WO1997029175A1

WO1997029175A1 - Nta/edta-containing detergent composition

Info

Publication number: WO1997029175A1
Application number: PCT/EP1997/000594
Authority: WO
Inventors: Patricia Anderson
Original assignee: Unilever NV
Current assignee: Unilever NV
Priority date: 1996-02-12
Filing date: 1997-02-10
Publication date: 1997-08-14
Anticipated expiration: 1998-08-12
Also published as: EP0880577A1; AU713088B2; ZA971163B; CA2243472A1; BR9707279A; AU1723297A

Abstract

NTA or EDTA is agglomerated using a liquid active detergent composition such as an aqueous solution of polyacrylic acid. This agglomerated NTA/EDTA can then be combined with other detergent active compositions to form a detergent which does not cake easily. The detergent can also be compressed to form a tableted detergent.

Description

NTA / EDTA-CONTAINING DETERGENT COMPOSITION

Field of the invention

The present invention relates to a detergent composition which incorporates sodium salts of nitrilotriacetic acid and/or ethylenediaminetetraacetic acid, as sequestering agents and detergent builders.

Background of the invention The institutional detergent market distributes a variety of products for washing silverware, pots and pans, dishes, floors, walls, stainless steel surfaces, tile and the like. Unlike products used in the home, institutional detergents are often sold in bulk and dispensed from mechanical dispensers. There are a variety of different forms these can take including liquids, powders, solidified bricks, granules and tablets. Several factors enter into the determination of which particular physical form is most suitable for the desired application. One particularly beneficial detergent form is the tablet. Large compressed tablets of detergent formulation can be formed and held in bulk. These can be dispensed by spraying water against the tablets, causing the detergent to dissolve, and collecting this dissolved, concentrated detergent solution for use. These tableted detergent compositions can take a variety of different forms and include many different detergent compositions, as desired. Powders are also widely used. These are also dispensed from spray dispensers. However, because of their form, care must be taken to assure that they do not cake up in the dispensers. Further, components of powdered detergents must be uniformly mixed. The physical properties of the components can affect this. Typical detergent compositions will include a source of alkalinity, a sequestering agent and/or builders, surfactants, antiredeposition aids and the like. Typically, phosphates are used as sequestering agents and detergent builders. However, in some applications it is desirable to replace the phosphates with other sequestrants and builders such as the alkali metal (preferably sodium) salts of nitrilotriacetic acid and ethylenediaminetetraacetic acid, also referred to as "NTA" or "EDTA." Unfortunately, these particular products are extremely fine powders. In powdered detergent formulations, these tend to cake up and clog the dispenser. These are also difficult to process and, due to their particle size, are almost impossible to blend and compress to form tablets. Accordingly, it is very difficult to replace all of the phosphates with NTA or EDTA in either a powdered detergent or in a tableted detergent.

SugBary of the Invention

Accordingly, it is object of the present invention to provide a detergent composition which incorporates NTA and/or EDTA as the builder replacing the phosphates. Further, it is an object of the present invention to provide an NTA/EDTA product which can be easily compacted to form a tableted detergent. The objects and advantages of the present invention are achieved through the use of an agglomerated NTA/EDTA. Accordingly, the present invention provides a chemical composition comprising an alkali metal salt selected from the group consisting of alkali metal salts of nitrilotriacetic acid and alkali metal salts of ethylenediaminetetraacetic acid, wherein said alkali metal salt is agglomerated with a liquid active detergent composition to form an agglomerated alkali metal salt. Hereinafter, the reference to NTA/EDTA will specifically include NTA, EDTA and mixtures of NTA and EDTA. More specifically, the NTA/EDTA is combined with a liquid in a mixing apparatus to cause the NTA/EDTA to form agglomerated particles. These agglomerated particles can then be mixed to form a detergent composition. If desired, the detergent composition can be compacted to form a tableted detergent.

