JPH0358889B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a nonwoven fabric for water absorption and drainage, and more specifically to a nonwoven fabric sheet with water absorption and drainage performance that is used for attachment to formwork used in concrete construction. It is.

(Prior art) Formwork used when constructing concrete structures is used to make the concrete surface more aesthetically pleasing, i.e. to remove water pock marks and air bubbles that occur on the surface that the formwork touches, to improve the durability of the concrete surface, and to improve the appearance of excess water. This affects the densification of concrete composition due to exclusion, and conventionally plywood panels and steel panels (metal foam) have been commonly used, but recently these have been used as actual construction methods for development and construction. At the same time, various attempts have been made to remove pockmarks in the concrete in contact with the formwork by attaching special materials to the formwork.

For example, in Japanese Patent Publication No. 57-42782, a hydrophilic sheet is pasted on the surface of the mold to improve mold release and increase the number of times it can be used. In the publication, a porous material is pasted on the inner surface of the formwork, a hole is made in a weir board and a porous material is pasted on top of it to release concrete and air bubbles to the outside, and surplus water is drained from the hole. It flows downward through the

Furthermore, in Japanese Utility Model Application Publication No. 62-9642, a sheet has a double structure, consisting of an outer layer structure with a dense structure that allows moisture and air to pass through, but does not allow solids such as cement particles to pass through, and an inner layer structure that has a coarse structure density. A formwork has been proposed that includes a synthetic resin plate having a group of protrusions that allow air and water coming out through the sheet to communicate with the protrusion gaps.

More recently, the special feature on ``Architectural Materials'', vol.44, No.
4, (1988) etc., it is effective to ``absorb excess water quickly, reach a certain amount in 30 minutes, and retain the absorbed water without releasing it'', so we have high hopes for super absorbent polymers. method, and a method in which a specially processed thick long-fiber nonwoven fabric is attached to a formwork and the water-absorbing effect is expected to be due to the water-absorbing power of the fibers themselves, was introduced as a water-absorbing formwork.
Thickness made of particularly highly absorbent fibers such as non-woven fabrics
A formwork with a non-woven fabric of about 0.4mm attached is explained.

On the other hand, conventional methods have been to provide fine non-water holes in the formwork as a water-permeable formwork, or to provide a water collection net or a water collection composite fiberboard between the formwork and the water-absorbing fabric; In "Building Materials" Special Feature), when excess water and air are drained from the fine drainage holes provided in the formwork, the required performance for the fiber material attached to the formwork is to allow only the water and air separated from the concrete to pass through. It is stated that a filter effect is required to keep the fine cement particles within the mold, and that it is preferable to use a special polyester fabric with high air permeability and water permeability.

(Problem to be solved by the invention) However, in our experience, there are still no fiber materials such as nonwoven fabric sheets used for drainage and water-permeable formwork as described above that are fully satisfactory, and it has not been widely used in industry. I haven't reached it yet.

This is because conventional fibrous materials such as non-woven fabrics are not smoothed, resulting in fluff, which increases adhesion to concrete during concrete placement and can only be used once, meaning it is disposable. This is probably because it is not economically acceptable.

The present invention focuses on the above-mentioned points, and by providing a suitable nonwoven fabric corresponding to these points, it has excellent water absorption and drainage performance, is highly economical, and can be easily removed from the mold frame, and can be removed several times. It is possible to use
The purpose is to improve the finish of the concrete surface.

(Means for Solving the Problems) That is, the nonwoven fabric of the present invention, which is applied to concrete formwork and is used for the above-mentioned purpose, is characterized by the fact that a fiber layer made of synthetic fibers and a synthetic fiber base fabric are bonded together by needles. After being integrated by punching, only the surface of the fiber layer is heat-processed to make it a smooth layer without fuzz, followed by an intermediate layer having a relatively coarse density made of the fiber layer and base fabric. It has a three-layer structure: a base fabric and a back layer in which the fibers exposed on the back side are integrated with the base fabric through heat treatment to form an adhesive surface, and the overall airflow rate is 2.0 to 0.5 cc/cm ² /sec. The structure has a vertical hydraulic permeability coefficient of 10 ^-2 to ^{10 -4} cm/sec, and the surface layer has small pores or fiber gaps with a pore size that does not allow the solid content of the cement paste to permeate.

