JP7724686B2 - Polyurethane elastomer - Google Patents

Description

The present invention relates to a polyurethane elastomer.

Polyurethane elastomers have hard segments formed by the reaction of polyisocyanate and low-molecular-weight polyol, and soft segments formed by the reaction of polyisocyanate and high-molecular-weight polyol. Polyurethane elastomers are rubbery elastic materials and are widely used in a variety of industrial fields.

More specifically, polyurethane elastomers obtained by the following method are known. Specifically, in this method, tolylene diisocyanate, polyoxytetramethylene glycol, and polycaprolactone polyol are first reacted to obtain an isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer is then reacted with 3,3'-dichloro-4,4-diaminodiphenylmethane (MOCA) to obtain a polyurethane elastomer (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-123767

On the other hand, depending on the application of the polyurethane elastomer, improved durability may be required. More specifically, improvements in the flex resistance and compression set of the polyurethane elastomer may be required.

This invention is a polyurethane elastomer that has excellent flex resistance and compression set.

The present invention [1] relates to a polyurethane elastomer comprising a reaction product of a prepolymer component containing an isocyanate-terminated prepolymer and a curing agent, wherein the isocyanate-terminated prepolymer comprises a reaction product of a polyisocyanate component and a polyol component containing a polyether polyol, the prepolymer component has an isocyanate group concentration of 6.0% by mass or less, and the curing agent comprises a halogenated diethyltoluenediamine.

The present invention [2] includes the polyurethane elastomer described in [1] above, in which the polyether polyol includes polytetramethylene ether polyol.

In the polyurethane elastomer of the present invention, the isocyanate-terminated prepolymer contained in the prepolymer component contains a reaction product of a polyisocyanate component and a polyol component containing a polyether polyol. The prepolymer component has an isocyanate group concentration of 6.0% by mass or less. The curing agent contains halogenated diethyltoluenediamine. This polyurethane elastomer exhibits excellent flex resistance and compression set.

The polyurethane elastomer is a thermoplastic polyurethane (TPU) or a thermosetting polyurethane (TSU). Preferably, the polyurethane elastomer is a thermosetting polyurethane (TSU). The polyurethane elastomer contains the reaction product of a prepolymer component and a curing agent (described below).

The prepolymer component contains an isocyanate-terminated prepolymer as the main component. The proportion of the main component is 90% by mass or more, preferably 95% by mass or more, based on the total amount of the prepolymer component. Furthermore, the proportion of the main component is typically 100% by mass or less, based on the total amount of the prepolymer component.

Isocyanate-terminated prepolymers are the reaction product of a polyisocyanate component and a polyol component.

Examples of polyisocyanate components include polyisocyanate monomers and polyisocyanate derivatives.

Examples of polyisocyanate monomers include aromatic polyisocyanates, aliphatic polyisocyanates, and araliphatic polyisocyanates. Examples of aromatic polyisocyanates include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), toluidine diisocyanate (TODI), paraphenylene diisocyanate, and naphthalene diisocyanate (NDI). Examples of aliphatic polyisocyanates include linear aliphatic polyisocyanates and alicyclic polyisocyanates. Examples of linear aliphatic polyisocyanates include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), and hexamethylene diisocyanate (HDI). Examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), methylenebis(cyclohexylisocyanate) (H ₁₂ MDI), and bis(isocyanatomethyl)cyclohexane (H ₆ XDI). Examples of aralkyl polyisocyanates include xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI). The polyisocyanate monomers can be used alone or in combination of two or more.

Polyisocyanate derivatives include modified products obtained by modifying polyisocyanate monomers using known methods. Examples of modified products include uretdione-modified products, isocyanurate-modified products, allophanate-modified products, polyol-modified products, biuret-modified products, urea-modified products, oxadiazinetrione-modified products, and carbodiimide-modified products. These can be used alone or in combination of two or more types.

The polyisocyanate component can be used alone or in combination of two or more types. As the polyisocyanate component, preferably, a polyisocyanate monomer is used, more preferably, a diisocyanate monomer is used. Furthermore, as the polyisocyanate monomer, more preferably, an aromatic polyisocyanate is used, even more preferably, diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI) are used, and tolylene diisocyanate (TDI) is particularly preferred. When tolylene diisocyanate (TDI) is used, particularly excellent flex resistance and compression set can be obtained if the curing agent (described below) contains halogenated diethyltoluenediamine.

