Low dielectric loss thermosetting resin composition

Abstract

The present disclosure relates to low dielectric loss thermoset resin compositions comprising a copolymer comprising monomer units of formula I and aliphatic unsaturated imide monomer units of formula II and at least one curing agent comprising maleimide, (meth) acrylate or vinyl groups. # imgabs 0 # wherein R1 represents hydrogen or an aliphatic group and R2 represents hydrogen, an aliphatic or aromatic group, and # imgabs 1 # wherein R3 is H or an alkyl group, R4 is an alkylene group, R5 is an alkanediyl group. The curing agent comprising a maleimide, a (meth) acrylate or a vinyl group is preferably polyfunctional. The resin composition may optionally contain a radical initiator. The resin composition may also include an additive selected from the group consisting of flame retardants, fillers, coupling agents. The present disclosure also relates to a prepreg or a copper clad laminate comprising the thermosetting resin composition.

Description

[0001] Related Applications

[0002] This application claims the benefit of European Application No. 22194425.9, filed on September 7, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to polymers of thermosetting resin compositions that can be used in the chemical field such as in the manufacture of products such as printed circuit boards. In particular, the present disclosure pertains to novel compositions and methods for preparing certain low dielectric loss thermosetting resin polymers. Background Art

[0004] The present disclosure relates to a low dielectric loss thermosetting resin composition comprising a copolymer containing monomer units having vinyl or vinyl derivatives, an aliphatic unsaturated imide, and a curing agent. The present disclosure also relates to a prepreg and a metal-clad laminate comprising the thermosetting resin composition. The present disclosure also relates to a printed circuit board comprising the prepreg and / or the metal-clad laminate.

[0005] Thermosetting resin compositions are known in the art. Thermosetting resins undergo a curing or crosslinking process that crosslinks polymer chains and thus joins the entire matrix together in a three-dimensional network. Once crosslinked, thermosetting resins can no longer be melted and reformed. Thermosetting resins tend to have high dimensional stability, high temperature resistance, and good solvent resistance due to their three-dimensional crosslinked structure (Office of Technology Assessment, U.S. Congress, June 1988).

[0006] Crosslinked thermosetting resin compositions such as epoxy resins, phenolic resins, bismaleimide resins, polyamine formaldehyde resins, and silicone resins can be used in electrical applications and electronic devices such as in printed circuit boards (PCBs). Thermosetting resins are required to provide long-life and high-reliability electrical insulation properties. Such compositions are used, for example, as fiber-reinforced prepregs and in metal-clad laminates such as copper-clad laminates (CCLs) suitable for printed circuit boards (PCBs).

[0007] CCL serves as the most important basic raw material contributing to the materials for PCB manufacturing, having four major functions including conduction, insulation, support, and signal transmission, and thus determining the performance, quality, manufacturing level, manufacturing cost, and long-term reliability of the PCB. The continuous development of PCBs and the increasing demands of electronic product applications have gradually imposed new technical requirements on CCLs, and at the same time provided a driving force for the technical development and manufacturing technology progress of CCLs.

[0008] CCLs typically use epoxy resins. Curing agents for epoxy resins include, for example, phenolic resins, poly(styrene-co-maleic anhydride) (SMA), benzoxazines, reactive esters, and cyanate esters. However, epoxy resin formulations do not meet the growing demand for lower dielectric loss. This is mainly because the polar groups formed during the curing process of epoxy resins adversely affect the dielectric loss.

[0009] An unsaturated thermosetting composition with improved dielectric properties is disclosed in US9245667. Generally, unsaturated difunctional low molecular weight poly(phenylene ether) (PPE) is used together with additional curing agents such as, for example, triallyl isocyanurate (TAIC), bismaleimide (BMI), polybutadiene, and polybutadiene-co-styrene. The disadvantages of these low molecular weight PPE resins are that PPE may have flow problems during the curing stage and does not have good wettability to glass cloth.

[0010] Fluorine-containing resins such as PTFE can also be used in PCBs and exhibit low dielectric loss. However, fluorine-containing resins are expensive and difficult to process, so their use is limited.

[0011] JP-A-58019316 discloses a thermosetting resin composition that provides improved heat resistance and thus improved insulation properties, where the thermosetting resin composition is provided by mixing a styrene copolymer having a specific imide bond with a free radical polymerization catalyst. The styrene copolymer preferably contains styrene and maleic anhydride, which undergoes an imidization reaction with, for example, allylamine. The resulting copolymer is heated in the presence of a known free radical polymerization catalyst such as an organic peroxide to obtain a heat-resistant thermosetting resin. The disadvantage of this cured thermosetting resin is that it still has a relatively high dielectric loss even at the reported 1 MHz. When the frequency increases, the dielectric loss increases, while high-speed PCB applications typically use higher frequencies (e.g., 1 GHz or higher). In addition, the cured resin shows a relatively low decomposition temperature, i.e., poor thermal stability. Thermal stability affects the processing performance and operating temperature. For example, poor thermal stability can lead to a short delamination time during the soldering process of PCB applications and may also cause thermal reliability and signal integrity problems during operation.

[0012] Therefore, thermosetting resins used in high-speed applications must meet many critical thermal, environmental, and electrical requirements to meet the performance standards required for microelectronic applications. These desired properties include thermal stability, low moisture absorption, copper adhesion, high breakdown voltage (low leakage current), low dielectric constant (Dk), and low dielectric loss (Df) (which can also be referred to as the loss tangent).

[0013] Therefore, there is a need to develop a thermosetting resin composition having excellent dielectric properties such as low dielectric constant (Dk) and low dielectric loss (Df), combined with other properties required in high-speed PCBs such as high Tg, low coefficient of thermal expansion, low water absorption, and high peel strength.

[0014] An object of the present disclosure is to provide a thermosetting resin composition having improved dielectric and thermal properties, which can be used in electronic applications such as high-speed PCBs. The improved dielectric properties refer to low dielectric loss and low dielectric constant (Dk) or low relative permittivity combined with better thermal stability. Summary of the Invention

[0015] In one aspect, the present disclosure provides a thermosetting resin composition comprising:

[0016] A copolymer comprising monomer units of formula I and an aliphatic unsaturated imide of formula II

[0017]

[0018] wherein R1 represents hydrogen or an aliphatic group, and R2 represents hydrogen, an aliphatic or aromatic group,

[0019]

[0020] wherein R3 is H or an alkyl group, R4 is an alkylidene group, and R5 is an alkanediyl group; and

[0021] At least one curing agent comprising a maleimide, (meth)acrylate or vinyl group.

[0022] In another aspect, the present disclosure provides a thermoset resin composition prepared by a method comprising the steps of: (i) contacting a styrene-maleic anhydride copolymer (SMA) with an unsaturated aliphatic amine to prepare a styrene-maleimide copolymer and / or (ii) crosslinking the styrene-maleimide copolymer with at least one curing agent.

[0023] In another aspect, the present disclosure provides a thermosetting resin composition comprising a styrene-maleimide copolymer crosslinked by at least one curing agent.

[0024] In another aspect, the present disclosure provides a prepreg comprising: a thermosetting resin composition or a thermoset resin composition as described herein, or a semi-cured product of a thermosetting resin composition or a thermoset resin composition as described herein; and a substrate.

[0025] In another aspect, the present disclosure provides a metal-clad laminate comprising: an insulating layer formed from a cured product of a prepreg composition as described herein or a thermosetting resin composition as described herein; and at least one metal layer formed on either or both surfaces of the insulating layer.

[0026] In another aspect, the present disclosure provides a printed circuit board comprising a prepreg composition as described herein, or a thermosetting resin composition as described herein, or a metal-clad laminate as described herein.

[0027] Additional embodiments, features, and advantages of the present disclosure will be apparent from the following detailed description and from the practice of the present disclosure. The compounds of the present disclosure may be described as embodiments of any of the items listed below. It should be understood that any one of the embodiments described herein can be used in combination with any other embodiment described herein to the extent that the embodiments are not mutually contradictory.

