Pressure-sensitive adhesive composition containing carboxylic acid tackifier and preparation method therefor

Abstract

The present invention provides a pressure-sensitive adhesive composition containing a carboxylic acid tackifier and a preparation method therefor. The pressure-sensitive adhesive composition comprises an adhesive matrix, a liquid tackifier, and a crosslinking agent, wherein the liquid tackifier includes a carboxylic acid tackifier, which is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid. The pressure-sensitive adhesive composition containing a carboxylic acid tackifier of the present invention has significantly improved initial tack, impact resistance, and bonding performance to low-polarity plates.

Description

[0001] PRESSURE-SENSITIVE ADHESIVE COMPOSITION CONTAINING CARBOXYLIC ACID TACKIFIER AND PREPARATION METHOD THEREFOR

[0002] Technical Field

[0003] The present invention relates to the technical field of adhesives or adhesive tapes, and more particularly to a pressure-sensitive adhesive composition containing an oligomeric acid tackifier and a preparation method therefor.

[0004] Background Art

[0005] Improving the performance of adhesives has always been a technology of concern. In order to meet increasingly stringent environmental requirements, more and more researchers do not only seek to improve the bonding performance of adhesives, but also expect that the adhesives can be made from environmentally friendly materials of biological origin, especially those used in daily necessities, such as furniture and household appliances.

[0006] Oligomeric organic carboxylic acids (hereinafter referred to as oligomeric acids) are mainly used in adhesives as structural units of various polyester resins or participate in polymerization reactions to produce adhesive materials. For example, an oligomeric acid is used as a structural unit of a hot melt adhesive containing a polyurethane system to condense with a polyamine functional group to prepare a polyamide resin; an oligomeric acid is used to react with an epoxy resin to prepare a PSA precursor; and furthermore, an oligomeric acid is used in the synthesis of polyester polyols and the like, to give adhesive compositions further excellent bonding performance. To date, however, it has not been found that an oligomeric acid when added to a pressure-sensitive adhesive can improve the bonding performance of the adhesive without participating in the polymerization reaction.

[0007] In addition, terpene-based resins, rosin resins, hydrogenated petroleum resins, and the like are often used as tackifying resins in pressure-sensitive adhesives to improve the bonding performance of the adhesives. However, although the pressure-sensitive adhesives using these common tackifying resins have good adhesive force, their initial tack is too low to meet the demand for high initial tack in daily applications. Moreover, such pressuresensitive adhesives are limited in the application for bonding low-polarity substrates due to their poor adhesive force on low-polarity substrates.

[0008] Summary of the Invention

[0009] In view of the foregoing, an object of the present invention is to provide a pressure-sensitive adhesive composition containing an oligomeric acid, and an adhesive sheet, wherein the oligomeric acid is used alone as a tackifier or as a mixture with a conventional tackifying resin, which can significantly improve the initial tack, impact resistance, and bonding performance to low-polarity substrates of the pressure-sensitive adhesive composition or the adhesive sheet.

[0010] Further, another object of the present invention is to provide a method for preparing the pressure-sensitive adhesive composition containing an oligomeric acid and the adhesive sheet. Since the oligomeric acid is compatible with the pressure-sensitive adhesive and the two are easy to mix uniformly, it is easy for the method of the present invention to produce a pressure-sensitive adhesive composition and an adhesive sheet having the above excellent performance.

[0011] Further, yet another object of the present invention is to provide use of an oligomeric acid as a tackifier in a pressure-sensitive adhesive composition or an adhesive sheet.

[0012] The above objects of the present invention are achieved by the following technical solutions.

[0013] In an aspect, the present invention provides a pressure-sensitive adhesive composition comprising an adhesive matrix, a liquid tackifier, and a crosslinking agent, wherein the liquid tackifier comprises a carboxylic acid tackifier, which is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid. Optionally, the carboxylic acid tackifier is selected from at least one of a C15-C20 unsaturated carboxylic acid and an oligomeric acid of a C15-C20 unsaturated carboxylic acid, and preferably from at least one of a C16-C18 unsaturated carboxylic acid and an oligomeric acid of a C16-C18 unsaturated carboxylic acid.

[0014] Optionally, the carboxylic acid tackifier is selected from the oligomeric acid, which has a degree of polymerization of 1 -10, preferably 1 -6, even preferably 2-6, and more preferably 2-4.

