New organic compounds and flame retardants using them

Abstract

One aspect of the present invention pertains to an organic compound represented by formula (1).　(1): X-Y (in the formula, X represents 9,10-dihydro-9-oxa-10-phosphaphenathren-10-yl-10-oxide, and Y represents a protective group.)

Description

[Technical Field]

[0001] The present invention relates to a novel organic compound and a flame retardant using the same. [Background technology]

[0002] Conventionally, organic halogen compounds such as decabromodiphenyl ether and brominated epoxy resins have been widely used as flame retardants for synthetic resins due to their excellent flame retardant effect, ease of application, and low cost.

[0003] However, synthetic resins containing organic halogen compounds have recently come under scrutiny because, when burned, they emit gases that are harmful to the human body and produce toxic by-products that have a significant impact on the environment.

[0004] Therefore, although there is a vigorous movement to replace organic halogen compounds with other flame retardants, this movement is not going smoothly, except for synthetic resins that are relatively easy to make flame retardant, such as phenolic resin, polycarbonate resin, and epoxy resin.

[0005] The reason is that other flame retardants are not as effective as organic halogen compounds in applying them to many synthetic resins and making them flame retardant. For example, flame retardancy using organic phosphorus compounds is generally achieved by accelerating the carbonization of synthetic resins, and by forming a carbonized layer on the surface during combustion, blocking the thermal energy of ignition sources or blocking the air necessary for combustion. Therefore, synthetic resins that can be easily flame retarded using organic phosphorus compounds are limited to those that are prone to forming a carbonized layer during combustion.

[0006] On the other hand, the flame retardant mechanism of organic halogen compounds is said to be a flame extinguishing effect caused by stable halogen radicals generated during combustion, and there are several reports that mention a similar fire extinguishing effect.

[0007] Patent Documents 1 and 2 describe the combined use of an organic phosphorus compound and 2,3-dimethyl-2,3-diphenylbutane, and Patent Document 3 describes the combined use of an organic halogen compound and 2,3-dimethyl-2,3-diphenylbutane, and both claim that the generation of halogen radicals during combustion contributes to flame retardancy.

[0008] Patent Document 4 describes organic peroxides with high decomposition temperatures, such as dicumyl peroxide and cumene hydroperoxide, as flame retardant assistants for expanded polystyrene, and suggests that they contribute to flame retardancy by generating radicals during combustion.

[0009] Non-Patent Document 1 also describes the unique flame retardant effect of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivatives as phosphorus compounds. Furthermore, it also describes the flame extinguishing effect of radical generation, i.e., 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl radical-10-oxide, which is not found in ordinary organic phosphorus compounds.

[0010] However, at present, there are very few reports or practical examples of halogen-free flame retardants that can impart flame retardancy to non-carbonizing resins, other than organic halogen compounds.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a novel organic compound that does not contain halogen atoms, has excellent flame retardancy and heat resistance, and can be used as a flame retardant for resins. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-34749 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-115763 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-1563 [Patent Document 4] Japanese Patent Application Publication No. 11-130898 [Non-patent literature]

[0013] [Non-Patent Document 1] Journal of the Society of Fiber Science and Technology, vol. 62, No. 10 (2006) Summary of the Invention

[0014] An organic compound according to one aspect of the present invention is characterized by being represented by the following formula (1):

