JP2019189804A - Polyurethane foam - Google Patents

Abstract

To provide a polyurethane foam having no physical property reduction with light weight, having moderate hardness, and excellent in flexibility.SOLUTION: There is provided a polyurethane foam consisting of a polyurethane raw material containing a polyol component, an isocyanate component, a filler, a foaming agent, a catalyst, and a foam stabilizer, the polyol component contains polytetramethylene ether glycol having number average molecular weight of 300 to 3500, average functional group number of 2 to 3, and average hydroxyl group value of 35 mgKOH/g to 200 mgKOH/g, the filler has specific gravity of 0.25 g/cmor more and less than 1.0 g/cm, and density of a polyurethane foam measured according to JIS K 7222 is 0.25 g/cmto 0.35 g/cm, and hardness of the polyurethane foam measured by using an Asker rubber hardness meter C type according to JIS K7312 is 50 to 65.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyurethane foam that is lightweight and has excellent bending resistance, and is suitable as a material for a shoe sole member.

  Conventionally, foams such as polyurethane foam and EVA (ethylene-vinyl acetate copolymer) foam have been used as shoe sole members. Foam soles are excellent in shock absorption, and are used as soles for sports shoes for walking, running, trekking as well as shoes for general use. In the case of athletic shoes, physical properties such as durability, light weight, and rebound resilience are required. In particular, for weight reduction, a method of reducing the density of a foam is known.

  However, it is known that the foam physical properties are inferior, for example, the hardness and the bending resistance are lowered as the density of the foam is reduced. In addition, when forming a shoe sole by molding, molding defects such as design defects, air defects, pinholes, surface voids, and the like due to defective filling of the mold are observed.

  In such a molding defect, for example, Patent Document 1 discloses that the generation of surface voids can be suppressed by including a silicone antifoaming agent and a silicon-containing inorganic powder in a polyurethane foam raw material.

JP 2005-298760 A

  However, Patent Document 1 does not disclose the suppression of foam physical properties such as hardness and bending resistance due to low density.

  Therefore, an object of the present invention is to provide a polyurethane foam that is lightweight but has no deterioration in physical properties, has an appropriate hardness, and is excellent in bending resistance.

  The present applicant has found that by adding a filler having a specific specific gravity, a polyurethane foam that can be reduced in weight can be obtained while suppressing a decrease in physical properties, and the present invention has been achieved.

That is, the present invention has the following gist:
(1) A polyurethane foam comprising a polyurethane raw material containing a polyol component, an isocyanate component, a filler, a foaming agent, a catalyst, and a foam stabilizer. The polyol component has a number average molecular weight of 300 to 3,500 and an average functional group number of 2. 3 or less and an average hydroxyl value of 35 mg KOH / g or more and 200 mg KOH / g or less of polytetramethylene ether glycol, the filler has a specific gravity of 0.25 g / cm ³ or more and less than 1.0 g / cm ³ , JIS K The polyurethane foam has a density of 0.25 g / cm ³ or more and 0.35 g / cm ³ or less measured according to 7222, and measured with an Asker rubber hardness tester C type according to JIS K 7312 The hardness is 50 or more and 65 or less, and it has bending resistance Polyurethane foam to be.
(2) The polyurethane foam according to (1) above, wherein the filler has an average particle size of 10 μm or more and less than 60 μm.
(3) The polyurethane foam according to the above (1) or (2), wherein the addition amount of the filler is 5 parts by mass or more and less than 20 parts by mass with respect to 100 parts by mass of the polyol component.
(4) A polyurethane foam formed so that the length is 120 mm, the width is 60 mm, and the thickness is 6 mm is prepared, and a composite body in which a resin-impregnated board having a thickness of 2 mm is bonded to the polyurethane foam is prepared. A bending back operation composed of an operation of bending the composite at a central position along the longitudinal direction by bending the half of the composite by 90 ° and returning the half of the composite to the original position is repeated at a speed of 144 times / minute. The polyurethane foam according to any one of the above (1) to (3), wherein the number of bending back operations until the occurrence of cracks in the polyurethane foam is 20,000 or more.
(5) The polyurethane foam according to any one of (1) to (4) above, wherein the compression set rate of the polyurethane foam measured in accordance with JIS K 6262 is 20% or less.
(6) The isocyanate component includes: i) an isocyanate group-terminated prepolymer having a number average molecular weight of 500 to 2000, an average functional group number of 2 to 3, and an isocyanate group content of 3 to 10% by mass; and ii) an isocyanate group. The polyurethane foam according to any one of (1) to (5) above, which contains a modified MDI having a content of 25 to 33% by mass.
(7) When a test piece made of polyurethane foam formed so as to have a thickness of 12.5 mm is prepared and a 5.1 kg weight collides with the test piece from a height of 50 mm, The polyurethane foam according to any one of (1) to (6), wherein the maximum impact load is 0.9 kN or less.
(8) The polyurethane foam according to any one of (1) to (7) above, wherein the resilience modulus of the polyurethane foam measured in accordance with JIS K 6255 is 60% or more.
(9) The polyurethane foam according to any one of (1) to (8), which is a molded product.
(10) A shoe sole member using the polyurethane foam according to any one of (1) to (9).

