Intrinsic flame-retardant waterborne polyurethane adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses an intrinsic flame-retardant waterborne polyurethane adhesive and a preparation method and application thereof.The preparation method includes the steps that 10-(2, 5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide and chlorinated trimellitic anhydride are used as raw materials to synthesize phosphorus-containing dianhydride, and the phosphorus-containing dianhydride is added into the raw materials to prepare the intrinsic flame-retardant waterborne polyurethane adhesive. Then carrying out two-step reaction on the phosphorus-containing bicyclic carbonate, glycerol carbonate and hydroxyethyl methylacrylate to obtain acrylate-modified phosphorus-containing bicyclic carbonate; and finally, carrying out reaction on the acrylate-modified phosphorus-containing bicyclic carbonate and polyamine to obtain the intrinsic flame-retardant waterborne polyurethane adhesive. The polyurethane adhesive prepared by the preparation method disclosed by the invention is applied to production of artificial boards and shows excellent bonding strength, water resistance and flame retardance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, relates to the preparation of polyurethane adhesives, and particularly relates to an intrinsic flame retardant water-based polyurethane adhesive and a preparation method and application thereof. Background Art

[0002] China is the world's largest producer and consumer of wood-based panels, and has a large demand for wood adhesives. Urea-formaldehyde resin, phenol-formaldehyde resin and melamine-formaldehyde resin are commonly used adhesives in the production of wood-based panels, referred to as trialdehyde adhesives. Although trialdehyde adhesives are cheap and produce high-strength boards, they release formaldehyde during the production and use of boards, which is harmful to health.

[0003] Due to the presence of polar or highly reactive groups such as carbamate and isocyanate groups in the structure of polyurethane, it can be combined with most materials in the form of chemical covalent bonds or hydrogen bonds, and has excellent bonding properties. In the field of artificial board industry, polyurethane adhesives have attracted much attention because there is no formaldehyde release problem, and they have many advantages such as low glue application amount and high bonding strength. However, in the traditional polyurethane molecular chain prepared by the reaction of polyisocyanate and polyol, the carbamate group is prone to hydrolysis, which makes the polyurethane water resistance poor, and the anti-permeability and acid and alkali resistance of the obtained product are also greatly reduced. In addition, the raw material isocyanate is highly toxic and humidity sensitive, and has strict requirements on storage and use conditions. On the other hand, polyurethane itself does not have flame retardancy. For artificial boards with flame retardant grade requirements, flame retardants need to be added, which also has problems with compatibility and flame retardant precipitation. Summary of the invention

[0004] In view of the deficiencies of the prior art, the object of the present invention is to provide an intrinsic flame retardant waterborne polyurethane adhesive, and another object of the present invention is to provide a preparation method and application of the intrinsic flame retardant waterborne polyurethane adhesive. The intrinsic flame retardant waterborne polyurethane adhesive of the present invention is used in the production of plywood, and the prepared board has high bonding strength, excellent water resistance and flame retardancy.

[0005] The present invention is achieved through the following technical solutions: An intrinsic flame retardant water-based polyurethane adhesive, the structural formula of which is as follows:

[0006] Wherein, -R- is derived from the structure of a polyamine, wherein the polyamine is 1,8-diamino-3,6-dioxaoctane or 3,6,9-trioxaundecane-1,11-diamine or diethylenetriamine or triethylenetetramine; and n is an integer of 8 to 18.

[0007] Furthermore, the solid content of the intrinsic flame retardant waterborne polyurethane adhesive is 30% to 50%.

