Polyolefin And Ethylene-amino Acrylate Copolymer Blend Dilute Acid Scoured And Dyed

Abstract

A process for acid dyeing polyolefin (isotactic polypropylene) shaped articles such as fibers is provided which gives full penetration of dye to heavy denier round fibers in relatively short periods of time as well as adequate penetration of very heavy tape and fibrillated film fibers. This process comprises (1) extruding a uniform blend of the polyolefin with about 2 to 15 percent by weight of a thermoplastic, essentially compatible nitrogen-containing polymer such as a copolymer of ethylene and dimethylaminoethyl methacrylate into fibers, (2) exposing the fibers to an aqueous prescour solution which contains about 3 to 200 percent, on weight of fiber, of various scour materials, preferably sodium bisulfate, and optionally a non-ionic surfactant, at a temperature of about 80.degree. to 1290.degree. C., and (3) exposing the fibers to an acid dye bath, containing an acid dye, a premetallized dye, a disperse dye or mixtures thereof.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to processes for preparing acid-dyeable polyolefin fibers and more particularly to processes for acid dyeing a blend of polypropylene and a thermoplastic essentially compatible nitrogen-containing polymer.

2. Description of the Prior Art

Polyolefins are difficult to dye in that they lack dye sites to which dye molecules may become attached. In the prior art it is known to add dye receptor materials such as various nitrogen-based polymers to the polyolefins to make them dyeable. For instance, in U.S. Pat. No. 3,361,843 issued to Robert Miller and Frederick C. Loveless on Jan. 2, 1968, various incompatible, basic nitrogen-based polymers are added to polymers, particularly polypropylene, given a treatment with high concentrations of certain acidic chemical reagents and then dyed in an acid dye bath. Although dyeing of the polypropylene fiber is somewhat improved, processing of the fiber is difficult due to the incompatible polymer, and the dye fastness properties and tinctorial strength are not as they should be to be commercially feasible.

It is well known that incompatible polymeric additives are difficult to process into fibers continuously due to build-up of the additive on the spinneret face plate and on the rolls of the processing equipment after several hours of operation. The incompatible material tends to cause blockage of screens and/or sand packs placed ahead of the spinneret to filter the polymer blend. Agglomeration of particles of the incompatible additive in the fiber leads to yarn breaks during the spinning and drawing operations. Also, the tinctorial strength of dyed fiber containing incompatible additive is highly dependent on the shear history of the polymer blend, i.e., samples having been exposed only to relatively low shear in the blending and spinning operations will contain large particles of the additive, while those samples exposed to high shear will contain small particles. In subsequent dyeings, fibers containing large particles will show dyed and undyed portions, while fibers containing very small particles will appear uniformly colored, but relatively weak in tinctorial strength. Between these extremes is an optimum particle size which gives best tinctorial strength. The molecular weight of the incompatible additive also affects tinctorial strength of the dyed fiber, lower molecular weight giving better tinctorial strength, but less resistance to extraction during dyeing operations. Molecular weight can be affected by the thermal history of the blend, excessive heat causing degradation of the additive.

Since shear history and thermal history both affect tinctorial strength of the incompatible polymeric additives disclosed in U.S. Pat. No. 3,361,843, and U.S. Pat. No. 3,433,853 issued to Ralph H. Earle, Alfred C. Schmalz and Charles A. Soucek on Mar. 18, 1969, it is difficult to obtain reproducibly dyed fibers from polypropylene modified by such additives.

In U.S. Pat. No. 3,395,198 issued to Isaji Taniguchi et al. on July 30, 1968, various compatible nitrogen-containing polymers are disclosed which, when blended with polyolefins, render fibers formed from the blend acid dyeable. However, dyeings of such modified polyolefin fibers, particularly polypropylene fibers, have required dyeing at pH values below 2.5 in order to obtain satisfactory fastness to light, crocking, washing and alkaline perspiration, i.e., properties dependent upon the structure of the dye molecule and penetration of the dye molecule to the fiber. Moreover, such dyeings also require a long dyeing cycle.

SUMMARY OF INVENTION

According to the present invention there is provided a process for dyeing shaped articles based on polyolefins comprising:

1. forming a uniform blend of about 98 to 85 percent by weight of a polyolefin and about 2 to 15 percent by weight of a thermoplastic, compatible basic nitrogen-containing polymer into a shaped article;

2. exposing the shaped article to an aqueous prescour solution containing about 3 to 200 percent, on weight of shaped article, of a scour material selected from the group consisting of hydrochloric acid, sulfuric acid, sulfamic acid, sodium bisulfate, phosphoric acid, p-toluene sulfonic acid, and sodium dihydrogen phosphate, at a temperature within the range of about 80.degree. to 120.degree. C.; and

3. exposing the prescoured shaped article to an acid dye bath containing an acid dye, a premetallized dye, a disperse dye or mixtures thereof, said bath having a pH within the range of 3 to 7.

There is also provided a preferred process for dyeing fibers based on polypropylene comprising:

1. uniformly blending isotactic polypropylene with about 4 to 10 percent by weight of an ethylene copolymer of about 60 to 80 percent by weight ethylene and about 40 to 20 percent by weight of an amino acrylate of the formula:

wherein R is hydrogen or methyl;

R.sup.1 is hydrogen or alkyl of one to three carbon atoms;

R.sup.2 is alkyl of one to three carbon atoms, or t-butyl where R.sup.1 is hydrogen; and

A is alkylene of two to three carbon atoms;

2. extruding the uniform blend into fibers;

3. exposing the fibers to an aqueous prescour bath containing about 5 to 15 percent, on weight of fiber of sodium bisulfate and about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant at a temperature of about 80.degree. to 120.degree. C.; and

4. exposing the prescoured fibers to an acid dye bath containing an acid dye, said bath having a pH within the range of about 3 to 7.

