KR100293014B1 - Formwork panel and its manufacturing method_ - Google Patents

Abstract

In order to provide a formwork panel with low cost and excellent waterproofness and strength, melamine resin is applied to a wood fiber manufactured from wood chips, dried, molded into a mat, and hot pressed A 79-82% by weight wood fiber of the panel and the mesobonded wood fibers comprising 12-15% by weight of the melamine resin of the entire panel, and a density of 750-850 kg / m 3 produced a medium density fiberboard. After attaching a tego film impregnated with phenolic resin on kraft paper on the surface of the medium density fiberboard, it is used as a formwork panel.

Description

Formwork panel and its manufacturing method

& Industrial use field &

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a formwork panel and a method for manufacturing the same, and more particularly, to a concrete formwork or metal formwork panel manufactured from a medium density fiber board (hereinafter referred to as “MDF”).

& Conventional technology

As a panel for concrete formwork or metal formwork, plywood is mainly used.

As most of the materials of plywood are dependent on imports, formwork panels that use plywood are expensive to manufacture, and internationally unstable timber prices are causing fluctuations in plywood prices, making it difficult for consumers to buy. In addition, since the wood grain exists on the surface of the plywood, the surface of the structure to be constructed with this plywood formwork is not smooth. In addition, in the case of plywood bonded to the tego film, due to the wood grain present on the surface of the plywood, the adhesion state between the tego film and the plywood is weak, so that when the number of use of the formwork increases, the tego film peels off from the plywood. do.

MDF was introduced in Korea in 1979 and has been used for general furniture, musical instruments, interior decoration, office furniture, and electronics exterior materials. MDF is manufactured using raw materials such as small timbers that cannot be used as lumber among imported timbers, thinning materials that occur during forest thinning, burned wood cut during forest fires, waste materials for sawmills, and various waste materials generated at construction sites. This is inexpensive and has the advantage of recycling resources.

However, the conventional MDF bonded with wood fibers using urea resin has a weak strength and waterproofness with an average bending strength of 406 kgf / cm 2 and an expansion ratio of 7.2% (based on MDF having a thickness of 12 mm). Therefore, when it is used as a panel for concrete formwork, the swelling of the panel occurs due to contact with moisture during concrete pouring, thereby lowering the strength of the panel. In addition, the panel may be severely damaged due to the impact generated when the concrete is poured and the collision between the molds when removing the formwork. Therefore, the conventional MDF to which wood fibers are bonded using urea resin is difficult to use for applications other than furniture.

In addition, MDF for floorboards using melamine resin is produced, which has a density of 900㎏ / ㎥ or more, a bending strength of 600㎏f / ㎠ or more, and a density gradient of 90% or less, and when used as a formwork panel, Excessive weight reduces productivity on the shop floor, high flexural strength, low resistance to shock, and severe panel breakage when colliding and nailing between panels.

In order to solve this problem, an object of the present invention is to provide a formwork panel that is low cost, and can improve the surface quality of the structure to be constructed.

Another object of the present invention is to provide a panel for formwork having excellent waterproofness, strength and workability.

Still another object of the present invention is to provide a method for producing the formwork panel.

1 is a graph showing the pressure change in the frame during the manufacturing process of the formwork panel according to an embodiment of the present invention.

Figure 2 is a graph showing a change in the width of the frame during the manufacturing process of the formwork panel according to an embodiment of the present invention.

In order to achieve the above object of the present invention, the present invention after manufacturing a wood fiber (wood fiber) from a wood chip (chip), the melamine resin is applied to the wood fiber, and dried. The wood fibers were then molded into mats and thermally pressed to comprise 79-82% by weight of wood fibers and 12-15% by weight of melamine resin as a means of mutually bonding the wood fibers, A formwork panel made of a medium density fiberboard having a density of 750-850 kg / m 3, a bending strength of 500-600 kgf / cm 2, and a density gradient of 90-100% is prepared. At this time, it is preferable to attach a tego film to the surface of the formwork panel.

