WO2019172201A1

WO2019172201A1 - Polyurethane foam and shoe sole member

Info

Publication number: WO2019172201A1
Application number: PCT/JP2019/008465
Authority: WO
Inventors: 宏生森; 拓磨南
Original assignee: アキレス株式会社
Priority date: 2018-03-08
Filing date: 2019-03-04
Publication date: 2019-09-12
Also published as: TWI718489B; JP7224713B2; TW201938625A; JPWO2019172201A1

Abstract

Provided is a polyurethane foam that has outstanding lightness of weight and can be used to form a shoe sole member without sacrificing the properties of durability, shock absorption, rebound resilience, and flex resistance. The polyurethane foam comprises a soft segment formed from a polyol constituent and a hard segment formed from a structure section that includes a urethane bonding section, wherein: the presence ratio of the soft segment and that of the hard segment, expressed as the mass ratio of the soft segment to the hard segment with the total of the soft segment and the hard segment being 100 parts by mass, is in the range of 70/30 to 80/20; the average bubble diameter of the polyurethane foam is 30 µm–100 µm; at least 90% of all air bubbles formed in the polyurethane foam have bubble diameters of 20–300 µm; the apparent density of the polyurethane foam, measured in accordance with JIS K 7222, is 0.25–0.50 g/cm³; and the hardness of the polyurethane foam, measured using a type C Asker durometer in accordance with JIS K 7312 is 50–65.

Description

Polyurethane foam and sole material

The present invention relates to a polyurethane foam and a sole member that can be used to form a sole member.

Polyurethane foam is widely used as a sole member because of its excellent shock absorption. Examples of commonly used shoe sole members include insole, midsole and outsole.

In addition, the sole member is required to have durability realized by a small compression set, shock absorption achieved by impact absorption and relaxation force applied to the foot, rebound resilience, and bending resistance. The Since the sole member is excellent in durability, the structure and function of the sole member can be maintained even if the shoe using the sole member is continuously used. Since the sole of the shoe sole is excellent in shock absorption, the impact on the sole during exercise can be suppressed and injury can be prevented. Since the sole member is excellent in rebound resilience, it is possible to effectively assist the movement of the foot when kicking out. Moreover, if the sole member is excellent in bending resistance, it is possible to suppress the possibility that the sole member is cracked by the bending operation of the sole.

Regarding these points, for example, Patent Document 1 describes an invention of a polyurethane foam having both impact absorption and rebound resilience. Patent Document 2 describes an invention of a polyurethane foam having improved bending resistance.

JP 2016-069658 A JP 2017-105913 A

However, a shoe sole member is required to have a further improved lightness without impairing the properties such as durability, impact absorption, rebound resilience, and bending resistance.

The present invention provides a polyurethane foam and a shoe sole member that are excellent in light weight without impairing properties such as durability, impact absorption, impact resilience, and bending resistance, and that can be used to form a shoe sole member. The purpose is to provide.

The present invention is (1) a polyurethane foam having a soft segment formed from a polyol component and a hard segment formed from a structural part having a urethane bond,
The abundance ratio of the soft segment and the hard segment is a mass ratio of the soft segment to the hard segment when the total of the soft segment and the hard segment is 100 parts by mass, and is 70/30 or more and 80/20 or less. Range,
The average cell diameter of the polyurethane foam is 30 μm or more and 100 μm or less,
90% or more of all the bubbles formed in the polyurethane foam have a bubble diameter of 20 μm or more and 300 μm or less,
The apparent density of the polyurethane foam measured in accordance with JIS K 7222 is 0.25 g / cm ³ or more and 0.50 g / cm ³ or less,
A polyurethane foam characterized in that the polyurethane foam has a hardness of 50 or more and 65 or less in accordance with JIS K 7312 and measured using an Asker rubber hardness tester C type;
(2) When a test piece made of the 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 test piece is moved to the test piece. The polyurethane foam according to (1), wherein the maximum impact load is 0.9 kN or less,
(3) The polyurethane foam according to the above (1) or (2), wherein the polyol component comprises a polytetramethylene ether polyol,
(4) The polyurethane foam according to any one of (1) to (3) above, wherein the rebound resilience of the polyurethane foam measured according to JIS K 6255 is 60% or more,
(5) The polyurethane foam according to any one of (1) to (4) above, wherein the compression set of the polyurethane foam measured in accordance with JIS K 6262 is 20% or less,
(6) 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 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 (1) to (5) above, wherein the number of bending back operations until the occurrence of cracks in the polyurethane foam is 30,000 or more,
(7) The polyurethane foam according to any one of (1) to (6) above, which is a molded body,
(8) 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 test piece is moved to the test piece. The maximum impact load is 0.9 kN or less,
The resilience modulus of the polyurethane foam measured in accordance with JIS K 6255 is 60% or more,
The compression set rate of polyurethane foam measured in accordance with JIS K 6262 is 20% or less,
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 adhering 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 composite at a central position along the vertical direction by 90 ° and an operation of returning the half of the composite to the original position is repeated at a speed of 144 times / minute Further, the polyurethane foam according to any one of claims 1 to 7, wherein the number of bending back operations until the occurrence of cracks in the polyurethane foam is 30,000 or more.
(9) The gist is a shoe sole member characterized by using the polyurethane foam according to any one of (1) to (8) above.

