WO2002098817A1

WO2002098817A1 - Plaster retarder

Info

Publication number: WO2002098817A1
Application number: PCT/EP2002/005754
Authority: WO
Inventors: Michael Schlag; Wolfgang Hater; Marlies Bodewig; Paulo Jorge Gomes Machado
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2001-06-02
Filing date: 2002-05-24
Publication date: 2002-12-12
Also published as: EP1392617A1; DE10127060A1

Abstract

The invention relates to the use of polymers containing carboxyl groups selected from a) polymerized amino acids, b) polymer sugars substituted with carboxyl groups, c) modified polyacrylates, wherein the polyacrylates are modified using phosphino groups or ethylacrylate groups, in order to retard the setting of plaster. The invention also relates to building materials which contain plaster and said polymers, and pourable material consisting of a carrier and the above-mentioned type of polymers containing carboxyl groups.

Description

"Gypsum delays setting"

The invention lies in the field of plaster and gypsum-based building materials. It concerns additives to delay the setting of the gypsum, as well as gypsum and building materials containing gypsum, which contain such additives.

When the term "gypsum" is used in the following, it means gypsum in a form capable of setting. Such gypsum which is capable of setting is produced on an industrial scale by partially dewatering calcium sulfate dihydrate. Semi-hydrates occur in different modifications, for example the modifications referred to as α- and ß.For example, gypsum occurring in natural deposits or gypsum obtained in flue gas desulfurization plants can be used as the raw material for dewatering to set gypsum.

For use in construction or for the production of moldings, gypsum or a gypsum-containing mortar mixture is mixed with water. Here the crystalline calcium sulfate dihydrate is formed from the low hydrates of the gypsum that arise during dewatering. As a result of the binding of the water and the growth of usually needle-shaped crystals of calcium sulfate dihydrate, the mortar hardens. Unless you add additives to delay curing (also called setting), curing usually begins within an hour. In practice, this setting time is usually too short to be able to process the gypsum mortar applied with water over a practical period. In practice, setting times of about 1 hour to about 4 hours are aimed for. To enable these extended setting times, setting retarders are added to the gypsum mixture.

In the article by Th. Mallon: "The retarding effect of gypsum retarders of different chemical composition depending on the pH value of the gypsum", cement-lime gypsum 4 (6), pages 309 to 311, 1988, tartaric acid and citric acid as setting retarders as well their salts, monocalcium phosphate and the under the trade name Tricosal and Retardan P known setting retarder based on degraded proteins. Retardan P is a reaction product of amino acids with formaldehyde. Although it has a good setting-retarding effect, it is harmful to health due to the possibility of formaldehyde elimination. Unneutralized carboxylic acids such as tartaric acid and citric acid can lead to undesirable foaming in the presence of carbonate-containing additives. Furthermore, these acids and their salts have the disadvantage of separating due to their crystal shape and crystal size by shaking during the transport of the powdery building material mixtures.

In the related field of silicon- and / or aluminum-containing cements, setting retarding additives are known which are copolymers of acrylic acid or methacrylic acid with other monomers. For example, EP-A-607 039 describes a setting-delayed cement which contains a copolymer of acrylic acid or methacrylic acid with an acrylamide derivative. EP-A-633 390 also describes an additive for delaying the setting of cement, which is a copolymer of an unsaturated carboxylic acid with a functionalized second monomer, the second monomer being for example vinylphosphonic acid. Furthermore, the second monomer can carry sulfonic acid groups or alkylammonium groups. US 5,488,991 discloses the use of polyacrylic acid phosphinate with a molecular weight of about 3,800 to retard the gel formation of alumina cement. No. 5,484,478 describes polymer setting retarders for hydraulic cement, the polymer being a polyacrylic acid, in the chain of which a P (O) (OH) group is bound to 2 acrylic acid units in each case.

From US 5 908 885 it is known to add polysuccinimide, polyaspartate or copolymers of succinimide and aspartate to cement mixtures in order to improve their processability. These polymers apparently act as dispersants, which have a positive influence on the flow behavior of the cement mixture. Furthermore, they have a favorable effect on the strength achieved after curing. This document does not contain any information as to whether these polymers influence the speed of curing.

The object of the invention is to provide improved setting retarders for gypsum and gypsum-containing building materials. In a first aspect, the invention relates to the use of polymers containing carboxyl groups selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups, c) modified polyacrylates, the polyacrylates being modified by phosphino groups or by ethyl acrylate groups to delay the setting of Plaster.

