A kind of wide temperature range cross-linked polycarboxylate water reducer and preparation method thereof

Abstract

The invention provides a wide-temperature-range cross-linked polycarboxylate water-reducing agent and a preparation method thereof. The water-reducing agent comprises the following components: 100 parts of a 6-carbon type macromonomer, 5-15 parts of a composite unsaturated functional small monomer, 0.1-0.5 parts of a composite reducing agent, 0.2-0.6 parts of a composite oxidant, 0.1-0.5 parts of a chain transfer agent, 0.001-0.01 parts of a polymerization inhibitor, 0.01-0.1 parts of a cross-linking agent and 100-160 parts of water. The polycarboxylate water-reducing agent effectively solves the problems of a narrow polymerization temperature range of a 6-carbon type macromonomer and a great influence of the polymerization temperature on the product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of polycarboxylate water reducers, and particularly relates to a wide temperature range cross-linked polycarboxylate water reducer and a preparation method thereof. Background Art

[0002] Concrete chemical admixtures are the sixth component of cement-based concrete in addition to stone, sand, water, cement and mineral admixtures. They can not only improve the workability, homogeneity, stability and durability of concrete, but also meet the requirements for the use of concrete under harsh conditions such as large volume, large load, large span, high-rise, deep sea, underground, and corrosive environment. Among them, the most widely used and important variety is water reducer.

[0003] Polycarboxylic acid-based high-performance water reducers are a new generation of water reducers that have attracted much attention at home and abroad. Due to the advantages of being able to design molecular structures according to the mechanism of action of dispersed cement, large degrees of freedom in molecular structure, multiple synthesis technologies, large room for high performance, and low pollution, as well as the technical performance characteristics of strong superdispersion, high slump retention, good plasticizing effect at low dosage, good fluidity retention, wide cement adaptability, significant concrete reinforcement effect, and reduced concrete shrinkage, polycarboxylic acid-based high-performance water reducers give concrete excellent construction and workability, good strength development, and excellent durability, which meets the needs of modern concrete engineering. Therefore, polycarboxylic acid-based high-performance water reducers are gradually becoming the preferred admixture for the preparation of high-performance concrete. The synthesis of polycarboxylic acid water reducers is a free radical polymerization process. Reaction temperature is one of the important factors affecting free radical polymerization, and the reaction temperature will also have an important impact on the molecular weight and product structure of the product.

[0004] At present, polyether macromonomers for preparing polycarboxylic acid water reducers often use 3-carbon (allyl polyethylene glycol ether), 4-carbon (isobutylene polyethylene glycol ether), and 5-carbon (isoprene polyethylene glycol ether) polyether macromonomers. With the development of the polyether monomer industry and changes in market demand, a new type of 6-carbon macromonomer (ethylene glycol monovinyl polyethylene glycol ether or 4-hydroxybutyl vinyl polyethylene glycol ether) has appeared on the market in recent years. This monomer is different from the traditional 3-carbon, 4-carbon, and 5-carbon macromonomers. The 6-carbon macromonomer has an unsaturated double bond with higher reactivity, so it can undergo polymerization at a lower polymerization temperature. Generally speaking, the optimal polymerization temperature of 6-carbon macromonomer is 15-25℃. When the temperature is low, the number of free radicals generated by the reaction system is small. Even if the activity of 6-carbon macromonomer is high, the copolymerization rate is still very slow and cannot be completely reacted. The measured fluidity does not reach the ideal effect. As the temperature gradually rises, the number of free radicals increases, and the polymerization rate of 6-carbon macromonomer accelerates, and the dispersion performance of the water reducer gradually improves. When the reaction temperature is too high, the reaction rate is too fast, and it is easy to cause explosion or induce side reactions, resulting in a decrease in the dispersion performance of the product. However, most areas in my country have the problem of high temperature in summer and low temperature in winter. Therefore, when using 6-carbon macromonomer for production, it is necessary to cool down or heat it to ensure the relative constancy of its polymerization process. This operation not only consumes a lot of energy, but also fails to meet the green environmental protection concept and the needs of enterprises for energy conservation, emission reduction and production efficiency improvement, and also poses a great risk to product quality. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a wide-temperature-range cross-linked polycarboxylic acid water-reducing agent and a preparation method thereof. The polycarboxylic acid water-reducing agent prepared in the present application effectively solves the problems of narrow polymerization temperature range of 6-carbon macromonomer and great influence of polymerization temperature on product quality.

