Sustained-release scale inhibiting product, process for preparing and usage of the scale inhibiting product

Abstract

The invention relates to a sustained-release scale inhibiting product, its production and use. The scale inhibiting product comprises at least one scale inhibitor, a water soluble or hygroscopic carrier or binder, Activated Carbon for controlling the release rate of the at least one scale inhibitor and an adhesive that adheres the components of the composite.

Description

[0001] Sustained-release scale inhibiting product , process for preparing and usage of the scale inhibiting product

[0002] The present invention relates to a sustained-release scale inhibiting product , a process for preparing said scale inhibiting product and usage of said scale inhibiting product according to claims 1 , 8 and 11 .

[0003] Hard water, i . e . water with a relatively high content of alkaline earth ions , especially soluble calcium and magnesium compounds , often has undesirable properties . In everyday li fe , hard water can cause inconvenience .

[0004] When hard water is boiled, a white foam may appear on the surface of the water . A precipitate may form at the bottom of a kettle and settle as a white deposit . When washing laundry with hard water, ions containing calcium and magnesium may react with the soap . Insoluble flakes of fatty acid calcium and fatty acid magnesium may form, which reduces the cleaning ability . This damages the laundry and results in unnecessarily high soap consumption .

[0005] When bathing and washing, people ' s skin and hair suf fer from hard water . The skin does not become smooth, and the hair becomes dull and lackluster .

[0006] Furthermore , water that is too hard can cause scale or limescale deposits on surfaces that come into contact with the water . This applies in particular to water pipes , storage tanks and sanitary installations in buildings and to water-carrying appliances such as cof fee machines , washing machines , dishwashers in households and commercial enterprises .

[0007] The thermal conductivity of limescale or scale respectively is very poor . Heat trans fer from heating elements to water can be severely af fected by scale deposits . The ef ficiency and ef fectiveness of equipment with scale deposits on the heating elements are poor, and energy consumption is unnecessarily high .

[0008] Furthermore , the li fetime of such systems can be signi ficantly shorter than that of systems without scale deposits . Limescale deposits on the inner walls of water heaters or boilers can lead to signi ficant risks such as leaks or explosions due to di f ferent thermal expansions during heating and cooling, as well as when certain areas of these water heaters are heated unevenly .

[0009] Currently, ion exchange technology, membrane separation technology, and molecular sieve adsorption technology are mainly used for the treatment of hard water . Ion exchange technology is a mature and widely adopted process . In this process , water is passed through a resin containing sodium ions , where calcium and magnesium ions are exchanged with sodium ions in a chemical reaction . The sodium ions are released into the water . Water treated with ion exchange technology is not suitable for long-term drinking as it could lead to health problems . Furthermore , the resin is suspectable to contamination and oxidation, which results in precipitation and necessitates frequent regeneration .

[0010] Common membrane separation technologies include nanofiltration membrane and Reverse Osmosis (RO) membrane technologies . These two technologies are characteri zed by obvious and stable ef fects , but there are higher requirements for water inflow pressure . The water utili zation rate is low and the membrane is easy plugged in high-hardness water areas . Therefore , they are usually not suitable for water softening in buildings and household appliances .

[0011] The molecular sieve has excellent ion exchange and adsorption functions , can adsorb calcium and magnesium ions very well , but there are defects of short service li fe , quick saturation and not be able to have long lasting ef fect of anti-scaling .

[0012] One obj ect of the present invention is to provide a scale inhibiting product with a long-lasting ef fect for the treatment of water, which overcomes at least some of the disadvantages of the prior art . Further obj ects are to speci fy a process for preparing the scale inhibiting product and the usage of the scale inhibiting product . These obj ects are solved by a sustained-release scale inhibiting product according to the features of claim 1 , by a process for preparing this scale inhibiting product according to the features of claim 8 and by a usage of the scale inhibiting product according to the features of claim 11 .

[0013] The scale inhibiting product comprises a ) at least one scale inhibitor selected from the group consisting of malic acid, polyaspartic acid, polyepoxysuccinic acid ( PESA) , tannin, citric acid, lignin and starch, b ) a water soluble or hygroscopic carrier or binder, in particular e . g . cyclodextrin, polyacrylic acid, starch, c ) Activated Carbon for controlling the release rate of the at least one scale inhibitor, d) A usually non water soluble adhesive , that adheres the components of the composite together e . g . a polyolefin like polyethylene ( PE ) , an epoxy resin or polytetrafluoroethylene .

