WO1999033945A1

WO1999033945A1 - A process for making a phosphate material

Info

Publication number: WO1999033945A1
Application number: PCT/US1997/024120
Authority: WO
Inventors: Junan Kao; Tianli Wen
Original assignee: The Procter & Gamble Company
Priority date: 1997-12-29
Filing date: 1997-12-29
Publication date: 1999-07-08
Also published as: AU5725698A

Abstract

The current invention is directed towards a process for forming and using a surface-structured phosphate material. An aspect of the process includes providing a phosphate material, providing a humid condition of at least 45 °C and having at least 0.054 kg of water per kg of dry air, and forming a surface-structured phosphate material by hydrating the phosphate material within the humid condition. A surface-structured phosphate material as made by the above process is also disclosed herein.

Description

A PROCESS FOR MAKING A PHOSPHATE MATERIAL

FIELD

The present invention relates to a process for hydrating phosphate materials. More specifically, the present invention relates to a process for , increasing the surface area of phosphate materials via hydration, and the phosphate materials created by this process.

BACKGROUND

Phosphate materials are used in many processes in which materials having a large surface area are desirable. More specifically, in agglomeration processes used to produce granular detergent compositions, phosphate materials having a large surface area are highly desired, because they absorb more surfactant active. The greater the surface area of the phosphate material used, the more surfactant active it can absorb. Because of the increased capacity to absorb surfactant active, less phosphate materials are necessary in formulating detergent compositions, thereby lowering formulation costs. Surfactant active loading capacity is described as the amount of surfactant active which can be absorbed by a phosphate material. A phosphate materials with a larger surface area possesses a higher surfactant active loading capacity. When it is desirable to create highly concentrated detergent formulations, phosphate materials having a higher surfactant active loading capacity provide a means to create these concentrated detergents.

Although there are other non-phosphate materials having higher surfactant active loading capacities which are used to absorb surfactant active in formulating concentrated detergents, e.g., zeolites, these alternate materials are generally significantly more expensive than phosphate materials. Accordingly, to keep formulation costs low, it is desired to use phosphate materials having an increased surfactant active loading capacity.

The surface area of a material is determined by factors such as the nature of material itself, and how finely ground the material is. The surface area of any specific material, such as a phosphate material, can be increased by grinding the material into smaller, finer particles. However, purchasing fine gπnding machinery is expensive and requires significant capital expenditures. Use of fine grinding machinery to produce larger surface area phosphate materials can therefore result in, for example, increased detergent production costs. Surface area of a phosphate material can also be increased by hydration.

Hydrated phosphate materials generally possess a higher moisture content and a greater surface area than unhydrated phosphate materials. Without intending to be limited by theory, it is believed that the increase in surface area of hydrated phosphate materials is directly proportional to the degree of hydration of the phosphate material. Various hydration methods and processes are known. For example, phosphate materials can be hydrated by spraying them with water, steam, organic solvents, and/or other chemicals. Furthermore, it is also known to increase the surface area of phosphate materials by grinding them into small particles while rapidly hydrating them by spraying them with steam. However, current hydration methods possess significant drawbacks. For example, when phosphate materials are hydrated by spraying them with steam or water, the liquid tends to cause the individual particles to adhere and cluster together, forming an aggregated mass. This type of aggregation reduces the surface area of the hydrated phosphate materials. Thus, these clustered phosphate materials may require further grinding and processing before they can be effectively utilized in a production process.

Furthermore, hydration methods which employ organic solvents and other chemicals in the hydration process can adversely affect the resulting phosphate material's performance and chemical reactivity. For example, these adverse effects can slow or impede the ability to absorb the surfactant active, or the ability to act as an effective builder in a detergent formulation.

SUMMARY

The current invention is directed towards a process for forming and using a surface-structured phosphate material. An aspect of the process includes providing a phosphate material, providing a humid condition of at least 45°C and having at least 0.054 kg of water per kg of dry air, and forming a surface- structured phosphate material by hydrating the phosphate material within the humid condition. Another aspect of the current invention is a surface-structured phosphate material as made by the above process.

These and other features, aspects, and advantages of the present invention will become evident to those skilled in the art from a reading of the present disclosure with the appended claims.

DETAILED DESCRIPTION

The current invention is directed towards a process for forming and using a surface-structured phosphate material having a large surface area. The current invention is also directed towards the surface-structured phosphate material formed by the process detailed herein.

All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (°C) unless otherwise specified. Furthermore, all temperatures herein are "dry bulb" temperatures unless otherwise noted. All documents cited are incorporated herein by reference.

