Composition for preparing polyolefin adhesive film and application thereof

Abstract

The invention belongs to the technical field of insulating materials for high-frequency and high-speed electronic equipment, and relates to a composition for preparing a polyolefin adhesive film and application of the composition. The composition comprises an unsaturated polymer containing a butadiene chain segment, benzocyclobutene, modified polyphenyl ether resin, an initiator and triallyl isocyanurate, the content of each component in the composition is strictly controlled; the dielectric loss of the unsaturated polymer containing the butadiene chain segment is 0.0002 to 0.0010; the modified polyphenyl ether resin is modified polyphenyl ether resin with carbon-carbon double bonds at the tail end of a molecular chain; the initiator can initiate the unsaturated polymer containing the butadiene chain segment to be copolymerized and crosslinked with the triallyl isocyanurate at a specific temperature. According to the application, the composition is prepared into a polyolefin adhesive film or a copper-clad substrate, and the preparation process comprises the steps of semi-curing treatment and hot-pressing curing treatment. The polyolefin adhesive film provided by the invention has ultra-low dielectric loss, is adaptive to the processing requirement of a copper-clad substrate, and is controllable in cost.

Description

Technical Field

[0001] This invention belongs to the technical field of insulating materials for high-frequency and high-speed electronic equipment, and relates to a composition for preparing polyolefin films and its application. Background Technology

[0002] With the rapid development of high-end electronic devices such as 5G communication, high-speed servers, and microwave radar, signal transmission continues to evolve towards higher frequencies and higher speeds. This places stringent requirements on the dielectric properties of the core supporting material of copper-clad laminates—the insulating core layer: the insulating core layer needs to have extremely low dielectric loss (Df) to reduce signal attenuation during transmission.

[0003] In traditional copper-clad laminates, while epoxy resin-based composite substrates offer excellent processability and low cost, the polar functional groups in their molecular structure result in a high dielectric constant and dielectric loss, ultimately making the copper-clad laminate unsuitable for high-frequency, high-speed signal transmission. In contrast, while polytetrafluoroethylene (PTFE) copper-clad laminates possess relatively superior dielectric properties (dielectric loss as low as 0.001) among traditional material systems, the high molecular structure of PTFE leads to extremely high melt viscosity and a narrow processing window. This necessitates high temperature and pressure to form the insulating core layer, and specialized equipment is required to prevent material decomposition, significantly increasing the difficulty and cost of forming the insulating core layer.

[0004] Polyolefin-based insulating core layers and matching copper-clad laminates are currently a research hotspot. For example, patent CN106867173B discloses a method for preparing polyolefin copper-clad laminates using ethylene propylene rubber, in which the insulating core layer uses glass fiber cloth as a reinforcing material, and a prepreg is prepared by impregnation with a resin solution. However, glass fiber cloth itself has high dielectric loss, and the interface with the resin matrix is ​​prone to signal scattering, directly resulting in generally high dielectric loss of the insulating core layer. At the same time, the use of glass fiber cloth also significantly increases the material cost of the insulating core layer, thereby increasing the cost of the copper-clad laminate, making it difficult to meet the cost-effectiveness requirements of high-frequency applications.

[0005] The dielectric properties of insulating core layers with polyphenylene oxide (PPO) as the core component are significantly affected by the component content. Patent CN116656111B uses methacrylate-modified and phenyl vinyl-modified carbon-carbon double-bond-terminated PPO resins to prepare insulating core layers. Its published data shows that when the modified PPO resin content is 15 parts, the dielectric loss of the insulating core layer is 0.0024; when the content increases to 30 parts, the dielectric loss of the insulating core layer rises to 0.0047, confirming that the higher the modified PPO content, the greater the dielectric loss of the insulating core layer. Even with optimized composition ratios, the dielectric properties of existing polyphenylene ether-based insulating core layers remain limited. For example, the dielectric loss of the polyphenylene ether composition / silica composite insulating core layer for high-frequency and high-speed applications disclosed in patent application CN118562277A is still between 0.0018 and 0.0020. Similarly, the dielectric loss of the liquid crystal polymer resin composition insulating core layer in patent CN114479419B can only be controlled within the range of 0.0016 to 0.0021. Both are at relatively high levels, resulting in the inability of the matching copper-clad substrate to meet the requirements of ultra-high frequency signal transmission.

