DE3917646C1 - Agglomeration of natural or synthetic polymer powder - obtd. by agglomerating small sized fractions of powder in presence of soln. or dispersion of agglomerating aid - Google Patents

Abstract

A dusting, water soluble or swellable agglomeration of natural or synthetic polymer powder is obtd. by agglomerating the less than 0.2mm, pref. less than 0.1 mm sized fractions of the powder in presence of a soln. or dispersion of an agglomerating aid in water and/or a non-miscible organic solvent or of the molten or sintered aid. Esp. 0.1-1 wt% aid, e.g. a (co)polymer of an olefin, a polyester, a polyvinyl ester, an epoxy resin, is used. The powder is a natural polysaccharide, or a synthetic (co)polymer based e.g. on maleic acid, (meth)acrylamide, cellulose. USE/ADVANTAGE - For absorption of body fluids, soil improvement, flocculating agent, thickener; the fines do not have to be separated from the rest of the powder to obtain the agglomerates.

Description

The invention relates to water-soluble or non-dusting water-swellable agglomerates of natural or synthetic Powdery polymers, process for their Production and use for the absorption of body fluids, as a soil conditioner, as a flocculant and thickener.

The powdery products made by grinding always contain in addition to the desired grain fraction also grain fractions with coarser and finer grain, the separated from the main grain fraction by sieving have to. The coarser grain fraction is used in the grinding process returned so that no loss of product arises. The screened fine grain fraction, which one does not use use the same purpose as the main fraction directly can, must therefore be further processed.

It is therefore inevitable with every grinding process, a screening the coarser and the finer ground particles downstream to an end product with the desired grain size distribution to obtain.

Fines in powdery products make it more difficult their application and processing. Except difficulties arise from the dust nuisance. B. in dosing due to reduced pourability and Loosening processes due to lump formation. These difficulties  also show up in water-swellable and water-soluble Polymers where the swelling / dissolving process by baking the fine particles are hindered. Polymer powder must therefore of fine particles below 200 microns, especially below 100 µm are largely exempt.

The for the separation of fine particles from a powder stream applied processes, such as screening or air jet classification are very expensive.

The object of the invention is without complex separation of the Fine parts to agglomerate them in the total powder.

In other words, the object of the invention is the very fine fractions less than 200 µm in powder, natural or synthetic Polymers without expensive separation from the coarser components essentially selective to one Agglomerate particle size above 200 microns.

Selective means that significant agglomeration or Particle enlargement from coarser to oversize not entry.

The solution to this task of selective agglomeration is carried out with an agglomeration aid that is suitable Finely distributed with the agglomerating polymer powder is brought together.

That in a pile, d. H. a powdery material, which contains all grain sizes from very fine to coarse and thus practically selectively agglomerates the very finest fractions be, while the coarser proportions are practically not agglomerating to oversize must be considered surprising will. This preferred agglomeration of the Kornfrak  ions smaller than a certain one, for application as the optimally recognized feature value, is subsequently referred to as called selective agglomeration.

According to one embodiment of selective agglomeration the agglomeration aid is in a solution or a dispersion in water, a water miscible or immiscible organic solvents or a mixture from water and such an organic solvent brought together with the polymer to be agglomerated.

The starting material is preferred during the agglomeration kept moving.

According to a further embodiment of selective agglomeration can also be used as an agglomeration aid powdery, meltable or softenable finely divided Solid be used. This causes the agglomeration, by the agglomeration aid by increasing the temperature at least partially softens or melts and thereby is able to agglomerate the finest components.

A suitable method is e.g. B. selective agglomeration in the fluidized bed using a suitable Inert gas or air is generated. The air is there partially heated to the full adhesive strength of the agglomeration aid reach and / or the water and / or remove the solvent from the system and the agglomerate to dry. Apparatus for the implementation of the Process a fluidized bed dryer as particularly advantageous exposed. The individual process parameters, such as amount of polymer added, amount of air, amount of agglomeration aid and air temperature and duration of the Agglomeration treatment can be done by simple ver  determine search. The agglomeration can also take place in the mechanically generated fluidized bed, on a heatable Vibratory conveyors.

The agglomeration can also be carried out in a free fall mixer or a compulsory mixer that contains rotating mixing tools and with an introduction device for the agglomeration aid is equipped to be carried out. The device can at room temperature or with existing heating or Cooling jacket operated at higher or lower temperatures to the necessary optimal working temperature for to reach the agglomeration aid.

