Polyurethane foam containing plant-derived raw material, and impact absorbing material

Abstract

A polyurethane foam containing a plant-derived raw material according to the present disclosure uses, as a raw material, a polyol containing a castor oil-based polyol, wherein the polyurethane foam: contains 1 to 40 parts by mass of the castor oil-based polyol in 100 parts by mass of the polyol; has a density of 80 kg / m3 to 230 kg / m3; and has an Asker C hardness of 50 or less.

Description

Polyurethane foam containing plant-derived materials, shock absorbing material

[0001] The present disclosure relates to polyurethane foams containing plant-derived materials that have excellent impact absorption properties.

[0002] Polyurethane foam is a foam obtained by mixing a polyol having a hydroxyl group with a polyisocyanate having an isocyanate group, and simultaneously undergoing a foaming reaction and a resinification reaction. The polyol typically used is a polyether polyol or a polyester polyol.

[0003] Japanese Patent Application Laid-Open Publication No. 2021-147461 discloses a polyurethane foam using a polycarbonate polyol of a specific structure instead of a polyether polyol or polyester polyol as the polyol. By using a polycarbonate polyol of a specific structure, a polyurethane foam with excellent chemical resistance, such as low resilience and chlorine resistance, is obtained (paragraph 0013). Furthermore, it is also disclosed that the low resilience of the produced polyurethane foam allows it to be used as an impact absorber or vibration absorber (paragraph 0090). However, the low resilience obtained using a polycarbonate polyol alone is insufficient to absorb shock when a large impact is applied. Furthermore, polycarbonate polyol has high viscosity and poor moldability (shrinkage and curing properties), so adding a large amount can be detrimental to the liquid flow of polyurethane foam raw materials during molding and the demoldability of the polyurethane foam. Furthermore, polycarbonate polyol is expensive, and its versatility as a raw material is low due to its cost.

[0004] Furthermore, Japanese Patent Laid-Open Nos. 2007-314672, 2010-53157, and 7-62051 disclose the use of plant-derived castor oil as a raw material for polyurethane foam to produce automobile seat cushions, bedding, etc., from the perspective of reducing environmental impact. However, castor oil has poor reactivity, which impairs the curing properties of molded urethane foam, and the reaction is not completed within the typical cycle time of about 5 minutes for demolding, resulting in poor productivity.

[0005] In general, improving impact absorption is effective by making the polyurethane foam sufficiently thick or increasing its density. However, increasing the thickness of the polyurethane foam improves impact absorption but also increases its bulk. Increasing the density of the polyurethane foam also improves impact absorption but also increases its weight. Depending on the application of the polyurethane foam, thickness may be limited or weight reduction may be required, and a polyurethane foam with excellent impact absorption properties is in demand even under such conditions.

[0006] The present disclosure has been made in view of the above, and an object of the present disclosure is to provide a polyurethane foam having excellent impact absorption properties.

[0007] The present inventors have discovered that when a predetermined amount of castor oil-based polyol is used as the polyol raw material for polyurethane foam and when the density and Asker C hardness are within predetermined ranges, the impact absorption of the polyurethane foam is improved and productivity is also improved, and have completed the present invention. The means for solving the above problems according to the present disclosure include the following aspects.

[0008] A first aspect of the present disclosure is a polyurethane foam using a polyol containing a castor oil-based polyol as a raw material, the castor oil-based polyol being contained in an amount of 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the polyol, and having a density of 80 kg / m ３ More than 230kg / m ３ and an Asker C hardness of 50 or less.

[0009] A second aspect of the present disclosure is the polyurethane foam containing a plant-derived material, wherein the castor oil-based polyol has a hydroxyl value of 70 mg KOH / g or more and 250 mg KOH / g or less in the first aspect.

[0010] A third aspect of the present disclosure is an impact absorbing material comprising a polyurethane foam containing the plant-derived raw material of the first or second aspect.

