Polyurethane foam and shoe insole

Abstract

This polyurethane foam has rebound resilience of 40% or more, elongation of 200% or more, a residual compressive strain of 20% or less, and density of 150 kg / m3 or more and 800 kg / m3 or less. Such polyurethane foam is obtained by reacting a raw material mixture including a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foaming gas, and foaming same. The polyol component preferably includes polyether polyol A having three to four functional groups and a weight average molecular weight of 3500-13000. The chain extender preferably includes a diol having a molecular weight of 200 or less. The polyisocyanate component preferably includes a bifunctional isocyanate.

Description

Polyurethane foam and shoe insoles

[0001] The present invention relates to a polyurethane foam and a shoe insole, and more particularly to a polyurethane foam having high impact resilience and excellent flexibility, and a shoe insole using the same.

[0002] Polyurethane refers to a polymeric compound having a urethane bond (-NH-C(O)O-). Polyurethane is generally obtained by reacting the hydroxyl group (-OH) of a polyol with the isocyanate group (-NCO) of a polyisocyanate. It is known that polyurethane exhibits a variety of properties by optimizing the type of polyol and / or polyisocyanate. For this reason, polyurethane is used in various automobile parts, synthetic leather, paints, adhesives, etc. Furthermore, polyurethane foam, which is made by foaming polyurethane, is used in insulation materials, cushioning materials, etc.

[0003] Polyurethane foam with enhanced resilience is also known as "high-resilience polyurethane foam." High-resilience polyurethane foam has strong resilience and is resistant to settling, making it suitable for use in apparel, sporting goods, toys, bedding, interior decor, and more.

[0004] Various proposals have been made regarding such high-resilience polyurethane foams. For example, Patent Document 1 discloses a foamed polyurethane elastomer obtained by foaming and curing a raw material mixture containing: (a) 85 parts of polytetramethylene ether glycol having an average functionality of 2 and a number-average molecular weight of 2,000; (b) 10 parts of polyoxypropylene polyol having an average functionality of 3 and a number-average molecular weight of 3,000; (c) 5 parts of 1,4-butanediol; (d) 1 part of a silicone foam stabilizer; (e) 0.31 parts of water; (f) 0.8 parts of an ultraviolet absorber; (g) 0.005 parts of dioctyltin dilaurate; and (h) 103.8 parts of an isocyanate-terminated prepolymer obtained by reacting 40 parts of MDI with 66.1 parts of polytetramethylene ether glycol having a molecular weight of 2,000, using a combination of mechanical foaming and water foaming.

[0005] The document states that by this method, (A) the pad density is 0.425 g / cm 3 (425 kg / m 3 ), (B) the strength at break (TB) is 1.3 MPa, (C) the elongation at break (EB) is 240%, (D) the compression set (50% compression, 70°C x 22h) is 2.7%, and (E) the rebound resilience is 79%.

[0006] Patent Document 2 discloses a polyurethane foam for molded automobile ceilings, which is not a high-resilience polyurethane foam, but is obtained by reacting and foaming a raw material mixture containing: (a) 32.4 parts of a polyether polyol having 3 functional groups and a molecular weight of 6,000, (b) 27.8 parts of a polyether polyol having 3 functional groups and a molecular weight of 700, (c) 32.4 parts of a polyether polyol having 3 functional groups and a molecular weight of 300, (d) 7.4 parts of 1,4-butanediol, (e) 0.1 part of a foam stabilizer (trade name: L-6168), (f) 0.1 part of a foam stabilizer (trade name: B-8462), (g) 5.1 parts of water, (h) 1.4 parts of an antioxidant, (i) 1.1 parts of a catalyst having a boiling point of 250°C or more, and (j) 148 parts of polymeric MDI.

[0007] The document states that such a method results in: (A) less odor problems; (B) a foam density of 26 kg / m 3 (C) a tensile strength of 21 N / cm 2 (D) The polyurethane foam has an elongation of 18%.

[0008] To increase the impact resilience of polyurethane foam, it is common to increase the degree of crosslinking by using an isocyanate with a large number of functional groups. However, generally, increasing the degree of crosslinking increases impact resilience, but tends to decrease flexibility and strength. When high-resilience polyurethane foam is used in applications where stress is applied, the decrease in flexibility and strength can cause breakage due to deformation stress.

[0009] JP 2011-038005 A JP 2019-157132 A

[0010] The problem to be solved by the present invention is to provide a polyurethane foam having high impact resilience and excellent flexibility, and a shoe insole using the same.

[0011] In order to solve the above problems, the polyurethane foam of the present invention has a rebound resilience of 40% or more, an elongation of 200% or more, a compression set of 20% or less, and a density of 150 kg / m 3 More than 800kg / m 3 The following is the result.

