Waterborne polyurethane resin and preparation method thereof

Abstract

The present invention discloses a waterborne polyurethane resin and a preparation method thereof. The preparation method of the waterborne polyurethane resin comprises: preparation of a prepolymer, dilution of the prepolymer, water dispersion and chain extension, and acrylic synthesis. The preparation method comprises mixing polyols and polyisocyanates to obtain a prepolymer, and then adding acrylic monomers for dilution. In the waterborne polyurethane resin of the present invention, at least one of the polyols, polyisocyanates, and acrylic monomers comprises a compound with a cyclic structure, thereby enhancing the intermolecular force, improving the thermal stability of the waterborne polyurethane resin, and achieving the purpose of improving heat-resistant yellowing.

Description

Technical Field

[0001] The invention relates to a waterborne polyurethane resin and a preparation method thereof, and in particular to a waterborne polyurethane resin containing a cyclic structure and a preparation method thereof. Background Art

[0002] Polyurethane resins have a wide range of applications, such as synthetic leather fabrics or surface treatment agents. In the process of producing polyurethane, a large amount of organic solvents are required, resulting in the problem that polyurethane products contain volatile organic compounds (VOCs). In recent years, with environmental awareness receiving much attention, waterborne polyurethane has gradually replaced solvent-based polyurethane and is widely used in textile coating, leather processing, adhesives, sealants and plastic molding. The synthesis method of waterborne polyurethane is to react polyether or polyester polyol with isocyanate to synthesize a high-viscosity prepolymer with an NCO functional group at the end.

[0003] When waterborne polyurethane resin is used in synthetic leather fabrics, such as automotive leather fabrics, under high temperature conditions (120°C x 7 days), its heat yellowing resistance and weathering resistance are poor. The existing technology achieves the purpose of improving yellowing by adding additives such as light stabilizers, antioxidants and heat stabilizers. However, the degree of improvement is still not ideal. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a waterborne polyurethane resin containing a cyclic structure and a preparation method thereof in view of the deficiencies in the prior art.

[0005] In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a method for preparing a waterborne polyurethane resin, which comprises the following steps: (1) Preparation of prepolymer: after vacuum dehydration of 15 to 25 wt% of a polyol, add it to a reaction tank, heat it in an oil bath to a temperature of 70 to 80° C., then add 5 to 12 wt% of a polyisocyanate to the reaction tank to make a synthesis reaction to obtain a prepolymer; (2) Dilution of prepolymer: add 10 to 30 wt% of an acrylic monomer to the prepolymer to dilute and reduce viscosity, maintain the temperature between 85 to 90° C., react for 2 to 3 hours until the NCO% reaches the target value, then add 1.8 to 3.7 wt% of a sulfonate hydrophilic agent, and continue the reaction for 25 to 40 minutes to obtain a polymer; (3) Water dispersion and chain extension: add the prepolymer of step The polymer of step (2) is cooled to room temperature, and 35 to 55 wt% of deionized water is added at a rotation speed of 500 rpm, and then 0.1 to 0.5 wt% of a chain extender is added to carry out a chain extension reaction for about 30 minutes to obtain a waterborne polyurethane; and (4) acrylic synthesis: 0.3 to 1.0 wt% of an emulsifier is added to the waterborne polyurethane of step (3) to form an emulsion, and the mixture is stirred evenly and heated to 50 to 70° C., and then 0.01 to 0.10 wt% of an initiator is added dropwise, and acrylic polymerization is carried out at a temperature of 75 to 85° C. for 1 to 3 hours, and after cooling to 50 to 70° C., 0.01 to 0.08 wt% of a reducing agent is added to obtain a waterborne polyurethane resin; wherein at least one of the polyol, the polyisocyanate and the acrylic monomer comprises a cyclic structure compound.

[0006] Preferably, the polyol, the polyisocyanate and the acrylic monomer all include compounds with a cyclic structure.

[0007] Preferably, the polyol is selected from the group consisting of polyester polyol, polyether polyol and polycarbonate polyol.

[0008] Preferably, the polyester polyol is polymerized from 1,4-cyclohexanedimethanol or tricyclodecane dimethanol and a dibasic acid.

[0009] Preferably, the polyisocyanate is a diisocyanate selected from the group consisting of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), and the like.

[0010] Preferably, the polyol and the polyisocyanate are reacted at an NCO / OH equivalent ratio of 1.1 to 2.3.

