JP7739779B2 - Polyurethane foam, and soles and sports shoes using the same - Google Patents

Description

The present invention relates to polyurethane foam suitable for use as a sole material for shoes.

Polyurethane foam is primarily produced by the reaction of isocyanate and polyol, and is widely used in a variety of applications, including cushioning for vehicles and furniture, insulation for buildings, storage tanks, ships, and other applications, structural materials, automotive interior materials such as steering wheels, and integral skin foams such as shoe soles.

Examples of polyols used in polyurethane foams include polytetramethylene glycol, polyester polyols, and polyalkylene oxides.

Polyurethane foams made with polyester polyols contain ester groups, which can lead to poor water resistance due to hydrolysis, and also have a high glass transition temperature (Tg), resulting in poor cold resistance.

Polyalkylene oxides, which are produced by addition polymerization of alkylene oxides such as propylene oxide, are generally liquid and have low viscosity, and polyurethane foams made using such polyalkylene oxides have excellent hydrolysis resistance and cold resistance.

Polyalkylene oxides are industrially produced by addition polymerization of alkylene oxides such as propylene oxide using an alkali metal such as potassium hydroxide as a catalyst. The polyalkylene oxides obtained by this method produce a large amount of monool as a by-product, and polyurethane foams using such polyalkylene oxides have the problem of poor impact resilience due to insufficient networking.

Patent Document 1 discloses a shoe sole made from a polyurethane foam using a polyalkylene oxide with a low monool content, with an unsaturation level reduced to 0.07 meq/g or less. However, the monool content was not sufficiently reduced and the molecular weight distribution was broad, so the product still had the problem of poor rebound resilience.

In addition, polyurethane foams made using polytetramethylene glycol have excellent hydrolysis resistance, cold resistance, and resilience, making them ideal for applications where these properties are required.

Patent Document 2 proposes an integral skin foam using polytetramethylene glycol.

However, polytetramethylene glycol is normally solid at room temperature, and polyol premixes using it tend to become waxy. Therefore, when used to mold polyurethane foam, they are usually heated before use, resulting in poor handling. Furthermore, polyurethane foams using it can exhibit crystallinity, and depending on the conditions of use, such as low temperature to room temperature, can have a high storage modulus and poor flexibility, so improvements have been sought. Furthermore, in certain environments, such as low temperature and high temperature conditions, the ratio (tan δ) of the loss modulus E" to the storage modulus E' can be high, resulting in insufficient rebound resilience, which limits the conditions of use.
Japanese Patent Application Publication No. 3-47202 International Publication No. 2016/167312

The present invention was made in consideration of the above-mentioned background art, and its purpose is to provide a polyurethane foam that has a low storage modulus and tan δ from low to high temperatures, and has excellent flexibility and rebound resilience, as well as soles and shoes made using the same.

As a result of extensive research into resolving the above-mentioned issues, the inventors discovered that the above-mentioned issues could be resolved by using units with a specific structure as the main structure and controlling the storage modulus and tan δ value in a specific temperature range and at room temperature, leading to the completion of the present invention.

That is, the present invention relates to the following polyurethane foam.
[1] A polyurethane foam containing an oxyethylene structure and an oxypropylene structure, wherein the content of unsaturated groups in a polyol fraction calculated by Colish decomposition is less than 0.08% by weight,
A polyurethane foam having a storage modulus of less than 3 x ¹⁰⁶ Pa at a frequency of 10 Hz in the range of 0 to 100°C, and a ratio (tan δ) of loss modulus E" to storage modulus E' of 0.15 or less.
[2] The content of the oxytetramethylene structure is less than 65% by weight,
2. The polyurethane foam according to claim 1, wherein the impact resilience at 25°C measured in accordance with JIS K7312 is 50% or more, and tan δ at a frequency of 10 Hz and 25°C is 0.10 or less.
[3] The polyurethane foam according to [1] or [2], having a core density of 100 to 800 g/L and a resilience at 25°C measured in accordance with JIS K7312 of 60% or more.
[4] The polyurethane foam according to any one of [1] to [3], having an average cell diameter of 50 to 150 μm and a closed cell structure of 50% or more.
[5] A polyurethane that is a reaction product of at least a polyol and a polyisocyanate,
The polyol contains a polyether polyol (A) containing an oxyethylene group and an oxypropylene group,
The degree of unsaturation of the polyether polyol (A) is 0.010 meq/g or less.
[1] - [4] The polyurethane foam according to any one of [1] to [4].
[6] The weight ratio of oxyethylene groups to oxypropylene groups in the polyether polyol (A) is in the range of 1:99 to 49:51, the primary hydroxyl group ratio is 40 to 99%, and the number average molecular weight calculated from the hydroxyl value is in the range of 1,500 to 30,000. [5] Polyurethane foam.
[7] The polyurethane foam according to [5] or [6], wherein the polyisocyanate is a modified isocyanate.
[8] A shoe sole made of the polyurethane foam according to any one of [1] to [7].
[9] A shoe sole including an outsole, an insole, and a midsole, wherein the midsole is a molded product of the polyurethane foam according to any one of [1] to [7].
[10] A sports shoe having a shoe sole including an outsole, an insole, and a midsole, wherein the insole is a molded product of the polyurethane foam according to any one of [1] to [7].
[11] A sports shoe having the shoe sole according to any one of [8] to [10].

The polyurethane foam of the present invention has low hardness and excellent rebound resilience from low to high temperatures.

In addition, soles made with this material are flexible and have excellent cushioning and resilience regardless of environmental conditions such as temperature, and when used in shoes, they not only provide excellent comfort and safety, but also reduce energy loss during running, resulting in excellent fatigue-reducing effects.

The present invention will be described in detail below.
<Polyurethane foam>
The polyurethane foam of one embodiment of the present invention contains an oxyethylene structure and an oxypropylene structure, and is characterized by having a storage modulus of less than 3 x 10 ⁶ Pa and a tan δ of 0.15 or less at any temperature in the range of 0 to 100°C under a frequency condition of 10 Hz.

The raw materials for such polyurethane foam are not particularly limited, but it can be obtained using polyol, polyisocyanate, and a blowing agent, and preferably has the structure and properties described below.

There are no particular limitations on the polyurethane foam, as long as it contains oxypropylene groups and oxyethylene groups and has specific properties. Polyurethane foam can be formed by reacting raw materials such as the above-mentioned polyols and polyisocyanates containing oxypropylene groups and oxyethylene groups in the presence of secondary materials such as the above-mentioned blowing agents, foam stabilizers, viscosity modifiers, and urethane catalysts, as needed.

Therefore, the polyurethane foam may contain secondary materials such as a blowing agent, foam stabilizer, viscosity modifier, and urethane catalyst. It is preferable for the polyurethane foam to contain 85 to 99.9% by weight of a polyurethane component, which is a reaction product of polyol, blowing agent, polyisocyanate, etc., and 0.1 to 15% by weight of the secondary materials. Among these, it is particularly preferable to contain 85 to 99.9% by weight of a polyurethane component, which is a reaction product of polyol, blowing agent, polyisocyanate, etc., 0.01 to 5% by weight of a foam stabilizer component, 0.001 to 15% by weight of a urethane catalyst, and 0.001 to 0.5% by weight of an antioxidant, as this tends to form cells with a good cell shape and exhibit good mechanical properties.

Furthermore, the potassium content in the polyurethane foam tends to form a uniform cell structure and increase the impact resilience, so it is preferable that the potassium content be less than 50 ppm, and more preferably less than 20 ppm.

The above polyurethane foam has an oxyethylene structure and an oxypropylene structure as essential components, but it may be derived from either a polyol or an isocyanate, and is not particularly limited.

By including an oxyethylene structure in addition to an oxypropylene structure, a polyurethane foam is formed in which the polyol components react uniformly. Even if it contains structures that are prone to crystallization, such as an oxytetramethylene structure or an oxyethylene structure, crystallization is easily inhibited, and the storage modulus at low and room temperatures is low, allowing it to exhibit flexibility from low to room temperatures.

The content of oxyethylene structures contained in polyurethane foam is not particularly limited, but is preferably 1 to 40% by weight, more preferably 3 to 30% by weight, and most preferably 5 to 20% by weight.

The content of oxypropylene structures contained in polyurethane foam is not particularly limited, but is preferably 15 to 70% by weight, more preferably 20 to 60% by weight, and most preferably 25 to 55% by weight.

The content of unsaturated groups contained in the polyurethane foam, calculated by Colish decomposition, is less than 0.08% by weight, preferably less than 0.03% by weight, and most preferably in the range of 0.0001 to less than 0.005% by weight.

