Technical Field
[0001] The present invention relates to a liquid composition, generally denoted for brevity
hereinafter as a "bath" or more specifically as a "tinplate-cleaning bath", that is
used to clean the surface of tinplate (i.e., tin plated steel), especially in the
form of sheet, strip, and products made by shaping them, e.g., cans and other containers
and the like. These various forms of tinplate are collectively known as tinplate stock.
The present invention also relates to a process for cleaning tinplate stock. In particular,
the present invention is excellently suited for cleaning "DI" tinplate cans that are
fabricated by the drawing and ironing of tinplate sheet and strip.
[0002] More particularly, the present invention relates to a novel tinplate-cleaning bath
and process that, when applied to the surface of tinplate, results in the removal
of organic materials (e.g., oil, lubricants, etc.) and inorganic materials (e.g.,
abrasives, etc.) and the generation of a surface condition that is well adapted for
conversion treatment. Moreover, this novel tinplate-cleaning bath and process are
strongly resistant to the deposition of the sludge that is caused by the insolubilization
of tin eluted by cleaning into the bath from the surface of the tinplate stock.
Background Art
[0003] The prior art for tinplate-cleaning baths is exemplified by Japanese Patent Publication
[Kokoku] Number Sho 59-2752 [2,752/1984] and Japanese Patent Application Laid Open
[Kokai or Unexamined] Numbers Hei 3-59993 [59,993/1991] and Hei 3-59994 [59,994/1991].
[0004] The alkaline cleaning bath of Japanese Patent Publication Number Sho 59-2752 contains
alkali metal silicate, alkali metal salt and alkali metal bicarbonate at ≤ 1.5-fold
(weight basis) of the amount of alkali metal silicate, and surfactant at ≤ 0.4-fold
(weight basis) of the amount of alkali metal silicate. This particular alkali component
(known as builder) is specified in order to inhibit excessive dissolution of the tinplate
surface due to line stoppage caused by problems in the degreasing line.
[0005] As for the bath discussed above, the alkaline cleaning bath of Japanese Patent Application
Laid Open Number Hei 3-59993 is intended to inhibit excess dissolution of the tinplate
surface. This bath is an aqueous solution that contains 1.5 to 10 grams per liter
(hereinafter often abbreviated "g/L") of alkali metal or ammonium salt of orthophosphoric
acid and 0.5 to 2 g/L of alkali metal nitrite. These two components are used in a
molar ratio (former : latter) of 1 : 1 to 3.86 : 1. Bath pH is regulated to 9 to 11
with alkali metal carbonate.
[0006] Again as for the baths discussed above, the alkaline cleaning bath of Japanese Patent
Application Laid Open Number Hei 3-59994 is intended to inhibit excess dissolution
of the tinplate surface. This bath is an alkaline aqueous solution with pH 9 to 13
that contains surfactant, alkali metal or ammonium salt of orthophosphoric acid, and
at least 0.005 g/L of at least 1 selection from the group comprising the alkaline
earth metal oxides, hydroxides, chlorides, bromides, iodides, carbonates, nitrates,
sulfates, and phosphates. This bath does not contain organic acid nor the salts of
organic acids.
[0007] Tinplate stock is typically cleaned by spraying. For example, the equipment for treating
the surface of tinplate DI can is generally known as a washer. The formed DI can is
continuously treated - while inverted - with the cleaning bath and conversion bath.
Existing washers are organized into 6 stations (preliminary cleaning, cleaning, water
wash, conversion treatment, water wash, and de-ionized water wash), and all the steps
are executed by spraying. The alkaline cleaning bath is sprayed onto a plural number
of DI cans in the preliminary cleaning and cleaning steps, and is then recycled to
a tank and returned to the spray.
[0008] The alkaline cleaning bath of Japanese Patent Publication Number Sho 59-2752 initially
has a good cleaning performance when actually used in a washer, but silicate salts
gradually precipitate and sediment from this cleaning bath. A satisfactory cleaning
operation is ultimately precluded because this precipitate - a solid generally known
as sludge - clogs the pipe system and nozzles in the spray equipment.
[0009] Japanese Patent Application Laid Open Number Hei 3-59993 teaches that the presence
of condensed phosphate salts in alkaline cleaning baths causes an increase in metal
solubilization and a deterioration in corrosion resistance both for unpainted and
painted tinplate stock. While the omission of condensed phosphate salts from this
bath does result in the inhibition of tin dissolution, moderate amounts of dissolved
tin still precipitate as, for example, tin phosphate. This results in the production
of sludge and thus the appearance of the same problem as outlined above.