  INDUSTRIAL APPLICABILITY The present invention can provide a polyurethane foam and a shoe sole member that are lightweight but have no deterioration in physical properties, have an appropriate hardness, and are excellent in bending resistance.

It is a figure for demonstrating the shape of the weight used by the drop impact test.

  The present invention is a polyurethane foam comprising a polyurethane raw material containing a polyol component, an isocyanate component, a filler, a foaming agent, a catalyst, and a foam stabilizer.

As the polyol component of the present invention, a polytetramethylene ether glycol (hereinafter referred to as the first compound) having a number average molecular weight of 300 to 3,500, an average functional group number of 2 to 3, and an average hydroxyl value of 35 mgKOH / g to 200 mgKOH / g. Of PTMG).
In the present invention, two or more kinds of PTMGs having different number average molecular weights may be mixed and used.

When the number average molecular weight of PTMG is less than 300 or the average hydroxyl value exceeds 200 mgKOH / g, the cell size of the obtained polyurethane foam becomes non-uniform, the flexibility tends to be impaired, and the desired bending resistance Cannot be obtained.
On the other hand, when the number average molecular weight exceeds 3500 or the average hydroxyl value is less than 35 mgKOH / g, the viscosity of the polyol increases and molding becomes difficult.
As a preferable range, the number average molecular weight is 1000 or more and 2500 or less, the average number of functional groups is 2 or more and 3 or less, and the average hydroxyl value is 50 mgKOH / g or more and 100 mgKOH / g or less.

  As the polyol component of the present invention, a polyol other than PTMG may be added to the extent that the effects of the present invention are not impaired. For example, polyether polyol, polyester polyol, and polymer polyol can be used.

  As the polyether polyol, for example, a polyether polyol obtained by ring-opening polymerization of alkylene oxide is suitable. Examples of the alkylene oxide include propylene oxide (PO), ethylene oxide (EO), butylene oxide, and the like. These may be used alone or in combination of two or more. If necessary, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, tetramethylene ether glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, sucrose, etc. An added polyether polyol may be used.

  Examples of the polyester polyol include polycondensation from aliphatic carboxylic acids such as malonic acid, succinic acid, and adipic acid, and aromatic carboxylic acids such as phthalic acid, and polyhydric alcohols such as ethylene glycol, diethylene glycol, and propylene glycol. The one obtained can be used.

  As the polymer polyol, a polyether polyol obtained by graft copolymerization of polyacrylonitrile, acrylonitrile-styrene copolymer or the like can be used.

In this invention, you may add a crosslinking agent as a polyol component as needed.
Examples of the crosslinking agent include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, tetramethylene ether glycol, glycerin, pentaerythritol, trimethylolpropane, monoethanolamine, diethanolamine, isopropanolamine, amino Alcohols such as ethylethanolamine, sucrose, sorbitol and glucose can be used. Of these, those having 3 or more functional groups are preferred.

  Examples of the isocyanate component of the present invention include aromatic isocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and isocyanate group-terminated prepolymers.

  More specifically, as an isocyanate component for reacting with a polyol, diphenylmethane diisocyanate (4,4′-MDI), polymeric MDI (crude MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2 , 6-tolylene diisocyanate (2,6-TDI) aromatic isocyanates, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI) aliphatic diisocyanate, isophorone diisocyanate, hydrogenated TDI, hydrogenated MDI, etc. Group diisocyanates, or isocyanate group-terminated prepolymers obtained by prepolymerizing these, and these can be used alone or in combination of two or more. Among the above-mentioned compounds, an isocyanate group-terminated prepolymer is preferable as the isocyanate component.

  Examples of the isocyanate component include those containing an isocyanate group-terminated prepolymer described later and a modified MDI described later. At this time, the content ratio of the isocyanate group-terminated prepolymer and the modified MDI is 80 in terms of the ratio of the isocyanate group-terminated prepolymer to the modified MDI when the total amount of the isocyanate group-terminated prepolymer and the modified MDI described later is 100 parts by mass. It is preferably in the range of / 20 to 100/0.

