JP2001009818A - Sheet for concrete form and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet for a concrete form which produces a less pockmarked concrete product with excellent surface smoothness in a short time and also shows working and diversion properties, and a method for manufacturing the sheet. SOLUTION: This sheet for a concrete form is a laminate comprises a filter layer made of a porous resin film and a water-permeable layer of a fiber- reinforced plastic sheet with continuous cells. The permeable amount of nitrogen gas in the thickness direction of the laminate is 6×1011 ml/m2.24 hr.atm or more and the bending rigidity is 15 gf.cm2/cm or more. In addition, the tensile strength of the laminate is 9 kgf/cm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet for a concrete form used as an inner adhesive for a form used for concrete construction in the fields of civil engineering and construction, and a method for producing the same. The present invention relates to a sheet for a concrete formwork which is not only capable of obtaining a concrete product having a small avatar in time but having good surface smoothness, and also having excellent workability and diversion property, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, air bubbles on a concrete surface,
For the purpose of forcibly discharging excess water and the like to reduce the occurrence of avatars, to shorten the concrete hardening time, and to shorten the construction period, various types of sheets to be internally applied to a mold have been proposed and used. For example, a laminated sheet in which a high-density woven fabric and a nonwoven fabric are point-bonded (Japanese Patent Application Laid-Open Nos. 5-329819 and 5-106517), or a nonwoven fabric made of polyethylene terephthalate or polypropylene, and a perforated polyolefin film bonded thereto. (Japanese Unexamined Patent Publication No. 50-15842), in which a nonwoven fabric having a fine mesh is impregnated with a superabsorbent polymer.
No. 98001) and the like.

[0003] However, if these sheets are applied to a mold and used to produce a concrete product in a short period of time and the curing time is insufficient, the concrete solidifies before excess water and air bubbles are completely removed. In some cases, the original purpose of the sheet was not exhibited, and many avatars remained on the concrete surface. In addition, there is also a problem that the shape of the sheet surface, that is, irregularities and a mesh pattern are transferred to the concrete surface.

On the other hand, the present inventors have previously described a laminate of a polyolefin film having pores and a porous sheet of fiber-reinforced polyolefin resin having continuous pores.
A concrete form sheet capable of obtaining a concrete product with less avatar in a short time has been proposed (Japanese Patent Laid-Open No. 8-1351).
No. 81).

[0005]

According to the sheet proposed by the present inventors, not only a concrete product with less avatar can be obtained in a short time, but also a thin and rigid sheet can be obtained. In addition, even when used for a formwork having a vertical surface or a curved surface, it can be easily attached, and the workability can be improved. However, when removing the mold, that is, when removing the formwork from the concrete molded product, the sheet is damaged depending on the method of operation, and it is not sufficient in that the sheet may not be diverted, that is, cannot be used repeatedly. Therefore, an object of the present invention is to provide a concrete form sheet that is capable of obtaining a concrete product having a small avatar and good surface smoothness in a short time, and having excellent workability and diversion property, and a method for producing the same. .

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have used a non-woven fabric as a raw material of a porous resin film to be a filter layer directly in contact with concrete. By laminating with a fiber reinforced plastic sheet that will be an aqueous layer, heating and pressing to fuse the non-woven fabric in the process of integrating the sheet and forming a porous resin film, compared to the case of using a normal perforated film It is expected that the strength of the film part will be drastically improved while maintaining the various properties required for the concrete form sheet, and as a result, the tensile strength of the entire sheet will be improved, thereby increasing the durability and improving the diversion property. As a result, the present invention has been completed.

That is, the gist of the present invention is, first, a laminate of a filter layer made of a porous resin film and a water-permeable layer made of a sheet made of fiber-reinforced plastic having continuous pores. 6 × 10 ¹¹ gas permeation
ml / m ² · 24 hr · atm or more, flexural rigidity of 15 gf · cm ² / cm or more, and tensile strength of 9 kg
It is a sheet for concrete formwork characterized by being at least f / cm.

