Phosphorus-containing compound, flame-retardant and heat-resistant composition, pre-preg, and metal-clad laminate

Abstract

are as defined in the specification. The phosphorus-containing compound can enhance the heat resistance and flame retardancy of an article to which it is applied, and is therefore particularly suitable for use in the technical field of printed circuit boards.

Description

[Technical Field]

[0001] This invention relates to a phosphorus-containing compound that improves heat resistance and flame retardancy, and is particularly suitable for use in the field of printed circuit boards. Therefore, this invention also relates to a flame-retardant and heat-resistant composition, a prepreg, and a metal foil laminate using the phosphorus-containing compound. [Previous Technology]

[0002] A printed circuit board (PCB) is the circuit board of an electronic device, which mounts other electronic components and electrically connects these components to provide a stable circuit operating environment. PCBs are generally made using copper clad laminates (CCLs). CCLs are mainly composed of resin, reinforcing materials, and copper foil. Common resins include epoxy resin, phenolic resin, polyphenylene ether resin, polyurethane, silicone, and polytetrafluoroethylene. Common reinforcing materials include fiberglass cloth, fiberglass mat, and insulating paper.

[0003] Generally, printed circuit boards can be manufactured by the following method. A reinforcing material is impregnated in a resin composition, and then the resin-impregnated reinforcing material is cured to a semi-cured state (i.e., B-stage) to obtain a semi-cured sheet. Subsequently, the semi-cured sheets are stacked, and a metal foil is stacked on the outer side to provide a laminate. This laminate is then subjected to a hot-pressing operation (i.e., C-stage) to obtain a metal foil laminate. The metal foil on the surface of the metal foil laminate is etched to form a specific circuit pattern. Holes are then drilled in the metal foil laminate, and conductive material is plated into the holes to form via holes, thus completing the fabrication of the printed circuit board.

[0004] When manufacturing printed circuit boards using resin compositions, various flame retardants, such as halogenated or phosphorus-containing flame retardants, are usually added to impart flame retardancy to electronic materials. However, the use of halogenated flame retardants has been restricted due to environmental concerns. Commonly used phosphorus-containing flame retardants include phosphazene compounds (such as SPB-100 produced by Otsuka Chemicals) or condensed phosphate esters (such as PX-200 produced by Daihachi Chemicals), but the heat resistance and flame retardancy of electronic materials imparted by conventional phosphorus-containing flame retardants still need improvement. [Summary of the Invention]

[0005] In view of the above-mentioned technical problems, the present invention provides a phosphorus-containing compound that is applicable to fields requiring improved heat resistance and flame retardancy. For example, the phosphorus-containing compound is particularly suitable for addition to the dielectric layer material of printed circuit boards to improve heat resistance and flame retardancy.

[0006] Therefore, one object of the present invention is to provide a phosphorus-containing compound having the structure of the following formula (I): Formula (I) wherein R1, R2, R3, and R4 are each independently selected from hydrogen atoms, C1 to C6 alkyl, C1 to C6 alkoxy, and C3 to C6 cycloalkyl, and each R1, each R2, each R3, and each R4 may be the same or different; R19 and R20 are each independently selected from , , , , and; R17 and R18 are each independently selected from hydrogen atoms, , , , , , , , , and; R6, R7, R9, and Ra are each independently selected from C1 to C6 hydrocarbon, C1 to C6 alkoxy, and C3 to C6 cycloalkyl, and when there are two or more R6, R7, R9, or Ra, each R6, each R7, each R9, or each Ra may be the same or different; R8 is selected from -CH2-, -C(CH3)2-, -CO-, -SO2-, and -O-; m and ma are each independent integers from 0 to 4, n is an integer from 0 to 3, p is 0 or 1, the sum of m and n does not exceed 4; and * represents the position of the bond.

[0007] In one embodiment of the present invention, R19 and R20 in formula (I) are each independently OR, and R17 and R18 are each independently OR, where p is 0, and R6, R8, Ra, m, and ma are as defined above. More specifically, R17 and R18 are each independently OR, and Ra and ma are as defined above.

