Flame-retardant water-based adhesive, method of making, uses and tape comprising same

Abstract

The present invention relates to a water-based adhesive, preferably a pressure sensitive adhesive, comprising: a) an acrylic polymer, b) a flame retardant, and c) a beta-cyclodextrin or a derivative thereof. Wherein the water-based adhesive comprises 15 to 45 parts by weight, preferably 15 to 40 parts by weight, preferably 15 to 35 parts by weight, preferably 20 to 35 parts by weight, more preferably 25 to 35 parts by weight of the flame retardant, per 100 parts by weight of the a) acrylic polymer.

Description

Technical Field

[0001] This invention relates to flame-retardant water-based adhesives, their preparation methods, uses, and tapes comprising the same. In particular, this invention relates to the use of β-cyclodextrin or its derivatives as flame-retardant synergists in water-based adhesives. Background Technology

[0002] Water-based adhesives are adhesives that use water as a solvent or dispersion medium; they are also called aqueous adhesives. These adhesives exhibit good flowability and chemical stability, and compared to traditional solvent-based adhesives, they offer advantages such as lower cost, lower volatile organic compound (VOC) content, and are therefore more environmentally friendly. As a result, these adhesives have become a rapidly developing type of adhesive in recent years. Among these adhesives, acrylic water-based adhesives are particularly outstanding in terms of bonding properties, water resistance, and high-temperature stability, and are widely used in packaging, construction, medical, electronics, and automotive industries.

[0003] Acrylic water-based adhesives are water-based adhesives made primarily from acrylates through processes such as emulsification and polymerization. While acrylic water-based adhesives offer many advantages as described above for applications in the electronics and automotive industries, they still lack the flame retardancy required for these applications. To overcome this problem, various powdered flame retardants are typically added in high amounts to the acrylic water-based adhesive system to achieve good flame retardant efficiency. However, due to the incompatibility between the water-based acrylic polymer emulsion and the flame retardant powder, high amounts of flame retardant can lead to a deterioration in adhesive performance. Conversely, if insufficient flame retardant is added to prevent adhesive performance degradation, the required flame retardant efficiency will not be met.

[0004] Therefore, providing acrylic water-based adhesives that combine good flame retardancy and adhesive properties is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] The object of the present invention is to provide an acrylic water-based adhesive comprising a flame retardant, which has excellent flame retardant properties and reduces degradation in adhesive properties, particularly peel adhesion and static shear properties, thereby meeting, for example, the requirements for flame retardant adhesives in the electronics and automotive industries.

[0006] The inventors of this invention have unexpectedly discovered that when β-cyclodextrin or its derivatives are added to acrylic water-based adhesives containing flame retardants, the flame retardant efficiency of conventional flame-retardant water-based adhesive systems can be significantly improved. Furthermore, the compatibility between the flame retardant powder and the water-based acrylic polymer emulsion can be improved, and the addition of the flame retardant powder does not lead to a significant loss of adhesive performance, thereby solving the aforementioned technical problems.

[0007] Therefore, in a first aspect, the present invention provides a water-based adhesive, preferably a pressure-sensitive adhesive, comprising:

[0008] a) Acrylic polymers,

[0009] b) Flame retardants,

[0010] c) β-cyclodextrin or its derivatives

[0011] The water-based adhesive comprises 15 to 45 parts by weight, preferably 15 to 40 parts by weight, preferably 15 to 35 parts by weight, preferably 20 to 35 parts by weight, more preferably 25 to 35 parts by weight, based on 100 parts by weight of a) acrylic polymer.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned water-based adhesive, comprising the following steps:

[0013] -Preparation of water-based acrylic polymer emulsions;

[0014] - Add β-cyclodextrin or its derivatives to the water-based acrylic polymer emulsion and mix to obtain a pre-dispersion;

[0015] - Add the flame retardant to the pre-dispersion and mix to obtain an emulsion; and

[0016] - The mixed emulsion is coated onto the release liner, then laminated with a PET film, and dried to obtain a water-based adhesive.

[0017] Thirdly, the present invention provides an adhesive tape comprising the water-based adhesive as described above.

[0018] Fourthly, the present invention also provides the use of the water-based adhesives or tapes described above in the electronics or automotive fields.

