DE2824358A1 - Prodn. of highly absorbent fibrous web - by forming gel of solvent and chemically modified cellulose, removing unbound solvent, spraying to separate fibre and forming web - Google Patents

Abstract

A highly absorbent fibrous web is made by (a) mixing chemically-treated cellulosic fibres with a solvent to form a fibre gel mixture; (b) removing unbound solvent from the gel to the extent that the amt. remaining is with 5 g/g fibre of the fibre (c) satn. pt. spraying the mixture in an air stream onto a moving carrier and drying the web on the carrier. The spraying acts to dry the mixture sufficiently to separate it into discrete fibres. The softness weight etc. of the web can be controlled by altering the various spraying parameters, e.g. air stream velocity, and directing the rate of movement of the carrier. The chemically-treated cellulose must be (i) cellulose that has been chemically substituted, etherified or esterified (and opt. crosslinked) or (ii) cellulose that has been grafted without dissolving the fibres to the extent that they are not identifiable.

Description

Method of making an absorbent fabric

The invention relates to high absorbency fabrics and methods for their production.

The fabrics to which the invention relates are made of chemical modified cellulose fibers that are not only highly absorbent, but also has excellent tactical properties such as softness and conformability. Such fabrics have adequate strength and controlled wicking properties that make them particularly suitable as an element of an article where liquids are removed from to be deducted from a surface and in a particular area or area focus on a particular spot. These products are, for example, commercially available Diapers, sanitary napkins, tampons, tablecloths, surgical sponges and the like.

The chemical modification of cellulose to increase its absorbency has already been described and can be broadly considered to be in three major classes of procedure can be viewed as falling.

a) chemical substitution, etherization or esterification; b) chemical substitution plus cross-linking; and c) polymeric grafting.

For example, U.S. Patent 3,997,647 shows an extrusion process for forming highly absorbent fiber fabrics from gel-like Extrudates. These extrudates contain puffed fibers made from chemically modified Cellulose that has not lost its individual identities. By extrusion the fibers are aligned and bound together to form fibers with channels and to form capillaries that are highly absorbent and have excellent wicking properties result. The connection of the fibers with each other, the hydrogen bonding, the through however, the process achieved in this patent tends to be rough, stiff To produce tissue, except when using drying solutions or other special drying agents used. However, drying solutions is relatively expensive in terms of value the operating costs as well as a capital investment to reuse the system. In addition, the use of solutions requires caution with regard to ecological, safety and health hazards.

The main object of the invention is to provide a method of manufacturing of soft, adaptable and highly absorbent fabrics made from chemically modified Specify fibers without solution drying.

According to the invention, the chemically modified cellulose fibers mixed with the sucked solution and drained to a gel-like mixture to produce with minimal external water content, that in a gas stream, usually Air, sprayed or injected.

The speed and direction of the air flow are preferred regulated so that the individual fibers can be separated and collected, to obtain an open, lightly bound fabric.

In this way, the binding of the fibers in the subsequent drying process kept as small as possible and the result is a soft, easily adaptable fabric. The density of the tissue can be determined by an external water content and by changing it the degree of drying of the fiber and the speed of the Easer can be regulated.

Fabrics can be made with a wide variety of structures from dense, compact fibers into loose, open fabrics and with a wide range of properties including the absorbency and the suction speed will. Higher drying speeds can be achieved by applying high energy how heated air or microwaves are obtained.

Preferred forms of chemically modified fibers contain phosphorylated fibers Cellulose, cross-linked carboxymethyl cellulose and grafted> krylonitrile cellulose. These fibers can be used alone to make highly absorbent fabrics or to improve the properties of other fibrous fabrics by admixture. Formed structures can be made by directing the flow of air onto molds will. Sheets with reinforced scrims or other films or fabrics can get through suitable application of the fibrous air flow can be established according to the invention.

The fabrics of the invention are particularly useful in improving the Execution of absorbent products such as wipes, surgical sponges, sanitary towels, Tampons, diapers, etc. application.

The invention is based on an exemplary embodiment with the aid of Drawing described. In the drawings is: Figure 1 is a flow chart the method according to the invention; Figures 2 to 5 show schematically in different Details of the method, embodiments according to the invention; Figure 6 shows Fiber saturation points; FIG. 7 Consistency ranges in comparison with contents outside Water, and Figure 8 areas of consistency compared with preferred tissue densities.

- For a full understanding of the invention, it is intended that it is Explanation of the meaning of certain terms used in the description.

"Chemically modified cellulose" refers to cellulosic fabrics that are their composition and / or structure transformed in such a way by derivation has been that their hydrophilic character is increased considerably. Examples of Derivative processes include carboxylation, phosphorylation, and grafting of acrylic segments.

The invention is not directed to cellulosic solutions or other cellulosic compounds directed, in which the individual fibers or other basic structures are their own Lose identity.

"Highly absorbent" is used here to indicate that the modified cellulose absorbs significantly more liquid, as unchanged among the same Conditions. It has been recognized that the respective absorption ratio is not depends only on the respective tested material but also on the conditions under where the measurements are made. For example, the absorbency of a material under pressure is quite different from that in an uncompressed state be.

"Fibers" is here chemically modified in connection with the fibers Cellulose used with a swelling solution for making the used Mixture are mixed in the method according to the invention. Regarding the cost if the fibers have a length of preferably about the size of the fiber used in papermaking, i.e.

about 0.5 to 5 mm and a diameter of preferably about 0.05 up to 0.08 mm although larger fibers such as cotton linter can also be used.

