Liquid modified one-component polyurethane moisture curing adhesive and preparation method thereof

Abstract

The present application relates to a kind of liquid modified single-component polyurethane moisture curing adhesive and its preparation method, the moisture curing adhesive includes the raw material as follows by weight parts: low viscosity polyol 35-50 parts, low crystallinity isocyanate 25-30 parts, bisphenol F type epoxy resin 15-25 parts, non-crystalline toughening resin 8-11 parts, tackifying resin 2-4 parts, defoaming agent 0.5-1 part, organic tin catalyst X-T-12 0.4-0.6 parts, wrapped organic cobalt catalyst 1-1.4 parts;Wherein, organic tin catalyst X-T-12 is obtained by low viscosity polyol dilution 10 times from organic tin catalyst T-12;Adhesive is liquid at normal temperature, can be applied at normal temperature;Adhesive layer curing speed is fast, curing time is lower to moisture, can effectively guarantee the smooth state inside and outside of adhesive layer, has high bonding strength to plastic, metal and other substrates, and has good temperature resistance, solvent resistance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a liquid-modified one-component polyurethane moisture-curing adhesive and its preparation method. Background Technology

[0002] In recent years, the country has placed increasingly stringent requirements on environmental protection, gradually banning some toxic and environmentally unfriendly adhesives. With the strengthening of environmental protection efforts, solvent-based adhesives are gradually being phased out of the global market. Research into solvent-free, environmentally friendly adhesives such as single-component polyurethane is also deepening. However, most commercially available polyurethane adhesives rely on moisture curing, and most single-component polyurethane moisture-curing adhesives are hot melt adhesives, which have complex application methods and significant energy consumption. Furthermore, during the curing process, excessive isocyanate groups react with moisture in the air. Due to the influence of air humidity, the surface curing rate is prone to be too fast when the ambient humidity is too high, leading to surface skin formation. The carbon dioxide produced by the reaction between the adhesive layer and moisture cannot dissipate in time, resulting in dense bubbles or blistering in the adhesive layer. In addition, most existing single-component liquid polyurethane adhesives are diluted with solvents to achieve room-temperature liquid properties, which is not environmentally friendly. Therefore, there is an urgent need to develop a single-component polyurethane moisture-curing adhesive that can overcome the above problems. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a liquid-modified one-component polyurethane moisture-curing adhesive, comprising the following raw materials in parts by weight: 35-50 parts of low-viscosity polyol, 25-30 parts of low-crystallinity isocyanate, 15-25 parts of bisphenol F epoxy resin, 8-11 parts of non-crystalline toughening resin, 2-4 parts of tackifying resin, 0.5-1 part of defoamer, 0.4-0.6 parts of organotin catalyst XT-12, and 1-1.4 parts of encapsulated organocobalt catalyst; wherein the organotin catalyst XT-12 is obtained by diluting organotin catalyst T-12 by 10 times with low-viscosity polyol.

[0004] Preferably, the low-viscosity polyol is one or both of polycarbonate polyol and polyester polyol.

[0005] Preferably, the low-crystallinity isocyanate isophorone diisocyanate.

[0006] Preferably, the amorphous toughening resin is a modified amorphous polyester resin with a low Tg point.

[0007] Preferably, the tackifying resin is one or two of oily terpene tackifying resin and aromatic petroleum resin.

[0008] Preferably, the defoamer is a high-efficiency, silicone-free defoamer.

[0009] The present invention also provides a method for preparing the above-mentioned liquid-modified one-component polyurethane moisture-curing adhesive, the preparation method comprising the following steps:

[0010] S1. Add the low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure reaches -0.058MPa. At the same time, adjust the temperature to 110℃ and stir at a stirring speed of 50-60r / min and a dispersion speed of 1000-1200r / min for 90-100min.

[0011] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add the low-crystallinity isocyanate and stir for 90-100 minutes at a stirring speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min.

[0012] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min for 90-100 minutes.

