TW202444799A - Polyimide oligomer, preparation method thereof and crosslinked product with low dielectric property prepared thereby - Google Patents

Abstract

The present disclosure provides a polyimide oligomer. The polyimide oligomer has a structure represented by formula (I) or formula (II), in which each symbol is as defined in the specification. Thus, a free radical curable polyimide oligomer is obtained by using the dimer diamine with the specific monomers and the ratio adjustment, and it has the good thermal property and the excellent low dielectric property after curing, so as to be used in the industry of high-frequency circuit boards.

Description

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

The present invention relates to an oligomer, a preparation method thereof and a cured product, and in particular to a polyimide oligomer derived from dimerized diamine, a preparation method thereof and a cured product prepared therefrom with low dielectric properties.

Nowadays, the rise of cloud technologies such as the Internet and data centers has made free radical curing systems highly valued in the application of printed circuit board materials. Noryl SA9000 sold by SABIC is a polyphenylene ether oligomer with a terminal difunctional acrylic group. Due to its low molecular weight, it has good organic solubility and good workability in the impregnation process. Therefore, Noryl SA9000 is endowed with basic physical properties through free radical curing of the terminal acrylic group, and the non-polar structure of polyphenylene ether itself and the fact that no polar groups are generated after free radical curing give its cured product excellent electrical performance, making Noryl SA9000 gradually become one of the mainstream materials for today's high-end printed circuit board materials. However, the preparation process of Noryl SA9000 is difficult to purify and produces a large amount of wastewater. Based on environmental protection considerations, developing usable materials with good electrical performance and low process pollution will help the development of printed circuit board materials while taking environmental protection issues into consideration.

In recent years, with the rise of environmental protection and carbon reduction awareness, many studies have begun to study the application of special bio-based diamines, for example, dimer diamine is mixed with aromatic diamine monomer m-tolidine and polymerized with 4,4'-bisphenol A dianhydride (BPADA) to obtain high molecular weight polyimide (PI), or dimer diamine is reacted with dianhydride to prepare polyimide oligomers or polymers with reactive functional groups at the end. Since the structure of dimer diamine is a large branched diamine with a large free volume, it is expected to provide low dielectric properties when introduced into the material, so that the electrical properties of the above-mentioned polyimide materials are very excellent, but there is still considerable room for improvement in heat resistance.

In view of this, how to synthesize a free radical-curable polyimide oligomer derived from bio-based dimerized diamine so that it can overcome the problem of poor thermal properties of dimerized diamine-derived products and at the same time have high-frequency and low-dielectric properties has become the goal of relevant industry players.

One purpose of the present invention is to provide a polyimide oligomer, a preparation method thereof and a cured product thereof with low dielectric properties. The free radical curable polyimide oligomer is obtained by combining dimerized diamine with other monomers and adjusting the ratio. The cured product has heat resistance and excellent electrical properties.

One embodiment of the present invention provides a polyimide oligomer having a structure as shown in formula (I) or formula (II): Formula (I), Formula (II), Wherein, X is independently hydrogen or methyl, _R1 is a cycloalkane having a total carbon number of 5 to 20 and having a carbon number of 5 or more, or a structure represented by formula (A), formula (B) or formula (C): Formula (A), Formula (B), Formula (C), _R2 is independently a saturated or unsaturated hydrocarbon having 36 carbon atoms, and A is independently a benzene ring, a biphenyl ring, a naphthyl ring, a cycloalkane having 4 to 6 carbon atoms, or a structure represented by formula (a), formula (b), formula (c), formula (d), formula (e), formula (f), formula (g), formula (h), or formula (i): Formula (a), Formula (b), Formula (c), Formula (d), Formula (e), Formula (f), Formula (g), Formula (h), Formula (i), Wherein, n is any number from 0 to 10, and m/p is any number from 0.5 to 5.

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

According to the polyimide oligomer described in the preceding paragraph, R ₂ may have a structure as shown in formula (G), formula (H), formula (I) or formula (J): Formula (G), Formula (H), Formula (I), Formula (J).

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): Formula (I-1), Formula (II-1).

Another embodiment of the present invention provides a method for preparing the aforementioned polyimide oligomer, comprising a first dissolving step, a second dissolving step, a mixing step, and an adding step. The first dissolving 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 dissolving 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 ring 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, and react and distill at a reaction distillation temperature to obtain a polyimide oligomer.

According to the preparation method of polyimide oligomer described in the previous paragraph, the first solvent and the second solvent can be selected from a group consisting of N,N-dimethylacetamide, N-methylpyrrolidone, dimethylformamide, anisole, dimethyl sulfoxide, cyclohexanone, and resorcinol.

