KR20070035526A - A method for manufacturing silicate-containing fiber - Google Patents

Abstract

The present invention relates to a method for producing silicate-containing fibers, wherein silicon dioxide is added to a viscose made of cellulose and a mixture of the formed viscose and silicon dioxide is led through a nozzle to a regenerated solution to which silicate is added.

Description

How to make silicate containing fibers {A METHOD FOR MANUFACTURING SILICATE-CONTAINING FIBER}

The present invention relates to a method for producing silicate containing fibers according to the preamble of the appended claim 1.

The use of materials that are not easily burned or noncombustible in furniture and textiles is increasing. For example, furniture materials such as fabrics, fibers that do not ignite easily, or fibers that are non-flammable and that prevent fire are used. Fibers of this kind are in particular silicate containing fibers.

One way of producing silicate containing fibers is to modify the viscose made of cellulose by adding silicon dioxide, and to spin and treat the resultant silicate containing fibers for further use. A method of this kind is described, for example, in GB patent 1064271, in which viscose containing sodium silicate is spun with an acidic spinning solution, regeneration of viscose into cellulose, and at the same time sodium silicate in viscose Precipitates with silicon acid, a water-containing silicon dioxide that is uniformly distributed throughout cellulose.

The process according to the above-mentioned patents corresponds to an inexpensive manner for producing silicate containing fibers. The problem is that the silicic acid in the fibers produced by this method is not durable to alkaline detergents used to wash fabrics. With repeated washings, the silicic acid contained in the fibers is dissolved in the alkaline washing liquid, reducing the fire resistance.

The above mentioned problem has been solved in FI patent 91778 (corresponding to US 5,417,752) by treating the spun silicate containing viscose fiber with sodium aluminate, wherein silicon dioxide present in the silicate form in the silicate reacts with the aluminate in silicic acid. Form aluminum silicate groups. The solubility of silicic acid containing aluminum silicate groups in alkaline detergents is very low, so that their products can be washed with conventional detergents without degrading the fire protection properties. In addition, products containing aluminum silicate groups have significantly better fire resistance than products made without aluminum.

However, a problem with the method according to the two documents mentioned above is the propensity of the silicates contained in the viscose. That is, silicic acid or silica (SiO ₂ · nH ₂ O) is dissolved in the spinning solution during spinning. Notably, hundreds of milligrams / liter of silicate may remain in the spinning solution during spinning. Uncontrolled dissolution of silicates and dispersion into spinning solutions leads to several problems. The silicates form a precipitate in the spinning bath, which causes contamination of the spinning bath and increases the friction between the tow and stretch rolls, ie, garrets and stretch stones, of thousands of fibers formed in the spinning bath. The friction between each fiber in the tow also increases, weakening the stretch of the tow and thus weakening the strength of each fiber. Friction between the fibers also wears the fibers in the spinner.

Uncontrolled dissolution of the silicates from the fibers into the spinning solution also results in their property modifications. This can be observed as a change in strength and titer, ie the weight / length value of the fiber, which degrades the fabric properties of the fiber. In addition, a decrease in the amount of silicate in the fiber weakens the fire resistance of the finished fiber because even a decrease in the amount of silicate in only 1 to 2% significantly reduces the fire resistance.

Brief Description of the Invention

It is therefore an object of the present invention to provide a method for the production of silicate containing fibers, which avoids the above mentioned problems and thus makes the fibers produced as high as possible for the silicate concentrations.

In order to achieve this object, the method according to the invention is mainly characterized by what is described in the characterizing part of claim 1 as independent claim.

Other dependent claims will show some preferred embodiments of the invention.

The present invention is based on the fact that the composition of the regeneration solution used to prepare the silicate containing fibers, ie the spinning solution used as the spinning bath, is formed such that the silicate concentration of the fibers produced is kept as high as possible. This is met by the method according to the invention with the surprising observation that the solubility of the silicates in the fibers into the spinning solution is reduced by adding the appropriate amount of soluble silicate in a controlled manner to the spinning solution. In this way, the amount of silicate contained in the viscose fiber can be kept as high as possible.

