CN1844022A - Shrinkage-reducing, crack-resistant graft copolymer concrete superplasticizer and preparation method thereof - Google Patents

Abstract

Disclosed is a shrinkage-reduction anti-cracking type grafted copolymer concrete superplasticiser, which is prepared from monomer a of acroleic acid or salts, monomer b of alkoxy polyether monoacrylate, monomer c of maleic anhydride hemiester or its salts, monomer d of alpha-propenol omega-methyl polyether and monomer e of phenylethene through free radical copolymerization reaction, wherein the molar ratio of the monomer a, b, c, d and e being 1 : 0.2-0.5 : 0.10-0.25 : 0.10-0.20 : 0-0.10.

Description

Shrinkage-reducing, crack-resistant graft copolymer concrete superplasticizer and preparation method thereof

technical field

The invention belongs to the technical field of concrete structures and concrete engineering, in particular to the technical field of concrete admixtures, in particular to a preparation method and application of a shrinkage-reducing and crack-resistant polycarboxylate concrete superplasticizer.

Background technique

Concrete has developed into the most important structural engineering material in the contemporary era. In 2005, China's annual cement output exceeded 1 billion tons. The amount of cement and concrete consumed by its infrastructure construction is in the leading position in the world. The production of cement not only consumes a lot of mineral resources and energy, and produces a large amount of CO ₂ and emits a large amount of dust. The sustainable development of the building materials industry is to reduce resources and energy consumption as much as possible in the use of raw materials and the production process of materials, and on the other hand to be green and energy-saving in the process of use. Therefore, the way out for the sustainable development of the concrete industry is to apply modern science and technology to improve the service life of concrete and minimize the waste and construction waste caused by repair or demolition. The volume stability is often the most important factor affecting the durability of concrete, and it is an important prerequisite for concrete to meet the durability requirements. The direct consequence of poor volume stability is the initiation of cracks. Therefore, how to improve the volume stability of concrete and the resulting cracking has been a major technical problem faced by concrete academics and engineering technicians for many years.

Concrete admixtures, especially superplasticizers, are the key to high-performance concrete. At present, naphthalene-based water reducers are the most commonly used, but their fatal weakness is that they increase the shrinkage of concrete. The cracks produced by the shrinkage of concrete will reduce the permeability of concrete, and ultimately affect the performance of concrete and reduce its service life. At present, adding concrete expansive agent is generally used to compensate the dry shrinkage of concrete at home and abroad, but the large amount (10-15% of cement content) pollutes the environment during production; and the concrete added with expansive agent must be wet-cured, which increases the construction control. Adding expansive agent to concrete with high water-binder ratio can compensate for the early drying shrinkage of soil, but the greater the early expansion, the greater the later shrinkage of concrete, and the poor expansion performance in concrete with low water-binder ratio, basically cannot compensate shrink. The new type of organic anti-shrinkage agent (shrinkage reducing agent) can effectively reduce the shrinkage of concrete, but the dosage is high (2-3% of the cement content), the cost increases greatly, and it does not have the function of reducing water, so it is difficult to use Even in high-strength concrete, it is very difficult to promote because of its adverse effect on strength.

The "Multifunctional Carboxylic Acid Comb Graft Copolymer Concrete Superplasticizer" (CN200510037872.6) developed by the applicant has good dispersion, slump retention and reinforcement functions, and can also reduce the drying shrinkage of concrete to a certain extent , but the reduction is far from enough, and it is difficult to compare with the shrinkage reduction effect of the shrinkage reducer at such a low dosage.

CN200510057130.X reported a polyacrylate shrinkage reducing agent and its preparation method. The admixture has a good shrinkage reduction effect, but the dosage is still high, accounting for 2% of the cement consumption. Although the water reducing rate can reach 15- 18%, but the 28d compressive strength ratio is only 108%, and the reinforcement effect is poor.

US2005/0096413 discloses a multifunctional admixture whose main component is a copolymer of α-allyl alcohol ω-methyl polyether-maleic anhydride. When ordinary silicon cement is used in water/cement, that is, W/C=0.30, the 24h self-drying shrinkage rate is 15%-25% lower than that of ordinary polycarboxylate superplasticizer Chupol HP-11 (produced by Takemoto Yushi Kabushhiki Kaisha) %. When silica fume cement is used at W/C=0.17, the 24h self-drying shrinkage is 18.4%-24.5% lower than that of ordinary polycarboxylate superplasticizer Chupol SSP-104 (produced by Takemoto Yushi KabushhikiKaisha). According to reports, the dosage is 0.27%-0.57% of the cement content, which is still far behind the shrinkage reduction effect of the shrinkage reducer.

US20050124737 discloses a multifunctional admixture whose main component is a copolymer of α-allyl alcohol ω-methyl polyether-maleic anhydride. It has been investigated that under the condition of W/C=0.47, the dosage is 0.35%-0.92% of the cement amount, and the drying shrinkage of the 26-week concrete in the embodiment is 4.9×10 ^-4 -5.6×10 ^-4 , and in the comparative example The drying shrinkage of concrete in 26 weeks is 5.4×10 ^-4 -7.7×10 ^-4 .