[0008] Another object of the present invention is to provide a flame-retardant and heat-resistant composition comprising: a first reactive component selected from the group consisting of: epoxy resins, phenolic resins, benzoxazine resins, polyphenylene ether resins having olefinic carbon-carbon double bonds, allyl compounds, maleimide compounds, copolymers of allyl compounds and maleimide compounds, and combinations thereof; and a phosphorus-containing compound as described above.

[0009] In one embodiment of the present invention, the polyphenylene ether resin having olefinic carbon-carbon unsaturated double bonds is selected from the group consisting of: dihydroxy polyphenylene ether resin, methacrylate polyphenylene ether resin, vinyl polyphenylene ether resin, and combinations thereof.

[0010] In one embodiment of the present invention, the allyl-containing compound is selected from the group consisting of diallyl bisphenol A, diallyl bisphenol F, diallyl bisphenol S, and combinations thereof.

[0011] In one embodiment of the present invention, the maleimide compound is selected from the group consisting of bismaleimide compounds, trimaleimide compounds, tetramaleimide compounds, and combinations thereof.

[0012] Another object of the present invention is to provide a semi-cured sheet, which is obtained by impregnating or coating a substrate with the flame-retardant and heat-resistant composition as described above, and drying the impregnated or coated substrate.

[0013] Another object of the present invention is to provide a metal foil laminate, which is made by laminating a prepreg as described above with a metal foil, or by coating a metal foil with a flame-retardant and heat-resistant composition as described above and drying the coated metal foil.

[0014] In order to make the above-mentioned objectives, technical features and advantages of the present invention more apparent and understandable, the following is a detailed description of some specific embodiments.

Implementation Method

[0015] The following will specifically describe some specific embodiments of the present invention; however, the present invention may be practiced in many different forms and the scope of protection of the present invention should not be limited to the specific embodiments described.

[0016] Unless otherwise stated, the terms “a”, “the” and similar terms used in this specification and the claims shall be understood to include both singular and plural forms.

[0017] Unless otherwise stated, when describing the proportion of components contained in a solution, mixture or composition in this specification and the claims, the weight of the solvent is not included.

[0018] Unless otherwise stated, the range of values ​​(e.g., 5 to 100) used in this specification and the claims should be understood to include all rational numbers in that range and any rational numbers in that range. Therefore, the range of values ​​used in this specification includes all possible combinations of values ​​between the listed minimum and maximum values.

[0019] The advantage of the present invention compared with the prior art is that it provides a phosphorus-containing compound that can improve the heat resistance and flame retardancy of the applied object, and is therefore particularly suitable for addition to the dielectric layer material of printed circuit boards.

[0020] 1. Phosphorus-containing compounds

[0021] The phosphorus-containing compound of the present invention has the structure of the following formula (I): Formula (I).

[0022] In formula (I), R1, R2, R3, and R4 are each independently selected from hydrogen atoms, C1 to C6 alkyl groups, C1 to C6 alkoxy groups, and C3 to C6 cycloalkyl groups, and each R1, each R2, each R3, and each R4 may be the same or different. Examples of the C1 to C6 alkyl groups include, but are not limited to, substituted or unsubstituted methyl, ethyl, propyl, butyl, pentyl, and hexyl, wherein the alkyl group may be straight-chain or branched. Examples of the C1 to C6 alkoxy groups include, but are not limited to, substituted or unsubstituted methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy, wherein the alkoxy group may be straight-chain or branched. Examples of the C3 to C6 cycloalkyl groups include, but are not limited to, substituted or unsubstituted cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0023] In formula (I), R19 and R20 are each independently selected from C1, C2, C3, C4, and C5, where * represents the bond position. R6, R7, and R9 are each independently selected from C1 to C6 hydrocarbon groups, C1 to C6 alkoxy groups, and C3 to C6 cycloalkyl groups, and when there are two or more R6, R7, or R9, each R6, each R7, or each R9 may be the same or different. The C1 to C6 hydrocarbon groups may be straight-chain or branched hydrocarbon groups, examples of which include, but are not limited to, substituted or unsubstituted methyl, ethyl, propyl, butyl, pentyl, and hexyl. Examples of the C1 to C6 alkoxy groups and C3 to C6 cycloalkyl groups are those listed above for R1, R2, R3, and R4. R8 is selected from -CH2-, -C(CH3)2-, -CO-, -SO2-, and -O-. m is an integer from 0 to 4, n is an integer from 0 to 3, p is 0 or 1, and the sum of m and n does not exceed 4.

