Polyurethane foam and method for manufacturing the same

Abstract

To provide a polyurethane foam with excellent moldability by controlling the progress of the polyurethane foaming reaction. To provide a method for manufacturing a polyurethane foam in which the progress of the polyurethane foaming reaction can be controlled. [Solution] The polyurethane foam is obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a microcapsule catalyst in which a core material having a catalyst is enclosed in a shell material. The core material of the microcapsule catalyst is an amine catalyst solution in which an amine catalyst is dissolved or dispersed in water, the shell material is made of a material with a melting point of 40°C to 70°C and that does not dissolve in water, and the average particle size of the microcapsule catalyst is 100 μm or less. The method for producing the polyurethane foam comprises the steps of producing a microcapsule catalyst, preparing a foamed urethane resin composition having the microcapsule catalyst, and foaming and curing the foamed urethane resin composition.

Description

Technical Field

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

Background Art

[0002] In vehicles such as automobiles, sound-absorbing materials, vibration-damping members, etc. are arranged at parts that are sources of vibration and noise to reduce the transmission of vibration and the diffusion of noise. For sound-absorbing materials and vibration-damping members, foams such as polyurethane foam with low weight and high sound insulation and vibration absorption properties are used. 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 mold and foaming and curing it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[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"). To increase productivity, a high reaction rate is desirable, and normally, when the foaming urethane resin composition raw material is injected into the mold, the foaming and curing reactions proceed immediately. However, if the foaming reaction proceeds too quickly, the mold may not be able to keep up. Also, if the curing reaction proceeds too quickly, insufficient foaming may occur, or the curing reaction may be completed before the raw material reaches the corners and details of the mold, potentially resulting in molding defects. Since the catalyst plays a significant role in the progress of the foaming urethane reaction, it is desirable to control the progress of the foaming urethane reaction by, for example, imparting temperature dependence to the catalyst.

[0005] For example, Patent Documents 2 and 3 describe methods for using catalysts by encapsulating them. By encapsulating a catalyst and releasing it under predetermined conditions, 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 a solid catalyst is dispersed or dissolved in an encapsulating agent such as a thermoplastic resin to form droplets, and then cooled and solidified by spray drying or the like. Patent Document 3 also describes a microencapsulated polyaddition catalyst consisting of a capsule core containing a solid polyaddition catalyst such as an alicyclic tertiary amine and a capsule shell containing an acrylic copolymer.

[0006] Patent documents 2 and 3 describe encapsulating solid catalysts. The present inventors have conducted extensive research on encapsulated catalysts and found that using solid catalysts presents the following problems. As catalysts for foam urethane formation reactions, solid amine catalysts at room temperature (5-35°C) are known. However, amine catalysts are hygroscopic and tend to aggregate as they are made finer. Therefore, when used as a core material, it is difficult to obtain microcapsule catalysts with small particle sizes. If the particle size of the microcapsule catalyst is large, it can cause clogging of the foam urethane resin raw material, and it takes time for the microcapsule catalyst to melt. In addition, because the released catalyst does not easily dissolve in the urethane material, uniform diffusion is difficult, which may lead to uneven reactions and a decrease in the reaction rate. On the other hand, if the catalyst is not sufficiently refined before attempting to reduce the particle size of the microcapsule catalyst, it is difficult to coat the entire catalyst with the shell material, and part of the catalyst is exposed on the surface. The exposed catalyst may remain on the surface in that state, but it may also dissolve during the manufacturing process of the microcapsule catalyst, and in the latter case, the amount of catalyst decreases. Furthermore, because amine catalysts easily pass through the shell material, they may be exposed on the surface of the microcapsule catalyst or sublimate, leading to a decrease in the amount of catalyst. Thus, with relatively small-particle microcapsule catalysts using solid catalysts, problems arise such as a decrease in pot life and reduced storage stability when mixed with other raw materials at room temperature. In addition, a decrease in the amount of catalyst can lead to a decrease in the reaction rate during heating, preventing the catalyst from fully accelerating the reaction.

[0007] Furthermore, as described in Patent Documents 2 and 3, spray drying is a known method for solidifying dispersions of encapsulated catalysts. However, with spray drying, the yield tends to be low due to catalyst sublimation. In addition, the catalyst is often not completely covered by the shell material, and a portion of the catalyst is exposed on the surface. If the catalyst is not completely covered, curing reactions begin due to the exposed catalyst, and the heat generated during these reactions melts the shell material, releasing the catalyst. As a result, the initial reaction delaying effect of the coating is not sufficiently obtained. Consequently, curing defects and other problems cannot be sufficiently suppressed, and moldability is reduced.

