Polyurethane particles having low dielectric properties and method for producing the same

Abstract

To provide solid polyurethane particles having excellent flexibility and low dielectric constant and low dielectric loss tangent. The above problem is solved by using polyurethane particles having a dielectric loss tangent of 0.0001 to 0.01 at 10 GHz.

Description

[Technical Field]

[0001] The present invention relates to polyurethane particles having low dielectric properties and flexibility, and a method for producing the polyurethane particles. [Background technology]

[0002] Conventionally, particles such as polyurethane beads, polybutadiene rubber, and polystyrene beads have been used in various electronic components such as electronic circuit boards, particularly in the insulating portions of electronic components. In order to increase the speed of information processing using electronic devices, there is a need to reduce the dielectric constant and dielectric loss tangent of the insulating portions of materials used in electronic components, and there is a demand for materials used in the insulating portions, such as polyurethane beads, polybutadiene rubber, and polystyrene beads, to have lower dielectric constants and lower dielectric loss tangents.

[0003] For example, Patent Document 1 discloses surface-modified silica particles having a hydrophobic surface obtained by silane treatment of the silica surface, and discloses the use of the surface-modified silica particles as a low-dielectric material. However, silica particles generally do not have the desired flexibility or have poor affinity with organic resins, so there is a demand for materials that are more flexible and have good affinity with resins. Furthermore, various literature has suggested using fluorine-based resins and polyimide resins as low-dielectric materials, but even when these resins are used, like the silica particles described above, they do not have the desired flexibility and / or have poor affinity with organic resins, so there is a demand for materials that are more flexible and have good affinity with resins.

[0004] Furthermore, for example, Patent Document 2 discloses hollow particles made of a polymer having a urea bond and / or a urethane bond, and discloses that the hollow particles are used to achieve a low dielectric constant and a low dielectric loss tangent. Similar to Patent Document 2, Patent Documents 3 and 4 disclose that hollow particles are used to lower the dielectric constant and the dielectric loss tangent. In more detail, Patent Document 3 discloses the production of hollow particles using an aromatic acrylic monomer, and Patent Document 4 discloses the production of hollow particles using an aromatic monofunctional monomer such as styrene and an aromatic acrylic monomer such as divinylbenzene.

[0005] The obtained material, i.e., the hollow particles, are generally blended with a binder or the like when applied to electronic components. However, there has been a problem in that it is difficult to maintain the hollow shape during the blending process and / or after the blending process, and the desired low dielectric constant and low dielectric loss tangent cannot be achieved. Furthermore, particles obtained from aromatic acrylic monomers or styrene monomers have excellent low dielectric properties, but have the problem of being poor in flexibility.

[0006] Furthermore, for example, Patent Document 5 discloses a method for obtaining fine styrene resin particles by pulverizing pelletized styrene resin, thereby achieving low dielectric constant. However, as mentioned above, although particles obtained from styrene-based monomers have excellent low dielectric properties, they have the problem of being poor in flexibility. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2023-61384. [Patent Document 2] Patent No. 6924533. [Patent Document 3] Patent No. 7396735. [Patent Document 4] Patent No. 7175447. [Patent Document 5] Patent Publication No. 2021-91791. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide particles that are excellent in flexibility and have a low dielectric constant and a low dielectric loss tangent. Specifically, an object of the present invention is to provide solid polyurethane particles that are excellent in flexibility and have a low dielectric constant and a low dielectric loss tangent. Another object of the present invention is to provide a method for producing the polyurethane particles, in addition to or in addition to the above object.

[0009] In order to achieve the above object, the present inventors have discovered the following invention. <1> Polyurethane particles having a dielectric loss tangent at 10 GHz of 0.0001 to 0.01, preferably 0.0005 to 0.009, more preferably 0.001 to 0.008, and most preferably 0.002 to 0.007.

[0010] <2> A polyol represented by the following formula (I) (wherein R represents a butane 1,2-diyl group or a butene 1,2-diyl group, and n represents the number of repeating units); or A polyisocyanate prepolymer represented by the following formula (II) (wherein R and n have the same definitions as above, and R' and R" may be the same or different and independently represent a divalent organic group. R' and R" may be the same or different and independently represent a linear or branched alkylene group having 4 to 20, preferably 5 to 15, more preferably 6 to 10 carbon atoms (provided that some carbon atoms in the alkylene group may be substituted with alicyclic hydrocarbons or aromatic hydrocarbons), or a linear or branched alkenylene group having 4 to 20, preferably 5 to 15, more preferably 6 to 10 carbon atoms (provided that some carbon atoms in the alkylene group may be substituted with alicyclic hydrocarbons or aliphatic hydrocarbons)); 1. Polyurethane particles formed from a composition having:

[0011] [ka]

[0012] <3> the above <1> In the above, the polyurethane particles may be formed from a composition having a polyol represented by the above formula (I) or a polyisocyanate prepolymer represented by the above formula (II).

