Process to prepare polymeric fibers with improved color and appearance

[0001] This application claims rights of priority under 35 U.S.C. 119 from U.S. patent application Ser. No. 09/604,990 filed on Jun. 28, 2000.

[0002] The invention relates generally to a process to prepare articles having improved color strength. More particularly, the invention relates to a process to form articles comprising melt-colored polyamide or polyester based resins, containing novel polyester ionomer additive(s) in combination with a colorant forming a pre-formed color concentrate, for improved color and aesthetics over articles of the prior art. In one embodiment, the invention relates to articles in the form of melt-colored fibers.

[0003] Coloration of fibers has a long history, and the science of dyeing, initially of natural fibers such as flax, cotton and wool, has been under continuous development since Neolithic times. The appearance of man-made fibers, e.g., cellulosics, acrylics, polyamides and polyesters, stimulated further developments in dyeing, and this method of coloring of fibers and articles made therefrom continues to be the most-practised technique for the production of colored fiber-based articles of manufacture.

[0004] In the case of fibers based on the more recent polymers such as polyolefins, polyamides and polyesters, which are spun from the melt, there exists an alternative method for coloration, i.e. addition of the colorant species into said melt and direct extrusion of colored fibers. While such a process may be carried out with dyes, it is more often carried out with pigments, although the said process is popularly known in the industry as solution dyeing. The major difference between dyes and pigments is that, under prevailing processing conditions, pigments are virtually insoluble in polymers, whereas dyes are soluble (see definitions in German Standards DIN 55943, 55944 and 55949).

[0005] As the technique of melt-pigmentation has been developed, it has been demonstrated that fibers made in this way can exhibit certain advantages over those made by post-spinning dyeing of fibers. Such advantages include improvements to resistance to degradation and fading in sunlight; lower susceptibility to fading and/or yellowing by polluting gases in the atmosphere, such as ozone and nitrogen oxides; improved resistance to chemicals, either in dry-cleaning processes or due to accidental spillage; less leaching or fading of color during laundering or cleaning process involving water and detergents; and no need for post-spinning dyeing, or the other processes involved in applying and fixing said dyes onto/into the fiber.

[0006] However, melt-pigmentation is also considered to have some disadvantages in terms of the color and appearance obtained in the final fiber. The fibers are known to those skilled in the art to exhibit degrees of lustre and low brightness which can render the said fibers unsuitable in certain applications.

[0007] The color change resulting from the addition of pigments to polymers is based on the wavelength-dependent absorption and scattering of light. The appearance and color of the final product being a combination of these two factors is as described in the Kubelka-Munk theory (for a description of this theory and the general concepts of color and its measurement, see Colour Physics for Industry, Roderick McDonald (Editor), The Society of Dyers and Colourists, Bradford, UK, 2^nd edition (1997)). Dyes can only absorb light and not scatter it, since the physical prerequisite for scattering (a certain minimum particle size) does not exist in the case of dyes in molecular solution. These colors are therefore transparent. In so far as the transparency is attributable to the dye, complete absorption of the light will result in black shades and selected absorption in colored shades.

[0008] The optical effect of pigments may in the same way be based on light absorption. If, however, the refractive index of the pigment differs appreciably from that of the polymer, which is almost always the case, and, if a specific particle size range is present, scattering takes place. In this case, the initially transparent polymer becomes white and opaque, or if selective absorption takes place at the same time, colored and opaque.

[0009] No scattering occurs when the particle sizes are very small, and none or very little if they are very large. With all colored pigments that selectively absorb, the shade and strength of the final color is thus influenced by particle size. The transparency and thickness of the colored substrate may additionally affect the color strength. While some pigments are available in so-called transparent grades, e.g., red and yellow iron oxides, a complete color range across the spectrum is not readily available. Many such ultra-low particle size colorants are expensive, and difficult to maintain at high dispersion when compounded into a polymer matrix. It is also known that very low particle size additives in polymer melts can exhibit a profound effect on the theological properties of said melt, resulting in formulations which are difficult to spin using standard equipment and techniques. Use of large particle size pigments is not a viable option either, as such additives will result in blocking of filtration systems and spinneret holes, and tend to lead to filament breaks in fiber production.

[0010] In any case, a large number of melt-pigmented fiber products are required to be opaque, and the problem lies in producing opaque colored fibers with levels of color brightness close to those of dyed products. Note that a fundamental difference between dyeing and pigmenting of fibers is that, while dyes are either colored or absorb all wavelengths, i.e., give black shades, pigmentation introduces an extra variable in that white pigments are readily available, whereas there is no such species as a white dye. The use of white pigments opens a different range of color possibilities than can be achieved with dyes alone.

[0011] Another potential problem with particulate colorants in a polymeric melt-extruded product is the phenomenon of dichroism, or optical anisotropy. Pigment particles are not necessarily isotropic in shape, and may be needle-shaped, rod-shaped, or platelets. They may thus become oriented in a particular direction in processing. The apparent color then depends on the direction of observation. The origin of this phenomenon is to be found in the fact that certain pigments crystallise in crystal systems of low symmetry resulting in directionally dependant physical properties. As far as the coloristic properties are concerned, this signifies that the absorption and scattering constants differ in the various principle crystallographic axes, i.e. such crystals are optically anisotropic.

[0012] With regard to the final fiber, as opposed to the pigments themselves, the appearance of a sample thereof can vary depending on the angle of illumination and/or observation. Fiber samples are normally prepared for color and appearance testing by carefully wrapping the fiber or yarn sample, under conditions of uniform tension and consistent positioning of the said fibers, around a flat card, and assessing the color properties, and more importantly any differences between said properties and those of the desired standard sample or data, under standard conditions of illumination and observation. This may be carried out visually, but more usually instrumentally. Methods and apparatus for carrying out the analysis of color and appearance in this manner are well known to those skilled in the art.

