Silicone oil modified polyether defoaming agent as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of a silicone oil modified polyether defoaming agent, which is characterized in that alkynol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether are subjected to addition reaction under the action of a catalyst to generate the silicone oil modified polyether defoaming agent. The silicone oil modified polyether defoaming agent disclosed by the invention has the characteristics of high foam breaking speed and long foam inhibition period; the defoaming agent provided by the invention has the advantages of high temperature resistance, excellent chemical stability and excellent compatibility, and compared with a traditional polyether defoaming agent, the defoaming agent provided by the invention can achieve a better defoaming effect under the condition of a relatively low addition amount.

Description

Technical Field

[0001] This application relates to the field of papermaking chemicals technology, and more specifically, to a silicone oil-modified polyether defoamer, its preparation method, and its application. Background Technology

[0002] In the papermaking industry, the formation and accumulation of foam is a common problem throughout the entire process, including pulping, papermaking, and coating, significantly impacting production efficiency and final paper quality. During the pulping stage, natural components such as fatty acids and resin acids in the raw materials react with chemicals like caustic soda and sodium sulfide to produce foaming substances such as fatty acid soaps and resin acid soaps. Simultaneously, high molecular weight compounds like cellulose act as foam stabilizers, forming a large amount of stable foam during pulp transport and mixing due to air entrainment. This type of foam not only interferes with subsequent washing, transport, and bleaching operations, causing problems like floating pulp and affecting pulp quality, but also enriches the black liquor with foaming and foam-stabilizing components. If the black liquor is not effectively defoamed, it will hinder subsequent processes and reduce alkali recovery efficiency. In the papermaking process, residual foaming and foam-stabilizing substances in the pulp are also prone to foam formation when air is introduced during mechanical operation. Foaming can cause reduced sizing uniformity, uneven basis weight distribution across the paper width, and may result in defects such as spots, light-transmitting points, or pinholes on the paper surface. In severe cases, it can even lead to paper breaks, directly affecting product quality and production continuity. During the coating process, the presence of easily foaming components such as pigments and alkaline substances, combined with air introduced through mechanical agitation, can easily form three-phase foam composed of liquid film, solid particles, and gas. This type of foam will cause appearance defects such as white spots on the coated surface, affecting the paper's visual appearance and printability.

[0003] While silicone-based defoamers are widely used in various industrial sectors, they still have several drawbacks in practical applications, which limit their applicability and stability of effectiveness in different systems. These drawbacks are as follows: (1) Organosilicon defoamers have the problem of being difficult to disperse in aqueous systems. Since polysiloxanes are themselves difficult to dissolve in water, dispersants are usually needed to assist in emulsification in order to achieve uniform dispersion in aqueous systems. However, excessive dispersant dosage will lead to an overly stable emulsion system, which will weaken the penetration and defoaming ability of the defoamer. Therefore, the amount of dispersant added needs to be strictly controlled, which increases the complexity of the process operation.

[0004] (2) The application effect in oily systems is also not ideal. This type of defoamer has a certain oil solubility and is easy to dissolve or migrate into the oil phase in the oil system, thereby reducing its enrichment ability at the bubble interface and affecting its defoaming efficiency in the actual oil system.

[0005] (3) The stability under high temperature or strong alkaline conditions is still insufficient. When exposed to high temperature for a long time, the silicone defoamer is prone to degradation or failure. In a strong alkaline medium, demulsification and stratification may occur, resulting in a decrease in defoaming performance. Therefore, there are limitations on the pH and temperature range of the environment in which it is used.

[0006] (4) Organosilicon defoamers have poor compatibility in polar solvents. Due to their molecular structure characteristics, they are difficult to achieve uniform dispersion in highly polar solvent systems, which can easily lead to local concentrations that are too high or too low, resulting in inconsistent defoaming effects.

[0007] (5) Such defoamers may have defects in applications such as high-gloss coatings and optical coatings where strict appearance quality requirements are required. Residual silicone components may cause unsightly appearances such as oil spots, haze, or uneven gloss on the surface of the finished product, affecting the visual appearance and performance of the final product.

