JP7780896B2 - Polyurethane foam - Google Patents

Description

This disclosure relates to polyurethane foams.

Patent Document 1 discloses a method for producing flexible polyurethane foam using a combination of multiple polyols with specific functional groups and OH equivalents. Patent Document 2 discloses a flexible polyurethane foam obtained by using a combination of a specific polyester polyol and a polyether polyol as polyols.

Japanese Patent Application Laid-Open No. 2004-300352 Japanese Patent Application Publication No. 10-025327

However, conventional polyurethane foams can become harder in winter and softer in summer depending on the outside temperature, leaving room for improvement in terms of temperature dependency.

The present disclosure aims to provide a polyurethane foam with low temperature dependency. This disclosure can be realized in the following forms.

A polyurethane foam obtained from a composition comprising a polyol and a polyisocyanate,
The polyol contains a polycarbonate polyol modified with a cyclic ester,
The polyurethane foam, wherein the content of the polycarbonate polyol is 7 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the total amount of the polyols.

This disclosure reduces the temperature dependence of polyurethane foam.

Here, a preferred example of the present disclosure will be described.
- A polyurethane foam, wherein the polycarbonate polyol has a functionality of 2.
- A polyurethane foam, wherein the hydroxyl value of the polycarbonate polyol is 35 mg KOH/g or more and 450 mg KOH/g or less.
- A polyurethane foam, wherein the number average molecular weight of the polycarbonate polyol is 1,100 or more and 3,500 or less.
- Polyurethane foam having an Asker C hardness of 28 or less at 0°C measured in accordance with JIS K7312.
A polyurethane foam having an absolute value of the difference between the Asker C hardness at 0°C and the Asker C hardness at 23°C, measured in accordance with JIS K7312, of 20 or less.
- Polyurethane foam having a resilience at 0°C of 45% or less, measured in accordance with JIS K6255.
A polyurethane foam having an absolute value of the difference between the resilience modulus at 0°C and the resilience modulus at 23°C, measured in accordance with JIS K6255, of 20% or less.

The present disclosure is explained in detail below. In this specification, when a numerical range is indicated using "-", it is considered to include both the lower limit and the upper limit unless otherwise specified. For example, the expression "10-20" includes both the lower limit of "10" and the upper limit of "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less."

1. Polyurethane Foam The polyurethane foam is obtained from a composition containing a polyol and a polyisocyanate. The polyol contains a polycarbonate polyol modified with a cyclic ester. The content of the polycarbonate polyol is 7 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the total amount of the polyol.

(1) Composition The composition contains a polyol and a polyisocyanate. The composition may contain at least one optional component selected from a blowing agent, a catalyst, a foam stabilizer, and a crosslinking agent. Each component of the composition will be described.

(1.1) Polyol The polyol contains a polycarbonate polyol modified with a cyclic ester (hereinafter also referred to as a modified polycarbonate polyol). As the modified polycarbonate polyol, a polycarbonate polyol containing a structure derived from a polyol having 2 to 12 carbon atoms and a structure derived from a cyclic ester can be used.

Examples of polyols having 2 to 12 carbon atoms include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, and dodecanediol, with butanediol, pentanediol, and hexanediol being preferred. Multiple polyols having 2 to 12 carbon atoms may be used in combination. Furthermore, to the extent that the functionality and properties of the desired polyurethane foam are not impaired, polyols having 2 to 12 carbon atoms containing a small amount of ether bonds in the molecule may be used in combination, or polyols containing a small amount of branched aliphatic polyol may be used in combination.

Examples of cyclic esters include propiolactone, butyrolactone, valerolactone, caprolactone, and laurolactone, with caprolactone being preferred. A single cyclic ester may be used, or multiple cyclic esters may be used in combination. Hydroxycarboxylic acids, which are hydrolyzed cyclic esters, may also be used. Cyclic esters may contain small amounts of branched or cyclic structures or unsaturated bonds, as long as they do not impair the functionality or properties of the desired polyurethane foam.

In the modified polycarbonate polyol, the molar ratio of the structure derived from the polyol having 2 to 12 carbon atoms to the structure derived from the cyclic ester (polyol-derived structure/cyclic ester-derived structure) is preferably 10/90-90/10, more preferably 15/85-85/15, and even more preferably 20/80-80/20.
The total amount of the structure derived from the polyol having 2 to 12 carbon atoms and the structure derived from the cyclic ester is preferably 95 mol % or more, more preferably 98 mol % or more, and even more preferably 99 mol % or more, based on the polycarbonate polyol.