  As the isocyanate group-terminated prepolymer, those having a number average molecular weight of 500 to 4000, an average functional group number of 2 to 3 and an isocyanate group content of 3% to 10% by weight are preferably used. More preferably, the number average molecular weight is 500 or more and 2000 or less.

  When the number average molecular weight of the isocyanate group-terminated prepolymer exceeds 4000 and / or the isocyanate group content is less than 3% by mass, the resulting polyurethane foam is hard to foam and becomes too hard, and the viscosity is too high. Large and easy to mix with other materials. When the isocyanate group-terminated prepolymer has a number average molecular weight of less than 500 and / or an isocyanate group content of more than 10% by mass, the resulting polyurethane foam tends to foam easily and becomes too soft, resulting in a desired Hardness, impact absorption and impact resilience may not be obtained.

  The said isocyanate group terminal prepolymer can be obtained by making a polyol and isocyanate react so that an isocyanate group (NCO group) may become excess.

  Examples of the polyol reacted with isocyanate include the following (α), (β), and (γ).

(Α): polyether polyol, polyester polyol.
(Β): Polymer polyol (for example, polyacrylonitrile, acrylonitrile-styrene copolymer or the like obtained by graft copolymerization with polyether polyol).
(Γ): A bifunctional alcohol among the alcohols mentioned as examples of the crosslinking agent.

  About the polyol made to react with isocyanate, what is shown to said ((alpha)), ((beta)), ((gamma)) may be independent or what mixed 2 or more types. Among the polyols (α), (β), and (γ), the polyol to be reacted with isocyanate is preferably a polyether polyol, more preferably polytetramethylene ether glycol (hereinafter referred to as a second PTMG). It is. In addition, the range of the second PTMG includes “first PTMG (polyethylene having a number average molecular weight of 300 to 3,500, an average functional group number of 2 to 3, and an average hydroxyl value of 35 mgKOH / g to 200 mgKOH / g”. Tetramethylene ether glycol) ”, and“ polytetramethylene ether in which at least one of the number average molecular weight, the average number of functional groups, and the average hydroxyl value is out of the range for satisfying the first PTMG ” Glycol ".

  As the isocyanate for forming the isocyanate group-terminated prepolymer, aromatic isocyanates, aliphatic diisocyanates, or alicyclic diisocyanates can be preferably used as exemplified in the above-mentioned isocyanate component. 4,4′-MDI is preferred.

  Therefore, the isocyanate group-terminated prepolymer constituting the isocyanate component is preferably one obtained by reacting the second PTMG with 4,4'-MDI. If the isocyanate group-terminated prepolymer is a prepolymer obtained by reacting 4,4′-MDI with the second PTMG, the PTMG portion has high crystallinity, and a urethane foam with high rebound resilience is easily obtained. As an isocyanate component, the familiarity when used in combination with a modified MDI is good. Furthermore, what is obtained by reacting 4,4'-MDI with the second PTMG has good mixing properties when the first PTMG is used as the polyol component, and the molecular structure is uniform. The quality of the resulting urethane foam can be stabilized.

  As the modified MDI, those having an isocyanate group content of 25% by mass or more and 33% by mass or less are preferably used. This is because such a modified MDI is liquid at room temperature, so that the viscosity of the isocyanate component can be lowered.

  If the modified MDI has an isocyanate group content of less than 25% by mass, the effect of increasing the NCO group content when mixed with the isocyanate group-terminated prepolymer is small. In this case, it is necessary to mix at a very high ratio, and the desired bending resistance may not be obtained. On the other hand, when the modified MDI has an isocyanate group content of more than 33% by mass, the NCO group content can be increased with a very small amount. However, since the amount of the modified MDI is small, the viscosity of the isocyanate group-terminated prepolymer is low. Cannot be reduced, and the mixing property when reacting with the first PTMG which is a polyol component is deteriorated.

  Specific examples of such modified MDI that is liquid at room temperature include polymeric (crude MDI), urethane modified, urea modified, allophanate modified, biuret modified, carbodiimide modified, uretonimine modified, uretdione modified. And isocyanurate-modified products. From the viewpoint of excellent molecular (crosslinked) structure after reaction with the above-mentioned polyol component, it is preferable to select a polymer (crude MDI) or a carbodiimide-modified product as the modified MDI.