[0008] In view of the above technical problems, those skilled in the art are dedicated to researching a silicone oil-modified polyether defoamer that solves the above problems while taking into account the environmental friendliness, high efficiency and low price of silicone defoamers, as well as its preparation method and application. Summary of the Invention

[0009] Based on the shortcomings of the existing technology, the purpose of this application is to solve the problems of difficult dispersion, poor defoaming effect of oil system and high requirements for acid and alkali environment of existing silicone defoamers, and to develop a silicone oil modified polyether defoamer with strong defoaming ability, environmental protection and low cost, as well as its preparation method and application.

[0010] Specifically, in a first aspect, this application provides a method for preparing a silicone oil-modified polyether defoamer, comprising the following steps: an addition reaction is carried out between an alkynyl alcohol (EO / PO type) block polyether and an allyl alcohol (PO / EO type) block polyether under the action of a catalyst to generate the silicone oil-modified polyether defoamer. Wherein, EO represents ethoxy, and PO represents propoxy.

[0011] The structural formula of alkynyl alcohol (EO / PO type) block polyether is shown in formula (I) below: Formula (I) Where m is an integer from 1 to 20; n is an integer from 0 to 100.

[0012] The structural formula of allyl alcohol (PO / EO type) block polyether is shown in formula (II) below: Equation (II) Where a is an integer from 1 to 20; b is an integer from 0 to 100.

[0013] Preferably, the specific steps include: S1, alkynol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether undergo a [2+2] cycloaddition reaction under the action of the first catalyst or photoinitiator to generate branched polyether containing a four-membered cyclobutene structure; S2. The branched polyether generated in step S1 and the hydrogen-containing silicone oil are subjected to hydrosilylation under the action of a second catalyst to generate the silicone oil modified polyether defoamer.

[0014] Preferably, step S1 specifically involves mixing alkynyl alcohol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether, adding the first catalyst or photoinitiator, and reacting for 4-8 hours under a nitrogen atmosphere, a temperature of 80-90℃, and ultraviolet light (wavelength 365nm) to generate a branched polyether containing a four-membered cyclobutene structure.

[0015] The reaction route for step S1 is as follows: Preferably, in step S1, the molar ratio of alkynyl alcohol (EO / PO type) block polyether to allyl alcohol (PO / EO type) block polyether is 1:(1-1.5).

[0016] Preferably, in step S1, the first catalyst is a transition metal catalyst, and the amount of the first catalyst is 50-1000 ppm, wherein the first catalyst is selected from Karstedt catalyst; And / or, the photoinitiator is selected from benzophenone, methyl benzoylformate or 4-phenylbenzophenone, and the mass of the photoinitiator added accounts for 0.5%-1.0% of the mass of all substances added in step S1.

[0017] Preferably, step S2 specifically involves mixing the branched polyether generated in step S1 with the hydrogen-containing silicone oil, adding the second catalyst, and reacting the mixture for 3-5 hours under a nitrogen atmosphere and at a temperature of 80-100°C to generate the silicone oil-modified polyether defoamer via a hydrosilylation reaction.

[0018] The reaction route for step S2 is as follows: Preferably, the molar ratio of the branched polyether and the hydrogen-containing silicone oil generated in step S1 is (1-6):1.

[0019] Preferably, the hydrogen-containing silicone oil is a side-hydrogen type hydrogen-containing silicone oil. The structural formula of the hydrogen-containing silicone oil is as follows (III): Equation (III) Where n is an integer between 10 and 150.

[0020] Preferably, the second catalyst is selected from Speier catalysts, Karstedt catalysts, platinum-phosphine complexes, Wilkinson catalysts, ruthenium-based catalysts, iridium-based catalysts, cobalt-based catalysts, or nickel-based catalysts; The amount of the second catalyst used is 3-50 ppm.

[0021] Secondly, this application provides a silicone oil-modified polyether defoamer, prepared by the aforementioned method for preparing silicone oil-modified polyether defoamers. The structural formula of the aforementioned silicone oil-modified polyether defoamer is as follows (IV): Formula (IV) Thirdly, this application provides a method for preparing a silicone oil-modified polyether defoamer, the silicone oil-modified polyether defoamer obtained therefrom, or the application of the silicone oil-modified polyether defoamer in papermaking defoaming treatment.