[0015] Optionally, the liquid tackifier further includes one or more of a liquid hydrocarbon tackifier, a terpene tackifying resin, and a rosin tackifying resin.

[0016] Optionally, the content of the liquid tackifier is 1 -45%, based on the weight of the adhesive matrix.

[0017] Optionally, the content of the carboxylic acid tackifier is 1 -25%, preferably 2-25%, even preferably 2-20%, and more preferably 3-15%, based on the weight of the adhesive matrix.

[0018] Optionally, the carboxylic acid tackifier is selected from oleic acid, linoleic acid, linolenic acid, a dimer acid or trimer acid of oleic acid, linoleic acid and linolenic acid, and a mixture of two or more thereof.

[0019] Optionally, the adhesive matrix is an acrylic adhesive.

[0020] In another aspect, the present invention provides a method for preparing the pressure-sensitive adhesive composition described above, the method comprising: adding a carboxylic acid tackifier and a crosslinking agent to an adhesive matrix; and stirring and mixing same until uniform to obtain the pressure-sensitive adhesive composition.

[0021] In another aspect, the present invention provides a pressure-sensitive adhesive bonding sheet comprising the pressure-sensitive adhesive composition described above and optionally an adhesive substrate.

[0022] In yet another aspect, the present invention provides a method for preparing a pressure-sensitive adhesive bonding sheet, the method comprising: coating the pressure-sensitive adhesive composition described above onto a substrate to form a coating layer; and attaching another substrate to the coating layer and applying pressure, and then removing the substrates on both sides of the coating layer to obtain a bonding sheet without substrate on both sides thereof, or removing either of the substrates on both sides of the coating layer, or removing no substrate to obtain a bonding sheet comprising substrates.

[0023] In yet another aspect, the present invention provides use of a carboxylic acid as a tackifier in a pressure-sensitive adhesive composition, wherein the carboxylic acid is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid.

[0024] The present invention can bring about the following beneficial technical effects:

[0025] The present invention is the first to add an unsaturated carboxylic acid or an oligomeric acid thereof as a carboxylic acid tackifier to a pressuresensitive adhesive composition, and the carboxylic acid tackifier substantially does not or does not participate in the polymerization reaction of the adhesive. In addition, since the carboxylic acid tackifier has a low glass transition temperature Tg, good flexibility, and good compatibility with the pressure-sensitive adhesive, the adhesive composition of the present invention has significantly improved initial tack, impact resistance, and bonding performance to low-polarity plates. Thus, the present invention solves problems such as poor initial tack, poor impact resistance, and poor adhesive force to low-polarity substrates of adhesives when a conventional liquid resin is used as a tackifier. Moreover, the carboxylic acid tackifier in the present invention may be an organic acid of plant origin, so that the adhesive composition of tackifier present invention is an environmentally friendly adhesive material.

[0026] Detailed Description of Embodiments

[0027] In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in view of the following specific embodiments of the present invention. Apparently, the specific embodiments described are a part of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without involving any inventive effort fall within the scope of protection of the present invention.

[0028] According to an aspect of the present invention, provided is a pressuresensitive adhesive composition comprising an adhesive matrix, a liquid tackifier, and a crosslinking agent, wherein the liquid tackifier comprises a carboxylic acid tackifier, which is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid. The carboxylic acid tackifier according to the present invention is preferably a liquid C10-C25 unsaturated carboxylic acid or an oligomeric acid thereof. This is because the liquid unsaturated carboxylic acid or the oligomeric acid thereof has low glass transition temperature Tg, good flexibility, and good compatibility with the adhesive matrix, such that a uniformly mixed adhesive composition with excellent initial tack, impact resistance, and peel force can be prepared. The glass transition temperature (Tg) refers to the temperature at which an amorphous polymer is transformed from a glassy state to a high-elastic state. Tg is directly related to the flexibility of molecular chains. A lower Tg indicates a more flexible molecular chain of a substance and accordingly better spreadability of the oligomeric acid of the present invention. The unsaturated carboxylic acid or the oligomeric acid thereof of the present invention has a glass transition temperature (Tg) of less than or equal to -40°C, preferably less than or equal to -45°C, more preferably less than or equal to -50°C, further preferably less than or equal to -70°C, and in particular preferably less than or equal to - 80°C.

