Method for forming a touch-dry peroxide composition

Abstract

A method for blending a liquid peroxide solution with a crystalline or amorphous solid material to obtain a touch-free peroxide-containing solid material.

Description

[Technical field]

[0001] The present invention relates to a method for blending a peroxide solution with a crystalline or amorphous solid material to provide a peroxide-containing powder material that is dry to the touch. [Background technology]

[0002] Liquid peroxides and solutions of peroxide compounds are useful for many applications, ranging from industrial sources of oxidants and free radicals to cosmetics and household disinfectants, but convenient storage and delivery has long been a challenge because they are generally liquid, unstable and highly reactive.

[0003] Solid forms of peroxide compounds, which may take the form of dry powders, pellets, tablets, beads, or bricks with long-term stability, have a wide range of applications. Examples include formulations for personal care, cosmetics, agriculture, and health care applications. US Patent Application Publication No. 2020 / 0299621 (incorporated herein by reference) describes a delivery system for one type of peroxide compound that uses an inorganic solid carrier that is inert to the peroxide compound and can adsorb a significant amount of liquid while remaining dry to the touch. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2020 / 0299621 Summary of the Invention [Problem to be solved by the invention]

[0005] The novel concept presented in this invention is a method of incorporating a peroxide compound, such as hydrogen peroxide, into a solid carrier to provide a peroxide-containing powder that is dry to the touch. The mixture is completely dry to the touch and does not bleed liquid or otherwise cause the final powder to feel moist or wet even after long periods of storage. The liquid peroxide component of the present invention can include hydrogen peroxide, peracetic acid, organic peroxide, or a combination of various peroxides or other water-based peroxide products. The liquid peroxide component can also include additives such as stabilizers. The liquid peroxide component is also incorporated into a solid carrier to form a dry to the touch powder loaded with the peroxide material. The solid carrier can be based on fumed or pyrogenic silica, precipitated silica, or a combination of both hydrophobic and hydrophilic types of silica in different ratios to achieve the desired carrier properties. Other solids, such as compounding agents, colorants, and binders, can also be loaded into the silica base to provide desired aspects to the final product, such as product color. [Means for solving the problem]

[0006] The peroxide component can be incorporated into the solid carrier component by various methods to achieve a suitable blend. Such blending methods include a simple mixing tank where the liquid is introduced by one or more nozzles, mister, spray ball, or dropwise technique using ribbon or paddle blenders, screw blenders, rotary plow blenders, plow blenders, double paddle blenders, tumbling blenders, V-cone blenders, double cone blenders, static blenders, drum blenders, planetary blenders, vertical blenders, homogenizers, or similar devices that allow thorough mixing of the powdered and liquid peroxide components. It is also possible to spray the liquid peroxide solution into the fluidized bed. The spray nozzles can be flat spray nozzles, cone spray nozzles, hollow cone spray nozzles, mist / fog nozzles. Other mixing techniques can also be employed, such as vibration-assisted mixing devices, sonic or ultrasonic mixing, and various shakers. There are many types of solid / liquid mixing devices. For the purposes of this invention, the terms mixer / mixing and blender / blending can be used interchangeably in describing the incorporation of the peroxide component into the solid carrier.

[0007] When producing solid peroxide materials, it is important to apply the appropriate amount of shear to the powdered solid carrier to form a uniform product. For example, simply mixing a liquid into a solid generally does not provide enough shear and the silica carrier particles tend to stick together and clump. It is also important not to over-shear the solid support in the blending operation while providing enough shear to provide a uniform product.

[0008] The blending operation used to form the solid peroxide product must be controlled to maintain the microstructural integrity of the carrier (typically silica). Excessive shear quickly and irreversibly destroys the physical structure of the silica. Subjecting the product to excessive shear can partially or completely destroy the structure of the silica carrier, resulting in an unusable wet, mushy product.

[0009] Typically, when spraying liquids onto solid particles, the operation should be performed with a Froude number (Fr) greater than 1. When Fr is less than 1, gravity is stronger than centrifugal force and the solid particles remain settled in the blender, moving but not cloudy. When Fr is greater than 1, centrifugal force tends to be stronger than gravity and the solid particles tend to lift and float in the blender. However, when operating with solid particles that have a very low bulk density, the solid particles become airborne and some of them are lost to the filter and air.

