Low-VOC (volatile organic compound) flame-retardant double-faced adhesive tape for automotive trim and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, and discloses a low-VOC flame-retardant double faced adhesive tape for automotive trim and a preparation method thereof.The preparation method comprises the steps that tetramethyl ethylene bis (epoxypropyl ammonium chloride) and bis (4-aminophenyl)-phenyl phosphate react to obtain a cationic flame retardant, then the cationic flame retardant is added into water-based acrylic resin emulsion, and the water-based acrylic resin emulsion is added into the cationic flame retardant to obtain the low-VOC flame-retardant double faced adhesive tape for automotive trim. The flame-retardant water-based acrylic resin adhesive and the flame-retardant double-faced adhesive tape are obtained. Cationic groups in the cationic flame retardant and sodium carboxylate anions in the water-based acrylic resin form electrostatic acting force, so that the crosslinking degree between molecular chains of the acrylic resin is improved, the cohesion is increased, and the adhesive property and the tensile shear strength of the adhesive are favorably improved. The cationic flame retardant contains a triphenyl phosphate flame retardant structure, has a condensed phase flame retardant effect, improves the limit oxygen index and flame retardant property of the adhesive, and has good practical application in the aspects of adhesives for new energy automobiles, double faced adhesive tapes and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to a low-VOC flame-retardant double-sided adhesive for automobile interior decoration and a preparation method thereof. Background Art

[0002] Double-sided tape primarily consists of adhesive, backing material, and release film. Water-based acrylic resin adhesives use water as a solvent, are low in VOCs, and are environmentally friendly. They can be made into pressure-sensitive tapes and double-sided tapes, and are widely used in automotive, furniture, building materials, electronics, and other applications. However, acrylic resin adhesives and their double-sided tape products have low shear strength and bonding properties, are easily flammable, and have poor flame retardancy, hindering their application in products such as new energy vehicles.

[0003] Flame retardants are typically added to acrylic resin adhesives to improve their flame retardancy. Traditional phosphorus-containing flame retardants are hydrophobic and water-insoluble, resulting in poor dispersibility in water-based acrylic resins and the tendency to form precipitates, which can affect the adhesive's storage stability and bonding properties. Patent application number CN118599452A discloses a water-based flame-retardant acrylic pressure-sensitive adhesive for carpet protective films, as well as its preparation method and application. The water-based flame-retardant acrylic pressure-sensitive adhesive is prepared using melamine, phytic acid, and acrylic acid monomers as raw materials. Compared to that patent application, the present invention utilizes a cationic flame retardant to improve the flame retardancy of the water-based acrylic resin adhesive and its double-sided tape, while also improving bonding performance. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a low-VOC flame-retardant double-sided adhesive for automobile interior and a preparation method thereof, which solves the problems of low shear strength and poor flame retardancy of acrylic resin adhesive.

[0005] The technical solution of the present invention is: a method for preparing low-VOC flame-retardant double-sided adhesive for automobile interior decoration:

[0006] (1) Add ethanol, tetramethylethylenedi(epoxypropylammonium chloride), and bis(4-aminophenyl)-phenyl phosphate to a flask, stir to react, and then cool in an ice-water bath. Filter, wash with ethanol, and dry to obtain a cationic flame retardant. The preparation reaction formula is:

[0007]

[0008] (2) Adding a water-based acrylic resin emulsion, a cationic flame retardant, and a defoaming agent into a container and stirring the mixture to obtain a flame-retardant water-based acrylic resin adhesive; finally, coating the adhesive on both sides of a substrate to obtain a low-VOC flame-retardant double-sided adhesive.

[0009] Furthermore, the ratio of tetramethylethylenedi(epoxypropylammonium chloride) to bis(4-aminophenyl)-phenyl phosphate in (1) is 1 mol:(1:1.1) mol.

[0010] Furthermore, the reaction in (1) is carried out at 45-70°C for 6-10 hours.

[0011] Furthermore, the ratio of the aqueous acrylic resin emulsion to the cationic flame retardant is 1 L: (15-50) g.

