JPS5818468B2 - Method for making cellulosic textile fibers flame resistant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to flame-retardant cellulosic textile fibers.
The present invention relates to a method for treating the fibers.

Such treatment shall be referred to herein as a flameproofing treatment for convenience, even though it does not completely suppress all flame formation.

The treatments to which this invention relates include tetrakishydroxymethylphosphonium salts (hereinafter referred to as THP salts) such as chlorides (
It consists of impregnating the fiber with a precombination of nitrogen-containing compound 9 and a nitrogen-containing compound, hereinafter referred to as THPC, and then treating it with ammonia.

In this way, a cross bonded polymer is formed on the fiber,
This makes them flame resistant.

Description of the Prior Art A prior art disclosure of a flame retardant treatment involving the use of THPC and a nitrogen compound is made by British Patent No. 740,269, in which the cross bonding or curing of the polymers is thermally induced. It was done.

U.S. Pat. No. 2,772,188 proposes the use of ammonia to cure polymers, while British Patent No. 9,06314, which ultimately achieved industrial success, proposes using ammonia to cure polymers. It describes a two-step application method, in which NH3 is applied in the first step as gaseous NH3 and in the second step as aqueous ammonia.

What is intended to be accomplished in this operation is to control the degree of bonding so as not to unduly damage the feel of the fabric due to the resin deposition required to impart flame resistance.

It is additionally desirable to obtain an acceptable level of washfastness, which has been substantially achieved by the gaseous/aqueous liquid two-stage process.

The best results in terms of adjusting the highest flame resistance and soft feel are obtained by using urea as the nitrogen compound and curing with ammonia.

Heat curing of urea polymers does not give satisfactory results and if heat curing must be used it is necessary to use more highly functional compounds such as melamine or mixtures of melamine and urea. Probably.

However, this method is not used in practice because it produces a woven fabric with a poor feel.

When using urea/THPC resins cured with ammonia, the correct ratio of urea:THPC is the proportion in which these reactants are present in the prepolymerization to be crosslinked with the aid of ammonia, i.e. 0.5:1. It has traditionally been thought that it is a molar ratio.

However, two recent developments have created difficulties in the use of this composition.

Firstly, there is a desire for flame-resistant woven fabrics that are lighter than conventional fabrics, and secondly, more stringent flame resistance is required for certain types of articles.

As to the first condition, the composition is satisfactory for woven fabrics weighing more than, say, 4 ounces per square yard, but when applied to lighter woven fabrics, the woven fabric becomes unacceptable as a commercial product. Damage the feel.

Attempts have been made to use ammonia-cured THPC alone without the addition of nitrogen compounds such as urea to address this problem.

To make this possible, the normal pH of THPC of about 3 to 7 was neutralized by adding a suitable alkali or base to THPC.

Such a method is the subject of British Patent No. 938,990, but some confusion has arisen because a similar method carried out using [THPOHJ] has been described.

In fact, the presence of said particular compound in the neutralized solution of THPO is somewhat hypothetical, and we simply refer to it as ``neutralized THP''.
It is recommended to use the expression OJ.

Flame resistance of textiles is controlled in many countries by specifications published from time to time by government agencies3 The first specification to be in force was British Standard (BS) 3119:195.
9, it was based on the vertical strip test method.

Currently children's sleepwear in the UK is B52963:1
958, in the United States, the US specification FF3-7
It is managed by 1.

We have determined that these latter tests are more stringent than those previously used and require greater coverage of THP-based flame resistant resins to pass these standards.

This ultimately results in a stiffer fabric feel, which is unacceptable even for fabrics that could be processed satisfactorily under the original specifications.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide a flame-retardant treatment process that meets all of the above specifications, yet does not result in woven fabrics that are unacceptably stiff.

It should be understood that these two conditions are mutually exclusive, and we can direct the fabric towards greater flame resistance or It has been found that it is possible to vary the feel towards even better feel, and that by selecting the ratio within the following limits, a woven fabric can be obtained which satisfies both conditions.