[0010] To ensure the integrity of the solid peroxide product, the blender must be operated under low shear conditions. This requires that the blender be operated under low Froude number conditions. However, when liquid injection into solids is performed, Froude numbers greater than 1 are typically employed. In the present invention, the use of high mixing speeds can result in loss of silica microstructure. The inventors have surprisingly found that when the blender is operated under Froude number conditions less than 1, the liquid injection rate must be reduced to allow time for proper distribution of the liquid.

[0011] Mixing time (t m ) for 5 to 45 minutes, preferably 10 to 35 minutes, more preferably 15 to 30 minutes. m By defining Froude number as the ratio of the volume of solid powder to the liquid feed flow rate at which the liquid is operated, operating at a low Froude number can reduce the shear on the solid particles while still allowing complete and uniform entrapment of the solid particles by the liquid.

[0012] If too little shear is used to incorporate the liquid peroxide solution into the solid particle silica carrier, some of the solid particles will agglomerate into balls that not only feel damp to the touch, like a wet snowball, but also contain a high concentration of peroxide solution. The present invention reduces or eliminates the formation of agglomerates and produces a uniform powder that is dry to the touch and has uniform hydrogen peroxide distribution throughout the solid carrier. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Detailed Description of Certain Embodiments of the Invention The inventors have found that when blending a solution of liquid peroxide into a silica powder carrier, special care must be taken to ensure that the silica is properly incorporated to reduce the number of unwanted agglomerates in the final product. Typically, some agglomerates are already present in the silica component. These agglomerates may form during packaging and shipping. Other agglomerates may appear when the silica particles are wetted by the addition of the liquid peroxide solution, causing uneven particle-to-particle adhesion. The present invention provides a process for wetting the silica carrier with a peroxide solution such that the distribution of peroxide throughout the silica is relatively uniform. The resulting wet silica has no or only a few agglomerates after the blending process is complete. A solid peroxide product is formed by the process of the present invention, which minimizes agglomerates in the silicate, avoids clumping due to proper wetting of the silica, and provides uniformity in the wetting process. The solid peroxide product formed by the process of the present invention is a dry to the touch powder.

[0014] A preferred method of blending the liquid peroxide component with the solid, i.e., silica carrier component, is to use a double-blade ribbon blender, paddle blender, or plow blender. A preferred method is to feed the peroxide solution to the silica carrier component with a spray nozzle while operating the ribbon blender, double ribbon blender, or paddle blender at a blade tip speed of preferably between about 0.5 and about 10.0 m / s, preferably about 1.0 m / s to about 5.0 m / s, more preferably about 0.5 to about 2.5 m / s. Other types of blenders may be operated at different tip speeds to achieve the desired mixing. When the desired amount of peroxide solution has been added to the silica carrier, the impeller continues to be operated, preferably at the same blade tip speed, to reduce the amount of lumps and ultimately produce a solid silica product (containing liquid peroxide) that is a substantially dry-to-the-touch powder. A feature of the present invention is to apply sufficient shear for good distribution of the silica carrier powder, but not so much shear that it adversely affects the silica structure. "Dry to the touch" shall mean that one ply of Georgia-Pacific's AccuWipe® brand #29712 will absorb less than 15% moisture by weight after being immersed in a peroxide-containing powder product for 24 hours at 25°C.

[0015] Along with the impeller tip speed, the Froude number is also an important parameter to consider with respect to the present invention. The Froude number is defined as the ratio of the centrifugal force to the gravity force: Fr=Rω 2 / g where R is the radius of the blender, ω is the angular velocity, and g is the force of gravity. When Fr is greater than 1, centrifugal forces dominate, i.e., the powder is thrown around in the blender, and the powder has a tendency to float up in the blender and become airborne. Typical operations for spraying liquids onto solids are performed with Fr greater than 1. However, when using very light, fluffy solid silica carriers, the air becomes filled with powder, causing extra losses to the filter (or atmosphere) and powder entrainment in the liquid nozzle. In the present invention, the blender is operated with Fr less than or equal to 1 and greater than 0.05, preferably less than 0.7 and greater than 0.075, more preferably less than 0.5 and greater than 0.1.

[0016] The inventors have surprisingly found that a good product can be produced at a low Fr. Using the proper geometry and flow rate from the nozzle, a dry to the touch powder is produced with minimal or no agglomerate formation. The blending time t m is defined as the ratio of the volume of product in the blending vessel to the liquid flow rate. t m = powder volume in blender / Q Where: Q is the volumetric flow rate.