[0008] Furthermore, the microencapsulated polyaddition catalyst described in Patent Document 3 does not release the catalyst by melting the shell material at a predetermined temperature, but rather by destabilizing the shell material through contact (chemical stimulation) with an isocyanate-curable substance such as a polyol or water, thereby releasing the catalyst. For this reason, when using the polyaddition catalyst described in Patent Document 3, it is not possible to control the foaming urethane reaction by temperature.

[0009] This disclosure has been made in view of the above circumstances, and aims to provide a polyurethane foam with excellent moldability by controlling the progress of the foaming urethane reaction. It also aims to provide a method for manufacturing a polyurethane foam in which the progress of the foaming urethane reaction can be controlled. [Means for solving the problem]

[0010] (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 microcapsule catalyst in which a core material having a catalyst is enclosed in a shell material, wherein the core material is an amine catalyst solution in which an amine catalyst is dissolved or dispersed in water, the shell material is made of a material having a melting point of 40°C or more and 70°C or less and is insoluble in water, and the average particle size of the microcapsule catalyst is 100 μm or less.

[0011] The polyurethane foam of this disclosure is manufactured using a foamed urethane resin composition having a microcapsule catalyst as a catalyst. In the microcapsule catalyst, the shell material melts at a temperature above its melting point, releasing the amine catalyst from the core material. In other words, the microcapsule catalyst does not act as a catalyst until it reaches a temperature at which the state of the shell material changes. By thus imparting temperature dependence to the catalyst, the timing of the catalyst's action can be delayed, allowing the foaming reaction and curing reaction to proceed in a well-balanced manner. As a result, the foamed urethane resin composition can reach even the corners and details of the mold before the curing reaction progresses and the viscosity increases. This suppresses the occurrence of insufficient foaming and insufficient filling, resulting in a polyurethane foam with excellent moldability. Furthermore, since the progress of the foaming urethane reaction can be controlled by temperature using the microcapsule catalyst, the foamed urethane resin composition, which is a mixture of isocyanate and polyol components, can be prepared in advance, improving workability. Furthermore, since the shell material has a melting point between 40°C and 70°C, it can be melted at the temperature at which the foamed urethane resin composition is foamed and cured (the molding temperature of polyurethane foam), thereby exhibiting a catalytic effect.

[0012] The core material of the microcapsule catalyst is not a solid, but an amine catalyst liquid in which the amine catalyst is dissolved or dispersed in water. Because the core material is liquid, it is easily dispersed in the shell material, making it easy to reduce the particle size of the microcapsule catalyst. Also, in the case of a liquid, it diffuses easily into the urethane material after being released. Thus, by using a microcapsule catalyst with a liquid core material and a relatively small particle size of 100 μm or less, the dispersibility and diffusivity in the urethane material during foam curing can be improved, and moldability can be improved. Furthermore, because the core material contains water, it does not easily mix with the shell material, which does not dissolve in water, and does not easily pass through the shell material. Therefore, the amount of catalyst does not decrease easily after manufacturing. Thus, the microcapsule catalyst used in the manufacture of polyurethane foam according to this disclosure has good storage stability and a long pot life when mixed with other raw materials at room temperature. In addition, the reaction-accelerating effect of the catalyst can be fully exerted when heated, allowing the foam urethane reaction to proceed rapidly.

[0013] (2) In the above configuration, the shell material may consist of one or more selected from wax, fatty acid ester, and fatty acid. With this configuration, it is easy to manufacture a microcapsule catalyst with a liquid core material by the melt dispersion cooling method described later.

[0014] (3) In any of the above configurations, the microcapsule catalyst may have a multicore structure in which a plurality of core materials are dispersed within the shell material. With this configuration, a relatively large number of tiny droplet core materials can be held within the microcapsule catalyst, making it easier to increase the amine catalyst content.

[0015] (4) In any of the above configurations, the content of the amine catalyst in the microcapsule catalyst may be 5% by mass or more when the mass of the microcapsule catalyst is 100% by mass. With this configuration, the reaction-promoting effect of the amine catalyst can be fully exhibited.

[0016] (5) In any of the above configurations, the amine catalyst may be one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine. These compounds are water-soluble and therefore suitable as core materials.

