Polyurethane foam and shoe insoles

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

[Technical Field]

[0001] The present invention relates to polyurethane foam and shoe insoles, and more particularly to polyurethane foam with high rebound elasticity and excellent flexibility, and shoe insoles using the same. [Background technology]

[0002] Polyurethane refers to a polymer compound having a urethane bond (-NH-C(O)O-). Generally, polyurethane is obtained by reacting the hydroxyl group (-OH) of a polyol with the isocyanate group (-NCO) of a polyisocyanate. Polyurethane is known to exhibit diverse properties by optimizing the type of polyol and / or polyisocyanate used. Therefore, polyurethane is used in various applications such as automotive parts, synthetic leather, paints, and adhesives. Furthermore, polyurethane foam, obtained by foaming polyurethane, is used in applications such as thermal insulation and cushioning materials.

[0003] Polyurethane foam with enhanced rebound elasticity is also known as "high-rebound polyurethane foam." Because high-rebound polyurethane foam has strong resilience and is resistant to sagging, it is used in apparel, sporting goods, toys, bedding, and interior furnishings.

[0004] Various proposals have been made regarding this type of high-rebound polyurethane foam. For example, Patent Document 1 contains: (a) Polytetramethylene ether glycol with an average number of functional groups of 2 and a number-average molecular weight of 2000: 85 parts, (b) Polyoxypropylene polyol with an average number of functional groups of 3 and a number-average molecular weight of 3000: 10 parts, (c) 1,4-butanediol: 5 parts, (d) Silicone foam stabilizer: 1 part, (e)Wednesday: 0.31 part, (f) UV absorber: 0.8 parts, (g) Dioctyl tin dilaurate: 0.005 parts, (h) Isocyanate-terminated prepolymer obtained by reacting MDI (40 parts) with polytetramethylene ether glycol with a molecular weight of 2000 (66.1 parts): 103.8 parts A foamed polyurethane elastomer is disclosed, which is obtained by foaming and curing a raw material mixture containing the above by using a combination of mechanical foaming and water foaming.

[0005] The document states that by this method, (A) Pad density is 0.425 g / cm³ 3 (425kg / m 3 ) and (B) The breaking strength (TB) is 1.3 MPa, (C) The elongation at rupture (EB) is 240%, (D) The compression residual set (50% compression, 70°C × 22h) was 2.7%, (E) The modulus of resilience is 79%. It is stated that foamed polyurethane elastomer can be obtained.

[0006] Patent Document 2 describes a material that is not a high-rebound polyurethane foam, (a) Polyether polyol with 3 functional groups and a molecular weight of 6000: 32.4 parts, (b) Polyether polyol with 3 functional groups and a molecular weight of 700: 27.8 parts, (c) Polyether polyol with 3 functional groups and a molecular weight of 300: 32.4 parts, (d) 1,4-butanediol: 7.4 parts, (e) Foam stabilizer (product name: L-6168): 0.1 part, (f) Foam stabilizer (product name: B-8462): 0.1 part, (g) Water: 5.1 parts, (h) Antioxidant: 1.4 parts, (i) Catalyst with a boiling point of 250°C or higher: 1.1 parts (j) Polymeric MDI: 148 parts A polyurethane foam for automotive molded ceilings is disclosed, obtained by reacting and foaming a raw material mixture containing [a specific substance].

[0007] In the same document, by such a method, (A) There are few odor problems, (B) The foam density is 26 kg / m 3 and (C) The tensile strength is 21 N / cm 2 (0.21 MPa), (D) The elongation is 18%. It is described that a polyurethane foam can be obtained.

[0008] When increasing the resilience of the polyurethane foam, it is common to use an isocyanate with a large number of functional groups to increase the crosslinking degree. However, generally, when the crosslinking degree is increased, the resilience increases, but the flexibility and strength tend to decrease. When using a high resilience polyurethane foam in applications where stress acts, the decrease in flexibility and strength causes damage due to deformation stress.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0011] In order to solve the above problems, the polyurethane foam according to the present invention is such that the resilience is 40% or more, the elongation is 200% or more, The compression residual strain is 20% or less, and the density is 150 kg / m 3 or more and 800 kg / m 3 or less.

