A waterborne polyurethane and its neutralization preparation method and application

Abstract

This invention relates to the field of polymer materials, and specifically discloses a waterborne polyurethane, its neutralization preparation method, and its applications. This waterborne polyurethane is prepared by mixing the following raw materials in parts by weight: 10-30 parts by weight of a polyurethane prepolymer containing carboxyl functional groups, 5-25 parts by weight of a polyurethane prepolymer containing amino functional groups, 0.6-2.0 parts by weight of an organic amine chain extender, and 50-80 parts by weight of deionized water; wherein the polyurethane solid content accounts for 20-50% of the total weight of the raw materials. The preparation process of this invention is simple, the product is stable during storage, and it does not contain volatile or migrating amine neutralizing agents such as triethylamine or dimethylethanolamine, thus meeting the stringent regulatory requirements for applications such as food contact materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to an aqueous polyurethane and its neutralization preparation method and application. Background Technology

[0002] The environmentally friendly properties of waterborne polyurethane are well-known, and its replacement of solvent-based polyurethane is an inevitable development trend. Waterborne polyurethane is mostly prepared using prepolymer mixing or acetone methods, employing dimethylolpropionic acid or dimethylolbutyric acid as hydrophilic monomers to introduce carboxyl functional groups. Tertiary amines such as triethylamine and dimethylethanolamine are added to neutralize and form salts, making it easy to disperse or emulsify in water. The resulting waterborne polyurethane exhibits stable storage, excellent performance, and a wide range of applications.

[0003] Of the products mentioned above, triethylamine and dimethylethanolamine only act as carboxyl neutralizers and do not actually link to the polymer macromolecules. During the drying and film-forming process, most of the triethylamine and dimethylethanolamine evaporate into the air, while a small portion remains in the polymer coating due to limitations in drying temperature and time. Besides affecting operations and the atmospheric environment, the migration of residual amines severely impacts the application of waterborne polyurethane products in food contact materials and other applications with stringent regulatory requirements. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a waterborne polyurethane, its neutralization preparation method, and its application. This waterborne polyurethane is stable during storage and does not contain volatile and migratable amine neutralizing agents such as triethylamine or dimethylethanolamine. The coating film prepared by this invention overcomes the volatilization and migration of organic amines during drying and use, and can meet the application requirements of food contact materials and other materials with strict regulatory requirements.

[0005] This invention is achieved through the following technical solution: A waterborne polyurethane is prepared by mixing the following raw materials in parts by weight: 10-30 parts by weight of polyurethane prepolymer containing carboxyl functional groups, 5-25 parts by weight of polyurethane prepolymer containing amino functional groups, 0.6-2.0 parts by weight of organic amine chain extender, and 50-80 parts by weight of deionized water; wherein the polyurethane solid content accounts for 20-50% of the total weight of the raw materials.

[0006] This invention designs a polyurethane prepolymer containing carboxyl functional groups and a polyurethane prepolymer containing amino functional groups. After mixing and neutralizing the two, they are dispersed or emulsified in water and then chain extended to form an aqueous polyurethane, so as to achieve the purpose of not containing volatile and migratable amine neutralizing agents such as triethylamine or dimethylethanolamine.

[0007] A more preferred technical solution of the present invention is as follows: The carboxyl-functionalized polyurethane prepolymer is composed of the following components in parts by weight: The polymer polyol comprises 30-80 parts by weight, isocyanate monomer comprises 10-50 parts by weight, dimethylolpropionic acid or dimethylolbutyric acid comprises 1.5-6.0 parts by weight, trimethylolpropane comprises 0-3 parts by weight, catalyst comprises organotin, organobismuth or organosilver comprises 0.01-0.03 parts by weight, and organic solvent comprises N-methylpyrrolidone, acetone or butanone comprises 0-30 parts by weight.

