JP3470280B2 - Concrete form sheet and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete formwork sheet and a method for producing the same, and more specifically, it is lightweight, has high strength, and is a PC concrete which has a good feel on the skin with less patter in a short time. The present invention relates to a concrete form sheet for providing a precast concrete product and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, there has been provided a concrete mold having a good appearance, capable of forming a high-strength concrete molded product, and having a good releasability, which can be repeatedly used. This concrete formwork is mainly composed of a formwork body having a formwork surface (usually an iron plate or plywood is used) and a formwork sheet lined on the formwork surface. As the frame sheet, various materials have been devised and used so that excess water and air bubbles in concrete can be removed.

As such a material, for example, a laminated sheet in which a high-density woven fabric and a non-woven fabric are point-bonded (Japanese Patent Laid-Open No. 5-3
29819, JP-A-5-106517),
A non-woven fabric made of PET or polypropylene and having a polyolefin-based perforated film attached to it (Japanese Patent Laid-Open No. Sho 5)
No. 0-15842), a non-woven fabric having a fine mesh impregnated with a superabsorbent polymer (Japanese Patent Application Laid-Open No. 3-153824).
No. 98001).

[0004]

However, when press cast concrete (PC concrete) products are produced in a short time using these form sheets, the dehydration time is too short and excess water and air bubbles escape. Since the concrete solidifies before long, the original purpose of the form sheet for removing excess water and air bubbles in the ready-mixed concrete is not fulfilled, and there is a problem that patter remains on the concrete surface. In view of such a situation, an object of the present invention is to provide a concrete form sheet for lining and a method for producing the same, which can obtain a PC concrete product having a good appearance with less patter in a short time.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a polyolefin resin porous sheet having continuous pores reinforced with fibers having a high elastic modulus is added to a polyolefin resin. The present invention has been achieved based on the finding that a film-laminated sheet has a high mechanical strength and that a form sheet that simultaneously satisfies the smoothness and releasability of the surface of PC concrete can be obtained.

That is, the first invention is a fiber-reinforced polyolefin resin porous sheet having continuous pores and a pore size of 1
A laminate with a polyolefin film having a thickness of 0 to 500 μm and a nitrogen gas permeation amount of 6 × 10 ¹¹ ml / m ² ·
The gist of the invention is a concrete formwork sheet characterized by being 24 hr · atm or more. Further, the second invention, after forming a sheet by dispersing and mixing short fibers and a polyolefin resin powder in water, laminate a polyolefin film on the sheet, higher than the melting point of the polyolefin resin constituting the sheet, The present invention is directed to a method for producing a concrete form sheet, which comprises heating under pressure at a temperature lower than the melting point of the polyolefin constituting the polyolefin film, and then cooling under pressure.

The present invention will be described in detail below. The concrete formwork sheet of the present invention is a laminate of a fiber-reinforced polyolefin-based porous sheet having continuous pores, and a polyolefin-based film having a pore diameter of the polyolefin film observed with an electron microscope of 10 to 500 μm, which will be described later. Nitrogen gas permeation amount calculated by 6 × 10 ¹¹ ml
/ M ² · 24 hr · atm or more.

A fiber-reinforced polyolefin resin porous sheet having continuous pores is one in which reinforcing fibers are uniformly dispersed in a polyolefin resin and continuous pores are formed between the resin and the fiber, which is excellent in porosity. is there. This porosity preferably has a porosity of 20 to 90% by volume.

Examples of the polyolefin resin constituting the porous sheet include homopolymers such as low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, polyisobutylene, 4-methylpentene and chlorinated polyethylene. , Ethylene and propylene, isobutylene, isopentene, 1-hexene,
It may be a copolymer with 4-methylpentene, acrylic acid, methacrylic acid, or vinyl acetate. In this case, 10 mol% is preferable as the copolymerization component other than ethylene. Among these, low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, and polypropylene are particularly preferable.

