JPH05331364A - Impact-absorbing material - Google Patents

Abstract

PURPOSE:To obtain a material which absorbs energy at a high efficiency, can be used satisfactorily even at a high temp., and is excellent in impact-absorbing capability by specifying the yield point in the stress-compression strain curve and stress during compression of a rigid polyurethane foam. CONSTITUTION:An impact-absorbing material comprises a rigid polyurethane foam which gives a stress-compression strain curve having no yield point when compressed at -30 to 100 deg.C and exhibits a constant stress in the range of compression of 10-65%. The foam is prepd. by mixing 100 pts.wt. polyhydroxy compd. with l-200 pts.wt, powder having a mean particle size of 0.05-100mum and reacting the mixture with a polyisocyanate compd. The powder dispersed is present in cell membranes of the foam, giving it an impact-absorbing capability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorbing material suitable for use as a wall or fence in a playground, a lining of a helmet, a shock absorbing member of an automobile body, and the like.

[0002]

2. Description of the Related Art Conventionally, in order to absorb energy in a collision, a wide range of shock absorbing materials have been used for playing field walls, fences, helmet linings, automobile bumpers, cushioning materials for packing, etc. It is used.

Thermoplastic resins such as polystyrene, polyethylene, and polypropylene are widely used as materials for such shock absorbing materials, and thermoplastic resin foams have a wide range of variation in energy absorption characteristics with respect to the environment or use temperature. However, there is a problem that the amount of energy absorption remarkably decreases particularly at high temperatures. Moreover, in the relationship between strain and stress, which represents the energy absorption characteristics, the stress tends to continuously increase as the strain increases as shown in FIG. 5, and it is desired to obtain a large energy absorption amount below the upper limit stress value. Not suitable for use in the case.

On the other hand, a polyurethane foam which is a thermosetting resin, especially a rigid polyurethane foam having a high cross-linking density, has an advantage that it is suitable for use at high temperatures because the range of change in energy absorption characteristics with respect to temperature is small.

However, in the conventional rigid polyurethane foam, in the relationship between strain and stress, the stress is less likely to change with respect to the strain as compared with the above-mentioned thermoplastic resin, but as shown in FIG. It is still not enough, for example, that there is a yield point where it rises and then descends.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide an impact absorbing material having high energy absorbing efficiency and excellent impact absorbing property that can be favorably used even at a high temperature.

[0007]

In order to achieve the above object, the present invention has a stress-compression strain curve having no yield point and a compressibility of 1 when an impact absorbing material is compressed at -30 to 100 ° C.
It is formed of a rigid polyurethane foam whose stress is substantially constant in the range of 0 to 65%.

In this case, as the rigid polyurethane foam, one in which powder having an average particle diameter of 0.5 to 100 μm is dispersed and contained is effectively used.

[0009]

That is, as a result of the investigations by the present inventors on an impact absorbing material having excellent impact absorption and high energy absorption efficiency, a polyurethane foam raw material containing a polyhydroxy compound and a polyisocyanate compound as main components was obtained. Foaming
When producing a rigid polyurethane foam by reaction, a powder having an average particle size of 0.05 to 100 μm is added to the foaming raw material in an amount of 1 per 100 parts by weight of the polyhydroxy compound.
When mixed in an amount of up to 200 parts by weight, the above-mentioned powder is dispersed and present in the cell membrane of the obtained rigid polyurethane foam.
When compressed at ℃, the stress is constant against the change of strain in the compressibility range of 10 to 65%, the yield point is not recognized, and the stress does not have such a yield point, and the stress is substantially in a wide strain range. It was discovered that a rigid polyurethane foam having a certain level has excellent properties as an impact absorbing material.

More specifically, as shown in FIG. 6, when the conventional rigid polyurethane foam is compressed, cell breakage occurs randomly, which results in a temperature of -30 to 100 ° C.
5 has a yield point as shown in FIG. 5 and the stress does not become constant in response to changes in strain. However, the shock absorber made of the rigid polyurethane foam of the present invention has
As shown in Fig. 1, cell fracture occurs sequentially from the side where compressive strain is applied. Therefore, there is no yield point as shown in Fig. 1, and strain and stress are almost proportional in the initial stage of compression, and after reaching a certain stress value. Has a characteristic that the stress becomes substantially constant with respect to the change in strain, and the stress increases at the end of compression.

Therefore, the impact absorbing material of the present invention has a high energy absorption efficiency and is high in temperature, for example, 70 to 10.
Even at 0 ° C, the change in energy absorption characteristics is small, and an excellent impact absorption effect is provided.

