JPH0127089B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is an anti-vibration cushioning material used in the manufacture of urethane sponge products that has excellent durability especially in terms of dynamic characteristics (breakage and fatigue) when repeatedly subjected to extremely large loads of 50 to 80% from the initial state. The present invention relates to a urethane elastomer composition for use. Urethane sponge products are lightweight and have excellent properties such as rubber elasticity, abrasion resistance, and weather resistance, so they are being considered for application as vibration isolating materials for passenger car shock absorbers and vehicle shaft springs. . Urethane elastomer compositions for vibration-proofing and cushioning materials for manufacturing urethane sponge products include 1,
5-Naphthalene diisocyanate (hereinafter referred to as “NDI”)
It is widely known that a crosslinking agent is uniformly mixed into a prepolymer obtained by reacting a polyester polyol with a polyester polyol. However, there are problems in using this composition because the above-mentioned NDI is extremely expensive and its manufacturing workability is poor. Therefore, instead of NDI, methylene diisocyanate (hereinafter abbreviated as "MDI") was used.
It is considered to use However, urethane sponge products manufactured from compositions using MDI instead of NDI,
Compared to urethane sponge products made from compositions using NDI, static properties such as specific gravity, tensile strength, elongation, tearing, etc., or dynamic properties when repeatedly subjected to a relatively small load of 0 to 50% from the initial state. The durability of shock absorbers for passenger cars is almost the same, but the dynamic properties when repeatedly subjected to a large load of 50 to 80% from the initial state, especially the durability against breakage and fatigue, are significantly worse. It was thought that stress could not be applied to vibration isolators and vibration isolators for vehicle axle springs. In view of this, the inventors used MDI, which is inexpensive and has good manufacturing workability, and managed to create a urethane elastomer composition for vibration-proofing and cushioning materials that has good durability in terms of dynamic properties when repeatedly subjected to large loads. While conducting a series of researches to see if it would be possible to produce a product, we selected a specific polyester diol as a polyester polyol, and created a reaction product by reacting this polyester diol with 4,4'-diphenylmethane diisocyanate as "MDI". The inventors discovered that the intended purpose could be achieved by using a prepolymer, and completed this invention. That is, this invention applies a foaming/crosslinking agent mainly containing water to a prepolymer obtained by reacting a polyester diol shown in the following item (A) with 4,4'-diphenylmethane diisocyanate. The gist of the present invention is a urethane elastomer composition for vibration damping and cushioning materials, which is characterized in that it is uniformly mixed. (A) Mixing molar ratio of both ethylene glycol (EG) and butylene glycol (BG) (EG/BG)
A polyester diol obtained by condensing a mixture of 70/30 to 30/70 with aadipic acid. As mentioned above, the specific polyester diol used in this invention contains ethylene glycol (EG) and butylene glycol (BG) at a mixing molar ratio (EG/BG) of 70/30 to 30/70, preferably 50. It is obtained by a condensation reaction between a mixture adjusted to have a ratio of 10% to 50% and adipic acid, and a polyester diol obtained by condensing ethylene glycol (EG) and adipic acid, butylene glycol (BG), and adipic acid. The object of the present invention cannot be achieved by mixing and adjusting the above ratio with a polyester diol obtained by condensation reaction. i.e. ethylene glycol (EG) and butylene glycol (BG) 70/30~3
Only by using polyester diol obtained by condensation reaction of a mixture adjusted at a ratio of 0/70 and adipic acid, it is possible to reduce the
A urethane elastomer composition for anti-vibration and cushioning materials that has a good recovery rate and quickly returns to its original state without breaking or faltering even after being repeatedly subjected to extremely large loads of 80%. in,
This is because a polyester diol obtained by reacting a mixture outside the above range with adipic acid cannot produce a product that satisfies the above properties. The adipic acid used in the condensation reaction with the mixture of ethylene glycol and butylene glycol is a commonly used adipic acid, and the condensation reaction is carried out in a conventional manner. Also, as MDI to be reacted with the above specific polyester diol, only 4,4'-diphenylmethane diisocyanate (pure MDI) is effective, and the reason for this is that 4,4'-diphenylmethane diisocyanate has a large number of functional groups is 2, the reaction product (prepolymer) with the above specific polyester diol has a chain structure, and the resulting urethane elastomer composition for vibration damping and cushioning materials can be a product with excellent breaking strength. On the other hand, MDI other than 4,4'-diphenylmethane diisocyanate, such as crude MDI and carbodiimide-modified MDI, have an average number of functional groups of 2 to 3, and the reaction product (prepolymer) has a network structure. This is because only products with poor elongation and low breaking strength can be obtained from the resulting urethane elastomer composition for vibration-proof and cushioning materials. Thus, in this invention, a special prepolymer obtained by reacting the above-mentioned specific polyester diol and 4,4'-diphenylmethane diisocyanate is used. A urethane sponge product can then be obtained by uniformly mixing and foaming a foaming/crosslinking agent mainly composed of water with this prepolymer. ^In this case, the density of the resulting product is adjusted by known methods (e.g. ^, adjusting the filling density of the mold, foaming, crosslinking, It is preferable to adjust the amount of the agent used, etc. In other words, by adjusting the density of the urethane sponge product as described above, it can be reduced by 50 to 80% from its initial state.
This is because the dynamic properties when repeatedly subjected to large loads, especially the durability against breakage and fatigue, are the best. In addition, in the mutual usage ratio of 4,4'-diphenylmethane diisocyanate and the above specific polyester diol, the NCO/OH molar ratio of the NCO group of 4,4'-diphenylmethane diisocyanate and the OH group of the polyester diol Choosing a value between 1.5 and 4.0 is also one of the more effective factors. In other words, when the NCO/OH molar ratio is less than 1.5, the viscosity of the prepolymer increases, resulting in insufficient mixing, and the resulting urethane elastomer composition for vibration damping materials is likely to break when repeatedly subjected to large loads. On the other hand, if it exceeds 4.0, it will not be sufficiently prepolymerized and excess isocyanate will remain, resulting in a urethane sponge product that has poor elongation and is easily broken when compressed repeatedly under heavy loads. It is from. The above specific polyester diol and 4,4′-
The foaming/crosslinking agent to be mixed with the reaction product (prepolymer) with diphenylmethane diisocyanate is not particularly limited, but it is more effective to use one mainly composed of water. Here, the term "mainly composed of water" means that water accounts for 0.5 equivalent or more of the foaming/crosslinking agent, and also includes the case where the foaming/crosslinking agent is entirely composed of water. Foaming/crosslinking agent components other than water include polyols such as ethylene glycol and butylene glycol. If a crosslinking agent other than a water-based foaming/crosslinking agent is used, for example, a polyol-based one, the resulting polyurethane elastomer will not have a well-organized network, but will have a disordered network in some places. This is because when repeatedly compressed under a load (compression ratio of 50 to 80%), the recovery rate is poor and the material is easily destroyed. On the other hand, if a foaming/crosslinking agent based on water is used (water acts as a curing agent and also as a blowing agent),
This results in a polyurethane elastomer sponge body that has a well-aligned molecular arrangement, does not have the above-mentioned drawbacks, and is lightweight. Therefore, it is more effective to use a foaming/crosslinking agent mainly composed of water to be mixed into the prepolymer. The method of mixing the prepolymer and the foaming/crosslinking agent mainly composed of water is not limited in any way, and various methods can be used. Further, the composition according to the present invention can further contain other components as necessary to make the composition suitable for the purpose. The urethane elastomer composition for vibration-proof cushioning materials according to the present invention uses 4,4'-diphenylmethane diisocyanate as the isocyanate in place of conventional NDI in the prepolymer obtained by reacting polyester diol and isocyanate. This has the effect of improving manufacturing workability and lowering the cost of urethane elastomer sponge products. In addition to the above effects, by using a specific polyester diol and 4,4'-diphelmethane diisocyanate in combination, the conventional combination of polyester diol and MDI can repeatedly apply a large load of 50 to 80% from the initial state. Breaking away from the conventional wisdom that it cannot be applied to products that require dynamic properties, it does not break or collapse prematurely even when repeatedly subjected to high compressive loads of not only 0-50% but also 50-80% of the initial state. We are now able to manufacture products with a high recovery rate that quickly return to their original state without any damage, and are widely used in products that are subject to repeated heavy loads, such as vibration isolators for shock absorbers in passenger cars and vibration isolators for shaft springs in vehicles. This has the effect of being applicable. Next, examples will be described together with comparative examples. [Example] First, a polyester diol (hereinafter abbreviated as "P(E/B)A") obtained by reacting a mixture of EG/BG = 50/50 with adipic acid and 4,4'-diphenyl The following amounts of enylmethane diisosocyanate and a foaming/crosslinking agent mainly composed of water were prepared. P(E/B)A (molecular weight: 2000)
: 100 parts by weight (hereinafter referred to as "parts") Pure MDI: 30 parts Water: 1.1 parts Urethane catalyst: 0.1 part Next, P(E/B)A was charged into a dehydrator, dehydrated, and transferred to a reaction equipment. Pure MDI was added thereto and reacted at 80°C for 2 hours to produce a prepolymer. Next, water and a urethanization catalyst were added to the produced prepolymer, and the mixture was sufficiently stirred and mixed at 80°C, and then cast into a mold and molded. Next, this molded product
After curing at 110°C for 24 hours, the product was aged at room temperature for 7 days to obtain the desired urethane sponge product. The static and dynamic properties of the urethane sponge product thus obtained are shown in the table below in comparison with the properties of the urethane sponge product obtained in the same manner as in the example using the raw materials shown in the table below. .