[0011] Preferably, the acrylic monomer is selected from the group consisting of cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBOMA), 2-hydroxyethyl acrylate (2-HEA), methyl methacrylate (MMA) and ethyl acrylate (EA).

[0012] Preferably, the acrylic monomer is (a) methyl methacrylate in an amount of 50 to 90 wt %; (b) 2-hydroxyethyl acrylate in an amount of 4 to 9 wt %; (c) ethyl acrylate in an amount of 2 to 6 wt %; (d) cyclohexyl methacrylate in an amount of 0 to 15 wt %; and (e) isobornyl methacrylate in an amount of 0 to 20 wt %.

[0013] Preferably, the initiator is selected from the group consisting of hydrogen peroxide, tert-butyl peroxide, sodium persulfate, potassium and lithium persulfate, and ammonium persulfate, and the amount of the initiator used is 0.01 to 3 weight ratio based on the total amount of acrylic acid type monomers.

[0014] Another technical solution adopted by the present invention is to provide a waterborne polyurethane resin, which is prepared by the preparation method of the waterborne polyurethane resin of the present invention, and the waterborne polyurethane resin includes a cyclic structure.

[0015] One of the beneficial effects of the present invention is that the waterborne polyurethane resin and the preparation method thereof provided by the present invention can improve the thermal stability of the resin through the technical scheme of "at least one of the polyol, the polyisocyanate and the acrylic monomer includes a compound with a cyclic structure".

[0016] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of the method for preparing the waterborne polyurethane resin. DETAILED DESCRIPTION

[0018] The following is an explanation of the implementation methods of the "waterborne polyurethane resin and its preparation method" disclosed in the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0019] See also Figure 1 The present invention provides a method for preparing a waterborne polyurethane resin, which comprises the following steps: S100 preparation of a prepolymer, S200 dilution of the prepolymer, S300 water dispersion and chain extension, and S400 acrylic synthesis, wherein at least one of the polyols, polyisocyanates, and acrylic monomers in the reactants for preparing the waterborne polyurethane resin comprises a compound with a cyclic structure. More specifically, at least one of the polyols, polyisocyanates, and acrylic monomers comprises a cyclic structure, and a compound with a cyclic structure refers to a compound in which atoms in the molecule are arranged in a ring, for example, an alicyclic compound or an aromatic hydrocarbon. Preferably, the acrylic monomer comprises a cyclic structure.

[0020] Preparation of S100 prepolymer: 15 to 25 wt% of polyol is vacuum dehydrated and then added to a reaction tank, which is heated to 70 to 80° C. in an oil bath, and 5 to 12 wt% of polyisocyanate is added to the reaction tank to undergo a synthesis reaction to obtain a prepolymer.

[0021] The polyol is selected from the group consisting of polyester polyol and polyether polyol. That is, polyester polyol or polyether polyol can be used alone, or a mixture of different polyester polyols and polyether polyols can be used.

[0022] The polyester polyol can be obtained by condensing a low molecular weight diol with a dicarboxylic acid. For example, a condensation-type polyester polyol is obtained by condensing a low molecular weight polyol such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, etc., with an aliphatic dicarboxylic acid such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, etc.

[0023] In addition, cyclic esters such as ε-caprolactone, polyester amide polyols in which a part of diol is reacted to form amines such as hexamethylenediamine and isophorone diamine, etc. can also be used.

[0024] In addition, polyester polyols can also be polymerized from 1,4-cyclohexanedimethanol or tricyclodecane dimethanol (TCD-alcohol) and dibasic acid. For example, polycyclohexane dimethyl ester polymerized from 1,4-cyclohexanedimethanol and dibasic acid, and polytricyclodecane dimethyl ester polymerized from tricyclodecane dimethanol (TCD-alcohol) and dibasic acid are shown below:

[0025]

[0026] The polyether polyol is selected from the group consisting of polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), and polyethylene glycol (PEG) in the main chain and the side chain.

[0027] The diisocyanate may be an aliphatic diisocyanate, an alicyclic diisocyanate or an aromatic diisocyanate. Preferably, the diisocyanate is an alicyclic diisocyanate having a cyclic structure.

[0028] For example, the aliphatic diisocyanate may be tetramethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, or lysine diisocyanate.