If the unsaturated group content is 0.08% by weight or more, the tackiness will be too great and the tan δ will be high, making it difficult to use.

Qualitative and quantitative analysis by Corish degradation is a commonly known method for analyzing polyurethane resins. (P. J. Corish, Anal. Chem, 31, (8), 1298 (1959)) This method allows the constituent components of the resin to be determined. Specifically, polyurethane resin is hydrolyzed in an alkaline aqueous solution, and the resulting decomposition product is extracted and separated with an organic solvent to separate it into water-soluble and oil-soluble components. The water-soluble components, acid and glycol, contained in the aqueous solution are then separated by pH adjustment, solvent extraction, etc., allowing for quantitative recovery of the polyester constituents. Meanwhile, the oil-soluble components, polyamine and polyether, contained in the organic solvent, are separated by adsorption, solvent extraction, etc., allowing for qualitative identification of the raw polyisocyanate, and further, the polyether component. The fractions after Corish degradation are analyzed and calculated using standard methods, such as 1H NMR, 13C NMR, HPLC, GPC, and IR.

The contents of oxyethylene structures, oxypropylene structures, oxytetramethylene groups, unsaturated groups, and aromatic structures in these polyurethane foams refer to the contents calculated using the above-mentioned qualitative and quantitative analysis method using Colish degradation.

The content of oxytetramethylene structures in polyurethane foam is not particularly limited, but because this tends to lower the storage modulus of the polyurethane foam at low to room temperatures and make it easier for it to exhibit flexibility at low to room temperatures, it is preferably less than 65% by weight of the polyurethane foam, more preferably in the range of 5 to less than 55% by weight, and most preferably in the range of 10 to less than 45% by weight. A higher content of oxytetramethylene structures in polyurethane foam tends to make it easier for it to exhibit high impact resilience, but it also tends to make it less flexible from low to high temperatures, and too much oxytetramethylene structure can cause crystallization, significantly reducing flexibility at low temperatures.

Since polyurethane foam tends to have high impact resilience, it is preferable for the polyurethane foam to contain an aromatic structure, more preferably one or more of the following: methylenediphenylene structure, 2,4-tolylene structure, 2,5-tolylene structure, and xylylene structure, and most preferably a methylenediphenylene structure. The content of aromatic structures in the polyurethane foam is not particularly limited, but is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, and most preferably 20 to 40% by weight.

The number average molecular weight of polyurethane foam is not particularly limited, but is preferably 30,000 or more, more preferably 50,000 or more, and most preferably 100,000 or more. The number average molecular weight of polyurethane foam refers to the number average molecular weight in terms of polystyrene determined by GPC measurement using dimethylformamide (DMF) as the solvent and polystyrene as the standard substance. If insoluble matter is present, it is the number average molecular weight of the DMF-soluble component (sol fraction).

The gel fraction of polyurethane foam is not particularly limited, but is in the range of 99.5% or less. To facilitate the production of flexible, cushiony polyurethane foam, it is preferably in the range of 0-70%, more preferably 0-40%, and most preferably 0-20%. The gel fraction of the above-mentioned polyurethane foam represents the percentage of insoluble matter that remains undissolved when 0.5 g of polyurethane foam is added to 100 ml of ethyl acetate and allowed to stand for 7 days.

<Method of manufacturing polyurethane foam>
The polyurethane foam can be produced by known methods such as slab foaming, mold foaming, injection foaming, spray foaming, panel foaming, reaction injection molding, etc. Alternatively, the polyurethane foam can be produced by adding a blowing agent to a pre-prepared polyurethane such as TPU and foaming it by heat or a chemical reaction.

In particular, when used for integral skin foams such as soles, mold foaming, slab foaming, and reaction injection molding are preferably used.

Specific examples include a method in which a polyol premix containing ingredients other than polyisocyanate is prepared and then mixed with polyisocyanate to foam, and a method in which some or all of the ingredients are introduced into the mixing head of a separate agitator mixer and foamed. In both methods, polyurethane foam can be produced by injecting the mixed liquid into a mold or onto a conveyor with walls on the top, bottom, left, and right.

The method for producing a sole using the polyurethane foam is not particularly limited, but can be achieved by reacting raw material components or foaming TPU pellets in a mold of a predetermined shape, or by cutting or punching the polyurethane foam into a predetermined shape to produce a polyurethane foam sole. The polyurethane foam can also be produced in the presence of an outsole, shank, upper material, etc., or by directly producing a composite sole made by printing, spinning, etc.

<Properties of polyurethane foam>
The polyurethane foam has low hardness from low to high temperatures and is excellent in resilience.

In addition, soles made from this material are flexible and have excellent cushioning and resilience regardless of environmental conditions such as temperature, and when used in shoes, they provide excellent comfort and safety and reduce energy loss during running, so it is preferable for them to exhibit the following viscoelastic behavior.

The storage modulus E' of the polyurethane foam at a frequency of 10 Hz and at 0 to 100°C is less than 3 x ¹⁰ Pa, preferably in the range of 5 x ¹⁰ Pa to 3 x ¹⁰ Pa, more preferably 7 x ¹⁰ Pa to less than 2.5 x ¹⁰ Pa, and most preferably 1 x ¹⁰ Pa to less than 2 x ¹⁰ Pa.

In particular, the rate of change in storage modulus E' between 0 and 100°C is preferably 65% or less within the above temperature range, more preferably 50% or less, and most preferably in the range of 20 to 45%, as this ensures that flexibility is less susceptible to changes depending on the surrounding environment and provides a high level of safety. The rate of change in storage modulus E' between 0 and 100°C can usually often be expressed as the ratio of storage modulus E' at 100°C to storage modulus E' at 0°C.

If the storage modulus E' at a frequency of 10 Hz and 0 to 100°C exceeds 3 x 10 ⁶ Pa, the urethane foam becomes too hard and has poor flexibility at that temperature, making it unusable, but if the storage modulus E' at a frequency of 10 Hz and 0 to 100°C is less than 3 x 10 ⁶ Pa, the polyurethane foam will exhibit good flexibility even when used in low temperature conditions such as in cold regions or when used on high road surfaces, and will be less dependent on the surrounding environment.When used as a sole, the foam will exhibit good cushioning properties regardless of the surrounding environment, such as when used in low temperature conditions such as in cold regions or when used on high road surfaces, and when used in shoes, the foam will be flexible, comfortable, and cushioned regardless of the surrounding temperature, and will be safe when running.

Furthermore, although not particularly limited, since the film has excellent heat resistance and is easy to handle, such as being resistant to settling during thermal drying, in applications requiring heat resistance, the storage modulus E' at a frequency of 10 Hz and 180°C is preferably 2 x 10 ⁵ Pa or more, more preferably 5 x 10 ⁵ Pa or more, and most preferably in the range of 5 x 10 ⁵ Pa to 1 x 10 ⁶ Pa.

Although not particularly limited, the storage modulus E' of the polyurethane foam at a frequency of 10 Hz and 25°C is preferably less than 2.8 x 10 ⁶ Pa. In particular, the storage modulus E' at a frequency of 10 Hz and 25°C is preferably 5 x 10 ⁵ Pa to 2.8 x 10 ⁶ Pa, more preferably 7 x 10 ⁵ Pa to 1.7 x 10 ⁶ Pa, and most preferably 1 x 10 ⁶ Pa to 1.7 x 10 ⁶ Pa. If the storage modulus E' at a frequency of 10 Hz and 25°C is less than 2.8 x 10 ⁶ Pa, the polyurethane foam tends to have low hardness and good flexibility at room temperature, and when used as a sole, the good flexibility provides excellent cushioning, and when used in sports shoes, the comfort and safety of the shoes are likely to be excellent.

The ratio (tan δ) of the loss modulus E" to the storage modulus E' of the polyurethane foam at a frequency of 10 Hz and 0 to 100°C is 0.15 or less. In particular, a tan δ of 0.02 to 0.15 at a frequency of 10 Hz and 0 to 100°C is preferred, and a range of 0.04 to 0.14 is even more preferred. When the ratio (tan δ) of the loss modulus E" to the storage modulus E' at a frequency of 10 Hz and 0 to 100°C is 0.15 or less, high resilience is exhibited regardless of the environment because little energy is converted into heat, etc., during use regardless of the ambient temperature. When used in soles, the foam exhibits good resilience regardless of the ambient temperature. When used in shoes, energy loss during running is reduced regardless of the environment, resulting in excellent running performance.