[0017] (6) A method for manufacturing polyurethane foam according to the present disclosure (hereinafter sometimes simply referred to as the "method for manufacturing according to the present disclosure") is one form of a method for manufacturing polyurethane foam having any of the configurations of (1) to (5) above, comprising: a catalyst manufacturing step for manufacturing the microcapsule catalyst; a composition preparation step for preparing the foamed urethane resin composition having the isocyanate component, the polyol component, and the microcapsule catalyst; and a foam curing step for foaming and curing the foamed urethane resin composition, wherein the catalyst manufacturing step involves adding the amine catalyst liquid to the molten shell material. The present invention is characterized by comprising: a first step of adding a material to produce a first emulsion by emulsifying and dispersing droplets of the amine catalyst solution within the shell material; a second step of adding the first emulsion to an aqueous medium in which one or more selected from a surfactant, a polymer dispersant, and a hydrophilic solid fine powder are dissolved or dispersed in water, and emulsifying and dispersing droplets of the first emulsion within the aqueous medium to produce a second emulsion; and a third step of cooling the second emulsion while stirring and solidifying the shell material to obtain a dispersion in which the microcapsule catalyst is dispersed within the aqueous medium.

[0018] In the manufacturing method disclosed herein, a melt-dispersion-cooling method is employed as the method for manufacturing microcapsule catalysts. The melt-dispersion-cooling method is a method for manufacturing capsules by dispersing a molten oil phase in a heated aqueous phase, and then cooling the oil phase to solidify it. According to the manufacturing method disclosed herein, in the first step of the catalyst manufacturing process, a core material is added to a molten shell material to produce a first emulsion (dispersed phase), in the second step, the dispersed phase is dispersed in an aqueous medium (continuous phase) to produce a second emulsion, and in the third step, the second emulsion is cooled to solidify the shell material. By employing the melt-dispersion-cooling method, it is possible to manufacture microcapsule catalysts having a liquid core material and relatively small particle size.

[0019] And according to the manufacturing method of the present disclosure, due to the initial reaction delay effect of the microcapsule catalyst, the foaming reaction and the curing reaction can proceed in a well-balanced manner, and a polyurethane foam can be manufactured with good formability. For example, before the curing reaction proceeds and thickens, the foamed urethane resin composition can be spread to the corners and details of the mold, so the occurrence of insufficient foaming and insufficient filling can be suppressed, and even a product with a complex shape can be manufactured with good formability.

[0020] (7) In the configuration of (6) above, the content of the amine catalyst in the amine catalyst solution added in the first step may be configured to be not more than the solubility in water at 70°C. According to this configuration, in the first step, at least at a temperature at which the shell material melts, the amine catalyst can be dissolved in water to create a state where there is no solid matter in the amine catalyst solution, so it becomes easier to finely disperse the amine catalyst solution in the shell material.

[0021] (8) In the configuration of (6) or (7) above, the stirring speed when producing the second emulsion in the second step may be configured to be smaller than the stirring speed when producing the first emulsion in the first step. According to this configuration, by adjusting the stirring speed, it is possible to suppress the droplets in the second emulsion from becoming too small and manufacture a microcapsule catalyst having a desired particle size.

Advantages of the Invention

[0022] The polyurethane foam of the present disclosure is manufactured from a foamed urethane resin composition using a liquid core material and a microcapsule catalyst with a relatively small particle size. Therefore, the dispersibility and diffusibility of the catalyst are good, and due to the initial reaction delay effect of the catalyst, the foaming reaction and the curing reaction proceed in a well-balanced manner, and the formability is excellent. According to the manufacturing method of the polyurethane foam of the present disclosure, due to the initial reaction delay effect of the microcapsule catalyst with good dispersibility and diffusibility, the foaming reaction and the curing reaction can proceed in a well-balanced manner, and a polyurethane foam can be manufactured with good formability.

Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments of the polyurethane foam of the present disclosure and a method for producing the same will be described. The embodiments are not limited to the following forms, and can be implemented in various modified forms and improved forms that can be carried out by those skilled in the art. The numerical range using "~" in this specification indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit values and lower limit values described individually can be arbitrarily combined. Further, the upper limit value and lower limit value of the numerical range can be replaced with the values shown in the examples.

[0024] <Polyurethane Foam> The polyurethane foam of the present disclosure is obtained by foaming and curing a foaming urethane resin composition having an isocyanate component, a polyol component, and a microcapsule catalyst in which a core material having a catalyst is encapsulated in a shell material.

[0025] [Isocyanate Component] The isocyanate component is not particularly limited as long as it forms a urethane bond by reacting with the polyol component. For example, it may 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 the derivative include a prepolymer obtained by reacting an isocyanate and a polyol, a modified polyisocyanate, a polymeric MDI (polynuclear body) having three or more isocyanate groups and benzene rings in one molecule, and the like. <The polyol component>

[0026] [Polyol Component] The polyol component can be appropriately selected from among 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, and others.

