Polyester polyol, polyurethane foam using the same and method for producing polyester polyol

Abstract

An object of the present invention is to provide a biomass-derived polyester polyol that has a high compatibility with a variety of foaming agents, and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced.　The present invention relates to a polyester polyol for a polyurethane foam, wherein the polyester polyol comprises a polyester polyol that is a reaction product of raw-material compounds containing:　 a rosin (a) containing a resin acid (a1) having a conjugated double bond;　 a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1);　 an α,β-unsaturated carboxylic acid (c); and　 a polyol (d) containing a diol (d1) having an ether bond.

Description

POLYESTER POLYOL, POLYURETHANE FOAM USING THE SAME AND METHOD FOR PRODUCING POLYESTER POLYOL

[0001] The present invention relates to a polyester polyol derived from biomass, a polyurethane foam produced using the same and a method for producing the polyester polyol.

[0002] Conventionally, polyurethane foams have been used as a heat insulating material in various applications.　Examples of the applications include architecture members (a roof, a ceiling, and a wall of architecture, etc.), appliances (a refrigerator, a hot-water supply, etc.), vehicles (an automobile, an aircraft, a ship, etc.), pipes, and tanks.

[0003] A polyurethane foam is produced by a reaction of a polyol with a polyisocyanate in the presence of a foaming agent.　As such a polyol, a polyester polyol is used.　For example, a polyester polyol is produced by dehydration condensation of a polybasic acid and a polyhydric alcohol.　A conventional polyester polyol is generally produced from raw materials derived from fossil resources, such as petroleum.

[0004] Patent Literature 1: Japanese Patent Application Laid-Open No. 2021-038409

[0005] In recent years, attention has largely been paid to problems such as global warming and depletion of fossil resources.　From such a viewpoint, a polyester polyol derived from biomass is desirably used in the production of a polyurethane foam.

[0006] However, investigation of influence of the biomass-derived polyester polyol on physical properties of the polyurethane foam is insufficient.　The present inventors have investigated and found that the biomass-derived polyester polyol may reduce the compressive strength of the polyurethane foam.

[0007] In the production of the polyurethane foam, a variety of foaming agents, such as a hydrocarbon and a hydrofluoroolefin, is used.　However, the conventional polyester polyol may have a low compatibility with the foaming agent.　A polyester polyol having a low compatibility with the foaming agent is difficult to use in the production of the polyurethane foam.　Therefore, a polyester polyol is required to have a high compatibility with a variety of foaming agents.

[0008] An object of the present invention is to provide a biomass-derived polyester polyol that has a high compatibility with a variety of foaming agents, and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced.

[0009] In view of the above-described problems, the inventors have made various investigations, and as a result found that the problems can be solved by the following polyester polyol.

[0010] The present invention is a polyester polyol for a polyurethane foam, 　　　 the polyester polyol including a polyester polyol that is a reaction product of raw material compounds containing: 　　　　　　　a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　　　　　a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　　　　　an α,β-unsaturated carboxylic acid 　　　　　　　a polyol (d) containing a diol (d1) having an ether bond.

[0011] The present invention can provide a biomass-derived polyester polyol that has a high compatibility with a variety of foaming agents and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced, despite use of a biomass raw material.

[0012] (Polyester polyol) 　　　 The present invention relates to a polyester polyol for a polyurethane foam.　The polyester polyol includes a polyester polyol that is a reaction product of raw material compounds containing: 　　　　　　　a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　　　　　a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　　　　　an α,β-unsaturated carboxylic acid (c); and 　　　　　　　a polyol (d) containing a diol (d1) having an ether bond.

[0013] The polyester polyol for a polyurethane foam is preferably the polyester polyol that is a reaction product of raw material compounds containing: 　　　　　　　a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　　　　　a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　　　　　an α,β-unsaturated carboxylic acid (c); and 　　　　　　　a polyol (d) containing a diol (d1) having an ether bond.

[0014] For the polyester polyol of the present invention, as raw materials derived from biomass, the rosin (a) containing the resin acid (a1) having a conjugated double bond, and the biomass-derived fatty acid (b) containing the unsaturated fatty acid (b1) are used.　To each of the rosin (a) and the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c) is added by a Diels-Alder reaction or an ene reaction, to obtain a polybasic acid having a plurality of carboxy groups.　Further, the carboxy groups are esterified with a hydroxyl group of the polyol (d), to obtain a polyester polyol.

[0015] As described above, the use of the rosin (a) modified by the α,β-unsaturated carboxylic acid (c) can reduce a reduction in compressive strength of a polyurethane foam.　However, the single use of the rosin (a) modified by the α,β-unsaturated carboxylic acid (c) may reduce the compatibility of the polyester polyol with a foaming agent.　As a countermeasure for this, the biomass-derived fatty acid (b) modified by the α,β-unsaturated carboxylic acid (c) is used to enhance the compatibility of the polyester polyol with a foaming agent.

[0016] Therefore, the rosin (a) modified by the α,β-unsaturated carboxylic acid (c) is used in combination with the biomass-derived fatty acid (b) modified by the α,β-unsaturated carboxylic acid (c).　Thus, a polyester polyol that has a high compatibility with a variety of foaming agents and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced, despite the use of a biomass raw material, can be provided.

[0017] In the present invention, "biomass" means an organic resource derived from an organism or a plant except for resources derived from fossil resources.　Examples of biomass include wood, seaweed, animal carcass and excreta, and plankton.

[0018] "Derived from biomass" means that a substance is produced using an organic resource derived from an organism or a plant as at least a portion of a raw material and a substance produced using only a resource derived from fossil resources alone is excluded.

[0019] In contrast, the substance produced using only a resource derived from fossil resources without using an organic resource derived from an organism or a plant is referred to as a substance "derived from fossil resources".　Examples of the resource derived from fossil include coal, petroleum, and natural gas.

[0020] The polyester polyol of the present invention is a reaction product of raw material compounds containing the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) as each described above.　Hereinafter, the raw material compounds constituting the polyester polyol of the present invention will be described in order.

[0021] (Rosin (a)) 　　　 The rosin (a) is derived from biomass and is used as one of the raw material compounds constituting the polyester polyol.　The rosin (a) is generally obtained by distilling plant oleoresin and removing a volatile component.　Examples of the plant oleoresin include a pine resin contained in Pinaceae plants.　Examples of the volatile component include turpentine oil.

[0022] The rosin (a) contains the resin acid (a1) having a conjugated double bond.　The number of carbon atoms of the resin acid (a1) having a conjugated double bond is preferably 12 or more, more preferably 15 or more, and more preferably 18 or more.　The number of carbon atoms of the resin acid (a1) having a conjugated double bond is preferably 35 or less, more preferably 30 or less, and more preferably 25 or less.　It is preferable that the resin acid (a1) having a conjugated double bond be a monocarboxylic acid having one carboxy group in a molecule.

[0023] To the conjugated double bond of the resin acid (a1), the α,β-unsaturated carboxylic acid (c) can be added by a Diels-Alder reaction.　The conjugated double bond of the resin acid (a1) is preferably at least one of an s-cis-type conjugated double bond, and a conjugated double bond capable of being isomerized to form an s-cis-type conjugated double bond.　An s-cis-type conjugated double bond is more preferred.　Examples of the conjugated double bond capable of being isomerized to form an s-cis-type conjugated double bond includes an s-trans-type conjugated double bond capable of being isomerized to form an s-cis-type conjugated double bond.　An s-cis-type conjugated double bond means a conjugated double bond in which two double bonds are placed on the same side (cis-type) with respect to a single bond (s) which binds the two double bonds in the conjugated double bond.　An s-trans-type conjugated double bond means that a conjugated double bond in which two double bonds are placed on a different side (trans-type) with respect to a single bond (s) which binds the two double bonds in the conjugated double bond.　It is preferable that the conjugated double bond of the resin acid (a1) do not include a double bond contained in an aromatic ring structure.　In addition, it is preferable that the resin acid (a1) having a conjugated double bond do not include an aromatic polycarboxylic acid (e) and an aromatic resin acid.

[0024] Examples of the resin acid (a1) having a conjugated double bond include alicyclic resin acids such as abietic acid, neoabietic acid, palustric acid, and levopimaric acid.　Among these, levopimaric acid is preferred.　Since levopimaric acid is in a s-cis conformation, levopimaric acid has high reactivity with the α,β-unsaturated carboxylic acid (c).　One type of the resin acid (a1) having a conjugated double bond may be used alone, or two or more types thereof may be used in combination.

[0025] Abietic acid, neoabietic acid, and palustric acid can be easily isomerized to levopimaric acid by heating in a reaction with the α,β-unsaturated carboxylic acid (c), and the like.　Therefore, as levopimaric acid, levopimaric acid to which abietic acid, neoabietic acid, and palustric acid are each isomerized can be used.　That is, levopimaric acid may be an isomerized product of at least one of abietic acid, neoabietic acid, or palustric acid.　It is preferable that levopimaric acid be an isomerized product of at least one of abietic acid, neoabietic acid, or palustric acid.