[0022] The technical solution of this application achieves the following technical effects: 1. The silicone oil modified polyether defoamer of this application has the characteristics of fast foam breaking speed and long foam suppression cycle. The rigid four-membered ring structure in the silicone oil modified polyether defoamer enhances the anchoring ability of molecules on the foam film surface. Due to the block structure between EO and PO, multiple polyether branches are added to the silicone oil chain to form a comb-like branched structure. The branched polyether chain diffuses rapidly to the gas-liquid interface through gradient hydrophilicity and hydrophobicity. The siloxane chain segment provides ultra-low surface tension (about 21 mN / m). The three work together to accelerate foam breaking and inhibit regeneration.

[0023] 2. The defoamer of this application exhibits excellent high-temperature resistance and chemical stability. Its cyclic structure can withstand temperatures above 150°C, its C / C bond energy is higher than that of linear chains, and the steric hindrance of the branched polyether reduces the attack of alkaline solutions (such as black liquor produced in chemical pulping with a pH of 10-13) on the molecular chains. Furthermore, the siloxane segments enhance chemical resistance. Therefore, the defoamer of this application demonstrates excellent resistance in harsh chemical environments such as strong alkalis and strong acids, and is not prone to demulsification or deterioration, greatly expanding its application range and adapting it to the entire papermaking process.

[0024] 3. The defoamer of this application has excellent compatibility with the pulp system. The EO segments of the branched polyether form weak hydrogen bonds with the aqueous phase and cellulose hydroxyl groups. The ring structure reduces molecular aggregation, avoids the "oil floating" problem of traditional organosilicon defoamers, does not interfere with subsequent additives (such as wet strength agents and sizing agents), and avoids the problem of reducing the physical properties of paper.

[0025] 4. The branched structure in the defoamer of this application increases the contact area between the molecules and the foam film. The synergistic effect of the siloxane and the ring structure improves the defoaming efficiency per unit mass and reduces the total dosage. Therefore, compared with traditional polyether defoamers, the defoamer of this application can achieve better defoaming effect at a lower dosage, which can meet the needs of enterprises to reduce costs and increase efficiency.

[0026] The following will further explain the concept, specific structure and technical effects of this application in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of this application. Attached Figure Description

[0027] Figure 1 This is a comparison chart of the defoaming effects of the silicone oil-modified polyether defoamer of this application. Detailed Implementation

[0028] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0029] Some exemplary embodiments of this application have been described for illustrative purposes. It should be understood that this application may be implemented in other ways not specifically shown in the accompanying drawings.

[0030] This application discloses a method for preparing a silicone oil-modified polyether defoamer, wherein an alkynyl alcohol (EO / PO type) block polyether and an allyl alcohol (PO / EO type) block polyether undergo an addition reaction under the action of a catalyst to generate a silicone oil-modified polyether defoamer.

[0031] The structural formula of alkynyl alcohol (EO / PO type) block polyether is shown in formula (I) below: Formula (I) Where m is an integer from 1 to 20; n is an integer from 0 to 100.

[0032] The structural formula of allyl alcohol (PO / EO type) block polyether is shown in formula (II) below: Equation (II) Where a is an integer from 1 to 20; b is an integer from 0 to 100.

[0033] The molecular weights of the alkynyl alcohol (EO / PO type) block polyether and the allyl alcohol (PO / EO type) block polyether in this application are between 100 and 5000.

[0034] The preparation method of the silicone oil modified polyether defoamer of this application specifically includes the following steps: S1. Alkynol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether undergo a [2+2] cycloaddition reaction under the action of a catalyst. Specifically, the alkynol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether are mixed in a molar ratio of 1:(1-1.5), and a first catalyst or photoinitiator is added, accounting for 0.5%-1.0% of the total mass of all added substances in step S1. The reaction is carried out under a nitrogen atmosphere, at a temperature of 80-90℃, and under ultraviolet light (wavelength 365nm) irradiation for 4-8 hours to generate a branched polyether containing a four-membered cyclobutene structure. The catalyst is a transition metal catalyst, selected from Karstedt catalyst (platinum-vinylsiloxane); the amount of the first catalyst is 50-1000 ppm. The photoinitiator is selected from benzophenone, methyl benzoylformate (MBF), or 4-phenylbenzophenone (PBP).