The polymers containing carboxyl groups are preferably added to the gypsum in an amount of 0.001 to 0.05 parts by weight, in particular 0.002 to 0.02 parts by weight, per 100 parts by weight of the mixture of gypsum and carboxyl group-containing Polymers too.

In one embodiment of the use according to the invention, carboxyl group-containing polymers of group a) can be used, which are selected from aspartic acid-containing polymers. Polyaspartic acid is preferably used, in which the aspartic acid units can be connected to one another with a so-called α or a so-called β linkage. It is preferred to use polyaspartic acid which has an average molecular weight (weight average) in the range from about 2,000 to about 20,000.

In a second embodiment of the use according to the invention, carboxyl group-containing polymers of group b) are used, which are selected from fructose-containing polymers in which 0.5 to 2.5 hydroxyl groups per molecule are carboxyalkylated, preferably carboxymethylated. These carboxyalkylated derivatives are derived from fructose-containing polymers known as inolin. They consist of linear chains of fructose units, which are usually linked by β (2-1) bonds. These chains are usually terminated by a glucose unit. The fructose units within the chain carry 3 hydroxyl groups which can be carboxyalkylated to form ether. This means that the hydrogen of the hydroxyl group is replaced by a carboxyalkyl group. In the context of the use according to the invention, for example, those inulin derivatives can be used in which one, on average 1, 5 or on average 2 hydroxyl groups per fructose unit are carboxyalkylated, in particular carboxymethylated. It is preferred to select carboxyalkylated inulin derivatives which have a molecular weight in the range from 2,000 to 10,000, in particular in the range from 2,200 to 5,000. A further embodiment of the invention consists in using modified polyacrylates c) which are selected from polyacrylates modified with phosphino groups and having an average molecular weight in the range from 400 to 3,000. "Molar mass" here means the molar weight relative to a polyacrylic acid standard. Higher molar masses, such as are present in the Belasol S-29 mentioned in US Pat. No. 5,488,991, lead to a noticeable but less pronounced setting delay for gypsum. This product has an average molecular weight in the range of 4,000.

Polyacrylates modified with phosphino groups are further preferred which have a phosphorus content (calculated as phosphate and based on the total mass of the polymer before neutralization) in the range from 5 to 50% by weight, in particular in the range from 10 to 30% by weight. exhibit.

Furthermore, the modified polyacrylates c) can be selected from polyacrylates modified with ethyl acrylate groups and having an average molecular weight in the range from 1,000 to 20,000, in particular in the range from 1,500 to 10,000.

If polyacrylates modified with ethyl acrylate groups are used, preference is given to selecting those in which the proportion of ethyl acrylate groups is 5 to 30 mol%, in particular 8 to 20 mol%, based on the total amount of acrylate groups and ethyl acrylate groups.

The modified polyacrylates mentioned are generally marketed as aqueous solutions or dispersions which have solids contents in the range from about 25 to about 65% by weight. Such solutions or dispersions are suitable for use in the context of the present invention, but are preferably first neutralized by mixing them with sodium hydroxide solution or potassium hydroxide solution.

Another aspect of the invention is a building material containing gypsum and a setting-retarding amount of carboxyl group-containing polymers selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups, c) modified polyacrylates, the polyacrylates being modified by phosphino groups or by ethyl acrylate groups are. A "setting-retarding amount" is understood to mean such an amount of carboxyl-containing polymers that the setting time of the gypsum is increased by at least 10% compared to the additive-free gypsum. However, the amount must not be so large that the gypsum within of 24 hours does not set at all. The quantities required for a desired setting time can be determined quickly by simple experiments. In the example part a test method is described with which the setting time can be determined. The building material preferably contains such carboxyl group-containing polymers of groups a ) to c) described above in connection with their use for delaying the setting of gypsum.

The building material can consist exclusively of the gypsum and the carboxyl-containing polymers and possibly still contain physically bound moisture. However, the building material can already be a mixture of the gypsum and the carboxyl group-containing polymers with adjusting agents, leaning agents, moisture and / or the carrier material described below for the carboxyl group-containing polymers. Accordingly, a building material according to the invention can be composed such that it contains 10 to 99.999% by weight of gypsum and 0.001 to 0.05% by weight of the carboxyl group-containing polymers, the total amount making up 100% by weight and a remainder remaining 100% by weight of adjusting agents, leaning agents, further agents for retarding or accelerating the setting according to the prior art, moisture and / or carrier material for the modified polyacrylates.

