JP6710117B2 - Polyurethane foam spring - Google Patents

Description

The present invention relates to a foamed polyurethane resin spring having a high impact resilience, toughness, and excellent resilience.

Conventionally, foamed polyurethane having a high impact resilience is used in various applications. For example, hit ball bats (high-repulsion baseball bats), railroad sleeper pads/track pads, automobile vibration-damping members/bumper springs/seat cushions, shoe sole cushions, sports vibration-damping members, ball games ball members, construction Under-floor anti-vibration material/roof-floor anti-vibration material/gap cushion, bicycle tires (puncture tires), foam tires for wheels of trolleys, wheelbarrows, wheelchairs, etc. Packing, button cushions for equipment, lightweight rugs and mattresses. These applications are so-called "resin springs" that are resistant to damage due to vertical movement, twisting, sliding, etc. during use, and therefore exhibit high strength and high spring characteristics and maintain those characteristics for a long time. Performance is required.

The railroad track pad, which is a specific example of a resin spring, is a pad material that is laid under the rail to reduce the impact on railroad cars while reducing the impact on railroad trees and the ground, but high load It is used under extremely harsh conditions such as centrifugal force and shearing force. Therefore, it is required to be extremely tough as a material and have long-term resilience. A foamed polyurethane resin spring is used as a spring material for such a severe application. (See Patent Document 1)

Further, the "high-repulsion baseball bat" is provided with a hitting ball portion, a taper portion, and a grip portion, and at least a hitting portion is provided with a recessed portion, and an elastic body which forms the outer peripheral surface of the hitting portion is formed integrally with the depression portion. A hit ball bat is known (see Patent Document 2). This hit ball bat is popular because the flight distance of the hit ball is extended. The foamed polyurethane resin spring used as the elastic body of this hitting bat has a high impact resilience and a high resilience (a property with a low compression set value) in order to extend the flight distance of the hit ball. It is also required to have excellent toughness while maintaining softness so as not to be broken by the impact at the time of hitting a ball.

As such a foamed polyurethane resin spring, a special foamed polyurethane resin spring using a prepolymer obtained from polyester polyol and naphthalene isocyanate is preferably used.

JP, 2014-190005, A JP, 2005-16039, A

However, this special foamed polyurethane resin spring is 1) difficult to further improve the impact resilience, 2) the storage stability of the prepolymer is poor, and it needs to be used up on the day of synthesis. Since it is a raw material, there are many problems such as that the obtained polyurethane foam material is easily hydrolyzed, and 4) the raw material is expensive.

For this reason, a polyurethane foam made of polytetramethylene glycol (hereinafter also referred to as "PTMG") and diphenylmethane diisocyanate (MDI)-based isocyanate (hereinafter also referred to as "MDI-based isocyanate") are used as versatile and inexpensive raw materials. Resin springs are being considered.

The foamed polyurethane resin spring using PTMG and MDI-based isocyanate should have a high apparent density of 200 to 500 kg/m ³ and satisfy the toughness by appropriately using a foaming agent, a foam stabilizer, a catalyst and the like. However, it usually has a closed-cell structure (closed-cell structure), and therefore does not satisfy high resilience (low compression set value). In addition, if the mold is released from the mold by heating (curing) for a short time, the product may expand during the mold release and shrink easily after cooling, resulting in unstable product dimensions or partial deformation. It is necessary to remove the mold after heating (curing) and obtaining sufficient green strength. In addition, the resulting product has a high compression set value (poor restoration) due to the closed cells. If the amount of the catalyst used as a measure against this foaming is reduced, product breakage, foam deformation, foam breakage, etc. due to unreacted products occur during demolding for a short time, while conversely, productivity is low for demolding for a long time.
High resilience is naturally required for foamed polyurethane resin springs using PTMG and MDI isocyanates.

As described above, it was revealed that the foamed polyurethane resin spring using PTMG and MDI-based isocyanate also needs improvement in order to satisfy the performance and to be economically produced.
On the other hand, there is a "railway track pad" as a resin spring that requires higher spring characteristics, and noise can be reduced by installing the "track pad" directly below the rails that high-load vehicles pass at high speed. It has the effects of improving ride comfort by reducing vibration and labor saving by reducing rail wear. In addition, as a recent tendency, there is a demand for a "orbital pad having a small spring constant", which has the above-mentioned effects more than those of the conventional products. It is difficult to realize this small spring constant with a non-foamed material, and the foamed type of track pad is becoming the mainstream. Therefore, a resin foam having high mechanical strength and high resilience is required. From the above, the "orbital pad" has a high level of durability, such as durability for continuous outdoor use, that the resin will not break or deform under repeated high loads, and that it will retain its resilience even after long-term use. Spring characteristics are required. In particular, in order to confirm high reliability, it is necessary to pass the “fatigue resistance test” which is a vertical motion test of 1 million times continuously. Specifically, under the prescribed vibration conditions (loading load 9±6 kN, vibration frequency 5 Hz, number of repetitions 10 ⁶ times), 1) there is no appearance of cracks, 2) It is required to be 10% or less.

Therefore, in view of the above facts, the present invention is a foamed polyurethane resin spring using PTMG and MDI-based isocyanate, which has high productivity and is easy to manufacture, while satisfying high impact resilience and at the same time having toughness. An object of the present invention is to provide a resin spring made of foamed polyurethane that satisfies a high restoration property.