The current invention is directed towards a process for forming a surface- structured phosphate material having a large surface area. The transformation of a phosphate material into a surface-structured phosphate material significantly increases the moisture content and the surface area of the phosphate material. The process includes providing a phosphate material, providing a humid condition of at least 45°C and having at least about 0.054 kg of water per kg of dry air, and forming a surface-structured phosphate material by hydrating the phosphate material within the humid condition. The phosphate material is hydrated by absorbing water from the humid condition, thereby increasing the moisture level. The increased moisture level corresponds to an increased surface area, which indicates formation of the surface-structured phosphate material. In the humid condition, the amount of water present in the air is measured in kilograms, relative to the dry air, as further explained below. Once hydrated by this process, the surface-structured phosphate material has a significantly increased surface area as compared to the surface area of the original, unhydrated phosphate material. Furthermore, this result is achieved while maintaining the surface-structured phosphate material's chemical reactivity and performance. This hydration method also can increase the surface area of the phosphate material without having to resort to grinding. Once formed, the surface-structured phosphate material can be dehydrated, and yet still retain a large surface area. This provides a surface-structured phosphate material possessing both a low moisture content and a surprisingly large surface area.

Surface-Structured Phosphate Material

The surface-structured phosphate material is formed by hydrating a phosphate material within a humid condition. When first formed, the surface- structured phosphate material is characterized by a high moisture content and a large surface area. Without intending to be limited by theory, it is believed that a delicate superstructure forms on the surface of the phosphate material; it is further believed that this delicate superstructure consists of a hydrate of the phosphate material, e.g., the hexohydrate form. Accordingly, it is believed that this delicate superstructure greatly increases the surface area of the surface- structured phosphate material, as compared to the starting phosphate material. The superstructure is believed to be made up of angled planar crystals which form on the surface of the hydrated phosphate material, so as to form the surface-structured phosphate material.

Typically, unhydrated phosphate materials have a moisture level of less than about 5%, usually less than about 3%. However, in the process described herein, the phosphate material is hydrated within the humid condition until the surface-structured phosphate material has a moisture level of at least about 10%, preferably from about 14% to about 25%, and more preferably from about 15% to about 23%, by weight of the surface-structured phosphate material. The moisture level can be measured by the Kett Moisture Analyzer process, whereby hydrated phosphate is placed under an infrared heating lamp and the moisture weight loss is measured by a balance underneath. This can also be conducted, for example, by using a Carl Fisher Moisture Analyzer or High Temperature Oven methods.

The surface-structured phosphate material formed by the process described herein has a surface area of at least about 0.5 rrrVgram, preferably from about 0.5 to about 1.5 m²/gram, and more preferably between about 0.8 and 1.5 m²/gram of surface-structured phosphate material. The total surface area of a sample of known mass can be measured by various methods, such as by measuring gas adsorption, such as m the Bruenauer Emmett Teller (BET) method. The BET method employs a pyncometer to measure the total surface area via helium displacement. A preferred apparatus for this test is a model Gemini 2375 surface analyzer, by Micromeritics. This type of method is preferred for particles smaller than about 50 microns in diameter.

An oil absorption test is a preferred test which measures the amount of organic matter which a 5.0 gram sample of phosphate material can absorb. Oil is mixed with and kneaded into the phosphate material until it is saturated. It is believed that the amount of organic matter absorbed by this type of test is directly proportional to the surface area of the phosphate material tested. The surface- structured phosphate material formed herein absorbs a significantly higher amount of a given oil than the unhydrated phosphate materials. Preferred equipment for conducting this oil absorption test includes: a graduated burette, a spatula, and a scientific balance.

Once formed, the surface-structured phosphate material can be optionally dehydrated prior to use. Dehydrated surface-structured phosphate materials are highly desired when the total moisture content of a composition is to be minimized or controlled, e.g., in granular detergent formulations. Furthermore, the surface-structured phosphate material can be dehydrated and yet still retain the large surface area. Preferred dehydration processes include those which retain the desired large surface area. Non-limiting examples of preferred dehydration processes are lyophilization, gentle heating (e.g., under a heat lamp), oven drying, fluid bed drying, fluidisation, and tumbler drying. If the surface-structured phosphate material is dehydrated, it is preferred that the surface-structured phosphate material maintains a surface area of at least about 0.5 m²/gram, preferably from about 0.50 to 1.5 m²/gram, more preferably from about 0.8 to about 1.5 m²/gram of surface-structured phosphate material.