As such modified polycarbonate polyols, for example, polycarbonate polyols containing repeating units of a structure derived from 1,6-hexanediol and a structure derived from caprolactone (ETERNACOLL (registered trademark) UHC, manufactured by Ube Industries, Ltd.) can be suitably used. Furthermore, carbonate polyols from the Placcel EC series (manufactured by Daicel Corporation) and the Placcel CD series (manufactured by Daicel Corporation) can also be used as modified polycarbonate polyols.

The number of functional groups, hydroxyl value, and number average molecular weight of the modified polycarbonate polyol are not particularly limited. The number of functional groups of the modified polycarbonate polyol is preferably 2. The hydroxyl value of the modified polycarbonate diol is preferably 35 mgKOH/g or more, and may be 40 mgKOH/g or more, 45 mgKOH/g or more, or 50 mgKOH/g or more. The hydroxyl value of the modified polycarbonate diol is preferably 450 mgKOH/g or less, and may be 200 mgKOH/g or less, 120 mgKOH/g or less, or 80 mgKOH/g or less. When the hydroxyl value is below the upper limit, a good foam can be obtained. When the hydroxyl value is above the lower limit, the polycarbonate diol can be easily mixed with other materials. From these viewpoints, the hydroxyl value of the modified polycarbonate diol is preferably in the range of 35 mgKOH/g to 450 mgKOH/g, and can be set to a range that appropriately combines the above upper and lower limits. The number average molecular weight of the modified polycarbonate polyol is preferably 900 to 4000, more preferably 1100 to 3500, and even more preferably 1500 to 2500.
The number average molecular weight of the modified polycarbonate polyol can be measured by gel permeation chromatography (GPC). When the modified polycarbonate polyol is a commercially available product, the catalog value may be used as the number average molecular weight of the modified polycarbonate polyol. In this specification, the number average molecular weight of polyols other than the modified polycarbonate polyol can be similarly defined.

The content of the modified polycarbonate polyol is 7 parts by mass or more and 35 parts by mass or less, where the total amount of polyols is 100 parts by mass. From the viewpoint of reducing temperature dependency, the content of the modified polycarbonate polyol is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. From the viewpoint of moldability, the content of the modified polycarbonate polyol is preferably 33 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. From these viewpoints, the content of the modified polycarbonate polyol is preferably 8 parts by mass or more and 33 parts by mass or less, more preferably 10 parts by mass or more and 30 parts by mass or less, and even more preferably 15 parts by mass or more and 25 parts by mass or less.

The polyol other than the modified polycarbonate polyol contained in the composition (hereinafter also referred to as the other polyol) is not particularly limited. The other polyol is preferably a polyether polyol. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethylene polypropylene glycol. The other polyols can be used alone or in combination of two or more.

The number of functional groups, hydroxyl value, and number average molecular weight of the polyether polyol are not particularly limited. As the polyether polyol, a combination of a plurality of polyether polyols A and B having different numbers of functional groups, hydroxyl values, etc. may be used.
The number of functional groups of polyether polyol A is preferably 3. The hydroxyl value of polyether polyol A is preferably 20 mgKOH/g or more and 100 mgKOH/g or less, more preferably 25 mgKOH/g or more and 60 mgKOH/g or less. The number average molecular weight of polyether polyol A is, for example, 4000 or more and 6000 or less. The content of polyether polyol A is, for example, 45 parts by mass or more and 93 parts by mass or less, when the total amount of polyol is 100 parts by mass.
The number of functional groups of polyether polyol B is preferably 3. The hydroxyl value of polyether polyol B is preferably more than 150 mgKOH/g and 300 mgKOH/g or less, more preferably 200 mgKOH/g or more and 250 mgKOH/g or less. The number average molecular weight of polyether polyol B is, for example, 500 or more and 1000 or less. The content of polyether polyol B is, for example, 5 parts by mass or more and 25 parts by mass or less, when the total amount of polyol is 100 parts by mass.

Furthermore, polyether polyol C having two functional groups may be used in combination as the polyether polyol. The hydroxyl value of polyether polyol C is preferably 35 mgKOH/g or more and 450 mgKOH/g or less, more preferably 50 mgKOH/g or more and 80 mgKOH/g or less. The number average molecular weight of polyether polyol C is, for example, 1,100 or more and 3,500 or less. The content of polyether polyol C is, for example, 0 parts by mass or more and 20 parts by mass or less, where the total amount of polyols is 100 parts by mass.

