WO2021091104A1 - Organic/inorganic nanocomposite preparation method using inorganic nanoparticles surface-treated with hydroxy acid and thermoplastic polymer and organic/inorganic nanocomposite prepared thereby - Google Patents

Abstract

The present invention relates to an organic/inorganic nanocomposite preparation method using inorganic nanoparticles, which are surface-treated with a hydroxy acid, and a thermoplastic polymer, and an organic/inorganic nanocomposite prepared thereby and, more specifically, to an organic/inorganic nanocomposite having enhanced insulation performance by means of surface-treating inorganic nanoparticles with a hydroxy acid and melting and mixing same with a thermoplastic polymer. According to the present invention, inorganic nanoparticles, which are surface-treated by means of a surface treatment agent comprising a hydroxy acid and silane, can be prepared in a simple manner, and an organic/inorganic nanocomposite having a high inorganic nanoparticle content as well as exhibiting excellent insulating performance can be obtained by means of a melting and mixing process with a thermoplastic polymer.

Description

Method for preparing organic-inorganic nanocomposite using inorganic nanoparticles and thermoplastic polymer surface-treated with hydroxy acid, and organic-inorganic nanocomposite prepared therefrom

The present invention relates to a method for preparing an organic-inorganic nanocomposite using an inorganic nanoparticle and a thermoplastic polymer surface-treated with hydroxy acid, and to an organic-inorganic nanocomposite prepared therefrom, and more particularly, to a hydroxy The present invention relates to an organic-inorganic nanocomposite with improved insulating performance by surface treatment with an acid and melt-mixing it with a thermoplastic polymer, and a method for manufacturing the same.

Thermoplastic polymer refers to a polymer that can be molded by heat, and it is very easy to mold in a process, and since it can be remolded by heat after being manufactured, it has received a lot of interest as a renewable material in recent years.

These thermoplastic polymers are widely used in various fields as well as daily life products and specialized industries. For example, polyethylene (PE), polypropylene (PP) and blending materials derived therefrom are low in price among polymer materials and have good mechanical properties and chemical resistance. It is widely used as an insulating material not only in general fields such as, but also in the electric and electronic industry, and is widely used as an insulating layer material for transmission cables as well as various small cables.

As the importance of long-distance transmission, increase in capacity, and ease of power control has recently emerged for the expansion and advancement of the next-generation power grid, the DC-type transmission method is emerging from the existing AC type. The importance of excellent insulating materials is increasing.

Currently, crosslinked PE (XLPE) is mainly used as an insulating material for AC and DC cables. XLPE is formed by adding a crosslinking agent from LDPE and curing at high temperature, in order to further increase the mechanical strength, insulation strength and heat resistance of PE. However, the crosslinking process and the degassing process for removing the crosslinking reaction by-products are involved, resulting in a decrease in fairness, a burden for the remaining crosslinking reaction by-products, and the formed XLPE is a thermosetting polymer, which makes it impossible to recycle.

On the other hand, since PP is manufactured as an insulating layer through a simple melting process without the need for a crosslinking process, the process is simple, mechanical strength and insulation performance are excellent, and heat resistance is superior to XLPE. In addition, unlike XLPE, since it is a recyclable thermoplastic resin, it has an advantage in terms of eco-friendliness, so XLPE is being replaced with PP in recent years.

However, since PP has lower thermal conductivity than XLPE, it has a disadvantage compared to XLPE in dissipating heat that accumulates inside during cable operation. Accordingly, despite being a material having better thermal stability than XLPE, these advantages are somewhat offset.

To solve this problem, there is a method of increasing thermal conductivity by compounding a high thermal conductivity filler in PP. In general, high thermal conductivity materials are expensive, and in general, it is difficult to clearly improve thermal conductivity with a small amount, so it is disadvantageous in terms of price competitiveness. do. As another solution, there is a method of reducing the thickness of the insulating layer, which requires stronger insulating performance.

On the other hand, since inorganic nanoparticles are not compatible with thermoplastic polymers, aggregating of the particles occurs severely during simple melt-mixing, making it impossible to achieve a desired improvement in physical properties. For this purpose, a surface treatment process of the inorganic nanoparticles is indispensable. In general, the surface treatment is performed by bonding a silane coupling agent to the surface of the inorganic nanoparticles.