[0028] 1. A thermosetting resin composition comprising:

[0029] a copolymer comprising monomer units of Formula I and an aliphatic unsaturated imide of Formula II

[0030]

[0031] wherein R1 represents hydrogen or an aliphatic group, and R2 represents hydrogen, an aliphatic or aromatic group,

[0032]

[0033] wherein R3 is H or an alkyl group, R4 is a sub-alkyl group and R5 is an alkanediyl group, and

[0034] at least one curing agent comprising a maleimide, (meth)acrylate or vinyl group.

[0035] 2. The thermosetting resin composition according to item 1, wherein the maleimide curing agent is a polyfunctional maleimide.

[0036] 3. The thermosetting resin composition according to item 2, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide or 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

[0037] 4. The thermosetting resin composition according to any one of items 1-2, wherein the curing agent comprising a (meth)acrylate group is a polyfunctional (meth)acrylate.

[0038] 5. The thermosetting resin composition according to item 4, wherein the polyfunctional (meth)acrylate is represented by formula XI

[0039]

[0040] n is an integer between 1 and 20.

[0041] 6. The thermosetting resin composition according to any one of items 1-2, wherein the curing agent containing a vinyl group is a polyfunctional vinyl-containing curing agent.

[0042] 7. The thermosetting resin composition according to item 6, wherein the polyfunctional vinyl curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenylethane, polyfunctional vinyl aromatic copolymer, vinyl cycloolefin resin or poly(arylene ether).

[0043] 8. The thermosetting resin composition according to item 7, wherein the poly(arylene ether) is represented by formula XII

[0044]

[0045] n is an integer between 1 and 20.

[0046] 9. The thermosetting resin composition according to any one of items 1-8, which further comprises a radical initiator.

[0047] 10. The thermosetting resin composition according to item 1, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II varies between 1:1 and 9:1.

[0048] 11. The thermosetting resin composition according to item 1, wherein the copolymer further comprises a saturated imide monomer unit of formula III

[0049]

[0050] wherein R6 is selected from saturated aliphatic or aromatic groups.

[0051] 12. The thermosetting resin composition according to item 11, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III varies between 1:0 and 1:2.

[0052] 13. The thermosetting resin composition according to any one of items 1-12, which further comprises at least one additive selected from flame retardants, fillers, coupling agents and any combination thereof.

[0053] 14. A prepreg comprising: a substrate, and a thermosetting resin composition according to any one of items 1-13 or a semi-cured product of the resin composition.

[0054] 15. A metal-clad laminate comprising an insulating layer formed from a cured product of the prepreg of item 14 and at least one metal layer formed on either or both surfaces of the insulating layer.

[0055] 16. A printed circuit board comprising the metal-clad laminate according to item 15.

[0056] 17. A thermosetting resin composition prepared by a method comprising the following steps:

[0057] (ii) Crosslinking a styrene-maleimide copolymer with at least one curing agent.

[0058] 18. The thermosetting resin composition of item 17, further comprising the following steps:

[0059] (i) Contacting a styrene-maleic anhydride copolymer (SMA) with an unsaturated aliphatic amine to prepare a styrene-maleimide copolymer.

[0060] 19. The thermosetting resin composition of item 17 or 18, wherein the styrene-maleimide copolymer comprises:

[0061] Monomer units of formula I

[0062]

[0063] wherein R1 is hydrogen or an aliphatic group, and R2 is hydrogen, an aliphatic group or an aromatic group; and

[0064] An aliphatic unsaturated imide of formula II

[0065]

[0066] wherein R3 is H or an aliphatic group, R4 is a sub-alkyl group, and R5 is an alkylene group.

[0067] 20. The thermosetting resin composition according to any one of items 17-19, wherein the styrene-maleimide copolymer further comprises a saturated imide monomer of formula III

[0068]

[0069] wherein R6 is a saturated aliphatic or aromatic group.

[0070] 21. The thermosetting resin composition according to any one of Items 17 - 20, wherein the at least one curing agent contains one or more maleimide groups, (meth)acrylate groups, and / or vinyl groups.

[0071] 22. The thermosetting resin composition according to any one of Items 17 - 20, wherein the at least one curing agent contains polyfunctional maleimide.

[0072] 23. The thermosetting resin composition according to Item 22, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide, and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

[0073] 24. The thermosetting resin composition according to any one of Items 17 - 20, wherein the at least one curing agent is polyfunctional (meth)acrylate.

[0074] 25. The thermosetting resin composition according to Item 24, wherein the polyfunctional (meth)acrylate has Formula XI,

[0075]

[0076] wherein n is an integer between 1 and 20.

[0077] 26. The thermosetting resin composition according to any one of Items 17 - 20, wherein the at least one curing agent is a polyfunctional vinyl-containing curing agent.

[0078] 27. The thermosetting resin composition according to Item 26, wherein the polyfunctional vinyl-containing curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenylethane, polyfunctional vinyl aromatic copolymer, vinylcycloolefin resin, and poly(arylene ether).

[0079] 28. The thermosetting resin composition according to Item 27, wherein the poly(arylene ether) has Formula XII,

[0080]

[0081] wherein n is an integer between 1 and 20.

[0082] 29. The thermosetting resin composition according to any one of Items 17 - 28, wherein step (ii) is carried out in the presence of one or more radical polymerization initiators.

[0083] 30. The thermosetting resin composition according to Item 29, wherein the one or more radical polymerization initiators contain azo compounds or organic peroxides.

[0084] 31. The thermosetting resin composition of item 30, wherein the azo compound is azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide).

[0085] 32. The thermosetting resin composition of item 30, wherein the organic peroxide is selected from benzoyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, bis(2-tert-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hex-3-yne, and cumene hydroperoxide.

[0086] 33. The thermosetting resin composition according to any one of items 18-32, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II in the styrene-maleimide copolymer is about 1:1 to 9:1.

[0087] 34. The thermosetting resin composition according to any one of items 19-33, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III is about 1:0 to 1:2.

[0088] 35. The thermosetting resin composition according to any one of items 17-34, wherein step (ii) is carried out in the presence of at least one additive selected from flame retardants, fillers, coupling agents, and combinations thereof.

[0089] 36. The thermosetting resin composition according to any one of items 17-35, wherein step (ii) is carried out under heating.

[0090] 37. The thermosetting resin composition according to any one of items 17-36, wherein step (ii) is carried out in the presence of a substrate.

[0091] 38. The thermosetting resin composition of item 37, wherein step (ii) is carried out under heating without providing complete curing of the thermosetting resin composition, and incomplete curing provides a prepreg composition of the thermosetting resin composition.

[0092] 39. A metal-clad laminate comprising the thermosetting resin composition of item 38, prepared by a method including contacting the thermosetting resin composition with one or more metal layers before completing step (ii).

[0093] 40. The metal-clad laminate of item 39, which comprises

[0094] i.) an insulating layer comprising the thermosetting resin of item 37, and

[0095] ii.) one or more metal layers, wherein the one or more metal layers are on either or both surfaces of the insulating layer.

[0096] 41. A printed circuit board comprising the prepreg of item 38 or the metal-clad laminate of item 40.

[0097] 42. A thermosetting resin composition comprising a styrene-maleimide copolymer crosslinked by at least one curing agent.

[0098] 43. The thermosetting resin composition of item 42, wherein the styrene-maleimide copolymer comprises: monomer units of formula I

[0099]

[0100] wherein R1 is hydrogen or an aliphatic group, and R2 is hydrogen, an aliphatic group or an aromatic group; and

[0101] an aliphatic unsaturated imide of formula II

[0102]

[0103] wherein R3 is H or an aliphatic group, R4 is a sub-alkyl group, and R5 is an alkylene group.

[0104] 44. The thermosetting resin composition of item 42 or 43, wherein the styrene-maleimide copolymer further comprises a saturated imide monomer of formula III

[0105]

[0106] wherein R6 is a saturated aliphatic or aromatic group.

[0107] 45. The thermosetting resin composition of any one of items 42-44, wherein the at least one curing agent comprises one or more maleimide groups, (meth)acrylate groups and / or vinyl groups.