Furthermore, although not particularly limited, if the tan δ at a frequency of 10 Hz and 25°C is 0.10 or less, the conversion of energy into heat, etc., when used at room temperature is significantly reduced, resulting in significantly high rebound resilience at room temperature, where use is frequent, and good rebound properties when used in soles. When used in sports shoes, the material significantly reduces energy loss during running at room temperature, where use is frequent, resulting in less fatigue and excellent running performance, and is particularly preferred. Tan δ at 25°C is preferably in the range of 0.02 to 0.10, more preferably 0.03 to 0.09, and most preferably 0.04 to 0.08.

Furthermore, although not particularly limited, it is preferable that tan δ at a frequency of 10 Hz and 100°C be 0.050 or less, and more preferably 0.045 or less, as this can significantly reduce energy loss when used on high-temperature road surfaces.

The glass transition temperature of the polyurethane foam is not particularly limited, but is preferably in the range of -80°C to -30°C. It is even more preferably in the range of -80°C to -50°C. A glass transition temperature in the range of -80°C to -30°C is preferable because flexibility is easily maintained even at low temperatures, and when used as a sole, it tends to provide shoes with high cushioning and safety even in cold climates.

In the present invention, storage modulus E', tan δ, and glass transition temperature refer to values measured using a dynamic viscoelasticity measuring device, Rheogel E-4000, manufactured by UBM, at a measurement temperature of -100°C to 200°C, a heating rate of 3°C/min, a frequency of 10 Hz, a constant strain of 0.04%, and in tensile mode. Test specimens were cut out so that they had a skin layer in the thickness direction. The temperature at which tan δ, which is the ratio of loss modulus E" to storage modulus E', peaks is evaluated as the glass transition temperature, and the value at 25°C refers to the ratio (tan δ) of loss modulus E" to storage modulus E' at 25°C.

<Physical properties of polyurethane foam>
The average cell diameter of polyurethane foam is not particularly limited, and varies depending on the foaming density and application, but is usually in the range of 20 to 200 μm, preferably in the range of 50 to 150 μm, and more preferably in the range of 70 to 130 μm. A diameter within the above range is preferred because it is likely to exhibit good mechanical properties.

The cell structure of the polyurethane foam is not particularly limited, but it is preferable for it to contain 50% or more of a closed cell structure (closed cell ratio), and even more preferably to contain 50-90% of a closed cell structure (closed cell ratio).

The core density of the polyurethane foam is preferably in the range of 100 to 800 g/L, and more preferably in the range of 150 to 500 g/L. If it exceeds 800 g/L, the cost may be high and it may not be practical, while if the core density is less than 100 g/L, the impact resilience and other properties may be poor.

The rebound resilience of the polyurethane foam at 25°C is not particularly limited, but is preferably 50% or higher. In particular, when used in applications requiring high resilience, the rebound resilience at 25°C is preferably 55% or higher, more preferably 60% or higher, and most preferably 63% or higher.

The rebound resilience of the polyurethane foam at 0°C is not particularly limited, but is preferably 40% or higher, and more preferably 45% or higher. In particular, when used in cold climates, the rebound resilience at 0°C is preferably 50% or higher, and more preferably 55% or higher.

Furthermore, the difference between the resilience modulus at 25°C and that at 0°C (change in resilience modulus) is not particularly limited, but is preferably within 10%, and more preferably within 5%.

The hardness of the polyurethane foam at 25°C is not particularly limited, but is preferably in the range of 27 to 55. When used in a midsole, the hardness is preferably in the range of 30 to 55, and more preferably in the range of 35 to 45. When used in an insole, the hardness is preferably in the range of 20 to 45, and more preferably in the range of 25 to 40.

The hardness of polyurethane foam at 0°C is not particularly limited, but is preferably in the range of 30 to 60. When used in midsoles, the hardness is preferably in the range of 35 to 60, and more preferably in the range of 40 to 50. When used in insoles, the hardness is preferably in the range of 30 to 45, and more preferably in the range of 35 to 45.

Furthermore, the difference between the hardness at 25°C and the hardness at 0°C is not particularly limited, but is preferably within 10 on the Asker C hardness scale, and more preferably within 5 on the Asker C hardness scale.

In the present invention, density was measured in accordance with JIS K7222, and hardness (Asker C, surface hardness with skin), tensile strength (No. 3 dumbbell), tensile elongation (No. 3 dumbbell), tear strength (B-type dumbbell), and rebound resilience (Lupke method) were measured in accordance with JIS K7312.

The rebound resilience and hardness at 0°C refer to the values measured within 10 seconds after removing a sample stored in a thermostatic chamber maintained at a temperature of 0±1°C for 24 hours, using the same method as above for room temperature.

<Polyol structure>
The polyol used in the polyurethane foam is not particularly limited, but is a compound having one or more hydroxyl groups per molecule at any position within the molecule, and examples thereof include polyether polyols such as polytetramethylene glycol and polyalkylene oxide, polyester polyols, and polycarbonate diols.

Among these, there are no particular limitations as long as the polyurethane foam contains an oxyethylene structure and an oxypropylene structure. However, since this facilitates the production of the polyurethane foam, it is preferable to include a polyether polyol (A) containing an oxyethylene group and an oxypropylene group as the polyol. In particular, since flexibility at low temperatures is readily apparent, it is preferable to use 10% by weight or more of such polyether polyol (A) in the polyol, more preferably 40% by weight or more of the polyol, and most preferably 55% by weight or more. By including 10% by weight or more of polyether polyol (A) containing oxyethylene groups in addition to oxypropylene groups in the polyol, crystallization in the urethane foam is more likely to be inhibited even when a crystalline polyol is used in combination, and flexibility at low temperatures is likely to be significantly improved, making this preferable.

Although not particularly limited, if there is too much oxytetramethylene structure, crystallization may occur, resulting in poor low-temperature properties and reduced flexibility at low to room temperatures. Therefore, the content of polytetramethylene glycol in the polyol is preferably 70% by weight or less, more preferably 50% by weight or less, and most preferably in the range of 5 to 40% by weight, as this tends to improve the rebound resilience while suppressing a decrease in flexibility. Although not particularly limited, the molecular weight of the polytetramethylene glycol used in combination is preferably in the range of 1,000 to 3,000.

The polyether polyol (A) is preferably an alkylene oxide adduct in which one or more active hydrogen-containing compounds R[-H]m are used and two or more three-membered alkylene oxides having 2 to 12 carbon atoms are added, and is preferably a polyalkylene oxide represented by the following general formula (1):

[In the above general formula (1), R is an m-valent group obtained by removing m active hydrogens from an active hydrogen-containing compound (R[—H] _m ), Z is an alkylene group or cycloalkylene group having 2 to 12 carbon atoms, and A is an alkylene group having 3 carbon atoms. When there are multiple Z or A, they may be the same or different. m is 2 to 100, p is 0 or an integer of 1 to 500, q is an integer of 1 to 1000, and r is an integer of 1 to 500.]
The active hydrogen-containing compound (R[—H] _m ) is not particularly limited as long as it has an active hydrogen group, and examples thereof include bifunctional diols such as water, propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, 1,6-hexanediol, tripropylene glycol, triethylene glycol, polyoxyalkylene diols such as Sannix PP-200, PP-400, PP-600, and PP-1000 manufactured by Sanyo Chemical Industries, Ltd., bisphenols such as bisphenol A, bisphenol F, and bisphenol AD, dihydrides such as catechol, resorcinol, and hydroquinone. Examples of the active hydrogen-containing compound include compounds having two active hydrogen groups such as hydroxybenzenes, amines such as methylamine, ethylamine, propylamine, and butylamine, triols such as glycerin, trimethylolpropane, 1,2,6-hexanetriol, and trifunctional low molecular weight polyols such as Sannix GP-250, GP-400, GP-600, and GP-1000 manufactured by Sanyo Chemical Industries, Ltd., tetraols such as pentaerythritol and diglycerin, hexol, ammonia, ethanolamine, diethanolamine, and triethanolamine, and compounds having three or more active hydrogens. The active hydrogen-containing compound (R[—H] _m ) can be one or a mixture of two or more selected from these.

The alkylene oxide to be added to the active hydrogen-containing compound (R[—H] _m ) is not particularly limited as long as it is a compound having one or more epoxy rings in the molecule, but examples thereof include alkylene oxides having 2 to 12 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, and styrene oxide, and one or more alkylene oxides may be used.

Among these, one or more alkylene oxides including alkylene oxides having 2 to 3 carbon atoms, such as propylene oxide and ethylene oxide, which are easily available industrially, are preferred, and two alkylene oxides, propylene oxide and ethylene oxide, are even more preferred.

In the above general formula (1), ZO preferably has a polyether structure derived from an alkylene oxide having 2 to 12 carbon atoms, such as ethylene oxide, propylene oxide, butylene oxide, or styrene oxide, as this tends to provide good urethane foam moldability. More preferred are polyether structures derived from one or more alkylene oxides selected from ethylene oxide and propylene oxide, and most preferred are polyether structures derived from one type of alkylene oxide selected from ethylene oxide and propylene oxide.

