Polyurethane foam

Abstract

This polyurethane foam is obtained by foaming and curing, in a mold, a foaming urethane resin composition having: a polyol component that has a plant-derived polyol and a petroleum-derived polyol; an isocyanate component, and a metal catalyst. The plant-derived polyol has a modified castor oil of which the main component is the compound represented by structural formula (a), wherein the content of the modified castor oil is 50-80 parts by mass, where the mass of the polyol component is 100 parts by mass.

Description

Polyurethane foam

[0001] This disclosure relates to polyurethane foam.

[0002] In vehicles such as automobiles, foams such as polyurethane foam, which are lightweight and have excellent cushioning, sound absorption, and vibration damping properties, are used as soundproofing materials and interior components. Until now, polyols derived from petroleum resources, such as polyether polyols, have been used as raw materials for polyurethane foam. However, in recent years, from the perspective of reducing environmental impact, it is desirable to use plant-derived polyols obtained from plant resources, in addition to petroleum-derived polyols. For example, Patent Document 1 describes a plant-derived polyol with a hydroxyl value of 130 mgKOH / g or less, with a density of 25 kg / m³. ３ The following polyurethane foam is described. The document states that, from the viewpoint of ensuring strength, the content of plant-derived polyols should be 75 parts by mass or less when the total of petroleum-derived polyols and plant-derived polyols is 100 parts by mass. Patent document 2 describes a polyurethane foam using plant-derived polyols and polymer polyols as polyols. The document states that the plant content (biomass content) should be 25% or more.

[0003] Japanese Patent Publication No. 2024-2575, International Publication No. 2024 / 024845

[0004] The reaction that forms polyurethane foam consists of two parts: a foaming reaction and a curing reaction (resinization reaction that forms urethane bonds) (hereinafter, these may be collectively referred to as the "foaming urethane reaction"). When the inventors investigated the behavior of the foaming urethane reaction when using plant-derived polyols, they found that plant-derived polyols have poor dispersibility with isocyanates, and in particular, the curing reaction is slow. As a result, the curing reaction cannot keep up with the foaming reaction, and the balance of the reaction is disrupted, which makes it easy for molding defects such as shrinkage to occur. Thus, because it is difficult to control the foaming urethane reaction when using plant-derived polyols, it is currently difficult to increase the proportion of plant-derived polyols (biomass content) in the polyol. In addition, castor oil and soybean oil are known as plant-derived polyol materials, but if, for example, unmodified castor oil is used, the polyurethane foam tends to become hard. For this reason, it is not suitable for applications that require cushioning properties, such as headrests.

[0005] This disclosure has been made in view of the above circumstances, and aims to provide a polyurethane foam that has desired hardness and satisfies moldability requirements using plant-derived polyols.

[0006] (1) In order to solve the above problems, the polyurethane foam of the present disclosure is a polyurethane foam obtained by foaming and curing a foamed urethane resin composition having a polyol component having a plant-derived polyol and a petroleum-derived polyol, an isocyanate component and a metal catalyst in a mold, wherein the plant-derived polyol has modified castor oil mainly composed of a compound represented by the following structural formula (a), and when the mass of the polyol component is 100 parts by mass, the content of the modified castor oil is 50 parts by mass or more and 80 parts by mass or less.

[0007] According to the polyurethane foam of this disclosure, by using modified castor oil mainly composed of the compound shown in structural formula (a) (hereinafter sometimes referred to as "compound (a)") as the polyol component, and employing a metal catalyst as the catalyst, it is possible to achieve the desired hardness and good moldability even with a relatively high biomass content. Compound (a) has a structure in which a fatty acid a1 or fatty acid a2 is esterified to an ester of glycerin and ricinoleic acid (ricinoleic acid ester), or propanediol is ether-condensed. (R in structural formula (a)) １ ~R ３ This is one of fatty acid a1, fatty acid a2, or propanediol. Hereinafter, fatty acid a1, fatty acid a2, and propanediol may be collectively referred to as "fatty acids, etc.") The reactivity of the curing reaction is increased when ricinoleic acid ester is modified with fatty acids, etc. Furthermore, the curing reaction can be accelerated by using a metal catalyst. This allows the foaming reaction and the curing reaction to proceed in a well-balanced manner. As a result, shrinkage in the molded product (polyurethane foam) is suppressed, and a molded product with the desired hardness can be obtained.

[0008] (2) In the above configuration, the petroleum-derived polyol may be a polyether polyol having 2 or more but less than 3 functional groups and a number average molecular weight of 2000 or more but 5000 or less. With this configuration, the reactivity of the petroleum-derived polyol can be increased, and the increase in viscosity during foam molding can be suppressed, thereby improving moldability.