DETAILED DESCRIPTION OF INVENTION

Polyolefins are not dyeable by acid dyes since they lack basic sites with which the dye may form a complex of low solubility. The most important polyolefin for use in formation of fibers at this time is isotactic polypropylene, which is rendered dyeable by the process of the present invention, and is commercially available from many sources. The polypropylene can contain the usual thermal, oxidative and ultraviolet light stabilizers. Optionally, the polypropylene can contain structural modifiers which do not provide basic sites for acid dyes. Such modifiers would include ethylene/vinyl acetate copolymers, hydrolyzed ethylene/vinyl acetate copolymers, waxes, paraffin oils, polycaprolactams, polycaprolactones, polyethylene oxides, or low molecular weight materials which modify the crystallization behavior of the composition.

Polypropylene is rendered dyeable by uniformly blending it into a polypropylene composition with 2 to 15 percent by weight, preferably 4 to 10 percent, of a thermoplastic, compatible nitrogen-containing polymer. The nitrogen-containing polymer provides basic sites which will form complexes with acid dyes. It is important that the nitrogen-containing polymer be both thermoplastic and compatible with polypropylene so that processing difficulties are minimized or prevented. By the term compatible is meant that the nitrogen-containing polymer does not separate into discrete particles in the polypropylene composition which are observable under an optical microscope at a magnification of 250 .times. to 500 .times.. Generally, the preferred polymers are copolymers of ethylene with an amine or amide compound.

Preferred nitrogen-containing polymers are copolymers of ethylene and an aminoalkyl acrylate compound as disclosed in U.S. Pat. No. 3,395,198. As therein described, the aminoalkyl acrylate compound has the general formula:

wherein R.sub.1 is hydrogen or methyl radical;

each of R.sub.2 and R.sub.3 is hydrogen or alkyl radicals of one to four carbon atoms; and

n is an integer of 1 to 4 inclusive

The copolymers contain 1 to 50 mole percent of the aminoalkyl acrylate compound.

Particularly preferred copolymers are the random and homogeneous copolymers of ethylene and aminoacrylate compounds disclosed in U.S. Pat. application Ser. No. 834,196, filed June 2, 1969, in the name of Clarence Frederick Hammer. These copolymers contain about 20 to 40 percent by weight of an amino acrylate of the formula:

wherein R is hydrogen or methyl;

R.sup.1 is hydrogen or alkyl of one to three carbon atoms;

R.sup.2 is alkyl of one to three carbon atoms or t-butyl when R.sup.1 is hydrogen; and

A is alkylene of two to three carbon atoms.

These copolymers have a melt index of 1 to 3,000, preferably from 30 to 1,000; have a compositional inhomogeneity (U) as defined therein of less than 0.3; and have a thermal stability such that when the temperature is raised at 10.degree. C./min., under flowing nitrogen, less than 0.75 percent of the copolymer weight has been lost at 300.degree. C.

Typical examples of aminoacrylate compounds to be copolymerized with ethylene are diethylaminoethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, dimethylaminopropyl acrylate or methacrylate, aminomethyl acrylate or methacrylate, amino-n-butyl acrylate or methacrylate, N-t-butyl-aminoethyl acrylate or methacrylate, or diisopropyl-aminoethyl acrylate or methacrylate. The preferred aminoacrylate compound is dimethylaminoethyl methacrylate. While the above copolymers of ethylene and aminoalkyl acrylate are preferred, other thermoplastic basic nitrogen-containing polymers that are compatible with polypropylene can be used.

It is important in carrying out the dyeing procedure of this invention that the polypropylene and nitrogen-containing polymer be uniformly blended prior to forming the blend into a shaped article, i.e., the fibers must be formed from a uniform blend. The blending can be accomplished in a separate step prior to forming, or the blending and extrusion can be carried out in the same operation if the extruder has a suitable mixing section. Poor blending can result in uneven dyeing even if the remaining steps of dyeing procedure are properly conducted.

The uniform blend of polypropylene and nitrogen-containing polymer is formed into the desired shaped article by any of the known techniques such as melt spinning in the case of fibers, casting or other known methods of film-making, extrusion or injection molding. The present invention is particularly useful with fibers and it has been found that fibers of various deniers can be adequately dyed with good dye utilization and without excessive scour bleed-loss and ring-dyeing. Generally, the fibers are from 1 to 1,500 denier and can be in the form of round or lobed fibers, tape or fibrillated film. Round or lobed fibers are for apparel, upholstery and carpet face yarn uses and can have a denier of about 1 to 60 without encountering dyeing problems by the present technique. These fibers can also be used in production of other articles, such as decorated ribbons or non-woven textiles. The tape fibers are generally used for carpet backing and are of heavier denier, i.e., about 500 to 1,500 denier. Fibrillated film fibers are used for cordage, carpet face yarn or upholstery.

