JPH07252340A - Microcellular polyurethane elastomer - Google Patents

Abstract

PURPOSE:To produce the subject elastomer improved in durability to fatigue failure, flatting, etc., and mechanical strengths by mixing a specified isocyanate- terminated prepolymer with a specified hydroxyl-terminated prepolymer and a blowing component, and foaming and curing the mixture. CONSTITUTION:A polyesterpolyol of a number-average molecular weight of 1000-3000 is reacted with diphenylmethane-4,4'-diiso-cyanate in a weight ratio of 1:(0.2-0.6) to obtain an isocyanateterminated prepolymer (A). 1mol of a polyesterpolyol of a number-average molecular weight of 1000-3000 is reacted with 0.050.5 mol of a polyisocyanate to obtain a hydroxyl-terminated prepolymer (B). Component A, component B and a blowing component (C) are mixed together in amounts to give a total of hydroxyl equivalents of 0.9-1.2, and the resultant mixture is foamed and cured by agitation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relatively low-foaming polyurethane elastomer composed of fine cells. The fine cell structure polyurethane elastomer of the present invention (hereinafter, also referred to as an elastomer) has high mechanical strength and dynamic characteristics when subjected to a large load repeatedly, particularly durability in fatigue fracture, fatigue, etc. Since it is excellent, it is used as a cushioning material for auxiliary springs of automobiles and the like.

[0002]

2. Description of the Related Art Polyurethane elastomers having a fine cell structure have hitherto been used as vibration damping materials, shock absorbing materials and the like. Conventionally, such an elastomer is obtained by adding alkylene oxide such as ethylene oxide, propylene oxide and 1,4-butylene oxide to ethylene glycol, propylene glycol, 1,4-butylene glycol, glycerin, trimethylolpropane and the like. Malonic acid, one or more of
A polyester polyol having a number average molecular weight of 1,000 to 3,000 (hereinafter sometimes referred to as a polyol) obtained by polycondensing one or more organic acids such as maleic acid, adipic acid and terephthalic acid. 2,4-
Tolylene diisocyanate, 2,6-tolylene diisocyanate and mixtures thereof, diphenylmethane-4,
4'-diisocyanate (MDI), naphthalene-1,
5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TOD
An isocyanate-terminated prepolymer obtained by reacting with a polyisocyanate such as I) (hereinafter referred to as NCO-terminated prepolymer) and a foaming component composed of water, a catalyst, a foam stabilizer, etc. are mixed and stirred to react. Has been obtained.

Among the elastomers obtained as described above, particularly when NDI is used as a polyisocyanate component, it has excellent mechanical strength, is hard to break even when repeatedly subjected to a high load, and has a small amount of sag. Since it has excellent durability, it is useful as a cushioning material for auxiliary springs of automobiles. However, NDI is an intermediate raw material for synthesizing pharmaceuticals, dyes, etc., and it is expensive because of its small production volume and narrow market, and the NCO-terminated prepolymer obtained by the reaction of polyol and NDI is There is a problem that the workability is high when the viscosity is high and the mixture is mixed with the foaming component and stirred to foam and cure. On the other hand, MDI, which is a general-purpose polyisocyanate component, is inexpensive and
Although the viscosity of the obtained NCO-terminated prepolymer is low and the workability at the time of producing an elastomer is good, an elastomer having sufficient performance in terms of mechanical strength, durability and the like cannot be obtained.

[0004]

The present invention overcomes the drawbacks of the above-mentioned conventional polyurethane elastomers having a fine cell structure, and it is an inexpensive MD as a polyisocyanate component.
I to obtain a low viscosity NCO-terminated prepolymer,
Moreover, it is an object of the present invention to provide an elastomer having mechanical strength, durability and the like equivalent to the case of using NDI.

[0005]

The fine cell structure polyurethane elastomer of the first invention is a fine cell structure polyurethane elastomer obtained by mixing an isocyanate-terminated prepolymer, a hydroxyl group-terminated prepolymer and a foaming component, stirring and foam-curing the mixture. The above isocyanate-terminated prepolymer has a number average molecular weight of 1,000 to 3,000.
Polyester polyol, diphenylmethane-4,
It is obtained by reacting 4'-diisocyanate in a weight ratio of 1: 0.2 to 0.6, and the hydroxyl group-terminated prepolymer contains 0.05 to 0 of polyisocyanate based on 1 mol of the polyester polyol. It is characterized by reacting 0.5 mol, and the foaming component contains water as a main foaming agent. The second invention is
A third invention is characterized in that the polyisocyanate is TODI, the viscosity of the NCO-terminated prepolymer is 2500 centipoise or less, and the number of durability tests in the durability test of the elastomer is 500,000 or more, and the amount of sag is It is characterized by being 10% or less.

