Hot tack pressure sensitive adhesive composition and pressure sensitive adhesive

Abstract

This invention provides a thermoplastic pressure-sensitive adhesive composition comprising the following components: an acrylate copolymer, a divinyl-terminated isocyanate, and an alkaline amine compound; wherein, relative to 100 parts by weight of the acrylate copolymer, the content of the divinyl-terminated isocyanate is 0.5 to 3 parts by weight, and the content of the alkaline amine compound is 0.5 to 12 parts by weight. The pressure-sensitive adhesive prepared by the thermoplastic pressure-sensitive adhesive composition of this invention has low initial peel strength, allowing for arbitrary tearing after bonding and providing positioning functionality; after bonding and exposure to high temperature, the peel strength is increased to achieve the high adhesive performance required for fixing components, thereby reducing component damage due to errors in the initial bonding stage, and is applicable to conventional high-viscosity pressure-sensitive adhesive applications.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesive technology, and more particularly to a heat-adhesive pressure-sensitive adhesive composition and a pressure-sensitive adhesive. Background Technology

[0002] Pressure-sensitive adhesives, also known as self-adhesives, are adhesives that are sensitive to pressure. They possess advantages such as excellent temperature resistance, a wide range of peel strengths, strong cohesion, good chemical and aging resistance, and a wide range of applications. Therefore, they are commonly used for bonding and protection in the industrial and electronic sectors, such as fixing and bonding electronic components and bonding batteries and their inner casings. However, these pressure-sensitive adhesives typically have high tack, with a peel force generally around 15N. This makes it difficult to reposition or adjust the adhesive after a bonding error, and once bonded, it is difficult to remove the adhesive layer without damaging the component, leading to component wear and tear. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a heat-adjustable pressure-sensitive adhesive composition and a pressure-sensitive adhesive prepared from this composition. The pressure-sensitive adhesive prepared from the heat-adjustable pressure-sensitive adhesive composition of this invention exhibits low peel strength in the initial bonding stage, ensuring that it can be easily torn off after bonding, facilitating positioning and adjustment. After bonding and exposure to high temperature, the peel strength increases to achieve the high adhesive performance required for component fixation, thereby reducing component damage caused by bonding errors in the initial bonding stage. Furthermore, it is suitable for conventional high-viscosity pressure-sensitive adhesive applications.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A first aspect of the present invention provides a thermoplastic pressure-sensitive adhesive composition comprising the following components: an acrylate copolymer, a divinyl-terminated isocyanate, and a basic amine compound;

[0006] The content of the dual-vinyl-terminated isocyanate is 0.5 to 3 parts by weight relative to 100 parts by weight of the acrylate copolymer, and the content of the basic amine compound is 0.5 to 12 parts by weight.

[0007] A second aspect of the present invention provides a pressure-sensitive adhesive comprising the heat-adhesive pressure-sensitive adhesive composition described in the first aspect of the present invention.

[0008] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0009] (1) The heat-adhesive pressure-sensitive adhesive composition provided by the present invention contains a double-end vinyl-terminated isocyanate. This type of double-end vinyl-terminated isocyanate can be grafted onto the molecular chain of acrylate copolymer through UV free radical reaction, thereby increasing the crosslinking density of the pressure-sensitive adhesive in the early stage of use, resulting in high modulus and low peel force in the early stage of use, making it easy to tear off at any time after bonding, thus suitable for initial positioning.

[0010] (2) The dual-end vinyl-terminated isocyanate added to the heat-adhesive pressure-sensitive adhesive composition provided by the present invention is subjected to high-temperature treatment (110-150°C) after initial positioning and accurate bonding, which can break the molecular chains formed in the initial bonding stage, thereby reducing the crosslinking density and modulus of the pressure-sensitive adhesive, and increasing its peel force to a high tack level, thus making it suitable for all conventional high-tack pressure-sensitive adhesive applications.

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Detailed Implementation

[0012] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0013] The first aspect of the present invention provides a thermoplastic pressure-sensitive adhesive composition comprising the following components: an acrylate copolymer, a divinyl-terminated isocyanate, and an alkaline amine compound; wherein, relative to 100 parts by weight of the acrylate copolymer, the content of the divinyl-terminated isocyanate is 0.5 to 3 parts by weight, and the content of the alkaline amine compound is 0.5 to 12 parts by weight.

[0014] Current pressure-sensitive adhesives generally have high tack, with an initial peel force of around 15N. If an adhesion error occurs, repositioning is difficult without damaging the component. Therefore, addressing the problems in the prior art, this invention provides a thermoplasticized pressure-sensitive adhesive composition. This composition incorporates a dual-vinyl-terminated isocyanate. This type of isocyanate can be grafted onto the molecular chain of the acrylate copolymer via UV free radical reaction, increasing the crosslinking density of the pressure-sensitive adhesive in the initial stage of use. This results in a high modulus and low peel force in the initial stage of use, allowing for easy tearing after adhesion, thus facilitating initial positioning.