For fibers to be fully penetrated by dye, the spinning and drawing processes should be conducted in a manner to produce a fiber with a uniform structure through its cross-section i.e., minimal sheath/core structural differences. On the other hand, greater economy of dye use in dyeable carpet backing made from woven tapes can be obtained if such tapes do possess a sheath/core structure. In these sheath/core structures, the sheath is dyeable, while the core exhibits very little dye pick-up. Thus, less dye is used to dye a backing which is made up from such fibers.

After spinning of the fibers, but before drawing, a spin finish can be applied to the fibers. If such a material is used, it should not be anionic since such a finish may be deleterious to dyeing, but preferably should be non-ionic in nature. Non-ionic spin finishes are commercially available and a preferred one is "Nopcostat" 2152P which is thought to be a modified coconut fatty acid ester.

Finishes which contain anionic surfactant components can affect dyeing by acting as dye uptake rate retarders. Also, finishes containing mineral oil can affect fiber physical properties, the mineral oil acting as a plasticizer. This plasticization can increase dye uptake rate at the fiber surface, but dye loss in a post-scour step is increased. A water-dispersible or water-soluble finish such as "Nopcostat" 2152P modified coconut fatty acid ester is preferred.

Finishing operations can optionally be performed on the fibers before dyeing. For example, the fibers can be texturized by mechanically crimping or forming such as described in "Ingenuity Spreads Texturizing--Rapidly," Modern Textiles Magazine, Aug. 1969, page 21.

The next operation is extremely important to the final dyeing step. The fibers are exposed to a dilute aqueous prescour solution containing about 3 to 200 percent, on weight of fiber, of sodium bisulfate, sulfamic acid, p-toluene sulfonic acid and sodium dihydrogen phosphate as the scour material; however, a preferred upper limit for economic reasons is 100 percent. It is especially preferred that about 5 to 15 percent, on weight of fiber, of sodium bisulfate be used as the scour material in an aqueous prescour bath also having present about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant to assist in wetting and penetration. The non-ionic surfactant can be added directly to the prescour bath or it can be carried over on the fibers as the spin finish. Over 2 percent non-ionic surfactant can be present if it is carried over as the spin finish and more added to the prescour bath. Non-ionic surfactants are well known to those skilled in the art. These surfactants and surfactants in general are shown in Detergents and Emulsifiers, McCutcheon, 1969 annual, Allured Publishing Corp., Ridgewood, N.J. 07450. At the higher concentrations of scour materials, the scour material itself can give a beneficial effect without a non-ionic surfactant; however, the use of surfactant is preferred. While aqueous mineral acids such as sulfuric, hydrochloric, and phosphoric acids can be used in the prescour solution, they are not preferred due to their corrosive action on processing equipment, with the exception of phosphoric acid. Conventional liquor to fiber ratios of 20:1 to 60:1 are most convenient for carrying out this step.

The temperature of the prescour bath should be within the range of about 80.degree. to 120.degree. C. and preferably at the boil (about 100.degree. C.). Of course, the lower the temperature, the longer the fibers must be in the bath. It is usually sufficient to have the fibers in the bath 15 minutes at the boil. Elevated temperatures achieved by operating at higher than atmospheric pressure are also effective in achieving the desired results. An upper temperature limit would be that at which fiber structure is charged to adversely affect fiber dyeing or physical properties.

The fibers are then dyed in an acid dye bath generally between pH 3 and pH 7 using conventional acid dyes and acid dyeing techniques. While it is preferred to drain the prescour bath, rinse the fibers and then make up the dye bath, the dye bath can be prepared from the prescour bath if it does not contain excessive amounts of dirt, spin finish, or surfactants. Use of the prescour prior to dyeing enables the fibers to be acid dyed at pH levels heretofore unattainable while obtaining good tinctorial strengths.

The pH level for the dyeing of round additive-modified polyolefin fibers or fibrillated film fibers or tapes alone in the dyebath is initially under 5, generally from 3 to 5 and usually around pH 4. When dyeing round or flat fibers competitively with nylon (i.e., in the same dyebath) as in a carpet consisting of a nylon/polypropylene face yarn or in a carpet tufted with nylon and backed with a polyolefin composition or in a fabric composed of a blend of the two fibers the initial pH should be set between pH 6 and 7 and then dropped to a pH between 3 and 4 when the dyebath has reached the boil. It is also preferred, when union dyeing a polyolefin with nylon, that the dyebath containing non-ionic surfactant (0.5 to 2.0 percent owf) which has some oleophilic character to assist the dyeing of the polyolefin and also an anionic surfactant (0.5 to 2.0 percent owf) to sufficiently retard the dyeing rate of the nylon until higher temperatures are reached. This procedure enables good shade depth and trueness of shade to be obtained on both the nylon and the polyolefin when dyeing with a single dye or with a compounded dye formulation consisting of as many as 5 dyes. Also when dyeing a nylon carpet backed with additive-modified polyolefin such as polypropylene, this procedure, involving a sequential drop in pH, allows the dye to be levelly applied across the width of the carpet.

When dyeing additive-modified polyolefin alone in the dyebath, the anionic surfactant can be omitted. For best results and for good dye penetration, the non-ionic surfactant (0.25 to 2.0 percent OWF) can be optionally employed.

A carpet comprised of a polyester face yarn and an additive-modified polypropylene backing can be dyed to a shade match with formulated dye by using standard polyester dyeing techniques. Ordinary polyester-type carriers are employed here.