[0024] In formula (I), R17 and R18 are each independently selected from hydrogen atoms, , , , , , , , , , and , where * represents the bond position. Ra are each independently selected from C1 to C6 hydrocarbon groups, C1 to C6 alkoxy groups, and C3 to C6 cycloalkyl groups, and when there are more than two Ra, each Ra may be the same or different. Examples of the C1 to C6 hydrocarbon groups are listed above for R19 and R20, and examples of the C1 to C6 alkoxy groups and C3 to C6 cycloalkyl groups are listed above for R1, R2, R3, and R4. ma is an integer from 0 to 4.

[0025] In one embodiment of the present invention, R19 and R20 in formula (I) are each independently OR, and R17 and R18 are each independently OR, more specifically, R17 and R18 are each independently OR, where p is 0, and R6, R8, Ra, m, and ma are as defined above.

[0026] 2. Flame-retardant and heat-resistant composition

[0027] The phosphorus-containing compound of the present invention can improve the heat resistance and flame retardancy of the applied object. Therefore, the present invention also provides a flame-retardant and heat-resistant composition comprising a first reactive component and the phosphorus-containing compound described above as essential components, as well as other optional components as needed.

[0028] 2.1. First reactive component

[0029] The first reactive component comprises one or more selected from epoxy resin, phenolic resin, benzoxazine resin, polyphenylene ether resin having olefinic carbon-carbon unsaturated double bonds, allyl compounds, maleimide compounds, and copolymers containing allyl compounds and maleimide compounds. In this document, epoxy resin refers to a thermosetting resin having at least two epoxy functional groups in one molecule, such as difunctional epoxy resin, tetrafunctional epoxy resin, octafunctional epoxy resin, or linear phenolic epoxy resin, and there is no particular limitation on its type. Phenolic resin refers to a resin obtained by the condensation of phenolic compounds and aldehyde compounds, examples of which include, but are not limited to, phenol-formaldehyde resin, cresol-formaldehyde resin, resorcinol-formaldehyde resin, etc. Examples of benzoxazine resin include, but are not limited to, phenolic benzoxazine resin, bisphenol A type benzoxazine resin, etc.

[0030] Examples of polyphenylene ether resins having olefin-type carbon-carbon unsaturated double bonds include, but are not limited to, dihydroxy polyphenylene ether resins (e.g., SA90 product from SABIC), methacrylate polyphenylene ether resins (e.g. SA9000 product from SABIC), and vinyl polyphenylene ether resins (e.g. OPE2ST product from Mitsubishi Gas Chemical), and each of the polyphenylene ether resins having olefin-type carbon-carbon unsaturated double bonds can be used alone or in any combination.

[0031] The allyl-containing compound is a polyfunctional allyl-containing compound, and preferably is selected from the group consisting of diallyl bisphenol A, diallyl bisphenol F, diallyl bisphenol S, and combinations thereof.

