Oligomer polyimide, methods for preparing those oligomers, and low dielectric curing products prepared from those oligomers.

Abstract

Invention details;

Description

Polyimide oligomer, preparation method thereof and cured product with low dielectric properties prepared therefrom Technical Field

[0001] The present invention relates to an oligomer, a preparation method thereof and a cured product, and more particularly to a polyimide oligomer derived from dimerized diamine, a preparation method thereof and a cured product prepared therefrom with low dielectric properties. Background Art

[0002] The rise of cloud technologies such as the internet and data centers has catapulted free radical curing systems into the mainstream of printed circuit board (PCB) materials. Noryl SA9000, marketed by SABIC, is a polyphenylene ether oligomer with difunctional acrylic end groups. Its low molecular weight provides excellent organic solubility and workability in impregnation processes. Noryl SA9000, through free radical curing of the acrylic end groups, imparts its fundamental physical properties. The inherent non-polar structure of polyphenylene ether, coupled with the absence of polar groups after free radical curing, imparts excellent electrical properties to the cured product, making Noryl SA9000 a mainstream material for high-end PCBs. However, the preparation process for Noryl SA9000 is challenging to purify and generates significant wastewater. For environmental reasons, developing viable materials with excellent electrical properties and low process pollution could contribute to the development of PCB materials while addressing environmental concerns.

[0003] With the growing awareness of environmental protection and carbon reduction in recent years, numerous studies have begun to explore the application of specialized bio-based diamines. For example, diamine (dimer diamine) is mixed with the aromatic diamine monomer m-tolidine and then polymerized with 4,4'-bisphenol A dianhydride (BPADA) to produce high-molecular-weight polyimide (PI). Alternatively, diamine (dimer diamine) is reacted with dianhydrides to produce polyimide oligomers or polymers with reactive terminal functional groups. Due to the bulky, branched structure of diamine (dimer diamine) with a large free volume, its incorporation into materials is expected to impart low dielectric properties, resulting in excellent electrical performance for these polyimide materials. However, considerable room for improvement remains in terms of heat resistance.

[0004] Therefore, the goal of relevant industry practitioners is to synthesize a free-radical curable polyimide oligomer derived from bio-based diamine that can overcome the poor thermal properties of diamine derivatives while also possessing high-frequency and low dielectric properties.

[0005] Summary of the Invention

[0006] An object of the present invention is to provide a polyimide oligomer, a preparation method thereof, and a cured product thereof having low dielectric properties. By combining dimerized diamine with other monomers and adjusting the ratio, a free radical-curable polyimide oligomer is obtained. The cured product has heat resistance and excellent electrical properties.

[0007] One embodiment of the present invention provides a polyimide oligomer having a structure as shown in Formula (I) or Formula (II):

[0008] wherein X is independently hydrogen or methyl, R1 is a cycloalkane having a total carbon number of 5 to 20 and having at least 5 carbon atoms, or a structure represented by formula (A), formula (B) or formula (C):

[0009] R2 is independently a saturated or unsaturated hydrocarbon having 36 carbon atoms, and A is independently a benzene ring, a biphenyl ring, a naphthalene ring, a cycloalkane having 4 to 6 carbon atoms, or a structure represented by formula (a), (b), (c), (d), (e), (f), (g), (h), or (i):

[0010] Here, n is any number from 0 to 10, and m / p is any number from 0.5 to 5.

[0011] According to the polyimide oligomer described in the preceding paragraph, the cycloalkanes having 5 or more carbon atoms may comprise a structure as shown in Formula (D), Formula (E), or Formula (F):

[0012] According to the polyimide oligomer described in the preceding paragraph, R2 may have a structure as shown in Formula (G), Formula (H), Formula (I), or Formula (J):

[0013] According to the polyimide oligomer described in the preceding paragraph, it may have a structure as shown in Formula (I-1) or Formula (II-1):

[0014] Another embodiment of the present invention provides a method for preparing the aforementioned polyimide oligomer, comprising performing a first dissolution step, performing a second dissolution step, performing a mixing step, and performing an addition step. The first dissolution step is to dissolve a dianhydride and a monoanhydride in a first solvent to form an anhydride solution, wherein the monoanhydride has an unsaturated double bond. The second dissolution step is to mix a dimerized diamine and a difunctional fatty amine and dissolve them in a second solvent to form a diamine solution, wherein the difunctional fatty amine has a rigid cyclic structure. The mixing step is to add the diamine solution to the anhydride solution and react at a polymerization temperature to form a mixed solution. The adding step is to add xylene to the mixed solution, react at a reaction distillation temperature and distill to obtain the polyimide oligomer.