In the silicate containing fibers formed in the spinning bath, the silicates are uniformly distributed in the fibers. However, the silicates on the outer surface of the fiber dissolve and crystallize into the spinning solution in contact with the spinning solution during spinning of the fiber. This crystallization is completely unregulated, leading to the problems mentioned above. By adding soluble silicates according to the invention to the spinning solution, uncontrolled dissolution and crystallization of the silicates on the fiber surface can be prevented.

The silicates added to the spinning bath may be water soluble alkali metal silicates such as sodium silicate such as water glass (Na ₂ O.nSiO ₂ ) or water soluble precipitated silicates. The silicate concentration of the spinning bath is 50 to 1,000 mg / l of spinning solution, advantageously 100 to 700 mg / l of spinning solution. Silicates are added to other chemicals that form the spinning solution directly in the spinning bath. The spinning solution is continuously recycled between the spinning solution and the treatment of the spinning bath upon spinning.

According to an advantageous embodiment of the invention, the spinning solution is kept saturated or nearly saturated by the soluble silicate by adding or removing the silicate to the spinning bath in a controlled manner. The extra silicate precipitated in the spinning bath can be removed by known filtration methods such as, for example, sand filtration, pressure filtration or curved screens.

According to a second embodiment of the invention, in the process of producing the silicate containing fibers, the silicate containing solution is used for stretching and washing the fibers after the spinning step.

Further, according to the third embodiment of the present invention, the silicate concentration of the silicate containing fibers can be adjusted to the desired level by controlling the amount of silicate to be added to the spinning solution.

By this method, uncontrolled dissolution of the silicate from the silicate containing fiber into the spinning solution is eliminated, and problems caused by friction between the fibers caused by the silicate powder precipitated in the spinning bath can also be eliminated. As a result, the change in the properties of the fibers is reduced. Deformation of the measured strength and titer of the fibers is smaller than in the fibers produced by the method according to the prior art, which improves their fabric properties. In addition, an increase in the amount of silicate contained in the fiber significantly increases the fire resistance of the fiber.

By this method, it is possible to produce viscose fibers in which the silicate concentration is adjusted to a certain level according to the needs of the consumer.

The application of the method is easy and simple, and is readily applied to the apparatus for producing silicate containing fibers already present.

Brief description of the drawings

In the following, the present invention is described in more detail with reference to the accompanying drawings, which diagrammatically shows a method for producing silicate containing fibers according to the present invention.

Detailed description of the invention

The figure shows the process for making the viscose fibers, in step 1, the soluble cellulose treated with sodium hydroxide (NaOH) was sludged with slush pulp. The cellulose was then pressed in step 2 to remove sodium hydroxide and the resulting alkaline cellulose was fragmented in step 3. Fragmented alkaline cellulose was led to the prematuring of step 4, where it was maintained under the influence of oxygen in air for about 3 to 5 hours at a temperature of about 35 to 45 ° C. In the pretreatment step, the alkaline cellulose is partially depolymerized.

Next, the pretreated alkaline cellulose was led to a sulfidation step (step 5), where carbon bisulfide (CS ₂ ) was mixed with alkaline cellulose and cellulose xanthate was formed. After the sulfidation step, weak sodium hydroxide (NaOH) was added to the xanthate in step 6 and mixed simultaneously to dissolve the xanthate, which was almost complete after 1 hour dissolution. The orange-yellow syrup viscose obtained from step 6 was introduced into the aging tank of step 7.

Viscose was filtered during aging and then in step 8. The next step 9 is the degassing step. Prior to degassing, for example, at the point indicated by arrow 10, a silicon dioxide solution was added to the viscose to form a mixed viscose formed by viscose and silicon dioxide. If desired, silicon dioxide may also be added at an earlier stage, ie, at a suitable treatment step / point of the spinning bath. Silicon dioxide added to the viscose can be, for example, commercially available silicon dioxide such as water glass (Na ₂ O.nSiO ₂ ) or a mixture of silicon dioxide and sodium hydroxide. In degassing step 9, air and gas bubbles were removed from the viscose / silicon dioxide-mixture viscose.

