Method for preparing aqueous polyurethane dispersion

Abstract

A method for preparing an aqueous polyurethane dispersion includes the following steps. The method characterized in that it introduces an ethoxy group to sodium ethylenediamine sulfonate (H2N—CH2CH2NHCH2CH2SO3Na) serving as an anionic chain extender to form sodium ethylenediamino ethoxyethyl sulfonate (H2NCH2CH2NHCH2CH2OCH2CH2SO3Na). Next, hydrophilic groups of sodium ethylenediamino ethoxyethyl sulfonate are used to prepare an aqueous polyurethane to improve the flowability of the resin, in which the polyurethane prepolymer has an isocyanate group at its end. More than one acrylate monomer is used for dilution and reduction of viscosity, and hydrophilic and amine groups containing sulfonate is used for water dispersion and to carry out a chain extension reaction. After that, an initiator is added for acrylic polymerization, so as to modify polyurethane with graft acrylic.

Claims

1. A method for preparing an aqueous polyurethane dispersion, composing: (1) a preparation step of sodium ethylenediamino ethoxyethyl sulfonate including: reacting sodium ethylenediamino sulfonate with ethylene glycol to obtain the sodium ethylenediamino ethoxyethyl sulfonate; (2) a preparation step of a prepolymer including: vacuum-dehydrating 15-25 wt % of a polyol and adding the vacuum-dehydrated polyol into a reactor equipped with a mixer, a thermometer and a condensing tube, and adding a metered amount of 5-12 wt % of a polyisocyanate into the reactor when an oil bath temperature reaches 70-80° C. to carry out a synthetic reaction so as to obtain the prepolymer; (3) a dilution and chain extension step of the prepolymer including: after reacting the prepolymer obtained from the step (2) for 2-3 hours, adding 10-30 wt % of more than one acrylic monomer to reduce the viscosity of the prepolymer and maintaining the reaction temperature at 85-90° C. until an NCO content (NCO %) of the prepolymer reaches a target value, and subsequently adding 1.8-3.7 wt % of the sodium ethylenediamino ethoxyethyl sulfonate obtained from the step (1) to continue the reaction for 25-40 minutes; (4) a water dispersion step including: cooling a polymer obtained from the step (3) to room temperature and adding 35-55 wt % of deionized water to the polymer under a high-speed shearing force that is generated at a rotation speed of 500 rpm, and subsequently adding a metered amount of 0.1-0.5 wt % a chain extender to carry out a chain extension reaction for 30 minutes so as to obtain a solvent-free sulfonate-type aqueous polyurethane dispersion; and (5) an acrylic synthesis step including: mixing the aqueous polyurethane dispersion obtained from the step (4) with 0.3-1.0 wt % of an emulsifier to form an emulsion, raising the reaction temperature to 50-70° C. after stirring evenly and then dropwise adding 0.01-0.10 wt % of an initiator, raising the reaction temperature to 75-85° C. to carry out an acrylic polymerization reaction for 1-3 hours, and adding 0.01-0.08 wt % of a reducing agent after reducing the reaction temperature to 50-70° C. so as to obtain an acrylic-grafting-modified aqueous polyurethane.

2. The method according to claim 1, wherein, in the step (2), the polyol is a polyester polyol, a polyether polyol, a polycarbonate polyol or any combination thereof and the polyisocyanate is a diisocyanate, and the polyol and the polyisocyanate are reacted in an NCO/OH equivalent ratio from 1.1 to 2.3.

3. The method according to claim 1, wherein, in the step (3), the more than one acrylic monomer is selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, 2-hydroxyethyl acrylate, isooctyl acrylate, butyl acrylate and ethylhexyl acrylate, and the more than one acrylic monomer is added in an amount of 10-30 wt % of the total amount of the reaction raw materials.

4. The method according to claim 3, wherein the more than one acrylic monomer includes 2-hydroxyethyl acrylate (2-HEA), methyl methacrylate (MMA) and ethyl acrylate (EA).

5. The method according to claim 4, wherein, based on the total weight of the more than one acrylic monomer, methyl methacrylate is present in an amount of 85-95 wt %, 2-hydroxyethyl acrylate is present in an amount of 4-9 wt %, and ethyl acrylate is present in an amount of 2-6 wt %.

