JP3420628B2 - Microcellular polyurethane elastomer and method for producing the same - Google Patents

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 and a method for producing the same. 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
Polyester polyol having a number average molecular weight of 1,000 to 3,000, obtained by polycondensing one or more kinds of 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,
An isocyanate-terminated prepolymer obtained by reacting with a polyisocyanate such as 3'-dimethyl-4,4'-biphenylene diisocyanate (hereinafter also referred to as a prepolymer), water, a catalyst, a foam stabilizer and the like. It is obtained by mixing and stirring the foaming component with stirring.

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 expensive and
The prepolymer obtained by the reaction of polyester polyol and NDI has a problem that the usable time thereof is short. On the other hand, M which is a general-purpose polyisocyanate component
DI is inexpensive, has good workability in the production of elastomers, and has a long usable prepolymer time, but to obtain an elastomer having sufficient performance in terms of mechanical strength, durability, etc. I can't.

[0004]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional polyurethane elastomers having a fine cell structure and is inexpensive as a polyisocyanate component.
Using DI, a prepolymer with a long service life is obtained,
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, and a method for producing the same.

[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 with a foaming component, stirring and foaming and curing the mixture. The polymer has a number average molecular weight of 1,000 to
3000 polyester polyol and diphenylmethane-4,4′-diisocyanate were mixed at 1: 0.2 to
The reaction is carried out at a weight ratio of 0.6, and thereafter, ethylene glycol, propylene glycol, 100 parts by weight of a reaction product of the polyol and the diisocyanate ,
1,4-butylene glycol, 1,5-pentamethylene
Glycol, 1,6-hexamethylene glycol and g
At least one selected from the group of trimethylolpropane
(Hereinafter, these are collectively referred to as "low molecular weight polyol".
U ) And are those obtained by addition reacting 0.1 to 2.0 parts by weight, the foaming component is characterized in that it is intended to include water as a main blowing agent. The second invention is characterized in that the resulting elastomer has a durability test of 500,000 times or more, a sag amount of 10% or less, and a usable time of the prepolymer of 4 hours or more. And

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 prepolymer produced by the reaction with the polyester polyol has a chain structure, and the resulting elastomer has excellent durability. In addition to pure MDI, for example, crude MDI and carbodiimide-modified MDI have an average number of functional groups of 2 to 3, a disordered network structure is formed in the prepolymer, and the resulting elastomer has a small elongation and is subjected to repeated heavy load. It becomes inferior in durability such as fatigue fracture.

The above-mentioned "isocyanate-terminated prepolymer"
Is the polyester polyol and the MDI are 1:
It is obtained by reacting in a weight ratio of 0.2 to 0.6. MDI
Is less than 0.2 relative to polyester polyol 1,
The free MDI content in the prepolymer is reduced,
When the prepolymer is formed, the viscosity of the liquid increases and the workability decreases. On the other hand, when it exceeds 0.6, the content of free MDI in the 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 "low molecular weight polyol" include ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,5-pentamethylene glycol, 1,6-hexamethylene glycol, trimethylolpropane and the like. Short chain low molecular weight alkylene polyols having 3 to 3 active hydrogen groups can be used. The "foaming component containing water as a main foaming agent" of the present invention is
In addition to water which is the main foaming agent, a catalyst, a foam stabilizer and the like are added. 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 have a network structure with a well-ordered molecular arrangement and are excellent in mechanical strength and especially in fatigue fracture when repeatedly subjected to a large load and durability against fatigue.

In the method for producing a fine cell structure polyurethane elastomer of the third invention, the number average molecular weight is 1000 to 30.
00 polyester polyol and diphenylmethane-
4,4'-diisocyanate, 1: 0.2-0.6
At a weight ratio of 100 parts by weight of the reaction product of the polyol and the diisocyanate.
Low molecular weight polyol (ethylene glycol, propylene
Glycol, 1,4-butylene glycol, 1,5-pepylene
N-methylene glycol, 1,6-hexamethylene glycol
A few selected from the group of coal and trimethylolpropane
0.1 to 2.0 parts by weight of at least one kind) is added and reacted to obtain a partially cross-linked isocyanate-terminated prepolymer, and then a pre-polymer and a foaming component containing water as a main foaming agent. Are mixed, stirred and reacted.

