POWDER COMPOSITIONS AND METHODOLOGY FOR MANUFACTURING SAME

Abstract: A method for manufacturing a powder composition the method comprising producing a pre-mix of powder and particulate material and then wetting the pre-mix a wetting agent to facilitate coating of the particulate material with powder. The wetting agnet comprises a carboxy compound, such as a co-polymer of acrylic acid maleic anhydride sodium salt. Powder compositions produced according to the methodology are also provided.

Description: Powder Compositions and Methodology for Manufacturing Same The present invention relates to powder compositions, and in particular but not exclusively to compositions comprising fine powder pigment, and nethodology of manufacturing same. Pigments in powder form have many industrial applications and the present application is primarily concerned with pigment compositions particularly for use in the manufacture of cementitious products and the like. However, it will be appreciated that the present invention can find applications in the manufacture of other types of products and in many other industries. A problem commonly encountered in the manufacture and handling of pigment powders is that the fine nature of the powders often gives them unsatisfactory flow characteristics, which are exacerbated when the powders become compacted and/or damp. Furthermore, powders can often prove difficult to evenly mix into liquid or semi-liquid media such as cementitious material to be coloured by the pigment powder. The tendency for powders to become air borne also presents potential health and contamination issues. Attempts to address these issues have involved producing pigment granules. However, the satisfactory manufacture of granules has proved problematic. According to the present invention there is provided a method for manufacturing a powder composition, the method comprising producing a pre- mix of powder and particulate material and then wetting the mixture with a wetting agent to facilitate coating of the particulate material with powder. Preferably the powder and particulate material are pre-mixed using a tumbling and/or blending action, such as for example in a drum mixer or ribbon blender, desirably until both the powder and particulate material are generally uniformly distributed throughout the pre-mix. Preferably the wetting agent is introduced to the powder and particulate material pre-mix as a spray, and desirably a fine mist spray. Preferably wetting agent is added in amounts to give the powder composition between 1 and 15%, and ideally between 2 and 6% wetting agent by weight. The wetting agent may be introduced in stages, in which case desirably at regμlar intervals. Preferably the pre-mix is tumbled as the wetting agent is introduced thereto. Wetted pre- mix is preferably mixed, desirably tumbled, for a predetermined period of time, and desirably for between 3 and 30 minutes. Preferably wetted pre-mix is tumbled in a drum revolving at a rate between 10 and 50 revolutions per minute. Preferably the wetting agent used is water-based. The wetting agent used may comprise a carboxy compound such as carboxylate and desirably a polycarboxylate, or a derivative thereof and water. Alternatively or in addition the wetting agent may comprise acrylic acid maleic anhydride sodium salt or a derivative thereof. The wetting agent may also include a polyvinyl alcohol or derivative thereof. The wetting agent may comprise polyvinyl acetate such as polyvinyl acetate versatate, polyvinyl alcohol and water. The carboxy compound or derivative preferably comprises between 10% and 90% by weight of the wetting agent and desirably between 20 and 65% by weight. The polyvinyl alcohol or derivative preferably comprises between 1.5% and 11% of the wetting agent by weight. Alternatively or in addition the wetting agent may comprise one or more of a polyhydroxy compound, a salt of a part-esterified copolymer of styrene and maleic acid, a copolymer of vinyl acetate and crotonic acid, alkylbenzene sulphonate, alkyl naphthalene sulphonate', lignin sulphonate, sulphonated polyglycol ether, melamine formaldehyde condensate, naphthalene formaldehyde condensate, gluconic acid. Preferably powder composition particles produced in this way may be further processed, for example by way of further tumbling, to compact the particles whereby to facilitate stability, for example for handling and transportation. Further tumbling is preferably for between two and fifteen minutes, desirably at a rate of 10 - 50 revolutions per minute. Particles of undesirable size may be removed, preferably prior to the aforesaid further processing step, for example by way of sifting. Preferably the particulate material