Polyurethane foam and cleaning sponge

Abstract

Provided is polyurethane foam which can be produced using a palm oil-derived polyol, which is a raw material with a low environmental load and high price advantage, wherein discoloration is suppressed in the polyurethane foam. The polyurethane foam is obtained by reacting a polyol component and a polyisocyanate component. In the polyol component, the proportion of a palm oil-derived polyol having no unsaturated bond between carbon atoms is 10% by mass or more, and the proportion of a palm oil-derived polyol having an unsaturated bond between carbon atoms is 6% by mass or less.

Description

Polyurethane foam, and cleaning sponge

[0001] The present invention relates to a polyurethane foam and a cleaning sponge.

[0002] Polyurethane foams, particularly flexible polyurethane foams, have excellent cushioning properties, and are thus widely used in applications including furniture or bedding such as beds, mattresses and pillows, daily miscellaneous goods (such as cleaning sponges), and packaging materials.

[0003] The polyurethane foam is produced by reacting a polyol component and a polyisocyanate component (urethane bond). As the polyol component, which is one of the raw materials for producing polyurethane foam, a petroleum-derived polyol component has been conventionally used. However, in recent years, from the perspective of reducing environmental impact, the use of plant-derived polyol components (biopolyols) as a substitute for at least part of petroleum-derived polyol components has been promoted.

[0004] Examples of the plant-derived polyol component (biopolyol) include vegetable oil-derived polyol components. Further, known vegetable oils as raw materials for producing biopolyols include castor oil, soybean oil, palm oil, sunflower oil and the like (for example, see Patent Document 1).

[0005] Japanese Unexamined Patent Application Publication No. 2009-167255

[0006] Among the substances mentioned above, palm oil is a vegetable oil obtained from the fruits of oil palms. The palm oil is mainly produced and distributed in tropical regions such as Malaysia and Indonesia. Since this palm oil has a higher yield per unit agricultural land area than the other vegetable oils mentioned above, it can be positioned as a polyurethane foam raw material with high price competitiveness. Based on such advantages, the present inventors have advanced research and development of polyurethane foam products using a palm oil-derived polyol component.

[0007] During the research and development process, the inventors manufactured a polyurethane foam with a black appearance by using a conventional palm oil-derived polyol component and further incorporating a black pigment. When this polyurethane foam was placed in a cold environment for a certain period of time, it was confirmed that it turned white (the black appearance became lighter). Based on this result and further investigations, it was found that polyurethane foam using a conventional palm oil-derived polyol component may discolor when placed in a certain cold environment. Since such discoloration is a concern from the standpoint of the design and quality of polyurethane foam products, it is necessary to avoid or minimize it as much as possible.

[0008] Therefore, the present invention aims to provide a discoloration-suppressed polyurethane foam that can be manufactured using palm oil-derived polyols, which are environmentally friendly and have a price advantage. Furthermore, the present invention aims to provide a discoloration-suppressed cleaning sponge using such polyurethane foam.

[0009] In other words, the gist of the present invention that solves the above problems is as follows.

[0010] [1] A polyurethane foam obtained by reacting a polyol component with a polyisocyanate component, wherein the polyol component is characterized in that the proportion of palm oil-derived polyols that do not have unsaturated bonds between carbon atoms is 10% by mass or more, and the proportion of palm oil-derived polyols that have unsaturated bonds between carbon atoms is 6% by mass or less.

[0011] [2] The polyurethane foam according to [1], wherein the total proportion of palm oil-derived polyols that do not have unsaturated bonds between carbon atoms and palm oil-derived polyols that have unsaturated bonds is 50% by mass or less.

[0012] [3] The polyurethane foam according to [1] or [2], which contains a coloring agent.

[0013] [4] A polyurethane foam according to any one of [1] to [3], wherein the tensile strength measured in accordance with JIS K6400-5 is 50 kPa or more.

[0014] [5] A polyurethane foam according to any one of [1] to [4], having a structure in which the cells are in communication with each other after the film has been removed.