JP8268741 has also reported a multifunctional admixture, the main component of which is also a copolymer of α-allyl alcohol ω-methyl polyether-maleic anhydride, which has both water-reducing and shrinkage-reducing functions. When mixed with 0.2%, The water reducing rate can reach 18%, and the drying shrinkage of the 28d concrete is reduced by about 35% compared with the benchmark (320kgC/m3, the benchmark concrete W/C=0.638, the tested concrete W/C=0.522, and the initial length is measured after 7 days of water curing ).

To sum up, there are still obvious deficiencies in multifunctional admixtures. These products basically use α-allyl alcohol ω-methyl polyether as the main raw material, and the price is relatively high. At the same time, α-allyl alcohol Alcohol omega-methyl polyether-maleic anhydride copolymer has poor dispersibility to cement and insufficient water reducing rate.

Contents of the invention

The present invention aims to solve the shortcomings of the above-mentioned existing multifunctional admixtures, and provide a kind of admixture with relatively simple production technology, high water-reducing rate, good reinforcement effect, low drying shrinkage rate, good crack resistance and low price. Shrinkage-reducing, crack-resistant graft copolymer concrete superplasticizer and its preparation process.

The applicant found that the main chain chemical structure of the graft copolymer has a great influence on the shrinkage of concrete, and the drying shrinkage of the graft copolymer with acrylic acid or α-allyl alcohol ω-methyl polyether as the main chain is the smallest.

The applicant also finds that the organic anti-shrinkage agent is generally a low molecular weight alkyl polyether, and the side chain (AO) in the graft copolymer is also an alkyl polyether, and its side chain chemical structure and properties are the same as those of the organic anti-shrinkage agent. Similarly, the introduction of a certain low molecular weight alkyl polyether into the graft copolymer can not only greatly reduce the drying shrinkage of concrete, but also improve the dispersibility of cement.

Based on above-mentioned research, the present invention adopts following technical scheme:

The present invention consists of monomer a: acrylic acid or its salt, monomer b: alkoxy polyether monoacrylate, monomer c: maleic anhydride half ester or its salt, monomer d: α-allyl alcohol ω-form The radical polyether and monomer c: styrene are prepared by free radical copolymerization, wherein the molar ratio of monomer a:monomer b:monomer c:monomer d:monomer e is 1:0.2～0.5:0.10 ~0.25:0.10~0.20:0~0.10.

Above-mentioned monomer a-monomer e are all known substances except monomer c, wherein:

Monomer a is represented by general formula 1:

In the formula, _M1 represents a hydrogen atom, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amino group.

Monomer b is represented by general formula 2:

In the formula, R is an alkyl group of 1 to 4 carbon atoms, AO is an oxyalkylene group of 2 to 4 carbon atoms or a mixture of two or more such oxyalkylene groups, if AO is two or more Such a mixture of oxyalkylene groups can be added in block or random form, and n is the average added mole number of oxyalkylene groups, which is 5-40.

The monomer b represented by general formula (2) is produced by the esterification reaction of monoalkoxy polyether represented by general formula (5) and acrylic acid under the conditions of a small amount of solvent medium, acid catalyst and a small amount of polymerization inhibitor .

In the formula, n is the average addition mole number of oxyalkylene groups, which is 5-40. Suitable oxyalkylenes include ethylene oxide, propylene oxide, butylene oxide, etc., and mixtures thereof. They can be linear or branched polymers, homopolymers or copolymers, random or block copolymers, diblock or multiblock copolymers. This alkoxy polyether monoacrylate is copolymerized into the main chain to provide a certain dispersion ability and shrinkage reduction function.

Monomer c is represented by general formula 3:

In the formula, _M2 represents a hydrogen atom, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amino group, p and q are integers from 0 to 8, and 2≤p+q≤8.

The monomer c represented by the general formula (3) is produced by the direct esterification reaction of the monoalkoxy polyether with shrinkage function represented by the general formula (6) and maleic anhydride under the condition of no solvent and a catalyst. Its copolymerization into the main chain of the polymer can not only reduce the shrinkage of concrete, but also provide a certain steric hindrance, thereby improving the dispersion ability of the copolymer.

In the formula, p and q are integers from 0 to 8, and 2≤p+q≤8.

The preparation method of the above-mentioned monomer c belongs to the traditional esterification reaction. This process is relatively easy and simple. Add the reduction component represented by the general formula (6) in the reaction vessel, and then add the maleic acid in an equimolar proportion to the reduction component. Acid anhydride, react at 100-160°C for 3 hours to obtain a brown-red transparent liquid, monomer c.

Monomer d is represented by general formula 4:

In the formula, m is an integer from 4 to 25

Monomer e is styrene.

According to the present invention, the preparation technology of carboxylic acid graft copolymer has at least three steps, and in the first step reaction, the alkoxy polyether monoacrylate described by general formula (2) and general formula (3) is formed by general formula The monoalkoxy polyether shown in formula (5) and acrylic acid carry out grafting reaction, and it can generate by esterification reaction under the condition of a small amount of solvent medium, acid catalyst and a little polymerization inhibitor according to common esterification method; In the second step reaction, maleic anhydride and the polyether esterification reaction with shrinkage function are relatively easy; the third step free radical copolymerization reaction, it can use known free radical initiators in milliseconds according to the usual method. Do it without difficulty. This process and process will be described in detail below.

Although monomer b is a known substance, it is not commercially available, and monomer c is an unknown substance, so the preparation method of the present invention comprises the following steps:

1. Preparation of monomer b

The preparation of monomer b adopts traditional esterification reaction, this method belongs to known technology, the molar ratio of acrylic acid and monoalkoxypolyether (is 1: 1 to 5: 1 in the reaction process, excess acrylic acid can remain in the mixture , to participate in the next step of the copolymerization reaction.