Examples of tolylene diisocyanates include 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. These can be used alone or in combination of two or more types. A preferred tolylene diisocyanate is a combination of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. Also preferred tolylene diisocyanate is the use of 2,4-tolylene diisocyanate alone. When these are used, particularly excellent mechanical properties are obtained.

A particularly preferred example of the tolylene diisocyanate is a combination of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. When 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used in combination, the content of 2,4-tolylene diisocyanate relative to the total amount of these is, for example, 40% by mass or more, preferably 60% by mass or more. The content of 2,4-tolylene diisocyanate is, for example, 90% by mass or less. The content of 2,6-tolylene diisocyanate is, for example, 10% by mass or more. The content of 2,6-tolylene diisocyanate is, for example, 60% by mass or less, preferably 40% by mass or less.

The polyol component contains polyether polyol as an essential component. Polyether polyol is a macropolyol. Macropolyols have two or more hydroxyl groups in their molecules and are relatively high molecular weight organic compounds. The number average molecular weight of macropolyols is, for example, 400 or more and, for example, 20,000 or less. The number average molecular weight can be calculated using a known method from the hydroxyl group equivalent weight and the average number of hydroxyl groups. The number average molecular weight can also be measured as a polystyrene-equivalent molecular weight using gel permeation chromatography (the same applies below).

Examples of polyether polyols include polyoxyalkylene polyols. Examples of polyoxyalkylene polyols include polyoxyalkylene (C2-3) polyols and polytetramethylene ether polyols.

Examples of polyoxyalkylene (C2-3) polyols include polyoxyethylene polyols, polyoxypropylene polyols, polyoxytriethylene polyols, and polyoxyethylene-polyoxypropylene polyols (random or block copolymers).

Examples of polytetramethylene ether polyols include ring-opening polymers (crystalline polytetramethylene ether glycol) obtained by cationic polymerization of tetrahydrofuran. Other examples of polytetramethylene ether polyols include amorphous polytetramethylene ether glycol. Amorphous polytetramethylene ether glycol is a copolymer of tetrahydrofuran with alkyl-substituted tetrahydrofuran and/or a dihydric alcohol. Crystalline refers to the property of being a solid at 25°C. Amorphous refers to the property of being a liquid at 25°C.

Polyether polyols can be used alone or in combination of two or more types. A preferred example of a polyether polyol is polytetramethylene ether polyol.

The number average molecular weight of the polyether polyol is, for example, 400 or more, preferably 500 or more, and more preferably 1,000 or more. The number average molecular weight of the polyether polyol is, for example, 15,000 or less, preferably 13,000 or less, more preferably 12,000 or less, even more preferably 10,000 or less, even more preferably 8,000 or less, and particularly preferably 5,000 or less.

The average number of hydroxyl groups in the polyether polyol is, for example, 2.0 or more. The average number of hydroxyl groups in the polyether polyol is, for example, 6.0 or less, preferably 4.0 or less, and more preferably 3.0 or less.

The polyol component can optionally contain polyols other than polyether polyols (hereinafter referred to as "other polyols"). Examples of other polyols include other macropolyols and low molecular weight polyols.

Other macropolyols are macropolyols other than polyether polyols. Examples of other macropolyols include polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer-modified polyols. The other macropolyols can be used alone or in combination of two or more types.

Low-molecular-weight polyols are organic compounds with two or more hydroxyl groups in their molecules and a relatively low molecular weight. The molecular weight of low-molecular-weight polyols is, for example, 40 or more but less than 400, preferably 300 or less. Examples of low-molecular-weight polyols include dihydric alcohols, trihydric alcohols, and tetrahydric or higher alcohols. Examples of dihydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and dipropylene glycol. Examples of trihydric alcohols include glycerin and trimethylolpropane. Examples of tetrahydric or higher alcohols include pentaerythritol and diglycerin. Low-molecular-weight polyols also include polymers obtained by addition polymerization of alkylene (C2-3) oxide with dihydric to tetrahydric alcohols so that the number-average molecular weight is less than 400. These can be used alone or in combination of two or more types.

The other polyols can be used alone or in combination of two or more types. From the viewpoints of flex resistance and compression set, the content of the other polyols is, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass, based on the total amount of the polyol components.