[0015] [6] A cleaning sponge characterized by comprising the polyurethane foam described in any of [1] to [5].

[0016] According to the present invention, it is possible to provide a discoloration-suppressed polyurethane foam that can be manufactured using palm oil-derived polyols, which are environmentally friendly and have a cost advantage. Furthermore, according to the present invention, it is possible to provide a cleaning sponge that uses such polyurethane foam and also has suppressed discoloration.

[0017] The polyurethane foam and cleaning sponge of the present invention will be described in detail below, based on their embodiments.

[0018] (Polyurethane Foam) A polyurethane foam according to one embodiment of the present invention (hereinafter sometimes referred to as "the polyurethane foam of this embodiment") is a polyurethane foam obtained by reacting a polyol component with a polyisocyanate component, characterized in that the polyol component has a proportion of 10% by mass or more of palm oil-derived polyols that do not have unsaturated bonds between carbon atoms, and a proportion of 6% by mass or less of palm oil-derived polyols that have unsaturated bonds between carbon atoms.

[0019] Hereinafter, among palm oil-derived polyols, those that do not have unsaturated bonds between carbon atoms may be referred to as "palm oil-derived polyol A," and those that do have unsaturated bonds between carbon atoms may be referred to as "palm oil-derived polyol B." In this specification, "unsaturated bonds between carbon atoms" refers to double or triple bonds between carbon atoms, and hereafter may simply be referred to as "unsaturated bonds." Also in this specification, "palm oil-derived polyol" refers to polyols made from palm oil as a raw material.

[0020] Palm oil is an esterified product of fatty acids, primarily palmitic acid (16 carbon atoms, 0 unsaturated groups, saturated fatty acid) and oleic acid (18 carbon atoms, 1 unsaturated group, unsaturated fatty acid), and glycerol. Palm oil has the advantage of being highly price-competitive. On the other hand, compared to other vegetable oils, palm oil has a higher proportion of saturated fatty acids in its composition, which tends to result in fewer reaction sites.

[0021] Furthermore, in known methods for producing polyols (palm oil-derived polyols) using palm oil, first, an epoxidation reaction is carried out on the unsaturated groups (carbon-carbon double bonds) in the unsaturated fatty acids that make up palm oil, and then an alcohol such as methanol is added to the formed epoxy groups. As a result, OH groups are formed at the locations where the double bonds were in the palm oil, and the double bonds (unsaturated bonds) disappear.

[0022] In this regard, palm oil-derived polyols with residual unsaturated bonds (i.e., palm oil-derived polyol B) do exist. That is, palm oil-derived polyols that do not have a sufficient amount of OH groups formed also exist. These OH groups generate urethane bonds during the manufacturing of polyurethane foam. In other words, polyurethane foam obtained from palm oil-derived polyols with residual unsaturated bonds tends to have a large amount of unreacted components that are not incorporated into the urethane skeleton, partly due to the small number of OH groups. It is presumed that this is what causes discoloration when placed in a certain cold environment.

[0023] In contrast, the polyurethane foam of this embodiment uses palm oil-derived polyol without unsaturated bonds (i.e., palm oil-derived polyol A) as one of the raw materials, at a ratio of 10% by mass or more of the total polyol components, and limits the proportion (amount used) of palm oil-derived polyol with unsaturated bonds (i.e., palm oil-derived polyol B) to 6% by mass or less. In short, palm oil-derived polyol without unsaturated bonds (i.e., palm oil-derived polyol A) has a richer amount of OH groups compared to the aforementioned palm oil-derived polyol with remaining unsaturated bonds, and can contribute to the efficient formation of a urethane skeleton during the manufacturing of polyurethane foam. As a result, it is believed that the polyurethane foam of this embodiment significantly suppresses discoloration even when placed in a certain cold environment because the amount of remaining unreacted components in the polyurethane foam is sufficiently reduced.

[0024] As mentioned above, palm oil is mainly distributed in tropical regions. Therefore, the problem of discoloration of the palm oil-derived polyurethane foam when placed in a cold environment has not been raised before, making it novel and unique to this invention.