[0035] S2. The branched polyether containing a four-membered cyclobutene structure generated in step S1 and the hydrogen-containing silicone oil undergo a hydrosilylation reaction under a second catalyst to obtain a silicone oil-modified polyether defoamer. The molar ratio of the branched polyether to the hydrogen-containing silicone oil is (1-6):1, and the reaction is carried out under a nitrogen atmosphere at a temperature of 80-100℃ for 3-5 hours. The second catalyst is selected from Speier catalyst, Karstedt catalyst, platinum-phosphine complex, Wilkinson catalyst, ruthenium-based catalyst, iridium-based catalyst, cobalt-based catalyst, or nickel-based catalyst; the amount of the second catalyst is 3-50 ppm; in the specific embodiments of this application, the Speier catalyst is selected from chloroplatinic acid alcohol solution, the Wilkinson catalyst is selected from rhodium chlorotris(triphenylphosphine)alkanoate or tetra(triphenylphosphine)palladium, and the ruthenium-based catalyst is selected from Ru3(CO). 12 The iridium-based catalyst is selected from IrCl(CO)(PPh3)2, the cobalt-based catalyst is selected from Co2(CO)8, and the nickel-based catalyst is selected from nickel-phosphine complexes. The hydrogen-containing silicone oil is a side-hydrogen type hydrogen-containing silicone oil, and its structural formula is shown in formula (III) below: Equation (III) Where n is an integer between 10 and 150.

[0036] The silicone oil-modified polyether defoamer of this application is produced after the aforementioned hydrosilylation reaction. Finally, the silicone oil-modified polyether defoamer obtained by the reaction is heated to 110-120℃ and degassed under vacuum (vacuum degree of -0.09 MPa) for 1-2 hours to remove low-boiling substances and unreacted monomers, thereby improving the purity of the defoamer.

[0037] It should be understood that alkynyl alcohol (EO / PO type) block polyether, allyl alcohol (PO / EO type) block polyether and hydrogen-containing silicone oil can be prepared by conventional methods in the art or purchased, as long as the [2+2] cycloaddition reaction in step 1 of this application can be achieved.

[0038] This application also provides a silicone oil-modified polyether defoamer, which is prepared by the above-described method, and the structural formula of the defoamer is shown in formula (IV) below: Formula (IV) This application also provides an application of a silicone oil-modified polyether defoamer in papermaking defoaming treatment, wherein the defoamer is prepared by the above-described preparation method. The steps for applying this defoamer in papermaking defoaming treatment are as follows: the silicone oil-modified polyether defoamer can be directly added to the defoaming process, or the silicone oil-modified polyether defoamer can be formulated into an emulsion for use in the defoaming process.

[0039] Example 1: Preparation of silicone oil-modified polyether defoamer A 1600 molecular weight alkynyl alcohol (EO / PO type) block polyether and an 800 molecular weight allyl alcohol (PO / EO type) block polyether were mixed at a molar ratio of 1:1. 0.5% (w / w) of benzophenone (photoinitiator) was added, and the mixture was reacted at 80°C under a nitrogen atmosphere with ultraviolet light irradiation (wavelength 365nm) for 4 hours to generate a branched polyether containing a butene four-membered ring. The branched polyether was then mixed with hydrosilicone oil at a molar ratio of 2:1, and a 0.03% (w / w) chloroplatinic acid-isopropanol solution (platinum content 2000 ppm) was added. The mixture was reacted at 80°C under a nitrogen atmosphere for 3 hours. The characteristic peak of the Si-H bond at 2160 cm⁻¹ was measured by infrared spectroscopy. -1 The disappearance of the substance indicates the end of the reaction, proving that a hydrosilylation reaction has occurred. Finally, the temperature is raised to 110°C and degassed under vacuum (0.09 MPa) for 1 hour to remove low-boiling-point substances and unreacted monomers, thereby improving the purity of the product and obtaining a silicone oil-modified polyether defoamer.