Next, the mixed viscose was led to spinning step 11 where viscose fibers were formed. The mixed viscose was guided into the spinning bath below the surface of the spinning solution through the nozzle of the small hole, the spinnerette of the spinning candles. The spinneret generally has about 8,000 to 50,000 holes, with a diameter of 50 to 80 μm. The spinning solution is an acidic liquid, which typically contains sulfuric acid (H ₂ SO ₄ ), zinc sulfate (ZnSO ₄ ) and sodium sulfate (Na ₂ SO ₄ ). Sodium sulfate is formed in solution when the sodium hydroxide in the mixed viscose reacts with the sulfuric acid in the solution. The spinning solution has a temperature of about 0 to 100 ° C., typically about 40 to 70 ° C. In the present invention, soluble silicates, such as sodium silicate, are also added to the spinning solution such that the silicates in the viscose / silicon dioxide-fibers formed in the spinning bath remain in the fiber without being dissolved in the spinning bath. The ratio of components contained in the spinning solution can vary in the following ways:

Sulfuric acid 40 to 150 g / antiseptic solution

20-40 wt% sodium sulfate

Zinc sulfate 0 to 100 g / spinning solution l

50 to 1,000 mg / l of spinning solution calculated as sodium silicate SiO ₂ ,

                         Advantageously between 100 and 700 mg / l

The composition of the spinning bath depends on the desired quality and properties of the fiber to be produced, for example its thickness.

The silicates are added in a controlled manner to the spinning bath, i.e., while the silicate concentration of the fibers being spun is kept as high as possible, so that the properties of the spinning solution and the silicates precipitated thereon are added without causing problems in spinning and spinning device operation. As such, the silicates may be added to the spinning bath continuously or at appropriate intervals as appropriate. The silicate precipitated in the spinning bath is removed in a controlled manner depending on the amount of silicate precipitated.

The solid cellulose-filament fibers formed in the spinning bath, the tow formed by the thousands of fibers exiting one spinneret, are first wound in a smaller stretch roll in step 12, and further stretch rolls through another stretch bath. That is, it was collected from the bath in a manner wound around the stretch stone. Stretch stretches the fiber 50 to 100% and increases its strength. After stretching, the formed tow of the fiber was led to cutting step 13 where it was cut to the desired length. The cut fibers were rinsed with water in washing step 14. As such, the fiber bundle can be split and individual fibers can be washed continuously in step 14.

In the drawing and washing step, it is also possible to use a silicate containing solution, which helps to keep the silicate concentration in the fiber as high as possible.

In washing step 14, it is also possible, if necessary, to treat the fibers with some aluminum containing solution such as sodium aluminum solution (NaAlO ₂ ). As a result, the silicic acid contained in the fiber is transformed into aluminum silicate, which gives the fiber the same feel as conventional viscose fibers while making it resistant to washing and even bleaching chemicals.

After possible sodium aluminate treatment, the fibers were further treated in step 14 in a general manner, ie they were washed, pH adjusted, and treated with a surface-active agent. Thereafter, the fibers were dried.

According to an advantageous embodiment, the amount of silicate added to the spinning bath is such that the spinning bath is saturated or nearly saturated with respect to the soluble silicate. The extra silicate precipitated in the spinning bath is removed in connection with the circulation of the spinning solution.

The above-described methods of making viscose fibers and the devices used in their operation are known to those skilled in the art and are therefore not described in more detail herein.

In the following, the test results of the method according to the invention for producing silicate containing fibers will be presented. In the test, the silicate concentration of the spinning solution was changed and at the same time the silicate concentration of the viscose fiber produced from the spinning was monitored.

Exam Preparation:

Viscose was prepared by the above-described and known viscose method, wherein sodium silicate, ie, water glass, was added to the viscose as silicon dioxide. The result was a mixed viscose containing 3.6% SiO ₂ , 8.2% alpha-cellulose and 7.4% NaOH. 3.5 dtex of fiber was spun into this mixed viscose. The temperature of the spinning solution is 50 ° C. and its composition is as follows without addition of silicate:

Sulfuric acid 65 g / spinning solution ℓ

20% by weight sodium sulfate

45 g of zinc sulfate / ℓ

A certain amount of silicate was added to the spinning bath at regular intervals in such a way that the silicate concentration of the spinning solution gradually increased. Commercially available water glass (SiO ₂ : Na ₂ O 2.5: 1, 30.9% SiO ₂ ) was used as the added silicate. After each addition, the fibers were spun into spinning solution in the manner described above. After the spinning bath, the fibers were stretched 90% longer than the original in the stretching bath, where the temperature of the stretching bath was 90 ° C. and contained 3 g / l sulfuric acid.

