NO125048B - - Google Patents

Description

Process for the production of acrylonitrile polymers.

The present invention relates to the production of acrylonitrile polymers.

Acrylonitrile polymers with an acrylonitrile content of approx. 85% or more are generally prepared from aqueous monomer solutions or dispersions using a persulfate catalyst, such as sodium or potassium persulfate, activated by a sulfoxy reducing agent, such as sodium or potassium metabisulfite. The ratio of activator to catalyst is usually kept below two parts of activator for each part of catalyst and such a ratio gives good yields of polymer. This method is satisfactory in terms of yield, but the polymers formed are not as white as desired and are not resistant to discolouration when heated.

When producing filaments, the acrylonitrile polymer is dissolved in an organic solvent, such as N,N-dimethylformamide, which requires heating a suspension of the polymer in the solvent for a certain time to dissolve it. The solution is also kept at a higher temperature while it is filtered and spun. Any lack of stability in the polymer's color results in fibers whose color can vary from cream-colored to light brown, and there is currently no practical method known to convert such discolored textile materials into semi-manent whites. Bleaching is sometimes used here, but this does not result in a permanent removal of the colour, as the bleached textile materials turn dark again when exposed to ultraviolet rays.

By means of the present invention

it is possible to produce polymers that are suitable for being transferred to white filaments, fibers, gam, film and other shaped products consisting of acrylonitrile polymers or of copolymers containing at least approx. 85% acrylonitrile. Furthermore, the invention provides a modification of the existing methods for producing acrylonitrile polymers, and this modified method results in the formation of permanently white filaments. The products obtained by means of the invention do not need to be bleached. With the help of the invention, white acrylic-nitrile copolymers are also obtained which can be dyed permanently with basic dyes.

According to the present invention, acrylonitrile polymers and copolymers are produced containing at least 85% acrylonitrile and with an exceptionally stable white color which allows the production of very white fibers or filaments. The main characteristic features of the invention are that the weight ratio of sulfoxy activator to peroxy catalyst is at least 6:1 and preferably at least 10:1, and optionally that the mixture also contains a highly polymerizable ethylenic unsaturated sulfonate, such as styrene sulfonate, and optionally methyl acrylate.

It is often advantageous to use less than 0.5 percent by weight of the peroxy catalyst based on the monomers.

Polymers which are distinguished by the fact that they can be dyed very well with basic dyes are obtained according to the invention by also having a copolymerizable ethylenic unsaturated sulfonate and preferably a styrene sulfonate present in the polymerization mixture. It is often advantageous that, next to the ethylenically unsaturated sulphonate, a third copolymerizable ethylenically unsaturated compound is also present in the polymerization mixture. It has been found that methyl acrylate is very beneficial as this third component. Persulfates and especially potassium or ammonium persulfate are the preferred catalysts. In connection with the persulphates, metabisulphite as an activator allows the polymerization to be directed in an advantageous manner and to regulate the whiteness of the polymerizate obtained.

Copolymers which form white yarn with good color stability and which, with good gloss and depth, can be dyed with basic dyes are obtained according to a preferred modification of the method according to the invention by copolymerizing a mixture of monomers containing at least 85% and preferably 90% acrylonitrile and one or more ethylenically unsaturated monomers, with a sufficient amount of ethylenically unsaturated sulfonate monomer preferably in the form of its alkali metal salt to provide additional sulfonate groups and sufficient to bring the total number of milliequivalents of it as ionizable sulfo- and sulfur groups are bound sulfur per kilograms of copolymer to at least 40. The polymerization is carried out in the presence of a persulfate catalyst and a sulfoxy reducing agent as activator, the ratio of activator to catalyst being kept at a higher value than approx. 6:1. The amount of catalyst present is usually from 0.05 to 1.0% based on the total amount of monomer present in the reaction zone.

In order to ensure a good ability to be dyed with basic dyes, the copolymer produced in this way must contain no less than 40 and preferably between 40 and 90 milliequivalents of bound sulfur as ionizable sulpho and sulfur groups per kilogram of copolymer and it must be free of strongly basic groups, such as quaternary ammonium compounds, pyridine or amines. The copolymer must also contain no less than 10 milliequivalents of sulfur 1 form of ionizable sulfo groups per kg of polymer, where the sulfur is bound to the intermediate carbon atoms in the polymer chain, i.e. the sulfur in the ionizable group is, by means of suitable conjugation, bound to a carbon atom in the polymer chain between the ends of the chain. The ionizable sulfo or sulfur groups are normally present as hydrolysable salts, but they can also exist as free acid groups. In the following, milliequivalents of sulfur per kg polymerizate only the sulfur that is present as ionizable sulfo or sulfur groups.

The method according to the present invention comprises polymerization of acrylonitrile either as a homogeneous polymer or as a copolymer in which the acrylonitrile content is not less than approx. 85%, in the presence of a persulphate catalyst and a sulphoxy reducing agent as activator, and at a ratio between the activator and the catalyst higher than approx. 6:1 and preferably higher than approx.

10 : 1. There is no upper limit i

this relationship with respect to efficiency in the production of white polymers, but conditions that are higher than approx. 2,000 : 1 reduces the yield to inadmissible values.