[0029] The carboxylic acid tackifier according to the present invention is more preferably an unsaturated carboxylic acid having one or more double bonds, for example, an unsaturated carboxylic acid containing 1 , 2, 3, 4, or 5 double bonds.

[0030] The carboxylic acid tackifier according to the present invention is preferably at least one of a C10-C25 unsaturated carboxylic acid or an oligomeric acid thereof, more preferably at least one of a C15-C20 unsaturated carboxylic acid or an oligomeric acid thereof, and even more preferably at least one of a C16-C18 unsaturated carboxylic acid or an oligomeric acid thereof.

[0031] The carboxylic acid tackifier according to the present invention is preferably an oligomeric acid of a C10-C25 unsaturated carboxylic acid, the oligomeric acid having a degree of polymerization of 1 -20, preferably 1 -10, more preferably 1 -6, even more preferably 2-6, and most preferably 2-4. For example, the degree of polymerization of the oligomeric acid is 2 or 3.

[0032] The carboxylic acid tackifier according to the present invention is preferably one of oleic acid, linoleic acid, linolenic acid, and a dimer, trimer or tetramer acid of oleic acid, linoleic acid and linolenic acid; or preferably a mixture of two or more of the aforementioned carboxylic acids or oligomeric acids. Commercially available dimer acids are usually C36 dimer acids formed from the polymerization of unsaturated C18 fatty acids. Commercially available trimer acids are C54 tricarboxylic acids formed from the polymerization of C18 unsaturated fatty acids such as oleic acid and linoleic acid.

[0033] The carboxylic acid tackifier according to the present invention is preferably of plant origin. For example, the carboxylic acid tackifier is derived from an unsaturated fatty acids containing 18 carbon atoms extracted from soybean and cotton seed sources, such as oleic acid, linoleic acid, and linolenic acid.

[0034] In the pressure-sensitive adhesive composition according to the present invention, the content of the liquid tackifier is 1 -45 wt.%, even preferably 2- 40 wt.%, more preferably 3-35 wt.%, even more preferably 3-30 wt.%, further preferably 3-25 wt.%, for example, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.5 wt.%, 8 wt.%, 8.5 wt.%, 9 wt.%, 9.5 wt.%, 10 wt.%, 12 wt.%, 14 wt.%, 16 wt.% or 18 wt.%, based on the weight of the adhesive matrix.

[0035] In the pressure-sensitive adhesive composition according to the present invention, the content of the carboxylic acid tackifier is preferably 1 -30 wt.%, even preferably 1 -25 wt.%, further preferably 1 .5-24%, more preferably 1 .8- 22%, even more preferably 2-20%, further more preferably 3-18%, for example, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.5 wt.%, 8 wt.%, 8.5 wt.%, 9 wt.%, 9.5 wt.%, 10 wt.%, 12 wt.%, 14 wt.% or 16 wt.%, based on the weight of the adhesive matrix.

[0036] In the pressure-sensitive adhesive composition according to the present invention, the liquid tackifier further comprises other liquid tackifiers, including one or more of a liquid hydrocarbon tackifier, a terpene tackifying resin, and a rosin tackifying resin. The content of the other liquid tackifier is preferably 0-40 wt.%, more preferably 0-30 wt.%, further preferably 0-25 wt.%, based on the weight of the adhesive matrix. From the consideration of improving the initial tack and impact resistance of the pressure-sensitive adhesive composition to a greater extent, the content of the other liquid tackifier is preferably 10 wt.% or less, more preferably 5 wt.% or less, even more preferably 3 wt.% or less, for example, 2 wt.% or less, 1 wt.% or less, and 0 wt.% (i.e., no other liquid tackifier).

[0037] In the pressure-sensitive adhesive composition according to the present invention, the adhesive matrix may be one that is commonly used in pressure-sensitive adhesives. For example, the adhesive matrix may be an acrylic adhesive, an epoxy adhesive, or a silicone adhesive. Preferably, the adhesive matrix is an acrylic adhesive.

