Rosin normal-pressure impregnated water-resistant glue-free wheat straw board and preparation method thereof

Abstract

The invention discloses a water-resistant glue-free wheat straw board impregnated by rosin under normal pressure and a preparation method thereof, relates to the technical field of straw boards and preparation, and solves the problems of complex process, accompanying pollution and energy consumption of rosin resin REMG used by the wheat straw board. The water-resistant glue-free wheat straw board comprises the following components in parts by weight: 80-100 parts of wheat straw chippings; 60 to 80 parts of hydrogenated rosin; 5 to 15 parts of a catalyst; 3 to 15 parts of sodium hydroxide; 1-3 parts of sodium sulfite; and 12 to 20 parts of absolute ethyl alcohol. Hydrogenated rosin is subjected to esterification reaction under catalysis of aluminum chloride and is embedded into a straw board in a hydrogen bond mode, grease, ash and part of lignin in wheat straw are removed through alkali treatment, cellulose and functional groups on the surface of the cellulose are exposed, and subsequent introduction of the hydrogenated rosin is accompanied, so that the wheat straw board is obtained. The density, the mechanical property, the hydrophobicity and the water resistance of the wheat straw plate are effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of straw board and preparation thereof, in particular to a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure and a preparation method thereof. Background Art

[0002] Wood-based panels are man-made panels made of wood fiber interwoven and glued together. Due to their good physical and mechanical properties and processing properties, they are widely used in furniture manufacturing, construction, interior decoration, etc. In 2023 alone, the global wood-based panel market value is as high as US$175.1 billion. Traditional wood-based panels are one of the main products of wood processing and utilization. On the one hand, the production process consumes a large amount of wood, and long-term deforestation and deforestation will lead to a reduction in forest area and limit the supply of wood; at the same time, excessive felling of trees will also cause a series of problems such as damage and deterioration of the natural environment.

[0003] Crop straw is rich in cellulose, hemicellulose and lignin, and is expected to replace wood as the main raw material for the production of wood-based boards. Wheat is one of the most widely distributed, largest-area and second-largest food crops in the world. Wheat straw, as an agricultural by-product of wheat, accounts for 66.7% of the total weight of wheat and has great application potential as a raw material for boards. However, the physical structure composed of minor components in wheat straw (such as wax and pectin) will reduce the compatibility and adhesion between wheat straw particles. At the same time, wheat straw also has a rigid epidermal tissue rich in silicon. The above characteristics make the self-adhesion of wheat straw hot-pressed boards poor.

[0004] The existing literature studies the improvement of fast-growing poplar performance by modified rosin. Acrylic rosin is used as a modifier, anhydrous ethanol is used as a solvent, and a 20% impregnation solution is prepared. The fast-growing poplar is modified by vacuum impregnation. The performance test results show that the performance of the modified materials has been improved, among which acrylic rosin has the most significant improvement on the performance of fast-growing poplar. The water resistance of acrylic rosin is significantly enhanced. Its water absorption rate after 12 days of impregnation is 79.68%, while the water absorption rate of the control wood is 186.28%. The contact angle of the fast-growing poplar modified by acrylic rosin at 180s is 88.78°, which is only 12% lower than 100.09° at 15s, while the contact angle of the control wood drops from 44.34° at 15s to 0° at 180s. In addition, compared with the control wood, the static bending strength, elastic modulus and compressive strength along the grain of acrylic rosin modified poplar wood increased by 18.09%, 27.51% and 17.85% respectively, which greatly improved the mechanical properties of fast-growing poplar wood. However, the preparation process of acrylic rosin is complicated, accompanied by pollution and energy consumption. The vacuum impregnation method requires the raw materials to be placed in a container such as a vacuum tank, and then a pressure of 0.095MPa is drawn. The equipment is complicated and requires good sealing. The cost is high and the raw material used is poplar wood, which has a higher value (such as a raw material for papermaking, etc.). It is a bit wasteful to use it in the direction of boards.

