FIELD OF THE INVENTION

The present invention relates to a polymeric dispersant useful for disperse dye, which comprises a random copolymer containing styrenic monomer units and ethylenically unsaturated sulphonic acid monomer units. The present invention also relates to an aqueous disperse dye composition comprising the polymeric dispersant and a process for producing the aqueous disperse dye composition.

BACKGROUND

Disperse dye is widely used in textile industry, particularly for dyeing polyester fabrics. Traditionally, disperse dye was mainly commercially supplied in powder form (i.e. , powder-form disperse dye), for the convenience of transportation and storage. The powder-form disperse dye is a composition generally produced by grinding press cake of a disperse dye in the presence of suitable auxiliaries such as filler and dispersant, and water, then spray-drying to a powder. The production and application of the powder-form disperse dye will inevitably involve powder handling and thus bring occupational health risk to workers exposed to dusts generated during powder handling.

With the increasing demand and awareness of sustainability, the interest of manufacturers in traditional powder-form disperse dye is gradually shifting towards disperse dye in liquid form (i.e., liquid-form disperse dye). The liquid-form disperse dye is an aqueous dispersion or suspension, which is generally produced by grinding press cake of a disperse dye in the presence of auxiliaries in water. Compared with powder-form disperse dye, liquid-form disperse dye allows higher dye uptake and improved homogeneity of color, due to the uniform dispersion of dye particles in the liquid. Reductive washing step can be eliminated to save water and energy. The higher dye uptake can bring an improved dye utilization and thus lower level of dye in the residual liquid. Additionally, less auxiliary agents (e.g., filler) are used for producing liquid-form disperse dye compared to the production of powder-form disperse dye, which will reduce chemical oxygen demand (COD) level in the residual liquid. Further, liquid-form disperse dye is more adaptable to upgrading automated dyeing facilities, such as padding and printing facilities, leading to lower cost and higher throughput.

Liquid-form disperse dye was less popular than powder-form disperse dye since the liquid-form disperse dye suffers from undesirable long-term storage stability and viscosity. A dispersant is critical to produce liquid-form disperse dye, which facilitates grinding press cake to produce a free-flowing suspension comprising dye particles with uniform and qualified micron-sized particle size (typically, D50 in the range of 0.5 to 1 micron) and endow the suspension with storage stability. The most popular dispersants on the market are based on methylnaphthalene sulfonate formaldehyde condensate (MF), benzylnaphthalene sulfonate formaldehyde condensate (CNF), sulfonated phenol formaldehyde condensate, ligninsulfonate or a combination thereof. While those popular dispersants provide basic dispersing ability and are quite cost-effective, they are not satisfactory for following reasons. The liquid-form disperse dye produced with those dispersants does not have sufficient long-term storage stability. Those dispersants need to be used in a relatively large amount, typically higher than 15% relative to disperse dye. The high dosage of dispersant will usually negatively impact the dyeing performance. The performance of those dispersants varied greatly depending on dye types and press cake qualities. The dispersing performance is often inadequate for certain types of disperse dye. Additionally, some conventional dispersants often involve hazardous chemicals such as formaldehyde and phenol.

Other dispersants for aqueous colorant system have been developed. For example, an anionic copolymer of styrene/maleic anhydride/sodium ethyl allylsulfonate was proposed in CN1102843121A as the dispersant in disperse dye inks to solve the sediment problem of jet-ink having small particles of 0.2 microns or lower.

JP 2000273373A describes a water-soluble polymer as the dispersant in aqueous jet inks for dispersing water-insoluble nano-sized colorants such as organic pigments, inorganic pigments, disperse dyes, oil-soluble dyes and the like. The water-soluble polymer comprises carboxylic acid groups and one or more other acid groups such as sulfonic acid groups and/or phosphoric acid groups in the form of free acids, and also a hydrophobic group which is preferable in terms of storage stability. It was described that the jet inks comprising the water-soluble polymer have various good performance including 1-week storage stability. However, the long-term storage stability of an aqueous disperse dye dispersion with higher particle size was not tested in the patent application. It is known that poor storage stability of aqueous disperse dye dispersions comprising nano-sized particles is mainly resulted from agglomeration of particles, while the poor storage stability of aqueous disperse dye dispersions comprising micron sized particles is mainly resulted from sedimentation of particles. Meanwhile, in the textile industry, it is typical to have dyes with micron-sized particles, limited by grinding facilities and grinding efficiency. Therefore, it cannot even be predicted that the water-soluble polymer will be effective to improve long-term storage stability of liquid-form disperse dye.