[0011] According to the present disclosure, a polyurethane foam having excellent impact absorption properties can be obtained.

[0012] 1 is a table showing the blending amounts and evaluation results of Examples 1 to 8. 2 is a table showing the blending amounts and evaluation results of Comparative Examples 1 to 7.

[0013] The present disclosure will be more fully understood from the following detailed description. Further scope of applicability of the present application will become apparent from the following detailed description. However, the detailed description and specific examples are preferred embodiments of the present disclosure and are set forth for illustrative purposes only. From this detailed description, various changes and modifications will be apparent to those skilled in the art within the spirit and scope of the present disclosure. The applicant does not intend to dedicate any of the described embodiments to the public, and the applicants claim that disclosed modifications and alternatives that may not literally fall within the scope of the claims are part of the invention under the doctrine of equivalents.

[0014] [Polyurethane foam] The present application relates to a polyurethane foam produced from a polyurethane foam raw material containing a plant-derived raw material. The polyurethane foam uses a polyol containing a castor oil-based polyol as a raw material, and the castor oil-based polyol is contained in an amount of 1 part by mass to 40 parts by mass per 100 parts by mass of the polyol, and has a density of 80 kg / m ３ More than 230kg / m ３The present disclosure discloses a polyurethane foam having an Asker C hardness of 50 or less and a viscosity of 100 psi or less. The polyurethane foam is obtained from a polyurethane foam raw material containing a polyol and a polyisocyanate. The polyol may include a polyether polyol in addition to a castor oil-based polyol. The polyether polyol may be a combination of two or more polyether polyols with different molecular weights. The polyurethane foam may also be a molded urethane (or molded urethane foam). "Molded urethane" is a polyurethane foam in which raw materials are injected into a mold with a lid and foamed and molded along the mold. It is characterized by its ability to foam and mold in a short period of time. Thus, the polyurethane foam of the present disclosure may be a low-resilience molded urethane foam made from a raw material containing a castor oil-based polyol. The raw materials may include a polyether polyol, or multiple polyether polyols may be used in combination. The polyurethane foam raw materials are described in detail below.

[0015] [Polyurethane Foam Raw Materials] The polyurethane foam raw materials (hereinafter also referred to as "composition") contain a polyol and a polyisocyanate. The composition may also contain at least one component selected from the group consisting of a crosslinking agent, a catalyst, a foam stabilizer, and a blowing agent.

[0016] Polyols Polyols include castor oil-based polyols. Castor oil-based polyols may be refined castor oil, semi-refined castor oil, or unrefined castor oil. Hydrogenated castor oil, or linear or branched polyesters obtained by reacting castor oil fatty acids with polyols, such as diglycerides and monoglycerides of castor oil fatty acids, mono-, di-, or triesters of castor oil fatty acids and trimethylolalkanes, or mono-, di-, or triesters of castor oil fatty acids and polypropylene glycol, may also be used. Among these, refined castor oil is preferred from the viewpoints of minimizing the loss of plant-based content due to modification and improving the liquid flow properties of the raw material. Like other vegetable oils, castor oil is a triglyceride in which fatty acids and glycerin are ester-bonded. Specifically, approximately 87% of the fatty acids are ricinoleic acid (12-hydroxy-9-decenoic acid), with the remaining approximately 10% containing oleic acid, linoleic acid, etc. Ricinoleic acid has a hydroxyl group (-OH) and a double bond per molecule. Glycerides of ricinoleic acid and glycerin are the main components of castor oil. The main component refers to the component that is most abundant. As shown in the examples of the present disclosure, commercially available castor oil can be used as is as a castor oil-based polyol. The "trimethylol alkane" may be, for example, trimethylol methane, trimethylol ethane, trimethylol propane, trimethylol butane, trimethylol pentane, trimethylol hexane, trimethylol heptane, trimethylol octane, trimethylol nonane, or trimethylol decane.

