Solvent-type polyacrylate pressure-sensitive adhesive having high solid content, preparation method therefor, and use thereof

Abstract

A solvent-type polyacrylate pressure-sensitive adhesive having a high solid content, a preparation method therefor, and the use thereof. The pressure-sensitive adhesive contains an acrylic resin polymer, the acrylic resin polymer being formed by polymerizing monomers under the actions of an initiator and a chain transfer agent in an organic solvent, the solid content of the acrylic resin polymer being 60-75%, the mass-average molecular mass of the acrylic resin polymer being 0.2-0.4 million, and the polydispersity of same being 1-1.3. The pressure-sensitive adhesive keeps excellent mechanical properties in the case of the ultra-high solid content, 180° peeling strength being 10-20 N / 25 mm, tack being > 2# ball, and holding power being > 72 hours.

Description

High-solid content solvent-based polyacrylate pressure-sensitive adhesive and its preparation method and application

[0001] This application claims priority to Chinese patent application No. 2024102258238, filed on February 29, 2024. This application incorporates the entirety of the aforementioned Chinese patent application. Technical Field

[0002] The present invention relates to the technical field of acrylic ester pressure-sensitive adhesives, and in particular to a high-solid-content solvent-based polyacrylate pressure-sensitive adhesive and a preparation method and application thereof. Background Art

[0003] The manufacturing process of home appliances requires large quantities of foam tape, tissue paper tape, and PET tape for bonding plastic, glass, and metal components. This requires pressure-sensitive adhesives with excellent adhesion and aging resistance. Solvent-based acrylic pressure-sensitive adhesives offer water resistance, aging resistance, excellent wettability, and excellent adhesion to a variety of substrates. Furthermore, their readily available raw materials and wide range of molecular structure adjustments make them a key component of the pressure-sensitive adhesive market, widely used in the automotive, home appliance, electronics, and building materials industries.

[0004] However, as global environmental pollution becomes increasingly serious, there is an urgent need to reduce solvent emissions. To this end, increasing the solid content of solvent-based resins has become one of the research directions. After the solid content is increased, the amount of wet glue applied can be significantly reduced when applying the same dry adhesive film, thereby reducing costs and energy consumption. In addition, since the amount of wet glue applied is reduced, solvent emissions can be reduced. During the polymerization process of solvent-based polyacrylate pressure-sensitive adhesives, the viscosity increases sharply with increasing solid content. The increased viscosity makes mixing and heat transfer of the polymerization system a problem. Therefore, the synthesis of high-solid-content pressure-sensitive adhesives is relatively difficult. In addition, how to balance the peeling force and holding power of the pressure-sensitive adhesive in the case of high solid content is an urgent problem to be solved.

[0005] Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a high-solid-content solvent-based polyacrylate pressure-sensitive adhesive and a preparation method and application thereof.

[0007] The present invention is achieved through the following technical solutions:

[0008] A high-solid content solvent-based polyacrylate pressure-sensitive adhesive contains an acrylic resin polymer, which is prepared by polymerizing monomers in an organic solvent under the action of an initiator. The acrylic resin polymer has a solid content of 60-75%, a weight-average molecular weight of 200,000-400,000, and a polydispersity of 1-1.3.

[0009] Preferably, the solid content of the acrylic resin polymer is 63-70%, for example, the solid content is 63%, 65%, 67%, 68%, 69%, or 70%; the weight-average molecular weight of the acrylic resin polymer is 200,000-400,000, more preferably 250,000-350,000, more preferably 300,000-330,000, and the polydispersity is 1-1.2.

[0010] As a preferred technical solution of the present invention, the monomer is composed of a soft monomer, a hard monomer and a functional monomer. Based on 100 parts by weight of the total monomers, the soft monomer is 88-92 parts, the hard monomer is 4-6 parts, and the functional monomer is 4-6 parts.

[0011] And / or, the soft monomer includes one or more of butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and ethyl acrylate; preferably, the soft monomer is selected from a mixture of isooctyl acrylate and butyl acrylate, preferably, isooctyl acrylate and butyl acrylate are mixed in a weight ratio of 3.5:1-1;

[0012] And / or, the hard monomer includes one or more of methyl acrylate, methyl methacrylate, vinyl acetate, acrylonitrile, isobornyl acrylate, isobornyl methacrylate, and tetrahydrofuranyl methacrylate; preferably, the hard monomer is selected from one or more of methyl acrylate, methyl methacrylate, and vinyl acetate;

[0013] And / or, the functional monomer includes one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, acrylamide, N-hydroxymethyl acrylamide, and glycidyl methacrylate; preferably, the functional monomer is selected from one or more of hydroxyethyl acrylate, acrylic acid, and glycidyl methacrylate.

