Detachable pressure-sensitive adhesives and their applications

Abstract

This invention relates to on-demand removable pressure-sensitive adhesives and laminating adhesive compositions and their uses. The removable pressure-sensitive adhesives and laminating adhesives are applied to a substrate to form an adhesive, and the adhesive can be peeled off from the substrate upon exposure to an electron beam or ultraviolet light energy. The removable pressure-sensitive adhesives and laminating adhesives are particularly suitable for recycling in a circular economy.

Description

Technical Field

[0001] This invention relates to on-demand removable pressure-sensitive adhesive compositions and their uses. The removable pressure-sensitive adhesives are particularly suitable for substrate recycling in a circular economy. Background of the Invention

[0003] Over 40% of plastics are discarded after a single use. Better recyclability can increase the reuse of plastics, thereby reducing landfill and pollution. Labels and laminates are typically applied to plastic substrates using adhesives. Pressure-sensitive adhesives and laminating adhesives retain the adhesive properties that make them difficult to recycle. The tackiness and rubbery properties of pressure-sensitive adhesives prevent substrate separation and recycling. To desorb or separate the layers from each other, dissolution and reprecipitation techniques are widely used in recycling machinery; however, this results in the machine becoming "glued." The very strong adhesion of laminating adhesives prevents substrate separation, therefore, many laminates end up in landfills.

[0004] To facilitate the desorption of adhesives from substrates or the separation of multilayer substrates, U.S. Patents 7,901,532 and 5,609,954 disclose the use of microspheres for rapid peeling and desorption; however, the initial bond strength is too poor for many applications. Some processes, particularly wafer bonding processes, use very high temperatures, exceeding the melting point of many plastics, and can lead to undesirable shrinkage, deformation, chemical degradation, or oxidation, making these processes unsuitable for plastics. Another process disclosed in U.S. Patent 9,565,773 teaches the use of a chemical for initial curing followed by a chemical for debonding, which adds complexity.

[0005] Therefore, there is a need in the art for a triggerable, on-demand release adhesive that can become non-stick and facilitate removal from substrates for recycling. This invention fulfills this need. Summary of the Invention

[0006] This invention provides removable pressure-sensitive adhesive compositions, their uses, and articles comprising the same. The removable pressure-sensitive adhesive is prepared such that, upon activation, it becomes substantially non-stick and readily detaches from the attached substrate, making it suitable for recycling systems. Typical pressure-sensitive adhesives, when applied to a surface and dried, exhibit significant residual surface tack, surface wetting, and adhesion; this allows the adhesive to be easily bonded to a variety of substrates with minimal application pressure without the application of heat. Some pressure-sensitive adhesives and laminating adhesives are used to bond multilayer substrates. The very strong adhesion of laminating adhesives prevents substrate layers from delaminating from the laminate. Therefore, on-demand detachment of these adhesives is difficult to achieve with pressure-sensitive and laminating adhesives. This invention relates to on-demand detachable pressure-sensitive and laminating adhesives to allow for easy separation and recycling without the use of dissolution and reprecipitation techniques.

[0007] In one embodiment, the present invention relates to a removable pressure-sensitive adhesive comprising:

[0008] i. One or more acrylic oligomers having

[0009] a. A viscosity of at least 300 cps to approximately 8,000 cps, measured according to ASTM D4402 at 60°C using a No. 27 rotor at 20 rpm; and

[0010] b. At least two acrylate functional groups, and

[0011] ii. At least one polymer having a solubility parameter greater than about 8 and less than about 15;

[0012] The residual strength ratio of the removable pressure-sensitive adhesive is less than 0.10.

[0013] Another embodiment of the invention relates to an article comprising a substrate bonded to a removable adhesive, the removable adhesive comprising:

[0014] a. An acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, said viscosity measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups.

[0015] b. At least one polymer having a solubility parameter greater than about 8 and less than about 15;

[0016] The residual strength ratio of the removable pressure-sensitive adhesive is less than 0.10.