In the above general formula (1), p is 0 or an integer from 1 to 500, preferably p = 0 or an integer from 1 to 100, and more preferably p = 0.

Examples of Z in the above general formula (1) include the structure shown in the following general formula (2):

[In the above general formula (2), R ₂ , R ₃ , R ₄ , and R ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, provided that the total number of carbon atoms of R ₂ to R ₅ does not exceed 10. Any two of R ₂ to R ₅ may be bonded to form a cycloalkyl group.]
Furthermore, AO in the above general formula (1) is preferably a polyether structure derived from an alkylene oxide having 3 carbon atoms, such as propylene oxide, because this tends to provide good flexibility when made into a polyurethane foam.

Examples of A in the above general formula (1) include structures shown in the following formula:

In the above general formula (1), q is an integer from 1 to 1000, preferably an integer from 10 to 500, and more preferably an integer from 15 to 100.

In the above general formula (1), r is 0 or an integer from 1 to 500. Because it is less likely to solidify at low temperatures and is easier to handle, r is preferably 0 or an integer from 1 to 100, and more preferably r is 0 or an integer from 1 to 50.

The relationship between p, q, and r in the above general formula (1) preferably satisfies p+q>r (where p+q is 10-1000, q is 10-1000, and r is 0 or 1-100), as this makes it difficult for polyurethane to crystallize and facilitates flexibility at low temperatures. Even more preferably, p+q>2r (where p+q is 15-300, q is 15-300, and r is 0 or 1-100) satisfies, and most preferably, 10r>p+q>2r (where p+q is 30-150, q is 30-150, and r is 5-50) satisfies.

The weight ratio of oxyethylene groups to oxypropylene groups in polyether polyol (A) is not particularly limited, but is preferably in the range of 1:99 to 49:51, more preferably 5:95 to 35:65, and most preferably 10:90 to 25:75. This weight ratio of oxyethylene groups to oxypropylene groups can be determined from the integral ratio of 1H NMR measured by a conventional method.

The primary hydroxyl group ratio in polyether polyol (A) is not particularly limited, but is preferably in the range of 40 to 99%, more preferably in the range of 60 to 95%, and most preferably in the range of 70 to 90%.

In particular, when 30% by weight or more of a polyol other than polyether polyol (A) is used as the polyol, the primary ratio is preferably in the range of 75 to 90%.

The primary hydroxyl group ratio in polyether polyol A can be calculated from the integral ratio of 1H NMR measured by a conventional method after pre-treating using trifluoroacetic anhydride or the like.

Polyether polyol (A) may be a combination of polyether polyol (A1) and polyether polyol (A2). In this case, a preferred combination is one in which polyether polyol (A1) is a diol with m = 2 and polyether polyol (A2) is a triol or tetraol with m = 3 or 4.

When polyether polyol (A1) and polyether polyol (A2) are used in combination, it is more preferable that both polyether polyol (A1) and polyether polyol (A2) have the above structure, but it is also preferable if the molecular structure of the polyether polyol contained in a greater amount has the above structure.

<Properties of polyol>
The polyol used for the polyurethane foam is not particularly limited, but it is preferable to use polyether polyol A having a significantly low degree of unsaturation, since it is easy to obtain a polyurethane foam having a significantly high impact resilience regardless of temperature conditions. When such a polyether polyol is not used as the polyol, it is preferable to use it as an isocyanate modifier and incorporate it into the urethane.

The degree of unsaturation of polyether polyol (A) is preferably 0.010 meq/g or less, more preferably in the range of 0.0005 to 0.005 meq/g, and most preferably in the range of 0.001 to 0.003 meq/g.

When polyether polyol (A1) and polyether polyol (A2) are used in combination as polyether polyol (A), it is preferable that the degree of unsaturation of each is within the above range, but the polyether polyol contained in the greater amount can be used preferably as long as its degree of unsaturation is within the above range.

When the degree of unsaturation is within the above range, the resulting polyurethane foam will contain significantly fewer dangling chains and low-molecular-weight components derived from unsaturated structures and mono-ol components, making it easier to obtain the high-resilience polyurethane foam of the present invention with a significantly low tan δ. This is preferable because the soles and shoes made therefrom tend to have significantly higher resilience, resulting in sports shoes with less energy loss and less fatigue during use.

In the present invention, the "degree of unsaturation (meq/g)" of a polyol refers to the total amount of unsaturated groups contained per gram of polyol. It refers to a value measured in accordance with the NMR method described in "Collaboration of Polymers, Vol. 50, No. 2, 121-126, 1993," with a scan count of 500 or more being preferred. Values measured in accordance with the method specified in JIS K1557 6.7 may not be accurate due to impurities. The degree of unsaturation of a polyether polyol is an indicator of the amount of monool present in the polyether polyol. An increase in the degree of unsaturation can decrease the average number of functional groups in the polyether polyol. When used as a polyurethane raw material, this can result in a termination reaction, leading to a decrease in the molecular weight of the polyurethane and an increase in uncrosslinked low-molecular-weight components. It can also function as dangling chains in the polyurethane, increasing tan δ and reducing impact resilience.

The number average molecular weight (M) calculated from the hydroxyl value of the polyol used in the polyurethane foam is not particularly limited, but it is preferable to use a polyether polyol (A) whose number average molecular weight (M) calculated from the hydroxyl value is 1,500 to 30,000, more preferably 1,500 to 15,000, and most preferably 2,500 to 7,500.

If the number average molecular weight (M) of the polyether polyol (A) is within the above range, the storage modulus of the resulting polyurethane foam at low temperatures tends to be low, and a polyurethane foam with excellent low-temperature properties is likely to be obtained, which is preferable.
When a combination of polyether polyol (A1) and polyether polyol (A2) is used as the polyether polyol (A), it is preferable that the molecular weights of the respective components are within the above-mentioned ranges. However, the polyether polyol contained in a larger amount can be suitably used as long as its molecular weight is within the above-mentioned range.

In the present invention, the number average molecular weight (M) calculated from the hydroxyl value of the polyol refers to a value calculated using the following mathematical formula (1) based on the hydroxyl value (OHV, unit: mgKOH/g) of the polyol.

Number average molecular weight = (56100/OHV) x number of hydroxyl groups per molecule (1)
Here, "OHV" is a 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, which is the initiator used as a raw material in producing each polyol. When the number of active hydrogen atoms of a commercially available initiator cannot be specified, the nominal functionality is used.

In the present invention, the polyether polyol (A) preferably used as the polyol is a liquid at room temperature and is preferably an amorphous compound. If the polyether polyol is liquid and amorphous at room temperature, it will have excellent moldability, such as being easy to use without heating.

In addition, the glass transition temperature of polyether polyol (A) is preferably -30°C or lower, as this makes it easier to obtain a polyurethane foam that is easy to handle and has a low storage modulus at low temperatures.

The viscosity of the polyether polyol (A) used as the polyol at 25°C is not particularly limited and can be selected appropriately depending on the application, but is preferably in the range of 0.1 to 2000 Pa·s (25°C), and more preferably 0.2 to 200 Pa·s (25°C). If the viscosity of the polyalkylene oxide (A) is in the range of 0.1 to 2000 Pa·s (25°C), molding is easy, and the physical properties of the resulting polyurethane foam tend to be stable.

In this invention, "viscosity" at 25°C refers to the value measured using a cone-plate rotational viscometer in accordance with JIS K1557-5, Section 6.2.3. Specifically, it refers to the viscosity at a shear rate of 0.1 (1/s). However, if the viscosity is outside the measurement range, the shear rate range may be adjusted to fall within the range of 0.01 to 10 (1/s) so that it falls within the measurement range.

The molecular weight distribution of the polyether polyol (A) used as the polyol, as determined by gel permeation chromatography (GPC) using polystyrene as the standard, is preferably 1.039 or less, since this results in uniform crosslinking in the resulting polyurethane foam, which tends to exhibit significantly high impact resilience. It is more preferably in the range of 1.003 to 1.039, even more preferably in the range of 1.005 to 1.029, and most preferably in the range of 1.006 to 1.019.