For example, according to a review paper ("Effect of different nanoparticles on tuning electrical properties of propylene nanocomposites" IEEE Transactions on Dielectrics and Electrical Insulation, vol24, No3, 1380~1389, 2017), MgO, SiO ₂ , TiO ₂ , Al _{A method of surface treatment of inorganic nanoparticles such as 2} O ₃ using silane having functional groups such as amine group, epoxy group, acrylic group, and vinyl group has been introduced.

As another example, according to the "flame-retardant polypropylene insulating resin composition with improved dispersibility and mechanical properties and an insulating wire using the same (registration number: 10-0997825)", various inorganic substances are added as a flame retardant to improve the flame retardancy of polypropylene. In order to secure acidity, the surface was hydrophobic treatment with stearic acid, oleic acid, fatty acids, aminosilane, and vinylsilane.

However, despite the fact that various literatures have introduced the surface treatment method through the above-described method for dispersing inorganic nanoparticles, the breakdown voltage or dielectric strength indicating insulation performance is improved only when it is small. The effect appears, and it has been reported that almost all of the results decrease again at a content of 1~3wt% or more.

Therefore, it is important to develop organic-inorganic nanocomposites with thermoplastic polymers so that insulation performance can be continuously maintained and improved even when inorganic nanoparticles are combined to a higher content in order to achieve high performance and compactness as a variety of insulating materials. to be.

The present invention was invented to solve the above problems, and organic/inorganic using inorganic nanoparticles and thermoplastic polymers surface-treated with hydroxy acid so that insulation performance can be improved through complexing of thermoplastic polymers and insulating inorganic nanoparticles. It is a technical solution to provide a method of manufacturing a nanocomposite and an organic-inorganic nanocomposite prepared therefrom.

In order to solve the above problems, the present invention includes forming a first solution in a form in which inorganic nanoparticles are dispersed in a solvent; Forming a second solution containing inorganic nanoparticles having a hydroxyl group (-OH) formed on the surface of the first solution by mixing a surface treatment agent containing hydroxy acid; Removing the solvent contained in the second solution to form a surface-treated inorganic nanoparticle powder; And forming an organic-inorganic nanocomposite by melt-mixing the surface-treated inorganic nanoparticle powder and a thermoplastic polymer; It provides a method of manufacturing a nanocomposite.

In the present invention, in the step of forming the second solution, silane is further contained in the surface treatment agent, and the hydroxy acid is formed on the surface of the inorganic nanoparticles through a sol-gel reaction of the silane. It is characterized in that the period (-OH) is formed.

In the present invention, the hydroxy acid in the step of forming the second solution is alpha-hydroxy acid, beta-hydroxy acid, omega-hydroxy acid (ω- hydroxy acid) or a mixture thereof.

In the present invention, in the step of forming the surface-treated inorganic nanoparticle powder, a precipitate containing a surface treatment agent combined with the surface of the inorganic nanoparticles by centrifuging the second solution, and the surface of the inorganic nanoparticles After separating into a supernatant containing a residual surface treatment agent that cannot be combined with, the precipitate is dried to form a surface-treated inorganic nanoparticle powder.

In the present invention, in the step of forming the organic-inorganic nanocomposite, the thermoplastic polymer and the surface treatment agent are melt-mixed at 100° C. to 250° C. to prevent oxidation and thermal decomposition.

In order to solve the above problems, the present invention provides an organic-inorganic nanocomposite using an inorganic nanoparticle surface-treated with hydroxy acid and a thermoplastic polymer, which is manufactured by the above manufacturing method.

The method for preparing an organic-inorganic nanocomposite using the inorganic nanoparticles and thermoplastic polymer surface-treated with hydroxy acid of the present invention according to the solution to the above problem, and the organic-inorganic nanocomposite prepared therefrom, are surface-treated with hydroxy acid. The treated inorganic nanoparticles can be conveniently prepared, and by producing an organic-inorganic nanocomposite having excellent insulating performance through melt-mixing with a thermoplastic polymer, there is an effect that can be applied as an insulating layer of various cables.

1 is a flow chart according to a preferred embodiment of the present invention.

2 is an SEM photograph of a cross section of a specimen broken in liquid nitrogen.

3 is a graph showing the results of the insulation breakdown voltage.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

That is, the present invention is formed through melt-mixing of the inorganic nanoparticles surface-treated with hydroxy acid and a thermoplastic polymer, thereby obtaining an organic-inorganic nanocomposite that can be applied as an insulating layer for various cables.