[0012]

EXAMPLES The present invention will be described in more detail below. The shock absorbing material of the present invention does not have a yield point on the stress-compression strain curve and has a compressibility of 10 when compressed at -30 to 100 ° C.
It consists of a rigid polyurethane foam with a substantially constant stress in the range of ˜65%.

In this case, as shown in FIG. 3, the impact absorbing material of the present invention has compression characteristics of length 50 mm, width 50 m.
Using a test piece having a size of m and a height of 50 mm, under a compression condition of a compression speed of 50 mm / sec in the height direction, the compression ratio is in the range of 10 to 65% and the stress is 2 to
Substantially constant in the range of 8 kg / cm ² (variation of stress is ±
0.5 kg / cm ² ).

Further, the rigid polyurethane foam is
To ensure the characteristics as a shock absorber, JIS-A-
Foam density measured by 9514 is 25-90 kg
/ M ³, Especially 30-80kg / m³Have a value in the range
And are preferred.

Further, as the above-mentioned polyurethane foam, one in which powder having an average particle diameter of 0.05 to 100 μm is dispersed and contained is preferably used.

The rigid polyurethane foam used for such an impact absorbing material is obtained by blending a powder into a polyurethane foam foaming raw material containing a polyhydroxy compound, a polyisocyanate compound, a catalyst, a foaming agent, a foam stabilizer, and foaming this.・ Can be obtained by reacting.

Here, as the polyhydroxy compound,
There is no particular limitation, for example, glycerin, sucrose,
Polyether polyols obtained by ring-opening addition polymerization of alkylene oxides such as ethylene oxide and propylene oxide with ethylenediamine and the like; adipic acid,
Examples thereof include polyester polyols obtained by polycondensation reaction of polybasic acids such as succinic acid and polyhydroxyl compounds such as ethylene glycol and propylene glycol, or ring-opening polymerization of lactones. One of these may be used alone or 2 One or more species can be used in combination. In this case, in order to improve the heat resistance of the rigid polyurethane foam, the average OH value of all polyhydroxy compounds is preferably 200 or more, more preferably 300 or more.

As the catalyst, any catalyst used in the field of urethane foam can be used. Examples thereof include organometallic compounds such as dibutyltin dilaurate, lead octoate and stannas octoate; amine compounds such as triethylenediamine and tetramethylhexamethylenediamine, and N, N ′,
N ″ -tris (diaminopropyl) hexahydro-s
-Triazine, potassium acetate, potassium octylate and the like used for isocyanurate modification can also be used.

As the foaming agent, any of those used in the production of rigid polyurethane foam can be used, and examples thereof include water, trichlorofluoromethane,
Chlorofluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane, hydrochlorofluorocarbons such as dichlorotrifluoroethane and dichlorotetrafluoroethane, hydrochlorocarbons such as methylene chloride, hexafluoro Hydrofluorocarbons such as propane and hydrocarbons such as pentane can be used. Among these, water is particularly preferable in view of the influence on the environment due to diffusion into the atmosphere. Generally, when a large amount of water is used, a large amount of heat is generated during foaming / reaction, and scorch is likely to be generated inside the obtained rigid urethane foam. Moreover, there is an advantage that the amount of heat generation is small and scorch can be prevented. The amount of water blended is 100 parts by weight of the polyhydroxy compound,
The range of 0.5 to 10 parts by weight is preferable.

Further, as the foam stabilizer, use should be made of all those which are effective for rigid polyurethane foam, such as polyoxyalkylene type compounds such as polyoxyalkylene alkyl ether and silicone type compounds such as organopolysiloxane. Surface tension is 16 ~
A foam stabilizer in the range of 22 dyn / cm, particularly 18 to 21.5 dyn / cm is preferable. Surface tension is 16 dyn / cm
When a smaller foam stabilizer is used, a phenomenon such as cell roughening may occur. On the other hand, when it is higher than 22 dyn / cm, the cells constituting the obtained rigid polyurethane foam become close to a spherical shape, and buckling may not occur stably under a constant stress. Explaining this in more detail, as shown in FIG. 4, when the cell is close to a sphere, the buckling stroke is short with respect to the input from the long axis direction of the cell,
As a result, the buckling region where the stress is constant even in macroscopic stress-compressibility characteristics as a foam that is an aggregate of cells,
That is, it is considered that the effective strain range becomes small and the energy absorption efficiency is lowered. Generally, the obtained stress itself is also related to the major axis / minor axis ratio of the cell, and when this ratio is large, the major axis direction shows the highest stress. Therefore, the impact absorbing material of the present invention has a cell major axis / minor axis ratio of 1 to
5, preferably in the range of 1.5 to 4, and is preferably used so that the major axis direction of the cell is along the stress input direction (compression direction), whereby high shock absorbing ability is exhibited. be able to.

