WO2006107119A1

WO2006107119A1 - Heat transfer fluid composition for injection molder

Info

Publication number: WO2006107119A1
Application number: PCT/KR2005/000976
Authority: WO
Inventors: Dae-Woon Park; Jin-Ho Kim
Original assignee: SK Chemicals Co Ltd
Current assignee: SK Chemicals Co Ltd
Priority date: 2005-04-04
Filing date: 2005-04-04
Publication date: 2006-10-12
Anticipated expiration: 2007-10-04
Also published as: CN101155894A

Abstract

The present invention relates to a heat transfer fluid composition for an injection molder, and more particularly to a heat transfer fluid composition for an injection molder comprising a glycol or its derivatives, an azole compound, specific an organic acid, and an aromatic compound which does not generate a vapor pressure, producing less scales, and preventing corrosion of metals by inhibiting pH drop, compared with the conventional water-based heat transfer fluid; and causing less thermal oxidation and carbonization, preventing offensive odor, discoloration, and carbide formation, having superior thermal stability sufficient to be used inthe temperature range of from room temperature to 200 °C, preventing generation of metal ions which catalyze thermal oxidation, and minimizing byproduct formation by thermal oxidation, compared with the conventional oil-based heat transfer fluid.

Description

HEAT TRANSFER FLUID COMPOSITION FOR INJECTION MOLDER

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a heat transfer fluid composition

for an injection molder, and more particularly to a heat transfer fluid

composition for an injection molder which does not generate a vapor

pressure, producing less scales, and preventing corrosion of metals by

inhibiting pH drop, compared with the conventional water-based heat

transfer fluid, and causing less thermal oxidation and carbonization,

preventing offensive odor, discoloration, and carbide formation, having

superior thermal stability sufficient to be used in the temperature range of

from room temperature to 200 °C , preventing generation of metal ions

which catalyze thermal oxidation, and minimizing byproduct formation by

thermal oxidation, compared with the conventional oil-based heat transfer

fluid.

(b) Description of the Related Art

A heat transfer fluid for an injection molder should be capable of

being used in a broad temperature range, have good heat transfer efficiency, and be capable of preventing scale formation and metal

corrosion.

Particularly, because water is used as heat transfer fluid for an

injection molder at a condition of under 100 "C , scales may cause a rupture

of the heater or corrosion of the molder. At a high-temperature condition

in which water cannot be used, an oil-based heat transfer fluid is used.

When mineral oil is used as an oil-based heat transfer fluid, it is easily

carbonized to be deposited inside the system as carbide, thereby

interrupting flow of the heat transfer fluid. In addition, thermal oxidation is

accompanied by carbonization and an offensive odor is generated.

Although a synthetic oil has been developed to solve the problems of the

mineral oil, it is expensive and smells offensive. In addition, the mineral oil

or the synthetic oil tends to contaminate industrial apparatuses easily.

I Currently, several glycol-based heat transfer fluids are known.

U.S. Patent No. 4,758,367 discloses a heat transfer fluid

comprising a glycol which comprises at least 91% triethylene glycol and a

mixture of metal oxide additives selected from the group consisting of

chromate, molybdate, and tungstate, which can be used in the temperature range of 93-204 ^°C. U.S. Patent No. 5,766,506 discloses a heat transfer

fluid comprised of a copolymer additive is to offer compatibility with hard

water. This heat transfer fluid also comprises a phosphate. Specifically,

it comprises 91-92% of an alkylene glycol, an alkylene glycol monoether,

and an alkylene glycol diether. U.S. Patent No. 5,484,547 discloses a

heat transfer fluid comprising 30-60 wt% of glycol, which can be used at a

low temperature. For the glycol, propylene glycol, glycerol, 1 ,3-butanediol,

diethylene glycol, triethylene glycol, etc. are used.

However, these heat transfer fluids are easily oxidized by heat

under the operation conditions of the injection molder, thereby experiencing

deterioration, negatively affecting such equipment as pumps and causing

corrosion of metals.

Although such additives as borate, phosphate, and amine are used

to prevent pH drop caused by a variety of acidic materials generated by

thermal oxidation of glycol, these buffer additives are not suitable to be

used at high temperature and may give a contrary effect.

Accordingly, research on heat transfer fluids causing less scaling,

being resistant to corrosion of metals, being capable of preventing thermal oxidation, offensive odor, discoloration, and carbide formation and having

superior thermal stability are urgently needed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a heat transfer

fluid composition for an injection molder generating a smaller vapor

pressure, producing less scales, and preventing corrosion of metals by

inhibiting pH drop, compared with the conventional water-based heat

transfer fluid, and causing less thermal oxidation and carbonization and

preventing offensive odor, discoloration, and carbide formation, compared

with the conventional oil-based heat transfer fluid.