[0010] An excellent cleaning performance is initially obtained for the use of the alkaline
earth metal oxides, hydroxides, and chlorides in the case of the alkaline cleaning
bath of Japanese Patent Application Laid Open Number Hei 3-59994. However, the tin
gradually eluting from the tinplate stock reacts with phosphoric acid or carbonic
acid present in the cleaning bath. This results in the precipitation and sedimentation
of phosphate or carbonate salts with the appearance of sludge.
[0011] EP-A-0 206 222 discloses a cleaning agent for tin-plated iron materials in a concentration
of 1-30 g/l and a pH of 10.5-13, comprising 0.5 to 25 parts by weight alkali silicate,
0.1-3 parts by weight alkali phosphate, 0.1-3 parts by weight complexing agent, such
as EDTA, and surfactants such as 0.05-1.5 parts by weight ethoxylated alcohols (nonionic)
and such as 0.05-1.5 parts by weight chloride derivatives of polyethoxylated aliphatic
alcohols (anionic). Spraying of the solution with a contact time of 30 to 60 s is
disclosed.
[0012] The application of phosphonic acid derivatives as complexing or chelating agents
and the selection of a pH above 8, preferably 9 to 12 can be derived from EP-A-0 111
284 and EP-A-0 124 815.
[0013] With regard to the sludge that is produced by continuous cleaning as described above,
a portion will sediment in the liquid tank while another portion will clog the pipe
system and nozzles of the spray equipment as the result of its circulation through
the pipe system. Clogging of the pipe system and/or nozzles results in a poor cleaning
performance due to a diminished quantity of spray on each DI can and nonuniform contact
with the DI cans.
[0014] Moreover, in the case of the industrial use of alkaline cleaning baths, small quantities
of the bath are continuously or intermittently drawn off in a method known as autodraining,
and the bath is supplemented with fresh cleaning bath. The released cleaning bath
is discharged through a wastewater treatment process. While the alkaline cleaning
baths as described above do not require a particularly high level of wastewater treatment,
their wastewater treatment nevertheless produces a solid product. Although this solid
product is generally known as "sludge", for the purposes of this application it will
be referred to as "wastewater treatment sludge" in order to differentiate it from
the sludge already discussed above.
[0015] As a result of the high alkali concentration during the cleaning process in the prior
alkaline cleaning baths, the corresponding wastewater treatment generates large overall
quantities of wastewater treatment sludge that must be processed. This wastewater
treatment sludge is currently disposed of as an industrial waste, but reductions in
the quantity of wastewater treatment sludge would be desirable from the standpoints
of reducing costs and environmental protection.
Disclosure of the Invention
Problems to Be Solved by the Invention
[0016] Thus, use of the prior alkaline cleaning baths is burdened by the requirement that
the pipe system and nozzles of the spray equipment be cleaned on a frequent and regular
basis. Since improvements in productivity in the cleaning of tinplate stock have recently
become a critical issue, there is strong demand for the provision of a cleaning bath
that lessens the burden of preventive cleaning, i.e., that does not lead to the development
of sludge in the bath even when subjected to continuous use. In addition, permissible
values for effluents have become increasingly stringent due to environmental considerations.
As a result, reducing the load on wastewater treatment has become an important topic.
Summary of the Invention
[0017] In order to solve the problems described hereinbefore, a tinplate-cleaning bath was
discovered that characteristically has a pH of 8 to 11 and comprises, preferably consists
essentially of, or more preferably consists of: water; 0.5 to 10.0 g/L of alkali builder
comprising one or more selections from the alkali metal hydroxides, alkali metal and
ammonium salts of inorganic phosphoric acid, alkali metal borates, and alkali metal
and ammonium carbonates; 0.05 to 1.0 g/L of chelating agent comprising one or more
selections from the hydroxyalkyldiphosphonic acids, aminotrialkylphosphonic acids,
ethylenediaminetetraacetic acid, nitrilotriacetic acid, condensed phosphoric acids,
and the alkali metal and ammonium salts of the preceding; and 0.05 to 2.0 g/L of surfactant.
The present invention was achieved based on this discovery.
[0018] The tinplate-cleaning bath of the present invention removes organic materials (e.g.,
oil, lubricants, etc.) and inorganic materials (e.g., abrasives, etc.) from the surface
of tinplate stock (sheet, strip, and moldings thereof such as can, etc.) and generates
a surface condition that is well suited for conversion treatment. Moreover, the tinplate-cleaning
bath of the present invention produces only vanishingly small quantities of the sludge
that forms from the tin eluting into the cleaning bath and the hard water components
present in the water used to make up the bath.
[0019] The cleaning bath of the present invention is excellently suited for cleaning DI
cans. In this process, large numbers of DI cans may be continuously cleaned with the
cleaning bath of the present invention - without the production of a hard water component/tin
sludge - by conveying the tinplate-cleaning bath of the invention from a storage tank
through a pipe system, then spraying the same from a nozzle onto the tinplate stock
to be cleaned, returning the bath to said storage tank, and subsequently re-spraying
the bath.