[0017] Another aspect of the present invention relates to a method for debonding an article, wherein the article comprises a substrate having a first surface and a second surface, and a debondable pressure-sensitive adhesive coated on the first surface of the substrate, the method comprising the following steps:

[0018] a. Preparing the article;

[0019] b. Applying an electron beam or ultraviolet light to the article, thereby making the removable adhesive substantially non-stick; and

[0020] c. Optionally agitating the removable adhesive or the substrate, thereby separating the removable adhesive from the substrate;

[0021] The removable adhesive comprises (1) an acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, the viscosity being measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) at least one polymer having a solubility parameter greater than about 8 to less than about 15; and (3) a residual strength ratio of less than about 0.10.

[0022] Another embodiment of the present invention relates to a method for debonding a laminate, wherein the laminate comprises a first substrate having a first surface and a second surface, a second substrate having a first surface and a second surface, and a debondable adhesive applied to and bonding the first surface of the first substrate and the second surface of the second substrate, the method comprising the following steps:

[0023] a. Preparing the article;

[0024] b. Applying an electron beam or ultraviolet light to the laminate, thereby making the removable adhesive substantially non-stick; and

[0025] c. Optionally, at least one substrate is agitated, thereby separating the at least one substrate from the removable adhesive or the laminate;

[0026] The removable adhesive comprises (1) an acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, the viscosity being measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) at least one polymer having a solubility parameter greater than about 8 to less than about 15; and (3) a residual strength ratio of less than about 0.10. Detailed Implementation

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of any conflict, this document (including the definitions) shall prevail. Although preferred methods and materials are described below, similar or equivalent methods and materials may be used in practice or testing of this disclosure. All publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not limiting.

[0028] As used in the specification and claims, the term "comprising" can include embodiments of "consisting of" and "substantially consisting of". As used herein, the terms "comprising", "including", "having", "has", "may", "contains", and variations thereof are intended as open-ended transitional phrases, terms, or words that require the presence of a specified ingredient / step and allow for the presence of other ingredients / steps. However, this description should be interpreted as also describing the composition or method as "consisting of the listed ingredients / steps" and "substantially consisting of the listed ingredients / steps", which allows for the presence of only the specified ingredient / step and any impurities that may result therefrom, and excludes other ingredients / steps.

[0029] When applied to any aspect of this disclosure, as used herein, the articles “a” and “an” refer to one (kind) or more (kinds). The use of “a” and “an” does not limit the meaning to a single feature unless such limitation is specifically stated. The article “described” preceding a singular or plural noun or noun phrase indicates one or more specifically defined features and may have a singular or plural meaning depending on the context in which it is used.

[0030] The numerical values ​​in the specification and claims of this application, particularly when they relate to polymers or polymer compositions, reflect average values ​​of compositions that may contain individual polymers with different properties. Furthermore, unless otherwise stated, the numerical values ​​should be understood to include values ​​that are the same when reduced to the same number of significant figures, and values ​​that differ from the stated value by less than the experimental error of conventional measurement techniques of the type used to determine the value as described in this application.

[0031] All ranges disclosed herein include the stated endpoints and can be combined independently (e.g., a range of “2 to 10” includes endpoints 2 and 10, as well as all intermediate values). The endpoints and any values ​​of the ranges disclosed herein are not limited to precise ranges or values; they are sufficiently imprecise to include values ​​close to these ranges and / or values. As used herein, approximate language can be applied to modify any quantitative representation that may vary without altering its underlying function. Thus, in some cases, a value modified by one or more terms such as “about” may not be limited to the specified precise value. In at least some cases, approximate language may correspond to the precision of the instrument used to measure the value. The modifier “about” should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression “about 2 to about 4” also discloses a range of “2 to 4”. The term “about” can refer to ±10% of a specified value. For example, “about 10%” can represent a range of 9% to 11%, and “about 1” can represent 0.9–1.1. Other meanings of “about” may be apparent from the context, such as rounding; therefore, for example, “about 1” can also represent 0.5 to 1.4.