[0040] Example 2 Preparation of silicone oil modified polyether defoamer A 100-molecular-weight alkynyl alcohol (EO / PO type) block polyether and a 159-molecular-weight allyl alcohol (PO / EO type) block polyether were mixed at a molar ratio of 1:1.3. 0.7% (w / w) of methyl benzoylformate (MBF) was added, and the mixture was reacted at 85°C under a nitrogen atmosphere with UV irradiation (365 nm) for 5 hours to generate a branched polyether containing a four-membered ring of butene. H-NMR analysis of this branched polyether showed peaks at 1.6 ppm, 2 ppm, 2.3 ppm, and 5.34 ppm, corresponding to different hydrogen environments of the four-membered ring butene, confirming the presence of a four-membered ring structure. The branched polyether was then mixed with hydrogen-containing silicone oil at a molar ratio of 4:1, and 10 ppm of the catalyst rhodium trichlorotriphenylphosphine was added. The mixture was reacted at 90°C under a nitrogen atmosphere for 4 hours, and the characteristic peak of the Si-H bond at 2160 cm⁻¹ was measured by infrared spectroscopy. -1 The disappearance of the substance indicates the end of the reaction. Finally, the temperature is raised to 110℃ and degassed under vacuum (vacuum degree of -0.09 MPa) for 1.3 hours to remove low-boiling substances and unreacted monomers, thereby improving the purity of the product and obtaining silicone oil modified polyether defoamer.

[0041] Example 3 Preparation of silicone oil modified polyether defoamer A 3600 molecular weight alkynyl alcohol (EO / PO type) block polyether and a 4700 molecular weight allyl alcohol (PO / EO type) block polyether were mixed at a molar ratio of 1:1.4. 1% (w / w) of 4-phenylbenzophenone (PBP) was added, and the mixture was reacted at 80°C under a nitrogen atmosphere with ultraviolet light irradiation (wavelength 365nm) for 7 hours to generate a branched polyether containing a butene four-membered ring. The branched polyether was then mixed with hydrosilicone oil at a molar ratio of 5:1, and 30 ppm of tetrakis(triphenylphosphine)palladium catalyst was added. The mixture was reacted at 95°C under a nitrogen atmosphere for 4 hours. The characteristic peak of the Si-H bond at 2160 cm⁻¹ was measured by infrared spectroscopy. -1 The disappearance of the substance indicates the end of the reaction. Finally, the temperature is raised to 115℃ and degassed under vacuum (vacuum degree of -0.09 MPa) for 1.5 hours to remove low-boiling substances and unreacted monomers, thereby improving the purity of the product and obtaining silicone oil modified polyether defoamer.

[0042] Example 4: Preparation of silicone oil-modified polyether defoamer A 5000 molecular weight alkynyl alcohol (EO / PO type) block polyether and a 5000 molecular weight allyl alcohol (PO / EO type) block polyether were mixed at a molar ratio of 1:1.5, and 1000 ppm of Karstedt catalyst was added. The mixture was reacted for 8 hours at 90°C under a nitrogen atmosphere and irradiated with ultraviolet light (wavelength 365 nm) to generate a branched polyether containing a butene four-membered ring. The branched polyether was then mixed with hydrogen-containing silicone oil at a molar ratio of 6:1, and 50 ppm of IrCl(CO)(PPh3)2 catalyst was added. The mixture was reacted for 5 hours at 100°C under a nitrogen atmosphere. The characteristic peak of the Si-H bond at 2160 cm⁻¹ was measured by infrared spectroscopy. -1 The disappearance of the substance indicates the end of the reaction. Finally, the temperature is raised to 120°C and degassed under vacuum (0.09 MPa) for 2 hours to remove low-boiling substances and unreacted monomers, thereby improving the purity of the product and obtaining the silicone oil-modified polyether defoamer.

