In-situ impregnation modified wood veneer wound PVC composite pipe

Abstract

The application discloses in-situ impregnation modified wood single plate winding PVC composite pipeline and belongs to the technical field of wood modification treatment. The PVC composite pipeline is prepared by performing in-situ impregnation modification treatment on wood single plates and coating the wood single plates on PVC pipes through a winding forming method; the PVC composite pipeline not only retains excellent characteristics of PVC material, but also overcomes the shortcomings of the PVC material in pressure bearing capacity, low-temperature brittleness and flame retardancy, and simultaneously expands the application field of the PVC and wood.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood modification treatment, and particularly relates to a PVC composite pipe wound by in-situ impregnation modified wood veneer. BACKGROUND

[0002] Traditional polyvinyl chloride (PVC) pipes are widely used in the fields of building, drainage system and power protection, and have good corrosion resistance, chemical resistance and easy processability. However, the PVC pipes have some shortcomings, such as low mechanical strength, large low-temperature brittleness, poor flame retardant performance, and outstanding environmental protection problems, which limit the application of the PVC pipes in wider fields.

[0003] In order to improve the performance of the PVC pipes, an outer coating material (such as foamed plastic, glass fiber, aluminum foil composite material) is usually used to enhance the mechanical strength, toughness or flame retardant performance, but the composite modified material is difficult to have multiple performances of the above requirements, that is, the integration of strength and toughness and flame retardant cannot be realized, and the introduction of secondary processing and other industrial materials increases the cost and environmental pressure, so it is necessary to find a low-cost green alternative material to realize the multifunctionalization of the PVC pipes.

[0004] At present, the green alternative materials mainly include wood wound pipes and bamboo wound pipes. The thick veneer used in the traditional wood wound pipe needs to be softened and balanced before being wound; the bamboo wound pipe is formed by bamboo splints, which has large hardness, many gaps and is easy to delaminate. Therefore, the processes of the two are complex and the processing cost is high. SUMMARY

[0005] In view of the above prior art situation, the purpose of the present application is to provide a PVC composite pipe wound by in-situ impregnation modified wood veneer. The present application coats the PVC pipe by the method of winding through the in-situ impregnation modification treatment of the wood veneer, and the PVC composite pipe is prepared. The PVC composite pipe of the present application not only retains the excellent properties of the PVC material, but also overcomes the shortcomings of the PVC material in pressure capacity, low-temperature brittleness and flame retardant performance, and expands the application field of the PVC and wood.

[0006] To achieve the above purpose, the present application adopts the following technical scheme:

[0007] A PVC composite pipe wound by in-situ impregnation modified wood veneer is prepared by the following method:

[0008] (1) The wood veneer is immersed in a pretreatment reagent, the pretreatment reagent is composed of glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid, and the wood veneer is treated at 100-140 DEG C for 2-8 h to obtain pretreated wood veneer;

[0009] (2) the pretreated wood veneer is impregnated with a modifier composed of sodium alginate and phenolic resin to obtain a modified wood veneer;

[0010] (3) the modified wood veneer is sequentially subjected to hot pressing treatment and resin coating treatment, and then the wood veneer coated with the resin is wound around a PVC pipe to be cured and formed to obtain an in-situ impregnated modified wood veneer wound PVC composite pipe.

[0011] Preferably, in step (1), the concentration of glycerol triglycidyl ether in the pretreatment reagent is 0.1-1M, the concentration of benzyltrimethylammonium chloride is 0.5-2M, and the concentration of lactic acid is 1-2M.

[0012] The pretreatment reagent composed of glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid in specific concentrations is used to modify and pretreat the wood veneer, which can effectively remove lignin in the wood veneer and increase porosity. The addition of glycerol triglycidyl ether can cross-link the cellulose component, which enhances the tissue adhesion of the vascular bundle and parenchyma cells and enhances the resistance to disintegration, so that the delignified wood does not crack during the pretreatment process, and a wood cellulose scaffold with high structural integrity and rich porous structure is prepared; subsequently, benzyltrimethylammonium chloride and lactic acid solution are used to remove lignin, in which process, benzyltrimethylammonium chloride as a hydrogen bond acceptor forms a hydrogen bond with the phenolic hydroxyl group in the lignin molecule, effectively destroying the hydrogen bond between lignin and carbohydrates and promoting the dissolution and separation of lignin. At the same time, lactic acid as a hydrogen bond donor forms a hydrogen bond with the hydroxyl group in the lignin molecule, enhancing the solubility of lignin in the eutectic solvent. The synergistic effect of the two organic molecules weakens the intermolecular and intramolecular forces of lignin molecules, so that lignin can be efficiently separated and removed from wood while the complete cellulose skeleton is retained.

