UV (ultraviolet) curing adhesive as well as preparation method and application thereof

Abstract

The invention provides a UV curing adhesive as well as a preparation method and application thereof, the UV curing adhesive comprises the following components in parts by weight: 100 parts of matrix resin, 10-50 parts of an active modifier and 0.05-0.5 part of a second photoinitiator, and the matrix resin comprises the following components: an unsaturated monomer, a first photoinitiator and a structure modifier. The UV curing adhesive has excellent cold and hot impact resistance, can prevent crack propagation, has good toughness and binding power, and has small influence on the rheological property of the adhesive.

Description

Technical Field

[0001] The invention belongs to the field of light-curing materials and relates to a UV curing adhesive and a preparation method and application thereof. Background Art

[0002] UV-curing adhesives include pressure-sensitive adhesives and structural adhesives, which are widely used in the electronics industry, daily consumer goods, printing and other industries. They have a series of advantages, including: fast curing speed, low energy consumption, and high production efficiency; they do not contain solvents and are an environmentally friendly alternative to traditional solvent-based adhesives; they are easy to process; and they are highly controllable, with the reaction rate controlled by selecting the light source and initiator.

[0003] The primary functional monomers of UV-curable adhesives are ethylenically unsaturated acrylic (ester) monomers. Under the action of a photoradical initiator, these monomers activate and couple olefinic bonds to form a cross-linked polymer system, resulting in certain adhesive properties. This type of adhesive has diverse usage scenarios and application environments, some of which must withstand harsh conditions such as high temperature and humidity, or alternating hot and cold weather. Therefore, the molecular design requirements for the key adhesive resins are very high.

[0004] Acrylic adhesives are widely used in existing technologies due to their excellent properties. However, their poor toughness and high glass transition temperature significantly limit their application in low-temperature environments or in environments subject to alternating hot and cold temperatures. This is because as the external temperature fluctuates, the cured polymer adhesive layer expands and contracts, deforming, and then recovering to its original state due to its own resilience. However, when the external temperature changes cause the deformation of the polymer adhesive layer to exceed the tolerance range of its resilience, the polymer adhesive layer loses its resilience, resulting in a significant reduction in mechanical properties, fracture, and even debonding. After thermal shock aging, the strength of ordinary acrylic adhesives can decrease by more than 50%, making them unsuitable for use in certain environments with severe temperature fluctuations.

[0005] Acrylic polymer resins are also highly brittle, lacking toughness and exhibiting low elongation at break, resulting in poor thermal shock resistance. Short thermal cycles, where the molecular chains rapidly expand and contract, can easily lead to molecular chain breakage. The general approach to improving impact resistance is to add external toughening agents, but these agents can be incompatible with the bulk polymer and remain free in the system, reducing the adhesive's shear strength and hindering its practical use. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention provides a UV-curable adhesive, a preparation method, and applications thereof. The UV-curable adhesive of the present invention exhibits excellent resistance to thermal shock, can prevent crack propagation, possesses good toughness and adhesion, and has minimal effect on the adhesive's rheological properties.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides a UV curable adhesive comprising the following components in parts by weight:

[0009] 100 parts of main resin, 10-50 parts of active modifier (for example, 10 parts, 15 parts, 18 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts or 50 parts), and 0.05-0.5 parts of second photoinitiator (for example, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts or 0.5 parts).

[0010] Preferably, the main resin includes the following components:

[0011] unsaturated monomer, a first photoinitiator and a structure modifier;

[0012] The unsaturated monomer is selected from acrylic acid or acrylate unsaturated monomers, and the structure modifier is selected from at least one of trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0013] Preferably, the unsaturated monomer includes at least one of alkyl acrylate or alkyl methacrylate, and also includes at least one of acrylic acid or hydroxyalkyl acrylate.

[0014] Preferably, the alkyl acrylate or alkyl methacrylate accounts for 75% to 90% by weight of the total weight of the unsaturated monomers, such as 75%, 78%, 80%, 83%, 85%, 88% or 90%.