According to the present invention, a polyurethane foam and a shoe bottom portion that are excellent in light weight without impairing properties such as durability, shock absorption, impact resilience, and bending resistance, and that can be used to form a shoe sole member. Material can be provided.

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

[Polyurethane foam]
The polyurethane foam has a soft segment and a hard segment.

(Soft segment and hard segment)
The soft segment is formed from a structure portion of a polyol component in a polymer structure forming polyurethane, and is a highly flexible molecular chain site. The hard segment is a molecular chain portion formed from a structural portion having a urethane bond portion formed by a reaction between an isocyanate group and a hydroxyl group in a polymer structure forming polyurethane. The hard segment is a rigid molecular chain site that is easily crystallized or aggregated by hydrogen bonding at the urethane bond. The hard segment is formed by a portion excluding a structural portion due to a polyol component.

In addition, the range of the structure part by the polyol component which forms a soft segment includes the site | part formed from polyol ((alpha)), ((beta)), and ((gamma)) used when forming the isocyanate group terminal prepolymer mentioned later. .

The structure part of the polyol component that forms the soft segment is a molecular chain site having higher flexibility than the structure part having a urethane bond. Therefore, the ratio between the soft segment and the hard segment has a great influence on the performance of the polyurethane foam.

(Existence ratio of soft segment and hard segment)
In the polyurethane foam of the present invention, the mass ratio of the soft segment to the hard segment is 70/30 or more and 80/20 when the total ratio of the soft segment and the hard segment is 100 parts by mass. The range is as follows. Polyurethane foam in which the mass ratio of the soft segment to the hard segment exceeds 80/20 cannot satisfy a specific hardness, and is inferior in durability to impact absorption. Moreover, the polyurethane foam whose mass ratio of the soft segment with respect to a hard segment is less than 70/30 becomes hard, and is inferior to shock absorption.

(Method for determining the ratio of soft segments to hard segments)
The abundance ratio of the soft segment and the hard segment in the present specification is a value obtained in advance according to the blending ratio of the polyol and the isocyanate.
For example, when a polyurethane foam is formed, a method for specifying the abundance ratio will be described with respect to an example in which the first PTMG described later is used as the polyol component and an isocyanate group-terminated prepolymer and modified MDI are used as the isocyanate component. In this specific example, the isocyanate group-terminated prepolymer is a reaction product of the second PTMG and MDI. In this case, the existence ratio of the soft segment and the hard segment can be specified as follows. First, the abundance ratio (%) of the soft segment is (the total amount of the first PTMG and the amount of the second PTMG component in the isocyanate group-terminated prepolymer) / (the first PTMG amount and the isocyanate group terminal). The sum of the blending amount of the prepolymer and the blending amount of the modified MDI) × 100. The abundance ratio (%) of the hard segment can be specified by 100− (abundance ratio of the soft segment).

The existence ratio of the soft segment and the hard segment can also be specified as follows. That is, the abundance ratio of the soft segment and the hard segment in the polyurethane foam is determined by pyrolysis GC / MS analysis of the polyurethane foam (pyrolysis gas chromatography mass spectrometry) and ¹ H-NMR (nuclear magnetic field) of the hydrolyzate of the polyurethane foam. (Resonance) measurement result. More specifically, the pyrolysis product is qualitatively determined by pyrolysis GC / MS analysis of the polyurethane foam. Moreover, a hydrolyzate is obtained by hydrolyzing a polyurethane foam. The polyurethane foam is decomposed into a diamine salt (compound derived from an isocyanate component) and a polyol by hydrolysis. From the integrated value of the ¹ H-NMR spectrum of the obtained hydrolyzate, the composition in the polyurethane foam can be identified. From these results, the isocyanate component and the polyol component, which are starting materials, can be converted into parts by mass, and the ratio can be determined.

