阅读说明：本技术 一种无氟液体速凝剂及其制备方法与应用 (Fluorine-free liquid accelerator and preparation method and application thereof ) 是由 张瑶瑶 王英维 王宏维 于 2020-12-30 设计创作，主要内容包括：本发明公开了一种无氟液体速凝剂,其包括以下组分的原料：硫酸铝、醇胺、有机醇、有机酸、粘度调节剂、改性纳米材料和水,其中,所述改性纳米材料为用分散剂处理改性的纳米材料。本发明的速凝剂在≤6％的掺量下即可满足混凝土对凝结时间的标准要求,且该速凝剂无氟无碱无氯,具有凝结时间短,早期强度高、后期强度保留率大、绿色无害的优点。(The invention discloses a fluorine-free liquid accelerator which comprises the following raw materials: the modified nano-material comprises aluminum sulfate, alcohol amine, organic alcohol, organic acid, a viscosity regulator, a modified nano-material and water, wherein the modified nano-material is a nano-material modified by a dispersant. The accelerator can meet the standard requirement of concrete on setting time under the condition that the doping amount is less than or equal to 6 percent, and has the advantages of no fluorine, no alkali or chlorine, short setting time, high early strength, high later strength retention rate, greenness and harmlessness.)

1. A fluorine-free liquid accelerator comprises the following raw materials: the modified nano-material comprises aluminum sulfate, alcohol amine, organic alcohol, organic acid, a viscosity regulator, a modified nano-material and water, wherein the modified nano-material is a nano-material modified by a dispersant.

2. The fluorine-free liquid accelerator according to claim 1, wherein the dispersant is selected from at least one of polyvinyl alcohol, maleic acid-acrylic acid copolymer, polyethylene oxide, polymethacrylic acid, and nitric acid; and/or the nano material is selected from at least one of nano silicon dioxide, nano calcium carbonate, nano lithium carbonate and nano aluminum oxide.

3. The fluorine-free liquid accelerator according to claim 1 or 2, wherein the fluorine-free liquid accelerator comprises the following components in percentage by weight based on the total weight of the fluorine-free liquid accelerator:

35 to 55 percent of aluminum sulfate;

1 to 7 percent of alcohol amine;

1% -8% of modified nano material;

1 to 2 percent of organic alcohol;

0.1 to 2.0 percent of organic acid;

0.3 to 1.0 percent of viscosity regulator;

the balance being water.

4. The fluorine-free liquid accelerator according to any one of claims 1 to 3, wherein the alcohol amine is selected from at least one of triethanolamine, diethanolamine and triisopropanolamine; and/or the organic alcohol is selected from at least one of ethylene glycol, glycerol, ethanol and methanol; and/or the organic acid is selected from at least one of polyacrylic acid, maleic acid-acrylic acid copolymer, polymethacrylic acid and oxalic acid; and/or the viscosity modifier is selected from at least one of carboxymethyl cellulose, carboxyethyl cellulose and organic bentonite.

5. The fluorine-free liquid accelerator according to any one of claims 1 to 4, wherein the preparation method of the modified nanomaterial comprises the steps of:

(1) mixing a dispersing agent, a nano material and a first dispersing solvent to obtain a mixture;

(2) sanding the mixture obtained in the step (1), and drying to obtain the modified nano material;

preferably, the first dispersion solvent is deionized water;

preferably, the sanding time in step (2) is not less than 15 minutes, more preferably 15 minutes to 1 hour.

6. The fluorine-free liquid accelerator according to claim 5, wherein in the step (1), the first dispersion solvent is 50 to 90 parts by mass, preferably 50 to 70 parts by mass; 0.1-3.0 parts of dispersant, preferably 0.5-2 parts; the nano material accounts for 20-50 parts, preferably 30-45 parts.

7. The fluorine-free liquid accelerator as claimed in claim 5 or 6, wherein in the step (1), the dispersant and the first dispersing solvent are mixed to obtain a mixed solution, and the nano material is mixed with the mixed solution to obtain a mixture.

8. A method for producing a fluorine-free liquid accelerator according to any one of claims 1 to 7, comprising the steps of:

s1, mixing alcohol amine, organic alcohol and a second dispersing solvent to obtain a mixed solution;

s2, heating the mixed solution obtained in the step S1 to 50-90 ℃, adding aluminum sulfate and stirring until the solution is transparent;

s3, sequentially adding organic acid, a modified nano material and a viscosity regulator into the solution obtained in the step S2, and mixing every two components to finally obtain the fluorine-free liquid accelerator;

preferably, the second dispersing solvent is water or a mixture of water and alcohol;

preferably, the temperature is raised to 65-80 ℃ in step S2.

9. The method according to claim 8, wherein the step S3 is performed at a temperature of 50-90 ℃, preferably 65-80 ℃; and/or in step S3, the mixing time is not less than 10 minutes, preferably 10 minutes to 1 hour.

10. Use of the fluorine-free liquid accelerator according to any one of claims 1 to 7 or prepared by the method according to claim 8 or 9 in shotcrete construction, preferably, the fluorine-free liquid accelerator is incorporated in the concrete in an amount of 3% to 6%, more preferably 3% to 5%.

Technical Field

The invention belongs to the technical field of concrete admixtures, and particularly relates to a fluorine-free liquid accelerator as well as a preparation method and application thereof.

Background

At present, most of alkali-free liquid accelerator products adopt industrial-grade aluminum sulfate as a main accelerating component, and the following problems are generally existed: (1) the mixing amount is high, and the standard requirement of the concrete on the setting time can be met only at high mixing amount; (2) the early strength is low, the early strength is low due to some fluorides, the compressive strength of the mortar is lower than 7.0MPa in 1 day, and the standard requirement is not met; (3) the stability is poor and the storage time is short. Therefore, the development of the liquid accelerator with low mixing amount, high early strength, high later strength retention rate and good stability becomes a necessary trend for the development of alkali-free liquid accelerators in the future.

The patent CN 111333362A discloses a low-doping high-early-strength alkali-free liquid accelerator and a preparation method thereof, and provides a low-doping high-early-strength alkali-free liquid accelerator which has the characteristics of good performance, simple preparation process, no hydrofluoric acid, no alkali, no chlorine, no corrosion to steel bars, low doping amount, good stability, high early strength and high later strength retention rate. However, the accelerator contains a certain amount of fluorine which is unfavorable for the early strength development of concrete, and excessive fluorine in human bodies can be manifested as fluorosis, thus threatening the health and safety of constructors.

The accelerator industry in China enters a new development stage, relevant specifications and standards are provided, and research and application of alkali-free liquid accelerators are stimulated and encouraged. With the current increasing concern on environmental friendliness and concrete durability, the development of accelerators free of fluorine, alkali and chlorine, small in doping amount, short in setting time, high in early strength, low in rebound amount and high in anti-permeability level is the research direction.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a fluorine-free liquid accelerator and a preparation method thereof. The accelerator can meet the standard requirement of concrete on setting time under the doping amount of less than or equal to 6 percent; the accelerator is free of fluorine, alkali and chlorine, and has the characteristics of high early strength, high retention rate of later strength, greenness and harmlessness.

The invention provides a fluorine-free liquid accelerator, which comprises the following raw materials:

the modified nano-material comprises aluminum sulfate, alcohol amine, organic alcohol, organic acid, a viscosity regulator, a modified nano-material and water, wherein the modified nano-material is a nano-material modified by a dispersant.

According to some embodiments of the invention, the dispersant is selected from at least one of polyvinyl alcohol, maleic-acrylic acid copolymer, polyethylene oxide, polymethacrylic acid, and nitric acid.

According to some embodiments of the present invention, the weight average molecular weight of the polyvinyl alcohol, maleic acid-acrylic acid copolymer, polyethylene oxide and polymethacrylic acid is 1000-.

According to some embodiments of the invention, the nanomaterial is selected from at least one of nanosilica, nanosilica and nanosilica.

According to some embodiments of the invention, the nanomaterial has a particle size distribution of 30-210 nm. In some embodiments, the nanomaterial has a particle size distribution of 30-180 nm. In other embodiments, the nanomaterial has a particle size distribution of 50 to 170 nm.

According to some embodiments of the invention, the fluorine-free liquid accelerator comprises the following components in percentage by weight based on the total weight of the fluorine-free liquid accelerator: 35-55% of aluminum sulfate, 1-7% of alcohol amine, 1-8% of modified nano material, 1-2% of organic alcohol, 0.1-2.0% of organic acid, 0.3-1.0% of viscosity regulator and the balance of water.

According to some embodiments of the present invention, the percentage by weight of the alcohol amine in the raw material is 2% to 5% based on the total weight of the fluorine-free liquid accelerator.

According to some embodiments of the invention, the alcohol amine is selected from at least one of triethanolamine, diethanolamine, and triisopropanolamine.

According to some embodiments of the invention, the organic alcohol is selected from at least one of ethylene glycol, glycerol, ethanol and methanol.

According to some embodiments of the invention, the organic acid is selected from at least one of polyacrylic acid, maleic-acrylic acid copolymer, polymethacrylic acid, and oxalic acid.

According to some embodiments of the invention, the viscosity modifier is selected from at least one of carboxymethyl cellulose, carboxyethyl cellulose and organobentonite.

According to some embodiments of the invention, the method of preparing the modified nanomaterial comprises the steps of:

(1) mixing a dispersing agent, a nano material and a first dispersing solvent to obtain a mixture;

(2) and (2) sanding the mixture obtained in the step (1), and drying to obtain the modified nano material.

According to the present invention, the first dispersion solvent is a solvent capable of effectively dispersing the dispersant and the nanomaterial therein, and serves only a dispersing function without reacting with the dispersant and the nanomaterial. According to some preferred embodiments of the invention, the first dispersing solvent is deionized water.

According to the present invention, the time for mixing in step (1) is selected from a wide range so that the raw material components can be sufficiently contacted, and is preferably not less than 10 minutes. In some embodiments, the mixing time in step (1) is from 10 minutes to 1 hour.

According to some preferred embodiments of the present invention, in the step (1), the dispersant and the first dispersing solvent are mixed to obtain a mixed solution, and then the nanomaterial is mixed with the mixed solution to obtain the mixture.

According to some preferred embodiments of the present invention, the time for mixing the dispersant with the first dispersion solvent is not less than 10 minutes, preferably 10 minutes to 1 hour.

According to some preferred embodiments of the present invention, in the step (1), the mixing time of the nanomaterial with the mixed solution of the dispersant and the first dispersion solvent is not less than 10 minutes, preferably not less than 30 minutes.

According to some embodiments of the present invention, in the step (2), the sanding is performed for a period of time such that the mixture is finely dispersed to obtain the modified nanomaterial with a narrow particle size distribution, preferably the particle size distribution is 30 to 100nm, and preferably the sanding is performed for a period of time not less than 15 minutes. In some embodiments, the sanding time is between 15 minutes and 1 hour.

According to some embodiments of the invention, in step (2), the sanding is performed in a sand mill, which is a conventional or known sand mill.

According to some embodiments of the present invention, in the step (1), the first dispersing solvent is 50 to 90 parts, the dispersing agent is 0.1 to 3.0 parts, and the nanomaterial is 20 to 50 parts by mass.

According to some preferred embodiments of the present invention, in the step (1), the first dispersion solvent is 50 to 70 parts by weight.

According to some preferred embodiments of the present invention, in step (1), the dispersant is 0.5 to 2 parts by weight.

According to some preferred embodiments of the present invention, in the step (1), the nano material is 30 to 45 parts by weight.

The second aspect of the present invention provides a method for preparing a fluorine-free liquid accelerator according to the first aspect of the present invention, which comprises the following steps:

s1, mixing alcohol amine, organic alcohol and a second dispersing solvent to obtain a mixed solution;

s2, heating the mixed solution obtained in the step S1 to 50-90 ℃, adding aluminum sulfate and stirring until the solution is transparent;

s3, adding organic acid, modified nano material and viscosity regulator into the solution obtained in the step S2 in sequence, and mixing each component to obtain the fluorine-free liquid accelerator.

According to the present invention, the second dispersion solvent is a solvent capable of effectively dispersing the alcohol amine and the organic alcohol therein, and serves only a dispersing function without reacting with the alcohol amine and the organic alcohol. According to some preferred embodiments of the invention, the second dispersing solvent is an aqueous solvent, preferably water or a mixture of water and an alcohol. In some embodiments, the second dispersing solvent is deionized water.

According to some embodiments of the invention, the temperature is raised to 65-80 ℃ in step S2.

According to some embodiments of the invention, step S3 is performed at a temperature of 50-90 ℃, preferably at a temperature of 65-80 ℃.

According to some embodiments of the present invention, the mixing time in step S3 is not less than 10 minutes, preferably 10 minutes to 1 hour. In some embodiments, the time for mixing after the addition of the organic acid is not less than 10 minutes. In other embodiments, the mixing time after adding the modified nanomaterial and the viscosity modifier is not less than 30 minutes.

The mixing according to the invention can be carried out by conventional methods which bring the reaction mass into intimate contact, for example by stirring.

In a third aspect, the invention provides a fluorine-free liquid accelerator according to the first aspect of the invention and/or a fluorine-free liquid accelerator prepared by the method according to the second aspect of the invention, and the application of the fluorine-free liquid accelerator in shotcrete construction.

According to some embodiments of the present invention, the fluorine-free liquid accelerator is added in the concrete in an amount of 3% to 6%, preferably 3% to 5%.

The nano material has both filling effect and reaction activity, so that the application of the nano material in concrete materials can obviously improve the early strength of concrete, on one hand, the addition of the nano material plays a role in filling gaps of a concrete structure, on the other hand, a part of the nano material plays a role in crystal nucleus induction in a cementing material system, and the hydration of cement is accelerated. However, the nano material has large surface area and high surface energy, is in an energy unstable state and is easy to aggregate to reach a stable state; a large amount of positive and negative charges are accumulated on the surface, and the aggregation of the surface charges causes the agglomeration of nano particles; the aggregation of the nanoparticles caused by the mutual attraction between the nanoparticles due to the action of surface hydrogen bonds and chemical bonds between the nanoparticles. Therefore, the problem of agglomeration of the nano material needs to be solved firstly by utilizing the nano material, and the invention selects the proper dispersant to modify the nano material, so that the defect is overcome and the nano material can be uniformly dispersed.

Compared with the prior art, the invention has the following beneficial effects:

1) the liquid accelerator disclosed by the invention is free of fluorine, alkali and chlorine, high in safety, simple in preparation method and process and harmless to human bodies.

2) The accelerator is low in dosage when in use, and can meet the standard requirement of 1-day compressive strength when the dosage is less than or equal to 6 percent.

3) The setting accelerator provided by the invention has the advantages of short setting time, high early strength, high retention rate of later strength and good stability.

Detailed Description

In order that the invention may be more readily understood, the following detailed description of the invention is given in conjunction with the examples which are given for purposes of illustration only and are not to be construed as limiting the scope of the invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents, instruments or materials used are not indicated by the manufacturer, and are conventional products which are commercially available or obtainable by known production methods.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Performance test method

1. Method for measuring neat paste setting time of liquid-doped accelerator

1) Clean slurry doped with liquid accelerator

The weighed water (140g minus the amount of water in the liquid accelerator) and 400g of cement were put into a stirred pot, and the stirrer was started and stopped at low speed for 30 seconds. And adding the weighed liquid accelerator into a 50mL syringe at one time, stirring at a low speed for 5s, stirring at a high speed for 15s, immediately filling the mixture into a round die after stirring, inserting the mixture into the round die by using a knife, slightly vibrating the mixture for a plurality of times, scraping redundant clear paste, and smoothing the surface. The total operating time from the addition of the accelerator should not exceed 50 s.

2) Determination of coagulation time

The initial setting time and final setting time were determined according to the method of GB/1346. The test was performed every 10s until initial and final setting.

2. Method for measuring strength of mortar doped with liquid accelerator

1) Examined mortar doped with liquid accelerator

The weighed water (450g minus the water content of the liquid accelerator) and 900g of cement are placed in turn in a stirred pot, the stirrer is started to stir at low speed for 30s, then standard sand is added uniformly during the second 30s stirring at low speed, followed by high speed stirring for 30 s. Stopping stirring for 90s, scraping mortar on the blades and the pot wall into the stirring pot by using a rubber scraper in the first 15s of stopping stirring, and continuing stirring at high speed for 30 s. Immediately adding a liquid accelerating agent with an experimental amount by using a 100mL syringe, stirring at a low speed for 5s, then stirring at a high speed for 15s, and finishing stirring. The mixed mortar is loaded into a cement mortar test mould as soon as possible, and the whole operation from adding the liquid accelerator to the mortar such as the mould does not exceed 50 s.

2) Preparation of test pieces

The test piece had a size of 40mm by 160mm, and was formed by vibration using a vibration table for 30 seconds. And uniformly filling all the stirred mortar into a discharging funnel, starting a vibrating table, allowing the mortar to flow into a test mold through the discharging funnel, and stopping the test mold after vibrating for 30 seconds. Taking down the test mold, scraping the mortar higher than the test mold and leveling the surface. And (5) conveying the test mould to a curing box or a curing room after marking. When each accelerator sample is tested, 3 groups of tested mortar samples and 1 group of reference mortar samples are required to be formed, and each group comprises 3 samples.

3) Maintenance of test piece

The procedure is as described in GB/T17671. Age calculation starting point of intensity test body: the liquid accelerator is added after the accelerator is added. The compression strength tests at different ages should be carried out in the following times: 1d +/-15 min; 28d +/-8 h; 90d +/-24 h.

4) Determination of compressive Strength

The procedure is as described in GB/T17671.

Materials used in the examples

Maleic acid-acrylic acid copolymer (CasNo: 29132-58-9, weight average molecular weight 3000, Kyoto Yinakai science Co., Ltd., Beijing).

Polyacrylic acid (CasNo: 9003-01-4, weight average molecular weight 3000, Okinawa Kay science Co., Ltd., Beijing).

Polymethacrylic acid (Shanghai Michellin Biochemical technology Co., Ltd., CAS number: 25087-26-7, weight average molecular weight 3000).

Example 1

(1) Process for preparing modified nano silicon dioxide

1) Adding 70 parts by weight of deionized water into a beaker, adding 1 part by weight of a dispersant maleic acid-acrylic acid copolymer, and stirring for 10 minutes to obtain a mixed solution;

2) adding 30 parts of nano silicon dioxide (with the particle size distribution of 30-170nm) into the mixed solution, and stirring for 30 minutes by using a stirring paddle to obtain a mixture;

3) sanding the mixture obtained in the step 2) for 15 minutes by using a sand mill, and thinning and dispersing to obtain the modified nano silicon dioxide with narrow particle size distribution (30-50 nm).

(2) Preparation method of fluorine-free liquid accelerator

The fluorine-free liquid accelerator comprises the following raw materials in parts by weight: 55% of aluminum sulfate, 5.0% of diethanolamine, 2.0% of modified nano-silica, 2.0% of glycerol, 1.0% of maleic acid-acrylic acid copolymer, 1.0% of carboxyethyl cellulose and 34% of water. The preparation method comprises the following steps:

1) stirring and mixing diethanolamine, glycerol and water uniformly, and heating to 72 ℃;

2) keeping the temperature at 72 ℃, adding aluminum sulfate and stirring until the solution is transparent;

3) keeping the temperature at 72 ℃, adding the maleic acid-acrylic acid copolymer, and mixing and stirring for 10 minutes;

4) keeping the temperature at 72 ℃, adding the modified nano silicon dioxide, mixing and stirring for 30 minutes;

5) and keeping the temperature at 72 ℃, adding the carboxyethyl cellulose, mixing and stirring for 30 minutes to obtain the fluorine-free accelerator.

Example 2

(1) Process for preparing modified nano alumina

1) Adding 70 parts by weight of deionized water into a beaker, adding 1 part by weight of dispersant nitric acid, and stirring for 10 minutes to obtain a mixed solution;

2) adding 30 parts of nano alumina (with the particle size distribution of 50-210nm) into the mixed solution, and stirring for 30 minutes by using a stirring paddle to obtain a mixture;

3) sanding the mixture obtained in the step 2) for 15 minutes by using a sand mill, and thinning and dispersing to obtain the modified nano-alumina with narrow particle size distribution (50-80 nm).

