DE1144565B - Process for the production of an activation mixture for the pretreatment of metal surfaces before phosphating and mixing or aqueous solution for this purpose - Google Patents

Description

The invention relates to the production of an activating agent for the pretreatment of metal surfaces for the reaction with phosphating solutions.

It is known from US Pat. No. 2,310,239 that disodium phosphate solutions containing titanium contain, activate the metal surface for subsequent treatment with phosphating solutions, so that the quality of the subsequently applied phosphate coating improves and the layer formation reaction is accelerated. However, the degree of activation in such solutions is not reproducible, so that the technical application causes difficulties. It is, therefore, to a particular one To maintain the degree of activation with certainty, necessary to use higher concentrations, than they would be necessary in any case.

The invention relates to a process for the preparation of an activating agent which these Does not have disadvantages, and the means produced by this process. The manufactured according to the invention Agent makes it possible to prepare metal surfaces so that phosphate coatings of high quality in more economical Can be applied in a way that was previously possible.

It was found that the degree of activation of titanium-containing pretreatment solutions, the Metal surfaces for subsequent reaction with phosphating solutions can be achieved in depends to a large extent on the type of manufacture. If the activating agent is under certain, carefully conditions to be monitored, its activating effect is in aqueous Solution so considerably strengthened that it is opposed to that of the previously used activating agents is substantially superior. The activating agent obtained by the process according to the invention is characterized by its constant and predictable pretreatment effect for phosphating so that it can be used at considerably lower concentrations than previously required for activating agents.

The pretreatment solution is made up of a dried activating agent, which is an essential ingredient containing a phosphate of sodium and a compound containing titanium.

In the production of the activating agent an aqueous slurry of a titanium-containing compound and a sodium phosphate in proportions such formed that the _pH value of the slurry is from 5.7 to 7.8 and the titanium content is at least 0.005 Vo, based on the weight

for the preparation of an activation mixture
for the pretreatment of metal surfaces

before phosphating

and mixture or aqueous solution

for this purpose

Applicant:

Metallgesellschaft Aktiengesellschaft,
Frankfurt / M., Reuterweg 14

Claimed priority:
V. St. v. America dated August 2, 1956 (No. 601 660)

Walter R. Cavanagh, Detroit, Mich.,
and James J. Mason, St. Clair Shores, Mich.

(V. St. A.),
have been named as inventors

the titanium-containing compound and the sodium phosphate. Here are the titanium compound first and at least some of the sodium phosphate and water combined at a maximum of 24 ° C and mixed. The temperature of the mixed sludge is then increased and the Mud, which was optionally supplemented with sodium phosphate, so long on the sufficiently high Maintained temperature so that the mud ages. Then the aged sludge is dried.

The initial dispersion or intimate mixing of the titanium compound with at least part of the sodium phosphate is carried out as quickly as possible in this procedure, and although in an aqueous phase at low temperature. Following this critical phase of manufacture in contacting the titanium compound with at least a portion of the sodium phosphate the mixture is heated to a minimum temperature for a minimum period of time, during which additional amounts of sodium phosphate can be added if desired. This treatment stage is called aging treatment in the following. From the aged mixture

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3 4

the activation mixture is obtained by drying. It has been found that titanyl sulfate is present in posed. The type of treatment according to the invention increases dilute acid, for example sulfuric acid, however the reactivity of the activating agent can thus also be dissolved in water. That in the trade considerable that its ability to the metal surface obtainable titanyl sulfate contains a certain amount to activate, shows itself already when it is in concen- 5 free sulfuric acid.

