Sealing resin composition for injection molding

Abstract

The sealing resin composition for injection molding of the present application contains a thermosetting resin, a curing agent, an inorganic filler, and an imidazole catalyst, and in a DSC curve obtained using a differential scanning calorimeter when raising the temperature from 30°C to 330°C at a temperature raising rate of 10°C / min, the peak temperature of the largest exothermic peak is 155°C or higher and less than 175°C, and the half-value width of the largest exothermic peak, which is calculated using a straight line connecting a point at which the heat flow before the largest exothermic peak is the smallest and a point at which the heat flow after the largest exothermic peak is the smallest as a baseline, is 32°C or less.

Description

Technical Field

[0001] This invention relates to a sealing resin composition for injection molding. Background Technology

[0002] Various studies have been conducted with the aim of stabilizing the heat treatment in the extruder for injection molding. For example, the technology described in Patent Document 1 can be cited as such a technology. According to this document, excellent thermal stability within the molding machine barrel is achieved by incorporating one or more specified dimethylurea curing accelerators.

[0003] Furthermore, Patent Document 2 describes an epoxy resin composition containing a specified epoxy resin, a phenolic curing agent, a curing catalyst, and an inorganic filler. When differential scanning calorimetry is performed on this epoxy resin composition at a heating rate of 10°C / min, the exothermic peak is above 150°C. According to this document, the cured product composed of this epoxy resin composition exhibits excellent high Tg properties, long-term weight retention at high temperatures, and retention of mechanical strength, and the epoxy resin composition also possesses excellent flowability.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-106771

[0007] Patent Document 2: International Publication No. 2014 / 065152 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, in the prior art described in Patent Documents 1 and 2, during the heat treatment in the extruder for injection molding, solidification occurs from the mixing zone to the nozzle zone in the injection molding process, which may result in poor mixing or blockage of the mold runner.

[0010] Therefore, the technical problem to be solved by the present invention is to provide a sealing resin composition for injection molding that is stable to heat treatment in the extruder of injection molding and does not produce the adverse phenomena described above, thereby shortening the molding cycle.

[0011] Means for solving technical problems

[0012] The inventors of this invention discovered that by ensuring the half-width of the maximum exothermic peak in the DSC curve obtained using a differential scanning calorimeter is within a specified range, the above-mentioned technical problem can be solved, thus completing this invention.

[0013] That is, the present invention can be described as follows.

[0014] According to the present invention, a sealing resin composition for injection molding is provided, comprising (A) a thermosetting resin, (B) a curing agent, (C) an inorganic filler, and (D) a curing accelerator. In the DSC curve obtained by using a differential scanning calorimeter at a heating rate of 10°C / min from 30°C to 330°C, the peak temperature of the maximum exothermic peak is 155°C or higher and less than 175°C. The half-width of the maximum exothermic peak, calculated using the straight line connecting the point of minimum heat flow before the maximum exothermic peak and the point of minimum heat flow after the maximum exothermic peak as a baseline, is 32°C or lower.

[0015] According to the present invention, a structure is provided comprising a cured product of the injection molding sealing resin composition.

[0016] Invention Effects

[0017] The sealing resin composition for injection molding of the present invention has excellent balanced thermal stability and curability, and therefore is stable to heat treatment in the extruder of injection molding, and is suitable for use as a sealing resin composition for injection molding with short molding cycles. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram illustrating an example of an in-vehicle electronic control unit according to an embodiment.

[0019] Figure 2 The DSC curves were obtained by DSC measurement of the sealing resin composition for injection molding in Example 1. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Furthermore, in all the drawings, the same reference numerals are used to refer to the same constituent elements, and descriptions are appropriately omitted. And, unless otherwise stated, “~” indicates “above” to “below”.

[0021] The sealing resin composition for injection molding in this embodiment comprises a thermosetting resin (A), a curing agent (B), an inorganic filler (C), and a curing accelerator (D). In the DSC curve obtained by using a differential scanning calorimeter to heat from 30°C to 330°C at a heating rate of 10°C / min, the peak temperature of the maximum exothermic peak is 155°C or higher and less than 175°C, preferably 155°C or higher and less than 170°C, more preferably 155°C or higher and less than 168°C. The half-width of the maximum exothermic peak, calculated using the straight line connecting the point of minimum heat flow before the maximum exothermic peak and the point of minimum heat flow after the maximum exothermic peak as a baseline, is 32°C or lower, preferably 30°C or lower. The lower limit is not particularly limited and is 20°C or higher.

[0022] The inventors focused on the maximum exothermic peak temperature in the DSC curve of the sealing resin composition and discovered that by using its half-width at half-maximum (WWHM) as an indicator, the thermal stability and curability of the sealing resin composition during the molding process, as well as their balance, can be evaluated. Based on this insight, further in-depth research was conducted, and it was found that by keeping the WWHM of the maximum exothermic peak temperature below a specified value, an excellent balance between thermal stability and curability is achieved. Therefore, curing can be controlled from the mixing zone to the nozzle zone in injection molding, suppressing poor mixing and mold runner blockage, stabilizing the heat treatment in the extruder for injection molding of the sealing resin composition, and improving the molding cycle, thus completing this invention.

