U.S. patent application number 14/476335 was filed with the patent office on 2014-12-18 for setting retarder for hydrate-forming binders.
This patent application is currently assigned to SIKA TECHNOLOGY AG. The applicant listed for this patent is SIKA TECHNOLOGY AG. Invention is credited to Christina HAMPEL, Joerg ZIMMERMANN.
Application Number | 20140366780 14/476335 |
Document ID | / |
Family ID | 44246137 |
Filed Date | 2014-12-18 |
United States Patent
Application |
20140366780 |
Kind Code |
A1 |
HAMPEL; Christina ; et
al. |
December 18, 2014 |
SETTING RETARDER FOR HYDRATE-FORMING BINDERS
Abstract
A setting retarder for hydrate-forming binders is produced by
reacting a first reactant A, including an amino acid and/or an
amino acid derivative, with a second reactant C, including an
amine-free carboxylic acid and/or an amine-free carboxylic acid
derivative, in a reaction mixture to form a reaction product, the
reaction mixture further containing at least one base, and
alternatingly adding partial quantities of the at least one base
and partial quantities of the second reactant C to the reaction
mixture so that the reaction is carried out at a pH value in a
range of from 7.5-11.5, wherein the setting retarder is in liquid
or solid form.
Inventors: |
HAMPEL; Christina; (Rutihof,
CH) ; ZIMMERMANN; Joerg; (Winterthur, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SIKA TECHNOLOGY AG |
Baar |
|
CH |
|
|
Assignee: |
SIKA TECHNOLOGY AG
Baar
CH
|
Family ID: |
44246137 |
Appl. No.: |
14/476335 |
Filed: |
September 3, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13978793 |
Jul 9, 2013 |
8853305 |
|
|
PCT/EP2012/054052 |
Mar 8, 2012 |
|
|
|
14476335 |
|
|
|
|
Current U.S.
Class: |
106/808 ;
564/192 |
Current CPC
Class: |
C04B 28/14 20130101;
C04B 40/0039 20130101; C04B 28/02 20130101; C04B 24/124 20130101;
C04B 28/02 20130101; C04B 24/123 20130101; C04B 2103/22 20130101;
C04B 24/04 20130101; C04B 24/04 20130101; C04B 24/123 20130101;
C04B 22/062 20130101; C04B 24/04 20130101; C04B 22/062 20130101;
C04B 24/123 20130101; C04B 22/062 20130101; C04B 24/04 20130101;
C04B 24/123 20130101; C04B 28/14 20130101; C04B 22/062 20130101;
C04B 40/0042 20130101; C04B 24/287 20130101; C04B 40/0042 20130101;
C04B 40/0039 20130101 |
Class at
Publication: |
106/808 ;
564/192 |
International
Class: |
C04B 24/12 20060101
C04B024/12; C04B 28/14 20060101 C04B028/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2011 |
EP |
11157796.1 |
Claims
1. A setting retarder for hydrate-forming binders produced by a
method comprising: reacting a first reactant A, comprising an amino
acid and/or an amino acid derivative, with a second reactant C,
comprising an amine-free carboxylic acid and/or an amine-free
carboxylic acid derivative, in a reaction mixture to form a
reaction product, the reaction mixture further containing at least
one base; and alternatingly adding partial quantities of the at
least one base and partial quantities of the second reactant C to
the reaction mixture so that the reaction is carried out at a pH
value in a range of from 7.5-11.5, wherein the setting retarder is
in liquid or solid form.
2. The setting retarder according to claim 1, wherein the first
reactant A comprises an amino acid, and the amino acid is lysine
and/or thereonine.
3. The setting retarder according to claim 1, wherein the second
reactant C comprises an amine-free carboxylic acid derivative.
4. The setting retarder according to claim 3, wherein the
amine-free carboxylic acid derivative is a carboxylic acid
anhydride.
5. The setting retarder according to claim 1, wherein the first
reactant A and the second reactant C are reacted to form an
amide.
6. The setting retarder according to claim 1, wherein the reaction
is carried out at a temperature in a range of from 20-60.degree.
C.
