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

Abstract

To provide solid polyurethane particles with excellent flexibility, featuring low dielectric constant and low dielectric loss tangent. [Solution] 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 Art

[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 speed up information processing using electronic devices, there is a need to reduce the dielectric constant and dielectric loss tangent of the insulating portions of the materials used in electronic components. There is a demand for reducing the dielectric constant and dielectric loss tangent of particles such as the materials, polyurethane beads, polybutadiene rubber, and polystyrene beads used in the insulating portions.

[0003] For example, Patent Document 1 discloses surface-modified silica particles having a hydrophobic surface by subjecting the silica surface to a silane treatment, and discloses using the surface-modified silica particles as a low dielectric material. However, since silica particles generally do not have the desired flexibility or have poor affinity with organic resins, a material having better flexibility and better affinity with resins is required. In addition, although the use of fluororesins and polyimide resins as low dielectric materials can be found in various documents, when these resins are used, as with the above silica particles, they do not have the desired flexibility and / or have poor affinity with organic resins. Therefore, a material having better flexibility and better affinity with resins is required.

[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 achieving a lower dielectric constant and a lower dielectric loss tangent with the hollow particles. Similar to Patent Document 2, Patent Documents 3 and 4 disclose methods for achieving low dielectric constant and low dielectric loss tangent using hollow particles. More specifically, Patent Document 3 discloses the production of hollow particles using aromatic acrylic monomers, while Patent Document 4 discloses the production of hollow particles using aromatic monofunctional monomers such as styrene and aromatic acrylic monomers such as divinylbenzene.

[0005] The resulting material, i.e., the hollow particles, is generally incorporated into binders and other materials when applied to electronic components. However, maintaining the hollow shape during and / or after the compounding process is difficult, resulting in the problem of not being able to achieve the desired low dielectric constant and low dielectric loss tangent. Furthermore, particles obtained from aromatic acrylic monomers or styrene monomers had the problem of having excellent low dielectric properties but poor flexibility.

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

[0007] [Patent Document 1] Japanese 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] Japanese Patent Publication No. 2021-91791. [Overview of the project] [Problems that the invention aims to solve]

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

[0009] To achieve the above objective, the inventors have discovered the following invention. <1> Polyurethane particles having a dielectric loss tangent 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 at 10 GHz.

[0010] <2> Polyols 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, 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 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein R' and R'' may be the same or different, and independently represent a linear or branched alkenylene group having 4 to 20 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein R' and R'' may be the same or different, and independently represent a linear or branched alkylene, and independently represent a linear or branched alkylene group having 4 to 20 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein R' and R'' may be the same, and independently represent a linear or branched alkylene group having 4 to 20 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein R' and R'' may be the same, and independently represent a divalent organic group. Polyurethane particles formed from a composition having the following properties.

[0011] [ka]

[0012] <3> In the above <1>, the polyurethane particles are preferably 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> In any of the above <1> to <3>, the glass transition temperature of the polyurethane particles is preferably -60 to 20 °C, more preferably -50 to 15 °C, still more preferably -40 to 10 °C, and most preferably -30 to 5 °C. <5> In any of the above <1> to <4>, the volume average particle diameter of the polyurethane particles is preferably 0.1 to 300 μm, more preferably 0.3 to 100 μm, still more preferably 0.5 to 50 μm, and most preferably 1 to 30 μm. <6> A material having the polyurethane particles described in any of the above <1> to <5>.

[0014] <7> (A) A step of preparing a polyol represented by the above formula (I); (B) A step of preparing a polyisocyanate; and (C) A step of subjecting the polyol and the polyisocyanate to suspension polymerization to form polyurethane particles; A method for producing polyurethane particles, comprising obtaining polyurethane particles.

[0015] <8> (D) A step of preparing a polyisocyanate prepolymer represented by the above formula (II); and (E) A step of performing suspension polymerization using the polyisocyanate prepolymer; A method for producing polyurethane particles, comprising obtaining polyurethane particles.

[0016] <9> In the above <8>, (A) A step of preparing a polyol represented by the above formula (I); (B’) A step of preparing a polyisocyanate monomer; and (C’) Reacting the polyol with the polyisocyanate monomer to form a polyisocyanate prepolymer represented by the above formula (II); It further has, and it is preferable to use the obtained polyisocyanate prepolymer in the step (D).