[0023] Furthermore, from the viewpoint of the effects of the present invention, when the torque value of the injection molding sealing resin composition of this embodiment is measured over time at a rotation speed of 30 rpm and a measurement temperature of 130°C using a Labo Plastomill, the time T1 during which the torque value is less than or equal to twice the minimum torque value a is 65 seconds to 200 seconds, preferably 90 seconds to 180 seconds, and more preferably 110 seconds to 170 seconds. Also, when the torque value is measured over time at a rotation speed of 30 rpm and a measurement temperature of 150°C, the time T1′ during which the torque value is less than or equal to twice the minimum torque value b is 35 seconds to 150 seconds, preferably 40 seconds to 120 seconds, and more preferably 45 seconds to 100 seconds.

[0024] By controlling the behavior of torque variation measured under specific conditions using the Labo Plastomill, it is possible to further improve the balance between shelf life and filling properties with curing properties and connection reliability at room temperature.

[0025] In this embodiment, from the viewpoint of the effects of the present invention, the minimum torque value a is 0.5 N·m or more and 10 N·m or less, preferably 0.8 N·m or more and 5.0 N·m or less, more preferably 1.0 N·m or more and 2.8 N·m or less, and the minimum torque value b is 0.1 N·m or more and 4 N·m or less, preferably 0.2 N·m or more and 2.5 N·m or less, more preferably 0.5 N·m or more and 2 N·m or less.

[0026] By controlling the curing properties measured by the Labo Plastomill in this way, it is possible to achieve a sealing resin composition for injection molding that has excellent filling properties, suppresses the generation of unfilled portions, and improves the molding cycle, i.e., a resin molding material with excellent moldability.

[0027] In addition, the peak temperature of the maximum exothermic peak in the DSC curve, the half-width of the maximum exothermic peak, and the temperature reaching T as measured by the vulcanizer are also important factors.10 Time and reaching T 90 The time can be controlled, for example, by appropriately adjusting the type and / or content of each component in the sealing resin composition for injection molding, the particle size distribution of the resin molding material, etc. In this embodiment, for example, adjusting the type and / or content of thermosetting resin, curing agent, inorganic filler, and imidazole catalyst can be used.

[0028] Furthermore, the peak temperature of the maximum exothermic peak in the DSC curve can also be shifted towards a lower temperature by adjusting the mixing conditions (temperature and time) of the sealing resin composition for injection molding.

[0029] The composition of the sealing resin composition for injection molding according to this embodiment will be described.

[0030] [Thermosetting resin (A)]

[0031] The thermosetting resin (A) includes, for example, one or more selected from epoxy resin, phenolic resin, oxetane resin, (meth)acrylate resin, unsaturated polyester resin, diallyl phthalate resin, and maleimide resin. Of these, epoxy resin is particularly preferred from the viewpoint of improving curability, shelf life, heat resistance, moisture resistance, and chemical resistance.

[0032] As the epoxy resin included in the thermosetting resin (A), any monomer, oligomer, or polymer having two or more epoxy groups within a molecule can be used, and its molecular weight and molecular structure are not particularly limited. In this embodiment, the epoxy resin includes, for example, one or more epoxy resins selected from the following: biphenyl-type epoxy resin; bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and tetramethylbisphenol F-type epoxy resin; piracene-type epoxy resin; phenolic varnish-type epoxy resins such as phenolic varnish-type epoxy resin and o-cresol phenolic varnish-type epoxy resin; multifunctional epoxy resins such as triphenolic methane-type epoxy resin and alkyl-modified triphenolic methane-type epoxy resin; and phenolic aralkyl-type epoxy resin having a phenylene backbone. Phenolic alkyl epoxy resins include phenolic alkyl epoxy resins such as naphthol alkyl-type epoxy resins with a phenylene backbone, phenolic alkyl-type epoxy resins with a biphenylene backbone, and naphthol alkyl-type epoxy resins with a biphenylene backbone; naphthol-type epoxy resins include dihydroxynaphthalene-type epoxy resins and epoxy resins obtained by glycidyl etherification of dihydroxynaphthalene dimers; epoxy resins containing triazine cores such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and phenolic epoxy resins modified with bridged cyclic hydrocarbon compounds such as dicyclopentadiene-modified phenolic epoxy resins.

[0033] From the viewpoint of the effects of the present invention, it is preferable to include one or more of o-cresol phenolic varnish epoxy resin, phenolic phenolic varnish epoxy resin and bisphenol A type epoxy resin.

[0034] The epoxy resin is preferably a multifunctional epoxy resin having three or more epoxy groups in the repeating structure of the epoxy resin backbone. By using a multifunctional epoxy resin, the glass transition temperature of the cured product can be increased.

[0035] There are no particular limitations on multifunctional epoxy resins; examples include tetraphenylethane-type epoxy resins, 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-(2,3-epoxypropoxy)phenyl]ethyl]phenyl]propane, tetra(glycidoxyphenyl)ethane, α-2,3-epoxypropoxyphenyl-ω-hydrogenated poly(n=1~7){2-(2,3-epoxypropoxy)benzyl-2,3-epoxypropoxyphenylene}, etc. These can be used alone or in combination.