[0025] The polyurethane foam of this embodiment can typically be obtained by mixing a polyisocyanate component with a composition containing a polyol component (polyol composition) and reacting them. The manufacturing method of the polyurethane foam of this embodiment is not limited; for example, it may be manufactured by slab molding or mold molding. In addition to the polyol component, the polyol composition may optionally contain colorants, catalysts, foaming agents, foam stabilizers, and other compounding agents. The components used or that can be used in the polyurethane foam of this embodiment will be described below.

[0026] <Polyol component> In the polyurethane foam of this embodiment, it is necessary to use a palm oil-derived polyol that does not have unsaturated bonds (i.e., palm oil-derived polyol A) as the polyol component.

[0027] Furthermore, whether or not palm oil-derived polyols have unsaturated bonds can be determined by analysis using nuclear magnetic resonance (NMR).

[0028] The palm oil-derived polyol A used in this embodiment is not particularly limited and can be produced by the following method. That is, an amount of oxidizing agent sufficient to complete the epoxidation of the unsaturated fatty acids constituting palm oil is added and epoxidation is carried out. Then, an alcohol is added to the formed epoxy group. This yields palm oil-derived polyol A. The oxidizing agent is not particularly limited, but hydrogen peroxide is an example.

[0029] Furthermore, in the polyurethane foam of this embodiment, the palm oil-derived polyol A must constitute 10% by mass or more of the total polyol component. In other words, the polyol component of the polyurethane foam of this embodiment must contain 10% by mass or more of the palm oil-derived polyol A. If the proportion of palm oil-derived polyol A is less than 10% by mass, the effect of significantly suppressing discoloration cannot be sufficiently obtained. Also, from the viewpoint of more effectively suppressing discoloration while maintaining good performance such as strength, cushioning, and water repellency, the proportion of palm oil-derived polyol A in the total polyol component is preferably 13% by mass or more, more preferably 18% by mass or more, more preferably 20% by mass or more, preferably 75% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0030] Furthermore, in the polyurethane foam of this embodiment, a palm oil-derived polyol having unsaturated bonds (i.e., palm oil-derived polyol B) may or may not be used as the polyol component. In other words, the polyol component in the polyurethane foam of this embodiment may or may not contain palm oil-derived polyol B. However, the polyol component in the polyurethane foam of this embodiment must contain palm oil-derived polyol B in proportion of 6% by mass or less. If the proportion of palm oil-derived polyol B exceeds 6% by mass, even if a predetermined amount of palm oil-derived polyol A is used, the effect of significantly suppressing discoloration cannot be sufficiently obtained. Also, from the viewpoint of more effectively suppressing discoloration while maintaining good performance such as strength, the proportion of palm oil-derived polyol B in the total polyol component is preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less.

[0031] Furthermore, using palm oil-derived polyol B together with palm oil-derived polyol A is advantageous in that it further enhances the advantages from the standpoint of effective utilization of palm oil and, consequently, the reduction of environmental impact. When using palm oil-derived polyol B together with palm oil-derived polyol A, from the viewpoint of reliably obtaining the effect of significantly suppressing discoloration, it is preferable that the polyol components in the polyurethane foam of this embodiment have a palm oil-derived polyol A ratio of 44% by mass or more and 49% by mass or less, and a palm oil-derived polyol B ratio of 1% by mass or more and 6% by mass or less.

[0032] Furthermore, in the polyurethane foam of this embodiment, it is preferable that the total proportion of palm oil-derived polyol A and palm oil-derived polyol B is 50% by mass or less. If the total proportion is 50% by mass or less, it is possible to maintain good performance such as strength while exhibiting a discoloration suppression effect. From a similar viewpoint, it is more preferable that the total proportion of palm oil-derived polyol A and palm oil-derived polyol B in the total polyol component be 40% by mass or less, even more preferable that be 30% by mass or less, and even more preferable that be 27% by mass or less.