6. The method according to claim 4, wherein, based on the total weight of the more than one acrylic monomer, methyl methacrylate is present in an amount of 92 wt %, 2-hydroxyethyl acrylate is present in an amount of 5 wt %, and ethyl acrylate is present in an amount of 3 wt %.

7. The method according to claim 1, wherein, in the step (3), the sodium ethylenediamino ethoxyethyl sulfonate is added in an amount of 80-90% of an NCO/OH equivalent ratio.

8. The method according to claim 1, wherein, in the step (3), the target value of the NCO content of the chain-extended prepolymer is 0.5-10%; the target value of the NCO content satisfies the following formula: (the amount of the polyisocyanate/the molecular weight of the polyisocyanate the amount of the polyol/the molecular weight of the polyol)×42×2 x %.

9. The method according to claim 1, wherein, in the step (4), the chain extender is selected from the group consisting of ethylenediamine, hexamethylenediamine, xylenediamine, isophoronediamine, diethylenetriamine or N-aminoethyl-N-ethanolamine, which has a molecular weight less than 500, and the chain extender is added in an amount of 10-20% of an NCO/OH equivalent ratio.

10. The method according to claim 1, wherein, in the step (5), the initiator is selected from the group consisting of hydrogen peroxide, tert-butyl peroxide, sodium persulfate, potassium persulfate, lithium persulfate and ammonium persulfate, and the initiator is added in an amount of 0.01-3 wt % based on the total amount of the more than one acrylic monomer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will become more fully understood from the following detailed description and accompanying drawings.

(2) FIG. 1 is a flow chart of a method for preparing an aqueous polyurethane dispersion of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(3) The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a”, “an”, and “the” includes plural reference, and the meaning of “in” includes “in” and “on”. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.

(4) The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first”, “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.

(5) Referring to FIG. 1, the present disclosure provides a method for preparing an aqueous polyurethane dispersion. The method is a five-stage polymerization method, which is favorable to synthesize a kind of solvent-free hydrophilic group-containing aqueous polyurethane whose chemical structure is grafted with acrylic monomers. The method for preparing a hydrophilic group-containing acrylic-grafting-modified aqueous polyurethane is taken as an implementation example for illustration, which includes the following steps.

(6) Step S1 is a preparation step of sodium ethylenediamino ethoxyethyl sulfonate.

(7) In the step S1, sodium ethylenediamino sulfonate is reacted with ethylene glycol to obtain sodium ethylenediamino ethoxyethyl sulfonate.

(8) Step S2 is a preparation step of a prepolymer.

(9) In the step S2, the polyol can be a polyester polyol, a polyether polyol, a polycarbonate polyol or any combination thereof.

(10) The polyester polyol is obtained by a condensation reaction between a low molecular weight polyol and a dicarboxylic acid. For example, a low molecular weight polyol selected from the group consisting of ethylene glycol, 1,3-propanediol and 1,4-butylene glycol and an aliphatic dicarboxylic acid selected from the group consisting of succinic acid, glutaric acid, adipic acid, heptanedioic acid, suberic acid, azelaic acid, sebacic acid, decane dicarboxylic acid and cyclohexane dicarboxylic acid are used to form a condensed polyester polyol.

(11) In addition, the polyol can also be an amide-based polyester amide polyol such as hexamethylene diamine and isophorone diamine, which is obtained from a cyclic ester (e.g., c-caprolactone) and a part of the diol component.

(12) The aforesaid polyols may be used alone or in any combinations thereof, and their copolymers can also be used.

(13) The polyether polyol is selected from the group consisting of poly(tetramethylene ether) glycol (PTMG), polypropanediol (PPG) and polyether polyols whose main chain and side chain(s) are poly ethylene glycol (PEG) chains.

(14) The film formed by a diisocyanate, preferably an aliphatic or alicyclic diisocyanate, has better physical strength and weather resistance.

(15) The aliphatic diisocyanate may be selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate and lysine diisocyanate, and preferably be hexamethylene diisocyanate.

(16) The alicyclic diisocyanate may be selected from the group consisting of isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate and tetramethylxylene diisocyanate, and preferably be isophorone diisocyanate.

(17) Urethane-modified compounds, carbodiimide-modified compounds, allophanate-modified compounds, urea-modified compounds, biuret-modified compounds, uretodion-modified compounds, uretonimine-modified compounds and isocyanurate-modified compounds of the aforesaid aliphatic diisocyanate or alicyclic diisocyanates can further be used in the step (2).