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

According to the preparation method of the polyimide oligomer described in the previous paragraph, the reaction distillation temperature can be 130 ^° C to 170 ^° C.

According to the preparation method of the polyimide oligomer described in the previous paragraph, the molar ratio of the dimerized diamine to the difunctional fatty amine can be 1:0.4 to 1:3.

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

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.

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.

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.

According to the curing material with low dielectric properties mentioned in the previous paragraph, the curing temperature can be 160 ^° C to 240 ^° C.

According to the curing material with low dielectric properties mentioned in the previous paragraph, the curing temperature can be 180 ^° C, 200 ^° C or 220 ^° C.

Thus, the polyimide oligomer of the present invention uses dimerized diamine as a raw material and a specific monomer for polymerization without the need for a purification step, so that the molecular chain end has a reactive unsaturated double bond, can be directly subjected to free radical thermal curing, and has good heat resistance and excellent electrical performance after curing and forming, and can be used as a potential material in high-frequency circuit board applications.

The following will discuss various embodiments of the present invention in more detail. However, this embodiment can be an application of various inventive concepts and can be specifically implemented in various different specific scopes. The specific embodiment is for illustrative purposes only and is not limited to the scope of the disclosure.

In the present invention, the compound structure is sometimes represented by a skeleton formula, which may omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. If the functional groups are clearly drawn in the structural formula, the drawn functional groups shall prevail.

In the present invention, "polyimide oligomer having a structure as shown in formula (I)" is sometimes expressed as polyimide oligomer shown in formula (I) or polyimide oligomer (I) for the sake of simplicity and fluency, and other compounds or groups may be expressed in the same manner.

In the present invention, if it is not particularly specified whether a group is substituted, the group may represent a substituted or unsubstituted group. For example, "alkyl" may represent a substituted or unsubstituted alkyl group.

＜Polyimide oligomer＞

The present invention provides a polyimide oligomer having a structure as shown in formula (I) or formula (II): Formula (I), Formula (II), Wherein, X is independently hydrogen or methyl, _R1 is a cycloalkane having a total carbon number of 5 to 20 and having a carbon number of 5 or more, or a structure represented by formula (A), formula (B) or formula (C): Formula (A), Formula (B), Formula (C), _R2 is independently a saturated or unsaturated hydrocarbon having 36 carbon atoms. A is independently a benzene ring, a biphenyl ring, a naphthyl ring, a cycloalkane having 4 to 6 carbon atoms, or a structure represented by formula (a), formula (b), formula (c), formula (d), formula (e), formula (f), formula (g), formula (h), or formula (i): Formula (a), Formula (b), Formula (c), Formula (d), Formula (e), Formula (f), Formula (g), Formula (h), Formula (i), Wherein, n is any number from 0 to 10, and m/p is any number from 0.5 to 5.

Specifically, the cycloalkanes having 5 or more carbon atoms may include a structure represented by formula (D), formula (E) or formula (F): Formula (D), Formula (E), Formula (F), However, the present invention is not limited thereto. In addition, R ₂ may have a structure as shown in formula (G), formula (H), formula (I) or formula (J): Formula (G), Formula (H), Formula (I), Formula (J).

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): Formula (I-1), Formula (II-1).

Thus, the polyimide oligomer of the present invention is derived from dimerized diamine, has a reactive unsaturated double bond at the end of the structure, and can be cured by free radical polymerization to form a cured product with good mechanical properties and heat resistance. Moreover, since the main structure is composed of a large number of aliphatic carbon chains, it can provide the material with good low dielectric properties and has considerable potential in the application of printed circuit board materials.

＜Method for preparing polyimide oligomer＞

Referring to FIG. 1 , it is a flow chart of the steps of a method 100 for preparing a polyimide oligomer according to an embodiment of the present invention. In FIG. 1 , the method 100 for preparing a polyimide oligomer comprises steps 110 , 120 , 130 , and 140 .

Step 110 is to perform a first dissolution step, which is to dissolve a diacid anhydride and a monoanhydride in a first solvent to form an anhydride solution, and the monoanhydride has an unsaturated double bond to meet the subsequent free radical curing requirements. Specifically, the monoanhydride can be but is not limited to maleic anhydride or itaconic anhydride.