[0008] A further improvement of the present invention is: A method for preparing an intrinsic flame retardant waterborne polyurethane adhesive comprises the following steps: S1: 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, trimellitic anhydride chloride, pyridine and anhydrous toluene are mixed, and refluxed for 5-7 hours under nitrogen protection to prepare phosphorus-containing dianhydride; S2: dissolving the phosphorus-containing dianhydride, glycerol carbonate and p-toluenesulfonic acid prepared in S1 in an appropriate amount of N,N-dimethylformamide solvent, reflux reaction for 3-5 hours, then adding hydroxyethyl methacrylate to the solution, continuing the reflux reaction for 3-5 hours, then adding triethanolamine to the solution, neutralizing reaction for 20-40 minutes, and removing the solvent under reduced pressure to obtain acrylate-modified phosphorus-containing bicyclic carbonate; S3: The acrylate-modified phosphorus-containing bicyclic carbonate and polyamine prepared in S2 are dissolved in an appropriate amount of acetone solvent, reacted at 75-80°C for 2-4 hours, cooled to below 40°C, added with initiator and distilled water, emulsified at high speed shearing, and acetone removed under reduced pressure to obtain an intrinsic flame-retardant water-based polyurethane adhesive with a solid content of 30%-50%.

[0009] The synthetic route is as follows:

[0010] Wherein, -R- is derived from the structure of a polyamine, wherein the polyamine is 1,8-diamino-3,6-dioxaoctane or 3,6,9-trioxaundecane-1,11-diamine or diethylenetriamine or triethylenetetramine; and n is an integer of 8 to 18.

[0011] Furthermore, in S1, the molar ratio of the 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide to trimellitic anhydride chloride is 2.5-3:1; and 100-150 mL of pyridine and 10-15 L of anhydrous toluene need to be added for every 1 mol of trimellitic anhydride chloride.

[0012] Furthermore, in S2, the molar ratio of the phosphorus diacid anhydride, glycerol carbonate, hydroxyethyl methacrylate and triethanolamine is 1:2.1~2.5:1.1~1.3:1; and the amount of p-toluenesulfonic acid used is 1~5wt% of the total amount of the reaction substrate.

[0013] Furthermore, in S3, the molar ratio of the acrylate-modified phosphorus-containing bicyclic carbonate, the polyamine and the initiator is 1:1.1-1.2:0.005-0.01; and 1.2-3.2 L of distilled water needs to be added for every 1 mol of the acrylate-modified phosphorus-containing bicyclic carbonate.

[0014] Furthermore, the initiator in S3 is tert-butyl perbenzoate or benzoyl peroxide or a mixture of the two; the polyamine is one or a mixture of two or more of 1,8-diamino-3,6-dioxaoctane, 3,6,9-trioxaundecane-1,11-diamine, diethylenetriamine or triethylenetetramine.

[0015] A further improvement of the present invention is: Application of the above intrinsic flame retardant waterborne polyurethane adhesive in the preparation of artificial boards.

[0016] Furthermore, the artificial board is plywood, particle board or fiberboard.

[0017] Furthermore, the use of the flame retardant waterborne polyurethane adhesive in the preparation of plywood, taking the preparation of plywood as an example, comprises the following steps: S1: Use intrinsic flame retardant water-based polyurethane adhesive to coat one or both sides of the veneer with a coating amount of 150~250g / m 2 , and then assemble several glue-coated veneers into required thickness specifications according to regulations to obtain slabs; S2: placing the slab for 15-30 minutes, and then pre-pressing it at 0.8-1.2 MPa for 30-60 minutes; S3: hot pressing the pre-pressed slab at 130-140°C and 0.8-1.2 MPa for 50-70 s / mm to obtain a plywood.

[0018] Furthermore, the veneer is selected from basswood, poplar, eucalyptus, paulownia, rubber wood, elm, birch or fir.

