Polyimide resin with excellent heat resistance and oxidation stability and method for producing the same

Abstract

The present invention relates to a polyimide resin with excellent heat resistance and oxidative stability and a method for producing the same. The present invention improves the heat resistance and oxidative stability of the polyimide resin by appropriately combining a rigid structure and a flexible structure through a specific combination of a diamine compound and a dianhydride compound, while preventing a decrease in mechanical properties such as tensile strength and elongation. Furthermore, when producing the polyimide resin, the azeotropic point and reaction temperature of the mixed solvent can be adjusted by mixing a first solvent and a second solvent that is insoluble in the starting materials, thereby controlling the apparent density of the final polyimide resin.

Description

[Technical Field]

[0001] The present invention relates to a polyimide resin having excellent heat resistance and oxidation stability, and a method for producing the same. [Background technology]

[0002] Polyimides have heat resistance and chemical resistance, and aromatic polyimides in particular have excellent mechanical properties and electrical insulation properties due to their rigid main chain structure.

[0003] To enhance the heat resistance of polyimide, rigid monomers are used. However, the use of such monomers can cause fusion between polyimide powder particles during molding, resulting in lower strength than expected.

[0004] Specifically, polyamic acid can be converted into polyimide by an imidization reaction in a solvent that dissolves the precursor, and a polyimide resin with excellent heat resistance can be obtained, but the polyimide resin has poor mechanical properties.

[0005] To solve the above problems, a method has been proposed in which polyamic acid is separated, powdered, and then subjected to an imidization reaction in a solid state. However, this method has limitations such as relatively low heat resistance and a complicated process. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polyimide resin having excellent heat resistance.

[0007] An object of the present invention is to provide a polyimide resin having excellent oxidation stability.

[0008] An object of the present invention is to provide a molded article in which powders containing polyimide resin are well fused together and which has excellent mechanical properties.

[0009] The objects of the present invention are not limited to the above-mentioned objects, but will become more apparent from the following description and will be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0010] The polyimide resin according to an embodiment of the present invention includes a reaction product of a diamine compound and a dianhydride compound, and may have a half-life of 150 minutes or more as measured as follows.

[0011] [Half-life] When the test piece is heat-treated at 520°C in an air atmosphere and the weight of the test piece is measured, the time until the measured weight becomes 50% of the initial weight of the test piece is measured.

[0012] The polyimide resin may have a tensile strength of 140 MPa or more.

[0013] The polyimide resin may have an apparent density of 0.15 g / cm 3 to 0.31 g / cm 3 .

[0014] The diamine compound may include at least one selected from the group consisting of p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-oxydianiline (ODA), and combinations thereof.

[0015] The diamine compound may contain 70 mol % to 92 mol % of p-phenylenediamine and 8 mol % to 30 mol % of 4,4'-oxydianiline.

[0016] The diamine compound may contain 70 mol % to 92 mol % of p-phenylenediamine and 8 mol % to 30 mol % of m-phenylenediamine.

[0017] The dianhydride compound may include at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and combinations thereof.

[0018] The dianhydride compound may contain 30 mol % to 70 mol % of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 30 mol % to 70 mol % of pyromellitic dianhydride.

[0019] The molar ratio of the diamine compound to the dianhydride compound may be 40:60 to 60:40.

[0020] A molded article according to an embodiment of the present invention may include the polyimide resin.

[0021] The molded body may further contain graphite.

[0022] The molded body may further include a conductive additive, and the conductive additive may include at least one selected from the group consisting of carbon nanotubes, carbon black, and combinations thereof.

[0023] A method for manufacturing a polyimide resin according to an embodiment of the present invention may include the steps of: preparing starting materials including a diamine compound and a dianhydride compound; preparing a mixed solvent including a first solvent that dissolves the starting materials and a second solvent that does not dissolve the starting materials; and adding the starting materials to the mixed solvent to react the starting materials.

[0024] The first solvent may include at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), pyridine, tetrahydrofuran (THF), and combinations thereof.

[0025] The second solvent may include at least one selected from the group consisting of xylene, water, ethanol, methanol, isopropyl alcohol, and combinations thereof.

[0026] The mixed solvent may contain 58% to 70% by weight of the first solvent and 30% to 42% by weight of the second solvent. [Effects of the Invention]

[0027] According to the present invention, a polyimide resin having excellent heat resistance and oxidation stability can be obtained.

[0028] According to the present invention, powders containing polyimide resins are well fused together to obtain a molded article having excellent mechanical properties.