[0036] As a multifunctional epoxy resin, tetraphenylethane-type epoxy resin is preferred.

[0037] In this embodiment, the thermosetting resin (A) is more preferably selected from one or more of o-cresol phenolic varnish type epoxy resin, phenolic phenolic varnish type epoxy resin, bisphenol A type epoxy resin and tetraphenylethane type epoxy resin as the epoxy resin.

[0038] The sealing resin composition for injection molding in this embodiment does not contain epoxy resin represented by the following general formula (1).

[0039]

[0040] In general formula (1), the average value of n is 0.2 to 4.0, and G represents glycidyl group.

[0041] The content of thermosetting resin (A) in the injection molding sealing resin composition is preferably 2% by mass or more, more preferably 3% by mass or more, and particularly preferably 4% by mass or more, relative to the total amount of the injection molding sealing resin composition. By setting the content of thermosetting resin (A) to the lower limit value mentioned above, the flowability during molding can be improved. Therefore, the shelf life at room temperature is better, and the filling performance and molding stability can be further improved. On the other hand, the content of thermosetting resin (A) in the injection molding sealing resin composition is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 15% by mass or less, relative to the total amount of the injection molding sealing resin composition. By setting the content of thermosetting resin (A) to the upper limit value mentioned above, the heat treatment in the extruder for injection molding is stabilized, and the molding cycle can be shortened.

[0042] The content of thermosetting resin (A) in the sealing resin composition for injection molding can be arbitrarily combined with the above-mentioned lower limit and upper limit. For example, it is preferably 2% by mass or more and 50% by mass or less relative to the total of the sealing resin composition for injection molding, more preferably 3% by mass or more and 30% by mass or less, and especially preferably 4% by mass or more and 15% by mass or less.

[0043] [Curing Agent (B)]

[0044] As curing agents (B), they can be broadly classified into three types: addition-polymerization curing agents, catalyst-type curing agents, and condensation-type curing agents.

[0045] The addition-polymerization curing agent used as curing agent (B) contains, for example, one or more substances selected from the following: polyamine compounds, including aliphatic polyamines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and m-phenylenediamine (MXDA); aromatic polyamines such as diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenyl sulfone (DDS); and dicyandiamide (DICY), organic acid dihydrazides, etc.; acid anhydrides, including hexahydrophthalic anhydride (… Alicyclic anhydrides such as HHPA, methyltetrahydrophthalic anhydride (MTHPA), aromatic anhydrides such as trimellitic anhydride (TMA), pyromellitic tetracarboxylic anhydride (PMDA), and benzophenone tetracarboxylic dianhydride (BTDA); phenolic resin curing agents such as phenolic varnish-type phenolic resin, polyvinylphenol, and aralkyl-type phenolic resin; polysulfides, thioesters, thioethers, and other polythiol compounds; isocyanate prepolymers, end-capped isocyanates, and other isocyanate compounds; and organic acids such as carboxylic acid-containing polyester resins.

[0046] The catalyst-type curing agent used as curing agent (B) includes, for example, one or more Lewis acids selected from tertiary amine compounds such as benzyl dimethylamine (BDMA) and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30); and BF3 coordination compounds.

[0047] The condensation-type curing agent used as curing agent (B) includes, for example, one or more of the following: methyl phenolic resin; urea resin containing hydroxymethyl urea resin, etc.; melamine resin containing hydroxymethyl melamine resin, etc.

[0048] From the perspective of improving the balance of flame retardancy, moisture resistance, electrical properties, curing properties, and storage stability, phenolic resin curing agents are preferred. As phenolic resin curing agents, all monomers, oligomers, and polymers having two or more phenolic hydroxyl groups within one molecule can be used, and their molecular weight and molecular structure are not particularly limited. Phenolic resin curing agents used as curing agents (B) include, for example, one or more substances selected from the following: phenolic varnish resins such as phenolic varnish resins, cresol varnish resins, and bisphenol varnish resins; polyvinylphenol; multifunctional phenolic resins such as triphenolmethane-type phenolic resins; modified phenolic resins such as terpene-modified phenolic resins and dicyclopentadiene-modified phenolic resins; phenolic aralkyl resins such as phenolic resins having a phenylene skeleton and / or a biphenylene skeleton, and naphthol aralkyl resins having a phenylene skeleton and / or a biphenylene skeleton; and bisphenol compounds such as bisphenol A and bisphenol F. From the viewpoint of improving the curability of the sealing resin composition for injection molding, it is more preferable to include at least one of phenolic varnish-type phenolic resin and phenolic alkyl-type phenolic resin.

[0049] The content of curing agent (B) in the sealant composition for injection molding is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, relative to the total sealant composition for injection molding. By setting the content of curing agent (B) to the lower limit mentioned above, better shelf life at room temperature is achieved, and excellent flowability during molding is realized, improving filling and moldability. On the other hand, the content of curing agent (B) in the sealant composition for injection molding is preferably 40% by mass or less, more preferably 25% by mass or less, and particularly preferably 10% by mass or less, relative to the total sealant composition for injection molding. By setting the content of curing agent (B) to the upper limit mentioned above, heat treatment in the extruder for injection molding is stabilized, and the molding cycle can be shortened.

