Molding material, acoustic matching member, and ultrasonic sensor

Abstract

To provide a molding material which enables manufacture of an acoustic matching layer having sufficient acoustic characteristics, and has good moldability, a molded article obtained using the molding material, an acoustic matching member and an ultrasonic sensor having the acoustic matching member as an acoustic matching layer.SOLUTION: A molding material contains (A) a thermosetting resin, (B) a reactive diluent, (C) a thermoplastic resin, (D) hollow inorganic particles, and (E) a thermal polymerization initiator, wherein the thermosetting resin (A) contains (a-1) at least one selected from the group consisting of an unsaturated polyester resin having a content of an ethylenic unsaturated group of 0.1 to 2.0 mol / kg, and a vinyl ester resin having a content of an ethylenic unsaturated group of 0.1 to 2.0 mol / kg, and a content of the ethylenic unsaturated group of the whole thermosetting resin (A) is 0.5 to 3.5 mol / kg.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a molding material, a molded product obtained by using the molding material, an acoustic matching member, and an ultrasonic sensor including the acoustic matching member as an acoustic matching layer. [Background technology]

[0002] In general, in ultrasonic sensors, an acoustic matching layer for acoustically matching the acoustic impedance of air is provided on the ultrasonic emitting surface of the piezoelectric body. It is known that the acoustic matching layer is formed by solidifying a resin in which hollow glass balloon particles are mixed and dispersed.

[0003] One method for producing such an acoustic matching layer is to mix hollow glass balloon particles into an uncured resin, thoroughly mix the mixture, and then place the mixture in a mold for thermal curing. This method is disclosed in, for example, Patent Document 1.

[0004] In general, by blending inorganic fillers or fiber reinforcing materials, various properties can be imparted to molding materials, but on the other hand, the specific gravity of the molded product increases. Therefore, various efforts have been made to reduce the specific gravity of the molded product. For example, Patent Document 2 describes a resin composition containing a hollow filler. Also, Patent Document 3 describes an acoustic impedance matching layer in which hollow spherical particles and inorganic solid particles are dispersed in a thermosetting polymer resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-143685 A [Patent Document 2] JP 2013-216879 A [Patent Document 3] Utility Model Registration No. 3219041 Summary of the Invention [Problem to be solved by the invention]

[0006] In the manufacturing method of an acoustic matching layer described in Patent Document 1, if the resin composition is caused to flow during molding, the resin composition may become non-uniform, making it impossible to obtain the uniform acoustic properties required for a matching layer, and the molding method is limited.

[0007] The resin composition described in Patent Document 2 can be used to obtain a uniform molded product by commonly known transfer molding or injection molding, but the acoustic properties are insufficient.

[0008] The acoustic impedance matching layer described in Patent Document 3 uses inorganic solid particles with high thermal conductivity, which results in a large specific gravity of the material, leading to problems such as insufficient acoustic characteristics required for a matching layer and poor molding characteristics.

[0009] The present invention has been made to solve the above-mentioned problems, and provides a molding material with good moldability that can be used to fabricate an acoustic matching layer having sufficient acoustic properties, a molded product obtained using the molding material, an acoustic matching member, and an ultrasonic sensor that has the acoustic matching member as an acoustic matching layer. [Means for solving the problem]

[0010] The present inventors have found that by using a thermosetting resin having specific physical properties as a molding material for forming an acoustic matching layer containing hollow inorganic particles, it is possible to produce an acoustic matching layer that has good moldability and sufficient acoustic characteristics.

[0011] That is, the present invention includes the following aspects. [1] (A) Thermosetting resin, (B) a reactive diluent; (C) thermoplastic resin, (D) hollow inorganic particles, and (E) Thermal polymerization initiator A molding material comprising: The (A) thermosetting resin includes (a-1) at least one selected from the group consisting of unsaturated polyester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and vinyl ester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, The content of ethylenically unsaturated groups in the entire thermosetting resin (A) is 0.5 to 3.5 mol / kg. Molding material. [2] The molding material according to [1], wherein the (A) thermosetting resin further contains (a-2) a thermosetting resin other than the (a-1). [3] The molding material according to [1] or [2], wherein the (E) thermal polymerization initiator has a 10-hour half-life temperature of 80° C. or lower. [4] The molding material according to any one of [1] to [3], wherein the (D) hollow inorganic particles have a median diameter (d50) of 10 to 70 μm. [5] The content of the (C) thermoplastic resin is 5 to 15 mass %, The true density of the (D) hollow inorganic particles is 0.3 to 0.7 g / cm 3 and The (D) hollow inorganic particles have a pressure resistance of 10 MPa or more, The molding material according to any one of [1] to [4], wherein the content of the (D) hollow inorganic particles is 35 to 70 volume %. [6] A molded article comprising the molding material according to any one of [1] to [5] or a cured product thereof. [7] An acoustic matching member comprising a cured product of the molding material according to any one of [1] to [5]. [8] An ultrasonic sensor comprising the acoustic matching member according to [7] as an acoustic matching layer. Effect of the Invention

[0012] The molding material of the present invention has good moldability and can realize an acoustic matching layer having sufficient acoustic characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described in detail, however, the present invention is not limited to the embodiments described below.

[0014] In this disclosure, "ethylenically unsaturated bond" means a double bond formed between carbon atoms other than those forming an aromatic ring.

[0015] In this disclosure, "(meth)acrylic" means acrylic or methacrylic, "(meth)acrylate" means acrylate or methacrylate, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acryloxy" means acryloxy or methacryloxy.