"Fusion bond" is the bond between fibers by welding them together or melted together.

The binder is an integral part and is generally used broken more easily than the fibers themselves.

"Water resistance" is in U.S. Patent 3,670,069 at column 6, lines 51 to 70 referred to as residual moisture in and on a wetted fiber sample, after 10 minutes at 1000 times normal gravitational acceleration in the centrifuge has been spun.

For most practical purposes this is synonymous with that 1 fiber saturation point to be mentioned ".

"Free standing salt absorbency" is a measure of the normal Salt capacity at zero load. It is determined by introducing a pre-weighed Sample in a normal saline solution for 30 seconds. The sample is then with a Trowel removed, left to dry for 30 seconds and weighed wet again. The recorded Salt is divided by the weight of the original dry sample and is that free standing salt absorbency.

"Sucking" is the introduction of a sample through concentric conductive Rings that are radially 27mm apart.

Liquid is poured into the center of the rings at a rate of 240 milliliters per minute added and current applied. When the liquid has reached the outer ring, the circle is closed and this time is called the suction speed. This test is also described in the cited patent.

"Tense" was determined using a TM Minstron Tensile Tester measured, which is provided with a "B" cell and on a sample 50 mm wide with a claw opening of 6.5 mm, a crosshead speed of 12.6 mm per Minute in the entire working range from 1000 grams to 10,000 grams and a measuring speed operated at 5 centimeters per minute. Wet clamping results are shown in same way with samples obtained for 30 seconds before testing in one normal salinity have been softened.

13 break length "results were obtained as follows: break length (meters) = Extensibility (g / cm) / 2. x1 / 1 basic weight (g / cm2) 100 "Extrudate" refers to a mass of extrudable, hydrophilic, fibrous cellulosic material, which is swollen by soaking up a solution that the individual cellulose fibers become plastic and can move independently. In In all cases the external water content is preferably as small as possible and does not exceed a range of + 5 g / g fiber of the fiber saturation point.

"Dry fiber consistency" means average weight percent dry fibrous material. The dry weight is determined by drying samples for 2 hours determined at 105 0C with one of the mentioned compositions or mixtures.

In the method of Figure 1, the first step is chemical provision modified cellulose fibers. Commercial products such as "Buckeye" are carbxylated Buckeye Corporation cellulose can modify this process to be used. The various results obtained are shown by starting with pulp or wood fibers and treating them by phosphorylation, carboxylation or increased acrylonitrile substitution, which will be explained in detail below.

A preferred type of chemically modified fiber to use in the invention is the phosphorylated pulp fiber. To make this fiber the following procedure may be used, although it will be recognized by those skilled in the art that changes and alterations in phosphorylation are also used can.

The particular pulp to be phosphorylated is not critical. For example, the northern spruce pulp is already available cheaply and gives acceptable results. This pulp can be used in the form of dry slices as supplied by the pulp manufacturers. The slices are preferably for about 15 to 45 minutes in a reagent mixture of, for example, about 5a ' Urea and about 32, o phosphoric acid immersed. The purpose of immersion is distribute these reagents evenly in the pulp and shows that the time and the reagent concentration in wide ranges depending on the factors such as operating speed and the desired degree of phosphorylation can be varied.

For example, to obtain 6% or better phosphorylation an uptake of about 200% to 300 »of this reagent solution takes place. Preferably the treatment bath is at a slightly higher temperature, for example 60 to 70 ° C to facilitate penetration of the pulp boards.

After immersion, the pulp is at a temperature of about 12500 Hardened to 19500 and preferably between 180 and 19000. Because by heating Energy for the phosphorylation reaction to be made available depends the time for this step of the shape and intensity of the applied energy as well the amount of pulp and the reagent concentration. One example is curing the wood pulp in an oven at 180 ° C preferably finished when the pulp has turned slightly brown. On the other hand, it can harden through the use a microwave oven can be accelerated significantly, keeping the temperature of the pulp indicates their hardness after getting a handy one first has kept a constant value. Using microwaves also gives something softer Tissue with very little discoloration resulting from standard oven curing, and is therefore preferred and also to shorten the hardening time.

After curing, the phosphorylized pulp is washed to remove excess Remove reagents. It is then made with dilute acid, preferably hydrochloric Acid (e.g. 2 to 5 weight percent) hydrolyzed. In some cases, depending on of the pulp used, clumps of hard fiber can arise and can be stirred gently serve to break and soften them. The hydrolysis at a temperature of about 50 to 90 ° C and preferably between 60 and 70 ° C for half an hour to two hours long is usually sufficient, after which the phosphorylated pulp again with water has been washed.

The resulting hydrolyzed phosphorylated pulp is sicli then in its acid form and is thereupon through contact with an excess of bases, e.g. sodium carbonate (3 to 6 wt. ° f) converted into its salt form.

This contact is preferably carried out with stirring for at least 15 minutes at room temperature. After washing and thus removing excess Base, the phosphorylated pulp is in its preferred chemically modified form Form, with this pulp or other chemically modified cellulose, if a fabric is to be produced with high absorbency or absorbs large amounts of liquid are to be cleaned, the chemically modified pulp is cleaned in the next step. While the invention does not be limited to a particular theory should, it is assumed that the cleaning is the outer skin or primary wall of the The fiber breaks open, allowing it to expand and absorb more liquid.