Phosphate Material

Providing a phosphate material useful herein requires selecting a phosphate material whose surface area can increase through hydration. The phosphate material useful in the process described herein include, for example, the alkali metal salts, ammonium salts, alkanolammonium salts, and acid forms of polyphosphates, tripolyphosphates, pyrophosphates, and mixtures thereof. Water soluble phosphate materials are especially useful herein.

A preferred phosphate material useful in the process described herein includes those which are useful in, for example, detergent formulations, such as the alkali metal salts, ammonium salts, alkanolammonium salts, and acid forms of tripolyphosphates, pyrophosphates, orthophosphates, metaphosphates, higher polyphosphates, and mixtures thereof.

It is preferred that before hydration, the phosphate material have an average particle size of less than about 300 microns, preferably from about 10 to about 100 microns, more preferably from about 20 to about 80 microns, and even more preferably, from about 20 and about 60 microns in diameter. If the average particle size is greater than about 300 microns in diameter, then the phosphate material can be prepared by first grinding a phosphate material. Alternatively, the phosphate material can often be purchased as a ground powder having particles of the desired average particle size. These phosphate materials are available, as, for example, FMC Powder, from FMC Corp. (USA), having an average particle size of about 22 microns; FMC granular, from FMC Corp. (USA), having an average particle size of about 200 microns; KunMing (China) STPP having an average particle size of about 46 microns; and Chemphil (Philippines) STPP having an average particle size of about 30 microns. Also useful herein is glassy hexamer ("Glassy H") phosphate material.

In a preferred process, the phosphate material is prepared by first grinding to an average particle size of about 30 microns. It is believed that this grinding step further improves the resulting surface-structured phosphate material because it increases the total surface area which is in contact with the humid condition, described below. It is believed that this results in improved kinetics and therefore, more efficient and rapid hydration of the phosphate material.

When providing a phosphate material for hydration, it is preferred that the phosphate material is spread evenly into a thin layer and/or frequently turned over.

Humid Condition

Providing a humid condition of at least 45°C, and having at least about 0.054 kg of water per kg of dry air, induces the phosphate material into forming the surface-structured phosphate material within an acceptable period of time. The surface-structured phosphate material is formed by hydrating the phosphate material within the humid condition. The humid condition is variable as to factors such as temperature and the amount of water present in the air. However, the temperature of the humid condition should be at least about 45°C, preferably from about 45°C to about 120°C, and more preferably from about 80°C to about 100°C. In the process herein, the temperature of the humid condition can vary during the hydration of the phosphate material, however, the average temperature of the humid condition during hydration of the phosphate material should be at least 45°C. In a preferred process, the temperature of the humid condition remains substantially constant during the hydration of the phosphate material, providing an average temperature of at least 45°C.

Furthermore, the water content in the air of the humid condition should be at least about 0.054 kg of water per kg of dry air, preferably from 0.054 to about 2.3, more preferably from about 0.06 to about 1.5 kg of water per kg of dry air, and even more preferably from about 0.07 kg to about 1.5 kg of water per kg of dry air. The amount of water per kg of dry air can be calculated by utilizing standard psychometric charts which relate the air's water content to temperature. See, for example, Perr^y's Chemical Engineer's Handbook. 6^th edition, p. 20-6 (McGraw-Hill; D.W. Green, Ed., 1984). Thus, for example, if the humid condition has 0.054 kg of water per kg of dry air, the amount of water present in the air is equal to: (0.054 kg water)^*(100) / (0.054 kg water + 1.000 kg of air) = 5.12%, by weight; at 50°C this corresponds to a relative humidity of about 65%.

In a process included herein, the humid condition has an amount of water in the air which varies during the hydration of the phosphate material, however, the average amount of water in the air of the humid condition during hydration is at least 0.054 kg of water per kg of dry air. In a preferred process, the humid condition has an amount of water in the air which remains substantially constant during the hydration of the phosphate material, providing an average amount of water in the air of at least 0.054 kg of water per kg of dry air. In a preferred process, the humid condition has substantially no liquid water suspended in the air; substantially all the water present in the air is in the gaseous form so as to minimize undesired aggregation during hydration. Generally, in the humid condition, higher temperatures are preferred over lower temperatures, while air with a higher water content is preferred over air with a lower water content.

