U.S. patent number 3,846,373 [Application Number 05/285,664] was granted by the patent office on 1974-11-05 for flame-retardant acrylic synthetic fibers having improved properties.
This patent grant is currently assigned to Japan Exlan Company, Limited. Invention is credited to Tadashi Ichimaru, Hiroshi Suzuki, Kenji Takeya.
United States Patent |
3,846,373 |
Takeya , et al. |
November 5, 1974 |
FLAME-RETARDANT ACRYLIC SYNTHETIC FIBERS HAVING IMPROVED
PROPERTIES
Abstract
Flame-retardant acrylic synthetic fibers containing a fluid
mixture obtained by dissolving halogen- and/or
phosphorus-containing solid organic compounds in a liquid
halogenated aliphatic phosphate.
Inventors: |
Takeya; Kenji (Okayama,
JA), Suzuki; Hiroshi (Okayama, JA),
Ichimaru; Tadashi (Okayama, JA) |
Assignee: |
Japan Exlan Company, Limited
(Osaka, JA)
|
Family
ID: |
13367426 |
Appl.
No.: |
05/285,664 |
Filed: |
September 1, 1972 |
Foreign Application Priority Data
|
|
|
|
|
Sep 4, 1971 [JA] |
|
|
46-68218 |
|
Current U.S.
Class: |
524/144; 524/142;
264/182 |
Current CPC
Class: |
C08L
33/20 (20130101); C08K 5/521 (20130101); C08K
5/521 (20130101) |
Current International
Class: |
C08K
5/00 (20060101); C08K 5/521 (20060101); C08g
051/58 () |
Field of
Search: |
;260/45.7P,45.95G,45.95R,45.7R,28.5A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Marquis; Melvyn I.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What we claim is:
1. A flame-retardant monocomponent acrylic synthetic fiber
comprising an acrylonitrile polymer selected from the group
consisting of homopolymers of acrylonitrile and copolymers
containing at least 70 percent acrylonitrile and up to 30 percent
of at least one monoethylenically unsaturated monomer copolymerized
therewith, and having incorporated in such fibers 3-40 percent by
weight of a fluid mixture having a viscosity of at least 6,000
centipoises at 25.degree.C obtained by dissolving (1) an organic
compound selected from the group consisting of halogenated
paraffins, halogenated aralkyl phosphates, halogenated aryl
phosphates, halogenated diphenyl ethers, halogenated phenols,
halogenated alkyl ethers of the halogenated phenols,
tetrabromobisphenol-A and etherified derivatives of
tetrabromobisphenol-A represented by the formula ##SPC7##
wherein each of R.sub.1 and R.sub.2, respectively, represents
alkyl, cycloalkyl, aralkyl or aryl which are unsubstituted or
substituted by halogen, said R.sub.1 and R.sub.2 groups
respectively having 2-20 carbon atoms, in (2) a liquid halogenated
aliphatic phosphate represented by the formula ##SPC8##
wherein each of R.sub.1, R.sub.2 and R.sub.3 represents a
halogenated aliphatic hydrocarbon radical having up to eight carbon
atoms.
2. The acrylic synthetic fiber of claim 1 wherein said fluid
mixture has a viscosity of up to 300,000 centipoises at
25.degree.C.
3. The acrylic synthetic fiber of claim 1 wherein the mixing ratio
of the halogenated aliphatic phosphate and the organic compound in
said fluid mixture is within the range of from 9.5:0.5 to 0.5:9.5
by weight.
4. The acrylic synthetic fiber of claim 3 wherein said mixing ratio
is within the range of from 9:1 to 3:7 by weight.
5. The acrylic synthetic fiber of claim 1 wherein said halogenated
aliphatic phosphate is a liquid having a refractive index of 1.44
to 1.60 at 25.degree.C.