[0038] According to another aspect of the present invention, the present invention further provides a method for preparing the pressure-sensitive adhesive composition described above, the method comprising: adding a carboxylic acid tackifier and a crosslinking agent to an adhesive matrix; and stirring and mixing same until uniform to obtain the pressure-sensitive adhesive composition. In the preparation method according to the present invention, the carboxylic acid tackifier used has a low glass transition temperature Tg, good flexibility, and good compatibility with the adhesive matrix, so that it is easy to prepare a uniformly mixed adhesive composition only by simply stirring and mixing. Therefore, the adhesive composition of the present invention has excellent initial tack, impact resistance, and peel force simultaneously.

[0039] According to another aspect of the present invention, the present invention further provides a pressure-sensitive adhesive bonding sheet comprising the pressure-sensitive adhesive composition described above and optionally an adhesive substrate. The pressure-sensitive adhesive bonding sheet can be prepared by coating the pressure-sensitive adhesive composition described above onto a carrier such as PET, SUS, and PE.

[0040] According to another aspect of the present invention, the present invention further provides a method for preparing a pressure-sensitive adhesive bonding sheet, the method comprising: coating the pressuresensitive adhesive composition described above onto a substrate to form a coating layer; and attaching another substrate to the coating layer and applying pressure, and then removing the substrates on both sides of the coating layer to obtain a bonding sheet without substrate on both sides thereof, or removing either of the substrates on both sides of the coating layer, or removing no substrate to obtain a bonding sheet comprising substrates. Since the liquid carboxylic acid tackifier in the present invention has a low glass transition temperature Tg, good flexibility, and good compatibility with the adhesive matrix, the adhesive composition of the present invention has good spreadability and can be used to easily prepare a pressure-sensitive adhesive bonding sheet.

[0041] According to yet another aspect of the present invention, the present invention further provides use of a carboxylic acid as a tackifier in a pressuresensitive adhesive composition, wherein the carboxylic acid is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid.

[0042] The adhesive composition, the adhesive sheet and the preparation methods therefor of the present invention can bring about the following beneficial technical effects: the present invention is the first to add an unsaturated carboxylic acid or an oligomeric acid thereof as a tackifier to a pressure-sensitive adhesive composition, and the carboxylic acid tackifier substantially does not or does not participate in the polymerization reaction of the adhesive; in addition, since the carboxylic acid tackifier has a low glass transition temperature Tg, good flexibility, and good compatibility with the pressure-sensitive adhesive, the adhesive composition of the present invention has significantly improved initial tack, impact resistance, and bonding performance to low-polarity plates. Thus, the present invention solves problems such as poor initial tack, poor impact resistance, and poor adhesive force to low-polarity substrates of adhesives when a conventional liquid resin is used as a tackifier. Moreover, the oligomeric acid in the present invention may be an organic acid of plant origin, so that the adhesive composition of the present invention is an environmentally friendly adhesive material.

[0043] Examples

[0044] The examples of the present invention use the following test methods for testing the initial tack, impact resistance and peel force performance.

[0045] 1. Test methods

[0046] (1 ) Initial tack test

[0047] The initial tack for an extremely short contact time was measured using the rolling-ball initial adhesion test. The adhesive composition was coated onto one side of a standard polyester carrier with a thickness of 23 pm (with a coating amount of 50 g / m2) to form a sample to be tested. A strip-shaped test sample with a length of approximately 10 cm was fixed horizontally on a test bench, with the adhesive side facing upwards. A steel ball (diameter: 1 1 mm; mass: 5.6 g) was washed with acetone and modulated under standard conditions (temperature: 23°C + / - 1 °C; relative humidity: 50% + / - 1%) for 2 h. During the measurement, the steel ball rolled down a 65 mm high slope (angle of inclination: 21 °) and was thereby accelerated under the action of the earth's gravity, allowing the steel ball to roll directly onto the adhesive surface of the sample from the slope. The distance traveled by the steel ball from arriving at the adhesive surface to stopping on the adhesive surface was measured. The rolling distance of the steel ball thus measured was taken as the initial tack of the adhesive composition. The shorter the distance measured, the higher the initial adhesion or the higher the initial tack, and vice versa. The test result for each sample was obtained by averaging the rolling distances of the steel ball after five separate measurements (in millimeters (mm)).

[0048] (2) Peel force test In the present invention, the performance of 180° peel force of the adhesive composition was tested on various substrates, namely stainless steel (SUS), polyethylene (PE), and polycarbonate (PC) substrates.

