A method for preparing fiberboard using hibiscus wood

Abstract

The present invention belongs to the technical field of the preparation method of fiberboard, and provides a method for preparing fiberboard by using hibiscus wood, including the preparation process of hibiscus fibers. The preparation process of hibiscus fibers includes the steps of obtaining chips, steam treatment, obtaining fibers, and adjusting the moisture content. In the step of obtaining chips, mixed chips are obtained by using hibiscus wood as raw material. The length of the mixed chips is 15 - 30 mm, the width is 5 - 10 mm, and the moisture content is less than 3%. In the step of steam treatment, the mixed chips are subjected to steam distillation to obtain distillate. In the step of obtaining fibers, the mixed chips are processed by grinding to obtain wood fibers and wood bark fibers. The moisture content of the wood fibers and the wood bark fibers is 5 - 8%, the diameter of the wood fibers is 0.2 - 0.5 mm, and the diameter of the wood bark fibers is 0.1 - 0.3 mm. In the step of adjusting the moisture content, the distillate is sprayed on the surfaces of the wood fibers and the wood bark fibers.

Description

Technical Field

[0001] The invention belongs to the technical field of methods for preparing fiberboards, and in particular relates to a method for preparing fiberboards by utilizing hibiscus wood. Background Art

[0002] Hibiscus is a woody plant that combines medicinal, edible, ornamental, greening, and fiber raw material values, and has high economic value. Hibiscus bark and hibiscus flower extracts, such as hibiscus bark extract essential oil or hibiscus flower extract essential oil, have the functions of insect-proof, deodorization, and refreshing and are applied to make various aromatherapy, or added in air purifier filters to assist in removing odors in the air and improving air quality. In addition, the hibiscus tree is easy to plant, and the yield rate is relatively high, making its resources relatively abundant and stable. It can be seen from this that the fiberboard prepared with the wood of the hibiscus tree has certain insect-proof, deodorization, and refreshing functions, and is an excellent board for processing and manufacturing indoor homes and decorative products such as wardrobes, wood veneers, floors, and wall panels.

[0003] Hibiscus wood has many advantages, but in actual production, no one has used it as a raw material to prepare fiberboard, and there are no related patents or papers. The reason is that the hibiscus tree branches are thin and the bark ratio is high. It cannot be peeled before conventional chipping, which increases the difficulty of chipping, and the bark part cannot be removed after chipping, which increases the difficulty of fiber grinding. In other words, it is difficult to obtain hibiscus fiber that meets the pressing size and conditions using the fiber preparation methods and equipment in the existing technology. Summary of the invention

[0004] The technical purpose of the present application is to overcome at least one of the above-mentioned technical problems and provide a method for preparing fiberboard using hibiscus wood.

[0005] In one aspect of the present application, a method for preparing fiberboard using hibiscus wood is provided, comprising the steps of preparing hibiscus fiber, mixing with glue, and pressing, wherein the preparation process of the hibiscus fiber includes the steps of preparing chips, steam treatment, preparing fibers, and adjusting moisture content;

[0006] In the step of preparing chips, mixed chips are obtained using hibiscus wood as raw material, wherein the mixed chips have a length of 15-30 mm, a width of 5-10 mm, and a moisture content of less than 3%;

[0007] In the steam treatment step, the mixed chips are subjected to steam distillation to obtain a distillate;

[0008] In the step of making fibers, the mixed chips are processed by grinding to obtain wood fibers and bark fibers. The moisture content of the wood fibers and the bark fibers is 5-8%, the diameter of the wood fibers is 0.1-0.5 mm, and the diameter of the bark fibers is 0.08-0.3 mm;

[0009] In the step of adjusting the moisture content, the distilled liquid is sprayed on the surfaces of the wood fibers and the bark fibers.

[0010] By the above method, by setting a steam treatment step between the step of making chips and the step of making fibers, thus: (1) The chip-making device only needs to process the branches of the hibiscus tree into relatively large-sized mixed chips (including pure wood chips and chips containing woody parts and bark parts), and there is no need to cut the branches of the hibiscus tree into smaller sizes considering the processing capacity of the grinding device. Therefore, it can effectively avoid the damage of the bark in the branches to the tools and devices; (2) After distillation treatment, the mixed chips hardly contain impurities, have fewer tyloses and inclusions, and are softened with reduced strength. Therefore, even in the case of relatively large-sized chips containing a considerable proportion of bark chips, the grinding device of the prior art can grind the mixed chips to obtain fibers in a form that meets the requirements for fiberboard pressing; (3) A distilled liquid with the functions of preventing insects, removing odors, and refreshing is extracted.

