IL24871A - Process for forming dyeable,flame resistant acrylonitrile interpolymers - Google Patents

Description

PROCESS FOR FORMING DYEABLE, FLAME RESISTAUT ACRYLOHI RILE U5TERP0LYMERS This invention relates to flame resistant, dyeable acrylonitrile polymers and fibers formed therefrom. More particularly, this invention relates to an inter-polymeric composition of acrylonitrile and vinyl acetate which is modified with a vinylidene chloride flame resistant monomer and an allyloxybenzenesulfonic acid salt basic dye receptive monomer.

It is well known in the art that polymers containing 80 percent or more of acrylonitrile are generally not highly receptive to basic dyes without the incorporation of certain basic dye receptive monomers nor do they have good flame resistant properties. Furthermore, it is known to obtain fibers from polymers or copolymers of acrylonitrile which contain a small percentage of other vinyl monomers. The vinyl monomer most generally used in the polymeric acrylonitrile composition is vinyl acetate which has the function of increasing the receptivity of the resultant fabrics for dyes as well as being a plastic izer therefore. It is believed that the acrylic polymers obtained by free radical polymerization by means of redox catalyst, for example, potassium persul ate and sulfur dioxide, have acid groups in the macromolecules, which are probably sulfonic or sulfate groups derived from the catalytic system and which determine the affinity of the composition for the basic dyestuffs. However, the effectiveness of these groups to receive basic dyes is reduced upon the addition of flame preventative monomers such as vinylidene chloride. Various additives and monomers have been tried to increase the basic dyeability and it has been found that the basic d eabi it thereof has been im roved b the incorporation therewith of various compounds containing sulfonic acid or sulfonate groups. It has been noted, however, that the addition of these as well as vinyl comonomers substantially change the physical properties of the resultant fibers and in particular worsen their sensitivity to heat, such as the softening point and the shrinkability at temperatures above 80°C. Furthermore, they do not improve any other property of the fiber, aside from the receptivity for dyes and the plastic izing effect thereon.

It has been found that copolymers of acrylonitrile and vinyl idene chloride do not substantially change the properties of the polyacrylonitrile. In particular, the copolymer of acrylonitrile with vinylidene chloride has two important advantages for the production of synthetic fibers, namely, the impartation of the fiber of the properties of resistance to inflameability particularly in such applications as carpets, curtains, covers and the like, and the glass transition temperature of the copolymers of acrylonitrile with vinylidene chloride is substantially raised changing from a value of from approximately 87°C. in the case of pure polyacrylonitrile for its copolymers with small amounts of vinyl acetate and other acrylic monomers to values of 110° to 135°C Since vinylidene chloride has the defect of not improving the receptivity of dyes of copolymers with acrylonitrile and even making them less dyeable then polyacrylonitrile itself, other dye receptive monomers have been sought which when copolymerized with the above-mentioned monomers has been found that the allyloxybenzenesulfonic acid salts improve the basic dyeability of the polymer.

By comparing the disclosed tetrapolymer with a standard copolymer consisting of acrylonitrile and vinyl acetate, the advantage of the former over the latter will be obvious and also, the difficulties in arriving at the disclosed tetrapolymer will be evident.

The standard acrylonitrile-vinyl acetate copolymer exhibits good properties in most areas although it is generally lammable) not highly receptive to basic dyes and is j-i¾rai5ee¾ie-. By the addition of an allyloxybenzenesul onic acid salt, the polymer is made more basic dyeable by the addition of the acid dye sites but the polymer still lacks flame resistant characteristics. Where vinylidene chloride was added to form a terpolymer with acrylonitrile and vinyl acetate, the resulting polymer was not as dyeable as the acrylonitrile-vinyl acetate copolymer nor and light stability as good; however, the thereof was greatly improved. It was also found that a terpolymer consisting of acrylonitrile, vinylidene chloride and an allyloxybenzenesulfonic acid salt had good flame retarding properties but, unexpectedly, the dyeability thereof was not significantly enhanced over the copolymer consisting of acrylonitrile and vinylidene chloride.

