JP2016121436A - Concrete form - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete form which readily absorbs external impact, utilizes conifer plywood or planted tree plywood having strong nodes and grains and widely used in Japan, is excellent in crack resistance, does not cause irregularities on the surface of the concrete form, has good appearance and is excellent in productivity.SOLUTION: A concrete form is produced by having a plywood (i) as a base plate, and sequentially laminating thereon an urethane foam layer (ii) as an undercoating film and a finish coating film (iii). The finish coating film (iii) can be formed by only one coating.SELECTED DRAWING: None

Description

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

  When building buildings, such as buildings, the concrete formwork method is widely used, in which the rebar is assembled with 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 molds has increased with the rise in the number of buildings. From the viewpoint of reducing construction costs, there is a demand for improved durability so that the concrete molds can be used repeatedly.

  As the concrete formwork, a plywood, a water-based coating film, and a concrete formwork in which an acrylic overcoat film is sequentially laminated have been widely used. Since the process is necessary, there is a problem that the plywood is easily warped and the durability is lowered.

  Accordingly, various studies have been made on the undercoat coating film. For example, reports have been made on the use of a moisture-curable polyurethane hot melt for the undercoat coating film (see, for example, Patent Document 1).

  When the moisture-curable polyurethane hot melt is used, a drying process is not required, and thus, although it is excellent in productivity, there is a problem that cracks are easily generated when a concrete formwork is repeatedly used.

JP 2014-15513 A

  The problem to be solved by the present invention is to provide a concrete mold having excellent crack resistance.

  The present invention provides a concrete formwork characterized in that a plywood (i), a foamed urethane layer (ii), and a top coat (iii) are sequentially laminated.

  The concrete formwork of the present invention is easy to absorb the impact from the outside by using the urethane foam layer (ii) for the undercoat film, and is excellent in crack resistance. Moreover, even if soft wood plywood or afforestation wood plywood, which is widely used in Japan, is used as a substrate, the surface of the concrete formwork is not raised, and the appearance is excellent. Further, the foamed urethane layer (ii) and the top coat film (iii) can be formed by one coat, and are excellent in productivity.

  The concrete mold of the present invention is a laminate in which a plywood (i), a urethane foam layer (ii), and a top coat (iii) are sequentially laminated.

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

  As conifers that can be used for the conifer plywood, for example, Japanese pine, Karamatsu, Japanese cypress, cedar and the like can be used. Moreover, as afforestation trees that can be used for the afforestation tree plywood, for example, poplar, falkata, chamelere, eucalyptus, rubber, erima, terminaria, camp nosperma, acacia mangum, gmelina, merckpine, radiata pine, etc. are used. Can do.

  In addition, although the ground treatment may be given on the said conifer plywood or a plantation tree plywood for the purpose of relieving the grain and omission which the said conifer plywood or afforestation tree plywood has, the foaming urethane layer used by this invention According to (ii), it is possible to obtain a concrete formwork that does not stand out due to knots and grain over time without performing the ground treatment.

  The foamed urethane layer (ii) is formed of a urethane resin having a foamed structure. As the urethane resin, for example, a urethane hot melt resin, a two-component urethane resin, a thermoplastic urethane resin, a urethane acrylate resin, or the like can be used. Among these, it is preferable to use a urethane hot melt resin from the viewpoint of further improving the crack resistance, the adhesiveness with the top coat film (iii), and the productivity of the concrete mold.

  The urethane hot melt resin preferably contains a urethane prepolymer having an isocyanate group. Moreover, it is preferable that the said urethane prepolymer is a thing obtained by making a polyol and polyisocyanate react.

  Examples of the polyol include polyester polyol and polyether polyol. Polycarbonate polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyacryl 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 better adhesiveness in a foam structure.

  As said polyester polyol, aromatic polyester polyol, polycaprolactone polyol, crystalline polyester polyol, amorphous polyester polyol etc. can be used, for example. 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 that the adhesive strength and the mechanical strength can be further improved.

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

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

  The amount used in the case of using the polyether polyol is preferably in the range of 5 to 70% by mass in the total amount of polyol, and 7 to 60% by mass from the viewpoint that the adhesive strength and mechanical strength can be further improved. 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 in the range of 800 to 3,000, from the viewpoint of adhesive strength and mechanical strength. The range of is more preferable. In addition, the number average molecular weight of the said polyol shows the value measured on condition of the following by 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.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 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, phenylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone. Aliphatic or alicyclic polyisocyanates such as diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, it is preferable to use diphenylmethane diisocyanate from the viewpoint of reactivity and adhesive strength.