6. The acrylic synthetic fiber of claim 1 wherein said halogenated
aliphatic phosphate is selected from the group consisting of
tris(.beta.-chloroethyl)phosphate,
tris(.beta.-bromoethyl)phosphate, tris(3-chloropropyl)phosphate,
tris(3-bromopropyl)phosphate, tris(2,3-dichloropropyl) phosphate,
tris(2,3-dibromopropyl)phosphate,
tris(1-bromo-3-chloroisopropyl)phosphate, tris(2,3-dichlorobutyl)
phosphate, tris(2,3-dibromobutyl)phosphate,
bis(2,3-dichloropropyl)2,3-dibromopropyl phosphate and
bis(2,3-dibromopropyl)2,3-dichloropropyl phosphate.
7. The acrylic synthetic fiber of claim 1 wherein said fluid
mixture consists essentially of
tris(1-bromo-3-chloroisopropyl)phosphate and
bis(2,3-dibromopropyl)ether of tetrabromobisphenol-A.
8. The acrylic synthetic fiber of claim 1 wherein said fluid
mixture consists essentially of
tris(1-bromo-3-chloroisopropyl)phosphate and
bis(.beta.-bromoethyl)ether of tetrabromobisphenol-A.
9. The acrylic synthetic fiber of claim 1 wherein said fluid
mixture consists essentially of tris(2,3-dibromopropyl) phosphate
and bis(.beta.-bromoethyl)ether of tetrabromobisphenol-A.
Description
The present invention relates to flame-retardant acrylic synthetic
fibers with improved chemical and physical properties, and also to
a method for producing such acrylic synthetic fibers. More
particularly, in producing flame retardant acrylic synthetic fibers
containing a liquid halogenated aliphatic phosphate, the present
invention relates to a method for improving the various properties
of the fibers such as touch, luster, anti-fibrillation property,
heat-settability, resilience, etc. and for augmenting the flame
retardant property of the fibers to a further extent as well as for
preventing the fluctuation in dyeability, characterized in that a
fluid mixture having a viscosity of at least 6,000 centipoises at
25.degree.C obtained by dissolving in the halogenated aliphatic
phosphate a solid organic compound which is soluble in the
halogenated aliphatic phosphate and contains halogen and/or
phosphorus, is introduced into the fibers.
It is well known that acrylic synthetic fibers can be rendered
flame retardant by introducing a halogenated aliphatic phosphate
into the fibers. When a proper amount of a halogenated aliphatic
phosphate is introduced into the fibers, the resultant fibers
certainly show not only desirable flame retardant property but also
good touch, good luster and other good properties. However, if the
halogenated aliphatic phosphate to be introduced into the fibers is
increased to such an amount as to make the fibers more
flame-retardant, the flame retardant property is further improved,
but other fiber qualities and properties will deteriorate with the
increase of the amount of the flame retardant additive. Therefore,
the various disadvantages resulting from the halogenated aliphatic
phosphate introduced into the fibers, such as the fibrillation
caused in the steps of forming the fibers containing the
halogenated aliphatic phosphate, lack in resilience of the products
in use, change of touch with the passage of time, etc. were
inevitable when a large amount of the halogenated aliphatic
phosphate was introduced.
The above-mentioned phenomenon can be more concretely explained
from the following fact: Thus, by introducing the above-mentioned
halogenated aliphatic phosphate into the fibers, it is possible to
obtain acrylic synthetic fibers for use in artificial hair having
excellent touch and luster like human hair and a flame retardant
property. However, when the fibers are sewed by machine in the step
of preparing hair products or when the products in use are combed
or brushed, there will be formed undesirable fibrillated, branched
or worn-out hair, or when the products are washed the curls and
waves of the artificial hair tend to vanish. Therefore, in such
products there is a problem of deteriorating the excellent touch
and luster of the fibers like human hair with the passage of time
during wearing. It is also a problem that the products are not
durable to a long time wear because of the lack in resilience of
the curls and waves or the loss of resilience with the passage of
time.
In order to avoid the disadvantages of deterioration of the fiber
qualities and properties resulting from introducing a large amount
of the above mentioned flame retardant additive into the fibers,
attempts have been made to reduce the amount of the halogenated
aliphatic phosphate to be added to the fibers by using, together
with the halogenated aliphatic phosphate, a solid flame retardant
additive such as antimony oxide which is entirely incompatible with
the halogenated aliphatic phosphate. However, a flame retardant
additive such as antimony oxide, which has no interaction with
acrylonitrile polymer in the fibers, has a disadvantage of being
more liable to cause the problem of fibrillation than in the case
of adding the halogenated aliphatic phosphate only.