[0108] 46. The thermosetting resin composition of any one of items 42-44, wherein the at least one curing agent comprises a polyfunctional maleimide.

[0109] 47. The thermosetting resin composition according to item 46, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

[0110] 48. The thermosetting resin composition according to any one of items 42 - 44, wherein the at least one curing agent is a polyfunctional (meth)acrylate.

[0111] 49. The thermosetting resin composition according to item 48, wherein the polyfunctional (meth)acrylate has the formula XI,

[0112]

[0113] wherein n is an integer between 1 and 20.

[0114] 50. The thermosetting resin composition according to any one of items 42 - 44, wherein the at least one curing agent is a polyfunctional vinyl-containing curing agent.

[0115] 51. The thermosetting resin composition according to item 50, wherein the polyfunctional vinyl-containing curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenylethane, polyfunctional vinyl aromatic copolymers, vinyl cycloolefin resins, and poly(arylene ether).

[0116] 52. The thermosetting resin composition according to item 51, wherein the poly(arylene ether) has the formula XII,

[0117]

[0118] wherein n is an integer between 1 and 20.

[0119] 53. The thermosetting resin composition according to any one of items 42 - 52, wherein the styrene-maleimide copolymer is crosslinked by the at least one curing agent in the presence of one or more free radical polymerization initiators.

[0120] 54. The thermosetting resin composition according to item 53, wherein the free radical polymerization initiator comprises an azo compound or an organic peroxide.

[0121] 55. The thermosetting resin composition according to item 54, wherein the azo compound is azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide).

[0122] 56. The thermosetting resin composition according to item 55, wherein the organic peroxide is selected from benzoyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, bis(2-tert-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, and cumene hydroperoxide.

[0123] 57. The thermosetting resin composition according to any one of items 42 - 56, wherein the styrene - maleimide copolymer is crosslinked by the at least one curing agent under heating.

[0124] 58. The thermosetting resin composition according to any one of items 42 - 57, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II in the styrene - maleimide copolymer is about 1:1 to 9:1.

[0125] 59. The thermosetting resin composition according to item 58, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III is about 1:0 to 1:2.

[0126] 60. The thermosetting resin composition according to any one of items 42 - 59, further comprising at least one additive selected from flame retardants, fillers, coupling agents, and combinations thereof.

[0127] 61. The thermosetting resin composition according to any one of items 42 - 60, further comprising a substrate.

[0128] 62. The thermosetting resin composition according to item 61, wherein the styrene - maleimide copolymer is not completely crosslinked by the at least one curing agent to provide a prepreg composition of the thermosetting resin composition.

[0129] 63. A metal - clad laminate comprising the thermosetting resin composition according to item 61 or 62, and comprising one or more metal layers on the thermosetting resin composition.

[0130] 64. The metal - clad laminate according to item 63, comprising:

[0131] i.) an insulating layer comprising the thermosetting resin according to item 61, and

[0132] ii.) one or more metal layers, wherein the one or more metal layers are on either or both surfaces of the insulating layer.

[0133] 65. A printed circuit board comprising the thermosetting resin composition according to item 62 or the metal - clad laminate according to item 63 or 64. Description of the Drawings

[0134] Figure 1 It is the TGA curve graphs of Example 3 and Comparative Example 3. Detailed Description

[0135] Before further describing the present disclosure, it should be understood that the present disclosure is not limited to the specific embodiments described, as these embodiments will undoubtedly vary. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting, as the scope of the present disclosure will be limited only by the appended claims.

[0136] Unless otherwise defined, all technical and scientific terms used herein will have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. All patents, applications, published applications, and other publications cited herein are incorporated by reference in their entirety. If the definitions set forth in this section are contrary to or inconsistent with the definitions set forth in the patents, applications, or other publications incorporated by reference herein, the definitions set forth in this section shall control.

[0137] As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the claims may be drafted to exclude any optional elements. Accordingly, this statement is intended to serve as a basis for the recitation of claim elements using exclusive terms such as "solely", "only", etc., or the use of "negative" limitations.

[0138] As used herein, the terms "comprising", "containing", and "including" are used in their open, non-limiting sense.

[0139] For the sake of providing a more concise description, some quantitative expressions given herein are not modified by the term "about". It should be understood that whether or not the term "about" is explicitly used, each quantity given herein is meant to refer to the actual given value and also to the approximation of such given value reasonably inferred based on ordinary skill in the art, including equivalents and approximations due to the experimental and / or measurement conditions of such given values. Whenever a yield is given as a percentage, the yield refers to the mass of the entity for which the yield is given relative to the maximum amount of the same entity obtainable under specific stoichiometric conditions. Unless otherwise indicated, concentrations given as percentages refer to mass ratios.

[0140] As used herein, the term "aliphatic" includes compositions of hydrocarbons that may be saturated or unsaturated. Aliphatic compositions are not aromatic and do not have alternating double bonds, such as π-electron conjugation. Aliphatic compositions may contain straight-chain, branched-chain, or cyclic hydrocarbons. Cyclic aliphatic compositions are not aromatic.

[0141] As used herein, the term "alkyl" refers to a monovalent saturated aliphatic chain of carbon atoms, which is optionally branched and contains 1 to 20 carbon atoms. It should also be understood that in certain embodiments, the alkyl may advantageously have a limited length, including C1-C 12 、C1-C 10, C1-C9, C1-C8, C1-C7, C1-C6, and C1-C4. Schematically, such particularly length-restricted alkyl groups, including C1-C8, C1-C7, C1-C6, and C1-C4, etc., may be referred to as "lower alkyl". Schematic alkyl groups include but are not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 2-pentyl, 3-pentyl, neopentyl, hexyl, heptyl, octyl, etc. The alkyl group can be substituted or unsubstituted. Typical substituent groups include cycloalkyl, aryl, heteroaryl, heterocycloalkyl, hydroxy, alkoxy, aryloxy, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, oxo, (=O), thiocarbonyl, O-carbamoyl, N-carbamoyl, O-thiocarbamoyl, N-thiocarbamoyl, C-amido, N-amido, C-carboxy, O-carboxy, nitro, and amino, or as described in the various embodiments provided herein.

[0142] As used herein, the terms "alkylene" and "alkanediyl" refer to a divalent saturated aliphatic chain of carbon atoms, which is optionally branched and contains 1 to 20 carbon atoms. It should also be understood that in certain embodiments, the alkylene or alkanediyl may advantageously have a restricted length, including C1-C 12 , C1-C 10 , C1-C9, C1-C8, C1-C7, C1-C6, and C1-C4. Schematically, such particularly length-restricted alkyl groups, including C1-C8, C1-C7, C1-C6, and C1-C4, etc., may be referred to as "lower alkylene" or "lower alkanediyl". Schematic alkylene or alkanediyl groups include but are not limited to methylene (methanediyl), ethylene (ethane-1,2-diyl), n-propylene (propane-1,3-diyl), isopropylene (propane-1,2-diyl), n-butylene (butane-1,4-diyl), sec-butylene (butane-1,3-diyl), n-pentylene (pentane-1,5-diyl), 2-pentylene (pentane-1,4-diyl), 3-pentylene (pentane-1,3-diyl), n-hexylene (hexane-1,6-diyl), n-heptylene (heptane-1,7-diyl), octylene (octane-1,8-diyl), etc. The alkylene or alkanediyl can be substituted or unsubstituted. Typical substituent groups include cycloalkyl, aryl, heteroaryl, heterocycloalkyl, hydroxy, alkoxy, aryloxy, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, oxo, (=O), thiocarbonyl, O-carbamoyl, N-carbamoyl, O-thiocarbamoyl, N-thiocarbamoyl, C-amido, N-amido, C-carboxy, O-carboxy, nitro, and amino, or as described in the various embodiments provided herein.

[0143] As used herein, the term "cycloalkyl" includes aliphatic rings of carbon atoms, which are optionally branched and contain 3 to 20 carbon atoms. It should also be understood that in certain embodiments, the cycloalkyl may advantageously have a limited length, including C3 to C 10 . Illustrative cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and the like.