[0015] According to the preparation method of the polyimide oligomer described above, the first solvent and the second solvent can be selected from the group consisting of N,N-dimethylacetamide, N-methylpyrrolidone, dimethylformamide, anisole, dimethyl sulfoxide, cyclohexanone, and resorcinol.

[0016] According to the preparation method of the polyimide oligomer described in the previous paragraph, the polymerization temperature can be 0°C to 90°C.

[0017] According to the method for preparing the polyimide oligomer described in the preceding paragraph, the reaction distillation temperature may be 130°C to 170°C.

[0018] According to the preparation method of the polyimide oligomer described in the preceding paragraph, the molar ratio of the dimerized diamine to the difunctional fatty amine may be 1:0.4 to 1:3.

[0019] According to the preparation method of the polyimide oligomer described in the preceding paragraph, the molar ratio of the diamine obtained by adding the diamine dimer to the difunctional fatty amine to the dianhydride can be 1.2:1 to 1.8:1.

[0020] Another embodiment of the present invention provides a cured product with low dielectric properties, which is prepared by adding a free radical initiator to the aforementioned polyimide oligomer and baking the product at a curing temperature.

[0021] According to the cured product with low dielectric properties described in the previous paragraph, the free radical initiator can be a peroxide, an azo initiator, or a mixture thereof.

[0022] According to the cured product with low dielectric properties described in the previous paragraph, the amount of the free radical initiator added can be 0.3 weight percent to 2 weight percent of the polyimide oligomer content.

[0023] According to the cured material with low dielectric properties described in the previous paragraph, the curing temperature may be 160° C. to 240° C.

[0024] According to the cured material with low dielectric properties described in the previous paragraph, the curing temperature may be 180°C, 200°C or 220°C.

[0025] The polyimide oligomer of the present invention is polymerized using dimerized diamine as a raw material and specific monomers, eliminating the need for purification. This results in reactive unsaturated double bonds at the ends of the molecular chains, allowing for direct free radical thermal curing. After curing, the resulting product exhibits excellent heat resistance and electrical properties, making it a promising material for high-frequency circuit board applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To make the above and other objects, features, advantages and embodiments of the present invention more apparent, the following descriptions of the accompanying drawings are given:

[0027] FIG. 1 is a flow chart illustrating a method for preparing a polyimide oligomer according to one embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will discuss various embodiments of the present invention in more detail. However, this embodiment can be applied to various inventive concepts and can be specifically implemented in various specific scopes. The specific embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure.

[0029] In this invention, compound structures are sometimes represented using skeleton formulas. This representation may omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. If a functional group is explicitly depicted in a structural formula, the depicted group shall prevail.

[0030] In the present invention, "a polyimide oligomer having a structure as shown in formula (I)" may sometimes be expressed as a polyimide oligomer represented by formula (I) or polyimide oligomer (I) for the sake of brevity and fluency, and the representation of other compounds or groups may be deduced similarly.

[0031] In the present invention, unless it is specifically indicated whether a group is substituted or not, the group may represent a substituted or unsubstituted group. For example, "alkyl" may represent a substituted or unsubstituted alkyl group.

[0032] <Polyimide oligomer>

[0033] The present invention provides a polyimide oligomer having a structure as shown in formula (I) or formula (II):

[0034] wherein X is independently hydrogen or methyl, R1 is a cycloalkane having a total carbon number of 5 to 20 and having at least 5 carbon atoms, or a structure represented by formula (A), formula (B) or formula (C):

[0035] R2 is independently a saturated or unsaturated hydrocarbon having 36 carbon atoms. A is independently a benzene ring, a biphenyl ring, a naphthalene ring, a cycloalkane having 4 to 6 carbon atoms, or a structure represented by formula (a), (b), (c), (d), (e), (f), (g), (h), or (i):

[0036] Here, n is any number from 0 to 10, and m / p is any number from 0.5 to 5.