[0015] X-Y (1) (In the formula, X is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl-10-oxide, and Y is a protecting group.) [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an infrared absorption spectrum (IR) of organic compound 1 obtained in Production Example 1. [Figure 2] FIG. 2 is a 1H-NMR spectrum of the organic compound 1 obtained in Production Example 1. [Figure 3] FIG. 3 shows the FD-MS of organic compound 1 obtained in Production Example 1. [Figure 4] FIG. 4 is an infrared absorption spectrum (IR) of organic compound 2 obtained in Production Example 2. [Figure 5] FIG. 5 is a 1H-NMR of organic compound 2 obtained in Production Example 2. [Figure 6] FIG. 6 shows the FD-MS of organic compound 2 obtained in Production Example 2. [Figure 7] FIG. 7 is an infrared absorption spectrum (IR) of organic compound 3 obtained in Production Example 3. [Figure 8] FIG. 8 is an infrared absorption spectrum (IR) of organic compound 4 obtained in Production Example 4. [Figure 9] FIG. 9 shows the FD-MS of organic compound 4 obtained in Production Example 4. [Figure 10] FIG. 10 is an infrared absorption spectrum (IR) of organic compound 5 obtained in Production Example 5. [Figure 11] FIG. 11 shows the FD-MS of organic compound 5 obtained in Production Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Organic compounds> The organic compound according to this embodiment is characterized by being represented by the following formula (1).

[0018] X-Y (1) In the formula (1), X represents 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl-10-oxide, and Y represents a protecting group.

[0019] According to the above-mentioned construction, it is possible to provide a novel organic compound that does not contain halogen atoms, has excellent flame retardancy and heat resistance, and can be used as a flame retardant for resins.

[0020] The organic compound of this embodiment has excellent thermal stability and flame retardancy despite not containing halogen atoms. This is thought to be due to the fire-extinguishing effect of stable radicals generated by homolytic cleavage of the compound during combustion. Although the mechanism is not completely clear, it is thought to be roughly as follows.

[0021] In other words, in the compound, the radical atom of X generated by liberation of the protecting group Y is stabilized by resonance with at least one adjacent aromatic ring, so that cleavage into the radical proceeds extremely smoothly and the generated radical is also stable. Therefore, the organic compound of this embodiment can be suitably used as a flame retardant.

[0022] In the compound, the protecting group Y is a substituent that is temporarily introduced to a specific functional group of a compound having a functional group to inactivate the reactivity of the functional group, with the assumption that the protecting group will be removed at a later stage, thereby increasing the chemical stability of the compound. In this embodiment, the later stage refers to the combustion of a resin composition containing the compound.

[0023] The protecting group used in this embodiment is not particularly limited as long as it is a protecting group introduced by a protecting reagent. Such a protecting reagent may be a protecting reagent derived from a protecting reagent that is generally available (e.g., commercially available) or that can be synthesized.

[0024] Specifically, examples of the protecting group Y include a silyl group, an acyl group, an allyl group, an allyloxycarbonyl group, a benzyl group, a benzyloxycarbonyl group, an acetal group, a thioacetal group, a 2,2,2-trichloroethoxycarbonyl group, an alkoxymethyl group, a tert-butoxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group, a trityl group, a sulfonyl group, etc. Among these, a group that is particularly preferred is one in which the total molecular weight of the compound of formula (1) is 250 or more and that, when the bond between X and Y is cleaved, is likely to cause the radical atom of Y to be stabilized by resonance with at least one adjacent aromatic ring, similar to the radical atom of X, to generate a stable radical.

[0025] Furthermore, the protecting group Y is preferably a group represented by the following formula (2).

[0026] [ka]

[0027] In the formula (2), R1, R2, and R3 each independently represent hydrogen, a benzoyloxy group, a vinylbenzyl group, an alkoxy group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms, and m each independently represents an integer of 1 to 5.

[0028] In the organic compound represented by formula (1), when the protecting group Y is a group represented by formula (2), each radical atom generated by cleavage of the organic compound is stabilized by resonance with at least one aromatic ring on one side (X side) and three aromatic rings on the other side (protecting group Y side), which is thought to facilitate cleavage into radical pairs, thereby more reliably achieving the flame retardant effect described above.

[0029] More specific examples of the group represented by the formula (2) include a trityl group, a 4-methoxytrityl group, a 4,4'-dimethoxytrityl group, and a 4,4',4''-tris(benzoyloxy)trityl group.

