Ultraviolet light-curable halogen-free flame retardant, solder resist ink containing the same, and application

Abstract

The application discloses an ultraviolet light curing halogen-free flame retardant, a solder resist ink containing the flame retardant and application, and belongs to the technical field of printing materials. The structural general formula of the ultraviolet light curing halogen-free flame retardant is shown in the following formula (I): wherein A is at least one selected from the group consisting of B is at least one selected from the group consisting of D is a hydrocarbon group. The application introduces a phosphorus-containing compound on an unsaturated anhydride, and then reacts with a secondary amine compound to obtain a phosphorus-nitrogen synergistic flame retardant, and finally introduces an unsaturated double bond into the flame retardant to obtain the ultraviolet light curing halogen-free flame retardant. The preparation process of the prepared flame retardant is simple, no solvent is needed, and the prepared product does not need to be post-treated, and the prepared solder resist ink shows excellent flame retardant performance, adhesion, pencil hardness, acid and alkali resistance and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of printing materials technology, and in particular to a UV-curable halogen-free flame retardant, solder resist ink containing the flame retardant, and its applications. Background Technology

[0002] Printed circuit boards (PCBs) are the substrates on which modern electronic devices mount and connect various electronic components. They are the largest industry in the electronics industry and are mainly used in products such as aerospace, military, mobile communications, laptops, computer peripherals, PDAs, and digital cameras.

[0003] To ensure insulation during the soldering of electrical components and to protect electronic products from changes in the external environment during use, a permanent protective layer, known as solder resist ink, needs to be coated on the surface of the printed circuit board (PCB). Solder resist ink prevents short circuits during component soldering and can adjust the amount of solder adhered, ultimately reducing component weight and increasing insulation. However, the high temperatures involved in component soldering pose safety hazards; therefore, solder resist ink must also possess good flame-retardant properties.

[0004] The simplest way to improve the flame retardant properties of solder resist ink is to add additive flame retardants. However, this method does not provide long-lasting flame retardancy and can easily lead to a decrease in the ink's own properties after curing. Reactive flame retardants can provide superior flame retardant properties at lower addition levels, but they often negatively impact the material's heat resistance, and their preparation process is complex and costly. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a UV-curable halogen-free flame retardant, a solder resist ink containing this flame retardant, and its applications. This invention obtains a phosphorus-nitrogen synergistic flame retardant by introducing a phosphorus-containing compound onto an unsaturated acid anhydride, followed by a reaction with a secondary amine compound. Finally, an unsaturated double bond is introduced into the flame retardant to obtain the UV-curable halogen-free flame retardant. The preparation process of this flame retardant is simple, the prepared product requires no post-processing, and the prepared solder resist ink exhibits excellent flame retardant properties, heat resistance, adhesion, acid and alkali resistance, and high pencil hardness, meeting the requirements for use as a solder resist ink.

[0006] The technical solution of the present invention is as follows: The first aspect of this invention provides a UV-curable halogen-free flame retardant, the general structural formula of which is shown in formula (Ⅰ) below: (I); in: A is selected from, At least one of the following; wherein B is selected from , At least one of the following; wherein D is a group containing a hydrocarbon group.

[0007] Preferably, D is selected from... , and At least one of them.

[0008] A second aspect of the present invention provides a method for preparing the ultraviolet-curable halogen-free flame retardant described in the first aspect above, comprising the following steps: (1) Dissolve phosphorus-containing monomers, unsaturated acid anhydrides and secondary amine monomers in an organic solvent in sequence, stir and react at 40-90 °C for 0.5-5 h, and then stir and react at 60-110 °C for 2-5 h to obtain a phosphorus-nitrogen synergistic flame retardant. (2) At 60-100℃, add the monomer containing unsaturated groups to the phosphorus-nitrogen synergistic flame retardant in step (1), heat to react, and cool to room temperature after the reaction is completed to obtain the UV-curable flame retardant.

