PAINT OR COATTNG COMPOSITION AND METHOD FOR PAINTING OR COATTNG SURFACES

The present invention relates to paint or coating compositions, me¬ thods for painting or coating surfaces and the use of particular 5 compositions for painting or coating particular structures.

TECHNICAL BACKGROUND

European Patent Application No. 79 104321.9 and the corresponding International Patent Application No. PCT/DK79/00047 discloses parti¬ cular materials showing extremely valuable properties with respect to 10 dense and durable structure and excellent shapeability in uncured state.

In the following specification and claims, these materials will be de¬ signated materials containing a "densified matrix". This term desig¬ nates any coherent binder matrix disclosed in the above-mentioned 15 patent applications. All of these binder matrices comprise

A) homogeneously arranged inorganic solid particles of a size of from about 50 A to about 0.5 μ, or a coherent structure formed from such homogeneously arranged particles, and

B) densely packed solid particles having a size of the order of 20 0.5 - 100 μ and being at least one order of magnitude larger than the respective particles stated under A), or a coherent structure formed from such densely packed particles,

the particles A or the coherent structure formed therefrom being homogeneously distributed in the void volume between the partic- 25 les B,

the dense packing being substantially a packing corresponding to the one obtainable by gentle mechanical influence on a system of

geometrically equally shaped large -particles in which locking su rface forces do not have any significant effect.

As described in the above-mentioned patent applications, additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A may be embedded in the matrix . Such additional are termed "bodies C" in I nternational Patent Application NO. PCT/DK79/00047 and comprise a wide variety of bodies, including particles such as sand or stone and fibers such as, e. g . , glass fibers, steel fibers , and plastics fibers .

In the following specification and claims, the term "a material com¬ prising the densified matrix" designates any material having the densified matrix as a binder matrix and optionally containing bodies C as defined above.

As discussed in the above-mentioned patent applications, the particles B are preferably Portland cement particles, and the particles A are preferably ultrafine silica particles ("silica dust") having a specific

2 surface area of about 50,000 - 2,000,000 cm /g, preferably about

2 250,000 cm /g, and preferred silica particles are described in detail in the said patent applications and comprise, e. g. , particles by growth from liquid or preferably vapou r phase such as particles formed as a byproduct in the production of ferrosilicium or silicium metal in electrical furnaces . As described in the above-mentioned patent applications, articles comprising the densified matrix may be made from an easily flowable composite material of an extremely low liquid content by shaping in a low stress field . I n the following specification and claims, the term "composite material" designates any composite material which, on cu ring, forms a material comprising the densified matrix . These composite materials are described in great detail in the above-mentioned patent applications . The composite material containing Portland cement particles as particles B comprises an extremely high amount of a dispersing agent, typically a concrete superplasticizer, and examples of useful concrete superplasticizers are given in the above-mentioned patent applications . Methods and mate¬ rials for producing, casting and fu rther treating the densified matrix

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as disclosed in the above-mentioned patent applications are also useful for producing the densified matrix in the context of the present ap¬ plication.

In the following specification and claims, the term "densely packed" is to be understood in accordance with the definition of "dense packing" given above. - • •

DESCRIPTION OF THE PRESENT INVENTION. "a

According to one aspect of the present invention, the densified matrix is utilized as protective coating for application on particular surfaces to be protected, in particular steel surfaces. In this utilization of the densified matrix, the density of the matrix with its inherent mechani¬ cal properties is utilized. When the surfaces to be protected are, e.g., surfaces to be protected against corrosion, in particular steel surfaces, the particles B preferably comprise cement particles, in particular Portland cement particles, or at least a major proportion of cement particles, in particular Portland cement particles, thereby resulting in a paint which has the well-known rust-prevention pro¬ perties of cement-containing paints. Surfaces which are suitably protected by means of such paint are, e.g., steel surfaces in ballast tanks, cargo holds, cofferdams, and other surfaces, especially on ship hulls or other marine structures, particularly in or on ships, or offshore structures, where rust prevention or resistance to other kinds of corrosion is to be obtained, including bridge undersides, the interior of offshore legs, ship cabins; ship decks and aircraft landing areas on ships or other constructions. Other structures which are protected by means of the paints or surface coatings comprising the densified matrix are drinking water tanks, underseals for containers, and jacketing for pipelines, etc. Also, ship structures such as cabin walls which are to be supplied with a superimposed insulating layer such as a layer of Rockwool® are typical surfaces being treated with the paints or surface coatings comprising the dense matrix. The present invention is not restricted to the use of the materials com¬ prising the densified matrix in or on marine or offshore structures;

also the painting or coating of other structu res, including industrial piants, containers, buildings, etc. is within the scope of the present invention .

