A low-temperature polyacrylate pressure-sensitive adhesive composition, its preparation method and application

Abstract

The present invention discloses a low-temperature polyacrylate pressure-sensitive adhesive composition, its preparation method and application. The low-temperature polyacrylate pressure-sensitive adhesive composition includes a polyacrylate polymer and a reactive plasticizer; the polyacrylate polymer has a first side chain, and the end group contains an isocyanate group; the reactive plasticizer has a second side chain, and the end group contains a hydroxyl group; the isocyanate group and the hydroxyl group are connected by a nucleophilic addition reaction. In the present invention, a reactive plasticizer with an extremely low Tg is grafted onto the main chain, effectively reducing the Tg of the entire system, thereby greatly improving its low-temperature performance; at the same time, the addition of the reactive plasticizer also effectively improves the peel strength of the polyacrylate pressure-sensitive adhesive. In addition, since the reactive plasticizer is chemically grafted onto the polyacrylate main chain, the so-called "plasticizer migration problem" will not occur even after long-term aging, thus achieving a balanced effect of excellent low-temperature adhesion performance and aging resistance performance.

Description

Technical Field

[0001] The present invention relates to a low-temperature polyacrylate pressure-sensitive adhesive composition, a preparation method and an application thereof, and belongs to the technical field of polymer materials. Background Art

[0002] The description in this part only provides background information related to the disclosure of the present invention, and does not directly constitute the prior art.

[0003] Compared with pressure-sensitive adhesives of other materials (such as rubber type, silicone, polyurethane, etc.), polyacrylate pressure-sensitive adhesives have many unique properties, such as excellent aging resistance (especially ultraviolet light aging resistance), excellent optical transparency, and moderate price, and are widely used in transportation, electronics, household appliances, and construction markets.

[0004] Commonly used polyacrylate pressure-sensitive adhesives are usually randomly copolymerized from soft monomers such as isooctyl acrylate (IOA) or 2-ethylhexyl acrylate (2-EHA), hard monomers such as isobornyl acrylate (IBOA), methyl methacrylate (MMA), and functional monomers such as acrylic acid (AA), methacrylic acid (MAA), and 2-hydroxyethyl acrylate (2-HEA). Such pressure-sensitive adhesives have relatively ideal peel strength and shear strength for most bonding surfaces.

[0005] The addition of hard monomers can improve the cohesion of polyacrylate pressure-sensitive adhesives, thereby increasing the peel force. However, it also increases the glass transition temperature (Tg) of polyacrylates, resulting in poor adhesion at low temperatures and even loss of tack. Although pure polyacrylate pressure-sensitive adhesives have tack and certain peel force and holding power, the peel force is not sufficient in many application scenarios. Generally, the method of adding tackifying resins is used to increase the peel force. However, the Tg of tackifying resins is generally relatively high, which causes the Tg of the entire system to increase, resulting in worse low-temperature performance of polyacrylate pressure-sensitive adhesives containing tackifying resins.

[0006] The method to improve the low-temperature performance of polyacrylate pressure-sensitive adhesives is generally to add plasticizers (for example, the technical solution disclosed in US Patent No. US6054213). Plasticizers generally have a lower Tg. The addition of plasticizers reduces the Tg of the entire system, thereby improving the low-temperature performance of the pressure-sensitive adhesive. However, plasticizers generally have poor compatibility with acrylates, and the problem of "plasticizer migration" will occur over time, which will not only affect the mechanical properties of the pressure-sensitive adhesive, but also cause the low-temperature performance of the pressure-sensitive adhesive to deteriorate.

[0007] To solve the above problems, the Chinese invention patent CN108587527A adopts a technical solution of preparing a polymer by mixing a C8-C10 branched acrylic monomer (methacrylic monomer), a functional monomer, an initiator, and a solvent in a certain proportion and placing them in a water bath container at a specific temperature for complete reaction. The prepared pressure-sensitive adhesive has good initial adhesiveness in a low-temperature environment. In the environment of -20°C to 60°C, its adhesive force can be well maintained. Compared with traditional acrylic pressure-sensitive adhesives, the operability of the tape in a low-temperature environment is significantly improved. However, the Tg of the C8-C10 branched acrylic monomer is still not low enough, and the low-temperature performance of the polyacrylate copolymerized therefrom still needs to be improved.

