Polyurethane foam and method for producing same

Abstract

This polyurethane foam is obtained by expanding and curing an expandable urethane resin composition that comprises an isocyanate component, a polyol component, and a catalyst. The catalyst comprises entirely coated particles in each of which a catalyst component is coated with a coating material and the catalyst component is not exposed on the surface, and the content of the catalyst component in the entirely coated particles is 60 mass% or more when the mass of the entirely coated particles is 100 mass%. This method for producing a polyurethane foam includes: a granulation step in which a coating material and base particles that serve as a catalyst component are stirred together to produce entirely coated particles that contain the catalyst component in an amount of 60 mass% or more; a composition preparation step in which an expandable urethane resin composition that comprises an isocyanate component, a polyol component, and a catalyst comprising the entirely coated particles is prepared; and an expanding and curing step in which the expandable urethane resin composition is expanded and cured.

Description

Polyurethane Foam and Method for Producing the Same

[0001] The present disclosure relates to a polyurethane foam suitable for a sound-absorbing material and a vibration-damping member used in vehicles, buildings, etc., and a method for producing the same.

[0002] In vehicles such as automobiles, sound-absorbing materials, vibration-damping members, etc. are arranged at sites that are sources of vibration and noise to reduce the transmission of vibration and the diffusion of noise. As the sound-absorbing material and the vibration-damping member, foams such as a polyurethane foam that is lightweight and has high sound insulation and vibration absorption properties are used. The polyurethane foam is produced, for example, as described in Patent Document 1, by injecting a raw material (foamed urethane resin composition) having an isocyanate component, a polyol component, a catalyst, a foaming agent, etc. into a molding die and causing it to foam and cure.

[0003] Japanese Patent Application Laid-Open No. 2020-2235 Japanese Patent Publication No. 2015-507050

[0004] The reaction for forming the polyurethane foam includes two reactions: a foaming reaction (foaming reaction) and a curing reaction (resinification reaction for forming a urethane bond) (hereinafter, these may be collectively referred to as a "foamed urethanization reaction" in some cases). The catalyst is greatly related to the progress of the foamed urethanization reaction. In order to improve productivity, it is desirable that the reaction rate be high. Usually, when the foamed urethane resin composition of the raw material is injected into the molding die, the foaming reaction and the curing reaction proceed immediately. At this time, if the progress of the foaming reaction is too fast, there is a risk that the mold clamping cannot catch up. Also, if the progress of the curing reaction is too fast, there may be a risk of insufficient foaming or the curing reaction may complete before the raw material spreads to the corners and details of the molding die, resulting in molding defects.

[0005] For example, Patent Document 2 describes a method for using a catalyst by encapsulating it. By encapsulating a catalyst and releasing it at a desired temperature, the progress of the reaction in which the catalyst acts can be controlled. Patent Document 2 describes a method for encapsulating a catalyst in which the catalyst is dispersed or dissolved in an encapsulating agent such as a thermoplastic resin, catalyst droplets are formed, and then cooled to solidify them. In addition to this, a conventional method of coating the surface of core particles (mother particles) with a coating material such as a resin has been known, which involves mixing the mother particles with the coating material and then spray-drying or pulverizing them.

[0006] However, with conventional methods, the catalyst is often not completely coated, and a portion of the catalyst is exposed on the surface. When such partially coated particles are used as a catalyst, the exposed catalyst initiates curing reactions, and the heat generated during these reactions melts the coating material, such as thermoplastic resin, releasing the catalyst. As a result, the initial reaction delaying effect of the coating is not sufficiently obtained. Consequently, curing defects cannot be adequately suppressed, and moldability is reduced. Furthermore, when using the spray drying method, if the amount of catalyst used as the mother particle is increased, the resulting particles will aggregate, forcing a reduction in the amount of catalyst contained in each particle. Consequently, the catalyst's inherent reaction-promoting effect is also reduced.

[0007] This disclosure has been made in view of the above circumstances, and aims to provide a polyurethane foam with excellent moldability and a method for producing the same by controlling the progress of the urethane foaming reaction.