[0016] <Molding material> The molding material of one embodiment includes (A) a thermosetting resin, (B) a reactive diluent, (C) a thermoplastic resin, (D) hollow inorganic particles, and (E) a thermal polymerization initiator. The molding material may further include (F) an optional component, if necessary, such as a fiber reinforcing material.

[0017] [(A) Thermosetting resin] The (A) thermosetting resin contains at least one selected from (a-1) an unsaturated polyester resin and a vinyl ester resin, and has specific physical properties as a whole. Specifically, the (a-1) thermosetting resin contains at least one selected from the group consisting of an unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and a vinyl ester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, and the (A) thermosetting resin as a whole has an ethylenically unsaturated group content of 0.5 to 3.5 mol / kg.

[0018] As long as the (A) thermosetting resin has an ethylenically unsaturated group content of 0.5 to 3.5 mol / kg, it may be composed of only one or a plurality of types selected from (a-1) unsaturated polyester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and vinyl ester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg.

[0019] The (A) thermosetting resin may further contain, in addition to the above-mentioned (a-1) which is an essential component, (a-2) a thermosetting resin other than (a-1), so long as the overall content of ethylenically unsaturated groups is 0.5 to 3.5 mol / kg.

[0020] (a-2) is a thermosetting resin other than (a-1). (a-2) is not particularly limited, and examples thereof include unsaturated polyester resins, vinyl ester resins, urethane (meth)acrylate resins, diallyl phthalate resins, epoxy resins, and combinations of two or more of these resins, each having an ethylenically unsaturated group content of more than 2.0 mol / kg.

[0021] In the present disclosure, each resin, such as an unsaturated polyester resin, a vinyl ester resin, etc., refers to a resin that does not contain a reactive diluent (B) described below.

[0022] The content of the (A) thermosetting resin is preferably 30 to 75 mass%, and more preferably 35 to 65 mass%, based on the total mass of the (A) thermosetting resin and the (B) reactive diluent described below. When the content of the (A) thermosetting resin is 30 mass% or more, the workability when obtaining a molded article from the molding material and the dimensional accuracy of the molded article are good. When the content of the (A) thermosetting resin is 75 mass% or less, the curability of the molding material is good.

[0023] As the unsaturated polyester resin, those known in the art can be used. Unsaturated polyester is generally a compound obtained by polycondensation (esterification) of a polyhydric alcohol, an unsaturated polybasic acid, and, if necessary, a saturated polybasic acid. In the present disclosure, it is sufficient to select and use it appropriately according to the desired characteristics. The unsaturated polyester resin of (a-1) or (a-2) above may be used alone or in combination of two or more kinds.

[0024] The polyhydric alcohol used in the synthesis of the unsaturated polyester resin is not particularly limited, and known polyhydric alcohols can be used. Examples of polyhydric alcohols include alkane diols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and neopentanediol; (poly)oxyalkylene polyols such as diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; glycerin; and bisphenol compounds such as hydrogenated bisphenol A, bisphenol A, and bisphenol F. These polyhydric alcohols can be used alone or in combination.

[0025] Among these, from the viewpoints of heat resistance and moldability, alkanediols and bisphenol compounds are preferred, it is more preferred to use two or more selected from the group consisting of alkanediols and bisphenol compounds in combination, and it is even more preferred to use two or more selected from the group consisting of propylene glycol, neopentanediol, bisphenol A, and hydrogenated bisphenol A in combination.

[0026] The unsaturated polybasic acid used in the synthesis of the unsaturated polyester resin is not particularly limited as long as it is a polybasic acid having an ethylenically unsaturated bond, and known polybasic acids can be used. Examples of the unsaturated polybasic acid include maleic acid, maleic anhydride, fumaric acid, citraconic acid, and itaconic acid.

[0027] Among these, maleic acid, maleic anhydride and fumaric acid are preferred from the viewpoints of heat resistance, moldability, etc. These unsaturated polybasic acids may be used alone or in combination.

[0028] The saturated polybasic acid used in the synthesis of the unsaturated polyester resin is not particularly limited as long as it is a polybasic acid that does not have an ethylenically unsaturated bond, and known ones can be used. Examples of the saturated polybasic acid include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, and tetrabromophthalic anhydride. These saturated polybasic acids can be used alone or in combination.

[0029] As the vinyl ester resin, those known in the technical field can be used. The vinyl ester resin is generally a compound having an ethylenically unsaturated bond obtained by a ring-opening reaction between an epoxy group in an epoxy compound having two or more epoxy groups and a carboxy group of an unsaturated monobasic acid having an ethylenically unsaturated bond and a carboxy group. Such vinyl ester resins are described, for example, in the Polyester Resin Handbook (published by Nikkan Kogyo Shimbun, 1988). The vinyl ester resins may be used alone or in combination of two or more kinds.

[0030] The urethane (meth)acrylate resin is not particularly limited, and for example, a resin obtained by introducing (meth)acryloyl groups into the hydroxyl groups or isocyanato groups at both ends of polyurethane obtained by reacting a polyisocyanate with a polyhydric alcohol can be used.

[0031] Examples of polyisocyanates used in the synthesis of urethane (meth)acrylate resins include aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, and trimethylhexane diisocyanate; cyclic aliphatic polyisocyanates such as hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6)-diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), and 1,3- (isocyanatomethyl) cyclohexane; aromatic polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate; and adducts, isocyanurates, and biuret bodies of these polyisocyanates. The polyisocyanates may be used alone or in combination of two or more.

