DE19654745C5 - Biodegradable absorbent, its manufacture and use - Google Patents

Abstract

A process for producing a porous absorbent from a crosslinked carboxymethyl or carboxy polysaccharide derivative, characterized in that a fully neutralized ionic carboxymethyl or carboxy polysaccharide derivative with a crosslinking, selected from the group consisting of malonic acid,
Succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, itaconic acid, sebacic acid, citric acid, mucic acid, sugar acid,
Furandicarboxylic acid and butanetetracarboxylic acid, or an ionic partially neutralized polysaccharide derivative without crosslinking in the presence of an amount of water of 10 to 80% by weight (based on the polysaccharide derivative), optionally in the presence of xanthan, alginic acid, pectin, pectic acid, guarane, tragacanth, karaya,
Carrageenane or gum arabic, and then the dough in a one-step process in a preheated reaction apparatus in the form of a drum dryer, powerful convection drying oven or waffle iron for 10 to 30 minutes at 130 to 180 ° C or in a microwave oven for 10 to 200 sec at 110 to 180 ° C with rapid evaporation of the water subjected to drying and crosslinking and then the product is crushed.

Description

The invention relates to networked Polysaccharide derivatives and the manufacture of absorbent materials Completely based on renewable raw materials and therefore completely organic are degradable. These absorbent materials can quickly become aqueous liquids in a big one Pick up and tie scope. The benefit is based on their use for the production of water storage agents for single use in Hygiene articles, animal hygiene articles, of moisture protection in packaging materials etc.

Absorbents with high absorbency for aqueous liquids have long been known. They are not based on renewable raw materials and are fully synthetic absorbents from petroleum products. These include, for example, cross-linked synthetic polymers and copolymers based on acrylic or polyacrylic acid. ( U.S. Patent 4,018,951 ). These known synthetic absorbents are practically insoluble in water, absorb many times their weight in aqueous liquids and are hardly biodegradable.

Furthermore, according to DE-OS 42 06 856 Mixtures of polysaccharides, polyacrylates, various auxiliaries (e.g. fibers) and additional crosslinking agents (e.g. addition of borates after component mixing) are proposed, the polyacrylate always being the main absorber. The polysaccharides are seen as building blocks for the absorber materials in order to obtain biodegradable components.

In the past, after today State of the art, processes described have the polysaccharides no decisive contribution as an absorber.

As the EP-A-0 670 180 Absorbents are known which can be obtained by reacting polysaccharide particles with a crosslinking agent. From the DE-A-42 06 856 Polymer compositions are known which essentially consist of a water-soluble and / or water-swellable polymer based on polysaccharides and a water-swellable synthetic polymer.

In the US-A-4,959,341 describes the production of an absorber based on carboxymethyl cellulose, which consists of a mixture of carboxymethyl cellulose, cellulose fibers, a hydrophobic component and Al (OH) ₂ OOCCH ₃ ⋅1 / 3H ₃ BO ₃ as crosslinking, the borate crosslinker only crosslinking the carboxymethyl starch of fluid intake. These absorbers have good absorptive properties, but show disadvantageous gel blocking (ie, when they come into contact with water, the outer layers of the absorber stick together and prevent further penetration into the absorber). In addition, these absorbers are easily separated by mechanical loads, such as screening or conveying, so that they are no longer present as a homogeneous product, which limits their possible uses.

The natural swelling agents from polysaccharides play only a subordinate as an absorbent material for aqueous liquids Role because they have a low absorbency. A composition from pectin (15–60%) and cellulose material (15-80%) only absorbs two to five times Amount of aqueous liquids across from the usual Zellstoffmatrial. Biodegradability, on the other hand, is advantageous such native swelling agents, since the natural polymers, such as cellulose, Strength, Proteins, as well as their derivatives in biological systems in relative terms be dismantled in a short time.

When developing absorbers (especially superabsorbers), the focus is not only on a very high free swelling capacity, also called free swelling capacity (FSC), but also on the gel strength. Absorptino capacity (free swelling capacity.) And gel strength, however, are opposing properties in a networked system, as is the case, for. B. in U.S. Patent Re 32,649 is described. This means that polymers with a particularly high absorption capacity have only a low strength of the swollen gel with the film that the gel is deformable under an applied pressure and prevents further liquid distribution and absorption. However, a balanced relationship between absorption absorbency and gel strength must be striven for, so that the absorption and transport of liquids are ensured when using such absorbers. It is not only important that the absorber can retain liquid under the action of a load after the absorber has been able to swell freely, but also that liquids are taken up against a simultaneous pressure, as is the case under practical circumstances with hygiene articles when a person is on a medical article sits or lies or it comes to the absorber gel due to body movements to develop shear forces. When shear forces occur, the gel strength is of particular importance.