[0013] S4. Extrude the material to obtain a moisture-curing adhesive.

[0014] Preferably, the organotin catalyst XT-12 is obtained by pre-mixing organotin catalyst T-12 with a separately selected low-viscosity polyol in a weight ratio of 1:9, wherein the separately selected low-viscosity polyol is one or more of the low-viscosity polyols used in step S1.

[0015] The beneficial effects of the above-mentioned technical solution of the present invention are as follows:

[0016] 1. The liquid-modified single-component polyurethane moisture-curing adhesive and its preparation method of the present invention, by selecting low-viscosity polyol, low-crystallinity isocyanate, bisphenol F type epoxy resin and non-crystalline toughening resin, the colloid can remain liquid at room temperature and can be applied at room temperature, effectively simplifying the adhesive application process, improving the work efficiency of enterprises, and greatly reducing energy consumption;

[0017] 2. The moisture-curing adhesive of the present invention, in the initial stage of curing, through the reaction of the isocyanate groups on the surface with moisture in the air, the adhesive has certain initial tack and surface dryness. During the curing process, while the isocyanate reacts with the moisture in the air, under the catalytic action of an organic cobalt catalyst, the epoxy groups in the system react with the isocyanate and the intermediate products generated by the isocyanate, reducing the generation of carbon dioxide, avoiding the formation of bubbles inside the adhesive layer, and reducing the dependence of the adhesive layer on moisture during curing, further improving the curing rate of the adhesive layer. By changing the curing conditions to adjust the curing time, heating and pressurizing can quickly dissipate the coating layer of the encapsulated organic cobalt catalyst, enabling it to quickly acquire catalytic effect and cure ahead of time.

[0018] 3. The moisture-curing adhesive of the present invention satisfies the requirements of room temperature liquid state by sacrificing some initial tack properties. When the isocyanate group reacts with moisture in the air, the epoxy resin reacts with the isocyanate group and urethane group through ring opening to form a cross-linked network structure to meet the strength requirements after curing. When the part is working under high temperature conditions, the epoxy group will further react with the molecular chain and cross-link and entangle, so that the strength is further improved.

[0019] 4. The moisture-curing adhesive of the present invention promotes the ring-opening reaction of bisphenol F epoxy resin with excess isocyanate groups in the system under the catalysis of an organic cobalt catalyst to generate an oxazolidinone structure, which greatly improves the temperature resistance, strength and solvent resistance of the adhesive layer.

[0020] 5. The liquid-modified single-component polyurethane moisture-curing adhesive of the present invention has a solid content of up to 99%, contains no organic solvents, reduces environmental pollution, and has high bonding strength with plastic, metal and other substrates after complete curing, and also has good temperature resistance and solvent resistance. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] This invention provides a liquid-modified one-component polyurethane moisture-curing adhesive, comprising the following raw materials in parts by weight: 35-50 parts of low-viscosity polyol, 25-30 parts of low-crystallinity isocyanate, 15-25 parts of bisphenol F epoxy resin, 8-11 parts of non-crystalline toughening resin, 2-4 parts of tackifying resin, 0.5-1 part of defoamer, 0.4-0.6 parts of organotin catalyst XT-12, and 1-1.4 parts of encapsulated organocobalt catalyst; wherein, the organotin catalyst XT-12 is obtained by diluting organotin catalyst T-12 by 10 times with low-viscosity polyol.

[0027] Among them, low-viscosity polyols are used to synthesize low-molecular-weight prepolymers with low-crystallinity isocyanates. By using low-viscosity polycarbonate polyols and polyester polyols with low-crystallinity isocyanates to synthesize amorphous, low-viscosity isocyanate-terminated prepolymers, the synthesized polyurethane prepolymers not only have low viscosity but also high strength and good physical properties.