There is still a need to provide a dispersant useful for liquid-form disperse dye without the above shortcomings, which is particularly useful for liquid-form disperse dye with a particle size of 0.5 microns or higher.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a dispersant useful for producing liquid-form disperse dye with desirable long-term storage stability, preferably in a lower dosage than conventional dispersants. Further objects of the present invention are to provide a liquid-form disperse dye and a process for production of the same.

It has been found that the objects of the present invention can be achieved by a random copolymer comprising styrenic monomer units and ethylenically unsaturated sulphonic acid monomer units. Accordingly, in the first aspect, the present invention provides a polymeric dispersant, which comprises a random copolymer containing or consisting of following monomer units a) 15 to 45% by weight of styrenic monomer units, b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units, which are in unneutralized, partially neutralized or fully neutralized form, and c) 0 to 40% by weight of ethylenically unsaturated monomer units other than the monomer units a) and b).

In the second aspect, the present invention provides an aqueous disperse dye composition, which comprises i) a disperse dye, ii) the random copolymer as described herein, and iii) water, wherein the random copolymer and the disperse dye are present at a weight ratio in the range of 1 : 50 to 1 : 3.

In the third aspect, the present invention provides a process for producing the aqueous disperse dye composition, which comprises grinding one or more press cakes of a disperse dye in the presence of the polymeric dispersant as described herein in water.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described in detail hereinafter. It is to be understood that the present invention may be embodied in many different ways and shall not be construed as limited to the embodiments set forth herein. Unless mentioned otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

As used herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

As used herein, the terms “comprise”, “comprising”, etc. are used interchangeably with “contain”, “containing”, etc. and are to be interpreted in a non-limiting, open manner. That is, e.g., further components or elements may be present. The expressions “consists of” or cognates may be embraced within “comprises” or cognates.

As used herein, the term “polymeric dispersant” refers to a composition having dispersing capability and comprising a polymer as active substance, any assistants originated from preparation of the polymer, and optionally a solvent.

As used herein, the term “liquid-form disperse dye” has its usual meaning in the art, and particularly refers to a disperse dye product supplied in form of an aqueous composition comprising the disperse dye and any auxiliaries such as a dispersant. In the first aspect, the present invention provides a polymeric dispersant, which comprises a random copolymer containing or consisting of following monomer units, a) 15 to 45% by weight of styrenic monomer units, b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units, which are in unneutralized, partially neutralized or fully neutralized form, and c) 0 to 40% by weight of ethylenically unsaturated monomer units other than the monomer units a) and b).

The monomer units a), i.e., styrenic monomer units, in the random copolymer may be derived from one or more styrenic monomers selected from styrene, Ci-C4-alkyl substituted styrene and a combination thereof. Suitable styrenic monomers particularly include, but are not limited to, styrene, a-methylstyrene, a-ethylstyrene, vinyl toluenes such as 2-methylstyrene, 3- methylstyrene and para-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, para,a- dimethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-isopropyl styrene, 3-isopropyl styrene, 4-isopropyl styrene, para- tert- butyl styrene and any combinations thereof. Preferably, the styrenic monomer units are derived from styrene, a-methylstyrene or a combination thereof.

The monomer units a) preferably account for 20 to 45 % by weight, more preferably 25 to 43% by weight of the random copolymer.

The monomer units b), i.e., the ethylenically unsaturated sulphonic acid monomer units, in the random copolymer may be derived from one or more ethylenically unsaturated monomers containing a sulphonic acid group, which may be unneutralized, partially neutralized or fully neutralized. Examples of the ethylenically unsaturated monomers containing a sulphonic acid group particularly include, but are not limited to, vinylic compounds containing a sulphonic acid group, allylic compounds containing a sulphonic acid group, styrenic compounds containing a sulphonic acid group, acrylic compounds containing a sulphonic acid group, and any combinations thereof, which may be unneutralized, partially neutralized or fully neutralized.

It will be appreciable that the “unneutralized”, “partially neutralized” and “fully neutralized” forms as mentioned within the context of the ethylenically unsaturated sulphonic acid monomer units or corresponding monomers mean that sulphonic acid groups therein are present in free acid form only, in a hybrid form of free acid and salt, and in salt form only, respectively.