[0019] Finally, the present invention provides the use of β-cyclodextrin or its derivatives as flame retardant synergists in water-based adhesives, wherein the water-based adhesives comprise a) acrylic polymers and b) flame retardants. Detailed Implementation

[0020] The above objectives are achieved through the subject matter defined according to the invention. Preferred designs according to the invention arise from further extensions of the invention and the following embodiments.

[0021] The preferred embodiments referred to below can be combined with features of other preferred embodiments referred to below. Therefore, combinations of two or more of the embodiments referred to below as particularly preferred are very particularly preferred. It is also preferred that features of one embodiment referred to in some respects as preferred are combined with one or more other features of another embodiment referred to in some respects as preferred. Therefore, combinations of various features are included in the invention, and in this case, different levels of preference are also included. Thus, for example, a combination of a first feature referred to as “preferred” and a second feature referred to as “particularly preferred” is included in the invention. Here, the features of the preferred tape and its use derive from the features of the preferred adhesive, and vice versa.

[0022] In a preferred embodiment of the invention, the water-based adhesive according to the invention is a pressure-sensitive adhesive comprising: a) an acrylic polymer, b) a flame retardant, and c) β-cyclodextrin or a derivative thereof, wherein the water-based adhesive comprises 15 to 45 parts by weight, preferably 15 to 40 parts by weight, preferably 15 to 35 parts by weight, preferably 20 to 35 parts by weight, more preferably 25 to 35 parts by weight, of the flame retardant, based on 100 parts by weight of a) the acrylic polymer.

[0023] As is known, pressure-sensitive adhesives according to the present invention should be understood to refer—particularly at room temperature—to substances with specific and lasting tack and adhesiveness. Pressure-sensitive adhesives are characterized by their ability to adhere to a substrate by applying pressure, without needing to define in detail the applied pressure and the duration of that pressure. In some cases, depending on the exact properties of the pressure-sensitive adhesive, temperature and humidity, and the substrate, a minimal pressure applied for a short period of time with gentle contact may be sufficient to achieve adhesion; in other cases, higher pressure and a longer application time may be necessary.

[0024] Pressure-sensitive adhesives possess specific characteristic viscoelastic properties, resulting in durable adhesion. Their characteristic is that, upon mechanical deformation, both a viscous flow process and the formation of an elastic restoring force occur. These two processes are specifically related to each other in their respective proportions, depending not only on the precise composition, structure, and degree of cross-linking of the pressure-sensitive adhesive material, but also on the rate and duration of deformation, and on the temperature.

[0025] A certain proportion of viscous flow is necessary for adhesion. The viscous component, generated solely by macromolecules with relatively high mobility, allows for effective wetting of the substrate to be bonded and efficient flow onto it. High viscous flow components result in high pressure-sensitive adhesive tack (also known as surface tack) and therefore often also high adhesive strength. Due to the lack of flowable components, highly cross-linked systems, crystalline or glassy cured polymers generally exhibit only very low pressure-sensitive adhesive tack or none at all.

[0026] A certain proportion of elastic restoring force is necessary for the realization of cohesion. These forces are generated, for example, by macromolecules with very long and highly coiled chains and by physical or chemical cross-linking, and allow the transmission of forces acting on the adhesive bond. This results in the adhesive bond being able to withstand long-term loads acting on it, such as in the form of long-term shear loads, for a relatively long period of time.

[0027] To more accurately describe and quantify the measures of elastic and viscous components, and the relationship between them, variables that can be determined by dynamic mechanical analysis (DMA, according to DIN EN ISO 6721) can be used: storage modulus (G′) and loss modulus (G″). G′ is a measure of the elastic component of the material, and G″ is a measure of the viscous component. Both variables depend on the deformation frequency and temperature.

[0028] The variable can be measured using a rheometer. Here, for example, the material under study is exposed to sinusoidal oscillating shear stress in a plate-plate arrangement. In the case of an instrument operating under shear stress control, the deformation is measured as a function of time, and the time shift of this deformation relative to the introduction of shear stress is measured. This time shift is called the phase angle δ.

[0029] The storage modulus G′ is defined as follows: G′=(τ / γ)·cos(δ) (τ=shear stress, γ=deformation, δ=phase angle=phase shift between the shear stress vector and the deformation vector). The loss modulus G″ is defined as follows: G″=(τ / γ)·sin(δ) (τ=shear stress, γ=deformation, δ=phase angle=phase shift between the shear stress vector and the deformation vector).