[0037] Specifically, the cycloalkanes having 5 or more carbon atoms may include a structure as shown in Formula (D), Formula (E), or Formula (F):

[0038] However, the present invention is not limited thereto. In addition, R2 may have a structure as shown in Formula (G), Formula (H), Formula (I) or Formula (J):

[0039] For example, when in the polyimide oligomer represented by formula (I) or formula (II), X is hydrogen, R1 is a structure represented by formula (D), R2 is a structure represented by formula (J), and A is a benzene ring, the polyimide oligomer has a structure represented by formula (I-1) or formula (II-1):

[0040] The polyimide oligomer of the present invention is derived from a dimerized diamine and has reactive unsaturated double bonds at its terminal ends. It can be cured by free radical polymerization to form a cured product with excellent mechanical properties and heat resistance. Furthermore, because the main structure is composed of a large number of aliphatic carbon chains, it can provide the material with excellent low dielectric properties and has considerable potential for application in printed circuit board materials.

[0041] <Preparation Method of Polyimide Oligomer>

[0042] 1 , which is a flow chart of a method 100 for preparing a polyimide oligomer according to one embodiment of the present invention, includes steps 110 , 120 , 130 , and 140 .

[0043] Step 110 is a first dissolution step, in which a dianhydride and a monoanhydride are dissolved in a first solvent to form an anhydride solution. The monoanhydride has an unsaturated double bond to meet the requirements of subsequent free radical curing. Specifically, the monoanhydride can be, but is not limited to, maleic anhydride or itaconic anhydride.

[0044] Step 120 is a second dissolution step, in which a dimerized diamine and a difunctional fatty amine are mixed and dissolved in a second solvent to form a diamine solution. The molar ratio of the dimerized diamine to the difunctional fatty amine may be 1:0.4 to 1:3, preferably 1:0.5 to 1:2. Specifically, the dimerized diamine is a bio-based diamine derived from a fatty acid, a diamine monomer with a multi-carbon aliphatic structure. The difunctional fatty amine has a rigid cyclic structure, which provides good heat resistance for the subsequent free radical curing of the derivative. Specifically, the difunctional fatty amine may be, but is not limited to, isophorone diamine or protobornene diamine.

[0045] In addition, the first solvent in step 110 and the second solvent in step 120 may be the same or different, and are selected from the group consisting of N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethylformamide (DMF), anisole, dimethyl sulfoxide (DMSO), cyclohexanone, and resorcinol (m-cresol).

[0046] Step 130 is a mixing step, in which the diamine solution is added to the anhydride solution and reacted at a polymerization temperature to form a mixed solution. The polymerization temperature can be 0°C to 90°C, preferably 40°C to 80°C. After the diamine solution is added to the anhydride solution, polymerization is carried out at the polymerization temperature. The molar ratio of diamine to dianhydride obtained by dimerizing diamine and difunctional fatty amine can be 1.2:1 to 1.8:1, preferably 1.4:1 to 1.6:1.

[0047] Step 140 is an addition step, in which xylene is added to the mixed solution, and the mixture is reacted and distilled at a reaction distillation temperature to obtain a polyimide oligomer. The reaction distillation temperature may be 130°C to 170°C, preferably 140°C to 160°C. Specifically, after the xylene is added to the mixed solution, a Dean-Stark apparatus is set up and the temperature is raised to the reaction distillation temperature for a closed-loop reaction and distillation to remove water. After cooling, a polyimide oligomer solution is obtained, which contains polyimide oligomers and a solvent.

[0048] <Cured Material with Low Dielectric Properties>

[0049] The present invention provides a cured product with low dielectric properties. The cured product is prepared by adding a free radical initiator to the aforementioned polyimide oligomer and baking the cured product at a curing temperature. The free radical initiator can be a peroxide, an azo initiator, or a mixture thereof. The amount of the free radical initiator added can be 0.3 to 2 weight percent, preferably 0.5 to 1.5 weight percent, of the polyimide oligomer. Furthermore, the free radical curing reaction can be carried out using a stepwise heating method, but is not limited to this method. The curing temperature can be 160°C to 240°C, preferably 180°C, 200°C, or 220°C.

[0050] Thus, the polyimide oligomer preparation method of the present invention overcomes the problem of poor thermal properties after curing by selecting and matching amines and adjusting their proportions, while maintaining high-frequency and low-dielectric properties. Furthermore, due to the improved monomer selection and feeding sequence, the polyimide oligomer can be produced without the addition of a catalyst and can be directly used in the circuit board impregnation process, reducing waste liquid production and solvent usage, thereby balancing the development of the circuit board industry and carbon reduction trends.

