KR20230162352A - Manufacturing method of prepreg compressed wood for 3D plastic processing - Google Patents

Abstract

A method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment includes a lumber preparation step of processing raw wood for three-dimensional plastic processing into lumber; A softening treatment step of heating the lumber; A heat compression treatment step of heat compressing 2 to 3 times the amount of voids calculated from the total dry weight of the wood; Wetting treatment step of moistening the heat-compressed wood; A three-dimensional curve processing step of processing the heat-compressed wood into a three-dimensional shape; A dimensional stabilization treatment step of treating the three-dimensional curved wood with high-pressure steam; and a three-dimensional molded product manufacturing step of obtaining a three-dimensional curved molded product of the wood.

Description

Manufacturing method of prepreg compressed wood for 3D plastic processing}

A method for manufacturing prepreg compressed wood for three-dimensional plastic processing is disclosed.

While forest decline and global warming are global problems, Korea boasts one of the world's highest forestry rates and is recognized by the United Nations as an advanced country in greening. However, Korea relies on imports from overseas for most of its wood, and its wood self-sufficiency rate is weak. The insufficient use rate of domestically produced materials is around 18%, which is a factor in preventing a virtuous cycle structure for domestic forests. In order to solve these problems, it is urgent to promote the effective use of domestic materials, focusing on unused resources such as thinning materials, and to promote healthy forest development by revitalizing domestic forestry. Wood scientists have been developing various wood use technologies. Wood is a viscoelastic material, but its tensile strain is extremely low, so curve processing is very difficult, and even if processed, it is not put to practical use due to dimensional recovery through elastic recovery.

On the other hand, general wood materials have a specific gravity of less than 1, so they have low hardness and have disadvantages such as lower hardness and durability compared to general industrial materials such as metal or plastic, but have the advantage of easy processing. Because of these advantages of wood, wood is widely used as daily necessities, but due to its weak surface hardness and high swelling and shrinkage rates in response to moisture, it may be accompanied by splitting or distortion.

The above-mentioned background technology is possessed or acquired by the inventor in the process of deriving the present invention, and cannot necessarily be said to be known technology disclosed to the general public before the application for the present invention.

Japanese Patent Publication No. 6944225 (2021.09.14.)

The purpose of one embodiment is to provide a three-dimensional processing method for wood that can be processed into a deep curved member by giving elasticity to the wood by using the property of compressed materials to recover to the original size by heat and moisture, and then subjecting the wood to shape fixation treatment. It is done.

The problems to be solved in the embodiments are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment to achieve the above object includes a lumber preparation step of processing raw wood for three-dimensional plastic processing into lumber; A softening treatment step of heating the lumber; A heat compression treatment step of heat compressing 2 to 3 times the amount of voids calculated from the total dry weight of the wood; Wetting treatment step of moistening the heat-compressed wood; A three-dimensional curve processing step of processing the heat-compressed wood into a three-dimensional shape; A dimensional stabilization treatment step of treating the three-dimensional curved wood with high-pressure steam; and a three-dimensional molded product manufacturing step of obtaining a three-dimensional curved molded product of the wood.

According to one side, the softening treatment step includes a first heating step of softening the lumber at 100 to 120 ° C. for 1 to 2 hours; and a second heating step of softening the lumber at 130 to 170° C. for 0.5 to 2 hours.

According to one side, between the wet treatment step and the three-dimensional curve processing step, a third heating step of softening the heat-compressed wood with steam for 0.5 to 1 hour may be further included.

According to one side, the dimension stabilization treatment step may be performed by treating the wood in a sealed state with high-pressure steam at 180 to 210°C.

According to one side, in the heat compression treatment step, the wood may be heat compressed so that the thickness of the wood is compressed to 50% or less.

According to one side, a thermosetting resin and a thermoplastic resin may be added in the softening treatment step or the dimensional stabilization treatment step.

According to one side, eco-friendly oil and paint may be added in the softening treatment step or the dimensional stabilization treatment step.

According to a method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment, elasticity is given to the wood by using the characteristic of the compressed material to recover to the original size by heat and moisture, and the shape is fixed after processing into a deep curved member. There is an effect that can be processed.

