Transparent flame-retardant polyurethane pouring sealant as well as preparation method and application thereof

Abstract

The invention provides a transparent flame-retardant polyurethane pouring sealant as well as a preparation method and application thereof. The polyurethane pouring sealant is prepared by mixing a component A and a component B according to a mass ratio of 2: 1, the component A is prepared from the following components in parts by weight: 10 to 20 parts of high molecular weight and high functionality polyether polyol, 10 to 20 parts of low molecular weight and high functionality polyether polyol, 10 to 20 parts of polyester polyol, 20 to 50 parts of phosphorus-containing active liquid flame retardant, 20 to 50 parts of phosphorus-containing inactive liquid flame retardant and 0.001 to 5 parts of catalyst; and the component B is isocyanate. The polyurethane pouring sealant is moderate in mixing viscosity, easy to operate, adjustable in operable time, transparent, flame-retardant, excellent in mechanical property, good in bonding force to various materials, free of plasticizers, environmentally friendly and capable of being widely applied to pouring and protection in the industries of household appliances and electronic components.

Description

Technical Field

[0001] The invention belongs to the technical field of potting adhesives, and in particular relates to a transparent flame-retardant polyurethane potting adhesive and a preparation method and application thereof. Background Art

[0002] Potting glue can be mainly divided into three categories: epoxy potting glue, polyurethane potting glue and silicone potting glue. Epoxy potting glue has poor toughness, easy to crack, and is not resistant to cold and hot shocks. Silicone potting glue has low hardness, low bonding strength and high cost. Polyurethane potting glue has the characteristics of adjustable hardness, moderate bonding strength, high elasticity, high impact resistance, high wear resistance and excellent low temperature resistance. Compared with epoxy potting glue and silicone potting glue, polyurethane potting glue is suitable for potting in more fields.

[0003] With the continuous development of science and technology, higher requirements are put forward for the comprehensive performance of polyurethane potting glue. More and more application fields, especially electronic products that require transparent appearance, require polyurethane potting glue to be transparent, flame retardant, and have excellent mechanical properties and aging resistance to meet the potting and protection requirements of household appliances and electronic components. In order to achieve high flame retardant, mechanical properties and aging resistance, a large amount of powder flame retardant is often needed to be added, which makes the potting glue opaque, affects the appearance, and makes it impossible to identify faulty electronic components.

[0004] Patent CN101928377A discloses a method for preparing a transparent flame retardant potting glue, but its flame retardant performance only reaches the V1 level, and its mechanical properties are poor, and its tensile strength is less than 1.5Mpa. Patent CN107286895A discloses a method for preparing a transparent flame retardant potting glue, but it uses a large amount of non-environmentally friendly plasticizers, and its non-reactive liquid flame retardant is easy to precipitate after long-term aging, reducing the flame retardant performance, and its mechanical properties are poor, and its tensile strength is 2~3Mpa. Patent CN117343276B discloses a method for preparing a transparent flame retardant potting glue. Although the use of reactive flame retardants solves the problem of decreased flame retardant performance after aging, in order to obtain high flame retardant performance, a large amount of reactive flame retardants, i.e., chain extenders, are used, resulting in a high hardness Shore A hardness of 94~99 and a tensile strength of 8.22~22.69Mpa, which reduces its shock absorption function and high and low temperature cycle resistance, which is not conducive to the protection of electronic components. Summary of the invention

[0005] In view of this, the present invention provides a transparent flame-retardant polyurethane potting adhesive and a preparation method and application thereof. The prepared polyurethane potting adhesive is transparent, which is convenient for inspecting electronic components, and has suitable viscosity, flame retardancy and mechanical properties, and can perfectly fit the potting of electronic components.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A transparent flame-retardant polyurethane potting adhesive, wherein the polyurethane potting adhesive is prepared by mixing component A and component B in a mass ratio of 2:1; The component A comprises the following components in parts by weight: 10-20 parts of high molecular weight high functionality polyether polyol, 10-20 parts of low molecular weight high functionality polyether polyol, 10-20 parts of polyester polyol, 20-50 parts of phosphorus-containing active liquid flame retardant, 20-50 parts of phosphorus-containing inactive liquid flame retardant, and 0.001-5 parts of catalyst; The component B is isocyanate; Wherein, the high molecular weight and high functionality polyether polyol has a molecular weight of 4000≤Mn≤8000 and a functionality ≥3; The low molecular weight and high functionality polyether polyol has a molecular weight of 300≤Mn<4000 and a functionality ≥3; The polyester polyol has a molecular weight of 500≤Mn≤5000 and is synthesized from 3-hydroxymethyl-1,5-pentanediol and aliphatic dibasic acid. The mass content of 3-hydroxymethyl-1,5-pentanediol is ≥30%.

[0007] Furthermore, the structure of the phosphorus-containing active liquid flame retardant is as follows: ; in, , 1≤n≤10.