[0009] (3) In any of the above configurations, the biomass content calculated by the following formula (I) may be 30% or more and 50% or less. Biomass content (%) = (Mass of plant-derived polyol / Total mass of foamed urethane resin composition) × 100 ... (I) With this configuration, the proportion of plant-derived polyol is relatively high, so the environmental burden can be further reduced.

[0010] (4) In any of the above configurations, the content of the metal catalyst in the foamed urethane resin composition may be 0.05 parts by mass or more and 0.25 parts by mass or less per 100 parts by mass of the polyol component. This configuration is suitable for promoting the curing reaction and suppressing shrinkage of the molded product and achieving the desired hardness.

[0011] (5) In any of the above configurations, the foamed urethane resin composition may have an amine catalyst. When a metal catalyst is used, the reaction rate tends to change rapidly. With this configuration, the amount of metal catalyst can be reduced and the reaction can proceed more gently.

[0012] (6) In any of the above configurations, the foamed urethane resin composition may have a carbon black content. Carbon black is suitable as a black pigment and is also thought to act as a nucleating agent for bubble formation. Therefore, this configuration makes it easier to achieve desired bubble structures such as open-cell structures.

[0013] (7) In any of the above configurations, the Asker F hardness may be set to 30 or more and 90 or less. This configuration is suitable for applications where cushioning is required, such as headrests and seat cushions.

[0014] The polyurethane foam disclosed herein has a low environmental impact because it uses plant-derived polyols, possesses the desired hardness, is less prone to shrinkage, and has excellent moldability.

[0015] Embodiments of the polyurethane foam of this disclosure will be described below. However, the embodiments are not limited to those described below, and can be implemented in various modified and improved forms as possible for those skilled in the art. In the numerical ranges described stepwise in this specification, the upper and lower limits described individually can be combined as desired. Furthermore, the upper and lower limits of the numerical ranges can be replaced with the values ​​shown in the examples.

[0016] The polyurethane foam of this disclosure is obtained by foaming and curing a foamed urethane resin composition having a predetermined polyol component, an isocyanate component, and a metal catalyst in a mold.

[0017] <Foamed urethane resin composition> [Polyol component] The polyol component includes plant-derived polyols and petroleum-derived polyols.

[0018] (1) Plant-derived polyols Plant-derived polyols include modified castor oil. Modified castor oil can be any oil produced using castor oil. The main component of the modified castor oil used in the production of the polyurethane foam of this disclosure is the compound shown in the following structural formula (a). R of compound (a) １ ~R ３ These components may all be the same, all be different, or only one be different. The "main component" of modified castor oil is the component that accounts for 60% or more by mass when the total modified castor oil is considered to be 100% by mass. Modified castor oil may also contain unavoidable components included in the manufacturing process, such as polypropylene glycol, polypropanediol, and sebacic acid. From the viewpoint of increasing the reactivity of the curing reaction, the proportion of compound (a) in the components of modified castor oil should be 70% by mass or more. It is even more preferable if it is 80% by mass or more, 90% by mass or more, and even 100% by mass.

[0019] The hydroxyl value of modified castor oil should be 40 mg KOH / g or higher, more preferably 50 mg KOH / g or higher, from the viewpoint of increasing the reactivity of the curing reaction. Conversely, from the viewpoint of suppressing the heat generation during foam curing, it should be 160 mg KOH / g or lower, more preferably 130 mg KOH / g or lower.

[0020] The number-average molecular weight of modified castor oil should be 2000 or higher, from the viewpoint of providing good cushioning properties due to its flexible molecular structure. 3000 or higher is more preferable. Conversely, from the viewpoint of suppressing the increase in liquid viscosity due to the extension of molecular chains and improving moldability, it should be 5000 or lower, more preferable than 4500.

[0021] The modified castor oil content is between 50 and 80 parts by mass, based on a polyol component mass of 100 parts by mass. If the modified castor oil content is higher than 80 parts by mass, the polyurethane foam tends to become hard. A suitable content is 75 parts by mass or less, and more preferably 70 parts by mass or less. Conversely, if the modified castor oil content is less than 50 parts by mass, the effect of reducing environmental impact will be small. A suitable content is 55 parts by mass or more, and more preferably 60 parts by mass or more.

[0022] As plant-derived polyols, only modified castor oil may be used, but unmodified castor oil, other vegetable oils, and their derivatives may also be used in combination. Examples of vegetable oils that can be used as raw materials for plant-derived polyols include castor oil, soybean oil, sunflower oil, rapeseed oil, linseed oil, cottonseed oil, tung oil, coconut oil, poppy oil, corn oil, and peanut oil.

