JP3056630B2 - Microcellular polyurethane elastomer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane elastomer composed of fine cells and having relatively low foaming. The polyurethane elastomer having a fine cell structure of the present invention (hereinafter sometimes referred to as an elastomer) is used as a vibration-proof material or a shock-absorbing material in applications requiring water resistance.

[0002]

2. Description of the Related Art Polyurethane elastomers having a fine cell structure have been conventionally used as vibration dampers, shock absorbers and the like. Conventionally, such an elastomer has, for example, a number average molecular weight of 500 to 500 obtained by addition polymerization of one or more alkylene oxides such as ethylene oxide, diethylene oxide, propylene oxide, and 1,4-butylene oxide. In the presence of 5000 bifunctional polyether polyols or low molecular weight triols such as glycerin and trimethylolpropane, the number average molecular weight obtained by addition polymerization of one or more of the above alkylene oxides is 500 to 500. 500
0, trifunctional polyether polyol, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and mixtures thereof, diphenylmethane-4,4'-diisocyanate, paraphenylene diisocyanate, Isocyanate-terminated prepolymer (hereinafter, also referred to as prepolymer) obtained by reacting with a polyisocyanate such as 3,3'-dimethyl-4,4'-biphenylenediisocyanate, and the above-mentioned or the above-mentioned polyether polyol, etc. And a polyol component composed of a polyol, water, a low molecular weight diol, a catalyst, a foam stabilizer and the like are mixed and stirred to react.

However, when a polyol component is reacted with a prepolymer obtained by reacting a polyether polyol and a polyisocyanate at a weight ratio of more than 1: 1 to 2, the balance between polymerization and foaming of the resin is lost, The foaming is rapid and the reaction is completed in a short time. Therefore, the obtained elastomer tends to be powdery, has low physical properties, has a large average cell diameter, and is not uniform in cell diameter. Also,
When the prepolymer obtained by setting the weight ratio of the polyether polyol and the polyisocyanate to 1: 0.2 to 1 and the polyol component are reacted, if the amount ratio of water to the low molecular weight diol or the polyether polyol is not appropriate,
The degree of foaming may be too low, resulting in a rubber-like inflexible elastomer, foaming being too rapid, insufficient strength, or shrinkage after the elastomer is formed.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of the conventional polyurethane elastomer having a fine cell structure, in which the average cell diameter is small, the cell diameter is uniform, and the foaming degree is appropriately low. It is another object of the present invention to provide an elastomer having excellent physical properties such as compression set, tensile strength and tear strength.

[0005]

Means for Solving the Problems The microcellular polyurethane elastomer of the first invention is obtained by foaming a foamable composition mainly composed of an isocyanate-terminated prepolymer, a polyether polyol (b), water and a low molecular weight diol. In the microcellular polyurethane elastomer obtained by curing, the prepolymer is obtained by reacting a polyether polyol (a) with a polyisocyanate at a weight ratio of 1: 0.5 to 1; ) Has a number average molecular weight of 5,000 to 10,000.
Ri, a polyether polyol having 2 or 3 functional molecular weight distribution of 1.11 to 1.15, the molar ratio of the water and the low molecular weight diol is 1: 0.3-3 der is, and
The weight ratio of the water and the polyether polyol (b) is
1:10 to 40 .

According to a second invention, the elastomer of the first invention has a tensile strength of 3.0 to 10.0 MPa and a tear strength of 1
It is characterized by being 5 to 50 kN / m.

The “polyether polyol (a)” includes ethylene glycol, propylene glycol,
A starting material such as glycerin, trimethylolpropane, triethanolamine or the like, to which propylene oxide, ethylene oxide, butylene oxide or the like is added, may have a number average molecular weight of 500 to 5000, and may have a bifunctional or trifunctional one. Alkylene oxides can be used alone or in combination, but those using propylene oxide are generally used, which is preferable from the viewpoint of raw material costs and physical properties of the elastomer.

[0008] The above-mentioned "polyisocyanate" includes tolylene diisocyanate conventionally used in polyurethane elastomers having a fine cell structure and 80 tons of 2,4- and 2,6- isomers of tolylene diisocyanate.
/ 20-65 / 35 (weight ratio) mixture (TDI), diphenylmethane-4,4′-diisocyanate (MD
All polyisocyanates such as I), phenylene diisocyanate and naphthalene diisocyanate can be used. The most frequently used of these are TDI and M
DI.

The above "isocyanate-terminated prepolymer"
Is obtained by reacting the polyether polyol (a) with the polyisocyanate at a weight ratio of 1: 0.5 to 1. Polyisocyanate is added in an amount of 0.
If it is less than 5, the content of the free polyisocyanate in the prepolymer decreases, and the viscosity of the liquid at the time of producing the prepolymer increases, and the workability decreases. On the other hand, if it exceeds 1, the content of free polyisocyanate in the prepolymer increases, the reaction with the foaming agent is fast, and the cell diameter and its shape become non-uniform. Furthermore, the tensile properties of the elastomer, especially the tensile elongation, are greatly reduced, and the tear strength is also extremely low.