This invention uses cellulosic textile fibers with a urea:tetrakishydroxymethylphosphonium molar ratio of 0.05:1.
~0.25:1, as well as the precondensate formed by the reaction of urea with the tetrakis hydroxymethyl phosphonium salt, and the pH is adjusted by addition of an alkali or base. by impregnating the fiber with an aqueous solution neutralized to 5 to 8 and treating the impregnated fiber with asimonia to produce a crosslinked polymer containing repeating units derived from the tetrakis hydroxymethylphosphonium, urea, and ammonia. A method for flame-retardating cellulosic textile fibers, the method comprising:

The impregnating solution used in this invention contains the required amount of urea and THPC.
can be made by mixing them in water and refluxing them to react and form a precondensate.

Alternatively, a solution with a molar ratio of urea:THP salt of 0.5:1 may be refluxed and the required amount of THPC to obtain the correct ratio of urea:THP may be added afterwards.

However, if a solution is made, the solution should be 5 to 8, preferably 5.8 to 8.
Neutralize to a pH of 7.

This can conveniently be done by adding caustic soda, but other alkalis such as sodium carbonate can also be used.

It should be understood that a lower pH within the aforementioned range is used since too high a pH will render the solution unstable.

The THP salts mentioned above are usually chlorides, but other chlorides such as bromides or other salts such as acetates, sulfates or phosphates can also be used.

The concentration of the precondensate solution is preferably 20% to 40% by weight.

A preferred value is 25% to 30% by weight.

It is convenient to first make a solution of about 50% strength and then dilute immediately before use.

It is preferable to carry out neutralization at this stage rather than at the solution manufacturing stage.

Treatment with ammonia involves first treating the fabric impregnated with the THP salt precondensate and drying with gaseous ammonia to produce a partially cured product, and then treating this partially cured product with aqueous ammonia. It may be carried out by a two-step gaseous/aqueous method consisting of completing the curing by passing the impregnated fabric through a closed device into a closed chamber, where the impregnated fabric is passed through a closed chamber by evaporation and/or chemical reaction. (having a device for preventing the generated condensate from dripping onto the fabric), the fabric is brought into contact with at least one conduit installed in the sealed chamber, and the conduit is brought into contact with the fabric. A rapid gas curing method may be used consisting of injecting gaseous ammonia through one or more orifices provided to penetrate the ammonia across the width of the fabric.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In order to better understand the invention, the following experimental results are described.

Five sets of solutions were made.

, each of these sets of solutions are urea:THPC as follows:
They had different values of molar ratio.

(a) Ol (b) 0.05, (c) 0.125, (d)
0.25, (e) 0.5 The solutions in each set were sequentially reduced in total THPC content to suitably vary the amount of THPC deposited on the treated fabric.

The most concentrated solution of each set. The solution has a total THPC content of 48% and an excess of THPC in the amount such that the urea:THPC molar ratio is required for the set [(e),
[except in the case of]] were prepared by preparing a solution of urea THPC precondensate (molar ratio -〇, 5:1).

By adding 5 parts of caustic soda per 100 parts of THPC, p
H was set at 5.9.

This solution was used as it was or by sequentially adding approximately 10% water to the set of solutions.

Cotton Winceyette weighing 150 grams per inch
A woven fabric sample was impregnated with each solution of each set to a wet wicking amount of about 80%, and the following THPC adhesion amount was calculated from the % of THPC in the solution and the wet wicking amount.

Each sample was dried at 85°C, then curing was carried out by passing ammonia gas continuously through the fabric at a rate of 251/min, and the sample was then passed through a synthetic detergent containing about 20% sodium persate. 4.5? /l solution at 50°C.
Wash for a minute, rinse thoroughly and dry.

The samples were then tested using the fire test described below.