[0032] The maleimide compound is preferably a polyfunctional maleimide compound, such as a bismaleimide compound, a trimaleimide compound, or a tetramaleimide compound, and more preferably a bismaleimide compound. Specifically, the maleimine compound may be selected from the group consisting of: 1,2-bismaleiminoethane, 1,6-bismaleiminohexane, 1,3-bismaleiminobenzene, 1,4-bismaleiminobenzene, 2,4-bismaleiminotoluene, 4,4'-bismaleiminodiphenylmethane, 4,4'-bismaleiminodiphenyl ether, 3,3'-bismaleiminodiphenyl sulfone, 4,4'-bismaleiminodiphenyl sulfone, 4,4'-bismaleiminodiphenyl sulfone, 4,4'-bismaleiminodiphenyl sulfone, etc. Maleimino dicyclohexylmethane, 3,5-bis(4-maleiminophenyl)pyridine, 2,6-bismaleiminopyridine, 1,3-bis(maleiminomethyl)cyclohexane, 1,3-bis(maleiminomethyl)benzene, 1,1-bis(4-maleiminophenyl)cyclohexane, 1,3-bis(dichloromaleimino)benzene, 4,4'-biscitraconimidodiphenylmethane lmethane), 2,2-bis(4-maleiminophenyl)propane, 1-phenyl-1,1-bis(4-maleiminophenyl)ethane, α,α-bis(4-maleiminophenyl)toluene, 3,5-bismaleimino-1,2,4-triazole, N,N'-epimethylene bismaleimide, N,N'-hexamethylene bismaleimide, N,N'-m-epimethylene bismaleimide, N,N'-p-epimethylene bismaleimide, N,N'- 4,4'-Diphenylmethane bismaleimide, N,N'-4,4'-diphenyl ether bismaleimide, N,N'-4,4'-diphenyl succinate bismaleimide, N,N'-4,4'-dicyclohexylmethane bismaleimide, N,N'-α,α'-4,4'-dimethylenecyclohexane bismaleimide, N,N'-m-xylene bismaleimide, N,N'-4,4'-diphenylcyclohexane bismaleimide, benzyl maleimide oligomers, and combinations thereof.

[0033] 2.2. Phosphorus-containing compounds

[0034] The phosphorus-containing compound is the phosphorus-containing compound of the present invention as described above. The content of the phosphorus-containing compound in the flame-retardant and heat-resistant composition can be adjusted as needed. Generally, the content of the phosphorus-containing compound can be from 0.1% by weight to 30% by weight, more specifically from 1% by weight to 25% by weight, based on the total weight of the first reactive component and the phosphorus-containing compound. For example, the content of the phosphorus-containing compound can be 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, or 25% by weight, or within the range of any two of the above values, but the present invention is not limited thereto.

[0035] 2.3. Selected Ingredients

[0036] In addition to the above-mentioned components, the flame-retardant and heat-resistant composition of the present invention may further include selected components, such as additives known in the art, without departing from the technical principles of the present invention, to improve the physicochemical properties of the metal foil laminate made by the flame-retardant and heat-resistant composition or the processability of the flame-retardant and heat-resistant composition during the manufacturing process.

[0037] Examples of the conventional additives mentioned include, but are not limited to, fillers, catalysts, elastomers, dispersants, toughening agents, viscosity modifiers, plasticizers, coupling agents, etc. These additives can be used alone or in combination. The use of such additives is something that those skilled in the art, upon viewing the disclosure of this specification, can do as needed based on their ordinary knowledge, and is not the focus of this invention; therefore, it will not be elaborated upon here.

[0038] 3. Prepreg

[0039] The present invention also provides a prepreg made from the above-described flame-retardant and heat-resistant composition, wherein the prepreg is obtained by impregnating a substrate with the above-described flame-retardant and heat-resistant composition or by coating a substrate with the above-described flame-retardant and heat-resistant composition, and then drying the impregnated or coated substrate. The substrate may be a reinforcing material commonly used in the field of printed circuit board technology, examples of which include, but are not limited to, paper, cloth, or felt made of glass fiber. In one embodiment of the present invention, 2116 glass fiber cloth is used as the substrate, and the prepreg is heated and dried at 170°C to obtain a prepreg in a semi-cured state.