Examples of the above-mentioned "polyester polyol" include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butylene glycol, glycerin and trimethylolpropane, as well as ethylene oxide, diethylene oxide, propylene oxide and 1,4-butylene oxide. 1 type or 2 types or more with addition of alkylene oxide, malonic acid,
It is possible to use those having a number average molecular weight of 1,000 to 3,000, which are obtained by polycondensing one or more kinds of organic acids such as maleic acid, adipic acid and terephthalic acid.

The "MDI" is pure MDI. Pure MD
I has 2 functional groups, the NCO-terminated prepolymer produced by the reaction with the above-mentioned polyol has a chain structure, and the obtained elastomer has excellent durability. Pure M
Other than DI, for example, crude MDI, carbodiimide-modified M
DI has an average number of functional groups of 2 to 3, and the elastomer obtained by the NCO-terminated prepolymer having a network structure has a small elongation and is inferior in durability such as fatigue fracture when a large load is repeatedly applied. Become.

The "NCO-terminated prepolymer" is the polyester polyol and the MDI in the range of 1: 0.2 to.
Obtained by reacting at a weight ratio of 0.6. When the MDI is less than 0.2 with respect to the polyol 1, the free MDI content in the NCO-terminated prepolymer becomes small, the viscosity of the liquid at the time of producing the NCO-terminated prepolymer increases, and the workability decreases. On the other hand, if it exceeds 0.6, the content of free MDI in the NCO-terminated prepolymer increases, the reaction with the foaming agent is rapid, and the cell diameter and its shape become nonuniform. Furthermore, the mechanical strength and durability of the elastomer are reduced.

Examples of the above-mentioned "polyisocyanate" for forming a hydroxyl group-terminated prepolymer (hereinafter referred to as OH-terminated prepolymer) include the above-mentioned 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and their compounds. Mixtures, MDI, NDI, etc. can be used without particular limitation. As polyisocyanate, TO
DI is particularly preferable, and an elastomer having more excellent durability can be obtained. The polyester polyol may be the same as that used for forming the NCO-terminated prepolymer, and may have a number average molecular weight of 1000 to 30.
Other polyester polyols of No. 00 may be used.

The OH-terminated prepolymer is obtained by mixing and stirring 0.05 to 0.5 mol of polyisocyanate with 1 mol of polyol and reacting them. If the amount of polyisocyanate is less than 0.05 mol, the heat resistance of the elastomer will be reduced and the durability will be poor. If it exceeds 0.5 mol, the viscosity of the OH-terminated prepolymer will increase as it approaches the equivalent amount, and The affinity with and becomes poor, and the layers are easily separated.
Further, the reaction with the NCO-terminated prepolymer becomes non-uniform, and the heat resistance of the obtained elastomer decreases. The OH-terminated prepolymer is used in an amount of 0.1 to 1.0 part by weight based on 100 parts by weight of the polyester polyol used for producing the NCO-terminated prepolymer. When the amount used is less than 0.1 parts by weight, the content of polyisocyanate such as TODI in the whole is small, so that the heat resistance of the obtained elastomer decreases and the durability becomes poor. On the other hand, if it exceeds 1.0 part by weight, the OH-terminated prepolymer is not sufficiently uniformly mixed with water. as a result,
The reaction with the NCO-terminated prepolymer becomes non-uniform, and the durability of the resulting elastomer decreases. With that, T
As the content of ODI or the like increases, the elastomer becomes hard, which is not preferable.

The above-mentioned "foaming component" contains water as a main foaming agent, and additionally contains a catalyst, a foam stabilizer and the like. The amount ratio of water in the foaming component is not particularly limited, but it can be obtained as long as the amount ratio of water which is a foaming agent and also acts as a cross-linking agent is 0.5 or more with respect to the total amount 1 of the foaming component. Elastomers are preferable because they are excellent in mechanical strength and especially in fatigue fracture when repeatedly subjected to a large load and durability against fatigue.

In the present invention, the NCO-terminated prepolymer, O
The H-terminated prepolymer and the foaming component are used by mixing so that the isocyanate equivalent of the NCO-terminated prepolymer and the total hydroxyl equivalent of the OH-terminated prepolymer and the foaming component are in the range of 0.9 to 1.2. It Further, other auxiliary agents can be used if necessary. As such an auxiliary agent, the viscosity of the elastomer raw material is lowered,
Various additives such as various liquid flame retardants, diluents or antioxidants, ultraviolet absorbers, colorants, etc. for facilitating stirring and mixing are included. The amount used is not particularly limited as long as the performance of the obtained elastomer is not significantly impaired.