[0027] 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.

[0028] [Microcapsule catalyst] In a microcapsule catalyst, a core material containing the catalyst is arranged within a shell material. The number of core materials in the microcapsule catalyst may be one or more. That is, the form of the microcapsule catalyst may be a core-shell structure in which a single core material is covered by a shell material, or a multi-core structure in which multiple core materials are dispersed within the shell material. The shape of the microcapsule catalyst is not particularly limited and may be spherical, flaky, or irregularly shaped. In this specification, "spherical" is not limited to a perfect sphere, but includes shapes close to a sphere (approximately spherical).

[0029] The average particle size of the microcapsule catalyst is 100 μm or less. From the viewpoint of further improving the dispersibility and diffusivity of the urethane material during foam curing, an average particle size of 80 μm or less, and more preferably 50 μm or less, is preferable. In this specification, the average particle size is the median diameter (D) determined from the volume-based particle size distribution measured by laser diffraction-scattering.50 )

[0030] The core material of the microcapsule catalyst is an amine catalyst solution in which the amine catalyst is dissolved or dispersed in water. The water can be tap water, deionized water, distilled water, or ultrapure water. The amine catalyst solution may be in a state where the amine catalyst is completely dissolved in water, or in a state where at least a portion is dispersed without dissolving. It may also be an aqueous solution of the amine catalyst, or a colloidal solution in which colloidal particles of the amine catalyst are dispersed in water. The amine catalyst content in the amine catalyst solution (concentration of the amine catalyst solution) is not particularly limited, but it is desirable to be, for example, below the solubility in water at 70°C. This ensures that, at least at the temperature at which the shell material melts, the amine catalyst dissolves in the water, creating a state where there are no solid particles in the amine catalyst solution. This makes it easier to finely disperse the amine catalyst solution within the shell material when manufacturing the microcapsule catalyst.

[0031] From the viewpoint of fully exhibiting the reaction-promoting effect, the amine catalyst content in the microcapsule catalyst is preferably 5% by mass or more, based on 100% by mass of the microcapsule catalyst. A content of 6% by mass or more is more preferable. Examples of amine catalysts include triethylenediamine, tetraethylenediamine, dimethylethanolamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine. Among these, from the viewpoint of being water-soluble and having high catalytic activity, it is desirable to use one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

[0032] The shell material of the microcapsule catalyst is made of a material with a melting point between 40°C and 70°C and is insoluble in water. Because its melting point is between 40°C and 70°C, the shell material is difficult to melt at temperatures near room temperature and easily melts at the molding temperature of polyurethane foam. Furthermore, since the shell material is insoluble in water, an emulsion (dispersed phase) can be produced by adding a core material containing water to the shell material, and the microcapsule catalyst can be manufactured by a melt-dispersion-cooling method.

[0033] Lipids can be used as the shell material. Specifically, a material with a melting point between 40°C and 70°C should be selected from among hydrophobic simple lipids and derived lipids. Examples of simple lipids include waxes and oils (fatty acid esters). Examples of waxes include natural waxes such as paraffin wax and microcrystalline wax, and synthetic waxes such as modified polyethylene wax. Examples of oils include fats and fatty oils (drying oils, non-drying oils, and hydrogenated oils). Examples of derived lipids include fatty acids (saturated fatty acids, unsaturated fatty acids) and cholesterol. One of these materials can be used alone, or two or more can be used in combination. In particular, it is preferable to use one or more selected from waxes, fatty acid esters, and fatty acids. It is desirable that the shell material is poorly soluble in the polyol component that comes into contact with it when preparing the foamed urethane resin composition. For example, it is preferable to use a material whose solubility parameter (SP value) is different from that of the polyol component.

[0034] [Other ingredients] The foamed urethane resin composition may, in addition to the aforementioned materials, 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. Water is preferred as the foaming agent. Other examples include methylene chloride, chlorofluorocarbons (CFCs), and carbon dioxide (carbonic acid gas). In this disclosure, the core material of the microcapsule catalyst is an amine catalyst solution containing water. Since the water in the amine catalyst solution acts as a foaming agent, it may not be necessary to add a separate foaming agent. 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.

[0035] <Method for manufacturing polyurethane foam> One embodiment of the method for manufacturing polyurethane foam according to this disclosure comprises a catalyst manufacturing step, a composition preparation step, and a foaming and curing step. Each step will be described below.

[0036] [Catalyst manufacturing process] This process is for manufacturing microcapsule catalysts. This process consists of the following three steps.