We have now found that the viscosity of the flame retardant
additive to be introduced into the fibers remarkably influences the
properties of the products, and further found that when a fluid
mixture prepared as to have a viscosity of more than 6,000
centipoises by dissolving a particular organic compound containing
halogen and/or phosphorus into the halogenated aliphatic phosphate
is introduced into acrylic synthetic fibers, the fiber properties
are remarkably improved, and the flame retardant property is
synergistically improved.
The main object of the present invention is to improve the
properties of flame retardant acrylic synthetic fibers.
An object of the present invention is to obtain acrylic synthetic
fibers which are improved not only in the properties including
touch, luster, anti-fibrillation, heat-settability, resilience,
etc., but also effectively prevented from the fluctuation in
dyeability, and moreover rendered highly flame retardant.
Another object of the present invention is to improve the various
properties of acrylic synthetic fibers and to augment the flame
retardant property to a further extent as well as to prevent the
fluctuation of dyeability by incorporating a fluid mixture having a
viscosity of at least 6,000 centipoises obtained by dissolving in
the liquid halogenated aliphatic phosphate a particular solid
organic compound containing halogen and/or phosphorus into the
fibers.
Other objects of the present invention will become apparent from
the following description.
In preparing flame retardant acrylic synthetic fibers containing a
liquid halogenated aliphatic phosphate represented by the general
formula: ##SPC1##
wherein each of R.sub.1, R.sub.2 and R.sub.3 stands for a
halogenated aliphatic hydrocarbon radical having no more than 8
carbon atoms, the above-mentioned objects of the present invention
can be attained by incorporating into the fibers a fluid mixture
having a viscosity of at least 6,000 centipoises at 25.degree.C
obtained by dissolving in the halogenated aliphatic phosphate a
solid organic compound containing halogen and/or phosphorus which
is soluble in the halogenated aliphatic phosphate.
The thus-obtained flame retardant acrylic synthetic fibers are
excellent not only in the flame retardant property but also in
other properties including touch, luster, anti-fibrillation,
heat-settability, resilience, etc. Therefore, for example,
artificial hair products having excellent toucn and luster like
human hair and excellent in the flame retardant property can be
prepared from the thus-obtained fibers. Accordingly, the artificial
hair products using the flame retardant fibers of this invention
are completely free from those defects of causing fibrillated,
branched or worn out hair upon combing or brushing, and of tending
to lose the curls and waves by washing, i.e., free from the changes
in the excellent human hair-like touch and luster with the passage
of time during wearing.
It is to be noted that the acrylic synthetic fibers according to
the present invention shows a much higher flame retardant property
than that of the conventional acrylic synthetic fibers containing
only a halogenated aliphatic phosphate when the amount of the flame
retardant additive incorporated into the fibers is the same.
It is also to be noted that the acrylic synthetic fibers obtained
according to the present invention do not show any fluctuations in
dyeability as contrasted to the conventional acrylic synthetic
fibers containing only a halogenated aliphatic phosphate.
Additionally, the flame retardant acrylic synthetic fibers obtained
according to the present invention, when used for preparing
artificial hair, can give more excellent human hair-like luster, by
using a compound having a refractive index at 25.degree.C ranging
from 1.44 to 1.60 as the above-mentioned halogenated aliphatic
phosphate.
The halogenated aliphatic phosphate to be used in this invention
and represented by the above indicated general formula include
liquid compounds such as tris(.beta.-chloroethyl)phosphate,
tris(.beta.-bromoethyl)phosphate, tris(3-chloropropyl)phosphate,
tris(3-bromopropyl) phosphate, tris( 2-chloropropyl)phosphate,
tris(2-bromopropyl)phosphate, tris(2,3-dichloropropyl)phosphate,
tris(2,3-dibromopropyl)phosphate,
tris(1-bromo-3-chloroisopropyl)phosphate,
tris(2,3-dichlorobutyl)phosphate , tris(2,3-dibromobutyl)phosphate,
bis(2,3-dichloropropyl) 2,3-dibromopropyl phosphate,
bis(2,3-dibromopropyl)2,3-dichloropropyl phosphate, etc.
