Polyurethane resin and synthetic leather comprising same

Abstract

[Problem] The present invention addresses the problem of developing a polyurethane resin material excellent in low temperature characteristics (in particular, flexibility and strength in a low temperature environment) and suitable for synthetic leather or the like having high flame retardancy.　[Solution] A polyurethane resin comprising at least a structural unit derived from an isocyanate group-terminated prepolymer formed with an isocyanate component and a high molecular weight polyol component, and a structural unit derived from an isocyanurate skeleton-containing polyol, and including a structural unit derived from a long-chain aliphatic polyol having 8-20 carbon atoms in the structure thereof is produced by the reaction of the isocyanate group-terminated prepolymer, the polyol and the isocyanurate-based polyisocyanate compound, and the obtained polyurethane resin is used to form a surface layer on a support to obtain a synthetic leather.

Description

Polyurethane resin and synthetic leather using the same

[0001] The present invention relates to a novel flame-retardant polyurethane resin. More specifically, the present invention relates to a polyurethane resin that uses plant-derived components and has a high biomass ratio, and that has excellent flame retardancy, flexibility, and strength (particularly flexibility, flex resistance, and tensile strength in low-temperature environments), and to synthetic leather made using the same.

[0002] Synthetic leather made from polyurethane resin is widely used as a seat material for automobiles. Polyurethane resins for such applications generally require high flexibility and flame retardancy. In particular, applications that involve severe temperature changes require that flexibility and flame retardancy not be lost even with temperature changes. However, conventional polyurethane resins tend to lose flexibility in low-temperature environments.

[0003] One known method for imparting flame retardancy to polyurethane resin is to mix a flame retardant into it. However, when a liquid flame retardant is used in a polyurethane resin material, the flame retardant can leak out depending on the environment in which the product is used, a phenomenon known as "bleeding."

[0004] When such resin materials are used in automobile seat materials, the bleed-out flame retardant evaporates, causing problems such as clouding of the automobile windows. While adding a solid flame retardant is an option, the resulting polyurethane resin tends to be hard. To maintain high flame retardancy, it is important to impart high flame retardancy to the polyurethane resin itself and reduce the amount of flame retardant added.

[0005] It is already known that flame-retardant polyurethane resins can be obtained by using an isocyanurate polyisocyanate component (see, for example, Patent Documents 1 to 5). However, polyurethane resins that use a relatively large amount of a polyfunctional isocyanate component such as an isocyanurate tend to be hard and are generally used, for example, as hard boards for building materials, but may not be suitable for materials that require relatively high flexibility, such as automotive seat materials.

[0006] In response to this, a method for improving flexibility, particularly flexibility in a low-temperature environment, has been proposed (Patent Document 6). However, it cannot be said that the performance obtained is fully satisfactory in terms of strength (tensile strength, bending resistance, etc.) in a low-temperature environment.

[0007] Meanwhile, in recent years, many biomass polyurethane resins have been developed that are obtained by using plant-derived polyol components and polyisocyanate components (Patent Documents 7 to 8), and from the perspective of reducing the environmental load, there is a demand for polyurethane resins with a higher biomass ratio.

[0008] There is a need for the development of polyurethane resin materials that are excellent in flexibility and strength, as well as highly flame-retardant, and that can also contribute to carbon neutrality, which aims to combat global warming and reduce the environmental impact.

[0009] JP 2019-090038 A International Publication WO2016 / 010042 JP 2022-022919 A ​​JP 2020-063410 A JP 2017-043667 A JP 2022-153302 A Japanese Patent No. 6178541 A JP 2022-22226 A

[0010] An object of the present invention is to develop a polyurethane resin material that has excellent low-temperature properties (particularly flexibility and strength in low-temperature environments) and high flame retardancy.

[0011] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by a polyurethane resin containing, as constituent components, a segment derived from a prepolymer of a specific polyol and an isocyanate, and a segment derived from an isocyanurate, and have thus completed the present invention.

[0012] That is, the present invention relates to the following polyurethane resin, flame-retardant polyurethane resin composition, synthetic leather, and methods for producing them: (1) A polyurethane resin containing at least a structural unit derived from an isocyanate-terminated prepolymer formed from an isocyanate component and a high-molecular-weight polyol component having a number-average molecular weight of 500 or more, and a structural unit derived from an isocyanurate skeleton-containing polyol, and containing a structural unit derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms in its structure.

[0013] (2) The polyurethane resin according to (1), wherein the isocyanate group content of the structural units derived from the isocyanate group-terminated prepolymer is 1 to 9%. (3) The polyurethane resin according to (1), wherein the high-molecular-weight polyol component forming the structural units derived from the isocyanate group-terminated prepolymer is a structural unit derived from a polycarbonate polyol having a number average molecular weight of 500 to 4,000.

[0014] (4) The polyurethane resin according to (1), wherein the content of structural units derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms in the polyurethane resin structure is 10% by mass or more. (5) The polyurethane resin according to (1), wherein the content of structural units derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms in the polyurethane resin structure is 10% by mol or more relative to the total amount of structural units derived from aliphatic polyols.

[0015] (6) The polyurethane resin according to (1), wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms is a linear long-chain aliphatic polyol having 8 to 20 carbon atoms. (7) The polyurethane resin according to (1), wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms accounts for 10 mol % or more of the total amount of aliphatic polyols constituting the high-molecular-weight polyol component that forms the structural units derived from the isocyanate group-terminated prepolymer.

[0016] (8) The polyurethane resin according to (1), wherein the proportion of structural units derived from an isocyanurate-type polyisocyanate compound in the structure of the polyurethane resin is 1 to 15 mass %. (9) The polyurethane resin according to (1), wherein the isocyanate component constituting the isocyanate group-terminated prepolymer contains structural units derived from 1,5-pentamethylene diisocyanate.

[0017] (10) The polyurethane resin according to (1), wherein the structural unit derived from the isocyanurate skeleton-containing polyol includes a structural unit derived from an isocyanurate polyisocyanate compound derived from 1,5-pentamethylene diisocyanate. (11) The polyurethane resin according to (1), wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms includes a plant-derived polyol compound.

[0018] (12) A flame-retardant polyurethane resin composition comprising the polyurethane resin according to any one of (1) to (11) and having a glass transition temperature of −30° C. or lower. (13) The flame-retardant polyurethane resin composition according to (12), which contains 0 to 20% by mass of a flame retardant.

[0019] (14) Synthetic leather comprising a support and a surface layer, characterized in that at least the surface layer is made of the flame-retardant polyurethane resin composition according to (12). (15) The synthetic leather according to (14), which is used as an interior material for a vehicle.

[0020] The polyurethane resin of the present invention contains structural units derived from specific polyol compounds and polyisocyanate compounds in its structure, and has excellent flame retardancy and can maintain high flexibility and strength, such as flexural resistance and tensile strength, even in low-temperature environments. Furthermore, not only can the content of flame retardant be kept low, but in some cases, high flame retardancy is achieved even without the use of flame retardants, eliminating the problem of bleeding. Such polyurethane resins and flame-retardant polyurethane resin compositions of the present invention are suitable for use in synthetic leather and other automotive seating materials that are used in harsh environments.

[0021] Furthermore, by using plant-derived polyisocyanate components and polyol components as raw materials for polyurethane resin, environmentally friendly polyurethane resin materials and synthetic leathers with a high biomass ratio can be obtained.

[0022] I. Polyurethane Resin The polyurethane resin of the present invention contains at least a structural unit derived from an isocyanate group-terminated prepolymer and a structural unit derived from an isocyanurate skeleton-containing polyol.

[0023] 1. Structural units derived from isocyanate-terminated prepolymers The structural units derived from the isocyanate-terminated prepolymers include structural units formed from an isocyanate component and a high-molecular-weight polyol component. Specifically, they include structural units derived from an isocyanate component (isocyanate units in prepolymers; hereinafter, "PP-isocyanate units") and structural units derived from a high-molecular-weight polyol component having a number-average molecular weight of 500 or more (high-molecular-weight polyol units in prepolymers; hereinafter, "PP-high-molecular-weight polyol units"). In the following description, "polyol" preferably refers to a diol (glycol).

