WO2021193363A1

WO2021193363A1 - Polyurethane foam and shoe sole member

Info

Publication number: WO2021193363A1
Application number: PCT/JP2021/011138
Authority: WO
Inventors: 京平大村; 宏生森
Original assignee: アキレス株式会社
Priority date: 2020-03-27
Filing date: 2021-03-18
Publication date: 2021-09-30
Also published as: JPWO2021193363A1; CN115315457A

Abstract

The present invention provides: a polyurethane foam which has an adequately low hardness and excellent mechanical strength, while maintaining good rebound resilience; and a shoe sole member which is obtained using this polyurethane foam.　This polyurethane foam is configured from a polyurethane starting material that contains a polyol component, a polyisocyanate component, a foaming agent, a catalyst and a foam stabilizer, while being configured such that: the polyol component contains a polytetramethylene ether glycol that has a number average molecular weight of from 600 to 3,000; the proportion of the polytetramethylene ether glycol in the polyol component is 90% by mass or more; the polyisocyanate component contains (i) an isocyanate group-terminated prepolymer that has a number average molecular weight of from 500 to 2,000, an average number of functional groups of 2 and an isocyanate group content of from 3% by mass to 10% by mass and (ii) a modified MDI that has an isocyanate group content of from 25% by mass to 33% by mass; and the isocyanate group content in the polyisocyanate component is from 11% by mass to 27% by mass. A shoe sole member is configured using this polyurethane foam.

Description

Polyurethane foam and sole member

The present invention relates to polyurethane foam and shoe sole members.

Conventionally, foams such as polyurethane foam and ethylene-vinyl acetate copolymer foam have been used as constituent members in various applications. For example, a sole member made of polyurethane foam has excellent shock absorption, and is used as a component of the sole of athletic shoes such as walking shoes, running shoes, and trekking shoes as well as general-purpose shoes. .. Further, the polyurethane foam is not limited to the use as a shoe sole member, but can also be used as a mat member such as a floor mat in a workplace or an underlay mat when installing a precision machine.

When used for the soles of exercise shoes, polyurethane foam is required to have good impact resilience in addition to shock absorption. Exercise shoes that use soles with excellent impact resilience are expected to have the effect of reducing the accumulation of fatigue during long-term running and walking because kicking is supported and foot movement is easy. In the present invention, the sole refers to the sole portion of the shoe, and the sole member refers to a constituent member (material) constituting the sole.

For example, the invention described in Patent Document 1 has an object of providing a polyurethane integral skin foam having a high rebound resilience in a wide temperature range and having excellent mechanical strength and productivity. Specifically, in Patent Document 1, the organic polyisocyanate composition (A), the polyol component (B), the catalyst (C), and the foaming agent (D) are used as raw materials, and the organic polyisocyanate composition (A) is diphenylmethane. The invention of polyurethane integral skin foam, which is a urethane modified product of diisocyanate and polytetramethylene ether glycol having a number average molecular weight of 1000 to 3500 and is an organic polyisocyanate (a1) having an isocyanate group content of 7 to 25% by mass, is disclosed. ing.

Further, the invention described in Patent Document 2 has an object of providing a polyurethane foam which is durable, has shock absorption and resilience at the same time, and also has bending resistance. Specifically, Patent Document 2 describes a polyurethane raw material containing a polyol component, a polyisocyanate component, a foaming agent, a catalyst, and a foam stabilizer, and the polyol component has a number average molecular weight of 300 to 3000 and an average number of functional groups of 2 to. 3. And polytetramethylene ether glycol having an average hydroxyl value of 50 to 200 mgKOH / g, and the polyisocyanate component contains a predetermined isocyanate group-terminated prepolymer and a predetermined modified MDI, and the prepolymer and the modified Polyurethane foams in which the MDI content, isocyanate index, and compression set are specified within a predetermined range are disclosed.

Japanese Unexamined Patent Publication No. 2016-204635 JP-A-2017-105913

By the way, when the impact resilience of the polyurethane foam is improved, the hardness of the polyurethane foam generally tends to increase. When the sole is constructed using polyurethane foam having a high hardness, it is preferable that the sole has a relatively high hardness because the advanced running person has muscular strength. Therefore, advanced running users can run comfortably by taking advantage of the high impact resilience.
However, beginners do not have enough muscle strength. Therefore, if a running beginner uses running shoes using a sole with high hardness, the impact on the knee is large, and the risk of causing a failure may increase.