In a preferred embodiment of the present invention, the liquid used to agglomerate the NTA/EDTA is a functionally active material which contributes to the detergency of the final blend, such as an aqueous dispersion of anti- redeposition polymer, a surfactant, a defoaming agent, or other liquid active detergent composition. This enables the functional liquid components or composition to be thoroughly mixed with the NTA/EDTA and subsequently uniformly mixed with the detergent composition. This facilitates uniform blending of low concentration liquid components. Further, the agglomerate NTA/EDTA will not cake as easily as untreated NTA/EDTA. This also enables the NTA/EDTA to be compacted easily to achieve a strong, nonfriable tablet, which is not possible on a commercial scale with powdered NTA/EDTA. Other objects and advantages of the present invention will be further appreciated in light of the following detailed description.

Detailed Description

The present invention is a detergent composition which incorporates NTA/EDTA in an agglomerated form. The detergent formulations of the present invention can include a variety of different compositions for use in institutional or industrial cleaning applications. These compositions would include, but not be limited to, blends suitable for use as ware washing detergents, cutlery presoaks, all purpose cleaners, floor cleaners, sanitizers, disinfectants, descalers, oven/grill cleaners, degreasers and rinse aids. Although these vary widely in composition, they can all incorporate the agglomerated NTA/EDTA of the present invention. One example of the present invention will be a ware washing detergent. Such ware washing detergents preferably include a source of alkalinity (typically caustic, silicates or soda ash) , a hardness sequestering system, low molecular weight water-soluble polymers, nonionic and/or defoaming surfactants, processing aids and optionally bleaching sources.

The hardness sequestering system of the present invention will primarily be formed from alkali metal salts of nitrilotriacetic acid and ethylenedinitrilotetraacetic acid. Optionally, the detergent composition can also include alkali metal salts of gluconic acid, the alkali metal salts of citric acid, and even the phosphates. However, phosphates would generally not be incorporated with the detergent composition of the present invention in combination with NTA/EDTA. Generally, the hardness sequestering system will form from 10% to 50% by weight of the overall detergent composition and preferably 25% to 50% by weight.

As discussed below, the NTA/EDTA is preferably agglomerated using a liquid component functionally active in the final detergent formulation. The NTA/EDTA is agglomerated using well-known chemical mixers which disperse a spray of liquid over the NTA/EDTA as it is being agitated. This eventually forms an agglomerated mass of the NTA/EDTA. Preferably, the liquid used to agglomerate the NTA/EDTA will be an active detergent composition. This can, for example, include a surfactant, a defoaming agent, an aqueous solution of polycarboxylic acid and/or other detergent compositions which are dissolved in water such as polysilicates and the like. Suitable liquids also include functionally active components which are liquid at an application temperature. Functionally active components which can be melted and applied (such as waxy materials) can also be included.

The most preferred liquid active detergent composition is selected from the group consisting of an aqueous solution of a polycarboxylic acid, surfactants, defoaming agents and mixtures thereof. An aqueous solution of a polycarboxylic acid being an especially preferred liquid for agglomerating the alkali metal salt of the present invention.

These liquids are combined onto the NTA/EDTA in an amount sufficient to agglomerate the NTA/EDTA and, at the same time, avoid the formation of a sticky mass. The rate of addition is typically controlled to allow any water or other solvent to evaporate off and/or be absorbed with the remaining liquid as it is mixed with the NTA/EDTA. Generally from about 1% to about 40% by weight of liquid component relative to the weight of the NTA/EDTA is combined to agglomerate the NTA/EDTA. Preferably, about 10% to 30% by weight of liquid component will be added and ideally about 20%. This will, of course, vary depending upon the liquid employed. Further, generally at least a portion will be removed by evaporation. An apparatus suitable for agglomeration is disclosed US Patent 4,182,683. Other blending equipment which permits the liquid component to be uniformly mixed with NTA/EDTA powder will, of course, work.

