JPS5828366B2 - Manufacturing method of various kinds of fibers - Google Patents

Description

DETAILED DESCRIPTION OF THE PRESENT EMBODIMENTS The present invention relates to a method for producing regenerated cellulose fiber which has excellent flame retardancy and further exhibits excellent flame retardancy even when mixed with synthetic fibers.

As a method for making recycled cellulose fiber flame retardant without using a post-processing method, phosphorus compounds (e.g., polyphosphonates, polyphosphonitriles, etc.) have been used.
A method is known in which a compound such as bromopropyl phosphate is added to a spinning solution and then the solution is spinned.

The yarn produced in this manner exhibits fairly good washability etc. and also exhibits a certain degree of flame retardancy.

However, it must be admitted that the yarn obtained here has the following two major problems.

(a) The flame retardant effect of phosphorus compounds on recycled cellulose fibers is not always sufficient, and a fairly large amount of flame retardant must be used in order to obtain a product with sufficient flame retardancy.

This results in a decline in yarn quality and an increase in product prices.

(b) In the case of blends of synthetic fibers such as polyester, sufficient flame retardancy cannot be obtained even if the polyester is sufficiently flame retardant.

In particular, with regard to (b), although there has been a very strong demand in recent years, mainly in the United States, for flame-retardant polyester/cellulose blends, there have been no successful examples anywhere in the world.

The reason for this is not clear, but polyester/cellulose blends are more flammable than each of the constituent fibers alone, and therefore even if the polyester has been flame-retardant modified, its mixture with recycled cellulose fibers modified using the conventional methods described above does not exhibit sufficient flame retardancy.

In order to obtain sufficient flame retardancy, some kind of post-processing is required to make the fabric flame-retardant, which results in deterioration of the fabric properties and feel, making it virtually impossible to produce practical flame-retardant fiber products.

It has been known that for certain materials that need to be flame retarded, the combined use of a phosphorus-based flame retardant and a bromine-based flame retardant can have a synergistic effect on flame retardancy. However, the flame retardant effect in such cases varies depending on the target material and the flame retardant used, and the synergistic effect is only realized in certain combinations.

However, this particular combination is only discovered by chance after an enormous amount of trial and error with a large number of flame retardants, and even if a favorable result is obtained in terms of flame retardant effect, in order to put it into practical use, it must satisfy all of the numerous manufacturing process and product physical property requirements up to the end product, such as compatibility with the target flame-retardant material, moldability, spinnability, stretchability, washability, colorability, weather resistance, strength and elongation properties, etc., making the search for this an almost hopelessly difficult undertaking.

However, due to strong market demand for flame retardancy, in spite of such difficulties, exploratory research into flame retardancy has been actively carried out in recent years.

The present inventors have carried out intensive research and investigations to obtain flame-retardant regenerated cellulosic fibers which provide such a synergistic flame-retardant effect for regenerated cellulosic fibers and which also provide excellent flame-retardant effects for mixed materials with synthetic fibers (especially polyester fibers) which are extremely difficult to make flame-retardant as described above. As a result, they have finally achieved the present invention which achieves the desired object. The gist of the present invention is a method for producing flame-retardant regenerated cellulosic fibers, which comprises adding a polymer (hereinafter referred to as a bromine-containing polyacrylate) obtained by polymerization using a compound represented by the following general formula CI) as at least one monomer component, and a phosphorus compound to a spinning dope, and then spinning the mixture in the usual manner.

l CH2=C-COOR2(I) (wherein R1 is a hydrogen atom or a carbon atom having 1
R2 represents an alkyl, aryl, alkylaryl or aralkyl group having at least one bromine atom as a substituent.

Specific preferred examples of the compound represented by the general formula [■] in the present invention include those in which R1 is a hydrogen atom, a methyl group,
ethyl group, and the like, where R2 is 2-bromoethyl group, 2,3-dibromopropyl group, tris-2,2,2-bromomethylethyl group, 2-bromopropyl group, 3-bromopropyl group, 2,4,6-tribromophenyl group, 4-bromophenyl group, 4-bromomethylphenyl group, and the like.