Also, conventionally, attempts have been made to provide polyurethane foam that suppresses hardness within an appropriate range while increasing impact resilience. However, in this case, there is a problem that it is difficult to maintain high mechanical strength. The soles of athletic shoes are required to have sufficient mechanical strength to withstand repeated use. Therefore, polyurethane foam, which has high impact resilience and low hardness but lacks mechanical strength, has been a problem as a shoe sole member.

It should be noted that the provision of the polyurethane foam in which the above-mentioned impact resilience, hardness, and mechanical strength are balanced is expected not only as a shoe sole member but also as a mat member, for example. From the above viewpoint, all of the polyurethane foams disclosed in Patent Documents 1 and 2 have room for improvement.

The present invention has been made in view of the above-mentioned problems. That is, an object of the present invention is to provide a polyurethane foam that exhibits moderately low hardness and is also excellent in mechanical strength while maintaining good impact resilience, and a shoe sole member made of the polyurethane foam.

The polyurethane foam of the present invention is a polyurethane foam made of a polyurethane raw material containing a polyol component, a polyisocyanate component, a foaming agent, a catalyst, and a foam stabilizer.
The polyol component contains polytetramethylene ether glycol having a number average molecular weight of 600 or more and 3000 or less, and the ratio of the polytetramethylene ether glycol in the polyol component is 90% by mass or more.
The polyisocyanate component is
i) An isocyanate group-terminated prepolymer having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less.
ii) Modified MDI having an isocyanate group content of 25% by mass or more and 33% by mass or less,
Including
The isocyanate group content in the polyisocyanate component is 11% by mass or more and 27% by mass or less.

Further, the shoe sole member of the present invention is characterized in that it is constructed by using the polyurethane foam of the present invention.

According to the present invention having the above structure, it is possible to provide a polyurethane foam which exhibits moderately low hardness and is also excellent in mechanical strength while maintaining good impact resilience.
Therefore, the sole member made of the polyurethane foam of the present invention can be preferably used as a sole member constituting the sole of an athletic shoe, particularly an athletic shoe for beginners.

[Polyurethane foam]
The polyurethane foam of the present invention is composed of a polyurethane raw material containing a polyol component, a polyisocyanate component, a foaming agent, a catalyst, and a foam stabilizer.
The polyol component contains polytetramethylene ether glycol (hereinafter, also referred to as PTMG) having a number average molecular weight of 600 or more and 3000 or less. In the present invention, the ratio of PTMG in the polyol component is adjusted to be 90% by mass or more.
The polyisocyanate component contains an isocyanate group-terminated prepolymer having predetermined characteristics and a modified MDI having predetermined characteristics, so that the isocyanate group content in the polyisocyanate component is 11% by mass or more and 27% by mass or less. It will be adjusted.
Here, the isocyanate group-terminated prepolymer having predetermined characteristics is an isocyanate group-terminated prepolymer having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less.
The modified MDI having a predetermined characteristic is a modified MDI having an isocyanate group content of 25% by mass or more and 33% by mass or less.

By satisfying the above-mentioned configuration, the present invention can provide a polyurethane foam having both high impact resilience and low hardness, and also having excellent mechanical strength. The polyurethane foam of the present invention will be described in more detail below.

(Polyol component)
The polyol component in the present invention contains 90% by mass or more of PTMG having a number average molecular weight of 600 or more and 3000 or less. In the present invention, two or more types of PTMGs having different number average molecular weights may be mixed and used. When two or more kinds of PTMGs are mixed and used, the number average molecular weight of the mixture of PTMGs may be adjusted to be within the above range.
If the number average molecular weight of PTMG is less than 600, good impact resilience may not be obtained. On the other hand, when the number average molecular weight of PTMG exceeds 3000, the obtained urethane foam may have a non-uniform cell size and may not easily exhibit low hardness, or may not have good mechanical strength. From the viewpoint that the obtained polyurethane foam has low hardness and exhibits good flexibility and easily exhibits good impact resilience, the number average molecular weight of PTMG is preferably in the range of 1000 or more and 2500 or less.
The polyol component in the present invention contains 90% by mass or more of PTMG. Therefore, the number average molecular weight of the polyol component is greatly affected by the number average molecular weight of the contained PTMG. In the present invention, it is preferable that the number average molecular weight of the polyol component is adjusted to 600 or more and 3000 or less.
Examples of the PTMG include a ring-opening polymer obtained by cation polymerization of tetrahydrofuran, an amorphous PTMG obtained by copolymerizing a dihydric alcohol with a polymerization unit of tetrahydrofuran, and the like. Amorphous means that it is liquid at room temperature (25 ° C.).
Examples of the amorphous PTMG include a copolymer of tetrahydrofuran and alkyl-substituted tetrahydrofuran, a copolymer of tetrahydrofuran and branched glycol, and the like. Examples of the alkyl-substituted tetrahydrofuran include 3-methyltetrahydrofuran. Further, as the branched glycol, neopentyl glycol is exemplified.