7. The setting retarder according to claim 1, wherein the base
comprises at least one member selected from the group consisting of
alkali hydroxides, earth alkali hydroxides and earth alkali
oxides.
8. The setting retarder according to claim 1, the method further
comprising first preparing an aqueous solution of the reactant A,
and then setting the pH range of the reaction mixture to the range
of from 7.5-11.5 by adding the at least one base to the reaction
mixture.
9. The setting retarder according to claim 1, the method further
comprising drying the reaction mixture.
10. The setting retarder according to claim 1, wherein the pH value
of the reaction mixture is held constant within the range of from
7.5-11.5 during the reaction.
11. The setting retarder according to claim 4, wherein the
carboxylic acid anhydride is succinic acid anhydride.
12. The setting retarder according to claim 7, wherein the base
comprises at least one member selected from the group consisting of
NaOH, KOH, CaO and Ca(OH).sub.2.
13. A binder composition comprising: the setting retarder according
to claim 1; and a hydrate-forming binder.
14. A molded body produced by a method comprising: mixing the
binder composition according to claim 13 with water; and then
hardening the mixed composition.
15. A method of delaying a start of setting of hydrate-forming
binders, comprising: adding the setting retarder according to claim
1 to the hydrate-forming binders.
Description
[0001] This application is a divisional application of U.S. patent
application Ser. No. 13/978,793 filed Jul. 9, 2013, which is the
U.S. national stage of PCT Application No. PCT/EP2012/054052 filed
Mar. 8, 2012. The entire disclosures of these earlier-filed
applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method for producing a setting
retarder for hydrate-forming binders, and to a corresponding
setting retarder. The invention further relates to a binder
composition containing a setting retarder and to a method for
producing said binder composition. A further aspect of the
invention involves the use of the setting retarder to retard the
start of setting of hydrate-forming binders.
BACKGROUND OF THE INVENTION
[0003] Large quantities of hydrate-forming binders, such as cement,
lime and gypsum materials, for example, are used in the
construction industry.
[0004] As gypsum materials, calcined gypsum and plaster are used,
either alone or in combination with lime, sand and lightweight
aggregates. However, the setting times for these gypsum materials
once they have been mixed with water are relatively short, so that,
unless additional measures are implemented, processing must be
carried out very quickly. However, it is known to delay the onset
of solidification of gypsum materials by mixing these materials
with setting retarders, thereby improving their processability.
Known setting retarders include, for example, fruit acids, such as
tartaric acid and citric acid, but also protein hydrolyzates, such
as the commercially available Plast Retard L (obtainable from Sicit
2000 S.p.A.).
[0005] In this connection, EP 2 108 628 A1 (Tricosal GmbH)
describes, for example, a setting retarder in the form of an adduct
based on an amino acid compound and a carboxylic acid or a
carboxylic acid derivative. This adduct is produced by reacting an
amino acid compound with a carboxylic acid or a carboxylic acid
derivative in an aqueous solution.
[0006] Although known setting retarders are highly effective, the
need still exists for an improved setting retarder which will
further retard, in particular, the onset of solidification after
being mixed with water.
SUMMARY OF THE INVENTION
[0007] The problem addressed by the present invention is therefore
that of devising an improved setting retarder and a method for
producing the same. In particular, the setting retarder that can be
produced according to the invention is intended to delay the onset
of solidification of hydrate-forming binders, in particular,
gypsum, for as long as possible. The method is further intended to
enable the most reliable, reproducible and safe production of an
improved setting retarder that is possible.
[0008] The problem relating to methods is solved according to the
invention by the features of claim 1. The problem relating to the
setting retarder is solved by the features of claim 13.
[0009] The main feature of the method according to the invention is
that the reaction of the two reactants A and C is carried out at a
pH value of 7.5-11.5, preferably 8-11, in particular, 8.5-10.5.