On the other hand, examples of the polyisocyanate compound include aromatic isocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate, aliphatic isocyanates such as hexamethylene diisocyanate, and crude products thereof. These can be used alone or in combination of two or more.

The amount of the polyisocyanate compound used relative to the total amount of the polyhydroxy compound and the compound having active hydrogen such as water, that is, the isocyanate index is in the range of 80 to 130 in the case of producing a usual rigid urethane foam, and isocyanurate. When producing a modified rigid urethane foam, the range of 150 to 350 is desirable.

The powder to be mixed with the foaming raw material is as follows:
The average particle size is 0.05 to 100 μm, preferably 0.5 to
It is necessary to use the one having a thickness of 50 μm, more preferably 1 to 30 μm, whereby a rigid polyurethane foam having a constant stress in a wide strain range against strain change can be obtained. The mechanism by which the powder is present in the cell film in such a manner that a constant stress is maintained with respect to the change in the compressibility has not been sufficiently clarified, but
It is presumed that the presence of foreign powders stabilizes the fracture stress of each cell. That is, it is considered that the presence of the powder serves as a stress concentration point in each cell, and an effect as if a notch is formed appears.

Here, the average particle size of the powder used is 0.
If it is less than 05 μm, the stress concentration point may not be formed, and if it exceeds 100 μm, it may be difficult to use it in a urethane foamer that is usually used.

As the material of the powder which can be used in the present invention,
There is no particular limitation as long as it has the above-mentioned average particle size, and for example, inorganic compounds such as calcium carbonate and aluminum hydroxide;
Metals such as iron and aluminum; and organic substances such as polyamide, vinyl chloride and melamine can be used, and one of these can be used alone or two or more can be used in combination.

The amount of the powder having such an average particle diameter used is 1 with respect to 100 parts by weight of the total polyhydroxy compound.
It is preferably in the range of ˜200 parts by weight, particularly 2 to 50 parts by weight. If the amount of powder used is less than 1 part, the stress concentration points may be too small and the stress against strain may not be constant, while if it exceeds 200 parts by weight, mixing and
The viscosity of the reaction liquid when forming rigid urethane foam by stirring remarkably increases, the mixing and stirring efficiency decreases, and non-reactive components increase. This may lead to a decrease, and as a result, the completion of the reaction may decrease, leading to insufficient strength.

When a rigid polyurethane foam is produced by foaming and reacting the above foaming raw material, the foaming and reaction can be carried out in the same manner as in the case of ordinary rigid polyurethane foam. 140
It is preferable to adjust the time in seconds, particularly in the range of 15 to 110 seconds. If the rise time is shorter than 10 seconds, necessary and sufficient stirring time may not be obtained and scorch may easily occur in the foam. On the other hand, when the time exceeds 140 seconds, the cell becomes nearly spherical, so that the energy absorption efficiency may decrease as described above.

The impact absorbing material of the present invention has high energy absorbing efficiency, excellent impact absorbing property, and little change in energy absorbing effect with respect to temperature change. Therefore, the wall of a playground, fence, lining of helmet, etc. In addition to being suitably used as a packaging impact material, it is particularly effectively used as an impact absorbing member to be mounted on bodies such as automobile bumpers, doors, fenders, pillars, floors and trunks.

Next, examples of the present invention and comparative examples will be shown.

Examples and Comparative Examples According to the formulation shown in Table 1, 200 g of a polyhydroxy compound was first weighed in a 1 liter paper cup, and a predetermined amount of catalyst, silicone foam stabilizer and water were added thereto. After being stirred for about 10 seconds by a propeller stirrer, a predetermined amount of the powder shown in Table 1 was further added and sufficiently mixed and stirred for about 30 seconds.

Next, a predetermined amount of crude diphenylmethane diisocyanate was added to this homogeneous mixed solution, and the mixture was stirred at room temperature for about 5 seconds at high speed, and the reaction solution stirred at high speed was heated to 250 m.
It was poured into a polyethylene bag set in a m × 250 mm × 250 mm wooden mold, and foamed and reacted at room temperature. The resulting foam is placed in an oven at 50 ° C for about 1
After-curing was performed for 0 minutes to obtain a rigid polyurethane foam. In this case, the time required from the start of high-speed stirring after the addition of crude diphenylmethane diisocyanate to the end of the apparent increase in volume of the reaction solution was taken as the rise time (foaming / curing time) of each foam.