[0037] (1) First step The first step involves adding an amine catalyst solution to the molten shell material and emulsifying and dispersing droplets of the amine catalyst solution within the shell material to produce a first emulsion (dispersed phase). The shell material and amine catalyst solution are as described in the previous embodiment of polyurethane foam. The amine catalyst content in the amine catalyst solution is preferably less than or equal to its solubility in water at 70°C. Adding an oil-soluble surfactant in this step improves the dispersion stability of the amine catalyst solution and makes it easier to miniaturize the droplets. This step should be carried out at a temperature above the melting point of the shell material, preferably about 10 to 15°C higher than the melting point. The emulsification and dispersion treatment can be carried out using a homogenizer or the like, and the stirring conditions should be adjusted as appropriate so that the droplets of the amine catalyst solution become the desired size. For example, stirring at a stirring speed of 6000 to 10000 rpm for 2 to 10 minutes is recommended. The size of the amine catalyst solution droplets in the first emulsion must be less than or equal to the particle size of the microcapsule catalyst, preferably 1 μm or less.

[0038] (2)Second process The second step involves adding the first emulsion (dispersed phase) produced in the previous step to an aqueous medium (continuous phase) in which one or more substances selected from surfactants, polymer dispersants, and hydrophilic solid fine powders (hereinafter sometimes referred to as "surfactants, etc.") are dissolved or dispersed in water, thereby producing a second emulsion by emulsifying and dispersing the droplets of the first emulsion in the aqueous medium. The surfactant and polymer dispersant should be water-soluble and capable of dispersing the droplets of the first emulsion so that they do not coalesce. For example, polyvinyl alcohol (PVA), methylcellulose, Tween® 20 (polyoxyethylene sorbitan monolaurate) can be used. Examples of hydrophilic solid fine powders include silica, titania, and montmorillonite. The concentration of the surfactant, etc. in the aqueous medium should be 0.1 to 2.0% by mass. The concentration of the dispersed phase when the dispersed phase is added to the continuous phase should be 5 to 30% by mass.

[0039] It is desirable to heat the aqueous medium to a temperature similar to that of the first step. In other words, this step should be carried out at a temperature similar to that of the first step. The emulsification and dispersion treatment in this step can also be carried out using a homogenizer or the like, similar to the first step, and the stirring conditions should be adjusted as appropriate so that the droplets of the first emulsion become the desired size. For example, stirring at a stirring speed of 500 to 5000 rpm for 0.5 to 3 minutes is recommended. In the emulsification and dispersion treatment of this step, it is preferable to use a stirring speed lower than that used in the emulsification and dispersion treatment of the first step. By doing so, it is possible to prevent the droplets in the second emulsion produced in this step from becoming too small, and to produce microcapsule catalysts with the desired particle size. The droplet size in the second emulsion should be 100 μm or less.

[0040] (3) Third step The third step involves cooling the second emulsion produced in the second step while stirring, thereby solidifying the shell material and obtaining a dispersion in which microcapsule catalysts are dispersed in an aqueous medium. In this step, a short solidification time for the shell material and a low cooling temperature are preferable to suppress the coalescence of droplets in the second emulsion and the separation of the amine catalyst solution. Therefore, a cooling temperature of 0 to 30°C is preferable. Stirring during cooling should be carried out using a blade agitator or the like at a stirring speed of 50 to 300 rpm for 2 to 10 minutes. The obtained dispersion can be filtered to separate the solid components at room temperature and dried to obtain the microcapsule catalyst.

[0041] [Composition preparation process] This process involves preparing a foamed urethane resin composition comprising an isocyanate component, a polyol component, and a microcapsule catalyst. In addition to the microcapsule catalyst, other catalysts may be used in combination as the catalyst for the urethane foaming reaction. The components of the foamed urethane resin composition are as described in the previous embodiment of polyurethane foam.

[0042] 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 microcapsule catalyst other than the isocyanate component, a chain extender, etc. 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 the container cleaning step that was required after each mixing, and improves the yield. Therefore, manufacturing costs can be reduced.

[0043] 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 the microcapsule catalyst as the catalyst, the progress of the foaming urethane reaction is suppressed until the predetermined temperature is reached. Therefore, the foamed urethane resin composition can be prepared in advance by mixing all components simultaneously without preparing a premix polyol. This improves workability.

[0044] [Foaming and curing process] This step 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 should be performed at a temperature at which the shell material melts, taking into account the melting point of the shell material. For example, the temperature of the foamed urethane resin composition should be between 40°C and 100°C. [Examples]

[0045] Next, the present disclosure will be described in more detail with reference to examples.