The invention primarily relates to polymers and copolymers which, when spun into filaments, yarns, fibers and the like, form white products which retain their white color when exposed to ultraviolet rays. Since the term "white" is relative and an object is designated as white when an even whiter object is not present, it is necessary to define this term as it is used here. As the polymers produced in accordance with the present invention are primarily used for the production of fibers and filaments, they are used to judge the color of the polymers. In order to determine the fibers' color value, hereinafter briefly referred to as ffv., staple fibers are first prepared by washing at boiling temperature for 30 minutes with deionized water containing 0.1% of a non-ionic surface-active agent. The samples are then rinsed twice

-anger with deionized water, squeezed out and centrifuged to remove any excess, after which they are dried in air at room temperature. About. 2 g of the thus obtained dry sample is carded so that the fibers are brought to lie parallel with the help of a hand carder, which results in a mat of unstacked fibers with approx. dimensions 75 mm x 150 mm. This is folded once lengthwise. The reflectance of the samples using the instrument's "green" and "blue" filter sets is measured with a Model IV Colormaster Differential Colorimeter, manufactured by the Manufacturing Engineering and Equipment Company of Hatboro, Pennsylvania, U.S.A. which is calibrated against the manufacturer's standard reflection plate.r and against the National Bureau of Standards standard reflection plate provided with a certificate. Two readings are taken on each side of the sample, the second reading being carried out with the sample rotated 90° from the position at the first reading.

reading. The fiber color value is then calculated from an average of four readings using the following formula:

hvoir r.f. green means ref leks ionfortiold with a green filter and r.f. blue means reflectance ratio with a blue filter.

Color measurements carried out on a number of different "white" samples of combed staple mats were noted and listed below:

These indications show that fibers according to the invention can be advantageously compared with other white synthetic fibers and are much whiter than the best previously known acrylonitrile polymer fibers. The designation "white" in relation to the fibers according to the present invention will therefore be used when reflection tests give values below 6, hereinafter referred to as "fibre color value".

As already mentioned, bleached acrylic-nitrile fibers turn dark again when exposed to ultraviolet rays. To prove this fact, experiments were carried out with samples of previously known acrylonitrile copolymers and with white fibers with a fiber color value below 6 produced according to the present invention. The fiber color values were determined in the experiment before and after the samples were exposed to ultraviolet rays in a Golor Fade-Ometer for 20 hours at 32° C. A sample of the previously known fibers was bleached with an acidified sodium hypochlorite solution to imitate industrial bleaching, then it was treated with sodium bisulphite as an anti-chlorine agent, after which the fibers were rinsed and dried. A comparison of the fiber color values is given below:

These results clearly prove that chemically bleached acrylonitrile polymer fibers become dark when exposed to ultraviolet rays, while untreated samples become whiter.

Another test for determining the final whiteness of the fibers and the stability of the polymer's color when heated is called "heating color value", abbreviated to "hfv". This test was carried out with samples of the polymer and it indicates in advance the degree of whiteness that can be expected for the finished filaments, fibers and yarn produced from the polymer in question. A comparison of heating color values with the color values is also important to show the stability of polymer samples when exposed to heating. Both experiments are explained below.

The method for determining the color

the method consists in preparing a standard solution, which is a 5.8% solution of the polymer in pure N,N-dimethylformamide that is free of dimethylamine and measuring the optical density of the solution at 400 millimicrons against a sample of a pure solvent using a Beckman Model DU spectrophotometer. The optical density multiplied by 100 is taken as the polymer's color value ("fv"). As the color can increase several times, e.g. 5 to 25 times, when the polymerizate solutions are kept for a time at higher temperatures, the method was adapted to the measurement of "heating color values"

(hfv). This is done by heating a 25% solution of the polymerizate in dimethylformamide at 100°C for four hours and then carrying out the method with a sample of this solution diluted to the standard test concentration (5.8% polymerizate

as described above). "Heating color values" of polymers can be compared well with actually measured color values for the fibers produced, if the temperature and heating time are practically equivalent to the temperature and the time the polymer stays in the solution before spinning. A low hfv is not so much indicative of a low initial color value for the polymer as it indicates greater stability in terms of to retain the original whiteness and it predicts the final color of filaments, yarns and fibers produced from the polymer.

There is a direct relationship between hfv and fiber color values (f f v). Thus, e.g. fibers with a ffv = 2 produced by a normal dry spinning process from a polymer with a hfv of approx. 6. If the hfv sample with the polymerizate gives values of 12 or 13, with normal preparation of the solution and dry tension, fibers with a ffv of approx. 6. The Hfv results can thus be used to fairly accurately predict the ffv that will be obtained by normal treatment and spinning of the polymer, as shown in example VII below.

