CA1050690A

CA1050690A - Fire-retardant fiber of aminoplast and polyvinyl alcohol

Info

Publication number: CA1050690A
Application number: CA227,363A
Authority: CA
Inventors: Kanzi Kashihara; Yasuo Yoshizawa; Nobuo Yoshizumi; Tatsuo Nogi; Yoshizo Tsuda
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 1974-05-21
Filing date: 1975-05-20
Publication date: 1979-03-13
Also published as: FR2272159B1; JPS50148623A; GB1498848A; FR2272159A1

Abstract

ABSTRACT OF THE DISCLOSURE
A flame-retardant fiber is made comprising 20-95% by weight of amino resin condensate of an amino compound and formaldehyde in which the amino compound may be a melamine, combined melamine and guanamine, combined melamine and urea, combined melamine, guanamine and urea, and benzoguanamine and/or urea, and in which the chemical bond linking the polymer chain is primarily a methylene linkage and 80-5% by weight of polyvinylalcohol, the resulting fiber being cured when necessary and having a tensile strength of at least 1.0 g/d, and having a break elongation of at least 5%. These flame retardant fibers find use in a wide variety of fabrics, either alone or ad-mixed with other fibers. They are particularly useful in the production of flame protective clothing.

Description

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The hazardous increase in fires from the combustibility of many fabrics and plastics resulting in the loss of human life and in th0 loss of property has necessitated the strict regrulation of fire-extinguishing or fire-prevention equipment and/or systems and in the discovery of fibers which are flame retardant.
The present inven~ion relates to a novel nonflammable fiber con-sisting essentially of amino resins and polyvinylalcohol (hereinafter re- ~`
ferred to~as PVA), with the amino resins being obtained by the reaction of formaldehyde wi~h amino resin-making amino compounds in water and/or in polar solvents such as dimethylsulfoxide ~DMS0), N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc) or hexamethyl phosphoamide (HMPA) in the presence of an acid or in an acidic condition. The mixture resulting from the amino resin obtained in the above manner and~PVA dissolved in the solvent is spun into fibers and cured when necessary.
; With the foregoing in mind, this invention seeks to provide a fiber which is flame-retardant and which can be used, therefore, without ear of combustibility and without the need of elaborate fire-extinguishing or fire-prevention equipment and systems.
The flame-retardant fibers made in accordance with the present 2Q invention are composed of 20-95% by weight of amino resin condensate in which the chemical bonds linking the polymer chain are for the most part methylene linkages and 80-5% by weight of PVA.
The fiber of the present invention is prepared by spinning a solution of 20-95% by weight of amino resins formed by the reaction of amino resin-forming amino compounds and formaldehyde in a polar solvent and 80-5%
by weight of PVA, followed by washing, drawing, heat treating and, when necessary, curing.
In practice, amino resins are generally used as adhesives, in plywoods, decorative laminates and paper impregnants. Urea-formaldehyde ~-3Q resins, melamine-formaldehyde resins and guanamine-formaldehyde resins are '~'~$ ;~ )' ., . , .. ,. . , , ~
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typical examples of amino resins which are widely used.
Uncured amino resins are generally known as methylol-type resins in which amino-functional groups o the amino compounds are hydroxymethylated.
The methylol-type resins are thus in the form of shaped articles cured to form insoluble and infusible thermosetting resins. However, these uncured amino resins comprising hydroxymethylated amino compound monomers or oligo mers are very unstable under heat and chemical reactions. A slight heating of these resins easily leads to crosslinking or gelation, making it impos-sible to apply these resins in further chemical reactions or blending them with other reactive materials. This instability has been a chief reason for the difficulty in obtaining a stable, blended solution of the amino resin and PVA which has many pendant hydroxy groups capable of reacting with the amino resin leading to a gradual increase in viscosity or gelation of the blend. Therefore, it has hitherto been possible to blend only a small amount of amino resin with PVA in a solution. ~ ;~
The amino resin of the present invention is particularly manu-factured to be soluble or homogeneously dispersible in water and/or in a `~ polar solvent such as DMS0, NMP, HMPA, D~c, or a proper combination thereof, and capable of reacting with proper aldehyde compounds to make higher mole-- 20 cules or crosslinked polymers, for making a stable solution in the presence - of the proper amount of PVA.
The amino resins in this invention are condensate products of amino compounds and formaldehyde in which the amino compound units are mainly connected by methylene bonds. ~`
For purposes of clarity, the term "methylene content" is defined as follows:
Methylene Content (%) = the methylene groups in the amino resin (moles? x 100 the sum o hydroxymethyl groups and methylene groups in the amino resin ~moles) The methylene content of the amino resins of the present invention ~o~
should be at least 50%, preferably more than about 70%.
The solutions of the amino resins of high methylene content of the present invention are stable at room temperature and even at elevated temperatures because of the small content of the reactive hydroxymethyl groups.
- The amino compounds used to obtain the amino resin used in the present invention include melamine or its derivatives such as cyclohexyl melamine; guanamine compounds such asbenzogu~mine or acetoguanamine, and urea and its derivatives such as methylurea. As will be seen hereinafter lQ certain combinations of these amino compounds are more favorable than others.
Other compounds capable of condensate reaction with formaldehyde such as sulfamide, guanidine, aniline, phenol, and xylene can be used as minor comonomer components. As the source of formaldehyde, formaline (an aqueous solution of formaldehyde) is conveniently used in obtaining the amino resin of this invention. Methanol or DMSO solutions of formaldehyde may also be used, and paraformaldehyde, trioxane and tetraoxymethylene which are capable of splitting off formaldehyde by decomposition in the course of reaction may also be used in the amino resin formation reaction in the place -~
of formaldehyde.
2Q The affinity of amino resin to solvents depends on the kind ofamino resin, the degree of polymerization and the acid content of the solu-- tion and therefore~ it is important to choose a suitable condition for poly- ;;
;~ merization. DMSO is an especially good solvent for the preparation of this amino resin in that it can dissolve well the amino compound, formaldehyde PVA and the formed amino resin which has several methylene bonds. Other polar solvents such as DMAc, HMPA and NMP are somewhat inferior to DMSO.
In an aqueous solution~ the polymerization of the amino resin of high methylene content is difficult in view of the poor solubility of the condensate in water. In this case, the condensate can be emulsified in water by the addition of some emulsifying agents or solubilized by the formation of an acid complex. -"

