A halogen-free vulcanized polysulfide adhesive remover

Abstract

The present application provides a halogen-free curing polysulfide glue remover, which is simple to configure and easy to prepare, contains only one substance at least, and is compatible when being multi-component, and only needs simple stirring; the raw material is easy to obtain, convenient to store and transport, safe and non-toxic; the acid and the plasticizer can be directly purchased, transported conveniently and safely, and non-toxic; the solidification point is low, the flash point is not low, the application is relatively safe; the toxicity is extremely small, and it is more environmentally friendly; the remover is very friendly to the parts to be removed, and is not easy to cause the metal substrate to rust and corrode; the operation is safe: it can be used at room temperature, and the risk coefficient of the glue removal operation is low; the glue removal effect is good, and the cured polysulfide glue can be removed without residue or directly dissolved, basically without damage to the adhered material; it can be reused, widely applied, suitable for large polysulfide glue factories, suitable for various factories and scenes needing glue removal, and also suitable for individual glue removal.

Description

Technical Field

[0001] This invention belongs to the field of polysulfide adhesive technology and relates to a halogen-free curing polysulfide adhesive remover. Background Technology

[0002] Polysulfide sealant (also known as polysulfide sealant or polysulfide adhesive) is a two-component paste-like sealant. Component A consists of liquid polysulfide rubber, plasticizers, fillers (such as calcium carbonate), silane coupling agents, and additives. Component B consists of curing agents (such as metal oxides like manganese dioxide and peroxides), plasticizers, fillers, and additives. While polysulfide sealant can be single-component or multi-component, two-component sealant is more common. After mixing components A and B, it is applied to the surface of the substrate. After a certain period, a three-dimensional network structure is formed, providing a certain strength and adhesion, enabling bonding or sealing. The cured polysulfide sealant is simply called polysulfide sealant. Because cured polysulfide sealant possesses excellent waterproof and oil-resistant properties, low water vapor permeability, and also exhibits certain strength and good elasticity, its applications are widespread and even irreplaceable in some fields (such as oil-resistant sealing and bonding). Its main applications include sealing aircraft fuel tanks, oil storage tanks, double sealing of insulated glass, and sealing of waterproof and oil-proof joints. When these bonded materials need to be recycled or the cured polysulfide adhesive needs to be reapplied after aging (it cannot be applied directly on top of the old adhesive, otherwise the bond strength between the old and new adhesives will be insufficient, affecting the bonding quality), a relatively simple method is needed to remove it without damaging the bonded objects. Due to its excellent water and oil resistance, the dissolution and removal of cured polysulfide adhesive is extremely difficult; its good strength and adhesion also make mechanical removal of cured polysulfide adhesive somewhat difficult. Convenient and practical methods are rarely seen. Although a composition mentioned in patent CN100567439C is named a "polysulfide sealant solvent," it is actually designed to solve the problem of air bubbles or pits after polysulfide adhesive has cured, and has nothing to do with the dissolution or removal of cured polysulfide adhesive. Domestically, some researchers have used microwave, ultrasonic, and high-energy radiation methods to degrade polysulfide adhesives, but the effects are limited and difficult to apply in practice. Internationally, some researchers have placed cured polysulfide adhesives in a mixed solution of diphenyl disulfide, butanethiol, and thiophenol for several to tens of hours, followed by heating to 180°C and maintaining the temperature for several to tens of hours to degrade them. However, the efficiency is too low and not practically feasible. Relevant information comes from patent CN102766274B, which mentions a more feasible polysulfide adhesive remover. A solution of haloalkanes, nitromethane, and metal halides (which can induce SS bond breakage) is then applied to a workpiece with cured polysulfide adhesive. This method can remove 3mm of polysulfide adhesive in 1 hour while keeping the workpiece intact, demonstrating a degree of feasibility. However, some challenges remain to be addressed. ① The use of both organic and inorganic chlorine has several drawbacks. Firstly, it can easily cause corrosion of metal workpieces (chloride ions or free radicals formed by the degradation of chlorine by short-chain chlorinated alkanes have a significant corrosive effect on metals). Secondly, the use of chlorinated alkanes is not environmentally friendly (due to their toxicity and ozone layer depletion). ② The composition is complex, and nitromethane is a hazardous chemical, making it inconvenient for sale, storage, transportation, and preparation of adhesive removers. ③ The adhesive removal efficiency is still low, and the dissolution of cured polysulfide adhesive by the adhesive remover is not mentioned (in some cases, it is necessary to completely dissolve the polysulfide adhesive).It is clear that there is still a need to find a safe, environmentally friendly, convenient, and fast adhesive remover to remove or even completely dissolve cured polysulfide adhesive.