[0009] Preferably, in step (1), the phosphorus-containing monomer includes at least one of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphorus oxide, and diphenyl phosphite; And / or, the unsaturated anhydride includes one or more of itaconic anhydride, maleic anhydride, and allyl succinic anhydride; And / or, the secondary amine monomer includes at least one selected from piperazine, 2-ethylpiperazine, 2-methylpiperazine, 2,3-dimethylpiperazine, 2,5-dimethylpiperazine, and N,N-diethylethylenediamine; The molar ratio of the phosphorus-containing monomer, unsaturated acid anhydride and secondary amine monomer is 2-2.5:2:1.

[0010] Preferably, in step (1), the organic solvent includes at least one of toluene, xylene, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, diethylene glycol methyl ether, and dimethyl sulfoxide.

[0011] Preferably, in step (2), the monomer containing unsaturated groups includes at least one of glycidyl methacrylate, glycidyl acrylate, glycidyl oleate, 1,2-epoxy-5-hexene, 1,3-butadiene monoepoxide, allyl glycidyl ether, 1,2-epoxy-7-octene, 3-(allyloxy)oxetane, and 1,2-epoxy-9-decene. And / or, the molar ratio of the phosphorus-nitrogen synergistic flame retardant to the monomer containing unsaturated groups is 1:2-2.2; And / or, the heating reaction is carried out at a temperature of 80-120 °C for a time of 2-10 h.

[0012] A third aspect of the present invention provides a solder resist ink, comprising an ultraviolet-curable flame retardant and other components, wherein the other components, by mass percentage, comprise the following raw material components: 30-55% matrix resin, 2-25% active monomer, 1-8% photoinitiator, 1-5% color paste, 5-40% filler, and 1-5% additives. The mass ratio of the UV-curable flame retardant to the other components is 3-5:100.

[0013] The UV-curable flame retardant is the UV-curable halogen-free flame retardant described in the first aspect above, or the UV-curable halogen-free flame retardant prepared by the preparation method described in the second aspect above.

[0014] Preferably, the matrix resin is obtained by mixing acrylate-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin, wherein the weight ratio of acrylate-modified phenolic epoxy resin to β-hydroxyethyl acrylate-modified melamine-formaldehyde resin is 4~1:1.

[0015] The active monomers include one or more of trimethylolpropane triacrylate, β-hydroxyethyl methacrylate, tripropylene glycol diacrylate, and pentaerythritol triacrylate; The photoinitiator includes one or more of 2-ethylanthraquinone, benzoin diethyl ether 651, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone; The color paste is prepared by mixing, dispersing, and grinding pigments, resins, and dispersants in a weight ratio of 1~3:7~9:0.01~0.05; Wherein, the resin is the same as the matrix resin; the dispersant includes at least one of polyacrylate and polyamide-modified polymeric carboxylate dispersants; The filler includes one or more of silica powder, talc powder, fumed silica, and barium sulfate; The additives include one or both of defoamers and leveling agents.

[0016] A fourth aspect of the present invention provides a method for preparing the solder resist ink described in the third aspect above, the method comprising the following steps: S1: According to the proportion of each raw material, mix the matrix resin, active monomer, UV-curable flame retardant, photoinitiator, color paste and filler in sequence, and mix them evenly at 1300-1800 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: Test the uniformly mixed material in step S2. After passing the test, adjust the viscosity to 100 Pa·s with active monomers, filter, and obtain solder resist ink. In step S1, the matrix resin is obtained by mixing acrylic acid-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin at a speed of 600~1200 r / min.

[0017] The fifth aspect of the present invention provides an application of the solder resist ink described in the third aspect above, or the solder resist ink prepared by the preparation method described in the fourth aspect above, wherein the solder resist ink is used to prepare a solder resist coating.

