Flame-retardant waterborne polyurethane coating agent and preparation method thereof

Abstract

The invention belongs to the technical field of surface treatment agent production, and discloses a flame-retardant waterborne polyurethane coating agent which is obtained by carrying out chain extension on a prepolymer obtained by carrying out nucleophilic reaction on polyester polyol and diisocyanate through a chain extender, the chain extender contains organic molecules simultaneously carrying hydroxyl and phosphorus element, and the organic molecules contain a hydroxyl group and a phosphorus element at the same time. The number of hydroxyl groups in a single organic molecule is not less than 2, chain extension treatment is performed through a chain extender containing phosphorus element and hydroxyl groups, and a chain-extended prepolymer with uniformly distributed phosphorus element is obtained, so that the flame retardant property of the finally prepared polyurethane is improved; the invention further discloses a preparation method of the flame-retardant waterborne polyurethane coating agent.

Description

Technical Field

[0001] The present application relates to the technical field of surface treatment agent production, and in particular to a flame retardant waterborne polyurethane finishing agent and a preparation method thereof. Background Art

[0002] Polyurethane has been widely used in the fields of construction, transportation, home appliances, furniture, etc. due to its high strength and high wear resistance. The synthesis of polyurethane usually requires the use of a large amount of organic solvents, which are harmful to the environment and people who come into contact with it. In recent years, with the increase in people's environmental awareness and the country's strict restrictions on volatile organic compounds, water-based polyurethanes that require almost no organic solvents in the preparation process have received more and more attention. Compared with traditional solvent-based polyurethanes, water-based polyurethanes have significant advantages such as strong adhesion, no volatile organic compounds, and no energy waste, which greatly reduces the market demand for traditional solvent-based polyurethanes and gradually shows a trend of replacing traditional solvent-based polyurethanes.

[0003] In recent years, the demand for waterborne coatings has been increasing, and people's requirements for waterborne coatings have become higher and higher. In addition to the pursuit of high performance, "multifunctionality" has also become a major development hotspot for waterborne coatings. As a high-end product among waterborne coatings, waterborne polyurethane has various modified coating varieties, which are widely used in furniture, construction, transportation and other fields. However, since the molecular chain of waterborne polyurethane is mainly composed of elements such as C, N, O, and H, the limiting oxygen index (LOI) is only about 18%, which is flammable, so the flame retardant modification of waterborne polyurethane has become a current research hotspot.

[0004] Flame-retardant waterborne polyurethane can be divided into two types according to the different preparation methods: physical addition type and chemical reaction type. No chemical reaction occurs during the preparation process of the addition type. The modification effect can be achieved by physically blending a sufficient amount of flame retardant with the waterborne polyurethane emulsion.

[0005] However, additive flame retardants often need to be added in a certain proportion to improve the flame retardant effect. Due to the characteristics of water-based polyurethane itself, excessive addition of flame retardants can easily cause emulsion demulsification, easy precipitation, poor film-forming properties, etc., and will also cause the loss of the original properties of water-based polyurethane such as mechanical properties and light transmittance.

[0006] The more common chemical reaction polyurethanes in the prior art include waterborne polyurethanes modified by modifying the soft segment, waterborne polyurethanes modified by modifying the hard segment, and chain extenders containing flame retardant elements introduced into the interior of the polyurethane chain during the chain extension stage.

[0007] Chinese patent application 201610012662.X discloses a post-chain extended flame retardant high hydrostatic pressure resistant waterborne polyurethane fabric coating agent, and the specific preparation steps are as follows:

[0008] Step 1, dehydrating polyether diol or polyester diol and polyether triol at 100-120° C.; the mass ratio of the polyether diol or polyester diol to the polyether triol is 4:1-9:1;

[0009] Step 2, cooling to 50-90°C, adding a solvent to dilute under the protection of nitrogen, and then adding an aromatic isocyanate after dilution; until the hydroxyl group reacts completely to obtain a prepolymer; the molar ratio of the isocyanate group to the hydroxyl group of the aromatic isocyanate is 1.2-3.0;