When used as a paint or su rface coating for application on the a- bove-mentioned surfaces or similar su rfaces, the composite material is preferably adapted to obtain - optimum adhesion to . the surface to be painted or protected, ordinarily a steel surface, and is suitably modified to fu rther enhance its adhesion to the surface and to im¬ prove the application properties of the paint and the flexibility and resistance against cracking of the final paint layer. According to the invention, this modification is performed by addition of additives of organic or inorganic character. Important additives are organic or inorganic binders, thixotropic agents, co-solvents, defoamers, disper¬ sing agents, pigments, and plasticizers .

According to one of the main aspects of the present invention, the composite material' or paint of the invention comprises - in addition to the components resulting in the formation of a densified matrix com¬ prising particles A, B, and optionally C - an organic binder. The organic binder is suitably incorporated as a water-based emulsion such as an acrylic emulsion , polyvinylacetate emulsion, polyvinylidene chloride emulsion , acryl-styrene emulsion, styrene-butadiene emulsion, polyvinyl chloride emulsion, wax emulsion, polyethylene derivative emulsion, polyvinylidene-butadiene emulsion , or vinyiacryl emulsion . Such emulsions are incorporated in an amount of typically 5 - 60% by weight, preferably, to obtain maximum flexibility, 20 - 40% by weight, calculated on the dry matter content of the emulsion and the total dry matter content of the composition; a - suitable compromise between adequate flexibility and economy of the composition is often obtained when the emulsion is incorporated in an amount of about 5 - 25% by weight, calculated on the same basis .

Other suitable modifying agents are thixotropic agents for improve¬ ment of the flowing properties of the paint, permitting the obtainment of thicker layers of the paint applied . The thixotropic agents are typically added in an amount of 0.5 - 10% by weight, preferably 1 -

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5% by weight, calculated on thixotropic agent dry matter and the total dry matter of the paint. Typical thixotropic agents are

Mineral thixotropic agents, including silicas bentonites and attapulgites - • - vegetable thixotropic agents, including cellulose, starch, dextrin, alginates, castor oil derivatives natural gums, thixotropic agents of animal origin, including gelatine, glue, casein, synthetic thixotropic agents, including synthetic cellulose derivatives including starch acetate, polyvinyl alcohols, polyvinylpyrrolidone, polyvinylether derivatives, polyacrylamides, polyurethanes.

When the paint of the invention contains an incorporated organic binder, e.g. a binder in the form of an emulsion as described above, an interesting embodiment of the invention comprises incorporating a "co-solvent" in the form of a water-miscible organic solvent in an amount of 1 -.5% by weight, calculated on the dry matter of the paint. Examples of co-solvents are glycolethers, e.g. ethoxyethanol, butoxyethanol (also termed "butylglycol"), glycoletheracetates, e.g. diethyleneglycolmonobutylether acetate (also termed "butyldigly'col acetate") and esters of carboxylic acids such as 2,2,4-trimethyl-l ,3- pentanediol-monoisobutyrate ("Texanol" from Eastman Kodak, USA). These co-solvents exert their effect when the water originally present

in the composite material gradually reacts , thus leaving a gradually increasing concentration of the solvent in the remaining liquid phase. The solvent thus gradually concentrated tends to migrate in the composite material and swell and coalesce the particles of emulsified binder, which tends to improve the flowing and film-forming proper¬ ties of the paint and to result in a film which is substantially free of any pores . - • -

In addition to binders which are of the emulsion type as exemplified above, it is also possible to use binders of the types which are soluble in water/alcohol mixtu res and incorporate alcohol in the water phase of the paint. Such combination can be used to secure a relati¬ vely fast drying of the paint surface as the alcohol evaporates, thereby securing that the water present beneath the dried su rface is prevented from evaporating and is thus retained for the desired reaction . with the inorganic binder. Binders soluble in water/alcohol mixtures and contemplated for this purpose are, e. g . , al kyds, allyl- ethers, acrylics, and styrene-maleic acid polymers . Such binders are used in the same amount as stated above for binders in emulsified form.

