 L;

[0072] The wood pulp fibers are added into the coating solution, the mass ratio of the wood pulp fibers to the ethylene-vinyl alcohol copolymer in the coating solution is 5.5:1, and the mixture is stirred for 1.5 h to make the ethylene-vinyl alcohol copolymer uniformly coated on the surface of the composite wood pulp fibers to form an organic coating layer, and the composite wood pulp fibers are obtained after filtration, washing and drying.

[0073] The embodiment further provides a preparation method of a composite reinforcing material comprising the composite wood pulp fibers, as shown in the following scheme: Figure 1 The preparation method specifically comprises the following steps:

[0074] (1) 12 parts of the composite wood pulp fibers prepared above, 42 parts of poly-L-lactic acid and 6 parts of polyglycolic acid are mixed and stirred at a speed of 850 rpm for 25 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first twin-screw extruder, the extrusion temperature of the first twin-screw extruder is set to 235°C, and the screw speed is set to 120 rpm, and the filler master batch is obtained after melt granulation;

[0075] (2) The filler master batch obtained in step (1), 52 parts of polybutylene adipate terephthalate, 3 parts of poly-D-lactic acid, 0.2 parts of antioxidant 1076, 0.6 parts of calcium stearate and 1.2 parts of phthalic acid diester are mixed and stirred at a speed of 1050 rpm for 22 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second twin-screw extruder, the first zone temperature of the second twin-screw extruder is set to 172°C, the second zone temperature is set to 192°C, the third zone temperature is set to 222°C, the fourth zone temperature is set to 242°C, and the fifth zone temperature is set to 232°C, the screw speed of the second twin-screw extruder is 85 rpm, and the composite reinforcing material is obtained after melt granulation.

[0076] Example 3

[0077] The embodiment provides a modification method of EVOH-coated modified composite wood pulp fibers, as shown in the following scheme: Figure 1 The modification method specifically comprises the following steps:

[0078] The ethylene-vinyl alcohol copolymer is added into an isopropanol aqueous solution (the volume ratio of isopropanol and water is 7:3), mixed and heated to 75°C and kept for 20 min until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution, wherein the ratio of the ethylene-vinyl alcohol copolymer to the organic aqueous solution is 45 g:1 L;

[0079] The wood pulp fibers are added into the coating solution, the mass ratio of the wood pulp fibers to the ethylene-vinyl alcohol copolymer in the coating solution is 6:1, and the mixture is stirred for 2 h to make the ethylene-vinyl alcohol copolymer uniformly coated on the surface of the composite wood pulp fibers to form an organic coating layer, and the composite wood pulp fibers are obtained after filtration, washing and drying.

[0080] The embodiment further provides a preparation method of a composite reinforcing material comprising the composite wood pulp fibers, as shown in the following scheme: Figure 1 The preparation method specifically comprises the following steps:

[0081] (1) 15 parts of the composite wood pulp fibers prepared above, 45 parts of poly-L-lactic acid and 7 parts of polyglycolic acid are mixed and stirred at a speed of 900 rpm for 20 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first twin-screw extruder, the extrusion temperature of the first twin-screw extruder is set to 240°C, and the screw speed is set to 150 rpm, and the filler master batch is obtained after melt granulation;

[0082] (2) The filler master batch obtained in step (1), 55 parts of polybutylene adipate terephthalate, 3.5 parts of poly-D-lactic acid, 0.3 parts of antioxidant 300, 0.7 parts of polyethylene wax, and 1.5 parts of diethyl phthalate are mixed and stirred at a speed of 1100 rpm for 25 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second twin-screw extruder, the first zone temperature of the second twin-screw extruder is set to 175°C, the second zone temperature is set to 195°C, the third zone temperature is set to 225°C, the fourth zone temperature is set to 245°C, and the fifth zone temperature is set to 235°C, the screw speed of the second twin-screw extruder is 90 rpm, and the composite reinforcing material is obtained after melt granulation.