According to this invention, a good indication of improved coloring ability with basic dyes is the values for milliequivalents of available ionizable sulpho and sulfur groups per kilogram of the polymer. One such milliequivalent corresponds to 0.032 g of sulphur. This content can be determined in different ways, but preferably using the following method: A solution of 1% polymer in dimethylformamide is prepared. This solution is allowed to pass through an ion-exchange column containing a dewatered mixture of strongly acidic and strongly basic ion-exchange resins, where the cationic exchange resin is 100% in the form of free acid and the anion-; ion exchange resin is 100% in the basic form as hydroxyl. Dewatering of the resins can be achieved by washing with acetone and subsequent displacement with dimethylformamide. A suitably mixed resin layer consists of Rohm und Haas Amberlite MB-3. The flow rate is so great that the solution is in contact with the resin for no less than 3 minutes.; The solution is then passed through a column containing a strongly acidic resin of the sulfonate type, as Rohm und Haas I.R. 120, 100% in the form of free acid, as the contact time here too is not less than 3 minutes. At these steps, all ionisables are removed contaminants in the solution and causes where a complete conversion of the ionizable acidic substances into the corresponding free acids. Equal amounts of the flowing dirnet<y>lformarnld<p>solution are taken out for determination of the polymer content and of the solution's polymer content acidity. Titration of the polymerizate acidity is carried out directly in dimethylformamide medium with a visible indicator or with a potentiometric endpoint with a standard solution in absolute methanol of a strong base, such as 0.005 N potassium hydroxide. The free acids of alkyl sulfates, alkyl and aryl sulfonates are titrated as strong acids in dimethylformamide medium, while the carboxylic acids are titrated as weak acids and can be determined separately if they are present. The results of the acidity determination are calculated and given in milliequivalents per kilogram of dry polymer. It has been found that a mathematical relationship exists between the total ionizable sulfonate and sulfate end groups in the polymer chain and the specific viscosity, when the polymerization conditions are constant, when changes such as is performed in the initiation system to vary the intrinsic viscosity or molecular weight. When this relationship is known, one can calculate from the polymer's total acidity the part that is introduced into the polymer chain by copolymerization of the ethylenically unsaturated sulphonate monomer component.

The ability to be dyed by basic dyes is usually insufficient at acidity values below 20 milliequivalents per kilogram of polymer, it is significant, but usually not sufficient for full shade dyeing at values between 20 and 35. At values above 40, however, full shade dyeing can be achieved in a reasonable time. Very high values such as 100 or more milliequivalents of sulfur per kilogram of polymer can be advantageous under certain conditions, but values of 40-90 are generally preferred.

The color capacity of fiber samples is proportional to milliequivalents of sulfur found by the method described above. As a further measure of this capacity, in the following examples, the dye capacities of the produced fibers using a common basic crystal violet dye (color index 681) are stated in percent of the dye required to saturate the fibers. It is important that the fibers have sufficient color capacity to satisfy requirements for deep shades. It is also important that the fibers are able to absorb the dye at a reasonable rate, so that you do not have to wait a long time to achieve the desired color depth. Dyeing of fibers of acrylonitrile copolymers with basic dyes follows a simple rate equation in the early stages of dyeing, e.g. up to 90 minutes cooking time. (See Vickerstaff, "The Physical Chemistry of Dyeing", p. 129, First Edition, 1950, Interscience Publishers, N.Y., U.S.A.). When you plot the amount of dye in percent on the fibers as abscissa against the square root of the dyeing time as ordinate, you get a straight line that allows you to determine a simple "rate constant", e.g. as indicated by the following equation:

In order to determine the relative dyeing rates for the fiber samples from examples given below, the following tests were carried out: A single sample of approx. 0.12 g of staple fibers. The carded sample was placed loosely in a bag with approx. 25 mm diameter cheese cloth of single thickness and whose ends were tied with a piece of bom wool yarn. A double experiment was carried out. Nameplates made of stainless steel with a weight of approx. 5 g is tied firmly approx. 5 cm from the bags and numbered for identification of the samples. These marking plates also serve to keep the samples under the surface of the dye bath. The plates are tied together so that they can be quickly removed from the dye bath. Up to 30 individual samples can be dyed simultaneously in the same dye bath.

Before dyeing, the bags containing the staple samples are washed for 30 minutes at 70°-80° C in a bath containing per liter in water, 1.0 g sulphonated lauryl alcohol or similar. Deionized water with a conductivity not greater than 1.0 x 10-°. mhos/cm is used for washing, rinsing and dyeing. After washing, the samples are rinsed once in water and centrifuged to remove water on their surface.

For each bath of 30 samples or less, use 0.300 g of pure crystal violet powder (color index 681), 1 ml of a 15% aqueous solution of acetic acid, 1 ml of a 15% aqueous solution of sodium acetate, and sufficient water to bring the total volume to 1500 ml. The dye bath is placed in a stainless steel beaker equipped with a reflux cooler and thermometer and is heated using a Bunsen burner. It is brought to a vigorous boil, after which the samples are placed in the bath. After 60 minutes, the samples are taken out of the bath, rinsed thoroughly with water at room temperature, centrifuged and dried at 70-75° C in a steam drying cabinet for two hours.

A portion of approx. 0.10 g of each colored sample is weighed on an analytical balance and placed in

a 100-ml measuring flask into which approx. 75 ml of pure gamma-butyrolactone and the fibers are dissolved by boiling in a water bath at a temperature of 70° C for 5-10 minutes. The solution in the flask is cooled and brought to the original volume by adding pure butyrolactone. This solution is then diluted to the necessary extent (usually approx. 20:100) so that it gives an optical density reading from 0.1 to 0.6. These solutions are examined in a Beckman Model DU spectrophotometer at 595 millimicrons (without filter). It has been found that solutions of dyes in butyrolactone follow Beer's rule up to an optical density of 1.0. A comparison sample containing 0.005 g of undyed fibers in 25 ml of butyrolactone is used there.