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Preparation of the soluble acid-polymer complex is carried out by *he addition of a quantitative aMount of acid which is used as a catalyst for preparing the amino resin condensate.
As a catalyst in the preparation of the amino resin used in the present invention, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acidJ etc.; organic acids such as oxalic acid, formic acid, etc.; Lewis acids such as aluminum chlor:ide, zinc chloride, and sulfonic acids such as p-toluenesulfonic acid may be used. Compounds which generate acid by hydrolysis, pyrolysis, etc., may also be used. The desirable quan-tity of such acid is 0.03-3.5 mole of acid per mole of the amino compound.
With reference to the degree of condensation of the resin, control is comparatively easy but is nonetheless important since it is closely re-lated to the stability of the resin solution.
Referring to the molar ratio ~F/A) of formaldehyde (F) to amino compound ~A) of the resin used in the present invention, such ratio is 0.6 -2Ø When this ratio is smaller than 0.6, the molecular weight of the resin is comparatively small and a large amount of unreacted monomer is apt to remain. On the other hand, when this ratio is larger than 2.0~ the mole-cular weight of resin is quite high and sometimes gelation occurs. Therefore, ; 20 it is desirable for the molar ratio (F/A) ~o be 0.7 - 1.5, and more prefer-ably 0.77 - 1.2. `
Other reaction conditions such as reaction time, temperature and concentration vary with the kind of amino compounds used. For example, the reactivity of melamine is comparatively great and hence it is desirable to make the monomer concentration and reaction temperature as low as possible.
On the other hand, the reactivity of guanamine and urea is comparatively small and therefore it is desirable to make the monomer concentration and reaction temperature as high as possible. The reaction temperature should be lower than the boiling point of the solvent, preferably 50-100C.
The proper concentration of the resin is dependent on the kind of -1(~5~
resin and the degree of polymerization. G~nerally, concentration is 1~70%
and preferably 5-~0% in order to obtain a practical and stable solution, which solution may be clear or turbid depending on the preparative conditions such as concentration, the kind of amino compound, the amount of acid, etc.
However, even when the solution is turbid, it is usually stable and uniorm.
This solution of reaction mixture can be precipitated using an organic solvent such as alcohol or acetone as the precipitating agent. The solid resin obtained is then dissolved again in the first solution, in the presence of proper acids when necessary.
The amino resin condensate has many methylene bonds as manifested by the oxygen content of the resin which is very low and by iodometry, usually used for the determination of the quantity of methylene bonds in an amino resin. A polar solvent such as DMSO hardly affects the iodometry.
Polyvinylalcohol (PVA) used in the present invention is obtained by saponification of polyvinylacetate with an alkali or acid. PVA having some acetyl groups and PVA which has been formalizedJ acetalized or bu~y-ralized may also be used. It is also possible to copolymerize othar vinyl ~ -mono~ers with vinyl acetate but it is desirable to use PVA resulting from a high degree of saponification. ~ -The method of blending the amino resins used in the present invention with PVA is not restrictive. For example, i~ is desirable to dissolve solid PVA in a solution of amino resin or to mix a solution of PVA
` with the solution of amino resins.
; The spinability and the flame-retardance of the fiber depend on the ratio of the amino resin to PVA. Therefore, it is necessary for the PVA
content in the resulting polymer-resin system to be about 5 - 80% by weight, preferably about 20 - 70% by weight. When said content is less than about ~ ;;
5% by weight, spinabili~y is impaired. On the other hand, when said content exceeds about 80% by weight, the flame-retardance capability of the result-ing fiber is adversely affected with the object of the present invention not ~:"
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being achieved.
Also, it is desirable for these amino resins to be reacted with ;
some parts of PVA, for PVA can also react with formaldehyde. When the chemi-cally bonded combination exists, the flame-retardance of the resulting fiber is improved.
The method used for spinning the resulting solution to fibers may be either a dry or a wet spinning method. The molecular weight of amino resins used is not restrictive, but it is necessary that said amino resins be soluble or homogeneously dispersible in the solven~. Generally, the amino Tesins having a high molecular weight have better spinability, but the amino resins having exceedingly high molecular weight are quite susceptible to gelation and spinning of the resùlting spinning solution may be difficult.
As a result, it is necessary that the viscosity of the spinning solution be properly controlled, said viscosity being about 10 - 1700 poises at the spinning temperature, preferably about 50 - 500 poises. Suitable concen- -tration of the spinning solution varies according to the spinning method employed and the kind of amino resins, PVA and the molecular weight of the PVA. Generally, however, it is about 5 - 80% by weight, preferably about ; 10 - 60% by weight. When said concentration is less than about 5% by weight, spinability and productivity are impaired. On the other hand, when said concentration exceeds about 80% by weight, the spinning solution tends to be heterogeneous and unstable.
M ditives may be mixed in the spinning solution to improve its blend and stability. As additives, viscosity stabilizing reagents, frosting reagents or reagents for enhancing flame-retardance are used. Of particular desirability is the adding of the acid used as catalyst for forming amin resins to the heterogeneous spinning solution, in which case the solution often becomes homogeneous and more stable.