[0032] As used in this article, oligomers are macromolecules composed of monomer units that are equal to or greater than about two monomer units.

[0033] As used herein, "adhered object" or "substrate" are used interchangeably and are part of an article in which an adhesive is applied to one substrate to adhere to another substrate, thereby sandwiching the adhesive between the two adhered objects. Each substrate can independently be paper, plastic, metal, fiber, wood, film, carpet, glass, rubber, composite material, crystal, mineral, or foam. The adhesive is used to attach one substrate to another similar or different substrate.

[0034] As used herein, pressure-sensitive adhesives are adhesives that form a bond when pressure is applied to bond the adhesive to the substrate. No solvents, water, or heating is required to activate the adhesive to form a bond with the substrate. Laminating adhesives provide strong adhesion to join similar to dissimilar substrates together in a laminate. Adhesives, pressure-sensitive adhesives, and laminating adhesives are formed as a single-phase homogeneous and compatible state. Each adhesive should be homogeneous and should remain a single phase during application and storage. Applying phase-separated adhesives to substrates results in inconsistent and poor adhesion. Suitable homogeneous mixtures also include pressure-sensitive adhesives and laminating adhesives containing block polymer structures with microdomains, and filler mixtures, provided that these domains and mixtures do not separate during application or storage.

[0035] Typical pressure-sensitive adhesives maintain permanent tack and have the ability to wet surfaces when in contact with minimal application pressure. Detachable pressure-sensitive adhesives can be activated or triggered to become substantially non-stick. In this substantially non-stick state, if the adhesive is less than about 10% by weight of the article, the adhesive can be recycled as is along with its substrate. The adhesive can also be separated, allowing the adhered objects to be easily separated from the adhesive, enabling the adhered objects to be repositioned or recycled.

[0036] On-demand debonding of pressure-sensitive or laminated adhesives is achieved by exposing the adhesive to energy such as electron beams or ultraviolet light. This type of debonding does not require solvents or corrosive exposure to the product. Substrate separation can be accomplished using low mechanical forces known in the art, such as roller brushes. Debonding of adhered materials from end-of-life products is particularly desirable to facilitate recycling. Depending on application requirements and constraints, source debonding must meet substrate requirements, such as low heat for plastic substrates, and should be environmentally friendly, cost-effective, and leave minimal or almost no adhesive residue on the substrate.

[0037] Adhesive strength measures the absolute tackiness and adhesiveness of a detachable adhesive. Therefore, a higher adhesive strength value indicates a stronger bond between the adhesive and a given substrate, and vice versa. In this paper, relative tackiness or residual strength is used as a measure of adhesive strength. (i) It is determined by the ratio of the initial strength to the residual strength of the adhesive after activation, which causes it to form a non-adhesive form.

[0038] The residual strength ratio is defined as:

[0039] .

[0040] Adhesive strength was measured according to ASTM D903 and operated at a peel rate of 12 inches / minute. A residual strength ratio of less than approximately 0.10 is desirable. In this document, "essentially non-stick" means that the adhesive strength of the cured removable adhesive is less than approximately 10% of the adhesive strength of the uncured removable adhesive. Therefore, adhesives with very high initial adhesive strength may still have some absolute adhesive strength after activation; however, this relative ratio should be less than 0.10 to contribute to recyclability. A ratio greater than approximately 0.10 provides undesirable resistance to substrate separation.

[0041] In one embodiment, the present invention relates to a removable pressure-sensitive adhesive comprising:

[0042] i. One or more acrylic oligomers having

[0043] (a) A viscosity of at least 300 cps to about 8,000 cps, said viscosity measured at 60°C according to ASTM D4402; and

[0044] (b) At least two acrylate functional groups, and

[0045] ii. At least one polymer having a solubility parameter greater than about 8 and less than about 15;

[0046] The residual strength ratio of the removable pressure-sensitive adhesive is less than 0.10.