1 is a flow chart according to a preferred embodiment of the present invention. As shown in FIG. 1, the organic-inorganic nanocomposite according to the present invention comprises the steps of forming a first solution (S10), forming a second solution (S20), and forming inorganic nanoparticle powder (S30). And forming the organic-inorganic nanocomposite (S40), and each characteristic will be described in more detail below.

First, a first solution in a form in which inorganic nanoparticles are dispersed in a solvent is formed (S10).

First, inorganic nanoparticles composed of one or two or more inorganic substances such as MgO, SiO ₂ , TiO ₂ , and Al ₂ O _{3 are prepared.}

Here, the inorganic nanoparticles are characterized by having a hydroxyl group (-OH) on the surface of the particle or a hydroxyl group (-OH) on the surface by surface treatment by a physicochemical method.

As a method of artificially generating hydroxyl groups on the surface of inorganic nanoparticles, the inorganic nanoparticles are dispersed in water for a certain period of time and stirred, or if necessary, hydrogen peroxide, acid, base, etc. are added and the temperature is raised to create a hydroxyl group more quickly. can do.

After drying the inorganic nanoparticles having a hydroxyl group on the surface, they are dispersed in a solvent. As the solvent for dispersing the inorganic nanoparticles, all general organic solvents may be used, but it is preferable to use a solvent having a polar group because a hydroxy group exists on the surface. For example, it may be selected from the group consisting of ethyl alcohol, isopropyl alcohol, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, acetone, and mixtures thereof, It is not necessarily limited to this, and any solvent having a polar group can be used in various ways.

On the other hand, as the solvent for dispersing the inorganic nanoparticles, a solvent having hydrophobicity or low polarity may be used depending on the degree of hydrophobicity of the surface treatment agent containing hydroxy acid. For example, hexane, toluene benzene, benzyl alcohol, butyl alcohol and It may be selected from the group consisting of mixtures thereof.

On the other hand, the solvent for dispersing the inorganic nanoparticles is hydrolysis of silanes to facilitate the sol-gel reaction between the hydroxy group and the silane coupling agent on the surface of the inorganic nanoparticles when silanes other than hydroxy acids are included in the surface treatment agent. It is more preferable to use a small amount of water in order to increase the surface coupling effect through the condensation reaction.

Dispersion in the dispersion of inorganic nanoparticles as the first solution can be accomplished by various methods such as mechanical stirring, ultrasonic waves, and ball mill, but it is preferable to perform a method having a forcible dispersing effect such as ultrasonic waves to minimize aggregation between inorganic nanoparticles. Do.

Next, a second solution containing inorganic nanoparticles having a hydroxyl group (-OH) formed on the surface is formed by mixing the surface treatment agent containing hydroxy acid in the first solution (S20).

That is, as a step of surface treatment of inorganic nanoparticles, hydroxy acid refers to a carboxylic acid having a hydroxy group (-OH). As the hydroxy acid, at least one of alpha-hydroxy acid, beta-hydroxy acid, and omega-hydroxy acid is used.

Alpha-hydroxy acid is a hydroxy group present on the carbon immediately adjacent to the carboxylic acid, 2-hydroxybutyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxypropanoic acid (lactic acid), 2-hydroxy-n-octanoic acid , 2-hydroxy-4-methylvaleric acid (leucic acid), 2-hycroxyplamitic acid, and 2-hydroxy-4-phenylbutyric acid may be selected from any one or more.

Beta-hydroxy acid has two carbons between the carboxylic acid and the hydroxy group. 3-hydroxymyristic acid, 3-hydroxy-3-methylvaleric acid, 3-hydroxybutyric acid, 3-hydroxy-3-methylbutyric acid, 2 Any one or more of -hydroxybenzoic acid (salicylic acid) and 2-hydroxycyclohexanecarboxylic acid may be selected.

Omega-hydroxy acid is a hydroxy group is located at the end group on the other side of the carboxylic acid, 15-hydroxypentadecanoic acid, 16-hydroxyhexadecanoic acid, 18-hydroxy stearic acid, and any one or more of 4-(hydroxymethyl)cyclohexanecarboxylic acid may be selected.

In addition to the above-described alpha-hydroxy acid, beta-hydroxy acid and omega-hydroxy acid, 12-hydroxystearic acid, 2,3,4,5-tetrahydroxyadipic acid (galataric acid), gluconic acid, etc. 1 between the terminal group and the carboxylic acid group Hydroxy acids containing more than one hydroxy group may also be selected and used.

