JPH089913B2 - Sheet for attaching formwork - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to a sheet for attaching a mold, and more particularly to a sheet capable of simultaneously improving the surface condition of cured concrete after hardening and its curing condition.

<< Prior Art >> In general, in order to improve the quality of a concrete structure, it is sufficient to minimize the water / cementation of the concrete poured during the construction. However, in order to ensure the workability at the time of placing, since excess water is usually added to concrete, it is necessary to remove water by placing it in the formwork and then compacting it.

However, since the water separated by compaction collects on the mold surface together with bubbles, patter may occur on the hardened concrete surface. This pockmark not only impairs the aesthetic appearance of the obtained concrete structure, but also causes cracking due to a section loss.

In addition, the excess water collected at the interface between the cast concrete and the formwork increases the water / cement ratio in this part,
It reduces the durability of concrete after hardening and accelerates its deterioration due to salt damage.

Such a problem remarkably occurs in a concrete structure having an inclined surface.

Therefore, as a method of solving such a problem, as disclosed in JP-A-61-274046 and JP-B-60-18629, water permeation is applied to a formwork surface which is contacted with concrete to be placed. Although a method of sticking a sheet having a water-absorbing property or a water-absorbing property has been proposed, the sheet used in such a method has the following problems.

<< Problems to be Solved by the Invention >> That is, the former method uses a woven fabric composed of a double structure of a dense structure and a coarse structure, so that excess water is drained from the time of placing concrete to the time of hardening. Then, the concrete at the interface portion is prevented from deteriorating, but there is a problem that the woven cloth becomes difficult to peel off when the woven cloth is kept in contact with the concrete for a long time. Since the woven fabric composed of this double structure has a dense layer that does not allow cement particles to pass through,
Compared with a normal woven fabric, the fabric is easier to peel off and is improved. However, since the structure is woven, the surface has irregularities, and the concrete entered the recesses, which made it difficult for the woven fabric to peel off from the concrete.

Further, in order to make the woven cloth have a high density so as not to allow the cement particles to pass therethrough, there is a problem that a high manufacturing technique is required, the manufacturing cost is increased, and the weight is increased.

Further, the woven fabric has a problem in that the fibers regularly occupy the space in the thickness direction and the plane direction due to its woven structure, so that the water passage is blocked and the drainage property is poor.

In order to make it easier to remove the woven cloth, it seems to be better to remove the sheet early before the concrete is completely hardened, but concrete curing is better under moderately wet conditions than in air. If the sheet is removed early, the curing of the concrete will be insufficient and strong concrete cannot be formed.

However, since the woven cloth has too high air permeability, it is difficult to maintain an appropriate wet state even if it is kept in contact with the concrete surface for a long time.

On the other hand, the latter method is one in which the superabsorbent polymer is interposed inside the nonwoven fabric in which the porosity of the inner part is made larger than that of the outer part, and the excess water of the cast concrete is absorbed by the superabsorbent polymer. However, there is a limit to the water absorption capacity of the superabsorbent polymer, and once the polymer absorbs water and gels, the voids in the non-woven fabric are closed and the water cannot be drained any further. The remaining problem is that sufficient surface strength of concrete cannot be obtained.

As means for solving these problems, the present inventors have considered a method of laminating a film having a fine pore having a size that does not allow solids in concrete milk to pass through and a non-woven fabric. There was a problem in durability due to insufficient strength of the film used on the surface, and a sufficient sheet for forming a frame could not be obtained.

The present invention has been made to solve the above-mentioned problems of the prior art, and can quickly drain excess water of concrete, and maintain an excessively wet state necessary for curing, and have sufficient durability. It is an object of the present invention to provide a sheet for attaching a formwork, which is capable of being easily peeled off after hardening of concrete.

<< Means for Solving the Problems >> In order to achieve the above object, in the present invention, the sheet for mold attachment includes a composite fiber composed of two or more resin components having different melting points. A sheet in which fibers are bonded by heat fusion of a low-melting point component, and one surface of the sheet has a surface of a network structure of the high-melting point component of the conjugate fiber, which has fine pores composed of the low-melting point component of the conjugate fiber. And a sheet covered with a smooth film having

<< Working >> According to the sheet having the above structure, since the film having fine pores composed of the low melting point component on the surface of the three-dimensional network structure of the high melting point component of the composite fiber is coated, water and air can pass through. However, substantially no solids in concrete milk are allowed to pass through. When pouring concrete, the micropores are surrounded by the solid content in the concrete milk, but since the pouring concrete has its own weight and this acts as a lateral pressure on the form, this pressure causes excess water to flow. It passes through the gap between the solid content of concrete milk and the membrane, enters the sheet through the fine holes, and is drained to the outside. At this time, since the inside of the sheet has a three-dimensional porous structure joined at the fiber intersections, the water passage is not blocked in any direction, and good drainage can be performed. In particular, in the thickness direction, since there is a density gradient from the surface on which the film is formed to the opposite surface, water flows quickly to the opposite surface.