It is another object of the present invention to provide a heat

transfer fluid composition for an injection molder having such superior

thermal stability so as to be used in the temperature range of from room

temperature to 200 °C , being capable of preventing generation of metal ions

which catalyze thermal oxidation, and being capable of minimizing

byproduct generation by thermal oxidation.

To attain the objects, the present invention provides a heat transfer

fluid composition for an injection molder comprising a) a glycol or its derivatives,

b) an azole compound,

c) an organic acid represented by the following Chemical Formula

1, and

d) an aromatic compound represented by the following Chemical

Formula 2:

R₁-COOH (1)

where

R₁ is an alkylbenzyl group having 1-8 carbon atoms or an alkyl

group having 1-8 carbon atoms; and

Ar-X (2)

where

X is -COOH, -SO₃H, or SO₂Ar and

Ar is represented by Chemical Formula 2-1 below:

where

R₂ is a hydrogen or an alkali metal, and R₃ is hydroxyl, alkyl, hydroxyalkyl, heteroalkyl, or

hydroxyheteroalkyl having 1-8 carbon atoms.

Preferably, the heat transfer fluid composition for an injection

molder of the present invention comprises:

a) 90-99.9 wt% of a glycol or its derivatives,

b) 0.01-3.0 wt% of an azole compound,

c) 0.05-5.0 wt% of an organic acid represented by Chemical

Formula 1 , and

d) 0.05-3.0 wt% of an aromatic compound represented by

Chemical Formula 2.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a circulation corrosion test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereunder is given a detailed description of the present invention.

The present inventors worked for a heat transfer fluid generating

less scales, being resistant to metal corrosion, being capable of preventing

thermal oxidation, offensive odor, discoloration, and carbide formation, and

having superior thermal stability. In doing so, they found that when an organic acid is used as an additive in the glycol or its derivatives and the

azole compound replacing the inorganic acid salt and an aromatic

compound having superior thermal oxidation stability is used as a buffer

additive, a heat transfer fluid experiencing less thermal oxidation and

carbonization, being able to prevent offensive odor, discoloration, and

carbide formation, being capable of preventing generation of metal ions

which catalyze thermal oxidation, being able to prevent corrosion of metals

by interrupting pH drop by minimizing generation of thermal oxidation

byproducts and having such superior thermal stability so as to be used in

the temperature range of from room temperature to 200 ^°C can be obtained.

The heat transfer fluid composition for an injection molder of the

present invention is characterized by comprising 90-99.9 wt% of a glycol or

its derivatives, 0.01-3.0 wt% of an azole compound, 0.05-5.0 wt% of an

organic acid represented by Chemical Formula 1 , and 0.05-3.0 wt% of an

aromatic compound represented by Chemical Formula 2.

The glycol or its derivatives used in the present invention is the

basic material of the heat transfer fluid. Because it has a boiling point

higher than that of water and is compatible with water, it can solve the problems of the conventional oil-based heat transfer fluid for an injection

molder.

The glycol or its derivatives may be glycol, diethylene glycol,

triethylene glycol, dipropylene glycol, tripropylene glycol, etc. Particularly,

it is preferable to use diethylene glycol or triethylene glycol, which are

stable in the operation temperature range of the injection molder because

of their high boiling points. More preferably, diethylene glycol, which is

less corrosive in a pure state, is used.

Preferably, the glycol or its derivatives is comprised at 90-99.9 wt%

per 100 wt% of the heat transfer fluid composition. If the content is below

90 wt%, thermal oxidation or carbonization may be promoted and excess

moisture contained in other components may cause the problems of

evaporation and corrosion. Otherwise, if the content exceeds 99.9 wt%,

the corrosion resistance may worsen.

The metal component of the system in which the heat transfer fluid

is used is typically copper, brass, or cast iron.

The azole compound is used to prevent corrosion of alloy.

The azole compound may be tolyltriazole, benzotriazole, 4-phenyI-1 ,2,3-triazole, 2-naphtotriazole, 4-nitrobenzotriazole, etc.

Preferably, benzotriazole is used.

Preferably, the azole compound is comprised at 0.01-3.0 wt%,

more preferably at 0.01-3.0 wt%, and most preferably at 0.05-0.5 wt% per

100 wt% of the heat transfer fluid composition. If the content is below 0.01

wt%, the effect of the azole compound is insufficient. Otherwise, if it

exceeds 3.0 wt%, thermal stability, precipitation stability, etc. may be

negatively affected.

The organic acid represented by Chemical Formula 1 is used to

prevent corrosion of iron-based metals.