[0144] As used herein, the terms "alkenyl" and "alkynyl" refer to unsaturated aliphatic chains of carbon atoms. As used herein, the term "alkenyl" includes chains of carbon atoms, which are optionally branched and contain 2 to 20 carbon atoms, and further includes at least one carbon-carbon double bond (i.e., C═C). It should be understood that in certain embodiments, the alkenyl may advantageously have a limited length, including C2-C 12 , C2-C9, C2-C8, C2-C7, C2-C6, and C2-C4. Illustrative alkenyl groups include, but are not limited to, vinyl, allyl, ethenyl, 1-propenyl, 2-propenyl, 1-, 2-, or 3-butenyl, and the like. As used herein, the term "alkynyl" includes chains of carbon atoms, which are optionally branched and contain 2 to 20 carbon atoms, and further includes at least one carbon-carbon triple bond (i.e., C≡C). It should be understood that in certain embodiments, the alkynyl may each advantageously have a limited length, including C2-C 12 , C2-C9, C2-C8, C2-C7, C2-C6, and C2-C4. Illustrative alkynyl groups include, but are not limited to, ethynyl, 1-propynyl, 2-propynyl, 1-, 2-, or 3-butynyl, and the like.

[0145] As used herein, the term "alkylidene" refers to a divalent functional group derived from an alkane by removing two hydrogen atoms from the same carbon atom, and the free valence is part of the double bond -R2C═, where the carbon atom is sp 2 hybridized. The sp 2 carbon atom can be located at any carbon in the chain. Illustrative alkylidene groups include, but are not limited to, methylene, ethylene, 1-propylidene, 2-propylidene, and the like.

[0146] As used herein, the term "aryl" refers to a fully conjugated π-electron system of 6 to 12 carbon atoms of a monocyclic or fused polycyclic group of all carbon atoms, such as "aromatic". It should be understood that in certain embodiments, the aryl may advantageously have a limited size, such as C6-C 10 aryl. Illustrative aryl groups include, but are not limited to, phenyl, naphthyl, and anthracenyl. The aryl group can be unsubstituted or substituted as described herein.

[0147] The term "substituted" means that the specified group or moiety bears one or more substituents. The term "unsubstituted" means that the specified group bears no substituents. When the term "substituted" is used to describe a structural system, substitution is intended to occur at any valence-allowed position on the system. In some embodiments, "substituted" means that the specified group or moiety bears one, two, or three substituents. In other embodiments, "substituted" means that the specified group or moiety bears one or two substituents. In still other embodiments, "substituted" means that the specified group or moiety bears one substituent. Typical substituent groups include alkyl, cycloalkyl, aryl, hydroxy, alkoxy, aryloxy, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, oxo, (=O), thiocarbonyl, nitro, and amino, or as described in the various embodiments provided herein.

[0148] An object of the present disclosure is achieved because there is provided a thermosetting resin composition comprising: a copolymer comprising monomer units of formula I and an aliphatic unsaturated imide of formula II, and at least one curing agent comprising a maleimide, (meth)acrylate, or vinyl group.

[0149]

[0150] Wherein R1 represents hydrogen or an aliphatic group, R2 represents hydrogen, an aliphatic or aromatic group, preferably R1 is methyl or H, and R2 is H.

[0151]

[0152] Wherein R3 is H or an alkyl group, R4 is an alkyl group, and R5 is an alkyl group. Preferably, R3 is H or a C1-C8 alkyl group, R4 is a C1-C4 alkylene group, and R5 is a C1-C4 alkanediyl group. More preferably, R3 is H, R4 is CH2, and R5 is CH2.

[0153] Surprisingly, it has been found that the thermosetting resin composition of the present disclosure has a low dielectric loss (Df) at high frequencies such as 5 GHz. In addition, the thermosetting resin composition of the present disclosure exhibits improved thermal stability. The low dielectric loss according to the present disclosure means that the dielectric constant (Dk) is less than 2.7, preferably less than 2.6, and the dielectric loss (Df) is less than 0.0040, preferably less than 0.0030, more preferably less than 0.0020 in a high frequency band (e.g., above 5 GHz).

[0154] The improved thermal stability according to the present disclosure means that the thermosetting resin system has a high thermal decomposition temperature, such as a thermal decomposition temperature above 350 °C, as determined by thermogravimetric analysis (TGA), at which the mass of the cured sample is 5.0% less than its mass measured at 50 °C, i.e., Td 5%.

[0155] The glass transition temperature (T g ) of the cured resin composition according to the present disclosure is at least higher than 110 °C, preferably higher than 150 °C, and more preferably higher than 170 °C. The Tg of the cured resin composition can be measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), or thermomechanical analysis (TMA).

[0156] The molar ratio of the monomer unit of formula I to the aliphatic unsaturated imide monomer unit of formula II varies between 1:1 and 9:1. Preferably, the molar ratio varies between 3:1 and 8:1.

[0157] The weight average molecular weight (g / mol) of the copolymer can range from 4,000 - 80,000, preferably 4,500 - 30,000, and more preferably 7,000 - 20,000.

[0158] As used herein, "polymer" means a substance or material composed of many repeating subunits or "monomers". As used herein, "copolymer" means a polymer composed of more than one monomer.

[0159] In the thermosetting resin composition of the present disclosure, the copolymer of the monomer unit of formula I and the aliphatic unsaturated imide monomer unit of formula II can optionally be combined with the saturated imide monomer unit of formula III. The introduction of the saturated imide monomer unit of formula III can change the thermal and dielectric properties of the copolymer according to the selection of R6.

[0160]

[0161] Wherein R6 is selected from saturated aliphatic or aromatic groups. Preferably, R6 is selected from methyl, ethyl, propyl, cyclohexyl, benzyl, phenyl, substituted phenyl, or naphthyl.

[0162] The molar ratio of the monomer unit of formula I to the combined aliphatic unsaturated imide monomer unit of formula II and the saturated imide monomer unit of formula III varies between 1:1 and 9:1. Preferably, the molar ratio varies between 3:1 and 8:1. The molar ratio of the aliphatic unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III varies between 1:0 and 1:2.

[0163] Preferably, the thermosetting resin composition according to the present disclosure comprises a copolymer according to formula IV or V.

[0164]

[0165] Where the molar ratio of n:m ranges from 1:1 to 9:1.

[0166]

[0167] wherein the molar ratio of n:(m + p) ranges from 1:1 to 9:1; the range of m:p is from 1:0 to 1:2.

[0168] The synthesis of the described copolymers is not particularly limited. For example, an aliphatic unsaturated maleimide such as N-allyl maleimide can be copolymerized with, for example, styrene, as disclosed in US4795692. Alternatively, an unsaturated aliphatic amine can be used to imidize a copolymer comprising monomer units of formula I and anhydride monomer units of formula VI.

[0169]

[0170] Examples of unsaturated aliphatic amines include but are not limited to allylamine, methallylamine, and butenylamine. Optionally, a saturated aliphatic amine or an aromatic amine can be used in combination with the unsaturated amine. The imidization method is known to those skilled in the art and is not particularly limited. It can be carried out in a solvent, water, or melt, at atmospheric pressure or elevated pressure. Optionally, a catalyst can be added to facilitate the imidization reaction, such as a tertiary amine like triethylamine. Preferably, allylamine is used to imidize a styrene-maleic anhydride copolymer (SMA). The weight-average molecular weight (g / mol) of the SMA copolymer can range from 4,000 - 80,000, preferably 4,500 - 30,000, more preferably 7,000 - 20,000, and the molar ratio of styrene to MA varies between 1:1 and 9:1, preferably 3:1 to 8:1.

[0171] The method for purifying the imidized polymer is not particularly limited and can consist of one or more of the following methods, namely distillation of the reaction solvent, precipitation, filtration, washing, and drying.

[0172] The thermosetting resin composition of the present disclosure comprises at least one curing agent comprising a maleimide, (meth)acrylate, or vinyl group.