[0013] The method of the present application is suitable for various wood veneers, such as poplar veneer, eucalyptus veneer, fir veneer, pine veneer, etc.

[0014] Preferably, in step (2), the concentration of sodium alginate in the modifier is 0.5-2M, and the content of phenolic resin is 10-30wt%.

[0015] Preferably, in step (2), the impregnation treatment conditions of the modifier are: vacuum degree -0.08MPa~ -0.1MPa, temperature 25℃-80℃.

[0016] The present invention impregnates pretreated wood veneer with a modifier. The modifier enters the pretreated veneer, filling the wood's pores and increasing its density, thereby increasing the strength of the modified wood. Simultaneously, the carboxyl groups of sodium alginate form strong dynamic hydrogen bonds with the hydroxyl groups on the wood, enhancing the toughness of the modified wood. Phenolic resin itself contains numerous benzene rings, and its unique conjugated π-electron system enables the benzene rings to maintain their structural stability when heated. Furthermore, when sodium alginate burns, it forms a carbon layer on the wood's exterior, isolating it from oxygen. The resulting double-crosslinked network of organic molecules created by the two organic compounds enhances the flame retardancy of the wood veneer.

[0017] Preferably, in step (3), the temperature of the hot pressing treatment is 80° C.-120° C., the hot pressing pressure is 10 MPa-20 MPa, and the time is 1-3 h.

[0018] The moisture content and compression rate of the modified wood veneer are regulated through hot pressing treatment, further reducing the wood pores, increasing the density, forming densified wood with shrunken cell cavities, and simultaneously improving the strength and toughness of the modified wood.

[0019] Preferably, in step (3), a thermosetting resin is used for resin impregnation; the thermosetting resin can be selected from one or more of epoxy resin, polyester resin, and phenolic resin.

[0020] Preferably, in step (3), the winding parameter conditions are: 0° winding angle, 5N winding tension, and 100mm / min winding speed.

[0021] Preferably, in step (3), the curing temperature is 40-120°C.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention first uses a pretreatment reagent to remove lignin from the wood veneer to further increase the porosity, and then uses a modifier to perform an impregnation treatment to generate a double-crosslinked network organic molecular structure inside the wood veneer, and synergistically performs a hot pressing treatment to improve the strength, toughness and flame retardancy of the wood, thereby obtaining a green, strong, tough and flame-retardant modified wood veneer. Then, after the surface of the modified wood veneer is coated with a thermosetting resin, it is wrapped on a PVC pipe through a winding process, and finally cured and formed to obtain an in-situ impregnated modified wood veneer wrapped PVC composite pipe. The present invention improves the mechanical properties and environmental adaptability of the PVC pipe, solves the problems of low mechanical properties, high brittleness and low flame resistance of traditional PVC pipes, and extends the service life of the pipe; the winding process is simple and the inner diameter is controllable, providing a new technical route for the application of wood veneer in composite materials, and has broad market prospects.

[0024] (2) The in-situ impregnated modified wood veneer wound PVC composite pipeline prepared by the method has wide application prospects in many fields, and is especially suitable for occasions with high requirements for pipeline pressure performance, toughness and flame retardant performance, such as high-pressure water pipeline, outdoor drainage system and power protection pipeline. In addition, the method has low cost, simple process and easy industrialization, and has good economic and social benefits. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The preparation flow chart of the wood veneer wound PVC composite pipeline of the present application.

[0026] Figure 2 The photo of the in-situ impregnated modified wood veneer wound PVC composite pipeline prepared in Example 1

[0027] Figure 3 The photo of the PVC composite pipeline A prepared in Comparative Example 1.

[0028] Figure 4 The photo of the PVC composite pipeline B prepared in Comparative Example 2.

[0029] Figure 5 The photo of the PVC composite pipeline C prepared in Comparative Example 3.

