A method of reducing the flammability of aramid products

 

(57) Abstract:

Reducing the Flammability of aramid products is achieved by contacting an aqueous solution of compounds of tungsten with the product of aramid, swollen in the solvent or never subjected to drying, for introducing it into the product, followed by drying of the product. Fibers of polyamides with high heat resistance is used for the manufacture of clothing for firefighters. 2 C. and 12 C.p. f-crystals, 1 table.

The invention relates to a method of reducing the Flammability of aramid products by contacting aramid products, swollen in the solvent or never subjected to drying with an aqueous solution of compounds of tungsten. Then aramid product is subjected to drying.

The aramids are polyamides derived from aromatic (di) acids and aromatic (di)amines. It is known that many of these polymers are resistant to fire, along with other useful physical properties, such as high strength, high temperature resistance and good abrazivoustoychivost. These are the properties of products made from these polymers and used in areas where there are high temperatures and/or flame.

For example, boosti of aramids is useful.

The essence of the invention.

The present invention relates to a method of reducing the Flammability of aramid products, including contacting an aqueous solution of compounds of tungsten with the product of aramid, swollen in the solvent or never subjected to drying, for the introduction of tungsten in the product in a quantity sufficient to reduce the Flammability, and subsequent drying of the product.

Detailed description of the invention.

A measure of the Flammability of a substance is the limiting oxygen index (CRP). When determining this characteristic determines the minimum number (percentage) of oxygen in the atmosphere, necessary to support combustion of the material. The higher the CRP, the less fuel is material.

According to this method turgid aramid or never subjected to the drying aramid contact with an aqueous solution of compounds of tungsten. Under swollen aramid mean polymer swollen in the solvent and/or solution of aramid in the solvent. Usually, such a solution has high viscosity and in contact with the aqueous solution of aramid retains the appropriate form.

The term has Never been drying" aramid means aramid, shahul). When getting in touch with nerastvorim polymer coagulates and most of the solvent is removed from aramid. The aramid has otkrytostju structure type sponge, which usually contains 150-200% by weight of aramid herstories (again usually water). It is to this otkrytosti structure type sponge containing herstorical, applies the term "never subjected to the drying aramid".

Many aramids are used as fibers and films> the Fiber can be obtained by a wet molding solution aramid, and the film produced by the method of irrigation thin layer of aramid. In both cases, the solution of aramid (or, as indicated above, aramid, swollen in the solvent) is usually in contact with aristotelem, for example water, which displaces the solvent, causing swelling aramid, and causes coagulation of aramid with obtaining a solid polymer, for example, as fiber or film. Therefore, in such ways water is often referred to as coagulant. A convenient method of contacting aramid, swollen in a solvent, with an aqueous solution of compounds of tungsten is the use of an aqueous solution containing tungsten as a coagulant in the method of forming fibers and films> Other never subjected to drying aramid with this solution.

Then the aramid dried, yielding the final product (fiber or film). Drying is usually carried out by mechanical removal of excess water and solvent aramid and then removing the residual water and solvent by evaporation, for example by heating. Conventional wet forming fibers known in the art and described in the publication of H. Mark et.al., Ed., Encyclopedia of Polymer Science and Technology, vol 6, John Wiley and Sons, New York, 1986, p. 802-839 included as a reference.

Especially suitable aramids are poly(p-phenyleneterephthalamide) and poly(m-phenyleneterephthalamide) because of their proven utility for the manufacture of fibers used in applications that require resistance.

You can use any compound of tungsten, capable of forming a stable aqueous solution. To the water solution can also add connections, contributing to solubilize compounds of tungsten.

Used compounds include tungsten WCl4(with citric acid to stabilize the solution), heteropolytungstates, for example, phosphorothionate acid, and homopolar wolframate, for example, ammonium tungstate and sodium tungstate. You can use any compound of tungsten, if it is soluble in water golfmania acid and metabolomic ammonium.

Some aramids, for example, poly(m-phenylenedimaleimide) soluble in organic solvents, which are almost neutral in aqueous solution, while the other aramids, for example, poly(p-phenyleneterephthalamide), usually dissolved in a strong acid, such as sulfuric acid. For aramids, dissolved in organic solvents, the preferred compound of tungsten is ammonium tungstate.

For aramids, dissolved in strong acids, the preferred compounds of tungsten are phosphorothionate acid. Therefore, it is necessary to apply a compound of tungsten, which will not precipitate when its aqueous solution is in contact with aramid, swollen in the solvent.

The concentration of tungsten in aqueous solution, the temperature and time of contact of an aqueous solution of compounds of tungsten and aramid, swollen in the solvent are not critical, provided that in aramid product introduced an effective amount of tungsten. In aqueous solution, the preferred concentration of tungsten (calculated as metal) of about 1 wt.% or more. The temperature at which the process is mainly limited temperatureoC, preferably 25 - 100oC. the Preferred time of contact of the aqueous solution of compounds of tungsten and aramid, swollen in the solvent ranges from 1-2 to less than 1 hour. The thicker the aramid, swollen in the solvent, the more time contacting.

All the above parameters can be adjusted so that the final amount of tungsten in the aramid (calculated as elemental tungsten), preferably, comprised of 0.1-25 wt.%. The increase in time of contact, increasing the concentration of tungsten in aqueous solution and reducing the thickness of the cross-section of aramid, swollen in the solvent will lead to a higher content of tungsten in the aramid and higher CRP values.