[0032] As the polyhydric alcohol used in the synthesis of the urethane (meth)acrylate resin, the compounds described as the raw materials for the above unsaturated polyester resin can be used without any particular limitation.

[0033] In the synthesis of a urethane (meth)acrylate resin, when introducing a (meth)acryloyl group, for example, a method of reacting a terminal isocyanato group with a hydroxyl group-containing (meth)acrylic compound, or a method of reacting a terminal hydroxyl group with an isocyanato group-containing (meth)acrylic compound such as 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, or 1,1-bis(acryloyloxymethyl)ethyl isocyanate can be used.

[0034] Examples of hydroxyl group-containing (meth)acrylic compounds used when introducing (meth)acryloyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, tris(hydroxyethyl)isocyanuric acid di(meth)acrylate, pentaerythritol tri(meth)acrylate, glycerin mono(meth)acrylate, and hydroxyethylacrylamide, with 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, and hydroxyethylacrylamide being preferred. The isocyanato group-containing (meth)acrylic compounds and hydroxyl group-containing (meth)acrylic compounds may each be used alone or in combination of two or more.

[0035] As the diallyl phthalate resin, any of those known in the art can be used. The diallyl phthalate resin may be used alone or in combination of two or more kinds.

[0036] The epoxy resin can be used without any particular limitation as long as it is a compound having two or more epoxy groups. It is preferably at least one selected from the group consisting of bisphenol type epoxy compounds and novolac phenol type epoxy compounds, and more preferably bisphenol type epoxy compounds. The epoxy resin may be used alone or in combination of two or more kinds.

[0037] Examples of bisphenol type epoxy compounds include those obtained by reacting a bisphenol compound such as bisphenol A, bisphenol F, bisphenol S, and tetrabromobisphenol A with epichlorohydrin and / or methylepichlorohydrin; and those obtained by reacting a condensate of a compound obtained by glycidyl etherifying one or more of the above bisphenol compounds with one or more of the above bisphenol compounds, and epichlorohydrin and / or methylepichlorohydrin.

[0038] Among these, from the viewpoint of durability, a reaction product of a bisphenol compound with epichlorohydrin is preferred, and a reaction product of bisphenol A with epichlorohydrin is more preferred.

[0039] Examples of novolak phenol type epoxy compounds include those obtained by reacting phenol novolak or cresol novolak with epichlorohydrin and / or methyl epichlorohydrin.

[0040] The weight average molecular weight of each of the resins (a-1) or (a-2), which are components of the thermosetting resin (A) before curing, is preferably 6,000 to 35,000, more preferably 7,000 to 20,000, and even more preferably 8,000 to 15,000. If the weight average molecular weight is 6,000 to 35,000, the moldability of the molding material is further improved.

[0041] In the present disclosure, the "weight average molecular weight" refers to a value measured by gel permeation chromatography (hereinafter also referred to as "GPC") under the following conditions at room temperature (23°C) and determined using a standard polystyrene calibration curve. Equipment: Shodex (registered trademark) GPC-101 (Showa Denko K.K.) Column: Shodex (registered trademark) LF-804 (Showa Denko K.K.) Column temperature: 40℃ Sample: 0.2% by mass solution of sample in tetrahydrofuran Flow rate: 1mL / min Eluent: Tetrahydrofuran Detector: Shodex (registered trademark) RI-71S (Showa Denko K.K.)

[0042] The content of ethylenically unsaturated groups in the entire thermosetting resin (A) is 0.5 to 3.5 mol, preferably 0.6 to 3.0 mol, and more preferably 0.7 to 2.7 mol per 1 kg of the total thermosetting resin (A).

[0043] If the content of ethylenically unsaturated groups in the entire (A) thermosetting resin is less than 0.5 mol / kg, the amount of ethylenically unsaturated groups in the molding material is insufficient, and the molded article obtained by curing is insufficiently crosslinked, resulting in poor demoldability.If the content of ethylenically unsaturated groups in the entire (A) thermosetting resin is more than 3.5 mol / kg, the rigidity of the molded article obtained from the molding material increases, and when used as an acoustic matching layer, the acoustic impedance increases, and the performance of the ultrasonic sensor to which the acoustic matching layer is applied decreases.

[0044] The content of ethylenically unsaturated groups in the entire thermosetting resin (A) can be calculated as the amount of ethylenically unsaturated groups per kg of the thermosetting resin (A) by measuring the iodine value in accordance with JIS K 0070:1992.

[0045] When two or more resins having ethylenically unsaturated groups are used as components of (A) thermosetting resin, and the amount of ethylenically unsaturated groups in each resin is known, the amount of ethylenically unsaturated groups per kg of (A) thermosetting resin may be calculated from the amount of ethylenically unsaturated groups in each resin and the blending amount.

[0046] When the (A) thermosetting resin contains only an unsaturated polyester resin, it can be calculated from the amount of raw materials charged when producing the unsaturated polyester and the amount of condensation water generated during the reaction, and can be obtained by the following formula. (A) Content of ethylenically unsaturated groups in thermosetting resin (moles / kg) = number of moles of unsaturated acid / {(mass of acid component (kg) + mass of glycol component (kg)) - mass of condensation water (kg)}

[0047] The (A) thermosetting resin contains at least one selected from the group consisting of unsaturated polyester resins and vinyl ester resins, and more preferably contains an unsaturated polyester resin. The unsaturated polyester resin and the vinyl ester resin may each be used alone or in combination of two or more.

[0048] The content of the unsaturated polyester resin and the vinyl ester resin in the thermosetting resin (A) is preferably 60 to 100 mass%, more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass%. If the content is 60 mass% or more, the curability and moldability are good.