[0003] Given that cured polysulfide adhesives are oil and water resistant, they are difficult to remove by swelling with organic solvents. Their main nemesis is their insensitivity to certain acids (generally organic acids, which can break the S-S bonds, degrading the cured polysulfide adhesive and thus dissolving or removing it, and may also damage the bonding interface). However, few documents mention which acids to use or how to use them. In our laboratory, we used the silica gel adhesive remover from patent CN115612573A, and found that even after 96 hours, it could not dissolve or remove the cured polysulfide adhesive. This indicates that this silica gel adhesive remover is not suitable for polysulfide adhesives, possibly because of its poor compatibility with cured polysulfide adhesives.

[0004] Of course, burning can also remove adhesive, but the burning temperature needs to be several hundred degrees Celsius. Most of the bonded specimens are not suitable for burning. Even if some specimens can be burned, it will cause certain deformation (such as changes in precision) and affect their use. Therefore, burning is not advisable. Direct mechanical adhesive removal is more troublesome and is prone to leaving residues, which is more likely to affect the strength and adhesion of subsequent adhesive application.

[0005] Therefore, there is an urgent need to develop an environmentally friendly (free of harmful substances and halogens such as chlorine), safe (high boiling and flash points), and efficient (fast and large-volume removal) adhesive remover that can completely remove cured polysulfide adhesive. Combined with appropriate adhesive removal methods, it can remove or dissolve large quantities and thick layers of polysulfide adhesive. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a halogen-free curing polysulfide adhesive remover that is environmentally friendly and free of harmful substances. It has a low freezing point but a relatively high flash point, making it safe for use in summer and preventing freezing in winter. It removes adhesive quickly and in large quantities, effectively and completely eliminating cured polysulfide adhesive.

[0007] The curing polysulfide adhesive remover of this invention has a simple formulation, which may only include acid, and plasticizers may be included for better results. During the research of this invention, screening tests were conducted on both the acid and the plasticizer, and propionic acid and dipropylene glycol dibenzoate showed the best results. Furthermore, the adhesive removal process of the curing polysulfide adhesive remover was studied. For adhesives that are easy to soak, direct soaking is sufficient for complete removal; for adhesives that are inconvenient to soak, covering or coating methods can be used for removal. Experimental results have demonstrated that both methods can achieve complete adhesive removal.

[0008] Extensive testing and verification of this invention have demonstrated that propionic acid or a solution containing the plasticizer dipropylene glycol dibenzoate has a good dissolving effect on cured polysulfide rubber. The adhesive remover containing the plasticizer has an even better dissolving effect because propionic acid itself can degrade the cured polysulfide rubber. As it degrades, the plasticizer carrying the propionic acid can better penetrate the interior of the cured polysulfide rubber, achieving a faster degradation process. The reason no bubbles are generated during the entire process is that pure propionic acid does not contain water, and therefore will not react with the calcium carbonate filler in the polysulfide rubber to produce carbon dioxide bubbles. Throughout the process, the acid acts only as a catalyst, rapidly breaking the S-S bonds to dissolve the cured polysulfide rubber, thus allowing for multiple reuses. The reason the system turns yellow is that the polysulfide rubber is composed of a slightly darker liquid polysulfide rubber, which dissolves in the system as the polymer degrades, causing the system to darken. Although carbon black (generally, a small amount of carbon black is added to the B component of polysulfide rubber as a pigment or filler) dissolves, no bubbles disturb the carbon black, so the system does not appear black. It is worth noting that in addition to improving the sol-gel effect, adding plasticizers can also lower the freezing point or raise the flash point of the entire system (for example, some organic acids have too high freezing points and will freeze in winter; some organic acids have too low flash points and are dangerous to use in summer), so that they will not freeze in winter or be unsafe in summer.