[0173] As used herein, "crosslinked" means a covalent connection between polymer chains, either directly or through one or more "curing agents" as described herein. As used herein, a "curing agent" means a chemical entity containing one or more functional groups that, when added to a polymer, can provide a "cured" or "crosslinked" polymer.

[0174] The curing agent containing maleimide groups may contain one or more maleimide groups per molecule. Monofunctional maleimide has one maleimide group per molecule, such as N-phenyl maleimide or N-cyclohexyl maleimide. Polyfunctional maleimide contains two or more maleimide groups per molecule. The maleimide curing agent is preferably soluble in common solvents such as methyl ethyl ketone (MEK) and / or toluene. Preferably, the curing agent is a polyfunctional maleimide resin. Examples of polyfunctional maleimides include but are not limited to 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide of formula VII, bisphenol A diphenyl ether bismaleimide of formula VIII, biphenyl-containing maleimide (such as MIR-3000 from Nippon Kayaku, having formula IX), and meta-arylene-containing maleimide (such as MIR-5000 from Nippon Kayaku, having formula X).

[0175]

[0176] where 1 < n ≤ 5

[0177]

[0178] where 1 < n < 5

[0179] Further examples of the curing agent containing maleimide groups are oligomers of phenylmethane maleimide, aliphatic bismaleimides (such as 1,6-bismaleimide-(2,2,4-trimethyl)hexane available from Daiwa Kasei or the non-hydrogenated dimer containing BMI available as BMI-689 from Designer Molecules). Chain-extended bismaleimides are also possible, where dianhydride is used in the BMI manufacturing process. BMI-3000 from Designer Molecules is an example of a commercially available chain-extended bismaleimide.

[0180] The curing agent containing (meth)acrylic groups may contain one or more (meth)acrylic groups per molecule. Preferably, polyfunctional (meth)acrylate is used as the curing agent. Examples of polyfunctional (meth)acrylates include but are not limited to tricyclodecane dimethanol dimethacrylate and (meth)acrylate-functional poly(arylene ether). The poly(arylene ether) is not particularly limited, but preferably contains two or more (meth)acrylic groups per molecule. SA9000 is commercially available from SABIC and is a poly(arylene ether) with methacrylic end groups of formula XI.

[0181]

[0182] n is an integer between 1 and 20.

[0183] The curing agent containing a vinyl group may contain one or more vinyl groups per molecule. Preferably, a polyfunctional vinyl-containing curing agent is used. Examples of polyfunctional vinyl-containing curing agents are polybutadiene, polybutadiene-co-styrene, divinylbenzene, bis-vinyl-phenylethane, polyfunctional vinyl aromatic copolymers, vinylcycloolefin resins, and poly(arylene ether). Poly(arylene ether) is not particularly limited, but preferably contains two or more vinyl groups per molecule, such as OPE-2St, which is commercially available from MGC and represented by Formula XII.

[0184]

[0185] n is an integer between 1 and 20.

[0186] In addition to the curing agent containing maleimide, (meth)acrylate, or vinyl, another curing agent containing an allyl group can also be used. Preferably, a polyfunctional allyl-containing curing agent is used. Examples of polyfunctional allyl-containing curing agents are triallyl isocyanurate (TAIC), trimethylallyl isocyanurate (TMAIC), diallyl alkyl isocyanurate, and diallyl phthalate.

[0187] Optionally, a radical polymerization initiator is present in the thermosetting resin composition of the present disclosure. Examples of commonly used initiators are azo compounds and organic peroxides, such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), benzoyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, di(2-tert-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, and cumene hydroperoxide. These initiators can be used alone or as a mixture of two or more of them. The type and amount of the initiator to be used can be changed according to the intended use of the thermosetting resin composition and the required curing conditions. Preferably, the initiator can be used in an amount of 0.001 to 5% by weight, preferably 0.001 to 1.0% by weight, based on the resin composition.

[0188] The thermosetting resin composition may further contain additives. The additives may include but are not limited to (reactive) flame retardants, fillers, coupling agents, and any combination thereof to further improve various properties of the thermosetting resin composition.

[0189] Examples of flame retardants include those known as SAYTEX 8010, ethylidene-1,2-bis(pentabromophenyl) available from Albemarle, and those known as SAYTEX BT93(W), ethylidene-bis-tetrabromophthalimide available from Albemarle. An example of a halogen-free flame retardant is the bis(DOPO) derivative XP7866 from Albemarle.

[0190] Examples of fillers include, but are not limited to, inorganic fillers such as silica, alumina, barium sulfate, talc, mica, kaolin, boehmite, beryllium oxide, barium titanate, potassium titanate, strontium titanate, calcium titanate, aluminum carbonate, magnesium hydroxide, aluminum hydroxide, aluminum borate, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, zinc borate, zinc stannate, aluminum oxide, zirconium oxide, mullite, magnesium oxide, zinc oxide, titanium oxide, silicon carbide, silicon nitride, and boron nitride.

[0191] The inorganic fillers can be used without surface treatment or can be surface-treated with a silane coupling agent, such as a silane coupling agent of the methacrylic acid silane type, vinyl silane type, phenylamino silane type, or epoxy silane type. Alternatively, the silane coupling agent can be added separately to the resin formulation containing the inorganic filler.

[0192] The thermosetting resin composition of the present disclosure can be particularly used for preparing prepregs and / or metal-clad laminates and printed circuit boards, which require a low dielectric constant and a low dielectric loss ("low loss").

[0193] As used herein, the term "prepreg" refers to a composite material made of a "pre-impregnated" substrate and a resin composition or a semi-cured product of the resin composition.

[0194] The present disclosure also relates to prepregs containing the thermosetting resin composition of the present disclosure. The prepreg includes a reinforcing substrate and an uncured or semi-cured thermosetting resin composition therein. Regarding the reinforcing substrate of the prepreg, known materials such as natural fibers (e.g., paper), but also inorganic fibers such as glass fibers. Schematic examples of glass fiber substrates include woven fabrics using E glass, C glass, D glass, S glass, NE glass, L glass, Q glass. E glass woven fabrics are commonly used. In some embodiments, in order to achieve a lower dielectric loss, NE glass or L glass or Q glass is preferred.

[0195] As used herein, the "semi-cured" state refers to an intermediate stage (stage B). The intermediate stage is the stage between the stage of the uncured resin composition (stage A) and the stage of the fully cured state (stage C). Heating the prepreg allows the resin composition to fully cure, thus becoming a cured product.

[0196] The reinforcing substrate has the form of a woven fabric, non-woven fabric, roving, chopped strand mat, surface mat, etc. At the same time, its material and form are selected according to the use or performance of the target formed material, where they can be used alone, or, if necessary, in combination of two or more materials and their forms.

[0197] In this specification, a resin composition including an organic solvent is referred to as a resin varnish. The organic solvent is not particularly limited as long as it can dissolve the copolymer, curing agent, etc. Examples are ketone-based solvents such as acetone, 2-butanone (MEK), and cyclohexanone, and hydrocarbon-based solvents such as toluene, xylene, and anisole. These organic solvents can be used alone or simultaneously as a mixture of two or more of them. Insoluble additives, such as silica particles and potential additive-based flame retardants, can be dispersed in the resin varnish.

[0198] The prepreg can be produced, for example, in such a way that first, the reinforcing substrate is impregnated with the resin varnish, and second, the solvent is removed. The solvent is removed by heating the impregnated reinforcing substrate. The temperature is preferably in the range of 80 to 200 °C because the organic solvent can be efficiently removed within this temperature range. At the same time, depending on the selected drying conditions, the prepreg obtained by such a process may contain uncured or semi-cured intermediates, while the prepreg after being converted to the C stage is regarded as a fully cured laminate.

[0199] The present disclosure also relates to a metal-clad laminate comprising the thermosetting resin composition according to the present disclosure. Metal-clad laminates for manufacturing printed circuit boards, especially copper-clad laminates, are well known in the art. The laminate generally comprises a (polymeric) substrate to which at least one thin sheet (foil) of a conductive material such as copper is bonded. Depending on the desired use, the substrate can be clad with metal foil on one or both sides and can be rigid or flexible, depending on the composition of the substrate, the choice of reinforcing material (if any), and the intended use of the laminate. Preferably, the polymeric substrate comprises the thermosetting resin composition of the present disclosure.