[0043] Comparative Example 1: Silicone Oil Defoamer Prepare silicone oil defoamer according to the following formula: Oil phase: Silicone oil defoamer paste (self-made, 25% by weight), wherein the silicone oil defoamer paste is prepared according to the following formula: Base silicone oil (main components): high viscosity dimethyl silicone oil (5000 cSt), methyl hydrogen silicone oil, accounting for 60% by mass. Hydrophobic reinforcing filler: Hydrophobic fumed silica (white carbon black, specific surface area 200 m²) 2 / g), accounting for 20% by weight. Emulsifying modifier: Polyether-modified silicone oil, 15% by weight. Structural stabilizer: microcrystalline wax, 5% by mass.

[0044] Emulsifier: Nonionic compound (sorbitan monostearate and polysorbate 80, HLB value 8~10, mass percentage 6%). Aqueous phase: Deionized water (65% by mass); Additives: Preservative (Kasone, 0.2% by mass), antifreeze (propylene glycol, 3.8% by mass).

[0045] The silicone oil defoamer paste was cooled to 40°C for later use. The emulsifier was added to the oil phase paste and stirred until homogeneous, forming an oil-phase mixture. Deionized water was added to a high-speed shear emulsifier, the temperature was raised to 50°C, and the oil-phase mixture was slowly added dropwise at a shear rate of 3000 r / min for 30 min to form a crude emulsion. The crude emulsion was processed three times using a high-pressure homogenizer (20 MPa) to control the emulsion particle size to 3 μm and improve its stability. After cooling to room temperature, preservatives and antifreeze were added, and the mixture was stirred at low speed for 10 min. The pH was adjusted to 6, finally yielding the silicone oil defoamer.

[0046] Comparative Example 2: Higher alcohol defoamer Prepare a higher alcohol defoamer according to the following formula: Higher alcohols: C16~C18 mixed fatty alcohols (17% by mass, melting point 50℃); Emulsifier: Nonionic (polyglycerol fatty acid ester + fatty alcohol polyoxyethylene ether, 5% by mass); Aqueous phase: Deionized water (75% by mass); Additives: co-emulsifier (ethylene glycol, 2.5% by mass), thickener (xanthan gum, 0.5% by mass).

[0047] Deionized water was added to the reaction vessel and heated to 70°C. Emulsifier, co-emulsifier, and thickener were added and stirred until completely dissolved to form a homogeneous aqueous phase. Higher alcohols were added to a melting vessel and heated to 75°C, stirred until completely molten (without solid particles). Under stirring conditions, the molten higher alcohol was slowly added dropwise to the aqueous phase (dropping rate 10 mL / min), maintaining the temperature at 80°C. The mixture was then subjected to high-speed shearing (2500 r / min) for 40 min in a high-speed shear emulsifier to form an oil-in-water emulsion. The emulsion was cooled at a rate of 60°C (holding for 10 min) → 50°C (holding for 10 min) → room temperature to avoid rapid cooling that could cause higher alcohol crystallization. The emulsion was filtered through a 200-mesh filter to remove impurities, and the particle size (5 μm) was measured to obtain the higher alcohol defoamer.

[0048] Comparative Example 3: Polyether Defoamer Polyether defoamer 8120 was purchased from Shanghai Dongda Chemical Co., Ltd.

[0049] Test Example 1: Laboratory Dynamic Defoaming Application Test Take 800ml of white water from a paper mill and add it to a bubbler. Set the test temperature to 55℃ and adjust the impact force to 200L / H to simulate a paper pulping system. The foam height is 500mm. The defoamer dosage is 5ppm. Compare the defoamers prepared in Example 1 and Comparative Examples 1-3. The test results are as follows: Figure 1 As shown.

[0050] from Figure 1As can be seen, all four defoamers reduced the foam height to the minimum value within the same time period. Although the silicone oil-modified polyether defoamer in Example 1 showed a slight increase in foam level, it maintained the foam within the minimum level range over time, demonstrating the fast defoaming speed and long foam suppression period of the silicone oil-modified polyether defoamer of this application. In contrast, the comparative defoamers showed varying degrees of foam level recovery in the later stages, indicating poor stability and defoaming performance. Therefore, the silicone oil-modified polyether defoamer of this application demonstrates high efficiency and long-lasting performance in defoaming and foam suppression, exhibiting excellent performance.