[0012] The polyurethane foam according to 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 foaming gas, where 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 3500 or more and 13000 or less, the chain extender includes a diol having a molecular weight of 200 or less, and the polyisocyanate component preferably contains a bifunctional isocyanate.

[0013] The insole for shoes according to the present invention includes the polyurethane foam according to the present invention.

Effects of the Invention

[0014] When a raw material mixture containing a high molecular weight polyol having a functional group number of 3 to 4, a bifunctional isocyanate, and a chain extender is reacted and foamed using the mechanical froth method, a polyurethane foam having high resilience and excellent flexibility can be obtained.

[0015] The improvement in resilience is (a) because the low molecular weight chain extender and the bifunctional isocyanate react first to form a hard segment, and then the high molecular weight polyol adds to the hard segment to form a soft segment, and (b) because the hard segments are bonded to each other through hydrogen bonds to form a crystalline phase, and the phase separation of the long branched main chain (soft segment) and the short chain (hard segment) is promoted It is considered. The increase in elongation is considered to be due to the appropriate decrease in the crosslink density by using a high molecular weight polyol. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows the relationship between the weight-average molecular weight and rebound elasticity of polyols. [Figure 2] This figure shows the relationship between the weight-average molecular weight and elongation of polyols. [Figure 3] This figure shows the relationship between the storage modulus G' and the 25% CLD hardness of the polyurethane foam obtained in Example 29. [Modes for carrying out the invention]

[0017] An embodiment of the present invention will be described in detail below. [1. Polyurethane foam] The polyurethane foam according to 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 foaming gas. The raw material mixture may further contain one or more selected from the group consisting of nucleating agents, hygroscopic agents, and antioxidants.

[0018] [1.1. Raw materials] [1.1.1. Polyol components] The polyol component is necessary for forming the soft segment of polyurethane. In the present invention, the polyol component includes polyether polyol A. "Polyether polyol A" refers to a polyether polyol having 3 to 4 functional groups and a weight-average molecular weight of 3500 to 13000. The polyol component may consist solely of polyether polyol A, or it may contain other polyether polyols besides polyether polyol A. To promote phase separation between the hard and soft segments and obtain high rebound elasticity, 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 its rebound elasticity, elongation, and strength. If the number of functional groups of polyether polyol A is too low, the rebound elasticity may decrease. Therefore, it is preferable that the number of functional groups of polyether polyol A be 3 or more. More preferably, the number of functional groups is 3.1 or more, or 3.2 or more. On the other hand, if the number of functional groups becomes excessive, the crosslinking density may increase and the elongation may decrease. Therefore, the number of functional groups in polyether polyol A is preferably 4 or less. More preferably, the number of functional groups is 3.9 or less, or 3.8 or less.

[0020] If the weight-average molecular weight of polyether polyol A becomes too small, the crosslinking density may increase, and the elongation may decrease. Therefore, the weight-average molecular weight of the polyether polyol is preferably 3500 or higher. More preferably, the weight-average molecular weight is 4000 or higher, 5000 or higher, or 6000 or higher. 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, which can reduce manufacturability. Therefore, the weight-average molecular weight of polyether polyol A is preferably 13,000 or less. More preferably, the weight-average molecular weight is 12,000 or less, 11,000 or less, or 10,000 or less.

[0021] [1.1.2. Chain extenders] Chain extenders are components necessary for forming hard segments of polyurethane. In the present invention, the chain extender includes a diol with a molecular weight of 200 or less. The diol may have a linear structure or a branched structure.

[0022] Diols with a linear structure are particularly preferred. When a diol has a linear structure, it becomes easier to achieve a high level of balance between rebound elasticity, elongation, and tensile strength. This is thought to be because the urethane bond (-NH-C(O)O-) present in one hard segment and the urethane bond present in another adjacent hard segment can easily be linked via hydrogen bonding, and crosslinking points with large molecular weights can be easily formed.