In addition, silane is included in the surface treatment agent when surface treatment of the inorganic nanoparticles is performed in this step. The silane may be a 1 to trivalent silane having a functional group such as an alkyl group, a vinyl group, an amine group, an epoxy group and a thiol group.

In particular, an acid such as hydroxy acid acts as a catalyst to promote a sol-gel reaction between the silane and the hydroxy group on the surface of the inorganic nanoparticles in the surface treatment of the 1- to 3-valent silane surface modifier. .

That is to say, the sol-gel reaction between the silane and the hydroxy group generally has a fast hydrolysis and condensation reaction rate in an acidic or basic atmosphere, so an acid or a basic substance is commonly used as a catalyst, and the hydroxy acid used in the present invention is also used as an acidic catalyst. It becomes possible to play a role of promoting the surface reaction of the inorganic nanoparticles.

In other words, the hydroxy acid of the present invention not only acts as a catalyst for a sol-gel reaction, but also a phenomenon in which the hydroxy acid itself binds to the surface of the inorganic nanoparticles. Accordingly, in the present invention, an alkyl group exists at the end such as alka hydroxy acid and beta-hydroxy acid than an omega-hydroxy acid having a hydroxy group at the end, and a hydroxy group exists at other positions, so that it is compatible with a hydrophobic polymer. It is more preferable to use a hydroxy acid.

It is important to note that when an aliphatic organic acid such as acetic acid, formic acid, phophoric acid, stearic acid and oleic acid, which is used as an acid catalyst for a conventional sol-gel reaction, is applied, there is no effect on the insulation performance, or rather the insulation performance is not affected. On the other hand, when the hydroxy acid is applied, the insulating performance is not decreased and the insulation performance is improved (see FIG. 3).

Therefore, using a hydroxy acid having an alkyl group compatible with the thermoplastic polymer at the end group, such as hydroxy acid, and a hydroxy group that can give affinity to the hydroxy group of inorganic nanoparticles, is present near the carboxylic acid. It is preferable to surface-treat the inorganic nanoparticles.

In addition, in general, hydroxy acids have a higher acidity than carboxylic acids having a similar molecular structure without hydroxy groups. As a result, hydroxy groups are better formed on the surface of inorganic nanoparticles. It is preferable to use a hydroxy acid having a large effect capable of accelerating the reaction.

The content of the hydroxy acid is determined according to the surface area of the inorganic nanoparticles, and it is preferable to use 1 to 20 parts by weight based on 100 parts by weight of the solid content of the inorganic nanoparticles. Excess hydroxy acid that is not surface-treated is removed during centrifugation and washing as described above.

The content of the silane surface treatment agent is determined according to the particle surface area by the particle size of the inorganic nanoparticles, like hydroxy acid, and it is preferable to use 0.1 to 20 parts by weight based on 100 parts by weight of the solid content of the inorganic nanoparticles. Even in this case, the amount remaining without being used for the surface treatment of the particles, like the hydroxy acid surface treatment, is removed through centrifugation and washing.

However, unlike hydroxy acids, when silane is used in an excessive amount, macromolecules and networks are formed before the reaction on the particle surface due to the self-sol-gel reaction between the silane surface treatment agents in the solution, resulting in lower particle surface treatment efficiency. Since there is a concern, in the case of using 10 parts by weight or more, it is preferable to induce a reaction on the surface of the particles by continuously adding or dividing the silane.

Next, the surface-treated inorganic nanoparticle powder is formed by removing the solvent contained in the second solution (S30).

That is, the surface-treated inorganic nanoparticle powder is obtained by removing and drying the dispersion solvent of the previously surface-treated inorganic nanoparticle dispersion.

It is preferable to remove the surface treatment agent remaining in the solvent without surface treatment by using a method such as a centrifugal separation method to remove the dispersion solvent. That is, only the particles that are precipitated on the floor are obtained through centrifugation, and the supernatant in which the residual surface treatment agent that is not bound to the inorganic nanoparticle surface is dissolved is separated, so that unnecessary residual surface treatment agent is not introduced when melt-mixed with the thermoplastic polymer. Do not.

The purification process using such a centrifugal separation method is repeatedly performed several times or more to obtain surface-treated inorganic nanoparticles, and then the remaining solvent is removed as much as possible through a high-temperature drying method to obtain surface-treated inorganic nanoparticle powder. In the case of high-temperature drying, it is preferable that the surface treatment agent be thermally decomposed within 250°C, and may be performed in the range of 50 to 250°C.

