Formwork sheet and formwork

Abstract

To provide a formwork sheet capable of significantly improving durability and quick drying properties, and a formwork to which the formwork sheet is attached.SOLUTION: A formwork sheet 10 is formed by thermal compression bonding a water absorption layer 11, which is a nonwoven fabric sheet made of polypropylene that has been hydrophilically treated with a thermal crosslinking hydrophilic agent and has the function of absorbing excess water in the fluid concrete mixture, and a mixture drainage layer 12, which is a nonwoven fabric sheet of a mixture containing at least polyester and has the function of discharging to the outside the excess water in the fluid concrete mixture absorbed by the water absorption layer 11 and the function of retaining cement fine particles of the fluid concrete mixture.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a form sheet and a form, and more particularly to a form sheet that is attached to the surface of a form used when pouring concrete, and a form with the form sheet attached to its surface. [Background technology]

[0002] When pouring concrete to produce a concrete structure, for example, a fluid concrete mixture is poured into a space surrounded by multiple fixed formwork sheets spaced apart from each other, and after waiting for the concrete mixture to harden in this state, the formwork is removed (removed from the mold), exposing the hardened concrete mixture as a concrete structure. If the excess water in the fluid concrete mixture before hardening is not drained to the outside during this concrete pouring, pinholes and pockmarks (air bubbles) will appear on the surface of the produced concrete structure.

[0003] Therefore, in order to drain excess water in the concrete mixture to the outside, formwork sheets or formwork have been disclosed in which a formwork sheet is attached to the concrete side surface of the formwork and the excess water in the concrete mixture is drained to the outside through the formwork sheet (see, for example, Patent Document 1).

[0004] The formwork sheet described in Patent Document 1 is composed of a laminate of sheet-shaped water absorption layer and drainage layer, and the back surface of the drainage layer is attached to the formwork so that the surface of the water absorption layer is in contact with the concrete. According to the formwork sheet described in Patent Document 1, the water absorption layer has a function of absorbing excess water in the poured concrete mixture and discharging it to the drainage layer, and the drainage layer has a function of taking in excess water in the concrete mixture discharged from the water absorption layer and discharging it to the outside, and a function of retaining cement particles in the concrete mixture, and is characterized in that the water absorption layer is a polyethylene (PE) nonwoven fabric sheet that has been hydrophilically treated with a thermal crosslinking type hydrophilic agent.

[0005] According to the formwork sheet described in Patent Document 1, when it is time to remove the formwork, the formwork sheet can be peeled off extremely easily from the surface of the hardened concrete structure without using a release agent. As a result, there is no need to provide a release layer on the surface of the formwork sheet or to remove any release agent remaining on the surface of the poured concrete structure, and work efficiency can be significantly improved compared to conventional methods. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-100096 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the form sheet described in Patent Document 1 has a problem in that the durability of the water absorption layer is low, and the form sheet can be reused only a limited number of times.

[0008] Also, the above-mentioned form sheet has been disclosed as having a drainage layer in the form of (1) a nonwoven fabric sheet in which a sheet-like absorbent nonwoven fabric and a core-sheath nonwoven fabric sheet are integrated by needle punching, and (2) a three-layer laminate structure in which a core-sheath nonwoven fabric sheet or a polypropylene or polyester nonwoven fabric sheet is laminated on top of a sheet-like absorbent nonwoven fabric, and a sheet-like polyethylene resin layer is laminated on top of that. However, the drainage layers of these structures take a long time to sufficiently dry the excess water in the concrete mixture that is taken in from the water absorption layer and discharged to the outside, so that the entire form sheet is difficult to dry and remains wet for a long time, especially in winter when it is in a low-temperature environment or when there is rainfall, causing problems.

[0009] For example, in construction work, there are cases where a concrete structure is dismantled from a formwork the day after concrete is poured, and in such cases, both the formwork sheet and the concrete structure are not completely dry and are dismantled while still containing moisture. As a result, the surface of the concrete structure is pulled together with the formwork sheet by the facing boards and joint bars, causing the dismantling, and there is a problem that defects and pinholes are generated on the surface of the poured concrete structure.