As it has been seen, all of the above-mentioned inter-polymers are deficient in one or more of the important desired qualities. Therefore, a tetrapolymer was developed which included acrylonitrile, vinyl acetate, vinylidene chloride and an allyloxybenzenesulfonic acid monomers were compatible and polymerized according to theory. The polymerization of these monomers was unusual for it is most difficult to find four monomers, especially varying in function as these do, which are compatible. Given four monomers, each may be compatible with each other but not with a third or a fourth. It should be pointed out that the use of either vinyl acetate or allyloxybenzenesulfonic acid salt alone does not give the proper dye receptivity; however, when used together, the dye uptake of the resulting polymer is greatly increased. One explanation of this phenomenon is that the vinyl acetate opens up the polymer and permits the basic dyes to penetrate thereinto and attach to the acid dye sites being provided by the allyloxybenzenesul onic acid salt.

An object of this invention is to provide a tetrapolymer which is both dyeable and flame resistant.

Another object of this invention is to provide acrylonitrile polymers which contain allyloxy-benzenesulfonic acid salts and vinylidene chlorides which respectively improve the basic dyeability and the flame resistance thereof.

A further object of this invention is to provide a process for preparing dyeable and flame resistant acrylonitrile polymers.

More specific objects and advantages will be apparent to those skilled in the art from the following more detailed description which illustrates a sc s t s o i i t e sco e of It has been found that copolymers of nyl idene chloride containing the proportions to impart the desired properties of nonflameability to the fibers acquire the properties of receptivity for dyes desired in practical use if in addition to the vinylidene chloride in an amount from about 5 to 25 percent, such copolymers contain co-polymerized therewith at least two other comonomeijs of particular functions. More particularly, if such copolymers also contain at least one percent and preferably from 3 to 8 percent of one or more other vinyl monomers having side groups of high steric hindrance dimensions, such as, vinyl acetate, and a small amount of from 0.123 percent and preferably from 0.5 percent to 2 percent of a monomer which has an acid function available for the fixing of basic dyes, such as for example, allyloxy-benzenesulfonic acid salt having the general formula: S0„Y wherein R and R may be hydrogen, methyl, ethyl or propyl, and Y represents an alkal metal such as sodium, potassium, lithium, cesium, or rubidium. Compounds which are embraced by this general formula include sodium allyloxybenzenesulfonic acid salt, potassium allyloxy-benzenesulfonic acid salt, lithium allyloxybenzenesulfonic sodium 2- ethylallyloxybenzenesulfonic acid salt, sodium 2-propylallyloxybenzenesulfonic acid salt, sodium 3-methylallyloxybenzenesulfonic acid salt, potassium methyl-allyloxybenzenesulfonic acid salt,potassium 2-ethyl-allyloxybenzenesulfonic acid salt, sodium 3-ethylallyloxy-benzenesulfonic acid salt, sodium 3-Pr°Pylallyl°x t>enzene-sulfonic acid selt and the like.

The basic dye receptive monomers of this invention may be employed within a wide range, the exact amount depending on the amount of basic dye acceptance desired. In general, it may be said that these monomers may be employed in an amount ranging from about 0.25 percent to 10 percent based on monomer weight. The dye receptive monomers should be mixed with the acrylic monomer prior to polymerization due to water solubility of the sulfonate compound in monomeric form. The allyloxybenzenesulfonic acid salt is a part of the polymer after polymerization and is no longer water soluble.