The percentage of dye in the fibers is calculated as follows:

liters of fibers in solution.

2. Optical density (at 595 millimicrons) x 0.00406 = grams per liter of solution of the dye.

vest fabric on the fibers.

The invention can be used for the polymerization of acrylonitrile with many other ethylenically unsaturated copolymerizable compounds, such as vinyl acetate, methyl vinyl ketone, methyl methacrylate, dimethyl itaconate, butyl methacrylate, butyl acrylate, diethyl maleate, vinyl trimethyl acetate, methacrylonitrile, styrene, vinyl ethyl hexyl ether, octyl methacrylate, α-methylstyrene, 4-methoxystyrene, ethylenesulfonic acid, allylsulfonic acid, metallysulfonic acid, halogenated mono-ethylene compounds, N-vinyl compounds, etc. Two or more copolymerizable compounds can be used if desired. Neutral monomers alone can be used to get better coloring due to the opening of the polymer structure, but copolymers containing both a neutral modifier and a strong acid group are preferred, such as acrylonitrile 85-95%, methyl acrylate, vinyl acetate, methyl vinyl ketone etc. 14-4 %, and a copolymerizable sulfonate such as sodium or potassium styrene sulfonate 0.1-5%.

For the production of dyeable and color-stable copolymers of acrylonitrile, in the absence of sequestration agents, it is necessary that the ratio between the sulfoxy activator and the persulfate catalyst is kept at a relatively high value. In the following examples, with the exception of Example XXI, this ratio is at least 8:1 and in many examples it is higher. The highest value is 91 : 1. The greatest degree of whiteness and the lowest tendency to discoloration in the absence of ice sequestration agents was obtained at this higher value of the ratio of activator to catalyst. The Hfv was then 6 and the fiber color value 2.0, which is equal to or even whiter than bleached cotton fibres. However, under certain conditions, when the ratio between the activator and the catalyst falls significantly below 8:1, e.g. to a value as low as 6:1, still few polymers and fibers with properties within the limits specified here. It is of course possible to use a ratio between the activator and the catalyst that is higher than 100:1, e.g. 200:1 or even 2000:1 and more and to obtain products with excellent whiteness and extremely rigid stability against discoloration, but turnover is low and the use of such high ratios is generally not possible for practical reasons.

In the following examples, certain persulfate catalysts and bisulfite activators are used, but other similar compounds may be used instead. The catalyst may consist of any water-soluble derivative of per-disulfuric acid used in combination with water-soluble oxidizable sulfoxy compounds in which one sulfur atom does not exceed 4, such as sodium bisulfite, sodium metabisulfite, sulfur dioxide, sodium hydrosulfite and other similar water-soluble salts .

While the dyeing capacity is dependent on the presence of ionizable sulfonate and sulfate groups, the dyeing rate is highly dependent on the amount and structure of the neutral polymerizable monomer component in the copolymer. It can be seen from the following examples that the dyeing rate constant varies widely from a maximum K value of 0.360 when the polymerizate contained approx. 14% methoxyethyl acrylate (Example: XVI) to a minimal value of 1.058 when the polymerizate contained approx. 8% styrene (Example XIII); With approximately the same amount of a neutral modifier in the form of N-tertiary butylacrylamide (Example IX), the dyeing speed is over three times greater than in Example XIII. Neutral copolymerizable monoethylenically unsaturated compounds vary considerably in their effect on rates of color uptake. Among the more advantageous polymerizable monomers from this point of view are methyl acrylate, methyl methacrylate, methyl vinyl ketone, methyl acrylamide, N-tertiary butyl acrylamide, vinyl methoxy ethyl ether, methoxy ethyl acrylate, etc.

Apart from the polymerizable sulfonate monomers indicated in the examples, there exist many others which can preferably be used in the form of their alkali metal or ammonium salts. Such monomers are the salts of allyloxyethylsulfonic acid, metalliyloxyethylsulfonic acid, allyloxypropanolsulfonic acid, allylthioethylsulfonic acid, allylthiopropanolsulfonic acid, isopropenylbenzenesulfonic acid, vinylbromobenzenesulfonic acid, vinylfluorobenzenesulfonic acid, vinylmethylbenzenesulfonic acid, vinylethylbenzenesulfonic acid, isopropenylisopropylbenzenesulfonic acid, vinylhydroxybenzenesulfonic acid, vinyldichlorobenzenesulfonic acid, vinyldichlorobenzenesulfonic acid. , vinyltrihydroxybenzenesulfonic acid, vinylhydroxynaphthalene - ■sulfonic acid, isopropenylnaphthalenesulfonic acid, sulfodichlorovinylnaphthalene, allylbenzenesulfonic acid, metallylbenzenesulfonic acid, isopropenylphenyl-n-butanesulfonic acid, vinylchlorophenylethanesulfonic acid, vinylhydroxyphenylmethanesulfonic acid, vinyltrihydroxyphenylethanesulfonic acid, isopropylethylenesulfonic acid, acetylethylenesulfonic acid, naphthylethylenesulfonic acid, biphenyloxyethylenesulfonic acid , propenesulfoic acid, butenesulfoic acid, hexenesulfoic acid, methylpentenesulfoic acid, methylbutenesulfoic acid, triisobutylenesulfoic acid, diisobutylenesulfoic acid, etc. Salts of di-acids such as of disulfoic acid can also be used, F. e.g. salts of sulfobutenesulfoic acid, vinylbenzenedisulfoic acid, vinylsulfophenylmethanesulfoic acid, allylidene sulfoic acid, etc.