This means, in particular, that the pH value is held constant
within the specified range during the reaction. This remains true
for the entire duration of the reaction of the two reactants A and
C. It has unexpectedly been found that setting retarders produced
in this manner are capable of significantly delaying the onset of
solidification of hydrate-forming binders, in particular, gypsum,
as compared with setting retarders produced according to known
methods. This is true, in particular, for setting retarders in the
form of di products, in particular, diamides. Furthermore, the
method according to the invention has proven to be extremely
reliable and easy to implement. In particular, the method according
to the invention enables the reproducible production of setting
retarders having improved efficacy.
[0010] Further aspects of the invention are the subject matter of
additional independent claims. Particularly preferred embodiments
of the invention are the subject matter of the dependent
claims.
[0011] Implementation of the Invention
[0012] A first aspect of the invention relates to a method, in
particular, for producing a setting retarder for hydrate-forming
binders, wherein [0013] a) a first reactant A, comprising an amino
acid and/or an amino acid derivative, is reacted with [0014] b) a
second reactant C, comprising an amine-free carboxylic acid and/or
an amine-free carboxylic acid derivative, to form a reaction
product, wherein the reaction is carried out at a pH value of
7.5-11.5, preferably 8-11, in particular 8.5-10.5.
[0015] The expression "hydrate-forming binder" in the present
context refers particularly to binders which react in the presence
of water in a hydration reaction to form solid hydrates or hydrate
phases. These can be, for example, hydraulic binders (e.g., cement
or hydraulic lime), latent hydraulic binders (e.g., slag or fly
ash) or non-hydraulic binders (gypsum or white lime).
[0016] The hydrate-forming binder preferably comprises or consists
of gypsum. The term "gypsum" in this context refers to any known
form of gypsum, in particular, calcium sulfate-.alpha.-hemihydrate,
calcium sulfate-.beta.-hemihydrate, calcium sulfate anhydrite
and/or mixtures thereof. In the present context, calcium
sulfate-.beta.-hemihydrate has proven particularly
advantageous.
[0017] The binder can also be a mixture of one or more
hydrate-forming binders with aggregates such as sand, gravel and/or
ground stone.
[0018] The term "reaction" in the present case refers particularly
to a chemical reaction of the two reactants A and C in which a
chemical bond, preferably a covalent chemical bond, between
reactants A and C is formed.
[0019] Reactant A comprises an amino acid and/or an amino acid
derivative. This can be, for example, a protein hydrolyzate, a pure
amino acid, an amino acid mixture, and/or hydrochlorides thereof.
Reactant A can also be a mixture of an amino acid and/or an amino
acid derivative with additional compounds. Reactant A
advantageously consists of an amino acid.
[0020] In the present context, the term "amino acid" is understood,
in particular, as a compound having at least one carboxyl group
(--COOH) and at least one amine group (--NH.sub.2), which are
present, in particular, as zwitterionic ammonium carboxylate.
Particularly suitable are .alpha.-amino acids terminated by a
carboxyl group and, directly adjacent thereto, a vicinal amine
group or an amine group in the a-position. In this case, the
carboxyl group can be deprotonated, for example, and can optionally
have added counterions, such as metal cations, for example. The
amine group can also be present in protonated form.
[0021] According to one preferred embodiment, the amino acid has
precisely one carboxyl group and precisely two amine groups. As
mentioned above, these can be present in protonated and/or
deprotonated form. In this manner, reactant C can be used to
produce di products, which have proven to be particularly effective
setting retarders.
[0022] The amino acid is chosen, in particular, from the group
consisting of alanine, arginine, asparagine, aspartic acid,
cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine,
leucine, lysine, lysine hydrochloride, methionine, phenylalanine,
proline, serine, threonine, tryptophan, tyrosine, valine and/or
aminobutanoic acid.
[0023] In one particularly preferred embodiment, the amino acid is
lysine and/or threonine. Lysine is particularly preferred. With
such amino acids, in particular with lysine, the advantages
according to the invention are particularly obvious.
[0024] Reactant C comprises an amine-free carboxylic acid and/or an
amine-free carboxylic acid derivative. The term "carboxylic acid"
within the context of this invention stands, in particular, for a
mono-, di- or polycarboxylic acid. In this context, a
monocarboxylic acid comprises precisely one carboxyl group, whereas
the dicarboxylic acid has precisely two thereof, and the
polycarboxylic acid contains at least three carboxyl groups. The
carboxyl group can be present, for example, in deprotonated form,
and can optionally have added counterions, such as metal cations,
for example.