Specific examples of the organic acid are benzoic acid,

p-førf-butylbenzoic acid, p-toluic acid, neodecanoic acid, 2-ethylhexanoic

acid, heptanoic acid, octanoic acid, etc. These compounds are used to

prevent corrosion of iron or aluminum metals.

Preferably, the organic acid is comprised at 0.05-5.0 wt%, more

preferably at 0.1-5.0 wt%, and most preferably at 0.1-2.0 wt%, per 100 wt%

of the heat transfer fluid composition. If the content is below 0.05 wt%, the

effect of the organic acid is insignificant. Otherwise, if it exceeds 5.0 wt%, such problems as corrosion and precipitation may occur.

The aromatic compound represented by Chemical Formula 2 acts

as a pH buffer.

Preferably, the aromatic compound is a monocyclic or polycyclic

aromatic compound having at least one hydroxyl group. More preferably,

it is a compound represented by Chemical Formula 3 below.

where, R₂ is a hydrogen or an alkali metal, and R₃ is hydroxyl, alkyl,

hydroxyalkyl, heteroalkyl, or hydroxyheteroalkyl.

Specific examples of the aromatic compound are

4,4'-dihydroxydiphenylsulone, isomers thereof, and mixtures thereof.

These compounds are used as a pH buffer.

Preferably, the aromatic compound is comprised at 0.05-3.0 wt%,

more preferably at 0.1-2.0 wt%, per 100 wt% of the heat transfer fluid

composition. If the content is below 0.05 wt%, the effect of the aromatic

compound is insignificant. Otherwise, if it exceeds 3.0 wt%, it may negatively affect the liquid phase.

The heat transfer fluid composition for an injection molder of the

present invention, which comprises a glycol or its derivatives, an azole

compound, an organic acid, and an aromatic compound, without an

inorganic acid additive, generates a smaller vapor pressure, produces less

scales, and prevents corrosion of metals by inhibiting pH drop, compared

with the conventional water-based heat transfer fluid, and causes less

thermal oxidation and carbonization, prevents offensive odor, discoloration,

and carbide formation, has superior thermal stability sufficient to be used in

the temperature range of from room temperature to 200 °C, prevents

generation of metal ions which catalyze thermal oxidation, and minimizes

byproduct formation by thermal oxidation, compared with the conventional

oil-based heat transfer fluid.

Hereinafter, the present invention is described in more detail

through examples. However, the following examples are only for the

understanding of the present invention and they do not limit the present

invention.

[Examples] Example 1

Additives presented in Table 1 below were added to diethylene

glycol. Thermal oxidation stability was performed at 150 °C for 48 hours.

During the test, copper ions and air were fed therein to facilitate oxidation.

Change of the liquid phase was evaluated by the Gardner color index

method. The results are given in Table 1. The number 1 means

colorlessness. As the number increases, the color darkens to dark brown.

The contents shown in Table 1 are by wt%.

Table 1

As seen in Table 1 , the liquid phase was poor at high temperature

when inorganic acid additives were added to diethylene glycol. On the

contrary, the thermal oxidation stability was superior when organic acid

additives were used. In particular, the thermal stability was best when

aromatic compounds were used as the organic acid additive. Among

them, benzotriazole offered the best thermal stability.

Examples 2-5

Heat transfer fluid compositions comprising 98-99 wt% of

diethylene glycol, 0.15-0.25 wt% of 50% NaOH, 0.2 wt% of benzotriazole,

0.2 wt% of tolyltriazole, 1 wt% of p-f-butylbenzoic acid, 1 wt% of

2-ethylhexanoic acid, and 0.5 wt% of 4,4'-dihydroxydiphenylsulfone were

prepared as in Table 2 below. The pH was maintained at 7.5.

Comparative Examples 1 -2 Heat transfer fluid compositions were prepared in the same manner

of Examples 2-5, except that 4,4'-dihydroxydiphenylsulfone was not used,

as in Table 3 below.

Comparative Examples 3-4

The heat transfer fluid composition of Comparative Example 3 was

prepared in the same manner of Examples 2-5, except that the azole

compound was not used. The heat transfer fluid composition of

Comparative Example 4 was prepared in the same manner of Examples

2-5, except that the compound represented by Chemical Formula 1 was not

used. Contents in Table 2 and Table 3 are by wt%.

Table 2

Thermal oxidation stability and circulation corrosion were tested as

follows for the heat transfer fluid compositions prepared in Example 2 and

Comparative Examples 1-4. The results are given in Tables 4 and 5

below.

a) Thermal oxidation stability - Content of oxidation byproducts

were analyzed with GC (gas chromatography), and change of the liquid

phase was evaluated by the Gardner color scale.

b) Circulation corrosion test - Circulation corrosion test was

performed as depicted in FlG. 1. Weight loss of the standard metal specimen was measured according to ASTM D1384.