[0014] Starch and lignin in particular are environmentally friendly biopolymers that also have an adhesive function . In scale inhibitor products , components such as starch can have the function of a scale inhibitor as well as a binder and / or curing agent . Preferably a binder like cyclodextrin has a cavity structure with a hydrophilic outer surface and a hydrophobic inner surface . It acts as a carrier for at least one scale inhibitor and for the activated carbon, which form inclusion compounds inside the cavity . The release rate of the active ingredient in water is thereby reduced, enhancing the performance of the scale inhibitor , a- , p- or y-cyclodextrin are particularly well suited for the production of scale inhibiting products . Other suitable binders are e . g . polyacrylic acid and starch .

[0015] In conj unction with the scale inhibitor, activated carbon contributes to extending the li fespan of the scaleinhibiting product . Activated carbon, particularly in combination with a binder, can further reduce the release rate of the active ingredient or scale inhibitor in water . This release rate can be influenced or controlled in the composite material by properties such as the weight fraction, particle si ze and in particular the number of pores of activated carbon . Preferably, activated carbon is used with particle si zes ranging from about 300 mesh to about 500 mesh . Preferably, activated carbon has a relatively high proportion of mesopores , which serve as pathways for the water to be treated . They enhance the loading capacity and duration of sustained release of the scale inhibitor especially in combination with the binder . Furthermore , such activated carbon can puri fy the water to be treated and, i f necessary, decolori ze it by adsorbing high molecular impurities such as dyes or colloidal suspensions . The surface area of activated carbon per unit mass ranges from about 200 m2 / g to about 2000 m2 / g .

[0016] The at least one scale inhibitor, similar to activated carbon, is in powder form before being processed together with activated carbon and the binder to form a composite material . The particle si ze of the scale inhibitor preferably ranges from about 200 mesh to about 300 mesh . This contributes to a sustainable slow release of the active ingredient during water treatment .

[0017] The composition of scale inhibitor products comprises also an adhesive , that adheres the components of the composite together . Preferably, the adhesive comprises at least one of a polyolefin, especially polyethylene , sodium carboxymethyl cellulose , starch and polyvinyl alcohol .

[0018] It signi ficantly enhances the stability, pressure resistance and temperature resistance of the scale inhibitor product .

[0019] The powdered adhesive is processed together with the other powdered substances , namely the scale inhibitor and activated carbon, during the production process of the composite material . It strengthens the bonding of the components and increases the stability of the composite . This effect is particularly pronounced when the composite material is treated, especially sintered in a process step, preferably at temperatures ranging from about 130°C to about 190°C, especially 155°C to 185°C e.g. during 30 to 60 minutes . During this process, polyethylene softens or melts and forms a stable matrix, when the temperature subsequently drops below the softening temperature again. This particularly enhances the pressure resistance of the scale inhibiting product, allowing it to be used in environments with elevated pressure.

[0020] The particle sizes of the grinded components are indicated in mesh, which is a common unit of measurement for sieves and particle sizes but cannot be directly expressed in metric units. The mesh values provided in the present patent application can be approximately converted to micrometers using the following formula: Value in micrometers (pm) = z / mesh value, where the value of z = 14900 is determined with a tolerance of approximately + / - 25%. This is just an approximation and the actual values may vary within the specified tolerance. value in mesh particle size in m 200 55 - 93

[0021] 300 37 - 62

[0022] 400 27 - 46

[0023] 500 22 - 37

[0024] 600 18 - 31 The following are exemplary suitable mass ratios for the production of scale-inhibiting products, where S represents the scale inhibitor, A represents activated carbon, and C represents the binder: ms: mA: mc= (0.5 to 1.5) (0.5 to 1) : 4

[0025] Here, m denotes the mass or weight of each component.

[0026] These values are provided as examples and are not intended to be limiting.