The solid organic compounds containing halogen and/or phosphorus
and soluble in the above mentioned halogenated aliphatic phosphate
are those which are solid at room temperature. Examples thereof are
halogenated paraffins such as chlorinated paraffins, brominated
paraffins; halogenated aralkyl or aryl phosphates (preferably
having not more than 20 carbon atoms) such as
tris(bromocresyl)phosphate, tris(dibromophenyl) phosphate, etc.;
tetrabromobisphenol-A or its etherified derivatives represented by
the following general formula: ##SPC2##
wherein each of R.sub.1 and R.sub.2 is alkyl, cycloalkyl, aralkyl
or aryl group which is unsubstituted or substituted with halogen
atom(s) and which has 2 to 20 carbon atoms, such as
bis(benzyl)ether of tetrabromobisphenol-A,
bis(chlorobromopropyl)ether of tetrabromobisphenol-A, etc.:
precondensates of tetrabromobisphenol-A with polyhalogenated
compounds or diepoxides, etc.: halogenated diphenyl ethers such as
chlorinated diphenyl ether, brominated diphenyl ether, etc.;
halogenated phenols or its halogenated alkyl (preferably not more
than 10 carbon atoms) ethers, etc. Besides these, any other solid
organic compounds containing halogen and/or phosphorus and soluble
in the halogenated aliphatic phosphate can be used.
Such a halogenated aliphatic phosphate and an organic compound
containing halogen and/or phosphorus may be mixed in various
combinations and dissolved to form a homogeneous fluid mixture
having a viscosity of at least 6,000 centipoises. Any mixing ratio
(by weight) of such a halogenated aliphatic phosphate and such
organic compounds containing halogen and/or phosphorus can be used,
if this ratio gives a fluid mixture satisfying the foregoing
viscosity. However, in general, it is desirable to use a ratio
within the range of from 9.5:0.5 to 0.5:9.5, preferably
9/1-3/7.
By the term "fluid mixture" as used herein is meant a homogeneous
composition which is fluid at room temperature or upon the
operation of introducing the mixture into the fibers. Also, it is
an essential requirement that the viscosity of the fluid mixture
should be at least 6,000 centipoises at 25.degree.C. When a fluid
mixture of less than that viscosity is used, it is difficult to
fully attain the objects of the present invention. The upper limit
of the viscosity of the fluid mixture according to the present
invention may vary depending on the particular combination of the
halogenated aliphatic phosphate and the organic compound containing
halogen and/or phosphorus to be used or on the degree of the
desired modifying effect of the fiber. Even a composition which is
solid at room temperature but is fluid upon introducing it into the
fibers can be used. However a viscosity of less than 300,000
centipoises is generally desirable for operation.
By introducing such a fluid mixture into the fibers in an amount of
not less than 3 percent on the weight of the fibers, it is possible
to obtain acrylic synthetic fibers having a high flame retardant
property and improved properties in various other respects. In
general, the upper limit of the amount of the fluid mixture to be
introduced into the fibers is desirable to be not to be more than
40 percent in consideration of the other fiber properties.
The most advantageous procedure to introduce such a fluid mixture
of halogenated aliphatic phosphate and organic compounds containing
halogen and/or phosphorus into the acrylic synthetic fibers are to
incorporate a fluid mixture having a viscosity within the
above-mentioned specified range into the spinning solution for
producing the fibers. Then the spinning solution containing said
fluid mixture is formed into filaments by a generally well known
wet spinning or dry spinning method. The spun filaments may further
be treated in a known manner. Thus, the filaments may be
water-washed, stretched, dried and heat-treated. Another procedure
for causing the above-mentioned fluid mixture to be contained in
the fibers is to treat the gel filaments (obtained by dry- or
wet-spinning an acrylic polymer solution through spinneret orifices
under general spinning conditions) in a treating bath containing a
fluid mixture of a viscosity within the above-mentioned specified
range, and then to carry out the usual post treatment steps. Thus
there can be various procedures to cause the above-mentioned
halogenated aliphatic phosphate and organic compound containing
halogen and/or phosphorus to be contained in the fibers according
to the present invention. By any of these procedures, the objects
of the present invention can be satisfactorily attained so far as a
specified amount of the fluid mixture of the present invention can
be incorporated into the acrylic synthetic fibers.