[0008] (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 an isocyanate component, a polyol component, and a catalyst, wherein the catalyst has fully coated particles in which the catalyst component is covered with a coating material and the catalyst component is not exposed on the surface, and the content of the catalyst component in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

[0009] The polyurethane foam of this disclosure is manufactured from a foamed urethane resin composition in which at least a portion of the catalyst is fully coated particles. Fully coated particles are coated catalyst particles in which the catalyst component is covered with a coating material, and in which the catalyst component is not exposed on the surface. In fully coated particles, when a predetermined temperature is reached, the coating material changes, such as melting, and the catalyst component is released. In other words, fully coated particles do not act as a catalyst until they reach the temperature at which the state of the coating material changes. By thus imparting temperature dependence to the catalyst, the timing of the catalyst's action can be delayed, and the foaming reaction and curing reaction can be carried out in a well-balanced manner. As a result, the foamed urethane resin composition can be spread to the corners and details of the mold before the curing reaction progresses and viscosity increases. This suppresses the occurrence of insufficient foaming and insufficient filling, and enables the realization of a polyurethane foam with excellent moldability. Furthermore, in fully coated particles, the catalyst component is not exposed on the surface. Therefore, the initial reaction delay effect due to the coating can be reliably obtained. In addition, 60% by mass or more of the fully coated particles is the catalyst component. Because it contains a relatively large amount of catalytic components, fully coated particles can fully exhibit the catalyst's inherent reaction-promoting effect, even in a coated form.

[0010] (2) In the above configuration, the solubility parameter value of the coating material may be set to 10 or higher. The solubility parameter (SP value) of the polyol component, which is the main component of the foamed urethane resin composition, is 8.6. With this configuration, since the SP value of the coating material is not too close to the SP value of the polyol component, the coating material does not easily dissolve in the polyol component. Therefore, the behavior of the coating material with respect to temperature, such as melting at a predetermined temperature, is not easily inhibited.

[0011] (3) In any of the above configurations, the coating material may be one or more selected from thermoplastic resin, wax, fatty acid, and ester compound. This configuration makes it easier to produce fully coated particles in which the coating material melts at a desired temperature.

[0012] (4) In the configuration of (3) above, the glass transition temperature of the thermoplastic resin may be 40°C or more and 70°C or less, and the melting points of the wax, the fatty acid, and the ester compound may be 40°C or more and 70°C or less. With this configuration, the coating material can be melted and the catalyst component released at the temperature at which the foamed urethane resin composition is foamed and cured (the molding temperature of the polyurethane foam).

[0013] (5) In the configuration of (3) or (4) above, the thermoplastic resin may be composed of polyvinyl butyrate, polyethylene oxide, and polystyrene. The SP value of these resins is 10 or more, and the glass transition temperature is 40°C to 70°C. Therefore, they are poorly soluble in the polyol component and can be melted at the molding temperature of polyurethane foam.

[0014] (6) In any of the above configurations, the catalyst component contained in the overall coated particles may be one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

[0015] (7) In any of the above configurations, the fully coated particle may have a core-shell structure comprising a coating layer forming the outermost layer of the particle and a catalyst component layer disposed inside the coating layer. This configuration makes it easy to produce fully coated particles in which the catalyst component content is 60% by mass or more and the catalyst component is not exposed on the surface.

[0016] (8) In the configuration of (7) above, the average particle size of the overall coating particles having a core-shell structure may be 5 μm or more and 800 μm or less, and the thickness of the coating layer may be 0.01 μm or more and 100 μm or less. With this configuration, the size of the overall coating particles becomes appropriate, the dispersibility in the foamed urethane resin composition is good, and polyurethane foam can be manufactured with good moldability.

[0017] (9) A method for producing polyurethane foam according to the present disclosure is one form of a method for producing polyurethane foam having any of the configurations of (1) to (8) above, comprising: a granulation step of stirring mother particles as a catalyst component and a coating material to produce fully coated particles in which the mother particles are coated with the coating material and the mother particles are not exposed on the surface; a composition preparation step of preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing the fully coated particles; and a foam curing step of foaming and curing the foamed urethane resin composition, wherein the content of the mother particles in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

[0018] According to the manufacturing method of this disclosure, the initial reaction delay effect of the overall-coating particles allows for a balanced progression of the foaming and curing reactions, enabling the production of polyurethane foam with good moldability. For example, before the curing reaction progresses and viscosity increases, the foamed urethane resin composition can reach even the corners and fine details of the mold, thereby suppressing insufficient foaming and insufficient filling, and enabling the production of products with complex shapes with good moldability.