• I. Die Absorber sollen vollständig aus Derivaten nativen Ursprungs bestehen.
• II. Die trockenen Absorber sollen eine hohe mechanische Festigkeit aufweisen.
• III. Die Absorber sollen eine vergleichsweise hohe Aufnahmegeschwindigkeit und Absorptionskapazität für wäßrige Flüssigkeiten besitzen.
• IV. Die Absorber sollen im gequollenen Zustand eine ausreichend hohe Gelstabilität aufweisen und die Absorberkörner weitgehend separiert, in einzelnen Partikeln vorliegen.
• V Die Absorber dürfen nicht zum Gelblocking neigen.
• VI. Die Absorber sollen eine genüge nd hohe Absorptionskapzität. unter Belastung nach freier Queellung und unter Druck während der Quellung für wäßrige Flüssigkeiten besitzen.
• VII. Die Absorber sollen weitgehend und in einem angemessenen Zeitraum biologisch abbaubar sein.
• VIII. Die Absorber sollen im trockenen Zustand eine gute Lagerstabilität. aufweisen.

There is therefore a need for absorbents with higher absorption capacities for aqueous liquids and higher gel strengths which, at the same time, are to be completely biodegradable, but which do not have the deficiencies described above. have, are particularly suitable for use in disposable items and meet the following requirements:

• I. The absorbers should consist entirely of derivatives of native origin.
• II. The dry absorbers should have a high mechanical strength.
• III. The absorbers are said to have a comparatively high absorption speed and absorption capacity for own aqueous liquids.
• IV. The absorbers should have a sufficiently high gel stability in the swollen state and the absorber grains should be largely separated and be present in individual particles.
• V The absorbers must not tend to gel blocking.
• VI. The absorbers should have a sufficiently high absorption capacity. under pressure after free swelling and under pressure during swelling for aqueous liquids.
• VII. The absorbers should be largely biodegradable within a reasonable period of time.
• VIII. The absorbers should have good storage stability when dry. exhibit.

• – Ein ionisches carboxylgruppenhaltiges Polysaccharid-Derivat, oder eine Mischung aus mehreren ionischen oder teilneutralisierten Polysaccharid-Derivaten.
• – Gegebenenfalls mehrfach funktionelle Vernetzer, vorzugsweise mehrbasige organische Säuren.
• – Wenig Wasser (10–80 Gew.-% bezogen auf das Polysaccharid-Derivat) als Homogemsierungmittel in der Ausgangsmischung (geringerer Anteil als von den Feststoffkomponenten Polysaccharid und Vernetzer) bei relativ kurzer Herstellungszeit oder Reaktionszeit.

The present invention is based on the finding that absorber materials can be produced simply and quickly from renewable raw materials with very little solvent (water), using a starting mixture which essentially consists of the following constituents

• - An ionic carboxyl-containing polysaccharide derivative, or a mixture of several ionic or partially neutralized polysaccharide derivatives.
• - If necessary, multi-functional crosslinking agents, preferably polybasic organic acids.
• - Little water (10-80 wt .-% based on the polysaccharide derivative) as a homogemating agent in the starting mixture (less than that of the solid components polysaccharide and crosslinker) with a relatively short production time or reaction time.

Included due to the native origin the absorbers obtained no residual monomers of concern like that Polyacrylate-based absorber. The absorbers according to the invention have a comparatively high absorption capacity and absorption speed for aqueous liquids (even under pressure). They show no tendency to gel blocking (i.e. H. the outer layers of the absorber stick when they come into contact with water not and do not prevent further penetration of the liquid in the absorber) and are mechanically stable. In swollen condition largely separate them into individual particles, they are not watery and show high gel stability on. These properties can can be set individually with the degree of networking.

The object of the invention is therefore a biodegradable, solid absorbent for water, aqueous solutions and Body fluids available by crosslinking an ionic carboxymethyl or carboxy polysaccharide derivative in the presence of 10-80 % By weight (based on the polysaccharide derivative) of water at 110-180 ° C., where in the event that crosslinking agents are used, the dicarbon, tricarbon or polycarboxylic are.

The absorbent according to the invention has high absorption capacity and high gel strength so that no sticking of the outer layers of the absorbent particles observed on contact with water can be.

Usually is networking about a period of 15 to 60 minutes. In the case of implementation in a microwave oven can considerably shorter Response times can be realized; for example in the seconds range. Because of the used according to the invention Temperature becomes regular at the same time drying of the product take place. The drying can can also be carried out in a separate step, if appropriate at a lower temperature, e.g. B. after the crosslinking reaction is about 80% complete. In principle, all ionic ones are suitable Polysaccharide derivatives, the. can be covalently networked. For this counting especially carboxymethyl or Carboxy derivatives of starch, Cellulose, guar gum, locust bean gum, amylose and amylopectin, z. B. carboxymethryl starch, Carboxy starch, dicarboxy starch, tricarboxy starch, carboxymethylamylnpectin, Carboxymethylamylose, carboxymethylguaran or carboxymethylcarobin in partially or fully neutralized form. The polysaccharide derivatives should have an average degree of substitution less than have three, preferably range from 0.3-2.0 and particularly preferred in the range of 0.3-1.5. Fully neutralized polysaccharides. are particularly easy to use Network multi-functional networkers. Are preferred to for this purpose dicarbonic, tricarboxylic or polycarboxylic acids and / or their anhydrides or partially neutralized salts used, e.g. As malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, itaconic acid, sebaic acid, citric acid, mucic acid, sugar acid, puranedicarboxylic acid, butanetetracarboxylic acid, polyacrylic acid, etc. In the case of partially neutralized ionic polysaccharides you can work without the addition of a crosslinker. The crosslinker is usually used in a concentration of 0.001 to 0.4 mol (based on 1 mol Polysaccharide derivative.), Preferably 0.005 to 0.15 mol, used. In the case of partially neutralized polysaccharide derivatives, i.e. H. without crosslinker, there is a molar ratio of the acid groups (H form) to free Hydroxyl groups (OH groups) from 0.003 to 0.2 have been proven.

