Polyurethane

Details Polyurethane Polyurethane

1996-05-20

1997-09-16

Short, Patricia A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

528 80, 528 83, C08G 1842

Patent

active

056682239

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a polyurethane having excellent hydrolysis resistance, weatherability, alkali resistance, etc. Said polyurethane is useful as a material for extrusion molding products such as hoses, tubes, films, sheets, belts, and rolls, a material for injection molding products such as packing materials, mechanical parts, and automobile parts, a material for artificial leathers, and coating materials such as paints, etc.


BACKGROUND ART

Polyurethane is produced by reacting a polyester polyol or a polyether polyol with a polyisocyanate, optionally in the presence of a low molecular weight compound such as diol, or diamine. A polyurethane which is produced by using a polyester polyol is inferior in hydrolysis resistance in comparison with a polyurethane which is produced by using a polyether polyol. On the other hand, the polyurethane which is produced by using a polyether polyol has drawbacks in mechanical properties, weatherability, and oil or solvent resistance. Therefore, the use of these polyurethanes is restricted.
A polyurethane which is produced by using a polycarbonate polyol is improved with respect to the faults described above. However, it does not have sufficient cold resistance and is very expensive. Thus its industrial utilization is restricted.
Some polyurethanes produced by using a polyester are known as polyurethanes having relatively good hydrolysis resistance; for example, a polyurethane which is produced by using a polycaprolactone polyol (Polyurethane Resin Handbook, published by Nikkan Kogyo Simbun on Sep. 25, 1987), and polyurethanes which are produced by using branched chain diols such as neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol (Japanese Published Unexamined Patent Application No. 229918/85), and 3-methyl-1,5-pentanediol (Japanese Published Examined Patent Application No. 54966/92). However, the hydrolysis resistance of these polyurethanes is insufficient for practical use.
It is desired to develop a polyurethane having excellent hydrolysis resistance, weatherability, alkali resistance, etc.


DISCLOSURE OF THE INVENTION

The present invention relates to a polyurethane having a polyester polyol in the molecule, said polyester polyol having a structural unit represented by formula (I): ##STR1##
The polyurethane of the present invention can be produced by reacting a polyester polyol with a polyisocyanate.
The polyester polyol can be obtained from 2,4-diethyl-1,5-pentanediol which is a component of the structural unit represented by formula (I) and dicarboxylic acid, according to a known method (e.g., the method described in Japanese Published Unexamined Patent Application No. 101496/73), for example, subjecting them to dehydration polycondensation under heating, optionally under reduced pressure.
As the dicarboxylic acid, succinic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, etc. are used alone or in combination. A part of 2,4-diethyl-1,5-pentanediol may be replaced with other diols. In this case, the ratio of 2,4-diethyl-1,5-pentanediol in the total diol is 30% or more, preferably 40% or more. Examples of other diols are ethylene glycol, propylene glycol, 1,4-butylene glycol, diethylene glycol, 1,6-hexane glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-l,5-pentanediol, and 1,4-bis(.beta.-hydroxyethoxy)benzene. When these diols other than 2,4-diethyl-1,5-pentanediol are used, the polycondensation proceeds at random.
The number-average molecular weight of the polyester polyol is 400.about.8,000, preferably 700.about.5,000.
Examples of the polyisocyanate are aromatic diisocyanate such as diphenylmethane diisocyanate, and 2,4-tolylene diisocyanate, alicyclic diisocyanate such as isophorone diisocyanate, and aliphatic diisocyanate such as hexamethylene diisocyanate, which are used alone or in combination.
The polyurethane can be produced by known polyaddition techniques for the formation of urethane. That is, the polyester polyol obtained as above and a low molecular weight compound having two or more active hy

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