Carbonation-promoting additive for hydraulic composition, hydraulic composition cured product containing same, and method for producing same

Abstract

The present invention pertains to an additive for use in a hydraulic composition. The additive contains organic fibers and an amine compound. The amine compound is attached only to the fiber surfaces of the organic fibers. The present invention also pertains to a hydraulic composition cured product that contains this carbonation-promoting additive for the hydraulic composition and that is cured through carbonation. As a result, provided are: a carbonation-promoting additive for a hydraulic composition, the carbonation-promoting additive being capable of enhancing carbon dioxide fixability after being cured; a hydraulic composition cured product containing the same; and a method for producing the same.

Description

Carbonation-promoting additive for hydraulic compositions, hardened hydraulic composition containing the same, and method for manufacturing the same.

[0001] The present invention relates to a carbonation-promoting additive for hydraulic compositions used in a hardened hydraulic composition capable of fixing carbon dioxide, a hardened hydraulic composition containing the same, and a method for producing the same.

[0002] Carbon dioxide (CO2) is one of the greenhouse gases that raises the Earth's average temperature. In recent years, the concentration of CO2 in the atmosphere has increased due to factors such as the massive consumption of fossil fuels, and the reduction of CO2 absorption by plants due to deforestation, which has led to a significant impact on global warming. Therefore, technologies are being developed to remove CO2 from the atmosphere by capturing, absorbing, storing, and fixing it in various ways. One such technology being considered is the fixation of CO2 in cement-hardened materials such as concrete, which can fix carbon dioxide. Meanwhile, Patent Document 1 describes a carbon dioxide absorbing fiber containing polyvinyl alcohol and an amine-based polymer.

[0003] International Publication No. 2021 / 200348

[0004] However, the aforementioned conventional fibers have the problem of not having very high carbon dioxide fixation capabilities, and further improvements are needed.

[0005] The present invention provides a carbonation-promoting additive for hydraulic compositions that, when used in hydraulic compositions, can enhance carbon dioxide fixation during curing and / or after hardening; a hardened hydraulic composition containing the same; and a method for producing the same.

[0006] The present invention relates to a carbonation-promoting additive for hydraulic compositions, wherein the additive comprises organic fibers and an amine compound, and the amine compound is attached only to the surface of the organic fibers.

[0007] The present invention also relates to a carbonation-promoting additive for hydraulic compositions, wherein the additive comprises a short fiber bundle of organic fibers and a liquid containing an amine compound and water, the short fiber bundle is wetted with the liquid containing the amine compound and water, and the moisture content is 5% by mass or more and 60% by mass or less.

[0008] The present invention also relates to a hardened hydraulic composition comprising the carbonation-promoting additive for the hydraulic composition, and which has been cured by carbonation.

[0009] The present invention also relates to a method for producing a carbonation-promoting additive for a hydraulic composition, comprising step A of treating the fiber surface of an organic fiber with an amine compound.

[0010] The present invention provides a carbonation-promoting additive for hydraulic compositions that, when used in hydraulic compositions, can enhance the carbon dioxide fixation properties of hardened hydraulic compositions such as cement hardened bodies during curing and / or after hardening, and a hardened hydraulic composition containing the same. According to the manufacturing method of the present invention, a carbonation-promoting additive for hydraulic compositions that, when used in hydraulic compositions, can enhance the carbon dioxide fixation properties of hardened hydraulic compositions such as cement hardened bodies can be obtained.

[0011] Figure 1 is an explanatory diagram showing the sampling locations of mineral composition test specimens and the results. Figure 2 is a cross-sectional photograph (magnification 400x) of the hollow fiber used in Example 19 of the present invention. Figure 3 is a cross-sectional photograph (magnification 300x) of the hollow fiber used in Example 25 of the present invention. Figure 4 is a graph showing the relationship between compressive strength and static elastic modulus for Examples 27-29 and Comparative Example 7 of the present invention. Figure 5 is a graph showing the pore size distribution and cumulative void amount measured by a mercury intrusion porosimeter immediately after demolding (age 1 day) for Examples 27-29 and Comparative Example 7 of the present invention. Figure 6 is a graph showing the pore size distribution at a position of 40-50 mm on the 7th day of carbonation curing for Examples 27-29 and Comparative Example 7 of the present invention. Figure 7 is a graph showing the pore size distribution at a position of 0-10 mm on the 7th day of carbonation curing for Examples 27-29 and Comparative Example 7 of the present invention.

[0012] The inventors have found that by using an additive in which an amine compound is attached only to the surface of organic fibers, CO2 from the air can be taken in from the outside of the cement molded product and fixed into the cement composition, thereby improving the carbon dioxide fixing ability of the hardened carbonated hydraulic composition. This is presumed to be due to the amine compound on the surface of the organic fibers ensuring a channel for CO2-containing air and increasing the amount of CO2 reaction (fixation). In Patent Document 1, since the amine polymer is kneaded into the fibers, the amount of amine compound present on the fiber surface is small, and the carbon dioxide fixing effect is poor.

[0013] (Carbonation-promoting additive for hydraulic compositions) The carbonation-promoting additive for hydraulic compositions can be used in hydraulic compositions such as cement compositions that can fix carbon dioxide during curing and / or after hardening, thereby promoting the carbonation of hardened hydraulic compositions such as hardened cement bodies. In this specification, "hydraulic composition that can fix carbon dioxide during curing and / or after hardening" means a hydraulic composition that reacts with carbon dioxide using calcium hydroxide, calcium silicate hydrate, etc., during curing and / or after hardening, thereby fixing carbon dioxide in the hardened body. Specifically, this includes cement compositions such as mortar and concrete.

[0014] In the first embodiment of the present invention, the carbonation-promoting additive for hydraulic compositions comprises organic fibers and an amine compound, wherein the amine compound is attached only to the surface of the organic fibers. In the second embodiment of the present invention, the carbonation-promoting additive for hydraulic compositions comprises a short fiber bundle of organic fibers and a liquid containing an amine compound and water, wherein the short fiber bundle is wetted with the liquid containing the amine compound and water, and its moisture content is 5% by mass or more and 60% by mass or less. Unless otherwise specified below, the description of the organic fibers and the amine compound applies to the carbonation-promoting additive for hydraulic compositions in both the first and second embodiments. In this specification, a moisture content of 5% by mass or more of the short fiber bundle of organic fibers means that the short fiber bundle of organic fibers is wetted with a liquid containing an amine compound and water. In this specification, a short fiber bundle of organic fibers also means that the fiber length of the single fiber is 50 mm or less.

[0015] Examples of the organic fibers include synthetic fibers, semi-synthetic fibers, regenerated fibers, and natural fibers. Examples of synthetic fibers include polyolefin resins such as polypropylene, polyethylene (including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.), polybutene-1, propylene copolymers (including propylene-ethylene copolymers and propylene-butene-1-ethylene copolymers), ethylene-vinyl alcohol copolymers, and ethylene-vinyl acetate copolymers; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN). Examples include polyester resins such as polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), and copolymers thereof; polyamide resins such as nylon 6, nylon 12, and nylon 66; acrylic resins containing acrylonitrile as a component; polyvinyl alcohol resins; polyurethane resins; and at least one selected from the group consisting of engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefins, as well as their elastomers. These may be used individually or in combination of two or more.

[0016] Examples of semi-synthetic fibers include acetate fibers. Examples of regenerated fibers include viscose rayon, cupro, solvent-spun cellulose, and polynosic. Examples of natural fibers include cotton, linen, silk, wool, and pulp.

[0017] Among the organic fibers mentioned above, synthetic fibers are preferred because they can be produced stably. Among synthetic fibers, those having alkali resistance and ultraviolet resistance are preferred from the viewpoint of improving the carbon dioxide fixation ability of the carbonation promoting additive for hydraulic compositions, such as polyolefin fibers, nylon fibers, vinylon fibers, and aramid fibers. The organic fibers are particularly preferably polyolefin resin fibers having moisture heat resistance and alkali resistance. The polyolefin resin fibers preferably contain 80% by mass or more of polyolefin resin, more preferably 90% by mass or more, and particularly preferably all (100% by mass) of the resin component is polyolefin resin.

[0018] Examples of the polyolefin resins include polypropylene resins, polyethylene resins, and polymethylpentene resins.

[0019] The polypropylene resin may be a propylene homopolymer or a propylene copolymer. Examples of propylene copolymers include copolymers of propylene and other α-olefins. The other α-olefin may be at least one selected from the group consisting of ethylene with 2 carbon atoms and α-olefins with 4 or more carbon atoms. Examples of α-olefins with 4 or more carbon atoms are not particularly limited, but include 1-butene, 1-pentene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-octadecene. In the propylene copolymer, the propylene content is preferably 85 mol% or more, 90 mol% or more, 95 mol% or more, or 98 mol% or more.

[0020] Examples of the polyethylene resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene.

