WO2013063743A1

WO2013063743A1 - High performance mortar for exterior insulation finish system

Info

Publication number: WO2013063743A1
Application number: PCT/CN2011/081560
Authority: WO
Inventors: Yanfeng Wu
Original assignee: Rohm And Haas Company
Priority date: 2011-10-31
Filing date: 2011-10-31
Publication date: 2013-05-10

Abstract

A mortar composition used in exterior insulation finish system containing 20%-35% by weight of Portland cement, 55%-70% by weight of fillers, 0.05%-0.5% by weight of cellulose ether, 6%-8.5% by weight of redispersible polymer powder and/or polymer emulsion, 0.05%-0.5% by weight of a hydrophobic agent, 0.05%-0.5% by weight of polymer fibers, and 0.2%-1.5% by weight of early strength agent, with percentages based on total dry weight of said mortar composition.

Description

HIGH PERFORMANCE MORTAR FOR EXTERIOR

INSULATION FINISH SYSTEM

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a mortar composition used in construction industry. Particularly, the present invention relates to a polymer mortar composition applicable for EIFS construction withstanding weathering test including wet freeze-thaw circulation. Introduction

Exterior Insulation Finish System (EIFS) is an exterior wall cladding system, and is also known as External Thermal Insulation Systems (ETICS) in Europe. It can be used on both residential and commercial buildings for the purpose of saving energy, improving room comfort and protecting walls against moisture and other external elements.

EIFS normally comprises a thermal insulation layer and polymer mortar layers.

Polymer mortar layers are normally used as an adhesive layer for adhering a thermal insulation board onto a substrate, such as an outer wall, and as a basecoat layer for leveling the surface to which a finish layer would be applied and reinforcing the flexibility of the system.

EIFS should have certain flexibility to maintain integrity even with slight deformity and outer impact. Impact resistance is a critical factor for evaluating flexibility of EIFS, especially for the building structures having a lower altitude, which are vulnerable to impact by accident.

Currently available polymer mortars for use in EIFS, such as those disclosed in CN101306938A and CN101786846A, usually have a polymer fraction less than 5% by weight based on the total dry weight of the mortar. Such mortars cannot maintain workable impact resistance greater than 3 Joules according to China Industrial Code JGl 49-2003 after a weathering test including a hot-rain circulation, a dry freeze-thawing circulation and a wet freeze-thawing circulation (which test is specified in latter part, "Weathering Test Method") and the impact resistance of some mortars is even lower than 1 Joule after the test. As a result, these mortars are not suitable for EIFS construction in Southern China where there are many rainy days in winter. It is desirable to develop an EIFS-applicable mortar composition that maintains acceptable impact resistance after a weathering test including wet freeze-thawing circulation.

BRIEF SUMMARY OF THE INVENTION

Surprisingly, inventors have found a mortar composition that keeps workable impact resistance as required for EIFS applications after a weathering test including wet freeze- thawing circulation. Thus, such mortar composition can be used in construction to prepare the mortar layers of EIFS in areas where it is rainy in winter.

Discovery of the present invention is partly a result of discovering a problem with current EIFS structures. It has been discovered that when EIFS are submersed in water during a weathering test water likely penetrates through the polymer mortar of the EIFS, resulting in a reduction in impact resistance of the EIFS. Water that penetrates the polymer mortar can accelerate a second hydration of the mortar, which increases stiffness of the mortar in the EIFS, resulting in a loss in flexibility. In addition, the polymer of a polymer mortar forms a film between inorganic particles, such as fillers, inside the polymer mortar. When the polymer gets wet, bonding strength of the polymer reduces thereby weakening the mortar. More seriously, when immersed water is frozen within a mortar, the mortar structure tends to be destroyed due to volume expansion of frozen water.

The present invention provides a mortar composition comprising 20 percent (%)- 35% by weight of Portland cement, 55%-70% by weight of fillers, 0.05%-0.5% by weight of cellulose ether, 6%-8.5% by weight of redispersible polymer powder and/or polymer emulsion, 0.05%-0.5% by weight of a hydrophobic agent, 0.05%-0.5% by weight of polymer fibers, and 0.2%- 1.5% by weight of early strength agent, with percentages based on total dry weight of said mortar composition.

Preferably, the inventive mortar composition comprises 23%-27% by weight of

Portland cement, 5%-10% by weight of calcium carbonate, 55%-60% by weight of quartz sand, 0.1%-0.3% by weight of cellulose ether, 7%-8% by weight of ethylene vinyl acetate RDP, 0.1%-0.3% by weight of silane-based hydrophobic agent, 0.1%-0.3% by weight of polypropylene fibers, and 0.5%-l% by weight of calcium formate, with percentages based on total dry weight of said mortar composition. A mortar layer prepared from the inventive mortar composition meet the EIFS requirements including the impact resistance and the ratio of compressive strength to flexural strength under China Industrial Code JG149-2003.

DETAILED DESCRIPTION OF THE INVENTION

As used herein:

Unless otherwise stated, all percentages (%) are by weight based on the total dry weight of the mortar composition. The descriptions of the various ingredients set forth below are non-limiting.

The units/abbreviations used in the description are illustrated as follows.

Unit Full name

m meter

m² square meter

mm millimeter

MPa Mega Pascal

s second

min minute

h hour

L liter

g/m² gram per square meter

Kg/m³ kilogram per cubic meter

mPa-s(i.e. centipoise, cp) milli-Pascal- second

e.g. for example

and/or and, or as an alternative

Re-dispersible power (RDP) is typically made by spray drying emulsion polymer in the presence of various additives such as a protective colloid, anti-caking agent, etc. Many types of polymers can be used to produce RDP including vinyl ester-ethylene copolymers, such as ethylene/vinylacetate copolymer, vinylacetate/vinyl-versatate copolymer,

styrene/acrylic esters copolymers, etc. To carry out spray drying, the dispersion of the copolymer, if appropriate together with protective colloids, is sprayed and dried. When mixed with water, these polymer powders can be re-dispersed to form an emulsion, which in turn forms continuous films within cement mortar later when the water is removed by evaporation and hydration of cement.

The following monomers could be used to synthesize an emulsion polymer for finally obtaining RDP. Preferred vinyl esters comprise vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate, and vinyl esters of alpha-branched monocarboxylic acids having from 5 to 11 carbon atoms. Some preferred examples include VEOVA™ 5 RTM, VEOVA™ 9 RTM, VEOVA™ 10 RTM, VEOVA™ 11 RTM (VEOVA is a trademark of Resolution Performance Products, LLC). Preferred methacrylic esters or acrylic esters include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n- butyl methacrylate, and 2-ethylhexyl acrylate. Preferred vinyl-aromatics include styrene, methylstyrene, and vinyltoluene. A preferred vinyl halide is vinyl chloride. The preferred olefins are ethylene and propylene, and the preferred dienes are 1,3-butadiene and isoprene.

More preferably, the RDP is obtained from vinyl ester-ethylene copolymer (also named ethylene vinyl acetate, EVA), such as FX2350 available from AkzoNobel.

The polymer emulsion is a two phase system having finely dispersed polymeric particles in solvent such as water. An aqueous emulsion polymer is normally composed of emulsion polymer particles, such as vinyl polymer or polyacrylic ester copolymer and a surfactant containing hydrophobic and hydrophilic moieties. The preferred aqueous emulsion polymer when applied as a coating on a substrate and cured at ambient or elevated temperature, has been found to have excellent solvent, chemical and water resistance;

exterior durability; impact resistance; abrasion resistance; excellent adhesion to a variety of substrates.

The inventive mortar composition typically comprises 5% or more, and can comprise

5.5% or more, even 6% or more, even 6.5% or more, even 7% or more, and at the same time typically comprises 9% or less, and can comprise 8.5% or less, even 8% or less, even 7.5%) or less by weight of at least one RDP and/or at least one polymer emulsion, where percent is weight-percent based on the total dry weight of the mortar composition. The weight percent of the polymer emulsion in the inventive mortar is calculated based on the dry weight of emulsion polymer contained in said emulsion. Inventors found that if the RDP concentration is below 5 wt% based on total dry weight of mortar composition the mortar lacks desirable flexibility; if the concentration above 9 wt% the mortar becomes too soft and unsuitable for EIFS applications.

Early strength agent, also named "accelerator", means a chemical substance mixed with cement slurry to reduce the time required for setting and hardening cement to develop sufficient compressive strength to enable demolding or drilling operations to continue. The early strength agent can be selected from nitrate salts (such as sodium nitrate and potassium nitrate); formate salts (such as sodium formate and calcium formate); chloride salts (such as sodium chloride, calcium chloride, and magnesium chloride); thiocyanate salts (such as sodium thiocyanate); nitrite salts (such as sodium nitrite); mono-, di- and triethanolamine; and highly alkaline agents including alkali hydroxide (such as sodium hydroxide, calcium hydroxide, and potassium hydroxide), alkali carbonate (such as sodium carbonate and potassium carbonate), alkali silicate (such as sodium silicate), and alkali aluminate (such as sodium aluminate). US5,605,571 also teaches an accelerator for hydraulic binders containing at least a nitrate- or sulfite component, at least a thio-cyanate component, at least an alkanolamine component and at least a carboxylic acid component.

Early strength agent is introduced in the inventive mortar to accelerate the hydrating, so that the inventive mortar could complete setting and hardening within a shorter time; therefore, penetration of the inventive mortar by outside moisture or water could be reduced and the possibility of the second cement hydration is lowered.

Preferably the early strength agent used in the inventive mortar is calcium formate.

The inventive mortar composition typically comprises 0.1% or more, and can comprise 0.2% or more, even 0.5% or more, even 0.7% or more, and at the same time typically comprises 1.8% or less, and can comprise 1.5% or less, even 1.2% or less, even 1% or less by weight of early strength agent based on the total dry weight of the mortar composition.

Hydrophobic agent is water repellant material incorporated into hydratable cementitious materials such as cement pastes, masonry cements, mortars, and concrete to achieve a degree of moisture impermeability. Exemplary hydrophobic agents suitable for the inventive mortar include an aliphatic carboxylic acid or salt or ester thereof, a fatty acid or salt or the ester thereof, a natural or synthetic wax, a natural or synthetic oil, a silicone compound, a silane compound, a siloxane compound, a naphthalene compound, a melamine compound, a dicarboxylic acid or the salt thereof, or a mixture of any of the foregoing. Preferably hydrophobic agents are silane-based. Silane-based hydrophobic agents are silanes that are chemical compounds of silicon and hydrogen and consist of a chain of silicon atoms covalently bonded to each other and to hydrogen atoms. Alkyl groups could be linked to the silicon chain of a siliane-based hydrophobic agent. For example, butyltrimethoxysilane and other silanes are commercially available from Dow Corning and AkzoNobel and are suitable silane-based hydrophobic agents.

The inventive mortar composition typically comprises 0.05% or more, and can comprise 0.1% or more, even 0.2% or more, and at the same time typically comprises 0.75% or less, and can comprise 0.5% or less, even 0.3% or less by weight of hydrophobic agent based on the total dry weight of the mortar composition.

Polymer fibers, also named as "synthesized fibers", are used to reinforce or otherwise improve the properties of concrete by applying them to aqueous based concrete mixes prior to the curing of the concrete. The types of polymer fibers in use or proposed for use in the present invention include those composed of polyolefins, especially polypropylene, polyester, polyamide, polyacrylic and polyvinyl alcohol. Polymer fibers can be produced by any well known melt spinning process.

In the inventive mortar, polymer fibers are used to enhance the flexibility of the mortar. Preferably, polymer fibers used in the inventive mortar are polypropylene fibers, such as the polypropylene fibers (8mm in length and 0.02- 0.03mm in diameter) available from Kaitai Fiber Cooperation. The use of polypropylene fibers is desirable for several reasons, including low raw material cost, excellent physical properties and the nonreactive properties of the polymer in the alkaline concrete mix.

The inventive mortar composition typically comprises 0.05% or more, and can comprise 0.1% or more, even 0.2% or more, and at the same time typically comprises 0.75% or less, and can comprise 0.5% or less, even 0.3% or less by weight of polymer fibers based on the total dry weight of the mortar composition.

Fillers are inorganic material without binding function. It includes coarse aggregate and fine filler. The particle size of coarse aggregate is larger with maximum size up to 8mm. The particle size of fine filler is smaller, generally less than 0.1mm. One example of aggregate is quartz sand which usage level is high (normally greater than 40% by weight in a mortar), while one example of fine filler is calcium carbonate (CaC0₃) powder. Quartz sand generally refers to all sorts of sand with quartz content at absolute high level, such as sea sand, fluvial sand and lake sand.

The inventive mortar composition typically comprises 50% or more, and can comprise 55% or more, even 60% or more, and at the same time typically comprises 75% or less, and can comprise 70% or less, even 65% or less by weight of fillers based on the total dry weight of the mortar composition.

In addition, the inventive mortar composition typically comprises 18% or more, and can comprise 20% or more, even 23% or more, and at the same time typically comprises 35%) or less, and can comprise 30% or less, even 27% or less by weight of Portland cement based on the total dry weight of the mortar composition. Preferably the Portland cement has a strength grade of 42.5R according to China National Code GB 175-2007, "Common Portland Cement".

Cellulose ether is also used in the inventive mortar for water retention and

workability improvement. Suitable cellulose ethers include hydroxyalkylcelluloses (e.g., hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC) and

hydroxypropylhydroxyethylcellulose (HPHEC)), carboxy-alkylcelluloses (e.g.,

carboxymethylcellulose (CMC)), carboxyalkylhydroxyalkylcelluloses (e.g.,

carboxymethylhydroxyethylcellulose (CMHEC), carboxymethyl-hydroxypropylcellulose (CMHPC)), sulphoalkylcelluloses (e.g., sulphoethylcellulose (SEC), sulphopropylcellulose (SPC)), carboxyalkylsulphoalkylcelluloses (e.g., carboxymethylsulphoethylcellulose

(CMSEC), carboxymethylsulphopropylcellulose (CMSPC)),

hydroxyalkylsulphoalkylcelluloses (e.g., hydroxyethylsulphoethylcellulose (HESEC), hydroxypropylsulphoethylcellulose (HPSEC) and hydroxyethylhyd

roxypropylsulphoethylcellulose (HEHPSEC)), alkylhydroxyalkylsulphoalkylcelluloses (e.g., methylhydroxyethylsulphoethylcellulose (MHESEC),

methylhydroxypropylsulphoethylcellulose (MHPSEC) and

methylhydroxyethylhydroxypropylsulphoethylcellulose (MHEHPSEC)), alkylcelluloses (e.g., methylcellulose (MC), ethylcellulose (EC)), binary or ternary alkylhydroxyalkylcellulose (e.g., hydroxyethylmethylcellulose (HEMC), ethylhydroxy ethylcellulose (EHEC),

hydroxypropylmethylcellulose (HPMC), ethylhydroxypropylcellulose (EHPC),

ethylmethylhydroxyethylcellulose (EMHEC), and ethylmethylhydroxypropylcellulose

(EMHPC)), alkenylcelluloses and ionic and nonionic alkenylcellulose mixed ethers (e.g., allylcellulose, allylmethylcellulose, allylethylcellulose and carboxy-methylallylcellulose)), dialkylaminoalkylcelluloses (e.g., Ν,Ν-dimethylaminoethylcellulose, N,N- diethylaminoethylcellulose), dialkylaminoalkylhydroxyalkylcelluloses (e.g., N,N- dimethylaminoethylhydroxyethylcellulose and N,N- dimethylaminoethylhydroxypropylcellulose), and aryl-, arylalkyl- and

arylhydroxyalkylcelluloses (e.g., benzylcellulose, methylbenzylcellulose and

benzylhydroxyethylcellulose).

Preferably, the cellulose ether used in the inventive mortar is methyl hydroxyethyl cellulose, such as CP 1425 available from The Dow Chemical Company.

The inventive mortar composition typically comprises 0.05% or more, and can comprise 0.1%> or more, even 0.2%> or more, and at the same time typically comprises 0.75%> or less, and can comprise 0.5%> or less, even 0.3%> or less by weight of cellulose ether based on the total dry weight of the mortar composition.

The dry-mix of the inventive mortar could be obtained by mixing silica sand and fibers, cellulose ether, RDP and calcium formate for 30 seconds to obtain a mixture, and then mixing the mixture with calcium carbonate and cement for 30 seconds. Upon application, water and other liquid components could be added under stirring to obtain the inventive mortar composition. Weathering Test Method

When a sample EIFS is subjected to weathering testing, the sample EIFS should go through three circulations in order: heat/rain circulation, dry freeze-thaw circulation, and wet freeze-thaw circulation. Testing apparatus and equipments, sample preparation and curing, and the testing processes of heat/rain circulation and dry freeze-thaw circulation follow China Industrial Code JG149-2003 "External thermal insulation composite systems based on EPS". The testing processes of wet freeze-thaw circulation are specified as below.

After the dry freeze-thaw circulation is completed, wait for 48h before initiating the wet freeze-thaw circulation. The surface temperature of the sample is increased to 20 ^°C .

The sample is kept at 20±5 ^°C and relative humidity no less than 80%> for lh. Water (15±5 ^°C) is sprayed onto the sample with a spraying water volume 1.0-1.5L/(m² sample surface area-min) for lh. The sample is then placed at 20±5 ^°C and relative humidity no less than 80% for lh. Then the surface temperature of the sample is decreased to -20 ^°C within 2h, and then the sample is kept at -20±5 ^°C for 7h. The sample is heated to 20 ^°C again to complete one cycle. The sample should experience five cycles in series without interruption.

Observe the sample surface after each wet freeze-thaw circulation to check the blister, cracking or spalling of the basecoat layer and the finish layer, and the size and position of such destroyed places are recorded.

Seven days after the weathering test the samples were tested for performance parameters including impact resistance and compressive strength/flexural strength (the ratio of compressive strength to flexural strength). Such testing was done according to Chinese Industrial Code JG149-2003. The average of each performance parameter for 3 samples is calculated as the testing result.