  The urethane prepolymer has an isocyanate group that can form a crosslinked structure by reacting with moisture present in the air or in an adherend to which the urethane prepolymer is applied.

  As a method for producing the urethane prepolymer, for example, the reaction mixture containing the polyisocyanate is heated after dropping the mixture of the polyol, and the isocyanate group of the polyisocyanate is compared with the hydroxyl group of the polyol. It can manufacture by making it react on the conditions which become excess.

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

  The urethane prepolymer can be usually produced in the absence of a solvent, but may be produced by reacting the polyol and polyisocyanate in an organic solvent. When reacting in an organic solvent, an organic solvent such as ethyl acetate, n-butyl acetate, methyl ethyl ketone, and toluene that does not hinder the reaction can be used, but by a method such as heating under reduced pressure during or after the reaction. It is necessary to remove the organic solvent.

  When manufacturing the said urethane prepolymer, a urethanation catalyst can be used as needed. The urethanization catalyst can be appropriately added at any stage of the reaction.

  Examples of the urethanization catalyst include compounds having nitrogen atoms such as triethylamine, triethylenediamine and N-methylmorpholine; metal salts such as potassium acetate, zinc stearate and tin octylate; organometallic compounds 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%, more preferably in the range of 1.5 to 5%, from the viewpoint that the adhesive strength and mechanical strength can be further improved. More preferred. In addition, the isocyanate group content rate of the said urethane prepolymer shows the value measured by the potentiometric titration method based on JISK1603-1: 2012.

  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 the applicability, adhesive strength, and mechanical strength, The range of 000 to 50,000 mPa · s is more preferable. In addition, the melt viscosity at 120 ° C. of the urethane prepolymer indicates a value obtained by measuring the urethane prepolymer melted at 120 ° C. with a cone plate viscometer (manufactured by ICI).

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

  Examples of the other additives include antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent brighteners, silane coupling agents, and waxes. 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 mechanical strength. The range of 5-50 MPa is more preferable. The 100% modulus was obtained by applying the urethane hot melt resin with an applicator to a thickness of 50 μm on a release paper in an atmosphere of 23 ° C. to obtain a cured film, 100% obtained by using Tensilon (Tensilon Universal Testing Machine “RTC-1210A” manufactured by Orientec Co., Ltd.) under an atmosphere of 25 ° C. and a humidity of 50% under conditions of a crosshead speed of 300 mm / min. Indicates the modulus value.

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

  Examples of the method for applying the urethane resin having a foam structure formed by the above method to the plywood (i) include a method using a knife coater, spray coater, T-die coater, roll coater, etc .; And the like. In addition, as the said application | coating system, when using a softwood plywood or a plantation tree plywood as said plywood (i), it is preferable to employ | adopt the application | coating system (knife coat system) by a knife coater. The reason is that the urethane resin can be neatly filled and applied with a knife coater even if there are missing nodes (nodes that become holes) or wood grain on the surface of the conifer plywood or afforestation tree plywood. The surface of the frame has no irregularities, and the appearance and crack resistance are further improved.

  In addition, some urethane resins have a very high viscosity, and a high viscosity urethane resin is generally very difficult to apply with a knife coater. However, in the present invention, the foamed structure is formed on the urethane resin by the above-described method, whereby the apparent viscosity at the time of application is lowered, so that the application by the knife coater can be performed efficiently.

The application 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 applicability.

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 that the crack resistance can be further improved. A range of 0.6 g / cm ³ is more preferable.

  As the top coat used for the top coat (iii), for example, a known top coat such as an acrylic paint, an epoxy paint or a urethane paint can be used. Among these, it is preferable to use an acrylic paint from the viewpoint of versatility.

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

  Examples of the (meth) acrylic compound include (meth) acrylic compounds having a carboxyl group such as (meth) acrylic acid and 2-carboxyethyl (meth) acrylate; (meth) acrylamide, N, N-dimethyl (meth) (Meth) acrylic compounds having amino groups such as acrylamide; (meth) acrylic compounds having amino groups such as dimethylaminoethyl (meth) acrylate; ethyl (meth) acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate (Meth) acrylic acid alkyl ester such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, etc. A (meth) acrylic compound to be used can be used.