Various kinds of spinning solution containing an acrylonitrile
polymer dissolved in a suitable solvent, which can be used in
producing the acrylic synthetic fibers of the present invention are
well known in the art. Representatives of such polymers and
solvents are disclosed in the specification of U.S. Pat. No.
2,948,581 granted to Cumming on Aug. 9, 1960 and other U.S. Patents
cited therein.
The representative compounds which may be copolymerized with
acrylonitrile to produce acrylonitrile polymers useful for the
practice of the present invention are those containing one
##SPC3##
Such compounds include, for example, vinyl esters of saturated
aliphatic carboxylic acids such as vinyl acetate, vinyl propionate,
vinyl butyrate, etc.; vinyl halides and vinylidene halides such as
vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride,
vinylidene bromide, vinylidene fluoride; allyl type alcohols such
as allyl alcohol, methallyl alcohol, ethallyl alcohol, etc.; allyl,
methallyl and other unsaturated alcohol ester of monobasic acids
such as allyl or methallyl acetate, laurate, cyanide, etc.; acrylic
acid, alkacrylic acids (such as methacrylic acid, ethacrylic acid,
etc.), and esters and amides of such acids (such as methyl, ethyl,
propyl, butyl acrylates and methacrylates; acrylamide,
methacrylamide, N-methyl, -ethyl, -propyl, -butyl acrylamides and
methacrylamides); methacrylonitrile, ethacrylonitrile, and other
hydrocarbon substituted acrylonitriles; unsaturated sulfonic acids
having one ##SPC4##
and their salts such as allylsulfonic acid, methallylsulfonic acid,
styrenesulfonic acid and their sodium salts and potassium salts;
unsaturated aliphatic hydrocarbon having one ##SPC5##
such as isobutylene; many other vinyl, acrylic and other compounds
having one ##SPC6##
which polymerize with acrylonitrile to produce thermoplastic
copolymers. Alkyl esters of .alpha.,.beta.-unsaturated
polycarboxylic acids such as dimethyl, -ethyl, -propyl, -butyl
esters of maleic acid, fumaric acid, citraconic acid also
copolymerize with acrylonitrile to form copolymers.
Usually, the molecular weight (average molecular weight) of the
acrylonitrile homopolymer or copolymer for producing
polyacrylonitrile shaped products is within the range of from
25,000 or 30,000 to 200,000 or 300,000, or higher, and the
particularly advantageous range is from 50,000 to 100,000. These
molecular weights are calculated from the viscosity of the polymer
in dimethylformamide calculated by the Staudinger's equation (refer
to the specification of U.S. Pat. No. 2,404,713 dated June 23,
1946.).
Preferably, the acrylic polymer to be used in this invention is an
acrylonitrile homopolymer or copolymer containing 30 percent or
less of at least one of the above mentioned monoethylenically
unsaturated monomer and at least 70 percent acrylonitrile, but
polymers containing a less amount of acrylonitrile may also be used
for the practice of the present invention.
The representative solvents which are useful to dissolve the
acrylonitrile polymer to prepare the spinning solution include
organic solvents such as dimethylformamide, dimethylacetamide,
ethylene carbonate, and dimethyl sulfoxide, and inorganic solvents
such as concentrated aqueous solution of inorganic salts, for
example sodium thiocyanate, zinc chloride, etc.
The spinning methods used for obtaining the fibers of the present
invention may be the generally known wet or dry spinning processes
described in Japanese Patent Publication Nos. 3645/50, 4821/53,
9516/57, 878/63 and 2589/61, and U.S. Pat. Nos. 2,404,725 to
2,404,728.
The following examples are for better explanation of the present
invention and are not intended to limit the scope of the invention.
All the percentages and parts in the examples are by weight unless
otherwise indicated.