[0013]

In the present invention, MDI is used, which is inexpensive and has excellent workability during the production of an elastomer. With the conventional technology, the obtained elastomer is durable, especially when it is repeatedly subjected to a large load. Is known to have poor performance. However, in the present invention, by combining the NCO-terminated prepolymer with the OH-terminated prepolymer and a foaming component containing water as a main blowing agent, the defect of MDI having a slightly low heat resistance is compensated, and especially TODI having a high heat resistance is used. NCO using NDI as polyisocyanate in the endurance test accompanied by heat generation by using polyisocyanate as the component of the OH-terminated prepolymer, even though MDI was used.
An elastomer having excellent performance equivalent to that of the terminal prepolymer can be obtained.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. (1) Raw materials used (a) Polyisocyanate Pure MDI: Nippon Polyurethane Co., trade name "Millionate MT" NDI: Mitsui Toatsu Co., trade name "Cosmonate N"
D "(b) Polyol Polyethylene adipate polyester polyol:
Product name "ODX-102" manufactured by Dainippon Ink and Chemicals (number average molecular weight: 2000, hydroxyl value: 56) Poly (ethylene / butylene) adipate polyester polyol: Product name "ODX-1" manufactured by Dainippon Ink Co., Ltd.
05 "(number average molecular weight: 2000, hydroxyl value: 56) Polyethylene adipate polyester polyol:
Product name “ODX-286” manufactured by Dainippon Ink and Chemicals (number average molecular weight: 1,000, hydroxyl value: 112)

(C) OH-terminated prepolymer TODI is 0.3 with respect to 1 mol of the above polyol.
Prepolymer obtained by carrying out molar reaction TODI is 0.3 with respect to 1 mol of the above-mentioned polyol.
Prepolymer obtained by carrying out molar reaction TODI is 0.4 with respect to 1 mol of the above-mentioned polyol.
Prepolymer obtained by carrying out molar reaction TODI is 0.4 with respect to 1 mol of the above-mentioned polyol.
Prepolymer obtained by carrying out molar reaction TODI is manufactured by Nippon Soda Co., Ltd. under the trade name "TOD".
I "

(D) Foaming agent Water-based mixture: Sumitomo Bayer, trade name "Additive SM" (e) Catalyst triethylenediamine (main component): Sankyo Air Products, trade name "DABCO 33LV" ( f) Foam stabilizer Silicone type: manufactured by Toray Dow Corning Silicone, trade name "SF-2962"

(3) Methods for Measuring Physical Properties The performance tests of the fine cell structure polyurethane elastomers obtained in Examples and Comparative Examples were conducted by the following methods. (a) Density: The weight of a test piece (dimensions: 120 × 100 × 3 mm) is divided by its volume. (b) Tensile strength and elongation at break: According to JIS K 6301, No. 3 test piece is used (c) Tear strength: According to JIS K 6301, B type test piece is used, tensile speed: 500 mm / min (d) Isocyanate-terminated prepolymer viscosity: viscometer;
B type (manufactured by Tokimec), rotor speed: 30 rp
m, rotor No; No. 3. Measurement temperature; 80 ° C. (e) Durability (endurance number): A load of 4.75 kN is repeatedly applied to the test piece at a cycle of 2 Hz, and the number of times until destruction is recorded. The goal is not to destroy even if a load is applied 500,000 times. (f) Settlement amount: The value obtained by subtracting the height of the test piece after measurement from the height of the test piece before measurement of the number of times of durability is divided by the height of the test piece before measurement and multiplied by 100 (%). Represents.

(3) Composition of Elastomer Raw Materials of Examples and Comparative Examples Table 1 shows the compositions of the elastomer raw materials of Examples 1 to 4 and Comparative Examples 1 and 2, respectively. The proportions of the respective components in Table 1 are all expressed in parts by weight when the polyol is 100 parts by weight.