As the filler of the present invention, those having a specific gravity of 0.25 g / cm ³ or more and less than 1.0 g / cm ³ can be used. Here, the specific gravity is the mass of the filler per volume occupied by the filler itself, and in the case of hollow fine particles, it indicates the apparent specific gravity including internal voids.
If the specific gravity of the filler is less than 0.25 g / cm ³ , physical properties will be greatly affected by the addition of a small amount, it will be difficult to adjust the desired hardness and flex resistance, and it will be very lightweight and into the air. It will be scattered and difficult to handle during molding. If the specific gravity is 1.0 g / cm ³ or more, an improvement in foam hardness cannot be expected with a small addition amount, and it is necessary to increase the addition amount. However, if the addition amount is increased, other physical properties are lowered and the weight is reduced. Becomes difficult.
More preferably, specific gravity of 0.46 g / cm ³ or more 1.0 g / cm ³ or less.

As the filler of the present invention, an inorganic filler or an organic filler can be used.
Inorganic fillers include silica, alumina, zeolite, pearlite, ceramics, mica (mica), magnesium carbonate, magnesium hydroxide, magnesium silicate, silicon oxide, calcium carbonate, titanium oxide, aluminum hydroxide, aluminum oxide, talc, hydro Particles obtained by grinding talcite, magnesium oxide, beryllium oxide, zinc oxide, boron nitride, silicon nitride, aluminum nitride, silicon carbide, copper, silver, iron, aluminum, nickel, glass, etc., or carbon fiber, cellulose fiber, glass fiber And fibrous materials such as aramid fibers.
The organic filler is a thermoplastic resin, for example, a polyolefin resin such as a polyethylene resin or a polypropylene resin, an acrylic resin, a vinyl chloride resin, a polystyrene resin, a polyamide resin, a polyester resin, a polycarbonate resin, Fine particles such as a polysulfone resin can be used. These resins also include copolymers such as olefin-polar monomer copolymers and vinyl chloride-vinyl acetate copolymers.

  Examples of the filler shape include spherical fine particles, non-spherical fine particles, hollow fine particles, fibrous shapes, and plate shapes, and spherical fine particles are preferable. When the filler shape is spherical, the filler has a large surface area and is less likely to cause friction with the resin, so that it is possible to suppress a decrease in flex resistance and further a decrease in physical properties such as rebound resilience. In the case of an inorganic filler, hollow fine particles are more preferable, and since the specific gravity is small, the number of fillers dispersed in the resin (the volume ratio of the filler in the foam) can be increased.

The filler of the present invention preferably has an average particle size of 10 μm or more and less than 60 μm. When the average particle diameter is less than 10 μm, the dispersibility in the raw material is good, but it is difficult to contribute to the improvement of foam hardness. When it is 60 μm or more, the dispersibility is inferior and it is difficult to obtain uniform foam properties.
Here, the average particle size of the present invention is a particle size measured using a laser diffraction particle size distribution measuring device (manufactured by Shimadzu Corporation, trade name “SALD”), and indicates a volume ratio equal to or less than a certain particle size. This is a value at 50 vol% in the cumulative distribution. Hereinafter, it may be indicated as an average particle diameter (d50).

The addition amount of the filler is preferably 5 parts by mass or more and less than 20 parts by mass with respect to 100 parts by mass of the polyol component. When the addition amount is less than 5 parts by mass, the foam hardness required for low density cannot be obtained. If it is 20 parts by mass or more, the hardness increases, but the foam is inferior in bending resistance.
More preferably, it is 5 to 10 parts by mass with respect to 100 parts by mass of the polyol component.

  The foam stabilizer of the present invention is not particularly limited as long as it can be used with urethane foam, but when urethane foam is used as a sole member for performing intense exercise such as sports shoes, higher resilience Therefore, it is preferable to use a silicone compound having a viscosity of 300 mPa · s (25 ° C.) to 2000 mPa · s (25 ° C.). When the viscosity of the silicone compound used as the foam stabilizer is less than 300 mPa · s (25 ° C.), the foam regulating action is weak, the cell is coarsened, and high rebound resilience is difficult to obtain. On the other hand, when the viscosity exceeds 2000 mPa · s (25 ° C.), it is difficult to uniformly disperse in the polyurethane raw material, and the cell size of the resulting foam is not uniform, and the physical properties change locally (measurement) The physical property value varies depending on the location). Considering these points, the viscosity of the silicone compound used as the foam stabilizer is more preferably 600 mPa · s (25 ° C.) or more and 1000 mPa · s (25 ° C.) or less. The viscosity of the silicone compound is a value measured with a B-type rotational viscometer.