Polyurethane foam molded by using other polyol components in combination with PTMG may not have sufficient breaking strength and breaking point elongation, resulting in insufficient mechanical strength. The shoe sole member made of polyurethane foam having weak mechanical strength in this way is vulnerable to repeated use and may deteriorate quickly, or is exhibited by high impact resilience and low hardness for ease of running and resistance to fatigue. May not last long.

As described above, in the present invention, the content of PTMG in the polyol component is 90% by mass or more. From the viewpoint of maintaining high mechanical strength more sufficiently, the content of PTMG in the polyol component is preferably 95% by mass or more, and more preferably 100% by mass.

In general, when the content of PTMG in the polyol component is high, the polyurethane foam to be molded tends to be hard, and it is difficult to reduce the hardness. On the other hand, in the present invention, by adjusting the isocyanate group content in the polyisocyanate component to be 11% by mass or more and 27% by mass or less, the machine exhibits high impact resilience while having an appropriately low hardness. It has made it possible to provide polyurethane foam with excellent physical strength.
In the polyurethane foam of the present invention having a high PTMG content, the isocyanate group content is specified in the above-mentioned preferable range, and the average cell diameter of the cells constituting the polyurethane foam described later is adjusted to the range of 100 μm or more and 150 μm or less. This can provide even better impact resilience, hardness, and mechanical strength.

If necessary, any component such as a cross-linking agent may be added to the above-mentioned polyol component.
Examples of the cross-linking agent include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, tetramethylene ether glycol, glycerin, pentaerythritol, trimethylolpropane, monoethanolamine, diethanolamine, isopropanolamine and amino. Alcohols such as ethylethanolamine, sucrose, sorbitol and glucose can be used. In particular, among these, those having three or more functionalities are preferable.

(Polyisocyanate component)
The polyisocyanate components include i) an isocyanate group-terminated prepolymer having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less, and ii) an isocyanate group content of 25% by mass. Includes modified MDI of 33% by mass or more. The modified MDI refers to a modified diphenylmethane diisocyanate.
The ratio of the isocyanate group-terminated prepolymer to the modified MDI (isocyanate group-terminated prepolymer / modified MDI) is not particularly limited, but is preferably 97/3 to 3/97 by mass ratio, and is 85/15 to 85/15. It is more preferably 15/85, and even more preferably 80/20 to 20/80.

Further stated from the viewpoint of the application of the polyurethane foam, when the polyurethane foam is used as a shoe sole member, the isocyanate group-terminated prepolymer / modified MDI, which is a mass ratio, is further 90/10 to 50/50 in the above range. It is preferably 85/15 to 55/45, more preferably 80/20 to 60/40. As described above, when the modified MDI is contained in the polyisocyanate component in the same amount or less than the isocyanate group-terminated prepolymer in a predetermined range, the breaking strength and the breaking point elongation of the polyurethane foam tend to be high. Thereby, it is possible to provide a polyurethane foam more suitable for the shoe sole member to which the impact is repeatedly applied.

i) Isocyanate group-terminated prepolymer:
As the above-mentioned i) isocyanate group-terminated prepolymer (hereinafter, also simply referred to as prepolymer), those having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less are used.
When a prepolymer having a number average molecular weight of more than 2000 or an isocyanate group content of less than 3% by mass is used, the foamability of the produced polyurethane foam may be insufficient and the hardness may be increased. Further, such a prepolymer may be inferior in the productivity of polyurethane foam because it has a high viscosity and tends to be difficult to mix with other materials.
On the other hand, when a prepolymer having a number average molecular weight of less than 500 or an isocyanate group content of more than 10% by mass is used, the produced polyurethane foam may foam too much and may not exhibit good impact resilience. be.

The above-mentioned i) prepolymer is a prepolymer having an isocyanate group at the terminal, which is obtained by reacting a polyol and a polyisocyanate so that an isocyanate group (NCO group) becomes excessive. Here, the excess isocyanate group means that the NCO group content in the prepolymer is in the range of 3% by mass or more and 10% by mass or less.

