An ultralow molecular weight cyclic olefin resin, a preparation method and application thereof

Abstract

This invention discloses an ultra-low molecular weight cyclic olefin resin, its preparation method, and its applications. The crosslinkable cyclic olefin resin contains repeating X, Y, and Z structural units, and exhibits a polymerization activity as high as 5 × 10⁻⁶ under the action of a metallocene catalyst. 7 g mol ‑1 h ‑1 The crosslinkable cyclic olefin resin has a number-average molecular weight of 2-10 kDa, a molecular weight distribution index of less than 1.5, and a glass transition temperature of 125-168℃. This resin is soluble in common organic solvents such as PGMEA, cyclohexanone, toluene, and xylene at room temperature, and exhibits good compatibility with traditional copper-clad laminate manufacturing processes. The thermosetting resin obtained by crosslinking it at room temperature possesses excellent low dielectric properties, with a dielectric constant Dk reaching 2.2-2.3 and a dielectric loss Df reaching 7-8 × 10⁻⁶. ‑4 It will not deform or suffer other adverse effects under high temperature conditions (290℃, 5 minutes) and can be widely used in 5G / 6G millimeter wave communication, electronic packaging materials, high frequency and high speed printed circuit boards and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functionalized polyolefin technology, specifically relating to an ultra-low molecular weight cyclic olefin resin, its preparation method, and its application. Background Technology

[0002] With the large-scale application of 5G mobile communication technology and the forward-looking advancement of 6G technology, the demand for high-frequency and high-speed signal transmission in the electronics and information industry is becoming increasingly urgent. Copper-clad laminates, as the core substrate of printed circuit boards, directly determine the integrity of signal transmission and the level of line loss based on their dielectric properties. Cycloolefin copolymers, as high-performance thermoplastic resins with addition polymerization structures, have become a key research direction in the field of high-frequency and high-speed substrates, following polytetrafluoroethylene (PTFE), due to their excellent low dielectric constant (Dk), low dielectric loss (Df), extremely low water absorption, and good optical properties and thermal stability.

[0003] To support the demand for high-capacity, low-latency signal transmission, mobile communication frequencies are gradually shifting from sub-6GHz bands to millimeter-wave and even terahertz bands. According to transmission loss theory, the loss of high-frequency signals in a dielectric is positively correlated with the transmission frequency and the dielectric loss factor of the material, which places extremely high performance requirements on electronic packaging and substrates. Traditional high-frequency substrates, such as modified epoxy resin (FR-4), polyphenylene ether (PPE), and polyimide (PI) resins, suffer from high molecular polarity and high moisture absorption, making it difficult to meet the requirements for ultra-low or extremely low loss grading in the millimeter-wave band. While polytetrafluoroethylene (PTFE) possesses excellent dielectric properties, its processing difficulties, significant cold flow, and high coefficient of thermal expansion limit its large-scale application in multilayer PCBs.

[0004] Against this backdrop, cyclic olefin copolymers, with their unique cyclic saturated hydrocarbon molecular structure, exhibit excellent dielectric properties comparable to PTFE. However, currently commercially available cyclic olefin resins have significant limitations: firstly, their molecular structure is non-polar (lacking active polar functional groups); secondly, they are thermoplastic resins, requiring high-temperature hot pressing molding above 230°C; and thirdly, they are significantly mismatched with the core requirements of PCB manufacturing and service processes, such as the adhesion and processability of the base resin (the base resin needs to dissolve and cross-link at room temperature).