[0015] Furthermore, after the initial positioning and accurate bonding are completed, the double-ended vinyl-terminated isocyanate is subjected to high-temperature treatment (110-150°C), which can break the molecular chains formed in the initial bonding stage, thereby reducing the crosslinking density and modulus of the pressure-sensitive adhesive, and increasing its peel force to a high tack level, making it suitable for all conventional high-tack pressure-sensitive adhesive applications.

[0016] Furthermore, during high-temperature processing, the isocyanate groups in the dual-vinyl-terminated isocyanate system are highly reactive and can crosslink with water in the air, resulting in a decrease in viscosity after the modulus is increased. To avoid this, the present invention also adds an alkaline amine compound to the heat-adhesive pressure-sensitive adhesive composition. This compound has a high boiling point and can consume the isocyanate groups in the system to generate carbamic acid, thereby preventing the isocyanate groups in the system from crosslinking with water molecules, improving the viscosity of the heat-adhesive pressure-sensitive adhesive in the later stage, and making it more in line with the market demand for high viscosity performance.

[0017] Furthermore, to increase the initial crosslinking density between the vinyl-terminated isocyanate and the acrylate copolymer, the content of the vinyl-terminated isocyanate is 0.5 to 3 parts by weight relative to 100 parts by weight of the acrylate copolymer. Specifically, the content of the vinyl-terminated isocyanate can be 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.3 parts by weight, 2.4 parts by weight, 2.5 parts by weight, 2.6 parts by weight, 2.7 parts by weight, 2.8 parts by weight, 2.9 parts by weight, 3 parts by weight, or any value within any two of the above ranges, preferably 1 to 2.5 parts by weight. When the content of dual-vinyl-terminated isocyanate and basic amine compounds is excessive relative to the acrylate copolymer, the crosslinking density will be too high. However, excessive basic amine will also lead to an excessive number of small molecules in the system, making the colloid too soft and easy to precipitate, thus contaminating the substrate. When the content of dual-vinyl-terminated isocyanate is too low relative to the acrylate copolymer, the amount of dual-vinyl-terminated isocyanate that can be grafted onto the acrylate copolymer is too small, which is not effective in improving the initial crosslinking density. As a result, the pressure-sensitive adhesive still has a high peel force in the early stage, making it difficult to peel off after application and unsuitable for repositioning after application errors.

[0018] Furthermore, to enhance the tackiness of the heat-treated pressure-sensitive adhesive and achieve high tack performance, the content of the alkaline amine compound is 0.5 to 12 parts by weight relative to 100 parts by weight of the acrylate copolymer. Specifically, the content of the alkaline amine compound can be 0.5 parts by weight, 1 part by weight, 1.25 parts by weight, 2 parts by weight, 2.5 parts by weight, 3.5 parts by weight, 4 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, or any value within any two of the above ranges, preferably 2.5 to 6 parts by weight. When the content of basic amine compounds is excessive, too many small molecules will affect the initial tack, resulting in high peel strength, poor rework performance, and die-cutting overflow. When the content of basic amine compounds is too low, the isocyanate groups in the system cannot be completely consumed. The highly active isocyanate groups will cross-link with water in the air, resulting in increased modulus, decreased tack in the later stage, unstable product performance, and poor practical performance.

[0019] In one specific embodiment, the weight ratio of the basic amine compound to the divinyl-terminated isocyanate is (1-4):1. Specifically, the weight ratio of the basic amine compound to the divinyl-terminated isocyanate can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any ratio within any of the above two extreme ranges, preferably (2-3):1. Since excess isocyanate groups will continue to react with the carbamic acid generated by the basic amine compound to form urea, it will cause the modulus of the pressure-sensitive adhesive to increase, resulting in a decrease in adhesion in the later stage. Therefore, by further controlling the weight ratio of the basic amine compound to the divinyl-terminated isocyanate, it is possible to ensure that the amount of basic amine compound is slightly more than the amount of isocyanate groups, thereby avoiding the reaction of excess isocyanate groups with carbamic acid.

[0020] In one specific embodiment, the basic amine compound includes at least one selected from dipropylamine and cyclohexylamine. In a preferred embodiment, the basic amine compound is selected from dipropylamine.

[0021] In this invention, a method for preparing the dual-vinyl-terminated isocyanate is also provided, which is as follows: Compound 1 is added to a reaction vessel, then an antioxidant and a first catalyst are added and mixed evenly, an inert gas is introduced, and then Compound 2 is added to react, thereby obtaining the dual-vinyl-terminated isocyanate.

[0022] The structural formula of compound 1 is shown in formula (1) or formula (2) below, and the structural formula of compound 2 is shown in formula (3) below:

[0023]

[0024] Wherein, n is an integer between 4 and 10. In a specific embodiment, n can be 4, 5, 6, 7, 8, 9 or 10, preferably 6;

[0025]

[0026] Wherein, p is an integer between 1 and 4. In a specific embodiment, p can be 1, 2, 3 or 4, preferably 2;

[0027]

[0028] Wherein, R1 is a hydrogen atom or a methyl group, and m is an integer between 1 and 4. In a specific embodiment, m can be 1, 2, 3 or 4, preferably 2 or 3.