As the polyol, one kind of material selected from the following α, β, and γ, or a mixed material of two or more kinds can be used. Among them, as the polyol, a polyether polyol is preferable, and a polytetramethylene ether glycol is more preferable.
α) Polyester polyol or Polyester polyol β) Polymer polyol (for example, a polyether polyol obtained by graft-copolymerizing polyacrylonitrile, acrylonitrile-styrene copolymer, etc.)
γ) Of the alcohols listed above as examples of cross-linking agents, bifunctional ones

Examples of the polyisocyanate include diphenylmethane diisocyanate (4,4'-MDI), polypeptide MDI (crude MDI), 2,4-tolylene diisocyanate (2,4-TDI), and 2,6-tolylene diisocyanate (2,6). Examples thereof include aromatic isocyanates such as -TDI), aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate (HDI), and alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated TDI and hydrogenated MDI. Can be used alone or in combination of two or more, and among them, 4,4'-MDI is preferable.

That is, as the i) prepolymer, those obtained by reacting polytetramethylene ether glycol as a polyol and 4,4′-MDI as a polyisocyanate are preferable.
The prepolymer formed by reacting this polytetramethylene ether glycol with 4,4'-MDI has high crystallinity of the polytetramethylene ether glycol moiety. Therefore, by using such a prepolymer, urethane foam having high impact resilience can be easily obtained, and ii) modified MDI used in combination as a polyisocyanate component has good compatibility with the prepolymer. Further, when such a prepolymer is used, an isocyanate component containing a prepolymer and a modified MDI obtained by reacting polytetramethylene ether glycol with 4,4'-MDI is reacted with polytetramethylene ether glycol which is a polyol component. The mixing property is also good. Therefore, the molecular structure of the member tends to be uniform, and the quality of the obtained urethane foam can be stabilized.

ii) Modified MDI:
In the present invention, the modified MDI having an isocyanate group content of 25% by mass or more and 33% by mass or less is used. Within this range, the modified MDI can be treated as a liquid at room temperature.
i) Prepolymers have a high molecular weight and therefore a high viscosity. However, by mixing the i) prepolymer and ii) modified MDI which is liquid at room temperature, the viscosity of the polyisocyanate component can be appropriately lowered. Therefore, the mixability of the polyisocyanate component and the polyol component can be improved.
If the NCO group content in the modified MDI is less than 25% by mass, the foamability of the produced polyurethane foam may be insufficient. On the other hand, the amount of the modified MDI having an NCO group content of more than 33% by mass in the polyisocyanate component is reduced from the viewpoint of adjusting the NCO group content. When the amount of the modified MDI is reduced in this way, it becomes difficult to adjust the polyisocyanate component containing the prepolymer having a large molecular weight to an appropriately low viscosity, and the mixing property when the polyisocyanate component and the polyol component are reacted with each other becomes difficult. May get worse.

Specific examples of the modified MDI that is liquid at room temperature include, for example, a polymeric (crude MDI), urethane modified, urea modified, allophanate modified, biuret modified, carbodiimide modified, uretonimine modified, and uretdione. Modified products, isocyanurate modified products and the like can be mentioned. Among them, a polypeptide (crude MDI) and / or a modified carbodiimide is preferably selected as the modified MDI because the molecular (crosslinked) structure after the reaction with the polyol component is excellent.

(Isocyanate group content in polyisocyanate component)
In the present invention, the polyisocyanate component containing the above-mentioned i) prepolymer and ii) modified MDI has an isocyanate group content of 11% by mass or more and 27% by mass or less. When the isocyanate group content is less than 11% by mass, the bubble diameter of the obtained polyurethane foam becomes small and the hardness becomes high. On the other hand, when the isocyanate group content exceeds 27% by mass, good impact resilience is not exhibited in the obtained polyurethane foam. From the above viewpoint, the isocyanate group content is preferably 12% by mass or more and 25% by mass or less, more preferably 12% by mass or more and 21% by mass or less, and further preferably 12% by mass or more and 17% by mass or less. It is particularly preferably 12% by mass or more and 15% by mass or less.
The polyisocyanate component in the present invention may further contain an isocyanate (third isocyanate) in addition to the above-mentioned i) prepolymer and ii) modified MDI.

(Foaming agent)
Water can be used as the foaming agent. The amount added 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 above-mentioned polyol component. Examples of the water include ion-exchanged water and distilled water, but ion-exchanged water is preferable.
If the amount of the foaming agent added is less than 0.5 parts by mass, foaming may be insufficient. On the other hand, if the amount of the foaming agent added exceeds 3 parts by mass, foaming may proceed too much and the resulting polyurethane foam cell may become rough. In this case, problems such as the inside of the obtained polyurethane foam being easily cracked occur, and as a result, the foam state tends to be inferior and the resilience tends to be inferior.