[0040] 4. Metal foil laminate

[0041] The present invention also provides a metal foil laminate, which is obtained by laminating the aforementioned prepreg and metal foil. Specifically, the metal foil laminate of the present invention comprises a dielectric layer and a metal layer, wherein the dielectric layer is provided by the prepreg as described above, wherein multiple layers of prepreg can be stacked as the dielectric layer, and a metal foil (such as copper foil, as the metal layer) is stacked on at least one outer surface of the dielectric layer to provide a laminate, and the laminate is subjected to a hot pressing operation to obtain the metal foil laminate. Alternatively, the flame-retardant and heat-resistant composition of the present invention can be directly coated onto the metal foil and the coated metal foil can be dried to obtain the metal foil laminate.

[0042] The outer metal foil of the metal foil laminate can be further patterned to obtain a printed circuit board. Patterning methods include, but are not limited to, etching.

[0043] 5. Examples

[0044] 5.1. Measurement Method Description

[0045] The present invention will be further illustrated by the following specific embodiments, wherein the measuring instruments and methods used are as follows:

[0046] [UL 94 Vertical Burning Test]

[0047] Copper foil laminates were etched to remove the copper foil from both sides, resulting in copper foil-free test pieces. The test pieces were fixed vertically and burned with a Bunsen burner to compare their self-extinguishing and combustion-supporting characteristics. According to the UL 94 flame retardancy test standard, a V0 rating indicates that after two 10-second flame tests, combustion ceased within 10 seconds without any burning drips; a V1 rating indicates that after two 10-second flame tests under the same conditions, combustion ceased within 30 seconds without any burning drips; and a V2 rating indicates that after two 10-second flame tests under the same conditions, combustion ceased within 30 seconds but with burning drips. Therefore, the flame retardancy ratings are ranked as follows: V0 is superior to V1, and V1 is superior to V2. In this test, five test pieces were taken from each group of samples and subjected to five UL 94 flame retardancy tests. Each test involved retesting the flame retardancy effect with a new test piece.

[0048] [Glass Transfer Temperature (Tg) Test]

[0049] Copper foil laminates were etched to remove copper foil from both sides, resulting in copper foil-free specimens. The glass transition temperature (Tg) of the specimens was measured using a thermomechanical analyzer (TMA). The test conditions were as follows: heating rate of 10°C / min, from 30°C to 330°C.

[0050] 5.2 Preparation of phosphorus-containing compounds

[0051] [Preparation Example 1]

[0052] 285 g of DOPO (3,4:5,6-dibenzo-2H-1,2-oxaphosphorin-2-oxide; CAS No. 35948-25-5) and 107 g of DHBP (bis(4-hydroxyphenyl)methanone; CAS No. 611-99-4) were added to a 1000 mL reactor. The mixture was slowly heated to 180 °C and stirred at 180 °C for 1.5 hours. Then, the temperature was lowered to 110 °C, and 1000 mL of toluene was added to the reactor. The mixture was then stirred at 110 °C for 30 minutes. The precipitate was removed by vacuum filtration and dried at 120 °C for 5 hours to obtain the intermediate product. The intermediate product was dissolved in 3000 mL of ethanol solution containing 24 g of potassium hydroxide (KOH) and stirred until completely dissolved. Then, 120 g of CMS (1-(chloromethyl)-4-vinylbenzene; CAS No. 1592-20-7) was added dropwise and stirred at room temperature for 48 hours. The precipitate was removed by vacuum filtration, and the solid was washed with water and ethanol and dried by rotary condensation to obtain a phosphorus-containing compound 1, which is a white powder with the following structure.

[0053] [Preparation Example 2]

[0054] 85.6 g of the phosphorus-containing compound 1 prepared in Preparation Example 1, 36.4 g of BBrBCB (4-bromobenzocyclobutene; CAS No. 1073-39-8), 2.4 g of palladium(II) acetate (CAS No. 3375-31-3), 2.62 g of TPP (triphenylphosphine; CAS No. 603-35-0), 120 mL of N,N-Diethylethanamine (CAS No. 121-44-8), and 120 mL of DMF (dimethylformamide; CAS No. 68-12-2) were added to a 500 mL reactor and stirred at 100 °C for 18 hours under a nitrogen atmosphere. Next, the solution was filtered to remove palladium black, then the solution was added dropwise to 1000 ml of water, the precipitate was removed by vacuum filtration, and dried by rotary concentration to obtain a white solid containing phosphorus compound 2 with the following structure.