An ethylenically unsaturated monomer is usually used as a third component together with the polymerizable sulphonate and acrylonitrile. Suitable monomers are methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, dimethylamidoethyl methacrylate, and the corresponding esters of acrylic acid, acrylamides and methacrylamides or their alkyl substitution products, unsaturated ketones such as methyl vinyl ketone, phenyl vinyl ketone, methyl iso-propenyl ketone and the like, vinyl carboxylates such as vinyl formate, vinyl acetate vinyl propionate, vinyl butyrate, vinyl thiolacetate, vinyl benzoate, esters of ethylene-a, |3-carboxylic acids such as maleinfumar-, citracon -, mesaconic, aconic acids, N-acyl-maleic acid amides, N-vinylcarbazole, N-vinyl-succinimide, N-vinyl-phthalimld, vinyl ethers, etc.

The amount of sulfonate monomer that is usually introduced into the copolymer is from approx. 0.1% to approx. 5.0%, depending on its molecular weight and on the number of sulfonate groups it contains. In general, it can make up up to 14% of the third monomer, but the best results are obtained when the acrylonitrile content is kept above 90% with no more than approx. 9% of the third monomer.

Polymers and copolymers according to the invention can be used in admixture with other polymers or copolymers. Thus, a sulfonate-containing copolymer according to the invention can be mixed with a homogeneous acrylonitrile polymer or with a polymer with two components, such as a polymer consisting of 95% acrylonitrile and 5% methyl acrylate, as well as with different terpolymers or the like. According to the invention, the amount of copolymer in such mixtures will depend on its content of ionizable sulfonate and sulfate groups and on the composition of the other polymers mixed with these. Generally, 5% to 95% of these polymer mixtures will consist of copolymers according to the present invention.

Polymers and copolymers according to the invention are particularly suitable for spinning textile filaments and fibres. Due to their great stability and whiteness and very good ability to be dyed very well, these are suitable for use in all types of textile materials. Apart from this, polymers and copolymers according to the invention are well suited for the production of film and other shaped objects for which a high degree of whiteness is desirable.

The high degree of whiteness of fibers or films according to the invention allows the use of light colors even with pastel shades. The fact that they largely retain their original whiteness even when heated to high temperatures means that these acryl-nitrile polymers according to the invention are perfectly suitable for all types of fine textiles, such as shirt materials, fine jersey fabrics, suit fabrics and the like, especially for white goods and materials that are colored in pastel shades.

The following examples are given to illustrate the invention. It is pointed out that any acrylonitrile copolymer with an acrylonitrile content of at least 85% can be used instead of the polymers indicated in the examples. Any alkali metal salt may likewise be used in place of sodium and potassium metabisulphite and persulphate, in any ratio within the above stated limits. Likewise, any of the ethylenically unsaturated monomers and the ethylenically unsaturated sulfonic acids or their salts may be used instead of the corresponding compounds indicated in the examples. Parts in the examples means parts by weight, unless otherwise stated.

Example 1:

A number of charge polymerizations of acrylonitrile were carried out with varying amounts and ratios of activator (sodium metabisulphite) and catalyst (potassium persulfate), as shown below in Table I. In all cases, in a laboratory polymerization -glass container placed 95 parts water acidified with sulfuric acid to a pH of approx. 3.5 and 5 parts of monomer, after which it was heated to 45° C. Each charge also contained iron in a concentration of approx. 0.2 parts per million parts. The amounts of sodium metabisulphite and potassium persulphate indicated for the various experiments in Table I were then added, the added amounts in weight percent being calculated on the amount of acrylonitrile in the system. The polymerization reaction was allowed to proceed for 2 hours with stirring at a constant temperature of 45° C. The results are shown in Table I below.

Example 2:

During the continuous polymerization of acrylonitrile, the amounts of potassium persulfate and sodium bisulfite became very important second, while the other conditions remained constant. Each experiment was carried out in an overflow polymerization vessel for continuous processes under conditions giving 1 hour "residence" time, i.e. the average residence time of "reaction residence time" and a pH value of 3.75. In each ponents in the polymerizer was one hour. experiment, there was a small regulated The polymerization container was originally amount of iron, i.e. approx. 0.2 parts per million half filled with water acidified with parts of sulphur. The percentage amount of monomeric acid to a pH of 3.75 and heated to 45° (100% acrylonitrile) is calculated on the C. This temperature was maintained un- total added material, while the percentage throughout the experiment. The reaction components ical amount of the persulphate and bisulphite is was added continuously with a constant has- calculated on the weight of the monomer in the presence and in the percentages given in Table II led material. The results are shown in table quantities, together with sufficient water II.