[0008] The amino-functionalized polyurethane prepolymer is composed of the following components in parts by weight: The polymer polyol comprises 30-80 parts by weight, isocyanate monomer comprises 20-50 parts by weight, methyl diethanolamine, diethanolamine or triethanolamine comprises 2.0-8.0 parts by weight, trimethylolpropane comprises 0-3 parts by weight, catalyst comprises organotin, organobismuth or organosilver comprises 0.01-0.03 parts by weight, and organic solvent comprises N-methylpyrrolidone, acetone or butanone comprises 0-30 parts by weight.

[0009] More preferably, in the polyurethane prepolymer containing carboxyl functional groups and the polyurethane prepolymer containing amino functional groups, the polymer polyol is one or more of polyester polyol, polytetrahydrofuran ether polyol, ethylene oxide polyether polyol, propylene oxide polyether polyol, polybutadiene polyol, polycarbonate polyol and polyacrylate polyol, with a molecular weight of 1000-3000 and a functionality of 2-3.

[0010] Further preferably, in the polyurethane prepolymer containing carboxyl functional groups and the polyurethane prepolymer containing amino functional groups, the isocyanate monomer is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, tetramethylphenyldimethyl diisocyanate, phenyldimethyl diisocyanate, and 2,4 / 2,6-toluene diisocyanate.

[0011] The organic amine chain extender is one or more of the following: ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, hydrazine hydrate, isophorone diamine, diethylenetriamine, 4,4-diaminodicyclohexylmethane, and dimethylethylenediamine.

[0012] This invention also discloses a method for neutralizing and preparing the above-mentioned waterborne polyurethane, comprising the following steps: S1, add polymer polyol, isocyanate monomer, dimethylolpropionic acid or dimethylolbutyric acid, trimethylolpropane, catalyst, and organic solvent to a reaction vessel according to the formula, wherein the isocyanate monomer is in excess, and react at 50-90℃ until the NCO content reaches or is less than the theoretical value to obtain a polyurethane prepolymer containing carboxyl functional groups. S2, add polymer polyol, isocyanate monomer, methyl diethanolamine or diethanolamine or triethanolamine, trimethylolpropane, catalyst and organic solvent to the reaction vessel according to the formula, wherein the isocyanate monomer is in excess, and react at 50-90℃ until the NCO content reaches or is less than the theoretical value to obtain a polyurethane prepolymer containing amino functional groups. S3, a polyurethane prepolymer containing carboxyl functional groups and a polyurethane prepolymer containing amino functional groups are mixed together, then dispersed in deionized water, and an organic amine chain extender is added to finally obtain waterborne polyurethane.

[0013] In the mixing process of the polyurethane prepolymer containing carboxyl functional groups and the polyurethane prepolymer containing amino functional groups of the present invention, hydrophilic polymers are formed by the neutralization and salt formation of carboxyl and amino groups, thereby achieving the water-dispersibility or emulsification of the polymer. After subsequent treatment with organic amine chain extenders, waterborne polyurethane is formed. At this time, the carboxyl neutralizing agent tertiary amine is anchored to the polymer macromolecular chain, avoiding its volatilization and migration during the film-forming and drying process.

[0014] More preferably, step S3 specifically includes the following steps: S31, the polyurethane prepolymer containing carboxyl functional groups obtained in step S1 and the polyurethane prepolymer containing amino functional groups obtained in step S2 are cooled to 20-40℃ respectively, and then the two are mixed together and stirred thoroughly. S32: The mixture obtained in S31 is dispersed at high speed into deionized water, and an organic amine chain extender is added to the deionized water. The mixture is reacted at 10-50℃ for 20-40 minutes to finally obtain waterborne polyurethane.

[0015] More preferably, in steps S1 and S2, when the organic solvent is acetone or butanone, the aqueous polyurethane is separated by heating and depressurization; if the organic solvent is N-methylpyrrolidone, the solvent does not need to be separated.

[0016] The present invention also discloses the application of the above-mentioned waterborne polyurethane in food contact materials, which meets the stringent requirements of relevant regulations.