[0018] The beneficial technical effects of this invention are as follows: This invention introduces a phosphorus-nitrogen synergistic flame retardant by introducing a phosphorus-containing compound onto an unsaturated acid anhydride and reacting it with a secondary amine compound. Finally, unsaturated double bonds are introduced into the flame retardant to obtain a UV-curable halogen-free flame retardant. This flame retardant has a high phosphorus and nitrogen content, exhibiting excellent condensed-phase and gas-phase flame retardant effects. The contained double bonds can participate in ink curing without losing their flame-retardant function due to migration or volatilization, achieving long-term flame retardancy. Furthermore, as a reactive flame retardant, it does not affect the overall performance of the ink itself. The synthesis method of the flame retardant is simple and environmentally friendly, with low viscosity and good processability. In summary, its use in modifying solder resist inks can improve the flame-retardant properties of solder resist inks.

[0019] This invention generates no waste during the preparation process, requires convenient or no post-processing, and is green, environmentally friendly, simple, and efficient in its production process.

[0020] The solder resist ink prepared by this invention has excellent flame retardant properties, and at the same time, the prepared solder resist ink has excellent adhesion, pencil hardness, acid and alkali resistance and heat resistance. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the embodiments.

[0022] It is understood that the halogen-free flame retardant of the present invention includes phosphorus-containing and nitrogen-containing structures with excellent flame retardant properties, as well as an unsaturated double bond structure that can participate in UV curing. Both flame-retardant structures can respond rapidly during ink combustion, quickly decomposing to generate phosphorus-containing free radicals, phosphates, and nitrogen-containing gases. These play roles in quenching free radicals, promoting char formation in the matrix, diluting heat, and dissipating combustible gases, respectively, thus providing excellent flame retardant properties for solder resist inks. Furthermore, the phosphorus-containing structure on the overhanging side groups does not affect the thermal properties of the main chain. The unsaturated double bond structure has high reactivity and can participate in the photocrosslinking of the ink matrix resin under UV irradiation without reducing the final mechanical properties and crosslinking density of the ink, thereby ensuring that the cured ink has high pencil hardness and good solvent resistance.

[0023] In some embodiments, the additives in the solder resist ink are defoamers and leveling agents; wherein the defoamer is selected from those containing organosilicon groups or silicone; and the leveling agent is a silicone-containing leveling agent.

[0024] In some embodiments, the ink includes a UV-curable flame retardant and other components, wherein the content of the matrix resin in the other components is preferably 35-50 wt%; the content of the active monomer is preferably 6-10 wt%; the content of the photoinitiator is preferably 2-5 wt%; the content of the color paste is preferably 2-4 wt%; and the composition of the filler is preferably 15-40 wt%.

[0025] In some embodiments, the solder resist ink is prepared as follows: (1) Mixing matrix resins: Add acrylic acid modified phenolic epoxy resin and β-hydroxyethyl acrylate modified melamine formaldehyde resin to a dispersion tank at a mass ratio of 4-1:1, and mix the two resins evenly with a high-speed disperser at 600~1200 r / min. (2) Preparation of color paste: The pigment, resin and dispersant are added to the dispersion tank in a weight ratio of 1-3:7-9:0.01-0.05, and the color paste is mixed evenly with a high-speed disperser at 800-1500 r / min; wherein the resin and the matrix resin have the same composition. (3) Material mixing: According to the mass fraction, the matrix resin, active monomer, UV-curable flame retardant, photoinitiator, color paste and filler are added to the dispersion tank in sequence and mixed at 1300-1800 r / min using a high-speed disperser; (4) Grinding: Grind the mixed material in step (3) three times using a three-roll mill until the ink fineness is less than 8μm, then add defoamer and leveling agent and mix evenly; (5) Filtration: The printing performance and heat resistance of the uniformly mixed material in step (4) are tested. After the test, the viscosity of the ink is adjusted to 100 Pa·s with active monomers and filtered with a 200-mesh filter to finally obtain flame-retardant and high-temperature resistant UV curable solder resist ink.

[0026] It is understandable that the above-mentioned solder resist ink is applied to the printed circuit board by screen printing to form a solder resist coating, and then exposed to ultraviolet light, developed, and cured.

[0027] The present invention will be further described below through examples and other means.