According to the invention, an absorbent or swelling agent for water, aqueous solutions and body fluids is thus obtained which can consist of 100% biodegradable, renewable raw materials. The main component. this absorbent is a polymer composition consisting of the crosslinked ionic carboxyl group-containing polysaccharide derivative. But it can also be a Wed several ionic polysaccharide derivatives. In addition to the crosslinked polysaccharide derivatives, other native polysaccharides can be used, such as xanthan, alginic acid, pectin, pectic acid, guar gum, tragacanth, karaya, carrageenans or gum arabic

The invention also relates to a method for producing the abovementioned absorbents and / or Swelling agent. In the method according to the invention, fully neutralized ionic polysaccharide derivatives with a crosslinker and / or partially neutralized ionic polysaccharide derivatives without crosslinker with water (or another suitable polar solvent, such as Ethanol) in one for that suitable mixing device mixed. or pasted. The amount of water should be around 10-80 % By weight (based on the polysaccharide derivative). Preferably becomes a water amount of 30-60 Wt .-% used. The mixing or pasting is then preferred at 110-180 ° C at 130-160 ° C, cross-linked. At the temperature specified here, a drying reaction also takes place instead, which is for the later Packaging to a solid absorbent has proven to be favorable Has. The period for crosslinking and drying is usually 5-60 minutes, preferably 15-30 minute The invention. method allows thus the production of a particularly advantageous product in particularly simple and environmentally friendly way.

Has been particularly preferred emphasized to carry out the crosslinking and drying in a microwave oven. in this connection is the for the reaction time required for networking is usually only 10-200 seconds.

Furthermore, it has proven to be beneficial exposed the mixing of the polysaccharide derivatives in dry or in a slightly moistened to swollen state with if necessary Carry out crosslinker and water in a mechanical mixing device, for example a trough kneader, single-shaft mixer, single-screw extruder, Twin shaft mixer with co-rotating and opposite Twin screw, twin-shaft continuous mixer, continuous multi-shaft device (for example Four-screw extruder) etc.

The invention also relates to the use of the absorbent material described above for recording and / or reluctance of water and / or aqueous solutions, especially of aqueous body fluids such as urine or blood, in disposable absorbent products for hygienic, surgical and other medical purposes such as baby diapers, incontinence articles, Tampons and sanitary napkins. The absorption material according to the invention can be but also for the absorption and / or retention of water and / or aqueous solutions in use technical products, for example in cable jackets, animal hygiene articles, Packaging materials, plant culture vessels, for soil improvement etc. In addition the absorption material is suitable for the following controlled Release of absorbed water and optionally in the aqueous polysaccharide gel dissolved or bound substances (e.g. nutrients or active ingredients) to one Environment, such as biological systems, seeds, plants or microorganisms. Stronger networked products with higher Degree of substitution are also suitable as ion exchangers (biological degradable) or as a waste water treatment agent.

As already stated above, are suitable all ionic polysaccharide derivatives that cross-link covalently let, for the preparation of the polysaccharide derivatives according to the invention. In the case of starch, Cellulose, guar gum, locust bean gum, amylose and amylopectin derivatives must the average degree of substitution (DS) must be less than three, otherwise would be there are no free networking points or it would have to selected the corresponding H-shape Diols or polyols can be used as crosslinking agents (e.g. Sorbitol). The carboxymethyl derivatives and the carboxy derivatives in are preferred their fully or partially neutralized form, especially the carboxymethyl starch and the carboxy starches, preferably with a DS of 0.3-2. The. native ionic Polysaccharides, such as carrageenans, alginic acid, pectic acid, tragacanth, Karaya, ghatti, gum arabic, xanthan, etc., are worse network, are not temperature-resistant and also much more expensive. With the same amount of crosslinker, carboxymethyl starch (CMS) and amylopectin (CMAp) very good, carboxymethylamylose (CMAm) good, Carboxymethylguaran (CMG) less well and carboxymethylcellulose (CMC) network poorly, reflecting the general reactivity of each Corresponds to polysaccharides.

Polysaccharide ethers, in particular Cellulose ethers have been around for a long time known. Methods for their preparation can be found in the general manuals for carbohydrates z. B. R.L. Whistler (Methods in Carbohydrate Chemistry, Academic Press, New York and London, Vol. IV, pp. 304-312, 1964).