In formulating a detergent, it is possible to either combine all of the liquid components together and add this mixture to the NTA/EDTA, or selectively add different liquid components. One preferred component which forms an agglomerated NTA/EDTA is the aqueous solution of polycarboxylic acid. This, when combined with the NTA/EDTA, forms an excellent agglomerate. The NTA/EDTA is preferably agglomerated to form particles having a size of 300 to 1500 microns or larger, and preferably 800-1500 microns. This will provide a free- flowing material which can be used as is or admixed with other similar active materials to form detergent blends having desirable properties and can be easily dispensed and/or further processed.

Industrial and commercial ware washing detergents generally include a caustic source such as sodium or potassium hydroxide, with sodium hydroxide being preferred. Generally, these may be included at a level from about 0 to 70% by weight, with 30% to 55% being preferred. For a high caustic detergent composition, the caustic content will generally be from about 45% to 55% by weight. The present invention can optionally include a bleaching agent such as alkali metal perborates and percarbonates. This is added in amounts up to 20% by weight.

In addition to the above, the detergent composition can include defoaming agents, typically nonionic surfactants. The nonionic surfactant used herein is selected from the group including alcohol ethoxylates, block copolymers and mixtures thereof. Generally, these will have a molecular weight of 900 to about 4000. One such surfactant is an ethylene oxide, propylene oxide block copolymer. Commercially available surfactants include Tritan CF32,

Tritan DF12, Plurafac LF131, Plurafac LF132, Plurafac LF231, Industrol N3, and Genepal PN30. These can be included in an amount from about 0.5% to about 5% with about 1.5% by weight preferred.

The detergent formulation can also include other surfactants, generally anionic surfactants. Particular anionic surfactants include alkyl aryl sulfonate and alkyl aryl sulfate. The ether sulfates in particular could act as the agglomerating agents. These are present in an amount of 1 to 20% by weight .

The detergent composition of the present invention can also include low molecular weight (2,000-20,000) , water soluble, polymeric acid such as polyacrylic acid, polymethacrylic acid or polymaleic acid or copolymers thereof . These are used as sequestering aids, to inhibit growth of calcium carbonate crystals and to improve rinsability. Preferably, the water soluble polymer will be a polycarboxylic acid such as polyacrylic acid having a molecular weight of around 5000. Generally, the composition of the present invention should include 1% to 10% by weight polyacrylic acid on an actives basis, with 2-5% preferred. These are generally available in a 50% aqueous solution.

The agglomerated NTA/EDTA can be dry mixed with other usually applied detergent components in amounts which meet the desired performance characteristics. These constituents are mixed to form effective powdered detergent formulations preferably including from 1% to 50% by weight of the chemical composition of the invention and a detergent builder. These powdered detergent formulations can be used in typical powdered detergent dispensers.

In a alternative preferred embodiment, the granulated NTA/EDTA is used to form a tableted detergent.To form a tableted detergent, the agglomerated NTA/EDTA is blended with the other solid detergent compositions and any remaining liquid components are separately combined and then sprayed onto this mixture of solid detergent components. With a highly caustic detergent, the caustic is added last after the liquid has been sprayed onto the remaining blend. This formed detergent blend which preferably comprises a detergent builder and from about 1 to about 50% by weight of the chemical composition according to the invention, is then compressed to form tablets using a standard tableting machine. One such machine suitable for use in the present invention is a Stokes brand tableter. Generally, to form tablets, the powder is subjected to 4 to 10 tons pressure. Generally, the tablet will have a thickness of 6 to 7 mm and a diameter of about 20 mm. The maximum diameter will be a function of the dispenser/feed water interface area. Tablets must be able to fall down upon the dispenser interface.

Test. Method To test the formulation of the present invention, granularized NTA was formed by granularizing NTA crystals with an aqueous solution of Accusol 445, a water-soluble polyacryiate. The Accusol 445 was combined with sufficient water to make it easily sprayable and was then added to NTA crystals using a granulator. The granularized product was then dried and ready for use. The granularized NTA included 90% NTA and 10% polyacryiate solids. These were then formulated into the following detergents: a machine dishwashing detergent, a powdered presoak detergent, and an all-purpose powder detergent.