[0017] The number of functional groups, hydroxyl value, and number average molecular weight of the castor oil-based polyol are not particularly limited. The castor oil-based polyol may be a castor oil-based polyol that satisfies the following conditions (hereinafter also referred to as polyol B). The number of functional groups of the castor oil-based polyol is preferably 2 to 4. The hydroxyl value of the castor oil-based polyol may be 50 mgKOH / g or more, or even 70 mgKOH / g to 250 mgKOH / g. The hydroxyl value is preferably 90 mgKOH / g to 230 mgKOH / g, more preferably 110 mgKOH / g to 210 mgKOH / g, even more preferably 130 mgKOH / g to 190 mgKOH / g, and particularly preferably 150 mgKOH / g to 170 mgKOH / g. When the hydroxyl value is 250 mgKOH / g or less, a good foam can be obtained. When the hydroxyl value is 50 mgKOH / g or more, the castor oil-based polyol can be easily mixed with other materials. The number average molecular weight of the castor oil-based polyol may be 500 or more and 5,000 or less. The number average molecular weight is preferably 600 or more and 4,000 or less, more preferably 700 or more and 3,000 or less, even more preferably 800 or more and 2,000 or less, and particularly preferably 900 or more and 1,100 or less. The number average molecular weight of the castor oil-based polyol can be measured by gel permeation chromatography (GPC). When the castor oil-based polyol is a commercially available product, the catalog value may be used as the number average molecular weight of the castor oil-based polyol. In this specification, the number average molecular weight of polyols other than castor oil-based polyols can be similarly defined.

[0018] The content of the castor oil-based polyol may be 1 part by mass or more from the viewpoint of impact absorption and 40 parts by mass or less from the viewpoint of moldability (i.e., 1% to 40% by mass of the total mass of the polyol), where the total amount of the polyol is taken as 100 parts by mass. The content is preferably 3 parts by mass or more and 37 parts by mass or less, more preferably 6 parts by mass or more and 34 parts by mass or less, even more preferably 8 parts by mass or more and 32 parts by mass or less, and particularly preferably 10 parts by mass or more and 30 parts by mass or less. The use of a castor oil-based polyol can enhance the effect of reducing environmental impact.

[0019] The polyols other than the castor oil-based polyols (hereinafter also referred to as "other polyols") contained in the composition are not particularly limited. As the other polyols, polyether polyols are preferred. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethylene polypropylene glycol. The other polyols can be used alone or in combination of two or more. However, in the polyurethane foam of the present disclosure, it is preferable that the raw polyol does not contain a polymer polyol. The absence of a polymer polyol makes it easier to prevent the polyurethane foam from becoming too hard or the foam raw material from becoming too viscous, which would result in poor liquid flow. Polymer polyol (POP) is a modified polyether polyol in which polymer microparticles obtained by radical polymerization of vinyl monomers such as acrylonitrile or styrene in a polyether polyol such as polyoxyalkylene polyol (PPG) are stably dispersed in the polyether polyol.

[0020] The number of functional groups, hydroxyl value, and number average molecular weight of the polyether polyol are not particularly limited. When one polyether polyol is used, it may be a polyether polyol that satisfies the following conditions (hereinafter also referred to as polyether polyol A or polyol A). The number of functional groups of polyether polyol A is preferably 2 to 4. The hydroxyl value of polyether polyol A may be 10 mgKOH / g to 60 mgKOH / g. The hydroxyl value is preferably 15 mgKOH / g to 55 mgKOH / g, more preferably 20 mgKOH / g to 50 mgKOH / g, even more preferably 25 mgKOH / g to 45 mgKOH / g, and particularly preferably 30 mgKOH / g to 40 mgKOH / g. The number average molecular weight of polyether polyol A may be 2,000 to 10,000. The number average molecular weight is preferably 3,000 or more and 8,000 or less, more preferably 3,500 or more and 7,000 or less, even more preferably 4,000 or more and 6,000 or less, and particularly preferably 4,500 or more and 5,500 or less. Polyether polyol A may be a polyether polyol obtained by using propylene oxide (hereinafter referred to as "PO") and ethylene oxide (hereinafter referred to as "EO") in combination. The blending ratio (molar ratio) of PO to EO is not particularly limited. Furthermore, the PO / EO (molar ratio) of polyether polyol A may be 90 / 10, 86 / 14, or 80 / 20. Within this range, the reactivity of the polyurethane foam raw materials and the physical properties of the polyurethane foam are improved.