[0017] <10> In the above <7> to <9>, the polyurethane particles preferably have the following characteristics (a) and / or (b) and have the characteristic (c): Characteristic (a): The 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; Characteristic (b): The dielectric constant at 10 GHz is 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; Characteristic (c): The 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> In the above <10>, the volume average particle diameter of the polyurethane particles is preferably 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.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide particles excellent in flexibility and having a reduced dielectric constant and a reduced dielectric loss tangent. Specifically, according to the present invention, it is possible to provide solid polyurethane particles excellent in flexibility and having a reduced dielectric constant and a reduced dielectric loss tangent. In addition, or in addition to the above effects, the present invention can provide a method for producing the above polyurethane particles.

Embodiments for Carrying Out the Invention

[0020] The invention described in this application (hereinafter sometimes abbreviated as "the present invention") will be explained below. This application provides polyurethane particles that are highly flexible and have low dielectric constant and low dielectric loss tangent. Specifically, this application provides polyurethane particles having one of the following characteristics (a) to (c), particularly characteristic (a), or two of them, preferably (a) and (c), or (b) and (c), and more preferably all of (a) to (c). Characteristic (a): The 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; Characteristic (b): The dielectric constant at 10 GHz is 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; Characteristic (c): The 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] Furthermore, in a composition having a polyol having repeating units such as the polyol represented by formula (I) above; or a polyisocyanate prepolymer having groups derived from a polyol having repeating units such as the polyol represented by formula (I) above, such as a polyisocyanate prepolymer represented by formula (II) above; the SP value of the groups within the repeating units is preferably 8.00 to 9.00, more 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, which is a value calculated by the Fedors method. When the groups within the repeating units have the above SP value, the resulting polyurethane particles are flexible and can achieve the desired low dielectric constant.

[0022] The polyurethane particles of the present invention preferably have one or two of the above characteristics (a) to (c), preferably (a) and (c), or (b) and (c), and more preferably all of (a) to (c). Furthermore, this application provides a method for producing polyurethane particles to obtain the above-mentioned polyurethane particles.

[0023] <Polyurethane particles> The polyurethane particles of the present invention have one or two of the properties (a) to (c), preferably (a) and (c), or (b) and (c), or more preferably all of (a) to (c). Characteristic (a): The 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; Characteristic (b): The dielectric constant at 10 GHz is 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; Characteristic (c): The 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] If the polyurethane particles of the present invention have any one of the above characteristics (a) to (c), it is particularly preferable that they have characteristic (a), i.e., a desired dielectric loss tangent. By having a desired dielectric loss tangent, a desired low dielectric constant can be achieved. Furthermore, the polyurethane particles of the present invention preferably have the above-mentioned characteristic (c), namely a desired glass transition temperature. By having a desired glass transition temperature, the polyurethane particles can be flexible.

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

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

[0027] <<Volume-average particle size>> The polyurethane particles of the present invention preferably have a volume-average particle diameter 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 this invention, the volume-average particle size of polyurethane particles can be measured using a laser diffraction particle size analyzer.

[0028] <<Polyurethane particles formed from a composition containing a polyol or polyisocyanate prepolymer>> The present invention provides polyurethane particles formed from a composition having a polyol represented by formula (I) above; or a polyisocyanate prepolymer represented by formula (II) above. Furthermore, polyurethane particles formed from a composition containing a polyol or polyisocyanate prepolymer also have the above properties, that is, one or two of the above properties (a) to (c), preferably (a) and (c), or (b) and (c), or more preferably all of (a) to (c). Furthermore, polyurethane particles formed from a composition containing a polyol or polyisocyanate prepolymer may have the particle size indicated by <<Volume-average particle diameter>>.

[0029] <<Polyol represented by formula (I)>> The polyol is preferably a polyol represented by the following formula (I). The polyol represented by formula (I) is commercially available or can be obtained by manufacturing it independently.

[0030] [ka]

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

[0032] [ka]

[0033] <<Polyisocyanate prepolymer represented by formula (II)>> The polyisocyanate prepolymer is preferably a polyisocyanate prepolymer represented by the following formula (II). Furthermore, R and n have the definitions 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'' may independently be a linear or branched alkylene group having 4 to 20 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein some of the carbon atoms of the alkylene group may be substituted with alicyclic hydrocarbons or aromatic hydrocarbons), or a linear or branched alkenylene group having 4 to 20 carbon atoms, preferably 5 to 15, more preferably 6 to 10 carbon atoms (wherein some of the carbon atoms of the alkylene group may be substituted with alicyclic hydrocarbons or aliphatic hydrocarbons).

