High-toughness pouring sealant and preparation method thereof

Abstract

The invention belongs to the technical field of adhesives, and particularly relates to a high-toughness pouring sealant and a preparation method thereof.The high-toughness pouring sealant comprises a component A and a component B. The component A comprises, by weight, 100 parts of polyurethane prepolymer; the component B is prepared from the following components in parts by weight: 20 to 40 parts of castor oil polyhydric alcohol, 15 to 25 parts of bisphenol A type polypropoxy polyhydric alcohol, 40 to 60 parts of polycaprolactone trihydric alcohol, 0.1 to 0.5 part of a de-foaming agent and 0.02 to 0.15 part of a catalyst; the raw materials of the polyurethane prepolymer comprise polyether amine and diisocyanate, and the mass ratio of the polyether amine to the diisocyanate is 1: (0.75-0.79); the volume ratio of the component A to the component B is 1: 1. Polyether amine and diisocyanate are adopted to synthesize a polyurethane prepolymer, amino groups in polyether amine molecules react with isocyanate groups to generate urea bonds, hydrogen-bond interaction can be formed among molecular chains, and the toughness, impact resistance and cohesion strength of cured colloid are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-toughness pouring sealant and a preparation method thereof, and belongs to the technical field of adhesives. BACKGROUND

[0002] Pouring sealant is a kind of sealing material widely used in the fields of electronics, electricity, automobiles, etc., for packaging and protecting components, and plays the role of insulation, moisture-proof, shock-proof, etc. Traditional polyurethane pouring sealant often has deficiencies in flexibility, and is prone to cracking, peeling, etc. Although epoxy resin pouring sealant has good mechanical strength and adhesion, it is often brittle and difficult to meet the application requirements of high impact resistance.

[0003] In the prior art, the toughness of pouring sealant has been improved by using polyol chain extension, but there are still problems such as poor viscosity control, insufficient adhesion, and low impact toughness. Therefore, it is still necessary to develop a new pouring sealant system with low viscosity and high toughness. SUMMARY

[0004] The present application provides a high-toughness pouring sealant and a preparation method thereof to solve the above technical problems of the prior art.

[0005] The technical solution of the present application to solve the above technical problems is as follows: One of the purposes of the present application is to provide a high-toughness pouring sealant, which comprises component A and component B, and the weight ratio of component A to component B is, The component A comprises 100 parts of polyurethane prepolymer. The component B comprises 20-40 parts of castor oil polyol, 15-25 parts of bisphenol A polypropylene polyol, 40-60 parts of polycaprolactone triol, 0.1-0.5 parts of defoaming agent, and 0.02-0.15 parts of catalyst. The raw materials of the polyurethane prepolymer include polyether amine and diisocyanate, and the mass ratio of the polyether amine to the diisocyanate is 1:0.75-0.79. The volume ratio of the component A to the component B is 1:1.

[0006] Further, the polyether amine is a secondary amine-based polyether diamine, and the molecular weight of the polyether amine is 2000±50.

[0007] Further, the molecular weight of the bisphenol A polypropylene polyol is 400±20.

[0008] Further, the molecular weight of the polycaprolactone triol is 2000±50.

[0009] Further, the diisocyanate is diphenylmethane diisocyanate.

[0010] The selection of the molecular weight of the polyether amine, bisphenol A type polypropylene polyol, and polycaprolactone triol is a selection that achieves the best balance among strength, elongation, and toughness. The polyurethane material product is a microscopically heterogeneous material, which is composed of two phases of soft segments (the main chain of the polyether amine, the long chain of the polyol component of the sealant, which provides flexibility and elasticity) and hard segments (formed by the reaction of isocyanate (NCO) and small molecule hydroxyl, which provides strength and hardness).

[0011] The hard segments and the soft segments are spontaneously separated and aggregated due to thermodynamic incompatibility, forming hard segment microzones and soft segment microzones, and this structure is called "microphase separation". The comprehensive performance of the material depends largely on the perfection of this microphase separation structure.