In wet spinning, the spinning solution is de-gassed, filtered and then is spun through wet spinning nozzles made of an alloy of gold and , platinum or stainless steel, each nozzle orifice having a diameter of 0.05 - 0.3 mm, into a coagulation bath. As a coagulation bath, alcohols such as methanol and butanol, ketones such as acet:one and cyclohexanone, aqueous solutions of salt such as Na2S04, (NH~)2SC)~I, K2S 4, 3 2 3 KCl, NH4Cl, CaC12 and a mixed solution of water and water-soluble solvent containing said salt are preferably used.
When the spinning solution contains a polar solvent, the polar solvent is added to the coagulation bath to control the coagulation power and to assure continuously stable spinning. This is preferable since change ?
of composition in the coagulation bath is often decreased during spinning and the coagulation power is controlled by the quanti~y of added solvent.
If the spinning solution contains an acid, the acid is preferably neutralized in spinning by adding an alkali to the coagulation bath. An aqueous solution of an al~ali such as NaOH, KOH or ammonia is preferable because it contributes to a neutralizing of the spinning solution and also to the improvement of coagulation power as well. In this case the salt produced by neutralizing the alkali is preferably added to the coagulation bath. The suitable composition and ratio of the coagulation bath varies, more or less, according to the kinds of amino resins and PVA, the ratio of amino resins to PVA, the condition of the mixed solution, and the concentration of the spinning solution.
Usually the spun undrawn yarn is drawn at a predeternlined draw ~
ratio by conventional methods in air or in a suitable bath, and then washed -iwith water.
Af~er the wet-spun fibers are washed with water, they are dried with hot air or a hot plate. Hot-drawing is usually carried out in order to improve the properties of the fibers. If necessary, a second or even a second and third stage of hot-drawing may be used. It is often preferred to `
heat treat the fibers at a temperature higher than hot-drawing which remark-ably decreases the shrinkage of the fibers. For dried fibers containing a ~oso~
rich amino resin, hot-drawing may be omit:ted and simple heat treatment carried ou~ to improve the properties of the fibers. The fibers are usually drawn at a temperature higher than 1~0C~ and the hot-drawing temperature varies with the ratio of amino resins to PVA or the water content in the fiber.
In the hot-drawing and heat treating processes, it is estimated that grass-like, tenacious and fireproofed fibers are formed as a resul~ of the orientation of PVA and the reaction of PVA and amino resin.
The dry-spinning technique may be applied to fiberize the mixture of PVA and amino resin. A concentrated solution of PVA and amino resin is extruded to an atmosphere the temperature and relative humidity of which are controlled. The fibrous materials thus formed are exposed to the drying action of hot air. It is preferable to carry out hot-drawing and heat treat-ment. It is preferable to cure those fibers produced by wet or dry spin-ning when such fibers do not have satisfactory resistance to heat and flame.
Curing is not to be limited to the finished fiber after hot-drawing and heat treatment, but the fibers in the coagulating bath, or in the process of being ~-washed with water or in the drying machine in the case of wet spinning. In dry spinning, curing may be carried out simultaneously with fiberization.
Aldehydes are used to cure ~hese fibers.
Curing of the uncured fibers is effected by heating in a liquid or `~
gaseous formaldehyde environment in the presence of a catalyst. It appears ~;
that the curing mechanism involves the diffusion of the formaldehyde into the ~ -fiber and the reaction of the amino resin and formaldehyde to bring about polymerization of the amino resin. In the curing process, it is estimated that formalization of PVA and cross~linking of PVA and amino resin wi~h forma-ldehyde also occurs. The cured fibers possess a number of highly desirable properties, such as remarkable resistance to heat and flame, and excellent mechanical properties.
To effect the presence of an acid catalyst during curing, one means ~s~6~a3 employed is to incorporate a small amount of a suitable acid into the spin-ning solution prior to fiberization. The fibers may then be treated in a liquid or gaseous formaldehyde-containillg environment.
Another means of preparing the cured fiber is blending the spin-ning solution with the compound evolving formaldehyde upon contact with an acid prior to fiberization. Then the fibers may be treated in the presence of an acid. Formaldehyde may be employed in a liquid or gaseous enviro-nment, but it is preferably used in a liquid environment in the presence of an acid catalyst. Paraformaldehyde, trioxane or tetraoxane as well as formaldehyde may be employed as the compound evolving formaldehyde. When curing is ;
carried out in a gaseous environment, hydrogen chloride or hydrogen bromide may be employed as an acid catalyst. When a solution is employed in the curing step, any of a wide variety of acids may be used as the catalyst, including mineral acids such as hydrochloric, sulfuric and phosphoric acid;
organic acids such as oxalic acid; sulfonic acids such as p-toluene sulfonic acid; Lewis acids such as aluminum chloride and zinc chloride, and acidic salts such as NaHS0~ and KH2P04, water is the preferable solvent. However, organic solvents may be employed, provided they do not adversely affect the fibers and are capable of dissolving the formaldehyde and acid.
The concentration of formaldehyde in the solution is not limited ~`