The bromine-containing polyacrylate in the present invention is a homopolymer or copolymer of the compound represented by the above general formula (I) or a copolymer of the compound with another monomer copolymerizable therewith (e.g., a vinyl monomer), and is a linear polymer obtained by a polymerization method such as radical polymerization in the presence or absence of a solvent or radical polymerization using an activator.

The polymer must be linear from the viewpoints of compatibility with the phosphorus compound used in combination and of preventing an increase in nozzle back pressure during spinning, and the number of repeat units may be about 5 or more.

However, in this case, if the monomer remains, it may have a negative effect on spinnability, odor, flame retardancy, etc.
The monomer needs to be removed.

The tolerable amount of monomer remaining in the polymer is 5 parts or less (preferably 3 parts or less).

The phosphorus compound used in the present invention may be any compound that has the effect of imparting flame retardancy to the regenerated cellulose fiber, but the phosphorus compounds represented by the following general formula Un(Vl) are particularly preferred.

(wherein, X is O or S, T, Y and Z are -O---S- and -N- (wherein, R is H)
1 represents an alkyl group or an aryl group having 1 to 6 carbon atoms.
each of which may be the same or different, is selected from the group consisting of
R3 is a divalent organic group having or without a substituent;
R4 is a monovalent organic group having or without a substituent;
a, b, c and d are the numbers 0 or 1 and b + c
+ d 22, n represents an integer of 3 or more.

In the above formula, R6 and R7 each represent a monovalent organic group which may or may not have a substituent, and m represents an integer of 3 or more.

) (wherein in formula m, R8, R9, and R10 are monovalent organic groups which may or may not have a substituent; X.

T, Y and Z are the same as those shown in the formula (m), a.

b, c and d are numbers 0 or 1 and b + c -
It is shown that 1-d≧2.

a, e, f and g are the numbers 0 or 1 and e + f + g ≧ 2; R11 and R12 are typically monovalent organic groups having or without a substituent; R13 is typically bivalent organic groups having or without a substituent;
represents an organic group having a valence.

R11 and R13, or R12 and R1,3 may form a ring.

Among the phosphorus compounds represented by the above general formula, taking into consideration durable flame retardancy and spinnability, it is particularly recommended to use the polymeric phosphorus compounds represented by the general formulas (III and IV).

When these polymeric phosphorus compounds are used in combination with other phosphorus compounds, it is advisable to ensure that the polymeric phosphorus compounds weigh 50 times more than the total weight of the phosphorus compounds used.

If necessary, a nitrogen-based flame retardant such as an amide compound or a phosphamide compound may be used in combination.

In the present invention, when the bromine-containing polyacrylate and the phosphorus compound are mixed into the spinning solution for producing regenerated cellulose fibers, it is particularly important that these compounds are uniformly dispersed in the spinning solution.

As a method for uniformly dispersing the particles, the following methods (1) to (3) are recommended.

(1) A bromine-containing polyacrylate, a phosphorus compound, and a nonionic surfactant in an amount less than the total amount of the two are mixed in a molten state, and the mixture is mechanically dispersed in a spinning dope.

(2) The three components listed in (1) are dissolved in a suitable solvent (e.g., acetone, benzene, etc.), the solvent is removed under normal or reduced pressure, and the resulting solution is dispersed in the spinning dope.

(3) An appropriate amount of carbon disulfide is mixed with the mixture of the three components obtained in (1) or (2) to obtain a solution with the same viscosity as the spinning solution, and then the solution is dispersed in the spinning solution.

etc.

It is important that the emulsifier used here is non-ionic, and preferably has an HLB of 6 to 14. The amount of the emulsifier used is desirably less than the total amount of the flame retardant components.

In principle, the mixing ratio of the phosphorus compound to the bromine-containing polyacrylate is arbitrary, but in order to achieve particularly efficient flame retardancy, it is better to use a larger amount of the phosphorus compound.

The mixing ratio of both components in the spinning solution varies depending on the phosphorus and bromine content of each compound, but is 5 to 100% relative to the cellulose component.
40 weight units, preferably 10 to 30 units.

Flame retardants consisting of both components or those to which a nonionic surfactant has been added usually do not cause problems in spinnability, the subsequent manufacturing processes, or the quality of the finished yarn. However, when the degree of polymerization of both the phosphorus compound and the bromine-containing polyacrylate is very high, they may cause an increase in the back pressure of the spinning nozzle.