[0017] In accordance with the present invention, the blender is operated for a period of more than 5 minutes to 45 minutes, preferably 10 to 35 minutes, more preferably 15 to 30 minutes. m This allows for operation at a lower Froude number, reducing shear on the powder, and also allows the solid silica support powder to be completely and uniformly coated with the peroxy liquid.

[0018] The position of the one or more spray nozzles and the spray geometry of the nozzles are aligned such that the spray from the nozzles does not strike the walls of the blending unit or other fixtures within the blending unit during the blending process. If the spray strikes the walls or any solid fixtures within the blending unit, wet spots can occur leading to the formation of unwanted agglomerates. Multiple nozzle configurations and geometries can be employed that avoid spray patterns striking the walls of the blending unit or internal equipment, or overlapping spray patterns. Overlapping spray patterns can result in localized spatial wet spots leading to undesirable agglomerates. The spray of the liquid peroxide component is designed to produce a uniform distribution of droplets within the blending unit under operating pressure conditions dependent on the nozzle type, with the alignment of the nozzles, while minimizing wet spots. Although a small droplet spray is preferred, it is possible under some circumstances to use nozzles that produce fine or ultrafine droplets leading to a fog or mist type spray.

[0019] In addition to the spray pattern, another feature of the present invention is the spray droplet size. A spray nozzle is used to disperse the liquid to produce droplets with high surface area that impact the solid surface. In the present invention, a spray device is used to disperse the peroxide liquid component with controlled droplet velocity. In the present invention, very high droplet velocity is undesirable since larger agglomerates may be formed, especially when combined with larger droplets. In the present invention, it is preferred to spray small droplets and have a nozzle with a low flow rate. It has been found that it is not possible to linearly increase the flow rate to improve productivity when forming the dry peroxide composition. It has been found that for scale-up, it is necessary to increase the number of spray nozzles to increase the flow rate of the peroxide component and maintain a uniform distribution with less overlap or spray hit on walls or other fixtures located in the blending unit during the blending process. The inventors have found that the ratio of the liquid peroxide component spray droplet size to the silica carrier particle size is preferably between 0.5 and 10,000, more preferably between 0.75 and 3,000. For example, if the silica is 0.2-0.3 μm, the liquid peroxide component spray droplet size will be between 0.1-300 μm.

[0020] A preferred spray nozzle for the liquid peroxide component would have a flow rate of less than about 1 gpm (3.78 liters / min) at 40 psig (276 kPa), preferably less than 0.5 gpm (1.89 liters / min) for a small 75 liter blending unit. A preferred droplet size distribution provided for reference (not a limiting factor for this process) would be 0.1 to 3,000 μm, preferably 1 to 1,000 μm, more preferably 5 to 800 μm. A variety of spray patterns (flat spray, cone, hollow cone, etc.) can be used. The choice of spray pattern depends on the size and shape of the blending unit. The viscosity of the liquid peroxide component also influences the flow rate and the choice of spray pattern to provide the features of the present invention.

[0021] The inventors have found that to provide a solid peroxide product with controlled agglomerate formation, the ratio between the associated blending unit size (and associated shear) and the flow rate at which the peroxide liquid component is added must be controlled. The ratio for a single nozzle is preferably in the range of about 0.01 to about 1.5 liters, more preferably about 0.05 to about 0.5 liters of liquid peroxide component sprayed per minute per nozzle per 100 L of blending unit space (working volume). Thus, for example, a 1273 L blending unit would require 2 to 6 nozzles flowing at about 1.5 L per minute to properly add the liquid peroxide component to the powdered silica component in the correct ratio to limit agglomerate formation.

[0022] To enhance the safety of handling liquid peroxide components such as hydrogen peroxide and peracetic acid, the blending unit is preferably operated under ventilated conditions at ambient temperatures ranging from about 4° C. to 35° C., preferably from about 10° C. to 30° C., and more preferably from about 15° C. to 25° C. Metal parts in contact with peroxide should be passivated to ensure product stability.

