High concentration aqueous solution of polyborate ions

Abstract

To provide an aqueous solution containing borate ions and / or polyborate ions at a high concentration in terms of boron.SOLUTION: Provided is an aqueous solution containing polyborate ions and ammonium ions and / or primary alkylammonium ions with a carbon number of 1 to 4, wherein a mass molar concentration of the polyborate ions, in terms of boron, exceeds the solubility of both ammonium tetraborate alone and ammonium pentaborate alone in water at the same temperature, and the aqueous solution contains the ammonium ions and / or the primary alkylammonium ions with a carbon number of 1 to 4 in an amount equal to or greater than the stoichiometric amount relative to the polyborate ions.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an aqueous solution containing polyborate ions and ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms, wherein the molar concentration of the polyborate ions, in terms of boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature, and the aqueous solution contains the ammonium ions and / or the primary alkylammonium ions having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ions. [Background technology]

[0002] 2. Description of the Related Art In recent years, in order to expand the use of domestic lumber, attention has been focused on flame-retardant lumber, semi-fireproof lumber and fireproof lumber, which are obtained by impregnating wood materials such as natural wood with a flame retardant. The inventors have previously developed a high-concentration aqueous solution of sodium borate obtained by mixing boric acid and borax in a certain ratio, and reported a technology for impregnating wood with this aqueous solution to make it flame retardant (Patent Nos. 4,439,234 and 5,079,983). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4439234 specification [Patent Document 2] Patent No. 5079983 specification Summary of the Invention [Problem to be solved by the invention]

[0004] However, there remains a need for flame retardants containing higher concentrations of boric acid and / or polyboric acid for more efficient flame retardancy. Therefore, an object of the present disclosure is to provide an aqueous solution containing borate ions and / or polyborate ions at a high concentration calculated as boron. [Means for solving the problem]

[0005] The present disclosure provides an aqueous solution containing polyborate ions and ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms, wherein the molar concentration of the polyborate ions, in terms of boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature, and the aqueous solution contains the ammonium ions and / or the primary alkylammonium ions having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ions.

[0006] The present disclosure also provides an aqueous solution containing polyborate ions, borate ions, and primary alkylammonium ions having 1 to 4 carbon atoms, wherein the total molar concentration of the polyborate ions and the borate ions, in terms of boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature, and the aqueous solution contains the primary alkylammonium ions having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ions and the borate ions.

[0007] The present disclosure also provides a solid composition comprising ammonium pentaborate and ammonium tetraborate, wherein a ratio of the total number of moles of boron to the number of moles of nitrogen (N / B ratio) of the ammonium pentaborate and the ammonium tetraborate is greater than 0.2 and less than 0.5, and the solubility in water (molar concentration in terms of boron) exceeds the solubility (molar concentration in terms of boron) of both ammonium tetraborate alone and ammonium pentaborate alone at the same temperature.

[0008] The present disclosure also provides a flame retardant comprising the aqueous solution or the solid composition.

[0009] The present disclosure also provides a method for producing an aqueous solution containing borate ions and / or polyborate ions, the method comprising the step of dissolving boric acid in water containing primary alkylammonium ions having 1 to 4 carbon atoms, wherein the boric acid is dissolved in the water containing the primary alkylammonium ions having 1 to 4 carbon atoms in an amount exceeding the solubility of the boric acid in water not containing the primary alkylammonium ions having 1 to 4 carbon atoms.

[0010] The present disclosure also provides a method for producing a flame-retardant material, comprising the steps of impregnating a material to be flame-retarded with the aqueous solution described above, and precipitating ammonium polyborate in the material to be flame-retarded after the impregnation. The present disclosure further provides a method for producing a flame retardant, comprising evaporating water from the aqueous solution described above. Effect of the Invention

[0011] The aqueous solution of the present disclosure contains a higher concentration of borate ions and / or polyborate ions than an aqueous solution in which boric acid or a boric acid-containing compound is dissolved alone, and is therefore useful for efficient flame retardancy. [Brief description of the drawings]

[0012] [Figure 1] 1 is a graph showing the relationship between the N / B ratio of a mixture of ammonium pentaborate tetrahydrate (NH4B5O8.4H2O) and ammonium tetraborate tetrahydrate ((NH4)2B4O7.4H2O) in Example 1 and Comparative Example 1, and the solubility in terms of boron (B mol / kg) in 1 kg of water at 45°C. [Diagram 2] 1 is a graph showing the relationship between the N / B ratio of a mixture of ammonium pentaborate (NH4B5O8.4H2O) and ammonium tetraborate ((NH4)2B4O7.4H2O) in Example 2 and Comparative Example 2, and the solubility in terms of boron (B mol / kg) in 1 kg of water at 25°C. [Diagram 3] 1 is a graph showing the relationship between the N / B ratio of boric acid and methylamine dissolved in water in Example 3 and Comparative Example 3 and the amount of boric acid dissolved in 1 kg of water at 25° C. converted to boron (B mol / kg). [Figure 4] 1 is an XRD pattern of a powder obtained from an aqueous solution having an N / B ratio of 0.375 in Example 6. [Diagram 5] FIG. 4 shows an XRD pattern of ammonium pentaborate tetrahydrate (NH4B5O8 4H2O) powder in Comparative Example 4-1. [Figure 6] This is an XRD pattern of ammonium tetraborate tetrahydrate ((NH4)2B4O7·4H2O) powder in Comparative Example 4-2. [Figure 7] 1 shows an XRD pattern of powder obtained by drying an aqueous solution of boric acid and methylamine with an N / B ratio of 0.2 at 115° C. in Example 7. [Figure 8] 1 shows an XRD pattern of a powder obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.13 at 115° C. in Example 8. [Figure 9] 1 shows an XRD pattern of powder obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.51 at 115° C. in Example 9. [Figure 10] 1 shows an XRD pattern of powder obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.17 at 115° C. in Example 10. [Figure 11] 1 shows a DTA-TG curve of a solid obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.2 at 115° C. in Example 11. [Figure 12] 1 shows a DTA-TG curve of a solid obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.25 at 115° C. in Example 12. [Figure 13] 1 shows a DTA-TG curve of a solid obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.142 at 115° C. in Example 13. [Figure 14] 1 shows a DTA-TG curve of a solid obtained by drying an aqueous solution of boric acid and methylamine having an N / B ratio of 0.125 at 115° C. in Example 14. [Figure 15]This is Raman spectral data for an aqueous solution of ammonium pentaborate tetrahydrate (NH4B5O8·4H2O) and ammonium tetraborate tetrahydrate ((NH4)2B4O7·4H2O) in Example 15 with an N / B ratio of 0.375. [Figure 16] 13 is Raman spectrum data for an aqueous solution of ammonium pentaborate tetrahydrate (NH4B5O8·4H2O) in Comparative Example 5. [Figure 17] 13 is Raman spectrum data for an aqueous solution of ammonium tetraborate tetrahydrate ((NH4)2B4O7·4H2O) in Comparative Example 6. [Figure 18] 13 shows Raman spectrum data for an aqueous solution of boric acid and methylamine with an N / B ratio of 0.2 in Example 16. [Figure 19] 13 is Raman spectrum data of an aqueous solution of boric acid and methylamine with an N / B ratio of 0.42 in Example 17. [Figure 20] 13 is Raman spectrum data of a 40% methylamine aqueous solution in Comparative Example 7. [Figure 21] 13 is Raman spectrum data of an aqueous boric acid solution in Comparative Example 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <High concentration aqueous solution of polyborate ions> The high-concentration aqueous solution of polyborate ions according to the present disclosure (hereinafter also simply referred to as the "aqueous solution of the present disclosure") contains polyborate ions and ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms, and is characterized in that the molar concentration of the polyborate ions, in terms of boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature, and the ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms are contained in a stoichiometric amount or more relative to the polyborate ions.

[0014] The aqueous solution of the present disclosure contains a relatively high concentration of polyborate ions at a relatively low temperature (e.g., 15 to 55°C), and therefore enables easier and / or more efficient flame retardancy (including flame retardancy or quasi-flame retardancy) of the target material to be flame retarded compared to conventional methods. Without being bound by theory, it is believed that the aqueous solutions of the present disclosure may contain higher concentrations of polyborate ions because at least a portion of the polyborate ions contained therein have formed (e.g., by interaction) a structure that is more stable in water and / or are present in a form that is more soluble in water.