Such a building material can be used, for example, for the production of molded parts such as plates or pipes. To do this, mix the building material with water, pour it into a suitable mold and let it set. Furthermore, the building material mentioned can be used for the production of mortar, which can generally be used for building purposes. Examples of such use in the construction sector are the plastering of walls and the laying of screeds.

For the purposes mentioned above, the polymers containing carboxyl groups are preferably used in at least 90% neutralized form. This means that at least 90% of the carboxylic acid groups are in anionic form. For cost reasons, it is preferably neutralized with sodium hydroxide solution. Potassium hydroxide solution is also suitable. The acid groups are preferably at least 95%, in particular practically 100%, neutralized. The polymers containing carboxyl groups are therefore preferably located largely in the form of their sodium or potassium salts. This has the advantage that at

The presence of carbonate-containing bulking agents in the building material prevents foaming due to the elimination of carbon dioxide.

In the context of this invention (use for retarding the setting of gypsum or gypsum-like, retarding building material), it is particularly preferred that the carboxyl group-containing polymers are applied to a carrier material which, after the application of the carboxyl group-containing polymers, has an average particle diameter in the range of 0 , 01 to 2 mm. If the individual particles of the carrier material aggregate into larger aggregates due to the application of the carboxyl group-containing polymers, they can be ground again to the desired particle diameter. It is hereby achieved that the setting retarder is present in the building material in the form of particles of a size which corresponds to the size of the particles of the other building material components. This prevents segregation by shaking during transport of the building material. In this aspect of the invention, too, it is preferred that the carboxyl group-containing polymers are at least 90% neutralized.

Accordingly, in order to avoid segregation during transport, it is preferred that the setting-retarding polymers are applied to a carrier material so that after application they are present in a particle size which corresponds to the particle size of the other components of the powdery building material mixture. Therefore, in a particular aspect, the invention relates to a free-flowing material with an average particle diameter in the range from 0.01 to 2 mm, consisting of a carrier material and applied carboxyl group-containing polymers selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups , c) modified polyacrylates, the polyacrylates being modified by phosphino groups or by ethyl acrylate groups. This material preferably contains 10 to 300 parts by weight, in particular 12 to 200 parts by weight, of carboxyl group-containing polymers per 100 parts by weight of carrier material.

Here, too, it is preferred that the carboxyl group-containing polymers are at least 90%, preferably at least 95% and in particular practically completely neutralized. Polymers of groups a) to c) can be used as polymers containing carboxyl groups, as described in more detail above. In principle, any material that has sufficient absorbency for the polymer solutions and that has no negative effects on the building materials is suitable as a carrier material. For example, powdered silicas, aluminum oxides or hydroxides or zeolites are suitable.

The carboxyl group-containing polymers mentioned and in particular the modified polyacrylates have the advantage over the degraded proteins cited at the outset that they are available in a colorless form. They therefore do not lead to undesirable dark discoloration of the plaster and the moldings or mortar produced with it.

If the setting-retarding carboxyl group-containing polymers of this invention are combined with substances which in turn accelerate the setting process, the setting time of the gypsum can be set to a narrow time interval around a preselected point in time. This can be particularly advantageous for the casting of molded parts, since this enables the cycle time between casting and demoulding to be set to a narrow time window. This makes the production process reliable and predictable.

embodiments

According to a standardized test method used by the building materials industry, 1,000 g of gypsum (AGFF = α-gypsum fine, finely ground) are mixed with 458.9 g of tap water and 11.1 g of a 0.4% by weight solution of the additive. After a total time for product dosing and mixer preparation of 30 seconds, mixing takes place for 90 seconds. Any adhering material is stripped from the edge and bottom of the mixing trough and stirred in within 15 seconds. The mixture is then immediately filled into 2 greased Vicat rings on greased glass plates. The automatic Vicat measuring device is preferably used for the measurement, the stiffening time being determined with the immersion cone. The measurement begins approx. 15 minutes after the water has been added at measuring intervals of 30 seconds. The start of stiffening (VB) is reached when the immersion cone gets stuck in the sample 18 mm above the glass plate. The stiffening end (VE) of the automatic Vicat device is reached when the immersion cone remains 37 mm above the glass plate. The fault tolerance is set at one mm. During the exam VE is achieved with the manual Vicat device if the immersion cone penetrates less than 1 mm into the paste surface.