Secondly, the above-mentioned method for producing a sheet for a concrete formwork, comprising laminating a nonwoven fabric and a sheet made of fiber reinforced plastic, and heating and pressurizing to melt the nonwoven fabric to form a porous resin film. Is the way.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The concrete form sheet of the present invention is a laminate of a filter layer made of a porous resin film and a water-permeable layer made of a fiber-reinforced plastic sheet having continuous pores.

[0010] The filter layer is required to have a function of directly contacting the concrete surface and transmitting air bubbles and excess water while avoiding the penetration of cement particles and sand particles, and to be quickly separated from the concrete surface upon demolding. From the viewpoint, a porous resin film is used. Examples of the resin constituting the porous resin film include polyolefin, polyester, polyamide, polyacetal,
A homopolymer or copolymer such as polyphenylene sulfide and fluororesin can be used. Among these, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer, which have excellent heat resistance, chemical resistance (alkali resistance), and ease of detachment from concrete at the time of demolding, and are also economical, are used. preferable.

As for the size of the pores in the porous resin film, when the maximum diameter of the pores observed by an electron microscope is taken as the pore size, it is preferable that the pores have a pore diameter of 10 μm or more. It is preferred not to have pores exceeding 200 μm, more preferably not having pores exceeding 200 μm. If the pore diameter is less than 10 μm, water permeability may decrease, while if it exceeds 500 μm, cement particles and sand particles may permeate, which is not preferable.

The thickness of the porous resin film is 30
It is preferably from 200 to 200 μm, more preferably from 50 to 100 μm. When the thickness is less than 30 μm, the film strength may be insufficient. On the other hand, when the thickness is more than 200 μm, water permeability and air permeability may decrease, which is not preferable.

As the water-permeable layer in the concrete form sheet (hereinafter sometimes abbreviated as form sheet) of the present invention, a fiber-reinforced plastic sheet having continuous pores is used. The use of a fiber-reinforced plastic sheet having continuous pores (hereinafter sometimes abbreviated as an FRP sheet) as a water-permeable layer not only serves as a discharge path for bubbles and excess water, but also provides mechanical characteristics of the form sheet. In particular, the bending rigidity is reinforced. The FRP sheet has continuous pores when 0.05 ml of methanol is dropped on the surface of the FRP sheet and the methanol is absorbed into the FRP sheet within 10 seconds.

The porosity of the FRP sheet is 20 to 9
It is preferably 0% by volume, more preferably 40 to 80% by volume. If the porosity is less than 20% by volume, it is difficult to discharge air bubbles and excess water, and the product may have an avatar concrete product. On the other hand, if the porosity exceeds 90% by volume, the strength of the form sheet is insufficient. Is not preferred. The porosity of the FRP sheet is determined by the following method. That is, the theoretical density assuming that the FRP sheet has no pores is D (g / c).
m ³ ) and the apparent density of the FRP sheet is ρ (g / c
m ³ ), the porosity V (volume%) is calculated by the following formula.

[0015]

(Equation 1)

As the matrix resin used for the FRP sheet, for example, polyolefin-based, polyester-based,
Examples thereof include homopolymers and copolymers such as polyamide, polyacetal, polyphenylene sulfide, and fluororesin, and these may be used alone or as a mixture. Among these, it has heat resistance, chemical resistance (alkali resistance),
Polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer, which are also excellent in economic efficiency, are preferred.

As the reinforcing fibers in the FRP sheet, various organic and inorganic fibers are used. For example, glass fibers, pitch-based or polyacrylonitrile-based carbon fibers, alumina fibers, aramid fibers, alumina fibers, polyester fibers And the like, and these are used alone or as a mixture. Preferably, the tensile modulus is 100
It is preferable to use fibers having a weight of 0 kgf / mm ² or more, and glass fibers are particularly preferable.

The average fiber length of the reinforcing fibers is from 1 to 50.
mm is preferable and 3 to 25 mm is more preferable. When the average fiber length is less than 1 mm, the strength of the FRP sheet tends to be insufficient. On the other hand, when the average fiber length exceeds 50 mm, it is difficult to mix uniformly with the matrix resin.
It is not preferable because it is difficult to form continuous pores with high porosity in the P sheet. The average fiber diameter of the reinforcing fibers is preferably 2 to 100 μm, and 5 to 50 μm.
Is more preferred. If the average fiber diameter is less than 2 μm, FRP
The water permeability of the sheet tends to decrease, while
If it exceeds m, it is difficult to mix it uniformly with the matrix resin, or the smoothness of the filter layer surface of the mold sheet may be impaired, which is not preferred.