1" British Standard 3119:1959 A general test for flame-resistant woven fabrics using a conditioned sample of l2-X2 "1" and igniting the sample by applying a standard high brightness flame of 1- for 12 seconds.

Department of Commerce FF3-71 Test method prescribed in the United States for children's sleepwear.

The pre-dried sample, with both vertical ends of the sample fixed in the gripping tool, is burned for 3 seconds with a l-standard high brightness flame.

British Standard 2963: 1958 Method A Test method prescribed for children's sleepwear in the UK.

A free strip of 6 ft. x 1-inch moisture-conditioned woven fabric 1" □ is ignited by placing it in a 1" standard high brightness flame for 12 seconds.

However, this method provides a consistent result for flame-resistant fabrics because the sample moves freely in and out of the flame.

This method uses shorter (15 inch) samples and
It was modified so that the ignition flame was continuously applied to the lower end of the sample until the entire width of the lower end of the sample was ignited (approximately 3 seconds), and then the ignition flame was immediately withdrawn.

The permissible limits for the above three methods are British Standard (BS) 31.
For No. 19, the maximum carbonization length of the sample was 41 inches
'', FF3-71''1.1. ．．゛i+! Fui′
10 for H and British Standard (BS) 2963.
Inches.

Although the severity of one particular test appears to be related to the allowable char length, the use of shorter ignition times favors sustained combustion once the sample ignites;
Although applying the vertical end for ignition as in B52963 allows for more rapid flame propagation, the severity of the test can also be determined by the ignition time.

Samples of treated woven fabrics can be classified into four grade groups:

FR grade: Fail all 13 tests FR grade: 2 Pass B53119, but FF3-71
and B52963 failed FR Grade 3 Passed B53119 and FF3-71 but failed B52963 FR Grade Passed all 43 tests In addition, the samples were classified for feel and divided into two groups of grades.

Group A: Fabric feel is acceptable Group 8: Fabric feel is excessively hard Table 1 shows the results regarding THPC coverage for the various grades.

In another set of experiments, solutions with various urea:THPC molar ratios and total THPC concentrations of 32% were prepared as described above and used to test the same fabric samples in the same manner.

The samples were flame tested and tactile tested as described above and T
Table 2 shows the results regarding HPC coverage, flame resistance, and feel.

All the tests described above were repeated using a solution with a total THPC concentration of 24% and the results obtained are listed in Table 3.

The results of Tables 1.2 and 3 are shown in the accompanying drawing in which the abscissa represents the urea:THPC molar ratio and the ordinate represents the % THPC deposition.

This figure shows the numbers in the table, and each number marks its FR grade number.

The distribution of each point in the diagram is distributed in such a way that it is divided into four areas, each representing one of the FR grades and each corresponding area.6 Curves H divide the area of the diagram according to the feel of each sample. , group A (acceptable 1.5 feel) is located below curve H, and group B (unacceptable feel) is located above curve H.

Woven fabrics that pass all flame resistance tests and have acceptable feel are solutions of sets (b), (e) and (d), i.e. urea:THPC molar ratios from 0.05:1 to
It can be seen that the sample was treated with a solution having a ratio of 0.25:1.

ADVANTAGES OF THE INVENTION An advantage of the present invention is that flame resistance of cellulosic textile fibers is achieved with good flame resistance and good feel of the treated fibers.

[Brief explanation of the drawing]

The figure shows the results of a flame resistance test and a feel test.

Claims (1)

[Claims] 1 Cellulosic textile fibers were prepared at a molar ratio of urea:tetrakishydroxymethylphosphonium of 0.05:1 to 0.1.
25:1, as well as the precondensate produced by the reaction of urea and tetrakishydroxymethylphosphonium salt, and the pH is adjusted to 5 to 5 by addition of an alkali or base. 8 and treating the impregnated fibers with ammonia to produce a cross-linked polymer containing repeating units derived from said tetrakishydroxymethylphosphonium, urea and ammonia. A method for making cellulosic textile fibers flame resistant.