[0019] The polyurethane foam of this disclosure is manufactured using a foamed urethane resin composition that employs fully coated particles in which the catalyst component is not exposed on the surface. As a result, the foaming reaction and curing reaction proceed in a well-balanced manner due to the initial reaction delay effect, resulting in excellent moldability. According to the method for manufacturing polyurethane foam of this disclosure, the foaming reaction and curing reaction can be carried out in a well-balanced manner due to the initial reaction delay effect of the fully coated particles, and polyurethane foam can be manufactured with good moldability.

[0020] The following describes embodiments of the polyurethane foam and its manufacturing method according to this disclosure. 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.

[0021] <Polyurethane Foam> The polyurethane foam of this disclosure is obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst.

[0022] [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, naphthalene diisocyanate (NDI), and derivatives thereof. 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.

[0023] [Polyol component] The polyol component 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, it is desirable to use polyether polyol as the main component. The "main component" is a component that accounts for 60% or more by mass when the total polyol component is considered to be 100% by mass. In other words, as the polyol component, either only polyether polyol may be used, or polyether polyol may be used as the main component in appropriate combination with other polyols. For example, from the viewpoint of improving moldability, it is desirable to use polyester polyol in combination. Furthermore, even when using only polyether polyol, multiple types with different functional group numbers, molecular weights, compatibility, etc. may be used in combination.

[0025] [Catalyst] The catalyst includes coated catalyst particles in which the catalyst component is covered with a coating material, and fully coated particles in which the catalyst component is not exposed on the surface. The catalyst may also include partially coated particles in which a part of the catalyst component is exposed on the surface. The catalyst may also include uncoated catalyst components. The mass ratio of fully coated particles to the total mass of the catalyst is preferably 50% by mass or more, when the total mass of the catalyst is considered as 100% by mass. 60% by mass or more, and more preferably 70% by mass or more, is preferred.

[0026] From the viewpoint of allowing the catalyst to exert its inherent reaction-promoting effect, the content of the catalyst component in the fully coated particles should be 60% by mass or more, based on the total mass of the fully coated particles being 100% by mass. A content of 65% by mass or more, or even 70% by mass or more, is more preferable. On the other hand, since a certain amount of coating material is also required to prevent the catalyst component from being exposed on the surface, the content of the catalyst component should be 95% by mass or less, and even 90% by mass or less.

[0027] The coating material constituting coated catalyst particles, such as fully coated particles, can be any material that changes state at a predetermined temperature and releases catalyst components. Examples include thermoplastic resins, waxes, fatty acids, and ester compounds. One or more of these can be used. For example, from the viewpoint of being less prone to change at temperatures near room temperature and more prone to change at the molding temperature, thermoplastic resins with a glass transition temperature (Tg) of 40°C to 70°C are desirable, and waxes, fatty acids, and ester compounds with a melting point (Tm) of 40°C to 70°C are desirable. Examples of thermoplastic resins with a Tg of 40°C to 70°C include polyvinyl butyrate, polyethylene oxide, polystyrene, terpene phenol, and acrylic resin. Examples of waxes with a Tm of 40°C to 70°C include paraffin wax, microcrystalline wax, and modified polyethylene wax. Examples of fatty acids include stearic acid, behenic acid, and maleic anhydride. Examples of ester compounds include distearyl 3,3'-thiodipropionic acid and behenyl behenate.

[0028] Furthermore, it is desirable that the coating material is poorly soluble in the polyol components that come into contact with it when preparing the foamed urethane resin composition. For this reason, it is desirable that the SP value of the coating material be as far apart as possible from the SP value of the polyol components. For example, it is desirable that the SP value of the coating material be 10 or higher. Examples of thermoplastic resins with a Tg of 40°C to 70°C and an SP value of 10 or higher include polyvinyl butyrate, polyethylene oxide, polystyrene, terpene phenol, and acrylic resin.

[0029] Examples of catalytic components that make up coated catalyst particles, such as fully coated particles, include amine catalysts such as triethylenediamine, tetraethylenediamine, dimethylethanolamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine, as well as metal catalysts such as tin laurate and tin octanoate. Among these, it is desirable to use one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine, from the viewpoint of high catalytic activity and ease of obtaining them in powder form.

