Urethane resin and bodily contact member

Abstract

This urethane resin is obtained by reacting an aliphatic polyisocyanate and / or a modified product thereof with a polyol and a monool, wherein the number-average molecular weight of the monool is 1,000 or more, and the gel fraction of the urethane resin is 30% or more.

Description

Urethane Resin and Biological Contact Member

[0001] The present disclosure relates to a urethane resin and a biological contact member.

[0002] A urethane resin refers to a polymer compound having a urethane bond (-NH-C(O)O-) in the molecule. A urethane resin is generally obtained by reacting a hydroxyl group (-OH) of a polyol with an isocyanate group (-NCO) of a polyisocyanate. In urethane resins, physical and mechanical properties such as hardness, thermal properties such as coefficient of linear expansion, electrical properties such as resistivity, and chemical properties such as acid resistance are controlled in accordance with various applications. In particular, urethane resins are sometimes required to have the properties of low toxicity and low hardness while maintaining shape.

[0003] For example, Japanese Patent No. 7323915 discloses a hydrophobic gel elastic coupler for ultrasonic flaw detectors. The hydrophobic gel elastic coupler disclosed in Japanese Patent No. 7323915 is made of a urethane resin, and is used by being interposed between a probe of an ultrasonic flaw detector and a flaw detection target. Examples of the flaw detection target include steel structures, metal welded portions, plastic structures, and concrete structures. The urethane resin used as the hydrophobic gel elastic coupler disclosed in Japanese Patent No. 7323915 is controlled to have low hardness so as to deform following the irregularities of the flaw detection target.

[0004] Furthermore, Japanese Patent No. 5122985, Japanese Patent No. 6276624, Japanese Patent No. 6533577, and Japanese National Publication of International Patent Application No. 2008-519872 disclose low-hardness polyurethane resins. These documents disclose that a low-hardness polyurethane resin can be obtained by containing a monool in addition to a polyol and a polyisocyanate.

[0005] As described above, although techniques for obtaining a urethane resin with low hardness while maintaining its shape are known, urethane resins further having the property of low toxicity have not been known. Accordingly, an object of an embodiment of the present disclosure is to provide a urethane resin and a biological contact member that have low hardness and low toxicity.

[0006] To achieve the above-mentioned objectives, the inventors conducted diligent research and found that by using an aliphatic polyisocyanate and / or a modified thereof as the polyisocyanate, setting the number-average molecular weight of the monool to 1000 or more, and the gel fraction to 30% or more, a low-hardness and low-toxicity urethane resin can be obtained, thus completing this disclosure. This disclosure includes the following:

[0007] <1> A urethane resin obtained by reacting an aliphatic polyisocyanate and / or a modified thereof with a polyol and a monool, wherein the number average molecular weight of the monool is 1000 or more and the gel fraction of the urethane resin is 30% or more. <2> The urethane resin according to <1>, wherein the average number of functional groups of the aliphatic polyisocyanate and / or a modified thereof is 3.0 or less. <3> The urethane resin according to <1> or <2>, wherein it contains a plasticizer, and the content of the plasticizer is in the range of 0% to 100% by mass with respect to 100% by mass of the total of the polyol, monool and isocyanate. <4> The urethane resin according to any one of <1> to <3>, wherein the Asker C hardness is 20 or less and the Asker F hardness is 100 or less. <5> The urethane resin according to any one of <1> to <4>, wherein it contains an antioxidant. <6> The urethane resin according to any one of <1> to <5>, wherein it is a urethane resin obtained by further reacting with a diol. A biocompatible member comprising a urethane resin as described in any one of <7>, <1>, to <6>. <8> A method for producing a urethane resin, comprising the step of reacting at least an aliphatic polyisocyanate and / or a modified thereof with a polyol and a monool having a number average molecular weight of 1000 or more. <9> The method for producing a urethane resin according to <8>, wherein the average number of functional groups of the aliphatic polyisocyanate is 3.0 or less. <10> The method for producing a urethane resin according to <8> or <9>, wherein the reacting step further involves mixing a plasticizer in a range of 0% to 100% by mass with respect to 100% by mass of the total of the polyol, monool and isocyanate. <11> The method for producing a urethane resin according to any one of <8> to <10>, wherein the urethane resin contains an antioxidant. <12> The method for producing a urethane resin according to any one of <8> to <11>, wherein the reacting step further involves reacting with a diol. <13> A method for producing a urethane resin according to any one of <8> to <12>, wherein the gel fraction is 30% or more. <14> A method for producing a urethane resin according to any one of <8> to <13>, wherein the Asker C hardness is 20 or less and the Asker F hardness is 100 or less.