[0015] Preferably, the alkyl acrylate is selected from any one or a combination of at least two of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isooctyl acrylate, cyclohexyl acrylate or lauryl acrylate.

[0016] In the present invention, the combination is a combination of acrylic acid and alkyl acrylate, alkyl methacrylate and hydroxyalkyl acrylate, or a combination of alkyl acrylate, alkyl methacrylate and hydroxyalkyl acrylate, a combination of acrylic acid and hydroxyalkyl acrylate, a combination of acrylic acid and hydroxyalkyl methacrylate, etc.

[0017] Preferably, the alkyl methacrylate is selected from at least one of methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, isodecyl methacrylate, cyclohexyl methacrylate, dicyclopentadienyl methacrylate or 2-methoxyethyl methacrylate.

[0018] Preferably, the hydroxyalkyl acrylate is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyisobutyl acrylate, hydroxyethoxyethyl acrylate, dimethylolpropane monoacrylate, polyethylene glycol monoacrylate or benzyl acrylate.

[0019] Preferably, the first photoinitiator is selected from at least one of 2-hydroxy-2-methylphenylpropanone (1173), 1-hydroxycyclohexylphenyl ketone (184), 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone (907), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TOP-1), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (IHT-PI 910), 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (659) or methyl benzoylformate (MBF).

[0020] Preferably, the weight ratio of the first photoinitiator to the unsaturated monomer is 0.1-5%, for example 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0021] Preferably, the structure modifier is a multifunctional structure modifier, preferably at least one of trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0022] Preferably, the weight ratio of the structure modifier to the unsaturated monomer is 0.1-1%, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0023] Preferably, the active modifier is selected from at least one of isobornyl methacrylate and pentaerythritol tetrakis(3-mercaptopropionate).

[0024] Preferably, the second photoinitiator is selected from at least one of 1173, 184, 907, TPO, TOP-1, IHT-PI 910, 659 or MBF.

[0025] In a second aspect, the present invention provides a method for preparing the UV curing adhesive as described above, the preparation method comprising the following steps:

[0026] S1, the unsaturated monomer and the first photoinitiator undergo polymerization reaction;

[0027] S2. When the viscosity of the polymerization reaction system reaches 1500-3000 cps, a structure modifier is added to carry out a condensation reaction to obtain a main resin;

[0028] S3, mixing the active additive, the second photoinitiator and the main resin, and cross-linking to obtain a UV-curable adhesive.

[0029] In the present invention, by polymerizing unsaturated monomers and adding a controlled structure modifier, an in-situ nano-toughening effect can be achieved, and the obtained UV curing adhesive has the characteristics of excellent resistance to cold and hot shocks.

[0030] This invention uses in-situ nanotoughening to achieve partial crosslinking by adding a certain amount of a multifunctional structural modifier after the bulk polymerization of the UV-curable adhesive resin has proceeded for a certain period of time. Before the addition of the multifunctional modifier, the polymerization system forms a linear polymer (soft segment). After the addition of the modifier, dispersion polymerization forms partial nanoblocks (hard segments), causing microphase separation and thus achieving nanotoughening.

[0031] During the polymerization synthesis of the main resin, the present invention controls the timing and amount of adding the structure modifier, achieving dispersed polymerization and partial crosslinking around the structure modifier to form nanospheres (hard segments), resulting in microphase separation and in-situ nanotoughening. The resulting main resin has increased elongation at break, preventing crack propagation and improving toughness during alternating hot and cold temperature shocks. The generated nanoparticles have no effect on rheological properties and do not increase the viscosity of the dispersion. Therefore, the resulting UV-curable adhesive exhibits excellent resistance to hot and cold shocks.

[0032] Preferably, the polymerization reaction in step S1 is carried out under the protection of an inert gas, and the inert gas is selected from nitrogen, argon, etc.

[0033] Preferably, the flow rate of the inert gas is 20-100 mL / min, for example, 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, 40 mL / min, 45 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min or 100 mL / min.

[0034] Preferably, the polymerization reaction in step S1 is carried out under intermittent irradiation of ultraviolet light.