[0030] If at room temperature, defined here as 23°C, in 10 0 -10 1 The deformation frequency range in rad / second (radians / second), where G′ is at least partially located within 10 3 -10 7 A substance is generally considered pressure-sensitive adhesive if it is within the range of Pa, and if G′ is also at least partially within that range, and is defined as pressure-sensitive adhesive in the sense of this invention. “Partially” means that at least a portion (at least a segment) of the G′ curve lies within the range from 10...0 rad / s (including endpoints) to 10 1 The range of deformation frequencies in rad / s (including endpoints) (x-axis) and from 10 3 (Including endpoints) Pa to 10 7 The range of G′ values ​​(vertical axis) across Pa (including endpoints) is within the window spanned. This applies accordingly to G″.

[0031] In the context of this invention, the acrylic polymers in the water-based adhesives according to the invention particularly relate to poly(meth)acrylates. In the context of this invention, as understood by those skilled in the art, the term "poly(meth)acrylate" encompasses polyacrylates and polymethacrylates, as well as copolymers of these polymers. Poly(meth)acrylates may contain a small amount of monomer units not derived from (meth)acrylates. Therefore, in the context of this invention, "poly(meth)acrylate" means a (co)polymer whose monomer base is composed of monomers selected from acrylic acid, methacrylic acid, acrylates, and methacrylates at a mass fraction of 70% or more, preferably 90% or more, particularly preferably 98% or more, or even 100% based on the mass fraction of the monomer base. Preferably, the mass fraction of acrylates and / or methacrylates is 50% or more, particularly preferably 70% or more. Poly(meth)acrylates can generally be obtained by free radical polymerization of monomers based on acrylic acid and / or methacrylic acid, and optionally other copolymerizable monomers. In principle, any commonly used acrylic acid, methacrylic acid, acrylate and methacrylate monomers can be used to form acrylic polymers according to the present invention.

[0032] In a particularly preferred embodiment, the acrylic polymer used according to the invention is based on (meth)acrylate alkyl esters, preferably (meth)acrylate C. 1-12 Alkyl esters, more preferably (meth)acrylic acid C 1-8Prepared from alkyl esters. In a further preferred embodiment, the (meth)acrylate alkyl ester is selected from methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, and their branched isomers, such as isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, and isooctyl methacrylate. In a particularly preferred embodiment, the (meth)acrylate alkyl ester is selected from methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. In a more preferred embodiment, the (meth)acrylate alkyl ester includes methyl methacrylate, n-butyl acrylate, and isooctyl acrylate.

[0033] Poly(meth)acrylates can be prepared from the respective monomers according to conventional processes, particularly by conventional free radical polymerization or controlled free radical polymerization. The polymer can be prepared by copolymerizing the monomer components using a common polymerization initiator, wherein polymerization can be carried out at conventional temperatures, preferably in water, as an emulsion polymerization. Poly(meth)acrylates can be prepared using a commonly used amount of polymerization initiator, wherein the polymerization initiator is generally added to the monomer base at a ratio of about 0.01 to 5%, particularly 0.1 to 2%, based on the weight of the monomer base.

[0034] Suitable polymerization initiators include, for example, free radical sources such as peroxides, hydroperoxides and azo compounds, and persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate, with persulfates being preferred.

[0035] Furthermore, emulsion polymerization of poly(meth)acrylates often involves the use of auxiliaries such as emulsifiers, buffers, activators, regulators, and aging inhibitors. In a preferred embodiment, no modifiers are added during the preparation of the poly(meth)acrylate according to the present invention; that is, the acrylic polymer according to the present invention is an unmodified acrylic polymer.

[0036] The water-based adhesive according to the invention comprises a flame retardant in an amount of 15 to 45 parts by weight, preferably 15 to 40 parts by weight, preferably 15 to 35 parts by weight, preferably 20 to 35 parts by weight, and more preferably 25 to 35 parts by weight, preferably in powder form, based on 100 parts by weight of the acrylic polymer.

[0037] In a preferred embodiment, the flame retardant is an intumescent flame retardant. Intumescent flame retardants are environmentally friendly green flame retardants, typically free of halogens and without antimony oxide as a synergist; their system itself has a synergistic effect. When the tape containing the intumescent flame retardant burns, a charred foam layer forms on its surface, providing heat insulation, oxygen barrier, smoke suppression, and anti-drip properties. It exhibits excellent flame retardant performance and produces low smoke, low toxicity, and no corrosive gases. In principle, commonly used intumescent flame retardants in the art can be used in this invention.