Competitive dyeing of polyolefins is particularly important and useful when dyeing styled carpets consisting of several different fibers such as nylon, polyester, etc. and a polyolefin. Different styling effects can be produced by controlling shade depth on each type of fiber present. Acid, disperse and premetallized dyes or combinations thereof, depending upon the fibers present, can be employed to obtain styling effects. Also, styling effects obtained from a fiber combination can be achieved by making a fabric or carpet face from polyolefin yarns containing varying amounts of nitrogenous polymer. Just as tweed effects can be produced in a nylon carpet by tufting with nylon fibers containing different levels of amine ends, so too can these styled, tweed effects be produced in a polyolefin fiber by controlling the concentration of dye sites. Print dyeing, space dyeing, and continuous dyeing can be carried out with fabrics made from such yarns.

Any of the acid dyes known to those skilled in the art can be used in the acid dye bath. There are many such dyes commercially available. Also, commercially available premetallized dyes and disperse dyes can be used in the dye bath.

An optional feature of the invention is the incorporation of a carrier into either the prescour bath or acid dye bath to aid the dye in penetrating difficult-to-dye fibers. It has been found that carriers useful in dyeing polyesters, such as hydrocarbons or chlorohydrocarbons are also useful in dyeing modified polypropylene fibers. Several carriers are listed in Knitted Outerwear Times, Aug. 24, 1964, page 21. Although not listed in the preceding reference "Varsol", Stoddard solvent, and xylene are especially preferred for the polypropylene. "Varsol" and Stoddard solvent are hydrocarbon solvents commonly used in the textile trade for prescour purposes. Other hydrocarbon solvents or naphthas having boiling points ranging from 75.degree. to 200.degree. C. can be used as carriers for the dyeing of the polypropylene. When used, these carriers are emulsified in equal parts of water using about 5 percent of a non-ionic surfactant and then added at the beginning of the dye cycle before the dye is added. While carriers are optional in carrying out the process of the present invention, when they are used it is essential that the polyester-type carrier be pre-emulsified prior to use, Carriers are important for the competitive dyeing of nylon and polypropylene with a disperse dye.

The invention can be further understood by referring to the following examples in which parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1

A polypropylene composition containing 93 percent by weight of a commercial fiber grade of isotactic polypropylene having a melt flow rate of 6.5 (ASTM D-1238-65 T, Condition L) and containing thermal, oxidative and ultraviolet light stabilizers and 7 percent by weight of a copolymer of ethylene dimethylaminoethyl methacrylate was prepared by first dry mixing the polymers and then melt blending the mix in a 1-inch Killion extruder at 200.degree. C. The ethylene copolymer contained 30 percent by weight of the aminomethacrylate comonomer, and had a melt flow rate of 300 (ASTM D-1238-64 T, Condition E). The resulting homogeneous, compatible polymer blend was cut into nibs after water-quenching, which were then fed to an experimental melt spinning apparatus and 8 denier per filament fiber was spun at 250.degree. C. A mineral-oil based finish containing anionic surfactants was applied to the fiber bundle after spinning, but before drawing. The fibers were drawn 3.times. over snub pins and a hot pipe to give a final denier of 8 per filament. The fibers were knitted on a latch-type circular knitting machine to produce a tubular-knit fabric. Five-gram samples of the fabric were dyed according to the procedure given below. All steps were carried out using a 40:1 liquor-to-goods ratio.

SAMPLE (A):

Prescour:

The sample was prescoured in a solution containing 1 percent (OWF) of an oleyl alcohol ethylene oxide condensation product non-ionic surfactant ("Merpol" HCS) for 20 min., at 80.degree. C., then rinsed in clear water.

Dyeing:

Following the prescour, the sample was next immersed in a dye bath containing 2 percent (OWF) "Merpacyl" Blue SW (C.I. Designation, Acid Blue 25, CI62055) and 1 percent (OWF) of a sodium alkyl diaryl sulfonate anionic dyeing assistant ("Alkanal" ND). The pH was adjusted to 3.0 with formic acid. The temperature of the bath was raised to the boil over a 1.5-hr. period and held for 3 hrs. The percentage of dye uptake onto the fibers of the fabric sample was measured colorimetrically at the end of the dyeing cycle, and found to be 98 percent.

Postscour:

The fabric sample from the dyeing step was squeezed dry and directly immersed into a postscour solution to determine the amount of dye not firmly bound. The solution contained 0.8 percent (OWF) of sodium lauryl sulfate anionic surfactant ("Duponol" D) and was adjusted to pH 9.5 with sodium carbonate. A 20-min. period at 80.degree. C. was allowed for this postscour step. Colorimetric analysis showed that scour loss for this dyeing was 33 percent.

The percentage dye utilization, i.e., percent dye uptake less percent dye loss, was 65 percent. There was no change in dye utilization by using a boiling water prescour (0.5 hr.) in place of the surfactant-containing prescour set forth above.

SAMPLES (B) through (D) were dyed using the prescour, dyeing and postscour procedures that were used with Sample (A) except the dye baths were adjusted to initial pH values of 4.0, 5.0, and 6.0, respectively.

SAMPLES (E) through (H) were dyed and postscoured in the same manner as Samples (A) through (D); however, a different prescour procedure was used. In this procedure, the samples were prescoured for 1 hour at the boil with a 5 percent solution of sodium bisulfate monohydrate (200 percent OWF of NaHSO.sub.4 .sup.. H.sub.2 O). The fabric samples were then dyed at pH values of 3, 4, 5 and 6, respectively.