[0035] Preferably, the switching frequency of the intermittent irradiation is 2-4 times / min, for example, 2 times / min, 3 times / min or 4 times / min.

[0036] Preferably, the wavelength of the ultraviolet light source is 300-400 nm (for example, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm or 400 nm), and the light intensity is 30-150 mW / cm 2 (e.g. 30mW / cm 2 , 40mW / cm 2 , 50mW / cm 2 , 70mW / cm 2 , 80mW / cm 2 , 100mW / cm 2 , 120mW / cm 2 or 140mW / cm 2 ), the irradiation time is 100-500s (for example, 100s, 150s, 200s, 250s, 300s, 350s, 400s, 450s or 500s).

[0037] In the present invention, when the polymerization reaction in step S1 is carried out and the system viscosity reaches 1500-3000 cps (e.g., 1500 cps, 1700 cps, 1800 cps, 2000 cps, 2200 cps, 2500 cps, 2800 cps or 3000 cps), a structure modifier is added to the system.

[0038] Preferably, the condensation reaction in step S2 is carried out under intermittent irradiation of ultraviolet light.

[0039] Preferably, the switching frequency of the intermittent irradiation is 2-4 times / min, for example, 2 times / min, 3 times / min or 4 times / min.

[0040] Preferably, the wavelength of the ultraviolet light source is 300-400 nm (for example, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm or 400 nm), and the light intensity is 30-150 mW / cm 2 (e.g. 30mW / cm 2 , 40mW / cm 2 , 50mW / cm 2 , 70mW / cm 2 , 80mW / cm 2 , 100mW / cm 2 , 120mW / cm 2or 140mW / cm 2 ).

[0041] Preferably, the condensation reaction time in step S2 is 5-500s (e.g., 5s, 10s, 20s, 40s, 50s, 100s, 150s, 200s, 250s, 300s, 350s, 400s, 450s or 500s).

[0042] Preferably, the crosslinking is carried out under irradiation with an ultraviolet light source having a wavelength of 300-400 nm (e.g., 300 nm, 320 nm, 340 nm, 360 nm, 380 nm or 400 nm) and a light intensity of 30-150 mW / cm 2 (e.g. 30mW / cm 2 , 40mW / cm 2 , 50mW / cm 2 , 70mW / cm 2 , 80mW / cm 2 , 100mW / cm 2 , 120mW / cm 2 or 140mW / cm 2 ).

[0043] Preferably, the cross-linking time is 100-300 s, for example, 100 s, 120 s, 150 s, 180 s, 200 s, 230 s, 250 s, 280 s or 300 s.

[0044] In a third aspect, the present invention provides use of the UV curable adhesive described above in a polarizer.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] In the UV-curable adhesive of the present invention, the main resin adopts an unsaturated monomer combined with a structural modifier, and dispersed polymerization and partial cross-linking are performed around the structural modifier to form nanospheres (hard segments), which will form microphase separation and thus play an in-situ nano-toughening role. The elongation at break of the main resin is increased, and the crack propagation can be prevented during alternating hot and cold temperature shocks, thereby improving toughness. The generated nanoparticles have no effect on rheological properties and will not cause an increase in the viscosity of the dispersion. Therefore, the obtained UV-curable adhesive has the characteristics of excellent resistance to hot and cold shocks. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] This embodiment provides a UV curable adhesive, the preparation method of which includes the following steps:

[0050] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was as follows: irradiation for 30 seconds, followed by a 30 seconds pause for cooling, and alternating irradiation (total irradiation time was 270 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 ; The system viscosity reached 2600cps, and then 0.3 parts of multifunctional structure modifier TMPTA was further added, and the condensation reaction was carried out under UV light for 180s to obtain a main resin system with a resin viscosity of about 7000cps.

[0051] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) and then a cross-linking reaction was carried out for 180s to obtain the specific target product adhesive D-1.