to any fixed value. Acid is employed as a catalyst~ but curing may be carried out in the presence of an acid in an amount greater than the amount needed as a catalyst. Curing is generally carried out at a temperature -~
ranging from room temperature to 200C, and more preferably from room tem-perature to 100 C in a liquid environment. In many cases it is preferred ~ ;;
to effect curing by hPating the ~mcured fiber in a liquid and gaseous environ- ;~ `~
ment. Also it is often desirable to carry out curing in the presence of a salt such as sodium sulfate or ammonium sulfate, under which circumstances ` adherence of fibers does not occur.
The typical mechanical properties of the cured fibers would be:
tensile strength 1.0 ~' 4.0 g/d, break elongation 5~~0%.

_g_ .. . . . . . .

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Various conventional textile techniques may be employed to pro-cess the cured fibers of the present invention into a variety of useful forms. By virture of their high hygroscopicity and ready dyeability with clear deep colors, such fibers are very useful for a wide variety of clothing fabrics. By vlrture of their resistance to flame, such fibers when made into fabrics are well suited for flame protective clothing, and such fibers~
in suitable forms, may be used as materials having heat and chemical resist-ance. The flame-retardant fibers of this invention may also be mixed with other fibers, such as wool, silk, cotton, polyamide fibers, polyester fibers and polyacrylic fibers.
The follc~wing examples are given for the purpose of further illustration of the present invention. In these examples, the content of methylene bond in the amino resin is measured by iodometry usually employed - to measure fornaldehyde.
Exam~le 1 A mixture comprising 32 parts of melamine, 21 parts of 37%
aqueous formaldehyde and 0.3 part of 35% hydrochloric acid were heated in 135 parts of DMS0 at a temperature of 60C for three hours with stirring.
The solution of the reaction mixture was poured into several ~`
times of methanol as the precipitating agent to obtain a solid resin which was treated by vacuum drying for three hours to remove the methanol and a very small amount of the solvent to obtain 35 parts of melamine formaldehyde resin, having 90% methylene content.
Next, this resin was dissolved in DMS0 at 60 & to prepare a uniform solution having a concentration of 21%. 52 Parts of PVA having a degree of polymerization of 2000 (Gohsenol NH-20~, manufactured by Nippon Synthetic Chemical Industry Co. ~td.) were dissolved in 295 parts o~ DMS0 at a temperature of 60C for two hours with stirring to obtain a uniform solution.
m e aforesaid resin solution was added at 50C with stirring for three hours to obtain a uniform mixed solution, which solution was spun as a spinning *Trade Mark i~