SAMPLES (I) through (L) were prescoured, dyed and postscoured in the same manner as Samples (E) through (H) except a 5 percent solution of p-toluene sulfonic acid monohydrate was used as the prescour.

SAMPLES (M) through (P) were prescoured, dyed and postscoured in the same manner as Samples (E) through (H) except a 5 percent solution of 85 percent orthophosphoric acid was used as the prescour.

Dye utilization values of Samples (B) through (P) were determined as with Sample (A) and these values are shown in Table I. ##SPC1##

Comparison of the above dye utilization data shows that Samples (E) through (P) dyed by the procedure of the present invention have much higher dye utilization values across the pH range of 3 to 6 than do Samples (A) through (D) dyed by a control procedure. For Samples (E) through (P) it is noted that the dye utilization at pH 6 is substantially the same as the dye utilization of Sample (A) dyed at pH 3. The greater dye utilization and the greater pH range for satisfactory dyeing is of great economic value.

EXAMPLE 2

To screen other useful agents, the same fabric used in Example 1 was prescoured with 5.0 percent solutions of (A) sulfamic acid, (B) sodium dihydrogen phosphate monohydrate, (C) ammonium sulfate, (D) boric acid, and (E) sodium sulfate, for 0.5 hr. at the boil followed by rinsing. Dyeings were carried out as in Example 1 at a pH adjusted to 4.0 for these tests, and the samples postscoured as in Example 1. The initial and final pH values of the prescour solution, as well as the dye utilization data, are given in Table II. These results show that improved dye utilization values are not the result of only the acidity of the prescour bath, as measured by pH. If this were the case, boric acid (initial pH 3.3) should have given higher dye utilization values than did sodium dihydrogen phosphate (initial pH 4.4) and sodium sulfate (initial pH 5.5). ##SPC2##

EXAMPLE 3

Using the prescour, dye bath and postscour of Samples (E) through (H) of Example 1, the dye baths were adjusted to pH values of 3.0, 4.0, 5.0, and 6.0, and into these dye baths were immersed 5.0 g. samples of the Example 1 fabric with an equal weight of nylon 66 -- a condensation product of hexamethylene diamine and adipic acid. The nylon had been previously prescoured with 1 percent (OWF) of an oleyl alcohol ethylene oxide condensation product non-ionic surfactant ("Merpol" HCS). Following the dyeing and postscouring steps, the modified polypropylene fabric and the nylon yarn were found to be closely matched in shade.

EXAMPLE 4

To determine the minimum effective concentration and conditions for the process of this invention, prescour solutions containing 1.0%, 0.5%, and 0.2% NaHSO.sub.4 .sup.. H.sub.2 O plus 0.1 percent ("Tergitol" 15-S-9) a polyethylene glycol ether of linear alcohol non-ionic surfactant were made up. Using a 40:1 liquor-to-goods ratio, the amounts of NaHSO.sub.4 .sup.. H.sub.2 O applied (OWF) are 40, 20, and 8 percent, respectively, with 4 percent (OWF) of surfactant. Using the polypropylene composition and spinning conditions of Example 1, the spun yarn was then drawn 5.times. to give 21 denier per filament material. Five-gram samples of this fiber were prescoured in the above-described solutions for periods of 15 min. and 30 min. at the boil. After rinsing, the fiber samples were dyed at a pH of 4.0 using the dye bath and postscour of Example 1. The results of these dyeings at pH 4 show that the various prescour agent concentrations, time and temperature conditions give, within experimental error, the same amount of dye uptake and scour loss, the average values being 97 and 13 percent, respectively, or a dye utilization value of 84 percent. In contrast, a sample of the same fiber dyed by the procedure of Sample (A) of Example 1 gives a dye utilization value of only 78 percent at a lower pH value of 3.0.

EXAMPLE 5

A. Twenty-four denier per filament polypropylene yarn modified with 7 percent of the ethylene copolymer additive described in Example 1 was spun using "Nopcostat" 2152P a modified coconut fatty acid ester, non-ionic spinning finish and then knitted into a tubular knit fabric. Four 5 g. samples of fabric were prescoured in a solution containing 0.2% NaHSO.sub.4 .sup.. H.sub.2 O and 0.1% sodium alkyl diaryl sulfonate anionic dyeing assistant ("Alkanol" ND) for 30 min. at the boil, rinsed, and dyed at pH 4.0 for 2 hrs. at the boil, using the following dyes, one sample for each dye bath: (1) 2 percent (OWF) of "Merpacyl" Blue SW (C.I. Designation, Acid Blue 25, C.I.6,2055), (2) 2 percent (OWF) of "Capracyl" Orange R, a premetallized dye (C.I. Designation, Acid Orange 60), 93) 2 percent (OWF) of acid red dye "Merpacyl" Red G, (C.I. Designation, Acid Red 337), and (4) 2 percent (OWF) of "Lanasyn" Brilliant Yellow 5GL, a monoazo neutralized metallized dye (C.I. Designation, Acid Yellow 127). Each sample was postscoured as in Example 1 and the results of these dyeings and lightfastness tests of the samples are shown in Table III. The lightfastness test was conducted and rated in accordance with AATCC 16E-1964 entitled "Color Fastness to Light, Water-Cooled Xenon Arc Lamp, continuously". A rating of 5 is the top rating. As can be seen the lightfastness results are outstanding. Photomicrographic cross-sections of fiber samples showed that dye had penetrated to 50 percent of the fiber diameter in these dyeings in which no surfactant or dyeing assistant was used in the dyebath.