According to another aspect of the present invention , the paint incorporates small amounts , e. g . 0.01 - 5% by weight, calculated on

^• the total dry matter content of the paint, of defoaming agents such as silicone-containing defoamers, e. g . , "Tegopren K 133" from Gold- schmidt, Essen, Federal Republic of Germany, or silicone-free de- foaming agents, e.g . , fatty acid derivatives such as "Bevaloid 688" or "Bevaloid 581 B" from "Bevaloid Ltd. , Yorkshire, England, or "Nopco NXZ" or "Nopco 8034" from Diamond Shamrock Corporation , Wilming¬ ton, Delaware, U . S . A. The defoaming agents prevent the incorpo¬ ration of air during the formulation , mixing and application of the paint, thus avoiding air voids in the dry coating .

The compositions used for the pu rpose of the present invention will usually have a liquid : powder ratio in the range of about 0.20 - 0.45 or even 0.50 by weight, in particular in the ^' range of 0.23 - 0.40, especially 0.27 - 0.38 by weight. (When the liquid is an emulsion, the

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binder content thereof is considered as pertaini ng to the powder and will normal ly be in the size range defined for particles A . )

According to a particular aspect of the invention , the paint incor¬ porating the densified matrix is prevented from prematu re cu ring or setting by using, instead of the water in the usual embodiment of the composite material disclosed -in the above-mentioned patent application , a water-miscible liquid such as a glycol , e. g . , ethylene glycol or propylene glycol . I n this manner, the paint may be produced and shipped in the "glycol form" where substantially no cu ring of the inorganic binder takes place. When the paint is applied on a wet surface, or is applied on a su rface which is thereafter wetted, the glycol is partially replaced with water, thus resulting in cu ring of the inorganic binder.

According to a particular embodiment of the present invention, the paint is formulated as an antifouling paint for application of ship hulls,, offshore structu res , or .other marine structu res . For this purpose, antifouling agents are incorporated in the paint. The ^' anti¬ fouling agents may be in the form of pa rticles (normally of the size corresponding to pa rticles B) such as cuprous oxide or zinc oxide, or they may be in the form of liquid antifouling agents . Particularly interesting antifouling agents are tin compounds of the general for¬ mula R~SnX wherein each R is a hydrocarbon group such as phenyl , benzyl, propyl, butyl, pentyl, octyl, or nonyl and X is an acid residue of a mineral or organic acid such as chloride, flou ride or acetate, or X is the acid residue of a polymeric acid such as poly- acrylic acid . Examples of such tin compounds are triphenyltin chlor¬ ide, triphenyltin fluoride, tributyltin fluoride, or tributyltin chloride. As an example of a liquid antifouling agent may be mentioned tributyl¬ tin oxide. The antifouling paint according to the invention may also be formulated with a content of a herbicide such as Diuron or anti¬ microbial enzymes such as protease, esterase, or cellulase to control fouling organisms .

The paint of the present invention is useful not on ly for normal application methods such as ai rless or ai r spraying , brushing, or

rolling, but also for application under water or in the splash zone by brushing, by means of brooms, by means of rollers, or by spraying .

I n some cases , it may be desirable to perform a pre-treatment of the surface on which the paint of the invention is to be applied, in order to increase the adhesion of the paint to the surface and enhance the protective efficiency of the pa-int. Examples of suitable p re-treatments are: Treatment with acids such as sulphu ric acid or phosphoric acid, treatment with bacteria such as sulfate-reducing and iron-oxidizing bacteria, dry or wet blasting with sand or grit, mechanical cleaning of the su rface, such as scraping, hammering, or high pressure wash¬ ing. One of the major advantages of the paint of the invention is that it can be effectively applied on a moist su rface.

When used in dark environments, such as ballast tanks, etc, the paint of the invention is suitably composed in such a manner that it has a substantially light colour so that it is easier to visually asses what surfaces have been treated . This may be obtained by incorpo¬ rating pigments as part of particles B, e.g . , zinc oxide or titanium dioxide, or by using particles A which are of a light colou r, such as white silica particles derived from the production of silicium and/or ferrosilicium in electrical fu rnaces .

On the other hand, the composition of the invention may be prepared in almost any desi red colou r. Thus, e.g . , using white cement and. tinting pastes, red, green , blue and black samples have been pre¬ pared .

I n order to improve the cracking resistence of the paint of the inven¬ tion, special pigments, including pigments of a plate-shaped character such as mica or asbestine, aluminum, micaceous iron oxide, or fibers, including asbestos, ch rysotil, graphite, b.asalt, polyethylene, cellulo- sic fibers, etc. may be incorporated as bodies C.