The above problems can be solved by the following means.

<1>
A composition containing polytetramethylene glycol having a number average molecular weight of 1,000 to 3,500, diphenylmethane diisocyanate-based isocyanate, a polyfunctional polyol having a functional group number of 3 or more, a foaming agent, a catalyst, and silicone oil. It consists of a cured product,
A foamed polyurethane resin spring having an apparent density of 200 to 500 kg/m ³ , an impact resilience of 60% or more, a 30% compression set of 10% or less and a 50% compression set of 20% or less.
<2>
The foamed polyurethane resin spring according to item <1>, wherein the silicone oil is a polysiloxane formed by copolymerization of a dimethylsiloxane unit and a methylphenylsiloxane unit.
<3>
The foamed polyurethane resin spring according to item <1>, wherein the silicone oil is polydimethylsiloxane.
<4>
The foamed polyurethane resin according to <3>, wherein the viscosity of the polydimethylsiloxane is 5 to 50 (25°C, mm ² /s), or 1,000 to 100,000 (25°C, mm ² /s). Spring.
<5>
The foamed polyurethane resin spring according to any one of <1> to <4>, wherein the composition further includes a cell opener, and the closed cell ratio is 0 to 20%.
<6>
The foamed polyurethane according to <5>, wherein the cell opener is at least one selected from the group consisting of a low-molecular diol, a polypropylene glycol-based bifunctional polyol, a polyether carboxylic ester, a polybutene, and a paraffin-based oil. Resin spring.
<7>
The foamed polyurethane resin spring according to <6>, wherein the polypropylene glycol-based bifunctional polyol is a bifunctional polyol having an ethylene oxide content of 0 to 80 mol% and a number average molecular weight of 400 to 4,000.

According to the present invention, a foamed polyurethane resin spring using PTMG and MDI isocyanates has high workability, is easy to manufacture, and has high impact resilience, and at the same time has high toughness and high resilience. A resin spring made of foamed polyurethane can be provided.

Hereinafter, an embodiment that is an example of the present invention will be described.

The foamed polyurethane resin spring according to the present embodiment is a polytetramethylene glycol (PTMG) having a number average molecular weight (hereinafter, also referred to as “Mn”) of 1,000 to 3,500 and a diphenylmethane diisocyanate-based isocyanate (MDI-based isocyanate). And a polyfunctional polyol having 3 or more functional groups, a foaming agent, a catalyst, and a silicone oil.
The foamed polyurethane resin spring has an apparent density of 200 to 500 kg/m ³ , a rebound resilience of 60% or more, a 30% compression set of 10% or less and a 50% compression set of 20% or less. Is.

The foamed polyurethane resin spring according to the present embodiment contains PTMG having a number average molecular weight of 1,000 to 3,500 and an MDI isocyanate in the presence of a silicone oil together with a polyfunctional polyol having a functional group of 3 or more, a foaming agent, and a catalyst. It is obtained by reacting and foaming. The components of this raw material improve the toughness, rebound resilience, and resilience, and at the time of demolding, the occurrence of expansion, shrinkage, skin breakage, foam deformation, foam breakage, etc. is suppressed, and manufacturing becomes extremely easy.
The reasons for these are not clear, but 1) whether silicone oil suppresses the formation of closed cells during foam molding, or even closed cells have high gas permeability and suppress various problems during demolding. It is possible that 2) Moreover, since the silicone oil bleeds (precipitates) on the surface of the polyurethane, the foamed polyurethane resin spring can be easily released from the mold. 3) When the foamed polyurethane resin spring is compressed, the silicone oil In order to prevent the cell walls from binding to each other, it is conceivable that even in the case of a closed cell, the impact resilience is improved and the compression set is reduced. In particular, the impact resilience is improved by 4 to 6% by containing the silicone oil as compared with the non-containing product.

Further, the foamed polyurethane resin spring using PTMG and MDI-based isocyanate has a high apparent density of 200 to 500 kg/m ³ by appropriately selecting and using a foaming agent and a catalyst, and using a foam stabilizer as needed. Higher density is also realized.

Therefore, the foamed polyurethane resin spring according to the present embodiment is a foamed polyurethane resin spring that has high productivity, is easy to manufacture, and has high resilience, as well as toughness and high resilience.
The foamed polyurethane resin spring according to the present embodiment is less likely to be damaged by impact and can exhibit spring characteristics for a long period of time. Specifically, for example, when the foamed polyurethane resin spring according to the present embodiment is used for a railroad track pad, it is difficult to tear even under impact or under high load and high shear, and long-term resilience is satisfied. Further, when used for a hit ball bat, the deformation of the ball itself is reduced, and the energy absorption of the foamed polyurethane resin is low, and as a result, the loss of kinetic energy possessed by the ball itself can be reduced. , The flight distance of a hit ball can be extended. When used as a puncture tire or a foam tire for a wheel, it is possible to provide a tire that is hard to break and has low "rolling resistance", that is, a tire that rotates with a light force.

Hereinafter, details of the foamed polyurethane resin spring according to the present embodiment will be described.

