EP0394298A1

EP0394298A1 - Polymers with high rate of absorption of aqueous fluids

Info

Publication number: EP0394298A1
Application number: EP88910033A
Authority: EP
Inventors: Miroslav Chmelir; Karl-Heinz Stukenbrock
Original assignee: Chemische Fabrik Stockhausen GmbH
Current assignee: Stockhausen GmbH and Co KG
Priority date: 1987-12-04
Filing date: 1988-12-01
Publication date: 1990-10-31
Also published as: JPH03501493A; EP0318989A1; EP0318989B1; ATE119556T1; GR3015344T3; DE3741158A1; ES2010960A4; WO1989005327A1; DE3853266D1; ES2010960T3; DE3741158C2; BR8807830A

Abstract

Water-soluble or water-dilutable natural or synthetic polymers with a marked capacity for absorbing water and aqueous fluids are obtained by an agglomeration of a fine-particle powdered starting material by means of a solution or dispersion of an agglomerating agent in water, an organic solvent miscible or immiscible with water or a mixture of water and an organic solvent of this type, and if necessary other agglomerating additives. Also described are the process for preparing them and their use as absorbants, disposable sanitary products, for example diapers and sanitary napkins, containing a polymer as described in claim 1 as an absorbant for body fluids such as water and/or urine.

Description

Polymers with high absorption speed for aqueous liquids.

The invention relates to polymers which rapidly absorb water and aqueous liquids, e.g. find use in absorbent, disposable products for hygiene articles (diapers and sanitary napkins) and for other medical purposes, or also as water-storing soil improvers, and a process for their preparation and their use as absorbents for water and aqueous liquids.

In recent years, a number of different polymers have been developed which have a high absorption capacity for water and body fluids. Most products were based on starch, such as starch-acrylonitrile graft polymers (US Pat. No. 3,997,404; 3,661, 815; 4,155,808; 3,935,099), gelatinized starch derivatives (DE-OS 27 02 701) or cellulose-based, such as derivatives of alkyl or HydroxyIkylcellulose (J PP S 77 / 125.401), Carboxymethylcellulose (BE-PS 862,130; GB-PS 1, 159,949) and based on polysaccharide (DE-OS 26 50 377). The fully synthetic absorbents described in numerous patents include crosslinked polymers and copolymers based on acrylic or methacrylic acid (DE-OS 24 29 236; DE-OS 26 14 662; US-P S 4,018,951; US-P S 3,926,091; US-PS 4,066,503 ; US-PS 4,062,817; D E-OS 27 12 043; DE-OS 26 53 135; DE-OS 26 50 377; DE-OS 28 13 634), maleic acid derivatives (US-PS 4,041, 220) or acrylamidopropanesulfonic acid copolymers (DE- PS 31 24 008). The known absorbents of this type are practically insoluble in water, absorb in equilibrium the multiple of their weight in water, urine or other aqueous solutions, the relatively slow rate of absorption of the aqueous liquids playing only a minor role so far, and they have only been mentioned in a few patents . For example, DE-OS 28 13 634 describes an acrylic acid / acrylonitrile / stearyl methacrylate mixture polymer which absorbs 38 times its own weight in artificial urine within 30 seconds.

According to DE-PS 31 28 100, the acceleration of the liquid absorption can be achieved by adding various water-soluble substances such as sugars, urea or aluminum sulfate.

A partial improvement in the blood uptake rate was achieved according to DE-OS 28 44 956 and EP-PS 0009977 in that a partially synthetic or fully synthetic absorbent in powder form subsequently with polyethers (DE-OS 28 44 956) or with fatty alcohols, fatty acids or esters ( EP-PS 0 009 977), mostly dissolved in organic solvents, is treated.

The object of the invention is to improve the known polymers used as absorbents with regard to their absorption rate for water and aqueous liquids such as urine or blood, and to increase the solubility and dissolution rate of water-soluble polymers. It has now surprisingly been found that the uptake rate for water and aqueous solutions can be significantly increased if a finely ground polymer having a particle size distribution of <0.2 mm, preferably less than 0.1 mm and particularly preferably less than 0.05 mm, by conventional methods agglomerated and thereby a coarser grain than the original product had, a grain distribution of 0.1 to 0.5 and particularly 0.2 to 1.0 mm being preferred in the agglomerated polymer. However, it is also possible to produce end products with particles that are larger than 1 mm.