trations that are far below the concentration, As sodium phosphate, which is the solution of the titanium

the compound that has hitherto been added for the preparation of the compound required is, according to the invention, used in aqueous solution. commonly used disodium orthophosphate. In addition, if the solutions can be prepared in place of the disodium phosphate, other reproducible sodium phosphates can be used, for example and predeterminable effects on the phosphate reduction which includes sodium tripolyphosphate or tetrasodium pyrophosphate, which was the case with earlier phate or mixtures thereof. Either of these two solutions was not the case. the latter can be used with particularly good effectiveness on activating agents containing titanium. Quantitatively, using game as previously prepared by adding disodium 15 sodium tripolyphosphate and / or Tetranatriumpyroorthophosphat in a little water at temperatures phosphate instead of Dinateiumphosphat dissolved 70-82 ⁰ C in a was and that in the amount of the same concentration of P ₂ O ₅ heated solution a soluble Titanvetfbindiung, z. B. there, as it is required for disodium phosphate. Titanyl sulfate, dispersed. An elevated temperature was therefore used, so that the solid 20 also part of the required disodium material can more easily be dissolved. The _pH value of the mixture replace phats, and for this purpose are also suitable other was adjusted to 8.5 to 9, and the phosphates of sodium, which also then dried solution together in a rotating Trommeltrock- with correspondingly decreased amounts Dinatriumner obtained. phosphate can be applied. In some

In contrast to this, according to the invention, in 25 cases, ^{an aqueous phosphate of sodium was formed by adding certain other low temperatures (up to 24 0} C) as a replacement of part of the sludge from a titanium-containing compound and the required amount of disodium phosphate from a sodium phosphate and the sludge with the activating agent shown get that mixes in each of this temperature. Only then will the relationship be comparable with those that were aged at the higher temperature at the temperature of the sludge increased and the same at the higher temperature obtained at the temperature of disodium phosphate alone. As other phosphates of sodium, mud can be dried. For example, an aqueous monosodium orthophosphate solution or dispersion of a titanium-containing phosphate and trisodium orthophosphate and compound is successfully prepared for this purpose and either a sodium mixture thereof is used therein. Determining triumphal phosphate solution or the dry salt dispersed 35 for the choice of sodium phosphate compound or yeast. The addition of the Phosphorsäureverbin- of mixtures of such compounds, the p _H value dung to the titanium solution or dispersion forms of the sludge resulting in the contacting with the titanium, a slurry of the compounds preferably containing at least 10 minutes, at a low temperature Thoroughly thorough. In general, any combination that is mixed can be used. The pg value of the sludge is kept between a maximum of 7.8 and a minimum of 5.7. Are located, which leads to a slurry whose _pH value _is the _pH value of the sludge outside these limits within the, as indicated above, einzudann one which is according to the invention to be achieved retaining p _H -region obtained, it being understood, Advantages do not. Preferably, the _pH value is of that this _pH value directly with the aid of the phosphate sludge maintained from 6.4 to 7.6. For the input and the sodium ion and for the adjustment of the pH value of the sludge, sulfuric acid or sodium hydroxide is preferably avoided if the addition of foreign ions in the form of acids and bases is required.

but only in relation to the sodium phosphate in the production of the sludge determines the

minor amounts, are used. The amount of titanium-containing compound is the amount of temperature of the mud during this first 50 of the sodium phosphate. The dispersion level should preferably not exceed 24.degree. Amount of the titanium-containing compound such that lower temperatures, preferably not below a dried powder with 1% titanium, is obtained. 15 ° C, do not disturb. There were also satisfactory Satisfactory results are, however, already produced activators from sludges obtained when the concentration of titanium in the first mixing at 1O ⁰ C maintained 55-dried powder is only affording 0.005%. One received. Preferably, however, the temperature is of practically no advantage if more titanium is kept between 18 and 21 ° C in the sludge. Holding compound in the sludge is used as a preferred titanium compound for economic reasons, titanyl sulfate is used for economic reasons, but it is necessary with 4% titanium.

can also use other compounds that contain titanium ions in 60 The amount of water required for the production of the Providing the solution, being used successfully, using sludge is not critical. Man delay. B. KaHumtitanfluorid. It is not important, preferably use the smallest possible amount, where the titanium ions come from. The titanium compound because the water has to be removed later. can be dissolved or dispersed at elevated temperature. You can and will use warm water will. But before the phosphate compound puffs- 65 generally do to forgive the titanium-containing compound will, the solution or dispersion in the bond will dissolve or disperse. In general above indicated area of lower temperatures, water at a temperature is used temperature and only then this mixture is pre-heated from about 77 ° C. If the titanium-containing compound

Binding dissolved or dispersed in the tub of water is, the solution is cooled until the temperature is in the above, for the mixture with Sodium phosphate specified temperature range '-'is.