[0020] In other words, with regard to the cleaning of DI can using washers, the tinplate-cleaning
process under consideration makes possible continuous and long-term cleaning without
the production of the sludge that forms from tin eluting into the cleaning bath and
hard water components present in the water used to make up the bath. Moreover, during
this run, the tinplate-cleaning process of the present invention removes organic materials
(e.g., oil, lubricants, etc.) and inorganic materials (e.g., abrasives, etc.) from
the surface of tinplate stock (sheet, strip, and products therefrom such as can, etc.)
and generates a surface condition that is strongly adapted for conversion treatment.
Sludge production is evaluated by the following procedure: Liquid is withdrawn into
a transparent container from the storage tank for the alkaline cleaning bath, and
the transparency of the sample is then evaluated with the unaided eye. The process
of the present invention makes possible a continuous sludge-free cleaning run under
the usual continuous treatment conditions, i.e., cleaning temperature = ambient to
80° C, spray time = 2 to 60 seconds/can, bath renewal/discharge = 0.04 to 0.08%/1,000
cans.
Description of Preferred Embodiments
[0021] The composition of the alkaline cleaning bath of the present invention and the cleaning
process of the present invention will be explained in greater detail below.
[0022] Among its various components, the alkaline cleaning bath of the present invention
contains 0.05 to 10.0 g/L of an alkali builder comprising one or more selections from
the alkali metal hydroxides, alkali metal and ammonium salts of inorganic phosphoric
acid, alkali metal borates, alkali metal silicates, and alkali metal and ammonium
carbonates. This component is designated as component A in the examples.
[0023] The alkaline cleaning bath of the present invention also contains 0.05 to 1.0 g/L
of compound(s) comprising one or more selections from the hydroxyalkyldiphosphonic
acids, aminotrialkylphosphonic acids, ethylenediaminetetraacetic acid, nitrilotriacetic
acid, condensed phosphoric acids, and the alkali metal and ammonium salts of these
compounds. This component is designated as component B in the examples.
[0024] The alkaline cleaning bath of the present invention also contains 0.05 to 2.0 g/L
of surfactant (designated as component C in the examples). Water is the balancing
component, and this water can be industrial-grade water or tapwater as well as deionized,
distilled, or other purified water. The tinplate-cleaning bath of the present invention
should have a pH of 8 to 11.
[0025] The alkali metal salts comprising the alkali builder consist of the potassium and
sodium hydroxides, carbonates, borates, and inorganic phosphates. Examples are potassium
hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate,
borax, trisodium phosphate, and so forth. These may be used singly or in combinations
of two or more selections. The particular alkali builder concentration should be selected
so as to provide a cleaning power (etching capacity) adapted to the surface condition
of the tinplate stock. The alkali builder will generally be used at a concentration
of from 0.5 to 10.0 g/L and is preferably used at a concentration of from 1.0 to 5.0
g/L. At a concentration below 0.5 g/L, cleaning will normally be unsatisfactory due
to inadequate etching. While an excellent cleaning performance can be obtained at
above 10.0 g/L, the use of such concentrations normally leads to an increase in the
wastewater treatment sludge.
[0026] The chelating agent (hydroxyalkyldiphosphonic acid, aminotrialkylphosphonic acid,
ethylenediaminetetraacetic acid, nitrilotriacetic acid, condensed phosphoric acid,
and the alkali metal and ammonium salts of the preceding) is added in order to promote
stable dispersion and/or solubility of the tin ions released from the tinplate stock
in the cleaning bath. Thus, tin ion accumulates in the bath during the continuous
cleaning of tinplate stock, and this tin ion reacts with phosphoric acid, silicic
acid, or carbonic acid to produce sludge. The listed compounds are believed to chelate
the tin ions and thereby inhibit the production of sludge (tin phosphate, etc.) in
the cleaning bath. This inhibition of sludge production results in a substantial reduction
in the work inputs for cleaning the pipe system and nozzles of the spray equipment.
[0027] In contrast to the preceding, the calcium and magnesium ions present as hard water
components in tapwater do not accumulate in the cleaning bath and thus will not hamper
the continuous process from this standpoint. Moreover, they will not be present in
the sludge as, e.g., calcium carbonate, etc., because they are also chelated by the
hydroxyalkyldiphosphonic acid, etc.
[0028] The hydroxyalkyldiphosphonic acid is exemplified by 1-hydroxyethylidene-1,1-diphosphonic
acid, with the formula given below:
[0029] Aminotrialkylphosphonic acid is exemplified by aminotrimethylenephosphonic acid.
