Degradable insulating paint and preparation method thereof

Abstract

The application discloses a degradable insulating paint and a preparation method thereof, and the paint comprises the following raw materials in parts by weight: 20-30 parts of polylactic acid, 10-15 parts of a modifier, 10-15 parts of an unsaturated polyester, 0.1-0.3 parts of an initiator and 0.1-0.3 parts of a surfactant. The modified polylactic acid is prepared by the following steps: the modifier and the polylactic acid are added into a double-screw extruder according to a weight ratio of 3-5:1, and then are melt-extruded to obtain the modified polylactic acid; the modified polylactic acid and the unsaturated polyester are used as a matrix, and the modified polylactic acid is prepared by blending modification of the modifier; after the modifier is blended with the polylactic acid matrix, the lignin itself can significantly improve the biodegradability and mechanical properties of the polylactic acid through the blending modification, and can also improve the heat resistance of the polylactic acid matrix in cooperation with a triazole structure, thereby improving the mechanical properties and heat resistance of the prepared paint film.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of enameled wires, and particularly relates to a degradable insulating paint and a preparation method thereof. BACKGROUND

[0002] The enameled wire is mainly applied in the fields of compressors, transformers and motors, and after reaching the service life, the enameled wire is basically recycled, and copper as a high-quality metal is the first object to be recycled. The enameled wire surface paint film needs to be removed for recycling the metal copper, and the existing removal methods include strong acid and strong alkali corrosion, incineration and mechanical breaking, and these methods have very serious environmental pollution problems, which is a problem to be solved for how to efficiently and greenly recycle the non-ferrous metal copper. Therefore, it is proposed that green environmental protection is a persistent problem, and not only the environmental protection requirements need to be improved in the production process of the enameled wire, but also efforts need to be made on the enameled wire product to develop green and environmentally-friendly enameled wires and increase new requirements of degradability and recyclability.

[0003] As a high-molecular material known by the public, polylactic acid is widely applied in the biomedical field due to good mechanical properties and biocompatibility. The polylactic acid is also widely applied in the packaging material field due to excellent degradability and environmental protection, but the polylactic acid itself has poor heat resistance, and is easily affected by temperature when used in the enameled wire, thereby being limited in use. SUMMARY

[0004] In order to solve the above technical problems, the application provides a degradable insulating paint and a preparation method thereof.

[0005] The purpose of the application can be achieved by the following technical solutions.

[0006] A degradable insulating paint comprises the following raw materials in parts by weight: 20-30 parts of polylactic acid, 10-15 parts of a modifier, 10-15 parts of an unsaturated polyester, 0.1-0.3 parts of an initiator and 0.1-0.3 parts of a surfactant.

[0007] The modified polylactic acid is prepared by the following steps.

[0008] The modifier and the polylactic acid are added into a double-screw extruder in a weight ratio of 3-5:1, and are melt-extruded to prepare the modified polylactic acid.

[0009] Further, the molecular weight of the polylactic acid is 40000-200000.

[0010] Further, the modifier is prepared by the following steps.

[0011] Step S1, adding alkali lignin and 48% hydrobromic acid into 30% lithium bromide aqueous solution, sealing, heating to 90-100℃, magnetic stirring for 1h, cooling to room temperature after stirring, filtering, washing the prepared filter cake with deionized water until neutral, drying, and preparing treated lignin;

[0012] In step S1, the alkali lignin is demethylated by lithium bromide and hydrobromic acid to increase the content of hydroxyl group, and the treated lignin is prepared;

[0013] Step S2, adding the treated lignin into N,N-dimethylformamide, adding epichlorohydrin after magnetic stirring for 1h, heating to 70-75℃, adding 20% sodium hydroxide aqueous solution at a constant speed, continuing to stir and react for 3h, removing unreacted epichlorohydrin by distillation under reduced pressure after the reaction, and washing with deionized water by centrifugation to prepare modified lignin;

[0014] In step S2, the epichlorohydrin reacts with the hydroxyl group on the treated lignin, and then the epoxy group is introduced into the lignin structure.

[0015] Step S3, adding 3-amino-1,2,4-triazole into N,N-dimethylformamide, adding modified lignin after nitrogen bubbling for 30min, adding at a constant speed and heating to 75-80℃, and reacting for 6h under nitrogen protection to prepare a modifier.

[0016] In step S3, the 3-amino-1,2,4-triazole reacts with the epoxy group on the modified lignin, and then the triazole structure is introduced into the lignin. When blended with a polylactic acid matrix, the lignin itself can significantly improve the biodegradability and mechanical properties of the polylactic acid through blending modification, and can also improve the heat resistance of the polylactic acid matrix in cooperation with the triazole structure, thereby improving the mechanical properties and heat resistance of the prepared paint film.