To produce the insoluble product, covalent crosslinking of the polysaccharide derivatives with organic acids is preferably carried out. When partially neutralized carboxymethyl starches are used, the crosslinking takes place via the non-neutralized carboxyl groups of the molecules, and the additional use of polybasic acids only leads to stronger crosslinking. The crosslinking takes place via ester bonds, which are premature for biodegradability. The following crosslinking agents are suitable: malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, itaconic acid, sebacic acid, citric acid, mucic acid, sugar acid, furandicarboxylic acid and butanetetracarboxylic acid. These acids can mainly be produced on the basis of renewable raw materials. The dicarboxylic acids show similar crosslinking properties and are similar to sodium dihydrogen citrate (lemons acid. partially neutralized to 1/3), which then results in analog product properties.

The anhydrides of these acids directly use is less advantageous because it is insufficient in water solve and the components are not sufficiently homogenized.

For good to very good gel strengths are not partially neutralized acids use, preferably succinic acid, citric acid, glutaric acid and Butane tetra-carbnnsäure. This can be explained by that these. Acids during the Reaction (or heating period) can form anhydrides react faster and more extensively, d. H. network. In contrast to other productions the acids are not partially neutralized here, since pH and degradation reactions while the relatively short heating are not envious.

Depending on the type of crosslinking agent and the one you want Degree of crosslinking (or the gel strength), 0.05 to 0.2 mol, based on one mole of polysaccharide derivative, required for the implementation.

First, the crosslinker will be in a little Water dissolved and partially neutralized with sodium hydroxide solution (option). The crosslinker solution is with an appropriate amount of carboxymethyl derivative to a homogeneous Mixed dough. Advantageous. is. kneading with a suitable one Apparatus (e.g. kneader, powerful mixer, etc.). The water content in the dough should be 20–50% amount, preferably 35-40% Water content to use. The mixing or kneading time is depending on water content and mixed intensity 5–60 minutes, preferably 20 Minutes.

The dough is preheated Reaction apparatus introduced. In principle, all devices are for this suitable that. a. rapid heat transfer onto the dough and thus allow the water to evaporate quickly. Roller dryers, powerful convection drying ovens, microwave ovens, waffle irons, Drum dryer, jacket-heated powerful. Mixer etc. at Use of tumble dryers and mixers will be partial. very fine-grained Products obtained (grain fractions are less than 150 microns), so that the grinding deleted but the product application options highly limited become. The temperature should be during the production are at 110-170 ° C. At higher Temperatures became too strong yellow-brown discoloration and observed worse properties. At low temperatures the dwell time in the reaction apparatus is too long. Preferably a temperature of 130–160 ° C should be selected. This was also done through thermogravimetric. Investigations confirmed.

In order to allow the dough water to evaporate quickly, the dough surface should be made as large as possible (e.g. by rolling it out). Depending on the initial water content, the specified temperature and the dough surface used, the product is made after 10–50 minutes. With a dough surface of approx. 250 cm ² (approx. 30 g) and a temperature of 150 ° C the product is ready after 20–30 minutes. Guaran derivatives are completed in about 40 minutes.

Through the use of microwave ovens the production is much shorter, but requires sufficient experience in handling and Execution. For example, the product is finished after approx. 100 seconds and after about 120 seconds of treatment it may be unusable; when using an RF output power of 500 W and a frequency of 2450 MHz.

After the product is dry (end. the reaction), further heating has no particular advantages (e.g. better product properties). By the rapid evaporation of the water swells the product, which makes it very porous (which means the fast absorption rate through the capillary forces explained in the pores; this can be derived from SEM images). The bloating is the stronger the more water was used.

The finished product in solid form is crushed, ground and sieved. The grain fraction 200–500 μm is used for the absorption tests.

The method according to the invention leads to the described embodiments to products that still contain a certain water-soluble fraction; at Most products have 10-15%, sometimes over 30%. For many Uses disrupts this share is not, so that a removal of the water-soluble Shares mostly superfluous. In some cases the further use of this absorbent product. the water-soluble part even advantageous because it has its adhesive strength, for example Polysaccharide underlays or surfaces increased (cellulose, cellulose fiber or films, or starch films). Should the water soluble Disrupt proportion so it can be removed using various washing methods. become. In most cases leads the Removal of water soluble Shares also for better absorption properties. This behavior is understandable, since the absorption results are based on one gram of product and in the case of technical products with soluble components, the whole Weighing taken into account will, although the soluble proportions nothing about absorptive capacity contribute. Have been advantageous in washing out the soluble fractions Water or aqueous-organic solvent shown. When using fully demineralized water for washing out it has to with a significant excess of water across from the absorber. Usually must on one kilogram of product approx. 50-100 Liters of water used. become. The washing process is carried out by stirring the swollen product carried out in the washing liquid with subsequent filtration. Preferably a drum filter is suitable for this, the washing water on is easily separated by centrifugation.