That is, the content of polyether polyol relative to the total amount of the polyol component is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In other words, the polyol component preferably consists of polyether polyol.

Isocyanate-terminated prepolymers can be obtained, for example, by reacting a polyisocyanate component and a polyol component in a specified ratio (prepolymer process).

The blending ratio of the polyisocyanate component and the polyol component is adjusted so that there is an excess of isocyanate groups relative to the hydroxyl groups. More specifically, the equivalent ratio of isocyanate groups in the polyisocyanate component to the hydroxyl groups in the polyol component (isocyanate groups/hydroxyl groups) is, for example, 1.5 or more, preferably 1.8 or more, more preferably 2 or more, and even more preferably 2.5 or more. Furthermore, the equivalent ratio of isocyanate groups in the polyisocyanate component to the hydroxyl groups in the polyol component (isocyanate groups/hydroxyl groups) is, for example, 10 or less, preferably 7 or less, more preferably 5 or less, and even more preferably 4.5 or less.

Polymerization methods include, for example, bulk polymerization and solution polymerization. In bulk polymerization, for example, the polyisocyanate component and the polyol component are reacted under a nitrogen stream. The reaction temperature is, for example, 50°C or higher. The reaction temperature is, for example, 250°C or lower, preferably 200°C or lower. The reaction time is, for example, 0.5 hours or higher, preferably 1 hour or higher. The reaction time is, for example, 15 hours or lower. In solution polymerization, the polyisocyanate component and the polyol component are reacted in the presence of a known organic solvent. The reaction temperature is, for example, 50°C or higher. The reaction temperature is, for example, 120°C or lower, preferably 100°C or lower. The reaction time is, for example, 0.5 hours or higher, preferably 1 hour or higher. The reaction time is, for example, 15 hours or lower.

If necessary, a known urethane-forming catalyst can be added. Examples of urethane-forming catalysts include amines and organometallic compounds. The proportion of urethane-forming catalyst added can be appropriately determined depending on the purpose and application.

This results in a reaction mixture containing an isocyanate-terminated prepolymer. The reaction mixture obtained by the above reaction may contain unreacted polyisocyanate (isocyanate monomer) in addition to the isocyanate-terminated prepolymer. If necessary, the unreacted polyisocyanate is removed from the reaction mixture by a known removal method. Examples of removal methods include distillation and extraction.

The prepolymer component may be a component containing an isocyanate-terminated prepolymer and unreacted polyisocyanate. Alternatively, the prepolymer component may be a component containing an isocyanate-terminated prepolymer but not containing unreacted polyisocyanate. The prepolymer component is preferably a component containing an isocyanate-terminated prepolymer but not containing unreacted polyisocyanate. In other words, the prepolymer component preferably consists of an isocyanate-terminated prepolymer.

Such a prepolymer component can be obtained, for example, by reacting a polyisocyanate component with a polyol component in an equivalent ratio and under reaction conditions that do not produce unreacted polyisocyanate. Alternatively, such a prepolymer component can be obtained by removing unreacted polyisocyanate from the above-mentioned reaction mixture.

The isocyanate group concentration of the prepolymer component is, for example, 1% by mass or more, preferably 1.5% by mass or more, and more preferably 2.0% by mass or more. The isocyanate group concentration of the prepolymer component is 6.0% by mass or less, preferably 5.0% by mass or less, more preferably 4.2% by mass or less, even more preferably 4.0% by mass or less, and particularly preferably 3.0% by mass or less. The isocyanate group concentration (isocyanate group content) can be determined by known methods such as titration with di-n-butylamine or FT-IR analysis.

When the isocyanate group concentration of the prepolymer component is below the above upper limit, particularly excellent flex resistance and compression set can be obtained if the curing agent (described below) contains halogenated diethyltoluenediamine. Furthermore, when the isocyanate group concentration of the prepolymer component is within the above range, excellent pot life can be obtained.

The polyurethane elastomer is then obtained by reacting the above prepolymer component with a curing agent (chain extension process).

The curing agent contains halogenated diethyltoluenediamine as an essential component. The use of halogenated diethyltoluenediamine results in a polyurethane elastomer with excellent flex resistance and compression set.