[0029] For example, the alicyclic diisocyanate can be toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), tetramethylxylenediisocyanate (tetramethylxylenediisocyanate), dicyclohexylmethane diisocyanate (4,4'-Methylene dicyclohexyldiisocyanate, H12MDI), trimethylhexamethylenediisocyanate (trimethylhexamethylenediisocyanate, TMDI).

[0030] For example, the aromatic polyisocyanate may be 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'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, -diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, aromatic diisocyanates such as 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, polyphenylene polymethylene polyisocyanate, and crude tolylene diisocyanate.

[0031] Preferably, the diisocyanate is isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (H12MDI).

[0032] Dilution of S200 prepolymer: 10 to 30 wt % of acrylic monomer is added to the prepolymer to dilute and reduce viscosity, and the temperature is maintained between 85 and 90° C. The reaction is carried out for 2 to 3 hours until the NCO% reaches the target value, and then 1.8 to 3.7 wt % of sulfonate hydrophilic agent is added, and the reaction is continued for 25 to 40 minutes to obtain a polymer.

[0033] The acrylic monomer can be selected from the group consisting of cyclohexyl methacrylate, isobornyl methacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, isooctyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, 2-hydroxyethyl acrylate, monomethyl maleate, monomethyl itaconate, monomethyl fumarate, and styrene. Preferably, the acrylic monomer is selected from a mixture of multiple monomers. More preferably, the acrylic monomer is an acrylic monomer combined with an acrylic monomer having a ring structure.

[0034] Preferably, the acrylic monomer is selected from the group consisting of cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBOMA), 2-hydroxyethyl acrylate (2-HEA), methyl methacrylate (MMA) and ethyl acrylate (EA).

[0035] In more detail, 2-hydroxyethyl acrylate, methyl methacrylate and ethyl acrylate can be used as solvents to omit acetone used in the general prior art. 2-hydroxyethyl acrylate contains a hydroxyl group (-OH) that can react with isocyanate. Methyl methacrylate and ethyl acrylate can increase the molecular weight of acrylic, thereby improving the mechanical strength and water resistance of waterborne polyurethane.

[0036] In addition, cyclohexyl methacrylate and isobornyl methacrylate both have a cyclic structure, which can improve the heat yellowing resistance of the resin, as shown in the following structural formula.

[0037]

[0038] Specifically, the acrylic monomer of the present invention is a combination of the following acrylic monomers:

[0039] The content of methyl methacrylate is 50 to 90 wt %;

[0040] The content of 2-hydroxyethyl acrylate is 4 to 9 wt %;

[0041] The content of ethyl acrylate is 2 to 6 wt%;

[0042] The content of cyclohexyl methacrylate is 0 to 15 wt %; and

[0043] The content of isobornyl methacrylate is 0 to 20 wt %.

[0044] Preferably, if only acrylic monomers are used, other cyclic components must be included in other components of the waterborne polyurethane. However, cyclohexyl methacrylate and isobornyl methacrylate having cyclic structures can provide better yellowing resistance.

[0045] More preferably, the acrylic monomer of the present invention is a combination of the following acrylic monomers:

[0046] The content of methyl methacrylate is 50 to 90 wt %;

[0047] The content of 2-hydroxyethyl acrylate is 4 to 9 wt %;

[0048] The content of ethyl acrylate is 2 to 6 wt%;

[0049] The content of cyclohexyl methacrylate is 7 to 14 wt %; and

[0050] The content of isobornyl methacrylate is 10 to 18 wt %.

[0051] The sulfonate hydrophilic agent is used as a polyurethane hydrophilic agent and can be used as a polymer emulsifier. Preferably, the sulfonate hydrophilic agent is sodium ethylenediamine ethoxyethane sulfonate.

[0052] The target NCO% value refers to the percentage of the weight of the remaining isocyanate groups in the weight of all reactants involved after the isocyanate groups (-NCO) of the polyisocyanate and the hydroxyl groups (-OH) contained in the polyols are completely reacted in the polyurethane (PU) reaction. The target NCO% value = (amount of polyisocyanate / molecular weight of polyisocyanate - amount of polyols / molecular weight of polyols) × 42 × 2 × %, and the target NCO% value is 0.5-10%. In the embodiment, the NCO% reaction titration value is the NCO% measured by dibutylamine titration method during the reaction, that is, before adding water and emulsifying in the preparation method.