[0047] The viscosity range of acrylic oligomers allows the adhesive to develop strong initial green strength against the substrate. When combined with polymers suitable for use in this invention, acrylic oligomers with a viscosity range greater than about 8000 cps at 60°C according to ASTM D4402 typically do not provide the initial tack required for pressure-sensitive adhesives. Acrylic oligomers may additionally include the following chemical bonds: epoxy, urethane, ester, ether, amide, and combinations thereof. Two or more acrylate functional groups on the acrylic oligomer provide curing to the adhesive upon activation, thereby facilitating easy detachment from the substrate. Monofunctional acrylate oligomers within the aforementioned viscosity range do not provide sufficient curing for easy detachment from the substrate.

[0048] Suitable acrylic oligomers include epoxy di or triacrylates (e.g., Sartomer CN 120Z or Genomer 2312), urethane di, tri, or tetraacrylates (e.g., Sartomer CN9167US, Genomer 4312, or Genomer 4425), and polyester di, tri, or tetraacrylates (e.g., Ebecryl 5849, Ebecryl 885, or Ebecryl 889) are particularly suitable as acrylic oligomers in desiccant pressure-sensitive adhesives.

[0049] The removable pressure-sensitive adhesive also comprises polymers with a solubility parameter greater than about 8 and less than about 15. Specifically, the polymers have a solubility parameter greater than 8.2 and less than 14.6. While not bound by any particular scientific theory, it is believed that polymers with a solubility parameter greater than 8.2 and less than 14.6 allow for adhesive compatibility and reduce the likelihood of phase separation during and after application to the substrate. Furthermore, the compatibility of the polymer with acrylic oligomers enables the polymer to provide strength and reinforcement to the compatible pressure-sensitive adhesive.

[0050] The solubility parameter (δ) is a dimensionless value based on the Hildebrand and Hansen solubility parameters, providing guidance on the solubility of a polymer in a solvent. The closer the solubility parameters of the polymer and solvent are, the more likely the polymer is to dissolve in a given solvent. The solubility parameters of many polymers, oligomers, and solvents are well-known and can be found in various references, including Signa Aldrich, the CRC Handbook of Chemistry and Physics, and the Merck Index. For other polymers and oligomers, they can be estimated by calculating the Hildebrand or Hansen solubility parameters. Alternatively, they can be determined experimentally by dissolving one or more grams of solute in 100 ml of various known solvents; the range of dissolution is the solubility range of the solute.

[0051] Suitable polymers include polyesters (e.g., Skybon ES 215 or Dynapol L323), polyurethanes, polyethers, polyacrylic acids (e.g., Kurairerity LA2330 or Elvacite 2967), polyvinyl acetate, polyethylene-vinyl acetate copolymers (e.g., Levapren 450 or Levamelt 800), polyvinyl alcohol, and polyamides (e.g., Unirez 2224 or Ancatherm 592).

[0052] The removable adhesive composition may also include photoinitiators, amines, amine-acrylate adducts, tackifiers, solvents, waxes, antioxidants, and mixtures thereof.

[0053] Another embodiment of the invention relates to an article comprising a first substrate bonded to a removable adhesive, the removable adhesive comprising:

[0054] a. An acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, said viscosity measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups.

[0055] b. At least one polymer having a solubility parameter of about 8 to less than about 15;

[0056] The residual strength ratio of the removable adhesive is less than 0.10.

[0057] The substrate can be paper, fiber, kraft paper, wood, metal, film, carpet, glass, rubber, composite material, crystal, mineral or foam.

[0058] Another aspect of the present invention relates to a method for debonding an article, wherein the article comprises a substrate having a first surface and a second surface, and a debondable adhesive coated and bonded to the first surface of the substrate, the method comprising the following steps:

[0059] a. Preparing the article;

[0060] b. Applying an electron beam or ultraviolet light to the article, thereby making the removable adhesive substantially non-stick; and

[0061] c. Optionally, agitate the removable adhesive or the substrate, thereby separating the removable adhesive from the substrate;

[0062] The removable adhesive comprises (1) an acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, the viscosity being measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) at least one polymer having a solubility parameter greater than about 8 to less than about 15; and (3) a residual strength ratio of less than about 0.10.