The composition for forming the foamed polyurethane resin spring according to the present embodiment includes a PTMG having a number average molecular weight of 1,000 to 3,500, an MDI isocyanate, a polyfunctional polyol having a functional group of 3 or more, and foaming. The agent, the catalyst, and the silicone oil are included. Further, in order to improve performance and productivity, it is preferable to appropriately use a foam stabilizer. The composition may further include a cell opener. In particular, when the composition contains a cell opener, the closed cell ratio of the foamed polyurethane resin spring is reduced (for example, the closed cell ratio is reduced to 0 to 20%), and the foam becomes a continuous cell by continuous compression. The change over time in repulsion elastic modulus and toughness caused by is suppressed.

(PTMG)
Examples of PTMG include polyalkylene glycol obtained by ring-opening polymerization of tetrahydrofuran. The PTMG may be a polyalkylene glycol having other alkylene structural units (ethyleneoxy structural unit, propyleneoxy structural unit, etc.) in addition to the tetramethyleneoxy structure. However, PTMG may have a tetramethyleneoxy structural unit content of 50% by weight or more (preferably 80% by weight or more, more preferably 90% by weight or more).
PTMG may be used alone or in combination of two or more.

The number average molecular weight of PTMG is 1,000 to 3,500, preferably 2,000 to 3,000.
When the number average molecular weight of PTMG is within the above range, the foamed polyurethane resin spring obtained has a high elongation, so that it is tough and excellent in impact resilience. Further, the hardness is less likely to increase even at low temperatures, which is preferable.

Here, the number average molecular weight is the molecular weight when the number of functional groups is determined to be 2 from the measured value of the hydroxyl value according to JIS K0070. The average molecular weights of other components are measured in the same manner.

The content of PTMG is preferably 50 to 85% by weight, more preferably 65 to 80% by weight, based on the total composition.
When the content of PTMG is in the above range, the resulting foamed polyurethane resin spring has a high elongation, so that it is tough and excellent in impact resilience. Further, the hardness is less likely to increase even at low temperatures, which is preferable.

(MDI isocyanate)
The MDI isocyanate is an isocyanate having a diphenylmethane diisocyanate skeleton.
Examples of the MDI isocyanate include diphenylmethane diisocyanate (MDI), crude MDI (cr-MDI), 4.4'-diphenylmethane diisocyanate (4.4'-MDI), 2.4'-MDI, 2.2'-MDI. , Crude MDI (cr-MDI), carbodiimide-modified MDI, prepolymer-modified MDI, and the like. Of these, the prepolymer-modified isocyanate, which is a modified form of 4.4'-MDI and 4.4'-MDI, has high reactivity and the resulting foamed polyurethane resin spring has excellent toughness and impact resilience. preferable.
The MDI isocyanates may be used alone or in combination of two or more.

The content of the MDI isocyanate is preferably 15 to 40 parts by weight, more preferably 18 to 30 parts by weight, based on 100 parts by weight of PTMG.
When the content of the MDI-based isocyanate is in the above range, the balance between the toughness and the impact resilience of the resulting foamed polyurethane resin spring is optimized, which is preferable.

Here, as the prepolymer-modified isocyanate (MDI-based isocyanate-containing prepolymer), ethylene glycol, propylene glycol, 1,3- or 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and 1,10 -C2-C18 divalent alcohols such as decanediol; PPG glycols; PTGM glycols; prepolymer-modified isocyanates obtained by modifying MDI isocyanates with polycarbonate glycols and the like. In this prepolymer-modified isocyanate, the content of the MDI-based isocyanate with respect to the prepolymer is 10% by weight or more and 50% by weight or less (preferably 15% by weight or more and 45% by weight or less) from the viewpoint of toughness, impact resilience and low temperature characteristics. Good to have.
The content of the MDI-based isocyanate-containing prepolymer is preferably 20 to 100 parts by weight, and more preferably 30 to 80 parts by weight, based on 100 parts by weight of PTMG.

(Polyfunctional polyol)
Examples of the polyfunctional polyol having 3 or more functional groups include a trifunctional polyol. Examples of the trifunctional polyol include a polyether polyol obtained by addition-polymerizing an alkylene oxide (ethylene oxide, propylene oxide, etc.) to a trivalent alcohol. The addition polymerization of plural kinds of alkylene oxides may be random addition polymerization or block addition polymerization. Examples of the trihydric alcohol include trihydric alcohols having 3 to 10 carbon atoms such as glycerin and trimethylolpropane.
Examples of the polyfunctional polyol include tetrafunctional polyols, and specific examples thereof include polyether polyols obtained by addition-polymerizing alkylene oxides with ethylenediamine, pentaerythritol, and the like.

Other polyfunctional polyols include ester polyols obtained by condensation of adipic acid and a short-chain diol such as ethylene glycol and 1.4-butanediol with a polyfunctional triol such as glycerin.

Since the polyfunctional polyol does not have the effect of improving compression set when it is bifunctional, trifunctional or higher is preferable, and as the number of functional groups increases, the recoverability becomes better (the compression set value is low). However, the number of functional groups is preferably 3 to 4, and the trifunctional polyol is most preferable because the closed cell ratio is increased accordingly.

The polyfunctional polyols may be used alone or in combination of two or more.

100-10,000 are preferable and, as for the number average molecular weight of polyfunctional polyol, 400-5,000 are more preferable.
When the number average molecular weight of the polyfunctional polyol is in the above range, the compression set can be effectively reduced without lowering the toughness (that is, not reducing elongation) and without increasing the closed cell ratio, which is preferable.

The content of the polyfunctional polyol is preferably 1 to 20 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of PTMG.
When the content of the polyfunctional polyol is within the above range, it is possible to suppress the decrease in elongation and effectively reduce the compression set without increasing the closed cell ratio, which is preferable.