[0055] [Preparation Example 3]

[0056] Add 285 g of DOPO (CAS No. 35948-25-5) and 107 g of DHBP (CAS No. 611-99-4) to a 1000 mL reactor, slowly heat to 180 °C, and stir at 180 °C for 1.5 hours. Then, cool to 110 °C, add 1000 mL of toluene to the reactor, and stir at 110 °C for 30 minutes. Filter the precipitate using vacuum filtration, dry at 120 °C for 5 hours to obtain the intermediate product. Dissolve 62.6 g of the intermediate product in 200 mL of DMSO (dimethyl sulfoxide), and add 17 g of sodium hydroxide (NaOH; 50 wt%), stirring until completely clear. Then, add 17 g of allyl chloride (CAS No. 107-05-1) dropwise, slowly heat to 65 °C, and stir for 30 minutes. Afterward, the mixture was allowed to cool naturally to room temperature, and then 500 mL of water was added for extraction with toluene. The solid obtained after drying the toluene was directly placed in a reaction vessel and stirred at 180°C for 6 hours under a nitrogen atmosphere. Next, the mixture was cooled to room temperature, and the solid was dissolved in a 3000 mL ethanol solution of 24 g of potassium hydroxide (KOH), stirred until completely dissolved, and then 120 g of CMS (CAS No. 1592-20-7) was added dropwise. The mixture was stirred at room temperature for 48 hours, filtered under vacuum to remove the precipitate, and then washed with water and ethanol. The solid was then dried by rotary condensation to obtain a yellowish-brown powder containing phosphorus compound 3 with the following structure.

[0057] 5.3 Preparation of flame-retardant and heat-resistant compositions

[0058] [Example 1]

[0059] Take 60 grams of 2,2'-diallyl bisphenol and polyamine-type maleimide polymer (60% by weight solids; commercial model: UB-20, purchased from Changchun Artificial Resin) and place them in a beaker. Heat the mixture to 130°C using an electromagnetic stirrer. Then add 2 grams of phosphorus-containing compound 1 and stir until clear to obtain the flame-retardant and heat-resistant composition of Example 1 containing 5% by weight of phosphorus-containing compound 1.

[0060] [Example 2]

[0061] A flame-retardant and heat-resistant composition of Example 2 containing 10% by weight of phosphorus compound 1 was prepared in the same manner as in Example 1, except that the amount of phosphorus compound 1 was adjusted to 4 grams.

[0062] [Example 3]

[0063] A flame-retardant and heat-resistant composition of Example 3 was prepared in the same manner as in Example 1, except that the amount of phosphorus compound 1 was adjusted to 6 grams, thereby obtaining a flame-retardant and heat-resistant composition of Example 3 containing 15% by weight of phosphorus compound 1.

[0064] [Example 4]

[0065] Take 57 grams of 2,2'-diallyl bisphenol and polyamine-type maleimide polymer (60% by weight solids; commercial model: UB-20) and place them in a beaker. Heat the mixture to 130°C using an electromagnetic stirrer. Then add 6 grams of phosphorus-containing compound 2 and stir until clear to obtain the flame-retardant and heat-resistant composition of Example 4 containing 15% by weight of phosphorus-containing compound 2.

[0066] [Example 5]

[0067] Take 57 grams of 2,2'-diallyl bisphenol and polyamine-type maleimide polymer (60% by weight solids; product model: UB-20) and place them in a beaker. Heat the mixture to 130°C using an electromagnetic stirrer. Then add 6 grams of phosphorus-containing compound 3 and stir until clear to obtain the flame-retardant and heat-resistant composition of Example 5 containing 15% by weight of phosphorus-containing compound 3.