[0063] Electron beams or ultraviolet light can also be selectively applied to a portion of the article, or only to the second surface of the removable adhesive or the first substrate. The electron beam or ultraviolet light can penetrate the first or second substrate and activate the removable adhesive located beneath the first substrate.

[0064] On-demand debonding can be achieved by exposing the debonded adhesive to the energy of an electron beam or ultraviolet light. This results in a residual strength ratio of less than about 0.10. Agitating the substrate or the substantially non-stick adhesive separates the various layers, such as the substrate or the debonded adhesive, from the article to aid in recycling. In another embodiment, if the non-stick adhesive is less than about 10% by weight of the article, preferably less than 5% by weight, the entire article comprising the substantially non-stick adhesive can be recycled as a whole.

[0065] Another embodiment of the present invention relates to a method for debonding a laminate, wherein the laminate comprises a first substrate having a first surface and a second surface, a second substrate having a first surface and a second surface, and a debondable adhesive applied to and bonding the first surface of the first substrate and the second surface of the second substrate, the method comprising the following steps:

[0066] a. To prepare products;

[0067] b. Apply an electron beam or ultraviolet light to the laminate;

[0068] c. Agitate at least one substrate, thereby separating the at least one substrate from the laminate;

[0069] The removable adhesive has (1) an acrylic oligomer having (i) a viscosity of at least 300 cps to about 8,000 cps, measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) at least one polymer having a solubility parameter greater than about 8 to less than about 15; and (3) a residual strength ratio of less than about 0.10.

[0070] Energy can travel through the substrate or multiple layers of the substrate and debond the adhesive embedded between the substrate layers, thereby separating each substrate layer. On-demand debonding can also be achieved by directly exposing an electron beam or ultraviolet light energy to a layer or portion of the laminate.

[0071] Example

[0072] The following embodiments are provided for illustrative purposes only, and it is not intended to impose any unnecessary limitations on them.

[0073] To prepare a sample containing solvent, mix the components of the formulation at 75°C until the mixture becomes homogeneous, then cool to ambient temperature before testing. To prepare a solvent-free sample, mix the components of the formulation at 130°C until the mixture becomes homogeneous.

[0074] Viscosity was measured at 25°C using a Brookfield viscometer with an RV-4 rotor at 20 or 50 rpm.

[0075] The adhesion test was performed using typical methods known to those skilled in the art, and is described in further detail below.

[0076] Test samples were prepared by hand-coating each solvent-containing adhesive onto a 75-gauge corona-treated oriented polypropylene (OPP) film using a 20-gauge Meyer's stick. The coatings were then dried in an oven at 85°C for 2 minutes to provide approximately 6 g / m³. 2 A dry adhesive coating is applied. Using a heating rod with a controlled gap, a test sample made of solvent-free adhesive is coated onto release paper at 150°C to provide a 0.001-inch coating. The solvent-free coating is then transferred to an OPP film, and the release paper is removed so that the coating can be tested. The solvent-free sample does not require drying.

[0077] Bond Strength Before Cure was measured as follows: First, using a cold-sealing press, a coated OPP film was laminated onto a 48-gauge corona-treated polyester (PET) film at 60 psi for 2 seconds. The laminate was not exposed to energy. The laminate was then cut into 1-inch wide test strips. At ambient temperature, the laminated test strips were pulled apart using a laboratory tensile tester at a rate of 12 inches per minute, and the force required to peel the adhesive laminate was recorded in grams per inch (gli).

[0078] Cured Coating Strength was measured as follows: First, the adhesive-coated OPP film was exposed to an energy source (electron beam or UV light). Then, the cured non-stick coating on the resulting OPP was removed, and using a cold-sealing press, it was laminated onto a 48-gauge corona-treated polyester (PET) film at 60 psi for 2 seconds. The laminate was cut into 1-inch wide test strips. At ambient temperature, the laminated test strips were pulled apart using a laboratory tensile tester at a rate of 12 inches per minute. The force required to peel off the adhesive laminate was recorded as the cured coating strength.