(Average bubble diameter)
When the polyurethane foam of the present invention has a uniform cell having an average cell diameter in a specific range and has no variation, impact absorption, rebound resilience, durability, and flex resistance are also improved. Can do. From the viewpoint of enhancing this effect, the average cell diameter of the polyurethane foam is preferably 30 μm or more and 100 μm or less.

(Distribution of bubble size)
Regarding the distribution of the size of the cell diameter formed in the polyurethane foam, 90% or more of the cells (cells) formed in the polyurethane foam have a cell diameter of 20 μm or more and 300 μm or less. It has a distribution like this. Here, the ratio of the number of bubbles having a certain range of bubble diameters to the whole is an index for determining the degree of variation. The number of bubbles having a specific range of bubble diameters accounting for 90% or more indicates a uniform state without variation. The bubble diameter indicates the cell diameter.

(Identification method for average bubble size and bubble size distribution)
The cell diameter distribution of the polyurethane foam can be specified as follows. First, the polyurethane foam is cut at a position selected in advance at random to expose the cut surface. On the cut surface, a predetermined area (for example, a rectangular area having a length of 4 mm and a width of 3 mm) is randomly selected as a selection area. Using a microscope, count the number of all bubbles present in the selected area. Next, the number of bubbles having a bubble diameter of 20 μm or more and 300 μm or less in the selected region is measured. The ratio of the total number of bubbles in the selected area to be a, the number of cells having a bubble diameter of 20 μm to 300 μm to b, and the ratio of cells having a bubble diameter of 20 μm to 300 μm to all cells is It is determined by the formula b / a × 100 (%).

The average bubble diameter can be specified as follows, for example. First, the polyurethane foam is cut at a randomly selected position to expose the cut surface. On the cut surface, a predetermined area (for example, a rectangular area having a length of 4 mm and a width of 3 mm) is randomly selected as a selection area. The number of cells existing in the selected area (the number of all cells) and the diameter of each bubble (cell diameter) are measured using a microscope. The average bubble diameter is specified as an arithmetic average value calculated from each bubble diameter.

(Apparent density)
In the polyurethane foam of the present invention, the apparent density of the polyurethane foam measured in accordance with JIS K7222 is 0.25 g / cm ³ or more and 0.50 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 0.50 g / cm ³ or less, the polyurethane foam has excellent impact absorbability, rebound resilience, durability, A polyurethane foam that retains physical properties such as flexibility 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)
The polyurethane foam of the present invention has a hardness of 50 or more and 65 or less in accordance with JIS K 7312 and measured using an Asker rubber hardness meter C type. When the hardness of the polyurethane foam is 50 or more and 65 or less, shoes using the polyurethane foam as a sole member are excellent in stability at the time of landing.

The hardness of polyurethane foam fluctuates under the influence of three variables: the abundance ratio of soft segments and hard segments, average cell diameter, and cell size distribution. However, the hardness is not determined only by setting these three variables within a specific range. On the other hand, in the present invention, it has been realized that the hardness of the polyurethane foam is in the range of 50 to 65 in consideration of the balance of three variables. And, in the present invention, while adjusting the abundance ratio of the soft segment and the hard segment, the average bubble diameter, and the distribution of the bubble diameter, the hardness and the apparent density range are set to a specific range, thereby reducing the weight. However, a polyurethane foam excellent in durability, impact absorbability, impact resilience and flex resistance described later can be obtained.

(Compression set)
The polyurethane foam of the present invention has a compression set of 20% or less measured in accordance with 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 the polyurethane foam exceeds 20%, shoes in which the polyurethane foam is used as a shoe sole member may be inferior in generally required durability performance.

(Flexibility)
The polyurethane foam of the present invention has bending resistance. This can be specified by performing the following flexibility confirmation test.