To explain this in more detail below, the nonwoven fabric of the present invention is first required to have water absorbency. However, if the water absorption is too rapid, it may cause embrittlement of the concrete surface, so it is necessary to control it appropriately. Therefore, it is best to promote the breathing phenomenon by absorbing water a little earlier than the breathing phenomenon, and to prevent excess water from remaining even after the phenomenon is over. Therefore, the surface layer has a relatively dense tissue and the capillary phenomenon occurs. The water absorption rate is 2.0 to 0.5 cc/cm ² /sec, preferably 1.0 to 0.5 cc/sec.
cm ² /sec, vertical hydraulic conductivity of 10 ^-2 to 10 ^-4 cm/sec, preferably 10 ^-2 to ^{10 -3} cm/sec. Become.

In addition, it is important that the surface in contact with the concrete has a smooth surface similar to that of a film without feathers, because even if the slag (dissolved cement) that adheres to the surface dries, it can be easily removed by washing with water. be.

In this case, the needle punching method and thermal processing method are appropriately selected depending on the type of fiber used.

In addition, drainage is also an important requirement for the nonwoven fabric of the present invention, and it is especially important to drain the water slowly. Therefore, the water permeability coefficient of non-woven fabric for drain material, which is commonly used as a sheet for civil engineering, is 10 ^-1.
cm/sec, but as mentioned above, 10 ^-2 to 10 ^-4
I try to keep it to cm/sec.

Furthermore, since the surface layer with a dense structure and the middle layer with a coarse structure play the role of drainage, there is no need for a separate sheet-like material or a synthetic resin board with protrusions or grooves for drainage.

Furthermore, in the nonwoven fabric of the present invention, it is also considered to avoid the permeation of cement particles, so that pores or interfiber voids are maintained in the surface layer, but solid particles of cement are generally distributed in the range of 100μ to 40μ. When it becomes a slurry, the size of the condensed particle agglomerates increases, so the pores or interfiber voids are 10 μm.
Hereinafter, an average value of several tens of microns is sufficient.

(Function) When using the nonwoven fabric of the present invention as described above by pasting it on a concrete formwork with an adhesive through its adhesive back layer, the water absorption rate can be controlled by selecting the airflow rate and water permeability coefficient, and the water absorption rate can be maintained at a slow rate. The surface layer of the nonwoven fabric absorbs water while avoiding penetration of cement particles.

The absorbed water is drained vertically within the nonwoven fabric toward the bottom of the formwork, but due to the water permeability coefficient, the water is drained at a slow speed.

Furthermore, at this time, the nonwoven fabric also functions as a filtering medium, so even if there are a small amount of cement particles in the water absorbed through the surface layer, they will be filtered by the intermediate layer, and the water drained will be clear water.

In addition, when pasting onto the formwork, the smooth, fluff-free surface will be in contact with the concrete surface, making it easy to remove from the mold, and even if the slag attached to the surface dries, it can be easily washed with water. It is removable and can be used several times.

(Embodiments) Hereinafter, embodiments of the present invention will be described with further reference to the accompanying drawings.

FIG. 1 is a partial cross-section of a nonwoven fabric according to the present invention. In the figure, 1 is a needle-punched intermediate layer consisting of a fiber layer 2 made of synthetic fibers and a synthetic fiber base fabric 3, and 4 is the surface side of the intermediate layer 1. The surface layer 5 is smoothed by heat processing, and 5 is the back layer made by heat treating the fibers produced by needle punching on the base back surface of the intermediate layer 1. Show each.