I n principle the composite material constituting the paint or coating composition of the present invention is prepared from particles A, particles B , a liquid, a surface-active dispersing agent and optionally

additional bodies C in the same manner as disclosed in the above-men ^¬ tioned patent applications . It is important that the amou nt of particles B substantially corresponds to dense packing thereof in the composite material with homogeneously packed or preferably densely packed 5 particles A in the voids between the particles B and that the amount of liquid substantially corresponds- to the amount necessary to fill the voids between particles A and B , and fu rther, that the amount of dispersing agent is sufficient to impa rt, to the composite material , a fluid to plastic consistency in a low stress field of less than 5 kg/-

2 10 cm2, preferably less than 100 g/cm . The additional constituents incorporated in accordance with most aspects of the present inven¬ tion, such as binders, thixotropic agents , and defoamers, are incor¬ porated by methods adapted in accordance with the character of the particular constituent. When the binder is a binder in the form of an

15 emulsion, the emulsion per se is used as part of or as the whole liquid constituent for preparing the composite material . When the additional components are added in powder form, these are suitably either mixed with the dry constituents before addition of liquid, or are incorporated du ring the mixing, after the liquid or part of the

20 liquid has been added, or they may be added in a form where they are dissolved or dispersed in liquid . As stated above, the liquid will normally be water, but it will be understood that it is also within the scope of the invention to use glycol or a glycol/water mixture as the liquid in order to obtain retardation of the cu ring of the inorganic

25 binder, and it is also within the scope of the invention to incorpo¬ rate, e. g . , alcohol or another organic solvent in order to coalesce or dissolve an incorporated organic binder in accordance with the prin¬ ciples discussed above.

I n the preparation of the composite material constituti ng the paint or 30 coating composition of the present invention , the dry constituents thereof may be mixed in any desired manner. Th us , e. g . , the partic¬ les B , typically Portland cement, may be mixed with the pa rticles A, and the resulting mixture may be admixed with any added dry con¬ stituents such as particles C and/or binder, thixotropic agent, or 35 defoamer, or the particles A may be mixed with any other dry con¬ stituents to be added, such as binder, thixotropic agent, or de-

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foamer, and thereafter mixed with the particles B and optionally particles C. When the particles B comprise, e. g . , Portland cement, an interesting mixing sequence is to mix all other constituents than the Portland cement, including particles A, added binder (when the binder is not constituted by the pa rticles A) , optionaly thivotropic agents and defoamers, and optional Pa rticles C and liquid, optionally including coalescing agent or a glycol , and then to add the cement to this mixtu re at the application site, preferably immediately before the application of the paint. I n all embodiments of the formulation of the paint, care must be taken to obtain a homogeneous mixture showing the essential characteristics of the materials resulting in the densified matrix, cf.- the above-mentioned patent applications .

The invention is now fu rther illustrated with reference to the draw¬ ing, in which

Fig. λ illustrates the size distribution of Portland cement, silica, and acrylic emulsion, respectively, and

Fig. 2 illustrates the packing density of compositions with varying cement/silica ratios with 15 parts by weight of acrylic emulsion and without acrylic emulsion ("Acronal" S 702 from BASF) , respectively.

Both curves in Fig. 2 are calculated theoretically on the basis of the particle size distribution illustrated in Fig . 1 . As appears from Fig . 2, the maximum density of the composition containing 15% of acrylic emulsion is obtained at a silica content of 10 g of silica per 90 g of cement, whereas the necessary amount of silica to obtain dense pack- ing without the emulsion is more than 20 g of silica per 80 g of cement. As will appear from the examples which follow, the best results are obtained at the maximum density of the emulsion-contain¬ ing composition .

EXAMPLE A -

Compatibility of Various Emulsion Types with Cement

In order to assess the compatibility between pure cement and various

types of emulsions comtemplated for the pu rpose of the present inven ^¬ tion , a series of experiments was performed . Va rious emulsion types were added to cement powder, whereafter water and optionally de- foamer were added . The ingredients and ratios appear from Table 1 .

Table 1 Va rious- Emulsion Types in Cement

Formula Latex type Addition De- Water/so¬ Viscosity

No. w/w pph foamer lids ratio Krebs Units on cement

1 Acrylic 10 _ 0.28 108

2 25 - 0.20 104

3 Styrene bu¬ tadiene . 10 + 0.33 paste

4 25 + 0.20 102

5 Vinyl ³ 10 + 0.48 108 ^•

6 25 + 0.42 paste

1 = Acronal S 702 from BASF

2 = Litex CA from HUIs

3 = Vinamui 6705 from Scado

4 = Nopco NXD from Diamond S hamrock pph = parts per hundred

I n all of the experiments, a stable mixtu re was obtained, which shows that there is full compatibility between these different latex emulsion types and the cement. Although the remaining working examples al! use the acrylic latex type, (wh ich is the preferred latex type because it results in the best fiber formation) , the results of the present experiments show that the other types of latex emulsion may also used for the pu rpose of the present i nvention .

