Patent Application
20250043084
The present invention relates to a highly heat-resistant and chemical-resistant polyimide powder and a preparation method thereof using a glass fiber powder.
In general, a polyimide (PI) is a polymer of imide monomers, which is formed by solution polymerization of a dianhydride and a diamine or diisocyanate, and has mechanical properties such as excellent strength, chemical resistance, weather resistance, and heat resistance, based on the chemical stability of an imide ring. In addition, polyimides are attracting attention as high-functional polymer materials applicable to a wide range of industrial fields such as electronics, communications, and optics due to their excellent electrical properties such as insulation and a low dielectric constant.
Meanwhile, conventional polyimide has excellent insulating and heat resistance properties, but has the problem of poor stability at a high temperature of about 800° C. Also, in order to maintain the high temperature stability of the conventional polyimide powder, when ceramic materials among inorganic materials are used, there is a problem that processing is difficult, and when metal materials among inorganic materials are used, due to their low insulating properties, there is a problem that they are difficult to use as an insulating material.
Therefore, there is a need for research for a method of preparing highly heat-resistant polyimide powder that may secure stability at a high temperature of about 800° C. while maintaining insulation properties.
The purpose of the present invention is to address the problems and technical challenges of the related art as described above.
The present invention provides a highly heat-resistant polyimide powder that may secure stability at a high temperature of about 800° C. while maintaining insulation properties, and a method of preparing the same.
The present invention also provides a chemically resistant polyimide powder that may secure stability against acids and/or bases, and a method of preparing the same.
The present invention relates to a polyimide powder and a method of preparing the same.
The polyimide powder according to the present invention has a dianhydride monomer component and a diamine monomer component as polymerized units.
As described above, conventional polyimide has excellent insulating and heat resistance properties, but has the problem of poor stability or chemical resistance at a high temperature of about 800° C. Also, to maintain the high temperature stability of the conventional polyimide powder, when ceramic materials among inorganic materials are used, there is a problem that processing is difficult, and when metal materials among inorganic materials are used, due to their low insulating properties, there is a problem that they are difficult to use as an insulating material.
The present invention may provide a highly heat-resistant polyimide powder that may secure stability at a high temperature of about 800° C. while maintaining insulation properties and may be a chemically resistant polyimide powder resistant to acids and alkalis, by polymerizing the dianhydride monomer component and the diamine monomer component using a glass fiber powder.
A method of preparing a polyimide powder according to one embodiment of the present invention includes preparing a polyamic acid solution by solution polymerizing a dianhydride monomer and a diamine monomer in an organic solvent including glass fibers; heating the polyamic acid solution to prepare a polyimide mixed solution; and filtering and drying a precipitate present in the mixed solution to obtain a polyimide powder.
Conventionally, a dianhydride monomer and a diamine monomer were dispersed in an aqueous solvent to prepare a dispersion, and then heat-treated to prepare a polyimide powder. However, when a dispersion is prepared and heat-treated by adding the glass fiber powder to an aqueous solvent as in the related art, there is a problem in that the glass fiber powder aggregates in the dispersion and the dispersibility deteriorates.
In a method of preparing a polyimide powder according to one embodiment of the present invention, since the dianhydride monomer, the diamine monomer, and the glass fiber are dispersed in a mixed organic solvent to form a polymerization solution (varnish), and then heat-treated to prepare a polyimide powder, the dispersibility of the glass fiber may be good.
In one embodiment, the shape of the glass fiber is not particularly limited, but may be used in the form of chopped strands or a powder obtained by powdering the same. In particular, considering dispersibility, the powder may have a diameter of 5 μm or more, 7 μm or more, or 9 μm or more, and in addition, a powder having a diameter of 18 μm or less, 15 μm or less, or 12 μm or less may be used.
In addition, the type of glass fiber is not particularly limited, but glass fibers with high acid resistance, base resistance, and electrical resistance may be used.
A content of the glass fiber included in the organic solvent may be, for example, 5 to 90 parts by weight, 6 to 70 parts by weight, 7 to 60 parts by weight, 8 to 55 parts by weight, or 10 to 50 parts by weight, based on 100 parts by weight of the total amount of the dianhydride monomer and diamine monomer. When the content of the glass fiber is too small, it is difficult to secure stability or chemical resistance at a high temperature of about 800° C., and when the content is too large, mechanical properties such as tensile strength or elongation may decrease.