[0021] The polymethylpentene resin may be a homopolymer of 4-methylpentene-1 or a copolymer of 4-methylpentene-1. Examples of copolymers of 4-methylpentene-1 include copolymers of 4-methylpentene-1 and other α-olefins. Examples of other α-olefins include copolymers of one or two α-olefins having 2 to 20 carbon atoms, preferably 8 to 18 carbon atoms, as described above. The copolymer of 4-methylpentene-1 may contain 85 mol% or more, 90 mol% or more, 95 mol% or more, or 95 mol% or more of 4-methylpentene-1.

[0022] The aforementioned polyolefin resin may be used alone or in combination of two or more types. Furthermore, the fiber surface of the polyolefin may be modified. For example, a modified polyolefin may be used in which acidic groups are copolymerized, such as by mixing a compound or polymer having reactive functional groups like carboxyl groups, or by graft polymerization of reactive functional groups like maleic acid.

[0023] The organic fiber is preferably a fiber on which hydrophilic functional groups are attached, and the amine compound is attached to its surface. In particular, hydrophobic resins such as polyolefin resins tend to have difficulty with the amine compound adhering to the fiber surface and tend to detach easily in cement slurry. By attaching hydrophilic functional groups to the fiber surface, the amine compound chemically bonds with the fiber, improving adhesion to the fiber surface and / or suppressing detachment in cement slurry.

[0024] The fibers to which the hydrophilic functional group is attached are not particularly limited as long as the functional group readily chemically bonds with the amine compound. For example, a carboxyl group-containing polyolefin resin obtained by copolymerizing a polyolefin resin with monomers containing carboxyl groups, such as unsaturated carboxylic acids like acrylic acid, methacrylic acid, maleic acid, and maleic anhydride, may be used. It is preferable to include a maleic acid-modified polyolefin resin. Examples of resins in which maleic acid is introduced as a hydrophilic functional group into a polyolefin (e.g., polypropylene) include Modic P908 (trade name) from Mitsubishi Chemical Corporation, Yumex 1001 (trade name) and Yumex 1010 (trade name) from Sanyo Chemical Industries, Ltd., and Rikeaid MG400P (trade name) from Riken Vitamin Co., Ltd.

[0025] The organic fiber may be a single fiber or a composite fiber. The composite fiber may be a core-sheath type composite fiber, a side-by-side type composite fiber, a split type composite fiber, or a sea-island type composite fiber. If the organic fiber is a core-sheath type composite fiber, it may be a concentric core-sheath type composite fiber or an eccentric core-sheath type composite fiber. If the organic fiber is a core-sheath type composite fiber, the composite ratio of the core component and the sheath component is not particularly limited, but the mass ratio of the core component / sheath component may be 90 / 10 or more and 10 / 90 or less, more preferably 80 / 20 or more and 20 / 80 or less, and most preferably 70 / 30 or more and 30 / 70 or less.

[0026] The cross-sectional shape of the organic fiber is not particularly limited; it may be a circular cross-section, or an irregular cross-section other than a circular cross-section (non-circular cross-section). Preferably, it is an irregular cross-section, more preferably a circular hollow cross-section or an irregular hollow cross-section, and even more preferably a triangular hollow cross-section or a pentagonal hollow cross-section.

[0027] The organic fiber is not particularly limited, but for example, from the viewpoint of workability, the fiber diameter of the single fiber is preferably 8 μm or more and 700 μm or less, more preferably 8 μm or more and 100 μm or less, and even more preferably 9 μm or more and 80 μm or less. In this specification, fiber diameter means the diameter of the fiber cross-section if the fiber cross-section is circular, the diameter of the circumscribed circle (maximum span length) of the fiber cross-section if the fiber cross-section is irregular, and if there is no circumscribed circle of the fiber cross-section, the fiber diameter means the maximum span length of the smallest inclusion circle.

[0028] The organic fibers are not particularly limited, but for example, from the viewpoint of workability, the fiber length of the single fiber is preferably 0.5 mm or more and 50 mm or less, more preferably 2 mm or more and 30 mm or less, and even more preferably 3 mm or more and 15 mm or less.

[0029] The amine compound may contain one or more amino groups selected from the group consisting of primary amino groups, secondary amino groups, and tertiary amino groups, and is not particularly limited. However, from the viewpoint of improving the carbon dioxide fixing ability of the carbonation promoting additive for hydraulic compositions, it is preferable that it contains one or more amino groups selected from the group consisting of primary amino groups and secondary amino groups, and more preferably that it contains a secondary amino group.

[0030] The amine compound preferably contains a tertiary amino group. While primary and secondary amino groups produce carbamates upon CO2 absorption, tertiary amino groups produce bicarbonates upon CO2 absorption, and are therefore presumed to be preferable as a source of carbonate ions into the hardened cement. The tertiary amino group is preferably present in an amount of 20 mol% or more in the amine compound composition.

[0031] Examples of the amine compounds include oligoamines such as ethylenediamine, propylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, phenylenediamine, metaxylenediamine, diethylenetriamine, triethylenetetraamine, and triaminopropane, as well as amino group-containing resins having amino groups such as polyvinylamine, polyethyleneimine, polyallylamine, and polylysine. Among these, polyethyleneimine can be preferably used. Polyethyleneimine is a water-soluble polymer obtained by polymerizing ethyleneimine, and generally contains primary amino groups, secondary amino groups, and tertiary amino groups, and for example, has a branched structure rather than a completely linear molecule. As for polyethyleneimine, from the viewpoint of enhancing the carbon dioxide fixation ability of the carbonation-promoting additive for hydraulic compositions, it is preferable that, when the total of primary, secondary, and tertiary amines is 100 mol%, the molar amount of primary and / or secondary amines exceeds 50 mol%, more preferably 55 mol% or more, and even more preferably 60 mol% or more. The amine compound is preferably a compound containing a tertiary amino group. For example, triisopropanolamine can be given as a tertiary amine.

[0032] The amine compound is not particularly limited, but for example, its weight-average molecular weight is preferably 100 g / mol or more and 10,000,000 g / mol or less, more preferably 1,000 g / mol or more and 5,000,000 g / mol or less, even more preferably 2,000 g / mol or more and 3,000,000 g / mol or less, and even more preferably 5,000 g / mol or more and 1,500,000 g / mol or less. In this specification, the weight-average molecular weight of the amine compound is measured as described in the examples.

[0033] The amine compound is not particularly limited. For example, the amine value (the number of mmol of amine contained in 1 g of solid content) is preferably 0.1 mmol / g or more and 50 mmol / g or less, more preferably 0.5 mmol / g or more and 40 mmol / g or less, even more preferably 2 mmol / g or more and 30 mmol / g or less, and even more preferably 5 mmol / g or more and 20 mmol / g or less. In this specification, the amine value of the amine compound is measured as described in the examples.

[0034] The organic fiber may be subjected to a physical treatment (hydrophilic treatment) on the fiber surface to impart hydrophilic functional groups. As the physical treatment, for example, it is preferable that an amine-based compound is attached to a fiber hydrophilized by at least one hydrophilic treatment selected from fluorine gas treatment, plasma discharge treatment, corona discharge treatment, ozone aqueous solution treatment, ultraviolet irradiation treatment, and sulfonation treatment, or that an amine compound is attached to the fiber by a crosslinking agent. With such a configuration, the amine-based compound is likely to be fixed on the surface of the organic fiber.

[0035] When performing the corona discharge treatment, although not particularly limited, the discharge amount per time in the corona discharge treatment is preferably 50 W / m 2 / min or more, and the total discharge amount is preferably 100 to 5000 W / m 2 / min. A more preferable total discharge amount is 250 to 5000 W / m 2 / min. Also, the plasma treatment is not particularly limited, but is preferably an atmospheric pressure plasma treatment, and it is advisable to perform the treatment at a voltage of 50 kV or more and 250 kV or less and a frequency of 500 pps or more and 3000 pps or less. With an atmospheric pressure plasma treatment, the treatment can be performed at a low voltage, so there is less deterioration of the fiber, which is convenient. Also, the fluorine gas treatment is not particularly limited, but for example, it can be performed using a mixed gas containing fluorine gas and oxygen gas or a mixed gas containing fluorine gas and sulfurous acid gas.

[0036] In the case of the second embodiment, the short fiber bundle of the organic fiber is wetted with a liquid containing the amine compound and water, and has a moisture content of 5% by mass or more and 60% by mass or less. When the moisture content of the short fiber bundle of the organic fiber is 5% by mass or more, it becomes easier to mix during kneading with cement. Further, when the moisture content of the short fiber bundle of the organic fiber is 60% by mass or more, adjustment of the amount of moisture in the cement slurry becomes complicated. The moisture content of the short fiber bundle of the organic fiber is preferably 5% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less. In this specification, the moisture content of the short fiber bundle of the organic fiber can be measured as described in the examples.

[0037] The organic fiber is not particularly limited, but preferably has a total nitrogen content on the fiber surface of 0.01% by mass or more and 2% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less, and even more preferably 0.01% by mass or more and 0.5% by mass or less. When the total nitrogen content on the fiber surface of the organic fiber is within the above range, the amine-based compound used in the fiber treatment agent is sufficiently adhered, so the carbon dioxide fixation property of the carbonation promoting additive for the hydraulic composition is enhanced. In this specification, the total nitrogen content on the fiber surface of the organic fiber can be measured as described in the examples.