Metal salts or quaternary ammonium salts may be particularly mentioned for the partially neutralized or fully neutralized form of the ethylenically unsaturated sulphonic acid monomer units or corresponding monomers.

Preferably, the ethylenically unsaturated sulphonic acid monomer units are derived from one or more monomers selected from acrylic sulphonic acid compounds having formula (I), salts of acrylic sulphonic acid compounds of the formula (I), or a combination thereof wherein

Ri is hydrogen, methyl or ethyl, and

R2 is a straight or branched Ci-Cs-alkylene group.

In some embodiments, the ethylenically unsaturated sulphonic acid monomer units are derived from one or more monomers selected from acrylic sulphonic acid compounds of the formula (I) in which R ¹ is hydrogen or methyl and R2 is a straight or branched Cs-Cs-alkylene group, or salts thereof, or a combination thereof. More preferably, in formula (1), R ¹ is hydrogen and R2 is a straight or branched C4-alkylene group. Most preferably, the ethylenically unsaturated sulphonic acid monomer units are derived from 2-acrylamido-2-methylpropanesulfonic acid, a salt thereof, or a combination thereof.

The salts of the acrylic sulphonic acid compounds having the formula (I) may be metal salts or quaternary ammonium salts. Particularly, alkali metal salts such as sodium salts and potassium salts, and quaternary ammonium salts may be mentioned.

The monomer units b) preferably account for 40 to 57 % by weight, more preferably 45 to 55 % by weight of the random copolymer.

Within the context of the present invention, the amount of the monomer units (b) in the random copolymer is expressed as the unneutralized form of the monomer units (b). It will be appreciated that the amounts of the monomer units (b) in partially neutralized or fully neutralized form can be converted to corresponding amounts of the unneutralized form by calculation.

The random copolymer may optionally comprise, and preferably comprise the monomer units c), i.e. , the ethylenically unsaturated monomer units other than the monomer units a) and b) as described herein.

Suitable monomer units c), also referred to as ethylenically unsaturated monomer units c) hereinbelow, may be derived from one or more monomers selected from ethylenically unsaturated carboxylic acids, or salts, esters, amides or anhydrides thereof, or any combinations thereof.

Examples of suitable ethylenically unsaturated carboxylic acids may include, but are not limited to acrylic acid, methacrylic acid, ethacrylic acid, a-chloroacrylic acid, p-methylacrylic acid (crotonic acid), a-phenylacrylic acid, p-acryloxypropionic acid, sorbic acid, cinnamic acid, p- stearylacrylic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid and fumaric acid, among which acrylic acid and methacrylic acid are preferred. Examples of suitable salts of the ethylenically unsaturated carboxylic acids may include but are not limited to alkali metal salts such as sodium salts and potassium salts or quaternary ammonium salts of the ethylenically unsaturated carboxylic acids as described above. Metal salts of acrylic acid and methacrylic acid are preferred, particularly alkali metal salts such as sodium salts and potassium salts.

Examples of suitable esters of the ethylenically unsaturated carboxylic acids may include, but are not limited to Ci-C4-alkyl esters, Ci-C4-hydroxylalkyl esters, and polyglycol esters of the ethylenically unsaturated carboxylic acids as described above. Particularly, Ci-C4-alkyl acrylate, Ci-C4-alkyl methacrylate, Ci-C4-hydroxylalkyl acrylate, Ci-C4-hydroxylalkyl methacrylate, polyethylene glycol acrylate and polyethylene glycol methacrylate may be mentioned.

Examples of suitable amides of the ethylenically unsaturated carboxylic acids may include, but are not limited to N-(Ci-C4-alkyl)amides and N,N-di(Ci-C4-alkyl)amides of the ethylenically unsaturated carboxylic acids as described above. Particularly, N-(CI-C4- alkyl)acrylamide, N-(Ci-C4-alkyl)methacrylamide, N,N-di(Ci-C4-alkyl)acrylamide, N,N-di(Ci-C4- alkyl)methacrylamide may be mentioned.

Examples of suitable anhydrides of the ethylenically unsaturated carboxylic acids may include but are not limited to anhydrides of the ethylenically unsaturated carboxylic acids as described above. Particularly, succinic anhydride, maleic anhydride, itaconic anhydride and citraconic anhydride may be mentioned.

Suitable ethylenically unsaturated monomer units c) may also be derived from vinyl monomers such as vinyl acetate and vinyl pyrrolidone.