[0036] The polyisocyanate prepolymer represented by formula (II) is industrially available or can be obtained by manufacturing it from a polyol and a polyisocyanate. When manufacturing it from a polyol and a polyisocyanate, the polyol represented by formula (I) above is often used, and R' and R'' are derived from the polyisocyanate used.

[0037] <<Polyisocyanate>> In this application, "polyisocyanate" means a compound having two or more isocyanate groups. Furthermore, in this application, "polyisocyanate monomer" refers to unmodified monomers, dimers, and trimers of "polyisocyanates." For example, polymers of tolylene diisocyanate, described later, do not fall under the definition of "polyisocyanate monomer" in this application. On the other hand, for example, trimers (isocyanurates) of the bifunctional isocyanates, described later, do fall under the definition of "polyisocyanate monomer" in this application.

[0038] Examples of polyisocyanates include difunctional isocyanates having two isocyanate groups and polyfunctional isocyanates having three or more isocyanate groups. As difunctional isocyanates, these 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(isocyanate methyl)cyclohexane (hydrogenated XDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate. Dimer acid diisocyanate, dianisidine diisocyanate, phenyl diisocyanate, halogenated phenyl diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene diisocyanate, octadecyl diisocyanate, 1,5-naphthalene diisocyanate, polymethylene polyphenylene diisocyanate, naphthalene diisocyanate, polymer of tolylene diisocyanate, polymer of diphenylmethane diisocyanate, polymer of hexamethylene diisocyanate ,3-phenyl-2-ethylene diisocyanate, cumene-2,4-diisocyanate, 4-methoxy-1,3-phenylenediisocyanate, 4-ethoxy-1,3-phenylenediisocyanate, 2,4'-diisocyanate diphenyl ether, 5,6-dimethyl-1,3-phenylenediisocyanate, 4,4'-diisocyanate diphenyl ether, benzidine diisocyanate, 9,10-anthracene diisocyanate, 4,4'-diisocyanate benzyl, 3,3'-dimethyl-4,4'-diisocyanate diphenyl Examples include, but are not limited to, methane, 2,6-dimethyl-4,4'-diisocyanate diphenyl, 3,3'-dimethoxy-4,4'-diisocyanate diphenyl, 1,4-anthracene diisocyanate, phenylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,0-decamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), norbornane diisocyanate, etc.

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

[0040] The polyisocyanate is not particularly limited as long as the resulting polyurethane particles have the desired flexibility and low dielectric strength, but it is preferable to use one that has good compatibility with the polyol used, such as IPDI, XDI, or its trimers.

[0041] <<Polyol>> It is preferable to use the polyol represented by the above formula (I) as the polyol. In addition, the following can be used as other polyols. Here, a polyol is defined as a compound that contains two or more hydroxyl groups (OH groups). Examples of polyols include, but are not limited to, 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.

[0042] <<A composition comprising a polyol represented by formula (I); or a polyisocyanate prepolymer represented by the above formula (II)>> The present invention provides polyurethane particles formed from a composition having a polyol represented by formula (I) above; or a polyisocyanate prepolymer represented by formula (II) above; the composition may contain an organic solvent. Furthermore, the material may contain substances other than the polyol represented by formula (I) above, or the polyisocyanate prepolymer represented by formula (II) above.

[0043] <<Organic solvent>> The organic solvent is not particularly limited as long as it is a compound that can be mixed with the polyol represented by formula (I) or the polyisocyanate prepolymer represented by formula (II). As the organic solvent, one with low solubility in water is preferred. Furthermore, as an organic solvent, one is preferred whose azeotropic point with water at 1013 hPa is 100°C or lower. Examples of organic solvents having an azeotropic point of 100°C or less with water 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.), and saturated aliphatic hydrocarbons (e.g., n-heptane, n-hexane, n-octane, etc.). These organic solvents may be used individually or in combination of two or more.

[0044] Examples of substances other than the polyol represented by formula (I) above, or the polyisocyanate prepolymer represented by formula (II) above, include, but are not limited to, resins, rubbers, fillers, functionalants, unavoidable impurities, etc. Examples of fillers include, but are not limited to, metals, metal compounds, carbon materials (carbon black, carbon nanotubes, expanded graphite, carbon fibers), glass, and minerals. Examples of functional additives include, but are not limited to, antioxidants, antistatic agents, flame retardants, plasticizers, clearing agents, antibacterial agents, and preservatives.