[0008] According to one embodiment of the present disclosure, it is possible to provide a urethane resin and a biocompatible material that have low hardness and low toxicity.

[0009] The embodiments of this disclosure are described below. However, this disclosure is not limited to the embodiments described below. In the embodiments described below, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0010] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of the process is achieved. In this disclosure, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in a described numerical range, the upper or lower limit of that range may be replaced with the value shown in the example. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0011] In this disclosure, "polyol" means a compound having two or more hydroxyl groups in its molecule. In this disclosure, "polyisocyanate" means a compound having two or more isocyanate groups in its molecule.

[0012] In this disclosure, the number-average molecular weight of a compound refers to the value calculated using the following formula (1) based on the hydroxyl value (OHV, in mgKOH / g) of the polyol. Formula: Number-average molecular weight = (56100 / OHV) × Number of hydroxyl groups per molecule ... (1). Here, "OHV" is the value measured in accordance with JIS K1557 6.4. Furthermore, "Number of hydroxyl groups per molecule" refers to the number of active hydrogen atoms per molecule of the active hydrogen-containing compound that is the initiator used as a raw material when manufacturing each polyol. If the number of active hydrogen atoms of the initiator cannot be specified for commercially available products, the nominal number of functional groups is used.

[0013] In this disclosure, the term "and / or" means one or both of the two phrases linked by "and / or". For example, A and / or B means either A or B, or both.

[0014] <Urethane Resin> A urethane resin according to one embodiment of the present disclosure is a urethane resin obtained by reacting an aliphatic polyisocyanate and / or a modified thereof with a polyol and a monool, wherein the number average molecular weight of the monool is 1000 or more, and the gel fraction of the urethane resin is 30% or more. The urethane resin of the present disclosure has the characteristics of low hardness and low toxicity due to the above-described composition, the number average molecular weight of the monool and the gel fraction.

[0015] -Aliphatic Polyisocyanates- Examples of aliphatic polyisocyanates in this disclosure include hexamethylene diisocyanate (hexane diisocyanate) (HDI), pentamethylene diisocyanate (pentane diisocyanate) (PDI), tetramethylene diisocyanate, trimethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate.

[0016] Furthermore, the aliphatic polyisocyanate in this disclosure may include alicyclic polyisocyanates. Examples of alicyclic polyisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 4,4'-methylenebis(cyclohexyl isocyanate), 2,4'-methylenebis(cyclohexyl isocyanate), 2,2'-methylenebis(cyclohexyl isocyanate) (hydrogenated MDI), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane (hydrogenated XDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate.

[0017] Furthermore, modified forms of aliphatic polyisocyanates include, for example, the above-mentioned polymers of aliphatic polyisocyanates (e.g., dimers, trimers (e.g., isocyanurates, iminooxadiazinediones), pentamers, heptamers, etc.), allophanate modified forms (e.g., allophanates produced by the reaction of the above-mentioned aliphatic polyisocyanates with monovalent or divalent alcohols), polyol modified forms (e.g., polyol modified forms produced by the reaction of the above-mentioned aliphatic polyisocyanates with trivalent alcohols (e.g., trimethylolpropane, etc.) (alcohol adducts, preferably trimethylolpropane adducts) Examples include: biuret modified compounds (for example, biuret modified compounds produced by the reaction of the above-mentioned aliphatic polyisocyanate with water or amines), urea modified compounds (for example, urea modified compounds produced by the reaction of the above-mentioned aliphatic polyisocyanate with diamines), oxadiazinetrione modified compounds (for example, oxadiazinetrione produced by the reaction of the above-mentioned aliphatic polyisocyanate with carbon dioxide), carbodiimide modified compounds (for example, carbodiimide modified compounds produced by the decarboxylation condensation reaction of the above-mentioned aliphatic polyisocyanate), uretdione modified compounds, uretonimine modified compounds, and the like.

[0018] In this disclosure, the aliphatic polyisocyanates and modified aliphatic polyisocyanates described above can be used alone or in combination of two or more types.

[0019] In the urethane resin of this disclosure, it is preferable to use an aliphatic polyisocyanate and its modified form having an average number of functional groups of 3.0 or less, and particularly preferable to use one having an average number of functional groups of 2.5 or less. Furthermore, in the urethane resin of this disclosure, it is preferable to use an aliphatic polyisocyanate and its modified form having an average number of functional groups of 2.3 or more, more preferably a form with an average number of functional groups greater than 2.3, even more preferably a form with an average number of functional groups of 2.4 or more, and particularly preferably a form with an average number of functional groups of 2.5 or more. The average number of functional groups in the aliphatic polyisocyanate and its modified form can be determined from the isocyanate group content (mass%) obtained by the method described in JIS K7301-1995 and the number average molecular weight of the aliphatic polyisocyanate and its modified form, which is determined by measuring the number average molecular weight relative to polystyrene using gel permeation chromatography (GPC). Furthermore, when using multiple aliphatic polyisocyanates and their modified forms, the average number of isocyanate functional groups of all the aliphatic polyisocyanates and their modified forms used can be determined based on the amount of each raw material used, the number of isocyanate functional groups of each raw material, and the polyisocyanate number-average molecular weight. By setting the average number of functional groups of the aliphatic polyisocyanates and their modified forms in the urethane resin of this disclosure to the above-mentioned range, the hardness of the urethane resin can be lowered and the toxicity can be further reduced.