[0030] The morphology of coated catalyst particles, such as fully coated particles, may be either a sea-island structure in which the catalyst component is dispersed within the coating material, or a core-shell structure in which the catalyst component forms the core layer and the coating material forms the shell layer. The core-shell structure makes it easier to coat a relatively large amount of catalyst component without exposing it to the surface. Therefore, it is desirable for fully coated particles to have a core-shell structure having a coating material layer forming the outermost layer of the particle and a catalyst component layer arranged inside the coating material layer.

[0031] The shape of the overall coating particles is not particularly limited and may include spherical, flaky, or irregularly shaped clumps. In this specification, "spherical" is not limited to perfectly spherical shapes, but includes shapes close to spherical (approximately spherical).

[0032] The particle size of the overall coating particles is not particularly limited and can be appropriately determined considering the dispersibility when preparing the foamed urethane resin composition and the viscosity when mixed with the polyol component. For example, it may be several tens to several hundred micrometers, or even just a few micrometers. For example, the average particle size of the overall coating particles can be between 5 μm and 800 μm. The overall coating particles may be used in their as-manufactured state, or they may be subjected to grinding or other processes to reduce their particle size. Reducing the particle size of the overall coating particles makes them easier to mix with the polyol component and the isocyanate component. Furthermore, when a premixed polyol is prepared by mixing the catalyst and the polyol component beforehand, and then mixed with the isocyanate component using a high-pressure jet foaming device, the limitations on nozzle diameter and other factors become less significant. For example, if the overall coating particles have a core-shell structure and the average particle size is between 5 μm and 800 μm, the thickness of the coating layer should be between 0.01 μm and 100 μm. In this specification, the average particle size is the median diameter (D) determined from the volume-based particle size distribution measured by laser diffraction and scattering. ５０ )

[0033] [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 colorants. 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. Various pigments can be used as colorants, and the presence of black pigments in particular can improve the weather resistance and sound insulation properties of the polyurethane foam.

[0034] <Method for Manufacturing Polyurethane Foam> One embodiment of the method for manufacturing polyurethane foam according to this disclosure comprises a granulation step, a composition preparation step, and a foaming and curing step. Each step will be described below.

[0035] [Granulation Process] This process involves stirring mother particles as catalyst components with a coating material to produce fully coated particles in which the mother particles are covered with the coating material and the mother particles are not exposed on the surface. The mixing ratio of mother particles to coating material should be adjusted so that the mother particle content is 60% or more of the total mass of the coated particles produced, with 100% being the mass. The stirring of the mother particles and coating material can be carried out using an appropriate method depending on the type of coating material, the size of the mother particles, etc. For example, it can be done by adding the mother particles to a coating material solution in which the coating material is dissolved in a solvent. Alternatively, it can be done by adding small amounts of water as a binder and the coating material to the mother particles. Alternatively, it can be done by adding water as a binder to the mother particles beforehand to wet the surface of the mother particles, and then adding the coating material. Stirring should be carried out at room temperature to about 30°C, as stirring at temperatures above 40°C may cause the catalyst components to sublimate or the coating material to melt. This process is for producing fully coated particles, but the coated catalyst particles produced by this process may also include partially coated particles.

[0036] [Composition Preparation Step] This step is for preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing fully coated particles. As the catalyst, not only fully coated particles but also partially coated particles or an uncoated catalyst component may be used. The components such as the catalyst are as described in the embodiments of the polyurethane foam of this disclosure.

[0037] The foamed urethane resin composition can be prepared, for example, as follows: First, a premixed polyol is prepared by pre-mixing a polyol component with a catalyst, blowing agent, etc., other than the isocyanate component. Next, the isocyanate component is mixed into 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 cleaning the containers that were required after each mixing, thus improving the yield. Therefore, manufacturing costs can be reduced.

[0038] It is desirable to blend the polyol component and the isocyanate component such that the isocyanate index (equivalent ratio of isocyanate groups to active hydrogen groups) is between 0.9 and 1.5. Furthermore, when using only fully coated particles as a catalyst, the progress of the foam urethane reaction is suppressed until the predetermined temperature is reached, allowing the foam urethane resin composition to be prepared in advance. This improves workability.