[0017] The preparation process of this invention is simple, the product is stable during storage, and it does not contain volatile or migrating amine neutralizing agents such as triethylamine or dimethylethanolamine, which can meet the application requirements of food contact materials with stringent regulations. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Example 1: Preparation of waterborne polyurethane This embodiment specifically includes the following steps: S1, The preparation method of polyurethane prepolymer containing carboxyl functional groups is as follows: First, add 59.1g of poly(1,4-butanediol) diol (molecular weight 2000), 2.1g of trimethylolpropane, 4.0g of dimethylolpropionic acid, 34.8g of isophorone diisocyanate, 0.01g of organic bismuth catalyst, and 20.0g of acetone (separated at the end and not included in the total weight) to a reactor and react at 58±0.5℃ for 3-4 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0020] S2, the preparation method of the amino-functionalized polyurethane prepolymer is as follows: First, add 68.5g of poly(1,4-butanediol) diol (molecular weight 2000), 3.5g of methyl diethanolamine, 28.0g of isophorone diisocyanate, 0.01g of organic bismuth catalyst, and 20.0g of acetone (separated at the end and not included in the total weight) to a reactor and react at 58-65℃ for 3.5 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0021] S3, mix all the polyurethane prepolymers with carboxyl functional groups and polyurethane prepolymers with amino functional groups prepared above together and stir thoroughly until homogeneous. The mixture was dispersed at high speed into 370.0 g of deionized water, and 7.8 g of chain extender ethylenediamine was added. The reaction was carried out at 25–35 °C for 30 minutes. The product was then separated from the acetone under heating and negative pressure conditions. The final solid content of the obtained waterborne polyurethane was 36.0%.

[0022] Example 2: Preparation of waterborne polyurethane This embodiment specifically includes the following steps: S1, The preparation method of polyurethane prepolymer containing carboxyl functional groups is as follows: First, add 67.2g of polytetrahydrofuran ether diol (molecular weight 3000), 3.6g of dimethylolpropionic acid, 17.2g of isophorone diisocyanate, 0.01g of organobismuth catalyst, and 12.0g of N-methylpyrrolidone to a reaction vessel and react at 75±0.5℃ for 3 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0023] S2, the preparation method of the amino-functionalized polyurethane prepolymer is as follows: First, add 47.5g of polytetrahydrofuran ether diol (molecular weight 2000), 1.3g of trimethylolpropane, 6.4g of methyldiethanolamine, 34.3g of isophorone diisocyanate, 0.01g of organic bismuth catalyst, and 10.5g of N-methylpyrrolidone to a reaction vessel and react at 75±0.5℃ for 4 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0024] S3. Take 100g of the polyurethane prepolymer containing carboxyl functional groups and 50g of the polyurethane prepolymer containing amino functional groups prepared above, mix them together, and stir thoroughly.

[0025] The mixture was dispersed at high speed into 234.5g of deionized water, and 2.8g of chain extender hydrazine hydrate was added. The mixture was reacted at 35°C for 30 minutes, and the final solid content of the resulting waterborne polyurethane was 35.0%.

[0026] Example 3: Preparation of waterborne polyurethane This embodiment specifically includes the following steps: S1, The preparation method of polyurethane prepolymer containing carboxyl functional groups is as follows: First, add 63.8g of propylene oxide polyether diol (molecular weight 2000), 6.2g of dimethylolpropionic acid, 30.0g of isophorone diisocyanate, and 0.01g of organic bismuth catalyst to a reaction vessel and react at 80±0.5℃ for 3 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 35℃ and keep it at that temperature for later use.

[0027] S2, the preparation method of the amino-functionalized polyurethane prepolymer is as follows: First, add 30.8g of propylene oxide polyether diol (molecular weight 2000), 30.8g of polytetrahydrofuran ether diol (molecular weight 2000), 5.4g of methyl diethanolamine, 33.0g of isophorone diisocyanate, and 0.01g of organic bismuth catalyst to a reaction vessel and react at 70±0.5℃ for 4 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 35℃ and keep it at that temperature for later use.