[0006] For polyolefin resin-based insulating core layers, existing technologies, such as patent application CN114379188A, often introduce styrene-butadiene-styrene (SBS) to improve the film-forming properties of the insulating core layer. Although this has a relatively small impact on the dielectric loss of the insulating core layer, it narrows the semi-curing process window of the insulating core layer, indirectly affecting the production stability and performance consistency of the copper-clad laminate. In addition, the dielectric loss of this type of insulating core layer is still relatively high (above 0.0010), and the copper-clad laminates used with it still cannot meet the requirements of ultra-high-speed signal transmission in fields such as 5G communication.

[0007] In summary, the core problem with existing copper-clad laminates lies in the difficulty of simultaneously achieving a balance between "ultra-low dielectric loss" and "fabrication compatibility and cost control" in the accompanying insulating core layer. Therefore, developing an insulating core layer with lower dielectric loss, strong process adaptability, and significant cost advantages, as well as a copper-clad laminate fabrication technology based on this insulating core layer, has become a key requirement for solving the bottleneck in the development of high-frequency and high-speed electronic devices. Summary of the Invention

[0008] The purpose of this invention is to address the problems existing in the prior art and to provide a composition for preparing polyolefin films and its application.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A composition for preparing polyolefin films comprises an unsaturated polymer containing butadiene segments, benzocyclobutene, modified polyphenylene ether resin, an initiator, triallyl isocyanurate, and inorganic fillers.

[0011] By weight, the composition used to prepare polyolefin films contains not less than 10 parts of unsaturated polymer with butadiene segments, not more than 12 parts of benzocyclobutene, 4-8 parts of modified polyphenylene ether resin, 0.3-0.6 parts of initiator, and 8-12 parts of triallyl isocyanurate.

[0012] The dielectric loss of the unsaturated polymer containing butadiene segments is 0.0002-0.0010, and the unsaturated polymer containing butadiene segments is one or more of polybutadiene, styrene-butadiene copolymer, styrene-butadiene-divinylbenzene copolymer, and styrene-butadiene-styrene triblock copolymer.

[0013] Modified polyphenylene ether resin is a modified polyphenylene ether resin with carbon-carbon double bonds at the ends of the molecular chain (i.e., both ends of the molecular chain are carbon-carbon double bonds) (such as methacrylate-modified polyphenylene ether resin and phenyl vinyl-modified polyphenylene ether resin).

[0014] Initiators are substances that can decompose at 135-160℃ to generate free radicals, initiating copolymerization and crosslinking of unsaturated polymers containing butadiene segments with triallyl isocyanurate, such as dicumyl peroxide.

[0015] As a preferred technical solution:

[0016] The composition for preparing a polyolefin film as described above has a dielectric loss of 0.0006-0.0008 for the unsaturated polymer containing butadiene segments.

[0017] The composition for preparing polyolefin films as described above, by weight, contains no more than 16 parts of unsaturated polymers with butadiene segments. This avoids excessive surface stickiness of the polyolefin film obtained through subsequent preparation processes, ensures the processability of the film, and maintains the thermal stability of the product (polyolefin film or copper-clad substrate) made from the composition.

[0018] The composition for preparing a polyolefin film as described above, by weight, contains not less than 6 parts of benzocyclobutene, which ensures that the polyolefin film prepared subsequently has excellent thermal properties and provides suitable flowability for the film preparation process.

[0019] The composition for preparing polyolefin films as described above contains 60-75 parts by weight of inorganic filler, which enables the composition to obtain suitable flowability during subsequent preparation of polyolefin films or copper-clad substrates, thereby ensuring the filling capacity of the polyolefin film and the forming effect of the copper-clad substrate.

[0020] The composition for preparing polyolefin films as described above uses spherical silica as the inorganic filler with an average particle size of 1-6 µm.