[0013] <4> the above <1> ~ <3> In any of the above, the glass transition temperature of the polyurethane particles is preferably from -60 to 20°C, more preferably from -50 to 15°C, more preferably from -40 to 10°C, and most preferably from -30 to 5°C. <5> the above <1> ~ <4> In any of the above, the volume average particle size of the polyurethane particles is preferably 0.1 to 300 μm, more preferably 0.3 to 100 μm, more preferably 0.5 to 50 μm, and most preferably 1 to 30 μm. <6> the above <1> ~ <5> 1. A material having polyurethane particles according to any one of the preceding items.

[0014] <7> (A) preparing a polyol represented by formula (I); (B) providing a polyisocyanate; and (C) suspension polymerizing the polyol and the polyisocyanate to form polyurethane particles; The method for producing polyurethane particles, wherein the polyurethane particles are obtained by having the above formula:

[0015] <8> (D) preparing a polyisocyanate prepolymer represented by formula (II); and (E) performing suspension polymerization using the polyisocyanate prepolymer; The method for producing polyurethane particles, wherein the polyurethane particles are obtained by having the above formula:

[0016] <9> the above <8> In (A) preparing a polyol represented by formula (I); (B') preparing a polyisocyanate monomer; and (C') reacting the polyol with the polyisocyanate monomer to form a polyisocyanate prepolymer represented by formula (II); The resulting polyisocyanate prepolymer is preferably used in the step (D).

[0017] <10> the above <7> ~ <9> In the above, the polyurethane particles may have the following properties (a) and / or (b) and may also have property (c): Property (a): Dielectric loss tangent at 10 GHz is 0.0001 to 0.01, preferably 0.0005 to 0.009, more preferably 0.001 to 0.008, and most preferably 0.002 to 0.007; Property (b): a dielectric constant at 10 GHz of 1.8 to 3.0, preferably 1.9 to 2.7, more preferably 2.0 to 2.5, and most preferably 2.1 to 2.3; Property (c): Glass transition temperature is -60 to 20°C, preferably -50 to 15°C, more preferably -40 to 10°C, and most preferably -30 to 5°C.

[0018] <11> the above <10> In the above, the volume average particle size of the polyurethane particles is preferably 0.1 to 300 μm, more preferably 0.3 to 100 μm, more preferably 0.5 to 50 μm, and most preferably 1 to 30 μm. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide particles that are excellent in flexibility and have a low dielectric constant and a low dielectric loss tangent. Specifically, the present invention can provide solid polyurethane particles that are excellent in flexibility and have a low dielectric constant and a low dielectric loss tangent. Furthermore, the present invention can provide a method for producing the polyurethane particles in addition to or in addition to the above-mentioned effects. DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention described in this application (hereinafter sometimes abbreviated as "the present invention") will be described below. The present application provides polyurethane particles that are excellent in flexibility and have a low dielectric constant and a low dielectric loss tangent. Specifically, the present application provides polyurethane particles having any one of the following properties (a) to (c), particularly property (a), or any two of them, preferably (a) and (c), or (b) and (c), or more preferably all of (a) to (c). Property (a): Dielectric loss tangent at 10 GHz is 0.0001 to 0.01, preferably 0.0005 to 0.009, more preferably 0.001 to 0.008, and most preferably 0.002 to 0.007; Property (b): a dielectric constant at 10 GHz of 1.8 to 3.0, preferably 1.9 to 2.7, more preferably 2.0 to 2.5, and most preferably 2.1 to 2.3; Property (c): Glass transition temperature is -60 to 20°C, preferably -50 to 15°C, more preferably -40 to 10°C, and most preferably -30 to 5°C.

[0021] In a composition containing a polyol having a repeating unit such as the polyol represented by formula (I) above, or a polyisocyanate prepolymer having a group derived from a polyol having a repeating unit such as the polyol represented by formula (I) above, such as the polyisocyanate prepolymer represented by formula (II) above, the SP value of the group in the repeating unit is preferably 8.00 to 9.00, preferably 8.05 to 8.90, more preferably 8.10 to 8.80, and most preferably 8.15 to 8.70. Here, the SP value refers to the solubility parameter, calculated by the Fedors method. When the group in the repeating unit has the above SP value, the resulting polyurethane particles have flexibility and can achieve the desired low dielectric constant.

