AU479213B2 - Refractory composition - Google Patents

Description

It) j

MD.26631

This invention relates to a mixture of a binder and an inhibitor for use in refractory compositions and to

refractory compositions containing the mixture.

Refractory compositions comprising a mixture of a

refractory aggregate, a binder which is an acidic material or which is a material capable of forming an acidic species, and a dispersant for the binder which is preferably a solvent lor the binder, e.g. water, are known to suffer from certain disadvantages where the compositions contain metallic impurit

47 92 13

7 5,7 9 2 /74 It is believed that in such compositions the acidic binder

or acidic species formed from the binder reacts with the

metallic impurities to liberate hydrogen. This leads to

difficulties of storage of such compositions and, when the

compositions are caused or allowed to set to produce shaped

articles, bloating occurs in the articles which are produced.

Bloating may be defined as the formation of voids in the

shaped article. The formation of voids results in articles

which may be somewhat misshapen, which have a decreased

density, and which show a decrease in strength when compared

with articles which have been produced from similar compositions

but which are not bloated.

Thus, we have found that in refractory compositions in

which the binder is a halogen-containing complex phosphate of

aluminium bloating may occur if metallic impurities are

present in the composition. Furthermore, we have now found

that the extent of the bloating which occurs may be reduced

and in some cases substantially eliminated if the composition

includes an inhibitor having a particular structure.

The present invention provides a mixture comprising at i44wduc1V and least one binderf-o a refractory aggregate/which 4bind-r is a

halogen-containing complex phosphate of aluminium containing

one or more chemically-bound molecules of water and/or one or

more chemically bound oxygen-containing organic molecules, and

at least one inhibitor which is an acetylenic alcohol having

47 9.2 1.3

792/74

the structure

HC SC CRjR 2 (Y)nOH (1) where R, and R2 which may be the same or different, are

selected from hydrogen atoms and organic groups, Y is a

divaleh Zogami and ri is an integer in the range 2 to

In a further embodiment of the invention there is

provided an essentially dry refractory composition comprisin<

a refractory aggregate and a mixture of a binder and an

inhibitor as herein described; and a settable refractory composition comprising a refractory aggregate, a mixture of

a binder and an inhibitor as herein described, and a liquid

diluent which is a solvent for the binder and the inhibitor

and in which the binder and inhibitor form a solution. The liquid diluent is conveniently water or a diluent containing

water, e.g. a mixture of water with an organic diluent.

The metallic impurities which may be present in the

refractory compositions may arise in a number of different

ways. For example, iron impurities may be present in the refractory aggregate and may arise from the use of steel ball

in the ball mills used in the production of ball mill fines aggregate. Iron also is often present as an impurity in aggregate derived from crushed refractory bricks which have

been recovered from furnaces. Metallic impurities other thai iron may be present in refractory compositions. For example chrome alumina slag may contain metallic chromium as a metall:

impurity.

4 47 9.213

75,792/74

In the inhibitor having the structure the groups R,

and R 2 are suitably selected from hydrogen atoms and alkyl

radicals having from 1 to 10 carbon atoms, e.g. methyl, ethyl

and propyl. The groups R, and R2 are conveniently both

hydrogen atoms as the inhibitor may then be prepared from the

readily available propargyl alcohol.

The group Y is preferably an oxyalkylene group as

inhibitors containing such groups are especially effective in

reducing the extent of bloating which occurs during use of the

mixture of binder and inhibitor in refractory compositions

containing metallic impurities. Thus, the inhibitor may, for

example, have the structure:

R, R4 I I HC C CR 1 R 2 (0 CH CH)nOH (2)

where R 3 and R 4 which may be the same or different, are aiLu4r vinqjhm 1 to selected from hydrogen atoms and erganic grup