[0021] The present invention also provides a method for preparing a polyolefin film, wherein the composition for preparing a polyolefin film as described in any of the above claims is first stirred and mixed in a solvent (such as toluene) to obtain an adhesive, and then the adhesive is coated into a film using a coating blade machine. The film is then dried to remove the solvent, and the dried film is then semi-cured to obtain a semi-cured sheet. Finally, the semi-cured sheet is hot-pressed and cured to obtain the polyolefin film.

[0022] The temperature for semi-curing is 135-160℃, and the time is 4-9 minutes;

[0023] The temperature for hot pressing curing is 200-230℃, the pressure is 6-10MPa, and the time is 90-180min.

[0024] As a preferred technical solution:

[0025] The method for preparing a polyolefin film as described above involves stirring at a speed of 1000-3000 rpm for 6-20 min; the viscosity of the adhesive is 4-7 Pa·s; the thickness of the film formed by scraping is 0.010-0.20 mm; and the drying temperature is 60-90℃ for 1-3 min.

[0026] In the polyolefin film preparation method described above, the thickness of the film formed by blade coating is 0.050-0.125 mm.

[0027] The present invention also provides a polyolefin film, which is prepared by the method for preparing a polyolefin film as described in any of the preceding claims.

[0028] As a preferred technical solution:

[0029] The polyolefin film described above has a dielectric loss ≤0.0010.

[0030] The present invention also provides a method for preparing a copper-clad substrate. First, a composition for preparing a polyolefin film as described in any of the above claims is stirred and mixed in a solvent (such as toluene) to obtain an adhesive. Then, the adhesive is coated into a film using a coating blade machine. The film is dried to remove the solvent. The dried film is then semi-cured to obtain a semi-cured sheet. Finally, copper foil is covered on both sides of the semi-cured sheet and then hot-pressed to cure it, thus obtaining the copper-clad substrate.

[0031] The temperature for semi-curing is 135-160℃, and the time is 4-9 minutes;

[0032] The temperature for hot pressing curing is 200-230℃, the pressure is 6-10MPa, and the time is 90-180min.

[0033] As a preferred technical solution:

[0034] The method for preparing a copper-clad substrate as described above involves stirring at a speed of 1000-3000 rpm for 6-20 min; the viscosity of the adhesive is 4-7 Pa·s; the thickness of the film formed by the blade coating is 0.010-0.20 mm; and the drying temperature is 60-90℃ for 1-3 min.

[0035] In the copper-clad substrate preparation method described above, the thickness of the film formed by scraping is 0.050-0.125 mm.

[0036] The present invention also provides a copper-clad substrate, which is prepared by a method for preparing a copper-clad substrate as described in any of the preceding claims.

[0037] Invention principle:

[0038] The preparation process of the polyolefin film of the present invention is as follows: preparing adhesive material → coating film by scraping → drying treatment → semi-curing treatment → hot pressing curing treatment.

[0039] During the drying stage, only the solvent is removed; no chemical reaction occurs.

[0040] During the semi-curing stage, the initiator decomposes to generate a large number of free radicals, which initiate the copolymerization and crosslinking of the unsaturated polymer containing butadiene segments with triallyl isocyanurate to form a preliminary free radical network. The terminal carbon-carbon double bonds of the modified polyphenylene ether resin participate in this copolymerization and are linked to the network, while benzocyclobutene does not react and is fixed in the network, giving the semi-cured sheet fluidity to adapt to subsequent processing.

[0041] During the hot-press curing stage, benzocyclobutene undergoes ring-opening to generate a conjugated diene intermediate, which undergoes Diels-Alder addition reaction with the unreacted terminal carbon-carbon double bonds in the modified polyphenylene ether resin and the unreacted allyl group in the triallyl isocyanurate. At the same time, the unreacted carbon-carbon double bonds in the initial free radical network continue to crosslink through thermal initiation, ultimately forming a uniform crosslinked network.