[0005] The existing patent CN112250576B discloses a bifunctional reactive rosin resin and its preparation method, as well as its application in improving the performance of fast-growing wood. The bifunctional rosin resin REMG is prepared by using hydrogenated rosin and maleic anhydride as the main raw materials through methods such as epoxy ring opening and esterification. The REMG is dissolved in anhydrous ethanol, and an initiator is added to prepare an impregnation solution; the fast-growing wood is placed in the impregnation solution, and after impregnation, drying and curing, a modified fast-growing wood is obtained. The prepared REMG has two double bonds in its flexible chain segment, which increases the cross-linking degree of the REMG, thereby increasing its bonding strength with the wood, and preparing a modified fast-growing wood with excellent performance. The rosin resin REMG process is complicated, accompanied by pollution and energy consumption;

[0006] Therefore, the existing demand is not met, and we propose a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure and a preparation method thereof. Summary of the invention

[0007] The purpose of the present invention is to provide a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure and a preparation method thereof, so as to solve the problems of complex rosin resin REMG process used in wheat straw boards proposed in the above background technology, accompanied by pollution and energy consumption.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure, comprising the following components by weight: 80 to 100 parts of wheat straw chips; 60 to 80 parts of hydrogenated rosin; 5 to 15 parts of catalyst; 3 to 15 parts of sodium hydroxide; 1 to 3 parts of sodium sulfite; and 12 to 20 parts of anhydrous ethanol.

[0009] Preferably, the catalyst is any one of aluminum chloride, hydrochloric acid and sulfuric acid.

[0010] Preferably, the particle size of the wheat straw debris is 5 mm.

[0011] A method for preparing a water-resistant, glue-free wheat straw board by impregnation with rosin at normal pressure comprises the following steps:

[0012] Step 1: Wash the wheat straw and then crush it, and soak the crushed wheat straw debris in a mixed solution of sodium hydroxide and sodium sulfite at 95°C for 4 hours;

[0013] Step 2: After vacuum filtration, place in a ventilated environment at 105°C and dry for 6 hours to obtain alkali-treated wheat straw debris;

[0014] Step 3: crush the block of hydrogenated rosin, pour it into anhydrous ethanol, and dissolve it at 80° C. for 1 hour to obtain ethanol-dissolved hydrogenated rosin;

[0015] Step 4: physically mixing the hydrogenated rosin dissolved in ethanol with the alkali-treated wheat straw debris, and stirring until the alkali-treated wheat straw debris is evenly dispersed to obtain a mixture of alkali-treated wheat straw debris, ethanol, and rosin;

[0016] Step 5: filtering the mixture of alkali-treated wheat straw chips, ethanol and rosin under reduced pressure, and drying at 80° C. for 6 hours to obtain a mixture of alkali-treated wheat straw and rosin;

[0017] Step 6: adding an aqueous solution of aluminum chloride to the alkali-treated wheat straw and rosin mixture, and performing vacuum filtration;

[0018] Step seven: perform wet hot pressing at 80° C. and 15 MPa for 4 hours to obtain a wheat straw rosin composite board.

[0019] Preferably, in step 1, the ratio of sodium hydroxide to sodium sulfite in the mixed solution of sodium hydroxide and sodium sulfite is 5:1.

[0020] Preferably, in step 3, the mass fraction of crushed block hydrogenated rosin in anhydrous ethanol is 20%.