[0021] The content of polyether polyol A may be 55 parts by mass or more and 95 parts by mass or less (i.e., 55% to 95% by mass of the total mass of the polyol) from the viewpoint of moldability, where the total amount of polyol is taken as 100 parts by mass. The content is preferably 56 parts by mass or more and 90 parts by mass or less, more preferably 57 parts by mass or more and 85 parts by mass or less, even more preferably 58 parts by mass or more and 82 parts by mass or less, and particularly preferably 60 parts by mass or more and 80 parts by mass or less.

[0022] When two or more polyether polyols are used in combination, the additional polyether polyol may be a polyether polyol satisfying the following conditions (hereinafter also referred to as polyether polyol C or polyol C). The number of functional groups of polyether polyol C is preferably 2 or more and 4 or less. The hydroxyl value of polyether polyol C may be 200 mgKOH / g or more and 700 mgKOH / g or less. The hydroxyl value is preferably 250 mgKOH / g or more and 600 mgKOH / g or less, more preferably 300 mgKOH / g or more and 500 mgKOH / g or less, even more preferably 350 mgKOH / g or more and 470 mgKOH / g or less, and particularly preferably 400 mgKOH / g or more and 450 mgKOH / g or less. The number average molecular weight of polyether polyol C may be 100 or more and less than 2000. The number average molecular weight is preferably 200 or more and 1500 or less, more preferably 250 or more and 1000 or less, even more preferably 300 or more and 700 or less, and particularly preferably 350 or more and 500 or less. When two or more polyether polyols are used in combination, it is preferable to combine a polyether polyol C having a number average molecular weight smaller than that of polyether polyol A, since this allows adjustment of the hardness of the polyurethane foam. Polyether polyol C may be a polyether polyol obtained by combining propylene oxide (hereinafter referred to as "PO") and ethylene oxide (hereinafter referred to as "EO"). The blending ratio (molar ratio) of PO to EO is not particularly limited. Furthermore, the PO / EO (molar ratio) of polyether polyol C may be 100 / 0, 90 / 10, or 80 / 20. Within this range, the reactivity of the polyurethane foam raw materials and the physical properties of the polyurethane foam are improved.

[0023] The content of polyether polyol C may be 0 to 50 parts by mass per 100 parts by mass of the total amount of polyol (i.e., 0 to 50% by mass of the total mass of polyol) from the viewpoint of hardness, assuming that the total amount of polyol is 100 parts by mass. The content is preferably 3 to 45 parts by mass, more preferably 5 to 40 parts by mass, even more preferably 8 to 35 parts by mass, and particularly preferably 10 to 30 parts by mass.

[0024] Crosslinking Agent A crosslinking agent may be blended to improve the hardness of the polyurethane foam. Examples of crosslinking agents include amines such as diethanolamine and polyethylene polyamines, and polyhydric alcohols such as trimethylolpropane, glycerin, 1,4-butanediol, and diethylene glycol. Two or more types of crosslinking agents may be used. The number of functional groups in the crosslinking agent is preferably 2 to 4. The content of the crosslinking agent may be 1.0 to 2.0 parts by mass per 100 parts by mass of polyol. The content is preferably 1.1 to 1.9 parts by mass, more preferably 1.2 to 1.8 parts by mass, even more preferably 1.3 to 1.7 parts by mass, and particularly preferably 1.4 to 1.6 parts by mass.