Using common separation processes (e.g. Reverse osmosis), the wash water can be removed from the soluble Shares are cleaned and reused. The severed soluble Shares can can be used again as starting material. To the considerable amounts To reduce wash water, we recommend. Use of organic-aqueous mixtures, preferably Methanol / water, ethanol / water or acetone / water. With that the Swelling of the product significantly reduced and to one kilogram Product will only be about 5-10 Liters of washing mixture are used, the mixing ratio being preferred Is 50%.

test methods

FSC (Free Swelling Capacity)

Weigh 0.2-0.25 g of product into a commercially available tea bag. The open end of the tea bag is sealed and the tea bag is placed in a photo bowl with a 0.9% NaCl solution. The tea bag is pressed briefly so that it is wetted by all the ropes due to the liquid. becomes. The test time is. a. Hour. The tea bag is then left to drain for 5 minutes, hanging on a clothespin. The tea bag is then weighed (in grams, g) and the absorption value is determined:

CRC (Centrifuge Retention Capacity)

The tea bag at the FSC determination is in a commercial spin-dryer (with an interior diameter of 24 cm) 3 minutes at 2800 rpm flung, which corresponds to 26.6 times the acceleration of gravity. The centrifuged product is then weighed. The calculation is carried out analogously to the formula given above.

Absorption under load. (Absorption Beast Load, AUL)

In this test procedure, round Small plastic pot (d = 2.985 cm) used, which is open at one end and at the other End with a net (mesh size 100–150 μm). Into this potty the product weighed in and evenly laid on the net. The product is weighed in two tests. 0.05 g and 0.4 g as tested. was that the AUL value worsens with increasing sample weight. The. usual weight is 0.15 g. This phenomenon is not due to errors, but on the behavior of the gel particles under pressure: at higher weights there are several layers of particles that. lie on top of each other. By the external pressure while absorption there is close contact between the layers and therefore also a good liquid transport. However, the gelatinous particles penetrate one another so that they do not there is always an isolated swelling of the individual grain. at low weights the granules isolated on the web surface distribute and swell freely so that a higher AUL value is obtained. This phenomenon is more or less pronounced in all absorbers (also in the synthetic). Even at high gel strengths. this effect too observe, since apparently the intrusion is inevitable. It is not a gel blocking since all layers or grains after the test. present swollen.

On the product. is after the initial weight a. with the potty rim final small plastic disc (d = 2.985 cm; in = 7.59 g ± 0.01 g) and with a cylindrical piece of metal (m = 316 g ± 0.24 g) complained. The tare weight (potty with disc, without metal piece) and Weighed samples are weighed. A glass frit is placed in a photo bowl. placed. The frit. comes with a filter paper (with the same Size.). So much 0.9% NaCl solution is poured into the photo dish that the liquid surface with the surface the frit closes.

Then the pots are placed on the prepared fries. The test time is one hour at a test pressure of 4550 Pa (or O, 66 psi or 46.3 g / cm ² or 300 g / in ² ). Then the metal piece is removed and the potty (potty + plastic disc + swollen product) weighed:

• – Gerät.: Rheometer CSL 100,
• – Meßbedingungen: Kegel-Platte-System, Kegeldurchrmesser 2 cm, Winkel 2°, Temperatur 25°C, Frequenz 1 Hz, vorgegebene Deformation = 2%.

The gel strength. G 'of the swollen absorber was based on U.S. Patent Re 32,649 (respectively. EP 02 05 674 ) certainly.

• - Device .: Rheometer CSL 100,
• - Measuring conditions: cone and plate system, cone diameter 2 cm, angle 2 °, temperature 25 ° C, frequency 1 Hz, predetermined deformation = 2%.

This test is about an oscillation attempt with a given deformation of the gel. The Using the deformation specification is very important as it is this is a linear viscoelastic area. When using of major deformations (e.g. more than 10%) irreversibly destroyed the gel and the values would be not reproducible (since the linear viscoelastic range in the go over the non-linear range would; s. also executions in W.-M. Kulicke flow behavior of substances and mixtures of substances, p. 90, section 2.2.1, Hüthig & Wepf Verlag Basel, Heidelberg, New York 1986).

At the same time, the required oscillating shear stress σ, the gel strength (or memory module) G 'and the loss modulus G '' or the tan (δ) value is determined. The shear stress σ gives how much force is required to get the gel at the given Deform factor. The gel strength is obtained via the memory module. With the help of the tan (δ) value (= G '' / G ') is determined whether the gel is elastic or viscous has (with a tan (δ) <1 the gel is elastic and a tan (δ)> 1 it is viscous flowing). clear shown. the gel is "slippery" if the resulting shear stress σ <10 Pa and the G '<100 Pa. On the other hand, the gel (very) fixed if σ> 100 Pa and G '> 5000 Pa.

Insoluble Shares (UA)

 The insoluble parts give one direct reference to the cross-linked portion of the polysaccharide. to exam a glass filter bowl (size 2) is used for the UA.