(Foaming agent)
Examples of the foaming agent include water, low-boiling organic solvents (cyclopentane, dichloromethane, etc.), halogenated hydrocarbons, and mixed solutions thereof. Further, foaming by a so-called mechanical floss method, in which an inert gas such as air or nitrogen is stirred into the raw material to be used by an Oaks mixer or the like to enclose air bubbles, is also preferable. The foaming agents may be used alone or in combination of two or more.
When water is used as the foaming agent, the addition amount is preferably 0.1 to 3.0 parts, and more preferably 0.5 to 2.0 parts, relative to 100 parts by weight of PTMG. When water is used as the foaming agent, it is preferable that the amount of addition is small because the repulsion elastic modulus of the foam becomes high. On the other hand, if the amount of water added is small, the amount of water may be insufficiently filled during molding, so the amount added needs to be determined in consideration of the shape and performance.

(catalyst)
Examples of the catalyst include organic metal compound catalysts and amine catalysts.
Examples of the organometallic compound catalysts include organometallic catalysts such as tin-based, titanium-based, bismuth-based, and nickel-based catalysts. Examples of the organotin compounds include stannous octylate and stannous dibutyl laurate. is there.
Examples of amine-based catalysts include amine-based catalysts such as monoamines, diamines, triamines, cyclic amines, alcohol amines, and ether amines. Examples thereof include triethylenediamine, triethylamine, n-methylmorpholine, and n-ethyl. Formolin, N,N,N′,N′-tetramethylbutanediamine and the like are available.
The catalyst may be used alone or in combination of two or more.

(Foam stabilizer)
Although the foam stabilizer is not an essential component, it is preferable to use the foam stabilizer because it produces a more suitable foam when used.
Examples of the type of foam stabilizer include a silicone compound, a fluorine compound, and the like, a typical example of which is a copolymer of polydimethylsiloxane and polyoxyalkylene polyol. The foam stabilizers may be used alone or in combination of two or more.
The content of the foam stabilizer is preferably 0.3 to 3 parts by weight, and more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of PTMG.

(Silicone oil)
As the silicone oil, 1) dimethylsiloxane _{([Si (CH 3) 2} O] consists of) structural units of "polydimethylsiloxane", 2) methylphenylsiloxane _{([Si (CH 3) (} C 6 H 5) O ]) “Polymethylphenylsiloxane” consisting of structural units, 3) Methylhydrogensiloxane ([Si(CH ₃ )(H)O]) containing “polymethylphenylsiloxane” structural units, 4) Methylphenyl siloxane _{([Si (C 6 H 5} ) (H) O]) contains a structural unit of the "poly-methyl phenyl siloxane", 5) above 1) to 4) siloxane units of the composite article, 6) described above Examples thereof include a mixture of polysiloxanes 1) to 5). Of these, the polymethylphenylsiloxanes have a high compatibility with the urethane component when the content of the phenyl group is high, and thus the impact resilience may be slightly reduced. Therefore, the phenyl group content is preferably less than 20% by weight. In addition, polymethyl hydrogen siloxanes may also be solidified by reaction with time and the impact resilience may decrease, so caution is required when using them. Therefore, polydimethylsiloxane is most preferable because it has a high addition effect and is economical. Also, there are alkyl-modified products of polysiloxane, but the cost is high, and if the ratio of alkyl-modification is high, the effect is reduced, so that it is not effective. From these viewpoints, when the polydimethylsiloxane contains other siloxane units, the other siloxane units are preferably contained in 0 to 20% by weight based on the total siloxane units.

The viscosity of the polydimethylsiloxane is preferably from 5 to 100,000 (25° C., mm ² /s), and from 5 to 50 (25, from the viewpoint of improving the impact resilience of the foamed polyurethane resin spring and reducing the compression set. ℃, ^mm 2 / s) or ^{1,000~100,000 (25 ℃, mm 2 /} s) is more preferable. Further, the viscosity of the polydimethylsiloxane is more preferably 5 to 50 (25° C., mm ² /s) when the application is a member that places importance on slidability, and the application has a low bleed-out property, a printing ink or another member. In the case of a member in which the adhesiveness is emphasized, it is more preferable to use a minimum amount of 1,000 to 100,000 (25° C., mm ² /s).
The viscosity of polydimethylsiloxane is a value measured by kinematic viscosity according to JIS Z 8803 under the environment of temperature (25°C).

The silicone oils may be used alone or in combination of two or more.

The content of silicone oil is preferably 0.1 to 3 parts by weight, and more preferably 0.3 to 1.2 parts by weight, based on 100 parts by weight of PTMG. When the amount is 3 parts by weight or more, the cell breakage action causes an increase in cell diameter due to disappearance and coalescence of cells, or causes a so-called "cell rough" state. Furthermore, partial concentration is likely to occur, resulting in a product lacking uniformity such as roughening of the interface (skin portion) and enlarging the cell diameter near the center of the foam. In addition, if the application is 1) a member that attaches importance to slidability, 2) a member that is less likely to have an adhesive attached, and 3) a member that sticks to other products or other parts is a problem, Is more preferable, and the usage is 1) a member that emphasizes low bleed-out properties, 2) a member that emphasizes adhesiveness during insert molding with printing ink and other members, and 3) an adhesive or adhesive tape after molding. In the case of a member to be bonded, 4) a member to be printed on the surface after molding, and 5) a member requiring low air permeability or uniform strength of cells, it is preferable to use a small amount.

