CN106883354A - A kind of powdery polycarboxylic-acid slump retaining agent and preparation method thereof - Google Patents

Abstract

A powdery polycarboxylate slump retaining agent of the present invention and a preparation method thereof, the preparation method comprising the following steps: preparing an ester monomer with acrylic acid or methacrylic acid and a polyhydric alcohol under the action of a catalyst, and then reacting with an acrylic acid ester Or methacrylate, unsaturated carboxylic acid and/or acid anhydride and polyether monomer, carry out bulk copolymerization under the action of composite initiator and hydrophobic chain transfer agent, obtain molten polycarboxylic acid series slump-retaining agent, and finally pass heat preservation The pipeline is sent to a frozen pulverizer for low-temperature pulverization to obtain a powdered polycarboxylate slump-retaining agent. The present invention prepares a powdery polycarboxylate water reducer by adjusting the acid-ether ratio, introducing acrylate or methacrylate and self-made ester monomers, and combining oil-soluble and water-soluble composite initiators. Polycarboxylate slump retaining agent. The slump-retaining agent of the invention has high slump retention performance, reduces the preparation cost, and the preparation process is safe and environment-friendly without solvent poisoning.

Description

A kind of powder polycarboxylate slump retaining agent and preparation method thereof

technical field

The invention belongs to the technical field of concrete admixtures in building materials, and in particular relates to a powdery polycarboxylate slump-retaining agent and a preparation method thereof.

Background technique

With the rise of my country's nuclear power, water conservancy, bridges, tunnels and other large-scale infrastructure, especially the large-scale implementation of the national railway passenger dedicated line network project, the market demand for polycarboxylate water reducers continues to grow. Compared with traditional high-efficiency water reducers, polycarboxylate water reducers have become the key materials for high-performance concrete due to their excellent properties such as high water reducing rate, low slump loss, and low alkali content.

Most of the polycarboxylate water reducers on the market are 10-50% liquid products. Due to their superior performance, they are increasingly used in various key projects. However, often due to the remote construction site and limited construction site, storage and transportation costs continue to increase. Therefore, the development of high-concentration or solid polycarboxylate products is important to reduce transportation costs and promote the widespread use of polycarboxylate-based water reducers. condition. The wide popularization and application of dry powder mortar has also put forward an urgent demand for the production and application of solid polycarboxylate superplasticizer. At present, most of the powder polycarboxylate water-reducers on the market are obtained by spray drying, but when they are diluted into liquids, their performance decreases compared with the liquid polycarboxylate water-reducers of the same concentration, which is mainly because The polycarboxylate water reducer is partially cross-linked after being heated. If you want to obtain polycarboxylate superplasticizer powder products with excellent performance, you can only operate at low temperature without destroying the structure of polycarboxylate superplasticizer.

CN102372458A reports a method for preparing a solid polycarboxylic acid-based water reducer, which is prepared by copolymerizing unsaturated acid and other unsaturated monomers in an organic solvent, followed by separation, precipitation and low-temperature drying. When the solid water reducer is dissolved in a water solvent, there is no difference in overall performance compared with commercially available liquid polycarboxylate water reducer products of the same concentration. However, this patent requires the use of organic solvents such as alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, esters, etc. After obtaining the polymerized product, it is necessary to dry and separate the solvent, and the production process is not green enough.

CN103554382A reports a method for solid-phase synthesis of polycarboxylic acid-based water reducers. Add polyether monomers, initiators and a small amount of water to a ball mill or colloid mill, start the machine and mix for 10 minutes, and then divide the small molecule several times. Add the mixture of monomer, reducing agent, chain transfer agent and water with 10% mass of small molecule monomer into the ball mill or colloid mill in equal parts. Acid-based water reducer.

CN103755885A proposes a method for microwave-assisted solid-phase synthesis of polycarboxylic acid-based water reducers, in which polyether monomers, initiators, small molecule monomers, reducing agents, chain transfer agents and small molecule monomers are mixed with 50% water The formed pasty mixture is placed in a microwave oven with adjustable power, and reacted for a certain period of time to obtain a solid or pasty polycarboxylate water reducer. The method in the above-mentioned patent is not suitable for large-scale industrial production.