[0011] At the same time, in the step of adjusting the moisture content in the above method, the functional distilled liquid obtained in the steam treatment step is sprayed back onto the surfaces of the wood fibers and the bark fibers. Thus, on the one hand, it can appropriately adjust the too low moisture content of the mixed fibers (wood fibers and bark fibers), and on the other hand, compared with the untreated fibers, the mixed fibers sprayed with the functional distilled liquid can more easily volatilize and release functional components during the use of the fiberboard to prepare a functional hibiscus fiberboard.

[0012] In some embodiments, a distilled liquid at 55-60 °C is obtained through the steam treatment step.

[0013] In some embodiments, a first distilled liquid and a second distilled liquid with condensation temperatures of 65-70 °C and 55-60 °C respectively are obtained through the steam treatment step, and the first distilled liquid and the second distilled liquid are mixed to obtain the distilled liquid.

[0014] In some embodiments, the mixing ratio of the first distilled liquid and the second distilled liquid is (1-1.5):1.

[0015] In some embodiments, the steam treatment step includes a first distillation treatment and a second distillation treatment; after the first distillation treatment, a first distillate with a condensation temperature of 55 - 60 °C is obtained, and the mixed chips are dried to a moisture content of less than 5% before the second distillation treatment is carried out to obtain a second distillate with a condensation temperature of 65 - 70 °C; the first distillate and the second distillate are mixed to obtain the distillate.

[0016] By this embodiment, the secondary steam treatment method can promote the softening of the mixed chips during the repeated process of steam treatment - drying - steam treatment, so as to further facilitate the grinding treatment to obtain mixed fibers with a more reasonable morphology.

[0017] In some embodiments, the mixing ratio of the first distillate and the second distillate is 1:(1 - 1.5).

[0018] In some embodiments, in the step of adjusting the moisture content, the distillate is sprayed on the surfaces of the wood fibers and the wood bark fibers in the form of an atomized liquid.

[0019] By this embodiment, the fiber strength of hibiscus wood is relatively low, so the mixed fibers prepared are prone to agglomeration. The atomized distillate can be sprayed relatively evenly on the surface of the mixed fiber flocs, and can better avoid further agglomeration of the mixed fibers, thus affecting the uniformity of sizing.

[0020] In some embodiments, the spraying amount of the distillate per cubic meter of the wood fibers and the wood bark fibers is 300 - 350 g.

[0021] In some embodiments, the pressing process includes stages of pre-pressing, hot pressing and rapid cooling.

[0022] By this embodiment, when the spraying amount of the distillate reaches 300 - 350 g / m 3When using the atomization spraying method, the distilled liquid can be sprayed onto the surface of the mixed fiber flocs, making the moisture content of the fibers on the surface of the mixed fiber flocs higher than that of the internal fibers. During hot pressing, the moisture (actually the moisture in the distilled liquid) boils on the surface of the mixed fiber flocs. The steam treatment step belongs to incomplete distillation. Therefore, during the rapid cooling stage, re-distillation occurs in this part of the fibers, and the cooled distilled liquid migrates towards the interior of the mixed fiber flocs under the drive of the moisture content gradient. While the fiberboard is being pressed into shape, the functional distilled liquid formed by the pseudo-distillation treatment occurring during the pressing stage is evenly distributed throughout the fiberboard. Thus, on the one hand, the functional distilled liquid is evenly distributed throughout the fiberboard, enabling the uniform slow release of the functional components; on the other hand, the functional components are not completely volatilized due to the relatively high temperature during the pressing and cooling stages.

[0023] In some embodiments, the cooling stage is to let the fiberboard blank pass through a cold environment with a certain length in a double-sided pressing state and cool down to 55 - 60 °C.