[0005] Therefore, how to solve the key problems faced by cyclic olefin resins in the process of printed circuit board manufacturing, while retaining their excellent low dielectric and thermal stability properties, and promoting them to become the core resin for high-frequency and high-speed copper clad laminates, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and develop an ultra-low molecular weight crosslinkable cyclic olefin resin. This type of resin is soluble in conventional solvents such as PGMEA (propylene glycol methyl ether acetate), cyclohexanone, toluene, and xylene at room temperature, and can achieve room temperature crosslinking. This solves many problems existing in the prior art, such as the inability of existing ordinary cyclic olefin resins to achieve crosslinking themselves during the preparation of copper clad laminates, poor compatibility with other reinforcing materials, and inability to match the room temperature crosslinking preparation process of copper clad laminates.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an ultra-low molecular weight cyclic olefin resin, wherein the ultra-low molecular weight cyclic olefin resin is a terpolymer comprising X structural units, Y structural units and Z structural units, as shown in formula (I): (I) Wherein, the X structural unit is an α-olefin monomer such as ethylene, propylene, or butene; The Y structural unit is a cyclic olefin monomer, which is a norbornene monomer containing a double bond and its derivatives. The Z structural unit is a cyclic olefin monomer, which is a norbornene monomer or its derivative containing at least two double bonds. The structure includes at least one or more six-membered carbon ring combinations, and at least one double bond is on the six-membered carbon ring combination. At the same time, at least one double bond is adjacent to or close to the six-membered ring or its combination ring. The X structural unit accounts for 20-70% of the polymer molar amount, the Y structural unit accounts for 30-60% of the polymer molar amount, and the Z structural unit accounts for 2-20% of the polymer molar amount.

[0010] As a preferred embodiment of the ultra-low molecular weight cyclic olefin resin of the present invention, the ultra-low molecular weight cyclic olefin resin has the following characteristics: The number-average molecular weight (Mn) of cyclic olefin resins ranges from 0.5 kDa to 30 kDa. It has a molecular weight distribution of less than 1.5, a glass transition temperature of 100~300 ℃, and is soluble in common solvents at room temperature.

[0011] As a preferred embodiment of the ultra-low molecular weight cyclic olefin resin of the present invention, wherein the monomer source of the Y structural unit is norbornene or tetracyclododecene.

[0012] As a preferred embodiment of the ultra-low molecular weight cyclic olefin resin of the present invention, wherein the monomer from which the Z structural unit is derived is dicyclopentadiene or ethylidene norbornene.

[0013] In this invention, the Y-structural unit is a norbornene monomer containing a double bond or its derivatives, preferably norbornene. Or tetracyclic dodecene ; According to the present invention, the Z structural unit is norbornene and its derivatives containing at least two double bonds, the structure of which includes at least one or more six-membered carbon ring combinations, and at least one double bond is on the six-membered carbon ring combination, while at least one double bond is adjacent to or close to the six-membered ring or the combination of rings. In addition to providing one double bond for ternary copolymerization, the Z-structure unit of this invention must also provide at least one double bond to enable further crosslinking of the polymer, ensuring that the crosslinkable cyclic olefin resin is converted into a thermosetting cyclic olefin resin after the crosslinking reaction.

[0014] The Z-structure unit of this invention is preferably dicyclopentadiene. Or ethylidene norbornene .

[0015] The cyclic olefin monomers in the ultra-low molecular weight crosslinkable cyclic olefin resin provided by this invention are norbornene or tetracyclododecene. During the copolymerization process, it can provide rigidity and the resulting cyclic olefin copolymer has a high glass transition temperature and high practical value. The ultra-low molecular weight crosslinkable cyclic olefin resin provided by this invention is obtained by polymerization of metallocene catalyst and co-catalyst in an inert solvent. Due to the low molecular weight of the polymer, it can be dissolved in solvents such as PGMEA, cyclohexanone, toluene, and xylene at room temperature, and can be further crosslinked at room temperature to prepare a thermosetting resin.

[0016] Experimental results show that the thermosetting resin prepared from ultra-low molecular weight crosslinkable cyclic olefin resin provided in this invention has excellent low dielectric properties. Tested values ​​show a Dk value of 2.2-2.3 and a Df value of 7-8 × 10⁻⁶. -4 It has low dielectric properties close to those of PTFE.

[0017] This invention provides a method for preparing the ultra-low molecular weight crosslinkable cyclic olefin resin described above, comprising the following steps: In an inert solvent, monomers of three structural units, X, Y, and Z, are added and polymerized in the presence of a catalyst to obtain a cyclic olefin copolymer with the structure of formula (I). Equation (I) In this polymer, the X structural unit accounts for 20-70% of the polymer molar amount, the Y structural unit accounts for 30-60% of the polymer molar amount, the Z structural unit accounts for 2-20% of the polymer molar amount, and p is 0 or 1; R1 and R2 are independent alkanes with fewer than 20 carbons, such as methyl and ethyl, and R1 and R2 can be the same or different.