[0012] The polyurethane foam according to the present invention is preferably obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas, wherein the polyol component contains polyether polyol A having 3 or more and 4 or less functional groups and a weight average molecular weight of 3,500 or more and 13,000 or less, the chain extender contains a diol having a molecular weight of 200 or less, and the polyisocyanate component contains a bifunctional isocyanate.

[0013] The shoe insole according to the present invention comprises the polyurethane foam according to the present invention.

[0014] A raw material mixture containing a high molecular weight polyol having 3 to 4 functional groups, a bifunctional isocyanate, and a chain extender is reacted and foamed using a mechanical froth method to produce a polyurethane foam with high impact resilience and excellent flexibility.

[0015] The improved impact resilience is thought to be due to (a) the low molecular weight chain extender and bifunctional isocyanate reacting first to form hard segments, and then the high molecular weight polyol adds to the hard segments to form soft segments, and (b) the hard segments bond together via hydrogen bonds to form a crystalline phase, promoting phase separation between the long branched main chain (soft segments) and the short chains (hard segments).The increased elongation is thought to be due to the moderate reduction in crosslink density caused by the use of the high molecular weight polyol.

[0016] 1 is a graph showing the relationship between the weight average molecular weight of a polyol and the impact resilience. 2 is a graph showing the relationship between the weight average molecular weight of a polyol and the elongation. 3 is a graph showing the relationship between the storage modulus G' and 25% CLD hardness of the polyurethane foam obtained in Example 29.

[0017] An embodiment of the present invention will be described in detail below. [1. Polyurethane Foam] The polyurethane foam of the present invention is obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas. The raw material mixture may further contain one or more selected from the group consisting of a nucleating agent, a moisture absorbent, and an antioxidant.

[0018] [1.1. Raw Materials] [1.1.1. Polyol Component] The polyol component is a component necessary for forming soft segments of polyurethane. In the present invention, the polyol component includes polyether polyol A. "Polyether polyol A" refers to a polyether polyol having 3 or more and 4 or less functional groups and a weight average molecular weight of 3,500 or more and 13,000 or less. The polyol component may consist solely of polyether polyol A, or may contain a polyether polyol other than polyether polyol A. In order to promote phase separation between hard segments and soft segments and obtain high impact resilience, it is preferable that the polyol component consists solely of polyether polyol A.

[0019] The number of functional groups and weight average molecular weight of polyether polyol A affect the impact resilience, elongation, strength, etc. If the number of functional groups of polyether polyol A is too small, the impact resilience may decrease. Therefore, the number of functional groups of polyether polyol A is preferably 3 or more. The number of functional groups is more preferably 3.1 or more, or 3.2 or more. On the other hand, if the number of functional groups is excessive, the crosslink density may increase and the elongation may decrease. Therefore, the number of functional groups of polyether polyol A is preferably 4 or less. The number of functional groups is more preferably 3.9 or less, or 3.8 or less.

[0020] If the weight-average molecular weight of polyether polyol A is too small, the crosslinking density may increase and the elongation may decrease. Therefore, the weight-average molecular weight of the polyether polyol is preferably 3,500 or more. The weight-average molecular weight is more preferably 4,000 or more, 5,000 or more, or 6,000 or more. On the other hand, if the weight-average molecular weight of polyether polyol A is excessive, the viscosity of the raw material mixture may become excessively high, and the manufacturability may decrease. Therefore, the weight-average molecular weight of polyether polyol A is preferably 13,000 or less. The weight-average molecular weight is more preferably 12,000 or less, 11,000 or less, or 10,000 or less.

[0021] [1.1.2. Chain extender] The chain extender is a component necessary for forming hard segments of polyurethane. In the present invention, the chain extender contains a diol having a molecular weight of 200 or less. The diol may have a linear structure or a branched structure.

[0022] Diols having a linear structure are particularly preferred. When the diol has a linear structure, it becomes easier to achieve high levels of impact resilience, elongation, and tensile strength. This is thought to be because a urethane bond (—NH—C(O)O—) in one hard segment is more likely to be linked to a urethane bond in another adjacent hard segment via a hydrogen bond, making it easier to form crosslinks with large molecular weights.

[0023] On the other hand, when the diol has a branched structure, if the amount of diol added is inappropriate, the impact resilience, elongation, and / or tensile strength may decrease. This is thought to be because the hard segments formed from the diol having a branched structure have steric hindrance (side chains), making it difficult for hydrogen bonds to form between adjacent hard segments.

[0024] Examples of chain extenders include: (a) diols with a linear structure such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, and (b) diols with a branched structure such as 2-methyl-1,3-propanediol and 3-methyl-1,5-pentanediol. The raw material mixture may contain any one of these chain extenders, or may contain two or more of them.