  The addition amount of the silicone compound added as a foam stabilizer is preferably 0.5 parts by mass or more and 9 parts by mass or less with respect to 100 parts by mass of the aforementioned polyol component. When the addition amount of the silicone compound is less than 0.5 parts by mass, the foam regulating action is weak, the cell size of the resulting polyurethane foam is greatly non-uniform, the rebound resilience is low, and the desired impact absorption and durability are low. It is difficult to obtain. When the addition amount of the silicone compound exceeds 9 parts by mass, not only the obtained polyurethane foam tends to be inferior in impact resilience, but also a bleed out that the foam stabilizer exudes from the foam surface occurs. There is also a possibility that it may be inferior in handleability. In particular, when the addition amount of the silicone compound exceeds 5 parts by mass, the desired resilience, impact absorption, and durability can be obtained, but there is a tendency for a tacky feeling (sticky feeling) to occur to the extent that there is no problem in use. is there. Considering this point, the addition amount of the silicone compound is more preferably 0.5 parts by mass or more and 5 parts by mass or less.

  As the foaming agent of the present invention, water (ion exchange water) can be preferably used. The addition amount of the foaming agent in the polyurethane raw material composition is preferably 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the aforementioned polyol component. If the addition amount is less than 0.5 parts by mass, foaming is insufficient and rebound resilience is exhibited, but the impact absorption is poor. When the added amount exceeds 3 parts by mass, cells of polyurethane foam obtained by excessive foaming are rough and the foam state is inferior, such as the inside being easily cracked, and the resilience tends to be inferior.

  The catalyst of the present invention is not particularly limited as long as it can be used for producing a polyurethane foam. Examples of the catalyst conventionally used include amine catalysts such as triethylenediamine and diethanolamine, and metal catalysts such as bismuth catalyst. The addition amount of the catalyst in the polyurethane raw material composition is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the aforementioned polyol component.

  In addition to the polyol component, the isocyanate component, the filler, the foaming agent, the catalyst, and the foam stabilizer, other additives are added to the polyurethane raw material composition raw material for producing the polyurethane foam of the present invention as necessary. May be. Examples of the other additives include plasticizers, antioxidants, defoamers, compatibilizers, colorants, stabilizers, and additives that can be generally used in the production of polyurethane foams. . The addition amount of other additives may be appropriately selected within a range that does not impair the effects of the present invention.

Generally, when filler is added to a polyurethane foam raw material, improvement in foam hardness can be expected, but it is known that foam physical properties are inferior. In particular, the tendency appears with respect to the bending resistance, but according to the present applicant, it has been found that the use of a filler having a specific gravity can suppress a decrease in bending resistance. Therefore, even a low-density foam having a density of 0.25 g / cm ³ or more and 0.35 g / cm ³ or less can obtain a foam having a C hardness of 50 or more and 65 or less and an appropriate hardness and excellent bending resistance. It is done. Moreover, in the present invention, a foam excellent in impact absorption, impact resilience, and durability can be obtained, and the function as a shoe sole member can be exhibited.

  The physical properties of the polyurethane foam of the present invention will be described below.

〔density〕
In the polyurethane foam of the present invention, the apparent density of the polyurethane foam measured according to JIS K 7222 is 0.25 g / cm ³ or more and 0.35 g / cm ³ or less. In the present invention, even if the apparent density of the polyurethane foam is a relatively small value of 0.25 g / cm ³ or more and 0.35 g / cm ³ or less, a polyurethane foam having a suitable hardness and bending resistance can be obtained. . In addition, a polyurethane foam having excellent impact absorption and retaining physical properties such as rebound resilience and durability can be obtained. Such a polyurethane foam of the present invention can be preferably used for applications such as a shoe sole member in which weight reduction is regarded as important.

〔hardness〕
About the polyurethane foam of this invention, the hardness of the polyurethane foam measured using Asker rubber hardness meter C type | mold based on JISK7312 is 50-65. When the hardness of the polyurethane foam is 50 or more and 65 or less, a shoe using the polyurethane foam as a sole member can be excellent in stability at the time of landing.

[Flexibility]
Polyurethane foam has bending resistance. This can be specified by performing the following flexibility confirmation test.

[Bending resistance test]
A polyurethane foam having a predetermined size (for example, length 120 mm, width 60 mm, thickness 6 mm) is prepared and used as a test piece. A composite in which a resin-impregnated board having a predetermined thickness (for example, 2 mm) is bonded to the polyurethane foam test piece is prepared, and half of the composite is bent 90 ° at a central position along the longitudinal direction. The bending back operation composed of the operation and the operation of returning half of the complex to the original position is repeated at a speed of 144 times / minute. If the number of bending back operations until the occurrence of cracks in the polyurethane foam is 20,000 times or more, the bending resistance is excellent. In the polyurethane foam of the present invention, the term “flexible” means that, as a result of the bending resistance confirmation test, the number of bending return operations until the occurrence of cracks is 20,000 times or more, preferably 30,000 times or more. is there.