and acid to maintain an hour's "up-

Here hfv is almost 100% greater with the corked Erlenmeyer flask without stirring, in the normal low ratio of activator-catalyst - approx. 20 hours at room temperature and at sator, while the conversion and limit visco- a pH value of from 3.0 to 3.3. Each charge teten [r|] is almost equal. of approx. 1400 g consisted of water containing approx. 0.2 p.p.m. parts per million parts of iron Example 3: and which was acidified with sulfuric acid, with 7% monomer (94% acrylonitrile, 6% methyl A series of charge-wise po- acrylate was carried out) calculated on the total weight of the charge and polymerisations in which the amounts of cata- the mixer and activator specified in Table III below were varied significantly for the potassium persulphate catalyst and to form copolymers of acrylonitrile and the trium bisulphite activator. These amount-methyl acrylate in a ratio of approx. 94 : 6. Ratios are stated in weight percent calculated on the search was in each case carried out in a 2-litre the monomer's weight.

The limiting viscosity ([i]]-results) in comparison of hfv with fv shows very these experiments varied significantly, but there will be greater stability against color changes easily seen that hfv decreased at least to 100 at high temperatures when the polymerizate when the ratio of activator to catalyst increased , is produced at a high asset ratio - and then it changed little. A tor for catalytic converter.

Example 4:

Another experiment with batchwise polymerization was carried out to form acrylonitrile/methyl acrylate copolymer (94/6) under similar conditions as in example 3, except that the temperature was kept at 45° C. The amounts of the catalyst and activator used as well as the results are shown in Table IV below.

Example 5:

An experiment was carried out with continuous polymerization similar to that described in example 2 to produce copolymers of acrylonitrile 93.5%, methyl acrylate 6% and potassium styrene sulfonate 0.5%. In all these experiments, the temperature was kept constant at 45° C, the pH value at approx. 3.5 and the amounts of potassium persulphate catalyst and sodium bisulphite activator were varied as shown in Table V below. Hfv bite then improved when the ratio between the activator and the catalyst increased.

Example 6:

In a series of experiments, continuous polymerization similar to that described in example 2 was carried out to form copolymers with the composition indicated in example 5. The washing water for the polymerizate contained in certain cases approx. 0.02% of a sequestering agent as shown in Table VI. It can be seen that the addition of ethylene-diaminetetraacetic acid or oxalic acid to the wash water caused a further lowering of hfv.

Example 7:

In a container for continuous polymer riser which was partially filled with water acid-

made with sulfuric acid to a pH value of 3.6 and heated to 45° C, an aqueous solution containing 0.3% sulfuric acid, an aqueous solution containing

0.4% potassium persulfate, an aqueous solution containing 8.0% sodium metabisulphite, an aqueous solution containing 1.0% sodium styrene sulfonate and a mixture of acrylonitrile and imethyl acrylate together with water containing a small amount of iron regulated so that approx. 0.2 parts of iron per million in the reaction mixture. The solution was calculated to give a residence time of 91 minutes in the reactor after steady state conditions had been established. The composition of the added material in parts by weight is given below:

An atmosphere of inert gas was maintained in the reaction vessel and the temperature was maintained at 45° C. The copolymer in the reaction mixture overflowing from the reactor was washed free of catalyst, activator and unreacted monomers. It was then dried to below 1% moisture at a temperature of 108° C. A 73% conversion of monomers to the polymer was obtained, the polymer having a specific viscosity of 1.45. The discoloring tendency of the copolymer, expressed as heating color value, was 10.1.

An amount of dry copolymer sufficient to form a suspension containing 29% polymer was suspended in deionized dimethylformamide and maintained at a temperature of 55°C for 8-16 hours. The temperature of the suspension was then raised to 80°C to achieve dissolution of the suspended material. The solution was then filtered at a temperature between 80° and 95°C and, with continued heating, led to an evaporation spinner from which it was extruded through a multi-aperture spinneret at a temperature of approx. 140° C. The total residence time during which the solution was kept at 80° C or higher temperature was approx. 30 minutes and at more than 100° C no longer than approx. 5 minutes. The yarn coming from the dry spinning cell was washed free of solvent with hot water (98° C) and drawn in hot (98° C) water 4X, shrunk, cut into 5 cm lengths and dried in the loose state for 6y2 min. at 127° C. The fiber color value was 4.8.

Example 8:

In a continuous polymerization vessel partially filled with water acidified with sulfuric acid to a pH of 3.6 and heated to 45° C, an aqueous solution containing 0.4% potassium persulfate, an aqueous solution containing 0.5% sulfuric acid, an aqueous solution containing 8.0% sodium metabisulphite, an aqueous solution containing 1 .0% sodium styrene sulphonate and a mixture of acrylonitrile and methyl acrylate together with a quantity of water containing a small quantity of iron regulated so that approx. 0.2 parts of iron per parts per million in the reaction mixture. The solution was calculated to give a 91-minute residence time in the reactor after steady state conditions had been established. The composition of the added material in parts by weight is stated below:

An atmosphere of inert gas was maintained in the reaction vessel and the temperature was maintained at 45° C. The copolymer in the reaction mixture overflowed from the reactor was washed free of catalyst, activator and unreacted monomer and then dried to below 1% moisture at a temperature of 108 ° C. A 73% conversion of monomer to the polymer was obtained. The copolymer had an intrinsic viscosity of 1.45. The formed copolymer was analyzed for total content of combined ionizable sulfo and sulfur groups and it was found that per kg of dry copolymer contained 44.1 milliequivalents of sulfur in this form. There were 13 milliequivalents of sulfur per kg in the chain. The tendency of the copolymer to discolor, expressed as heating color values, was 10.1.