[0050] The content of curing agent (B) in the sealant composition for injection molding can be arbitrarily combined with the above-mentioned lower limit and upper limit. For example, it is preferably 1% by mass or more and 40% by mass or less relative to the total sealant composition for injection molding, more preferably 2% by mass or more and 25% by mass or less, and especially preferably 3% by mass or more and 10% by mass or less.

[0051] [Inorganic filler (C)]

[0052] The sealing resin composition for injection molding in this embodiment contains an inorganic filler (C).

[0053] As an inorganic filler (C), it may include, for example, one or more selected from silica such as glass fiber, molten silica, and crystalline silica, alumina, aluminum hydroxide, magnesium hydroxide, calcium carbonate, silicon nitride, and aluminum nitride. From the viewpoint of excellent versatility, it is preferable to include glass fiber, molten silica, and calcium carbonate, and more preferably, it includes glass fiber and molten silica.

[0054] The inorganic filler (C), in particular by including molten and crushed silica, can reduce the manufacturing cost of the vehicle-mounted electronic control unit 10. When the inorganic filler (C) includes crushed silica, the content of crushed silica can be, for example, more than 10% by weight and less than 95% by weight relative to the total inorganic filler (C), more preferably more than 15% by weight and less than 90% by weight.

[0055] When the inorganic filler (C) contains silica, it is preferable to contain, for example, an average particle size D. 50 It is silica with a particle size of 1μm to 50μm. This allows for a more effective improvement in the balance of filling properties, adhesion, moisture resistance, and heat resistance. Furthermore, the average particle size D of the silica... 50 For example, a commercially available laser particle size analyzer (such as the SALD-7000 manufactured by Shimadzu Corporation) can be used for measurement.

[0056] The content of inorganic filler (C) in the injection molding sealant composition is preferably 50% by weight or more, more preferably 60% by weight or more, relative to the total volume of the injection molding sealant composition. By setting the content of inorganic filler (C) to the lower limit or above, low moisture absorption and low thermal expansion can be improved, and the moisture resistance and reflow soldering resistance of automotive electronic control units can be improved more effectively. On the other hand, the content of inorganic filler (C) in the injection molding sealant composition is preferably 90% by weight or less, more preferably 85% by weight or less, relative to the total volume of the injection molding sealant composition. By setting the content of inorganic filler (C) to the upper limit or below, the flowability and filling properties of the injection molding sealant composition can be improved more effectively.

[0057] The content of inorganic filler (C) in the sealant composition for injection molding can be any combination of the lower and upper limits mentioned above. For example, it is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less, relative to the total sealant composition for injection molding.

[0058] [Curing Accelerator (D)]

[0059] The sealing resin composition for injection molding in this embodiment includes a curing accelerator (curing catalyst) (D). The curing accelerator (D) can be any substance capable of promoting the crosslinking reaction between the thermosetting resin (A) and the curing agent (B), and known curing accelerators can be used.

[0060] Examples of curing accelerators (D) include imidazole, 2-undecylimidazolium, 2-heptadecaylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium (EMI24), 2-phenylimidazolium, 2-phenyl-4-methylimidazolium (2P4MZ), 1-benzyl-2-phenylimidazolium, 1-benzyl-2-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trioxide, 1-cyanoethyl-2-phenylimidazolium trioxide, 2,4-diamino-6-[2'-methylimidazoline(1')]-ethyl-triazine, and 2,4-diamino-6-[2'-undecylimidazolium trioxide]. Imidazole catalysts such as [2'-(2-methyl-1-imidazoline)ethyl-triazine]-ethyl-triazine, 2,4-diamino-6-[2'-ethyl-4-methylimidazoline(1')]-ethyl-triazine, isocyanuric acid adducts of 2,4-diamino-6-[2'-methylimidazoline(1')]-ethyl-triazine, isocyanuric acid adducts of 2-phenylimidazolium, isocyanuric acid adducts of 2-methylimidazolium, 2-phenyl-4,5-dihydroxydimethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2-phenyl-4,5-dihydroxymethylimidazolium, 2,4-diamino-6-[2-(2-methyl-1-imidazoline)ethyl]-1,3,5-triazine; urea catalysts such as 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), N,N'-dimethylurea, etc. These can be used individually or in combination of two or more.

[0061] From the viewpoint of improving low-temperature curing and filling properties, it is preferable to contain one or more of 2-phenyl-4,5-dihydroxymethylimidazolium, 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea) and N,N'-dimethylurea.

[0062] Furthermore, from the viewpoint of balancing low-temperature curing properties and filling properties, the functional groups of the curing accelerator (D) are preferably three or less, and more preferably two or less.

[0063] The sealing resin composition for injection molding in this embodiment does not contain dimethylurea curing accelerators represented by the following chemical formulas (1) to (3).

