Enclosed waterborne polyurethane resin as well as synthesis method and application thereof

Abstract

The invention belongs to the field of waterborne polyurethane high polymer materials, and particularly relates to closed waterborne polyurethane resin as well as a synthesis method and application thereof. The closed type waterborne polyurethane resin is prepared from the following raw materials: macromolecular polyol, a micromolecular chain extender, a hydrophilic chain extender, diisocyanate, a sealing agent, diethanol amine and a neutralizer. The waterborne polyurethane resin with a special structure is synthesized by utilizing the tailorable property of the molecular structure of the waterborne polyurethane. The blocked waterborne polyurethane resin is synthesized by adopting a prepolymer method, the blocked waterborne polyurethane contains part of hydroxyl groups, and blocked isocyanate can be deblocked and released at a certain temperature, so that the blocked isocyanate and the hydroxyl groups contained in the blocked isocyanate are subjected to a cross-linking reaction. The closed waterborne polyurethane resin provided by the invention does not have the problem of opening time in use, has a high crosslinking degree compared with double components, and has fewer side reactions and lower cost after high-temperature deblocking.

Description

Technical Field

[0001] The invention belongs to the field of waterborne polyurethane polymer materials, and in particular relates to a closed waterborne polyurethane resin and a synthesis method and application thereof. Background Art

[0002] Waterborne polyurethane resins include two-component waterborne polyurethanes and blocked waterborne polyurethanes. Two-component waterborne polyurethanes are systems composed of a prepolymer containing an isocyanate group (component A) and an active hydrogen waterborne polyurethane emulsion containing hydroxyl groups, amino groups, etc. (component B). This system combines the environmental friendliness of waterborne polyurethanes and the excellent properties of polyurethanes, making it an important high-performance resin in modern industry. From the composition, it can be seen that the two-component waterborne polyurethane resin is two components. Before use, the isocyanate-containing component A is added to the active hydrogen-containing waterborne polyurethane emulsion B, which is dispersed and mixed by stirring before use. Although two-component waterborne polyurethanes have excellent physical and chemical properties, a large amount of isocyanates react with water when added to a system containing water. Therefore, two-component waterborne polyurethane resins have three disadvantages:

[0003] 1. Open time problem: When components A and B are mixed, a chemical reaction occurs, resulting in a shortened open time.

[0004] 2. Cross-linking degree problem: When component A is added to component B, because the water-based polyurethane emulsion contains a large amount of water, the isocyanate contained in component A will react with water, thereby reducing the cross-linking degree of the two-component system.

[0005] 3. High cost: The occurrence of side reactions will lead to a decrease in the degree of crosslinking. To achieve the same performance, it is necessary to increase the amount of component A, resulting in high costs.

[0006] At present, the synthesis of closed waterborne polyurethane resin is basically as follows (such as CN110903458A, CN102731746A, CN114836163A): polyether polyol, hydrophilic chain extender, small molecule chain extender react with isocyanate at a certain temperature, and when the theoretical NCO is reached, a semi-blocking agent is added, and the reaction is carried out at a certain temperature until the NCO is zero. The closed waterborne polyurethane synthesized by this method is fully closed, and there is no hydroxyl group in its molecular structure, and the probability of self-crosslinking at high temperature is low.

[0007] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a closed waterborne polyurethane resin, which includes the following preparation raw materials: macromolecular polyol, small molecule chain extender, hydrophilic chain extender, diisocyanate, blocking agent, diethanolamine and neutralizer.

[0009] Preferably, the blocked waterborne polyurethane resin is characterized by comprising the following raw materials in parts by weight: 50-60 parts of macromolecular polyol, 6-8 parts of small molecule chain extender, 6-9 parts of hydrophilic chain extender, 25-30 parts of diisocyanate, 8-10 parts of blocking agent, 6-8 parts of diethanolamine and 6-8 parts of neutralizer.

[0010] Preferably, the macromolecular polyol is a polyether diol or a polycarbonate diol;

[0011] And / or, the small molecule chain extender is methyl propylene glycol, 1,4-butanediol or cyclohexanedimethanol;

[0012] And / or, the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid;

[0013] and / or, the diisocyanate is isophorone diisocyanate or hydrogenated phenylmethane diisocyanate;

[0014] And / or, the blocking agent is pyrazole or methyl ethyl ketone oxime;

[0015] And / or, the neutralizing agent is triethylamine or dimethylethanolamine.

[0016] Based on the same technical concept, the present invention further provides a method for synthesizing a blocked waterborne polyurethane resin, the method comprising the following steps:

[0017] (1) dehydrating a macromolecular polyol to obtain a dehydrated polyol;

[0018] (2) mixing the dehydrated polyol, a small molecule chain extender, and a hydrophilic chain extender uniformly, and then adding diisocyanate to react;

[0019] (3) after the reaction in step (2) is completed, a blocking agent, diethanolamine, and a neutralizing agent are added in sequence to continue the reaction to obtain a prepolymer;

[0020] (4) The prepolymer and deionized water are mixed and filtered to obtain the blocked waterborne polyurethane resin.