(catalyst)
The catalyst may be any catalyst conventionally used in the production of polyurethane foam, and examples thereof include amine-based catalysts such as triethylenediamine and diethanolamine, and metal catalysts such as bismuth catalysts, but the catalysts are not particularly limited. No.
The amount to be added is preferably 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the above-mentioned polyol component.

(Foaming agent)
In the present invention, urethane is formed by reacting the above-mentioned polyol component containing 90% by mass or more of PTMG with the above-mentioned polyisocyanate component containing an isocyanate group-terminated prepolymer and a modified MDI, and foaming and curing it in a mold. A polyurethane foam is formed by causing a reaction and foaming.
A defoaming agent is contained in order to improve the cell size of the polyurethane foam obtained by such urethane foaming. The foam stabilizer is not particularly limited as long as it can be used in the production of urethane foam. From the viewpoint that good impact resilience can be easily obtained, the viscosity of the defoaming agent is preferably 300 mPa · s (25 ° C.) or more and 2000 mPa · s (25 ° C.) or less, and 800 mPa · s (25 ° C.) or more and 1000 mPa. -It is more preferably s (25 ° C.) or less. A silicone-based compound defoaming agent having such a suitable viscosity range is particularly preferable.
If the viscosity of the defoaming agent is less than 300 mPa · s (25 ° C.), the defoaming action is weak, the cells become coarse, and high impact resilience may not be obtained. On the other hand, if the viscosity exceeds 2000 mPa · s (25 ° C.), it becomes difficult for the defoaming agent to be uniformly dispersed in the polyurethane raw material. As a result, it is difficult for the cell size of the obtained foam to be uniform, and there is a risk that the physical properties will change locally.

When a silicone compound having a suitable viscosity range is used as a defoaming agent, the silicone compound is added in a range of 0.5 parts by mass or more and 9 parts by mass or less with respect to 100 parts by mass of the above-mentioned polyol component. It is preferable, and it is more preferable to add it in the range of 0.5 parts by mass or more and 5 parts by mass or less.
If it is less than 0.5 parts by mass, the foam regulating action is weak, the cell becomes coarse, and there is a possibility that high impact resilience cannot be obtained.
On the other hand, if it exceeds 9 parts by mass, the impact resilience of the obtained polyurethane foam may be inferior. In addition, if it exceeds 9 parts by mass, bleed-out may occur in which the foam stabilizer exudes from the surface of the obtained polyurethane foam, and as a result, the adhesion between the polyurethane foam and other members is hindered, and the handleability is improved. May also be inferior. By setting the addition amount of the silicone compound in the above-mentioned suitable viscosity range to 5 parts by mass or less with respect to 100 parts by mass of the above-mentioned polyol component, the surface of the polyurethane foam does not become sticky and is of high quality. Polyurethane foam can be provided.

The raw material of the polyurethane foam of the present invention includes a polyol component, an isocyanate component, a foaming agent, a catalyst, a foam stabilizer, as well as a plasticizer, a filler, an antioxidant, a defoaming agent, and a compatibilizer, if necessary. , Colorants, stabilizers, UV absorbers and other additives commonly used in the production of polyurethane foam may be used as long as the effects of the present invention can be obtained.

(Polyurethane foam)
Average cell diameter:
The polyurethane foam of the present invention preferably has an average cell diameter of 100 μm or more and 150 μm or less in the cells constituting the foam. By intentionally adjusting the bubble diameter to be slightly large in this way, it is easy to provide a polyurethane foam having high rebound resilience, low hardness, and excellent mechanical properties such as breaking strength and breaking point elongation.
If the average cell diameter is less than 100 μm, the mechanical properties are impaired, and if the average cell diameter exceeds 150 μm, high impact resilience is unlikely to be exhibited. The average bubble diameter is more preferably more than 100 μm and 150 μm or less, further preferably more than 100 μm and 135 μm or less, further preferably more than 100 μm and 130 μm or less, and more than 100 μm. It is particularly preferably 120 μm or less.

The average bubble diameter can be specified by the following method. First, the polyurethane foam is cut at a randomly selected position to expose the cut surface. On the cut surface, a region having a predetermined dimension is randomly selected as a selected region. The region having a predetermined dimension is, for example, a rectangular region having a length of 4 mm and a width of 3 mm. The number of cells (bubbles) existing in the selected region (the number of all cells) and the diameter of each cell (diameter of each bubble) are measured using a microscope. The arithmetic mean value of each cell diameter measured as described above is obtained, and this is used as the average cell diameter in the present invention.