Condensed phosphoric acid is exemplified by pyrophosphoric acid, tripolyphosphoric
acid, and tetrapolyphosphoric acid. Hydroxyalkyldiphosphonic acid, aminotrialkylphosphonic
acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, and condensed phosphoric
acid can be used in the cleaning bath in acid form or as the alkali metal salt or
ammonium salt. These compounds can be used singly or in combinations of two or more
selections, and this component should be present at 0.05 to 1.0 g/L and preferably
at 0.1 to 0.5 g/L. At less than 0.05 g/L, there will normally be a strong tendency
for sludge to be produced in the cleaning bath because of an inadequate chelating
capacity. Quantities in excess of 1.0 g/L do not cause any particular problems, but
are less economical due to the associated increase in costs.
[0030] Ethylenediaminetetraacetic acid, nitrilotriacetic acid, and condensed phosphoric
acids are refractory to wastewater treatment because they are only poorly sedimentable
by slaked lime (calcium hydroxide). When the amenability to wastewater treatment becomes
particularly critical as discussed above, the use of the hydroxyalkyldiphosphonic
acids and their metal (ammonium) salts is recommended, since these species are very
sedimentable by slaked lime. Moreover, inasmuch as the eutrophication of rivers, lakes,
and marshes has recently become a serious problem, the use of condensed phosphoric
acid-free cleaning agents has become correspondingly desirable. Finally, the effects
of the present invention are not impaired by the supplemental addition of another
type of chelating agent, for example, an organic acid such as gluconic acid as well
as the alkali metal and ammonium salts of such organic acids.
[0031] A cleaning agent that leads readily to a wastewater that is free from phosphorus
and nitrogen will be particularly useful in regions where wastewater regulations are
particularly stringent. In such a case, the alkali builder for the present invention
may be selected from the hydroxides, carbonates, and borates and the chelating agent
may be selected from the hydroxyalkyldiphosphonic acids and aminotrialkylphosphonic
acids. This can be managed to produce a wastewater that is free from phosphorus and
nitrogen since the hydroxyalkyldiphosphonic acids and aminotrialkylphosphonic acids
- while containing phosphorus and in the latter case also containing nitrogen - are
easily sedimented with slaked lime as noted above.
[0032] Furthermore, because hydroxyalkyldiphosphonic acid, etc., has a cleaning activity,
the cleaning bath of the present invention can employ alkali salt concentrations as
low as ≤ 4 g/L, which is lower than that reported in experimental examples of the
prior art. This reduction in the use quantity of alkali builder also makes possible
a reduction in the quantity of wastewater treatment sludge produced during wastewater
treatment.
[0033] The surfactant is selected from the anionic and nonionic surfactants. Nonionic surfactants
are exemplified by hydrocarbon derivatives, abietic acid derivatives, ethoxylated
primary alcohols, and modified polyethoxylated alcohols. In either case, the surfactant
can be used in the form of a single species or as a combination of two or more species.
It should be present at a concentration of from 0.05 to 2.0 g/L and preferably at
a concentration of from 0.2 to 1.0 g/L. The organic material on the surface of the
tinplate stock will sometimes not be completely removed when the surfactant is used
at a concentration of less than 0.05 g/L. On the other hand, the use of more than
2.0 g/L surfactant is not associated with any particular problems in terms of cleaning
effects, but rather is economically undesirable due to the higher cost.
[0034] The cleaning bath should have a pH in the range of 8 to 11 and preferably in the
range of 9 to 10. At a pH below 8, the etching capacity is diminished and it becomes
difficult if not impossible to obtain a good cleaning effect. Moreover, there is a
strong tendency for sludge production to occur at a pH below 8. In contrast, etching
is undesirably strong at pH values above 11, resulting in a deterioration in appearance.
The pH can be adjusted using the usual alkalis and acids, i.e., sodium hydroxide,
potassium hydroxide, sulfuric acid, phosphoric acid, and the like, and no specific
restriction exist in this regard.
[0035] The cleaning bath of the present invention may be used at treatment temperatures
ranging from ambient temperature to 80° C, but it is preferably heated generally to
40 to 60 ° C for use. The treatment time should be 2 to 60 seconds. A satisfactory
cleaning effect is not usually obtained at below 2 seconds, while treatments in excess
of 60 seconds do not usually result in any further improvement in cleaning effect.
The treatment method may be either immersion or spray, but as discussed above the
present invention produces particularly good effects when used with spray equipment.
[0036] For wastewater treatment of the tinplate-cleaning bath, the metal ion is first dissociated
from the chelate compound in the acidic pH range. Solid-liquid separation is then
carried out by the addition of calcium hydroxide and polymer flocculent to give the
wastewater treatment sludge. Since the cleaning bath of the present invention has
a low alkali concentration, it generates only small quantities of sludge for disposal.