[0025] Catalysts: Known catalysts for polyurethane foams can be used alone or in combination. Examples of catalysts include amine catalysts such as aliphatic amine catalysts and aromatic amine catalysts, and metal catalysts such as tin octoate. The catalyst content may be 0.5 to 1.5 parts by mass per 100 parts by mass of polyol. The content is preferably 0.6 to 1.4 parts by mass, more preferably 0.7 to 1.3 parts by mass, even more preferably 0.8 to 1.2 parts by mass, and particularly preferably 0.9 to 1.1 parts by mass.

[0026] The foam stabilizer may be any foam stabilizer that is commonly used as a polyurethane foam raw material, such as a silicone compound or a nonionic surfactant. The content of the foam stabilizer may be 0 to 0.9 parts by mass per 100 parts by mass of the polyol. The content is preferably 0.2 to 0.8 parts by mass, more preferably 0.3 to 0.7 parts by mass, even more preferably 0.4 to 0.6 parts by mass, and particularly preferably 0.45 to 0.55 parts by mass.

[0027] Blowing Agent Water, alternative chlorofluorocarbons, or hydrocarbons such as pentane can be used alone or in combination as the blowing agent. Water is particularly preferred as the blowing agent. In the case of water, carbon dioxide gas is generated during the reaction of polyol and polyisocyanate, and the carbon dioxide gas causes foaming. The amount of water used as the blowing agent may be 1.0 to 3.0 parts by mass per 100 parts by mass of polyol. The amount of water is preferably 1.2 to 2.8 parts by mass, more preferably 1.4 to 2.6 parts by mass, even more preferably 1.6 to 2.4 parts by mass, and particularly preferably 1.8 to 2.2 parts by mass.

[0028] Other Components Other components that may be appropriately blended into the composition include, for example, a networking agent, a flame retardant, and an antioxidant. Examples of the networking agent include polyether polyols with a high EO addition ratio, polyethylene glycol, and silicone foam stabilizers that improve breathability (have cell-breaking properties). The amount of the networking agent is preferably 0.5 parts by mass or more and 15.0 parts by mass or less per 100 parts by mass of polyol. Examples of polyether polyols with a high EO addition ratio include polyether polyols with an EO ratio of 60 mol% or more, 70 mol% or more, and 100 mol% or less.

[0029] Polyisocyanate The polyisocyanate is not particularly limited. The polyisocyanate may be an MDI-based polyisocyanate (diphenylmethane diisocyanate-based isocyanate) or a TDI-based polyisocyanate (toluene diisocyanate). Specific examples of MDI-based polyisocyanates include monomeric MDIs such as 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), and 4,4'-diphenylmethane diisocyanate (4,4'-MDI); polymeric MDIs, which are mixtures of diphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanate; urethane-modified, carbodiimide-modified, urea-modified, allophanate-modified, biuret-modified, and isocyanurate-modified versions of these; and MDI prepolymers obtained by reacting these polyisocyanates with polyols. Multiple types of MDI-based polyisocyanates may be used in combination. Among these, it is preferable that the polyisocyanate contains urethane-modified MDI. Specifically, the TDI-based polyisocyanate may be a mixture of 2,4-TDI and 2,6-TDI in a blending ratio (mass ratio: 2,4-TDI / 2,6-TDI) of 100 / 0 to 50 / 50, or a mixture of 80 / 20 to 65 / 35.

[0030] The isocyanate index (INDEX) may be 80 or more and 120 or less. The isocyanate index is preferably 85 or more and 115 or less, more preferably 90 or more and 110 or less, even more preferably 95 or more and 105 or less, and particularly preferably 98 or more and 102 or less. The isocyanate index is a value obtained by dividing the number of moles of isocyanate groups in the isocyanate by the total number of moles of active hydrogen groups such as hydroxyl groups of the polyol and water as a blowing agent, and multiplying the result by 100, and is calculated as [NCO equivalent of isocyanate / active hydrogen equivalent × 100].