[0019] The beneficial effects of the present invention are: The present invention prepares a phosphorus-containing bicyclic carbonate modified by acrylate, and reacts it with a polyamine to obtain a non-isocyanate polyurethane with a side chain containing a methacrylate group, a phosphaphenanthrene group and a carboxylic acid ammonium salt. The carbonyl oxygen atom in the carbamate bond of the repeating unit structure in the main chain of the molecule can form a relatively stable state of an intramolecular six-membered ring structure with the hydroxyl group on the β-position carbon atom through hydrogen bonding force, thereby improving the hydrolysis resistance of the carbamate bond, so that the polyurethane has excellent water resistance, permeation resistance and chemical resistance. The carbonyl oxygen atom in the methacrylate group on the side chain can also form a hydrogen bonding force with the hydroxyl group on the main chain, and when heated and cured, the carbon-carbon double bond can be cross-linked to form a three-dimensional network structure, which significantly improves the bonding strength of the polyurethane, and the artificial board prepared by using the same has excellent mechanical properties. The phosphaphenanthrene group on the side chain releases phosphorus-containing free radicals and phenoxy free radicals when burning, which can capture high-activity free radicals such as HO· and H· generated during the combustion process, quench the combustion chain reaction in the gas phase, play a flame retardant effect, and make the polyurethane have excellent flame retardant properties. At the same time, the phosphaphenanthrene group is connected to the polyurethane molecular chain in the form of a covalent bond, so there is no problem of migration and precipitation in the matrix. The carboxylic acid ammonium salt on the side chain makes the polyurethane very hydrophilic, and it can spontaneously disperse in water to form an emulsion to obtain a water-based polyurethane. Compared with the method of dispersing polyurethane particles in water by adding an emulsifier, this self-emulsifying emulsion has a smaller particle size and high emulsion stability, avoiding the influence of the added emulsifier on the performance of the cured polyurethane film. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with specific embodiments.

[0021] Example 1: Preparation of intrinsic flame retardant waterborne polyurethane adhesive (1) 810 g of 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, 210 g of trimellitic anhydride chloride, 150 mL of pyridine and 10 L of anhydrous toluene were added into a reaction kettle, heated to 110° C. for reflux reaction for 5 h under nitrogen protection, then cooled to room temperature and filtered, then washed with chloroform and dried to obtain phosphorus-containing dianhydride; (2) 672 g of phosphorus-containing dianhydride prepared by S1, 248 g of glycerol carbonate and 18 g of p-toluenesulfonic acid were dissolved in 5 L of N,N-dimethylformamide solvent, and refluxed for 5 h. Then, 156 g of hydroxyethyl methacrylate was added to the solution, and refluxed for 3 h. Then, 149 g of triethanolamine was added to the solution, and neutralized for 30 min. The solvent was removed under reduced pressure to obtain an acrylate-modified phosphorus-containing bicyclic carbonate. (3) 1170 g of the acrylate-modified phosphorus-containing bicyclic carbonate prepared by S2 and 123 g of diethylenetriamine were dissolved in 5 L of acetone solvent, reacted at 80 °C for 3 h, cooled to 30 °C, added with 2 g of benzoyl peroxide and 1.9 L of distilled water, emulsified at high speed shearing, and acetone was removed under reduced pressure to obtain a waterborne polyurethane with a solid content of 40%; Example 2: Preparation of intrinsic flame retardant waterborne polyurethane adhesive (1) 810 g of 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, 210 g of trimellitic anhydride chloride, 150 mL of pyridine and 10 L of anhydrous toluene were added into a reaction kettle, heated to 110° C. for reflux reaction for 5 h under nitrogen protection, then cooled to room temperature and filtered, then washed with chloroform and dried to obtain phosphorus-containing dianhydride; (2) 672 g of phosphorus-containing dianhydride prepared by S1, 248 g of glycerol carbonate and 18 g of p-toluenesulfonic acid were dissolved in 5 L of N,N-dimethylformamide solvent, and refluxed for 5 h. Then, 156 g of hydroxyethyl methacrylate was added to the solution, and refluxed for 3 h. Then, 149 g of triethanolamine was added to the solution, and neutralized for 30 min. The solvent was removed under reduced pressure to obtain an acrylate-modified phosphorus-containing bicyclic carbonate. (3) 1170 g of the acrylate-modified phosphorus-containing bicyclic carbonate prepared by S2 and 178 g of 1,8-diamino-3,6-dioxaoctane were dissolved in 5 L of acetone solvent, reacted at 80 °C for 4 h, cooled to 30 °C, added with 2 g of benzoyl peroxide and 2 L of distilled water, emulsified at high speed shearing, and acetone was removed under reduced pressure to obtain a waterborne polyurethane with a solid content of 40%; Example 3: Preparation of plywood The water-based polyurethane with a solid content of 40% prepared in Example 1 was applied to both sides of the eucalyptus veneer using a roller coater, and the amount of adhesive applied was 150 g / m 2 ; The five veneers after gluing are assembled in such a way that the fiber directions of the adjacent veneers are perpendicular to each other to obtain a five-layer glued slab; After the slab was placed for 15 min, it was pre-pressed at a pressure of 0.8 MPa for 30 min; The pre-pressed slab was hot pressed at 135°C and 1 MPa for 5 min to obtain a 5-layer plywood. Example 4: Preparation of plywood In this embodiment, the glue application amount of the single board is 200g / m 2 , except for this, this embodiment is exactly the same as Embodiment 3 and will not be described in detail here.

