Polyurethane insulating resin as well as preparation method and application thereof

Abstract

The invention relates to the technical field of materials, and discloses polyurethane insulating resin and a preparation method and application thereof.The polyurethane insulating resin is prepared through the steps that polyether polyol serves as a soft segment, binary isocyanate serves as a hard segment, and a coating modified wollastonite fiber additive and a multi-element flame retardant are added in the polymerization reaction process; wherein the advantages of the wollastonite fibers can be efficiently played by adding the coated modified wollastonite fibers, the mechanical property and the high temperature resistance of the polyurethane material are enhanced, the migration and precipitation phenomena can be avoided after the multi-element flame retardant is limited in a polyurethane molecular chain, and in addition, due to the fact that the structure of the multi-element flame retardant contains the phosphorus element and the nitrogen element at the same time, the flame retardance of the polyurethane material is improved. The flame retardant can quickly form an expanded carbon layer when polyurethane burns, oxygen and heat are isolated, and continuous inward burning is prevented, so that the effect that the flame retardant property of the polyurethane material can be greatly improved by adding a small amount of the flame retardant can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a polyurethane insulating resin and a preparation method and application thereof. Background Art

[0002] As an emerging organic polymer material, polyurethane is known as the "fifth plastic" due to its unique chemical structure and excellent physical properties. The main chain of polyurethane contains carbamate groups (-NHCOO), which not only have excellent mechanical properties, wear resistance, and oil resistance, but also show excellent insulation properties, with extremely high insulation resistance and breakdown voltage, which can effectively prevent current leakage and electric shock, and ensure the safe operation of electrical equipment. Therefore, it plays a vital role in the field of electrical manufacturing.

[0003] Since electrical equipment generates heat during operation, it often needs to operate continuously at high temperatures for a long time. This requires that the polymer materials used to manufacture electrical equipment need to have good high temperature resistance. In addition, for safety reasons, the polymer materials used to manufacture electrical equipment should have good flame retardancy. However, polyurethane itself has poor high temperature resistance, resulting in a short service life of electrical equipment. In addition, polyurethane also has poor flame retardant performance and poses certain safety hazards. These shortcomings have severely limited the further application of polyurethane in the field of electrical equipment manufacturing. Therefore, it is urgent to modify polyurethane.

[0004] At present, it is common to improve the comprehensive properties of flame retardancy, high temperature resistance, etc. of polymer materials such as polyurethane by adding functional additives. For example, the invention patent with application number CN202410009374.3 discloses a halogen-free flame retardant polyurethane cable outer sheath material. By preparing cyclic phosphates, hyperbranched polyphosphates, etc. as additives, the flame retardancy level of polyurethane can be effectively improved. However, common small molecule halogen-free flame retardants are difficult to exist in polyurethane materials for a long time, and generally there will be precipitation phenomenon, which leads to the long-term flame retardancy of polyurethane materials cannot be guaranteed. In addition, most inorganic flame retardants are not effective and require a large amount of addition, which will have a negative impact on the mechanical properties of polyurethane materials. Based on this, the present invention provides a polyurethane resin with good high temperature resistance, flame retardancy and other functionalities, which can be used in the manufacture of electrical equipment. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies in the prior art, the present invention provides a polyurethane insulating resin and a preparation method and application thereof.

[0007] (II) Technical solution

[0008] A method for preparing a polyurethane insulating resin, wherein the polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0009]

[0010] The preparation method comprises the following steps:

[0011] The first step is to weigh each raw material according to the weight portion for use;

[0012] Step 2: First, dehydrate the polyether polyol at 100-110°C under vacuum conditions, then reduce the temperature to 40-50°C, then add diisocyanate and two-thirds of the tin catalyst, mix well, gradually increase the temperature to 60-70°C, keep warm and stir for 3-6 hours to form a prepolymer;

[0013] The third step is to add the chain extender and multi-component flame retardant to the prepolymer, stir for 1-2 hours, then add the coated modified wollastonite fiber additive and the remaining amount of tin catalyst. After adding, continue stirring for 4-8 hours, pour into the mold, and cure at a temperature of 80-100°C until it is completely cured.