[0045] <Material having polyurethane particles according to the present invention> The present invention provides a material having the above-described polyurethane particles. The material may contain materials other than the polyurethane particles described above. Other materials besides polyurethane particles include, but are not limited to, paper, media (water, heat transfer fluid), thermoplastic resins, thermosetting resins, rubber, elastomers, and thermoplastic elastomers. For example, the polyurethane particles of the present invention may be arranged on at least one surface of a support made of a sheet-like material such as synthetic paper, plastic film, rubber sheet, metal sheet, or glass. This polyurethane particle layer may optionally further contain a binder resin (for example, a UV-curing 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 such resins include, but are not limited to, paper, media (water, heat transfer fluid), thermoplastic resins, thermosetting resins, rubber, elastomers, and thermoplastic elastomers. The content of polyurethane particles in the material containing polyurethane particles is not particularly limited.

[0046] The polyurethane particles of the present invention and the materials having 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 having the polyurethane particles of the present invention can be used, but are not limited to, electronic components such as electronic circuit boards, build-up substrates, encapsulants, and prepregs, as well as automotive components such as high-frequency sensors, millimeter-wave radars, and communication modules.

[0047] <Method for producing polyurethane particles according to the present invention - Part 1 -> The polyurethane particles of the present invention can be manufactured, for example, as follows. (A) A step of preparing the polyol represented by the above formula (I); (B) Steps for preparing polyisocyanates; and (C) A step of forming polyurethane particles by suspension polymerization of the polyol and the polyisocyanate; By having this, polyurethane particles can be obtained.

[0048] Step (A) is the step of preparing the polyol represented by the above formula (I). The polyol can be commercially available or obtained by manufacturing it independently. Step (B) is the step of preparing the polyisocyanate. As the polyisocyanate, the polyisocyanates described above under <<Polyisocyanate>> can be used.

[0049] Step (C) is a step of forming polyurethane particles by suspension polymerization of the polyol and the polyisocyanate. (C) In step (C), an organic solvent may 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 mentioned above. The organic solvents described in <<organic solvent>> above may be used.

[0050] (C) The suspension polymerization in step (C) should be carried out in the presence of a suspension stabilizer. The suspension stabilizer may be added in advance to the dispersion medium, such as water. For example, if the dispersion medium, such as water, further contains the suspension stabilizer, the suspension state tends to be stabilized, and urethane particles can be manufactured more easily. Examples of suspension stabilizers include, but are not limited to, cellulosic water-soluble resins such as methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose, as well as polyvinyl alcohol, polyacrylates, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. A suspension stabilizer may be used alone or in combination of two or more types.

[0051] Furthermore, step (C) may be carried out together with a suspension stabilizer, or in the presence of a surfactant instead of a suspension stabilizer. Surfactants may be added in advance to a dispersion medium such as water. For example, if the dispersion medium such as water further contains a surfactant, the suspension state tends to stabilize, and urethane particles can be manufactured more easily. Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Surfactants may be used individually or in combination of two or more types.

[0052] Furthermore, a catalyst can be used in step (C). Examples of such catalysts include, but are not limited to, organotin compounds such as dibutyltin dilaurate and dinormal octyl suzumalate, organozirconium compounds such as zirconium tetraacetylacetonate, zirconium octoate compounds and zirconyl chloride compounds, and organotitanium compounds such as titanium ethyl acetate.

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

[0054] The above manufacturing 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, washing, drying, and classification steps.

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

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

[0057] Step (A) is the same as the step described in <Method for producing polyurethane particles of the present invention - Part 1 ->. Step (B') is the step of preparing polyisocyanate monomers. As mentioned above, polyisocyanate monomers refer to unmodified monomers, dimers, and trimers of "polyisocyanates". Depending on the polyol used and the properties of the desired polyisocyanate prepolymer, it is preferable to use polyisocyanate monomers such as hexamethylene isocyanate (HDI), tolylene diisocyanate (TDI), or isophorone diisocyanate (IPDI). Step (C') is a step in which the polyol and the polyisocyanate monomer are reacted to form a polyisocyanate prepolymer represented by 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) above may be used. The conditions for solution polymerization depend on the polyol and polyisocyanate monomer used, but can be carried out under conditions such as a temperature of 70°C and a pressure of 1013 hPa, but are not limited to these.

[0059] (C') 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 in <<organic solvent>> above can be used.

[0060] Step (E) is a step in which suspension polymerization is carried out 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 subjected to suspension polymerization using the polyisocyanate and / or polyol in addition to the polyisocyanate prepolymer. The suspension polymerization in step (E) can be carried out using the same reaction method as the suspension polymerization in step (C) above. Depending on the polyisocyanate prepolymer used in step (E), for example, the organic solvent, suspension stabilizer, surfactant, catalyst, conditions, etc., as described above in step (C) can be used.