Weigh exactly 1 g into a beaker and add 300 ml of double-distilled water. The. Solution is stirred for 30 minutes. Then the solution is left 5 Stand minutes, whereby the gel settles and a supernatant solution forms. The supernatant solution is decanted off via the glass filter tipple and the remaining gel is filled up with 300 ml of fresh bidistilled water. The mixture is stirred for a further 30 minutes. This process is repeated two more times.

Finally, the entire solution is filtered. The beaker is distilled with 100 ml. Washed out water and this. The washing liquid is also filtered through the same glass filter pan. The glass filter plate with the swollen sample is dried for 6 hours in a forced-air drying cabinet at 120 ° C. The glass filter plate is then cooled to room temperature and weighed:

Effects of the washing frequency on the insoluble parts UA (in%) of two samples:

The information in brackets (UA ') refer to the insoluble Proportion of starch derivative used, because the staining takes place only on the starch derivative.

Example of UA and UA '

In sample 1, citric acid and carboxymethyl starch (CMS01) were used as the starting material for crosslinking. The proportion of citric acid in the dry matter was 12.3%, the CMS01 proportion was 83.6% and the rest of 4.1% was due to NaCl (as an impurity of CMS01). Since the degree of crosslinking is normally low (or should be; approx. 1–5%) and NaCl is irrelevant, only the CMS01 can make up the insoluble components. I.e. in this cross-linked sample, 16.4% (12.3% + 4.1%) are soluble anyway. Shares available. Only the remaining 83.6% of the sample are examined for insolubility. When 82.1% of the insoluble parts UA of the entire sample were determined, 98.2% (= UA ') of the CMS01 became insoluble den (98.2% = 82.1 / 83.6⋅100%). This approach is more of a theoretical nature, since this information gives a direct indication of the degree of networking of the CMS.

Determination of the Vernetzergchaltes

Here the proportion of the bound Crosslinker in the purum product determined, the proportion in milligrams Crosslinker per gram of product was carried out. This titrimetric determination with copper sulfate takes place according to the regulation in: H. Klaushofer, E. Berghofer, R. Pieber, strength / Siarch, Vol. 31, pp. 259-261, 1979.

starting materials

The usual short names with a code for the corresponding degree of substitution are used, e.g. B .:
CMS01 = carboxymethyl starch with DS = 0.1
CMS07 = carboxy methyl starch with DS = 0.7
CMC12 = carboxymethyl cellulose with DS = 1.2
CMGl5 = carboxymethylguaran with DS = 1.5
CMAp12 = carboxymethylamylopectin with DS = 1.2

Preparation Examples

All of the following samples in the examples were produced according to the same principle: dissolving the crosslinking agent in an appropriate amount of water, adding the derivative and then mixing or kneading (10 minutes), heating for 20 minutes at 150 ° C. and a dough area of 250 cm ² in one Waffle irons (or in a forced-air drying oven with the same results), grinding and screening to 200–500 μm; this product is referred to below as a technical product. The rest of the sieving is washed twice with an excess of water (100 ml of water are used on 1 g), filtered and then soaked in a forced air drying cabinet at 120 ° C. for 4 hours (depending on the water content). If the gel is very swollen, centrifugation or pressure filtration of the gel is recommended. This product is called product product.

example 1

Product made from 30 g CMS01, 1.118 g citric acid and 16.2 g of water.

Example 2

Product made from 30 g CMS01, 1.677 g citric acid and 16.2 g of water.

Example 3

Product made from 30 g CMS01, 1.957 g citric acid and 16.2 g of water.

example

Product made from 30 g CMS01, 1.246 g sodium dihydrogen citrate and 16.2 g water.

Example 5

Product made from 30 g CMS01, 1.87 g sodium dihydrogen citrate and 16.2 g water.

Example 6

Product manufactured. from 30 g CMS01, 2.181 g sodium dihydrogen citrate and 16.2 g water.

Example 7

Product made from 30 g CMS01, 4.269 g of disodium hydrogen citrate hydrate and 16.2 g of water.

Example 8

Product made from 30 g CMS01, 5.337 g disodium hydrogen citrate hydrate and 16.2 g water.

Example 9

Product made from 30 g CMS01, 6.404 g of disodium hydrogen citrate hydrate and 16.2 g of water.

Example 10

Product made from 30 g CMS01, 1.1l8 g citric acid and 16.2 g of water. The finished one. Dough was sealed for 18 hours ditched.

Example 11

Product made from 30 g CMS01, 1.677 g citric acid and 16.2 g of water. The finished one. Dough was sealed for 18 hours ditched.

Example l2

Product made from 30 g CMSO1, 1.246 g sodium dihydric citrate and 16.2 g water. The finished dough was left locked for 18 hours.

Example 13

Product made from 30 g CMS01, 1.87 g sodium dihydrogen citrate and 16.2 g water. The finished dough has been. Leave closed for 18 hours.

Example 14

Product made from 30 g CMS01, 4.269 g of disodium hydrogen citrate hydrate and 16.2 g of water. The finished one The dough was left closed for 18 hours.