Preferably, the random copolymer contains ethylenically unsaturated monomer units c) derived from one or more monomers selected from acrylic acid, methacrylic acid, metal salt of acrylic acid, metal salt of methacrylic acid, maleic anhydride, vinyl acetate, vinyl pyrrolidone, or any combination thereof.

More preferably, the random copolymer contains ethylenically unsaturated monomer units c) derived from one or more monomers selected from acrylic acid, methacrylic acid, alkali metal salt of acrylic acid, alkali metal salt of methacrylic acid, or any combination thereof.

The ethylenically unsaturated monomer units c) preferably account for 5 to 40 % by weight, more preferably 10 to 30 % by weight, most preferably 10 to 20 % by weight of the random copolymer.

In some particular embodiments, the polymeric dispersant comprises a random copolymer containing or preferably consisting of a) 15 to 45% by weight of styrenic monomer units derived from one or more monomers selected from styrene, Ci-C4-alkyl substituted styrene or any combinations thereof; b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units derived from one or more monomers selected from acrylic sulphonic acid compounds of the formula (I), salts of acrylic sulphonic acid compounds of the formula (I), or a combination thereof in which

R ¹ is hydrogen or methyl, and R2 is a straight or branched Cs-Cs-alkylene group, and c) 5 to 40% by weight ethylenically unsaturated monomer units derived from one or more monomers selected from acrylic acid, methacrylic acid, metal salt of acrylic acid, metal salt of methacrylic acid, maleic anhydride, vinyl acetate, vinyl pyrrolidone, or any combinations thereof.

In some other particular embodiments, the polymeric dispersant comprises a random copolymer containing or preferably consisting of a) 15 to 45% by weight of styrenic monomer units derived from one or more monomers selected from styrene, a-methylstyrene or a combination thereof; b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units derived from one or more monomers selected from acrylic sulphonic acid compounds of the formula (I), salts of acrylic sulphonic acid compounds of the formula (I), or a combination thereof, in which

R ¹ is hydrogen, and R2 is a straight or branched C4-alkylene group, and c) 5 to 40% by weight ethylenically unsaturated monomer units derived from one or more monomers selected from acrylic acid, methacrylic acid, alkali metal salt of acrylic acid, alkali metal salt of methacrylic acid, or any combination thereof.

In those particular embodiments, it is preferable that the random copolymer contains or consists of 20 to 45 % by weight of the monomer units a), 40 to 57 % by weight of the monomer units b), and 10 to 30 % by weight of the monomer units c).

It is more preferable that the random copolymer contains or consists of 25 to 43 % by weight of the monomer units a), 45 to 55% by weight of the monomer units b), and 10 to 20 % by weight of the monomer units c).

The random copolymer has a weight-average molecular weight (M _w ) of 3,000 to 100,000 g/mol preferably 7,000-60,000 g/mol, preferably 10,000-40,000 g/mol, and more preferably 12, DOO- 35, 000 g/mol, as measured by GPC. The random copolymer has a polydispersity (PDI) typically in the range of 3 to 10, as measured by GPC.

The polymeric dispersant according to the present invention may comprise the random copolymer as described herein as the sole active substance. In other words, the polymeric dispersant according to the present invention may or may not comprise any other substance having a dispersing capability.

The polymeric dispersant may be in form of an aqueous solution comprising the random copolymer. In this case, water is present in the polymeric dispersant as a solvent or medium for the random copolymer. Optionally, the polymeric dispersant further comprises an organic solvent, which may be originated from preparation of the polymer, for example. Preferably, the organic solvent is a high molecular weight compound, for example polyether alcohols, alkyl polyether alcohols, such as polyethylene glycols or alkyl terminated polyethylene glycols.

There is no particular restriction to the solid content of the aqueous solution, which may be 25 to 70 % by weight, preferably 30 to 60% by weight, based on the total weight of the aqueous solution.

The polymeric dispersant, when present as an aqueous solution comprising the random copolymer, may have a pH in the range of 4.0 to 5.5, preferably about 5.

The polymeric dispersant may also comprise any assistants originated from preparation of the random copolymer, for example initiators, polymerization regulators, pH regulators, surfactants, and the like.

The random copolymer may be prepared by radical polymerization of the monomers for deriving the monomer units a), b) and c) as described hereinabove under a homogeneous condition. Any known processes of homogeneous radical polymerization may be applied to prepare the random copolymer, without any particular restrictions.