The agglomeration is preferably carried out with an aqueous solution or a water-containing mixture of the agglomeration aid, in that the agglomeration aid is brought together in a suitable manner with the polymer to be agglomerated. The agglomeration aid is preferably sprayed onto the polymer to be agglomerated in aqueous solution or dispersion while it is kept in motion. However, the agglomeration aid can also be dissolved or dispersed in a water-miscible or immiscible organic solvent or a mixture of water and such a solvent. Very good. the fluidized bed, which can be operated by means of a suitable inert gas, preferably air, is suitable for this. The air is advantageously heated immediately to remove the water from the system and to dry the type of agglomer. In terms of apparatus, a fluidized bed dryer has proven to be particularly advantageous for carrying out the method. The individual process parameters as stated The amount of polymer, amount of air, amount of agglomeration aid and air temperature and duration of the agglomeration treatment can be determined by simple experiments.

The agglomeration can also be carried out in a mixer equipped with a spraying device and with a rotating mixing tool equipped with guide vanes which thoroughly scrape the walls of the mixer. After a certain speed of the agitator is reached, the individual granules are thrown out of the material mass when the rotating guide vanes of the mixing tool emerge, and a fluidized-bed powder is formed in this way. At this stage, the dispersed or dissolved agglomeration aid is sprayed on with a nozzle. The device can be operated at room temperature or with an existing heating or cooling jacket at higher or lower temperatures.

The polymers that can be agglomerated 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 hydroxyalkyl cellulose, starch and starch derivatives and vegetable gum (xanthan gum, alginic acid) and their salts the polymers or copolymers based on (meth) acrylic acid or (meth) acrylic acid derivatives are also suitable, these being primarily the homo- or copolymers of acrylic, methacrylic, acrylamidomethyl propane sulfonic acid, the salts of these acids , the acrylic or methacrylamide with each other or with Vinyl pyrrole idon and / or vinyl acetate. The above polymers can also be crosslinked by means of an at least bi-functional crosslinker so that they are only swellable but not soluble in water. All of these polymers are made by known methods.

As an agglomeration aid, the starting material itself, i.e. the water-soluble or water-swellable polymers are used on a synthetic or natural basis (polysaccharide base in dissolved or swollen state). Examples of such water-soluble or water-swellable polymers on a natural basis are starch, in particular maize starch, cellulose derivatives such as carboxymethyl cellulose, alkyl or hydroxyalkyl cellulose, starch and starch derivatives and vegetable gum (xanthan gum, alginic acid) and their salts, and the polymers or copolymers based on them on a synthetic basis of (meth) acrylic acid or (meth) -acrylic acid derivatives such as the homo- or copolymers of acrylic, methacrylic, acrylamidomethylpropanesulfonic acid, the salts of these acids, of acrylic or methacrylamide with each other or with vinyl pyrrolidone and / or vinyl acetate and polyvinyl alcohol. The above polymers can also be crosslinked by an at least bifunctional ionic crosslinking agent so that they are only swellable but not soluble in water.

However, it is also possible to use low or high molecular weight polymers which are present as emulsion polymers in an aqueous dispersion in the form of the tiny spherical particles solubilized by the emulsifier, both forms of emulsion "Oil-in-water" (for water-insoluble polymers) and "water-in-oil" (for water-soluble polymers) are possible. As is known, the oil phase usually consists of water-immiscible organic solvents such as aliphatic or aromatic carbon water (eg hexane, toluene).

Examples of polymers which can form oil-in-water emulsions are polymers of butadiene, styrene, isoprene, chloroprene, acrylonitrile, vinyl acetate, vinyl and vinylidene chloride, alkyl acrylate and methacrylate and copolymers of these monomers with one another and also with one another Methylstyrene, isobutylene or ethylene.

As examples of polymers that are used in water-in-oil emulsions, the above-mentioned. water-soluble or water-swellable polymers or /. Copolymers based on (meth) acrylic acid derivatives, which can be uncrosslinked or crosslinked.

In addition, other substances that are capable of agglomeration can also be used. Thus, agglomeration aids can also be used in products which, according to DE-PS 31 28 100, are added to the polymers to improve the rate of liquid absorption.

To determine the uptake rate, the uptake of model urine is carried out according to the demand absorbency test (WF hose, lecture index 1978, Amsterdam) and the uptake rate after 60 seconds as well as the maximum uptake and retention 20 or 40 minutes determined. The measuring device consists of a burette, which is filled with the model urine solution (2.0% urea, 0.9% NaCl, 0.1% MgSO ₄ and 0.06% CaCl ₂ dissolved in distilled water), and a sample table, which is provided with an opening for the model urine solution outlet connected to the measuring burette. 0.5 g of the product according to the invention is mixed with 5 mg of Aerosil 200 in the form of a circular surface of 4.5 cm in diameter, centered over the liquid outlet, sprinkled uniformly on the sample table covered with a thin fleece (10 × 13.5 cm). By closing the hose and applying slight pressure, the model urine solution is brought into contact with the powder product so that the model urine solution can be absorbed by the product according to the invention. The absorbing amount of the model urine solution is read after 60 seconds and after 20-30 minutes the first maximum value. The retention was then determined by loading the swollen gel with a weight of 10 g / cm ² ; the time of exposure was 5 minutes. The 60 second, maximum and retention values determined are summarized in the examples in tables.