[0024] (1) PP-Isocyanate Unit The isocyanate compound capable of forming the PP-isocyanate unit is not particularly limited as long as it is an isocyanate compound used in conventional polyurethane resins. Specific examples include diisocyanates such as aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates.

[0025] The usable aliphatic or alicyclic diisocyanates are preferably those having a carbon number of 4 to 30. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,2,4- (or 2,4,4-) trimethyl-1,6-hexamethylene diisocyanate, and lysine diisocyanate.

[0026] Examples of alicyclic diisocyanates include isophorone diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, 1,4-diisocyanate cyclohexane, 1,3-bis(diisocyanate methyl) cyclohexane, and 4,4'-dicyclohexylmethane diisocyanate.

[0027] Examples of aromatic diisocyanates include 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0028] These diisocyanates may be used alone or in combination. Aliphatic diisocyanate compounds having 4 to 6 carbon atoms are more preferred. Among these, 1,6-hexamethylene diisocyanate is preferred due to its weather resistance and ease of industrial availability. Furthermore, in consideration of the impact on the environment, it is preferable to use environmentally friendly 1,5-pentamethylene diisocyanate, which is a plant-derived isocyanate.

[0029] (2) PP-High Molecular Weight Polyol Unit A PP-high molecular weight polyol capable of forming a PP-high molecular weight polyol unit is a compound having two or more hydroxyl groups in one molecule and having a number average molecular weight of 500 or more. Preferably, the number average molecular weight is 1,000 or more, more preferably 1,500 or more, and particularly preferably 1,800 or more. A number average molecular weight of 500 or more has the advantage of providing a cured product with excellent low-temperature flexibility.

[0030] The upper limit of the number average molecular weight of the PP-high molecular weight polyol is not particularly limited, but is preferably 10,000 or less, more preferably 8,000 or less, even more preferably 6,000 or less, particularly preferably 4,000 or less, and most preferably 3,000 or less. The number average molecular weight can be determined by measurement by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0031] The PP-high molecular weight polyol is not particularly limited as long as it is a relatively high molecular weight polyol used in conventional polyurethane resins, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, fluorine polyols, and vinyl monomer-modified polyols. These can be used alone or in combination of two or more. More preferred PP-high molecular weight polyols include polyether polyols, polyester polyols, and polycarbonate polyols, and particularly preferred is polycarbonate polyol. A preferred polycarbonate polyol is polycarbonate diol.

[0032] The polycarbonate polyol as a PP-high molecular weight polyol includes a polycondensate of a relatively low molecular weight aliphatic polyol (a polyol constituting the polycarbonate polyol; hereinafter referred to as a "PC-polyol compound") and a carbonate compound.

[0033] The number-average molecular weight of the polycarbonate polyol may be 500 or more, preferably 1,200 or more, more preferably 1,500 or more, and even more preferably 1,800 or more. When the number-average molecular weight of the polycarbonate polyol capable of forming an isocyanate group-terminated prepolymer is within this range, there is an advantage in that the cured product has excellent flexibility at low temperatures. The upper limit of the number-average molecular weight of the polycarbonate polyol is not particularly limited, but is preferably 8,000 or less, more preferably 6,000 or less, even more preferably 4,000 or less, and particularly preferably 3,000 or less.

[0034] The carbonate compound may contain one type of carbonate or two or more types of carbonates. The carbonate may be any compound capable of condensing with a polyol to produce a polycarbonate polyol. Examples of the carbonate compound include dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and dipropyl carbonate; alkylene carbonates such as ethylene carbonate and propylene carbonate; and diaryl carbonates such as diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate, and bis(tetrahydronaphthyl carbonate).

[0035] The PC-polyol compound is a relatively low molecular weight aliphatic polyol (preferably a diol). The relatively low molecular weight aliphatic polyol preferably has a molecular weight of less than 500, more preferably less than 400, and particularly preferably less than 350. Specific examples include aliphatic polyols having 1 to 20 carbon atoms.

[0036] Examples of such aliphatic polyols include short-chain aliphatic polyols having 7 or less carbon atoms and long-chain aliphatic polyols having 8 or more carbon atoms. When a PP-high molecular weight polyol other than polycarbonate polyol is used, it is also preferable to use a similar aliphatic polyol compound.

[0037] The aliphatic hydrocarbon constituting the aliphatic polyol may be either a chain aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon, but from the viewpoint of superior flexibility in a low-temperature environment, a chain aliphatic hydrocarbon is preferred. The chain aliphatic hydrocarbon may be linear or branched, but from the viewpoint of superior strength in a low-temperature environment, a linear chain aliphatic hydrocarbon is preferred.

[0038] The short-chain aliphatic polyol preferably has a carbon number of 1 to 7, more preferably 2 to 6, and particularly preferably 3 to 6. Specific examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 1,4-cyclohexanediol.

[0039] From the viewpoint of strength particularly in low-temperature environments, it is more preferable to use an unbranched linear aliphatic diol. Even more preferable to use a linear aliphatic diol having 4 to 6 carbon atoms. Specifically, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol are used. Particularly preferable are 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. These short-chain aliphatic polyols may be used alone or in combination of two or more.

[0040] The proportion of branched short-chain aliphatic polyols relative to the total amount of short-chain aliphatic polyols is preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 5 mol% or less, and it is most desirable that no branched short-chain aliphatic polyols are contained.

[0041] The long-chain aliphatic polyol is preferably an aliphatic polyol having 8 to 20 carbon atoms, more preferably an aliphatic polyol having 8 to 12 carbon atoms, and particularly preferably an aliphatic polyol having 8 to 10 carbon atoms. Furthermore, these long-chain aliphatic polyols are preferably linear long-chain aliphatic diols.

[0042] Examples of linear long-chain aliphatic polyols include linear aliphatic diols such as 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, and 1,20-eicosanediol. These long-chain aliphatic polyols may be used alone or in combination of two or more.

[0043] Among these, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol are more preferred. Furthermore, in order to increase the biomass ratio, plant-derived 1,10-decanediol is particularly preferred.

[0044] In particular, from the viewpoint of strength in a low-temperature environment, it is more preferable to reduce the proportion of branched long-chain aliphatic polyol. The proportion of branched long-chain aliphatic polyol relative to the total amount of long-chain aliphatic polyols is preferably 5 mol % or less, more preferably 3 mol % or less, and particularly preferably 1 mol % or less, and it is most preferable that no branched long-chain aliphatic polyol is contained.

[0045] The short-chain aliphatic polyol and the long-chain aliphatic polyol may be used alone. The short-chain aliphatic polyol and the long-chain aliphatic polyol may also be used in combination. When used in combination, the ratio is not particularly limited, but preferably the long-chain aliphatic polyol:short-chain aliphatic polyol (molar ratio) is 5:95 to 50:50, more preferably 10:90 to 45:55, even more preferably 15:85 to 40:60, particularly preferably 20:80 to 40:60, and most preferably 25:75 to 35:65.

[0046] The content of the long-chain aliphatic polyol having 8 to 20 carbon atoms relative to the total amount of aliphatic polyols constituting the PP-high molecular weight polyol is preferably 5 mol% or more, more preferably 10 mol% or more, particularly preferably 15 mol% or more, and most preferably 25 mol% or more. There is no upper limit, but it is preferably 50 mol% or less, more preferably 40 mol% or less, and particularly preferably 35 mol% or less.

[0047] From the viewpoint of strength in a low-temperature environment, the proportion of branched polyol relative to the total amount of PC-polyol compounds is preferably 5 mol % or less, more preferably 3 mol % or less, particularly preferably 1 mol % or less, and it is most desirable that no branched polyol is contained.

[0048] The polycarbonate polyol can be obtained by polycondensing the above-mentioned PC-polyol compound with a carbonate compound by a conventionally known method.