[0083] Example 4

[0084] The embodiment provides a modification method of EVOH-coated modified composite wood pulp fibers, as shown in the following scheme: Figure 1 The modification method specifically comprises the following steps:

[0085] The ethylene-vinyl alcohol copolymer is added into an isopropanol aqueous solution (the volume ratio of isopropanol to water is 7.5:2.5), mixed and heated to 78°C and kept for 15 min until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution, wherein the ratio of the ethylene-vinyl alcohol copolymer to the organic aqueous solution is 48 g:1 L.

[0086] The wood pulp fibers are added into the coating solution, the mass ratio of the wood pulp fibers to the ethylene-vinyl alcohol copolymer in the coating solution is 6.5:1, and the mixture is stirred for 2.5 h to uniformly coat the ethylene-vinyl alcohol copolymer on the surface of the composite wood pulp fibers to form an organic coating layer, and the composite wood pulp fibers are obtained after filtration, washing and drying.

[0087] The embodiment further provides a preparation method of a composite reinforcing material comprising the composite wood pulp fibers, as shown in the following scheme: Figure 1 The preparation method specifically comprises the following steps:

[0088] (1) 18 parts of the composite wood pulp fibers prepared above, 48 parts of poly-L-lactic acid and 9 parts of polyglycolic acid are mixed and stirred at a speed of 950 rpm for 15 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first twin-screw extruder, the extrusion temperature of the first twin-screw extruder is set to 245°C, and the screw speed is set to 180 rpm, and the filler master batch is obtained after melt granulation;

[0089] (2) The filler master batch obtained in step (1), 58 parts of polybutylene adipate terephthalate, 4 parts of poly-D-lactic acid, 0.4 parts of antioxidant 1790, 0.8 parts of paraffin wax, and 1.8 parts of dibutyl phthalate are mixed and stirred at a speed of 1150 rpm for 28 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second twin-screw extruder, the first zone temperature of the second twin-screw extruder is set to 178°C, the second zone temperature is set to 198°C, the third zone temperature is set to 228°C, the fourth zone temperature is set to 248°C, and the fifth zone temperature is set to 238°C, the screw speed of the second twin-screw extruder is 95 rpm, and the composite reinforcing material is obtained after melt granulation.

[0090] Example 5

[0091] The embodiment provides a modification method of EVOH-coated modified composite wood pulp fibers, as shown in the following scheme: Figure 1 The modification method specifically comprises the following steps:

[0092] The ethylene-vinyl alcohol copolymer is added into an isopropanol aqueous solution (the volume ratio of isopropanol to water is 8:2), mixed and heated to 80°C and kept for 10 min until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution, wherein the ratio of the ethylene-vinyl alcohol copolymer to the organic aqueous solution is 50 g:1 L;

[0093] The wood pulp fibers are added into the coating solution, the mass ratio of the wood pulp fibers to the ethylene-vinyl alcohol copolymer in the coating solution is 7:1, and the mixture is stirred for 3 h to make the ethylene-vinyl alcohol copolymer uniformly coated on the surface of the composite wood pulp fibers to form an organic coating layer, and the composite wood pulp fibers are obtained after filtration, washing and drying.

[0094] The embodiment further provides a preparation method of a composite reinforcing material comprising the composite wood pulp fibers, as shown in the following scheme: Figure 1 The preparation method specifically comprises the following steps:

[0095] (1) 20 parts of the composite wood pulp fibers prepared above, 50 parts of poly-L-lactic acid and 10 parts of polyglycolic acid are mixed and stirred at a speed of 1000 rpm for 10 min to obtain a reinforcing filler mixture; the reinforcing filler mixture is injected into a first twin-screw extruder, the extrusion temperature of the first twin-screw extruder is set to 250°C, and the screw speed is set to 200 rpm, and the filler master batch is obtained after melt granulation;

[0096] (2) The filler master batch obtained in step (1), 60 parts of polybutylene adipate terephthalate, 5 parts of poly-D-lactic acid, 0.5 parts of antioxidant DSTBP, 1 part of glycerol monostearate and 2 parts of dicyclohexyl phthalate are mixed and stirred at a speed of 1200 rpm for 30 min to obtain a reinforcing material mixture; the reinforcing material mixture is injected into a second twin-screw extruder, the first zone temperature of the second twin-screw extruder is set to 180°C, the second zone temperature is set to 200°C, the third zone temperature is set to 230°C, the fourth zone temperature is set to 250°C, and the fifth zone temperature is set to 240°C, the screw speed of the second twin-screw extruder is 100 rpm, and the composite reinforcing material is obtained after melt granulation.