[0017] Further, in step S1, the amount ratio of lignin, hydrobromic acid, and lithium bromide is controlled to be 1-3g:3-5mL:15-25g.

[0018] Further, in step S2, the amount ratio of treated lignin, epichlorohydrin, sodium hydroxide aqueous solution, and N,N-dimethylformamide is controlled to be 1-3g:10-15mL:3-5mL:100mL.

[0019] Further, in step S3, the amount ratio of modified lignin, 3-amino-1,2,4-triazole, and N,N-dimethylformamide is controlled to be 1-2g:1-2g:50-80mL.

[0020] Further, the solvent is one or more of toluene, xylene, and aromatic hydrocarbon solvent oil mixed in any proportion.

[0021] Further, the initiator is one or more of dibenzoyl peroxide, methyl ethyl ketone peroxide, tert-butyl peroxy octanoate mixed in any ratio.

[0022] Further, the surfactant is a polyacrylic resin surfactant.

[0023] A preparation method of a degradable insulating paint comprises the following steps:

[0024] In the first step, the modified polylactic acid is added into half of the solvent, stirred at a uniform speed and heated to 60 DEG C until dissolved, to prepare a mixture a, and cooled to 50 DEG C for standby; the unsaturated polyester is added into another reaction kettle, the remaining solvent is added, heated to 80 DEG C and stirred until dissolved, to prepare a mixture b, and cooled to 50 DEG C for standby;

[0025] In the second step, the mixture a and the mixture b are mixed while hot, stirred for 1 h, the surfactant is added, and stirred for 1 h, then cooled to room temperature, the initiator is added, and stirred for 1 h, to prepare the degradable environment-friendly insulating paint.

[0026] The present application has the following beneficial effects: the present application prepares a degradable insulating paint, which takes the modified polylactic acid and the unsaturated polyester as the matrix, the modified polylactic acid is prepared by blending the modifier, after the modifier is blended with the polylactic acid matrix, the lignin itself can significantly improve the biodegradability and mechanical properties of the polylactic acid through the blending modification, and can also improve the heat resistance of the polylactic acid matrix in cooperation with the triazole structure, to improve the mechanical properties and heat resistance of the prepared paint film. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0028] Embodiment 1: a degradable insulating paint, comprising the following raw materials by weight: 20 parts of polylactic acid, 10 parts of a modifier, 10 parts of an unsaturated polyester, 0.1 part of an initiator, and 0.1 part of a surfactant.

[0029] A preparation method of a degradable insulating paint comprises the following steps:

[0030] In the first step, the modified polylactic acid is added into half of the solvent, stirred at a uniform speed and heated to 60 DEG C until dissolved, to prepare a mixture a, and cooled to 50 DEG C for standby; the unsaturated polyester is added into another reaction kettle, the remaining solvent is added, heated to 80 DEG C and stirred until dissolved, to prepare a mixture b, and cooled to 50 DEG C for standby;

[0031] The second step, after mixing mixture a and mixture b, stirring for 1h, adding surfactant, continue stirring for 1h, then cooling to room temperature, adding initiator, continue stirring for 1h, to prepare the degradable environment-friendly insulating paint.

[0032] The modified polylactic acid is prepared by the following steps:

[0033] The modifier and polylactic acid are added into the twin-screw extruder at a weight ratio of 3:1, melt extruded, to prepare the modified polylactic acid.

[0034] The molecular weight of the polylactic acid is 40000-200000.

[0035] The modifier is prepared by the following steps:

[0036] Step S1, adding alkali lignin and hydrogen bromide acid with a mass fraction of 48% into lithium bromide aqueous solution with a mass fraction of 30%, sealing, heating to 90℃, magnetic stirring for 1h, cooling to room temperature after stirring, filtering, washing the prepared filter cake with deionized water until neutral, drying, to prepare treated lignin, controlling the usage ratio of lignin, hydrogen bromide acid and lithium bromide as 1g:3mL:15g;

[0037] Step S2, adding treated lignin into N,N-dimethylformamide, adding epichlorohydrin after magnetic stirring for 1h, heating to 70℃, uniformly stirring and adding sodium hydroxide aqueous solution with a mass fraction of 20% dropwise, continuing stirring and reacting for 3h, removing unreacted epichlorohydrin by distillation under reduced pressure after reaction, washing by centrifugation with deionized water, to prepare modified lignin, controlling the usage ratio of treated lignin, epichlorohydrin, sodium hydroxide aqueous solution and N,N-dimethylformamide as 1g:10mL:3mL:100mL;

[0038] Step S3, adding 3-amino-1,2,4-triazole into N,N-dimethylformamide, adding modified lignin after nitrogen bubbling for 30min, uniformly stirring and heating to 75-80℃, reacting for 6h under nitrogen protection, to prepare the modifier, controlling the usage ratio of modified lignin, 3-amino-1,2,4-triazole and N,N-dimethylformamide as 1g:1g:50mL.