(Cell opener)
The cell opener is a component that functions as a defoaming agent or a defoaming agent.
Cell openers include well-known defoaming agents such as low-molecular diols, polypropylene glycol-based monofunctional or bifunctional polyols, polyethercarboxylic acid esterified products, polybutene, liquid polybutadiene, polyethylene wax, paraffin-based oils, and long-chain aliphatic alcohols. Agents or defoamers. However, addition of a monofunctional polyol is not preferable because it causes an increase in compression set value and a decrease in tensile strength/elongation.

Among them, as a cell opener, from the viewpoint of effectively reducing the closed cell ratio of the resin spring made of polyurethane foam, from the viewpoint of not adversely affecting other physical properties and not deteriorating the appearance of the product, a low molecular diol, polypropylene glycol. At least one selected from the group consisting of polyfunctional polyols, polyethercarboxylic acid esterified products, polybutenes, and paraffinic oils is preferable, and in particular, polypropylene glycol-based bifunctional polyols (hereinafter also referred to as “PPG-based bifunctional polyols”). Preferred). Since this PPG-based bifunctional polyol has a functional group, it does not become a low-molecular compound that bleeds out when it becomes a product, and therefore peeling of the adhesive or the double-sided tape is less likely to occur in post-processing. In addition, since the functional group firmly adheres to the inserted member during molding, peeling is unlikely to occur.

As the PPG-based bifunctional polyol, propylene oxide (hereinafter also referred to as “PO”) is addition-polymerized to a dihydric alcohol, or propylene oxide and an alkylene oxide other than propylene oxide (ethylene oxide (hereinafter also referred to as “EO”). ) And the like) are added to polymerize the polyether polyol. The addition polymerization of propylene oxide and other alkylene oxide may be random addition polymerization or block addition polymerization.
Here, as the dihydric alcohol, for example, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, etc. And a divalent alcohol having 2 to 10 carbon atoms.

The number average molecular weight of the PPG-based bifunctional polyol is preferably 100 to 10,000, more preferably 400 to 4,000.
When the number average molecular weight of the PPG-based bifunctional polyol is in the above range, the effect of reducing the closed cell ratio is appropriate, the cells are not roughened, other physical properties are not adversely affected, and the product appearance is good, which is preferable. ..

Among these, the PPG-based bifunctional polyol has an ethylene oxide content of 0 to 80 mol% (preferably from the viewpoint of effectively reducing the closed cell ratio of the foamed polyurethane resin spring, from the viewpoint of toughness and low temperature characteristics). Is 0 to 50 mol%) and the number average molecular weight is 100 to 10,000 (preferably 400 to 4,000).
Here, the ethylene oxide content is the ratio (molar ratio) of ethylene oxide to the total alkylene oxide content obtained by addition polymerization.

The cell openers may be used alone or in combination of two or more.

The content of the cell opener is preferably 0 to 15 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of PTMG.
When the content of the cell opener is in the above range, the appearance of the product is not adversely affected and the closed cell ratio can be reduced, which is preferable.

(Other additives)
The composition for forming the foamed polyurethane resin spring according to the present embodiment contains well-known additives such as an antioxidant, a colorant, an ultraviolet absorber, and an inorganic filler such as calcium carbonate, in addition to the above components. You can leave.

(Characteristics of resin spring made of foamed polyurethane)
The apparent density of the foamed polyurethane resin spring according to the present embodiment is 200 to 500 kg/m ³ .

The repulsion elastic modulus of the foamed polyurethane resin spring according to the present embodiment is 60% or more. By setting the impact resilience of the foamed polyurethane resin spring to 60% or more, the characteristics of the resin spring are improved (especially when the foamed polyurethane resin spring is applied to a ball hitting bat, the flight distance of the hit ball is extended. Easier).

The foamed polyurethane resin spring according to the present embodiment has a 30% compression set of 10% or less and a 50% compression set of 20% or less, preferably 5% or less and 10% or less. By setting the 30% compression set of the foamed polyurethane resin spring to 10% or less and the 50% compression set to 20% or less, the characteristics of the resin spring are improved (particularly, the foamed polyurethane resin spring is used for a hit ball bat). When applied, it has good resilience and makes it difficult for the resin to settle or deform over a long period of time.

The closed cell ratio of the foamed polyurethane resin spring according to the present embodiment is preferably 0 to 20%, more preferably 0 to 5%. By setting the closed cell rate of the foamed polyurethane resin spring to 0 to 20%, the spring characteristics are deteriorated even by repeated compression (especially, when the foamed polyurethane resin spring is applied to a hit ball bat, repeated hit balls). Is suppressed. Further, when the foamed polyurethane resin spring is formed, the manufacturing becomes easy even with an economical catalyst amount in the molding cycle. In other words, it is difficult for the product to expand and contract during demolding and shrink after cooling, the product dimensions are stable, partial deformation is less likely to occur, and productivity is increased.

The tensile strength of the foamed polyurethane resin spring according to this embodiment is preferably 1,000 kPa or more, more preferably 2,000 kPa or more. By setting the tensile strength of the foamed polyurethane resin spring to 1,000 kPa or more, the toughness of the foamed polyurethane resin spring increases, and damage due to repeated compression (especially when the foamed polyurethane resin spring is applied to a ball hitting bat) , Breakage due to impact at the time of hitting the ball) is easily suppressed.