[0038] In a particularly preferred embodiment, the intumescent flame retardant according to the invention is a phosphate-based intumescent flame retardant, more preferably an intumescent flame retardant comprising polyphosphates (e.g., ammonium polyphosphate) and triazines, or an intumescent flame retardant comprising organic phosphinates and polyols. In a particularly preferred embodiment, the intumescent flame retardant according to the invention is a mixture of polyphosphates (e.g., ammonium polyphosphate), triazines, and alkyl phosphinates, or a mixture of organic phosphinates, polyols, melamine polyphosphates, and polyol phosphate esters. Such intumescent flame retardants are particularly suitable for applications in the electronics and automotive industries and produce excellent flame retardant effects.

[0039] In a further preferred embodiment, the flame retardant according to the invention further includes a flame retardant synergist. In principle, commonly used flame retardant synergists in the art, particularly those commonly used in intumescent flame retardants, can be used in this invention, such as at least one of the following: zinc borate, lithium oxide, zinc oxide, phosphate glass powder, borate glass powder, silicate glass powder, kaolin, mica powder, talc powder, clay, montmorillonite, bentonite, wollastonite, surface-modified wollastonite, modified hydrotalcite, magnesium oxide, aluminum oxide, zirconium oxide, silicon dioxide, titanium dioxide, silicon carbide, mullite, feldspar, and attapulgite. Those skilled in the art can select specific flame retardant synergists and their amounts according to actual needs. The flame retardant synergist is typically added in amounts less than 5 parts by weight, based on 100 parts by weight of the intumescent flame retardant.

[0040] Preferably, the flame retardant synergist can be a borate, such as zinc borate hydrate, or a hydrotalcite, such as ternary organic modified hydrotalcite. Particularly preferably, when the flame retardant synergist is a hydrotalcite, such as ternary organic modified hydrotalcite, it can better achieve flame retardant performance, while further reducing the deterioration of adhesive performance, especially the peel adhesion and shear properties of the adhesive.

[0041] In a preferred embodiment, the water-based adhesive according to the invention comprises β-cyclodextrin or its derivatives in an amount of 0.01 to 3 parts by weight, preferably 0.1 to 3 parts by weight, preferably 0.2 to 2.8 parts by weight, preferably 0.5 to 2.5 parts by weight, preferably 0.8 to 2.2 parts by weight, and more preferably 1 to 2 parts by weight, based on 100 parts by weight of a) an acrylic polymer. When β-cyclodextrin or its derivatives are added to the water-based adhesive comprising the acrylic polymer and the flame retardant in the stated amounts, on the one hand, the flame retardant efficiency of the flame-retardant water-based adhesive system can be significantly improved, and on the other hand, the compatibility between the acrylic emulsion and the flame retardant powder can be improved, and the presence of the flame retardant powder does not lead to a significant loss of adhesive properties, particularly the peel adhesion and shear properties of the adhesive.

[0042] In a preferred embodiment, the derivatives of β-cyclodextrin that can be used in this invention include esters, alkyl ethers, hydroxyalkyl ethers, alkoxycarbonyl alkyl ethers, or carboxylalkyl ethers of β-cyclodextrin, preferably esters of β-cyclodextrin, such as β-cyclodextrin phosphate esters, or hydroxyalkylcyclodextrin derivatives obtained by hydroxyl substitution.

[0043] For example, esters of β-cyclodextrin may include β-cyclodextrin phosphate, β-cyclodextrin sulfate, and β-cyclodextrin sulfonate, with β-cyclodextrin phosphate being preferred.

[0044] For example, in alkyl ethers, hydroxyalkyl ethers, alkoxycarbonylalkyl ethers, and carboxylalkyl ethers of β-cyclodextrin, the alkyl group may be C. 1-12 Alkyl, preferably C 1-6 Alkyl and more preferably C 1-4 alkyl.