Table 4

As seen in Tables 4 and 5, the pH of the heat transfer fluid

compositions in which pH buffers were added (Examples 2-5) changed by

less than -1.0. On the contrary, in heat transfer fluid compositions in which

no pH buffer was added (Comparative Examples 1 and 2), the pH changed

by -2.0 or more. This is because the buffer effectively interrupts pH drop

by formation of oxides, thereby preventing free oxidation of the organic acid

anticorrosive. If the organic acid anticorrosive oxidizes freely, the

corrosiveness increases. In particular, the solder corrodes severely. For

Comparative Example 3, in which no copper anticorrosive was added, the

pH change was not large, but corrosion of copper and brass was severe,

and thus over 10% of oxide byproducts were generated. For Comparative

Example 4, in which no iron anticorrosive was added, corrosion of cast iron

was severe and over 10% of oxide byproducts were generated. As a

result, change of the liquid phase was severe and the pH dropped significantly. However, the heat transfer fluid compositions of the present

invention prepared in Examples 2-5 generated less than 10% of oxidation

byproducts and showed superior corrosion resistance and thermal

oxidation stability.

The heat transfer fluid composition of the present invention

generates a smaller vapor pressure, produces less scales, and prevents

corrosion of metals by inhibiting pH drop, compared with the conventional

water-based heat transfer fluid, and causes less thermal oxidation and

carbonization, prevents offensive odor, discoloration, and carbide formation,

has superior thermal stability sufficient to be used in the temperature range

of from room temperature to 200 "C, prevents generation of metal ions

which catalyze thermal oxidation, and minimizes byproduct formation by

thermal oxidation, compared with the conventional oil-based heat transfer

fluid, without using an inorganic acid additive.

While the present invention has been described in detail with

reference to the preferred embodiments, those skilled in the art will

appreciate that various modifications and substitutions can be made thereto

without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A heat transfer fluid composition for an injection molder comprising

a) a glycol or its derivatives,

b) an azole compound,

c) an organic acid represented by the following Chemical Formula

1 , and

d) an aromatic compound represented by the following Chemical

Formula 2:

R₁-COOH (1)

Where, R₁ is an alkylbenzyl group or an alkyl group having 1-8

carbon atoms, and

Ar-X (2)

Where, X is -COOH, -SO₃H, or SO₂Ar; and

Ar is a compound represented by Chemical Formula 2-1 below:

Where, R₂ is a hydrogen or an alkali metal; and

R₃ is hydroxy!, alkyl, hydroxyalkyl, heteroalkyl, or hydroxyheteroalkyl.

2. The heat transfer fluid composition of claim 1 , which comprises

a) 90-99.9 wt% of a glycol,

b) 0.01-3.0 wt% of an azole compound,

c) 0.05-5.0 wt% of the organic acid represented by Chemical

Formula 1 , and

d) 0.05-3.0 wt% of the aromatic compound represented by

Chemical Formula 2.

3. The heat transfer fluid composition of claim 1 , wherein the a) glycol or its

derivatives is at least one selected from the group consisting of glycol,

diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene

glycol.

4. The heat transfer fluid composition of claim 1 , wherein the b) azole

compound is at least one selected from the group consisting of tolyltriazole,

benzotriazole, 4-phenyl-1 ,2,3-triazole, 2-naphtotriazole, and 4-nitrobenzotriazole.

5. The heat transfer fluid composition of claim 1 , wherein the c) organic acid

is at least one selected from the group consisting of benzoic acid,

p-feAf-butylbenzoic acid, p-toluic acid, neodecanoic acid, 2-ethylhexanoic

acid, heptanoic acid, and octanoic acid.

6. The heat transfer fluid composition of claim 1 , wherein the d) aromatic

compound is a monocyclic or polycyclic aromatic compound having at least

one hydroxyl group.

7. The heat transfer fluid composition of claim 1 , wherein the d) aromatic

compound is at least one selected from the group consisting of

4,4'-dihydroxydiphenylsulfone, isomers thereof, and mixtures thereof.

8. The heat transfer fluid composition of claim 1 , wherein the d) aromatic

compound is the compound represented by Chemical Formula 3 below:

where, R₂ is a hydrogen or an alkali metal, and R₃ is hydroxyl, alkyl,

hydroxyalkyl, heteroalkyl, or hydroxyheteroalkyl.

9. The heat transfer fluid composition of claim 1 , which is used in the

temperature range of from room temperature to 200 ⁰C .