[0097] Example 6

[0098] The embodiment provides a preparation method of a composite reinforcing material, which is different from that of the embodiment 1 in that the ratio of ethylene-vinyl alcohol copolymer to organic aqueous solution is adjusted to 35g:1L when the composite wood pulp fiber is prepared, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0099] Example 7

[0100] The embodiment provides a preparation method of a composite reinforcing material, which is different from that of the embodiment 1 in that the ratio of ethylene-vinyl alcohol copolymer to organic aqueous solution is adjusted to 55g:1L when the composite wood pulp fiber is prepared, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0101] Example 8

[0102] The embodiment provides a preparation method of a composite reinforcing material, which is different from that of the embodiment 1 in that the adding amount of poly-L-lactic acid is adjusted to 35 parts when the composite reinforcing material is prepared, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0103] Example 9

[0104] The embodiment provides a preparation method of a composite reinforcing material, which is different from that of the embodiment 1 in that the adding amount of poly-L-lactic acid is adjusted to 55 parts, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0105] Example 10

[0106] The embodiment provides a preparation method of a composite reinforcing material, which is different from that of the embodiment 1 in that the adding amount of poly-L-lactic acid is adjusted to 55 parts, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0107] Example 11

[0108] The embodiment provides a preparation method of a composite reinforcing material, which is different from the embodiment 1 in that the adding amount of polyglycolic acid is adjusted to 12 parts, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0109] Example 12

[0110] The embodiment provides a preparation method of a composite reinforcing material, which is different from the embodiment 1 in that the adding amount of poly-D-lactic acid is adjusted to 1 part, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0111] Example 13

[0112] The embodiment provides a preparation method of a composite reinforcing material, which is different from the embodiment 1 in that the adding amount of poly-D-lactic acid is adjusted to 8 parts, and other process conditions and operation steps are completely same as those of the embodiment 1.

[0113] Comparative Example

[0114] The comparative example provides a preparation method of a composite reinforcing material, which is different from the embodiment 1 in that the EVOH coating modification treatment on wood pulp fibers is omitted, the unmodified wood pulp fibers are mixed with poly-L-lactic acid and polyglycolic acid to obtain a filler master batch by melt extrusion, and then the filler master batch, polybutylene adipate terephthalate, poly-D-lactic acid, an antioxidant, a lubricant and a plasticizer are mixed and melt-extruded to obtain the composite reinforcing material, and other operation steps and process parameters are completely same as those of the embodiment 1.

[0115] Figure 2 and Figure 3 respectively are the cross-section electron microscope images of the composite reinforcing materials prepared in the embodiment 1 and the comparative example, and it can be seen from the images that the composite wood pulp fibers coated by EVOH are uniformly distributed in the resin matrix and are closely combined with the resin matrix, and the cross-section of the wood pulp fibers is irregular and in a tearing shape, which indicates that the combination between the composite wood pulp fibers coated by EVOH and the resin matrix is good. Figure 2 It can be seen from the images that the unmodified wood pulp fibers are combined with the resin matrix at many gaps, and in addition, there are many cavities left by the wood pulp fibers pulled out from the resin matrix in the cross-section of the composite reinforcing material, which indicates that the interface combination between the unmodified wood pulp fibers and the resin matrix is poor. Figure 3

[0116] The tensile strength, tensile modulus and bending strength of the composite reinforcing materials prepared in the embodiment 1 to 13 and the comparative example are tested, and the specific test method is as follows: ​

[0117] (1) Tensile strength

[0118] Tensile mechanical property test refers to ASTM D638-10, sample size refers to standard dumbbell type II, sensor is 10 KN, test speed is 5 mm / min, 5 samples are tested for each example (comparative example), and average value is taken.

[0119] The calculation formula of tensile strength is as follows:

[0120]

[0121] In the formula, σ1 is tensile strength (MPa), F is maximum load (N), b is specimen width (mm), and h is specimen thickness (mm).

