JP6808910B2 - Concrete formwork - Google Patents

Description

The present invention relates to a concrete formwork having excellent crack resistance.

When building a building such as a building, the concrete formwork method is widespread, in which the assembled reinforcing bars are surrounded by a concrete formwork, concrete is poured into the enclosed space, and the concrete formwork is removed after the concrete is solidified. It's being used. In recent years, the consumption of concrete formwork has increased along with the increase in the number of buildings, and from the viewpoint of reducing construction costs, it is required to improve the durability so that the concrete formwork can be used repeatedly.

As the concrete formwork, plywood, a water-based coating film, and a concrete formwork in which an acrylic topcoat film is sequentially laminated have been widely used, but the water-based resin used for the undercoat film is dried. Since a process is required, the plywood tends to warp, and there is a problem that the durability is lowered.

Therefore, various studies have been conducted on the undercoat coating film, and for example, it has been reported that a moisture-curable polyurethane hot melt is used for the undercoat coating film (see, for example, Patent Document 1).

When the moisture-curable polyurethane hot melt is used, a drying step is not required, so that the productivity is excellent, but there is a problem that cracks are likely to occur when the concrete mold is used repeatedly.

Japanese Unexamined Patent Publication No. 2014-15513

An object to be solved by the present invention is to provide a concrete formwork having excellent crack resistance.

The present invention provides a concrete formwork in which a plywood (i), a urethane foam layer (ii), and a topcoat coating film (iii) are sequentially laminated.

By using the urethane foam layer (ii) for the undercoat film, the concrete formwork of the present invention easily absorbs an impact from the outside and has excellent crack resistance. In addition, even if softwood plywood or planted wood plywood with strong knots and wood grain, which are widely used in Japan, is used as a substrate, unevenness does not appear on the surface of the concrete formwork and the appearance is excellent. Further, the urethane foam layer (ii) and the top coat film (iii) can be formed with only one coat, and the productivity is also excellent.

The concrete formwork of the present invention is one in which a plywood (i), a urethane foam layer (ii), and a topcoat coating film (iii) are sequentially laminated.

As the plywood (i), for example, Lauan plywood, China plywood, softwood plywood, planted tree plywood and the like can be used. The plywood structure using these trees may be a single layer or a plurality of layers made of one kind of trees, or may be a plurality of layers made of two or more kinds of trees. As the plywood (i), it is preferable to use softwood plywood or planted tree plywood because of the recent depletion of lauan wood and the promotion of effective utilization of domestic wood.

As the softwood that can be used for the softwood plywood, for example, Abies sachalinensis, larch, Japanese cypress, cedar and the like can be used. Further, as the plantation trees that can be used for the plantation tree plywood, for example, poplar, falcata, chamelele, eucalyptus, rubber, erima, terminaria, camp nosperma, acacia mangume, gumerina, merkusipine, radiata pine and the like should be used. Can be done.

The softwood plywood or planted wood plywood may be subjected to a base treatment for the purpose of alleviating the grain and missing nodes of the softwood plywood or planted wood plywood, but the urethane foam layer used in the present invention. According to (ii), a concrete mold that does not stand out due to knots or grain over time can be obtained without performing the base treatment.

The urethane foam layer (ii) is formed of a urethane resin having a foamed structure. As the urethane resin, for example, urethane hot melt resin, two-component urethane resin, thermoplastic urethane resin, urethane acrylate resin and the like can be used. Among these, urethane hot melt resin is preferably used from the viewpoint of further improving crack resistance, adhesion to the topcoat coating film (iii), and productivity of the concrete formwork.

The urethane hot melt resin preferably contains a urethane prepolymer having an isocyanate group. Further, the urethane prepolymer is preferably obtained by reacting a polyol with a polyisocyanate.

Examples of the polyol include polyester polyol and polyether polyol. Polycarbonate polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyacrylic polyol, dimer diol and the like can be used. These polyols may be used alone or in combination of two or more. Among these, it is preferable to use a polyol containing a polyester polyol and a polyether polyol from the viewpoint of having even more excellent adhesiveness in the foamed structure.

As the polyester polyol, for example, an aromatic polyester polyol, a polycaprolactone polyol, a crystalline polyester polyol, an amorphous polyester polyol, or the like can be used. These polyester polyols may be used alone or in combination of two or more. Among these, it is preferable to use an aromatic polyester polyol and / or a polycaprolactone polyol from the viewpoint of further improving the adhesive strength and the mechanical strength.

When the polyester polyol is used, the amount used is preferably in the range of 30 to 95% by mass, and 50 to 90% by mass, based on the total amount of the polyol, from the viewpoint of further improving the adhesive strength and the mechanical strength. The range is more preferred.