Various types of fibers such as nylon, polyester, and polypropylene fibers can be used as the synthetic fibers forming the synthetic fiber intermediate layer 1, but the most practical ones include a polypropylene fine denier short fiber layer and a polypropylene flat thread fabric. An example is a combination with a base fabric. In this case, the short fibers may be ordinary polypropylene fibers or fibers with a low melting point, such as a core made of ordinary polypropylene and a sheath made of low melting point polyester or polypropylene, each of which is suitable for thermal processing. By performing the steps accordingly, the desired structure can be obtained.

Therefore, when creating a nonwoven fabric having the above structure, the fiber layer 2 and the base fabric 3 are integrated by needle punching, and then the surface fibers are melted by thermally processing the surface of the fiber layer. It is obtained by partially smoothing the fabric to a film-like state to form the surface layer 4, and on the other hand, the fibers exposed on the back surface are integrated with the base fabric by heat treatment to form the back layer 5.

In this case, thermal processing of the surface is performed using processing methods such as sliding contact on a hot plate or infrared heating.
This is done by heat treatment at a temperature of around 200℃ for a few seconds to several tens of seconds.On the other hand, the heat treatment on the back side is usually done by burning the base fabric and creating a state where the base fabric is integrated and no peeling occurs. If possible, it is sufficient.

The features of each layer will be further described below.

(b) Surface layer 4: The surface of the needle-punched intermediate layer 1 is partially formed into a smooth layer similar to a film and without fuzz by the above-mentioned thermal processing, and this surface layer usually has small holes. Alternatively, the fiber gaps are set to a size that does not allow the solid content of the cement paste to pass through, and has appropriate air permeability and water permeability.

However, these small holes or fiber gaps are punched to prevent internal fiber fuzz from coming out even when the nonwoven fabric is used several times.

(b) Intermediate fiber layer 1: The fiber layer 2 is integrated with the base fabric 3 by needle punching, and communicates with the above-mentioned small pores or fiber gaps in the surface layer to absorb water by capillary phenomenon. It's becoming like that.

Then, this absorbed water is permeated in the horizontal direction of the nonwoven fabric and drained, and the base fabric 3 also plays a role in this drainage.
This intermediate fiber layer 1 also has a cushioning function that receives concrete surface pressure.

In addition, when needle punching the fiber layer 2 and the base fabric 3, do not punch from the back side of the base fabric 3, but only from the fiber layer 3 side, taking into consideration the type, depth, and number of needles used. is valid.

In addition, the base fabric 3 only needs to have sufficient tensile strength to withstand the forces applied during the nonwoven fabric production process, as well as sufficient tensile and tear resistance when using formwork. Tissue fabrics are used in practice.

(c) Back layer 5: The fibers of fiber 2 needle-punched against base fabric 3 pass through the base fabric and come out on the back side,
By heat-treating it, a back layer that is integrated with the base fabric surface is formed. Then, apply an adhesive or the like to this to adhere it to the formwork.

Thus, the nonwoven fabric of the present invention is formed by the three-layer structure consisting of each layer as described above, and this nonwoven fabric usually has a basis weight of 300 to 800 g/m ² , a thickness of around 1 mm, and has a high air permeability for use in concrete formwork. is 2.0~0.5
cc/cm ² /sec, preferably 1.0 to 0.5cc/cm ² /sec,
It has a vertical hydraulic conductivity of 10 ^-2 to 10 ^-4 cm/sec, preferably 10 ^-2 to ^{10 -3} cm/sec.

Of course, these values are not critical, but our experiments have shown that it is extremely effective to have values within the above range from the viewpoint of water absorption rate and the risk of carrying cement particles.

Figure 2 shows an example in which a nonwoven fabric with the above structure is attached to a concrete formwork, and the small holes 7
The back surface of the non-woven fabric is attached as an adhesive surface to the inner surface of the concrete formwork 6 having an adhesive.