Hereinafter, the present invention will be described in more detail.

Wood chips are made by slicing the same species of wood with a water content of about 45% and a specific gravity of about 0.4. At this time, the length of the wood chips is preferably about 20mm. The sand, bark, iron or other foreign matter incorporated into the wood chips is sorted out and transferred to the wood fiber manufacturing process. The transferred wood chips are cooked for a period of time at high temperature, and then the wood fibers are separated by grinding with a disk rotating at high speed. The lignin, which binds the wood fibers to each other, is softened by the cooking process, so that individual wood fibers can be separated without being damaged in a subsequent wood fiber separation process. The cooking process also thermally decomposes the cellulose components present in the wood to form acetic acid, which acts to enhance the curing of the resin and the bonding force between the wood fibers in the thermocompression process. The cooking process is preferably carried out at 160-170 ° C for 3-5 minutes. If outside this temperature and time range, the above-described role of the cooking process cannot be preferably achieved.

Subsequently, a process of evenly applying the melamine resin to the separated wood fibers is carried out. The melamine resin coating process has an important effect on the waterproofness and strength of the formwork panel. Melamine resin has excellent water resistance, chemical resistance and alkali resistance, and it is harmless to human body because it hardly emits formaldehyde. In addition, it is convenient to use the curing temperature is about 105 ℃, can provide a formwork panel excellent in waterproof and strength. The solids content, viscosity and pH of the melamine resin used also affect the strength and water resistance of the formwork panel. The solid content of the melamine resin is preferably 60-70%, more preferably 64-66%. When the solid content is less than 60%, the strength of the formwork panel may be lowered, and when the solid content is more than 70%, the melamine resin coating process is not easy. The viscosity of the melamine resin is preferably 110-140cps. If the viscosity of the melamine resin is less than 110cps may take an excessive time for the subsequent drying process, the resin coating process is not easy when the viscosity of the melamine resin is more than 140cps. The pH of the melamine resin is preferably 7.4-8.4. The bearing ratio, the ratio of the weight of melamine resin to the weight of wood fibers used, also directly affects the waterproofness of the formwork panel. It is preferable that the said content rate is 12-15%. If the content rate is less than 12%, the adhesion and waterproofness of the panel and the tego film is lowered, and if the content rate is more than 15%, the dispersion of the resin becomes uneven and agglomeration between the fibers occurs. As such, when the formwork panel is manufactured from the MDF in which the aggregation of the fibers occurs, the properties of the MDF surface itself are not constant, so the wall state is not constant when the concrete is placed.

The wood fiber coated with melamine resin is introduced into the drying process via the transfer pipe. Melamine resin is more evenly coated on the surface of the wood fibers as the wood fibers move against each other within the conveying pipe. As a result, the strength and waterproofness of the formwork panel are further improved. Melamine resin is applied to the wood fibers to remove some of the water contained in the wood fibers and to carry out a drying process to have a proper water content. Cold air is passed through a radiator to raise the temperature of the air to the range of 110-140 ° C., more preferably 110-130 ° C., and then the air is used to blow-dry the wood fibers coated with melamine resin. At this time, when the temperature of the air is less than 110 ℃ can not preferably achieve a drying process, if the temperature of the air exceeds 140 ℃ may be a resin applied to the wood fibers harden. The drying process is preferably carried out to adjust the water content of the wood fibers to 11-13%, more preferably to about 12%. This moisture content has an important influence on the thickness of the board in the thermopressing process and the curing rate of the melamine resin.

The wood fibers thus dried are molded into mats having a constant weight and height using a molding machine, and then put into a hot pressing process. In the case of formwork MDF, the most important physical property after waterproofing is flexural strength. In general, the flexural strength and the water resistance are improved as the density of the panel increases, but the difference between the surface density and the middle layer density is large, and the panel tends to be easily damaged by external impact. In order to solve this problem, the present invention resets the conditions in the hot press process differently from the conventional hot press process in the MDF manufacturing process to lower the surface density and increase the middle layer density so that the conditions in the hot press process that can withstand the external impact as much as possible. Developed.