[0042] The polyolefin film of the present invention has lower dielectric loss and is better suited for high-frequency and high-speed applications, for the following reasons:

[0043] (1) In this invention, unsaturated polymers containing butadiene segments and benzocyclobutene (dielectric loss ≤0.001) are selected as the main resin in polyolefin films. The C-C bonds and CH bonds in the molecules of both have low polarization and extremely low dielectric loss, which can reduce the dielectric loss of polyolefin films from the source.

[0044] (2) Due to the following reasons, a uniform and complete cross-linked network is formed inside the polyolefin film. On the one hand, the uniform and complete cross-linked network has a three-dimensional rigid structure, which strictly restricts the slip and rotation of molecular chains, greatly reduces the degree of freedom required for dipole reorientation and polarization, and reduces energy dissipation during polarization relaxation. On the other hand, the uniform and complete cross-linked network can effectively block free volume, block the migration path of conductive impurities, and at the same time increase the electron transition barrier, thereby suppressing Joule heat loss caused by leakage current from the root. Therefore, the dielectric loss of the polyolefin film can be comprehensively reduced.

[0045] ① The modified polyphenylene ether resin can participate in the free radical polymerization of unsaturated polymers containing butadiene segments and triallyl isocyanurate, and bond to the free radical crosslinking network. On the other hand, its terminal carbon-carbon double bond can act as a dienophile and undergo a Diels-Alder reaction with the conjugated diene intermediate generated by the ring opening of benzocyclobutene, thus achieving a "linear link" between the two polymerization systems.

[0046] ② Triallyl isocyanurate contains three allyl groups, which participate in the free radical polymerization of unsaturated polymers containing butadiene segments and triallyl isocyanurate to increase crosslinking density. It also acts as a Diels-Alder reaction intermediate for the conjugated diene structure generated by the ring-opening of dienophiles and benzocyclobutene, realizing the "point-like linking" of the two polymerization systems. In synergy with the "linear linking" of modified polyphenylene ether, a uniform and complete crosslinking network is formed.

[0047] (3) In the composition used to prepare polyolefin films, the proportion of each component is strictly controlled: if the proportion of modified polyphenylene ether resin is too high, the dielectric loss will increase and the brittleness of the film will increase, and the film-forming properties will deteriorate. If the proportion is too low, the dielectric loss will be affected due to insufficient crosslinking. If the proportion of triallyl isocyanurate is too low, the crosslinking degree will be insufficient, and unreacted carbon-carbon double bonds will remain in the system, which will increase the dielectric loss. If the proportion is too high, short and highly mobile polar groups will be formed, which will also increase the dielectric loss. If the proportion of unsaturated polymer containing butadiene segments is too low or the proportion of benzocyclobutene is too high, the dielectric loss performance of the film will be affected. If the initiator content is too high, the reaction will be too fast in the semi-curing stage, and not enough unreacted carbon-carbon double bonds will be left to react with benzocyclobutene in the curing stage, which will increase the dielectric loss. If the content is too low, the free radical polymerization reaction will not be fully initiated, which will affect the dielectric loss.

[0048] Beneficial effects:

[0049] (1) The polyolefin film of the present invention has ultra-low dielectric loss, while adapting to the processing requirements of copper-clad substrates and having controllable cost, thus solving the core problem that existing insulating core layers cannot balance ultra-low dielectric loss, processing adaptability and cost.

[0050] (2) This invention does not rely on glass fiber cloth as a reinforcing material, thus avoiding the problems of increased dielectric loss and increased material cost caused by glass fiber cloth. At the same time, the structural integrity of the polyolefin film is ensured through component synergy.

[0051] (3) The present invention broadens the semi-curing process window and improves the stability of the copper clad substrate production process and the consistency of product performance by rationally combining components such as unsaturated polymers containing butadiene segments, modified polyphenylene ether resin, and benzocyclobutene, and by stepwise curing process. Detailed Implementation

[0052] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0053] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturer information of the substances is specified in this invention; in addition, products from other manufacturers that conform to the limitations of this invention are also applicable.

[0054] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0055] Viscosity: Measured using a rotational rheometer; test temperature: 25℃, rotor type: #7 rotor, shear rate: 10 rpm.