[0023] Aspect 1: A method of making a combination of liquid peroxide and a dry solid support comprising spraying a liquid peroxide solution onto a dry silica solid support, The method includes mixing hydrophobic or hydrophilic silica powders in a blending unit comprising a mixing device and one or more spray nozzles to form a relatively agglomerate-free powder, the spray nozzles being oriented to minimize the impact of the spray on surfaces of the blending unit or mixing device, the ratio of liquid peroxide spray droplet size to particle size of the silica solid support being about 0.5 to 10,000, and the blending unit being operated at a Froude number of 1 or less.

[0024] Aspect 2: The method of aspect 1, wherein the flow rate of the liquid peroxide solution comprises an aqueous solution.

[0025] Aspect 3: The method of aspect 1 or 2, wherein the liquid peroxide solution comprises hydrogen peroxide, peracetic acid, an organic peroxide, or a combination thereof.

[0026] Aspect 4: The method according to any one of Aspects 1 to 3, wherein the concentration of the liquid peroxide solution is about 0.5% to 90%, preferably 35% to 70%, and more preferably 50% to 70%.

[0027] Aspect 5: The method of any one of Aspects 1-4, wherein the dry silica solid support comprises fumed silica, pyrogenic silica, precipitated silica, or a combination thereof.

[0028] Aspect 6: The method of any one of aspects 1 to 5, wherein the dry silica solid support is in the form of a powder or granules.

[0029] Aspect 7: The method of any of aspects 1-6, wherein the mixing apparatus comprises a blender operated at a blade tip speed between about 0.5 m / s and about 10.0 m / s.

[0030] Aspect 8: The method according to any one of aspects 1 to 7, wherein the ratio of the liquid peroxide spray droplet size to the particle size of the silica solid support is between about 0.5 and 10000, preferably between about 0.75 and 3000.

[0031] Aspect 9: The method of any of aspects 1-8, wherein the flow rate of the liquid peroxide component through each one of the one or more nozzles ranges from about 0.3 gpm (1.13 liters / minute) to about 2 gpm (7.57 liters / minute) at 40 psig (276 kPa).

[0032] Aspect 10: The method of any of aspects 1 to 9, wherein the one or more spray nozzles are selected from the group consisting of flat spray nozzles, cone spray nozzles, hollow cone spray nozzles, mist / fog nozzles, and combinations thereof.

[0033] Aspect 11. The method of any of aspects 1-10, wherein the blender is operated at a Froude number less than 1 and greater than 0.05, preferably less than 0.7 and greater than 0.075, more preferably less than 0.5 and greater than 0.1.

[0034] Aspect 12: The method of any of aspects 1 to 11, wherein the spray delivery system is operated for a mixing time of from 5 to 45 minutes, preferably from 10 to 35 minutes, more preferably from 15 to 30 minutes.

[0035] Although embodiments have been described herein in a manner that enables a clear and concise specification to be written, it is intended and will be understood that the embodiments can be variously combined or separated without departing from the invention. For example, it will be appreciated that all of the preferred features described herein are applicable to all aspects of the invention described herein.

[0036] In some embodiments, the invention can be construed to exclude any component or process step that does not materially affect the basic and novel characteristics of the composition or the method of using the composition. Further, in some embodiments, the invention can be construed to exclude any component or process step not specified herein. EXAMPLES

[0037] Example 1: A 75 L double ribbon blender was operated at 60 rpm. A Bete PJ24 90° spray angle nozzle was operated at high pressure (100 psig or 689 kPa) and delivered 50% liquid hydrogen peroxide solution at 0.16 gpm (0.60 liters per minute) to 2.5 kg of Cab-O-Sil® M5 silica to produce 8.6 kg of product. The spray pattern resulted in the spray hitting the walls of the blending unit. The resulting product contained numerous agglomerates, was moist to the touch, and had a "snowball" texture.

[0038] Example 2: In the same 75 L double ribbon blending unit, a Teejet® nozzle giving a flat spray pattern was used to deliver a component flow rate of 0.2 gpm (0.76 liters / min) of 50% liquid hydrogen peroxide solution at 40 psig (276 kPa) to 2.5 kg of Cab-O-Sil® M5 silica to produce 8.6 kg of product. Product quality was improved, but there was still some wet agglomerate formation.

[0039] Example 3: In the same 75 L double ribbon blending unit, using a Teejet® nozzle equipped with a flat spray nozzle, delivering 2.5 kg of Cab-O-Sil® M5 silica at a flow rate of approximately 0.067 gpm (0.25 liters / minute) at a pressure of up to 40 psig (276 kPa), a total of 8.6 kg of good quality product, dry to the touch powder, with minimal agglomerate formation was obtained.

