WO1997003111A2

WO1997003111A2 - Solid polymeric products and their use

Info

Publication number: WO1997003111A2
Application number: PCT/GB1996/001638
Authority: WO
Inventors: Simon Alexander Hanson Rose; Peter Chamberlain
Original assignee: Allied Colloids Ltd
Current assignee: Ciba Specialty Chemicals Water Treatments Ltd
Priority date: 1995-07-13
Filing date: 1996-07-08
Publication date: 1997-01-30
Anticipated expiration: 1998-01-13
Also published as: GB9514283D0; ZA965952B; AU6366096A; WO1997003111A3

Abstract

A product is provided which comprises particles of water-soluble or water-swellable polymeric material dispersed in a matrix of water-soluble or water-swellable bonding agent wherein the matrix includes water activatable effervescent agent and/or is foamed. Such products provide polymeric material in easily dispersible and dissolvable form.

Description

Solid Polymeric Products and Their Use

This invention relates to solid products which comprise water-soluble or water-swellable polymeric particles. In use these may first be activated into an aqueous composition (for instance for use as a viscosifier or flocculant) or they may be scattered in particulate form (for instance as a soil conditioner or pelletisation binder) .

Soluble or swellable polymer particles can be made by reverse phase emulsion polymerisation to provide a relatively stable emulsion of very small (below lOμm) hydrous or anhydrous polymer particles in oil. These can be agglomerated, for instance as in W092/13912 or US 3,891,592 or the emulsion may be treated as in unpublished PCT/GB95/00283. Usually, however, the emulsion is used without treatment. Direct addition of the emulsion to the suspension or other medium which is to be treated tends to be unsatisfactory, for instance because of destabilisation of the emulsion during the addition with consequential aggregation of the polymer particles, and so usually the emulsion is activated by dissolution in water in the presence of an oil-in-water emulsifier which serves as an activator and the resultant solution is then added to the medium which is to be treated. Water-soluble or water-swellable polymer particles in the form of powder are usually made by reverse phase bead polymerisation followed by drying and recovery of particles or by gel polymerisation followed by drying and comminution. These methods generally provide a relatively coarse particle size typically in the range 200 to l,000μm. However the powder will usually also include some finer particles and if desired the manufacturing technique can be conducted so as to maximise the amount of fines.

When the powder is to be activated by mixing with water to form a stable aqueous solution of dispersion, for instance before use as a viscosifier or flocculant, it is usual practice first to expose the particles to water under conditions that allow full hydration of the particles either to form a solution of the polymeric material or to form a suspension of highly swollen particles in water. Various problems can arise in handling the polymer particles prior to and during the exposure to the water. For instance the particles may tend to acquire a gel layer upon initial exposure, which gel layer may inhibit access of water and cause aggregation, thus interfering with dissolution or swelling of the particles. This problem can be minimised in many instances by appropriate selection of the exposure conditions but in some instances it is not possible to optimise these.

When polymers are used in particulate form, eg as soil conditioners, rapid activation under ambient conditions is usually desirable so as to release the polymer. Sometimes activation is undesirably slow.

In order to minimise these activation problems it is known to provide the particles with a coating of inorganic salt or other material, optionally in combination with a binding agent to promote adhesion of the inorganic salt to the polymer particles. For instance in U.S. 3,657,182 a composition contains 0 to 5% polyethylene glycol and 5 to 90% sodium sulphate, while in JP 57162610 a composition contains 9 to 49% inorganic salt and 1 to 10% polyethylene glycol.

The presence of fines tends to cause undesirable environmental, flow and dissolution problems and so it is common to separate the fines fraction and to aggregate it. Aggregation can be by contact with water or an aqueouε bonding agent. In U.S. 4,389,506 fines in a polyvinyl alcohol powder are agglomerated by contacting the powder with 0.5 to 4% molten polyethylene glycol. Other processes of coating or agglomerating polymer particles are described in DE-A-2616639, JP-A-57049643 and JP-A-57162610. U.S. 3,839,500 is concerned with improving the dispersion into water of particulate acrylamide polymers. It lists a large number of materials which it states are ineffective for this purpose, and included amongst such materials are urea, citric acid salts, sodium sulphate, sodium carbonate, trisodium phosphate, calcium silicate and gassing salt mixtures such as citric acid plus sodium carbonate or bicarbonate. It describes that the water dispersibility of the polymer particles can be improved by coating the polymer with 0.1 to 20%, usually 0.1 to 10%, by weight polyalkylene glycol. It is mentioned that the process results in reducing the proportion of fines by agglomeration to form larger particles. The glycol is generally applied from a solution but it is mentioned that the coating can be achieved by mixing the particles with solid granulated polyalkylene glycol in a rotating drum or blender at a temperature sufficient to melt the glycol, the blended product is then cooled while mixing, and the cooled product is discharged from the blender.