[0024] In summary, a method for preparing a fiberboard using hibiscus wood according to the present invention can prepare a fiberboard with qualified physical and chemical properties using hibiscus wood, and this kind of fiberboard has certain functions of preventing insects, removing odors, and refreshing. Detailed implementation manners

[0025] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0026] Embodiment

[0027] A method for preparing a fiberboard using hibiscus wood includes process A. the preparation process of hibiscus fibers, process B. the glue mixing process, and process C. the pressing process. The preparation process of hibiscus fibers includes step A(a). the step of making chips, step A(b). the steam treatment step, step A(c). the step of making fibers, and step A(d). the step of adjusting the moisture content. The following specifically elaborates on each step of the preparation process of hibiscus fibers.

[0028] A(a). In the step of making chips, hibiscus wood, specifically hibiscus branches, is used as raw material to obtain mixed chips. The mixed chips consist of pure wood chips and chips that are partially wood and partially bark. The length of the mixed chips is 15 - 30 mm, and the width is 5 - 10 mm. The mixed chips are dried to a moisture content of less than 3% (bone dry state) by means of existing technology.

[0029] A(b). In the step of steam treatment, the mixed chips are subjected to steam distillation to obtain a distillate.

[0030] The step of steam treatment can remove impurities, tyloses and inclusions in the mixed chips, making the mixed chips soften and suitable for grinding devices of existing technology. This step can also extract a distillate with the functions of preventing insects, removing odors and refreshing. The method of steam distillation can be that of existing technology. For example, the mixed chips are soaked in distilled water, the distilled water is heated to boiling, and the steam generated by boiling is cooled to obtain and collect the distillate.

[0031] In Example 1, the step of steam treatment is implemented by using one - time steam distillation to obtain one kind of distillate. In other words, steam is passed through a cooling pipe, and the cooling temperature of the cooling pipe is 57 ± 2 °C, so as to obtain a distillate at 55 - 60 °C, and the distillate is filtered.

[0032] In Example 2, the step of steam treatment is implemented by using one - time steam distillation to obtain two kinds of distillates. In other words, steam is passed through two cooling pipes. The two cooling pipes can be in a series structure or a parallel structure. The cooling temperature of one cooling pipe is 67 ± 2 °C, so as to obtain a first distillate with a condensation temperature of 65 - 70 °C; the cooling temperature of the other cooling pipe is 57 ± 2 °C, so as to obtain a second distillate with a condensation temperature of 55 - 60 °C. The first distillate and the second distillate are mixed in a mass ratio of (1 - 1.5):1 to obtain a distillate, and the distillate is filtered.

[0033] In Example 3, the step of steam treatment includes a first distillation treatment and a second distillation treatment. First, the mixed chips are subjected to the first distillation treatment, and the cooling temperature of the first distillation treatment is 57 ± 2 °C, so as to obtain a first distillate with a condensation temperature of 55 - 60 °C; then, the mixed chips are dried to a moisture content of less than 5%; then, the dried mixed chips are subjected to the second distillation treatment, and the cooling temperature of the second distillation treatment is 67 ± 2 °C, so as to obtain a second distillate with a condensation temperature of 65 - 70 °C; finally, the first distillate and the second distillate are mixed in a mass ratio of 1:(1 - 1.5) to obtain a distillate, and the distillate is filtered.

[0034] The method of secondary steam treatment can promote the softening of the mixed chips during the repeated process of steam treatment - drying - steam treatment, so as to further facilitate the grinding process to obtain mixed fibers with a more reasonable morphology.

[0035] A(c). In the step of producing fibers, mixed chips are added to the grinding device of the prior art to obtain wood fibers and wood bark fibers, that is, mixed fibers. The moisture content of the mixed fibers is 5 - 8%. Since the strengths of the woody part and the wood bark part in the mixed chips after steam treatment are different, the obtained wood fibers have a diameter of 0.2 - 0.5 mm and a length of 1.2 - 1.5 mm, and the wood bark fibers have a diameter of 0.1 - 0.3 mm and a length of 0.6 - 0.8 mm.

[0036] A(d). In the step of adjusting the moisture content, the distillate is sprayed on the surfaces of the wood fibers and the wood bark fibers. By spraying the functional distillate back onto the surface of the mixed fibers, on the one hand, the too low moisture content of the mixed fibers can be appropriately adjusted, and on the other hand, compared with the untreated fibers, the mixed fibers sprayed with the functional distillate can more easily volatilize and release the functional components during the use of the fiberboard, so as to prepare a functional hibiscus fiberboard.