[0020] In this disclosure, the content of aliphatic polyisocyanates and / or their modified forms can be 1.0% to 50.0% by mass, preferably 2.0% to 25.0% by mass, more preferably 3.0% to 20.0% by mass, and even more preferably 4.0% to 15.0% by mass, relative to the total urethane resin of this disclosure. By setting the content of aliphatic polyisocyanates and / or their modified forms within this range, the hardness of the urethane resin can be lowered and the toxicity can be further reduced.

[0021] -Polyols- The polyols in this disclosure are not particularly limited and include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, polyolefin polyols, acrylic polyols, silicone polyols, fluorine polyols, vinyl monomer-modified polyols, and the like, which are commonly used as raw materials for polyurethane resins. Preferably, the polyols in this disclosure are polyether polyols, polyester polyols, and polycarbonate polyols.

[0022] Examples of polyether polyols include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose. Furthermore, examples of polyether polyols include those obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to the aforementioned polyhydric alcohols. Examples of polyester polyols include those obtained by polycondensation of aliphatic carboxylic acids such as malonic acid, succinic acid, and adipic acid, or aromatic carboxylic acids such as phthalic acid, with aliphatic glycols such as ethylene glycol, diethylene glycol, and propylene glycol.

[0023] Examples of polycarbonate polyols include those obtained by the reaction of a polyol with a carbonate compound such as a dialkyl carbonate, alkylene carbonate, or diaryl carbonate. As the polyol constituting the polycarbonate polyol, the polyhydric alcohols exemplified earlier as components of polyester polyols can be used. Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

[0024] In this disclosure, the polyols described above can be used alone or in combination of two or more types.

[0025] In this disclosure, the polyol content can be 10% to 50% by mass, preferably 15% to 45% by mass, more preferably 20% to 40% by mass, and even more preferably 25% to 35% by mass, relative to the total urethane resin of this disclosure. By setting the polyol content within this range, the hardness of the urethane resin can be lowered and the toxicity can be further reduced.

[0026] In this disclosure, the number-average molecular weight of the polyol can be 500 to 15000, preferably 1000 to 10000, more preferably 3000 to 7000, and even more preferably 4000 to 6000. By setting the polyol content within this range, the hardness of the urethane resin can be lowered and the toxicity can be further reduced.

[0027] In particular, the urethane resin of this disclosure preferably contains a diol as one component of the polyol, with a number average molecular weight in the range of 500 to 15,000, preferably 500 to 5,000, and more preferably 1,000 to 5,000. The amount of diol blended can be 1% to 25% by mass, preferably 5% to 20% by mass, and more preferably 10% to 15% by mass, relative to the total urethane resin of this disclosure. By setting the content of diol as one component of the polyol within this range, the amount of monool blended, as described later, can be reduced, and the peel strength can be reduced while maintaining low toxicity. In the case of using the urethane resin of this disclosure by applying it to animals, reducing the peel strength can prevent pain and skin damage when peeling it off.

[0028] -Monool- In the urethane resin of this disclosure, the monool is not particularly limited as long as it is a compound that contains one active hydrogen group in its molecule and has a number average molecular weight of 1000 or more. Examples include aliphatic monools, alicyclic monools, aromatic monools, ether monools, ester monools, etc. Examples of monools include monoalkyl esters in which one terminal hydroxyl group of the above-mentioned polyol is substituted with an alkyl ester group, and monoalkyl ethers in which one terminal hydroxyl group of the above-mentioned polyol is substituted with an alkyl ether group.

[0029] In the urethane resin of this disclosure, the monool content can be 10% to 90% by mass, preferably 20% to 85% by mass, more preferably 30% to 80% by mass, and even more preferably 40% to 75% by mass, based on the total mass of the urethane resin of this disclosure. By setting the monool content within this range, the hardness of the urethane resin can be further reduced. In the urethane resin of this disclosure, the amount of monool blended is preferably greater than that of the polyol described above. Specifically, the monool content is preferably more than 50% by mass, preferably 60% or more by mass, preferably 70% or more by mass, and preferably 80% or more by mass, based on the total mass of the monool and polyol. Furthermore, the monool content is preferably 90% or less by mass, and preferably 85% or less by mass, based on the total mass of the monool and polyol. By setting the amount of monool blended within this range compared to that of polyol, the hardness of the urethane resin can be further reduced.