[0038] (Method for producing a carbonation promoting additive for a hydraulic composition) The carbonation promoting additive for a hydraulic composition is, as described above, used for a hydraulic hardened product such as a cement composition that can immobilize carbon dioxide during curing and / or after curing, and is an organic fiber or a short fiber bundle of an organic fiber. The method for producing the carbonation promoting additive for a hydraulic composition, more specifically, the carbonation promoting additive for a hydraulic composition according to the first or second embodiment described above, is not particularly limited, but for example, preferably includes a step A of subjecting an organic fiber to an adhesion treatment with an amine compound. As the organic fiber and the amine compound, the organic fiber and the amine compound described above can be used, respectively.

[0039] In step A, it is preferable to treat the organic fibers with an amine compound using a treatment solution containing an amine compound and water, by at least one means selected from the group consisting of immersion, coating, and spraying. In step A, it is preferable to use the organic fibers in the form of a continuous long fiber bundle (tow) in which multiple single fibers are bundled together. Specifically, a hydrophobic resin can be melt-spun, the resulting spun filament (undrawn filament) can be drawn, and the drawn filament (organic fiber in the form of a continuous long fiber bundle in which multiple single fibers are bundled together) can be used in step A. After step A, in step B, the long fiber bundle treated with the treatment solution can be cut to a predetermined fiber length to obtain a short fiber bundle. The cut length is preferably, for example, 0.5 mm or more and 50 mm or less, more preferably 2 mm or more and 30 mm or less, and even more preferably 3 mm or more and 15 mm or less. After step A and before step B, in step C, the moisture content of the long fiber bundle treated with the treatment liquid is adjusted to 5% by mass or more and 60% by mass or less, thereby obtaining the carbonation-promoting additive for hydraulic compositions of the second embodiment (short fiber bundle of organic fibers) after step B. After step B, the short fiber bundle of organic fibers may be dried. By drying, the carbonation-promoting additive for hydraulic compositions of the first embodiment (short organic fibers) can be obtained.

[0040] When the organic fiber is a polyolefin resin fiber, the carbonation-promoting additive for hydraulic compositions can be manufactured, for example, as described below.

[0041] First, using one or more of the polyolefin resins, melt spinning is performed at the temperature at which the polyolefin resin melts, using a single-type or composite-type nozzle that produces a predetermined shape, and the material is taken up at a draw speed of 100 m / min to 2000 m / min, thereby obtaining spun filaments with a single fiber fineness of 4 decitex to 80 decitex. Hereinafter, "decitex" will be abbreviated as "dtex". The spinning temperature may be, for example, 250°C to 310°C or 270°C to 300°C if the polyolefin resin is a polypropylene resin, and for example, 260°C to 320°C or 280°C to 300°C if the polyolefin resin is a polymethylpentene resin.

[0042] Next, the spun filament is drawn to obtain a drawn filament. This improves the single-fiber strength of the organic fiber. The drawn filament preferably has a single-fiber fineness of 0.5 dtex or more and 30 dtex or less, more preferably 0.8 dtex or more and 20 dtex or less, and even more preferably 1.0 dtex or more and 6 dtex or less. The drawing temperature and drawing ratio are not particularly limited, but for example, it is preferable to draw the filament at a drawing temperature of 80°C or more and 140°C or less and a drawing ratio of 1.1 times or more and 8 times or less. A more preferable drawing temperature is 100°C or more and 150°C or less. A more preferable drawing ratio is 2 times or more and 6 times or less. The stretching method is not particularly limited, and the stretching process can be carried out using known methods such as wet stretching, which involves stretching while heating with a high-temperature liquid such as hot water; dry stretching, which involves stretching while heating in a high-temperature gas or with a high-temperature metal roll; and steam stretching, which involves stretching while heating the fibers with steam at 100°C or higher at atmospheric pressure or under pressure. These stretching methods can also be combined, such as performing wet stretching followed by dry stretching, or performing dry stretching multiple times. The stretching process may be carried out as a single-stage stretching process or as a so-called multi-stage stretching process divided into multiple stages. If only wet stretching is performed, the material should be dried before use in step A.

[0043] Next, in step A, the stretched filament (organic fiber) is treated with an amine compound. Preferably, the stretched filament (organic fiber) is treated using a treatment solution containing the amine compound and water, by at least one means selected from the group consisting of immersion, coating, and spraying. The treatment solution preferably contains 0.1% to 20% by mass of the amine compound in terms of solid content (active ingredient), more preferably 0.5% to 10% by mass, and even more preferably 1% to 5% by mass. The temperature of the treatment solution is not particularly limited, but may be, for example, 10°C to 90°C, 20°C to 80°C, 30°C to 75°C, or 35°C to 70°C. The viscosity of the aforementioned treatment solution at 25°C is preferably 0.1 mPa·s to 10 mPa·s, more preferably 0.5 mPa·s to 7 mPa·s, and even more preferably 1 mPa·s to 4 mPa·s, from the viewpoint of improving the adhesion of the amine compound to the fiber surface of the organic fiber.

[0044] The organic fiber is preferably obtained by mixing a resin or compound having hydrophilic functional groups with the organic material constituting the fiber, and / or by subjecting the surface of the organic fiber to a hydrophilic treatment. By subjecting the organic fiber to the hydrophilic treatment, hydrophilic functional groups can be imparted to the surface of the organic fiber. By imparting hydrophilic functional groups to the surface of the organic fiber, the amine compound may be made to adhere or fix more easily. As for the method of mixing the resin or compound having hydrophilic functional groups with the organic material, if the organic material is a thermoplastic resin, it can be obtained by melt kneading using methods such as dry blending or liquid addition.

[0045] The aforementioned hydrophilization treatments include corona discharge treatment, plasma treatment, fluorine gas treatment (for example, treatment using a mixed gas containing fluorine gas and oxygen gas, or a mixed gas containing fluorine gas and sulfur dioxide), ozone treatment (for example, treatment with an aqueous ozone solution or ozone gas treatment), and sulfonation treatment (in addition to sulfonation treatment using anhydrous sulfuric acid gas, sulfonation treatment using fuming sulfuric acid, sulfonation treatment using sulfur dioxide gas, and sulfonation treatment using hot concentrated sulfuric acid). From the viewpoint of ease of processing, corona discharge treatment or plasma treatment is preferred. The conditions for each are as described above.

[0046] The hydrophilization treatment is not particularly limited as long as it is a process that can process organic fibers. For example, if the organic fiber is a thermoplastic fiber, the hydrophilization treatment may be performed on the filament after stretching before the amine compound is applied.

[0047] After step A, in step B, the long fiber bundle treated with the processing liquid is cut to a predetermined fiber length to obtain a wet short fiber bundle. Before step B, crimp may be applied as needed. After step B, the wet short fiber bundle is dried to obtain the carbonation promoting additive for the hydraulic composition of the first embodiment (short organic fibers). The drying temperature is not particularly limited, but for example, it is preferably 80°C to 150°C, more preferably 90°C to 140°C, and even more preferably 100°C to 130°C.

[0048] After step A and before step B, in step C, the moisture content of the long fiber bundle treated with the treatment liquid is adjusted to 5% by mass or more and 60% by mass or less, preferably 10% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, thereby obtaining the carbonation-promoting additive for hydraulic compositions of the second embodiment (short fiber bundle of organic fibers) after step B. The moisture content can be adjusted by squeezing the long fiber bundle treated with the amine compound using a mangle roll or the like. After step B, the short fiber bundle of organic fibers may be dried. By drying, the carbonation-promoting additive for hydraulic compositions of the first embodiment (short organic fibers) can be obtained.

[0049] (Hydraulic Composition Hardened Body) A hydraulic composition hardened body such as a cement hardened body contains the above-mentioned carbonation promoting additive for hydraulic compositions (hereinafter also simply referred to as the additive). In the hydraulic composition hardened body such as a cement hardened body, the content of the additive is not particularly limited, but is preferably 0.01 Vol% or more and 5 Vol% or less, more preferably 0.02 Vol% or more and 2 Vol% or less, and even more preferably 0.05 Vol% or more and 0.3 Vol% or less. When the content of the additive in the hydraulic composition hardened body such as a cement hardened body is 0.01 Vol% or more, the carbon dioxide fixing ability of the hydraulic composition hardened body such as a cement hardened body is improved. When the content of the additive in the hydraulic composition hardened body such as a cement hardened body is 5 Vol% or less, it is easier to suppress the generation of fiber balls when preparing a hydraulic composition (slurry) such as a cement composition, and it is possible to suppress the decrease in mechanical strength such as the compressive strength of the hydraulic composition hardened body such as a cement hardened body.

[0050] The hydraulic composition hardened body, such as the cement hardened body, can be obtained by hardening a cement composition containing the additive, cement, water, and aggregate, and then curing it by carbonation. The cement is not particularly limited, and various types of cement can be used, such as ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, fly ash cement, and blast furnace cement.