[0030] For example, when the protecting group Y is a trityl group, the organic compounds of this embodiment are as follows (however, compounds (1-2) to (1-4) other than compound (1-1) are reference compounds): [ka]

[0031] Furthermore, for example, when the protecting group Y is a 4-methoxytrityl group, the organic compounds of this embodiment are as follows (however, compounds (2-2) to (2-4) other than compound (2-1) are reference compounds): [ka]

[0032] Furthermore, for example, when the protecting group Y is a 4,4'-dimethoxytrityl group, the organic compounds of this embodiment are as follows (however, compounds (3-2) to (3-4) other than compound (3-1) are reference compounds): [ka]

[0033] Furthermore, when the protecting group Y is a 4,4',4''-tris(benzoyloxy)trityl group, the organic compounds of this embodiment are as follows (however, compounds (4-2) to (4-4) other than compound (4-1) are reference compounds): [ka]

[0034] In addition, it is generally known that compounds that readily undergo homolytic cleavage, such as organic peroxides, have low decomposition temperatures, making them unsuitable for addition to various synthetic resins as flame retardants. In contrast, the organic compound of the present embodiment can be set to a decomposition temperature of 200°C or higher, at which stable radicals are generated, making it highly suitable for use as a flame retardant.

[0035] Furthermore, 2,3-dimethyl-2,3-diphenylbutane, used in the technologies described in Patent Documents 1 and 2, possesses a fire-extinguishing effect due to two cumyl radicals generated by homolytic cleavage during combustion. However, because its molecular weight is less than 250, when added to a synthetic resin at high temperatures, most of it volatilizes, deteriorating the work environment and adversely affecting its flame-retardant properties. In contrast, the organic compound of this embodiment can be designed to have a molecular weight of 250 or more, which has the advantage of suppressing volatility and fully demonstrating its additive effects even when added to a synthetic resin at high temperatures. Therefore, the organic compound of this embodiment preferably has a weight-average molecular weight of 250 or more, more preferably 300 or more, and even more preferably 400 or more. While there is no particular upper limit to the molecular weight, a molecular weight of 1,000 or less, or even 900 or less, is preferred from the perspective of the number of radical generating sources per molecular weight.

[0036] <Method for synthesizing organic compounds> The method for synthesizing the organic compound of this embodiment is not particularly limited, but for example, the organic compound represented by formula (1) of this embodiment can be obtained by condensing compound X (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl-10-oxide) with a protecting reagent having a group that specifically reacts with the functional group of compound X, in the presence or absence of a base. Specific protecting reagents that can be used include, for example, trityl chloride, 4-methoxytrityl chloride, 4,4'-dimethoxytrityl chloride, and 4,4',4''-tris(benzoyloxy)trityl bromide.

[0037] <Flame retardant> The organic compound of the present embodiment has excellent thermal stability and flame retardancy, and therefore can be suitably used, for example, as a flame retardant for resin compositions, etc. That is, the present invention also encompasses flame retardants made of the above-described organic compounds.

[0038] The flame retardant of this embodiment contains the organic compound described above, and therefore exhibits a flame retardant effect when X and Y in formula (1) are cleaved to generate radicals.

[0039] The flame retardant of this embodiment can be applied to a wide range of resins without any particular limitations. In other words, the flame retardant of this embodiment can be applied to both thermosetting resins and / or thermoplastic resins. For example, in the case of thermosetting resins, epoxy resins, low-molecular-weight polyphenylene ether resins, cyanate ester resins, phenolic resins, benzoxazines, acid anhydrides, and resins containing unsaturated groups (acrylic, methacrylic, allyl, styryl, butadiene, maleimide, etc.) can be used alone or as copolymers. Examples of thermoplastic resins include polyphenylene ether resins, polyphenylene sulfide resins, liquid crystal polymers, polyethylene resins, polystyrene resins, polyurethane resins, polypropylene resins, ABS resins, acrylic resins, polyethylene terephthalate resins, polycarbonate resins, polyacetal resins, polyimide resins, polyamide-imide resins, polytetrafluoroethylene resins, cycloolefin polymers, cycloolefin copolymers, and styrene-based elastomers. These resins can be used alone or in combination.