[0010] Step 3, adding a lipophilic chain extender to the prepolymer obtained in step 2 until the hydroxyl groups in the lipophilic chain extender react completely to obtain solution A; the amount of the lipophilic chain extender added is 1 to 2% of the total mass of the system; the total mass of the system refers to the sum of the masses of the monomer polyether diol or polyester diol, polyether triol, aromatic isocyanate, lipophilic chain extender, hydrophilic chain extender and triethylamine;

[0011] Step 4: adding a hydrophilic chain extender to the solution A obtained in step 3 until the hydroxyl groups in the hydrophilic chain extender react completely to obtain a solution B; the amount of the hydrophilic chain extender added is 3-6% of the total mass of the system;

[0012] Step 5: Cool to room temperature, add triethylamine to the solution B obtained in step 4 to neutralize, and obtain solution C after the reaction is complete;

[0013] Step 6, stirring the solution C obtained in step 5, and adding deionized water at 0-10° C. for emulsification, and then adding a phosphorus-containing diamine flame retardant for post-chain extension reaction, and removing the solvent after the reaction is complete to obtain an aqueous polyurethane emulsion; the molar ratio of the amino group of the phosphorus-containing diamine flame retardant to the remaining isocyanate group in the solution C is 0.2-1.0;

[0014] When the waterborne polyurethane prepared by this scheme is applied to polyester low-elastic silk cloth, it not only has high hydrostatic pressure resistance (hydrostatic pressure resistance value is in the range of 20-100kPa), but also has a certain flame retardant effect (can pass the B1 level in the vertical method of GB / T5455-1997 textile combustion performance test). In addition, the emulsion has good storage stability and the film has excellent comprehensive performance. When applied to fabric finishing, the coating is transparent, has a good feel, good adhesion, is non-toxic and environmentally friendly;

[0015] Further observation of step six of the scheme shows that the scheme achieves improved flame retardancy by introducing phosphorus-containing elements in the post-chain extension stage through the phosphorus-containing diamine flame retardant.

[0016] The problem to be solved by this scheme is: how to develop a flame retardant waterborne polyurethane finishing agent which is different from the prior art and has good flame retardancy. Summary of the invention

[0017] The purpose of the present application is to provide a flame-retardant waterborne polyurethane finishing agent, which first obtains a prepolymer by the reaction between polyester polyol and isocyanate, introduces a hydrophilic group into the prepolymer, and finally performs chain extension treatment with a chain extender containing phosphorus element and hydroxyl group to obtain a flame-retardant waterborne polyurethane finishing agent with uniform distribution of phosphorus element.

[0018] To achieve the above-mentioned purpose, the present application discloses a flame-retardant waterborne polyurethane finishing agent, which is obtained by chain-extending a prepolymer obtained by nucleophilic reaction of polyester polyol and diisocyanate with a chain extender;

[0019] The chain extender is an organic molecule containing hydroxyl groups and phosphorus elements, and the number of hydroxyl groups in a single organic molecule is not less than 2.

[0020] Preferably, the organic molecule has a general structural formula as shown in Formula 1:

[0021]

[0022] In the formula, the R1 group is selected from an alkane or a benzene ring having 1 to 6 carbon atoms.

[0023] Preferably, the chain extender comprises at least an organic molecule of the structural formula shown in Formula 2:

[0024]

[0025] Preferably, the chain extender is a mixture of an organic molecule of the structural formula shown in Formula 2 and an organic molecule of the structural formula shown in Formula 3:

[0026]

[0027] Preferably, the following components are included by weight:

[0028]

[0029] Preferably, the polyester polyol is selected from any one of polyethylene adipate diol, polybutylene adipate diol and polycaprolactone diol.

[0030] Preferably, the diisocyanate is selected from at least one of dicyclohexylmethane diisocyanate, isophorone diisocyanate and xylylene diisocyanate.

[0031] Preferably, the solvent is selected from at least one of toluene and acetone.

[0032] In addition, the present application also discloses a method for preparing the flame-retardant waterborne polyurethane coating agent, wherein ester polyol and diisocyanate are mixed and reacted to obtain a prepolymer, and then a chain extender is used to extend the prepolymer to obtain a flame-retardant waterborne polyurethane coating agent.