The placing of the phosphate materials within the humid condition induces formation of the surface-structured phosphate material of the invention. Without intending to be limited by theory, it is believed that the kinetics of hydration of the phosphate material are such that higher temperatures and a higher water content in the air produce more rapid formation of the surface-structured phosphate material. Furthermore, it is believed that a humid condition having both a temperature of at least 45°C and a water content of at least 0.054 kg of water per kg of dry air induces the rapid formation of a larger proportion of the desired superstructure, leading to a larger surface area. The phosphate material must be placed within the humid condition for a period of time sufficient for the moisture level of the surface-structured phosphate to increase to at least about 10%, preferably from about 14% to about 25%, and more preferably from about 15% to about 22%, by weight of the surface- structured phosphate material. As noted above, the kinetics of formation are dependent upon factors such as the temperature, and water content of the air of the humid condition. Without intending to be limited by theory, it is also believed that the relative proportion of superstructure induced in the surface-structured phosphate material and the increase of the moisture level therein are directly related to the length of time the phosphate material is hydrated within the humid condition; i.e. for a given humid condition, the longer the exposure, the higher the proportion of superstructure formed. In a preferred process, the phosphate material is hydrated within the humid condition for at least about 48 hours, more preferably, for between 2 days and 3 weeks, and even more preferably for between 1 week and 3 weeks so as to form the surface-structured phosphate material. If the phosphate material is spread into a thin layer and/or frequently turned over while it is within the humid condition, hydration can be much quicker, and it is preferred that the phosphate material hydrate in the humid condition for at least about 48 hours, more preferably for between 2 days and 10 days, and even more preferably for 4 days to 6 days. Various equipment can be used to provide the humid condition, or to otherwise contain the humid condition. Equipment having sealed environments for containing the humid condition are preferred, as are those pieces of equipment which automatically control both the temperature and the water content of the air, therein. Preferred equipment for providing the humid condition controlled temperature and controlled humidity room made by Tabai Espec Corp. (Japan), model TBRR-2W4SJ. Preferred equipment allows for independent control of the room temperature and the water content of the air therein, and are available from, for example, Rika Industrial KK. Methods of Use

The surface-structured phosphate materials of the current invention can be used in many production processes where materials having a large surface area are desired. For example, the surface-structured phosphate material of the invention can be used in its hydrated state immediately after formation, or alternatively, it can be first dehydrated and then used. The surface-structured phosphate material can replace and/or augment the use of normal phosphate materials wherever such materials having a large surface area phosphates are desired. The amount of surface-structured phosphate materials used can be more, less, or the same as the amount of unhydrated phosphate materials that they replace.

In a preferred production process, the surface-structured phosphate material is not ground in between the time it is formed, and the time it is used. This maximizes retention of the delicate superstructure of the surface-structured phosphate material. However, after reacting/aggregating the surface-structured phosphate material with other compounds, grinding of the resulting compound/agglomerate is permitted in this preferred process. In a preferred process, the humid condition induces the phosphate materials to form the surface-structured phosphate material, which is then used in an agglomeration process without further grinding or compacting. In a preferred process, the humid condition induces the phosphate material into forming the surface- structured phosphate. The surface-structured phosphate is then dehydrated over low heat and used in an agglomeration process without further grinding or compacting. If desired, the surface-structured phosphate material can be first hydrated and then subsequently dehydrated with the same piece of equipment. In a preferred process, the humid condition is provided by equipment which allows for independent control of both the temperature and the water content of the air therein. The equipment provides a humid condition therein of a temperature of at least about 45°C and having a water content of at least about 0.054 kg of water per kg of dry air. The phosphate material is hydrated within the humid condition to form the surface-structured phosphate material. While keeping the temperature constant, the water content of the air is subsequently lowered, thereby leading to the dehydration of the surface-structured phosphate material without ever removing it from within the equipment. Phosphate-Containing Detergent Compositions

Detergent compositions often contain phosphate materials, where they serve, for example, as builders. Some phosphate-containing detergent compositions contain phosphate materials as structurants. In agglomeration processes for granular detergents, for example, phosphate materials having a large surface area are very desirable. Without intending to be limited by theory, it is believed that phosphate materials having a larger surface area absorb more surfactant active, per weight of phosphate. Also without intending to be limited by theory, it is believed that the use of the surface-structured phosphate material leads to the production of significantly finer agglomerates having a smaller average particle size; finer agglomerates are desirable because they can possess, for example, higher surfactant active loadings, decreased dissolving time due to their smaller particle size, and faster dissolution rate. In a preferred process, a phosphate-containing detergent composition is made by: providing a phosphate material, providing a humid condition of at least 45°C and having at least about 0.054 kg of water per kg of dry air, forming a surface-structured phosphate material by hydrating the phosphate material in the humid condition, dehydrating the surface-structured phosphate material, and using the surface-structured phosphate material to make a detergent composition. In a preferred process, surface-structured phosphate materials are used in the agglomeration process to make concentrated granular detergents.