[0028] Example 1: A UV-curable halogen-free flame retardant has the following structural formula (1): (1) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 11.2 g (0.1 mol) of itaconic anhydride, 21.6 g (0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 4.3 g (0.05 mol) of anhydrous piperazine were dissolved in a single-necked flask containing 51.3 mL of N,N-dimethylformamide and reacted at 60 °C for 8 h under reflux to obtain a phosphorus-nitrogen synergistic flame retardant.

[0029] (2) After the reaction in step (1) is completed, 14.2 g (0.1 mol) glycidyl methacrylate is added directly to step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0030] Example 2: A UV-curable halogen-free flame retardant has the following structural formula (2): (2) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 9.8 g (0.1 mol) of maleic anhydride, 21.6 g (0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 4.3 g (0.05 mol) of anhydrous piperazine were dissolved in a single-necked flask containing 45.5 mL of N,N-dimethylacetamide and reacted at 80 °C for 8 h under reflux to obtain phosphoric anhydride.

[0031] (2) After the reaction in step (1) is completed, 9.8 g (0.1 mol) of 1,2-epoxy-5-hexene is added directly to the reaction in step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0032] Example 3: A UV-curable halogen-free flame retardant has the following structural formula (3): (3) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 11.2 g (0.1 mol) of itaconic anhydride, 20.2 g (0.1 mol) of diphenyl phosphorus oxide and 4.3 g (0.05 mol) of anhydrous piperazine were dissolved in a single-necked flask containing 47.1 mL of N,N-dimethylformamide and reacted at 60 °C for 3 h under reflux to obtain a phosphorus-nitrogen synergistic flame retardant; (2) After the reaction in step (1) is completed, 11.4 g (0.1 mol) of allyl glycidyl ether is added directly to the reaction in step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0033] Example 4: A UV-curable halogen-free flame retardant has the following structural formula (4): (4) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 14.0 g (0.1 mol) of allyl succinic anhydride, 20.2 g (0.1 mol) of diphenyl phosphorus oxide and 5.8 g (0.05 mol) of N,N-diethylethylenediamine were dissolved in a single-necked flask containing 49.8 mL of diethylene glycol methyl ether. The mixture was refluxed and reacted at 50 °C for 3 h. The temperature was then raised to 90 °C and the reaction was continued for 4 h to obtain a nitrogen-synergistic flame retardant. (2) After the reaction in step (1) is completed, 9.8 g (0.1 mol) of 1,2-epoxy-5-hexene is added directly to the reaction in step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0034] Example 5: A UV-curable halogen-free flame retardant has the following structural formula (5): (5) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 11.2 g (0.1 mol) of itaconic anhydride, 23.4 g (0.1 mol) of diphenyl phosphite and 4.3 g of anhydrous piperazine were dissolved in a single-necked flask containing 22.4 mL of xylene and reacted at 60 °C for 8 h under reflux to obtain a phosphorus-nitrogen synergistic flame retardant. (2) After the reaction in step (1) is completed, 14.2 g (0.1 mol) glycidyl methacrylate is added directly to step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0035] Comparative Example 1: A UV-curable halogen-free flame retardant, the structural formula of which is shown in formula (D1): (D1) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 13.0 g of itaconic anhydride and 21.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dissolved in a single-necked flask containing 51.3 mL of N,N-dimethylformamide and reacted at 90 °C for 5 h under reflux to obtain phosphoric anhydride. (2) After the reaction in step (1) is completed, 14.2 g glycidyl methacrylate is added directly to the reaction in step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0036] Comparative Example 2: A UV-curable halogen-free flame retardant, the structural formula of which is shown in formula (D2): (D2) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 11.2 g (0.1 mol) of itaconic anhydride, 11.0 g (0.1 mol) of dimethyl phosphite and 4.3 g (0.05 mol) of anhydrous piperazine were dissolved in a single-necked flask containing 22.4 mL of 1,4-dioxane and reacted at 60 °C for 8 h under reflux to obtain a phosphorus-nitrogen synergistic flame retardant; (2) After the reaction in step (1) is completed, 14.2 g (0.1 mol) glycidyl methacrylate is added directly to step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0037] Comparative Example 3: A UV-curable halogen-free flame retardant, the structural formula of which is shown in formula (D3): (D3) The preparation method of the above-mentioned UV-curable halogen-free flame retardant includes the following steps: (1) 11.2 g (0.1 mol) of itaconic anhydride, 13.8 g (0.1 mol) of diethyl phosphite and 4.3 g (0.05 mol) of anhydrous piperazine were dissolved in a single-necked flask containing 22.4 mL of toluene and reacted at 60 °C for 8 h under reflux to obtain a phosphorus-nitrogen synergistic flame retardant; (2) After the reaction in step (1) is completed, 14.2 g (0.1 mol) glycidyl methacrylate is added directly to step (1), and the reaction is continued at 90 °C for 10 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a UV-curable halogen-free flame retardant.