[0068] [Comparative Example 1]

[0069] Take 80 grams of 2,2'-diallyl bisphenol and polyamine maleimide polymer (60% by weight solids; commercial model: UB-20) and place them in a beaker. Heat the mixture to 130°C using an electromagnetic stirrer to obtain the flame-retardant and heat-resistant composition of Comparative Example 1.

[0070] [Comparative Example 2]

[0071] 57 grams of 2,2'-diallyl bisphenol and a polyamine-type maleimide polymer (60% by weight solids; trade name: UB-20) were placed in a beaker and heated to 130°C using an electromagnetic stirrer. Then, 6 grams of a phosphorus-containing compound PX-200 (purchased from Daihachi Chemical) having the following structural formula were added. After stirring until clear, a flame-retardant and heat-resistant composition of Comparative Example 2 containing 15% by weight of a phosphorus-containing compound was obtained. PX-200

[0072] [Comparative Example 3]

[0073] 60 grams of 2,2'-diallyl bisphenol and a polyamine-type maleimide polymer (60% by weight solids; trade name: UB-20) were placed in a beaker and heated to 130°C using an electromagnetic stirrer. Then, 4 grams of a phosphorus-containing compound Di-DOPO (preparation method according to US 20120053265 A1) with the following structural formula were added and stirred until clear to obtain the flame-retardant and heat-resistant composition of Comparative Example 3 containing 10% by weight of a phosphorus-containing compound. Di-DOPO

[0074] 5.4. Preparation and performance testing of metal foil laminates

[0075] The obtained flame-retardant and heat-resistant compositions were used to prepare the metal foil laminates of Examples 1 to 5 and Comparative Examples 1 to 3, respectively. First, glass fiber cloth (model: 2116) was impregnated with the flame-retardant and heat-resistant compositions of Examples 1 to 5 and Comparative Examples 1 to 3, respectively. Next, the impregnated glass fiber was placed in a dryer at 170°C and heated and dried for 3 minutes to obtain a semi-cured sheet in a semi-cured state (B-stage). Then, the semi-cured sheet was cut into test pieces with a length and width of 13 cm, and a copper foil was laminated on each side. Subsequently, it was vacuum hot-pressed at 220°C for 2 hours to obtain the metal foil laminate.

[0076] The flame retardancy and heat resistance of the metal foil laminates of Examples 1 to 5 and Comparative Examples 1 to 3 were measured according to the measurement methods described above, and the results are recorded in Table 1.

[0077] Table 1: UL94 test (seconds) UL94 rating Phosphorus content (by weight %) Tg (°C) first The second The third Fourth Fifth Example 1 18.5 / 0.0 18.7 / 0.8 17.4 / 0.5 19.8 / 0.5 18.7 / 0.3 V1 0.36 187.3 Example 2 12.2 / 0.0 13.0 / 0.0 13.7 / 0.0 14.1 / 0.0 12.5 / 0.0 V1 0.72 188.7 Example 3 1.5 / 0.0 3.2 / 0.0 2.9 / 0.0 1.7 / 0.0 2.5 / 0.0 V0 1.08 191.0 Example 4 4.2 / 0 4.7 / 0 5.2 / 0 4.1 / 0 5.1 / 0 V0 0.87 195.3 Example 5 3.2 / 0 3.3 / 0 4.0 / 0 4.2 / 0 3.1 / 0 V0 0.99 195.1 Comparative Example 1 15.6 / 1.1 16.5 / 1.0 14.5 / 0.9 14.2 / 0.8 18.1 / 2.0 V1 0.0 178.1 Comparative Example 2 1.2 / 0.0 1.0 / 0.0 0.7 / 0.0 1.5 / 0.0 1.0 / 0.0 V0 1.35 138.2 Comparative Example 3 11.0 / 0.0 9.7 / 0.0 14.0 / 0.0 8.5 / 0.0 16.0 / 0.0 V1 1.35 183.4