As the short fibers constituting the porous sheet, inorganic or organic fibers are used, preferably glass fibers having a tensile elastic modulus of 1,000 kg / mm ² or more, pitch fibers or polyacrylonitrile. Examples thereof include carbon fibers of a series, para aramid fibers, and alumina fibers, which can be used alone or in combination. The average fiber length of the short fibers is preferably 1 to 50 mm, more preferably 3 to 25 mm. When the average fiber length is shorter than 1 mm, the thermal expansion during the production of the porous sheet is insufficient, the porosity tends to be low, and it is difficult to obtain a porous sheet having a smooth surface, and sufficient strength is obtained. Hard to get. Also, the average fiber length is 50 mm
If it exceeds, the thermal expansion during the production of the porous sheet tends to be insufficient and the porosity tends to be low, and sufficient uniformity between the fiber and the polyolefin resin may not be obtained. Furthermore, as the average fiber diameter of the short fibers,
The thickness is preferably 2 to 100 μm, more preferably 5 to 50 μm. When the average fiber diameter is less than 2 μm, the water permeability and gas permeability tend to be reduced, and 100 μm
If it exceeds, there is a tendency that sufficient uniformity between the fiber and the polyolefin resin cannot be obtained.

The ratio of the short fibers to the polyolefin resin used is 100 parts by weight of the polyolefin resin.
The short fiber content is preferably 5 to 500 parts by weight, particularly 2
It is preferably from 0 to 200 parts by weight. When the use ratio of the short fibers is less than 5 parts by weight with respect to 100 parts by weight of the polyolefin resin, thermal expansion at the time of manufacturing the porous sheet becomes insufficient, so that it may be difficult to secure the porosity. If the usage ratio exceeds 500 parts by weight, it may be difficult to obtain sufficient uniformity.

The polyolefin film laminated with the fiber reinforced polyolefin resin porous sheet has a pore size of 10 to 500 μm as observed with an electron microscope. The thickness of the polyolefin film is 30
It is preferably about 200 μm. When the thickness is less than 30 μm, the film strength decreases, and when the thickness exceeds 200 μm, water permeability and gas permeability decrease, which is not preferable as a form sheet for PC concrete.

The concrete formwork sheet of the present invention can be obtained, for example, as follows. The fiber-reinforced polyolefin resin sheet and the polyolefin film can be laminated and heated under pressure. First, the fiber-reinforced polyolefin resin sheet is manufactured as follows. The fiber-reinforced polyolefin resin sheet can be manufactured by various methods. For example, it can be obtained by dispersing and mixing short fibers and polyolefin resin powder in water and making a paper. As a result, the short fibers and the polyolefin resin powder are sufficiently mixed and dispersed to form a composite state in which the short fibers are uniformly dispersed in the polyolefin resin. The polyolefin resin used in this case is used as a powder, and the particle size of the polyolefin resin powder is preferably a powder having a JIS standard of 48 mesh or less.
If the particle size is larger than 48 mesh, sufficient uniformity may not be obtained. The above-mentioned average fiber length of the short fibers is used.

When the short fibers and the polyolefin resin powder are dispersed in water to form a composite, for example, a binder is preferably used, and the amount of the binder added is 100 parts by weight of the polyolefin resin powder. It is preferable to contain 0.1 to 10 parts by weight, and particularly preferably 0.2 to 5 parts by weight. Such binders include:
For example, a bonded polymer such as an acrylic polymer or a styrene / butadiene polymer containing a bonded sulfonium group, a sulfooxonium group, an isothiouronium group, a pyridinium group, a quaternary ammonium group, a sulfate group, a sulfonate group or a carboxylate group. Mention may be made of polymer latices consisting of substantially water-free organic polymers having an ionic or cationic charge.

As the binder, it is also possible to use starch, in particular linear starch such as natural starch or corn starch and enzymatically or chemically modified starch containing cationic starch. Further, when the short fiber and the polyolefin powder resin are compounded in water, it is also preferable to use an organic coagulant together. Examples of such an organic coagulant include aluminum polychloride (aluminum hydroxychloride), Various organic flocculants such as partially hydrolyzed polyacrylamide, modified cationic polyacrylamide, diallyldiethyl ammonium chloride and the like can be mentioned.
The addition amount of this coagulant is 100
It is preferably contained in an amount of less than about 3 parts by weight, and particularly preferably less than about 1 part by weight.