[0049] The peel force in the present invention was measured at a temperature of 23°C ± 1 °C and a relative humidity of 50% ± 5%. The specimens were cut to a width of 20 mm and adhered to an SUS substrate, a PE substrate, and a PC substrate, respectively. The substrates were cleaned and modulated before measurement. The side facing away from the test substrate was then lined with a plastic film such as PET and PVC having a thickness of 25 pm or other to prevent the stretching or deformation of the adhesive layer of the test specimen during the test. The test specimen was then pressed onto the substrate by rolling the adhesive tape back and forth 5 times with a 4 kg roller at a rolling rate of 10 m / min. A steel plate was inserted immediately after the rolling process, allowing testing of the peel force of the specimen at an angle of 180°. The peel force was measured using a Zwick tensile testing machine at a speed of 300 mm / min. The test result for each sample was represented by the average of three measurement results (N / cm).

[0050] (3) DuPont impact resistance test

[0051] At a temperature of 23 ± 1 °C and a humidity of 50 ± 5%, the pressuresensitive adhesive composition was cut into a homocentric-squares-shaped sample with an inner side length of 29 mm x 29 mm and an outer side length of 33 mm x 33 mm by laser. A 45 mm x 45 mm frame of PC and a 35 mm x 35 mm lens were wiped with ethanol and left to stand for 2 h. The homocentric-squares-shaped adhesive sheet to be tested was attached between the frame and the lens, and a pressure of 248 N was applied and held for 5 s. After standing for 24 h, a 150 g impact head was then used for impact testing, with the detachment of the lens with the frame being defined as failure. The 150 g impact head fell freely from a height of 5 cm to impact the test sample. If the sample did not fail, the free fall impact was continued with the height increased by 5 cm, i.e., from a height of 10 cm; and if the sample still did not fail, the free fall impact is performed again with the height increased by 5 cm, i.e., from a height of 15 cm, and so on. The height when the sample failed was recorded. The DuPont impact resistance was calculated as W = mgh (where m was 150 g, g was gravitational acceleration, i.e., 9.8 m / s2, and h was the final failure height of the sample).

[0052] 2. Raw materials and abbreviations thereof

[0053] The raw materials used in the examples of the present invention and abbreviations thereof were shown in Table 1 below.

[0054] Table 1 . Raw materials used in examples of the present invention and abbreviations thereof

[0055] (1 ) Preparation of (meth)acrylic glue A

[0056] The (meth)acrylic glue A was prepared following the steps below: The monomer components, in the proportions as shown in Table 2, were charged into a reaction vessel equipped with a condensing tube, a nitrogen introduction tube, a thermometer and a stirring device. 0.20 parts by weight of 2,2’-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator and toluene as a polymerization reaction solvent, which allowed the content of the monomer components to be 70 wt.%, were added. Nitrogen was circulated for nitrogen replacement for about 1 hour while stirring. The reaction vessel was then heated to 65°C for reaction for 6 hours. The reaction vessel was then heated to 80°C for reaction for 3 hours to prepare the (meth)acrylic polymer A with a weight average molecular weight (Mw) of 670,000.

[0057] (2) Preparation of tackifying resin-modified (meth)acrylic glue B1

[0058] A (meth)acrylic polymer b1 was prepared following the steps below:

[0059] The monomer components, in the proportions as shown in Table 2, were charged into a reaction vessel equipped with a condensing tube, a nitrogen introduction tube, a thermometer and a stirring device. 0.18 parts by weight of 2,2’-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator and toluene as a polymerization reaction solvent, which allowed the content of the monomer components to be 70 wt.%, were added. Nitrogen was circulated for nitrogen replacement for about 1 hour while stirring. The reaction vessel was then heated to 63°C for reaction for 7 hours. The reaction vessel was then heated to 80°C for reaction for 3 hours to prepare the (meth)acrylic polymer b1 with a weight average molecular weight (Mw) of 850,000.

[0060] The tackifying resin-modified (meth)acrylic glue B1 was prepared following the step below:

[0061] To the (meth)acrylic polymer b1 synthesized as above, 0.42 parts by weight of a terpene phenolic resin (trade name: H150, softening point: 150°C, manufactured by DRT Industries) with respect to the dry mass of 100 parts by weight of the (meth)acrylic polymer were added, so as to prepare the tackifying resin-modified (meth)acrylic glue B1 .