[0029] The effects of the present invention are not limited to those mentioned above, and should be understood to include all effects that can be inferred from the following description. DETAILED DESCRIPTION OF THE INVENTION

[0030] The above and other objects, features, and advantages of the present invention will be readily understood from the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and so that the concept of the present invention will be fully conveyed to those skilled in the art.

[0031] In the description of each drawing, like reference numerals are used for like components. In the accompanying drawings, the dimensions of structures are exaggerated for clarity of the present invention. Terms such as "first," "second," etc. may be used to describe various components, but the components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be designated as a "second component," and similarly, a second component may be designated as a "first component," without departing from the scope of the present invention. A singular term includes a plural term unless otherwise specified in the context.

[0032] As used herein, terms such as "comprise" or "have" are intended to specify the presence of a specified feature, numeral, step, operation, component, part, or combination thereof, but should be understood not to preclude the possibility of the presence or addition of one or more other features, numerals, steps, operations, components, parts, or combinations thereof. Furthermore, when a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part between them. Conversely, when a layer, film, region, plate, or other part is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there is another part between them.

[0033] Unless otherwise expressly stated, all numbers, values, and / or expressions expressing quantities of ingredients, reaction conditions, polymer compositions, and formulations used herein are approximations reflecting various uncertainties of measurement that arise in deriving such values ​​from those that are inherently different and should be understood in all instances as modified by the term "about." Also, when numerical ranges are disclosed herein, such ranges are continuous and include all values ​​from the minimum value to the maximum value, inclusive, unless otherwise stated. Furthermore, when such ranges refer to integers, they include all integers from the minimum value to the maximum value, inclusive, unless otherwise stated.

[0034] The polyimide resin according to the present invention may contain a reaction product of a diamine compound and a dianhydride compound.

[0035] The present invention is characterized by enhancing the heat resistance and oxidation stability of polyimide resins through the specific combination of the diamine compound and dianhydride compound. In particular, the diamine compound and dianhydride compound are appropriately combined to have rigid and flexible structures, thereby enhancing the heat resistance of polyimide resins while preventing deterioration of mechanical properties such as tensile strength and elongation.

[0036] The formulation of the polyimide resin is not particularly limited, and may be, for example, a powder form, an emulsion form, a dispersion form, or the like.

[0037] The reactant may include a copolymer of the diamine compound and the dianhydride compound. The reactant may include a unit structure derived from the diamine compound and a unit structure derived from the dianhydride compound. The reactant may also include a random copolymer, a block copolymer, or an alternating copolymer.

[0038] The diamine compound may include at least one selected from the group consisting of p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-oxydianiline (ODA), and combinations thereof.

[0039] Preferably, the diamine compound may contain 70 mol % to 92 mol % of p-phenylenediamine and 8 mol % to 30 mol % of 4,4'-oxydianiline. Alternatively, the diamine compound may contain 70 mol % to 92 mol % of p-phenylenediamine and 8 mol % to 30 mol % of m-phenylenediamine. Although p-phenylenediamine has a rigid structure and 4,4'-oxydianiline and m-phenylenediamine have flexible structures, using them in appropriate amounts can improve the heat resistance, oxidation stability, and mechanical properties of the polyimide resin in a balanced manner.

[0040] The dianhydride compound may include at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and combinations thereof.

[0041] Preferably, the dianhydride compound may contain 30 mol % to 70 mol % of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 30 mol % to 70 mol % of pyromellitic dianhydride. 3,3',4,4'-biphenyltetracarboxylic dianhydride has a flexible structure, while pyromellitic dianhydride has a rigid structure. By using these dianhydrides in appropriate amounts, the heat resistance, oxidation stability, and mechanical properties of the polyimide resin can be improved in a balanced manner.

[0042] The molar ratio of the diamine compound to the dianhydride compound may be 40:60 to 60:40, or 50:50.

[0043] The heat resistance and oxidation stability of the polyimide resin can be evaluated using its half-life.

[0044] The half-life may refer to the time it takes for a test specimen containing the polyimide resin to lose 50% of its weight when heat-treated in an air atmosphere. The weight loss may refer to the ratio of the weight of the test specimen at the time of measurement to the weight of the test specimen before the heat treatment. The method for measuring the half-life will be described later.

[0045] The half-life of the polyimide resin may be 150 minutes or more. The upper limit of the half-life is not particularly limited, and may be, for example, 300 minutes or less, 250 minutes or less, or 210 minutes or less.

[0046] The tensile strength of the polyimide resin may be 140 MPa or more. The upper limit of the tensile strength is not particularly limited, and may be, for example, 200 MPa or less, 190 MPa or less, 180 MPa or less, or 170 MPa or less.