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solution through spinning nozzles, each havlng a diameter of 0.08 mm, into a coagulating bath of sodium sulfate/water t20/100). The resulting undrawn yarn was continuously drawn, at a draw ratio of 3, in sodium sulfate/water ~30/100), and washed sufficiently with water to remove the remaining solvent and salt, and was then dried.
The dried yarn was further dx-awn at a ratio of 3 on a hot plate - at 230c by the usual method.
To cure, drawn yarn was immersed at 50C in a mixture of 10 parts of 37% aqueous formaldehydeg 10 parts of concentrated sulfuric acid, 10 parts of sodium sulfate and 70 parts of water. The cured yam was re-moved, washed with water and dried in air at about 80C. The denier of the resulting yarn was 4.5 and had an average tensile strength of 1.8 g/d, an average break elongation of 20%, and an average elastic modulus of 38 g/d.
This fiber was self-extinguishing and showed an affinity for acidic dyes.
Under standard conditions of 65% relative humidity and 20C, the fiber came to equilibrium from the dry state at 8.5%.
-; Example 2 32.8 Parts of melamine, 39.4 parts of benzoguanamine and 38.8 paxts of 37% aqueous foxmaldehyde were dissolved at 80& in 294 parts of -DMS0. 4 Parts of 35% hydrochloric acid were added to the resulting DMSO
solution and heated at 80C for six hours with stirring. The methylene con-tent of this resin was 80%. 26 Parts of PVA having a degree of polymeriza-tion of 2600 (Gohsenol NH-26*, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.) was dissolved little by little at 80& in DMSO to prepare a 17.3% solution. Thereafter, the aforesaid resin solution was added to the ' - PVA solution and the mixed solution was stirred for three hours at a temper-ature of 50C. A solution having a viscosity of about 60 poises at 50c and ; polymer concen~ration of about 14% by weight was obtained.
Thia solution was spun shrough spinning nozzles, each having a diameter of o.o8 mm, into a methanol coagulating bath. The resulting yarn ~Trade Mark ~B
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was continuously c~awn 6 times in methanol and :Ln hot air at 220C. The drawn yarn was self extinguishing and had an average tensile strength of 2.5 g/d3 and an average break elongation of 7%.
Next, the drawn yarn was cured at 30C for 20 minutes in a curing solution comprising 5 parts of sulfuric acidl 5 parts of 37% aqueous formaldehyde, 10 parts of sodium sulfate and 80 parts of water. This yarn had an average tensile strength of 1.6 ~/cl, and an average break elongation of 11%. m e fk~rle-retardancy of this flber was excellent.
Example 3 A mixture comprising 65 parts of mek~Lne, 60 parts of urea and 120 parts of 37% aqueous formaldehyde was dissolved at 60C in 600 parts of ~ DMSO. 3 Parts of 35% hydrochloric acid was added to this solution and then ; heated at 60C for five hours with stirring. The methylene content Or this ~-condensate was 92%. Ihis reaction mixture was blended with a 12% DMSO solu-tion containing 143 parts of PVA (Gohsenol NH-33~, nanufactured by Nippon Synthetic Chemical Industry Co. Ltd.) to obtain a uniform spinning solution.
This solution was spun through spinning nozzles, each having a diameter of 0 08 mm, into a sodium sulfate-water (Na2S04/water = 20/100) coagulating bath.
Ihe undrawn yarn was drawn 9 times and treated with heat at 220 & .
2Q This yarn was then cured by heat treating at 40C for 15 minutes in an aqueous solution containing each 10% by weight of 37% aqueous formaldehyde, concen-trated sulfuric acid and sodium sulfate.
~he cured yarn was washed with water and dried in air at about 80 & . The resulting yarn had an average denier of 3.5, an average tensile strength of 2.3 g/d and an average break elongation of 29%.
This fiber was of a fire-proofing property and dyeable with clear acidic dyes.
Example 4 40 Parts of urea and 54 parts of 37% aqueous formaldehyde were dissolved at 60C in 206 parts of DMS0 and a small amount of sodium hydroxide ~rade M~rk .~ . , .