[0012] The above molecular weight and molecular structure and molecular segment morphology selected by the DOE experiment of the application ensure that the soft segment length is moderate, providing sufficient space for the aggregation of the hard segment, having good microphase separation, and the hard segment can orderly aggregate to form firm "islands" (hard segment microzones), and the hard segment microzones are strong enough to effectively bear the load and are dispersed in the soft "sea" (soft segment phase). These hard segment microzones serve as physical crosslinking points to connect the flexible polyether chains into a network, and the long and flexible polyether chains can fully stretch and crystallize, providing a large deformation capacity and giving the material excellent toughness (toughness: the ability of a material to absorb energy before breaking, i.e. the area under the stress-strain curve), high strength combined with high elongation, so that the material can resist deformation (strength) and absorb energy through large deformation (elongation) when subjected to impact, thus showing excellent impact resistance and tear resistance.

[0013] Further, the content of isocyanate groups in the polyurethane prepolymer is 12% to 12.5%.

[0014] The application adopts the reaction of a secondary amine-based polyether diamine and diisocyanate to generate a polyurethane prepolymer, and the reaction condition is mild and easy to control, and the obtained polyurethane prepolymer has a low viscosity. Since the reactivity of the secondary amine (R2NH) is significantly lower than that of the primary amine (RNH2) and most primary hydroxyl groups (ROH), the reaction rate of the secondary amine with isocyanate is slower, and the reaction can be carried out without catalyst or under mild conditions, effectively avoiding the gel phenomenon caused by local overheating, thereby improving the production safety and process controllability.

[0015] The reaction process of the secondary amine-based polyether diamine and diisocyanate in the application has few side reactions and low crosslinking risk, so that the prepolymer has a narrow molecular weight distribution, and the obtained polyurethane prepolymer has the characteristics of low viscosity, and its viscosity is usually significantly lower than that of the traditional polyether polyol type prepolymer under the same NCO% content, facilitating subsequent processing operations.

[0016] In addition, the tertiary urea bond generated in the polyurethane prepolymer has excellent chemical stability. Since there is no active hydrogen atom on the nitrogen atom, the tertiary urea bond is not prone to hydrolysis, and its hydrolysis resistance is better than that of structures containing ester groups (-COO-) or ordinary urea bonds (-NH-CO-NH-), so that the obtained polyurethane material has a longer service life in humid or underwater environments, and shows good resistance to chemicals such as acids and bases. At the same time, the thermal decomposition temperature of the tertiary urea bond is high, which endows the material with excellent thermal stability. As a strong hydrogen bond site, the tertiary urea bond can cooperate with the urethane bond to form a regular and stable hard segment microzone, and the flexibility of the polyether segment, so that the material has good mechanical properties and durability.

[0017] Further, the defoaming agent is a silicone-based defoaming agent or a polyether-modified silicone-based defoaming agent, preferably YRXP-07B of Guangzhou Yourun.

[0018] Further, the catalyst is one or both of an organotin catalyst and an organic bismuth catalyst.

[0019] The second object of the present application is to provide a preparation method of the high-toughness potting adhesive as described above, comprising the following steps: Preparation of component A: After dehydration of the polyether amine by heating, diisocyanate is added, and the reaction is carried out under nitrogen protection. After cooling, a polyurethane prepolymer is obtained, that is, component A is obtained; Preparation of component B: Castor oil polyol, bisphenol A type polypropylene glycol, polycaprolactone triol, defoaming agent and catalyst are stirred and mixed under vacuum conditions to obtain component B; The A component and the B component are mixed in a volume ratio of 1:1 for use.

[0020] Further, the preparation of component A specifically comprises: polyether amine is added to a reaction container, heated to 100-110 DEG C, vacuumized to remove water, then cooled to 45-55 DEG C, diisocyanate is added, and the reaction is carried out under nitrogen protection at a temperature of 70-75 DEG C for 2-3 hours until the content of NCO is 12-12.5%, and then cooled to room temperature to obtain a polyurethane prepolymer, that is, component A.

[0021] Further, during the preparation of component B, the mixing temperature is ≤60 DEG C, the vacuum degree is -0.08 MPa to -0.09 MPa, and the stirring time is 1-2 hours.

[0022] The present application has the following advantages: The polyurethane prepolymer of the present application is synthesized by polyether amine and diisocyanate, the amino group in the molecule of polyether amine reacts with isocyanate group to form urea bond, and hydrogen bond can be formed between the molecular chains, which significantly improves the toughness, impact resistance and cohesive strength of the cured glue. The structure of the polyurethane prepolymer of the present application and the synergistic effect of the castor oil polyol and the high molecular weight polycaprolactone triol in the B component exhibit excellent bonding performance and adhesion to various substrates such as metals and coatings. Through the ingenious design and ratio optimization of the core raw materials of A and B components, the present application can achieve a good balance of high toughness and high adhesion without adding complex additives such as toughening agent, coupling agent and anti-settling agent, and the formula system is simple and stable in performance. The present application is a two-component solvent-free system with low viscosity and good leveling property, which is suitable for potting of complex structures and has a long pot life, facilitating construction operation. DETAILED DESCRIPTION

[0023] The principles and features of the present application are described below, and the examples are only used to explain the present application and not to limit the scope of the present application.