[0029] In a preferred preparation method, the molar ratio of compound 1 to compound 2 is 1:1.

[0030] In a preferred preparation method, the mixing temperature of compound 1, antioxidant and first catalyst is maintained at a constant temperature of 15°C.

[0031] In a preferred preparation method, the inert gas is nitrogen.

[0032] In a preferred preparation method, the reaction temperature for adding compound 2 is 15–20°C. Specifically, the reaction temperature is 15°C, 16°C, 17°C, 18°C, 19°C, or 20°C, or any value between these two extremes.

[0033] In a preferred preparation method, compound 2 is added by uniform dropwise addition.

[0034] In a preferred preparation method, after compound 2 is added dropwise, the reaction temperature is maintained at 20°C, and the reaction continues for 12 hours.

[0035] In a preferred preparation method, the antioxidant is butylated hydroxytoluene, and its addition amount is 0.01 to 0.1 g relative to 1 mol of compound 1. Specifically, its addition amount can be 0.01 g, 0.02 g, 0.03 g, 0.04 g, 0.05 g, 0.06 g, 0.07 g, 0.08 g, 0.09 g, 0.1 g, or any value between the two extremes, preferably 0.05 g.

[0036] In a preferred preparation method, the first catalyst is dibutyltin dicerylsilicate, and its addition amount is 0.05-0.2g relative to 1 mol of compound 1. Specifically, its addition amount can be 0.05g, 0.06g, 0.07g, 0.08g, 0.09g, 0.1g, 0.12g, 0.14g, 0.16g, 0.18g, 0.2g, or any value between the two extremes, preferably 0.1g.

[0037] In a preferred preparation method, compound 1 adopts the structure of formula (1) and n = 6; compound 2 adopts the structure of formula (3) and m = 3, R1 is methyl; the prepared divinyl-terminated isocyanate is propyl methacrylate isocyanate (3-octenyl-phenol) ester, the structure of which is shown in formula (4) below:

[0038]

[0039] In a preferred preparation method, compound 1 adopts the structure of formula (1) and n = 6; compound 2 adopts the structure of formula (3) and m = 3, R1 is a hydrogen atom; the prepared divinyl-terminated isocyanate is propyl acrylate isocyanate (3-octenyl-phenol) ester, the structure of which is shown in formula (5) below:

[0040]

[0041] In a preferred preparation method, compound 1 adopts the structure of formula (2) and p = 2; compound 2 adopts the structure of formula (3) and m = 2, R1 is a hydrogen atom; the prepared divinyl-terminated isocyanate is (1-methyl-4-pentene) cyanoacrylate isocyanate, the structure of which is shown in formula (6) below:

[0042]

[0043] In a preferred preparation method, compound 1 adopts the structure of formula (2) and p = 2; compound 2 adopts the structure of formula (3) and m = 2, R1 is methyl; the prepared divinyl-terminated isocyanate is (1-methyl-4-pentene) cyanomethacrylate ethyl isocyanate, the structure of which is shown in formula (7) below:

[0044]

[0045] In this invention, the divinyl-terminated isocyanates listed above are not limited to these; divinyl-terminated isocyanates with different structures can be prepared based on compounds with different structures. The double bond groups at both ends of the divinyl-terminated isocyanate include vinyl groups and / or isopropenyl groups. That is, both ends of the divinyl-terminated isocyanate can be vinyl groups simultaneously, or one end can be a vinyl group and the other end can be an isopropenyl group.

[0046] In one specific embodiment, based on a total monomer content of 100 wt% for the acrylate copolymer, the acrylate copolymer comprises the following monomer components: 5-15 wt% hard monomers and 85-95 wt% soft monomers.

[0047] In one specific embodiment, based on the total amount of monomers constituting the acrylate copolymer being 100 wt%, the hard monomer accounts for 5 to 15 wt%, specifically 5 wt%, 8 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, or any value between the two extremes, preferably 8 to 12 wt%.

[0048] In one specific embodiment, the hard monomer includes at least one of methyl methacrylate, styrene, acrylic acid, vinyl acetate, ethyl methacrylate, isobutyl methacrylate, acrylonitrile, cyclohexyl methacrylate, and isobornyl methacrylate.

[0049] In one specific embodiment, based on the total amount of monomers constituting the acrylate copolymer being 100 wt%, the proportion of the soft monomer is 85-95 wt%, specifically 85 wt%, 88 wt%, 90 wt%, 92 wt%, or 95 wt%, or any value between the two extremes, preferably 88-92 wt%.

[0050] In one specific embodiment, the soft monomer includes at least one of butyl acrylate, isooctyl acrylate, ethyl acrylate, n-octyl acrylate, and lauryl (meth)acrylate.

[0051] In one specific embodiment, the acrylate copolymer further includes a first initiator, the content of which is 0.1 to 0.5 parts by weight relative to 100 parts by weight of the total amount of monomers constituting the acrylate copolymer, specifically 0.1, 0.2, 0.3, 0.4, or 0.5 parts by weight, or any value between the two extremes, preferably 0.1 to 0.3 parts by weight.