The effects of the prepreg compressed wood manufacturing method for three-dimensional plastic processing according to one embodiment are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

Figure 1 is a flowchart showing a method of manufacturing prepreg compressed wood for three-dimensional curve processing.
Figure 2 shows the magnitude of tensile strain and compressive strain of dry wood and steam-treated wood.
Figure 3 shows a micrograph of the cross-sectional compressed shape of softwood and the cell wall shape after pulp recovery.
Figure 4 shows a curved processing material using the compressive strain of a pine cross-sectional material.
Figure 5 shows the shape of the curved processing and fixing frame with a radius of curvature of 4 cm of broadleaf wood.
The following drawings attached to this specification illustrate a preferred embodiment of the present invention, and serve to further understand the technical idea of the present invention along with the detailed description of the invention. Therefore, the present invention is limited to the matters described in such drawings. It should not be interpreted in a limited way.

Hereinafter, embodiments will be described in detail through exemplary drawings. When adding reference numerals to components in each drawing, it should be noted that identical components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, when describing an embodiment, if a detailed description of a related known configuration or function is judged to impede understanding of the embodiment, the detailed description will be omitted.

Additionally, in describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. When a component is described as being "connected," "coupled," or "connected" to another component, that component may be directly connected or connected to that other component, but there is no need for another component between each component. It should be understood that may be “connected,” “combined,” or “connected.”

Components included in one embodiment and components including common functions will be described using the same names in other embodiments. Unless stated to the contrary, the description given in one embodiment may be applied to other embodiments, and detailed description will be omitted to the extent of overlap.

A method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment relates to the production of prepreg compressed wood for three-dimensional curve processing manufactured by a compression processing method of wood, and more specifically, rubber As an alternative to plastic products, wood, a carbon-neutral material, can be applied to a wide range of fields occupied by plastic materials as industrial materials, such as furniture materials and automobile interior materials, using a manufacturing method that allows three-dimensional curve processing of wooden materials that do not stretch. It relates to a method of manufacturing three-dimensional molded wood by manufacturing prepreg compressed wood.

Figure 1 is a flowchart showing a method of manufacturing prepreg compressed wood for three-dimensional curve processing.

Figure 2 shows the magnitude of tensile strain and compressive strain of dry wood and steam-treated wood.

Figure 3 shows a micrograph of the cross-sectional compressed shape of softwood and the cell wall shape after pulp recovery.

Figure 4 shows a curved processing material using the compressive strain of a pine cross-sectional material.

Figure 5 shows the shape of the curved processing and fixing frame with a radius of curvature of 4 cm of broadleaf wood.

Referring to FIG. 1, the method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment includes a lumber preparation step (S1), a softening treatment step (S2, S3), a heat compression treatment step (S4), and a wet lumber preparation step (S1). It may include a processing step (S5), a third heating step (S6), a three-dimensional curve processing step (S7), a dimensional stabilization step (S8), and a three-dimensional molded product manufacturing step (S9).

Specifically, in the lumber preparation step (S1), raw wood for 3D plastic processing can be processed into lumber. For example, lumber can be processed to a certain thickness.

In the softening treatment steps (S2, S3), the lumber may be heated. The softening treatment steps (S2, S3) may include a first heating step (S2) and a second heating step (S3).

In the first heating step (S2), the lumber may be heated at 100-120°C for 1-2 hours. In the second heating step (S3), the lumber may be heated at 130-170°C for 0.5-2 hours. Through these softening treatment steps (S2, S3), hard lumber can be softened.

In the heat compression treatment step (S4), the softened lumber can be heat compressed to 2 to 3 times the amount of voids calculated from the total dry weight of the wood. At this time, in the heat compression treatment step (S4), the wood can be heat compressed so that the thickness of the wood is compressed to 50% or less. Wood heat-compressed in this way may be referred to as prepreg wood. That is, the heat compression treatment step (S4) may be a step in which prepreg compressed wood is manufactured. Surface hardness or strength can be imparted to lumber by heat compression treatment.

In the wetting treatment step (S5), heat-compressed wood, that is, prepreg compressed wood, may be wet treated. Prepreg compressed wood can become saturated by, for example, immersion in water.

Between the wetting step (S5) and the three-dimensional curve processing step (S7), a third heating step (S6) may be performed, and in the third heating step (S6), the prepreg compressed wood is heated for 0.5 to 1 hour. It can be softened by steam during processing.

In the three-dimensional curve processing step (S7), prepreg compressed wood can be processed into a three-dimensional shape.

In the dimensional stabilization treatment step (S8), the 3D curve-processed wood can be treated with high-pressure steam. At this time, in the dimensional stabilization treatment step (S8), the wood can be treated with high-pressure steam at 180-210°C in a sealed state.

In the 3D molded product manufacturing step (S9), a 3D curved wood molded product can be obtained.

