Calcium phosphate manufacturing method

Abstract

To provide calcium phosphate further excellent in orientation.SOLUTION: Calcium phosphate includes a needle-like particle 10 having a length L in a longitudinal direction, a length T in a thickness direction, and a length D in a width direction. The needle-like particle 10 has an aspect ratio (L / T) of 80 or more and 150 or less. The needle-like particle 10 has the length D in the width direction of 0.5 μm or more and 2.0 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to calcium phosphate. [Background technology]

[0002] Because calcium phosphate has low surface activity, no hygroscopicity, biocompatibility, and high safety, its use as a filler for structural materials has been investigated (for example, Patent Document 1). From the viewpoint of dimensional stability of resins, fillers for structural materials are desired to be in the form of fine particles with a high aspect ratio. Patent Document 1 discloses flaky calcium hydrogen phosphate with an average aspect ratio of 5 or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-29693 Summary of the Invention [Problem to be solved by the invention]

[0004] For use as a filler, further improvements have been desired for calcium phosphate so that the orientation can be further improved. An object of the present invention is to provide calcium phosphate having excellent orientation. [Means for solving the problem]

[0005] Calcium phosphate according to one aspect of the present disclosure relates to the following aspects.

[0006] [Aspect 1] The calcium phosphate contains acicular particles each having a length L in the longitudinal direction, a length T in the thickness direction, and a length D in the width direction. The acicular particles have an aspect ratio (L / T) of 80 or more and 150 or less. The acicular particles have a length D in the width direction of 0.5 μm or more and 2.0 μm or less.

[0007] [Aspect 2] The needle-shaped particle is the calcium phosphate according to aspect 1, having a flat end face at one end in the longitudinal direction.

[0008] [Aspect 3] The acicular particles are calcium phosphate according to aspect 1 or 2, produced by jet mixing of an aqueous phosphoric acid solution with a suspension of calcium hydroxide.

[0009] [Aspect 4] Aspect 4 is a method for producing calcium phosphate according to any one of Aspects 1 to 3, wherein the acicular particles are produced by mixing an aqueous phosphoric acid solution and a suspension of calcium hydroxide using a double-pipe mixer. The double-pipe mixer includes an outer pipe and an inner pipe disposed within the outer pipe. The calcium hydroxide suspension is supplied to the outer pipe. The aqueous phosphoric acid solution is supplied to the inner pipe.

[0010] [Aspect 5] 2. The calcium phosphate according to aspect 1, having a bulk specific volume of 5 mL / g or more and 15 mL / g or less.

[0011] [Aspect 6] The method for producing calcium phosphate includes a mixing step of mixing an aqueous phosphoric acid solution with a suspension of calcium hydroxide to obtain a slurry. In the mixing step, the aqueous phosphoric acid solution and the suspension are mixed by a jet stream.

[0012] [Aspect 7] Aspect 6 is a method for producing calcium phosphate according to aspect 6, wherein the mixing step uses a double-pipe mixer. The double-pipe mixer includes an outer pipe and an inner pipe disposed within the outer pipe. The calcium hydroxide suspension is supplied to the outer pipe. The phosphoric acid aqueous solution is supplied to the inner pipe.

[0013] [Aspect 8] The method for producing calcium phosphate includes an aging step of aging the slurry at a temperature of 60°C or higher and 100°C or lower. The aging step is a method for producing calcium phosphate according to aspect 7, in which an aging tank is used. The aging tank is provided downstream of the double-pipe mixing section. The aging tank receives the slurry discharged from the double-pipe mixing section.

[0014] [Aspect 9] A method for producing calcium phosphate according to any one of aspects 6 to 8, wherein the calcium phosphate comprises acicular particles each having a length L in the longitudinal direction, a length T in the thickness direction, and a length D in the width direction. The acicular particles have an aspect ratio (L / T) of 80 or more and 150 or less. The length D in the width direction is 0.5 μm or more and 2.0 μm or less. [Effects of the Invention]

[0015] The calcium phosphate according to the present invention has excellent orientation. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an SEM observation photograph (1) of calcium phosphate according to the present embodiment. [Figure 2] 1 is an SEM observation photograph (2) of calcium phosphate according to the present embodiment. [Figure 3] 1 is a schematic diagram showing an apparatus for producing calcium phosphate according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram showing a double-pipe mixing section according to the present embodiment. [Figure 5] 1 shows SEM observation photographs of samples according to an example and a reference example. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Calcium phosphate] Calcium phosphate according to one embodiment of the present invention will be described below with reference to the drawings. Figure 1 is an SEM photograph (1) of calcium phosphate according to this embodiment, and Figure 2 is an SEM photograph (2) of calcium phosphate according to this embodiment.