[0030] Figure 6 The photo of the vertical combustion test experiment; in the figure, A is a PVC pipeline, B is the PVC composite pipeline prepared in Comparative Example 1, and C is the in-situ impregnated modified wood veneer wound PVC composite pipeline prepared in Example 1. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0032] As described previously, the existing PVC pipeline has problems of low mechanical strength, large low-temperature brittleness, poor flame retardancy and the like, which limits its application. Wood is a green renewable raw material, and using wood as the outer cladding material of the PVC pipeline is a green and environmentally friendly PVC pipeline modification method. However, due to the large cell cavity, loose material, small density, low strength and easy burning of wood, it is difficult to meet the practical requirements by directly cladding the PVC pipeline with wood veneer.

[0033] Therefore, the present application provides a new in-situ impregnated modified wood veneer wound PVC composite pipeline and a preparation method thereof. The preparation flow chart of the in-situ impregnated modified wood veneer wound PVC composite pipeline of the present application is as shown in Figure 1The present application first uses glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid to constitute a pretreatment reagent to pretreat the wood single board to remove lignin in the wood and further increase porosity; then uses a modifier composed of sodium alginate and phenolic resin to perform in-situ impregnation treatment to form a double-crosslinked network organic molecular structure in the interior of the wood single board; then regulates moisture and compression rate of the impregnated wood single board by regulating hot-pressing temperature, time and hot-pressing pressure to avoid the formation of pores due to water evaporation in the pipe preparation process; regulates the type, viscosity, time, etc. of the resin to uniformly coat the wood single board, so that the wood single board after coating the resin has the characteristics of thermal curing and forming; regulates the winding angle, speed, tension, PVC pipe diameter, etc. to perform composite pipe forming preparation; and regulates the temperature, rotation speed to achieve good pipe curing, and finally prepares a wood single board winding PVC composite pipe.

[0034] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0035] The test materials used in the examples and comparative examples of the present application are all conventional test materials in the art and can be purchased through commercial channels. The experimental methods not specified in detail are carried out according to the conventional test methods or according to the operation instructions recommended by the suppliers. Among them:

[0036] The CAS accession number of glycerol triglycidyl ether is 13236-02-7; the CAS accession number of benzyltrimethylammonium chloride is 56-93-9; and the CAS accession number of sodium alginate is 9005-38-3.

[0037] The size of the PVC pipe used in the present application is 100*3mm.

[0038] The phenolic resin is purchased from Beijing Tail Chemical Co., Ltd.; and the E54 epoxy resin is purchased from Guangzhou Yuebao Chemical Technology Co., Ltd.

[0039] Example 1: Preparation of in-situ impregnation modified wood single board winding PVC composite pipe

[0040] (1) A poplar single board with a thickness of 0.5mm and a width of 40mm is immersed in a pretreatment reagent composed of glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid, wherein the concentration of glycerol triglycidyl ether in the pretreatment reagent is 0.5M, the concentration of benzyltrimethylammonium chloride is 1M, and the concentration of lactic acid is 1.5M; 120℃ treatment for 4h to obtain a pretreated wood single board;

[0041] (2) The pretreated wood single board is in-situ impregnated with a modifier under the conditions of a vacuum degree of -0.08 MPa and a temperature of 25°C to obtain a modified wood single board; the modifier is composed of sodium alginate and phenolic resin, and in the modifier, the concentration of sodium alginate is 1M and the solid content of phenolic resin is 20wt%;

[0042] (3) The modified wood single board is hot-pressed at 15 MPa and 120°C for 2h, and then coated with E54 epoxy resin (the coating amount is 20g / m 2 ); the wood single board after coating the resin is wound around a PVC pipe, and the winding parameter conditions are: a winding angle of 0°, a winding tension of 5N, and a winding speed of 100mm / min; after one winding, 80°C curing is performed to obtain an in-situ impregnated modified wood single board wound PVC composite pipe.

[0043] Comparative Example 1:

[0044] The poplar single board with a thickness of 0.5mm and a width of 40mm is directly coated with E54 epoxy resin (the coating amount is 20g / m 2 ), and the wood single board after coating the resin is wound around a PVC pipe, and the winding parameter conditions are: a winding angle of 0°, a winding tension of 5N, and a winding speed of 100mm / min; after one winding, 80°C curing is performed to obtain a PVC composite pipe A.

[0045] Comparative Example 2:

[0046] The poplar single board with a thickness of 0.5mm and a width of 40mm is immersed in a pretreatment reagent composed of glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid, and in the pretreatment reagent, the concentration of glycerol triglycidyl ether is 0.5M, the concentration of benzyltrimethylammonium chloride is 1M, and the concentration of lactic acid is 1.5M; 120°C treatment for 4h obtains a pretreated wood single board;

[0047] The pretreated wood single board is hot-pressed at 15 MPa and 120°C for 2h, and then coated with E54 epoxy resin (the coating amount is 20g / m 2 ); the wood single board after coating the resin is wound around a PVC pipe, and the winding parameter conditions are: a winding angle of 0°, a winding tension of 5N, and a winding speed of 100mm / min; after one winding, 80°C curing is performed to obtain a PVC composite pipe B.