In detergent-making processes, the surface-structured phosphate material can be used in the same manner as a normal unhydrated phosphate material would be used; simply replacing the unhydrated phosphate material with a comparable amount of surface-structured phosphate material is sufficient. Alternatively, a comparatively lower weight amount of surface-structured phosphate material may be useful, for example, in making concentrated detergent compositions. Or, for example, a comparatively higher weight amount of surface-structured phosphate material may be useful in making lighter or fluffier detergent compositions. Also, detergent compositions containing a combination of both surface-structured phosphate materials and normal unhydrated phosphate materials are included within the scope of the current invention. The phosphate-containing detergent compositions described herein can further contain any of various detersive ingredients known in the art, and can be made by known detergent composition production processes.

Examples of the invention are set forth hereinafter by way of illustration and are not intended to be in any way limiting of the invention.

EXAMPLE 1

A phosphate material is placed in a humid condition of about 68°C and having about 0.1 kg of water per kg of dry air. This corresponds to a relative humidity of about 50%. The phosphate material is hydrated in the humid condition for 1 week to form a surface-structured phosphate material.

The surface-structured phosphate material has an increased moisture level and an increased surface area as compared to that of the original phosphate material. EXAMPLE 2

A ground phosphate material having an average particle size of about 300 microns is placed in a humid condition of about 50°C and having about 0.0675 kg of water per kg of air. The phosphate material is hydrated within the humid condition for 2 weeks to form a surface-structured phosphate material. The surface-structured phosphate material is removed from the humid condition and then dehydrated by placing it under a heat lamp for 2 days.

EXAMPLE 3

A surface-structured phosphate material is prepared according to Example

2, except that STPP from FMC, USA, (FMC Powder) is used therein, and the humid condition has about 0.06 kg of water per kg of air and a temperature of about 80°C. The phosphate material is frequently turned over while therein, and remains hydrating therein for 2 days.

EXAMPLE 4 A surface-structured phosphate material is prepared according to Example 4, except that: the humid condition is of about 45°C and about 0.054 kg of water per kg of air; and the phosphate material remains hydrating therein for about 1.5 weeks.

The dehydrated surface-structured phosphate material is used in an agglomeration process to make a granular detergent composition. EXAMPLE 5

A surface-structured phosphate material is prepared according to Example 2, except that the phosphate material is hydrated in the humid condition for 4 weeks.

Claims

WHAT IS CLAIMED IS:

1. A process for forming a surface-structured phosphate material comprising the steps of: a. providing a phosphate material; b. providing a humid condition of at least 45┬░C and having at least about 0.054 kg water per kg dry air; and c. forming a surface-structured phosphate material by hydrating the phosphate material within the humid condition.

2. The process of Claim 1 , wherein the phosphate material has an average particle size of less than about 300 microns in diameter.

3. The process of Claim 1 , wherein the surface-structured phosphate material has a moisture level of at least about 10% by weight of the surface-structured phosphate material.

4. The process of Claim 1 , further comprising the step of: a. dehydrating the surface-structured phosphate material, wherein the surface-structured phosphate material maintains a surface area of at least about 0.50 m²/gram of surface-structured phosphate material.

5. A surface-structured phosphate material as made by the process of Claim 1.

6. The process of Claim 2, wherein the phosphate material is selected from the group consisting of alkali metal salts, ammonium salts, alkanolammonium salts, and acid forms of tripolyphosphates, pyrophosphates, orthophosphates, metaphosphates, higher polyphosphates, and mixtures thereof.

7. The process of Claim 2, wherein the phosphate material is hydrated within the humid condition for at least about 48 hours.

8. The surface-structured phosphate material of Claim 7, having a surface area of at least about 0.50 m²/gram of surface-structured phosphate material.

9. A process for making a phosphate-containing detergent composition comprising the steps of: a. providing a phosphate material; b. providing a humid condition of at least 45┬░C and having at least about 0.054 kg water per kg dry air; c. forming a surface-structured phosphate material by hydrating the phosphate material within the humid condition; d. dehydrating the surface-structured phosphate material; and e. using the surface-structured phosphate material to make a detergent composition.

10. A phosphate-containing detergent composition as made by the process of Claim 9.