[0025] [1.1.3. Foam Stabilizer] A foam stabilizer is used to facilitate the dispersion of entrained gas during mechanical foaming of the raw material mixture, stabilize bubbles, and adjust the bubble structure. In the present invention, the type of foam stabilizer is not particularly limited. Examples of foam stabilizers include silicone-based foam stabilizers and fluorine-containing compound-based foam stabilizers. The raw material mixture may contain any one of these foam stabilizers, or may contain two or more of them.

[0026] [1.1.4. Catalyst] The catalyst is an additive for accelerating the resinification reaction. In the present invention, the type of catalyst is not particularly limited. Examples of the catalyst include amine catalysts and metal catalysts.

[0027] Examples of the amine catalyst include N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaminoethanol, N,N',N'-trimethylaminoethylpiperazine, and triethylenediamine.

[0028] Examples of metal catalysts include: (a) Sn-based catalysts such as stannous octoate and dibutyltin dilaurate, (b) Hg-based catalysts such as phenylmercury propionate, (c) Pb-based catalysts such as lead octenate, (d) Fe-based catalysts such as iron acetylacetonate, and (e) Ni-based catalysts such as nickel acetylacetonate, nickel octoate, and nickel naphthenate. The raw material mixture may contain any one of these catalysts, or may contain two or more of them.

[0029] [1.1.5. Nucleating Agent] The raw material mixture may contain a nucleating agent. A nucleating agent is an additive that functions as a starting point for foam nuclei during the foam formation process. Adding a nucleating agent to the raw material mixture facilitates the formation of foam nuclei at the interface between the liquid raw material and the nucleating agent. As a result, fine bubbles can be uniformly formed within the foam.

[0030] In the present invention, the type of nucleating agent is not particularly limited as long as it exhibits the above-mentioned functions. Examples of nucleating agents include: (a) metal hydroxides such as aluminum hydroxide (Al(OH)), magnesium hydroxide (Mg(OH)), and calcium hydroxide (Ca(OH)), (b) talc, (c) light calcium carbonate, heavy calcium carbonate, and calcium carbonate, (d) core-shell rubber particles, and (e) silica powder. The raw material mixture may contain any one of these nucleating agents, or may contain two or more of them.

[0031] [1.1.6. Moisture absorbent] The raw material mixture may contain a moisture absorbent. The moisture absorbent is an additive for removing moisture that inevitably gets mixed into the raw material mixture. When foaming is performed using the mechanical froth method, if moisture gets mixed into the raw material mixture, the water reacts with the polyisocyanate to generate CO2. As a result, it may become difficult to control the bubbles and to uniformly form fine bubbles. On the other hand, adding a moisture absorbent to the raw material mixture suppresses unintended reactions between water and polyisocyanate. As a result, it becomes easier to uniformly form fine bubbles.

[0032] In the present invention, the type of moisture absorbent is not particularly limited. Examples of moisture absorbents include zeolite, silica powder, alumina powder, lithium hydroxide powder, barium hydroxide powder, and calcium chloride powder. The raw material mixture may contain any one of these moisture absorbents, or may contain two or more of them.

[0033] [1.1.7. Antioxidant] The raw material mixture may contain an antioxidant. The antioxidant is used to suppress deterioration of the polyurethane due to oxidation. In the present invention, the type of antioxidant is not particularly limited. Examples of antioxidants include hindered phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0034] [1.1.8. Polyisocyanate Component] The polyisocyanate component is a component necessary for forming urethane bonds in the polymer chain. In the present invention, the polyisocyanate component contains a bifunctional isocyanate. The polyisocyanate component may consist solely of a bifunctional isocyanate, or may contain a polyisocyanate having more than two functional groups. In order to promote phase separation between the hard segment and the soft segment and obtain high impact resilience, the polyisocyanate component is preferably composed solely of a bifunctional isocyanate.

[0035] Examples of bifunctional isocyanates include: (a) diisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), and tolidine diisocyanate (TODI); (b) bifunctional isocyanate group-terminated prepolymers obtained by reacting diols with diisocyanates; and (c) mixtures of diisocyanates (e.g., 4,4′-MDI) and bifunctional isocyanate group-terminated prepolymers.

[0036] The raw material mixture may contain any one of these difunctional isocyanates, or may contain two or more of them. In particular, the difunctional isocyanate preferably contains a difunctional isocyanate-terminated prepolymer. The difunctional isocyanate-terminated prepolymer already has a molecular structure corresponding to the hard segments of polyurethane. Therefore, when a polyurethane foam is produced using this prepolymer, it is believed that the formation of high-molecular-weight crosslinks (physical crosslinks where adjacent hard segments are connected via hydrogen bonds) is facilitated. As a result, a polyurethane foam with high impact resilience and excellent flexibility is obtained.