[0048] Comparative Example 3:

[0049] The poplar wood veneer with a thickness of 0.5 mm and a width of 40 mm is in-situ impregnated with a modifier under the conditions of a vacuum degree of -0.08 MPa and a temperature of 25 DEG C to obtain modified wood veneer; the modifier is composed of sodium alginate and phenolic resin, and in the modifier, the concentration of sodium alginate is 1 M, and the solid content of phenolic resin is 20 wt.%;

[0050] The modified wood veneer is hot-pressed at 15 MPa and 120 DEG C for 2 h, and then coated with E54 epoxy resin (coating amount: 20 g / m 2 ); the wood veneer after coating the resin is wound around a PVC pipe, and the winding parameter conditions are: a winding angle of 0 DEG, a winding tension of 5 N, and a winding speed of 100 mm / min; after one winding, 80 DEG C is used for curing to obtain a PVC composite pipe C.

[0051] Test Example: Performance test of PVC composite pipe

[0052] The PVC composite pipes prepared by the examples and the comparative examples are subjected to performance tests, and the details are as follows:

[0053] 1. Flame-retardant performance test:

[0054] The pipe samples prepared by Example 1 and Comparative Example 1 are cut and ground, and the limiting oxygen index of the pipe is tested according to GB / T2406.1-2008. A 10 mm long burning distance mark is made, an HC-2 oxygen index tester is used, the sample is vertically fixed in a burning cylinder, oxygen and nitrogen are mixed, the burning end of the sample is ignited from bottom to top, the time is recorded and the burning length of the sample is observed; the oxygen concentration is changed, and when the sample is in a continuous and stable burning state, the oxygen concentration is the minimum, and the limiting oxygen index is calculated, and the results are shown in Table 1.

[0055] Table 1: Limiting oxygen index test results

[0056]

[0057] The limiting oxygen index is an index representing the burning behavior of a material, and the higher the limiting oxygen index, the more difficult the material is to burn. A material with a limiting oxygen index of less than 22% is considered flammable, and a material with a limiting oxygen index of more than 27% is considered difficult to burn. As shown in Table 1, the limiting oxygen index of the in-situ impregnated modified wood wound pipe prepared by the present application is more than 27%, so the material prepared by the present application has good flame-retardant performance, while the limiting oxygen index of the material prepared by Comparative Example 1 is only 18.2%.

[0058] In addition, according to the ASTM D2863-2017 standard, the vertical burning behavior of the material was tested using a vertical burning tester (czf-5 burning tester, Beijing Zhonghang Times Instruments, Beijing, China), 12 sample strips were tested in parallel for each group, and the average value was taken as the result. The sample size was 130x13x3mm (LxRxT).

[0059] To comprehensively study whether the wood veneer wound pipe prepared by in-situ impregnation modification has flame retardancy, the fireproof effect is evaluated, and the vertical burning test is carried out.

[0060] Figure 6 The alcohol lamp vertical burning experiment of each sample shows that the PVC pipe and the PVC composite pipe prepared in Comparative Example 1 are easily ignited and burn violently until they are completely burned out. The PVC composite pipe prepared in Example 1 is not ignited after 10s, showing resistance to flammability. Therefore, the double network structure formed by in-situ impregnation has obvious contribution to the flame retardance of the wood veneer wound pipe.

[0061] 2. Compression resistance detection:

[0062] The pipe samples prepared in Comparative Examples 1-3 and Example 1 and the PVC pipe sample were cut, and the ring stiffness of the pipe at a deformation of 3% and the ring stiffness at a low temperature for 24h were tested according to GB / T9647-2015 / ISO 9969:2007. The length area of the pipe material was 75cm. The pipe material was placed on a mechanical testing machine for compression, and the maximum force at a deformation of 3% of the pipe material was determined according to the force displacement curve, and then the ring stiffness (KPa) of the pipe material was obtained.