[0022] The polyurethane particles of the present invention may have any one or any two of the above properties (a) to (c), preferably (a) and (c), or (b) and (c), and more preferably all of (a) to (c). Furthermore, the present application provides a method for producing polyurethane particles, by which the polyurethane particles described above can be obtained.

[0023] <Polyurethane particles> The polyurethane particles of the present invention may have any one or any two of the properties (a) to (c), preferably (a) and (c), or (b) and (c), or more preferably all of (a) to (c). Property (a): Dielectric loss tangent at 10 GHz is 0.0001 to 0.01, preferably 0.0005 to 0.009, more preferably 0.001 to 0.008, and most preferably 0.002 to 0.007; Property (b): a dielectric constant at 10 GHz of 1.8 to 3.0, preferably 1.9 to 2.7, more preferably 2.0 to 2.5, and most preferably 2.1 to 2.3; Property (c): Glass transition temperature is -60 to 20°C, preferably -50 to 15°C, more preferably -40 to 10°C, and most preferably -30 to 5°C.

[0024] When the polyurethane particles of the present invention have any one of the above properties (a) to (c), it is particularly preferable that they have property (a), i.e., a desired dielectric loss tangent. By having the desired dielectric loss tangent, it is possible to achieve a desired low dielectric constant. The polyurethane particles of the present invention preferably have the above-mentioned property (c), i.e., a desired glass transition temperature, which allows the polyurethane particles to have flexibility.

[0025] <<Measurement of dielectric loss tangent and dielectric constant>> In the present invention, the values ​​of the dielectric loss tangent and the dielectric constant are values ​​measured using a cavity resonator in accordance with Japanese Industrial Standard JIS C2565, specifically, values ​​measured for the dielectric loss tangent at 10 GHz and the dielectric constant at 10 GHz.

[0026] <<Glass transition temperature>> In the present invention, the glass transition temperature can be measured using a differential scanning calorimeter (DSC). Specifically, the glass transition temperature can be determined from the base shift in the DSC curve, which is the measurement result.

[0027] <<Volume average particle size>> The polyurethane particles of the present invention have a volume average particle size of 0.1 to 300 μm, preferably 0.3 to 100 μm, more preferably 0.5 to 50 μm, and most preferably 1 to 30 μm. In the present invention, the volume average particle size of the polyurethane particles can be measured using a laser diffraction particle size distribution analyzer.

[0028] <<Polyurethane particles formed from a composition containing a polyol or a polyisocyanate prepolymer>> The present invention provides polyurethane particles formed from a composition having a polyol represented by the above formula (I) or a polyisocyanate prepolymer represented by the above formula (II). It is noted that polyurethane particles formed from a composition containing a polyol or a polyisocyanate prepolymer also have the above-mentioned properties, i.e., any one or any two of the above properties (a) to (c), preferably (a) and (c), or (b) and (c), or more preferably all of (a) to (c). Additionally, polyurethane particles formed from a composition having a polyol or a polyisocyanate prepolymer may have a particle size described as "volume average particle size."

[0029] <<Polyol represented by formula (I)>> The polyol is preferably a polyol represented by the following formula (I): Polyols of formula (I) are commercially available or can be obtained by independent preparation.

[0030] [ka]

[0031] In formula (I), R represents a divalent organic group, and is a butane 1,2-diyl group represented by the following formula (A) or a butene 1,2-diyl group represented by the following formula (B). n represents the number of repeating units, and is particularly preferably 16 to 65, more preferably 18 to 55, even more preferably 20 to 35, and most preferably 22 to 26.

[0032] [ka]

[0033] <<Polyisocyanate prepolymer represented by formula (II)>> The polyisocyanate prepolymer is preferably a polyisocyanate prepolymer represented by the following formula (II): Here, R and n have the same definitions as described in <<Polyol represented by formula (I)>>.

[0034] [ka]

[0035] In formula (II), R' and R" may be the same or different and independently represent a divalent organic group. In particular, R' and R" are independently a linear or branched alkylene group having 4 to 20, preferably 5 to 15, more preferably 6 to 10 carbon atoms (however, some carbon atoms in the alkylene group may be substituted with an alicyclic hydrocarbon or an aromatic hydrocarbon), or a linear or branched alkenylene group having 4 to 20, preferably 5 to 15, more preferably 6 to 10 carbon atoms (however, some carbon atoms in the alkylene group may be substituted with an alicyclic hydrocarbon or an aliphatic hydrocarbon).

[0036] The polyisocyanate prepolymer represented by formula (II) is commercially available or can be obtained by producing it from a polyol and a polyisocyanate. When producing it from a polyol and a polyisocyanate, it is preferable to use a polyol represented by formula (I) above as the polyol, and R' and R" are derived from the polyisocyanate used.