[0061] The above manufacturing method may include steps other than steps (D) to (E), as long as the desired polyurethane particles can be produced. More specifically, the above manufacturing 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, washing steps, drying steps, and classification steps. [Examples]

[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> In a 2L separable flask equipped with a stirrer, 1160g of hydrogenated polybutadiene with hydroxyl groups at both ends (number average molecular weight Mn=1500, GI-1000, manufactured by Nippon Soda Co., Ltd.), having an R SP value of 8.2 and the following structure, was charged as the polyol component, and 240g of hexamethylene diisocyanate (HDI) was charged as the isocyanate component. After raising the temperature 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 solid content of 70%.

[0063] [ka]

[0064] <Synthesis Example 2> In a 2L autoclave that had been thoroughly purged with nitrogen gas and dried, 750g of trimethylolpropancaprolactone polyol (number average molecular weight Mn=830, Praxel 308, manufactured by Daicel Chemical Industries, Ltd.), in which the SP value within the repeating unit, i.e., the SP value of the group within the repeating unit of the structural formula below is 10.1, was charged as the polyol component, and 1000g of hexamethylene diisocyanate (HDI) was charged as the isocyanate component. After further upward displacement with nitrogen gas, the autoclave was sealed and reacted by stirring and mixing at 120°C for 20 hours. After removing unreacted HDI under reduced pressure, toluene was added to obtain prepolymer B with a solid content of 90%.

[0065] [ka]

[0066] <Example 1> 400g of water was placed in a 2L separable flask equipped with a stirrer, and 10g of hydroxypropyl methylcellulose and 2g of sodium di-2-ethylhexyl sulfosuccinate were dissolved in it to prepare an aqueous dispersion medium. Separately, 320 g of prepolymer A obtained in Synthesis Example 1 above, 75 g of isocyanurate-type isocyanate of 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) as the isocyanate component, and 95 g of toluene as a diluent were mixed to prepare particle raw materials.

[0067] The aqueous dispersion medium obtained above was stirred at 400 rpm while the particle raw materials were added to prepare a suspension. Next, the suspension was heated to 60°C under continuous stirring and reacted for 4 hours. After cooling to room temperature, solid-liquid separation was performed, and after thorough washing with water, it was dried at 70°C for 20 hours to obtain polyurethane particles A1 with a volume-average particle size of 4.1 μm. The volume-average particle size was measured using a laser diffraction particle size analyzer (SALD2300, Shimadzu Corporation). Although not shown in the diagram, polyurethane particles A1 were solid particles (not hollow particles, but particles filled with solid material).

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

[0069] <Example 2> A dispersion medium aqueous solution was prepared by dissolving 15 g of hydroxypropyl methylcellulose and 1 g of sodium di-2-ethylhexyl sulfosuccinate in a 2 L separable flask equipped with a stirrer. Separately, particle raw materials were prepared by mixing 175g of GI-1000 (manufactured by Nippon Soda Co., Ltd.), which has an R SP value of 8.2, as the polyol component; 125g of isocyanurate-type isocyanate of 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) as the polyisocyanate monomer component; 0.0075g of dibutyltin dilaurate as the catalyst; and 100g of toluene as the diluent.

[0070] The aforementioned dispersion medium aqueous solution was stirred at 400 rpm while the particle raw materials were added to prepare a suspension. From this point onward, the same procedure as in Example 1 was followed to obtain polyurethane particles A2 with a volume-average particle diameter of 3.4 μm. Although not shown in the figures, polyurethane particles A2 were solid particles (not hollow particles, but particles filled with solid material). The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained 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 obtained polyurethane particles A2 possessed the desired flexibility and low dielectric constant, as indicated by their glass transition temperature of -15°C.

[0071] <Comparative Example 1> 300g of water was placed in a 2L separable flask equipped with a stirrer, and 10g of hydroxypropyl methylcellulose was dissolved in it to prepare an aqueous dispersion medium. Separately, 450g of prepolymer B obtained in Synthesis Example 2 above was mixed with 50g of toluene as a diluent to prepare particle raw materials. The aforementioned dispersion medium aqueous solution was stirred at 400 rpm while the particle raw materials were added to prepare a suspension. From this point onward, the same procedure as in Example 1 was followed to obtain polyurethane particles C1 with a volume-average particle diameter of 15.0 μm. Although not shown in the figures, the polyurethane particles C1 were solid particles (not hollow particles, but particles filled with solid material). The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained 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 obtained polyurethane particles C1 were flexible, as indicated by their glass transition temperature of -13°C, but they did not provide the desired low dielectric strength.