Moreover, the wastewater treatment efficiency is also good because the hydroxyalkyldiphosphonic
acids and aminotrialkylphosphonic acids are highly sedimentable by calcium hydroxide
and polymer flocculants.
[0037] As discussed hereinbefore, tin ions accumulate during the cleaning of tinplate stock,
and it is estimated that the tin ion concentration in the cleaning bath is 0.01 to
0.1 g/L when sludge is produced. The sludge produced by its precipitation is very
sticky and adheres to the interior of the nozzles and pipe system and thus impedes
the cleaning operation. This adhesion problem can be avoided by inhibiting dissolution
of the tinplate surface in order to prevent an increase in tin ion concentration.
However, there are limitations on the application of this approach to large-scale
cleaning runs. The present invention has therefore devised the use of a particular
component, as described above, in addition to alkali builder and surfactant
[0038] As a result use of the cleaning bath of the present invention to clean the surface
of tinplate stock (sheet, strip, and moldings) leads to a removal of both organic
and inorganic materials from the surface of the tinplate stock and thereby provides
a surface state that is very well adapted for conversion treatment. Moreover, this
cleaning is accomplished with the precipitation of vanishingly small quantities of
the sludge that is produced by tin eluting into the cleaning bath.
Examples
[0039] The cleaning bath of the present invention will be explained in greater detail below
using illustrative examples. Its utility will be demonstrated with reference to comparison
examples.
(1) Test material
[0040] The test material consisted of 1,000 uncleaned cans (66 mm diameter x 124 mm height)
that had been fabricated by the drawing and ironing of tin-plated steel sheet. Cleaning
was conducted in a conventional washer.
(2) Treatment process
[0041] Treatment was conducted in accordance with the following process [1] or process [2].
Process [1]
[0042]
1. Cleaning
2. Water wash (10 seconds, spray)
3. Wash with deionized water (10 seconds, spray)
4. Drying (180° C, hot air)
Process [2]
[0043]
1. Cleaning
2. Water wash (10 seconds, spray)
3. Conversion treatment (30 seconds, spray)
Treatment agent: PALFOS® K3482, registered brand name of Nihon Parkerizing Company,
Limited concentration: 3 %, temperature: 60° C
4. Water wash (10 seconds, spray)
5. Wash with de-ionized water (10 seconds, spray)
6. Drying (180° C, hot air)
(3) Test methods for property evaluation
Water wettability
[0044] After completion of the wash with de-ionized water in step 3 of process [1], the
can was allowed to stand for 30 seconds. The water-wetted surface area at this point
was evaluated in %. Values of at least 90 % are generally considered to be excellent.
Degreasing performance
[0045] The degreasing performance was evaluated based on the quantity of residual oil on
the surface. After treatment by process [1], the can was ultrasonically cleaned using
carbon tetrachloride, and the oil fraction eluted into the carbon tetrachloride from
the can surface was determined using an instrument for measuring the oil concentration
(POC-100 from Kabushiki Kaisha Shimadzu Seisakusho). This value is reported as the
residual quantity of oil per unit surface of the can. Values ≤ 2 mg/m
2 are generally considered excellent.
Corrosion resistance
[0046] After treatment by process [2], the corrosion resistance was evaluated using the
iron exposure value (IEV). The IEV was measured based on United States Patent Number
4,332,646. Lower IEV values indicate a better corrosion resistance. Values ≤ 150 are
generally considered excellent.
Paint adherence
[0047] In order to measure the paint adherence, the can was first treated by process [2],
and the surface of the can was then coated with an epoxy/urea can paint to a paint
film thickness of 5 to 7 micrometers. After baking for 4 minutes at 215° C, the can
was cut into 5 x 150 mm strips, and the test specimen was prepared by hot-press bonding
with polyamide film. This was peeled using the 180° peel test method in order to evaluate
the peel strength. Larger peel strength values indicate a better paint adherence.
Values ≥ 1.5 kgf/5 mm width are generally considered excellent.
Sludge production in the cleaning bath
[0048] The cleaning bath used in the particular example or comparison example was prepared
without using the surfactant. 0.1 g/L of tin was added (using stannic chloride) to
the cleaning bath thus prepared, and after this addition the pH was adjusted with
potassium hydroxide. After standing for 1 day, the condition of the bath was inspected.
In the preferred state, the bath was transparent and free of precipitate.
Wastewater treatability
[0049] The wastewater treatability was evaluated as follows. The treatment bath was first
diluted 1/10, which is equivalent to the degree of dilution in the wastewater treatment
of process baths in actual operations, and the pH of the resulting bath was brought
to 2.5 with sulfuric acid. Aqueous aluminum sulfate solution was then added to give
20 ppm as aluminum, and the pH was subsequently brought to 10 with calcium hydroxide.