[0037] <<Polyisocyanate>> In this application, the term "polyisocyanate" refers to a compound having two or more isocyanate groups. In addition, in this application, the term "polyisocyanate monomer" refers to unmodified monomers, dimers, and trimers of "polyisocyanates." For example, the polymer of tolylene diisocyanate described below does not fall under the category of "polyisocyanate monomer" in this application. In addition, for example, the trimer (isocyanurate) of bifunctional isocyanate described below falls under the category of "polyisocyanate monomer" in this application.

[0038] Examples of polyisocyanates include bifunctional isocyanates having two isocyanate groups and polyfunctional isocyanates having three or more isocyanate groups. Difunctional isocyanates include hexamethylene isocyanate (HDI), tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), lysine diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4 (or 2,6)-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated XDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate. Dimer diisocyanate, dianisidine diisocyanate, phenyl diisocyanate, halogenated phenyl diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene diisocyanate, octadecylene diisocyanate, 1,5-naphthalene diisocyanate, polymethylene polyphenylene diisocyanate, naphthalene diisocyanate, tolylene diisocyanate polymer, diphenylmethane diisocyanate polymer, hexamethylene diisocyanate polymer , 3-phenyl-2-ethylene diisocyanate, cumene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-ethoxy-1,3-phenylene diisocyanate, 2,4'-diisocyanate diphenyl ether, 5,6-dimethyl-1,3-phenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, benzidine diisocyanate, 9,10-anthracene diisocyanate, 4,4'-diisocyanate benzyl, 3,3'-dimethyl-4,4'-diisocyanate diphenyl Examples of the isocyanate include, but are not limited to, methylmethane, 2,6-dimethyl-4,4'-diisocyanatodiphenyl, 3,3'-dimethoxy-4,4'-diisocyanatodiphenyl, 1,4-anthracene diisocyanate, phenylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,0-decamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), and norbornane diisocyanate.

[0039] Examples of polyfunctional isocyanates include triphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 2,4,4'-triisocyanatodiphenyl ether, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, and trimers of bifunctional isocyanates (biuret, isocyanurate, adduct).

[0040] The polyisocyanate is not particularly limited as long as the resulting polyurethane particles have the desired flexibility and low dielectric constant. For example, it is preferable to use one that has good compatibility with the polyol used, such as IPDI, XDI, or a trimer thereof.

[0041] <<Polyol>> As the polyol, it is preferable to use a polyol represented by the above formula (I). Other polyols that can be used include the following: Here, polyol refers to a compound having two or more hydroxyl groups (OH groups) in the compound. Examples of polyols include polyester polyols, polyether polyols, polycarbonate polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, acrylic polyols, polycaprolactone polyols, and aliphatic polyhydric alcohols having 1 to 20 carbon atoms, but are not limited to these.

[0042] <<Composition Having Polyol Represented by Formula (I); or Polyisocyanate Prepolymer Represented by Formula (II)>> The present invention provides polyurethane particles formed from a composition containing a polyol represented by formula (I) above or a polyisocyanate prepolymer represented by formula (II) above, and the composition may contain an organic solvent. Furthermore, the composition may contain a substance other than the polyol represented by the above formula (I) or the polyisocyanate prepolymer represented by the above formula (II).

[0043] <<Organic solvents>> The organic solvent is not particularly limited as long as it is a compound that can be mixed with the polyol represented by the above formula (I) or the polyisocyanate prepolymer represented by the above formula (II). The organic solvent preferably has low solubility in water. Moreover, the organic solvent preferably has an azeotropic point with water of 100° C. or lower at 1013 hPa. Examples of organic solvents having an azeotropic point with water of 100°C or less at 1013 hPa include, but are not limited to, aromatic compounds (e.g., toluene, benzene, etc.), ester compounds (e.g., methyl acetate, ethyl acetate, butyl acetate, etc.), ketone compounds (e.g., acetone, methyl ethyl ketone, etc.), saturated aliphatic hydrocarbons (e.g., n-heptane, n-hexane, n-octane, etc.), etc. These organic solvents may be used alone or in combination of two or more.

[0044] Examples of substances other than the polyol represented by the above formula (I) or the polyisocyanate prepolymer represented by the above formula (II) include, but are not limited to, resins, rubbers, fillers, function-imparting agents, and inevitable impurities. Examples of fillers include, but are not limited to, metals, metal compounds, carbon materials (carbon black, carbon nanotubes, expanded graphite, carbon fibers), glass, minerals, and the like. Functional agents can include, but are not limited to, antioxidants, antistatic agents, flame retardants, plasticizers, clarifying agents, antibacterial agents, and preservatives.