[0053] Since the NCO% reaction titration value of the polyurethane resin is between 50% and 85% of the NCO% theoretical value, it is in a stable dispersed state in the aqueous polyurethane dispersion, and the polyurethane resin is prevented from generating agglomeration gel. If the polyisocyanate is consumed excessively during the synthesis of polyurethane, so that the NCO% reaction titration value is lower than 50% of the NCO% target value, the polyurethane network structure crosslinking degree is too high due to the excessive reaction of the polyurethane, and then the polyurethane generates a large amount of agglomeration gel in the water phase and fails; if the NCO% reaction titration value is higher than 85% of the NCO% target value, the network structure ratio of the synthesized polyurethane is insufficient, resulting in excessive viscosity on the surface of the waterborne polyurethane film after processing, which is easy to cause adhesion between films and cause scrapping.

[0054] S300 water dispersion and chain extension: cool the polymer in step S200 to room temperature, add 35 to 55 wt% of deionized water at a speed of 500 rpm, and then add 0.1 to 0.5 wt% of chain extender to carry out chain extension reaction for about 30 minutes to obtain waterborne polyurethane.

[0055] By adjusting the ratio of diisocyanate, polyol and ionized water, the foaming properties of the finished product can be improved. The chain extender can be a low molecular weight polyamine with a (number average) molecular weight of less than 500 such as ethylenediamine, hexamethylenediamine, xylene diamine, isophorone diamine, diethylenetriamine, N-aminoethyl-N-ethanolamine, etc.

[0056] S400 acrylic synthesis: add 0.3 to 1.0 wt% of emulsifier to the waterborne polyurethane in step S300 to form an emulsion, stir evenly and heat to 50 to 70° C., then drop 0.01 to 0.10 wt% of initiator, polymerize acrylic at 75 to 85° C. for 1 to 3 hours, cool to 50 to 70° C. and add 0.01 to 0.08 wt% of reducing agent to obtain a waterborne polyurethane resin.

[0057] Specifically, the emulsifier may be anionic, nonionic or reactive emulsifiers. For example, octylphenoxyethyl poly(39)-ethoxyethanol, dodecyloxy poly(10)ethoxyethanol, nonylphenoxyethyl-poly(40)ethoxyethanol, polyethylene glycol 2000 monooleate, hydroxyethylated castor oil, fluorinated alkyl esters and alkoxylates, polyoxyethylene (20) sorbitol monolaurate, sucrose monococonut ester, di(2-butyl)phenoxy poly(20)ethoxyethanol, hydroxyethylcellulose polybutyl acrylate graft copolymer. Emulsifier is a surfactant that can greatly reduce the surface tension and transform the immiscible oil-water phases into a stable and non-separable white emulsion through stirring.

[0058] The ionic emulsifier can be sodium dodecyl sulfate (SLS), sodium dodecylbenzene sulfonate, potassium stearate, sodium dioctyl sulfosuccinate, sodium dodecyl diphenyloxy disulfonate, nonylphenoxyethyl poly (1) ethoxyethyl sulfate ammonium salt, sodium styrene sulfonate, sodium dodecyl allyl sulfosuccinate, linseed oil fatty acid, sodium or ammonium salt of ethoxylated nonylphenol phosphate, sodium octoxynol-3-sulfonate, sodium cocoyl sarcosine, sodium 1-alkoxy-2-hydroxypropyl sulfonate, sodium α-olefin (C14-C16) sulfonate, sulfate of hydroxyalkanol, tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinamate, disodium N-octadecyl sulfosuccinamate, disodium alkanoyl polyethoxy sulfosuccinate, disodium ethoxylated nonphenol sulfosuccinate half ester, sodium ethoxyethyl sulfate.

[0059] Further, the initiator may be hydrogen peroxide, tert-butyl peroxide, alkali metal persulfates such as sodium, potassium and lithium persulfates, and ammonium persulfate (APS).

[0060] Further, the reducing agent can be a sulfite such as alkali metal metasulfite, bisulfite and hyposulfite, sodium formaldehyde sulfoxylate (SFS), tert-butyl hydroperoxide (TBHP) and reducing sugars such as ascorbic acid and isoascorbic acid. In the later stage of emulsion polymerization, in order to avoid emulsion coagulation caused by temperature increase, a reducing agent can be used to post-eliminate the monomer at 50-70°C to reduce the monomer residual rate.

[0061] The present invention is further described by the following examples and comparative examples. However, the examples are only feasible implementations and are not intended to limit the present invention.