[0056] Dielectric loss: Measured using the cavity resonator method according to standard IPC-TM-650 2.5.5.5; test frequency: 10 GHz, test temperature: 22±2℃, test humidity: 40±5%.

[0057] Example 1

[0058] A method for preparing a copper-clad laminate, comprising the following steps:

[0059] (1) Preparation of materials;

[0060] Composition: By weight, it consists of 12 parts of an unsaturated polymer containing butadiene segments (a mixture of polybutadiene and styrene-butadiene-divinylbenzene copolymer in a mass ratio of 1:1, with a dielectric loss of 0.0006), 9 parts of benzocyclobutene, 5 parts of modified polyphenylene ether resin (manufacturer: SABIC, catalog number SA9000), 0.5 parts of dicumyl peroxide, 9 parts of triallyl isocyanurate, and 65 parts of spherical silica (average particle size of 6µm).

[0061] Solvent: Toluene;

[0062] Copper foil;

[0063] (2) First, the composition is stirred and mixed in a solvent to obtain a colloid with a viscosity of 6 Pa·s. Then, the colloid is scraped into a film with a thickness of 0.125 mm. The film is dried. The dried film is then semi-cured to obtain a semi-cured sheet. The two sides of the semi-cured sheet are covered with copper foil and then hot-pressed to obtain a copper-clad substrate.

[0064] The stirring speed was 2000 rpm for 6 minutes; the drying temperature was 90℃ for 2 minutes; the semi-curing temperature was 160℃ for 9 minutes; and the hot-press curing temperature was 230℃, the pressure was 10 MPa, and the time was 180 minutes.

[0065] The final copper-clad substrate consists of a polyolefin film and copper foil covering both sides of it. The dielectric loss of the polyolefin film is 0.0006.

[0066] Example 2

[0067] A method for preparing a copper-clad laminate, comprising the following steps:

[0068] (1) Preparation of materials;

[0069] Composition: By weight, it consists of 14 parts of an unsaturated polymer containing butadiene segments (a mixture of polybutadiene and styrene-butadiene-divinylbenzene copolymer in a mass ratio of 1:1, with a dielectric loss of 0.0006), 10 parts of benzocyclobutene, 6 parts of modified polyphenylene ether resin (manufacturer: SABIC, catalog number SA9000), 0.5 parts of dicumyl peroxide, 10 parts of triallyl isocyanurate, and 60 parts of spherical silica (average particle size of 6µm).

[0070] Solvent: Toluene;

[0071] Copper foil;

[0072] (2) First, the composition is stirred and mixed in a solvent to obtain a colloid with a viscosity of 6 Pa·s. Then, the colloid is scraped into a film with a thickness of 0.125 mm. The film is dried. The dried film is then semi-cured to obtain a semi-cured sheet. The two sides of the semi-cured sheet are covered with copper foil and then hot-pressed to obtain a copper-clad substrate.

[0073] The stirring speed was 2000 rpm for 6 minutes; the drying temperature was 90℃ for 3 minutes; the semi-curing temperature was 160℃ for 9 minutes; and the hot-press curing temperature was 230℃, the pressure was 10 MPa, and the time was 180 minutes.

[0074] The final copper-clad substrate consists of a polyolefin film and copper foil covering both sides of it. The dielectric loss of the polyolefin film is 0.0006.

[0075] Example 3

[0076] A method for preparing a copper-clad laminate, comprising the following steps:

[0077] (1) Preparation of materials;

[0078] Composition: By weight, it consists of 10 parts of an unsaturated polymer containing butadiene segments (a mixture of polybutadiene and styrene-butadiene-divinylbenzene copolymer in a mass ratio of 1:1, with a dielectric loss of 0.0006), 6 parts of benzocyclobutene, 8 parts of modified polyphenylene ether resin (manufacturer: Jinan Shengquan Group Co., Ltd., item number: SQP1201), 0.4 parts of dicumyl peroxide, 12 parts of triallyl isocyanurate, and 65 parts of spherical silica (average particle size of 4µm).