[0018] The present invention does not impose any special restrictions on the source of the cyclic olefin monomers; they can be commercially available products or self-made products.

[0019] According to the present invention, the catalyst is a metallocene catalyst, which is a metallocene catalyst with substituents at different positions on the cyclopentadienyl ring, and the specific structure is as follows: Wherein, Ra-Rd and Ra1-Rd1 are N-containing substituents or hydrogens directly connected to the fluorene ring on the catalyst, and the metallocene catalyst has at least one N-containing substituent on the fluorene ring. M is Ti, Zr, or Hf; Preferably, the substituent connected to N is a straight-chain, branched, cyclic saturated alkane or unsaturated alkane with 20 or fewer carbon atoms. In this context, Ra and Ra1 can be the same or different; similarly, Rb and Rb1, Rc and Rc1, and Rd and Rd1 can be the same or different. The present invention preferably provides a cyclic olefin monomer solution dissolved in an inert solvent, three structural unit monomers X, Y, and Z, and the catalyst solution are added to an inert solvent and subjected to a polymerization reaction to obtain a cyclic olefin copolymer with the structure of formula (I).

[0020] In this invention, the reaction solution is preferably filled with ethylene gas, and ethylene gas is continuously introduced into the reactor to maintain the ethylene pressure preferably from 1 bar to 100 bar, more preferably from 1 bar to 40 bar.

[0021] The molar ratio of the catalyst to the cyclic olefin monomer is 1:6000-100000, more preferably 1:8000-80000; the molar ratio of the catalyst to the co-catalyst is preferably 1:1-5000, more preferably 1:1-3000.

[0022] This invention utilizes a metallocene catalyst with substituents at different positions on the cyclopentadienyl ring as the main catalyst. During the polymerization reaction, this main catalyst exhibits excellent copolymerization catalytic activity, resulting in high reactivity of the polymerization reaction. Furthermore, due to the special structure on the cyclopentadienyl ring, the molecular weight of the copolymer prepared is significantly reduced compared to unsubstituted metallocene catalysts.

[0023] According to the present invention, the cocatalyst comprises one or more of methylaluminoxane, modified methylaluminoxane, trialkylaluminum, dialkylaluminum chloride, monoalkylaluminum chloride, and trialkylaluminum trichloride; the boron compound cocatalyst is one or more of N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate, N,N-diethylphenylammonium tetra(pentafluorophenyl)borate, N,N-di(hexadecyl)phenylammonium tetra(pentafluorophenyl)borate, tri(pentafluorophenyl)borate, triphenylcarbamonium tetra(pentafluorophenyl)borate, and triphenylmethyltetra(pentafluorophenyl)borate.

[0024] According to the present invention, the temperature of the polymerization reaction is preferably 30 ℃-200 ℃, and the time of the polymerization reaction is preferably 5 minutes-240 minutes.

[0025] After the polymerization reaction is completed, the present invention preferably performs post-treatment on the reaction solution obtained from the polymerization reaction. Specifically, the present invention can mix the reaction solution with an ethanol solution of hydrochloric acid to terminate the growth of the polymerization chain and obtain the reaction product; the reaction product is then subjected to solid-liquid separation and dried to obtain a cyclic olefin copolymer. The present invention does not have any particular limitation on the method of terminating the polymerization chain growth; the above-mentioned method of mixing the reaction solution with an ethanol solution of hydrochloric acid can be used, wherein the volume fraction of the ethanol solution of hydrochloric acid is preferably 5% to 15%. The present invention preferably employs filtration to separate the reaction products into solid and liquid phases, and washes the filtered products. In the present invention, the washing reagent is preferably acetone, and the washing is preferably performed twice. The present invention does not impose any special restrictions on the drying method, and any drying technology known to those skilled in the art can be used. In the present invention, the drying is vacuum drying, the drying temperature is 50 ℃-80 ℃, and the drying time is preferably 16 hours to 24 hours.