[0031] [Physical Properties of Polyurethane Foam] The polyurethane foam according to the present disclosure may be a flexible polyurethane foam, and has the following physical properties.

[0032] Density The density of polyurethane foam (JIS K7222) is 80 kg / m ３ More than 230kg / m ３ The density may be less than or equal to 85 kg / m ３ More than 220kg / m ３ More preferably, it is 90 kg / m or less. ３ More than 210kg / m ３ More preferably, it is 95 kg / m or less. ３ More than 205kg / m ３ or less, and particularly preferably 100 kg / m ３ More than 200kg / m ３ The following is the result.

[0033] Impact absorption: The maximum stress when a 30 J impact is applied is preferably 30 kN or less, more preferably 25 kN or less. The smaller the maximum stress, the better, so from this perspective, it is preferably 0 to 30, more preferably 0 to 25. In this example, a drop weight test was performed, and a 5 kg iron ball was dropped from a height of 60 cm to evaluate the maximum stress measured when a 30 J impact was applied to a 10 mm thick polyurethane foam.

[0034] Asker C Hardness The Asker C hardness at room temperature (23°C), measured in accordance with JIS K7312, is preferably 50 or less, and more preferably 40 or less, from the viewpoint of flexibility. The Asker C hardness is preferably 3 or more, and more preferably 5 or more, from the viewpoint of reducing bottoming out. From these viewpoints, the Asker C hardness at room temperature is preferably 3 or more and 50 or less, and more preferably 5 or more and 40 or less.

[0035] [Method for Producing Polyurethane Foam] Polyurethane foam can be produced by a known foaming method in which the composition is stirred and mixed to react the polyol and polyisocyanate. Foaming methods include slab foaming and mold foaming, and either method is acceptable, but mold foaming is more preferred. Mold foaming is a method in which a mixed polyurethane resin composition is filled into a mold (forming tool) and foamed within the mold. Molded urethane molding methods using mold foaming are suitable for producing molded products with complex three-dimensional shapes. The thickness of the polyurethane foam produced is not particularly limited. When mold foaming is used as the foaming method, any thickness that can be produced by mold foaming is sufficient. The thicker the polyurethane foam, the higher the impact absorption. However, the polyurethane foam of the present disclosure exhibits improved impact absorption even when the thickness is about 10 mm.

[0036] [Uses of Polyurethane Foam] According to the present disclosure, a low-resilience polyurethane foam with excellent impact absorption properties can be realized. In the examples, it has been shown that even a polyurethane foam with a thickness of 10 mm exhibits excellent impact absorption properties. In addition to such impact absorption properties, the moldability, demoldability, and conformability of the polyurethane foam according to the present disclosure are believed to be achieved by blending a castor oil-based polyol in a predetermined ratio. Furthermore, by combining a castor oil-based polyol with two types of polyether polyols with different molecular weights, a polyurethane foam with even better impact absorption properties, moldability, demoldability, and conformability can be obtained. Such polyurethane foams are suitable as impact absorbers.

[0037] There are no particular limitations on the types of articles in which the polyurethane foam of the present disclosure can be used. The polyurethane foam is suitable for sports protectors or supports for joints such as elbows and knees, protective padding for helmets, cushions, automobile headrests, armrests, motorcycle saddles, seats, bicycle saddles, etc. In particular, the polyurethane foam of the present disclosure, which has excellent shock absorption properties even when its thickness is 10 mm or less (e.g., 5 mm, 6 mm, 7 mm, 8 mm, or 9 mm), is suitable for components that support at least a part of the human body, such as protectors or supports for joints such as elbows and knees, protective padding for helmets, etc.