[0051] The present invention is further illustrated by the following specific examples, which are intended to facilitate those skilled in the art to which the present invention relates, so that they can fully utilize and practice the present invention without excessive interpretation. These examples should not be construed as limiting the scope of the present invention, but are intended to illustrate how to implement the materials and methods of the present invention.

[0052] <Examples / Comparative Examples>

[0053] Example 1: 20 g (0.0917 mole) of pyromellitic anhydride (PMDA) and 8.99 g (0.0917 mole) of maleic anhydride were dissolved in 90 g of N,N-dimethylacetamide (DMAc) to prepare an anhydride solution. Next, 36.79 g (0.0688 mole) of Priamine 1075 (available from Croda) and 11.71 g (0.0688 mole) of isophoronediamine (IPDA) were dissolved in 73 g of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution is then slowly dripped into the anhydride solution in a water bath controlled to not exceed 60°C. After the dripping is complete, the temperature is raised to 80°C and the reaction is allowed to proceed for 3 hours. Afterward, 54 grams of xylene is added to form a mixed solution to be separated. The polyimide oligomer solution is then separated from the mixed solution by distillation. For example, using a Dean-Stark apparatus, the mixed solution is heated to 150°C to remove water for 4 hours, then further heated to 160°C to remove water until the desired amount of water is removed, and then cooled to obtain the polyimide oligomer solution of Example 1. Specifically, the polyimide oligomer of Example 1 has the structure shown in Formula (I-1), wherein m / p is 1. As measured by gel permeameter chromatography (GPC), the number average molecular weight (Mn) is 2095 and the weight average molecular weight (Mw) is 4841.

[0054] Example 2: 20 grams (0.0917 mole) of pyromellitic anhydride and 8.99 grams (0.0917 mole) of maleic anhydride were dissolved in 90 grams of N,N-dimethylacetamide to prepare an anhydride solution. Next, 24.53 grams (0.0459 mole) of dimerized diamine (Priamine 1075, available from Croda) and 15.62 grams (0.0917 mole) of isophorone diamine were dissolved in 56.54 grams of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution was then slowly dripped into the anhydride solution in a water bath controlled to not exceed 60°C. After the addition was complete, the temperature was raised to 80°C and the reaction continued for 3 hours. Afterwards, 48.85 grams of xylene was added. The remaining steps were the same as in Example 1 to obtain the polyimide oligomer solution of Example 2. Specifically, the polyimide oligomer in Example 2 has a structure as shown in Formula (I-1), wherein m / p is 2, and after measurement by gel permeameter (GPC), its number average molecular weight (Mn) is 1448 and its weight average molecular weight (Mw) is 3049.

[0055] Example 3: 20 g (0.0917 mole) of pyromellitic anhydride and 8.99 g (0.0917 mole) of maleic anhydride were dissolved in 90 g of N,N-dimethylacetamide (DMAc) to prepare an anhydride solution. Next, 49.05 g (0.0917 mole) of dimerized diamine (Priamine 1075, available from Croda) and 7.81 g (0.0458 mole) of isophorone diamine were dissolved in 90.07 g of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution was then slowly dripped into the anhydride solution in a water bath controlled to not exceed 60°C. After the dripping was complete, the temperature was raised to 80°C and the reaction continued for 3 hours. Afterwards, 60.02 g of xylene was added. The remaining steps were the same as in Example 1 to obtain the polyimide oligomer solution of Example 3. Specifically, the polyimide oligomer in Example 3 has a structure as shown in Formula (I-1), wherein m / p is 0.5, and after measurement by gel permeameter (GPC), its number average molecular weight (Mn) is 1050 and its weight average molecular weight (Mw) is 2373.

[0056] Example 4: 20 g (0.0917 mole) of pyromellitic anhydride and 10.28 g (0.0917 mole) of itaconic anhydride were dissolved in 90 g of N,N-dimethylacetamide to prepare an anhydride solution. Next, 24.53 g (0.0459 mole) of dimerized diamine (Priamine 1075, available from Croda) and 15.62 g (0.0917 mole) of isophorone diamine were dissolved in 56.54 g of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution was then slowly dripped into the anhydride solution in a water bath controlled to not exceed 60°C. After the addition was complete, the temperature was raised to 80°C and the reaction was allowed to proceed for 3 hours. Afterwards, 48.85 g of xylene was added. The remaining steps were the same as in Example 1 to obtain the polyimide oligomer solution of Example 4. Specifically, the polyimide oligomer in Example 4 has a structure as shown in Formula (II-1), wherein m / p is 2, and after measurement by gel permeameter (GPC), its number average molecular weight (Mn) is 2235 and its weight average molecular weight (Mw) is 5669.