[0037] There are various ways to spray the distillate. Preferably, the distillate is sprayed onto the surfaces of the wood fibers and the wood bark fibers through an atomizing nozzle, and the spraying amount reaches 300 - 350 g / m 3 . In Examples 1 - 3, the spraying amount of 320 g / m 3 is taken as an example.

[0038] In fact, the fiber strength of hibiscus wood is relatively low, so the prepared mixed fibers are prone to agglomeration, that is, the fiber diameter of the sieve is larger than the fiber diameter measured by electron microscopy. The atomized distillate can be sprayed more evenly on the surface of the mixed fiber flocs, and can better avoid further agglomeration of the mixed fibers, thus affecting the uniformity of sizing.

[0039] The device for spraying the distillate can be in any form. For the purpose of shortening the cycle and reducing turnover, preferably, a distillate spraying pipeline is added between the fiber drying pipeline and the fiber sizing pipeline of the prior art. The composition and structure of the distillate spraying pipeline are roughly the same as those of the fiber sizing pipeline, and only the glue spraying head needs to be replaced with an atomizing water nozzle. Thus, the distillate spraying pipeline can spray the atomized distillate onto the mixed fibers while the mixed fibers are tumbling and feeding.

[0040] B. The process of mixing glue can adopt the form of existing technologies, such as the aforementioned fiber glue mixing pipeline. The adhesive used is preferably an isocyanate adhesive. Under the condition that the production cost permits, a low-temperature curing isocyanate adhesive can also be used, for example, the curing temperature is 150 - 160 °C. In Examples 1 - 3, an isocyanate adhesive with a curing temperature of 180 - 200 °C is taken as an example.

[0041] C. The process of pressing can adopt the form of existing technologies, such as a continuous hot pressing line. Preferably, the process of pressing includes C(a). a pre-pressing stage, C(b). a hot pressing stage, and C(c). a rapid cooling stage. The following specifically elaborates on each step of the pressing process.

[0042] C(a). In the pre-pressing stage, a relatively low pre-pressing temperature of 60 - 65 °C and a relatively small pre-compression amount of 30 - 35% of the actual compression amount should be used. The purpose is to both achieve the purpose of pre-pressing to avoid problems caused by direct pressing and reduce the influence of the pre-pressing process on the distribution of moisture (distillate) in the mixed fiber flocs, as well as the problem that moisture (distillate) may reach the boiling point in advance before the start of the hot pressing stage.

[0043] C(b). In the hot pressing stage, the hot pressing temperature is 180 - 185 °C, and the pressing thickness is 16 mm.

[0044] C(c). In the rapid cooling stage, the fiber board blank is passed through a cold environment with a certain length in a state of double-sided pressing and cooled to 55 - 60 °C within 60 - 70 s. Specifically, the fiber board blank is conveyed on a conveyor line, with a circulating pressure belt on the front that can press on the surface of the fiber board blank. Cooling units capable of providing low temperature are provided on both the conveyor belt of the conveyor line and the back of the pressure belt. For example, a liquid nitrogen spraying device or a cold water circulation device.

[0045] Control Example

[0046] The control example prepares hibiscus fiber board by using the conventional method of existing technologies. Specifically, first, hibiscus tree branches are added to a chipping device to obtain relatively small mixed chips. The mixed chips include pure wood chips and chips that are partly wood and partly bark. The length of the mixed chips is 10 - 20 mm, and the width is 3 - 5 mm. The mixed chips are dried to a moisture content of less than 3% (absolute dry state) by means of existing technologies. Subsequently, the mixed chips are added to a grinding device to obtain wood fibers and bark fibers, and the moisture content of the mixed fibers is 5 - 8%. Limited by the processing level of the existing grinding device, among the mixed fibers, the diameter of the wood fibers is 0.8 - 1.5 mm and the length is 5.0 - 10.0 mm, and the diameter of the bark fibers is 0.6 - 1.2 mm and the length is 5.0 - 10.0 mm.

[0047] Table 1 shows the experimental data of the physical and chemical properties of the hibiscus fiberboards of Examples 1-3 and the control example, and Table 2 shows the experimental data of the functional effects of the hibiscus fiberboards of Examples 1-3 and the control example.