[0038] The polyurethane foam of the present disclosure can be a polyurethane foam with improved impact absorption properties by including a castor oil-based polyol in the polyurethane foam raw material. Furthermore, by using two types of polyether polyols with different molecular weights in addition to the castor oil-based polyol, a polyurethane foam with excellent impact absorption properties can be obtained even if it is lightweight and thin-walled. In this way, by selecting and combining two types of polyether polyols with different molecular weights in addition to the castor oil-based polyol and adjusting the blending amounts, a polyurethane foam can be obtained that not only has excellent impact absorption properties but also has excellent moldability and removability, which are necessary for molded urethanes, and excellent conformability, which is necessary for use as an article.

[0039] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0040] [Production of Polyurethane Foam] Compositions were prepared by blending raw materials in the proportions shown in the tables of Figures 1 and 2, and polyurethane foams of the examples and comparative examples were produced by mold foaming. The "foam bio content (%) in the tables" (bio content in the urethane foam) was calculated using the following formula (1): Foam bio content (%) = (mass (g) of polyol C / mass (g) of total blend) × 100 (1)

[0041] The following raw materials were used: Polyol A is a high molecular weight polyether polyol, and Polyol C is a low molecular weight polyether polyol. Polyol A: V4701, polyether polyol, polypropylene oxide having ethylene oxide at the end (VORANOL4701, manufactured by Dow Chemical Japan Co., Ltd.), hydroxyl value 35 mg KOH / g, functionality 3, number average molecular weight 5000. Polyol B: H30, castor oil polyol, unmodified (purified), (H-30, manufactured by Ito Oil Mills Co., Ltd.), molecular weight 945, functionality 2.7, hydroxyl value 160 mg KOH / g. Polyol C: GP400, polyether polyol (SANNICS GP400, manufactured by Sanyo Chemical Industries, Ltd.), PO / EO (molar ratio) = 100 / 0, functionality 3, hydroxyl value 421 mg KOH / g, number average molecular weight 400. Crosslinker: glycerin, functionality 3 (Dynamite Glycerin, manufactured by NOF Corporation). Catalyst: 33LSI, an amine catalyst (DABCO 33LSI, manufactured by Evonik Japan Co., Ltd., resinification catalyst), a 33 mass % dipropylene glycol solution of triethylenediamine. Foam stabilizer: B8738LF2, a silicone foam stabilizer (TEGOSTAB B8738LF2, manufactured by Evonik Japan Co., Ltd.). Blowing agent: water. Isocyanate: MP-102, a urethane-modified MDI (Lupranate MP-102, manufactured by BASF INOAC Corporation), NCO=22.7%.

[0042] [Evaluation Method] Test specimens were cut from the polyurethane foams produced using the above raw materials, and the density, impact absorption, moldability, demoldability, and conformability (Asker C hardness) were evaluated by the following methods. In the tables of Figures 1 and 2, A indicates excellent, B indicates good, and C indicates poor.

[0043] Density: Measured in accordance with JIS K7222. JIS (Japanese Industrial Standards) are Japanese standards for industrial and mineral products, processing technology, electromagnetic recording, services, business management, etc. Impact absorption: Evaluated using a drop weight test, measuring the maximum stress when a 5 kg iron ball was dropped from a height of 60 cm. A was given for 25 kN or less, B for over 25 kN to 30 kN, and C for over 30 kN. Moldability: Determining the condition of the polyurethane foam when a test piece measuring 400 x 150 x 10 mm was prepared. Visual observation was performed to determine whether shrinkage occurred without crushing or significant cell roughness. A was given for no abnormalities, B for very minor abnormalities, and C for abnormalities. Demoldability: A test piece measuring 400 x 150 x 10 mm was prepared, and the condition of the polyurethane foam was evaluated when demolded 5 minutes after the start of foaming. A rating of A was given to foam that could be demolded without any problems, a rating of B to foam that retained its shape even if it was somewhat soft and could be demolded, and a rating of C to foam that was difficult to demold due to insufficient curing. - Conformability: The degree of conformability (flexibility, wearing comfort) with the object when used as a protector was evaluated by surface hardness. The hardness of the polyurethane foam was evaluated in accordance with JIS K7312 using an Asker C hardness tester. The test temperature was room temperature (23°C). A rating of A was given for 40 or less, a rating of B for more than 40 and less than 50, and a rating of C for more than 50. - Evaluation: Polyurethane foams that had a rating of "C" in even one of the evaluation items were evaluated as "C." Polyurethane foams that had only "A" and "B" in the evaluation items and had an impact absorption rating of "A" were evaluated as "A." All other polyurethane foams were evaluated as "B."