[0033] In addition to palm oil-derived polyol A and palm oil-derived polyol B, other polyol components may also be used as polyol components. Specific examples of such polyol components include, for example, plant-derived polyols other than palm oil-derived polyols (e.g., castor oil-derived polyols, soybean oil-derived polyols, etc.), petroleum-derived polyols, and the like.

[0034] Examples of the above-mentioned petroleum-derived polyols include polyether polyols, polyester polyols, polyether polyester polyols, and polymer polyols (generally, those in which organic particles are dispersed in a polyether polyol). These petroleum-derived polyols may be used individually or in combination of two or more types.

[0035] Examples of the polyether polyols mentioned above include compounds obtained by adding alkylene oxides such as propylene oxide and ethylene oxide to polyols such as ethylene glycol, glycerin, and sorbitol.

[0036] Examples of the above-mentioned polyester polyols include polyester polyols obtained by polycondensation reactions of polyols such as ethylene glycol, glycerin, and sorbitol with polycarboxylic acids such as malonic acid, maleic acid, succinic acid, adipic acid, tartaric acid, sebacic acid, oxalic acid, phthalic acid, terephthalic acid, and trimellitic acid; and ring-opening polymers of cyclic esters such as polycaprolactone.

[0037] Examples of polyether polyester polyols include compounds obtained by reacting an intermediate compound, which is acquired by adding an alkylene oxide such as propylene oxide or ethylene oxide to a polyol such as ethylene glycol, glycerin, or sorbitol, with a polycarboxylic acid such as malonic acid, maleic acid, succinic acid, adipic acid, tartaric acid, sebacic acid, oxalic acid, phthalic acid, terephthalic acid, or trimellitic acid.

[0038] Examples of polymer polyols include those in which polymer fine particles such as polyacrylonitrile and polyacrylonitrile / styrene copolymer are dispersed in a specific polyol.

[0039] When using petroleum-derived polyols, polyether polyols and polymer polyols are preferred among those mentioned above.

[0040] Furthermore, from the viewpoint of more reliably obtaining the desired effect, the polyol component used in this embodiment preferably consists only of palm oil-derived polyols (palm oil-derived polyol A and any palm oil-derived polyol B) and petroleum-derived polyols.

[0041] <Coloring Agent> The polyurethane foam of this embodiment preferably contains a coloring agent. By using a coloring agent, the polyurethane foam can be given a predetermined color, thereby enhancing its design appeal. Furthermore, the polyurethane foam of this embodiment has the effect of significantly suppressing discoloration, particularly whitening. Therefore, this effect is particularly advantageous compared to conventional polyurethane foam when a coloring agent that gives a color (appearance) that makes whitening noticeable is used. Typically, a coloring agent that gives a color (appearance) that makes whitening noticeable is a black coloring agent. The coloring agent may be used alone or in combination of two or more types.

[0042] Examples of black colorants include black pigments such as carbon black, graphite, iron black, titanium black, aniline black, and cyanine black; and black dyes such as nigrosine dyes, azo dyes, and azine dyes.

[0043] The amount of colorant used can be approximately 0.1 to 20 parts by mass per 100 parts by mass of the polyol component. It is preferable to appropriately adjust the amount of colorant used, taking into consideration the desired aesthetic qualities of the resulting polyurethane foam.

[0044] <Catalyst> In the production of the polyurethane foam of the present embodiment, a catalyst can be used. That is, the above polyol composition may contain a catalyst. Examples of the catalyst include amine catalysts and metal catalysts. These catalysts may be used singly or in combination of two or more. In particular, in the present embodiment, it is preferable to use an amine catalyst and a metal catalyst in combination from the viewpoint of more reliably obtaining the desired polyurethane foam.

[0045] Examples of the amine catalyst include 6-dimethylamino-1-hexanol, tetramethylhexamethylenediamine, pentamethyldiethylenetriamine, dimethylcyclohexylamine, bis-(dimethylaminoethyl) ether, tetramethylpropylenediamine, trimethylaminoethylpiperazine, tetramethylethylenediamine, dimethylbenzylamine, methylmorpholine, ethylmorpholine, triethylenediamine and the like. These amine catalysts may be used singly or in combination of two or more.