[0013] During such examinations, there are two additional effects which might be observed if the sample is illuminated or observed at a number of different angles. U.S. Pat. No. 4,479,718 discloses a process for multi-angle appearance testing of materials. The total amount of light reflected from the sample, per unit area, may change. The perceived color may also change. Unless such effects are specifically desired for particular aesthetic effects in a final article of manufacture, the appearance of either may result in the rejection of the fiber by the prospective customer. Eradication or reduction of such effects thus is important in obtaining first quality product.

[0014] U.S. Pat. No. 5,674,948 teaches that that end-capping of the amino end-groups of polyamides results in improvements to the brightness of compositions colored with organic pigments which are capable of themselves reacting with such amino end-groups. N-acetyl lactam is noted as a particularly preferred end-capper. The effect is limited to a particular set of organic pigments. The levels of additive end-capper are also quite high.

[0015] U.S. Pat. No. 4,374,641 discloses use of color concentrates for coloring thermoplastics via making solutions or dispersions of pigments and dyes in water or polar organic solvents, e.g. methanol, with various water dispersible or solvent dispersible addition or polycondensation polymers to achieve dispersion. Such a mixture requires removal of the solvent entailing and extra step and potentially generating waste and emissions.

[0016] There still exists a need for a simple method to provide pigmented polymeric articles, especially melt-spun fibers, with improved color and appearance, while still using standard grades of pigment commonly known to those skilled in the art, as well as equipment and techniques known to produce melt-pigmented fibers having desired properties for use in articles such as fabrics, textiles, carpets, threads, etc.

[0017] Applicants have surprisingly found that the addition of sulfonated polyester ionomer copolymers results in the production of polyamide or polyester melt-pigmented fibers which exhibit improved color and appearance and reduced variation in color and appearance. The improvement in appearance between two samples can be measured as color strength.

[0018] Applicants have further found that found that pre-mixing the colorant with the sulfonated polyester ionomer copolymer, and then subsequently melt mixing that color concentrate with a polyamide or polyester resin, and forming the entire mixture into an article such as a drawn fiber, gives enhanced color appearance as compared to simply combining all ingredients to make fiber in a single step.

[0019] The invention relates to a process to prepare a colored synthetic polyamide or polyester article with improved color strength that comprises a) melt blending (i) a base polyamide or polyester resin with (ii) a colorant system comprising one or more colorants selected from the set of inorganic and/or organic colorants, optionally sulfonated salt polyester copolymer carrier resins for the colorants; and optionally (iii) one or more sulfonated polyester copolymers; and b) forming an article in the form of a fiber or a textile from said resin composition.

[0020] Base Polymer Matrix. The polymer used as the base, or matrix, in the practice of this invention is selected from the set of polyamides and polyesters.

[0021] Polyamides include those synthesised from lactams, alpha-omega amino acids, and pairs of diacids and diamines. Such polyamides include, but are not limited to, polycaprolactam polyamide 6, polyundecanolactam polyamide 11, polylauryllactam polyamide 12, poly(hexamethylene adipamide) polyamide 6,6, poly(hexamethylene sebacamide) polyamide 6,10, poly(hexamethylene dodecanediamide) polyamide 6,12, and copolymers and blends thereof.

[0022] In one embodiment of the invention, the polyamide is polyamide 6. In another embodiment, the polyamide is polyamide 6,6.

[0023] Polyesters include those synthesised from one or more diacids and one or more glycols. Such polyesters include, but are not limited to, poly(ethylene terephthalate) PET, poly(propylene terephthalate) PPT, poly(butylene terephthalate) PBT, poly(ethylene naphthalate) PEN, polybutylene naphthanoate PBN, polypropylene naphthanoate PPN, polycyclohexane dimethanol terephthalate PCT and copolymers and blends thereof.

[0024] In one embodiment of the invention, the polyesters are PET, PBT or PPT.

[0025] Colorants. Colorants used in the practise of this invention may be selected from the categories of dyes, inorganic or organic pigments, or combinations thereof. Any number of different colorants may be used, in any proportions, although it will be understood by those skilled in the art that the total loading of colorants in the polymer matrix, and the number of different colorants used, will be kept to a minimum commensurate with obtaining the color required. In one embodiment of the invention, the level of colorants ranges from 0.1 to 8.0% of the total weight of the article, e.g., the fibers.

[0026] In one embodiment of the invention, inorganic pigments are used. They include, but are not limited to, metal oxides, mixed metal oxides, sulfides, aluminates, sodium sulfo-silicates, sulfates and chromates. Non-limiting examples of these include: carbon blacks, zinc oxide, titanium dioxides, zinc sulfides, zinc ferrites, iron oxides, ultramarine blue, Pigment Brown 24, Pigment Red 101, and Pigment Yellow 119.

[0027] In another embodiment of the invention, organic pigments are used. Examples of organic pigments include azos, di-azos, quinacridones, perylenes, naphthalene tetracarboxylic acids, flavanthrones, isoindolinones, tetrachloroisoindolinones, anthraquinones, anthanthrones, dioxazines, phthalocyanines, and azo lakes. Non-limiting examples of these include Pigment Blue 60, Pigment Red 122, Pigment Red 149, Pigment Red 177, Pigment Red 179, Pigment Red 202, Pigment Violet 29, Pigment Blue 15, Pigment Green 7, Pigment Yellow 147 and Pigment Yellow 150.