(Bending resistance confirmation 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 test piece is prepared. Then, the bending back operation is repeated at a speed of 144 times / minute. The bending back operation includes an operation A for bending a half of the composite by 90 ° at a central position along the longitudinal direction, and an operation B for returning the half of the composite to the original position. This is an operation of repeating A and the above operation B. When the operation A and the operation B are successively performed once, the number of bending back operations is counted as one.
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, as a result of the bending resistance confirmation test, the number of bending back operations until the occurrence of cracks is 20,000 times or more, preferably 30,000 times or more.

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, a core material of an insole or an insole. 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.

(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 dropped from a height of 50 mm to collide with the test piece. 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.

(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.

As described above, the polyurethane foam of the present invention has a relatively small apparent density of not less than 0.25 g / cm ^{3 and not} more than 0.50 g / cm ³ and is excellent in light weight, but also has an impact absorption property. It has a sufficient hardness while being excellent in impact resilience, durability, and bending resistance.

[Production method of polyurethane foam]
The polyurethane foam of the present invention can be formed by reacting a polyurethane raw material composition containing a polyol component, an isocyanate component, a foaming agent, a catalyst, and a foam stabilizer.

[Polyol component]
The polyol component becomes a material for forming the structure portion of the soft segment of the polyurethane foam. Examples of the polyol component that is a material for forming the structural part include polyether polyol and polyester polyol.

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 an aliphatic carboxylic acid such as malonic acid, succinic acid, or adipic acid, or an aromatic carboxylic acid such as phthalic acid, and a polyhydric alcohol such as ethylene glycol, diethylene glycol, or propylene glycol. Those obtained by condensation can be used.

The range of the polyol component includes the polyol used for reacting with the isocyanate, and includes, for example, the compounds shown in (α), (β), and (γ) described later. *

The polyol component is preferably a polyether polyol 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. For example, polytetramethylene ether glycol (also referred to as first PTMG) may be used. In the present invention, two or more kinds of first PTMGs having different number average molecular weights may be mixed and used as the polyol component.

When the number average molecular weight of the polyol component is less than 300, and / or when the average hydroxyl value exceeds 200 mgKOH / g, the cell diameter of the resulting urethane foam tends to be non-uniform and flexibility is likely to be impaired. The desired bending resistance may not be obtained. When the number average molecular weight of the polyol component exceeds 3500 and / or when the average hydroxyl value is less than 35 mgKOH / g, the existing ratio of the soft segment to the hard segment increases, and the impact absorption of the resulting polyurethane foam is obtained. However, the desired resilience may not be obtained. *

In addition, you may add a crosslinking agent to 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.

[Isocyanate component]
The hard segment is formed by a structure part having a urethane bond part formed by a reaction between an isocyanate group and a hydroxyl group, and the material for forming the structure part includes an isocyanate component. Specific examples include aromatic isocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and isocyanate group-terminated prepolymers.

More specifically, as an isocyanate component for reacting with a polyol, 4,4′-diphenylmethane diisocyanate (4,4′-MDI), polymeric MDI (crude MDI), 2,4-tolylene diisocyanate (2,4 -TDI), or aromatic isocyanates such as 2,6-tolylene diisocyanate (2,6-TDI), aliphatic diisocyanates such as tetramethylene diisocyanate or hexamethylene diisocyanate (HDI), isophorone diisocyanate, hydrogenated TDI, Alternatively, alicyclic diisocyanates such as hydrogenated MDI, or isocyanate group-terminated prepolymers obtained by prepolymerizing these may be used, and these may 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 97 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. A range of / 3 to 80/20 is preferred.

(Isocyanate group-terminated prepolymer)
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.

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 There is a possibility that impact absorbability and impact resilience cannot be obtained.

The isocyanate group-terminated prepolymer can be obtained by reacting a polyol and an isocyanate so that the isocyanate group (NCO group) becomes excessive. *

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

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

Regarding the polyol to be reacted with isocyanate, those shown in the above (α), (β), and (γ) may be used alone or in combination of two or more. 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 the second PTMG with 4,4'-MDI, the crystallinity of the PTMG portion is increased. Therefore, it is easy to obtain a urethane foam with high impact resilience, and the compatibility when used in combination with modified MDI as an isocyanate component is good. Furthermore, the isocyanate group-terminated prepolymer obtained by reacting 4,4′-MDI with the second PTMG has good mixing properties when reacting with the first PTMG used as the polyol component, and has a molecular structure. Tends to be uniform. Therefore, the quality of the urethane foam obtained can be stabilized.

(Modified MDI)
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.