[0015] In one embodiment, the aqueous solution of the present disclosure comprises polyborate ions, optionally borate ions, and ammonium ions, the combined molar concentration of the polyborate ions and the borate ions (if present) being greater than the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature, calculated on a boron basis, and the aqueous solution of the present disclosure comprises ammonium ions in a stoichiometric amount or more relative to the polyborate ions and the borate ions (if present). In a specific embodiment, the aqueous solution of the present disclosure comprises ammonium ions in a stoichiometric amount relative to the polyborate ions and the borate ions (if present).

[0016] In one embodiment, the aqueous solution of the present disclosure comprises polyborate ions, optionally borate ions, and primary alkylammonium ions having 1 to 4 carbon atoms, the total molar concentration of the polyborate ions and the borate ions (if present) exceeding the solubility of both ammonium tetraborate alone and ammonium pentaborate alone in water at the same temperature, calculated on a boron basis, and the aqueous solution comprises the primary alkylammonium ions having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ions and the borate ions (if present).

[0017] In this specification, examples of water used as a solvent for the aqueous solution of the present disclosure include pure water, distilled water, tap water, household water, industrial water, and groundwater.

[0018] Polyborate ions are compounds that combine two or more borate ions (BO3 3- ) is a condensed form of ion, and there are several types with different degrees of condensation. In this specification, the polyborate ion is preferably a diborate ion (B2O5 4- ), triborate ion (B3O5 - ), tetraborate ion (B4O7 2- ), pentaboric acid ion (B5O8 - ) and octaborate ion (BO 13 2- ), more preferably, one or more types including tetraborate ion and / or pentaborate ion selected from the above group, and more preferably, one or two types selected from the group consisting of tetraborate ion and pentaborate ion.

[0019] In this specification, the primary alkyl ammonium ion having 1 to 4 carbon atoms is RNH3 + (wherein R is a linear or branched C1-C4 alkyl group) or R'(NH2)(NH3 + ) or R'(NH3 + )2 (wherein R' is a linear or branched C2-C4 alkylene group). The primary alkylammonium ion having 1 to 4 carbon atoms is, for example, one or more selected from the group consisting of a methylammonium ion, an ethylammonium ion, a propylammonium ion, a monoisopropylammonium ion, an n-butylammonium ion, an s-butylammonium ion, a t-butylammonium ion, an ethyleneamineammonium ion, and an ethylenediammonium ion, preferably a methylammonium ion and / or an ethylammonium ion, more preferably a methylammonium ion.

[0020] The combined molar concentration of polyborate ions and borate ions (if present) in the aqueous solution of the present disclosure exceeds the solubilities, in terms of boron, of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature. The solubility of ammonium tetraborate in water is, for example, 1.90 mol / kg water (12.5 g / 100 g water) at 25° C. and 3.92 mol / kg water (25.8 g / 100 g water) at 45° C., while the solubility of ammonium pentaborate is, for example, 2.00 mol / kg water (10.9 g / 100 g water) at 25° C. and 3.20 mol / kg water (17.4 g / 100 g water) at 45° C. When the aqueous solution of the present disclosure contains a substance that affects the water solubility of polyborate ions and / or borate ions (for example, a chelating agent and / or a surfactant; excluding ammonium ions and primary alkylammonium ions having 1 to 4 carbon atoms), the total molar concentration of polyborate ions and borate ions (if present) in the aqueous solution of the present disclosure, in terms of boron, preferably exceeds the solubility of both ammonium tetraborate alone and ammonium pentaborate alone in a solution obtained by removing the ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms from the aqueous solution at the same temperature.

[0021] In this specification, the term "boron equivalent" in relation to the number of moles refers to converting the number of moles of a compound or ion containing boron into the number of moles of boron atoms contained in the compound or ion. In other words, a compound or ion y mol containing N boron atoms in one molecule is equivalent to N x y mol in boron equivalent. For example, when 1 mol of ammonium pentaborate tetrahydrate (NH4B5O8·4H2O) is converted into boron equivalent, it is 1 mol x 5 = 5 mol because ammonium pentaborate tetrahydrate contains 5 borons, and tetraborate ion (BO7 2- ) contains 4 boron atoms, so 1 mole of it is equivalent to 1 mol × 4 = 4 moles of boron. In this specification, the term "nitrogen equivalent" in relation to the number of moles means that the number of moles of a nitrogen-containing compound or ion is converted into the number of moles of nitrogen atoms contained in the compound or ion. In other words, 1 mole of an ammonium ion or primary alkyl ammonium ion containing one nitrogen atom per molecule is 1 mole in terms of nitrogen.

[0022] The aqueous solution of the present disclosure contains ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ions and borate ions (if present) present in the aqueous solution. As used herein, the term "stoichiometric amount" refers to the amount of ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms that are required to form salts with all of the polyborate ions and borate ions (if present) present in the aqueous solution of the present disclosure. In terms of stoichiometry, salts of polyborates may be, for example, (RNH3)4B2O5, RNH3B3O5, (RNH3)2B4O7, RNH3B5O8, and (RNH3)2B8O, corresponding to the polyborates present in the aqueous solutions of the present disclosure. 13 and the salt of borate ion is (RNH3)3BO3, where R is H or a straight or branched C1-C4 alkyl group.

[0023] The pH of the aqueous solution of the present disclosure is not particularly limited, but is, for example, 7 or higher, preferably 7.5 or higher, more preferably 8 or higher, more preferably 8 to 12, more preferably 8 to 10, and more preferably 8 to 9. The aqueous solution of the present disclosure may contain a surfactant and / or a chelating agent, or may not contain a surfactant or a chelating agent. In one embodiment, the aqueous solution of the present disclosure does not contain a surfactant or a chelating agent. In this specification, even if the aqueous solution of the present disclosure contains a substance that is generally recognized as being capable of acting as a surfactant or a chelating agent, as long as the substance does not act as a surfactant or a chelating agent (more specifically, in the environment of the aqueous solution of the present disclosure, the substance cannot act as a surfactant or a chelating agent), the aqueous solution is interpreted as not containing a surfactant or a chelating agent.

[0024] The aqueous solution of the present disclosure has a Raman spectrum of 990±10 cm -1 Within and / or 1422±50 cm -1 These peaks are not present in aqueous solutions of ammonium pentaborate or ammonium tetraborate. In one specific embodiment, the aqueous solutions of the present disclosure have a peak at 990±10 cm in the Raman spectrum. -1 In another specific embodiment, the aqueous solution of the present disclosure has a peak at 1422±50 cm in the Raman spectrum. -1 In yet another specific embodiment, the aqueous solution of the present disclosure has a peak within 990±10 cm in the Raman spectrum. -1 Within and 1422±50 cm -1 The peak is within 990±10 cm -1 The peak preferably has an intensity of 870±10 cm -1 It is preferably 10% or more, more preferably 20% or more, more preferably 30% or more, more preferably 40% or more, more preferably 50% or more, more preferably 60% or more, more preferably 70% or more, more preferably 80% or more, more preferably 90% or more, and more preferably 100% or more of the intensity of the peak in the 1422±50 cm -1 The peak preferably has an intensity of 870±10 cm -1The intensity of the peak in the range of 10% or more, more preferably 15% or more, and even more preferably 20% or more.

[0025] In one embodiment, the aqueous solution of the present disclosure includes polyborate ions and ammonium ions. In one specific embodiment, the aqueous solution of the present disclosure includes pentaborate ions, tetraborate ions, and ammonium ions. The aqueous solution of this specific embodiment can be produced, for example, by dissolving an anhydrate or hydrate (preferably the tetrahydrate) of ammonium pentaborate (NH4B5O8) and an anhydrate or hydrate (preferably the tetrahydrate) of ammonium tetraborate ((NH4)2B4O7) in water at ambient temperature (e.g., 15-35°C, more specifically, 20-30°C) or in heated water (e.g., 35-60°C, more specifically, 35-55°C, more specifically, 35-50°C).