(18) The aforesaid aliphatic diisocyanate or alicyclic diisocyanates may be used alone or in any combinations of two thereof.

(19) The aromatic isocyanate may be selected from at least of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 4,4′-diphenylpropanediisocyanate, m-phenyl diisocyanate, p-phenyl diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1, 5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate, polyphenylene polymethylene polyisocyanate and crude tolylene diisocyanate.

(20) Low molecular weight polyol(s) may be suitable for the urethane reaction in which the main raw material includes polyol(s) and diisocyanate(s).

(21) The examples of the low molecular weight polyol include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentadiol, 1,6-hexanediol, 3-methyl-1,5-pentadiol, neopentadiol, 1,8-ethohexadiol, 1,9-nonanediol, 3,3-dihydroxymethylheptane, diglycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2-ethyl-1,3-propanediol, 2-n-propyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2-n-butyl-1,3-propanediol, 2-isobutyl-1,3-propanediol, 2-tert-butyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-propyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-3-ethyl-1,4-butylene glycol, 2-methyl-3-ethyl-1,4-butylene glycol, 2,3-diethyl-1,5-pentadiol, 2,4-diethyl-1,5-pentadiol and 2,3,4-triethyl-1,5-pentadiol; or is selected from the group consisting of trimethylolpropane, dimethylol propionic acid, dimethylol butanoic acid, diacid diol, glycerol, pentaerythritol and alkylene oxide adducts of bisphenol A.

(22) Preferably, the urethane reaction is carried out at a NCO/OH equivalent ratio between 1.1 and 2.3.

(23) Step S3 is a dilution and chain extension step.

(24) In the step S3, more acrylate monomers can be used together, which can be acrylate-based monomers selected from more than one of methyl acrylate, methyl methacrylate (MMA), ethyl acrylate (EA), isooctyl acrylate, butyl acrylate, methylbutyl acrylate, ethylhexyl acrylate and 2-hydroxyethyl acrylate (2-HEA), monomethyl maleate, methylhydrogen itaconate, monomethyl fumarate, and styrene and mixtures thereof. Three acrylate monomers, namely 2-hydroxyethyl acrylate, methyl methacrylate and ethyl acrylate, used together can provide complementary and synergistic effects on physical properties and act as solvents. 2-hydroxyethyl acrylate (2-HEA) containing hydroxyl groups (—OH) can react with isocyanate, and methyl methacrylate (MMA) and ethyl acrylate (EA) can increase the molecular weight of acrylic and remedy the shortcomings of polyurethane including poor heat resistance and low mechanical strength, so as to possess both excellent physical properties and solvent effect. In addition, no acetone is used so that the synthesis reaction yield can be significantly increased and the production cost is effectively reduced. Based on the total weight of the acrylic monomers, methyl methacrylate is present in an amount of 85-95 wt %, 2-hydroxyethyl acrylate is present in an amount of 4-9 wt %, and ethyl acrylate is present in an amount of 2-6 wt %.

(25) The proportions of the aforesaid three acrylate monomers, based on the total weight of the acrylate monomers, are: (a) 85-95 wt % of methyl methacrylate (b) 4-9 wt % of 2-hydroxyethyl acrylate; and (c) 2-6 wt % of ethyl acrylate.

(26) Preferably, methyl methacrylate (MMA) is present in an amount of 92 wt %, 2-hydroxyethyl acrylate is present in an amount of 5 wt %, and ethyl acrylate is present in an amount of 3 wt %.

(27) The sulfonate not only can serve as a hydrophilic agent of polyurethane, but also may serve as a polymer emulsifier. The sulfonate can be sodium ethylenediamino ethoxyethyl sulfonate.

(28) Step S4 is a water dispersion step.

(29) In the step S4, after dispersion in water, a metered amount of a water-soluble diamine-based chain extender is added to carry out a chain extension reaction. The chain extender can be selected from the group consisting of low molecular weight polyamines having a (number average) molecular weight less than 500, including ethylenediamine, hexamethylenediamine, xylenediamine, isophoronediamine, diethylenetriamine and N-amino ethyl-N-ethanolamine.

(30) Step S5 is an acrylic synthesis step.