[0045] In an embodiment of the present invention, a method for preparing the water-based adhesive and further water-based adhesive tape according to the present invention includes the following steps:

[0046] -Preparation of water-based acrylic polymer emulsions;

[0047] - Add β-cyclodextrin or its derivatives to the water-based acrylic polymer emulsion and mix to obtain a pre-dispersion;

[0048] - Add the flame retardant to the pre-dispersion and mix to obtain an emulsion; and

[0049] - The mixed emulsion is coated onto the release liner, dried, and then laminated with the release liner to obtain a water-based adhesive in the form of a transfer tape. The obtained water-based adhesive is then laminated with a carrier to obtain a water-based adhesive tape.

[0050] In a preferred embodiment of the method according to the invention, the material is dried at 120°C for 5 minutes and then laminated with a release liner.

[0051] In a preferred embodiment of the method according to the invention, the obtained water-based adhesive is laminated with a PET film.

[0052] In a further preferred embodiment of the method according to the invention, after removing the release liner from the water-based adhesive in the form of a transfer tape, it is laminated with a 23 μm PET film to obtain a water-based adhesive in the form of a single-sided pressure-sensitive tape.

[0053] In one embodiment, the method may further include adding a flame retardant synergist. The flame retardant synergist may be added during the preparation of the pre-dispersion or during the preparation of the emulsion, preferably during the preparation of the pre-dispersion.

[0054] In an embodiment of the method according to the present invention, the preparation of the water-based acrylic polymer emulsion includes at least the following steps:

[0055] Add the emulsifier to the water and stir until the emulsifier dissolves;

[0056] The appropriate monomers for forming acrylic polymers are added to the emulsifier solution and stirred to obtain a pre-emulsion;

[0057] An aqueous solution of an initiator is added to a pre-emulsion to polymerize the monomers in solution to obtain a water-based acrylic polymer emulsion.

[0058] The water-based adhesive prepared by the method according to the invention is preferably provided in the form of tape, particularly single-sided tape.

[0059] Therefore, the present invention also provides tapes, preferably pressure-sensitive tapes, comprising the water-based adhesive according to the present invention.

[0060] The term "tape" is clear to those skilled in the art of adhesives. In the context of this invention, the term "tape" refers to all thin, sheet-like structures, i.e., structures having a primary extent in two dimensions, especially films.

[0061] The water-based adhesive of the present invention can be provided, for example, directly in the form of tape, preferably pressure-sensitive tape, and preferably transfer tape, i.e., a carrier-free double-sided adhesive tape. In the transfer tape, the adhesive is applied between flexible pads before application, the flexible pads having a release layer and / or anti-sticking properties. During application, one pad can be removed first, the pressure-sensitive adhesive applied, and then the second pad removed. Therefore, the adhesive can be used directly to bond two surfaces. Using such a carrier-free transfer tape, very precise adhesion can be achieved in terms of positioning and dosage.

[0062] The flexible pad described is known to those skilled in the art and is also referred to as a release liner. In addition to covering the double-sided adhesive tape, the liner ensures that the adhesive is not smudged before application. However, such a liner is not an integral part of the tape, but merely an aid for its manufacture, storage, and / or further processing, such as by stamping. Furthermore, unlike a permanent carrier, the liner is not firmly bonded to the adhesive layer but acts as a temporary carrier, i.e., a carrier that can be removed from the adhesive layer.

[0063] However, considering the most advantageous processing properties possible, particularly advantageous results are often obtained when the water-based adhesive of the present invention is used as an adhesive layer in a single-sided or double-sided tape that also includes a carrier layer. Therefore, the present invention also relates to tapes comprising a carrier layer and the water-based adhesive of the present invention.

[0064] The carrier layer typically refers to a layer in a multilayer adhesive tape that significantly determines the tape's mechanical and physical properties, such as tear resistance, tensile strength, insulation capacity, or resilience. Common materials used for the carrier layer include, for example, woven fabrics, nonwoven fabrics, and polymer films, such as PET films and polyolefin films, with PET films being particularly preferred. In a particularly preferred embodiment, the tape of the present invention is a single-sided pressure-sensitive tape, wherein the water-based adhesive of the present invention is applied only to one side of the carrier layer.

[0065] The tapes according to the invention are particularly suitable for the electronics and automotive industries due to their excellent flame-retardant properties. Therefore, the invention also provides the use of the water-based adhesives or tapes according to the invention in the electronics and automotive industries, particularly for bonding materials such as batteries.