[0009] On one hand, the present invention provides a curing polysulfide adhesive remover, comprising an acid, or comprising an acid and a plasticizer;

[0010] The acid includes one or more acids having the following general formula:

[0011] R-COOH

[0012] Wherein, R is selected from linear or branched C1-C10 alkyl, linear or branched C2-C10 alkenyl, linear or branched C2-C10 alkynyl, and unbranched or branched C3-C10 cycloalkyl; any one or more of the alkyl, alkenyl, alkynyl, or cycloalkyl groups may be substituted by one or more substituents, each of which is independently selected from: cyano, hydroxyl, –ORa group, –C(=O)Ra group, –C(=O)ORa group, carboxyl, or glycidyl, wherein each Ra group is independently selected from linear or branched C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, and C3-C4 cycloalkyl;

[0013] The plasticizer includes any one or more of the following: acetylated tributyl citrate, trioctyl trimellitate, diisononyl cyclohexane-1,2-dicarboxylic acid, dipropylene glycol dibenzoate, diethylene glycol dibenzoate, neopentyl glycol dibenzoate, triethylene glycol dibenzoate, glyceryl tribenzoate, trimethylolpropane tribenzoate, propylene glycol dibenzoate, octyl benzoate, and special liquid resins.

[0014] Furthermore, the acid includes any one or more of lactic acid, formic acid, acetic acid, oxalic acid, propionic acid, phosphoric acid, acrylic acid, butyric acid, and citric acid.

[0015] Preferably, the acid is propionic acid.

[0016] Preferably, the plasticizer is dipropylene glycol dibenzoate.

[0017] Furthermore, calculated by mass parts, the cured polysulfide adhesive remover includes 1-100 parts of acid and 0-100 parts of plasticizer.

[0018] Preferably, the cured polysulfide adhesive remover comprises 1-5 parts acid and 0-5 parts plasticizer by weight.

[0019] Preferably, the cured polysulfide adhesive remover comprises 1 part acid and 0.8 to 1.5 parts plasticizer by weight.

[0020] More preferably, the cured polysulfide adhesive remover comprises 1 part acid and 1 part plasticizer, calculated by weight parts.

[0021] In some embodiments, the cured polysulfide adhesive remover comprises 1 part acid and 0.8 parts plasticizer by weight.

[0022] In some embodiments, the cured polysulfide adhesive remover comprises 1 part acid and 1.5 parts plasticizer, calculated by weight parts.

[0023] In some embodiments, the cured polysulfide adhesive remover also includes fillers.

[0024] In some embodiments, the cured polysulfide adhesive remover is in the form of a paste.

[0025] In some embodiments, the filler comprises any one or more of silica, carbon black, cellulose, silica, and polyvinyl alcohol.

[0026] Adding an appropriate amount of thixotropic filler, such as silica, to the adhesive remover and mixing it yields a thixotropic adhesive remover paste. This paste, when applied to vertically oriented or top-down cured polyurethane, will not drip or sag, making it suitable for objects that cannot be immersed. After application, removing the adhesive with a scraper also yields excellent results.

[0027] On the other hand, the present invention provides a method for removing cured polysulfide adhesive, wherein the cured polysulfide adhesive remover is used to fully contact the cured polysulfide adhesive to be treated.

[0028] Furthermore, the cured polysulfide adhesive can be soaked in the cured polysulfide adhesive remover, or covered with a cloth or degreased cotton soaked in the cured polysulfide adhesive remover, or coated with the cured polysulfide adhesive remover.

[0029] In some methods, before soaking, covering, or coating, deep scratches are made on the surface of the cured polysulfide adhesive with a knife.

[0030] In another aspect, the present invention provides the use of a composition for preparing a fast and complete removal agent for cured polysulfide adhesives, said composition comprising propionic acid and dipropylene glycol dibenzoate.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This adhesive remover is simple to prepare and easy to formulate. The formulation of this invention contains at least one substance, and the multi-component adhesive remover has good compatibility, requiring only simple stirring; while some patented adhesive removers for cured polysulfide adhesives have more components, making the formulation slightly more complex.

[0033] 2. The raw materials for this adhesive remover are readily available, easy to store and transport, and safe and non-toxic: the acid and plasticizer can be purchased directly, and the transportation is convenient, safe and non-toxic;

[0034] 3. This adhesive remover has a low freezing point and a relatively low flash point, making it safe to use.

[0035] 4. Minimal toxicity and more environmentally friendly: The ingredients in this adhesive remover formula are basically non-toxic, while some other adhesive removers contain halogens (especially chlorine), which are not environmentally friendly.

[0036] 5. This adhesive remover is extremely friendly to the parts being removed. General adhesive removers require external force to remove the adhesive and are difficult to completely dissolve it. This adhesive remover can easily dissolve cured polysulfide adhesive. The adhesive remover itself does not contain halogens and will not cause metal parts to rust or corrode due to the adhesive remover itself. The acid is also relatively mild and does not contain water, so it is generally not likely to cause the metal substrate to rust or corrode.