Example 15

Product made from 30 g CMSO1, 6.404 g of disodium hydrogen citrate hydrate and 16.2 g of water. The finished one Batter became. Left locked for 18 hours.

Example 16

Product made from 20 g CMS07, 0.615 g citric acid and 10.8 g of water.

Example 17

Product made from 20 g CMS07, 0.923 g citric acid. and 10.8 g of water.

Example 18

Product made from 20 g CMSO1, 0.686 g sodium dihydrogen citrate and 10.8 g water.

Example 19

Product made from 20 g CMSO1, 1.028 g sodium dihydrogen citrate and 10.8 g water.

Example 20

Product made from 20 g CMS01, 2.348 g disodium hydrogen citrate hydrate and 10.8 g water.

Example 21

Product made from 20 g CMSO1, 3.522 g disodium hydrogen citrate hydrate and 10.6 g water.

Example 22

Product manufactured. as in example 18, but the ground product was again with 10.8 g of water transferred and processed again according to the same procedure determine whether rewetting and heating is worthwhile is.

Example 23

Product made as in example 20, but the ground product was again with 10.8 g of water transferred and processed again according to the same procedure determine whether rewetting and heating is worthwhile is.

Example 24

Product made as in example 4, however, the ground. Product again with 16.2 g of water moved and processed again according to the same procedure determine whether rewetting and heating is worthwhile is.

Example 25

Product made as in example 24 to determine if the repeat procedure is reproducible can be designed and the Properties similar fail.

Example 26

Product made from 20 g CMAp12, 0.578 g sodium dihydrogen citrate and 10.8 g water.

Example 27

Product made from 20 g CMApl2, 1.98 g disodium hydrogen citrate hydrate and 10.8 g water.

Example 28

Product made from 20 g CMAp12,1,164 g sodium dihydrogen citrate. and 10.8 g of water.

example 29

Product made from 15 g CMAp04, 1.8 g of disodium hydrogen citrate hydrate and 10 g of water.

Example 30

Product made from l5 g CMAp04, 3.7 g of disodium hydrogen citrate hydrate and 10 g of water.

EXAMPLE 31

Product made from l5 g CMC12, 0.402 g citric acid and 16.2 g of water.

Example 32

Product made from 15 g CMC12, 0.448 g sodium dihydrogen citrate and 16.2 g water.

example 33

Product made from a mixture with 15 g CMSO1 and 1.5 g xanthan gum, 2.3 g disodium hydrogen citrate hydrate and 10 g water.

Example 34

Product manufactured. from a mixture with 15 g CMSO1 and 3.5 g xanthan gum, 2.6 g disodium hydrogen citrate hydrate and 10 g water.

Example 35

Product made from a mixture with 1.5 g CMSO1 and 1.5 g alginic acid (Na salt), 2.3 g disodium hydrogen citrate hydrate and 10 g water.

Example 36

Product made from a mixture with 15 g CMSO1 and 3.5 g alginic acid (Na salt), 2.6 g disodium hydrogen citrate hydrate and 10 g water.

example 37

Product made from a mixture with 20 g CMSO1 and 4.6 g guaran, 1.2 g sodium dihydrogen citrate and 33.1 g of water.

Example 38

Product made from a mixture with 20 g CMSO1 and 4.6 g guaran, 3.6 g disodium hydrogen citrate hydrate and 36.9 g of water.

EXAMPLE 39

Product made from a mixture with 20 g CMSO1 and 4.6 g tragacanth, 1.2 g sodium dihydrogen citrate and 36.9 g of water.

EXAMPLE 40

Product made from a mixture with 20 g CMSO1 and 4.6 g tragacanth, 3.7 g disodium hydrogen citrate hydrate. and 37 g water.

Example 41

Product made from a mixture with 20 g CMSO1 and 4.6 g karaya, 1.2 g sodium dihydrogen citrate and 36.9 g water.

Example 42

Product made from a mixture with 20 g CMSO1 and 4.6 g karaya, 3.7 g disodium hydrogen citrate hydrate and 37 g water.

The following samples in the examples were made according to the same scheme: dissolution of the Crosslinker in an appropriate amount of water, addition of the derivative and followed by Mixing or kneading (10 minutes). The rolled up dough (Diameter: approx. 4-5 cm) was in a commercially available Microwave oven, with a side radiation source. and turntable, 90-100 Treated for seconds, with an RF output power of 500 W and a frequency of 2450 MHz. The dough doubled. Volume out and you got a dry after the treatment period Product that was worked up as in the examples above.

example 43

Product made from 20 g CMS07, 0.615 g citric acid and 10.8 g of water.

Example 44

Product made from 20 g CMS07, 0.615 g citric acid and 10.8 g water (repetition of Example 43).

example 45

Product made from 20 g CMS07,0,923 g citric acid and 10.8 g of water.