[0028] Polyester ionomers. Polyester ionomers, in the context of the present invention, are defined as polyester polymers derived from the reaction residue of an aryl carboxylic acid sulfonate salt, an aromatic dicarboxylic acid, an aliphatic diol or any of their ester-forming derivatives. The said polyester ionomers comprise some monovalent and/or divalent sulfonate salt units represented by the formula 1A:

[0029] or formula 1B:

[0030] wherein p1-3, d1-3, and pd2-6, and A is an aryl group containing one or more aromatic rings: for example, benzene, naphthalene, anthracene, biphenyl, terphenyl, oxy diphenyl, sulfonyl, diphenyl or alkyl diphenyl, where the sulfonate substituent is directly attached to an aryl ring. These groups are incorporated into the polyester through carboxylic ester linkages. The aryl groups may contain one or more sulfonate substituents (d1-3) and may have one or more carboxylic acid linkages (p1-3). Groups with one sulfonate substituent (d1) and two carboxylic linkages (p2) are preferred. M is a metal, with valency n1-5. Preferred metals are alkali metals or alkaline earth metals, where n1 or 2. Zinc is also a preferred metal. R is an alkyl spacer group: for example, CH₂CH₂, CH₂CH₂OCH₂CH₂, CH(CH₃)CH₂, CH₂CH₂CH₂, CH₂CH₂CH₂CH₂.

[0031] Typical sulfonate substituents that may be incorporated into the metal sulfonate polyester copolymer may be derived from the following carboxylic acids or their ester-forming derivatives: sodium sulfoisophthalic acid, potassium sulfoterephthalic acid, sodium sulfonaphthalenedicarboxylic acid, calcium sulfoisophthalate, potassium 4,4-di(carbomethoxy)biphenyl sulfonate, lithium 3,5-di(carbomethoxy)benzene sulfonate, sodium p-carboxymethoxybenzene sulfonate, dipotassium 5-carbomethoxy-1,3-disulfonate, sodio sulfonaphthalene-2,7-dicarboxylic acid, 4-lithio sulfophenyl-3,5-dicarboxybenzene sulfonate, 6-sodio sulfo-2-naphthyl-3,5-dicarbomethoxybenzene sulfonate and dimethyl-5-4-(sodiosulfo)phenoxy isophthalate. Other suitable sulfonate carboxylic acids and their ester-forming derivatives are described in U.S. Pat. Nos. 3,018,272 and 3,546,008 herein incorporated by reference. The most preferred sulfonate polyesters are derived from lithium or sodium 3,5-dicarbomethoxybenzene sulfonate.

[0032] In one embodiment of the invention, the ionomer polyester polymer comprises divalent ionomer units represented by the formula 2:

[0033] wherein R is hydrogen, halogen, alkyl or aryl, and M is a metal.

[0034] In another embodiment, the polyester ionomer has the formula 3:

[0035] where the ionomer units, x, are from 0.1-50 mole percent of the polymer with 5 to 13 mole percent being preferred and 8 to 12 mole percent being especially preferred; y is defined to be 100x mole %. Most preferably R is hydrogen. It is also preferred that the polyester sulfonate resin be water insoluble. In general water insoluble resins will be of high molecular weight (Intrinsic Viscosity greater than or equal to 0.2 dl/g in 60/40 phenol/tetrachloroethane solution) and have less than 15 mole percent sulfonate units in the polyester chain. Sulfonate copolymer polyester resins with IV0.3 dl/g and with 8-12 mole percent sulfonate units are preferred.

[0036] Typical glycol or diol reactants, R¹, include straight chain, branched or cycloaliphatic alkane diols and may contain from 2 to 12 carbon atoms. Examples of such diols include, but are not limited to, ethylene glycol; propylene glycol, i.e. 1,2- and 1,3-propanediol; butane diol, i.e. 1,3- and 1,4-butanediol; diethylene glycol; 2,2-dimethyl-1,3-propanediol; 2-ethyl-2-methyl-1,3-propanediol; 1,3-pentanediol; 1,5-pentanediol, dipropylene glycol; 2-methyl-1,5-pentanediol; 1,6-hexanediol, dimethanol decalin; dimethanol bicyclooctane; 1,4-cyclohexane dimethanol and particularly its cis- and trans-isomers; triethylene glycol, 1,10-decanediol; and mixtures of any of the foregoing. A preferred cycloaliphatic diol is 1,4-cyclohexane dimethanol or its chemical equivalent. When cycloaliphatic diols are used as the diol component, a mixture of cis- and trans-isomers may be used; it is preferred to have a trans-isomer content of 70% or more. Chemical equivalents to the diols include esters, such as dialkyl esters, diaryl esters and the like.

[0037] Examples of aromatic dicarboxylic acid reactants, as represented by the decarboxylated residue A¹, are isophthalic acid or terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4-dicarboxydiphenyl ether-4,4-bisbenzoic acid and mixtures thereof. All of these acids contain at least one aromatic nucleus. Acids containing fused rings can also be present, such as in 1,4-, 1,5- or 2,6-naphthalenedicarboxylic acids. The preferred dicarboxylic acids are terephthalic acid, isophthalic acid or mixtures thereof.

[0038] In one embodiment, the ionomer copolyesters are poly(ethylene terephthalate) PET, poly(propylene terephthalate) PPT or poly(1,4-butylene terephthalate) PBT ionomers. It is most preferred that the polyester metal sulfonate salt copolymers be insoluble in water.

[0039] Also contemplated herein are the above ionomers with minor amounts, e.g. from about 0.5 to about 15 percent by weight, of units derived from aliphatic acids and/or aliphatic polyols to form copolyesters. The aliphatic polyols include glycols, such as poly(ethylene glycol) or poly(butylene glycol). Such copolyesters can be made following the teachings of, for example, U.S. Pat. Nos. 2,465,319 and 3,047,539.

[0040] The amount of polyester ionomer(s) used in the practise of the present invention will vary depending on the types and amounts of colorants used to obtain any particular color. In one embodiment, an addition of said polyester ionomers to the melt formulation for spinning into fiber which produces a final sulfur level of between about 200 and about 5000 ppm gives excellent results. In another embodiment, the sulfonate polyester copolymers are to be used at 0.5 to 30% by weight of the fiber.

[0041] Optional components. Besides the matrix polymers, colorants and polyester ionomers described above, the formulations used in the practise of the present invention may contain other components. These may include, but are not limited toantioxidants, UV stabilisers, antiozonants, soilproofing agents, stainproofing agents, antistatic additives, antimicrobial agents, lubricants, melt viscosity enhancers, flame retardants and processing aids.