The reason for removing the solvent used for the surface treatment is to prevent the problem that the solvent boils or excessive vapor is generated at a high temperature when the surface-treated inorganic nanoparticles are melt-mixed with a thermoplastic polymer. In addition, since moisture and polar solvents present on the surface of the inorganic nanoparticles may cause side effects of lowering the insulating performance, it is preferable to use the surface-treated inorganic nanoparticles after drying as much as possible.

Finally, the surface-treated inorganic nanoparticle powder and the thermoplastic polymer are melt-mixed to form an organic-inorganic nanocomposite (S40).

First, the thermoplastic polymer used in the step of forming the organic-inorganic nanocomposite may be polypropylene (PP), polyolefin elastomer (POE), or a mixture thereof.In addition to the above types, various thermoplastic polymers can also be applied. Do.

1 to 10 parts by weight of the surface-treated inorganic nanoparticle powder may be mixed with respect to 100 parts by weight of the thermoplastic polymer. If the surface-treated inorganic nanoparticle powder is less than 1 part by weight, it is difficult to achieve the desired physical properties. Even if the particles are surface-treated, if it exceeds 10 parts by weight, aggregation may occur between the surface-treated inorganic nanoparticle powders, which makes it difficult to control the insulation performance.

In the case of melt mixing, it can be manufactured by any method if it is a thermoplastic polymer molding process such as an internal mixer, extrusion, or injection molding.

In particular, melt-mixing may be performed within 250°C, but if it is less than 100°C, the inorganic nanoparticle powder and the thermoplastic polymer cannot be properly melt-mixed, and if it exceeds 250°C, oxidation and thermal decomposition of the thermoplastic polymer and the surface treatment agent occur. Regarding the time of melt-mixing, it is sufficient if it is made within 30 minutes, but if it is less than 1 minute, it is difficult to achieve sufficient mixing, and if it exceeds 30 minutes, there is a concern that all physical properties including degradation of insulation performance may be deteriorated. For this reason, it is preferable to perform melt mixing at 100° C. to 250° C. for 1 minute to 30 minutes.

At this time, an antioxidant may be added for the purpose of preventing thermal oxidation at high temperatures during melt mixing, and any antioxidant that can be applied in a conventional melt mixing process may be used.

The organic-inorganic nanocomposite composed of the surface-treated inorganic nanoparticles and thermoplastic polymer prepared in this way satisfies other mechanical and thermal properties and has excellent insulation performance, so it is an insulating material in various electric and electronic fields such as wires and cables and power cables. It can be used as.

Hereinafter, an embodiment of the present invention will be described in more detail as follows. However, the following examples are merely illustrative to aid in understanding of the present invention, and the scope of the present invention is not limited thereby.

<Example 1>

Based on 100 parts by weight of magnesium oxide (MgO, particle diameter ~ 50 nm), isopropyl alcohol was added so that the solid content became 10 wt%, and ultrasonic waves were applied for 30 minutes to disperse the particles.

Thereafter, a solution in which 1 part by weight of lactic acid (LA) and 10 parts by weight of trimethoxymethylsilane (MTMS) were dissolved in 20 parts by weight of toluene was added together with a small amount of distilled water, and ultrasonic dispersion was further performed for 30 minutes. Then, the reaction was completed by stirring at 60° C. for 18 hours.

The surface-treated MgO dispersion solution was subjected to vacuum drying at 60° C. for 24 hours after separating the precipitate using centrifugation to obtain the surface-treated MgO in powder form.

The surface-treated MgO and polypropylene (PP), a thermoplastic polymer, were melt-mixed at 200° C. for 10 minutes using an internal mixer. It was mixed so as to be 1 part by weight of MgO based on 100 parts by weight of PP (MgO 1 part), and a small amount of antioxidant was also added. After that, press the hot press at 200℃ for 15 minutes at 15MPa, then circulate the cooling water of 15~20℃ through the pipe connected to the hot prerss and cool it (water cooling method) to complete the preparation of the organic-inorganic nanocomposite specimen made of PP and MgO. (Sample thickness ~0.46mm).

According to ASTM D149, the insulation strength of the specimen is determined by placing the specimen between sphere/sphere electrodes impregnated with insulating oil and boosting it to 1.5 kV/sec at 60 Hz using a high-voltage power supply. breakdown voltage, BDV) was measured and analyzed. For each type, 10 specimens were measured and the average value and error were compared.