[0010] The present invention has been made in consideration of the above points, and has an object to provide a form sheet that can significantly improve durability and quick-drying properties, and a form to which the form sheet is attached. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the formwork sheet of the present invention has a structure in which an absorbent layer which is a nonwoven fabric sheet that has been hydrophilically treated with a thermally crosslinking hydrophilic agent and has the function of absorbing and discharging excess water in a fluid concrete mixture, and a sheet-like mixture drainage layer which has the function of discharging to the outside excess water in the fluid concrete mixture absorbed and discharged by the absorbent layer and the function of retaining the cement fine particles of the fluid concrete mixture are laminated by thermocompression, and is characterized in that the absorbent layer is a nonwoven fabric sheet made of polypropylene, and the mixture drainage layer is a nonwoven fabric sheet of a mixture containing at least polyester.

[0012] In addition, in order to achieve the above-mentioned object, the formwork of the present invention is a formwork consisting of a formwork body and a formwork sheet attached to the surface of the formwork body, wherein the formwork sheet has a function of absorbing and discharging excess water in the fluid concrete mixture when in contact with the fluid concrete mixture, and is characterized in that it has a structure in which a water absorption layer which is a nonwoven fabric sheet of polypropylene that has been hydrophilically treated with a thermally crosslinking hydrophilic agent, and a drainage layer which is a nonwoven fabric sheet of a mixture containing at least polyester, which has a function of discharging to the outside the excess water in the fluid concrete mixture that has been absorbed and discharged by the water absorption layer and a function of retaining the cement fine particles of the fluid concrete mixture, are laminated by thermocompression. Effect of the Invention

[0013] According to the present invention, the number of times that formwork sheets can be reused can be significantly increased, and even when the formwork sheets are used in winter or in rainy conditions that make them difficult to dry and then dismantled in a short period of time, defects and pinholes that can occur on the surface of a poured concrete structure can be significantly reduced or eliminated compared to conventional methods. [Brief description of the drawings]

[0014] [Figure 1] 1 is a structural cross-sectional view of one embodiment of a formwork sheet according to the present invention. FIG. [Diagram 2] FIG. 1 is a schematic diagram of an example of a thermocompression bonding device used in producing a form sheet of the present invention. [Diagram 3] 1 is a cross-sectional view of one embodiment of a formwork according to the present invention during concrete pouring. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Next, an embodiment of the present invention will be described with reference to the drawings.

[0016] Fig. 1 shows a structural cross-sectional view of one embodiment of the form sheet according to the present invention. In the figure, the form sheet 10 of this embodiment is a sheet-like laminate in which a polypropylene water absorption layer 11 and a mixture drainage layer 12 for draining moisture from the polypropylene water absorption layer 11 to the outside are laminated.

[0017] The polypropylene water absorption layer 11 is a polypropylene nonwoven fabric sheet that has been hydrophilically treated with a thermal crosslinking hydrophilic agent, and its surface comes into contact with the concrete mixture before hardening, absorbs excess water (moisture) in the concrete mixture, and discharges it from its back side to the mixture drainage layer 12. The polypropylene water absorption layer 11 is characterized by its excellent durability compared to polyethylene, its resistance to scratches and wrinkles, and its resistance to tearing. In addition, it is resistant to heat and does not shrink easily, and is therefore less susceptible to deterioration due to sunlight.

[0018] In addition, the polypropylene water absorption layer 11 has a smoothing function that makes the surface of the concrete structure obtained when the concrete mixture that comes into contact with its surface hardens smooth and free of fraying, and a peeling function that allows the hardened concrete structure to be easily peeled off without sticking even without the use of a release agent when demolding.

[0019] Compared with the polyethylene used in the water-absorbing layer of Patent Document 1, polypropylene has excellent strength, a high melting point, and is environmentally friendly in that it does not generate toxic gases. In addition, polypropylene nonwoven sheets have a hard surface and excellent abrasion resistance, are easy to bend, are scratch-resistant, lightweight, water-resistant, and inexpensive. Furthermore, they are excellent in mechanical strength, such as tensile strength, impact strength, and compression strength, and in heat resistance.

[0020] As described above, the polypropylene water absorption layer 11 has excellent durability, so it is less likely to get scratched or wrinkled on the surface when dismantled, and is less likely to tear. In addition, it has excellent heat resistance, so it is less likely to shrink due to heat from sunlight, etc. Therefore, the form sheet 10 using the polypropylene water absorption layer 11 can be reused significantly more times than before (about 1.5 to 2 times more than before).