In this case, when compacting the concrete, the air bubbles that emerge from the concrete 8 due to the breathing phenomenon flow from the surface layer 4 into the intermediate layer 1 as shown by the arrow, without passing through the cement particles. Formwork 6 through the upper and back layer
It is discharged through the small hole 7 of.

On the other hand, water separated from the concrete during concrete compaction flows into the nonwoven fabric intermediate layer 1 through the surface layer 4, is absorbed by the intermediate layer 1, and is drained downward as shown by the arrow. Furthermore, the air bubbles and water are discharged downward at a leisurely pace depending on the ventilation amount and hydraulic permeability coefficient. Therefore, after the concrete has hardened, the formwork surface is finished beautifully without leaving any water pock marks or air bubbles due to excess water.

In fact, as described above, when the nonwoven fabric of the present invention was adhered to a formwork and used on a vertical surface of concrete, clean water slowly drained downward, and when the formwork was removed after the concrete had solidified, the mold removal was completely smooth. Although solidified slag was attached to the surface layer, it was easily removed by washing with water. Furthermore, there was no problem in attaching the nonwoven fabric to the formwork, and of course the surface of the concrete was smooth and dense, and its strength fully met the expected values.

(Effects of the Invention) As described above, the present invention consists of three layers: a smooth surface layer, a relatively low-density intermediate layer, and a back layer, and has a specified range, air permeability, and vertical permeability coefficient as a whole. The smooth surface layer prevents the inflow of cement particles and prevents the water and air that float up due to the breathing phenomenon to flow slowly into the intermediate layer by moderately suppressing the water and air at a not too fast speed. Filtered through layers, even if some particles are mixed with cement,
This is captured and slowly drained as clear water to the outside along with the air, preventing the concrete surface from becoming brittle due to the high rate of water absorption, not only maintaining the required strength on the concrete surface, but also creating a smooth surface. Since it comes into contact with the concrete surface, it has the remarkable effect of increasing the smoothness and density of the concrete surface and giving it a good external finish.

In addition, since the above-mentioned smooth surface layer is in contact with the concrete surface, it is completely easy to release the mold, and even if the slag attached to the surface dries, it is easily removed by washing with water.
It can withstand multiple uses, is highly economical, and the surface layer is finely needle-punched and heat-treated, so no matter how many times you use it, the fibers will not come out from inside as fuzz, and it is even more durable than the base fabric. It has various advantages such as the fact that the fiber layer and the fiber layer are integrated and there is no risk of delamination occurring when the mold is removed, and its practical effects as a nonwoven fabric for concrete formwork are extremely large.

The nonwoven fabric of the present invention is light in both the fiber layer and the base fabric, has a total thickness of 1 mm, and has a basis weight of about 800 to 300 g/ ^m2 , and is easy to attach to the formwork. as 500~1000
It costs only yen/m ² and is economically effective.

[Brief explanation of drawings]

FIG. 1 is a partial side sectional view of a nonwoven fabric according to the present invention;
FIG. 2 is a partial explanatory diagram of the nonwoven fabric applied to a concrete formwork. 1... Intermediate layer, 2... Fiber layer, 3... Base fabric, 4
...surface layer, 5...back layer.

Claims (1)

[Claims] 1 A non-woven fabric to be attached to concrete formwork, in which a fibrous layer made of synthetic fibers and a synthetic fiber base fabric are integrated by needle punching, and then only the surface of the fibrous layer is thermally processed. A smooth surface layer without fuzz, followed by an intermediate layer with relatively low density consisting of the fiber layer and the base fabric, and the fibers exposed on the back side of the base fabric are integrated with the base fabric surface by heat treatment. It consists of three layers, including an adhesive surface and a surface layer, with an overall airflow rate of 2.0 to 0.5 cc/cm ² /sec,
1. A nonwoven fabric for water absorption and drainage, characterized in that the vertical hydraulic conductivity is 10 ^-2 to ^{10 -4} cm/sec, and the surface layer has small pores or fiber gaps that do not allow solid content to pass through the cement paste.