[0052] Example 2

[0053] Compared with Example 1, the amount of the multifunctional structure modifier was adjusted while keeping the amounts of other materials unchanged. After adjustment, the amount of the multifunctional structure modifier TMPTA was 0.1 part, and adhesive D-2 was obtained.

[0054] Example 3

[0055] Compared with Example 1, the amount of the multifunctional structure modifier was adjusted while keeping the amounts of other materials unchanged. After adjustment, the amount of the multifunctional structure modifier TMPTA was 1.0 part, and adhesive D-3 was obtained.

[0056] Example 4

[0057] Compared with Example 1, the amounts of acrylic acid and methyl methacrylate were adjusted while keeping the amounts of other materials unchanged. After adjustment, 4 parts of acrylic acid (as reaction monomer I) and 20 parts of hydroxyethyl acrylate (as reaction monomer III) were used to obtain adhesive D-4.

[0058] Example 5

[0059] Compared with Example 4, only 76 parts of isooctyl acrylate was used as the reaction monomer II, and the contents of other material components remained unchanged, to obtain adhesive D-5.

[0060] Example 6

[0061] Compared with Example 4, the changed conditions are: removing acrylic acid from reaction monomer I, increasing isooctyl acrylate to 68 parts (as reaction monomer II), and keeping the contents of other material components unchanged, to obtain adhesive D-6.

[0062] Example 7

[0063] Reaction monomers I and III were omitted, and only reaction monomer II was retained. The material components of reaction monomer 2 were 88 parts of isooctyl acrylate, 10 parts of butyl acrylate, and 2 parts of methyl methacrylate. Other materials and reaction conditions were the same as in Example 1 to obtain adhesive D-7.

[0064] Example 8

[0065] Basically similar to Example 5, the changed conditions are: not using reactive monomer II, and adjusting the component contents of reactive monomer I and reactive monomer III at the same time, adjusting 4 parts of acrylic acid (as reactive monomer I) and 20 parts of hydroxyethyl acrylate (as reactive monomer III) to obtain adhesive D-8.

[0066] Example 9

[0067] The reaction was basically similar to Example 1, except that the contents of photoinitiator #1 were adjusted to 0.25 parts of TPO-L, 0.3 parts of PETA, and 0.1 parts of photoinitiator #2 to obtain adhesive D-9.

[0068] Example 10

[0069] The reaction was basically similar to Example 1, except that the contents of photoinitiator #1 were adjusted to 0.25 parts of IHT-PI, 0.3 parts of DTMPT4, and 0.1 parts of photoinitiator #2 to obtain adhesive D-10.

[0070] Example 11

[0071] Basically similar to Example 1, the changed conditions are: adjusting the 1# photoinitiator to MBF / 0.25 parts, the multifunctional structure modifier to DPPA / 0.3 parts, and the 2# photoinitiator to TOP-1 / 0.1 parts to obtain adhesive D-11.

[0072] Example 12

[0073] Basically similar to Example 1, the changed conditions are as follows: adjusting the 1# photoinitiator to 659 / 0.25 parts, the multifunctional structure modifier to PETA / 0.3 parts, and the 2# photoinitiator to 184 / 0.1 parts to obtain adhesive D-12.

[0074] Example 13

[0075] Compared with Example 1, with the other material parts unchanged, the type of reaction monomer II was adjusted to 64 parts of cyclohexyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), and 4 parts of methyl methacrylate (as reaction monomer II) to obtain adhesive D-13.

[0076] Example 14

[0077] Compared with Example 1, with the other material parts unchanged, the type of reaction monomer II was adjusted to 64 parts of isobutyl acrylate (as reaction monomer II), 19 parts of lauryl acrylate (as reaction monomer II), and 4 parts of ethyl methacrylate (as reaction monomer II) to obtain adhesive D-14.

[0078] Example 15

[0079] Compared with Example 1, with the amounts of other materials remaining unchanged, the type of reactive monomer III was adjusted to 10 parts of hydroxybutyl acrylate to obtain adhesive D-15.

[0080] Comparative Example 1

[0081] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was: on for 30 seconds, off for 30 seconds to cool, and irradiated alternately 9 times (irradiation time was 270 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 .