[0066] Finally, the present invention also provides the use of β-cyclodextrin or its derivatives as flame retardant synergists in water-based adhesives, wherein the water-based adhesives comprise acrylic polymers and flame retardants. Adding β-cyclodextrin or its derivatives to a water-based adhesive system comprising a flame retardant can significantly improve the flame retardant efficiency of the flame-retardant water-based adhesive system, and can also improve the compatibility between the flame retardant and the water-based acrylic polymer emulsion, ensuring that the addition of the flame retardant does not lead to a significant loss of adhesive performance.

[0067] Example

[0068] The present invention will be described in detail below through embodiments, but it is not intended to limit the present invention as such.

[0069] Experimental materials

[0070] Table 1. Raw Material List

[0071]

[0072] Preparation of waterborne acrylic polymers

[0073] The acrylic polymers in the water-based pressure-sensitive adhesives of the embodiments and comparative examples according to the present invention are all based on butyl acrylate (BA), isooctyl acrylate (2-EHA), and methyl methacrylate (MMA). Specifically, 1 part by weight of emulsifier (DES-30:CM-30 = 1:4) and 25 parts by weight of deionized water are added to a single-necked flask and stirred continuously until the emulsifier is completely dissolved. Then, 18 parts by weight of BA, 62 parts by weight of 2-EHA, and 20 parts by weight of MMA are added to the flask, and the mixture is stirred again for 10 minutes until the contents of the flask are a milky white emulsion that no longer separates into layers. Next, 0.3 parts by weight of APS and 25 parts by weight of deionized water were added to a four-necked flask equipped with a thermometer, a stirrer, a condenser, and a latex tube. The temperature was raised to 85°C and stabilized. Then, 0.2 parts by weight of APS and the prepared pre-emulsion were slowly added dropwise to the flask. After the addition was completed, the temperature was stabilized and kept warm for 4 hours. Then, the water bath temperature was lowered to room temperature. Ammonia was added to the emulsion to adjust the pH to 5-6. The emulsion was filtered twice using 100-mesh and 300-mesh filters to obtain the final waterborne acrylic polymer emulsion.

[0074] Preparation of water-based adhesives in the examples

[0075] Step 1: Obtain an aqueous acrylic polymer emulsion using the method described above;

[0076] Step 2: Add β-cyclodextrin and flame retardant synergist (when used) to the emulsion of the waterborne acrylic polymer according to the amounts shown in Tables 1 and 2 below, mix for 10 minutes to obtain a pre-dispersion;

[0077] Step 3: Add the corresponding intumescent flame retardant powder to the pre-dispersion according to the amounts shown in Tables 1 and 2 below, mix for 20 minutes to obtain a uniform emulsion.

[0078] Step 4: Coat the emulsion from Step 3 onto a 50μm thick PET release liner to a thickness of 50μm, and dry it in an oven at 120℃ for 5 minutes to obtain a water-based adhesive transfer tape.

[0079] Step 5: After removing the release liner from the transfer tape obtained in Step 4, laminate it with a 23μm PET film to obtain a water-based adhesive in the form of a single-sided pressure-sensitive tape.

[0080] In addition, as with Reference Example 1 (pure PSA), pure acrylic polymer obtained by the method for preparing acrylic polymers was coated onto a release liner, and then laminated with a 23 μm PET film to obtain a single-sided adhesive tape comprising pure acrylic polymer. As with Reference Example 2 (pure PSA + β-cyclodextrin), a water-based adhesive was prepared in the same manner as in the examples, except for the flame retardant.

[0081] As a comparative example, a water-based adhesive was prepared in the same manner as in the examples, except that β-cyclodextrin was not added.

[0082] According to the composition of the flame-retardant expander shown below, the embodiments and comparative examples of the present invention are divided into five groups consisting of individual embodiments and their corresponding comparative examples.

[0083] The composition of the intumescent flame retardant used in each group is as follows:

[0084] Group 1: HYG+B80, where the amounts of HYG and B80 are shown from left to right in the relevant columns for flame retardant expanders in Tables 2 and 4.

[0085] Group 2: HYG + ADP, where the amounts of HYG and ADP are shown from left to right in the relevant columns for flame retardant expanders in Tables 2 and 4.

[0086] Group 3: G1+MC+XP, where the amounts of G1, MC, and XP are shown from left to right in the relevant columns for flame retardant expanders in Tables 2 and 4.