[0026] After obtaining the cyclic olefin copolymer, the present invention identifies the structure and tests the performance of the ultra-low molecular weight crosslinkable cyclic olefin resin.

[0027] The ultra-low molecular weight crosslinkable cyclic olefin resin has a glass transition temperature (Tg) of 125-168 °C, providing a wide range of thermal processing possibilities. This ultra-low molecular weight crosslinkable cyclic olefin resin can be dissolved at room temperature using solvents such as PGMEA, cyclohexanone, toluene, and xylene. A crosslinking agent is then added to induce a crosslinking reaction of the double bonds at room temperature, thereby converting the ultra-low molecular weight crosslinkable cyclic olefin resin into a thermosetting cyclic olefin resin. The preparation process meets the requirements of copper clad laminate processing technology.

[0028] There are no particular limitations on the specific cross-linking method for the cross-linking reaction. It can be achieved by adding an appropriate vulcanizing agent, a free radical initiator, a compound containing hydrosilane, or by radiation-induced cross-linking.

[0029] The free radical initiator is selected from: oil-soluble initiators such as azobisisobutyronitrile, azobisisoheptanenitrile, azodimethylbutyronitrile, and dimethyl azobisisobutyrate; organic peroxide initiators such as benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, peracetic acid, and cumene hydroperoxide; and persulfate-sulfite, persulfate-thiosulfate, hydroperoxide-ferrous salt, benzoyl peroxide-N,N-dimethylaniline, and cumene hydroperoxide-ferrous salt, etc., among redox initiators.

[0030] Beneficial effects of this invention: This invention relates to an ultra-low molecular weight crosslinkable cyclic olefin resin prepared by a metallocene catalyst containing special substituents. Its characteristic is that the polymerization exhibits high activity, reaching 5 × 10⁻⁶. 7 g mol -1 h -1 The prepared polymers have extremely low molecular weights (number average molecular weight 2-10 kDa) and low dispersibility (PDI less than 1.5). Their glass transition temperature is controllable, and they can be directly dissolved in solvents such as PGMEA, cyclohexanone, toluene, and xylene at room temperature. They can also be directly crosslinked at room temperature, making them compatible with the early-stage preparation process of copper-clad laminates. In contrast, cyclic olefin copolymers prepared using metallocene catalysts without substituent groups typically have number average molecular weights greater than 100 kDa, making it impossible to achieve the dissolution and further crosslinking of the prepared cyclic olefin resins in various solvents at room temperature. Furthermore, the thermosetting cyclic olefin resins prepared by crosslinking ultra-low molecular weight crosslinkable cyclic olefin resins exhibit excellent low dielectric properties, with a Dk value of 2.2-2.3 and a Df value of 7-8 × 10⁻⁶. -4 With low dielectric properties very close to those of polytetrafluoroethylene, it is expected to break through the limitations of cyclic olefin resin materials in replacing traditional epoxy resins and polyphenylene ethers, enabling applications in fields such as 5G / 6G millimeter-wave communication, electronic packaging, and high-frequency high-speed printed circuit boards. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is the DSC curve of the copolymer in Example 5 of the present invention; Figure 2 The high temperature of the copolymer of Example 5 of the present invention 1 H-NMR spectrum; Figure 3 The high temperature of the copolymer of Example 5 of the present invention 13 C-NMR spectrum; Figure 4 The present invention uses the metallocene catalyst Cat4. 1 H-NMR spectrum; Figure 5 The cross-linked thermosetting cyclic olefin resin of Example 5 of the present invention. Detailed Implementation

[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Unless otherwise specified, the raw materials used in the present invention are all commercially available products.

[0033] Example 1 First, the 1 L pressure reactor connected to the gas pipeline was vacuum dried at 110 °C for 6 h, and then adjusted to the preset polymerization temperature, as shown in Table 1. Then, under an inert atmosphere (nitrogen), 300 mL of toluene, 96 g of norbornene, 4 g of dicyclopentadiene, and 12 mL of MAO (methylaluminoxane, 1.5 M) were added to the reactor. Subsequently, 16.0 μmol of Cat 4 (selected from monosubstituted N-groups containing long-chain alkanes with Rc) was dissolved in 8 mL of toluene and injected into the polymerization system via a syringe. Ethylene was introduced under rapid stirring (1000 rpm) and maintained at 6 bar.