As a further method for determining the liquid absorption rate over a short period of time, a teabag test was carried out, the liquid absorption of 0.2 g test substance without aerosil additive being determined gravimetrically after 15 seconds in a teabag, and converted to 1 g product. The invention further relates to disposable products for hygiene articles, such as diapers or sanitary napkins, containing a polymer according to claim 1 as an absorbent for body fluids, such as water and urine.

Examples 1 to 7;

The agglomeration of the powdery polymer was carried out in a fluidized bed dryer. The device consists of a vertical conical metal cylinder, which is closed at the lower end with a sieve bottom and provided with a device for sucking in air. An adjustable amount of air flows through the granular product to be treated in this cylinder until the individual granules start to move, as a result of which the fluidized or fluidized bed is thoroughly mixed. At this stage, the dissolved agglomeration aid is sprayed on using a nozzle. The amount of the auxiliary, the amount of air and the air temperature can be varied within certain limits.

For examples 1 to 7, the device was filled with 1000 g of finely ground, powdery, partially crosslinked polyacrylic acid, with 90% by weight grain fraction, below 90 μ and a model urine uptake rate of 15 ml / g (DAT 60 sec value) and to 110 ° C warmed with the air flow. The polymer was then agglomerated in the fluidized bed within 5 to 15 minutes by spraying on the aqueous solutions of low molecular weight polyacrylic acids. The test conditions and the results are summarized in the table below. A yield of the agglomerated particles of 89-95% by weight of the grain fraction 90-630 μm was obtained, the agglomerated product showing an improvement in the initial absorption rate (DAT-60-Sec value) from 15 to 230 ml and more .

Examples 8 to 12:

In the same device, the finely ground polymer as in Examples 1 to 7 but with a different particle size distribution (88% by weight of less than 150 μm, see Table 2) at 120 ° C air temperature with an aqueous solution of high molecular weight acrylic acid / acrylamide copolymer (M. _v = 8.10 ⁶ g / mol) agglomerated with and without the addition of sodium chloride. A yield of the grain fraction 150-850 μm of 53 to 90% by weight was obtained and an improvement in the initial absorption rate. The results are summarized in the table below.

Examples 13 to 15

A finely ground acrylic acid copolymer with a very low degree of crosslinking and 100% by weight grain size below 90 μ (model urine uptake rate -DAT 60 sec value of 2.2 ml / g) was mixed at 120 ° C. with an aqueous solution of high molecular acrylic acid / acrylamide copolymer ( M _v = 0.10 ⁶ g / mol) agglomerated and then sprayed with an aqueous solution of aluminum sulfate at the same temperature. After this treatment, the initial absorption rate of this product rose from 2.2 ml / min to 12-14 ml / min, with a yield of the grain fraction 90-630 μm of 72-85 wt. -% was achieved. The test conditions and the results are listed in Table 3.

Examples 16 and 17

A finely ground, partially crosslinked acrylic acid copolymer with a grain weight of 96% by weight below 90 μ and model urine uptake speed of 18 ml / g (15 sec, teabag test) was at 50 ° C with an aqueous solution of low molecular weight polyacrylic acid (M _v = 6,000), in which a very finely ground, weakly crosslinked polymer was swollen, agglomerated in the same device as in the previous examples. The solution of the agglomeration aid was metered in with a peristaltic pump and sprayed under pressure.

A yield of the grain fraction 90-300 μm of 60 to 65% by weight and of the grain fraction of 300-800 μm of approximately 24% by weight was obtained. The results and test conditions are summarized in Table 4 below.

Examples 18 and 19

A finely ground, high molecular weight, water-soluble polyacrylamide with 92% by weight grain size below 90 μ and a molecular weight of 4.10 ⁶ was agglomerated at 65 ° C. with an aqueous solution of polyacrylic acid in a fluidized bed dryer.

A yield of 80-85% by weight of the grain fraction 90-300 μm and 6-20% was obtained. -% of the grain fraction 300 - 800 μm obtained. The test conditions and results are summarized in Table 5.

When 0.1% solutions were prepared, it was found that the agglomerated products (Examples 18 and 19) dissolve completely in water very quickly, within 20-30 seconds. In contrast, the starting product dissolves much more slowly, lumps form when the solution is prepared under the same conditions, and it takes 20-30 minutes to produce a homogeneous solution.

Examples 20 to 22:

A finely ground, partially cross-linked acrylic acid copolymer with 92% by weight grain size below 90 μ and a model urine uptake rate of 18 ml / g (teabag test, 15 sec) at 90 ° C with an aqueous solution of an agglomeration aid (starch, polyvinyl alcohol) in the same device as in the previous ones Examples agglomerated. The solution was dosed with a peristaltic pump and sprayed under nitrogen pressure. There was a yield of the grain fraction 90-300 μm of 55-65 Gevi. -% and obtained on the grain fraction of 300-800 microns from 32 - 42 wt .-%. The results and test conditions are summarized in Table 6.