The organic solvent of the present invention may be a mixed solvent of an aprotic solvent and a protic solvent. The use of the mixed solvent has the advantage of excellent moldability and processability compared to the use of an aprotic solvent alone or a protic solvent alone.
Without being bound by theory, it is believed that in the case of the aprotic solvent, it acts as a kind of imidization catalyst, and in the case of the protic solvent, it plays a role in increasing a molecular weight.
The aprotic solvent may include, without limitation, one or more selected from the group consisting of toluene, xylene, naphtha, anisole, cresol, ethylbenzene, propylbenzene, chlorobenzene, dichlorobenzene, trichlorobenzene, biphenyl, terphenyl, diphenyl ether, diphenyl sulfide, and acetophenone, chlorinated biphenyl, and chlorinated diphenyl ether. The protic solvent may include, without limitation, one or more selected from the group consisting of N-methyl-pyrrolidone (NMP), N,N′-dimethylformamide (DMF), N,N′-diethylformamide (DEF), N,N′-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), N,N-diethylacetamide (DEAc), 3-methoxy-N,N-dimethylpropanamide (KJCMPA), and gamma-butyrolactone (GBL).
The mixed solvent may include 10 to 90 wt % of the aprotic solvent and 10 to 90 wt % of the protic solvent, for example, 20 to 80 wt % of the aprotic solvent and 20 to 80 wt % of the protic solvent. When the content of the aprotic solvent is too small, imidization is not sufficiently achieved in a heating process, which has the disadvantage of not ensuring moldability and lowering the intrinsic viscosity (IV), and when the content is too large, the molecular weight of the polymerization solution is formed too late (chains are too small), which has the disadvantage that moldability cannot be secured when forming molded products later.
The preparing of the polyamic acid solution may be performed at 50 to 100° C., for example, 60 to 90° C., 65 to 85° C., or 70 to 80° C., and the preparing of the polyimide mixed solution may be performed at 160 to 200° C., for example, 170 to 190° C. or 175 to 185° C.
When the heating temperature is lower than the above range, mechanical properties such as elongation and tensile strength may decrease and fracture may occur during molding processing, resulting in lower yield and lower processability. In addition, when the heating temperature is higher than the above range, the color of the powder may darken and the particle size may increase.
The preparing of the polyamic acid solution and/or preparing of the polyimide mixed solution may be performed under pressurized conditions, for example, 1 to 10 bar. In particular, in one embodiment of the present invention, since the dianhydride monomer, the diamine monomer, and the glass fiber powder are dispersed in a mixed solvent for polymerization, the polymerization reaction may be performed under normal pressure or pressurized conditions of 1 to 3 bar or less. Pressurization may be done by injecting an inert gas into the reactor or using water vapor generated inside the reactor. The inert gas may be nitrogen, argon, helium, or neon.
When the pressurized conditions are lower than the above range, mechanical properties such as elongation and tensile strength may decrease and fracture may occur during molding processing, resulting in lower yield and lower processability. In addition, when the pressurized conditions are higher than the above range, the color of the powder may darken and the particle size may increase.
The reaction time of preparing the polyamic acid solution and/or preparing the polyimide mixed solution may be 1 to 20 hours, for example, 1 to 10 hours, 1 to 8 hours, 1 to 6 hours, or 1 to 4 hours.
When the reaction time is lower than the above range, the reaction yield decreases, mechanical properties such as elongation and tensile strength may decrease and fracture may occur during molding processing, resulting in lower yield and lower processability. In addition, when the reaction time is higher than the above range, the color of the powder may darken and the particle size may increase.
The obtaining of the polyimide powder is filtering and drying a precipitate present in the mixed solution to obtain a polyimide powder.
The filtering and drying method is not particularly limited, and for example, vacuum drying or oven drying may be used.
The dianhydride monomer is not particularly limited as long as it can react with the diamine monomer to form polyimide. For example, the dianhydride monomer according to the present invention may include at least one selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), and p-phenylenebis(trimellitate anhydride) (TAHQ).
The diamine monomer is not particularly limited as long as it can react with the dianhydride monomer to form polyimide. For example, the diamine monomer according to the present invention may include at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4′-diaminodiphenyl ether (ODA), 4,4′-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxy benzene (TPE-Q), bisaminophenoxybenzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).
