Ultralow-temperature-resistant urea bond-containing polyurethane adhesive and preparation method thereof

Abstract

The invention discloses an ultralow-temperature-resistant urea-bond-containing polyurethane adhesive and a preparation method thereof, and relates to the technical field of adhesives, and the ultralow-temperature-resistant urea-bond-containing polyurethane adhesive is characterized by comprising the following components in parts by weight: 50-65 parts of urea-bond-containing isocyanate prepolymer; 10 to 20 parts of isocyanate; 0.05 to 1 part of a composite catalyst; 0.2 to 1.5 parts of a latent curing agent; 0.05 to 2 parts of a water absorbent; 5-10 parts of a diluent; the invention has the advantages that the preparation process is simple, interlayer lamination can be carried out at low temperature, the curing speed after bonding is high, the ultra-low temperature resistance and hydrolysis resistance are very good, and the problems of slow curing, low peel strength, ultra-low temperature brittleness and the like of the existing product can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and more specifically to an ultra-low temperature resistant urea-bond-containing polyurethane adhesive and a preparation method thereof. Background Art

[0002] Adhesive refers to a material with good adhesive properties that can form a thin film between the surfaces of two objects and firmly bond them together. It is generally formulated from components such as adhesive resin, curing agent, toughening agent, diluent and modifier. It is widely used in many fields such as daily life, automobiles, ships, energy, rail transportation, etc. With the growing global demand for clean energy, LNG, as an efficient and clean energy source, is increasingly widely used. However, the storage and transportation of LNG needs to be carried out at extremely low temperatures, usually around -162°C. In this ultra-low temperature environment, ordinary adhesives are difficult to meet the sealing and bonding requirements, and are prone to hardening, brittleness, cracking, etc., which leads to sealing failure and weak bonding, causing safety hazards.

[0003] Several low-temperature resistant adhesives have been reported in the prior art. For example, CN102634318A discloses a low-temperature resistant solvent-type polyurethane adhesive and a preparation method thereof, the lowest test temperature of the adhesion strength is higher than -50°C, and the adhesive has a slow curing speed and cannot tolerate the application under ultra-low temperature conditions of -162°C. CN111073587B discloses an ultra-low temperature resistant and environmentally friendly two-component polyurethane adhesive and its preparation and application, which is prepared by mixing component A and component B, component A is an isocyanate-terminated polyurethane prepolymer; component B includes polypropylene carbonate polyol, polytetramethylene glycol modified substance, vegetable oil polyol, cross-linking agent, catalyst, latent curing agent, adhesion promoter, filler, thixotropic agent, and can be used for the bonding of polyurethane foam and fiberglass for LNG ship insulation box. However, since it is a two-component adhesive, the mixing process requires more precision, which increases the difficulty of construction and the complexity of operation, and affects the bonding effect.

[0004] Therefore, in order to solve the above technical problems, the present application proposes an ultra-low temperature resistant urea-bond-containing polyurethane adhesive and a preparation method thereof. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an ultra-low temperature resistant urea-bonded polyurethane adhesive and a preparation method thereof. The adhesive has excellent ultra-low temperature toughness, can achieve a long-lasting strong adhesion effect in an ultra-low temperature environment, and provides a new technical solution to solve the limitations of adhesive application scenarios.

[0006] To achieve the above object, the present invention provides the following technical solution: an ultra-low temperature resistant urea-bonded polyurethane adhesive, wherein the raw materials used include, by weight: 50-65 parts of urea-bonded isocyanate prepolymer; 10-20 parts of isocyanate; 0.05-1 part of composite catalyst; 0.2-1.5 parts of latent curing agent; 0.05-2 parts of water absorbent; 5-10 parts of diluent; 0.5-3 parts adhesion promoter; 0-15 parts of thixotropic agent; 0-30 parts of filler; 0 to 5 parts of pigment.

[0007] Preferably, the urea-bond-containing isocyanate prepolymer is prepared by prepolymerization of polyol, polyaspartic acid ester and isocyanate; The polyol is one or more of polytetramethyl glycol, polyethylene glycol, ethylene oxide polyol, polyester, polyether polyol or polytetrahydrofuran polyol; The isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

[0008] Preferably, the isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate, and the composite catalyst is two or more of dibutyltin dilaurate, stannous octoate, bismuth isooctanoate, zinc isooctanoate, lead isooctanoate, dibutyltin oxide, and tetraisopropyl titanate.