In the above-mentioned esterification reaction, it may be advantageous to use a catalyst. The catalysts that can be used include concentrated sulfuric acid, p-toluenesulfonic acid, solid superacid, phosphoric acid and phosphorous acid, which can be used alone or in combination in any proportion. The dosage of the catalyst is 0.5-5% of the reaction material (the total weight of the monoalkoxy polyether represented by the general formula (5) and acrylic acid).

In the above-mentioned esterification reaction, the efficiency of esterification can be improved by using an organic solvent as a water-carrying agent, and the water-carrying agent forms an azeotropic mixture together with the water generated by the reaction. Organic solvents suitable for water-carrying agents include aliphatic hydrocarbons, cycloalkanes or aromatic hydrocarbons, aliphatic hydrocarbons are selected from hexane, decane, undecane, dodecane; cycloalkanes are selected from cyclohexane, methylcyclohexane; aromatic The hydrocarbon is selected from benzene, toluene, o-, m-, p-xylene. The content of the water-carrying agent in the reaction mixture should be 10-40% of the reaction material (the total weight of monoalkoxy polyether represented by general formula (5) and acrylic acid).

In order to prevent premature polymerization of acrylic acid and the resulting unsaturated esters, some traditional polymerization inhibitors must be used, such as hydroquinone, phenothiazine, hydroquinone-methyl ether or di-tert-butyl-p-methyl Phenol, they can be used alone or mixed in any proportion, and the amount of polymerization inhibitor is 0.005-0.8% of the weight of acrylic acid.

The esterification reaction temperature is 80-160°C, which is related to the boiling point of the water-carrying agent used, and it is advisable to control the temperature at the reflux of the water-carrying agent. The time of the esterification reaction can be monitored by determining the amount of water produced, and when the actual water received is close to the theoretical water output, the reaction is stopped.

For example, when preparing methoxypolyethylene glycol monoacrylate, first put methoxypolyethylene glycol with a specific molecular weight and excess acrylic acid into a dry reaction vessel with a water separator, and then put into the measured polymerization inhibitor Add an appropriate amount of acid catalyst to accelerate the esterification reaction after stirring evenly, and then add a measured organic solvent as a water-carrying agent and a viscosity-adjusting component of the material, slowly heat up to solvent reflux, and maintain 6 at this temperature and reflux speed ~15 hours, when the actually received water is close to the theoretical water output, stop the reaction, and at this temperature, recover the solvent from the water separator, and when the solvent recovery is nearing the end, apply a little negative pressure, and further Collect solvent. After the esterification reaction, the excess acrylic acid and the prepared methoxypolyethylene glycol monoacrylate solution in the esterification process can directly participate in the next step of the polymerization reaction without additional separation steps.

2. Preparation of monomer c

The shrinkage functional macromonomer c described by the general formula (3) is produced by the esterification reaction of the monoalkoxy polyether represented by the general formula (6) and maleic anhydride under the condition of a little catalyst, and the monoalkoxy The molar ratio of polyether-based polyether to maleic anhydride is maintained at 1:1, or a slight excess of maleic anhydride. The selection of catalyst is also very important, including concentrated sulfuric acid, p-toluenesulfonic acid and solid super acid, which can be used alone or in combination. The consumption of acid catalyst is 0.5～5% of reaction mass (the gross weight of monoalkoxy polyether shown in general formula (6) and maleic anhydride), when consumption is lower than 0.5%, esterification efficiency can be large The magnitude decreased, prolonging the esterification reaction time. If the dosage is higher than 5%, the color of the product will become darker, and not only side reactions will increase, but also unnecessary waste will be caused.

The temperature of the esterification reaction is preferably in the range of 100-160° C., and the temperature in an appropriate range can effectively control the viscosity of the reaction material, which is beneficial to the progress of the reaction. If the temperature is too low, the viscosity of the reaction material will be high, which will increase the resistance of stirring, the reaction speed will be greatly reduced, the reaction time will be prolonged, and the temperature exceeds 160 ° C, which will increase the probability of side reactions. Degradation may occur affecting final product properties. The time of the esterification reaction is not strictly limited, generally within 2 to 6 hours, and a brown transparent liquid is obtained.

3. Copolymerization reaction

Carry out free radical copolymerization reaction of monomer a, monomer b, monomer c, monomer d and monomer e according to the molar ratio of 1:0.2～0.5:0.10～0.25:0.10～0.20:0～0.10, and add alkali After neutralization reaction, the pH value is adjusted to 7.0-8.5 to obtain the finished product.

In step 3, monomer a is necessary, and the excess acrylic acid after the esterification reaction in step 2 can be directly used as the reaction material in step 3, that is, monomer a, whose carboxylic acid group provides adsorption points and electric repulsion in the copolymer.

Monomer b, that is, alkoxy polyether monoacrylate represented by general formula (2), is copolymerized into the main chain, and its branches mainly provide steric hindrance and at the same time provide a certain shrinkage function. The molar ratio of b/a is controlled at 0.2-0.5. If the proportion of monomer b is too low, the produced copolymer will have poor shrinkage reduction effect. If the ratio is too high, the resulting copolymer has weak dispersion.