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was added to prepare the m.ethylol urea. Next, 2 parts of 35% hydrochloric acid was added to the resulting ~SO solution and heated at 60C :Eor five hours with stirring. rLhe urea resin in the solution was analyzed by Iodom.etry to have m.ethylene content of 85%. The solution was diluted wlth 160 parts of ~ISO and 40 parts of PVA havlng a degree of polym.erization of 2000 (Gohsenol NE~-20*, manufactured by Nippon Synthetic Chen~cal Industry Co.
Ltd.) and blended little by little to obtain a uniform solution.
me thus obtained spinning solution was extruded through a spin-neret into a coagulating bath composed of a sodium sulfate solution and thereafter, the coagulated yarn was drawn 8 tim.es and then treated with heat at 225C.
The drawn yarn was imnersed at 50C for 30 minutes in a curing ; solution comprising sulfuric acid, formaldehyde (37%)~ sodium sulfate and water (10/30/10/50).
me cured yarn had an average tensile strength of 2.0 g/d, an average break elongation of 23% and was self-extinguishing.
Exalr~ples 5-8 32.8 Parts of melamine, 39.4 parts of benzoguanamine and 38.8 parts of 37% aqueous formaldehyde were dissolved at 80& in 294 parts of DMSO. Next, 14 parts of 35% hydrochloric acid were added to the resulting DMSO solution and heated at 80& for six hours with stirring. The methylene content of this condensate was 9ll%. PVA having a degree of polymerization - of 2000 (Gohsenol NH-20*, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.) was dissolved little by little at 80& in DMS0 to obtain a solution of 15% solid po~ymer content.
The two aforesaid solutions were mixed to prepare spirn~ing solu-tions containing 25, 40, 60, 85% of PVA.
Each of these spinning solutions was spun through spir~ing - nozzles, each having a diam.eter of o.o8 mn, into a solvent-water (DMSO/water=
30/70) coagulating bath containing 5% of sodium hydroxide and 10% of sodium *I~ade Mark ;,, .

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chloride.
The undrawn yarn was continuously drawn and cured by the same method as in Example l.
The mechanical properties and fire-proofing (LOI) property of this fiber were as follows:
. ... __ __ .__ ._. ,, , ExampleAmino resin PVA ~enacity Elongation L.O.I.*
(wt.%) (wt.%)(g/d) (%) (%) . _ _ ... __ . . _ .
1.5 12 35 :
.. . .__ .
6 60 40 2.9 18 30 ~.
_ ~ __ _._ .~ : ', 7 40 60 3.8 26 28 ~
. _ ~ - - _.~ _ ~ '. ' 8 15 85 5.5 32 22 :, ~Limiting oxygen index -E ample 9 - A mixture comprlsing 31 parts of melamine, 38 parts of benzo `
gu~namine and 36 parts of 37% aqueous formaldehyde were dissolved in 296 parts of DMSO~ Into this solution~ 14 parts of concentrated sulfuric acid was poured and stirred for five hours a~ 60c.
74 Parts of PVA having a degree of polymerization of 2000 (Gohsenol N~I-20~, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.) was dissolved in 338 parts of DMSO.
The two aforesaid solutions were mixed to prepare the spinning solu~ion.
This solution was spun through spinning nozzles, each having a diameter of o.o8 mm, into a solvent-water (D~SO/water = 20/80) coagulating bath containing ammonium sul~onate ((NH4)2S04/solvent-water = 20/100). ~ I

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~he undrawn yarn was continuously drawn 9 times and cured by the same method as in Example 1.
The resulting yarn had an average denier of 3.2, an average tensile strength of 2.3 g/d1 an average break elongation of 19% and an average elastic modulus of 45 g/d.
The fire-proofing property of this fiber was excellent and clearly dyeable with acidic dyes.
Example 10 Using the same part of phosphoric acid in place of the sulfuric ~ ;
acid used in Example 9~ the amino resin was polymerized in DMS0 and mixed ~ -with PVA (Gohsenol NH-20~). The resulting solution was spun through a spin-ning nozzle having a diameter of o.o8 mm into a solvent-water (DMS0/water =
20/80) coagulating bath containing 20% by weight of ammonium phosphonate and a sm~ll amount of ammonium hydro~ide. m e undrawn yarn was continuously ~-drawn 3 times in the wet solution and then 3 times at 220C.
The resulting yarn was superior in fire-proofing without curing, and had an average denier of 4.2, an average tensile strength of 2.9 g/d, an average break elongation of 12% and an average elastic modulus of 40 g/d.
Example 11 18.7 Parts of benzoguanamine and 10.5 parts of 37% aqueous form-aldehyde were condensed in 60 parts of DMS0 at 85C for three hours in exist-ence of 0.3 part of 35% hydrochloric acid with stirring. m e methylene con-tent of this resin was 80%. ;~
This reacti~n mixture was blended with 12% DMS0 solution contain-ing 13.5 parts of PVA having a degree of polymerization of 2300 (Gohsenol GH-23*, manufactured by Nippon Synthetic Chemical Industry Co. I,td.) to obtain a uniform spinning solution. m is solution was spun through spinning nozzles, each having a diameter of 0.1 mm~ into a coagulating bath of sodium sulfate-water (Na2S04/water = 20/100) containing a small amount of sodium hydroxide. The undrawn yarn was drawn 8 times and then heat treated at 220C.