[0087] Group 4: G1 + MC + XP + Flame Retardant Synergist ZB, where the amounts of G1, MC, XP, and ZB are shown from left to right in the relevant columns for flame retardant expanders in Tables 3 and 4. Group 5: G1 + MC + XP + Flame Retardant Synergist LDH, where the amounts of G1, MC, XP, and LDH are shown from left to right in the relevant columns for flame retardant expanders in Tables 3 and 4.

[0088] The adhesive properties and flame retardant properties of the water-based adhesives of each embodiment, comparative example, and reference example (pure PSA) were tested, and the results are shown in Tables 2 to 4 below.

[0089] Table 2: Performance Comparison of Water-Based Adhesives in Examples and Comparative Examples without Flame Retardant Synergists

[0090]

[0091]

[0092] HB: Failed UL-94 test

[0093] By comparing Reference Examples 1 and 2, Comparative Examples, and Examples, it can be found that adding only a small amount of β-cyclodextrin has almost no effect on the adhesive properties of the water-based adhesive itself and the performance of the tape, demonstrating good compatibility. Furthermore, adding flame retardants (in amounts insufficient to produce flame retardant efficiency) significantly reduces the adhesive properties of water-based acrylic adhesives due to the poor compatibility between the flame retardant powder and the water-based acrylic polymer emulsion. The introduction of β-cyclodextrin, using the same amount of flame retardant, not only significantly improves the flame retardant properties of the tape but also significantly reduces the loss of adhesive properties, particularly the loss of static shear strength. For flame retardant systems including organic phosphinates, polyols, melamine phosphates, and polyol phosphonates (Group 3), the introduction of β-cyclodextrin achieves better results than flame retardant systems including ammonium polyphosphate, triazine, and hypophosphite in both improving flame retardant properties and reducing the loss of adhesive properties. It is particularly important to note that the amount of β-cyclodextrin introduced should be kept appropriate. Because small molecules are prone to precipitation on the tape surface, when the amount of β-cyclodextrin added exceeds 3 parts by weight, although the flame retardant properties are still excellent, the adhesive properties will be reduced.

[0094] Table 3: Performance Comparison of Water-Based Adhesives Containing Flame Retardant Synergists in Examples and Comparative Examples

[0095]

[0096]

[0097] HB: Failed UL-94 test;

[0098] As shown in Table 3, the introduction of β-cyclodextrin into water-based acrylic adhesive systems with the use of flame retardant synergists can still significantly improve the flame retardant properties of the tape while simultaneously reducing the loss of adhesive properties. Specifically, with the same amount of flame retardant synergist, for the same flame retardant, the ternary organic modified hydrotalcite synergist (Group 5) achieved better results than the zinc borate hydrate synergist in improving flame retardant properties and reducing the loss of adhesive properties.

[0099] Table 4: Effect of β-cyclodextrin addition on the compatibility of flame retardants with water-based acrylic polymer emulsions

[0100]

[0101]

[0102] As shown in Table 3, the addition of β-cyclodextrin can reduce the haze of the tape, which reflects the improved compatibility between the flame retardant and the water-based acrylic polymer emulsion.

[0103] Test methods

[0104] Unless otherwise specified, measurements are performed under test conditions of 23±1℃ and 50±5% relative humidity.

[0105] Test Method 1: Peel Adhesion (for SUS Stainless Steel)

[0106] The other side of the water-based adhesive tape with a 23μm thick PET reinforced film was attached to a steel plate (SUS stainless steel). Then, it was pressed back and forth 5 times under a roller with a force of 4kg and a speed of 10m / min. Immediately afterwards, the peel adhesion was measured at a peel rate of 300mm / min and a peel angle of 180°. The measured value (N / cm) was obtained from the average of three measurements.

[0107] Test Method 2: Static Shear Strength

[0108] Cut the water-based adhesive transfer tape into 20mm wide strips, then apply the Al film to one side and press it onto the other side at a 260mm width. 2 A 13*20mm bonding area was applied to a steel plate, and then pressed back and forth twice under a roller with a force of 2kg and a speed of 300mm / min. A 1kg weight was suspended at the bottom of the sample, and the time it took for the weight to fall was recorded. The longer the time, the higher the static shear strength. The measured value (min) is obtained from the average of three measurements.

