A halogen-free flame-retardant UV-curable pressure-sensitive adhesive and its preparation method

Abstract

This invention discloses a halogen-free flame-retardant UV-curable pressure-sensitive adhesive, comprising the following components: 40-60 parts by weight of an epoxidized soybean oil-dibutyl phosphate modifier, 40-60 parts by weight of an acrylate monomer, 0.1-25 parts by weight of aluminum hydroxide, 0.1-1 parts by weight of a crosslinking agent, and 0.3-1 parts by weight of a photoinitiator. This invention also discloses a method for preparing the epoxidized soybean oil-dibutyl phosphate modifier. This invention uses environmentally friendly, green, and renewable epoxidized soybean oil reacted with non-flame-retardant dibutyl phosphate to prepare the modifier. This not only introduces phosphorus into the pressure-sensitive adhesive system but also acts as a tackifying resin to improve the adhesive properties of the pressure-sensitive adhesive. Furthermore, through the synergistic flame-retardant effect with aluminum hydroxide, the flame-retardant effect is significantly improved without adversely affecting the adhesive properties of the pressure-sensitive adhesive. This greatly reduces the amount of aluminum hydroxide used and significantly minimizes its impact on the adhesive properties of the pressure-sensitive adhesive.

Description

Technical Field

[0001] This invention relates to the field of modified epoxidized soybean oil and UV-curable pressure-sensitive adhesive technology, specifically to a halogen-free flame-retardant UV-curable pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives are a special type of viscoelastic polymer that can adhere to various substrate surfaces with light pressure applied within a short time, without requiring activation by heating, solvents, or water. Due to their sufficient cohesive strength and elasticity, they leave no residue when removed from smooth surfaces. Acrylic pressure-sensitive adhesives are among the fastest-growing and most widely used types, finding extensive applications in high-tech fields (such as the automotive, electronics, and aerospace industries) and everyday life (such as printing, magnetic tapes, labels, and medical products).

[0003] As the application range of acrylic pressure-sensitive adhesives gradually expands, the requirements for their performance are also becoming increasingly stringent. However, ordinary acrylic pressure-sensitive adhesives are flammable, limiting their use in some fields. Although flame-retardant acrylic pressure-sensitive adhesives have emerged on the market, these products mainly use halogenated flame retardants, which does not align with the concept of green development. Furthermore, the excessively high proportion of aluminum hydroxide in existing halogen-free flame-retardant pressure-sensitive adhesives negatively impacts their bonding performance. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing methods, the present invention aims to provide a novel halogen-free flame-retardant acrylic pressure-sensitive adhesive that combines flame retardancy and adhesive properties, thereby improving the flame retardancy and adhesive properties of the acrylic pressure-sensitive adhesive.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A halogen-free flame-retardant UV-curable pressure-sensitive adhesive, comprising the following components by weight:

[0007]

[0008] Preferably, the crosslinking agent has a weight ratio of 0.2.

[0009] Preferably, the aluminum hydroxide has a particle size of 800-8000 mesh.

[0010] Preferably, the crosslinking agent includes one or more of 1,6-hexanediol diacrylate and trimethylolpropane triacrylate.

[0011] Preferably, the photoinitiator is one of 1173 photoinitiator, 184 photoinitiator, or TPO-L photoinitiator.

[0012] Preferably, in the acrylate monomers, the soft monomer is isooctyl acrylate and the hard monomer is acrylic acid.

[0013] More preferably, the isooctyl acrylate is in the amount of 20-30 parts by weight, and the acrylic acid is in the amount of 20-30 parts by weight.

[0014] A method for preparing a halogen-free flame-retardant UV-curable pressure-sensitive adhesive, the specific steps of which are as follows:

[0015] The acrylate monomer, crosslinking agent, photoinitiator, and epoxidized soybean oil-dibutyl phosphate modifier are thoroughly stirred and dissolved. Then, aluminum hydroxide is added and stirred until uniformly mixed to obtain an unreacted adhesive. The unreacted adhesive is then UV-cured in the absence of oxygen to obtain the halogen-free flame-retardant UV-curable pressure-sensitive adhesive.