When the cleaning is finished, the individual fibers are under Maintaining their respective identities in a heavily bloated, gel-like manner Form with a concentration preferably in the range of 5 to 2% o. At this point The pH value of the fibers becomes particularly important where physiological effects have to be taken into account in the range of about 4 to 9 and preferably between 5.5 and 8% if necessary Addition of diluted acid or base. It can be seen that this Step can be carried out at a different time in the overall procedure or omitted entirely can where dermatological factors are not to be considered.

As so produced, the following is the phosphorylated pulp composite extrudate sometimes referred to as "standard phosphorylated extrudate".

Drainage is important because it removes most of the outside water should be so that only + 5 g / g fiber of the fiber saturation point before spraying the mixture remains.

The actual consistency of the mixture with removal of the unbound Water varies with the type of chemical fiber modification and previous one Treatment of the pulp.

In all cases it is important (Figure 7) that the water is drained to this extent will, that the remaining external water is in the Be range of + 5 grams per gram of fiber and preferably + 3 grams per gram fiber of the fiber saturation point, which will be explained, and that the total residual water is about at least 4 grams per gram of fiber and preferably in the range of t 3 grams per gram of fiber of the fiber saturation point lies. Outside water is that which in the centrifuge in 30 minutes at egg; ier acceleration 1000 times the gravitational acceleration can be removed. The extrudates after of the invention, however, do not include sludge or other compositions that are significant Contain amounts of free water, as is the case with conventional papermaking techniques be used.

Figure 2 shows that the extrudate 10 from the pump 11 by the Spray nozzle 12 is injected into the forming section, which separates the extrudate into individual fibers 16 facilitated. A stream 14 of separated fibers 16 is passed through the air is sprayed immediately onto a collecting surface 18, which is an endless, rolling over driven belt 19 can be. Direction, temperature and speed of the air flow 14 and the carrier 18 are controlled so that they have a desired degree of fiber separation, Achieve placement and drying and so an undesirable hydrogen bond is avoided. Preferably the air flow is at a temperature between 30 ° C and 160C to improve drying. However, the nozzle 12 be an airless spray nozzle. The fibers 16 are formed from the carrier 18 as Tissue 20 collected.

A vacuum box 21 can be used to form the tissue to support and increase the speed of the chamfer drying. The fabric 20 can also be dried by dryer 22 and is shown wound in rolls 24. It can be seen, however, that this results from the method according to the invention Fabrics directly into devices for the production of end products, such as sanitary napkins, Diapers etc. is passed.

Figure 13 shows an embodiment for forming fabrics in greater detail. The drying chamber 30 includes an inlet 28 for the one Fan 30 supplied and heated in a heater 32 air. Even in the drying chamber 26 is a spray nozzle 12, which is from the pump 11 with extrudate 10 and from the line 34 is supplied with compressed air. The dried fibers 16 exit at opening 36 and are vented at 38 with the exhaust air. The arbitrary one Laying the fibers on the carrier 18 form flakes 40, which are further dried and treated can be, as Figure 2 shows. The drying chamber 26 leaves the fibers 16 in front the shelf practically dry so that they are lighter and a thick fluffy air mat with a high degree of Z-orientation of the Fanorm.

Pigur 4 shows an embodiment in which the method according to Figure 2 by adding compressed air to the spray nozzle 12 and a heating device for the air in the dryer 22 is modified. The fibers 16 are wet when the fabric 20 is formed, and this is dried as it passes through dryer 22.

Pgur 5 shows a third exemplary embodiment for production from Fabrics that are partially dried in a primary drying chamber 26A and final drying is performed in a secondary drying chamber 22A.

Both dryers are supplied with heated air for faster drying.

The invention will now be described by means of specific examples.

Example 1 A phosphorylated standard extrudate with a dry fiber consistency of 6.5% from a standard 20 milliliter syringe that acts as a pump and reservoir acts, the appropriate fitting pieces used, in the fluid opening of a pneumatic Extruded spray nozzle suitable for compressed air of 0.2 kg / cm². the pneumatic spray nozzle was provided with a slotted distribution tip and 5 milliliters Extrudate was released through the pneumatic sprayer (Spraying. Systems Company, Model 1/4 J, provided with distributor tip No. 125328 SS over a distributor head No. 2050 with a liquid opening of 12.6 mm) injected by hand to the fibers to isolate.

The compressed air was in the air vent at room temperature introduced. The fiber suspension was in a uniform layer of separated fibers on a plate of 300 x 300 x 6.3 mm made of fluorinated ethylene propylene resin (Teflon) and thereafter for five minutes using a high speed air stream dried out of the spray nozzle. The result was a flake-like accumulation of Fibers with a dry fiber consistency of 85.2 ».

EXAMPLE 2 Example 1 was repeated except that the fiber build-up With air at a temperature of 850C from a heat gun for 2 minutes from Taster hppliance Laboratory (model no. HG 301J) was dried.

The resulting flaky fiber aggregate had a dry fiber consistency of 86s5n / o Example 3 The extrudate according to Example 1 was passed through a doctor device sprayed into a thin film about 2.5mm thick and sprayed on for 18 hours Gradually dried at a temperature of 10500 in a rotating "Blau M" oven.

The resulting plate was hard, encrusted, and slow to come back wettable, partially swollen when wet under microscopic observation.