[0023] (2) Petroleum-derived polyols Petroleum-derived polyols are not particularly limited. For example, they can be appropriately selected from polyhydric hydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, etc.

[0024] For example, from the viewpoint of excellent hydrolysis resistance, it is desirable that the main component of petroleum-derived polyols be polyether polyols. The "main component" of petroleum-derived polyols refers to the component that accounts for 60% or more by mass when the total amount of petroleum-derived polyols is considered to be 100% by mass. In this case, polyether polyols may be used alone, or they may be combined with other petroleum-derived polyols such as polyester polyols and polymer polyols. Furthermore, even when using only polyether polyols, multiple types with different functional group numbers, molecular weights, etc., can be combined.

[0025] Examples of polyether polyols include those obtained by adding alkylene oxides such as ethylene oxide (EO) and propylene oxide (PO) to polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. From the viewpoint of increasing the reactivity of petroleum-derived polyols and suppressing the increase in viscosity during foam molding to improve moldability, it is desirable that the number of functional groups of the polyether polyol be 2 or more and less than 3. Furthermore, it is desirable that the number-average molecular weight of the polyether polyol be 2000 or more and 5000 or less.

[0026] In the polyurethane foam of this disclosure, the biomass content based on the components of the foamed urethane resin composition is calculated by the following formula (I): Biomass content (%) = (Mass of plant-derived polyol / Total mass of foamed urethane resin composition) × 100 ... (I) To reduce the environmental burden, it is desirable that the biomass content be 30% or more. A more preferable biomass content is 35% or more. On the other hand, considering the hardness of the polyurethane foam, it is desirable that the biomass content be 50% or less. A more preferable biomass content is 48% or less.

[0027] [Isocyanate Component] The isocyanate component is not particularly limited as long as it forms a urethane bond through reaction with the polyol component. For example, it can be appropriately selected from tolylene diisocyanate (TDI), phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and their derivatives. Examples of derivatives include prepolymers obtained by reaction of isocyanate and polyol, modified polyisocyanates, and polymeric MDI (multinuclear) having three or more isocyanate groups and benzene rings in one molecule. For example, MDI is desirable from the viewpoint of high crystallinity and ease of molding polyurethane foam. Polymeric MDI is particularly suitable due to its high reactivity.

[0028] [Catalyst] A metal catalyst is used as the catalyst. Organometallic catalysts such as tin laurate and tin octanoate are preferred as metal catalysts. From the viewpoint of promoting the curing reaction, the content of the metal catalyst in the foamed urethane resin composition is preferably 0.05 parts by mass or more per 100 parts by mass of the polyol component. More preferably 0.10 parts by mass or more. On the other hand, from the viewpoint of preventing the curing reaction rate from becoming excessively high, it is preferably 0.25 parts by mass or less per 100 parts by mass of the polyol component. More preferably 0.20 parts by mass or less.

[0029] In addition to metal catalysts, other catalysts such as amine catalysts may be used. Examples of amine catalysts include tetraethylenediamine, triethylenediamine, and dimethylethanolamine. By using amine catalysts in combination, the amount of metal catalyst can be reduced, allowing the curing reaction to proceed more gently while maintaining a good balance between the foaming and curing reactions.

[0030] [Other Components] In addition to the above materials, the foamed urethane resin composition may also contain known materials used in the manufacture of polyurethane foam, such as foaming agents, chain extenders, foam stabilizers, crosslinking agents, plasticizers, flame retardants, antistatic agents, viscosity reducers, stabilizers, fillers, and pigments. Of these, water is preferred as the foaming agent. Other examples include methylene chloride, chlorofluorocarbons (CFCs), and carbon dioxide (carbonic acid gas). Examples of chain extenders include ethylene glycol, diethylene glycol, propylene glycol, 3-methyl-1,5-pentanediol, and 1,9-nonanediol. Examples of foam stabilizers include polyether-modified silicone compounds and polyester-modified silicone compounds. Examples of crosslinking agents include triethanolamine and diethanolamine. Examples of flame retardants include expanded graphite, phosphorus-based, halogen-based, and metal hydroxide-based flame retardants. Examples of pigments include black pigments such as carbon black. The inclusion of carbon black can improve the weather resistance and sound insulation properties of the polyurethane foam. Furthermore, because it is thought to act as a nucleating agent for bubble formation, it facilitates the realization of desired bubble structures, such as open-cell structures.