CN102993387B reports a preparation method for directly synthesizing pure solid polycarboxylate water reducer in one step, heating unsaturated polyoxyethylene ether to 50-70°C to melt, adding molecular weight regulator, (methyl ) acrylic acid or its mixture with unsaturated carboxylic acid monomer and initiator, and the stirring time between each addition is 5-20 minutes, continue to heat up to 75-95 ° C for bulk polymerization for 1.5-8 hours, and cool to room temperature to obtain Pure solid polycarboxylate superplasticizer. The above two methods have the defects of high temperature or complex process.

Contents of the invention

In view of the above problems, the present invention discloses a powdery polycarboxylate slump-retaining agent and its preparation method, through the adjustment of the carboxyl group density in the copolymer molecule, the length of the side chain and the introduction of functional groups such as slow-release ester groups , to prepare a concrete slump retaining agent with high slump retention performance, which has good compatibility with polycarboxylate water reducer and excellent slump retention ability.

The present invention relates to a kind of preparation method of powdery polycarboxylic acid series slump-retaining agent, it is characterized in that by weight percentage, comprises following raw material composition:

The polyhydric alcohol is one of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol and dipropylene glycol.

The catalyst is p-toluenesulfonic acid or sulfamic acid, and the polymerization inhibitor is one of hydroquinone, phenothiazine and diphenylamine.

The polyether monomer is methallyl alcohol polyoxyethylene ether, methallyl alcohol polyoxyethylene polyoxypropylene ether, prenyl alcohol polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, and isopentenyl alcohol polyoxyethylene ether with a molecular weight of 600-4000. One of ethylene polyoxypropylene ethers.

The unsaturated carboxylic acid is that the acid anhydride is at least one of acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, or the unsaturated carboxylic acid is an unsaturated carboxylic acid and the acid anhydride is acrylic acid, methyl A mixture of at least one of acrylic acid, fumaric acid, maleic acid, and maleic anhydride.

Described acrylate comprises one in methyl acrylate, ethyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate; Described methacrylate comprises methyl methacrylate, ethyl methacrylate , one of isooctyl methacrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

The oil-soluble initiator is azobisisobutyronitrile, azobisisoheptanonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, benzoyl tert-butyl peroxide, methyl ethyl ketone peroxide A kind of, described water-soluble initiator is a kind of in ammonium persulfate, sodium persulfate and potassium persulfate.

The chain transfer agent is a hydrophobic chain transfer agent, including butyl mercaptan, octyl mercaptan, decyl mercaptan, lauryl mercaptan, hexadecyl mercaptan, octadecyl mercaptan, octyl 2-mercaptopropionate , 3-octyl mercaptopropionate, octyl thioglycolate, and 2-ethylhexyl thioglycolate can be used alone or in combination of two or more.

The preparation method of above-mentioned powdery polycarboxylate series slump-retaining agent, comprises the following steps:

Acrylic acid or methacrylic acid and polyhydric alcohol are prepared as an ester monomer under the action of a catalyst, and then mixed with acrylate or methacrylate, unsaturated carboxylic acid and/or acid anhydride, and polyether monomer, in the composite initiator Bulk copolymerization under the action of a hydrophobic chain transfer agent to obtain a molten polycarboxylate slump retaining agent, and finally sent to a freezing pulverizer through an insulated pipeline for low-temperature pulverization to obtain a powdered polycarboxylate slump retainer. The present invention prepares a powdery polycarboxylate water reducer by adjusting the acid-ether ratio, introducing acrylate or methacrylate and self-made ester monomers, and combining oil-soluble and water-soluble composite initiators. Polycarboxylate slump retaining agent.

More specifically, the steps of the preparation method are: (1) Preparation of ester monomers: add metered acrylic acid or methyl Acrylic acid, polyol, catalyst and polymerization inhibitor are heated to 90-120°C under stirring, stirred and refluxed for 2-7 hours, and the water layer is separated with a water separator and cooled to 60-70°C;

(2) Preparation of molten polycarboxylic acid-based slump-retaining agent: add metered polyether monomer into the reactor, stir and melt, then add oil-soluble initiator and stir to dissolve; then add water-soluble initiator, chain transfer agent and acrylic acid Make a mixed solution, and use a constant flow pump to drip it within 2 to 4 hours; continue to keep warm for 2 to 4 hours after dropping, add a certain amount of powder alkali and stir evenly;

(3) Preparation of powdered polycarboxylate-based slump-retaining agent: the melted product is sent to a frozen pulverizer through an insulated pipeline, and is ground at -20 to -40°C at a low temperature to obtain a powder with a fineness of 100 to 200 meshes. Polycarboxylate slump retaining agent.