Example 4 A phosphorylated standard extrudate was in a slurry suspended from acetone and a solution prepared in the manner according to the patent 3,997,647 has been dried.

The resulting mat of loosened dry fibers was soft, snuggly, quickly wettable again and swollen when wet under microscopic observation.

Example 5 A cross-linked carboxymethyl cellulose extrudate with 3.0% dry fiber consistency was drier by mixing 1.0 gram fluffy fibers of buckleye Cellulose Company (CLD SR-447) in Treated 32.3 grams of distilled water. This extrudate was made using a pneumatic spray nozzle formed into a fabric and dried as in Example 1. The resulting fiber accumulation was soft, fluffy, very slowly rewettable and greatly swollen when wet under microscopic observation. the Dry fiber consistency of the resulting fabric was 81.3 ».

Example 6 Example 2 was carried out using carboxymethyl cellulose extrudate according to example 5 repeated. The resulting fiber accumulation was soft, flaky, very slowly rewettable and under microscopic observation in the wet state badly swollen. The mat had a dry fiber consistency of 82, o 'example 7 Example 3 was carried out using the carboxymethyl cellulose extrudate Example 5 repeated. The resulting plate was hard, crusted, very slow to wet again, but very much swollen under microscopic observation.

Example 8 A sample of cross-linked carboxymethyl cellulose from Buckeye Company, CSR 44) was previously solution dried as received from the supplier. The soft flakes were very slowly releasable and under a microscope Observation very swollen.

-The following table summarizes the given example and the results comprised of 1000 G hold tests that have been performed with water and saline solutions are.

Table 1 1000 G resistance example pulp dry process (gram / gram) Water Salt 1 Phosphory-Hochgeschwindigliert keitsluft according to 1.45 5.45 of the inventor.

2 "hot air according to the invention. 8.27 3.17 3" thick film air drying of extrudate 3.51 2.16 4 "acetone dry.

of fiber mat 8.77 3.52 5 CMC high speed air n.d.

Inventor 49.76 20.83 6 "hot air according to the invention 35.90 15.72 | 7 "Thick film air drying of extrudate 21.47 13.53 S" As received from supplier 67.97 18.72 These examples show materials according to the invention (Examples 1, 2, 5 and 6) obtained according to the invention and absorbent properties show virtually the same as those of the same fibers obtained after solution drying techniques have been dried and on over the thick film dried (Examples 3 and 7).

They also show that, according to the invention, highly absorbent fibers individually through the use of pneumatic spray devices, air sprayers, centrifugal sprayers etc.

can be suspended individually. The highly absorbent fibers can be in a desired soft, puffy mat shape without solution drying techniques treated, which saves considerable costs, and over conventional dry roads can be done. The results according to Example 8 are of flake form but not a fabric, but that shows high absorbency.

The following examples show the diversity with other designs of results obtainable according to the invention.

Example 9 A phosphorylated standard extrudate with a dry fiber consistency of 6.5% was extracted from a 20 milliliter syringe through a 16 mm needle (inner diameter - 0.115 mm) extruded into an air line, the air at room temperature and a Delivers a pressure of 0.1 kg / cm2. The sprayer was about 30 cm above a collection area manually operated and the individually suspended fibers are at a temperature of 85 0C in a special air stream from a distance of about 30 cm on the Quilt directed. The partially dried fibers were made on a plate spun polypropylene of 6.48 g / m² collected under the trademark "EVOLUPICN" is on the market and has been placed over a vacuum box with laboratory vacuum. Sixty milliliters of the extrudate was sprayed and 15 minutes long dried. This construction had a dry fiber consistency of 83.2% and the following characteristics: thickness 0.56 cm, bulk density 0.031 grams / cm3m free standing salt absorbency = 33.1 grams of liquid / gram of fiber, 1000 grams Water absorption = 3.93 grams of liquid / gram of fiber, suction time = 0.12 minutes, Extensibility = 830 grams / centimeter, length at break = 475 meters, wet extensibility = 43 Grams / centimeter and wet fracture length = 25 meters.

Example 10 Example 9 was repeated with the exception that only 20 milliliters of extrudate was sprayed and dried for 5 minutes. This structure had a dry fiber consistency of 83, Wo and the following characteristics: Thickness = 0.13 cm, filling weight 0.047 gr / cm3, free-standing salt absorption capacity = 43.6 g liquid / gr fiber, 1000 g water absorption - 2.92 g liquid / large fiber, suction time 0.35 minutes, stretchability 150 g / cm, breaking length 246 m, wet stretchability , 4 g / cm and wet fracture length = 6 m.

Example 11 Example 9 was repeated except that the quilt was an "EVOLUTION" spun polypropylene on a flat solid surface had been placed and the fibers aligned at a 450 angle were to make the individually suspended fibers bulge upward and then soft fall downwards (a distance of about 90 cm) onto the quilt. Two laboratory heat guns blew Air with a temperature of 8500 on this area. It About 200 milliliters of extrudate was sprayed and dried for 30 minutes. Of the resulting construction had a dry fiber consistency of 87.0% and the following Characteristics: thickness = 0.22 cm, bulk density = 0.11 gr / cm3, free-standing salt absorption capacity = 28.9 g liquid / gr.

Fiber, 1000 g water absorption = 6.41 g liquid / g fiber, 1000 G Salt holding capacity = 2.51 g liquid / g fiber, suction time = very long, elasticity = 96 g / cm, bridge length 384 m wet extensibility = not measurable, and NaB fracture length n not measurable.