[0037] [1.1.9. Foam-forming gas] The foam-forming gas is not particularly limited as long as it does not adversely affect the reaction between the polyol and the polyisocyanate. Examples of foam-forming gases include: (a) dry air, and (b) inert gases such as nitrogen.

[0038] [1.2. Content] The "content (parts by mass)" of each component (excluding the polyisocyanate component and the foam-forming gas) contained in the raw material mixture refers to the mass of each component when the mass of polyether polyol A is taken as 100.

[0039] [1.2.1. Chain extender content] The chain extender has a higher collision probability with the bifunctional isocyanate than the high-molecular-weight polyether polyol A. Therefore, when a raw material mixture containing the polyether polyol A, the chain extender, and the bifunctional isocyanate is reacted, the chain extender and the bifunctional isocyanate are thought to react first to form hard segments. The polyether polyol A is then added to the hard segments to form soft segments.

[0040] If the content of the chain extender is too low, the reaction rate of the initial reaction (the reaction to form hard segments) may be slow, which may slow the reaction rate of the resinification reaction. This may also lead to the tendency for bubbles to coalesce, which may cause cell roughness. Therefore, the content of the chain extender is preferably 1.3 parts by mass or more. The content is more preferably 1.5 parts by mass or more, or 1.7 parts by mass or more.

[0041] On the other hand, if the chain extender content is excessive, the polyurethane foam may become excessively hard. Furthermore, the reactivity of the raw material mixture may become too high, resulting in reduced manufacturability. Therefore, the chain extender content is preferably 8.5 parts by mass or less. The content is more preferably 8.2 parts by mass or less, 8.0 parts by mass or less, or 7.8 parts by mass or less.

[0042] [1.2.2. Content of foam stabilizer] If the content of foam stabilizer is too low, cell roughness may occur. Therefore, the content of foam stabilizer is preferably 5.0 parts by mass or more. The content is more preferably 6.0 parts by mass or more, or 7.0 parts by mass or more. On the other hand, if the content of foam stabilizer is excessive, the secondary components contained in the foam stabilizer (e.g., monools or diols used as diluents) may react with the bifunctional isocyanate, resulting in a decrease in elongation and impact resilience. In addition, bleeding of the components contained in the foam stabilizer may occur. Therefore, the content of foam stabilizer is preferably 15.0 parts by mass or less. The content is more preferably 14.0 parts by mass or less, and even more preferably 13.0 parts by mass or less.

[0043] [1.2.3. Catalyst Content] If the catalyst content is too low, the resinification reaction will be difficult to proceed. Therefore, the catalyst content is preferably 1.0 part by mass or more. The content is more preferably 1.5 parts by mass or more, or 2.0 parts by mass or more. On the other hand, if the catalyst content is excessive, curing may proceed too rapidly, resulting in a decrease in manufacturability. Therefore, the catalyst content is preferably 10.0 parts by mass or less. The content is more preferably 9.0 parts by mass or less, or 8.0 parts by mass or less.

[0044] [1.2.4. Nucleating Agent Content] If the nucleating agent content is too low, it may be difficult to uniformly form fine bubbles. Therefore, the nucleating agent content is preferably 3.0 parts by mass or more. The content is more preferably 4.0 parts by mass or more, or 5.0 parts by mass or more. On the other hand, if the nucleating agent content is excessive, the nucleating agent may be more likely to separate from the raw material mixture. Furthermore, excessive nucleating agent may cause a decrease in the strength and surface properties of the polyurethane foam. Therefore, the nucleating agent content is preferably 20.0 parts by mass or less. The content is more preferably 19.0 parts by mass or less, or 18.0 parts by mass or less.

[0045] [1.2.5. Moisture absorbent content] If the moisture absorbent content is too low, the moisture mixed in the raw material may react with the bifunctional isocyanate, making it difficult to adjust the density of the polyurethane foam. Furthermore, cell roughness may occur in the polyurethane foam. Therefore, the moisture absorbent content is preferably 0.1 parts by mass or more. The content is more preferably 0.3 parts by mass or more, or 0.5 parts by mass or more.

[0046] On the other hand, the moisture absorbent may function as a catalyst for the resinification reaction. Therefore, if the content of the moisture absorbent is excessive, the reactivity of the raw material mixture may become excessively high. Therefore, the content of the moisture absorbent is preferably 3.0 parts by mass or less. The content is more preferably 2.8 parts by mass or less, or 2.6 parts by mass or less.

[0047] [1.2.6. Antioxidant Content] When the raw material mixture is heated and cured, some of the raw materials may oxidize. Furthermore, after the polyurethane foam is formed, the polyurethane foam may discolor due to oxidation. On the other hand, adding an antioxidant to the raw material mixture can suppress oxidation of the raw materials and the polyurethane foam. To achieve this effect, the antioxidant content is preferably 0.05 parts by mass or more. The content is more preferably 0.07 parts by mass or more, or 0.10 parts by mass or more.