[0037] 6. No operational danger: This adhesive remover can be used at room temperature, and the adhesive removal operation has a low risk factor;

[0038] 7. Excellent adhesive removal effect: This adhesive remover has a better adhesive removal effect and can remove or directly dissolve cured polysulfide adhesive without leaving any residue, and will basically not cause damage to the bonded materials.

[0039] 8. This adhesive remover is reusable, making it more economical and saving labor.

[0040] 9. Wide range of applications: It can solve most of the problems that require dissolving, adhering and curing polysulfide adhesives. It is suitable for large-scale polysulfide adhesive manufacturing plants, various factories and scenarios that require adhesive removal, and also suitable for personal adhesive removal. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to embodiments. It should be noted that the embodiments described below are intended to facilitate understanding of the present invention and are not intended to limit it in any way. Reagents not specifically mentioned in this embodiment are all known products obtained by purchasing commercially available products.

[0042] Example 1: Preparation of the curing polysulfide adhesive remover and the corresponding adhesive removal process provided by the present invention.

[0043] The formula for the cured polysulfide adhesive remover provided in this embodiment is as follows:

[0044] Calculated by mass parts, including 1 to 100 parts of acid and 0 to 100 parts of plasticizer.

[0045] The acid has the following general structural formula: R-COOH; R is selected from linear or branched (C1-C10) alkyl, linear or branched (C2-C10) alkenyl, linear or branched (C2-C10) alkynyl, unbranched or branched (C3-C10) cycloalkyl, and each group may optionally be substituted with one or more substituents: cyano, hydroxyl, -OR a Group, -C(=O)R a Group, -C(=O)OR a Groups, carboxyl groups, glycidyl groups, where R a Each group is independently selected from linear or branched (C1-C4) alkyl, (C2-C4) alkenyl, (C2-C4) ynyl, or (C3-C4) cycloalkyl groups.

[0046] The acid can be one or more of these, such as lactic acid, formic acid, acetic acid, oxalic acid, propionic acid, acrylic acid, butyric acid, citric acid, etc.

[0047] Plasticizers can be any type that can be used in the preparation of polysulfide rubber, but some plasticizers are not used due to their potential carcinogenicity and reproductive toxicity (such as butyl benzyl phthalate), and some containing chlorine elements (such as chlorinated paraffin) are also not used because they can easily cause metal corrosion. The plasticizers are one or more of the following: acetyl citrate tributyl ester (ATBC), trioctyl trimellitate (TOTM), diisononyl cyclohexane-1,2-dicarboxylic acid (DINCH), dipropylene glycol dibenzoate (DPGDB), diethylene glycol dibenzoate (DEGDB), neopentyl glycol dibenzoate, triethylene glycol dibenzoate, glyceryl tribenzoate, trimethylolpropane tribenzoate, propylene glycol dibenzoate, octyl benzoate, and special liquid resin (CAS No.: 68512-30-1).

[0048] Therefore, the preferred formulation of the adhesive remover provided in this embodiment is: 1 part by mass of propionic acid and 1 part by mass of dipropylene glycol dibenzoate. The preparation method is as follows: simply stir and mix 1 part by mass of propionic acid and 1 part by mass of dipropylene glycol dibenzoate.

[0049] The adhesive removal process provided in this embodiment can be divided into the following categories based on whether the object to be removed can be soaked in the adhesive remover:

[0050] ① You can use the soaking method to dissolve the adhesive, remove the excess adhesive layer, and make deep marks on it with a knife (1-2cm apart, so that the adhesive remover can penetrate), soak at room temperature for 96 hours or longer (stirring slightly during this time), and it will dissolve.

[0051] ② For items that are too large to be easily dissolved by soaking, remove the excess adhesive layer first, and make deep marks on them with a knife (1-2cm apart). Cover them with a cloth or cotton wool soaked in adhesive remover, and wait for 60 minutes or longer (during which time remember to re-wet the covering). Remove the adhesive with a knife. If it doesn't work the first time, repeat the process several times.

[0052] ③ You can also add an appropriate amount of silica (or carbon black, cellulose, silica, polyvinyl alcohol, etc.) to the adhesive remover and mix them to obtain a thixotropic adhesive remover paste. It will not drip when applied to non-horizontal surfaces or top-down cured polysulfide adhesives. It is suitable for objects that cannot be soaked. After application, the adhesive can be removed with a scraper, which can also achieve good results.