[0064]

[0065] In this embodiment, the lower limit of the content of the curing accelerator (D) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more, relative to the total solids content of the sealant composition for injection molding. By setting the content of the curing accelerator to the above-mentioned lower limit or above, the curability during molding can be effectively improved. On the other hand, the upper limit of the content of the curing accelerator (D) is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less, relative to the total solids content of the sealant composition for injection molding. By setting the content of the curing accelerator to the above-mentioned upper limit or less, the fluidity during molding can be improved.

[0066] The content of the curing accelerator (D) in the sealant composition for injection molding can be arbitrarily combined with the above-mentioned lower limit and upper limit. For example, it is preferably 0.1% by mass or more and 3.0% by mass or less relative to the total solid content of the sealant composition for injection molding, more preferably 0.2% by mass or more and 2.0% by mass or less, and especially preferably 0.3% by mass or more and 1.5% by mass or less.

[0067] Furthermore, the lower limit of the content of the curing accelerator (D) relative to the total solids content of the epoxy resin is preferably 3.5% by mass or more, more preferably 4.0% by mass or more, and particularly preferably 5.0% by mass or more. By setting the content of the curing accelerator (D) to the above-mentioned lower limit or above, the low-temperature curing property during molding can be effectively improved. On the other hand, the upper limit of the content of the curing accelerator (D) relative to the total solids content of the epoxy resin is preferably 12.0% by mass or less, more preferably 11.0% by mass or less, and particularly preferably 10.0% by mass or less. By setting the content of the curing accelerator (D) to the above-mentioned upper limit or less, the fluidity during molding can be improved.

[0068] The content of the curing accelerator (D) in the sealing resin composition for injection molding can be arbitrarily combined with the above-mentioned lower limit and upper limit. For example, it is preferably 3.5% by mass or more and 12.0% by mass or less relative to the total solid content of epoxy resin, more preferably 4.0% by mass or more and 11.0% by mass or less, and especially preferably 5.0% by mass or more and 10.0% by mass or less.

[0069] (Other ingredients)

[0070] In the sealing resin composition for injection molding of this embodiment, one or more of various additives such as release agents, colorants, ion traps, oils, stress reducers, and flame retardants may be appropriately added as needed.

[0071] The release agent may include, for example, one or more selected from natural waxes such as carnauba wax, synthetic waxes such as lignite ester wax or oxidized polyethylene wax, higher fatty acids such as zinc stearate and their metal salts, and paraffin wax. The colorant may include, for example, any one or both of carbon black and black titanium dioxide.

[0072] Ion scavengers may include, for example, hydrotalcite. Oils may include, for example, silicone oil. Stress-reducing agents may include, for example, silicone rubber. Flame retardants may include, for example, one or more selected from magnesium hydroxide, zinc borate, zinc molybdate, and phosphazene.

[0073] Antioxidants may include one or more of the following: aromatic amine antioxidants, hindered phenolic antioxidants, hindered amine antioxidants, sulfur-containing antioxidants, and phosphorus-containing antioxidants.

[0074] As a hindered phenolic antioxidant, octadecyl 3-(4′-hydroxy-3′,5′-di-tert-butylphenyl)propionate is preferred.

[0075] The content of antioxidant in the sealant composition for injection molding is preferably 0.05% by mass or more and 2.0% by mass or less relative to the total amount (100% by mass) of the sealant composition for injection molding, and more preferably 0.1% by mass or more and 1.0% by mass or less. By keeping the content of antioxidant within the above range, the deterioration of the sealant composition for injection molding can be suppressed during the molding process.

[0076] <Sealant Composition for Injection Molding>

[0077] The sealant composition for injection molding of this embodiment can be obtained by mixing the above-mentioned components using existing known methods. The cured product (sealant) obtained by heating and curing the sealant composition for injection molding of this embodiment is composed of the above-mentioned formulation, therefore, it has excellent mechanical strength and the generation of cracks is suppressed.

[0078] As a structure of the cured product of the injection molding sealing resin composition of this embodiment, an example is an electronic control unit for vehicles.

[0079] [Vehicle-mounted electronic control unit]

[0080] The vehicle-mounted electronic control unit 10 is used to control the engine and various vehicle-mounted devices, such as... Figure 1As shown, the vehicle-mounted electronic control unit 10 includes, for example, a wiring board 12; a plurality of electronic components 16 mounted on at least one side of the wiring board 12; and a sealing resin 14 sealing the electronic components 16. The wiring board 12 has a connection terminal 18 for external connection on at least one side. In one example of this embodiment, the vehicle-mounted electronic control unit 10 is electrically connected to the aforementioned target connector via the connection terminal 18 by fitting the connection terminal 18 and the target connector.

[0081] Wiring board 12, for example, is a wiring board on one or both of one side and the other side opposite to that side, where circuit wiring is provided. Figure 1 As shown, the wiring substrate 12 has, for example, a flat plate shape. In this embodiment, an organic substrate formed of an organic material such as polyimide can be used as the wiring substrate 12. The wiring substrate 12 may, for example, have a through-hole 120 that connects one side and the other side through the wiring substrate 12. In this case, the wiring provided on one side of the wiring substrate 12 and the wiring provided on the other side are electrically connected via a conductor pattern provided in the through-hole 120.

