Modified polyurethane and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane modification, in particular to modified polyurethane and a preparation method thereof.The modified polyurethane is of a core-shell structure, a core of the modified polyurethane comprises polyurethane, a shell layer of the modified polyurethane comprises polyacrylate, and the shell layer of the modified polyurethane comprises a core-shell structure. Polyurethane and polyacrylate are connected through a connecting group with a structural formula as shown in a formula I or a formula II, and an N element and a P element contained in the connecting group have a synergistic flame retardant effect, so that the flame retardant property of the modified polyurethane is greatly improved. And meanwhile, the stability of the core-shell structure is also remarkably improved in a chemical bonding manner, so that the impact resistance and the flame-retardant stability of the modified polyurethane are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane modification, and in particular to a modified polyurethane and a preparation method thereof. Background Art

[0002] Waterborne polyurethane emulsion and waterborne acrylic emulsion are two types of polymer materials that are currently widely used and have been widely used as base materials for coatings, inks, and adhesives. Among them, waterborne polyurethane emulsion has excellent low temperature resistance, wear resistance, and solvent resistance, but poor stability, low solid content, and high cost; the biggest feature of waterborne acrylic emulsion is low cost, high hardness, multiple modification methods, and relatively high solid content, but there is an obvious disadvantage of "hot sticky and cold brittle". Waterborne polyurethane and waterborne acrylic ester each have their own characteristics. The waterborne polyurethane acrylic ester copolymer emulsion formed by copolymerizing the two combines the advantages of both. It has been increasingly valued and widely used in furniture, papermaking, construction and other industries. The core-shell polyurethane-acrylic emulsion or modified polyurethane disclosed in the prior art mostly improves the stability or mechanical strength of polyurethane, but cannot improve the flame retardant properties, resulting in it still having safety hazards. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor flame retardancy of polyurethane or modified polyurethane in the prior art, thereby providing a modified polyurethane and a preparation method thereof.

[0004] To this end, the present application provides a modified polyurethane, the modified polyurethane having a core-shell structure, the core of the modified polyurethane comprising polyurethane, the shell of the modified polyurethane comprising polyacrylate, the polyurethane and the polyacrylate being connected via a connecting group, the connecting group having a structural formula shown in Formula I or Formula II:

[0005]

[0006] Wherein, in Formula I or Formula II, Ring A is a five-membered to seven-membered N-containing heterocyclic ring, preferably, Ring A is a pyrazole ring or an imidazole ring;

[0007] R1 and R2 are selected from C2-C6 alkylene groups; preferably, R1 and R2 are selected from C2-C3 alkylene groups;

[0008] The * end of the linking group is connected to polyurethane, and the # end is connected to polyacrylate;

[0009] More preferably, the linking group is selected from or

[0010]

[0011] Furthermore, the raw materials of the modified polyurethane include modified polyurethane aqueous dispersion, acrylate monomer and initiator;

[0012] Preferably, the raw materials of the modified polyurethane aqueous dispersion include polyisocyanate, polyol, linking monomer, chain extender and water; the linking monomer has a structural formula shown in Formula III or Formula IV:

[0013]

[0014] Wherein, in Formula I or Formula II, Ring A is a five-membered to seven-membered N-containing heterocyclic ring, preferably, Ring A is a pyrazole ring or an imidazole ring;

[0015] R3 and R4 are selected from C2-C6 alkenyl or C2-C6 alkynyl; preferably, R3 and R4 are selected from C2-C3 alkenyl;

[0016] More preferably, the linking monomer is selected from or

[0017] More preferably, the modified polyurethane aqueous dispersion comprises the following raw materials in parts by weight:

[0018] 10-30 parts of polyisocyanate;

[0019] Polyol 20-50 parts;

[0020] 1-10 copies of connecting monomers;

[0021] Chain extender 1-7 parts;

[0022] 50-60 parts of water.

[0023] Furthermore, the polyisocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane dimethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0024] Furthermore, the polyol includes one or more polyols with a functionality of 2 to 4; preferably, the polyol includes one or more of polytetramethylene glycol, polycarbonate diol, polycaprolactone diol, polypropylene glycol, polybutylene adipate diol, polyneopentyl adipate diol, polyhexane adipate diol, and polyglycerol; preferably, the weight average molecular weight of the polyol is 500 to 5000.

