Bio-based block copolymer water reducing agent and preparation method thereof

Abstract

The invention relates to a bio-based block copolymer water reducing agent and a preparation method thereof. The bio-based block copolymer water reducing agent is prepared from the following raw materials: an unsaturated acid monomer, a functional anchoring monomer, a polyether macromonomer and a bio-based rigid monomer. The general formula of the bio-based rigid monomer is as follows: R1-O-CO-R2-CH = CH2; wherein R1 is a tannic acid residue, a lignin phenolic group or a rosin group, and R2 is a C1-C4 alkylene group. The bio-based block copolymer water reducer product has viscosity reduction, dispersion and enhancement properties, can maintain excellent fluidity and strength stability under a low mixing amount, and avoids the contradiction between fluidity and strength in a traditional system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete admixtures, in particular to a bio-based block copolymer water reducing agent and a preparation method thereof. BACKGROUND

[0002] Polycarboxylate superplasticizer is the most widely used dispersant in high-performance concrete systems, and its molecular structure is usually composed of carboxylic acid adsorption groups and polyether main chains. In order to further improve its rheological properties and environmental adaptability, the existing technology introduces natural bio-based components (such as lignin, tannic acid, etc.) to enhance the renewable nature of the material and the anti-interference ability to impurities such as clay. For example, Chinese patent documents CN111560105B and CN111718448B disclose star-shaped polycarboxylic acid superplasticizers with amine-modified tannic acid as the core, which enhance the adsorption capacity in the mud-containing system by introducing quaternary ammonium salt groups. However, such systems mainly focus on improving adsorption performance, and the synergistic regulation ability between viscosity control and mechanical strength enhancement, which is crucial for concrete workability, is still insufficient.

[0003] The current bio-based superplasticizer system mainly has the following defects: first, the commonly used tannic acid or lignin modified monomers are mostly in the form of amination, which has high molecular flexibility but insufficient rigidity, and is prone to chain segment collapse in the hydration environment, leading to degradation of dispersion performance and reduction of flowability. Second, the existing polymerization process mostly uses single-pot copolymerization method, which lacks precise control of polymer sequence structure, resulting in mixed distribution of adsorption segments and stabilizing segments, and cannot realize directional design and functional optimization of molecular structure. The consequences are limited viscosity reduction effect, poor rheological stability, and difficulty in ensuring the early strength of concrete.

[0004] The root cause of the above problems is that on the one hand, the chemical bond type of the existing bio-based monomer is relatively single, and the molecular chain lacks sufficient steric hindrance and stereorigidity to maintain a stable extended conformation; on the other hand, the lack of sequence control in the polymerization process causes the functional groups to be randomly distributed on the molecular chain. Although bio-based polyphenols have polarity, they tend to form a curled conformation in the flexible main chain, which weakens their directional adsorption efficiency on the surface of cement particles. Due to the failure to achieve sequence structure regulation with "rigidity and flexibility", the rheological response of the polymer is often lagging, ultimately leading to reduced flowability of the cement slurry and uneven strength development.

[0005] If the amount of bio-based monomer is simply increased or rigid components are introduced by physical blending, it is easy to cause the deterioration of water-solubility of the polymer, and the system is precipitated. If too many strong polar monomers are introduced for enhanced adsorption, the viscosity of the mixture will increase sharply, and the workability will be lost. In addition, the conventional copolymerization method is difficult to realize the sequence separation and positioning of bio-based rigid segments and polyether flexible segments at the molecular level, so there is a contradiction between viscosity reduction and enhancement in performance optimization. How to maintain the controllability of the polymerization system and the water-solubility of the product under the premise, and construct the block structure of rigid-flexible synergistic effect through controllable polymerization method has become a technical bottleneck that needs to be broken through in the field. SUMMARY

[0006] Therefore, it is necessary to provide a bio-based block copolymer water reducing agent and a preparation method thereof, which aims to solve the problems in the prior art.

[0007] To achieve the above-mentioned purpose, the present application provides a technical solution:

[0008] A bio-based block copolymer water reducing agent, characterized in that the preparation raw materials of the bio-based block copolymer water reducing agent comprise unsaturated acid monomers, functional anchoring monomers, polyether macromonomers and bio-based rigid monomers.

[0009] The general formula of the bio-based rigid monomer is R1-O-CO-R2-CH=CH2.

[0010] Wherein, R1 is a tannic acid residue, a lignin phenol group or a rosin group, and R2 is a C1-C4 alkylene group.