Example 12 Example 11 was repeated except that the The quilt was a 300 x 300 mm (200 mesh) copper wire mesh and the fibers could fall softly when wet. This structure was made in a "Blau-M" oven brought to 105 ° C and dried for five minutes. The resulting structure had a dry fiber consistency of 82.5% and the following characteristics: Thickness = 0.18 cm, bulk density 0.012 gr / cm³, free-standing salt absorbency = 29.3 g liquid / g fiber, 1000 g water absorption - 6.47 g liquid / gr fiber, 1000 g salt holding capacity = 2.16 gr liquid / gr fiber.

Suction time X very long, extensibility = 59 gr / cm, breaking length I 281 m, Wet extensibility and wet fracture length were not measurable.

Example 13 A sample was prepared by the method of the aforementioned Treated patent using the extrudate according to Example 4. That resulting fabrics had a dry fiber consistency of 85% and the following Characteristics: thickness - 0.48 cm, bulk density = 0.033 gr / cm3, free-standing salt absorbency = 20.5 g / g, 1000 g water absorption = 7.86 g liquid / g fiber, 1000 g salt holding capacity = 3.69 g liquid / g fiber, suction time = 0.90 minutes, extensibility (M.1).) = 70 g / cm, breaking length (M.D.) - 43 m. Wet extensibility and breaking length were not measurable.

As can be seen, the invention lies in Examples 9, 10, 11 and 12 and can be used to produce a fabric that, in thickness, bulk density and salt uptake rate is similar to solution dried materials. More important is based on the fact that they are materials manufactured according to the invention a greater free standing salt absorbency (33.1 g / g compared to only 20.5 g / g solution dried Material - Example 13) and better fabric and dry stretch properties (830) g / cm compared to just 70 g / cm for solution dried material plus one Wet extensibility of 43 g / cm in comparison with the fact that these properties by standard techniques using on the Instron Tensile Tester with solution dried Material was not measurable.

Example 11 shows a material with a very low bulk density and low strength as it is the effect of the speed of the sprayed Fibers on the structure shows that formed on the quilt has been.

This material is similar to that prepared according to Example 12 Material-like physical characteristics.

In Example 11, the fibers were partially dried during spraying and then afterwards collected on the collecting area dried.

In example 12 an even lower degree of initial drying was obtained, since the fibers were sprayed wet as in Example 11 without an auxiliary stream of dry air are.

The result was a wet, open structure approximately thick 9.5 mm. This fabric was placed in a rotary oven to dry. These examples of the invention exhibit characteristics common to air-made paper products are similar but have surprising strength and absorbency.

Example 14 As in Example 1, phosphorylated pulp was prepared for a Pressure of 2.1 kg / cm² using a Zenith pump model BPB 4391 through a point TEJET No. SS 6501 is pumped to an airless spray under environmental conditions to train on black blotting paper. A somewhat fluffy fabric was created. A more uniform fabric would be expected at high pressures.

In a further embodiment of the invention, an improved Material can be obtained that the chemically modified fibers with other high absorbent materials combined. For example, acrylonitriles were grafted Starch granulate available but it resulted in difficulties due to congestion, displacement and relocation problems, those on the free flow of such materials are related when treating and incorporating into absorbent products. By Combine these granular or powdery materials with a mesh size of e.g. 14 to 400 with chemically modified fibers before the complete one Drying is an integrated composite material that is treated and the generation of dust is reduced. The following examples show this embodiment.

Example 15 Phosphorylated cuff with 7.2% was made from a reservoir Phosphorus and a consistency of 10.5% bases to a Zenith laboratory measuring device (model 175 G) sprayed with a vortex pump type BPB (1.7 cc / rev.) Via a high pressure hose is equipped with a 1/4 J pneumatic nozzle from the Spraying System Company, which is fitted on a liquid cap 60100 and an air cap 125328. the The nozzle was 45 cm above a shaping wire, with the flat air jump cap in the transverse direction aligned and the nozzle rotated approximately 600 from vertical was. The gel was pumped into the nozzle and sprayed pneumatically. From a Syncron vibrator tray of General Mills, grains of Polymer 502 S were exposed approximately 38 cm into the fiber spray dropped and the composite material was collected on a mold wire. After drying through at 30 ° C., a plate was made of 5% phosphorylated fibers and 95 wt. 5'o high tensile strength (361 g / cm) kernels, a 1000 g salt hold of 25.4 g / g, a density of 0.15 g / cc and a thickness of 0.25 cm.

- Example 16 A phosphorylated pulp gel (8.3% phosphorus) with a Consistency of 10.2 °, solids was sprayed as in Example 12 and a gain processing polymer 35-A-100 was dispensed from a separatory funnel into the spray at the outlet of the spray cap sifted out. After collecting on a wire and drying at 70 ° C, a Composition of 10% phosphorylated fibers and 9O / o polymer with a tensile strength of 35 g / cm, a 1000 g salt content of 12.1 g / g, a density of 0.08 g / cc and a thickness of 0.22 cm.

Example 17 Earboxymethyl cellulose (Hercules Aqualon "R") fiber gel was mixed with water to a consistency of 1% and to a consistency of 7.85o 'drained.