Furthermore, when a difunctional polyether polyol (A1) and a tri- or higher functional polyether polyol (A2) are used in combination as the polyether polyol (A), it is more preferable that the molecular weight distributions (Mw/Mn) of the polyether polyol (A1) and the polyether polyol (A2), as determined by gel permeation chromatography (GPC) using polystyrene as the standard substance, are each within the above-mentioned range. However, the polyether polyol contained in a larger amount can be suitably used as long as its molecular weight distribution (Mw/Mn) is within the above-mentioned range.
In particular, when a polyether polyol having a molecular weight distribution (Mw/Mn) of more than 1.039 or a polyether polyol having a degree of unsaturation of more than 0.010 meq/g is used as the polyether polyol (A), the molecular weight between crosslinking points in the resulting polyurethane foam will be non-uniform, making it difficult to obtain a flexible, highly resilient polyurethane foam. Therefore, the content of such polyether polyol (A) in the polyol is preferably in the range of less than 30% by weight, more preferably in the range of less than 10% by weight.

The molecular weight distribution (Mw/Mn) determined by gel permeation chromatography (GPC) using polystyrene as the standard substance is preferably measured and analyzed using four separation columns packed with 3 μm particle size packing material connected in series, a resistance tube connected to the reference side, and tetrahydrofuran as the developing solvent. It is the molecular weight distribution (Mw/Mn) calculated using a third-order approximation calibration curve using standard polystyrene.

The method for producing the polyether polyol (A) used as the polyol is not particularly limited, but it is preferable to produce it by ring-opening polymerization of an alkylene oxide in the presence of an active hydrogen-containing compound, a base catalyst, and a Lewis acid at as low a temperature as possible, as this makes it easier to obtain a urethane foam with significantly high impact resilience. It is more preferable to produce it by carrying out the reaction under the above conditions in a catalyst system that reduces impurities that may be the cause of by-products and produces by-products with low boiling points, and it is most preferable to produce it by removing the by-products sufficiently under reduced pressure and then adsorbing them onto a solid, in addition to the above conditions.
<Polyisocyanate>
The polyisocyanate used in the polyurethane foam is not particularly limited, but is a compound having one or more isocyanate groups per molecule at any position within the molecule, and specific examples thereof include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, and 1,6-hexamethylene diisocyanate. , 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, pentamethylene diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, isocyanate-containing prepolymers obtained by reacting these with polyols, and mixtures of two or more of these. Furthermore, modified products of these isocyanates (for example, modified products containing a urethane group, a carbodiimide group, an allophanate group, a urea group, a biuret group, an isocyanurate group, an amide group, an imide group, a uretonimine group, a uretdione group, or an oxazolidone group) and condensates (sometimes referred to as polynuclear compounds) of polymethylene polyphenylene polyisocyanate (polymeric MDI) and the like are also included.

Among these, one or more modified isocyanates selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, and partially carbodiimide-modified isocyanates thereof are preferred, as these tend to result in a lower tan δ at room temperature and higher impact resilience at room temperature. Even more preferred are urethane-modified isocyanates of one or more polyisocyanates selected from the group consisting of 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, and partially carbodiimide-modified isocyanates thereof with polyalkylene oxide and/or polytetramethylene glycol.

Among these, the most preferred are 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, and a urethane-modified product of one or more polyisocyanates selected from the group consisting of these with a polyether polyol having an unsaturation degree of 0.010 meq/g or less and containing oxypropylene groups and/or polytetramethylene glycol with a number average molecular weight of 1500 to 3500, and having an isocyanate group content of 7 to 25% by weight. Even if polyether polyol A containing oxyethylene groups and oxypropylene groups is not used as the polyol, using such a polyether polyol A as an isocyanate modifier is preferred because it makes it easier to obtain the above-mentioned polyurethane foam.

The amount of polyisocyanate used in the polyurethane foam is not particularly limited as long as it does not impair the spirit of the present invention; however, if the amount is too large, the elastic modulus at low temperatures will increase, making it difficult to obtain a polyurethane foam that is flexible regardless of temperature. Therefore, the amount is preferably in the range of 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, and most preferably 30 to 70 parts by weight per 100 parts by weight of polyol.

The addition ratio of the polyisocyanate used in the polyurethane foam is not particularly limited, but is preferably in a range such that the ratio of the total number of NCO groups in the polyisocyanate (B) to the total number of OH groups in the active hydrogen-containing compound including the polyol (referred to as the NCO/OH ratio) is 0.5 to 1.5 (molar ratio), and more preferably 0.6 to 1.1 (molar ratio).
<Blowing Agent>
The blowing agent used as the polyurethane foam raw material is not particularly limited, and known commercially available physical blowing agents and/or chemical blowing agents can be used. Examples of physical blowing agents include low-boiling halogenated hydrocarbons such as chlorofluorocarbons, hydrochlorofluoroolefins, hydrochlorofluorocarbons, hydrofluoroolefins, hydrofluorocarbons, perfluorocarbons, and methylene chloride; hydrocarbons such as acetone, methyl formate, hexane, isopentane, pentane, and cyclopentane; and gases or cryogenic liquids such as air, nitrogen, and carbon dioxide. Examples of chemical blowing agents include those that react with polyurethane raw materials, such as water, organic acids, inorganic acids such as boric acid, alkali carbonates, cyclic carbonates, dialkyl carbonates, and azo compounds, or decompose by heat or the like to generate gas, with water being preferred.

Depending on the type and formulation of catalyst, when water alone is used as the blowing agent, the amount is preferably in the range of 0.1 to 5 parts by weight per 100 parts by weight of polyol, and more preferably in the range of 0.3 to 2.5 parts by weight.

<Additives>
The polyurethane foam may contain additives, which are not particularly limited, but specific examples thereof include foam stabilizers, viscosity modifiers such as viscosity reducers and thickeners, urethane catalysts, fillers, flame retardants, antioxidants, ultraviolet absorbers, light stabilizers, antifungal agents, antibacterial agents, VOC catchers, and mold release agents.
Among these, it is preferable to use a foam stabilizer and a thickener, since these can easily suppress the reduction of the cell diameter of the polyurethane foam and can easily develop high mechanical properties.

The foam stabilizer is not particularly limited, and examples thereof include known surfactants such as organic silicone surfactants, including nonionic surfactants such as organosiloxane-polyoxyalkylene copolymers and silicone-grease copolymers. The amount of foam stabilizer added to the polyurethane foam is preferably in the range of 100 to 50,000 ppm.

The thickener is not particularly limited, and known thickeners and rheology control agents can be used, including fine powder thickeners such as carbon black and finely divided silica, hydrogenated castor oil wax, fatty acid amide wax, and urea-based rheology control agents such as BYK-410, BYK-415, BYK-420, and BYK-430 manufactured by BYK-Chemie.

Viscosity reducers include phthalates such as dibutyl phthalate, diheptyl phthalate, di(2-ethylhexyl) phthalate, dioctyl phthalate, dioctyl adipate, dioctyl sebacate, dibutyl sebacate, isodecyl succinate, tricresyl phosphate, tributyl phosphate, epoxidized soybean oil, and benzyl epoxy stearate; non-aromatic dibasic acid esters; aliphatic esters; esters of polyalkylene glycols; trimellitic acid esters; chlorinated paraffins; hydrocarbon oils; process oils; polyethers; epoxy plasticizers; and polyester plasticizers. The amount of viscosity reducer used is not particularly limited, but it is preferably less than 25% by weight of the polyurethane foam.

The filler is not particularly limited, and any filler can be selected and used, such as inorganic fillers, organic fillers, fibrous fillers, etc.

Specific examples include silica such as fumed silica, precipitated silica, crystalline silica, fused silica, dolomite, silicic anhydride, and hydrous silicic acid; calcium carbonate such as fatty acid-treated calcium carbonate, heavy calcium carbonate, and colloidal calcium carbonate; pigments such as carbon black, magnesium carbonate, magnesium hydroxide, iron oxide, zinc oxide, diatomaceous earth, calcined clay, clay, talc, titanium oxide, barium sulfate, kaolin, zeolite, bentonite, organic bentonite, aluminum, and flint powder; shirasu balloons, glass microballoons, synthetic resin powders such as phenolic resin, vinylidene chloride resin, polyvinyl chloride, polymethyl methacrylate, and polystyrene; asbestos, glass fiber, and glass filament. These fillers can be used alone or in combination, and may be surface-treated with an appropriate surface treatment agent. The filler content is not particularly limited, but it is preferably less than 25% by weight of the polyurethane foam.

The antioxidant is not particularly limited, and examples include compounds that are effective in inhibiting the oxidation of polymer chains, such as thioether-based compounds, phosphorus-based antioxidants, and hindered phenol-based compounds. Examples of such antioxidants include Irganox manufactured by Ciba Corporation and Adeka Stab manufactured by Adeka Corporation.

Among these, hindered phenol-based antioxidants are preferred, and because they are more likely to provide antioxidant properties to urethane, it is particularly preferred to use one or more antioxidants selected from 2,6-di-t-butyl-4-methylphenol (BHT) and IRGANOX-1010, IRGANOX-1024, IRGANOX-1035, IRGANOX-1076, and IRGANOX-1081 manufactured by Ciba Japan.