In the above method, after the reaction of the polyester polyol and MDI, before the addition of the foaming component containing water as the main foaming agent (in the absence of the foaming agent), the reaction formation of the polyester polyol and MDI is produced. A low molecular weight polyol is added to the product and reacted to prepare a prepolymer partially cross-linked. By partially cross-linking the prepolymer in this way, ND can be used even though MDI is used as the polyisocyanate.
An elastomer having the same mechanical strength and durability as when I is used can be obtained. In addition, the addition amount of the low molecular weight polyol is characterized in that it is a very small amount of 0.1 to 2.0 parts by weight with respect to 100 parts by weight of the reaction product of the polyester polyol and MDI. Within the above range, the resulting elastomer has a network structure with a well-ordered molecular arrangement, and excellent mechanical strength and durability are realized.

In the present invention, the prepolymer and the foaming component are mixed and used so that the isocyanate equivalent of the prepolymer and the hydroxyl equivalent of the foaming component are in the range of 0.9 to 1.2. . Further, other auxiliary agents can be used if necessary. As such auxiliary agents, various additives such as various liquid flame retardants, diluents or antioxidants, ultraviolet absorbers, coloring agents, etc. for decreasing the viscosity of the elastomer raw material and facilitating stirring and mixing, etc. Is mentioned. 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, the reaction product of the polyester polyol and MDI is allowed to react with a small amount of a low molecular weight polyol before contacting with water or the like which acts as a foaming agent and a cross-linking agent, thereby forming the above reaction product. It is considered that a part of the molecule is bonded by a cross-linking reaction to form a prepolymer having an enhanced internal structure.
Despite the use of DI, it is possible to obtain an elastomer having the same excellent durability and the like as in the case of the prepolymer using NDI as the polyisocyanate.

[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) Polyester polyol Polyethylene adipate polyester polyol:
Product name “ODX-102” manufactured by Dainippon Ink and Chemicals, Inc. (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: 1000, hydroxyl value: 112) Poly (ethylene / butylene) adipate polyester polyol: Product name "ODX-1" manufactured by Dainippon Ink and Chemicals
05 "(number average molecular weight; 2000, hydroxyl value; 56)

(C) Low molecular weight polyol Ethylene glycol: manufactured by Nisso Yuka Kogyo Co., Ltd. (number average molecular weight: 62, hydroxyl value; 1808) 1,4-butylene glycol: manufactured by BASF (number average molecular weight: 90, hydroxyl value) 1245) 1,6-hexane glycol: manufactured by BASF (number average molecular weight: 118, hydroxyl value: 950) (d) Mixture mainly composed of foaming agent water: manufactured by Sumitomo Bayer, trade name "Additive SM" (e ) Catalyst triethylenediamine (main component): Sankyo Air Products, trade name "DABCO 33LV" (f) Foam stabilizer silicone type: Toray Dow Corning Silicone, trade name "SF-2962"

(3) Method of Measuring Physical Properties The performance test was performed on the fine cell structure polyurethane elastomers obtained in Examples and Comparative Examples by the following methods. (a) Specific gravity: The weight of a test piece (dimensions: 120 × 100 × 3 mm) is divided by its volume. (b) Tensile strength, elongation at break: conforming to JIS K 6301, using No. 3 dumbbell (c) Tear strength: conforming to JIS K 6301, using B-type dumbbell, tensile speed; 500 mm / min (d) Durability : Add 4.75 KN to the test piece repeatedly at a frequency of 2 Hz, and record the number of times until destruction. Fifty
The goal is not to be destroyed even if the load is applied 10,000 times. (e) Settling: The value obtained by subtracting the height of the test piece after the test from the height of the test piece before the durability test is divided by the height of the test piece before the test and multiplied by 100 to express the value. (f) Prepolymer usable time: After preparation of the prepolymer,
Elastomer using the prepolymer does not cause cracking or swelling during demolding, and is expressed as the time required to obtain a good product.

(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 polyester polyol is 100 parts by weight.

[0018]

[Table 1]

Examples 1 to 4 and Comparative Examples 1 to 2 Polyester polyols and polyisocyanates shown in the section of prepolymer in Table 1 were put into a reactor and reacted, and then the obtained reaction products were added. A low molecular weight polyol is added, stirred, mixed and reacted to obtain an isocyanate-terminated prepolymer. On the other hand, the foaming agent, the catalyst and the foam stabilizer shown in the item of foaming component in Table 1 are mixed and stirred uniformly.
The prepolymer and the foaming component were each adjusted to a predetermined temperature, mixed and stirred at a predetermined ratio, and then cast into a mold to obtain a polyurethane elastomer having a relatively low foaming ratio.
The physical properties of the obtained elastomer were measured according to the methods described above. The results are shown in Table 2.