[0018] 1 and 2, calcium phosphate contains a plurality of acicular particles 10 each having a length L in the longitudinal direction, a length T in the thickness direction, and a length D in the width direction. The acicular particles 10 may be agglomerated with other acicular particles 10 contained in the calcium phosphate and with irregular particles other than the acicular particles 10, or may exist independently without agglomerating with other particles.

[0019] Examples of calcium phosphate include calcium hydrogen phosphate, calcium hydrogen phosphate dihydrate, calcium dihydrogen phosphate, calcium dihydrogen phosphate monohydrate, tricalcium phosphate, octacalcium phosphate, hydroxyapatite, fluorapatite, chlorapatite, carbonate apatite, whitlockite, amorphous calcium phosphate, tetracalcium phosphate, and calcium pyrophosphate.

[0020] The aspect ratio (L / T) of the acicular particle 10 is 80 or more and 150 or less. The longitudinal length L is the length of the longest axis of the acicular particle 10 of interest. The thickness length T is the length of the shortest axis corresponding to the longitudinal length L of the acicular particle 10 of interest.

[0021] The width direction length D of the acicular particle 10 is 0.5 μm or more and 2.0 μm or less. The width direction length D is the length in the direction perpendicular to the longitudinal direction and thickness direction of the acicular particle 10 of interest. In other words, the width direction length D is the distance between both sides of the acicular particle 10 along the longitudinal axis, with the plane containing the longitudinal axis and the width direction axis of the acicular particle 10 of interest being the front face. The width direction length at one longitudinal end of the acicular particle 10 and the width direction length at the opposite end are not necessarily the same in the front face. The width direction length of the acicular particle 10 may gradually increase or decrease from one longitudinal end to the other. The width direction length D of the acicular particle 10 is the maximum value from one longitudinal end to the other. The width direction length D of the acicular particle 10 is preferably 0.7 μm or more and 1.3 μm or less.

[0022] For example, as shown in Fig. 1, the longitudinal length L is specified as L1 to L5. The widthwise length D is specified as D1 to D5. Furthermore, the thicknesswise length T is specified by selecting an acicular particle 10 suitable for measuring the thickness direction, as shown in Fig. 2.

[0023] The acicular particles 10 according to this embodiment have an aspect ratio (L / T) of 80 to 150 and a width D of 0.5 μm to 2.0 μm, which results in excellent orientation. The acicular particles 10 have an aspect ratio (L / T) of 80 to 150 and a width D of 0.7 μm to 1.3 μm, which results in even better orientation.

[0024] The acicular particle 10 preferably has a flat end face 12 at one end in the longitudinal direction of the acicular particle 10 of interest. The end face 12 is a surface that connects both sides that intersect in the width direction of the acicular particle 10 at one end in the longitudinal direction of the front of the acicular particle 10 of interest. The end face 12 does not need to be parallel to the width direction, but may also be inclined. The acicular particle 10 may have a flat end face at each end in the longitudinal direction.

[0025] The calcium phosphate preferably has a bulk specific volume of 5 mL / g or more and 15 mL / g or less, and more preferably 9 mL / g or more and 12 mL / g or less. The calcium phosphate has a large bulk specific volume because it contains acicular particles 10 with an aspect ratio (L / T) of 80 or more and 150 or less and a width direction length D of 0.5 μm or more and 2.0 μm or less. The bulk specific volume in this embodiment is a loose bulk specific volume. The packed bulk specific volume is about half of the loose bulk specific volume.

[0026] [Calcium phosphate manufacturing equipment] An example of a calcium phosphate production apparatus for producing the above calcium phosphate will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic diagram showing a calcium phosphate production apparatus according to this embodiment, and Fig. 4 is a schematic diagram showing a double-pipe mixer according to this embodiment. The production apparatus 14 includes a double-pipe mixer 16. The reaction apparatus 14 may further include an aging section 18.

[0027] The double-pipe mixing section 16 rapidly mixes the calcium hydroxide suspension and the phosphoric acid aqueous solution. The double-pipe mixing section 16 preferably mixes the calcium hydroxide suspension and the phosphoric acid aqueous solution by jet flow. The double-pipe mixing section 16 has an outer pipe 20 and an inner pipe 22. The inner pipe 22 is disposed within the outer pipe 20. The outer pipe 20 and the inner pipe 22 are preferably disposed coaxially.