[0023] On the other hand, when the diol has a branched structure, if the amount of diol added is not appropriate, the rebound elasticity, elongation, and / or tensile strength may decrease. This is thought to be because hard segments formed from diols with 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, (b) Diols with branched structures, such as 2-methyl-1,3-propanediol and 3-methyl-1,5-pentanediol These are some examples. The raw material mixture may contain one of these chain extenders, or it may contain two or more of them.

[0025] [1.1.3. Foam stabilizers] A foam stabilizer is used to facilitate the dispersion of entrained gases, stabilize bubbles, and adjust the bubble structure when mechanically foaming a raw material mixture. In this 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 one of these foam stabilizers, or it may contain two or more.

[0026] [1.1.4. Catalyst] The catalyst is an additive used to promote the resinification reaction. In this invention, the type of catalyst is not particularly limited. Examples of catalysts include amine-based catalysts and metal catalysts.

[0027] Examples of amine-based catalysts include, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaminoethanol, N,N',N'-trimethylaminoethylpiperazine, triethylenediamine These are some examples.

[0028] Examples of metal catalysts include, (a) Sn-based catalysts such as stanus octoate and dibutylthin dilaurate, (b) Hg-based catalysts such as phenylmercury propionate, (c) Pb-based catalysts such as lead octonate (d) Fe-based catalysts such as iron acetylacetonate, (e) Ni-based catalysts such as nickel acetylacetonate, nickel octylate, and nickel naphthenate. These are some examples. The raw material mixture may contain one of these catalysts, or it may contain two or more of them.

[0029] [1.1.5. Nucleoforming agents] The raw material mixture may contain a nucleating agent. The nucleating agent is an additive that functions as a starting point for foam nuclei during the foam formation process. When a nucleating agent is added to the raw material mixture, foam nuclei are more easily formed 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 performs the functions described above. Examples of nucleating agents include: (a) Metal hydroxides such as aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), and calcium hydroxide (Ca(OH)2), (b) Talc, (c) Light calcium carbonate, heavy calcium carbonate, calcium carbonate, (d) Core-shell rubber particles, (e) Silica powder These are some examples. The raw material mixture may contain one of these nucleating agents, or it may contain two or more of them.

[0031] [1.1.6. Desiccant] The raw material mixture may contain a desiccant. The desiccant is an additive used to remove moisture that inevitably becomes mixed into the raw material mixture. When foaming is performed using the mechanical flossing method, if moisture is mixed into the raw material mixture, the water reacts with the polyisocyanate, generating CO2. As a result, it becomes difficult to control the bubbles, and it may be difficult to form fine bubbles uniformly. On the other hand, adding a desiccant 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 desiccant is not particularly limited. Examples of desiccant include zeolite, silica powder, alumina powder, lithium hydroxide powder, barium hydroxide powder, and calcium chloride powder. The raw material mixture may contain one of these desiccant types, or it may contain two or more types.

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

[0034] [1.1.8. Polyisocyanate components] Polyisocyanate components are necessary for forming urethane bonds in polymer chains. In the present invention, the polyisocyanate component includes a bifunctional isocyanate. The polyisocyanate component may consist solely of a difunctional isocyanate, or it may contain a polyisocyanate with more than two functional groups. To promote phase separation between the hard and soft segments and obtain high rebound elasticity, the polyisocyanate component is preferably composed solely of a difunctional 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), tolidine diisocyanate (TODI), (b) A difunctional isocyanate-terminated prepolymer obtained by reacting a diol with a diisocyanate, (c) A mixture of diisocyanate (e.g., 4,4'-MDI) and a bifunctional isocyanate-terminated prepolymer. These are some examples.

[0036] The raw material mixture may contain one of these bifunctional isocyanates, or it may contain two or more of them. In particular, difunctional isocyanates that contain a difunctional isocyanate-terminated prepolymer are preferred. Difunctional isocyanate-terminated prepolymers already possess a molecular structure corresponding to the hard segments of polyurethane. Therefore, it is believed that using them to produce polyurethane foam facilitates the formation of crosslinking points with large molecular weights (physical crosslinking points where adjacent hard segments are linked via hydrogen bonds). As a result, it is believed that a polyurethane foam with high rebound elasticity and excellent flexibility can be obtained.