Functional monomer c, namely the maleic anhydride half-ester and salt with reduction function shown in general formula (3), is copolymerized into the main chain, and its side chain mainly provides reduction function and steric hindrance, thereby improving adhesion. The dispersibility of branch copolymers to cement. Monomer c accounts for 0.10-0.25 (mol ratio) of monomer a component. If the proportion of monomer c is too low, the synthesized copolymer will have poor shrinkage and crack resistance. If the proportion is too high, the produced copolymer will be harmful to The dispersion ability of cement is poor.

Monomer d, which is the general formula (4), represents that α-allyl alcohol ω-methyl polyether is copolymerized into the main chain as a comonomer to provide shrinkage reduction, crack resistance and steric hindrance. Monomer d accounts for 0.10 to 0.20 (mol ratio) of monomer a component. If the ratio of monomer d is too low, the effect of the synthesized copolymer on reducing concrete shrinkage will be poor. If the ratio is too high, the produced Copolymers have poor dispersibility to cement.

Monomer e is optional, and generally the ratio of monomer a to monomer a is 0-0.10 (mol ratio).

The free-radical polymerization itself is relatively unimportant and can be carried out without difficulty according to usual methods using known free-radical initiators. Suitable initiators known to those skilled in the art for the process of the present invention are conventional oil-soluble free radical initiators and mixtures thereof, including azobisisobutyronitrile, azobisisoheptanonitrile or benzene peroxide. Formyl or isopropyl hydroperoxide or diisopropyl peroxydicarbonate, etc., all initiators added to the reaction mixture should account for about 1.0 to 4.0% of the total molar weight of the monomers added, and the actual amount added and the amount used The type of initiator is very relevant.

The molecular weight of the copolymers can be selectively controlled using polymeric chain transfer agents such as mercaptopropionic acid, thioglycolic acid, mercaptoethanol, and dodecanethiol. The amount of the polymer chain transfer agent used in the polymerization process is 1.0-5.0% of the total weight of the monomers a+b+c+d+e.

The monomer b mixture prepared in the first step, the monomer c prepared in the second step, and monomer a (if the excess monomer a is not enough when preparing monomer b, it needs to be added), monomer d, and even A small amount of monomer e component, initiator and chain transfer agent are mixed according to a certain ratio, and stirred evenly to form a monomer mixture, and the monomer mixture is slowly added while stirring within 2 to 6 hours, and the temperature is 60 to 100 ° C for quantitative In the organic solvent, the amount of organic solvent is in the range of 15-40% to control the weight concentration of the monomer in the copolymerization reaction. After the slow addition, the heat preservation reaction is carried out under the condition of stirring for 2-5 hours, and a light yellow uniform transparent viscose is prepared. Thick solution. The reaction medium used in the copolymerization reaction is polar solvents such as ethyl acetate, tetrahydrofuran, methyl isobutyl ketone, etc.

After the polymerization reaction is over, distill the solvent off under reduced pressure, add water to cool, and add alkali to convert the carboxylic acid or anhydride into a salt form. The pH of the finished product is preferably adjusted to 7.0-8.5. If the pH is too low or too high, then The storage stability of the copolymers was not good.

The weight-average molecular weight in the present invention is not particularly limited, and generally ranges from 10,000 to 80,000. If the molecular weight is too small or too large, its dispersibility to cement is not good.

When the present invention is in use, the conventional dosage is 0.15-0.3% of the total glue material weight, the water-reducing rate can reach 15%-30%, and the 28d drying shrinkage rate is reduced by 40-40% compared with the concrete mixed with naphthalene-based water-reducing agent. 50%, which is 30-50% lower than the benchmark concrete. If the added amount is less than 0.10%, the dispersion effect and shrinkage reduction effect are not satisfactory. On the contrary, if the added amount exceeds 0.3%, it will not only produce economic waste, but also will not bring corresponding increase in effect. Therefore, the product of the present invention is a multifunctional concrete admixture with functions such as shrinkage reduction, crack resistance, water reduction, and reinforcement. It can be widely used in Portland cement concrete and mortar. The product mainly replaces naphthalene series, shrinkage reducing agent and Expansive agent, mainly suitable for high-performance concrete projects such as high crack resistance and low shrinkage.

Of course, the product of the present invention can also be mixed with at least one selected from known sulfamic acid-based water reducers, lignin-based common water-reducers and existing polycarboxylic acid-based admixtures in the prior art.

In addition, in addition to the known concrete water reducers mentioned above, the present invention can also add air-entraining agents, retarders, early strength agents, tackifiers, shrinkage reducers and defoamers when used.

Shrinkage-reducing, anti-crack type carboxylic acid graft copolymer concrete superplasticizer of the present invention has following characteristics:

1. the graft copolymer prepared in the present invention also shows outstanding dispersibility at very low dosage, in conventional concrete, add 0.10-0.3% (effective solid content) of cement consumption, this adding can bring Come a lot of satisfying effects. When the cement content is 0.2%, the water reducing rate can reach more than 25%, and the 28d compressive strength ratio can reach more than 170% compared with the reference concrete. The 28d drying shrinkage is 40-50% lower than that of the concrete mixed with naphthalene-based water reducer, and 30-50% lower than that of the benchmark concrete.

2. The graft copolymer prepared in the present invention has significantly improved the anti-cracking performance of concrete, and the cracking time of concrete has been extended 2 days compared with mixing naphthalene-based water reducing agent, and the cracking area is only 13% of mixing FDN, and the cracking time Also greatly delayed.