used comprises alumino-silicate, and desirably may comprise glass or glass-like material. The particulate material may comprise cenospheres, which may comprise fused silico-aluminate shells encapsulating gaseous contents, which may include carbon dioxide and/or nitrogen. Alternatively or in addition the particulate material may comprise one or more of sand, an inert mineral, an inert chemical product, plastics material. Preferably the particulates are considerably greater in size than the fine particles of the powder used. Preferably the powder used comprises pigment which may be inorganic and/or organic. The pigment may comprise one or more synthetic dyestuff. The relative amount of particulate material used in the pre-mix may be predetermined according to the desired colour, tone, shade and/or tint strength of the powder composition, but desirably falls within the range 1-20% by weight. Preferably for red iron oxide pigment powders the amount of particulate material used comprises 3-16% of the composition by weight, and desirably 7- 9%. Preferably for black iron oxide pigment powders the amount of particulate material used comprises 3-15% of the composition by weight, and desirably 6-8%. Preferably for yellow iron oxide pigment powders the amount of particulate material used comprises 5-20% of the composition by weight, and desirably 11-13%. Preferably for orange iron oxide pigment powders the amount of particulate material used comprises 5-20% of the composition by weight, and desirably 9-11%. Preferably for brown iron oxide pigment powders the amount of particulate material used comprises 3-15% of the composition by weight, and desirably 8-10%. Preferably for .chrome oxide green pigment powders the amount of particulate material used comprises 3-15% of the composition by weight, and desirably 8-10%. Preferably for cobalt oxide blue pigment powders the amount of particulate material used comprises 4-18% of the composition by weight, and desirably 10-12%. Preferably for cobalt oxide green pigment powders the amount of particulate material used comprises 4-18% of the composition by weight, and desirably 10-12%. Preferably for titanium dioxide white pigment powders the amount of particulate material used comprises 2-12% of the composition by weight, and desirably 7-9%. Preferably for nickel-titanium yellow pigment the amount of particulate material used comprises 2-15% of the composition by weight and desirably 6- 11%. Preferably for chromium titanium orange pigment the amount of particulate material used comprises 2-15% of the composition by weight and desirably 7-10%. Preferably for spinell black pigments the amount of particulate material used comprises 3-15% of the composition by weight and desirably 6-10%. Preferably the amount of wetting agent used gives the powder composition a wetting agent presence of between 1 and 15% by weight, and desirably between 2 and 6%. The invention further provides a powder composition according to any of the preceding twenty two paragraphs. The invention still further provides a pre-mix composition of powder and particulate material according to any of the preceding twenty three paragraphs. The present invention further provides a product, such as concrete, asphalt coloured by a composition substantially as defined in any of the preceding two paragraphs. The invention further provides a method of colouring product, in particular cementitious product, such as concrete, the method comprising dispersing into the product a composition substantially as defined in any of the preceding three paragraphs. An embodiment of the present invention will now be described by way of example only. The present invention provides a method for manufacturing a powder composition the method comprising producing a pre-mix of powder and particulate material and then wetting the pre-mix with a wetting agent to facilitate coating of the particulate material with powder. The invention is exemplified in relation to the manufacture of pigment powder compositions for use in colouring cementitious products, but it will be appreciated that the invention can find uses in other industries. The powder used in this example is therefore a pigment powder. It will be appreciated that more than one powder could be used and therefore more than one pigment, as referred to later. The particulate material used is an alumino-silicate in the form of small hollow spheres, often termed microspheres or cenospheres. These comprise a hard, fused silico-aluminate shell encapsulating gaseous content which may include carbon dioxide and/or nitrogen gases. The particles may be produced as a by-product of the generation of electrical power from coal and may be a component