As the polyolefin film to be laminated with the fiber reinforced polyolefin resin sheet, non-porous and perforated polyolefin films are used. In the present invention, it is preferable to use a polyolefin perforated film,
Usually, a commercially available breathable and moisture-permeable film having a pore size of 0.01 to 3 μm is used, but the invention is not limited thereto.

When laminating the fiber-reinforced polyolefin resin sheet and the polyolefin film, under pressure,
The heating is performed at a temperature higher than the melting point of the polyolefin resin forming the fiber-reinforced polyolefin resin sheet and lower than the melting point of the polyolefin forming the polyolefin film, preferably 5 to 30 ° C. lower than the melting point of the polyolefin forming the polyolefin film. For this reason,
The melting point of the polyolefin forming the polyolefin film needs to be higher than the melting point of the polyolefin forming the fiber reinforced polyolefin resin sheet, for example, the polyolefin forming the fiber reinforced polyolefin resin sheet is low density polyethylene, high density polyethylene, Or, when it is an ethylene copolymer, polypropylene or polypropylene copolymer or an ultra high molecular weight polyethylene film is used, and when the polyolefin constituting the fiber reinforced polyolefin resin sheet is an ultra high molecular weight polyethylene. As the polypropylene, a polypropylene or a polypropylene-based copolymer film is used.

By heating at the above temperature, in the fiber-reinforced polyolefin resin sheet, the polyolefin resin is melted in the bent short fibers, and the entire sheet is heated by the elastic recovery force of the short fibers. By expanding, a porous sheet having continuous pores is obtained, and at the same time, the polyolefin-based film is appropriately broken by contact with the short fibers of the fiber-reinforced polyolefin resin sheet, and as a result, holes having a pore size of 10 to 500 μm are formed. It is presumed that it was formed. At this time, in order to suppress the degree of thermal expansion within a desired range, the conditions of pressurization during heating should be such that the sheet is not compressed below a predetermined thickness and no further pressure is applied to the sheet (for example, a constant value). It is desirable to use a press machine that is set so that it is not narrower than the interval. Next, the laminate is cooled under pressure to obtain a concrete form sheet. The pressure at this time is preferably 5 to 100 kg / cm ² . Also in this case, it is desirable to apply pressure under the same conditions as when heating.

The above-mentioned method is a method in which a polyolefin film is directly laminated on a composite sheet obtained by papermaking under pressure. Separately, one or more fiber-reinforced polyolefin resin sheets are laminated. It is also possible to heat under pressure and then cool under pressure to obtain a dense sheet, and laminate a polyolefin film on this to obtain a concrete form sheet in the same manner as described above. At this time, the temperature at which the dense sheet is obtained is 10 to 60 ° C. higher than the melting point of the polyolefin resin used, and the pressure is preferably 5 to 100 kg / cm ² , and the pressure is 20 to 50 ° C. Cooling at temperature is preferred. In addition, it is desirable that the pressurizing condition for obtaining the dense sheet is smaller than the above-mentioned predetermined thickness so as not to be compressed, but the thickness is set to be small.

The concrete formwork sheet thus obtained has a two-layer structure and has a high mechanical strength in spite of the fact that the fiber-reinforced polyolefin resin porous sheet as the substrate has a large porosity. Since it has strength and the polyolefin film which is one layer has a pore size of 10 to 500 μm, it becomes possible to enhance water permeability and gas permeability. Further, since the polyolefin film is laminated on the surface, the surface is smooth and the releasability is better. Therefore, it can be suitably used as a PC concrete formwork (including formwork sheet).

[0021]

The concrete formwork sheet of the present invention has a two-layer structure of a fiber-reinforced polyolefin resin porous sheet having continuous pores and a polyolefin film having a pore diameter of 10 to 500 μm, and the fiber-reinforced polyolefin which is the base thereof. Since the resin porous sheet has a porosity of 20 to 90% by volume and the polyolefin film which is one layer has a pore diameter of 10 to 500 μm, the nitrogen gas permeation amount is 6 × 10 ¹¹ ml / It exhibits high water permeability and gas permeability of m ² · 24 hr · atm or more, can quickly remove excess water and air bubbles, can sufficiently cope with short dehydration time, and has little patter It is possible to produce a PC concrete product having an excellent appearance in a short time. Moreover, even though the fiber-reinforced polyolefin resin porous sheet, which is a substrate having a two-layer structure, has a porosity of 20 to 90% by volume, it has high mechanical strength and is a polyolefin film which is one layer. Since it has a smooth surface and good releasability, it can be suitably used as a PC concrete formwork (including formwork sheet).