[0026] The aqueous solution of this specific embodiment has an N / B ratio that is preferably greater than 0.2 and smaller than 0.5, more preferably 0.25 to 0.48, more preferably 0.27 to 0.40, more preferably 0.36 to 0.42, and particularly preferably 0.36 to 0.39. In this specification, the N / B ratio is the ratio of the number of moles of boron-containing compounds and / or ions (when the aqueous solution of the present disclosure contains two or more kinds of boron-containing compounds and / or ions, the total number of moles of boron for each compound and / or ion) to the number of moles of nitrogen-containing compounds and / or ions (when the aqueous solution of the present disclosure contains two or more kinds of nitrogen-containing compounds and / or ions, the total number of moles of nitrogen for each compound and / or ion). For example, the N / B ratio of an aqueous solution of ammonium tetraborate ((NH4)2B4O7) (alone) is 2 / 4 = 0.5 regardless of the concentration, the N / B ratio of an aqueous solution of ammonium pentaborate (NH4B5O8) (alone) is 1 / 5 = 0.2, and the N / B ratio of an aqueous solution containing 2.1 mol of anhydrous or hydrated ammonium tetraborate ((NH4)2B4O7) and 1.2 mol of anhydrous or hydrated ammonium pentaborate (NH4B5O8) is (2 x 2.1 + 1 x 1.2) / (4 x 2.1 + 5 x 1.2) = 0.375.

[0027] The total molar concentration of pentaborate ions and tetraborate ions in the aqueous solution of this specific embodiment in terms of boron exceeds the solubility of both ammonium pentaborate and ammonium tetraborate in water at the same temperature, and is, for example, at 25°C, preferably 4 mol / kg or more, more preferably 5 mol / kg or more, more preferably 6 mol / kg or more, and particularly preferably 7 mol / kg or more; for example, at 45°C, preferably 4 mol / kg or more, more preferably 5 mol / kg or more, more preferably 6 mol / kg or more, more preferably 7 mol / kg or more, and particularly preferably 8 mol / kg or more. The aqueous solution of this specific embodiment has a Raman spectrum of 990±10 cm -1 Within and / or 1422±50 cm -1 It may have a peak within.

[0028] In one embodiment, the aqueous solution of the present disclosure comprises pentaborate ions, optionally borate ions, and primary alkylammonium ions having 1 to 4 carbon atoms. The aqueous solution of this embodiment has an N / B ratio of, for example, 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, and more preferably 0.37 or more. The upper limit of the N / B ratio is not particularly limited, but is, for example, 1.5 or less, more specifically 1.2 or less, more specifically 1.0 or less, more specifically 0.8 or less, more specifically 0.6 or less, and more specifically 0.5 or less.

[0029] The boron-equivalent molar concentration of the total of the pentaborate ions and borate ions (if present) in the aqueous solution of this embodiment is a value exceeding the solubility of ammonium pentaborate alone in water at the same temperature, for example at 25° C., and is preferably 4 mol / kg or more, more preferably 6 mol / kg or more, more preferably 8 mol / kg or more, and particularly preferably 10 mol / kg or more.

[0030] The aqueous solution of this embodiment can be produced, for example, by dissolving boric acid in an aqueous solution of a primary alkylamine having 1 to 4 carbon atoms. The temperature of the aqueous solution of the primary alkylamine during dissolution is not particularly limited as long as it is a temperature above 0°C, but is, for example, a temperature above 0°C and not higher than 45°C, preferably 10°C to 45°C, more preferably 15°C to 40°C, and more preferably 20°C to 30°C.

[0031] In a specific embodiment, the primary alkylammonium ion having 1 to 4 carbon atoms is a methylammonium ion. The aqueous solution of this specific embodiment has a Raman spectrum of 990±10 cm -1 It may have a peak within.

[0032] <Method for producing polyborate ions and highly concentrated aqueous solutions of borate ions> The method for producing polyborate ions and a high-concentration aqueous solution of borate ions according to the present disclosure (hereinafter also simply referred to as the "method for producing a high-concentration aqueous solution according to the present disclosure") is characterized by comprising a step of dissolving boric acid in water containing primary alkylammonium ions having 1 to 4 carbon atoms, and dissolving the boric acid in the water containing the primary alkylammonium ions having 1 to 4 carbon atoms in an amount exceeding the solubility of the boric acid in water not containing the primary alkylammonium ions having 1 to 4 carbon atoms.

[0033] Without being bound by theory, it is believed that in the method for producing a high-concentration aqueous solution of the present disclosure, in the presence of a primary alkylammonium ion having 1 to 4 carbon atoms, borate ions and boric acid or borate ions undergo a condensation reaction to form polyborate ions (e.g., pentaborate ions) that are more soluble in water, thereby producing a highly concentrated aqueous solution containing (poly)boric acid. In addition, in the presence of a primary alkylammonium ion having 1 to 4 carbon atoms, at least a portion of the polyborate ions forms a structure that is more stable in water (e.g., by interaction) and / or exists in a form that shows higher solubility in water, so that an aqueous solution containing a higher concentration of (poly)boric acid ions can be produced.

[0034] The primary alkylammonium ion having 1 to 4 carbon atoms is as described above in the section <High concentration aqueous solution of polyborate ion>. The water containing the primary alkylammonium ion having 1 to 4 carbon atoms may be a commercially available product as is or after dilution. Alternatively, the water containing the primary alkylammonium ion having 1 to 4 carbon atoms may be an aqueous solution obtained by dissolving a primary alkylamine having 1 to 4 carbon atoms in water, and the aqueous solution may be used as is or after dilution. The primary alkylamine having 1 to 4 carbon atoms is, for example, one or more selected from the group consisting of methylamine, ethylamine, propylamine, monoisopropylamine, n-butylamine, s-butylamine, t-butylamine, and ethylenediamine, preferably methylamine and / or ethylamine, and more preferably methylamine.

[0035] The concentration of the water containing a primary alkylammonium ion having 1 to 4 carbon atoms is, for example, 1 to 50% by weight, preferably 2 to 50% by weight, more preferably 5 to 50% by weight, more preferably 8 to 40% by weight, more preferably 10 to 35% by weight, and more preferably 15 to 30% by weight. Alternatively, the concentration of the water containing a primary alkylammonium ion having 1 to 4 carbon atoms is, for example, 0.15 to 7 mol / kg, preferably 0.3 to 7 mol / kg, more preferably 0.7 to 7 mol / kg, more preferably 1 to 5.5 mol / kg, more preferably 1.5 to 5 mol / kg, and more preferably 2 to 4 mol / kg. The temperature in the dissolving step is not particularly limited as long as it is above 0°C, but may be, for example, a temperature above 0°C and not higher than 45°C, preferably 10°C to 45°C, more preferably 15°C to 40°C, and more preferably 20°C to 30°C.

[0036] <Solid composition containing ammonium polyborate> The ammonium polyborate-containing solid composition of the present disclosure (hereinafter also simply referred to as the "solid composition of the present disclosure") contains ammonium pentaborate and ammonium tetraborate, and is characterized in that the ratio of the total number of moles of boron converted to the number of moles of nitrogen converted (N / B ratio) of the ammonium pentaborate and the ammonium tetraborate is greater than 0.2 and less than 0.5, and the solubility in water (mass molar concentration in terms of boron) exceeds the solubility (mass molar concentration in terms of boron) of both ammonium tetraborate alone and ammonium pentaborate alone at the same temperature.

[0037] The solid composition of the present disclosure has higher solubility in water than conventional compositions obtained by simply mixing a solid (e.g., powder) anhydrous or hydrated ammonium pentaborate with a solid (e.g., powder) anhydrous or hydrated ammonium tetraborate, and is therefore useful for the instant production of an aqueous solution containing high concentrations of pentaborate ions and tetraborate ions (one embodiment of the aqueous solution of the present disclosure). The solid composition of the present disclosure may also be used as a flame retardant directly.

[0038] Without being bound by theory, it is believed that the solid composition of the present disclosure has a higher solubility in water than both ammonium tetraborate and ammonium pentaborate alone because at least a portion of the ammonium pentaborate and ammonium tetraborate contained therein form a structure that is more stable in water (e.g., by interaction) and / or are present in a form that exhibits higher solubility in water.

[0039] The N / B ratio is preferably from 0.25 to 0.48, more preferably from 0.27 to 0.40, more preferably from 0.36 to 0.42, and particularly preferably from 0.36 to 0.39. The solubility of the solid composition of the present disclosure, for example at 25° C., is preferably 4 mol / kg or more, more preferably 5 mol / kg or more, more preferably 6 mol / kg or more, and particularly preferably 7 mol / kg or more. Furthermore, the solubility of the solid composition of the present disclosure, for example at 45° C., is preferably 4 mol / kg or more, more preferably 5 mol / kg or more, more preferably 6 mol / kg or more, more preferably 7 mol / kg or more, and particularly preferably 8 mol / kg or more. The solid composition of the present disclosure may include a surfactant and / or a chelating agent, or may be free of surfactants and chelating agents. In one embodiment, the solid composition of the present disclosure is free of surfactants and chelating agents. Aqueous solutions of the solid compositions of the present disclosure have a Raman spectrum of 990±10 cm -1 It may have a peak within 990±10cm -1 The peak preferably has an intensity of 870±10 cm -1 The intensity of the peak in the range of 10% or more, more preferably 15% or more, and even more preferably 20% or more. A solid composition of the present disclosure may be provided in powder or granular form.