[0033] More preferably, the method specifically comprises the following steps:

[0034] Step 1: Mix polyester polyol, diisocyanate and solvent at a temperature of 70 to 80° C. and react for 2 to 5 hours to obtain a prepolymer;

[0035] Step 2: Mix the chain extender and the prepolymer and react at a temperature of 60 to 105° C. for 1 to 3 hours to obtain a chain-extended prepolymer;

[0036] Step 3: Add 2,2-dihydroxymethylpropionic acid to the chain-extended prepolymer and react for 1 to 2 hours, then add triethylamine to carry out neutralization reaction for 30 to 50 minutes, and then add deionized water to emulsify to obtain a flame-retardant waterborne polyurethane coating agent.

[0037] The beneficial effects of this application are:

[0038] The flame-retardant waterborne polyurethane coating agent disclosed in the present application first obtains a prepolymer by the reaction between polyester polyol and isocyanate, and then performs chain extension treatment through a chain extender containing phosphorus element and hydroxyl group to obtain a chain-extended prepolymer with uniform distribution of phosphorus element, and finally introduces hydrophilic groups into the prepolymer to obtain a flame-retardant waterborne polyurethane coating agent with good flame retardant properties. DETAILED DESCRIPTION

[0039] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that, if no specific conditions are specified in the embodiments, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0040] Before the examples are presented, the following necessary explanations are first made on the raw materials and preparation methods involved in the examples:

[0041] The raw material information of the embodiment is shown in Table 1:

[0042] Table 1

[0043]

[0044] The preparation method of the polyurethane finishing agent in the embodiment and comparative example is:

[0045] Step 1: Mix polyester polyol, diisocyanate and solvent at a temperature of 75±5°C and react for 3.5±1h to obtain a prepolymer;

[0046] Step 2: Mix the chain extender and the prepolymer at a temperature of 80±15°C and react for 2±0.5h to obtain a chain-extended prepolymer;

[0047] Step 3: Add 2,2-dihydroxymethylpropionic acid to the chain-extended prepolymer and react for 1.5±0.5h, then add triethylamine at a mass of 10±2% of the total mass of the prepolymer for neutralization reaction for 30-50min, then add deionized water for emulsification to obtain a flame-retardant waterborne polyurethane coating agent.

[0048] Further, the specific formulations are described in detail in the embodiments and comparative examples.

[0049] Examples 1-4

[0050] A flame retardant waterborne polyurethane finishing agent, the formula of which is shown in Table 2:

[0051] Table 2

[0052]

[0053] It should be noted that in Examples 1-4, the polyester polyol is specifically polycaprolactone diol;

[0054] The diisocyanate is specifically dicyclohexylmethane diisocyanate;

[0055] The solvent is specifically acetone;

[0056] The chain extender is an organic molecule with the structural formula shown in Formula II:

[0057]

[0058] Example 5

[0059] The method is substantially the same as Example 1, except that an organic molecule having a structural formula shown in Formula III is used as a chain extender;

[0060]

[0061] Example 6

[0062] The method is basically the same as Example 1, except that a mixture of an organic molecule having the structural formula shown in Formula II and an organic molecule having the structural formula shown in Formula III is used, and the mass ratio of the organic molecule having the structural formula shown in Formula II to the organic molecule having the structural formula shown in Formula III is 3:1.

[0063] Example 7

[0064] The method is basically the same as Example 1, except that a mixture of an organic molecule having the structural formula shown in Formula II and an organic molecule having the structural formula shown in Formula III is used, and the mass ratio of the organic molecule having the structural formula shown in Formula II to the organic molecule having the structural formula shown in Formula III is 4:1.

[0065] Example 8

[0066] The method is basically the same as Example 1, except that a mixture of an organic molecule having the structural formula shown in Formula II and an organic molecule having the structural formula shown in Formula III is used, and the mass ratio of the organic molecule having the structural formula shown in Formula II to the organic molecule having the structural formula shown in Formula III is 2:1.

[0067] Example 9

[0068] The method is substantially the same as Example 1, except that polyethylene adipate glycol is used to replace polycaprolactone glycol.