[0028] The outer pipe 20 extends from upstream to downstream. An upstream end 20U of the outer pipe 20 is connected to an outer pipe side liquid feed pump (not shown). The calcium hydroxide suspension fed from the outer pipe side liquid feed pump flows from upstream to downstream in the outer pipe 20. A downstream end 20D of the outer pipe 20 is connected to the aging section 18.

[0029] The inner pipe 22 extends from upstream to downstream. An upstream end 22U of the inner pipe 22 is connected to an inner pipe side liquid feed pump (not shown). The phosphoric acid aqueous solution fed from the inner pipe side liquid feed pump flows from upstream to downstream through the inner pipe 22. As shown in FIG. 4, the downstream end 22D of the inner pipe 22 may terminate upstream of the downstream end 20D of the outer pipe 20. In other words, the double-pipe mixing section 16 may have a predetermined distance PL from the downstream end 22D of the inner pipe 22 to the downstream end 20D of the outer pipe 20 (FIG. 4).

[0030] The aging section 18 has an aging tank 24 and a discharge pipe 25. The aging tank 24 has an inlet 26 and an outlet 28. The aging tank 24 receives the slurry discharged from the double-pipe mixing section 16 through the inlet 26. The aging tank 24 holds and matures the slurry in the aging tank 24 under conditions such as a temperature of 60°C to 100°C for 2 minutes to 1 hour, and preferably a temperature of 80°C to 100°C for 30 minutes to 1 hour. The discharge pipe 25 is connected to the outlet 28. The aging section 18 discharges the aged slurry from the aging tank 24 to the discharge pipe 25 through the outlet 28.

[0031] [Method of producing calcium phosphate] A method for producing calcium phosphate will be described using the above-mentioned production apparatus 14 as an example. Calcium phosphate can be produced by a mixing step. The method for producing calcium phosphate may further include an aging step. These steps will be described in order below. The mixing step involves rapidly mixing an aqueous phosphoric acid solution with a suspension of calcium hydroxide to obtain a slurry.

[0032] First, a mixture is mixed from the outer pipe 20 of the double-pipe mixing section 16 at a predetermined linear velocity V out The calcium hydroxide suspension is delivered at a linear velocity V out is the flow rate of the calcium hydroxide suspension flowing through the pipe divided by the cross-sectional area of the pipe. out The inner pipe 22 of the double-pipe mixing section 16 is fed with a predetermined linear velocity V in The phosphoric acid aqueous solution is delivered at a linear velocity V inis the value obtained by dividing the flow rate of the phosphoric acid aqueous solution flowing through the pipe by the cross-sectional area of the pipe. The volume mean diameter (MV) of calcium hydroxide contained in the calcium hydroxide suspension may be, for example, 6 to 10 μm. Linear velocity V in and linear velocity V out may be the same or different.

[0033] The aqueous phosphoric acid solution and the calcium hydroxide suspension come into contact with each other at the predetermined linear velocity and are mixed by the jet flow. The mixing of the aqueous phosphoric acid solution and the calcium hydroxide suspension is completed through the mixing zone Z (Figure 4).

[0034] The mixing section Z is a section where the phosphoric acid aqueous solution and the calcium hydroxide suspension flowing out from the pipe join together and form a steady flow. As a result, a slurry containing acicular particles 10 is produced in the mixing section Z and further downstream from the mixing section Z.

[0035] The linear velocity V of the phosphoric acid solution flowing through the pipe in and the linear velocity V of the calcium hydroxide suspension flowing through the pipe. out Ratio to (V in / V out ) is preferably 10 or more and 20 or less. The linear velocity V of the aqueous phosphoric acid solution in and the linear velocity V of the calcium hydroxide suspension out When the linear velocity ratio is within the above range, the calcium hydroxide suspension and the phosphoric acid aqueous solution can be mixed quickly.

[0036] In this embodiment, the calcium hydroxide suspension and the phosphoric acid aqueous solution pass through the mixing zone Z and become a steady flow, thereby completing the mixing. That is, in order to quickly mix the calcium hydroxide suspension and the phosphoric acid aqueous solution, it is preferable that the mixing zone Z is short. The linear velocity V of the phosphoric acid aqueous solution in and the linear velocity V of the calcium hydroxide suspension out Linear velocity ratio (V in / V out ) is larger, the shorter the blending interval is.

[0037] When mixing a suspension of calcium hydroxide with an aqueous phosphoric acid solution, it is preferable that the dissipation energy ε, represented by the following formula 1, is large.