At this time, the molar ratio (b/a), which represents the number of moles (b) of the diamine monomer component to the number of moles (a) of the di anhydride monomer component, is 1 or less. For example, the upper limit of the molar ratio (b/a) of the diamine monomer component to the dianhydride monomer component may be 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, or 0.95 or less, the lower limit of the molar ratio may be 0.9 or more, 0.91 or more, 0.92 or more, 0.93 or more, or 0.94 or more, and specifically, the molar ratio of the diamine monomer component to the dianhydride monomer component may be 0.9 to 0.99, 0.93 to 0.99, 0.94 to 0.99, 0.95 to 0.99, 0.95 to 0.98, or 0.96 to 0.98.
For example, the present invention uses fewer moles of the diamine monomer component than the number of moles of the dianhydride monomer component. Stoichiometrically, polyimide can be produced by a 1:1 reaction of the dianhydride monomer and the diamine monomer, but because the reaction proceeds mainly in the presence of a solvent and/or catalyst and at this time, a side reaction between the functional group of the solvent or catalyst and the diamine may proceed, generally, diamine is added in excess or dianhydride and diamine are added in equal molar numbers.
The solid content in the mixed solvent may be 1 to 30% by weight. The solid content may refer to the dianhydride monomer component and the diamine monomer component. For example, the solid content in the mixed solvent may be 1 to 20% or 10 to 20%. By having the above solid content, the intrinsic viscosity of the polyimide powder may be adjusted to have appropriate processability.
In particular, in the method of preparing a polyimide powder according to one embodiment of the present invention, since the dianhydride monomer component, the diamine monomer component, and the glass fiber powder are dispersed in a mixed solvent to form a polymerization solution (varnish), the intrinsic viscosity of the polyimide powder is higher (>0.9 dL/g) compared to the conventional water-based polymerization method, resulting in excellent moldability and processability.
The polyimide powder according to another embodiment of the present invention includes a polyimide matrix having polymerized units derived from the dianhydride monomer and the diamine monomer, and glass fibers dispersed in the polyimide matrix, and satisfies one or more of the following conditions:
The glass fiber powder may be included in an amount of 0.01 to 90 parts by weight, preferably 0.1 to 50 parts by weight, based on 100 parts by weight of the polyimide powder. The glass fiber powder may be included during polymerization of the polyimide powder, or additionally, may be mixed with the polyimide powder.
The polyimide powder may have a weight loss rate of 35% or less, for example, 34% or less, 33% or less, 10 to 35%, 15 to 34%, or 18% to 32%, as measured after being left at 800° C. for 25 hours. When the weight loss rate is more than 35%, high-temperature heat resistance may be insufficient.
The polyimide powder may have a surface resistance of 1014 Ω/cm2 or more as measured according to ASTM D257. For example, the polyimide powder according to the present invention may have a lower limit of surface resistance that is 1014 Ω/cm2 or more and an upper limit of surface resistance that is 1015 Ω/cm2 or less, as measured according to ASTM D257. When the surface resistance is less than 1014 Ω/cm2, insulation properties may be insufficient.
The polyimide powder may have a weight loss rate of 2.6% or less, for example 2.5% or less, 0.5 to 2.6%, or 1 to 2.5%, as measured after immersion for 168 hours in an acidic aqueous solution with a pH of 5 or less. The acidic aqueous solution with a pH of 5 or less is not particularly limited, but for example, a 45 to 55 wt % aqueous hydrofluoric acid solution may be used. The measurement temperature or pressure is not particularly limited, but measurement may be performed at room temperature or atmospheric pressure.
The polyimide powder may have a weight loss rate of 15% or less, for example 13% or less, 1 to 11%, or 2 to 10%, as measured after immersion for 168 hours in an alkaline aqueous solution with a pH of 9 or more. The alkaline aqueous solution with a pH of 5 or more is not particularly limited, but for example, a 20 to 30 wt % ammonia aqueous solution may be used. The measurement temperature or pressure is not particularly limited, but measurement may be performed at room temperature or atmospheric pressure.
The dianhydride monomer of the polyimide powder may include at least one selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), and p-phenylenebis(trimellitate anhydride) (TAHQ).