The amount of sodium phosphate to be used is preferably that which is required to obtain a dry activation mixture which is 0.005 to 4% Titanium based on the weight of sodium phosphate plus titanium containing compound. if for example, commercially available titanyl sulfate and disodium phosphate are used and a concentration of 1% titanium in the dried activation mixture strives, then per 4.5 kg of titanyl sulfate for sludge production about 41 kg Disodium phosphate used.

The entire amount of sodium phosphate can be added to the solution or dispersion at low temperature add the titanium-containing compound in the first dispersion. Preferably, however less than the required amount of sodium phosphate compound is added at this point and the Remaining only immediately before or during the aging treatment at high temperature. Usually sets only about 20% of the sodium phosphate required during the first, at low temperature carried out production of the sludge. It was found that even an addition of only r% of the required amount still leads to satisfactory pretreatment results at this point. If less sodium phosphate is used than the total required when mixing the sludge lower temperature too, then a major benefit is the rest of the required Add amount at an average temperature which is below the temperature to which the Sludge needs to be heated for aging treatment.

Mixing the sludge at low temperature is done regardless of the amount of sodium phosphate, who is present at this stage of treatment, as briefly as possible. The shortest possible time while the sludge is kept under the control of the temperature as indicated above depends to some extent on the amount of material that is mixed, and therefore cannot be precisely defined. Some trials under the working conditions leave for everyone determine the minimum permissible time in a special case. In general, it is enough to soak the mud for 10 minutes to keep at -low temperature, although usually 30 minutes to 1 hour in practice can be applied.

The sludge is then heated (aged). The pH of the sludge does not normally change during the aging treatment from that which it was adjusted to when it was dispersed. It is important in any case that the _pH value lies in the aging treatment from 5.7 to 7.8.

The temperature range in which the aging of the sludge takes place is preferably between about 74 and 88 ° C. Preferably the aging treatment is carried out between 79 and 82 ° C. the The time that the sludge is kept at the elevated temperature for aging depends on the amount of the ingredients subjected to the treatment and also the one used Aging temperature. In general, the sludge must be aged longer, if lower Temperatures are applied. The shortest possible time cannot generally be stated. Usually however, 30 minutes is sufficient. Prolonged aging does no harm to the temperature is kept within the specified limits.

During the aging treatment, the pg of the solution is preferably monitored to ensure that it remains within the specified limits. It is easiest to do this monitoring when the remainder of the required amount of sodium phosphate is added. It is also possible to add the rest of the Natriurnphosphatverbindung at a lower temperature, for example 60 ° C, while the slurry is heated to the aging temperature, the procedure is in this way, then preferably the _pH value of the slurry regardless of the addition of the remaining sodium phosphate checked at least once during the aging treatment. As already indicated, it has been found in practice that an adjustment of the p _H -value is generally not necessary because the mud the Acedität which he had in the mixing at low temperature maintains, unless substantial amounts of the sodium phosphate can only be added after the dispersion stage.

When the sludge has aged long enough under the monitored conditions outlined above then it is dried to give a powdered activator. Like this drying is not critical. For example, a conventional rotary drum dryer can be used will. The temperature of the drum surface in the rotary drum dryer is based on the Practice according to the temperature of the steam used, corresponding generally from 5.6 to 7 atm.

When selecting the titanium compound and sodium phosphate in the mixing ratio and the above treated sludge in this way, then a dry activation mixture is obtained, which preferably contains 0.005 to 4 percent by weight of titanium, based on the total amount of salt (soluble, titanium-containing compound and sodium phosphate).