[0030] Furthermore, when the above-mentioned diol is incorporated as a component of the polyol in the urethane resin of this disclosure, the amount of monool incorporated can be reduced. Specifically, the total amount of the incorporated diol and monool can be 10% to 90% by mass, preferably 20% to 85% by mass, more preferably 30% to 80% by mass, and even more preferably 40% to 75% by mass, relative to the total amount of the urethane resin of this disclosure. By setting the total amount of diol and monool incorporated within this range, the peel strength can be reduced while maintaining a lower hardness in the urethane resin.

[0031] The number-average molecular weight of the monool is 1000 or more, but is particularly preferably 1500 or more, more preferably 2000 or more, and even more preferably 2500 or more. Furthermore, there is no particular upper limit to the number-average molecular weight of the monool, but it can be 5000 or less, preferably 4500 or less, and more preferably 4000 or less.

[0032] -Plasticizer- The urethane resin of this disclosure achieves low hardness and low toxicity through the above-described structure, so the amount of plasticizer used can be reduced compared to ordinary low-hardness urethane resins, or it may not be necessary to use a plasticizer at all. The plasticizers that can be used in the urethane resin are not particularly limited, but examples include propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, and the like.

[0033] In the urethane resin of this disclosure, if a plasticizer is included, the content of the plasticizer is preferably 0% to 100% by mass, more preferably 0% to 70% by mass, even more preferably 0% to 50% by mass, even more preferably 0% to 25% by mass, even more preferably 0% to 10% by mass, even more preferably 0% to 1% by mass, and even more preferably 0% to 0.5% by mass, based on 100% by mass of the total of the polyol, monool, and isocyanate. In the urethane resin of this disclosure, it is most preferable not to include a plasticizer. In the urethane resin of this disclosure, by not including a plasticizer, or by including a plasticizer within the above range, the toxicity can be greatly reduced. In particular, in the urethane resin of this disclosure, by blending a plasticizer within the above range, the peel strength can be reduced while maintaining low toxicity.

[0034] - Antioxidant - The urethane resin of this disclosure is preferably made to contain an antioxidant, in particular from the viewpoint of suppressing thermal degradation. The antioxidant is not particularly limited, but antioxidants used as food additives such as vitamin E derivatives, vitamin C derivatives, and polyphenol derivatives can be used. Furthermore, the antioxidant is not limited to those used as food additives, but phenolic antioxidants, amine antioxidants, and especially BHT (dibutylcresol), hindered phenols, etc. can be used.

[0035] Vitamin E derivatives are compounds having a tocopherol skeleton or a tocotrienol skeleton, and include, for example, tocopherols, tocotrienols, and their derivatives (esters, salts, etc.). Specifically, examples of vitamin E derivatives include α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, DL-α-tocopherol, and their derivatives. Examples of tocotrienols include α-tocotrienol, β-tocotrienol, γ-tocotrienol, δ-tocotrienol, and their derivatives.

[0036] Vitamin C derivatives are compounds having an ascorbic acid skeleton, and include, for example, ascorbic acid (L-ascorbic acid) and its derivatives (salts, esters, etc.). Specifically, examples of vitamin C derivatives include L-ascorbic acid, salts of L-ascorbic acid (e.g., sodium ascorbate, calcium ascorbate, potassium ascorbate, magnesium ascorbate, etc.), fatty acid esterified ascorbic acid (e.g., ascorbic acid palmitate, ascorbic acid stearate, ascorbic acid laurate, ascorbic acid myristic acid, ascorbic acid oleate, etc.), oxidized forms of ascorbic acid (e.g., dehydroascorbic acid, etc.), and stereoisomers and derivatives of ascorbic acid (e.g., erythorbic acid (isoascorbic acid), sodium erythorbate, calcium erythorbate, etc.).

[0037] Polyphenol derivatives include compounds and their derivatives that have an aromatic compound skeleton with multiple phenolic hydroxyl groups and exhibit antioxidant activity. Polyphenol derivatives may be of natural or synthetic origin. Specifically, examples of polyphenol derivatives include flavonoids, phenolic acids, stilbenes, lignans, tannins, catechins, anthocyanins, coumarins, xanthones, and their derivatives. For example, polyphenol derivatives include catechin, epicatechin, epigallocatechin, epigallocatechin gallate, gallocatechin, gallocatechin gallate, gallic acid, propyl gallate, octyl gallate, dodecyl gallate, chlorogenic acid, caffeic acid, ferulic acid, p-coumaric acid, resveratrol, quercetin, rutin, myricetin, kaempferol, apigenin, luteolin, naringenin, hesperidin, genistein, daidzein, anthocyanins, and the like.