10 ppm of polymer flocculant was added and a solid-liquid separation was then carried
out. The residual sludge (solids) was dried for 24 hours at 100° C, then cooled and
weighed. The wastewater treatability was evaluated based on this weight, i.e., low
quantities of sludge production are desirable.
Example 1
[0050] Cleaning was conducted at 50° C for 30 seconds using cleaning bath 1. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
1.
cleaning bath 1
[0051]
sodium carbonate |
(A) |
2.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
sodium tripolyphosphate |
(B) |
0.4 g/L |
nonylphenol/11 EO adduct |
(C) |
0.2 g/L |
pH 9.6 (adjusted with sodium hydroxide)
Example 2
[0052] Cleaning was conducted at 50° C for 30 seconds using cleaning bath 2. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
2.
cleaning bath 2
[0053]
potassium carbonate |
(A) |
1.0 g/L |
potassium bicarbonate |
(A) |
2.0 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.2 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.3 g/L |
pH 9.6 (adjusted with sodium hydroxide)
Example 3
[0054] Cleaning was conducted at 50° C for 30 seconds using cleaning bath 3. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
3.
cleaning bath 3
[0055]
sodium carbonate |
(A) |
2.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
sodium ethylenediaminetetraacetate |
(B) |
0.5 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.2 g/L |
pH 10.0 (adjusted with sodium hydroxide)
Example 4
[0056] Cleaning was conducted at 50° C for 60 seconds using cleaning bath 4. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
4.
cleaning bath 4
[0057]
sodium carbonate |
(A) |
1.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.3 g/L |
nonylphenol/11 EO adduct |
(C) |
0.2 g/L |
pH 8.7 (adjusted with sulfuric acid)
Example 5
[0058] Cleaning was conducted at 40° C for 15 seconds using cleaning bath 5. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
5.
cleaning bath 5
[0059]
sodium hydroxide |
(A) |
0.3 g/L |
disodium hydrogen phosphate |
(A) |
1.0 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.3 g/L |
nonylphenol/11 EO adduct |
(C) |
0.4 g/L |
pH 10.5 (adjusted with sodium hydroxide)
Example 6
[0060] Cleaning was conducted at 60° C for 60 seconds using cleaning bath 6. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
6.
cleaning bath 6
[0061]
sodium carbonate |
(A) |
1.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
sodium tripolyphosphate |
(B) |
0.1 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.3 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.4 g/L |
pH 8.7 (adjusted with sulfuric acid)
Example 7
[0062] Cleaning was conducted at 30° C for 60 seconds using cleaning bath 7. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
7.
cleaning bath 7
[0063]
sodium carbonate |
(A) |
1.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
borax |
(A) |
1.0 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.3 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.4 g/L |
pH 10.2 (adjusted with sodium hydroxide)
Comparison Example 1
[0064] Cleaning was conducted at 50° C for 30 seconds using cleaning bath 8. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
8.
cleaning bath 8
[0065]
sodium carbonate |
(A) |
1.0 g/L |
sodium bicarbonate |
(A) |
2.0 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.4 g/L |
pH 9.6 (adjusted with sodium hydroxide)
Comparison Example 2
[0066] Cleaning was conducted at 50° C for 30 seconds using cleaning bath 9. The water wettability,
degreasing performance, corrosion resistance, and paint adherence were evaluated.
Sludge production and wastewater treatability were also evaluated for cleaning bath
9.
cleaning bath 9
[0067]
potassium carbonate |
(A) |
1.0 g/L |
potassium bicarbonate |
(A) |
2.0 g/L |
1-hydroxyethylidene-1,1-diphosphonic acid |
(B) |
0.2 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.4 g/L |
pH 7.5 (adjusted with sulfuric acid)
Comparison Example 3
[0068] Cleaning was conducted at 60° C for 60 seconds using cleaning bath 10. The water
wettability, degreasing performance, corrosion resistance, and paint adherence were
evaluated. Sludge production and wastewater treatability were also evaluated for cleaning
bath 10.
cleaning bath 10
[0069]
sodium metasilicate |
(A) |
2.5 g/L |
sodium carbonate |
(A) |
2.5 g/L |
higher alcohol/5 EO/10 PO adduct |
(C) |
0.3 g/L |
pH 11.0 (adjusted with sodium hydroxide)
Comparison Example 4
[0070] Cleaning was carried out for 30 seconds at 50° C using the 1% cleaning bath of a
commercial cleaning agent for tinplate DI can that contained alkali builder and surfactant
as effective components (FINE CLEANER™ 4361A, registered brand name of Nihon Parkerizing
Company, Limited). The water wettability, degreasing performance, corrosion resistance,
and paint adherence were evaluated. Sludge production and wastewater treatability
were also evaluated for this cleaning bath.