The radical polymerization is preferably carried out in water and optionally an organic solvent. Preferably, any volatile organic solvent, if used in the radical polymerization, will be removed after finishing the polymerization.

The polymeric dispersant may be the polymerization product obtained directly from the radical polymerization, or may be produced after treating the polymerization product obtained directly from the radical polymerization, for example removing any volatile organic solvent, dilution with water, or removing any volatile organic solvent and then dilution with water.

In the second aspect, the present invention provides an aqueous disperse dye composition, which comprises i) a disperse dye, ii) a random copolymer containing or consisting of following monomer units, a) 15 to 45% by weight of styrenic monomer units, b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units, which are in unneutralized, partially neutralized or fully neutralized form, and c) 0 to 40% by weight of ethylenically unsaturated monomer units other than the monomer units a) and b), and iii) water, wherein the random copolymer and the disperse dye are present at a weight ratio in the range of 1 : 50 to 1 : 3.

The disperse dye is preferably selected from mono-azo dyes, di-azo dyes, anthraquinone dyes, or any combinations thereof.

Particularly, the disperse dye may be selected from C.l. disperse orange 288, C.l. disperse orange 30, C.l. disperse red 167, C.l. disperse blue 291 , C.l. disperse blue 79, C.l. disperse violet 93, and any combination thereof.

In the aqueous disperse dye composition, the disperse dye is present in form of particles having a D50 value in the range of 0.5 to 1.5 microns, preferably 0.5 to 1.0 micron as measured by laser diffraction. Preferably, the particles of the disperse dye have a D90 value of no higher than 3.0 microns, preferably no higher than 2.0 microns as measured by laser diffraction.

The disperse dye may be present in the aqueous disperse dye composition in an amount of 20 to 40% by weight, preferably 25 to 35% by weight, based on the total weight of the aqueous disperse dye composition.

The random copolymer may be the same as that comprised in the polymeric dispersant according to the present invention. Any general description and preferences described hereinabove for the random copolymer within the context of the polymeric dispersant are applicable here by reference.

The random copolymer may be present in the aqueous disperse dye composition in an amount of 0.3 to 10 % by weight, preferably 1 to 8% by weight, more preferably 1.5 to 5% by weight, based on the total weight of the aqueous disperse dye composition.

Particularly, the random copolymer and the disperse dye are present in the aqueous disperse dye composition at a weight ratio in the range of 1 : 30 to 1 : 5, preferably 1 : 30 to 1 : 6, more preferably 1 : 20 to 1 : 7.

The aqueous disperse dye composition may further comprise one or more additives customarily added in a liquid-form disperse dye, for example preservatives, antioxidants, defoamers, viscosity regulators, and surfactants other than the random copolymer as described herein. Additionally, the aqueous disperse dye composition may comprise components originated from preparation of the random copolymer, for example non-volatile organic solvents and/or assistants such as initiators, polymerization regulators, pH regulators and surfactants.

When any additives and/or components originated from preparation of the random copolymer are present in the aqueous disperse dye composition, the total amount will be up to 5% by weight and preferably up to 1% by weight, based on the weight of the aqueous disperse dye composition.

The water is present in the aqueous disperse dye composition in an amount of 50 to 75% by weight, preferably 60 to 70 % by weight based on the total weight of aqueous disperse dye composition.

The aqueous disperse dye composition typically has a pH in the range of 4 to 6.5, preferably 4.5 to 6.

In some illustrative embodiments, the present invention provides an aqueous disperse dye composition, which comprises i) 20 to 40 % by weight of a disperse dye, ii) 0.3 to 10% by weight of the random copolymer as described herein, and iii) 50 to 75% by weight of water, based on the total weight of the aqueous disperse dye composition, wherein the random copolymer and the disperse dye are present in the aqueous disperse dye composition at a weight ratio in the range of 1 : 50 to 1 : 3.

In further illustrative embodiments, the present invention provides an aqueous disperse dye composition, which comprises i) 25 to 35 % by weight of a disperse dye, ii) 1 to 8% by weight of the random copolymer as described herein, and iii) 60 to 70 % by weight of water, based on the total weight of the aqueous disperse dye composition, wherein the random copolymer and the disperse dye are present in the aqueous disperse dye composition at a weight ratio in the range of 1 : 30 to 1 : 5, preferably 1 : 30 to 1 : 6.