[0062] Example 1

[0063] Tricyclodecane dimethanol (TCD-alcohol) and adipic acid (AA) are used to synthesize polyester polyol. 78.8g PTMG2000 (polyether diol, molecular weight 2000), 6.44g 1,4-BG (1,4-butanediol, molecular weight 90) and 20g of the above polyester polyol are mixed in a reaction tank, stirred at a constant speed and heated to 80°C, 51.3g dicyclohexylmethane diisocyanate (H12MDI) is added, the temperature is raised to 85 to 90°C, and the reaction is carried out at this temperature for 2 to 3 hours. Next, 147.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), and 4.8 g of ethyl acrylate (EA) were added in batches as acrylic monomers, and 26.4 g of sodium ethylenediamine ethoxyethanesulfonate was added to the prepolymer. After the reaction was continued for 25 to 40 minutes, the temperature was lowered to room temperature, 472.6 g of deionized water was added at a rotation speed of 500 rpm, and then 1.9 g of ethylenediamine was added to carry out chain extension reaction for about 30 minutes to obtain waterborne polyurethane.

[0064] 4.8 g of sodium dodecyl sulfate (SLS) was added to the above waterborne polyurethane under rapid stirring, and the temperature was raised to 50 to 70° C., and then 0.40 g of ammonium persulfate aqueous solution (APS) was added dropwise, and the temperature was continued to rise to 75 to 85° C. and kept constant at this temperature for 1 to 3 hours. After cooling to 50 to 70° C., 0.15 g of reducing agent tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) were added, and the reaction was carried out for 30 minutes to obtain acrylic grafted modified waterborne polyurethane.

[0065] Example 2

[0066] Mix 98.8g PTMG2000 (polyether diol, molecular weight 2000) and 6.44g 1,4-BG (1,4-butanediol, molecular weight 90) in a reaction tank, stir at a constant speed and heat to 80°C, add 43.5g isophorone diisocyanate (IPDI), heat to 85 to 90°C, and react at this temperature for 2 to 3 hours. Next, 127.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 4.8 g of ethyl acrylate (EA), 16.8 g of cyclohexyl methacrylate (CHMA) and 22.2 g of isobornyl methacrylate (IBOMA) were added in batches as acrylic monomers, 26.4 g of sodium ethylenediamine ethoxyethanesulfonate was added to the prepolymer, and the reaction was continued for 25 to 40 minutes, then cooled to room temperature, 472.6 g of deionized water was added at a rotation speed of 500 rpm, and then 1.9 g of ethylenediamine was added to carry out chain extension reaction for about 30 minutes to obtain waterborne polyurethane.

[0067] 4.8 g of sodium dodecyl sulfate (SLS) was added to the above waterborne polyurethane under rapid stirring, and the temperature was raised to 50 to 70° C., and then 0.40 g of ammonium persulfate aqueous solution (APS) was added dropwise, and the temperature was continued to rise to 75 to 85° C. and kept constant at this temperature for 1 to 3 hours. After cooling to 50 to 70° C., 0.15 g of reducing agent tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) were added, and the reaction was carried out for 30 minutes to obtain acrylic grafted modified waterborne polyurethane.

[0068] Example 3

[0069] Tricyclodecane dimethanol (TCD-alcohol) and adipic acid (AA) are used to synthesize polyester polyol. 78.8g PTMG2000 (polyether diol, molecular weight 2000), 6.44g 1,4-BG (1,4-butanediol, molecular weight 90) and 20g of the above polyester polyol are mixed in a reaction tank, stirred at a constant speed and heated to 80°C, 51.3g dicyclohexylmethane diisocyanate (H12MDI) is added, the temperature is raised to 85 to 90°C, and the reaction is carried out at this temperature for 2 to 3 hours. Next, 127.2 g of methyl methacrylate (MMA), 8 g of 2-hydroxyethyl acrylate (2-HEA), 4.8 g of ethyl acrylate (EA), 16.8 g of cyclohexyl methacrylate (CHMA) and 22.2 g of isobornyl methacrylate (IBOMA) were added in batches as acrylic monomers, 26.4 g of sodium ethylenediamine ethoxyethanesulfonate was added to the prepolymer, and the reaction was continued for 25 to 40 minutes, then cooled to room temperature, 472.6 g of deionized water was added at a rotation speed of 500 rpm, and then 1.9 g of ethylenediamine was added to carry out chain extension reaction for about 30 minutes to obtain waterborne polyurethane.