Examples 23 to 26

A finely ground acrylic acid polymer as in Examples 20-22 was sprayed at 80 ° C. in a fluidized bed dryer with a solution of a water-soluble compound (component B) according to DE-PS 31 28 100. The solution was dosed with a peristaltic pump and sprayed with compressed air. The results and test conditions are summarized in Table 7.

Examples 27-33:

A finely ground, partially crosslinked acrylic acid copolymer with 91.5% by weight grain size below 90 μ and a model absorption rate of 18 ml / g (15 sec tea bag test) was at 40 ° C. with an aqueous dispersion of polyacrylic acid ester or polyvinyl acetate in the same device as in the previous examples agglomerated. The dispersion of the agglomeration aid, possibly diluted with water, was metered in with a peristaltic pump and sprayed under pressure. There was a yield of 90 to 300 μm in the grain fraction of 50 to 88% by weight and in the grain fraction of 300 to 800 μm from 10 to 50% by weight. -% receive. The results and test conditions are summarized in Table 8 below.

At games 34 -38:

The agglomeration of the powdery polymer was carried out in a mixer with a rotating mixing tool. The device consists of a vertical or horizontal metal cylinder (volume 6000 ml), the mixing tool of which is equipped with guide vanes, which scrape the walls of the mixer thoroughly, and a device for spraying. After a certain speed (300 rpm) of the agitator has been reached, a powder fluidized bed forms over the entire length of the metal cylinder when the rotating guide vanes of the mixing tool emerge from the individual granules of the bulk material that have been thrown out. At this stage, the dispersed or dissolved agglomeration aid was sprayed on with a nozzle. The device was operated at room temperature.

For Examples 34 to 38, the device was filled with 1000 g of finely ground, powdery, partially crosslinked polyacrylic acid, which had a grain weight of 88% by weight below 90 μ and a model urine absorption capacity of 16.5 ml / g (15 sec teabag test) Stir at normal temperature within 5 -15 minutes by spraying the aqueous solutions and / or dispersions agglomerated. The test conditions and the results are summarized in Table 9 below. A good yield of the agglomerated particles (84-99% by weight of the grain fraction 90-800 μm) was obtained, the agglomerated product improving the initial absorption rate (15 sec teabag test) from 16 (starting product) to 32 to 45 ml / G showed.

Claims

PATENT CLAIMS

1. Water-soluble or water-swellable natural or synthetic polymers with high absorption capacity for water and aqueous liquids, obtainable by agglomeration of a finely divided, powdery starting material by means of a solution or dispersion of an agglomeration aid in water, a water-miscible or immiscible organic solvent or a mixture of water and such an organic solvent and, if appropriate, further additives which have an agglomerating action.

2. A process for the preparation of water-soluble or water-swellable natural or synthetic polymers with high absorption capacity for water and aqueous liquids, characterized in that a finely divided, powdery starting material of the polymer by means of a solution or dispersion of the agglomeration aid in water, a water-miscible or not miscible organic solvent or a mixture of water and a water-miscible or immiscible organic solvent agglomerated.

3. The method according to claim 2, characterized in that one uses a starting material with a grain size of <0.2 mm, preferably <0, 01, in particular <0.05 mm.

4. The method according to any one of claims 2 to 3, characterized in that the agglomeration by means of an aqueous solution or a water-containing Dispersion of the agglomeration aid is made.

5. The method according to any one of claims 2 to 3, characterized in that the agglomeration is carried out by means of an aqueous solution or a water-containing mixture of the agglomeration aid.

6. The method according to claim 5, characterized in that the agglomeration is carried out in the fluidized bed.

7. The method according to any one of claims 2 to 6, characterized in that the agglomeration is carried out by spraying on the aqueous solution or mixture of the agglomeration aid.

8. The method according to any one of claims 2 to 7, characterized in that natural polymers based on eblysaccharides or synthetic polymers based on (meth) acrylic acid derivatives are used as the starting material, which are optionally weakly crosslinked.

9. The method according to any one of claims 2 to 7, characterized in that the agglomerating aid as the agglomerating polymer itself or low molecular weight polymers based on

(Meth) acrylic acid is used.

10. The method according to claim 6, characterized in that the fluidized bed is operated with heated air.

11. Use of the polymers according to claims 1 to 10 as absorbents for water and aqueous liquids, in particular body fluids.

12. Disposable products for hygiene articles, such as Diapers or sanitary napkins containing a polymer according to claim 1 as an absorbent for body fluids, such as water and urine.