[0014] As a further embodiment of the present invention, the molecular weight of the polyether polyol is 1000-4000 and the functionality is 2-3; the diisocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate or isofluorinated ketone diisocyanate; and the tin catalyst is at least one of dibutyltin didodecylsulfide, dibutyltin dilaurate, dibutyltin diacetate or stannous octoate.

[0015] As a further solution of the present invention, the preparation method of the coated modified wollastonite fiber additive is as follows:

[0016] Step 1, disperse the wollastonite fiber in a 70% ethanol solution by volume, then add the aminosilane coupling agent to the formed dispersion, stir and mix, then gradually increase the temperature to 70-80°C, keep stirring for 4-8 hours, separate the solid matter, and obtain the modified material;

[0017] Step 2, mix the modified material with N, N-dimethylformamide, ultrasonicate for 20-30 minutes, then add epoxidized natural rubber, stir and mix, pass nitrogen for protection, then increase the temperature to 60-70 ° C, stir for 3-6 hours, centrifuge the product, wash and dry it, and obtain the coated modified wollastonite fiber additive.

[0018] As a further embodiment of the present invention, in Step 1, the aminosilane coupling agent is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0019] As a further embodiment of the present invention, in Step 2, the mass ratio of the epoxidized natural rubber to the modified material is 2-3:1.

[0020] In the above scheme, the surface of wollastonite fiber is first modified by aminosilane coupling agent, and active amino substituents are modified on the surface of wollastonite fiber to obtain modified material. Then, by utilizing the high reactivity of amino substituents, the modified material undergoes ring-opening addition with epoxy groups in the structure of epoxidized natural rubber under heating conditions, thereby modifying the rubber molecular chains on the surface of wollastonite fiber to form wollastonite fiber with rubber molecular chains coated on the surface, that is, coated modified wollastonite fiber additive.

[0021] As a further embodiment of the present invention, the preparation method of the multi-component flame retardant is as follows:

[0022] Toluene and N-hydroxy-5-norbornene-2,3-dicarboximide are added to the reactor, stirring is started until a homogeneous solution is formed, a phosphorus compound and a catalyst are added, nitrogen is passed to exhaust the air, and after heat treatment at 90-100° C. for 3-5 hours, the solvent is evaporated, the temperature is reduced and the material is discharged to obtain a multi-component flame retardant.

[0023] As a further embodiment of the present invention, the catalyst is azobisisobutyronitrile.

[0024] As a further embodiment of the present invention, the phosphorus compound is any one of dimethyl phosphite, diethyl phosphite, diphenyl phosphite or dibenzyl phosphite.

[0025] In the above scheme, azobisisobutyronitrile is used as a catalyst to catalyze the addition of the unsaturated olefin functional group in the structure of N-hydroxy-5-norbornene-2,3-dicarboximide and the PH in the structure of the phosphite compound, thereby obtaining a multi-element flame retardant containing both nitrogen and phosphorus elements in the structure.

[0026] A polyurethane insulating resin, characterized in that it is prepared by adopting the above preparation method.

[0027] An application of a polyurethane insulating resin, which uses the polyurethane insulating resin in the manufacture of electrical appliances.

[0028] (III) Beneficial technical effects

[0029] (1) The present invention first prepares a coated modified wollastonite fiber additive. Since substituted hydroxyl groups are generated during the ring-opening addition reaction, these substituted hydroxyl groups can participate in the reaction during the polymerization of polyurethane, and thus can act as a cross-linking agent. On the one hand, the compatibility of wollastonite fiber and polyurethane is improved, thereby effectively exerting the advantages of wollastonite fiber. In addition, the rubber molecular chain can produce a buffering effect and synergistically enhance the mechanical properties of the polyurethane material with the wollastonite fiber. On the other hand, the wollastonite fiber is connected to the polyurethane in the form of a chemical bond, which can act as a chemical cross-linking point, increase the density of the polyurethane molecular chain, and restrict the movement of the molecular chain, thereby effectively improving the high temperature resistance of the polyurethane.