[0082] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for a period of time to obtain the specific target product adhesive M-1.

[0083] Comparative Example 2

[0084] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was: on for 30 seconds, off for 30 seconds to cool, and irradiated alternately 9 times (irradiation time was 270 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 ; The system viscosity reached 2600cps, and then 0.01 parts of multifunctional structure modifier TMPTA was further added, and the condensation reaction was carried out under UV light for 15s to obtain a main resin system with a resin viscosity of about 7500cps.

[0085] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for a period of time to obtain the specific target product adhesive M-2.

[0086] Comparative Example 3

[0087] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was: on for 30 seconds, off for 30 seconds to cool, and irradiated alternately 9 times (irradiation time was 270 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 ; The system viscosity reached 3000cps, and then 10 parts of a multifunctional structure modifier TMPTA was further added, and a condensation reaction was carried out under UV light for 15s to obtain a main resin system with a resin viscosity of about 7000cps.

[0088] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for a period of time to obtain the specific target product adhesive M-3.

[0089] Comparative Example 4

[0090] This comparative example provides a UV curing adhesive, the preparation method of which comprises the following steps:

[0091] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). 0.3 parts of the multifunctional structural modifier TMPTA were added. After nitrogen replacement, nitrogen was continuously supplied at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization reaction. The intermittent irradiation pattern of the ultraviolet light source was: on for 30 seconds and off for 30 seconds to cool down, alternating irradiation for 6 times (irradiation time was 180 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 ; A main resin system with a resin viscosity of about 7000cps is obtained.

[0092] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for a period of time to obtain the specific target product adhesive M-4.

[0093] Comparative Example 5

[0094] This comparative example provides a UV curing adhesive, the preparation method of which comprises the following steps:

[0095] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was as follows: irradiation for 30 seconds, followed by a 30 seconds pause for cooling, and alternating irradiation for 7 times (total irradiation time of 210 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 When the viscosity of the system reaches 1000 cps, 0.3 parts of a multifunctional structure modifier TMPTA is further added, and the condensation reaction is carried out under UV light for 180 seconds to obtain a main resin system with a resin viscosity of about 7000 cps.

[0096] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for 180s to obtain the target adhesive M-5.

[0097] Comparative Example 6

[0098] This comparative example provides a UV curing adhesive, the preparation method of which comprises the following steps:

[0099] In a multi-necked flask equipped with a stirring device for circulating cooling medium and a nitrogen supply device, 0.25 parts of photoinitiator 184 were placed, followed by 3 parts of acrylic acid (as reaction monomer I), 64 parts of isooctyl acrylate (as reaction monomer II), 19 parts of butyl acrylate (as reaction monomer II), 4 parts of methyl methacrylate (as reaction monomer II), and 10 parts of hydroxyethyl acrylate (as reaction monomer III). After nitrogen replacement, nitrogen flow was continuously maintained at a nitrogen flow rate of 60 mL / min. Under stirring at a stirring rate of 300 r / min, the reaction system was intermittently irradiated with an ultraviolet light source to carry out polymerization. The intermittent irradiation pattern of the ultraviolet light source was as follows: irradiation for 30 seconds, followed by a 30 seconds pause to cool, and alternating irradiation for 12 times (total irradiation time of 360 seconds). The ultraviolet light wavelength was 365 nm and the light intensity was 50 mW / cm 2 The viscosity of the system reached 4000 cps, and then 0.3 parts of a multifunctional structure modifier TMPTA was further added, and the condensation reaction was carried out under UV light for 90 seconds to obtain a main resin system with a resin viscosity of about 7000 cps.

[0100] In the main resin system prepared above, 0.3 parts of IBOMA (as active diluent I) and 0.75 parts of PETMP (as active diluent II) were added, and then 0.1 parts of the second photoinitiator TPO-L was added. Under the ultraviolet light source (wavelength of 365nm, light intensity of 50mW / cm 2 ) for 180s to obtain the target adhesive M-6.