  Here, the resin-impregnated board is a pulp board (impregnated paper) impregnated with synthetic resin, synthetic rubber, natural rubber or the like, and is used as, for example, an insole or an insole core material. As the resin-impregnated board, a commercially available one can be appropriately selected. For example, a trade name “Texon Board 437” manufactured by Vontex, Inc. can be used.

[Rebound resilience]
The polyurethane foam of the present invention preferably has a rebound resilience measured in accordance with JIS K 6255 of 60% or more. When the rebound resilience of the polyurethane foam is 60% or more, it is possible to obtain a rebound resilience suitable as a sole member of a sports shoe.

(Shock absorption)
The impact absorption of polyurethane foam can be specified by the maximum impact load. In the polyurethane foam of the present invention, the maximum impact load is preferably 0.9 kN or less. The maximum impact load can be specified by the following drop impact test. The smaller the maximum impact load value, the more impact is absorbed. When the maximum impact load on the polyurethane foam is 0.9 kN or less, it is possible to obtain a polyurethane foam having an impact absorbability enough to be used as a shoe sole member.

(Drop impact test)
A polyurethane foam formed to have a thickness of 12.5 mm is prepared and used as a test piece. A 5.1 kg weight is made to collide with a polyurethane foam test piece from a height of 50 mm. As the weight, a bullet-shaped weight W as shown in FIG. 1 may be used. And the maximum impact load in that case is specified. The maximum impact load can be measured using, for example, trade name dynaup GRC8200 manufactured by Instron.

〔durability〕
The polyurethane foam of the present invention has a compression set rate of 20% or less of the polyurethane foam measured according to JIS K 6262. However, the measurement conditions for measuring the compression set are those of a compression rate of 25%, 40 ° C., and 24 hours. When the compression set of polyurethane foam exceeds 20%, the durability performance required for shoes may be inferior when polyurethane foam is used as a shoe sole member.

  The polyurethane foam of the present invention preferably has an average cell size of 30 μm or more and 100 μm or less. Flexibility, impact absorption, rebound resilience, and durability can be improved when a uniform cell having a specific average cell size and no variation is formed.

  The polyurethane foam is preferably formed by reacting the above-described polyurethane raw material composition by molding. Here, the mold molding is a method in which the polyurethane raw material (stock solution) is poured into a mold (molding die), foamed and cured in the mold, and then demolded to obtain a foam.

  When the polyurethane foam is produced by molding a polyurethane raw material composition, the cell size can be uniformly reduced by the compression effect at the time of foaming. Moreover, when a polyurethane raw material composition is molded, the density of the obtained polyurethane foam can be easily adjusted by the injection amount of the polyurethane raw material composition with respect to the volume in the mold.

  The polyurethane foam of the present invention is a material that is lightweight but has an appropriate hardness and bending resistance, and also has both impact absorption and rebound resilience, and has a low compression set and excellent durability. For example, it can be suitably used as a shoe sole member. When used as a shoe sole member, the polyurethane foam can be used for any of an outsole, a midsole, and an insole. When the polyurethane foam is used for a shoe sole member, not only the polyurethane foam of the present invention is provided on the entire surface of the shoe sole, but also a recess is formed in a midsole formed of another material, and the polyurethane foam of the present invention is formed there. It is also possible to partially arrange such as inserting. Further, as the shoe sole, the polyurethane foam of the present invention may be used for the midsole, and an outsole made of a rubber material having anti-slip properties may be laminated on the ground contact surface side. In that case, the outsole may be arranged at any location on the midsole ground plane side, or the midsole on the ground plane side may be partially exposed by cutting out a part of the outsole. Good. Since the polyurethane foam of the present invention is excellent in bending resistance, even if a load is applied to the boundary portion between the midsole and the outsole, the midsole does not crack.

  The polyurethane foam of the present invention is suitable for applications requiring impact absorption, rebound resilience, durability, flex resistance, etc. in addition to shoe sole members, such as inside helmets, protectors, cushioning materials for vehicles, and flooring materials. Can be used for

Examples 1-12, Comparative Examples 1-9
While preparing a mold of a predetermined shape and mixing them by stirring the polyol component, isocyanate component, filler, catalyst, foaming agent, and foam stabilizer using a screw as shown in Table 1 and Table 2. Injection into the mold. The number of rotations of the screw was set to 3500 rpm. The amount of the polyurethane raw material composition injected into the mold is as shown in the “filling amount” column of Tables 1 and 2. The polyurethane raw material composition is formed by mixing a polyol component, an isocyanate component, a filler, a catalyst, a foaming agent, and a foam stabilizer using a screw. After the polyurethane raw material composition was injected into the mold, the polyurethane raw material composition was reacted under the condition of a mold temperature of 40 ° C. After the reaction, it was demolded to obtain a polyurethane foam. In addition, the unit of the numerical value which shows the mixing | blending of the material in Table 1, 2 is a mass part.