[0040] The solid composition of the present disclosure can be produced, for example, by dissolving an anhydrate or hydrate (preferably tetrahydrate) of ammonium pentaborate (NH4B5O8) and an anhydrate or hydrate (preferably tetrahydrate) of ammonium tetraborate ((NH4)2B4O7) in water at ambient temperature (e.g., 15 to 35°C, more specifically, 20 to 30°C, more specifically, 20 to 25°C) or in warm water (e.g., 35 to 60°C, more specifically, 35 to 55°C, more specifically, 35 to 50°C) so that the N / B ratio is within the above range, and precipitating from the resulting aqueous solution. In addition, for example, the solid composition of the present disclosure can also be produced by precipitating from one embodiment of the aqueous solution of the present disclosure described above. Precipitation can be carried out by, for example, evaporating water from the aqueous solution, more specifically, by a spray-drying method.

[0041] <Flame retardants> The flame retardant of the present disclosure is characterized in that it contains the aqueous solution of the present disclosure or the solid composition of the present disclosure. When the flame retardant of the present disclosure is in the form of a solid composition, it can be used by dissolving it in water. Regarding "flame retardancy," laws and regulations have been established according to the material and its application, and detailed standards and evaluation methods have been standardized. Among them, terms such as "non-flammable," which means that combustion with flames cannot occur, "flame retardant," which means that fire does not spread, and other terms such as "fireproof" and "fire resistance" are used, but in this specification, all of these terms are defined as "flame retardant." Materials that can be flame-retarded by the flame retardant of the present disclosure include, for example, wood, wood materials, bamboo materials, paper, woven fabrics, nonwoven fabrics, and resins.

[0042] When the flame retardant of the present disclosure is in liquid form, it can be impregnated into or applied to the material to be flame retarded, and when it is in solid form (particularly powder form), it can be (melted) kneaded with the material to be flame retarded to impart flame retardancy to the material to be flame retarded. The impregnation amount can be, for example, 50 g or more, more specifically 100 g or more, more specifically 200 g or more, more specifically 500 g or more per kg of the material to be flame retarded. The coating is performed in such a manner that the weight increase rate of the material to be flame retarded is, for example, 5 to 400%, more specifically, 60 to 80%, or the amount of coating is, for example, 0.004 to 1.5 g / cm 2 , more specifically 0.01 to 0.1 g / cm 2 This can be done so that In kneading, the blending amount can be 5 to 70 parts, more specifically 5 to 50 parts, more specifically 5 to 30 parts, and more specifically 15 to 20 parts, per 100 parts of the resin.

[0043] The flame retardant of the present disclosure may contain additives as long as they do not impair the effects of the present invention. With regard to additives, "as long as it does not impair the effect of the present invention" means that the boron-equivalent molar concentration of polyborate ions and borate ions (if present) in the flame retardant containing the substance in question still exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature. More specifically, the boron-equivalent molar concentration of polyborate ions and borate ions (if present) in the flame retardant containing the substance in question is not lower than the boron-equivalent molar concentration of polyborate ions and borate ions (if present) in the flame retardant not containing the substance by more than 10%, more specifically by more than 5%, more specifically by more than 2%, more specifically by more than 1%.

[0044] In the case of liquid flame retardants, additives include, for example, penetrating agents or film-forming agents. The penetrant has the effect of promoting the impregnation of the boron compound into the material to be flame retarded. Examples of such penetrants include alcohols such as methanol, ethanol, propanol, butanol, pentanol, and hexanol; diols such as ethylene glycol and propylene glycol; triols such as glycerin; polyols such as alditols (also called glycitols) having 3 to 11 carbon atoms, polyphenols, and surfactants that act to reduce interfacial tension. Among these, ethylene glycol is preferred. The amount of the penetrant added may be, for example, 0.05 to 20% by weight, more specifically, 0.5 to 2% by weight, when the flame retardant is an aqueous solution.

[0045] Film-forming agents are used to form a flame-retardant coating layer containing a flame-retardant component on a material to be flame-retarded. Examples of such film-forming agents include aqueous polyurethane emulsions, ethylene-vinyl acetate copolymer (EVA) emulsions, and ethylene-acrylic acid copolymer (EEA) emulsions. The amount of the film-forming agent added may be 2 to 15% by weight, more specifically 2 to 5% by weight, when the flame retardant is an aqueous solution.

[0046] The flame retardant may also contain sugars, which have been confirmed to have a flame retardant effect and can improve the flame retardant performance of the flame retardant of the present disclosure (for example, JP 2006-233006 A and JP 2011-162743 A). The amount of saccharides added may be, for example, 5 to 2000 parts, more specifically 30 to 150 parts, for monosaccharides or oligosaccharides, and for example, 1 to 2000 parts, more specifically 1 to 15 parts, for polysaccharides, per 100 parts of the boron compound.

[0047] The flame retardant of the present disclosure in the form of a solid composition can be prepared by evaporating water from the aqueous solution of the present disclosure described above. Evaporation of water can be accomplished by methods known in the art.

[0048] The flame retardant of the present disclosure is preferably used at a temperature at which the ammonium salt of polyboric acid and / or the salt of primary alkylammonium having 1 to 4 carbon atoms (including precipitates in an aqueous solution) that may be contained therein is completely dissolved. The flame retardants of the present disclosure, compared to conventional flame retardants, contain higher concentrations of polyborate ions and borate ions (if present) at lower temperatures (in the case of liquid flame retardants) or can be obtained as such liquid flame retardants simply by dissolving in water (in the case of solid flame retardants), thereby achieving more efficient flame retardancy. Since the flame retardant of the present disclosure does not contain a metal salt (especially a sodium salt), in a specific embodiment, the efflorescence phenomenon in a flame-retardant material flame-retarded using the flame retardant of the present disclosure can be relatively suppressed. Also, in a specific embodiment, the water resistance of a flame-retardant material flame-retarded using the flame retardant of the present disclosure can be relatively improved.

[0049] <Method of manufacturing flame retardant materials> The method for producing a flame-retardant material according to the present disclosure is characterized by including a step of impregnating a material to be flame-retarded with the aqueous solution according to the present disclosure, and a step of precipitating ammonium polyborate in the material to be flame-retarded after the impregnation. The aqueous solution of the present disclosure can contain a high concentration of flame retardant components (polyboric acid and boric acid) even at a relatively low temperature, so that a sufficient amount of the flame retardant components can be impregnated into the material to be flame retarded at a lower temperature and / or in a shorter time of impregnation step. As a result, the flame retardant material can be efficiently produced.

[0050] The material to be flame retarded used in the flame retardant manufacturing method of the present disclosure is not particularly limited as long as it can be impregnated with the aqueous solution used, and examples thereof include wood materials (including wood and bamboo), paper, woven fabrics, nonwoven fabrics, and resins. Examples of wood materials include cedar, spruce, cypress, paulownia, plywood, zelkova, SPF laminated lumber (a composite material made by bonding together spruce (spruce), pine (pine) and fir (fir)), CLT (cross-laminated timber), and LVL (laminated veneer lumber). Examples of the paper include Japanese paper, sliding door paper, and Western paper. Examples of the woven fabric include cotton fabric, polyester woven fabric, polypropylene woven fabric, nylon woven fabric, acrylic woven fabric, vinylon woven fabric, aramid woven fabric, and polyethylene terephthalate (PET) woven fabric. Examples of the nonwoven fabric include polyester nonwoven fabric, polypropylene nonwoven fabric, nylon nonwoven fabric, acrylic nonwoven fabric, vinylon nonwoven fabric, and aramid nonwoven fabric.