[0038] When using the UV-curable halogen-free flame retardants obtained in Examples 1, 2, 3, 4, and 5, post-treatment can be performed depending on the process requirements. Specifically, the post-treatment involves removing the solvent from the product through vacuum distillation. In all examples of this invention, the solvent was not removed. However, it is understood that laboratory tests showed that removing the solvent resulted in better flame retardant performance, but at the same dosage, the flame retardant without solvent removal also exhibited the same excellent flame retardant performance.

[0039] Application Examples 1-5 Application Examples 1-5 each provide an ink, comprising the flame retardant prepared in Example 1 and other components. The mass of the flame retardant and other components, as well as the raw materials and their mass fractions in the other components, are shown in Table 1. Taking Application Example 2 as an example, the ink of Application Example 2 contains 5g of flame retardant and 100g of other components. The 100g of other components, by mass percentage, includes 50% matrix resin (in which the mass ratio of acrylic-modified phenolic epoxy resin to β-hydroxyethyl acrylate-modified melamine-formaldehyde resin is 4:1), 10% reactive monomer, 4% photoinitiator, 3.4% color paste, 32% filler, 0.3% defoamer, and 0.3% leveling agent.

[0040] The matrix resin was obtained by mixing acrylate-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin according to the proportions in Table 1, and then stirring at 800 r / min; the color paste was prepared by mixing, dispersing and grinding 20 wt% pigment, 79.5 wt% matrix resin and 0.5 wt% dispersant; the filler was silica powder; the photoinitiator was 2-ethylanthraquinone; the active monomer was trimethylolpropane triacrylate; the defoamer was a silicone-containing defoamer; and the leveling agent was a silicone-containing leveling agent.

[0041] The preparation method of the above ink is as follows: S1: According to Table 1, mix the matrix resin, active monomer, flame retardant of Example 1, photoinitiator, color paste and filler in sequence, and mix them evenly at 1500 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: Test the uniformly mixed material in step S2. After passing the test, adjust the viscosity to 100 Pa·s with active monomers, filter, and obtain solder resist ink.

[0042] Application Example 6-7 Application Examples 6-7 each provide an ink comprising the flame retardant prepared in Example 2, the components of which are shown in Table 1 (the meanings of the corresponding values ​​for each raw material in Table 1 are the same as in Application Example 2). The types or parameters of each component are the same as in Application Example 1.

[0043] The preparation method of the above ink is as follows: S1: According to Table 1, mix the matrix resin, active monomer, flame retardant of Example 2, photoinitiator, color paste and filler in sequence, and mix them evenly at 1500 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: The material that was mixed evenly in step S2 was tested. After passing the test, the viscosity was adjusted to 100 Pa·s with active monomers and filtered to obtain the solder resist inks of Application Example 6 and Application Example 7, respectively.

[0044] Application Example 8-9 Application Examples 8-9 each provide an ink comprising the flame retardant prepared in Example 3, the composition of which is shown in Table 1 (the meaning of the corresponding values ​​of each raw material in Table 1 is the same as in Application Example 2). The type or parameters of each component are the same as in Application Example 1.