[0040] Among these, application to flammable resins and non-carbonizing resins is particularly effective, and the efficacy of the flame retardant of this embodiment can be more fully demonstrated.

[0041] When the organic compound of the present embodiment is added as a flame retardant to a resin composition containing the resin described above, the amount added is typically 0.5% by mass to 100% by mass, more preferably 1% by mass to 80% by mass, relative to 100% by mass of the resin.

[0042] It is believed that a sufficient flame retardant effect can be obtained when the amount of the flame retardant added is 0.5% by mass or more, whereas an amount exceeding 100% by mass is not only not very effective but may also adversely affect the properties of the resin composition, which is undesirable.

[0043] The resin composition containing the organic compound of the present embodiment as a flame retardant has high thermal stability and flame retardancy, and therefore can be suitably used as various electronic materials such as prepregs, metal-clad laminates, resin-coated metal foils, and insulating layers for wiring boards (circuit boards).

[0044] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. [Example]

[0045] Physical properties in the following synthesis examples were measured by the methods shown below. (NMR analysis) The Bruker Biospin AVANCE NEO cryo-500 nuclear magnetic resonance apparatus was used, and 1H-NMR analysis was performed using DMSO-d6 as the solvent for dissolving the sample.

[0046] (mass spectrometry) The apparatus used was a JEOL JMS-T100GC AccuTOF GC, and the ionization source was FD (Field Desorption). DMSO was used as the solvent for dissolving the sample, and the analysis was carried out according to a predetermined protocol.

[0047] (IR analysis) The equipment used was a Shimadzu Fourier transform infrared spectrophotometer IRAffinity-1, and the prism used was a PIKE technologies MIRacleA (ZnSe) single-reflection horizontal total reflection absorption measurement device, and the analysis was performed according to the specified protocol.

[0048] <Synthesis of organic compounds> (Production Example 1) Preparation of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-trityl-10-oxide (organic compound 1)

[0049] A 300 ml hard glass four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a gas inlet was charged with 21.6 g (Mw 216.2 × 0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 183 g of acetonitrile.

[0050] The temperature was raised while blowing nitrogen gas through the gas blowing port, and when the temperature reached 70° C., trityl chloride was started to be added in portions. After the initial addition of 9.3 g of trityl chloride, the operation of adding 9.3 g of trityl chloride every hour was repeated until a total of 27.9 g (Mw 278.8 × 0.1 mol) of trityl chloride was added in portions.

[0051] After the divided additions were completed, the temperature of the reactor was set to 80°C, and dehydrochloric acid aging was carried out for 24 hours, after which cooling was initiated. When the reactor temperature had dropped to around 25°C, the precipitated crystals were filtered by suction, and then the filtered crystals were washed with purified water until the pH of the filtrate was approximately neutral, after which they were dried.

[0052] By the above procedure, 44.4 g of white crystals of organic compound 1 (Mw 458.5) having a melting point of about 250°C was obtained.

[0053] Liquid chromatography (LC) analysis confirmed that this organic compound 1 had a purity of 99%. Its infrared absorption spectrum (IR) is shown in Figure 1, its 1H-NMR in Figure 2, and its FD-MS in Figure 3, confirming that the obtained organic compound 1 was a compound having the following chemical structure.

[0054] [ka]

[0055] (Reference example 2) Preparation of trityldiphenylphosphine oxide (organic compound 2)

[0056] A 500 ml hard glass four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a gas inlet was charged with 25 g of diphenylphosphine oxide (Mw 202.2 × 0.124 mol) and 220 g of acetonitrile.