③Compared with the micro-expansion admixture, not only the dosage is low, but also there is no special requirement for the maintenance of concrete (mortar), and C20～C60 anti-crack and anti-seepage concrete can be prepared under the temperature condition of -5℃～38℃.

④Compared with the organic anti-shrinkage agent, the content of the copolymer is less than 10% of the organic anti-shrinkage agent. At the same time, it has the effect of water reduction and enhancement; it solves the defects of high cost and unfavorable strength of the current new type of organic anti-shrinkage agent.

Detailed ways

The following examples describe in more detail the process and copolymer properties of the graft copolymer prepared according to the method of the present invention, and these examples are given by way of illustration, but these examples in no way limit the scope of the invention, wherein The monomer codes and structures used in the examples are shown in Table 1, and the admixture amounts mentioned in the application examples all refer to the percentage by weight of cement.

a) Tested with a Sigma730 numerical surface tension meter (ring method), the polymer concentration is 0.5%

b) In the examples of the present invention, the weight-average molecular weight of the polymer is measured by Wyatt technology corporation gel permeation chromatography (miniDAWN Tristar laser light scattering detector).

c) In the application examples of the present invention, the cement adopted is Nantong Huaxin 425R.PO, and the sand is the fineness modulus $m,=2.6$ The medium sand and stones are continuously graded crushed stones with a particle size of 5-20 mm.

d) The water reducing rate and air content test method shall refer to the relevant provisions of GB8076-1997 "Concrete Admixtures", and the concrete compressive strength and compressive strength ratio shall refer to the relevant provisions of GB/T50081-2002 "Standards for Test Methods of Mechanical Properties of Ordinary Concrete" Regulations are enforced.

e) The mixing ratio of concrete drying shrinkage performance adopts the mixing ratio specified in GB8076-1997, and its test method refers to the relevant regulations of GBJ82-85 "Test Method for Long-term Performance and Durability of Ordinary Concrete".

f) The early plastic cracking test method refers to the "Guidelines for Durability Design and Construction of Concrete Structures", and the size of the specimen is 600mm×600mm×63mm.

Table 1 Monomer a Formula (1) a-1 acrylic acid monomer b Formula (2) b-1 Methoxypolyethylene glycol monoacrylate (n=9) b-2 Methoxypolyethylene glycol monoacrylate (n=17) b-3 Methoxypolyethylene glycol monoacrylate (n=5) b-4 Methoxypolyethylene glycol monoacrylate (n=33) b-5 Methoxypentaethylene glycol tetrapropylene glycol monoacrylate (n=9) monomer c Formula (3) c-1 Butoxy polypropylene glycol polyethylene glycol maleic anhydride monohalf ester (p=2, q=2, M ₂ =H) c-2 Butoxy polypropylene glycol maleic anhydride monohalf ester (p=0, q=2, M ₂ =H) c-3 Butoxy polyethylene glycol maleic anhydride monohalf ester (p=4, q=0, M ₂ =H) c-4 Butoxy polypropylene glycol polyethylene glycol maleic anhydride monohalf ester p=4, q=4, M ₂ =H) Monomer d Formula (4) d-1 Allyl Methoxy Polyether (m=12) d-2 Allyl Methoxy Polyether (m=6) d-3 Allyl Methoxy Polyether (m=23) monomer e e-1 Styrene

Remarks: Monomer b is prepared by the method described in step 1;

Monomer c was prepared by the method described in step 2.

Example 1

In the 2000ml glass reactor equipped with thermometer, stirrer, dropping funnel, nitrogen inlet tube and reflux condenser, add 600ml ethyl acetate, purging reaction vessel with nitrogen while stirring, and be warming up to 75 ℃. Then 1.0 mol of monomer a-1, 0.35 mol of monomer b-1 (n=9) and 0.2 mol of monomer c-1 (p=2, q=2, M ₂ =H), 0.15 mol of monomer d -1 (m=12) and 0.05mol styrene, 0.027mol azobisisobutyronitrile (AIBN), 8.5g mercaptopropionic acid, also add 200ml ethyl acetate simultaneously, and stir to make uniform monomer aqueous solution, will Add it dropwise to the reactor for 3 hours. After the dropwise addition, keep it warm for 4 hours, and then raise the temperature to recover the ethyl acetate organic solution, which can be used multiple times. Add water to dilute and cool, and add alkali to neutralize to a pH value of 7.5 to obtain a solid The content is 30.7% brown transparent liquid, the molecular weight is 42,000.

Example 2

In the 2000ml glass reactor equipped with thermometer, stirrer, dropping funnel, nitrogen inlet tube and reflux condenser, add 600ml ethyl acetate, purging reaction vessel with nitrogen while stirring, and be warming up to 75 ℃. Then 1.0 mol of monomer a-1, 0.20 mol of monomer b-2 (n=17) and 0.15 mol of monomer c-3 (p=4, q=0, M ₂ =H) and 0.15 mol of monomer d -1 (m=12), 0.040mol azobisisobutyronitrile (AIBN), 10.2g mercaptopropionic acid, and 200ml ethyl acetate, and stirred to make a uniform monomer aqueous solution, which was added dropwise to the reactor , the dropping time is 5 hours, after the dropping is completed, keep warm for 3 hours, and then heat up to recover the ethyl acetate organic solution, which can be used multiple times, dilute and cool with water, and neutralize with alkali to pH 7.5, the solid content is 30.2% brown transparent Liquid, molecular weight 29,000.