[0038] Phenolic antioxidants include compounds that have a phenolic hydroxyl group and suppress oxidative degradation through radical scavenging. Examples of phenolic antioxidants include hindered phenolic antioxidants, bisphenolic antioxidants, polyphenolic antioxidants, aromatic compounds having a phenolic hydroxyl group, and their derivatives. Specifically, examples of phenolic antioxidants include octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, tris(3,5-di-tert-butyl-4-hydroxybenzyl)trimesinate, and derivatives thereof.

[0039] The amount of antioxidant added is preferably 0.05 to 3 parts by mass, and more preferably 0.05 to 1.0 part by mass, per 100 parts by mass of polyol.

[0040] -Other Components- In addition to the components described above, the urethane resin of this disclosure may contain various components that are normally found in urethane resins. Examples of such components include conventionally known heat stabilizers, ultraviolet absorbers, UV stabilizers, fillers, pigments, dyes, flame retardants, defoamers, dispersants, surface modifiers, moisture adsorbents, catalysts, etc. The urethane resin of this disclosure may also be used by mixing one or more of these components.

[0041] <Method for Producing Urethane Resin> The method for producing urethane resin according to the present disclosure is a method for producing urethane resin comprising the step of reacting an aliphatic polyisocyanate and / or a modified thereof with a polyol and a monool having a number average molecular weight of 1000 or more. In the method for producing urethane resin according to the present disclosure, the aliphatic polyisocyanate and / or a modified thereof, the polyol, and the monool having a number average molecular weight of 1000 or more are as described above. In addition, the reaction may proceed with other components included in this step.

[0042] In particular, in the method for producing urethane resin according to this disclosure, it is preferable to use a catalyst to advance the urethane reaction. As the catalyst for advancing the urethane reaction, any known catalyst can be used without limitation, but tertiary amines such as triethylenediamine, N,N,N',N'-tetramethylhexanediamine, and bis(2-dimethylaminoethyl) ether, metal catalysts such as bismuth neodecanoate, bismuth octoate, tin octoate, di-n-butyltin dilaurate, and lead octoate can be used. These may be used individually or in combination of two or more. However, from the viewpoint of producing a low-toxicity urethane resin, it is preferable to use a catalyst other than a tin-containing catalyst. For example, from the viewpoint of producing a low-toxicity urethane resin, it is preferable to use an organometallic catalyst containing bismuth, and it is preferable that the number of carbon atoms is higher. That is, from the viewpoint of producing a low-toxicity urethane resin, it is preferable to use bismuth neodecanoate.

[0043] As a method for reacting an aliphatic polyisocyanate and / or a modified product thereof with a polyol and a monool having a number average molecular weight of 1,000 or more, examples include a one-shot method in which these components are reacted all at once, and a prepolymer method in which a reaction product (prepolymer) obtained by reacting an aliphatic polyisocyanate and / or a modified product thereof with a polyol in advance is reacted with the monool.

[0044] When producing a urethane resin by the one-shot method, the reaction temperature is preferably, for example, 20°C to 220°C, more preferably 45°C to 180°C, and still more preferably 70°C to 140°C. The reaction time is, for example, preferably 50 minutes to 900 minutes, more preferably 100 minutes to 600 minutes, and still more preferably 150 minutes to 300 minutes.

[0045] When producing a urethane resin by the prepolymer method, the reaction temperature for obtaining the prepolymer is preferably, for example, 20°C to 200°C, more preferably 45°C to 150°C, and still more preferably 70°C to 100°C. The reaction time for obtaining the prepolymer is not particularly limited, and the reaction may be continued until the isocyanate group concentration in the reaction solution reaches a desired value; for example, it is 10 minutes to 400 minutes, 20 minutes to 200 minutes, or 30 minutes to 100 minutes. The reaction temperature for reacting the prepolymer with the monool is preferably, for example, 20°C to 220°C, more preferably 45°C to 180°C, and still more preferably 70°C to 140°C. The reaction time is, for example, preferably 420 minutes or less, more preferably 360 minutes or less, and still more preferably 300 minutes or less.

[0046] Furthermore, if necessary, the produced urethane resin may be subjected to heat treatment at 100°C or lower for 1 hour to 100 hours.