[0051] Examples of the resin include polypropylene, polyethylene, polyurethane (hard and soft), polystyrene, vinyl chloride, polycarbonate, phenolic resin, urea resin, melamine resin, vinyl acetate resin, methacrylic resin, epoxy resin, acrylic resin, polyurethane (hard and soft), vinyl chloride resin, polyvinylidene chloride, Teflon (registered trademark) resin, ABS (acrylonitrile butadiene styrene) resin, AS (acrylonitrile styrene) resin, polyacetal, modified polyphenylene ether resin, polybutylene terephthalate resin, butadiene rubber, neoprene (chloroprene) rubber, styrene butadiene rubber (SBR), butadiene acrylonitrile rubber (NBR), isobutene isoprene rubber, polyvinyl acetate, polyethylene terephthalate (PET), and molded bodies and films of composite materials thereof.

[0052] To impregnate the material to be flame retarded, a method known in the art can be used. The impregnation is preferably carried out under heating and / or pressure and / or reduced pressure, which conditions can be appropriately set depending on the type and shape of the material to be flame retarded. The pressurization may be, for example, 0.2 to 20 MPa (absolute pressure; the same applies below), more specifically 0.5 to 10 MPa, and more specifically 0.8 to 5 MPa. The reduced pressure may be, for example, 1 to 100 kPa (absolute pressure; the same applies below), more specifically 2 to 50 kPa, more specifically 3 to 30 kPa, and more specifically 5 to 10 kPa. The temperature during heating can be, for example, 30 to 60°C, more preferably 30 to 55°C, more preferably 35 to 55°C, more preferably 35 to 50°C, more preferably 40 to 50°C. The impregnation time is not particularly limited as long as it is a time that allows the flame retardant component to sufficiently impregnate the material to be flame retarded, and may be, for example, 15 minutes to 24 hours, preferably 15 minutes to 5 hours, preferably 15 minutes to 3 hours, preferably 15 minutes to 1 hour, and more preferably 20 to 30 minutes.

[0053] The amount of impregnation is not particularly limited as long as the material to be flame retarded produced by the flame retardant production method disclosed herein exhibits the desired flame retardant effect (including non-flammable and semi-non-flammable). When the material to be flame retarded is wood, the amount of impregnation is an amount in which the flame retardant component penetrates the wood at a mass of, for example, 5 to 200%, more specifically 10 to 100%, more specifically 20 to 80%, and more specifically 30 to 70% of the dry weight of the wood. The precipitation can be carried out by drying the material to be flame retarded, i.e., by evaporating the water in the aqueous solution impregnated in the material to be flame retarded. The method and conditions for drying the material to be flame retarded are not particularly limited as long as the flame retardant component and the material to be flame retarded are not altered and / or deformed, and can be appropriately set depending on the material to be flame retarded, for example.

[0054] Since the aqueous solution of the present disclosure used in the flame retardant manufacturing method of the present disclosure does not contain metal salts (especially sodium salts), the flame retardant manufactured by the flame retardant manufacturing method of the present disclosure may be relatively inhibited from undergoing efflorescence and / or may have relatively improved water resistance.

[0055] The present invention will be described below with reference to the drawings. The configurations shown in the drawings and the following description are examples and are not limited thereto. EXAMPLES

[0056] Preparation of ammonium borate solution Using ammonium pentaborate tetrahydrate NH4B5O8·4H2O (manufactured by Yoneyama Chemical Co., Ltd., the same applies below) and ammonium tetraborate tetrahydrate (NH4)2B4O7·4H2O (manufactured by Kanto Chemical Co., Ltd., the same applies below), an aqueous solution containing polyborate ions and ammonium ions was prepared, and the solubility in water was calculated. The detailed method is shown below. Example 1 Ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate were prepared so that the N / B ratio described as Example 1 in Table 1 (0.2 < N / B ratio < 0.5) was obtained. A stir bar was placed in a 300 mL beaker, 100 g of distilled water was weighed, and heated to 45°C. The previously prepared ammonium borate was added to the distilled water, and while maintaining the aqueous solution at 45°C, it was stirred at 700 RPM using a stirrer. From the amount of ammonium borate dissolved in the distilled water, the solubility of the prepared ammonium borate in 100 g of water was determined. Further, from the average formula weight and compositional formula of the prepared ammonium borate, the solubility of ammonium borate in terms of boron was converted to a molality (mol / kg). The results are shown in Table 1 and Figure 1. 〔Comparative Example 1〕 As ammonium borates with N / B ratios of 0.2 and 0.5, except for using ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate respectively, in the same manner as the method described in Example 1, the solubility of ammonium borates with N / B ratios of 0.2 and 0.5 in 100 g of water was determined, and the solubility of ammonium borate in terms of boron was converted to a molality (mol / kg). The results are shown in Table 1 and Figure 1.

[0057]

Table 1

[0058] From the results of Example 1, it was found that the solubility of ammonium borate prepared to have an N / B ratio of 0.225 to 0.475 in water was higher than that of ammonium borate with N / B ratios of 0.2 and 0.5 in Comparative Example 1. That is, under the condition of a water temperature of 45 °C, it was shown that the solubility in water of a mixture of ammonium pentaborate and ammonium tetraborate was higher than that of ammonium pentaborate alone or ammonium tetraborate alone in water. In particular, ammonium borate prepared by mixing ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate so that the N / B ratio was 0.36 to 0.42 had a higher solubility in water, and when the N / B ratio was 0.375, the solubility in water was the highest. The pH of the aqueous solution in which ammonium borate with an N / B ratio of 0.375 was dissolved was about pH 8.0 to 8.2.

[0059] [Example 2] Ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate were prepared so that the N / B ratio (0.2 < N / B ratio < 0.5) described as Example 2 in Table 2 was obtained. A stir bar was placed in a 300 mL beaker, 100 g of distilled water was weighed, and it was heated to 25 °C. The previously prepared ammonium borate was added to the distilled water so that the aqueous solution reached 25 °C, and it was stirred at 700 RPM using a stirrer. From the amount of ammonium borate dissolved in distilled water, the solubility of 100 g of the prepared ammonium borate in water was determined. Furthermore, from the average formula weight and compositional formula of the prepared ammonium borate, the solubility of ammonium borate in terms of boron was converted to a molality (mol / kg). The results are shown in Table 2 and Figure 2. [Comparative Example 2] As ammonium borate with N / B ratios of 0.2 and 0.5, except that ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate were used respectively, in the same manner as the method described in Example 2, the solubility of 100 g of ammonium borate with N / B ratios of 0.2 and 0.5 in water was determined, and the solubility of ammonium borate in terms of boron was converted to a molality (mol / kg). The results are shown in Table 2 and Figure 2.

[0060] [Table 2]

[0061] From the results of Example 2, it was found that the solubility in water of ammonium borate prepared so that the N / B ratio was 0.225 to 0.475 was higher than that of ammonium borate prepared in Comparative Example 2 with N / B ratios of 0.2 and 0.5. That is, it was shown that the solubility in water of the mixture of ammonium pentaborate and ammonium tetraborate was higher than that of ammonium pentaborate alone or ammonium tetraborate alone under the water temperature condition of 25°C. In particular, ammonium borate prepared from ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate prepared so that the N / B ratio was 0.36 to 0.42 had a higher solubility in water, and the highest solubility in water was obtained when the N / B ratio was 0.375. The pH of the aqueous solution in which ammonium borate with an N / B ratio of 0.375 was dissolved was about pH 8.0 to 8.2.

[0062] Dissolution of boric acid in aqueous primary alkylamine solutions Boric acid (US Borax, hereinafter the same) was dissolved in a 40% methylamine aqueous solution (Kanto Chemical, hereinafter the same) to prepare an aqueous solution containing polyborate ions and methylamine ions (primary alkylammonium ions with one carbon atom), and the solubility was determined. The detailed method is shown below.

[0063] Example 3 A stirrer was placed in a 300ml or 1000ml beaker, and 100g or 300g of distilled water was weighed out. 40% methylamine aqueous solution and boric acid were added in the amounts shown in Table 3, and stirred at 25°C and 700 RPM. For the test plots in which boric acid was completely dissolved, the N / B ratio and the amount of boric acid dissolved in 100g of water were examined from the masses of distilled water, 40% methylamine aqueous solution, and boric acid, and the amount of boric acid dissolved in terms of boron was converted to a molar mass concentration (mol / kg). The results are shown in Table 3 and Figure 3. Figure 3 also shows plots of test plots in which boric acid was not completely dissolved, although they are not shown in Table 3.

[0064] Comparative Example 3 A stirrer was placed in a 300 ml beaker, 100 g of water was measured out, and boric acid was added without using a 40% methylamine aqueous solution, and the mixture was stirred at 25°C and 700 RPM. The solubility of boric acid in 100 g of water was examined, and the solubility of boric acid in terms of boron was converted to molar mass concentration (mol / kg). The results are shown in Table 3 and Figure 3.