The initiator is a composite initiator containing both oil-soluble and water-soluble initiators, and its addition method is that the oil-soluble initiator is put into the reaction kettle at one time as a base material, and the water-soluble initiator is dissolved in unsaturated carboxylic acid and slowly added dropwise into the reactor.

Compared with the prior art, the inventive method has the following beneficial effects:

(1) The powdery polycarboxylate slump-retaining agent prepared by the present invention can avoid problems such as chemical side reactions or wall-hanging burning caused by spray drying, and enrich the method for preparing polycarboxylate-based slump-retaining agents.

(2) The preparation process is safe, environmentally friendly, solvent-free, clean and pollution-free, the reaction raw materials used are simple and common, and the synthesis process does not require nitrogen protection, which greatly reduces the production cost.

(3) According to the theory of molecular design, the present invention partially replaces acrylic acid or methacrylic acid with ester monomers and acrylate or methacrylate introduced in the polymer, which reduces the carboxyl density in the molecular main chain and adjusts the adsorption balance , to achieve the control of polymer dispersion performance and slump retention performance, and because the hydrolysis rate of each monomer is different, the duration of the slump retention effect can be adjusted according to the actual situation, and the adaptability is better.

(4) The slump-retaining agent prepared by the present invention can still show better fluidity retention ability at a lower dosage, and shows strong adaptability to different types of cement. In addition, the slump-retaining agent product is stable, does not crystallize when stored at low temperature, and its performance is not affected after low-temperature storage, which is conducive to industrialization and application, and has good economic and social benefits.

(5) The powdery polycarboxylate series slump-retaining agent of the present invention can be widely used in commercial mortar, grouting mortar and various special mortars, making up for the deficiency that only retarders can be used in dry powder mortar in the past or plastic-retaining agents. Due to the inconvenience of application caused by the use of liquid slump retaining agent, it can effectively promote the development of dry powder mortar technology.

detailed description

The implementation of the present invention will be described in detail below with specific examples, so as to fully understand and implement the process of how to apply technical means to solve technical problems and achieve technical effects in the present invention.

In the embodiment of the present invention, a solid polycarboxylic acid is prepared in a molten state by adjusting the acid-ether ratio of the polycarboxylic acid-based water reducer, introducing self-made ester monomers, and combining oil-soluble and water-soluble composite initiators. Department of anti-slump agent. Since there is no large amount of water, storage and transportation are more convenient, and transportation costs are greatly reduced.

Example 1:

(1) Preparation of ester monomers: add 312.8kg methacrylic acid, 94.0kg ethylene glycol, 8.1kg sulfamic acid to the reaction kettle equipped with thermometer, stirring paddle, constant flow pump, condenser and water separator and 2.0kg of hydroquinone, heat up to 110-120°C under stirring, stir and reflux for 3-3.5 hours, separate the water layer with a water separator and lower the temperature to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 4168kg isopentenol polyoxyethylene ether (molecular weight 2400), stir and melt, then add 29.2kg benzoyl peroxide and stir to dissolve; then 19.5kg over Sodium sulfate, 38.9kg of octyl thioglycolate, 86.8kg of ethyl acrylate and 187.6kg of acrylic acid were mixed into a mixed solution, which was dripped with a constant-flow pump within 3.5-4 hours; Stir 53.1kg powder alkali evenly;

(3) Preparation of powdered polycarboxylate-based slump-retaining agent: the melted product is sent to a freezer pulverizer for low-temperature pulverization through an insulated pipeline to obtain a white powder-like polycarboxylate-based slump-retaining agent.