[0047] <Gel fraction of urethane resin> The urethane resin of the present disclosure is characterized by having a gel fraction of 30% or more. In the urethane resin of the present disclosure, the gel fraction is particularly preferably 35% or more, more preferably 40% or more, still more preferably 45% or more, still more preferably 50% or more, and even more preferably 55% or more. When the gel fraction of the urethane resin of the present disclosure falls within this range, exudation of unreacted components, plasticizers, other components and the like can be prevented, and the toxicity is further reduced. In the production of the urethane resin of the present disclosure, the number of functional groups of isocyanate is adjusted, and the number of functional groups of monool and polyol is adjusted in order to achieve lower hardness. Thus, according to the present disclosure, it is shown that a urethane resin having a gel fraction of 30% or more can be produced by adjusting the number of functional groups of each raw material such as isocyanate, monool and polyol.

[0048] In the present disclosure, the gel fraction is a value calculated as follows. Specifically, solvent extraction is performed on the urethane resin to be tested using tetrahydrofuran (under stirring conditions at room temperature for 24 hours). Thereafter, the urethane resin is taken out and dried under vacuum at 70°C for 2 hours. The gel fraction is calculated by the following formula from the mass of the urethane resin before solvent extraction and the mass of the urethane resin after drying. Formula: [Gel fraction] = (mass of urethane resin after drying / mass of urethane resin before solvent extraction) × 100

[0049] <Hardness of Urethane Resin> As described above, the urethane resin of this disclosure has the characteristics of low hardness and low toxicity. In this disclosure, low hardness means that the urethane resin is at least gel-like in nature and can maintain its shape. Specifically, the hardness of the urethane resin of this disclosure is preferably such that the Asker C hardness is 20 or less and the Asker F hardness is 100 or less. In particular, the Asker C hardness of the urethane resin of this disclosure is more preferably 15 or less, even more preferably 10 or less, and even more preferably 5 or less. Furthermore, the Asker F hardness of the urethane resin of this disclosure is more preferably 90 or less, even more preferably 80 or less, and even more preferably 75 or less. Because the hardness of the urethane resin of this disclosure is within this range, it can be easily applied, for example, to sheets that are attached to uneven surfaces.

[0050] The Asker C hardness and Asker F hardness of the urethane resin were determined using an Asker C hardness tester and an Asker F hardness tester, respectively. The Asker C hardness was measured in accordance with JIS K 7312, and the Asker F hardness was measured by gently placing the pressure surface of the hardness tester on the urethane resin being tested, with the weight of the hardness tester (520 g) used as the measurement pressure.

[0051] <Toxicity of Urethane Resin> As described above, the urethane resin of this disclosure has the characteristics of low hardness and low toxicity. Here, the toxicity of the urethane resin of this disclosure refers to toxicity to animals, including humans, and can be evaluated based on cytotoxicity tests. In this disclosure, the cytotoxicity test is performed using the colony formation inhibition method in accordance with ISO 10993-5 cytotoxicity test, and the tested urethane resin is evaluated as having cytotoxicity or not having cytotoxicity.

[0052] <Bio-contacting materials> As described above, the urethane resin of this disclosure has the characteristics of low hardness and low toxicity. Due to these characteristics, it is preferable to use the urethane resin of this disclosure as a bio-contacting material. However, the urethane resin of this disclosure is not limited to use as a bio-contacting material and can be applied to any other application. Here, a bio-contacting material means a material that can be used in articles that come into contact with animals, including humans. The urethane resin of this disclosure can also be used as a bio-contacting material for articles that come into contact with animals, including humans. Articles that come into contact with animals, including humans, may be for medical or non-medical purposes. Examples of medical articles include medical devices such as artificial organs, artificial blood vessels, artificial hip joints, sutures, catheters, stents, and dental composite materials, medical adhesives, regenerative medicine devices such as cell culture sheets, and pads for covering cuts, abrasions, lacerations, puncture wounds, or bites. Examples of non-medical articles include wearable products such as smartwatches. Furthermore, the urethane resin of this disclosure is not limited to use in articles that come into direct contact with animals, including humans, but can also be used in articles that come into indirect contact with animals, including humans, via covering materials, etc. The covering material is not particularly limited, but examples include resin films, cloths, etc. Examples of such articles include gel puffs (silicone puffs), shock-absorbing pads, pressure-distributing cushions, protectors, pressure ulcer prevention devices, pillows and mattresses, and other bedding.

[0053] The urethane resin of this disclosure is molded to a shape suitable for its intended use. For example, it can be molded to a shape suitable for the purpose by a method in which the material is shaped before the reaction and then solidified by reaction, a method in which it is softened and melted by heating after the reaction and then molded, or a method in which it is molded using a solution dissolved after the reaction. Specific examples of molding methods are not particularly limited, but include known and conventional molding methods such as coating, casting, vacuum forming, extrusion, calendering, blow molding, inflation molding, rotational molding, slush molding, foam molding, compression molding, stamping, casting, and dipping.