[0049] ((a-1): Unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and vinyl ester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg) (A) The thermosetting resin includes (a-1) at least one selected from the group consisting of an unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and a vinyl ester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg.

[0050] By incorporating (a-1), which has a low content of ethylenically unsaturated groups, into the (A) thermosetting resin, the amount of ethylenically unsaturated groups and the amount of crosslinking contained in the molding material can be adjusted, and the moldability and acoustic properties of the molded product can be balanced.

[0051] The content of the ethylenically unsaturated group in (a-1) having a low content of the ethylenically unsaturated group is preferably 0.2 to 1.5 mol, more preferably 0.3 to 1.0 mol, per 1 kg of the resin. If the content of the ethylenically unsaturated group is less than 0.1 mol / kg, the amount of the ethylenically unsaturated group contained in the molding material is insufficient, and the molded product obtained by curing has insufficient crosslinking, so that good demoldability cannot be obtained. If the content of the ethylenically unsaturated group exceeds 2.0 mol / kg, the rigidity of the molded product obtained from the molding material becomes high, so that when it is used as an acoustic matching layer, the acoustic impedance increases, and the performance of the ultrasonic sensor to which the acoustic matching layer is applied decreases.

[0052] The content of at least one ethylenically unsaturated group selected from the group consisting of (a-1) unsaturated polyester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and vinyl ester resins having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg can be adjusted by changing the ratio of the unsaturated compound and the saturated compound used as raw materials in the synthesis of (a-1).

[0053] For example, when (a-1) is an unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, the content of the ethylenically unsaturated group can be reduced by decreasing the ratio of the unsaturated polyacid / saturated polyacid. In this case, the degree of unsaturation of the unsaturated polyester resin is preferably 5 to 50 mol%, more preferably 10 to 40 mol%, and even more preferably 15 to 30 mol%.

[0054] The degree of unsaturation of the unsaturated polyester resin can be calculated from the number of moles of the unsaturated polybasic acid and the saturated polybasic acid used as raw materials according to the following formula. Degree of unsaturation (mol%)={(number of moles of unsaturated polybasic acid × number of ethylenically unsaturated bonds per molecule of unsaturated polybasic acid) / (number of moles of unsaturated polybasic acid + number of moles of saturated polybasic acid)}×100

[0055] In addition, when (a-1) is an unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, a saturated polyester is produced by polycondensing (esterifying) a polyhydric alcohol and a saturated polybasic acid, and then the terminal hydroxyl or carboxyl group is modified to introduce an ethylenically unsaturated group, thereby providing an (a-1) thermosetting resin in which the amount of ethylenically unsaturated groups is adjusted.

[0056] In this case, the modification reaction may be, for example, a method in which a saturated polyester having a hydroxyl group terminal is reacted with a polyisocyanate, and the remaining unreacted isocyanato groups are reacted with an ethylenically unsaturated compound having a hydroxyl group to introduce an ethylenically unsaturated group at the terminal.

[0057] As for the polyhydric alcohol and saturated polybasic acid, the same compounds as those used as the raw materials for the unsaturated polyester resins listed in (A) Thermosetting resins can be used.

[0058] As the polyisocyanate, the same compounds as those used as the raw material of the urethane (meth)acrylate resin listed in (A) thermosetting resin can be used. For example, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate can be mentioned. These diisocyanate compounds may be used alone or in combination of two or more kinds.

[0059] The diisocyanate compound is preferably isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, or hydrogenated xylylene diisocyanate, and more preferably isophorone diisocyanate.

[0060] As the ethylenically unsaturated compound having a hydroxyl group, the same compound as the hydroxyl group-containing (meth)acrylic compound used as the raw material of the urethane (meth)acrylate resin listed in (A) thermosetting resin can be used. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, phenoxy hydroxypropyl acrylate, phenoxy hydroxypropyl methacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, dipropylene glycol monoacrylate, and dipropylene glycol monomethacrylate can be mentioned. These hydroxyl group-containing (meth)acrylates may be used alone or in combination of two or more.

[0061] The hydroxyl group-containing (meth)acrylate is preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, phenoxyhydroxypropyl acrylate, or phenoxyhydroxypropyl methacrylate, more preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, or 2-hydroxybutyl methacrylate, and even more preferably 2-hydroxyethyl acrylate.

[0062] On the other hand, when (a-1) is a vinyl ester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, the amount of the ethylenically unsaturated group can be adjusted to be low by, for example, increasing the molecular weight of the epoxy compound and / or unsaturated monobasic acid used as the raw material, or replacing a portion of the unsaturated monobasic acid with a saturated monobasic acid.

[0063] The content of (a-1) in the thermosetting resin (A) is not particularly limited, but is preferably from 50 to 100% by mass, and more preferably from 60 to 100% by mass.

[0064] ((a-2): Thermosetting resin other than (a-1)) (a-2) is a thermosetting resin other than (a-1). (a-2) preferably contains an ethylenically unsaturated group, and examples thereof include unsaturated polyester resins, vinyl ester resins, urethane (meth)acrylate resins, diallyl phthalate resins, epoxy resins, and combinations of two or more of these resins, each having an ethylenically unsaturated group content of more than 2.0 mol / kg. In addition, (a-2) may be a thermosetting resin other than unsaturated polyester resins and vinyl ester resins, each having an ethylenically unsaturated group content of 2.0 mol / kg or less, as long as the total ethylenically unsaturated group content of the (A) thermosetting resin is 0.5 to 3.5 mol / kg.