In addition, the method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to one embodiment is necessary due to the specificity of the tree species that is the raw material of wood. Thermosetting resins and thermoplastic resins may be used in the softening treatment step (S2, S3) or the dimensional stabilization treatment step (S8). Accordingly, three-dimensional curve processing becomes easier, dimensional stability can be improved, and strength characteristics can be provided.

In addition, the method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to one embodiment is manufactured only by physical methods without adding any chemicals, but when necessary due to the specificity of the species that is the raw material of wood, softening In the treatment steps (S2, S3) or the dimensional stabilization treatment step (S8), environmentally friendly oils and paints can be used. Accordingly, three-dimensional curve processing becomes easier, and dimensional stability, durability, and aesthetic characteristics can be improved.

The method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to the above-described embodiment involves applying a large deformation to the wood by softening the wood using high frequency or steam, and then fixing the shape using high-temperature and high-pressure steam. You can. By using this method, surface hardness and strength can be imparted to low-density, low-strength softwood by heat-consolidation, and log lumber such as thinning lumber with a thin diameter and not straight can be compressed and molded into square lumber as is. In addition, by applying this compression technology, it is possible to decorate letters and designs on the surface of wood, or to mold trays without binder by compressing laminated veneer. Furthermore, it is possible to use wood powder to mold wood into pot shapes without binder. Three-dimensional processing is also possible.

Deformation processing for wood is generally limited to compression molding processing or bending processing using the Thonet method, and rolling processing used in forming metal has been considered difficult.

Referring to Figure 2, wood can be greatly deformed by compressing the cell walls for compressive deformation, but processing is difficult due to peeling due to the composite intercellular layer for tensile deformation, so it is limited to one-dimensional bending processing on the compression side. You can. In other words, since destruction of wood occurs below a tensile strain of 1%, bending using compressive strain can be used to deform wood.

However, if it is possible to give elasticity to wood, it can be stretched by the length reduced by compression, so the method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to one embodiment involves the compressed material recovering to its original size by heat and moisture. By utilizing the properties, it is possible to subject wood to rolling processing as shown in Figure 3. Therefore, as shown in Figures 4 and 5, the method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to one embodiment involves cutting wood from a drying set material and softening and recovering it by steam. After processing into a deep curved member, the shape is fixed, and thus the purpose of processing wood can be achieved by attempting a new three-dimensional processing method of wood. The method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to this embodiment makes it possible to mold wood materials into various shapes and simultaneously improve hardness by applying compression, making it an alternative resource for plastic. This makes it possible to effectively utilize wood.

In research so far, when wood is softened and compressed under conditions of 80 to 100°C, it recovers dimensions by absorption at room temperature, making it difficult to use in three-dimensional molding processing. Therefore, the softening conditions were used to fix the compressed wood. By approaching the temperature, it is necessary to obtain fluid prepreg compressed wood that does not cause recovery under weak conditions. Additionally, because this processing is performed by stretching wood set in a molding jig by pressing, the wood used as a raw material is required to have high elasticity and flexibility. In other words, it is necessary to develop materials with a certain level of strength to prevent cracking during the stretching process by stretching greatly with weak force, and examining the optimal manufacturing conditions to obtain them. Once this condition is clarified, curved wood products with dimensional stability and hardness can be manufactured by providing a three-dimensional molding and processing method for the target wood.

In one embodiment of the method for manufacturing prepreg compressed wood for three-dimensional plastic processing, prepreg compressed wood is manufactured under various temperature and time conditions using cedar (Cryptomeria japonica), which has a low density and is easy to compress, and is tensioned. By measuring strength, elongation, and bending strength tests, each physical property was measured, and the purpose was to establish manufacturing conditions that could obtain prepreg compressed wood optimal for three-dimensional molding processing.

This method is an unprecedented wood processing method using wood molding. To establish this method, the development of elastic and flexible prepreg compressed wood that provides optimal physical properties for three-dimensional molding and the identification of optimal wood softening conditions were required. need. In this study, prepreg compressed wood was manufactured using cedar wood under various temperature and time conditions and its mechanical properties were investigated.

Experiment example

1. Disclosure materials

Square lumber cut from cedar logs with a diameter of 400 mm or more, avoiding cutting, so that L (fiber direction) × T (tangential direction) × R (radial direction) = 500 used.