As shown in Figures 1 and 2, the thermocompression process is carried out continuously with changing pressure and distance conditions for each section in the frame. In the case of the conventional MDF (thickness 12mm) the initial pressure in the frame is 130bar in 1 section, 135bar in 2 sections, 100bar in 3 sections, 80bar in 4 sections, 50bar in 5 sections to increase the surface density to maintain the overall flexural strength. In case of formwork MDF according to the present invention, the initial pressure is given as 1 section 140-150bar, 2 sections 140-160bar, 3 sections 130-150bar, 4 sections 100-140bar, 5 sections 70-110bar and the surface density is lowered and the middle layer density To increase elasticity against external impact. The average surface density of the formwork MDF according to the present invention is suitable for 1050-1200kg / ㎥, the average middle layer density between 700-800kg / ㎥. In addition, in the case of the conventional MDF or MDF for floorboards, the density gradient is between 80-90%, in the case of the formwork MDF according to the present invention is suitable between 90-100%. Subsequently, constant pressure and temperature are maintained in sections 6-13 of the frame. At this time, since the heat is transferred from the surface layer of the mat to the middle layer to increase the temperature of the middle layer, the melamine resin is cured. Finally, the boards with the proper thickness are produced by increasing the pressure again in the 14-18 sections of the frame, and the curing of the melamine resin located in the middle layer is completed. In addition, as shown in Figure 2, by varying the width, that is, the distance of the frame through which the wood fibers pass to produce a board having a suitable thickness and strength. At this time, it is preferable that the temperature conditions are maintained at 178-182 ° C for 1-2 sections, 223-227 ° C for 3-5 sections, 225-229 ° C for 6-15 sections, and 186-190 ° C for 16-18 sections. As such, the wood fiber becomes soft due to the thermo-pressure process performed under high temperature and pressure, so that a board of an appropriate thickness can be manufactured, and the melamine resin is cured by maintaining the temperature condition of the heat pressure and the frame section, thereby providing excellent water resistance and strength. Formable MDF can be produced.

The manufactured formwork MDF is made of wood fibers and melamine resin to bond the wood fibers, the wood fiber content is 79-82% by weight of the entire board, the melamine resin content is 12-15% of the whole board It is preferable. In addition, the final thickness of the manufactured board is preferably 12 ± 0.2 mm, more preferably 12 mm. The average density of the manufactured board is preferably 750-850 kg / m 3, the middle layer density is 700-800 kg / m 3, the surface layer density is 1050-1200 kg / m 3, and the density gradient is 90-100%.

After the hot pressing process, the MDF is cut to a long width of 8 'x 16', and then cooled while temporarily stored in a cooling turner. Since the MDF from the press of the thermo-pressure process maintains a high temperature of about 90 ° C., when it is put into the polishing process as it is, the polishing surface becomes rough and the cooling process is required because it may cause warpage due to temperature variation during loading. . The surface of the cooled MDF is polished to an appropriate thickness and cut to a size of 4 '× 8' in a cutting line to complete the formwork panel platelet.

Then, the tego film is bonded to both sides of the formwork panel platelet to improve the waterproofing. The Tego film is impregnated with phenolic resin in kraft paper, and it is preferable to use a film produced by Casco, Sweden.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

& Example 1 &

Wood fibers were made from wood chips. Melamine resin was apply | coated to this wood fiber. Melamine resin-coated wood fibers were dried and molded into mats. The molded wood fibers were thermopressed under the conditions shown in FIGS. 1 and 2 to form a panel for formwork having a thickness of 12 mm and a density of 790 kg / m 3.

& Example 2 &

It carried out similarly to Example 1 except the density of the formwork panel being 816 kg / m <3>.

& Example 3 &

It carried out similarly to Example 1 except the density of the formwork panel being 833 kg / m <3>.