[0030] (2) The multi-element flame retardant prepared by the present invention contains substituted hydroxyl groups in its structure, which can also participate in the polymerization reaction of polyurethane, so that it can be confined in the polyurethane molecular chain, avoiding the migration and precipitation phenomenon. In addition, since its structure contains both phosphorus and nitrogen elements, it can quickly form an expanded carbon layer when the polyurethane burns, isolate oxygen and heat, and prevent the combustion from continuing inward. Therefore, it can achieve the effect of greatly improving the flame retardant properties of the polyurethane material by adding a small amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0032] Figure 1 This is the infrared analysis test chart of multi-element flame retardant. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0034] Example 1

[0035] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0036]

[0037] The preparation method of the polyurethane insulating resin comprises the following steps:

[0038] The first step is to weigh each raw material according to the weight portion for use;

[0039] Step 2: First, dehydrate the polyether polyol at 100°C under vacuum conditions, then reduce the temperature to 40°C, then add diphenylmethane diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 60°C, and stir for 3 hours to form a prepolymer;

[0040] The third step is to add 2,2-dihydroxymethylpropionic acid and multi-component flame retardant to the prepolymer, stir for 1 hour, then add the coated modified wollastonite fiber additive and the remaining amount of dibutyltin dilaurate. After adding, continue stirring for 4 hours, pour into the mold, and cure at a temperature of 80°C until it is completely cured.

[0041] The polyether polyol is polytetramethylene ether diol, and the number average molecular weight is 2000, and the same shall apply to the following.

[0042] Example 2

[0043] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0044]

[0045] The preparation method of the polyurethane insulating resin comprises the following steps:

[0046] The first step is to weigh each raw material according to the weight portion for use;

[0047] Step 2: First, dehydrate the polyether polyol at 110°C under vacuum conditions, then reduce the temperature to 45°C, then add toluene-2,4-diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 65°C, keep warm and stir for 4 hours to form a prepolymer;

[0048] The third step is to add 2,2-dihydroxymethylpropionic acid and multi-component flame retardant to the prepolymer, stir for 2 hours, then add the coated modified wollastonite fiber additive and the remaining amount of dibutyltin dilaurate. After adding, continue stirring for 6 hours, pour into the mold, and cure at a temperature of 100°C until it is completely cured.

[0049] Example 3

[0050] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0051]

[0052] The preparation method of the polyurethane insulating resin comprises the following steps:

[0053] The first step is to weigh each raw material according to the weight portion for use;

[0054] Step 2: First, dehydrate the polyether polyol at 110°C under vacuum conditions, then reduce the temperature by 50°C, then add toluene-2,4-diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 70°C, keep warm and stir for 6 hours to form a prepolymer;

[0055] The third step is to add 2,2-dihydroxymethylpropionic acid and multi-component flame retardant to the prepolymer, stir for 2 hours, then add the coated modified wollastonite fiber additive and the remaining amount of dibutyltin dilaurate. After adding, continue stirring for 8 hours, pour into the mold, and cure at a temperature of 100°C until it is completely cured.

[0056] Comparative Example 1

[0057] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0058]

[0059] The preparation method of the polyurethane insulating resin comprises the following steps:

[0060] The first step is to weigh each raw material according to the weight portion for use;

[0061] Step 2: First, dehydrate the polyether polyol at 110°C under vacuum conditions, then reduce the temperature to 45°C, then add toluene-2,4-diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 65°C, keep warm and stir for 4 hours to form a prepolymer;

[0062] The third step is to add 2,2-dihydroxymethylpropionic acid to the prepolymer, stir for 2 hours, then add the coated modified wollastonite fiber additive and the remaining amount of dibutyltin dilaurate. After adding, continue stirring for 6 hours, pour into the mold, and cure at a temperature of 100°C until it is completely cured.