[0040] Example 4: In a commercial size 1273 L paddle blender, 139 pounds (63 kg) of silica (Cab-O-Sil® M5 from Cabot Corp.) was loaded into the blender. This filled approximately 90% of the blender volume. The spray nozzles were placed directly on the outside of the silica. The blender was operated at a speed of 20.5 rpm and five TeeJet® flat nozzles were used at a flow rate of 0.4 gpm (1.5 liters / min) and a pressure of 30 psig (207 kPa), positioned so that the spray patterns did not overlap or strike the side walls of the blender. This resulted in a good quality product that was a dry to the touch powder without the formation of agglomerates. The Froude number was calculated to be 0.21, which is significantly less than the literature's ideal value of 1 for powder and liquid mixing. The tip speed of the paddle was approximately 1 m / s. The blender was operated with no noticeable dust in the dust collector. The 50.1% hydrogen peroxide addition was made over a 19 minute period for a total of 366 pounds (166 kg) of hydrogen peroxide added, although 9 pounds (4 kg) was charged to the feed line, so it was calculated that 357 pounds (162 kg) actually entered the blender. After the hydrogen peroxide addition, the blender was blended for an additional 5 minutes with the chopper running for 5 seconds every minute. The resulting product was a free-flowing, dry-to-the-touch powder that was analyzed to be 36% hydrogen peroxide incorporated into the silica.

Claims

1. 1. A method for producing a combination of liquid peroxide and a dry solid support comprising spraying a liquid peroxide solution onto a dry silica solid support, The method includes mixing hydrophobic or hydrophilic silica powders in a blending unit comprising a mixing device and one or more spray nozzles to form a powder, said spray nozzles being oriented to minimize the impact of the spray on surfaces of the blending unit or the mixing device, said ratio of liquid peroxide spray droplet size to particle size of silica solid support being about 0.5 to 10,000, and said blending unit being operated at a Froude number of 1 or less.

2. The method of claim 1 , wherein the flow rate of the liquid peroxide solution comprises an aqueous solution.

3. The method of claim 1 , wherein the liquid peroxide solution comprises hydrogen peroxide, peracetic acid, an organic peroxide, or a combination thereof.

4. The method of claim 1, wherein the liquid peroxide solution has a concentration of about 0.5% to 70%.

5. The method of claim 1, wherein the liquid peroxide solution has a concentration of 35% to 70%.

6. The method of claim 1, wherein the liquid peroxide solution has a concentration of 50-70%.

7. 10. The method of claim 1, wherein the dry silica solid support comprises fumed silica, pyrogenic silica, precipitated silica, or a combination thereof.

8. 2. The method of claim 1, wherein the dry silica solid support is in the form of a powder or granules.

9. 10. The method of claim 1, wherein the mixing device comprises a blender operated at a blade tip speed of between about 0.5 m / s and about 10.0 m / s.

10. 2. The method of claim 1, wherein the ratio of liquid peroxide spray droplet size to particle size of the silica solid support is between about 0.5 and 10,000.

11. 10. The method of claim 1, wherein the ratio of liquid peroxide spray droplet size to particle size of the silica solid support is between about 0.75 and 3000.

12. 10. The method of claim 1, wherein the flow rate of the liquid peroxide component through each one of the one or more nozzles ranges from about 0.5 gpm (1.89 liters / min) to about 2 gpm (7.57 liters / min) at 40 psig (276 kPa).

13. 10. The method of claim 1, wherein the one or more spray nozzles are selected from the group consisting of flat spray nozzles, cone spray nozzles, hollow cone spray nozzles, mist / fog nozzles, and combinations thereof.

14. 10. The method of claim 1 , wherein the blender is operated at a Froude number of less than 1 and greater than 0.

05.

15. 15. The method of claim 14, wherein the blender is operated at a Froude number less than 0.7 and greater than 0.

075.

16. 15. The method of claim 14, wherein the blender is operated at a Froude number of less than 0.5 and greater than 0.

1.

17. 10. The method of claim 1, wherein the blender is operated for a mixing time of between 5 and 45 minutes.

18. The method of claim 17, wherein the blender is operated for a mixing time of from 10 to 35 minutes, more preferably from 15 to 30 minutes.

19. The method of claim 17, wherein the blender is operated for a mixing time of 15 to 30 minutes.

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