[0021] The polypropylene water absorption layer 11 is a sheet-like film obtained by subjecting a polypropylene nonwoven fabric sheet to a hydrophilic treatment using a thermal crosslinking hydrophilic agent, and then dissolving it during thermocompression bonding with the composite drainage layer 12 described below. The above hydrophilic treatment is a treatment to reduce the hydrophobicity of the polypropylene nonwoven fabric sheet and provide sufficient water absorption for practical use, since the polypropylene nonwoven fabric sheet is hydrophobic and does not easily absorb and pass excess water in the concrete mixture.

[0022] The hydrophilic treatment is a treatment method in which the surface of a polypropylene nonwoven fabric sheet is coated with a hydrophilic treatment solution by impregnating the surface with the hydrophilic treatment solution prepared by diluting a hydrophilic agent with water or by applying the hydrophilic treatment solution by spraying. As the hydrophilic agent, for example, a thermally crosslinked hydrophilic agent made of a commercially available nonionic silicone polymer can be used. By the hydrophilic treatment using the thermally crosslinked hydrophilic agent, the polypropylene nonwoven fabric sheet is polymerized by a crosslinking reaction caused by heat, resulting in a net-like molecular structure that is insoluble in water, which becomes entangled with the fibers of the nonwoven fabric sheet and is less likely to flow out.

[0023] Next, the composite material drainage layer 12 will be described. The composite material drainage layer 12 quickly drains excess water in the concrete mixture that is input through the polypropylene water absorption layer 11 to the outside of the formwork sheet 10, and at the same time has the drainage and water retention properties to adequately retain the fine cement particles in the concrete mixture, and is particularly characterized by its quick-drying properties, diffusing and evaporating water in a short time.

[0024] The composite drainage layer 12 is a nonwoven fabric sheet of a mixture of polyester, which is a mixture of polyethylene terephthalate and polyethylene terephthalate copolymer, and a small amount of additives such as oils, and has excellent quick-drying properties that allow moisture to diffuse and evaporate in a short time. Therefore, according to the formwork sheet 10 of this embodiment having the composite drainage layer 12, even if it is used in winter or in rainy conditions where it is difficult to dry, and is dismantled in a short time, such as the day after pouring concrete, defects and pinholes that may occur on the surface of the poured concrete structure can be significantly reduced or prevented compared to conventional methods. Note that the drainage layer 12 is also preferably hydrophilized with a thermal crosslinking hydrophilic agent, like the water absorption layer 11.

[0025] Next, a method for producing the form sheet 10 of this embodiment will be described. The form sheet 10 of this embodiment is produced by thermocompression bonding a water absorption layer 11 made of polypropylene and a drainage layer 12 made of a mixture.

[0026] 2 is a schematic diagram of an example of a thermocompression bonding device used to produce the form sheet 10. As shown in the figure, the thermocompression bonding device 20 is composed of a heat roller 21 and a resin roller 22 arranged closely opposite each other and rotating in the same direction. Meanwhile, the first nonwoven fabric sheet A made of hydrophilically treated polypropylene described above, which has a constant width and is long, is unwound from an unwinder (not shown) and moved by a first moving means (e.g., a belt conveyor) in a direction perpendicular to the width direction to enter between the heat roller 21 and the resin roller 22.

[0027] At the same time, a long second nonwoven fabric sheet B made of the above-mentioned mixture with a constant width is unwound from an unwinder (not shown), moved in a direction perpendicular to the width direction by a second moving means (e.g., a belt conveyor), laminated on the first nonwoven fabric sheet A, and then enters between the heat roller 21 and the resin roller 22.

[0028] 2, the heat roller 21 and the resin roller 22 press the entering laminated sheet of the first nonwoven fabric sheet A and the second nonwoven fabric sheet B, and heat the first nonwoven fabric sheet A in contact with the heat roller 21 side to melt it and make it into a sheet-like film, which is then fused (thermocompression bonded) to the second nonwoven fabric sheet B, producing a laminated sheet C in which the two are thermocompression bonded together. Therefore, the laminated sheet C has a structure in which a sheet-like film is thermocompression bonded onto the second nonwoven fabric sheet B.