[0011] Preferably, the functional anchoring monomer comprises at least one of 2-acrylamide-2-methylpropane sulfonic acid and vinyl phosphonic acid.

[0012] Preferably, the bio-based rigid monomer comprises at least one of tannic acid propyl ester, allylated lignin phenol and rosin acid acrylate.

[0013] Preferably, the polyether macromonomer comprises at least one of methyl allyl polyoxyethylene ether and iso-pentenyl polyoxyethylene ether.

[0014] Preferably, the preparation raw materials of the bio-based block copolymer water reducing agent comprise, by weight fraction:

[0015]

[0016] The present application also provides a preparation method of a bio-based block copolymer water reducing agent, comprising the following steps:

[0017] The unsaturated acid monomer, the functional anchoring monomer, and the bio-based rigid monomer are subjected to segmented feeding block polymerization to obtain the bio-based block copolymer water-reducing agent.

[0018] Preferably, the specific steps of segmented feeding block polymerization include:

[0019] S100. Unsaturated acid monomers and functional anchoring monomers are subjected to anchoring block polymerization to obtain anchoring block prepolymer;

[0020] S200. Add polyether macromonomers and bio-based rigid monomers to the anchoring section prepolymer system for block copolymerization to obtain the bio-based block copolymer water-reducing agent.

[0021] Preferably, the mass ratio of the anchoring prepolymer to the bio-based block copolymer water-reducing agent is 1:(1-2).

[0022] Preferably, in step S100, the reaction temperature is 30℃-50℃ and the reaction time is 1h-3h.

[0023] Preferably, in step S200, the reaction temperature is 40℃-50℃ and the reaction time is 3h-5h.

[0024] The beneficial effects of this invention are:

[0025] 1. Green and renewable raw material sources

[0026] This invention uses tannic acid, lignin phenol, and rosin acid as bio-based rigid monomers, replacing some of the petrochemical raw materials in the prior art, which can reduce the environmental burden and meet the requirements of sustainable development.

[0027] 2. Reasonable structural design

[0028] This invention uses stepwise polymerization to form two parts: an anchoring segment and a stable segment. Bio-based rigid monomers and polyether macromonomers synergistically construct an ester-ether block structure with a clear molecular chain sequence and stable conformation.

[0029] 3. Excellent polymerization controllability

[0030] This invention controls the polymerization sequence by step-by-step feeding, enabling precise adjustment of the ratio of anchoring blocks and stabilizing blocks, thereby improving the repeatability of the polymerization reaction and the consistency of the products.

[0031] 4. Overall performance improvement

[0032] The bio-based block copolymer water-reducing agent prepared by this invention has the properties of viscosity reduction, dispersion and reinforcement. It can maintain excellent flowability and strength stability at low dosage, avoiding the contradiction between flowability and strength in traditional systems.

[0033] 5. The process is simple and can be scaled up.

[0034] The reaction conditions of this invention are mild, the solvent system is water, the entire process is green and safe, it is compatible with the polycarboxylate superplasticizer mother liquor system, and it is easy to promote industrialization.

[0035] 6. Stable storage and use

[0036] The bio-based block copolymer water-reducing agent prepared by this invention is a water-soluble liquid with a pH range of 6.5–7.0. It can remain stable for more than six months without coagulation, precipitation or stratification, and is suitable for various concrete mix proportion systems. Detailed Implementation

[0037] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0038] In the embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0039] A bio-based block copolymer water-reducing agent, characterized in that the raw materials for preparing the bio-based block copolymer water-reducing agent include unsaturated acid monomers, functional anchoring monomers, polyether macromonomers, and bio-based rigid monomers;

[0040] The general formula of the bio-based rigid monomer is: R1-O-CO-R2-CH=CH2;

[0041] R1 is a tannic acid residue, lignin phenol group or rosin group, and R2 is a C1-C4 alkylene group.

[0042] In some embodiments, the functional anchoring monomer includes at least one of 2-acrylamido-2-methylpropanesulfonic acid and vinylphosphonic acid.

[0043] In some embodiments, the bio-based rigid monomer includes at least one of propyl tannate, allylated ligninol, and rosin acrylate.

[0044] In some embodiments, the polyether macromonomer includes at least one of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether.

[0045] In some embodiments, the raw materials for preparing the bio-based block copolymer water-reducing agent, by weight, include:

[0046]

[0047] This invention also provides a method for preparing a bio-based block copolymer water-reducing agent, comprising the following steps:

[0048] The unsaturated acid monomer, the functional anchoring monomer, and the bio-based rigid monomer are subjected to segmented feeding block polymerization to obtain the bio-based block copolymer water-reducing agent.