[0026] It is preferable that abietic acid, neoabietic acid, and palustric acid be isomerized to levopimaric acid by heating.　The heating temperature is preferably 150 to 300°C, and more preferably 175 to 200°C.

[0027] The content of the resin acid (a1) having a conjugated double bond in the rosin (a) is preferably 25% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, and more preferably 55% by mass or more.　The content of the resin acid (a1) having a conjugated double bond in the rosin (a) is preferably 100% by mass or less, more preferably 90% by mass or less, more preferably 80% by mass or less, and more preferably 70% by mass or less.

[0028] The rosin (a) preferably contains a resin acid (a2) which is at least one of an alicyclic resin acid having no conjugated double bond and an aromatic resin acid.　The number of carbon atoms of the resin acid (a2) is preferably 12 or more, more preferably 15 or more, and more preferably 18 or more.　The number of carbon atoms of the resin acid (a2) is preferably 35 or less, more preferably 30 or less, and more preferably 25 or less.　It is preferable that the resin acid (a2) be a monocarboxylic acid having one carboxy group in a molecule.

[0029] Examples of the resin acid (a2) include alicyclic resin acids having no conjugated double bond such as pimaric acid, isopimaric acid and sandaracopimaric acid; and aromatic resin acids such as dehydroabietic acid.　Among these, pimaric acid, isopimaric acid, and dehydroabietic acid are preferred, and pimaric acid and dehydroabietic acid are more preferred.　One type of the resin acid (a2) may be used alone, or two or more types thereof may be used in combination.

[0030] The content of the resin acid (a2) in the rosin (a) is preferably 1% by mass or more, and more preferably 15% by mass or more.　The content of the resin acid (a2) in the rosin (a) is preferably 50% by mass or less, more preferably 40% by mass or less, and more preferably 35% by mass or less.

[0031] Examples of the rosin (a) containing the resin acid (a1) having a conjugated double bond include rosins derived from biomass, such as a gum rosin, a tall oil rosin, and a wood rosin.　Among these, a tall oil rosin is preferred.　The use of a tall oil rosin can reduce a reduction in compressive strength of a polyurethane foam.　One type of the rosin derived from biomass may be used alone, or two or more types thereof may be used in combination.

[0032] The content of the rosin (a) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more.　The content of the rosin (a) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 35% by mass or less, more preferably 25% by mass or less, and particularly preferably 23% by mass or less.　The rosin (a) in a content that is equal to or more than the lower limit value can reduce a reduction in compressive strength of the polyurethane foam.　The rosin (a) in a content that is equal to or less than the upper limit value makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.

[0033] (Biomass-Derived Fatty Acid (b)) 　　　 The biomass-derived fatty acid (b) is used as one of the raw material compounds constituting the polyester polyol.　The biomass-derived fatty acid (b) contains the unsaturated fatty acid (b1).　The unsaturated fatty acid (b1) is also derived from biomass.

[0034] The biomass-derived fatty acid (b) is an aliphatic monocarboxylic acid having one carboxyl group at a terminal of a linear or branched hydrocarbon chain.　Examples of the biomass-derived fatty acid (b) includes an aliphatic monocarboxylic acid represented by R-COOH (wherein R is a linear or branched, saturated or unsaturated, monovalent hydrocarbon group).

[0035] Examples of the unsaturated fatty acid (b1) includes an aliphatic monocarboxylic acid represented by R1-COOH (wherein R1is a linear or branched, unsaturated monovalent hydrocarbon group).

[0036] The number of carbon atoms of the unsaturated fatty acid (b1) is preferably 12 or more, more preferably 14 or more, and more preferably 16 or more.　The number of carbon atoms of the unsaturated fatty acid (b1) is preferably 30 or less, and more preferably 25 or less.

[0037] Examples of the unsaturated fatty acid (b1) include myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, eicosenoic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, and arachidonic acid.　Palmitoleic acid, oleic acid, and linoleic acid are preferred, and oleic acid and linoleic acid are more preferred.　One type of the unsaturated fatty acid (b1) may be used alone, or two or more types thereof may be used in combination.

[0038] The content of the unsaturated fatty acid (b1) in the biomass-derived fatty acid (b) is preferably 50% by mass or more, and more preferably 70% by mass or more.　The content of the unsaturated fatty acid (b1) in the biomass-derived fatty acid (b) is preferably 100% by mass or less, more preferably 97% by mass or less, more preferably 95% by mass or less, and more preferably 93% by mass or less.

[0039] It is preferable that the biomass-derived fatty acid (b) contain a saturated fatty acid (b2).　Examples of the saturated fatty acid (b2) includes an aliphatic monocarboxylic acid represented by R2-COOH (wherein R2is a linear or branched, saturated monovalent hydrocarbon group).

[0040] Examples of the saturated fatty acid (b2) include octanoic acid (caprylic acid), nonanoic acid, decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid), eicosanoic acid (arachidic acid), docosanoic acid (behenic acid), and tetracosanoic acid.　Among these, palmitic acid, heptadecanoic acid, and stearic acid are preferred.　One type of the saturated fatty acid (b2) may be used alone, or two or more types thereof may be used in combination.

[0041] The content of the saturated fatty acid (b2) in the biomass-derived fatty acid (b) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and more preferably 2% by mass or more.　The content of the saturated fatty acid (b2) in the biomass-derived fatty acid (b) is preferably 30% by mass or less, more preferably 20% by mass or less, and more preferably 10% by mass or less.

[0042] Examples of the biomass-derived fatty acid (b) include a linseed oil fatty acid, a tung oil fatty acid, a castor oil fatty acid, a soybean oil fatty acid, a tall oil fatty acid, a rice bran oil fatty acid, a palm oil fatty acid, a coconut oil fatty acid, a dehydrated castor oil fatty acid, a sunflower oil fatty acid, a rapeseed oil fatty acid, a canola oil fatty acid, and a cotton seed oil fatty acid.　Among these, a tall oil fatty acid is preferred.　One type of the biomass-derived fatty acid (b) may be used alone, or two or more types thereof may be used in combination.

[0043] The content of the biomass-derived fatty acid (b) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 17% by mass or more, and particularly preferably 19% by mass or more.　The content of the biomass-derived fatty acid (b) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 35% by mass or less, more preferably 30% by mass or less, more preferably 25% by mass or less, more preferably 24% by mass or less, and particularly preferably 22% by mass or less.　The biomass-derived fatty acid (b) in a content that is equal to or more than the lower limit value makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.　The biomass-derived fatty acid (b) in a content that is equal to or less than the upper limit value can reduce a reduction in compressive strength of the polyurethane foam.

[0044] The mass ratio [(a) / (b)] of the rosin (a) to the biomass-derived fatty acid (b) in the raw material compounds is more preferably 0.13 or more, more preferably 0.50 or more, more preferably 0.75 or more, and particularly preferably 0.80 or more.　The mass ratio [(a) / (b)] of the rosin (a) to the biomass-derived fatty acid (b) in the raw material compounds is preferably 2.00 or less, more preferably 1.50 or less, and particularly preferably 1.20 or less.　The mass ratio [(a) / (b)] that is equal to or more than the lower limit value can reduce a reduction in compressive strength of the polyurethane foam.　The mass ratio [(a) / (b)] that is equal to or less than the upper limit value makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.

[0045] (α,β-unsaturated Carboxylic acid (c)) 　　　 The α,β-unsaturated carboxylic acid (c) is used as raw material compounds constituting the polyester polyol.　The α,β-unsaturated carboxylic acid (c) is added to the aforementioned rosin (a) and biomass-derived fatty acid (b), respectively, by a Diels-Alder reaction or an ene reaction.　Thus, a carboxy group can be introduced into each of the rosin (a) and the biomass-derived fatty acid (b).　As a result, the rosin (a) and the biomass-derived fatty acid (b) can be introduced into the molecular structure of the polyester polyol.　The α,β-unsaturated carboxylic acid (c) is preferably an α,β-unsaturated aliphatic carboxylic acid.

[0046] Examples of the α,β-unsaturated carboxylic acid (c) include an α,β-unsaturated dicarboxylic acid (c1) and an α,β-unsaturated monocarboxylic acid (c2).　Among these, the α,β-unsaturated dicarboxylic acid (c1) is preferred.　One type of the α,β-unsaturated carboxylic acid (c) may be used alone, or two or more types thereof may be used in combination.

[0047] The α,β-unsaturated carboxylic acid (c) preferably contains the α,β-unsaturated dicarboxylic acid (c1).　The α,β-unsaturated dicarboxylic acid (c1) has unsaturated bonds.　Thus, the α,β-unsaturated dicarboxylic acid (c1) can serve as dienophiles in the Diels-Alder reaction and enophiles in the ene reaction.　Examples of the unsaturated bonds include a carbon-carbon double bond, and a carbon-carbon triple bond.　Among these, a carbon-carbon double bond is preferable.　The α,β-unsaturated dicarboxylic acid (c1) is preferably an α,β-unsaturated aliphatic dicarboxylic acid.