Comparison 1 (standard)

Additive = anhydrous citric acid: VB: 58 minutes, VE: 72 minutes

example 1

Additive = aqueous dispersion of phosphinoacrylic acid with 46.1% solids content, average molecular weight 4,000, phosphorus content 3% calculated as phosphate and based on the polymer solution. This product is believed to correspond to the Belasol S-29 mentioned in US 5,488,991. VB: 42 minutes, VE: 54 minutes. This product is therefore less retarding than the standard citric acid.

Example 2

Additive = aqueous solution or dispersion of phosphinoacrylic acid with 27.1% solids content, average molecular weight 900, phosphorus content (calculated as phosphate and based on the aqueous suspension) 7.4%. VB: 84 minutes, VE: 106 minutes.

The following results were achieved with a second plaster batch (also AGFF):

Comparison 2

Without delaying additive: VB: 27.5 minutes, VE: 35.5 minutes.

Comparison 3

Additive = citric acid. VB: 44 minutes, VE: 53.5 minutes.

Example 3

Additive = 55% solution of an acrylic polymer, average molecular weight 2,000, consisting of

10 mole% ethyl acrylate and 90 mole% acrylate. VB: 52 minutes, VE: 66 minutes.

As expected, the setting time depends on the amount of polymer dispersion used. If the amount is increased from 0.005% polymer dispersion to 0.01% polymer dispersion, based in each case on the amount of gypsum, the setting time increases by 60 to 70%. An amount of 0.015% of the polymer dispersion is also still suitable, while from an amount of 0.02%, the gypsum batch used is only cured after the period of 1 day that is no longer practical. For further experiments, the polymer dispersions were sprayed onto powdered silica with an average particle size of 0.1 mm (Sipernat ^R 22, Degussa-Hüls) with mixing and dried.

Example 4

200 g of the polymer dispersion from Example 2 was neutralized with 48 g of 50% sodium hydroxide solution. 57.5 g of this neutralized mixture were sprayed onto 50 g of Sipernat ^R 22 with mixing and dried to a free-flowing powder (microscopically measured particle size: 0.01-1 mm).

Example 5

The polymer dispersion from Example 3 was neutralized with 50% sodium hydroxide solution. 53 g of the neutralized dispersion were sprayed onto 50 g of Sipernat ^R 22 with mixing and dried.

To test the setting behavior, 1000 g of gypsum (AGFF) are mixed with 470 g of an aqueous solution or suspension, which is composed as follows. The composition is chosen so that the gypsum is mixed with the same amount of setting retarding additive.

a) 458.9 g of tap water + 11.1 g of a 0.4% citric acid solution (standard for comparison): Result: VB = 62 minutes.

b) 453.9 g of tap water + 16.1 g of the polymer / carrier mixture from Example 4. Result: VB = 85 minutes.

c) 449.2 g of tap water + 20.8 g of the polymer / carrier mixture from Example 5. Result: VB = 72 minutes. Example 6

The setting-retarding effect of polyaspartic acid (sodium salt, average molecular weight: 5000) was determined in comparison with the standard citric acid using the standardized test method described above.

Result: Citric acid (comparison): VB 47.5 minutes, VE 57 minutes. Polyaspartic acid: VB 44 minutes, VE 56 minutes.

A setting-retarding effect comparable to the standard is therefore observed.

Example 7

The setting-retarding effect of carboxymethylated inulin with an average chain length of 10 sugar units and with different degrees of carboxymethylation (products a) to c) compared to the standard citric acid was determined according to the standardized test method described above.

a) carboxymethylinulin, average degree of carboxylation = 1, average molecular weight: 2400, b) carboxymethylinulin, average degree of carboxylation = 1, 5, average molecular weight: 2800, c) carboxymethylinulin, average degree of carboxylation = 2, average molecular weight: 3200,

Result: Citric acid (comparison): VB 47.5 minutes, VE 57 minutes

Product a) VB 44.5 minutes, VE 55 minutes. Product b) VB 40 minutes, VE 51 minutes. Product c) VB 35 minutes, VE 45 minutes.