[0028] In addition, bisphenol F epoxy resin has low viscosity. The addition of bisphenol F epoxy resin can catalyze the reaction of groups in the colloid, increasing the crosslinking density and giving the colloid higher strength during later curing. Furthermore, non-crystalline toughening resin provides the colloid with corresponding toughness and increases its adhesion to the substrate. Additionally, tackifying resin can increase the initial tack performance of the colloid. Defoamers are used to eliminate bubbles generated by mechanical stirring and reaction. Furthermore, organotin catalysts can accelerate the synthesis rate of polyurethane prepolymers and also accelerate the reaction of hydroxyl groups in epoxy resin with isocyanates at low temperatures, thus accelerating epoxy resin grafting. The encapsulated organocobalt catalyst, with solvent encapsulation, exhibits catalytic effects after being exposed to air at room temperature for 8 hours, promoting the reaction of epoxy groups with isocyanates.

[0029] More specifically, the bisphenol F type epoxy resin can be selected from Nan Ya brand NPEF-170 bisphenol F type epoxy resin. Specifically, the organotin catalyst T-12 can be selected from Guangdong Wengjiang Chemical Reagent Co., Ltd.; due to the extremely low addition amount of organotin catalyst T-12, to facilitate the addition of the organotin catalyst and reduce errors, it is diluted with the low viscosity polyol used at a ratio of 1:9 to obtain organotin catalyst XT-12. The encapsulated organocobalt catalyst can be selected from Huiyuan (Dongguan) New Material Technology Co., Ltd.'s encapsulated organocobalt catalyst HY-3352.

[0030] Specifically, the low-viscosity polyol is one or both of polycarbonate polyol and polyester polyol.

[0031] More specifically, the polycarbonate polyol can be PCDL T5652 polycarbonate polyol from Asahi Kasei Chemicals Co., Ltd. of Japan, with a hydroxyl value of 51-61 KOH / g and a molecular weight of 2000; the polyester polyol can be polyester diol BY-3005 from Beijing Baiyuan Chemical Co., Ltd. BY-3005 is a low-viscosity liquid polyester diol with a hydroxyl value of 54-60 mg KOH / g and a molecular weight of 2100.

[0032] Specifically, the low-crystallinity isocyanate isophorone diisocyanate.

[0033] Since isophorone diisocyanate (IPDI) is a low-crystallinity isocyanate, the use of isophorone diisocyanate, combined with the above-mentioned low-viscosity polyol, can ensure that the prepolymer is in a liquid state. The isophorone diisocyanate can be selected from Wanhua Chemical Group Co., Ltd.

[0034] Specifically, the amorphous toughening resin is a modified amorphous polyester resin with a low Tg point.

[0035] The non-crystalline toughening resin uses a low-Tg polyester resin instead of conventional solid acrylic resin, lowering the overall Tg point of the adhesive and allowing it to remain liquid before reaction. This ensures that the cured adhesive layer retains excellent adhesion to various plastics such as PC and metals, and also strengthens PC plastic substrates. A suitable non-crystalline toughening resin is the modified non-crystalline polyester resin Vylon 670 from Toyobo Co., Ltd. of Japan.

[0036] Specifically, the tackifying resin is one or two of oily terpene tackifying resin and aromatic petroleum resin.

[0037] More specifically, the tackifying resin can be selected from oily terpene tackifying resin BY04 from Shenzhen Yoshida Chemical Co., Ltd., or FTR-6100 aromatic petroleum resin from Mitsui Co., Ltd.

[0038] Specifically, the defoamer is a high-efficiency, silicone-free defoamer.

[0039] More specifically, the defoamer is a high-efficiency, silicone-free defoamer, which is more environmentally friendly. BYK-A515 from BYK Chemical Company of Germany can be selected.

[0040] The present invention also provides a method for preparing the above-mentioned liquid-modified one-component polyurethane moisture-curing adhesive, the preparation method comprising the following steps:

[0041] S1. Add the low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure reaches -0.058MPa. At the same time, adjust the temperature to 110℃ and stir at a stirring speed of 50-60r / min and a dispersion speed of 1000-1200r / min for 90-100min.

