Modified wollastonite, preparation method thereof and application of modified wollastonite in epoxy pouring sealant

Abstract

The invention provides modified wollastonite, a preparation method thereof and application of the modified wollastonite in an epoxy pouring sealant, and belongs to the technical field of inorganic nonmetallic materials. The wollastonite powder is subjected to composite surface modification treatment and iron removal treatment; the composite surface modification treatment is carried out by adopting a composite surface modifier, and the composite surface modifier comprises an epoxy silane coupling agent, a phosphate modifier and a polyether modifier. The modified wollastonite prepared by the production method disclosed by the invention has the advantages of high length-diameter ratio, low oil absorption value and good dispersing performance in the epoxy pouring sealant, the viscosity of the epoxy pouring sealant can be reduced, the mechanical property and insulating property of an adhesive tape can be improved, and the size shrinkage rate can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, in particular to modified wollastonite, a preparation method thereof and application of the modified wollastonite in epoxy potting adhesive. Background Art

[0002] Epoxy potting compound refers to a type of liquid encapsulation or potting material made primarily from epoxy resin, supplemented with various functional additives, and a suitable curing agent. Due to its superior overall performance, epoxy potting compound is widely used for insulating and moisture-proofing electronic components such as electronic transformers, negative ion generators, modular power supplies, high-voltage transformers, aquarium pumps, relays, capacitors, ignition coils, mutual inductors, AC / DC modules, LEDs, LED modules, AC capacitors (vertical, horizontal, box, and film), lighting, and electrical appliances. With the demands of development, the requirements for epoxy potting compound are also increasing, particularly in terms of insulation, heat dissipation, flame retardancy, mechanical properties, and dimensional shrinkage.

[0003] Wollastonite is a chain metasilicate with fibrous and needle-like shapes. Due to its excellent insulation, high whiteness, good dielectric properties, and high heat and weather resistance, it is widely used in ceramics, chemicals, metallurgy, papermaking, plastics, coatings, rubber, adhesives, and other fields. It is a new inorganic non-metallic material with very comprehensive properties.

[0004] The formula of epoxy potting compound mainly consists of epoxy resin, curing agent, diluent, filler, etc. Among them, common fillers include wollastonite and silica powder, which are used to improve the mechanical properties, thermal properties, electrical insulation properties, etc. of the compound. Silica powder has a granular structure and is slightly insufficient in mechanical strength and dimensional shrinkage, and cannot meet the performance requirements of epoxy potting compound for high mechanical strength and low dimensional shrinkage. Although wollastonite has a needle-like structure and a large aspect ratio, and excels in mechanical strength and dimensional shrinkage, its surface hydrophilicity makes it difficult to disperse in the potting compound, and its interfacial bonding with epoxy resin is weak. This results in a small amount of wollastonite added to the potting compound, high production costs, and the mechanical properties, thermal properties, and insulation of the potting compound are also below expectations. Summary of the Invention

[0005] The purpose of the present invention is to provide a modified wollastonite and a preparation method thereof and application in epoxy potting compound, so as to solve the technical problems of poor dispersion, high viscosity and poor mechanical properties of wollastonite powder in epoxy potting compound.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing modified wollastonite, comprising the following steps:

[0008] The wollastonite powder can be subjected to composite surface modification and iron removal treatment;

[0009] The composite surface modification treatment is performed using a composite surface modifier, which comprises an epoxy silane coupling agent, a phosphate modifier and a polyether modifier.

[0010] Furthermore, the composite surface modifier also contains anhydrous ethanol and water, and the mass ratio of the epoxy silane coupling agent, phosphate modifier, polyether modifier, anhydrous ethanol and water is 3-8:2-6:1-4:5-15:0.5-1.5.

[0011] Furthermore, the epoxysilane coupling agent comprises 3-(2,3-epoxypropyloxy)propylmethyldiethoxysilane and / or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane;

[0012] The phosphate modifier comprises one or more of polyoxyethylene ether phosphate, polyarylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether phosphate and nonylphenol polyoxyethylene ether phosphate;

[0013] The polyether modifier comprises polyether trisiloxane and / or polyether-modified polydimethylsiloxane.

[0014] Furthermore, the composite surface modification treatment is carried out under heating and stirring, the heating temperature is 60 to 100° C., and the stirring time is 20 to 50 minutes.

[0015] Furthermore, the addition amount of the composite surface modifier is 1.2-2.4% of the mass of the wollastonite powder, and the composite surface modifier is sprayed on the wollastonite powder to perform composite surface modification treatment.

[0016] Furthermore, the D50 of the wollastonite powder is 11 to 15 μm, and the aspect ratio is 10 to 15:1.