[0070] 4.8 g of sodium dodecyl sulfate (SLS) was added to the above waterborne polyurethane under rapid stirring, and the temperature was raised to 50 to 70° C., and then 0.40 g of ammonium persulfate aqueous solution (APS) was added dropwise, and the temperature was continued to rise to 75 to 85° C. and kept constant at this temperature for 1 to 3 hours. After cooling to 50 to 70° C., 0.15 g of reducing agent tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) were added, and the reaction was carried out for 30 minutes to obtain acrylic grafted modified waterborne polyurethane.

[0071] Comparative Example 1

[0072] Mix 98.8g PTMG2000 (polyether diol, molecular weight 2000) and 6.44g 1,4-BG (1,4-butanediol, molecular weight 90) in a reaction tank, stir at a uniform speed and heat to 80°C, add 43.5g isophorone diisocyanate (IPDI), heat to 85 to 90°C, and react at this temperature for 2 to 3 hours. Then, add 147.2g methyl methacrylate (MMA), 8g 2-hydroxyethyl acrylate (2-HEA), and 4.8g ethyl acrylate (EA) in batches to dilute and reduce viscosity, add 26.4g sodium ethylenediamine ethoxyethanesulfonate to the prepolymer, continue to react for 25 to 40 minutes, cool to room temperature, add 472.6g deionized water at 500rpm, and then add 1.9g ethylenediamine to carry out chain extension reaction for about 30 minutes to obtain waterborne polyurethane.

[0073] 4.8 g of sodium dodecyl sulfate (SLS) was added to the above waterborne polyurethane under rapid stirring, and the temperature was raised to 50 to 70° C., and then 0.40 g of ammonium persulfate aqueous solution (APS) was added dropwise, and the temperature was continued to rise to 75 to 85° C. and kept constant at this temperature for 1 to 3 hours. After cooling to 50 to 70° C., 0.15 g of reducing agent tert-butyl hydroperoxide aqueous solution (TBHP) and 0.16 g of sodium formaldehyde sulfoxylate (SFS) were added, and the reaction was carried out for 30 minutes to obtain acrylic grafted modified waterborne polyurethane.

[0074] The compositions of the above-mentioned Examples 1 to 3 and Comparative Example 1 are listed in Table 1, respectively. Furthermore, a plurality of waterborne polyurethane resins were applied to synthetic leather and the physical properties of the products were tested. The results are shown in Table 2:

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] [Beneficial Effects of Embodiments]

[0080] One of the beneficial effects of the present invention is that the waterborne polyurethane resin and the preparation method thereof provided by the present invention can improve the thermal stability of the resin through the technical scheme of "at least one of the polyol, the polyisocyanate and the acrylic monomer includes a compound with a cyclic structure".

[0081] Specifically, when the waterborne polyurethane resin of the prior art is used in synthetic leather fabrics or surface treatment agents, under high temperature conditions (120°C x 7 days), the heat yellowing resistance and weathering resistance are poor. Generally, additives such as light stabilizers, antioxidants and heat stabilizers are added to improve the yellowing. However, the degree of improvement is still not ideal.

[0082] Furthermore, the polyol of the present invention is preferably polycyclohexane dimethyl ester polymerized from 1,4-cyclohexanedimethanol and a dibasic acid, polytricyclodecane dimethyl ester polymerized from tricyclodecane dimethanol (TCD-alcohol) and a dibasic acid, and the diisocyanate is preferably isophorone diisocyanate (IPDI) and dicyclohexylmethane diisocyanate (H12MDI), and the structures of the multiple compounds all contain cyclic structures.

[0083] Furthermore, the acrylic monomer may be a combination of 2-hydroxyethyl acrylate (2-HEA), methyl methacrylate (MMA) and ethyl acrylate (EA), and further combined with cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBOMA) having a cyclic structure.

[0084] The invention introduces cyclic structures into polyol, polyisocyanate and acrylic monomer respectively, changes the segment structure, and enhances the intermolecular force to improve the thermal stability of waterborne polyurethane resin. The invention is applied to PVC rubber and PU synthetic leather treating agent, and can achieve the property of low heat yellowing ΔE at 120°C x 7 days.