[0008] Therefore, it is necessary to develop a polyacrylate pressure-sensitive adhesive with better low-temperature performance and aging resistance to expand its application scenarios, such as applying films outdoors in the north in winter, label materials for blood bags or vaccine outer packages that need to be stored at low temperatures, etc.

[0009] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solution of the present invention and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art just because these solutions are described in the background art part of the present invention. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a low-temperature polyacrylate pressure-sensitive adhesive composition, its preparation method and application, and solve the technical problem that the existing acrylic pressure-sensitive adhesives cannot have both better low-temperature bonding performance and aging resistance.

[0011] To solve the above technical problems, the first aspect of the present invention provides a low-temperature polyacrylate pressure-sensitive adhesive composition, which includes: an acrylate polymer and a reactive plasticizer; the acrylate polymer has a first side chain, and the end group of the first side chain contains an isocyanate group; the reactive plasticizer has a second side chain, and the end group of the second side chain contains a hydroxyl group; in the composition, the isocyanate group and the hydroxyl group are connected to the reactive plasticizer and the acrylate polymer through a nucleophilic addition reaction.

[0012] Further, the monomer of the acrylate polymer is an acrylate monomer or a methacrylate monomer.

[0013] Further, the acrylate polymer is at least copolymerized from a first monomer and a second monomer; the first monomer is selected from acrylate alkyl ester monomers in which the number of alkyl carbon atoms connected to the ester group is 1 to 12.

[0014] The second monomer is selected from acrylate monomers having an isocyanate group at the end of a group linked to an ester group.

[0015] Further, the first monomer includes any one or a combination of two or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, where the methyl group is optional.

[0016] Further, the second monomer includes any one or a combination of two of ethyl 2-isocyanatoacrylate and isocyanatoethyl methacrylate.

[0017] Further, in the total mass of the monomers, the mass fraction of the first monomer is 75-97%; the mass fraction of the second monomer is 3-25%.

[0018] Further, the hydroxyl groups in the reactive plasticizer are stoichiometric or sub-stoichiometric with the isocyanate groups in the acrylate polymer.

[0019] Further, the viscosity of the low-temperature acrylate pressure-sensitive adhesive composition is 200-50000 cPs.

[0020] The second aspect of the present invention provides a method for preparing a low-temperature acrylate pressure-sensitive adhesive composition, which includes the following steps:

[0021] Provide an acrylate polymer and a reactive plasticizer. The acrylate polymer has a first side chain, and the end group of the first side chain contains an isocyanate group. The reactive plasticizer has a second side chain, and the end group of the second side chain contains a hydroxyl group.

[0022] Mix the acrylate polymer and the reactive plasticizer to form a reaction system, and cause the isocyanate group and the hydroxyl group to undergo a nucleophilic addition reaction to connect the acrylate polymer and the reactive plasticizer, thereby obtaining a low-temperature acrylate pressure-sensitive adhesive composition.

[0023] Further, the synthesis method of the reactive plasticizer includes:

[0024] Provide an initial plasticizer and a polyol. The molecular chain of the initial plasticizer contains a double bond, and the polyol contains a mercapto group.

[0025] Cause the mercapto group and the double bond to undergo an addition reaction under the action of an initiator to synthesize the reactive plasticizer.

[0026] Further, the polyol is selected from mercapto glycerol.

[0027] Further, the end condition of the nucleophilic addition reaction is that free isocyanate groups are not detected in the reaction system.

[0028] The third aspect of the present invention also provides an application of the above-mentioned low-temperature polyacrylate pressure-sensitive adhesive composition in the preparation of pressure-sensitive tapes.