[0022] Example 5: Preparation of plywood In this embodiment, the glue application amount of the single board is 250g / m2 , except for this, this embodiment is exactly the same as Embodiment 3 and will not be described in detail here.

[0023] Example 6: Preparation of plywood In this embodiment, the water-based polyurethane with a solid content of 40% prepared in Example 2 is used to apply glue on both sides of the eucalyptus veneer. Other than this, this embodiment is exactly the same as Example 3 and will not be described in detail here.

[0024] The relevant performance test results of the above embodiments are shown in Table 1, wherein the combustion performance grade is tested according to GB8624-2006 standard, the plywood category and bonding strength are tested according to GB / T9846-2015 and GB / T 17657-2013 standards, and the formaldehyde emission is tested according to GB18580-2017 standard.

[0025] Table 1 Performance test data of Examples 3 to 6 Test items Example 3 Example 4 Example 5 Example 6 Combustion level B B B B Plywood Type Ⅰ Ⅰ Ⅰ Ⅰ Bonding strength (MPa) 0.95 1.14 1.28 0.87 <![CDATA[Formaldehyde emission (mg / m 3 )]]> 0.01 0.01 0.01 0.01 Note: The formaldehyde emission of the eucalyptus veneer used in the example is 0.01 mg / m 3 The difference between Examples 3 to 5 is that the amount of glue applied to the veneer gradually increases. From the data in the above table, it can be seen that the plywood prepared using the intrinsic flame-retardant water-based polyurethane adhesive provided by the present invention has excellent flame retardant effect, and the combustion grade is Class B. The plywood meets the use environment requirements of Class I plywood, and the bonding strength gradually increases with the increase in the amount of glue applied. The formaldehyde emission of the plywood is equivalent to that of the original wood veneer, indicating that the adhesive does not release formaldehyde.

[0026] Compared with the performance of Example 3, the bonding strength of Example 6 is slightly lower. The difference between Example 6 and Example 3 is that Example 6 uses the polyurethane adhesive prepared in Example 2, while Example 3 uses the polyurethane adhesive prepared in Example 1. The difference between the polyurethane adhesives prepared in Example 2 and Example 1 is that the structures of the polyamines are different. Compared with the diethylenetriamine in Example 1, the 1,8-diamino-3,6-dioxaoctane in Example 2 contains an ether bond in its molecular structure and has a longer carbon chain, so the flexibility of the polyurethane molecular chain prepared therefrom is higher than that of Example 1. Therefore, the bonding strength of the plywood prepared in Example 6 is slightly lower than that of Example 3.

[0027] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An intrinsic flame retardant waterborne polyurethane adhesive, characterized in that: The structural formula of the intrinsic flame retardant waterborne polyurethane adhesive is as follows: ； Wherein, -R- is derived from the structure of a polyamine, wherein the polyamine is one or a mixture of two or more of 1,8-diamino-3,6-dioxaoctane, 3,6,9-trioxaundecane-1,11-diamine, diethylenetriamine or triethylenetetramine; and n is an integer of 8 to 18.

2. The intrinsic flame retardant waterborne polyurethane adhesive according to claim 1, characterized in that: The solid content of the intrinsic flame retardant waterborne polyurethane adhesive is 30% to 50%.