[0063] Comparative Example 2

[0064] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0065]

[0066]

[0067] The preparation method of the polyurethane insulating resin comprises the following steps:

[0068] The first step is to weigh each raw material according to the weight portion for use;

[0069] Step 2: First, dehydrate the polyether polyol at 110°C under vacuum conditions, then reduce the temperature to 45°C, then add toluene-2,4-diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 65°C, keep warm and stir for 4 hours to form a prepolymer;

[0070] The third step is to add 2,2-dihydroxymethylpropionic acid and multi-component flame retardant to the prepolymer, stir for 2 hours, then add wollastonite fiber and the remaining amount of dibutyltin dilaurate. After adding, continue stirring for 6 hours, pour into the mold, and cure at a temperature of 100°C until it is completely cured.

[0071] Comparative Example 3

[0072] A polyurethane insulating resin is prepared from the following raw materials in parts by weight:

[0073]

[0074] The preparation method of the polyurethane insulating resin comprises the following steps:

[0075] The first step is to weigh each raw material according to the weight portion for use;

[0076] Step 2: First, dehydrate the polyether polyol at 110°C under vacuum conditions, then reduce the temperature to 45°C, then add toluene-2,4-diisocyanate and two-thirds of dibutyltin dilaurate, mix well, gradually increase the temperature to 65°C, keep warm and stir for 4 hours to form a prepolymer;

[0077] The third step is to add 2,2-dihydroxymethylpropionic acid and multi-component flame retardant to the prepolymer and stir for 2 hours. After adding the remaining amount of dibutyltin dilaurate, continue stirring for 6 hours, pour into the mold, and cure at 100°C until it is completely cured.

[0078] The coated modified wollastonite fiber additive in the above examples and comparative examples is prepared by the following method:

[0079] Step 1, 1.8g of wollastonite fiber was dispersed in a 70% ethanol solution by volume, and then 2.5g of 3-aminopropyltriethoxysilane was added to the formed dispersion, and after the addition, the mixture was stirred and mixed, and then the temperature was gradually increased to 75°C, and after the mixture was stirred for 6 hours, the solid matter was separated to obtain a modified material;

[0080] Step 2, mix 1.2g of modified material with N,N-dimethylformamide, ultrasonicate for 25min, then add 3g of epoxidized natural rubber, stir and mix, pass nitrogen for protection, then raise the temperature to 65℃, stir for 4h, centrifuge the product, wash and dry it to obtain the coated modified wollastonite fiber additive.

[0081] The multi-component flame retardants in the above examples and comparative examples were prepared by the following method:

[0082] Add toluene and 1.5 g of N-hydroxy-5-norbornene-2,3-dicarboximide into the reactor and start stirring until a homogeneous solution is formed. Then add 1 g of dimethyl phosphite and 0.1 g of azobisisobutyronitrile. Expel the air through nitrogen. After heat treatment at 95°C for 4 hours, evaporate the solvent, cool and discharge the material to obtain a multi-component flame retardant.

[0083] Figure 1 This is the infrared analysis test chart of the multi-element flame retardant, where 3267cm -1 The absorption peak at 2890-2985cm is the characteristic absorption peak of hydroxyl group OH. -1 The absorption peaks appearing at 1679 cm-1 are the characteristic absorption peaks of CH for methyl, methylene and methine. -1 The absorption peak at 1218 cm is the characteristic absorption peak of C=O of the imide group. -1 The absorption peak that appears at is the characteristic absorption peak of P=O.