[0051] The aggregate is not particularly limited and examples include silica sand, river sand, sea sand, beach sand, and crushed stone. The particle size of the aggregate can be selected from among the aggregates according to the intended use of the concrete composition and used as appropriate as fine aggregate or coarse aggregate. Fine aggregate or coarse aggregate may be used alone or in combination of two or more types.

[0052] The cement composition may further contain admixtures. There are no particular restrictions on the admixtures, and various cement admixtures can be used as appropriate. For example, blast furnace slag powder, fly ash, and silica fume can be commonly used. The admixtures may be used individually or in combination of two or more. As admixtures, from the viewpoint of improving the CO2 fixation properties of hydraulic compositions such as cement hardened bodies, fine powders or adsorbents capable of adsorbing CO2, calcium oxide (CaO) powder, etc., may be used. As fine powders or adsorbents capable of adsorbing carbon dioxide, slag containing γ-2CaO・SiO2 (also called γ-C2S) is preferred. In the cement composition, the amount of γ-C2S is preferably 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of cement. Excellent carbon dioxide adsorption capacity is exhibited within this range, and the mechanical properties are also excellent.

[0053] The hydraulic composition, such as the cement composition, may further contain admixtures. Various admixtures, such as AE agents, AE water-reducing agents, high-performance AE water-reducing agents, fluidizers, hardening accelerators, rust inhibitors, setting retarders, quick-setting agents, and shrinkage-reducing agents, can be appropriately selected and used depending on the purpose and application. Examples of high-performance AE water-reducing agents (also called defoaming agents) include naphthalene sulfonate-based, polycarboxylic acid-based, melamine sulfonic acid-based, and aminosulfonic acid-based agents, with polycarboxylic acid-based water-reducing agents being preferred. The admixtures may be used individually or in combination of two or more.

[0054] A hardened hydraulic composition, such as a cement composition, can be obtained by hardening the hydraulic composition and then curing it by carbonation. Specifically, the cement composition can be filled into a mold of a predetermined shape, and after casting the cement composition, sufficient moisture can be supplied to prevent the surface of the cement composition from drying out, followed by wet curing, demolding, and then carbonation curing. In wet curing, known methods for supplying moisture include flooding, watering, dampening, wet sand curing, and spray curing, allowing the cement composition to be cured while simultaneously being supplied with water to its surface. The carbonation curing process involves curing the hardened hydraulic composition obtained during the hardening process in an environment with a volume concentration of 5% or more of carbon dioxide to allow the hardened hydraulic composition to absorb and fix carbon dioxide. The volume concentration of carbon dioxide is not particularly limited, but can be between 5% and 100%. The hardened hydraulic composition, such as the cement hardened body, has a compressive strength of 15 N / mm² at a young age of 7 days, for example. 2 It is preferable that the load is greater than or equal to 20 N / mm², and more preferably 20 N / mm². 2 The above is preferable, and more preferably 30 N / mm 2 That's all.

[0055] The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples. The measurement methods used in the examples and comparative examples will be described below.

[0056] (Viscosity) The viscosity of the surface treatment agent at 25°C was measured in accordance with JIS Z 8803:2011-9, the method for measuring viscosity using a single-cylindrical rotational viscometer.

[0057] (Fiber diameter) The cross-sections of 30 arbitrarily selected fibers were observed using a scanning electron microscope (Hitachi High-Technologies Corporation, model number "SU3500"), and the diameter of each fiber cross-section was measured using 2D image measurement software (SCALA Corporation, MicroMeasure). The arithmetic mean of these measurements was defined as the fiber diameter.

[0058] (Total Nitrogen Amount) The nitrogen amount was measured using a Sumigraph NC-220F (combustion method, elemental analyzer) manufactured by Sumitomo Chemical Co., Ltd. as an elemental analyzer. With the Sumigraph NC-220F, the sample was completely combusted on a quartz boat, and the generated nitrogen gas was measured by a GC-TCD in the instrument. The amount of nitrogen (weight %) was calculated from the peak area of ​​the nitrogen gas obtained from the GC-TCD analysis and the sample weight entered before measurement. Aspartic acid was used as the standard sample. The analysis procedure was as follows: (1) The quartz boat and quartz filter paper were baked to remove any adhering nitrogenous substances. (2) The sample was placed on the quartz boat and quartz filter paper after baking, and the weight was recorded. The amount of sample was approximately 500 mg, and the balance was manually calibrated before use. (3) After confirming that the detector value of the instrument was stable, the measurement was started. (4) After the measurement was completed, the analysis was started.

[0059] (Moisture content) The moisture content was measured in accordance with JIS L 1015 8.1.2. Specifically, approximately 5 g of short fiber bundles were taken as samples. The mass of the sample and the mass under standard conditions were measured, and the moisture content (%) was calculated using the following formula. The average of the two measurements was rounded to one decimal place according to JIS-Z-8401. f =(m-m') / m'×100 R f : Moisture content (%) m: Mass of the sample at the time of sampling (g) m': Mass of the sample under standard conditions (g)

[0060] (Compressive strength of hardened cement) The compressive strength was measured in accordance with JIS A 1108.

[0061] (CO2 fixation amount of cement hardened material) The prepared mortar test specimens were sliced ​​every 20 mm from the exposed surface and finely ground to obtain samples. Next, the samples were burned in an oxygen atmosphere using a carbon-sulfur analyzer (TC) to determine the amount of carbon in the samples. After eliminating the amount of carbon originating from the material by subtracting the measured amount of carbon in the sample of the mortar test specimen that was cured in air from the measured amount of carbon in the mortar test specimen that was cured in carbon dioxide, the result was converted to CO2 and determined as the amount of CO2 fixation of the cement hardened material.

[0062] (Mineral composition of hardened cement) was measured by energy-dispersive X-ray spectroscopy (SEM-EDX). The electron microscope used was a Hitachi High-Tech SU3500 scanning electron microscope, with the following measurement conditions: acceleration voltage of 15 kV, vacuum of 50 Pa, and BSE detector. The energy-dispersive X-ray analyzer used was an Oxford Instruments X-Max N20, with line scan measurement mode.

[0063] In the examples, the amine compounds shown in Table 1 below were used. In Table 1 below, the weight-average molecular weight, amine value, composition ratio, and solid content concentration of the amine compounds are the values ​​provided by the manufacturer. Note that in Table 1 below, Epomin is a registered trademark.

[0064] (Example 1) A polypropylene resin (polypropylene homopolymer, manufactured by Nippon Polypropylene Co., Ltd., product name "SA01A", melting point 160°C) was melt-extruded using a spinning nozzle with a circular nozzle hole shape at a spinning temperature of 290°C, and taken up at a take-up speed of 222 m / min to produce a 15 dtex spun filament (undrawn yarn). The obtained spun filament was dry-drawn 2.5 times at 130°C (single-stage drawing). The obtained drawn yarn was immersed in a 60°C treatment solution containing A1 as an amine compound and water (concentration of the active ingredient A1 is 3% by mass, viscosity at 25°C is 1.303 mPa·s), then squeezed with a mangle roll to adjust the moisture content to 40%, and cut to a fiber length of 6 mm to obtain short fiber bundles of polypropylene fibers (circular cross-section) and polypropylene fibers (short fibers) with a single fiber fineness of 5.4 dtex.

[0065] (Example 2) A short fiber bundle of polypropylene fibers and polypropylene fibers (short fibers) were obtained in the same manner as in Example 1, except that a treatment solution containing A2 as an amine compound and water at 60°C (with a concentration of the active ingredient A2 of 3% by mass and a viscosity of 3.23 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0066] (Example 3) A short fiber bundle of polypropylene fibers and polypropylene fibers (short fibers) were obtained in the same manner as in Example 1, except that a treatment solution containing A3 as an amine compound and water at 60°C (with a concentration of the active ingredient A3 of 3% by mass and a viscosity of 1.26 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0067] (Example 4) A short fiber bundle of polypropylene fibers and polypropylene fibers (short fibers) were obtained in the same manner as in Example 1, except that a treatment solution containing A4 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A4 and a viscosity of 1.297 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0068] (Example 5) A short fiber bundle of polypropylene fibers and polypropylene fibers (short fibers) were obtained in the same manner as in Example 1, except that a treatment solution containing A5 as an amine compound and water at 60°C (with a concentration of 3% by mass of the active ingredient A5 and a viscosity of 1.313 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0069] (Example 6) A short fiber bundle of polypropylene fibers and polypropylene fibers (short fibers) were obtained in the same manner as in Example 1, except that a treatment solution containing A6 as an amine compound and water at 60°C (with a concentration of the active ingredient A6 of 3% by mass and a viscosity of 1.333 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0070] (Example 7) A polypropylene resin (polypropylene homopolymer, manufactured by Nippon Polypropylene Co., Ltd., product name "SA01A", melting point 160°C) was used as the core component, and a polymethylpentene resin (4-methylpentene-1 homopolymer, manufactured by Mitsui Chemicals, Inc., product name "DX820", melting point 233°C) was used as the sheath component. Using a concentric core-sheath composite nozzle, the core component was spun at a spinning temperature of 290°C and the sheath component at a spinning temperature of 270°C, so that the composite ratio of the core component and the sheath component was 60:40 by mass ratio. The fibers were taken up at a take-up speed of 222 m / min to produce a 15 dtex spun filament (undrawn yarn). The obtained spun filament was dry-drawn 2.5 times at 130°C (single-stage drawing). The resulting drawn yarn was immersed in a 60°C treatment solution containing A1 as an amine compound and water (with an active ingredient concentration of 3% by mass of A1 and a viscosity of 1.303 mPa·s at 25°C). The yarn was then squeezed using a mangle roll to adjust the moisture content to 40%, cut to a fiber length of 6 mm, and short fiber bundles of core-sheath composite fibers (circular cross-section) and core-sheath composite fibers (short fibers) with a single fiber fineness of 5.4 dtex were obtained.