The method for adjusting the average cell size of the polyurethane foam is not particularly limited, but for example, a polyurethane foam showing an average cell size in a desired range can be formed by adjusting the amount of the catalyst or foaming agent added.

hardness:
The hardness of the polyurethane foam of the present invention is preferably less than 50, more preferably less than 47, from the viewpoint of exhibiting appropriate flexibility. A sole member made of polyurethane foam having a hardness of less than 50 is suitable for a sole member such as an athletic shoe for beginners. By using such a shoe sole member, the burden on the knee or the like at the time of touchdown can be reduced.
From the viewpoint of maintaining good shock absorption, the hardness is preferably 35 or more, more preferably 40 or more. Polyurethane foam with too low hardness cannot absorb the impact and may cause a risk of failure when used as a shoe sole member. Even when the polyurethane foam of the present invention is used as a mat member, the hardness is preferably in the above range.
The hardness of the polyurethane foam of the present invention is measured in accordance with JIS K 7312 using an Asker rubber hardness tester C type under a temperature condition of 23 ± 2 ° C.

Apparent density:
The apparent density of the polyurethane foam of the present invention is not particularly limited, but is preferably in the range of ^{0.30 g / cm 3} or more and 0.35 g / cm ^{3 or less.} Further, in the present invention, it is more preferable that the apparent density is in the above range and the average cell diameter is 100 μm or more and 150 μm or less.
The apparent density of the polyurethane foam of the present invention is measured according to JIS K 7222.

Modulus of impact:
The elastic modulus of the polyurethane foam of the present invention is preferably 50% or more, preferably 55% or more, from the viewpoint of good kicking and smooth foot movement when the polyurethane foam is used for a shoe sole or a mat. Is more preferable, and 60% or more is further preferable.
On the other hand, in the present invention, the upper limit of the rebound resilience is not particularly limited, but from the viewpoint of easily achieving a good balance with hardness and mechanical properties, it is preferably less than 80%, and preferably less than 75%. More preferably, it is less than 70%.

The elastic modulus of the polyurethane foam of the present invention is measured in accordance with JIS K 6255.

It is particularly preferable that the polyurethane foam of the present invention has a hardness of less than 50 and a rebound resilience of 50% or more. With such a polyurethane foam, it is possible to provide an excellent sole that is easy to run even for a beginner, absorbs the impact at the time of touchdown well, and reduces the burden on the knee and the like.

Breaking strength:
The breaking strength of the polyurethane foam of the present invention is preferably 1.0 MPa or more, more preferably 1.5 MPa or more, from the viewpoint of improving the durability of the article made of the polyurethane foam. It is preferably 2.0 MPa or more, and more preferably 2.0 MPa or more. In particular, when polyurethane foam having a breaking strength of 1.5 MPa or more is used as a sole member of exercise shoes, even if the sole is used in a harsh usage environment such as being repeatedly impacted or curved. Deterioration in a short period of time can be prevented.

The method for measuring the breaking strength of the polyurethane foam of the present invention is measured in accordance with JIS K6251.

Break point elongation:
The elongation at break point of the polyurethane foam of the present invention is not particularly limited, but is preferably 300% or more, preferably 350% or more, when used for applications where repeated bending is expected, such as soles. More preferably, it is more preferably 400% or more.

The method for measuring the elongation at break of the polyurethane foam of the present invention is measured in accordance with JIS K6251.

Maximum impact load:
The maximum impact load of the polyurethane foam of the present invention is such that the maximum impact load measured as follows is 1.5 kN or less from the viewpoint of improving the impact absorption of the article made of the polyurethane foam. It is preferable to have. The maximum impact load is measured by a product manufactured by Instron when a bullet-shaped weight w (made of iron, 5.1 kg) is collided from a height of 50 mm in a drop impact test of a test piece cut to a thickness of 12.5 mm. It can be done using the name "dynatup GRC8200".

Flexibility:
The flexibility of the polyurethane foam of the present invention is not particularly limited, but when it is used for applications where repeated bending is expected, such as soles, the number of bendings until cracks occur in the following test is 10,000. It is preferably more than once. In the test, a test piece prepared by adhering a test piece cut to a thickness of 6 mm to a texon board (trade name "# 347" manufactured by Bontex) having a thickness of 2 mm was formed at an angle of 90 ° at a speed of 100 times / minute. It is done by bending.