[0062] (3) Preparation of tackifying resin-modified (meth)acrylic glue B2

[0063] A (meth)acrylic polymer b2 was prepared following the steps below:

[0064] The mixture of the monomer components as shown in Table 1 was charged into a reaction vessel equipped with a condensing tube, a nitrogen introduction tube, a thermometer and a stirring device. 0.18 parts by weight of 2,2’-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator and toluene as a polymerization reaction solvent, which allowed the content of the monomer components to be 70 wt.%, were added. Nitrogen was circulated for nitrogen replacement for about 1 hour while stirring. The reaction vessel was then heated to 59°C for reaction for 8 hours. The reaction vessel was then heated to 80°C for reaction for 3 hours to prepare the (meth)acrylic polymer b2 with a weight average molecular weight (Mw) of 1 ,000,000.

[0065] The tackifying resin-modified (meth)acrylic glue B2 was prepared following the step below:

[0066] To the (meth)acrylic polymer b2 synthesized as above, 0.42 parts by weight of a rosin resin (trade name: D135, softening point: 135°C, manufactured by Arakawa Chemical Industries Co., Ltd.) with respect to the dry mass of 100 parts by weight of the (meth)acrylic polymer were added, so as to prepare the tackifying resin-modified (meth)acrylic glue B2.

[0067] Table 2. Monomer components of (meth)acrylics (mass percentage0 / ,)

[0068] 3. Examples 1 -30 and Comparative examples 1 -1 1 Examples 1 -5

[0069] 100 parts by weight of the (meth)acrylate polymer A were weighed, and a monocarboxylic acid (trade name: HY-90, manufactured by Anhui Hongtai New Materials Co., Ltd.) in varying amounts (relative to the mass percentages of the polymer A) was added respectively, as shown in Table 3. 0.06 parts by weight of an epoxy crosslinking agent (trade name: GA-240, manufactured by Huntsman Chemical Corporation) was added. The mixture was stirred thoroughly for 30 minutes. The above adhesive composition solution was coated on a polyethylene terephthalate (PET) isolating liner (trade name: 20459, manufactured by Mitsubishi Chemical Corporation) in a manner such that the final thickness (thickness of the adhesive layer) is 50 pm, so as to form a coating layer (adhesive composition layer). Next, the coating layer was dried in a dryer at 120°C for 5 minutes to volatilize the solvent and a very small amount of residual monomers. In this way, a PET isolating liner was provided on the above coating layer, thus obtaining a substrate-free double-sided adhesive sheet containing an adhesive layer and isolating liners protecting both sides of the adhesive layer.

[0070] Examples 6-10

[0071] 100 parts by weight of the (meth)acrylate polymer A were weighed, and a dimer acid (trade name: HY-13, manufactured by Anhui Hongtai New Materials Co., Ltd.) in varying amounts was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0072] Examples 11 -15

[0073] 100 parts by weight of the (meth)acrylate polymer A were weighed, and a dimer acid (trade name: Pripol 1006, manufactured by Croda) in varying amounts was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0074] Examples 16-20

[0075] 100 parts by weight of the (meth)acrylate polymer A were weighed, and a trimer acid (trade name: TMA-3085, manufactured by Shanghai Zeepur Chemical Co., Ltd.) in varying amounts was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0076] Examples 21 -26

[0077] 100 parts by weight of the tackifying resin-modified (meth)acrylate glue B1 were weighed, and the above monocarboxylic acid, dimer acid and trimer acid in varying amounts were added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0078] Examples 27-30

[0079] 100 parts by weight of the tackifying resin-modified (meth)acrylate polymer B2 were weighed, and a dimer acid in varying amounts was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0080] Comparative example 1

[0081] 100 parts by weight of the (meth)acrylate polymer A were weighed, and no carboxylic acid tackifier was added. The subsequent steps were the same as those in Examples 1 -5.

[0082] Comparative example 2 100 parts by weight of the tackifying resin-modified (meth)acrylic polymer B1 were weighed, and no carboxylic acid tackifier was added. The subsequent steps were the same as those in Examples 1 -5.