[0008] Furthermore, the phosphorus-containing inactive liquid flame retardant is selected from at least one of tris(2-chloropropyl) phosphate (TCPP), triethyl phosphate (TEP), triisopropylphenyl phosphate (IPPP), tricresyl phosphate (TCP), trimethyl phosphate (TMP), triisobutyl phosphate (TIBP), diphenyl isooctyl phosphate (DPOP), diphenyl isodecyl phosphate (DPDP), trioctyl phosphate (TOP), pentaerythritol phosphate (PEPA), toluene diphenyl phosphate (CDP), triphenyl phosphate (TPP), and tris(2-chloroethyl) phosphate (TCEP).

[0009] Furthermore, the catalyst is selected from at least one of an organic tin catalyst, an organic bismuth catalyst, and an amine catalyst.

[0010] Furthermore, the isocyanate of component B is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0011] The preparation method of the polyurethane potting adhesive comprises the following steps: S1. Add high molecular weight and high functionality polyether polyol, low molecular weight and high functionality polyether polyol, polyester polyol, phosphorus-containing active liquid flame retardant, and phosphorus-containing inactive liquid flame retardant to a mixer according to weight fraction, evacuate, heat and stir, mix evenly, cool with nitrogen, add a catalyst, stir for 15 to 30 minutes, and seal the discharge to obtain component A; Among them, polyester polyol is obtained by dehydration condensation reaction of 3-hydroxymethyl-1,5-pentanediol and aliphatic dibasic acid; S2. The prepared component A and component B (sealed and packaged under nitrogen protection before use) are mixed evenly in a weight ratio of 2:1, and cured to obtain the polyurethane potting adhesive.

[0012] Furthermore, the heating and stirring conditions in step S1 are as follows: temperature 100-120° C., stirring 1.5-2.5 h; nitrogen is passed through to cool the mixture to 60-80° C.

[0013] Furthermore, the curing conditions in step S2 are: curing at 25° C. for 24 to 36 hours, or curing at 60° C. for 3 to 6 hours.

[0014] The above polyurethane potting glue is used in potting of household appliances and electronic components industries.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The polyurethane potting glue prepared by the present invention has moderate viscosity (5000-7000 mPa·s), adjustable operating time (15-60 min), and is easy to construct and operate. After curing, it is transparent, reaches V0 flame retardancy, and realizes high strength (5-8 Mpa) and high elongation at break (200%-300%). After aging, its mechanical properties are well maintained, no cracking and the like occurs, and it is still V0 flame retardant and has good transparency, and can be well applied to the potting of electronic components in various use environments. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0017] Example 1 This embodiment provides a transparent flame retardant polyurethane potting glue and a preparation method thereof, and the specific operations are as follows: S1. Take 10 parts of high molecular weight and high functionality polyether polyol (Mn=4000, functionality 3), 20 parts of low molecular weight and high functionality polyether polyol (Mn=300, functionality 3), 10 parts of polyester polyol, 20 parts of phosphorus-containing active liquid flame retardant (n=1 at this time), and 50 parts of phosphorus-containing inactive liquid flame retardant IPPP by weight, add them to a mixer, evacuate, heat to 100°C and stir for 2 hours, mix evenly, cool to 60°C through nitrogen, add 0.001 parts of dibutyltin dilaurate as a catalyst, stir for 20 minutes, and seal the discharge to obtain component A.

[0018] Among them, polyester polyol (Mn=2000) is prepared by dehydration condensation reaction of 3-hydroxymethyl-1,5-pentanediol and adipic acid.

[0019] S2. The prepared component A and component B (diphenylmethane diisocyanate modified by carbodiimide) are uniformly mixed in a weight ratio of 2:1, and cured at 25° C. for 24 hours to obtain the polyurethane potting adhesive.

[0020] Example 2 This embodiment provides a transparent flame retardant polyurethane potting glue and a preparation method thereof, and the specific operations are as follows: S1. Take 20 parts of high molecular weight and high functionality polyether polyol (Mn=8000, functionality 3), 10 parts of low molecular weight and high functionality polyether polyol (Mn=3500, functionality 3), 20 parts of polyester polyol, 50 parts of phosphorus-containing active liquid flame retardant (n=5 at this time), and 20 parts of phosphorus-containing inactive liquid flame retardant TCPP by weight, add them to a mixer, evacuate, heat to 120°C and stir for 2 hours, mix evenly, cool to 80°C through nitrogen, add 5 parts of bismuth isooctanoate catalyst, stir for 30 minutes, and seal the discharge to obtain component A.

[0021] Among them, polyester polyol (Mn=5000) is prepared by dehydration condensation reaction of 3-hydroxymethyl-1,5-pentanediol and adipic acid.

