Cooling medium for use at elevated temperatures

Details Cooling medium for use at elevated temperatures Cooling medium for use at elevated temperatures

1998-04-03

2001-03-27

Gupta, Yogendra (Department: 1751)

Compositions

Heat-exchange, low-freezing or pour point, or high boiling...

Organic components

C252S070000

Reexamination Certificate

active

06207072

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cooling mediums at elevated temperatures, such as 130° C.
2. Description of the Prior Art
Heat-stabilized, glass-fibre-reinforced polyamide (PA) 66 is successfully used throughout the world in motor vehicle coolant systems. The economical and efficient manufacture of cooling water tanks, water pipes and thermostatic valve housings in addition to high dynamic loading capacity and resistance to the cooling medium at 108° C. predestines PA 66 for this field of application. Development work to increase the efficiency of internal combustion engines expects higher temperature stresses in the cooling medium. Demands on mechanical properties following contact with the cooling medium at 130° C. are increasing.
A mixture comprising ethylene glycol:water in the ratio 1:1 is described as cooling medium in the motor vehicle field. The mixture solidifies at −30° C. and boils at 108° C. Azeotropic distillation is not involved. First of all, the water distils off at 108° C. The temperature of the boiling material increases as the ethylene glycol content increases, until pure glycol distils at 197.4° C.
If the temperature of the cooling medium in the closed cooling system rises to 130° C., the internal pressure rises to 2 bars. With the increase in the operating temperature of the cooling medium, in addition to very good tightness, high mechanical strength values at 130° C. in the state saturated with cooling medium are a prerequisite for the operation of the cooling system. If part of the cooling medium escapes as steam, the ethylene glycol content in the cooling medium increases. Components made of polyamide may partially dissolve if glycol content and temperature increase perceptibly.
The object of the invention was therefore to develop a cooling medium which operates at the desired temperatures (approx. 130° C.) without pressure increase and does not perceptibly impair the mechanical properties of polyamide.
The invention provides a cooling medium containing
A) 35-65, preferably 45 to 55 wt. % of polyethylene glycol
B) 35-65, preferably 45 to 55 wt. % of ethylene glycol.
The cooling medium is suitable for cooling motor vehicle engines.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Polyethylene glycols of the formula HO—(CH
2
—CH
2
—O)
n
—H, with an average molar mass between 285 and 420 g/mol, a hydrolysis value between 271-315 and a density between 1.12-1.15 g/cm
3
are suitable as polyethylene glycol (A) of the mixture according to the invention.
Technical ethylene glycols of the formula HO—CH
2
—CH
2
—OH, a molar weight of 60.05 g/mol and a density of 1.10 to 1.13 g/cm
3
are suitable as ethylene glycol (B) of the mixture according to the invention.
Stabilizers may additionally be added to the mixture.
Metal deactivators, phosphites and anti-oxidants, such as are conventionally used in the stabilization of a cooling medium, are suitable as stabilizer. The stabilizer is conventionally added in quantities up to 2 wt. %, related to 100 wt. % of mixture comprising A) and B).
It has surprisingly been found that glass-fibre-reinforced PA 6 is also resistant to this cooling medium at 130° C. PA 6 can therefore also be used for the manufacture of components in the cooling system, such as cooling water tanks, thermostatic valve housings, cooling water pipes.
The glass fibre content is generally 25-45 wt. %, preferably 30-35 wt. % (related to the total moulding compound).


REFERENCES:
patent: 4320025 (1982-03-01), Diebel
patent: 4873011 (1989-10-01), Jung et al.
patent: 5064552 (1991-11-01), Oppenlaender et al.
patent: 5073283 (1991-12-01), Goddard et al.
patent: 5213669 (1993-05-01), Guttman
patent: 242 900 (1987-10-01), None
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patent: 131751 (1985-12-01), None
patent: 157616 (1992-06-01), None
patent: 161390 (1993-06-01), None
Chemical Abstracts 82:35387, Chudnov et al, “Effect of the Additions of Polyethylene Glycols on the Freezing Temperature of Di-and Triethylene Glycols”, 1974 No Month Available.

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