For use, the dried activating agent is preferably used in such amounts Dissolved water to obtain an aqueous pretreatment solution containing titanium in a concentration from 0.0004 to 0.05% and 0.01 to 2% sodium phosphate contains. The pg value of the pretreatment solution is generally the same as the pjj value the sludge from which the dried activation mixture was obtained. Metal surfaces, that have been brought into contact with the pretreatment solution, in particular iron surfaces and Zinc surfaces are therefore suitable for the subsequent application of phosphating solutions on the Activated based on layer-forming phosphates. Metal surfaces that are affected by the pretreatment solutions according to the invention activated and then provided with a zinc or manganese phosphate coating, have a particularly distant and dense appearance crystalline coating.

In the following there are given examples of slurries of such a composition that that of them

obtained and 'at the same temperature and time dried activating agent contained 1% titanium. ^{Unless otherwise stated, 20 fl} / o of the total sodium phosphate to be added was added during the dispersion stage at low temperature and the remainder was added during the aging treatment at a higher temperature. The lower temperature in the dispersing step was maintained for 10 minutes and was 21 ° C for each example. The higher temperature aging treatment was carried out at 82 ° C for 30 minutes. Each of the dried activation mixtures was made up in an aqueous solution to produce pretreatment solutions in various concentrations up to 5 g / l. After pickling or medium to strongly alkaline cleaning and subsequent water rinsing, metal sheets were pretreated with these solutions by immersion or spraying and then phosphated with a phosphating solution. While coarsely crystalline phosphate layers, in some cases not even completely covering the metal surface, were formed without activation, closed, finely crystalline, thinner phosphate coatings resulted after activation of the surface. The activation achieved can therefore be easily recognized by the appearance of the phosphate layer. The minimum concentration of the individual dried activating agents in the pretreatment solution that was required to achieve an activating effect on steel surfaces was entered in the table.

3.2 g
3.0 g

27.0 g

Example 4

commercial titanyl sulfate, disodium phosphate (initial addition),
Disodium phosphate,

60.0 cm ^{3 of} water.

Example 5

3.2 g commercial titanyl sulfate, 1.5 g disodium phosphate (initial addition),

28.5 g disodium phosphate, 60.0 cm »water.

Example 6

3.2 g commercial titanyl sulfate, 0.3 g disodium phosphate (initial addition),

29.7 g disodium phosphate, 60.0 cm ³ water.

Example 7

A slurry was made using monosodium phosphate in place of disodium phosphate. The thereby resulting _pH value of the sludge was outside the critical area.

3.2 g of commercially available titanyl sulfate, 29.0 g of monosodium phosphate, 60.0 cm ^{3 of} water.

_D. ■, ι Example 8

Example 1 . ^c

A mud was produced in which only

A slurry was _{/ o of the} required Dinatriumphosphats prepared from the following components _{35 5} <used: were.

3.2 g commercial titanyl sulfate, 30.0 g disodium phosphate, 60.0 cm ³ "water.

Example 2

A slurry was prepared in such a way that the commercially available titanyl sulfate was dispersed in 2.5% sulfuric acid. Characterized the titanyl sulfate from 0.9 to 0.5 of _pH value was lowered.

19.2 g of commercially available titanyl sulfate, 180.0 g of disodium phosphate, 360.0 cm ^{3 of} 2.5% sulfuric acid.

Example 3

A slurry was made using sodium tripolyphosphate instead of disodium phosphate was used.

3.2 g of commercially available titanyl sulfate, 16.0 g of sodium tripolyphosphate, 60.0 cm ^{3 of} water.

Similar results were obtained with sodium tetrapyrophosphate instead of disodium phosphate.

In the following three examples, not 20% of the total disodium phosphate was added in the dispersion stage carried out at low temperature, but in one case 10 "/ o, in the other 5 * / o and in another 1%. The remainder of the total amount was added during the Aging treatment at the higher temperature added: 3.2 g of commercially available titanyl sulfate, 1.5 g of disodium phosphate in total in the dispersion stage, 60.0 cm ^{3 of} water.

The _pH value of the slurry was not determined in this example. However, it was obviously outside the critical area, as indicated by the pH value of the pretreatment solution prepared with this mixture.