(31) In the step S5, the at least one emulsifier required for emulsion polymerization is a surfactant that can significantly reduce surface tension. Accordingly, oil and water phases that are insoluble to each other can be transformed by stirring into a stable white emulsion which is not easily separated into layers. The at least one emulsifier may be selected from the group consisting of anionic emulsifiers, nonionic emulsifiers and reactive emulsifiers. One or more nonionic or anionic emulsifiers or surfactants may be used, including tert-octylphenoxyethyl poly(39)-ethoxyethanol, dodecyloxy poly(10) ethoxyethanol, nonyl phenoxyethyl-poly(40) ethoxyethanol, polyethyleneglycol(2000) mono-oleate, hydroxyethylated castor oil, fluorinated alkyl esters and alkyl oxide, polyethylene oxide (20) sorbitol monolaurate, sucrose monococoate, bis(2-butyl) phenoxy poly(20) ethoxyethanol, and hydroxyethyl cellulose polybutyl acrylate graft copolymer.

(32) Suitable examples of the anionic emulsifier include sodium lauryl sulfate (SLS), sodium dodecyl benzene sulfonate, potassium stearate, sodium dioctyl sulfosuccinate, sodium dodecyldiphenyloxy disulfonate, sodium styrene sulfonate, nonylphenoxy poly ethyl (1) ethoxyethyl sulfate ammonium, sodium dodecyl allyl sulfosuccinate, linseed oil fatty acid, ethoxylated nonylphenol phosphate sodium, ethoxylated nonylphenol phosphate ammonium, sodium octoxynol-3-sulfate, sodium cocoyl sarcosinate, 1-alkoxy-2-sodium hydroxypropyl sulfonate, sodium alpha-olefin (C14-C16) sulfonate, sulfate of hydroxyl anol, N-(1,2-dicarboxyethyl)-N-octadecylsulfonylsuccinamate tetrasodium, N-octadecylsulfonylsuccinamyldisodium, alkylamidepolyethoxy sulfonylsuccinic acid disodium, disodium ethoxylated nonylphenol sulfonylsuccinate and sodium ethoxyethyl sulfate. The at least one emulsifier is present in an amount less than 3 wt % of the total weight of the acrylate monomers, i.e., is present in an amount of 0.3-1.0 wt % based on the total amount of the reaction raw materials.

(33) The initiator can be a water-soluble free-radical initiator. Specific examples of the water-soluble free-radical initiator include hydrogen peroxide, tert-butyl peroxides and alkali metal persulfates such as sodium persulfate, potassium persulfate, lithium persulfate and ammonium persulfate (APS). The initiator is present in an amount of 0.01-3.0 wt % of the total weight of the acrylate monomers, i.e., is present in an amount of 0.01-1.0 wt % based on the total amount of the reaction raw materials.

(34) At a subsequent stage of emulsion polymerization, in order to avoid the emulsion condensation caused by heating, the reducing agent can be used at 50-70° C. to post-eliminate the monomers to reduce the monomer residual rate. Specific examples of the reducing agent include sulfites such as alkali metal metabisulfites, hydrogen sulfites and hydrosulfites, sodium formaldehyde sulfoxylate (SFS), tert-butyl hydroperoxide (TBHP), and reducing sugars such as ascorbic acid and erythorbic acid. Sodium formaldehyde sulfoxylate (SFS) is suitable for post-elimination of methyl methacrylate and 2-hydroxyethyl acrylate, and tert-butyl hydroperoxide (TBHP) is suitable for post-elimination of ethyl acrylate and butyl acrylate. The reducing agent is present in an amount of 0.1-0.3 wt % of the total weight of the acrylate monomers, i.e., is present in an amount of 0.01-0.08 wt % based on the total amount of the reaction raw materials.

(35) As described above, according to the present disclosure, a method for preparing a solvent-free hydrophilic group-containing aqueous polyurethane dispersion can be provided.

(36) The present disclosure is further illustrated by the following examples and comparative examples, but the scope of the present disclosure is not limited to such examples.

EXAMPLE 1

(37) The resulting product of Example 1 is formed by mixing an aqueous polyurethane as Resin A and a polyacrylate emulsion as Resin B. The process is described as follows.