[Shoe sole member]
The polyurethane foam of the present invention described above is used for various purposes. Above all, the polyurethane foam of the present invention is preferably used as a shoe sole member because it exhibits good impact resilience, its hardness is suppressed to a low level, and its mechanical properties are also excellent.
The sole made of the polyurethane foam of the present invention supports the user's kicking, facilitates leg movement, and exhibits good flexibility to provide good comfort. Not only that, the occurrence of failure can be reduced. Therefore, the shoes provided with the soles are excellent as various exercise shoes, and are particularly suitable for beginners and elderly people of exercise.
The sole member of the present invention may be a constituent member that constitutes a part of the sole, or may be a constituent member that constitutes the entire sole. Here, the sole may be a sole portion of the shoe and may have an integral structure, or may be composed of a plurality of parts such as an insole and / or a midsole and an outsole. For example, the entire one or more parts constituting the sole such as the insole, the midsole, and the outsole may be composed of the sole member of the present invention, or any part of one part may be made of the sole member of the present invention. It can also be configured.

[mat]
Further, the polyurethane foam of the present invention can be suitably used as a constituent member of a mat. That is, the polyurethane foam of the present invention exhibits excellent impact resilience, is suppressed to a low hardness, and is excellent in mechanical properties, and thus exhibits an excellent effect even in a mat, particularly a floor mat.
When a mat made of the polyurethane foam of the present invention is laid on the floor and the mat is used for a long time such as working, walking, or standing, the accumulation of fatigue is reduced.

With the formulation shown in Table 1, the polyol component, catalyst, defoaming agent, and foaming agent are mixed to prepare solution A, and the solution A and solution B (polyisocyanate component) are mixed at the compounding ratio shown in Table 1. The mixture was poured into a mold and reacted under the condition of a mold temperature of 40 ° C., and then demolded to obtain a polyurethane foam.
The unit of the numerical value indicating the composition of the materials in Table 1 is a mass part.

<Polyol component>
-PTMG2000: Polytetramethylene ether glycol (number average molecular weight 2000, hydroxyl value 57.2 mgKOH / g, average number of functional groups 2)
<Catalyst>
・ Amine-based catalyst: Triethylenediamine <foaming agent>
-Silicone compound: Viscosity: 900 mPa · s (25 ° C)
<foaming agent>
・ Ion-exchanged water <polyisocyanate component>
-Isocyanate group-terminated prepolymer (prepolymer obtained by reacting PTMG2000 with 4, 4'-MDI; number average molecular weight 1000, average number of functional groups 2, isocyanate group content 8.01% by mass)
-Carbodiimide-modified MDI (carbodiimide-modified product, average number of functional groups 2, isocyanate group content 28.2%)

The polyurethane foams obtained in each Example and each Comparative Example were appropriately cut to prepare test pieces, and the measurements shown below were carried out. The measurement results are shown in Table 1.
<Average cell diameter (μm)>
The resulting polyurethane foam was cut at randomly selected positions to expose the cut surface. A rectangular region of 4 mm × 3 mm was randomly selected as the selected region on the cut surface. The number of cells (bubbles) existing in the selected region (the number of all cells) and the diameter of each cell (diameter of each bubble) were measured using a microscope. The arithmetic mean value of each cell diameter measured as described above was calculated and used as the average cell diameter.
<Appearance density (g / cm ³ )>
The apparent density was measured according to JIS K 7222 using a test piece cut into a rectangular parallelepiped of 15 mm × 15 mm × 10 mm.
<Hardness>
Asker C hardness Using a test piece cut to a thickness of 12.5 mm, the hardness of polyurethane foam (Asker C hardness) was measured using an Asker rubber hardness tester C type in accordance with JIS K 7312. <Repulsive modulus (%)>
The elastic modulus was measured according to JIS K 6255 using a test piece cut to a thickness of 12.5 mm.
<Breaking strength (MPa)>
Using a test piece cut into a dumbbell shape (No. 2 type), the breaking strength of the polyurethane foam was measured according to JIS K 6251.
<Elongation at breaking point (%)>
Using a test piece cut into a dumbbell shape (No. 2 type), the break point elongation of the polyurethane foam was measured according to JIS K 6251.
<Maximum impact load (kN)>
In the drop impact test of a test piece cut to a thickness of 12.5 mm, when a bullet-shaped weight w (made of iron, 5.1 kg) was made to collide from a height of 50 mm, the product name "dynatup GRC8200" manufactured by Instron was used. Then, the measured maximum impact load value is used as an index. The smaller the value of the maximum impact load, the more the impact is absorbed, and in the present invention, it is judged that the impact absorption is good when the value is 1.5 kN or less.
<Flexibility test (10,000 times)>
A test piece prepared by adhering a test piece cut to a thickness of 6 mm to a texton board having a thickness of 2 mm (trade name “# 347” manufactured by Bontex Co., Ltd.) was used. The test piece was bent at an angle of 90 ° and a speed of 100 times / minute, and the number of times until a crack occurred was counted. In the present invention, it was determined that the flexibility is good if the number of times is 10,000 or more.