[0037] [1.1.9. Gases for foaming] The foaming gas is not particularly limited, as long as it does not adversely affect the reaction between the polyol and the polyisocyanate. Examples of foaming gases include, (a) Dry air, (b) Inert gas such as nitrogen These are some examples.

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

[0039] [1.2.1. Content of chain extender] The chain extender has a higher collision probability with the bifunctional isocyanate compared to the high molecular weight polyether polyol A. Therefore, when a raw material mixture containing polyether polyol A, the chain extender, and the bifunctional isocyanate is reacted, it is thought that the chain extender and the bifunctional isocyanate react first to form a hard segment. Subsequently, polyether polyol A is added to the hard segment, forming a soft segment.

[0040] If the chain extender content is too low, the reaction rate of the initial reaction (the reaction that forms the hard segments) will be slow, which may slow down the reaction rate of the resinification reaction. In addition, this may lead to increased bubble aggregation and cell roughness. Therefore, the chain extender content is preferably 1.3 parts by mass or more. More preferably, the content is 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. Also, the reactivity of the raw material mixture may become too high, reducing manufacturability. Therefore, the chain extender content is preferably 8.5 parts by mass or less. More preferably, the content is 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. Foam stabilizer content] If the foam stabilizer content is too low, cell roughness may occur. Therefore, the foam stabilizer content is preferably 5.0 parts by mass or more. More preferably, the content is 6.0 parts by mass or more, or 7.0 parts by mass or more. On the other hand, if the foam stabilizer content is excessive, the by-components contained in the foam stabilizer (for example, monools and diols used as diluents) may react with the bifunctional isocyanate, causing a decrease in elongation and rebound elasticity. In addition, bleeding of components contained in the foam stabilizer may occur. Therefore, the foam stabilizer content is preferably 15.0 parts by mass or less. More preferably, the content is 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 not proceed easily. Therefore, the catalyst content is preferably 1.0 part by mass or more. More preferably, the content is 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 rapidly, and manufacturability may decrease. Therefore, the catalyst content is preferably 10.0 parts by mass or less. More preferably, the content is 9.0 parts by mass or less, or 8.0 parts by mass or less.

[0044] [1.2.4. Content of nucleating agent] If the nucleating agent content is too low, it may become difficult to uniformly form fine bubbles. Therefore, the nucleating agent content is preferably 3.0 parts by mass or more. More preferably, the content is 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 easily separate from the raw material mixture. Also, an excess of 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. More preferably, the content is 19.0 parts by mass or less, or 18.0 parts by mass or less.

[0045] [1.2.5. Content of desiccant] If the amount of desiccant is too low, the moisture mixed into the raw material may react with the bifunctional isocyanate, making it difficult to adjust the density of the polyurethane foam. In addition, cell roughness may occur in the polyurethane foam. Therefore, the amount of desiccant is preferably 0.1 parts by mass or more. More preferably, the amount is 0.3 parts by mass or more, or 0.5 parts by mass or more.

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

[0047] [1.2.6. Antioxidant Content] When a raw material mixture is heated and cured, some of the raw materials may oxidize. Furthermore, after the polyurethane foam is formed, it may discolor due to oxidation. On the other hand, adding an antioxidant to the raw material mixture can suppress the 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. More preferably, the content is 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, the content is 0.4 parts by mass or less, or 0.3 parts by mass or less.

[0049] [1.2.7. Isocyanate Index] The "isocyanate index" is the value obtained by multiplying the ratio of the equivalent amount of isocyanate groups in the polyisocyanate in the raw material mixture to the equivalent amount of active hydrogen groups in the raw material mixture by 100.

[0050] If the isocyanate index becomes too low, 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, an isocyanate index of 97 or higher is preferable. More preferably, the isocyanate index is 98 or higher, 99 or higher, or 100 or higher.

[0051] On the other hand, if the isocyanate index becomes too high, the polyurethane foam may become excessively hard and brittle. Therefore, an isocyanate index of 115 or less is preferable. More preferably, the isocyanate index is 114 or less, 113 or less, or 112 or less.