[0053] Example 2: The adhesive removal effect of the adhesive removal agent and adhesive removal process provided by the present invention.

[0054] This embodiment uses commercially available polysulfide adhesive. After mixing in a specific ratio, the polysulfide adhesive is applied to a stainless steel substrate (approximately 3mm thick) and left to cure for 7 days to simulate the situation in a polysulfide adhesive manufacturing plant where various stainless steel parts are adhered and require adhesive removal. The stainless steel substrate coated with cured polysulfide adhesive is then immersed in the adhesive remover solution at room temperature for 24 hours (deep scratches are made with a knife before immersion for better results). The solution turns a deep yellow, and a small amount of the cured polysulfide adhesive dissolves. When handled with tweezers, the polysulfide adhesive is found to be relatively soft but cannot be crushed. Immersion continues at room temperature for 96 hours. The system turns an even deeper yellow, and half of the polysulfide adhesive dissolves. The remaining polysulfide adhesive is flocculent and can be easily powdered with tweezers, making it completely removable without corroding the stainless steel parts. Therefore, the adhesive remover and removal process provided by this invention can completely remove the cured polysulfide adhesive from a 3mm thick stainless steel substrate after immersion at room temperature for 96 hours. The acid itself is relatively mild and anhydrous, generally not causing corrosion to the metal substrate.

[0055] To simulate the removal of polysulfide adhesive from glass plates, polysulfide adhesive was applied to glass plate specimens (approximately 3 mm thick) and left to cure for 7 days, resulting in glass plate specimens with a 25 mm x 3 mm thick layer of cured polysulfide adhesive (hardness 50 Shore A). This simulated the need for removing polysulfide-coated glass plates in actual use. One group was immersed in the adhesive remover solution for 20 minutes (deep scratches were made with a knife before immersion for better results), while the other group served as a control. Comparison revealed that the cured polysulfide adhesive from the immersed specimen could be easily removed without residue using a blunt-tipped scraper, while the untreated specimen could not be removed. This demonstrates that a 3 mm thick layer of polysulfide adhesive on a glass plate can be removed without residue using this adhesive remover after 20 minutes of immersion.

[0056] The above-mentioned stainless steel substrate and glass plate specimens demonstrate the process of removing adhesive from the two most commonly used materials in practice. The adhesive remover and adhesive removal process provided by this invention can completely remove the cured polysulfide adhesive from the surface of the above two materials without corroding the materials themselves.

[0057] For materials that are inconvenient to dissolve by soaking, we applied polysulfide adhesive to a glass plate specimen (approximately 3 mm thick) and left it for 7 days to fully cure. This resulted in a glass plate specimen coated with cured polysulfide adhesive (hardness 50 Shore A) measuring 25 mm in length and width and 3 mm in thickness. We then made deep incisions on the specimen with a knife (1-2 cm apart), covered it with a cloth soaked in adhesive remover, and waited for 60 minutes. During this time, we repeatedly moistened the covering. We found that the cured polysulfide adhesive could be easily removed without residue using a blunt-tipped scraper.

[0058] Take the same glass plate coated with cured polysulfide adhesive as described above, and make deep marks on it with a knife (1-2 cm apart). Then invert it (glass plate on top, cured polysulfide adhesive on the bottom). Add 0.1 parts by weight of silica to 1 part by weight of adhesive remover and mix well to obtain a thixotropic adhesive remover paste. Apply it to the surface of the cured polysulfide adhesive. It will not drip when inverted. After application, wait 60 minutes. The cured polysulfide adhesive on the surface of the glass plate can be easily removed without residue with a blunt-tipped scraper.

[0059] Therefore, it can be seen that for substances that are difficult to soak, the cured polysulfide adhesive can also be completely removed by covering or coating with a paste.

[0060] Example 3: Effect of different adhesive remover formulations on adhesive removal effect

[0061] First, the effect of different adhesive remover formulations on swelling effect was examined. Several cured polysulfide rubbers (filler containing calcium carbonate, black, 10 Shore A) with a length, width, and thickness of 12 mm were taken as test objects. Multiple sets of adhesive removers were prepared: ① 100 g of dipropylene glycol dibenzoate; ② 100 g of phosphoric acid; ③ 100 g of propionic acid; ④ 50 g of dipropylene glycol dibenzoate + 50 g of propionic acid; ⑤ 100 g of water; ⑥ 100 g of silicone adhesive remover from patent CN115612573A; ⑦ polysulfide rubber remover from patent CN102766274B (15 g of ferric oxide was dissolved in 85 g of nitromethane to prepare a 15 wt% aluminum oxide / nitromethane solution, and 200 g of the above solution was mixed evenly with 400 g of chloropentane to prepare a sealant remover with chloropentane as solvent). The test objects were then immersed in different adhesive removers for 96 hours, and the swelling effect was observed at 24 hours and 96 hours. The results are shown in Table 1.