[0006] To achieve the above purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0007] A wide range of synthetic temperature cross-linked polycarboxylate water reducer, the structural formula of which is as follows:

[0008]

[0009] in,

[0010] R 1 =H,CH 3 ,COOH

[0011]

[0012] R 3 =CH 2 CH 2 , CH 2 CH 2 CH2 CH 2

[0013] R 4 =CH 2 , CH 2 CH 2 , CH 2 CH 2 CH 2 , CH 2 CH 2 CH 2 CH 2

[0014] Among them, a, b, c are 0-20, n is 30-100, and m is 5-30;

[0015] The raw materials include the following components in parts by weight: 100 parts of 6-carbon type macromonomer, 5-15 parts of composite unsaturated functional small monomer, 0.1-0.5 parts of composite reducing agent, 0.2-0.5 parts of composite oxidant, 0.1-0.5 parts of chain transfer agent, 0.001-0.01 parts of inhibitor, 0.01-0.1 parts of crosslinking agent and 100-160 parts of water.

[0016] Furthermore, the 6-carbon type macromonomer is ethylene glycol monovinyl polyethylene glycol ether and / or 4-hydroxybutyl vinyl polyethylene glycol ether, and the molecular weight of the 6-carbon type macromonomer is 2000-4000.

[0017] Furthermore, the complex unsaturated functional small monomer includes at least one of an acrylic acid / sodium acrylate mixture, an acrylic acid / sodium propylene sulfonate mixture, an acrylic acid / sodium methacrylic sulfonate mixture, an acrylic acid / itaconic acid mixture, an acrylic acid / hydroxyethyl acrylate mixture, and an acrylic acid / hydroxypropyl acrylate mixture.

[0018] Further, the composite oxidant includes at least one of a hydrogen peroxide / ammonium persulfate mixture, a hydrogen peroxide / dibenzoyl peroxide mixture, a hydrogen peroxide / tert-butyl perbenzoate mixture, a hydrogen peroxide / isopropylbenzene hydroperoxide mixture, and a hydrogen peroxide / azobisisobutyronitrile mixture.

[0019] Furthermore, the composite reducing agent includes at least one of an ascorbic acid / transition metal salt mixture, a bleaching powder / transition metal salt mixture, a sodium bisulfite / transition metal salt mixture, an N-isopropylhydroxylamine / transition metal salt mixture, and a dimethylaniline / transition metal salt mixture.

[0020] Further, the transition metal salt includes FeSO 4 、CuSO 4 、CoSO 4 、NiSO 4 、ZnSO 4At least one of .

[0021] Further, the chain transfer agent includes at least one of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, aliphatic mercaptan and dodecyl mercaptan.

[0022] Further, the polymerization inhibitor includes at least one of hydroquinone, p-benzoquinone, methylhydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone.

[0023] Further, the cross-linking agent includes at least one of glyoxal, malondialdehyde, succinaldehyde and glutaraldehyde.

[0024] The preparation method of the wide-range synthetic temperature range cross-linked polycarboxylate water-reducing agent comprises the following steps:

[0025] (1) Mixing the 6-carbon macromonomer, the polymerization inhibitor, the composite oxidant and water uniformly under stirring to prepare a solution A;

[0026] (2) mixing the composite unsaturated functional small monomer and water to obtain solution B;

[0027] (3) uniformly mixing the composite reducing agent, the chain transfer agent and water to prepare a solution C;

[0028] (4) Under stirring, the initial temperature of solution A is controlled at 10-40° C., and then solution B and solution C are added dropwise to solution A. The addition time of solution B is 30-60 min, and the addition time of solution C is 10-30 min longer than that of solution B;

[0029] (5) adding a crosslinking agent thereto while stirring and keeping the temperature for 30-60 minutes to carry out a crosslinking reaction to obtain the product.

[0030] The beneficial effects produced by the present invention are:

[0031] First, in the present application, the use of a composite oxidant and a composite reductant enables the redox initiation system to adapt to a wider polymerization temperature range. The combined use of an oxidant and a reductant can effectively reduce the thermal decomposition activation energy of the oxidant, thereby making it easier to initiate a free radical polymerization reaction. However, the combined use of a single oxidant and a reductant is more suitable for the production of polycarboxylic acid water-reducing agents with a narrower polymerization temperature range, and the polymerization temperature still directly affects the polymerization process of the polycarboxylic acid water-reducing agent. Too low a temperature reduces the decomposition efficiency of the oxidant, and too high a temperature causes the oxidant to decompose too quickly, which is not conducive to the use of a wider polymerization temperature range. In a system of multiple oxidants and reductants, different combinations of oxidants and reductants have different thermal decomposition activation energies and are better adaptable to changes in polymerization temperature. The use of composite oxidants and composite reductants enriches the redox initiation system and ensures the stable generation of free radicals in a wider polymerization temperature range, thereby allowing free radical polymerization reactions to occur stably.