[0049] (3) Method for Producing Isocyanate-Terminated Prepolymers The constitutional units derived from the isocyanate-terminated prepolymers are incorporated into the structure of the polyurethane resin by reacting an isocyanate-terminated prepolymer, which has been produced in advance as a raw material component, with other raw material components during the production of the polyurethane resin.

[0050] The isocyanate-terminated prepolymer is a reaction product obtained by, for example, blending the above-mentioned isocyanate component and polyol component in a predetermined ratio and subjecting them to a prepolymerization reaction.

[0051] The blending ratio in the prepolymerization reaction is adjusted so that the equivalent ratio (first equivalent ratio, NCO / OH) of the isocyanate group of the isocyanate component to the hydroxyl group of the polyol component falls within a predetermined range. Specifically, it is desirable to blend the isocyanate component and the polyol component so that the NCO / OH ratio of the isocyanate group-terminated prepolymer is preferably 1.1 or more, more preferably 1.2 or more, and particularly preferably 1.5 or more.

[0052] The molecular weight of the constituent unit derived from the isocyanate group-terminated prepolymer is not particularly limited, but from the viewpoint of flexibility and strength in a low-temperature environment, the isocyanate group content (NCO%), which is an indicator of molecular weight, is preferably 9% or less, more preferably 6% or less, and particularly preferably 4.5% or less. The lower limit of the NCO% is not particularly limited, but is preferably 1% or more, more preferably 1.2% or more, and particularly preferably 1.5% or more.

[0053] If the NCO% is too low (the molecular weight of the constituent units derived from the isocyanate group-terminated prepolymer is too high), the isocyanurate skeleton of the entire polyurethane resin structure may become sparse, resulting in poor flammability. If the NCO% is too high (the molecular weight of the constituent units derived from the isocyanate group-terminated prepolymer is too low), flexibility and strength at low temperatures may be impaired. The isocyanate group content (%) is given by the content (g) of isocyanate groups contained in 100 g of a sample, and can be measured by a conventionally known method.

[0054] 2. Structural Units Derived from Isocyanurate Skeleton-Containing Polyols The polyurethane resin of the present invention contains structural units derived from isocyanurate skeleton-containing polyols. The structural units derived from isocyanurate skeleton-containing polyols consist of structural units derived from an isocyanurate-type polyisocyanate compound ("isocyanurate units") and structural units derived from a polyol ("NU-polyol units") bonded to at least a portion of the isocyanate groups possessed by the isocyanurate rings.

[0055] (1) Isocyanurate-Type Polyisocyanate Compounds Isocyanurate-type polyisocyanate compounds capable of forming an isocyanurate skeleton are compounds having one or more isocyanurate rings in one molecule.

[0056] The isocyanurate polyisocyanate compound having one or more isocyanurate rings per molecule is preferably an isocyanurate polyisocyanate having one isocyanurate ring per molecule as the main component, although this does not exclude the case where a small amount of an isocyanurate polyisocyanate having two or more isocyanurate rings per molecule is contained as a by-product in the production stage of the isocyanurate polyisocyanate.

[0057] The isocyanurate polyisocyanate can be synthesized from a diisocyanate such as an aliphatic diisocyanate, an alicyclic diisocyanate, or an aromatic diisocyanate.

[0058] The usable aliphatic or alicyclic diisocyanates are preferably those having a carbon number of 4 to 30. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,2,4- (or 2,4,4-) trimethyl-1,6-hexamethylene diisocyanate, and lysine diisocyanate.

[0059] Examples of alicyclic diisocyanates include isophorone diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, 1,4-diisocyanate cyclohexane, 1,3-bis(diisocyanate methyl) cyclohexane, and 4,4'-dicyclohexylmethane diisocyanate.

[0060] Examples of aromatic diisocyanates include 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0061] These diisocyanates may be used alone or in combination. Of these, 1,6-hexamethylene diisocyanate is preferred because of its weather resistance and ease of industrial availability. Furthermore, considering the impact on the environment, it is preferred to use environmentally friendly 1,5-pentamethylene diisocyanate, which is a plant-derived isocyanate.

[0062] The isocyanurate-type polyisocyanate compound can be obtained by subjecting a diisocyanate to an isocyanuration reaction in the presence of an isocyanuration catalyst. The NCO % of the obtained isocyanurate-type polyisocyanate compound is not particularly limited, but is preferably 20 to 30%.

[0063] Specific examples of the isocyanurate-type polyisocyanate compound (having one isocyanurate ring) in the present invention include the following: Each of the following triisocyanurates may be used alone or in combination of two or more.

[0064] HDI3N: an isocyanurate triisocyanate synthesized from 1,6-hexamethylene diisocyanate, HTMDI3N: an isocyanurate triisocyanate synthesized from trimethylhexamethylene diisocyanate, PDI3N: an isocyanurate triisocyanate synthesized from 1,5-pentamethylene diisocyanate, IPDI3N: an isocyanurate triisocyanate synthesized from isophorone diisocyanate, HTDI3N: an isocyanurate triisocyanate synthesized from hydrogenated tolylene diisocyanate, HXDI3N: an isocyanurate triisocyanate synthesized from hydrogenated xylene diisocyanate, NBDI3N: an isocyanurate triisocyanate synthesized from norbornane diisocyanate, and HMDI3N: Isocyanurate type triisocyanate synthesized from hydrogenated diphenylmethane diisocyanate, MDI3N: Isocyanurate type triisocyanate synthesized from diphenylmethane diisocyanate, TDI3N: Isocyanurate type triisocyanate synthesized from tolylene diisocyanate, XDI3N: Isocyanurate type triisocyanate synthesized from xylene diisocyanate

[0065] Of the above, particularly preferred are structural units derived from an isocyanurate-type polyisocyanate compound derived from 1,5-pentamethylene diisocyanate, or structural units derived from an isocyanurate-type polyisocyanate compound derived from 1,6-hexamethylene diisocyanate.

[0066] (2) NU-Polyol Examples of polyols capable of forming NU-polyol units include high-molecular-weight polyols ("NU-high-molecular-weight polyols") similar to PP-high-molecular-weight polyols capable of forming isocyanate-terminated prepolymers.

[0067] The number average molecular weight of the NU-high molecular weight polyol is preferably 300 or more, more preferably 400 or more, and particularly preferably 500 or more. There is no particular upper limit, but it is preferably 1,500 or less, more preferably 1,200 or less. Furthermore, it is preferable that the molecular weight of the NU-high molecular weight polyol is lower than that of the PP-high molecular weight polyol. When the molecular weight of the PP-high molecular weight polyol is higher than that of the NU-high molecular weight polyol, the advantages of excellent mechanical strength and flexibility tend to be obtained. The number average molecular weight is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

[0068] The NU-high molecular weight polyol is not particularly limited as long as it is a relatively high molecular weight polyol used in conventional polyurethane resins, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, fluorine polyols, and vinyl monomer-modified polyols. These can be used alone or in combination of two or more. More preferred NU-high molecular weight polyols include polyether polyols, polyester polyols, and polycarbonate polyols, and particularly preferred is polycarbonate polyol. A preferred polycarbonate polyol is polycarbonate diol.

[0069] The polycarbonate polyol capable of forming the NU-high molecular weight polyol contains a polycondensate of a relatively low molecular weight aliphatic polyol compound (PC-polyol compound) and a carbonate compound.

[0070] As the carbonate compound, the same carbonate compounds as those usable for the polycarbonate polyol capable of forming the above-mentioned isocyanate group-terminated prepolymer can be used.

[0071] As the PC-polyol compound, the same PC-polyol compounds as those usable for the polycarbonate polyol capable of forming the above-mentioned isocyanate group-terminated prepolymer can be used.

[0072] The PC-polyol compound is preferably a relatively low molecular weight aliphatic polyol (preferably a diol). Specific examples include aliphatic polyols having 1 to 20 carbon atoms. Examples of such aliphatic polyols include short-chain aliphatic polyols having 7 or less carbon atoms and long-chain aliphatic polyols having 8 or more carbon atoms. When a NU-high molecular weight polyol other than polycarbonate polyol is used, it is also preferable to use a similar aliphatic polyol compound.