Example 3

In the 2000ml glass reactor equipped with thermometer, stirrer, dropping funnel, nitrogen inlet tube and reflux condenser, add 800ml ethyl acetate, purging reaction vessel with nitrogen while stirring, and be warming up to 75 ℃. Then 1.0 mol of monomer a-1, 0.45 mol of monomer b-3 (n=5) and 0.25 mol of monomer c-2 (p=0, q=2, M ₂ =H) and 0.20 mol of monomer d -2 (m=6), and 0.05mol styrene, 0.05mol azobisisobutyronitrile (AIBN), 3.0g mercaptopropionic acid, also add 400ml ethyl acetate simultaneously, and stir to make uniform monomer aqueous solution, Add it dropwise to the reactor for 4 hours. After the dropwise addition, keep it warm for 4 hours, then raise the temperature to recover the ethyl acetate organic solution, which can be used multiple times, add water to cool, and add alkali to neutralize to a pH value of 7.5. It is a 30.2% brown transparent liquid with a molecular weight of 35,000.

Example 4

In the 2000ml glass reactor equipped with thermometer, stirrer, dropping funnel, nitrogen inlet tube and reflux condenser, add 600ml ethyl acetate, purging reaction vessel with nitrogen while stirring, and be warming up to 75 ℃. Then 1.0 mol of monomer a-1, 0.20 mol of monomer b-4 (n=33) and 0.10 mol of monomer c-4 (p=4, q=4, M ₂ =H) and 0.12 mol of monomer d -3 (m=23), and 0.08mol styrene, 0.030mol azobisisobutyronitrile (AIBN), 8.0g mercaptopropionic acid, also add 200ml ethyl acetate simultaneously, and stir to make uniform monomer aqueous solution, Add it dropwise to the reactor for 6 hours. After the dropwise addition, keep it warm for 2 hours, then raise the temperature to recover the ethyl acetate organic solution, which can be used multiple times, add water to cool, and add alkali to neutralize to pH 7.5. It is a 30.2% brown transparent liquid with a molecular weight of 37,000.

Example 5

In the 2000ml glass reactor equipped with thermometer, stirrer, dropping funnel, nitrogen inlet tube and reflux condenser, add 600ml ethyl acetate, purging reaction vessel with nitrogen while stirring, and be warming up to 75 ℃. Then 1.0 mol of monomer a-1, 0.35 mol of monomer b-5 (n=9) and 0.15 mol of monomer c-1 (p=2, q=2, M ₂ =H) and 0.15 mol of monomer d -3 (m=23), 0.020mol azobisisobutyronitrile (AIBN), 15.5g mercaptopropionic acid, and 200ml ethyl acetate, and stirred to make a uniform monomer aqueous solution, which was added dropwise to the reactor , the dropping time is 4 hours, after the dropping is completed, keep warm for 3 hours, then heat up to recover the ethyl acetate organic solution, which can be used many times, add water to cool, and add alkali to neutralize to pH 7.5, the solid content is 30.2% brown transparent liquid , with a molecular weight of 40,000.

Table 2 Copolymer Copolymer monomer structure and molar ratio molecular weight Surface Tension (a) Moore (b) Moore (c) Moore (d) Moore (e) Moore M _w mN.m ^-1 Example 1 a-1 1.0 b-1 0.35 c-1 0.20 d-1 0.15 e-1 0.05 42000 43.5 Example 2 a-1 1.0 b-2 0.20 c-3 0.15 d-1 0.15 - - 29000 39.8 Example 3 a-1 1.0 b-3 0.45 c-2 0.25 d-2 0.20 e-1 0.05 35000 40.2 Example 4 a-1 1.0 b-4 0.20 c-4 0.10 d-3 0.12 c-1 0.08 37000 44.5 Example 5 a-1 1.0 b-5 0.35 c-1 0.10 d-3 0.10 - - 40000 41.3

Application Example 1

Evaluate the dispersibility of the carboxylic acid graft copolymer synthesized by Synthesis Example 1-5, the strengthening effect and the effect of reducing shrinkage, with reference to GB8076-1997 "Concrete Admixture" proportioning, the fixed water-cement ratio is 0.42, by adjusting Copolymer dosage controls the concrete slump at 8 ± 1cm, comparative example 1 is naphthalene sulfonate formaldehyde condensation product water reducer (abbreviated as FDN), the dosage is 0.47% of cement weight, and comparative example 2 is mixed with 0.45% % naphthalenesulfonate formaldehyde condensation product water reducer and 0.20% diethylene glycol dipropylene glycol monobutyl ether shrinkage reducer (abbreviated as SRA), the test results are shown in Table 3: Dosage (%) Gas content (%) Compressive strength (Mpa) Drying shrinkage (×10 ^-6 ) 3d 7d 28d 28d 60d Example Example 1 0.20 2.7 47.2 59.8 66.3 -153.167 -216.383 Example 2 0.16 2.3 48.6 63.7 68.9 -168.091 -256.122 Example 3 0.29 2.9 45.3 61.5 65.1 -142.356 -203.421 Example 4 0.15 2.5 49.1 63.2 67.5 -173.375 -248.678 Example 5 0.20 2.5 48.7 62.9 68.5 -165.323 -208.337 comparative example Comparative example 1 0.47 3.0 45.3 54.3 60.9 -278.812 -412.433 Comparative example 2 0.45+2.0 4.7 40.3 48.5 54.1 -162.337 -232.785