[0020]

[Table 2]

According to the results shown in Table 2, an example using a prepolymer obtained by adding a low molecular weight polyol to a reaction product of a polyester polyol and a polyisocyanate and adding it to the reaction product before adding a foaming component to the reaction product In Nos. 1 to 4, the obtained elastomer had excellent tensile strength, tear strength, etc., regardless of the type of polyester polyol and low molecular weight polyol used, and the durability test results were 500,000 times. Fatigue fracture does not occur even after the repeated load of 5 and the amount of fatigue is 5 to 6
It can be seen that it has very excellent durability at about%. Further, the usable time of the prepolymer is as long as 6 hours.

On the other hand, in Comparative Example 1 in which a foaming component composed of a direct foaming agent, a catalyst and a foam stabilizer was added to the reaction product of polyester polyol and polyisocyanate, the tensile strength, tear strength and usable time of the prepolymer were determined. Shows almost the same performance as that of each example, but in the durability test, the test piece fatigue-fractured under a 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, the mechanical strength and durability were comparable to and excellent in each Example, but the usable time of the prepolymer was 3 hours, which is half of each Example. 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. For example, with respect to the reaction product of polyester polyol and polyisocyanate, in Examples 1-2, 0.1-1.0
Parts by weight of ethylene glycol, in Example 3 0.1-1.5 parts by weight of 1,4-butylene glycol and in Example 4 0.2-2.0 parts by weight of 1,6-hexahexaene. By adding methylene glycol and reacting it, a prepolymer having a long usable time can be obtained as in each example, and an elastomer having excellent mechanical strength and durability can be obtained.

[0024]

The fine cell structure polyurethane elastomer of the first invention maintains the advantage that the prepolymer can be used for a long time when MDI is used as the polyisocyanate constituting the prepolymer, and It is possible to improve the fatigue fracture or settling when repeatedly receiving a large load, which has been a drawback, and to obtain an elastomer whose durability is equivalent to that when NDI is used as polyisocyanate. Further, in the second invention, the durability of the elastomer in the durability test is 500,000 times or more,
It is possible to obtain a polyurethane elastomer having a fine cell structure in which the amount of sag is 10% or less and the usable time of the prepolymer is 4 hours or more. Furthermore, in the third invention, the foaming component is caused to act on the specific prepolymer partially cross-linked by the low molecular weight polyol, whereby the excellent elastomer of the first and second inventions can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI C08L 75:04 (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 18/08-18/12 C08G 18/65 -18/66 C08G 18/40-18/42 C08J 9/00-9/02

Claims (3)

(57) [Claims] 1. A fine cell structure polyurethane elastomer obtained by mixing an isocyanate-terminated prepolymer and a foaming component, stirring and foaming and curing the mixture, wherein the prepolymer has a number average molecular weight of 1,000 to 300.
0 polyester polyol and diphenylmethane-
4,4'-diisocyanate, 1: 0.2-0.6
At a weight ratio of 100 parts by weight of the reaction product of the polyol and the diisocyanate.
Ethylene glycol, propylene glycol, 1,4-
Butylene glycol, 1,5-pentamethylene glycol
1,6-hexamethylene glycol and trimethylo
At least one selected from the group of propane
˜2.0 parts by weight was added and reacted, and the foaming component contains water as a main foaming agent. 2. The fine particles according to claim 1, wherein the elastomer has a durability test of 500,000 times or more, a set amount is 10% or less, and a usable time of the prepolymer is 4 hours or more. Cell structure polyurethane elastomer. 3. A polyester polyol having a number average molecular weight of 1000 to 3000 and diphenylmethane-4,4 '.
Diisocyanate is reacted in a weight ratio of 1: 0.2 to 0.6, and then ethylene is added to 100 parts by weight of a reaction product of the polyol and the diisocyanate.
Glycol, propylene glycol, 1,4-butylene
Glycol, 1,5-pentamethylene glycol, 1,
6-hexamethylene glycol and trimethylol pro
0.1-2.0 at least one selected from the group of bread
Partially crosslinked isocyanate-terminated prepolymer is obtained by adding parts by weight, and then the prepolymer and a foaming component containing water as a main foaming agent are mixed, stirred and reacted. Method for producing cell structure polyurethane elastomer.