[0048] On the other hand, if the antioxidant content is excessive, it may inhibit the reaction of the raw material mixture. Therefore, the antioxidant content is preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, or even 0.3 parts by mass or less.

[0049] [1.2.7. Isocyanate Index] The term "isocyanate index" refers to the ratio of the equivalent weight of isocyanate groups of the polyisocyanate in the raw material mixture to the equivalent weight of active hydrogen groups in the raw material mixture, multiplied by 100.

[0050] If the isocyanate index is too small, a large amount of unreacted active hydrogen groups will remain. As a result, the polyurethane foam may become tacky. The reactivity of the raw material mixture will also decrease. Therefore, the isocyanate index is preferably 97 or more. The isocyanate index is more preferably 98 or more, 99 or more, or 100 or more.

[0051] On the other hand, if the isocyanate index is too high, the polyurethane foam may become too hard and brittle. Therefore, the isocyanate index is preferably 115 or less. The isocyanate index is more preferably 114 or less, 113 or less, or 112 or less.

[0052] [1.2.8. Content of foam-forming gas] The "content of foam-forming gas" refers to the volume of the foam-forming gas when the volume of the raw material excluding the foam-forming gas is taken as 100.

[0053] If the content of the foam-forming gas is too low, foaming may be insufficient. Therefore, the content of the foam-forming gas is preferably 10 parts by volume or more. The content is more preferably 40 parts by volume or more, or 50 parts by volume or more. On the other hand, if the content of the foam-forming gas is excessive, bubbles tend to break or coalesce in the foamed liquid. Therefore, the content of the foam-forming gas is preferably 95 parts by volume or less. The content is more preferably 85 parts by volume or less, or 75 parts by volume or less.

[0054] [1.3. Reaction of Raw Material Mixture] The polyurethane foam of the present invention is produced using a mechanical froth method. The "mechanical froth method" refers to a method in which: (a) a raw material mixture is mixed using a high-shear mixer while blowing in an inert gas to produce a foaming raw material mixture containing fine bubbles; (b) the foaming raw material mixture is applied to the surface of a substrate (e.g., a PET film); and (c) the coating is heated to a predetermined temperature and cured. In the present invention, the reaction conditions for the raw material mixture are not particularly limited, and optimal conditions can be selected depending on the purpose.

[0055] 1.4. Properties 1.4.1. Rebound resilience The term "rebound resilience" refers to a value measured in accordance with JIS K 6400-3.

[0056] The polyurethane foam of the present invention exhibits high resilience because it uses polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy specific requirements as raw materials. When the manufacturing conditions are optimized, the resilience can be 40% or more. When the manufacturing conditions are further optimized, the resilience can be 45% or more, or even 50% or more.

[0057] [1.4.2. Elongation] "Elongation" refers to a value measured in accordance with JIS K 6251:2010.

[0058] The polyurethane foam of the present invention exhibits high elongation because it uses polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy specific requirements as raw materials. When the manufacturing conditions are optimized, the elongation can be 200% or more. When the manufacturing conditions are further optimized, the elongation can be 220% or more, 240% or more, 260% or more, 280% or more, 300% or more, or 320% or more.

[0059] [1.4.3. Compression Set] "Compression set" refers to a value measured in accordance with JIS K 6401:2011.

[0060] The polyurethane foam of the present invention exhibits low compression set because it uses polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy specific requirements as raw materials. When the manufacturing conditions are optimized, the compression set is 20% or less. When the manufacturing conditions are further optimized, the compression set is 10% or less, or even 5% or less.

[0061] [1.4.4. Density] "Density" refers to a value measured in accordance with JIS K 6401:2011.

[0062] The polyurethane foam of the present invention is produced using a mechanical froth method, so the density can be controlled over a wide range. When the production conditions are optimized, the density can be controlled to 150 kg / m 3 More than 800kg / m 3 By controlling the content of foaming gas, a polyurethane foam having a density of 600 kg / m or less can be obtained. 3 or less, or 400 kg / m 3 The following is the result.

[0063] [1.4.5. Tensile Strength] "Tensile strength" refers to a value measured in accordance with JIS K 6251:2010.

[0064] The polyurethane foam of the present invention exhibits high tensile strength because it uses polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy specific requirements as raw materials. When the production conditions are optimized, the tensile strength becomes 0.20 MPa or more. When the production conditions are further optimized, the tensile strength becomes 0.30 MPa or more, 0.40 MPa or more, 0.50 MPa or more, 0.60 MPa or more, or 0.70 MPa or more.

[0065] [1.4.6. Storage Modulus] "Storage modulus (G')" refers to a value measured under the conditions described below. "Storage modulus difference (ΔLOG(G'))" refers to the absolute value of the difference between the common logarithm of the storage modulus G' at -40°C and the common logarithm of the storage modulus G' at 30°C.