Modified MDI having an isocyanate group content of less than 25% by mass has little effect of increasing the NCO group content when mixed with an isocyanate group-terminated prepolymer. Therefore, in order to sufficiently increase foamability and reduce the density of the foam while using a modified MDI having an isocyanate group content of less than 25% by mass, the modified MDI must be mixed at a very high ratio. However, in this case, the produced polyurethane foam may not obtain the desired bending resistance. On the other hand, a modified MDI having an isocyanate group content exceeding 33% by mass can increase the NCO group content in a very small amount. However, since the amount of the modified MDI becomes small, the viscosity of the isocyanate group-terminated prepolymer cannot be lowered, and the mixing property when reacting with the first PTMG as the 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.

[Foaming agent]
As the foaming agent, 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 the impact resilience is exhibited, but the impact absorption tends to be inferior. 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.

[catalyst]
The catalyst 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.

[Foam stabilizer]
The foam stabilizer is not particularly limited as long as it can be used in urethane foam. When urethane foam is used as a sole member for performing intense exercise such as sports shoes, higher resilience is required. Therefore, it is preferable to use a silicone compound having a viscosity of 300 mPa · s (25 ° C.) or more and 2000 mPa · s (25 ° C.) or less as the foam stabilizer. 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 becomes difficult to uniformly disperse the foam stabilizer in the polyurethane raw material. As a result, not only the bubble diameter of the obtained foam is not uniform, but also the physical properties change locally (the physical property values change depending on the measurement 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 the 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 above-described polyol component. When the addition amount of the silicone compound is less than 0.5 parts by mass, the foam regulating action is weak, and the resulting polyurethane foam has a large and uneven cell diameter, low rebound resilience, and desired shock absorption and durability. 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. *

[Other additives]
In addition to the polyol component, the isocyanate component, the foaming agent, the catalyst, and the foam stabilizer, the polyurethane raw material composition raw material for producing the polyurethane foam of the present invention may further contain other additives as necessary. Also good. Examples of other additives include plasticizers, fillers, antioxidants, defoamers, compatibilizers, colorants, stabilizers, and UV absorbers that can be generally used in the production of polyurethane foam. be able to. The addition amount of other additives may be appropriately selected within a range that does not impair the effects of the present invention.

[Polyurethane foam molding]
The polyurethane foam is preferably produced by reacting the above-mentioned polyurethane raw material composition by molding. Here, 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.

Since the polyurethane foam is produced by molding a polyurethane raw material composition, the cell diameter can be made uniform and fine due to the compression effect during 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.

In manufacturing polyurethane foam by molding, a polyurethane raw material composition is formed by mixing a polyol component, an isocyanate component, a foaming agent, a catalyst, and a foam stabilizer using a screw. Furthermore, in order to obtain a uniform polyurethane foam with no variation in cell diameter, the screw rotation speed when mixing the polyol component, isocyanate component, foaming agent, catalyst, and foam stabilizer is 2000 rpm or more and 20000 rpm or less. preferable. If the rotational speed is less than 2000 rpm, the dispersion of the bubble diameter is large, and the resulting polyurethane foam tends to be inferior in bending resistance. On the other hand, if it exceeds 20000 rpm, the solidification speed becomes high and the injection into the mold remains incomplete. It will harden.

[Use of polyurethane foam]
The polyurethane foam of the present invention is a material having both impact absorption and impact resilience, and has a low compression set and excellent durability, and has high bending resistance, hardness and excellent lightness. Therefore, the polyurethane foam of the present invention can be suitably used as, for example, 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 midsole formed using the polyurethane foam of the present invention is excellent in bending resistance, the midsole will not be cracked even if a load is applied to the boundary between the midsole and the outsole.

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 to 3, 7, and 8, Comparative Examples 1, 3, 4, 6
Prepare a mold of a predetermined shape, and as shown in Table 1 and Table 2, the polyol component, isocyanate component, catalyst, foaming agent, and foam stabilizer are mixed in the mold by stirring them using a screw. Injected into. 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 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, catalyst, foaming agent, and foam stabilizer in Tables 1 and 2 are as shown below.

[Polyol component]
Regarding the polyol component, PTMG (first PTMG) is polytetramethylene ether glycol (number average molecular weight 2000, hydroxyl value 57.2 mgKOH / g, average number of functional groups 2), and PPG is polyoxypropylene glycol (number average) The molecular weight is 2200, the hydroxyl value is 51 mgKOH / g, and the average number of functional groups is 2).