(38) Preparation of Aqueous Polyurethane (Resin A):

(39) Firstly, 98.8 g of PTMG2000 (polyether diol, molecular weight 2000) and 6.44 g of 1,4-BG (1,4-butylene glycol, molecular weight 90) are added into a reactor in order. The resulting mixture is heated to 80° C. while stirring at uniform speed. After that, 43.5 g of isophorone diisocyanate is added and the temperature is raised to 85-90° C. for reaction for 2-3 hours. At this time, 147.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 4.8 g of ethyl acrylate (EA) are added for dilution and reduction of viscosity of the resulting prepolymer. After that, 10.7 g of sodium ethylenediamino sulfonate (AAS) is added to the prepolymer to continue the reaction for 25-40 minutes. After cooling to room temperature, 236.3 g of deionized water is added under a rotary speed of 500 rpm and 0.95 g of ethylenediamine is added for chain extension for 30 minutes, so as to obtain a solvent-free sulfonate-based aqueous polyurethane emulsion.

(40) Preparation of Polyacrylate Emulsion (Resin B):

(41) Firstly, 4.8 g of sodium lauryl sulfate (SLS) is added to the aforesaid sulfonate-based aqueous polyurethane emulsion under high-speed stirring. The resulting mixture is heated to 50-70° C. and subsequently 0.40 g of ammonium persulfate aqueous solution (APS) is dropwise added. The temperature is raised to 75-85° C. and maintained thereat for 1-3 hours. After cooling to 50-70° C., 0.15 g of tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) serving as reducers are added for reaction for 30 minutes, so as to obtain an acrylic-grafting-modified aqueous polyurethane.

(42) The solid contents of the resulting product of Example 1 are: Resin A and Resin B at a ratio of 1:1. Resin A is synthesized by sodium ethylenediamino sulfonate (AAS).

EXAMPLE 2

(43) Similar to Example 1, the resulting product of Example 2 is formed by mixing an aqueous polyurethane as Resin A and a polyacrylate emulsion as Resin B, but sodium ethylenediamino ethoxyethyl sulfonate is used in place of sodium ethylenediamino sulfonate (AAS) for synthesis of Resin A. The process is described as follows.

(44) Preparation of Aqueous Polyurethane (Resin A):

(45) Firstly, 98.8 g of PTMG2000 (polyether diol, molecular weight 2000) and 6.44 g of 1,4-BG (1,4-butylene glycol, molecular weight 90) are added into a reactor in order. The resulting mixture is heated to 80° C. while stirring at uniform speed. After that, 43.5 g of isophorone diisocyanate is added and the temperature is raised to 85-90° C. for reaction for 2-3 hours. At this time, 147.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 4.8 g of ethyl acrylate (EA) are added for dilution and reduction of viscosity of the resulting prepolymer. After that, 13.2 g of sodium ethylenediamino ethoxyethyl sulfonate is added to the prepolymer to continue the reaction for 25-40 minutes. After cooling to room temperature, 236.3 g of deionized water is added under a rotary speed of 500 rpm and 0.95 g of ethylenediamine is added for chain extension for 30 minutes, so as to obtain a solvent-free sulfonate-based aqueous polyurethane emulsion.

(46) Preparation of Polyacrylate Emulsion (Resin B):

(47) Firstly, 4.8 g of sodium lauryl sulfate (SLS) is added to the aforesaid sulfonate-based aqueous polyurethane emulsion under high-speed stirring. The resulting mixture is heated to 50-70° C. and subsequently 0.40 g of ammonium persulfate aqueous solution (APS) is dropwise added. The temperature is raised to 75-85° C. and maintained thereat for 1-3 hours. After cooling to 50-70° C., 0.15 g of tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) serving as reducers are added for reaction for 30 minutes, so as to obtain an acrylic-grafting-modified aqueous polyurethane.

(48) The solid contents of the resulting product of Example 2 are: Resin A and Resin B at a ratio of 1:1. Resin A is synthesized by sodium ethylenediamino ethoxyethyl sulfonate.

EXAMPLE 3

(49) Similar to Example 2, the resulting product of Example 2 is formed by mixing an aqueous polyurethane as Resin A and a polyacrylate emulsion as Resin B, but Resin A is present in a higher proportion. The process is described as follows.