As the polyether polyol, for example, polyethylene polyol, polypropylene polyol, polytetramethylene polyol, polyoxyethylene polyoxypropylene polyol, polyoxyethylene polyoxytetramethylene polyol, polyoxypropylene polyoxytetramethylene polyol, or the like can be used. it can. These polyether polyols may be used alone or in combination of two or more.

When the polyether polyol is used, the amount used is preferably in the range of 5 to 70% by mass, and 7 to 60% by mass, based on the total amount of the polyol, from the viewpoint of further improving the adhesive strength and the mechanical strength. The range of is more preferable.

The number average molecular weight of the polyol is preferably in the range of 500 to 8,000, more preferably in the range of 700 to 5,000, and more preferably 800 to 3,000 in terms of adhesive strength and mechanical strength. The range of is more preferable. The number average molecular weight of the polyol is a value measured under the following conditions by a gel permeation chromatography (GPC) method.

Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8 mm I.D. x 30 cm) x 1 "TSKgel G4000" (7.8 mm I.D. x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 This "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (Differential Refractometer)
Column temperature: 40 ° C
Eluent: tetrahydrofuran (THF)
Flow velocity: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

Examples of the polyisocyanate include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, phenylenediocyanate, tolylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, cyclohexanediisocyanate, and isophorone. An aliphatic or alicyclic polyisocyanate such as diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, or tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, diphenylmethane diisocyanate is preferably used from the viewpoint of reactivity and adhesive strength.

The urethane prepolymer has an isocyanate group capable of forming a crosslinked structure by reacting with water existing in the air or in the adherend to which the urethane prepolymer is applied.

As a method for producing the urethane prepolymer, for example, a mixture of the polyol is added dropwise to a reaction vessel containing the polyisocyanate and then heated, and the isocyanate group of the polyisocyanate is directed to the hydroxyl group of the polyol. It can be produced by reacting under excessive conditions.

The equivalent ratio (NCO / OH) of the isocyanate group of the polyisocyanate to the hydroxyl group of the polyol is preferably in the range of 1.1 to 5 from the viewpoint of further improving the adhesive strength and the mechanical strength. The range of 1.5 to 3 is more preferable.

The urethane prepolymer can usually be produced without a solvent, but it may be produced by reacting the polyol with a polyisocyanate in an organic solvent. When the reaction is carried out in an organic solvent, an organic solvent such as ethyl acetate, n-butyl acetate, methyl ethyl ketone and toluene that does not inhibit the reaction can be used, but by a method such as vacuum heating during or after the reaction is completed. It is necessary to remove the organic solvent.

When producing the urethane prepolymer, a urethanization catalyst can be used if necessary. The urethanization catalyst can be added as appropriate at any stage of the reaction.

The urethanization catalyst is, for example, a compound having a nitrogen atom such as triethylamine, triethylenediamine and N-methylmorpholine; a metal salt such as potassium acetate, zinc stearate, tin octylate; an organic metal compound such as dibutyltin dilaurate and the like. Can be used. These urethanization catalysts may be used alone or in combination of two or more.

The isocyanate group content (NCO%) of the urethane prepolymer is preferably in the range of 1 to 10%, preferably in the range of 1.5 to 5%, from the viewpoint of further improving the adhesive strength and the mechanical strength. More preferred. The isocyanate group content of the urethane prepolymer is based on JIS K1603-1: 2012 and shows a value measured by a potentiometric titration method.

The viscosity of the urethane prepolymer at 120 ° C. is preferably in the range of 1,000 to 100,000 mPa · s from the viewpoint of further improving coatability, adhesive strength, and mechanical strength. The range of 000 to 50,000 mPa · s is more preferable. The melt viscosity of the urethane prepolymer at 120 ° C. indicates a value measured by a cone plate viscometer (manufactured by ICI) of the urethane prepolymer melted at 120 ° C.

The urethane hot-melt adhesive may be composed only of the urethane prepolymer, but may contain other additives if necessary.

As the other additives, for example, antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent whitening agents, silane coupling agents, waxes and the like can be used. These additives may be used alone or in combination of two or more.

The 100% modulus of the cured film of the urethane hot melt resin (unfoamed material) is preferably in the range of 1 to 70 MPa from the viewpoint of further improving the adhesive strength and the mechanical strength. The range of .5 to 50 MPa is more preferable. The 100% modulus is obtained by applying the urethane hot melt resin to a release paper in an atmosphere of 23 ° C. with an applicator so as to have a thickness of 50 μm to obtain a cured film. 100% obtained by measuring with Tencilon (Tencilon universal testing machine "RTC-1210A" manufactured by Orientec Co., Ltd.) in an atmosphere of 25 ° C. and 50% humidity at a cross head speed of 300 mm / min. Indicates the modulus value.

As a method of forming a foamed structure in the urethane resin, for example, an inert gas such as nitrogen gas or carbon dioxide gas is applied to the urethane resin by using a foaming machine such as a gear pump, a medium pressure foaming machine, or an ultrafoam mix. Examples include injection and mixing methods. Further, the foam injected with the inert gas may be further refined using a mixer or the like.

As a method of applying the urethane resin having a foamed structure formed by the above method to the plywood (i), for example, a method using a knife coater, a spray coater, a T-die coater, a roll coater, or the like; a multi-row bead coating method. Etc. can be mentioned. As the coating method, when softwood plywood or planted tree plywood is used as the plywood (i), it is preferable to adopt a coating method using a knife coater (knife coating method). The reason is that even if there are loose knots (hole knots) or grain on the surface of the softwood plywood or planted wood plywood, the urethane resin can be neatly filled and applied by the knife coater, so that the concrete mold can be obtained. The surface of the frame has no irregularities, and the appearance and crack resistance are further improved.

Some of the urethane resins have a very high viscosity, and it is generally very difficult to apply a highly viscous urethane resin with a knife coater. However, in the present invention, by forming the foamed structure on the urethane resin by the above-mentioned method, the apparent viscosity at the time of coating is lowered, so that the coating with the knife coater can be efficiently performed.

The coating amount of the urethane resin is preferably in the range of ²⁰ to 150 g / m ² from the viewpoint of crack resistance, appearance, and coatability.

The density of the urethane foam layer (ii) obtained by the above method is preferably in the range of 0.1 to 0.8 g / cm ³ from the viewpoint of further improving crack resistance, and is 0.2 to 0.8 g / cm ^3. A range of 0.6 g / cm ³ is more preferred.

As the topcoat paint used for the topcoat coating film (iii), for example, known topcoat paints such as acrylic paints, epoxy paints, and urethane paints can be used. Among these, it is preferable to use an acrylic paint from the viewpoint of versatility.

The acrylic coating material contains an acrylic polymer obtained by polymerizing a (meth) acrylic compound.

Examples of the (meth) acrylic compound include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate and other (meth) acrylic compounds having a carboxyl group; (meth) acrylamide, N, N-dimethyl (meth). (Meta) acrylic compound having an amino group such as acrylamide; (meth) acrylic compound having an amino group such as dimethylaminoethyl (meth) acrylate; ethyl (meth) acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate (Meta) acrylic acid alkyl esters such as 2-hydroxyethyl (meth) acrylates, 4-hydroxybutyl (meth) acrylates, pentaerythritol tri (meth) acrylates, pentaerythritol tetra (meth) acrylates, etc. ) Acrylic compounds and the like can be used.

In addition to the acrylic polymer, the acrylic paint may contain an organic solvent, an aqueous medium, or the like, if necessary.

Examples of the organic solvent include n-hexane, n-heptane, n-octane, cyclohexane, cyclopentane, toluene, xylene, ethylbenzene, ethyl acetate, butyl acetate, amyl acetate, ethylene glycol monomethyl ether acetate and the like, acetone and methyl ethyl ketone. , Methyl Isobutyl Ketone, Methyl Amyl Ketone, Cyclohexanone, Diethylene Glycol Dimethyl Ether, Diethylene Glycol Diethyl Ether, Diethylene Glycol Dibutyl Ether, Dipropylene Glycol Dimethyl Ether, Ethyl Glycol Methyl Ether Acetate, Propylene Glycol Methyl Ether Acetate, Diethylene Glycol Methyl Ether Acetate, 1,2-Dimethoxyethane , Tetrahydrofuran, dioxane, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, ethylene carbonate and the like can be used. These organic solvents may be used alone or in combination of two or more.

As the aqueous medium, ion-exchanged water, distilled water; a mixture of these and the organic solvent can be used.

Examples of the method of applying the topcoat paint on the urethane foam layer (ii) include a method using a knife coater, a spray coater, a T-die coater, a roll coater, and the like; a multi-row bead coating method and the like. When a roll coater is used, the urethane resin having the foamed structure and the topcoat paint are stored in the two liquid reservoirs provided on the roll coater, respectively, and the urethane foam layer (ii) and the urethane foam layer (ii) are stored. , The top coat (iii) can be applied at the same time to form two layers at the same time.

The amount of the topcoat coating applied is, for example, in the range of 5 to 300 g / m ² .