The powdery starting polymer is mixed with the agglomeration aid at a temperature of 0 to 250 ° C preferably brought into contact from 20 to 160 ° C. The temperature depends on the type of agglomeration and the one used Agglomeration aids. Is by means of aqueous or aqueous-organic solutions or dispersions of an agglomeration aid worked, so are temperatures in Range of 50 to 120 ° C is particularly preferred. Using with a powdery, but meltable or sinterable Agglomeration aids must of course at least are heated to a temperature at which the agglomeration aid softens or at least becomes sticky. Agglomeration aids are preferably used here, those in the range of 20 to 200 ° C and especially in the range are powdery from 50 to 160 ° C and soften or melt within this temperature range.

However, such agglomeration aids are also suitable that only at lower temperatures, e.g. B. 0 ° C in powder form are, however, at room temperature z. B. sticky. Such Substances are made by cold grinding at low temperatures, where they are brittle, powdered, cold with the poly  mixed and then z. B. to room temperature warmed up.

Also the amount of agglomeration aid used is easy for the person skilled in the art to determine by simple experiments and depends on the mode of operation of the type of agglomeration aid from. The amount of agglomeration aid can be within a relatively wide range vary. The amount of agglomeration aid will naturally kept as small as possible, but that is Amount is not critical when used as an agglomeration aid e.g. B. the starting product to be agglomerated itself in Form of an aqueous solution or dispersion is used. For practical purposes, amounts of 0.001 to 10% by weight preferably 0.05 to 5% by weight and particularly preferably 0.1 to 1 wt .-% agglomeration aids, each based sufficient to the starting material to be agglomerated proven.

As powdery products whose fine grain fractions are based on can agglomerate in this way, are both the water-soluble and water-swellable polymers based on Polysaccharides such as cellulose, cellulose derivatives such as Carboxymethyl cellulose, alkyl or hydroxy cellulose, starch and starch derivatives and vegetable gum (xanthan gum, alginic acid) and their salts as well as the polymers or copolymers based on (meth) acrylic acid or (meth) acrylic acid derivatives suitable. The method according to the invention relates primarily the selective agglomeration of the polymers of acrylic acid and methacrylic acid alone as homopolymer or as a copolymer, but also the polymers of other monomers - except acrylic acid and methacrylic acid, such as acrylamide, methacrylonitrile and acrylonitrile, vinyl pyrrolidone, Vinyl acetate - as well as other water-soluble ones Monomers (polymerizable acids and their salts,  in particular the Malein, Fumar, Itacon, Vinylsulfon- or Acrylamidopropanesulfonic acid; also containing hydroxy groups Esters of polymerizable acids, especially the hydroxyethyl and hydroxypropyl esters of acrylic and methacrylic acid), further the polymers of those containing amino groups and esters and amides containing ammonium groups are more polymerizable Acids (dialkylamino esters, especially the Dimethyl and the diethylamino alkyl esters of acrylic and Methacrylic acid, as well as trimethyl and triethylam monium alkyl ester) and the polymers of the corresponding Amides. In addition, small amounts of crosslinking monomers, such as B. Monomers with more than one polymerizable Group to be contained in the molecule of the polymer.

The polymers of the above monomers can be used alone as homo- or among themselves as copolymers be agglomerated. When using acrylic acid and / or Methacrylic acid as monomer building blocks of the polymers are the above in the production of copolymers listed water-soluble monomers preferred.

In smaller quantities, other water-insoluble ones can also be used Monomers can be contained in the polymer like the esters of Acrylic and / or methacrylic acid with C₁-C₁₀ alcohols, styrene and alkylated styrenes. In general, the proportion is on the water-soluble monomers based on 20 to 100 wt .-% on all of the monomers. The share of cross-linking Comonomers is 0 to 20% by weight, preferably 0.01 up to 2.0 wt .-% based on the total of the monomers. The water-insoluble (hydrophobic) monomers make in the Rule 0 to 60 wt .-% of the monomers.

Crosslinking monomers are bifunctional or multifunctional Monomers, e.g. B. amides such as methylenebisacrylic or meth  acrylamide or ethylene bisacrylamide, furthermore esters of polyols, such as diacrylates or triacrylates, e.g. B. butanediol or Ethylene glycol diacrylate or methacrylate, trimethylolpropane triacrylate, also vinyl methacrylate and allyl compounds, such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl ester, Polyallyl esters, tetraallyloxiethan, triallylamine, Tetraallylethylenediamine, allyl esters of phosphoric acid or phosphorous acid, also crosslinkable monomers, such as the N-methylol compounds of amides such as methacrylamide or acylamide and the ethers derived therefrom.

All of these polymers are made by known methods.