2. Wood compaction

2.1 Compression under various temperature conditions

The compression of the wood was performed using a compression molding device and following the wood compression molding method using steam treatment. The cedar wood used as the raw material was loaded so that the sapwood part was at the bottom, and compression was performed in the radial direction. In order to avoid that only the surface temperature rises due to rapid temperature increase, steaming at 110°C for 2 hours was performed as a preliminary softening treatment prior to treatment under each set temperature condition. At this time, the temperature increase rate was about 10°C/min. After that, water vapor was introduced to raise the temperature inside the device to each set temperature. The set temperature was in the range of 100°C to 180°C, and after reaching the set temperature, steaming was performed for 1 hour as the main softening treatment. After treatment, pressing was performed, and cedar with a density of about 0.3 was compressed to a target density of 0.6 g/cm3 or more. Immediately after, water vapor was discharged from the device, the press was left overnight to cool, and then the prepreg compressed wood was taken out.

2.2 Compression under various softening time conditions

The preliminary softening time was examined using the optimal softening treatment temperature conditions derived from compression. The compression method was performed by setting the preliminary softening times to 1 hour, 2 hours, and 3 hours, respectively. The temperature of the preliminary softening treatment was 110°C, the temperature of the main softening treatment was the temperature optimally derived from the above test, and the treatment time was 1 hour.

2.3 Measurement of physical properties

2.3.1 Measurement of tensile strength and elongation

In order to evaluate the suitability for use in three-dimensional processing, the tensile strength and elongation of prepreg compressed wood were measured. The measurement was performed by applying a load in the R direction using a universal strength tester. From the prepreg compressed wood obtained above, a plate with a thickness of about 3 mm was cut from the RL surface, dried naturally, and then cut into rectangles of 15 mm in the L direction and 50 mm in the R direction as test specimens in an air-dried state. In addition, test specimens in a wet state were those that were immersed in distilled water at room temperature for more than 30 minutes immediately before measurement. These test specimens were set in a universal strength tester, and the loading speed was measured at 10 mm/min. The maximum load and extended length when the sample was broken were measured, and the elongation, recovery, and transverse tensile strength were measured.

2.3.2 Bending test

A 15 mm thick plate was cut from the prepreg compressed wood and untreated wood on the RL surface, air-dried at room temperature (moisture content approximately 10%), and then cut into 10 mm wide pieces in the L direction to serve as a test specimen. The test piece was set in a universal strength tester, a load was applied in the T direction (tangential direction) at a loading speed of 30 mm/min, and a three-point bending strength test was performed.

3. Experiment results

3.1 Review of optimal molding conditions

go. Molding of prepreg compressed wood under different temperature conditions

Table 1 shows the compression rate and average density of prepreg compressed wood molded at each temperature condition. It was possible to compress up to a density of around 0.6 g/cm3 under all conditions, and there was no significant effect on the compression ratio due to temperature conditions. Materials treated at 150℃ exhibit particularly high elongation, and can be stretched to more than 1.5 times the original size even in air-dried conditions and more than twice in wet conditions. Untreated material can hardly be stretched in both air-dried and wet conditions. The elongation and recovery rates of wood treated above 160℃ are rapidly decreasing, but it is believed that this is due to shape fixation occurring as the processing conditions approach 180℃, which is the temperature used for fixing compressed wood. Additionally, it is presumed that high-temperature steam treatment causes decomposition of lignin and hemicellulose and deteriorates cell walls, thereby lowering the tensile strength of the material subjected to high-temperature treatment. Materials treated at relatively low temperatures of 100°C and 120°C exhibit slightly lower tensile strength, and there is a possibility that partially weak points may occur due to load during compression due to insufficient softening, and a large overall elongation rate cannot be obtained.

Table 1. Properties of prepreg compressed wood under various temperature conditions.

Ash treated at 150℃ shows high tensile strength and high elongation, so it is considered to be a treatment condition that does not cause deterioration due to treatment and is unrelated to dimensional fixation. The condition of 150℃ was judged to be the optimal softening treatment temperature.

me. Molding of prepreg compressed wood according to softening treatment time conditions

Table 2 shows the physical properties of prepreg wood formed after using 150°C for the main softening treatment and dividing the pre-softening time into 1 to 3 hours. In terms of tensile strength, the pre-softening time of 2 hours showed the highest value. This suggests that when the preliminary softening time is 1 hour, there is an internal load due to insufficient softening and there is variation in compression, and when the preliminary softening time is 3 hours, the processing time is excessive. Therefore, it is speculated that at the same time as material deterioration occurs, a phenomenon similar to fixation processing, such as a partial change in the crystal structure of cellulose, may occur. When preliminary softening treatment was performed for 2 hours, it showed stably high elongation and strength. In the bending test conducted when examining temperature conditions, most samples were deformed into a U shape without being destroyed. The ash from the 2-hour treatment was able to produce the greatest deformation with a high failure load, and together with the results of the tensile test, it was determined that prepreg compressed wood molded under these conditions was most suitable for three-dimensional processing.