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The dra~n yarn was cured by treating at 50C for 15 minutes in a curing solution of 37% aqueous fo~n~ldehyde, concentrated sulfuric acid, sodium sulfate and water (10/10/10/70 by weight).
The resultlng yarn had an average denier of 3.6 an a~erage tensile strength of 2.1 g/~ and an average break elongation of 14%. The fire-proof-ing property of this fiber was superior.
Exam~le 12 10 Parts of melamine, 5 parts of benzoguanamine, 5 parts of urea and 15.3 parts of 37% aqueous ~ormaldehyde were dissolved in 107.7 parts of DMS0 at 60 & with stirring. Then, 3.7 parts of 35% hydrochloric acid was added and then was stirred at 60C for one hour. The methylene content of the resulting resin was 60%.
Next, 128.6 parts of DMS0 and 22.3 parts of P~A having a degree of polymerization of 1800 (Gohsenol NH-18*, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.) were added portion by portion to the aforesaid solution and then stirred at 70 & for two hours. Viscosity of this~solution was 117 poises at 50C.
This spinning solution was spun, drawn, and cured by the same method as in Example 1. The resulting yarn had an average denier of 3.7, an average tensile strength of 2.8 g/d, an average break elongation of 22% and an average elastic modulus of 42 g/d. -Example 13 32.8 Parts of melamine, 39.4 parts of benzoguanamine and 38.8 ; parts of 37% aqueous formaldehyde were dissolved in 294 parts of NMP. 14 Parts of 35% hydrochloric acid were added and stirred at 80c for five hours. The - methylene content of this resin was 92%.
26 Parts of PVA, having a degree of polymerization of 2000 `~
(Gohsenol NH-20*, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.) ~-were dissolved in HMPA to prepare a solution of 10% solid polymer content.
The aforesaid two solutions were mixed at 50C with stirring. The solution ..

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showed 35 poises at 30C.
This sp~nning solution was spun~ drawn and cured by the same method as in Exa~?le l.
; The mechanical properties of this cured yarn were as follows:
denier: 3.7, tenacity: 2.2 g/d, elongat:ion: 12%, elastic modulus: 40 g/d.
The fire-retardancy of this flber was very superior.
Example 14 A mixture comprising 48 parts of melamine, 47.1 par~s of 37%
aqueous fo~naldehyde, 3 parts of PVA having a de~ree of polymerization of 2000 (Gohsenol NH-20*, manufactured by Nippon Synthetic Chemical Industry Co.
Ltd.) and 3 parts of l N sodium hydroxide solution was dissolved in 277.2 parts of water. After heating this solution at 80C for l hour, 39.6 parts of 35% hydrochloric acid were added and stirred at 80C for 70 minutes. The methylene content of the resulting resin was 90%. ~;
lhis amino resin solution was blended with a solution containing 60 parts of PVA (Gohsenol NH-20~ and dissolved in 273.3 parts of water and then stirred for two hours at 30c. Viscosity of this solution was 53 poises - at 30c and after seven hours was 56 poises at 30&.
This solution was spun through spinning nozzles, each having a diameter of o.o8 mm, into a sodium sulfate/sodium hydroxide/water, (25/5/lO0) coagulating bath at 30&. The resulting undrawn ya~n was continuously drawn 3.5 times in sodium sulfate/water (20/lO0) and washed with water to remove the sodium sulfate, and then dried. The dried yarn was further drawn 3 times on a hot plate at 220& by the usual method. The cured yarn was prepared as in Example l.
Ihe denier of the resulting yarn was 2.8, the tensile strength averaged 2.9 g/d, the break elongation averaged 24% and the elastic modulus averaged 45 g/d.
This fiber was self-extinguishing and showed an affinity for acidic dyes.

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Exa~ple 15 48 Parts of melamine, 12 parts of urea and 47.1 parts of 37%
aqueous forn~aldehyde were dissolved in 366.6 parts of water containing 2.7 parts of 1 N aqueous sodium hydroxide. After stirr~ng at 80 C for 75 minutes, 39.6 parts of 35% hydrochloric acid were added and then heated at 80C for 145 minutes. Ihe methylene content of amino resin in the emulsion was 88%.
This emulsion was blended with 383.3 parts of 20% aqueous PVA solution to ob-tain a uniform spir~ing solution.
This spinning solution was spun through spirming nozzles, each having a diameter of 0.1 mm, into a coagulating bath comprising sodium sulfate~
water (30/100). After drawing 9 times, the drawn yarn was cured by the same method as in Example 1. The cured yarn had an average denier of 2.2, an aver-age tensile strength of 3.2 g/d, an average break elongation of 20%, and was self-extinguishable.
Examples 16-18 The resin solution was prepared in accordance with the procedure described in Exa~,ple 14.
PVA, having a degree of polymerization of 2000 (Gohsenol NH-20*), was dissolved portion by portion at 80C in water to prepare a solution of 20% solid polymer content. The aforesaid two solutions were mlxed to prepare a spinning solution containing 70/60/40% of resin. Viscosities of these solutions were as follcws: ~
I ~ --------- ...... I ::
Example Amino resin/PVA (weight)Viscosity (poise)(30C) 16 70/30 12.7 ~ .. . __ . .
17 60/40 27.4 ~
,__ . _ _ . ._ . ~ ., _ _ 18 40/60 107.0 :~
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i~5a 6~
Each of these spinning solutlons was extruded through the spin-neret into a coagulating bath composed of sodium sulfate, sodium hydroxide and water (25/5/loO) and thereafter, treated :Ln accordance with the procedure de-scribed in Ex~n~ple 14.
The mechanical properties and L.O.I. of the resulting drawn un-cured and cured yarns are shown in the table below.