In some other illustrative embodiments, the present invention provides an aqueous disperse dye composition, which comprises i) 25 to 35 % by weight of a disperse dye, ii) 1.5 to 5% by weight of the random copolymer as described herein, and iii) 60 to 70 % by weight of water, based on the total weight of the aqueous disperse dye composition, wherein the random copolymer and the disperse dye are present in the aqueous disperse dye composition at a weight ratio in the range of 1 : 20 to 1 : 7.

In the above illustrative embodiments, the random copolymer contains or preferably consists of following monomer units a) 15 to 45% by weight of styrenic monomer units, b) 30 to 60% by weight of ethylenically unsaturated sulphonic acid monomer units, which are in unneutralized, partially neutralized or fully neutralized form, and c) 5 to 40% by weight of ethylenically unsaturated monomer units other than the monomer units a) and b).

In the above illustrative embodiments, it is preferable that the random copolymer contains or preferably consists of 20 to 45 % by weight of the styrenic monomer units a), 40 to 57 % by weight of the monomer units b), and 10 to 30 % by weight of the monomer units c).

In the above illustrative embodiments, it is more preferable that the random copolymer contains, preferably consists of 25 to 43 % by weight of the monomer units a), 45 to 55 % by weight of the monomer units b), and 10 to 20 % by weight of the monomer units c).

In the third aspect, the present invention provides a process for producing the aqueous disperse dye composition, which comprises grinding one or more press cakes of a disperse dye in the presence of the polymeric dispersant as described in the first aspect of the present invention in water.

The polymeric dispersant will be used in an amount such that the weight ratio of the random copolymer and the disperse dye is in the range of 1 : 50 to 1 : 3, particularly 1 : 30 to 1 : 5, preferably 1 : 30 to 1 : 6, more preferably 1 : 20 to 1 : 7.

The grinding may be carried out in the presence of one or more additives customarily used in a liquid-form disperse dye, for example preservatives, antioxidants, defoamers, viscosity regulators, and surfactants other than the random copolymer as described herein.

It will be appreciable that the grinding may be carried out by any technical means known in the art as long as an aqueous disperse dye composition as described in the second aspect of the present invention can be obtained.

The invention will be further illustrated by following Examples, which set forth particularly advantageous embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

Examples

I. Description of Materials and Measurements

Materials:

PEG solvent: polyethylene glycol monomethyl ether, Mn=500; from BASF;

Defoamer: modified polydimethylsiloxane-based defoamer, from BASF; AMPS-Na: 50% aqueous solution of 2-Acrylamido-2-methylpropanesulfonic acid sodium salt, from All-Plus Chemicals;

TBPEH: tert-butylperoxy-2-ethylhexanoate, from Adamas-beta;

Acrylic acid (AA), styrene, n-butanol, isopropanol, 95 zirconia beads, sodium metabisulfite and sodium persulfate (NaPS): from Sinopharm Chemical Reagent;

Mercaptoethanol (ME): from TCI;

MF: methylnaphthalene sulfonate formaldehyde condensate, from Zhejiang Wulong New Materials Co. Ltd.

Disperse Blue 79 and Disperse Red 167: from Anoky;

Disperse Orange 288, Disperse Blue 291 , Disperse Violet 93: from Zhejiang Longsheng Group Co., Ltd.

Measurements:

1) Molecular Weight

The molecular weight was measured by water phase GPC test. Samples were dissolved in an eluent at 1.5 mg/mLfor2h at room temperature, filtered by a 0.45|jm membrane before injection. The test was conducted in accordance with following setting and conditions.

Column: TSKgel GMPWXL13|jm x 2, 300 x 7.8mm

Column Temp: 35 °C

Eluent: H2O + 0.01M Phosphate Buffer + 0.1M NaCI, pH = 7.4

Flow rate: 0.8 mL/min

Injection: 100 uL

Detection: Refractive Index

The standard curve of water phase is calibrated with solutions of narrow dispersity Polyacrylic acid, with molecular weights ranging from 1 ,250 to 1 , 100,000, which were also conducted under the conditions as described above.

2) Particle Size

The particle sizes, D50 and D90, were measured by a laser diffraction instrument, Malvern Mastersizer 3000, in the general mode with the absorption index being set as 1.

3) Composition of Random Copolymers

The composition of the copolymers was confirmed by ¹ H-NMR spectrum. The conversions of all monomers in the polymerization process are higher than 99%.