[0025] The carboxylic acid in the present case is an amine-free
carboxylic acid. In other words, this means that the carboxylic
acid is not derived from an amino acid and/or does not contain an
amine group. Accordingly, the amine-free carboxylic acid derivative
also does not contain an amine group.
[0026] With particular preference, amine-free dicarboxylic acids
and/or derivatives thereof, in particular, inner acid anhydrides of
dicarboxylic acids, are used. The corresponding reaction with
reactant C, e.g., an amino acid such as lysine, then results in a
simple manner in a reaction product which contains free carboxyl
groups, which has proven advantageous in the present context.
[0027] Reactant C can be a pure amine-free carboxylic acid and/or a
pure amine-free carboxylic acid derivative, for example. Also
possible are mixtures of various amine-free carboxylic acids and/or
amine-free carboxylic acid derivatives. Reactant C can also be
present in the form of a mixture with other compounds. Preferably,
however, an amine-free carboxylic acid and/or an amine-free
carboxylic acid derivative is used as compound C.
[0028] An amine-free carboxylic acid derivative is preferably
chosen from the group consisting of carboxylic acid anhydrides,
carboxylic acid halides and/or carboxylic acid esters.
[0029] In particular, the amine-free carboxylic acid and/or the
amine-free carboxylic acid derivative is chosen from the group
consisting of oxalic acid, acetic acid, propionic acid,
1,3-dipropionic acid, butanoic acid, succinic acid, maleic acid,
fumaric acid, phthalic acid, pyromellitic acid, malic acid,
tartaric acid, citric acid and/or the acid halides, acid anhydrides
and/or esters of the specified compounds.
[0030] It has been found that reactant C advantageously comprises
an amine-free carboxylic acid derivative, in particular, an
amine-free carboxylic acid anhydride. With particular preference,
the carboxylic acid anhydride is succinic acid anhydride. In
particular, when combined with amino acids having two amine groups,
e.g., lysine, particularly effective setting retarders of high
purity can be produced in high yield.
[0031] Reactants A and C are reacted, in particular, to form an
amide, preferably a diamide. With particular preference, reactants
A and C are reacted to form a di product, wherein, in particular,
1.5-3 mol reactant C, e.g., succinic acid anhydride, are reacted
per 1 mol reactant A, in other words, lysine, for example. More
preferably, 1.8-2.5 mol, particularly preferably 2.0 mol reactant
C, are reacted per 1 mol reactant A.
[0032] It has been found that the reaction can be advantageously
carried out at a temperature of 20-60.degree. C., preferably
35-55.degree. C., particularly preferably 40-50.degree. C. Within
such temperature ranges, in the pH range according to the
invention, particularly high yields of well-defined reaction
products can be obtained.
[0033] Reaction is carried out, in particular, in an aqueous
solution.
[0034] In particular, at least one base is added to the reaction
mixture. Suitable bases include alkali hydroxides, earth alkali
hydroxides and/or earth alkali oxides, for example. The at least
one base advantageously comprises NaOH, KOH, Ca(OH).sub.2, and/or
CaO, and is particularly added in the form of an aqueous solution.
Bases of this type have proven particularly suitable in the present
context. Suitable concentrations of aqueous solutions are, e.g.,
40-60 wt/% base in water. However, in principle, other bases can
also be used. In some cases, however, the reaction is impeded
thereby.
[0035] According to one preferred embodiment, the base comprises or
consists of NaOH and/or KOH. NaOH is preferred. With this
embodiment, liquid setting retarders can be efficiently
produced.
[0036] In another preferred embodiment, the base comprises or
consists of CaO and/or Ca(OH).sub.2, Mixtures of CaO and/or
Ca(OH).sub.2 with NaOH and/or KOH can also optionally be used. It
has been found that with this variant, by drying the setting
retarder once the reaction is complete, e.g., by spray drying, a
solid, in particular, powdered product can be obtained.