of fly-ash. These particles are considerably greater in size than the fine particles of the pigment powder. Pigment powder and particulate material are mixed to form a pre-mix, the percentages of each in the powder composition are determined according to the nature of the powder composition being produced, and in the field of pigments, the colour of the pigment powder is relevant to the amount of particulate material in the pre-mix and the desired colour and tone of the composition. Specific examples are provided later in the specification. The powder and particulate material are mixed in suitable mixing apparatus, for example in a drum mixer or a ribbon blender until both are uniformly mixed throughout the pre-mix. , The pre-mix is then sprayed at regular intervals with a fine mist spray of wetting agent. The wetting agent used is a water-based product and comprises a carboxy compound, a preferred material being a neutralised co-polymer of acrylic acid maleic anhydride sodim salt (polycarboxylic sodium maleate- acrylate co-polymer), polyvinyl alcohol and water. A particular supplier of the carboxy compound material is ao Corporation SA of Barcelona, Spain who supply the product under the brand name CELLESH. As an alternative or in addition ■ polyglycol ether carboxylates may be used. One or more carboxylate and/or polycarboxylate compound derivatives may be used. Derivatives of polyvinyl alcohol may also be used. The carboxy compound, polyvinyl alcohol and water are mixed with the carboxy compound comprising between 10% and 90% of the wetting agent by weight, and desirably between 20% and 65%. The pre-mix may be continually tumbled as the wetting agent is added, or alternatively the wetting agent may be added and then tumbling of the pre-mix and wetting agent commenced. The amount of wetting agent added is varied according to the nature of the powder and the composition of the wetting agent itself, however sufficient is added such that the wetting agent comprises between 1 and 15% by weight of the powder composition when added and desirably between 2 and 6% by weight. After the wetting agent has been introduced to the pre-mix, mixing, by tumbling in a rotary drum, continues for between 5 and 30 minutes at a rate of 10-50 revolutions per minute. This produces a powder composition in which the particulate material is coated with pigment powder, the wetting agent facilitating releasable adhesion of the pigment powder to the particulate material. The product produced is a free flowing particulate powder composition. The composition may be sieved to remove undersized particles. This can be either by gentle sifting using gravitational effect, or forced sifting under higher pressures. The composition may be subjected to further processing, by way of further tumbling for between 2-15 minutes, again at a rate of between 10 and 50 revolutions per minute to compact the powder on the particulate material to improve the stability and durability of the powder composition, for example to improve transportation and handling characteristics. Tumbling for longer than 15 minutes tends to act to undesirably break down the powder composition. The following are specific examples of compositions suitable for use in the methodology of the present invention, and to produce product also in accordance with the present invention. The powder and cenospheres were pre- mixed for varying times within the aforementioned 5-30 minute range at tumbling rates within the 10-50 ranges. The wetted pre-mix was tumbled at various times and rates again within the aforementioned ranges. Composition 1 Powder - red iron oxide 86-95% of the composition by weight Particulate material cenospheres 3-8% by weight Wetting agent 2-6% by weight Formulation of wetting agent:- Cellesh (polycarboxylic sodium maleate - acrylate co-polymer) 7o Rhoximat BM2 (Polyvinyl Alcohol) 4% Water 50% Composition 2 Powder - black iron oxide 86-94% of the composition by weight Particulate material cenospheres 3.5-8% by weight Wetting agent 2.5-6% by weight Formulation:- Cellesh (polycarboxylic sodium maleate - acrylate co-polymer) 7o Rhoximat BM2 (Polyvinyl Alcohol) 4% Water 50% Composition 3 Powder - yellow iron oxide 82-91% of the composition by weight Particulate material cenospheres 5-11% by weight Wetting agent 4-7% by weight Formulation:- Cellesh (polycarboxylic sodium maleate - acrylate co-polymer) 69% Rhoximat BM2 (Polyvinyl Alcohol) 6% Water 25% Composition 4 Powder - orange iron oxide 83-92% of the composition by weight Particulate material cenospheres 5-10% by weight Wetting agent 3-7% by weight Formulation:- Carboxy compound 60% Polyvinyl alcohol 5.5% Water 34.5% Composition 5 Powder - brown iron oxide 84-93% of the