[0057] Comparative Example 1: 20 grams (0.0917 mole) of pyromellitic anhydride and 8.99 grams (0.0917 mole) of maleic anhydride were dissolved in 90 grams of N,N-dimethylacetamide to prepare an anhydride solution. Next, 23.42 grams (0.1375 mole) of isophorone diamine was dissolved in 24.14 grams of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution was then slowly added dropwise to the anhydride solution in a water bath controlled to not exceed 60°C. After the addition was complete, the temperature was raised to 80°C and the reaction was allowed to proceed for 3 hours. Afterward, 38.14 grams of xylene was added. The remaining steps were identical to those in Example 1 to obtain the polyimide oligomer solution of Comparative Example 1. Specifically, gel permeameter (GPC) measurement of Comparative Example 1 revealed a number average molecular weight (Mn) of 2117 and a weight average molecular weight (Mw) of 2950.

[0058] Comparative Example 2: 20 g (0.0917 mole) of pyromellitic anhydride and 1.798 g (0.0813 mole) of maleic anhydride were dissolved in 80 g of N,N-dimethylacetamide to prepare an anhydride solution. Subsequently, 26.98 g (0.0504 mole) of dimerized diamine (Priamine 1075, available from Croda) and 8.59 g (0.0504 mole) of isophorone diamine were dissolved in 39.6 g of N,N-dimethylacetamide to prepare a diamine solution. Afterwards, the diamine solution was slowly dripped into the anhydride solution, and the water bath temperature was controlled not to exceed 60°C. After the dripping was completed, the temperature was raised to 80°C and reacted for 3 hours. After the reaction, 39.87 g of xylene was added. The remaining steps were the same as in Example 1. However, a large amount of salts were generated during the preparation process and were difficult to eliminate, resulting in the inability to successfully obtain the product. The reason was that the molar ratio of diamine to dianhydride was changed to 1.1:1.

[0059] Comparative Example 3: 20 g (0.0917 mole) of pyromellitic anhydride and 8.99 g (0.0917 mole) of maleic anhydride were dissolved in 90 g of N,N-dimethylacetamide to prepare an anhydride solution. Next, 36.79 g (0.0688 mole) of dimerized diamine (Priamine 1075, available from Croda) and 11.71 g (0.0688 mole) of isophorone diamine were dissolved in 73 g of N,N-dimethylacetamide to prepare a diamine solution. The anhydride solution was then slowly added dropwise to the diamine solution. However, the reaction was vigorous during the addition process, resulting in rapid gelation and failure to obtain a product. This was due to the different order in which the diamine solution and the anhydride solution were added.

[0060] Comparative Example 4: 20 grams (0.0917 mole) of pyromellitic anhydride and 8.99 grams (0.0917 mole) of maleic anhydride were dissolved in 90 grams of N,N-dimethylacetamide to prepare an anhydride solution. Next, 73.58 grams (0.1375 mole) of diamine (Priamine 1075, available from Croda) was dissolved in 127.28 grams of N,N-dimethylacetamide to prepare a diamine solution. The diamine solution was then slowly dripped into the anhydride solution in a water bath controlled to not exceed 60°C. After the addition was complete, the temperature was raised to 80°C and the reaction was allowed to proceed for 3 hours. Afterwards, 72.43 grams of xylene was added. The remaining steps were the same as in Example 1 to obtain the polyimide oligomer solution of Comparative Example 4. Specifically, after measurement by gel permeameter (GPC), the number average molecular weight (Mn) of Comparative Example 4 was 1937, and the weight average molecular weight (Mw) was 2480.

[0061] <Preparation of Cured Material>

[0062] Example 5: 5 g of the polyimide oligomer solution of Example 1 (solid content 30%, solvent DMAc) was added with 0.015 g (1 wt% of the polyimide oligomer) of dicumyl peroxide (DCP) to prepare a prepolymer solution. The prepolymer solution was then poured into a mold and baked at a temperature of 80°C to 140°C to remove the solvent. The solution was then further heated to cure. The curing process was a staged heating process. In this example, a three-stage curing process was performed at 180°C, 200°C, and 220°C for 2 hours each to obtain the cured product of Example 5.