[0200] The present disclosure also relates to a printed circuit board comprising a prepreg and / or a metal-clad laminate, the prepreg and the metal-clad laminate comprising the thermosetting resin composition according to the present disclosure.

[0201] The thermosetting resin composition of the present disclosure can be used in high-speed PCB applications such as servers, switches, routers, base station backplanes, or in other applications such as radomes, automotive radar domes, antenna substrates, microchip packages, especially for 5G applications.

[0202] Additional embodiments of the present disclosure may be described as embodiments of any of the embodiments listed below. It should be understood that any one of the embodiments described herein can be used in combination with any other embodiment described herein to the extent that the embodiments are not mutually contradictory.

[0203] 1. A thermosetting resin composition comprising:

[0204] A copolymer comprising monomer units of formula I and an aliphatic unsaturated imide of formula II

[0205]

[0206] wherein R1 represents hydrogen or an aliphatic group, and R2 represents hydrogen, an aliphatic or aromatic group,

[0207]

[0208] wherein R3 is H or an alkyl group, R4 is a sub-alkyl group and R5 is an alkanediyl group, and

[0209] At least one curing agent comprising a maleimide, (meth)acrylate or vinyl group.

[0210] 2. The thermosetting resin composition according to embodiment 1, wherein the maleimide curing agent is a polyfunctional maleimide.

[0211] 3. The thermosetting resin composition according to embodiment 2, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide or 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

[0212] 4. The thermosetting resin composition according to any one of embodiments 1-2, wherein the curing agent containing a (meth)acrylate group is a polyfunctional (meth)acrylate.

[0213] 5. The thermosetting resin composition according to embodiment 4, wherein the polyfunctional (meth)acrylate is represented by formula XI

[0214]

[0215] n is an integer between 1 and 20.

[0216] 6. The thermosetting resin composition according to any one of embodiments 1-2, wherein the curing agent containing a vinyl group is a polyfunctional vinyl-containing curing agent.

[0217] 7. The thermosetting resin composition according to embodiment 6, wherein the polyfunctional vinyl curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenyl ethane, polyfunctional vinyl aromatic copolymer, vinylcycloolefin resin, or poly(arylene ether).

[0218] 8. The thermosetting resin composition according to embodiment 7, wherein the poly(arylene ether) is represented by formula XII

[0219]

[0220] n is an integer between 1 and 20.

[0221] 9. The thermosetting resin composition according to any one of embodiments 1-8, further comprising a radical initiator.

[0222] 10. The thermosetting resin composition according to embodiment 1, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II varies between 1:1 and 9:1.

[0223] 11. The thermosetting resin composition according to embodiment 1, wherein the copolymer further comprises a saturated imide monomer unit of formula III.

[0224]

[0225] wherein R6 is selected from saturated aliphatic or aromatic groups.

[0226] 12. The thermosetting resin composition according to embodiment 11, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III varies between 1:0 and 1:2.

[0227] 13. The thermosetting resin composition according to any one of embodiments 1-12, further comprising at least one additive selected from flame retardants, fillers, coupling agents, and any combination thereof.

[0228] 14. A prepreg comprising: a substrate, and the thermosetting resin composition according to any one of embodiments 1-13 or a semi-cured product of the resin composition.

[0229] 15. A metal-clad laminate comprising an insulating layer formed from a cured product of the prepreg of embodiment 14 and at least one metal layer formed on either or both surfaces of the insulating layer.

[0230] 16. A printed circuit board comprising the metal-clad laminate according to embodiment 15.

[0231] The present disclosure will now be described in detail with reference to the following non-limiting examples, which are illustrative.

[0232] List of Abbreviations and Chemicals

[0233]

[0234]

[0235] Xylene was supplied by Carl Roth. Allylamine, acetone and MEK were supplied by Sigma Aldrich. Noryl SA9000 was obtained from SABIC. XIRAN EF-grade was obtained from Polyscope. BMI-5100 was obtained from Daiwa Kasei. 181 was obtained from Cray Valley.

[0236] Test Items and Test Methods

[0237] Pure Resin

[0238] Fourier transform infrared spectroscopy (FTIR) was performed using an ALPHA II FT-IR spectrometer from Bruker equipped with a PLATINUM-ATR module.

[0239] Size exclusion chromatography (SEC) was carried out using a PSS WinGPC system from PSS. A 5 μm, 8.0 mm x 50 mm guard column was used, followed by three 8.0 mm x 300 mm, 8.0 mm x 300 mm columns. A differential refractive index detector (RID) was used. The eluent was THF containing 5% acetic acid. The injection volume was 100 μL and the flow rate was 1.0 ml / min. The sample concentration was 5 g / L. The temperature was 23 °C. The molecular weight was calculated using calibrated polystyrene molar mass standards.

[0240] Pure Resin Castings:

[0241] Dk and Df were measured at 5.1 GHz at room temperature using a separated post dielectric resonator (SPDR) equipped with a microwave frequency Q-meter (5 GHz) from QWED. Pure resin castings were measured directly after baking at 200 °C for 1 hour.

[0242] Differential scanning calorimetry (DSC) was performed using a DSC 2STARe from METTLER TOLEDO. Under a nitrogen gas flow rate of 50 mL / min, DSC measurements were carried out on the prepared pure resin castings from 30 °C to 220 °C using a heating rate of 20 °C / min and a cooling rate of 10 °C / min. The second heating rate was carried out at 20 °C / min from 30 °C to 250 °C. The sample weight was approximately 10 mg. Data analysis was performed using STARe software. The crosslinking Tg value of the prepared pure resin castings was determined using the midpoint function and the data from the second heating run.

[0243] Thermogravimetric analysis (TGA) was performed using a TGA 2STARe from METTLER TOLEDO. The TGA samples were first dried using TGA under a nitrogen gas flow rate of 50 mL / min with a heating rate of 10 °C / min from 30 °C to 200 °C. Subsequently, the dried samples were measured in TGA under a nitrogen gas flow rate of 50 mL / min using a heating rate of 10 °C / min from 30 °C to 700 °C. Data analysis was performed using STARe software. The thermal decomposition temperature at 5% weight loss and the residual amount at 600 °C were determined using the Step Horizon Function (starting temperature of 50 °C).

[0244] Examples and Comparative Examples

[0245] Example 1 (Synthesis of XIRAN EL819)

[0246] XIRAN EF80 (0.201 mol anhydride) was added to a 1000 mL four-necked round-bottom flask equipped with a Dimroth condenser, a mechanical stirrer, a nitrogen inlet, and a constant-pressure dropping funnel. 360 g of xylene was charged into the round-bottom flask. 0.221 mol of allylamine was slowly added. The reaction temperature was raised to 40 °C for 1.5 hours to form an amic acid. Subsequently, 0.050 mol of triethylamine (TEA) was added and the reaction mixture was heated to reflux. The solution was refluxed for 12 hours and cooled to room temperature. Another 0.060 mol of allylamine was added. The reaction mixture was raised to 40 °C for 1.5 hours. 0.004 mol of TEA was added and the solution was refluxed for another 12 hours. The solution was cooled to room temperature, the solvent was removed in a rotary evaporator, and the resulting resin powder was further dried overnight in a vacuum oven at 80 °C. FT-IR analysis indicated the presence of imide groups and allyl groups. The modified polymer was soluble in common solvents including acetone, MEK, toluene, xylene, and anisole. As indicated by SEC measurements, no chain extension or crosslinking occurred in the modified polymer.