[0048] The number of carbon atoms of the α,β-unsaturated dicarboxylic acid (c1) is preferably 10 or less, more preferably 8 or less, and more preferably 5 or less.　The number of carbon atoms of the α,β-unsaturated dicarboxylic acid (c1) is preferably 3 or more, and more preferably 4 or more.

[0049] Examples of the α,β-unsaturated dicarboxylic acid (c1) include an α,β-unsaturated dicarboxylic acid and an anhydride thereof, and an α,β-unsaturated aliphatic dicarboxylic acid and an anhydride thereof are preferable.　Specific examples include fumaric acid, itaconic acid, maleic acid, mesaconic acid, citraconic acid, and anhydrides thereof.　Among these, maleic acid and maleic anhydride are preferable, and maleic anhydride is more preferable.　As the α,β-unsaturated dicarboxylic acid (c1), itaconic acid, mesaconic acid, citraconic acid, or anhydrides thereof formed by the thermal decomposition of citric acid can also be used.　One type of the α,β-unsaturated dicarboxylic acid (c1) may be used alone, or two or more types thereof may be used in combination.

[0050] The content of the α,β-unsaturated dicarboxylic acid (c1) in the α,β-unsaturated carboxylic acid (c) is preferably 50% by mass or more, more preferably 80% by mass or more, more preferably 98% by mass or more, and more preferably 99% by mass or more.　The content of the α,β-unsaturated dicarboxylic acid (c1) in the α,β-unsaturated carboxylic acid (c) is preferably 100% by mass or less.

[0051] The α,β-unsaturated carboxylic acid (c) may contain α,β-unsaturated monocarboxylic acid (c2).　The α,β-unsaturated monocarboxylic acid (c2) is preferably an α,β-unsaturated aliphatic monocarboxylic acid.

[0052] The number of carbon atoms of the α,β-unsaturated monocarboxylic acid (c2) is preferably 10 or less, more preferably 8 or less, and more preferably 5 or less.　The number of carbon atoms of the α,β-unsaturated monocarboxylic acid (c2) is preferably 3 or more.　Examples of the α,β-unsaturated monocarboxylic acid (c2) include an α,β-unsaturated monocarboxylic acid and an anhydride thereof, and an α,β-unsaturated aliphatic monocarboxylic acid and an anhydride thereof are preferred.　Specific examples thereof include acrylic acid, methacrylic acid, and crotonic acid.　One type of the α,β-unsaturated monocarboxylic acid (c2) may be used alone, or two or more types thereof may be used in combination.

[0053] In the raw material compounds, the mass ratio [(c) / (a)] of the α,β-unsaturated carboxylic acid (c) to the rosin (a) is preferably 0.15 or more, more preferably 0.30 or more, more preferably 0.45 or more, and particularly preferably 0.47 or more.

[0054] In the raw material compounds, the mass ratio [(c) / (a)] of the α,β-unsaturated carboxylic acid (c) to the rosin (a) is preferably 2.00 or less, more preferably 1.50 or less, more preferably 0.90 or less, more preferably 0.55 or less, and particularly preferably 0.51 or less.

[0055] In the raw material compounds, the mass ratio [(c) / (a + b)] of the α,β-unsaturated carboxylic acid (c) to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.05 or more, more preferably 0.10 or more, more preferably 0.19 or more, and particularly preferably 0.21 or more.

[0056] In the raw material compounds, the mass ratio [(c) / (a + b)] of the α,β-unsaturated carboxylic acid (c) to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.45 or less, more preferably 0.30 or less, more preferably 0.26 or less, and particularly preferably 0.24 or less.

[0057] The content of the α,β-unsaturated carboxylic acid (c) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 5.0% by mass or more, more preferably 7.5% by mass or more, more preferably 7.7% by mass or more, and particularly preferably 8.5% by mass or more.　The content of the α,β-unsaturated carboxylic acid (c) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 15.0% by mass or less, more preferably 12.0% by mass or less, more preferably 11.0% by mass or less, more preferably 10.5% by mass or less, more preferably 9.5% by mass or less, and particularly preferably 9.0% by mass or less.　The α,β-unsaturated carboxylic acid (c) in a content that is equal to or more than the above-mentioned lower limit can introduce a sufficient amount of the carboxy group into the rosin (a) and the biomass-derived fatty acid (b).　The α,β-unsaturated carboxylic acid (c) in a content that is equal to or less than the above-mentioned upper limit can reduce a reduction in the compressive strength of the polyurethane foam.

[0058] (Polyol (d)) 　　　 The polyol (d) is used as one of the raw material compounds constituting the polyester polyol.　The polyol (d) contains a diol (d1) with an ether bond.　Use of the diol (d1) with an ether bond makes it possible to provide a polyester polyol having further improved compatibility with a foaming agent.

[0059] Examples of the diol (d1) with an ether bond include an aliphatic diol with an ether bond.　Specific examples thereof include a polyethylene glycol such as diethylene glycol, triethylene glycol, and tetraethylene glycol; and a polypropylene glycol such as dipropylene glycol, tripropylene glycol, and tetrapropylene glycol.　Among these, a polyethylene glycol is preferable.　Furthermore, diethylene glycol, triethylene glycol, and tetraethylene glycol are preferable, and diethylene glycol is more preferable.　One type of the diol (d1) may be used alone, or two or more types thereof may be used in combination.

[0060] In the raw material compounds, the mass ratio [(d1) / (a + b)] of the diol (d1) with an ether bond to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.30 or more, more preferably 0.70 or more, more preferably 1.10 or more, and particularly preferably 1.12 or more.　The mass ratio [(d1) / (a + b)] that is equal to or more than the above-mentioned lower limit makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.

[0061] In the raw material compounds, the mass ratio [(d1) / (a + b)] of the diol (d1) with an ether bond relative to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 2.00 or less, more preferably 1.50 or less, and particularly preferably 1.35 or less.　The mass ratio [(d1) / (a + b)] that is equal to or less than the above-mentioned upper limit makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.

[0062] The content of the diol (d1) with an ether bond in the polyol (d) is preferably 20% by mass or more, more preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more.　The content of the diol (d1) with an ether bond in the polyol (d) is preferably 100% by mass or less, more preferably 99% by mass or less, and more preferably 98% by mass or less.

[0063] The polyol (d) preferably contains a trivalent or higher polyol (d2).　Use of a trivalent or higher polyol (d2) makes it possible to moderately improve the degree of branching of the polyester polyol, and to improve the reactivity with a polyisocyanate.　This makes it possible to further reduce the reduction in the compressive strength of the polyurethane foam.

[0064] The trivalent or higher polyol (d2) is preferably a trivalent or higher aliphatic polyol.　Examples thereof include glycerin, trimethylolethane, trimethylolpropane, erythritol, diglycerin, pentaerythritol, sorbitol, sorbitan, and dipentaerythritol.　Among these, an aliphatic polyol having 3 to 12 carbon atoms is preferable.　Furthermore, glycerin, trimethylolethane, and trimethylolpropane are more preferable, and glycerin is more preferable.　One type of the polyol (d2) may be used alone, or two or more types thereof may be used in combination.

[0065] The trivalent or higher polyol (d2) may be derived from biomass.　For example, glycerin derived from biomass can also be used.　Examples of the biomass-derived glycerin include glycerin obtained by hydrolyzing triglycerides contained in fats and oils.

[0066] In the raw material compounds, the mass ratio [(d2) / (a + b)] of the trivalent or higher polyol (d2) relative to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.03 or more.　The mass ratio [(d2) / (a + b)] that is equal to or more than the above-mentioned lower limit makes it possible to reduce a reduction in compressive strength of the polyurethane foam.

[0067] In the raw material compounds, the mass ratio [(d2) / (a + b)] of the trivalent or higher polyol (d2) relative to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.35 or less, more preferably 0.20 or less, more preferably 0.08 or less, and particularly preferably 0.05 or less.　The mass ratio [(d2) / (a + b)] that is equal to or less than the above-mentioned upper limit makes it possible to lower the viscosity of the polyester polyol and to improve compatibility with a foaming agent.

[0068] The content of the trivalent or higher polyol (d2) in the polyol (d) is preferably 0.3% by mass or more, more preferably 2.5% by mass or more, and more preferably 2.7% by mass or more.　The content of the trivalent or higher polyol (d2) in the polyol (d) is preferably 30.0% by mass or less, more preferably 10.0% by mass or less, more preferably 6.0% by mass or less, and particularly preferably 4.0% by mass or less.