It was sprayed as in Example 15 and at the spray nozzle with General Mills polymer 502 S mixed with a vibra screw feeder (model SCR -! '20 ") became. The composition was dried at 30 ° C and gave a fabric with 17% Fibers and 83% granules with a tensile strength of 220 gr / cm, a 1000 G salt content value of 28.5 g / g, a density of 0.09 g / cc and a thickness of 0.19 cm.

Example 18 Unpurified 700 Canadian Standard Milled Phosphorylated Pulp gel with 7.0% phosphorus and a consistency of 6.7% solids (fiber saturation point 4.5 g / g, total water content 14 g / g) from one under pressure standing Reservoir pumped into a Zenith laboratory measuring device type 1-QF, which is equipped with a vortex pump, Type BPB (1.7 cc / rev.) And then through a high pressure hose to a pneumatic Spraing-Systems-Company nozzle, 1/4 J pumped on a liquid cap 100150 and an air cap 189 351 is attached. The nozzle was 1 meter above one Center line attached by a 482 mm long shaping wire, with the flat spray cap with the pneumatic spray nozzle aligned in the transverse direction and the nozzle attached in this way true that the fiber was sprayed directly down to the forming wire, the one at 100 mm / minute was moved. For separating the gel into fibers with a minimum of excess air Sufficient air was used. The zenith sum was at 35 (equal to 250 rev / min) set. Approximately four feet of undried fabric was produced. This then became through a 1.22 m tunnel through dryer approximately 3.05 m from the spray nozzle guided. The through dryer was set at 100 ° C. The fabric was very special to dry, but after 25 minutes inspected it was dry. The resulting Tissue was crusty and unsuitable for many purposes.

Example 19 Example 18 was repeated except that the Pulp gel was at a consistency of 8, o '(total water 10.5 g / g). To the pneumatic Separating the gel fibers were applied 0.84 kg "cm2. The tissue was created in 11 minutes dried out. A pure quality fabric resulted.

Example 20 Example 18 was repeated except that the Pulp gel had a consistency of 13.04 (total water 6.7 g / g). For pneumatic cutting of the gel fibers were applied 2 kg / cm2. The fabric dried through in 6 minutes. A good quality fabric was obtained.

Example 21 Example 18 was repeated except that the Pulp gel had a consistency of 18.4 (total water 4.4 g / g). To the pneumatic Separation of the gel fibers was used at 4.55 kg / cm2. The tissue was in a minute dried out. The result was a fabric of excellent quality and foam-like Appearance.

Example 22 Example 18 was repeated except that the Pulp gel has been refined to a Canadian 400 grind standard. It was at one Consistency of 6, '7 "o' sprayed (total water 74 g / g, fiber saturation point 8.5 g / g). 0.35 kg / cm2 was used for the pneumatic separation of the gel fibers. The mesh was completely dry in 21 minutes.

The quality of the fabric was very poor and looked crusty.

Example 23 Example 22 was repeated except that the Pulp gel had a consistency of 8.7 ». (total water 10.5 g / g). To the pneumatic Separating the gel fibers, 1.05 kg / cm2 was used. Although the content of external Water was in the preferred range because of the fabric high Degree of cleaning a bit crusty.

Example 24 Example 22 was repeated except that the Pulp gel was at a consistency of 13 °, 6 (total water 6.7 g / g dehydrated through Vacuum). 3.00 kg / cm2 were used for the pneumatic separation of the gel fibers. That Tissue was dry through in 6 minutes. A good foam-like fabric resulted.

Example 25 Example 22 was repeated except that the Pulp gel was at a consistency of 13.0 ° h (total water 6.7 g / g dehydrated in Vacuum); For the pneumatic firing of the gel fibers, 2.24 cm2 were used, and the fabric was dried for 6 minutes. A good foamy fabric was achieved.

Example 26 Example 18 was repeated except that the Pulp gel was carboxymethyl cellulose (Hercules equality "R").

It was sprayed at a consistency of 3.3 / o (total water 30 g / g, fiber saturation point 16.5 g / g). Was used to pneumatically separate the gel fibers 1.60 kg / cm2 used.

The forming wire ran at 100mm per minute and the fabric was in 25 Minutes dry. A poor paper-like fabric was obtained.

Example 27 Example 26 was repeated except that the Pulp gel had a consistency of 4.0 »(total water 24.0 g / g). 2.45 kg / cm2 were used for the pneumatic separation of the gel fibers. The forming wire was 200 mm / min and the fabric was completely dry in 6 minutes. It became a bad tissue scored.

Example 28 Example 26 was repeated except that the Pulp gel had a consistency of 5.0 »(total water 19.0 g / g). To the pneumatic Separation was used at 0.84 kg / cm2. The mold rotated at 75 mm per minute and the fabric was dry in three minutes. A good fabric was obtained.

Example 29 Example 26 was repeated except that the Gel at a consistency of 5.8 s (total water 16.4 g / g). To the pneumatic Separation of the gel fibers was used at 75 kg / cm2. The shaped wire ran at 52 mm per minute. A good fabric was obtained.

Example 30 Example 22 was repeated except that used to pneumatically separate the gel instead of 0.35 kg / cm2 60 kg / cm ' became. The gel feed pump was set to 3 instead of 35. The forming wire was stopped due to the reduced feed rate, a reasonable amount of sprayed fibers To build up a basic weight of about 30 cm, so that about 30 cm tissue is produced became. The fabric dried through in a minute and was very soft. A goodness Drying occurred during training due to the high air gel ratio during spraying which gave a material at or near the fiber saturation point despite the high gel water content. Similar results were obtained in example 1.