[0073] The aliphatic hydrocarbon constituting the aliphatic polyol may be either a chain aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon, but from the viewpoint of superior flexibility in a low-temperature environment, a chain aliphatic hydrocarbon is preferred. The chain aliphatic hydrocarbon may be linear or branched, but from the viewpoint of superior strength in a low-temperature environment, a linear chain aliphatic hydrocarbon is preferred.

[0074] Specific examples of the short-chain aliphatic polyol include the same diols as those listed above as the short-chain aliphatic polyols capable of forming the polycarbonate polyol used in the isocyanate group-terminated prepolymer.

[0075] From the viewpoint of strength, particularly in low-temperature environments, unbranched linear aliphatic diols are more preferred. Even more preferred are linear aliphatic diols having 2 to 6 carbon atoms. Specific examples include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. 1,3-propanediol or 1,4-butanediol are particularly preferred. These short-chain aliphatic polyols may be used alone or in combination of two or more.

[0076] The proportion of branched short-chain aliphatic polyols relative to the total amount of short-chain aliphatic polyols is preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 5 mol% or less, and it is most desirable that no branched short-chain aliphatic polyols are contained.

[0077] The long-chain aliphatic polyol may be the same as the long-chain aliphatic polyol capable of forming the polycarbonate polyol used in the isocyanate group-terminated prepolymer. Preferably, an aliphatic polyol having 8 to 20 carbon atoms is used, more preferably an aliphatic polyol having 8 to 12 carbon atoms, and particularly preferably an aliphatic polyol having 8 to 10 carbon atoms. Furthermore, it is preferable that these long-chain aliphatic polyols are linear long-chain aliphatic diols.

[0078] Specific examples of the long-chain aliphatic polyol include the same diols as those listed above as long-chain aliphatic polyols capable of forming the polycarbonate polyol used in the isocyanate group-terminated prepolymer.

[0079] Among these, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol are more preferred. Furthermore, in order to increase the biomass ratio, plant-derived 1,10-decanediol is particularly preferred.

[0080] In particular, from the viewpoint of strength in a low-temperature environment, it is more preferable to reduce the proportion of branched long-chain aliphatic polyol. The proportion of branched long-chain aliphatic polyol relative to the total amount of long-chain aliphatic polyols is preferably 5 mol % or less, more preferably 3 mol % or less, and particularly preferably 1 mol % or less, and it is most preferable that no branched long-chain aliphatic polyol is contained.

[0081] The short-chain aliphatic polyol and the long-chain aliphatic polyol may be used alone. Alternatively, the short-chain aliphatic polyol and the long-chain aliphatic polyol may be used in combination. When used in combination, the ratio is not particularly limited, but preferably the long-chain aliphatic polyol:short-chain aliphatic polyol (molar ratio) is 5:95 to 50:50, more preferably 15:85 to 40:60, and particularly preferably 25:75 to 35:65.

[0082] From the viewpoint of strength in a low-temperature environment, the proportion of branched polyol relative to the total amount of PC-polyol compounds is preferably 5 mol % or less, more preferably 3 mol % or less, particularly preferably 1 mol % or less, and it is most desirable that no branched polyol is contained.

[0083] The polycarbonate polyol can be obtained by polycondensing the above-mentioned PC-polyol compound with a carbonate compound by a conventionally known method.

[0084] The polycarbonate polyol that can be used for the isocyanurate skeleton-containing polyol is the same as the polycarbonate polyol that can be used for the isocyanate group-terminated prepolymer.

[0085] It is preferable that the number average molecular weight (n-NU) of the polycarbonate polyol used in the isocyanurate skeleton-containing polyol is smaller than the number average molecular weight (n-PP) of the polycarbonate polyol that can be used in the isocyanate group-terminated prepolymer. Furthermore, it is more preferable that n-NU / n-PP = 500 / 3,000 to 1,000 / 1,500. When the molecular weight of the polycarbonate polyol that can be used in the isocyanate group-terminated prepolymer is higher than that of the polycarbonate polyol used in the isocyanurate skeleton-containing polyol, the advantages of excellent mechanical strength and flexibility tend to be obtained.

[0086] The structural units derived from the isocyanurate skeleton-containing polyol in the present invention are formed by the reaction of the above-mentioned isocyanurate-type polyisocyanate compound with a polyol compound (NU-high molecular weight polyol).

[0087] 3. Structure of Polyurethane Resin The polyurethane resin of the present invention contains at least a structural unit derived from the isocyanate group-terminated prepolymer and a structural unit derived from an isocyanurate skeleton-containing polyol. The isocyanurate skeleton-containing polyol contains a structural unit derived from an isocyanurate-type polyisocyanate compound (isocyanurate unit) and a structural unit derived from a NU-high molecular weight polyol (NU-polyol unit).

[0088] The polyurethane resin of the present invention is believed to have a high molecular weight three-dimensional structure in which relatively linear, high molecular weight urethane chains, known as isocyanate-terminated prepolymers, and isocyanurate rings are linked by NU-polyol units. The length of the prepolymer maintains the spacing between the isocyanurate rings, preventing them from becoming too dense, which is thought to enable the resin to maintain flexibility and strength (toughness such as tensile strength) even at low temperatures.

[0089] The NU-high molecular weight polyol may link isocyanate group-terminated prepolymers together or may link isocyanurate type polyisocyanates together, in addition to linking isocyanate group-terminated prepolymers and isocyanurate rings.

[0090] In the polyurethane resin structure, the constituent units derived from the isocyanate group-terminated prepolymer are contained in an amount of preferably 40 to 90 mass%, more preferably 50 to 85 mass%, and in the polyurethane resin structure, the constituent units derived from the isocyanurate polyisocyanate compound (isocyanurate units) are contained in an amount of preferably 1 to 20 mass%, more preferably 1.5 to 15 mass%.

[0091] The polyurethane resin of the present invention has an isocyanurate skeleton in its structure and forms three-dimensional crosslinks. The final molecular weight range is not particularly limited, but it is preferable that the thermal softening point is 160°C or higher, more preferably 180°C or higher, as measured by dynamic viscoelasticity measurement (DMA measurement).

[0092] In the structure of the polyurethane resin, the polyol-derived structural units include structural units derived from a high-molecular-weight polyol component constituting the isocyanate-terminated prepolymer (PP-high-molecular-weight polyol unit) and structural units derived from a polyol constituting the isocyanurate skeleton-containing polyol (NU-polyol unit).

[0093] Furthermore, the PP-high-molecular-weight polyol units and the NU-polyol units each contain low-molecular-weight aliphatic polyol units that constitute them. For example, when the PP-high-molecular-weight polyol and the NU-high-molecular-weight polyol that respectively form the PP-high-molecular-weight polyol units and the NU-polyol units are both polycarbonate polyols, each polycarbonate polyol contains constituent units derived from the aliphatic polyol (PC-polyol compound) that constitutes it.

[0094] That is, the aliphatic polyol-derived structural units contained in the structure of the polyurethane resin of the present invention include both the aliphatic polyol-derived structural units that form the PP-high molecular weight polyol and the NU-high molecular weight polyol.

[0095] The aliphatic polyol (for example, in the case of a polycarbonate polyol, the PC-polyol compound that forms it) may be a short-chain aliphatic polyol having 7 or less carbon atoms or a long-chain aliphatic polyol having 8 or more carbon atoms, but the polyurethane resin of the present invention contains in its structure at least a structural unit derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms. Preferably, a structural unit derived from a linear long-chain aliphatic polyol having 8 to 20 carbon atoms is contained.

[0096] The content of structural units derived from long-chain aliphatic polyols having 8 to 20 carbon atoms is not particularly limited, but the content of structural units derived from long-chain aliphatic polyols having 8 to 20 carbon atoms in the structure of the polyurethane resin of the present invention (the total amount of long-chain aliphatic polyols having 8 to 20 carbon atoms in the aliphatic polyols constituting the PP-high molecular weight polyol and the NU-high molecular weight polyol) is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more. There is no particular upper limit, but it is preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0097] In this case, the constituent unit derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms is typically a unit formed from the long-chain aliphatic polyol and a carbonate compound, which corresponds to one unit constituting a polycarbonate polyol, and this unit is mainly used as the basis for calculating the mass.