Although it is customary to treat a flowing suspension with flocculant pre-dissolved as an aqueous solution, it is also known to treat a flowing suspension by placing a block of treatment aid in the flowing suspension so as to allow erosion of the block into the suspension. In JP-B-4726584 (JP-A-44102922) a foamed block is formed from a polyacrylic ester polymer, alginate polymer, aluminium sulphate, water and a foam-forming material. The polyacrylic ester polymer is said to have a molecular weight of at least 10,000 and so it seems that the main water treatment chemical in this block is the aluminium sulphate.

It is also known to provide blocks containing particulate polymeric flocculant. For instance in EP-A- 255,283 blocks are formed of water-soluble multivalent metal coagulant and particulate polymeric flocculant, whereby the surface of the blocks is eroded by immersion in a flowing stream to form a solution of the coagulant in which the flocculant particles are entrained. In US 3,305,019 and 3,435,618 Katzer describes blocks formed from polyelectrolyte and polyethylene oxide wax. A problem with all blocks containing high molecular weight polymeric particles is that there is a tendency for these particles to form a protective layer of partially dissolved polymer gel around the blocks. For instance this can occur in some slow flowing suspensions used for treating blocks as described in unpublished application PCT/GB95/00282. In some formulations, the inclusion of inorganic salt can facilitate dissolution but this tends to be rather ineffective when very high molecular weight polymers are present. This is a particular problem when the main purpose of the block is to administer the polymer into the suspension since adding sufficient salt to give a useful change in erosion rate will in practice result in the block containing, and therefore supplying to the suspension, less polymer.

It would be desirable to provide a block formulation which is more readily erodible even when it contains a high proportion of high molecular weight polymeric particles. In particular, it would be desirable to provide a particulate composition which can more easily be activated, either when used as powder or when it is being preactivated into solution before use.

According to the invention we provide a product which comprises particles of water-soluble or water-swellable polymeric material dispersed in a matrix of water-soluble or water-swellable bonding agent, and in this product the matrix is a foamed matrix or includes a water-activatable effervescent agent.

The invention is of particular value when the product is granular and the granules each comprise the polymer particles dispersed in the matrix of bonding agent and the matrix includes the water activatable effervescent agent.

The granules generally have a size such that at least

90% by weight of the granules are below 10, and usually below 5, m and preferably below 1 mm. Preferred granular products of the invention have at least 90% by weight of the granules between 200 and l,000μm, often between 200 and 700μm. The granules can have any convenient particulate shape such as conventional powder shapes or flakes.

The effervescent agent in the matrix can be any material which, upon contact of the product with water, will cause effervescence. The combination of the contact with water and the effervescence tends to disrupt the water-soluble or water-swellable bonding agent matrix. This will therefore tend to cause the individual polymer particles in the granular product to separate from one another and therefore promotes individual activation of the polymer particles when they are being used (for instance in iron ore pelletisation or as soil conditioner) or when they are being activated in water before use.

When the granules are being activated in water the effervescence will tend to cause the granular product to float. A normal problem with activation of particulate polymer with water under relatively static conditions is that the polymer particles may sediment in the water and tend to agglomerate due to the creation of an aqueous gel layer around the sedimented particles. The flotation effect due to the effervescence prevents this agglomeration and, in particular, tends to cause them to rise out of any initial sediment.

If the flotation effect is too strong, it may cause all the granules to float rapidly to the surface, and again there may then be some risk of agglomeration between the resultant surface layer of granules. Preferably the flotation effect is selected so that in static water (or in whatever activation conditions are being used) the flotation effect is sufficient for the granules to disintegrate while the granules are floating with substantially no formation of a surface layer of granules or polymer particles.