Before drying through, the fabric had a consistency of 17.1%.

The results of these examples are shown in Table 2. As can be seen, good (soft, non-crusty) tissues can be achieved by choosing a combination Flow and drying conditions generated from consistency for maximum fiber separation which requires a minimum of subsequent drying. According to Figure 8 preferred fabric densities after drying in the range of 0.015 to 0.050 grams / cc with the range of about 0.015 to 0.040 is particularly preferred.

Table 2 NORMALIZED NORMALIZED FIBER SPRAY WES THICKNESS TENSILE THRU SATURATION PRIOR TO CENTIMETERS kg / 15 mm DRYING MODIFIED POINT BASE CEL THRU DRYING BASIS AT A BASIS AT A BASIS TIME CELLULOSE 900 "G" GRAMS H2O / 1/2 1/2 WEIGHT DENSITY WEIGHT WEIGHT STRETCH AT 100 ° C EXAMPLE TYPE q / c GRAM FIBER CONSISTENCY CONSISTENCY q / m² q / cc 200 g / m² 200 g / cm²% MINUTES 18 Phosphory- 4.5 14.8 6.7 6.9 163 .083 .24 1.7 .86 25 lated Unrefined 19 Phosphory 4.5 10.5 8.7 9.1 182 .047 .42 1.9 .87 11 lated Unrefined 20 Phosphory- 4.5 6.7 12.0 - - 184 .028 .72 1.0 4.52 6 lated Unrefined 21 Phosphory 4.5 4.4 18.4 - - 85 .016 1.26 1.1 8.05 1 lated Unrefined 22 Phosphory 5.5 14.0 6.7 6.8 150 .065 .31 3.6 .77 31 lated Unrefined 23 Phosphory- 8.5 10.5 8.7 9.2 127 .058 .14 3.1 1.64 10 lated Unrefined 24 Phosphory- 3.5 9.0 10.0 - - 198 .036 .66 1.4 2.67 6 lated Unrefined 25 Phosphory- 8.5 6.7 11.0 - - 177 .033 .59 1.4 2.77 6 lated Unrefined 26 CNC 16.5 30.0 3.2 3.4 162 .050 .40 2.9 1.99 25 Unrefined 27 CNC 16.5 14.0 4.0 4.2 112 .051 .39 2.4 2.02 8 Unrefined 28 CNC 16.5 19.0 5.0 5.1 149 .035 .57 2.5 3.00 6 Unrefined 29 CNC 16.5 16.4 5.8 6.1 162 .034 .59 1.5 1.72 3 Unrefined 30 CNC 6.5 14.0 6.7 17.1 65 .015 1.32 1.0 13.86 1 lated Unrefined The invention is not limited to any particular theory, rather, the results obtained are explained below.

When dry cellulose fibers are immersed in water, the latter penetrates into the fiber wall and allows it to swell until there is tension in the fiber wall are in balance with the capillary forces that the water in the fiber wall push. The water content of the fully saturated fibers becomes the fiber saturation point ("FSP") and is commonly expressed in grams of water per gram of dry fiber. Figure 6 shows the fiber saturation points of representative materials according to the invention.

When the fibers are immersed in water, some of the water is in held by the fiber walls and the rest is under the fibers and in the Lumens. For explanation, the water contained in the fiber walls becomes the inner one Called water, while the water outside the fibers is called outer water will. Figures 7 and 8 describe external and internal water contents for the used Materials including preferred areas.

The most accurate methods for determining the fiber saturation point is the solute exclusion technique.

Dry fibers are placed in an aqueous solution of a dextran, whose molecules are too large to penetrate the capillaries of the fiber walls. Water is sucked through the fibers to the exclusion of the dissolved substances, out the measured increase in the concentration of dissolved substances in the surrounding dextran solution can calculate the weight of the water sucked in, i.e. the fiber saturation point will. This method of determining the fiber saturation point is highly laboratory and it has been shown (Scallan and Charles, ttSvensk Papperstidning "75 (1972) (609), that between the fiber saturation values as determined by the solute exclusion technique and the water retention values (7RV) of most fiber samples a very good correlation with the semi-permanent exposure to a centrifugal force of 900 G consists.

If by some chemical means hydrophilic groups on the surface and brought into amorphous areas of cellulose fibers (e.g. phosphorylation), absorb more water with an increase in the fiber saturation point, like it in that mentioned article by Scallan and Carles is described. Stirring and cleaning also increases the saturation point of the fibers. The saturation point (or water holding value) of wood pulp fibers is rarely above 2 g / g.

The fiber saturation point is for dry and re-treated pulp fibers not more than 1 g / g.

Shows the fiber saturation points of some chemically modified fibers Table 3.

Table 3 Material FSP external water g / g g / g at consistency material FSP external water g / g g / g at 5% consistency Phosphorylated fiber (unbeaten) 4.5 14.5 Table 3 Phosphorylated fiber (whipped) 8.5 10.5 Carboxy-carboxymethyl cellulose (Aquuelon-R) (undefeated) 16.5 2.5 wood pulp (average) 1.5 17.5 The data in Table 3 shows that chemically modified fibers have more interior Contain water (higher fiber saturation point) than wood pulp fibers. For example With a consistency of 5% (95 grams of water, 5 grams of fibers), the amount fluctuates of the outer water with the fiber saturation point, as shown in Table 3, second column shows.