[0098] Of the polyol-derived structural units constituting the polyurethane resin of the present invention, the content of structural units derived from long-chain aliphatic polyols having 8 to 20 carbon atoms relative to the total amount of structural units derived from low-molecular-weight aliphatic polyols is preferably 5 mol% or more, more preferably 10 mol% or more, and particularly preferably 20 mol% or more. There is no particular upper limit, but it is preferably 60 mol% or less, more preferably 50 mol% or less, and particularly preferably 40 mol% or less. If the content of long-chain aliphatic polyol is too low, the strength in low-temperature environments may be insufficient.

[0099] The proportion of the structural units derived from the isocyanurate-type polyisocyanate compound in the polyurethane resin structure is not particularly limited, but is preferably 1% by mass or more, more preferably 1.5% by mass or more, and particularly preferably 2% by mass or more. The upper limit is not particularly limited, but is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

[0100] In the structure of the polyurethane resin, the content ratio of the constituent component derived from the isocyanurate polyisocyanate relative to the total amount of constituent units derived from the isocyanate compound is not particularly limited, but is preferably 10 to 70 mass%, more preferably 20 to 60 mass%, and particularly preferably 30 to 50 mass%.

[0101] The polyurethane resin of the present invention preferably has a glass transition temperature of −20° C. or lower, more preferably −25° C. or lower, and even more preferably −30° C. or lower, which may provide the advantage of excellent flexibility at low temperatures.

[0102] The polyurethane resin of the present invention has high flame retardancy by itself and has excellent flexibility and strength (flexural resistance and tensile strength) in low-temperature environments. Because the polyurethane resin itself has flame retardancy, a flame-retardant polyurethane resin composition can be obtained with a low content of flame retardant.

[0103] 4. Method for Producing Polyurethane Resin The polyurethane resin of the present invention is a reaction product obtained by reacting raw material components including an isocyanate-terminated prepolymer, an isocyanurate-type polyisocyanate compound, and a polyol component (NU-high molecular weight polyol). Therefore, it can be produced by a method including a step of reacting these raw material components. Specifically, it can be obtained by subjecting these raw material components to treatments such as heating, drying, and curing.

[0104] The isocyanate-terminated prepolymer is obtained by blending the above-mentioned isocyanate compound for prepolymer and PP-polyol compound in a predetermined ratio and carrying out a prepolymerization reaction. The blending ratio in the prepolymerization reaction is adjusted so that the equivalent ratio of the isocyanate groups of the isocyanate component to the hydroxyl groups of the PP-polyol component (first equivalent ratio, NCO / OH) falls within a predetermined range.

[0105] More specifically, the equivalent ratio (NCO / OH) of the isocyanate group of the isocyanate compound to the hydroxyl group of the PP-polyol component is preferably 1.1 or more, more preferably 1.2 or more, and particularly preferably 1.5 or more. There is no particular upper limit to this equivalent ratio (NCO / OH), but it is preferably 5.0 or less, more preferably 4.0 or less, and particularly preferably 3.0 or less.

[0106] The reaction conditions for the prepolymerization reaction are not particularly limited and are set appropriately. Specifically, the prepolymerization reaction can be carried out by bulk polymerization or solution polymerization under an inert gas atmosphere and normal pressure (atmospheric pressure), at a reaction temperature of, for example, 20° C. or higher, preferably 50° C. or higher, more preferably 70° C. or higher and 150° C. or lower, preferably 120° C. or lower, more preferably 100° C. or lower, for a reaction time of, for example, 30 minutes or longer, preferably 1 hour or longer, and 12 hours or shorter, preferably 6 hours or shorter.

[0107] In the prepolymerization reaction, known organic solvents, prepolymerization catalysts, known additives, etc. can be added as needed. Examples of additives include antioxidants, heat stabilizers, light stabilizers, and cocatalysts. These can be used alone or in combination of two or more. This results in an isocyanate-terminated prepolymer as the reaction product of the prepolymerization reaction.

[0108] The isocyanurate-type polyisocyanate compound can be obtained by subjecting a diisocyanate to an isocyanuration reaction in the presence of an isocyanuration catalyst. Examples of the isocyanuration catalyst include a trimerization catalyst that reacts the isocyanate groups contained in the diisocyanate to trimerize them and promote the formation of isocyanurate rings.

[0109] Examples of isocyanurate catalysts that can be used include nitrogen-containing aromatic compounds such as tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol, and 2,4,6-tris(dialkylaminoalkyl)hexahydro-S-triazine; alkali metal salts of carboxylic acids such as potassium acetate, potassium 2-ethylhexanoate, and potassium octoate; tertiary ammonium salts such as trimethylammonium salt, triethylammonium salt, and triphenylammonium salt; and quaternary ammonium salts such as tetramethylammonium salt, tetraethylammonium, and tetraphenylammonium salt. These can be used alone or in combination of two or more.

[0110] The amount of the isocyanurate catalyst added is preferably in the range of 0.001 to 0.1 parts by mass, and most preferably in the range of 0.005 to 0.05 parts by mass, per 100 parts by mass of diisocyanate.

[0111] A polyurethane resin can be obtained by reacting the isocyanate-terminated prepolymer obtained by the above method with an isocyanurate-type polyisocyanate compound and a NU-polyol using a conventionally known method for producing polyurethane.

[0112] By producing a polyurethane resin using a previously produced isocyanate-terminated prepolymer, the spacing between isocyanurate rings is maintained by the isocyanate-terminated prepolymer structural units having a predetermined molecular weight, preventing excessive density, which is thought to make it possible to maintain flexibility and strength (toughness such as tensile strength) even at low temperatures.

[0113] The content of the isocyanate group-terminated prepolymer in the raw material components for producing the polyurethane resin is preferably 40 to 90 mass %, more preferably 50 to 85 mass %, and particularly preferably 60 to 80 mass %.

[0114] The content of the isocyanurate polyisocyanate compound in the raw material components for producing a polyurethane resin is preferably 1 to 20% by mass, more preferably 1.5 to 15% by mass, and particularly preferably 2 to 10% by mass.

[0115] The content of the NU-high molecular weight polyol in the raw material components for producing a polyurethane resin is preferably 10 to 60 mass %, more preferably 15 to 50 mass %, and particularly preferably 20 to 40 mass %.

[0116] The content ratio of the isocyanurate-type polyisocyanate compound relative to the total amount of isocyanate compounds in the raw material components for producing a polyurethane resin is not particularly limited, but is preferably 10 to 70 mass%, more preferably 20 to 60 mass%, and particularly preferably 30 to 50 mass%. The total amount of isocyanate compounds is the sum of the isocyanate compounds for the isocyanate group-terminated prepolymer and the isocyanurate-type polyisocyanate compounds.

[0117] Examples of low-molecular-weight aliphatic polyols used in the production of polyurethane resins include the aliphatic polyols used in the formation of PP-high-molecular-weight polyols and NU-high-molecular-weight polyols. The content of long-chain aliphatic polyols having 8 to 20 carbon atoms in the raw material components for the production of polyurethane resins is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more. While there is no particular upper limit, it is preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0118] The content ratio of this long-chain aliphatic polyol having 8 to 20 carbon atoms is calculated based on the mass of one unit formed from the long-chain aliphatic polyol and a carbonate compound when polycarbonate polyol is used as the PP-high molecular weight polyol and the NU-high molecular weight polyol.

[0119] The content of the long-chain aliphatic polyol having 8 to 20 carbon atoms relative to the total amount of the aliphatic polyol is preferably 5 mol% or more, more preferably 10 mol% or more, and particularly preferably 20 mol% or more. There is no particular upper limit, but it is preferably 60 mol% or less, more preferably 50 mol% or less, and particularly preferably 40 mol% or less. If the amount of long-chain aliphatic polyol used is too small, the strength in low-temperature environments may be insufficient.