In the present invention, short fibers and polyolefin resin powder are dispersed and mixed in water to form a sheet, and then a polyolefin film is pressed onto the sheet,
Since they are laminated under heating and then cooled under pressure, mass production is possible at low cost.

[0023]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The performance in the examples was evaluated by the following method. (1) Porosity If the theoretical density of a composite composed of a polyolefin resin having no pores and short fibers is Ag / cm ^3, and the apparent density of the fiber-reinforced polyolefin resin porous sheet is Bg / cm ³ , the porosity is , (A−B) / A × 100%. (2) Pore size The SEM S-4000 type field emission scanning electron microscope manufactured by Hitachi, Ltd. was used to observe the state of the surface of the polyon film at five locations, and the pore size was determined from a 100 × 100 mm size photo magnified 100 times the actual size. Read all with a caliper and go to the next 3
When divided into stages (0.5 to 1 mm, 1 to 50 mm, and larger than 50 mm), when the number of pores in the range of 1 to 50 mm is 90% or more, the pore diameter of the polyolefin film is 10 to 500 μm. And However, the maximum length of the hole is defined as the hole diameter, and those that are less than 0.5 mm (hole diameter of 5 μm) that cannot be visually observed are not counted.

(3) Nitrogen gas permeation amount Measured by a precision membrane flow meter method. That is, a sample obtained by punching out a concrete form sheet with a diameter of 4.8 cm was set in a sample fixing cell, and a water column 1.4 cm (1.
Flow rate of N ₂ gas (ml) set to 35 × 10 ^-3 atm)
/ Min) was measured with a volume tube (foam flow meter). This measured value was set to A, the value when the sample was not set in the cell was set to B, and the nitrogen gas permeation amount was calculated from the following equation.

[Equation 1]

Example 1 180 g of xanthan gum was added to 5 m ^{3 of} water with stirring, and then 12.5 kg of glass fiber having an average fiber length of 5 mm (415 BB manufactured by Owens Corning Fiberglass) was added as a reinforcing fiber. And stirred for 30 minutes to disperse the glass fibers. Then, a high-density polyethylene powder (Sumitomo Seika Chemical Co., Ltd., FLOWSEN M) was added to this dispersion.
After adding 12.5 kg and 200 g of solid latex,
12 kg of 0.5% by weight of a cationic flocculant [Betz Laboratories, Inc., trade name Betz1260] was gradually added to flocculate to obtain a slurry.

50 cm of this slurry together with 5 m ³ of water
It was added to a continuous paper machine with a constant width at a constant feed rate, dehydrated on a 400-mesh screen to obtain a wet sheet, and then the obtained sheet was dried at 110 ° C. to obtain 200 g / m ²
A glass fiber reinforced high density polyethylene sheet having a fabric weight of 1 was continuously wound up. The glass fiber content of this sheet is 10 parts by weight per 100 parts by weight of high density polyethylene.
It was 0 part by weight. Then, as a polyolefin film, a polypropylene perforated film having a thickness of 100 μm (manufactured by Tokuyama Soda Co., Ltd., NF sheet, pore size 1 to 3 μm) was laminated on one side of the glass fiber reinforced high density polyethylene sheet, and under a pressure of about 1500 KPa (thickness 16 at 0.6mm setting)
A concrete formwork sheet of about 0.6 mm thickness after being continuously heated under pressure at 5 ° C. for 2 minutes and then continuously cooled under pressure at the same pressure for 2 minutes at 30 ° C. Got
The porosity of the portion of this concrete formwork sheet excluding the polyolefin film was 70%, the pore diameter of the polyolefin film was in the range of 10 to 500 μm, and the nitrogen gas permeation amount of the sheet was 9.0 × 10 ¹² ml / m ^2.・ 24h
It was r.atm.