[0009] Preferably, the latent curing agent is one or more of 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine, diphenylmethanebisaldehyde imine, methyl ethyl ketone imine or polycarbodiimide.

[0010] Preferably, the diluent is one or more of ethyl acetate, butyl acetate, xylene, propylene carbonate, and mixed dibasic acid esters; the adhesion promoter is one or more of γ-glycidyloxypropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane; and the thixotropic agent is fumed silica.

[0011] Preferably, the filler is one or more of calcium carbonate, nano calcium carbonate, aluminum hydroxide, and nano aluminum hydroxide.

[0012] The preparation method of the ultra-low temperature resistant urea-containing polyurethane adhesive comprises the following steps: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials: The polyol and polyaspartic acid ester are heated in a reaction kettle, and after the heating is completed, vacuum is drawn to dehydrate, and finally cooled; S2: Addition of isocyanate raw materials: Slowly adding isocyanate to the treated urea-bond-containing isocyanate prepolymer raw material, stirring and heating, to obtain the urea-bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients The water absorbent, diluent and pigment are dried and then mixed and ground evenly; S4: Overall mixing and vacuum degassing After uniform mixing and grinding, the prepared urea-containing isocyanate prepolymer, diisocyanate, thixotropic agent, composite catalyst, latent curing agent, adhesion promoter and dried filler are added in sequence, mixed and stirred evenly, and then vacuum degassing is performed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0013] In S1, the specific steps of pre-treating the urea-bond isocyanate prepolymer raw material are: S1.1: heating the polyol and polyaspartic acid ester in a reaction kettle to 100-105°C; S1.2: Vacuum dehydration at 100-105°C for 1.5-2.5h; S1.3: Finally cool to below 40°C.

[0014] In S2: The specific steps of adding the isocyanate raw material are: S2.1: Slowly add isocyanate, control the addition time to 0.5 to 1 hour, and continue stirring for 1 to 2 hours after addition; S2.2: Then, the mixture is heated to 65-85° C. and stirred for 1-4 hours to obtain the urea-bond-containing isocyanate prepolymer.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The adhesive of the present invention is a single-component room temperature curing type, which can save the glue preparation link during construction and avoid the introduction of factors that affect the bonding quality; 2. The technical solution provided by the present invention introduces a certain amount of low-temperature compliant polytetramethylene glycol (which is contained in the urea-bonded isocyanate prepolymer), which greatly improves the ultra-low temperature resistance of the adhesive; the polyaspartic acid ester polyurea (which is also contained in the urea-bonded isocyanate prepolymer) structure introduced can form multiple interactions with a variety of substrates. In addition, its dosage is relatively low to avoid forming a hard phase region itself, and reliable and long-term adhesion can be achieved on a variety of substrates in an ultra-low temperature environment (liquid nitrogen). Long-term immersion in liquid nitrogen can maintain a high adhesion strength, which can meet the use requirements of ultra-low temperature environments below -162°C; at the same time, multiple interactions make the interface between the adhesive and the substrate more stable, reducing the channels for moisture penetration. When moisture tries to enter the interface between the adhesive and the substrate, it is difficult to penetrate due to the existence of multiple interactions, thereby improving the hydrolysis resistance of the adhesive; 3. The present invention uses a combination of a composite catalyst system (i.e., a composite catalyst) such as "tin-bismuth" and "tin-zinc" and a latent curing agent, which greatly improves the curing speed of the single-component moisture-curing adhesive. The operating time at 20°C is 15 to 20 minutes, the surface drying time at 20°C is about 2 hours, and the complete curing time is about 20 hours. In addition, the product actually processed in this way has basically no air bubbles, thereby further improving the peel strength of the adhesive; In summary, the ultra-low temperature resistant urea-bond polyurethane adhesive described in the present invention has a simple preparation process, can be laminated at low temperatures, has a fast curing speed after bonding, has excellent ultra-low temperature resistance and hydrolysis resistance, and can effectively solve the problems of slow curing, low peel strength, and ultra-low temperature brittleness of existing products. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is the property of the adhesive used in the experiment of the present invention at room temperature; Figure 2 This is a photo of the effect of the thermal insulation foam block being bonded with the adhesive used in the experiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention provides an ultra-low temperature resistant urea-bond-containing polyurethane adhesive, wherein the raw materials used include, by weight: 50-65 parts of urea-bonded isocyanate prepolymer; 10-20 parts of isocyanate; 0.05-1 part of composite catalyst; 0.2-1.5 parts of latent curing agent; 0.05-2 parts of water absorbent; 5-10 parts of diluent; 0.5-3 parts adhesion promoter; 0-15 parts of thixotropic agent; 0-30 parts of filler; 0 to 5 parts of pigment.