composition by weight Particulate material cenospheres 4.25-9.75% by weight Wetting agent 2.75-6.25% by weight Formulation:- Carboxy compound 55% Polyvinyl alcohol 4.75% Water 40.25% Composition 6 Powder - chrome oxide green 85-90% of the composition by weight Particulate material cenospheres 3.5-7.5% by weight Wetting agent 2.5-6.5% by weight Formulation:- Carboxy compound 60% Polyvinyl alcohol 5.5% Water 34.5% Composition 7 Powder - cobalt oxide blue 78-90% of the composition by weight Particulate material cenospheres 6-12% by weight Wetting agent 4-10% by weight Formulation:- Carboxy compound 65% Polyvinyl acetate versatate 5.75% Water 29.25% Composition 8 Powder - cobalt oxide green 78-90% of the composition by weight Particulate material cenospheres 6-12% by weight Wetting agent 4-10% by weight Formulation:- Polycarboxylate 65% Polyvinyl acetate 5.75% Water 29.25% Composition 9 Powder - titanium dioxide 87-92% of the composition by weight white pigment Particulate material cenospheres 6.5-8% by weight Wetting agent 1.5-5% by weight Formulation:- Carboxy compound or derivative 46% Polyvinyl alcohol or derivative Water Composition 10 Powder - nickel titanium 84-94% of the composition by weight yellow Particulate material cenospheres 3-8.5% by weight Wetting agent 3-7.5% by weight Formulation:- CELLESH 70% Rhoximat BM 2 6% Water 24% Composition 11 Powder - chromium titanium 82-91% of the composition by weight orange Particulate material cenospheres 4.5-8% by weight Wetting agent 4-8% by weight Formulation:- CELLESH 7o Rhoximat BM 2 6% Water 22% Composition 12 Powder - spinell black 86-92% of the composition by weight Particulate material cenospheres 4-6.5% by weight Wetting agent 4-7.5% by weight Formulation:- Carboxylate Compound 55% Polyvinyl acetate 5% Water 40% The powder composition produced according to the present invention has good flow characteristic and transportation characteristics. Moreover, the composition has good mixing characteristic when added to products to be coloured thereby, for example cementitious mixtures such as concrete. The invention therefore also provides cementitious products produced using compositions according to the present invention and also a method of colouring cementitious products. Various modifications may be made without departing from the spirit or scope of the present invention. For example more than one powder may be comprised in the composition, which could include more than one pigment powder. Further, other suitable additives may be added to the composition to provide a composition with a desired characteristic. The wetting agent may be added at irregular intervals, or indeed in a single application. The amount of wetting agent added at each interval may be the same, or selectively varied. The wetting agent may comprise either as an alternative or in addition to carboxy compound, one or more of a polyhydroxy compound, a salt of a part-esterified copolymer of styrene and maleic acid, a copolymer of vinyl acetate and crotonic acid, alkylbenzene sulphonate, alkyl naphthalene sulphonate, lignin sulphonate, sulphonated polyglycol ether, melamine formaldehyde condensate, naphthalene formaldehyde condensate, gluconic acid. Alternatively or in addition the particulate material may comprise one or more of sand, an inert mineral, and inert chemical product or plastics material. The colour of the particulate material may be chosen to give desired colour characteristics to the composition. The above examples are of inorganic pigments, but it will be appreciated that the present invention also includes the use of organic pigments such as Carbon Black, and/or synthetic dyestuffs either instead of inorganic pigments or in any combination therewith. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims: Claims 1. A method for manufacturing a powder composition, the method comprising producing a pre-mix of powder and particulate material and then wetting the mixture with a wetting agent to facilitate coating of the particulate material with powder. 2. A method as claimed in claim 1, in which mixing is conducted until both the powder and particulate material are generally uniformly distributed throughout the pre-mix. 3. A method as claimed in claim 1 or claim 2, in which the powder and particulate material are tumbled, for example in a drum mixer. 4. A method as claimed in claim 1 or claim 2, in which the powder and particulate material are blended, for example in a ribbon blender. 5. A method as claimed in any preceding claim, in which the wetting agent is introduced to the powder and particulate material pre-mix as a spray. 