[0052] In one specific embodiment, the first initiator includes at least one selected from benzoin and its derivatives, benzoyl derivatives, acetophenone derivatives, α-hydroxyalkylphenyl ketones, α-aminoketone derivatives, and acylphosphine oxides. In a preferred embodiment, the first initiator is selected from α-hydroxyalkylphenyl ketones. In another specific embodiment, the first initiator is selected from 1-hydroxycyclohexylphenyl ketone (UV-184).

[0053] In one specific embodiment, the acrylate copolymer further includes a chain transfer agent, the content of which is 0.01 to 0.3 parts by weight relative to 100 parts by weight of the total amount of monomers constituting the acrylate copolymer, specifically 0.01 parts by weight, 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight or 0.3 parts by weight, or any value between the two extremes, preferably 0.1 to 0.2 parts by weight.

[0054] In one specific embodiment, the chain transfer agent includes one or more of isooctyl 3-mercaptopropionate, n-dodecyl mercaptan, and tert-dodecyl mercaptan.

[0055] In this invention, a method for preparing an acrylate copolymer is also provided. Specifically, the method for preparing the acrylate copolymer can be as follows: the soft monomer, hard monomer, first initiator and chain transfer agent are added to a reaction vessel, mixed evenly, and the monomer is initiated by UV LED light source to carry out polymerization reaction. After the reaction is completed, the acrylate copolymer can be obtained.

[0056] In a preferred preparation method, the irradiation distance of the UVLED light source is 20-30 cm.

[0057] In a preferred preparation method, the wavelength of the UVLED lamp can be 365 nm, and the light intensity can be 82 mW / cm². 2 .

[0058] In a preferred preparation method, the reaction temperature of the polymerization reaction is between 5 and 15°C, specifically 5°C, 7°C, 10°C, 13°C or 15°C, or any value between the two extremes.

[0059] In a preferred preparation method, the viscosity of the prepared acrylate copolymer is 3,000 to 6,000 cPs. Controlling the viscosity of the copolymer within this range in this invention facilitates coating.

[0060] In one specific embodiment, the heat-adhesive pressure-sensitive adhesive composition further includes a second initiator. The content of the second initiator relative to 100 parts by weight of the acrylate copolymer is 0.01 to 0.8 parts by weight, specifically 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8 parts by weight, or any value between these two extremes, preferably 0.1 to 0.3 parts by weight. The second initiator can initiate a UV free radical reaction of the divinyl-terminated isocyanate to graft onto the molecular chain of the acrylate copolymer, thereby increasing the initial crosslinking density of the pressure-sensitive adhesive and reducing the peel force.

[0061] In one specific embodiment, the second initiator includes at least one selected from benzoin and its derivatives, benzoyl derivatives, acetophenone derivatives, α-hydroxyalkylphenyl ketones, α-aminoketone derivatives, and acylphosphine oxides. In a preferred embodiment, the second initiator is selected from α-hydroxyalkylphenyl ketones. In one specific embodiment, the first initiator is selected from 1-hydroxycyclohexylphenyl ketone.

[0062] In one specific embodiment, the heat-adhesive pressure-sensitive adhesive composition further includes a second catalyst. The content of the second catalyst is 0.1 to 1 part by weight relative to 100 parts by weight of the acrylate copolymer, specifically 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 1 part by weight, or any value between these two extremes, preferably 0.2 to 0.5 parts by weight. The second catalyst can be used to promote the desealing of the vinyl-terminated isocyanate at high temperatures, causing the vinyl-terminated isocyanate to break from the molecular chain of the acrylate copolymer, reducing the crosslinking density of the pressure-sensitive adhesive in the later stages, increasing the peel force, and thus rapidly improving the adhesion in the later stages of bonding.

[0063] In one specific embodiment, the second catalyst is a metal salt catalyst, which may include at least one of dibutyltin dilaurate and dibutyltin diacetate. In a preferred embodiment, the second catalyst is selected from dibutyltin dilaurate.

[0064] In one specific embodiment, the heat-adhesive pressure-sensitive adhesive composition further includes a crosslinking monomer. The crosslinking monomer content is 0-3 parts by weight relative to 100 parts by weight of the acrylate copolymer, specifically 0 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, or 3 parts by weight, or any value between the two extremes, preferably 0.1-2 parts by weight. In this invention, the crosslinking monomer may not be added; in this case, the divinyl-terminated isocyanate can play a crosslinking role. However, after adding the crosslinking monomer, the acrylate copolymer is partially crosslinked with the crosslinking monomer and partially with the divinyl-terminated isocyanate, resulting in a stronger crosslinking effect.

[0065] In one specific embodiment, the crosslinking monomer is selected from at least one of 1,6-hexanediol diacrylate (HDDA) and polyurethane acrylates. The polyurethane acrylate may be selected from difunctional and / or trifunctional polyurethane acrylates.