[0065] [(B) Reactive diluent] The (B) reactive diluent is a monomer compound having at least one polymerizable ethylenically unsaturated bond as a polymerizable functional group in the molecule. The (B) reactive diluent may be a monofunctional monomer or a polyfunctional monomer. By making the molding material contain the (B) reactive diluent, it becomes easy to adjust the viscosity.

[0066] (B) Examples of monofunctional monomers used as reactive diluents include (meth)acrylamide compounds such as (meth)acrylamide, N-methylol (meth)acrylamide, methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, and butoxymethoxymethyl (meth)acrylamide; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-3- Examples of the (meth)acrylate compounds include phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxyethyl phthalate, glycerin mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, and half (meth)acrylate of phthalic acid derivatives; aromatic vinyl compounds such as styrene, α-methylstyrene, α-chloromethylstyrene, and vinyltoluene; and carboxylic acid esters such as vinyl acetate and vinyl propionate. The monofunctional monomers may be used alone or in combination of two or more.

[0067] Examples of polyfunctional monomers used as the (B) reactive diluent include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2-hydroxy-3-(meth)acryloyloxypropyl(meth)acrylate, ethylene glycol diglyceride diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, glycerin triacrylate, glycerin polyglycidyl ether poly(meth)acrylate, urethane (meth)acrylate (e.g., polyisocyanates such as tolylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, and hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate Examples of the polyfunctional monomer include (meth)acrylate compounds such as tris(hydroxyethyl)isocyanurate tri(meth)acrylate, aromatic vinyl compounds such as divinylbenzene, diallyl phthalate, and diallylbenzene phosphonate, dicarboxylic acid esters such as divinyl adipate, triallyl cyanurate, and (meth)acrylamide compounds such as methylene bis(meth)acrylamide, (meth)acrylamide methylene ether, and condensates of polyhydric alcohols and N-methylol (meth)acrylamide. The polyfunctional monomers may be used alone or in combination of two or more.

[0068] Among these, from the viewpoints of availability and cost, styrene monomer is preferred as the reactive diluent (B).

[0069] The total content of the (A) thermosetting resin and the (B) reactive diluent is preferably 25 to 80 mass%, more preferably 30 to 65 mass%, and even more preferably 35 to 50 mass% based on the total molding material. When the total content of the (A) thermosetting resin and the (B) reactive diluent is 25 mass% or more, the fluidity during kneading to obtain the molding material or during molding of the molding material is good. When the total content of the (A) thermosetting resin and the (B) reactive diluent is 80 mass% or less, the dimensional accuracy of the molded product or the moldability of the molding material is good.

[0070] [(C) Thermoplastic resin] The thermoplastic resin (C) is not particularly limited as long as it exhibits plasticity against heat, and any resin known in the art can be used. By using the thermoplastic resin (C), the integrity of the molding material is improved, so that the content of the hollow inorganic particles (D) can be increased while maintaining good moldability, and thus the specific gravity of the molding material can be reduced.

[0071] Examples of the thermoplastic resin (C) include polystyrene, polymethyl methacrylate, polyvinyl acetate, saturated polyester, and styrene-butadiene rubber. These thermoplastic resins may be used alone or in combination of two or more. Among them, polystyrene and styrene-butadiene rubber are preferred from the viewpoint of dimensional accuracy or color unevenness of the molded product.

[0072] The content of the (C) thermoplastic resin is 5 to 15 mass % and preferably 7 to 13 mass % based on the total molding material. When the content of the (C) thermoplastic resin is 5 mass % or more, the dimensional stability of the molded product or the kneadability of the molding material is good. When the content of the (C) thermoplastic resin is 15 mass % or less, the curability of the molding material is good.

[0073] [(D) Hollow inorganic particles] (D) hollow inorganic particles include, for example, glass balloons, silica balloons, and alumina balloons. Among them, glass balloons are preferred from the viewpoint of pressure resistance. These hollow inorganic particles may be used alone or in combination of two or more. (D) hollow inorganic particles can be used to reduce the specific gravity of the molding material, which can be molded to obtain a molded product with a low specific gravity.

[0074] The volume-based median diameter (d50) of the (D) hollow inorganic particles is preferably 10 to 70 μm, more preferably 15 to 60 μm, and even more preferably 20 to 50 μm. When the median diameter (d50) of the (D) hollow inorganic particles is 10 μm or more, the viscosity as a molding material can be kept within an appropriate range. When the median diameter (d50) of the (D) hollow inorganic particles is 70 μm or less, the (D) hollow inorganic particles are not destroyed during the production of the molding material or during molding, and the (D) hollow inorganic particles do not become highly dense, so that the surface smoothness and specific gravity of the molded product are good.

[0075] In the present disclosure, the median diameter (d50) of the (D) hollow inorganic particles is determined by a laser diffraction / scattering method.

[0076] (D) The true density of the hollow inorganic particles is 0.3 to 0.7 g / cm 3 and preferably 0.3 to 0.5 g / cm 3 and preferably 0.38 to 0.45 g / cm 3 (D) The true density of the hollow inorganic particles is more preferably 0.3 g / cm. 3 If the true density of the hollow inorganic particles (D) is less than 0.7 g / cm, the pressure resistance strength of the hollow inorganic particles (D) themselves will be insufficient, and the hollow inorganic particles (D) will be damaged during the production of the molding material or during molding. 3 If it is larger, the specific gravity of the hollow inorganic particles (D) becomes high. In either case, the desired low specific gravity as a molding material cannot be achieved, which is not preferable.