It is often preferred to include a weighting agent in the granular product in order to allow adjustment of the density of the granular product and thereby to allow control of the degree of flotation. The amount of weighting agent (if present) and the amounts of the other components of the granules are preferably such that the granules initially sediment when added to static water but then float due to effervescence of the effervescent agent and disintegrate while floating, and preferably the disintegration is sufficiently complete that no significant layer of dissolving granules accumulates on the surface of the water.

The effervescent agent can be any material which, when dissolved in water, results in the suitable release of a gas. Generally it is a combination of solid materials which react in water to release a gas. Preferably it is a combination of a solid water-soluble acid with a soli_d water-soluble carbonate or bicarbonate. The carbonate or bicarbonate is usually of sodium, but potassium or other water-soluble carbonates or bicarbonates may be used.

The solid water soluble acid may be, for instance, particulate citric acid, tartaric acid, benzoic acid, sulphamic acid or a polymeric carboxylic acid, generally a solid water-soluble polymer of acrylic or methacrylic acid. Although it is preferred that the acid should be solid under ambient conditions when separate from the remainder of the granular product, a liquid polymeric or other acid is suitable provided that the other components of the granules are such that the acid is absorbed into a component of the granules or the granules (without reaction with the carbonate) to provide solid, substantially non- sticky, granules. The preferred acid is citric acid. The preferred effervescent agent is a mixture of citric acid and sodium bicarbonate.

The proportions of the components in the effervescent agent will be selected so as to obtain suitable effervescence and are usually within 50 to 150% of stoichiometric proportions, and preferably the proportions are stoichiometric. A suitable weighting agent that can be used is barium sulphate, but any other dense, finely divided, non-toxic, particulate material can be used.

The polymer which forms the polymer particles is chosen according to the intended use of the product. The products of the invention are suitable for use in many applications, for instance iron ore pelletisation, flocculation of mineral suspensions, flocculation of sewage sludge, soil conditioning, for instance as flocculants in field irrigation, and as agricultural anti-drift agents.

The polymer particles can be relatively coarse (for instance having a size up to 1 mm, when the granular size is coarse (for instance having a size up to 5 mm) . The product can be a mixture of aggregates of polymer particles with non-aggregated polymer particles which are coated with the bonding agent and effervescent agent but are not aggregated with other polymer particles. Generally, however, substantially all the granules are aggregates of polymer particles and thus the polymer particle size will generally be significantly less than the granule size. Generally at least 90% by weight of the polymer particles have a size below 500μm and preferably below 300μm.

The invention is of particular value when the polymer particles are polymer fines separated during the production of coarser polymer powder. Thus preferably at least 90% by weight of the particles are below 150μm and usually below lOOμm, often in the range 10 to 70μm. Preferably the particles are beads made by reverse phase polymerisation.

Instead of using polymer fines having a size mainly above lOμm, the polymer particles may be particles made by reverse phase emulsion polymerisation to a size below lOμm, for instance in the range 0.01 or, more usually, 0.05 or O.lμ up to 5μm.

The water-soluble or swellable polymer particles are generally formed from water-soluble monoethylenically unsaturated monomer or monomer blend, and the water- swellable polymer particles are generally made by cross- linking such a polymer, for instance by including a polyethylenically unsaturated cross-linking agent in the polymerisation mixture. Preferably the monomers are acrylic monomers although some allyl or other vinyl monomers are suitable.

The monomers can be anionic or cationic or non-ionic. Blends can be amphoteric but are generally formed from anionic and non-ionic monomers or cationic and non-ionic monomers. Suitable anionic monomers include (meth) acrylic acid (including alkali metal, ammonium or amine salts) and other ethylenically unsaturated carboxylic or sulphonic acid monomers. Suitable cationic monomers include dialkylaminoalkyl (meth)-acrylamide and - acrylate, generally as quaternary ammonium or acid addition salts, and diallyl dimethyl ammonium chloride. Suitable non-ionic monomers include acrylamide and N-vinyl formamide. The monomers and the polymerisation conditions will be chosen in conventional manner having regard to the desired end use of the product. Thus the invention provides a convenient and novel way of formulating a polymer which is otherwise of standard composition for its intended end use.