[0057] The temperature was raised while blowing nitrogen gas through the gas blowing port, and when the temperature reached 70° C., trityl chloride was started to be added in portions. After the initial addition of 11.5 g of trityl chloride, the operation of adding 11.5 g of trityl chloride every hour was repeated until a total of 34.5 g (Mw 278.8 × 0.124 mol) of trityl chloride was added in portions.

[0058] After the divided additions were completed, the temperature of the reactor was set to 80°C, and dehydrochloric acid aging was carried out for 24 hours, followed by slow cooling. When the reactor temperature had dropped to around 25°C, the precipitated crystals were filtered by suction, and then the filtered crystals were washed with purified water until the pH of the filtrate was approximately neutral, after which they were dried.

[0059] By the above procedure, 45 g of white crystals of organic compound 2 (Mw 444.5) having a melting point of 237°C was obtained.

[0060] Liquid chromatography (LC) analysis confirmed that organic compound 2 had a purity of 99%. Its infrared absorption spectrum (IR) is shown in Figure 4, its 1H-NMR in Figure 5, and its FD-MS in Figure 6, confirming that the obtained organic compound 2 was a compound having the following chemical structure.

[0061] [ka]

[0062] (Production Example 3) Preparation of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-(4-methoxytrityl)-10-oxide (organic compound 3)

[0063] A 500 ml hard glass four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a gas inlet was charged with 26.8 g (Mw 216.2 × 0.124 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 181.6 g of acetonitrile.

[0064] The temperature was raised while blowing nitrogen gas through the gas blowing port, and when the temperature reached 50°C, 4-methoxytrityl chloride was started to be added in portions.

[0065] After the initial addition of 12.8 g of 4-methoxytrityl chloride, the operation of adding 12.8 g of 4-methoxytrityl chloride every hour was repeated, and a total of 38.4 g (Mw 308.8×0.124 mol) of 4-methoxytrityl chloride was added in portions.

[0066] After the addition of the divided portions, the mixture was dehydrochlorinated and aged for 24 hours, and then 181.6 g of purified water was added. After the temperature of the vessel was reduced to about 25°C, the precipitated crystals were filtered by suction, and the filtered crystals were washed with purified water until the pH of the filtrate was approximately neutral, and then dried.

[0067] By the above procedure, 54.6 g of white crystals of organic compound 3 (Mw 488.5) having a melting point of 132°C was obtained.

[0068] Liquid chromatography (LC) analysis confirmed that organic compound 3 had a purity of 99%. Its infrared absorption spectrum (IR) is shown in FIG. 7, and it was confirmed that the obtained organic compound 3 was a compound having the following chemical structure.

[0069] [ka]

[0070] (Reference example 4) Preparation of 9-tritylcarbazole (organic compound 4)

[0071] A 500 ml hard glass four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 20.9 g (Mw 167.2 × 0.125 mol) of carbazole, 17.3 g (Mw 138.2 × 0.125 mol) of potassium carbonate, and 256 g of n,n-dimethylformamide.

[0072] After the charging, the temperature was raised, and when the temperature reached 40° C., trityl chloride was added in portions. After the initial addition of 1.8 g of trityl chloride, 3 g of trityl chloride was added approximately every 10 minutes, and the procedure was repeated until a total of 34.8 g (Mw 278.8 × 0.125 mol) was used.

[0073] After the addition of the divided portions, the temperature of the reactor was set to 80°C, and aging was carried out for 2 hours. 110 g of purified water was added, and then slow cooling was started. When the temperature of the reactor had dropped to around 25°C, the precipitated crystals were filtered by suction, and then the filtered crystals were washed with purified water until the pH of the filtrate was almost neutral, and then dried.

[0074] By the above procedure, 41 g of white crystals of organic compound 4 (Mw 409.5) having a melting point of 257°C was obtained.

[0075] Liquid chromatography (LC) analysis confirmed that organic compound 4 had a purity of 99%. Its infrared absorption spectrum (IR) is shown in FIG. 8, and its FD-MS spectrum is shown in FIG. 9. It was confirmed that the obtained organic compound 4 was a compound having the following chemical structure.