[0083] Comparative example 3

[0084] 100 parts by weight of the tackifying resin-modified (meth)acrylic polymer B2 were weighed, and no carboxylic acid tackifier was added. The subsequent steps were the same as those in Examples 1 -5.

[0085] Comparative examples 4-8

[0086] 100 parts by weight of the (meth)acrylate polymer A were weighed, and a conventional liquid hydrocarbon resin (Wintack 10, manufactured by TotalEnergies) in varying percentage contents was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0087] Comparative examples 9-10

[0088] 100 parts by weight of the tackifying resin-modified (meth)acrylic polymer B1 were weighed, and a conventional liquid hydrocarbon resin (Wintack 10, manufactured by TotalEnergies) in varying percentage contents was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0089] Comparative examples 1 1 -12

[0090] 100 parts by weight of the tackifying resin-modified (meth)acrylic polymer B2 were weighed, and a conventional liquid hydrocarbon resin (Wintack 10, manufactured by TotalEnergies) in varying percentage contents was added respectively, as shown in Table 3. The subsequent steps were the same as those in Examples 1 -5.

[0091] 4. Effect on initial tack

[0092] The initial tack of the pressure-sensitive adhesive compositions prepared in Examples 1 -30 and Comparative examples 1 -12 was measured using the rolling-ball initial tack test method described above, and the results were shown in Table 3 below.

[0093] Table 3. Effect of monocarboxylic acid or oligomeric acids on initial tack of adhesive compositions

[0094]

[0095]

[0096] The results of the initial tack test in Table 3 above show that the addition of the monocarboxylic acid HY-90 or the oligomeric acids HY-13, Pripol 1006 and TMA-3085 as a tackifier to the adhesive composition results can significantly improve the initial tack of the pressure-sensitive adhesive composition. In addition, the monocarboxylic acid or oligomeric acids added as a tackifier in the present invention have a more significant effect on improving the initial tack of the adhesive composition than other commonly used liquid tackifying resins. Moreover, the results of the initial tack test in Table 3 above also show that for the pressure-sensitive adhesives (e.g., B1 and B2) that have been modified with tackifying resins, the addition of the monocarboxylic acid HY-90 and the oligomeric acids HY-13, Pripol 1006 and TMA-3085 also improves the initial tack of the modified pressure-sensitive adhesives; in addition, compared with the above improvement effect of the monocarboxylic acid or oligomeric acids on the initial tack of the pressuresensitive adhesives, other common liquid tackifying resins cannot improve the initial tack of the pressure-sensitive adhesives, or result in the initial tack thereof dissatisfying the requirements of use.

[0097] 5. Effect on peel force

[0098] The pressure-sensitive adhesive compositions prepared in some of the examples and comparative examples above were tested for peel force (i.e., bonding performance) on various polar substrates. The specific test results were shown in Table 4 below. Table 4. Effect of monocarboxylic acid or oligomeric acids on peel force on various polar substrates

[0099] Note: zip indicates that the adhesive had poor wettability, and the stickslip phenomenon occurred when the adhesive was peeled off from the adhered substrate.

[0100] The results of the peel force test in Table 4 above show that when oligomeric acids HY-13 and Pripol 1006 were added to the pressuresensitive adhesive composition as a tackifier, the peel force (or bonding performance) of the pressure-sensitive adhesive composition on the surface of low-polarity substrates PE and PC was significantly improved. Whereas, when using the other liquid tackifying resins Wintack 10 and Y308, the pressure-sensitive adhesive composition had poor wettability to low-polarity substrates PE and PC, resulting in bonding failure. In addition, a stick-slip (jerking motion) phenomenon (zip) occurred when the adhesive was peeled off from the low-polarity substrates, which led to measured values fluctuating back and forth, making it impossible to measure the peel force accurately. Therefore, adding carboxylic acid tackifiers to pressure-sensitive adhesive compositions can significantly improve the bonding performance of the adhesives on low-polarity substrates, while other common liquid tackifiers cannot improve the bonding performance or may result in bonding failure.

[0101] 6. Effect on impact resistance

[0102] The pressure-sensitive adhesive compositions prepared in some of the examples and comparative examples above were tested for impact resistance using the DuPont impact resistance test method described above. The specific test results were shown in Table 5.