[0025] Furthermore, the linking monomer is obtained by condensation reaction of an amino-substituted nitrogen heterocyclic compound and a phosphate-based unsaturated monomer;

[0026] Preferably, the amino-substituted nitrogen heterocyclic compound includes one or more of amino-substituted imidazole and amino-substituted pyrazole; more preferably, the diamino-substituted nitrogen heterocyclic compound includes one or more of 1,2-diaminoimidazole, 2-aminoimidazole and 3,5-diaminopyrazole;

[0027] Preferably, the phosphate ester unsaturated monomer is selected from one or more of C2-C6 alkenyl phosphates and C2-C6 alkynyl phosphates; preferably, the phosphate ester unsaturated monomer is selected from one or more of C2-C3 alkenyl phosphates; more preferably, the phosphate ester unsaturated monomer is selected from one or more of vinyl phosphate and allyl phosphate.

[0028] Furthermore, the condensation reaction temperature is 20-40° C., and the time is 1-2 hours.

[0029] Furthermore, the molar ratio of the amino-substituted nitrogen heterocyclic compound to the phosphate unsaturated monomer is 1-5:1-5, preferably 1:1.

[0030] Further, the chain extender is selected from one or more of sulfonate diamines and carboxylate diamines; preferably, the chain extender includes ethylenediamine sulfonate; more preferably, the sulfonate diamine includes one or more of sodium ethylenediamine ethanesulfonate, potassium ethylenediamine ethanesulfonate, sodium 2,4-diaminobenzenesulfonate, and potassium 2,4-diaminobenzenesulfonate.

[0031] Wherein, the carboxylate diamine includes one or more of sodium 2,3-diaminopropionate, sodium 2,4-diaminobutyrate, potassium 2,3-diaminopropionate, and potassium 2,4-diaminobutyrate.

[0032] Furthermore, in parts by weight, the mass ratio of the modified polyurethane aqueous dispersion to the acrylate monomer and the initiator is 40-150:10-50:0.1-2.

[0033] Further, the acrylate monomer includes one or more of ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, phenyl methacrylate and trimethacrylate; and / or, the initiator includes one or more of ammonium persulfate, sodium persulfate and potassium persulfate.

[0034] The present invention also provides a method for preparing any of the above-mentioned modified polyurethanes, comprising mixing a modified polyurethane aqueous dispersion with an acrylate monomer and an aqueous solution containing an initiator, and reacting the mixture to obtain a modified polyurethane emulsion;

[0035] Preferably, the preparation method of the modified polyurethane aqueous dispersion comprises the following steps:

[0036] Step S1: Polyisocyanate and polyol are polymerized to obtain a polyurethane prepolymer;

[0037] Step S2: The polyurethane prepolymer is mixed with the linking monomer and the chain extender, reacted, and dispersed in water to obtain a modified polyurethane aqueous dispersion.

[0038] Furthermore, in step S1, the polymerization reaction temperature is 60-80°C and the time is 4-6h; and / or, the reaction temperature in step S2 is 30-50°C and the time is 20-40min; and / or, the reaction temperature in step S3 is 80-90°C and the time is 8-10h.

[0039] Furthermore, the mass percentage of the initiator in the aqueous solution containing the initiator is less than 5%, preferably 1-5%.

[0040] The technical solution of the present invention has the following advantages:

[0041] 1. The modified polyurethane provided by the present invention has a core-shell structure, wherein the core of the modified polyurethane comprises polyurethane, and the shell of the modified polyurethane comprises polyacrylate, and the polyurethane and the polyacrylate are connected by a connecting group of the structural formula shown in Formula I or Formula II, and the nitrogen-containing heterocyclic unit in the connecting group has a synergistic flame retardant effect with the N element contained in the amino group and the P element on the phosphate unit, which greatly improves the flame retardant properties of the modified polyurethane. At the same time, such a chemical bonding method also significantly improves the stability of the core-shell structure, thereby significantly improving the impact resistance and flame retardant stability of the modified polyurethane.

[0042] 2. In the modified polyurethane provided by the present invention, when the ring A in the connecting group is selected from a pyrazole ring or an imidazole ring, the flame retardant property of the modified polyurethane is better.