[0045] <Materials containing polyurethane particles of the present invention> The present invention provides a material comprising the polyurethane particles described above. The material may comprise materials other than the polyurethane particles mentioned above. Examples of materials other than polyurethane particles include, but are not limited to, paper, a medium (water, a heat medium), a thermoplastic resin, a thermosetting resin, rubber, an elastomer, and a thermoplastic elastomer. For example, the polyurethane particles of the present invention may be disposed on at least one surface of a support made of a sheet-like material such as synthetic paper, plastic film, rubber sheet, metal sheet, glass, etc. This polyurethane particle layer may further contain, as necessary, a binder resin (e.g., a UV-curable resin such as urethane acrylate or acrylic acrylate), a thickener, a leveling agent, a binder resin curing agent (organic peroxide, photoradical generator), etc. These may be used in combination. In particular, the polyurethane particles of the present invention are preferably mixed with a resin to provide a resin containing polyurethane particles. Examples of the resin include, but are not limited to, paper, a medium (water, a heat medium), a thermoplastic resin, a thermosetting resin, a rubber, an elastomer, and a thermoplastic elastomer. The content of the polyurethane particles in the material containing the polyurethane particles is not particularly limited.

[0046] The polyurethane particles of the present invention and materials containing the polyurethane particles of the present invention can be used in fields where low dielectric constant and flexibility are required. The polyurethane particles of the present invention and materials containing the polyurethane particles of the present invention can be used in, for example, electronic circuit boards, build-up boards, sealing materials, prepregs, and other electronic components, high-frequency sensors, millimeter-wave radars, communication modules, and other automobile components, but are not limited to these.

[0047] <Method of producing polyurethane particles of the present invention -Part 1-> The polyurethane particles of the present invention can be produced, for example, as follows. (A) preparing a polyol represented by formula (I); (B) providing a polyisocyanate; and (C) suspension polymerizing the polyol and the polyisocyanate to form polyurethane particles; By having the above, polyurethane particles can be obtained.

[0048] Step (A) is a step of preparing a polyol represented by the above formula (I). The polyols may be commercially available or may be obtained by proprietary production. Step (B) is a step of preparing a polyisocyanate. As the polyisocyanate, the polyisocyanates described above in <<Polyisocyanate>> can be used.

[0049] The step (C) is a step of forming polyurethane particles by suspension polymerization of the polyol and the polyisocyanate. In step (C), an organic solvent can be used. The organic solvent is not particularly limited as long as it is a compound that can be mixed with the polyisocyanate and polyol. The organic solvents described above in "Organic Solvents" can be used as the organic solvent.

[0050] The suspension polymerization in step (C) is preferably carried out in the presence of a suspension stabilizer. The suspension stabilizer may be added in advance to a dispersion medium such as water. For example, when the dispersion medium such as water further contains a suspension stabilizer, the suspension tends to be stabilized, making it possible to produce urethane particles more easily. Examples of suspension stabilizers include, but are not limited to, cellulose-based water-soluble resins such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose, polyvinyl alcohol, polyacrylates, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. The suspension stabilizers may be used alone or in combination of two or more.

[0051] Step (C) may be carried out in the presence of a surfactant together with or instead of a suspension stabilizer. The surfactant may be added in advance to a dispersion medium such as water. For example, when the dispersion medium such as water further contains a surfactant, the suspension tends to be stabilized, making it possible to produce urethane particles more easily. Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. The surfactants may be used alone or in combination of two or more.

[0052] In step (C), a catalyst can be used, including, but not limited to, organotin compounds such as dibutyltin dilaurate and di-n-octyltin maleate, organozirconium compounds such as zirconium tetraacetylacetonate, zirconium octylate compounds and zirconyl chloride compounds, and organotitanium compounds such as titanium ethylacetoacetate.

[0053] Step (C) can be carried out under conditions such as, but not limited to, a temperature of 60° C. and a pressure of 1013 hPa, depending on the type and amount of the polyol and polyisocyanate used.

[0054] The above-mentioned production method may include steps other than steps (A) to (C) as long as the desired polyurethane particles can be produced. Examples of such steps include, but are not limited to, a washing step, a drying step, and a classification step.

[0055] <Method of producing polyurethane particles of the present invention -Part 2-> The polyurethane particles of the present invention can be produced, for example, as follows. (D) preparing a polyisocyanate prepolymer represented by formula (II); and (E) a step of carrying out suspension polymerization using the polyisocyanate prepolymer obtained in step (D); By having the above, polyurethane particles can be obtained.