As described above, the concrete formwork of the present invention is excellent in crack resistance because it easily absorbs an impact from the outside by using the urethane foam layer (ii) for the undercoat film. In addition, even if softwood plywood or planted wood plywood with strong knots and wood grain, which are widely used in Japan, is used as a substrate, unevenness does not appear on the surface of the concrete formwork and the appearance is excellent. Further, the urethane foam layer (ii) and the top coat film (iii) can be formed with only one coat, and the productivity is also excellent.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Synthesis Example 1]
It was obtained by reacting an aromatic polyester polyol (6 mol adduct of bisphenol A propylene oxide, isophthalic acid and sebacic acid) in a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux cooler. 60 parts by mass (number average molecular weight 2,000), 10 parts by mass polytetramethylene glycol (number average molecular weight 2,000), polycaprolactone polyol ("CAPA6400" manufactured by Perstop, number average molecular weight 38,000) 10 parts by mass was added, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content in the flask became 0.05% by mass or less.
Next, the inside of the flask is cooled to 90 ° C., 20 parts by mass of 4,4′-diphenylmethane diisocyanate melted at 70 ° C. is added, and the mixture is reacted at 110 ° C. for about 3 hours in a nitrogen atmosphere until the isocyanate group content becomes constant. As a result, a urethane prepolymer having an isocyanate group (melt viscosity at 120 ° C.; 5,000 mPa · s, NCO%; 3.5%) was obtained, and a urethane hot melt resin (1) (hereinafter, “UH resin (1)”” was obtained. It is abbreviated as.) The 100% modulus value of the cured film of the obtained urethane hot melt resin was 3 MPa.

[Example 1]
The UH resin (1) obtained in Synthesis Example 1 is mixed with nitrogen gas using a medium-pressure foaming machine "Toho A-201 type mixer" manufactured by Toho Kikai Kogyo Co., Ltd. to have a density of 0.4 g / g. A foam of cm ³ was formed and applied to a fir plywood (with missing knots) by a knife coating method at a coating amount of 80 g / m ² . After the UH resin (1) is cured, the acrylic paint "Acridic A-1300" (hereinafter abbreviated as "Ac paint-1") manufactured by DIC Corporation is applied at a coating amount of 80 g / m ² and dried. By doing so, I got a concrete mold.

[Examples 2 to 5, Comparative Example 1]
A concrete formwork was obtained in the same manner as in Example 1 except that the foaming machine used, the coating method, the type of plywood, and the type of the design layer were changed as shown in Table 1.

[Evaluation method of crack resistance]
Using the concrete formwork obtained in the examples and comparative examples, Article 4 "3. Test method" of the Japanese Agricultural Standards (Ministry of Agriculture, Forestry and Fisheries Notification No. 853, June 1999) for plywood for concrete formwork. (8) Crack resistance test (cold heat repetition test) based on cold heat repetition test and (9) Crack resistance test (alkali resistance test) based on alkali resistance test were performed to evaluate whether cracks occur. .. In any case, it was evaluated as "T" when no crack occurred and "F" when crack occurred.

"Ultra Foam Mix": Applied using "Foam-Cube" manufactured by Nordson Corporation.

It was found that Examples 1 to 5, which are the concrete formwork of the present invention, are excellent in crack resistance.

On the other hand, in Comparative Example 1, instead of the urethane foam layer (ii), a urethane layer having no foam structure was used, but the crack resistance was poor.

Claims (4)

The plywood (i), the urethane foam layer (ii), and the topcoat coating (iii) are sequentially laminated, and the urethane foam layer (ii) is a urethane hot melt resin having a foamed structure derived from an inert gas. It is a cured product, and the urethane hot melt resin is characterized by containing an aromatic polyester polyol and a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol containing a polyether polyol and polyisocyanate. Concrete mold. The concrete formwork according to claim 1, wherein the density of the urethane foam layer (ii) is in the range of 0.1 to 0.8 g / cm ³ . The concrete formwork according to claim 1 or 2 , wherein the plywood (i) is a softwood plywood or a planted tree plywood. A method for manufacturing a concrete mold in which a plywood (i), a urethane foam layer (ii), and a topcoat coating (iii) are sequentially laminated, wherein the urethane foam layer (ii) is derived from an inert gas. A urethane having an isocyanate group, which is a cured product of a urethane hot melt resin having a foamed structure, wherein the urethane hot melt resin is a reaction product of an aromatic polyester polyol and a polyol containing a polyether polyol and polyisocyanate. It contains a prepolymer, and after injecting an inert gas into the urethane hot melt resin, it is applied on the plywood (i) in one coat using a knife coater to form a urethane foam layer. (Ii) A method for manufacturing a concrete mold, which comprises forming (ii).