[0045] The preparation method of the above ink is as follows: S1: According to Table 1, mix the matrix resin, active monomer, flame retardant of Example 3, photoinitiator, color paste and filler in sequence, and mix them evenly at 1500 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: The material that was mixed evenly in step S2 was tested. After passing the test, the viscosity was adjusted to 100 Pa·s with active monomers and filtered to obtain the solder resist inks of Application Example 8 and Application Example 9, respectively.

[0046] Application Example 10-11 Application Examples 10-11 each provide an ink comprising the flame retardant prepared in Example 4, the components of which are shown in Table 1 (the meanings of the corresponding values ​​for each raw material in Table 1 are the same as in Application Example 2). The types or parameters of each component are the same as in Application Example 1.

[0047] The preparation method of the above ink is as follows: S1: According to Table 1, mix the matrix resin, active monomer, flame retardant of Example 4, photoinitiator, color paste and filler in sequence, and mix them evenly at 1500 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: The material that was mixed evenly in step S2 was tested. After passing the test, the viscosity was adjusted to 100 Pa·s with active monomers and filtered to obtain the solder resist inks of Application Example 10 and Application Example 11, respectively.

[0048] Application Example 12-13 Application Examples 12-13 each provide an ink comprising the flame retardant prepared in Example 5, the components of which are shown in Table 1 (the meanings of the corresponding values ​​for each raw material in Table 1 are the same as in Application Example 2). The types or parameters of each component are the same as in Application Example 1.

[0049] The preparation method of the above ink is as follows: S1: According to Table 1, mix the matrix resin, active monomer, flame retardant of Example 5, photoinitiator, color paste and filler in sequence, and mix them evenly at 1500 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: The material that was mixed evenly in step S2 was tested. After passing the test, the viscosity was adjusted to 100 Pa·s with active monomers and filtered to obtain the solder resist inks of Application Example 12 and Application Example 13, respectively.

[0050] Table 1. Raw materials and content of each application example corresponding to the embodiments.

[0051] Comparative Application Examples 1-3 Comparative Application Examples 1-3 each provide an ink comprising the flame retardant prepared in Comparative Examples 1-3, the proportions of which are shown in Table 2 (the meanings of the corresponding values ​​for each raw material in Table 1 are the same as in Application Example 2). The base resin is obtained by mixing acrylate-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin according to the proportions in Table 1, followed by stirring at 800 r / min. The color paste is prepared by mixing, dispersing, and grinding 20 wt% pigment, 79.5 wt% base resin, and 0.5 wt% dispersant. The filler is silica powder. The photoinitiator is 2-ethylanthraquinone. The active monomer is trimethylolpropane triacrylate. The defoamer is a silicone-containing defoamer. The leveling agent is a silicone-containing leveling agent.

[0052] The preparation method of the ink is basically the same as that of Application Example 1, except that the raw materials used and the proportions of each raw material are the same as those in this comparative example.

[0053] Table 2: Raw materials and content of application examples corresponding to the comparative examples

[0054] Test example: The performance of the inks obtained from corresponding use cases and comparative application examples was tested using the following methods: ① Pencil hardness was tested according to GB / T 6739-2006, "Determination of Hardness of Paints and Varnishes by Pencil Method"; ② The adhesion of the coating was determined using an HGQ type cross-cut tester according to GB / T 9268-1998. If the area of ​​coating peeling off was less than 5%, the adhesion performance was deemed satisfactory. Otherwise, it is ×; ③ The temperature resistance test is the temperature data that the sample coated with solder resist ink can withstand in a 10-second, three-time solder resistance test according to GB / T 4677-2002; ④ Immerse the application example coating in 10 vol% H2SO4 and 10 wt% NaOH for 30 min, wash it with clean water and dry it. Apply 3M tape (610#) three times. If there is no oil residue, it indicates that the acid and alkali resistance test is satisfactory. Otherwise, it is ×; ⑤ Flame retardancy is tested according to GB / T 22472-2008: the mixed resin is prepared into a 125 mm × 13 mm × 3 mm sample for vertical burning test, and the flame retardancy level of the material is classified according to the test results and with reference to Table 3.