II. Preparation of Polymeric Dispersants Example 1

370.15g PEG Solvent, 12.45g AA and 79.23g AMPS-Na was initially charge into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. Then, 180g styrene, a solution of 112.07g AA and 713.12g AMPS-Na (AA/AMPS-Na solution), a solution of 42.04g NaPS in 126.13g water (NaPS solution) and a solution of 42.04g sodium metabisulfite in 126.13g water (sodium metabisulfite solution) were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the NaPS solution was fed over 240min and the sodium metabisulfite solution was fed over 210min. After finishing feeding, the polymerization was continued for 120min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%.

The weight-average molecular weight (M _w ) of the obtained copolymer is 30,300g/mol, having a polydispersity (PDI) of 5.3.

The copolymer consists of about 27% by weight of monomer units from styrene, about 54% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 19% by weight of monomer units from acrylic acid.

Examples 2 to 5

329.34g PEG Solventwas initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. Then, 180g styrene, a solution of 124.54g AA and 792.38g AMPS-Na (AA/AMPS-Na solution), a solution of 21.02g TBPEH in 21.02g PEG Solvent(TBPEH solution), and a certain amount of mercaptoethanol (ME) were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the TBPEH solution was fed over 150min, and ME was fed over 120min. After finishing feeding, the polymerization was continued for 180min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%. The dosage of ME in each Example and characterization of the copolymers are shown in the table below:

Each copolymer consists of about 27% by weight of monomer units from styrene, about 54% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 19% by weight of monomer units from acrylic acid. Example 6

261.96g n-Butanol was initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 180g styrene, a solution of 124.54g AA and 792.38g AMPS-Na (AA/AMPS- Na solution), a solution of 21 ,02g TBPEH in 88.40g n-Butanol (TBPEH solution) and 21 ,02g ME were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the TBPEH solution was fed over 150min, and ME was fed over 120min. After finishing feeding, the polymerization was continued for 180min, and then subjected to steam distillation to remove all n-butanol to obtain a polymer aqueous solution with solid content of 50%.

The weight-average molecular weight (M _w ) of the copolymer is 7,650g/mol, having a polydispersity (PDI) of 3.4.

The copolymer consists of about 27% by weight of monomer units from styrene, about 54% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt(expressed as AMPS), and about 19% by weight of monomer units from acrylic acid.

Example 7 to 10

344.95g PEG Solvent was initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 300g styrene, a solution of 103.79g AA and 660.29g AMPS-Na (AA/AMPS- Na solution), a solution of 22.01g TBPEH in 22.01g PEG Solvent(TBPEH solution), and a certain amount of mercaptoethanol (ME) were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the TBPEH solution was fed over 180min and ME was fed over 150min. After finishing feeding, the polymerization was continued for 180min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%. The dosage of ME in each Example and characterization of the copolymers are shown in the table below:

Each copolymer consists of about 43% by weight of monomer units from styrene, about 42% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 15% by weight of monomer units from acrylic acid. Example 11

370.15g PEG Solvent, 12.45g AA and 79.23g AMPS-Na were initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 180g styrene, a solution of 112.07g AA and 713.12g AMPS-Na (AA/AMPS-Na solution), a solution of 42.04g NaPS in 126.13g water (NaPS solution) and 42.04g ME were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the NaPS solution was fed over 240min and ME was fed over 210min. After finishing feeding, the polymerization was continued for 120min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%.

The weight-average molecular weight (M _w ) of the copolymer is 3,720g/mol, having a polydispersity (PDI) of 2.5.

The copolymer consists of about 27% by weight of monomer units from styrene, about 54% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 19% by weight of monomer units from acrylic acid.

Example 12

344.95g PEG Solvent was initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 300g styrene, a solution of 103.79g AA and 660.29g AMPS-Na (AA/AMPS- Na solution), a solution of 22.01g TBPEH in 22.01g PEG Solvent (TBPEH solution) and 44.03g ME were fed into the reactor simultaneously and separately. Styrene was fed over 120min, the AA/AMPS-Na solution was fed over 90min, the TBPEH solution was fed over 180min and ME was fed over 150min. After finishing feeding, the polymerization was continued for 180min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%.

The weight-average molecular weight (M _w ) of the copolymer is 3,280g/mol, having a polydispersity (PDI) of 2.5.

The copolymer consists of about 43% by weight of monomer units from styrene, about 42% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 15% by weight of monomer units from acrylic acid.