[0012] Furthermore, the preparation method of the water-based acrylic resin emulsion is as follows: adding acrylic acid monomer, acrylate monomer, and emulsifier to water to obtain a monomer solution; then introducing nitrogen into the flask, dropwise adding the monomer solution and initiator solution, adding a buffer, heating to 75-85° C., reacting for 30-40 minutes, then dropwise adding the monomer solution and initiator solution, reacting for 3-4 hours, adding a neutralizer to adjust the pH to 7-8, and obtaining the water-based acrylic resin emulsion.

[0013] Furthermore, the buffer comprises sodium bicarbonate.

[0014] Furthermore, the neutralizing agent includes sodium hydroxide.

[0015] Furthermore, the ratio of acrylic acid monomer, acrylic ester monomer, initiator and emulsifier is (6-10) g: (90-94) g: (0.4-0.7) g: (2-3) g.

[0016] Furthermore, the acrylic monomer includes acrylic acid and methacrylic acid.

[0017] Furthermore, the acrylate monomer includes methyl methacrylate and butyl acrylate.

[0018] Furthermore, the initiator includes potassium persulfate or ammonium persulfate.

[0019] Furthermore, the emulsifier includes sodium lauryl sulfate and OP-10.

[0020] Furthermore, low-VOC flame-retardant double-sided tape is used in automotive interiors.

[0021] The present invention has the beneficial technical effect of producing a cationic flame retardant by ring-opening polymerization of tetramethylethylenedi(epoxypropylammonium chloride) and bis(4-aminophenyl)-phenyl phosphate. This is then added to a water-based acrylic resin adhesive and coated on a substrate to produce a low-VOC flame-retardant double-sided adhesive. The cationic flame retardant polymer chain contains hydrophilic cationic groups, hydroxyl groups, and imino groups, exhibiting excellent hydrophilicity and water solubility. It dissolves well in the water-based acrylic resin emulsion, resulting in an adhesive with good dispersibility and no precipitation. The adhesive uses water as a solvent, does not contain any organic solvents, has a very low VOC content, and is environmentally friendly.

[0022] The cationic groups in the cationic flame retardant of the present invention form electrostatic forces with the sodium carboxylate anions in the water-based acrylic resin, while the hydroxyl groups and imino groups form hydrogen bonding forces with the ester groups, carboxylic acid groups and other groups in the water-based acrylic resin, thereby increasing the crosslinking degree between the acrylic resin molecular chains and increasing the cohesive force, which is beneficial to improving the bonding performance of the adhesive and exhibiting higher tensile shear strength.

[0023] The cationic flame retardant of the present invention contains a triphenyl phosphate flame retardant structure, has a condensed phase flame retardant effect, improves the limiting oxygen index and flame retardant performance of the adhesive, and has good practical applications in adhesives for new energy vehicle interiors, double-sided tapes, and the like. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Tetramethylethylenedi(epoxypropylammonium chloride) was prepared according to the method of the journal Molecules, 2023, 28, 4120; the article "Influence of a Composite Polylysine-Polydopamine-Quaternary Ammonium Salt Coating on Titanium on Its Ostogenic and Antibacterial Performance"

[0026] The structural formula is

[0027] Bis(4-aminophenyl)-phenyl phosphate was prepared according to the method of the literature "Synthesis and Performance Study of Bis(4-aminophenyl)-phenyl phosphate" published in the journal "China Adhesives", Vol. 16, No. 4, April 2007. The structural formula is

[0028] Example 1:

[0029] (1) Add 150 mL of ethanol, 40 mmol of tetramethylethylenedi(epoxypropylammonium chloride), and 40 mmol of bis(4-aminophenyl)-phenyl phosphate into a flask, heat to 60° C., stir and react for 10 hours, cool in an ice-water bath, filter, wash with ethanol, and dry to obtain a cationic flame retardant.