[0042] Processing. Colorants may be added to the matrix polymer in a variety of ways. This may include direct additions of the colorant(s) to the matrix polymer, addition of the single pigment dispersions (i.e., addition of each colorant as a separate concentrate in a carrier resin), and addition of multiple colorant dispersions (i.e., addition of a single concentrate of mixed colorants, providing the desired color or let down into the matrix polymer, in a carrier resin). The addition method may be carried out in a single compounding step prior to melt spinning, or may be carried out on the melt.

[0043] In one embodiment of the invention, the polyester ionomers are incorporated into the matrix polymer either during a melt-compounding step prior to fiber spinning, or during the fiber spinning process itself.

[0044] In a second embodiment of the invention, the polyester ionomers are first combined with the colorant, or mixture or colorants, to form a color concentrate which is next incorporated into the matrix polymer during a melt-compounding step or during the fiber spinning process. Additional sulfonated salt polyester copolymers may be added in a separate process to the addition of the pigments if desired. While the addition of some sulfonated salt polyester resin to the colored fiber improves the fiber color, the use of the sulfonated salt polyester copolymer as a pre-compounded color concentrate gives surprising further improvement to the fiber color.

[0045] In one embodiment of the invention, colorants are first melt blended with a sulfonated salt polyester copolymer as described herein, to form a color concentrate. The color concentrate can be made using a single colorant, often called a single pigment dispersion, or a mixture of colorants. In one embodiment, the color concentrate contains from about 5-70 wt. % colorant. Other compatible resins may also be added during the preparation of the color concentrate, including but not limited to, the set consisting of fiber-forming polyamides or polyesters as described above.

[0046] The color concentrate or several different color concentrates can then be combined with a polyamide of polyester resin in a melt process to form a colored filament that is drawn into a fiber. The color concentrates or mixture of color concentrates can be combined with the base resin in any number of ways.

[0047] The color concentrate can be melt processed in a number of ways known to those skilled in the art. In one embodiment, the melt-processing is done via extrusion on a single or twin screw extruder. In a second embodiment, the color concentrate comprises from 5-70% colorant.

[0048] The color concentrate is used in the preparations of articles having improved color strength in various forms, including any of a cloth, flocked cloth, fabric, woven fabric, pile fabric, knitted fabric, filaments, floor-cover, textile, fiber, rug, yarn, carpet, and the like.

[0049] In one embodiment of a process to prepare an article having an improved color in the form of a fiber, the color concentrate addition is carried out on the melt-spinning apparatus itself at any stage of the fiber forming process, for example at the extruder throat, at any addition port on the extruder barrel, at the melt pump, or at the spinneret chamber. In a second embodiment, the color concentrate is combined with the fiber forming base resin prior to introduction to the melt spinning apparatus. In a third embodiment wherein more than one color concentrate (single pigment dispersion) is used, more than one addition point is used for the addition of the color concentrate. In yet a fourth embodiment, the fibers may contain additional sulfonated salt polyester copolymer as the carrier resin in the color concentrate to further improve color or for other for other purposes.

[0050] The separate compounding process and the fiber spinning process may be carried out using techniques and equipment well known to those ordinarily skilled in the arts of polymer compounding and fiber melt-spinning.

[0051] The fibers of this invention have a very fine phase separate morphology. The phase separation allows the matrix resin to maintain its desirable mechanical properties. However, given the phase separation between the matrix resin and the sulfonated salt polyester the improved, uniform color of the resultant fiber is especially surprising.

[0052] Article forming processforming a fiber. In one embodiment of the invention, the article in the form of fibers are drawn from the sulfonated polyester blends to achieve the full improvement in color strength and appearance. The optimum draw ratio will vary with the exact nature of the fiber matrix, colorant type and loading, sulfonate polyester type and concentration, fiber diameter and cross section shape. The draw ratio is defined as the ratio of the final length to the original length per unit weight of the yarn resulting from the drawing process. The optimum draw ratio for a given system can readily be determined by comparing the color strength of as spun fiber with that of the same fiber drawn under different conditions. In general a draw ratio from 1.05 to 7.00 may be used, with a draw ratio of 1.10 to 6.00 being more preferred. Fiber drawing may be achieved by any standard methods known in the art. The fiber may be drawn between two godet rolls, or pairs of rolls, or over a draw pin or pins, or a mixture of the two. The drawing may be done in single or multiple stages. The fiber is usually heated to a temperature above the glass transition temperature prior to, or during, drawing to minimise fiber breakage, although heating is not a requirement for the invention. The heating may be carried out via heating of godet rolls, plates, slits, pins or other means such as use of a heated chamber; hot gas such as steam, or hot liquid, such as water, may also be used. Depending on the fiber forming base resin chosen, the preferred heating device is selected.

[0053] The fibers produced from the practise of the present invention may be of a range of deniers per filament (dpf) depending on the ultimate use to which such fibers may be putlow dpf for textile use, higher dpf for use in carpets. The cross-sectional shape of the fibers may also be any of a wide range of possible shapes, including round, delta, trilobal, tetralobal, grooved, or irregular. These product fibers may be subjected to any of the known downstream processes normally carried out on melt-spun fibers, including crimping, bulking, twisting etc., to produce yarns suitable for incorporation into a variety of articles of manufacture, such as apparel, threads, textiles, upholstery and carpets.

[0054] These examples are provided to illustrate the invention but are not intended to limit the scope of the invention in any way.

[0055] Color Strength Measurements: The color strength is defined as the color yield or color intensity of a given quantity of a colorant in a sample (batch) in relation to a standard, (or another sample). Higher color strength means a sample has a more intense color compared to the standard. The higher the color strength the greater the difference in color intensity compared to the standard. When samples with the same type and amount of pigment are compared, as is the case in all examples of this invention, a higher color strength means that the more intense colored sample formulation can reach the same intensity as the standard with less pigment. This allows for more efficient use of the colorant.