[0069] Example 10

[0070] The method is substantially the same as Example 1, except that a mixture of polyethylene adipate diol and polycaprolactone diol is used to replace polycaprolactone diol, and the mass ratio of polyethylene adipate diol to polycaprolactone diol is 0.8:1.

[0071] Embodiment 11

[0072] The process is substantially the same as Example 1, except that isophorone diisocyanate is used instead of dicyclohexylmethane diisocyanate.

[0073] Example 12

[0074] The method is substantially the same as Example 1, except that a mixture of isophorone diisocyanate and dicyclohexylmethane diisocyanate is used to replace dicyclohexylmethane diisocyanate, and the mass ratio of isophorone diisocyanate to dicyclohexylmethane diisocyanate is 1:1.

[0075] Comparative Example 1

[0076] The method is basically the same as Example 1, except that 1,2-propylene glycol is used to replace the organic molecule with the structural formula shown in Formula II.

[0077] Comparative Example 2

[0078] The method is basically the same as Example 1, except that pentaerythritol phosphate containing only one hydroxyl group in a single organic molecule is used to replace the organic molecule shown in Formula II.

[0079] Comparative Example 3

[0080] The method is basically the same as Example 1, except that phenyl phosphoramide is used to replace the organic molecule shown in Formula II.

[0081] Performance Test:

[0082] Referring to GB / T5454-1997 "Textile Combustion Performance Test - Oxygen Index Method", a limiting oxygen index tester was used to measure the limiting oxygen index (LOI) of polyester fabrics before and after finishing, and the sample size was 150mm×58mm.

[0083] Referring to GB / T5455-1997 "Vertical method for testing the burning performance of textiles", the burning performance of polyester fabrics before and after finishing was measured using a fabric flame retardant performance tester (vertical method). The sample size was 80mm×300mm. The test results are shown in Table 3:

[0084] Table 3

[0085]

[0086]

[0087] Result analysis:

[0088] 1. It can be seen from Examples 1-4 that when the four methods slightly adjusted the amount of each raw material added in the polyurethane formula, Examples 1-4 did not show obvious differences in the afterburning time and smoldering time during the vertical combustion performance test, and no molten droplet dripping occurred. However, Examples 1-4 showed certain differences in the damage length and limiting oxygen index. It is speculated that this may be related to the amount of chain extender added. As the proportion of chain extender in polyurethane increases, the content of phosphorus increases, thereby producing more advantageous flame retardant properties.

[0089] 2. It can be seen from Examples 1 and 5 that when an organic molecule having a structural formula shown in Formula III is used as a chain extender, its damage length and limiting oxygen index are improved to varying degrees relative to Example 1. It can be seen that the flame retardant effect of the organic molecule having a structural formula shown in Formula III when used as a chain extender is not as good as that of the organic molecule shown in Formula II. It is speculated that the reason may be that the benzene ring structure of the organic molecule shown in Formula II provides higher thermal stability and carbonization ability, and a relatively more stable carbon layer may be generated during the combustion process. This carbon layer can isolate oxygen and slow down the combustion process;

[0090] Further observation of Example 6 shows that when Example 6 uses a mixture of organic molecules of Formula II and organic molecules of Formula III as chain extenders, its flame retardant performance is not only better than Example 5, but even better than Example 1. It should be noted that through Examples 1 and 5, we can clearly see that the flame retardant performance of the organic molecules of Formula III is not as good as that of the organic molecules of Formula II in Example 1. However, after the two are mixed, the flame retardant performance of the polyurethane in Example 6 is not only better than that of Example 5, but also better than that of Example 1. It is speculated that the reason for this phenomenon may be that the decomposition products of the two compounds may react chemically at high temperatures to generate substances with higher flame retardant performance. This chemical synergistic effect can further improve the flame retardant effect of the material;

[0091] Further observation of Examples 7-8 shows that when the mass ratio between the organic molecule represented by Formula II and the organic molecule represented by Formula III is further adjusted on the basis of Example 6, the flame retardant ability of Examples 7-8 is reduced relative to that of Example 6. It can be seen that when the mass ratio between the organic molecule represented by Formula II and the organic molecule represented by Formula III is 3:1, the decomposition products of the two react more fully at high temperature, generating more substances with high flame retardant performance;