[0014] As a preferred technical solution of the present invention, the initiator includes one or both of dibenzoyl peroxide and azobisisobutyronitrile;

[0015] The amount of the initiator used is 0.1% to 0.4% of the total weight of the monomers, preferably 0.15% to 0.35%, and more preferably 0.2% to 0.3%.

[0016] As a preferred technical solution of the present invention, the organic solvent is a solvent that is miscible with the monomer, including one or more of toluene, ethyl acetate, acetone-n-hexane, methanol, and butanone. Preferably, the organic solvent is ethyl acetate;

[0017] The amount of the organic solvent used is 50% to 60% of the total weight of the monomers, preferably 54% to 58%.

[0018] As a preferred technical solution of the present invention, the chain transfer agent includes one or more of n-dodecyl mercaptan, 2,4-diphenyl-4-methyl-1-pentene (AMSD), and isooctyl mercaptopropionate. Preferably, the chain transfer agent is selected from n-dodecyl mercaptan;

[0019] The amount of the chain transfer agent used is 0.05% to 0.25% of the total weight of the monomers, preferably 0.12% to 0.20%.

[0020] A method for preparing a high-solid content solvent-based polyacrylate pressure-sensitive adhesive comprises the following steps:

[0021] (1) preparing a monomer mixture solution by uniformly mixing all monomers, a chain transfer agent, an initiator, and a solvent to prepare a monomer mixture solution for use;

[0022] (2) Prepare the bottom liquid of the kettle, take 5-20% of the total weight of the monomer mixture and add it to the reactor, then add solvent 2 and mix evenly, heat to 70-90°C, and start the reaction when reflux and foaming occur, and start the reaction for 5-20 minutes from the start of the reaction;

[0023] (3) adding the remaining monomer mixture dropwise over a period of 100 to 180 minutes and keeping the mixture warm for 1 to 2 hours;

[0024] (4) After the addition is completed, initiator 2 and solvent 3 are added, and the temperature is kept at 2 to 4 hours to obtain an acrylic resin polymer.

[0025] As a preferred technical solution of the present invention, in step (1), the chain transfer agent is 0.05% to 0.25% of the total weight of the monomers, preferably 0.1% to 0.2%; the initiator 1 is 0.15% to 0.35% of the total weight of the monomers; the solvent 1 is 1% to 3% of the total weight of the monomers, preferably 1.5% to 2.5%;

[0026] And / or, in step (2), 8-12% of the total weight of the monomer mixture is added to the reactor, and the second solvent is 45%-55% of the total weight of the monomers, preferably 48%-52%; in step (2), heating to 80-85°C, and starting the reaction time from the appearance of foam for 8-12 minutes;

[0027] and / or, in step (3), the remaining monomer mixture is dripped over 100 to 140 minutes;

[0028] And / or, in step (4), the second initiator is 0.08% to 0.12% of the total weight of the monomers, preferably 0.1%; the third solvent is 2% to 4% of the total weight of the monomers, preferably 3%.

[0029] As a preferred technical solution of the present invention, a tackifying resin is added to the acrylic resin polymer prepared in step (4) and stirred until completely dissolved.

[0030] Preferably, the amount of the tackifying resin added is 10-15% by weight of the acrylic resin polymer;

[0031] Preferably, the tackifying resin includes one or more of rosin resin, modified rosin resin, terpene resin, and modified terpene resin.

[0032] A high-solids solvent-based polyacrylate pressure-sensitive adhesive is used as an adhesive for plastics, glass, and metal. A crosslinker is added to the acrylic pressure-sensitive adhesive. Preferably, the crosslinker is added in an amount of 0.3-0.6% by weight of the acrylic pressure-sensitive adhesive. The adhesive tape produced from this pressure-sensitive adhesive exhibits a 180° peel strength of 10-20 N / 25 mm, an initial tack greater than that of a #2 ball, and a holding power greater than 72 hours.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention addresses the polymerization problem of high-solid content solvent-based polyacrylate pressure-sensitive adhesives. By adopting a semi-continuous polymerization method and controlling the formula of the monomer mixture and the kettle bottom liquid, a solvent-based acrylic resin with ultra-high solid content (over 65%) is successfully prepared. The peel force, initial adhesion and holding force of the pressure-sensitive adhesive are well balanced. By compounding a tackifying resin and a cross-linking agent, the resin has excellent application performance.