[0031] <Properties of Polyurethane Foam> [Hardness] When the polyurethane foam of the present disclosure is used as a material for products that require cushioning properties, such as headrests and seat cushions, which are interior parts of vehicles, it is desirable that the Asker F hardness of the polyurethane foam is 90 or less. On the other hand, if the Asker F hardness is too small, there is a concern that sufficient shock absorption performance cannot be obtained. Therefore, it is desirable that the Asker F hardness is 30 or more. In the present disclosure, as the Asker F hardness, the peak value measured by the "Asker Rubber Hardness Tester F Type" manufactured by Kobunshi Keiki Co., Ltd. is adopted.

[0032] [Density] When the polyurethane foam of the present disclosure is used as a material for products that require cushioning properties, such as headrests and seat cushions, which are interior parts of vehicles, from the viewpoint of achieving appropriate hardness and elasticity, the density of the polyurethane foam is ３ 20 kg / m or more and ３ 200 kg / m or less. If the density is too large, it becomes hard and the elasticity decreases. A more suitable density is 150 kg / m ３ or less. On the contrary, if the density is too small, it becomes difficult to obtain the desired rigidity. A more suitable density is 30 kg / m ３ or more. In the present disclosure, as the density, the value calculated by dividing the mass of the polyurethane foam to be measured by its volume is adopted.

[0033] <Method for Manufacturing Polyurethane Foam> The polyurethane foam of this disclosure is manufactured by foam molding a foamed urethane resin composition. As an example of the manufacturing method, first, a premixed polyol is prepared by pre-mixing a polyol component with a catalyst other than the isocyanate component, a blowing agent, etc. Next, the isocyanate component is mixed with the prepared premixed polyol. The premixed polyol and the isocyanate component may be mixed by mechanical stirring with a stirring blade or the like, or by using a high-pressure jet foaming device to spray the two materials at high pressure and mix them by impact (impact stirring method). Compared to the mechanical stirring method, the impact stirring method eliminates the need for the container cleaning step that was required after each mixing, and improves the yield. Therefore, manufacturing costs can be reduced. In addition, continuous production is possible, making it suitable for mass production. It is desirable that the polyol component and the isocyanate component be blended so that the isocyanate index (equivalents of isocyanate groups / equivalents of active hydrogen groups × 100) is 60 or more and 120 or less, preferably 70 or more and 110 or less. If the isocyanate index is less than 60 or greater than 120, moldability may be reduced.

[0034] Next, the present disclosure will be described in more detail with reference to examples.

[0035] <Preparation of Polyurethane Foam Samples> Nine types of polyurethane foam samples were prepared using the materials shown in Table 1 below. First, a premix polyol was prepared by adding a crosslinking agent, a foaming agent, amine catalyst a, amine catalyst b, a metal catalyst (except for Comparative Example 3), and a pigment to the polyol component and mixing. Next, the prepared premix polyol and the isocyanate component were mixed so that the isocyanate index was 90 to prepare a foamed polyurethane resin composition. Then, the foamed polyurethane resin composition was injected into a mold cavity (a rectangular parallelepiped with dimensions of 150 mm in length, 150 mm in width, and 100 mm in height) that had been preheated to 60°C, sealed, and foamed for 5 minutes. After that, the polyurethane foam was removed from the mold and used as a sample.

[0036] Table 1 shows the compounding ratios of the materials used in the production of the polyurethane foam samples and the biomass content. The biomass content was calculated by the previous formula (I). The details of the materials are as follows. (A) Polyol component (A-1) Petroleum-derived polyol Polyether polyol: Polypropylene glycol (functionality 2, number average molecular weight 4000), "Sunnex (registered trademark) FA-718" manufactured by Sanyo Chemical Industries, Ltd. (A-2) Plant-derived polyol Modified castor oil a: The compound represented by the previous structural formula (a). Hydroxyl value 55 mg KOH / g, number average molecular weight 3000. The production method is as follows. Into a reaction flask, 930 parts by mass of refined castor oil ("URIC H-30" manufactured by Ito Oil Co., Ltd.), 1415 parts by mass of ricinoleic acid, and 912 parts by mass of 1,3-propanediol were charged, and nitrogen gas was introduced. The reaction was carried out for 7 hours under a nitrogen gas atmosphere at a temperature of 160 to 200 °C to obtain compound (a) (the ratio of compound (a) in modified castor oil a is 100% by mass). By-product water was distilled out of the system using a distillation tube. Modified castor oil b: "URIC SE-2013C" manufactured by Ito Oil Co., Ltd. (sebacic acid-based polyester polyol starting from castor oil). The content ratio of the compound represented by the previous structural formula (a) is 0% by mass. Hydroxyl value 56 mg KOH / g, number average molecular weight 2000. Refined castor oil (unmodified castor oil): "URIC H-30" manufactured by Ito Oil Co., Ltd. Hydroxyl value 160 mg KOH / g, number average molecular weight 1000. (B) Catalysts Amine catalyst a: "DABCO (registered trademark) NE310" manufactured by EVONIK. Amine catalyst b: "DABCO (registered trademark) 33LSI" manufactured by EVONIK. Metal catalyst: Dibutyltin dilaurate (DBTDL). (C) Blowing agent: Water. (D) Crosslinking agent: Diethanolamine. (E) Pigment Carbon black: "FT 1576 BLACK" manufactured by Dainichi Seika Kogyo Co., Ltd. (F) Isocyanate component: Diphenylmethane diisocyanate (MDI).