[0029] By means of the above technical solutions, the beneficial effects of the present invention at least include:

[0030] The pressure-sensitive adhesive composition and its preparation method provided by the present invention graft and introduce a reactive plasticizer with an extremely low Tg on the main chain of the polyacrylate, effectively reducing the Tg of the entire system, thereby greatly improving its low-temperature performance; at the same time, the addition of the reactive plasticizer also effectively improves the peel strength of the polyacrylate pressure-sensitive adhesive. In addition, since the reactive plasticizer is chemically grafted onto the main chain of the polyacrylate, even after long-term aging, there will be no so-called "plasticizer migration problem", thus achieving a balanced effect of excellent low-temperature adhesion performance and aging resistance. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects, and there is no sequence between them, nor can they be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0033] A low-temperature polyacrylate pressure-sensitive adhesive composition according to a preferred embodiment of the present specification, which includes: an acrylate polymer and a reactive plasticizer; the acrylate polymer has a first side chain, and the end group of the first side chain contains an isocyanate group; the reactive plasticizer has a second side chain, and the end group of the second side chain contains a hydroxyl group; in the composition, the isocyanate group and the hydroxyl group are connected to the reactive plasticizer and the acrylate polymer through a nucleophilic addition reaction.

[0034] Corresponding to the above composition, its preparation method includes the following steps:

[0035] Provided are an acrylate polymer and a reactive plasticizer. The acrylate polymer has a first side chain, and the end group of the first side chain contains an isocyanate group. The reactive plasticizer has a second side chain, and the end group of the second side chain contains a hydroxyl group.

[0036] Mix the acrylate polymer and the reactive plasticizer to form a reaction system, and cause the isocyanate group and the hydroxyl group to undergo a nucleophilic addition reaction to connect the acrylate polymer and the reactive plasticizer, thereby obtaining a low-temperature acrylate pressure-sensitive adhesive composition.

[0037] Furthermore, the embodiments of the present invention also exemplify the specific application of the above-mentioned pressure-sensitive adhesive composition in the preparation of pressure-sensitive tapes.

[0038] Using the technical solution exemplified in the embodiments of the present invention, a polyacrylate pressure-sensitive adhesive composition grafted with a reactive plasticizer can be produced. It can not only improve the peel strength of the polyacrylate pressure-sensitive adhesive, but also maintain good high-temperature holding power; at the same time, significantly improve its low-temperature properties. When the polyacrylate pressure-sensitive adhesive composition grafted with the reactive plasticizer mentioned in the present invention is applied, it can usually be coated on a substrate (PET film, PP film, PE film, PVC film, paper, non-woven fabric, etc.) in a liquid form (which may contain a solvent), and then through the processes of oven heating, drying, and curing, different types of pressure-sensitive adhesive tape products are prepared.

[0039] In a more specific preferred embodiment, the polyacrylate pressure-sensitive adhesive composition grafted with the reactive plasticizer mentioned in the present invention is composed of the following several components: a poly(meth)acrylate containing an isocyanate functional group as component (A), and a reactive plasticizer containing a hydroxyl functional group as component (B). Among the ranges of various acrylate polymers, the inventors have found that methacrylate polymers have achieved better comprehensive effects compared to other polymers such as polyacrylate and polyethyl acrylate. Specific examples can be seen in the following examples; it should be noted that the percentages mentioned in the present invention are weight percentages unless otherwise specified.

[0040] In a more preferred embodiment, the poly(meth)acrylate containing an isocyanate functional group as component (A) contains the following monomer components (formed by copolymerization of the following monomers):

[0041] (a1) A (meth)acrylate monomer with an alkyl group having 1 to 12 carbon atoms

[0042] (a2) A (meth)acrylate monomer containing an isocyanate functional group

[0043] In one embodiment of the present invention, the (meth)acrylic acid alkyl esters in component (a1) may include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc., and include their possible isomeric forms. Further preferably, the (meth)acrylic acid alkyl ester in component (a1) is selected from any one or a mixture of two or more of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and tert-butyl (meth)acrylate. More preferably, the (meth)acrylic acid alkyl ester in component (a1) is selected from butyl (meth)acrylate, methyl (meth)acrylate, isooctyl (meth)acrylate or a mixture of two or more of them. Herein, the methyl in the parentheses represents whether it can be optionally methyl acrylate or acrylate.

[0044] In one embodiment of the present invention, the selection of component (a2) is preferably ethyl 2-isocyanatoacrylate (CAS No. 13641-96-8) or isocyanatoethyl methacrylate (CAS No. 30674-80-7) monomer, or a mixed monomer of the two.

[0045] Regarding the optimal ratio of the monomers of the present invention, in some preferred cases, the amount of monomer (a1) is 75-97% by weight, preferably 85-95% by weight, and the above weight fractions are based on the total weight of all the monomers used (i.e., the one or more monomers, which may also contain monomers other than a1 and a2).