[0046] <Manufacturing of microencapsulated catalysts> [Example 1] (1) First step First, deionized water was added to the catalyst triethylenediamine (TEDA) powder to prepare an aqueous TEDA solution in which TEDA was dissolved in water. The concentration of the aqueous TEDA solution was 27.9% by mass, and the TEDA content was less than 150 [g / 100g-H2O] in water at 70°C. Next, paraffin wax (HNP-5, manufactured by Nippon Seiro Co., Ltd., melting point 63°C) as the shell material was placed in a container, and the container was placed in a constant temperature water bath heated to 75°C to melt the paraffin wax. Subsequently, the aqueous TEDA solution as the core material was added to the melted paraffin wax, and the mixture was emulsified and dispersed at 75°C using a homomixer (Labo-Solution®, manufactured by Primix Co., Ltd., with the stirring section being "Homomixer MARK II") at a stirring speed of 8000 rpm for 3 minutes to obtain the first emulsion, which would become the dispersed phase. The proportions of each component used to manufacture the microcapsule catalyst are as follows, assuming the total mass of all components is 100% by mass: TEDA core material is 6.2% by mass, water is 16% by mass, and shell material is 77.8% by mass. The "TEDA aqueous solution" in this process is included in the concept of "amine catalyst solution" in this disclosure.

[0047] (2)Second process First, when the total of the dispersed phase (first emulsion) and the continuous phase (PVA aqueous solution) produced in this process is set to 100% by mass, ion-exchanged water was measured and heated to 75°C so that the first emulsion constituted 10% by mass. Polyvinyl alcohol (PVA, degree of polymerization approximately 500) was dissolved in this ion-exchanged water to prepare a 0.5% by mass PVA aqueous solution that would become the continuous phase. Next, the first emulsion (dispersed phase) was added to the PVA aqueous solution (continuous phase) heated to 75°C, and the mixture was emulsified and dispersed for 1 minute at a stirring speed of 4000 rpm using a homomixer (same as above) to obtain the second emulsion. The "PVA aqueous solution" in this process is included in the concept of "aqueous medium" in this disclosure.

[0048] (3) Third step First, a container containing the second emulsion was placed in water at 15°C, and the second emulsion was stirred using a blade agitator at a stirring speed of 150 rpm for 2 minutes to produce a dispersion containing the microcapsule catalyst. Next, the dispersion was filtered at room temperature, the filtered material was washed with water, and then dried at room temperature for 24 hours to obtain the microcapsule catalyst. The obtained microcapsule catalyst is referred to as the microcapsule catalyst of Example 1.

[0049] [Example 2] The microcapsule catalyst of Example 2 was manufactured in the same manner as in Example 1, except that the shell material was replaced with a paraffin wax with a different melting point (Paraffin WAX-115, manufactured by Nippon Seiro Co., Ltd., with a melting point of 48°C), and the melting temperature of the paraffin wax and the emulsification dispersion treatment temperature in the first step were changed to 60°C.

[0050] [Example 3] The microcapsule catalyst of Example 3 was manufactured in the same manner as in Example 1, except that the shell material was replaced with a paraffin wax with a different melting point (Paraffin WAX-155, manufactured by Nippon Seiro Co., Ltd., melting point 69°C), and the melting temperature of the paraffin wax and the emulsification dispersion treatment temperature in the first step were changed to 80°C.

[0051] [Example 4] The microcapsule catalyst of Example 4 was manufactured in the same manner as in Example 1, except that the stirring speed of the homomixer in the second step of emulsification and dispersion was changed to 500 rpm.

[0052] [Comparative Example 1] The microcapsule catalyst of Comparative Example 1 was manufactured in the same manner as in Example 1, except that in the first step, water was not used as the core material; in other words, instead of manufacturing an aqueous TEDA solution, TEDA powder was added directly to the molten paraffin wax. The blending amounts (charging amounts) of each component for manufacturing the microcapsule catalyst of Comparative Example 1 were 22.2% by mass for the TEDA core material and 77.8% by mass for the shell material, assuming the total mass of the components is 100% by mass.

[0053] [Comparative Example 2] The microcapsule catalyst of Comparative Example 2 was manufactured in the same manner as in Example 1, except that, similar to the microcapsule catalyst of Comparative Example 1, water was not used as the core material, and TEDA powder was added directly to molten paraffin wax, and in the second step, the PVA aqueous solution to which the dispersed phase was added was stirred using a blade agitator instead of a homomixer. Stirring with the blade agitator was performed at a speed of 150 rpm for 1 minute.

[0054] [Comparative Example 3] In the second step, the PVA aqueous solution to which the dispersed phase was added was stirred using a bladed agitator instead of a homomixer, except that the microcapsule catalyst of Comparative Example 3 was produced in the same manner as in Example 1. The stirring with the bladed agitator was performed at a speed of 150 rpm for 1 minute.