The polymers are usually of high molecular weight and the soluble polymers usually have intrinsic viscosity above 4 dl/g and often above 8 dl/g, for instance up to 20 or 30 dl/g. These very high intrinsic viscosity values are of particular value for polymers which are to be used as viscosifiers or bridging flocculants.

When the polymer is to be used as a soil conditioner or pelletisation aid the intrinsic viscosity is usually in the range 3 to 12 dl/g and the polymer is usually anionic

(for instance a copolymer of acrylamide and sodium acrylate) . When the polymer is to be used as a flocculant which is a coagulant, the intrinsic viscosity is generally in the range 0.3 to 3 dl/g, often 0.7 to 2.5 dl/g, and the polymer is usually formed from at least 50% by weight, and usually at least 80% by weight diallyldimethyl ammonium chloride or other cationic monomer.

The polymer may have been made from the chosen monomer or monomers by a conventional technique such as gel polymerisation followed by comminution and drying or reverse phase bead polymerisation followed by drying and separation of the beads, and optionally comminution, or reverse phase emulsion polymerisation optionally followed by distillation to render the polymer emulsion particles substantially anhydrous.

The water-soluble or water-swellable bonding agent can be any material which will provide a matrix which interconnects the particulate polymeric material, and thus the bonding agent should be film forming. It should normally be applied in non-aqueous form, to avoid activation of any water-soluble effervescent agent in the mixture. In order to avoid the need to evaporate organic solvent after contacting the polymer particles with a solution of bonding agent, it is preferred to use a bonding agent which is a wax which melts at a temperature between 20 and 250°C. The granular product can be made by aggregating the polymer particles and effervescent agent with molten wax and solidifying the wax.

The wax may be any substance or mixture of substances that is solid at normal temperatures but which can be liquid at convenient manufacturing temperatures, for instance the temperature at which molten wax is blended with the polymer particles. Usually the melting point of the wax should be above 30°C and often above 40°C. It is usually undesirable to have to heat the mixture to too high a temperature and so preferably the melting point of the wax is not above 200°C, and most preferably it is not above 120°C. These are the melting points of the matrix, and so may be the melting point of the single material, when the matrix is formed of a single material, or may be the melting point of the molten blend that forms the matrix. The wax matrix consists of or comprises water-soluble or water dispersible wax. The amount of such waxes is preferably the predominant amount (above 50% by weight of the matrix) and is preferably above 80% by weight of the matrix. Examples include polyethylene glycols, for example, PEG 1450, PEG 4000, PEG 8000, polyethylene glycol esters, for example, PEG 8000 distearate, fatty acids, for example stearic acid or salts for example sodium or ammonium stearate, amides of fatty acids, for example, stearic acid diethanolamide, fatty alcohols, quaternary fatty waxes such as N-hydroxyethyl ethylene diamine reacted with stearic acid and then quaternised with dimethyl sulphate, or a mixture of two or more of these compounds.

Oil miscible, low melting, waxy surfactants (e.g. , the materials sold under the trade name "Dobanol") may be used as part or all of the wax matrix.

The preferred bonding agent is polyethylene glycol. The amount of wax must be sufficient to provide enough of a matrix structure to aggregate the polymer particles into granules. Amounts as low as 3% may be usable but generally the amount is above 5% and more usually above 10% by weight of the granules. If the amount is too low it can be very difficult to achieve adequate distribution of the bonding agent through the product. Usually the amount is above 15% and preferably it is at least 20% by weight of the granules. The amount of bonding agent can be high, for instance up to about 70%, but since the granular product is usually intended primarily to deliver the polymeric particles to the desired location it is usually preferred for the amount of bonding agent to be as low as is consistent with convenient manufacture and dissolution characteristics. Usually therefore the amount of bonding agent is below 60% by weight of the granular product and preferably it is not more than 50% by weight. The amount of polymer particles in the product is usually as high as is conveniently possible and is normally at least 35 or 40%, and preferably at least 50%. The use of very high amounts can lead to difficulties in manufacture and so generally the amount of polymer particles is not more than 80% and is usually below 75%. The total amount of polymer particles and wax is usually at least 70%, and preferably at least 80%, by weight of the product.