[0043] 3. The modified polyurethane provided by the present invention comprises raw materials of a modified polyurethane aqueous dispersion, an acrylate monomer and an initiator. Under the action of the initiator, the acrylate monomer is cross-linked with the unsaturated bonds on the connecting monomer to obtain a modified polyurethane having a shell of polyacrylate and a core of polyurethane.

[0044] The raw materials of the modified polyurethane aqueous dispersion include polyisocyanate, polyol, linking monomer, chain extender and water. The polyisocyanate and polyol are used as raw materials for preparing isocyanate prepolymer. The linking monomer is used to modify the isocyanate prepolymer (the primary amino group or secondary amino group on the linking monomer reacts with the NCO on the isocyanate to generate an amide group). The modified polyurethane aqueous dispersion (emulsion state) is formed in the presence of the chain extender and water.

[0045] 4. The preparation method of the modified polyurethane provided by the present invention comprises the following steps: comprising: mixing a modified polyurethane aqueous dispersion with an acrylate monomer and an aqueous solution containing an initiator, reacting to obtain a modified polyurethane emulsion; preferably, the preparation method of the modified polyurethane aqueous dispersion comprises the following steps: Step S1: preparing a polyurethane prepolymer by polymerization reaction of polyisocyanate and polyol; Step S2: mixing the polyurethane prepolymer with a connecting monomer and a chain extender, reacting, and dispersing in water to obtain a modified polyurethane aqueous dispersion; the reaction steps and process conditions are simple and suitable for industrial production. DETAILED DESCRIPTION

[0046] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0047] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0048] Example 1

[0049] This embodiment provides a modified polyurethane, wherein the modified polyurethane has a core-shell structure, wherein the core of the modified polyurethane comprises polyurethane, and the shell of the modified polyurethane comprises polyacrylate, wherein the polyurethane and the polyacrylate are connected via a connecting group, and the connecting group has the following structural formula: The * end of the linking group is connected to polyurethane, and the # end is connected to polyacrylate.

[0050] Its raw materials are shown in Table 1:

[0051] Table 1 Raw materials and dosage

[0052]

[0053] The process route and preparation method of the connecting monomer used above are as follows:

[0054]

[0055] The method comprises the following steps: mixing vinyl phosphoric acid and 2-aminoimidazole at a molar ratio of 1:1, adding water in an amount of 1.5 times the sum of the mass of the vinyl phosphoric acid and the 2-aminoimidazole, and reacting at 30° C. for 1.5 hours to obtain a connecting monomer.

[0056] This embodiment also provides a method for preparing a modified polyurethane, comprising the following steps:

[0057] Step S1: weigh the raw materials of modified polyurethane aqueous dispersion for use, put polyisocyanate and polyol into a reaction bottle, start stirring, and obtain polyurethane prepolymer through polymerization reaction, the polymerization reaction temperature is 80° C., and the reaction time is 5 h;

[0058] Step S2: Cool the polyurethane prepolymer obtained in step S1 to 30°C, transfer it to a dispersion bottle and start stirring, add the linking monomer and chain extender, mix, react for 30 minutes, add water and stir to obtain a modified polyurethane aqueous dispersion;

[0059] Step S3: weigh the raw material of polyacrylate and set aside, add the initiator into water to prepare an initiator aqueous solution, add the acrylate monomer and the initiator aqueous solution dropwise into the modified polyurethane aqueous dispersion prepared in step S2, react at 85° C. for 10 hours, and prepare a modified polyurethane emulsion.

[0060] Example 2

[0061] This embodiment provides a modified polyurethane, which is basically the same as that of Embodiment 1, except that 3,5-diaminopyrazole is used instead of 2-aminoimidazole during the preparation of the linking monomer.

[0062] Example 3

[0063] This embodiment provides a modified polyurethane, which is basically the same as that of embodiment 1, except that 1,2-diaminoimidazole is used in the preparation process of the connecting monomer. Replace 2-aminoimidazole.

[0064] Example 4

[0065] This embodiment provides a modified polyurethane, which is basically the same as that of Embodiment 2, except that 2-propenyl phosphoric acid is used instead of vinyl phosphoric acid during the preparation of the linking monomer.

[0066] Example 5

[0067] This embodiment provides a modified polyurethane, the raw materials of which are shown in Table 2:

[0068] Table 2 Raw materials and dosage

[0069]

[0070] The preparation method is the same as that in Example 1. The preparation method of the connecting monomer is the same as that in Example 2.