When the poured concrete gradually hardens and the lateral pressure acting on the formwork decreases, the fine pores are blocked by the solid content in the concrete milk, so the drainage also decreases accordingly, and it is difficult for the concrete to harden. The necessary moisture is secured, and curing is performed in an excessively wet condition.

Further, since the smooth film made of the low melting point component of the composite fiber is in contact with the cast concrete surface, it can be easily peeled off even after the concrete is sufficiently hardened.

Incidentally, the sheet for formwork sticking of the present invention is a sheet in which fibers are bonded by heat fusion of the low melting point component of the composite fiber, and the one side of the sheet has a network structure of the high melting point component of the composite fiber. Since the surface of the sheet is covered with a film having fine pores composed of a low-melting point component, it is a firmly bonded and integrated body as a whole, such as a film obtained by laminating a film having fine pores and a nonwoven fabric. It does not peel off and has excellent durability.

<< Examples >> The present invention will be described below based on Examples.

The sheet for pasting formwork of the present invention contains a composite fiber composed of two or more resin components having different melting points. Examples of this composite fiber include polyethylene and polypropylene,
A low melting point polyester and a low melting point component such as polyester and a high melting point component are used. At the temperature at which the low-melting point component is fused, the high-melting point component needs to maintain its skeletal structure, and therefore it is desirable that the melting points of the both have a difference of 20 ° C. or more.

As the structure of the composite fiber, a low melting point component is concentrically arranged around the high melting point component, a so-called core-sheath type, an eccentric type in which the position of the high melting point component is deviated from the center, a high melting point component and a low melting point component A side-by-side type having a structure in which and are adjacent to each other is suitable. Since the low melting point component is used for bonding between fibers, it is desirable that it is exposed to the outside of the fibers, and since the high melting point component forms the skeleton of the sheet, it is desirable that it is continuous within each fiber.

In order to provide the sheet with sufficient strength and to form a film having micropores on one side of the sheet, it is desirable that the sheet contains at least 50%, preferably 70%, of the composite fiber. In addition, it is desirable that a large amount of the composite fibers be distributed on the surface forming the film in the sheet.

As a method for forming a sheet by bonding fibers by fiber adhesion, a method of using heat-fusible fibers in which the entire fibers are composed of the same component can be considered. However, in this method, the heat-fusible fiber itself does not remain as the skeleton of the sheet after being melted, so that the sheet strength becomes low when a large amount of the heat-fusible fiber is used to form a film on one side, Moreover, since the film-formed portion is not sufficiently supported by the skeleton of the fiber, a large opening is formed, or conversely, there is no opening, which is difficult to adjust, which is not suitable.

On the other hand, since the sheet of the present invention uses the composite fiber, the high melting point component remains as the skeleton of the sheet even after the heat fusion with the low melting point component, and the initially set three-dimensional network structure is maintained. Therefore, it has excellent sheet strength. In addition, since a film made of a low melting point component is formed on one side of the sheet with the skeleton of the high melting point component as a starting point, the film is firmly supported by the skeleton of the high melting point component, and the size of the micropores is also large. Easy to control.

As the fibers other than the composite fibers used for the sheet, various fibers such as synthetic fibers such as polyethylene, polypropylene and polyester, regenerated fibers such as rayon, and natural fibers such as cotton are used. In order to increase the height, it is preferable to use a fiber composed of the same component as either one of the composite fibers. In particular, polyester fibers are excellent in light resistance and may be used as the high melting point component of the composite fibers.

The above-mentioned composite fiber and fibers other than the composite fiber are made into a fibrous web by, for example, carding. The fibrous web is laminated with one or more layers.

When a plurality of layers are laminated, it is desirable to arrange a layer containing a large amount of the composite fiber on the side on which the film having fine pores is formed in order to increase the strength of the film. Further, in order to improve the smoothness of the surface, control the size of the fine pores, and provide a density gradient that enhances drainage in the sheet, a composite fiber having a small fineness is formed on the side where the film having the fine pores is formed. Is desirable. The fibrous web may be lightly entangled with a needle punch or the like for easy handling during production.