In the examples the following abbreviations are used:

DMAC - N,N-dimethylacetamide

CRP - limiting oxygen index

MFI - poly(m-phenylenedimaleimide)

CFT - poly(p-phenyleneterephthalamide)

In the following examples, the tungsten content determined using the method of inductive plasma-atomic emission spectroscopy according to ASTM C-88. CRP was measured according to ASTM D2863-77.

In the following examples, the fabrication of films on glass plates PL is prevent excessive shrinkage. In examples 3-13 control samples MFIs (not containing tungsten) are characterized by CRP, equal to 28.2 and 27,0 and control samples CFT have the value of CRP, $ 27.2-27,5.

Example 1.

5% aqueous solution of metavolume ammonium is obtained by adding 10 g of metavolume ammonium to 190 g of water and heating at 60oC until complete dissolution. Five grams of fiber from not subjected to drying IFIs (the moisture content of 155%) are added to a solution of ammonium tungstate with a temperature of 60oC. After 50 min, the fiber is removed and dried at 120oC in an oven for 1 hour. SIC fibers equal to 39.7. The same fiber, not treated with ammonium tungstate, has CRPS equal 28,0.

Example 2.

Carry out the contacting of the sample fibers are not subjected to drying PTF with a solution of ammonium tungstate according to the method of example 1. This fiber has CRPS, equal to 31.7. Control sample fiber from CFT, not treated with a solution of ammonium tungstate, has CRPS equal to 27.0.

Example 3.

A solution of 20% CFT in 100,5% sulfuric acid (0.5% of SO3) cast dry chamber on a glass plate at 90oC using the applicator to a wet film thickness of 0.13 mm Film on the glass plate) is provided equal 100oC for 45 minutes and Then the film was washed for 15 min with water, immersed for 4 hours in 0.1 M NaOH solution and then again for 15 min, washed with water. The film is dried in a vacuum oven at 100oC during the night. CRP film is equal to 45.4, it contains 13.4% of tungsten and 0.26% of phosphorus.

Example 4.

A solution of 20% CFT in 100,5% sulfuric acid (0.5% of SO3) cast dry chamber on a glass plate with a temperature of 90oC using the applicator to a wet film thickness of 0.13 mm Film on the glass plate) is dipped in water to remove the (mostly) sulfuric acid and coagulation of the polymer. The film is placed in a 5% aqueous solution Fosfornomolibdenovoi acid (Fisher Scientific Co. N A-248), the temperature of which is maintained equal to 100oC for 45 minutes and Then the film is washed over. 15 min running water, immersed for 4 hours in 0.1 M NaOH solution and then again for 15 min, washed with water. The film is dried in a vacuum oven at 100oC during the night. CRP film is equal to 44.0, it contains 42% tungsten and 0.17% of phosphorus.

Example 5.

On a glass plate applied with a watering solution containing 20% MFIs 9% CaCl2and 71% DMAC using the applicator to a wet film thickness of 0.13 mm Glass plate heat is key. The film is placed for 45 min in 5% aqueous solution fosfornomolibdenovoi acid (Fisher Scientific Co. N A-248), the temperature of which is maintained equal to 100oC. the Film is dried in a vacuum oven at 100oC during the night. CRP film is equal to 47.8, it contains 21.6% of tungsten, 0.39 phosphorus and 0.62% calcium.

Examples 6-13.

In these examples, using the methods of examples 3, 4 and 5. In all these examples, the concentration of tungsten in aqueous solution is 5%. The table shows the conditions and findings.

1. A method of reducing the Flammability of aramid products, comprising contacting an aqueous solution of the compound with the product of aramid, swollen in the solvent or never subjected to drying, for introducing it into the product in a quantity sufficient to reduce the Flammability of the product, and subsequent drying of the product, characterized in that the link quality is used as a compound of tungsten.

2. The method according to p. 1, wherein the aramid is poly(p-phenyleneterephthalamide) or poly(m-phenylenedimaleimide).

3. The method according to p. 2, wherein the aramid is never subjected to the drying of the aramid.

4. The method according to p. 1, characterized in that as aedib under item 1, characterized in that compounds of tungsten are used fosforilamido acid or ammonium tungstate.

6. The method according to p. 1, characterized in that compounds of tungsten using homopolar tungstate and aramid is poly(m-phenylenedimaleimide).

7. The method according to p. 6, characterized in that compounds of tungsten using ammonium tungstate.

8. The method according to p. 1, wherein the aramid is poly(p-phenyleneterephthalamide) and as a compound of tungsten used fosforilamido acid.

9. The method according to p. 1, wherein the process is carried out at a temperature of ~ 25 - 100oC.

10. The method according to p. 1, characterized in that the aqueous solution used coagulant used in forming fiber.

11. The method according to p. 1, characterized in that the aqueous solution used coagulant used in forming films.

12. The method according to p. 1, characterized in that an aqueous solution containing ~ 1 wt.% or more of tungsten.

13. The method according to p. 10, wherein the aramid is never subjected to the drying of the aramid.

14. A method of reducing the Flammability of Aram the foreign Ministry) to introduce into the product in the quantity sufficient to reduce the Flammability of the product, and subsequent drying of the product, wherein the solution is an aqueous solution WCl4that is a coagulant in forming films, and the process is carried out at 100oC.

 

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