The polyurethane foam of the present invention has excellent impact resilience, is maintained at a low hardness, and is also excellent in mechanical properties such as breaking strength and breaking point elongation. In addition, the polyurethane foam of the present invention is suitable as a shoe sole member because it has excellent shock absorption and flexibility. In addition, the polyurethane foam of the present invention requires shock absorption, impact resilience, moderate flexibility, good mechanical strength, etc. for mat members, helmet interiors, protectors, vehicle cushioning materials, flooring materials, etc. Widely used in applications that are used.

The present invention described above includes the following technical ideas.
(1) A polyurethane foam made of a polyurethane raw material containing a polyol component, a polyisocyanate component, a foaming agent, a catalyst, and a foam stabilizer.
The polyol component contains polytetramethylene ether glycol having a number average molecular weight of 600 or more and 3000 or less, and the ratio of the polytetramethylene ether glycol in the polyol component is 90% by mass or more.
The polyisocyanate component is
i) An isocyanate group-terminated prepolymer having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less.
ii) Modified MDI having an isocyanate group content of 25% by mass or more and 33% by mass or less,
Including
A polyurethane foam having an isocyanate group content of 11% by mass or more and 27% by mass or less in the polyisocyanate component.
(2) The polyurethane foam according to (1) above, wherein the average cell diameter of the cells constituting the polyurethane foam is 100 μm or more and 150 μm or less.
(3) The polyurethane foam according to (1) or (2) above, wherein the ratio of polytetramethylene ether glycol in the polyol component is 95% by mass or more.
(4) The hardness of the polyurethane foam measured using the Asker rubber hardness tester C type in accordance with JIS K 7312 is less than 50.
The polyurethane foam according to any one of (1) to (3) above, wherein the rebound resilience of the polyurethane foam measured in accordance with JIS K 6255 is 60% or more.
(5) The polyurethane foam according to any one of (1) to (4) above, wherein the breaking strength of the polyurethane foam measured in accordance with JIS K 6251 is 1.0 Mpa or more.
(6) The polyurethane foam according to any one of (1) to (5) above, wherein the breaking point elongation of the polyurethane foam measured in accordance with JIS K 6251 is 400% or more.
(7) A shoe sole member comprising the polyurethane foam according to any one of (1) to (6) above.

Claims

A polyurethane foam made of a polyurethane raw material containing a polyol component, a polyisocyanate component, a foaming agent, a catalyst, and a foam stabilizer.
The polyol component contains polytetramethylene ether glycol having a number average molecular weight of 600 or more and 3000 or less, and the ratio of the polytetramethylene ether glycol in the polyol component is 90% by mass or more.
The polyisocyanate component is
i) An isocyanate group-terminated prepolymer having a number average molecular weight of 500 or more and 2000 or less and an isocyanate group content of 3% by mass or more and 10% by mass or less.
ii) Modified MDI having an isocyanate group content of 25% by mass or more and 33% by mass or less,
Including
A polyurethane foam having an isocyanate group content of 11% by mass or more and 27% by mass or less in the polyisocyanate component.
The polyurethane foam according to claim 1, wherein the average cell diameter of the cells constituting the polyurethane foam is 100 μm or more and 150 μm or less.
The polyurethane foam according to claim 1 or 2, wherein the ratio of polytetramethylene ether glycol in the polyol component is 95% by mass or more.
According to JIS K 7312, the hardness of the polyurethane foam measured using the Asker rubber hardness tester C type is less than 50.
The polyurethane foam according to any one of claims 1 to 3, wherein the elastic modulus 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 breaking strength of the polyurethane foam measured in accordance with JIS K6251 is 1.0 Mpa or more.
The polyurethane foam according to any one of claims 1 to 5, wherein the breaking point elongation of the polyurethane foam measured in accordance with JIS K6251 is 400% or more.
A shoe sole member comprising the polyurethane foam according to any one of claims 1 to 6.