[0035] On the one hand, the present invention controls the formula of the monomer mixture, and adds appropriate amounts of solvent, initiator and chain transfer agent to the monomer components composed of soft monomers, hard monomers and functional monomers, wherein the solvent plays a dissolving role and can help the monomers to dissolve well with the initiator and chain transfer agent, but too little solvent cannot achieve an effective dissolution and mixing effect, and too much solvent reduces the concentration ratio of the initiator and the chain transfer agent, which is not conducive to the polymerization; the initiator is used to initiate the polymerization reaction, and an appropriate amount of initiator can ensure the progress of the polymerization reaction. Too much initiator leads to too fast a polymerization speed, and too little initiator leads to too slow a polymerization speed, affecting the colloid properties; the chain transfer agent plays a role in regulating the molecular weight of the polymer, and can react with the active center on the polymer chain to change the molecular weight distribution of the polymer. Too much chain transfer agent leads to too low a molecular weight of the polymer, and too little chain transfer agent may lead to too high a molecular weight of the polymer.

[0036] On the other hand, the present invention controls the amount of solvent added to the kettle bottom liquid and the amount of the initially added monomer mixture to carry out a suitable polymerization reaction. To prepare a high-solid polyacrylic acid resin, the amount of solvent added to the kettle bottom liquid is controlled to account for 45% to 55% of the total weight of the monomers, and the initially added monomer mixture is controlled to account for 8% to 12% of the total weight. At the initial stage of the reaction, the monomer concentration in the kettle bottom material is low. A lower initial reaction monomer concentration ratio means a lower molecular weight, which is beneficial to the subsequent dropwise polymerization reaction. By slowly dropwise adding the remaining monomer mixture to carry out the polymerization reaction, mixing and heat transfer problems caused by the rapid increase in viscosity are alleviated, thereby ensuring the smooth progress of the polymerization process.

[0037] 2. The present invention has discovered that the key to high-solids solvent-based polyacrylate pressure-sensitive adhesives is to control the molecular weight of the acrylic resin polymer. Specifically, an acrylic resin polymer with an appropriate molecular weight can balance the various properties of a high-solids polyacrylate pressure-sensitive adhesive. While meeting the high solids requirement, if the molecular weight of the acrylic resin polymer is too low, such as when the weight-average molecular weight of the acrylic resin is less than 200,000, the product's viscosity is low, but the polymer's cohesion is insufficient, resulting in a large amount of adhesive residue during application and substandard 180° peel strength. If the molecular weight of the acrylic resin polymer is too high, such as when the weight-average molecular weight of the acrylic resin is greater than 400,000, the product's viscosity increases significantly, polymerization becomes more difficult, and the prepared product becomes unusable. Therefore, the present invention controls the amount of solvent, initiator, and chain transfer agent used, and through process control, achieves a weight-average molecular weight of 200,000 to 400,000, preferably 250,000 to 350,000, so that the mechanical properties of the resulting pressure-sensitive adhesive meet application requirements.

[0038] 3. A crosslinker is added to the acrylic pressure-sensitive adhesive of this invention to improve cohesive energy, temperature resistance, and adhesive stability. Adhesive tapes made with this pressure-sensitive adhesive exhibit good adhesion to steel, glass, copper foil, polyester film, and PC boards, with excellent holding power, including a 180° peel force of 10-20 N / 25 mm, an initial tack greater than that of a #2 ball, and a holding power greater than 72 hours. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0040] The specific raw material composition of the embodiment is shown in Table 1.

[0041] Table 1 Example raw material composition (unit g)

[0042] The high solid content solvent-based polyacrylate pressure-sensitive adhesive is prepared by the following method:

[0043] Step 1: Prepare the materials according to the recipe and mix all monomers, solvent, chain transfer agent, and initiator to obtain a monomer mixture. Take a small portion of the monomer mixture and add it to a reaction flask. Add the solvent to the reaction flask and gradually heat it to 80-85°C while stirring. Observe the reaction system and start the reaction from the appearance of foam. The reaction time is 5-20 minutes.