Dry copolymer, in an amount sufficient to form a suspension containing 29% polymer, was suspended in deionized dimethylformamide and kept at a temperature of 55° C. for 8-16 hours. The temperature of the suspension was then raised to 80°C to dissolve the suspended material, after which the solution was filtered at a temperature between 80° and 95°C. With continued heating, the solution was then led to a dry spinning head, from which it was extruded through a spinning nozzle equipped with many openings at a temperature of approx. 140° C. The total residence time during which the solution was held at 80° C or higher was approx. 30 minutes and at temperatures above 100° C no longer than 5 minutes. The yarn from the dry spinning cell was washed free of solvent with hot water (98° C) and drawn in hot (98° C) water 4X, shrunk, cut into 5 cm lengths, then dried loose for 6y2 minutes at 1270° C. The fiber color value was 4.8. The fibers had a dye capacity equivalent to 1.79% crystal violet and a dye rate constant (K) of 0.087 when tested as previously described.

Example 9:

In the manner described in example 8, the substances specified below were introduced into a container for continuous polymerization together with an amount of water sufficient to allow a stay of 60 minutes in the container. Monomers and other reaction components were introduced into the reactor in the following proportions:

The temperature in the reaction vessel was 45° C. and an atmosphere of inert gas was maintained therein. The resulting polymer was washed free of unreacted monomers and salts and then dried. Dry polymerizate was obtained with a yield of 70%. It had an intrinsic viscosity of 1.51. The polymerizate contained 41.6 milliequivalents of sulfur as ionizable sulfo and sulfur groups. The heating color value was 11.2. The polymer was spun and processed as described in Example 8 to form crimped staple fibers. The test results give a fiber color value for the fibers of 5.1, a dye capacity equivalent to 1.69% crystal violet and a dyeing rate constant (K) of 0.191.

Example 10:

A copolymer of acrylonitrile, methyl acrylate and sodium styrene sulphonate was treated in the same way as described in example 8 with the following concentrations of reaction components in the feed stream to the polymerization vessel:

The temperature of the reaction mixture was 48° C. during the reaction and the residence time was 76 minutes. The reaction component was protected with inert gas during the polymerization. The yield of washed, dried copolymer was 75% calculated on the entire amount of monomer. The product had an intrinsic viscosity of 1.46. The copolymer was analyzed for total sulfur as ionizable sulfur and sulfo groups and examined for the heating color value. The fibers which were spun from the copolymer as described in example 8 were assessed with regard to dyeing capacity, dyeing speed and color. The results were as follows:

Example 11:

A copolymer of acrylonitrile, methyl vinyl ketone and sodium metalyl sulphonate was prepared as indicated in the previous examples with the following ratio between the reaction components:

The reaction mixture was kept in the polymerization vessel at a temperature of 45° C. The residence time was 90 minutes. The washed, dried copolymer was obtained with a yield of 74%. The product's limiting viscosity was 1.4. The copolymer and fibers spun from it and treated as described above had the following sulfur content, heating color value, color capacity, dyeing speed and fiber color value:

Example 12:

A copolymer of acrylonitrile, vinyl acetate and ammonium vinyl sulphonate was prepared as indicated in the preceding examples, the following substances being added to the polymerization vessel in the following proportions:

During the reaction in the polymerization vessel, a temperature of 48° C. was maintained. The residence time was 90 minutes. The copolymer had an intrinsic viscosity of 1.7 and the conversion was 70%. The sulfur content, heating color value, dyeability and color of fibers spun from the copolymer were as follows:

Example 13:

A copolymer of acrylonitrile, styrene and sodium styrene sulfonate was prepared as indicated in the previous examples. The material that was added to the polymeriser-ihgs container had the following composition:

During the reaction in the polymerization vessel, a temperature of 45° C. was maintained. The residence time was 90 minutes. The yield of the copolymer was 70% and its intrinsic viscosity was 1.5. The copolymer contained 55 milliequivalents of sulfur and had a heating color value of 12.1. The spun fibers had a dye capacity equivalent to 2.24% crystal violet, a dye rate constant (K) of 0.058 and a fiber color value of 5.8.

Example 14:

A copolymer of acrylonitrile, acrylamide and sodium styrene sulfonate was prepared as indicated in the preceding examples. let laughing. The composition of the added material was as follows:

The residence time in the reactor was 60 minutes at a temperature of 45° C. 63% of the monomers were converted to polymer. The polymer had an intrinsic viscosity of 1.13. Analysis of the polymer on sulfur and hfv gave the following results:

Staple fibers spun and treated as described in example 8 of this polymer had a fiber color value of 6.0, a dye capacity equivalent to 1.96% crystal violet and a dyeing rate constant (K) of 0.101.