[0046] The usage amount of the amine catalyst (the content of the amine catalyst in the polyol composition) can be about 0 to 5.0 parts by mass relative to 100 parts by mass of the polyol component. The usage amount of the amine catalyst is preferably appropriately adjusted in consideration of the proportion of the palm oil-derived polyol A in the entire polyol component, the usage amount of other compounding agents, and the like.

[0047] Examples of the metal catalyst include tin-based catalysts such as stannous octoate, dibutyltin dilaurate, and stannous 2-ethylhexanoate. These metal catalysts may be used singly or in combination of two or more.

[0048] The usage amount of the metal catalyst (the content of the metal catalyst in the polyol composition) can be about 0 to 5.0 parts by mass relative to 100 parts by mass of the polyol component. The usage amount of the metal catalyst is preferably appropriately adjusted in consideration of the proportion of the palm oil-derived polyol A in the entire polyol component, the usage amount of other compounding agents, and the like.

[0049] <Foaming Agent> In the production of the polyurethane foam of this embodiment, a foaming agent can be used. That is, the polyol composition may contain a foaming agent. Examples of foaming agents include water and low-boiling point organic compounds. Examples of low-boiling point organic compounds include trichloromonofluoromethane, dichlorodifluoromethane, monochlorodifluoromethane, trichlorotrifluoroethane, methylene chloride, etc. These foaming agents may be used individually or in combination of two or more.

[0050] For example, when water is used as a blowing agent, the amount of the blowing agent (the amount of the blowing agent in the polyol composition) can be about 1.0 to 8.0 parts by mass per 100 parts by mass of the polyol component. It is preferable to appropriately adjust the amount of the blowing agent, taking into consideration the proportion of palm oil-derived polyol A in the total polyol component, the amount of other compounding agents used, etc.

[0051] <Foam stabilizers> In the production of the polyurethane foam of this embodiment, foam stabilizers can be used. That is, the polyol composition may contain a foam stabilizer. Examples of foam stabilizers include organopolysiloxanes, alkyl carboxylates, alkylbenzene sulfonates, etc. These foam stabilizers may be used individually or in combination of two or more.

[0052] The amount of foam stabilizer added (the foam stabilizer content in the polyol composition) can be approximately 0 to 2.0 parts by mass per 100 parts by mass of the polyol component. It is preferable to appropriately adjust the amount of foam stabilizer, taking into consideration the proportion of palm oil-derived polyol A in the total polyol component, the amount of other additives used, and other factors.

[0053] <Other Compounding Agents> In the manufacture of the polyurethane foam of this embodiment, other compounding agents other than those described above can be used. That is, the polyol composition and polyurethane foam may contain other compounding agents other than those described above. Such other compounding agents can be appropriately selected depending on the use and purpose of the polyurethane foam, and examples include crosslinking agents, fillers such as calcium carbonate, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, antibacterial agents, etc.

[0054] <Polyisocyanate component> In this embodiment, a polyisocyanate component is used. The polyisocyanate component is not particularly limited and includes, for example, aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, and modified polyisocyanates obtained by modifying them. These polyisocyanate components may be used individually or in combination of two or more types.

[0055] Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and polymethylene polyphenyl diisocyanate.

[0056] Examples of alicyclic polyisocyanates include cyclohexylmethane diisocyanate and cyclohexane diisocyanate.

[0057] Examples of aliphatic polyisocyanates include hexamethylene diisocyanate and cyclohexanemethane diisocyanate.

[0058] The amount of polyisocyanate component used is preferably such that the isocyanate index is typically around 80 to 130. If the isocyanate index is 80 or higher, shrinkage defects in the resulting polyurethane foam can be sufficiently suppressed, and if it is 130 or lower, foam-down can be sufficiently suppressed. The isocyanate index is expressed as a percentage of the equivalent ratio of isocyanate groups of the polyisocyanate component to active hydrogen groups such as hydroxyl groups of the polyol component and blowing agent (water).