[0055] [Comparative Example 4] The microcapsule catalyst of Comparative Example 4 was manufactured in the same manner as in Example 1, except that the shell material was replaced with palm oil (melting point 37.5°C), and the melting temperature of the palm oil and the emulsification dispersion treatment temperature in the first step were changed to 50°C.

[0056] [Comparative Example 5] The microcapsule catalyst of Comparative Example 5 was manufactured in the same manner as in Example 1, except that the shell material was replaced with a paraffin wax with a different melting point (HNP-51, manufactured by Nippon Seiro Co., Ltd., melting point 77°C), and the melting temperature of the paraffin wax and the emulsification dispersion treatment temperature in the first step were changed to 90°C.

[0057] <Characteristics of microencapsulated catalysts> [Average particle size] The average particle size (median diameter: D) of the manufactured microcapsule catalyst. 50 The particle size distribution was determined from the particle size distribution obtained by dry measurement using a laser diffraction / scattering particle size distribution analyzer (LMS-3000, manufactured by Seishin Corporation).

[0058] [Catalyst residual rate] To evaluate the storage stability of the microcapsule catalyst, the amount of catalyst (TEDA) inside the microcapsule was measured immediately after manufacturing and one month after manufacturing. The microcapsule catalyst was stored at room temperature in a sealed polypropylene bottle for one month. Since only the catalyst contains nitrogen in the microcapsule catalyst, the amount of nitrogen in the microcapsule catalyst was measured, and the amount of catalyst was calculated based on that value. A trace organic element analyzer (UNICUBE®, manufactured by elementar) was used to measure the amount of nitrogen. Storage stability was considered good if the catalyst retention rate relative to the initial charge was 80% or more (indicated by ○ in Table 1 below), and poor storage stability was considered if it was less than 80% (indicated by × in the same table).

[0059] <Manufacturing of polyurethane foam> Polyurethane foam was manufactured using a microcapsule catalyst immediately after production. First, a premix polyol was prepared by adding 1 part by mass of diethylene glycol as a chain extender and the microcapsule catalyst immediately after production in the amounts shown in Table 1 below to 100 parts by mass of polypropylene glycol (PPG) (VORANOL® CP 6001, manufactured by DOW, average molecular weight 6000, 3 functional groups) as the polyol component, and mixing. For the microcapsule catalysts of Comparative Examples 1 and 2, which did not contain water in the core material of the microcapsule catalyst, 1.3 parts by mass of water was added separately as a blowing agent. In addition, an isocyanate agent having polymeric MDI (Millionate MR-200, manufactured by Tosoh Corporation) was prepared as the isocyanate component.

[0060] Next, a foamed urethane resin composition was prepared by mixing and stirring a premixed polyol and an isocyanate agent until the isocyanate index reached 0.95. Immediately thereafter, the foamed urethane resin composition was poured into aluminum cups maintained at two different temperatures, 20°C and 80°C, and allowed to foam and cure with the cups open while measuring the viscosity of the foamed urethane resin composition using a tuning fork vibrating viscometer (A&D Company, Limited, "SV-100"). The curing reaction delay and reactivity were then evaluated based on the measured viscosity values ​​as follows.

[0061] [Delayed] In the viscosity change over time when foam curing was performed at 20°C, if the viscosity of the premix polyol and isocyanate agent 120 seconds after the start of stirring was less than 70 Pa·s, it was determined that the reaction delay effect of the microcapsule catalyst was exhibited (indicated by ○ in Table 1 below). Conversely, if the viscosity was 100 Pa·s or higher, it was determined that no reaction delay effect was obtained (indicated by × in the same table).

[0062] [Responsiveness] In the change in viscosity over time when foaming and curing at 80°C, if the viscosity of the premix polyol and isocyanate agent 120 seconds after the start of stirring was 100 Pa·s or higher, it was determined that the reaction-accelerating effect of the microcapsule catalyst was exhibited (indicated by ○ in Table 1 below). Conversely, if the viscosity was less than 70 Pa·s, it was determined that no reaction-accelerating effect was obtained (indicated by × in the same table).