[0063] Example 6: 5 g of the polyimide oligomer solution of Example 2 (solid content 30%, solvent: DMAc) was added with 0.015 g (1 wt% of the polyimide oligomer) of diisopropylbenzene peroxide to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Example 6.

[0064] Example 7: 0.015 g (1 wt% of the polyimide oligomer) of diisopropylbenzene peroxide was added to 5 g of the polyimide oligomer solution of Example 3 (solid content 30%, solvent: DMAc) to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Example 7.

[0065] Example 8: 0.015 g (1 wt% of the polyimide oligomer) of diisopropylbenzene peroxide was added to 5 g of the polyimide oligomer solution of Example 4 (solid content 30%, solvent: DMAc) to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Example 8.

[0066] Comparative Example 5: 5 g of the polyimide oligomer solution of Comparative Example 1 (solid content 30%, solvent DMAc) was added with 0.015 g (1 wt% of the polyimide oligomer) of diisopropylbenzene peroxide to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Comparative Example 5. However, the cured product had severe foaming and high brittleness, and a complete film could not be successfully prepared.

[0067] Comparative Example 6: 5 g of the polyimide oligomer solution of Comparative Example 4 (solid content 30%, solvent: DMAc) was added with 0.015 g (1 wt% of the polyimide oligomer) of diisopropylbenzene peroxide to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Comparative Example 6.

[0068] Comparative Example 7: 5 g of polyphenylene ether resin (Noryl SA9000, purchased from SABIC) was added with 0.015 g of dicumyl peroxide to prepare a prepolymer solution, which was then poured into a mold. The remaining steps were the same as in Example 5 to obtain the cured product of Comparative Example 7.

[0069] <Evaluation Test Method>

[0070] Glass transition temperature (T g ) : A dynamic mechanical analyzer (DMA) was used to measure the glass transition temperature of the cured product at a heating rate of 5°C / min.

[0071] Dielectric analysis method: To evaluate the dielectric properties of the cured product obtained by curing the polyimide oligomer of the present invention, the dielectric constant (D k ) and dielectric loss (D f ).

[0072] The above evaluation test method was performed on Examples 5 to 8 and Comparative Examples 6 to 7, and the results are recorded in Table 1.

[0073] As shown in Table 1 above, after free radical curing of the polyimide oligomers of Examples 1 to 4, the glass transition temperatures of the cured products of Examples 5 to 8 obtained were all above 100°C. Furthermore, as the amount of rigid isophorone diamine increased, the glass transition temperatures of Examples 6 and 8 reached above 180°C. Although the heat resistance of the cured products of Comparative Example 7, which was prepared using the widely used polyphenylene ether resin SA9000, was inferior, the heat resistance of the cured products of Examples 5 to 8 was significantly improved compared to the cured product of Comparative Example 6, which did not contain rigid isophorone diamine.

[0074] In addition, the cured products of Examples 5 to 8 exhibited superior insulation properties under high-frequency measurement compared to Comparative Example 7 made from the widely used polyphenylene ether resin SA9000. For Example 6, which had the best heat resistance, its dielectric constant (D k ) can show a level similar to that of Comparative Example 7, but the dielectric loss (D f ) is much improved. However, as the amount of diamine used increases, the resulting cured product can exhibit even better insulation properties. For example, in Example 7, where the amount of diamine used is the highest, the dielectric constant (D k ) can reach 2.21, dielectric loss (D f ) can reach 0.0027, showing excellent electrical performance and can be used in the production of high-frequency printed circuit boards.

[0075] In addition, the dielectric constant (D k ) is not better than that of Example 7, but the dielectric loss (D f ) can be further optimized to 0.0018, indicating that the diamine structure has a certain effect on the dielectric constant (D k ) will gradually become smaller, and the contribution of dielectric loss (D f ) can be further improved, but in terms of heat resistance, the heat resistance of Comparative Example 6 will also be greatly reduced, which limits its application in circuit boards with heat resistance requirements.

[0076] In summary, the polyimide oligomer of the present invention, using dimerized diamine as a raw material and a rigid bifunctional diamine monomer, has indeed improved heat resistance while maintaining good electrical properties. The material even exhibits electrical properties superior to those of the currently widely used polyphenylene ether resin. This demonstrates the potential application of the polyimide oligomer in the circuit board industry and can alleviate the environmental issues associated with material development.