[0032] Second, by introducing unsaturated functional small monomers with different structures, the polymerization process of polycarboxylate water reducer can be changed. During the polymerization process of polycarboxylate water reducer, 6-carbon macromonomers and unsaturated functional small monomers have different polymerization activities. The higher the polymerization activity, the easier it is to self-polymerize, the reaction monomers are more inclined to homopolymerization, and the molecular structure of polycarboxylate water reducer tends to form block copolymers, which is not conducive to the use of polycarboxylate water reducer. However, even though the polymerization activity of 6-carbon macromonomers has been significantly improved compared with other polyether monomers, the polymerization activity of the commonly used unsaturated functional small monomer-acrylic acid is still much higher than that of 6-carbon macromonomers. Acrylic acid is prone to homopolymerization, and polycarboxylate water reducer is still a block copolymer; the structure of unsaturated functional small monomers directly affects its polymerization activity. Introducing other unsaturated functional small monomers with polymerization activities between 6-carbon macromonomers and acrylic acid during the polymerization process can make the reaction monomers easier to copolymerize, and the molecular chain of polycarboxylate water reducer tends to produce alternating copolymers to form a comb-shaped structure.

[0033] Third, by introducing inhibitors, the free radical activity is weakened or excess free radicals are annihilated, the free radical polymerization rate is reduced or the free radical polymerization reaction is stopped, thereby weakening the effect of polymerization temperature on the free radical chain growth polymerization process. At the same time, the inhibitor will also prevent the 6-carbon macromonomer from being oxidized and deactivated at high temperatures;

[0034] In addition, the cross-linking agent improves the water retention of the polycarboxylate water-reducing agent and the adsorption of the surface of the cementitious material. The polycarboxylate water-reducing agent is adsorbed on the surface of the cementitious material by adsorption, and the dispersion of the cementitious material is achieved by mutual repulsion through charge and steric hindrance. If the molecular weight is too small, the steric hindrance is weakened. If the molecular weight is too large, the polycarboxylate water-reducing agent cannot fully cover the surface of the cementitious material, and it is difficult to effectively achieve the dispersion of the cementitious material. The use of the cross-linking agent increases the molecular weight and molecular distribution of the polycarboxylate water-reducing agent, and at the same time obtains a certain cross-linking structure, so that the polycarboxylate water-reducing agent with different molecular chain lengths is fully adsorbed on the surface of the cementitious material, making the dispersion of the cementitious material more sufficient, and the formation of the cross-linking network also improves the water retention performance of the product.

[0035] Therefore, by combining different polymerization-active unsaturated functional small monomers, introducing appropriate amounts of inhibitors and crosslinking agents, and using a composite redox system, the invention overcomes the problems of narrow polymerization temperature range of 6-carbon macromonomers and the great influence of polymerization temperature on product quality, reduces production energy consumption, improves product quality stability and raw material adaptability, and has good water retention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the preparation process of Guangcheng temperature range cross-linked polycarboxylate water reducer. DETAILED DESCRIPTION

[0037] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0038] Example 1

[0039] A wide range of cross-linked polycarboxylate water reducer, comprising the following components in parts by weight: 100 parts of ethylene glycol monovinyl polyglycol ether with a molecular weight of 3000, 5 parts of acrylic acid, 8 parts of sodium acrylate, 0.2 parts of ascorbic acid, FeSO 4 0.1 parts, 0.1 parts of hydrogen peroxide, 0.2 parts of ammonium persulfate, 0.3 parts of mercaptoethanol, 0.002 parts of hydroquinone, 0.05 parts of glutaraldehyde and 120 parts of water.

[0040] The preparation method of the above-mentioned wide-range synthetic temperature range cross-linked polycarboxylate water reducer is as follows:

[0041] (1) Under stirring, 100 parts of 3000 molecular weight ethylene glycol monovinyl polyethylene glycol ether, 0.1 parts of hydrogen peroxide, 0.2 parts of ammonium persulfate, 0.002 parts of hydroquinone and 100 parts of water are uniformly mixed to obtain solution A;

[0042] (2) 5 parts of acrylic acid, 8 parts of sodium acrylate and 10 parts of water were mixed evenly to obtain solution B;

[0043] (3) 0.2 parts ascorbic acid and 0.1 parts FeSO 4 , 0.3 parts of mercaptoethanol and 10 parts of water were mixed evenly to obtain solution C;

[0044] (4) Under stirring, solution B and solution C were added dropwise to solution A, and the polymerization starting temperature was controlled to be 10°C, the addition time of solution B was 40 min, and the addition time of solution C was 55 min;

[0045] (5) After the dropwise addition, 0.05 parts of glutaraldehyde was added under stirring and the mixture was kept warm for 50 minutes to obtain a polycarboxylic acid water reducer.