[0044] Step 2: Add the remaining mixture dropwise over 100-180 minutes and keep warm for 2-4 hours;

[0045] Step 3: After the dropwise addition is completed, the initiator and solvent are added and the temperature is kept at 2 to 4 hours to obtain an acrylic resin polymer;

[0046] Step 4: After cooling, add an appropriate amount of tackifying resin, stir until the tackifying resin is completely dissolved in the above polymer solution, and cool and discharge.

[0047] Taking Example 1 as an example, a high solid content solvent-based polyacrylate pressure-sensitive adhesive was prepared by the following method:

[0048] (1) Weigh 45g of isooctyl acrylate, 45g of butyl acrylate, 5g of vinyl acetate, 1g of hydroxyethyl acrylate, 4g of acrylic acid, 2g of ethyl acetate, 0.15g of n-dodecyl mercaptan, and 0.04g of azobisisobutyronitrile and mix them evenly to prepare a monomer mixture; take 10g of the monomer mixture and add it to a reaction flask, weigh 50g of ethyl acetate and put it into the reaction flask, gradually heat it to 80-85°C under stirring conditions, observe the reaction system, start timing from the appearance of foam, and react for 10 minutes; (2) add the remaining mixture dropwise, add it over 120 minutes, and keep it warm for 2 hours; (3) take 0.25g of azobisisobutyronitrile and 3g of ethyl acetate, mix them evenly, add them to the reaction flask, and keep it warm for 3 hours; (4) cool, add 10g of rosin resin GA100 and 10g of terpene resin 803L, stir until the tackifying resin is completely dissolved in the above polymer solution, cool and discharge.

[0049] The preparation methods of the remaining embodiments are roughly the same as those of Example 1.

[0050] The specific raw material composition of the comparative example is shown in Table 2.

[0051] Table 2 Comparative Example Raw Material Composition (Unit: g)

[0052] The preparation method of the comparative example is roughly the same as that of Example 1.

[0053]

Product performance effect test

[0054] The pressure-sensitive adhesives prepared in the above examples and comparative examples were tested:

[0055] Solid content: refer to GB / T 20623-2006;

[0056] Weight average molecular weight: refer to SH / T1759-2007

[0057] Viscosity: Brookfield LV rotor 4#, 60 r / min, 25°C;

[0058] The pressure-sensitive adhesive liquid was prepared into a tape sample, and the 180° peel strength, initial tack and holding force were tested. The 180° peel strength test was based on GB / T2792-1998; the initial tack test was based on GB / T 4852-2002; and the holding force test was based on GB4851-1998. The specific method was as follows: 100 g of the adhesive liquid prepared in the above embodiment and comparative example were respectively weighed, 0.2 g of epoxy crosslinking agent GA240 was added, 30 g of ethyl acetate was added to dilute, the mixture was stirred evenly, and the mixture was coated on a 25 μm transparent polyester film. The film was placed in an oven at 110°C for 3 minutes, the film was taken out, the thickness of the dry adhesive layer was controlled to 25 μm, and the film was placed at 50°C for post-curing for 2 days to obtain a tape sample with stable performance.

[0059] The specific test results are shown in Table 3.

[0060] Table 3 Test results of physical properties and application performance of pressure-sensitive adhesive

[0061] As shown in Table 3, the pressure-sensitive adhesive of the embodiment of the present invention has an ultra-high solid content, low viscosity, and is easy to apply. At the same time, the peeling force, initial adhesion, and holding power remain good. Comparative Examples 1 and 2 increase the amount of chain transfer agent and initiator compared to Example 1. As a result, the molecular weight of the acrylic polymer prepared is too small, and residual glue appears during the 180° peeling force test. The pressure-sensitive adhesive has insufficient cohesive force and is difficult to meet application requirements. Comparative Examples 3 and 4 increase the amount of initiator 1 compared to Examples 1 and 3. The polymerization process releases a large amount of heat, which is difficult to control. The polymer molecular weight is on the low side, and the pressure-sensitive adhesive has poor cohesive energy. There is local residual glue on the steel plate surface during the 180° peeling force test, and the holding power is less than 72 hours. Comparative Examples 5 and 6 reduce the chain transfer amount compared to the embodiment, and increase the amount of solvent. The prepared acrylate polymerization molecular weight is too large, and the viscosity of the pressure-sensitive adhesive surges and cannot be used.

[0062] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A high solid content solvent-based polyacrylate pressure-sensitive adhesive containing an acrylic resin polymer, characterized in that: The acrylic resin polymer is prepared by polymerizing monomers in an organic solvent under the action of an initiator and a chain transfer agent. The solid content of the acrylic resin polymer is 60-75%, the weight average molecular weight of the acrylic resin polymer is 200,000-400,000, and the polydispersity is 1-1.