[0017] Furthermore, the iron removal treatment adopts a magnetic separation method, the magnetic field strength is 13000-15000Gs, and the excitation power is 12-13W.

[0018] The present invention also provides modified wollastonite prepared by the above preparation method.

[0019] The invention provides an application of modified wollastonite in epoxy potting adhesive.

[0020] Beneficial effects of the present invention:

[0021] The modified wollastonite prepared by the production method of the present invention has a high aspect ratio, low oil absorption value and good dispersibility in epoxy potting glue, can reduce the viscosity of the epoxy potting glue, improve the mechanical properties and insulation properties of the glue strip, and reduce the dimensional shrinkage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a process flow chart of the preparation method of the present invention;

[0023] Figure 2 This is a microscopic electron microscope image of the modified wollastonite prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing modified wollastonite, comprising the following steps:

[0025] The wollastonite powder can be subjected to composite surface modification and iron removal treatment;

[0026] The composite surface modification treatment is performed using a composite surface modifier, which comprises an epoxy silane coupling agent, a phosphate modifier and a polyether modifier.

[0027] In the present invention, the composite surface modifier further comprises anhydrous ethanol and water, and the mass ratio of the epoxy silane coupling agent, the phosphate modifier, the polyether modifier, the anhydrous ethanol and the water is 3-8:2-6:1-4:5-15:0.5-1.5, preferably 4-6:3-5:2-3:6-10:0.6-1.0, and further preferably 4-5:4-5:2-2.5:6-9:0.8-1.0.

[0028] In the present invention, the epoxysilane coupling agent comprises 3-(2,3-epoxypropyloxy)propylmethyldiethoxysilane and / or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, preferably 3-(2,3-epoxypropyloxy)propylmethyldiethoxysilane.

[0029] In the present invention, the phosphate modifier comprises one or more of polyoxyethylene ether phosphate, polyarylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether phosphate and nonylphenol polyoxyethylene ether phosphate, preferably polyoxyethylene ether phosphate.

[0030] In the present invention, the polyether modifier comprises polyether trisiloxane and / or polyether-modified polydimethylsiloxane, preferably polyether trisiloxane.

[0031] In the present invention, the composite surface modification treatment is carried out under heating and stirring, the heating temperature is 60-100°C, preferably 70-90°C, more preferably 75-80°C; the stirring time is 20-50 min, preferably 30-50 min.

[0032] In the present invention, the addition amount of the composite surface modifier is 1.2-2.4% of the mass of the wollastonite powder, preferably 1.5-2.0%, and more preferably 1.8%; the composite surface modifier is sprayed on the wollastonite powder to perform composite surface modification.

[0033] In the present invention, the preparation method of the wollastonite powder is:

[0034] 1) Selecting wollastonite concentrate with a calcium silicate content of ≥90% and a diameter of 5-10 cm, crushing it with a jaw crusher and then grinding it with a Raymond mill to a wollastonite coarse powder with a D50 of 25-35 μm, preferably 28-32 μm;

[0035] 2) The wollastonite coarse powder is ground by a jet mill to obtain long-fiber wollastonite fine powder with a D50 of 11 to 15 μm, preferably 12 to 14 μm, and an aspect ratio of 10 to 15:1, preferably 13 to 15:1.

[0036] In the present invention, the jaw crusher and Raymond mill are both commercially available conventional products; the jaw crusher has a power of 30KW and a main shaft speed of 275rpm; the Raymond mill is a commonly used grinding equipment for non-metallic minerals, which can grind the ore crushed by the crusher to 0.173-0.044mm; the center shaft speed of the Raymond mill is 105rpm, the grinding ring diameter is 1400mm, the grinding roller diameter is 410mm, the grinding roller height is 190mm, the main motor power of the Raymond mill is 75KW, and the fan motor power is 75KW;

[0037] The jet mill is a common ultrafine non-metallic powder pulverizing equipment, which can grind the powder to 3-100 μm; the air pressure of the jet mill is 0.65-1.2 MPa, preferably 0.8-1.0 MPa, and the air consumption is 20-80 m 3 / min, preferably 40-60m 3 / min, power is 255KW;

[0038] The high-speed mixer is a conventional product available on the market, with an effective capacity of 400 L, a motor power of 20 kW, an overall dimension of 1500×1090×1300 mm, and a main shaft speed of 0-1400 rpm.

[0039] In the present invention, the iron removal treatment is performed by magnetic separation, with a magnetic field strength of 13,000 to 15,000 Gs, preferably 15,000 Gs; and an excitation power of 12 to 13 W, preferably 12.5 W. The iron removal treatment of the present invention can remove iron filings generated during the powder grinding and modification process, maintain a low content of magnetic material in the powder, and improve the insulation properties of the powder.