[0039] [Foaming and Curing Process] This process involves foaming and curing the prepared foamed urethane resin composition. For example, the prepared foamed urethane resin composition can be injected into a mold and foamed while sealed or open. Foaming and curing should be performed at a temperature at which the state of the coating material changes, such as when the coating material melts, taking into consideration the glass transition point or melting point of the coating material constituting the overall coating particles. For example, the temperature of the foamed urethane resin composition should be between 40°C and 100°C.

[0040] Next, the present disclosure will be described in more detail with reference to examples.

[0041] <Manufacture of Coated Catalyst Particles> [Granulation Method] Triethylenediamine particles of the catalyst component were put into a stirring and mixing granulator manufactured by Powrex Corporation, and while stirring at room temperature, water of the binder and the coating material were added little by little to manufacture coated catalyst particles. Seven types of coated catalyst particles were manufactured by changing the blending ratio of the catalyst component and the coating material and the type of the coating material. The composition of the coated catalyst particles is as shown in Table 1 given later (Examples 1 to 6, Comparative Example 6).

[0042] [Spray Drying Method] A dispersion liquid in which triethylenediamine particles of the catalyst component and polyvinyl butyrate of the coating material were added to acetone was spray-dried using a spray dryer manufactured by Yamato Scientific Co., Ltd. to manufacture coated catalyst particles. Four types of coated catalyst particles were manufactured by changing the blending ratio of the catalyst component and the coating material. The composition of the coated catalyst particles is as shown in Table 1 given later (Comparative Examples 2 to 5).

[0043] [Regarding the Manufactured Coated Catalyst Particles] In Table 1, cases where the yield of the coated catalyst particles was 50% or more are indicated by ○ marks, and cases where the yield of the coated catalyst particles was less than 50% due to aggregation of the particles etc. are indicated by × marks. Regarding Comparative Example 6, coated catalyst particles were manufactured by the granulation method, but the yield of the coated catalyst particles was less than 50%. The reason for this is considered to be that the blending ratio of the coating material was large, making it easy to aggregate. For the manufacture of the polyurethane foam, only the coated catalyst particles having a composition with a yield of 50% or more were used (Examples 1 to 6, Comparative Examples 2, 3).

[0044] In the coated catalyst particles of Examples 1 to 6 manufactured by the granulation method and having a yield of 50% or more, at least 50% by mass of the particles were entirely coated particles in which the catalyst component was not exposed on the surface. On the other hand, in the coated catalyst particles of Comparative Examples 2 and 3 manufactured by the spray drying method, since the content of the catalyst component was low, they were less likely to aggregate and the yield was 50% or more, but entirely coated particles were not manufactured, and almost all were partially coated particles.

[0045] <Manufacturing of Polyurethane Foam> First, a premix polyol was prepared by adding 1 part by mass of diethylene glycol as a chain extender, 1.5 parts by mass of water as a blowing agent, and the manufactured coated catalyst particles in the amounts shown in Table 1 to 100 parts by mass of polypropylene glycol (PPG) (VORANOL® CP 6001, manufactured by DOW, with an average molecular weight of 6000 and 3 functional groups) as the polyol component and mixing. Next, an isocyanate agent having polymeric MDI (Millionate MR-200, manufactured by Tosoh Corporation) was prepared as the isocyanate component. Then, the premix polyol and the isocyanate agent were mixed and stirred so that the isocyanate index was 0.95 to prepare a foamed urethane resin composition. Immediately thereafter, the foamed urethane resin composition was poured into aluminum cups maintained at two different temperatures, 20°C and 80°C. The foamed urethane resin composition was then allowed to foam and harden with the cups open while measuring the viscosity of the foamed urethane resin composition using a tuning fork vibration viscometer (A&D Company, Limited, "SV-100"). The retardation and reactivity of the curing reaction were then evaluated based on the measured viscosity values ​​as follows.