EXAMPLE 1

Formulations of densified cement matrices with acrylic emulsion, added in an amount ranging from 10 to 50 pph, were prepared. The ingredi¬ ents and their ratios appear from Table 2.

- • -Table 2

Addition of Acrylic Emulsion to Densely Packed Cement

.. . 2 3

Formula No. Cement C SMil-ica 1 Acronal PI; asticizer Retarder g 9 g g g

7 80 20 10 1.6 -

8 80 20 15 1.6 -

9 80 20 25 1.6 -

10 80 20 30 1.6 -

11 80 20 50 1.6 -

12 95 5 15 - 0.1

13 90 10 15 - 0.1

14 80 20 15 - 0.1

15 80 20 15 1.6 0.1

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(Table 2 continued)

Formula no. Water/ Viscosity Pot- life ⁴ Film Fo rmation solids Krebs Cured at Cured at ratio Units ambient cor I- 100% R.H. ditions

7 0.26 108 ~20 min. crack OK

8 0.26 no ~20 min. crack OK

10 9 0.26 108 1/2 hour crack OK

10 0.27 104 1/2 hour crack OK

11 ^" 0.28 106 1/2 hour crack OK

12 0.26 108 1 hour OK OK

13 0.24 116 1/2 hour micro-crac k OK

15 14 >0.40 paste

15 0.28 100 1 hour crack OK

1 = Silica 100 from Elkem

2 = Mighty

20 3 = Natrosol 250 LR from Hercules

4 = Time until viscosity reaches 130 Krebs Units

The products were prepared in the same manner as in Example A, the cement and the silica being dry mixed before addition of the emulsion. The emulsion was added in varying amounts. In all cases, excellent

25 paint properties with respect to viscosity, pot life and film formation (when curing at 100% relative humidity) were obtained, such as ap¬ pears from Table 2.

EXAMPLE 2

Influence of the Amount of Fine Powder

30 Three compositions of the same type as described in Example 1 were prepared, with varying amount of silica. The compositions were pre-

pared in the same manner as described in Example 1 . The the propor¬ tions of ingredients and the results obtained appear from Table 3.

Table 3

Water/Sol ic Is Ratio

Formula Cement Silica Acronal Plasti- Water/so¬ Viscosity

1

No. cizer lids ratio Krebs Units g g g g

16 95 5 15 0.15 0.23 100

17 90 10 15 0.15 0.33 100

18 80 20 15 0.15 0.50 no

1 = Kleenoplast from Akzo

It will be noted that in order to obtain the same viscosity with vary¬ ing amounts of silica, different amounts of water were ^' used . I n ail cases, excellent paints were obtained.

EXAMPLE 3

Application of Compositions of the I nvention on Steel Surfaces

Two compositions of the invention were applied on steel panels by means of a conventional spray technique, using a pistol G FG-50 from DeVill Biss, nozzle 0.030" . The ingredients and their relative ratios, etc. appear from Table 4 in which "Sa 3" and "St 3" indicate the degree of cleanness of the steel according to Swedish Standard No. S IS 055900-1967. For determination of the .anti-corrosion properties of the compositions, the panels with the compositions were immersed in sea water for -3 months at Kyndby, Denmark. The results of this test appear from Table 4.

Other application methods which have been tested in practice and found to be suitable are pressu re pot application using a PQM 5499 equipment from DeVill Biss , nozzle 0.064", or hoppergun application , using an equipment from Joe, Sweden .

Table 4

Compositions Immersed in Seawater for 3 Months

Formula Cement Silica Acronal Plasti- Fibres Retar- Water/

1 No. cizer der solids g g g g g g ratio

19 80 20 1 .6 6 - 0.24

20 90 10 15 _ - 0. 1 0.38

19 Seawater Immersion

Blistering Rust ⁴

Sa 3 10 10

St 3 10 10

20 Seawater Immersion

Blistering Rust ⁴

•*.

Sa 3 10 10

St 3 10 10

1 = Mighty

2 = Rockwool FPX from Rockwool 3 = Natrosol 250 LR from Hercules

4 = Scale from 0 to 10, 10 best

As appears from Table 4, the coating was non-blistering and gave maximum rust protection in all cases .