(1.2) Blowing Agent Water, alternative chlorofluorocarbons, or hydrocarbons such as pentane can be used alone or in combination as the blowing agent. Water is particularly preferred as the blowing agent. In the case of water, carbon dioxide gas is generated during the reaction of polyol and polyisocyanate, and foaming is caused by the carbon dioxide gas. The amount of water used as the blowing agent is preferably 0.5 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of polyol.

(1.3) Catalyst Known catalysts for polyurethane foams can be used alone or in combination. Examples of catalysts include amine catalysts such as aromatic amine catalysts and metal catalysts such as tin octoate. The total amount of catalyst is preferably 0.3 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of polyol.

(1.4) Foam Stabilizer The foam stabilizer may be any foam stabilizer that is commonly used as a raw material for urethane foam, such as a silicone compound, a nonionic surfactant, etc. The amount of foam stabilizer is preferably 0.2 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of polyol.

(1.5) Crosslinking Agent A crosslinking agent can be blended to improve the hardness of the polyurethane foam. Examples of crosslinking agents include amines such as diethanolamine and polyethylene polyamines, and polyhydric alcohols such as trimethylolpropane, glycerin, 1,4-butanediol, and diethylene glycol. Two or more types of crosslinking agents may be used. The amount of crosslinking agent is preferably 0.3 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of polyol.

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

(1.7) Polyisocyanate The polyisocyanate is not particularly limited. As the polyisocyanate, an MDI-based polyisocyanate (diphenylmethane diisocyanate-based isocyanate) is preferred. When an MDI-based polyisocyanate is used, the surface of the polyurethane foam can have a softer feel than, for example, when a TDI (toluene diisocyanate)-based polyisocyanate is used.
Specific examples of MDI polyisocyanates include monomeric MDIs such as 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), and 4,4'-diphenylmethane diisocyanate (4,4'-MDI), polymeric MDIs which are mixtures of diphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanate, and urethane-modified, carbodiimide-modified, urea-modified, allophanate-modified, biuret-modified, and isocyanurate-modified products thereof, as well as MDI prepolymers obtained by reacting these polyisocyanates with polyols. Multiple types of MDI polyisocyanates may be used in combination.
Among these, the polyisocyanate preferably contains urethane-modified MDI.

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

(2) Physical Properties of Polyurethane Foam The physical properties of the polyurethane foam can be appropriately set depending on the application, etc. The polyurethane foam is preferably a flexible polyurethane foam.
The polyurethane foam preferably has the following physical properties:

(2.1) Asker C Hardness The Asker C hardness at 0°C measured in accordance with JIS K7312 is preferably 28 or less, more preferably 25 or less, and even more preferably 23 or less, from the viewpoint of flexibility in a low-temperature environment. The Asker C hardness at 0°C is preferably 3 or more, and more preferably 5 or more, from the viewpoint of reducing bottoming out. From these viewpoints, the Asker C hardness at 0°C is preferably 3 or more and 28 or less, and more preferably 5 or more and 25 or less.
The Asker C hardness at 23° C. measured in accordance with JIS K7312 is preferably 3 or more and 28 or less, and more preferably 5 or more and 25 or less.
The Asker C hardness at 40° C. measured in accordance with JIS K7312 is preferably 3 or more and 28 or less, and more preferably 5 or more and 25 or less.
The absolute value of the difference between the Asker C hardness at 0°C and the Asker C hardness at 23°C, measured in accordance with JIS K7312, is preferably 20 or less, and more preferably 15 or less. The absolute value of the difference between the Asker C hardness at 0°C and the Asker C hardness at 23°C is 0 or more.

(2.2) Rebound Resilience The rebound resilience at 0°C measured in accordance with JIS K6255 is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less, from the viewpoint of low resilience in a low-temperature environment. The lower limit of the rebound resilience at 0°C is not particularly limited, but from the viewpoint of ensuring a moderate resilience, it is preferably 20% or more, and more preferably 25% or more. From these viewpoints, the rebound resilience at 0°C is preferably 20% or more and 50% or less, and more preferably 25% or more and 45% or less.
The impact resilience at 23° C., measured in accordance with JIS K6255, is preferably 20% or more and 50% or less, and more preferably 25% or more and 45% or less.
The impact resilience at 40° C. measured in accordance with JIS K6255 is preferably 20% or more and 50% or less, and more preferably 25% or more and 45% or less.
The absolute value of the difference between the rebound resilience at 0°C and the rebound resilience at 23°C, measured in accordance with JIS K6255, is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. The absolute value of the difference between the rebound resilience at 0°C and the rebound resilience at 23°C is 0% or more.