[0077] The pressure resistance of the (D) hollow inorganic particles is preferably 10 MPa or more, and more preferably 20 MPa or more. If the pressure resistance of the (D) hollow inorganic particles is less than 10 MPa, the (D) hollow inorganic particles are broken during the production of the molding material or during molding, and the desired low specific gravity of the molded product cannot be achieved, which is not preferable. The upper limit of the pressure resistance of the (D) hollow inorganic particles is not particularly limited, but is generally 200 MPa or less.

[0078] In the present disclosure, the pressure resistance of the (D) hollow inorganic particles is the pressure value at which 10 volume % of the (D) hollow inorganic particles are destroyed when pressure is applied to the (D) hollow inorganic particles dispersed in glycerol in accordance with ASTM D3102-78 (1982) "Practice for Determination of Isostatic Collapse Strength of Hollow Glass Microspheres".

[0079] The content of the (D) hollow inorganic particles is preferably 35 to 70% by volume, more preferably 50 to 70% by volume, and more preferably 55 to 70% by volume, based on the entire molding material. If the content of the (D) hollow inorganic particles is less than 35% by volume, the specific gravity of the molded product will be high, which is undesirable. If the content of the (D) hollow inorganic particles is more than 70% by volume, the molding material will not have integrity and will not be kneaded sufficiently. As a result, the moldability of the molding material will deteriorate, and the surface smoothness of the molded product will be significantly reduced.

[0080] Since the kneadability and moldability of the molding material are significantly affected by the content (volume %) of the hollow inorganic particles (D), it is preferable to control the content of the hollow inorganic particles (D) on a volume basis rather than a mass basis.

[0081] [(E) Thermal polymerization initiator] As the (E) thermal polymerization initiator, peroxides known in the art can be used. As the (E) thermal polymerization initiator, for example, peroxide polymerization initiators such as t-butyl peroxy octoate, benzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, 1,1-di-t-hexylperoxy-cyclohexanoate, t-butylperoxy isopropyl carbonate, t-butylperoxy benzoate, dicumyl peroxide, and di-t-butyl peroxide can be mentioned. Among these, those having a 10-hour half-life temperature of 80°C or less are preferred, and t-hexylperoxy-2-ethylhexanoate is more preferred. These thermal polymerization initiators may be used alone or in combination of two or more.

[0082] The content of the (E) thermal polymerization initiator is preferably 0.1 to 5 mass % based on the total mass of the molding material, more preferably 0.4 to 4 mass %, and even more preferably 0.5 to 3 mass %. When the content of the (E) thermal polymerization initiator is within the above range, good curability as a molding material can be obtained.

[0083] [(F) Optional component] In addition to the above components, the molding material of one embodiment may contain optional components as necessary. (F) Optional components include, for example, fiber reinforcement, inorganic filler, release agent, thickener, viscosity reducer, and pigment. When these components are used, each component may be used in the amount usually used for the respective purpose.

[0084] (F) The optional fiber reinforcing material is not particularly limited, but may be, for example, a fibrous material with an aspect ratio of at least 3. The aspect ratio can be measured by a microscopic method described in JIS Z 8900-1:2008 "Particles for Calibration of Particle Size Measuring Devices."

[0085] (F) Optional fiber reinforcement materials include, for example, organic fibers such as glass fiber, pulp fiber, Tetron (registered trademark) fiber, vinylon fiber, carbon fiber, aramid fiber, and wollastonite, and inorganic fibers. Examples of the form of the fiber reinforcement materials include sheets, rovings, and chopped strands using continuous or non-continuous fibers. (F) Optional fiber reinforcement materials may be used alone or in combination of two or more. Among them, glass fiber is preferred from the viewpoint of cost and dispersibility, and chopped strand glass is more preferred.

[0086] The fiber length of the optional fiber reinforcing material (F) is not particularly limited, but is preferably 1 mm to 25 mm, more preferably 1.5 mm to 15 mm, and even more preferably 1.5 mm to 13 mm. If the fiber length is 1 to 25 mm, the kneadability with the resin component in the molding material or the fluidity during molding will be good. The fiber length is a number average value measured with a caliper or a micrometer of an optical microscope for 100 fibers randomly taken.

[0087] (F) The optional inorganic filler is not particularly limited, but examples thereof include powders such as calcium carbonate, aluminum hydroxide, wollastonite, clay, talc, mica, and silicic anhydride.

[0088] (F) The optional release agent is not particularly limited, but for example, stearic acid, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, or carnauba wax can be used in an appropriate ratio.

[0089] (F) The optional thickener is not particularly limited, but examples thereof include metal oxides such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium oxide, and isocyanate compounds.

[0090] <Method of manufacturing molding material> The form of the molding material is not particularly limited, but from the viewpoints of diversifying the shapes of the cured product and providing excellent productivity, it is preferable for the molding material to be in a form such as bulk molding compound (hereinafter referred to as "BMC") or sheet molding compound (hereinafter referred to as "SMC").

[0091] The molding material, which is BMC, can be produced by a method used in ordinary BMC production, for example, by kneading under the following conditions using a kneader. The components (A) to (F) except for the optional fiber reinforcement (F) are charged into a twin-arm kneader with the jacket temperature set to the range of 20 to 50°C, the lid is closed, and the components are kneaded for 20 to 60 minutes until each component is sufficiently dispersed and becomes a putty. After the mixture becomes a putty, the lid is opened, and the fiber reinforcement is gradually charged over 1 to 2 minutes while kneading. After the specified amount is charged, the lid is closed, and the fiber reinforcement is kneaded for 5 to 60 minutes until the fiber reinforcement is uniformly dispersed, thereby obtaining a molding material, which is BMC. After kneading is completed, the obtained BMC is packaged with a laminate film of a polyethylene film and a polyethylene terephthalate film, a vinylon film, or the like.