[0048] Table 1. Comparison Table of Physical and Chemical Properties of Hibiscus Fiberboards of Examples 1-3 and the Control Example

[0049]

[0050] Table 2. Comparison Table of Functional Effects of Hibiscus Fiberboards of Examples 1-3 and the Control Example

[0051] Group Ethanol concentration Unit <![CDATA[mg / m 3 > Example 1 0.06 Example 2 0.06 Example 3 0.08 Control example 0

[0052] The concentration of ethanol can be used to evaluate the concentration of the functional insect-proof components released by the hibiscus fiberboard. It can be found from Table 2 that when a 1 m 2 hibiscus fiberboard is placed in a 1 m 3 sealed space, the ethanol concentration of Examples 1-3 was significantly higher than that of the control example after 72 hours. This shows that the hibiscus fiberboard prepared by the technical solution of the present invention can release functional components (taking ethanol as an example) during actual use to achieve functional effects. In contrast, the ethanol concentration of the hibiscus fiberboard prepared by the method of the control example could not be detected, and it can be considered that it hardly releases functional components.

[0053] The above description is for illustration purposes and not for limitation. Many embodiments and many applications other than the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but should be determined by reference to the appended claims and the full scope of equivalents to which those claims are entitled. For the sake of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to abandon such subject matter, nor should it be considered that the applicant has not considered such subject matter as part of the disclosed subject matter of the application.

Claims

1. A method for preparing fiberboard using hibiscus wood, including the processes of preparing hibiscus fibers, mixing glue, and pressing. Characterized in that, The process of preparing the hibiscus fibers includes the steps of obtaining chips, steam treatment, obtaining fibers, and adjusting the moisture content; In the step of obtaining chips, mixed chips are obtained using hibiscus wood as the raw material. The length of the mixed chips is 15 - 30 mm, the width is 5 - 10 mm, and the moisture content is less than 3%. In the step of steam treatment, the mixed chips are subjected to steam distillation to obtain a distillate. In the step of obtaining fibers, the mixed chips are processed by grinding to obtain wood fibers and bark fibers. The moisture content of the wood fibers and the bark fibers is 5 - 8%, the diameter of the wood fibers is 0.1 - 0.5 mm, and the diameter of the bark fibers is 0.08 - 0.3 mm. In the step of adjusting the moisture content, the distillate is sprayed on the surfaces of the wood fibers and the bark fibers.

2. The method for preparing fiberboard using hibiscus wood according to claim 1, Characterized in that, A distillate at 55 - 60 °C is obtained through the step of steam treatment.

3. The method for preparing fiberboard using hibiscus wood according to claim 1, Characterized in that, A first distillate with a condensation temperature of 65 - 70 °C and a second distillate with a condensation temperature of 55 - 60 °C are obtained through the step of steam treatment, and the first distillate and the second distillate are mixed to obtain the distillate.

4. The method for preparing fiberboard using hibiscus wood according to claim 3, Characterized in that, The mixing ratio of the first distillate and the second distillate is (1 - 1.5):

1.

5. The method for preparing fiberboard using hibiscus wood according to claim 1, Characterized in that, The step of steam treatment includes a first distillation treatment and a second distillation treatment; a first distillate with a condensation temperature of 55 - 60 °C is obtained after the first distillation treatment, and the mixed chips are dried to a moisture content less than 5% before the second distillation treatment to obtain a second distillate with a condensation temperature of 65 - 70 °C; the first distillate and the second distillate are mixed to obtain the distillate.

6. The method for preparing fiberboard using hibiscus wood according to claim 5, Characterized in that, The mixing ratio of the first distillate and the second distillate is 1:(1 - 1.5).

7. The method for preparing fiberboard using hibiscus wood according to claim 1, Characterized in that, In the step of adjusting the moisture content, the distillate is sprayed on the surfaces of the wood fibers and the bark fibers in the form of an atomized liquid.

8. The method for preparing fiberboard using hibiscus wood according to claim 7, Characterized in that, The spraying amount of the distillate per cubic meter of the wood fibers and the bark fibers is 300 - 350 g.

9. The method for preparing fiberboard using hibiscus wood according to claim 7 or 8, Characterized in that, The pressing process includes stages of pre-pressing, hot pressing, and rapid cooling.

10. The method for preparing fiberboard using hibiscus wood according to claim 9, characterized in that, the cooling stage is to pass the fiberboard blank through a cold environment with a certain length in a state of double-sided pressing and cool it down to 55-60°C.

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