[0062] Table 1. Effect of different adhesive removers on swelling effect

[0063]

[0064]

[0065] Experiments ① and ⑤ show that polysulfide rubber has excellent oil and water resistance.

[0066] Experiment ② shows that phosphoric acid has a weak dissolving ability for polysulfide adhesive. Because commercially available phosphoric acid contains water, it reacts with calcium carbonate to produce carbon dioxide, thus generating bubbles and dissolving part of the carbon black powder in the polysulfide adhesive (hence the blackening). However, phosphoric acid is not very compatible with cured polysulfide adhesive, so it only dissolves the part and softens it slightly, but it cannot be crushed with tweezers. It is evident that an acid compatible with cured polysulfide adhesive must be found to have a better dissolving and removing ability for cured polysulfide adhesive.

[0067] Experiments ③ and ④ show that propionic acid or its solution containing the plasticizer dipropylene glycol dibenzoate has a good dissolving effect on cured polysulfide rubber, dissolving a 6mm thick layer of cured polysulfide rubber in 96 hours. The adhesive remover containing the plasticizer has an even better dissolving effect because propionic acid itself can degrade the cured polysulfide rubber. As it degrades, the plasticizer carrying the propionic acid can better penetrate the interior of the cured polysulfide rubber, achieving a faster degradation. The reason no bubbles are generated during the entire process is that pure propionic acid does not contain water, and therefore will not react with the calcium carbonate filler in the polysulfide rubber to generate carbon dioxide bubbles. Throughout the process, the acid acts only as a catalyst, rapidly breaking the S-S bonds, thus achieving the "dissolution" of the cured polysulfide rubber, allowing for multiple reuses. The reason the system turns yellow is that the polysulfide rubber is composed of slightly darker liquid polysulfide rubber, which dissolves in the system as the polymer degrades, causing the system to darken. Although carbon black dissolves, no bubbles disturb the carbon black, so the system does not appear black.

[0068] Experiment 6 shows that the silicone adhesive remover has no effect on the swelling or dissolution of cured polysulfide adhesive;

[0069] Experiment ⑦ shows that the polysulfide rubber remover in patent CN102766274B, i.e., the halogen-containing rubber remover, has a poor swelling effect on cured polysulfide rubber and cannot be used in situations where it is necessary to completely dissolve the polysulfide rubber.

[0070] Secondly, we examined the effect of different adhesive remover formulations on the adhesive removal effect. We used a glass sheet coated with cured polysulfide adhesive (hardness 50 Shore A) with a length and width of 25mm and a thickness of 3mm as the test object and selected the following three adhesive removers: ① 50g dipropylene glycol dibenzoate + 50g propionic acid; ② 100g silicone adhesive remover from patent CN115612573A; ③ polysulfide rubber remover from patent CN102766274B. The test results are shown in Table 2.

[0071] Table 2. Effect of different adhesive removers on adhesive removal efficiency

[0072] Serial Number Glue removal results ① Soaking for 20 minutes will remove all residue. ② Unable to remove ③ It cannot be scraped off after soaking for 20 minutes, but can be scraped off with force after soaking for 60 minutes, with a slight residue.

[0073] According to the test results, silicone adhesive remover cannot remove cured polysulfide adhesive. The halogen-free cured polysulfide adhesive remover provided by this invention has a better adhesive removal effect than the polysulfide rubber remover in patent CN102766274B. It can remove polysulfide adhesive without residue after soaking for 20 minutes. It is also halogen-free, safer, and will not corrode the workpiece.

[0074] Therefore, the halogen-free polysulfide adhesive remover provided by this invention is superior in terms of its swelling effect on cured polysulfide adhesive and the time required to remove it from the workpiece surface. It significantly accelerates the swelling of the cured polysulfide adhesive, allowing its use in situations where complete dissolution or removal of the polysulfide adhesive is necessary, thus broadening its application range and reducing the removal time. It is worth noting that the addition of a plasticizer to the polysulfide adhesive remover provided by this invention not only enhances the solvent-solubilizing effect but also lowers the freezing point or raises the flash point of the entire system, preventing freezing in winter and ensuring safety in summer. Therefore, a combination of acid and plasticizer should be preferred for removing cured polysulfide adhesives.