[0018] Furthermore, the urea-bond-containing isocyanate prepolymer is prepared by prepolymerization of polyol, polyaspartic acid ester and isocyanate; The polyol is one or more of polytetramethyl glycol, polyethylene glycol, ethylene oxide polyol, polyester, polyether polyol or polytetrahydrofuran polyol; The isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

[0019] The isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; the composite catalyst is two or more of dibutyltin dilaurate, stannous octoate, bismuth isooctanoate, zinc isooctanoate, lead isooctanoate, dibutyltin oxide, and tetraisopropyl titanate; the latent curing agent is 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine, diphenylmethanediimide, methyl ethyl ketone, or the like. The invention relates to one or more imide or polycarbodiimide, the diluent is one or more of ethyl acetate, butyl acetate, xylene, propylene carbonate, and mixed dibasic acid esters, the adhesion promoter is one or more of γ-glycidyloxypropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane, the thixotropic agent is fumed silica, and the filler is one or more of calcium carbonate, nano-calcium carbonate, aluminum hydroxide, and nano-aluminum hydroxide.

[0020] It should be noted that when producing polyurethane adhesives containing urea bonds, thixotropic agents, fillers and pigments are sometimes not needed. This is because thixotropic agents are mainly used to improve the rheological properties of adhesives. If the use scenario of the adhesive does not require high rheological properties, such as in vertical surfaces or small area bonding, the viscosity of the adhesive itself can meet the construction requirements, and there is no need to add thixotropic agents. The addition of thixotropic agents may have an adverse effect on other properties of the adhesive, such as bonding strength, water resistance, and chemical corrosion resistance. For fillers, although they can reduce costs, increase the volume of adhesives, and improve hardness and wear resistance, factors such as the type, particle size, shape and content of fillers will have a complex effect on the performance of adhesives. Improper selection may lead to problems such as increased viscosity, slower curing speed, and decreased bonding strength. In some applications with strict performance requirements, fillers may not be used to ensure stable adhesive performance. Pigments are mainly used to change the color of adhesives. If there are no specific requirements for the color of the adhesive, or in some application scenarios with extremely high requirements for purity, the addition of pigments may introduce impurities and affect the performance of the adhesive, so they may not be used.