[0092] 3. It can be seen from Examples 1 and 9-10 that when the polyester polyol is a mixture of polyethylene adipate glycol and polycaprolactone glycol, the flame retardant performance of Example 10 further shows a certain improvement trend relative to Example 1 and Example 8. The reason for this may be that the two may lead to the formation of a microscopic phase separation structure inside the material. This structure can provide a physical barrier effect during the combustion process, slow down the transfer of heat and mass, and thus improve the flame retardant performance of the polyurethane;

[0093] 4. It can be seen from Example 1 and Examples 11-12 that when Example 12 uses a mixture of isophorone diisocyanate and dicyclohexylmethane diisocyanate, the flame retardant properties of Examples 1, 11 and 12 show a certain fluctuation trend, and the flame retardant properties of Example 12 show a certain improvement trend relative to those of Examples 1 and 11. The reason may be that the mixture of the two may change the thermal decomposition path of polyurethane to a certain extent, resulting in the generation of more carbonized products and non-combustible gases, thereby improving the flame retardant properties of polyurethane.

[0094] 5. It can be seen from Example 1 and Comparative Examples 1-2 that when the organic molecule lacks phosphorus or the number of hydroxyl groups in the organic molecule is less than 2, the flame retardant properties of Comparative Examples 1-2 will show a significant downward trend. Furthermore, when Comparative Example 3 uses an organic substance with phosphorus and 2 amino groups to replace the organic molecule shown in Formula II in Example 1, although there is a significant gap in the afterflaming time and smoldering time tests compared with Example 1, the damage length and limiting oxygen index are still a certain distance away from Example 1.

Claims

1. A flame retardant waterborne polyurethane finishing agent, characterized in that: The prepolymer obtained by the nucleophilic reaction of polyester polyol and diisocyanate with a chain extender is chain extended to obtain the product; The chain extender contains organic molecules carrying hydroxyl groups and phosphorus elements at the same time, and the number of hydroxyl groups in a single organic molecule is not less than 2.

2. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: The organic molecule has a general structural formula as shown in Formula 1: In the formula, the R1 group is selected from an alkane or a benzene ring having 1 to 6 carbon atoms.

3. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: The chain extender comprises at least an organic molecule of the structural formula shown in Formula 2:

4. The flame retardant waterborne polyurethane finishing agent according to claim 3, characterized in that: The chain extender is a mixture of an organic molecule of the structural formula shown in Formula 2 and an organic molecule of the structural formula shown in Formula 3:

5. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: By mass, it includes the following components:

6. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: The polyester polyol is selected from any one of polyethylene adipate diol, polybutylene adipate diol and polycaprolactone diol.

7. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: The diisocyanate is selected from at least one of dicyclohexylmethane diisocyanate, isophorone diisocyanate and xylylene diisocyanate.

8. The flame retardant waterborne polyurethane finishing agent according to claim 1, characterized in that: The solvent is selected from at least one of toluene and acetone.

9. A method for preparing the flame-retardant waterborne polyurethane finishing agent according to any one of claims 1 to 8, characterized in that: The ester polyol and the diisocyanate are mixed and reacted to obtain a prepolymer, and then a chain extender is used to extend the chain of the prepolymer to obtain a flame retardant waterborne polyurethane finishing agent.

10. The method for preparing the flame-retardant waterborne polyurethane finishing agent according to claim 9, characterized in that: The specific steps include: Step 1: Mix polyester polyol, diisocyanate and solvent at a temperature of 70 to 80° C. and react for 2 to 5 hours to obtain a prepolymer; Step 2: Mix the chain extender and the prepolymer and react at a temperature of 60 to 105° C. for 1 to 3 hours to obtain a chain-extended prepolymer; Step 3: Add 2,2-dihydroxymethylpropionic acid to the chain-extended prepolymer and react for 1 to 2 hours, then add triethylamine to carry out neutralization reaction for 30 to 50 minutes, then add deionized water for emulsification to obtain a flame-retardant waterborne polyurethane coating agent.

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