The amount of effervescent agent will be selected so as to provide the desired degree of effervescence. Usually it is at least 3% and usually at least 5% by weight of the granules. It can be as much as, for instance, 30% by weight or even more but it is generally preferred that it is in the range 8 to 20%.

Minor amounts of other components may be included in the granules. For instance surfactant can be included to promote wetting of the granules with water. A release aid may be included in the granules, or may be coated onto the granules, so as to improve flow properties and to minimise aggregation of the granules.

The granular product is made by forming a mixture of the polymer particles, molten wax and the effervescent agent and cooling and converting this mixture to form the solid granules. For instance polymer powder may be blended with the wax which can be melted before or during the blending. Often the proportions are such that a melt dispersion iε formed of the polymer particles and effervescent agent in the molten wax. Another way of forming such a melt dispersion is by forming a reverse phase dispersion or emulεion of εubstantially anhydrous polymer particles in a volatile organic liquid, dissolving wax into this liquid at a temperature at which the wax is molten, and evaporating the volatile liquid, as described in PCT/GB95/00283.

The mixing conditions may be such that the particles are formed while mixing is continuing, for instance by use of a mixer which resembles a domestic food blender, in which event cooling and solidification of the wax may be conducted during the mixing or during or immediately after discharge from the mixer. For instance the particles may be cooled while entrained in an air stream which carries them out of the mixer.

Other ways of forming the desired granular product include spraying or otherwise distributing the molten mixture as droplets, for instance onto a release coating or by spray chilling, or by extrusion into the desired granular form or by comminution of larger granules, blocks sheets which have been formed from the molten product. The matrix of the granules can additionally have a foamed structure, for instance as a result of thermal decomposition of effervescent agent during the melt mixing. However it is usually preferred for the granules to be substantially non-foamed and for the effervescence to be confined to effervescence that occurs during contact with water.

The invention also includes block products, ie products which are larger than granules and which normally have a minimum dimension of at least 10 mm. For instance the product can be in the form of one or more blocks having a minimum dimension of at least 20mm and often 30mm or 50mm or more and having a maximum dimension of up to 50mm, 100mm, 500mm or more. Typical blocks can have a weight of 0.02 to 10kg, often 0.05 to 5kg. For instance where prolonged relatively slow release iε required it may be appropriate to provide blocks of 1 to 5kg for immersion in a flowing stream but where faster releaεe is required it may be more appropriate to εupply blocks of 0.05 to 0.5kg. Block products according to the invention can be made from the same materials and by the same general techniques as described above with respect to granular products, with appropriate modification of the molding or other shaping technique by which the molten mix is converted into the final solid block form.

The effervescence which occurs when such blocks are immersed in a flowing stream or are exposed to a falling cascade of water can result in improved dissolution performance of the blocks. However it is particularly preferred in the invention that the blocks should have a foamed matrix. The foaming is preferably provided by thermal dissociation of a gas-forming compound during the manufacture of the block. Thus the block is preferably made by shaping a melt dispersion of the polymer particles and gas-forming compound in the wax while it is molten and allowing thermal decomposition to occur, and solidifying the foamed melt dispersion. Thuε the gas-forming compound liberates gas in the melt and the reεultant foam is trapped upon solidification of the dispersion. Some or all of the foaming may occur during the cooling and solidification of the wax. The gas-forming compound can be part of an effervescent agent combination, in which event the block will have a foamed εtructure and will effervesce upon contact with water. Often, however, the block does not εubstantially efferveεce on contact with water and the gas forming compound may be included primarily or only to cause foaming of the matrix.

The preferred gas-forming compounds are heat- decomposable carbonates and bicarbonates, preferably the sodium salts. Thus preferably sodium bicarbonate or other heat decomposable, gaε-forming, compound iε included as the only foaming or effervescent agent in the melt dispersion. The amount of gas forming compound is typically in the range 3 to 20% by weight of the molten mixture. However the use of the higher amounts tendε to make handling of the mixture more difficult and εo generally the amount iε not more than about 10 or 15% by weight of the molten mixture.