[0037] Depending on the storage conditions and the use of the
setting retarder, either a setting retarder in liquid form or a
setting retarder in solid or powdered form can be advantageous,
[0038] In particular, reactants A and C, and optionally the base
are metered in during the reaction in such a way that the pH value
of the reaction solution remains constant during the reaction,
within the range of 7.5-11.5, in particular 8-11, particularly
preferably 8.5-10.5. According to a particularly advantageous
embodiment, in a first process step an aqueous solution of reactant
A is prepared and is set to a pH of 7.5-11.5, in particular 8-11,
particularly preferably 8.5-10.5 by adding base. In a further
process step, partial quantities of base and partial quantities of
reactant C are advantageously added alternatingly. The partial
quantities are measured, in particular, such that the pH value of
the reaction solution remains within the range of 7.5-11.5, in
particular 8-11, particularly preferably 8.5-10.5 during the
reaction. In this manner, pH value fluctuations can be optimally
compensated for, thereby improving the yield of the reaction and
ultimately increasing the efficacy of the setting retarder.
[0039] However, it is also possible to add reactant A and/or
reactant C and/or the optionally used base continuously. In this
case, the pH value can be regulated, e.g., by using different
addition rates, or can be held constant within the range of
7.5-11.5, in particular 8-11, particularly preferably 8.5-10.5. The
aqueous solution of the setting retarder obtained in this manner
can be used immediately following completion of the reaction. It is
not necessary to process the reaction solution after production of
the setting retarder.
[0040] Optionally, the liquid setting retarder produced in this
manner can be subjected to a further process step, a drying
process, preferably a spray drying process. This is carried out, in
particular, if the reaction is run using one or more earth alkali
hydroxides and/or earth alkali oxides, e.g., CaO and/or
Ca(OH).sub.2, as a base. The setting retarder can thereby be
converted in a more effective mariner to a paste-like or solid
substance, in particular, a powdered product.
[0041] Suitable drying methods are known to a person skilled in the
art. With the spray drying, which in this connection is
particularly advantageous, the product to be dried is ordinarily
introduced via a nozzle or a rotating disk atomizer into a hot air
stream, where it can be dried to a fine powder and can be separated
and removed, for example, by means of a centrifugal separator.
[0042] When spray drying is carried out, it can be advantageous to
add at least one spray additive, preferably chosen from the group
consisting of limestone dust, lignin sulfonate, talcum, silicic
acid, polyacrylates and/or polyvinyl alcohols, before and/or during
spray drying.
[0043] A further aspect of the invention relates to a method for
producing a hydrate-forming binder composition, wherein a setting
retarder is produced as described above and is mixed with a
hydrate-forming binder, in particular, gypsum.
[0044] Referred to 100 wt/% of the hydrate-forming binder in dry
form, 0.001 -0.5 wt/%, preferably 0.001-0.1 wt/% of the setting
retarder is advantageously added.
[0045] The invention further relates to a setting retarder, in
particular, for hydrate-forming binders, which can be obtained by
the method described above. Setting retarders of this type have
proven particularly effective, as compared with setting retarders
produced according to known methods. It has been found that the two
reactants A and C can be made to react, resulting in high yields
when a suitable reaction is run. The percentage of ineffective
secondary products or secondary products that decrease the
retarding effect in the setting retarder (e.g., unreacted reactants
A and C) can thereby be kept extremely low. Referred to the total
molar amount of the setting retarder, the setting retarder
advantageously consists of at least 90 mol/%, preferably at least
95 mol/%, particularly preferably at least 98 mol/% of the reaction
product of the two reactants A and C.
[0046] In this connection, the reaction product is particularly
preferably a di product, formed from two molar fractions of
reactant C with one molar fraction of reactant A. The di product is
particularly a diamide, formed from two molar fractions of succinic
acid anhydride and one molar fraction of lysine. Based upon the
reaction according to the invention, the di product or diamide can
thereby be obtained in high yield, wherein the ratio of unreacted
reactants A, C and/or mono products (e.g., consisting of one molar
fraction of lysine and one molar fraction of succinic acid
anhydride) in the setting retarder is extremely low. Surprisingly,
the retarding effect of the setting retarder according to the
invention can be significantly improved in this manner.