[0021] Preferably, in step (1), the dehydration conditions are: vacuum dehydration at 100-110° C. for 1-2 h.

[0022] Preferably, in step (2), the reaction temperature is 80-85° C., and the reaction time is 2.0-4.5 h.

[0023] Preferably, in step (3), after the reaction in step (2) is completed, a blocking agent is first added and the mixture is reacted at 80-85° C. for 1.5 h, then the temperature is lowered to 50-55° C. and diethanolamine is added and the mixture is reacted for 1.5 h, and finally a neutralizing agent is added and the reaction is continued for 30-45 min to obtain a prepolymer.

[0024] Preferably, in step (4), the mixing time is 1 to 1.5 hours.

[0025] Based on the same technical concept, the present invention further provides an application of a closed waterborne polyurethane resin in the fields of leather, textiles, and industrial coatings.

[0026] The beneficial effects of the present invention are:

[0027] The present invention utilizes the "tailorability" of the molecular structure of waterborne polyurethane to synthesize a waterborne polyurethane resin with a special structure. The present invention adopts a prepolymer method to synthesize a closed waterborne polyurethane resin, which contains some hydroxyl groups. Under certain temperature conditions, the closed isocyanate will be unblocked, releasing the isocyanate, and then undergoing a cross-linking reaction with the hydroxyl groups contained in the closed waterborne polyurethane resin. The closed waterborne polyurethane resin involved in the present invention has no open time problem during use, has a high degree of cross-linking compared with two components, has fewer side reactions after being unblocked at high temperature, and has reduced costs.

[0028] Specific:

[0029] 1. The present invention adopts the prepolymer method, the synthesis process is simple, the synthesis process adopts a solvent-free method or uses a small amount of environmentally friendly solvent, and the synthetic product is a green and environmentally friendly product.

[0030] 2. Through the "tailoring" of the water-based polyurethane molecular structure, a partially closed water-based polyurethane resin containing hydroxyl groups in the molecular structure is synthesized.

[0031] 3. At a certain temperature, the sealant is unblocked and NCO can undergo chemical cross-linking reaction with substances containing active hydrogen, solving the problems of short open time, low cross-linking degree and high cost of two-component waterborne polyurethane resin.

[0032] 4. The blocked waterborne polyurethane resin of the present invention is suitable for synthetic leather adhesives, fabric treatment agents, industrial coatings, etc., and has a wide range of applications. DETAILED DESCRIPTION

[0033] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a method for preparing a blocked waterborne polyurethane resin, the preparation method comprising the following steps:

[0036] (1) Add 60 g of polyether diol into a four-necked round-bottom flask, heat to 100° C. under stirring, and dehydrate under vacuum for 2 h to obtain dehydrated polyether diol;

[0037] (2) cooling to 60° C., adding 6 g of methyl propylene glycol and 8 g of dimethylol propionic acid to the dehydrated polyether diol and mixing them evenly, and then adding 30 g of isophorone diisocyanate and reacting at 80° C. for 4 h;

[0038] (3) After the reaction is completed, 6 g of pyrazole is added and reacted at 80° C. for 1.5 h, and then 8 g of diethanolamine is added and reacted for 1.5 h. After the reaction is completed, the temperature is lowered to 50° C., and 6 g of triethylamine is added and reacted for 30 min to obtain a prepolymer;

[0039] (4) Weigh deionized water and place it in a dispersing device, turn on the disperser, and slowly add the prepolymer while stirring. After the prepolymer is added, stir for 1.0 hour and filter to obtain a blocked waterborne polyurethane resin.

[0040] In addition, it should be emphasized that sampling needs to be performed during the reaction to test the NCO content.

[0041] Example 2

[0042] This embodiment provides a method for preparing a blocked waterborne polyurethane resin, the preparation method comprising the following steps:

[0043] (1) Add 65 g of polycarbonate diol into a four-necked round-bottom flask, heat to 110° C. under stirring, and dehydrate under vacuum for 1 h to obtain dehydrated polycarbonate diol;

[0044] (2) cooling to 60° C., adding 6 g of 1,4-butanediol and 7 g of dimethylolbutyric acid to the dehydrated polycarbonate diol and mixing them evenly, and then adding 35 g of hydrogenated phenylmethane diisocyanate and reacting at 85° C. for 2 h;

[0045] (3) After the reaction is completed, 6 g of methyl ethyl ketone oxime is added and reacted at 85° C. for 1.5 h, and then 8 g of diethanolamine is added and reacted for 1.5 h. After the reaction is completed, the temperature is lowered to 55° C., and 9 g of dimethylethanolamine is added and reacted for 45 min to obtain a prepolymer;

[0046] (4) Weigh deionized water and place it in a dispersing device, turn on the disperser, and slowly add the prepolymer while stirring. After the prepolymer is added, stir for 1.0 hour and filter to obtain a blocked waterborne polyurethane resin.