The starting material can be used as an agglomeration aid itself, d. H. the water-soluble or water-swellable polymers on a synthetic or natural basis (poly saccharide base in dissolved or swollen state), be used. Examples of such water-soluble or are water-swellable polymers on a natural basis Starch, especially corn starch, cellulose derivatives, such as Carboxymethyl cellulose, alkyl or hydroxyalkyl cellulose, Starch and starch derivatives and vegetable gum (xanthan gum, Alginic acid) and its salts, as well as on a synthetic basis the polymers or copolymers based on (Meth) acrylic acid or (meth) acrylic acid derivatives, such as the Homo- or copolymers of acrylic, methacrylic, acrylamido methylpropanesulfonic acid, the salts of these acids, the acrylic or (meth) acrylamides with each other or with vinyl pyrrolidone and / or vinyl acetate and polyvinyl alcohol. The The above polymers can also by a at least bifunctional crosslinkers must be networked with it they are only swellable in water but not soluble.  

Low or high molecular weight polymers can also be used as emulsion polymers in an aqueous dispersion in Shape of the tiny spherical solubilized by emulsifier Particles are present, being used both forms of emulsion - "oil in water" (for water-insoluble Polymers) and "water-in-oil" (for water-soluble polymers) - possible are. As is well known, the oil phase usually consists of water-immiscible organic solvents such as aliphatic or aromatic hydrocarbons (e.g. Hexane, toluene).

Examples of polymers containing oil-in-water emulsions are polymers of butadiene, styrene, isoprene, Chloroprene, acrylonitrile, vinyl acetate, vinyl and Vinylidene chloride, alkyl acrylates and methacrylates and copolymers of these monomers with each other as well as with Methylstyrene, isobutylene or ethylene.

As an example of polymers used in water-in-oil emulsions can be used, the above. water soluble or water-swellable polymers or copolymers Basis of (meth) acrylic acid derivatives that are not cross-linked or can also be networked.

In addition, you can also use other substances that are used for Agglomeration are able to use. So as agglomeration aids such products are also used according to DE-PS 31 28 100 to improve the liquid uptake rate can be added to the polymers. Such products are, for example, the most harmless to health Salts of inorganic or organic acids, e.g. B. the chlorides, bromides, iodides, sulfates, hydrogen sulfates, Phosphates, hydrogen or dihydrogen phosphates, tetraborates, Nitrates, carbonates or bicarbonates as salts  of inorganic acids or the salts of vinegar, ants, Adipic, citric or tartaric acids as salts organic carboxylic acid. The salts are also suitable of low molecular weight polymeric carbonic or sulfonic acids with a molecular weight between 300 and 100,000, preferably 2000 to 20,000, based on homopolymers and copolymers unsaturated mono- or dicarboxylic acids, sulfonic acids, aldehydes, Alcohols and (meth) acrylamide. With the above mentioned water-soluble, at normal temperature as free-flowing powder of an inorganic salt or organic acid, the ammonium, sodium, Calcium, lithium, calcium, magnesium, zinc, aluminum and / or iron salts are preferred. Instead of the salts you can Powdery inorganic solid even at normal temperature Acids such as boric acid or phosphoric acid, or an organic Mono- or polycarboxylic acid, preferably lemon, wine or Adipic acid or a low molecular weight polymer carbon or Sulfonic acid with molecular weights between 3000 and 100,000, preferably between 2,000 and 20,000 based of homo- or copolymers of unsaturated mono- or dicarboxylic acids, Sulfonic acids, aldehydes, alcohols as well (Meth) acrylamides are used, as are those in Normal temperature solid water-soluble derivatives of a carboxylic acid such as an amide or diamide, e.g. B. urea, or a Urea derivative, preferably thiourea, methyl or Ethyl urea. Mono- or can also be used Oligosaccharides, preferably glucose, fructose, manose or Sucrose.

As agglomeration aids which cause agglomeration of the water-soluble or swellable polymers when heated by melting or sintering, z. B. can be used:
Homopolymers and copolymers of polyolefins, polyacrylates, polyvinyl and polyallyl derivatives, polyamides, polyesters, polyalkylene oxides, polyurethanes and epoxy and urea-formaldehyde resins. Fatty acids, their salts and derivatives such as B. the polyglycol esters and oxalkylates of H-active compounds can be used.

Also to be mentioned are cellulose esters or natural ones Resins such as B. rosin and hard paraffins and their oxidates as well as citric acid · 1 H₂O in their water of crystallization melts.

Common to the powdery agglomeration aids, that they have a melting or softening point above of 0 ° C and preferred in a grain size of 1-300 microns 5-80 µm.