Explanations

Tables 1 and 2

Column 1: Example number

Column 2: Carboxymethyl derivative used

Column 3: Crosslinker used (CiS = Citric acid; N / A CiS = sodium dihydrogen citrate; N / A₂CiS = disodium hydrogen citrate)

Column 4: Molar ratio F of crosslinker and polysaccharide derivative

Column 5: FSC of the technical product

Column 6: CRC of the technical product

Column 7: AUL of the technical product. Numerical values with double information refer to a sample weight of 0.6 g (without bracket) and 0.05 g (with bracket). Numerical values with simple details refer to a weight of 0.15 g.

Column 8: Insoluble shares in% of the technical product

Column 9: Insoluble fractions in% on the polysaccharide derivative

Column 10: shear stress f for 2% deformation of the swollen technical sample

Column 11: memory module G 'in Pa the swollen technical sample

Column 12: Loss angle δ or tan (δ) of the swollen technical sample

Column 13: FSC of the purum product

Column 14: CRC of the purum product

Column 15: AUL of the purum product. Numerical values with double information refer to a sample weight of 0.6 g (without bracket) and 0.05 g (with bracket). Numerical values with simple details refer to a weight of 0.15 g.

Column 16: Linked crosslinker in Milligrams per gram of purum product

Column 17: shear stress in Pa for 2% deformation the swollen purum sample

Column 18: storage module G 'in Pa of the swollen purum sample

Column l9: loss angle δ or tan (δ) of the swollen purum sample.

Abbreviations

N. = not applicable (no provision)
nb = not determined (determination not carried out)
n.mögl. = not possible (determination not possible)
∞ = infinite (value is infinite and cannot be determined)

Table 3

Column 1: Example number

Column 2: Carboxymethyl derivative used

Column 3: proportion of the carboxymethyl derivative in the polysaccharide mixture

Column 4: additionally mixed polysaccharide

Column 5: Share of the additional Polysaccharides in the polysaccharide mixture

Column 6: Crosslinker used (CiS = citric acid; NaCiS = sodium dihydrogen citrate; Na ₂ CiS = disodium hydrogen citrate)

Column 7: Molar ratio F of crosslinker and polysaccharide derivative

Column 8: FSC of the technical product

Column 9: CRC of the technical product

Column 10: AUL of the technical product Numerical values with double information refer to a sample weight of 0.6 g (without bracket) and 0.05 g (with bracket). Numerical values with simple details refer to a weight of 0.15 g.

Column ll: Insoluble shares in% of the technical product

Column 12: Insoluble fractions in% on the polysaccharide derivative

Column 13: shear stress for 2% deformation the swollen technical sample

Column 14: memory module G 'in Pa of the swollen technical sample

Column 15: Loss angles δ and tan (δ) of the swollen ones technical sample

Column l6: FSC of the purum product

Column 17: CRC of the purum product

Column 18: AUL of the purum product. Numerical values with double information refer to a sample weight of 0.6 g (without bracket) and 0.05 g (with bracket). Numerical values with simple details refer to a weight of 0.15 g.

Column l9: shear stress in Pa for 2% deformation the swollen purum sample

Column 20: Memory module G 'in Pa of the swollen one purum sample

Column 21: Loss angle δ or tan ( δ ) of the swollen purum sample

Abbreviations

N. = not applicable (determination not applicable here)
nb = not determined (determination not carried out)
n. possible = not possible (determination not possible)
∞ = infinite (value is infinite and cannot be determined)

Claims (5)

A process for producing a porous absorbent from a crosslinked carboxymethyl or carboxy polysaccharide derivative, characterized in that a fully neutralized ionic carboxymethyl or carboxy polysaccharide derivative with a crosslinking, selected from the group consisting of malonic acid, succinic acid, glutaric acid, Adipic acid, maleic acid, malic acid, tartaric acid, itaconic acid, sebacic acid, citric acid, mucic acid, sugar acid, furandicarboxylic acid and butane tetracarboxylic acid, or an ionic partially neutralized polysaccharide derivative without crosslinking in the presence of an amount of water of 10 to 80% by weight (based on the polysaccharide derivative optionally in the presence of xanthan, alginic acid, pectin, pectic acid, guar gum, tragacanth, karaya, carrageenans or gum arabic, and then the dough in a one-step process in a preheated reaction apparatus in the form of a drum dryer, powerful Circulating air drying oven or waffle iron for 10 to 30 minutes at 130 to 180 ° C or in a microwave oven for 10 to 200 seconds at 110 to 180 ° C with rapid evaporation of the water, subjected to drying and crosslinking and then the product is crushed. A method of manufacturing according to claim 1, wherein the used Polysaccharide derivatives have an average degree of substitution less than 3, preferably in the range 0.3 to 2.0. Method according to one of the preceding claims; carboxymethyl- neutralized as polysaccharide derivatives or carboxy derivatives are used. The method of claim 3, wherein the polysaccharide derivative is itself of strength, Cellulose, guar gum, locust bean gum, amylose or amylopectin derives. A method according to claim 3, wherein in the absence of a crosslinker partially neutralized polysaccharide derivatives with a molar ratio of SäuregrupH form) to free hydroxyl groups (OH groups) from 0.003 to 0.2 were.