[0066] A second aspect of the present invention provides a pressure-sensitive adhesive comprising the heat-adhesive pressure-sensitive adhesive composition described in the first aspect of the present invention, or a pressure-sensitive adhesive prepared from the heat-adhesive pressure-sensitive adhesive composition.

[0067] The present invention also provides an adhesive sheet, which is prepared from the pressure-sensitive adhesive described in the second aspect of the present invention, or contains the heat-adhesive pressure-sensitive adhesive composition described in the first aspect of the present invention.

[0068] The present invention also provides a protective film comprising a substrate layer and an adhesive layer disposed on at least one surface of the substrate layer, wherein the adhesive layer is the aforementioned adhesive sheet.

[0069] In this invention, the product is limited to a protective film only for practical use. In fact, as long as it contains the thermoplastic pressure-sensitive adhesive composition of this invention, it can also be designed as other products. For example, the protective film can also be a thermoplastic pressure-sensitive adhesive tape, a thermoplastic pressure-sensitive adhesive label, a thermoplastic pressure-sensitive adhesive film, and a thermoplastic pressure-sensitive adhesive membrane, etc.

[0070] In one specific embodiment, a release film layer is provided on the side surface of the adhesive layer opposite to the substrate layer.

[0071] In one specific embodiment, the thickness of the substrate layer is 12 to 100 μm, specifically 12 μm, 20 μm, 25 μm, 30 μm, 50 μm, 70 μm, 75 μm, 80 μm or 100 μm, preferably 25 to 75 μm.

[0072] In one specific embodiment, the thickness of the adhesive layer is 20 to 200 μm, specifically 20 μm, 25 μm, 30 μm, 50 μm, 70 μm, 75 μm, 80 μm, 100 μm or 200 μm, preferably 20 to 75 μm.

[0073] In one specific embodiment, the thickness of the release film layer is 25-75 μm, specifically 25 μm, 30 μm, 38 μm, 40 μm, 50 μm, 60 μm, 65 μm, 70 μm or 75 μm, preferably 38-50 μm.

[0074] In this invention, the material of the substrate layer is not specifically limited. Materials commonly used in the art as tape substrates can be selected. For example, the substrate layer can be polyethylene terephthalate (PET), polyimide (PI), etc.

[0075] In this invention, the release film layer can be selected from one or more of PET (polyethylene terephthalate), PE (polyethylene), and OPP (biaxially oriented polypropylene). Since the release film layer only serves a release function to facilitate product packaging and transportation, it will be peeled off during actual application, allowing the adhesive layer to adhere to the surface of the object. Therefore, the thickness of the release film layer is not limited in this invention, and a suitable thickness can be selected according to actual usage requirements.

[0076] In this invention, a method for preparing a protective film is also provided, which specifically includes the following steps: applying the above-mentioned pressure-sensitive adhesive to the surface of a substrate layer, drying and curing it, and then laminating a release film to obtain the above-mentioned protective film with a heat-adhesive pressure-sensitive adhesive layer.

[0077] In a preferred preparation method, the curing is performed using UV LED light curing, with the curing lamp having a light source wavelength of 365nm, a light power of 18W, a curing time of 4-8min, and an irradiation distance of 8-12cm.

[0078] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0079] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0080] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0081] In the following examples, unless otherwise specified, all ingredients used were commercially available analytical grade. 1g represents 1 part by weight.

[0082] Preparation of acrylate copolymers

[0083] Preparation Example A Group

[0084] This preparation example is used to prepare acrylate copolymers. The only difference between the groups is the content of each component, and the preparation methods are the same. The substance contents of each preparation example are shown in Table 1:

[0085] Table 1. Content of each component in the acrylate copolymer (unit: g)

[0086]

[0087] Preparation method: Weigh out parts by weight of butyl acrylate, acrylic acid, methyl methacrylate, 1-hydroxycyclohexylphenyl ketone (UV-184), and n-dodecyl mercaptan and add them to the reaction vessel. Mix well and purge with nitrogen gas for 30 minutes. Initiate monomer polymerization by irradiation with a UVLED light source. The distance between the UVLED light source and the bottom of the vessel is fixed at 25 cm. The wavelength of the UVLED lamp is 365 nm and the light intensity is 82 mW / cm. 2 By controlling the reaction temperature within the range of 5 to 15°C, acrylate copolymers can be obtained.

[0088] Preparation of divinyl-terminated isocyanates:

[0089] Preparation Example B Group

[0090] This set of preparation examples is used to prepare divinyl-terminated isocyanates. The only difference between the different preparation examples is the specific substances and amounts of compound 1 and compound 2. All other components and preparation methods are the same, as shown below:

[0091] Preparation method: 1 mol of compound 1, 0.05 g of butylated hydroxytoluene, and 0.1 g of dibutyltin dilaurate were added to a reaction vessel. The mixture was stirred at a constant temperature of 15°C and dry nitrogen gas was blown out. 1 mol of compound 2 was added dropwise, and the reaction temperature was maintained in the range of 15-20°C. The mixture was added dropwise at a uniform rate for 1 h. After the addition was completed, the temperature was maintained at 20°C for 12 h. After the reaction was completed, IR was used to confirm whether the isocyanate ions were completely consumed. Finally, a divinyl-terminated isocyanate compound was obtained, which was a colorless and transparent liquid.