[0071] (Example 8) Short fiber bundles of core-sheath composite fibers and core-sheath composite fibers (short fibers) were obtained in the same manner as in Example 7, except that a treatment solution containing A2 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A2 and a viscosity of 3.23 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0072] (Example 9) Short fiber bundles of core-sheath composite fibers and core-sheath composite fibers (short fibers) were obtained in the same manner as in Example 7, except that a treatment solution containing A3 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A3 and a viscosity of 1.26 mPa·s at 25°C) was used instead of the treatment solution containing A1 as an amine compound and water.

[0073] (Example 10) Short fiber bundles of core-sheath composite fibers and core-sheath composite fibers (short fibers) were obtained in the same manner as in Example 7, except that a treatment solution containing A4 as an amine compound and water at 60°C (with a concentration of the active ingredient A4 of 3% by mass and a viscosity of 1.297 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0074] (Example 11) Short fiber bundles of core-sheath composite fibers and core-sheath composite fibers (short fibers) were obtained in the same manner as in Example 7, except that a treatment solution containing A5 as an amine compound and water at 60°C (with a concentration of the active ingredient A5 of 3% by mass and a viscosity of 1.313 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0075] (Example 12) Short fiber bundles of core-sheath composite fibers and core-sheath composite fibers (short fibers) were obtained in the same manner as in Example 7, except that a treatment solution containing A6 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A6 and a viscosity of 1.333 mPa·s at 25°C) was used instead of the treatment solution containing A1 as an amine compound and water.

[0076] The moisture content and total nitrogen content of the short fiber bundles obtained in Examples 1 to 12 were measured as described above, and the results are shown in Table 2 below. In addition, the fiber diameter of the single fibers in the short fiber bundles obtained in Examples 1 to 12 was measured as described above, and the results are shown in Table 2 below.

[0077] (Example 13) <Preparation of Carbonation-Promoting Additive for Hydraulic Composition> Short fiber bundles of polypropylene fibers with a single fiber fineness of 0.6 dtex (hereinafter also referred to as A1 (fiber)) were obtained in the same manner as in Example 1, except that the draw speed was 690 m / min and the stretch ratio was 2.76 times. <Preparation of Hardened Cement> The materials shown in Table 3 below and the A1 (fiber) obtained above were stirred and mixed in the proportions shown in Table 4 below to obtain a cement composition (mortar composition). In Table 4 below, W means water. The obtained cement composition was poured into a rectangular prism-shaped formwork (4 × 4 × 16 cm) and a cylindrical formwork (diameter 5 cm, height 10 cm), respectively, and cured in the formwork at room temperature for 1 day. Subsequently, the specimens were left to stand for 7 days in an atmosphere of 20°C and 60% RH, followed by carbonation curing for 7 days in an atmosphere of 20% CO2 concentration, 20°C, and 60% RH. After that, they were cured in air until 28 days of age, yielding prismatic and cylindrical specimens. For the prismatic specimens, the CO2 exposure surface during carbonation curing was the end face, and the rest was sealed with aluminum tape before curing. The cylindrical specimens were cured with the entire surface open.

[0078] (Example 14) A short fiber bundle of polypropylene fibers (hereinafter also referred to as A2 (fiber)) and a cement hardened body containing A2 (fiber) were prepared in the same manner as in Example 13, except that a treatment solution containing A2 as an amine compound and water at 60°C was used instead of a treatment solution containing A1 as an amine compound and water (the concentration of the active ingredient A2 was 3% by mass, and the viscosity at 25°C was 3.23 mPa·s).

[0079] (Example 15) A short fiber bundle of polypropylene fibers (hereinafter also referred to as A3 (fiber)) and a cement hardened body containing A3 (fiber) were prepared in the same manner as in Example 13, except that a treatment solution containing A3 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A3 and a viscosity of 1.26 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0080] (Example 16) A short fiber bundle of polypropylene fibers (hereinafter also referred to as A4 (fiber)) and a cement hardened body containing A4 (fiber) were prepared in the same manner as in Example 13, except that a treatment solution containing A4 as an amine compound and water at 60°C (concentration of the active ingredient A4 was 3% by mass, viscosity at 25°C was 1.297 mPa·s) was used instead of a treatment solution containing A1 as an amine compound and water.

[0081] (Example 17) A short fiber bundle of polypropylene fibers (hereinafter also referred to as A5 (fiber)) and a cement hardened body containing A5 (fiber) were prepared in the same manner as in Example 13, except that a treatment solution containing A5 as an amine compound and water at 60°C was used instead of a treatment solution containing A1 as an amine compound and water (the concentration of the active ingredient A5 was 3% by mass, and the viscosity at 25°C was 1.313 mPa·s).

[0082] (Example 18) A short fiber bundle of polypropylene fibers (hereinafter also referred to as A6 (fiber)) and a cement hardened body containing A6 (fiber) were prepared in the same manner as in Example 13, except that a treatment solution containing A6 as an amine compound and water at 60°C (with an active ingredient concentration of 3% by mass of A6 and a viscosity of 1.333 mPa·s at 25°C) was used instead of a treatment solution containing A1 as an amine compound and water.

[0083] (Comparative Example 1) A cementitious body was prepared in the same manner as in Example 13, except that no fibers were added.

[0084] (Comparative Example 2) A cementite was prepared in the same manner as in Example 13, except that a treatment solution containing A1 as an amine compound and water (hereinafter also referred to as A1 (solution)) was added so that the active ingredient of A1 was 0.2% by mass relative to the cement, without the addition of fibers.

[0085] The moisture content and total nitrogen content of the short fiber bundles obtained in Examples 13 to 18 were measured as described above, and the results are shown in Table 7 below. In addition, the fiber diameter of the single fibers in the short fiber bundles obtained in Examples 13 to 18 was measured as described above, and the results are shown in Table 3 below.

[0086] (Reference Examples 1-8) Prismatic and cylindrical test specimens were obtained in the same manner as in Examples 13-18 and Comparative Examples 1-2, except that carbonation curing was not performed, and after formwork curing for one day, the material was cured in air at 20°C and 60% RH until the age of 28 days. The cement composition is shown in Table 4, and the results are shown in Tables 5-6. In Tables 5-6 below, W represents water.

[0087] The compressive strength of the cylindrical specimens obtained in Examples 13-18 and Comparative Examples 1-2 was measured as described above. Furthermore, the amount of CO2 fixed in the mortar specimens obtained by carbonation curing in Examples 13-18 and Comparative Examples 1-2 was measured as described above. In measuring the amount of CO2 fixed, the mortar specimens obtained in Reference Examples 1-8 were used as air-cured mortar specimens corresponding to the mortar specimens obtained by carbonation curing in Examples 13-18 and Comparative Examples 1-2. The results are shown in Table 7 below.

[0088] As can be seen from Table 6 above, the compressive strength of the mortar test specimens in Examples 13 to 18, which used short fiber bundles of polyolefin resin fibers surface-treated with an amine compound, is slightly lower than that of Comparative Example 1, which did not use fibers, and Comparative Example 2, which used a solution of an amine compound. However, since the amount of air in Examples 13 to 18 is approximately the same as or less than that of Comparative Example 2, this may be due to the effect of the addition of an antifoaming agent.

[0089] Furthermore, as can be seen from Table 6 above, the mortar specimens of Examples 13 to 18, which used short fiber bundles of polyolefin resin fibers surface-treated with an amine compound, showed an increased amount of CO2 fixation in the top 10 mm compared to the mortar specimen of Comparative Example 1, which did not use fibers. In particular, Example 13, which used A1 (fiber) as the short fiber bundle of polyolefin resin fibers surface-treated with an amine compound, showed a tendency for the amount of CO2 fixation to increase even inside the mortar specimen. In addition, the total amount of CO2 fixation up to a depth of 80 mm in the mortar specimens of Examples 13 to 18 increased compared to Comparative Example 1. Moreover, the total amount of CO2 fixation up to a depth of 80 mm in the mortar specimen of Example 13, which used A1 (fiber) as the short fiber bundle of polyolefin resin fibers surface-treated with an amine compound, also increased compared to Comparative Example 2, which used a solution of the amine compound (A1 (solution)). The mineral composition of the mortar specimens of Example 13 and Comparative Examples 1-2 was analyzed as described above, and the results are shown in Figure 1. In Figure 1, (a), (b), and (c) correspond to Comparative Example 1, Comparative Example 2, and Example 13, respectively. As can be seen from Figure 1, in Comparative Examples 1(a) and 2(b), the amount of C (carbon) in the neutralized portion was about 100 CPS, but in Example 13(c), carbon of about 200 CPS was measured at a position slightly away from directly above the fibers. Since Ca was also detected at the same position, it is possible that amine compounds on the fiber surface acted as a catalyst to promote the carbonation of cement hydrate.