[0047] The polyimide resin may have an elongation of 5% or more. The upper limit of the elongation is not particularly limited, and may be, for example, 20% or less, 18% or less, or 15% or less.

[0048] The half-life, heat resistance, tensile strength, and elongation may be physical properties of a molded article containing the polyimide resin.

[0049] The molded article according to the present invention may contain the polyimide resin.

[0050] The form of the molded product is not particularly limited, and may be in the form of a sheet, pellets, or the like.

[0051] The method for producing the molded body is not particularly limited, and the molded body can be produced by compression-molding the polyimide resin and then baking it. For example, the method for producing the molded body may involve baking the compression-molded polyimide resin in a nitrogen atmosphere at a temperature of 300°C to 450°C for 5 hours to 36 hours.

[0052] The molded product may further contain graphite. A molded product obtained by compounding polyimide resin and graphite can be used as a functional material in various fields.

[0053] The molded body may further include a conductive additive. The conductive additive may include any material having electrical conductivity, such as at least one carbon material selected from the group consisting of carbon nanotubes, carbon black, and combinations thereof.

[0054] A method for producing a polyimide resin according to the present invention may include the steps of: preparing starting materials including a diamine compound and a dianhydride compound; preparing a mixed solvent including a first solvent that dissolves the starting materials and a second solvent that does not dissolve the starting materials; and adding the starting materials to the mixed solvent to react the starting materials.

[0055] The diamine compound and dianhydride compound, which are the starting materials, have been described above and will not be described further below.

[0056] The present invention is characterized by combining the first and second solvents in an appropriate ratio to precisely adjust the solubility of the mixed solvent with the starting materials. Furthermore, unlike conventional techniques, the azeotropic point and reaction temperature of the mixed solvent can be adjusted by combining the first solvent with a second solvent that does not dissolve the starting materials. The apparent density of the final polyimide resin can be adjusted to an appropriate level using the solubility and reaction temperature. The apparent density is a physical property related to the loading amount of the polyimide resin during the production of a molded article, and the apparent density of the polyimide resin may be 0.15 g / cm3 to 0.31 g / cm3. When the apparent density of the polyimide resin falls within the above range, fusion of the polyimide resins occurs easily, preventing a decrease in the mechanical strength of the molded article.

[0057] The first solvent may include a solvent that dissolves the starting material. Dissolving the starting material may mean dissolving the starting material to 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100%. The ratio may be expressed in units of mass, volume, or mole.

[0058] The first solvent may include at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), pyridine, tetrahydrofuran (THF), and combinations thereof.

[0059] The second solvent may include a solvent that has no solubility for the starting material. The term "no solubility for the starting material" may refer to a property that dissolves the starting material to 20% or less, 10% or less, or 0%. The ratio may be expressed in units of mass, volume, or mole.

[0060] The second solvent may include at least one selected from the group consisting of xylene, water, ethanol, methanol, isopropyl alcohol, and combinations thereof.

[0061] The mixed solvent may include 58% to 70% by weight of the first solvent and 30% to 42% by weight of the second solvent. When the contents of the first solvent and the second solvent are within the above ranges, the above-described effects of the present invention can be realized.

[0062] Other aspects of the present invention will be described in more detail below using examples. The following examples are merely illustrative examples to aid in understanding the present invention, and are not intended to limit the scope of the present invention.

[0063] Example 1 A reactor equipped with a Dean-Stark trap, a stirrer, a temperature controller, and a nitrogen inlet was prepared, and the reactor was purged with nitrogen.

[0064] A mixed solvent was prepared by mixing 65 wt % of N-methyl-2-pyrrolidone (NMP) as a first solvent and 35 wt % of xylene as a second solvent, and the mixed solvent was charged into the reactor.

[0065] Diamine compounds, 85 mol% of p-phenylenediamine (p-PDA) and 15 mol% of 4,4'-oxydianiline (ODA), were dissolved in the mixed solvent. After the diamine compounds were fully dissolved, 50 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 50 mol% of pyromellitic dianhydride (PMDA) were added to the resulting solution. The molar ratio of the diamine compounds to the dianhydride compounds was adjusted to 1:1.

[0066] The temperature of the reactor was raised to about 70°C, and the reaction was allowed to proceed for about 3 hours. Then, the temperature of the reactor was raised to about 150°C, and the imidization reaction was allowed to proceed for about 2 hours. Water produced during the reaction was removed using a Dean-Stark trap. After the reaction was completed, the resulting powder-form polyimide resin was collected, filtered, washed with acetone, and thoroughly dried in a vacuum oven.

[0067] The polyimide resin powder was molded at a pressure of 100,000 psi and sintered at 400° C. for 11 hours to prepare molded test specimens.