[0069] The content of the polyol (d) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 25.0% by mass or more, more preferably 35.0% by mass or more, and particularly preferably 45.0% by mass or more, and particularly preferably 50.0% by mass or more.　The content of the polyol (d) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) is preferably 70.0% by mass or less, more preferably 60.0% by mass or less, and particularly preferably 55.0% by mass or less.　The polyol (d) in a content that is equal to or more than the above-mentioned lower limit can increase the cross-linking density of the polyurethane foam, and reduce a reduction in the compressive strength.　The polyol (d) in a content that is equal to or less than the above-mentioned upper limit can increase the cross-linking density of the polyurethane foam, and reduce a reduction in the compressive strength.

[0070] (Aromatic Polycarboxylic acid (e)) 　　　 The raw material compounds preferably further include an aromatic polycarboxylic acid (e).　That is, the polyester polyol of the present invention is preferably a polyester polyol that is a reaction product of raw material compounds containing: 　　　 a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　 a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　 an α,β-unsaturated carboxylic acid (c); 　　　 a polyol (d) containing a diol (d1) having an ether bond; and 　　　 an aromatic polycarboxylic acid (e).

[0071] The use of the aromatic polycarboxylic acid (e) can improve the compressive strength of the polyurethane foam.

[0072] Examples of the aromatic polycarboxylic acid (e) include an aromatic polycarboxylic acid and an anhydride thereof.　Specific examples thereof include orthophthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, trimellitic acid, pyromellitic acid, and anhydrides thereof.　Among these, orthophthalic acid, isophthalic acid, terephthalic acid, and anhydrides thereof are preferable, and isophthalic acid and orthophthalic anhydride (anhydride of orthophthalic acid) are more preferable.　One type of the aromatic polycarboxylic acid (e) may be used alone, or two or more types thereof may be used in combination.

[0073] Terephthalic acid can be produced in the reaction mixture by hydrolyzing polyethylene terephthalate obtained from plastic products that are industrial waste.

[0074] From a viewpoint of the compressive strength, in the raw material compounds, the mass ratio [(e) / (a + b)] of the aromatic polycarboxylic acid (e) relative to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.05 or more, more preferably 0.10 or more, more preferably 0.20 or more, and particularly preferably 0.23 or more.　The mass ratio [(e) / (a + b)] that is equal to or more than the above-mentioned lower limit makes it possible to reduce a reduction in compressive strength of the polyurethane foam.

[0075] In the raw material compounds, the mass ratio [(e) / (a + b)] of the aromatic polycarboxylic acid (e) relative to the total amount of the rosin (a) and the biomass-derived fatty acid (b) is preferably 0.35 or less, more preferably 0.30 or less, more preferably 0.27 or less, and particularly preferably 0.25 or less.　The mass ratio [(e) / (a + b)] that is equal to or less than the above-mentioned upper limit makes it possible to lower the viscosity of the polyester polyol.

[0076] The content of the aromatic polycarboxylic acid (e) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), the polyol (d), and the aromatic polycarboxylic acid (e) is preferably 3.0% by mass or more, more preferably 5.0% by mass or more, more preferably 7.6% by mass or more, more preferably 8.1% by mass or more, and particularly preferably 8.6% by mass or more.　The content of the aromatic polycarboxylic acid (e) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), the polyol (d), and the aromatic polycarboxylic acid (e) is preferably 15.0% by mass or less, more preferably 10.0% by mass or less, and particularly preferably 9.5% by mass or less.　The aromatic polycarboxylic acid (e) in a content that is equal to or more than the above-mentioned lower limit makes it possible to reduce a reduction in compressive strength of the polyurethane foam.　The aromatic polycarboxylic acid (e) in a content that is equal to or less than the above-mentioned upper limit value makes it possible to provide a polyester polyol having improved compatibility with a foaming agent.

[0077] As described above, the polyester polyol of the present invention is a reaction product of the rosin (a), biomass-derived fatty acid (b), α,β-unsaturated carboxylic acid (c), and polyol (d).　The rosin (a) and the fatty acid (b) are each derived from biomass and are reacted with the α,β-unsaturated carboxylic acid (c) in order to introduce these components into the molecular structure of the polyester polyol.

[0078] Specifically, the rosin (a) contains the resin acid (a1) having a conjugated double bond.　The biomass-derived fatty acid (b) contains the unsaturated fatty acid (b1).　Therefore, when these components are reacted with the α,β-unsaturated carboxylic acid (c), the α,β-unsaturated carboxylic acid (c) is added to the resin acid (a1) by the Diels-Alder reaction, thereby forming an adduct.　In addition, the α,β-unsaturated carboxylic acid (c) is added to the unsaturated fatty acid (b1) by the Diels-Alder reaction or the ene reaction to form an adduct.

[0079] The polyester polyol of the present invention includes units derived from the above-mentioned adducts.　Examples of the units derived from the above-mentioned adducts include a unit (I) derived from the adduct obtained by adding the α,β-unsaturated carboxylic acid (c) to the resin acid (a1), and a unit (II) derived from the adduct obtained by adding the α,β-unsaturated carboxylic acid (c) to the unsaturated fatty acid (b1).

[0080] As the unit (I), a unit derived from an adduct obtained by adding maleic acid or maleic anhydride to levopimaric acid by a Diels-Alder reaction is preferable.　Levopimaric acid may be an isomerized product of at least one of abietic acid, neoabietic acid, and palustric acid.　The unit (II) is preferably at least one of a unit derived from an adduct obtained by adding maleic acid or maleic anhydride to oleic acid by an ene reaction, or a unit derived from an adduct obtained by adding maleic acid or maleic anhydride to linoleic acid by a Diels-Alder reaction, and more preferably both of the above units.

[0081] As described above, the Diels-Alder reaction or the ene reaction using the α,β-unsaturated carboxylic acid (c) makes it possible to introduce the rosin (a) and the biomass-derived fatty acid (b) into the molecular structure of the polyester polyol.

[0082] Furthermore, a plurality of carboxyl groups derived from the rosin (a), biomass-derived fatty acid (b), and α,β-unsaturated carboxylic acid (c) used as raw material compounds are subjected to a condensation reaction with the hydroxyl group of the polyol (d) to form an ester bond, thereby obtaining the polyester polyol.

[0083] (Method for Producing Polyester Polyol) 　　　 A method for producing the polyester polyol of the present invention includes a step of reacting the raw material compounds containing the rosin (a) containing the resin acid (a1) having a conjugated double bond, the biomass-derived fatty acid (b) containing the unsaturated fatty acid (b1), the α,β-unsaturated carboxylic acid (c), and the polyol (d) containing the diol (d1) having an ether bond, to obtain the polyester polyol.

[0084] The reaction of the raw material compounds is performed preferably by heating the raw material compounds.　The heating temperature is preferably 150 to 300°C.　The heating promotes the Diels-Alder reaction, the ene reaction, and the esterification reaction as described above, to obtain the polyester polyol.　The reaction of the raw material compounds may be performed while inert gas such as nitrogen is blown into a reaction system.

[0085] The reaction of the raw material compounds may be performed in the presence of a catalyst for promoting the Diels-Alder reaction and the ene reaction or a catalyst for promoting the esterification reaction.　The Diels-Alder reaction or the ene reaction can be easily promoted by heating the raw material compounds.　Therefore, the catalyst for promoting the Diels-Alder reaction or the ene reaction may not be used.　Examples of the catalyst for promoting the esterification reaction include lithium acetate and magnesium acetate.　One type of each of the catalysts may be used alone, or two or more types thereof may be used in combination.

[0086] An order of reacting the rosin (a), the biomass-derived fatty acid (b), and the α,β-unsaturated carboxylic acid (c) is not particularly limited.　For example, the following synthesis methods (I) to (III) are adapted.

[0087] (Synthesis Method (I)) 　　　 Each of the rosin (a) and the biomass-derived fatty acid (b), and the α,β-unsaturated carboxylic acid (c) are first subjected to the Diels-Alder reaction or the ene reaction, to obtain adducts.　Subsequently, the adducts and the polyol (d), and if necessary, the aromatic polycarboxylic acid (e) are subjected to the esterification reaction, to obtain the polyester polyol.

[0088] (Synthesis Method (II)) 　　　 The α,β-unsaturated carboxylic acid (c), and if necessary, the aromatic polycarboxylic acid (e), and the polyol (d) are first subjected to the esterification reaction, to obtain an esterified product.　Subsequently, the esterified product, and the rosin (a) and the biomass-derived fatty acid (b) are subjected to the Diels-Alder reaction or the ene reaction, to obtain the polyester polyol.

[0089] (Synthesis Method (III)) 　　　 The rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) are mixed and simultaneously subjected to the Diels-Alder reaction or the ene reaction and the esterification reaction.　The aromatic polycarboxylic acid (e) is then mixed, if necessary, resulting in the esterification reaction.　Thus, the polyester polyol can be obtained.

[0090] The synthesis method (I) is preferred.　The polyester polyol obtained by the synthesis method (I) has a moderately branched molecular structure and high reactivity with a polyisocyanate.　This can reduce a reduction in compressive strength of the polyurethane foam.　From such a viewpoint, it is preferable that the polyol (d) further contain a trivalent or higher polyol (d2).