[0078] The metal foil laminates of Examples 1 to 5 all achieved a V1 rating, and even a V0 rating, in five UL 94 vertical burning tests, and exhibited excellent heat resistance (high Tg). In contrast, Comparative Example 1, which did not use a flame retardant, achieved a V1 rating in flame retardancy, but its heat resistance was poor (below 180°C). Comparative Examples 2 and 3 showed that even with higher phosphorus content, good heat resistance and flame retardancy could not be simultaneously achieved when using other phosphorus-containing compounds not of the present invention. The above experimental results clearly demonstrate that the phosphorus-containing compounds of the present invention can indeed provide the effect of improving the heat resistance and flame retardancy of the applied object.

[0079] The above embodiments are merely illustrative of the principles and effects of the present invention and to illustrate the technical features of the present invention, and are not intended to limit the scope of protection of the present invention. Any changes or arrangements that can be easily made by those skilled in the art without departing from the technical principles of the present invention are within the scope claimed by the present invention. Therefore, the scope of protection of the present invention is as set forth in the appended claims.

Claims

1. A phosphorus-containing compound having the structure of formula (I): Formula (I) wherein, R1, R2, R3, and R4 are each independently selected from hydrogen atoms, C1 to C6 alkyl groups, C1 to C6 alkoxy groups, and C3 to C6 cycloalkyl groups, and each R1, each R2, each R3, and each R4 may be the same or different; R19 and R20 are each independently selected from -CH2-, -C(CH3)2-, -CO-, -SO2-, and -O-; R17 and R18 are each independently selected from -CH2-, -C(CH3)2-, -CO-, -SO2-, and -O-; m and ma are each independently integers from 0 to 4, n is an integer from 0 to 3, p is 0 or 1, and the sum of m and n does not exceed 4; And * represents the location of the bond.

2. The phosphorus-containing compound as claimed in claim 1, wherein R19 and R20 are each independently of or, and R17 and R18 are each independently of,,,,, or, wherein p is 0, and R6, R8, Ra, m, and ma are as defined in claim 1.

3. The phosphorus-containing compound as described in claim 2, wherein R17 and R18 are each independently or, and Ra and ma are as defined in claim 1.

4. A flame-retardant and heat-resistant composition comprising: a first reactive component selected from the group consisting of: epoxy resins, phenolic resins, benzoxazine resins, polyphenylene ether resins having olefinic carbon-carbon double bonds, allyl compounds, maleimide compounds, copolymers of allyl compounds and maleimide compounds, and combinations thereof; and a phosphorus-containing compound as described in any one of claims 1 to 3.

5. The flame-retardant and heat-resistant composition as claimed in claim 4, wherein the polyphenylene ether resin having olefinic carbon-carbon unsaturated double bonds is selected from the group consisting of: dihydroxy polyphenylene ether resins, methacrylate polyphenylene ether resins, vinyl polyphenylene ether resins, and combinations thereof.

6. The flame-retardant and heat-resistant composition as claimed in claim 4, wherein the allyl compound is selected from the group consisting of diallyl bisphenol A, diallyl bisphenol F, diallyl bisphenol S, and combinations thereof.

7. The flame-retardant and heat-resistant composition as claimed in claim 4, wherein the maleimide compound is selected from the group consisting of bismaleimide compounds, trimaleimide compounds, tetramaleimide compounds, and combinations thereof.

8. The flame-retardant and heat-resistant composition as described in any one of claims 4 to 7 further comprises an ingredient selected from the group consisting of fillers, catalysts, elastomers, dispersants, toughening agents, viscosity modifiers, plasticizers, coupling agents, and combinations thereof.

9. A prepreg, which is prepared by impregnating or coating a substrate with a flame-retardant and heat-resistant composition as described in any one of claims 4 to 8, and drying the impregnated or coated substrate.

10. A metal foil laminate, which is made by laminating a prepreg as described in claim 9 with a metal foil, or by coating a flame-retardant and heat-resistant composition as described in any one of claims 4 to 8 onto a metal foil and drying the coated metal foil.