[0071] In all the descriptions of the specific cleaning baths above, "EO" means ethylene
oxide, "PO" means propylene oxide, and the number preceding these symbols in the description
of the adducts indicates the average number of moles of the indicated oxyalkylene
groups in the adduct per mole of the alcohol or phenol first specified in the description.
[0072] The results are shown in Table 1.
TABLE 1
|
Water Wettability, % |
Degreasing Performance, mg/m2 |
Corrosion Resistance, IEV |
Adherence, kgf/5 mm |
Sludge Production |
Wastewater Treatability, grams |
Ex. 1 |
100 |
1.5 |
100 |
3.0 |
transparent |
0.8 |
Ex. 2 |
100 |
1.2 |
70 |
3.0 |
transparent |
0.6 |
Ex. 3 |
100 |
1.6 |
100 |
3.0 |
transparent |
0.8 |
Ex. 4 |
100 |
1.3 |
70 |
3.0 |
transparent |
0.6 |
Ex. 5 |
100 |
1.4 |
70 |
3.0 |
transparent |
0.6 |
Ex. 6 |
100 |
1.5 |
70 |
3.0 |
transparent |
0.6 |
Ex. 7 |
100 |
1.5 |
70 |
3.0 |
transparent |
0.6 |
Comp. Ex. 1 |
100 |
1.8 |
120 |
2.5 |
white turbidity, precipitation |
0.9 |
Comp. Ex. 2 |
80 |
2.1 |
200 |
1.5 |
moderate turbidity |
0.9 |
Comp. Ex. 3 |
100 |
1.7 |
120 |
2.5 |
white turbidity, precipitation |
2.5 |
Comp. Ex. 4 |
100 |
1.5 |
100 |
3.0 |
moderate turbidity |
2.0 |
Benefits of the Invention
[0073] As demonstrated by Table 1 (summary of examples and comparison examples), the present
invention exhibits an excellent cleaning performance in the cleaning of tin-plated
DI can as evaluated on the basis of the generally critical properties of water wettability,
degreasing performance, corrosion resistance, and adherence. This cleaning performance
is equivalent to that afforded by the prior art. However, the present invention is
superior to the prior art with regard to sludge inhibition and wastewater treatability.
[0074] While the examples concern the cleaning of DI can, it is clear that the same performance
will be obtained for other types of products formed from sheet and strip as well as
for the starting tinplate sheet and strip. Thus, the present invention provides extremely
good results in terms of increasing the efficiency in the cleaning of tinplate stock
and reducing the load on wastewater treatment.
1. Flüssige wäßrige Stoffzusammensetzung, die sich zur Reinigung von Weißblechmaterial
eignet, wobei die Zusammensetzung einen pH-Wert im Bereich von 8 bis 11 hat und im
wesentlichen aus Wasser sowie:
(A) 0,5 bis 10,0 g/l Alkalibuilderkomponente, die aus der Gruppe ausgewählt ist, die
aus Alkalimetallhydroxiden, Alkalimetall- und Ammoniumsalzen von anorganischer Phosphorsäure,
Alkalimetallboraten, Alkalimetall- und Ammoniumcarbonaten und Gemischen von zwei oder
mehreren davon besteht;
(B) 0,05 bis 1,0 g/l Chelatisierungsmittelkomponente, die aus der Gruppe ausgewählt
ist, die aus Hydroxyalkyldiphosphonsäuren, Aminotrialkylphosphonsäuren, Ethylendiamintetraessigsäure,
Nitrilotriessigsäure, kondensierten Phosphorsäuren, den Alkalimetall- und Ammoniumsalzen
dieser Säuren und Gemischen von zwei oder mehreren davon besteht; sowie
(C) 0,05 bis 2,0 g/l einer Tensidkomponente, die aus der Gruppe ausgewählt ist, die
aus nichtionischen und anionischen Tensiden besteht.
2. Zusammensetzung gemäß Anspruch 1, wobei Komponente (B) aus der Gruppe ausgewählt ist,
die aus Hydroxyalkyldiphosphonsäuren, Aminotrialkylphosphonsäuren, ihren Alkalimetall-
und Ammoniumsalzen sowie Gemischen von zwei oder mehreren davon besteht.
3. Zusammensetzung gemäß Anspruch 1 oder 2, wobei die Konzentration der Komponente (A)
im Bereich von 1,0 bis 5,0 g/l liegt.
4. Zusammensetzung gemäß den Ansprüchen 1 bis 3, wobei die Konzentration der Komponente
(B) im Bereich von 0,1 bis 0,5 g/l liegt.
5. Zusammensetzung gemäß einem der Ansprüche 1 bis 4, wobei die Konzentration der Komponente
(C) im Bereich von 0,2 bis 1,0 g/l liegt.