[0046] Meanwhile, based on the total weight of all the monomers used (i.e., the one or more monomers), the amount of monomer (a2) is usually 3-25% by weight, preferably 5-15% by weight. This is because, in long-term practice, the inventors found that monomer (a2) with an amount within this range is beneficial to the low-temperature resistance and adhesion of the pressure-sensitive adhesive. Since the isocyanate group mainly originates from monomer (a2), its amount significantly affects the density of the isocyanate side-chain end groups on the main chain, and this density is decisive for the density of the reactive plasticizer in combination. If the reactive plasticizer is too dense, it may lead to a decrease in the flexibility of the molecular chain, and if it is too sparse, it will lead to poor low-temperature performance. Therefore, controlling the reasonable ratio of monomer (a2) is a crucial factor for achieving the technical effects of the present invention.

[0047] In some very specific application examples, the molecular structure of an acrylate polymer is shown, for example, by the following formula a

[0048]

[0049] Wherein R1 is an H atom or a methyl group; R2 is a monomer or a mixture of (meth)acrylates with 1 to 12 carbon atoms in the alkyl group; m and n are determined according to the mass ratio of the above monomers and the final required viscosity of the adhesive solution, for example, by controlling the polymerization time to adjust the molecular weight.

[0050] On the other hand, as the reactive plasticizer of component (B), its molecular structural formula and a specific exemplary preparation reaction equation are shown in the following formula b, and it contains a hydroxyl functional group that can react with the isocyanate functional group in (A). The reactive plasticizer containing a hydroxyl functional group can react with the isocyanate functional group in (A) and graft copolymerize into the main chain of the acrylate copolymer, which can play the role of "internal plasticization". On the one hand, it can effectively reduce the Tg of the polyacrylate, so that the pressure-sensitive adhesive can be used at a lower temperature; on the other hand, this reactive plasticizer is not prone to the problem of "plasticizer migration" during long-term use (or after aging). The content of the reactive plasticizer as component (B) in the pressure-sensitive adhesive composition should be consistent with the molar number of the isocyanate-containing monomer in component (A). When it cannot be completely controlled to be consistent, it should be reduced. For example, the reactive plasticizer is controlled between 90-95% of the stoichiometry corresponding to the isocyanate group. This is because if the content of the reactive plasticizer is too high, "free" plasticizer components will be formed, resulting in potential "plasticizer migration" problems, thus affecting the long-term aging performance of the pressure-sensitive adhesive.

[0051]

[0052] And the viscosity of the pressure-sensitive adhesive composition of the present invention grafted with the reactive plasticizer prepared by the above method before coating should be controlled between 200 and 50,000 cPs, and a more preferable viscosity should be between 1500 and 16,000 cPs. Too high or too low viscosity is not conducive to the coating of the pressure-sensitive adhesive composition.

[0053] Regarding the specific application, the embodiment of the present invention exemplifies the preparation of a pressure-sensitive tape. The above-mentioned pressure-sensitive adhesive composition of the present invention grafted with the reactive plasticizer can be coated on a substrate in a liquid form by a traditional coating method, and then through a drying and curing process, so as to form a glue film with the required thickness, and then combined into a tape.

[0054] In practice, it is usually possible to adopt the method of a continuous coating and drying production line. The reference implementation conditions are, for example, that the temperature setting of the oven and the line speed can be set with reference to the following parameters:

[0055] Zone1: 40°C, length 8m; Zone2: 70°C, length 8m; Zone3: 90°C, length 8m; Zone4: 110°C, length 8m; The linear velocity of the substrate in the oven is 15 m / min, where Zone represents a temperature zone of the oven.

[0056] The above is a general example of an exemplary solution of the present invention. The following will fully demonstrate the present invention through very specific embodiments. It should be noted that the following embodiments are representative and preferred cases among many feasible implementation cases of the present invention, rather than all cases. The scope of implementation of the present invention is not limited to the scope shown in the following specific embodiments.

[0057] Furthermore, the raw material information to be used in the embodiments is shown in Table 1 below. In addition, unless otherwise specified, other reagents, equipment, and process means used in the following embodiments are all conventional commercially available or common means in the art; the reaction conditions adopted in the following embodiments are conventional reaction conditions in the fields of polymerization or organic synthesis, such as temperature and other parameters. In specific implementation, as long as the corresponding product can be reacted to generate, it is not limited to the specific parameter values shown in the following examples.