[0247] Example 2 (Synthesis of XIRAN EL419)

[0248] XIRAN EF40 (0.321 mol anhydride) was added to a 1000 mL four-necked round-bottom flask equipped with a Dimroth condenser, a mechanical stirrer, a nitrogen inlet, and a constant-pressure dropping funnel. 394 g of xylene was charged to the round-bottom flask. 0.353 mol of allylamine was added slowly. The reaction temperature was raised to 40 °C for 1.5 h to form an amic acid. Subsequently, 0.064 mol of triethylamine (TEA) was added and the reaction mixture was heated to reflux. The solution was refluxed for 12 h and cooled to room temperature. Another 0.060 mol of allylamine was added. The reaction mixture was raised to 40 °C for 1.5 h. 0.005 mol of TEA was added and the solution was refluxed for another 12 h. The solution was cooled to room temperature, the solvent was removed in a rotary evaporator, and the resulting resin powder was further dried overnight in a vacuum oven at 80 °C. FT-IR analysis indicated the presence of imide groups and allyl groups. The modified polymer was soluble in common solvents including acetone, MEK, toluene, xylene, and anisole. As indicated by SEC measurement, no chain extension or crosslinking occurred for the modified polymer.

[0249] Preparation Methods of Varnish and Pure Resin Castings

[0250] First, varnishes were prepared by dissolving the respective components in MEK according to the formulations presented in Tables 1 and 3. Once all components were dissolved, the solvent was removed overnight at 65 °C under vacuum in an oven to obtain resin powders. Pure resin castings were prepared from the resulting resin powders using a vacuum hot press, employing a hot pressing curing schedule of 1.5 h at 220 °C. Example 4 used a hot pressing curing schedule of 1.5 h at 240 °C and was thermally crosslinked without an initiator. The pure resin castings were removed from the mold and post-baked at 200 °C for 1 h in a vacuum oven. The thickness of the pure resin castings was approximately 1 mm.

[0251] Results of Examples and Comparative Examples

[0252] The resin composition (parts per hundred resin) of the prepared pure resin castings and the dielectric results tested are presented in Tables 1 and 3 below and Figure 1 in.

[0253] Figure 1 The TGA curves of Example 3 and Comparative Example 3 are given in. As can be seen from the figure, Ex 3 showed improved thermal stability at temperatures of 300 °C or higher.

[0254] Table 1

[0255] Table 1 below relates to Examples (Ex) 1 - 5 and Comparative Examples (CE) 1 - 3 containing the indicated formulations.

[0256] *--Unable to determine dielectric properties (deformation during post-curing)

[0257]

[0258] As is clearly visible from Table 1, Ex 1 - 5 show excellent dielectric properties, and the Df values are in the range of 0.0012 - 0.0038. The allyl - modified copolymer can be thermally cross - linked with maleimide without a free - radical initiator (Ex 4), which results in a reduced dielectric loss value compared to Ex 1. The dielectric loss of CE2 is surprisingly high, and the Df value is 0.0121. The dielectric properties of CE 1 with the addition of RICON181 are better than those of CE 2. However, the Dk and Df values are still higher compared to those of Examples Ex 1 - 5. Since the pure resin casting deformed during the post - curing in a vacuum oven, the dielectric properties of CE3 could not be measured.

[0259] Table 2 Thermal Properties of Selected Pure Resin Castings

[0260] Compared with Comparative Example 3, Examples Ex 1 - 5 all show a significant improvement in Td5 and have a significantly higher residue amount at 600 °C.

[0261] Table 2

[0262] Td, 5% (°C) Residual Amount at 600 °C (wt%) Ex 1 380.5 14.52 Ex 2 396.3 25.18 Ex 3 402.6 24.12 Ex 4 386.6 15.34 Ex 5 388.4 18.53 CE 3 347.6 1.78

[0263] Compared with Comparative Example C3, Examples E1 - E5 all show a significant improvement in Td5 and have a significantly higher residue amount at 600 °C.

[0264] Table 3 Dielectric Properties and Tg of Pure Resin Castings

[0265] Table 3 relates to Examples 6 - 8 containing the indicated formulations.

[0266] The formulation containing Xiran EL419 has a Df below 0.003. As the proportion of BMI 5100 in the formulation increases, the Df value of the cured resin system changes slightly, but the T g value increases with the increase of BMI 5100.

[0267] Table 3

[0268] Ex 6 Ex 7 Ex 8 XIRAN EL-419 90 80 70 BMI-5100 10 20 30 Luperox F 0.8 0.8 0.8 Dk (5.1 GHz) 2.63 2.66 2.63 Df (5.1 GHz) 0.0028 0.0028 0.0025 Tg (°C, DSC) 150 171 181

Claims

1. A thermosetting resin composition, the thermosetting resin composition comprising: A copolymer, the copolymer comprising monomer units of formula I and an aliphatic unsaturated imide of formula II Wherein R1 represents hydrogen or an aliphatic group, and R2 represents hydrogen, an aliphatic or aromatic group, Wherein R3 is H or an alkyl group, R4 is an alkylene group and R5 is an alkanediyl group, and At least one curing agent, the curing agent comprising a maleimide, (meth)acrylate or vinyl group.

2. The thermosetting resin composition according to claim 1, wherein the maleimide curing agent is a polyfunctional maleimide.

3. The thermosetting resin composition according to claim 2, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide or 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

4. The thermosetting resin composition according to any one of claims 1-2, wherein the curing agent containing a (meth)acrylate group is a polyfunctional (meth)acrylate.

5. The thermosetting resin composition according to claim 4, wherein the polyfunctional (meth)acrylate is represented by formula XI n is an integer between 1 and 20.

6. The thermosetting resin composition according to any one of claims 1-2, wherein the curing agent containing a vinyl group is a polyfunctional vinyl-containing curing agent.

7. The thermosetting resin composition according to claim 6, wherein the polyfunctional vinyl curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenyl ethane, polyfunctional vinyl aromatic copolymer, vinyl cycloolefin resin or poly(arylene ether).

8. The thermosetting resin composition according to claim 7, wherein the poly(arylene ether) is represented by formula XII n is an integer between 1 and 20.

9. The thermosetting resin composition according to any one of claims 1-8, the thermosetting resin composition further comprising a radical initiator.

10. The thermosetting resin composition according to claim 1, wherein the molar ratio of the monomer units of formula I to the unsaturated imide monomer units of formula II varies between 1:1 and 9:

1.

11. The thermosetting resin composition according to claim 1, wherein the copolymer further comprises saturated imide monomer units of formula III Wherein R6 is selected from saturated aliphatic or aromatic groups.

12. The thermosetting resin composition according to claim 11, wherein the molar ratio of the unsaturated imide monomer units of formula II to the saturated imide monomer units of formula III varies between 1:0 and 1:

2.

13. The thermosetting resin composition according to any one of claims 1-12, the thermosetting resin composition further comprising at least one additive selected from flame retardants, fillers, coupling agents and any combination thereof.

14. A prepreg, the prepreg comprising: a substrate, and a thermosetting resin composition according to any one of claims 1-13 or a semi-cured product of the resin composition.

15. A metal-clad laminate, the metal-clad laminate comprising an insulating layer formed from a cured product of the prepreg according to claim 14 and at least one metal layer formed on either or both surfaces of the insulating layer.

16. A printed circuit board, the printed circuit board comprising the metal-clad laminate according to claim 15.

17. A thermosetting resin composition, the thermosetting resin composition being prepared by a method comprising the following steps: (ii) crosslinking a styrene-maleimide copolymer with at least one curing agent.

18. The thermosetting resin composition according to claim 17, further comprising the following step: (i) contacting a styrene-maleic anhydride copolymer (SMA) with an unsaturated aliphatic amine to prepare the styrene-maleimide copolymer.

19. The thermosetting resin composition according to claim 17 or 18, wherein the styrene-maleimide copolymer comprises: Monomer units of formula I wherein R1 is hydrogen or an aliphatic group, and R2 is hydrogen, an aliphatic group or an aromatic group; and An aliphatic unsaturated imide of formula II wherein R3 is H or an aliphatic group, R4 is a secondary alkyl group, and R5 is an alkylene group.

20. The thermosetting resin composition according to any one of claims 17-19, wherein the styrene-maleimide copolymer further comprises a saturated imide monomer of formula III wherein R6 is a saturated aliphatic or aromatic group.