[0071] Example 6

[0072] This embodiment provides a modified polyurethane, the raw materials of which are shown in Table 3:

[0073] Table 3 Raw materials and dosage

[0074]

[0075]

[0076] This embodiment also provides a method for preparing a modified polyurethane, comprising the following steps:

[0077] Step S1: weigh the raw materials of modified polyurethane aqueous dispersion for use, put polyisocyanate and polyol into a polymerization reaction bottle, start stirring, and obtain polyurethane prepolymer through polymerization reaction, the polymerization reaction temperature is 60° C., and the reaction time is 6 hours;

[0078] Step S2: Cool the polyurethane prepolymer obtained in step S1 to 40° C., transfer it to a dispersion bottle and start stirring, add the linking monomer and chain extender obtained by the method of Example 2, mix, react for 40 minutes, add water and stir to obtain a modified polyurethane aqueous dispersion;

[0079] Step S3: weigh the raw material of polyacrylate and set aside, add the initiator into water to prepare an initiator aqueous solution, add the acrylate monomer and the initiator aqueous solution dropwise into the modified polyurethane aqueous dispersion prepared in step S2, react at 80° C. for 8 hours, and prepare a modified polyurethane emulsion.

[0080] Comparative Example 1

[0081] This embodiment provides a modified polyurethane and a preparation method thereof, which is basically the same as that of Embodiment 1, except that no linking monomer is added.

[0082] Comparative Example 2

[0083] This embodiment provides a modified polyurethane and a preparation method thereof, which is basically the same as that of Embodiment 1, except that vinyl formic acid is used instead of vinyl phosphoric acid during the preparation of the linking monomer.

[0084] Comparative Example 3

[0085] This embodiment provides a modified polyurethane and a preparation method thereof, which are basically the same as those in Embodiment 1, except that 1,3-diaminobenzene is used instead of 3,5-diaminopyrazole during the preparation of the linking monomer.

[0086] Test Example 1

[0087] Equal amounts of the emulsions obtained in Examples 1-6 and Comparative Examples 1-3 were coated on 20 cm*20 cm glass sheets, respectively, and then placed in a 60°C oven for 24 hours to obtain films to be tested. Five films to be tested were prepared for each Example and Comparative Example, and the flame retardant properties of each group of modified polyurethane samples to be tested were tested according to GB8624-2012 Classification of Combustion Performance of Building Materials and Products.

[0088] The films to be tested prepared by the above film-forming method in each embodiment and comparative example were tested for impact resistance (observation of cracks and measurement of peeling area) by free fall of a 1kg weight (100cm away from the film), and at the same time, a 1kg weight was used to perform drop impact at a distance of 5cm multiples (5cm, 10cm, 15cm, and so on). When cracks appeared, the experiment was stopped and the impact strength was calculated. Each group was tested five times and the average value was taken. The results are shown in Table 4.

[0089] Table 4 Test results

[0090]

[0091]

[0092] It can be seen from the above results that compared with comparative examples 1-3, the flame retardant properties and impact resistance of the modified polyurethanes prepared in each embodiment of the present invention are significantly improved, and the impact resistance of the modified polyurethanes prepared using the connecting monomer of Example 2 is higher.

[0093] Test Example 2

[0094] Equal amounts of the emulsions obtained in Examples 1-6 and Comparative Examples 1-3 were used to prepare films according to the method of Test Example 1, and were immersed in tap water for 5 days to accelerate the simulation of the effect of moisture on the coating in a rain environment. After drying, the films were tested according to the method of Test Example 1. The results are shown in Table 5.

[0095] Table 5 Test results

[0096]

[0097]

[0098] It can be seen from the above results that, compared with Comparative Examples 1-3, the flame retardant properties and impact resistance of the modified polyurethanes prepared in the embodiments of the present invention are significantly improved in stability during long-term use.