[0030] (2) 35 g of acrylic acid, 190 g of methyl methacrylate, 275 g of butyl acrylate, 8 g of sodium lauryl sulfate, and 4 g of OP-10 were added to 500 mL of water to obtain a monomer solution; nitrogen was then introduced into the flask, 120 mL of the monomer solution, 3 mL of an aqueous solution of 0.6 g of ammonium persulfate, and 0.23 g of sodium bicarbonate were added dropwise, and the mixture was heated to 75° C. and reacted for 40 min. The remaining monomer solution and 8 mL of an aqueous solution containing 2 g of ammonium persulfate were then added dropwise, and the mixture was reacted for 4 h. Sodium hydroxide was added to adjust the pH to 8 to obtain a water-based acrylic resin emulsion.

[0031] (3) 1 L of water-based acrylic resin emulsion, 15 g of cationic flame retardant, and 6 g of defoaming agent BYK-021 were added to a container and stirred to obtain a flame-retardant water-based acrylic resin adhesive; finally, the adhesive was coated on both sides of a polypropylene substrate to obtain a low-VOC flame-retardant double-sided adhesive.

[0032] Example 2:

[0033] (1) Add 200 mL of ethanol, 40 mmol of tetramethylethylenedi(epoxypropylammonium chloride), and 44 mmol of bis(4-aminophenyl)-phenyl phosphate into a flask, heat to 45°C, stir and react for 10 hours, cool in an ice water bath, filter, wash with ethanol, and dry to obtain a cationic flame retardant.

[0034] (2) 50 g of acrylic acid, 160 g of methyl methacrylate, 290 g of butyl acrylate, 10 g of sodium lauryl sulfate, and 5 g of OP-10 were added to 500 mL of water to obtain a monomer solution; nitrogen was then introduced into the flask, 150 mL of the monomer solution, 5 mL of an aqueous solution of 0.9 g of potassium persulfate, and 0.28 g of sodium bicarbonate were added dropwise, and the mixture was heated to 85° C. and reacted for 30 min. The remaining monomer solution and 10 mL of an aqueous solution containing 2.6 g of potassium persulfate were then added dropwise, and the mixture was reacted for 3 h. Sodium hydroxide was added to adjust the pH to 7 to obtain a water-based acrylic resin emulsion.

[0035] (3) 1 L of water-based acrylic resin emulsion, 30 g of cationic flame retardant, and 9 g of defoaming agent BYK-021 were added to a container and stirred to obtain a flame-retardant water-based acrylic resin adhesive; finally, the adhesive was coated on both sides of a polypropylene substrate to obtain a low-VOC flame-retardant double-sided adhesive.

[0036] Example 3:

[0037] (1) Add 200 mL of ethanol, 40 mmol of tetramethylethylenedi(epoxypropylammonium chloride), and 40 mmol of bis(4-aminophenyl)-phenyl phosphate into a flask, heat to 70° C., stir and react for 6 h, cool in an ice-water bath, filter, wash with ethanol, and dry to obtain a cationic flame retardant.

[0038] (2) 30 g of methacrylic acid, 220 g of methyl methacrylate, 250 g of butyl acrylate, 6.5 g of sodium lauryl sulfate, and 3.5 g of OP-10 were added to 600 mL of water to obtain a monomer solution; nitrogen was then introduced into the flask, 150 mL of the monomer solution, 3 mL of an aqueous solution containing 0.5 g of ammonium persulfate, and 0.26 g of sodium bicarbonate were added dropwise, and the mixture was heated to 80° C. and reacted for 40 min. The remaining monomer solution and 10 mL of an aqueous solution containing 1.5 g of ammonium persulfate were then added dropwise, and the mixture was reacted for 3 h. Sodium hydroxide was added to adjust the pH to 8 to obtain a water-based acrylic resin emulsion.

[0039] (3) 1 L of water-based acrylic resin emulsion, 50 g of cationic flame retardant, and 5 g of defoaming agent BYK-021 were added to a container and stirred to obtain a flame-retardant water-based acrylic resin adhesive; finally, the adhesive was coated on both sides of a polypropylene substrate to obtain a low-VOC flame-retardant double-sided adhesive.

[0040] Comparative Example 1: The difference between this comparative example and Example 1 is that no cationic flame retardant is added.

[0041] (1) 1 L of aqueous acrylic resin emulsion and 6 g of defoamer BYK-021 were added to a container and stirred to obtain a aqueous acrylic resin adhesive; finally, the adhesive was applied to both sides of a polypropylene substrate to obtain a double-sided tape.