[0058] Table 1 Reagent information used in the embodiments of the present invention

[0059]

[0060] Example 1

[0061] This example illustrates the preparation process of an acrylate polymer (Component A), which is specifically as follows:

[0062] Add 2-EHA, Karenz AOI, ethyl acetate, and the free radical thermal initiator Vazo TM 64 according to the composition in Table 2 into a 5-liter flask equipped with nitrogen and a water bath heating and reflux device. Under stirring, react at 60°C for 24 hours and then stop the reaction. After cooling, a transparent viscous liquid is obtained, which is a poly(meth)acrylate (A) containing isocyanate functional groups. This substance can be directly used in subsequent reactions without any treatment.

[0063] By changing different ratios, polymers with various different monomer ratios are obtained, and their specific ratios are shown in Table 2 below.

[0064] Table 2 Different ratios in Example 1

[0065] <![CDATA 2-EHA > <![CDATA Karenz AOI > <![CDATA Ethyl acetate > <![CDATA Vazo TM 64 <!-- 6 -->]]> <![CDATA A1 > <![CDATA 97 > <![CDATA 3 > <![CDATA 150 > <![CDATA 0.2 > <![CDATA A2 > <![CDATA 94 > <![CDATA 5 > <![CDATA 150 > <![CDATA 0.2 > <![CDATA A3 > <![CDATA 85 > <![CDATA 15 > <![CDATA 150 > <![CDATA 0.2 > <![CDATA A4 > <![CDATA 75 > <![CDATA 25 > <![CDATA 150 > <![CDATA 0.2 >

[0066] Example 2

[0067] This example illustrates the preparation process of a reactive plasticizer (Component B), which is specifically as follows:

[0068] Into a 1 L three-necked round-bottom flask filled with nitrogen, add 250 g of toluene, 200 g RP-1020, 43.26 g of 1-mercapto glycerol, and 3.75 g of photoinitiator Irgacure 651. Start the stirring device until the system becomes a clear and transparent solution. Under stirring, turn on the UV LED (385 nm) lamp and irradiate for 6 minutes, then stop the UV light irradiation. After cooling, a translucent milky viscous solution is obtained, which is the toluene solution of the reactive plasticizer (B) containing hydroxyl functional groups.

[0069] Transfer the above clear and transparent solution to a rotary evaporator, and remove the toluene solvent under reduced pressure at 70 °C to obtain about 243.26 g of a clear and transparent viscous liquid, which is the reactive plasticizer (B) containing hydroxyl functional groups.

[0070] Examples 3 - 6

[0071] This example demonstrates the preparation process of a low-temperature polyacrylate pressure-sensitive adhesive composition, which is specifically as follows:

[0072] Add the poly(meth)acrylate (A) containing isocyanate functional groups to a 1 L three-necked round-bottom flask equipped with a water bath heater, filled with nitrogen, and having a reflux device according to the measurement in Table 3, and start the stirring device. Gradually heat up to 70 °C. Weigh the reactive plasticizer (B) containing hydroxyl functional groups into a dropping funnel, and control the dropping rate to complete the dropping in about 1 hour. After the dropping is completed, maintain at 70 °C and continue to react for 3 - 5 hours until the absorption peak of the isocyanate functional group cannot be detected by infrared spectroscopy, then stop the reaction.

[0073] Prepare using various polymers in Example 1 and the reactive plasticizer provided in Example 2, and the ratios are as shown in Samples 2, 4, 6, and 8 in Table 3 below.

[0074] Comparative Examples 1 - 4

[0075] This comparative example demonstrates a set of blank control examples, which are generally the same as Examples 3 - 6 above, except that the reactive plasticizer (B) is not added, and it is heated at the same temperature for the same time.

[0076] The ratios are as shown in Samples 1, 3, 5, and 7 in Table 3 below.