[0122] (2) Tensile modulus

[0123] The calculation formula of tensile modulus is as follows:

[0124]

[0125] In the formula, E1 is tensile modulus (MPa), ΔF is load increment of initial straight line segment on load-displacement curve (N), ΔL is deformation increment within gauge length L0 corresponding to load increment ΔF (mm), b is specimen width (mm), and h is specimen thickness (mm).

[0126] (3) Bending strength

[0127] Sample treatment refers to standard ASTM D618-08, and the sample is balanced in a constant temperature and humidity box with a temperature of 23°C and a humidity of 50% for 88 h. Bending mechanical test refers to standard ASTM D790-10, specimen size is 160 mm x 14 mm x 8 mm, sensor is 2 kN, test speed is 17 mm / min, 5 samples are tested for each example (comparative example), and average value is taken.

[0128] The calculation formula of bending strength is as follows:

[0129]

[0130] In the formula, σ2 is bending strength (MPa), P is maximum load (N), b is specimen width (mm), h is specimen thickness (mm), and l is span (mm).

[0131] The test results are shown in Table 1.

[0132] Table 1

[0133] Tensile strength MPa Tensile modulus MPa Flexural strength MPa Example 1 58.6 3576 84.1 Example 2 60.3 3624 89.3 Example 3 65.5 3740 92.4 Example 4 68.4 3854 95.6 Example 5 69.2 3890 96.5 Example 6 50.3 3115 73.6 Example 7 52.1 3142 75.1 Example 8 42.7 2754 63.7 Example 9 44.0 2837 65.2 Example 10 46.4 2971 66.9 Example 11 48.2 3010 69.8 Example 12 47.5 2994 68.5 Example 13 49.3 3058 72.3 Comparative Example 35.8 2540 56.0

[0134] As can be seen from the test data provided by Example 1, Example 6 and Example 7, the tensile strength, tensile modulus and bending strength of the composite reinforcing material prepared in Example 6 and Example 7 are all lower than those of Example 1, which is because,

[0135] As can be seen from the test data provided by Example 1, Example 8 and Example 9, the tensile strength, tensile modulus and bending strength of the composite reinforcing material prepared in Example 8 and Example 9 are all lower than those of Example 1, which is because, the addition amount of poly-L-lactic acid is too high or too low, which will affect the mechanical properties of the composite reinforcing material.

[0136] As can be seen from the test data provided by Example 1, Example 10 and Example 11, the tensile strength, tensile modulus and bending strength of the composite reinforcing material prepared in Example 10 and Example 11 are all lower than those of Example 1, which is because, the addition amount of polyglycolic acid is too high or too low, which will affect the mechanical properties of the composite reinforcing material.

[0137] As can be seen from the test data provided by Example 1, Example 12 and Example 13, the tensile strength, tensile modulus and bending strength of the composite reinforcing material prepared in Example 12 and Example 13 are all lower than those of Example 1, which is because, the addition amount of poly-D-lactic acid is too high or too low, which will affect the mechanical properties of the composite reinforcing material.

[0138] As can be seen from the test data provided by Example 1 and the comparative example, the tensile strength, tensile modulus and bending strength of the composite reinforcing material prepared in the comparative example are far lower than those of Example 1, which is because, the wood pulp fiber is subjected to EVOH coating modification treatment in the present application, which can greatly improve the interfacial compatibility between the wood pulp fiber and the resin matrix, thereby improving the mechanical properties of the adhesive plaster composite reinforcing material.

[0139] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which falls within the protection scope and disclosure scope of the present application.

Claims

1. A composite reinforcement material comprising composite wood pulp fibers, characterized in that, The composite reinforcing material comprises composite wood pulp fiber, poly-L-lactic acid, polyglycolic acid, polybutylene adipate terephthalate, poly-D-lactic acid, antioxidant, lubricant and plasticizer; The composite reinforcing material comprises the following components by weight: Composite wood pulp fiber 10-20 parts; Poly-L-lactic acid 40-50 parts; Polyglycolic acid 5-10 parts; Polybutylene adipate terephthalate 50-60 parts; Poly-D-lactic acid 2-5 parts; Antioxidant 0.1-0.5 parts; Lubricant 0.5-1 part; Plasticizer 1-2 parts; The composite wood pulp fiber is prepared by the following method: The ethylene-vinyl alcohol copolymer is added into an organic aqueous solution and heated until the ethylene-vinyl alcohol copolymer is completely melted to obtain a coating solution; wood pulp fiber is added into the coating solution and mixed and stirred to uniformly coat the ethylene-vinyl alcohol copolymer on the surface of the composite wood pulp fiber to form an organic coating layer, and the composite wood pulp fiber is obtained after filtration, washing and drying.