[0065] [Table 3]

[0066] From the results of Comparative Example 3 in Table 3, the solubility of boric acid in water at 25°C was calculated to be 5.39 g / 100 g water, and the molar concentration of boric acid converted to boron was 0.872 mol / kg, which was roughly consistent with the previously reported solubility of boric acid (5.43 g / 100 g water, Linke, 1958). Comparing Comparative Example 3 with Example 3, it was found that the solubility of boric acid in water was significantly increased by adding the boric acid to water together with the aqueous methylamine solution.

[0067] From Table 3 and Figure 3, it was found that when the N / B ratio is in the range of 0.126 to 0.359, the N / B ratio and the amount of boric acid dissolved (mol / kg) converted to boron show a positive correlation shown by the following approximation formula (represented by the dashed line in Figure 3). 2 The value was 0.9669. From the approximation formula, it was found that when the N / B ratio was in the range of 0.126 to 0.359, the amount of boric acid converted to boron could be dissolved in a molar concentration of approximately 4.72 to 4.95 mol / kg. As shown in Figure 3, from the plot position of the test area where boric acid was not completely dissolved, it is considered that this approximation formula can show a value close to the solubility of boric acid in water containing methylamine in the N / B ratio range of 0.126 to 0.359. (Amount of boric acid dissolved converted to boron mol / kg) = 1.0172 × (N / B ratio) + 4.5995

[0068] When the N / B ratio exceeds 0.375, the amount of boric acid that can be dissolved in water increases rapidly, and the amount of dissolved boric acid converted to boron reaches 12.11 to 12.44 mol / kg in terms of molar concentration. Regarding the range of N / B ratios tested in Example 3, when the N / B ratio exceeds 0.375, the amount of dissolved boric acid does not increase or decrease even if the N / B ratio is increased further.

[0069] Production and combustion testing of fire-retardant wood The aqueous solutions obtained in Examples 1 to 3 were used to evaluate the flame retardancy. In order to receive non-combustible certification under the Building Standards Act, a material must pass either a non-combustible test or a combustion test. In the non-combustible test, a cylindrical piece of wood with a diameter of 40 mm and a height of 55 mm is placed in an electric furnace at 750°C for 20 minutes to check the rate of weight loss; a necessary condition for passing is that the rate of weight loss must be 30% or less. In addition, in the combustion test, a sample is given heat equivalent to the initial stage of a fire using a cone calorimeter, and the total heat generated over a 20-minute period is 8MJ / m 2 In general, the former condition is stricter than the latter, and the total calorific value required to satisfy the latter condition is 8MJ / m or less. 2 In the former test, the sample showed a weight loss rate of about 44% (see Tsuyumoto and Oshio). In other words, if the weight loss rate when heated at 750°C for 20 minutes is approximately 44% or less, it is likely to meet the condition of "non-combustible."

[0070] Example 4 The mass of a 4 cm square cedar wood piece was measured and dried in a dryer at 115°C for 24 hours. The mass of the dried cedar wood piece was measured and impregnated with an aqueous solution of ammonium borate with an N / B ratio of 0.375 described in Example 1 under heating and pressure for 24 hours (setting conditions: 1.0 MPa, 45.0°C). After impregnation, the mass of the cedar wood piece was measured and dried in a dryer at 115°C for 24 hours or more. The mass after drying was measured and burned at 750°C for 20 minutes in a muffle furnace (KDF S-90 manufactured by Denken Hydental Co., Ltd., the same applies below). The weight after burning was measured. The test was performed with n=2. The results of the mass measurement of the cedar wood piece are shown in Table 4.

[0071] [Table 4]

[0072] The weight of the cedar wood chips increased by 8.668g and 8.29g after impregnation and drying, respectively, compared to the weight after drying before impregnation. This increase in weight was thought to be due to ammonium borate that was introduced into the wood. Moreover, the mass loss rates after the combustion test were 56% and 54%, respectively, and it was confirmed that the aqueous ammonium borate solution with an N / B ratio of 0.375 obtained in Example 1 imparts high flame retardancy to wood.

[0073] During the combustion test using the muffle furnace, no flames or smoke were produced, and the cedar wood pieces were simply carbonized. Furthermore, the carbonized wood did not easily crumble even when force was applied. When the borate salt is introduced into the wood, it melts and turns glassy when heated, which is thought to cover the surface of the material and cut off the supply of oxygen, thereby preventing ignition and flame spread. Ammonium salts also produce ammonia gas. Ammonia gas is known to have the effect of expanding the glassy coating and to impart flame retardancy due to the non-flammable nature of ammonia gas itself. In Example 4, it is thought that flame retardancy was imparted to the cedar wood chips through these mechanisms, but the present invention is not limited to the mechanisms described above.

[0074] Example 5 The test was carried out in the same manner as in Example 4, except that an aqueous solution of boric acid and methylamine with an N / B ratio of 0.398 was used as described in Example 3. The results of measuring the mass of the cedar wood pieces are shown in Table 5.

[0075] [Table 5]

[0076] The weight of the cedar wood chips increased by 13.843g and 14.444g after impregnation and drying, respectively, compared to the weight after drying before impregnation. This increased weight was thought to be the methylamine borate that was introduced into the wood. In addition, the mass loss rate after the combustion test was 50.1% and 53.6%, and it was confirmed that the aqueous solution of boric acid and methylamine with an N / B ratio of 0.398 described in Example 3 provides high flame retardancy to wood.

[0077] During the combustion test using the muffle furnace, no flames or smoke were produced, and the cedar wood pieces were simply carbonized. Furthermore, the carbonized wood did not easily crumble even when force was applied. It is believed that the boric acid introduced into the interior of the wood melts and turns glassy when heated, which coats the surface of the material and blocks the supply of oxygen, thereby preventing ignition and flame spread. In Example 5, it is believed that the flame retardancy of the cedar wood pieces was imparted at least by the mechanism of imparting flame retardancy by boric acid described above, but the present invention is not limited only to the mechanism described.

[0078] XRD measurements of solids obtained from aqueous solutions To investigate the factors that contribute to the increased solubility of ammonium borate in the aqueous solutions described in Examples 1 and 2, the aqueous solutions were heated, evaporated to dryness, and the resulting precipitate was analyzed by XRD. Crystals diffract X-rays in a manner that is characteristic of their structure. Thus, X-ray diffraction can detect peaks that are characteristic of the crystalline or amorphous solid state of the components of the sample. Example 6 Ammonium pentaborate tetrahydrate and ammonium tetraborate tetrahydrate were mixed so that the N / B ratio was 0.375, and an aqueous ammonium borate solution was obtained in the same manner as in Example 2. The mixture was then dried in a thermostatic chamber at 115° C. for 24 hours to obtain a white powdery solid. The obtained powder was ground in an agate mortar and subjected to powder X-ray diffraction using CuKα radiation (1.5418 Å) with an X-ray diffractometer (Shimadzu XD-D1). The measurement results are shown in Figure 4.

[0079] Comparative Example 4-1 Ammonium pentaborate tetrahydrate powder was ground in an agate mortar and subjected to powder X-ray diffraction analysis, the results of which are shown in Figure 5.

[0080] Comparative Example 4-2 Ammonium tetraborate tetrahydrate powder was ground in an agate mortar and subjected to powder X-ray diffraction analysis, the results of which are shown in Figure 6.

[0081] Comparing the results of Example 6 with those of Comparative Example 4-1 and Comparative Example 4-2, the peaks at 2θ=7.08, 9.9, 14.16, 15.64, 21.46, 28.24, 28.86, 45.66 and 47.28 observed in the XRD results of Example 6 were considered to be derived from ammonium pentaborate tetrahydrate, and the peaks at 2θ=24.24 and 43.6 were considered to be derived from ammonium pentaborate anhydrate (FIGS. 4 and 5). The peaks at 2θ=15.04, 16.14, 16.42, 21.20, 24.92, 26.48, 27.34, 30.64, 33.42, 33.70 and 41.52 were considered to be derived from ammonium tetraborate tetrahydrate (FIGS. 4 and 6). From these results, it was suggested that the powder obtained by evaporating the aqueous solution of ammonium borate mixture with an N / B ratio of 0.35 to dryness contained a mixture of ammonium tetraborate tetrahydrate and ammonium pentaborate tetrahydrate.