In such a case, the problem can be solved by adding an appropriate amount of a low molecular weight phosphorus compound.

The regenerated fiber in the present invention refers to rayon, polynosic rayon, etc., and the flame retardant of the present invention is added to the spinning dope and mechanically mixed and dispersed therein.

There is no particular restriction on the timing of adding the flame retardant, but it is preferable to add and mix it immediately before spinning in order to prevent the phosphorus compound from dropping into the spinning solution due to hydrolysis.

The present invention is configured as described above, and by utilizing the synergistic effect of the bromine-containing polyacrylate and the phosphorus compound, it is possible to produce recycled cellulose fiber with extremely excellent flame retardancy without any trouble in the manufacturing process and without impairing the inherent physical properties of the recycled cellulose fiber. Furthermore, the obtained flame-retardant recycled cellulose fiber exhibits excellent flame retardancy even in synthetic fiber blends, which are extremely difficult to make flame-retardant.
This is of immense usefulness.

The effects of the present invention will be further clarified by the following examples.

In the examples, the phosphorus compounds and bromine-containing polyacrylates shown in Table 1 were used.

Example 1: Alpha cellulose with a concentration of 80% was obtained from wood pulp through the steps of soaking, squeezing, crushing, aging, sulfurization and dissolution in a conventional manner.
A flame retardant dope as shown in Table 2 was added to a normal viscose stock solution having a viscosity of 35 seconds, a caustic soda concentration of 6.0%, and a falling ball viscosity of 35 seconds, so that the total amount of the flame retardant was 20% relative to the α-cellulose.
The mixture was mixed and dispersed by weight using an injection machine and an on-plate immediately before spinning.

Thereafter, the fiber was spun into a Muller's acid bath through a nozzle having an orifice diameter of 0.07 mm and 2,000 orifices, and then desulfurized, washed with water, bleached, and the like in the usual manner to obtain regenerated cellulose fibers.

The fibers thus obtained were cut into 30 cIrL pieces, thoroughly twisted, and then folded in two to produce a twisted product.

The sample was hung on a limiting oxygen index (LOI) measuring device according to JIS K-7201, and ignited from below to determine the LOI value.

The results obtained are shown in Table 2.

As shown in Table 2, in the case of wastes 1. to 5.0 according to the present invention, the LOI value of the obtained regenerated cellulose fiber was all 2.
1 or more, 45° to 6. for phosphorus compounds alone, and A2B for bromine-containing polyacrylates alone.

The LOI value is far superior to those in the cases of 1 to 9, and it is apparent that a synergistic effect is obtained by using the bromine-containing polyacrylate and the phosphorus compound in combination.

Example 2 2.2-bis(4-(2-hydroxyethoxy)3.5
Flame retardant polyethylene terephthalate filament copolymerized with 1,2-dibromophenyl]propane (LOI value 21.5
) and the rayon yarn obtained in Example 1 in a weight ratio of 6.
Twist it together tightly so that it becomes 5:35, and cut it into a length of 15z.
A twisted material was prepared.

Using this sample, the LOI value was measured according to the method of Example 1.0.

The results are shown in Table 3. In the table, the symbols for the rayon yarn are the same as those shown in Table 2.

As shown in Table 3, the blends of flame-retardant rayon yarn (43 and 4) and flame-retardant polyester fiber produced according to the present invention have a high LOI value of 21 or more, and therefore exhibit excellent flame retardancy.

On the other hand, the mixture of flame-retardant rayon yarn (46, to 9) produced by a method not belonging to the present invention and flame-retardant polyester fiber has an LOI value lower than the LOI value of each of the constituent fibers, and the reduced flame retardancy of the mixture is clear.

Claims (1)

[Claims] 1. A polymer obtained by polymerization using a compound represented by the following general formula [■] as at least one monomer component,
A method for producing flame-retardant regenerated cellulose fiber, comprising adding a phosphorus compound to a spinning solution and then spinning the solution in a conventional manner.
Rz represents an alkyl group, an aryl group, an alkylaryl group or an aralkyl group having at least one bromine atom as a substituent.