/Suitable organic groups include alkyl and branched alkyl groups having from 1 to 10 carbon atoms, e.g. methyl, ethyl,

propyl and butyl; substituted alkyl groups, e.g. chloromethyl; and aromatic groups, e.g. phenyl. Preferably, both R 3 and R 4 are hydrogen or one of R 3 and R 4 is hydrogen and the other is

an alkyl group, e.g. methyl. The oxyalkylene groups in the

inhibitor of structure may comprise a mixture of groups of

different structures in some of which, for example, both R 3

and R 4 are hydrogen and in others of which, for example, one of

R 3 and R 4 is hydrogen and the other is an alkyl group. The

47 92 13

7 5,7 92/74 groups may be present in the form of random or block co- polymers. Inhibitors in which the groups R3 and R 4 are hydrogen or methyl or a mixture thereof, that is, in which the groups Y are oxyethylene or oxypropylene or a mixture thereof, are especially preferred as they may be prepared from the readily available ethylene oxide and propylene oxidc or from a mixture thereof.

The inhibitor used in the present invention may comprise a mixture of compounds of structure of differing values of n such that in the mixture of inhibitors n is on average not a whole number. Preferably, n is on average in the range 2 to 12, e.g. approximately 7 as inhibitors having n in this range are more readily prepared than inhibitors with higher values of n.

The acetylenic alcohols forming a part of the mixture of the present invention are substantially less volatile and sub- stantially less toxic than is propargyl alcohol, and they are therefore much more conveniently usable as inhibitors than is propargyl alcohol. In view of its volatility propargyl alcohol would present substantial toxicity hazards, especially when subjected to elevated temperatures during use of refracto compositions. The hazards associated with the use of acetylei alcohols present in the mixtures of the present invention are substantially less.

The acetylenic alcohol inhibitor of structure may be prepared by reacting propargyl alcohol, or a substituted

47 92 1 3

75,7 9 :74 derivative thereof, with a source of the group Y. For

example, where the group Y is an oxyalkylene group the

inhibitor may be prepared by reacting propargyl alcohol, or

a substituted derivative thereof, with an alkylene oxide,

especially with an 1,2-alkylene oxide, e.g. a 1,2-alkylene

oxide of the structure:

R3 R 4 I CH- I CH (3)

A mixture of two or more alkylene oxides may be used in

the reaction.

The reaction may be carried out in the presence of a

catalyst, e.g. a tertiary amine, an acid, an alkali metal

hydroxide or alkaline earth metal hydroxide. Use of elevated temperatures and pressures may be required especially if

inhibitors with high values of n are desired.

In the mixture of binder and inhibitor the binder is a

halogen-containing complex phosphate of aluminium containing

one or more chemically-bound molecules of water and/or one or

more chemically bound oxygen-containing organic molecules.

The complex aluminium.phosphate binder may be made by

reacting aluminium or an aluminium compound, for example, a

halogen-containing aluminium compound, e.g. an aluminium

halide, with phosphoric acid, a phosphoric acid ester or a

compound capable of forming phosphoric acid or a phosphoric

acid ester. Where aluminium or an aluminium compound other

47 92 13

75,792.7^ also than a halogen-containing compound is used then it is

necessary to use in the reaction the corresponding halogen or acid. The reaction is effected in the presence of water

an oxygen-containing organic molecule and the reaction

mixture produced is generally a solution. The complex

one phosphate separated from the reaction mixture contains

or more chemically-bound molecules of water and/or oxygen-

The preparation is preferably containing organic molecules. 0 carried out at a temperature in the range 0 C to 50 C and the

with a noi complex phosphate may be separated by precipitation freeze-dryin4 solvent, by concentration of the solution, or by

or spray-drying of the solution. Chlorine is the preferred

be a bromine- o halogen although the complex may, for example

iodine-containing complex. The phosphate is preferably orth

be used. phosphate although meta- and pyrophosphate may

Suitable oxygen-containing organic molecules include and parti- hydroxy compounds, esters, aldehydes and ketones, co- cularly oxygen-containing organic molecules which form

ordination compounds with aluminium salts. Preferred hydrox alcoh compounds are aliphatic alcohols, for example aliphatic containing 1 to 10 carbon atoms; it is especially preferred f use aliphatic alcohols containing from 1 to 4 carbon atoms,

example ethyl alcohol. to tf The ratio of the number of gram atoms of aluminium phosphate n number of gram atoms of phosphorus in the complex 2:1, more vary over a wide range, for example from 1:2 to

i7 1

75,7 92:74 especially 1:1 to 2:1, but is preferably substantially 1:1,

that is, in the range of about 0.8:1 to 1.2:1, as complex

phosphates having this ratio decompose at low temperatures

directly to form aluminium orthophosphate having greater

chemical stability and refractoriness than aluminium phosphates

formed from complex phosphates with other ratios. The ratio

of the number of gram atoms of aluminium to the number of gram

atoms of halogen in the complex phosphates may vary over a

wide range, e.g. from 2:1 to 1:3 but is suitably substantially

1:1.