The content of the reinforcing fibers in the FRP sheet is preferably 5 to 500 parts by weight, more preferably 20 to 500 parts by weight, based on 100 parts by weight of the matrix resin.
Preferably it is 200 parts by weight. If the content of the reinforcing fiber is less than 5 parts by weight, the effect of the reinforcing fiber is hardly obtained, while if it exceeds 500 parts by weight, the FRP sheet tends to become brittle, which is not preferable.

The thickness of the concrete form sheet of the present invention is preferably 0.1 to 3 mm, and 0.3 to 1 mm.
Is more preferred. If the thickness is less than 0.1 mm, the strength and rigidity of the form sheet tend to be insufficient, while the thickness is 3 m.
If it exceeds m, air permeability and water permeability may be reduced, or workability such as cutting or bending may be poor, which is not preferable.

The nitrogen gas permeation amount in the thickness direction of the form sheet of the present invention is 6 × 10 ¹¹ ml / m ² · 24 hr · a
tm or more and 10 × 10 ¹¹ ml /
m ² · 24 hr · atm or more, preferably 20 × 10 ¹¹
It is more preferably at least ml / m ² · 24 hr · atm. Nitrogen gas permeation amount is 6 × 10 ¹¹ ml / m ² · 24 hr · at
If it is less than m, air permeability is insufficient and avatars are likely to remain on the concrete surface. Further, the water permeability coefficient in the thickness direction of the form sheet is preferably 1 × 10 ⁻⁴ cm / sec or more as a value measured according to the constant water permeability test method of JIS A-1218, and 1.5 × It is more preferably at least 10 ^-4 cm / sec. Permeability is 1 × 10 ^-4 cm / sec
If the amount is less than the above, it is not preferable because the excess water of the concrete tends to be difficult to discharge.

The bending rigidity of the form sheet of the present invention is as follows.
It is necessary to be 15 gf · cm ² / cm or more,
Considering the flexibility, 30 to 400 gf · cm ² / c
m is preferable, and 50 to 200 gf · cm ² / cm is more preferable. When the flexural rigidity is less than 15 gf · cm ² / cm, workability at the time of attaching to a formwork having a vertical surface or a curved surface is reduced. The bending stiffness is defined as the bending moment per 1 cm width of the form sheet as M (gf · cm · c).
m ^-1 ) and the curvature is K (cm ^-1 ), the bending stiffness R (g
f · cm ² / cm) is calculated from the following formula.

[0023]

(Equation 2)

The tensile strength of the form sheet of the present invention is required to be 9 kgf / cm or more.
1 kgf / cm or more is more preferable. 9kg tensile strength
If it is less than f / cm, the mold sheet may be damaged during demolding. In addition, the said tensile strength is the maximum tensile load until a 1 cm-wide form sheet breaks by tension.

Further, in the form sheet of the present invention,
In addition to the filter layer and water layer, for the purpose of reinforcement,
Alternatively, a back layer may be laminated on the side opposite to the filter layer for the purpose of improving the adhesion to the mold via a double-sided adhesive tape or an adhesive. As such a back layer, various sheet materials such as a nonwoven fabric, a film, a woven fabric, and a net may be used as long as the object of the present invention is not impaired.

Next, a method of manufacturing the form sheet of the present invention will be described. First, the method of manufacturing the FRP sheet is not particularly limited, for example, by heating the particles or fibrous resin and the reinforcing fibers dry-mixed and deposited at a temperature equal to or higher than the melting point of the resin. How to make a sheet,
It is possible to adopt a method in which, after forming a sheet from a slurry in which a particulate or fibrous resin and a reinforcing fiber are dispersed and in the manner of papermaking, the sheet is heated and pressed at a temperature equal to or higher than the melting point of the resin. In the present invention, a uniform and high porosity FRP
From the point that a sheet can be easily manufactured, as described below, a method of forming a sheet from a slurry obtained by dispersing and mixing resin particles and reinforcing fibers in an aqueous medium in a papermaking manner, and then heating and pressurizing the sheet. It is preferably used.