[0027] The percentage of the additional adhesive weight on the total weight of the composition is in the range of 5% to 25%, preferably in the range of about 10% to about 20%, particularly in the range of 13% to 15%.

[0028] The components of the scale inhibiting product are processed into a composite material. This can be achieved, in particular, by carrying out the following process steps :

[0029] A) Preparing a saturated aqueous solution of the binder.

[0030] B) Providing one or more powdered scale inhibitors in a predetermined weight ratio and with a predetermined particle size, preferably ranging from 200-300 mesh. This can be achieved, for example, by grinding and sieving one or more scale inhibitors. C) Providing powdered activated carbon with a predetermined particle size, preferably ranging from 300-600 mesh, wherein the activated carbon preferably has a relatively high proportion of mesopores.

[0031] D) Adding the scale inhibitor or scale inhibitors and activated carbon to the saturated aqueous solution of the binder, with the temperature preferably ranging from 25-30°C.

[0032] E) Mixing the substances, preferably using a stirring device, for 12-24 hours at a stirring speed of e.g. 150-250 rpm, followed by allowing it to rest for approximately 24 hours.

[0033] F) Centrifugation for separating the sediment.

[0034] G) Rinse with 95% ethanol to remove any remaining scale inhibitor and activated carbon.

[0035] H) By drying the sediment at room temperature, the composite material is obtained as a powder.

[0036] I) Adding and mixing an adhesive, usually in form of a powder, to the composite material

[0037] J) Shaping the composite material e.g. by extruding or pressing in a mold to bring it into a more convenient form, for example, tablets, balls, pellets, granules or generally into shaped bodies with a predetermined shape. Preferably, the maximum diameter is in the range of about 2mm to about 6mm, for example 5mm

[0038] K) Heating or sintering, for example, in an oven with a temperature ranging from 155°C to 185°C, preferably for about 30 to 60 minutes . This process can signi ficantly enhance the stability of the scale inhibiting product .

[0039] These process steps and the values and ranges of parameters speci fied therein exempli fy, but are not limited to , a simple manufacturing process for the scale inhibiting product .

[0040] In the preparation of scale inhibiting product , the stirring and mixing promotes the adhesion of scale inhibitor to the activated carbon and facilitates the bonding with the binder, including the penetration of the inclusion mixture into inner cavities of the binder, i f such are present . Since the components of the scale inhibitor are water-soluble , they dissolve further into smaller particles in the solution saturated with carbon and the binder . Particles of the scale inhibitor penetrate into the pores of the activated carbon and are adsorbed by the activated carbon . Then the activated carbon and scale inhibitor bond with the binder and / or enter the inner cavities , i f such are present .

[0041] Together with the binder, activated carbon and the scale inhibitor form inclusion complexes that fully exploit the synergistic ef fect of the components . This reduces the release rate of the active substances in the water to be treated and extends the usable duration of the scale inhibitor . This allows for ef ficient and ef fective utili zation of the scale inhibitor and extends the li fespan of scale-inhibiting products , thereby conserving resources in their manufacturing . When using such products to prevent or reduce scale formation in water-carrying parts , the usable duration is high . Service cycles are comparatively long, resulting in relatively small associated costs . Additionally, activated carbon can adsorb large organic molecules and other impurities in the water, thereby puri fying it .

[0042] When water gets into contact with the scale inhibitor components during the application of the scale inhibitor product , they slowly dissolve out of the pores of the activated carbon and then they release slowly from the bond with the binder . The speed and dosage of the release thus become more permanent and precise .

[0043] The following are examples of characteristic values for several embodiments of the scale-inhibiting product .

[0044] Embodiment 1

[0045] Binder C : starch or polyacrylic acid;

[0046] Scale inhibitor S : malic acid, particle si ze 200 mesh;

[0047] Activated carbon A: Particle si ze 300 mesh, relative surface area 400m2 / g; ms: mA: mc= 1 . 5 : 0 . 5 : 4

[0048] Adhesive (weight percentage ) : Polyethylene ( 25% )

[0049] Embodiment 2

[0050] Binder C : cyclodextrin or starch; Scale inhibitors S: polyaspartic acid and polyepoxysuccinic acid, weight ratio 55:45, particle size 300 mesh;