The complex aluminium phosphate may contain, for example,

from 1 to 5 molecules of water and/or organic oxygen-containing

molecule. Examples of suitable complex phosphates of

aluminium are described in our British Patent Specifications

Nos. 1,322,722 and 1,322,724.

Examples of complex aluminium phosphates include the

following.

That containing chlorine and ethyl alcohol and having the

empirical formula AlPCH 25C 08. The infra-red and X-ray

characteristics of the compound are described in Example 1

of the aforesaid specification No. 1,322,722. It may be

referred to as ACPE.

That containing chlorine and water and having the empirical

formula AlPClH11 0 The infra-red and X-ray characteristics

of the compound are described in Example 1 of the aforesaid

specification No. 1,322,724. It may be referred to as ACPH.

47 92 13

7 9 2 ,74: That containing bromine and ethyl alcohol and having the empirical formula APBrH25C808. The infra-red and X-ray characteristics of the compound are described in Example of the aforesaid specification No. 1,322,722. It may be referred to as ABPE.

It is to be understood, however, that these empirical formulae in no way imply any particular molecular structures for the complex phosphates.

Solid phosphate binders are often hygroscopic and we find that the binder when in admixture with the inhibitor may have a reduced tendency to hygroscopicity.

The mixture of complex aluminium phosphate binder and inhibitor may be produced merely by mixing of the solid binder and the inhibitor, e.g. by tumble-blending. A convenient method of producing the mixture is to add the inhibitor to a solution of the complex aluminium phosphate binder in a liquid diluent, for example to a solution as formed during preparation of the complex aluminium phosphate, and then separate the mixture from solution, for example, by precipitation with a non-solvent, by concentration of the solution, or by freeze- drying or spray-drying the solution. Preferably, the inhibitor is soluble in the liquid diluent. The concentration of binder in the solution may conveniently be in the range 1F to 505 by weight of the solution.

The amount of inhibitor which is present in the mixture will depend, inter alia, on the precise nature of the complex

47 9.213

75,7 922 74 metallic aluminium phosphate binder and on the amount of compositions. impurities which are present in the refractory the For a given binder and a given refractory aggregate a required amount of inhibitor which is needed to produce by simple amount of inhibition of bloating may be chosen and varying experiment by making up refractory compositions as to produce the amount of inhibitor in the compositions so bloating. articles which contain the desired inhibition of that in In the mixture of binder and inhibitor we find 5% of general at least 0.2% and generally from 0.2% to

inhibitor by weight of the binder in the mixture is suitable, where the mixture and preferably 0.5% to 4% by weight, although a relatively high is used in-a refractory composition containing inhibitor greater proportion of metallic impurity proportions of by weight, may than 5% by weight of the binder, e.g. up to 10% low be required. Where the amount of metallic impurities is of binder may be then as little as 0.1% of inhibitor by weight

required. or neutral The refractory aggregate is preferably an acidic use of a basic aggregate aggregate although we do not exclude the of a basic particularly an aggregate containing a proportion may aggregate. A mixture of two or more different aggregates clay. be used. The refractory composition may also include a form The refractory aggregate may be in any suitable is to be put. depending on the use to which the composition but it may also be in the Generally it is in the form of a powder

47 9.213

7 5,7 9 2 4 form of, for example, fibres, chips and flakes. Aggregates

consisting of mixtures of coarse and fine particles are

preferred since the strengths of products obtained using suc

mixtures are generally higher than the strengths of products

obtained from compositions in which all the aggregate partic

are of similar size.