[0047] The pH value of the setting retarder advantageously ranges
from 7-11, in particular, 8-9. An optimal retarding effect in
hydrate-forming binders, in particular, gypsum is achieved in this
manner.
[0048] If desired, one or more additives from the list consisting
of rheologic agents, solvents, defoaming agents, accelerators,
fillers, drying agents, dyes, preservatives, rust inhibitors,
hydrophobing agents and/or pigments can be added to the setting
retarder.
[0049] Particularly advantageously, a preservative is added to the
setting retarder. This allows its storage stability to be
significantly improved.
[0050] In one preferred embodiment, the setting retarder is
provided in liquid form. According to another advantageous
embodiment, the setting retarder consists of a paste-like or solid
product, in particular, a powder.
[0051] A further aspect of the invention relates to a binder
composition containing a setting retarder according to the
invention and a hydrate-forming binder, in particular, gypsum.
Referred to 100 wt/% of the hydrate-forming binder in dry form, the
binder composition advantageously contains 0.001 -0.5 wt/%,
preferably 0.001-0.1 wt/% of the setting retarder. Based on the
setting retarder produced according to the invention, binder
compositions of this type, after being mixed with water, can be
processed for unexpectedly long periods of time before the binder
begins to set.
[0052] It is also possible to mix the additives specified above in
connection with the setting retarder with the binder
composition.
[0053] Binder compositions of this type harden after the addition
of water, forming hydrate phases. Molded bodies can therefore be
produced by mixing a binder composition with water and then
hardening it. A binder composition mixed with water can, in
principle, be cast into any mold, so that molded bodies of nearly
any shape can be produced.
[0054] The setting retarder is suitable, in particular, for
retarding the setting of hydrate-forming binders or compositions.
The setting retarder is added before, during and/or after
preparation of the hydrate-forming binder or the hydrate-forming
composition.
[0055] Additional advantageous embodiments and combinations of
features of the invention are specified in the following embodiment
examples and in the totality of the patent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] FIG. 1, which is used to illustrate embodiment examples,
shows the temperature development of aqueous gypsum mixtures having
different setting retarders as a function of time.
EXAMPLES
[0057] Production example 1
[0058] In a first process step, 320 g lysine (reactant A) were
placed in a reaction vessel at room temperature and 792 g water
were added with agitation. Diluted base in the form of a solution
of 50 wt/% NaOH in water was then added until the reaction solution
reached a pH of 10.5. The temperature of the mixture was then
adjusted to approximately 45.degree. C.
[0059] In a subsequent process step, partial quantities of succinic
acid anhydride (reactant C) and diluted base (50 wt/% NaOH in
water) were then added alternatingly, so that the pH value of the
reaction solution remained consistently within the range of
8.5-10.5. The temperature during addition was held constant within
a range of 40-50 .degree. C. The total quantity of succinic acid
anhydride added was 220.8 g, and the total quantity of diluted base
added was 264 g (including the base added during the first process
step). The pH value of the reaction solution once the total amount
of succinic acid anhydride and the total amount of diluted base had
been added was 8-9.
[0060] The reaction solution was then agitated at a temperature of
40-50 .degree. C. for approximately 30 minutes longer, and was then
cooled with agitation.
[0061] Solutions produced in this manner can be used directly,
without further processing, as setting retarders in hydrate-forming
binders. In the following, these are referred to as setting
retarder AE1.
Production example 2 (comparison example)
[0062] For purposes of comparison, a further setting retarder was
produced in a manner similar to production example 1. In contrast
to production example 1, however, the total quantity of diluted
base was added in a single portion directly in the first process
step. In the second process step, the total quantity of succinic
acid anhydride was then also added in one portion. The pH value of
the reaction solution at the start of the reaction was
significantly above 11.5, and then dropped rapidly during the
reaction, within only a few minutes, to an inert level, to a value
significantly below 7.5, with a temperature increase in the
reaction solution. The setting retarder produced in this manner is
referred to in the following as setting retarder AV.
[0063] Production example 2 corresponds essentially to the method
described in EP 2 108 628 A1.