6. A method as claimed in claim 5, in which the spray is a fine mist. 7. A method as claimed in any preceding claim, in which wetting agent is added in amounts to give the powder composition between 1 and 15% wetting agent by weight. 8. A method as claimed in any preceding claim, in which wetting agent is added in amounts to comprise between 2 and 6% of the composition by weight. 9. A method as claimed in any preceding claim, in which the wetting agent is introduced in stages. 10. A method as claimed in claim 9, in which the wetting agent is added at regular intervals. 11. A method as claimed in any preceding claim, in which the pre-mix is tumbled as the wetting agent is introduced thereto. 12. A method as claimed in any preceding claim, in which wetted pre-mix is mixed for a predetermined period of time, 13. A method as claimed in claim 12, in which wetted pre-mix is tumbled. 14. A method as claimed in claim 12 or claim 13, in which wetted pre-mix is mixed for between 5 and 30 minutes. 15. A method as claimed in claim 13 or claim 14, in which wetted pre-mix is tumbled in a drum revolving at a rate between 10 and 50 revolutions per minute. 16. A method as claimed in any preceding claim, in which the wetting agent used is water-based. 17. A method as claimed in claim 16, in which the wetting agent used comprises a carboxy compound or one or more derivatives thereof and water. 18. A method as claimed in claim 17, in which the caboxy compound or derivative(s) comprises between 10% and 90% by weight of the wetting agent. 19. A method as claimed in claim 17 or 18, in which the carboxy compound comprises a carboxylate and/or a polycarboxylate. 20. A method as claimed in any of claims 16 to 19, in which the wetting agent includes polyvinyl alcohol or derivative(s) thereof. 21. A method as claimed in any of claims 16 to 20, in which the wetting agent includes 1.5% to 11% polyvinyl alcohol or one or more derivatives thereof by weight. 22. A method as claimed in any of claims 16 to 21, in which the agent comprises acetate, such as polyvinyl acetate versatate. 23. ' A method as claimed in any of claims 17 to 21, in which the carboxy compound or derivative(s) used comprise(s) between 20 and 65% by weight of the wetting agent. 24. A method as claimed in any preceding claim, in which the wetting agent comprises one or more of a polyhydroxy compound, a salt of a part-esterified copolymer of styrene and maleic acid, a copolymer of vinyl acetate and crotonic acid, alkylbenzene sulphonate, alkyl naphthalene sulphonate, lignin sulphonate, sulphonated polyglycol ether, melamine formaldehyde condensate, naphthalene formaldehyde condensate, gluconic acid. 25. A method as claimed in any preceding claim, in which powder composition particles produced in this way are further processed to compact the particles whereby to facilitate stability, for example for handling and transportation. 26. A method as claimed in claim 25, in which particles are tumbled. 27. A method as claimed in claim 26, in which tumbling is for between two and fifteen minutes. 28. A method as claimed in claim 26 or claim 27, in which tumbling is at a rate of 10 - 50 revolutions per minute. 29. A method as claimed in any preceding claim, in which particles of undesirable size are removed. 30. A method as claimed in claim 29, in which particles of undesirable size are removed prior to the aforesaid further processing step. 31. A method as claimed in claim 29 or claim 30, in which the particles of undesirable size are removed by sifting. 32. A method as claimed in any preceding claim, in which the particulate material used comprises alumino-silicate. 33. A method as claimed in claim 32, in which the particulate material comprises glass or glass-like material. 34. A method as claimed in claim 32 or claim 33, in which the particulate material used comprises cenospheres. 35. A method as claimed in claim 33 or claim 34, in which the material comprises fused silico-aluminate shells encapsulating gaseous contents, which may include carbon dioxide and/or nitrogen. 36. A method as claimed in any preceding claim, in which the particulate material comprises one or more of sand, cenospheres, an inert mineral, an inert chemical product, plastics material. 37. A method as claimed in any preceding claim, in which the particulate material is considerably greater in size than the fine particles of the powder used. 38. ' A method as claimed in any preceding claim, in which the powder used comprises pigment. 39. A method as claimed in claim 38, in which the powder used comprises one or more of inorganic pigment, organic pigment and synthetic dyestuff. 40. A method as claimed in claim 38 or claim 39, in which the relative amount of particulate material used in the pre-mix is predetermined according to the desired colour of the powder composition. 