[0054] The present disclosure will be described in more detail below with reference to examples, but the technical scope of the present disclosure is not limited to the following examples.

[0055] [Examples 1-7, Comparative Examples 1-3] <Production of Urethane Resin> In this example, the polyols, monools, and aliphatic polyisocyanates, plasticizers, and catalysts shown in Table 1 were used. Note that "EO" indicates ethylene oxide, "PO" indicates propylene oxide, and "molecular weight" represents the number average molecular weight.

[0056]

[0057] To a 100 ml container, the catalyst, polyol, monool, aliphatic polyisocyanate, and / or modified thereof were added in the parts by mass shown in Table 2, then stirred and degassed. The resulting solution was poured into a mold, which had been sized to produce a gel layer of the desired thickness, placed on top of a release polyethylene terephthalate (PET) sheet. The mold was then covered with another release PET sheet, sandwiched between glass plates, and cured at room temperature (24°C for 12 hours). The curing process may also be heated (for example, 130°C for 15 minutes). The urethane resin of the example was produced in the manner described above.

[0058] Furthermore, the comparative urethane resin was manufactured in the same manner as the urethane resin in the examples, except that the catalyst, polyol, monool, aliphatic polyisocyanate, and / or modified thereof were used in the parts by mass shown in Table 3. In addition, Exceel's product name: "Human Skin Gel" was also used as the comparative urethane resin.

[0059] - Degree of Crosslinking - The degree of crosslinking was calculated for the urethane resin in the example and the urethane resin in the comparative example. The degree of crosslinking was calculated by dividing the sum of the values ​​obtained by multiplying the mol of trifunctional raw materials (polyols, monools, aliphatic polyisocyanates, and their modified forms) by 3, by the sum of the values ​​obtained by multiplying the mol of each raw material by the number of functional groups of that raw material. That is, the degree of crosslinking is given by the following formula: Formula: [Degree of Crosslinking] = Σ (mol of trifunctional raw material × 3) / Σ (mol of raw material × number of functional groups of that raw material)

[0060] -Hardness- The Asker C hardness and Asker F hardness were measured for the urethane resin of the example and the urethane resin of the comparative example. Specifically, the Asker C hardness and Asker F hardness were measured using an Asker C hardness tester (manufactured by Polymer Instruments Co., Ltd., product name: Asker Rubber Hardness Tester Type C) and an Asker F hardness tester (manufactured by Polymer Instruments Co., Ltd., product name: Asker Rubber Hardness Tester F), respectively. The Asker C hardness was measured in accordance with JIS K 7312, and the Asker F hardness was measured by gently placing the pressure surface of the hardness tester on the urethane resin and using the weight of the hardness tester as the measurement pressure (520g).

[0061] -Gel Fraction- To calculate the gel fraction of the urethane resin in the example and the urethane resin in the comparative example, solvent extraction was performed on the urethane resin using tetrahydrofuran. The solvent extraction was carried out at room temperature for 24 hours under stirring conditions. After that, the urethane resin was removed and dried under vacuum at 70°C for 2 hours. The gel fraction (%) was calculated from the mass of the urethane resin before solvent extraction and the mass of the urethane resin after drying using the following formula: Formula: [Gel Fraction] = (Mass of urethane resin after drying / Mass of urethane resin before solvent extraction) × 100

[0062] -Cytotoxicity Test- Cytotoxicity tests were conducted on the urethane resin of the example and the urethane resin of the comparative example. For the cytotoxicity test, a colony formation inhibition method in accordance with ISO 10993-5 cytotoxicity test was performed to evaluate whether cytotoxicity was present or absent. In the colony formation inhibition method, 10 mL of culture medium was added to 1 g of the urethane resin of the example or comparative example, and the mixture was left to stand in a 37°C carbon dioxide incubator for 24 hours to be used as the extraction medium. Cytotoxicity was considered present if the colony formation rate when using the extraction medium was less than 70% compared to the negative control. The colony formation rate was calculated by counting the number of colonies under a stereomicroscope and setting the number of colonies in the negative control to 100%.

[0063] Table 2 shows the composition, degree of crosslinking, hardness, gel fraction, and cytotoxicity test results of the urethane resin in the example, and Table 3 shows the composition, degree of crosslinking, hardness, gel fraction, and cytotoxicity test results of the urethane resin in the comparative example. The average number of functional groups shown in Tables 2 and 3 refers to the average number of functional groups calculated based on the number of functional groups and the amount used of the aliphatic polyisocyanate and its modified form used in the urethane resin. The INDEX shown in Tables 2 and 3 is the value obtained by multiplying the ratio of the number of moles of all hydroxyl groups in the urethane resin to the number of moles of isocyanate groups in the isocyanate compound by 100 (moles of NCO / moles of hydroxyl groups × 100).