Example 15:

A copolymer of acrylonitrile, ethyl acrylate, acrylamide and sodium styrene sulfonate was prepared as indicated in the previous examples. The material fed to the reactor had the following composition:

The residence time in the reactor was 45 minutes at a temperature of 45° C. 57% of the monomers were converted to polymer. of the polymer. limit viscosity was 1.5. Analysis of the copolymer and tests with spun and drawn fibers gave the following results:

Example 16:

A copolymer of acrylonitrile, methoxyethyl acrylate and sodium styrene sulphonate 2 was prepared as indicated in the previous examples. The composition of the added material was as follows:

The residence time in the reactor was 45 minutes at a temperature of 46° C. 57% of the monomers were converted to polymer. The intrinsic viscosity of the copolymer formed was 1.63. Sulfur content, Hfv,, fiber color and dyeability were as follows:

Example 17:

A copolymer of acrylonitrile, vinyl formate and sodium styrene sulphonate was prepared as indicated in the previous examples, the material being fed to the reactor having the following composition:

The residence time was 45 minutes at a temperature of 45° C, while the conversion was 45.5% and the intrinsic viscosity of the copolymer was 1.73. There were 48.1 milliequivalents of sulfur per kg copolymer and hfv was 9.8. Staple fibers spun from this copolymer had a fiber color value of 4.7, a dye capacity equivalent to 1.95% crystal violet and a dyeing rate constant (K) of 0.069.

Example 18:

Fibers of a copolymer of acrylonitrile, methyl acrylate and potassium styrene sulphonate were produced as described in example 8. The composition of the added material, the polymerization conditions and the results were as follows:

Example 19:

A copolymer of acrylonitrile, ethyl acrylate and sodium styrene sulphonate was prepared as indicated in Example 8 with the following composition of the added material, conditions and results:

A copolymer of acrylonitrile, ethyl acrylate and sodium styrene sulphonate was prepared as indicated above. The composition of the feed material, the polymerization conditions and the results were as follows:

Spun fibers were produced as described in example 8 from mixtures of these two copolymers in a ratio which gives 50 milliequivalents of sulfur as ionizable sulpho and sulfur groups per kg polymerized. These fibers had a color value of 6, a dye capacity equivalent to 2.05% crystal violet and a dyeing rate constant (K) of 0.082.

Example 20:

A copolymer of acrylonitrile, methyl acrylate and potassium styrene sulfonate was prepared as indicated in the preceding examples of sensing:

The polymerization was carried out at a temperature of 45°C and gave a conversion of 65.2% to a polymer having an intrinsic viscosity of 1.27. The sulfur content as ionizable sulpho and sulfur groups was 71.7 milliequivalents per kg and hfv was 10.8. Fibers prepared as described in Example 8 had a dye capacity equivalent to 2.92% crystal violet, a dye rate constant (K) of 0.120 and a fiber color value of 5.0.

Example 21: A solution of 0.01 g per liter of ethylenediaminetetraacetic acid, in deionized water. 10.71 liters of the solution was added to a stainless steel polymerization vessel. Acrylonitrile, methyl acrylate, sodium styrene sulfonate, potassium persulfate, sodium metabisulfite and sulfuric acid were then added in the following amounts: Acrylonitrile 702.0 g Methyl acrylate 45.0 g Sodium styrene sulfonate 3.0 g Potassium persulfate 24.8 g Sodium metabisulphite 33.0 g

Sulfuric acid to a pH value of 3.0-3.3

The solution was left to stand for 48 hours without stirring at room temperature. The conversion was 45%, the polymer's intrinsic viscosity [t|] was 1.90 and the polymer's heating value was 2.8. The total sulfur bound in ionizable sulfo and sulfur groups was 40 milliequivalents per kg dry copolymer. A spinning solution prepared and spun as set forth in Example 8 produced fibers which, when similarly drawn, shrunk, cut and dried, had a fiber color value of 1.4. The dye rate constant (K) was 0.058 and the dye capacity was equivalent to 1.62% crystal violet.

Example 22:

A copolymer of acrylonitrile and sodium styrene sulfonate was prepared as in the previous examples from the following:

The polymerization was carried out at a temperature of 48°C and gave a conversion of 62% to a polymer having an intrinsic viscosity of 1.5. The total sulfur content as ionizable sulpho and sulfur groups was 100 milliequivalents per kg of polymer with 70 milliequivalents of sulfur per kg of polymer in the chain. The heating color value of the polymer was 11. Fibers prepared as indicated in Example 8 had a color capacity equivalent to 4.06% crystal violet, a dyeing rate constant (K) of 0.076 and a fiber color value of 4.9.

Claims (2)

1. Process for the production of white acrylonitrile polymers or copolymers with at least 85% acrylonitrile, whereby a mixture containing acrylonitrile is polymerized in the presence of a peroxy-sulfoxy-redox catalyst system, characterized in that the weight ratio of sulfoxy-activator to peroxy-catalyst is at least 6:1 and preferably at least 10:1 and optionally in that the mixture also contains a copolymerizable ethylenically unsaturated sulfonate, such as styrene sulfonate, and optionally methyl acrylate. 2. Method according to claim 1, characterized in that less than 0.5% by weight of peroxy catalyst calculated for the monomer(s) is used.