[0082] The wiring substrate 12 has a solder resist layer on one side, for example, where the electronic component 16 is mounted. This solder resist layer can be formed using a solder resist forming resin composition commonly used in the semiconductor device field. In this embodiment, for example, solder resist layers can be provided on both one side and the other side of the wiring substrate 12.

[0083] The solder resist layer provided on one side or both sides of the wiring substrate 12 is formed, for example, from a resin composition containing an organosilicon compound. This allows for the creation of a solder resist layer with excellent surface smoothness.

[0084] In the manufacture of the vehicle electronic control unit 10, it is sometimes difficult to improve the adhesion of the sealing resin to the wiring substrate on which a solder resist layer containing an organosilicon compound or the like is formed on the top layer. In this embodiment, an injection molding sealing resin composition containing a thermosetting resin and an imidazole compound, and whose behavior is controlled by measuring torque changes under specific conditions using a Labo Plastomill, is used. Therefore, as described above, even when a solder resist layer containing an organosilicon compound or the like is provided on the top layer of the wiring substrate 12, it is possible to improve the balance between the filling properties of the injection molding sealing resin composition and the adhesion of the sealing resin 14 to the wiring substrate 12.

[0085] like Figure 1As shown, multiple electronic components 16 are respectively mounted on one side and the other side of the wiring board 12. Alternatively, the electronic components 16 may be provided only on one side of the wiring board 12 and not on the other side. There are no particular limitations on the electronic components 16, as long as they can be mounted in an electronic control unit for vehicles; for example, a microcomputer can be used.

[0086] The sealing resin 14 is formed by molding and curing an injection-molded sealing resin composition to seal the electronic component 16. In this embodiment, the sealing resin 14 is formed, for example, to seal the wiring substrate 12 together with the electronic component 16. Figure 1 In the example shown, a sealing resin 14 is provided to seal one and the other sides of the wiring board 12, as well as the electronic components 16 mounted on the wiring board 12. Furthermore, the sealing resin 14 is formed, for example, to seal part or all of the wiring board 12. Figure 1 The example illustrates a situation where the sealing resin 14 is provided in such a way that the connection terminal 18 in the wiring board 12 is not sealed, but the rest of the board is sealed, so that the connection terminal 18 is exposed.

[0087] In the vehicle-mounted electronic control unit 10 of this embodiment, the wiring board 12 may be mounted on a metal substrate, for example. The metal substrate may function as a heat sink for dissipating heat generated from the electronic components 16. In this embodiment, the vehicle-mounted electronic control unit 10 may be formed by integrally sealing the metal substrate and the wiring board 12 mounted on the metal substrate using an injection molding sealant composition. The metal material constituting the metal substrate is not particularly limited, and may include, for example, iron, copper, and aluminum, as well as alloys containing one or more of these materials. Alternatively, the vehicle-mounted electronic control unit 10 may not have a metal substrate.

[0088] Figure 1 The illustrated vehicle-mounted electronic control unit 10 is formed by injection molding, which uses a sealing resin composition for injection molding to seal multiple electronic components 16.

[0089] Specifically, first, a wiring board 12, which houses multiple electronic components 16, is placed inside the cavity of a mold. Then, the sealing resin composition for injection molding according to this embodiment is fed into an extruder (barrel) with a screw inside via a hopper, and the sealing resin composition for injection molding is melted at an extruder temperature of 80°C to 100°C. The molten resin is moved within the extruder by the screw and injected into the cavity of the mold via a gate, thereby sealing the multiple electronic components 16.

[0090] The sealing resin composition for injection molding of this embodiment has a maximum exothermic peak temperature in the DSC curve within a specified range, and the half-value width of the maximum exothermic peak temperature is also within a specified range. Therefore, it is stable at the heat treatment temperature in the extruder and has a short molding cycle.

[0091] The embodiments of the present invention have been described above, but these are merely examples of the present invention. Various configurations other than those described above may be used without impairing the effects of the present invention.

[0092] [Example]

[0093] The present invention will be described in more detail below through embodiments, but the present invention is not limited thereto.

[0094] [Examples 1-5 and Comparative Examples 1-8]

[0095] For Examples 1-5 and Comparative Examples 1-8, sealing resin compositions for injection molding were prepared in the following manner.

[0096] First, according to the formulation shown in Table 1, the components were premixed for 20 minutes in a Henschel mixer (200 liters capacity, 900 rpm) set to room temperature. Next, using a continuous rotary ball mill (a MYD25 dynamic mill manufactured by NIPPON COKE & ENGINEERING.CO., LTD., screw speed 500 rpm, alumina ball diameter 10 mm, ball volume fill rate 50% relative to the unit volume), the material temperature was maintained below 30°C at a feed rate of 200 kg / hr, while the resulting mixture was micronized. Then, the micronized mixture was kneaded using two 10-inch rollers. The roller temperatures were set to 105°C and 15°C for kneading. The kneading time was 5 minutes. Additionally, the kneading time in Example 4 was 20 minutes, and in Example 5 it was 40 minutes. Finally, the kneaded mixture was cooled and pulverized to obtain a sealing resin composition for injection molding. Furthermore, each step, from premixing using a Henschel mixer to obtaining the sealing resin composition for injection molding, is performed continuously. Details of each component in Table 1 are as follows. Also, the units in Table 1 are by weight%.