Example 2:

(1) Preparation of ester monomers: add 417.8kg methacrylic acid, 125.5kg ethylene glycol, 10.9kg sulfamic acid to the reaction kettle equipped with thermometer, stirring paddle, constant flow pump, condenser and water separator and 2.7kg of hydroquinone, heat up to 110-120°C under stirring, stir and reflux for 3-3.5 hours, separate the water layer with a water separator and cool down to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 3712kg isopentenol polyoxyethylene polyoxypropylene ether (molecular weight 1600), stir and melt, then add 29.0kg azobisisoheptanonitrile and stir to dissolve; then Mix 19.2kg of ammonium persulfate, 33.9kg of butanethiol, 269.1kg of hydroxyethyl acrylate and 299.2kg of methacrylic acid into a mixed solution, and drop it with a constant-current pump within 2.5 to 3 hours; continue to keep warm for 4 hours after dropping, Add 80.9kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Example 3:

(1) Preparation of ester monomers: add 707.0kg methacrylic acid, 212.4kg ethylene glycol, 18.4kg sulfamic acid to the reaction kettle equipped with thermometer, stirring paddle, constant flow pump, condenser and water separator and 4.6kg of hydroquinone, heated up to 100-110°C under stirring, stirred and refluxed for 4-5 hours, separated the water layer with a water separator and lowered the temperature to 60-70°C;

(2) Preparation of molten polycarboxylate slump-retaining agent: add 3140kg isopentenol polyoxyethylene ether (molecular weight 1200), stir and melt, then add 384.8kg maleic anhydride and 33.5kg benzoyl peroxide and stir to dissolve ; Then 14.4kg of sodium persulfate, 38.5kg of 3-mercaptopropionate octyl and 340.3kg of hydroxyethyl methacrylate are formulated into a mixed solution, and are dripped with a constant flow pump within 3 hours; Add 106.1kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Example 4:

(1) Preparation of ester monomers: add 220.6kg acrylic acid, 146.6kg dipropylene glycol, 5.5kg sulfamic acid and 1.9kg of phenothiazine, heat up to 110-120°C under stirring, stir and reflux for 3-3.5 hours, separate the water layer with a water separator and cool down to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 4280kg isopentenol polyoxyethylene ether (molecular weight 4000), stir and melt, then add 34.1kg dimethyl azobisisobutyrate and stir to dissolve; then Mix 14.7kg of ammonium persulfate, 29.3kg of decyl mercaptan, 69.6kg of hydroxypropyl acrylate and 154.1kg of acrylic acid to make a mixed solution, and use a constant flow pump to drop it within 2 to 2.5 hours; after the drop, continue to keep warm for 3.5 to 4 hours , add 43.6kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Example 5:

(1) Preparation of ester monomers: add 382.1kg acrylic acid, 254.0kg dipropylene glycol, 9.5kg sulfamic acid and 3.2kg of phenothiazine, heat up to 100-110°C under stirring, stir and reflux for 4-5 hours, separate the water layer with a water separator and cool down to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 3708kg isopentenol polyoxyethylene ether (molecular weight 2000), stir and melt, then add 24.1kg methyl ethyl ketone peroxide and stir to dissolve; then 24.1kg potassium persulfate , 33.7kg octyl thioglycolate, 159.4kg methyl acrylate and 318.8kg methacrylic acid to make a mixed solution, and drop it with a constant flow pump within 3 hours; after dropping, continue to keep warm for 4 hours, add 83.1kg powder alkali and stir Uniform;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Embodiment 6:

(1) Preparation of ester monomers: add 693.2kg acrylic acid, 460.7kg dipropylene glycol, 17.3kg sulfamic acid and 5.8kg of phenothiazine, heat up to 110-120°C under stirring, stir and reflux for 3-3.5 hours, separate the water layer with a water separator and cool down to 60-70°C;

(2) Preparation of molten polycarboxylate slump-retaining agent: add 2690kg isopentenol polyoxyethylene ether (molecular weight 800), stir and melt, then add 23.9kg methyl ethyl ketone peroxide and stir to dissolve; then 23.9kg potassium persulfate , 28.6kg octyl mercaptan, 437.2kg hydroxypropyl acrylate and 484.3kg acrylic acid to make a mixed solution, and use a constant flow pump to drip it within 2~2.5h; Stir the alkali evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Embodiment 7:

(1) Preparation of ester monomers: add 307.7kg of acrylic acid, 141.6kg of diethylene glycol, and 8.1kg of p-toluenesulfonic acid into a reaction kettle equipped with a thermometer, a stirring blade, a constant flow pump, a condenser and a water separator and 2.2kg of diphenylamine, heated to 100-110°C under stirring, stirred and refluxed for 4-4.5 hours, separated the water layer with a water separator and lowered the temperature to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 3804kg methallyl alcohol polyoxyethylene ether (molecular weight 2400), stir and melt, then add 459.6kg fumaric acid and 33.8kg benzoyl peroxide and stir Dissolve; then mix 14.4kg of potassium persulfate, 38.7kg of 2-ethylhexyl mercaptoacetate and 103.0kg of hydroxyethyl methacrylate into a mixed solution, and drop it with a constant flow pump within 2 to 2.5 hours; After that, continue to keep warm for 3.5-4 hours, add 86.9kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Embodiment 8:

(1) Preparation of ester monomers: (1) Preparation of ester monomers: add 255.8kg acrylic acid, 117.8kg bismuth Ethylene glycol, 6.7kg of p-toluenesulfonic acid and 1.9kg of diphenylamine are heated to 110-120°C under stirring, stirred and refluxed for 3-3.5 hours, and the water layer is separated with a water separator and cooled to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 3953kg isopentenol polyoxyethylene ether (molecular weight 3000), stir and melt, then add 29.1kg benzoyl peroxide and stir to dissolve; 19.4kg of sodium persulfate, 24.2kg of octyl 2-mercaptopropionate, 242.5kg of isooctyl acrylate and 283.3kg of methacrylic acid were prepared as a mixed solution, and the solution was dripped with a constant flow pump within 2 to 2.5 hours; Keep warm for 3.5-4 hours, add 66.3kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Embodiment 9:

(1) Preparation of ester monomers: (1) Preparation of ester monomers: add 446.8kg acrylic acid, 205.5kg dihydrogen to the reaction kettle equipped with thermometer, stirring paddle, constant flow pump, condenser and water separator Ethylene glycol, 11.8kg of p-toluenesulfonic acid and 3.2kg of diphenylamine are heated to 90-95°C under stirring, stirred and refluxed for 5.5-6 hours, and the water layer is separated with a water separator and cooled to 60-70°C;

(2) Preparation of molten polycarboxylic acid series slump-retaining agent: add 3680kg methallyl alcohol polyoxyethylene polyoxypropylene ether (molecular weight 2400), stir and melt, then add 29.2kg azobisisobutyronitrile and stir to dissolve; Then, 19.3kg of ammonium persulfate, 29.2kg of lauryl mercaptan, 220.9kg of hydroxypropyl methacrylate and 276.1kg of acrylic acid were formulated into a mixed solution, which was dripped with a constant flow pump within 2h to 2.5h; after dripping, continue Keep warm for 3-3.5 hours, add 78.0kg powder alkali and stir evenly;

(3) Preparation of powdery polycarboxylate slump retaining agent: same as Example 1.

Application Example 1:

The fluidity of cement slurry refers to the national standard GB/T 8077-2012 "Concrete Admixture Homogeneity Test Method". Jinning sheep P·II52.5 grade of Cement Co., Ltd.; the comparative liquid polycarboxylate slump retaining agent is TX-209 from Nanjing Ruidi High-tech Co., Ltd. and ST-412 from a factory in Jiangsu. The amount is 0.2% (based on the weight of cement after folding), and the test results are shown in Table 1.

Table 1 Comparison of net slurry fluidity and loss of different slump-retaining agents

As can be seen from the results in Table 1, the solid polycarboxylate-based slump-retaining agent of the present invention has a large difference in the fluidity of the initial cement paste in different cements, but all have good fluidity retention capabilities, and generally have a time-dependent growth. The performance is similar to that of the comparative liquid polycarboxylate slump retaining agent TX-209, and better than the commercially available liquid polycarboxylate slump retainer ST-412.

Application Example 2:

Refer to the relevant provisions of the national standard GB 8076-2008 "Concrete Admixtures". The benchmark cement was used for the test cement, and the admixtures were solidly mixed with 0.2%. The concrete mix ratio is shown in Table 2, and the test results are shown in Table 3 below.

Table 2 Concrete mix ratio (kg/m ³ )

cement sand Zhongshi small stone water Admixture 360 820 600 400 178 0.72

Table 3 Concrete performance comparison of different polycarboxylate slump-retaining agents

The results show that the solid polycarboxylate slump retaining agent of the present invention has good concrete slump retention ability, and the concrete still has good fluidity after 2 hours, compared with the liquid polycarboxylate slump retaining agent TX-209 of contrast The performance is close to that of the commercially available liquid polycarboxylate slump retaining agent ST-412.