[0075] Example 4: Effect of different acids on degumming effect

[0076] This embodiment uses the method provided in Example 1 to prepare a remover for cured polysulfide adhesive. Eight different acid catalysts, as shown in Table 1, are used. An equal mass of plasticizer dipropylene glycol dibenzoate is added according to the method in Example 1 to obtain eight removers. Stainless steel sheets coated with 12mm thick cured polysulfide adhesive are left to cure for 14 days. They are then immersed in three of the removers for 24 hours and 96 hours respectively, and the removal effect is tested. The influence of different acids on the removal effect is investigated based on factors such as solution color and whether the cured polysulfide adhesive can be crushed with tweezers. The results are shown in Table 2.

[0077] Table 2. Effects of different acids on degumming effect

[0078]

[0079] Table 2 shows that the use of different acids in the adhesive remover directly affects the swelling properties of the cured polysulfide adhesive during the soaking process. Lactic acid, formic acid, acetic acid, propionic acid, acrylic acid, and butyric acid were all selected as the adhesive remover, and all exhibited a certain degree of adhesive removal effect. Among them, propionic acid showed the best effect, and its adhesive removal efficiency far exceeded that of the other acids. This is because propionic acid has the best interaction with the polysulfide adhesive; under the guidance of the plasticizer, it easily penetrates into the interior of the polysulfide adhesive, simultaneously achieving degradation both inside and outside the adhesive. After 24 hours of soaking, the solution is deep yellow, and the polysulfide adhesive is soft. After 96 hours of soaking, the solution is brown, half of the polysulfide adhesive has dissolved, and the remainder appears as flocculent material, easily pulverized into powder with tweezers.

[0080] Example 5: Effect of different plasticizers on desizing effect

[0081] This embodiment uses the method provided in Example 1 to prepare a descaling agent for cured polysulfide adhesive, wherein 1 part by weight of propionic acid and 1 part by weight of plasticizer are selected from the 12 plasticizers in Table 2. Semi-stainless steel sheets coated with 12mm thick glass glue, and stainless steel parts whose polysulfide adhesive has completely cured after 14 days, were immersed in the 12 descaling agents respectively. After immersion for 24 hours and 96 hours, the descaling effect of the cured polysulfide adhesive was tested. The influence of different plasticizers on the descaling effect was investigated based on factors such as solution color and whether the cured polysulfide adhesive could be crushed with tweezers. The results are shown in Table 3.

[0082] Table 3. Effects of different plasticizers on adhesive removal efficiency

[0083]

[0084] As shown in Table 3, plasticizers carrying propionic acid can penetrate the cured polysulfide adhesive more effectively, resulting in faster degradation. However, the effectiveness of polysulfide adhesive removers varies depending on the plasticizer used. The plasticizers used include tributyl acetyl citrate (ATBC), trioctyl trimellitate (TOTM), diisononyl cyclohexane-1,2-dicarboxylic acid (DINCH), dipropylene glycol dibenzoate (DPGDB), diethylene glycol dibenzoate (DEGDB), and neopentyl glycol dibenzoate. Detergents for cured polysulfide adhesives prepared from triethylene glycol dibenzoate, glyceryl tribenzoate, trimethylolpropane tribenzoate, propylene glycol dibenzoate, octyl benzoate, a special liquid resin (CAS No.: 68512-30-1), and propionic acid all exhibit certain adhesive removal effects. Among them, the adhesive remover prepared from diethylene glycol dibenzoate (DEGDB) and propionic acid shows the best adhesive removal performance. This is because the two have good compatibility and can better interact with the polysulfide adhesive, causing degradation both on the outside and inside of the polysulfide adhesive. Immersion for 96 hours can completely remove the cured polysulfide adhesive from the surface.