[0097] (A) Thermosetting resin

[0098] • Epoxy Resin 1: o-Cresol Phenolic Resin for Clear Varnish (EPICLON N-670, manufactured by DICCorporation)

[0099] • Epoxy Resin 2: Tetraphenylethane type epoxy resin (JER 1031S, manufactured by Mitsubishi Chemical Corporation)

[0100] (B) Curing agent

[0101] • Phenolic Resin 1: Phenolic varnish type phenolic resin (PR-53195, manufactured by Sumitomo Bakelite Co., Ltd., hydroxyl equivalent 104 g / eq)

[0102] (C) Inorganic fillers

[0103] • Fiberglass: CS3E479, manufactured by Nitto Boseki Co., Ltd.

[0104] • Silica 1: Crushed silica (RD-8, manufactured by Tatsumori Ltd., average particle size D) 50 =15μm)

[0105] • Silica 2: Crushed silica (F-207, manufactured by FUMITEC Co., Ltd., average particle size D) 50 =7μm)

[0106] (D) Curing catalyst

[0107] • Curing catalyst 1: 2-Phenyl-4,5-dihydroxymethylimidazolium (melting point 225-235°C, molecular weight 204, activity temperature range 155-175°C, 2PHZ-PW, manufactured by Shikoku Kasei Holdings Corporation, micro powder)

[0108] In this embodiment, the active temperature region is measured using the method described above.

[0109]

[0110] • Curing catalyst 2: 2-Phenylacetyl-4-methylimidazolium (melting point 174-184°C, molecular weight 172, active temperature range 110-125°C (2P4MZ, manufactured by Shikoku Kasei Corporation))

[0111]

[0112] • Curing catalyst 3: 2-Phenylimidazole represented by the following chemical formula (melting point 137-147°C, molecular weight 144, active temperature range 105-125°C (2PZ, manufactured by Shikoku Kasei Corporation)).

[0113]

[0114] • Curing catalyst 4: N,N'-dimethylurea (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0115] • Curing catalyst 5: 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea) (AMICURE UR2T, manufactured by Evonik Industries AG)

[0116]

[0117] (E) Other ingredients

[0118] • Low-stress agent: Silicone rubber (CF2152, manufactured by Dow Corning Co., Ltd.)

[0119] • Release agent: calcium stearate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0120] • Colorant: Carbon black (#5, manufactured by Mitsubishi Chemical Corporation)

[0121] (DSC measurement)

[0122] The injection molding sealing resin compositions obtained in each example and comparative example were micronized using a mortar and pestle, and 3-5 mg were weighed into an aluminum pan as a sample. Next, differential scanning calorimetry (DSC) measurements were performed on this sample using a differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Co., Ltd.) under the conditions of an initial temperature of 30°C, a measurement temperature range of 30-330°C, and a heating rate of 10°C / min. The peak temperature (°C), half-maximum width (WWHM) of the maximum exothermic peak, the minimum temperature before the maximum exothermic peak (°C), and the minimum temperature after the maximum exothermic peak (°C) were calculated from the obtained DSC curves.

[0123] Figure 2The DSC curves were obtained by DSC measurement of the sealing resin composition for injection molding obtained in Example 1. Hereinafter, taking Example 1 as an example, the calculation method of the half-width (°C) of the maximum exothermic peak in each example and each comparative example is described.

[0124] The half-value width (°C) of the maximum exothermic peak is calculated as follows: First, the baseline is determined by the straight line connecting point A (minimum temperature before the maximum exothermic peak) and point B (minimum temperature after the maximum exothermic peak) with the minimum heat flow before the maximum exothermic peak. Next, point D is defined as the intersection of the perpendicular line to the X-axis passing through point C (maximum heat flow at the peak of the exothermic peak) and the baseline. Then, when a straight line is drawn passing through point E (midpoint of straight line CD) and parallel to the X-axis, the points intersecting the DSC curve are defined as points F and F′, respectively. The length of the straight line FF′ is determined as the half-value width.

[0125] (Measurement of time T1, T1′, and minimum torque values ​​a and b in the Labo Plastomill testing machine)

[0126] The injection molding sealant compositions obtained in each embodiment and comparative example were measured for time T1, T1′, and minimum torque value as follows. First, the melt torque of the injection molding sealant composition was measured over time using a Labo Plastomill testing machine (manufactured by Toyo Seiki Seisaku-sho, Ltd., 4C150) at a rotation speed of 30 rpm and a measurement temperature of 130°C. Next, the time T1 at which the torque value is less than twice the minimum torque value was calculated based on the measurement results. The measurement starting point was the point where the torque began to decrease after a sharp increase following the initial input of material into the Labo Plastomill testing machine. Furthermore, the minimum torque value a was calculated based on the measurement results.

[0127] Similarly, the melting torque of the sealant composition for injection molding was measured over time at a rotation speed of 30 rpm and a measurement temperature of 150°C. Based on the measurement results, the time T1 when the torque value was less than twice the minimum torque value and the minimum torque value b were calculated. The results are shown in Table 1. In Table 1, the units of time T1 and T1′ are seconds, and the units of minimum torque values ​​a and b are N·m.