[0091] A method for producing the polyester polyol through the synthesis method (I) includes a step (I-1) of subjecting the rosin (a) containing the resin acid (a1) having a conjugated double bond and the biomass-derived fatty acid (b) containing the unsaturated carboxylic acid (b1), and the α,β-unsaturated carboxylic acid (c) to the Diels-Alder reaction or the ene reaction.

[0092] In the step (I-1), an adduct of the resin acid (a1) and the α,β-unsaturated carboxylic acid (c) and an adduct of the unsaturated fatty acid (b1) and the α,β-unsaturated carboxylic acid (c) are obtained by the Diels-Alder reaction or the ene reaction.

[0093] In the step (I-1), it is preferable that the Diels-Alder reaction or the ene reaction be performed by heating the rosin (a) containing the resin acid (a1) having a conjugated double bond, the biomass-derived fatty acid (b) containing the unsaturated fatty acid (b1), and the α,β-unsaturated carboxylic acid (c).　The heating temperature is preferably 175 to 200°C.

[0094] The method for producing the polyester polyol through synthesis method (I) further includes a step (I-2) of subjecting the adduct of the resin acid (a1) and the α,β-unsaturated carboxylic acid (c), the adduct of the unsaturated fatty acid (b1) and the α,β-unsaturated carboxylic acid (c), the polyol (d) containing the diol (d1) having an ether bond, and if necessary, the aromatic polycarboxylic acid (e) to the esterification reaction, to obtain the polyester polyol.

[0095] In the step (I-2), it is preferable that the esterification reaction be performed by heating the adducts, the polyol (d), and if necessary, the aromatic polycarboxylic acid (e).　The heating temperature is preferably 245 to 255°C.

[0096] In the present invention, the α,β-unsaturated carboxylic acid (c) is used in the Diels-Alder reaction or the ene reaction, to introduce the rosin (a) and the biomass-derived fatty acid (b) into the molecular structure of the polyester polyol.　The rosin (a) and the fatty acid (b) are both derived from biomass.　Therefore, the polyester polyol of the present invention can achieve a high biomass use rate.

[0097] The hydroxyl value of the polyester polyol is preferably 215 mgKOH / g or more, more preferably 223 mgKOH / g or more, and particularly preferably 225 mgKOH / g or more.

[0098] The hydroxyl value of the polyester polyol is preferably 500 mgKOH / g or less, more preferably 350 mgKOH / g or less, and particularly preferably 265 mgKOH / g or less.

[0099] The hydroxyl value of the polyester polyol can be measured in accordance with ASTM D4274-16C.

[0100] In the case of using a plurality of types of polyester polyols, the hydroxyl value of the polyester polyol is a hydroxyl value obtained by weighted averaging the hydroxyl values of the respective polyester polyols.　Specifically, the weighted averaged hydroxyl values are determined by the following expression. 　　　 Weighted average hydroxyl value (mgKOH / g) 　　　　　　　　　　　= [H1×W1+H2×W2+・・・+Hn×Wn] / 100 　　　 In the expression, n is the number of types of polyester polyols, Hnis the hydroxyl value (mgKOH / g) of n-th polyester polyol, and Wnis the percent by mass (% by mass) of the n-th polyester polyol.

[0101] The viscosity at 23°C of the polyester polyol is preferably 100 Pa・s or less, more preferably 50 Pa・s or less, and particularly preferably 10 Pa・s or less.　In general, a polyester polyol obtained using a raw material derived from biomass may have a high viscosity and may be difficult to use in the production of the polyurethane foam.　However, in the present invention, the use of the rosin (a) and the fatty acid (b) as the raw materials derived from biomass can reduce the viscosity of the polyester polyol.　A polyester polyol having a viscosity that is equal to or less than the upper limit value has high flowability.　Such a polyester polyol can be uniformly mixed with a polyisocyanate and a foaming agent.

[0102] The viscosity at 23°C of the polyester polyol is preferably 2.5 Pa・s or more, more preferably 3.0 Pa・s or more, and particularly preferably 4.5 Pa・s or more.　The viscosity that is equal to or more than the lower limit value makes it possible to provide a polyester polyol having flowability enough to be uniformly mixed with a polyisocyanate and a foaming agent.

[0103] The viscosity at 23°C of the polyester polyol is measured with the following measurement device under the following measurement conditions. 　　　 ・ Measurement device: rotational rheometer (e.g., trade name "MCR 92 type rheometer" manufactured by Anton Paar GmbH) 　　　 ・ Geometory: cone plate having a cone radius of 25 mm 　　　 ・ Shear speed: 25 (s-1)

[0104] The number average molecular weight (Mn) of the polyester polyol is preferably 500 or more, more preferably 600 or more, and particularly preferably 725 or more.

[0105] The number average molecular weight (Mn) of the polyester polyol is preferably 900 or less, more preferably 780 or less, and particularly preferably 775 or less.　The polyester polyol having a number average molecular weight (Mn) that is equal to or less than the upper limit value has a reduced viscosity.

[0106] The number average molecular weight (Mn) of the polyester polyol is calculated by size-exclusion chromatography (SEC) in terms of polystyrene.　Measurement conditions of SEC are as follows. 　　　 Eluent: tetrahydrofuran solution containing 0.02% by volume of acetic acid 　　　 Flow rate of eluent: 1 mL / min 　　　 Column (stationary phase): Agilent PLGel Mixed B column × 3 　　　 Standard substance: polystyrene (molecular weight: 580 to 6,500,000 g / mol) 　　　 Column temperature: 30°C

[0107] (Polyurethane foam) 　　　 The polyurethane foam is a foam of a foaming composition containing a polyol (P), a polyisocyanate (I), and a foaming agent.　As the polyol (P) that is a raw material for the polyurethane foam, the polyester polyol derived from biomass of the present invention can be used.

[0108] The polyurethane foam contains a urethane resin having a urethane bond that is formed by a reaction of the polyol (P) with the polyisocyanate (I).　It is preferable that the urethane resin further have an isocyanurate ring structure that is formed by a trimerization reaction of an isocyanate group of the polyisocyanate (I).　The polyurethane foam which contains the urethane resin having the isocyanurate ring structure is generally called "polyisocyanurate foam".　Since the polyisocyanurate foam has the isocyanurate ring structure, high flame retardance can be exerted.

[0109] (Polyol (P)) 　　　 The foaming composition contains the polyol (P).　The polyol (P) includes the polyester polyol derived from biomass of the present invention.　Herein, the polyester polyol derived from biomass of the present invention may be simply called "polyester polyol (P1)".

[0110] As described above, the polyester polyol (P1) derived from biomass has a high compatibility with a variety of foaming agents and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced.　Therefore, the polyester polyol (P1) derived from biomass can be suitably used as the polyol (P).

[0111] As the polyol (P), only the polyester polyol (P1) derived from biomass may be used.　Alternatively, the polyol (P) may contain the polyester polyol (P1) and other polyol (P2) such as a polyol derived from fossil resources.　Due to the combination use of the rosin (a) and the fatty acid (b), the polyester polyol (P1) of the present invention has a high compatibility with not only the foaming agent but also the other polyol (P2).　Therefore, even in the case of using the other polyol (P2), the polyurethane foam can be easily produced.

[0112] The content of the polyester polyol (P1) in the polyol (P) is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 30% by mass or more.　In this case, the polyurethane foam in which the usage rate of a biomass raw material is high can be produced.

[0113] The content of the polyester polyol (P1) in the polyol (P) is preferably 100% by mass or less, more preferably 85% by mass or less, more preferably 75% by mass or less, and more preferably 50% by mass or less.　Even when the other polyol (P2) is used, the polyurethane foam in which the usage rate of a biomass raw material is high can be produced.

[0114] When the other polyol (P2) is used, the content of the other polyol (P2) in the polyol (P) is preferably 1% by mass or more, more preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 50% by mass or more.　The content of the other polyol (P2) in the polyol (P) is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 80% by mass or less.

[0115] The other polyol (P2) may be a polyol that is generally used for producing the polyurethane foam.　Examples of the other polyol (P2) include a polylactone polyol, a polycarbonate polyol, a polyester polyol, a polymeric polyol, and a polyether polyol.　Examples of the polyester polyol include an aromatic polyester polyol.　One type of the other polyol (P2) may be used alone, or two or more types thereof may be used in combination.

[0116] The other polyol (P2) may be a polyol derived from biomass or a polyol derived from fossil resources, and is preferably a polyol derived from fossil resources.

[0117] The other polyol (P2) preferably contains a polyether polyol.　The use of the polyester polyol (P1) and the polyether polyol as the other polyol (P2) can improve the compressive strength of the polyurethane foam.

[0118] When the polyol (P) contains the polyester polyol (P1) and the polyether polyol as the other polyol (P2), it is preferable that the polyol (d) contained in the raw material compounds of the polyester polyol (P1) further contains the trivalent or higher polyol (d2).