[0068] Examples 2 and 3 and Comparative Examples 1 to 3 Polyimide resins and molded test pieces were prepared in the same manner as in Example 1, except that the ratio of the diamine compounds was adjusted as shown in Table 1 below.

[0069] [Table 1]

[0070] The half-lives of the polyimide resins according to Examples 1 to 3 and Comparative Examples 1 to 3 were measured as follows.

[0071] A portion of the polyimide molded specimen was placed in a thermogravimetric analyzer (TGA). The analyzer was filled with nitrogen and the temperature was increased to 520°C at a rate of 10°C per minute. Because the analyzer was filled with an oxygen-free nitrogen atmosphere, there was almost no weight loss during the temperature increase, which did not significantly affect the results. When the temperature reached 520°C, the inside of the analyzer was filled with air, and the time until the specimen's weight reached 50% of its original weight was measured.

[0072] Therefore, the half-life may refer to the time until the weight of a test specimen reaches 50% of the initial weight when the test specimen is heat-treated at 520°C in an air atmosphere. As described above, since the inside of the analyzer is a nitrogen atmosphere during the temperature rise section, the test specimen does not oxidize and does not lose weight. Therefore, the initial weight of the test specimen may be the weight of the test specimen before it is inserted into the analyzer, or the weight of the test specimen when the temperature reaches 520°C.

[0073] The tensile strength and elongation of the polyimide resin molded product test pieces of Examples 1 to 3 and Comparative Examples 1 to 3 were measured in accordance with ASTM D-1708.

[0074] The half-life, tensile strength, and elongation of the polyimide resin molded product test pieces according to Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0075] [Table 2]

[0076] Comparative Example 2, in which the diamine compound 4,4'-oxydianiline (ODA) content was less than 8 mol%, exhibited a half-life similar to that of the Examples, but was very poor in tensile strength and elongation. On the other hand, Comparative Examples 1 and 3, in which the 4,4'-oxydianiline (ODA) content was more than 30 mol%, exhibited excellent tensile strength and elongation, but showed poor oxidation stability, as evidenced by the very short half-life.

[0077] Referring to Table 2, it can be seen that Examples 1 to 3, which are reaction products of diamine compounds and dianhydride compounds in specific combinations and contents proposed in the present invention, have balanced improvements in oxidation stability and mechanical strength.

[0078] Examples 4 and 5 and Comparative Examples 4 and 5 Polyimide resins and molded specimens were prepared in the same manner as in Example 1, except that the types and ratios of diamine compounds were adjusted as shown in Table 3 below.

[0079] [Table 3]

[0080] The half-life, tensile strength, and elongation of the polyimide resin molded specimens of Examples 4 and 5 and Comparative Examples 4 and 5 were measured as described above. The results are shown in Table 4 below.

[0081] [Table 4]

[0082] Comparative Example 4, in which the content of the diamine compound m-phenylenediamine (m-PDA) was less than 8 mol%, had very poor tensile strength and elongation, and Comparative Example 5, in which the content of m-phenylenediamine (m-PDA) exceeded 30 mol%, had a very short half-life.

[0083] In contrast, Examples 4 and 5, which are reaction products of diamine compounds and dianhydride compounds in specific combinations and contents proposed in the present invention, exhibit well-balanced improvements in oxidation stability and mechanical strength.

[0084] Examples 6 and 7 and Comparative Examples 6 and 7 Polyimide resins and molded specimens were prepared in the same manner as in Example 1, except that the ratio of the dianhydride compounds was adjusted as shown in Table 5 below.

[0085] [Table 5]

[0086] The half-life, tensile strength, and elongation of the polyimide resin molded specimens of Examples 6 and 7 and Comparative Examples 6 and 7 were measured as described above. The results are shown in Table 6 below.

[0087] [Table 6]

[0088] Comparative Example 6, in which the content of the dianhydride compound 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is less than 30 mol%, has poor mechanical properties, and Comparative Example 7, in which the content of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is more than 70 mol%, has a short half-life.

[0089] In contrast, Examples 6 and 7, which are reaction products of diamine compounds and dianhydride compounds in specific combinations and contents proposed in the present invention, exhibit well-balanced improvements in oxidation stability and mechanical strength.

[0090] Examples 8 to 13 and Comparative Examples 8 to 11 Polyimide resins and molded specimens were prepared in the same manner as in Example 1, except that the types and ratios of mixed solvents were adjusted as shown in Table 7 below.