  The polyol component, isocyanate component, filler, catalyst, foaming agent, and foam stabilizer in Tables 1 and 2 are as shown below.

Polyol I: Polytetramethylene ether glycol (number average molecular weight 2000, hydroxyl value 57.2 mgKOH / g, average functional group number 2)
Filler A: Glass hollow fine particles (specific gravity 0.60 g / cm ³ , average particle diameter (d50) 18 μm, manufactured by 3M, trade name “3M Glass Bubbles IM30K”)
Filler B: Glass hollow fine particles (specific gravity 0.46 g / cm ³ , average particle diameter (d50) 20 μm, manufactured by 3M, trade name “3M Glass Bubbles IM16K”)
Filler C: Glass hollow fine particles (specific gravity 0.25 g / cm ³ , average particle size (d50) 55 μm, manufactured by 3M, trade name “3M Glass Bubbles K25”)
Filler H: Glass hollow fine particles (specific gravity 0.20 g / cm ³ , average particle diameter (d50) 60 μm, manufactured by 3M, trade name “3M Glass Bubbles K20”)
Filler D: Ceramic hollow fine particles (specific gravity 0.60 to 0.90 g / cm ³ , average particle size (d50) 53 μm, manufactured by Kansai Matec Co., Ltd., trade name “Kinospheres 100”)
Filler E: polyethylene fine particles (specific gravity 0.94 g / cm ³ , average particle diameter (d50) 30 μm, manufactured by Mitsui Chemicals, trade name “Miperon XM220”)
Filler F: Mica (specific gravity 2.7 to 3.1 g / cm ³ , scaly, average particle diameter (d50) 2.1 μm, manufactured by Yamaguchi Mica, trade name “A-11”)
Filler G: Glass fiber (specific gravity 2.3 g / cm ³ , average fiber diameter 10 μm, average fiber length 80 μm, manufactured by Nippon Electric Glass Co., Ltd., trade name “Milled Fiber”)
Catalyst A: Triethylenediamine (manufactured by Tosoh Corporation, trade name TEDA-L33)
Catalyst B: Bismuth catalyst (Nippon Chemical Industry Co., Ltd., trade name: PUCCAT 25)
Foam stabilizer A: silicone compound (viscosity 900 mPa · s (25 ° C.))
Foaming agent: ion-exchanged water isocyanate end group prepolymer: prepolymer obtained by reacting polytetramethylene ether glycol and 4,4'-MDI (number average molecular weight 1000, average number of functional groups 2, isocyanate group content 7.9%)
Modified MDI: Modified carbodiimide (average functional group number 2, isocyanate group content 29.0%)

For the polyurethane foams obtained in Examples 1 to 12 and Comparative Examples 1 to 7 and 9, the hardness of the polyurethane foam was measured using an Asker rubber hardness tester C type according to JIS K 7312. Further, the polyurethane foams obtained in Examples 1 to 12 and Comparative Examples 1 to 7 and 9 were appropriately cut to prepare test pieces, and the following measurements were performed using the test pieces. The results are as shown in Tables 1 and 2.
In Comparative Example 8, filling of the resin into the mold was insufficient, and molding was impossible.

(Apparent density)
A rectangular solid having a length of 15 mm, a width of 15 mm, and a thickness of 10 mm is cut out from the polyurethane foam to obtain a test piece for density measurement, and the apparent density (g / cm ³ ) is measured using this test piece for density measurement in accordance with JIS K7222. It was.

(Bending resistance confirmation test)
Cut from a polyurethane foam into a rectangular parallelepiped shape having a length of 120 mm, a width of 60 mm, and a thickness of 6 mm, and this is used as a bending test piece. A composite was prepared by adhering a 2 mm thick resin-impregnated board (trade name: Texon board 437, manufactured by Vontex) to this bending test piece, and 90% of the composite was 90% in the center position along the vertical direction. A bending back operation comprising a bending operation and an operation of returning half of the composite to the original position was repeated at a speed of 144 times / minute. Then, the bending back operation was repeated until the occurrence of cracks in the bending test piece in the composite, and the number of times when the occurrence of cracks was observed was measured. In addition, although a result is described in Tables 1 and 2, in Tables 1 and 2, it is described whether or not a crack has occurred in units of 10,000 times. In addition, in this invention, the said bending resistance test shall have bending resistance about 20,000 times or more. Comparative Examples 2, 3, 5 to 7 did not have bending resistance because cracks occurred less than 20,000 times.