[0079] The electron beam energy and conditions used for curing are typical to those skilled in the art. Electron beam curing conditions were used at 125 keV, with a dose of 3 mRad, a sample tray speed of 75 feet / minute, and nitrogen inertization to less than 200 ppm oxygen.

[0080] The UV energy and conditions used for curing are typical to those skilled in the art. A UV lamp employing a type D UV bulb is used at a belt speed of 50 feet per minute and a dose of 200 mJ, without nitrogen inertization.

[0081] Residual strength ratio (ii) The strength of the cured coating is calculated by dividing the strength of the PSA adhesive before curing.

[0082] .

[0083] The strength of the cured laminate was measured as follows: First, using a cold-sealing press, a coated OPP film was laminated onto a 48-gauge corona-treated polyester (PET) film at 60 psi for 2 seconds. The laminate was then exposed to energy (electron beam or UV light). The laminate was cut into 1-inch wide test strips and, at ambient temperature, pulled apart using a laboratory tensile tester at a rate of 12 inches per minute. The force required to peel these adhesive laminates was recorded as the strength of the cured laminate.

[0084] Residual Lamination Strength Ratio (iii) The strength of the cured laminate is calculated by dividing the PSA adhesive strength before curing:

[0085] .

[0086] Tests were conducted using typical industrial curing conditions. Electron beam curing conditions were: 3 MRad dose, 125 keV, 75 ft / min, and less than 200 ppm oxygen. UV curing conditions were: approximately 200 mJ dose, 50 ft / min, using a type D UV lamp, and no nitrogen inertization required.

[0087] Example 1. Comparative Sample

[0088] Comparative samples CE1, CE2 and CE3 are detailed in Table 1.

[0089] Table 1. Comparative Examples

[0090]

[0091] Hot-melt pressure-sensitive adhesives (CE1 and CE2) and solvent-based pressure-sensitive adhesives (CE3) were prepared, and their residual ratios were tested. A ratio greater than 0.8 for the comparative examples indicates that the cured material still retains significant tackiness. Such adhesives provide adhesion during recycling and prevent easy separation of the adhesive from the substrate.

[0092] Example 2. On-demand removable adhesive

[0093] Table 2 details the components of the on-demand removable adhesive of the present invention. As shown, Examples 4-8 provide a residual strength ratio of less than about 0.1. This indicates that the substrate readily detaches from the article or delaminates from other substrate layers.

[0094] Table 2. Detachable adhesives available upon request

[0095]

[0096] The residual strength ratio and residual laminate strength ratio of Examples 4-8 are less than 0.1. This indicates that the substrates are easily detached from the article or delaminated from other substrate layers, thus making them suitable for recycling processes.

[0097] Examples 4 and 5 are pressure-sensitive adhesives made from acrylic oligomers and vinyl acetate polymers with varying vinyl acetate contents. Upon exposure to electron beam energy, they readily detangle, as shown in the residual strength ratios and residual laminate strength ratios in Table 2. As shown in Example 4, optional tackifiers can be added to improve adhesion to various substrates. The addition of polyfunctional acrylates maintains or increases adhesive strength while further reducing detangle forces, as indicated by the lower residual strength ratio in Example 5.

[0098] Example 6 is formed from acrylic oligomers, polymers, and a photoinitiator. Upon exposure to ultraviolet (UV) energy, it readily debonds, as shown at low ratios. The addition of both the photoinitiator and the polyfunctional amine-acrylate (Photomer 4250) makes the formulation sensitive to UV energy and prevents oxygen inhibition.

[0099] Example 7 uses polar polyester and acrylic oligomers.

[0100] Example 8 uses acrylic polymers and acrylic oligomers.