EXAMPLE 4

A number of fiber-containing - compositions of the invention were made in the same manner as described in Example 2; the fibers were added together with the water.

The amounts of the ingredients and the results obtained appear from Table 5.

Table 5 Addition of Fibres

2)

Formula Cement Sil ica Acro- Plasti- Fibre Retarder

No. nal - cizer 1) Type Amount g g - ^• g- g 9 S -

21 90 10 15 1.8 4) 6 0.1

22 90 10 15 1.8 4) 4 0.1

23 90 10 15 1.8 4) 2 0.1

24 90 10 15 1.8 5) 6 0.1

25 90 10 15 1.8 5) 4 0.1

26 95 5 15 1.9 5) 6 0.1

27 95 5 15 1.9 5) 4 0.1

Formula Water/so- - Viscosity Pot-life ³⁾ Film Form lation

No. jids ratic > Krebs Units Cured at am- Cured at bient con di- 100% R.H. tions

21 0.32 112 -1/2 h OK OK

22 0.29 106 -1/2 h OK OK

23 0.28 114 -1/2 h crack OK

24 0.26 108 -1/2 h crack OK

25 0.27 104 -1/2 h crack OK

26 0.27 100 1/2 h OK OK

27 0.27 108 1/2 h OK OK

1) Mighty 2) Natrosol 250 LR from Hercules

3) Time until viscosity reaches 130 Krebs Units

4) Rockwool FPX from Rockwool

5) Wollastonite from Nyco

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I n all cases , good film formation was obtained by ccr-.parϊng the results stated in Table 5 with the data apparent from Table 2, it will be noted that the incorporation of fibers results in a considerable increase in the resistance to crack w hen the film is cured at ambient conditions .

EXAMPLE 5

Effect of I ncorporation of Piasticϊzer

Various compositions were made using the ratios of ingredients stated in Table 6. The method was the same as described in Example 2.

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Table 6 i ncorporation of Plasticizer

Formula Cement Silica Acronal Pi asticizεr Natrosol

No. Type Amount 250 LR g S ^• g g g

28 80 20 _ _ - -

29 80 20 15 - - -

10 30 80 20 0 2) 3.2 -

31 80 20 15 2) 1 .6 0.1

32 80 20 15 2) 3.2 0. 1

33 80 20 15 3) 3.2 -

8 80 20 15 4) 1 .6 -

15

Formula Water/solids Viscosity Pot-life Film Formation

No. ratio Krebs Unit Cured at Cured at

- ambient 100% R. H . conditions

20

28 >50 Dry lumps

29 >40 Paste

30 0.23 100 10 crack OK

31 0.39 Thixotropic -1/2 h crack OK

25 32 0.30 100 20 crack OK

33 0.28 100 -1/2 h crack OK

8 0.26 no -20 m crack OK

1) Time until viscosity reaches 130 Krebs Units 30 2) Darachem from G race

3) Sikament from Sika- Beton

4) Mighty

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lt will be noted from Table 6 that the incorporation of a plasticizer in a high amount is essential to the obtainment of a composition accor¬ ding to the invention : in the two cases where the plasticizer was omitted, it was not possible to obtain a workable composition .

EXAMPLE 7

Influence of Retarders on Pot Life

In the same manner as described in Example 2, various compositions were prepared with and without retarder; the compositions and the results obtained appear from Table 7. In all cases, the retarder showed good compatibility with the other constituents of the compo¬ sition . It will be noted that the incorporation of the retarder resulted in a considerably increased pot life.

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Table 7 Influence of Retarders

Formula Cement Silica Acronal Plasti R eta rdi er

No. cizer 1) Typ >e A mount g g - ^{• •} g g g

34 100 0 15 1.6 - -

35 90 10 15 1.6 - -

36 100 0 15 - 3) 0.1

37 95 5 15 - 3) 0.1

38 90 10 15 - 3) 0.1

39 90 10 15 1.8 4) 0.1

Formula 2) Water/solids Viscosity Pot-life Film Formation No. ratio Krebs Units Cured at Cured at ambient 100% R.H. conditions

34 0.21 110 10 m OK OK

35 0.22 112 15 m crack

36 0.26 114 1 h OK

37 0.26 108 1 h OK OK

38 .0.24 116 1/2 h micro-crack OK

39 0.29 110 edge crack OK

1) Mighty

2) Time until viscosity reaches 130 Krebs Units

3) Natrosol 250 LR from Hercules

4) Natrosol 250 HHR from Hercules