The "foamable composition" of the present invention comprises the above prepolymer and a polyol component, wherein the polyol component comprises "polyether polyol (b)" and "water" and "low molecular weight diol" as blowing agents. Main component. The polyether polyol (b) has a number average molecular weight of 5,000 to 1 among those using the same starting material and alkylene oxide as the polyether polyol (a).
0000 bi- or tri-functional ones can be used. In addition,
Since there are few by-products that are pure, the molecular weight distribution is
As narrow as 1.11 to 1.15 are used. In particular, those having a narrow molecular weight distribution and trifunctionality are more preferable from the viewpoint of improving the physical properties of the obtained elastomer. If the number average molecular weight of the polyether polyol (b) is less than 5,000, physical properties such as tensile strength are reduced. If it is more than 10,000, the viscosity of the foamable composition becomes high, air escape during foaming is poor, and elastomer is formed. It causes later shrinkage.

The low molecular weight diol includes a molecular weight of 1
50 or less diols, for example, ethylene glycol, propylene glycol, 1,4-butanediol and the like. The molar ratio of water to low molecular weight diol is 1: 0.
If the ratio of diol to water is less than 0.3, the desired fine cell structure will not be obtained, and the tensile strength and tear strength of the physical properties will be greatly reduced. When the number of diols exceeds 3, an elastomer having a fine cell structure and a low foaming degree can be obtained, but the tensile strength and the tear strength are greatly reduced as described above. In addition, the amount ratio of water to polyether polyol (b) is also important. If 10 to 40 polyether polyol (b) is used in a weight ratio of 1 to water, an elastomer having more excellent physical properties can be obtained. Can be

As the components of the foamable composition of the present invention, in addition to the above prepolymer, polyether polyol, and the like, a catalyst, a foam stabilizer, and if necessary, other auxiliaries can be used. As such auxiliary agents, other additives such as various liquid flame retardants, diluents or antioxidants, ultraviolet absorbers, coloring agents, etc., for lowering the viscosity of the foamable composition and facilitating stirring and mixing. Agents and the like. Their use amount is not particularly limited as long as the performance of the obtained elastomer is not significantly impaired.

[0013]

According to the present invention, by using a specific foamable composition, the tensile properties and tear strength of the obtained elastomer are remarkably excellent as compared with those obtained outside the range of the present invention. In the foaming composition of the same type, there is a prior art that discloses that the compression set is deteriorated when the molecular weight of the polyether polyol exceeds 5000, but the compression set of the elastomer of the present invention is about 3 to 10,
Very good despite its high molecular weight. Although the reason for the improvement of the physical properties is not clear, the polyol and the polyisocyanate constituting the prepolymer have excellent weight balance of the water and the low molecular weight diol, and the number average molecular weight of the polyether polyol as the polyol component is large, and the molecular weight is high. This is probably due to a synergistic effect with the narrow distribution.

[0014]

The present invention will be described below in detail with reference to examples and comparative examples. (1) Raw materials used (a) Polyisocyanate Diphenylmethane diisocyanate: Nippon Polyurethane Co., Ltd., trade name “Millionate MT” (b) Polyol polytetramethylene glycol: Sanyo Chemical Co., Ltd., trade name “PTMG-1000” (number average molecular weight; 100
0, hydroxyl value; 56) Polytetramethylene glycol: trade name “PTMG-2000” (manufactured by Sanyo Chemical Industries, Ltd .; number average molecular weight: 200)
0, hydroxyl value; 56) polypropylene ether glycol: manufactured by Asahi Glass Co., Ltd.
Trade name "PML-7003" (number average molecular weight; 600
0, molecular weight distribution; 1.13, hydroxyl value; 28) polypropylene ether glycol: manufactured by Sanyo Kasei Co., Ltd., trade name “GP-3000” (number average molecular weight; 300)
0, molecular weight distribution; 1.05, hydroxyl value; 56) polypropylene ether glycol: manufactured by Asahi Glass Co., Ltd.
Trade name "EXCENOL-837" (number average molecular weight; 6
000, molecular weight distribution; 1.21, hydroxyl value; 28)

(C) Low molecular weight diol 1,4-butanediol: manufactured by BASF Ethylene glycol: manufactured by Nisso Oil Chemical Co., Ltd. (d) Catalyst triethylenediamine (main component): manufactured by Sankyo Air Products, trade name "DABCO" 33LV "(e) Foam stabilizer Silicone:" SF-2962 "manufactured by Dow Corning Toray Silicone Co., Ltd.