Then, this fiber web is heat-treated under no pressure to bond the fibers with the low melting point component of the composite fiber, and then one is composed of a heating roll having a smooth surface such as a steel roll and the other is composed of a rubber roll, a cotton roll, etc. By passing between a pair of elastic rolls, the low melting point component of the composite fiber is melted to form a coating film having fine pores on one surface, whereby the sheet of the present invention is obtained. At this time, a film is formed on the side that comes into contact with a heating roll having a smooth surface such as a steel roll, and the fiber layer is densified to generate a density gradient in the sheet, thereby improving the drainage property.

The heat treatment step for binding the constituent fibers in the sheet, and the heat treatment step with a heating roll for forming a smooth film having fine pores on one surface of the sheet, the order may be different in some cases. It may be reversed, or simultaneously.

The size of the fine pores formed in the film is affected by the apparent density of the fiber web, the type of low melting point component of the composite fiber, the compounding amount of the composite fiber, the heating and pressurizing conditions of the roll, and the like. It is desirable that the size is adjusted to 1 to 100 μm so that the solid content in the concrete milk does not pass through.

The obtained sheet is attached, for example, to the inner surface of the formwork before installation by using an adhesive or the like, or an appropriate place is attached by mechanical means. At this time, a smooth film having fine pores of the sheet is formed. The formed surface is placed in contact with the concrete to be poured.

When concrete is poured from the injection port of the formwork and the concrete is placed in the formwork, the concrete is compacted by the lateral pressure and vibration.

Since concrete comes into contact with the smooth membrane having fine pores of the sheet of the present invention, the fine pores are apparently plugged relatively early by the solid content in the concrete, but they were cast. Since concrete has its own weight, which acts as lateral pressure, excess water in concrete moves to the formwork side under pressure, forming voids between the solid content in concrete and the membrane, and Penetration into the sheet through the holes. The sheet has a density gradient in the thickness direction from the side where the film is formed to the opposite side, and since the fibers form a three-dimensional network structure and secure a water passage, excess water is It is quickly drained to the outside.

Then, when the poured concrete is gradually hardened and hardness is developed, the lateral pressure acting on the mold is lowered, and accordingly, the fine pores of the film are closed by the solid content in the concrete, The amount of wastewater also decreases accordingly. For this reason, the moisture necessary for hardening the concrete is secured, the contact between the concrete and the air is blocked, and curing in a wet state is performed.

Further, since the cast concrete is in contact with the surface of the sheet on which the smooth film is formed, the sheet can be easily peeled off even after the curing and the hardening of the concrete.

This makes it possible to obtain concrete in which pits do not occur on the surface of the constructed structure and which has higher strength than that when it is cured in air.

Further, since the film on the surface of the sheet is formed by melting the low melting point component of the composite fiber, it is firmly integrated with the skeleton of the high melting point component, so there is no worry of peeling, and
Even if the low-melting point component is welded, the high-melting point component maintains the initial skeletal structure, so the sheet strength is high, so there was no trouble such as tearing or peeling when laying or stripping the sheet or when handling the construction. .

(Example 1) Olefin-based composite fiber having a fineness of 0.9 denier and a fiber length of 38 mm (core-sheath type composite fiber composed of polypropylene as a high melting point component and polyethylene as a low melting point component) and 60% by weight.
After mixing 40% by weight of denier and 25% racon fiber with a fiber length of 25 mm, a fiber web having a weight of 200 g / m ² was prepared using a carding device.

Next, this fiber web was heat-treated at 150 ° C. to melt the low melting point component of the olefin-based composite fiber to obtain a bulky sheet.

This bulky sheet was passed through a calender roll, one side of which was heated to 130 ° C., to form a smooth film having fine pores on one side, and a 0.5 mm-thick formwork-sticking sheet was obtained.

This sheet was attached to one surface of the water-resistant plywood using a stapler with the smooth film surface facing up, the test form was assembled, and concrete was poured into the sheet. Drainage was observed. Also,
When the mold was removed from the mold after 4 days, it could be easily peeled off, the concrete surface was dense, and the pock ratio was 1% or less.

The pockmark ratio is obtained by observing the concrete surface by image processing and dividing the total area of the pockmark parts by the measurement area.