[0052] [1.2.8. Content of foaming gas] "Foaming gas content" refers to the volume of foaming gas when the volume of the raw materials excluding the foaming gas is set to 100.

[0053] If the foaming gas content is too low, foaming may be insufficient. Therefore, the foaming gas content is preferably 10 parts by volume or more. More preferably, the content is 40 parts by volume or more, or 50 parts by volume or more. On the other hand, if the foaming gas content is excessive, foam collapse and coalescence are more likely to occur in the foamed liquid. Therefore, the foaming gas content is preferably 95 parts by volume or less. More preferably, the content is 85 parts by volume or less, or 75 parts by volume or less.

[0054] [1.3. Reaction of the raw material mixture] The polyurethane foam according to the present invention is manufactured using the mechanical flossing method. The "mechanical flossing method" refers to: (a) Using a high-shear mixer, the raw material mixture is mixed while blowing in an inert gas to obtain a foamed raw material mixture containing fine bubbles. (b) Apply the foaming raw material mixture to the surface of a substrate (e.g., PET film), (c) Heat the coating to a predetermined temperature and cure it. It refers to a method. In this invention, the reaction conditions for the raw material mixture are not particularly limited, and optimal conditions can be selected according to the purpose.

[0055] [1.4. Characteristics] [1.4.1. Rebound elasticity] "Rebound elasticity" refers to the value measured in accordance with JIS K 6400-3.

[0056] The polyurethane foam according to the present invention exhibits high resilience because it uses polyether polyol A, a chain extender, and a bifunctional isocyanate as raw materials that meet predetermined conditions. When the manufacturing conditions are optimized, the rebound elasticity becomes 40% or more. When the manufacturing conditions are further optimized, the rebound elasticity becomes 45% or more, or even 50% or more.

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

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

[0059] [1.4.3. Compression Residual Strain] "Compressive residual strain" refers to the value measured in accordance with JIS K 6401:2011.

[0060] The polyurethane foam according to the present invention uses a polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy predetermined conditions as raw materials, and thus exhibits low compressive residual strain. When the production conditions are optimized, the compressive residual strain becomes 20% or less. When the production conditions are further optimized, the compressive residual strain becomes 10% or less, or 5% or less.

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

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

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

[0064] The polyurethane foam according to the present invention uses a polyether polyol A, a chain extender, and a bifunctional isocyanate that satisfy predetermined conditions as raw materials, and thus exhibits high tensile strength. 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 the value measured under the conditions described later. "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 according to the present invention uses polyether polyol A, a chain extender, and a bifunctional isocyanate as raw materials that meet predetermined conditions, and therefore does not harden easily even at low temperatures. In other words, the polyurethane foam according to the present invention exhibits a storage modulus close to that of room temperature even at low temperatures. By optimizing the manufacturing conditions, the difference in storage modulus becomes less than 1.40 MPa. By further optimizing the manufacturing conditions, the difference in storage modulus becomes 1.20 MPa or less, 1.00 MPa or less, or 0.80 MPa or less.

[0067] [1.5. Usage] The polyurethane foam according to the present invention can be used in apparel, sporting goods, toys, bedding, interior furnishings, shoe insoles, inter-cell cushions for EV batteries, cushions for pressure sensors, and the like. The polyurethane foam according to the present invention is particularly suitable as an insole for shoes. Furthermore, since the polyurethane foam according to the present invention exhibits viscoelasticity even at low temperatures, it is suitable for packaging materials, cushioning materials, and insulation materials for cold climates, which are intended for use at sub-zero temperatures.

[0068] [2. Effect] When a raw material mixture containing a high molecular weight polyol with two functional groups, a polyisocyanate with more than two functional groups, and a chain extender is reacted and foamed using the mechanical flossing method, a polyurethane foam exhibiting high rebound elasticity is obtained. However, 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 with 3 to 4 functional groups, a bifunctional isocyanate, and a chain extender is reacted and foamed using the mechanical flossing method, a polyurethane foam with high rebound elasticity and excellent flexibility is obtained.