[0039] The solvent is toluene.

[0040] The initiator is dibenzoyl peroxide.

[0041] The surfactant is polyacrylate-1.

[0042] Example 2: a degradable insulating paint, including the following raw materials by weight: 25 parts of polylactic acid, 12 parts of modifier, 12 parts of unsaturated polyester, 0.2 parts of initiator, 0.2 parts of surfactant;

[0043] A preparation method of a degradable insulating paint, comprising the following steps:

[0044] In the first step, the modified polylactic acid is added into half of the solvent, stirred at a constant speed and heated to 60 DEG C until dissolved, to prepare a mixture a, and then cooled to 50 DEG C for standby; the unsaturated polyester is added into another reaction kettle, the remaining solvent is added, heated to 80 DEG C and stirred until dissolved, to prepare a mixture b, and then cooled to 50 DEG C for standby;

[0045] In the second step, the mixture a and the mixture b are mixed while hot, stirred for 1 h, the surfactant is added, and then stirred for 1 h, and then cooled to room temperature, the initiator is added, and then stirred for 1 h, to prepare the degradable environment-friendly insulating paint.

[0046] The modified polylactic acid is prepared by the following steps:

[0047] The modifier and the polylactic acid are added into a double-screw extruder according to a weight ratio of 4:1, melt-extruded, to prepare the modified polylactic acid.

[0048] The polylactic acid has a molecular weight of 40,000-200,000.

[0049] The modifier is prepared by the following steps:

[0050] In step S1, the alkali lignin and the hydrogen bromide acid with a mass fraction of 48% are added into the lithium bromide aqueous solution with a mass fraction of 30%, sealed, heated to 100 DEG C, magnetically stirred for 1 h, cooled to room temperature after the stirring, filtered, the prepared filter cake is washed to neutral with deionized water, and dried, to prepare the treated lignin, and the lignin, the hydrogen bromide acid and the lithium bromide are controlled according to a ratio of 2g:4mL:20g.

[0051] In step S2, the treated lignin is added into the N,N-dimethylformamide, magnetically stirred for 1 h, then the epichlorohydrin is added, heated to 74 DEG C, stirred at a constant speed and added dropwise with the sodium hydroxide aqueous solution with a mass fraction of 20%, continuously stirred and reacted for 3 h, the unreacted epichlorohydrin is removed by distillation under reduced pressure after the reaction, and then washed by centrifugation with deionized water, to prepare the modified lignin, and the treated lignin, the epichlorohydrin, the sodium hydroxide aqueous solution and the N,N-dimethylformamide are controlled according to a ratio of 2g:14mL:4mL:100mL.

[0052] In step S3, the 3-amino-1,2,4-triazole is added into the N,N-dimethylformamide, nitrogen is bubbled for 30 min, then the modified lignin is added, stirred at a constant speed and heated to 75-80 DEG C, and then reacted for 6 h under nitrogen protection, to prepare the modifier, and the modified lignin, the 3-amino-1,2,4-triazole and the N,N-dimethylformamide are controlled according to a ratio of 1.5g:1.5g:60mL.

[0053] The solvent is xylene.

[0054] The initiator is methyl ethyl ketone peroxide.

[0055] The surfactant is polyacrylate-1.

[0056] Example 3: A degradable insulating paint, comprising the following raw materials by weight: 30 parts of polylactic acid, 15 parts of a modifier, 15 parts of an unsaturated polyester, 0.3 parts of an initiator, and 0.3 parts of a surfactant.

[0057] A preparation method of a degradable insulating paint, comprising the following steps:

[0058] In the first step, the modified polylactic acid is added to half of the solvent, stirred at a constant speed and heated to 60°C until dissolved to prepare a mixture a, and then cooled to 50°C for standby; the unsaturated polyester is added to another reaction kettle, the remaining solvent is added, heated to 80°C and stirred until dissolved to prepare a mixture b, and then cooled to 50°C for standby.

[0059] In the second step, the mixture a and the mixture b are mixed while hot, stirred for 1h, the surfactant is added, and then stirred for 1h, and then cooled to room temperature, the initiator is added, and then stirred for 1h to prepare the degradable environmental protection insulating paint.