[catalyst]
Regarding the catalyst, the amine-based catalyst is triethylenediamine (trade name TEDA-L33, manufactured by Tosoh Corporation), and the bismuth-based catalyst is bismuth catalyst (trade name: Pcat 25, manufactured by Nippon Chemical Industry Co., Ltd.).

[Foam stabilizer]
The foam stabilizer A is a silicone compound (viscosity 900 mPa · s (25 ° C.)), and the foam stabilizer B is a silicone compound (viscosity 250 mPa · s (25 ° C.)).

[Foaming agent]
The foaming agent is ion exchange water.

[Isocyanate component]
Regarding the isocyanate component, the isocyanate group-terminated prepolymer is a prepolymer obtained by reacting the second PTMG and 4,4′-MDI (number average molecular weight 1000, average functional group number 2, isocyanate group content 7.9%). The modified MDI is a modified carbodiimide (average number of functional groups: 2, isocyanate group content: 29.0%).

Example 4
A polyurethane foam was obtained in the same manner as in Example 1 except that the screw rotation speed was 3000 rpm and the filling amount was changed.
Example 5
A polyurethane foam was obtained in the same manner as in Example 1 except that the screw rotation speed was 15000 rpm and the filling amount was changed.
Example 6
A polyurethane foam was obtained in the same manner as in Example 1 except that the screw rotation speed was 2500 rpm and the filling amount was changed.

Comparative Example 2
A polyurethane foam was obtained in the same manner as in Example 1 except that the screw rotation speed was 1500 rpm and the filling amount was changed.

Comparative Example 5
A polyurethane foam was obtained in the same manner as in Comparative Example 3 except that foam stabilizer B was used as the foam stabilizer and the screw rotation speed was 1500 rpm.

For the polyurethane foams obtained in Examples 1 to 8 and Comparative Examples 1 to 6, 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 8 and Comparative Examples 1 to 6 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.

(Existence ratio of soft segment and hard segment)
The abundance ratio of the soft segment and the hard segment (soft segment / hard segment) was specified according to the blending ratio of the polyol component and the isocyanate component described above.

(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.

(Average bubble diameter)
Polyurethane foam was cut at randomly selected locations to expose the cut surface. Among the cut surfaces, a rectangular range of 4 mm in length and 3 mm in width was randomly selected to be a selected region. The number of cells present in the selected region (the number of all cells) and the diameter of each bubble (cell diameter) were measured using a microscope. The average bubble diameter (μm) was an arithmetic average value calculated from each bubble diameter.

(Percentage of cells having a bubble diameter in the range of 20 μm to 300 μm)
When the total number of cells is a and the number of cells having a bubble diameter of 20 μm or more and 300 μm or less is b, the ratio of cells having a bubble diameter of 20 μm or more and 300 μm or less (cells with a bubble diameter of 20 μm or more and 300 μm or less are all The ratio of the number of cells to the cell) is determined by the equation b / a × 100 (%). Here, based on the number of all cells specified when measuring the average bubble diameter and the number of cells having a bubble diameter of 20 μm to 300 μm, the ratio of cells having a bubble diameter of 20 μm to 300 μm. (%) Was identified.

(Rebound resilience)
A specimen having a diameter of 29 mm and a thickness of 12.5 mm was cut out from the polyurethane foam to obtain a test piece for measuring the resilience modulus. The rebound resilience (%) was measured according to JIS K 6255 using the rebound resilience measurement test piece.

(Maximum impact load)
A test piece for measuring an impact load was cut from a polyurethane foam into a rectangular parallelepiped shape having a length of 70 mm, a width of 60 mm, and a thickness of 12.5 mm. The maximum impact load was measured by a drop impact test using the test piece for impact load measurement. The drop impact test is performed using a “dynaup GRC8200 (manufactured by Instron)” with a bullet-shaped weight W (iron, 5.1 kg) as shown in FIG. This was done by specifying the maximum impact load (kN) when dropped and collided.

(Compression set)
A specimen having a diameter of 29 mm and a thickness of 12.5 mm was cut out from the polyurethane foam to obtain a test piece for measuring compression set. The compression set (%) was measured in accordance with JIS K 6262 under the conditions of a compression rate of 25%, 40 ° C., and 24 hours using the above-mentioned compression set test piece.