[0022] S2. The prepared component A and component B (diphenylmethane diisocyanate MDI-50) are uniformly mixed in a weight ratio of 2:1, and cured at 25° C. for 36 hours to obtain the polyurethane potting adhesive.

[0023] Example 3 This embodiment provides a transparent flame retardant polyurethane potting glue and a preparation method thereof, and the specific operations are as follows: S1. Take 15 parts of high molecular weight and high functionality polyether polyol (Mn=6000, functionality 4), 15 parts of low molecular weight and high functionality polyether polyol (Mn=1000, functionality 3), 15 parts of polyester polyol, 35 parts of phosphorus-containing active liquid flame retardant (n=10 at this time), and 35 parts of phosphorus-containing inactive liquid flame retardant TOP by weight, add them to a mixer, evacuate, heat to 110°C and stir for 2 hours, mix evenly, cool to 70°C through nitrogen, add 3 parts of catalyst N,N-dimethylcyclohexylamine, stir for 30 minutes, and seal the discharge to obtain component A.

[0024] Among them, polyester polyol (Mn=500) is prepared by dehydration condensation reaction of 3-hydroxymethyl-1,5-pentanediol and adipic acid.

[0025] S2. The prepared component A and component B (hexamethylene diisocyanate HDI) are uniformly mixed in a weight ratio of 2:1, and cured at 25° C. for 30 hours to obtain the polyurethane potting adhesive.

[0026] Example 4 This embodiment provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are substantially the same as those of Embodiment 1, except that the polyester polyol in component A is prepared from 3-hydroxymethyl-1,5-pentanediol and sebacic acid (Mn=2000), and the rest remain unchanged.

[0027] Comparative Example 1 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those in Example 1, except that the low molecular weight and high functionality polyether polyol (Mn=300, functionality is 3) in component A is replaced by an equal amount of high molecular weight and high functionality polyether polyol (Mn=4000, functionality is 3), and the rest remain unchanged.

[0028] Comparative Example 2 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those in Example 1, except that the high molecular weight and high functionality polyether polyol (Mn=4000, functionality is 3) in component A is replaced by an equal amount of low molecular weight and high functionality polyether polyol (Mn=300, functionality is 3), and the rest remain unchanged.

[0029] Comparative Example 3 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those of Example 1, except that the polyester polyol in component A adopts a conventional polyester polyol of equal molecular weight (prepared by dehydration condensation reaction of diethylene glycol and adipic acid).

[0030] Comparative Example 4 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are substantially the same as those of Example 1, except that the polyester polyol in component A is replaced by an equal amount of castor oil, and the rest remain unchanged.

[0031] Comparative Example 5 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those of Example 1, except that the phosphorus-containing active liquid flame retardant in component A is replaced by an equal amount of phosphorus-containing inactive liquid flame retardant, and the rest remain unchanged.

[0032] Comparative Example 6 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those of Example 1, except that the phosphorus-containing inactive liquid flame retardant in component A is replaced by an equal amount of phosphorus-containing active liquid flame retardant, and the rest remain unchanged.

[0033] Comparative Example 7 This comparative example provides a transparent flame-retardant polyurethane potting adhesive and a preparation method thereof. The material composition and preparation method thereof are basically the same as those of Example 1, except that the phosphorus-containing active liquid flame retardant in component A is replaced by an equal amount of phosphorus-containing active liquid flame retardant FR-600 (Qingdao Lianmei Chemical), and the rest remain unchanged.

[0034] Furthermore, in order to understand the specific performance of the polyurethane potting adhesives prepared in the above embodiments and comparative examples, the following tests were conducted, and the test results are shown in Table 1.

[0035] Table 1 Test results of various properties of prepared polyurethane potting glues

[0036] Furthermore, in order to understand the anti-aging performance of the above polyurethane potting glues, the polyurethane potting glues prepared by the same method as above were aged respectively, and the specific aging conditions were as follows: 1. High temperature aging: 85℃ for 500 hours; 2. High and low temperature impact aging: -40~85℃ cycle 500 times.

[0037] After the aging treatment, the samples were taken out and placed at room temperature for 24 hours, and tensile strength, elongation at break, flame retardancy test and appearance observation were performed. The results are shown in Table 2.

[0038] Table 2 Properties of polyurethane potting glue after aging

[0039] From the experimental results in Table 1, it can be seen that the polyurethane potting glue provided in Examples 1-4 has moderate viscosity (5000-7000 mPa·s), adjustable operating time (15-60 min), and is easy to construct and operate. It achieves high strength (5-8 Mpa) and high elongation at break (200%-300%), and is V0 flame retardant with excellent transparency.

[0040] The mechanical properties of Comparative Examples 1, 3, 4, 5 and 7 are all poor, with low strength, poor toughness, and the flame retardant grade can only reach V2 or V1. Comparative Example 3 is opaque. Although the flame retardant grade of Comparative Examples 2 and 6 can reach V0, the strength is too high, and the materials are hard and brittle.