[0103] Table 5. Effect of carboxylic acid tackifiers on impact resistance

[0104] The resu ts of the impact resistance test in Table 5 above show that the addition of the oligomeric acids HY-13 and Pripol 1006 significantly improves the impact resistance of the pressure-sensitive adhesives; in addition, the oligomeric acids HY-13 and Pripol 1006 provide greater improvements in impact resistance than the other liquid resin, i.e., Wintack 10. Moreover, the results of the impact resistance test in Table 5 above show that for the pressure-sensitive adhesives (B1 and B2) that have been modified with other resins, the addition of the oligomeric acids HY-13 and Pripol 1006 also improves the impact resistance of the pressure-sensitive adhesives. Therefore, compared to common liquid tackifying resins, the oligomeric acids, when added to adhesives, can significantly improve the impact resistance of the adhesives.

[0105] The technical solutions of the present invention are not limited to the above specific embodiments or examples. The above specific embodiments or examples are merely illustrative and non-limiting, and many improvements and variations can further be made by those skilled in the art in light of the specific embodiments or examples recited in the present invention without departing from the spirit of the present invention and the scope of protection of the claims, which all fall into the scope of protection of the present invention.

Claims

CLAIMS1. A pressure-sensitive adhesive composition, characterized by comprising an adhesive matrix, a liquid tackifier, and a crosslinking agent, wherein the liquid tackifier comprises a carboxylic acid tackifier, which is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid.

2. The pressure-sensitive adhesive composition according to claim 1 , characterized in that the carboxylic acid tackifier is selected from at least one of a C15-C20 unsaturated carboxylic acid and an oligomeric acid of a C15- C20 unsaturated carboxylic acid, and preferably from at least one of a C16- C unsaturated carboxylic acid and an oligomeric acid of a C16-C18 unsaturated carboxylic acid.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, characterized in that the carboxylic acid tackifier is selected from the oligomeric acid, which has a degree of polymerization of 1 -10, preferably 1 - 6, even preferably 2-6, and more preferably 2-4.

4. The pressure-sensitive adhesive composition according to any one of claims 1 -3, characterized in that the liquid tackifier further comprises one or more of a liquid hydrocarbon tackifier, a terpene tackifying resin, and a rosin tackifying resin.

5. The pressure-sensitive adhesive composition according to any one of claims 1 -4, characterized in that the content of the liquid tackifier is 1 - 45%, based on the weight of the adhesive matrix.

6. The pressure-sensitive adhesive composition according to any one of claims 1 -5, characterized in that the content of the carboxylic acid tackifier is 1 -25%, preferably 2-25%, even preferably 2-20%, and more preferably 3-15%, based on the weight of the adhesive matrix.

7. The pressure-sensitive adhesive composition according to any one of claims 1 -6, characterized in that the carboxylic acid tackifier is selected from oleic acid, linoleic acid, linolenic acid, a dimer or trimer acid of oleic acid, linoleic acid and linolenic acid, and a mixture of two or more thereof.

8. The pressure-sensitive adhesive composition according to any one of claims 1 -7, characterized in that the adhesive matrix is an acrylic adhesive.

9. A method for preparing the pressure-sensitive adhesive composition of any one of claims 1 -8, characterized by comprising: adding a carboxylic acid tackifier and a crosslinking agent to an adhesive matrix; and stirring and mixing same until uniform to obtain the pressure-sensitive adhesive composition.

10. A pressure-sensitive adhesive bonding sheet, characterized by comprising the pressure-sensitive adhesive composition of any one of claims 1 -8 and optionally an adhesive substrate.1 1. A method for preparing a pressure-sensitive adhesive bonding sheet, characterized by comprising: coating a pressure-sensitive adhesive composition of any one of claims 1 -8 onto a substrate to form a coating layer; and attaching another substrate to the coating layer and applying pressure, and then removing the substrates on both sides of the coating layer to obtain a bonding sheet without substrate on both sides thereof, or removing either of the substrates on both sides of the coating layer, or removing no substrate to obtain a bonding sheet comprising substrates.

12. Use of a carboxylic acid as a tackifier in a pressure-sensitive adhesive composition, characterized in that the carboxylic acid is selected from at least one of a C10-C25 unsaturated carboxylic acid and an oligomeric acid of a C10-C25 unsaturated carboxylic acid.

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