The diamine monomer of the polyimide powder may include at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4′-diaminodiphenyl ether (ODA), 4,4′-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N, N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxybenzene (TPE-Q), bisaminophenoxy benzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).
In addition, the present invention provides a method of manufacturing a polyimide molded article, including pressure molding the above-described polyimide powder.
The pressure molding may be performed at a pressure of 30 to 1000 MPa, and the pressure molding may be performed at a temperature of 200 to 500° C. In addition, the pressure molding may be performed at room temperature and may further include sintering the pressure molded polyimide powder at 200 to 500° C. When the pressure is lower than the above range, the moldability of the powder may be insufficient during molding, and when it is higher than the above range, the processability of the molded article may be reduced. When the temperature is lower than the above range, the fluidity of the molecules may not be secured and moldability may be greatly reduced, and when it is higher than the above temperature range, some parts may be oxidized due to overheating.
The present invention also provides a molded article manufactured using the polyimide powder. The polyimide powder prepared according to the present invention may be manufactured into molded articles by various molding methods, for example, compression molding, injection molding, slush molding, blow molding, extrusion molding, or spinning methods. The form of the molded article is not limited, but may be a film, a sheet, a pellet, a tube, a belt, an injection molded article, or an extrusion molded article.
The polyimide powder prepared according to the present invention may be used in various fields such as electrical/electronics, semiconductors, displays, automobiles, medicine, batteries, and aerospace.
According to the present application, it is possible to prepare a highly heat-resistant polyimide powder that can secure stability at a high temperature of about 800° C. while maintaining insulation properties.
The polyimide powder according to the present application can increase the surface resistance of the molded article to 1014 (2/cm2 or more, making it possible to maintain insulation.
In addition, the polyimide powder according to the present application can secure stability at a high temperature of about 800° C. while maintaining insulation properties unlike other fillers, by including glass fiber powder as filler.
In addition, the polyimide powder according to the present application has a mass change rate of 1.0% to 2.6% as measured when immersed in a hydrofluoric acid solution and a mass change rate of 2.0% to 10.0% as measured when immersed in ammonia water, and has excellent chemical resistance compared to conventional polyimide powder.
However, effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.
Hereinafter, the present invention will be described in more detail through examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited by the examples presented below.
900 g of a mixed solvent of 30 wt % m-xylene and 70 wt % N-methylpyrrolidone (NMP), 46 g of ODA, 10 g of a glass fiber powder, 40 g of PMDA, and 14 g of ODPA were sequentially input to a glass reactor and stirred at 75° C. for 2 hours to prepare a polyamic acid solution. The completed polyamic acid solution was heated to 180° C. for 2 hours at atmospheric pressure to prepare a polyimide mixed solution. The powder precipitated in the mixed solution was filtered, washed with ethanol, and dried for 24 hours to prepare a polyimide powder. The prepared powder was pressure-molded at >50 MPa and >300° C. to prepare a molded article.
A molded article was manufactured in the same manner as Example 1, except that 15 g of a glass fiber powder was used.
A molded article was manufactured in the same manner as Example 1, except that 20 g of a glass fiber powder was used.
A molded article was manufactured in the same manner as Example 1, except that 30 g of a glass fiber powder was used.
A molded article was manufactured in the same manner as Example 1, except that 40 g of a glass fiber powder was used.
A molded article was manufactured in the same manner as Example 1, except that 50 g of a glass fiber powder was used.
Polyimide powder was prepared in the same manner as in Example 1, except that the filler components were different, as shown in Table 1 below.
Specifically, Comparative Example 1 is a case in which no filler was added, and Comparative Examples 2 to 5 are a case in which fillers of various components, which are conventionally input, were added.
The physical properties of the prepared polyimide powder were measured using the following methods, and the results are shown in Table 1 below.
To analyze the weight loss rate, a compression molded specimen (5 mm*5 mm*5 mm cube shape) of a polyimide powder was used, and the weight loss rate (%) at 800° C. was measured using a thermogravimetric analyzer (TGA). Specifically, the weight loss rate was compared after leaving the specimen at 800° C. for 25 hours under 0.61 Mpa air pressure.