[0021] The preparation method of the ultra-low temperature urea-containing polyurethane adhesive of the present invention is described in detail by the following examples: Example 1 The first preparation method of the ultra-low temperature resistant urea-containing polyurethane adhesive of this embodiment is as follows: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials Weigh 500 kg of polytetrahydrofuran polyether polyol (Mw=2000), 150 kg of polyether diol (Mw=1000) and 50 kg of polyaspartic acid ester NH1520 in a reactor, heat it up, vacuum dehydrate it at 102°C for 2 hours, and then cool it to below 40°C; S2: Addition of isocyanate raw materials Slowly add 300 kg of diphenylmethane diisocyanate MDI-100, control the addition time to be 0.5 h, continue stirring for 1 h after the addition, start heating to 80° C., and continue stirring for 3.5 h to obtain the urea bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients Mix and grind 13Kg of dried molecular sieve (water absorbent), 80Kg of ethyl acetate (diluent), 18Kg of titanium dioxide and 2Kg of carbon black (pigment) and add them evenly into the reactor; S4: Overall mixing and vacuum degassing In the reactor, 600 kg of the prepared urea-containing isocyanate prepolymer, 140 kg of diphenylmethane diisocyanate MDI-50, 40 kg of fumed silica (thixotropic agent), 2.5 kg of dibutyltin dilaurate, 3.5 kg of bismuth isooctanoate (dibutyltin dilaurate and bismuth isooctanoate are composite catalysts), 6 kg of diphenylmethanebisaldehyde imine (latent curing agent), 15 kg of γ-glycidyloxypropyltrimethoxysilane (adhesion promoter), 65 kg of dried nano-calcium carbonate and 15 kg of dried aluminum hydroxide (nano-calcium carbonate and aluminum hydroxide are fillers) are added in sequence, mixed and stirred evenly, and then vacuumed and degassed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0022] It should be noted that the urea-bond-containing isocyanate prepolymer is prepared by prepolymerization of polyol, polyaspartic acid ester, isocyanate and polyether diol, wherein the polyol comprises polytetramethylene glycol polyether polyol, the isocyanate comprises diphenylmethane diisocyanate, and the isocyanate comprises diphenylmethane diisocyanate. Example 2 This embodiment provides a second preparation method of a warm urea-containing polyurethane adhesive, and the preparation method is as follows: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials Weigh 350 kg of polytetrahydrofuran polyether polyol (Mw=1000), 300 kg of polyether diol (Mw=2000) and 42 kg of polyaspartic acid ester NH1420 in a reactor, heat it up, vacuum dehydrate it at 105°C for 2 hours, and then cool it to below 40°C; S2: Addition of isocyanate raw materials Slowly add 308 kg of diphenylmethane diisocyanate (liquefied MDI3051), control the addition time to be 0.5 h, continue stirring for 1 h after the addition, start heating to 85° C., continue stirring for 3 h, and obtain the urea bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients Mix and grind 14 kg of dried calcium oxide (water absorbent), 90 kg of butyl acetate (diluent), 10 kg of titanium dioxide and 8 kg of medium chrome yellow (pigment) and add them evenly into the reaction kettle; S4: Overall mixing and vacuum degassing In the reactor, 600 kg of the prepared urea-containing isocyanate prepolymer, 120 kg of diphenylmethane diisocyanate (liquefied MDI2020), 50 kg of fumed silica (thixotropic agent), 3.5 kg of dibutyltin dilaurate, 3.5 kg of zinc isooctanoate (dibutyltin dilaurate and bismuth isooctanoate are composite catalysts), 6 kg of 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine (latent curing agent), 13 kg of γ-aminopropyltriethoxysilane (adhesion promoter), 40 kg of dried nano calcium carbonate and 42 kg of dried calcium carbonate (nano calcium carbonate and calcium carbonate are fillers) are added in sequence, mixed and stirred evenly, and then vacuumed and degassed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0023] Example 3 This embodiment provides a third method for preparing a super low temperature resistant urea-containing polyurethane adhesive, and the preparation method is as follows: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials Weigh 450 kg of polytetrahydrofuran polyether polyol (Mw=1000), 200 kg of polyester diol (Mw=2000) and 47 kg of polyaspartic acid ester NH1420 in a reactor, heat it up, vacuum dehydrate it at 105°C for 2 hours, and then cool it to below 40°C; S2: Addition of isocyanate raw materials 303 kg of diphenylmethane diisocyanate (liquefied MDI2020) was slowly added, and the addition time was controlled to be 0.5 h. After the addition was completed, stirring was continued for 1 h. The mixture was heated to 83° C. and stirring was continued for 3.5 h to obtain the urea-bond-containing isocyanate prepolymer.