[0021] Preferably, the mass fraction of aluminum chloride in the aluminum chloride aqueous solution in step six is ​​2%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention removes oil, ash and part of lignin in wheat straw by alkali treatment through esterification reaction of hydrogenated rosin in aluminum chloride catalysis and embedding hydrogen bonds into the interior of straw board, thereby exposing cellulose and functional groups on its surface, and subsequently introducing hydrogenated rosin, thereby effectively increasing the density of wheat straw board, enhancing the mechanical properties of the board, and enhancing the hydrophobicity and water resistance of the wheat straw board. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the SEM characterization picture of WSB and R-WSB of the present invention;

[0025] Figure 2 It is the infrared characterization curve diagram of WSB and R-WSB of the present invention;

[0026] Figure 3 The dynamic contact angle curves of WSB and R-WSB of the present invention;

[0027] Figure 4 It is a water resistance curve diagram of WSB and R-WSB of the present invention;

[0028] Figure 5 The present invention is a flow chart for the preparation of water-resistant glue-free wheat straw board impregnated with rosin at normal pressure. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] See also Figures 1 to 5 The present invention provides an embodiment: a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure, which comprises the following components by weight: wheat straw chips: 80 to 100 parts; hydrogenated rosin: 60 to 80 parts; catalyst: 5 to 15 parts; sodium hydroxide: 3 to 15 parts; sodium sulfite: 1 to 3 parts; anhydrous ethanol: 12 to 20 parts.

[0031] The catalyst is any one of aluminum chloride, hydrochloric acid and sulfuric acid, and the particle size of the wheat straw debris is 5 mm.

[0032] A method for preparing a water-resistant, glue-free wheat straw board by impregnation with rosin at normal pressure comprises the following steps:

[0033] Step 1: Wash the wheat straw and then crush it, soak the crushed wheat straw debris in a mixed solution of sodium hydroxide and sodium sulfite at 95°C for 4 hours, wherein the ratio of sodium hydroxide to sodium sulfite in the mixed solution of sodium hydroxide and sodium sulfite is 5:1;

[0034] Step 2: After vacuum filtration, place in a ventilated environment at 105°C and dry for 6 hours to obtain alkali-treated wheat straw debris;

[0035] Step 3: crush the block hydrogenated rosin, pour it into anhydrous ethanol, the mass fraction of the crushed block hydrogenated rosin in anhydrous ethanol is 20%, dissolve it at 80° C. for 1 hour, and obtain ethanol-dissolved hydrogenated rosin. The purpose of using ethanol is to dissolve the rosin;

[0036] Step 4: physically mixing the hydrogenated rosin dissolved in ethanol with the alkali-treated wheat straw debris, and stirring until the alkali-treated wheat straw debris is evenly dispersed to obtain a mixture of alkali-treated wheat straw debris, ethanol, and rosin;

[0037] Step 5: filtering the mixture of alkali-treated wheat straw chips, ethanol and rosin under reduced pressure, and drying at 80° C. for 6 hours to obtain a mixture of alkali-treated wheat straw and rosin;

[0038] Step 6: adding an aluminum chloride aqueous solution to the alkali-treated wheat straw and rosin mixture, wherein the aluminum chloride mass fraction of the aluminum chloride aqueous solution is 2%, and performing vacuum filtration;

[0039] Step seven: perform wet hot pressing at 80° C. and 15 MPa for 4 hours to obtain a wheat straw rosin composite board.

[0040] The purpose of straw washing and crushing is to remove impurities such as ash on its surface. The purpose of NaOH and Na2SO3 is to remove part of the lignin in the straw, exposing components such as cellulose, so that the hydroxyl groups (-OH) on the surface of cellulose are fully exposed.

[0041] The choice of hydrogenated rosin is based on the consideration that the stability of rosin will be improved after hydrogenation;

[0042] The purpose of adding AlCl3 is to act as a catalyst to catalyze the esterification reaction between the hydroxyl groups on the surface of cellulose and the carboxyl groups of the hydrogenated rosin molecules;

[0043] The final enhancement of board performance is firstly due to the esterification reaction of the functional groups contained in rosin and cellulose, and secondly due to the hydrogen bonds between the hydroxyl groups on the surface of cellulose.

[0044] The role of rosin is, on the one hand, to improve the bonding strength between fibers, and on the other hand, to improve the water resistance of the board.