[0063] Table 1 summarizes the composition of the microcapsule catalyst, the composition of the foamed urethane resin composition, and the evaluation results. The polyurethane foams of Examples 1 to 4 shown in Table 1 are included in the concept of polyurethane foam in this disclosure. [Table 1]

[0064] As shown in Table 1, the microcapsule catalysts of Examples 1 to 4 exhibited good storage stability, with over 80% of the catalyst in the core material remaining even after one month of storage. Furthermore, the curing reaction retardation and reactivity were satisfactory. Specifically, the curing reaction was suppressed at 20°C, while it proceeded at the molding temperature of 80°C. In contrast, the microcapsule catalyst of Comparative Example 1 had a solid core material instead of an aqueous solution. Therefore, the catalyst was prone to aggregation, and the reduced particle size made it easier for the catalyst to be exposed on the capsule surface. In addition, the catalyst easily passed through the shell material and leached out. Consequently, the catalyst retention rate was low immediately after manufacturing, resulting in poor storage stability. Also, due to the low catalyst content in the microcapsule catalyst, reactivity was low at both 20°C and 80°C. Similar to Comparative Example 1, the microcapsule catalyst of Comparative Example 2, which also had a solid core material instead of an aqueous solution, had a large particle size. While encapsulation was possible even if the catalyst aggregated, it easily passed through the shell material and leached out. Therefore, the catalyst retention rate was low after one month of storage, resulting in poor storage stability. Furthermore, because the catalyst in the core material is solid and has a large particle size, it does not dissolve easily in the urethane material at a molding temperature of 80°C, resulting in poor diffusion. Consequently, the desired reaction-promoting effect could not be obtained.

[0065] The microcapsule catalyst in Comparative Example 3 has a large particle size despite the core material being an aqueous solution, resulting in poor diffusion in the urethane material. Therefore, the desired reaction-accelerating effect could not be obtained. The microcapsule catalyst in Comparative Example 4 has a low melting point for the shell material, causing it to gradually melt and release the catalyst from the core material even at 20°C. Therefore, the desired reaction-delaying effect could not be obtained. Conversely, the microcapsule catalyst in Comparative Example 5 has a high melting point for the shell material, requiring time for catalyst release from the core material at a molding temperature of 80°C. Therefore, the desired reaction-accelerating effect could not be obtained. [Industrial applicability]

[0066] The polyurethane foam disclosed herein is suitable for use as a sound-absorbing material, vibration-damping material, etc., in vehicles, buildings, and the like.

Claims

1. A polyurethane foam obtained by foaming and curing a foamed urethane resin composition having an isocyanate component, a polyol component, and a microcapsule catalyst in which a core material having a catalyst is enclosed in a shell material, The core material is an amine catalyst solution in which an amine catalyst is dissolved or dispersed in water. The shell material is made of a material with a melting point of 40°C to 70°C and is insoluble in water. A polyurethane foam characterized in that the average particle size of the microcapsule catalyst is 100 μm or less.

2. The polyurethane foam according to claim 1, wherein the shell material comprises one or more selected from wax, fatty acid ester, and fatty acid.

3. The polyurethane foam according to claim 1, wherein the microcapsule catalyst has a multicore structure in which a plurality of the core materials are dispersed within the shell material.

4. The polyurethane foam according to claim 1, wherein the content of the amine catalyst in the microcapsule catalyst is 5% by mass or more when the mass of the microcapsule catalyst is 100% by mass.

5. The polyurethane foam according to claim 1, wherein the amine catalyst is one or more selected from triethylenediamine, quinuclidine, hexamethylenetetramine, and 4-aminopyridine.

6. A method for producing polyurethane foam according to claim 1, A catalyst manufacturing process for producing the aforementioned microcapsule catalyst, A composition preparation step for preparing the foamed urethane resin composition having the isocyanate component, the polyol component, and the microcapsule catalyst, A foam curing step for foaming and curing the foamed urethane resin composition, It has, The catalyst manufacturing process is as follows: A first step involves adding the amine catalyst solution to the molten shell material and emulsifying and dispersing droplets of the amine catalyst solution within the shell material to produce a first emulsion. A second step involves adding the first emulsion to an aqueous medium in which one or more selected from surfactants, polymer dispersants, and hydrophilic solid fine powders are dissolved or dispersed in water, and emulsifying and dispersing droplets of the first emulsion in the aqueous medium to produce a second emulsion. A third step involves cooling the second emulsion while stirring to solidify the shell material, thereby obtaining a dispersion in which the microcapsule catalyst is dispersed in the aqueous medium. A method for producing polyurethane foam, characterized by having the following features.

7. The method for producing polyurethane foam according to claim 6, wherein the content of the amine catalyst in the amine catalyst solution added in the first step is less than or equal to its solubility in water at 70°C.

8. The method for producing polyurethane foam according to claim 6, wherein the stirring speed when producing the second emulsion in the second step is smaller than the stirring speed when producing the first emulsion in the first step.

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