<Example 2>

An organic-inorganic nanocomposite made of PP-MgO was prepared so that the MgO content was 3 parts by weight based on 100 parts by weight of PP, but the rest of the process was carried out in the same manner as in Example 1.

<Example 3>

An organic-inorganic nanocomposite made of PP-MgO was prepared so that the MgO content was 5 parts by weight based on 100 parts by weight of PP, but the rest of the process was carried out in the same manner as in Example 1.

<Example 4>

An organic-inorganic nanocomposite made of PP-MgO was prepared so that the MgO content was 7 parts by weight based on 100 parts by weight of PP, but the rest of the process was carried out in the same manner as in Example 1.

The results for the specimens (thickness ~0.46mm) corresponding to Examples 1 to 4 are summarized in Table 1 and shown.

		Example 1	Example 2	Example 3	Example 4
Polymer		PP	PP	PP	PP
MgO		One	3	5	7
Surface treatment		LA	LA	LA	LA
		MTMS	MTMS	MTMS	MTMS
BDV(kV/mm)	Average	64.1	64.1	68.8	66.0
	error	2.9	3.3	5.0	4.3

<Comparative Example 1> Only PP and an antioxidant were used, and melt mixing and specimen preparation were carried out in the same manner as in Example 1.

<Comparative Example 2>

MgO powder was used after drying in a vacuum oven at 60° C. for 24 hours without a surface treatment process, after which the melt mixing and specimen preparation processes were performed in the same manner as in Example 1. It was made to be 1 part by weight (1 part) of MgO based on 100 parts by weight of PP.

<Comparative Example 3>

The same as Comparative Example 2, but was made to be 3 parts by weight of MgO (3 parts) for 100 parts by weight of PP.

<Comparative Example 4>

It was the same as Comparative Example 2, but was made to be 5 parts by weight (5 parts) of MgO based on 100 parts by weight of PP.

<Comparative Example 5>

It was the same as Comparative Example 2, but was made to be 7 parts by weight (7 parts) MgO for 100 parts by weight of PP.

The results for the specimens (thickness ~0.46mm) corresponding to Comparative Examples 1 to 5 are summarized in Table 2 and shown.

		Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4	Comparative Example 5
Polymer		PP	PP	PP	PP	PP
MgO		0	One	3	5	7
Surface treatment		-	-	-	-	-
		-	-	-	-	-
BDV(kV/mm)	Average	58.5	55.2	56.3	53.0	52.0
	error	1.4	2.8	3.4	6.1	5.5

2 is an SEM photograph of a cross section of a specimen broken in liquid nitrogen. That is, FIG. 2 shows an SEM image of a cross-section of the PP/MgO (5 part) specimen of Example 3 broken in liquid nitrogen. As shown in FIG. 2, MgO nanoparticles having a diameter of ~50 nm are relatively well dispersed in PP. It can be confirmed that it was done.

3A is a graph showing the dielectric breakdown voltage according to Examples 1 to 4 and Comparative Examples 1 to 5; In addition to FIG. 3A, as shown in Tables 1 and 2, it can be seen that the tendency of the dielectric breakdown voltage according to the MgO content in the case of surface treatment and the case of not surface treatment is significantly different.

In other words, when MgO is not surface-treated and mixed with PP, the insulation strength is significantly reduced, whereas when MgO is used by surface treatment with LA and MTMS, the insulation strength increases significantly, and even with a high content of 7 parts, pure PP It shows higher insulation performance.

Meanwhile, a specimen was prepared using polypropylene (PP) and polyolefin elastomer (POE) as a thermoplastic polymer.

<Example 5>

The surface treatment of MgO was carried out in the same manner as in Example 1. As in Example 1, except that PP and POE were used together as a thermoplastic polymer during melt mixing to make a PP/POE blending material (PP/POE=80/20, wt ratio) and the specimen thickness was ~0.16mm. In the same way, an organic-inorganic nanocomposite composed of PP/POE-MgO (MgO 1 part) was prepared.

<Example 6>

For the surface treatment of MgO, octyl triethoxysilane (OTES) was used with LA instead of MTMS, and the remaining surface treatment was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, an organic-inorganic nanocomposite composed of PP/POE-MgO (MgO 1 part) was prepared.

<Example 7>

The surface treatment of MgO was used alone without MTMS or OTES, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, an organic-inorganic nanocomposite composed of PP/POE-MgO (MgO 1 part) was prepared.