[0120] II. Flame-Retardant Polyurethane Resin Composition The flame-retardant polyurethane resin composition of the present invention contains a reaction product of polyurethane resin raw material components including the above-described isocyanate-terminated prepolymer, an isocyanurate-type polyisocyanate compound, and a NU-high molecular weight polyol, and optionally a flame retardant.

[0121] (1) Other Raw Material Components In addition to the raw material components of the polyurethane resin described above, the flame-retardant polyurethane resin composition of the present invention may further contain, as necessary, a crosslinking agent, a chain extender, a curing accelerator (catalyst component), an organic solvent, etc. It may also contain a foaming agent, an antifoaming agent, a thickener, a surface conditioner, a surfactant, a filler, a weather resistance improver, an ultraviolet absorber, water, a dispersant, a color pigment, a pH adjuster, etc.

[0122] The chain extender is not particularly limited, but generally a relatively low molecular weight diol is used. Examples include petroleum-derived diols such as ethylene glycol, diethylene glycol, propanediol, butanediol, hexanediol, and PEG, and plant-derived diols such as 1,3-propanediol and 1,2-hexanediol. These diols may be used alone, or two or more may be used in combination as needed. Diamines and the like can also be used as needed. The amount of chain extender used is not particularly limited, but is generally about 1 to 5 parts by mass per 100 parts by mass of the flame-retardant polyurethane resin composition of the present invention.

[0123] A curing accelerator (catalyst component) can also be used. Specific examples include metal catalysts such as titanium diisopropoxybis(ethylacetoacetate), amine catalysts, and DBU catalysts. The amount of the curing accelerator used is not particularly limited, but is generally about 0.01 to 1 part by mass per 100 parts by mass of the flame-retardant polyurethane resin composition of the present invention.

[0124] The organic solvent is not particularly limited, but examples thereof include polar solvents inactive to isocyanate groups, such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and organic solvents such as methyl ethyl ketone (MEK), toluene, and xylene.

[0125] (2) Flame Retardant Examples of flame retardants that may be contained in the flame-retardant polyurethane resin composition of the present invention include known flame retardants. For example, organic phosphorus compounds include phosphate esters and their salts, phosphite esters and their salts, phosphonic acid and its derivatives (including salts), phosphinic acid and its derivatives (including salts), phosphine, phosphine oxide, biphosphine, phosphonium salts, and phosphazene. Examples of inorganic phosphorus compounds include phosphates, such as ammonium polyphosphate. In addition to the above compounds, simple red phosphorus may also be used.

[0126] Examples of flame retardants other than phosphorus compounds include melamine compounds such as melamine cyanurate and melamine, metal hydrates such as aluminum hydroxide and magnesium hydroxide, and antimony compounds such as antimony trioxide and antimony pentoxide. Among these, phosphinates are preferred because they have good flame retardancy and little effect on physical properties.

[0127] The content of the flame retardant is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 12.5% ​​by mass or less, and particularly preferably 10% by mass or less, based on the total amount of the flame-retardant polyurethane resin composition of the present invention. There is no particular lower limit, and the flame retardant may not be blended. The content is preferably 0% by mass or more, more preferably 2.5% by mass or more, and particularly preferably 5% by mass or more.

[0128] (3) Other Additives Additives such as foaming agents, antifoaming agents, thickeners, surface conditioners, surfactants, fillers, weather resistance improvers, ultraviolet absorbers, organic solvents, water, dispersants, color pigments, and pH adjusters may be blended into the flame-retardant polyurethane resin composition of the present invention, as needed, within limits that do not impair the physical properties of the polyurethane resin obtained by curing.

[0129] In addition, optional components such as urethanization catalysts, silane coupling agents, thixotropy-imparting agents, tackifiers, waxes, heat stabilizers, light resistance stabilizers, fluorescent brighteners, thermoplastic resins, thermosetting resins, dyes, pigments, conductivity-imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, hollow foams, crystal water-containing compounds, water absorbents, moisture absorbents, deodorizers, foam stabilizers, antifungal agents, preservatives, anti-algae agents, pigment dispersants, inert gases, antiblocking agents, and hydrolysis inhibitors can also be used as needed. These additives can be used alone or in combination of two or more.

[0130] (4) Method for Producing Flame-Retardant Polyurethane Resin Composition The flame-retardant polyurethane resin composition of the present invention is obtained by mixing polyurethane resin raw material components including the above-mentioned isocyanate group-terminated prepolymer, isocyanurate-type polyisocyanate compound, and NU-high molecular weight polyol, as well as other raw material components used as needed, with other additives such as a flame retardant used as needed, to obtain a flame-retardant polyurethane resin blend, which is then molded as needed and then heat-cured.

[0131] The content of the isocyanate group-terminated prepolymer relative to 100 parts by mass of the flame-retardant polyurethane resin compound is 40 to 90% by mass, more preferably 50 to 85% by mass, and particularly preferably 60 to 80% by mass.

[0132] The content of the isocyanurate polyisocyanate compound relative to 100 parts by mass of the flame-retardant polyurethane resin compound is preferably 1 to 20% by mass, more preferably 1.5 to 15% by mass, and particularly preferably 2 to 10% by mass.

[0133] The content of the NU-high molecular weight polyol relative to 100 parts by mass of the flame-retardant polyurethane resin compound is preferably 10 to 60% by mass, more preferably 15 to 50% by mass, and particularly preferably 20 to 40% by mass.

[0134] The heat curing conditions are preferably a temperature of 80 to 140°C and a time of 1 to 10 minutes. If necessary, a step of drying and removing liquid components such as organic solvents may also be included. For example, polyurethane resin raw materials, flame retardants, and other additives may be blended, followed by molding, drying, and heat curing. Drying and heat curing may be performed in a single step or separately.

[0135] For example, when a layer made of a flame-retardant polyurethane resin composition is formed on a support (such as a base fabric) of the synthetic leather of the present invention as described below, the flame-retardant polyurethane resin composition can be applied to the support, and then subjected to treatments such as drying and heat curing.

[0136] Alternatively, the polymer may be prepared by pre-reacting some or all of the raw material components, preferably in the presence of a chain extender, and then mixing in a flame retardant and other additives. An organic solvent may also be added when pre-reacting some or all of the raw material components before mixing in the flame retardant and other additives.

[0137] When applying the flame-retardant polyurethane resin formulation to a substrate, it is preferable to adjust the formulation so that it has a viscosity that can be applied without the addition of a solvent, although if necessary, the addition of an organic solvent to achieve a viscosity suitable for application is not excluded.

[0138] III. Synthetic Leather The synthetic leather of the present invention comprises at least a support (base fabric) and a surface layer. The synthetic leather of the present invention has excellent flexibility and flame retardancy, and does not suffer from bleeding problems. Therefore, the synthetic leather or artificial leather that combines flexibility and flame retardancy can be suitably used as a material for automobile seats, etc.

[0139] (1) Support The support (base fabric) used in the synthetic leather of the present invention can be any conventionally known synthetic leather substrate, and is not particularly limited. Examples include fibrous fabrics such as woven or knitted fabrics made of twill or plain weave, raised fabrics obtained by mechanically raising the cotton fabric of such woven fabrics, rayon fabric, nylon fabric, polyester fabric, Kevlar fabric ("Kevlar" is a registered trademark), nonwoven fabrics (polyester, nylon, various latexes, etc.), various synthetic resin films and sheets, natural leather, etc. These may be selected appropriately depending on the purpose. Preferred examples include fibrous fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics.

[0140] The thickness of the support can be appropriately set taking into consideration the material, structure, texture of the resulting synthetic leather, and application, but is preferably 100 to 2,000 μm, and particularly preferably 200 to 1,000 μm.

[0141] (2) Surface Layer The synthetic leather of the present invention has a surface layer containing the flame-retardant polyurethane resin composition on at least one surface of a support. The surface layer may be either a porous layer or a non-porous layer.