[0084] Test Case

[0085] Refer to standard ASTM D638 for tensile performance test;

[0086] Refer to standard GB / T 1633 to conduct Vicat softening temperature test;

[0087] Refer to standard GB / T 2408-2008 and conduct UL94 vertical burning test;

[0088] The test results are shown in the table below:

[0089] Tensile strength / MPa Vicat softening temperature / ℃ UL94 rating Example 1 21.7 147 V-0 Example 2 22.0 149 V-0 Example 3 21.4 149 V-0 Comparative Example 1 21.1 145 V-2 Comparative Example 2 18.5 130 V-0 Comparative Example 3 14.1 126 V-0

[0090] The analysis results show that the polyurethane insulating resin prepared with coated modified wollastonite fiber additives and multi-component flame retardants as raw materials obviously shows excellent mechanical strength, flame retardant properties of high temperature resistance, and various functions required for the manufacture of composite electrical equipment. After removing the multi-component flame retardant, the mechanical strength and high temperature resistance did not decrease significantly, but the flame retardant performance decreased significantly. After replacing the coated modified wollastonite fiber additive with unmodified wollastonite fiber, there may be problems of interface incompatibility, and the buffering effect of the rubber molecular chain cannot be utilized, resulting in a significant decrease in mechanical properties. At the same time, the cross-linking density of the polyurethane molecular chain is reduced, resulting in a significant decrease in high temperature resistance. The mechanical properties and high temperature resistance of the polyurethane insulating resin prepared without adding wollastonite fiber further decreased.

[0091] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a polyurethane insulating resin, characterized in that: The polyurethane insulating resin is made of the following raw materials in parts by weight: The preparation method comprises the following steps: The first step is to weigh each raw material according to the weight portion for use; Step 2: First, dehydrate the polyether polyol at 100-110°C under vacuum conditions, then reduce the temperature to 40-50°C, then add diisocyanate and two-thirds of the tin catalyst, mix well, gradually increase the temperature to 60-70°C, keep warm and stir for 3-6 hours to form a prepolymer; The third step is to add the chain extender and multi-component flame retardant to the prepolymer, stir for 1-2 hours, then add the coated modified wollastonite fiber additive and the remaining amount of tin catalyst. After adding, continue stirring for 4-8 hours, pour into the mold, and cure at a temperature of 80-100°C until it is completely cured.

2. The method for preparing a polyurethane insulating resin according to claim 1, characterized in that: The molecular weight of the polyether polyol is 1000-4000, and the functionality is 2-3; the diisocyanate is at least one of diphenylmethane diisocyanate, toluene diisocyanate or isofluorinated ketone diisocyanate; the tin catalyst is at least one of didodecylsulfide dibutyltin, dibutyltin dilaurate, dibutyltin diacetate or stannous octoate.

3. The method for preparing a polyurethane insulating resin according to claim 1, characterized in that: The preparation method of the coated modified wollastonite fiber additive is as follows: Step 1, using aminosilane coupling agent to treat the surface of wollastonite fiber to obtain modified material; Step 2: Using N,N-dimethylformamide as a medium and epoxidized natural rubber as a coating material, chemical grafting is performed with the modified material to obtain a coated modified wollastonite fiber additive.

4. The method for preparing a polyurethane insulating resin according to claim 3, characterized in that: In Step 1, the aminosilane coupling agent is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

5. The method for preparing a polyurethane insulating resin according to claim 3, characterized in that: In Step 2, the mass ratio of the epoxidized natural rubber to the modified material is 2-3:

1.

6. The method for preparing a polyurethane insulating resin according to claim 1, characterized in that: The preparation method of the multi-component flame retardant is as follows: With toluene as the reaction medium, N-hydroxy-5-norbornene-2,3-dicarboximide and a phosphorus compound are subjected to heat preservation treatment at 90-100°C for 3-5 hours in the presence of a catalyst, the solvent is evaporated, the temperature is lowered and the material is discharged, thereby obtaining a multi-component flame retardant.

7. The method for preparing a polyurethane insulating resin according to claim 6, characterized in that: The catalyst is azobisisobutyronitrile.

8. The method for preparing a polyurethane insulating resin according to claim 6, characterized in that: The phosphorus compound is any one of dimethyl phosphite, diethyl phosphite, diphenyl phosphite or dibenzyl phosphite.

9. A polyurethane insulating resin, characterized in that: The method is prepared according to claim 1.

10. An application of polyurethane insulating resin, characterized in that: The polyurethane insulating resin is applied in the manufacture of electrical appliances.

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