[0092] Preparation Example B1: Compound 1 adopts the structure of formula (1), and n = 6; Compound 2 adopts the structure of formula (3), and m = 3, R1 is methyl; the structure of the prepared divinyl-terminated isocyanate is as follows:

[0093]

[0094] Preparation Example B2: Compound 1 adopts the structure of formula (1), and n = 6; Compound 2 adopts the structure of formula (3), and m = 3, R1 is a hydrogen atom; the structure of the prepared divinyl-terminated isocyanate is as follows:

[0095]

[0096] Preparation Example B3: Compound 1 adopts the structure of formula (2), and p = 2; Compound 2 adopts the structure of formula (3), and m = 2, R1 is a hydrogen atom; the structure of the prepared divinyl-terminated isocyanate is as follows:

[0097]

[0098] Preparation Example B4: Compound 1 adopts the structure of formula (2), and p = 2; Compound 2 adopts the structure of formula (3), and m = 2, R1 is methyl; the structure of the prepared divinyl-terminated isocyanate is as follows:

[0099]

[0100] Example 1

[0101] Preparation of pressure-sensitive adhesive: Weigh 100g of the acrylate copolymer prepared in Preparation Example A1 and place it in a reaction vessel. Add 2g of the vinyl-terminated isocyanate prepared in Preparation Example B1, 0.2g of 1-hydroxycyclohexylphenyl ketone, 5g of dipropylamine, 0.3g of dibutyltin dilaurate and 1.5g of HDDA. Stir evenly and degas to obtain the heat-adhesive pressure-sensitive adhesive.

[0102] Example 2

[0103] Example 2 was conducted in accordance with Example 1, but the raw material composition of the pressure-sensitive adhesive was different. Its preparation method was the same as in Example 1, with the specific differences as follows:

[0104] 0.5 g of the vinyl-terminated isocyanate prepared in Example B1;

[0105] Dipropylamine, 1.25g;

[0106] 1-Hydroxycyclohexylphenyl ketone, 0.1g;

[0107] Dibutyltin dilaurate, 0.1g;

[0108] HDDA, 0.1g.

[0109] Example 3

[0110] Example 3 was conducted in accordance with Example 1, but the raw material composition of the pressure-sensitive adhesive was different. Its preparation method was the same as in Example 1, with the specific differences as follows:

[0111] 3 g of the vinyl-terminated isocyanate prepared in Example B1;

[0112] Dipropylamine, 7.5g;

[0113] 1-Hydroxycyclohexylphenyl ketone, 0.8g;

[0114] Dibutyltin dilaurate, 1g;

[0115] HDDA, 3g.

[0116] Example 4

[0117] Example 4 was conducted in accordance with Example 1, but the raw material composition of the pressure-sensitive adhesive was different. Its preparation method was the same as in Example 1, with the specific differences as follows:

[0118] 1 g of the vinyl-terminated isocyanate prepared in Example B1;

[0119] Dipropylamine, 2.5g;

[0120] 1-Hydroxycyclohexylphenyl ketone, 0.1g;

[0121] Dibutyltin dilaurate, 0.2g;

[0122] HDDA, 1g.

[0123] Example 5

[0124] Example 5 was carried out in accordance with Example 1, but the raw material composition of the pressure-sensitive adhesive was different. Its preparation method was the same as in Example 1, and the specific differences are as follows:

[0125] 2.4 g of the vinyl-terminated isocyanate prepared in Example B1;

[0126] Dipropylamine, 6g;

[0127] 1-Hydroxycyclohexylphenyl ketone, 0.3g;

[0128] Dibutyltin dilaurate, 0.5g;

[0129] HDDA, 2g.

[0130] Example 6 group

[0131] Example 6 was prepared in accordance with Example 1, except that a different vinyl-terminated isocyanate prepared in Preparation Example B was used. The preparation method, amount, and other components remained unchanged, as shown below:

[0132] Example 6-1: A vinyl-terminated isocyanate prepared using Preparation Example B2;

[0133] Example 6-2: A vinyl-terminated isocyanate prepared using Preparation Example B3;

[0134] Example 6-3: The divinyl-terminated isocyanate prepared using Preparation Example B4.

[0135] Example 7 group

[0136] Example 7 was conducted in accordance with Example 1, except that the mass ratio of dipropylamine to divinyl-terminated isocyanate was changed by adjusting the amount of dipropylamine added. The composition and preparation method of other substances were the same as in Example 1. Specific differences are as follows:

[0137] Example 7-1: Dipropylamine, 2g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 1:1;

[0138] Example 7-2: Dipropylamine, 8g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 4:1;

[0139] Example 7-3: Dipropylamine, 4g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 2:1;

[0140] Example 7-4: Dipropylamine, 6g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 3:1;

[0141] Example 7-5: Dipropylamine, 10g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 5:1;

[0142] Examples 7-6: Dipropylamine, 1g, with a mass ratio of dipropylamine to divinyl-terminated isocyanate of 0.5:1.