[0119] When the polyol (P) contains the polyester polyol (P1) and the polyether polyol as the other polyol (P2), the content of the trivalent or higher polyol (d2) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) in the raw material compounds of the polyester polyol (P1) is preferably 7% by mass or more, more preferably 10% by mass or more.　The trivalent or higher polyol (d2) in a content that is equal to or more than the above-mentioned lower limit can increase the compressive strength of the polyurethane foam.

[0120] When the polyol (P) contains the polyester polyol (P1) and the polyether polyol as the other polyol (P2), the content of the trivalent or higher polyol (d2) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) in the raw material compounds of the polyester polyol (P1) is preferably 20% by mass or less, more preferably 15% by mass or less.　The trivalent or higher polyol (d2) in a content that is equal to or less than the above-mentioned upper limit can lower the viscosity of the polyester polyol (P1).

[0121] The other polyol (P2) preferably contains an aromatic polyester polyol.　The use of the polyester polyol (P1) and the aromatic polyester polyol as the other polyol (P2) can improve thermal insulation of the polyurethane foam.

[0122] When the polyol (P) contains the polyester polyol (P1) and the aromatic polyester polyol as the other polyol (P2), it is preferable that the polyol (d) contained in the raw material compounds of the polyester polyol (P1) further contains the trivalent or higher polyol (d2).

[0123] When the polyol (P) contains the polyester polyol (P1) and the aromatic polyester polyol as the other polyol (P2), the content of the trivalent or higher polyol (d2) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) in the raw material compounds of the polyester polyol (P1) is preferably less than 7% by mass, more preferably 4% by mass or less.　The trivalent or higher polyol (d2) in a content that is less than the above-mentioned upper limit can lower the viscosity of the polyester polyol (P1).

[0124] When the polyol (P) contains the polyester polyol (P1) and the aromatic polyester polyol as the other polyol (P2), the content of the trivalent or higher polyol (d2) relative to the total mass of the rosin (a), the biomass-derived fatty acid (b), the α,β-unsaturated carboxylic acid (c), and the polyol (d) in the raw material compounds of the polyester polyol (P1) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more.　The trivalent or higher polyol (d2) in a content that is equal to or more than the above-mentioned lower limit can increase the hydroxy value of the polyester polyol (P1).

[0125] The hydroxyl value of the polyol (P) is preferably 150 to 500 mgKOH / g, more preferably 200 to 350 mgKOH / g, and more preferably 220 to 280 mgKOH / g.

[0126] As a method for measuring the hydroxyl value of the polyol (P), the same method as the method for measuring the hydroxyl value of the polyester polyol is used.

[0127] (Polyisocyanate (I)) 　　　 The foaming composition contains the polyisocyanate (I).　The polyisocyanate (I) has two or more isocyanate groups (-NCO) in a molecule.

[0128] Examples of the polyisocyanate (I) include an aliphatic polyisocyanate, an alicyclic polyisocyanate and an aromatic polyisocyanate.　Among these, the aromatic polyisocyanate is preferred.　One type of the polyisocyanate (I) may be used alone, or two or more types thereof may be used in combination.

[0129] Examples of the aromatic polyisocyanate include toluene diisocyanate, diphenylmethane diisocyanate (MDI) and polymethylene polyphenylene polyisocyanate (PMDI).　Among these, polymethylene polyphenylene polyisocyanate (PMDI) is preferred.

[0130] (Foaming Agent) 　　　 The foaming composition contains the foaming agent.　Examples of the foaming agent include water and low boiling point foaming agents such as a hydrocarbon, a hydrofluoroolefin, a hydrochlorofluorocarbon, a hydrofluorocarbon, a hydrochlorocarbon, and a chlorofluorocarbon.　The boiling point of the low boiling point foaming agent is preferably 100°C or lower, and more preferably 50°C or lower.　The "boiling point" is a boiling point under a standard condition (1 atm (101.325 kPa), 25°C).　The foaming agent may be used alone, or two or more types thereof may be used in combination.

[0131] A hydrocarbon and a hydrofluoroolefin are preferred as the foaming agent.　These foaming agents are unlikely to cause environmental issue such as global warming and ozone depletion, but may have a low compatibility with the polyol derived from biomass.　However, the polyester polyol (P1) derived from biomass of the present invention has a high compatibility with the foaming agent as described above.　Therefore, a hydrocarbon and a hydrofluoroolefin are preferred, and a hydrocarbon is more preferred since they can exert the effects of the present invention.

[0132] Examples of the hydrocarbon include propane, butane, pentane, hexane, heptane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane.　Among these, pentane and cyclopentane are preferred, and n-pentane, isopentane, and cyclopentane are more preferred.　The hydrocarbon may be used alone, or two or more types thereof may be used in combination.　The content of the hydrocarbon in the foaming agent is preferably 10 to 100% by mass, more preferably 50 to 99% by mass, and more preferably 93 to 97% by mass.

[0133] Examples of the hydrofluoroolefin include HFO-1336mzz(Z) (cis-1,1,1,4,4,4-hexafluorobut-2-ene), HFO-1234yf (2,3,3,3-tetrafluoro-1-propene), HFO-1224yd(Z) (trans-1-chloro-2,3,3,3-tetrafluoropropene), HFO-1233zd(E) (trans-1-chloro-3,3,3-trifluoropropene), and HFO-1224yd(Z) (trans-1-chloro-2,3,3,3-tetrafluoropropene).　The hydrofluoroolefin may be used alone, or two or more types thereof may be used in combination.　The content of the hydrofluoroolefin in the foaming agent is preferably 10 to 100% by mass, more preferably 50 to 99% by mass, and more preferably 93 to 97% by mass.

[0134] It is preferable that the foaming agent further contain water.　Water is also unlikely to cause environmental issue such as global warming and ozone depletion.　The content of water in the foaming agent is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, more preferably 1.5 to 7.5% by mass, and more preferably 1.5 to 7% by mass.

[0135] The content of the foaming agent in the foaming composition is preferably 0.5 parts by mass or more, more preferably 1 parts by mass or more, more preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and more preferably 14 parts by mass or more, relative to 100 parts by mass of the polyol (P).　The content of the foaming agent in the foaming composition is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and more preferably 25 parts by mass or less, relative to 100 parts by mass of the polyol (P).

[0136] (Catalyst for formation of Urethane) 　　　 It is preferable that the foaming composition contain a catalyst for formation of urethane that promotes a reaction for producing a urethane bond.

[0137] Examples of the catalyst for formation of urethane include an amine-based catalyst, an ammonium salt-based catalyst, an organic potassium salt-based catalyst, and an organic metal catalyst.　Among these, the amine-based catalyst is preferred.　The catalyst for formation of urethane may be used alone, or two or more types thereof may be used in combination.

[0138] The content of the catalyst for formation of urethane in the foaming composition is preferably 0.05 parts by mass or more, more preferably 0.25 parts by mass or more, and more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyol (P).　The content of the catalyst for formation of urethane in the foaming composition is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, relative to 100 parts by mass of the polyol (P).

[0139] (Trimerization Catalyst) 　　　 It is preferable that the foaming composition contain a trimerization catalyst for promoting production of an isocyanurate ring.　By a trimerization reaction of the isocyanate group, an isocyanate ring is formed.

[0140] Examples of the trimerization catalyst include carboxylate salts such as an alkali metal salt of carboxylic acid and a quaternary ammonium salt of carboxylic acid.　An alkali metal salt of carboxylic acid is preferred.　Examples of the alkali metal salt of carboxylic acid include potassium acetate and potassium 2-ethylhexanoate.　The trimerization catalyst may be used alone, or two or more types thereof may be used in combination.

[0141] (Flame Retarder) 　　　 It is preferable that the foaming composition contain a flame retarder.　Examples of the flame retardant include halogen-containing flame retardants such as tricresyl phosphate, tris(2-chloro-1-methylethyl) phosphate, tris(2-chloroethyl) phosphate, tris(2-chloroisopropyl) phosphate, tris(1,3-dichloropropyl) phosphate, and tris(2,3-dibromopropyl) phosphate, and flame retarders containing no halogen such as triethyl phosphate.　The flame retarder may be used alone, or two or more types thereof may be used in combination.

[0142] (Foam Stabilizer) 　　　 It is preferable that the foaming composition contain a foam stabilizer.　By using the foam stabilizer, a polyurethane foam in which the content of closed cell is high can be produced.

[0143] Examples of the foam stabilizer include silicone-based surfactants such as an organopolysiloxane, an organopolysiloxane-polyoxyalkylene copolymer, a polyalkenylsiloxane having a polyoxyalkylene side chain, and a silicone-grease copolymer.　The foam stabilizer may be used alone, or two or more types thereof may be used in combination.　The content of the foam stabilizer in the foaming composition is preferably 0.5 to 10 parts by mass, and more preferably 1.0 to 5 parts by mass, relative to 100 parts by mass of the polyol (P).