[0042] Comparative Example 2: The difference between this comparative example and Example 1 is that bis(4-aminophenyl)-phenyl phosphate is used instead of the cationic flame retardant.

[0043] (1) 1 L of aqueous acrylic resin emulsion, 15 g of bis(4-aminophenyl)-phenyl phosphate, and 6 g of defoamer BYK-021 were added to a container and stirred to obtain a aqueous acrylic resin adhesive; finally, the adhesive was coated on both sides of a polypropylene substrate to obtain a double-sided tape.

[0044] Comparative Example 3: The difference between this comparative example and Example 1 is that ethylene glycol diglycidyl ether is used instead of tetramethylethylenedi(epoxypropylammonium chloride).

[0045] (1) Add 150 mL of ethanol, 40 mmol of ethylene glycol diglycidyl ether, and 40 mmol of bis(4-aminophenyl)-phenyl phosphate into a flask, heat to 60° C., stir and react for 10 hours, cool in an ice water bath, filter, wash with ethanol, and dry to obtain a polymer flame retardant.

[0046] (2) 1 L of aqueous acrylic resin emulsion, 15 g of polymer flame retardant, and 6 g of defoaming agent BYK-021 are added to a container and stirred to obtain a aqueous acrylic resin adhesive; finally, the adhesive is coated on both sides of a polypropylene substrate to obtain a double-sided tape.

[0047] Comparative Example 4: The difference between this comparative example and Example 1 is that benzyl diamine is used instead of bis(4-aminophenyl)-phenyl phosphate.

[0048] (1) Add 150 mL of ethanol, 40 mmol of tetramethylethylenedi(epoxypropylammonium chloride), and 40 mmol of benzyldiamine to a flask, heat to 60°C, stir and react for 10 hours, cool in an ice-water bath, filter, wash with ethanol, and dry to obtain a cationic polymer.

[0049] (2) 1 L of aqueous acrylic resin emulsion, 15 g of cationic polymer, and 6 g of defoamer BYK-021 were added to a container and stirred to obtain a aqueous acrylic resin adhesive; finally, the adhesive was coated on both sides of a polypropylene substrate to obtain a double-sided tape.

[0050] The water-based acrylic resin adhesive was placed at room temperature for 3 months, and the dispersion state of the adhesive was observed.

[0051] The water-based acrylic resin adhesive is poured into the mold and then baked and cured at 60°C for 6 hours to form an adhesive film. The flame retardant properties are in accordance with GB / T 2406.1-2008 standards.

[0052] Double-sided tape was used to bond two pieces of tinplate, and then they were cured by baking at 60°C for 8 hours, and finally left at room temperature for 12 hours. The tensile shear strength was tested according to GB / T 7124-2008 standard.

[0053] Table 1 Performance test

[0054]

[0055] The limiting oxygen index of the water-based acrylic resin adhesive of Comparative Example 1 is only 18.3%, and the tensile shear strength is only 16.8 MPa, with poor flame retardancy and bonding properties. Each embodiment adds a cationic flame retardant, and its polymer molecular chain contains hydrophilic cationic groups, hydroxyl groups, and imino groups, which have good hydrophilicity and water solubility, can be well dissolved in the water-based acrylic resin emulsion, and the adhesive has good dispersibility and no precipitation. The cationic groups in the cationic flame retardant form electrostatic forces with the sodium carboxylate anions in the water-based acrylic resin, while the hydroxyl groups and imino groups form hydrogen bonding forces with the ester groups, carboxylic acid groups, etc. in the water-based acrylic resin, thereby increasing the crosslinking degree between the acrylic resin molecular chains and increasing the cohesive force, which is conducive to improving the bonding properties of the adhesive and showing higher tensile shear strength. At the same time, the cationic flame retardant contains a triphenyl phosphate flame retardant structure, has a condensed phase flame retardant effect, and improves the limiting oxygen index and flame retardant properties of the adhesive.