[0056] Color strength was determined from the spectrophotometric data using the (K/S) summation method, where (K/S) (or K/S) is the Kubelka-Munk function, where K is the absorption coefficient and S is the scattering coefficient. The % color strength of a sample is defined as the ratio of the sum of (K/S) for the sample to the sum of (K/S) for the standard expressed as a percentage. A percentage less than 100% indicates that the sample is less intense in color strength than the standard; a percentage greater than 100% indicates that the sample is more intense than the standard. Further details of the (K/S) summation method can be found in Colour Physics for Industry, Roderick McDonald (Ed.), The Society of Dyers and Colourists, Bradford, UK, 2^nd edition (1997).

[0057] In the examples, spectrophotometric measurements were made using an Optronik Multiflash M45 spectrophotometer and a commercial color evaluation software package. CIE illuminant D₆₅ was used. Prior to the spectrophotometric measurements the yarn was precisely wound on to a plastic or metal card to produce a card wrap sample. Sufficient yarn was wound on to the card such that the card was not visible through the yarn. The color strength was read from the card wrap sample at measurement angles from the specular of 20, 25, 35, 45, 55, 65, 75 and 115 degrees. Color Strength values are the average of all 8 viewing angles. Color strength measured as percent for the examples of the invention using a SPBT color concentrate are measured by comparison to the same blend with no sulfonated polyester (SPBT) or to a fiber where the same amount of SPBT was added independent of the colorants.

[0058] SPBT (sulfonated polybutylene terephthalate) was made by polymerization of dimethyl terephthalate, butane diol and dimethyl sodium sulfo isophthalate. The copolymer contains 13 wt. % sodium sulfo isophthalate. It has an intrinsic viscosity in 60/40 phenol tetrachloroethane of 0.45 dl/g. The same SPBT was used in all examples. This SBPT is water insoluble which facilitates isolation of the SBPT, subsequent handling as well a fiber production.

[0059] Polyamide Viscosity: The relative solution viscosity (RV) of the polyamides used in the examples was determined by first preparing a 0.55% wt. solution of the dried polyamide in 96% sulfuric acid. Solution flow times were determined in a Cannon-Ubbelohde size 2 viscometer suspended in a temperature controlled water bath set at a temperature of 25 C.0.02 C. The flow times of the sulfuric acid were also measured. The RV was then calculated by dividing the flow time of the polyamide solution by the flow time of the sulfuric acid. Polyamide 6,6 of the examples has a RV of 3.1, and the polyamide 6 has a RV2.7.

[0060] All yarn denier values have the units g/9000 m.

[0061] The following colorants were used in the examples: PY147pigment yellow 147, PB15:1pigment blue 15:1, PR202pigment red 202; PY150pigment yellow 150, PV29pigment violet 29, PBk7pigment black 7, PBk6pigment black 6, PW6pigment white 6, PR101pigment red 101, PR179pigment red 179, PG7pigment green 7, PBr24pigment brown 24, ZnOzinc oxide (pigment white 4). Cu Halcopper halide.

[0062] For the examples of Tables 1-4, colorants were compounded as concentrates in PA6 or PET.

[0063] Polyamide 6,6 pellets were melt blended with 16 wt. % of a SPBT copolymer along with polyamide 6 color concentrates as shown in Table 1, on a single screw extruder at 285 C. All resins had been dried to below 1000 ppm moisture prior to extrusion. The resultant extrudate was chopped into pellets, dried and extruded into fibers on a slow speed spinning line. The fibers were 1850 denier with a trilobal (Y) cross section. Take up speed was 470 m/min. The different colored yarns had 30 filaments per bundle and are referred to as the 1850/30Y samples. The yarn was then heated to 170 C. and single stage drawn at a draw ratio of 3.6 to produce the drawn (1850/30Y DWN) samples. The drawn yarn was then precision wound onto an aluminium card on which spectrophotometric measurements were made.

[0064] Control samples where the 16 wt. % SPBT was replaced with polyamide 6,6 were prepared using the same pigments and the same process. The yarn samples of the invention were compared to the controls of the same color and the color strength compared. In Table 1 it can be seen that the K/S color strength of the drawn SPBT containing samples is 104 to 135.8% more intense than the control colors with no SPBT. The improved color strength is greatest in examples 2 and 4, the ochre and olive colors, but still significant in the red and teakwood colors (examples 1 and 3).

TABLE 1
	1	2	3	4
Examples	Teakwood	Ochre	Red	Olive
Color	1850/30Y DWN	1850/30Y DWN	1850/30Y DWN	1850/30Y DWN
Polyamide 6,6 3.1RV/wt. %	78.966	79.0005	79.5447	79.0329
Polyamide 6	4.8	4.6	3.7	4.7
SPBT 13 wt. % SIP	16.0	16.0	16.0	16.0
Colorants/wt. %	PBr24 0.0534	PY150 0.1873	PY150 0.0054	PY150 0.10
	PR101 0.0094	PR101 0.0758	PR179 0.6063	PG7 0.0093
	PBk6 0.0054	PBk6 0.0240	PBk6 0.0136	PBk7 0.0277
	PW6 0.0858	PW6 0.0324	PW 0.050	PW6 0.0501
	ZnO 0.050	ZnO 0.050	ZnO 0.050	ZnO 0.050
Stabilizer/ wt. %	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03
Draw ratio	3.6	3.6	3.6	3.6
Color Strength K/S	104	112.7	102.1	135.8
SPBT 13 wt. % Na sulfoisophthalate PBT copolymer
Color Strength with SPBT vs. control with no SPBT and same pigments

[0065] The formulated pigmented fibers of these examples were produced in a manner similar to those described above. All polyamide 6,6 was replaced with polyamide 6 of a RV2.7. SPBT was used at 20 wt. % of the formulation (Table 2). Extrusion was run at 250 C. The blends were spun into fibers with a round cross section on a high speed spinning line to produce fibers of a 250 denier, 25 filaments per bundle (250/25R). The take up speed was 3700 m/min., with a drawdown ration of 470:1. These samples were then heated at 120 C. and drawn at a draw ratio of 1.25 to produce the drawn (250/25R DWN) samples. Cardwraps of both, yarns were prepared for color strength measurements as described above.