[0079] Solvent: Toluene;

[0080] Copper foil;

[0081] (2) First, the composition is stirred and mixed in a solvent to obtain a colloid with a viscosity of 5 Pa·s. Then, the colloid is scraped into a film with a thickness of 0.125 mm. The film is dried. The dried film is then semi-cured to obtain a semi-cured sheet. The two sides of the semi-cured sheet are covered with copper foil and then hot-pressed to obtain a copper-clad substrate.

[0082] The stirring speed was 2000 rpm for 10 min; the drying temperature was 90℃ for 2 min; the semi-curing temperature was 150℃ for 6 min; and the hot-press curing temperature was 230℃, the pressure was 10 MPa, and the time was 120 min.

[0083] The final copper-clad substrate consists of a polyolefin film and copper foil covering both sides of it. The dielectric loss of the polyolefin film is 0.0010.

[0084] Example 4

[0085] A method for preparing a copper-clad laminate, comprising the following steps:

[0086] (1) Preparation of materials;

[0087] Composition: By weight, it consists of 16 parts of an unsaturated polymer containing butadiene segments (a mixture of polybutadiene, styrene-butadiene-divinylbenzene copolymer and styrene-butadiene-styrene triblock copolymer in a mass ratio of 1:1:1, with a dielectric loss of 0.0008), 12 parts of benzocyclobutene, 4 parts of modified polyphenylene ether resin (manufacturer: SH Energy Chemical Co., Ltd., Korea, catalog number MPE-9700), 0.6 parts of dicumyl peroxide, 8 parts of triallyl isocyanurate, and 60 parts of spherical silica (average particle size of 1µm).

[0088] Solvent: Toluene;

[0089] Copper foil;

[0090] (2) First, the composition is stirred and mixed in a solvent to obtain a colloid with a viscosity of 4 Pa·s. Then, the colloid is scraped into a film with a thickness of 0.075 mm. The film is dried. The dried film is then semi-cured to obtain a semi-cured sheet. The two sides of the semi-cured sheet are covered with copper foil and then hot-pressed to obtain a copper-clad substrate.

[0091] The stirring speed was 1000 rpm for 20 min; the drying temperature was 75℃ for 3 min; the semi-curing temperature was 160℃ for 4 min; and the hot-press curing temperature was 210℃, the pressure was 8 MPa, and the time was 150 min.

[0092] The final copper-clad substrate consists of a polyolefin film and copper foil covering both sides of it. The dielectric loss of the polyolefin film is 0.0008.

[0093] Example 5

[0094] A method for preparing a copper-clad laminate, comprising the following steps:

[0095] (1) Preparation of materials;

[0096] Composition: By weight, it consists of 10 parts of an unsaturated polymer containing butadiene segments (styrene-butadiene-divinylbenzene copolymer, dielectric loss of 0.0008), 6 parts of benzocyclobutene, 4 parts of modified polyphenylene ether resin (manufacturer: SH Energy Chemical Co., Ltd., Korea, catalog number MPE-9700), 0.3 parts of dicumyl peroxide, 8 parts of triallyl isocyanurate, and 75 parts of spherical silica (average particle size of 5µm).

[0097] Solvent: Toluene;

[0098] Copper foil;

[0099] (2) First, the composition is stirred and mixed in a solvent to obtain a colloid with a viscosity of 7 Pa·s. Then, the colloid is scraped into a film with a thickness of 0.05 mm. The film is dried. The dried film is then semi-cured to obtain a semi-cured sheet. The two sides of the semi-cured sheet are covered with copper foil and then hot-pressed to obtain a copper-clad substrate.

[0100] The stirring speed was 3000 rpm for 6 min; the drying temperature was 60℃ for 1 min; the semi-curing temperature was 135℃ for 8 min; and the hot-press curing temperature was 200℃, the pressure was 6 MPa, and the time was 90 min.

[0101] The final copper-clad substrate consists of a polyolefin film and copper foil covering both sides of it. The dielectric loss of the polyolefin film is 0.0010.

[0102] Comparative Example 1

[0103] The method for preparing a copper-clad substrate differs from that in Example 5 in that, by weight, the content of unsaturated polymer containing butadiene segments in the composition is 9 parts.