B. The same fabric of Example 5 (A) was prescoured by boiling in water for 30 min., dyed with 2 percent (OWF) of "Merpacyl" Blue SW, acid blue dye C.I. 62055 "Capracyl" Blue SW at pH 4.0 and then postscoured as in Example 1. Photomicrographs of the fiber cross-sections of this sample showed ring dyeing, i.e., the dye was concentrated on the fiber surface. The data in Table III show that scour loss is increased and lightfastness decreased by dyeing according to this conventional procedure.

C. Another sample of the fabric of Example 5 (A), was prescoured as in (A), but rather than rinsing the fabric, the scour solution was adjusted to pH 4.0 with sodium hydroxide, 2 percent (OWF) of "Merpacyl" Blue SW, acid blue dye C.I. 62,055 added, and the sample dyed and postscoured as in Example 5 (A). The dye utilization value and lightfastness for this sample is outstanding, and a photomicrographic cross-section showed complete penetration of the fiber by dye. This result shows that "Nopcostat" 2152 P, a modified coconut fatty acid ester finish, applied to the fiber during processing, did not deleteriously affect the dyeing behavior of the fiber and, in fact, the non-ionic character of the finish greatly aids in the dye penetration. ##SPC3##

EXAMPLE 6

Two other fabric samples of Example 5 (A) were prescoured separately and in different solutions for 30 min. at the boil at a 40:1 liquor-to-goods ratio. The solutions were as follows: (A) 8 percent (OWF) of NaHSO.sub.4 and 1 percent (OWF) of "Alkanol" ND, sodium alkyl diaryl sulfonate nionic dyeing assistant, and (B) with 8 percent (OWF) NaHSO.sub.4 .sup.. H.sub.2 O and 1 percent (OWF) of a polyethylene glycol ether of linear alcohol non-ionic surfactant ("Tergitol" 15-S-9). Following rinsing, both samples were dyed separately in baths containing 2% (OWF) of "Merpacyl" Blue SW (C.I. Designation, Acid Blue 25, C.I.62055) and 1% (OWF) of a polyethylene glycol ether of linear alcohol non-ionic surfactant "Tergitol" 15-S-9. The temperature was raised to the boil over a 1 -hr. period and held at the boil for 2 hrs. Small fiber samples were removed from the main sample when the dye bath reached the boil, 1 hr. after the boil, and 2 hrs. after the boil.

Photomicrographic cross-sections of the fibers showed that the sample prescoured by procedure (A) had fibers about 50 percent penetrated by dye when the boil was reached, with little or no increase in the amount of dye penetration after 1 hr. and 2 hrs. at the boil. These results are similar to those obtained in Example 5 (A) (1).

In contrast, the sample prescoured by procedure (B), using a solution containing non-ionic surfactant, had fibers greater than 50 percent penetrated by dye when the boil was reached, and about 100 percent penetration after 1 hr. at the boil. This example shows the great advantage of using a non-ionic surfactant in the prescour bath liquor.

EXAMPLE 7

Commercial isotactic polypropylene was blended with 7 percent of the ethylene copolymer additive described in Example 1, and spun into fiber at 250.degree. C. The spun fiber was wound up and subsequently drawn 5.times. through a hot water bath to give yarn composed of 20 denier per filament fibers. "Mopcostat" 2152 P, a modified coconut fatty acid ester non-ionic spinning finish was applied to the fibers after drawing. In a like manner, other ethylene copolymer additives containing 20, 26, and 28 percent dimethylaminoethyl methacrylate comonomer at 130, 300, and 140 melt index, respectively, were blended with polypropylene and spun into fibers. Dyeings were carried out as in Example 6 (B), except a different polyethylene glycol ether of linear alcohol non-ionic surfactant was used. "Tergitol" 15-S-7. While the ethylene copolymer additive containing 20 percent comonomer gave a dye utilization value of 58 percent, the others gave dye utilization values of greater than 80 percent in these dyeings.

EXAMPLE 8

Competitive Dyeing 846 Nylon-Modified Polypropylene

A piece of carpeting tufted in a 5/1 ratio of face to backing with nylon 66 (20 dpf) and backed with a woven polypropylene tape backing (500 d.p.f.) containing 7 percent of the ethylene copolymer additive as described in Example 1 was prescoured on a 6 inch dye beck in an 8 percent (OWF) sodium bisulfate solution containing 0.75 percent (OWF) "Merpol" HCS of an ethylene oxide condensation product of oleyl alcohol non-ionic surfactant for 15 min. at 90.degree. to 100.degree. C. A 40/1 liquor-to-goods ratio was maintained throughout the prescour and the dye bath. The prescour was drained and the beck was refilled with a solution containing 0.75 percent (OWF) "Duponol" D of a mixed sodium long-chain alcohol sulfates anionic surfactant, 1.5 percent (OWF) of a fatty alcohol ethylene oxide condensation product non-ionic surfactant "Merpol" OE and 2.5 percent (OWF) sodium acetate. The pH of this solution was between 6.6 and 6.8. The carpeting was run through the beck for 5 min. and the pH was reset with dilute Na.sub.2 CO.sub.3 solution. A 2 percent (OWF) solution of "Merpacyl" Blue SW acid blue dye C.I. 62055 was evenly added to the beck. The temperature was programmed to the boil (45 min.) at which time the pH was lowered to 3.0 with 5% NaHSO.sub.4 solution. The boil was maintained for 2 hrs. The dye bath was then drained and the beck was refilled and the carpeting rinsed well with distilled water. The carpet was dried at 120.degree. C. in a forced air oven. The color obtained on both the nylon face yarn and the modified polypropylene backing was essentially the same.