[0045] The above-mentioned NaOH and Na2SO3 can be replaced by other alkaline substances, such as Ca(OH)2;

[0046] AlCl3 can be replaced by other acidic catalysts, such as HCl (hydrochloric acid) and sulfuric acid, which catalyzes the esterification reaction;

[0047] Wheat straw can be replaced by other woody cellulosic biomass raw materials, such as rice straw, sunflower straw, etc.

[0048] like Figure 1 As shown, the wheat straw board without rosin is marked as WSB, and the wheat straw board with rosin is marked as R-WSB. Figure 1 SEM characterization pictures of WSB and R-WSB.

[0049] like Figure 2 As shown, the infrared results showed that the rosin component and straw component of R-WSB were fully compounded.

[0050] like Figure 3 As shown, the results indicate that R-WSB is more hydrophobic than WSB.

[0051] like Figure 4 As shown, the results indicate that R-WSB has enhanced water resistance compared with WSB.

[0052] Compare the performance of WSB and R-WSB boards, as shown in the following table:

[0053]

[0054] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. Water-resistant glue-free wheat straw board impregnated with rosin at normal pressure, characterized in that: The composition comprises the following components by weight: 80 to 100 parts of wheat straw chips; 60 to 80 parts of hydrogenated rosin; 5 to 15 parts of catalyst; Sodium hydroxide: 3-15 parts; Sodium sulfite: 1-3 parts; Anhydrous ethanol: 12-20 parts.

2. The water-resistant glue-free wheat straw board impregnated with rosin at normal pressure according to claim 1, characterized in that: The catalyst is any one of aluminum chloride, hydrochloric acid, and sulfuric acid.

3. The water-resistant glue-free wheat straw board impregnated with rosin at normal pressure according to claim 1, characterized in that: The wheat straw debris has a particle size of 5 mm.

4. A method for preparing a water-resistant glue-free wheat straw board impregnated with rosin at normal pressure as claimed in any one of claims 1 to 3, characterized in that: The steps include: Step 1: Wash the wheat straw and then crush it, and soak the crushed wheat straw debris in a mixed solution of sodium hydroxide and sodium sulfite at 95°C for 4 hours; Step 2: After vacuum filtration, place in a ventilated environment at 105°C and dry for 6 hours to obtain alkali-treated wheat straw debris; Step 3: crush the block of hydrogenated rosin, pour it into anhydrous ethanol, and dissolve it at 80° C. for 1 hour to obtain ethanol-dissolved hydrogenated rosin; Step 4: physically mixing the hydrogenated rosin dissolved in ethanol with the alkali-treated wheat straw debris, and stirring until the alkali-treated wheat straw debris is evenly dispersed to obtain a mixture of alkali-treated wheat straw debris, ethanol, and rosin; Step 5: filtering the mixture of alkali-treated wheat straw chips, ethanol and rosin under reduced pressure, and drying at 80° C. for 6 hours to obtain a mixture of alkali-treated wheat straw and rosin; Step 6: adding an aqueous solution of aluminum chloride to the alkali-treated wheat straw and rosin mixture, and performing vacuum filtration; Step seven: perform wet hot pressing at 80° C. and 15 MPa for 4 hours to obtain a wheat straw rosin composite board.

5. The method for preparing water-resistant glue-free wheat straw board material by impregnation with rosin at normal pressure according to claim 4, characterized in that: In step 1, the ratio of sodium hydroxide to sodium sulfite in the mixed solution of sodium hydroxide and sodium sulfite is 5:

1.

6. The method for preparing water-resistant glue-free wheat straw board material by impregnation with rosin at normal pressure according to claim 4, characterized in that: In step 3, the mass fraction of crushed block hydrogenated rosin in anhydrous ethanol is 20%.

7. The method for preparing water-resistant glue-free wheat straw board material by impregnation with rosin at normal pressure according to claim 4, characterized in that: The mass fraction of aluminum chloride in the aluminum chloride aqueous solution in step six is ​​2%.

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