[0028] S3, mix all the polyurethane prepolymers with carboxyl functional groups and polyurethane prepolymers with amino functional groups prepared above together and stir thoroughly until homogeneous. The mixture was dispersed at high speed into 466.0 g of deionized water, and 5.1 g of chain extender hydrazine hydrate and 6.8 g of isophorone diamine were added. The mixture was reacted at 40 °C for 30 minutes. The final solid content of the resulting waterborne polyurethane was 31.1%.

[0029] Example 4: Preparation of waterborne polyurethane This embodiment specifically includes the following steps: S1, The preparation method of polyurethane prepolymer containing carboxyl functional groups is as follows: First, add 30.0g of polycarbonate diol (molecular weight 2000), 30.0g of poly(2-methylpropanediol adipate) diol (molecular weight 1500), 3.0g of dimethylolpropionic acid, 12.0g of isophorone diisocyanate, 10.0g of dicyclohexylmethane diisocyanate, 0.01g of organic bismuth catalyst, and 15.0g of N-methylpyrrolidone to a reaction vessel and react at 75±0.5℃ for 4 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0030] S2, the preparation method of the amino-functionalized polyurethane prepolymer is as follows: First, add 49.2g of poly(2-methylpropanediol adipate) diol (molecular weight 1500), 2.3g of diethanolamine, 20.0g of isophorone diisocyanate, 0.01g of organic bismuth catalyst, and 28.5g of N-methylpyrrolidone to a reaction vessel and react at 65±0.5℃ for 4 hours until the NCO content reaches or is slightly less than the theoretical value. Then, cool the polymer to 25℃ and keep it at that temperature for later use.

[0031] S3. Take all the polyurethane prepolymers containing carboxyl functional groups and polyurethane prepolymers containing amino functional groups prepared above, mix them together, and stir thoroughly until homogeneous.

[0032] The mixture was dispersed at high speed into 140.2g of deionized water, and 3.3g of chain extender hydrazine hydrate was added. The mixture was reacted at 30°C for 30 minutes, and the final solid content of the resulting waterborne polyurethane was 45.5%.

[0033] Application example: The products obtained in Examples 1-4 were tested for solid content and emulsion storage stability, and the results are as follows: Example 1 Example 2 Example 3 Example 4 Test methods Solid content (%) 36.0 35.0 31.1 45.5 GB / T1725-2007 Storage stability No agglomeration, clumping, or other residues. No agglomeration, clumping, or other residues. No agglomeration, clumping, or other residues. No agglomeration, clumping, or other residues. 10 days at 50℃ .

[0034] Currently, in the packaging industry, most commercially available anionic waterborne polyurethane products use triethylamine, dimethylethanolamine, diethanolamine, and triethanolamine as amine neutralizing agents. According to the current national standard GB9685-2016, "National Food Safety Standard for the Use of Additives in Food Contact Materials and Articles" (including Amendment No. 1), triethylamine and diethanolamine are not included in the list of permitted additives. Dimethylethanolamine is authorized for use, with a specific range (SML) of 0.1 mg / kg. Although no specific SML is set for triethanolamine, its migration amount still needs to meet the general requirements in the standard, namely, the total specific migration amount should be ≤60 mg / kg (≤15 mg / kg for infant food contact materials and articles; the SML in EU regulations is 0.05 mg / kg).

[0035] Commercially available waterborne polyurethane products PUD-987F, PUD-805H, and PUD-1209 were selected and compared with the products obtained in Examples 1-4 above in coating tests. The dry film thickness was 8 micrometers, and the drying conditions were 130°C for 5 minutes. The migration amount of organic amines in the dried coating was measured. The experimental results are as follows: .

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A waterborne polyurethane, characterized in that, It is made by mixing the following raw materials in parts by weight: 10-30 parts by weight of polyurethane prepolymer containing carboxyl functional groups, 5-25 parts by weight of polyurethane prepolymer containing amino functional groups, 0.6-2.0 parts by weight of organic amine chain extender, and 50-80 parts by weight of deionized water; wherein the polyurethane solid content accounts for 20-50% of the total weight of the raw materials.