Halogenated diethyltoluenediamines are halides of diethyltoluenediamine. Examples of diethyltoluenediamine include 2,4-diethyltoluenediamine and 2,6-diethyltoluenediamine. These can be used alone or in combination of two or more types.

In other words, halogenated diethyltoluenediamines are compounds in which the hydrogen atom directly bonded to the benzene ring of diethyltoluenediamine has been replaced with a halogen atom. Halogenated diethyltoluenediamines include compounds in which the hydrogen at the 6th position of 2,4-diethyltoluenediamine has been replaced with a halogen atom. Furthermore, halogenated diethyltoluenediamines include compounds in which the hydrogen at the 4th position of 2,6-diethyltoluenediamine has been replaced with a halogen atom.

Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. Halogen atoms can be used alone or in combination of two or more types. Preferred halogen atoms are chlorine and bromine, and more preferably chlorine.

Examples of halogenated diethyltoluenediamines include 4-chloro-3,5-diethyltoluene-2,6-diamine, 6-chloro-3,5-diethyltoluene-2,4-diamine, 4-bromo-3,5-diethyltoluene-2,6-diamine, and 6-bromo-3,5-diethyltoluene-2,4-diamine. These can be used alone or in combination of two or more. Preferred halogenated diethyltoluenediamines include 4-chloro-3,5-diethyltoluene-2,6-diamine and 6-chloro-3,5-diethyltoluene-2,4-diamine, and more preferably, a combination of 4-chloro-3,5-diethyltoluene-2,6-diamine and 6-chloro-3,5-diethyltoluene-2,4-diamine.

The curing agent can optionally contain other polyamines. The other polyamines are polyamine compounds other than halogenated diethyltoluenediamine.

Other polyamines include, for example, aromatic polyamines, araliphatic polyamines, aliphatic polyamines, and alicyclic polyamines.

Aromatic polyamines include, for example, aromatic diamines. Examples of aromatic diamines include 2,4-diethyltoluenediamine, 2,6-diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-diphenylmethanediamine, 3,3'-dichloro-4,4'-diphenylmethanediamine (MOCA), 4,4'-methylenebis(n-sec-butylaniline), 4,4'-methylenebis(2,6-diethylaniline), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, and tetrachloro-4,4'-diaminodiphenylmethane. Commercially available aromatic polyamines are also available. Commercially available products include Ethacure 100 (a mixture of 2,4-diethyltoluenediamine and 2,6-diethyltoluenediamine, manufactured by Albemarle), Ethacure 300 (dimethylthiotoluenediamine, manufactured by Albemarle), Ethacure 420 (4,4'-methylenebis(n-sec-butylaniline), manufactured by Albemarle), LonzaCure M-DEA (4,4'-methylenebis(2,6-diethylaniline), manufactured by Lonza), Curehard MED-J (4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane), and TCDAM (tetrachloro-4,4'-diaminodiphenylmethane, manufactured by Ihara Chemical Co., Ltd.).

Examples of araliphatic polyamines include araliphatic diamines. Examples of araliphatic diamines include 1,3-xylylenediamine and 1,4-xylylenediamine.

Examples of alicyclic polyamines include alicyclic diamines. Examples of alicyclic diamines include 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis-(4-aminocyclohexyl)methane, diaminocyclohexane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminoethyl)cyclohexane, and 1,4-bis(aminoethyl)cyclohexane.

Aliphatic polyamines include, for example, aliphatic diamines. Examples of aliphatic diamines include ethylenediamine, propylenediamine, pentamethylenediamine, hexamethylenediamine, hydrazine, 1,2-diaminoethane, 1,2-diaminopropane, and 1,3-diaminopentane.

The other polyamines can be used alone or in combination of two or more types. The content of the other polyamines can be adjusted as appropriate as long as the excellent effects of the present invention are not impaired. From the viewpoint of pot life, the content of the other polyamines is, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass, relative to the total amount of the curing agent. In other words, the curing agent preferably does not contain any other polyamines.

The curing agent can optionally contain a low-molecular-weight polyol. Examples of low-molecular-weight polyols include those listed above as polyol components. These can be used alone or in combination of two or more types. From the viewpoints of flex resistance and compression set, the content of the low-molecular-weight polyol is, for example, 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass, relative to the total amount of the curing agent. In other words, the curing agent preferably does not contain a low-molecular-weight polyol.