Preferably, the amount of dye receptive monomer employed should be less than one percent, from about 0.3 percent to about 0.6 percent was found to be quite satisfactory for most compositions. Any suitable polymerization process known in the art may be used, such as, mass polymerization methods, solution polymerization methods or aqueous emulsion procedures. However, the preferred practice utilizes suspension polymerization wherein a batch procedure is used involving the charging of the monomers with an aqueous medium containing the necessary catal st and dis ersin a ent. Another method involves reactor containing the aqueous medium is continuously charged with the desired monomers and the polymer coninuously withdrawn. The use of these aeld and groups is surprising in view of the act that the eomonomers having hindrance side groups in the comon-omere of acid function, if used individually, are not effective* It will he apparent from an examination of the values in the examples for the various types of fibers that only these fibers obtained from the copolymers which are the subject matter of the present invention exhibit* together with the property of withstanding the propagation of flames· good receptivity for basic dispersed dyes* These fibers also have a substantially pure and pleasing white color and have excellent physical properties* The polymerization is normally catalyzed by fcnowa catalysts and is carried out in equipment general* y used in the art* Entirely continuous methods involving the gradual addition of monomers and the continuous withdrawal of polymer can also be employed* The polymerization is catalyzed by means of water-soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and other water-soluble compounds containing the peroxy group: ( o 0 ) A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3-0 percent by weight of the polymerizable monomer may be used. The so-called redox catalyst system also may be used. Redox agents are generally compounds in a lower valent state which are readily oxidized to the higher valent state under the conditions of reaction. Through the use of this reduction oxidation system, it is possible to obtain polymerization to a substantial extent at lower temperatures than otherwise would be required. This method is the preferred one for this invention since the vinylidene chloride, tends to turn brown at higher temperatures before polymerization. Suitable "redox" agents are sulfur dioxide, the alkali metal and ammonium bisulfites, and sodium formaldehyde sulfoxylate. The catalyst may be charged at the outset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in regard to its chemical and physical properties.

Although the uniform distribution of the reactants throughout the reaction mass can be achieved promote the uniform distribution of reagents by using inert wetting agents, or emulsion stabilizers. Suitable reagents for this purpose are the water-soluble salts of fatty acids, such as sodium oleate and potassium stearate, mixtures of water-soluble fatty acid salts, such as common soaps prepared by the saponification of animal and vegetable oils, the "amino soaps," such as salts of triethanolamine and dodecylmethylamine, salts of resin acids and mixtures thereof, the water-soluble salts of half esters of sulfonic acids and long chain aliphatic alcohols, sulfonated hydrocarbons, such as alkyl aryl sulfonates, and any iariet ^1' other of a wide fSHw*^ of wetting agents, which are in general organic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agent will depend upon the particular agent selected, the ratio of monomer to be used and the conditions of polymerization. In general, however, from 0.1 to 1.0 weight percent based on the weight of the monomers can be employed.

The emulsion polymerizations are preferably conducted in glass or glass-lined vessels provided with means for agitating the contents therein. Generally, rotary stirring devices are the most effective means of insuring the intimate contact of the reagents, but other methods may be successfully employed, for example, by rocking or rotating the reactors. The polymerization equipment generally used is conventional in the art and the adaptation of a particular type of apparatus to the reaction contemplated is within the province of one skilled in the art. fiber-forming acrylonitrile polymers involve the use of polymerization regulators to prevent the formation of polymer units of excessive molecular weight. Suitable regulators are the alkyl and aryl mercaptans, carbon tetrachloride, chloroform, dibutyltin oxide, antimony trioxide dithioglycidol and alcohols. The regulators may be used in amounts varying from 0.001 to two percent, based on the weight of the monomer to be polymerized.

The polymers from which the filaments are produced in accordance with the present invention have specific viscosities within the range of 0.10 to 0.t).0. The specific viscosity value, as employed herein, is represented by the formula: U = Time of flow of polymer solutions in seconds sp Time of flow of the solvent in seconds Viscosity determination of the polymer solutions and solvent are made by allowing said solutions to flow by gravity at 25°C. through a capillary viscosity tube. In the determination herein, a polymer solution containing 0.1 gram of the polymer dissolved in 100 ml. of N,N-di-methylformamide was employed, also Ν,Ν-dime thylacetamide may be used. The most effective polymers for the preparation of filaments are those of uniform physical and chemical properties and of relatively high molecular weight.

The following examples are cited to illustrate the invention and they are not intended to limit the invention in any way. Unless otherwise noted "parts" are expressed in the examples indicate parts by weight.