[0016] Preferably, the preparation method of the epoxidized soybean oil-dibutyl phosphate modified product includes the following specific steps:

[0017] (1) Add epoxidized soybean oil and dibutyl phosphate to the reaction apparatus and stir;

[0018] (2) The temperature is raised at a constant rate using a heating device, and the reaction is continued after adding a catalyst to obtain the epoxidized soybean oil-dibutyl phosphate modified product.

[0019] More preferably, the uniform heating rate specifically refers to uniformly heating to 85-90°C.

[0020] More preferably, the continued reaction specifically refers to a continued reaction for 4-6 hours.

[0021] Preferably, the epoxy value of the epoxidized soybean oil is 6-7%.

[0022] Preferably, the catalyst is one of triphenylphosphine or N,N-dimethylbenzylamine.

[0023] More preferably, the catalyst is triphenylphosphine.

[0024] Preferably, the amount of catalyst added is 0.2-1.2 parts by weight.

[0025] More preferably, the catalyst is added in an amount of 0.5 parts by weight.

[0026] Preferably, the weight ratio of the epoxidized soybean oil to the dibutyl phosphate is 55:30-60.

[0027] More preferably, the weight ratio of the oxygenated soybean oil to the dibutyl phosphate is 55:45.

[0028] The present invention has the following advantages and beneficial effects compared with existing methods:

[0029] (1) The present invention uses environmentally friendly, green and renewable epoxidized soybean oil and non-flame retardant dibutyl phosphate to prepare a modified product. This can introduce phosphorus into the pressure-sensitive adhesive system and also act as a tackifying resin to improve the adhesion performance of the pressure-sensitive adhesive. Furthermore, through the synergistic flame retardant effect with aluminum hydroxide, the flame retardant effect is significantly improved. Aluminum hydroxide decomposes upon heating to produce alumina and water vapor. The epoxidized soybean oil-dibutyl phosphate modifier decomposes upon heating to produce phosphorus-containing free radicals and phosphate compounds. At this point, on the surface of the pressure-sensitive adhesive, water vapor evaporation reduces the system's calorific value. Alumina adsorbs combustible solid particles, phosphorus-containing free radicals consume some active free radicals, and the alumina and phosphate compounds covering the pressure-sensitive adhesive surface promote hydroxyl dehydration to form a char layer. However, due to insufficient strength of the char layer to prevent heat transfer, the epoxidized soybean oil-dibutyl phosphate and aluminum hydroxide inside the pressure-sensitive adhesive continue to decompose upon heating, producing a large amount of gas and water vapor, leading to increased internal pressure and sample expansion. When the pressure exceeds a critical value, a large amount of non-combustible gas and water vapor breaks through the char layer, creating numerous pores in the char layer while also diluting the concentration of combustible gases and oxygen on the surface, thus reducing the calorific value. The epoxidized soybean oil-dibutyl phosphate modifier and aluminum hydroxide work synergistically, acting both inside and outside the pressure-sensitive adhesive, in both the gas phase and the solidification phase, effectively improving the flame-retardant properties of the pressure-sensitive adhesive.

[0030] The key point of this invention is that the epoxidized soybean oil-dibutyl phosphate modified compound is only a phosphorus-containing compound and not a flame retardant. When compounded with aluminum hydroxide, it significantly reduces the amount of aluminum hydroxide used while maintaining excellent flame retardant properties in the pressure-sensitive adhesive without adversely affecting its bonding performance. Compared with other solutions that simply use aluminum hydroxide as a flame retardant, this invention greatly reduces the amount of aluminum hydroxide used and significantly reduces the impact on the bonding performance of the pressure-sensitive adhesive. Furthermore, the UV-cured polymerization method used in this invention has advantages such as simple operation, low energy consumption, minimal environmental pollution, virtually no volatile components, and good economic benefits.

[0031] (2) In this invention, the ratio of soft monomers to hard monomers is 1:1. Since the epoxidized soybean oil-dibutyl phosphate modifier itself has a certain viscosity and acts similarly to a tackifying resin, compared to other UV pressure-sensitive adhesives, the formulation of this invention has a higher content of hard monomers, which can also increase the physical crosslinking points and cohesive strength. Combined with the aforementioned specific types of crosslinking agents, the chemical crosslinking density of the pressure-sensitive adhesive can be increased, thereby improving the cohesive strength and ultimately enhancing the adhesive strength. The halogen-free flame-retardant UV-curable pressure-sensitive adhesive prepared by this invention can achieve a flame retardancy rating of V-0 and a maximum 180° peel strength of 29.5 N / 25 mm, exhibiting both good flame retardant properties and excellent adhesive properties. Attached Figure Description

[0032] Figure 1 This is a reaction mechanism diagram of epoxidized soybean oil-dibutyl phosphate modified product. Detailed Implementation

[0033] The invention's objective will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the implementation of the invention is not limited to the following embodiments.