Table 2. Properties of prepreg compressed wood according to softening time

As can be seen in Table 2, although the preliminary softening time was set to 2 hours and the main softening treatment was set to 1 hour, the results showed the highest tensile strength and the elongation rate also showed a stable high value. According to the results of the bending test, the prepreg compressed wood obtained by pre-softening for 2 hours and main softening for 1 hour has the best value, so the optimal molding conditions for prepreg compressed wood suitable for three-dimensional processing of cedar wood are It was determined under the conditions of preliminary softening at 110°C for 2 hours and main softening at 150°C for 1 hour.

The method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to one embodiment has the great advantage that wood materials, which are zero-carbon materials, can be replaced with plastic products, and is beneficial in terms of preserving the global environment and promoting low-carbon green growth of the country. It shows an effect that can greatly contribute to . The contribution of this invention is expected to be very significant in the current government policy targeting carbon 2050, and it has the advantage of providing functionality that can replace plastics.

A method of manufacturing prepreg compressed wood for three-dimensional plastic processing according to an embodiment relates to a three-dimensional molding method of wood to make wood an alternative resource to plastic. In particular, wood resources used for limited purposes are subjected to plastic processing. By enabling three-dimensional curve processing through the manufacturing process, it can be used for multiple purposes across all industrial fields, including furniture, crafts, construction, vehicles, ships, and industrial use.

A method of manufacturing prepreg compressed wood for 3D plastic processing according to an embodiment involves compressing general wood materials using a thermo-hydraulic machine without pretreatment with chemicals such as chemicals, and then producing pretreated compressed wood for 3D plastic processing. Prepreg compressed wood can be manufactured. In addition, it can be expected to process wood into free shapes and at the same time give high strength to molded products, which has the advantage of expanding the possibility of using high value-added wood as an alternative resource for plastic.

As described above, the embodiments of the present invention have been described with specific details such as specific components and limited examples and drawings, but this is only provided to facilitate a more general understanding of the present invention, and the present invention is limited to the above embodiments. This does not mean that various modifications and variations can be made from this description by those skilled in the art. For example, the described techniques may be performed in a different order than the described method, and/or components of the described structure, device, etc. may be combined or combined in a form different from the described method, or may be used with other components or equivalents. Appropriate results can be achieved even if replaced or substituted by . Therefore, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described below as well as all things that are equivalent or equivalent to the scope of the claims will be said to fall within the scope of the spirit of the present invention. .

Claims (7)

Lumber preparation step of processing logs into lumber for 3D plastic processing;
A softening treatment step of heating the lumber;
A heat compression treatment step of heat compressing 2 to 3 times the amount of voids calculated from the total dry weight of the wood;
Wetting treatment step of moistening the heat-compressed wood;
A three-dimensional curve processing step of processing the heat-compressed wood into a three-dimensional shape;
A dimensional stabilization treatment step of treating the three-dimensional curved wood with high-pressure steam; and
A three-dimensional molded product manufacturing step of obtaining a three-dimensional curved molded product of the wood;
Method for manufacturing prepreg compressed wood for three-dimensional plastic processing, including.
According to paragraph 1,
The softening treatment step is,
A first heating step of softening the lumber at 100-120°C for 1-2 hours; and
A second heating step of softening the lumber at 130-170°C for 0.5-2 hours;
Method for manufacturing prepreg compressed wood for three-dimensional plastic processing, including.
According to paragraph 1,
A method of manufacturing prepreg compressed wood for three-dimensional plastic processing, further comprising a third heating step of softening the heat-compressed wood with steam for 0.5 to 1 hour between the wet treatment step and the three-dimensional curve processing step. .
According to paragraph 1,
The dimensional stabilization treatment step is a method of manufacturing prepreg compressed wood for three-dimensional plastic processing in which the wood in a sealed state is treated with high-pressure water vapor at 180 to 210 ° C.
According to paragraph 1,
In the heat compression treatment step, a method of manufacturing prepreg compressed wood for three-dimensional plastic processing, in which the wood is heat compressed so that the thickness of the wood is compressed to 50% or less.
According to paragraph 1,
A method of manufacturing prepreg compressed wood for three-dimensional plastic processing in which a thermosetting resin and a thermoplastic resin are added in the softening treatment step or the dimensional stabilization treatment step.
According to paragraph 1,
A method of manufacturing prepreg compressed wood for three-dimensional plastic processing in which eco-friendly oil and paint are added in the softening treatment step or dimensional stabilization treatment step.

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