[0091] [Table 7]

[0092] The tensile strength and elongation of the polyimide resin molded specimens of Example 1, Examples 8 to 13, and Comparative Examples 8 to 11 were measured as described above. The apparent density of the polyimide resin was calculated by filling a container with the polyimide resin, measuring its weight, and then dividing the weight by the volume of the container. The results are shown in Table 8 below.

[0093] [Table 8]

[0094] Comparative Examples 8 to 11, in which the content of the second solvent is outside the range of 30% by weight to 42% by weight proposed by the present invention, are very poor in mechanical properties.

[0095] In contrast, Examples 8 to 13, which used mixed solvents in specific combinations and contents proposed in the present invention, had excellent mechanical properties and an apparent density at an appropriate level.

[0096] Although the experimental examples and examples of the present invention have been described in detail above, the scope of the present invention is not limited to the above experimental examples and examples, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the appended claims are also included in the scope of the present invention.

Claims

1. a reaction product of a diamine compound and a dianhydride compound, A polyimide resin having a half-life of 150 minutes or more as measured as follows. [Half-life] The test piece was heat-treated at 520°C in an air atmosphere, and the weight of the test piece was measured. The time until the measured weight reached 50% of the initial weight of the test piece was measured.

2. The polyimide resin according to claim 1, having a tensile strength of 140 MPa or more.

3. 2. The polyimide resin according to claim 1, having an apparent density of 0.15 g / cm to 0.31 g / cm.

4. 2. The polyimide resin according to claim 1, wherein the diamine compound comprises at least one selected from the group consisting of p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-oxydianiline (ODA), and combinations thereof.

5. The diamine compound is 70 mol% to 92 mol% of p-phenylenediamine, 2. The polyimide resin according to claim 1, further comprising 8 mol % to 30 mol % of 4,4'-oxydianiline.

6. The diamine compound is 70 mol % to 92 mol % of p-phenylenediamine; 2. The polyimide resin according to claim 1, comprising 8 mol % to 30 mol % of m-phenylenediamine.

7. 2. The polyimide resin according to claim 1, wherein the dianhydride compound comprises at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and combinations thereof.

8. The dianhydride compound is 30 mol % to 70 mol % of 3,3',4,4'-biphenyltetracarboxylic dianhydride; 30 mol % to 70 mol % of pyromellitic dianhydride.

9. 2. The polyimide resin according to claim 1, wherein the molar ratio of the diamine compound to the dianhydride compound is 40:60 to 60:

40.

10. A molded article comprising the polyimide resin according to any one of claims 1 to 9.

11. The compact of claim 10 further comprising graphite.

12. The molded body further contains a conductive additive, The molded article according to claim 10 , wherein the conductive additive comprises at least one selected from the group consisting of carbon nanotubes, carbon black, and combinations thereof.

13. providing starting materials including a diamine compound and a dianhydride compound; preparing a mixed solvent including a first solvent that dissolves the starting material and a second solvent that does not dissolve the starting material; adding the starting materials to the mixed solvent to react the starting materials; A method for producing a polyimide resin, the half-life of which is 150 minutes or more as measured by the following method. [Half-life] The test piece was heat-treated at 520°C in an air atmosphere, and the weight of the test piece was measured. The time until the measured weight reached 50% of the initial weight of the test piece was measured.

14. The method for producing a polyimide resin according to claim 13, wherein the polyimide resin has a tensile strength of 140 MPa or more.

15. The method for producing a polyimide resin according to claim 13, wherein the apparent density is 0.15 g / cm to 0.31 g / cm.

16. The diamine compound is 70 mol % to 92 mol % of p-phenylenediamine; and 8 mol % to 30 mol % of 4,4'-oxydianiline.

17. The diamine compound is 70 mol % to 92 mol % of p-phenylenediamine; and 8 mol % to 30 mol % of m-phenylenediamine.

18. The dianhydride compound is 30 mol % to 70 mol % of 3,3',4,4'-biphenyltetracarboxylic dianhydride; The method for producing a polyimide resin according to claim 13, comprising: 30 mol% to 70 mol% of pyromellitic dianhydride.

19. The method for producing a polyimide resin according to claim 13, wherein the molar ratio of the diamine compound to the dianhydride compound is 40:60 to 60:

40.

20. 14. The method for producing a polyimide resin according to claim 13, wherein the first solvent comprises at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), pyridine, tetrahydrofuran (THF), and combinations thereof.

21. 14. The method for producing a polyimide resin according to claim 13, wherein the second solvent comprises at least one selected from the group consisting of xylene, water, ethanol, methanol, isopropyl alcohol, and combinations thereof.

22. The mixed solvent is 58% to 70% by weight of the first solvent; and 30% by weight to 42% by weight of the second solvent.

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