While the present invention has been described by way of examples, the examples are not intended to limit the invention. Those skilled in the art can make various modifications and improvements within the scope of the spirit of the present invention, such as the adjustment of component ratios or time ranges. The effect after this adjustment is predictable, so it is also within the scope of the protection of the present invention. within range. Therefore, the protection scope of the present invention should be determined by the protection scope defined by the same or equivalent technical features of the claims of this application.

Claims (10)

1. A powdery polycarboxylate system slump-retaining agent, is characterized in that, by weight percentage, comprises following raw material: 2. powdery polycarboxylic acid series slump-retaining agent according to claim 1, is characterized in that: described polyvalent alcohol is ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, a One of dipropylene glycol. 3. powdery polycarboxylate slump-retaining agent according to claim 1, is characterized in that: described catalyzer is p-toluenesulfonic acid or sulfamic acid, and described polymerization inhibitor is hydroquinone, phenothiazine , one of diphenylamine. 4. The powdery polycarboxylate slump-retaining agent according to claim 1, characterized in that: the polyether monomer is methallyl alcohol polyoxyethylene ether, methallyl alcohol with a molecular weight of 600-4000 One of polyoxyethylene polyoxypropylene ether, isopentenol polyoxyethylene ether, isopentenol polyoxyethylene polyoxypropylene ether. 5. The powdery polycarboxylate slump-retaining agent according to claim 1, characterized in that: the unsaturated carboxylic acid is at least one of acid anhydride, acrylic acid, methacrylic acid, fumaric acid, and maleic acid , or the unsaturated carboxylic acid is a mixture of unsaturated carboxylic acid and acid anhydride being at least one of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride. 6. The powdery polycarboxylate slump-retaining agent according to claim 1, characterized in that: said acrylate comprises methyl acrylate, ethyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate ; The methacrylate includes methyl methacrylate, ethyl methacrylate, isooctyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate. 7. powdery polycarboxylate slump retaining agent according to claim 1, is characterized in that: described oil-soluble initiator is azobisisobutyronitrile, azobisisoheptanonitrile, azobisisobutyric acid One of dimethyl esters, benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide, and the water-soluble initiator is one of ammonium persulfate, sodium persulfate and potassium persulfate. 8. The powdery polycarboxylate slump-retaining agent according to claim 1, characterized in that: the chain transfer agent is a hydrophobic chain transfer agent, comprising butanethiol, octyl mercaptan, decyl mercaptan, lauryl Mercaptan, hexadecyl mercaptan, octadecyl mercaptan, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate, octyl thioglycolate, 2-ethylhexyl mercaptoacetate species or several. 9. a preparation method of the powdery polycarboxylate slump-retaining agent described in any one of claims 1-8, is characterized in that, comprises the following steps: Acrylic acid or methacrylic acid and polyhydric alcohol are prepared as an ester monomer under the action of a catalyst, and then mixed with acrylate or methacrylate, unsaturated carboxylic acid and/or acid anhydride, and polyether monomer, in the composite initiator Bulk copolymerization under the action of a hydrophobic chain transfer agent to obtain a molten polycarboxylate slump retaining agent, and finally sent to a freeze pulverizer for low-temperature pulverization to obtain a powdered polycarboxylate slump retainer. 10. the preparation method of powdery polycarboxylic acid series slump-retaining agent according to claim 9, is characterized in that, specifically comprises the following steps: (1) Preparation of ester monomers: Add metered acrylic acid or methacrylic acid, polyol, catalyst and polymerization inhibitor into the reaction kettle, heat up to 90-120°C under stirring, stir and reflux for 2-7 hours, and separate the water layer and lower the temperature to 60-70°C; (2) Preparation of molten polycarboxylic acid-based slump-retaining agent: add metered polyether monomer into the reactor, stir and melt, then add oil-soluble initiator and stir to dissolve; then add water-soluble initiator, chain transfer agent and acrylic acid Make a mixed solution, and drop it within 2-4 hours; continue to keep warm for 2-4 hours after dropping, add a certain amount of powder alkali and stir evenly; (3) Preparation of powdered polycarboxylate-based slump-retaining agent: the melted product is sent to a frozen pulverizer through an insulated pipeline, and is ground at -20 to -40°C at a low temperature to obtain a powder with a fineness of 100 to 200 meshes. Polycarboxylate slump retaining agent.