(Example 2) 100 wt% of an olefin-based composite fiber having a fineness of 0.9 denier and a fiber length of 38 mm was made into a fibrous web having a weight of 50 g / m ² by using a carding device, and the fibrous web was passed through a calender roll heated to 130 ° C. A 0.2 mm thick smooth sheet having a film having fine pores formed on the surface thereof was obtained.

Next, 50% by weight of an olefin-based composite fiber having a fineness of 6 denier and a fiber length of 64 mm and 50% by weight of rayon fiber having a fineness of 3 denier and a fiber length of 51 mm were mixed and the weight was 100 g / m ² using a carding device. A fibrous web was created.

Lay this fibrous web on top of the smooth sheet and
The sheet was heat treated at ℃ to obtain a sheet for sticking to a rigid frame having a thickness of 1 mm.

When this sheet was used by adhering it to a mold in the same manner as in Example 1, it was easy to remove the mold, the concrete surface could be densely formed, and the pock ratio was 1% or less.

(Example 3) 75% by weight of polyester composite fiber having a fineness of 2 denier and a fiber length of 51 mm (core-sheath composite fiber composed of polyester having a melting point of 250 ° C. and low melting point polyester having a melting point of 130 ° C.) and a fineness
25% by weight of polyester fiber with 1.5 denier and 38 mm fiber length
And were mixed and a fiber web having a weight of 80 g / m ² was prepared using a carding device.

Next, 50% by weight of a polyester-based composite fiber having a fineness of 3 denier and a fiber length of 51 mm and 50% by weight of a polyester fiber having a fineness of 6 denier and a fiber length of 51 mm were mixed and the weight was 70 g / m ² using a carding device. A fibrous web was created.

After laminating the above two kinds of fibrous webs and entangled with each other by needle punching, one of them is a steel roll heated to 180 ° C. and the other is a rubber roll, and heat compression bonding is performed between the rolls to obtain a smooth surface having fine holes on one side. Formed a simple film.

Then, heat treatment was performed at 150 ° C. to obtain a sheet for attaching a mold frame having a thickness of 1.5 mm.

When this sheet was used by being attached to a mold in the same manner as in Example 1, it was easy to remove the mold, the concrete surface could be formed densely, and the pock ratio was 1% or less.

<< Effects of the Invention >> The sheet for attaching a formwork of the present invention has the above-described configuration, and therefore exhibits the following effects.

Since the smooth film is formed on the surface of the sheet, it can be easily peeled off when peeling the sheet from the concrete after curing by placing concrete on the mold.

Since fine holes are formed in this smooth film, excess water in the concrete enters the sheet by the lateral pressure of the concrete and is quickly drained. In the present invention,
Usually, when forming a membrane, the portion of the sheet on the membrane side is densified, so that a density gradient is formed from the membrane surface to the surface on the opposite side, resulting in excellent drainage.

When the excess water of the concrete is drained, the lateral pressure is reduced and the fine pores of the membrane are blocked by the solid content in the concrete, so that the concrete is not exposed to the outside air and can be sufficiently cured.

As described above, sufficient curing can be performed with a low water / cement ratio, and the sheet can be easily peeled off. Therefore, concrete with a dense surface, no pocking, and excellent durability can be cured.

Since the smooth film having the fine pores described above is formed from the low melting point component of the composite fiber, the bonding force with the network structure of the high melting point component of the composite fiber is strong, and the durability of the sheet surface is excellent. There is.

In particular, when a composite fiber having a small fineness is used on the side on which the film is formed, a smoother film having finer pores can be formed, and the density gradient can be increased. improves.

As described above, the sheet for attaching a mold of the present invention is extremely useful because it exerts an excellent effect in curing concrete.

Claims (3)

[Claims] 1. A sheet containing composite fibers composed of resins of two or more components having different melting points, wherein the fibers are bonded by thermal fusion of the low melting point components of the composite fibers, and one side of the sheet. In the sheet for formwork attachment, the surface of the network structure of the high melting point component of the composite fiber is coated with a fine film made of the low melting point component of the composite fiber and having a fine structure. 2. The ratio of the composite fiber in the sheet is 50.
The sheet for attaching a formwork according to claim 1, wherein the sheet is 100% to 100%. 3. Among the composite fibers used for the sheet,
The sheet for attaching a mold frame according to claim 1 or 2, wherein the fineness of the composite fiber used on the side on which the film is formed is the smallest.