[0143] Example 8

[0144] Example 8 was carried out in accordance with Example 1, except that the pressure-sensitive adhesive did not contain the crosslinking monomer HDDA, while the other components and preparation methods were the same as in Example 1.

[0145] Example 9 group

[0146] Example 9 was conducted in accordance with Example 1, except that the acrylate copolymer prepared by different preparation examples (Group A) was used. The preparation method, amount, and other components remained unchanged, as detailed below:

[0147] Example 9-1: An acrylate copolymer prepared using Preparation Example A2;

[0148] Example 9-2: Acrylate copolymer prepared using Preparation Example A3;

[0149] Examples 9-3: Acrylate copolymers prepared using Preparation Example A4;

[0150] Examples 9-4: Acrylic ester copolymers prepared using Preparation Example A5.

[0151] Comparative Example 1

[0152] Comparative Example 1 was carried out in accordance with Example 1, except that no dual-end vinyl-terminated isocyanate was added to the pressure-sensitive adhesive.

[0153] Comparative Example 2

[0154] Comparative Example 2 was carried out in accordance with Example 1, except that dipropylamine was not added to the pressure-sensitive adhesive.

[0155] Comparative Example 3

[0156] Comparative Example 3 was carried out in accordance with Example 1, except that the raw material composition of the pressure-sensitive adhesive was different, while its preparation method was the same as that of Example 1. The specific differences are as follows:

[0157] Preparation Example B1: 0.1 g of dipropylamine and 0.25 g of vinyl-terminated isocyanate were prepared, maintaining the mass ratio of dipropylamine to vinyl-terminated isocyanate at 2.5:1.

[0158] Comparative Example 4

[0159] Comparative Example 4 was conducted in accordance with Example 1, except that the raw material composition of the pressure-sensitive adhesive was different, while its preparation method was the same as in Example 1. The specific differences are as follows:

[0160] Preparation Example B1: 5 g of dipropylamine and 12.5 g of vinyl-terminated isocyanate were prepared, maintaining the mass ratio of dipropylamine to vinyl-terminated isocyanate at 2.5:1.

[0161] Test Case of Thermally Tackified Pressure-Sensitive Adhesive Protective Film

[0162] The pressure-sensitive adhesives prepared in the above embodiments and comparative examples were coated onto a 50 μm thick PET substrate and cured by UV lamp irradiation. Irradiation conditions: the light source wavelength of the curing lamp was 365 nm, the light power was 18 W, the curing time was 6 min, and the distance from the lamp was 10 cm. After curing, a 50 μm thick PET release film was laminated to obtain a heat-adhesive pressure-sensitive adhesive protective film with an adhesive layer thickness of 75 μm. The heat-adhesive pressure-sensitive adhesive protective films prepared in the above embodiments and comparative examples were subjected to the following tests:

[0163] (1) Initial / Later Peel Strength Test

[0164] The peel strength test was conducted according to ASTM D3330, "Standard for Testing the Peel Strength of Pressure-Sensitive Adhesive Tapes".

[0165] The above protective film was made into a 25mm wide strip. The initial peel force test was carried out according to the above test standard. The peel force test was carried out by bonding it to a steel plate at room temperature, and the data was recorded in Table 2.

[0166] The peel strength test was first performed by high temperature treatment. The adhesion enhancement operation steps are as follows: the 25mm wide strip made of the above protective film was placed in an environment of 140℃ for 30 minutes, the wide strip was taken out and left to stand at room temperature for 30 minutes, and then it was attached to the steel plate for peel strength test. The data were recorded in Table 2.

[0167] (2) Initial / Later Holding Strength Test

[0168] According to ASTM D3330 "Standard for Testing the Peel Strength of Pressure-Sensitive Adhesive Tapes", the holding power is tested by cutting a 25mm*10cm protective film strip, using a 2kg pressure roller to adhere it to a mirror steel plate at a speed of 300mm / min, letting it stand for 20 minutes, and then hanging it in a holding power testing machine to observe the drop time (min).

[0169] Later retention test: Place the cut sample in an oven at 140℃ for 30 minutes; after taking it out and letting it stand at room temperature for two hours, test the later retention using the same method as the initial test, and record the data in Table 2.

[0170] (3) Initial / Later Modulus Testing: Room Temperature Rheological Testing

[0171] The pressure-sensitive adhesives prepared in each embodiment and comparative example were coated onto release films. After curing and drying, a substrate-free adhesive layer with a thickness of 100 μm was obtained. The adhesive layers were stacked to 900 μm, and the temperature scan curve, i.e., the initial modulus, was tested using an Anton Paar rheometer. The adhesive layer was placed in an environment of 140°C for 30 min for high-temperature treatment. After being removed and allowed to stand at room temperature for 30 min, the rheological test was performed to obtain the later modulus. The rheometer test scan frequency was 0.05 Hz, and the data were recorded in Table 2.