It can be seen from the test results in Table 3 that the graft copolymers synthesized in the examples of the present invention not only have good dispersibility to cement, but also have obvious reinforcing effects. Under the condition of the same water-cement ratio, the enhancement effect of mixing the embodiment of the present invention with the naphthalene sulfonate formaldehyde condensate water reducer is remarkable. have an adverse effect on strength. From the perspective of drying shrinkage performance, the copolymer synthesized in the embodiment of the present invention can effectively reduce the drying shrinkage of concrete, and at the same water-cement ratio, it is 30 to 50 times lower than that of the naphthalenesulfonate formaldehyde condensate water reducer. %, the shrinkage reduction effect is equivalent to that of 0.20% shrinkage reducer, or even better, but the dosage is greatly reduced.

Application Example 2

Taking the synthesized carboxylic acid graft copolymer of Example 1 as an example to investigate the influence of different copolymer dosages on water reduction and strengthening effect, with reference to the proportion of GB8076-1997 "Concrete Admixture", change the copolymer dosage, The concrete slump is controlled at 8±1cm by adjusting the water consumption, and the test results are shown in Table 4.

Table 4 Dosage (%) Water cement ratio Water reduction rate (%) Gas content (%) Compressive strength (MPa)/compressive strength ratio (%) R3 R7 R28 Example 1 00.160.200.240.300.36 0.5380.4380.4200.410.4020.398 /18.622.323.825.225.5 2.33.12.52.32.52.5 25.8/10045.4/17645.6/17748.2/18751.2/19850.3/195 36.5/10060.3/16561.2/16762.7/17265.9/18064.2/176 41.7/10064.8/15566.2/15967.3/16169.2/16667.8/163 FDNFDN+SRA 0.450.45+2.0 0.4220.413 21.623.2 3.14.9 47.2/18340.6/157 55.6/15250.5/138 57.3/13753.7/129

When the mixing amount of the embodiment of the present invention is 0.16% of cement, it has a water reducing rate of 18.6%, and when the mixing amount is 0.20%, it has a water reducing rate of 22.3%. When the level of water agent is greater than 0.30% of the cement dosage, the water reducing rate can reach 25%. As the amount of admixture increases, the rate of water reduction increases very little, and the amount of admixture is 0.30%, basically reaching the saturation point. And it does not delay the setting time of concrete. The graft copolymer synthesized by the present invention has a good reinforcing effect, the compressive strength of 3d is increased by 70-120%, the compressive strength of 7d is increased to 70-100%, and the compressive strength of 28d can be increased by 60-80%. , The compressive strength of 60d can be increased by 50-70%. When the content increases to 0.30% of the cement content, the strength increases slowly, or even decreases slightly. Therefore, from the perspective of water reduction enhancement and economy, the optimum dosage is between 0.20% and 0.30%.

The results of the comparison test also show that the mixed shrinkage reducing agent has an adverse effect on the compressive strength. In the case of keeping the amount of water reducing agent unchanged, although the addition of shrinkage reducing agent reduces the water consumption, the strength decreases instead.

Application Example 3

Taking the carboxylic acid graft copolymer synthesized in this embodiment 1 as an example to investigate the influence of the amount of copolymer on the shrinkage performance of concrete, the initial slump of freshly mixed concrete is 8 ± 1cm by adjusting the water consumption, and the test results See Table 5.

When adding 0.16% graft copolymer of the present invention, the 28d drying shrinkage decreased by 24% compared with the benchmark, and the 60d decreased by 25.1%; when adding 0.20%, the 28d drying shrinkage decreased by 44% compared with the benchmark, and the 60d decreased 45%, basically achieved the shrinkage reduction effect of compounding 2% shrinkage reducing agent. Continue to increase the dosage, increase to 0.30%, 28d drying shrinkage decreased by 41.5%, 60d decreased by 35.3%, the effect of reducing shrinkage was weakened compared with 0.20%.

Table 5 Effects of various dosages on concrete dry shrinkage Admixture Dosage % Shrinkage rate at different ages (×10 ^-6 ) 1d 3d 7d 14d 28d 60d Blank FDNFDN+SRA /0.450.45+2.0 -5.22088-18.0723-1.80723 -41.7671-56.3253-24.2972 -95.9839-108.635-58.2329 -165.863-179.016-96.5863 -270.08-283.584-155.823 -381.2-401.4-223.0 Example 1 0.160.200.240.30 -10.44188.0321293.2128513.212851 -46.28513.313254-17.8554-14.0562 -83.5341-31.0241-51.6867-41.1647 -131.827-72.6908-88.8554-84.739 -206.627-145.783-149.839-158.233 -285.8-209.4-213.8-246.6

Application Example 4

The impact of the graft copolymer synthesized in Example 1 on the cracking performance was evaluated by flat plate cracking test. Huaxin 42.5PO cement was used, and naphthalene-based high-efficiency water reducer (FDN) and organic anti-shrinkage agent SRA were used as comparisons. The water-binder ratio is fixed at 0.32, the sand rate is 0.40, the amount of cementitious material is 470kg/m ³ , and the slump of the concrete is controlled at 18-20cm.