[0070] The rebound elasticity has improved because (a) Because a low molecular weight chain extender and a bifunctional isocyanate react first to form a hard segment, and then a high molecular weight polyol is added to the hard segment to form a soft segment, and (b) The hard segments bonded to each other via hydrogen bonds to form a crystalline phase, which promoted the phase separation of the long, branched main chain (soft segment) and the short chain (hard segment). It is thought that... The increase in elongation is thought to be due to a moderate decrease in crosslink density caused by the use of high molecular weight polyols. [Examples]

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

[0072] [Table 1]

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

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

[0075] [2.2. Rebound elasticity] A 50mm x 50mm x 50mm test specimen was prepared from polyurethane foam. The rebound elasticity of the obtained test specimen was measured in accordance with JIS K 6255.

[0076] [2.3. Growth] A dumbbell-shaped test specimen (No. 3) was prepared from polyurethane foam. The elongation of the obtained specimen was measured in accordance with JIS K 6251:2010. The tensile speed of the specimen was 200 mm / min. The elongation was calculated using the following formula, based on the initial gauge length L0 and the gauge length L at the time of specimen cutting. Elongation (%) = (L - L0) × 100 / L0

[0077] [2.4. Tensile Strength] A dumbbell-shaped test specimen (No. 3) was prepared from polyurethane foam. The tensile strength of the obtained test specimen was measured in accordance with JIS K 6251:2010. The tensile speed of the test specimen was 200 mm / min. The area S [m²] of the parallel section of the test specimen was measured. 2 Using the maximum tensile force F[N] until the test specimen broke, the tensile strength was calculated using the following formula. Tensile strength [MPa] = F / S

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

[0079] [3. Results] The results are shown in Tables 2-5. Tables 2-5 also show the raw material composition for each sample. The values ​​for each raw material represent parts by mass. Regardless of the type of chain extender, the amount of chain extender added was 0.023 mol equivalent, 0.046 mol equivalent, or 0.069 mol equivalent per 100 parts by mass of polyether polyol A.

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

[0081] (1) Comparative Example 1 has low elongation and tensile strength. This is thought to be because the degree of crosslinking was excessively high due to the use of crude MDI with 2.4 functional groups as the polyisocyanate component. (2) When the weight-average molecular weight of the polyol was 3000 (Comparative Examples 2-9, 11), the elongation was less than 200%, regardless of the type of chain extender. Also, with the exception of Comparative Examples 4, 6, and 7, the rebound elasticity was less than 40%.

[0082] (3) When the weight-average molecular weight of the polyol is 3500 or more, and the chain extender has a linear structure (Examples 1-26), it was found that the rebound elasticity is 40% or more and the elongation is 200% or more. (4) Examples 3, 12, and 21 showed high rebound elasticity and elongation, but their tensile strength was less than 0.20 MPa. This is thought to be because the molecular weight of the main polyol was relatively low, and the content of the chain extender was also relatively low, resulting in insufficient phase separation of the hard segment phase and a reduced physical crosslinking force due to hydrogen bonding.

[0083] (5) When 1,6-hexanediol was used as a chain extender (Examples 19-26, Comparative Examples 8-11), the number of samples with compressive residual strain exceeding 10% increased. This is thought to be because 1,6-hexanediol has a relatively long molecular chain, resulting in a weak ability to form hard segment phases, and the physical crosslinking points are easily destroyed by heating and compression, impairing the springiness (resilience) of the polyurethane.

[0084] (6) Comparative Example 10 had a rebound elasticity 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 3500 or more, and the chain extender had a linear structure. However, the compressive residual strain of Comparative Example 10 was 23.4%. This is thought to be because there was an excess of reaction intermediates formed between 1,6-hexanediol and diisocyanate in the initial stages of the reaction, and because the reactivity between the main polyol and diisocyanate decreased.

[0085] (7) When a diol with a linear structure was used as the chain extender (Examples 1-26, Comparative Examples 2-11), it was observed that as the amount of chain extender added increased, the rebound elasticity and tensile strength increased, the elongation decreased, and the compressive residual strain increased. (8) When a diol with a branched structure was used as a chain extender (Examples 27-28, Comparative Examples 12-15), the properties tended to be slightly lower compared to when a diol with a linear structure was used. However, it was found that even when a diol with a branched structure was used, increasing the amount added made it possible to achieve both high rebound elasticity and high elongation.