[0144] The foaming composition may contain another additive.　Examples of the additive include an antioxidant, a thermal stabilizer, a metal-induced degradation inhibitor, a charging inhibitor, a stabilizer, a lubricant, a softening agent, a pigment, and a dye.

[0145] The foaming composition contains the polyol (P) containing the polyester polyol (P1), the polyisocyanate (I), and the foaming agent.　The foaming composition is obtained by mixing the polyol (P) with the polyisocyanate (I) and the foaming agent.

[0146] During production of the foaming composition, the polyol (P) may be mixed with a solvent in advance to obtain a polyol composition.　This polyol composition may be mixed with the polyisocyanate (I) and the foaming agent to obtain the foaming composition.

[0147] Examples of the solvent of the polyol composition include benzene, toluene, xylene, mesitylene, chlorobenzene, o-dichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, trichloroethylene, tetrachloroethane, tetrachloroethylene, tetrahydrofuran, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, and sulfolane.　The solvent may be used alone, or two or more types thereof may be used in combination.

[0148] The polyol composition may contain a component that may be contained in the foaming composition.　Examples of the component include catalysts such as a catalyst for formation of urethane and a trimerization catalyst; and additives such as a flame retarder, a foam stabilizer, an antioxidant, a thermal stabilizer, a metal-induced degradation inhibitor, a charging inhibitor, a stabilizer, a lubricant, a softening agent, a pigment, and a dye.　One type of the catalyst may be used alone, or two or more types thereof may be used in combination.　One type of the additive may be used alone, or two or more types thereof may be used in combination.

[0149] The isocyanate index of the foaming composition is preferably 90 or more, and more preferably 110 or more.　The isocyanate index that is equal to or more than the lower limit value allows to form the polyurethane foam that is stable in three dimensions and hardly collapse.

[0150] In particular, the isocyanate index of the foaming composition is preferably 250 or more, and more preferably 275 or more.　The isocyanate index that is equal to or more than the lower limit value allows an excess amount of polyisocyanate (I) over the polyol (P) to undergo the trimerization reaction to produce an isocyanurate ring.　Thus, a polyurethane foam which contains the urethane resin having the isocyanurate ring can be produced.

[0151] The isocyanate index of the foaming composition is preferably 450 or less, and more preferably 400 or less.　The isocyanate index that is equal to or less than the upper limit value makes it possible to provide a polyurethane foam having excellent mechanical strength, heat insulating properties, and sound-proof properties.

[0152] When the polyol (P) contains the polyester polyol (P1) and the polyether polyol as the other polyol (P2), the isocyanate index of the foaming composition is preferably 90 to 250, and more preferably 110 to 160.　The isocyanate index of 90 or more can help form the polyurethane foam that hardly collapse.　The isocyanate index of 250 or less can form the polyurethane foam with good mechanical and thermal insulation properties.

[0153] When the polyol (P) contains the polyester polyol (P1) and the aromatic polyester polyol as the other polyol (P2), the isocyanate index of the foaming composition is preferably more than 250, and preferably 450 or less.　The isocyanate index of more than 250 allows for the formation of isocyanurate units.　The isocyanate index of 450 or less can form the polyurethane foam with good mechanical and thermal insulation properties.

[0154] The isocyanate index of the foaming composition can be calculated by the following expression. 　　　 Isocyanate index = 100 × (number of equivalents of isocyanate group of polyisocyanate (I)) / (number of equivalents of active hydrogen groups of polyol (P) + number of equivalents of active hydrogen groups of water)

[0155] The number of equivalents of isocyanate group of the polyisocyanate (I) can be calculated by the following expression. 　　　 Number of equivalents of isocyanate group of polyisocyanate (I) = 100 × content (% by mass) of isocyanate group in polyisocyanate (I) × amount (g) of polyisocyanate (I) mixed / molecular weight of (42 g / mol) of isocyanate group

[0156] The number of equivalents of active hydrogen group of the polyol (P) can be calculated by the following expression. 　　　 Number of equivalents of active hydrogen group of the polyol (P) 　　　　　 =(W1×H1 / 56100)+(W2×H2 / 56100)+・・・+(Wm×Hm / 56100) In the expression, Wmis the content (g) of m-th polyol in the whole polyol (P), Hmis the hydroxyl value (mgKOH / g) of m-th polyol, and m is an integer indicating the number of types of the polyol (P).

[0157] The hydroxyl value of the m-th polyol can be measured in accordance with ASTM D4274-16C.

[0158] The number of equivalents of active hydrogen group of water can be calculated by the following expression.　When the foaming composition contains water as a foaming agent, it is necessary to consider the number of equivalents of active hydrogen group of water during calculation of isocyanate index of the foaming composition. 　　　 Number of equivalents of active hydrogen group of water = amount (g) of water mixed × 2 / 18

[0159] The compressive strength in the thickness direction of the polyurethane foam is more preferably 160 kPa or more, more preferably 180 kPa or more, and more preferably 200 kPa or more.　The polyester polyol (P1) described above can reduce a reduction in compressive strength of the polyurethane foam although the raw material derived from biomass is used.　Therefore, a polyurethane foam having a high compressive strength of 160 kPa or more can be produced.　Accordingly, the polyurethane foam is preferably a rigid polyurethane foam, more preferably a rigid polyisocyanurate foam.

[0160] The compressive strength in the thickness direction of the polyurethane foam is preferably 375 kPa or less, more preferably 350 kPa or less, and more preferably 300 kPa or less.

[0161] The compressive strength in the thickness direction of the polyurethane foam can be measured in accordance with European Norm EN826:2013 except that test specimens have the following dimensions: a width of 40 mm, a length of 40 mm and a thickness of 40 mm.　In the measurement of compressive strength, for example, a universal testing machine (Tinius Olesen 10 ST) equipped with a 10-kN load cell can be used.

[0162] A foaming ratio of the polyurethane foam is preferably 29 to 36 times, and more preferably 31 to 34 times.　The foaming ratio of 29 times or more can reduce the weight of the polyurethane foam per covered area.　The foaming ratio of 36 times or less can increase the compressive strength of the polyurethane foam.

[0163] The foaming ratio of the polyurethane foam is measured with the following measuring method.　The polyurethane foam is first cut to obtain a specimen that is a cube with a side of 40 mm.　A thickness of the specimen is measured in accordance with ISO 1923 (1981) "Cellular plastics and rubbers - Determination of linear dimensions".　The thickness of the specimen is measured at freely-selected five positions and an arithmetic average thereof is calculated.　The obtained value is defined as a thickness of the specimen.　An apparent volume [V (cm3)] of the specimen is calculated with the thickness of the specimen.　In addition, weight [W (g)] of the specimen is measured.　The foaming ratio of the polyurethane foam is calculated with the following formula. 　Foaming ratio [times] of the polyurethane foam = V / W

[0164] A closed cell rate of the polyurethane foam is preferably 75% or more, more preferably 80% or more, and more preferably 85% or more.　The closed cell rate of the polyurethane foam is preferably 100% or less.　The closed cell rate of 75% or more can improve thermal insulation and increase the compressive strength of the polyurethane foam.

[0165] The closed cell rate of the polyurethane foam is measured in accordance with the standard ASTM D6226-15.

[0166] As a method for foaming the foaming composition to obtain the polyurethane foam, a conventionally known method can be used.　Examples of the method include a lamination method in which the foaming composition is supplied between two plane members and foamed, a spraying method in which the foaming composition is sprayed to an adherend with a sprayer and foamed, and a foam-in-place method in which the foaming composition is injected into a cavity or a mold and freely foamed.

[0167] In the spraying method, the polyisocyanate (I) and another component such as the polyol (P) may be prepared separately, then sprayed to the adherend while mixing them.　Alternatively, the polyisocyanate (I) and another component such as the polyol (P) may be sprayed to the adherend immediately after mixing.

[0168] Since the polyurethane foam has high compressive strength, the polyurethane foam can be suitably used as a heat insulating material or a sound-proof material.　Examples of applications of the heat insulating material or the sound-proof material include architecture members such as a roof, a ceiling, and a wall of architecture, appliances such as a refrigerator and a hot-water supply, vehicles such as an automobile, an aircraft, and a ship, pipes, and tanks.

[0169] Hereinafter, the present invention will be described more specifically using Examples, but the present invention is not limited to the Examples.

[0170] (Synthesis of Polyester Polyol (P1))Examples A1 to A6, Comparative Examples A1, A2 and A4

[0171] To a reactor, tall oil rosin (a) and tall oil fatty acid (b) were each supplied in a mixing amount of Table 1 and uniformly stirred at 175°C in a nitrogen atmosphere, to obtain a solution.　Subsequently, to the reactor, maleic anhydride (c1) was supplied in a mixing amount of Table 1 and heated at 200°C for 1 hour, to cause a Diels-Alder reaction and an ene reaction.　To the reactor, diethylene glycol (d1), glycerin (d2), and 1,6-hexanediol were each supplied in a mixing amount of Table 1, and isophthalic acid or orthophthalic anhydride was then supplied in a mixing amount of Table 1, to obtain a mixture.　The mixture was heated to 245°C, and 0.1 parts by mass of magnesium acetate was then supplied to the reactor.　Subsequently, the mixture was heated to 250°C, and an esterification reaction was performed until the acid value of the mixture was lower than 2.0 mgKOH / g.　The mixture was cooled to 235°C and an excess amount of the diethylene glycol (d1) in the mixture was removed in vacuum.　As a result, a polyester polyol (P1) was obtained.