[0037]

[0038] <Evaluation of samples> The Asker F hardness of the manufactured samples was measured to evaluate the hardness. Also, the shrinkage amount was measured to evaluate the moldability.

[0039] [Measurement Method] (1) The peak value measured using the "Asker Rubber Hardness Tester Type F" manufactured by Asker F Hardness Polymer Instruments Co., Ltd. was defined as the Asker F hardness of the sample. A value of 90 or less was evaluated as suitable (indicated by a circle in Table 1), and a value greater than 90 was evaluated as unsuitable (indicated by a cross in the same table).

[0040] (2) Shrinkage Amount A sample of polyurethane foam (a rectangular parallelepiped measuring 150 mm in length, 150 mm in width, and 100 mm in height) removed from the mold was left indoors for one day to observe the degree of shrinkage. If any indentation was observed due to shrinkage, the depth of the indentation was measured with calipers, and the maximum value was taken as the shrinkage amount of the sample. A shrinkage amount of less than 3 mm was evaluated as very good moldability (indicated by ◎ in Table 1), a shrinkage amount of 3 mm or more but less than 6 mm was evaluated as good moldability (indicated by ○ in Table 1), and a shrinkage amount of 6 mm or more was evaluated as poor moldability (indicated by × in the same table).

[0041] [Measurement Results] Table 1 above summarizes the evaluation results for hardness and moldability of each sample. The samples of Examples 1 to 5 are included in the concept of polyurethane foam of this disclosure. As shown in Table 1, the samples of Examples 1 to 5, which contained 50 to 80 parts by mass of modified castor oil a, mainly composed of compound (a), as the polyol component, and used a metal catalyst, exhibited the desired hardness, small shrinkage, and good moldability even with a high biomass content of 36% to 48%. In particular, the sample of Example 3 showed no shrinkage (shrinkage amount 0 mm) and very good moldability. In contrast, the sample of Comparative Example 1 had a larger shrinkage and poor moldability because the content of modified castor oil a was greater than 80 parts by mass. Furthermore, the sample of Comparative Example 2, which used unmodified refined castor oil, and the sample of Comparative Example 4, which used modified castor oil b without compound (a), both became hard and had poor moldability. Furthermore, the sample of Comparative Example 3, which did not use a metal catalyst, also became hard and had poor moldability.

[0042] The polyurethane foam disclosed herein is suitable for soundproofing materials and interior components for vehicles, furniture such as sofas and chairs, and shoe soles.

Claims

1. A polyurethane foam obtained by foaming and curing a foamed urethane resin composition having a polyol component having a plant-derived polyol and a petroleum-derived polyol, an isocyanate component, and a metal catalyst in a mold, wherein the plant-derived polyol has modified castor oil mainly composed of a compound represented by the following structural formula (a), and the content of the modified castor oil is 50 parts by mass or more and 80 parts by mass or less when the mass of the polyol component is 100 parts by mass.

2. The polyurethane foam according to claim 1, wherein the petroleum-derived polyol is a polyether polyol having two or more functional groups and a number average molecular weight of 2,000 or more and 5,000 or less.

3. The polyurethane foam according to claim 1 or claim 2, wherein the biomass content calculated by the following formula (I) is 30% or more and 50% or less. Biomass content (%) = (Mass of plant-derived polyol / Total mass of foamed urethane resin composition) × 100 ... (I) 4. The polyurethane foam according to any one of claims 1 to 3, wherein the content of the metal catalyst in the foamed urethane resin composition is 0.05 parts by mass or more and 0.25 parts by mass or less per 100 parts by mass of the polyol component.

5. The polyurethane foam according to any one of claims 1 to 4, wherein the foamed urethane resin composition has an amine catalyst.

6. The polyurethane foam according to any one of claims 1 to 5, wherein the foamed urethane resin composition comprises carbon black.

7. The polyurethane foam according to any one of claims 1 to 6, wherein the Asker F hardness is 30 or more and 90 or less.

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