41. A method as claimed in claim 38, 39 or 40, in which the particulate material used in the pre-mix is predetermined according to the desired colour characteristics, such as tone, shade and/or tint strength. 42. A method as claimed in any preceding claim, in which the amount of particulate material used is between 1 and 20% by weight of the powder composition. 43. A method as claimed in claim 42, in which for red iron oxide pigment powders the amount of particulate material used comprises 3-16% of the composition by weight. 44. A method as claimed in claim 43, in which the amount is 7-9% by weight. 45. A method as claimed in claim 42, in which for black iron oxide pigment powders the amount of particulate material used comprises 3-15% of the composition by weight. 46. A method as claimed in claim 45, in which the amount is 6-8% by weight. 47. A method as claimed in claim 42, in which for yellow iron oxide pigment powders the amount of particulate material used comprises 5-20% of the composition by weight. 48. A method as claimed in claim 47, in which the amount is 11-13% by weight. 49. A method as claimed in claim 42, in which for orange iron oxide pigment powders the amount of particulate material used comprises 5-20% of the composition by weight. 50. A method as claimed in claim 49, in which the amount is 9-11% by weight. 51. A method as claimed in claim 42, in which for brown iron oxide pigment powders the amount of particulate material used comprises 3-15% of the composition by weight. 52. > A method as claimed in claim 51, in which the amount is 8-10% by weight. 53. A method as claimed in claim 42, in which for chrome oxide green pigment powders the amount of particulate material used comprises 3-15% of the composition by weight. 54. A method as claimed in claim 53, in which the amount is 8-10% by weight. 55. A method as claimed in claim 42, in which for cobalt oxide blue pigment powders the amount of particulate material used comprises 4-18% of the composition by weight. 56. A method as claimed in claim 55, in which the amount is 10-12% by weight. 57. A method as claimed in claim 42, in which for titanium dioxide white pigment powders the amount of particulate material used comprises 2-12% of the composition by weight. 58. A method as claimed in claim 57, in which the amount is 7-9% by weight. 59. A method as claimed in claim 42, in which for the cobalt oxide green pigment powders the amount of particulate material used comprises 4-18% of the composition by weight. 60. A method as claimed in claim 59, in which the amount is 10-12% by weight. 61. A method as claimed in claim 42, in which for nickel titanium yellow pigment the amount of particulate material used comprises 2-15% of the composition by weight. 62. ' A method as claimed in claim 61, in which the amount is 6 11% by weight. 63. A method as claimed in claim 42, in which for chromium titanium orange pigments the amount of particulate material comprises 2-15% of the composition by weight. 64. A method as claimed in claim 63, in which the amount is 7-10% by weight. 65. A method as claimed in claim 42, in which for spinell black pigment the amount of particulate material used comprises 3-15% of the composition by weight. 66. A method as claimed in claim 65, in which the amount is 6-10% by weight. 67. A method as claimed in any preceding claim, in which the amount of wetting agent used gives the powder composition a wetting agent presence of between 1 and 15% by weight. 68. A method as claimed in any preceding claim, in which the amount of wetting agent used gives the composition a wetting agent presence of between 2 and 6% by weight. 69. A powder composition according to any of the preceding claims. 70. A pre-mix of powder and particulate material as defined in any of the preceding claims. 71. A product, such as concrete, cement, mortar, asphalt coloured by a composition as defined in any of the preceding claims. 72. A method of colouring product, in particular cementitious product, such as concrete, the method comprising dispersing into the product a composition as defined in any of the preceding claims. 73. A method substantially as hereinbefore described. 74. A powder composition substantially as hereinbefore described. 75. A pre-mix substantially as hereinbefore described. 76. A cementitious product substantially as hereinbefore described. 77. A method of colouring substantially as hereinbefore described. 78.' Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.

Inventors: DAWS ROBERT ARTHUR, DAWS, ROBERT, ARTHUR
Applicants: DAWS ROBERT ARTHUR, SAITRON LTD, DAWS, ROBERT, ARTHUR, SAITRON LIMITED
Application year: 2001
Main classification: C09C3
IPC codes: C09B67, C09C3