An example of the above preferred method will now be described in more detail. First, the particles (powder) that will be the matrix resin
A resin and a reinforcing fiber are dispersed and mixed in an aqueous medium such as water to prepare a slurry. As the average particle diameter of the particulate resin in this case, from the viewpoint of dispersibility in an aqueous medium,
It is preferably 600 μm or less. When the synthetic resin and the reinforcing fibers are dispersed and mixed in water, a small amount of the binder is used, that is, the total amount of the particulate resin and the reinforcing fibers in the slurry (hereinafter, referred to as slurry solid content). ) 100 to 100 parts by weight of binder 0.1 to 5 parts by weight, especially 0.3
It is preferred to use up to 3 parts by weight.

As the binder used above, for example,
Attached anionic or cationic charges, such as acrylic or styrene-butadiene polymers containing bound sulfonium, isothiouronium, pyridinium, quaternary ammonium, sulfate, sulfonate or carboxylate groups. And a polymer latex comprising a substantially water-insoluble organic polymer. Also, starches, including starches, particularly enzymatically or chemically modified starches, including natural starch or linear starch such as corn starch and cationic starch can be used as binders.

Further, when using the above binder,
It is preferable to use an organic coagulant in combination. Suitable organic coagulants include various organic coagulants such as aluminum polychloride (aluminum hydroxychloride), partially hydrolyzed polyacrylamide, modified cationic polyacrylamide, diallyldiethylammonium chloride, and the like. The amount of the coagulant added is less than 3% by weight, especially 1% by weight, based on 100 parts by weight of the solid content of the slurry.
It is preferred that the amount is less than the weight%. Further, in order to improve dispersibility, a slurry viscosity modifier such as xanthan gum can be used. The amount of such a viscosity modifier is preferably less than 2% by weight based on 100 parts by weight of the solid content of the slurry.

After the synthetic resin and the reinforcing fibers are mixed in the aqueous medium in this manner, the solid content in the aqueous medium is desirably converted into a sheet by using a paper machine or the like in a wet papermaking manner. Solid-liquid separation. Next, the wet sheet is dried to obtain a composite sheet composed of particulate resin and reinforcing fibers.

The above-mentioned composite sheet is heated and pressed at a temperature higher than the melting point of the resin, preferably at a temperature in the range of about 20 ° C. higher than the melting point to melt the resin, and then cooled,
An FRP sheet is obtained. In the heating, pressurizing and cooling processes, for example, a mold having a certain interval is used in a space having a certain interval, or a metal plate and a metal plate are mixed so that the thickness of the FRP sheet becomes a desired thickness. It may be carried out using a spacer together or between press plates or nip rolls set at regular intervals. At this time, the apparent density of the FRP sheet is adjusted by the basis weight and the thickness of the composite sheet, so that the FRP sheet having a desired porosity can be obtained. The step of heating and pressing and cooling the above composite sheet may be performed simultaneously with the step of laminating the nonwoven fabric described below and then fusing the nonwoven fabric to form a porous resin film. The method is preferably adopted, and in the production method of the present invention, laminating a nonwoven fabric and a sheet made of fiber-reinforced plastic and heating and pressing means laminating the nonwoven fabric and the composite sheet and heating and pressing. Including.

Next, as the non-woven fabric which is a raw material of the porous resin film constituting the formwork sheet of the present invention together with the FRP sheet, a known non-woven fabric comprising fibers of a resin capable of forming the porous resin film of the present invention is optional. Can be used for The resin fiber may be one kind or a mixture of two or more kinds of fibers. For example, a conjugated fiber such as a polyolefin-based material in which the core is made of polypropylene and the sheath is made of modified propylene, and the core is made of polyethylene terephthalate and the sheath is made of polyethylene A core-sheath structure conjugate fiber or the like having a sheath portion having a lower melting point than the core portion, such as a polyester-based sheath made of low-melting polyester may be used.