[0063] Table 2: Compression resistance detection results

[0064]

[0065] The ring stiffness is an evaluation of the anti-deformation ability of the pipe and pipe structure under external load. As can be seen from Table 2, the ring stiffness of the wood veneer wound PVC composite pipe prepared by the present application reached 592.09kPa, which was significantly higher than that of the PVC pipe; and after being placed at a low temperature of-60℃ for 24h, it still had a ring stiffness of 555.54kPa; compared with Comparative Examples 1-3, it can be seen that the combination of pretreatment agent and modifier has a synergistic effect on improving the ring stiffness of the prepared pipe compared with the pretreatment agent alone and the modifier alone, achieving an effect of 1+1>2.

[0066] 3. Bending strength detection:

[0067] The pipe samples prepared in Comparative Examples 1-3 and Example 1 and the PVC pipe samples were cut according to GB / T 17657-2013 to test the bending strength of the pipes. The size of the pipe material was 100mm x 20mm x 2.5mm. The pipe material was placed on a mechanical testing machine for bending compression, and the bending strength (MPa) and bending modulus (GPa) of the pipe material were determined according to the stress-strain curve.

[0068] Table 3: Bending strength and bending modulus test results

[0069]

[0070] Bending strength refers to the maximum stress that a material can withstand under bending load until it breaks or reaches a specified bending moment. This stress is the maximum normal stress in bending, measured in MPa (megapascals). It reflects the material's ability to resist bending and is used to measure the bending performance of the material. As shown in Table 3, the wood veneer wrapped PVC composite pipe significantly enhances the mechanical properties of the PVC pipe.

[0071] 4. Impact strength test:

[0072] The pipe samples prepared in Comparative Examples 1-3 and Example 1 and the PVC pipe samples were cut according to GB / T 18743.1-2022 to test the impact strength of the pipes. The size of the pipe material was 120mm x 10mm x 2.5mm. The pipe material was placed on an impact testing machine for impact, and the impact energy displayed on the testing machine was then used to obtain the impact strength of the pipe material (KJ / cm 2 ).

[0073] Table 4: Impact strength test results

[0074]

[0075] Impact strength is a measure of material toughness, usually defined as the energy absorbed per unit cross-sectional area when the sample breaks or cracks under impact load. As shown in Table 4, the wood veneer wrapped PVC composite pipe prepared by the present application significantly enhances the impact strength of the PVC pipe.

[0076] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the technical combination of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an in-situ impregnated modified wood veneer wrapped PVC composite pipe, characterized in that: Prepared by the following steps: (1) immersing the wood veneer in a pretreatment reagent consisting of glycerol triglycidyl ether, benzyltrimethylammonium chloride and lactic acid, and treating at 100-140° C. for 2-8 hours to obtain a pretreated wood veneer; (2) impregnating the pretreated wood veneer with a modifier consisting of sodium alginate and phenolic resin to obtain a modified wood veneer; (3) The modified wood veneer is subjected to hot pressing treatment and resin coating treatment in sequence, and then the resin-coated wood veneer is wrapped around the PVC pipe and cured to form an in-situ impregnated modified wood veneer wrapped PVC composite pipe; In step (1), in the pretreatment reagent, the concentration of glycerol triglycidyl ether is 0.1-1M, the concentration of benzyltrimethylammonium chloride is 0.5-2M, and the concentration of lactic acid is 1-2M; In step (2), the concentration of sodium alginate in the modifier is 0.5-2M, and the content of phenolic resin is 10-30wt%; In step (2), the conditions for the modifier impregnation treatment are: vacuum degree -0.08MPa~-0.1MPa, temperature 25℃-80℃.

2. The method for preparing an in-situ impregnated modified wood veneer wrapped PVC composite pipe according to claim 1, characterized in that: In step (3), the temperature of the hot pressing treatment is 80°C-120°C, the hot pressing pressure is 10MPa-20MPa, and the time is 1-3h.

3. The method for preparing an in-situ impregnated modified wood veneer wrapped PVC composite pipe according to claim 1, characterized in that: In step (3), a thermosetting resin is used for resin coating treatment; the thermosetting resin is selected from one or more of epoxy resin, polyester resin, and phenolic resin.

4. The method for preparing an in-situ impregnated modified wood veneer wrapped PVC composite pipe according to claim 1, characterized in that: In step (3), the winding parameter conditions are: 0° winding angle, 5N winding tension, and 100mm / min winding speed.

5. The method for preparing an in-situ impregnated modified wood veneer wrapped PVC composite pipe according to claim 1, characterized in that: In step (3), the curing temperature is 40-120°C.

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