[0142] The thickness of the surface layer can be appropriately set taking into consideration the texture and use of the resulting synthetic leather, the material and shape of the support, etc., but is preferably 5 to 300 μm.

[0143] In the present invention, the surface layer may be colored, gloss adjusted, or patterned with an uneven surface, for the purpose of improving the surface strength and design of the synthetic leather. Furthermore, the synthetic leather may be configured with two or more layers, if necessary. When the synthetic leather is configured with two or more layers, examples of the layer other than the layer made of the flame-retardant polyurethane resin composition of the present invention include a heat-insulating layer and a foam layer.

[0144] (3) Method for Producing Synthetic Leather The synthetic leather of the present invention is produced by a method including the steps of laminating the above-mentioned compound for a flame-retardant polyurethane resin on a support and heat-treating it to form a surface layer.

[0145] The surface layer can be formed, for example, by applying a flame-retardant polyurethane resin formulation capable of forming the flame-retardant polyurethane resin composition to at least one surface of a support using a coating method. Examples of coating methods include coating the flame-retardant polyurethane resin formulation directly onto fabric using a knife coater, comma coater, roll coater, die coater, or lip coater. The thickness of the polyurethane resin formulation is not particularly limited, but is preferably 5 to 300 μm.

[0146] It is preferable to adjust the formulation of the polyurethane resin compound so that it has a viscosity that can be applied without the addition of a solvent, but if necessary, a solvent can be added to adjust the viscosity. Examples of the solvent include known organic solvents such as DMF, DMSO, MEK, toluene, and xylene. In this case, it is preferable to use a solution in which the solid content is dispersed at a concentration of about 60 to 100% by mass.

[0147] After the coating step, the formed coating layer is dried and heat-treated to thermally cure the flame-retardant polyurethane resin blend and form a layer made of a flame-retardant polyurethane resin composition. The drying and heat-curing can be performed in one step or in separate steps. For example, after the coating layer is formed, it is preferable to perform the treatment at a temperature of 80 to 140°C for 1 to 10 minutes.

[0148] Alternatively, the substrate can be produced by a dipping method in which a support is impregnated with the polyurethane resin blend.

[0149] Furthermore, the film can also be produced by a lamination method in which a separately formed surface layer is laminated to a support, for example, by forming a surface layer by coating the polyurethane resin composition on a releasable substrate, laminating the surface layer to a support, and then peeling off the releasable substrate.

[0150] Examples of bonding methods include a method using an adhesive or the like, and a method in which the flame-retardant polyurethane resin formulation of the present invention is semi-cured by heating to make it sticky, and then bonded to a support, and the flame-retardant polyurethane resin formulation is then heated again to fully cure it.

[0151] Coating methods include known methods such as comma coating, knife coating, roll coating, gravure coating, die coating, and spray coating. After the film is formed, it is appropriately dried to form a surface layer. A fabric is directly pressed onto this surface layer, or an adhesive is applied by a known method, and then the surface layer is applied and pressed onto the support. The surface layer is then heat-cured by heat treatment (drying or heating), and then peeled off from the releasable substrate to obtain synthetic leather.

[0152] The pressure bonding conditions are preferably a temperature of 20 to 140°C, a pressure of 0.1 to 10 MPa, and a time of 0.0005 to 3 minutes. The heat treatment conditions are preferably a temperature of 80 to 140°C, and a time of 1 to 10 minutes.

[0153] When the surface layer is bonded to the support via an adhesive, examples of the adhesive that can be used include the flame-retardant polyurethane resin composition described above, as well as conventional adhesives based on polyurethane resins, acrylic resins, epoxy resins, etc., made from petroleum-based raw materials. The adhesive may be applied to either the surface layer side or the support side.

[0154] The releasable substrate is not particularly limited, and examples thereof include a film made of a resin (such as an olefin resin or a silicone resin; hereinafter referred to as a release agent) that has releasability against a polyurethane resin, and release paper, release cloth, or release film in which a release layer made of a release agent is laminated on a substrate such as paper, cloth, or film.

[0155] The releasable substrate may have an uneven pattern. By using such a releasable substrate, a resin film having an uneven pattern on its surface can be formed, which prevents blocking between film surfaces and allows the production of synthetic leather that feels good to the touch.

[0156] Among the above methods, the lamination method is preferably used in terms of the physical properties and texture of the resulting synthetic leather, but the present invention is not limited to these methods.

[0157] The synthetic leather of the present invention as described above is suitable for shoes, clothing, bags, furniture, vehicle interior materials (for example, instrument panels, doors, consoles, seats), etc.

[0158] The synthetic leather obtained in this manner can be subjected to further post-processing such as surface treatment and kneading, as necessary. In addition to the support and surface layer described above, an adhesive layer, a surface protective layer, etc. can also be provided. The adhesive layer is provided between the support and the surface layer, etc. The surface protective layer can be provided on the outside of the surface layer. Examples of the surface protective layer include a layer formed from a known polyurethane resin.

[0159] For example, a polyurethane resin to be a surface protective layer (outermost layer) is applied to a releasable substrate, dried, and then the flame-retardant polyurethane resin formulation of the present invention is applied thereon. The flame-retardant polyurethane resin formulation is semi-cured by heating to leave a tacky state, and the layer made of the flame-retardant polyurethane resin formulation is then laminated to a substrate. The flame-retardant polyurethane resin formulation layer is then heat-treated to fully cure it, thereby obtaining synthetic leather having a surface protective layer as the outermost layer in addition to a substrate and a skin layer.

[0160] The physical properties of the film forming the surface layer made of the flame-retardant polyurethane resin composition preferably satisfy a 100% modulus of 0.4 MPa to 2.0 MPa, a strength at break of 2.0 to 6.0 MPa, and an elongation at break of 150 to 500%. Furthermore, the flame retardancy measured in accordance with the test method of the U.S. automobile safety standard FMVSS 302 preferably has a maximum burning rate of 80 mm / min or less. By providing a surface layer whose physical properties satisfy the above ranges, a synthetic leather can be obtained that has good mechanical strength, texture (flexibility), and high flame retardancy.

[0161] The flame retardancy of synthetic leather formed from a surface layer made of the flame-retardant polyurethane resin composition and a support preferably has a maximum burning rate of 80 mm / min or less as measured in accordance with the test method of U.S. automobile safety standard FMVSS 302. Synthetic leather whose various physical properties satisfy the above ranges has high flame retardancy and also has good mechanical strength and texture (flexibility).

[0162] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Evaluations in the examples were carried out according to the following methods. The amounts in the following examples, including the amounts shown in Tables 1 and 2, are in parts by mass unless otherwise specified.

[0163] Flame retardancy was evaluated in accordance with the test method of the US automobile safety standard FMVSS 302. A test piece (synthetic leather; thickness: 1,000 μm) cut to a width of 100 mm and a length of 350 mm was ignited by applying a flame from a gas burner to the edge of the piece for 15 seconds, and the distance and time from when the ignited flame crossed a marked line 38 mm from the edge until it extinguished were measured. The burning rate was calculated and evaluated according to the following criteria.

[0164] ◯: The test piece did not ignite, or the ignited flame was extinguished before the marked line, or the maximum burning rate was less than 50 mm / min. △: The maximum burning rate was between 50 mm / min and 80 mm / min. ×: The maximum burning rate was more than 80 mm / min.

[0165] [Glass Transition Temperature] The glass transition temperature was evaluated by DMA measurement of polyurethane. Specifically, a measurement sample (test piece) measuring 200 mm x 5 mm x 0.15 mm thick was first prepared. Next, using a dynamic viscoelasticity measuring device (manufactured by UBM Co., Ltd., product name "Rheogel E-4000"), the peak temperature (glass transition temperature) of the loss modulus (E") was determined under conditions of -100°C to 200°C, a heating rate of 3°C / min, and a frequency of 10 Hz. The results are shown in Table 2.