To determine the application properties the intake of model urine according to the demand absorbency test (DAT) (W. F. Schlauch, Lecture Index 1978, Amsterdam) and the recording speed after 60 seconds as well the maximum intake and retention after 20 or 40 minutes determined. The measuring device consists of a burette with the model urine solution (2.0% urea, 0.9% NaCl, 0.1% MgSO₄ and 0.06% CaCl₂, dissolved in distilled water) is filled, and a sample table, which is connected to the Measuring burette connected opening for the model urine solution outlet is provided. On the with a thin fleece (10 × 13.5 cm) covered sample table is 0.5 g of the invention Product, mixed with 5 mg Aerosil 200, in the form a circular area of 4.5 cm in diameter sprinkled evenly over the liquid outlet. By Closing the hose and light pressure will Contact of the model urine solution with the powder product, so that the model urine solution by the fiction  moderate product can be absorbed. The absorbent amount the model urine solution turns 60 after seconds and after 20 to Read the first maximum value for 30 minutes. Subsequently became the retention by loading the swollen gel determined with a weight of 10 g / cm²; the time of stress was 5 minutes. The determined 60 seconds, Maximum and retention values are tabular in the examples summarized.

As another method for determining the rate of fluid intake for a short time was a teabag test carried out, taking 0.2 g of test substance in a tea bag filled and immersed in the test solution. After 15 The fluid intake is determined gravimetrically in seconds and converted to 1 g of product.

The invention is illustrated by the following examples:

Examples 1-6

The agglomeration of the powdery polymer was in carried out a fluidized bed dryer. The device consists of a vertical tapered metal cylinder at the bottom Ended with a sieve bottom and a device is provided for sucking in air. The one to be treated granular product is in this cylinder of an adjustable Air flows through until the individual granules in Start moving, causing the fluidized or fluidized bed to be thorough is mixed. Spraying takes place at this stage the dissolved agglomeration aid with the help a nozzle. The amount of the auxiliary, the amount of air as well the air temperature can vary within certain limits will.  

For Examples 1 to 6, the device was each 1000 g finely ground, powdery, partially cross-linked polyacrylic acid with a grain distribution of 9.4 wt .-% grain fraction 90 µm, 89.6% by weight grain fraction 90-630 µm and 1.0% by weight Grain fraction 630 µm, the application technology through the model urine absorption rate of 17 ml / g (DAT 60 sec. Value) was characterized, filled and at 110 ° C with flowing Air warmed. Then the polymer was in Fluid bed within 5-15 minutes by spraying on the aqueous solutions of low or high molecular weight polyacrylic acids agglomerated. The test conditions and the Results are summarized in the table below. The yield of the main fraction 90-630 μm was 93-95% by weight obtained, the agglomerated product no deterioration the application properties (DAT values) showed.

The coarse fraction (630 µm) was practically unchanged (1.2-1.6% by weight) or increased only slightly (3.4-5.2% by weight). The fine grain fraction (90 µm) was largely, depending on selected conditions, up to 87% selectively agglomerated.  

Table 1: Agglomeration of acrylic acid powder polymer, consisting of 90% by weight grain fraction 90-630 µm and approx. 10% fine grain fraction (<90 µm)

Examples 7-15

In Examples 7 to 10, a finely ground acrylic acid polymer was used with 92 wt .-% grain fraction below 90 microns and 8 wt .-% grain fraction 90-630 microns under the same conditions as in Examples 1-6 at 110 ° C in a fluid bed dryer sprayed with an aqueous solution of aluminum sulfate or urea and then dried. The test conditions and the results are summarized in the tables below.

There was a complete selective agglomeration of the Fine grain fraction (as from the results in Table 2) is seen), with only insignificant proportions of the grain fraction over 800 µm were created.

In Examples 11-15 a coarsely ground was used for comparison Acrylic acid polymer (particle size 90-630 µm) under the same conditions and with the same agglomeration aids treated in a fluidized bed dryer, as in the Examples 7-10. The treated products showed only one Improvement in initial absorption rate, but it no agglomeration was observed in this case (see Table 2).

In Examples 7 to 15 the agglomeration of the finely ground grain fraction (grain distribution below 90 µm) and the coarsely ground grain fraction (grain distribution 90-630µm) compared and checked the selectivity of the agglomeration. Both grain fractions were made under the same conditions and treated with the same agglomeration aids. On the one hand the powder articles with grain distribution were under 90 µm (in the presence of coarser particles) completely agglomerated, on the other hand, the coarsely ground  Grain fraction (90-630 µm) no further agglomeration observed.  