The particle size of refractory aggregate may vary over

wide range depending on the intended use of the refractory

composition. For example, where the settable refractory co:

position is to be used as a gunning mix it may be desired to

use a relatively coarse powder whose particle size substanti

falls within the range of 0.35 to 1.0 mm. Fine powders sub

stantially the whole of which has a particle size of less th,

0.05 mm may also be used.

For moulds used in investment casting, it is preferred

use a refractory powder at least 50% by weight of which has

particle size of less than 0.15 mm and more preferably less

0.075 mm. On the other hand, the refractory aggregate may

have a particule size of up to 2 cm or even greater.

Silica, alumina, for example, calcined alumina, tabular

alumina and fused alumina, and zirconia are especially usefu

as refractory aggregates, as are zirconium silicates. Furth

examples of refractory aggregates which may be used include

titanium oxide; aluminium silicates, e.g. sillimanite,

andalusite, mullite and molochite; porcelain and china clay!

carbides, e.g. silicon and tungsten carbides; nitrides, e.g

silicon and boron nitrides; boron; asbestos; ferric oxide

47 9213

7 5,7 92 7

chromium oxide; chromite; mica; carbon, e.g. graphite.

The binder is suitably present in the essentially dry

refractory composition in a proportion of 0.5% to 40% by

weight of the composition. Proportions of 2% to 30% and 2%

to 10% by weight of the composition are more preferred.

In the refractory compositions of the invention we find

that in general at least 0.01% and generally from 0.01% to 1%

of inhibitor by weight of aggregate is suitable, and

preferably 0.02% to 0.5% by weight.

The amount of liquid diluent used in the settable

refractory composition of the present invention should be such

as to produce a composition having a consistency suitable for

the particular application for which it is to be used.

Generally, the amount of liquid diluent will be in the range

to 25% by weight of the settable refractory composition,

but it is preferably in the range 2% to 15% and more preferably

in the range 5% to 10% by weight of the composition.

The diluent is generally a solvent for the binder and for

the inhibitor although the binder may be dispersed in the

diluent, for example as a suspension, sol or gel. A preferred

diluent is water. The diluent may be an organic liquid, for

example, a polar organic liquid, e.g. methyl alcohol, ethyl

alcohol, isopropyl alcohol, butyl alcohol, ethylene glycol or

monoethyl ethyl ether. Mixtures of diluents may be used

especially mixtures containing water.

47?2 13

75,7 92/74 The essentially dry refractory composition may be made

by mixing the refractory aggregate with the binder and with

the inhibitor, or with the premixed binder and inhibitor, e.g.

by tumble-blending or by grinding, and the settable refractory

composition may be made by addition of the desired amount of

diluent to the essentially dry refractory composition.

Alternatively, the settable refractory composition may be made

by mixing the refractory aggregate with a mixture of, and

preferably with a solution of the binder in the diluent,

optionally containing the inhibitor.

The settable refractory compositions may be used for a

wide range of purposes including the production of shaped

articles, especially by moulding, and also for purposes in

which the hardening of the composition and its adhesion to its

surroundings can be utilised, as for example as a coating com-

position, especially on metal substrates. The settable

refractory compositions may also be used as a ramming mix, a

pressing mix, a gunning mix, or as a mortar, cement or filler,

for example for binding ceramics, but they are especially usef

in high temperature applications, for example, in furnace wall

and linings. The proportions of the components and the con-

sistency of the settable refractory compositions may be chosei

to make them of optimum value for the use intended. Shaped

articles which may be produced from the settable refractory

compositions include bricks, for example, furnace bricks, and

other shaped structures, e.g. rectangular and hexagonal-shape(

47 9.2 13

7 5, 7 2 7 blocks; moulds, especially casting moulds; and sheets and

other monoliths, for example, monolithic linings for high

temperature applications.

The settable refractory composition may be converted to

a hard, handleable product, that is it may be set, by heating

the composition at an elevated temperature or by including in

the composition a setting agent which reacts with the binder.