6. Zusammensetzung gemäß Anspruch 5, wobei der pH-Wert im Bereich von 9 bis 10 liegt.
7. Verfahren zur Reinigung von Weißblechmaterial durch In-Kontakt-Bringen des Weißblechmaterials
während einer Zeit im Bereich von 2 bis 60 Sekunden mit einer Zusammensetzung gemäß
einem der Ansprüche 1 bis 6.
8. Verfahren gemäß Anspruch 7, umfassend die Schritte:
(1) Befördern der Reinigungszusammensetzung aus einem Lagertank durch ein Röhrensystem;
(2) Sprühen der Reinigungszusammensetzung aus dem Röhrensystem durch eine Düse auf
das zu reinigende Weißblechmaterial;
(3) Rückführen der Reinigungszusammensetzung, die während Schritt (2) mit dem zu reinigenden
Weißblechmaterial in Kontakt war, in den Lagertank und
(4) anschließendes erneutes Befördern der Reinigungszusammensetzung aus dem Lagertank
durch ein Röhrensystem und Sprühen der Reinigungszusammensetzung auf weiteres zu reinigendes
Weißblechmaterial.
9. Verfahren gemäß Anspruch 8, wobei die Reinigungszusammensetzung während Schritt (2)
innerhalb eines Temperaturbereichs von 40 bis 60°C gehalten wird.
1. Composition liquide semi-aqueuse de matière apte au nettoyage de tôle noire pour fer
blanc, la composition ayant une valeur de pH dans la plage de 8 à 11 et consistant
essentiellement d'eau et :
(A) de 0,5 à 10,0 g/ℓ d'un composant adjuvant alcalin choisi parmi le groupe constitué
par des hydroxydes des métaux alcalins, un métal alcalin et des sels d'ammonium d'acide
phosphorique minéral, de borate de métaux alcalins, de carbonate d'ammonium et de
métaux alcalins et de mélanges de deux ou de plus de deux de ceux-ci ;
(B) de 0,05 à 1,0 g/ℓ d'un composant agent chélatant choisi dans le groupe constitué
par des acides hydroxyalkyldiphosphoniques, des acides aminotrialkylphosphoniques,
l'acide éthylène-diamine tétraacétique, l'acide nitrilotriacétique, des acides phosphoriques
condensés, les sels d'ammonium et de métaux alcalins de ces acides, et les mélanges
de deux ou de plus de deux de ceux-ci ; et
(C) de 0,05 à 2,0 g/ℓ d'un composant tensioactif choisi dans le groupe constitué par
des agents tensioactifs non ioniques ou anioniques.
2. Composition selon la revendication 1, dans laquelle le composant (B) est choisi à
partir du groupe constitué par des acides hydroxyalkyldiphosphoniques, des acides
aminotrialkylphosphoniques, leurs sels d'ammonium et de métaux alcalins, et les mélanges
de deux ou de plus de deux de ceux-ci.
3. Composition selon la revendication 1 ou 2, dans laquelle la concentration du composant
(A) se situe dans la plage de 1,0 à 5,0 g/ℓ.
4. Composition selon les revendications 1 à 3, dans laquelle la concentration du composant
(B) se situe dans la plage de 0,1 à 0,5 g/ℓ.
5. Composition selon l'une quelconque des revendications 1 à 4, dans laquelle la concentration
du composant (C) se situe dans la plage de 0,2 à 1,0 g/ℓ.
6. Composition selon la revendication 5, dans laquelle le pH se situe dans la plage de
9 à 10.
7. Procédé pour le nettoyage de tôle noire pour fer blanc par mise en contact de la tôle
noire pour fer blanc pendant une durée dans la plage de 2 à 60 secondes avec une composition
selon l'une quelconque des revendications 1 à 6.
8. Procédé selon la revendication 7, comprenant les étapes consistant à :
(1) acheminer la composition de nettoyage à partir d'un réservoir de stockage par
l'intermédiaire d'un système de tuyauterie ;
(2) pulvériser la composition de nettoyage à partir du système de tuyauterie par une
tuyère sur la tôle noire pour fer blanc à nettoyer ;
(3) renvoyer la composition de nettoyage qui a été mise en contact avec la tôle noire
pour fer blanc à nettoyer pendant l'étape (2) vers le récipient de stockage ; et
(4) consécutivement, acheminer un nouveau la composition de nettoyage à partir du
réservoir de stockage par l'intermédiaire d'un système de tuyauterie et pulvériser
la composition de nettoyage sur la tôle noire pour fer blanc par l'intermédiaire d'un
système de tuyauterie et pulvériser la composition de nettoyage sur la tôle noire
pour fer blanc à nettoyer.
9. Procédé selon la revendication 8, dans lequel la composition de nettoyage est maintenue
dans une plage de température de 40 à 60°C au cours de l'étape (2).