[0040] The working principle of the present invention is to use air flow mill to prepare long-fiber wollastonite fine powder with a high aspect ratio. The aspect ratio structure significantly improves the mechanical properties of wollastonite in a resin matrix and reduces the dimensional shrinkage rate; at the same time, the bridge effect of the epoxy silane coupling agent is used to organically combine the inorganic long-fiber wollastonite fine powder with the organic epoxy resin, thereby improving the mechanical properties of the epoxy adhesive; the wollastonite powder is modified by a phosphate modifier and a polyether modifier so that the wollastonite maintains good dispersion performance and low viscosity in the epoxy potting adhesive, the adhesive has good fluidity, can flow to the potting location, and the adhesive surface maintains good gloss and flatness after curing.

[0041] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] Wollastonite concentrate with a calcium silicate content of ≥90% and a diameter of 5-10CM was selected, crushed by a jaw crusher and then ground by a Raymond mill to a wollastonite coarse powder with a D50 of 30μm; the wollastonite coarse powder was conveyed to a jet mill and ground to a long-fiber wollastonite fine powder with a D50 of 12μm and an aspect ratio of 13:1; the long-fiber wollastonite fine powder was added to a high-speed mixer and heated to 80°C, and a composite material with a mass fraction of 1.6% of wollastonite powder was added by spraying. The modifier (3-(2,3-epoxypropoxy)propylmethyldiethoxysilane: polyoxyethylene ether phosphate: polyether trisiloxane: anhydrous ethanol: distilled water) was added in a ratio of 5:3:2:10:1 and stirred for 3 hours, and stirring was continued for 35 minutes; the modified long-fiber wollastonite fine powder was finally subjected to an electromagnetic dry powder magnetic separator at an intensity of 15000Gs and an excitation power of 12.5W for iron removal, and the modified wollastonite powder was obtained after packaging and collection.

[0044] Example 2

[0045] Wollastonite concentrate with a calcium silicate content of ≥90% and a diameter of 5-10CM was selected, crushed by a jaw crusher, and then ground by a Raymond mill to a wollastonite coarse powder with a D50 of 32μm; the wollastonite coarse powder was conveyed to a jet mill and ground to a long-fiber wollastonite fine powder with a D50 of 13μm and an aspect ratio of 13:1; the long-fiber wollastonite fine powder was added to a high-speed mixer and heated at 80°C, and a composite modifier (2 -(3,4-epoxycyclohexyl)ethyltriethoxysilane: polyarylphenol polyoxyethylene ether phosphate: polyether-modified polydimethylsiloxane: anhydrous ethanol: distilled water are added in a ratio of 5:2:2:9:0.9, and stirred for 2.5 hours, and then stirred for 30 minutes; the modified long-fiber wollastonite fine powder is finally subjected to an electromagnetic dry powder magnetic separator at an intensity of 15,000 Gs and an excitation power of 12.5 W for iron removal, and the modified wollastonite powder is obtained after packaging and collection.

[0046] Example 3

[0047] Wollastonite concentrate with a calcium silicate content of ≥90% and a diameter of 5-10CM is selected, crushed by a jaw crusher and then ground by a Raymond mill to a wollastonite coarse powder with a D50 of 35μm; the wollastonite coarse powder is conveyed to a jet mill and ground to a long-fiber wollastonite fine powder with a D50 of 14μm and an aspect ratio of 14:1; the long-fiber wollastonite fine powder is added to a high-speed mixer and heated to 80°C, and a composite modified product with a mass fraction of 1.5% of wollastonite powder is added by spraying. The modified wollastonite powder was prepared by adding a prepolymer (3-(2,3-epoxypropoxy)propylmethyldiethoxysilane: fatty alcohol polyoxyethylene ether phosphate: polyether trisiloxane: anhydrous ethanol: distilled water in a ratio of 4:2:1:8:0.8 and stirring for 2 hours) and continuing to stir for 30 minutes. The modified long-fiber wollastonite fine powder was finally subjected to an electromagnetic dry powder magnetic separator at an intensity of 15000 Gs and an excitation power of 12.5 W for iron removal, and then packaged and collected to obtain the modified wollastonite powder.