Exa~lple Amlno/PVA Denier Tenacity Flonga- Elastic LØI.
No. resin (d) (g/d) tion(%) modulus (%) (wt.ratio) (g/d) . ~__ ~ _ __ __ ~_ ____ . I
drawn yarn 16 70/30 2.6 3.1 8 80 38 17 60/40 2.7 4.1l 9 95 32 18 40/60 2.7 5.8 14 105 27 cured _ _ yarn 16 70/30 2.9 2.2 15 40 40 17 60/40 2.9 3.1 27 46 36 i-_ 18 40/60 3.0 3.7 30 52 __ -- Example 19 27 Parts of melamine~ 3 parts of benzoguanamine and 22.3 parts of lo 35% hydrochloric acid was stirred in 135 parts of water at 70& for one hour.
18.7 Parts of 37% aqueous formaldehyde was added to this solution and then stirred at 70C for one hour. Methylene content of this resin was 94.5%.
PVA having a degree of polymerization of 1700 (Gohsenol AH-17*, manufactured by Nippon Synthetic Chemical Industry Co. Ltd~) was dissolved in ~. .
water to prepare a solu~ion of 15% solid polymer content. The aforesaid two solutions were mixed to prepare a spinning solution.
me ratio of amino resin to PVA was about 55/45. Viscosity of this solution was 46 poises at 30C.
Ihis spinning solution was spun through spinning nozzles, each having a diameter of 0.08 mm into a sodium sulfate-water (Na2S04/water-20/100) coagulating bath. Coagulating yarn was drawn and cured the same as in Example 14.

*Trade Mark ~B~

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Mechanical properties of the cured yarn were as follows:
denier: 4.1, tenacity: 3.2 g/d, elongation: 28%, elastic modulus 59 g/d.
This fiber was self-extinguishing and showed an afMnity for acidic dyeæ.
~ e~ 20 48 Parts of mela~ne, 12 parts of urea, 47.1 parts of 37% aqueous for~ldehyde and 60 parts of PVA, having a degree of polymerization of 1400 (Gohsenol NH-14~, manufactured by Nippon Synthetic Chemical Industry Co. Ltd.~ -were dissolved in 1060.7 parts of water. After stirring this mixture at 80c - for one hour3 3906 parts of 35% hydrochloric acid were added and stirred at 60 C for one hour. The methylene content of this resin was 78% and viscosity of the solution was 47.6 poises at 30c.
This spinning solution was spun and coagulating yarn was drawn and cured the same as in Example 11.
This yarn was self-extinguishable and its mechanical properties were as follows:
denier: 3.4, tenacity: 2.8 g/d, elongation 28% and Young's modulus 47 g/d.

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*Trade Mark

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flame-retardant fiber comprising about 20 - 95% by weight of amino resin condensate of an amino compound and formaldehyde in which a majority of the chemical bonds linking the polymer chain are methylene link-ages, and about 80 - 5% by weight of polyvinylalcohol.

2. A flame-retardant fiber in accordance with claim 1, wherein the methylene percentage based on the sum of hydroxymethyl groups and methylene groups in the amino resin condensate is more than 50%.

3. A flame-retardant fiber in accordance with claim 1, wherein the methylene percentage based on the sum of hydroxymethyl groups and methylene groups in the amino resin condensate is more than about 70%.

4. A flame-retardant fiber in accordance with claim 1, wherein the amino compounds are melamines.

5. A flame-retardant fiber in accordance with claim 1, wherein the amino compounds are melamines together with one or more amino compounds from the group comprising guanamines and ureas.

6. A flame-retardant fiber in accordance with claim 1, wherein the amino compounds are chosen from at least one of benzoguanamines and ureas.

7. A flame-retardant fiber in accordance with claim 1, wherein the content of the amino resin condensate in the fiber is 30 - 95%.

8. A flame-retardant fiber in accordance with claim 1 in which the fiber is cured.

9, A flame-retardant fiber in accordance with claim 8 having a tensile strength of at least 1.0 g/d and a break elongation of at least 5%.