[0055] Table 3. Flame Retardant Test Material Classification Table

[0056] The test results are shown in the table below.

[0057] Table 4 Performance Tests of Each Application Example and Comparative Application Examples

[0058] As shown in Table 4, the flame retardant used in Application Examples 1, 2, 3, and 5 was the same flame retardant prepared in Example 1, and the addition amount was 5 wt% for all examples. The only difference was the proportion of the base resin. By changing the proportion of the base resin, it was found that the higher the proportion of the β-hydroxyethyl acrylate modified melamine-formaldehyde resin component, the better the flame retardant performance of the coating was, the higher the pencil hardness of the coating, and the better its heat resistance. The only difference between Application Examples 4 and 5 was the amount of flame retardant added, with 3 wt% and 5 wt% of the flame retardant prepared in Example 1 added, respectively. The results showed that the UL-94 rating of Application Example 4 was only V-1, while the UL-94 test rating of Application Example 5 reached V-0, indicating that under the same formulation conditions, the higher the amount of flame retardant added, the better the flame retardant performance of the coating. Application Examples 5, 7, 9, 11, 13, 14, 15, and 16 all had the same formulation and flame retardant addition amount, differing only in the type of flame retardant. Among them, the coatings obtained in Application Examples 5, 7, 9, 11, and 13 exhibited good flame retardant properties, achieving a UL-94 V-0 rating, while Application Examples 14, 15, and 16 showed poorer flame retardant properties, only achieving a UL-94 V-2 rating. This is because the flame retardants used in Application Examples 5, 7, 9, and 11 contained both phosphorus-containing and nitrogen-containing structures. The phosphorus-containing structure decomposed during combustion, generating phosphorus-oxygen free radicals that quenched flammable free radicals. Simultaneously, the resulting phosphoric acid substances promoted the dehydration and char formation of the matrix. Furthermore, the non-flammable nitrogen-containing gas generated by the decomposition of the nitrogen-containing structure diluted flammable free radicals and oxygen, and the benzene ring structure provided a large amount of graphitized carbon layer. Although the phosphorus-containing structure in the flame retardant used in Application Example 13 produces fewer phosphorus-containing free radicals during combustion, it provides a large amount of aromatic structures as a high-quality char source. Therefore, the coatings in Application Examples 5, 7, 9, 11, and 13 all exhibit good flame-retardant properties. In contrast, the flame retardant used in the coating of Comparative Application Example 1 does not contain nitrogen, thus lacking gas-phase interaction during the flame-retardant process, resulting in a less significant flame-retardant effect. The coatings in Comparative Application Examples 2 and 3 show poor flame-retardant properties, mainly because the phosphorus in dimethyl phosphite and diethyl phosphite only functions in the condensed phase during combustion, with insignificant gas-phase interaction. Furthermore, the two phosphorus-containing monomers provide insufficient char sources, thus failing to provide good flame-retardant properties. In addition, these two monomers have lower decomposition temperatures, fewer rigid structures in their molecules, and poorer heat resistance, further hindering their ability to provide good overall performance. In summary, flame retardants prepared by combining phosphorus-containing structures with nitrogen-containing structures containing aromatic groups provide the best flame retardant performance, indicating that the synergistic effect of phosphorus and nitrogen elements in the flame retardant process can more effectively improve the flame retardant performance of coatings.

[0059] This invention provides a halogen-free flame retardant that can be cured by ultraviolet light through a low-cost and simple process. While providing good flame retardant properties for solder resist inks to meet the requirements of welding, it can also ensure good processing performance and heat resistance.