(Bending resistance confirmation test)
A test piece for bending was 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. A composite was prepared by bonding a resin-impregnated board having a thickness of 2 mm (trade name, Texon board 437, manufactured by Vontex Co., Ltd.) to this bending test piece. A bending back operation comprised 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 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. Specifically, in Table 1, in Examples 1 and 2 and Comparative Example 6, generation of cracks was not observed even when the bending back operation was repeated more than 100,000 times. In Examples 3, 4, 6 and Comparative Example 3, generation of cracks was not observed even when the bending back operation was repeated from 30,000 times to less than 40,000 times. In Example 5, no crack was observed even when the bending back operation was repeated from 50,000 times to less than 60,000 times. In Example 7 and Comparative Examples 2 and 5, no crack was observed even when the bending back operation was repeated from 20,000 times to less than 30,000 times. In Example 8, no crack was observed even when the bending back operation was repeated from 80,000 times to less than 90,000 times. In Comparative Example 1, no crack was observed even when the bending back operation was repeated from 40,000 times to less than 50,000 times. In Comparative Example 4, cracking was observed when the bending back operation was repeated less than 10,000 times.

In any of Examples 1 to 8, the polyurethane foam was maintained in the range of hardness of 50 or more and 65 or less even with a low apparent density of 0.5 g / cm ³ or less, and the maximum impact load (kN) was from Comparative Example 1. It was lower than any of 6. That is, all of the examples were found to be excellent in impact absorption while maintaining lightness and hardness.

W ・・・ Weight

Claims

A polyurethane foam having a soft segment formed from a polyol component and a hard segment formed from a structure having a urethane bond,
The abundance ratio of the soft segment and the hard segment is a mass ratio of the soft segment to the hard segment when the total of the soft segment and the hard segment is 100 parts by mass, and is 70/30 or more and 80/20 or less. Range,
The average cell diameter of the polyurethane foam is 30 μm or more and 100 μm or less,
90% or more of all the bubbles formed in the polyurethane foam have a bubble diameter of 20 μm or more and 300 μm or less,
The apparent density of the polyurethane foam measured in accordance with JIS K 7222 is 0.25 g / cm 3 or more and 0.50 g / cm 3 or less,
A polyurethane foam characterized in that the polyurethane foam has a hardness of 50 to 65 in accordance with JIS K 7312 and measured using an Asker rubber hardness meter C type.
When a test piece made of the polyurethane foam formed so as to have a thickness of 12.5 mm was prepared and a weight of 5.1 kg was collided with the test piece from a height of 50 mm, The polyurethane foam according to claim 1, wherein the impact load is 0.9 kN or less.
The polyurethane foam according to claim 1 or 2, wherein the polyol component contains a polytetramethylene ether polyol.
The polyurethane foam according to any one of claims 1 to 3, wherein the rebound resilience of the polyurethane foam measured according to JIS K 6255 is 60% or more.
The polyurethane foam according to any one of claims 1 to 4, wherein the compression set rate of the polyurethane foam measured according to JIS K 6262 is 20% or less.
A polyurethane foam formed so that the length is 120 mm, the width is 60 mm, and the thickness is 6 mm,
A composite in which a resin-impregnated board having a thickness of 2 mm is bonded to the polyurethane foam is prepared, and the half of the composite is bent 90 ° at a central position along the longitudinal direction, and the half of the composite is When the bending back operation constituted by the operation of returning to the original position is repeated at a speed of 144 times / minute, the number of bending back operations until the occurrence of cracks in the polyurethane foam is 30,000 times or more. The polyurethane foam according to any one of claims 1 to 5.
The polyurethane foam according to any one of claims 1 to 6, which is a molded body.
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 maximum impact on the test piece The load is 0.9 kN or less,
The resilience modulus of the polyurethane foam measured in accordance with JIS K 6255 is 60% or more,
The compression set rate of polyurethane foam measured in accordance with JIS K 6262 is 20% or less,
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 adhering 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 composite at a central position along the vertical direction by 90 ° and an operation of returning the half of the composite to the original position is repeated at a speed of 144 times / minute Further, the polyurethane foam according to any one of claims 1 to 7, wherein the number of bending back operations until the occurrence of cracks in the polyurethane foam is 30,000 or more.
A shoe sole member using the polyurethane foam according to any one of claims 1 to 8.