[0029] Next, the laminated sheet C of the sheet-like film and the second nonwoven fabric sheet B output from between the heat roller 21 and the resin roller 22 is moved by a third moving means (e.g., a belt conveyor) not shown, and is cut to a desired size by, for example, a cutting device not shown, to produce a form sheet. The produced form sheet is the form sheet 10 having the structure shown in FIG. 1, in which the sheet-like film of the laminated sheet C corresponds to the polypropylene water absorption layer 11, and the second nonwoven fabric sheet B corresponds to the mixture drainage layer 12. Note that, instead of the heat roller 21 and the resin roller 22, a known heat roll press machine that heat-seals both the front and back sheets of the input laminated sheet can also be used.

[0030] Next, the formwork of the present invention will be described. Fig. 3 shows a cross-sectional view of one embodiment of the formwork of the present invention during concrete pouring. In the figure, the formwork 30 of this embodiment is composed of a formwork main body 31 and a formwork sheet 32 ​​attached to the surface of the formwork main body 31 by means of adhesion or the like. The formwork sheet 32 ​​is the formwork sheet of the present invention, and is the formwork sheet 10 having the structure of Fig. 1.

[0031] In FIG. 3, the back surface of the mixed material drainage layer 12 of the form sheet 10 (i.e., the surface opposite to the polypropylene water absorption layer 11) is attached to the surface of the form body 31 by means of adhesion or other means. Before concrete is poured, the surface of the polypropylene water absorption layer 11 of the form sheet 10 faces the space, and no release layer made of a release agent is formed. In other words, in the form sheet and form of the present invention, no release agent is used on the surface of the form sheet 32 ​​(10). However, a release agent may be used.

[0032] When pouring concrete, first, a fluid concrete mixture is filled into a desired closed space surrounded by a plurality of formwork 30 with formwork sheets 32 attached to the surface of the formwork body 31, with the formwork sheets 32 facing each other at a distance. As a result, as shown in FIG. 3, the concrete mixture 41 is pressed against the surface of the polypropylene water absorption layer 11 of the formwork sheet 32 ​​(10). In this state, excess water contained in the concrete mixture 41 passes through the polypropylene water absorption layer 11 and enters the mixture drainage layer 12 as shown by the arrow 42 in FIG. 3, and is further discharged from the mixture drainage layer 12 to the outside of the formwork 30 by its own weight, and the hardening of the concrete mixture 41 progresses. In addition, the cement fine particles contained in the concrete mixture 41 are appropriately held in the mixture drainage layer 12.

[0033] Then, after waiting for the concrete mixture 41 to harden, the hardened concrete mixture 41 is removed (demolded) from the formwork 30 to expose the concrete mixture 41 as a concrete structure. At this time, the polypropylene water absorption layer 11 in contact with the concrete mixture 41 of the formwork sheet 32 ​​(10) is far superior in durability and heat resistance to conventional formwork sheets that use polyester as a water absorption layer, so that the number of times the formwork sheet can be reused is greatly increased compared to the conventional formwork sheets.

[0034] In addition, since the polypropylene water absorption layer 11 is a film-like sheet, the surface of the concrete structure is smooth and not frayed, and can be easily peeled off without sticking to the polypropylene water absorption layer 11. Therefore, in the formwork 30 of this embodiment, the formwork sheet 32 ​​(10) can be very easily peeled off from the surface of the hardened concrete structure without using a release agent when removing the formwork, and a concrete structure with a flat surface can be obtained. Therefore, according to this embodiment, there is no need to provide a release layer on the surface of the formwork sheet or to remove the release agent remaining on the surface of the cast concrete structure, and the work efficiency can be significantly improved compared to the conventional method. Moreover, in this embodiment, a concrete structure with a flat surface can be cast.

[0035] Next, the results of a comparative experiment between the form sheet and formwork according to the present invention and the form sheet and formwork described in Patent Document 1 will be described.

[0036] A test concrete form measuring 21 cm wide, 30 cm long, and 2 cm thick was prepared and concrete was poured into it. The first test concrete form had a water-absorbing layer described in Patent Document 1 that was a polyethylene (PE) nonwoven fabric sheet, and a drainage layer that was a nonwoven fabric sheet obtained by integrating a sheet-like water-absorbing nonwoven fabric and a core-sheath nonwoven fabric sheet by needle punching. When pouring concrete into this first test concrete form and removing it from the form four times (fourth reuse), it was confirmed that a tear hole of about 1 cm had occurred when observing the form sheet surface (i.e., the surface of the water-absorbing layer) of the form removed from the form after the form was removed.