(2) Preparation method of fluorine-free liquid accelerator

The accelerator comprises the following raw materials in parts by weight: 55% of aluminum sulfate, 5.0% of triethanolamine, 2.0% of modified nano-alumina, 2.0% of glycerol, 1.0% of polyacrylic acid, 1.0% of carboxymethyl cellulose and 34% of water. The preparation method comprises the following steps:

(1) stirring and mixing triethanolamine, glycerol and water uniformly, and heating to 68 ℃;

(2) keeping the temperature at 68 ℃, adding aluminum sulfate and stirring until the solution is transparent;

(3) keeping the temperature at 68 ℃, adding polyacrylic acid, mixing and stirring for 10 minutes;

(4) keeping the temperature at 68 ℃, adding the modified nano-alumina, mixing and stirring for 30 minutes;

(5) and keeping the temperature at 68 ℃, adding carboxymethyl cellulose, mixing and stirring for 30 minutes to obtain the fluorine-free accelerator.

Example 3

(1) Process for preparing modified nano calcium carbonate

1) Adding 70 parts by weight of deionized water into a beaker, adding 1 part by weight of dispersant polymethacrylic acid, and stirring for 10 minutes to obtain a mixed solution;

2) adding 30 parts of nano calcium carbonate (with the particle size distribution of 50-180nm) into the mixed solution, and stirring for 30 minutes by using a stirring paddle to obtain a mixture;

3) and (3) sanding the mixture obtained in the step (2) for 15 minutes by using a sand mill, and refining and dispersing to obtain the modified nano calcium carbonate with narrow particle size distribution (50-90 nm).

(2) Preparation method of fluorine-free liquid accelerator

The accelerator comprises the following raw materials in parts by weight: 55% of aluminum sulfate, 5.0% of triethanolamine, 2.0% of modified nano calcium carbonate, 2.0% of glycerol, 1.0% of polymethacrylic acid, 1.0% of carboxymethyl cellulose and 34% of water. The preparation method comprises the following steps:

1) stirring and mixing triethanolamine, glycerol and water uniformly, and heating to 75 ℃;

2) keeping the temperature at 75 ℃, adding aluminum sulfate and stirring until the solution is transparent;

3) keeping the temperature at 75 ℃, adding polyacrylic acid, mixing and stirring for 10 minutes;

4) keeping the temperature at 75 ℃, adding the modified nano alumina, mixing and stirring for 30 minutes;

5) and keeping the temperature at 75 ℃, adding carboxymethyl cellulose, mixing and stirring for 30 minutes to obtain the fluorine-free accelerator.

Example 4

The method is the same as that of example 1, except that the accelerator comprises the following raw materials in parts by weight: 35% of aluminum sulfate, 2.0% of diethanolamine, 8.0% of modified nano-silica, 1.0% of glycerol, 1.0% of maleic acid-acrylic acid copolymer, 1.0% of carboxyethyl cellulose and 52% of water.

Example 5

The method is the same as example 1 except that 50 parts by weight of deionized water, 1 part by weight of dispersant and 45 parts by weight of nano-silica are used in the preparation of the modified nano-silica.

Example 6

The method is the same as example 1 except that 90 parts by weight of deionized water, 1 part by weight of dispersant and 20 parts by weight of nano-silica are used in the preparation of the modified nano-silica.

Example 7

The process is the same as in example 1 except that the fluorine-free quick-setting admixture is prepared at a temperature different from the above-mentioned temperature, which is 50 ℃.

Example 8

The method is the same as example 1, except that the temperature of the preparation method of the fluorine-free setting accelerator is different from that of the preparation method of the fluorine-free setting accelerator, and the temperature is 90 ℃.

Comparative example 1

The process is the same as example 1 except that the nanosilica is not modified.

Performance testing

The liquid setting accelerators obtained in examples 1 to 8 and comparative example 1 were tested according to the above performance test method, and the blank samples were tested according to the method except that the setting accelerator was not added during the process, and the blending amount of the liquid setting accelerator and the performance test results are shown in Table 1 below.

TABLE 1

As shown in the results of Table 1, after the dispersant modified nano material is added into the accelerator, the setting time is short, the early strength is high, and the retention rate of the later strength is high.

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not set any limit to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.