[0072] <Comparative Example 2> 600g of water was placed in a 2L separable flask equipped with a stirrer, and 12g of sodium di2-ethylhexyl sulfosuccinate was dissolved in it to prepare an aqueous dispersion medium. Separately, a particle raw material was prepared by mixing 60g of polyester polyol P-2010 (manufactured by Kuraray Co., Ltd.), obtained by reacting 3-methyl-1,5-pentanediol with adipic acid as the polyol component with R=10.7; 80g of the nurate form of hexamethylene diisocyanate (HDI) and 80g of the water-dispersible isocyanate WB40-100 (manufactured by Asahi Kasei Corporation) as the isocyanate component; 0.024g of dibutyltin dilaurate as the catalyst; and 160g of toluene as the diluent. The dispersion medium was stirred at 400 rpm while the particle raw materials were added to prepare a suspension. From this point onward, the same procedure as in Example 1 was followed to obtain polyurethane particles C2 with a volume-average particle diameter of 12.5 μm. Although not shown in the figures, the polyurethane particles C2 were solid particles (not hollow particles, but particles filled with solid material). 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 were flexible, as indicated by their glass transition temperature of 20°C, but they did not provide the desired low dielectric strength.

[0073] <Comparative Example 3> 900g of water was placed in a 2L separable flask equipped with a stirrer, and 2g of sodium alkyldiphenyl ether disulfonate was dissolved in it to prepare an aqueous dispersion medium. Separately, a particle raw material was prepared by mixing 250 g of styrene and 5 g of divinylbenzene as acrylic monomers, and 0.25 g of t-butyl hydroperoxide as an initiator. While stirring the dispersion medium aqueous solution at 200 rpm, the dispersion aqueous solution was heated to 60°C under a nitrogen flow, and the particle raw materials were added dropwise over 4 hours. After the addition was complete, the reaction solution was heated to 80°C, and the aging reaction was carried out for an additional 4 hours. Then it was 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 in the figures, the polyurethane particles C3 were solid particles (not hollow particles, but particles filled with material). 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 strength, but they lacked flexibility, as indicated by their glass transition temperature of 90°C.

[0074] <Comparative Example 4> A dispersion medium aqueous solution was prepared by placing 600g of water in a 2L separable flask equipped with a stirrer and dissolving 20g of hydroxypropyl methylcellulose in it. Separately, 200 g of polymeric diphenylmethane diisocyanate (PMDI) was mixed with 200 g of toluene as a diluent to prepare the particle raw material. The aforementioned dispersion medium aqueous solution was stirred at 400 rpm while the particle raw materials were added to prepare a suspension. Next, the suspension was heated to 60°C under continuous stirring and reacted for 4 hours. After cooling to room temperature, solid-liquid separation was performed, and after thorough washing with water, it was dried at 70°C for 20 hours to obtain polyurethane particles C4 with a volume-average particle size of 10.0 μm. Although not shown in the figures, the polyurethane particles C4 were hollow particles (not solid particles, but particles with voids inside). The dielectric constant, dielectric loss tangent, and glass transition temperature of the obtained 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 lacked flexibility, as indicated by their glass transition temperature of 35°C. Furthermore, they failed to provide the desired low dielectric strength.

[0075] [Table 1]

Claims

1. Polyurethane particles having a dielectric loss tangent of 0.0001 to 0.01 at 10 GHz.

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, independently representing a divalent organic group); Polyurethane particles formed from a composition having the following properties. 【Chemistry 1】

3. 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, independently representing a divalent organic group); Polyurethane particles according to claim 1, formed from a composition having the following characteristics. 【Chemistry 2】

4. Polyurethane particles according to claim 1, wherein the glass transition temperature is -60 to 20°C.

5. The polyurethane particles according to claim 1, wherein the volume-average particle diameter is 0.1 to 300 μm.

6. A material having polyurethane particles according to any one of claims 1 to 5.

7. (A) A step of 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) A step of preparing polyisocyanate; and (C) A step of forming polyurethane particles by suspension polymerization of the polyol and the polyisocyanate; A method for producing polyurethane particles, comprising having [a certain characteristic]. 【Transformation 3】

8. (D) A step of 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; A method for producing polyurethane particles, comprising having [a certain characteristic]. 【Chemistry 4】

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