Comparative Example 13

184.64g PEG Solvent was initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 200g styrene, a solution of 46.13g AA and 293.46g AMPS-Na (AA/AMPS-Na solution), a solution of 11.79g TBPEH in 11.79g PEG Solvent (TBPEH solution) and 3.54g ME were fed into the reactor simultaneously and separately. Styrene was fed over 90min, the AA/AMPS-Na solution was fed over 100min, the TBPEH solution was fed over 180min and ME was fed over 150min. After finishing feeding, the polymerization was continued for 180min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%. The weight-average molecular weight (M _w ) of the copolymer is 35,200g/mol, having a polydispersity (PDI) of 5.2.

The copolymer consists of about 53% by weight of monomer units from styrene, about 35% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 12% by weight of monomer units from acrylic acid.

Comparative Example 14

159.46gPEG Solvent, 6.92g AA and 44.02g AMPS-Na were initially charged into a 2L glass reactor and heated to 95 °C under N2 purge and stirring. 50g styrene, a solution of 62.27g AA and 396.17g AMPS-Na (AA/AMPS-Na solution), a solution of 10.18g TBPEH in 10.18g PEG Solvent (TBPEH solution) and 3.05g ME were fed into the reactor simultaneously and separately. Styrene was fed over 150min, the AA/AMPS-Na solution was fed over 90min, the TBPEH solution was fed over 180min and ME was fed over 150min. After finishing feeding, the polymerization was continued for 120min, and then cooled down to 40 °C and diluted with deionized water to a solid content of 50%.

The weight-average molecular weight (M _w ) of the copolymer is 37,300g/mol, having a polydispersity (PDI) of 5.5.

The copolymer consists of about 17% by weight of monomer units from styrene, about 62% by weight of monomer units from 2-acrylamido-2-methylpropanesulfonic acid sodium salt (expressed as AMPS), and about 21 % by weight of monomer units from acrylic acid.

III. Application Tests

General Procedure for Production of Liquid-form Disperse Dye

Liquid-form disperse dye sample was prepared by grinding a press cake of dye in the presence of a polymeric dispersant as obtained from each Preparation Example in PMQW2 Omnibearing Planetary Ball Mill from Nanjing Chi Shun Technology Development Co., Ltd. A general formulation of the liquid-form disperse dye is summarized in the table below. calculated as solid contents

The grinding was conducted by means of 70 parts by weight of 95 Zirconia beads, relative to 100 parts by weight of the formulation of the liquid-form disperse dye. A few extra steel balls (20mm diameter ball x 2 and 10mm diameter ball x 20) were added during the grinding. The grinding condition was set as 12 hours under 200 rpm.

Storage Performance Evaluation

Liquid-form disperse dye samples as prepared were stored at room temperature, unless otherwise specified, and checked regularly. The storage performance was evaluated with respect to sedimentation and flowability in accordance with the standards as shown in the table below.

Application Test 1

Liquid-form disperse dye samples with black color were prepared with various dispersants in accordance with the above general procedure, except that the amount of dispersant is 3.0% by weight and the amount of dye is 28.0% by weight, calculated as solid contents. A mixture of Disperse Orange 288, Disperse Blue 291 and Disperse Violet 93 at a weight ratio of 12.5: 8: 7.5 was used to provide the black color. The measurement results are summarized in Table 1.

Table 1

It can be seen, when compared with conventional dispersant MF, the inventive dispersants comprising the random copolymers according to the present invention (Examples 1 to 11) provided better flowability and storage stability to liquid-form disperse dye, while the comparative dispersants did not.

Application Test 2

Liquid-form disperse dye samples with black color were prepared by the same process as described in Application Test 1 , except that lower amounts of dispersant was used. The measurement results are summarized in Table 2.

Table 2 calculated as solid content

The results in Table 2 show that the dispersants from Examples 1 , 4 and 5 can provide free- flowing composition without any sedimentation for more than 4 weeks at reduced dosages.

Application Test 3

Liquid-form disperse dye samples with various colors were prepared in accordance with the above general procedure, except that the amount of dye in each case is 30.0% by weight, and the amounts of dispersant are 4.0% by weight for Disperse Red 167 and Disperse Blue79, and 3.0% by weight for Disperse Blue 291 , Disperse Violet 93 and Disperse Orange 288, each being calculated as solid contents. The measurement results are summarized in Table 3.

Table 3

The results in Table 3 show that the dispersants according to the present invention are also applicable to various colour dyes, providing better or at least comparable flowability and storage stability to liquid-form disperse dyes, as compared with conventional dispersant MF.