[0128] (glass transition temperature (Tg))

[0129] JIS 6911 bending test pieces were molded at 175℃ for 3 minutes, and TMA measurements were performed in the flow direction. The bending point was taken as Tg. The temperature was increased at a rate of 5℃ / min. It can be considered that the higher the Tg after molding (uncured), the shorter the molding cycle can be.

[0130] (Thermal stability test)

[0131] ISO 178 dumbbell test pieces (specimens) were molded using a 100t electric injection molding machine (product number: EC-100SXR, manufactured by Shibaura Machine Co., Ltd.). The mold temperature of the 100t electric injection molding machine was set to 165℃, and the nozzle temperature was set to 85℃ / 65℃ / 45℃. The injection time was set to 15 seconds, and the curing time was set to 100 seconds. The injection speed was set to 5 mm / sec, and the holding pressure was set to 30 MPa for 5 seconds. Injection molding was performed with an injection waiting time of 0 minutes or 5 minutes after weighing, and the total weight of the resulting specimens (2 ISO test pieces + runner + manifold) was measured. The weight after injection molding with a waiting time of 0 minutes is designated W0, and the weight after injection molding with a waiting time of 5 minutes is designated W5. (W5 / W0)×100 being 98% or higher is indicated as ○, and (W5 / W0)×100 being less than 98% is indicated as ×.

[0132]

[0133] As shown in Table 1, the following is clearly defined: According to the DSC curve obtained by using a differential scanning calorimeter at a heating rate of 10°C / min from 30°C to 330°C, the peak temperature of the maximum exothermic peak is above 155°C and below 175°C, and the half-width of the maximum exothermic peak is below 65°C. The sealing resin composition for injection molding of the embodiment exhibits excellent thermal stability, high Tg, and excellent curability. Due to the balanced excellence of these characteristics, it is stable for heat treatment in the extruder for injection molding and is suitable for injection molding with short molding cycles.

[0134] This application claims priority based on Japanese Patent Application No. 2021-023120, filed on February 17, 2021, and all its disclosures are incorporated herein by reference.

[0135] Explanation of reference numerals in the attached figures

[0136] 10 Vehicle-mounted electronic control unit, 12 Wiring board, 14 Sealing resin, 16 Electronic components, 18 Connection terminal, 120 Through hole.

Claims

1. A sealing resin composition for injection molding, characterized in that, Include: (A) Thermosetting resin; (B) Curing agent; (C) Inorganic filler materials; and (D) Curing accelerator, Thermosetting resin (A) comprises one or more selected from o-cresol phenolic varnish epoxy resin, phenolic phenolic varnish epoxy resin, bisphenol A type epoxy resin and tetraphenylethane type epoxy resin, and does not comprise epoxy resin represented by the following general formula (1). In general formula (1), the average value of n is 0.2 to 4.0, and G represents glycidyl group. Curing agent (B) includes phenolic resin curing agents. Inorganic filler material (C) contains glass fiber. Curing accelerator (D) does not contain dimethylurea curing accelerators represented by the following chemical formulas (1) to (3). In the DSC curve obtained using a differential scanning calorimeter at a heating rate of 10℃ / min from 30℃ to 330℃, The peak temperature of the maximum exothermic peak is above 165℃ but below 175℃. The half-value width of the maximum heat release peak is calculated using the straight line connecting the point with the minimum heat flow before the maximum heat release peak and the point with the minimum heat flow after the maximum heat release peak as the baseline. The half-value width of the maximum heat release peak is above 20°C and below 32°C.

2. The sealing resin composition for injection molding according to claim 1, characterized in that: When measuring torque values ​​over time using a Labo Plastomill at a speed of 30 rpm and a measurement temperature of 130°C, the time T1 during which the torque value is less than twice the lowest torque value a is between 65 and 200 seconds. When measuring the torque value over time at a speed of 30 rpm and a measurement temperature of 150 ℃, the time T1' when the torque value is less than twice the minimum torque value b is between 35 seconds and 150 seconds.

3. The sealing resin composition for injection molding according to claim 2, characterized in that: The minimum torque value 'a' is between 0.5 N·m and 10.0 N·m. The minimum torque value b is between 0.1 N·m and 4.0 N·m.

4. The sealing resin composition for injection molding according to any one of claims 1 to 3, characterized in that: The curing accelerator (D) comprises one or more selected from 2-phenyl-4,5-dihydroxymethylimidazolium, 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea) and N,N'-dimethylurea.

5. The sealing resin composition for injection molding according to any one of claims 1 to 3, characterized in that: Inorganic filler material (C) contains an average particle size D measured using a laser particle size analyzer. 50 It is a filler material with a thickness of 1μm to 50μm.

6. The sealing resin composition for injection molding according to any one of claims 1 to 3, characterized in that: The inorganic filler material (C) contains molten and broken silica.

7. A structure, characterized in that: Cured products of the sealing resin composition for injection molding according to any one of claims 1 to 6.

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