(50) Preparation of Aqueous Polyurethane (Resin A):

(51) Firstly, 197.6 g of PTMG2000 (polyether diol, molecular weight 2000) and 12.9 g of 1,4-BG (1,4-butylene glycol, molecular weight 90) are added into a reactor in order. The resulting mixture is heated to 80° C. while stirring at uniform speed. After that, 87 g of isophorone diisocyanate is added and the temperature is raised to 85-90° C. for reaction for 2-3 hours. At this time, 147.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 4.8 g of ethyl acrylate (EA) are added for dilution and reduction of viscosity of the resulting prepolymer. After that, 26.4 g of sodium ethylenediamino ethoxyethyl sulfonate is added to the prepolymer to continue the reaction for 25-40 minutes. After cooling to room temperature, 482.6 g of deionized water is added under a rotary speed of 500 rpm and 1.9 g of ethylenediamine is added for chain extension for 30 minutes, so as to obtain a solvent-free sulfonate-based aqueous polyurethane emulsion.

(52) Preparation of Polyacrylate Emulsion (Resin B):

(53) Firstly, 4.8 g of sodium lauryl sulfate (SLS) is added to the aforesaid sulfonate-based aqueous polyurethane emulsion under high-speed stirring. The resulting mixture is heated to 50-70° C. and subsequently 0.40 g of ammonium persulfate aqueous solution (APS) is dropwise added. The temperature is raised to 75-85° C. and maintained thereat for 1-3 hours. After cooling to 50-70° C., 0.15 g of tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) serving as reducers are added for reaction for 30 minutes, so as to obtain an acrylic-grafting-modified aqueous polyurethane.

(54) The solid contents of the resulting product of Example 3 are: Resin A and Resin B at a ratio of 1:1. Resin A is synthesized by sodium ethylenediamino ethoxyethyl sulfonate.

COMPARATIVE EXAMPLE 1

(55) In this example, an aqueous polyurethane, which is synthesized by the acetone method without mixing with a polyacrylate emulsion. The process is described as follows.

(56) Preparation of Aqueous Polyurethane (Resin A):

(57) Firstly, 75 g of PTMG2000 (polyether diol, molecular weight 2000) and 7.3 g of 1,4-BG (1,4-butylene glycol, molecular weight 90) are added into a reactor in order. The resulting mixture is heated to 80° C. while stirring at uniform speed. After that, 58.8 g of isophorone diisocyanate is added and the temperature is raised to 85-90° C. for reaction for 2-3 hours. After cooling to 30-50° C., 160 g of acetone is added for dilution and reduction of viscosity of the resulting prepolymer. Twenty minutes later, 17.5 g of sodium ethylenediamino sulfonate (AAS) is added to continue the reaction for 25-40 minutes. After cooling to room temperature, 266.6 g of deionized water is added under a rotary speed of 500 rpm and 1.1 g of ethylenediamine is added for chain extension for 30 minutes. After distillation of acetone, an acrylic-free sulfonate-based aqueous polyurethane emulsion is obtained.

Results

(58) The resulting products of Examples 1-3 and Comparative Example 1 are respectively applied to synthetic leathers for evaluation tests on physical properties. The results are shown in Table 1.

(59) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 2 Example 3 Example 1 Test Crumpling resistance No damage No damage No damage No damage results (1.5 Kg*1000 times) Corner whitening No whitening No whitening No whitening No whitening (3 Kg*24 hours) Heat-resistant adhesion No sticking No sticking No sticking Seriously (70° C.*3 Kg*24 hours) sticking Hydrolysis resistance No cracks No cracks No cracks Serious (10% NaOH*8 hours) cracks Level property Good Good Good Good Weather resistance Normal for Normal for Normal for Normal for (70° C.*95% RH) 14 weeks 14 weeks 10 weeks 5 weeks Acetone content (ppm) None None None 1486

(60) Based on the above, in the embodiments of the present disclosure, sodium ethylenediamino ethoxyethyl sulfonate is used in place of sodium ethylenediamino sulfonate (AAS) to achieve better flowability, and uses the acrylic graft modification is used to increase heat resistance and hydrolysis resistance. Furthermore, the increase of the proportion of acrylic monomer can increase weather resistance, and acrylic graft modification can remedy the shortcomings of polyurethane including poor heat, weather and hydrolysis resistances. In addition, the present disclosure can solve the problem of residual acetone and can meet the aqueous requirements.

(61) The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

(62) The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope.