GB2593467A

GB2593467A - Binder

Info

Publication number: GB2593467A
Application number: GB2004179.4A
Authority: GB
Inventors: Williams Darren; dale Charles; Russell Vivian
Original assignee: LONGCLIFFE QUARRIES Ltd
Current assignee: LONGCLIFFE QUARRIES Ltd
Priority date: 2020-03-23
Filing date: 2020-03-23
Publication date: 2021-09-29
Also published as: IE20210062A2; GB202004179D0

Abstract

A binder for screed compositions comprising: calcium carbonate, neopentylglycol, a superplasticiser comprising one or more modified polycarboxylated ethers, a stabiliser comprising a high molecular weight synthetic polymer/powder; and a curing agent. The curing agent may comprise a fatty alcohol. the curing agent may comprise a carrier material such as silica gel.

Description

Binder

Field

The invention relates to a binder for screed compositions and a method of manufacture thereof. In particular, the invention relates to a binder for screed compositions comprising calcium carbonate and a curing agent.

Background

Screed is a levelled layer of material which is typically applied to a floor or other surface.

It is predominantly used as a top finishing layer, as it has a smoother texture compared to concrete. Screed is made using a binder system, wherein a binder material is mixed with wet ingredients (predominantly water) to form a free flowing material. However, some problems can arise when applying screed. In particular, screed formulations, if applied in the absence of a curing agent, will often harden too quickly, resulting in plastic cracking. Therefore, curing agents are sprayed onto screed formulations after application to the floor to retard setting. Whilst this post-application of curing agents prevents cracking, it introduces an additional step into the screed application process, wherein the correct amount of curing agent must be evenly applied to the screed surface before it sets. As a result of insufficient or uneven application of the curing agent, cracks can appear in screed despite the use of curing agents.

Further, cracking can also occur if the formulation of the binder and/or the proportions of binder to the wet ingredients is not adequate. Other problems include segregation and bleeding. Also, sometimes screed can take a long time to dry, which is not only inconvenient but can also cause setbacks to further work scheduled, which may have cost implications both for the contractor and for the customer.

Plasticisers and superplasticisers are used in screed compositions (or the like) to improve the workability and flow enablement of the mixture. However, they are usually added in liquid form as a final step in the mixing process. EP 2423365 Al discloses a process for preparation of cement/mortar/concrete systems, wherein the calcium carbonate based filler used is treated with an efficient amount of a treating agent, which comprises one or more superplasticisers. The aim of the pre-treatment step is to produce improved high performance fluid cement (or the like). Specifically, EP 2423365 Al refers to well-known liquid plasticisers for use as a treating agent, such as Dynamon NRG 100 and CHRYSaEPremia 196.

It would be beneficial to manufacture a binder composition for use in screed compositions, which has one or more of the properties of improved workability, ease of dispensing, self-levelling capabilities, is fast drying, and wherein the resultant screed composition is simple and cost effective to manufacture. It would also be beneficial to provide a binder or screed composition in which all actives, in particular the superplasticiser and the curing agent are integral to the formulation, and ideally in powder form removing the need for the mixing of components in different phases (e.g. solid and liquid) or the need for a post-application step.

The invention is intended to overcome or ameliorate at least some aspects of these problems.

Accordingly, in a first aspect of the invention there is provided a binder for screed compositions comprising: calcium carbonate, neopentylglycol, superplasticiser comprising one or more modified polycarboxylated ethers, stabiliser comprising a high molecular weight synthetic polymer/powder, and a curing agent. Often, the binder will comprise one or more of the components independently in amounts of 95-99.5 wt% calcium carbonate; 0.5-2.5 wt% neopentylglycol; 0.1-1 wt% of a superplasticiser comprising one or more modified polycarboxylated ethers; 0.1-0.5 wt% of a stabiliser comprising a high molecular weight synthetic polymer/powder; and 0.05 -1 wt% curing agent. In many cases, one or more of the components may be present at the level 9698.5 wt% calcium carbonate; 1-2 wt°/0 neopentylglycol; 0.25-0.75 wt% of a superplasticiser comprising one or more modified polycarboxylated ethers; 0.2-0.4 wt% of a stabiliser comprising a high molecular weight synthetic polymer/powder; and 0.1 - 0.8 wt% curing agent.

The applicant has found that the binder according to the invention, when used in screed compositions or the like, results in a fluid, easy to dispense, self-levelling and rapid drying final product that is essentially free of cracks. The applicant has found that, in some instances, the final product can dry within 24 hours offering huge benefits relative to existing systems which can take a number of days to dry. The rapid drying reduces the down time in build projects, improving efficiency and reducing costs as projects can be finished more rapidly with less construction down time.

For ease of reference, the term "screed composition" includes any one of a screed composition, a cement composition, a mortar composition, a concrete composition Or similar cementous products.

The curing agent may be any component which promotes "curing" (i.e. toughening or hardening of the screed) at a controlled rate, in particular the curing agents described herein will typically slow drying slightly (e.g. by 10%) to ensure that the surface dries without cracking often by preventing early shrinkage. Often the curing agent will be a powder, although liquid curing agents may also be used. In many cases, the curing agent will comprise a straight or branched chain fatty alcohol, often of chain length in the range C8 -C22. In some examples, the curing agent may comprise a carrier material, such as a silicon dioxide-containing compound, to act as a carrier for the fatty alcohol. As such, the curing agent may comprise a fatty alcohol on (supported on, for instance by absorption or adsorption) an inorganic carrier material, such as a silicon dioxide-containing material, for instance silica gel. This may improve the stability of the curing agent, by preventing degradation of the fatty alcohol. In addition, as some fatty alcohols are liquids at room temperature, combining these with the carrier material provides for a curing agent which is in powder form, and so is easier to store and transport. It may be that the density of the powder is in the range 500 -750 kg/m3, often in the range 540 -740 kg/m3.

The integral presence of the curing agent removes the need for the post-application of curing agent after the screed has been laid, ensuring even distribution of the curing agent throughout the screed composition, such that localised cracking due to poor application of the screed to the surface is minimised or eliminated. Further, it has been found that by incorporating the curing agent directly into the composition the surface produced is harder and so more robust than surfaces where the curing agent is applied using post-application methods.

Neopentyl glycol can be incorporated within the binder to prevent shrinkage and cracking of the resultant screed composition. However, finely dispersed particles of neopentyl glycol can form explosive mixtures in air. The applicant has found that mixing and milling neopentyl glycol with inert limestone (calcium carbonate), often in a premixing step to form an adjuvant, renders the finely dispersed neopentyl glycol particles non-explosive.

A superplasticiser may be incorporated within the binder to act as a flow enabler, aiding the working of the resultant screed composition. As mentioned previously, standard practice in the field of cement and screed manufacture is to add a liquid plasticiser separately at the point of use, reducing efficiency and making the screed formation process more time consuming for the user. Further, there is also a need to remember the extra step of adding the plasticiser, which means a higher chance of error in the formation process. However, inclusion of a superplasticiser in the initial binder composition removes the need for this additional step, simplifying the manufacturing process and saving cost. Further, superplasticisers comprising polycarboxylate ethers provide cement dispersion by steric stabilisation as opposed to electrostatic repulsion, which results in a screed composition with good workability.

Segregation of a screed composition is where the constituent materials separate, resulting in a weaker material, due to the lack of homogeneity. Bleeding is a particular form of segregation where water in the concrete, cement, screed or the like rises to the surface, as the solid material is unable to retain all the water; this process inevitably weakens the structure of the material. Inclusion of a stabiliser within the binder assists in the prevention of bleeding and segregation, and will result in a binder which will produce a more structurally sound screed composition.

As noted above, the term "screed" is intended to include not only screeds, but also concretes, cements or similar cementous products. In particular, however, the binder is intended for use with screed products or shrink resistant concretes. The binder lends itself particularly to use in screeds as it provides excellent fluidity, a property of particular importance to the levelling process. As such a self-levelling screed can be provided.

Optionally, there is provided a binder according to the first aspect of the invention, comprising: calcium carbonate, the curing agent, and an adjuvant, the adjuvant comprising: further calcium carbonate, the neopentylglycol, the superplasticiser, and the stabiliser.

It may be that the binder comprising the adjuvant will comprise, independently, one or more of the components in the levels: 80-90 wt% binder calcium carbonate; 0.05-1 wt% binder curing agent; and 10-20 wt% of an adjuvant, the adjuvant comprising: 68.5-85.5 wt% calcium carbonate; 10-20 wt% neopentylglycol; 2.5-7.5 wt% of a superplasticiser comprising one or more modified polycarboxylated ethers; and 2-4 wt% of a stabiliser comprising a high molecular weight synthetic polymer/powder.

As noted above, the pre-formation of the adjuvant stabilises the neopentyl glycol, ensuring safer handling of the binder during manufacture and in subsequent use. Further, inclusion of a powdered plasticiser instead of a liquid plasticiser allows for better dispersion within the binder, resulting in a final product with enhanced workability.

Adding the curing agent directly to the calcium carbonate, and not to the adjuvant, can be advantageous in terms of overall product stability, as the adjuvant cannot be stably stored for as long when the curing agent is in direct contact with the other adjuvant components.

The curing agent will often be present in the range 1 -10 kg/m3, often 2 -8 kg/m3 or 4 -6 kg/m3 of the screed, although the range 1 -10 kg/m3 would provide for binders which prevent cracking when used in screed compositions. Alternatively, the curing agent could be said to be present in the range 0.05 -1 wt%, 0.1 to 0.8 wt% or 0.2 - 0.6 wt% of the binder, or in the range 0.5 -5 wt% or 1 -4 wt% of an adjuvant which is then added to calcium carbonate to form the binder. Although improvements are observed below these levels, above the minimum levels suggested here, cracking is almost never observed. Above the maximum levels suggested here, cracking is prevented and so there is no need to add more curing agent to the composition beyond the 10 kg/m3, and often the 8 kg/m3 or 6 kg/m3 suggested.

The binder will often be "dry" in the sense that it will not be diluted with liquids. The "dry" binder may be flaked, granular or in powder form. Often, the binder will be in powder form. Dry products are easier to both transport and store than pre-formed liquid products, making transport more cost effective for the manufacturer and the customer.

Powder is the preferred dry form of the binder as powders form homogeneous mixtures most easily.

It will generally be the case that the calcium carbonate of the binder is in the range 98- 99.5 wt% pure. This ensures consistent product performance, as such high purity of the primary component of the mixture means that few by-products are produced. Preferably, the calcium carbonate comprises in the range 0.001-0.1 wt% water, as a dry product will form a chemically stable and consistent binder.

Generally, the calcium carbonate will be from the same source, regardless of whether it is in the adjuvant or bulk binder. Therefore, all references to the physical properties of the calcium carbonate (or limestone, used herein interchangeably), apply to calcium carbonate in the adjuvant and/or in the bulk binder. It is generally the case that the particle size of the calcium carbonate be in the range of 1-75 pm. Typically, greater than 7 5 % of the calcium carbonate particles are of size in the range of 1-75 pm. Preferably, greater than 95%. Ensuring that the particle size distribution is well controlled, and that the particles are of defined particle size with minimal particles outside the distribution, will ensure a good distribution of particles throughout the binder, making it easier to produce a homogeneous product.

The particle sizes of the other components of the adjuvant/binder will be in a similar range to the calcium carbonate, so as to ensure thorough mixing of all components within the adjuvant/binder.

It is also generally the case that the neopentylglycol of the binder is in the range 9999.9 wt% pure, to ensure minimal side reactions within the binder or screed composition.

According to a second aspect of the invention, there is provided a screed comprising the binder of the first aspect of the invention. Further provided, in a third aspect of the invention, there is provided a concrete comprising the binder of the first aspect of the invention.

The screed or concrete may comprise one or more of sand, cement and water as would be known to the person skilled in the art.

In a fourth aspect of the invention there is provided a method for producing a binder for screed compositions, comprising the steps of: (i) combining calcium carbonate, neopentylglycol, a plasticiser comprising one or more modified polycarboxylated ethers, a stabiliser comprising starch and a curing agent; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with calcium carbonate to form a binder. The method may comprise, independently, the following levels of components, such that the method may comprise the steps of: (i) combining by weight of the adjuvant formed 68.5-85.5 wt% calcium carbonate, 10-20 wt% neopentylglycol, 2.5-7.5 wt% of a plasticiser comprising one or more modified polycarboxylated ethers, 2-4 wt% of a stabiliser comprising starch, and 0.5 to 5 wt% curing agent; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with 80-90 wt% by weight of the binder calcium carbonate to form a binder.

In some examples, the curing agent may be added after the other components of the binder have been combined, this can improve the storage stability and workability of the resulting binder. In such cases, the adjuvant comprises calcium carbonate, neopentylglycol, plasticiser and stabiliser as described above, and the adjuvant and curing agent are added to the calcium carbonate to form a binder, such that there is provided a method for producing a binder for screed compositions, comprising the steps of: (i) combining calcium carbonate, neopentylglycol, a plasticiser comprising one or more modified polycarboxylated ethers, a stabiliser comprising starch; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with calcium carbonate, and curing agent to form a binder. This method could be further defined as a method for producing a binder for screed compositions, comprising the steps of: (i) combining, independently by amount, by weight of the adjuvant 68.5-85.5 wt% adjuvant calcium carbonate, 10-20 wt% adjuvant neopentylglycol, 2.5-7.5 wt% adjuvant of a plasticiser comprising one or more modified polycarboxylated ethers, and 2-4 wt% adjuvant of a stabiliser comprising starch; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with 80-90 wt% of the binder calcium carbonate, and 0.05 -1 wt% of the binder curing agent to form a binder.

It is generally the case that combining steps (i) and/or (iii) comprise mixing of the components for a time in the range 1 to 5 minutes as this balances homogenous mixing with the time spent ensuring an effective binder mix. Often the range will be 1 to 3 20 minutes.

Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, although all aspects of the invention preferably "comprise" the features described in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art.

Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also disclosed as a possible value for the parameter.

In addition, unless otherwise stated, all numerical values appearing in this application are to be understood as being modified by the term "about".

In order that the invention may be more readily understood, it will be described further with reference to the specific examples hereinafter.

Examples

Binder Compositions A and B Example Binders are described below: Binder Composition A Wt% SuperlonTM filler L150 97.64 (Limestone -sold by Longcliffe) Neopentyl glycol (NPG) 1.5 ViscocreteTM 520P 0.55 (Plasticiser -sold by Sika) StarvisTM 3040F 0.31 (Stabiliser -sold by BASF) Me!flux 5919F Powder Dosed at 0.4 -0.8 wt% as required (Curing Agent -sold by BASF) Binder Composition B Wt% SuperlonTM filler L150 97.64 (Limestone -sold by Longcliffe) Neopentyl glycol (NPG) 1.5 MelfluxTM AP101F 0.55 (Plasticiser -sold by BASF) StarvisTM 3040F 0.31 (Stabiliser -sold by BASF) Me!flux 5919FPowder Dosed at 0.4 -0.8 wt% as required (Curing Agent -sold by BASF) Method of manufacture of Binder Compositions A and B Binder compositions A and B can both be prepared by the method outlined below.

Firstly, SuperlonTM filler L150, neopentyl glycol (NPG), ViscocreteTM 520P (or MelfluxTM AP101F for Binder composition B), and StarvisTM 3040F, are combined in a ploughshare batch mixer to form an adjuvant. Specifically, the components are combined in the following proportions by weight: (H) Adjuvant Wt% SuperlonTM filler L150 76.4 Neopentyl glycol (NPG) 15 ViscocreteTM 520P (or MelfluxTM AP101F) 5.5 StarvisTM 3040F 3.1 The four components of the adjuvant are then metered into a ploughshare batch mixer via loss in weight control systems. The residence time of the four components within the mixer is in the range of 1 to 3 minutes (adjustable by computer control).

After mixing in the ploughshare is complete, the resulting adjuvant will be discharged into a turbine mill.

The adjuvant is then transported and stored, so that it can be used to prepare Binder Composition A or B. Binder Compositions A and B are produced by mixing the respective adjuvant with SuperIon L150, and the curing agent powder in the following proportions: SuperlonTM filler 1150 (or equivalent such as SuperlonTM L100 or SuperlonTM A6) 90 wt% Adjuvant 9.2 -9.6 wt% Me!flux 5919F 0.4 -0.8 wt% The adjuvant, curing agent and SuperlonTM filler L150 are discharged into a continuous ploughshare mixer via a metered loss in weight system. The retention time within the mixer is between 1 and 3 minutes. The retention time is controlled by adjustment of a weir at the exit of the mixer. Finished Binder Composition A and B may then be pneumatically conveyed into dedicated storage silos ready for use in concrete or cement or the like.

The resulting binder compositions can provide screed formulations with excellent compressive ( 25 N/mm2 after 28 days) and flexural (E) N/mm2) strength.

It would be appreciated that the process and apparatus of the invention are capable of being implemented in a variety of ways, only a few of which have been illustrated and described above.

Claims

Claims 1. A binder for screed compositions comprising: calcium carbonate, neopentylglycol, superplasticiser comprising one or more modified polycarboxylated ethers, stabiliser comprising a high molecular weight synthetic polymer/powder, and a curing agent.
2. A binder according to claim 1, comprising: calcium carbonate, the curing agent, and an adjuvant, the adjuvant comprising: calcium carbonate, the neopentylglycol, the superplasticiser, and the stabiliser.
3. A binder according to claim 1 independently comprising: 96-98.5 wt% calcium carbonate; 1-2 wt% the neopentylglycol; 0.1-1.0 wt% of the superplasticiser; 0.2-0.4 wt% of the stabiliser; and/or 0.05-1 wt% the curing agent.
4. A binder according to claim 2, independently comprising: 80-90 wt% calcium carbonate; 0.05-1 wt% the curing agent; and 10-20 wt% of an adjuvant, the adjuvant comprising: 68.5-85.5 wt% calcium carbonate; 10-20 wt% the neopentylglycol; 2.5-7.5 wt% of the superplasticiser; and 2-4 wt% of the stabiliser.
5. A binder according to any preceding claim, wherein the binder is powder form.
6. A binder according to any preceding claim, wherein the calcium carbonate is in the range 98-99.5 wt% pure.
7. A binder according to any preceding claim, wherein the calcium carbonate comprises in the range 0.001-0.1 wt% water.
8. A binder according to any preceding claim, wherein the calcium carbonate is of particle size in the range of 1-75 pm.
9. A binder according to claim 8, wherein greater than 95% of the calcium carbonate particles are of size in the range of 1-75 pm.
10. A binder according to any preceding claim, wherein the neopentylglycol is in the range 99-99.9 wt% pure.
11. A binder according to any preceding claim, wherein the curing agent comprises a fatty alcohol.
12. A binder according to claim 11, wherein the fatty alcohol is of chain length in the range C8 -C22.
13. A binder according to any preceding claim wherein the curing agent comprises a carrier material.
14. A binder according to any preceding claim wherein the carrier material comprises silica gel.
15. A screed comprising the binder of any preceding claim.
16. A concrete comprising the binder of any one of claims 1 to 14.
17. A screed or concrete according to claim 15 or claim 16, further comprising one or more of sand, cement and water.
18. A method for producing a binder for screed compositions, comprising the steps of: (i) combining calcium carbonate, neopentylglycol, a plasticiser comprising one or more modified polycarboxylated ethers, a stabiliser comprising starch and a curing agent; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with calcium carbonate to form a binder.
19. A method for producing a binder for screed compositions, comprising the steps of: (i) combining calcium carbonate, neopentylglycol, a plasticiser comprising one or more modified polycarboxylated ethers, a stabiliser comprising starch; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with calcium carbonate, and curing agent to form a binder.
20. A method according to claim 18, comprising the steps of: (i) combining 68.5-85.5 wt% calcium carbonate, 10-20 wt% the neopentylglycol, 2.57.5 wt% of the plasticiser, 2-4 wt% of the stabiliser and 0.5-5 wt% the curing agent; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with 80-90 wt% calcium carbonate to form a binder. 5
21. A method according to claim 19, comprising the steps of: (i) combining 68.5-85.5 wt% adjuvant calcium carbonate, 10-20 wt°/0 adjuvant the neopentylglycol, 2.5-7.5 wt% adjuvant of the plasticiser, and 2-4 wt% adjuvant of the stabiliser; (ii) milling the combination of (i) to form an adjuvant; and (iii) combining the adjuvant with 80-90 wt% of the binder calcium carbonate, and 0.05-1 wt% of the binder of the curing agent to form a binder.
22. A method according to any of claims 18 -21, wherein the combining steps (i) and/or (iii) comprise mixing of the components for a time in the range 1-5 minutes.