[0024] S3: Pre-treatment of excipients 5Kg of dried calcium hydroxide, 10Kg of molecular sieve (calcium hydroxide and molecular sieve are water absorbents), 95Kg of xylene (diluent), 8Kg of titanium dioxide and 7Kg of phthalocyanine blue (pigment) are mixed and ground evenly and added into the reactor. S4: Overall mixing and vacuum degassing Into the reactor, 620 kg of the prepared urea-containing isocyanate prepolymer, 100 kg of diphenylmethane diisocyanate liquefied MDI-50, 45 kg of fumed silica (thixotropic agent), 3.5 kg of dibutyl tin oxide, 4.5 kg of bismuth isooctanoate (dibutyl tin oxide and bismuth isooctanoate are composite catalysts), 5 kg of polycarbodiimide (latent curing agent), 12 kg of γ-glycidyloxypropyl triethoxysilane (adhesion promoter), 28 kg of dried nano aluminum hydroxide and 57 kg of dried calcium carbonate (nano aluminum hydroxide and aluminum hydroxide are fillers) are added in sequence, mixed and stirred evenly, and then vacuumed and degassed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0025] Comparative Example 1 The preparation method of the ultra-low temperature resistant urea-bonded polyurethane adhesive in this comparative example is as follows: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials Weigh 500 kg of polytetrahydrofuran polyether polyol (Mw=2000) and 200 kg of polyether diol (Mw=1000) in a reactor, heat it, vacuum dehydrate it at 102°C for 2 hours, and then cool it to below 40°C; S2: Addition of isocyanate raw materials Slowly add 300 kg of diphenylmethane diisocyanate MDI-100, control the addition time to be 0.5 h, continue stirring for 1 h after the addition, start heating to 80° C., and continue stirring for 3.5 h to obtain the urea bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients Mix and grind 13Kg of dried molecular sieve (water absorbent), 80Kg of ethyl acetate (diluent), 18Kg of titanium dioxide and 2Kg of carbon black (pigment) and add them evenly into the reactor; S4: Overall mixing and vacuum degassing In the reactor, 600 kg of the prepared urea-containing isocyanate prepolymer, 140 kg of diphenylmethane diisocyanate MDI-50, 40 kg of fumed silica (thixotropic agent), 2.5 kg of dibutyltin dilaurate, 3.5 kg of bismuth isooctanoate (dibutyltin dilaurate and bismuth isooctanoate are composite catalysts), 6 kg of diphenylmethanebisaldehyde imine (latent curing agent), 15 kg of γ-glycidyloxypropyltrimethoxysilane (adhesion promoter), 65 kg of dried nano-calcium carbonate and 15 kg of dried aluminum hydroxide (nano-calcium carbonate and aluminum hydroxide are fillers) are added in sequence, mixed and stirred evenly, and then vacuumed and degassed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0026] Comparative Example 2 The preparation method of the ultra-low temperature resistant urea-bonded polyurethane adhesive in this comparative example is as follows: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials Weigh 350 kg of polytetrahydrofuran polyether polyol (Mw=1000), 300 kg of polyether diol (Mw=2000) and 42 kg of polyaspartic acid ester NH1420 in a reactor, heat it up, vacuum dehydrate it at 105°C for 2 hours, and then cool it to below 40°C; S2: Addition of isocyanate raw materials Slowly add 308 kg of diphenylmethane diisocyanate (liquefied MDI3051), control the addition time to be 0.5 h, continue stirring for 1 h after the addition, start heating to 85° C., continue stirring for 3 h, and obtain the urea bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients 14Kg of dried calcium oxide, 90Kg of butyl acetate, 10Kg of titanium dioxide and 8Kg of medium chrome yellow were mixed and ground and evenly added into the reaction kettle; S4: Overall mixing and vacuum degassing Into the reactor, 600 kg of prepared urea-containing isocyanate prepolymer, 120 kg of diphenylmethane diisocyanate (liquefied MDI2020), 50 kg of fumed silica (thixotropic agent), 7 kg of dibutyltin dilaurate (composite catalyst), 6 kg of 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine (latent curing agent), 13 kg of γ-aminopropyltriethoxysilane (adhesion promoter), 40 kg of dried nano calcium carbonate and 42 kg of dried calcium carbonate (nano calcium carbonate and calcium carbonate are fillers) are added in sequence, mixed and stirred evenly, and then vacuumed and degassed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

[0027] Experimental Summary The performance of the ultra-low temperature resistant urea-bond-containing polyurethane adhesives described in Examples 1 to 3 and Comparative Examples 1 and 2 was tested.