(3) Method of Measuring Various Physical Properties A performance test was performed on the polyurethane elastomer having a fine cell structure obtained in Examples and Comparative Examples by the following method. (a) Specific gravity: The weight of a specimen (dimensions: 120 × 100 × 3 mm) is divided by its volume. (b) Tensile strength and elongation at break: No. 3 dumbbell is used in accordance with JIS K 6031. (c) Tear strength: based on JIS K 6031, using a B-type dumbbell, tensile speed: 500 mm / min. (d) Molecular weight distribution: by gel permeation chromatography. (e) Compression set: 50% -compressed and allowed to stand in an atmosphere of 70 ° C. for 22 hours.

(3) Compositions of Foamable Compositions of Examples and Comparative Examples Table 1 shows compositions of foamable compositions of Example 1 and Comparative Examples 1 to 5 , respectively. The proportions of each component of the foamable composition in Table 1 are all expressed in parts by weight. In Table 1, * indicates that the value is out of the numerical range.

[0018]

[Table 1]

Example 1 and Comparative Examples 1 to 5 Polyisocyanate and polyether polyol (a) shown in the section of prepolymer in Table 1 are charged into a reactor and reacted to produce an isocyanate-terminated prepolymer.
On the other hand, water, a low molecular weight diol, a polyether polyol (b), a catalyst and a foam stabilizer shown in the section of the polyol component in Table 1 are mixed and uniformly stirred. The prepolymer and the polyol component were each adjusted to a predetermined temperature, mixed and stirred at a predetermined ratio, and then cast into a mold to obtain a low-foaming polyurethane elastomer. The physical properties of the obtained elastomer were measured according to the above methods. Table 2 shows the results.

[0020]

[Table 2]

According to the results shown in Table 2, the weight ratio of the polyol constituting the prepolymer to the polyisocyanate is 1:
0.65, the molar ratio of water to low molecular weight diol is 1: 1.
6 der is, polyether polyols having a molecular weight of 1.13
In Example 1 using (b), it can be seen that the foaming degree is moderately low (expressed by specific gravity), and all of the tensile strength, tear strength and compression set are extremely excellent. On the other hand , in Comparative Example 1 using the polyether polyol (b) having a rather wide molecular weight distribution , the physical properties were significantly reduced.
However, in Comparative Example 2 in which the amount of the polyether polyol (b) used with respect to water was small , the decrease in physical properties was larger.
I understand.

Further, the weight ratio of polyol and polyisocyanate 1: In 1.8 and Comparative Example 3 exceeds the upper limit, although the degree of foaming is low, the tensile strength, elongation at break, both tear strength and compression set Is also extremely poor, and particularly the elongation at break is extremely low. Furthermore , in Comparative Example 4 , in which the molar ratio of water to the low molecular weight diol was 1: 5.4 and exceeded the upper limit, the degree of foaming did not decrease so much, and the tensile strength, tear strength and compression set were all very low. And the number of moles is 1:
In Comparative Example 5 , which is much lower than the lower limit of 0.12, it can be seen that although a low-cell foamed elastomer is obtained with a fine cell structure, the physical properties are very low as in the other Comparative Examples.
It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention according to the purpose and application.

[0023]

The polyurethane elastomer having a fine cell structure of the first invention uses a polyether polyol for both the polyol for producing the prepolymer and the polyol for producing the elastomer, and has extremely excellent water resistance and low foaming. In addition, since the diameter of the foam cell is small and the diameter is uniform, it is excellent in physical properties such as compression set, tensile strength and tear strength, and is an elastomer useful as a vibration-proof material and shock-absorbing material requiring water resistance. is there. Further, the elastomer of the first invention has excellent tensile strength and tear strength in a specific range as in the second invention .

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-57598 (JP, A) JP-A-5-59146 (JP, A) JP-A-4-285641 (JP, A) JP-A-6-59 206967 (JP, A) JP-A-61-81420 (JP, A) JP-A-5-506688 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 18/00-18 / 87

Claims (2)

(57) [Claims] 1. A microcellular polyurethane elastomer obtained by foaming and curing an expandable composition containing isocyanate-terminated prepolymer, polyether polyol (b), water and a low molecular weight diol as main components, wherein the prepolymer is Is obtained by reacting a polyether polyol (a) with a polyisocyanate at a weight ratio of 1: 0.5 to 1, and the polyether polyol (b) has a number average molecular weight of 5,000 to 10,000 and a molecular weight distribution of
There a polyether polyol having 2 or 3 functional is from 1.11 to 1.15, the molar ratio of the water and the low molecular weight diol is 1: 0.3-3 der is, and the water and the port
When the weight ratio of the reether polyol (b) is 1:10 to 40
A polyurethane elastomer having a fine cell structure, characterized in that: 2. The polyurethane elastomer having a fine cell structure according to claim 1, wherein the polyurethane elastomer has a tensile strength of 3.0 to 10.0 MPa and a tear strength of 15 to 50 kN / m.