Example

A comparison test was designed for testing the impact resistance and compressive strength/flexural strength of sample EIFS made from different basecoat mortars.

A sample EIFS was prepared following JG149-2003. The insulation board used in the sample EIFS is STYROFOAM™ XPS extruded polystyrene board (STYROFOAM is a trademark of Dow Chemical) with a density of 30kg/m³. An adhesive mortar meeting the requirement of JG149-2003 was used to adhere the insulation board onto a wall in the testing equipment. Such adhesive mortar comprises 34% 42.5R Portland cement, 62.9% silica sand, 2.6% EVA, 0.2% methyl hydroxyethyl cellulose (viscosity 35000-45000 mPa-s) and 0.3%) calcium formate. The basecoat mortar was then applied onto the insulation board. An alkali-resistant fiberglass mesh meeting the requirement of JG 149-2003 was embedded into the basecoat mortar layer. Such mesh has a mass per unit area of 130g/m². Finally a finish layer is applied on the basecoat mortar layer. Such finish layer is a SUZUKA

elastomeric coating (available from SUZUKA International (Shanghai) Co., Ltd.) for exterior wall meeting the requirements of Chinese Industrial Code JG/T 172-2005,

"Elastomeric Wall Coatings".

Components used in basecoat mortars are listed in Table 1 as below. The dry-mix of the inventive mortar was obtained by mixing silica sand and fibers, cellulose ether, RDP and calcium formate for 30 seconds to obtain a mixture, and then mixing the mixture with calcium carbonate and cement for 30 seconds.

Table 1 : Specification/model and producer of mortar components

The formulations of different mortars and performance test results are shown in 2. Examples HT1, HT4 and HT5 have a RDP fraction of 6-8.5 wt.% and represent inventive mortars. Examples HT2, HT3 and HT6 are comparative examples.

Table 2: Formulations and performance test results for EIFS samples (unless otherwise indicated, values are in units of wt.% relative to total dry weight of a mortar composition.)

redispersible polymer

8 3 10 6 7 9

powder EVA

Cellulose ether 0.2 0.2 0.2 0.2 0.2 0.2

calcium formate 0.7 0.7 0.7 0.7 0.7 0.7

PP fiber(8mm) 0.2 0.2 0.2 0.2 0.2 0.2

hydrophobic agent seal 80 0.2 0.2 0.2 0.2 0.2 0.2

Test results

Impact resistance after

>3 <3 >3 >3 >3 >3

weathering test (Joule)

Ratio of Compressive too soft too soft strength to flexural 1.8 2.8 to be 2.0 2.0 to be strength tested tested

It can be seen that the inventive mortars HT1, HT4 and HT5 achieve a ratio of compressive strength to flexural strength less than 3.0 while keeping impact resistance greater than 3 joules thereby meeting the requirement of JG149-2003. HT2 has a lower dosage RDP than inventive mortars and could not keep workable impact resistance. HT3 and HT6 have higher dosage RDP than inventive mortars but the mortar samples are too soft and are not suitable for EIFS application.

Claims

WHAT IS CLAIMED IS:

1. A mortar composition comprising

(a) 20%-35% by weight of Portland cement,

(b) 55%-70% by weight of fillers,

(c) 0.05%-0.5% by weight of cellulose ether,

(d) 6%-8.5% by weight of redispersible polymer powder and/or polymer emulsion,

(e) 0.05%-0.5% by weight of a hydrophobic agent,

(f) 0.05%-0.5% by weight of polymer fibers, and

(g) 0.2%- 1.5% by weight of early strength agent,

with percentages based on total dry weight of said mortar composition.

2. The mortar composition of Claim 1, wherein said redispersible polymer powder or polymer emulsion is selected from ethylene-vinyl acetate copolymer and acrylic polymer.

3. The mortar composition of Claim 1, wherein said hydrophobic agent is selected from silanes.

4. The mortar composition of Claim 1, wherein said early strength agent is calcium formate.

5. The mortar composition of Claim 1, wherein said polymer fibers are polypropylene fibers.

6. The mortar composition of Claim 1, wherein said mortar composition comprises

(a) 23%-27% by weight of Portland cement,

(b) 5%-10% by weight of calcium carbonate,

(c) 55%-60% by weight of quartz sand,

(d) 0. l%-0.3% by weight of cellulose ether,

(e) 7%-8% by weight of ethylene vinyl acetate RDP,

(f) 0.1%-0.3% by weight of silane-based hydrophobic agent,

(g) 0.1%-0.3% by weight of polypropylene fibers, and (h) 0.5%-l% by weight of calcium formate,

with percentages based on total dry weight of said mortar composition.