[0076] [ka]

[0077] (Production Example 5) Preparation of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-[4,4',4''-tris(benzoyloxy)]-10-oxide (organic compound 5)

[0078] A 300 ml hard glass four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a gas inlet was charged with 7.9 g (Mw 216.2 × 0.0366 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 120 g of acetonitrile.

[0079] The temperature was raised while blowing nitrogen gas through the gas inlet, and when the temperature reached 70°C, the addition of 4,4',4''-tris(benzoyloxy)trityl bromide in portions began. After the initial addition of 5.0 g of 4,4',4''-tris(benzoyloxy)trityl bromide, the operation of adding 5.0 g every hour was repeated until a total of 25.0 g (Mw 683.6 × 0.0366 mol) of 4,4',4''-tris(benzoyloxy)trityl bromide was added in portions.

[0080] After the divided additions were completed, the temperature of the reactor was set to 80°C, and dehydrochloric acid aging was carried out for 24 hours, after which cooling was initiated. When the reactor temperature had dropped to around 25°C, the precipitated crystals were filtered by suction, and then the filtered crystals were washed with purified water until the pH of the filtrate was approximately neutral, after which they were dried.

[0081] By the above procedure, 28.4 g of white crystals of organic compound 1 (Mw 818.8) having a melting point of about 233°C was obtained.

[0082] Liquid chromatography (LC) analysis confirmed that organic compound 5 had a purity of 99%. Its infrared absorption spectrum (IR) is shown in FIG. 10, and its FD-MS spectrum is shown in FIG. 11. It was confirmed that the obtained organic compound 5 was a compound having the following chemical structure.

[0083] [ka]

[0084] <Evaluation Test 1> Example 1 100 parts by mass of a styrene-based elastomer resin ("Septon V9827 (product name)" manufactured by Kuraray Co., Ltd.) was added to toluene and stirred for 60 minutes to completely dissolve it, and then 79 parts by mass of organic compound 1 obtained in Production Example 1 above was added as a flame retardant, and the mixture was stirred for 60 minutes to obtain a varnish-like resin composition (resin varnish).

[0085] (Comparative Example 1) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 1, except that 9,10-dihydro-10-(2,5-dihydroxyphenyl)-9-oxa-10-phosphaphenanthrene-10-oxide (HCA) having the following chemical structure (manufactured by Sanko Co., Ltd.) was used as the flame retardant instead of organic compound 1, and 26 parts by mass of HCA was added so that the phosphorus content was the same as in Example 1.

[0086] [ka]

[0087] (Comparative Example 2) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 1, except that 2,3-diphenyl-2,3-dimethylbutane (product name: Nofumer BC-90, manufactured by NOF Corporation) having the following chemical structure was used as the flame retardant instead of organic compound 1, and 40 parts by mass was added so that the radical concentration at the time of radical cleavage would be the same as in Example 1.

[0088] [ka]

[0089] (Comparative Example 3) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 1, except that an aromatic condensed phosphate ester having the following chemical structure ("PX-200 (product name)", manufactured by Daihachi Chemical Industry Co., Ltd.) was used as the flame retardant instead of organic compound 1, and 50 parts by mass was added so that the phosphorus content was the same as in Example 1.

[0090] [ka]

[0091] <Evaluation sample> Resin-coated films were prepared using the resin varnishes obtained in Example 1 and Comparative Examples 1 to 4. A PET film ("SP-PETO1" manufactured by Mitsui Chemicals Tohcello, Inc.) was used as the substrate. The resin varnish was applied to the surface of the substrate so that the thickness after drying was 100 μm, and this was heated and dried at 120 to 160°C for approximately 2 to 5 minutes to obtain a resin-coated film. The substrate was then peeled off from the obtained resin-coated film, and four sheets were stacked. The resulting films were sandwiched between 18 μm-thick copper foils and heated and pressurized at 200°C and 2 MPa for 2 hours to obtain a copper-clad substrate with an insulating layer thickness of 400 μm. The copper-clad substrate was then etched to remove the copper foil, yielding an evaluation substrate.