[0051] Test Example 2: Resistance to High Temperatures and Strong Acids / Alkalis High-temperature stability test: The defoamers of Example 1 and Comparative Examples 1-3 were placed in sealed bottles and placed in an oven at 60°C for 7 days to test their defoaming ability; black liquor from a paper mill was taken and bubbled using a bubbler to conduct a bubble test. The activity retention rate was the defoaming rate of the unheated sample compared to the defoaming rate of the heated sample.

[0052] Strong acid and strong alkali resistance test: 1% sodium hydroxide aqueous solution or 1% phosphoric acid aqueous solution was added to the defoamers of Example 1 and Comparative Examples 1-3, respectively, to obtain pH values ​​of 12 or 2. The solutions were then placed in an oven and kept at 40°C for 2 hours. The test results for high temperature resistance and strong acid and alkali resistance are shown in Table 1.

[0053] Table 1 As can be seen from Table 1, the defoaming rate of the comparative defoamer slowed down after high temperature and the activity retention rate decreased significantly. In contrast, the silicone oil modified polyether defoamer of this application has excellent high temperature resistance. Furthermore, under strong acid and strong alkali conditions, the silicone oil modified polyether defoamer of this application has excellent tolerance to harsh chemical environments such as strong alkali and strong acid, and is not prone to demulsification or deterioration.

[0054] Test Example 3 Compatibility Test Wet pulp from a paper mill's headbox was prepared into a 0.5% (w / w) pulp suspension in a beaker. The beaker was placed on a magnetic stirrer at 300 rpm for 5 minutes to ensure uniform fiber dispersion. The stirred suspension was quickly poured into a cuvette (to avoid air bubbles) and the transmittance at 660 nm was measured using a spectrophotometer, recorded as T1. Defoamer from Examples 1 and Comparative Examples 1-3 was added at 0.1% of the concentration, and the stirring speed was maintained at 300 rpm for 10 minutes to ensure thorough mixing of the defoamer with the pulp suspension. After stirring, the mixture was allowed to stand for 30 seconds (to eliminate interference from air bubbles generated during stirring). The upper suspension was then poured into a cuvette and the transmittance at 660 nm was measured, recorded as T2.

[0055] Light transmittance retention rate (%) = T2 / T1 * 100% The light transmittance retention rate can reflect the effect of defoamer on the dispersibility of pulp suspension. The higher the retention rate, the better the compatibility.

[0056] Preparation of blank control group: The wet pulp was prepared into a pulp suspension with a mass fraction of 0.3% in a beaker and magnetically stirred for 5 min at a speed of 300 r / min to ensure that the fibers were evenly dispersed and there were no obvious bubbles.

[0057] Preparation of sample groups: Take pulp suspensions of the same concentration and volume, add the defoamer of Example 1 and Comparative Examples 1-3 at an addition amount of 0.1%, continue stirring for 10 min to fully mix the defoamer with the pulp, and then proceed with sheet making. The specific operation is as follows.

[0058] Check the cleanliness of the hand-operated paper machine filter. Place the machine in a water tank, add the pulp suspensions from the blank control group and sample group, and stir slowly and evenly to avoid fiber clumping. Lift the machine at a uniform speed to drain excess water. Once the wet paper sheet has formed on the filter, use absorbent paper to remove excess surface moisture. Transfer the wet paper sheet to a felt and place it in a rapid dryer at 105°C for 10-15 minutes; or dry it in an oven to constant weight, ensuring a consistent moisture content in the finished paper (approximately 6%-8%). After drying, remove the paper sheet and cut it into standard samples using a paper cutter: whiteness test samples are 50 mm × 50 mm, and tensile strength test samples are 15 mm × 200 mm (longitudinal sampling, meeting standard requirements). Place all samples in a standard constant temperature and humidity chamber for equilibration for 24 hours to eliminate the influence of ambient temperature and humidity on paper properties and ensure accurate test data. The whiteness test (GB / T 7974 standard method) and tensile strength test (GB / T 12914 standard method) were used to test the whiteness and tensile strength of the sample groups obtained from the blank control group and Examples 1 and Comparative Examples 1-3. The results are shown in Table 2.