[0104] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0012.

[0105] Compared with Comparative Example 1 and Example 5, the dielectric loss of the polyolefin film was significantly increased. This is because the proportion of unsaturated polymers containing butadiene segments in the composition was too low, resulting in an insufficient proportion of low dielectric loss main components. The proportion of relatively high polarity resins in the formulation passively increased, the proportion of polar groups increased, and the dielectric loss of the film increased accordingly.

[0106] Comparative Example 2

[0107] The method for preparing a copper-clad substrate differs from that in Example 4 in that the content of benzocyclobutene in the composition is 13 parts by weight.

[0108] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0013.

[0109] Compared with Comparative Example 2 and Example 4, the dielectric loss of the polyolefin film was significantly increased. This is because the proportion of benzocyclobutene in the composition was too high, and benzocyclobutene underwent a self-polymerization reaction. Compared with crosslinking with unsaturated polymers containing butadiene segments and modified polyphenylene ether resin, the self-polymerization product of benzocyclobutene has a high dielectric loss, and the dielectric loss of the film increases accordingly.

[0110] Comparative Example 3

[0111] The method for preparing a copper-clad substrate differs from that in Example 4 in that the content of modified polyphenylene ether resin in the composition is 3 parts by weight.

[0112] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0013.

[0113] Compared with Comparative Example 3 and Example 4, the dielectric loss of the polyolefin film increased significantly. This is because the proportion of modified polyphenylene ether resin in the composition was too low, which could not fully exert its linear linking effect, resulting in insufficient uniformity and integrity of the crosslinking network, thus affecting the dielectric loss.

[0114] Comparative Example 4

[0115] The method for preparing a copper-clad substrate differs from Example 3 in that the content of modified polyphenylene ether resin in the composition is 9 parts by weight.

[0116] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0015.

[0117] Compared with Comparative Example 4 and Example 3, the dielectric loss of the polyolefin film was significantly increased. This is because the modified polyphenylene ether resin accounted for too high a proportion in the composition, and the modified polyphenylene ether resin has a high dielectric loss, which in turn increased the dielectric loss of the film.

[0118] Comparative Example 5

[0119] A method for preparing a copper-clad substrate differs from Example 5 in that the content of triallyl isocyanurate in the composition is 7 parts by weight.

[0120] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0014.

[0121] Compared with Comparative Example 5 and Example 5, the dielectric loss of the polyolefin film was significantly increased. This is because the proportion of triallyl isocyanurate in the composition was too low, which could not fully exert its dot-linking effect, resulting in insufficient cross-linking and unreacted carbon-carbon double bonds remaining in the system, thus increasing the dielectric loss.

[0122] Comparative Example 6

[0123] The method for preparing a copper-clad substrate differs from Example 3 in that the content of triallyl isocyanurate in the composition is 13 parts by weight.

[0124] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0015.

[0125] Compared with Comparative Example 6 and Example 3, the dielectric loss of the polyolefin film was significantly increased. This is because the proportion of triallyl isocyanurate in the composition was too high, which would form shorter and more active polar groups, resulting in increased dielectric loss.

[0126] Comparative Example 7

[0127] The method for preparing a copper-clad substrate differs from that in Example 5 in that a modified polyphenylene ether resin (manufacturer: SABIC, product number SA90) is used instead.

[0128] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0020.

[0129] Compared with Example 5, the dielectric loss of the polyolefin film in Comparative Example 7 was significantly increased. This is mainly because the modified polyphenylene ether resin used in Comparative Example 7 does not contain carbon-carbon double bonds at the end of its molecular chain. It cannot participate in the free radical polymerization of polymers containing butadiene segments and triallyl isocyanurate, nor can it undergo the Diels-Alder reaction with the ring-opening product of benzocyclobutene as a dienophile. This results in insufficient uniformity of the crosslinking network and unreacted carbon-carbon double bonds remaining in the system, leading to a significant increase in dielectric loss.

[0130] Comparative Example 8

[0131] A method for preparing a copper-clad substrate differs from Example 5 in that triallyl isocyanurate is replaced with diallyl isocyanurate.