Then, the foam density of the obtained foam was measured according to JIS-A-9514, and the stress-strain characteristic was measured by the following method. These measurements were carried out after leaving the foam for 3 days after foaming and curing.

Method for measuring stress-strain characteristics The obtained rigid polyurethane foam was cut into a test piece having a height of 30 mm, a width of 50 mm and a length of 50 mm, and compressed between flat plates using an autograph AGS-500A manufactured by Shimadzu Corporation. The test piece was compressed in the height direction (the major axis direction of the cell, that is, the foaming direction) at a descending speed of 50 mm / sec. The result is shown in FIG.

In the table, the stress-strain characteristics are shown as stress at 50% strain and effective strain. The stress at 50% strain is shown in FIG.
As shown in, the compressibility in the height direction of the test piece is 50
The stress and effective strain when reaching 100% represent the compressive strain at which the stress starts to rise rapidly.

[0035]

[Table 1] (Note) (1) Polyhydroxy compound: Polyether polyol GR30C (OH value = 430) manufactured by Takeda Pharmaceutical Co., Ltd. (2) Foam stabilizer: Silicone foam stabilizer L-5430 manufactured by Nippon Unicar Co., Ltd. Surface tension 19.2 dyn / cm The surface tension of the foam stabilizer was measured at 25 ° C. using a CBVP type surface tensiometer A-3 type manufactured by Kyowa Chemical Co., Ltd. (3) Catalyst: Tetramethylhexamethylenediamine manufactured by Kao Corporation, Kaolizer No. 1 (4) Powder A: heavy calcium carbonate manufactured by Shiraishi Calcium Co., Ltd., Whiten SB (average particle size 1.8 μm) (5) Powder B: barium ferrite manufactured by Toda Kogyo Co., Ltd., GP- 500 (Average particle size 1.2 μm) (6) Polyisocyanate: Crude diphenylmethane diisocyanate manufactured by Sumitomo Bayer Urethane Co., Ltd., 4
4V20

From the results shown in FIG. 1 and Table 1, those without the powder (Comparative Example) have a yield point, a large effective strain, and a low energy absorption efficiency. On the other hand, when the powder is blended, the compressibility is 10 to 6 as shown in FIG.
It is recognized that the stress is almost constant in the range of 5%, the stability of the stress against strain is extremely high, the yield point is not observed, and the energy absorption efficiency is high. This means that when the foams obtained in Example 1 and Comparative Example are observed to be compressed, the foams obtained in Example 1 are buckled sequentially from the compression direction as shown in FIGS. Occurs,
The portion where no buckling occurs maintains the cell shape of the foam itself, so the stress is constant with respect to strain in the range where there is a portion where buckling does not occur, whereas the comparative example has
It is considered that the buckling occurs almost inside the foam and the stress is applied to each cell, so that the stress varies with the strain.

[0037]

The shock absorbing material of the present invention is excellent in shock absorbing ability and therefore widely used as a wall or fence in a playground, a lining of a helmet, a shock absorbing member for automobile bumpers or bodies, a cushioning material for packing, etc. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing stress with respect to compressive strain of foams obtained in Examples and Comparative Examples.

FIG. 2 is an explanatory view showing a compressed state of the foam observed when the foam obtained in Example 1 was compressed.

FIG. 3 is a graph showing stress against compressive strain of rigid polyurethane foam obtained by the method of the present invention.

FIG. 4 is a schematic diagram showing a state where pressure is applied to an elliptical cell having a long cross section and a circular cell having a cross section.

FIG. 5 is a graph showing stress against compressive strain of polystyrene foam and rigid polyurethane foam.

FIG. 6 is an explanatory diagram showing a compressed state of a foam observed when the foam obtained in a comparative example is compressed.

Claims (2)

[Claims] 1. When compressed at -30 to 100 ° C., the stress-compression strain curve has no yield point and the compressibility is 10 to 65%.
An impact absorbing material comprising a rigid polyurethane foam having a substantially constant stress in the range. 2. The shock absorbing material according to claim 1, wherein the rigid polyurethane foam contains powder having an average particle diameter of 0.5 to 100 μm dispersed therein.