Example 2 65 g of xanthan rubber was added to 2 m ^{3 of} water with stirring, and then a polyacrylonitrile-based carbon fiber having an average fiber length of 3 mm (Besphite HTA-C3-, manufactured by Toho Rayon Co., Ltd.) was used as a reinforcing fiber. PL) Add 3.0 kg 2
The carbon fiber was dispersed by stirring for 0 minutes. Then, a high-density polyethylene powder (P, Showa Denko KK, P
-50) After adding 7.0 kg and 80 g of solid latex, 0.5% by weight of a cationic coagulant [manufactured by Betz Laboratories,
4.0 kg of trade name Betz 1260] was gradually added to cause aggregation to obtain a slurry. This slurry was added together with 2 m ³ of water to a continuous paper machine having a width of 50 cm at a constant feed rate, dehydrated on a 400 mesh screen to obtain a wet sheet, and then the obtained sheet was heated at 110 ° C.
The carbon fiber-reinforced high-density polyethylene sheet having a basis weight of 200 g / m ² was continuously wound up by drying. The content of carbon fibers in this sheet was 43 parts by weight with respect to 100 parts by weight of high-density polyethylene.

Then, as a polyolefin film, 1
A 20 μm thick polypropylene perforated film (NF sheet, Tokuyama Soda Co., Ltd., pore size 1 to 3 μm) is laminated on one side of a carbon fiber reinforced high density polyethylene sheet to give about 20
160 under pressure of 00KPa (setting thickness 0.6mm)
After continuously pressurizing and heating at a temperature of ℃ for 2 minutes, under the same pressure (setting a thickness of 0.6 mm), it was cooled under pressure at 30 ℃ for 2 minutes to obtain a concrete formwork sheet having a thickness of about 0.6 mm. . The porosity of the portion of this concrete formwork sheet excluding the polyolefin film was 70%, the pore diameter of the polyolefin film was in the range of 10 to 500 μm, and the nitrogen gas permeation amount of the sheet was 7.0 × 10 ¹² ml / m 2. ² · 24hr
・ It was atm.

Examples 3 and 4 The concrete form sheets obtained in Examples 1 and 2 were lined on the sides of an iron form using adhesive tape to form a form, and then the slump value was placed in the form. Was poured into fresh concrete having a height of 8.0 cm. At this time, a bar-shaped vibrator having a vibrating part having a diameter of 25 mmφ and vibrating at 1400 rpm was inserted into the filled concrete and vibrated for 2 to 3 minutes so that the fresh concrete could enter the corner part. After standing for a whole day and night, the form was peeled off and the concrete surface was evaluated. As a result, it was possible to obtain a PC concrete product with less pockmark and excellent smoothness. In addition, the mold release property of the concrete form sheet was good, and it was possible to use it repeatedly.

Comparative Examples 1 and 2 Commercial product A (laminated sheet in which high-density woven fabric and non-woven fabric are spot-bonded, nitrogen gas permeation amount 5 × 10 ¹¹ ml / m ² · 24 hr ·
atm) and a commercial product B (a non-woven fabric laminated with a polyolefin perforated film, a nitrogen gas permeation amount of 4 ×)
A PC concrete product was prepared in the same manner as in Examples 3 and 4 using 10 ¹¹ ml / m ² · 24 hr · atm).

[0031]

As is clear from the above description, the concrete formwork sheet of the present invention is lightweight and has high strength, and when the concrete formwork sheet of the present invention is used, it does not flutter in a short time. It is possible to provide a PC concrete product having an excellent surface quality.

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Claims (2)

(57) [Claims] 1. A laminate of a fiber-reinforced polyolefin resin porous sheet having continuous pores and a polyolefin film having a pore diameter of 10 to 500 μm, having a nitrogen gas permeation amount of 6 × 10 ¹¹ ml / m ² · 24 hr · Concrete formwork sheet characterized by having atm or more. 2. A short film and a polyolefin resin powder are dispersed and mixed in water to form a sheet, and then a polyolefin film is laminated on the sheet to obtain a polyolefin film having a melting point higher than that of the polyolefin resin constituting the sheet. A method for producing a concrete form sheet, which comprises heating under pressure at a temperature lower than the melting point of the constituent polyolefin and then cooling under pressure.