[0092] The molding material, which is SMC, can be manufactured by the following method using a general SMC manufacturing device. First, the components (A) to (F) except for the optional fiber reinforcement (F) are mixed with a mixer or the like to obtain a mixture. There is no particular restriction on the order in which the raw materials are mixed and on the mixer, but the temperature during mixing is preferably 20 to 45°C. Next, the mixture is applied to carrier films installed above and below the SMC manufacturing device so as to have a uniform thickness. There is no particular restriction on the carrier film as long as it is a commonly used one, but polyethylene film, polypropylene film, etc. can be used. Next, the fiber reinforcement cut to a predetermined length, such as 12 to 25 mm, is scattered on the lower carrier film on which the resin mixture has been applied, and then the fiber reinforcement cut to a predetermined length, such as 12 to 25 mm, is sandwiched between the upper and lower carrier films, and is made into a sheet by passing it between impregnated rolls while applying pressure to the whole, and is then wound into a roll or packaged in a zigzag shape. The obtained sheet is preferably aged by heating at a temperature of room temperature to 60°C for 1 to 240 hours. By maturing the composition at room temperature to 60° C. for 1 to 240 hours, the carrier film can be easily peeled off, and when the carrier film is peeled off, the sheet is less sticky and has good workability.

[0093] <Molded products> One embodiment is a molded article obtained by molding the above molding material. By molding using the above molding material, a molded article having a low specific gravity and excellent physical properties such as surface smoothness, rigidity, and heat resistance can be obtained. By heating the molding material after molding as necessary, a molded article containing a cured product of the molding material can also be obtained.

[0094] The specific gravity of the molded article is preferably 0.5 to 0.8, and more preferably 0.6 to 0.8. When the specific gravity of the molded article is 0.5 or more, the moldability is good. When the specific gravity of the molded article is 0.8 or less, a sufficiently low specific gravity can be achieved. The specific gravity of the molded article in the present disclosure is the numerical value of the specific gravity of the compression molded article measured according to JIS K 6911:2006.

[0095] <Method of manufacturing molded products> The molded article can be produced by subjecting the above-mentioned molding material to various molding means, such as compression molding, transfer molding, and injection molding.

[0096] <Acoustic matching material> One embodiment is an acoustic matching member obtained by molding the above molding material.

[0097] Piezoelectric bodies have an acoustic impedance, and gases and liquids that are the medium into which ultrasonic waves are emitted in ultrasonic sensors also have an acoustic impedance. Since it is difficult to efficiently transmit ultrasonic waves between objects with different acoustic impedances, for example, an ultrasonic sensor for both transmission and reception that is equipped with a piezoelectric element has an acoustic matching layer that serves as an acoustic matching member on the surface of the piezoelectric body. The acoustic matching layer has the function of matching the acoustic impedance by being interposed between media with different acoustic impedances, and has an acoustic impedance that is between the acoustic impedance of the piezoelectric body and the acoustic impedance of the medium. By providing an acoustic matching layer with an acoustic impedance between the two between the piezoelectric body and the medium, ultrasonic waves can be efficiently transmitted between the piezoelectric body and the medium.

[0098] The acoustic matching member according to one embodiment can provide an acoustic matching layer having sufficient acoustic characteristics.

[0099] <Ultrasonic sensor> One embodiment is an ultrasonic sensor comprising, as an acoustic matching layer, an acoustic matching member obtained by molding the above molding material.

[0100] An ultrasonic sensor having an acoustic matching layer made of the acoustic matching member obtained by molding the above molding material has stable characteristics because it has an acoustic matching layer with sufficient acoustic characteristics. EXAMPLES

[0101] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0102] [Raw materials] The following raw materials were used:

[0103] <(A) Thermosetting resin> (a-1): An unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg

[0104] [Unsaturated polyester resin (ethylenically unsaturated group content: 0.4 mol / kg)] A saturated polyester resin obtained by polycondensing adipic acid (100 mol) and ethylene glycol (100 mol) was reacted with isophorone diisocyanate (100 mol) to extend the terminals, and the remaining isocyanate groups were then reacted with 2-hydroxyethyl acrylate (100 mol) to obtain a soft unsaturated polyester. The ethylenically unsaturated group content of the obtained soft unsaturated polyester was 0.4 mol / kg, and the weight average molecular weight was 18,000.

[0105] [Unsaturated polyester resin (ethylenically unsaturated group content: 0.8 mol / kg)] An unsaturated polyester resin was obtained by polycondensation of phthalic acid (40 mol), terephthalic acid (40 mol), maleic acid (20 mol), and diethylene glycol (100 mol). The content of ethylenically unsaturated groups in the obtained unsaturated polyester was 0.8 mol / kg. The weight average molecular weight was 8000, and the degree of unsaturation was 20 mol%.

[0106] (a-2): Resin other than (a-1) [Unsaturated polyester resin (ethylenically unsaturated group content: 6.1 mol / kg)] An unsaturated polyester was obtained by polycondensation of fumaric acid (100 mol) and propylene glycol (50 mol). The content of ethylenically unsaturated groups in the obtained unsaturated polyester was 6.1 mol / kg, the weight average molecular weight was 11,000, and the degree of unsaturation was 100 mol%.