That is, the content of halogenated diethyltoluenediamine relative to the total amount of curing agent is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In other words, the curing agent preferably consists of halogenated diethyltoluenediamine.

The blending ratio of the prepolymer component and the curing agent is adjusted as the equivalent ratio of the active hydrogen groups of the curing agent to the isocyanate groups of the prepolymer component. The active hydrogen groups are hydroxyl groups and/or amino groups, preferably amino groups.

More specifically, for example, the equivalent ratio of the active hydrogen groups (amino groups) of the curing agent to the isocyanate groups in the prepolymer component (active hydrogen groups/isocyanate groups) is, for example, 0.75 or more, preferably 0.9 or more, and for example, 1.3 or less, preferably 1.2 or less.

The reaction between the prepolymer component and the curing agent may be carried out, for example, by bulk polymerization and/or solution polymerization. The reaction temperature is, for example, room temperature or higher, preferably 50°C or higher. The reaction temperature is, for example, 200°C or lower, preferably 150°C or lower. The reaction time is, for example, 5 minutes or longer, preferably 1 hour or longer. The reaction time is, for example, 72 hours or shorter, preferably 48 hours or shorter. When mixing the prepolymer component and the curing agent, a urethane catalyst can be added in an appropriate ratio, if necessary.

This results in a polyurethane elastomer containing the reaction product of the prepolymer component and the curing agent.

Preferably, the mixture of the prepolymer component and curing agent is degassed if necessary, cured in a preheated mold, and then demolded. This results in a polyurethane elastomer molded into the desired shape.

The polyurethane elastomer can also be heat-treated. The heat treatment temperature is, for example, 50°C or higher, preferably 80°C or higher. The heat treatment temperature is, for example, 200°C or lower, preferably 150°C or lower. The heat treatment time is, for example, 30 minutes or longer, preferably 1 hour or longer. The heat treatment time is, for example, 30 hours or shorter, preferably 20 hours or shorter.

The polyurethane elastomer can also be cured. The curing temperature is, for example, 10°C or higher, preferably 20°C or higher. The curing temperature is, for example, 50°C or lower, preferably 40°C or lower. The curing time is, for example, 1 hour or longer, preferably 10 hours or longer. The curing time is, for example, 20 days or shorter, preferably 10 days or shorter.

The polyurethane elastomer may contain known additives in addition to the reaction product of the prepolymer component and the curing agent, as needed. In other words, the polyurethane elastomer may be a polyurethane elastomer composition.

Additives include, for example, antioxidants, heat stabilizers, UV absorbers, light stabilizers, antiblocking agents, release agents, pigments, dyes, lubricants, fillers, hydrolysis inhibitors, rust inhibitors, and bluing agents. The amount and timing of additive addition are determined appropriately depending on the purpose and application.

In the above polyurethane elastomer, the isocyanate-terminated prepolymer contained in the prepolymer component contains a reaction product of a polyisocyanate component and a polyol component containing a polyether polyol. The prepolymer component has an isocyanate group concentration of 6.0% by mass or less. The curing agent contains halogenated diethyltoluenediamine. This polyurethane elastomer has excellent flex resistance and compression set. Furthermore, the above polyurethane elastomer also has excellent mechanical properties.

As a result, polyurethane elastomers can be molded into any shape. These molded products are suitable for use in a variety of industrial fields. There are no particular limitations on the molding method for polyurethane elastomers. Examples of molding methods include thermal compression molding, injection molding, extrusion molding, and melt spinning. Furthermore, the shape of the molded product can be, for example, pellets, plates, fibers, strands, films, sheets, pipes, bottles, hollow shapes, boxes, and buttons.