[0172] Table 2

[0173]

[0174]

[0175] As can be seen from the test results in Table 2 above, the pressure-sensitive adhesive prepared by the present invention has a good tackifying effect, high peel force after heating, and good initial and later holding power.

[0176] The test results of Example 6 show that different structures of dual-end vinyl-terminated isocyanates can all achieve good tackifying properties of pressure-sensitive adhesives.

[0177] The test results of Example 7 show that controlling the mass ratio of alkaline amine compound to dual-vinyl-terminated isocyanate within a certain range can yield a pressure-sensitive adhesive with better tackification effect. If the ratio is lower than this value, the excessive amount of dual-vinyl-terminated isocyanate will result in low initial peel strength, poor initial bonding effect, and reduced practical performance. If the ratio is higher than this value, the excessive amount of alkaline amine in the early stage will result in a softer adhesive, high initial peel strength, poor reworkability, and poor holding power leading to adhesive overflow, resulting in poor practical performance.

[0178] The comparative examples show that if the present invention does not contain dual-end vinyl-terminated isocyanate, the initial peel force is high, and rework is not possible; if it does not contain basic amine compounds, the initial peel force is too low, and normal bonding may not be possible; if the content of both dual-end vinyl-terminated isocyanate and basic amine compounds is low, the low degree of crosslinking in the early stage will lead to a high initial peel force, making rework difficult; if the content of both dual-end vinyl-terminated isocyanate and basic amine compounds is high, the crosslinking density will be too high, and the increase in small molecules of basic amine compounds will make the colloid softer, and the overall modulus will decrease, resulting in a high initial peel force. In actual use, too many small molecules will migrate and contaminate the bonded object.

[0179] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A heat-activated pressure sensitive adhesive, characterized in that, The hot tack pressure sensitive adhesive is composed of 100 parts by weight of an acrylate copolymer, 0.5-3 parts by weight of a di-vinyl terminated isocyanate, 0.5-12 parts by weight of a basic amine compound, 0.01-0.8 parts by weight of a second initiator, 0.1-1 parts by weight of a second catalyst, and 0-3 parts by weight of a crosslinking monomer; the di-vinyl terminated isocyanate is grafted onto the molecular chain of the acrylate copolymer through UV radical reaction. The preparation method of the di-vinyl terminated isocyanate is as follows: compound 1 is added into a reaction container, antioxidant and a first catalyst are added and uniformly mixed, inert gas is introduced, and compound 2 is added for reaction, so that the di-vinyl terminated isocyanate is prepared. The structure of the compound 1 is shown in the following formula (1) or formula (2), and the structure of the compound 2 is shown in the following formula (3): Formula (1), wherein n is an integer between 4 and 10; Formula (2), wherein p is an integer between 1 and 4; Formula (3), wherein R1is a hydrogen atom or a methyl group, and m is an integer between 1 and 4. The structure of the di-vinyl terminated isocyanate is one of the following formula (4), (5) and (6). Equation (4), Equation (5), Equation (6); The molar ratio of the compound 1 to the compound 2 is 1:

1.

2. The hot-tack pressure sensitive adhesive of claim 1 wherein, The content of the di-vinyl terminated isocyanate is 1-2.5 parts by weight, and the content of the basic amine compound is 2.5-6 parts by weight, relative to 100 parts by weight of the acrylate copolymer.

3. The hot-tack pressure sensitive adhesive of claim 1 or 2 wherein, The weight ratio of the basic amine compound to the di-vinyl terminated isocyanate is (1-4):

1.

4. The hot-tack pressure sensitive adhesive of claim 3 wherein, The weight ratio of the basic amine compound to the di-vinyl terminated isocyanate is (2-3):

1.

5. The hot-tack pressure sensitive adhesive of claim 1 wherein, The acrylate copolymer includes the following monomer components, taking the total amount of the monomers of the acrylate copolymer as 100 wt%: 5-15 wt% of a hard monomer and 85-95 wt% of a soft monomer. The hard monomer includes at least one of methyl (meth) acrylate, styrene, acrylic acid, vinyl acetate, ethyl methacrylate, isobutyl methacrylate, acrylonitrile, cyclohexyl methacrylate, and isobornyl methacrylate. The soft monomer includes at least one of butyl acrylate, isooctyl acrylate, ethyl acrylate, n-octyl acrylate, and lauryl (meth) acrylate.

6. The hot-tack pressure sensitive adhesive of claim 1 wherein, The basic amine compound includes at least one of dipropylamine and cyclohexylamine.

7. The hot-tack pressure sensitive adhesive of claim 1 wherein, The second initiator includes at least one of benzoin and its derivatives, benzoin derivatives, acetophenone derivatives, α-hydroxyalkyl phenone, α-amino ketone derivatives, and acyl phosphine oxide.

8. The hot-tack pressure sensitive adhesive of claim 1 wherein, The second catalyst includes at least one of dibutyl tin dilaurate and dibutyl tin diacetate.

9. The hot tack pressure sensitive adhesive according to claim 1, wherein the crosslinking monomer includes at least one of 1,6-hexanediol diacrylate and polyurethane acrylate.

Images