[0042] The purpose of this step is to dry the raw materials to prevent the moisture in them from affecting the subsequent prepolymerization reaction.

[0043] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add the low-crystallinity isocyanate and stir for 90-100 minutes at a stirring speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min.

[0044] The purpose of this step is to synthesize a prepolymer by reacting a low-viscosity polyol with a low-crystallinity isocyanate.

[0045] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min for 90-100 minutes.

[0046] The purpose of this step is to graft and blend the prepolymer with bisphenol F epoxy resin.

[0047] S4. Extrude the material to obtain a moisture-curing adhesive.

[0048] The nitrogen gas used in the above method does not react with the raw materials, and the nitrogen atmosphere can prevent the raw materials and colloids from contacting the air, thus protecting the raw materials.

[0049] Specifically, the organotin catalyst XT-12 is obtained by pre-mixing organotin catalyst T-12 with a separately selected low-viscosity polyol in a weight ratio of 1:9, and the separately selected low-viscosity polyol is one or more of the low-viscosity polyols used in step S1.

[0050] This invention designs five embodiments and provides a comparative example. The adhesive used in the comparative example is an existing hot melt adhesive product of the applicant, and its specific components and contents are shown in Table 1:

[0051] Table 1. Components and contents of Examples 1-5 and Comparative Examples

[0052]

[0053]

[0054] In the comparative examples, DOW VORANOL 1000LM is the polyether polyol VORANOL 1000LM from Dow Chemical Company, MDI is 4,4'-diphenylmethane diisocyanate from Tosoh Corporation of Japan, BR-116 is the thermoplastic acrylic resin BR-116 from Mitsubishi Corporation of Japan, and BYK-054 is BYK-054 from BYK Chemical Company of Germany.

[0055] Preparation method of Example 1:

[0056] The preparation method of the liquid-modified one-component polyurethane moisture-curing adhesive in Example 1 of this invention includes the following steps:

[0057] S1. Add low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 110℃ and stir for 90 minutes at a stirring speed of 50r / min and a dispersion speed of 1200r / min.

[0058] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add the low-crystallinity isocyanate and stir for 90 minutes at a stirring speed of 60 r / min and a dispersion speed of 1000 r / min.

[0059] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a stirring speed of 60 r / min and a dispersion speed of 1000 r / min for 90 min.

[0060] S4. Extrude the material to obtain a moisture-curing adhesive.

[0061] Preparation method of Example 2:

[0062] The preparation method of the liquid-modified one-component polyurethane moisture-curing adhesive in Example 2 of this invention includes the following steps:

[0063] S1. Add low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 110℃ and stir for 90 minutes at a stirring speed of 60r / min and a dispersion speed of 1000r / min.

[0064] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add low-crystallinity isocyanate and stir for 90 minutes at a stirring speed of 50 r / min and a dispersion speed of 1200 r / min.

[0065] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a stirring speed of 50 r / min and a dispersion speed of 1200 r / min for 90 min.

[0066] S4. Extrude the material to obtain a moisture-curing adhesive.

[0067] Preparation method of Example 3:

[0068] The preparation method of the liquid-modified one-component polyurethane moisture-curing adhesive in Example 3 of this invention includes the following steps:

[0069] S1. Add low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 110℃ and stir for 90 minutes at a stirring speed of 60r / min and a dispersion speed of 1000r / min.

[0070] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add low-crystallinity isocyanate and stir for 90 minutes at a stirring speed of 60 r / min and a dispersion speed of 1200 r / min.

[0071] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a stirring speed of 60 r / min and a dispersion speed of 1000 r / min for 90 min.

[0072] S4. Extrude the material to obtain a moisture-curing adhesive.

[0073] Preparation method of Example 4:

[0074] The preparation method of the liquid-modified one-component polyurethane moisture-curing adhesive in Example 4 of this invention includes the following steps:

[0075] S1. Add low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 110℃ and stir for 90 minutes at a stirring speed of 50r / min and a dispersion speed of 1000r / min.