Applications of molded articles include, but are not limited to, transparent hard plastics, coating materials, pressure-sensitive adhesives, adhesives, waterproofing materials, potting agents, inks, binders, films, sheets, bands, belts, tubes, blades, speakers, sensors, outsoles, threads, fibers, nonwoven fabrics, cosmetics, footwear, insulation materials, sealing materials, tape materials, encapsulants, solar power generation components, robot components, android components, wearable components, clothing, hygiene products, cosmetics, furniture components, food packaging components, sporting goods, leisure goods, medical supplies, nursing care products, housing components, acoustic components, lighting components, vibration-damping components, soundproofing components, daily necessities, miscellaneous goods, cushions, bedding, stress absorption materials, stress relaxation materials, automotive interior materials, automotive exterior materials, railway components, aircraft components, optical components, office equipment components, miscellaneous surface protection materials, semiconductor encapsulants, self-repairing materials, health appliances, eyeglass lenses, toys, packing, cable sheaths, wire harnesses, telecommunications cables, automotive wiring, computer wiring, industrial products, shock absorbers, and semiconductor components.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited by these. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values such as blending ratios (content ratios), physical property values, and parameters used in the following description can be substituted with the corresponding upper limit values (numeric values defined as "equal to or less than") or lower limit values (numeric values defined as "equal to or greater than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the "Description of the Invention" above.

Preparation Example 1 (Preparation of Prepolymers 1 to 7)
The following prepolymers 1 to 7 (commercially available products) were prepared.
Prepolymer 1: Hyprene (registered trademark) L-80 (TDI/polyoxytetramethylene ether glycol prepolymer, NCO=2.9%, manufactured by Mitsui Chemicals)
Prepolymer 2: Hyprene (registered trademark) L-100 (TDI/polyoxytetramethylene ether glycol prepolymer, NCO=4.3%, manufactured by Mitsui Chemicals)
Prepolymer 3: Takenate (registered trademark) L-2760 (TDI/polyoxytetramethylene ether glycol prepolymer, NCO=6.4%, manufactured by Mitsui Chemicals)
Prepolymer 4: Takenate (registered trademark) L-1170 (TDI/polyoxypropylene glycol-based prepolymer, NCO=2.5%, manufactured by Mitsui Chemicals)
Prepolymer 5: Hyprene (registered trademark) U-62 (TDI/polyoxypropylene glycol-based prepolymer, NCO=4.5%, manufactured by Mitsui Chemicals)
Prepolymer 6: Cyanaprene (registered trademark) A-8QM (TDI/polyester polyol-based prepolymer, NCO=3.1%, manufactured by Mitsui Chemicals)
Prepolymer 7: Cyanaprene (registered trademark) D-5QM (TDI/polyester polyol-based prepolymer, NCO=5.0%, manufactured by Mitsui Chemicals)

Examples 1 to 4 and Comparative Examples 1 to 12
The prepolymers listed in Tables 1 to 4 were heated to 80°C. The curing agents listed in Tables 1 to 4 were heated to 120°C. The prepolymer components and the curing agents were mixed in an equivalent ratio (active hydrogen groups/NCO) of 0.95. The mixture was then poured into a mold whose temperature had been adjusted to 110°C and cured in an oven at 110°C for 2 hours to obtain a polyurethane elastomer. The polyurethane elastomer was then demolded from the mold. The polyurethane elastomer was then heat-treated in an oven at 110°C for 16 hours. This resulted in a polyurethane elastomer in the form of a sheet.

The molds used were a sheet-shaped mold with a thickness of 2 mm and a button-shaped mold with a diameter of 29 mm and a thickness of 12 mm.
<Evaluation>
(1) Pot life The time from the start of mixing the prepolymer component and the curing agent until the fluidity was lost was measured.

(2) Flexibility A 2 mm thick sheet of polyurethane elastomer was used. A polyurethane elastomer test piece was prepared in accordance with JIS K 6260 (2010). A 2.5 mm diameter hole was drilled in the test piece. The test piece was then flexed 150,000 times at a speed of 300 times/min using a DeMacha flex tester (manufactured by Ueshima Seisakusho Co., Ltd., model: FT-1503). The number of flexes required until the test piece cracked was then measured.

(3) Hardness A polyurethane elastomer button having a diameter of 29 mm and a thickness of 12 mm was used. The Shore A hardness of the polyurethane elastomer was measured in accordance with JIS K 7312 (1996).

(4) Rebound Resilience A polyurethane elastomer button having a diameter of 29 mm and a thickness of 12 mm was used. The rebound resilience of the polyurethane elastomer was measured in accordance with JIS K 7311 (1995).

(5) Tensile Strength A polyurethane elastomer sheet having a thickness of 2 mm was used. The tensile strength of the polyurethane elastomer was measured in accordance with JIS K 7312 (1996). A No. 3 dumbbell-shaped test piece was used. The tensile speed was 500 mm/min.