[0101] Table 1 is a comparison table of material feed ratios (parts by weight) for the above-mentioned embodiments and comparative examples; Table 2 is a comparison table of reaction conditions for the above-mentioned embodiments and comparative examples; and Table 3 is a comparison table of adhesive properties obtained for the above-mentioned embodiments and comparative examples.

[0102] Table 1. Comparison table of material feed ratios (parts by weight) of various embodiments and comparative examples (NG means unqualified)

[0103]

[0104]

[0105]

[0106] Table 2. Comparative table of reaction conditions for various examples and comparative examples

[0107]

[0108] The performance of the adhesive is tested as follows:

[0109] (1) Viscosity: GB / T 2794-2022 “Adhesives—Determination of viscosity” / ASTM D1084 “Adhesives—Test method for viscosity”.

[0110] (2) Residual adhesive: GB / T 25256-2010 “Test method for 180° peeling force and residual adhesion of release films for optical functional films”.

[0111] (3) Initial tack: GB / T 4852-2002 “Test method for initial tack of pressure-sensitive adhesive tapes” / ASTM D3654-2016 “Standard test method for initial tack of pressure-sensitive adhesive tapes”.

[0112] (4) Adhesion: GB / T 7124-2008 “Determination of tensile shear strength of adhesives (rigid material to rigid material)” / ASTM D1002 “Determination of tensile lap shear strength of adhesives (metal to metal)”.

[0113] (5) Peel force: GB / T 25256-2010 "Test method for 180° peel force and residual adhesion of release films for optical functional films" / ASTM D903 "Quasi-test method for peel or peel strength of adhesives".

[0114] (6) Thermal shock: GB / T 2423.22-2012 “Environmental testing - Part 2: Test method - Test N: Temperature change”.

[0115] Table 3. Comparative table of adhesive properties obtained in various examples and comparative examples (NG means unqualified)

[0116]

[0117]

[0118] Judging from the performance listed in the above embodiments and comparative examples, in the hot and cold temperature alternation experiment between -40 and 80°C, the adhesive samples without adding the multifunctional structural modifier or with an improper proportion of the multifunctional structural modifier will crack and fail in a single impact; while the adhesive samples used in the present invention, in which an appropriate amount of the multifunctional structural modifier is added in the second half of the polymerization reaction, still maintain adhesion after more than 100 (or even more than 200) hot and cold shock tests, thereby ensuring good reliability of the adhesive in harsh temperature environments.

[0119] Combined with the data in the attached table and the feeding conditions of each embodiment, the experimental results of the acrylic resin using in-situ nano-toughening technology are analyzed in depth. When the amount of multifunctional structural modifier added and monomer I, monomer II, monomer III, and 1# photoinitiator are basically unchanged, the thermal shock resistance and mechanical properties of the acrylic resin are significantly improved compared to those without the addition of multifunctional structural modifier. Among them, the mechanical properties of Examples 1-5 are the most excellent. While the thermal shock resistance is significantly improved, the adhesion is increased by more than 50% compared to the acrylic resin without the in-situ nano-toughening technology. If the amount of multifunctional structural modifier added is inappropriate, such as too little or too much multifunctional structural modifier added in Comparative Examples 2 and 3, the thermal shock resistance and mechanical properties are unqualified. This shows that the appropriate addition of structural modifier plays a key role in improving the thermal shock resistance and mechanical properties of acrylic resin.

[0120] The positive and beneficial effect of the present invention is that the UV-curable adhesive has excellent resistance to cold and hot shocks. During the polymerization synthesis process of the main resin, the timing and amount of the addition of the multifunctional structural modifier are controlled. When no modifier is added, conventional polymerization forms a linear polymer (soft segment); after adding a small amount of modifier, dispersed polymerization and partial cross-linking are carried out around the modifier to form nanospheres (hard segments), which will form microphase separation and play an in-situ nano-toughening role. The elongation at break of the resulting resin is increased, and it can prevent crack propagation and improve toughness during alternating hot and cold temperature shocks; and the generated nanoparticles have no effect on rheology, that is, the viscosity of the dispersion does not increase.