[0092] <Evaluation method> (Flame retardant) Using the evaluation board obtained above, flammability was evaluated in accordance with the UL94 flammability test. However, the flame was only exposed once because the evaluation board dripped. The evaluation criteria were as follows:

[0093] Complete burning: The flame rises from the bottom end of the test board where it is in contact with the flame to the top end where it is chucked, and the test board is completely burned.

[0094] Flame extinction: No flame rises from the bottom edge of the test board to the top edge of the chuck, and the flame extinguishes within 5 seconds after 10 seconds of contact with the flame.

[0095] (Thermogravimetric measurement) The obtained evaluation substrate was subjected to thermogravimetry in a nitrogen atmosphere in accordance with the method of IPC TM-650 2.4.24.1, and the temperature at which the weight loss reached 5% was evaluated.

[0096] The above results are summarized in Table 1.

[0097] [Table 1]

[0098] (Consideration) As a result, Example 1 had good flame retardancy and very high thermal stability. Comparative Example 1 had good flame retardancy but lower thermal stability than Example 1, and Comparative Example 2 had poor flame retardancy. In Comparative Example 3, when the resin-coated film was heated and pressurized, the resin flowed and became very tacky, making it impossible to maintain the shape of the evaluation substrate.

[0099] As is clear from the above results, it was confirmed that the laminate using the organic compound of the present invention as a flame retardant can achieve both superior flame retardancy and heat resistance compared to the comparative laminate using the conventionally used phosphorus-based flame retardant or 2,3-diphenyl-2,3-dimethylbutane, which has a fire-extinguishing effect due to radicals.

[0100] <Evaluation Test 2> Example 2 70 parts by weight of modified polyphenylene ether resin ("SA9000 (product name)" manufactured by SABIC Innovative Plastics), 30 parts by weight of curing agent ("TAIC" triallyl isocyanurate manufactured by Nippon Kasei Chemical Co., Ltd.), and 2 parts by weight of reaction initiator ("Perbutyl P" 1,3-bis(butylperoxyisopropyl)benzene manufactured by Nippon Oil & Fats Co., Ltd.)) were added to toluene (solvent) and thoroughly dissolved. Then, 42.5 parts by weight of organic compound 1 obtained in Preparation Example 1 above was added as a flame retardant, followed by 100 parts by weight of inorganic filler ("SC2300-SVJ" vinylsilane-treated spherical silica manufactured by Admatechs Co., Ltd.). The mixture was stirred for 60 minutes and then dispersed using a bead mill. This produced a varnish-like resin composition (varnish).

[0101] Comparative Example 4 A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 2, except that no flame retardant was added.

[0102] (Comparative Example 5) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 2, except that 9,10-dihydro-10-(2,5-dihydroxyphenyl)-9-oxa-10-phosphaphenanthrene-10-oxide (HCA) having the above chemical structure (manufactured by Sanko Co., Ltd.) was used as the flame retardant instead of organic compound 1, and 16.5 parts by mass of HCA was added so that the phosphorus content was the same as in Example 2.

[0103] (Comparative Example 6) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 2, except that 2,3-diphenyl-2,3-dimethylbutane (product name: Nofumer BC-90, manufactured by NOF Corporation) having the above chemical structure was used as the flame retardant instead of organic compound 1, and 23 parts by mass of the compound was added so that the radical concentration at the time of radical cleavage was the same as in Example 2.

[0104] (Comparative Example 7) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 2, except that an aromatic condensed phosphate ester having the above chemical structure ("PX-200 (product name)", manufactured by Daihachi Chemical Industry Co., Ltd.) was used as the flame retardant instead of organic compound 1, and 29.2 parts by mass was added so that the phosphorus content was the same as in Example 2.