[0101] Example 3. Acrylic oligomers

[0102] Table 3 lists the various acrylic oligomers, the specific number of their functional groups, and their viscosity at 60°C.

[0103] Table 3. Various acrylic oligomers

[0104]

[0105] The above-mentioned acrylic oligomers were then tested as on-demand release adhesives, and the measurement results of residual strength ratio and residual laminate strength ratio are shown in Table 4.

[0106] Table 4. Effects of acrylic oligomers

[0107]

[0108] When acrylic oligomers having at least two functional groups and a viscosity of less than about 8,000 cps (60°C) are combined with polymers having a solubility parameter of about 8 to about 15, a suitable release adhesive is provided. Example B contains a monofunctional acrylate oligomer with high viscosity and provides a higher ratio than 0.1, thus failing to provide the desired on-demand release effect.

[0109] Table 5 lists the solubility parameters of the polymers found in the references. Various acrylic oligomers were tested in known solvents to determine the suitable range of polymer solubility parameters for compatibility shown in Table 6. The solubility parameter for each acrylic oligomer was determined experimentally based on its solubility in known solvents. Five grams of acrylic oligomer were dissolved in 100 ml of solvent to determine compatibility (soluble, cloudy, or insoluble).

[0110] Table 5. Polymer solubility parameters

[0111]

[0112] 1.http: / / www.sigmaaldrich.com / content / dam / sigma-aldrich / docs / Aldrich / General_Information / polymer_solutions.pdf

[0113] 2.http: / / www.cool.conservation-us.org / coolaic / sg / bpg / annual / v03 / bp03-04.html

[0114] 3. https: / / en.wikipedia.org / wiki / Hildebrand_solubility_parameter

[0115] 4. Average estimates of solvent solubility parameters for Elvax 40W determined in Eastman Chemical Resin Solubility Chart RES-001.

[0116] Table 6. Determination of oligomer solubility using known solvents

[0117]

[0118] 1.http: / / www.sigmaaldrich.com / content / dam / sigma-aldrich / docs / Aldrich / General_Information / polymer_solutions.pdf

[0119] Based on the above experiments, the solubility of Sartomer CN120Z is 8.3 to 14.5, the solubility of Sartomer CN9167US and Rahn Genomer 4425 is 8.3 to 10.0, and the solubility of CN966H90 is 8.3 to 9.1.

[0120] The effect of polymer solubility was tested, and the results are shown in Table 7.

[0121] Table 7. Effects of polymer solubility parameters

[0122]

[0123] As shown in Table 7, polymers with solubility greater than about 8 but less than about 15 are suitable for on-demand adhesives. If outside these solubility parameter ranges, the adhesive cannot form a compatible single-phase system.

[0124] Example 5. High-strength on-demand lamination adhesive

[0125] For certain applications, high initial bond strength is required, but on-demand debonding is still necessary. Initial bond strength can be controlled by selecting acrylic oligomers. As demonstrated in Table 8, careful selection of acrylic oligomers can provide high initial strength for such applications. Adhesives with very high initial bond strength are prepared in Table 8, which are ideally suited as laminating adhesives. Solvent-free adhesives can also be prepared by changing the composition (Example Z).

[0126] Table 8. High-strength laminating adhesives

[0127]

[0128] Many modifications and alterations can be made to this invention without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are provided by way of example only, and the invention is limited only by the terms of the appended claims and the full scope of their equivalents.

Claims

1. A removable pressure-sensitive adhesive, comprising the following components: i. One or more acrylic oligomers having a. A viscosity of at least 300 cps to 8,000 cps, measured at 60°C according to ASTM D4402; and b. At least two acrylate functional groups, and ii. At least one polymer having a solubility parameter greater than 8 and less than 15, said solubility parameter being determined by dissolving one gram or more of solute in 100 ml of various known solvents; and iii. Optional tackifiers, solvents, waxes, antioxidants, and mixtures thereof; and iv. Photoinitiators, amines, amine-acrylate adducts, and mixtures thereof, which may be present by choice; The residual strength of the removable pressure-sensitive adhesive is less than 0.10, and the residual strength is measured as follows: ， The adhesive strength is measured according to ASTM D903.