[0109] Test Method 3: UL-94 Rating

[0110] Flame retardancy testing was conducted according to UL-94 testing standards ASTM D4804 or ISO 9773. Before testing, the sample was placed under test conditions of 23±1℃ and 50±5% relative humidity for 48 hours. A 200*50mm sample was rolled into a tubular and conical shape (around a metal shaft with a 13mm diameter). The rolled sample was then subjected to two 3-second flames vertically under a Bunsen burner. The afterflame time and the time it took for the sample to burn to the 125mm mark were recorded. Additionally, whether dripping occurred during the combustion process and whether the dripping ignited absorbent cotton were recorded for flame retardancy evaluation. Based on the test results, the samples were classified into four levels from highest to lowest: VTM-0, VTM-1, VTM-2, and HB (failure).

[0111] Test Method 4: Haze

[0112] Following ASTM D1003 standards, the release liner on one side of the water-based adhesive transfer tape was removed. Then, the adhesive layer was pressed onto a 1mm thick glass plate using a pressure roller, ensuring no impurities or air bubbles were present at the bonding interface. The other side of the release liner was then removed, and the resulting laminate was placed in a vacuum bonding chamber with the laminate facing upwards. Another 1mm thick glass plate was then placed on top, and vacuum bonding was performed under conditions below 200 Pa for 10 seconds. The resulting laminate was then degassed under conditions of 40°C, 0.5 MPa, and 30 minutes. The resulting laminate was then placed under test conditions of 23±1°C and 50±5% relative humidity for 24 hours. The haze value was then measured using a BYK haze-gard plus (purchased from BYK-GARDNER GMBH, GERMANY).

Claims

1. Water-based adhesives, preferably pressure-sensitive adhesives, including: a) Acrylic polymers, b) Flame retardants, c) β-cyclodextrin or its derivatives The water-based adhesive comprises 15 to 45 parts by weight, preferably 15 to 40 parts by weight, preferably 15 to 35 parts by weight, preferably 20 to 35 parts by weight, more preferably 25 to 35 parts by weight, based on 100 parts by weight of a) acrylic polymer.

2. The water-based adhesive according to claim 1, wherein the water-based adhesive comprises 0.01 to 3 parts by weight, preferably 0.1 to 3 parts by weight, preferably 0.2 to 2.8 parts by weight, preferably 0.5 to 2.5 parts by weight, preferably 0.8 to 2.2 parts by weight, more preferably 1 to 2 parts by weight of β-cyclodextrin or its derivatives, based on 100 parts by weight of a) acrylic polymer.

3. The water-based adhesive according to claim 1 or 2, wherein the flame retardant is an intumescent flame retardant, preferably an intumescent flame retardant based on phosphates, more preferably an intumescent flame retardant comprising polyphosphates and triazines, or an intumescent flame retardant comprising organic phosphonates and polyols.

4. The water-based adhesive according to claim 1 or 2, wherein the derivative of β-cyclodextrin includes esters, alkyl ethers, hydroxyalkyl ethers, alkoxycarbonyl alkyl ethers, or carboxylalkyl ethers of β-cyclodextrin, preferably β-cyclodextrin phosphate esters.

5. The water-based adhesive according to claim 1 or 2, wherein the flame retardant further comprises a flame retardant synergist.

6. The water-based adhesive according to claim 1 or 2, wherein the acrylic polymer is based on alkyl (meth)acrylate, preferably (meth)acrylate C 1-12 Alkyl esters, more preferably (meth)acrylic acid C 1-8 Prepared from alkyl esters.

7. A method for preparing a water-based adhesive according to any one of claims 1 to 6, comprising the following steps: Preparation of water-based acrylic polymer emulsions; β-cyclodextrin or its derivatives are added to the water-based acrylic polymer emulsion and mixed to obtain a pre-dispersion. The flame retardant was added to the pre-dispersion and mixed to obtain an emulsion; and The mixed emulsion is coated onto the release liner, dried, and then laminated with the release liner to obtain a water-based adhesive in the form of a transfer tape. The obtained water-based adhesive is then laminated with a carrier to obtain a water-based adhesive tape.

8. A tape comprising a water-based adhesive according to any one of claims 1 to 6.

9. Use of the water-based adhesive according to any one of claims 1 to 6 or the tape according to claim 8 in the electronics or automotive fields.

10. Use of β-cyclodextrin or its derivatives as flame retardant synergists in water-based adhesives, wherein the water-based adhesives comprise a) acrylic polymers and b) flame retardants.

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