The silicon dioxide content of the spinning solution was measured by spectrophotometer using the so-called molybdenum sine method. Before the measurement, the spinning solution was circulated for about 1 hour so that the acid balance was leveled.

The effect of silicate addition on the silicate concentration of the viscose fiber produced from the spinning was monitored by analyzing the SiO ₂ concentration of the spun fiber after each silicate addition. The SiO ₂ content of the fibers was measured by ashing the fibers in a furnace at 750 ° C. and measuring the weight of the ash produced. The silicon dioxide in the fiber was found to be almost pure SiO ₂ .

The table below shows the effect of silicate concentration of the spinning bath on the SiO ₂ -concentration of the fibers.

Table 1. The amount of silicate added to the spinning bath, the silicate concentration measured in the bath, and the SiO ₂ -concentration of the fibers spun with this spinning bath

Exam number Water glass g / ℓ added to the spinning bath SiO ₂ / ppm in spinning bath SiO ₂ % in fiber One 0 <20 (not added) 24.7 2 1.25 250 27.2 3 1.75 336 32.2 4 1.75 347 32.9 5 2.25 466 33.0 6 2.25 477 32.9 7 2.75 535 33.0

From the results in Table 1, it was detected that the addition of silicate to the spinning bath increased the silicate concentration of the fibers obtained as a result of spinning. That is, the dissolution of the silicate in the fiber into the spinning bath was reduced. The saturation point of the spinning solution in relation to the silicate was reached in test 4. Since then, more silicate addition to the spinning bath did not affect the silicate concentration of the fibers and remained constant.

In addition, when comparing fibers spun with a silicate-saturated spinning solution (test 4) and fibers spun with very little or no silicate spinning solutions (tests 1 and 2), if no silicate is added, spinning It was found that about 8% by weight of the fibers were lost. That is, the silicate dissolution from the fiber to the spinning solution was remarkable. This affects the fire protection properties of the fibers. Indeed, the fibers produced by tests 1 and 2 have insufficient fire protection properties and unexpected fiber loss prevents fiber dtex (weight / length) control. By keeping the silicate concentration at a suitable level in the bath, these problems can be solved.

Some of the fibers produced in the tests described above (tests 1-7) were also treated with aluminum. Treatment with sodium aluminum solution (1 g Na aluminate, calculated as ₃ g / Al ₂ O ₃ , solution ratio 1:10, temperature 50 ° C.) gives the ash content of the fiber 2 to 2.5 of the values described in Table 1. Increased by%. As such, the ash also contained aluminum.

It is not intended to be exhaustive or to limit the invention to the above-described embodiments, which are intended to be broadly applicable within the spirit of the invention as defined by the appended claims.

Claims (9)

A method for producing silicate containing fibers, wherein silicon dioxide is added to a viscose made of cellulose, and the resulting mixture of viscose and silicon dioxide is guided through a nozzle into a regeneration solution, where the silicate containing fibers are formed. Is added to the regeneration solution. The method of claim 1 wherein the silicate added to the regeneration solution is a soluble alkali metal silicate or precipitated silicate. 3. Process according to claim 1 or 2, characterized in that 50 to 1,000 mg / l silicate, advantageously 100 to 700 mg / l silicate, calculated as SiO ₂ is added to the regeneration solution. 4. A process according to any one of claims 1 to 3, wherein the amount of silicate added to the regeneration solution is such that the regeneration solution is saturated by the soluble silicate. 5. The method according to claim 4, wherein the silicate precipitated with the regeneration solution is removed from the regeneration solution in relation to the circulation of the regeneration solution. The process according to claim 1, wherein the silicate is added directly to the regeneration solution directed to the spinning step (11) before the mixture of viscose and silicon dioxide is led to the regeneration solution. The process according to any one of claims 1 to 6, wherein the regeneration solution also contains sulfuric acid, sodium sulfate and sulfuric acid salt. The method of claim 1 wherein the silicate is added to the regeneration solution and removed from the regeneration solution. 9. The method of claim 8, wherein the addition and removal of the silicate from the regeneration solution is performed in a controlled manner such that the silicate concentration in the regeneration solution is maintained at a suitable level.

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