[0060] The modified polylactic acid is prepared by the following steps:

[0061] The modifier and the polylactic acid are added to a twin-screw extruder according to a weight ratio of 5:1, and then melt-extruded to prepare the modified polylactic acid.

[0062] The molecular weight of the polylactic acid is 40,000-200,000.

[0063] The modifier is prepared by the following steps:

[0064] In step S1, the alkali lignin and hydrogen bromide with a mass fraction of 48% are added to a lithium bromide aqueous solution with a mass fraction of 30%, sealed, heated to 100°C, and magnetically stirred for 1h, and then cooled to room temperature after stirring, filtered, and the prepared filter cake is washed with deionized water until neutral, and then dried to prepare the treated lignin, and the amount ratio of the lignin, the hydrogen bromide, and the lithium bromide is controlled to be 3g:5mL:25g.

[0065] Step S2, the treated lignin is added into N, N-dimethylformamide, and after magnetic stirring for 1 h, epichlorohydrin is added, the temperature is increased to 70-75 DEG C, uniform stirring and dropwise addition of 20% sodium hydroxide aqueous solution by mass fraction are carried out, and stirring and reaction are continued for 3 h, after the reaction is completed, unreacted epichlorohydrin is removed by distillation under reduced pressure, and the modified lignin is prepared by centrifugal washing with deionized water, and the amount ratio of the treated lignin, epichlorohydrin, sodium hydroxide aqueous solution and N, N-dimethylformamide is controlled to be 3 g: 15 mL: 5 mL: 100 mL;

[0066] Step S3, 3-amino-1, 2, 4-triazole is added into N, N-dimethylformamide, and after nitrogen bubbling for 30 min, the modified lignin is added, uniform stirring and temperature increase to 80 DEG C are carried out, and the modified agent is prepared by keeping the reaction for 6 h under nitrogen protection, and the amount ratio of the modified lignin, 3-amino-1, 2, 4-triazole and N, N-dimethylformamide is controlled to be 2 g: 2 g: 80 mL.

[0067] The solvent is aromatic hydrocarbon solvent oil.

[0068] The initiator is tert-butyl peroxy octanoate.

[0069] The surfactant is polyacrylate-1.

[0070] Comparative Example 1: Compared with Example 1, the polylactic acid is not modified by the modifier, and the rest is the same as Example 1.

[0071] Comparative Example 2: Compared with Example 1, the polylactic acid is modified by lignin as the modifier, and the rest is the same as Example 1.

[0072] The insulating varnish prepared in Examples 1-3 and Comparative Examples 1-2 is used to prepare finished enameled wire, and the enameled wire is tested for related performance, including film thickness, eccentricity, room temperature voltage, softening breakdown, high voltage pinhole and biodegradation performance test; wherein the basic performance test is determined according to the method in GB / T4074, the compost degradation test is tested according to GB / T19811-2005 "Determination of the degree of disintegration of plastic materials under defined composting conditions", and the specific test results are shown in Tables 1-2:

[0073] Table 1: Basic performance

[0074] Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Line surface OK OK OK OK OK Eccentricity 1.15 1.16 1.18 1.20 1.18 Paint film thickness (μm) 41.8 42.0 41.6 41.5 41.8 Softening breakdown (270℃, 2min) PASS PASS PASS PASS PASS High pressure pinhole (30m, 1500V <5) 0 0 0 0 0 Breakdown voltage (kV) 9.88 9.80 9.75 8.88 9.98 Thermal shock (175℃, 30min) PASS PASS PASS PASS PASS Winding (1D) PASS PASS PASS PASS PASS Solvent resistance (≥H) PASS PASS PASS PASS PASS One-way paint scraping 16.28 16.40 16.36 15.01 15.88

[0075] The compost degradation experiment refers to GB / T 19811-2005 "Determination of the degree of disintegration of plastic materials in defined composting test conditions". The 10 cm sample is placed in a vacuum oven and dried at 60 DEG C for 12 h to constant weight. The initial weight of each sample is accurately weighed and recorded by a balance, and recorded as m0. Then each group of samples is buried in a self-made paper box filled with commercially available flower nutrient soil, with a depth of 6 cm and a spacing of 4 cm. After preparation, the paper box is placed in a forced air oven, set at a temperature of 58 DEG C, and sprayed regularly to control the soil humidity between 55% and 70%. The compost degradation experiment period is 9 weeks, and sampling is carried out at 3 weeks, 5 weeks, 7 weeks and 9 weeks, with 3 parallel samples for each group. After sampling, the samples are washed with deionized water, then placed in a vacuum oven and dried at 60 DEG C for 12 h to constant weight, then accurately weighed and recorded as m1. After weighing, the weight loss rate of the sample strip and the change in the appearance of the sample strip are calculated, and the results are averaged. Finally, the weight loss rate of each group is calculated according to the weight loss rate (%) = (m0-m1) / m0x100%.