Step 120 is to perform a second dissolving step, which 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 molar ratio of the dimerized diamine to the difunctional fatty amine can be 1:0.4 to 1:3, preferably 1:0.5 to 1:2. Specifically, the dimerized diamine is a bio-based diamine, which is a diamine monomer derived from fatty acids, and the main structure is a multi-carbon aliphatic, and the difunctional fatty amine has a rigid ring structure to provide good heat resistance for subsequent free radical curing derivatives. Specifically, the difunctional fatty amine can be but is not limited to isophorone diamine or protobornene diamine.

In addition, the first solvent of step 110 and the second solvent of 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 m-cresol.

Step 130 is a mixing step, which is to add the diamine solution into the anhydride solution and react at a polymerization temperature to form a mixed solution, wherein 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 will be carried out at the polymerization temperature, and the molar ratio of the diamine obtained by dimerizing diamine and difunctional fatty amine to the dianhydride can be 1.2:1 to 1.8:1, preferably 1.4:1 to 1.6:1.

Step 140 is to perform an adding step, which is to add xylene to the mixed solution, and react and distill at a reaction distillation temperature to obtain polyimide oligomer, wherein the reaction distillation temperature can be 130 ^° C. to 170 ^° C., preferably 140 ^° C. to 160 ^° C. In detail, after xylene is added to the mixed solution, a Dean-Stark apparatus is set up, and the temperature is raised to the reaction distillation temperature to perform a closed-loop reaction and distill to remove water, and the polyimide oligomer solution can be obtained after cooling, and the polyimide oligomer solution contains polyimide oligomer and solvent.

＜Cured material with low dielectric properties＞

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 at a curing temperature, wherein the free radical initiator can be a peroxide, an azo initiator or a mixture thereof, and the amount of the free radical initiator added can be 0.3 weight percent to 2 weight percent of the polyimide oligomer content, preferably 0.5 weight percent to 1.5 weight percent. In addition, the free radical curing reaction can be carried out by a staged heating method, but is not limited to this heating method, and the curing temperature can be 160 ^° C to 240 ^° C, preferably 180 ^° C, 200 ^° C or 220 ^° C.

Thus, the preparation method of the polyimide oligomer of the present invention can overcome the problem of poor thermal properties of the product after curing and maintain high-frequency and low-dielectric properties through the selection and proportion adjustment of amines. In addition, due to the improvement of the selection of monomers and the feeding sequence in the process, the polyimide oligomer can be prepared without adding a catalyst, and can be directly used in the circuit board impregnation process, reducing the output of waste liquid and the use of solvents, so as to balance the development of the circuit board industry and the carbon reduction trend.

The present invention is further illustrated by the following specific embodiments, which are used to facilitate those skilled in the art to which the present invention belongs, so that the present invention can be fully utilized and practiced without excessive interpretation. These embodiments should not be regarded as limiting the scope of the present invention, but are used to illustrate the materials and methods for implementing the present invention.

＜Example/Comparative Example＞

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. Then, 36.79 g (0.0688 mole) of dimer diamine (Priamine 1075, purchased 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. Afterwards, the diamine solution is slowly dripped into the anhydride solution, and the temperature of the water bath is controlled not to exceed 60 ^° C. After the dripping is completed, the temperature is raised to 80 ^° C for reaction for 3 hours. After the reaction is completed, 54 grams of xylene is added to form a mixed solution to be separated, and the polyimide oligomer solution is separated from the mixed solution to be separated by distillation. For example, the mixed solution to be separated is heated to 150 ^° C for dehydration for 4 hours using a Dean-Stark apparatus, and then further heated to 160 ^° C for dehydration. After the amount of water distilled reaches the expected amount of water, the temperature is lowered to obtain the polyimide oligomer solution of Example 1. Specifically, the polyimide oligomer in Example 1 has a structure as shown in formula (I-1), wherein m/p is 1, and after measurement by gel chromatography permeameter (GPC), its number average molecular weight (Mn) is 2095 and its weight average molecular weight (Mw) is 4841.

Example 2: 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. Then, 24.53 g (0.0459 mole) of dimer diamine (Priamine 1075, purchased 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. 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 for reaction for 3 hours. After the reaction was completed, 48.85 g of xylene was added, and the remaining steps were the same as those 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 being measured by gel chromatography permeameter (GPC), its number average molecular weight (Mn) is 1448 and its weight average molecular weight (Mw) is 3049.

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. Then, 49.05 g (0.0917 mole) of dimer diamine (Priamine 1075, purchased 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. 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 for reaction for 3 hours. After the reaction was completed, 60.02 g of xylene was added, and the remaining steps were the same as those 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 being measured by gel chromatography permeameter (GPC), its number average molecular weight (Mn) is 1050, and its weight average molecular weight (Mw) is 2373.