(2.3) Apparent Core Density, Tensile Strength, Elongation, and Tear Strength The apparent core density (JIS K7222) is preferably 80 kg/m ³ or more and 300 kg/m ³ or less.
The tensile strength (JIS K6400-55) is preferably 80 kPa or more, more preferably 150 kPa or more, and even more preferably 300 kPa or more. The upper limit of the tensile strength is not particularly limited, but may be, for example, 500 kPa or less.
The elongation (JIS K6400-5 5) is preferably 50% or more and 500% or less, and more preferably 100% or more and 200% or less.
The tear strength (JIS K6400-5 6 B method) is more preferably 10 N/cm or more. The upper limit of the tear strength is not particularly limited, but may be, for example, 25 N/cm or less.

2. Method for Producing Polyurethane Foam Polyurethane foam can be produced by a known foaming method in which the composition is stirred and mixed to react the polyol and polyisocyanate. The foaming method includes slab foaming and mold foaming, and either molding method may be used.
Mold foaming is a method in which a mixed polyurethane resin composition is filled into a mold (forming tool) and foamed within the mold. Mold foaming is suitable for producing molded products with complex three-dimensional shapes.

3. Uses of Polyurethane Foam According to the present disclosure, a low-resilience polyurethane foam with reduced temperature dependence can be realized. The reason for the reduced temperature dependence is presumably because the glass transition temperature of the polyurethane foam is lowered by incorporating a specified proportion of modified polycarbonate polyol compared to a polyurethane foam without the modified polycarbonate polyol. Such polyurethane foam is suitable for use in components that support at least part of the human body, where changes in hardness and rebound resilience are likely to affect performance and usability.

There are no limitations on the products in which the polyurethane foam of the present disclosure can be used. The polyurethane foam is suitable for use in supports for joints such as elbows and knees, cushions, automobile headrests, armrests, motorcycle saddles, etc.

The present invention will be specifically described below using examples. In Tables 1 and 2, when an "*" is added, such as "Experimental Example 1*," it indicates that the example is a comparative example. Experimental Examples 6-8 are examples, and Experimental Examples 1-5 and 9-11 are comparative examples.
1. Production of Polyurethane Foams Compositions blended in the proportions shown in Tables 1 and 2 were prepared, and polyurethane foams of the Examples and Comparative Examples were produced by mold foaming.

The details of each raw material are as follows:
Polyether polyol A: Polyether polyol, polypropylene oxide having ethylene oxide at the end (VORANOL 4701, manufactured by Dow Chemical Japan Co., Ltd.), hydroxyl value 35 mg KOH/g, number of functional groups 3, number average molecular weight 5000
Polyether polyol B: Polyether polyol, polypropylene glycol (GP750NS, manufactured by Sanyo Chemical Industries, Ltd.), hydroxyl value 225 mg KOH/g, number of functional groups 3, number average molecular weight 750, EO ratio 0 mol%
Polyether polyol C: Polyether polyol (D2000, manufactured by Asahi Glass Co., Ltd.), hydroxyl value 56 mg KOH/g, number of functional groups 2, number average molecular weight 2000, EO ratio 0 mol%
Modified polycarbonate polyol: Polycarbonate diol containing repeating units of a structure derived from 1,6-hexanediol and a structure derived from caprolactone (ETERNACOLL UHC50-200, manufactured by Ube Industries, Ltd.), 56 mg KOH/g, functionality 2, number average molecular weight 2000
Polycarbonate polyol: Polycarbonate diol containing repeating units of a structure derived from 1,6-hexanediol and a structure derived from 1,5-pentanediol (ETERNACOLL PH-200, manufactured by Ube Industries, Ltd.), 56 mg KOH/g, functionality 2, number average molecular weight 2000
Interconnecting agent: polyether polyol with a high EO addition ratio (VORANOL CP1421, manufactured by Dow Chemical Japan Co., Ltd.), functionality 3, hydroxyl value 35 mg KOH/g, molecular weight 5000, EO ratio 70 mol%
Crosslinking agent: diethanolamine Catalyst 1: amine catalyst (terminal amine reactive resinification catalyst)
Catalyst 2: Aromatic amine catalyst Foam stabilizer: Silicone foam stabilizer Foaming agent: Water Polyisocyanate: Urethane-modified MDI (Lupranate MP-102, manufactured by BASF INOAC)