[0064]

[0065]

[0066] As shown in Table 2, the urethane resins of Examples 1 to 7 were found to have low hardness and low toxicity. In contrast, as shown in Table 3, the urethane resin of Comparative Example 1 exhibited cytotoxicity despite its low hardness. This was presumed to be due to the low gel fraction of the urethane resin of Comparative Example 1, which led to the leaching of plasticizers and other substances, resulting in cytotoxicity. Furthermore, as shown in Table 3, the polyurethane resins of Comparative Examples 2 and 3 had extremely low gel fractions and could not maintain their shape as gels. In addition, the product name "Human Skin Gel" from Exceel Co., Ltd., which was used as the urethane resin in the comparative example, had a gel fraction of 24% and an Asker C hardness of 0, indicating low hardness, but it also exhibited cytotoxicity. This was presumed to be due to the use of 1,2-cyclohexanedicarboxylic acid diisononyl as a plasticizer and a tin-based catalyst.

[0067] [Examples 8-9] <Manufacturing of urethane resin>

[0068] A catalyst, polyol, monool, aliphatic polyisocyanate, and / or a modified thereof were added to a 100 ml container in the parts by mass shown in Table 4, and a urethane resin was produced in the same manner as in Examples 1 to 7. The antioxidant "Adekastab AO-50" used in the polyurethane resin of Example 9 is octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0069] Furthermore, for the urethane resins of Examples 8 and 9, crosslinking degree, hardness, and cytotoxicity tests were performed in the same manner as in Examples 1 to 7, and the gel fraction was measured before and after the aging test. The aging test was performed under conditions of heating at 70°C for 4 weeks. The results are shown in Table 4.

[0070]

[0071] As shown in Table 4, in the polyurethane resins of Examples 8 and 9, the gel fraction after the thermal aging test remained the same as the value before the thermal aging test, clearly demonstrating that thermal degradation can be prevented by antioxidants.

[0072] [Examples 10-11] <Manufacturing of urethane resin>

[0073] A catalyst, polyol, monool, diol, aliphatic polyisocyanate, and / or modified thereof were added to a 100 ml container in the parts by mass shown in Table 5, and a urethane resin was produced in the same manner as in Examples 1 to 7. Actcol D-3000, used in the polyurethane resin of Example 11, is a polyoxypropylene diol (molecular weight 3000) with 3 functional groups and a hydroxyl value of 37.4 mg KOH / g.

[0074] Furthermore, for the urethane resins of Examples 10 to 11, crosslinking degree, hardness, gel fraction, and cytotoxicity tests were performed in the same manner as in Examples 1 to 7, and peel strength tests were also conducted. The peel strength of the polyurethane resin was measured in accordance with JIS Z 0237:2022. Specifically, a stainless steel plate (SUS plate) was used as the adherend, and a test sample with a width of 25 mm, a length of 100 mm, and a thickness of 100 μm was attached to the SUS plate. Next, a TPU film (product name: DUS202, manufacturer: Seedam, width 25 mm, length 150 mm, thickness 100 μm) was attached to the surface of the sample as a polyurethane resin film to create a laminate. A 180° peel test was performed on the obtained laminate using an autograph (tensile testing machine), gripping the TPU film side. In the test, the peel speed was set to 300 mm / min, and the load when peeling the TPU film from the sample was measured. The peel strength was calculated by dividing the average load at the time of peeling by the width of the test piece (N / 25 mm). The results are shown in Table 5.

[0075]

[0076] As shown in Table 5, the polyurethane resins of Examples 10 and 11 exhibited low peel strength while maintaining low hardness and low toxicity. In particular, when a portion of the monool was replaced with a diol in the formulation, it was possible to further reduce the peel strength while maintaining low hardness and low toxicity. Furthermore, by reducing the peel strength of the urethane resin, it is possible to prevent pain and skin damage when removing the urethane resin applied to animal skin.

[0077] The disclosure of Japanese Patent Application No. 2025-032319, filed on 28 February 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A urethane resin obtained by reacting an aliphatic polyisocyanate and / or a modified thereof with a polyol and a monool, wherein the number average molecular weight of the monool is 1000 or more, and the gel fraction of the urethane resin is 30% or more.

2. The urethane resin according to claim 1, wherein the average number of functional groups of the aliphatic polyisocyanate and / or its modified form is 3.0 or less.

3. The urethane resin according to claim 1, comprising an antioxidant.

4. The urethane resin according to claim 1, which is obtained by further reacting with a diol.

5. A biocompatible member comprising the urethane resin described in any one of claims 1 to 4.

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