[0047] In addition, it should be emphasized that sampling needs to be performed during the reaction to test the NCO content.

[0048] Example 3

[0049] This embodiment provides a method for preparing a blocked waterborne polyurethane resin, the preparation method comprising the following steps:

[0050] (1) Add 70 g of polyether diol into a four-necked round-bottom flask, heat to 105° C. under stirring, and dehydrate under vacuum for 1.5 h to obtain dehydrated polyether diol;

[0051] (2) cooling to 60° C., adding 7 g of cyclohexanedimethanol and 6 g of dimethylolbutyric acid to the dehydrated polyether diol and mixing them evenly, and then adding 26 g of isophorone diisocyanate and reacting at 85° C. for 2 h;

[0052] (3) After the reaction is completed, 6 g of methyl ethyl ketone oxime is added and reacted at 85° C. for 1.5 h, and then 5 g of diethanolamine is added and reacted for 1.5 h. After the reaction is completed, the temperature is lowered to 50° C., and 5 g of triethylamine is added and reacted for 30 min to obtain a prepolymer;

[0053] (4) Weigh deionized water and place it in a dispersing device, turn on the disperser, and slowly add the prepolymer while stirring. After the prepolymer is added, stir for 1.0 hour and filter to obtain a blocked waterborne polyurethane resin.

[0054] In addition, it should be emphasized that sampling needs to be performed during the reaction to test the NCO content.

[0055] Verification Example

[0056] The blocked waterborne polyurethane resin of the present invention (the blocked waterborne polyurethane resin obtained in Example 1 was used for testing) was first partially blocked with a blocking agent, and then diethanolamine was added to synthesize a blocked waterborne polyurethane having a hydroxyl group in its molecular structure. At a certain temperature, after the blocking agent is unblocked, NCO can react with -OH to undergo a chemical crosslinking reaction, thereby improving the comprehensive performance of the resin. The specific data are shown in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A closed waterborne polyurethane resin, characterized in that: The preparation raw materials include: macromolecular polyol, small molecule chain extender, hydrophilic chain extender, diisocyanate, blocking agent, diethanolamine and neutralizing agent.

2. The blocked waterborne polyurethane resin according to claim 1, characterized in that: The preparation comprises the following raw materials in parts by weight: 50-70 parts of macromolecular polyol, 5-10 parts of small molecule chain extender, 5-10 parts of hydrophilic chain extender, 20-40 parts of diisocyanate, 5-15 parts of blocking agent, 5-15 parts of diethanolamine and 5-10 parts of neutralizer.

3. The blocked waterborne polyurethane resin according to claim 1 or 2, characterized in that: The macromolecular polyol is a polyether diol or a polycarbonate diol; And / or, the small molecule chain extender is methyl propylene glycol, 1,4-butanediol or cyclohexanedimethanol; And / or, the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid; and / or, the diisocyanate is isophorone diisocyanate or hydrogenated phenylmethane diisocyanate; And / or, the blocking agent is pyrazole or methyl ethyl ketone oxime; And / or, the neutralizing agent is triethylamine or dimethylethanolamine.

4. The method for synthesizing the blocked waterborne polyurethane resin according to any one of claims 1 to 3, characterized in that: The synthesis method comprises the following steps: (1) dehydrating a macromolecular polyol to obtain a dehydrated polyol; (2) mixing the dehydrated polyol, a small molecule chain extender, and a hydrophilic chain extender uniformly, and then adding diisocyanate to react; (3) after the reaction in step (2) is completed, a blocking agent, diethanolamine, and a neutralizing agent are added in sequence to continue the reaction to obtain a prepolymer; (4) The prepolymer and deionized water are mixed and filtered to obtain the blocked waterborne polyurethane resin.

5. The method for synthesizing a blocked waterborne polyurethane resin according to claim 4, characterized in that: In step (1), the dehydration conditions are: vacuum dehydration at 100-110° C. for 1-2 h.

6. The method for synthesizing a blocked waterborne polyurethane resin according to claim 4, characterized in that: In step (2), the reaction temperature is 80-85° C., and the reaction time is 2.0-4.5 h.

7. The method for synthesizing a blocked waterborne polyurethane resin according to claim 4, characterized in that: In step (3), after the reaction in step (2) is completed, a blocking agent is first added to react at 80-85° C. for 1.5 h, then the temperature is lowered to 50-55° C. and diethanolamine is added to react for 1.5 h, and finally a neutralizing agent is added to continue the reaction for 30-45 min to obtain a prepolymer.

8. The method for synthesizing a blocked waterborne polyurethane resin according to claim 4, characterized in that: In step (4), the mixing time is 1 to 1.5 hours.

9. Use of the blocked waterborne polyurethane resin according to any one of claims 1 to 3 in the fields of leather, textiles and industrial coatings.

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