EXAMPLE I To an adequately equipped glass reactor, there were continuously added 90 parts of acrylonitrile, parts by weight of vinylidene chloride, 3 parts of vinyl acetate and 600 parts of water. A catalyst solution was fed at a rate of 5 grams per minute and was composed of approximately 0.3 percent aqueous solution of potassium persulfate. An activator solution was fed at approximately the same rate and was composed of 1.20 percent of sulfur dioxide and 0.122 parts per million Pe++ (added as PeSO^ . 7H20). Sodium bicarbonate was added to maintain the pH at a value of about 3· The resulting polymer was composed of approximately 87 percent acrylonitrile, 10 percent vinylidene chloride, and 3 percent vinyl acetate. The receptivity of this copolymer for dyes was very poor and practically, it showed no receptivity at all. Fibers spun from this polymer were flame resistant but very poor in basic dye receptivity. It should be noted that sodium p-methyallyloxybenzenesulfonic acid salt was not added.

EXAMPLE II ,000 ml. glass reactor being equipped with internal baffles, an agitator and a constant temperature water bath was charged with 896 grams of de- ionized water. The temperatures of the water was increased to ij.50C. and the reactor feeds consisting of a monomer mix, a catalyst solution and an activator solution were added thereto. The monomer mix was fed to the reactor at a 93.5,· chloride. The catalyst solution was fed at a rate of 5»^0 grams per minute and was composed of a 0.294 percent aqueous solution of potassium persulfate. The activator solution was fed at a rate of 5.^8 grams per minute and was composed of 1.16 percent sulfur dioxide, Ο.ίφΐ percent sodium p-methya1lyloxybe zenesulfonic acid salt and 0.122 parts per million of Fe* (added as Pe SO^ . 7Ho0) in the ionized water.

Approximately 7 minutes after the start of the reactor feeds, the polymerization of the monomers had begun and the polymer was visible in the reactor.

The reactor temperature was maintained at about $1° plus or minus 1°C. by controlling the temperature of the surrounding water bath at l|.9° to 50°C, since the polymerization is exothermic.

After the reactor feeds were exhausted, the polymer slurry contents were heated from 90° to 95°C. to distill off and recover any unreacted monomers. The polymer was then recovered by filtration, washed to remove any impurities therein, dried, and ground for use in fiber production.

The fiber which was spun from the polymer did not propagate flames and showed a high degree of brightness and purity when tested on a General Electric Spectrophotometer. The basic dye acceptance was determined by applying a standard basic dyestuff, Sevron Blue 2G (Color Index Basic Blue 22), to the fibers in a standard dye bath and determining the amount of dyestuff fixed to the fibers. The basic dye acceptance of the EXAMPLE III Using the polymeriza ion process of Example II, the polymerization container was charged with 500 parts of water, 81.5 parts of acrylonitrile, 2 parts of vinyl acetate, 15 parts of vinylidene chloride and 1.5 parts of sodium p-methyallyloxybenzenesulfonic acid 0 salt. The resulting polymer which had a N of sp -©.177 had a basic dye acceptance of 28.6 percent which resulted in a highly dyeable fiber which was also flame resistant.

EXAMPLE IV Using the process of Example II, the polymerization container was charged with 500 parts of water, 76.5 parts of acrylonitrile, 7.0 parts of vinyl acetate, 15 parts of vinylidene chloride and 1.5 parts of sodium p-methyallyloxybenzensulfonic acid salt. The resulting polymer had a Ngp of 0.2l|8 and had a basic dye acceptance of 25·β percent. The spun fiber was highly dyeable and also flame resistant.

It will be understood to those skilled in the art that many apparent widely different embodiments of this invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

Claims (1)

1 A flame polymer characterized by at least 85 percent by of about 10 percent by weight about percent by weight of vinyl acetate and at least percent of an acid interpolymer of claim characterized in that said acid salt is sodium aoid The interpolymer of claim 1 or characterized by being in form of a textile method of forming a flame interpolymer of any of 1 and eharaeterized by contacting a monomer mixture ing at least 85 peroent by of about percent by weight of vinyl about peroent by weight of chloride and at least percent by weight of an allyloxybenzenesulfonie salt with a free radical oatalyst at a temperature of approximately The method of claim characterized by charging a reactor with said monomer adding to said monomer mixture a potassium persulate and initiating the polymerization reaction by means of a sulfur dioxide The method of characterized in that said mixture in said reactor is maintained at a ature of approximately A of a flame interpol substantially as described in the herein A flam resisting interpolymer whenever produced by the method claimed in any one of claims 1 to icants insufficientOCRQuality