[0166] [Cold resistance] The obtained synthetic leather was subjected to a bending test (-30°C, 100 times / min) using a flexometer (Yasuda Seiki Seisakusho Co., Ltd., "Flexometer with low-temperature bath"), in which the leather was bent 10,000 times. N=2 samples were measured for each, and the synthetic leather surface was observed for cracks and evaluated as follows: ◯: No cracks were observed on the surface of both samples △: Cracks were observed on the surface of only one sample ×: Cracks were observed on the surface of both samples

[0167] Synthesis Example 1: PP-1 to PP-3 Isocyanate group-terminated prepolymers (PP-1, PP-2, PP-3) were each produced as follows: A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was purged with nitrogen gas, and then polyol 1 and / or polyol 2 were added in the proportions (parts by mass) shown in Table 1.

[0168] Next, the flask was heated to 60°C and Polyol 1 and / or Polyol 2 were thoroughly mixed, after which Isocyanate 1 was added in the proportion (parts by mass) shown in Table 1. The mixture was reacted at 80°C for about 4 hours under a nitrogen atmosphere until the isocyanate group content (NCO%) became constant, yielding isocyanate-terminated prepolymers (PP-1 to PP-3). The NCO% and NCO / OH of the obtained prepolymers are shown in Table 1.

[0169] The polyol 1, polyol 2, and isocyanate 1 used were as follows: [Polyol 1] Polycarbonate polyol of 1,10-decanediol:1,4-butanediol=3:7 (trade name "NL2030DS", number average molecular weight: 2,000, manufactured by Mitsubishi Chemical Corporation) [Polyol 2] Polycarbonate polyol of 1,6-hexanediol (trade name "UH-200", number average molecular weight: 2,000, manufactured by UBE Corporation) [Isocyanate 1] 1,5-pentamethylene diisocyanate (trade name "Stabio PDI", NCO%=54.5%, manufactured by Mitsui Chemicals, Inc.)

[0170]

[0171] Examples 1 to 6 and Comparative Examples 1 to 3 (Production of Synthetic Leather) 100 parts of an aqueous urethane resin (trade name "Hydran WLS286BP" manufactured by DIC Corporation), 20 parts of a black pigment (trade name "P39-611 Black" manufactured by Stahl), and 4 parts of a carbodiimide crosslinking agent (trade name "CL-7070" manufactured by Seiko Chemical Co., Ltd.) were blended and applied to a textured release paper (trade name "R-86M" manufactured by Lintec Corporation), and then dried to form a surface protective layer with a thickness of 40 μm.

[0172] A polyurethane surface layer was formed on the formed surface protective layer using the components shown in Table 2 in the amounts shown in Table 2. Specifically, the components were thoroughly mixed until homogeneous, and then applied to the surface protective layer with an applicator to a wet film thickness of 200 μm.

[0173] Thereafter, the polyurethane surface layer was cured in a dryer at 100°C for 1.5 minutes, and then a polyester tricot fabric (support; thickness: 800 μm) was superimposed on the resulting polyurethane surface layer. After curing in a dryer at 130°C for 10 minutes, the release paper was peeled off to obtain the synthetic leather of the present invention (thickness: 1,000 μm).

[0174] The evaluation results for the above Examples and Comparative Examples are shown in Table 2. The numerical values ​​for the components in the table represent parts by mass.

[0175]

[0176] The materials used in Tables 1 to 3 are as follows: (1) Polyol 1: Polycarbonate polyol of 1,10-decanediol:1,4-butanediol = 3:7 (trade name "NL2030DS", number average molecular weight: 2,000, manufactured by Mitsubishi Chemical Corporation) (2) Polyol 2: Polycarbonate polyol of 1,6-hexanediol (trade name "UH-200", number average molecular weight: 2,000, manufactured by UBE Corporation) (3) Polyol 3: Polycarbonate polyol of 1,10-decanediol:1,4-butanediol = 3:7 (trade name "NL1030DS", number average molecular weight: 1,000, manufactured by Mitsubishi Chemical Corporation) (4) Polyol 4: Polycarbonate polyol of 1,3-propanediol (number average molecular weight: 1,000, manufactured by Toyokuni Oil Mills Co., Ltd.) (5) Isocyanate 1 1,5-Pentamethylene diisocyanate (trade name "Stabio PDI", NCO%=54.5%, manufactured by Mitsui Chemicals, Inc.) (6) Isocyanate 2 (isocyanurate-type polyisocyanate compound) Isocyanurate-modified 1,5-pentamethylene diisocyanate (trade name "Stabio D-370N", NCO%=25.0%, manufactured by Mitsui Chemicals, Inc.)

[0177] The polyurethane resin of the present invention contains structural units derived from specific polyol compounds and polyisocyanate compounds in its structure, and has excellent flame retardancy and can maintain high flexibility, flexural resistance, tensile strength, and other strengths even in low-temperature environments. Furthermore, not only can the content of flame retardants be kept low, but in some cases, high flame retardancy can be achieved without the use of flame retardants, eliminating the problem of bleeding. Furthermore, by using plant-derived polyisocyanate components and polyol components as raw material components, an environmentally friendly polyurethane resin material with a high biomass ratio can be obtained.

[0178] Therefore, a flame-retardant polyurethane resin composition suitable for synthetic leather, artificial leather, etc., which require strength and flame retardancy in low-temperature environments, can be obtained, and the composition can be used in various fields such as clothing, bags, shoes, vehicle interior materials, etc. In particular, the composition can be suitably used for vehicle interior materials, including automobile seats, ceiling materials, dashboards, door linings, and steering wheels.

Claims

1. A polyurethane resin containing at least a constituent unit derived from an isocyanate group-terminated prepolymer formed from an isocyanate component and a high-molecular-weight polyol component having a number-average molecular weight of 500 or more, and a constituent unit derived from an isocyanurate skeleton-containing polyol, and containing within its structure a constituent unit derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms.

2. The polyurethane resin according to claim 1, wherein the isocyanate group content of the structural units derived from the isocyanate group-terminated prepolymer is 1 to 9%.

3. The polyurethane resin according to claim 1, wherein the high molecular weight polyol component forming the structural units derived from the isocyanate group-terminated prepolymer is a structural unit derived from a polycarbonate polyol having a number average molecular weight of 500 to 4,000.

4. The polyurethane resin according to claim 1, wherein the content of structural units derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms in the polyurethane resin structure is 10% by mass or more.

5. The polyurethane resin according to claim 1, wherein the content of structural units derived from a long-chain aliphatic polyol having 8 to 20 carbon atoms is 10 mol % or more of the total amount of structural units derived from aliphatic polyols contained in the polyurethane resin structure.

6. The polyurethane resin according to claim 1, wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms is a linear long-chain aliphatic polyol having 8 to 20 carbon atoms.

7. The polyurethane resin according to claim 1, wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms accounts for 10 mol% or more of the total amount of aliphatic polyols constituting the high-molecular-weight polyol component that forms the structural units derived from the isocyanate-terminated prepolymer.

8. The polyurethane resin according to claim 1, wherein the proportion of structural units derived from an isocyanurate-type polyisocyanate compound in the structure of the polyurethane resin is 1 to 15 mass %.

9. The polyurethane resin according to claim 1, wherein the isocyanate component constituting the isocyanate group-terminated prepolymer contains structural units derived from 1,5-pentamethylene diisocyanate.

10. The polyurethane resin according to claim 1, wherein the structural units derived from the isocyanurate skeleton-containing polyol include structural units derived from an isocyanurate-type polyisocyanate compound derived from 1,5-pentamethylene diisocyanate.

11. The polyurethane resin according to claim 1, wherein the long-chain aliphatic polyol having 8 to 20 carbon atoms comprises a plant-derived polyol compound.

12. A flame-retardant polyurethane resin composition comprising the polyurethane resin according to any one of claims 1 to 11 and having a glass transition temperature of -30°C or lower.

13. The flame-retardant polyurethane resin composition according to claim 12, which contains 0 to 20% by mass of a flame retardant.

14. Synthetic leather comprising a support and a surface layer, wherein at least the surface layer is made of the flame-retardant polyurethane resin composition according to claim 12.

15. The synthetic leather according to claim 14, which is used as an interior material for a vehicle.

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