[0066] Both the as-pun and the drawn samples were compared to control samples that were made by replacing all 20 wt. % SPBT with polyamide 6. The as-spun SPBT samples (250/25R) and the SPBT drawn samples (250/25R DWN) were compared to the controls having no SPBT. As can be seen in Table 2 the DWN samples (examples 5,6 and 7) have greater color strength (106.8, 104, 105.4) than the drawn controls with no SPBT. On the other hand the as spun fibers with SPBT (controls A and B) show inferior color strength to the as spun controls with no SPBT, (98.3 and 97.6%).

[0067] The red color shows somewhat different behaviour. The as spun SPBT sample (Control C) shows higher color strength than the as spun control with no SPBT (102.5%) but the drawn sample with SPBT (example 7) has even better color strength (105.4%).

[0068] This set of experiments shows the benefit of drawing the SPBT containing fibers to achieve improved color strength.

TABLE 2
	5	Control A	6	Control B	7	Control C
Examples	Blue	Blue	Ochre	Ochre	Red	Red
Color	250/25R DWN	250/25R	250/25R DWN	250/25R	250/25R DWN	250/25R
Polyamide 6 wt %	79.3824	79.3824	79.6805	79.6805	79.3247	79.3247
SPBT 13 wt % SIP	20.0	20.0	20.0	20.0	20.0	20.0
Colorants/ wt. %	PV29 0.0035	PV29 0.0035	PY150 0.1873	PY150 0.1873	PY150 0.0054	PY150 0.0054
	PB15:1 0.6055	PB15:1 0.6055	PR101 0.0758	PR101 0.0758	PR179 0.6063	PR179 0.6063
	PBk7 0.0021	PBk7 0.0021	PBk6 0.0240	PBk6 0.0240	PBk6 0.0136	PBk6 0.0136
	PW6 0.0065	PW6 0.0065	PW6 0.0324	PW6 0.0324	PW 0.050	PW 0.050
	ZnO 0.050	ZnO 0.050	ZnO 0.050	ZnO 0.050	ZnO 0.050	ZnO 0.050
Stabilizer/wt. %	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03	Cu Hal 0.03
Draw ratio	1.25	as spun	1.25	as spun	1.25	as spun
Color Strength K/S	106.8	98.3	104	97.6	105.4	102.5
SPBT 13 wt. % Na sulfoisophthalate PBT copolymer
Color Strength with SPBT vs. control with no SPBT and same pigments

[0069] Polyamide 6,6 pellets were extruded with 15 wt. % SPBT and 4 wt. % of a 25:75 Pigment Yellow 150 (PY150):polyamide 6 color concentrate (batch 1) by weight at 285 C. All materials had been dried to less than 1000 ppm moisture before extrusion. The chopped extrudate was melt spun into fibers on a slow speed spinning line to produce an undrawn yarn of 2100 denier at a take up speed of 470 m/min. The fibers had a trilobal (Y) cross section and 34 filaments per bundle. The yarn was then drawn at 170 C. at a draw ratio of 3.6 to produce the 2100/34Y DWN samples shown in Table 3.

[0070] A control sample with added polyamide 6,6 replacing the 15 wt. % SPBT was prepared with the same color concentrate in the same manner. The drawn SPBT yarn was compared to the drawn control with no SPBT. Example 8 shows a color strength improved to 129% in the SPBT containing yarn.

[0071] The experiment was then repeated with a different 25:75 PY150/polyamide 6 color concentrate (batch 2). It is known that different batches of color concentrates often give different color strengths even when used in the same formulation processed under similar conditions. Example 9 shows the color strength of a drawn yarn using PY150 batch 2 compared to a control using no SPBT made with PY150 batch 2. The color strength is improved to 115.6%.

[0072] In order to further examine the color differences between the two PY150 color concentrate batches two experiments were performed. The drawn 2100/34Y fiber made with no SPBT using PY150 batch 1 was compared to the same composition using PY150 batch 2 (Control D). A color strength value of only 89.1% indicates a large difference in color intensity between the two samples. These two samples would be expected to give similar color strengths. In practice in order to use batch 2 to make fibers of the same yellow color it would be necessary to adjust the amount of color concentrate. This adjustment would result in more difficulty in making fibers of matching colors. Batch to batch variation of fiber colors would be very detrimental to the manufacture of uniform woven, knitted or pile textiles, carpets or floorcoverings.

[0073] When the same two batches of PY150 polyamide 6 concentrate were used to color a polyamide 6,6 2100/34Y DWN drawn fiber sample with 15 wt. % SPBT there is much less variation in the color strength. Example 10 compares the color strength of a drawn fiber made with 15 wt. % SPBT and PY150 batch 2 concentrate to the same type of drawn fiber made with the batch 1 concentrate. The color strength of the batch 2 sample compared to the batch 1 sample is 98.5% indicating that the two samples are closely color matched.