[0082] Next, in order to investigate the factors that contribute to the improvement of the solubility of borate ions in the aqueous solution described in Example 3, the aqueous solution was heated and evaporated to dryness, and the obtained precipitate was analyzed by XRD.

[0083] Example 7 Measurement at N / B ratio of 0.2 3.1 g of methylamine and 12.35 g of boric acid were dissolved in 100.1 g of distilled water. The aqueous solution was dried in a thermostatic chamber at 115° C. for 24 hours to precipitate a solid. Powder X-ray diffraction was performed in the same manner as in Example 6. The measurement results are shown in FIG.

[0084] Example 8 Measurements with an N / B ratio of 0.13 4.75 g of methylamine and 30.0 g of boric acid were dissolved in 100.1 g of distilled water. Powder X-ray diffraction was performed in the same manner as described in Example 6. The measurement results are shown in FIG.

[0085] Example 9 Measurement at N / B ratio of 0.51 19.0 g of methylamine and 30.0 g of boric acid were dissolved in 100.0 g of distilled water. Powder X-ray diffraction was performed in the same manner as described in Example 6. The measurement results are shown in FIG.

[0086] Example 10 Measurements with an N / B ratio of 0.17 2.0 g of methylamine and 9.6 g of boric acid were dissolved in 100.0 g of distilled water. Powder X-ray diffraction was performed in the same manner as described in Example 6. The measurement results are shown in FIG.

[0087] In all of Examples 7 to 10, the aqueous solutions were dried to dryness to obtain white powdery solids.

[0088] The solids obtained from the aqueous solutions with N / B ratios of less than 0.2 (Examples 8 and 10) and the solids obtained from the aqueous solutions with N / B ratios of 0.2 or more (Examples 7 and 9) had similar XRD patterns, but the XRD patterns were different between the former and latter. From this, it is considered that a common salt is formed in the powders obtained from the aqueous solutions of boric acid and methylamine with an N / B ratio of 0.2 or more as described in Examples 7 and 9, and that the N / B ratio is considered to be 0.2. On the other hand, in the XRD pattern of the solid obtained from the aqueous solution having an N / B ratio of less than 0.2, in addition to the peaks observed in the XRD pattern of the solid obtained from the aqueous solution having an N / B ratio of 0.2 or more, peaks were observed at 2θ=14.62, 20.14, 21.40, 25.58, and 28.48 in FIG. 10 of Example 8 (FIG. 8). This diffraction peak was determined to correspond to the peak of metaboric acid (HBO2) by referring to 00-009-0015 Hydrogen Borate, HBO2 in ICDD PDF-4 of the XRD database. From this, it was considered that the powder obtained from the aqueous solution having an N / B ratio of less than 0.2 contains boric acid in addition to the salt with an N / B ratio of 0.2.

[0089] Measurement of DTA-TG In order to further investigate the factors that contribute to the improvement of the solubility of borate ions in the aqueous solution described in Example 3, the aqueous solution was evaporated to dryness and the resulting precipitate was analyzed by DTA-TG measurement. In DTA-TG measurement, differential thermal analysis (DTA) and thermogravimetry (TG) are performed simultaneously to obtain information about the phenomena occurring in the sample being measured.

[0090] Example 11 An aqueous solution of methylamine and boric acid with an N / B ratio of 0.2 was prepared by the method described in Example 3. The aqueous solution was dried in a thermostatic oven at 115°C, and the solid obtained was subjected to DTA-TG measurement. The measurement was performed in an air atmosphere. The results of the DTA-TG measurement are shown in Figure 11. Example 12 An aqueous solution of methylamine and boric acid with an N / B ratio of 0.25 was prepared by the method described in Example 3. DTA-TG was measured in the same manner as in Example 11. The results of the DTA-TG measurement are shown in Figure 12. Example 13 An aqueous solution of methylamine and boric acid with an N / B ratio of 0.142 was prepared according to the method described in Example 3. DTA-TG was measured in the same manner as in Example 11. The results of the DTA-TG measurement are shown in FIG. Example 14 An aqueous solution of methylamine and boric acid with an N / B ratio of 0.125 was prepared according to the method described in Example 3. DTA-TG was measured in the same manner as in Example 11. The results of the DTA-TG measurement are shown in Figure 14.

[0091] In the solid obtained from the aqueous solution with an N / B ratio of less than 0.2 (Examples 13 and 14), and in the solid obtained from the aqueous solution with an N / B ratio of 0.2 or more (Examples 11 and 12), similar DTA-TG curves were obtained. However, the shapes of the DTA-TG curves were different between the former and the latter. Specifically, in the solid obtained from the aqueous solution with an N / B ratio of less than 0.2, weight loss accompanied by endothermic heat was observed three times, near 100°C, near 170°C, and near 250°C (FIGS. 13 and 14). On the other hand, in the solid obtained from the aqueous solution with an N / B ratio of 0.2 or more, weight loss accompanied by endothermic heat was observed twice, near 100°C and near 250°C (FIGS. 11 and 12). The result that the properties of the precipitates obtained change when the N / B ratio reaches the boundary of 0.2 is consistent with the XRD results, and is considered to be further supporting the suggestion made by the XRD results that "in the powders obtained from aqueous solutions of boric acid and methylamine with an N / B ratio of 0.2 or more, a common salt is thought to be formed, and the N / B ratio for this salt is 0.2." For a sample with an N / B ratio of 0.2, after weight loss near 100°C, the weight was 87% and 55% above 600°C. Because boric acid releases water and becomes B2O3 above 600°C and because the XRD results suggest that boron and methylamine form a salt in a ratio of 5:1, the chemical formula after weight loss near 100°C is thought to be CH3NH3B5O8 4H2O (methylamine pentaborate tetrahydrate). A substance with this chemical formula has not been reported before and is a new compound.

[0092] In the results of DTA-TG of solids obtained from aqueous solutions with N / B ratios less than 0.2, one additional endothermic weight loss occurred near 170°C. This is thought to be due to the presence of excess boric acid in the precipitate that did not form methylammonium pentaborate tetrahydrate CH3NH3B5O8·4H2O. It is known that boric acid releases water at temperatures between 130°C and 200°C to become HBO2 (Ishihara, 1989), and this reaction may correspond to the endothermic weight loss observed near 170°C.

[0093] On the other hand, in solutions with an N / B ratio greater than 0.2, methylamine is expected to be in excess, but because the boiling point of methylamine is -6.7°C, the excess methylamine volatilizes together with water when the solution is evaporated to dryness. Therefore, the results of DTA-TG of the solid obtained from an aqueous solution with an N / B ratio greater than 0.2 are expected to reflect the properties of methylammonium pentaborate tetrahydrate, CH3NH3B5O8 4H2O.

[0094] When the methylammonium pentaborate tetrahydrate obtained by evaporating the aqueous solution to dryness was dissolved again in distilled water, it showed high solubility similar to that of the aqueous methylamine solution and boric acid dissolved in distilled water. When the methylammonium pentaborate tetrahydrate was redissolved, it dissolved up to 27.5 g in 100 g of water at 25°C.

[0095] From the above results, it was considered that by adding methylamine at the same time as dissolving boric acid in distilled water, methylammonium pentaborate CH3NH3B5O8, a highly soluble salt, is formed in the aqueous solution, and a highly concentrated aqueous solution of boric acid is obtained. Furthermore, it was also found that the solubility increases sharply when methylamine is added in excess of the stoichiometric ratio at which methylammonium pentaborate is formed. As described above, the mechanism by which the solubility of boric acid is improved in the presence of methylamine has been estimated, but the present invention is not limited to this mechanism alone.

[0096] Measurement of Raman spectra The Raman spectra of the aqueous solutions described in Examples 1 and 2 were measured in order to investigate the properties of the aqueous solutions in more detail. In the Raman spectrum measurement, a peak is detected at a specific Raman shift for each chemical bond, so that information reflecting differences in molecular structure can be obtained.

[0097] Example 15 40 g of ammonium borate, which was prepared so that the N / B ratio was 0.375, was dissolved in 100 g of water. The Raman spectrum of the obtained aqueous solution was measured at 25° C. using a wavelength of 532 nm with a JASCO RMP-100. The results are shown in FIG. Comparative Example 5 10 g of ammonium pentaborate tetrahydrate was dissolved in 100 g of water. The Raman spectrum was measured by the method described in Example 15. The results are shown in FIG. Comparative Example 6 12 g of ammonium tetraborate tetrahydrate was dissolved in 100 g of water. The Raman spectrum was measured by the method described in Example 15. The results are shown in FIG.