[0066] The polyurethane foam of the present invention uses polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy specific requirements as raw materials, so it does not harden even at low temperatures. In other words, the polyurethane foam of the present invention exhibits a storage modulus close to room temperature even at low temperatures. When the manufacturing conditions are optimized, the storage modulus difference is less than 1.40 MPa. When the manufacturing conditions are further optimized, the storage modulus difference is 1.20 MPa or less, 1.00 MPa or less, or 0.80 MPa or less.

[0067] [1.5. Applications] The polyurethane foam of the present invention can be used for apparel, sporting goods, toys, bedding, interior goods, shoe insoles, inter-cell cushioning in EV batteries, cushioning for pressure-sensitive sensors, etc. The polyurethane foam of the present invention is particularly suitable as a shoe insole. Furthermore, since the polyurethane foam of the present invention exhibits viscoelasticity even at low temperatures, it is suitable for cold-climate packaging materials, cold-climate cushioning materials, cold-climate heat insulating materials, etc., which are intended to be used below freezing.

[0068] [2. Function] When a raw material mixture containing a high-molecular-weight polyol having a functionality of 2, a polyisocyanate having a functionality of more than 2, and a chain extender is reacted and foamed by the mechanical froth method, a polyurethane foam exhibiting high impact resilience can be obtained. However, the polyurethane foam obtained by this method tends to have reduced flexibility.

[0069] In contrast, when a raw material mixture containing a high molecular weight polyol having 3 to 4 functional groups, a bifunctional isocyanate, and a chain extender is reacted and foamed using the mechanical froth method, a polyurethane foam with high impact resilience and excellent flexibility is obtained.

[0070] The improved impact resilience is thought to be due to (a) the low molecular weight chain extender and bifunctional isocyanate reacting first to form hard segments, and then the high molecular weight polyol adds to the hard segments to form soft segments, and (b) the hard segments bond together via hydrogen bonds to form a crystalline phase, promoting phase separation between the long branched main chain (soft segments) and the short chains (hard segments).The increased elongation is thought to be due to the moderate reduction in crosslink density caused by the use of the high molecular weight polyol.

[0071] (Examples 1 to 28, Comparative Examples 1 to 15) [1. Preparation of Samples] Table 1 shows a list of the raw materials used. Lupranate (registered trademark) M5S is crude MDI. Lupranate (registered trademark) MP102 is urethane-modified MDI, and is a mixture of 4,4'-MDI (50 mass%) and a difunctional isocyanate-terminated prepolymer (50 mass%).

[0072]

[0073] The above raw materials were blended in a predetermined ratio. The raw material mixture was placed in a mixing head and stirred to homogeneity while mixing in an inert gas (nitrogen), to obtain a foaming raw material mixture containing fine bubbles. The foaming raw material mixture was applied to a PET film, and the coating was heat-cured at 200°C. The amount of inert gas mixed in was such that the volume of the inert gas was 70 when the volume of the raw materials was 100.

[0074] [2. Test Method] [2.1. Density] A 50 mm x 50 mm prismatic test piece was prepared from the polyurethane foam. The density of the obtained test piece was measured in accordance with JIS K 6401:2011.

[0075] [2.2. Rebound Resilience] Test pieces measuring 50 mm x 50 mm x 50 mm were prepared from the polyurethane foam. The resulting test pieces were used to measure the rebound resilience in accordance with JIS K 6255.

[0076] [2.3. Elongation] Dumbbell No. 3 shaped test pieces were prepared from polyurethane foam. The obtained test pieces were used to measure elongation in accordance with JIS K 6251:2010. The test piece was tensile at a speed of 200 mm / min. Using the initial gauge length L0 and the gauge length L when the test piece was cut, the elongation was calculated according to the following formula: Elongation (%) = (L - L0) x 100 / L0

[0077] [2.4. Tensile strength] A dumbbell No. 3 shaped test piece was prepared from the polyurethane foam. Using the obtained test piece, the tensile strength was measured in accordance with JIS K 6251:2010. The test piece was pulled at a speed of 200 mm / min. The area S [m 2 The tensile strength was calculated by the following formula using the maximum tensile force F [N] until the test piece broke and the tensile strength [MPa] = F / S

[0078] [2.5. Compression Set] A 50 mm x 50 mm prismatic test piece was prepared from the polyurethane foam. Using the obtained test piece, the compression set was measured in accordance with JIS K 6401:2011. The test piece was compressed to a thickness of 50% of the initial thickness T0 and left in a constant temperature bath at 70°C for 22 hours. Next, the test piece was removed from the constant temperature bath and left at room temperature for 30 minutes, after which the thickness T1 of the test piece was measured. Using T0 and T1, the compression set was calculated according to the following formula: Compression set [%] = (T0 - T1) x 100 / T0

[0079] [3. Results] The results are shown in Tables 2 to 5. Tables 2 to 5 also show the raw material composition of each sample. The numerical value for each raw material represents parts by mass. The amount of chain extender added was 0.023 mol equivalent, 0.046 mol equivalent, or 0.069 mol equivalent relative to 100 parts by mass of polyether polyol A, regardless of the type of chain extender.