[0024] Example 1 1. Preparation of prepolymer Preparation of polyurethane prepolymer: 100g of polyether amine (Huntsman production) with a molecular weight of 2000 was put into a flask and heated to 105℃, vacuumed to remove water, then cooled to below 50℃, and 77g of diphenylmethane diisocyanate (Bayer production) was slowly added through a separatory funnel under nitrogen protection, the reaction temperature was controlled at 70℃, and the stirring was continued for 2.5h, when the NCO value was measured to be 12.2%, it was cooled to room temperature, and the polyurethane prepolymer, i.e. component A, was prepared. 2. Preparation of two-component high toughness potting adhesive: D1, A component: polyurethane prepolymer 100g; D2, B component: 30g of castor oil polyol, 20g of bisphenol A type polypropylene polyol (Zhejiang Royal New Material production) with a molecular weight of 400, 50g of polycaprolactone triol (Hubei Juren Chemical Industry production) with a molecular weight of 2000, 0.3g of YRXP-07B, and 0.022g of organic tin catalyst were put into a stirring kettle, vacuumed and stirred for 1.5h, the mixing temperature was ≤60℃, the vacuum degree was-0.08-0.09MPA, and the B component was obtained.

[0025] Example 2 1. Preparation of polyurethane prepolymer as in example 1.

[0026] 2. Preparation of two-component high toughness potting adhesive: D1, A component: polyurethane prepolymer 100g; D2, B component: castor oil polyol 36 g, bisphenol A type polypropylene glycol with molecular weight of 400 24 g, polycaprolactone triol with molecular weight of 2000 40 g, YRXP-07B 0.3 g, organic tin catalyst 0.022 g. Put into stirring kettle, vacuum stirring for 1.5 h, mixing temperature ≤ 60 ℃, vacuum degree -0.08-0.09 MPA, to obtain B component.

[0027] Example 3 1. Preparation of polyurethane prepolymer as in example 1; 2. Preparation of two-component high-toughness pouring sealant: D1, A component: polyurethane prepolymer 100 g; D2, B component: castor oil polyol 24 g, bisphenol A type polypropylene glycol with molecular weight of 400 16 g, polycaprolactone triol with molecular weight of 2000 60 g, YRXP-07B 0.3 g, organic tin catalyst 0.022 g, put into stirring kettle, vacuum stirring for 1.5 h, mixing temperature ≤ 60 ℃, vacuum degree -0.08-0.09 MPA, to obtain B component.

[0028] Comparative example 1 1. Preparation of prepolymer as in example 1; 2. Preparation of two-component pouring sealant D1, A component: polyurethane prepolymer 100 g; D2, B component: castor oil polyol 23 g, bisphenol A type polypropylene glycol with molecular weight of 400 15 g, polycaprolactone triol with molecular weight of 2000 62 g, YRXP-07B 0.3 g, organic tin catalyst 0.022 g, put into stirring kettle, vacuum stirring for 1.5 h, mixing temperature ≤ 60 ℃, vacuum degree -0.08-0.09 MPA, to obtain B component.

[0029] Comparative example 2 1. Preparation of prepolymer as in example 1; 2. Preparation of two-component pouring sealant D1, A component: polyurethane prepolymer 100 g; D2, B component: castor oil polyol 37 g, bisphenol A type polypropylene glycol with molecular weight of 400 25 g, polycaprolactone triol with molecular weight of 2000 38 g, YRXP-07B 0.3 g, organic tin catalyst 0.022 g, put into stirring kettle, vacuum stirring for 1.5 h, mixing temperature ≤ 60 ℃, vacuum degree -0.08-0.09 MPA, to obtain B component.