[0059] <Properties of Polyurethane Foam> The polyurethane foam in this embodiment may be, for example, a flexible polyurethane foam. "Flexible polyurethane foam" refers to a polyurethane foam that has open cells and resilience to load. This flexible polyurethane foam is distinct from the so-called "rigid polyurethane foam" used as thermal insulation.

[0060] The polyurethane foam of this embodiment preferably has a tensile strength of 50 kPa or more, as measured in accordance with JIS K6400-5. In this case, the strength required for polyurethane foam products, particularly cleaning sponges, can be ensured. From a similar viewpoint, the above tensile strength is more preferably 80 kPa or more, even more preferably 100 kPa or more, even more preferably 110 kPa or more, and even more preferably 115 kPa or more. On the other hand, the upper limit of the above tensile strength is not particularly limited, but can be, for example, 500 kPa or less. The tensile strength of the polyurethane foam can be changed by appropriately controlling the composition of the compounding materials and various conditions during manufacturing.

[0061] In this embodiment, the polyurethane foam preferably has a structure in which the cells are interconnected after the film has been removed. By performing a film removal treatment on the polyurethane foam, the water repellency is enhanced, making it particularly suitable for use as a cleaning sponge. Generally, when a film removal treatment is performed on polyurethane foam, the degree of shine in appearance decreases and the color tends to appear darker. In other words, whitening becomes more noticeable, but the polyurethane foam of this embodiment has the effect of significantly suppressing discoloration, especially whitening. Therefore, this effect is particularly advantageous when the polyurethane foam is subjected to a film removal treatment.

[0062] The defilm removal process can be carried out by chemically removing the film remaining between the polyurethane foam skeletons after the polyurethane foam has been molded with foaming (for example, dissolving the film with an alkaline solution); by physical treatment (for example, blowing off the film with air pressure); or by heat treatment (for example, filling a furnace with combustion gas and igniting it to instantaneously melt and blow off the film); etc.

[0063] (Cleaning Sponge) A cleaning sponge according to one embodiment of the present invention (hereinafter sometimes referred to as "the sponge of this embodiment") is characterized by comprising the polyurethane foam of this embodiment described above. Since the sponge of this embodiment is manufactured using palm oil-derived polyol, it contributes to reducing environmental impact. Furthermore, since the sponge of this embodiment uses the polyurethane foam of this embodiment described above, discoloration is significantly suppressed even when placed in a cold environment.

[0064] The sponge of this embodiment can be used for cleaning various objects such as dishes, cooking utensils, washbasins, bathrooms, and toilets. The size and shape of the sponge of this embodiment are not particularly limited and can be appropriately selected according to the purpose.

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples and can be modified as appropriate without changing its essence.

[0066] (Preparation of palm oil-derived polyol A1) Palm oil was prepared. Next, a sufficient amount of hydrogen peroxide to complete the epoxidation was added, and the epoxidation reaction was carried out at the unsaturated groups (double bonds) in the unsaturated fatty acids constituting the palm oil to obtain epoxidized palm oil. Next, an alcohol was added to the epoxy groups of the epoxidized palm oil. As a result, OH groups were formed at the sites where the double bonds were in the palm oil, and palm oil-derived polyol A1 was obtained.

[0067] NMR analysis of the obtained palm oil-derived polyol A1 confirmed that it does not contain unsaturated bonds.

[0068] (Preparation of palm oil-derived polyol B1) Palm oil was prepared. Next, an epoxidation reaction was carried out using hydrogen peroxide at the unsaturated groups (double bonds) in the unsaturated fatty acids constituting the palm oil to obtain epoxidized palm oil. Next, an alcohol was added to the epoxy groups of the epoxidized palm oil. As a result, OH groups were formed at the locations where the double bonds were in the palm oil, and palm oil-derived polyol B1 was obtained. The amount of hydrogen peroxide used in the preparation of palm oil-derived polyol B1 was less than the amount used in the preparation of palm oil-derived polyol A1.