Table 2: Treatment of finely ground powder polymer (main grain fraction <90 µm) with water-soluble compounds (component B - according to DE-PS 31 28 100)

Table 3: Treatment of powder polymer with a particle size distribution of 90-630 μm with aqueous aluminum sulfate and urea solution (component B according to DE-PS 31 28 100)

Comparative examples

Example 16

A water-swellable product made by solution polymerization Polymer powder from crosslinked polyacrylic acid, the 70 mol% is present as the sodium salt, with 5% by weight of polyethylene powder grain size 5-300 µm (melt index: 200 g / 10 min., 190 ° C / 2.16) and a softening temperature of 105 ° C mixed. This mixture is mixed with thermal oil given at 145 ° C vibratory conveyor. One after one Dwell time of 30 minutes at a powder temperature of Sample taken at 135 ° C shows the table 4 Grain distribution.

Table 4

Example 17

A powder mixture of 1400 g is placed in a fluidized bed water-swellable polymer from Example 16 with the particle size distribution, as indicated in Table 5, and 15 g of a polyethylene powder grain size 5-80 µm (melt index: 7 g / 10 min., 190 ° C / 2) and a softening range of 109-112 ° C granulated by heating to 140 ° C. The supply air temperature  tur is 180 ° C and the air speed 0.45 m / sec. The composition of the end product is shown in Table 5.

Table 5

Examples 18-20

Powder mixtures are made in a heatable free-fall mixer from a water-swellable polymer from Example 16 the grain distribution given in Table 6 and 1% by weight an agglomeration aid heated to 130 ° C. The grain distribution the final products are shown in Table 6.  

Table 6

Claims (14)

1. Non-dusting water-soluble or water-swellable agglomerates of natural or synthetic powder Polymers obtainable by agglomeration of grain fraction fractions <0.2 mm, preferably <0.1 mm, in powder form Starting material by means of an agglomeration aid, that dissolves or disperses in water, one with water miscible or immiscible organic solvents or a mixture of water and such an organic Solvent is, or that as a solid without Solvent in the molten or sintered state located. 2. Process for the production of water-soluble or water-swellable natural or synthetic polymers Claim 1, characterized in that the very fine fractions a grain size of <0.2 mm, preferably <0.1 mm, in powdery starting material of the polymer by spraying a solution or dispersion of at least one Agglomeration aids in water, a water-miscible or immiscible organic solvents or a mixture of water and such an organic solvent agglomerated. 3. Process for the production of water-soluble or water-swellable natural or synthetic polymers Claim 1, characterized in that the powdered Starting material of the polymer with a powdery, meltable or sinterable substance as agglomeration aid brings in contact and the very fine fractions agglomerated.   4. The method according to claims 2 to 3, characterized in that the powdered starting polymer with the agglomeration aid at a temperature of 0-250 ° C, preferably 20-160 ° C, in contact. 5. The method according to claims 2 to 4, characterized in that 0.001-10 wt .-%, preferably 0.005-5 wt .-%, and particularly preferably 0.1-1% by weight, agglomeration aids, based on raw material used. 6. The method according to claims 2 to 5, characterized in that natural polymers are used as starting polymers Base of saccharides or synthetic polymers and copolymers based on maleic acid, (meth) acrylic acid, partly saponified (meth) acrylonitrile, (meth) acrylamide or (Meth) acrylic acid esters, graft polymers of (meth) acrylonitrile, (Meth) acrylamide, (meth) acrylic acid on starch or Uses cellulose. 4. The method according to any one of claims 2 to 6, characterized in that that the starting polymers used at least partly as ammonium, alkali or alkaline earth salts are available. 4. The method according to claims 2 and 4 to 7, characterized in that the starting polymers as agglomeration aids in dissolved or partially swollen or dispersed form can be used. 9. The method according to claims 3 to 7, characterized in that as agglomeration aids polymers and Copolymers based on polyolefins, polyamides, polyesters, Poly (meth) acrylates, poly (meth) acrylonitriles, Polyalkylene oxides, polyvinyl esters, chloride, polyurethanes  or epoxy resins dispersed or used in powder form will. 10. The method according to claims 2 and 4 to 8, characterized in that as agglomeration aid at least one inorganic and / or organic compound is used, which is available as a free-flowing powder at normal temperature and is water soluble. 11. Use of agglomerates according to claims 1 to 10 for Absorption of body fluids. 12. Use of agglomerates according to claims 1 to 10 as Soil improvers. 13. Use of agglomerates according to claims 1 to 10 as Flocculant. 14. Use of agglomerates according to claims 1 to 10 as Thickener.