[0034] After 5 minutes, the pressure reactor was emptied, hydrochloric acid and ethanol were added to quench the polymerization reaction, the polymer was filtered and settled, and then dried to constant weight in a vacuum oven.

[0035] The specific reaction conditions and results are shown in Table 1.

[0036] The synthesis method of the catalyst (Cat4) is as follows: ① Dissolve 5 g of 2-diaminofluorene in 40 mL of toluene, then add 10.3 mL of dipentyl sulfate and reflux for 2 h. Next, add 10 mL of 1 M NaOH aqueous solution and react for another 0.5 h. After the reaction is complete, add 20 mL of ethanol, filter while hot, extract with ethyl acetate, and evaporate to dryness. Recrystallize the solid from ethanol to obtain a white solid, 2-dipentylaminofluorene, with a yield of 29%. ② At -78 ℃, add 9 mL of n-butyllithium (1.6 M) to a THF solution of 2-dipentylaminofluorene (2 g), and slowly heat overnight; remove the solvent by vacuum, and add 30 mL of diethyl ether and 1.25 mL of 6,6-dimethylfulne. The reaction lasted for 2 hours. The solution was then quenched with an appropriate amount of water, extracted, dried, filtered, and the solvent removed by rotary evaporation to obtain a yellowish-white solid. The solid was washed with methanol, filtered, and dried to obtain a white catalyst ligand with a yield of 52%. ③ In an ice-water bath, add 31 mL of n-butyllithium (1.6 M) to the diethyl ether solution of the catalyst ligand (8.52 g). After the addition is complete, remove from the cold bath and stir overnight. After the reaction was complete, the solvent was dried, the solid was transferred to a glove box, and appropriate amounts of THF and ZrCl4 (6.55 g) were added. The mixture was stirred overnight. After filtration, the solid was washed several times with THF, and the solvent was dried to collect the catalyst. The yield was 42%.

[0037] Metallocene catalyst Cat4 at room temperature 1 See H-NMR (CDCl3) Figure 4 .

[0038] Example 2 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 1.

[0039] Example 3 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 1.

[0040] Example 4 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 1.

[0041] Example 5 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 1.

[0042] The comonomers in Examples 1-5 are ethylene, norbornene, and dicyclopentadiene. The crosslinkable low molecular weight cyclic olefin resin structures in Examples 1-5 are as follows: Where X represents the molar percentage of ethylene in the polymer, Y represents the molar percentage of norbornene in the polymer, and Z represents the molar percentage of dicyclopentadiene in the polymer, X+Y+Z=1.

[0043] The DSC curve of the copolymer in Example 5 is shown in [reference needed]. Figure 1 The DSC curve can provide the glass transition temperature of the polymer, i.e., Tg. High-temperature NMR of the copolymer in Example 5 1See the H-NMR spectrum. Figure 2 Example 5: High-temperature NMR of the copolymer 13 See the C-NMR spectrum. Figure 3 .

[0044] Example 6 First, the 1 L pressure reactor connected to the gas pipeline was vacuum dried at 110 °C for 6 h, and then adjusted to 110 °C. Then, under an inert atmosphere, 300 mL of toluene, 88 g of tetracyclododecene, 4 g of dicyclopentadiene, and 12 mL of MAO (methylaluminoxane, 1.5 M) were added to the reactor. Subsequently, 16.0 μmol of Cat 4 (selected from monosubstituted N-groups containing long-chain alkanes with Rc) was dissolved in 8 mL of toluene and injected into the polymerization system via a syringe. Ethylene was introduced under rapid stirring (1000 rpm) and maintained at 2 bar.

[0045] After 5 minutes, the pressure reactor was emptied, hydrochloric acid and ethanol were added to quench the polymerization reaction, the polymer was filtered and settled, and then dried to constant weight in a vacuum oven.