[0077] Table 3 Raw material ratios of corresponding samples in examples and comparative examples

[0078] A1 A2 A3 A4 B Sample 1 250 Sample 2 250 12.93 Sample 3 250 Sample 4 250 21.55 Sample 5 250 Sample 6 250 64.65 Sample 7 250 Sample 8 250 107.75

[0079] Test Example 1

[0080] This test example presents the low-temperature and aging resistance tests and test results of the pressure-sensitive adhesive compositions provided in the above Examples 3-6 and Comparative Examples 1-4, as follows:

[0081] The test items involved in this test example include:

[0082] 1. 180-degree peel strength (room temperature)

[0083] The test method for 180-degree peel strength is carried out according to the national standard (GB 2792-81).

[0084] Cut the tape into strips 1 inch (2.54 cm) wide and longer than 200 mm. Gently attach them to a standard stainless-steel test plate (meeting the requirements of GB / T 3280-1992). Roll a 2.04 kg hard-rubber roller over the specimen at a speed of about 300 mm / min. Note that when rolling, only the force generated by the mass of the roller should be applied to the specimen, and roll back and forth three times. Place it in an environment controlled at a constant temperature of 23°C ± 2°C and a constant humidity of 50% RH ± 5% RH for 72 hours. Use a standard tensile machine (meeting the requirements of JB706-77 for testing machines) to test the peel force at a speed of 12 inches / minute (303 mm / min). Test each sample three times and take the average value, with the unit of N / mm.

[0085] 2. 180-degree peel strength (low temperature -5°C)

[0086] The sample preparation method is the same as above, except that the preparation and placement of the tape samples need to be carried out in a low-temperature environment of -5°C.

[0087] 3. High-temperature static shear strength (adhesion retention)

[0088] The test method for high-temperature static shear strength (adhesion retention) is carried out according to the national standard (GB / T4851).

[0089] Cut the tape into strips 1 inch (2.54 cm) wide and about 100 mm long. Paste the strips parallel to the longitudinal direction of the plate in the middle of two adjacent standard stainless-steel test plates (meeting the requirements of GB / T 3280-1992) to ensure that the bonding area is 1 square inch. Roll a 2.04 kg hard-rubber roller over the specimen at a speed of about 300 mm / min. Note that when rolling, only the force generated by the mass of the roller should be applied to the specimen, and roll back and forth three times. Place it in an environment controlled at a constant temperature of 23°C ± 2°C and a constant humidity of 50% RH ± 5% RH for 72 hours. Then vertically fix the test plate on the test rack, and gently connect the loading plate and a 1 kg weight with a pin. Place the entire test rack in a test chamber adjusted to 70°C. Record the time when the specimen detaches from the test plate. Test each sample three times and take the average value, with the unit of minutes.

[0090] 4. Evaluation of Mechanical Properties after Aging

[0091] The tape samples were aged at 85°C / 85% relative humidity for 10 days. After being placed in an environment controlled at a constant temperature of 23°C ± 2°C and a constant humidity of 50% RH ± 5% RH for 72 hours, the first three mechanical properties were evaluated to observe the changes in mechanical properties after aging.

[0092] After conducting the above test items, the measured test results are listed in Table 4 below:

[0093] Table 4 Test Results of the Pressure-Sensitive Adhesive Properties of Examples and Comparative Examples

[0094]

[0095]

[0096] In the table, the unit of the pasting strength is N / mm, and the unit of the shear strength is min.

[0097] From the above test results, it can be found that at room temperature, the addition of the reactive plasticizer has no significant effect on the pasting performance of the tape formed by the obtained pressure-sensitive adhesive composition. However, at low temperature, on the one hand, there is an obvious decrease in the pasting strength of the even-numbered samples corresponding to the examples. Moreover, its aging resistance also decreases, and the change in the pasting strength before and after aging is more obvious. In addition, from the shear strength at high temperature, the addition of the reactive plasticizer also significantly improves the aging resistance regarding the shear strength.

[0098] Comparative Example 5

[0099] This comparative example illustrates the preparation and performance testing of a pressure-sensitive adhesive composition compounded with a non-reactive plasticizer, as follows:

[0100] It is substantially the same as Example 3, with the main difference being that Component B is replaced by the original plasticizer RP-1020 that has not undergone the thioglycerol graft reaction. The rest of the reaction process remains unchanged.

[0101] The pressure-sensitive adhesive prepared in this example shows similar pasting performance at room temperature as that of Example 3. However, after aging, there is a more obvious decrease in the pasting strength, dropping to about 0.7. And at low temperature, the initial pasting performance (0.7) changes little, but the degree of decrease in the pasting strength after aging (0.45) is significantly more inferior compared to Example 3.