A setting-retarding effect comparable to the standard is therefore observed. Like citric acid, the inulin derivatives have the advantage of being biodegradable. Example 8

In addition to Examples 1 to 7, which were carried out with α-gypsum, further tests for the setting behavior of β-gypsum (alabaster gypsum, β-hemihydrate) were carried out. Test method: 0.65 ml of a 10% by weight aqueous additive solution together with 28 g of water are placed in a beaker and then 65 g of β-gypsum is added. After a waiting time of 45 seconds, the mixture is stirred 4 times by hand with a spoon spatula. A thermocouple PT 100 is then inserted into the mass and the cup is covered. The temperature curve as a function of time is recorded. The start of stiffening VB is the point in time at which the temperature begins to rise, the end of stiffening VE is the point in time at which the temperature begins to drop again.

Results:

Claims

claims

1. Use of carboxyl group-containing polymers selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups, c) modified polyacrylates, the polyacrylates being modified by phosphino groups or by ethyl acrylate groups to delay the setting of gypsum.

2. Use according to claim 1, characterized in that the gypsum is added the carboxyl group-containing polymers in an amount of 0.001 to 0.05 parts by weight per 100 parts by weight of the mixture of gypsum and carboxyl group-containing polymers.

3. Use according to one or both of claims 1 and 2, characterized in that carboxyl group-containing polymers of group a) are used, which are selected from aspartic acid-containing polymers.

4. Use according to one or both of claims 1 and 2, characterized in that carboxyl group-containing polymers of group b) are used, which are selected from fructose-containing polymers in which on average 0.5 to 2.5 hydroxyl groups per Molecule are carboxyalkylated.

5. Use according to one or both of claims 1 and 2, characterized in that carboxyl group-containing polymers of group c) are used, which are selected from polyacrylates modified with phosphino groups and having an average molecular weight in the range from 400 to 3000.

6. Use according to one or both of claims 1 and 2, characterized in that carboxyl group-containing polymers of group c) are used which are selected from polyacrylates modified with ethyl acrylate groups, the proportion of ethyl acrylate groups being 5 to 30 mol% based on makes up the total amount of the acrylate groups and the ethyl acrylate groups.

7. Building material containing gypsum and a setting-retarding amount of carboxyl-containing polymers selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups, c) modified polyacrylates, the polyacrylates being modified by phosphino groups or by ethyl acrylate groups

8. Building material according to claim 7, characterized in that it contains 10 to 99.999% by weight of gypsum and 0.001 to 0.05% by weight of the carboxyl group-containing polymers, the total amount making up 100% by weight and a remainder may consist of 100% by weight of adjusting agents, leaning agents, further setting retarding or accelerating additives, moisture and / or carrier material for the carboxyl group-containing polymers.

9. Building material according to one or both of claims 7 and 8, characterized in that it contains carboxyl group-containing polymers of group a) which are selected from aspartic acid-containing polymers.

10. Building material according to one or both of claims 7 and 8, characterized in that it contains carboxyl group-containing polymers of group b) which are selected from fructose-containing polymers in which on average 0.5 to 2.5 hydroxyl groups per Molecule are carboxyalkylated.

11. Building material according to one or both of claims 7 and 8, characterized in that it contains carboxyl group-containing polymers of group c) which are selected from polyacrylates modified with ethyl acrylate groups, the proportion of ethyl acrylate groups being 5 to 30 mol% based on makes up the total amount of the acrylate groups and the ethyl acrylate groups.

12. Use of a building material according to one or more of claims 7 to 11 for the production of moldings.

13.Use of a building material according to one or more of claims 7 to 11 for the production of mortar.

14. Building material according to one or more of claims 7 to 11 or use according to one or more of claims 1 to 6, characterized in that the carboxyl-containing polymers in at least 90% neutralized form starts.

15. Building material according to one or more of claims 7 to 11 or use according to one or more of claims 1 to 6, characterized in that the carboxyl group-containing polymers are applied to a carrier material which has a medium after the application of the carboxyl group-containing polymers Has particle diameter in the range of 0.01 to 2 mm.

16. Free-flowing material with an average particle diameter in the range from 0.01 to 2 mm, consisting of a carrier material and carboxyl group-containing polymers applied thereon selected from a) polymerized amino acids, b) polymeric sugars substituted with carboxyl groups, c) modified polyacrylates, where the polyacrylates are modified by phosphino groups or by ethyl acrylate groups

17. Material according to claim 16, characterized in that it contains 10 to 300 parts by weight of carboxyl-containing polymers per 100 parts by weight of carrier material.