The following are exampleε of the invention. Example 1

67 parts by weight bead fines of a water-εoluble copolymer of acrylamide and sodium acrylate IV 13 dl/g were dry mixed with 3.3 pbw citric acid powder and 3.3 pbw sodium bicarbonate powder in a food blender into which 28 pbw molten polyethylene glycol 4,000 was slowly added over a period of about 1 minute.

The resulting agglomerated mix had a particle size between 200μm and 5 mm and was chilled at 4^βC for 30 minutes and was then ground to a particle size of between 200 and 700μm.

On addition to water, the granular product initially settled to the bottom of the vessel but then started to effervesce whereupon the granules slowly rose and disintegrated, allowing the individual polymer particles to activate and dissolve independently into the water.

The resultant solution can be used as a flocculant solution for a mineral suspension. Example 2 60 pbw of a particulate homopolymer of diallyl dimethylammonium chloride IV 2 dl/g particle size 90% below 425μm were blended in the general manner of Example 1 with 10 pbw citric acid, 10 pbw sodium bicarbonate and 20 pbw polyethyleneglycol. Upon addition to water, the granuleε effervesced and disintegrated and the polymer dissolved quickly into the water.

The reεultant polymer solution can be used as a coagulant εolution for the treatment of a suspension. Example 3

The process of Example 1 is repeated using 60 pbw of a cationic copolymer of acrylamide and dimethylaminoethyl acrylate quaternised with methyl chloride, IV 7 dl/g, 1₀ pbw citric acid, 10 pbw sodium bicarbonate and 20 pbw polyethylene glycol.

The resultant solution can be used for flocculating sewage sludge. Example 4

A bonding agent for pelletising iron ore comprises a blend of 45 pbw lightly crosε-linked, partially soluble, fines (below 200μm) copolymer of acrylamide and sodium acrylate and 20 pbw sodium carbonate. This mixture was blended with 9 pbw citric acid and 26 pbw polyethylene glycol in the same general manner as in Example 1.

When the resultant granules were added to water, they disintegrated quickly, as in Example 1. When the resultant granules were scattered onto a moist pelletising mix, as in the conventional pelletisation of iron ore, they disintegrated quickly to release the individual polymer particles. Example 5 A blend was formed of 50 pbw bead fines of a copolymer of acrylamide and sodium acrylate having IV 18 dl/g (sieved from a bead product made by reverse phase bead polymerisation) and 50 pwb polyethylene glycol 4,000 by mixing the materials at a temperature at which the polyethylene glycol is molten. The resultant melt dispersion was cast into blocks and allowed to cool.

This process was also conducted with the addition into the melt dispersion of amounts of sodium bicarbonate ranging from 2 to 15 pbw. The blocks were then positioned under falling water and the rate of dissolution of the blocks was observed.

As regards manufacture, it was found that the melt disperεion became increasingly difficult to handle and cast as the amount of sodium bicarbonate increased, especially above 10 pbw.

As regards the rate of disεolution, it waε found that thiε increased as the amount of sodium bicarbonate in the melt dispersion increased, and that the best combination of solubility and workability waε achieved at around 6 to ₁0 pbw sodium bicarbonate.

Observation of the blocks showed that the solid blocks had a foamed structure due to the liberation of carbon dioxide from the sodium bicarbonate during the melt mixing and as the molten mix was gradually cooled to form blocks. Example 6

A product for use as an agricultural anti-drift agent comprises a blend of 64.9 pbw of a water-soluble copolymer of acrylamide and sodium acrylate, IV 10 dl/g, 28 pbw PEG 4000, 2 pbw citric acid and 5.1 pbw sodium bicarbonate. Granules are prepared in the same general manner as in Example 1.

When added to water, the granules effervesce and disintegrate so that the polymer can dissolve quickly into the water. Example 7

This example demonstrates the provision of soil conditioners in the form of the products of the invention.

Soil trays measuring 16 x 20 cm were filled with a sandy silt loam, which had been dried and sieved tc produce aggregates between 710 and 8,000 μm. The soil (containing 2.6% organic matter and with pH 7.45) was known to be extremely poorly εtructured. Two rowε of onion seeds were sown per tray, at a rate of six seeds per row, to a depth of 1 cm. The following treatments were applied dry to the soil surface above the seed row.