[0090] (Example 19) Polypropylene resin (manufactured by Nippon Polypropylene Corporation, trade name "SA01A") was used. Using a spinning nozzle for hollow fibers, melt extrusion was performed at a spinning temperature of 270°C, and the take-up speed was 952 m / min to obtain a spun filament (undrawn yarn) with a fineness of 15 dtex. The obtained spun filament was dry drawn 2.8 times at 130°C. For the obtained drawn filament, corona discharge treatment was performed under the condition of a total discharge amount of 0.3 kW / m 2 / min to make it hydrophilic, and then it was immersed in a treatment liquid at 60°C containing amine compound A5 and water (the concentration of the active ingredient of A5 was 3% by mass, and the viscosity at 25°C was 1.313 mPa·s) as a fiber treatment agent, and then dried at 120°C for 5 minutes and cut into a fiber length of 6 mm to obtain a short fiber bundle and short fibers 19 of hollow fibers with a fineness of 5.4 dtex. A cross-sectional photograph of the hollow fiber is shown in FIG. 2.

[0091] (Example 20) As the core component, polypropylene resin (manufactured by Nippon Polypropylene Corporation, trade name "SA01A") was used, and as the sheath component, a resin mixture of polypropylene resin (manufactured by Nippon Polypropylene Corporation, trade name "SA01A") and maleic acid-modified polypropylene (manufactured by Mitsubishi Chemical Corporation, trade name "Modic", product number "P908", acid value: 12.8) mixed so that the mass ratio was 90:10 was used. Using a spinning nozzle for hollow core-sheath composite fibers, the core-sheath ratio was made 7:3. The core component was melt extruded at a spinning temperature of 270°C, and the sheath component was melt extruded at a spinning temperature of 270°C, and the take-up speed was 952 m / min to obtain a spun filament (undrawn yarn) with a fineness of 15 dtex. The obtained spun filament was dry drawn 2.8 times at 130°C. For the obtained drawn filament, corona discharge treatment was performed under the condition of a total discharge amount of 0.3 kW / m 2 / min to make it hydrophilic, and then it was immersed in a treatment liquid at 60°C containing amine compound A5 and water (the concentration of the active ingredient of A5 was 3% by mass, and the viscosity at 25°C was 1.313 mPa·s) as a fiber treatment agent, and then dried at 120°C for 5 minutes and cut into a fiber length of 6 mm to obtain a short fiber bundle and short fibers 20 of hollow fibers with a fineness of 5.4 dtex. The fiber cross-section of the obtained short fibers 20 has the same shape as that of the short fibers 19.

[0092] <Preparation of hardened cement> The materials shown in Table 8 below and the short fibers 19 and 20 shown in Table 9 below, obtained above, were stirred and mixed in the proportions shown in Table 10 below to obtain the cement compositions (mortar compositions) of Examples 21 to 24 and Comparative Examples 3 to 4. In Table 10 below, W represents water. The obtained cement compositions were poured into cylindrical molds (5 cm in diameter, 10 cm in height) and cured in the molds at room temperature for one day. Cylindrical test specimens were obtained by curing under the following conditions: - Curing in air followed by carbonation: left to stand for 6 days in an atmosphere of 20°C and 60% RH (air curing), and then left to stand for 7 days in an atmosphere of 60% CO2 concentration, 20°C, and 60% RH (carbonation curing). - During carbonation curing, the CO2 exposure surface was left completely open to obtain hardened cement (mortar specimens). Hardened cement without added fibers was also prepared for comparison. The results of the obtained hardened cement are shown in Table 11 below. The amount of CO2 fixed in hardened cement was measured by the following method: (Amount of CO2 fixed in hardened cement) The prepared mortar test specimens were split, sprayed with phenolphthalein solution, and two uncolored areas (neutralized areas) and one colored area (non-neutralized area) were taken as samples. Next, the samples were burned in an oxygen atmosphere using a carbon-sulfur analyzer (TC) to determine the amount of carbon in the samples. After excluding the amount of carbon derived from the material by subtracting the TC value of the fiber content (calculated assuming that polypropylene fibers contain approximately 70% of the carbon) from the measured amount of carbon in the carbon-cured mortar test specimens, the value was converted to CO2 content and determined as the amount of CO2 fixed in hardened cement. Mortar test specimens with short fibers 20 added tended to have higher TC analysis values ​​compared to mortar test specimens with short fibers 19 added. Furthermore, as shown in Table 9, the OPU values ​​after washing were higher for short fibers 20 than for short fibers 19. Therefore, compared to the short fibers 19, the short fibers 20, in which maleic acid-modified propylene was mixed during the spinning stage to concentrate the functional groups on the fiber surface, exhibited a stronger affinity for the oil during surface treatment. This significantly suppressed the detachment of amines from the fiber surface during mortar mixing, leading to an increase in the amount of carbon dioxide fixed at the fiber-matrix interface by amines, and consequently, an increase in the TC value. Also, as shown in Table 11, regardless of the presence or absence of a carbonation admixture (powder mainly composed of γ-C2S), all mortar specimens with added fibers showed higher TC values ​​than specimens without added fibers, and the specimen with added short fibers 20 showed the highest TC value.

[0093] (Example 25) A resin mixture was used, which consisted of polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., trade name "SA01A") and maleic acid-modified polypropylene (manufactured by Mitsubishi Chemical Corporation, trade name "Modic", product number "P908", acid value: 12.8) mixed in a mass ratio of 90:10. Using a spinning nozzle with a pentagonal hollow nozzle hole shape, melt extrusion was performed at a spinning temperature of 260°C, and the material was taken up at a take-up speed of 200 m / min to produce a spun filament (undrawn yarn) with a fineness of 36 dtex. The obtained spun filament was dry-drawn three times at 130°C. The total discharge rate for the obtained drawn filament was 0.3 kW / m 2 The fibers were treated with corona discharge under conditions of / min to make them hydrophilic, and then 3% by mass of a 60°C treatment solution containing amine compound A5 and water was applied as a fiber treatment agent. The fibers were dried at 105°C for 15 minutes, cut to a length of 10 mm, and short fiber bundles and short fibers 25 of pentagonal hollow fibers with a fineness of 12 dtex were obtained. A cross-sectional photograph of the hollow fibers is shown in Figure 3.

[0094] (Example 26) Short fiber bundles of pentagonal hollow fibers and short fibers 26 were obtained in the same manner as in Example 25, except that a 60°C treatment solution containing A7 as an amine compound and water (with a concentration of 3% by mass of the active ingredient A7) was used instead of the treatment solution containing A5 as an amine compound and water. The fiber cross-section of the obtained short fibers 26 had the same shape as that of the short fibers 25. <Preparation of cement hardened body> The materials shown in Table 12 below, the short fibers 25 and short fibers 26 obtained above as shown in Table 13 were stirred and mixed in the proportions shown in Table 14 below to obtain a cement composition (mortar composition). In Table 14 below, W means water. The obtained cement composition was poured into a rectangular prism-shaped mold (4 × 4 × 16 cm) and a cylindrical mold (5 cm in diameter, 10 cm in height), respectively, and cured in the mold at room temperature for one day. After that, it was cured under the following conditions to obtain rectangular prism and cylindrical test specimens. Curing 1 (carbonation curing only): Left to stand for 7 days in an atmosphere of 60% CO2 concentration, 20°C, and 60% RH (carbonation curing) Curing 2 (carbonation curing after air curing): Left to stand for 14 days in an atmosphere of 20°C and 60% RH (air curing), and then left to stand for 7 days in an atmosphere of 60% CO2 concentration, 20°C, and 60% RH (carbonation curing) During the carbonation curing of the rectangular prism test specimens, only one side of the end face was exposed to CO2, and the other faces were sealed with aluminum tape before curing. Cylindrical test specimens were cured with the entire surface open to obtain hardened cement (mortar specimens). For comparison, hardened cement without added fibers was also prepared. The results for the obtained hardened cement are shown in Table 15 below. The amount of CO2 fixed, carbonation depth, and carbonation area ratio of the hardened cement were measured by the following methods. (Amount of CO2 fixed in hardened cement) The prepared mortar test specimens were sliced ​​every 20 mm from the exposed surface and finely ground to obtain samples. Next, the samples were burned in an oxygen atmosphere using a carbon-sulfur analyzer (TC) to determine the amount of carbon in the samples. After eliminating the amount of carbon derived from the material by subtracting the TC value of the fiber content (calculated assuming that polypropylene fibers contain approximately 70% of the carbon) from the measured amount of carbon in the carbonation cured mortar test specimens, the amount was converted to CO2 content and obtained as the amount of CO2 fixed in the hardened cement. (Carbonation depth) To measure the carbonation depth after each curing period, a 4 × 4 × 16 cm rectangular prism test specimen was used, cut perpendicular to the casting surface, and phenolphthalein solution was sprayed on it. The depth from the surface to the colored area was measured with calipers. (Neutralization Area Ratio) Based on the measured neutralization depth, the neutralization area ratio of each specimen was calculated using the following formula: ・Neutralization Area Ratio = {40 2 -(40-a) 2} / 40 2×100 a = carbonation depth (mm) From Table 15, regardless of the curing period, carbonation progressed and the TC value was higher at all levels where amine-coated fibers were added compared to the level where no fibers were added. Similarly, from the results for curing 1, which had a shorter curing period, the short fibers 26, which were surface-treated with an amine compound with a high content of tertiary amino groups (100%), tended to have a higher TC value than the short fibers 25, which were surface-treated with an amine compound composed of primary to tertiary amino groups. This suggests that the amine efficiently supplied concentrated CO2 into the cement hardened body such as concrete, acting as a source of carbonate ions for calcium carbonate production, and that tertiary amino groups, which actively produce bicarbonates, are effective as a source of carbonate ions.