If desired, setting of the composition may be achieved by a

combination of heating and use of a setting agent. By

suitable choice of setting agent the composition may be made

cold-setting, that is, it may be made capable of being set in

the cold to produce a cast product having sufficient green

strength for the cast product to be handleable. A preferred

setting agent is magnesium oxide as described iin our copending

application British Patent Application No. 23885/72, now

published as Netherlands Patent Application No. 7306526.

The product is then treated by heating, for example, at a

temperature in the range 80 0 C to 1200 0 C, to produce a refractory

product. Suitably, this heating is carried out in two stages.

In a first stage the product in its "green" state is dried, e.g.

at a temperature in the range 80°C to 250 0 C, and in a second

stage the product is transferred to a furnace for high tempera-

ture firing, e.g. at a temperature of 800C to 1000 0 C to produce

a refractory product.

When the settable refractory compositions are used as

coating compositions they may be applied to the substrate by

47 231. 3

7 9 2,'7 conventional means, for example, by dipping, spraying or

brushing. The substrate may be a metal, but may be any other

desired substrate and in any form.

A wide range of other additives may be incorporated into

the compositions of the invention. Surface-active agents may

be added to aid wetting. Pigments and/or non-refractory

fillers may be added if desired. Plasticisers are useful

when the settable refractory composition is used as a ramming

or gunning mix, for example, bentonite and other clays or sub-

stitutes therefor, for example cellulose derivatives. Clays

may also be used to increase the hot strength of the final

product.

The invention is illustrated by the following Examples ir

which all parts are expressed as parts by weight.

EXAMPLES 1 AND 2

135 parts of anhydrous aluminium chloride were added sloi

to 300 parts of water and to the resulting solution there were

added 110 parts of 890 aqueous orthophosphoric acid. The

resultant yellow solution was dehydrated in a co-current spray

drier having a spinning disc atomiser and a chamber at 0 atmospheric pressure. Air inlet temperature was 140 C and aj 0 outlet temperature was 70 C. A yellow water-soluble powder v

produced which had the following analysis:

Al Cl PO4 HO0

by weight 11.4 17.4 39.3 30.0

Proportion 1.00 1.00 1.12

The powder will hereinafter be referred to as ACPH.

47 92 13

7 5,7 9 2 In two separate Examples 96 parts of graded Bauxite

aggregate containing 1.25 by weight of iron were thoroughly ACPH and mixed with 4 parts of high alumina clay, 5 parts of

0.4 part of magnesium oxide setting agent (Magnorite 100F),

and in the separate Examples there was added, respectively,

0.05 part (Example 1) and 0.1 part (Example 2) of inhibitor

which is a mixture of compounds having the structure

R, I HC S C.CH 2 (O-CH-CH)n-OH

R 4

in which -O-CH-CH- is a mixture of ethylene oxy and propylene

R4

6 parts of water were then oxy units and n is on average 7.5. doughs were added to each of the mixtures and the resultant 4 inch x A inch x cast into moulds having cavities of dimensions for 15 minutes, inch,the doughs were allowed to set by standing

and the resultant 4 inch x inch x inch test pieces were then 0 The for 16 hours. removed from the moulds and heated at 110 C 0 of 1000 C for test pieces were then heated at a temperature

2 hours. The test pieces, after removal from the moulds, the case of those showed a very small amount of bloating in 0.05 part of inhibitor and produced from the mixture containing containing 0.1 part of the test pieces produced from the mixture

inhibitor showed no sign of bloating.

1 1

'9 2/ 74 By way of comparison the above procedure was repeated

except that the inhibitor was omitted. The resultant test

pieces showed a considerable amount of bloating and in

particular the top surface of the test pieces, which had not

been constrained by the mould surfaces, was very porous and

had been expanded above the level of the mould due to the

formation of voids in the test pieces.

EXAMPLE 3

The procedure of Example 1 was repeated except that there

was used 0.1 part of an inhibitor having the structure

R,

HC C.CH 2 (O-CH-CH) -OH in which n 2 and one of R 3 and R 4 i

R4

methyl and the other is hydrogen. The dimensions of the moul which were used were 2 inch x 22 inch x 22 inch, and the step 0 of heating at 110 C and 10000 C were omitted. The test pieces removed from the moulds showed no sign of the formation of voi<

due to bloating.