[0056] Comparative Example 2: Bis(4-aminophenyl)-phenyl phosphate was added to the water-based acrylic resin adhesive. The water solubility of bis(4-aminophenyl)-phenyl phosphate was very poor, resulting in obvious precipitates in the adhesive emulsion, which affected the bonding properties of the adhesive and resulted in low tensile shear strength.

[0057] In Comparative Example 3, ethylene glycol diglycidyl ether and bis(4-aminophenyl)-phenyl phosphate are polymerized, and the resulting flame retardant does not contain a cationic group, resulting in poor water solubility of the polymer flame retardant, poor dispersibility in the water-based acrylic resin adhesive, and obvious precipitation, which will affect the bonding performance of the adhesive. At the same time, the polymer flame retardant does not contain a cationic group, and it is difficult to form an electrostatic force with the sodium carboxylate anion in the water-based acrylic resin, and the cross-linking degree between the acrylic resin molecular chains is not well improved, resulting in low bonding performance and tensile shear strength of the adhesive.

[0058] Comparative Example 4: In a polymerization reaction between benzyl diamine and tetramethylethylenedi(epoxypropylammonium chloride), the obtained cationic polymer does not contain the flame retardant structure of triphenyl phosphate, resulting in a low limiting oxygen index of the flame retardant and poor flame retardancy.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a flame retardant double-sided adhesive tape, characterized in that: The preparation method comprises: (1) adding ethanol, tetramethylethylenedi(epoxypropylammonium chloride), and bis(4-aminophenyl)-phenyl phosphate into a flask, stirring for reaction, cooling in an ice-water bath, filtering, washing, and drying to obtain a cationic flame retardant; (2) Adding a water-based acrylic resin emulsion, a cationic flame retardant, and a defoaming agent into a container and stirring the mixture to obtain a flame-retardant water-based acrylic resin adhesive; finally, coating the adhesive on both sides of a substrate to obtain a low-VOC flame-retardant double-sided adhesive.

2. The method for preparing the low-VOC flame retardant double-sided adhesive according to claim 1, characterized in that: The ratio of tetramethylethylenedi(epoxypropylammonium chloride) to bis(4-aminophenyl)-phenyl phosphate in (1) is 1 mol:(1:1.1) mol.

3. The method for preparing the low-VOC flame retardant double-sided adhesive tape according to claim 1, characterized in that: The reaction in (1) is carried out at 45-70°C for 6-10 hours.

4. The method for preparing the low-VOC flame retardant double-sided adhesive tape according to claim 1, characterized in that: The ratio of the aqueous acrylic resin emulsion to the cationic flame retardant is 1L:(15-50)g.

5. The method for preparing the low-VOC flame retardant double-sided adhesive tape according to claim 1, characterized in that: The preparation method of the water-based acrylic resin emulsion comprises the following steps: adding acrylic acid monomer, acrylate monomer, and emulsifier into water to obtain a monomer solution; then introducing nitrogen into a flask, dropwise adding the monomer solution and an initiator solution, adding a buffer, heating to 75-85° C., reacting for 30-40 minutes, then dropwise adding the monomer solution and the initiator solution, reacting for 3-4 hours, and adding a neutralizer to adjust the pH to 7-8 to obtain the water-based acrylic resin emulsion.

6. The method for preparing the low-VOC flame-retardant double-sided adhesive tape according to claim 5, characterized in that: The buffering agent includes sodium bicarbonate, and the neutralizing agent includes sodium hydroxide.

7. The method for preparing the low-VOC flame retardant double-sided adhesive tape according to claim 5, characterized in that: The ratio of the acrylic acid monomer, the acrylic ester monomer, the initiator and the emulsifier is (6-10) g: (90-94) g: (0.4-0.7) g: (2-3) g.

8. The method for preparing the low-VOC flame retardant double-sided adhesive tape according to claim 7, characterized in that: The acrylic acid monomer includes acrylic acid and methacrylic acid; the acrylate monomer includes methyl methacrylate and butyl acrylate; the initiator includes potassium persulfate or ammonium persulfate; and the emulsifier includes sodium lauryl sulfate and OP-10.

9. A low-VOC flame-retardant double-sided adhesive tape obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the low-VOC flame-retardant double-sided adhesive tape according to claim 9 in automobile interior decoration.

Images