[0019]

[Table 1]

Examples 1 to 4 and Comparative Examples 1 to 2 The polyols and polyisocyanates shown in the section of prepolymer in Table 1 are put into a reactor and reacted to obtain NCO-terminated prepolymers. On the other hand, the raw material used in (1) above, (c)
O produced by using the polyol and polyisocyanate described in the section of OH-terminated prepolymer in the same manner as described above.
The H-terminated prepolymer, the foaming agent, the catalyst and the foam stabilizer are mixed and stirred uniformly. The NCO-terminated prepolymer and the foaming component are each adjusted to a predetermined temperature, and mixed at a ratio such that the isocyanate equivalent of the NCO-terminated prepolymer and the total hydroxyl equivalent of the OH-terminated prepolymer and the foaming component are 1.1. After stirring, the mixture was cast into a mold to obtain a polyurethane elastomer having a relatively low foaming. The physical properties of the obtained elastomer were measured according to the methods described above. The results are shown in Table 2.

[0021]

[Table 2]

According to the results in Table 2, in Examples 1 to 4 in which an OH-terminated prepolymer and a foaming component containing water as a main blowing agent were used, the obtained elastomers were used in the production of the OH-terminated prepolymer. Irrespective of the type of the polyester polyol, which has excellent tensile strength, tear strength, etc., and in the results of the durability test, no fatigue fracture occurs even after the repeated load of 500,000 times, Further, it can be seen that the amount of sagging is about 5 to 6%, and the durability is extremely excellent. Further, the viscosity of the NCO-terminated prepolymer is in the range of 1800 to 2400 centipoise, which is easy to handle.

On the other hand, in Comparative Example 1 in which an elastomer was obtained in the same manner as in Example 1 except that the OH-terminated prepolymer was not used, the tensile strength, the tear strength and the viscosity of the NCO-terminated prepolymer were different from each other. However, in the durability test, the fatigue fracture of the test piece was caused by the repeated load of 100,000 times, and therefore the amount of sag could not be measured. Further, in Comparative Example 2 in which NDI was used as the polyisocyanate for forming the NCO-terminated prepolymer, the mechanical strength and durability were the same as those in each Example and were excellent, but the viscosity of the NCO-terminated prepolymer was excellent. It is about twice as large as that of the example, and it can be seen that this point is very inferior. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0024]

EFFECT OF THE INVENTION The fine cell structure polyurethane elastomer according to the first aspect of the present invention has been considered to be a drawback thereof while maintaining the advantage that the NCO-terminated prepolymer has a low viscosity and is easy to handle when MDI is used as the polyisocyanate. It is an elastomer whose fatigue fracture or settling upon repeated heavy load is improved and whose durability is equivalent to that when NDI is used as polyisocyanate. Further, in the second invention using TODI as the polyisocyanate for forming the OH-terminated prepolymer, an elastomer having particularly excellent durability can be obtained. Furthermore, in the third invention, the NCO-terminated prepolymer has a viscosity of 2500 centipoise or less, is excellent in workability during elastomer production, and has a durability test of 500,000 times or more in a durability test of the elastomer, and has a sag amount. 1
A polyurethane elastomer having a fine cell structure of 0% or less can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08G 101: 00) C08L 75:04

Claims (3)

[Claims] 1. A fine cell structure polyurethane elastomer obtained by mixing an isocyanate-terminated prepolymer, a hydroxyl group-terminated prepolymer and a foaming component, stirring and foam-curing, wherein the isocyanate-terminated prepolymer has a number average molecular weight of 1,000 to 3,000. Of polyester polyol and diphenylmethane-4,4′-diisocyanate,
The hydroxyl group-terminated prepolymer is obtained by reacting at a weight ratio of 1: 0.2 to 0.6, and the polyisocyanate is added in an amount of 0.05 to 0.05 to 1 mol of the polyester polyol.
A fine cell structure polyurethane elastomer characterized in that it is reacted with 0.5 mol and the foaming component contains water as a main foaming agent. 2. The polyisocyanate is 3,3′-
The microcellular polyurethane elastomer according to claim 1, which is dimethyl-4,4'-biphenylene diisocyanate. 3. The isocyanate-terminated prepolymer according to the following measurement method has a viscosity of 2500 centipoise or less, and the elastomer has a durability test of 500,000 or more and a sag amount of 10% or less in a durability test. Item 1. A polyurethane elastomer having a fine cell structure according to item 1 or 2. Viscosity: B-type viscometer, rotor rotation speed: 30 rpm, rotor No. 3, measurement temperature: 80 ° C. Durability: Number of times to break when a load of 4.75 kN is repeatedly applied to the test piece at a cycle of 2 Hz. Set amount: The value obtained by subtracting the height of the test piece after measurement from the height of the test piece before measurement of the above-mentioned durability count, divided by the height of the test piece before measurement, and multiplied by 100.