[0098] Comparing the results of Example 15 with those of Comparative Example 5 and Comparative Example 6, the Raman spectrum of the aqueous solution of ammonium borate prepared to have an N / B ratio of 0.375 showed a peak that was not observed in the Raman spectrum of the aqueous solution of ammonium tetraborate or ammonium pentaborate alone. -1 and 1422±50cm -1 A peak was observed at (Figure 15). Boric acid B(OH)3 aqueous solution has a peak at 871±10 cm in its Raman spectrum. -1 It is known that when it is dissolved in water at a concentration of about 0.025 mol / L or more under conditions of pH 7 to 10, polyborate ions are formed, and a different peak is detected in the Raman spectrum. 990±10cm -1 The peak is due to the high concentration of boric acid (1.5 mol dm -3In a paper summarizing the Raman spectrum of ) in the pH range of 6 to 12, the spectrum was reported under conditions of pH 6.38 to pH 8.28 (Maeda, 1979). However, the 990±10 cm -1 The intensity of the peak at 871 ± 10 cm originates from boric acid B(OH)3. -1 The intensity was less than 4% of the peak intensity of 990±10cm -1 The chemical species to which this band belongs has not been identified. In Example 15, 990±10 cm -1 and 871±10cm -1 The intensity after subtracting the background value from the peak intensity (actual intensity) is 990±10cm -1 The intensity of the peak is 871±10 cm -1 The actual intensity was calculated by using the Legendre orthogonal polynomials as the background function and the pseudo-Voigt function as the peak profile function, and the nonlinear least squares method to minimize the residual sum of squares with the actual measured value.

[0099] Next, in order to investigate the properties of the aqueous solution described in Example 3 in more detail, the Raman spectrum of the aqueous solution was measured at room temperature. Example 16 12.4 g of a 40% aqueous methylamine solution and 3.1 g of boric acid (N / B ratio 0.2) were dissolved in 100 g of water. The Raman spectrum was measured by the method described in Example 15. The results are shown in FIG. Example 17 140 g of 40% methylamine aqueous solution and 270 g of boric acid (N / B ratio 0.42) were dissolved in 300 g of water. The Raman spectrum was measured by the method described in Example 15. The results are shown in FIG. Comparative Example 7 A 40% aqueous methylamine solution was used as a sample to measure the Raman spectrum by the method described in Example 15. The results are shown in FIG. Comparative Example 8 4 g of boric acid (H3BO3) was dissolved in 100 g of water. The Raman spectrum was measured by the method described in Example 15. The results are shown in Figure 21.

[0100] In the Raman spectra of Examples 16 and 17, the peaks observed in Comparative Examples 7 and 8, i.e., the peaks due to methylamine and boric acid, were similarly confirmed. In the Raman spectra of Examples 16 and 17, the peaks at 990±10 cm -1 A peak was detected at 100° C., which was not observed in Comparative Examples 7 and 8. When comparing Example 16 and Example 17, the difference in the balance of peak intensities is thought to be due to the difference in the N / B ratio and the difference in the amount of boric acid dissolved. 990±10cm -1 The peak at 990±10 cm is as described in the discussion of Example 15. -1 The peak intensity is 871±10cm -1 These peak intensities were approximately 20% and 288%, respectively, which were significantly larger than those reported previously. In particular, as shown in Example 17, in an aqueous solution containing a high concentration of borate ions and / or polyborate ions, the peak intensity was 990±10 cm -1 The signal intensity of the peak increases.

[0101] References WF Linke, “Solubilities: Inorganic and Metal-Organic Compounds”, 1958, American Chemical Society, Washington, DC. Shigehisa Ishihara, "Boron and its compounds as fire retardants for wood", 1989, Wood Preservation, Vol. 15-6, pp248-260 Maeda, “Raman spectra of polyborate ions in aqueous solution”, 1979, J. Inorg. nucl. Chem. Vol. 41, pp1217-1220 Isao Tsuyumoto, Tomokazu Oshio, "Development of fireproofing technology for wood using sodium polyborate solution", 2007, Zairyo (Journal of the Japan Society for Materials Science), Vol. 56, No. 5, 472-476 Isao Tsuyumoto and Tomokazu Oshio, "Development of Fire Resistant Laminated Wood Using Concentrated Sodium Polyborate Aqueous Solution", 2009, Journal of Wood Chemistry and Technology, 29 [4], 277-285.

Claims

1. An aqueous solution containing polyborate ions and ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms, The molar concentration of the polyborate ions, calculated as boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature; An aqueous solution containing the ammonium ion and / or the primary alkylammonium ion having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ion.

2. The aqueous solution according to claim 1, which contains the primary alkyl ammonium ion having 1 to 4 carbon atoms and further contains a borate ion, the total molar concentration of the polyborate ions and the borate ions, calculated as boron, exceeds the solubility of both ammonium tetraborate and ammonium pentaborate alone in water at the same temperature; The aqueous solution contains the primary alkylammonium ion having 1 to 4 carbon atoms in a stoichiometric amount or more relative to the polyborate ion and the borate ion.

3. 3. The aqueous solution according to claim 1, having a pH of 7.5 or more.

4. 3. The aqueous solution according to claim 1, which is free of any surfactant or chelating agent.

5. 2. The aqueous solution according to claim 1, wherein the polyborate ions are pentaborate ions and tetraborate ions, and the ammonium ions and / or primary alkylammonium ions having 1 to 4 carbon atoms are ammonium ions.

6. 6. The aqueous solution according to claim 5, wherein the ratio (N / B ratio) of the total number of moles of the pentaborate ions and the tetraborate ions converted into boron to the number of moles of the ammonium ions converted into nitrogen is greater than 0.2 and smaller than 0.

5.

7. 7. The aqueous solution according to claim 6, wherein the N / B ratio is from 0.36 to 0.

42.

8. 3. The aqueous solution according to claim 1, wherein the polyborate ion is a pentaborate ion, and the ammonium ion and / or the primary alkylammonium ion having 1 to 4 carbon atoms is a methylammonium ion.

9. 9. The aqueous solution according to claim 8, wherein the ratio (N / B ratio) of the total number of moles of the pentaborate ions and the borate ions in terms of boron to the number of moles of the methylamine ions in terms of nitrogen is 0.37 or more.

10. 990±10 cm in the Raman spectrum －１ The aqueous solution according to claim 1 or 2, having a peak within the range of 0.1 to 0.5%.

11. The above 990±10cm －１ The peak has an intensity of 870±10 cm －１ 11. The aqueous solution according to claim 10, wherein the intensity of the peak in the aqueous solution is 10% or more of the intensity of the peak in the aqueous solution.

12. A solid composition comprising ammonium pentaborate and ammonium tetraborate, a ratio of the total number of moles of boron of the ammonium pentaborate and the ammonium tetraborate to the number of moles of nitrogen (N / B ratio) is greater than 0.2 and smaller than 0.5; A solid composition having a solubility in water (molar concentration in terms of boron) that exceeds the solubility (molar concentration in terms of boron) of both ammonium tetraborate and ammonium pentaborate alone at the same temperature.

13. A flame retardant comprising the aqueous solution of claim 1 or 2 or the solid composition of claim 12.

14. A method for producing an aqueous solution containing borate ions and / or polyborate ions, comprising the step of dissolving boric acid in water containing primary alkylammonium ions having 1 to 4 carbon atoms, wherein the boric acid is dissolved in the water containing the primary alkylammonium ions having 1 to 4 carbon atoms in an amount exceeding the solubility of the boric acid in water not containing the primary alkylammonium ions having 1 to 4 carbon atoms.

15. The method according to claim 14, wherein the primary alkylammonium ion having 1 to 4 carbon atoms is a methylammonium ion.

16. The method according to claim 14 or 15, wherein the dissolving step is carried out at 15°C to 40°C.

17. 3. A method for producing a flame-retardant material, comprising the steps of: impregnating a material to be flame-retarded with the aqueous solution according to claim 1; and precipitating ammonium polyborate in the material to be flame-retarded after the impregnation.

18. The method according to claim 17, wherein the aqueous solution has a temperature of 40 to 50°C.

19. The method of claim 17, wherein the material to be flame retarded is wood.

20. A method for producing a flame retardant, comprising the step of evaporating water from the aqueous solution according to claim 1 or 2.

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