[0041] From the experimental results in Table 2, it can be seen that the polyurethane potting glue provided by Examples 1-4 maintains good mechanical properties after aging, and is still V0 flame retardant and has excellent transparency. The mechanical properties of Comparative Examples 1, 3, 4, 5, and 7 are still poor, and the flame retardant level can only reach V2 or V1, and Comparative Example 3 is still opaque; although the flame retardant level of Comparative Examples 2 and 6 can reach V0, they all crack due to excessive strength and poor toughness.

[0042] The present invention prepares a transparent flame-retardant polyurethane potting glue by compounding high-functionality polyether polyols with high and low molecular weights, adding polyester polyols prepared with 3-hydroxymethyl-1,5-pentanediol as raw materials and active and inactive phosphorus-containing liquid flame retardants, and reasonably matching them. The potting glue has moderate viscosity, is easy to operate, and has an adjustable operating time; it is transparent and reaches V0 flame retardancy; it has excellent mechanical properties, high strength and toughness, a tensile strength of 5-8Mpa, and an elongation at break of 200%-300%; it has excellent aging resistance, can still reach V0 flame retardancy after aging, has excellent transparency, and does not have cracking and other phenomena.

[0043] Other raw materials or structures not specifically described in the present invention already exist in the prior art and can be directly purchased from the market.

[0044] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A transparent flame retardant polyurethane potting adhesive, characterized in that: The polyurethane potting glue is prepared by mixing component A and component B in a mass ratio of 2:1; The component A comprises the following components in parts by weight: 10-20 parts of high molecular weight high functionality polyether polyol, 10-20 parts of low molecular weight high functionality polyether polyol, 10-20 parts of polyester polyol, 20-50 parts of phosphorus-containing active liquid flame retardant, 20-50 parts of phosphorus-containing inactive liquid flame retardant, and 0.001-5 parts of catalyst; The component B is isocyanate; Wherein, the high molecular weight and high functionality polyether polyol has a molecular weight of 4000≤Mn≤8000 and a functionality ≥3; The low molecular weight and high functionality polyether polyol has a molecular weight of 300≤Mn<4000 and a functionality ≥3; The polyester polyol has a molecular weight of 500≤Mn≤5000, is synthesized from 3-hydroxymethyl-1,5-pentanediol and aliphatic dibasic acid, and the mass content of 3-hydroxymethyl-1,5-pentanediol is ≥30%; The structure of the phosphorus-containing active liquid flame retardant is as follows: ;in, , 1≤n≤10.

2. The polyurethane potting adhesive according to claim 1, characterized in that: The phosphorus-containing inactive liquid flame retardant is selected from at least one of tris(2-chloropropyl) phosphate (TCPP), triethyl phosphate (TEP), triisopropylphenyl phosphate (IPPP), tricresyl phosphate (TCP), trimethyl phosphate (TMP), triisobutyl phosphate (TIBP), diphenyl isooctyl phosphate (DPOP), diphenyl isodecyl phosphate (DPDP), trioctyl phosphate (TOP), pentaerythritol phosphate (PEPA), toluene diphenyl phosphate (CDP), triphenyl phosphate (TPP), and tris(2-chloroethyl) phosphate (TCEP).

3. The polyurethane potting adhesive according to claim 1, characterized in that: The catalyst is selected from at least one of an organic tin catalyst, an organic bismuth catalyst and an amine catalyst.

4. The polyurethane potting adhesive according to claim 1, characterized in that: The isocyanate of the B component is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate.

5. A method for preparing the polyurethane potting adhesive according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Add high molecular weight and high functionality polyether polyol, low molecular weight and high functionality polyether polyol, polyester polyol, phosphorus-containing active liquid flame retardant, and phosphorus-containing inactive liquid flame retardant to a mixer according to weight fraction, evacuate, heat and stir, mix evenly, cool with nitrogen, add a catalyst, stir for 15 to 30 minutes, and seal the discharge to obtain component A; Among them, polyester polyol is obtained by dehydration condensation reaction of 3-hydroxymethyl-1,5-pentanediol and aliphatic dibasic acid; S2. The prepared component A and component B are mixed evenly in a weight ratio of 2:1, and cured to obtain the polyurethane potting adhesive.

6. The preparation method according to claim 5, characterized in that: The heating and stirring conditions in step S1 are as follows: temperature 100-120° C., stirring 1.5-2.5 h; cooling to 60-80° C. by nitrogen gas.

7. The preparation method according to claim 5, characterized in that: The curing conditions in step S2 are: curing at 25° C. for 24 to 36 hours, or curing at 60° C. for 3 to 6 hours.

8. Application of the polyurethane potting adhesive according to any one of claims 1 to 4 in potting of household appliances and electronic components.

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