To measure surface resistance, a compression molded specimen of a polyimide powder was used, and the surface resistance of Examples and Comparative Examples was measured according to the ASTM-D257 standard. Specifically, surface resistance was measured under the conditions of 55% RH and 23° C., and an applied voltage of 500V according to the ASTM-D257 measurement method, and the measurement equipment was a 4-point probe meter (CMT-SR 1000N, AIT).
Referring to Table 1, in the case of Examples 2, 4, 5, and 6, which are polyimide powders having a dianhydride monomer component and a diamine monomer component as polymerized units and further including a glass fiber powder as in the present invention, the surface resistance is 1014 Ω/cm2 or more and the weight loss rate (%) at 800° C. is 18.1% to 31.5%, indicating that stability may be secured at a high temperature of about 800° C. while maintaining insulation properties. In particular, in Example 6, when a content of the glass fiber powder was 50 wt %, the weight loss rate (%) at 800° C. was 18.1%, showing that the powder had excellent high heat resistance properties. For this reason, in the case of Examples 2, 4, 5, and 6 of the present invention, because the molded article has a resistance of 1014 Ω/cm2 or more and may have a reduced weight loss rate (%) at 800° C., it can be seen that stability can be secured at a high temperature of about 800° C. while maintaining insulation properties.
On the other hand, when no filler is added (Comparative Example 1) or when a conventional filler is input (Comparative Examples 2 to 5), it can be seen that there is a problem that the surface resistance is lowered and the insulation properties are lowered, or the weight loss rate (%) at 800° C. increases and high temperature stability decreases.
In addition, since the method of preparing a polyimide powder according to the present application is achieved by mixing glass fibers during in-situ polymerization, the dispersibility of the polyimide powder is excellent and the glass fibers act as a seed, enabling more uniform powder preparation.
In addition, since the polyimide powder according to the present application includes aromatic chains and further includes a glass fiber powder as a filler, it may have better heat resistance than conventional polyimide powder.
For chemical resistance analysis, polyimide molded articles were processed into cube-shaped specimens of 5 mm*5 mm*5 mm. The cubic specimen was immersed in a 49% hydrofluoric acid solution for 168 hours. After immersion, the change in appearance and weight loss rate were measured.
In the same way, the cube-shaped specimen was immersed in 25-28% ammonia water for 168 hours, and the change in appearance and weight loss rate before and after immersion were measured.
Referring to Table 2, in the case of Examples 1, 3, 4, and 6, which include a glass fiber powder dispersed in a polyimide matrix having polymerized units derived from a dianhydride monomer and a diamine monomer as in the present invention, it was found that the weight loss rate measured when immersed in a hydrofluoric acid solution is 1.0% to 2.6%, and the weight loss rate measured when immersed in an aqueous ammonia solution is 2.0% to 10.0%, indicating excellent chemical resistance.
On the other hand, in the case where filler was not added (Comparative Example 1), it was found that the weight loss rate measured when immersed in the hydrofluoric acid solution and the aqueous ammonia was high, indicating low chemical resistance.
Table 3 below shows experimental results comparing intrinsic viscosity (IV), formability, and processability according to Examples using a mixed solvent of the aprotic solvent and the protic solvent according to one embodiment of the present invention and Comparative Examples using the aprotic solvent alone or the protic solvent alone.
Specifically, Comparative Example 6 shows a case where m-cresol was used alone, and Comparative Example 7 was the same as Example 1 except that NMP was used alone. In addition, Example 7 shows a case of a 50/50 wt % mixed solution of m-cresol/NMP, Example 8 shows a case of a 30/70 wt % mixed solution of m-cresol/NMP, and Example 9 is the same as Example 1 except that it shows a case of a 30/70 wt % mixed solution of m-cresol/NMP.
As shown in Table 3, in the case of Comparative Examples 6 and 7 in which only the protic solvent or the aprotic solvent was used, it can be seen that the intrinsic viscosity (IV) was low and it was difficult to secure moldability and processability.
On the other hand, in the case of Examples 7 to 9 using a mixed solvent of the protic solvent and the aprotic solvent as in the embodiment of the present invention, it can be seen that the intrinsic viscosity (IV) is high and both moldability and processability are excellent.
The present invention described above is not limited to the above-described embodiments, as various substitutions and changes can be made by those skilled in the art without departing from the technical spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0174321 | Dec 2021 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/019855 | 12/7/2022 | WO |