The results for the specimens (thickness ~ 0.16mm) corresponding to Examples 5 to 7 are summarized in Table 3 below.

		Example 5	Example 6	Example 7
Polymer		PP/POE	PP/POE	PP/POE
MgO		One	One	One
Surface treatment		LA	LA	LA
		MTMS	OTES	-
BDV(kV/mm)	Average	141.9	139.2	129.7
	error	7.8	9.4	4.9

<Comparative Example 6> Compared with Example 5, only PP, POE, and antioxidant were used, and melt mixing and specimen preparation were carried out in the same manner as in Example 5 to prepare a PP/POE blended thermoplastic polymer.

<Comparative Example 7>

For the surface treatment of MgO, an aqueous ammonia solution (NH ₃ ) was used instead of LA with MTMS, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, a thermoplastic polymer nanocomposite made of PP/POE-MgO (MgO 1 part) was prepared.

<Comparative Example 8>

For the surface treatment of MgO, acetic acid (AA) was used instead of LA together with MTMS, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, a thermoplastic polymer nanocomposite made of PP/POE-MgO (MgO 1 part) was prepared.

<Comparative Example 9>

For the surface treatment of MgO, formic acid (FA) was used instead of LA together with MTMS, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, a thermoplastic polymer nanocomposite made of PP/POE-MgO (MgO 1 part) was prepared.

<Comparative Example 10>

For the surface treatment of MgO, phosphoric acid (PA) was used instead of LA together with MTMS, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, a thermoplastic polymer nanocomposite composed of PP/POE-MgO (MgO 1 part) was prepared.

<Comparative Example 11>

For the surface treatment of MgO, oleic acid (OLA) was used instead of LA together with MTMS, and the rest of the surface treatment process was performed in the same manner as in Example 1. Subsequently, in the same manner as in Example 5, a thermoplastic polymer nanocomposite made of PP/POE-MgO (MgO 1 part) was prepared.

The results for the specimens (thickness ~0.16mm) according to Comparative Examples 6 to 11 are summarized in Table 4 below.

		Comparative Example 6	Comparative Example 7	Comparative Example 8	Comparative Example 9	Comparative Example 10	Comparative Example 11
Polymer		PP/POE	PP/POE	PP/POE	PP/POE	PP/POE	PP/POE
MgO		-	One	One	One	One	One
Surface treatment		-	NH 3	AA	FA	PA	OLA
		-	MTMS	MTMS	MTMS	MTMS	MTMS
BDV(kV/mm)	Average	136.7	89.7	77.0	79.3	76.2	90.4
	error	10.0	23.3	7.0	4.7	4.1	6.7

The insulation strength of the specimens of Examples 5 to 7 and Comparative Examples 6 to 11 can be confirmed through Fig. 3b (M denotes MTMS, O denotes OTES), Table 3 and Fig. 4, and the simple thermoplasticity of Comparative Example 6 Compared with the polymer (PP/POE), the insulating performance is improved only when MgO is surface-treated by using LA, an alpha-hydroxy acid, together with silanes such as MTMS and OTES. In the case of using the remaining various acids (acetic acid, phosphoric acid, formic acid, oleic acid) and base (aqueous ammonia solution), the insulation performance is significantly lowered. Even when LA alone without silane is used as in Example 7, compared to a polymer without MgO In view of the fact that the insulation performance only slightly decreases, and the insulation performance of the remaining acids and basic substances greatly decreases even when used together with silane, the hydroxy acid used in the present invention has the effect of maintaining or improving the insulation performance. It is confirmed to be superior to other materials. In particular, it is confirmed that the insulating performance is most preferably improved when hydroxy acid and silane are used together as in Examples 1 to 4 and 5 and 6.

On the other hand, specimens according to MgO content were prepared using polypropylene (PP) and polyolefin elastomer (POE) as thermoplastic polymers.

<Example 8>

The surface treatment of MgO was carried out in the same manner as in Example 1, and the melt-mixing with the thermoplastic polymer was performed in the same manner as in Example 5 to obtain a PP/POE-MgO thermoplastic nanocomposite (MgO 1 part). After that, in the process of preparing the specimen using a hot press, it was pressed at 200°C for 15 minutes at 15 MPa pressure, transferred to a separate cold press maintained at 10°C, and then rapidly cooled while applying 15 MPa pressure to prepare the specimen (quick cooling). Condition). That is, compared to Example 5, a specimen was prepared by varying the cooling rate during specimen molding.