[0044] [Results] Example 1-2 and Comparative Example 3 are compared in the tables of Figures 1 and 2. Example 1-2 contains castor oil polyol, while Comparative Example 3 does not. The formulation of other components is the same. Comparative Example 3 was inferior to Example 1-2 only in impact absorption. This shows that the use of castor oil polyol improves the impact absorption of polyurethane foam. By adding castor oil polyol, it was possible to improve impact absorption while maintaining productivity. However, Comparative Example 5 had poor moldability and demoldability because the amount of castor oil polyol was too high (or the amount of high-molecular-weight polyether polyol was too low).

[0045] Examples 3-5 and 1-2 are compared in the tables of Figures 1 and 2. Example 3-5 contains a castor oil polyol and a low molecular weight polyether polyol, while Example 1-2 contains a castor oil polyol but does not contain a low molecular weight polyether polyol. Example 3-5 has excellent impact absorption properties despite a lower castor oil polyol content than Example 1-2. This indicates that the addition of a low molecular weight polyether polyol improves the impact absorption properties of polyurethane foams. However, Comparative Example 4 showed poor demoldability and conformability due to an excessive amount of low molecular weight polyether polyol (or an excessively small amount of high molecular weight polyether polyol). Furthermore, Comparative Examples 6 and 7, which did not contain castor oil polyol but contained a low molecular weight polyether polyol, also showed poor moldability, demoldability, and conformability.

[0046] Examples 5 and 7-8 are compared. Examples 5 and 7-8 differ in the density of the polyurethane foam. Examples 5, 7-8, and Comparative Example 2 showed that higher densities result in better impact absorption. However, Comparative Example 2 showed that if the density is too high, moldability and conformability are poor. Furthermore, Comparative Example 1 showed that if the density is too low, underfill occurs, making molding impossible.

[0047] All references, including publications, patent applications, and patents, cited in this specification are herein incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference, and the contents of each reference are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference.

[0048] The use of nouns and similar referents in connection with the description of this disclosure (particularly in connection with the claims that follow) shall be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The words "comprises," "has," "includes," and "comprises" shall be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The recitation of numerical ranges herein is merely intended to serve as a shorthand method for individually referring to each value falling within the range, unless otherwise indicated herein, and each value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any examples or exemplary language used herein (e.g., "e.g., "etc.") are intended merely to better illustrate the disclosure and do not pose limitations on the scope of the disclosure, unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the present disclosure.

[0049] Preferred embodiments of the disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Variations of these preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventors anticipate that skilled artisans will apply such variations as appropriate, and intend to practice the disclosure otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, this disclosure includes any combination of the above-described elements in all variations thereof unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A polyurethane foam using a polyol containing a castor oil-based polyol as a raw material, wherein the castor oil-based polyol is contained in an amount of 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the polyol, and the density is 80 kg / m ３ or more and 230 kg / m ３ or less, and the Asker C hardness is 50 or less, and the polyurethane foam contains a plant-derived raw material.

2. The polyurethane foam containing the plant-derived raw material according to claim 1, wherein the hydroxyl value of the castor oil-based polyol is 70 mgKOH / g or more and 250 mgKOH / g or less.

3. A shock absorber comprising the polyurethane foam containing the plant-derived raw material according to claim 1 or claim 2.

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