The tensile elongation of the foamed polyurethane resin spring according to the present embodiment is preferably 200% or more, more preferably 300% or more. By setting the tensile elongation of the foamed polyurethane resin spring to 200% or more, the toughness of the foamed polyurethane resin spring increases, and damage due to repeated compression (particularly when the foamed polyurethane resin spring is applied to a ball hitting bat, It is easy to suppress breakage due to impact at the time of hitting a ball. Further, by being flexibly deformed during compression (especially when a foamed polyurethane resin spring is applied to a ball hitting bat, at the time of ball impact), conversion of kinetic energy into heat energy is suppressed, and a high impact resilience is obtained. be able to.

The above-mentioned properties of the foamed polyurethane resin spring according to the present embodiment can be obtained by adjusting the types and amounts of components for obtaining the foamed polyurethane resin spring.

(Manufacture of foamed polyurethane resin springs)
The foamed polyurethane resin spring according to the present embodiment can be manufactured according to a known method. For example, after mixing components other than MDI-based isocyanate, MDI-based isocyanate is mixed with this mixed solution to prepare a urethane raw material liquid. This urethane raw material liquid is poured into a mold having a desired shape or a desired forming portion (for example, when a foamed polyurethane resin spring is applied to a hitting bat, the hitting portion of the hitting bat) and then heated. As a result, a foamed polyurethane resin spring is obtained. Further, the foamed polyurethane resin spring may be attached later to a target position (for example, when the foamed polyurethane resin spring is applied to a hitting bat, the hitting portion of the hitting bat).

Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following description, all “parts” and “%” relating to the blending amount (content, addition amount) are based on weight unless otherwise specified.

<Comparative Example 1>
The following polyol components, which have been preheated to 50° C., are precisely weighed in a polycup, and are manufactured by PRIMIX Corporation high-speed emulsification/dispersion machine T.E. K. Stir with a homodisper 2.5 type (DH-2.5/1001) at 3000 rpm for 1 minute.
Main polyol: polytetramethylene glycol "PTMG3000 (manufactured by Mitsubishi Chemical Corporation, functional group number = 2, Mn = 3,000)" 100 parts

-Polyfunctional polyol: polyether polyol "Sannicx GP3000 (manufactured by Sanyo Chemical Industry Co., Ltd., PO/EO (molar ratio) = 100/0, number of functional groups f = 3, Mn = 3000)" 3 parts-Cell opener: Polyether polyol "Sannix PL910 (manufactured by Sanyo Kasei Co., Ltd., PO/EO (molar ratio) = 84/16, functional group number f = 2, Mn = 900) 5 parts-Foam stabilizer: silicone foam stabilizer " DOW CORNING TORAY SZ-1642 (manufactured by Toray Dow Corning Co., Ltd.) 1 part-Catalyst: Amine catalyst "DABCO 33-LV (manufactured by Air Products Japan Co., Ltd.)" 0.7 part-Blowing agent: distilled water 0.8 copy

Next, 22.7 parts (equivalent to Index=105) of isocyanate [monomeric MDI “Millionate MT (manufactured by Tosoh Corp.)] preheated to 50° C. was added to the obtained polyol component-containing solution, and primics was applied. A urethane raw material liquid is prepared by stirring at 5,000 rpm for 10 seconds with "High-speed emulsification/dispersion machine TK homodisper 2.5 type (DH-2/1001)" manufactured by Co., Ltd.

Next, the obtained urethane raw material liquid was formed into a rectangular frame consisting of an aluminum frame mold (internal length 180 mm × width 140 mm × thickness 10 mm) and a lower plate (thickness 10 mm) which had been heated to 50°C in advance. A predetermined amount (about 95 g) is put into the depression. After charging the urethane raw material liquid, quickly place an upper lid (made of aluminum, thickness 10 mm) and fix it with a vise at four locations.
In addition, the inside of the aluminum frame and the upper lid (the urethane raw material liquid contact surface) was previously coated with a release agent "Rimurikei N848 (Chukyo Yushi Co., Ltd.)" so that it could be peeled off after curing. Warm for 30 minutes at 100°C.

Next, an aluminum container (a container consisting of a frame and an upper lid) fixed with a vise is held in an oven at 50° C. for 10 minutes, then taken out of the oven and cooled at room temperature for 10 minutes. Then, the vise is removed, the upper lid and the lower plate are removed, and the foamed polyurethane foam is taken out from the frame mold.
After confirming the expansion (contraction) and skin breakage of the obtained expanded polyurethane foam, it was placed in an oven at 75° C. for 8 hours for the purpose of completing the reaction.
Then, the foamed polyurethane was taken out of the oven, the burrs at the ends of the foamed polyurethane were removed by a cutter or the like, and left in an environment of 23°C for 2 days or more.

Through the above operation, the desired foamed polyurethane resin spring was obtained.

<Examples 1 to 22, Comparative Examples 2 to 32>
According to Tables 1 to 7, the target foamed polyurethane resin spring was obtained in the same manner as in Comparative Example 1 except that the types and amounts (parts) of the components were changed.

(Evaluation)
The properties of the foamed polyurethane resin spring obtained in each example were measured, and various tests were performed for evaluation.