[0076] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add low-crystallinity isocyanate and stir for 90 minutes at a stirring speed of 60 r / min and a dispersion speed of 1200 r / min.

[0077] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a stirring speed of 50 r / min and a dispersion speed of 1200 r / min for 90 min.

[0078] S4. Extrude the material to obtain a moisture-curing adhesive.

[0079] Preparation method of Example 5:

[0080] The preparation method of the liquid-modified one-component polyurethane moisture-curing adhesive in Example 5 of the present invention includes the following steps:

[0081] S1. Add low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 110℃ and stir for 90 minutes at a stirring speed of 50r / min and a dispersion speed of 1200r / min.

[0082] S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add low-crystallinity isocyanate and stir for 90 minutes at a stirring speed of 60 r / min and a dispersion speed of 1200 r / min.

[0083] S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer, and always maintain a nitrogen atmosphere. Stir at a stirring speed of 50 r / min and a dispersion speed of 1200 r / min for 90 min.

[0084] S4. Extrude the material to obtain a moisture-curing adhesive.

[0085] It should be noted that the organotin catalyst XT-12 used in Examples 1-5 was obtained by pre-mixing organotin catalyst T-12 and BY-3005 polyol in a weight ratio of 1:9. The BY-3005 polyol used here was obtained separately and is not part of the amount of BY-3005 polyol used in Table 1.

[0086] Comparative hot melt adhesive preparation method:

[0087] S1. Add polyol, defoamer, and organotin catalyst T-12 to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure is -0.058MPa. At the same time, adjust the temperature to 120℃ and stir for 120 minutes at a stirring speed of 60r / min and a dispersion speed of 1000r / min.

[0088] S2. Adjust the temperature to 60℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to a slight positive pressure. Add isocyanate and stir for 90 minutes at a stirring speed of 60 r / min and a dispersion speed of 1000 r / min.

[0089] S3. Add the tackifying resin and toughening resin to a 2L vacuum mixer, and always maintain the nitrogen range. Adjust the temperature to 120℃. After the system temperature stabilizes, stir at a stirring speed of 60r / min and a dispersion speed of 1000r / min for 90min.

[0090] S4. Extrude the material to obtain hot melt adhesive.

[0091] Relevant performance tests and results:

[0092] 1. Viscosity test

[0093] Viscosity testing was performed using an NDJ-79 rotary viscometer (Shanghai Weiling Scientific Instruments Co., Ltd.), in accordance with the ASTM D1084-2016 standard.

[0094] 2. Mechanical property testing

[0095] 2.1 Initial bond strength of Examples 1-5 of the present invention: According to the sample size in ASTM D1002-10, the adhesive is applied to the substrate by dispensing to bond the substrates together. After curing in a room temperature environment with 65% humidity for 30 minutes, the initial bond strength sample is obtained, and the shear strength is tested according to ASTM D638 standard.

[0096] Comparative initial tack strength: According to the specimen size in ASTM D1002-10, the adhesive was first heated to 120°C to melt it, and then applied to the substrate by dispensing to bond the substrates together. After curing in a normal temperature environment with 65% humidity for 30 minutes, the initial tack strength specimen was obtained, and the shear strength was tested according to ASTM D638 standard.

[0097] 2.2 Fully cured strength and strength decay rate

[0098] (1) Fully cured strength of Examples 1-5 of the present invention: According to the sample size in ASTM D1002-10, the adhesive was applied to the substrate by dispensing to bond the substrate. After curing in a normal temperature environment with a humidity of 65% for 72 hours, the fully cured sample of the example was obtained. The shear strength was tested according to ASTM D638 standard.