Light stabilizers are not particularly limited, but examples include compounds that have the effect of imparting light resistance and weather resistance, such as benzotriazole-based compounds, triazine-based light stabilizers, benzophenone-based light stabilizers, ultraviolet absorbers such as benzoate-based compounds, and hindered amine-based light stabilizers, and examples of trade names include Tinuvin manufactured by Ciba Japan.

Of these, it is preferable to use one or more light stabilizers selected from Tinuvin 234, Tinuvin 144, Tinuvin C353, and Tinuvin B75. These antioxidants and light stabilizers can also be used in combination.

Urethanization catalysts include, for example, organic lead compounds, organic tin compounds, bismuth compounds such as bismuth octoate, tertiary amines, and quaternary ammonium salts, with one or more catalysts selected from organic tin compounds and tertiary amine catalysts being preferred.

Examples of tertiary amines include triethylenediamine, dimethylcyclohexylamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, N,N,N',N",N"',N"'-hexamethyltriethylenetetramine, bis(dimethylaminoethyl)ether, 1,3,5-tris(N,N-dimethylaminopropyl)hexahydro-S-triazine, N-dimethylaminoethyl-N'-methylpiperazine, N,N,N',N'-tetramethylhexamethylenediamine, 1,2-dimethylimidazole, and N,N-dimethyl Examples include amine compounds such as aminopropylamine and bis(dimethylaminopropyl)amine, and alkanolamines such as N,N-dimethylaminoethanol, N,N,N'-trimethylaminoethylethanolamine, 2-(2-dimethylaminoethoxy)ethanol, N,N,N'-trimethyl-N'-hydroxyethyl bisaminoethyl ether, N-(3-dimethylaminopropyl)-N,N-diisopropanolamine, N-(2-hydroxyethyl)-N'-methylpiperazine, N,N-dimethylaminohexanol, and 5-dimethylamino-3-methyl-1-pentanol.

Examples of organotin compounds include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, and tin 2-ethylhexanoate.
If the amount of these urethanization catalysts added is too small, foaming delay may occur, resulting in reduced productivity, while if it is too large, foaming may become non-uniform, resulting in unstable foam properties. Therefore, the amount of tertiary amines added to the polyurethane foam is preferably in the range of 0.01 to 15% by weight, and the amount of organotin compounds added is preferably in the range of 0.05 to 1% by weight.
<Applications of polyurethane foam>
The polyurethane foam according to one embodiment of the present invention can be used in a variety of applications for which flexible polyurethane foams, semi-rigid polyurethane foams, and rigid polyurethane foams are generally used.

Applications include, but are not limited to, insulation and structural materials in construction and civil engineering; insulation for freezers, refrigerators, and freezer showcases in electrical equipment; insulation for LPG and LNG tankers and pipelines in plants and ships; insulation for refrigerator cabinets and refrigerated trucks in vehicles, and instrument panels. Applications requiring cushioning and rebound resilience include bedding, bicycle saddles, motorcycle seats, automobile seats, cushioning, sound-absorbing materials, vibration-damping materials, flooring, sports surfaces, racing tracks, floor coverings, and balls; steering wheels, headrests, gear lever knobs, armrests, helmet interiors, cushioning parts for protectors, vehicle cushioning; shoe materials for high heels, geta sandals, and multi-purpose shoes; and soles, shanks, and other shoe materials for sports shoes such as tennis shoes, basketball shoes, running shoes, walking shoes, and sports sandals.

In particular, it has high flexibility and resilience from low to room temperature and high temperatures, and its physical properties are resistant to changes in the environment. This makes it ideal for use in shoe soles such as midsoles and insoles, and for sports shoes such as basketball shoes, running shoes, walking shoes, and sports sandals.

Shoe soles made from the above-mentioned polyurethane foam include, but are not limited to, sole-shaped urethane foam obtained by foaming in a mold of a predetermined shape, or by cutting or punching polyurethane foam into a predetermined shape, as well as sole-shaped urethane foam composited with fabric, printing, or other cushioning materials such as EVA, and composites with outsole materials such as rubber, shanks, and upper materials. These have high flexibility and resilience from low to high temperatures, and offer excellent cushioning, making them ideal for use as components of shoes.

Sports shoes that are one embodiment of the present invention are not particularly limited, and examples include sports shoes constructed entirely or in part from the polyurethane foam described above.

Preferably, these include sports shoes that are comprised of at least an outsole, an insole, and a midsole, with the midsole made of a molded polyurethane foam, and sports shoes that are comprised of at least an outsole, an insole, and a midsole, with the insole made of a molded polyurethane foam, and preferably also contain an upper material, a shank, a heel counter, shoelaces, gel cushioning material, and adhesive components such as urethane adhesive as necessary.

More preferably, the sports shoes have a midsole bonded to the outsole with an adhesive or by spinning, an insole constructed on top of that, a shank in the center of the outsole, the midsole and upper material bonded to the outsole with an adhesive or by spinning, and the upper material and heel counter are constructed, and it is preferable that the insole and/or midsole contain the above-mentioned polyurethane foam.

In particular, it is preferable that the sports shoes have any of the above configurations, contain 50% by weight or more of the polyurethane foam in the insole and/or midsole, and that 20% by weight or more of the weight of the sports shoes be made up of the polyurethane foam.

It is preferable that the outsole material used in the above sports shoes is rubber, and the shank and adhesive are made of urethane.

The present invention will be explained in more detail below using examples, but the present invention should not be construed as being limited to the following examples as long as the gist of the invention is not exceeded. The raw materials and evaluation methods used in the following examples and comparative examples are as follows.
(raw materials)
<Polyol>
The properties of the polyols used in the examples and comparative examples are shown in Table 1.

Polyols (A1) to (A3): A bifunctional polyalkylene oxide obtained by thoroughly dehydrating and removing solvent using an imino group-containing phosphazenium salt (IPZ) catalyst in combination with triisopropoxyaluminum, followed by block copolymerization of sufficiently dehydrated propylene oxide and ethylene oxide with bifunctional polyoxypropylene glycol having a molecular weight of 200, followed by removal of the catalyst using standard methods, and incorporating the antioxidant BHT.

Polyol (A4): Commercially available polytetramethylene glycol (PTMG-1000 manufactured by Mitsubishi Chemical Corporation).

Polyol (A5): Commercially available polytetramethylene glycol (PTMG-3000 manufactured by Mitsubishi Chemical Corporation).

Polyol (A6): A polyalkylene oxide produced by adding propylene oxide and ethylene oxide using a potassium hydroxide catalyst in a conventional manner.

Polyol (A7): A bifunctional polyalkylene oxide obtained by thoroughly dehydrating and removing solvents using an imino group-containing phosphazenium salt (IPZ) catalyst in combination with triisopropoxyaluminum, polymerizing only sufficiently dehydrated propylene oxide into a bifunctional polyoxypropylene glycol with a molecular weight of 200, removing the catalyst using standard methods, and incorporating the antioxidant BHT.

The above polyols were heated and vacuum dehydrated before use. For non-commercially available products, the catalyst was removed using standard methods before use.

Polyol (A1) had a significantly lower degree of unsaturation and a narrower molecular weight distribution than polyol (A6). Polyols (A2) and (A3) had a lower degree of unsaturation and a narrower molecular weight distribution.

<Polyisocyanate>
Polyisocyanate (C1): A modified isocyanate obtained by adding 20% by weight of PTMG to a partially carbodiimide-modified isocyanate of 4,4'-diphenylmethane diisocyanate (manufactured by Tosoh Corporation, trade name Millionate MTL).

Polyisocyanate (C2): 4,4'-diphenylmethane diisocyanate (4,4'-MDI, manufactured by Tosoh Corporation, trade name Millionate MT)
These were used as is without purification.

<Additives>
Urethane catalyst: 1-isobutyl-2-methylimidazole (manufactured by Evonik, trade name DABCO NCIM)
1,4-BD: 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd.)
Si foam stabilizer: commercially available silicone foam stabilizer (manufactured by Toray Dow Corning Co., Ltd., product name SRX-280A)
The above commercially available product was used as is. Ion-exchanged water was used as the foaming agent.
(Polyol Evaluation Method)
<Hydroxyl value, molecular weight>
The hydroxyl value (OHV) of the polyol was measured according to the method of JIS-K1557-1. The number average molecular weight of the polyol was calculated using the above mathematical formula (1) based on the hydroxyl value of the polyol.