[0038]

number

[0039] Q is the flow rate, ΔP is the pressure loss in the space of interest, V is the volume of the space of interest, ρ is the density, and τ is the residence time. The dissipated energy ε can be increased by narrowing the flow path through which the fluid flows or increasing the flow rate to shorten the residence time. Also, if a mixed fluid made by mixing a calcium hydroxide suspension and an aqueous phosphoric acid solution is made into a jet, ΔP increases. As a result, the dissipated energy ε can be increased.

[0040] In the aging step, the slurry obtained in the mixing step is aged in the aging section 18 by holding it at a temperature of 60°C or higher and 100°C or lower for 2 minutes to 1 hour, preferably at a temperature of 80°C or higher and 100°C or lower for 30 minutes to 1 hour. By passing through the aging step, the slurry becomes calcium phosphate with high purity.

[0041] The production method may further include a washing step and a drying step. In the washing step, the slurry after the aging step is first suction filtered using filter paper to obtain a cake. The obtained cake is then washed with ion-exchanged water. By passing through the washing step, impurities can be removed and the purity can be further increased. In the drying step, dried acicular particles can be obtained by heating the cake.

[0042] [Action and effect] Calcium phosphate contains acicular particles 10 having an aspect ratio (L / T) of 80 to 150 and a width D of 0.5 μm to 2.0 μm, and therefore has better orientation than plate-shaped, foil-shaped, and palisade-shaped particles. Because of its excellent orientation, calcium phosphate can be suitably used, for example, as a filler. Calcium phosphate can be used, for example, as a filler for paints, resins, and pharmaceuticals.

[0043] The acicular particles 10 have a flat end face 12 at one end in the longitudinal direction, and therefore are easier to maintain their particle shape compared to particles with pointed tips. The acicular particles 10 have an aspect ratio (L / T) of 80 to 150 and a width D of 0.5 μm to 2.0 μm, and therefore calcium phosphate having a bulk specific volume of 5 mL / g to 15 mL / g can be obtained.

[0044] Calcium phosphate can be produced by a production method including a mixing step of mixing an aqueous phosphoric acid solution with a suspension of calcium hydroxide to obtain a slurry, and an aging step of aging the slurry at a temperature of 80°C or higher. In the mixing step, the aqueous phosphoric acid solution and the suspension are mixed by a jet stream. By rapidly mixing the aqueous phosphoric acid solution with the suspension of calcium hydroxide, for example, by a jet stream, acicular particles 10 can be obtained.

[0045] In the manufacturing method of this embodiment, by using the double-pipe mixer 16, it is possible to more reliably generate a jet stream of a mixture of the phosphoric acid aqueous solution and the calcium hydroxide suspension.

[0046] The slurry obtained in the double-pipe mixing section 16 can be continuously processed by receiving and maturing it in the maturing tank 24, and calcium phosphate can be obtained more efficiently.

[0047] [Measurement method] (aspect ratio and width) The size of the acicular particles is determined by observing the acicular particles of calcium phosphate with a scanning electron microscope (SEM). The magnification of the SEM observation is, for example, 5,000 to 20,000 times. From the captured image, for example, five acicular particles are randomly selected, and their longitudinal length L and width length D are measured. In addition, the same number of acicular particles (five in this case) suitable for measuring the thickness length T are randomly selected, and their thickness length T is measured. The average value of the aspect ratio (L / T) is calculated from the sum of the measured longitudinal lengths L and thickness lengths T. This average value is defined as the aspect ratio (L / T) of the calcium phosphate. In addition, the average value calculated from the sum of the width length D is defined as the width length D of the calcium phosphate.

[0048] (Bulk ratio) Gently place 5 g of calcium phosphate into a 50 mL measuring cylinder, level it, and read the volume of the calcium phosphate. Divide the mass of the packed calcium phosphate by the volume to calculate the value, and use this calculated value as the loose bulk specific volume.

[0049] [Variations] The present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the present invention. For example, in the above-described embodiments, the acicular particles have a flat end face at one end in the longitudinal direction, but the present invention is not limited to this. The acicular particles may have an end face including a convex portion or a concave portion at one or both ends in the longitudinal direction.

[0050] Although the acicular particles in the above embodiment are produced using a double-pipe mixer, the present invention is not limited to this. The acicular particles may be produced using other methods as long as the calcium hydroxide suspension and the phosphoric acid aqueous solution can be mixed quickly, for example, by a jet stream. [Example]

[0051] The present invention will be described in more detail below with reference to examples. However, these examples are merely examples shown for the convenience of explanation, and the present invention is not limited to these examples in any sense.

