Hydroxyapatite Powder Composition Beyond Nanomaterial Size Limits
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Solution Overview
Problem
Existing methods for producing hydroxyapatite powders result in materials that fall under the definition of 'nanomaterials', raising concerns in the food industry due to their ability to penetrate biomembranes, and the resulting large specific surface areas are undesirable for certain applications.
Innovation Solution
A method is developed to produce hydroxyapatite powder with primary particles having a median size >0.10 μm, an aspect ratio <5, specific surface area ≤10 m²/g, and bulk density >550 g/l, achieved by reacting milk of lime with phosphoric acid at controlled temperatures and pH, followed by repeated separation and layering of hydroxyapatite layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional hydroxyapatite production methods are used, then hydroxyapatite powder is obtained, but the primary particles fall under the definition of nanomaterials with dimensions in the range of 1-100 nm
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH range (6.0-13.0) and temperature (>20°C and <105°C) during the reaction of milk of lime with phosphoric acid. These parameter adjustments result in primary particles with a median size >0.10 μm, which exceeds the nanomaterial definition threshold and eliminates the harmful nanomaterial properties while maintaining manufacturing precision.
2Ease of manufacture
If hydroxyapatite powders with large specific surface area are produced, then the material can be obtained through conventional methods, but the large specific surface area causes undesirable absorption properties
Solution Approach 1:
The patent changes the particle size parameter by controlling the reaction conditions (pH 6.0-13.0, temperature >20°C and <105°C) to produce larger primary particles with median size >0.10 μm. This parameter change reduces the specific surface area to ≤10 m²/g, thereby eliminating the harmful absorption properties while keeping the production process simple and straightforward.
3Length of stationary object
If sintering is used to obtain larger particles, then particle size increases, but the specific surface area remains very large (well in excess of 10.0 m²/g)
Solution Approach 1:
The patent applies preliminary action by controlling the particle growth during the precipitation reaction itself, rather than relying on subsequent sintering. By adjusting the pH and temperature parameters during the reaction of milk of lime with phosphoric acid, the process directly produces particles with median size >0.10 μm and specific surface area ≤10 m²/g, achieving both size increase and surface area reduction in one step.
4Ease of manufacture
If milk of lime is reacted with phosphoric acid, then hydroxyapatite is formed, but very fine acicular primary particles are created that agglomerate to form secondary particles in the micrometer range
Solution Approach 1:
The patent changes the reaction parameters by controlling the pH range (6.0-13.0) and temperature (>20°C and <105°C) during the reaction of milk of lime with phosphoric acid. These parameter modifications transform the particle morphology from very fine acicular shapes to larger particles with median size >0.10 μm, achieving manufacturing precision while maintaining the simplicity of the milk of lime and phosphoric acid reaction method.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The produced hydroxyapatite powder avoids nano-properties, ensuring better membrane permeability and improved flow properties, suitable for food applications and other uses requiring low specific surface area and high bulk density.
Implementation Method 1
reacting milk of lime with phosphoric acid to form hydroxyapatite
Implementation Method 2
separating at least a portion of the hydroxyapatite particles out of the suspension
Data Source
AI summary
In order to provide a hydroxyapatite that can be used without reservation in the food industry, a hydroxyapatite powder is provided composed of primary particles. The median size of the primary particles from which the powder is made is >0.10 μm and the aspect ratio of the primary particles is <5. The specific surface area of the hydroxyapatite powder is ≤10 m2/g, and the bulk density is >550 g/l. Also disclosed is a method with which such a hydroxyapatite powder can be obtained.