Treatment Application rate

1 Control Zero

2 Composition of Example 1 0.033g/row (67% active) (Effervescent Granule)

3 Granular polymer 0.022g/row

The granular polymer had the same chemical composition as the fine granules used to form the effervescent granule. The particle size of the granular polymer was similar to that of the effervescent granule.

A soil 'cap' was created by spraying water onto the surface of the soils, via a Lurmark Flat Fan nozzle 015 F80°. A compressed air cylinder was used to deliver the water at a preεsure of 3 bar. The trays were periodically watered with identical amounts of tap water, taking care not to disturb the soil 'cap'. All trays were placed below UV lights for 9 hours per day. Germination counts (expressed as percentage of total seeds) were taken at regular periods and were as shown in Table l below. Table 1

Number of Treatment days after

(1) Control sowing (2) (3) Granular

Effervescent Polymer Granule

15 0 50.0 33.3 17 0 100.0 50.0 21 0 100.0 50.0 24 0 100.0 50.0

These resultε demonstrate that significantly higher germination count was observed with the polymer in the form of effervescent granules in compariεon with standard granular polymer. It can be seen then that polymers provided in the form of the product of the invention can be applied and distributed more efficiently than standard granular polymer and can thus be more effective.

Claims

1. A product comprising particles of water-soluble or water-swellable polymeric material dispersed in a matrix of water-soluble or water-swellable bonding agent wherein the matrix includes water-activatable effervescent agent and/or is foamed.

2. A product according to claim 1 in which the bonding agent is a wax which melts at a temperature between 20 and 250°C and which iε soluble or swellable in water.

3. A product according to claim 2 in which the bonding agent is polyethylene glycol.

4. A product according to claim 2 or claim 3 in which the amount of bonding agent is 10 to 60% by weight of the product and the amount of polymer particles is 35 to 80% by weight and the total amount of bonding agent and polymer particles is at least 70% by weight of the block.

5. A product according to any preceding claim wherein the matrix includes water activatable effervescent agent which is a solid mixture of water-soluble acid and water-soluble carbonate or bicarbonate.

6. A product according to claim 5 in which the efferveεcent agent includeε sodium carbonate and/or sodium bicarbonate.

7. A product according to claim 5 or claim 6 in which the effervescent agent includes an acid selected from citric acid, tartaric acid, benzoic acid, polymeric carboxylic acids and sulphamic acid.

8. A product according to any preceding claim in which the matrix include sodium bicarbonate and citric acid.

9. A product according to any preceding claim in which the polymer particles have a size 90% by weight below 150μm.

10. A product according to any preceding claim in the form of granules having a size below 5 mm wherein the matrix includes water activatable effervescent agent.

11. A product according to claim 10 in which the granules have a size at least 90% by weight in the range 20 to l,000μm.

12. A product according to claim 10 or claim ll in which the granules include a particulate weighting agent.

13. A product according to any of claims 10 to 12 in which the granules sediment when added to static water and then effervesce and float and disintegrate while floating.

14. A product according to claim 13 in which the granules disintegrate while floating substantially without the formation of a surface layer of dissolving granules on the static water.

15. A product according to any of claims 1 to 9 in the form of a block having a minimum dimension of at leaεt 10 mm and formed of water-soluble or water-swellable polymeric particles dispersed in a foamed matrix formed of a wax which melts at a temperature between 20 and 250°C.

16. A product according to claim 15 which has been made by shaping a melt dispersion of the polymer particles in the wax while the wax is molten and then solidifying the wax, and in which the matrix haε been foamed by thermal diεεociation of a gaε-forming compound in the melt dispersion.

17. A product according to claim 16 which has been formed by shaping a melt dispersion of the polymer particleε in molten wax which includes heat decomposable carbonate or bicarbonate and thereby liberating carbon dioxide into the melt matrix, and solidifying the melt.

18. Uεe of a product according to any of claims 10 to 14 for scattering as a soil conditioner or pelletisation binder or for activation to give an aqueous solution for use as viscosifier or flocculant.