[0059] Table 2 As shown in Table 2 of the compatibility test, the pulp suspension treated with the silicone oil-modified polyether defoamer of this application exhibits a high light transmittance retention rate, indicating its excellent compatibility with the pulp suspension. Furthermore, after treatment with the silicone oil-modified polyether defoamer of this application, the paper exhibits the least decrease in whiteness and the least loss in tensile strength, proving that the use of the silicone oil-modified polyether defoamer of this application does not reduce the physical properties of the paper, avoiding the problem of traditional organosilicon defoamers interfering with the function of subsequent additives and reducing the physical properties of the paper. In summary, the silicone oil-modified polyether defoamer of this application demonstrates superior compatibility with the pulp system compared to traditional polyether defoamers.

[0060] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A method for preparing a silicone oil-modified polyether defoamer, characterized in that, Alkyne alcohol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether undergo an addition reaction under the action of a catalyst to generate the silicone oil modified polyether defoamer.

2. The preparation method of the silicone oil-modified polyether defoamer according to claim 1, characterized in that, Specifically, the steps include the following: S1, alkynol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether undergo a [2+2] cycloaddition reaction under the action of the first catalyst or photoinitiator to generate branched polyether containing a four-membered cyclobutene structure; S2. The branched polyether generated in step S1 and the hydrogen-containing silicone oil are subjected to hydrosilylation under the action of a second catalyst to generate the silicone oil modified polyether defoamer.

3. The preparation method of the silicone oil-modified polyether defoamer according to claim 2, characterized in that, Step S1 specifically involves mixing alkynyl alcohol (EO / PO type) block polyether and allyl alcohol (PO / EO type) block polyether, adding the first catalyst or photoinitiator, and reacting for 4-8 hours under a nitrogen atmosphere, a temperature of 80-90℃, and ultraviolet light irradiation to generate branched polyether containing a four-membered cyclobutene structure.

4. The preparation method of the silicone oil-modified polyether defoamer according to claim 2, characterized in that, In step S1, the molar ratio of alkynyl alcohol (EO / PO type) block polyether to allyl alcohol (PO / EO type) block polyether is 1: (1-1.5).

5. The preparation method of the silicone oil-modified polyether defoamer according to claim 2, characterized in that, In step S1, the first catalyst is a transition metal catalyst, and the amount of the first catalyst is 50-1000 ppm; And / or, the photoinitiator is selected from benzophenone, methyl benzoylformate or 4-phenylbenzophenone, and the mass of the photoinitiator added accounts for 0.5%-1.0% of the mass of all substances added in step S1.

6. The method for preparing the silicone oil-modified polyether defoamer according to claim 2, characterized in that, Step S2 specifically involves mixing the branched polyether generated in step S1 with the hydrogen-containing silicone oil, adding the second catalyst, and reacting the mixture for 3-5 hours under a nitrogen atmosphere and at a temperature of 80-100°C to generate the silicone oil-modified polyether defoamer via a hydrosilylation reaction.

7. The preparation method of the silicone oil-modified polyether defoamer according to claim 6, characterized in that, In step S2, the molar ratio of the branched polyether and the hydrogen-containing silicone oil generated in step S1 is (1-6):

1. The hydrogen-containing silicone oil is a side-hydrogen type hydrogen-containing silicone oil.

8. The method for preparing the silicone oil-modified polyether defoamer according to claim 6, characterized in that, In step S2, the second catalyst is selected from Speier catalyst, Karstedt catalyst, platinum-phosphine complex, Wilkinson catalyst, ruthenium catalyst, iridium catalyst, cobalt catalyst or nickel catalyst; The amount of the second catalyst used is 3-50 ppm.

9. A silicone oil-modified polyether defoamer, characterized in that, It is prepared by the method of any one of claims 1-8 for the preparation of silicone oil modified polyether defoamer.

10. The application of the silicone oil modified polyether defoamer prepared by the method of any one of claims 1-8, or the silicone oil modified polyether defoamer as described in claim 9, in the defoaming treatment of papermaking.

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