<Unsaturation degree>
Measurement was carried out using a nuclear magnetic resonance (NMR) spectrometer according to the method described in Polymer Research Papers 1993, 50, 2, 121-126, and confirmation was carried out according to the method of JIS K1557 6.7.

<Molecular weight distribution (Mw/Mn)>
10 mg of polyol and 10 ml of THF were added to a sample bottle, dissolved by leaving it to stand overnight, and filtered through a PTFE cartridge filter (0.5 μm) to obtain a sample. The detector was an RI detector RI8020, and the measurement column was a separation column packed with a particle size of 3 μm. Two Tskgel Super H4000 columns and two Tskgel Super H3000 columns (manufactured by Tosoh) were connected in series. Five resistance tubes were connected to the reference side. Wako Co., Ltd. special grade tetrahydrofuran containing BHT stabilizer was used as the developing solvent. The separation column flow rate was 0.6 ml / min, the reference side flow rate was 0.15 ml / min, and the column temperature was 40 ° C. Analysis was performed under these conditions. A cubic approximation curve using eight standard polystyrenes manufactured by Tosoh Corporation with known molecular weights was used as a calibration curve, and the molecular weight distribution (Mw / Mn) was analyzed. The measurement device used was a Tosoh HLC-8320GPC, and the analysis was performed using a Tosoh HLC-8320GPC-ECOSEC-WorkStation.

<EO content (wt%)>
H NMR was measured using a nuclear magnetic resonance (NMR) spectrometer and tetramethylsilane-containing deuterated chloroform as a deuterated solvent. The ethylene oxide content in the polyol was calculated from the integral values in the range of 0.8 to 1.5 ppm (propylene oxide chain) and the integral values in the range of 3.2 to 3.9 ppm (propylene oxide chain and ethylene oxide chain).

<Primary OH group ratio>
Using a nuclear magnetic resonance (NMR) spectrometer, 1H NMR of the sample treated with trifluoroacetic anhydride was measured using tetramethylsilane-containing deuterated chloroform as a deuterated solvent. The ratio of primary OH groups in the polyol was calculated from the integral value around 4.3 ppm (methylene bonded with esters derived from primary OH groups) and the integral value around 5.2 ppm (methine bonded with esters derived from secondary OH groups) of the sample treated with trifluoroacetic anhydride.
(Evaluation of polyurethane foam properties)
<Dynamic viscoelasticity>
The storage modulus E', tan δ, and glass transition temperature were measured using a dynamic viscoelasticity measuring device, Rheogel E-4000, manufactured by UBM, under conditions of a measurement temperature of -100°C to 200°C, a heating rate of 3°C/min, a frequency of 10 Hz, a constant strain of 0.04%, and tensile mode, and test specimens were used that were cut out so that a skin layer was present in the thickness direction. The temperature at which tan δ, which is the ratio of the loss modulus E" to the storage modulus E', peaks was evaluated as the glass transition temperature, and the value at each temperature, for example 25°C, was evaluated as the ratio (tan δ) of the loss modulus E" to the storage modulus E' at 25°C.

If the storage modulus is less than 3×10 ⁶ Pa at any temperature in the range of 0° C. to 100° C., the flexibility is high in the low to high temperature range of use, and the cushioning properties are remarkably good, and it was judged as ○ (pass).

In particular, if the rate of change in storage modulus E' between 0 and 100°C is 65% or less, it is deemed to be acceptable, as flexibility is unlikely to change depending on the surrounding environment and safety is high. The rate of change in storage modulus within the above range was determined by the value (maximum value - minimum value) / maximum value x 100.

If the storage modulus at 25° C. is less than 2.8×10 ⁶ Pa, the flexibility is particularly high at room temperature where use is frequent, and the cushioning properties are remarkably good, and therefore the product is judged to be acceptable.

Furthermore, if the storage modulus E' at 180°C is 2 x 10 ⁵ Pa or more, heat resistance during drying etc. can be expected and the sample was judged to be acceptable (◯).

If tanδ is 0.15 or less at any temperature between 0°C and 100°C, it is considered to pass, as it is expected to have little energy loss and high rebound resilience across a range of operating temperatures from low to high. If tanδ exceeds 0.15, it is considered to fail, as it will have large energy loss depending on the operating environment and will be difficult to use across a wide range of temperatures.

Furthermore, if tan δ at 25 is 0.10 or less, it is deemed to pass, as it is expected to have significantly less energy loss and high rebound resilience at room temperature, where it is most frequently used. However, if it exceeds 0.10, it will not exhibit any outstanding characteristics, particularly at room temperature, where it is most frequently used, making it difficult to use, and it is therefore deemed to fail.

<Foam Cell>
The cell shape of the foam cells was observed under an optical microscope, and the average cell diameter was calculated. The closed cell ratio was calculated from the ratio of the apparent volume of a 5 mm thick strip of foam measured using an AsOne NTK-01 digital volume meter to the measured value.

<Urethane composition>
The polyurethane foam was subjected to alkaline decomposition, and the composition of the urethane component was calculated by analyzing each fraction. The unsaturated group content, oxypropylene structure, oxyethylene structure, and oxytetramethylene structure were calculated from the integral ratio of 1H NMR and 13C NMR.

Additives were also extracted from the polyurethane foam using DMF, and the content of each component and the GPC molecular weight of the polyurethane foam were determined.

The gel fraction of the urethane foam was determined by adding 0.5 g of urethane foam to 100 ml of ethyl acetate, leaving the mixture standing for 7 days, and determining the proportion (%) of insoluble matter remaining undissolved.
(Evaluation of physical properties of polyurethane foam)
In the present invention, density was measured in accordance with JIS K7222, and hardness (Asker C, surface hardness with skin), tensile strength (No. 3 dumbbell), tensile elongation (No. 3 dumbbell), tear strength (B-type dumbbell), and rebound elasticity (Lupke method) were measured in accordance with JIS K7312.

The impact resilience and hardness at 0°C refer to values measured within 10 seconds after removing a sample stored in a thermostatic chamber whose temperature is adjusted to 0±1°C for 24 hours, using the same method as for room temperature.
(Production of polyurethane foam)
The raw material compositions of the foams produced in the Examples and Comparative Examples are shown in Table 3, the storage moduli E' and tan δ of the resulting foams at various temperatures are shown in Table 4, and the physical properties of the foams are shown in Table 5.

Table 5 shows the calculated values calculated from the raw material costs of the urethane component and auxiliary material components in the resulting polyurethane foam.

Example 1
A polyol premix was prepared by uniformly mixing the components excluding the isocyanate in a tabletop disper in the proportions shown in Table 2. The isocyanate component and the polyol premix, which had been adjusted to 45°C, were mixed and stirred in a tabletop mixer at a rotation speed of 7,000 rpm.

The mixture was heated to 60°C, a release agent was applied, and then the mixture was poured into a dry 300mm x 300mm x 5mm metal mold, which was then covered and allowed to cure for 7 minutes. After curing, the mold was removed and a urethane foam test piece (hereinafter referred to as TP) was obtained. The urethane structure, urethane properties, and physical properties of the resulting TP were evaluated.

The resulting polyurethane foam had a low storage modulus in the range of 0°C to 100°C, and good cushioning properties over a wide temperature range. However, because tan δ was low and energy loss was small over a wide temperature range, high rebound resilience could be expected over a wide temperature range. Furthermore, because tan δ was significantly low at 25°C, energy loss was characteristically small at room temperature, where usage is frequent. Furthermore, the storage modulus was high at 180°C, and heat resistance was high.

The urethane foam's resilience was over 60% at both 0°C and 25°C, demonstrating significantly high resilience at both low and room temperatures. Furthermore, the Asker C hardness was below 50 at both 0°C and 25°C, demonstrating low hardness at both low and room temperatures, and the change in hardness was minimal.

The polyurethane foam of this example had a molecular weight of over 50,000, a gel fraction of less than 40%, and contained oxyethylene and oxypropylene structures in the urethane component, with significantly less unsaturated structures.

Example 2
Using the same method as in Example 1, urethane foam test pieces (hereinafter referred to as TP) were prepared with the formulation shown in Table 2, and the urethane structure, urethane properties, and physical properties were evaluated.

The resulting polyurethane foam had a tan δ of 0.10 at 25°C, which was higher than in Examples 1 and 3-8. However, in addition to having a lower tan δ than the foam of Comparative Example 3, the foam also had a significantly lower storage modulus and significantly better flexibility, making it suitable for applications where flexibility is particularly required in addition to rebound resilience.

Although the storage modulus is low in the range of 0°C to 100°C, providing good cushioning over a wide temperature range, the low tan δ and small energy loss over a wide temperature range means that high rebound resilience can be expected over a wide temperature range. Furthermore, because the tan δ at 25°C is low, energy loss is characteristically small at room temperature, where use is frequent. Furthermore, the storage modulus is high at 180°C, providing high heat resistance.