The following example shows the significance of this is that the desired _pH value is to be obtained mainly in the sludge by use of the phosphate ion and the sodium ion, because otherwise these components are not present in the required quantities.

Example 9

A slurry, which was prepared according to Example 8 were 1.5 g of sodium carbonate was added up to fix the _pH value to a normal slurry.

60

Example 10

The activation effect was investigated with a sludge as it was prepared according to Example 1, without drying after aging.

In the following four examples, about 5 and about 10 percent, respectively, of the total disodium phosphate were used replaced by monosodium phosphate or trisodium phosphate and the relevant compound in the Mixing added at lower temperature.

Example 11

10

19.2 g of commercial titanyl sulfate, 19.2 g

27.0 g disodium phosphate (initial addition 36.0 g

sentence), ₅ ^1O8 '° §

9.0 g of monosodium phosphate

Additive), 36.0 g

144.0 g disodium phosphate, 360.0 cm ³ water.

Example 12

19.2 g commercial titanyl sulfate, 18.0 g disodium phosphate (initial addition),
18.0 g monosodium phosphate (initial

Additive),

144.0 g disodium phosphate, 360.0 cm ³ water.

Example 13

19.2 g commercial titanyl sulfate, 27.0 g disodium phosphate (initial addition),

11.5 g trisodium phosphate (initial addition), 144.0 g disodium phosphate, 360.0 cm ³ water.

Example 14

19.2 g commercially available titanyl sulfate,

18.0 g disodium phosphate (initial addition),

23.0 g trisodium phosphate (initial addition),

144.0 g disodium phosphate, 360.0 cm ³ water.

In the following four examples, about 20, 40, 60, and 80% of the total disodium phosphate were used replaced by monosodium phosphate and this phosphate during the aging treatment added at high temperature. In the subsequent example 19, 25% of the total Amount of disodium phosphate replaced by trisodium phosphate and this during the aging treatment added at higher temperature. Even more extensive replacement with trisodium phosphate during this stage of treatment did not achieve the goal. Disodium phosphate was present in all five examples below during the mixing treatment at low temperature in amounts of 20% of the total phosphate addition added.

Example 15

19.2 g of commercially available titanyl sulfate, 36.0 g of disodium phosphate, 36.0 g of monosodium phosphate (added on

End),

108.0 g disodium phosphate (addition at the end), 360.0 cm ³ water.

Example 17

Commercially available titanyl sulfate, disodium phosphate, monosodium phosphate (added on End),

Disodium phosphate (added at the end), 360.0 cm ^{3 of} water.

Example 18

19.2 g of commercially available titanyl sulfate, 36.0 g of disodium phosphate, 144.0 g of monosodium phosphate (added on

End),
360.0 cm ^{3 of} water.

Example 19

19.2 g of commercially available titanyl sulfate, 36.0 g of disodium phosphate, 46.0 g of trisodium phosphate (addition at the end), 108.0 g of disodium phosphate (addition at the end), 360.0 cm ^{3 of} water.

Tabel

Ph p _H the previous Minimal of the mud treatment concentration No. of after addition solution on dried Example all Activation Chemicals 7.5 medium g / l 1 7.5 6.9 0.16 2 6.7 7.35 0.32 3 - 7.52 0.63 4th 7.45 7.51 0.32 5 7.55 7.55 0.32 6th 7.45 3.77 0.16 7th 2.99 2.40 * 8th - 7.60 * 9 7.45 - 10 7.5 7.18 * 11 7.2 7.18 0.32 12th 7.1 7.35 0.32 13th 7.5 7.75 0.08 14th 7.6 7.0 2.5 15th 6.8 6.63 0.32 16 6.4 6.15 0.32 17th 5.9 5.70 0.63 18th 5.0 7.9 * 19th 8.0 *

*) Up to a concentration of 5 g activating agent per liter no activating effect.