[0056] Step (D) is a step of preparing a polyisocyanate prepolymer represented by the above formula (II). The polyisocyanate prepolymer can be obtained, for example, by the following process. That is, (A) a step of preparing a polyol represented by the above formula (I); (B') preparing a polyisocyanate monomer; and (C') reacting the polyol with the polyisocyanate monomer to form a polyisocyanate prepolymer represented by formula (II); By having the above, a polyisocyanate prepolymer can be obtained.

[0057] The step (A) is the same step as that described in <Method for producing polyurethane particles of the present invention -Part 1->. Step (B') is a step of preparing a polyisocyanate monomer. As described above, the polyisocyanate monomer refers to unmodified monomers, dimers, and trimers of "polyisocyanates." While it depends on the polyol used and the properties of the desired polyisocyanate prepolymer, it is preferable to use, for example, hexamethylene isocyanate (HDI), tolylene diisocyanate (TDI), isophorone diisocyanate (IPDI), etc. as the polyisocyanate monomer. Step (C') is a step of reacting the polyol with the polyisocyanate monomer to form a polyisocyanate prepolymer represented by the above formula (II).

[0058] In step (C'), the reaction is preferably carried out by solution polymerization. In step (C'), the same catalyst as in step (C) may be used. The solution polymerization conditions depend on the polyol and polyisocyanate monomer used, but can be, for example, but are not limited to, a temperature of 70°C and a pressure of 1013 hPa.

[0059] In step (C'), an organic solvent can be used. The organic solvent is not particularly limited as long as it is a compound that can be mixed with the polyisocyanate monomer and the polyol. The organic solvents described above in <<Organic Solvents>> can be used as the organic solvent.

[0060] Step (E) is a step of carrying out suspension polymerization using the polyisocyanate prepolymer obtained in step (D). In step (E), the polyisocyanate prepolymer obtained in step (D) may be subjected to suspension polymerization alone, or the polyisocyanate prepolymer may be used in addition to the above-mentioned polyisocyanate and / or polyol to perform suspension polymerization. The suspension polymerization in step (E) can be carried out in the same manner as the suspension polymerization in step (C) described above. Although it depends on the polyisocyanate prepolymer used in step (E), for example, the organic solvents, suspension stabilizers, surfactants, catalysts, conditions, etc. described above in step (C) can be used.

[0061] The above-mentioned production method may include steps other than steps (D) to (E) as long as the desired polyurethane particles can be produced. More specifically, the above-mentioned production method may include steps other than steps (A) to (E) as long as the desired polyurethane particles can be produced. Examples of such steps include, but are not limited to, a washing step, a drying step, and a classification step. [Example]

[0062] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. <Synthesis Example 1> A 2L separable flask equipped with a stirrer was charged with 1160g of hydrogenated polybutadiene (number average molecular weight Mn=1500, GI-1000, manufactured by Nippon Soda Co., Ltd.) with an R SP value of 8.2 as the polyol component and the following structure, and 240g of hexamethylene diisocyanate (HDI) as the isocyanate component. After heating to 70°C, 0.7g of dibutyltin dilaurate was added as a catalyst and the mixture was stirred and mixed for 3 hours to allow the reaction to proceed. Toluene was then added to obtain prepolymer A with a solids content of 70%.

[0063] [ka]

[0064] <Synthesis Example 2> A 2-liter autoclave that had been thoroughly purged with nitrogen gas and dried was charged with 750 g of trimethylolpropane caprolactone polyol (number average molecular weight Mn=830, PLACCEL 308, manufactured by Daicel Chemical Industries, Ltd.) as the polyol component, in which the SP value of the repeating unit, i.e., the SP value of the group in the repeating unit of the following structural formula, is 10.1, and 1,000 g of hexamethylene diisocyanate (HDI) as the isocyanate component. The autoclave was further thoroughly purged upward with nitrogen gas, and then the autoclave was sealed and reacted with stirring and mixing at 120°C for 20 hours. Thereafter, unreacted HDI was removed under reduced pressure, and toluene was added to obtain Prepolymer B with a solid content of 90%.

[0065] [ka]

[0066] Example 1 A 2 L separable flask equipped with a stirrer was charged with 400 g of water, and 10 g of hydroxypropylmethylcellulose and 2 g of sodium di-2-ethylhexyl sulfosuccinate were dissolved therein to prepare an aqueous dispersion medium solution. Separately, 320 g of the prepolymer A obtained in Synthesis Example 1 above, 75 g of an isocyanurate-type isocyanate of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) as an isocyanate component, and 95 g of toluene as a dilution solvent were mixed to prepare a particle raw material.