3. The method for preparing an intrinsic flame retardant waterborne polyurethane adhesive according to claim 1 or 2, characterized in that: The following steps are involved: S1: 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, trimellitic anhydride chloride, pyridine and anhydrous toluene are mixed, and refluxed for 5-7 hours under nitrogen protection to prepare phosphorus-containing dianhydride; S2: dissolving the phosphorus-containing dianhydride, glycerol carbonate and p-toluenesulfonic acid prepared in S1 in an appropriate amount of N,N-dimethylformamide solvent, reflux reaction for 3-5 hours, then adding hydroxyethyl methacrylate to the solution, continuing the reflux reaction for 3-5 hours, then adding triethanolamine to the solution, neutralizing reaction for 20-40 minutes, and removing the solvent under reduced pressure to obtain acrylate-modified phosphorus-containing bicyclic carbonate; S3: The acrylate-modified phosphorus-containing bicyclic carbonate and polyamine prepared in S2 are dissolved in an appropriate amount of acetone solvent, reacted at 75-80°C for 2-4 hours, cooled to below 40°C, added with initiator and distilled water, emulsified at high speed shearing, and acetone removed under reduced pressure to obtain an intrinsic flame-retardant water-based polyurethane adhesive with a solid content of 30%-50%.

4. The method for preparing an intrinsic flame retardant waterborne polyurethane adhesive according to claim 3, characterized in that: In S1, the molar ratio of the 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide to trimellitic anhydride chloride is 2.5-3:1; and 100-150 mL of pyridine and 10-15 L of anhydrous toluene need to be added for every 1 mol of trimellitic anhydride chloride.

5. The method for preparing an intrinsic flame retardant waterborne polyurethane adhesive according to claim 3, characterized in that: In S2, The molar ratio of the phosphorus dianhydride, glycerol carbonate, hydroxyethyl methacrylate and triethanolamine is 1:2.1-2.5:1.1-1.3:1; the amount of p-toluenesulfonic acid is 1-5wt% of the total amount of the reaction substrate.

6. The method for preparing an intrinsic flame retardant waterborne polyurethane adhesive according to claim 3, characterized in that: In S3, the molar ratio of the acrylate-modified phosphorus-containing bicyclic carbonate, the polyamine and the initiator is 1:1.1-1.2:0.005-0.01; 1.2-3.2 L of distilled water needs to be added for every 1 mol of the acrylate-modified phosphorus-containing bicyclic carbonate.

7. The method for preparing an intrinsic flame retardant waterborne polyurethane adhesive according to claim 3 or 6, characterized in that: The initiator in S3 is tert-butyl perbenzoate or benzoyl peroxide or a mixture of the two; the polyamine is one or a mixture of two or more of 1,8-diamino-3,6-dioxaoctane, 3,6,9-trioxaundecane-1,11-diamine, diethylenetriamine or triethylenetetramine.

8. Use of an intrinsic flame retardant waterborne polyurethane adhesive as claimed in claim 1 or 2 in the preparation of artificial boards.

9. Use of an intrinsic flame retardant waterborne polyurethane adhesive in the preparation of artificial boards according to claim 8, characterized in that: The artificial board is plywood, particle board or fiberboard, and the preparation of the plywood comprises the following steps: S1: Use intrinsic flame retardant water-based polyurethane adhesive to coat one or both sides of the veneer with a coating amount of 150~250g / m 2 , and then assemble several glue-coated veneers into required thickness specifications according to regulations to obtain slabs; S2: placing the slab for 15-30 minutes, and then pre-pressing it at 0.8-1.2 MPa for 30-60 minutes; S3: hot pressing the pre-pressed slab at 130-140° C. and 0.8-1.2 MPa for 50-70 s / mm to obtain a plywood.

10. Use of an intrinsic flame retardant waterborne polyurethane adhesive in the preparation of artificial boards according to claim 9, characterized in that: The veneer is selected from basswood, poplar, eucalyptus, paulownia, rubber wood, elm, birch or fir.

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