[0037] In addition, after concrete was poured using the first test concrete formwork in a low-temperature winter environment, the formwork sheet was dismantled the following day and the surface of the formwork sheet was observed, revealing that pieces of undried concrete were still attached.

[0038] On the other hand, when pouring and demolding concrete was repeated seven times (seventh reuse) using the second test concrete formwork, which is the formwork of this embodiment and has the same size as the above, the surface of the formwork sheet of the demolded formwork became rough and the strength of the formwork sheet itself weakened, so the reuse was discontinued. In other words, the number of reuses was seven in this embodiment, which was a significant improvement over the number of reuses of the conventional formwork using the first test concrete formwork. However, in the case of the second test concrete formwork, some laitance had adhered to the surface of the formwork sheet after the fifth reuse, but this was scraped off with a rubber spatula and reuse was continued, and it was confirmed that it could be reused up to the seventh time.

[0039] Furthermore, after pouring concrete using the second test concrete form under the same winter environmental conditions as when pouring concrete using the above first test concrete form, it was dismantled the next day and the surface of the form sheet was observed, and no concrete pieces were found to be adhering. Furthermore, when concrete was poured using the second test concrete form at a construction site on a rainy day and then dismantled the next day, it was confirmed that no concrete pieces were adhering to the surface of the form sheet.

[0040] The present invention is not limited to the above embodiment, and for example, a hot melt resin layer may be provided as an adhesive layer to increase the adhesion between the polypropylene water absorption layer 11 and the composite drainage layer 12 without impairing the water absorption and drainage properties. In this case, for example, hot melt powder is sprinkled on the surface of the second nonwoven fabric sheet B that becomes the composite drainage layer 12, or hot melt resin is applied thereto, and the sheet is then placed between the heat roller 21 and the resin roller 22 in a state where it is overlapped with the first nonwoven fabric sheet A.

[0041] The heat roller 21 and resin roller 22 press the entering first nonwoven fabric sheet A, hot melt powder (or hot melt resin), and second nonwoven fabric sheet B in a stacked state, and heat the first nonwoven fabric sheet A in contact with the heat roller 21 side to melt it into a sheet-like film, which is then fused (thermocompressed) to the second nonwoven fabric sheet B via a hot melt resin layer made of the hot melt powder (or hot melt resin), to produce a laminated sheet C in which they are thermocompressed together.

[0042] Furthermore, the form sheet of the present invention is not limited to the form sheet 10 of the embodiment shown in Figure 1, and for example, a nonwoven fabric sheet alone having the same structure as the hydrophilically treated mixture drainage layer 12 can also be used. [Explanation of symbols]

[0043] 10, 32 Formwork sheet 11 Polypropylene absorbent layer 12 Drainage layer made of mixture 20 Thermocompression bonding equipment 21 Heat roller 22 Resin roller 30 Formwork 31 Formwork body 41 Concrete Mix

Claims

1. A water-absorbing layer is a nonwoven fabric sheet that has been hydrophilically treated with a thermal crosslinking hydrophilic agent and has the function of absorbing and discharging excess water in a fluid concrete mixture; a sheet-like mixture-made drainage layer having a function of discharging to the outside excess water in the fluidized concrete mixture that has been absorbed and discharged by the water absorption layer and a function of retaining cement fine particles of the fluidized concrete mixture; The water-absorbing layer is a polypropylene nonwoven fabric sheet, The formwork sheet, wherein the composite drainage layer is a nonwoven fabric sheet made of a composite containing at least polyester.

2. A formwork comprising a formwork body and a formwork sheet attached to a surface of the formwork body, The formwork sheet is a water-absorbing layer that is a nonwoven fabric sheet of polypropylene that has been hydrophilically treated with a thermal crosslinking hydrophilic agent and has a function of absorbing and discharging excess water in the fluid concrete mixture when in contact with the fluid concrete mixture; A formwork having a function of discharging to the outside excess water in the fluid concrete mixture that has been absorbed and discharged by the water absorption layer, and a function of retaining the cement fine particles of the fluid concrete mixture, characterized in that it has a structure in which a drainage layer which is a nonwoven fabric sheet of a mixture containing at least polyester is laminated by thermal compression.

Images