[0067] The particle raw material was added to the dispersion medium aqueous solution obtained above while stirring at 400 rpm to prepare a suspension. Next, the suspension was heated to 60°C while continuing to stir, and reacted for 4 hours, then cooled to room temperature, solid-liquid separated, thoroughly washed with water, and dried at 70°C for 20 hours to obtain polyurethane particles A1 with a volume average particle diameter of 4.1 μm. The volume average particle diameter was measured using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, "SALD2300"). Although not shown, the polyurethane particles A1 were solid particles (not hollow particles, but solid particles).

[0068] The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained polyurethane particles A1 were measured using a cavity resonator (measurement frequency: 10 GHz) in accordance with Japanese Industrial Standard JIS C2565. The glass transition temperature was measured using a differential scanning calorimeter DSC ("DSCvesta" manufactured by Rigaku Corporation). As a result, the dielectric constant was 2.155, the dielectric dissipation factor was 0.0025, and the glass transition temperature was −28° C. These results are shown in Table 1. The resulting polyurethane particles A1 had the desired flexibility, as indicated by a glass transition temperature of −28° C., and also had the desired low dielectric constant.

[0069] <Example 2> A 2 L separable flask equipped with a stirrer was charged with 600 g of water, and 15 g of hydroxypropylmethylcellulose and 1 g of sodium di-2-ethylhexyl sulfosuccinate were dissolved therein to prepare an aqueous dispersion medium solution. Separately, a particle raw material was prepared by mixing 175 g of GI-1000 (manufactured by Nippon Soda Co., Ltd.) as a polyol component with an R SP value of 8.2, 125 g of isocyanurate-type isocyanate of 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) as a polyisocyanate monomer component, 0.0075 g of dibutyltin dilaurate as a catalyst, and 100 g of toluene as a dilution solvent.

[0070] The particle raw materials were added to the aqueous dispersion medium solution while stirring at 400 rpm to prepare a suspension. Thereafter, polyurethane particles A2 having a volume average particle diameter of 3.4 μm were obtained by carrying out the same procedure as in Example 1. Although not shown, the polyurethane particles A2 were solid particles (not hollow particles, but solid particles). The dielectric constant, dielectric loss tangent, and glass transition temperature of the resulting polyurethane particles A2 were measured in the same manner as in Example 1 and were found to be 2.221, 0.0065, and −15° C., respectively. These results are shown in Table 1. The resulting polyurethane particles A2 had the desired flexibility and the desired low dielectric constant, as indicated by a glass transition temperature of -15°C.

[0071] <Comparative Example 1> A 2 L separable flask equipped with a stirrer was charged with 300 g of water, and 10 g of hydroxypropylmethylcellulose was dissolved therein to prepare an aqueous dispersion medium solution. Separately, 450 g of the prepolymer B obtained in Synthesis Example 2 above and 50 g of toluene as a dilution solvent were mixed to prepare a particle raw material. The particle raw materials were added to the aqueous dispersion medium solution while stirring at 400 rpm to prepare a suspension. Thereafter, polyurethane particles C1 having a volume average particle diameter of 15.0 μm were obtained by performing the same procedure as in Example 1. Although not shown, the polyurethane particles C1 were solid particles (not hollow particles, but solid particles). The dielectric constant, dielectric loss tangent, and glass transition temperature of the resulting polyurethane particles C1 were measured in the same manner as in Example 1 and were found to be 2.753, 0.0371, and −13° C., respectively. These results are shown in Table 1. The resulting polyurethane particles C1 had flexibility, as indicated by a glass transition temperature of -13°C, but were unable to provide the desired low dielectric constant.

[0072] <Comparative Example 2> A 2 L separable flask equipped with a stirrer was charged with 600 g of water, and 12 g of sodium di-2-ethylhexyl sulfosuccinate was dissolved therein to prepare an aqueous dispersion medium solution. Separately, a particle raw material was prepared by mixing 60 g of polyester polyol P-2010 (manufactured by Kuraray Co., Ltd.) obtained by reacting 3-methyl-1,5-pentanediol and adipic acid as a polyol component with R = 10.7, 80 g of nurate type hexamethylene diisocyanate (HDI) and 80 g of water-dispersible isocyanate WB40-100 (manufactured by Asahi Kasei Corporation) as isocyanate components, 0.024 g of dibutyltin dilaurate as a catalyst, and 160 g of toluene as a dilution solvent. The particle raw materials were added to the dispersion medium while stirring at 400 rpm to prepare a suspension. Thereafter, polyurethane particles C2 having a volume average particle diameter of 12.5 μm were obtained by carrying out the same procedure as in Example 1. Although not shown, the polyurethane particles C2 were solid particles (not hollow particles, but solid particles). The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained polyurethane particles C2 were measured in the same manner as in Example 1 and were found to be 2.629, 0.0181, and 20° C., respectively. These results are shown in Table 1. The obtained polyurethane particles C2 had flexibility, as indicated by a glass transition temperature of 20° C., but were unable to provide the desired low dielectric constant.