2. Evaluation Methods Test specimens were cut out from the polyurethane foams produced using the above raw materials, and the Asker C hardness, rebound resilience, etc. were measured by the following methods. Experimental Examples 10 and 11 were not evaluated for physical properties due to poor molding.
(1) Asker C Hardness Asker C hardness was measured in accordance with JIS K7312. The test temperatures were 0°C, 23°C, and 40°C. The test piece was left to stand at the test temperature for 24 hours or more before measurement.
(2) Rebound Resilience The rebound resilience (%) was measured in accordance with JIS K6255. The test temperatures were 0°C, 23°C, and 40°C. The test specimen was left to stand at the test temperature for 24 hours or more before measurement.
(3) Apparent Core Density, Tensile Strength, Elongation, and Tear Strength The apparent core density was measured in accordance with JIS K7222.
The tensile strength (kPa) was measured in accordance with JIS K6400-55.
The elongation (%) was measured in accordance with JIS K6400-55.
The tear strength (N/cm) was measured in accordance with JIS K6400-5 6 B method.

3. Results The results are shown in Tables 1 and 2. In Tables 1 and 2, "-" indicates that no measurement was performed. The column "Asker C hardness, 0°C: H1" shows the Asker C hardness at 0°C. The column "Asker C hardness, 23°C: H2" shows the Asker C hardness at 23°C. The column "Asker C hardness, 40°C" shows the Asker C hardness at 40°C. The column "Difference between Asker C hardness at 0°C and 23°C: |H1-H2|" shows the absolute value of the difference between the Asker C hardness at 0°C and the Asker C hardness at 23°C. The column "Rebound resilience (%), 0°C: R1" shows the rebound resilience at 0°C. The column "Rebound resilience (%), 23°C: R2" shows the rebound resilience at 23°C. The column "Rebound resilience (%), 40°C" shows the rebound resilience at 40°C. The column "Rebound resilience (%), difference between 0°C and 23°C: |R1-R2|" shows the absolute value of the difference between the rebound resilience at 0°C and the rebound resilience at 23°C.

For Experimental Example 6-8, the Asker C hardness measured at 0°C, 23°C, and 40°C was between 5 and 28. Experimental Example 6-8 had a practical Asker C hardness. Furthermore, for Experimental Example 6-8, the difference between the Asker C hardness at 0°C and the Asker C hardness at 23°C was 20 or less. It was confirmed that Experimental Example 6-8 has little temperature dependency.

Experimental Examples 6-8 had a rebound resilience of 40% or less when measured at 0°C, 23°C, and 40°C. Experimental Examples 6-8 had a practically acceptable rebound resilience. Furthermore, for Experimental Examples 6-8, the difference between the rebound resilience at 0°C and the rebound resilience at 23°C was 20% or less. Experimental Examples 6-8 were confirmed to have little temperature dependency.

4. Effects of the Examples According to the above examples, the temperature dependency of polyurethane foam can be reduced.

This disclosure is not limited to the examples detailed above, and various modifications and variations are possible within the scope of this disclosure.

Claims (4)

A polyurethane foam obtained from a composition comprising a polyol and a polyisocyanate,
The polyol contains a polycarbonate polyol modified with a cyclic ester,
the content of the polycarbonate polyol is 7 parts by mass or more and 35 parts by mass or less, when the total amount of the polyol is 100 parts by mass,
A polyurethane foam that satisfies the following (1) and/or (2) :
(1) Tensile strength (JIS K6400-5 5) is 500 kPa or less
(2) Tear strength (JIS K6400-5 6 B method) is 25 N/cm or less 2. The polyurethane foam according to claim 1, having an apparent core density (JIS K7222) of 80 kg/m ^<3> or more and 300 kg/m ^<3> or less. 3. The polyurethane foam according to claim 1, having an Asker C hardness at 0°C of 28 or less, measured in accordance with JIS K7312 . A polyurethane foam obtained from a composition comprising a polyol and a polyisocyanate,
the polyol contains a polycarbonate polyol modified with a cyclic ester and a polyether polyol having a hydroxyl value of 20 mgKOH/g or more and 100 mgKOH/g or less,
the content of the polycarbonate polyol is 7 parts by mass or more and 35 parts by mass or less, when the total amount of the polyol is 100 parts by mass,
The polyurethane foam has a content of the polyether polyol of 45 parts by mass or more and 93 parts by mass or less, relative to 100 parts by mass of the total amount of the polyols.