Hereinafter, various measuring methods and various tests performed in this example will be described. The various values of the present invention are values measured by the following measuring methods.

(Measuring method)
-Apparent density-
The apparent density is measured by the following method.
First, a sample to be measured (approximate size: vertical 180 mm×horizontal 140 mm×thickness 10 mm) is prepared in an environment of 23±3° C. Next, the weight of the sample is measured with a precision balance with an accuracy of 1/100 g. Next, a digital gauge is used, a thickness of the sample is measured at 9 points with a precision of 1/100 mm, and an average value is obtained using a stylus having a diameter of 10 mm and a load of about 0.6 N. The vertical dimension and the horizontal dimension of the sample are measured at three points using a digital caliper, and the average is obtained. The volume of the sample is calculated from the obtained dimensions. Then, the apparent density is calculated by the formula: apparent density=weight/volume.

-Repulsion elastic modulus-
The impact resilience is measured according to JIS K 6400 (1997/A method). For the measurement, a sample to be measured (approximate size: vertical 180 mm×horizontal 140 mm×thickness 10 mm) is stored in an environment of 23±3° C. for one day or more. The measurement is performed in an environment of 23±3° C. using “FR-1 type” manufactured by Kobunshi Keiki Co., Ltd.

-Tensile strength/elongation-
The tensile strength and elongation are measured according to JIS K 6400-5. For the measurement, a dumbbell No. 2 shape is punched out from the measurement target, a sample is obtained, and the thickness is measured. The obtained sample is subjected to “Tensilon universal material testing machine UCT-500” manufactured by Orion Tech Co., Ltd. at a speed of 200 mm/min. Then, the strength and elongation at break of the sample are measured.

-Closed cell rate-
The closed cell ratio is measured in accordance with the Beckman method (air comparison specific gravity measuring method: ASTM D 2856-70). Specifically, a sample of size: 20 mm×20 mm×thickness mm was cut out from the measurement target, and the volume (cm ³ ) of the obtained sample was measured using BECKMAN-TOSHIBA, LTD. It is measured with a manufactured “air comparison type hydrometer 930” (pressurizing method). The volume of the measured sample is used as the measured value. On the other hand, the volume was measured in a state where the sample was not put in the "air-comparison hydrometer 930 type" to obtain a background measurement value (blank value). Then, the closed cell rate (closed cell rate per space volume) Vc (%) is calculated by the following formula.
Formula: Vc(%)=[(ΔV−E)/(V−E)]×100
ΔV: {(measured value)-(blank value)} (cm ³ ).
V: Apparent volume of sample by water immersion method (cm ³ )
E: Volume of resin (polyurethane) (cm ³ )={(weight of sample)/(true specific gravity of sample)}

-30% compression hardness-
The 30% compression hardness is measured according to JIS K 6400-2 (2012). Specifically, a sample having a size of 20 mm×20 mm is cut out from the measurement target, and the thickness of the obtained sample is measured. Next, the sample is compressed at a speed of 10 mm/min using "Tensilon Universal Material Testing Machine UCT-500" manufactured by Orion Tech Co., Ltd. Then, the stress at the time of 30% compression with respect to the sample thickness is measured, and the measured value is taken as 30% compression hardness.

-30% compression set-
The 30% compression set is measured according to JIS K 6400-4 A method (2004). Specifically, a sample having a size of 20 mm×20 mm is cut out from the measurement target, and the thickness of the obtained sample is measured. Next, the sample is sandwiched between two stainless steel plates via a spacer having a thickness corresponding to 70% of the sample thickness, and fixed in a 30% compressed state. In that state, it is kept in an oven at 70° C. for 22 hours. Then remove from the oven and remove the sample from the stainless plate. Then, the thickness of the sample which is left at room temperature of 23° C. for 30 minutes is measured. Then, the 30% compression set is calculated based on the following formula.
Formula: CS=(t0-t)/t0×100
t0: thickness of sample before compression t: thickness of sample after compression

-50% compression set-
The 50% compression set was calculated in the same manner as the 30% compression set, except that the compression state when sandwiching and fixing the sample between two stainless steel plates was 50% compression state.

-Situation during demolding-
After taking out the polyurethane foam from the frame mold. The situation at the time of demolding of the obtained polyurethane foam was evaluated.
As for the situation at the time of demolding, the situation of expansion (or contraction) of foamed polyurethane and skin breakage was confirmed. In addition, odor (odor of isocyanate) was also confirmed. In addition, in the table, the situation in which the foamed polyurethane is excessively expanded (or contracted) is referred to as “expansion (or contraction)”, and the condition in which it is expanded (or contracted) to some extent is referred to as “swelling (or contraction)”. The situation in which it is expressed and slightly expanded (or contracted) is described as “slightly expanded (or slightly contracted)”. Further, when there was no particular problem at the time of demolding, it was described as “good”.

Hereinafter, the measurement results of the physical properties of each example and the results of various tests are listed in Tables 1 to 7.

From the above results, it is understood that the foamed polyurethane of this example has a high apparent density and a high impact resilience and can reduce the compression set, and is suitable as a foamed polyurethane resin spring. From this, it is understood that the resin spring using the polyurethane foam of the present embodiment is hard to be damaged by compression and can exhibit the spring function.
It is also understood that the foamed polyurethane resin spring of this example does not cause expansion (or contraction), skin breakage, etc. at the time of demolding, and has high productivity and easy manufacture.