The fiber length of the fibers constituting the nonwoven fabric may be either long fibers or short fibers, but the strength of the nonwoven fabric is excellent and the workability during production is excellent, and the porous resin obtained is From the point that the strength of the film tends to increase,
Nonwoven cloth made of long fibers is preferably used. The basis weight of the nonwoven cloth is preferably 5 to 400 g / m ² ,
200 g / m ² is more preferred.

The nonwoven fabric is laminated with the above-described composite sheet or the FRP sheet subjected to the heating, pressurizing and cooling steps and, if necessary, further laminating a sheet material as a back layer, to form at least the nonwoven fabric. The resin is heated and pressed at a temperature equal to or higher than the melting point of one type of resin, preferably at a temperature within a range of about 20 ° C. higher than the melting point, preferably at a pressing pressure of 0.1 kgf / cm ² or higher. Cool while holding.

Examples of the apparatus for performing the heating and pressurizing and cooling include a known batch press apparatus and a continuous press apparatus such as a double belt press apparatus capable of continuously pressing between a pair of opposed metal endless belts. However, a double belt press is particularly preferable in that a long sheet can be continuously processed with high productivity. In the FRP sheet constituting the form sheet, a spring-back force for expanding the thickness of the FRP sheet acts when the matrix resin is softened by heating due to the elastic action of the reinforcing fibers. The force facilitates the formation of continuous pores in the FRP sheet. Therefore, the thickness of the form sheet can be adjusted by controlling the press pressure according to the springback force, but as a method of adjusting the thickness,
For example, when performing a batch press, a mold having a certain interval may be used, a metal plate and a spacer may be used in combination, or the control may be performed by an interval (clearance) between belts of a double belt press device. The heating time may be appropriately selected within a range where the mold sheet of the present invention is obtained and the resin is not thermally deteriorated.

As a result of heating, pressurizing and cooling as described above, the nonwoven fabric becomes a porous resin film having a smooth surface without fluffing, and is adhered to the FRP sheet to obtain the formwork sheet of the present invention. . In addition, in the porous resin film which is a filter layer of the form sheet obtained as described above, the fiber shape may remain inside as long as the surface is smooth without fuzz. In addition, according to the above method, the FRP sheet, which is the water-permeable layer of the form sheet, has continuous pores not only in the thickness direction but also in the in-plane direction, and the drainage capacity is particularly excellent. .

[0037]

Next, the present invention will be described specifically with reference to examples. The physical properties of the form sheet were determined by the following methods. (1) Nitrogen gas permeation amount The nitrogen gas permeation amount in the thickness direction was measured by a precision membrane flow meter method. That is, a sample obtained by punching out a form sheet into a circular shape having a diameter of 4.8 cm is set in a sample fixing cell, and the gas pressure P (atm) is set to a 1.4 cm water column (1.35 cm).
The flow rate of the nitrogen gas when set to (× 10 ⁻³ atm) was measured by a volume tube (bubble flow meter SF-1100 manufactured by ESTEC Co., Ltd.). The measured value is A (ml / min), and the measured value when the sample is not set in the cell is B (ml / mi).
n), the effective area of the sample is S (cm ² ), and the nitrogen gas permeation amount Q (ml / m ² · 24 hr)
Atm).

[0038]

(Equation 3)

(2) Permeability Coefficient It was measured by a constant water permeability test method of JIS A-1218. (3) Tensile strength A sample obtained by cutting a form sheet into a width of 1 cm and a length of 17.5 cm is subjected to a tensile test at a speed of 5 mm / min using a universal testing machine (manufactured by Intesco Corporation), and the sample breaks. The maximum load was measured to determine the tensile strength. (4) Flexural rigidity It was measured using a pure bending tester (KES-FBZ manufactured by Kato Tech).