[0048] Test Case

[0049] In this example, the modified wollastonite prepared in Examples 1-3 was tested for relevant indicators according to JC / T 535-2023. The relevant indicators are shown in Table 1 below:

[0050] Table 1 Performance indexes of modified wollastonite

[0051]

[0052] Example 4

[0053] In this example, the modified wollastonite prepared in Examples 1-3 was applied to an epoxy potting compound. Viscosity was measured in accordance with the provisions of GB / T 2794. Impact strength was tested according to the method specified in GB / T 1043.1. Tensile strength was tested according to the method specified in GB / T 1040, and dielectric strength was measured according to the provisions of GB / T 1409. Dielectric loss was measured according to the provisions of GB / T 1409. Volume resistivity was measured according to the method specified in GB / T 15662-1995. The coefficient of thermal expansion was measured according to the provisions of GB / T 1036-2008.

[0054] Preparation method of epoxy potting compound component A: epoxy resin, toughening agent, diluent, and dispersant are mixed according to mass ratio, stirred for 5 minutes using a high-speed disperser at 1200 rpm, modified wollastonite is added, and after the epoxy resin and modified wollastonite are completely mixed, defoamer and anti-settling agent are added, stirred for 5 minutes, and finally vacuum degassing is performed to obtain epoxy component A;

[0055] Preparation method of epoxy potting compound component B: stir the anhydride curing agent, accelerator, and diluent in a high-speed disperser at 1200 rpm for 5 minutes, add modified wollastonite, wait until the curing agent and modified wollastonite are completely mixed, then add an appropriate amount of defoaming agent, stir for 5 minutes, and finally vacuum degas to obtain epoxy potting compound component B.

[0056] The usage of epoxy potting adhesive is to measure components A and B in a weight ratio of 3:1, mix them evenly, and then perform potting after vacuum degassing. After fully curing at 60°C for 2 hours, measure the mechanical and electrical properties.

[0057] The basic formula of epoxy powder filling glue is as follows: Table 2 and Table 3:

[0058] Table 2A component formula

[0059]

[0060] Table 3B Component Formula

[0061]

[0062] Table 4 Performance indicators of modified wollastonite prepared in Examples 1 to 3 used in epoxy potting adhesive

[0063]

[0064] Table 4 shows that the modified wollastonite produced in this embodiment can meet the performance index requirements of epoxy potting adhesive. The modified wollastonite prepared in the present invention has low viscosity, good mechanical and electrical properties, and low thermal expansion coefficient when used in epoxy potting adhesive.

[0065] As can be seen from the above examples, the present invention provides a modified wollastonite, its preparation method, and its use in epoxy potting compounds. The modified wollastonite prepared by the present production method has a high aspect ratio, low oil absorption, and good dispersibility in epoxy potting compounds. This reduces the viscosity of the epoxy potting compound, improves the mechanical and insulating properties of the adhesive strip, and reduces dimensional shrinkage.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing modified wollastonite, characterized in that: The following steps are involved: The wollastonite powder can be subjected to composite surface modification and iron removal treatment; The composite surface modification treatment is performed using a composite surface modifier, which comprises an epoxy silane coupling agent, a phosphate modifier and a polyether modifier.

2. The method for preparing modified wollastonite according to claim 1, wherein The composite surface modifier further comprises anhydrous ethanol and water, and the mass ratio of the epoxy silane coupling agent, the phosphate modifier, the polyether modifier, the anhydrous ethanol and the water is 3-8:2-6:1-4:5-15:0.5-1.

5.

3. The method for preparing modified wollastonite according to claim 1 or 2, characterized in that: The epoxy silane coupling agent comprises 3-(2,3-epoxypropyloxy)propylmethyldiethoxysilane and / or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; The phosphate modifier comprises one or more of polyoxyethylene ether phosphate, polyarylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether phosphate and nonylphenol polyoxyethylene ether phosphate; The polyether modifier comprises polyether trisiloxane and / or polyether-modified polydimethylsiloxane.

4. The method for preparing modified wollastonite according to claim 3, wherein The composite surface modification treatment is carried out under heating and stirring, the heating temperature is 60-100° C., and the stirring time is 20-50 minutes.

5. The method for preparing the modified wollastonite according to claim 1, 2 or 4, wherein: The addition amount of the composite surface modifier is 1.2-2.4% of the mass of the wollastonite powder, and the composite surface modifier is sprayed to perform composite surface modification on the wollastonite powder.

6. The method for preparing modified wollastonite according to claim 5, wherein The D50 of the wollastonite powder is 11 to 15 μm, and the aspect ratio is 10 to 15:

1.

7. The method for preparing modified wollastonite according to claim 1, wherein The iron removal treatment adopts a magnetic separation method, the magnetic field strength is 13000-15000Gs, and the excitation power is 12-13W.

8. Modified wollastonite prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified wollastonite according to claim 8 in epoxy potting adhesive.

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