[0099] Comparative fully cured strength: According to the specimen size in ASTM D1002-10, the adhesive was first heated to 120°C to melt it, and then applied to the substrate by dispensing to bond the substrate. After curing in a normal temperature environment with 65% humidity for 96 hours, a comparative fully cured specimen was obtained, and the shear strength was tested according to ASTM D638 standard.

[0100] (2) Strength of Double 85 in one week:

[0101] The fully cured specimens were placed in an environment with 85% humidity and 85°C for one week in accordance with GB / T2423.3-2006 standard. The specimens with double 85 one-week strength were then removed and tested for shear strength in accordance with ASTM D638 standard.

[0102] (3) Strength test at 120℃ for one week and at -40℃ for one week:

[0103] The fully cured specimens were placed in environments with temperatures of 120℃ and -40℃ for one week, respectively, in accordance with GB / T2423.2-2008. The specimens were then removed to obtain strength specimens after one week at 120℃ and strength specimens after one week at -40℃, and the shear strength was tested according to ASTM D638.

[0104] (4) Calculation of intensity attenuation rate:

[0105] The attenuation rate is the percentage decrease in shear strength of a fully cured specimen after environmental testing relative to the shear strength of the fully cured specimen.

[0106] The performance test results of the adhesives in Examples 1-5 and the comparative examples of the present invention are shown in Table 2.

[0107] Table 2. Performance test results of adhesives in different embodiments and comparative examples of the present invention.

[0108]

[0109]

[0110] Note: Since PC, Al, and steel are common substrates, the shear strength between the adhesive and the substrate after complete curing in the embodiments and comparative examples of this invention was tested. Specifically, the steel is 304 stainless steel, and the Al is 1060 aluminum. When testing the strength and strength decay rate, due to the physical characteristics of hot melt adhesives, after heating and melting, the Al substrate has a high thermal conductivity and cools quickly during dispensing, resulting in the adhesive not completely wetting the substrate. However, the liquid moisture-curing adhesive of this invention does not require heating and melting, so its wettability to the substrate is not affected. Therefore, the shear strength between the adhesive of the present invention and the Al substrate can be tested on the Al substrate. In addition, since the Al substrates in the laboratory are all manually polished to simulate anodizing, the surface of the manually polished samples has many scratches, which makes them more susceptible to corrosion in a humid environment such as 85°C, resulting in a further increase in the attenuation rate and non-standard test results. However, using PC substrate, which does not require polishing, the performance of the hot melt adhesive tested is more standardized. Therefore, the shear strength between the adhesive of the present invention and the comparative example and the PC substrate was selected for testing, and the strength attenuation rate was calculated.

[0111] As shown in Table 2 above, the adhesives of Examples 1-5 of the present invention are liquid with a viscosity between 15000-29000 mPa·s and an initial tack strength on PC between 0.25-0.4 MPa; the adhesives of the comparative examples are solid, waxy solids, and have an initial tack strength on PC of 0.95 MPa.

[0112] Furthermore, as shown in Table 2 above, after complete curing, the shear strength between the adhesives of Examples 1-5 of the present invention and PC, Al, and steel substrates is between 9.6-11.95 MPa, 9.55-12.15 MPa, and 9.95-14.05 MPa, respectively. Compared with the shear strength of the adhesives of the comparative examples and their corresponding substrates (8.25 MPa, 6.50 MPa, and 8.10 MPa), the shear strength is increased by at least 16%, 47%, and 23%, respectively. This indicates that the bonding strength between the adhesives of the present invention and the substrates is higher than that between the adhesives of the comparative examples and their corresponding substrates.

[0113] Furthermore, as shown in Table 2 above, the fully cured samples prepared on Al substrates using the adhesives of Examples 1-5 of the present invention showed a certain degree of improvement in the shear strength between the adhesive and the substrate after being placed in environments of 85°C and 120°C for one week compared to the fully cured samples. Moreover, the higher the temperature, the greater the increase in shear strength. However, after being placed in an environment of -40°C for one week, the shear strength of the samples was the same as that of the fully cured samples.