[0073] <Comparative Example 3> A 2 L separable flask equipped with a stirrer was charged with 900 g of water, and 2 g of sodium alkyldiphenyletherdisulfonate was dissolved therein to prepare an aqueous dispersion medium solution. Separately, 250 g of styrene and 5 g of divinylbenzene as acrylic monomers and 0.25 g of t-butyl hydroperoxide as an initiator were mixed to prepare a particle raw material. While stirring the aqueous dispersion medium solution at 200 rpm, the aqueous dispersion solution was heated to 60°C under a nitrogen flow, and the particle raw materials were added dropwise over 4 hours. After the dropwise addition was completed, the reaction solution was heated to 80°C and subjected to an aging reaction for an additional 4 hours, then cooled to room temperature and dried at 70°C for 20 hours to obtain polystyrene particles C3 with a volume average particle diameter of 0.3 μm. Although not shown, the polyurethane particles C3 were solid particles (not hollow particles, but solid particles). The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained polystyrene particles C3 were measured in the same manner as in Example 1 and were found to be 2.099, 0.00054, and 90° C., respectively. These results are shown in Table 1. The resulting polyurethane particles C3 were able to provide the desired low dielectric constant, but lacked flexibility, as indicated by the glass transition temperature of 90°C.

[0074] <Comparative Example 4> A 2 L separable flask equipped with a stirrer was charged with 600 g of water, and 20 g of hydroxypropylmethylcellulose was dissolved therein to prepare an aqueous dispersion medium solution. Separately, 200 g of polymeric diphenylmethane diisocyanate (PMDI) as an isocyanate component and 200 g of toluene as a dilution solvent were mixed together to prepare a particle raw material. The particle raw materials were added to the aqueous dispersion medium solution while stirring at 400 rpm to prepare a suspension. The suspension was then heated to 60°C while continuing to stir, reacted for 4 hours, cooled to room temperature, separated into solid and liquid, thoroughly washed with water, and dried at 70°C for 20 hours to obtain polyurethane particles C4 having a volume average particle size of 10.0 µm. Although not shown, polyurethane particles C4 were hollow particles (particles having voids inside, rather than solid particles). The dielectric constant, dielectric loss tangent, and glass transition temperature of the resulting polyurethane particles C4 were measured in the same manner as in Example 1 and were found to be 2.820, 0.0219, and 35° C., respectively. These results are shown in Table 1. The obtained polyurethane particles C4 had no flexibility, as indicated by a glass transition temperature of 35° C. Furthermore, the desired low dielectric constant was not achieved.

[0075] [Table 1]

Claims

1. A polyol represented by the following formula (I) (wherein R represents a butane 1,2-diyl group or a butene 1,2-diyl group, and n represents the number of repeating units); or A polyisocyanate prepolymer represented by the following formula (II): (wherein R and n have the same definitions as above, and R′ and R″ may be the same or different and independently represent a divalent organic group); 1. Polyurethane particles formed from a composition having Polyurethane particles having a dielectric loss tangent at 10 GHz of 0.0001 to 0.01, a glass transition temperature of -60 to 20°C, and being solid particles. 【Chemical 1】

2. 2. The polyurethane particles according to claim 1, having a volume average particle size of 0.1 to 300 μm.

3. A material comprising polyurethane particles according to claim 1 or 2.

4. (A) preparing a polyol represented by the following formula (I): (wherein R represents a butane 1,2-diyl group or a butene 1,2-diyl group, and n represents the number of repeating units); (B) providing a polyisocyanate; and (C) suspension polymerizing the polyol and the polyisocyanate to form polyurethane particles; By having the above formula (1), polyurethane particles that are solid particles and have a dielectric loss tangent at 10 GHz of 0.0001 to 0.01 and a glass transition temperature of −60 to 20° C. are obtained. 【Chemistry 2】

5. (D) preparing a polyisocyanate prepolymer represented by the following formula (II): (wherein R represents a butane 1,2-diyl group or a butene 1,2-diyl group, n represents the number of repeating units, and R′ and R″ may be the same or different and independently represent a divalent organic group); and (E) a step of carrying out suspension polymerization using the polyisocyanate prepolymer; By having the above formula (1), polyurethane particles that are solid particles and have a dielectric loss tangent at 10 GHz of 0.0001 to 0.01 and a glass transition temperature of −60 to 20° C. are obtained. 【Chemistry 2】

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