[0052] [sample] According to the above "Calcium phosphate manufacturing method", samples were produced using the double-pipe mixing unit shown in "Calcium phosphate manufacturing apparatus". Details of each material are explained below.

[0053] Example 1 A 4.9 mol% aqueous solution of phosphoric acid, temperature adjusted to 80°C, and a 3.7 mol% suspension of calcium hydroxide, temperature adjusted to 80°C, were prepared. A double-pipe mixing section was prepared, with an outer pipe having an inner diameter of 8 mm, an inner pipe having an inner diameter of 1.8 mm, and the length of the PL portion in Figure 4 being 80 mm.

[0054] Next, using a constant volume pump, an aqueous phosphoric acid solution was supplied to the outer tube, and a calcium hydroxide suspension was supplied to the inner tube. They were supplied to the double-tube mixing section so that the phosphorus to calcium ratio during the reaction was 1:1. The supply rate of the aqueous phosphoric acid solution and the calcium hydroxide suspension was 180 ml / min. The reaction continued under these conditions for 2 minutes, yielding 716 mL of slurry. The resulting slurry was suction filtered using filter paper to obtain a cake. The resulting cake was washed with 975 mL of ion-exchanged water. It was then dried overnight at 105°C, yielding calcium hydrogen phosphate of Example 1.

[0055] Example 2 The same procedure as in Example 1 was carried out except that the slurry obtained after the reaction was aged at 80° C. for 1 hour, thereby obtaining calcium hydrogen phosphate of Example 2.

[0056] (Reference example 1) 100 mL of ion-exchanged water was placed in a batch reaction tank, and the temperature was adjusted to 80°C. While stirring the ion-exchanged water at 300 rpm, a 0.51 mol / L aqueous solution of phosphoric acid and a 0.51 mol / L solution of calcium chloride were mixed, and a 0.67 mol / L solution of sodium hydroxide was simultaneously poured into the mixture over about 1 minute to initiate the reaction. After the pouring was completed, the mixture was filtered, washed, and dried in the same manner as in Example 1, to obtain a sample of Reference Example 1. (Reference example 2) After the addition was completed, the same procedure as in Reference Example 1 was carried out, except that the obtained slurry was aged at 80° C. for 1 hour, to obtain a sample of Reference Example 2.

[0057] [Measurement results] The measurement results of the obtained acicular particles are shown in Table 1, and an SEM photograph is shown in FIG.

[0058] [Table 1] As shown in Table 1 and FIG. 5, it was confirmed that Example 1 yielded acicular particles having an aspect ratio (L / T) of 80 or more and 150 or less, and a width direction length D of 1.4 μm to 1.6 μm or less. It was confirmed from the SEM observation photographs that the aspect ratio (L / T) and width direction length D of Example 2 were equivalent to those of Example 1. In contrast, as is clear from the SEM observation photographs, Reference Examples 1 and 2 yielded thin plate-like particles with a large width direction length. It was also confirmed that Examples 1 and 2 had a larger bulk specific volume than Reference Examples 1 and 2. [Explanation of symbols]

[0059] 10 Acicular particles 12 End face 14 Manufacturing equipment 16 Double tube mixing section 18. Aging Section 20 outer tube 20D Downstream end 20U upstream end 22 Inner tube 22D Downstream end 22U upstream end 24 Aging tank 25 Discharge piping 26 Entrance 28 Exit

Claims

1. A mixing step of mixing an aqueous phosphoric acid solution with a suspension of calcium hydroxide to obtain a slurry, The mixing step includes mixing the phosphoric acid aqueous solution and the calcium hydroxide suspension by a jet stream using a double-pipe mixing section, The double-pipe mixing section includes an outer pipe and an inner pipe disposed within the outer pipe, The phosphoric acid aqueous solution is supplied to the outer tube, and the calcium hydroxide suspension is supplied to the inner tube, A method for producing calcium phosphate, wherein the ratio (V in / V out ) of the linear velocity V in at which the aqueous phosphoric acid solution flows through the pipe to the linear velocity V out at which the calcium hydroxide suspension flows through the pipe is 10 or more and 20 or less.

2. further comprising an aging step of aging the slurry at a temperature of 60° C. or higher and 100° C. or lower for 2 minutes to 1 hour; The aging step uses an aging tank, 2. The method for producing calcium phosphate according to claim 1, wherein the aging tank is provided downstream of the double-pipe mixing section and receives the slurry discharged from the double-pipe mixing section.

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