TABLE 3
	8	9	Control D	10
Examples	PY150	PY150	PY150	PY150
Color	2100/34Y DWN	2100/34Y DWN	2100/34Y DWN	2100/34Y DWN
Polyamide 6,6 3.1RV/wt. %	81.0	81.0	96.0	81.0
Polyamide 6/ wt. %	3.0	3.0	3.0	3.0
SPBT 13 wt. % SIP	15.0	15.0	0	15.0
PY150 Batch 1/wt. %	1.0	0	1.0	0
PY150 Batch 2/wt. %	0	1.0	0	1.0
Draw ratio	3.6	3.6	3.6	3.6
Color Strength K/S	129.4	115.6*	89.1**	98.5***
SPBT 13 wt. % Na sulfoisophthalate PBT copolymer
Color Strength with SPBT vs. control with no SPBT and same pigments
* Color Strength PY150 batch 2 with SPBT vs. PY150 Batch 1 no SPBT
** Color Strength PY150 batch 1 no SPBT vs. PY150 Batch 2 no SPB
*** Color Strength PY150 batch 2 with SPBT vs. PY150 Batch 1 with SPBT

[0074] These examples extend the invention to PET fibers. In this case PET pellets (IV0.67 dl/g) were combined with 15 wt. % SPBT and the indicated single pigment concentrates. PET was used as the carrier resin for the concentrates. This mixture of pellets was ground to a fine powder and dried to less than 50 ppm moisture and extruded into filaments at 285 C. at a take up speed of 3250 m/min. As indicated in Table 4 two colors were made. The fibers were 255 and 170 denier with a round cross section with 34 filaments per bundle. A similar set of fibers was prepared using the same pigments but replacing the SPBT with PET.

[0075] Example 11 compares a drawn navy color SPBT blend with a drawn control having no SPBT. Color Strength is improved to 111.2%. In a yellow color the drawn SPBT blend shows a color strength of 106.0% compared to a drawn control with no SPBT (example 12).

[0076] Control examples E and F show that the as spun fibers with SPBT, with no drawing, do not show the enhanced color strength achieved in the SPBT containing drawn fibers of the invention.

TABLE 4
	11	Control E	12	Control F
Examples	Navy	Navy	Sunstraw	Sunstraw
Color	170/34R DWN	170/34R	255/34R DWN	255/34R
PET 0.67 IV/wt. %	83.179	83.179	84.0109	84.0109
SPBT 13 wt. % SIP	15.0	15.0	15.0	15.0
Colorants/wt. %	PB15:1 0.9218	PB15:1 0.9218	PY150 0.2758	PY150 0.2758
	PR149 0.6008	PR149 0.6008	PR101 0.4412	PR101 0.4412
	PBk7 0.2256	PBk7 0.2256	PBk6 0.0465	PBk6 0.0465
	PW6 0.0728	PW6 0.0728	PW6 0.2256	PW6 0.2256
Draw ratio	1.25	as spun	1.25	as spun
Color Strength K/S	111.2	98.8	106	99.4
SPBT 13 wt. % Na sulfoisophthalate PBT copolymer
Color Strength with SPBT vs. control with no SPBT and same pigments.

[0077] The colorants listed in table 5 were individually compounded at 25 wt. % in a 13 wt. % sodium sulfoisophthalate polybutylene terephthalate copolymer (SPBT). Similar color concentrates were made compounding the same colorants at the same level using polyamide 6 of 2.7 RV.

TABLE 5
Key to Pigment Dispersions:
	Dispersion ID	Pigment Loading	Pigment	Carrier
	PA6/21-1911	25%	PR 202	PA6
	SPBT/21-1913	25%	PR 202	SPBT
	PA6/31-944	25%	PY 147	PA6
	SPBT/31-946	25%	PY 147	SBPT
	PA6/51-2265	25%	PB 15:1	PA6
	SPBT/51-2267	25%	PB 15:1	SPBT

[0078] Single color concentrates of PR202, PY147 and PB15:1 were prepared by melt blending 25% of the colorant with either SPBT or polyamide 6 using a twin screw extruder at 275 C. These color concentrates were used in all subsequent experiments.

[0079] The SPBT and polyamide 6 resins had been dried to below 300 and 1000 ppm moisture respectively prior to extrusion. The resultant extrudate was stranded and chopped into pellets.

[0080] Uncolored polyamide 6 pellets were melt blended with various levels of the SPBT color concentrate and compared to similar fibers with the same level of colorant delivered as a polyamide 6 color concentrate. All pellets were dried prior to being extruded into fibers on a high speed spinning line to produce partially oriented yarn (POY). The fibers were 180 denier with a round (R) cross section. Take up speed was 4000 m/min. The different colored yarns had 34 filaments per bundle and are referred to as the 180/34 R samples. The yarn was then heated to 120 C. and drawn at a draw ratio of 1.2 to produce drawn 150/34R samples. The card wrap samples were produced on which spectrophotometric measurements were made.

[0081] Table 6 (examples 13-21) shows a comparison of the color strength of polyamide 6 fibers made using a polyamide 6 color concentrate at various pigment loading compared to the fiber made with the same level of colorant introduced as a SPBT concentrate. If the two fibers had the same color strength the % difference would be 100%. Higher color strength shows a more intense color at the same colorant loading.

[0082] For the three pigment loadings (0.25% pigment1% color concentrate, 0.5% pigment2% color concentrate and 1.0% pigment4% color concentrate) of PR202, PY147 and PB15:1 the SPBT carrier give significantly better (104 to 166%) color in the polyamide 6 fibers than the polyamide 6 carrier.

TABLE 6
Example	Standard	Batch	Colorant	% Pigment in Fiber	% Color Strength
13	PA6/21-1911	SPBT/21-1913	PR 202	0.25	166
14	PA6/21-1911	SPBT/21-1913	PR 202	0.50	157
15	PA6/21-1911	SPBT/21-1913	PR 202	1.00	150
16	PA6/31-944	SPBT/31-946	PY 147	0.25	119
17	PA6/31-944	SPBT/31-946	PY 147	0.50	119
18	PA6/31-944	SPBT/31-946	PY 147	1.00	104
19	PA6/51-2265	SPBT/51-2267	PB 15:1	0.25	123
20	PA6/51-2265	SPBT/51-2267	PB 15:1	0.50	129
21	PA6/51-2265	SPBT/51-2267	PB 15:1	1.00	116

[0083] Table 7 shows polyamide 6 fibers prepared under the same conditions as examples 13-21. The yarn samples of the invention were compared to the controls of the same color and color strength differences determined. In Table 7, it can be seen that the color strength of the samples prepared using a SPBT color concentrate is 119 to 157% more intense than the control colors with no SPBT (examples 23, 26 & 29).