To illustrate the advantage of a compatible basic nitrogen-containing polymer, competitive disperse dyeing of polyester or nylon with the modified polypropylene was carried out using a standard polyester disperse dyeing procedure. A piece of carpeting tufted in a 5/1 ratio of face to backing with "Enkron" polyester American Enka, 20 d.p.f.) and backed with a woven polypropylene tape backing (500 d.p.f.) containing 7 percent of the Example 1 ethylene copolymer additive was prescoured on a 6 inch dye beck in a solution containing 1.5 g./l. of an ethylene oxide condensation product of oleyl alcohol "Merpol" HCS non-ionic surfactant ("Merpol" HCS) and 1.5 g./l. tetrasodium pyrophosphate as a buffer at 70.degree. to 80.degree. C. for 15 min. For disperse dyeing, a scour material is not essentially in the prescour solution. A 30/1 liquor-to-goods ratio was maintained throughout the prescour, dye bath and the postscour. The prescour was drained and the beck was refilled with a solution containing 0.5 percent (OWF) of a fortified sodium ethylene oxide condensate non-ionic surfactant ("Merpol" DA), 1.0 percent (OWF) anionic hydrocarbon sodium sulfonate surfactant ("Avitone" T) and the dye formulation consisting of the following disperse dyes:

0.20 percent (OWF) C.I. Disperse Yellow ("Latyl" Yellow 3G) 54

1.00 percent (OWF) C.I. 26070 ("Latyl" Yellow 4RL

0.05 percent (OWF) C.I. Disperse Blue 62 ("Latyl" Blue LS)

The beck was run up to 75.degree. C. at a pH 6.0. A self-emulsifiable carrier (6 percent OWF) of the biphenyl type ("Carolid" 3F-Tanatex) was added at this point. The dye bath was then held at the boil for 1.5 hrs. The dye bath was drained and the carpet was postscoured with a solution containing 1.0 g./l. Na.sub.2 CO.sub.3 and 1 percent (OWF) of an ethylene oxide condensation product of oleyl alcohol non-ionic surfactant ("Merpol" HCS) for 15 min. at 70.degree. C. The carpet was then rinsed well with water and dried at 120.degree. C. in a forced air oven. The color obtained on both the polyester face yarn and the modified polypropylene backing was essentially the same.

A piece of carpeting tufted in a 5/1 ratio of face to backing with nylon 66 (DuPont 20 d.p.f.) and backed with a woven polypropylene tape backing (500 d.p.f.) containing 7 percent of the Example 1 ethylene copolymer additive was prescoured in a 1 percent (OWF) solution of an ethylene oxide condensation product of oleyl alcohol non-ionic surfactant ("Merpol" HCS) for 15 min. at 70.degree. C. As with the polyester above, a scour material is not needed in the prescour solution for disperse dyeing. A 40/1 liquor-to-goods ratio was maintained throughout the prescour, the dye bath and the postscour. The prescour was drained, the carpeting was rinsed with water and placed in a dye bath containing 0.5 percent (OWF) of a fortified sodium ether-alcohol sulfate anionic surfactant ("Duponol" RA) 2 percent (OWF) of a yellow disperse dye -- "Latyl" Yellow 3 G, and 25 percent (OWF) of a 50 percent aqueous emulsion of "Varsol" prepared as described in Example 9. The temperature was raised to the boil (1 hr.) and held there for 2 hrs. The carpet was then postscoured well with a solution containing 1 percent (OWF) of a fortified sodium ether-alcohol sulfate anionic surfactant ("Duponol" RA) at 80.degree. C. for 15 min., at which time the sample was rinsed well with water and dried at 120.degree. C. in a forced air oven. The color of both the nylon face and modified polypropylene backing was essentially the same.

EXAMPLE 9

Carrier Dyeing

Loose, isotactic polypropylene round fibers (22 d.p.f.) (containing 7 percent of the ethylene copolymer additive of Example 1 ) were prescoured in an 8 percent (OWF) sodium disulfate solution for 15 min. at 90.degree. to 100.degree. C. The liquor-to-goods ratio was maintained at 40/1 throughout the prescour, dye bath and postscour. The fibers were rinsed and samples were placed in separate dye baths containing 2 percent (OWF) "Merpacyl" Blue SW (C.I. Acid Blue 25, C.I.62055) and from 5 to 20 percent (OWF) of one of the following pre-emulsified carriers: a biphenyl type - "Carolid" 3F (Tanatex); butyl benzoate - DAC 888 (Cindet); methyl naphthalene; a biphenyl type - "Chemcryl" KCD (Chem. Proc. of Georgia); a modified ester type - "Carolid" PSS (Tanatex), and trichlorobenzene. It is essential for best results that the carrier be of the pre-emulsified variety as are those listed. It was also found that emulsions prepared by mixing 50 weight percent of an aqueous solution of xylene, toluene or "Varsol" hydrocarbon solvent (Esso) with 5 percent of an octyl phenoxy polyethoxy ethanol non-ionic surfactant ("Triton" X-100) could also be used quite effectively as carriers. Sodium acetate (2.5 percent OWF) was also added as a buffer. The pH of the baths were set at 4 with acetic acid and then taken to the boil over a 1-hr. period. The baths were held at the boil for 2 hrs., at which time the fibers were removed and postscoured with a solution containing 0.8 g./l. of mixed sodium long-chain alcohol sulfates non-ionic surfactant ("Duponol" D) (pH 9.5 Na.sub.2 CO.sub.3) for 15 min. at 75.degree. to 80.degree. C. The color in all dyed fibers was uniform and the fibers were fully penetrated to the center. Best results were obtained by using xylene or "Varsol" emulsions and with "Larasol" DP methyl naphthalene, "Carolid" 3 F and "Chemcryl" KCD.