[0080] Figure 1 shows the relationship between the weight-average molecular weight of a polyol and impact resilience. Figure 2 shows the relationship between the weight-average molecular weight of a polyol and elongation. In Figures 1 and 2, "EG" represents ethylene glycol, "1,4BD" represents 1,4-butanediol, and "1,6HD" represents 1,6-hexanediol. Furthermore, "L" represents an amount of chain extender added equivalent to 0.023 mol, "M" represents an amount of chain extender added equivalent to 0.046 mol, and "H" represents an amount of chain extender added equivalent to 0.069 mol. The following can be seen from Tables 2 to 5 and Figures 1 and 2.

[0081] (1) Comparative Example 1 had low elongation and tensile strength. This is thought to be due to the excessively high degree of crosslinking caused by the use of crude MDI with a functionality of 2.4 as the polyisocyanate component. (2) When the weight-average molecular weight of the polyol was 3,000 (Comparative Examples 2 to 9 and 11), the elongation was less than 200%, regardless of the type of chain extender. Furthermore, except for Comparative Examples 4, 6, and 7, the impact resilience was less than 40%.

[0082] (3) When the weight-average molecular weight of the polyol was 3,500 or more and the chain extender had a linear structure (Examples 1 to 26), it was found that the rebound resilience was 40% or more and the elongation was 200% or more. (4) In Examples 3, 12, and 21, the rebound resilience and elongation were high, but the tensile strength was less than 0.20 MPa. This is thought to be because the molecular weight of the main polyol was somewhat low and the content of the chain extender was also somewhat low, resulting in insufficient phase separation of the hard segment phase and a decrease in the physical crosslinking force due to hydrogen bonding.

[0083] (5) When 1,6-hexanediol was used as a chain extender (Examples 19 to 26, Comparative Examples 8 to 11), the number of samples with a compression set exceeding 10% increased. This is thought to be because 1,6-hexanediol has a relatively long molecular chain, which weakens its ability to form hard segment phases and makes the physical crosslinks easily destroyed by heat compression, impairing the springiness (resilience) of the polyurethane.

[0084] (6) Comparative Example 10 had a rebound resilience of 51%, an elongation of 305%, and a tensile strength of 1.09 MPa. This is thought to be because the weight-average molecular weight of the polyol was 3,500 or more and the chain extender had a linear structure. However, the compression set of Comparative Example 10 was 23.4%. This is thought to be because an excessive number of reaction intermediates between 1,6-hexanediol and diisocyanate were formed in the early stages of the reaction, and because the reactivity of the main polyol with diisocyanate decreased.

[0085] (7) When a diol having a linear structure was used as the chain extender (Examples 1 to 26, Comparative Examples 2 to 11), the greater the amount of chain extender added, the higher the rebound resilience and tensile strength, the lower the elongation, and the greater the compression set. (8) When a diol having a branched structure was used as the chain extender (Examples 27 to 28, Comparative Examples 12 to 15), the properties tended to be slightly lower than when a diol having a linear structure was used. However, even when a diol having a branched structure was used, it was found that by increasing the amount added, both high rebound resilience and high elongation could be achieved.

[0086]

[0087]

[0088]

[0089]

[0090] (Examples 29 to 32, Comparative Example 16) [1. Sample Preparation] Table 6 shows a list of the raw materials used. The raw materials in Table 6 were blended in a predetermined ratio. The raw material mixture was placed in a mixing head and stirred and mixed to a homogeneous mixture while mixing in an inert gas (nitrogen), to obtain a foaming raw material mixture containing fine bubbles. The foaming raw material mixture was applied to release paper, and the coating was heat-cured at 200°C.

[0091]

[0092] [2. Test Method] [2.1. Storage Modulus] The viscoelasticity of the obtained polyurethane foam was measured. The measuring device used was a TA Instruments ARE-G2 viscoelasticity measuring device. Periodic strain was applied to the sample by vibration, and the storage modulus, loss modulus, and loss tangent were measured from the shear stress waveform as a response and their phase difference. The glass transition point was defined as the temperature at which the peak value of the loss tangent appeared. Detailed measurement conditions were as follows:

[0093] Measurement temperature range: -80°C to 50°C Heating rate: 3°C / min Mode: Parallel blade mode Sample size: 8mmφ Strain: 0.5% Frequency: 1Hz

[0094] [2.2. 25% CLD Hardness] The 25% CLD hardness was measured in accordance with JIS K 6254:2010.