Because of the different amounts of external water, Aqualon R is at one Consistency of 5% a gel with plastic characteristics, while wood pulp is one is free flowing mud. The phosphorylated fibers have properties between these two extreme values.

The fabrics according to the invention are characterized by a structure with an airy, mat-like appearance and (1) high absorbency, (2) adjustable Absorption or distribution properties, (3) adjustable dry strength properties, from a flake-like cotton wool to a soft tissue-like disc a hard, pliable, foam-like disc; and (4) adjustable wet strength can be changed.

The invention thus provides an improved superabsorbent material and a method of making the same with some or more of the following Advantages: 1. To keep the suction and absorption properties of the highly absorbent Fibers are necessary in solution drying. This saves considerable costs.

2. Inner fiber bandages are easy in the fabrics by regulating the amount of the binding hydrogen between individual fibers when drying with the following Affecting results: a) By keeping the external water in sprayed low Fibers, the collected fibers form a bulky, loosely bound mat made of physically forms intergrown fibers, b) by partially drying all fibers before collecting and after subsequent drying on the collecting surface, an airy mat is taken up Fibers made with high strength, flexibility and softness.

3. A means is provided for introducing granular materials; 4. The fluid capacity of the tissue contains a higher capillary capacity between the fibers as well as the swollen capacity; ). The fibers can by changing the angle of the spray template in relation to the quilt with the following Results aligned or arbitrarily distributed: a) by spraying directly on the collecting surface, the fibers are randomly distributed; b) by spraying at a sharp angle on the quilt will be most Fibers aligned in the direction of spray.

6. When using an extrudate containing phosphorylated fibers, are the flame-retardant properties for spray drying in heated air without Particularly suitable danger of lightning fire.

The method according to the invention can with various modifications Finally, spraying extrudable fibers into a heated stream of high air Speed like through a dryer nozzle and collecting dry fibers a continuous wire to create a new fabric, spray extrudable Place fibers on a continuous collecting surface and dry the structure in a through dryer for making a new continuous fabric and spraying extrudable fibers in a heated cyclone, flash drying and collecting on a continuous surface can be used to create a new tissue.

The method according to the invention can also be used for mechanical integration different materials with highly absorbent fibers can be used. For example creates the premixing of the material into the extrudate and spraying it into one high speed heated airflow e.g. through a dryer nozzle and collecting the dried fibers on a continuous wire Tissue. The spraying of extrudable fibers into one side of a heated air stream high speed e.g. through a dryer nozzle and bubbles of pulled pulp, for example fibers in the other side of the air flow and collecting the integrated dried fibers on a continuous wire creates a very airy fabric. Spraying extrudable fibers into a heated cyclone, flash drying, blowing by the fan of a roll pulp gripper while picking up a roll Pulp and collecting the integrated dried fibers on a continuous wire provides an integrated fabric. Spraying extrudable fibers in a meltblown process, as described in U.S. Patent 3,849,241, for example, is simultaneously using the high-absorbency fibers in the melted blown fabric a high speed, heated air stream of the meltblown process and integrate.

These and other examples of the invention are familiar to those skilled in the art. They show the highly absorbent airy, mat-like structures that after of the invention by regulating the interbond during air drying can be. There are many ways to make new high absorbency ones Fabrics according to the invention in an on-going manner for use as a component of finished products. The highly absorbent benefits can be used as sanitary napkins, tampons, Diapers, mops and other similar products are used.

L e r s e i t e

Claims (11)

Claims 1. A method for producing an absorbent Tissue characterized by the following steps: Forming a gel by mixing chemically modified cellulosic fibers with a solvent, the fibers either cellulose are those of chemical substitution, etherization or esterification that is cross-chained to this exposed cellulose, or the Cellulose is polymerically grafted without dissolving the fibers to such an extent that it becomes are not identifiable and the solvent from the gel mixture is bound so far that is removed that an amount in the range of + 5 grams per gram of fiber of the fiber saturation point remains. Spraying the gel mixture to separate the fibers, collect the fibers and sprayed into a fabric with high Z-orientation of the fibers and in the end Drying the fibers. 2. The method according to claim 1, characterized in that the solvent Water is and the fibers are phosphorylized pulp, or acronitrile grafted pulp are cross-linked Eaboxymethylcellulose. 3. The method according to the preceding claims, characterized in, that the gel mixture is sprayed in a gas stream to accelerate drying. 4. The method according to claims 1 and 2, characterized in that that the fibers are cleaned with the solvent before mixing. 5. The method according to claim 4, characterized in that the gas stream heated air is. 6. The method according to the preceding claims, characterized in that that the fabric formed is bound according to a template. 7. The method according to the preceding claims, characterized in that that the fabric is formed on a reinforced fabric. 8. The method according to the preceding claims, characterized in that that a spherical material is added to the sprayed fibers. 9. Fabric characterized by the manufacture according to the preceding Claims. 10.'Gewebe according to claim 9, characterized in that it is more chemical Substitution, atherization or esterization is exposed, or the cellulose is polymerically grafted with the fibers practically oriented in the direction and from a gel with an external solvent content in the range of + 5 ° A g / g fiber the saturation point is established. 11. Fabric according to claim 10, characterized in that the fibers phosphorylated pulp, acronolite-grafted pulp, or cross-linked carboxymethyl cellulose is.