[0069] NMR analysis of the obtained palm oil-derived polyol B1 confirmed that it contains unsaturated bonds.

[0070] (Preparation of Polyurethane Foam) In each example, the polyol components shown in Table 1 were used as the polyol components. In each example, the following components were used with 100 parts by mass of the polyol components, and the polyisocyanate components were reacted to prepare polyurethane foam (flexible polyurethane foam). The obtained polyurethane foam was black in color due to the inclusion of black pigment.

[0071] Black pigment ("POLYTON BLACK UE2030-T"): 1.1 parts by mass, Amine catalyst (manufactured by Tosoh Corporation, "TEDA-L33"): 0.195 parts by mass, Amine catalyst (manufactured by Tosoh Corporation, "Toyocat ET-33B"): 0.150 parts, Metal catalyst (tin-based catalyst, manufactured by Nippon Chemical Industries, Ltd., "Nikka Octic Tin"): 0.16 parts by mass, Foaming agent (water): 3.3 parts by mass, Foam stabilizer (manufactured by Momentive Performance Materials LLC, "L-580"): 1.268 parts by mass, Polyisocyanate component (manufactured by Mitsui Chemicals, Inc., "T-80" (tolyl diisocyanate)): 42.403 parts by mass, Antibacterial agent (Sinanen Zeomic "AW10NS"): 2.000 parts by mass

[0072] Furthermore, the prepared polyurethane foam was subjected to a defilming treatment by physical means. This defilming treatment connected the cells in the polyurethane foam to each other.

[0073] The polyurethane foam obtained in each example was subjected to the following measurements and evaluations.

[0074] <Measurement of Tensile Strength> The tensile strength of the polyurethane foam obtained in each example was measured in accordance with JIS K6400-5. The results are shown in Table 1.

[0075] <Visual Evaluation of Whitening> The polyurethane foam obtained in each example was held (cured) at 5°C for 50 hours. After that, the degree of whitening of the polyurethane foam in each example was visually checked in comparison to the polyurethane foam before being held at 5°C for 50 hours, and evaluated according to the following criteria. The results are shown in Table 1. The evaluation is in the order of A, B, and C, from best to worst. A: No whitening at all. B: Slight whitening. C: Extremely noticeable whitening.

[0076]

[0077] *1 Petroleum-derived polyol: Sanyo Chemical Industries, Ltd., "GS-3000R", polyether polyol

[0078] Table 1 shows that the polyurethane foam according to the present invention did not show any visible whitening after curing. On the other hand, the comparative polyurethane foam tended to show visible whitening after curing.

[0079] According to the present invention, it is possible to provide a discoloration-suppressed polyurethane foam that can be manufactured using palm oil-derived polyols, which are environmentally friendly and have a cost advantage. Furthermore, according to the present invention, it is possible to provide a cleaning sponge that uses such polyurethane foam and also has suppressed discoloration.

Claims

1. A polyurethane foam obtained by reacting a polyol component with a polyisocyanate component, wherein the polyol component is characterized in that the proportion of palm oil-derived polyols that do not have unsaturated bonds between carbon atoms is 10% by mass or more, and the proportion of palm oil-derived polyols that have unsaturated bonds between carbon atoms is 6% by mass or less.

2. The polyurethane foam according to claim 1, wherein the total proportion of palm oil-derived polyols that do not have unsaturated bonds between carbon atoms and palm oil-derived polyols that have unsaturated bonds between carbon atoms is 50% by mass or less.

3. The polyurethane foam according to claim 1, comprising a coloring agent.

4. The polyurethane foam according to claim 1, wherein the tensile strength measured in accordance with JIS K6400-5 is 50 kPa or more.

5. The polyurethane foam according to claim 1, having a structure in which the cells are in communication with each other after the film has been removed.

6. A cleaning sponge characterized by comprising the polyurethane foam described in any one of claims 1 to 5.

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