[0095] A cementitious body was prepared using the short fibers 25 and 26 prepared in Examples 25 and 26 described above. <Preparation of Cementitious Body> (Example 27) The concrete materials used are shown in Table 16. For the cement, blast furnace cement type C with an SO3 content of 3.56% was used, and as an admixture, GCS (carbonated admixture) that solidifies by reacting with CO2 was mixed in at a mass ratio of 30% of the cement, replacing the fine aggregate. Fine and coarse aggregates were natural aggregates, and polycarboxylic acid-based high-performance water-reducing agents and defoaming agents were used as chemical admixtures. The fibers to be mixed into the concrete were short fibers 25 (Example 25) and short fibers 26 (Example 26). Regarding the surface treatment agent for the fibers, a solution containing an amine was used as a surface treatment agent to promote the adsorption of CO2 moving along the fiber interface to the cement hydrate. Amines have two effects: fixing CO2 within the amine itself and supplying carbonate ions to the cement hydrate via the amine. In this study, we assumed the physical effect of forming fine voids at the interface between the fiber surface and the cement paste due to fiber mixing, and the effect of selectively adsorbing and concentrating the penetrating CO2 gas on the fiber surface due to the presence of the amine, thereby efficiently diffusing carbonate ions into the concrete. In this example, two types of amines were used: fiber 27, which contains a tertiary amino group (main component: polyacrylamine), and fiber 28, which consists only of a tertiary amine (main component: triisopropanolamine). The reason for using tertiary amines in both cases in this study is that it was judged that tertiary amines that form bicarbonates are in line with the purpose of this study. The concrete mix and test specimen shape are as follows. The concrete mix is ​​shown in Table 17. W / C = 55%, s / a = 0.42, unit water volume 175 kg / m³ 3 This was kept constant. Blast furnace cement type C was used, and GCS was not included as a binder, but 30% was replaced with fine aggregate and mixed. Regarding fibers, no fibers were used as comparative example 7 (blank), and 25 short fibers were used with a fiber content of 1 kg / m. 3 The additive was used for the standard test specimen of Example 27, and the short fibers 26 were used with a fiber content of 1 kg / m². 3 The additive was used for the standard test specimen in Example 28, and the short fiber 25 had a fiber content of 3 kg / m. 3 The additive was used as the reference test specimen for Example 29. Note that surface water was present on the fibers, and this was subtracted from the unit water content before use. Regarding freshness, the chemical admixture was adjusted to achieve fluidity sufficient to prevent material separation and avoid hindering the weaving process. Regarding air content, since the amount of air was thought to affect the ease of CO2 movement, an antifoaming agent was used to adjust it to 2.0% or less. As shown in the freshness test results in the table, although the slump varied considerably, all formulations had an air content of 2.0% or less. The test specimens to be prepared were cylindrical specimens of φ10 × 20 cm for compressive strength testing and rectangular prism specimens of 10 × 10 × 40 cm for measuring and analyzing carbonation depth. Two curing methods were used: one involved curing the formwork for one day at room temperature of 20°C after casting, then demolding at 1 day of age and curing until 7 days of age in an indoor air environment at 20°C and RH 60%; and the other involved accelerated carbonation curing in a carbonation curing tank controlled to 20°C, RH 60-70%, and CO2 concentration 80%. In both curing conditions, the test specimens were removed after 4 and 8 days of age, and various tests were performed. For the carbonation conditions of each test specimen, the cylindrical specimens were left completely open, while for the rectangular prism specimens, two sides of the casting surface were used as the test surface, and the other sides were covered with aluminum tape. The specimens were cut at predetermined ages and sliced ​​10 mm thick from the test surface. <Test Methods> (1) Compressive Strength Test The compressive strength test was conducted using cylindrical specimens of φ10 × 20 cm in accordance with JIS A 1108, and the compressive strength and static elastic modulus were measured at 1 day, 4 days, and 8 days of age. (2) Carbonation Depth Test To measure the carbonation depth after each curing period, a rectangular specimen of 10 × 10 × 40 cm was used, and at 1 day, 4 days, and 8 days of age, it was cut to a thickness of approximately 5 cm, sprayed with phenolphthalein solution, and the depth from the surface to the colored area was measured with calipers. (3) Total Carbon Content Analysis Total carbon content analysis was performed using the specimens cut in the carbonation depth test. The specimens for analysis were cut to a thickness of 1 cm from the surface and immersed in acetone for more than one day to stop hydration. After that, the acetone was vaporized with an aspirator, the coarse aggregate was removed by crushing with a hammer, and the material was pulverized until it passed through a 150 μm sieve to obtain the analytical sample. Total carbon content analysis was performed using an infrared absorption analyzer to measure the amount of carbon from the carbon dioxide produced when the sample was burned in an oxygen atmosphere. (4) Measurement of pore size distribution A portion of the test piece obtained by cutting in the neutralization depth test was used to measure the pore size using a mercury intrusion porosimeter. The test specimen was roughly crushed with a hammer to remove the coarse aggregate, then roughly crushed until it could pass through a sieve of about 2.5 mm, and then degassed under vacuum to be used as the measurement sample. <Test results> 1. Compressive strength and static elastic modulus Table 18 shows the results of the compressive strength test. First, looking at the test results immediately after demolding at 1 day of age, all formulations using fibers showed strengths comparable to BCG, and the amine used in this study did not affect the demolding strength even when used as a surface treatment agent for short fibers. The strength after 4 days of age and standing in an air environment was also ±2 N / mm². 2 The fluctuations were limited, and no effect of using amine-coated fibers was observed in an airborne environment. Next, looking at the strength test results when carbonation curing was applied, all formulations showed strengths of 9 to 17 N / mm² compared to air curing using GCS. 2 The compressive strength has increased to some extent. Regarding the effect of the fibers, there is an overall increasing trend, and in Example 29, at an age of 8 days, it was 8 N / mm² compared to the fiber-free example (Comparative Example 7). 2 The result was an increase of a certain degree. Figure 4 is a graph showing the relationship between compressive strength and static elastic modulus for Examples 27-29 and Comparative Example 7 of the present invention. In the GCS-mixed system examined this time, the static elastic modulus also increased with increasing compressive strength, and no change in the static elastic modulus due to carbonation curing was observed. Furthermore, it was comparable to structural calculation standard formula 7 shown by the Architectural Institute of Japan for reference. 2. Carbonation depth Table 19 shows the carbonation depth of prismatic specimens after air curing and carbonation curing for 3 to 7 days. Furthermore, no carbonation depth was observed immediately after demolding. First, regarding the test specimens subjected to air curing, no carbonation depth was observed up to 8 days of age. This is likely because the CO2 concentration in the general air environment is not high, and from immediately after demolding until about 8 days of age, there is an abundance of water inside the concrete, making it difficult for CO2 to penetrate into the concrete, and thus the pH did not drop to the point of carbonation. Next, looking at the case where carbonation curing was performed in an environment with a CO2 concentration of 80%, the carbonation depth was 5 mm or more at 4 days of age (3 days of carbonation period) and 14 mm or more at 8 days of age (7 days of carbonation period). Regarding the effect of fibers, the carbonation depth increased compared to the case without fibers in all cases of fiber and fiber amount. In addition, the carbonation depth was greater in Example 28 than in Example 27 at both 4 and 8 days of age, and surface treatment agent B resulted in a greater increase in carbonation depth. Furthermore, although it was expected that Example 29, which has a larger fiber amount, would be more prone to carbonation due to the increase in fiber interfaces, in reality, Example 27 showed a greater carbonation depth. The cause of this is under investigation, but in the specimen of Example 29, the compressive strength was high at both 4 and 8 days of age, suggesting that calcium carbonate precipitated near the concrete surface due to the GCS reaction, preventing CO2 from penetrating into the interior. 3. Amount of carbon fixed In calculating the total amount of carbon, the polypropylene fibers (short fibers 25, short fibers 26) used in this study contain a large amount of carbon. Therefore, the amount of carbon contained in the materials used was excluded and analyzed using the method of formula (1). TC' (%) = TC (%) - TCi (%) Formula (1) Where TC': Total amount of carbon considering the initial value (%) TC: Total amount of carbon in each sample after each curing period (%) TCi: Total amount of carbon in the sample taken from the specimen immediately after demolding (%) Table 20 shows the distribution of carbon fixed from the surface of the specimen after 7 days of air curing or carbonation curing. First, looking at the analysis results after 7 days of air curing, an increase of approximately 0.3% in carbon content due to CO2 in the indoor air was confirmed up to 10 mm from the surface. However, no increase in carbon content was confirmed at depths greater than 10 mm, suggesting that even when GCS and fibers are mixed, CO2 fixation hardly progresses in the short term at CO2 concentrations similar to those of general atmospheric air. Next, looking at the results of accelerated carbonation in a high-concentration CO2 environment with a concentration of 80%, the total carbon content increased significantly in all test specimens. The slope was gentle up to the surface 20 mm, and since all formulations had roughly the same amount of carbon, it is possible that CO2 fixation had progressed to near the maximum amount that cement hydrate and other materials could fix. Differences between formulations could be confirmed from a depth of 30 mm onward, with formulations containing Examples 27 and 28 showing a greater amount of fixed carbon than Comparative Example 7. Furthermore, focusing on the differences in amine types, amine solution A5 showed a slightly larger amount at the surface, but there was no significant difference in the amount of fixed carbon beyond 20 mm. On the other hand, Example 29, which increased the amount of fiber to further increase the amount of fixed carbon, showed a large amount of fixation up to 10 mm, but as suggested by the test results for neutralization depth, the increase in the amount of fixed carbon inside was small, and the amount of fixed carbon was about the same as or less than that of Comparative Example 7. In addition, even though the neutralization depth was only about 20 mm in all formulations, the amount of fixed carbon increased beyond 20 mm. This is because phenolphthalein is a chemical that qualitatively shows a change in pH when it reacts with alkaline substances such as calcium hydroxide. Therefore, even if calcium carbonate is produced by carbonation, if calcium hydroxide remains, it will change color due to phenolphthalein. For this reason, it is considered that the amount of carbon fixation in concrete cannot be determined simply by the carbonation depth alone. 4. Pore size distribution Figures 5, 6, and 7 show the pore size distribution and cumulative void amount measured by a mercury intrusion porosimeter immediately after demolding (1 day old) and 7 days after carbonation curing (8 days old). First, looking at the measurement results immediately after demolding (Figure 5), there was no significant difference in the distribution of void size in any of the mixes, and a large peak was shown around 0.2 to 0.3 μm in void size. Regarding the cumulative void amount shown by the dashed line, there were differences for each mix, and Example 29, which had a high fiber content, had a slightly higher initial void amount than Comparative Example 7. On the other hand, Examples 27 and 28 had slightly less cumulative void amount despite the mixing of fibers. Next, Figures 6 and 7 show the pore size distribution in the central part (unneutralized region: 40-50 mm position) and the surface layer (neutralized region: 0-10 mm position) of the test specimen after 7 days of carbonation curing.Figure 6 shows the results at 40-50 mm after 7 days of carbonation curing. Figure 7 shows the results at 0-10 mm after 7 days of carbonation curing. First, looking at the results in the center of the specimens, the void size distribution has changed due to the hydration reaction as the material ages. In all specimens, voids of about 0.2 μm have decreased, and fine voids of 0.01 μm or less have increased. However, no clear differences were observed between the formulations. Regarding the cumulative void amount, Example 29, which had a large initial void amount, had the largest cumulative void amount. Looking at the results in the carbonation region of the surface layer shown in Figure 7, the void size distribution has a shape similar to the distribution immediately after demolding, but the peak height has decreased. In particular, the change in voids of 0.1 μm or less from immediately after demolding has been small, suggesting that the hydration reaction may not have progressed due to drying or carbonation. Also, when considered together with the total pore size, Examples 27 and 28, which had fibers added, have a relatively large number of voids around 0.2-0.3 μm. From this, it is thought that when approximately 1 kg of fibers treated with an amine as a surface treatment agent were mixed, voids into which CO2 could diffuse were formed, and the amount of carbon fixed increased. In Example 29, the pore size distribution was similar to that of Comparative Example 7, in which no fibers were added. In the void structure of the unneutralized region, the amount of voids was the largest, and in the total carbon content distribution in Table 20, the amount of carbon fixed was greatest in the surface layer of 10 mm. Therefore, it is thought that the GCS reaction occurred in the surface layer, causing densification, which reduced the amount of voids and suppressed the diffusion of CO2 into the interior.