[0077] Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0078] Explanation of symbols:

[0079] 100: Preparation method of polyimide oligomer 110, 120, 130, 140: Steps

Claims

DEPCT691. Oligomer polyimide, characterized by a structure as shown in formula (I) or formula (II): (chemical formula) formula (I), (chemical formula) formula (II), where X independently of each group is a hydrogen or methyl group, R1 has a total of 5 to 20 carbon atoms and contains a cycloalkane of 5 or more carbon atoms, structure as shown in formula (A), formula (B), or formula (C): (chemical formula) (chemical formula) (chemical formula) formula (A), formula (B), formula (C), R2 independently of each group is a saturated or unsaturated hydrocarbon with 5 or more carbon atoms. Each group, consisting of 36 carbon atoms, A, independently comprises the benzene, biphenyl, naphthalene, and cycloalkanes, each with 4 to 6 carbon atoms, as shown in formulas (a), (b), (c), (d), (e), (f), (g), (h), or (i): (chemical formula)(chemical formula)(chemical formula)(a), (b), (c), (chemical formula)(chemical formula)(chemical formula)(d), (e), (f), (chemical formula)(chemical formula)(chemical formula)(g), (h), (i), where n is any random number from 0 to 10, and m / p is any random number from 0.5 to 52.

1. Oligomer polyimide of claim 1, characterized in which a cycloalkane of 5 or more carbon atoms is incorporated with a structure as shown in formula (D), formula (E), or formula (F): (chemical formula)(chemical formula)(chemical formula)Formula (D), Formula (E), Formula (F)3. Oligomer polyimide of claim 1, characterized in which R2 has a structure as shown in formula (G), formula (H), formula (I), or formula (J): (chemical formula)Formula (G), (chemical formula)Formula (H), (chemical formula)Formula (I), (chemical formula)Formula (J)4. Oligomer polyimide of claim 1, characterized by having a structure as shown in formula (I-1) or formula (II-1): (chemical formula)Formula (I-1), (chemical formula)Formula (II-1)5.The method for preparing the oligomer polyimide of claim 1, characterized by the following combination: a first dissolution step involving dissolving the dianehydride and monoanehydride in a first solvent to form an anhydride solution, where the monoanehydride has an unsaturated double bond; a second dissolution step involving mixing the dimered diamine and bifunctional fatty amine and dissolving them in a second solvent to form a diamine solution, where the bifunctional fatty amine has a rigid cyclic structure; a mixing step involving adding the diamine solution to the anhydride solution for reaction at the polymerization temperature to form a mixed solution; and an addition step involving adding xylene to the mixed solution and performing a reaction and distillation at the reaction distillation temperature to obtain the oligomer polyimide6.The preparation method of the oligomer polyimide of claim 5 is characterized in which the first and second solvents are selected from a group consisting of N,N-dimethylacetamide, N-menylpyrrolidinone, dimethylformamide, anizole, dimethyl sulfoxide, cyclohexanone, and metabenzenediol.

7. The preparation method of the oligomer polyimide of claim 5 is characterized in which the polymerization temperature is 0°C to 90°C.

8. The preparation method of the oligomer 9. Preparation methods for oligomer polyimide of claim 5, characterized in which the molar ratio of dimerized diamine to bifunctional fatty amine is 1:0.4 to 1:

3.

10. Preparation methods for oligomer polyimide of claim 5, characterized in which the molar ratio of diamine to dianehydride is 1.2:1 to 1.8:1, and diamine is obtained by adding dimerized diamine to bifunctional fatty amine.

11. A cured product with low dielectric properties, characterized by preparation by adding a free radical initiator to one of the polyimide oligomers of claims 1 to 4 and curing at the curing temperature.

12. A ready-cured product with low dielectric properties of claim 11, characterized in which the free radical initiator is perion.

13. A product with low dielectric properties of claim 11, characterized by the addition of free radical initiators of 0.3% by weight to 2% by weight of polyimide oligomers.

14. A product with low dielectric properties of claim 11, characterized by the incubation temperature of 160°C to 240°C. 15.The cured product, with its low dielectric properties as per claim 14, is characterized when the curing temperature is 180°C, 200°C, or 220°C.

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