[0051] Activated carbon A: Particle size 400 mesh, relative surface area 600m2 / g; ms: mA: mc= 1.5 : 1 : 4

[0052] Adhesive (weight percentage) : Sodium Carboxymethyl Cellulose (15%)

[0053] Embodiment 3

[0054] Binder C: polyacrylic acid;

[0055] Scale inhibitors S: polyaspartic acid, polyepoxysuccinic acid and starch, weight ratio 45:30:25, particle size 300 mesh;

[0056] Activated carbon A: Particle size 500 mesh, relative surface area 600m2 / g; ms: mA: mc= 1 : 1 : 4

[0057] Adhesive (weight percentage) : Polyethylene (12%)

[0058] Embodiment 4

[0059] Binder C: starch;

[0060] Scale inhibitors S: polyaspartic acid, tannin and lignin, weight ratio 45:30:20, particle size 300 mesh;

[0061] Activated carbon A: Particle size 300 mesh, relative surface area 600m2 / g; ms: mA: mc= 1.5 : 1 : 4

[0062] Adhesive (weight percentage) : Starch (20%)

Claims

Claims1 . Sustained-release scale inhibiting product comprising a composite of a ) at least one scale inhibitor ( S ) selected from the group consisting of malic acid, amino acid, polyaspartic acid, polyepoxysuccinic acid ( PESA) , tannin, citric acid, lignin and starch, b ) a water soluble or hygroscopic carrier or binder, c ) Activated Carbon (A) for controlling the release rate of the at least one scale inhibitor ( S ) , d) an adhesive , that adheres the components of the composite together .2 . Sustained-release scale inhibiting product according to claim 1 , characteri zed in that the carrier or binder is at least one of starch, cyclodextrin, polyacrylic acid, sodium carboxymethyl cellulose or polyvinyl alcohol .3 . Sustained-release scale inhibiting product according to any one of claims 1 or 2 , characteri zed in that adhesive comprises at least one of a polyolefin, especially polyethylene , epoxy resin or polytetraf luoroethylen .4 . Sustained-release scale inhibiting product according to claim 3 , characteri zed in that the weight ratiomP: mAof the adhesive and the Activated Carbon (A) is in the range of 10% to 20%.

5. Sustained-release scale inhibiting product according to any one of claims 1 to 4, characterized in that the weight ratio ms: mA: mcof scale inhibitor (S) , Activated Carbon (A) , and binder (C) is in the range of (0.5 to 1.5) : (0.5 to 1) : 4.

6. Sustained-release scale inhibiting product according to any one of claims 1 to 5, characterized in that the Activated Carbon comprises mesopores, a relative surface area in the range of 200m2 / g to 2000m2 / g, and particle sizes in the range of 300 mesh to 500 mesh.

7. Sustained-release scale inhibiting product according to any one of claims 1 to 6, characterized in that at least a part of the scale inhibitor is adsorbed in the mesopores of the Activated Carbon.

8. A process for preparing a scale inhibiting product according to any one of claims 1 to 7, characterized by comprising the following steps:- Preparing a saturated aqueous solution of a binder, especially at least one of starch, cyclodextrin, polyacrylic acid, sodium carboxymethyl cellulose or polyvinyl alcohol,- Adding at least one powdered scale inhibitor and powdered Activated Carbon, and mixing the substances ,- Centri fuging to separate the composite material as sediment ,- Drying the composite material to get a composite powder,- Adding and mixing an adhesive to the composite powder and shaping the composites by extruding or pressing in a mold,- drying or sintering and solidi fying the shaped composites at a temperature of 155 ° C- 185 ° C .9 . A process according to claim 8 , characteri zed in that the adhesive comprises at least one of a Polyolefin, especially Polyethylene , epoxy resin or Polytetrafluoroethylene , and that the percentage of the adhesive weight on the total weight is in the range of 5% to 25% .10 . A process according to any one of claims 8 or 9 , characteri zed in that the composite material is formed into tablets , spheres or pellets whose maximum dimensions are in the range of 2mm to 6mm .11 . Usage of a scale inhibiting product according to any one of claims 1 to 7 for impeding or preventing scaleformation in water-conducting parts of buildings or devices .