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. Then, 24.53 g (0.0459 mole) of dimer diamine (Priamine 1075, purchased 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. 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 for reaction for 3 hours. After the reaction was completed, 48.85 g of xylene was added, and the remaining steps were the same as those 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 being measured by gel chromatography permeameter (GPC), its number average molecular weight (Mn) is 2235, and its weight average molecular weight (Mw) is 5669.

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. Then, 23.42 grams (0.1375 mole) of isophorone diamine was dissolved in 24.14 grams of N,N-dimethylacetamide to prepare a diamine solution. After that, 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 was completed, 38.14 grams of xylene was added. The remaining steps were the same as those in Example 1 to obtain the polyimide oligomer solution of Comparative Example 1. Specifically, the number average molecular weight (Mn) of Comparative Example 1 was 2117 and the weight average molecular weight (Mw) was 2950 after being measured by gel chromatography permeameter (GPC).

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. Then, 26.98 g (0.0504 mole) of dimer diamine (Priamine 1075, purchased 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 for reaction for 3 hours. After the reaction was completed, 39.87 g of xylene was added. The remaining steps were the same as those in Example 1. However, a large amount of salts were generated during the preparation process and were difficult to eliminate, resulting in the failure to obtain the product smoothly. The reason was that the molar ratio of diamine to dianhydride was changed to 1.1:1.

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. Then, 36.79 g (0.0688 mole) of dimer diamine (Priamine 1075, purchased 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. Afterwards, the anhydride solution was slowly dripped into the diamine solution. However, the reaction was violent during the dripping process, causing the reaction to gel quickly and the product could not be obtained smoothly. The reason was that the diamine solution and the anhydride solution were added in a different order.

Comparative Example 4: 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. Then, 73.58 g (0.1375 mole) of dimer diamine (Priamine 1075, purchased from Croda) was dissolved in 127.28 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 for reaction for 3 hours. After the reaction was completed, 72.43 g of xylene was added. The remaining steps were the same as those of Example 1 to obtain the polyimide oligomer solution of Comparative Example 4. Specifically, after being measured by gel chromatography permeameter (GPC), Comparative Example 4 had a number average molecular weight (Mn) of 1937 and a weight average molecular weight (Mw) of 2480.

＜Preparation of cured product＞

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, which 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. This example was a three-stage curing process, which was performed at 180 ^° C, 200 ^° C, and 220 ^° C for 2 hours each to obtain the cured product of Example 5.

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 those of Example 5 to obtain the cured product of Example 6.

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 those of Example 5 to obtain the cured product of Example 7.

Example 8: 5 g of the polyimide oligomer solution of 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 those of Example 5 to obtain the cured product of Example 8.

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 those of 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.

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 those of Example 5 to obtain the cured product of Comparative Example 6.

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

＜Evaluation test method＞

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.

Dielectric analysis method: In order to evaluate the dielectric properties of the cured product obtained by curing the polyimide oligomer of the present invention, the present invention measures the dielectric constant (D _k ) and dielectric loss (D _f ) of the cured product at 10 GHz.

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. Table 1 _Tg ( ^o C) D _{k D} Embodiment 5 132 2.57 0.0038 Embodiment 6 193 2.69 0.0048 Embodiment 7 115 2.21 0.0027 Embodiment 8 180 2.78 0.0055 Comparison Example 6 35 2.23 0.0018 Comparative Example 7 228 2.77 0.0071

From the results in Table 1 above, it can be seen that after the polyimide oligomers of Examples 1 to 4 are cured by free radicals, the glass transition temperatures of the cured products of Examples 5 to 8 obtained are all higher than 100 ^° C, and as the amount of rigid isophorone diamine used increases, the glass transition temperatures of Examples 6 and 8 can reach above 180 ^° C. Although the heat resistance is poorer than that of Comparative Example 7 made from the currently widely used polyphenylene ether resin SA9000, the heat resistance of the cured products of Examples 5 to 8 is indeed significantly improved compared to the cured product of Comparative Example 6 without the addition of rigid isophorone diamine.

In addition, the cured products of Examples 5 to 8 can show better insulation than Comparative Example 7 made of the currently widely used polyphenylene ether resin SA9000 under high-frequency measurement. For Example 6 with 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, according to the increase in the amount of dimerized diamine used, the obtained cured product can show better insulation. For Example 7 with the highest amount of dimerized diamine used, its dielectric constant (D _k ) can reach 2.21 and the dielectric loss (D _f ) can reach 0.0027, showing excellent electrical performance and can be applied to the production of high-frequency printed circuit boards.