[0085] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the protection scope of the claims of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention description and drawings are included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing an aqueous polyurethane resin, characterized in that: The preparation method of the waterborne polyurethane resin comprises the following steps: (1) Preparation of prepolymer: 105.24 g of a polyol was vacuum dehydrated and added to a reaction tank, heated in an oil bath to a temperature of 70 to 80° C., and then 51.3 g of a polyisocyanate was added to the reaction tank to undergo a synthesis reaction to obtain a prepolymer; (2) Dilution of the prepolymer: 179 g of an acrylic monomer is added to the prepolymer to dilute and reduce viscosity, and the temperature is maintained between 85 and 90° C. The reaction is carried out for 2 to 3 hours until the NCO% reaches the target value, and then 26.4 g of a sulfonate hydrophilic agent is added and the reaction is continued for 25 to 40 minutes to obtain a polymer; and (3) Water dispersion and chain extension: The polymer of step (2) was cooled to room temperature, and 472.6 g of deionized water was added at a rotation speed of 500 rpm, and then 1.9 g of a chain extender was added to carry out a chain extension reaction for about 30 minutes to obtain a waterborne polyurethane; and (4) Acrylic synthesis: 4.8 g of an emulsifier is added to the waterborne polyurethane in step (3) to form an emulsion, and the mixture is stirred evenly and then heated to 50 to 70° C., and then 0.4 g of an initiator is added dropwise, and acrylic polymerization is carried out at a temperature of 75 to 85° C. for 1 to 3 hours. After cooling to 50 to 70° C., 0.15 g of a reducing agent is added to obtain a waterborne polyurethane resin; Wherein, at least one of the polyol, the polyisocyanate and the acrylic monomer comprises a compound having a cyclic structure; Wherein, the acrylic monomer includes cyclohexyl methacrylate and isobornyl methacrylate.

2. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The polyol, the polyisocyanate and the acrylic monomer all include compounds with a cyclic structure.

3. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The polyol is selected from the group consisting of polyester polyol, polyether polyol and polycarbonate polyol.

4. The method for preparing an aqueous polyurethane resin according to claim 3, characterized in that: The polyester polyol is prepared by polymerizing 1,4-cyclohexanedimethanol or tricyclodecane dimethanol and a dibasic acid.

5. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The polyisocyanate is a diisocyanate selected from the group consisting of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and the like.

6. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The polyol reacts with the polyisocyanate at an NCO / OH equivalent ratio of 1.1 to 2.

3.

7. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The acrylic monomer further includes an acrylic acid monomer, and the acrylic acid monomer is selected from the group consisting of 2-hydroxyethyl acrylate, methyl methacrylate and ethyl acrylate.

8. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The content of the cyclohexyl methacrylate was 16.8 g, and the content of the isobornyl methacrylate was 22.2 g.

9. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The acrylic monomer is: (a) methyl methacrylate content: 127.2 g; (b) 2-hydroxyethyl acrylate content 8 g; (c) ethyl acrylate content 4.8 g; (d) cyclohexyl methacrylate content 16.8 g; and (e) Content of isobornyl methacrylate: 22.2 g.

10. The method for preparing an aqueous polyurethane resin according to claim 1, characterized in that: The initiator is selected from the group consisting of hydrogen peroxide, tert-butyl peroxide, sodium persulfate, potassium and lithium persulfate, and ammonium persulfate, and the amount of the initiator used is 0.01 to 3 weight ratio based on the total amount of acrylic acid monomers.

11. The method for preparing an aqueous polyurethane resin according to any one of claims 1, 8 or 9, characterized in that: The polymer polyol includes polyester polyol, and the polyester polyol is polymerized by tricyclodecane dimethanol and adipic acid.

12. The method for preparing an aqueous polyurethane resin according to any one of claims 1, 8 or 9, characterized in that: The polyol comprises 20 g of polyester polyol, 78.8 g of polyether diol and 6.44 g of 1,4-butanediol; wherein the polyester polyol is polymerized by tricyclodecane dimethanol and adipic acid.

13. The method for preparing an aqueous polyurethane resin according to claim 12, characterized in that: The polyisocyanate is dicyclohexylmethane diisocyanate.

14. A waterborne polyurethane resin, characterized in that The waterborne polyurethane resin is prepared according to the preparation method of the waterborne polyurethane resin according to claim 1, and the waterborne polyurethane resin includes a cyclic structure.

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