[0095] [3. Results] The results are shown in Table 7. Table 7 also shows the raw material composition of each sample. The numerical value for each raw material represents parts by mass. Figure 3 shows the relationship between the storage modulus G' and 25% CLD hardness of the polyurethane foam obtained in Example 29. The following can be seen from Table 7 and Figure 3.

[0096] (1) In Comparative Example 16, the storage modulus difference exceeded 1.40 MPa. This is believed to be due to the use of a polyether polyol with a molecular weight of less than 3,500. (2) In Examples 29 to 32, the storage modulus difference was less than 0.80 MPa. This result indicates that using a polyether polyol with a molecular weight of 3,500 or more, preferably 4,000 or more, or 5,000 or more as the main raw material makes the ball less likely to harden even at low temperatures, and maintains good rebound resilience at low temperatures. (3) A strong correlation was observed between the storage modulus G' and the 25% CLD hardness. See Figure 3. From Figure 3, it is estimated that Examples 29 to 32 all maintained a 25% CLD hardness of 0.15 MPa or less at -40°C.

[0097]

[0098] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0099] The polyurethane foam according to the present invention can be used for apparel, sporting goods, toys, bedding, interior goods, shoe insoles, cushions between cells of EV batteries, cushions for pressure-sensitive sensors, and the like.

Claims

1. The foam is obtained by reacting and foaming a raw material mixture that contains a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas, but does not contain water; The polyol component includes a polyether polyol A having a functional group number of 3 or more and 4 or less and a weight average molecular weight of 3,500 or more and 13,000 or less, The chain extender comprises a diol having a molecular weight of 200 or less, The polyisocyanate component contains a difunctional isocyanate. A polyurethane foam comprising: The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

2. 2. The polyurethane foam according to claim 1, having a tensile strength of 0.20 MPa or more.

3. (delete)

4. The polyurethane foam according to claim 1 , wherein the raw material mixture further comprises a nucleating agent and / or a moisture absorbing agent.

5. A shoe insole comprising the polyurethane foam according to claim 1 , 2 or 4 .

6. The foam is obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas, the polyol component is composed solely of a polyether polyol A having a functional group number of 3 or more and a weight average molecular weight of 3,500 or more and 13,000 or less, The chain extender comprises a diol having a molecular weight of 200 or less, The polyisocyanate component contains a difunctional isocyanate. A polyurethane foam comprising: The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

7. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is as follows: The storage modulus difference is less than 1.40 MPa. Polyurethane foam.

8. A polyurethane foam obtained by reacting and foaming a raw material mixture containing a moisture absorbent, The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

9. The foam is obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, a foam-forming gas, and a nucleating agent, The polyol component includes a polyether polyol A having a functional group number of 3 or more and 4 or less and a weight average molecular weight of 3,500 or more and 13,000 or less, The chain extender comprises a diol having a molecular weight of 200 or less, The polyisocyanate component includes a difunctional isocyanate, The nucleating agent includes at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, and core-shell rubber particles; A polyurethane foam having a nucleating agent content of 3.0 parts by mass or more and 20.0 parts by mass or less, The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

10. The foam is obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas, The polyol component includes a polyether polyol A having a functional group number of 3 or more and 4 or less and a weight average molecular weight of 6,000 or more and 13,000 or less, The chain extender comprises a diol having a molecular weight of 200 or less, The polyisocyanate component contains a difunctional isocyanate. A polyurethane foam comprising: The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

11. The foam is obtained by reacting and foaming a raw material mixture containing a polyol component, a chain extender, a foam stabilizer, a catalyst, a polyisocyanate component, and a foam-forming gas, The polyol component includes a polyether polyol A having a functional group number of 3 or more and 4 or less and a weight average molecular weight of 3,500 or more and 13,000 or less, The chain extender comprises a diol having a molecular weight of 200 or less, The polyisocyanate component contains a difunctional isocyanate. A polyurethane foam comprising: The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is as follows: The tensile strength is 0.20 MPa or more and 0.96 MPa or less. Polyurethane foam.

12. A polyurethane foam obtained by reacting and foaming a water-free raw material mixture, The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Polyurethane foam.

13. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Packaging material for cold climates featuring polyurethane foam.

14. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Cushioning material for cold climates featuring polyurethane foam.

15. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Cold climate insulation with polyurethane foam.

16. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Battery inter-cell cushioning with polyurethane foam.

17. The impact resilience is 40% or more, The elongation is 200% or more, The compression set is 20% or less, Density is 150 kg / m ３ More than 800kg / m ３ is less than or equal to Cushion for pressure-sensitive sensors with polyurethane foam.