It was noted when these were formulated that the granular NTA was signficantly easier to blend than crystalline NTA. Further, these powdered detergents using the granulated NTA were less likely to cake as a result of the presence of the NTA. However, the presoak and all-purpose did cake due to the high concentration of soda ash. But again, these were easier to formulate than detergent compositions including only crystalline, non-agglomerated NTA.

Machine Dishwashinσ Detergent Powder

To a clean, dry mixer, add the following:

Granular NTA (10% polyacryiate) 44.5% Soda Ash 9.50 mix 2 minutes, then slowly add:

Nonionic surfactant [Industrol N3] 1.00 mix 5 minutes, then add:

Caustic Bead 45.00 mix 5 minutes, then pack out into capsules.

Presoak Powder

To a clean, dry mixer, add the following:

Granular NTA (10% polyacryiate) 22.00% Soda Ash 50.00

Sodium Metasilicate Pentahydrate 5.00

Sodium Sulfate 18.00 mix 2 minutes, then slowly add: LAS Acid 2.75 mix 2 minutes, then slowly add:

Nonionic Surfactant [Neodol 91-6] 2.25 mix 5 minutes, then pack out into a capsule.

All Purpose Powder To a clean, dry mixer, add the following:

Granular NTA (10% polyacryiate) 27.70%

Soda Ash 39.30

Sodium Metasilicate Pentahydrate 9.00

Sodium LAS 6.00 Boric Acid 10.00 mix 2 minutes, then slowly add:

Neodol 91-6 8.00 mix 5 minutes, then pack out in a capsule.

Tableted Detergent

Granular NTA (10% polyacryiate) 42.0?

Soda Ash 11.5

Nonionic Surfactant [Pluronic 25R8] 1.5

Caustic Bead 45.0

The detergents of the present invention can be placed in a container and dispensed. The optimum shape and configuration of the container will obviously vary, depending upon the particular dispenser. The agglomerated NTA/EDTA of the present invention can be used in a wide variety of tableted detergent compositions.

Other advantages of the present invention will be readily apparent to one of ordinary skill in the art.

Claims

1. A chemical composition, comprising an alkali metal salt selected from the group consisting of alkali metal salts of nitrilotriacetic acid and alkali metal salts of ethylene¬ diaminetetraacetic acid, wherein said alkali metal salt is agglomerated with a liquid active detergent composition to form an agglomerated alkali metal salt.

2. The chemical composition claimed in claim 1, wherein said liquid active detergent composition is selected from the group consisting of an aqueous solution of a polycarboxylic acid, surfactants, defoaming agents and mixtures thereof.

3. The chemical composition claimed in claim 2, wherein said liquid active detergent composition comprises an aqueous solution of a polycarboxylic acid.

4. A powder detergent formulation, comprising from 1% to 50% by weight of the chemical composition claimed in claim 1 and detergent builder.

5. The detergent formulation claimed in claim 4, wherein said liquid active detergent composition comprises an aqueous solution of a polycarboxylic acid.

6. The detergent formulation claimed in claim 4, comprising 10 to 50% of said alkali metal salt.

7. The detergent formulation claimed in claim 5, comprising 1-10% by weight polyacrylic acid on an actives basis.

8. The detergent formulation claimed in claim 4, further comprising about 0.5 to about 5% nonionic surfactant.

9. The detergent formulation claimed in claim 4, further comprising 1 to 20% by weight of an anionic surfactant.

10. A compressed tableted detergent composition, comprising detergent builder and 1% to 50% of an agglomerated alkali metal salt selected from the group consisting of alkali metal salts of nitrilotriacetic acid and ethylenediaminetetraacetic acid, wherein said alkali metal salt is agglomerated with a liquid active detergent composition.

11. The tableted detergent composition claimed in claim 11, wherein said liquid active detergent composition is a polycarboxylic acid.

12. The tableted detergent composition claimed in claim 13, wherein said polycarboxylic acid is a polyacryiate.