[0102] Example 7

[0103] This example is substantially the same as Example 3, with the main difference being that:

[0104] Replace component a1 with n-butyl methacrylate and component a2 with isocyanatoethyl methacrylate.

[0105] The pressure-sensitive tape obtained has the same adhesion strength and aging resistance as that of Example 3.

[0106] Example 8

[0107] This example is generally the same as Example 3, and the main difference lies in:

[0108] Replace component a1 with n-propyl acrylate and component a2 with isocyanatoethyl methacrylate.

[0109] The pressure-sensitive tape obtained has the same adhesion strength and aging resistance as that of Example 3.

[0110] Based on the above examples and comparative examples, it can be clearly seen that the pressure-sensitive adhesive composition and its preparation method provided by the embodiments of the present invention graft and introduce a reactive plasticizer with an extremely low Tg on the main chain of the polyacrylate, effectively reducing the Tg of the entire system, thereby greatly improving its low-temperature performance; at the same time, the addition of the reactive plasticizer also effectively improves the peel strength of the polyacrylate pressure-sensitive adhesive. In addition, since the reactive plasticizer is chemically grafted onto the main chain of the polyacrylate, there will be no so-called "plasticizer migration problem" even after long-term aging, thus achieving a better balance between low-temperature adhesion performance and aging resistance performance.

[0111] The above-mentioned embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims

1. A low-temperature polyacrylate pressure-sensitive adhesive composition, characterized in that Comprising: An acrylate polymer and a reactive plasticizer; the acrylate polymer has a first side chain, and the end group of the first side chain contains an isocyanate group; the reactive plasticizer has a second side chain, and the end group of the second side chain contains a hydroxyl group; in the composition, the isocyanate group and the hydroxyl group are connected to the reactive plasticizer and the acrylate polymer through a nucleophilic addition reaction; The acrylate polymer is formed by copolymerization of at least a first monomer and a second monomer; the first monomer is selected from acrylate monomers with an alkyl group having 1 to 12 carbon atoms; the second monomer is selected from acrylate monomers having an isocyanate group at the end of the group connected to the ester group, and in the total mass of the monomers, the mass fraction of the first monomer is 75-97%; The mass fraction of the second monomer is 3-25%; The synthesis method of the reactive plasticizer includes: providing an initial plasticizer and a polyol, the molecular chain of the initial plasticizer contains a double bond, and the polyol contains a mercapto group; the mercapto group and the double bond undergo an addition reaction under the action of an initiator to synthesize the reactive plasticizer, and the polyol is selected from mercapto glycerol; the end condition of the nucleophilic addition reaction is that no free isocyanate group is detected in the reaction system.

2. The low-temperature polyacrylate pressure-sensitive adhesive composition according to claim 1, characterized in that, The first monomer includes any one or a combination of two or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, where the methyl is optional; and / or, the second monomer includes any one or a combination of two of ethyl 2-isocyanatoacrylate and isocyanatoethyl methacrylate.

3. The low-temperature polyacrylate pressure-sensitive adhesive composition according to claim 1, characterized in that The hydroxyl group in the reactive plasticizer is stoichiometric with the isocyanate group in the acrylate polymer; and / or, the viscosity of the low-temperature acrylate pressure-sensitive adhesive composition is 200 to 50000 cPs.

4. A method for preparing the low-temperature polyacrylate pressure-sensitive adhesive composition according to any one of claims 1-3, characterized in that, Comprising: Providing an acrylate polymer and a reactive plasticizer, the acrylate polymer has a first side chain, the end group of the first side chain contains an isocyanate group, the reactive plasticizer has a second side chain, the end group of the second side chain contains a hydroxyl group; mixing the acrylate polymer and the reactive plasticizer to form a reaction system, and making the isocyanate group and the hydroxyl group undergo a nucleophilic addition reaction to connect the acrylate polymer and the reactive plasticizer to obtain a low-temperature acrylate pressure-sensitive adhesive composition.

5. Use of the low-temperature acrylate pressure-sensitive adhesive composition according to any one of claims 1-3 in the preparation of a pressure-sensitive tape.

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