[0105] (Comparative Example 8) A varnish-like resin composition (resin varnish) was obtained in the same manner as in Example 2, except that an aromatic condensed phosphate ester having the above chemical structure ("PX-200 (product name)", manufactured by Daihachi Chemical Industry Co., Ltd.) was used as the flame retardant instead of organic compound 1, and 15 parts by mass was added so that the phosphorus content was 1.2%.

[0106] <Evaluation sample> The resin varnishes obtained in Example 2 and Comparative Examples 4 to 8 were used to impregnate glass substrates (#2116 type, "E Glass" (manufactured by Nitto Boseki Co., Ltd.) respectively, and then heated and dried at 120°C for approximately 3 minutes to obtain prepregs. The thickness was adjusted to 110 μm. Four sheets of each of the obtained prepregs were then stacked, and copper foil "FV-WS foil 18 μm (manufactured by Furukawa Electric Co., Ltd.)" was placed on both sides. The stack was heated and pressed at a temperature of 200°C for 2 hours at a pressure of 3 MPa to obtain copper-clad substrates for evaluation with a thickness of 440 μm. The copper-clad substrates obtained were then etched to remove the copper foil, yielding evaluation substrates.

[0107] <Evaluation method> (Flame retardant) Using the evaluation boards obtained above, flammability (average number of seconds) was evaluated in accordance with the UL94 flammability test. Specifically, five evaluation boards were exposed to flame twice, for a total of 10 exposures, and the average number of seconds it took for the flame to go out was measured and calculated. The evaluation standard was 25 seconds or less, which was considered a pass. Note that "total burn" in the table means that the flame rose from the bottom end of the evaluation board, where it was exposed to flame, to the top end, where it was chucked, and the board was burned.

[0108] (glass transition temperature (Tg)) Using the evaluation substrate, Tg was measured using a viscoelasticity spectrometer "DMS100" manufactured by Seiko Instruments Inc. Dynamic mechanical analysis (DMA) was performed using a tensile module at a frequency of 10 Hz, and the temperature at which tan δ reached a maximum when the temperature was increased from room temperature to 320°C at a heating rate of 5°C / min was defined as Tg. In this test, a Tg of 250°C or higher was evaluated as passing.

[0109] The above results are summarized in Table 2.

[0110] [Table 2]

[0111] (Consideration) As is clear from Table 2, it was confirmed that Example 2 had good flame retardancy and a high Tg. On the other hand, sufficient flame retardancy could not be obtained in Comparative Examples 4, 6, and 8. Furthermore, Comparative Examples 5 and 7 had relatively good flame retardancy, but their Tg was significantly lower than that of Example 2.

[0112] As is clear from the above results, it was confirmed that the laminate using the organic compound of the present invention as a flame retardant can achieve both superior flame retardancy and heat resistance compared to the comparative laminate using the conventionally used phosphorus-based flame retardant or 2,3-diphenyl-2,3-dimethylbutane, which has a fire-extinguishing effect due to radicals.

[0113] This application is based on Japanese Patent Application No. 2021-81740, filed on May 13, 2021, the contents of which are incorporated herein by reference.

[0114] In order to express the present invention, the present invention has been properly and sufficiently described above through embodiments with reference to specific examples, drawings, etc., but it should be recognized that those skilled in the art can easily make changes and / or improvements to the above-described embodiments. Therefore, unless changes or improvements made by those skilled in the art deviate from the scope of the claims set forth in the claims, such changes or improvements are construed as being encompassed within the scope of the claims. [Industrial Applicability]

[0115] The present invention has wide industrial applicability in the technical fields of electronic materials, electronic devices, optical devices, and the like.

Claims

1. An organic compound represented by the following structural formula: 【Chemistry 1】

2. A flame retardant containing the organic compound according to claim 1.

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