EXAMPLE 1
A fluid mixture having a viscosity of 230,000 centipoises at
25.degree.C consisting of 70 parts
tris(1-bromo-3-chloroisopropyl)phosphate having a viscosity of
about 3,000 centipoises at 25.degree.C and 30 parts chlorinated
paraffin containing 70 percent chlorine was prepared. The fluid
mixture was then added to a spinning solution composed of 11 parts
of a copolymer consisting of 88 percent acrylonitrile and 12
percent vinyl acetate and 89 parts of a 44 percent aqueous solution
of sodium thiocyanate, the amount of the fluid mixture being 40
percent on the basis of the weight of the polymer. Thereafter, the
fluid mixture was thoroughly dispersed in the spinning solution by
a high shear mixer (Homomixer SL Type, manufactured by Tokushu Kika
Co., Japan). Thus thus-obtained spinning solution was then extruded
through a spinneret having eight orifices of each 0.2 mm in
diameter into a 12 percent aqueous solution of sodium thiocyanate
at -2.degree.C. The formed filaments were stretched ten times the
original length in hot water, washed with water and then
steam-relaxed at 110.degree.C to obtain acrylic synthetic fibers of
50 denier per filament.
The thus-obtained acrylic synthetic fibers were evaluated for
flammability to show extremely high self-extinguishability.
Further, no fibrillation was observed upon dyeing, cutting and
sewing the fibers to prepare artificial hair products.
For comparison, when tris(1-bromo-3-chloroisopropyl)phosphate was
singly introduced into the fibers instead of the above-mentioned
fluid mixture, the flame-resistance of the thus-obtained fibers was
observed to be much inferior to that of the fibers according to the
present invention. Furthermore, in the sewing step for producing
artificial hair products, the fibers in contact with the sewing
machine turned white, which showed the occurrence of
fibrillation.
EXAMPLE 2
In table 1 are shown several properties of various acrylic
synthetic fibers obtained by the method as shown in Example 1 in
which various amounts of the conventional flame retardant additive
tris(1-bromo-3-chloroisopropyl) phosphate singly as well as a
homogeneous fluid mixture having a viscosity of 24,400 centipoises
at 25.degree.C consisting of 70 percent said phosphate and 30
percent bis(2,3-dibromopropyl)ether of tetrabromobisphenol A were
introduced into the fibers.
As apparent from the results in Table 1, it is observed that, by
the method of the present invention, the acrylic synthetic fibers
containing the conventional halogenated aliphatic phosphate can be
remarkably improved in the fiber properties including the flame
retardant property and dyeability.
In the above table the flammability was determined by filling 4 g.
of the fibers into a metal wire basket (6.5 cm. in diameter and 7.5
cm. in height), and contacting a burner flame to the bottom of the
basket for 7 seconds. The burning time and burnt off weight were
measured. The fibrillation was determined as follows. Thus a bundle
of 800 monofilaments (40 cm. in length) was subjected to 200 times
brushing and the number of fibrillated monofilaments was counted.
The dyeability was determined as follows. Thus the fibers were dyed
under the following conditions:
Cationic dye: C.I. Basic Orange 21 (C.I. 48035) 2% o.w.f. Cationic
retarder: 0.3% o.w.f. Acetic acid: 1% o.w.f. Liquor ratio: 1/100
Temperature: Increased from 60.degree.C. to 100.degree.C. at a rate
of 1.degree.C./min. and maintained at 100.degree.C. for 45 min.
After dyeing, the presence of unevenness in dyeing was
observed.