EXAMPLE 10

Dyeing of Fibrillated Film Fiber

Loose, isotactic polypropylene fibrillated film fiber containing 7 percent of the ethylene copolymer additive described in Example 1 was prescoured in an 8 percent (OWF) sodium bisulfate solution for 15 min. 90.degree. to 100.degree. C. The liquor-to-goods ratio was maintained at 40/1 throughout the prescour, dye bath and postscour. The fibers were rinsed and placed in a dye bath containing 2 percent (OWF) acid blue dye C.I.62055. "Merpacyl" Blue SW. Sodium acetate (2.5 percent OWF) was added as a buffer to the dye bath. The pH was set at 4 with acetic acid and the bath taken to the boil over a 1-hr. period. The bath was held at the boil for 2 hrs., at which time the fibers were removed and postscoured with a solution containing 0.8 g./l. of mixed sodium long-chain alcohol sulfates non-ionic surfactant ("Duponol" A) (pH 9.5 Na.sub.2 CO.sub.3) for 15 min. at 25.degree. to 80.degree. C. Adding about 5 percent of a 50 percent aqueous emulsion of "Varsol" to the dye bath increased the dye utilization.

Claims

What is claimed is:

1. A process for dyeing shaped articles based on a polyolefin comprising: (1) forming into a shaped article a uniform blend of about 98 to 85 percent by weight of a polyolefin and about 2 to 15 percent by weight of an ethylene copolymer comprising about 60 to 80 percent by weight ethylene and about 40 to 20 percent by weight of an amino acrylate of the formula

wherein R is hydrogen or methyl:

R.sup.1 is hydrogen or alkyl of one to three carbon atoms;

R.sup.2 is alkyl of one to three carbon atoms, or t-butyl when R.sup.1 is hydrogen; and

A is alkylene of two to three carbon atoms;

(2) exposing the shaped article to a dilute aqueous prescour solution which is separate from the dye bath containing about 3 to 200 percent, on weight of shaped article, of a scour material selected from the group consisting of hydrochloric acid, sulfuric acid, sulfamic acid, sodium bisulfate, phosphoric acid, p-toluene sulfonic acid, and sodium dihydrogen phosphate, at a temperature within the range of about 80.degree. to 120.degree. C.; and (3) exposing the prescoured shaped article to an acid dye bath containing an acid dye, a premetallized dye, a disperse dye or mixtures thereof, said bath having a pH within the range of 3 to 7.

2. The process of claim 1 wherein the polyolefin is isotactic polypropylene and the shaped articles are fibers.

3. The process of claim 2 wherein the prescour solution additionally contains about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant.

4. The process of claim 3 wherein the prescour solution contains about 5 to 15 percent, on weight of fiber, of sodium bisulfate.

5. The process of claim 4 wherein a non-ionic spinning finish is applied to the extruded fibers.

6. The process of claim 4 wherein the dye bath additionally contains about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant.

7. The process of claim 6 wherein the dye bath additionally contains a carrier.

8. The process of claim 7 wherein the carrier is a hydrocarbon, chlorinated hydrocarbon or mixtures of either.

9. A process for dyeing fibers based on polypropylene comprising: (1) uniformly blending isotactic polypropylene with about 4 to 10 percent by weight of an ethylene copolymer of about 60 to 80 percent by weight ethylene and about 40 to 20 percent by weight of an amino acrylate of the formula:

wherein R is hydrogen or methyl;

R.sup.1 is hydrogen or alkyl of one to three carbon atoms;

R.sup.2 is alkyl of one to three carbon atoms, or t-butyl

when R.sup.1 is hydrogen; and

A is alkylene of two to three carbon atoms; (2) extruding the uniform blend into fibers; (3) exposing the fibers to a dilute aqueous prescour bath which is separate from the dye bath containing about 5 to 15 percent, on weight of fiber, of sodium bisulfate and about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant at a temperature of about 80.degree. to 120.degree. C.; and (4) exposing the prescoured fibers to an acid dye bath containing an acid dye, said bath having a pH within the range of about 3 to 7.

10. The process of claim 9 wherein the amino acrylate is dimethylaminoethyl methacrylate.

11. The process of claim 10 wherein the dye bath additionally contains about 0.25 to 2 percent, on weight of fiber, of a non-ionic surfactant.

12. The process of claim 11 wherein the extruded fibers are round fibers of about 1 to 60 denier and the initial pH of the dye bath is within the range of about 3 to 5.

13. The process of claim 11 wherein the extruded fibers are tape fibers of about 500 to 1,500 denier and are dyed together with nylon fibers in a dye bath containing both an anionic and non-ionic surfactant and in which the initial pH of the dye bath is within the range of about 6 to 7 and is decreased to less than pH 4 when the bath temperature reaches at least about 80.degree. C.