3.

2. The high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: The solid content of the acrylic resin polymer is 63-70%, and the weight average molecular weight of the acrylic resin polymer is 250,000-350,000.

3. The high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: The monomers are composed of soft monomers, hard monomers and functional monomers. Based on 100 parts by weight of the total monomers, the soft monomers are 88-92 parts, the hard monomers are 4-6 parts, and the functional monomers are 4-6 parts. And / or, the soft monomer includes one or more of butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and ethyl acrylate; preferably, the soft monomer is selected from a mixture of isooctyl acrylate and butyl acrylate; And / or, the hard monomer includes one or more of methyl acrylate, methyl methacrylate, vinyl acetate, acrylonitrile, isobornyl acrylate, isobornyl methacrylate, and tetrahydrofuranyl methacrylate; preferably, the hard monomer is selected from one or more of methyl acrylate, methyl methacrylate, and vinyl acetate; And / or, the functional monomers include one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, acrylamide, N-hydroxymethyl acrylamide, and glycidyl methacrylate; preferably, the functional monomers include one or more of The monomer is selected from one or more of hydroxyethyl acrylate, acrylic acid, and glycidyl methacrylate.

4. The high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: The initiator includes one or two of dibenzoyl peroxide and azobisisobutyronitrile; The amount of the initiator used is 0.1% to 0.4% of the total weight of the monomers.

5. The high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: The organic solvent is a solvent that is miscible with the monomer, including one or more of toluene, ethyl acetate, acetone-n-hexane, methanol, and butanone. Preferably, the organic solvent is ethyl acetate. The amount of the organic solvent used is 50% to 60% of the total weight of the monomers, preferably 54% to 58%.

6. The high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: The chain transfer agent includes one or more of n-dodecyl mercaptan, 2,4-diphenyl-4-methyl-1-pentene, and isooctyl mercaptopropionate. Preferably, the chain transfer agent is selected from n-dodecyl mercaptan; The amount of the chain transfer agent used is 0.05% to 0.25% of the total weight of the monomers, preferably 0.12% to 0.20%.

7. The method for preparing a high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, wherein: The following steps are involved: (1) preparing a monomer mixture solution by uniformly mixing all monomers, a chain transfer agent, an initiator, and a solvent to prepare a monomer mixture solution for use; (2) Prepare the bottom liquid of the kettle, take 5-20% of the total weight of the monomer mixture and add it to the reactor, then add solvent 2 and mix evenly, heat to 70-90°C, and start the reaction when reflux and foaming occur, and start the reaction for 5-20 minutes from the start of the reaction; (3) adding the remaining monomer mixture dropwise over a period of 100 to 180 minutes and keeping the mixture warm for 1 to 2 hours; (4) After the addition is completed, initiator 2 and solvent 3 are added, and the temperature is kept at 2 to 4 hours to obtain an acrylic resin polymer.

8. The method for preparing a high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 7, characterized in that: These include: In step (1), the chain transfer agent is 0.05% to 0.25% of the total weight of the monomers, the initiator 1 is 0.15% to 0.35% of the total weight of the monomers; the solvent 1 is 1% to 3% of the total weight of the monomers, preferably 1.5% to 2.5%; And / or, in step (2), 8-12% of the total weight of the monomer mixture is added to the reactor, and the second solvent is 45%-55% of the total weight of the monomers, preferably 48%-52%; in step (2), heating to 80-85°C, and starting the reaction time from the appearance of foam for 8-12 minutes; and / or, in step (3), the remaining monomer mixture is dripped over 100 to 140 minutes; And / or, in step (4), the second initiator is 0.08% to 0.12% of the total weight of the monomers, preferably 0.1%; the third solvent is 2% to 4% of the total weight of the monomers, preferably 3%.

9. The method for preparing a high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 8, characterized in that: Add tackifying resin to the acrylic resin polymer prepared in step (4) and stir until completely dissolved. Preferably, the amount of the tackifying resin added is 10-15% by weight of the acrylic resin polymer; Preferably, the tackifying resin includes one or more of rosin resin, modified rosin resin, terpene resin, and modified terpene resin.

10. The use of a high solid content solvent-based polyacrylate pressure-sensitive adhesive according to claim 1, characterized in that: This pressure-sensitive adhesive is used as an adhesive for plastic, glass, and metal.

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