By way of comparison the above procedure was repeated

except that the inhibitor was omitted. In this case the test pieces removed from the moulds were porous due to bloating, an( the top surfaces of the test pieces which had not been con-

strained by the mould surfaces were porous and had expanded abc

the level of the mould. Because of the bloating the test piec

had a volume 11% greater than the volume of the test pieces mac

from the composition containing inhibitor.

9 -A-:;13

75,7 9 2;7 EXAMPLE 4

The procedure of Example 2 was repeated except that

0.05 part of inhibitor was used. In the resultant test

pieces there was no sign of bloating.

EXAMPLE

The procedure of Example 3 was repeated except that there

was used 0.1 part of an inhibitor having the structure

R3 HC S C.CH 2 (0-CH-CH)n-OH in which n 2 and both of R 3 and R 4

R4

are hydrogen. In the test pieces removed from the moulds there

was no sign of bloating.

EXAMPLE 6

The procedure of Example 5 was repeated except that

0.05 part of inhibitor was used. In the resultant test pieces

there was no sign of bloating.

47 92 1

Claims (1)

1. 75,792/ The claims defining the invention are as follows

   1. A mixture comprising at least one binder/for/a refractory and aggregatewivhich binder is a halogen-containing complex

   phosphate of aluminium containing one or more chemically-

   bound molecules of water and/or one or more chemically-

   bound oxygen-containing organic molecules, and at least

   one inhibitor which is an acetylenic alcohol having the

   structure

   HC S C CR 1 R2 (Y)nOH (1)

   where R, and R 2 which may be the same or different, are selected from hydrogen atoms and organic groups, Y is a di aPt y.qm/V4.virn, Itok c1sni/ atom4 valent iga"ni groZ", and n is an integer in the range 2 t

   2. A mixture as claimed in Claim 1 in which the groups R I and

   R 2 are both hydrogen atoms.

   3. A mixture as claimed in Claim 1 or in Claim 2 in which the group Y is an oxyalkylene group having the structure

   Ra R4

   0 CH CH

   where-:R 3 and R 4 which may be the same or different, are

   selected from hydrogen atoms and-/-,fncG

   4. A mixture as claimed in any one of Claims 1 to 3 in which

   n is on average a number in the range 2 to 12.

   A mixture as claimed in any one of Claims 1 to 4 in which

   the group Y comprises oxyethylene or oxypropylene groups o

   a mixture thereof.

   47 9.213

   7 5,7 9 2/7 in which 6. A mixture as claimed in any one of Claims 1 to 6 the binder comprises a chlorine-containing complex

   phosphate of aluminium. which 7. A mixture as claimed in any one of Claims 1 to 6 in the complex phosphate of aluminium contains from-l to

   molecules of chemically-bound water.

   8. A mixture as claimed in any one of Claims 1 to 7 in which

   the number of gram atoms of aluminium to the number of

   gram atoms of phosphorus in the complex phosphate of aluminium is in the range 0.8:1 to 1.2:1.

   9. A mixture as claimed in any one of Claims 1 to 8 which

   contains 0.2% to 5% of inhibitor by weight of the binder.

   A mixture as claimed in Claim 1 substantially as herein- 1 to 6. before described and as shown in any one of Examples a 11. An essentially dry refractory composition comprising refractory aggregate and a mixture of a binder and an

   inhibitor as claimed in any one of Claims 1 to in 12. An essentially dry refractory composition as claimed Claim 11 in which the binder is present in the composition

   in a proportion of 0.5% to 405 by weight of the composition.

   13. A settable refractory composition comprising a refractory as aggregate, a mixture of a binder and an inhibitor claimed in any one of Claims 1 to 10 and a liquid diluent

   which is a solvent for the binder and for the inhibitor. Claim 13 in 14. A settable refractory composition as claimed in which the liquid diluent is present in a proportion of

   to 25% by weight of the composition.

   DATED: 26 November, 1974 IMPERIAL CHEMICAL INDUSTRIES LIMITED By its Patent Attorneys 7 ,ND FITZPATRICK 7 92 PHILLIPS ORMONDE 21 47 9.