[0084] Example 22 compared a polyamide fiber made with 2% of the PR202 polyamide 6 color concentrate (PA6/21-1911) with 1.5% SPBT to a polyamide 6 fiber made with the same level of pigment red 202 with no SPBT. There is a small improvement in color strength to 109%. However, if the same level of SPBT is used as a pigment red carrier (SPBT/21-1913), the resultant polyamide 6 fiber has much greater color strength (157%) compared to the polyamide 6 fiber made using the polyamide 6 color concentrate (example 23) or the polyamide 6 color concentrate with SPBT added separately (example 24). In all cases, the colorant loading is the same.

[0085] In example 24, the compositions of the two fibers being compared are identical but by first combining the SPBT with the pigment red 202 into a color concentrate (SPBT/21-1913) much better fiber color strength (153%) is achieved than simply adding the SPBT when making the fiber using a polyamide color concentrate

[0086] In a similar fashion, polyamide 6 fibers were made using 0.5% pigment yellow 147 in fiber. The PY147 SPBT concentrate (SPBT/31-946) give a stronger color (119%) in a polyamide 6 fiber than the PA6/31-944 concentrate (Example 26) or than the polyamide 6 concentrate with SPBT added separately (example 27, color strength 166%).

[0087] Simply adding 1.5% SPBT to the fiber mixture with polyamide 6 color concentrate improved the color strength to only 101% (example 25).

[0088] Pigment Blue 15:1 colored polyamide 6 fibers show a similar trend. Use of a 25% blue SPBT concentrate (SPBT/51-2267) in the polyamide fiber at 2.0% gave color strength of 129% compared to the polyamide 6 color concentrate (example 29). Addition of SPBT along with the polyamide 6 color concentrate (PA6/51-2265) did not give the same color strength as the use of the same amount of SPBT as the color carrier resin example 30).

TABLE 7
				% Pigment	% Color
Example	Standard	Batch	Colorant	in Fiber	Strength
22	PA6/21-1911	PA6/21-1911 1.5% SPBT	PR 202	0.50	109
23	PA6/21-1911	SPBT/21-1913	PR 202	0.50	157
24	PA6/21-1911 1.5% SPBT	SPBT/21-1913	PR 202	0.50	153
25	PA6/31-944	PA6/31-944 1.5% SPBT	PY 147	0.50	101
26	PA6/31-944	SPBT/31-946	PY 147	0.50	119
27	PA6/31-944 1.5% SPBT	SBPT/31-946	PY 147	0.50	166
28	PA6/51-2265	PA6/51-2265 1.5% SPBT	PB 15:1	0.50	90
29	PA6/51-2265	SPBT/51-2267	PB 15:1	0.50	129
30	PA6/51-2265 1.5% SPBT	SPBT/51-2267	PB 15:1	0.50	161

[0089] The formulated pigmented fibers of these examples were produced in a manner similar to those described above but using polyamide 6,6 as the fiber forming resin. Extrusion was done at 285 C. The blends were spun into fibers with addition of either a 25% color concentrate based on polyamide 6 or SPBT. Fibers were made with a trilobal (Y) cross section on a slow speed spinning line to produce fibers of an 1850 denier, 30 filaments per bundle (1850/30Y). The take up speed was 470 m/min. These samples were then heated at 170 C. and drawn at a draw ratio of 3.6 to produce drawn 514/30Y samples. Card wrap samples were prepared for color strength measurements.

[0090] Example 31 shows only a slight improvement in color when 1.5% SBPT is added to a PR202 (red) fiber compared to a fiber made using a polyamide 6 color concentrate. Example 32 shows higher color strength (134%) when the SBPT is used in a pre-formed color concentrate (SPBT/21-1913).

[0091] Example 33 shows that the use of SBPT to make a preformed concentrate gives a red polyamide 6,6 fiber with 132% color strength compared to adding the same amount of SPBT to the fiber with a polyamide 6 color concentrate (PA6/21-1911)

[0092] In a yellow polyamide 6,6 fiber, the addition of SPBT with polyamide 6 color concentrate gives a color strength of 101% compared to the blend with no SPBT (example 34). However in this case (example 35), the SPBT color concentrate gives no color strength (100%) compared to the polyamide 6 color concentrate. This shows that the effect of the SBPT on improving color will, to some extent, be effected by the colorant, the matrix resin, the processing conditions and the concentration.

[0093] Example 36 shows that use of the SPBT in a concentrate gives improved color strength (112%) compared to addition of the same level of SPBT with a polyamide 6 concentrate.

[0094] In blue polyamide 6,6 fiber, the SPBT concentrate gives 114% color strength compared to the polyamide 6 concentrate (example 38). Addition of SPBT with the polyamide 6 concentrate gives 110% color strength (example 37) and the SPBT added as a concentrate gives 106% color strength compared to addition of the same amount of SPBT with a polyamide 6 color concentrate (example 39).

TABLE 7
				% Pigment	% Color
Example	Standard	Batch	Colorant	in Fiber	Strength
31	PA6/21-1911	PA6/21-1911 1.5% SPBT	PR 202	0.50	101
32	PA6/21-1911	SPBT/21-1913	PR 202	0.50	134
33	PA6/21-1911 1.5% SPBT	SPBT/21-1913	PR 202	0.50	132
34	PA6/31-944	PA6/31-944 1.5% SPBT	PY 147	0.50	101
35	PA6/31-944	SPBT/31-946	PY 147	0.50	100
36	PA6/31-944 1.5% SPBT	SBPT/31-946	PY 147	0.50	112
37	PA6/51-2265	PA6/51-2265 1.5% SPBT	PB 15:1	0.50	110
38	PA6/51-2265	SPBT/51-2267	PB 15:1	0.50	114
39	PA6/51-2265 1.5% SPBT	SPBT/51-2267	PB 15:1	0.50	106