[0034] Example 1

[0035] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 25 parts by weight of aluminum hydroxide, 0.2 parts by weight of 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0036] The preparation method of the halogen-free flame-retardant UV-curable pressure-sensitive adhesive in this embodiment includes the following steps:

[0037] (1) Add epoxidized soybean oil and dibutyl phosphate to the reaction apparatus and start stirring;

[0038] (2) Turn on the heating device and heat it to 90°C at a constant rate. Add the catalyst and continue the reaction for 6 hours to obtain the epoxidized soybean oil-dibutyl phosphate modified product; (3) Weigh the epoxidized soybean oil-dibutyl phosphate modified product, acrylate monomer, crosslinking agent and photoinitiator prepared above and stir them thoroughly until completely dissolved. Finally, add aluminum hydroxide and stir thoroughly until evenly dispersed to obtain the unreacted pressure-sensitive adhesive liquid;

[0039] (4) The unreacted adhesive is UV cured in the absence of oxygen to obtain the halogen-free flame-retardant UV-curable pressure-sensitive adhesive.

[0040] The reaction mechanism diagram of the epoxidized soybean oil-dibutyl phosphate modified product is shown below. Figure 1 As shown, by Figure 1 It is known that the epoxy groups on the epoxidized soybean oil molecule and the phosphate groups in dibutyl phosphate undergo a ring-opening reaction under the action of a catalyst, and dibutyl phosphate is grafted onto the epoxidized soybean oil to obtain the epoxidized soybean oil-dibutyl phosphate modified product.

[0041] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive sample of this embodiment was cut into strips and preserved. The 180° peel strength of the adhesive strips was tested on an electronic tensile testing machine according to GB / T 2792-2014 standard; the flame retardancy rating of the adhesive strips was tested on a horizontal and vertical flame tester according to UL94-2006 standard. The test results are shown in Table 1.

[0042] Example 2

[0043] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0044] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0045] Example 3

[0046] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 15 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0047] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0048] Example 4

[0049] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 10 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0050] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0051] Example 5

[0052] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 5 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0053] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0054] Example 6

[0055] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 40 parts by weight of acrylate monomer, 60 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0056] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0057] Example 7

[0058] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 45 parts by weight of acrylate monomer, 55 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0059] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0060] Example 8

[0061] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 55 parts by weight of acrylate monomer, 45 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0062] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0063] Example 9

[0064] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 60 parts by weight of acrylate monomer, 40 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0065] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0066] Example 10

[0067] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 70 parts by weight of acrylate monomer, 30 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0068] The preparation steps are the same as in Example 1.

[0069] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive sample of this embodiment was cut into strips and preserved. The flame retardancy rating of the adhesive strips was tested on a horizontal and vertical flame tester according to the UL94-2006 standard. The test results are shown in Table 1.

[0070] Example 11

[0071] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent trimethylolpropane triacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0072] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0073] Example 12

[0074] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.3 parts by weight of 1173 photoinitiator.

[0075] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0076] Example 13

[0077] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 1 part by weight of 1173 photoinitiator.

[0078] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0079] Example 14

[0080] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 184 photoinitiator.

[0081] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0082] Example 15

[0083] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of TPO-L photoinitiator.

[0084] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0085] Comparative Example 1

[0086] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 50 parts by weight of acrylate monomer, 50 parts by weight of epoxidized soybean oil-dibutyl phosphate modifier, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0087] The preparation method of the halogen-free flame-retardant UV-curable pressure-sensitive adhesive in this embodiment includes the following steps:

[0088] (1) Add 55 parts by weight of epoxidized soybean oil and 45 parts by weight of dibutyl phosphate into the reaction apparatus and start stirring;

[0089] (2) Turn on the heating device, raise the temperature to 90°C at a constant rate, add the catalyst, and continue the reaction for 6 hours to obtain the epoxidized soybean oil-dibutyl phosphate modified product.