[0114] Furthermore, as shown in Table 2 above, the fully cured samples prepared on PC substrates using the adhesives of Examples 1-5 of the present invention did not show any decrease in shear strength between the adhesive and the substrate after being placed in environments of 85°C and 120°C for one week compared to the fully cured samples. However, the fully cured samples prepared on PC substrates using the comparative adhesives showed a decrease in shear strength between the adhesive and the substrate of 35% and 40%, respectively, after being placed in environments of 85°C and 120°C for one week compared to the fully cured samples.

[0115] 3. Surface condition after complete curing in a high humidity environment

[0116] The adhesives of Examples 1-5 of this invention are applied to the substrate by dispensing and are fully cured after 72 hours in a room temperature environment with 80% humidity. Observation shows that the surface of the adhesive layer is smooth and free of bubbles, indicating that the surface condition is good. This shows that the adhesive of this invention can avoid the formation of bubbles inside the adhesive layer.

[0117] When applying the comparative adhesive, it was first heated to 120°C to melt and then applied to the substrate by dispensing. After curing for 96 hours in a room temperature environment with 80% humidity, it was found that slight bubbling occurred inside the adhesive layer, indicating that the surface condition was not very good.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A liquid-modified one-component polyurethane moisture-curing adhesive, characterized in that, The moisture-curing adhesive comprises the following raw materials in parts by weight: 35-50 parts of low-viscosity polyol, 25-30 parts of low-crystallinity isocyanate, 15-25 parts of bisphenol F epoxy resin, 8-11 parts of non-crystalline toughening resin, 2-4 parts of tackifying resin, 0.5-1 part of defoamer, 0.4-0.6 parts of organotin catalyst XT-12, and 1-1.4 parts of encapsulated organocobalt catalyst; wherein, the organotin catalyst XT-12 is obtained by diluting organotin catalyst T-12 by 10 times with low-viscosity polyol; The low-viscosity polyol is one or two of polycarbonate polyol and polyester polyol; The low-crystallinity isocyanate isophorone diisocyanate; The non-crystalline toughening resin is a modified non-crystalline polyester resin of Toyobo, Japan, model Vylon 670. The defoamer used is BYK-A515 from BYK Chemical Company, Germany.

2. The liquid-modified one-component polyurethane moisture-curing adhesive according to claim 1, characterized in that, The tackifying resin is one or two of oily terpene tackifying resin and aromatic petroleum resin.

3. A method for preparing a liquid-modified one-component polyurethane moisture-curing adhesive as described in any one of claims 1 to 2, characterized in that, The preparation method includes the following steps: S1. Add the low-viscosity polyol, defoamer, organotin catalyst XT-12, and non-crystalline toughening resin to a 2L vacuum double planetary mixer. While evacuating the system, purge with nitrogen until the system pressure reaches -0.058MPa. At the same time, adjust the temperature to 110℃ and stir at a stirring speed of 50-60r / min and a dispersion speed of 1000-1200r / min for 90-100min. S2. Adjust the temperature to 80℃, close the vacuum valve, open the exhaust valve, and continuously introduce nitrogen gas to fill the system with nitrogen gas to positive pressure. Add low-crystallinity isocyanate and stir for 90-100 minutes at a stirring speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min. S3. Adjust the temperature to room temperature. After the system temperature stabilizes, add bisphenol F epoxy resin, encapsulated organic cobalt catalyst, and tackifying resin to a 2L vacuum mixer and maintain a nitrogen atmosphere. Stir at a speed of 50-60 r / min and a dispersion speed of 1000-1200 r / min for 90-100 minutes. S4. Extrude the material to obtain a moisture-curing adhesive.

4. The preparation method according to claim 3, characterized in that, The organotin catalyst XT-12 is obtained by pre-mixing organotin catalyst T-12 with a separately selected low-viscosity polyol in a weight ratio of 1:

9. The separately selected low-viscosity polyol is one or more of the low-viscosity polyols used in step S1.

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