[0028] The specific experimental steps are as follows: Step 1: If Figure 1 As shown, the adhesives for the experiment (one each of Examples 1-3 and Comparative Examples 1-2) were prepared and mixed into different colors for the purpose of distinction; Step 2: If Figure 2 As shown, the above adhesive is bonded to the thermal insulation foam block, and the operation time and surface drying time are recorded; Step 3: Then place the foam block in a liquid nitrogen environment (i.e. -162°C) to test the performance and record the shear strength data; Step 4: Cover the bonded foam block insulation layer on the aluminum foil layer of the LNG ship insulation box pipe. The actual internal operating temperature is -183.5℃, which is lower than the LNG operating temperature of -170℃. Test whether it can be used for the LNG ship insulation box pipe. Step 5: After the experiment, open the insulation layer and observe the glue bonding. The adhesives of Examples 1-3 are all well bonded.

[0029] Table 1 Shear strength performance data of adhesives obtained from different embodiments and comparative examples Further analysis shows that the adhesive prepared in the present invention greatly improves the curing speed of the single-component moisture-curing adhesive due to the use of a composite catalytic system such as "tin-bismuth" and "tin-zinc" with an operable time and a latent curing agent. The operable time at 20°C is 15 to 20 minutes, and the surface drying time is 2 to 2.5 hours, while the drying time of the two comparative examples is relatively slow.

[0030] By comparing Example 1 with Comparative Example 1, no polyaspartic acid ester was added to the polyurethane adhesive system, and the shear strength at -162°C was reduced by 31.0%, which can reflect that the introduced polyaspartic acid ester polyurea structure can form multiple interactions with a variety of substrates, achieve reliable and long-term adhesion on a variety of substrates in an ultra-low temperature environment (liquid nitrogen), and maintain a high adhesion strength after long-term immersion in liquid nitrogen, which can meet the use requirements of ultra-low temperature environments below -162°C.

[0031] Comparing Example 2 and Comparative Example 2, a single tin catalyst is used in the polyurethane adhesive system without adding a zinc isooctanoate catalyst. The adhesive is easy to foam, resulting in a 47.8% reduction in shear strength at -162°C. By comparing Example 2 with Example 1 and Example 2, it can be seen that when bismuth isooctanoate is used, the shear strength is not much different. Therefore, composite catalyst systems such as "tin-bismuth" and "tin-zinc" can be selected for use in the production of warm urea-containing polyurethane adhesives.

[0032] In summary, the ultra-low temperature resistant urea-bond polyurethane adhesive of the present invention has the characteristics of fast curing speed and high shear strength at ultra-low temperature. By comparing Example 3 with Example 1, the amount of polyaspartic acid ester added in Example 3 is slightly less than that in Example 1, but the shear strength is still enhanced. It can be reflected from the side that the amount of polyaspartic acid ester added is not the more the better. In actual production, it is best to take a lower amount to avoid forming a hard phase region by itself. At the same time, a certain amount of low-temperature compliant polytetrahydrofuran polyol (introduced when producing urea-bond isocyanate prepolymer) can also be selectively introduced into the technical solution of the present invention to improve The adhesive has ultra-low temperature resistance (polytetramethylene glycol polyol has a unique molecular structure. Its molecular main chain is composed of ether bonds, and the internal rotation barrier of the ether bonds is low, so that the molecular chain can maintain high flexibility and activity at low temperatures. In contrast, some traditional polyol molecular structures may have more rigid groups, which tend to become rigid at low temperatures, resulting in a decrease in adhesive performance). The ultra-low temperature resistant urea-bonded polyurethane adhesive involved in the present invention is mainly used in bonding in deep cold environments such as LNG ship insulation boxes. It is a single-component room temperature curing type, which can save the glue preparation step during construction and avoid introducing factors that affect the bonding quality.

[0033] The following is a description of the reaction mechanism: Urea bonds are formed by prepolymerization of polyols, polyaspartic acid esters and isocyanates in the raw materials. The conventional two-component adhesive is improved into a single component through prepolymerization. Its main function is to increase the crosslinking density and cohesion of the adhesive, thereby improving its strength and durability, but at the same time simplifying the construction difficulty.