[0076] Table 2 Comparison of weight loss rate in compost degradation test

[0077] 3rd week 5th week 7th week 9th week Example 1 0.80% 1.72% 3.56% 9.88% Example 2 0.78% 1.70% 3.45% 9.58% Example 3 0.80% 1.77% 3.58% 9.99% Comparative Example 1 0.60% 1.56% 2.88% 5.68% Comparative Example 3 0.72% 1.62% 3.05% 7.65%

[0078] As can be seen from Table 1, the insulating paint prepared in Examples 1-3 and Comparative Examples 1-2 has excellent insulating properties, and the modifier in Example 1-3 can synergize with the polylactic acid matrix to improve the biodegradation performance.

[0079] The above is only an example and description of the concept of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. A biodegradable insulating varnish, characterized in that, It includes the following raw materials by weight: 20-30 parts polylactic acid, 10-15 parts modifier, 10-15 parts unsaturated polyester, 0.1-0.3 parts initiator, and 0.1-0.3 parts surfactant; Modified polylactic acid is prepared through the following steps: Modified polylactic acid is obtained by adding modifier and polylactic acid in a weight ratio of 3-5:1 into a twin-screw extruder and then melt-extruding. The modifier is prepared by the following steps: Step S1: Add alkali lignin and 48% hydrobromic acid to a 30% lithium bromide aqueous solution, seal, heat to 90-100℃, stir magnetically for 1 hour, cool to room temperature after stirring, filter, wash the obtained filter cake with deionized water until neutral, dry, and obtain the treated lignin. Step S2: Add the treated lignin to N,N-dimethylformamide, stir magnetically for 1 hour, then add epichlorohydrin, heat to 70-75℃, stir at a constant speed and add dropwise 20% sodium hydroxide aqueous solution, continue stirring and react for 3 hours, after the reaction is completed, distill under reduced pressure, wash with deionized water by centrifugation to obtain modified lignin. Step S3: Add 3-amino-1,2,4-triazole to N,N-dimethylformamide, bubble with nitrogen for 30 min, then add modified lignin, stir at a uniform speed and heat to 75-80℃, keep the reaction under nitrogen protection for 6 h to obtain the modifier.

2. The biodegradable insulating varnish according to claim 1, characterized in that, The molecular weight of the polylactic acid is 40,000-200,000.

3. The biodegradable insulating varnish according to claim 1, characterized in that, In step S1, the ratio of lignin, hydrobromic acid, and lithium bromide is controlled to be 1-3g: 3-5mL: 15-25g.

4. The biodegradable insulating varnish according to claim 1, characterized in that, In step S2, the ratio of lignin, epichlorohydrin, sodium hydroxide aqueous solution, and N,N-dimethylformamide after treatment is controlled to be 1-3g: 10-15mL: 3-5mL: 100mL.

5. The biodegradable insulating varnish according to claim 1, characterized in that, In step S3, the ratio of modified lignin, 3-amino-1,2,4-triazole and N,N-dimethylformamide is controlled to be 1-2g:1-2g:50-80mL.

6. The biodegradable insulating varnish according to claim 1, characterized in that, It also includes solvents, which are one or more of toluene, xylene and aromatic solvent oils mixed in any proportion.

7. The biodegradable insulating varnish according to claim 1, characterized in that, The initiator is one or more of benzoyl peroxide, methyl ethyl ketone peroxide, and tert-butyl peroxyoctanoate, mixed in any proportion.

8. The biodegradable insulating varnish according to claim 1, characterized in that, The surfactant is a polyacrylic acid resin surfactant.

9. The method for preparing a biodegradable insulating varnish according to claim 1, characterized in that: Includes the following steps: Step 1: Add modified polylactic acid to half of the solvent, stir at a constant speed and heat to 60°C until dissolved to obtain mixture a, cool to 50°C and set aside; add unsaturated polyester to another reactor, add the remaining solvent, heat to 80°C and stir until dissolved to obtain mixture b, cool to 50°C and set aside. Step 2: While still hot, mix mixture a and mixture b, stir for 1 hour, add surfactant, continue stirring for 1 hour, then cool to room temperature, add initiator, and continue stirring for 1 hour to obtain biodegradable and environmentally friendly insulating varnish.