Processing method of straws and manufacturing method of straw fiber plate

Abstract

The invention discloses a processing method of straws, which comprises the steps of: (1) cutting off straws which are harvested just now into segments of 5-15 mm in length, then removing iron by a magnetic drum, and then crushing the segments into straw blocks of 5-10 in length, width and height; (2) performing microwave radiation on the straw blocks; and (3) immerging the straw blocks in water, adding hydrofluoric acid, mixing until pH is 5-6 and washing with water until the pH is 6.5-7, and then centrifuging and separating. The invention has the beneficial effects as follows: by processing the straws with microwaves, partial or all the silicon cells and suberisation cells are damaged so that the hydrofluoric acid in the acidifying step immerges into the cells to dissolve SiO2, thereby reducing content of the SiO2 in the straw fiber, improving bonding performance of the straw fiber and further improving intensity of a straw fiber plate. The straw fiber plate in the invention has dense texture; and after a saw cutting process, the straw fiber plate compared with the normal shaving board has an even, bright and clean surface and has an internal bonding intensity of 0.56-0.65 MPa, a static bending strength of 30-60 MPa, an elastic modulus of 3000-4000 MPa and a screw holding capability of the plate surface of 1600-1750 N.

Description

technical field [0001] The invention relates to a straw processing method and a straw fiber board manufacturing method. Background technique [0002] The use of crop straw to produce wood-based panels probably originated in the 1920s. At that time, the United States established the world's first bagasse fiberboard factory. After the end of the 1940s, wood-based panel factories using economic crop stalks such as bagasse, hemp stalks, and cotton stalks as raw materials have developed to varying degrees in some countries, but most of them have not, except for a few bagasse board factories and hemp chip board factories. survived for a long time. In recent years, due to the shortage of resources brought about by the increasing demand for wood and wood-based panel resources, especially more and more countries and regions have banned or restricted the burning of crop straws in order to protect the environment, which has aroused people's interest in using crop straws to manufactur...

AI Technical Summary

Problems solved by technology

After the end of the 1940s, wood-based panel factories using economic crop stalks such as bagasse, hemp stalks, and cotton stalks as raw materials have developed to varying degrees in some countries, but most of them have not, except for a few bagasse board factories and hemp chip board factories. long-term survival

[0004] Due to the characteristics of straw raw materials, there are some technical difficulties and difficulties in the actual use of the process plan of using isocyanate as adhesive and mechanically crushing straw scraps to produce particleboard or particleboard.

The surface of most straw raw materials (especially wheat straw and rice straw) is rich in waxy layer and ash (mainly composed of SiO 2 ), which brings the following technical difficulties in production: 1) it is not possible to use a chipper when preparing wood shavings

Because the wax layer and ash will increase the wear of the tool, frequent tool replacement will also increase the downtime of the production line, which will increase the production cost

2) The gluing performance of straw scraps is not good, and isocyanate adhesive must be used, but the price is higher

3) The isocyanate adhesive has no initial tack, and the integrity and continuity of the paved slab after sizing is not good, and it is prone to collapse and fall off during the transportation process, causing difficulties in transportation

In addition, due to the use of isocyanate adhesives, there is a sticking problem during the hot pressing process.

Although it can be treated with a release agent, it increases the production process on the one hand, and increases the production cost on the other hand

4) The finished board produced will also contain a small amount of wax and ash, which will increase the wear of the tools in the post-processing section and the abrasive belt of the sander, and increase the production cost

In this way, the effective fiber yield of thermal grinding is also low

Moreover, due to the complex chemical composition of straw raw materials, more complex waste will be brought in the production process.

[0006] In conclusion, since there is a layer of dense tissue on the surface of the straw, namely the epidermis, the epidermis is the outermost layer of cells of the straw, which includes almost filled SiO 2 Si cells and cork cells, while SiO 2 A non-polar surface structure is formed in the fiber, which affects the adsorption of adhesives and the formation of hydrogen bonds, reducing the strength of the board

At the same time, there is an obvious waxy layer on the surface of the straw, and the friction between the straws is small. After using the adhesive, it is difficult to enter the interior of the straw through the surface, and the ability to chemically react with the hydroxyl group is greatly reduced. The production of straw fiberboard adversely affect

[0007] A chemical-thermomechanical treatment is disclosed in WO99 / 02318, whereby an acid (or alkaline) detergent can be applied to the straw, but the result of the treatment is that the cohesion is only improved, but the unexpected stickiness is not produced. bond performance and did not produce sufficient adhesion to meet commercial standards

Chinese patent 028108183 believes that the above patent is not for SiO 2 The dissolution of SiO is 2 The modification of the dense surface layer, the patent proposes a technical solution for high-pressure steam extraction. We believe that the technical solution of WO99 / 02318 cannot dissolve the dense surface layer, and its technical solution cannot achieve the effect of dissolving the dense surface layer. To improve the cohesion of fibers, Chinese patent 028108183 mainly applies physical methods to modify the dense layer

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