Example 1 180 g of xanthan gum was added to 5 m ^{3 of} water while stirring, and then 30 kg of glass fiber having a mean fiber length of 5 mm (trade name: 415BB, manufactured by Owens Corning Fiberglass Co.) was added as a reinforcing fiber. The glass fibers were dispersed in water by stirring for 30 minutes, and then 30 kg of a high-density polyethylene resin powder (produced by Sumitomo Seika Co., Ltd., trade name: Flowsen M) having an average particle diameter of 160 μm, and solid latex containing 60% water 480 g (Boncoat SFC-55, manufactured by Dainippon Ink and Chemicals, Inc.) was added and dispersed, and thereafter, a cationic coagulant (Betz Laboratories, trade name Be) having an active ingredient concentration of 0.5% by weight was added.
tz1260) was gradually added to obtain a coagulated slurry. Using a continuous paper machine (manufactured by Saito Tekko Co., Ltd.), the above slurry was supplied at a constant feed rate together with the same amount of water, and dewatered on a 400-mesh screen to obtain a width of 50 c.
m, and the remaining sheet is removed by a hot air dryer set at 110 ° C., and continuously wound to form a composite sheet composed of high-density polyethylene resin and glass fiber with a basis weight of 240 g / m ² . I got Basis weight 2 serving as a filter layer on one side of the composite sheet obtained above
0 g / m ² polypropylene nonwoven fabric (manufactured by Shintec,
On the other surface, a nylon nonwoven fabric having a basis weight of 30 g / m ² (manufactured by Unitika, trade name P0203WTO), which is a back layer, is laminated on the other surface, and the thickness is 0.6 m.
m between two molds having spacers arranged therein, and using a heating press machine at a surface pressure of 5 kgf / cm ² and a temperature of 180 ° C.
After heating and pressurizing for a minute, and then cooling to room temperature while maintaining this pressure, a mold sheet having a thickness of 0.6 mm was obtained. In addition, the surface of the filter layer of the obtained mold sheet was a film-like smooth surface without fluff.

Example 2 A composite sheet comprising the high-density polyethylene resin obtained in Example 1 and glass fiber was used.
0 g / m ² polypropylene nonwoven fabric (manufactured by Shintec,
6620-1A), and heated and pressed and cooled in the same manner as in Example 1 to obtain a 0.6 mm-thick formwork sheet having a film-like filter layer.

Comparative Example 1 A composite sheet comprising the high-density polyethylene resin obtained in Example 1 and glass fiber was used.
By laminating a perforated polypropylene film (manufactured by Tokuyama, NF sheet) having a thickness of 0.6 μm having a film-like filter layer by heating and pressing and cooling by the same operation as in Example 1. A formwork sheet was obtained.

Comparative Example 2 A composite sheet made of the high-density polyethylene resin and glass fiber obtained in Example 1 was inserted between two molds provided with spacers having a thickness of 0.6 mm, and heated using a press machine. By heating and pressing at a surface pressure of 5 kgf / cm ² and a temperature of 180 ° C. for 2 minutes,
Next, by cooling to room temperature while maintaining this pressure, a fiber reinforced plastic sheet (FRP sheet) having continuous pores having a porosity of 71% and a thickness of 0.6 mm was obtained. On one side of this FRP sheet, the polypropylene non-woven fabric used in Example 1 was point-adhered at 25 places per 1 m ² using a urethane-based adhesive (approximately 1 m in diameter of the adhesion point).
m) to obtain a mold sheet having a nonwoven fabric filter layer on the surface.

Incidentally, 0.05 ml of methanol was dropped on the FRP sheet surface, which is a water-permeable layer of each of the mold sheets obtained in the above Examples and Comparative Examples (the back of the mold sheet of Example 1). Layer was forcibly peeled off)
However, all within 1 second methanol is absorbed inside,
It was confirmed to have continuous pores. Table 1 below shows the results of examining the physical properties of the form sheets obtained in the above Examples and Comparative Examples.