The details of the abbreviations in the table are as follows.

-Main polyol-
-PTMG3000: Polytetramethylene glycol "PTMG3000 (manufactured by Mitsubishi Chemical Corporation, functional group number f=2, Mn=3,000)"
-PTMG2000: Polytetramethylene glycol "PTMG2000" manufactured by Mitsubishi Chemical Corporation, number of functional groups f=2, Mn=2000)"
GP3000: Polyether polyol "Sannicks GP3000 (manufactured by Sanyo Chemical Industry Co., Ltd., PO/EO (molar ratio)=100/0, number of functional groups f=3, Mn=3000)"

-Polyfunctional polyol-
GP3000: Polyether polyol "Sannicks GP3000 (manufactured by Sanyo Kasei Co., Ltd., PO/EO (molar ratio)=100/0, number of functional groups f=3, Mn=3,000)"

-Cell opener-
-PL910: Polyether polyol "SANNIX PL910 (manufactured by Sanyo Chemical Industry Co., Ltd., PO/EO (molar ratio) = 84/16, number of functional groups f = 2, Mn = 900)

-Foam stabilizer-
-SZ-1642: Silicone foam stabilizer "DOW CORNING TORAY SZ-1642 (manufactured by Toray Dow Corning Co., Ltd.)"

-Silicone oil-
"Dimethyl silicone oil"
KF-96L 5cs: Silicone oil "KF-96L 5cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 5cSt"
KF-96-100cs: Silicone oil "KF-96 100cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity=100cSt"
KF-96-300cs: Silicone oil "KF-96 300cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 300cSt"
KF-96-500cs: Silicone oil "KF-96 500cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 500cSt"
KF-96-1,000cs: Silicone oil "KF-961,000cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 1,000cSt"
KF-96-5,000cs: Silicone oil "KF-965,000cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 5,000cSt"
-KF-96H-10,000 cs: Silicone oil "KF-96H 10,000 cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 10,000 cSt"
KF-96H-50,000cs: Silicone oil "KF-96H 50,000cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 50,000cSt"
KF-96H-100,000 cs: Silicone oil "KF-96H 100,000 cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 100,000 cSt"

"Copolymerized silicone oil of dimethylsiloxane unit and methylphenylsiloxane unit"
KF-50-100cs: Silicone oil "KF-50 100cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 100cSt"
KF-50-3000cs: Silicone oil "KF-50 3,000cs (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 3,000cSt"
"Methyl hydrogen silicone oil"
-KF-99: Silicone oil "KF-99 (manufactured by Shin-Etsu Chemical Co., Ltd.), viscosity = 20 cSt"

-Catalyst-
DABCO 33-LV: amine catalyst "DABCO 33-LV (manufactured by Air Products Japan Co., Ltd.)"

-Isocyanate-
・Millionate MT: Monomeric MDI "Millionate MT (manufactured by Tosoh Corporation)"

Claims (8)

A composition containing polytetramethylene glycol having a number average molecular weight of 1,000 to 3,500, diphenylmethane diisocyanate-based isocyanate, a polyfunctional polyol having a functional group number of 3 or more, a foaming agent, a catalyst, and silicone oil. It consists of a cured product,
Apparent density of 200~500kg / ^{m 3,} and a rebound resilience of 60% or more, Ri 30% compression set 10% or less and 50% compression set der than 20%,
A foamed polyurethane resin spring in which the silicone oil is a polysiloxane composed of a copolymer of dimethylsiloxane units and methylphenylsiloxane units . A composition containing polytetramethylene glycol having a number average molecular weight of 1,000 to 3,500, diphenylmethane diisocyanate-based isocyanate, a polyfunctional polyol having a functional group number of 3 or more, a foaming agent, a catalyst, and silicone oil. It consists of a cured product,
Apparent density of 200~500kg / ^{m 3,} and a rebound resilience of 60% or more, Ri 30% compression set 10% or less and 50% compression set der than 20%,
The composition further comprises a cell opener, and the closed cell ratio is 0 to 20%,
A foamed polyurethane resin spring in which the cell opener is at least one selected from the group consisting of a low-molecular diol, a polypropylene glycol-based bifunctional polyol, a polyether carboxylic ester, a polybutene, and a paraffin-based oil . The foamed polyurethane resin spring according to claim 2 , wherein the silicone oil is a polysiloxane formed by copolymerization of a dimethylsiloxane unit and a methylphenylsiloxane unit. The foamed polyurethane resin spring according to claim 2 , wherein the silicone oil is polydimethylsiloxane. The foamed polyurethane resin according to claim 4 , wherein the polydimethylsiloxane has a viscosity of 5 to 50 (25°C, mm ² /s) or 1,000 to 100,000 (25°C, mm ² /s). Spring. The foamed polyurethane resin spring according to claim 1 , wherein the composition further comprises a cell opener, and the closed cell ratio is 0 to 20%. The foamed polyurethane according to claim 6 , wherein the cell opener is at least one selected from the group consisting of low-molecular diols, polypropylene glycol-based bifunctional polyols, polyether carboxylic ester compounds, polybutenes, and paraffin-based oils. Resin spring. The foamed polyurethane resin spring according to claim 7 , wherein the polypropylene glycol-based bifunctional polyol is a bifunctional polyol having an ethylene oxide content of 0 to 80 mol% and a number average molecular weight of 400 to 4,000.