[0046] The specific reaction conditions and results are shown in Table 1.

[0047] Example 7 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 6.

[0048] Example 8 The monomer content and reaction conditions were adjusted according to Table 1, and the rest were the same as in Example 6.

[0049] The comonomers of Examples 6-8 are ethylene, tetracyclododecene, and dicyclopentadiene. The crosslinkable low molecular weight cyclic olefin resin structures of Examples 6-8 are as follows: Where X represents the molar percentage of ethylene in the polymer, Y represents the molar percentage of tetracyclododecene in the polymer, and Z represents the molar percentage of dicyclopentadiene in the polymer, X+Y+Z=1.

[0050] Comparative Example 1 The comonomers of Comparative Example 1 were ethylene, norbornene, and dicyclopentadiene.

[0051] The monomer contents and reaction conditions in Comparative Example 1 were adjusted according to Table 1, and the catalyst was replaced with a metallocene catalyst without substitution on the cyclopentadienyl ring: , The catalyst was prepared by adding 33.1 mL of n-butyllithium (2.4 M) to a THF solution of fluorene (12 g) in an ice-water bath, stirring for 2 h, then adding 7.66 g of 6,6-dimethylfulne, and stirring overnight.

[0052] After the reaction was complete, the mixture was quenched with water, extracted with diethyl ether, and the organic layer was dried, filtered, and evaporated to dryness. The evaporated product was washed with methanol, filtered, and dried under vacuum to obtain a yellow catalyst ligand, with a yield of 53%.

[0053] In an ice-water bath, 7.0 mL of n-butyllithium (1.6 M) was added to a THF solution of the catalyst ligand (1.494 g), and the mixture was stirred at room temperature for 3 h. The solvent was removed by vacuum drying, the mixture was transferred to a glove box, the solid was washed with hexane, and the lithium salt was collected by filtration. 0.6 g of solid ZrCl4 was added to a hexane solution of the lithium salt (997 mg), and the mixture was stirred overnight. After the reaction was complete, the mixture was filtered, the filter cake was extracted with CH2Cl2, the solution was collected and concentrated to the precipitated solid, filtered, and the orange-red catalyst was collected, with a yield of 32%.

[0054] The other processes are the same as in Example 2.

[0055] Several important properties of cycloalkenes: molecular weight - measured by high-temperature GPC; glass transition temperature - measured by DSC; unit cell content - measured by high-temperature NMR. 13 Measured by C-NMR; polymer dielectric constant was measured by a vector network analyzer combined with a resonant cavity.

[0056] Table 1. Preparation of ultra-low molecular weight crosslinkable cyclic olefin resins by ternary copolymerization Note: All data are based on results from at least two parallel trials (unless otherwise stated); Activity: at 10 7 gmol -1 h -1 The unit is [unit]; the molar percentage of the unit structure content in the polymer is expressed as [high temperature]. 13 C-NMR testing is the standard; Mn and PDI are the number-average molecular weight and polymer dispersibility index, respectively, determined by GPC in 1,2,4-trichlorobenzene at 150 °C, relative to polystyrene standards.

[0057] Table 1. Conclusions of Polymerization Data: The terpolymerization of ethylene, norbornene, and dicyclopentadiene conducted in Examples 1-3, at 90 °C, showed that with increasing dicyclopentadiene content, the dicyclopentadiene content in the polymer increased from 2.5% to 7.1%. The overall polymerization activity was high, with all values ​​exceeding 7.3 × 10⁻⁶. 7 g mol -1 h -1The number-average molecular weight of the polymer is between 8,000 and 10,000. DCPD, as a crosslinking point in the preparation of ultra-low molecular weight crosslinkable cyclic olefin resins, is generally controlled to have a content between 2% and 10% in the polymer.

[0058] In Examples 4-5, as the polymerization temperature increases, the activity of the ternary copolymer is improved to a certain extent. The glass transition temperature of the polymer and the insertion rate of dicyclopentadiene are significantly increased. More significantly, the number-average molecular weight of the polymer can be reduced to below 3,000.