  In addition to the acrylic polymer, the acrylic paint may contain an organic solvent, an aqueous medium, or the like as 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, 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, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate, diethylene glycol methyl ether acetate, 1,2-dimethoxyethane , Tetrahydrofuran, dioxane, - methylpyrrolidone, dimethylformamide, dimethylacetamide, it may be used ethylene carbonate. These organic solvents may be used alone or in combination of two or more.

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

  Examples of a method for applying the top coat onto the foamed urethane layer (ii) include a method using a knife coater, a spray coater, a T-die coater, a roll coater, etc .; a method such as a multi-strip bead coating method. In the case of using a roll coater, the urethane resin having the foam structure and the top coat paint are respectively stored in two liquid reservoir portions provided on the roll coater, and the urethane foam layer (ii) and The top coat film (iii) can be applied simultaneously to form two layers simultaneously.

The coating amount of the top coat, for example, in the range of 5~300g / ^{m 2.}

  As mentioned above, the concrete formwork of this invention is easy to absorb the impact from the outside by using a foaming urethane layer (ii) for undercoat, and is excellent in crack resistance. Moreover, even if soft wood plywood or afforestation wood plywood, which is widely used in Japan, is used as a substrate, the surface of the concrete formwork is not raised, and the appearance is excellent. Further, the foamed urethane layer (ii) and the top coat film (iii) can be formed by one coat, and are excellent in productivity.

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

[Synthesis Example 1]
A four-necked flask equipped with a thermometer, stirrer, inert gas inlet and reflux condenser was obtained by reacting aromatic polyester polyol (6 mol adduct of bisphenol A with propylene oxide, isophthalic acid and sebacic acid). 60 parts by mass of a number average molecular weight of 2,000), 10 parts by mass of polytetramethylene glycol (number average molecular weight of 2,000), polycaprolactone polyol (“CAPA6400” manufactured by Perstorp, number average molecular weight of 38,000) 10 parts by mass was added, mixed, and dehydrated by heating at 100 ° C. under reduced pressure until the water content in the flask was 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 reaction is performed at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content becomes constant. Thus, 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 referred to as “UH resin (1)”). 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 was mixed with nitrogen gas using a medium pressure foaming machine “Toho A-201 type mixing device” manufactured by Toho Machine Industry Co., Ltd., so that the density was 0.4 g / It was made into the foam of cm < ³ >, and it apply | coated with the application amount of 80 g / m < ² > to the Japanese pine plywood (with a knot) by the knife coat system. After the UH resin (1) is cured, an acrylic paint “Acridic A-1300” (hereinafter abbreviated as “Ac paint-1”) manufactured by DIC Corporation is applied at an application amount of 80 g / m ² and dried. As a result, a concrete formwork was obtained.

[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, coating method, plywood type and design layer type used were changed as shown in Table 1.

[Evaluation method of crack resistance]
Using the concrete molds obtained in the examples and comparative examples, Article 4 “3. Test Method” of the Japanese Agricultural and Forestry Standard (Ministry of Agriculture, Forestry and Fisheries No. 853, 1999 June) for plywood for concrete molds (8) A crack resistance test (cold heat repeat test) based on the cold heat test and (9) a crack resistance test (alkali resistance test) based on the alkali resistance test were conducted to evaluate whether cracks occurred. . In any case, the evaluation was “T” when no crack occurred, and “F” when the crack occurred.

“Ultrafoam mix”: Applied using “Foam-Cube” manufactured by Nordson Corporation.

  It turned out that Examples 1-5 which are the concrete molds of this invention are excellent in crack resistance.

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

Claims (4)

A concrete form, wherein a plywood (i), a urethane foam layer (ii), and a top coat (iii) are sequentially laminated. The concrete formwork according to claim 1, wherein the urethane foam layer (ii) is a cured product of a urethane hot melt resin having a foam structure. The concrete formwork of Claim 1 whose density of the said foaming urethane layer (ii) is the range of 0.1-0.8 g / cm < ³ >. The concrete formwork according to claim 1, wherein the plywood (i) is a softwood plywood or a plantation tree plywood.