2. The composite reinforcement material of claim 1, wherein, The organic aqueous solution is an isopropanol aqueous solution.

3. The composite reinforcement material of claim 2, wherein, The volume ratio of isopropanol to water in the isopropanol aqueous solution is (6-8):(2-4).

4. The composite reinforcement material of claim 1, wherein, The ratio of the ethylene-vinyl alcohol copolymer to the organic aqueous solution is (40-50) g:1 L.

5. The composite reinforcement material of claim 1, wherein, The heating temperature is 70-80℃.

6. The composite reinforcement material of claim 1, wherein, The heating time is 10-30 min.

7. The composite reinforcement material of claim 1, wherein, The mass ratio of the wood pulp fiber to the ethylene-vinyl alcohol copolymer in the coating solution is (5-7):

1.

8. The composite reinforcement material of claim 1, wherein, The mixing and stirring time of the composite wood pulp fiber in the coating solution is 1-3 h.

9. The composite reinforcement material of claim 1, wherein, The lubricant comprises any one or a combination of at least two of paraffin wax, zinc stearate, calcium stearate, polyethylene wax, glycerol monostearate or glycerol distearate.

10. The composite reinforcement material of claim 1, wherein, The antioxidant comprises any one or a combination of at least two of antioxidant 1010, antioxidant 1076, antioxidant 300, antioxidant 1790, antioxidant DSTBP, antioxidant 1098, antioxidant 168, antioxidant 691.

11. The composite reinforcement material of claim 1, wherein, The plasticizer comprises any one or a combination of at least two of polypropylene glycol, phthalic acid diester, diethyl phthalate, dibutyl phthalate or dicyclohexyl phthalate.

12. A method of producing the composite reinforcement material according to any one of claims 1 to 11, characterized in that, The preparation method comprises: (I) mixing the composite wood pulp fiber, poly-L-lactic acid and polyglycolic acid and then high-speed stirring to obtain a reinforcing filler mixture, injecting the reinforcing filler mixture into a first double screw extruder, and then melt granulating to obtain a filler master batch; (II) mixing the filler master batch obtained in step (I), polybutylene adipate terephthalate, poly-D-lactic acid, antioxidant, lubricant and plasticizer and then high-speed stirring to obtain a reinforcing material mixture, injecting the reinforcing material mixture into a second double screw extruder, and then melt granulating to obtain the composite reinforcing material.

13. The method of claim 12, wherein, In step (I), the high-speed stirring time is 10-30 min.

14. The method of claim 12, wherein, In step (I), the high-speed stirring speed is 800-1000 rpm.

15. The preparation method according to claim 12, characterized in that, In step (I), the extrusion temperature of the first double screw extruder is 230-250℃.

16. The method of claim 12, wherein, In step (I), the screw rotation speed of the first double screw extruder is 100-200 rpm.

17. The method of claim 12, wherein, The time of the high-speed stirring in step (II) is 20-30 min.

18. The method of claim 12, wherein, The rotating speed of the high-speed stirring in step (II) is 1000-1200 rpm.

19. The method of claim 12, wherein, In the second twin-screw extruder, the temperature of the first zone is 170-180℃. In the second twin-screw extruder, the temperature of the second zone is 190-200℃. In the second twin-screw extruder, the temperature of the third zone is 220-230℃. In the second twin-screw extruder, the temperature of the fourth zone is 240-250℃. In the second twin-screw extruder, the temperature of the fifth zone is 230-240℃. The rotating speed of the second twin-screw extruder in step (II) is 80-100 rpm.

20. The method of claim 12, wherein, ​

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