[0059] The terpolymerization of ethylene, tetracyclododecene, and dicyclopentadiene in Examples 6-8, conducted at 110 °C, showed that as the amount of dicyclopentadiene increased, the dicyclopentadiene content in the polymer increased from 4.9% to 9.9%, while the polymerization still maintained high activity, and the number-average molecular weight of the polymer decreased to 3,000 to 4,000. Notably, the molecular weight distribution of all polymers was no higher than 1.5.

[0060] The terpolymerization of ethylene, norbornene, and dicyclopentadiene in Comparative Example 1, under the same polymerization conditions as Example 2, resulted in a polymer with a number-average molecular weight of over 110,000. This difference is determined by the performance of the catalyst itself.

[0061] Example 9 The copolymers of Examples 1-8 and Comparative Example 1 were subjected to solubility tests. 0.2 g of the polymer was dissolved in 4-6 mL of solvent at room temperature. The test results are shown in Table 2. Table 2 Solubility Tests of Commonly Used Polymer Solvents

[0062] Solubility: X is insoluble, O is slightly soluble, OO is soluble, and OOO is very soluble.

[0063] Table 2 data conclusions: The number-average molecular weights of Examples 1-3 were between 8,000 and 9,000, and they were normally soluble in PGMEA, cyclohexanone, toluene, and xylene at room temperature. The number-average molecular weights of Examples 4-8 were lower, only between 2,000 and 4,000, and they showed good solubility in PGMEA, cyclohexanone, toluene, and xylene at room temperature. In contrast, the terpolymer prepared in Comparative Example 1 had a number-average molecular weight of over 110,000, was almost insoluble in PGMEA and cyclohexanone at room temperature, and was also difficult to dissolve in toluene and xylene.

[0064] Example 10 Five g of the ultra-low molecular weight crosslinkable cyclic olefin resins obtained in Examples 5 and 8 were dissolved in toluene solution under nitrogen protection. Ten mg of methyl ethyl ketone peroxide free radical initiator was added, and the reaction was carried out at room temperature for 15 minutes. The solid obtained after the reaction was the thermosetting cyclic olefin resin. The resin was washed with ethanol, dried, and placed in a die-casting press at 120°C for 5 hours. After cooling, the dielectric constant, dielectric loss, and DSC of the obtained samples were tested. The results are shown in Table 3.

[0065] Example 5: A physical image of the cross-linked thermosetting cyclic olefin resin is shown below. Figure 5 .

[0066] In this process, a flat sheet sample (2 cm × 2 cm) is placed into the resonant cavity. The resonant frequency and quality factor of the cavity under no load and after the sample is placed are measured using a vector network analyzer. Combined with the sample thickness, the dielectric constant Dk and dielectric loss Df are directly calculated by the system software. The average value is taken after each group is tested multiple times.

[0067] Table 3 Performance Tests of Crosslinked Cycloolefin Resins

[0068] Dielectric constant and dielectric loss test conditions: 13.3 GHz. Table 3 data conclusions: The ultra-low molecular weight crosslinkable cyclic olefin copolymers prepared in Examples 5 and 8 could not be observed at their glass transition temperature in DSC after crosslinking, indicating that the polymer was fully crosslinked. Meanwhile, the dielectric constant Dk of the crosslinked resin was approximately 2.2-2.3, and the dielectric loss Df was 7-8 × 10⁻⁶. -4 Compared with PTFE, it has superior low dielectric constant and low dielectric loss performance.