[0099] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A modified polyurethane, characterized in that: The modified polyurethane has a core-shell structure, the core of the modified polyurethane includes polyurethane, the shell of the modified polyurethane includes polyacrylate, the polyurethane and the polyacrylate are connected via a connecting group, and the connecting group has a structural formula shown in Formula I or Formula II: Wherein, in Formula I or Formula II, Ring A is a five-membered to seven-membered N-containing heterocyclic ring, preferably, Ring A is a pyrazole ring or an imidazole ring; R1 and R2 are selected from C2-C6 alkylene groups; preferably, R1 and R2 are selected from C2-C3 alkylene groups; The * end of the linking group is connected to polyurethane, and the # end is connected to polyacrylate; More preferably, the linking group is selected from or 2. The modified polyurethane according to claim 1, characterized in that The raw materials of the modified polyurethane include modified polyurethane water dispersion, acrylate monomer and initiator; Preferably, the raw materials of the modified polyurethane aqueous dispersion include polyisocyanate, polyol, linking monomer, chain extender and water; the linking monomer has a structural formula shown in Formula III or Formula IV: Wherein, in Formula I or Formula II, Ring A is a five-membered to seven-membered N-containing heterocyclic ring, preferably, Ring A is a pyrazole ring or an imidazole ring; R3 and R4 are selected from C2-C6 alkenyl or C2-C6 alkynyl; preferably, R3 and R4 are selected from C2-C3 alkenyl; More preferably, the linking monomer is selected from or More preferably, the modified polyurethane aqueous dispersion comprises the following raw materials in parts by weight:

3. The modified polyurethane according to claim 2, characterized in that The polyisocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane dimethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

4. The modified polyurethane according to claim 2, characterized in that The polyol includes one or more polyols with a functionality of 2 to 4; preferably, the polyol includes one or more of polytetramethylene glycol, polycarbonate diol, polycaprolactone diol, polypropylene glycol, polybutylene adipate diol, polyneopentyl adipate diol, polyhexane adipate diol, and polyglycerol; preferably, the weight average molecular weight of the polyol is 500 to 5000.

5. The modified polyurethane according to claim 2, characterized in that The connecting monomer is prepared by a condensation reaction between an amino-substituted nitrogen heterocyclic compound and a phosphate-based unsaturated monomer; Preferably, the amino-substituted nitrogen heterocyclic compound includes one or more of amino-substituted imidazole and amino-substituted pyrazole; more preferably, the amino-substituted nitrogen heterocyclic compound includes one or more of 1,2-diaminoimidazole, 2-aminoimidazole and 3,5-diaminopyrazole; Preferably, the phosphate ester unsaturated monomer is selected from one or more of C2-C6 alkenyl phosphates and C2-C6 alkynyl phosphates; preferably, the phosphate ester unsaturated monomer is selected from one or more of C2-C3 alkenyl phosphates; more preferably, the phosphate ester unsaturated monomer is selected from one or more of vinyl phosphate and allyl phosphate.

6. The modified polyurethane according to claim 2, characterized in that The chain extender is selected from one or more of sulfonate diamines and carboxylate diamines; preferably, the chain extender includes ethylenediamine sulfonate; more preferably, the sulfonate diamine includes one or more of sodium ethylenediamine ethanesulfonate, potassium ethylenediamine ethanesulfonate, sodium 2,4-diaminobenzenesulfonate, and potassium 2,4-diaminobenzenesulfonate.

7. The modified polyurethane according to claim 2, characterized in that In terms of parts by weight, the mass ratio of the modified polyurethane aqueous dispersion to the acrylate monomer and the initiator is 40-150:10-50:0.1-2.

8. The modified polyurethane according to claim 2 or 7, characterized in that The acrylate monomer includes one or more of ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, phenyl methacrylate and trimethacrylate; and / or, the initiator includes one or more of ammonium persulfate, sodium persulfate and potassium persulfate.

9. A method for preparing the modified polyurethane according to any one of claims 1 to 8, characterized in that: The method comprises mixing a modified polyurethane aqueous dispersion with an acrylate monomer and an aqueous solution containing an initiator, and reacting the mixture to obtain a modified polyurethane emulsion; Preferably, the preparation method of the modified polyurethane aqueous dispersion comprises the following steps: Step S1: Polyisocyanate and polyol are polymerized to obtain a polyurethane prepolymer; Step S2: The polyurethane prepolymer is mixed with the linking monomer and the chain extender, reacted, and dispersed in water to obtain a modified polyurethane aqueous dispersion.

10. The preparation method according to claim 9, characterized in that: In step S1, the polymerization reaction temperature is 60-80°C and the reaction time is 4-6h; and / or, the reaction temperature in step S2 is 30-50°C and the reaction time is 20-40min; and / or, the reaction temperature in step S3 is 60-90°C and the reaction time is 8-10h.

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