[0107] [Vinyl ester resin (ethylenically unsaturated group content: 2.8 mol / kg)] The vinyl ester used had a blend ratio of bisphenol A epoxy resin / methacrylic acid=1 equivalent / 1 equivalent. The vinyl ester had an ethylenically unsaturated group content of 2.8 mol / kg and a weight average molecular weight of 4,500.

[0108] (B) Reactive diluent Styrene monomer (specific gravity: 0.91, Asahi Kasei Corporation)

[0109] (C)Thermoplastic resin Polystyrene (weight average molecular weight: 200,000, specific gravity: 1.05, Sekisui Plastics Co., Ltd.) Styrene-butadiene rubber (SBR) (product name: Asaprene (trademark) T-411, styrene / butadiene ratio = 30 / 70, specific gravity: 0.95, Asahi Kasei Corporation)

[0110] (D) Hollow inorganic particles Glass balloon (product name: S-32HS, median diameter (d50): 25 μm, true density: 0.32 g / cm 3 , Compression strength: 41MPa, 3M Japan Ltd.) Glass balloon (product name: K46, median diameter (d50): 40 μm, true density: 0.46 g / cm 3 , Compression strength: 41MPa, 3M Japan Ltd.)

[0111] (E) Thermal polymerization initiator t-Hexylperoxy-2-ethylhexanoate (10-hour half-life temperature: 72.1°C, NOF Corporation) t-Butyl peroxybenzoate (10-hour half-life temperature: 104.3°C, NOF Corporation)

[0112] (F) Optional ingredient: Release agent Calcium stearate (NOF Corporation)

[0113] [Preparation of molding material] <Example 1> Using a twin-arm kneader with the jacket temperature set at 30° C., the components according to the composition shown in Table 1 were kneaded for 30 minutes to obtain the molding material of Example 1.

[0114] <Examples 2 to 4> Molding materials of Examples 2 to 5 were obtained in the same manner as in Example 1, except that the materials shown in Table 1 were used and the compositions shown in Table 1 were used.

[0115] <Comparative Examples 1 to 5> Molding materials of Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the materials shown in Table 2 were used and the compositions shown in Table 2 were used.

[0116] [Evaluation method] The molding materials prepared in the examples and comparative examples were evaluated for the following items.

[0117] (1)(D) Content of hollow inorganic particles (volume%) The calculation was made using the theoretical volume calculated from the specific gravity and amount of each raw material.

[0118] (2) Theoretical specific gravity It was calculated from the amount of molding material.

[0119] (3) Molded product specific gravity A shrink disk as specified in JIS K 6911:2006 was molded by compression molding at a molding temperature of 120°C, a molding pressure of 2 MPa, and a molding time of 3 minutes. A test piece was cut out and the specific gravity (23°C) was measured based on JIS K 6911:2006.

[0120] (4) Demovability The bending test pieces specified in JIS K 6911:2006 were prepared by compression molding at a molding temperature of 120°C, a molding pressure of 10 MPa, and a molding time of 3 minutes. The demoldability was evaluated based on the presence or absence of cracks in the test pieces and the presence or absence of the test pieces remaining in the mold. The test pieces were evaluated as good when they had no cracks and did not remain in the mold, as acceptable when they had some cracks but did not remain in the mold, and as poor when they had cracks and remained in the mold.

[0121] (5) Tensile modulus Test pieces were obtained by compression molding at a molding temperature of 120°C, a molding pressure of 10 MPa, and a molding time of 3 minutes according to the method specified in JIS K 7161-1: 2014. Tensile tests were performed on the obtained test pieces to obtain the tensile modulus of elasticity.

[0122] (6) Speed ​​of sound Calculated using (elastic modulus / specific gravity)^0.5.

[0123] (7) Acoustic impedance Calculated by multiplying specific gravity by sound speed.

[0124] [Table 1]

[0125] [Table 2]

Claims

1. (A) thermosetting resin, (B) a reactive diluent, (C) thermoplastic resin, (D) hollow inorganic particles, and (E) Thermal polymerization initiator A molding material comprising: The (A) thermosetting resin includes (a-1) at least one selected from the group consisting of an unsaturated polyester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg and a vinyl ester resin having an ethylenically unsaturated group content of 0.1 to 2.0 mol / kg, The content of ethylenically unsaturated groups in the entire thermosetting resin (A) is 0.5 to 3.5 mol / kg. Molding material.

2. The molding material according to claim 1, wherein the (A) thermosetting resin further comprises (a-2) a thermosetting resin other than the (a-1).

3. The molding material according to claim 1 or 2, wherein the thermal polymerization initiator (E) has a 10-hour half-life temperature of 80° C. or lower.

4. The molding material according to any one of claims 1 to 3, wherein the (D) hollow inorganic particles have a median diameter (d50) of 10 to 70 µm.

5. The content of the thermoplastic resin (C) is 5 to 15 mass %, The true density of the hollow inorganic particles (D) is 0.3 to 0.7 g / cm ３ and The (D) hollow inorganic particles have a pressure resistance of 10 MPa or more, The molding material according to any one of claims 1 to 4, wherein the content of the hollow inorganic particles (D) is 35 to 70 volume %.

6. A molded article comprising the molding material according to any one of claims 1 to 5 or a cured product thereof.

7. An acoustic matching member comprising a cured product of the molding material according to any one of claims 1 to 5.

8. 8. An ultrasonic sensor comprising the acoustic matching member according to claim 7 as an acoustic matching layer.

Images