[0069] This invention primarily targets cyclic olefin resins with a weight-average molecular weight of 100,000 and above. For example, commercially available cyclic olefin resins have a molecular weight of around 100,000, which is suitable for large-scale industrial preparation and injection molding. There are also reports of preparing ultra-high molecular weight cyclic olefin resins with a weight-average molecular weight reaching millions. Low molecular weight cyclic olefin resins (number-average molecular weight less than 10,000) are rarely mentioned. Firstly, their low molecular weight limits their application value and direction. Secondly, while ultra-low molecular weight cyclic olefin resins can be prepared using common metallocene catalysts, excessive chain transfer agents are typically added, resulting in extremely low polymerization activity, making industrial production impossible. This invention provides an application outlet for ultra-low molecular weight cyclic olefin resins and solves the problem of low polymerization activity. Currently, under the use of special metallocene catalysts, the activity can reach 5 x 10⁻⁶. 7 g mol -1 h -1The above fully meets industrial standards, and the cross-linked thermosetting cyclic olefin resin has good low dielectric properties.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. An ultra-low molecular weight cyclic olefin resin, characterized in that: The ultra-low molecular weight cyclic olefin resin is a terpolymer containing X structural units, Y structural units, and Z structural units, as shown in formula (I): （Ⅰ） Wherein, the X structural unit is an α-olefin monomer such as ethylene, propylene, or butene; The Y structural unit is a cyclic olefin monomer, which is a norbornene monomer containing a double bond and its derivatives. The Z structural unit is a cyclic olefin monomer, which is a norbornene monomer or its derivative containing at least two double bonds. The structure includes at least one or more six-membered carbon ring combinations, and at least one double bond is on the six-membered carbon ring combination. At the same time, at least one double bond is adjacent to or close to the six-membered ring or its combination ring. p is 0 or 1; R1 and R2 are alkanes with fewer than 20 carbon atoms; The X structural unit accounts for 20-70% of the polymer molar amount, the Y structural unit accounts for 30-60% of the polymer molar amount, and the Z structural unit accounts for 2-20% of the polymer molar amount.

2. The ultra-low molecular weight cyclic olefin resin as described in claim 1, characterized in that: The ultra-low molecular weight cyclic olefin resin has the following characteristics: The number-average molecular weight (Mn) of cyclic olefin resins ranges from 0.5 kDa to 30 kDa. It has a molecular weight distribution of less than 1.5, a glass transition temperature of 100~300 ℃, and is soluble in common solvents at room temperature.

3. The ultra-low molecular weight cyclic olefin resin as described in claim 1 or 2, characterized in that: The Y-structure unit is derived from norbornene or tetracyclododecene.

4. The ultra-low molecular weight cyclic olefin resin as described in claim 1 or 2, characterized in that: The Z-structure unit is derived from the monomer of dicyclopentadiene or ethylidene norbornene.

5. The method for preparing the ultra-low molecular weight cyclic olefin resin according to any one of claims 1 to 4, characterized in that: include, In an inert solvent, monomers of structural units X, Y, and Z are polymerized in a reactor in the presence of a metallocene catalyst and a co-catalyst to obtain a three-membered cyclic olefin copolymer.

6. The preparation method according to claim 5, characterized in that: The cocatalyst is an alkylaluminum or boron salt, and the inert solvent is hexane, cyclohexane, methylcyclohexane, or aromatic hydrocarbons.

7. The preparation method according to claim 5, characterized in that: The structure of the metallocene catalyst is as follows: Wherein, Ra-Rd and Ra1-Rd1 are N-containing substituents or hydrogens directly connected to the fluorene ring on the catalyst, and the metallocene catalyst has at least one N-containing substituent on the fluorene ring; M is Ti, Zr, or Hf.

8. The preparation method according to claim 7, characterized in that: The substituents attached to N on the fluorene ring are straight-chain, branched, cyclic saturated alkanes or unsaturated alkanes with fewer than 20 carbons. Among them, Ra and Ra1 are the same or different, Rb and Rb1, Rc and Rc1, and Rd and Rd1 are the same or different; The molar ratio of the metallocene catalyst to the cyclic olefin monomer is 1:6000~100000; The polymerization reaction is carried out at a temperature of 30~200 ℃, a polymerization pressure of 1~100 bar, and a polymerization time of 5~240 minutes.

9. A method for preparing a thermosetting cyclic olefin resin, characterized in that: This includes dissolving the ultra-low molecular weight cyclic olefin resin of claim 1 at room temperature, adding a crosslinking agent for pre-forming at room temperature, and then further crosslinking to completely convert it into a thermosetting cyclic olefin resin.

10. The thermosetting cyclic olefin resin prepared by the method of claim 9 is used in 5G / 6G millimeter-wave communication, packaging materials, and circuit boards.

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