[0049] In some embodiments, the specific steps of segmented feeding block polymerization include:

[0050] S100. Unsaturated acid monomers and functional anchoring monomers are subjected to anchoring block polymerization to obtain anchoring block prepolymer;

[0051] S200. Add polyether macromonomers and bio-based rigid monomers to the anchoring section prepolymer system for block copolymerization to obtain the bio-based block copolymer water-reducing agent.

[0052] In some embodiments, the mass ratio of the anchoring prepolymer to the bio-based block copolymer water-reducing agent is 1:(1-2).

[0053] In some embodiments, in step S100, the reaction temperature is 30°C-50°C and the reaction time is 1h-3h.

[0054] In some embodiments, in step S200, the reaction temperature is 40°C-50°C and the reaction time is 3h-5h.

[0055] Example 1:

[0056] Weigh out 10g of acrylic acid (AA), 3g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 2g of vinylphosphonic acid (VPA) and 0.2g of sodium hypophosphite, and prepare solution A;

[0057] Weigh 45g of methyl allyl polyoxyethylene ether (MPEG, Mn=2000) and 6g of propyl tannate, and prepare solution B.

[0058] S100. First Stage (Anchoring Segment Convergence):

[0059] Add 100g of deionized water to a 500mL four-necked reactor, purge with nitrogen for 30min to remove oxygen, heat to 60℃, add solution A dropwise to the four-necked reactor, and add 0.6g of ammonium persulfate (APS) at the same time. The reaction continues for 2 hours to form an anchoring prepolymer rich in carboxyl and sulfonic acid groups.

[0060] S200. Second Stage (Stable Block Aggregation):

[0061] Maintain the reaction temperature at 40℃–50℃ and begin adding solution B dropwise over 3 hours. During this process, continue adding 0.4g of APS to maintain the free radical concentration. After the reaction is complete, keep the temperature constant for 1 hour to ensure complete monomer conversion.

[0062] S300. Post-processing:

[0063] After the reaction is complete, the mixture is allowed to cool naturally to room temperature, and the pH is adjusted to 6.8 using 25 wt.% sodium hydroxide. After filtering out impurities, a light yellow, transparent liquid product is obtained, which is the bio-based block copolymer water-reducing agent.

[0064] The steps in other embodiments are the same as in Embodiment 1, with the differences shown in Table 1.

[0065] Table 1 Conditions in each embodiment

[0066] Project Example 2 Example 3 Bio-based rigid monomer Allylated lignin phenol Rosin acid acrylate Polyether macromonomer TPEG (Mn = 1800) MPEG (Mn = 1500) Anchoring segment monomer ratio (AA:AMPS:VPA) 10:3:2 12:3:3 Bio-based monomer content (wt%) 8 10 Oxidant amount (g) 1.2 0.8 Reducing agent amount (g) 0.4 0.7 Reaction temperature (°C) 60 65 Reaction time (h) 3 4

[0067] Implementation Instructions and Work Requirements

[0068] 1. The polymerization reaction system of the present invention uses water as a solvent, requiring no organic solvents or surfactants, making the operation safe and environmentally friendly.

[0069] 2. The stepwise feeding process requires high control over the reaction temperature and initiator concentration. It is recommended to use an automatic dropping device to maintain a constant rate.

[0070] 3. After polymerization, avoid high-temperature drying to prevent polymer chain breakage; it is recommended to store it in the form of mother liquor.

[0071] 4. The product is suitable for cement dosages of 300–500 kg / m³. 3 The admixture dosage in the concrete system is 0.15–0.25 wt% of the cement mass.

[0072] In order to objectively evaluate the beneficial effects of the present invention, we designed the following comparative examples and compared them based on the method of controlling variables.

[0073] 1. Comparative Example 1 (without bio-based monomers)

[0074] The other steps are exactly the same as in Example 1, except that:

[0075] In the preparation of bio-based block copolymer water-reducing agent, no bio-based rigid monomer (propyl tannate) is added, and the mass of polyether macromonomer MPEG is increased to 51g to keep the total monomer amount unchanged.

[0076] 2. Comparative Example 2 (no stepwise polymerization, single-stage feeding)

[0077] The other steps are exactly the same as those in Example 1, except that:

[0078] In the preparation of the bio-based block copolymer water-reducing agent, all monomers (including acrylic acid, AMPS, VPA, MPEG and propyl tannate) are added to the reactor at one time and reacted at 60°C for 4 hours.

[0079] 3. Comparative Example 3 (Commercial Water-Reducing Agent Control)

[0080] Point-S polycarboxylate superplasticizer, produced by Kezhijie New Materials Group Co., Ltd., is based on random copolymer and has a solid content of 20%.

[0081] All examples and comparative examples were tested according to the same verification method. The verification method mainly referred to the Chinese national standards "GB / T 50080-2016 Standard for Test Methods of Performance of Concrete Mixtures" and "GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test conditions were uniformly set as follows: C50 concrete mix proportion (cement content 500 kg / m³). 3 (Water-cement ratio 0.4), the water-reducing agent dosage was 0.4% of the cementitious material mass, and the results are shown in Table 2.

[0082] Table 2 Verification Results

[0083]

[0084] As shown in Table 2, compared with Comparative Example 3 (100%), the 28-day compressive strength ratios of Examples 1 to 3 of the present invention all achieved a significant improvement of more than 10% (110%-113%).

[0085] Comparative Example 1 (non-biobased) vs. Example 1:

[0086] The strength ratio of Comparative Example 1 was 108%, which was better than that of the commercial product, but significantly lower than that of Example 1 (112%). This clearly demonstrates that introducing bio-based rigid monomers into the stepwise polymerization framework can provide an additional strength gain of approximately 4%.

[0087] Comparative Example 2 (one-time feeding) vs. Example 1:

[0088] The strength ratio of Comparative Example 2 was only 102%, far lower than that of Example 1 (112%). This fully demonstrates that even with the exact same raw materials, without precise control of the molecular sequence through stepwise block polymerization, ideal performance cannot be obtained.

[0089] Even the defective Comparative Examples 1 and 2 showed slightly higher strength ratios (108% and 102%) than the commercial products, demonstrating the overall superiority of the technical route (stepwise block polymerization) of the present invention.

[0090] However, the higher data (110%-113%) in Examples 1-3 demonstrate the synergistic amplification effect of combining the "introduction of bio-based rigid monomers" with "stepwise block polymerization".

[0091] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A bio-based block copolymer water-reducing agent, characterized in that, The raw materials for preparing the bio-based block copolymer water-reducing agent include unsaturated acid monomers, functional anchoring monomers, polyether macromonomers, and bio-based rigid monomers. The general formula of the bio-based rigid monomer is: R1-O-CO-R2-CH=CH2; R1 is a tannic acid residue, lignin phenol group or rosin group, and R2 is a C1-C4 alkylene group.

2. The bio-based block copolymer water-reducing agent according to claim 1, characterized in that, The functional anchoring monomer includes at least one of 2-acrylamide-2-methylpropanesulfonic acid and vinylphosphonic acid.

3. The bio-based block copolymer water-reducing agent according to claim 1, characterized in that, The bio-based rigid monomer includes at least one of propyl tannin, allylated lignin phenol, and rosin acid acrylate.

4. The bio-based block copolymer water-reducing agent according to claim 1, characterized in that, The polyether macromonomer includes at least one of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether.

5. The bio-based block copolymer water-reducing agent according to claim 1, characterized in that, The raw materials for preparing the bio-based block copolymer water-reducing agent, by weight, include:

6. A method for preparing a bio-based block copolymer water-reducing agent as described in any one of claims 1 to 5, characterized in that, Including the following steps: The unsaturated acid monomer, the functional anchoring monomer, and the bio-based rigid monomer are subjected to segmented feeding block polymerization to obtain the bio-based block copolymer water-reducing agent.

7. The method according to claim 6, characterized in that, The specific steps of segmented feeding block polymerization include: S100. Unsaturated acid monomers and functional anchoring monomers are subjected to anchoring block polymerization to obtain anchoring block prepolymer; S200. Add polyether macromonomers and bio-based rigid monomers to the anchoring section prepolymer system for block copolymerization to obtain the bio-based block copolymer water-reducing agent.

8. The method according to claim 7, characterized in that, The mass ratio of the anchoring section prepolymer to the bio-based block copolymer water-reducing agent is 1:(1-2).

9. The method according to claim 7, characterized in that, In step S100, the reaction temperature is 30℃-50℃ and the reaction time is 1h-3h.

10. The method according to claim 7, characterized in that, In step S200, the reaction temperature is 40℃-50℃ and the reaction time is 3h-5h.

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