[0172] The tall oil rosin (a) contained as a resin acid (a1) having a conjugated double bond 40.2% by mass of abietic acid, 14.5% by mass of palustric acid, and 4.9% by mass of neoabietic acid, and as a resin acid (a2) 0.4% by mass of pimaric acid and 23.2% by mass of dehydroabietic acid.

[0173] The tall oil fatty acid (b) contained as an unsaturated fatty acid (b1) 44.8% by mass of oleic acid and 28.8% by mass of linoleic acid, and as a saturated fatty acid (b2) 0.7% by mass of palmitic acid, 3.6% by mass of stearic acid, and 0.7% by mass of heptadecanoic acid.

[0174] The glycerin (d2) was derived from biomass.　The glycerin (d2) was obtained by hydrolyzing a triglyceride contained in oil and fat.Comparative Example A3

[0175] As a polyester polyol (P1), a polyester polyol derived from fossil resources (trade name "STEPANPOL (registered trademark) PS2352" available from Stepan Company) was used.　The polyester polyol derived from fossil resources was obtained by an esterification reaction of phthalic anhydride derived from fossil resources with diethylene glycol derived from fossil resources.　A raw material for the polyester polyol derived from fossil resource was not biomass.

[0176] (Evaluation) 　　　 The hydroxyl value, the viscosity at 23°C, and the number average molecular weight of the polyester polyol (P1) were measured by the above-described methods.　The results are shown in Table 1.

[0177] For the polyester polyol (P1) of each of Examples and Comparative Examples, the compatibility with cyclopentane (boiling point: 49°C), isopentane (boiling point: 28°C), or cis-1,1,1,4,4,4-hexafluorobut-2-ene (boiling point: 33 to 33.5°C) as a foaming agent was evaluated by the following procedure.　The results are shown in Table 1.

[0178] (Compatibility of Polyester Polyol (P1) with Foaming Agent) 　　　 100 parts by mass of the polyester polyol (P1) was placed in a vial in an atmosphere of 23°C.　Subsequently, 20 parts by mass of cyclopentane, 10 parts by mass of isopentane, or 25 parts by mass of cis-1,1,1,4,4,4-hexafluorobut-2-ene as a foaming agent was added to the vial.　The vial was sealed.　By stirring with a vortex mixer for the vial, the mixture in the vial was uniformly mixed.　After 48 hours, the presence or absence of phase separation of the mixture in the vial was confirmed by visual inspection and evaluated in accordance with the following evaluation criteria. <Evaluation Criteria> 　　　 "++": the mixture was not phase-separated and was clear. 　　　 "+": the mixture was not phase-separated and was almost clear.　There is no problem in actual use. 　　　 "+ / -": the mixture was not phase-separated, but was cloudy.　Phase separation is most likely to occur at a later time. 　　　 "-": Phase separation occurred.

[0179] (Production of Polyisocyanurate Foam)Examples B1 to B7 and Comparative Examples B1 to B4

[0180] In a reactor, 0.7 parts by mass of amine-based catalyst (trade name "Niax C-5" available from Momentive), 4 parts by mass of trimerization catalyst (solution containing 50% by mass or more of potassium 2-ethylhexanate, trade name "Niax K-ZeroG" available from Momentive), 1 part by mass of water, 2 parts by mass of surfactant (trade name "Niax L-5466" available from Momentive) as a foam stabilizer, and 15 parts by mass of flame retarder (tris(2-chloro-1-methylethyl) phosphate, trade name "Roflam P" available from PCC Rokita SA) were placed and uniformly mixed, to obtain an additive composition.

[0181] Next, 100 parts by mass of polyol (P) and 18 parts by mass of cyclopentane were added to the reactor, and the mixture was stirred at 1,000 rpm for 20 seconds.　The polyol (P) contained the polyester polyol (P1) of Examples A1 to A6 and Comparative Examples A1 to A4 in a mixing amount of Table 2.　To the reactor, polymeric methylene diphenyl diisocyanate (trade name "Suprasec 5025" available from Huntsman) was added in a mixing amount of Table 2 and stirred at 2,000 rpm for 6 seconds.　As a result, a foaming composition having an isocyanate index of 250 was obtained.　The foaming composition was supplied to an aluminum tray and foamed, and then heated in an oven at 70°C for 1 hour.　Thus, a polyisocyanurate foam was obtained.

[0182] In Comparative Example B1, the polyester polyol (P1) of Comparative Example A1 was used as the polyol (P).　Since the polyester polyol (P1) of Comparative Example A1 had a low compatibility with a foaming agent, phase separation occurred in the foaming composition.　Thus, in Comparative Example B1, a polyisocyanurate foam was not produced.

[0183] The compressive strengths in the thickness direction of the polyisocyanurate foams was measured by the above-described methods.　The results are shown in Table 2.　Foaming ratios and closed cell rates of the polyisocyanurate foams are shown in Table 2.

[0184]

[0185]

[0186] The present invention can provide the polyester polyol that has a high compatibility with a variety of foaming agents and can be used to produce a polyurethane foam in which a reduction in compressive strength is reduced, despite use of a biomass raw material.　Thus, the polyester polyol is preferably used for a polyol for producing a polyurethane foam.

Claims

1. A polyester polyol for a polyurethane foam, the polyester polyol comprising a polyester polyol that is a reaction product of raw-material compounds containing: 　　　 a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　 a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　 an α,β-unsaturated carboxylic acid (c); and 　　　 a polyol (d) containing a diol (d1) having an ether bond.

2. The polyester polyol according to claim 1, wherein a weight ratio [(a) / (b)] of the rosin (a) to the biomass-derived fatty acid (b) in the raw-material compounds is 0.13 or more and 2.00 or less.

3. The polyester polyol according to claim 1, wherein a weight ratio [(c) / (a)] of the α,β-unsaturated carboxylic acid (c) to the rosin (a) in the raw-material compounds is 0.15 or more and 2.00 or less.

4. The polyester polyol according to claim 1, wherein a weight ratio [(c) / (a+b)] of the α,β-unsaturated carboxylic acid (c) to the total amount of the rosin (a) and the biomass-derived fatty acid (b) in the raw-material compounds is 0.05 or more and 0.45 or less.

5. The polyester polyol according to claim 1, wherein a weight ratio [(d1) / (a+b)] of the diol (d1) having an ether bond to the total amount of the rosin (a) and the biomass-derived fatty acid (b) in the raw-material compounds is 0.30 or more and 2.00 or less.

6. The polyester polyol according to claim 1, wherein the raw-material compounds further contain an aromatic polycarboxylic acid (e).

7. The polyester polyol according to claim 6, wherein a weight ratio [(e) / (a+b)] of the aromatic polycarboxylic acid (e) to the total amount of the rosin (a) and the biomass-derived fatty acid (b) in the raw-material compounds is 0.05 or more and 0.35 or less.

8. A polyurethane foam, being a foam of a foamable composition containing a polyol (P), a polyisocyanate (I), and a foaming agent, 　　　 wherein the polyol (P) comprises the polyester polyol according to any one of claims 1 to 7.

9. A method for producing a polyester polyol for a polyurethane foam, comprising a step of obtaining the polyester polyol by reacting raw-material compounds containing: 　　　 a rosin (a) containing a resin acid (a1) having a conjugated double bond; 　　　 a biomass-derived fatty acid (b) containing an unsaturated fatty acid (b1); 　　　 an α,β-unsaturated carboxylic acid (c); and 　　　 a polyol (d) containing a diol (d1) having an ether bond.

10. The method for producing a polyester polyol for a polyurethane foam according to claim 9, comprising: 　　　 a step of carrying out a Diels-Alder reaction or an ene reaction of the rosin (a) containing the resin acid (a1) having a conjugated double bond and the biomass-derived fatty acid (b) containing the unsaturated fatty acid (b1) with the α,β-unsaturated carboxylic acid (c) to obtain an adduct of the resin acid (a1) and the α,β-unsaturated carboxylic acid (c), and an adduct of the unsaturated fatty acid (b1) and the α,β-unsaturated carboxylic acid (c); and 　　　 a step of carrying out an esterification reaction of the adduct of the resin acid (a1) and the α,β-unsaturated carboxylic acid (c) and the adduct of the unsaturated fatty acid (b1) and the α,β-unsaturated carboxylic acid (c) with the polyol (d) containing the diol (d1) having an ether bond to obtain the polyester polyol.

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