The urethane foam's impact resilience was over 50% at both 0°C and 25°C, demonstrating high impact resilience at both low and room temperatures. Furthermore, the Asker C hardness was 36 or less at both 0°C and 25°C, demonstrating significantly low hardness at both low and room temperatures, and the change in hardness was significantly small.

The polyurethane foam of this example had a molecular weight of over 50,000, a gel fraction of less than 40%, and contained oxyethylene and oxypropylene structures in the urethane component, with significantly less unsaturated structures.

Examples 3 to 9
Using the same method as in Example 1, urethane foam test pieces (hereinafter referred to as TP) were prepared with the formulation shown in Table 2, and the urethane structure, urethane properties, and physical properties were evaluated.

The resulting polyurethane foam had a low storage modulus in the range of 0°C to 100°C, and good cushioning properties over a wide temperature range. However, because tan δ was low and energy loss was small over a wide temperature range, high rebound resilience could be expected over a wide temperature range. Furthermore, because tan δ was significantly low at 25°C, energy loss was characteristically small at room temperature, where usage is frequent. Furthermore, the storage modulus was high at 180°C, and heat resistance was high.

The urethane foam's impact resilience was over 50% at both 0°C and 25°C, demonstrating high impact resilience at both low and room temperatures. Furthermore, the Asker C hardness was below 50 at both 0°C and 25°C, demonstrating low hardness at both low and room temperatures, and the change in hardness was small.

All of the polyurethane foams obtained in Examples 1 to 9 had a uniform cell structure, an average cell diameter of 50 to 130 μm, and a closed-cell structure of 50 to 90%. All of the polyurethane foams obtained in Examples 1 to 9 also had a potassium content of less than 50 ppm.

Comparative Example 1
Polyurethane elastomer (TPU) pellets prepared in advance according to the formulation shown in Table 2 were foamed in a heated mold with a physical foaming agent to prepare polyurethane foam test pieces.

The polyurethane foam obtained had a high tan δ of 0.19 at 0°C and a high storage modulus of 3.3 x 10 ⁶ Pa, making it difficult to use at low temperatures and lacking wide temperature characteristics.

Furthermore, the storage modulus at 180°C was significantly low, and the heat resistance was poor.

The urethane foam of this comparative example does not contain oxyethylene or oxypropylene structures in the urethane component, and is rich in polyoxytetramethylene structures, resulting in a high storage modulus and poor flexibility at low to room temperatures. Its Asker C hardness exceeded 50 at both 0°C and 25°C, and its hardness also varied significantly, making it difficult to use depending on the environment. It also had a large change in rebound resilience, making its properties susceptible to change depending on the usage environment. Furthermore, the polyurethane foam had a low molecular weight and an uneven, fine cell structure, meaning its mechanical properties were not as promising. The foam's closed cell ratio also exceeded 90%.

Comparative Example 2
Test pieces of urethane foam were prepared using the formulation shown in Table 2 in the same manner as in Example 1, and the urethane structure, urethane properties, and physical properties were evaluated.

The resulting polyurethane foam had a good tan δ at 0°C and 25°C, but did not contain an oxyethylene structure or an oxypropylene structure in the urethane component, and had a significantly high storage modulus at low temperatures, presumably due to crystallization of the polyoxytetramethylene moiety. As a result, the foam became hard at low temperatures, and cushioning properties could not be expected, making it difficult to use.
In addition, the rate of change in storage modulus between 0°C and 25°C was high, and the film did not have wide temperature characteristics.

The urethane foam had good impact resilience at 0°C and 25°C, but its Asker C hardness exceeded 50 in both cases, meaning it had poor flexibility from low to room temperature and its hardness changed significantly, making it difficult to use depending on the environment. The foam's closed cell ratio also exceeded 90%.

Comparative Example 3
Using the same method as in Example 1, test pieces of urethane foam containing a large amount of unsaturated structures were prepared using a formulation containing a polyether polyol with a large amount of unsaturated groups as shown in Table 2, and the urethane structure, urethane properties, and physical properties were evaluated.

The polyurethane foam of this comparative example contains oxyethylene and oxypropylene structures in the urethane component, but the resulting polyurethane foam had a high tan δ value at 25°C, a tacky feel, and an insufficient rebound resilience of less than 50%, making it difficult to use.

The polyurethane foam in this comparative example contained many unsaturated structures and had a low molecular weight. Because the cells were tiny, less than 50 μm in size, the foam did not offer the expected mechanical properties.

Comparative Example 4
Using the same method as in Example 1, test pieces of urethane foam not containing an oxyethylene structure were prepared using the formulation of polyether polyol not having an oxyethylene group and polytetramethylene glycol shown in Table 2, and the urethane structure, urethane properties, and physical properties were evaluated.

The polyurethane foam of this comparative example had a non-uniform, elongated cell structure, a low molecular weight of less than 50,000 for the soluble components, a highly open urethane foam with a closed cell ratio of less than 50%, and was brittle and dented when pressed with a finger.

The resulting polyurethane foam had a high tan δ value at 25°C and a high storage modulus of 5.5 x 10 ⁶ Pa at 0°C, making it difficult to use at low temperatures and lacking wide temperature characteristics. Furthermore, the urethane had tacky properties and was brittle, resulting in a significantly low impact resilience of 25, making the foam difficult to use.

Comparative Example 5
Commercially available EVA pellets were foamed in a heated mold with a physical foaming agent to prepare EVA foam test pieces.

The EVA foam in this comparative example had a significantly high storage modulus at low to room temperatures, meaning that cushioning properties could not be expected within the operating temperature range. It also had a high tan δ of 0.19 at 25°C, resulting in a foam with significant energy loss.

Furthermore, the storage modulus at 180°C was significantly low, and the heat resistance was poor.

The EVA foam had low impact resilience at 0°C and 25°C, and its Asker C hardness exceeded 50 at both temperatures. It also had poor flexibility from low to room temperature and showed large hardness changes, making it difficult to use depending on the environment.

Claims (12)

Contains an oxyethylene structure and an oxypropylene structure derived from a bifunctional polyether polyol , and an oxytetramethylene structure derived from a polytetramethylene glycol ,
The content of the oxytetramethylene structure is in the range of 5 to 45% by weight,
the content of unsaturated groups in the polyol fraction calculated by Colish decomposition is less than 0.08% by weight in the polyurethane foam;
A polyurethane foam having a storage modulus of less than 3 x 10 ⁶ Pa and a ratio (tan δ) of loss modulus E" to storage modulus E' of 0.15 or less at a frequency of 10 Hz in the range of 0 to 100°C. The content of the oxypropylene structure is in the range of 20 to 60% by weight,
2. The polyurethane foam according to claim 1, wherein the content of the oxyethylene structure is in the range of 5 to 20% by weight . 3. The polyurethane foam according to claim 1 , which has a rebound resilience of 50% or more at 25°C, measured in accordance with JIS K7312, and a tan δ of 0.10 or less at a frequency of 10 Hz and 25°C. 4. The polyurethane foam according to claim 1, wherein the core density is 100 to 800 g/L and the impact resilience at 25° C. measured in accordance with JIS K7312 is 60% or more. 5. The polyurethane foam according to claim 1 , having an average cell diameter of 50 to 150 μm and a closed cell structure of 50% or more. A polyurethane that is a reaction product of at least a polyol and a polyisocyanate,
The polyol contains a polyether polyol (A) containing an oxyethylene group and an oxypropylene group,
6. The polyurethane foam according to claim 1 , wherein the polyether polyol (A) is a bifunctional polyether polyol, which is an adduct of propylene oxide and ethylene oxide to a bifunctional polyoxypropylene glycol, and has an unsaturation degree of 0.010 meq/g or less. 7. The polyurethane foam according to claim 6, wherein the weight ratio of oxyethylene groups to oxypropylene groups in the polyether polyol ( A ) is in the range of 1:99 to 49:51, the ratio of primary hydroxyl groups is 40 to 99%, and the number average molecular weight calculated from the hydroxyl value is in the range of 1,500 to 15,000. 8. The polyurethane foam according to claim 6, wherein the polyisocyanate is a modified isocyanate. A shoe sole made of the polyurethane foam according to any one of claims 1 to 8 . A shoe sole comprising an outsole, an insole and a midsole, wherein the midsole is a molded product of the polyurethane foam according to any one of claims 1 to 8 . A shoe sole comprising an outsole, an insole and a midsole, wherein the insole is a molded product of the polyurethane foam according to any one of claims 1 to 8 . A sports shoe comprising the shoe sole according to any one of claims 9 to 11 .