21. The thermosetting resin composition according to any one of claims 17-20, wherein the at least one curing agent comprises one or more maleimide groups, (meth)acrylate groups and / or vinyl groups.

22. The thermosetting resin composition according to any one of claims 17-20, wherein the at least one curing agent comprises a polyfunctional maleimide.

23. The thermosetting resin composition according to claim 22, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

24. The thermosetting resin composition according to any one of claims 17-20, wherein the at least one curing agent is a polyfunctional (meth)acrylate.

25. The thermosetting resin composition according to claim 24, wherein the polyfunctional (meth)acrylate has formula XI, wherein n is an integer between 1 and 20.

26. The thermosetting resin composition according to any one of claims 17-20, wherein the at least one curing agent is a polyfunctional vinyl-containing curing agent.

27. The thermosetting resin composition according to claim 26, wherein the polyfunctional vinyl-containing curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenylethane, polyfunctional vinyl aromatic copolymer, vinyl cycloolefin resin, and poly(arylene ether).

28. The thermosetting resin composition according to claim 27, wherein the poly(arylene ether) has the formula XII, wherein n is an integer between 1 and 20.

29. The thermosetting resin composition according to any one of claims 17-28, wherein step (ii) is carried out in the presence of one or more free radical polymerization initiators.

30. The thermosetting resin composition according to claim 29, wherein the one or more free radical polymerization initiators comprise an azo compound or an organic peroxide.

31. The thermosetting resin composition according to claim 30, wherein the azo compound is azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide).

32. The thermosetting resin composition according to claim 30, wherein the organic peroxide is selected from benzoyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, di(2-tert-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, and cumene hydroperoxide.

33. The thermosetting resin composition according to any one of claims 18-32, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II in the styrene-maleimide copolymer is about 1:1 to 9:

1.

34. The thermosetting resin composition according to any one of claims 19-33, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III is about 1:0 to 1:

2.

35. The thermosetting resin composition according to any one of claims 17-34, wherein step (ii) is carried out in the presence of at least one additive selected from flame retardants, fillers, coupling agents, and combinations thereof.

36. The thermosetting resin composition according to any one of claims 17-35, wherein step (ii) is carried out under heating.

37. The thermosetting resin composition according to any one of claims 17-36, wherein step (ii) is carried out in the presence of a substrate.

38. The thermosetting resin composition according to claim 37, wherein step (ii) is carried out under heating without providing complete curing of the thermosetting resin composition, and incomplete curing provides a prepreg composition of the thermosetting resin composition.

39. A metal-clad laminate, the metal-clad laminate comprising the thermosetting resin composition according to claim 38, prepared by a method comprising contacting the thermosetting resin composition with one or more metal layers before completing step (ii).

40. The metal-clad laminate according to claim 39, wherein the metal-clad laminate comprises i.) an insulating layer comprising a thermosetting resin according to claim 37, and ii.) one or more metal layers, wherein the one or more metal layers are on either or both surfaces of the insulating layer.

41. A printed circuit board, wherein the printed circuit board comprises a prepreg according to claim 38 or a metal-clad laminate according to claim 40.

42. A thermosetting resin composition, wherein the thermosetting resin composition comprises a styrene-maleimide copolymer crosslinked by at least one curing agent.

43. The thermosetting resin composition according to claim 42, wherein the styrene-maleimide copolymer comprises: Monomer units of Formula I wherein R1 is hydrogen or an aliphatic group, and R2 is hydrogen, an aliphatic group or an aromatic group; and An aliphatic unsaturated imide of Formula II wherein R3 is H or an aliphatic group, R4 is a sub-alkyl group, and R5 is an alkylene group.

44. The thermosetting resin composition according to claim 42 or 43, wherein the styrene-maleimide copolymer further comprises a saturated imide monomer of Formula III wherein R6 is a saturated aliphatic or aromatic group.

45. The thermosetting resin composition according to any one of claims 42-44, wherein the at least one curing agent comprises one or more maleimide groups, (meth)acrylate groups and / or vinyl groups.

46. The thermosetting resin composition according to any one of claims 42-44, wherein the at least one curing agent comprises a polyfunctional maleimide.

47. The thermosetting resin composition according to claim 46, wherein the polyfunctional maleimide is selected from bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, biphenyl-containing maleimide, meta-arylene-containing maleimide and 1,6-bismaleimide-(2,2,4-trimethyl)hexane.

48. The thermosetting resin composition according to any one of claims 42-44, wherein the at least one curing agent is a polyfunctional (meth)acrylate.

49. The thermosetting resin composition according to claim 48, wherein the polyfunctional (meth)acrylate has Formula XI, wherein n is an integer between 1 and 20.

50. The thermosetting resin composition according to any one of claims 42-44, wherein the at least one curing agent is a polyfunctional vinyl-containing curing agent.

51. The thermosetting resin composition according to claim 50, wherein the polyfunctional vinyl-containing curing agent is selected from polybutadiene, polybutadiene-co-styrene, divinylbenzene, divinylphenyl ethane, polyfunctional vinyl aromatic copolymer, vinyl cycloolefin resin and poly(arylene ether).

52. The thermosetting resin composition according to claim 51, wherein the poly(arylene ether) has Formula XII, wherein n is an integer between 1 and 20.

53. The thermosetting resin composition according to any one of claims 42 - 52, wherein the styrene - maleimide copolymer is crosslinked by the at least one curing agent in the presence of one or more radical polymerization initiators.

54. The thermosetting resin composition according to claim 53, wherein the radical polymerization initiator comprises an azo compound or an organic peroxide.

55. The thermosetting resin composition according to claim 54, wherein the azo compound is azobisisobutyronitrile, 2,2'-azobis(2 - methylbutyronitrile), 2,2'-azobis(2,4,4 - trimethylpentane), 2,2'-azobis(N - butyl - 2 - methylpropionamide).

56. The thermosetting resin composition according to claim 55, wherein the organic peroxide is selected from benzoyl peroxide, tert - butyl hydroperoxide, dicumyl peroxide, tert - butyl perbenzoate, methyl ethyl ketone peroxide, cyclohexanone peroxide, acetyl peroxide, di - tert - butyl peroxide, tert - butyl perbenzoate, bis(2 - tert - butylperoxy - isopropyl)benzene, 2,5 - dimethyl - 2,5 - bis(tert - butylperoxy)hex - 3 - yne, and cumene hydroperoxide.

57. The thermosetting resin composition according to any one of claims 42 - 56, wherein the styrene - maleimide copolymer is crosslinked by the at least one curing agent under heating.

58. The thermosetting resin composition according to any one of claims 42 - 57, wherein the molar ratio of the monomer unit of formula I to the unsaturated imide monomer unit of formula II in the styrene - maleimide copolymer is about 1:1 to 9:

1.

59. The thermosetting resin composition according to claim 58, wherein the molar ratio of the unsaturated imide monomer unit of formula II to the saturated imide monomer unit of formula III is about 1:0 to 1:

2.

60. The thermosetting resin composition according to any one of claims 42 - 59, the thermosetting resin composition further comprises at least one additive selected from flame retardants, fillers, coupling agents, and combinations thereof.

61. The thermosetting resin composition according to any one of claims 42 - 60, the thermosetting resin composition further comprises a substrate.

62. The thermosetting resin composition according to claim 61, wherein the styrene - maleimide copolymer is not completely crosslinked by the at least one curing agent to provide a prepreg composition of the thermosetting resin composition.

63. A metal - clad laminate, the metal - clad laminate comprising the thermosetting resin composition according to claim 61 or 62, and comprising one or more metal layers on the thermosetting resin composition.

64. The metal - clad laminate according to claim 63, the metal - clad laminate comprising: i.) an insulating layer comprising the thermosetting resin according to claim 61, and ii.) one or more metal layers, wherein the one or more metal layers are on either or both surfaces of the insulating layer.

65. A printed circuit board, the printed circuit board comprising the thermosetting resin composition according to claim 62 or the metal - clad laminate according to claim 63 or 64.

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