[0090] (3) Weigh 50 parts by weight of the epoxidized soybean oil-dibutyl phosphate modified product prepared above, add 50 parts by weight of acrylate monomer, 0.2 parts by weight of 1,6-hexanediol diacrylate and 0.5 parts by weight of 1173 photoinitiator and stir thoroughly until completely dissolved to obtain unreacted pressure-sensitive adhesive liquid.

[0091] (4) The unreacted adhesive is UV cured in the absence of oxygen to obtain the halogen-free flame-retardant UV-curable pressure-sensitive adhesive.

[0092] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive sample of this embodiment was cut into strips and preserved. The 180° peel strength of the adhesive strips was tested on an electronic tensile testing machine according to GB / T 2792-2014 standard; the flame retardancy rating of the adhesive strips was tested on a horizontal and vertical flame tester according to UL94-2006 standard. The test results are shown in Table 1.

[0093] The preparation steps and testing methods were the same as in Example 1, and the test results are shown in Table 1.

[0094] Comparative Example 2

[0095] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive of this embodiment comprises the following raw materials by weight: 100 parts by weight of acrylate monomer, 20 parts by weight of aluminum hydroxide, 0.2 parts by weight of crosslinking agent 1,6-hexanediol diacrylate, and 0.5 parts by weight of 1173 photoinitiator.

[0096] The preparation steps are the same as in Example 1.

[0097] The halogen-free flame-retardant UV-curable pressure-sensitive adhesive sample of this embodiment was cut into strips and preserved. The flame retardancy rating of the adhesive strips was tested on a horizontal and vertical flame tester according to the UL94-2006 standard. The test results are shown in Table 1.

[0098] Table 1 shows the formulation (wt%), peel strength, and flame retardant rating of the halogen-free flame-retardant UV-curable pressure-sensitive adhesives in each embodiment.

[0099] Table 1

[0100]

[0101] As shown in Table 1, the combination of epoxidized soybean oil-dibutyl phosphate modifier and aluminum hydroxide can greatly improve the flame retardant and adhesive properties of pressure-sensitive adhesives, with most of them having a 180° peel strength exceeding 20N / 25mm.

[0102] As shown in Examples 1-5 and Comparative Example 1, when the contents of acrylate monomer and epoxidized soybean oil-dibutyl phosphate modifier remain constant, the pressure-sensitive adhesive (PSA) is not flame-retardant without the addition of aluminum hydroxide. This indicates that simply adding epoxidized soybean oil-dibutyl phosphate modifier cannot impart flame-retardant properties to the PSA. With increasing aluminum hydroxide content, the flame-retardant effect of the PSA improves, reaching a V-0 rating at 10 parts by weight. Adding only 10-25 parts by weight of aluminum hydroxide to the PSA also fails to provide flame retardancy, indicating a synergistic effect between the epoxidized soybean oil-dibutyl phosphate modifier and aluminum hydroxide. Furthermore, the peel strength of the PSA does not change significantly with varying aluminum hydroxide content, indicating that aluminum hydroxide does not affect the adhesive properties of the PSA at low concentrations. Therefore, the PSA balances both flame-retardant and adhesive properties.

[0103] As shown in Examples 2, 6-10, and Comparative Example 2, when the aluminum hydroxide content in the pressure-sensitive adhesive remains unchanged, the pressure-sensitive adhesive does not possess flame-retardant properties without the addition of epoxidized soybean oil-dibutyl phosphate modifier, indicating that a low content of aluminum hydroxide cannot impart flame-retardant properties to the pressure-sensitive adhesive. When the content of epoxidized soybean oil-dibutyl phosphate modifier gradually increases, the flame-retardant properties of the pressure-sensitive adhesive improve, which also indicates that there is a synergistic effect between epoxidized soybean oil-dibutyl phosphate modifier and aluminum hydroxide. The adhesive properties of the pressure-sensitive adhesive (PSA) first increase and then decrease with increasing content of epoxidized soybean oil-dibutyl phosphate modifier. This is because when the content of epoxidized soybean oil-dibutyl phosphate modifier is low, the hard monomer acrylic acid content in the PSA is high, forming more hydrogen bonds within the colloid, increasing intermolecular forces, resulting in excessive cohesive strength and poor wettability on the test steel plate, leading to poor adhesive performance. As the content of epoxidized soybean oil-dibutyl phosphate modifier increases, the modifier with very few polar groups dilutes the concentration of acrylic acid within the colloid, reducing intermolecular forces and increasing the mobility of molecular chains. This increases the wettability of the PSA on the test steel plate, thus improving adhesive performance. However, with further increases in the content of epoxidized soybean oil-dibutyl phosphate modifier, the proportion of non-polar groups becomes too high, reducing the interaction force between the PSA and the surface of the test steel plate, thus decreasing adhesive performance.