[0060] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A UV-curable halogen-free flame retardant, characterized in that, The general structural formula of the UV-curable halogen-free flame retardant is shown below: 。 2. A method for preparing the UV-curable halogen-free flame retardant according to claim 1, characterized in that, Includes the following steps: (1) Dissolve phosphorus-containing monomers, unsaturated acid anhydrides and secondary amine monomers in an organic solvent in sequence, stir and react at 40-90 °C for 0.5-5 h, and then stir and react at 60-110 °C for 2-5 h to obtain a phosphorus-nitrogen synergistic flame retardant. (2) At 60-100℃, add the monomer containing unsaturated groups to the phosphorus-nitrogen synergistic flame retardant of step (1), heat to react, and cool to room temperature after the reaction is completed to obtain the UV-curable flame retardant; In step (1), the phosphorus-containing monomer is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; The unsaturated acid anhydride is maleic anhydride; The secondary amine monomer is piperazine; In step (2), the monomer containing unsaturated groups is 1,2-epoxy-5-hexene.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of the phosphorus-containing monomer, unsaturated acid anhydride and secondary amine monomer is 2-2.5:2:

1.

4. The preparation method according to claim 2, characterized in that, In step (1), the organic solvent includes at least one of toluene, xylene, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, diethylene glycol methyl ether, and dimethyl sulfoxide.

5. The preparation method according to claim 2, characterized in that, In step (2), The molar ratio of the phosphorus-nitrogen synergistic flame retardant to the monomer containing unsaturated groups is 1:2-2.2; And / or, the heating reaction is carried out at a temperature of 80-120 °C for a time of 2-10 h.

6. A solder resist ink, characterized in that, It includes a UV-curable flame retardant and other components, which, by mass percentage, include the following raw material components: 30-55% matrix resin, 2-25% active monomer, 1-8% photoinitiator, 1-5% color paste, 5-40% filler, and 1-5% additives. The UV-curable flame retardant is the UV-curable halogen-free flame retardant according to claim 1, or the UV-curable halogen-free flame retardant prepared by the preparation method according to any one of claims 2-5; The mass ratio of the UV-curable flame retardant to the other components is 3-5:

100.

7. The solder resist ink according to claim 6, characterized in that, The matrix resin includes at least one of acrylate-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin; The active monomers include one or more of trimethylolpropane triacrylate, β-hydroxyethyl methacrylate, tripropylene glycol diacrylate, and pentaerythritol triacrylate; The photoinitiator includes one or more of 2-ethylanthraquinone, benzoin diethyl ether 651, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone; The color paste is prepared by mixing, dispersing, and grinding pigments, resins, and dispersants in a weight ratio of 1-3:7-9:0.01-0.

05. Wherein, the resin is the same as the matrix resin; the dispersant includes at least one of polyacrylate and polyamide-modified polymeric carboxylate dispersants; The filler includes one or more of silica powder, talc powder, fumed silica, and barium sulfate; The additives include one or both of defoamers and leveling agents.

8. The solder resist ink according to claim 6, characterized in that, The matrix resin is obtained by mixing acrylate-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin.

9. The solder resist ink according to claim 6, characterized in that, The weight ratio of the acrylate-modified phenolic epoxy resin to the β-hydroxyethyl acrylate-modified melamine-formaldehyde resin is 4-1:

1.

10. A method for preparing the solder resist ink according to any one of claims 6-9, characterized in that, The preparation method includes the following steps: S1: According to the proportion of each raw material, mix the matrix resin, active monomer, UV-curable flame retardant, photoinitiator, color paste and filler in sequence, and mix them evenly at 1300-1800 r / min. S2: Grind the mixed material from step S1 to a fineness of less than 8 μm, then add the additives and mix evenly; S3: Test the uniformly mixed material in step S2. After passing the test, adjust the viscosity to 100 Pa·s with active monomers, filter, and obtain solder resist ink. In step S1, the matrix resin is obtained by mixing acrylic acid-modified phenolic epoxy resin and β-hydroxyethyl acrylate-modified melamine-formaldehyde resin at a speed of 600-1200 r / min.

11. The application of the solder resist ink according to any one of claims 6-9, or the solder resist ink prepared by the preparation method of claim 10, characterized in that, The solder resist ink is used to prepare a solder resist coating.

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