[0034] In ultra-low temperature environments, the activity of molecular chains in conventional polyurethane adhesives will be greatly weakened, but compounds containing hydrogen bonds and other physical effects can still play a role in low temperature environments.

[0035] The hydrogen bonding between the adhesive and the bonded material strengthens the intramolecular force, making the bond stronger. In addition, the soft segment (polytetrahydrofuran structure chain) in the adhesive can still maintain flexibility at ultra-low temperatures, which helps maintain the adhesive's adhesion properties.

[0036] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art may make some simple modifications, equivalent changes or modifications using the technical contents disclosed above, which all fall within the protection scope of the present invention.

Claims

1. A super low temperature resistant urea-bond polyurethane adhesive, characterized in that: The raw materials used include, by weight: 50-65 parts of urea-bonded isocyanate prepolymer; 10-20 parts of isocyanate; 0.05-1 part of composite catalyst; 0.2-1.5 parts of latent curing agent; 0.05-2 parts of water absorbent; 5-10 parts of diluent; 0.5 to 3 parts of adhesion promoter.

2. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The raw materials used include, by weight: 0-15 parts of thixotropic agent; 0-30 parts of filler; 0 to 5 parts of pigment.

3. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The urea-bond-containing isocyanate prepolymer is prepared by prepolymerization of polyol, polyaspartic acid ester and isocyanate; The polyol is one or more of polytetramethyl glycol, polyethylene glycol, ethylene oxide polyol, polyester, polyether polyol or polytetrahydrofuran polyol; The isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

4. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The isocyanate is one or more of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; and the composite catalyst is two or more of dibutyltin dilaurate, stannous octoate, bismuth isooctanoate, zinc isooctanoate, lead isooctanoate, dibutyltin oxide, and tetraisopropyl titanate.

5. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The latent curing agent is one or more of 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine, diphenylmethanebisaldehyde imine, methyl ethyl ketone imine or polycarbodiimide.

6. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The diluent is one or more of ethyl acetate, butyl acetate, xylene, propylene carbonate, and mixed dibasic acid esters; the adhesion promoter is one or more of γ-glycidyloxypropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane; and the thixotropic agent is fumed silica.

7. The ultra-low temperature resistant urea-bond polyurethane adhesive according to claim 1, characterized in that: The filler is one or more of calcium carbonate, nano calcium carbonate, aluminum hydroxide, and nano aluminum hydroxide.

8. A method for using the bearing turning processing equipment according to any one of claims 1 to 7, characterized in that: The steps include: S1: Pretreatment of urea-containing isocyanate prepolymer raw materials: The polyol and polyaspartic acid ester are heated in a reaction kettle, and after the heating is completed, vacuum is drawn to dehydrate, and finally cooled; S2: Addition of isocyanate raw materials: Slowly adding isocyanate to the treated urea-bond-containing isocyanate prepolymer raw material, stirring and heating, to obtain the urea-bond-containing isocyanate prepolymer; S3: Pre-treatment of excipients The water absorbent, diluent and pigment are dried and then mixed and ground evenly; S4: Overall mixing and vacuum degassing After uniform mixing and grinding, the prepared urea-containing isocyanate prepolymer, diisocyanate, thixotropic agent, composite catalyst, latent curing agent, adhesion promoter and dried filler are added in sequence, mixed and stirred evenly, and then vacuum degassing is performed to obtain an ultra-low temperature resistant urea-containing polyurethane adhesive.

9. The method for using the bearing turning processing equipment according to any one of claims 8, characterized in that: In S1, the specific steps of pre-treating the urea-bond isocyanate prepolymer raw material are: S1.1: heating the polyol and polyaspartic acid ester in a reaction kettle to 100-105°C; S1.2: Vacuum dehydration at 100-105°C for 1.5-2.5h; S1.3: Finally cool to below 40°C.

10. The method for using the bearing turning processing equipment according to any one of claims 8, characterized in that: In S2: the specific steps of adding the isocyanate raw material are: S2.1: Slowly add isocyanate, control the addition time to 0.5 to 1 hour, and continue stirring for 1 to 2 hours after addition; S2.2: Then, the mixture is heated to 65-85° C. and stirred for 1-4 hours to obtain the urea-bond-containing isocyanate prepolymer.

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