Example 16

19.2 g commercially available titanyl sulfate, 36.0 g disodium phosphate,

72.0 g of monosodium phosphate (added on

End),

72.0 g disodium phosphate (addition at the end), 360.0 cm ³ water.

Example 20

Samples of dried activating agents were prepared in the hitherto customary manner for comparison with activating agents prepared according to the invention. In the hitherto customary manner, 410 kg of disodium phosphate were dissolved in hot water at 82 ° C. for each batch. 44 kg of commercially available titanyl sulfate and a small amount of caustic soda were added to the disodium phosphate solution at an elevated temperature. The _pH value of the slurry was maintained at 8.5 and the slurry then dried in a rotating drum. Samples from the dried activation mixtures of the various approaches were used to prepare pretreatment solutions

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used at a concentration. From two hundred and seventy tested samples showed no activation effect in ninety-one samples a concentration of 5 g of dried activation mixture per liter. Huodert twenty-four Samples gave an activating effect at 5 g per liter. Forty-five samples gave one Effect at 2.5 g per liter, fourteen samples at 1.25 g per liter and two samples even at 0.15 g in liter.

In contrast to this, batches were prepared according to the method according to the invention, 91 kg of disodium phosphate being dissolved in cold water at a temperature of 21.degree. Separately, 44 kg of commercially available titanyl sulfate were dispersed in hot water at 71 ° C. and the dispersion was cooled to 18 ° C. before it was mixed with the disodium phosphate solution. Mixing was carried out at a temperature below 21 ° C. The P _{11 of} the resulting sludge was held at 7.3 and the sludge mixed for 45 minutes. Thereafter, the temperature of the mixture was raised to 60 ° C. and the remainder of the required amount of disodium phosphate, ie 318 kg, was added. The mixture was aged at 80 ° C for 1 hour. The sludge was then placed on a rotary drum dryer and dried. Samples of the dried activating agent from each batch were dissolved in water. With practically all pretreatment solutions that were prepared in this way, an activation effect was achieved at a concentration of 0.63 g of dried activation mixture per liter of solution. The lowest possible concentration for these samples has not been determined.

Claims (6)

PATENT CLAIMS: 1. A process for the production of a dried activation mixture, which, when dissolved in water, serves to pretreat metal surfaces for the reaction with phosphate solutions, from a sodium phosphate and a titanium compound, characterized in that an aqueous sludge is formed from a titanium-containing compound and a sodium phosphate in such proportions that the pg value of the sludge is between 5.7 and 7.8 and the titanium content is at least 0.005%, based on the weight of the titanium-containing compound and the sodium phosphate, in such a way that initially the titanium compound and at least one Part of the sodium phosphate and water are combined and mixed at a maximum of 24 ° C, the temperature of the sludge formed is then increased and the sludge, optionally supplemented with sodium phosphate, is kept at a sufficiently high temperature for the sludge to age and the aged sludge to be dried. 2. The method according to claim 1, characterized in that the sludge by mixing of the components at temperatures not below 15 ° C., preferably 18 to 21 ° C., and the formed sludge is aged at 74 to 88 ° C and the aged sludge is dried. 3. Process according to Claims 1 and 2, characterized in that the sodium phosphate is used Disodium phosphate, sodium tripolyphosphate or tetrasodium pyrophosphate or mixtures thereof be used. 4. The method according to claim 3, characterized in that 1 to 20% of the required Amount of phosphate during the mixing treatment at low temperature and the rest of the required Amount added during the aging treatment at the higher temperature will. 5. Dried activation mixture for the preparation of pretreatment solutions for the Activation of metal surfaces for reaction with phosphating solutions, prepared according to claims 1 to 4, characterized in that it consists of a titanium-containing compound and a sodium phosphate compound in such proportions that it is 0.005 to Contains 4% titanium, based on the total weight of the mixture. 6. Pretreatment solution for activating metal surfaces for reaction with phosphating solutions, obtained by dissolving the mixture according to claim 5 in water, consisting of an aqueous solution as essential Components contains 0.0004 to 0.05% titanium and 0.01 to 2% sodium phosphate. © 309 537/394 2.