[0030] Comparative example 3 1. Preparation of polyurethane prepolymer: 100 g of a dihydric polyether PEG-2000 (Lansheng East Chemical) with a molecular weight of 2000 was put into a flask and warmed to 105 DEG C, vacuumized to remove water, then cooled to below 50 DEG C, and then 77 g of diphenylmethane diisocyanate was added, and the reaction was carried out under nitrogen protection, heated to 70 DEG C, and continuously stirred for 3 h, and when the NCO value was measured to be 12.2%, it was cooled to room temperature, and the polyurethane prepolymer, i.e., component A, was prepared.

[0031] 2. Preparation of two-component pouring sealant D1, Component A: 100 g of the above polyurethane prepolymer; D2, 30 g of castor oil polyol, 20 g of bisphenol A type polypropylene glycol with a molecular weight of 400, 50 g of polycaprolactone triol with a molecular weight of 2000, 0.3 g of YRXP-07B, and 0.022 g of organic tin catalyst were put into a stirred tank, vacuumized and stirred for 1.5 h, the mixing temperature was ≤60 DEG C, the vacuum degree was -0.08-0.09 MPA, and component B was obtained.

[0032] Test The pouring sealants prepared in the examples and the comparative examples were subjected to the following performance tests, and the results are shown in Table 1.

[0033] 1. Mechanical property test The tensile shear strength was determined according to GB / T7124-2008.

[0034] The bonding substrates were aluminum plates and epoxy coated plates.

[0035] The elongation at break was determined according to GB / T2567-2008.

[0036] The impact toughness was determined according to GB / T1843-2008 Table 1 Comparison of test data of examples and comparative examples

[0037] The test results show that the pouring sealant prepared in the examples of the present application is significantly superior to the comparative examples in terms of key mechanical property indicators such as tensile strength, elongation at break, shear strength and impact toughness, and fully embodies the excellent effect of the present application in improving the toughness and comprehensive mechanical properties of the pouring sealant.

[0038] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high-toughness potting compound, characterized in that, Includes component A and component B, in parts by weight. Component A comprises 100 parts of polyurethane prepolymer; Component B comprises: 20-40 parts castor oil polyol, 15-25 parts bisphenol A type polypropoxy polyol, 40-60 parts polycaprolactone triol, 0.1-0.5 parts defoamer, and 0.02-0.15 parts catalyst; The raw materials for the polyurethane prepolymer include polyetheramine and diisocyanate, wherein the mass ratio of polyetheramine to diisocyanate is 1:0.75-0.79; The volume ratio of component A to component B is 1:

1.

2. The high-toughness potting compound according to claim 1, characterized in that, The polyetheramine is a secondary amine-based polyether diamine with a molecular weight of 2000±50.

3. The high-toughness potting compound according to claim 1, characterized in that, The polyurethane prepolymer contains 12% to 12.5% ​​isocyanate groups.

4. The high-toughness potting compound according to claim 1, characterized in that, The molecular weight of the bisphenol A type polypropoxy polyol is 400±20.

5. The high-toughness potting compound according to claim 1, characterized in that, The molecular weight of the polycaprolactone triol is 2000±50.

6. The high-toughness potting compound according to claim 1, characterized in that, The defoamer is an organosilicon defoamer or a polyether-modified organosilicon defoamer.

7. The high-toughness potting compound according to claim 1, characterized in that, The catalyst is one or both of organotin catalysts and organobismuth catalysts.

8. A method for preparing a high-toughness potting compound as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Preparation of component A: After heating and dehydrating polyetheramine, diisocyanate is added, and the reaction is carried out under nitrogen protection. After cooling, polyurethane prepolymer is obtained, which is component A. Preparation of component B: Castor oil polyol, bisphenol A type polypropoxy polyol, polycaprolactone triol, defoamer and catalyst are stirred and mixed under vacuum to obtain component B; Mix component A and component B in a 1:1 volume ratio.

9. The method for preparing the high-toughness potting compound according to claim 8, characterized in that, The preparation of component A specifically includes: adding polyetheramine to a reaction vessel, heating to 100℃~110℃, evacuating to remove water, then cooling to 45℃~55℃, adding diisocyanate, and reacting at 70℃~75℃ for 2 to 3 hours under nitrogen protection until the NCO content is 12%~12.5%, then cooling to room temperature to obtain polyurethane prepolymer, which is component A.

10. The method for preparing the high-toughness potting compound according to claim 8, characterized in that, When preparing component B, the mixing temperature is ≤60℃, the vacuum degree is -0.08MPa~-0.09MPa, and the stirring time is 1 hour~2 hours.

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