Table 6 Effect of admixture varieties on early plastic cracking of concrete Admixture type cracking time Maximum crack width/mm Crack area/mm ³ Example 1 Comparative Example 1, Doped with FDN Comparative Example 2 Re-doped with FDN+2%SRA 6h20min3h10min4h40min 0.271.O0.6 100.15763.32293.05

The early cracking area of the concrete mixed with FDN is the largest, and the crack width is the widest, reaching 1mm. The cracking area of the graft copolymer of the present invention is only 13% of that of FDN, and the crack width is only 0.27mm. The cracking time is also greatly delayed, and the anti-cracking effect is better than It is better when FDN and shrinkage reducing agent are compounded.

Claims (13)

1, a kind ofly reduce, the anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that by monomer a: vinylformic acid or its salt, monomer b: alkoxy polyether mono acrylic ester, monomer c: maleic anhydride half-ester or its salt, monomer d: α-vinyl carbinol ω-methyl polyethers and monomer c: vinylbenzene is prepared from by free radicals copolymerization reaction, aforementioned monomer a: monomer b: monomer c: monomer d: the mol ratio of monomer c is 1: 0.2～0.5: 0.10～0.25: 0.10～0.20: 0～0.10.

2, as claimed in claim 1ly reduce, the anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that described monomer a represents with general formula 1:

M in the formula ₁Expression hydrogen atom, monovalence atoms metal, divalent metal atom, ammonium or organic amino group.

3, as claimed in claim 1ly reduce, the anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that described monomer b represents with general formula 2:

R is the alkyl of 1～4 carbon atom in the formula, and AO is the oxyalkylene group of 2～4 carbon atoms or the mixture of two or more this oxyalkylene groups, and n is the average addition mole number of oxyalkylene group, is 5～40.

4, as claimed in claim 1ly reduce, the anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that described monomer c represents with general formula 3:

M in the formula ₂Expression hydrogen atom, monovalence atoms metal, divalent metal atom, ammonium or organic amino group, p and q are 0～8 integers, and 2≤p+q≤8.

5, as claimed in claim 1ly reduce, the anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that described monomer d represents with general formula 4:

M is 4～25 integer in the formula.

6, claim 1 to 5 describedly reduce, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that comprising the steps:

1) preparation monomer b: under the condition that azeotropic agent, acid catalyst and stopper exist, carry out esterification by 1: 1 to 5: 1 mol ratio by monoalkoxy polyethers shown in the general formula (5) and vinylformic acid;

2) preparation monomer c: by 1: 1 mol ratio esterification takes place directly under the condition of catalyzer by the monoalkoxy polyethers shown in the general formula (6) and maleic anhydride with reducing function;

3) monomer a, monomer b, monomer c, monomer d and monomer e are carried out free radicals copolymerization reaction by 1: 0.2～0.5: 0.10～0.25: 0.10～0.20: 0～0.10 mol ratio under the condition that radical initiator exists, and adding the alkali neutralization reaction, the pH value is adjusted to 7.0～8.5 and promptly makes finished product.

7, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that adoptable catalyzer comprises the vitriol oil, tosic acid, solid super-strong acid, phosphoric acid and phosphorous acid in the step 1), they can mix use separately or with arbitrary proportion; Catalyst consumption is being 0.5～5% of the monoalkoxy polyethers shown in the general formula (5) and acrylic acid gross weight.

8, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that adopting in the step 1) organic solvent to make azeotropic agent, the organic solvent that is fit to do azeotropic agent comprises aliphatic hydrocarbon, naphthenic hydrocarbon or aromatic hydrocarbon, wherein aliphatic hydrocarbon is selected from hexane, decane, undecane, dodecane; Naphthenic hydrocarbon is selected from hexanaphthene, methylcyclohexane; Aromatic hydrocarbon is selected from benzene, toluene, adjacent,, right-dimethylbenzene; The content of azeotropic agent in reaction mixture should be 10～40% of the monoalkoxy polyethers shown in the general formula (5) and acrylic acid gross weight.

9, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that stopper is selected from Resorcinol in the step 1), thiodiphenylamine, Resorcinol-methyl ether or two-tertiary butyl-p-cresol, its consumption are 0.005～0.8% of vinylformic acid weight.

10, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that step 2) in adoptable catalyzer comprise the vitriol oil, tosic acid and solid super-strong acid, they can be used alone or as a mixture; The consumption of acid catalyst is being 0.5～5% of the gross weight of monoalkoxy polyethers with reducing function shown in the general formula (6) and maleic anhydride.

11, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that step 1) and 2) temperature of reaction be 100～160 ℃.

12, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, it is characterized in that the initiator in the step 3) is conventional oil soluble radical initiator and composition thereof, comprise Diisopropyl azodicarboxylate, 2,2'-Azobis(2,4-dimethylvaleronitrile) or benzoyl peroxide or different third hydrogen peroxide or peroxy dicarbonate diisopropyl fat; The consumption of initiator is each monomer integral molar quantity about 1.0～4.0% in the step 3.

13, as reduce as described in the claim 6, the preparation method of anti-cracking grafted copolymer as concrete super-plasticizing agent, the molecular weight that it is characterized in that the multipolymer that step 3) generates can utilize the polymeric chain transfer agent to select control, aforementioned polymeric chain transfer agent selected from mercapto propionic acid, Thiovanic acid, mercaptoethanol and Dodecyl Mercaptan, its consumption be in the step 3) each total monomer weight 1.0～5.0%.