(6) Elongation A polyurethane elastomer sheet having a thickness of 2 mm was used. The elongation at break of the polyurethane elastomer was measured in accordance with JIS K 7312 (1996). A No. 3 dumbbell-shaped test piece was used. The tensile speed was 500 mm/min.

(7) Tear Strength: A 2 mm thick sheet of polyurethane elastomer was used. The tear strength of the polyurethane elastomer was measured in accordance with JIS K 7312 (1996). An angle-shaped test piece was used. The tear speed was 500 mm/min.

(8) Compression Set A polyurethane elastomer button having a diameter of 29 mm and a thickness of 12 mm was used. The compression set of the polyurethane elastomer was measured in accordance with JIS K 6262 (2013). The measurement temperature was 70°C, the compression ratio was 25%, and the compression time was 24 hours.

Details of the abbreviations in the table are given below.
MOCA: 3,3'-dichloro-4,4'-diphenylmethanediamine Ethacure 100: a mixture of 2,4-diethyltoluenediamine and 2,6-diethyltoluenediamine, manufactured by Albemarle Ethacure 300: a mixture of 3,5-bis(methylthio)-2,6-toluenediamine and 3,5-bis(methylthio)-2,4-toluenediamine, manufactured by Albemarle P-25: Lonzacure P-25, a mixture of 4-chloro-3,5-diethyltoluene-2,6-diamine and 6-chloro-3,5-diethyltoluene-2,4-diamine, manufactured by Lonza Prepolymer: prepolymer component obtained in preparation example NCO concentration: isocyanate group concentration of the prepolymer component is 6.0 mass%
PTMEG: Polytetramethylene ether glycol PPG: Polyoxypropylene glycol PES: Polyester polyol

<Consideration>
In Example 1 and Comparative Examples 10 to 12, the polyol component contains a polyether polyol, and the isocyanate group concentration of the prepolymer component is 6.0 mass% or less. In such cases, the polyurethane elastomer of Example 1 (curing agent P-25) has superior flex resistance and compression set compared to the polyurethane elastomers of Comparative Examples 10 to 12 (curing agents MOCA, Ethacure 100, and Ethacure 300).

Furthermore, in Example 2 and Comparative Examples 13 to 15, the polyol component contains a polyether polyol, and the isocyanate group concentration of the prepolymer component is 6.0% by mass or less. In such cases, the polyurethane elastomer of Example 2 (curing agent P-25) has superior flex resistance and compression set compared to the polyurethane elastomers of Comparative Examples 13 to 15 (curing agents MOCA, Ethacure 100, and Ethacure 300).

In other words, under the above conditions, if the curing agent contains halogenated diethyltoluenediamine, superior flex resistance and compression set can be obtained compared to when the curing agent does not contain halogenated diethyltoluenediamine.

On the other hand, in Comparative Examples 1 to 4, the polyol component does not contain polyether polyol. In such cases, the flex resistance of the polyurethane elastomer of Comparative Example 1 (curing agent P-25) is comparable to the flex resistance of the polyurethane elastomers of Comparative Examples 2 to 4 (curing agents MOCA, Ethacure 100, and Ethacure 300).

Furthermore, the isocyanate group concentration of the prepolymer component exceeds 6.0% by mass in Comparative Examples 6 to 9. In such cases, the compression set of the polyurethane elastomer of Comparative Example 6 (curing agent P-25) is comparable to the compression set of the polyurethane elastomers of Comparative Examples 7 to 9 (curing agents MOCA, Ethacure 100, and Ethacure 300).

Claims (2)

A polyurethane elastomer comprising a reaction product of a prepolymer component including an isocyanate group-terminated prepolymer and a curing agent,
the isocyanate group-terminated prepolymer comprises a reaction product of a polyisocyanate component and a polyol component including a polyether polyol;
The isocyanate group concentration of the prepolymer component is 6.0% by mass or less,
the curing agent comprises a halogenated diethyltoluenediamine;
The content of the polyether polyol is 50% by mass or more based on the total amount of the polyol components,
A polyurethane elastomer , wherein the content of the halogenated diethyltoluenediamine is 50 mass% or more relative to the total amount of the curing agent . The polyurethane elastomer according to claim 1, wherein the polyether polyol comprises polytetramethylene ether polyol.