[0046] Example 2

[0047] Based on the comparative document 1, the polymerization starting temperature in step (4) is adjusted to 20°C.

[0048] Example 3

[0049] Based on the comparative document 1, the polymerization starting temperature in step (4) is adjusted to 30°C.

[0050] Example 4

[0051] Based on the comparative document 1, the polymerization starting temperature in step (4) is adjusted to 40°C.

[0052] Example 5

[0053] On the basis of Example 4, the composite oxidant was adjusted to 0.2 parts of hydrogen peroxide and 0.3 parts of dibenzoyl peroxide; the composite reductant was adjusted to 0.3 parts of sodium bisulfite and 0.1 parts of FeSO 4 ; Adjust the complex unsaturated functional small monomer to 5 parts of acrylic acid and 8 parts of hydroxyethyl acrylate.

[0054] Comparative Example 1

[0055] A wide range cross-linked polycarboxylate water reducer comprises the following components in parts by weight: 100 parts of ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000, 13 parts of acrylic acid, 0.3 parts of ascorbic acid, 0.3 parts of hydrogen peroxide, 0.3 parts of mercaptoethanol, 0.002 parts of hydroquinone, 0.05 parts of glutaraldehyde and 120 parts of water.

[0056] The preparation method of the above-mentioned wide-range synthetic temperature range cross-linked polycarboxylate water reducer is as follows:

[0057] (1) Under stirring, 100 parts of 3000 molecular weight ethylene glycol monovinyl polyethylene glycol ether, 0.3 parts of hydrogen peroxide, 0.002 parts of hydroquinone and 100 parts of water are uniformly mixed to obtain solution A;

[0058] (2) 13 parts of acrylic acid and 10 parts of water were mixed evenly to obtain solution B;

[0059] (3) 0.3 parts of ascorbic acid, 0.3 parts of mercaptoethanol and 10 parts of water were mixed to obtain solution C;

[0060] (4) Under stirring, solution B and solution C were added dropwise to solution A, and the polymerization starting temperature was controlled to be 10°C, the addition time of solution B was 40 min, and the addition time of solution C was 55 min;

[0061] (5) After the dropwise addition, 0.05 parts of glutaraldehyde was added under stirring and the mixture was kept warm for 50 minutes to obtain a polycarboxylic acid water reducer.

[0062] Comparative Example 2

[0063] Based on Comparative Example 1, the polymerization starting temperature in step (4) was adjusted to 20°C.

[0064] Comparative Example 3

[0065] Based on Comparative Example 1, the polymerization starting temperature in step (4) was adjusted to 30°C.

[0066] Comparative Example 4

[0067] Based on Comparative Example 1, the polymerization starting temperature in step (4) was adjusted to 40°C.

[0068] Comparative Example 5

[0069] A wide range of cross-linked polycarboxylate water reducer, comprising the following components in parts by weight: 100 parts of ethylene glycol monovinyl polyglycol ether with a molecular weight of 3000, 5 parts of acrylic acid, 8 parts of sodium acrylate, 0.2 parts of ascorbic acid, FeSO 4 0.1 parts, 0.1 parts of hydrogen peroxide, 0.2 parts of ammonium persulfate, 0.3 parts of mercaptoethanol and 120 parts of water.

[0070] The preparation method of the above-mentioned wide-range synthetic temperature range cross-linked polycarboxylate water reducer is as follows:

[0071] (1) Under stirring, 100 parts of 3000 molecular weight ethylene glycol monovinyl polyethylene glycol ether, 0.1 parts of hydrogen peroxide, 0.2 parts of ammonium persulfate and 100 parts of water are uniformly mixed to obtain solution A;

[0072] (2) 5 parts of acrylic acid, 8 parts of sodium acrylate and 10 parts of water were mixed evenly to obtain solution B;

[0073] (3) 0.2 parts ascorbic acid and 0.1 parts FeSO 4 , 0.3 parts of mercaptoethanol and 10 parts of water were mixed evenly to obtain solution C;

[0074] (4) Under stirring, solution B and solution C were added dropwise to solution A, and the polymerization starting temperature was controlled to be 10°C, the addition time of solution B was 40 min, and the addition time of solution C was 55 min;

[0075] (5) After the dropwise addition is completed, the reaction is kept warm for 50 minutes under stirring to obtain a polycarboxylic acid water-reducing agent.