(Compression set)
Cut out from a polyurethane foam into a cylindrical shape having a diameter of 29 mm and a thickness of 12.5 mm to obtain a test piece for measurement of compression set, and using a test piece for measurement of compression set at a compression rate of 25%, 40 ° C. for 24 hours, According to JIS K 6262, compression set (%) was measured.

(Rebound resilience)
Cut out from a polyurethane foam into a cylindrical shape having a diameter of 29 mm and a thickness of 12.5 mm to obtain a test piece for measuring the resilience modulus, and the resilience modulus (%) was measured in accordance with JIS K 6255 using the test specimen for measuring the resilience modulus. It was.

(Maximum impact load)
The polyurethane foam was cut into a rectangular parallelepiped shape having a length of 70 mm, a width of 60 mm, and a thickness of 12.5 mm to obtain a test piece for measuring impact load, and the maximum impact load was measured by a drop impact test using the test piece for measuring impact load. In the drop impact test, a “dynaup GRC8200 (manufactured by Instron)” is used to collide a bullet-shaped weight w (made of iron, 5.1 kg) as shown in FIG. It was carried out by specifying the maximum impact load (kN) at the time.

According to Examples 1 to 12, when a filler having a specific gravity is used, even if it is a low density foam having a density of 0.25 g / cm ³ or more and 0.35 g / cm ³ or less, the C hardness is 50 or more and 65 or less. A foam having excellent bending resistance was obtained. That is, it has been clarified that the polyurethane foam of the present invention is excellent in bending resistance while maintaining light weight and hardness.

On the other hand, in Comparative Example 1 in which no filler was added, the obtained foam hardness was insufficient. Further, Comparative Examples 4 to 7 using fillers whose specific gravity deviates from a specific range also have insufficient foam hardness or poor bending resistance, and have a density of 0.25 g / cm ³ or more and 0.35 g. In the case of a low density foam of / cm ³ or less, a foam excellent in both hardness and bending resistance was not obtained.

W weight

Claims (10)

A polyurethane foam comprising a polyurethane raw material containing a polyol component, a polyisocyanate component, a filler, a foaming agent, a catalyst, and a foam stabilizer,
The polyol component includes polytetramethylene ether glycol having a number average molecular weight of 300 to 3,500, an average functional group number of 2 to 3, and an average hydroxyl value of 35 mgKOH / g to 200 mgKOH / g,
The filler has a specific gravity of 0.25 g / cm ³ or more and less than 1.0 g / cm ³ ;
The density of the polyurethane foam measured in accordance with JIS K 7222 is 0.25 g / cm ³ or more and 0.35 g / cm ³ or less,
In accordance with JIS K 7312, the hardness of the polyurethane foam measured using an Asker rubber hardness meter C-type is 50 or more and 65 or less,
Polyurethane foam characterized by having bending resistance.   The polyurethane foam according to claim 1, wherein an average particle size of the filler is 10 µm or more and less than 60 µm.   The polyurethane foam according to claim 1 or 2, wherein an addition amount of the filler is 5 parts by mass or more and less than 20 parts by mass with respect to 100 parts by mass of the polyol component.   A polyurethane foam formed to have a length of 120 mm, a width of 60 mm, and a thickness of 6 mm is prepared, and a composite is prepared by bonding a resin-impregnated board having a thickness of 2 mm to the polyurethane foam. When a bending back operation consisting of an operation of bending a half of the complex at a central position along the vertical direction by 90 ° and an operation of returning the half of the complex to the original position is repeated at a speed of 144 times / min. The polyurethane foam according to any one of claims 1 to 3, wherein the number of bending back operations until the occurrence of cracks in the polyurethane foam is 20,000 or more.   The polyurethane foam as described in any one of Claim 1 to 4 whose compression set rate of the polyurethane foam measured based on JISK6262 is 20% or less. The isocyanate component is
i) an isocyanate group-terminated prepolymer having a number average molecular weight of 500 to 2000, an average functional group number of 2 to 3, and an isocyanate group content of 3 to 10% by mass;
The polyurethane foam according to any one of claims 1 to 5, comprising ii) a modified MDI having an isocyanate group content of 25 to 33% by mass.   When a test piece made of polyurethane foam formed to have a thickness of 12.5 mm is prepared, and a 5.1 kg weight collides with the test piece from a height of 50 mm, the maximum impact load on the test piece The polyurethane foam according to any one of claims 1 to 6, wherein is 0.9 kN or less.   The polyurethane foam according to any one of claims 1 to 7, wherein the rebound resilience of the polyurethane foam measured in accordance with JIS K 6255 is 60% or more.   The polyurethane foam according to any one of claims 1 to 8, which is a molded product. A shoe sole member using the polyurethane foam according to any one of claims 1 to 9.

Images