[0104] As can be seen from Examples 2 and 11, changing the type of crosslinking agent does not affect the flame retardant properties of the pressure-sensitive adhesive, but changes in crosslinking density will affect the adhesive properties of the pressure-sensitive adhesive.

[0105] As demonstrated in Examples 2 and 12-15, changing the type and amount of photoinitiator within a certain range does not affect the flame retardant properties of the pressure-sensitive adhesive, while changes in the degree of reaction affect its adhesive properties. In summary, this invention achieves good flame retardant and adhesive properties within a specific ratio range through the synergistic effect of epoxidized soybean oil-dibutyl phosphate modifier and aluminum hydroxide. On the one hand, it introduces green and renewable epoxidized soybean oil into the pressure-sensitive adhesive system, reducing the use of acrylic acid raw materials; on the other hand, the synergistic effect reduces the amount of aluminum hydroxide used, minimizing its impact on the adhesive properties of the pressure-sensitive adhesive.

[0106] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the method of the present invention are included within the protection scope of the present invention.

Claims

1. A method for preparing a halogen-free flame-retardant UV-curable pressure-sensitive adhesive, characterized in that, The specific steps are as follows: The acrylate monomer, crosslinking agent, photoinitiator, and epoxidized soybean oil-dibutyl phosphate modifier are thoroughly stirred and dissolved. Then, aluminum hydroxide is added and stirred until uniformly mixed to obtain an unreacted adhesive. The unreacted adhesive is then UV-cured in the absence of oxygen to obtain the halogen-free flame-retardant UV-curable pressure-sensitive adhesive. The proportions of each component, by weight, are as follows: Epoxidized soybean oil-dibutyl phosphate modified product 40-55; acrylate monomer 45-60; Aluminum hydroxide 5-25; Crosslinking agent 0.1-1; Photoinitiator 0.3-1; The preparation of the epoxidized soybean oil-dibutyl phosphate modified product is as follows: (1) Add epoxidized soybean oil and dibutyl phosphate to the reaction apparatus and stir; the epoxy value of the epoxidized soybean oil is 6-7%; (2) The temperature is raised to 85-90℃ at a constant rate using a heating device. After adding the catalyst, the reaction continues for 4-6 hours to obtain the epoxidized soybean oil-dibutyl phosphate modified product. The catalyst is either triphenylphosphine or N,N-dimethylbenzylamine. The structure of the epoxidized soybean oil-dibutyl phosphate modified product is shown in the following formula: 。 2. The preparation method of the halogen-free flame-retardant UV-curable pressure-sensitive adhesive according to claim 1, characterized in that, The weight ratio of the epoxidized soybean oil to the dibutyl phosphate is 55:30-60.

3. The preparation method of a halogen-free flame-retardant UV-curable pressure-sensitive adhesive according to claim 1, characterized in that, The aluminum hydroxide has a particle size of 800-8000 mesh.

4. The preparation method of a halogen-free flame-retardant UV-curable pressure-sensitive adhesive according to claim 1, characterized in that, The crosslinking agent includes one or more of 1,6-hexanediol diacrylate and trimethylolpropane triacrylate.

5. The preparation method of a halogen-free flame-retardant UV-curable pressure-sensitive adhesive according to claim 1, characterized in that, The photoinitiator is one of 1173 photoinitiator, 184 photoinitiator and TPO-L photoinitiator.

6. The preparation method of a halogen-free flame-retardant UV-curable pressure-sensitive adhesive according to claim 1, characterized in that, Of the acrylate monomers, the soft monomer is isooctyl acrylate and the hard monomer is acrylic acid.

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