Production example 3
[0064] In a first process step, 800 g lysine (reactant A) were
placed in a reaction vessel at room temperature, and 2000 g water
were added with agitation. 50 g Ca(OH).sub.2 were then added. The
pH value of the solution following the addition of Ca(OH).sub.2 was
between 10 and 11.5. The temperature of the mixture was then
adjusted to approximately 45.degree. C.
[0065] In a subsequent process step, partial quantities of succinic
acid anhydride (reactant C) and diluted base (50 wt/% NaOH in
water) were then added alternatingly, so that the pH value of the
reaction solution was held continuously within a range of 8.5-10.5.
The temperature during addition was held constant within a range of
40-50.degree. C. The total quantity of succinic acid anhydride
added was 552 g, and the total quantity of diluted base added was
650 g. The pH value of the reaction solution once all the succinic
acid anhydride and all the diluted base had been added was 7-8.
[0066] The reaction solution was then agitated for approximately 30
min. longer at a temperature of 40-50.degree. C., and was then
cooled with agitation.
[0067] Solutions produced in this manner can be converted in a
spray dryer to a powder, which is referred to in the following as
AE2.
Comparison experiments with gypsum
[0068] The efficacy of various setting retarders in aqueous gypsum
mixtures was tested.
[0069] To produce the gypsum mixtures, calcium
sulfate-.beta.-hemihydrate (alabaster gypsum Almod BCL8098) was
slurried at room temperature with water in a weight ratio of water
to gypsum=0.6, and was mixed with 0.02 wt/% Amylotex (a thickener
having a starch ether base, e.g., available from Aqualon). The
quantity of Amylatex was referred in each case to the calcium
sulfate-.beta.-hemihydrate. For this purpose, each of the setting
retarders listed in Table 1 below was mixed in a concentration of
0.029 wt/%, referred to the calcium sulfate-.beta.-hemihydrate.
[0070] All the gypsum mixtures were produced under essentially
identical conditions to form the various setting retarders.
TABLE-US-00001 TABLE 1 Produced gypsum mixtures Gypsum mixture
Setting retarder G1 AE1 (according to production example 1) G2 AV
(according to production example 2) G3 AE2 (according to production
example 3) G4 Retardan L (commercially available from Sika
Deutschland GmbH) G5 Plast Retard L (commercially available from
Sicit 2000 S.p.A.)
[0071] The temperature development of freshly prepared gypsum
mixtures G1-G5 was then measured in a known manner as a function of
time. FIG. 1 shows the corresponding temperature profiles. The
x-axis in this figure indicates the time elapsed since the
production of the respective gypsum mixture G1-G5, while the y-axis
indicates the temperature difference from the temperature of the
freshly produced gypsum mixture (room temperature). All the
measurements were carried out under essentially identical
conditions.
[0072] As is clear from FIG. 1, gypsum mixtures G1 and G3 with
setting retarders AE1 and AE2 according to the invention have the
best retarding effects. A significant increase in temperature and
therefore the start of setting of the respective gypsum mixture is
not observed until approx. 115 min. have elapsed. Setting retarder
AE2 (gypsum mixture G3) is even more effective than setting
retarder AE1 (gypsum mixture G1). The remaining gypsum compositions
G2, G4 and G5, all of which contain conventional setting retarders,
are capable of delaying the start of setting by only 95 min. at
best. Therefore, the setting retarders produced according to the
invention enable an extension of the processing time by at least
20% over known retarders.
[0073] The above-described embodiment examples are intended merely
as illustrative examples, which can be modified in any way within
the scope of the invention.
[0074] For example, it is possible to use a different amino acid
and/or amino acid derivative, such as threonine, for example in
place of or in addition to lysine. In place of or in addition to
succinic acid anhydride, another carboxylic acid derivative and/or
a carboxylic acid can also be used. The setting retarders can also
be used in hydrate-forming binders other than gypsum, for
example.
[0075] It can also be advantageous to mix additives, particularly
preservatives, in with the setting retarders according to the
invention. Suitable substances are known to a person skilled in the
art.
* * * * *