[0046] (1) Reaction Delay In the change in viscosity over time when foam curing is performed at 20°C, if the viscosity of the premix polyol and isocyanate agent 120 seconds after the start of stirring is less than 70 Pa·s, it was determined that the reaction delay effect due to the fully coated particles was exhibited (indicated by ○ in Table 1 below). If the viscosity is 70 Pa·s or more and less than 100 Pa·s, it was determined that the reaction delay effect was small and insufficient (indicated by △ in the same table), and if the viscosity is 100 Pa·s or more, it was determined that no reaction delay effect was obtained (indicated by × in the same table).

[0047] (2) Reactivity When the viscosity changes over time when foaming and curing at 80°C, if the viscosity 120 seconds after the start of stirring of the premix polyol and the isocyanate agent is 100 Pa·s or more, it was determined that the reaction acceleration effect by the fully coated particles was exhibited (indicated by ○ in Table 1 shown later). Also, when the viscosity is 70 Pa·s or more and less than 100 Pa·s, it was determined that the reaction acceleration effect is small and not sufficient (indicated by △ in the same table), and when the viscosity is less than 70 Pa·s, it was determined that the reaction acceleration effect was not obtained.

[0048] Table 1 summarizes the composition of the coated catalyst particles, the composition of the foamed urethane resin composition, and the evaluation results. The polyurethane foams of Examples 1 to 6 shown in Table 1 are included in the concept of the polyurethane foam of the present disclosure. Note that the polyurethane foam of Comparative Example 1 was produced using triethylenediamine particles, which are the mother particles of the coated catalyst particles, instead of the produced coated catalyst particles.

[0049] As shown in Comparative Example 1 of Table 1, when only the uncoated catalyst was used, the curing reaction proceeded and the viscosity increased even at 20°C close to room temperature. On the other hand, as shown in Examples 1 to 6, when 50 mass% or more of the catalyst was the fully coated particles, both the delay of the curing reaction and the reactivity were satisfactory. That is, the curing reaction was suppressed at 20°C, and the curing reaction proceeded at the molding temperature of 80°C. Also, for the coated catalyst particles of Comparative Examples 2 and 3 produced by the spray drying method, almost all were partially coated particles, so the reaction delay effect was small even when using them. Also, in the coated catalyst particles of Comparative Examples 2 and 3, since the content of the catalyst component was small, the reactivity also decreased.

[0050] The polyurethane foam of the present disclosure is suitable for sound-absorbing materials, vibration-proof members, etc. used in vehicles, buildings, etc.

Claims

1. A polyurethane foam obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst, wherein the catalyst has fully coated particles in which the catalyst component is covered with a coating material and the catalyst component is not exposed on the surface, and the content of the catalyst component in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

2. The polyurethane foam according to claim 1, wherein the solubility parameter value of the coating material is 10 or more.

3. The polyurethane foam according to claim 1 or claim 2, wherein the coating material is one or more selected from thermoplastic resins, waxes, fatty acids, and ester compounds.

4. The polyurethane foam according to claim 3, wherein the glass transition temperature of the thermoplastic resin is 40°C or higher and 70°C or lower, and the melting points of the wax, the fatty acid, and the ester compound are 40°C or higher and 70°C or lower.

5. The polyurethane foam according to claim 3 or 4, wherein the thermoplastic resin is polyvinyl butyrate, polyethylene oxide, or polystyrene.

6. The polyurethane foam according to any one of claims 1 to 5, wherein the catalyst component contained in the overall coated particles is one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

7. The polyurethane foam according to any one of claims 1 to 6, wherein the overall coated particles have a core-shell structure comprising a coating layer forming the outermost layer of the particles and a catalyst component layer disposed inside the coating layer.

8. The polyurethane foam according to claim 7, wherein the average particle diameter of the overall coating particles having a core-shell structure is 5 μm or more and 800 μm or less, and the thickness of the coating layer is 0.01 μm or more and 100 μm or less.

9. A method for producing polyurethane foam, comprising: a granulation step of stirring mother particles as a catalyst component and a coating material to produce fully coated particles in which the mother particles are coated by the coating material and the mother particles are not exposed on the surface; a composition preparation step of preparing a foamed urethane resin composition having an isocyanate component, a polyol component, and a catalyst containing the fully coated particles; and a foam curing step of foaming and curing the foamed urethane resin composition, wherein the content of the mother particles in the fully coated particles is 60% by mass or more when the mass of the fully coated particles is 100% by mass.

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