& Example 4 &

The density of the formwork panel was 839 kg / m 3, and the same procedure as in Example 1 was carried out except that a tego film having a weight of 0.45 mg / m 2 was attached to both sides of the formwork panel.

& Comparative example 1 &

Wood fibers were made from wood chips. Urea resin was applied to the wood fibers. Urea resin-coated wood fibers were dried and molded into mats. Molded wood fibers were thermopressed under the conditions shown in FIGS. 1 and 2 to form panels for formwork.

& Comparative example 2 &

12 mm thick plywood (manufacturer: Sungchang Corporation) was used as the formwork panel.

& Comparative example 3 &

A 12 mm thick plywood (manufacturer: Lee Gun Industry Co., Ltd.) with Tego film was used as the formwork panel.

& Comparative example 4 &

A plywood (manufacturer: Daesung Wood Co., Ltd.) having a thickness of 12 mm with Tego film attached thereto was used as a formwork panel.

& Comparative example 5 &

A Malaysian plywood (manufacturer: Merbok) having a thickness of 12 mm with Tego film was used as a formwork panel.

After measuring the properties of the formwork panel of the Examples and Comparative Examples based on KSF3200 and the results are shown in Table 1.

Density (㎏ / ㎥) Adhesive force (㎏ / ㎠) Flexural strength (㎏ / ㎠) Expansion rate (24hr) Absorption rate (%) Comparative Example 1 720 9.0 370 8.0 - Comparative Example 2 668 5.4 584 4.2 - Comparative Example 3 614 11.8 555 1.1 29.9 Comparative Example 4 634 5.5 502 5.3 16.8 Comparative Example 5 704 11.5 666 5.9 24.5 Example 1 790 9.0 480 3.7 16.8 Example 2 816 9.1 538 3.5 15.6 Example 3 833 10.6 600 2.0 10.5 Example 4 839 8.5 590 0.8 6.0

As shown in Table 1, it can be seen that the formwork panel of the embodiment is very excellent in the properties of strength, expansion rate, water absorption rate compared to Comparative Example 1 to which the urea resin is applied. In addition, the formwork panel of the embodiment can be seen that the properties, such as adhesive strength, strength, similar to or superior to Comparative Example 2-5 plywood to which the Tego film is attached, in particular, it can be seen that the expansion rate, the absorption rate is very excellent.

The present invention provides a formwork panel having excellent waterproof and strength by attaching a tego film to the surface of an MDF to which melamine resin is applied. The use of MDF is also inexpensive, saves resources and contributes to international environmental protection by replacing wood-based plywood. In addition, since the formwork panel does not have wood grain as in plywood, the surface quality of the structure manufactured during concrete work is excellent, thereby facilitating plastering work.

Claims (3)

Wood fibers, 79-82% by weight of the total panel; And The wood fibers are bonded to each other, including 12-15% by weight of melamine resin, the average density of 750-850kg / ㎥, middle layer density 700-800kg / ㎥, surface density of 1050-1200kg Formwork panel made of medium-density fibreboard with a density of 90-100% / m 3 / m 3. The formwork panel of claim 1, wherein the formwork panel has a tego film attached to a surface of which kraft paper is impregnated with phenolic resin. Manufacturing wood fibers from wood chips; Applying 12-15% melamine resin of the entire panel to the wood fibers; Drying the wood fibers to which the melamine resin is applied; Molding the dried wood fibers into a mat; And Molded wood fiber has an initial pressure of 140-150 bar for 1 section, 140-160 bar for 2 sections, 130-150 bar for 3 sections, 100-140 bar for 4 sections, 70-110 bar for 5 sections, and 178-182 for 1-2 sections. A method for manufacturing a panel for formwork comprising a step of hot pressing into a frame having a temperature of 15 ° C., 3-5 sections 223-227 ° C., 6-15 sections 225-229 ° C., and 16-18 sections 186-190 ° C.