2. The waterborne polyurethane as described in claim 1, characterized in that, The carboxyl-functionalized polyurethane prepolymer is composed of the following components in parts by weight: 30-80 parts by weight of polymeric polyol, 10-50 parts by weight of isocyanate monomer, 1.5-6.0 parts by weight of dimethylolpropionic acid or dimethylolbutyric acid, 0-3 parts by weight of trimethylolpropane, 0.01-0.03 parts by weight of catalyst organotin, organobismuth or organosilver, and 0-30 parts by weight of organic solvent N-methylpyrrolidone, acetone or butanone.

3. The waterborne polyurethane as described in claim 1, characterized in that, The amino-functionalized polyurethane prepolymer is composed of the following components in parts by weight: 30-80 parts by weight of polymeric polyol, 20-50 parts by weight of isocyanate monomer, 2.0-8.0 parts by weight of methyldiethanolamine, diethanolamine or triethanolamine, 0-3 parts by weight of trimethylolpropane, 0.01-0.03 parts by weight of catalyst organotin, organobismuth or organosilver, and 0-30 parts by weight of organic solvent N-methylpyrrolidone, acetone or butanone.

4. The waterborne polyurethane as described in claim 1, characterized in that: The organic amine chain extender is one or more of the following: ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, hydrazine hydrate, isophorone diamine, diethylenetriamine, 4,4-diaminodicyclohexylmethane, and dimethylethylenediamine.

5. The waterborne polyurethane as described in claim 2 or 3, characterized in that: The polymer polyol is one or more of polyester polyol, polytetrahydrofuran ether polyol, ethylene oxide polyether polyol, propylene oxide polyether polyol, polybutadiene polyol, polycarbonate polyol and polyacrylate polyol, with a molecular weight of 1000-3000 and a functionality of 2-3.

6. The waterborne polyurethane as described in claim 2 or 3, characterized in that: The isocyanate monomer is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, tetramethylphenyldimethyl diisocyanate, phenyldimethyl diisocyanate, and 2,4 / 2,6-toluene diisocyanate.

7. The method for neutralizing and preparing waterborne polyurethane according to any one of claims 1-4, characterized in that, The process includes the following steps: S1, adding polymer polyol, isocyanate monomer, dimethylolpropionic acid or dimethylolbutyric acid, trimethylolpropane, catalyst, and organic solvent to a reaction vessel according to the formula, wherein the isocyanate monomer is in excess, and reacting at 50-90℃ until the NCO content reaches or is less than the theoretical value, to obtain a polyurethane prepolymer containing carboxyl functional groups; S2, adding polymer polyol, isocyanate monomer, methyl diethanolamine or diethanolamine or triethanolamine, trimethylolpropane, catalyst, and organic solvent to a reaction vessel according to the formula, wherein the isocyanate monomer is in excess, and reacting at 50-90℃ until the NCO content reaches or is less than the theoretical value, to obtain a polyurethane prepolymer containing amino functional groups; S3, mixing the polyurethane prepolymer containing carboxyl functional groups and the polyurethane prepolymer containing amino functional groups together, then dispersing them in deionized water, while adding an organic amine chain extender, to finally obtain waterborne polyurethane.

8. The neutralization preparation method according to claim 7, characterized in that... Step S3 specifically includes the following steps: S31, cooling the polyurethane prepolymer containing carboxyl functional groups obtained in step S1 and the polyurethane prepolymer containing amino functional groups obtained in step S2 to 20-40℃ respectively, then mixing the two together and stirring thoroughly; S32, dispersing the mixture obtained in S31 into deionized water at high speed, adding an organic amine chain extender to the deionized water, and reacting at 10-50℃ for 20-40 min to finally obtain waterborne polyurethane.

9. The neutralization preparation method according to claim 7, characterized in that: In steps S1 and S2, when the organic solvent is acetone or butanone, the aqueous polyurethane is separated by heating and depressurization.

10. The use of the waterborne polyurethane as described in any one of claims 1-4 in food contact materials.