[0132] The dielectric loss of the polyolefin film in the final copper-clad substrate is 0.0016.

[0133] Compared with Comparative Example 8 and Example 5, the dielectric loss of the polyolefin film was significantly increased. This is because the number of allyl groups in diallyl isocyanuric acid is small, which cannot provide enough cross-linking sites, resulting in insufficient cross-linking of the system and residual unreacted carbon-carbon double bonds, which in turn increases the dielectric loss.

Claims

1. A composition for preparing polyolefin films, characterized in that, It is composed of an unsaturated polymer containing butadiene segments, benzocyclobutene, modified polyphenylene ether resin, initiator, triallyl isocyanurate and inorganic filler; By weight, the composition used to prepare polyolefin films contains not less than 10 parts of unsaturated polymer with butadiene segments, not more than 12 parts of benzocyclobutene, 4-8 parts of modified polyphenylene ether resin, 0.3-0.6 parts of initiator, and 8-12 parts of triallyl isocyanurate. The dielectric loss of the unsaturated polymer containing butadiene segments is 0.0002-0.0010, and the unsaturated polymer containing butadiene segments is one or more of polybutadiene, styrene-butadiene copolymer, styrene-butadiene-divinylbenzene copolymer, and styrene-butadiene-styrene triblock copolymer. The modified polyphenylene ether resin is a modified polyphenylene ether resin with carbon-carbon double bonds at the ends of its molecular chain. The initiator is a substance that can decompose at 135-160℃ to generate free radicals, which can initiate the copolymerization and crosslinking of unsaturated polymers containing butadiene segments with triallyl isocyanurate.

2. The composition for preparing a polyolefin film according to claim 1, characterized in that, By weight, the composition used to prepare polyolefin films contains no more than 16 parts of unsaturated polymer with butadiene segments, no less than 6 parts of benzocyclobutene, and 60-75 parts of inorganic filler.

3. The composition for preparing a polyolefin film according to claim 1, characterized in that, The inorganic filler is spherical silica with an average particle size of 1-6µm.

4. A method for preparing a polyolefin film, characterized in that, First, the composition for preparing a polyolefin film as described in any one of claims 1 to 3 is stirred and mixed in a solvent to obtain an adhesive. Then, the adhesive is coated into a film and dried. The dried film is then semi-cured to obtain a semi-cured sheet. Finally, the semi-cured sheet is hot-pressed and cured to obtain the polyolefin film. The temperature for semi-curing is 135-160℃, and the time is 4-9 minutes; The temperature for hot pressing curing is 200-230℃, the pressure is 6-10MPa, and the time is 90-180min.

5. The method for preparing a polyolefin film according to claim 4, characterized in that, The viscosity of the adhesive is 4-7 Pa·s; the thickness of the film formed by the scraping is 0.010-0.20 mm.

6. A polyolefin film, characterized in that, It is prepared by the method for preparing a polyolefin film as described in claim 4 or 5.

7. A polyolefin film according to claim 6, characterized in that, The dielectric loss of the polyolefin film is ≤0.0010.

8. A method for preparing a copper-clad laminate, characterized in that, First, the composition for preparing polyolefin film as described in any one of claims 1 to 3 is stirred and mixed in a solvent to obtain an adhesive. Then, the adhesive is coated into a film and dried. The dried film is then semi-cured to obtain a semi-cured sheet. Finally, copper foil is covered on both sides of the semi-cured sheet and then hot-pressed to cure it, thus obtaining a copper-clad substrate. The temperature for semi-curing is 135-160℃, and the time is 4-9 minutes; The temperature for hot pressing curing is 200-230℃, the pressure is 6-10MPa, and the time is 90-180min.

9. A method for preparing a copper-clad substrate according to claim 8, characterized in that, The viscosity of the adhesive is 4-7 Pa·s; the thickness of the film formed by the scraping is 0.010-0.20 mm.

10. A copper-clad substrate, characterized in that, It is prepared by the method described in claim 8 or 9 for the preparation of a copper-clad substrate.