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] [Table 5]

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

[0091] [Table 6]

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

[0093] Measurement temperature range: -80℃~50℃ 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 for each sample. The values ​​for each raw material represent parts by mass. Figure 3 shows the relationship between the storage modulus G' and the 25% CLD hardness of the polyurethane foam obtained in Example 29. From Table 7 and Figure 3, the following can be observed.

[0096] (1) Comparative Example 16 showed a storage modulus difference exceeding 1.40 MPa. This is thought to be due to the use of a polyether polyol with a molecular weight of less than 3500. (2) In all of Examples 29 to 32, the difference in storage modulus was less than 0.80 MPa. This result indicates that when a polyether polyol with a molecular weight of 3500 or more, preferably 4000 or more, or 5000 or more is used as the main raw material, it does not harden easily even at low temperatures and good rebound elasticity is maintained 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 all of Examples 29 to 32 maintain a 25%CLD hardness of 0.15 MPa or less at -40°C.

[0097] [Table 7]

[0098] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

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

Claims

1. It 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 foaming gas, and without water. The polyol component includes polyether polyol A having 3 to 4 functional groups and a weight-average molecular weight of 3500 to 13000. The chain extender comprises a diol with a molecular weight of 200 or less. The aforementioned polyisocyanate component is a polyurethane foam containing a difunctional isocyanate, The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ Shoe insoles featuring the following polyurethane foam.

2. The shoe insole according to claim 1, wherein the tensile strength is 0.20 MPa or more.

3. The shoe insole according to claim 1, wherein the raw material mixture further comprises a nucleating agent and / or a hygroscopic agent.

4. It 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 foaming gas. The aforementioned polyol component consists solely of polyether polyol A, which has 3 to 4 functional groups and a weight-average molecular weight of 3500 to 13000. The chain extender comprises a diol with a molecular weight of 200 or less. The aforementioned polyisocyanate component is a polyurethane foam containing a difunctional isocyanate. There is, The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ The following is polyurethane foam.

5. It contains polyether polyol A having 3 to 4 functional groups and a weight-average molecular weight of 3500 to 13000. Difunctional isocyanates and A polyurethane foam obtained from a raw material mixture containing a chain extender, The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ The following: Polyurethane foam with a storage modulus difference of less than 1.40 MPa.

6. Obtained by reacting and foaming a mixture of raw materials containing a desiccant, The aforementioned desiccant is a polyurethane foam comprising at least one selected from zeolite, silica powder, lithium hydroxide powder, barium hydroxide powder, and calcium chloride powder. The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ The following is polyurethane foam.

7. It 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 foaming gas. The polyol component includes polyether polyol A having 3 to 4 functional groups and a weight-average molecular weight of 3500 to 13000. The chain extender comprises a diol with a molecular weight of 200 or less. The aforementioned polyisocyanate component is a polyurethane foam containing a difunctional isocyanate, The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. The density is 400 kg / m ３ or more and 800 kg / m ３ or less, and A polyurethane foam having a tensile strength of 0.20 MPa or more and 0.96 MPa or less.

8. Contains a desiccant, A polyurethane foam obtained by reacting and foaming a water-free raw material mixture, The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ The following is polyurethane foam.

9. An intercell cushion for a battery comprising the polyurethane foam described in any one of claims 4 to 8.

10. A cushion for a pressure sensor comprising the polyurethane foam described in any one of claims 4 to 8.

11. A cushioning material for cold climates comprising the polyurethane foam described in any one of claims 4 to 8.

12. The rebound elasticity is 40% or more. The growth rate is over 200%, The compression set is 20% or less. Density of 150 kg / m³ ３ More than 800kg / m ３ Cold-weather packaging material equipped with polyurethane foam, as described below.

13. A cold-weather insulation material comprising the polyurethane foam described in any one of claims 4 to 8.

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