<Example 9>

Samples were prepared in the same manner as in Example 8, except that MgO was 3 parts by weight (3 parts) based on 100 parts by weight of the thermoplastic polymer made of PP/POE.

<Example 10>

Samples were prepared by a rapid cooling method in the same manner as in Example 8, but MgO was 5 parts by weight (5 parts) based on 100 parts by weight of the thermoplastic polymer made of PP/POE.

<Comparative Example 12>

In the same manner as in Example 8, the specimen was prepared by the rapid cooling method, but the specimen was prepared only by PP/POE without MgO.

In the specimens (thickness ˜0.16 mm) according to Examples 8 to 11 and Comparative Example 12, the results according to the MgO content are summarized in Table 5 below.

		Example 8	Example 9	Example 10	Comparative Example 12
Polymer		PP/POE	PP/POE	PP/POE	PP/POE
MgO		One	3	5	-
Surface treatment		LA	LA	LA	-
		MTMS	MTMS	MTMS	-
BDV(kV/mm)	Average	164.1	162.7	141.4	141.0
	error	9.9	3.4	5.7	12.3

According to Table 5, the results of Examples 8 to 10 and Comparative Example 12 can be confirmed, which are shown in a graph in FIG. 3C. As can be seen from the results, a more pronounced improvement in insulation strength is achieved when the MgO content is 1 to 3 wt%, and it shows a tendency to be maintained without deterioration compared to the PP/POE polymer even at 5 wt%. Examples 5 to 7 and 8 to 10 PP/POE blending polymer is a material that is widely used as an insulating material for AC and DC type power cables by supplementing the mechanical brittleness of PP. In addition, in the actual cable manufacturing process, since cooling is performed within a short period of time, the cooling conditions of the examples and comparative examples in Table 5 are more similar to the actual process conditions.

Therefore, as described above, the organic-inorganic nanocomposite prepared from inorganic nanoparticles (MgO) surface-treated with thermoplastic polymer and hydroxy acid/silane in the present invention can be used as an insulating material with excellent performance in various electric power fields. There is a great meaning.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be interpreted by the claims, and all technical thoughts within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (6)

1. Forming a first solution in a form in which inorganic nanoparticles are dispersed in a solvent;

   Forming a second solution containing inorganic nanoparticles having a hydroxyl group (-OH) formed on the surface of the first solution by mixing a surface treatment agent containing hydroxy acid;

   Removing the solvent contained in the second solution to form a surface-treated inorganic nanoparticle powder; And

   Forming an organic-inorganic nanocomposite by melt-mixing the surface-treated inorganic nanoparticle powder and a thermoplastic polymer; and organic-inorganic nanoparticles using a hydroxy acid-treated inorganic nanoparticle and a thermoplastic polymer. Method of making a composite.
2. The method of claim 1,

   In the step of forming the second solution,

   Hydroxy acid, characterized in that the silane is further contained in the surface treatment agent to form the hydroxy group (-OH) on the surface of the inorganic nanoparticles through a sol-gel reaction between the hydroxy acid and the silane. Method for producing organic-inorganic nanocomposites using inorganic nanoparticles and thermoplastic polymers surface-treated by.
3. The method of claim 1,

   The hydroxy acid in the step of forming the second solution,

   Surface by hydroxy acid, characterized in that it is alpha-hydroxy acid, beta-hydroxy acid, omega-hydroxy acid, or a mixture thereof. Manufacturing method of organic-inorganic nanocomposite using treated inorganic nanoparticles and thermoplastic polymer.
4. The method of claim 1,

   In the step of forming the surface-treated inorganic nanoparticle powder,

   After separating the second solution into a precipitate containing a surface treatment agent bonded to the surface of the inorganic nanoparticles through centrifugation and a supernatant containing a residual surface treatment agent that cannot be combined with the surface of the inorganic nanoparticles, the precipitate is separated. Drying to form a surface-treated inorganic nanoparticle powder.
5. The method of claim 1,

   In the step of forming the organic-inorganic nanocomposite,

   A method for producing an organic-inorganic nanocomposite using a hydroxy acid-treated inorganic nanoparticle and a thermoplastic polymer, characterized in that the thermoplastic polymer and the surface treatment agent are melt-mixed at 100° C. to 250° C. to prevent oxidation and thermal decomposition.
6. An organic-inorganic nanocomposite using inorganic nanoparticles and thermoplastic polymer surface-treated with hydroxy acid, which is prepared by the method of any one of claims 1 to 5.

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