[0096] The carbonation-promoting additive for hydraulic compositions of the present invention can be suitably used in hydraulic compositions such as cement compositions that can fix various types of carbon dioxide during curing and / or after hardening.

Claims

1. An additive for use in a hydraulic composition, wherein the additive comprises organic fibers and an amine compound, and the amine compound is attached only to the surface of the organic fibers, characterized in that it is a carbonation-promoting additive for hydraulic compositions.

2. The carbonation-promoting additive for hydraulic compositions according to claim 1, wherein the organic fibers are in the form of short fiber bundles and further contain a liquid containing water, the short fiber bundles are wet with the liquid containing the amine compound and water, and the moisture content is 5% by mass or more and 60% by mass or less.

3. The amine compound comprises a secondary amino group, wherein the carbonation-promoting additive for hydraulic compositions is as described in claim 1 or 2.

4. The amine compound comprises a tertiary amino group, wherein the carbonation-promoting additive for hydraulic compositions is as described in any one of claims 1 to 3.

5. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 4, wherein the total nitrogen content on the fiber surface of the organic fiber is 0.01% by mass or more and 2% by mass or less.

6. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 5, wherein the organic fiber is a polyolefin resin fiber.

7. The carbonation-promoting additive for hydraulic compositions according to claim 6, wherein the polyolefin resin fiber is a fiber containing at least one resin selected from the group consisting of polypropylene resins and polymethylpentene resins.

8. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 7, wherein the organic fiber is a fiber on which hydrophilic functional groups are attached to the fiber surface, and the amine compound is attached to the surface thereof.

9. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 7, wherein the fiber to which the hydrophilic functional group is provided comprises a maleic acid-modified polyolefin resin.

10. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 9, wherein the organic fiber has a single fiber diameter of 8 μm or more and 700 μm or less.

11. The carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 10, wherein the organic fiber has a single fiber length of 0.5 mm or more and 50 mm or less.

12. A hardened hydraulic composition comprising a carbonation-promoting additive for hydraulic compositions according to any one of claims 1 to 11, and which has been carbonation-cured.

13. The hydraulic composition cured body according to claim 12, wherein the additive for the carbonation-promoting hydraulic composition comprises 0.01 Vol% to 5 Vol% of the hydraulic composition cured body with respect to 100 Vol%.

14. A method for producing a carbonation-promoting additive for a hydraulic composition according to any one of claims 1 to 11, comprising step A of treating the fiber surface of an organic fiber with an amine compound.

15. The method for producing a carbonation-promoting additive for a hydraulic composition according to claim 14, wherein the amine compound comprises a secondary amino group and / or a tertiary amino group, and in step A, the surface of the organic fiber is treated using a treatment solution containing the amine compound and water by at least one means selected from the group consisting of immersion, coating, and spraying.

16. A method for producing a carbonation-promoting additive for a hydraulic composition according to claim 14 or 15, wherein in step A, the organic fibers are used in the form of a continuous long fiber bundle (tow) in which multiple single fibers are bundled together.

17. A method for producing a carbonation-promoting additive for a hydraulic composition according to claim 16, comprising step B, after step A, of cutting the long fiber bundle treated with the treatment liquid to a predetermined fiber length.

18. A method for producing a carbonation-promoting additive for a hydraulic composition according to claim 17, comprising step C, after step A and before step B, for adjusting the moisture content of the long fiber bundle treated with the treatment liquid to 5% by mass or more and 60% by mass or less.

19. The method for producing a carbonation-promoting additive for hydraulic compositions according to any one of claims 14 to 18, wherein the organic fiber is made by mixing a resin or compound having hydrophilic functional groups with an organic material constituting the fiber, and / or by subjecting the surface of the organic fiber to a hydrophilic treatment.

20. The method for producing a carbonation-promoting additive for a hydraulic composition according to claim 19, wherein the hydrophilization treatment is at least one selected from corona discharge treatment, plasma treatment, ozone aqueous solution treatment, fluorination treatment, ultraviolet irradiation, and sulfonation treatment.

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