Table 1
__________________________________________________________________________
Content Flammability Fibril- Stickiness Unevenness of lation in
dyed additive Burning Weight colors time in burnt seconds off
__________________________________________________________________________
Introduction 28% 17 33% 13 Observed Observed of the halogenated 26
52 77 -- Observed Observed aliphatic slightly slightly phosphate 23
59 81 -- Observed Observed only slightly slightly Introduction 28 3
29 none none none of the same after being 26 3 23 -- none none
formed into the fluid 23 2 24 -- none none mixture of the present
invention
__________________________________________________________________________
EXAMPLE 3
Tris(1-bromo-3-chloroisopropyl)phosphate, which is a halogenated
aliphatic phosphate flame retardant additive, was added to an
acrylic spinning solution composed of 11 parts of a copolymer
consisting of 90 percent acrylonitrile and 10 percent
methylacrylate and 89 parts of 44 percent aqueous solution of
sodium thiocyanate such that the flame retardant additive is 20
percent based on the weight of the copolymer. Thereafter, the flame
retardant additive was dispersed in the spinning solution
thoroughly by a high shear mixer. The thus-obtained spinning
solution was then extruded into a 12 percent aqueous solution of
sodium thiocyanate at -2.degree.C through a spinneret having 50
orifices of each 0.2 mm in diameter. The formed filaments were
stretched 10 times the original length in hot water, washed with
water and then steam-relaxed at 115.degree.C to obtain acrylic
synthetic fibers of three denier per filament. After combing the
thus-obtained fibers 500 times, considerable fibrillation was
observed.
On the other hand, a fluid mixture having a viscosity of 6,800
centipoises at 25.degree.C consisting of 10 parts of the
above-mentioned flame retardant additive and 30 parts of
pentabromobiphenyl ether was prepared. This fluid mixture was used
instead of the above-mentioned flame retardant additive, and
acrylic synthetic fibers of three denier per filament were obtained
in the same way. After combing the thus-obtained fibers, no
substantial fibrillation was observed even after 500 times
combing.
The same procedure was repeated except that a fluid mixture having
a viscosity at 25.degree.C of 36,000 centipoises and consisted of
70 percent of tris(1-bromo-3-chloroisopropyl)phosphate and 30
percent of bis(.beta.-bromoethyl)ether of tetrabromobisphenol-A was
used as the fluid to be added to the spinning solution. The
resultant fibers were excellent in flame-retardancy, hand (touch),
lustre and even dyeability as compared with the fibers obtained by
the use of each of the above two compounds singly.
EXAMPLE 4
A fluid mixture having a viscosity at 25.degree.C of 46,000
centipoises and consisting of 70 percent of
bis(2,3-dichloropropyl)2,3-dibromopropyl phosphate and 30 percent
of bis (.beta.-bromoethyl)ether of tetrabromobisphenol-A was added
to an acrylic spinning solution consisting of 11 parts of an
acrylic copolymer (92 percent acrylonitrile and 8 percent vinyl
acetate) and 89 parts of a 44 percent aqueous solution of sodium
thiocyanate, the amount of the fluid mixture being 10 percent based
on the copolymer in the spinning solution. Then the fluid mixture
was fully dispersed in the spinning solution by the use of a high
shear mixer. The spinning solution was extruded through a spinneret
(50 holes, each 0.09 mm in diameter) into a 12 percent aqueous
solution of sodium thiocyanate at -2.degree.C to form filaments.
The filaments were stretched 10 times the length, washed with water
and steam-relaxed at 120.degree.C to obtain acrylic fibers
(referred to as A) having 3 denier per monofilament.
For comparison, the same procedure was repeated except that
bis(2,3-dichloropropyl)2,3-dibromopropyl phosphate alone or
bis(.beta.-bromoethyl)ether of tetrabromobisphenol-A alone was used
as the additive for the spinning solution to obtain fibers B or
fibers C respectively.
In respect of these fibers A, B and C flammability was evaluated in
the same manner as in Example 2. It was observed that the fibers A
are far more excellent in flame-retardancy than the fibers B and C.
Further the fibers B had a somewhat sticky hand and the fibers C
were extremely delustered and tended to fibrillation, but the
fibers A of this invention were not sticky, excellent in hand and
lustre and had no tendency to fibrillation.
The same procedure was repeated except that a fluid mixture having
a viscosity at 25.degree.C of 9,200 centipoises and consisting of
70 percent of tris(2,3-dibromopropyl) phosphate and of 30 percent
bis(.beta.-bromoethyl)ether of tetrabromobisphenol-A was used as
the fluid to be added to the spinning solution. The resultant
fibers were excellent in flame-retardancy, hand, lustre,
anti-fibrillation, etc. as compared with the fibers obtained by the
use of each of the above two compounds singly.
* * * * *