[0121] The applicant states that while the above-described embodiments illustrate the UV-curable adhesive, its preparation method, and its application, the present invention is not limited to these embodiments. This does not necessarily mean that the present invention must rely on these embodiments for implementation. Those skilled in the art will understand that any improvements to the present invention, equivalent substitutions for raw materials in the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A UV curing adhesive, characterized in that: The UV curing adhesive comprises the following components in parts by weight: 100 parts of main resin, 10-50 parts of active modifier, and 0.05-0.5 parts of second photoinitiator.

2. The UV curing adhesive according to claim 1, characterized in that The main resin includes the following components: unsaturated monomer, a first photoinitiator and a structure modifier; The unsaturated monomer is selected from acrylic acid or acrylate unsaturated monomers, and the structure modifier is selected from at least one of trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

3. The UV curing adhesive according to claim 2, characterized in that The acrylic acid or acrylic acid ester ethylenically unsaturated monomer includes at least one of acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate, hydroxyalkyl acrylate, and hydroxyalkyl methacrylate; Preferably, the alkyl acrylate is selected from at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isooctyl acrylate, cyclohexyl acrylate or lauryl acrylate; Preferably, the alkyl methacrylate is selected from at least one of methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, isodecyl methacrylate, cyclohexyl methacrylate, dicyclopentadienyl methacrylate or 2-methoxyethyl methacrylate; Preferably, the hydroxyalkyl acrylate is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyisobutyl acrylate, hydroxyethoxyethyl acrylate, dimethylolpropane monoacrylate, polyethylene glycol monoacrylate or benzyl acrylate.

4. The UV curing adhesive according to any one of claim 2, characterized in that The first photoinitiator is selected from at least one of 2-hydroxy-2-methylphenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone or methyl benzoylformate; Preferably, the weight ratio of the first photoinitiator to the unsaturated monomer is 0.1-5%; Preferably, the structure modifier is a multifunctional structure modifier, preferably at least one of trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate; Preferably, the weight ratio of the structure modifier to the unsaturated monomer is 0.1-1%.

5. The UV curing adhesive according to any one of claims 1 to 4, characterized in that: The active modifier is selected from isobornyl methacrylate or pentaerythritol tetrakis(3-mercaptopropionate); Preferably, the second photoinitiator is selected from at least one of 1173, 184, 907, TPO, TOP-1, IHT-PI 910, 659 or MBF.

6. A method for preparing the UV curing adhesive according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, the unsaturated monomer and the first photoinitiator undergo polymerization reaction; S2. When the viscosity of the polymerization reaction system reaches 1500-3000 cps, a structure modifier is added to carry out a condensation reaction to obtain a main resin; S3, mixing the active additive, the second photoinitiator and the main resin, and cross-linking to obtain a UV-curable adhesive.

7. The preparation method according to claim 6, characterized in that The polymerization reaction is carried out under the protection of an inert gas, wherein the inert gas is selected from nitrogen or argon; Preferably, the flow rate of the inert gas is 20-100 mL / min; Preferably, the polymerization reaction is carried out under intermittent irradiation of ultraviolet light; Preferably, the switching frequency of the intermittent irradiation is 2-4 times / min; Preferably, the wavelength of the ultraviolet light source is 300-400nm and the light intensity is 30-150mW / cm 2 , the irradiation time is 100-500s.

8. The preparation method according to claim 6, characterized in that The condensation reaction is carried out under intermittent ultraviolet light irradiation, and the switching frequency is 2-4 times / min; Preferably, the wavelength of the ultraviolet light source is 300-400nm and the light intensity is 30-150mW / cm 2 ; Preferably, the condensation reaction time is 5-500s.

9. The preparation method according to claim 6, characterized in that The crosslinking is carried out under the irradiation of an ultraviolet light source with a wavelength of 300-400 nm and a light intensity of 30-150 mW / cm 2 ; Preferably, the cross-linking time is 100-300s.

10. Use of the UV curable adhesive according to any one of claims 1 to 5 in polarizers.

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