[Table] The static properties and dynamic properties were measured as follows. (1) Static properties Γ Specific gravity, tensile strength, elongation, tearing are based on JIS
Measured according to K6301. (2) Dynamic characteristics Γ Fatigue settling: A sample with dimensions of 30 x 30 x 25 (thickness) mm was sandwiched between a pair of templates and compressed to a compression ratio of 55%. Then, after further compressing to a compression ratio of 70%, the compression force is loosened again to a compression ratio of 55%, and this is counted as one time.
Hz x 200,000 times. After conducting the test in this manner, the state of settling of the sample was compared with the initial state. Γ Durability: A load of 700 kg is applied to the surface of the test sample to compress it (compression ratio 70%), and then the load is removed. This was done once and repeated at intervals of 2 Hz until the sample was destroyed, and the number of times was measured.

Claims (1)

[Scope of Claims] 1. A foaming/crosslinking agent mainly composed of water is added to a prepolymer obtained by reacting the polyester diol shown in the following item (A) with 4,4'-diphenylmethane diisocyanate. A urethane elastomer composition for vibration-proof cushioning material, characterized in that it has a density of 0.3 to 0.7 g/cm ³ when mixed uniformly to form a foamed product. (A) Ethylene glycol (EG) and butylene glycol (BG) at a mixing ratio (EG/BG) of 7.
A polyester diol obtained by condensing a mixture adjusted to have a ratio of 0/30 to 30/70 with adipic acid. 2 The ratio of polyester diol and 4,4'-diphenylmethane diisocyanate is
The NCO/OH molar ratio between the NCO group and the latter OH group is 1.5
The urethane elastomer composition for a vibration-proof cushioning material according to claim 1, wherein the urethane elastomer composition is selected to have a value of 4.0.