2. The removable pressure-sensitive adhesive according to claim 1, wherein the polymer is selected from ethylene-vinyl acetate copolymers, polyester polymers, acrylic polymers, and mixtures thereof.

3. The removable pressure-sensitive adhesive according to claim 1, wherein the acrylic oligomer further comprises the following functional groups: epoxy, urethane, ester, ether, amide, or a combination thereof.

4. An article comprising a first substrate bonded to a removable adhesive, said removable adhesive being composed of: a. An acrylic oligomer having (i) a viscosity of at least 300 cps to 8,000 cps, said viscosity measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups. b. At least one polymer having a solubility parameter greater than 8 and less than 15, said solubility parameter being determined by dissolving one gram or more of solute in 100 ml of various known solvents; c. Photoinitiators, amines, amine-acrylate adducts, tackifiers, solvents, waxes, antioxidants, and mixtures thereof, which may be present by choice; The residual strength ratio of the removable adhesive is less than 0.10, and the residual strength ratio is measured as follows: ， The adhesive strength is measured according to ASTM D903.

5. The article of claim 4, further comprising a second substrate bonded to the removable adhesive, wherein the removable adhesive is sandwiched between the first substrate and the second substrate.

6. The article according to claim 5, wherein it is a laminate.

7. A method for detaching an article from its substrate, wherein the article comprises a substrate having a first surface and a second surface, and a detachable adhesive coated on the first surface and bonded to the substrate, the method comprising the following steps: a) Prepare the article; and b) Applying an electron beam or ultraviolet light to the article, thereby making the removable adhesive substantially non-stick; as well as The removable adhesive comprises the following components: (1) An acrylic oligomer having (i) a viscosity of at least 300 cps to 8,000 cps, said viscosity being measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) At least one polymer having a solubility parameter greater than 8 and less than 15, said solubility parameter being determined by dissolving one gram or more of solute in 100 ml of various known solvents; and (3) Photoinitiators, amines, amine-acrylate adducts, tackifiers, solvents, waxes, antioxidants and mixtures thereof, which may be present by choice; The removable adhesive has a residual strength ratio of less than 0.10, wherein the residual strength ratio is measured as follows: ， The adhesive strength is measured according to ASTM D903.

8. A method for debonding a laminate, wherein the laminate comprises a first substrate having a first surface and a second surface, a second substrate having a first surface and a second surface, and a debondable adhesive applied to and bonding the first surface of the first substrate and the second surface of the second substrate, the method comprising the following steps: a. To prepare products; b. Apply an electron beam or ultraviolet light to the laminate; c. Agitate at least one substrate, thereby separating the at least one substrate from the laminate; The removable adhesive comprises the following components: (1) An acrylic oligomer having (i) a viscosity of at least 300 cps to 8,000 cps, said viscosity being measured at 60°C according to ASTM D4402; and (ii) at least two acrylate functional groups; and (2) At least one polymer having a solubility parameter greater than 8 and less than 15, said solubility parameter being determined by dissolving one gram or more of solute in 100 ml of various known solvents; and (3) Photoinitiators, amines, amine-acrylate adducts, tackifiers, solvents, waxes, antioxidants and mixtures thereof, which may be present by choice; The removable adhesive has a residual strength ratio of less than 0.10, wherein the residual strength ratio is measured as follows: ， The adhesive strength is measured according to ASTM D903.

9. The method for debonding a laminate according to claim 8, wherein the first substrate and the second substrate are independently paper, plastic, metal, fiber, wood, film, carpet, glass, rubber, composite material, mineral, or foam.

10. The method for debonding a laminate according to claim 8, wherein in step (b) the electron beam or the ultraviolet light is applied to a second surface of a first substrate or a first surface of a second substrate.

11. The method for debinding a laminate according to claim 9, wherein the mineral is crystal.

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