[0045]

[Table 1]

[Concrete Casting Test] The mold sheet obtained in the above Examples and Comparative Examples was placed on a 30 cm × 50 cm iron mold member surface with a surface opposite to the filter layer by 10 mm.
After forming the form by internally sticking using a double-sided pressure-sensitive adhesive tape having a width, a ready-mixed concrete having a slump value of 5.5 cm was poured into a form having a side wall portion as shown in FIG. 1 and left overnight. After the mold was removed, the surface of the obtained concrete molded product was observed and evaluated. The ready-mixed concrete was prepared by mixing cement: sand: gravel with a weight ratio of 1: 2: 3, and adding water to the cement to ２ of the weight of the cement. In addition, at the time of casting, it has a vibrating part having a diameter of 25 mmΦ and has a speed of 1400 rpm.
The vibrator was inserted into the filled concrete and vibrated for 3 minutes so that the ready-mixed concrete could enter the corners.

When the form sheets of Examples 1 and 2 and Comparative Example 1 were used, the form could be easily removed from the concrete surface, and no avatar was observed on the surface of the concrete molded product. It had good touch and excellent smoothness. Further, the filter layer of the form sheet hardly permeated the cement particles and the sand particles, and was in a state where it could be sufficiently reused. On the other hand, when the form sheet of Comparative Example 2 was used, the form sheet was fixed to the concrete surface when the mold was released, and when the form sheet was peeled off, the adhesion between the filter layer and the water-permeable layer of the form sheet was reduced. Partially peeled off. Further, the fiber pattern of the nonwoven fabric was transferred to the surface of the concrete molded product, a small amount of fibers were also attached, and five avatars were also confirmed. In addition, cement particles and sand particles permeated and clogged the water-permeable layer of the form sheet, which was not suitable for reuse.

[Evaluation of diversion property] The same concrete casting test was performed again on the formwork using the formwork sheets of Examples 1 and 2 and Comparative Example 1 used in the above concrete casting test. Thus, a concrete molded product having a smooth surface was obtained. When this was repeated, only the mold sheet of Comparative Example 1 having poor tensile strength was damaged at the time of the third mold release. In addition, about the form using the form sheet of Examples 1 and 2, the concrete casting test can be performed two more times to obtain a concrete molded product having a smooth surface.
The mold sheet could be removed without damage.

[0049]

The concrete form sheet of the present invention is
Since the filter layer in contact with the concrete surface is made of a porous resin film with a smooth surface, and the water-permeable layer is made of a fiber-reinforced plastic sheet having continuous pores,
After the concrete is cast, a concrete product with a smooth surface can be obtained in a short time, and the demolding is easy. In addition, because it has high tensile strength and durability, it is excellent in diversion that can be used repeatedly.For example, it is possible to drill holes in the form sheet and fix it to the form with bolts or use staples to fix it In this case, there is little risk of damage from the fixed portion. Furthermore, because it has a moderate bending rigidity, there is no need to worry about bending or wrinkling when attaching to a formwork having a vertical surface or a curved surface. Is improved. Therefore, the sheet for concrete formwork of the present invention is suitable for production of various precast concretes, for on-site construction of civil engineering and construction work, and for other uses utilizing excellent filter performance, for example, for sewage purification treatment. Can also be used as a filter material. Further, according to the production method of the present invention, such a sheet for concrete formwork can be easily produced using inexpensive raw materials.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a side wall portion of one side of a concrete form in an embodiment of a concrete form using the concrete form sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Concrete form sheet 2 Filter layer 3 Water passage layer 4 Iron form member 5 Double-sided adhesive tape 6 Casting concrete 7 Base

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidenobu Yamazaki 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory F-term (reference) 4G053 AA07 AA19 BB13 BB17 BF08 CA21 DA03 DA11 EB02 EB05

Claims (2)

[Claims] 1. A laminate comprising a filter layer made of a porous resin film and a water-permeable layer made of a fiber-reinforced plastic sheet having continuous pores, and having a nitrogen gas permeation amount in the thickness direction of 6 × 10 ¹¹ ml /. A sheet for a concrete formwork having a m ² · 24 hr · atm or more, a flexural rigidity of 15 gf · cm ² / cm or more, and a tensile strength of 9 kgf / cm or more. 2. The concrete mold sheet according to claim 1, wherein the nonwoven fabric and the fiber reinforced plastic sheet are laminated and heated and pressed to melt the nonwoven fabric to form a porous resin film. Production method.