[0085] Example 6: Effect of acid to plasticizer ratio on descaling effect

[0086] Above, we discussed and obtained the optimal combination of curing polysulfide adhesive: propionic acid and dipropylene glycol dibenzoate. Therefore, we further investigated the effect of their ratio on the adhesive removal effect. We fixed propionic acid at 1 part by mass and adjusted the mass of dipropylene glycol dibenzoate to prepare different adhesive removers. Several stainless steel sheets coated with 12mm thick glass sealant, and stainless steel parts whose polysulfide adhesive had fully cured after 14 days, were immersed in the above adhesive removers. After immersion for 24 hours and 96 hours, the adhesive removal effect was tested. The influence of different ratios of acid and plasticizer on the adhesive removal effect was investigated based on factors such as solution color and whether the cured polysulfide adhesive could be crushed with tweezers. The results are shown in Table 4.

[0087] Table 4. Effect of acid and plasticizer ratio on descaling effect

[0088]

[0089] As shown in Table 4, the ratio of acid to plasticizer affects the adhesive removal effect. Adhesive removers prepared with 1 part by mass of propionic acid and 0 to 100 parts by mass of dipropylene glycol dibenzoate all have a certain adhesive removal effect on cured polysulfide adhesives. Among them, the adhesive remover prepared with 1 part by mass of propionic acid and 1 part by mass of dipropylene glycol dibenzoate has the best adhesive removal effect on cured polysulfide adhesives, and can completely remove the cured polysulfide adhesive on the surface after soaking for 96 hours.

[0090] This invention has been described in detail, but the above embodiments are exemplary. The specific features, structures, materials, or characteristics described can be combined and integrated in any suitable manner in one or more embodiments. Based on this invention, some modifications or improvements can be made, which will be obvious to those skilled in the art. Therefore, all such modifications, improvements, substitutions, or variations made without departing from the spirit of this invention are within the scope of protection claimed by this invention.

Claims

1. A curing polysulfide adhesive remover, characterized in that, Composed of acid and plasticizer; The acid includes one or more acids having the following general formula: R-COOH Wherein, R is selected from linear or branched C1-C10 alkyl, linear or branched C2-C10 alkenyl, linear or branched C2-C10 alkynyl, and unbranched or branched C3-C10 cycloalkyl; any one or more of the alkyl, alkenyl, alkynyl, or cycloalkyl groups may be substituted by one or more substituents, each substituent being independently selected from: cyano, hydroxyl, –ORa group, –C(=O)Ra group, –C(=O)ORa group, carboxyl, or glycidyl, wherein the Ra group is independently selected from linear or branched C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, and C3-C4 cycloalkyl; the acid includes any one or more of lactic acid, formic acid, acetic acid, oxalic acid, propionic acid, acrylic acid, butyric acid, and citric acid. The plasticizer includes any one or more of the following: tributyl acetyl citrate, trioctyl trimellitate, diisononyl cyclohexane-1,2-dicarboxylate, dipropylene glycol dibenzoate, diethylene glycol dibenzoate, neopentyl glycol dibenzoate, triethylene glycol dibenzoate, glyceryl tribenzoate, trimethylolpropane tribenzoate, propylene glycol dibenzoate, octyl benzoate, and a special liquid resin; the CAS number of the special liquid resin is 68512-30-1.

2. The curing polysulfide adhesive remover as described in claim 1, characterized in that, The acid is propionic acid.

3. The curing polysulfide adhesive remover as described in claim 2, characterized in that, The plasticizer is dipropylene glycol dibenzoate.

4. The curing polysulfide adhesive remover as described in claim 3, characterized in that, The cured polysulfide adhesive remover comprises 1-100 parts of acid and 1-100 parts of plasticizer, calculated by weight.

5. The curing polysulfide adhesive remover as described in claim 4, characterized in that, The cured polysulfide adhesive remover comprises 1-5 parts acid and 1-5 parts plasticizer, calculated by weight.

6. A method for removing cured polysulfide adhesive, characterized in that, The curing polysulfide adhesive remover as described in any one of claims 1 to 5 is used to fully contact the curing polysulfide adhesive to be treated.

7. The method as described in claim 6, characterized in that, The cured polysulfide adhesive can be soaked in the curing polysulfide adhesive remover as described in any one of claims 1 to 5, or covered with a cloth or degreased cotton soaked in the curing polysulfide adhesive remover as described in any one of claims 1 to 5, or coated with the curing polysulfide adhesive remover as described in any one of claims 1 to 5.

8. The method as described in claim 7, characterized in that, Before soaking, covering, and coating, make deep scratches on the surface of the cured polysulfide adhesive with a knife.

9. Use of a composition in the preparation of a remover for rapidly and completely removing cured polysulfide adhesive, characterized in that, The composition consists of propionic acid and dipropylene glycol dibenzoate.

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