[0076] Comparative Example 6

[0077] On the basis of Comparative Example 5, the polymerization starting temperature in step (4) was set to 20°C.

[0078] Comparative Example 7

[0079] On the basis of Comparative Example 5, the polymerization starting temperature in step (4) was set to 30°C.

[0080] Comparative Example 8

[0081] On the basis of Comparative Example 5, the polymerization starting temperature in step (4) was set to 40°C.

[0082] Test example

[0083] The water reducers prepared in Examples 1-5 and Comparative Examples 1-8 and commercially available samples were compared to test their molecular weight, monomer conversion rate, cement paste fluidity, concrete fluidity over time, and concrete water retention. The test method refers to GB8076-2016 "Specifications for Concrete Admixtures", GB8077-2012 "Test Methods for Homogeneity of Concrete Admixtures" and GB / T50080-2016 "Standards for Test Methods for Performance of Ordinary Concrete Mixtures". The water-cement ratio of cement paste fluidity is controlled to be 0.29, and the water reducer solid content is 0.2% of the cement dosage; the same compound formula is used and applied to C30 concrete, and the concrete fluidity over time is compared at room temperature. Among them, the cement is Esheng P.O42.5, and the fineness modulus of machine-made sand is 2.8; the crushed stone is a continuously graded crushed stone with a particle size of 5-25mm, and the polycarboxylic acid water reducer solid content is 1wt%. The test results are shown in Tables 1 and 2.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088] It can be seen from the above data that the water reducers in Examples 1-5 of the present application have more stable performance and smaller pressure water bleeding rate; while the water reducing performance stability in Comparative Examples 1-4 is poor and the pressure water bleeding rate is small; the water reducers in Comparative Examples 5-8 have worse stability and larger pressure water bleeding rate.

Claims

1. A wide temperature range cross-linked polycarboxylate water reducer, characterized in that: The invention comprises the following components in parts by weight: 100 parts of ethylene glycol monovinyl polyglycol ether with a molecular weight of 3000, 5 parts of acrylic acid, 8 parts of sodium acrylate, 0.2 parts of ascorbic acid, 0.1 parts of FeSO4, 0.1 parts of hydrogen peroxide, 0.2 parts of ammonium persulfate, 0.3 parts of mercaptoethanol, 0.002 parts of hydroquinone, 0.05 parts of glutaraldehyde and 120 parts of water; The wide-range cross-linked polycarboxylate water-reducing agent is prepared by the following steps: (1) While stirring, ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000, hydroquinone, hydrogen peroxide, ammonium persulfate and water are uniformly mixed to prepare a solution A; (2) Evenly mix acrylic acid, sodium acrylate and water to prepare solution B; (3) Mix ascorbic acid, FeSO4, mercaptoethanol and water to obtain solution C; (4) Under stirring, control the initial temperature of solution A to be 10-40°C, then drop solution B and solution C into solution A, with the dropwise addition time of solution B being 30-60 min, and the dropwise addition time of solution C being 10-30 min longer than that of solution B; (5) Add glutaraldehyde thereto under stirring and keep warm for 30-60 minutes to carry out a cross-linking reaction to obtain the product.

2. A wide temperature range cross-linked polycarboxylate water reducer, characterized in that: The invention comprises the following components in parts by weight: 100 parts of ethylene glycol monovinyl polyglycol ether with a molecular weight of 3000, 5 parts of acrylic acid, 8 parts of hydroxyethyl acrylate, 0.3 parts of sodium bisulfite, 0.1 parts of FeSO4, 0.2 parts of hydrogen peroxide, 0.3 parts of dibenzoyl peroxide, 0.3 parts of mercaptoethanol, 0.002 parts of hydroquinone, 0.05 parts of glutaraldehyde and 120 parts of water; Wherein, the wide synthetic temperature range cross-linked polycarboxylate water reducer is prepared by the following steps: (1) While stirring, uniformly mix ethylene glycol monovinyl polyglycol ether with a molecular weight of 3000, hydroquinone, hydrogen peroxide, dibenzoyl peroxide and water to prepare a solution A; (2) Evenly mix acrylic acid, hydroxyethyl acrylate and water to prepare solution B; (3) Evenly mix sodium bisulfite, FeSO4, mercaptoethanol and water to prepare solution C; (4) Under stirring, control the initial temperature of solution A to be 10-40°C, then drop solution B and solution C into solution A, with the dropwise addition time of solution B being 30-60 min, and the dropwise addition time of solution C being 10-30 min longer than that of solution B; (5) Add glutaraldehyde thereto under stirring and keep warm for 30-60 minutes to carry out a cross-linking reaction to obtain the product.

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