In addition, the dielectric constant (D _k ) of the cured product of Comparative Example 6 without adding rigid diamine is not better than that of Example 7, but the dielectric loss (D _f ) can be further optimized to 0.0018, indicating that the contribution of the dimerized diamine structure to the dielectric constant (D _k ) will gradually decrease after a certain usage amount, and the dielectric loss (D _f ) can be further improved. However, 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.

In summary, the polyimide oligomer of the present invention, which uses dimerized diamine as a raw material and a rigid bifunctional diamine monomer, has indeed improved the problem of heat resistance and allowed the material to retain good electrical properties, and even exhibited better electrical properties than the polyphenylene ether resin currently widely used in the industry. This shows that the polyimide oligomer proposed by the present invention has its application potential in the circuit board industry and can improve the environmental problems caused by material development.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

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

In order to make the above and other purposes, features, advantages and embodiments of the present invention more clearly understood, the attached drawings are described as follows: Figure 1 is a flow chart showing the steps of the preparation method of polyimide oligomer according to one embodiment of the present invention.

100: Preparation method of polyimide oligomer

110,120,130,140: Steps

Claims (15)

A polyimide oligomer having a structure as shown in formula (I) or formula (II): Formula (I), Formula (II), Wherein, X is independently hydrogen or methyl, _R1 is a cycloalkane having a total carbon number of 5 to 20 and having a carbon number of 5 or more, or a structure represented by formula (A), formula (B) or formula (C): Formula (A), Formula (B), Formula (C), _R2 is independently a saturated or unsaturated hydrocarbon having 36 carbon atoms, and A is independently a benzene ring, a biphenyl ring, a naphthyl ring, a cycloalkane having 4 to 6 carbon atoms, or a structure represented by formula (a), formula (b), formula (c), formula (d), formula (e), formula (f), formula (g), formula (h), or formula (i): Formula (a), Formula (b), Formula (c), Formula (d), Formula (e), Formula (f), Formula (g), Formula (h), Formula (i), Wherein, n is any number from 0 to 10, and m/p is any number from 0.5 to 5. The polyimide oligomer as described in claim 1, wherein the cycloalkane having 5 or more carbon atoms comprises a structure represented by formula (D), formula (E) or formula (F): Formula (D), Formula (E), Formula (F). The polyimide oligomer as described in claim 1, wherein R ₂ has a structure as shown in formula (G), formula (H), formula (I) or formula (J): Formula (G), Formula (H), Formula (I), Formula (J). The polyimide oligomer as described in claim 1 has a structure as shown in formula (I-1) or formula (II-1): Formula (I-1), Formula (II-1). A method for preparing a polyimide oligomer as described in claim 1, comprising: performing a first dissolving step, which 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; performing a second dissolving step, which 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 ring structure; performing a mixing step, which is to add the diamine solution to the anhydride solution and react at a polymerization temperature to form a mixed solution; and An adding step is performed, which is to add xylene to the mixed solution, and react and distill at a reaction distillation temperature to obtain the polyimide oligomer. A method for preparing a polyimide oligomer as described in claim 5, wherein the first solvent and the second solvent are selected from a group consisting of N,N-dimethylacetamide, N-methylpyrrolidone, dimethylformamide, anisole, dimethyl sulfoxide, cyclohexanone, and resorcinol. The method for preparing a polyimide oligomer as described in claim 5, wherein the polymerization temperature is 0 ^° C to 90 ^° C. The method for preparing polyimide oligomer as described in claim 5, wherein the reaction distillation temperature is 130 ^° C to 170 ^° C. A method for preparing a polyimide oligomer as described in claim 5, wherein the molar ratio of the dimerized diamine to the difunctional fatty amine is 1:0.4 to 1:3. A method for preparing a polyimide oligomer as described in claim 5, wherein the molar ratio of the diamine obtained by adding the dimerized diamine to the difunctional fatty amine to the dianhydride is 1.2:1 to 1.8:1. A cured product with low dielectric properties is prepared by adding a free radical initiator to the polyimide oligomer as described in any one of claims 1 to 4 and baking the product at a curing temperature. A cured product with low dielectric properties as described in claim 11, wherein the free radical initiator is a peroxide, an azo initiator or a mixture thereof. A cured product with low dielectric properties as described in claim 11, wherein the amount of the free radical initiator added is 0.3 weight percent to 2 weight percent of the polyimide oligomer content. The cured product with low dielectric properties as described in claim 11, wherein the curing temperature is 160 ^° C to 240 ^° C. The cured material with low dielectric properties as described in claim 14, wherein the curing temperature is 180 ^° C, 200 ^° C or 220 ^° C.

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