Synthesis and purification method of high molecular weight dielyl-terminated polypropylene glycol for MS adhesive

Abstract

This invention discloses a method for synthesizing and purifying high molecular weight dielyl-terminated polypropylene glycol for MS adhesives, comprising the following steps: polypropylene glycol, an aqueous alkaline catalyst solution, toluene, and a phase transfer catalyst are sequentially added to a reaction vessel; water is completely removed during the reaction; the mixture is cooled to 70-75°C, and allyl chloride is added dropwise over 1-2 hours; the mixture is then aged at 70-75°C for 2-7 hours; a certain amount of deionized water is added, and the aqueous phase is removed by washing; a certain amount of CaCl2 is added to the organic layer, and the mixture is stirred for 2 hours, allowing it to stand and separate into layers to obtain the organic phase; a certain amount of magnesium silicate and diatomaceous earth are added to the organic phase, and after adsorption and stirring for 2 hours, the mixture is filtered; the organic phase is then distilled under reduced pressure to remove toluene, yielding the final product. The product prepared using this invention is transparent, light in color, has a high end-capping rate, low potassium and sodium ion content, and exhibits good reactivity.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for synthesizing and purifying high molecular weight dielyl-terminated polypropylene glycol for MS adhesives. Background Technology

[0002] High molecular weight diallyl-terminated polypropylene glycol (PPG) has highly reactive allyl groups at both ends of its molecule, making it an ideal crosslinking agent for polymerization reactions. PPG also has low unsaturation; silyl-terminated polyethers prepared from this low-unsaturation polyether are the base polymers for MS sealants.

[0003] Because this base polymer has a low double bond content, containing both polyoxypropylene ether as the main chain and silane as the curing functional group, it combines many advantages of silicone sealants and polyurethane sealants: its free radical reaction under ultraviolet light is weak, which will not lead to polymer chain breakage or degradation, thus greatly improving the sealant's UV resistance; the long polyoxypropylene chains in the molecular chain give the molecule low surface energy, and the sealant prepared from this base polymer is also a low surface energy sealant, which makes the sealant have good wetting ability for most inorganic, plastic and metal-based materials.

[0004] Meanwhile, polyether has a lower viscosity than polysulfide or polyurethane of the same molecular weight over a wide temperature range. This low viscosity gives it excellent permeability and diffusion. The synergistic effect of this excellent permeability and diffusion with its low surface energy has become one of the important factors for MS sealant to achieve good adhesion to the substrate. MS sealant has the characteristics of high and low temperature resistance, storage stability, wide range of bonding objects, high strength, oil and media corrosion resistance, and non-staining properties, which are unmatched by other sealants and have a very broad market prospect.

[0005] Currently, the processes available for the synthesis and purification of high molecular weight dielyl-terminated polypropylene glycol are as follows:

[0006] Chinese patent CN 102604069A discloses a method for preparing diallyl-terminated polyethers using monoethylene (propylene) glycol diglycidyl ether or polyethylene (propylene) glycol diglycidyl ether and monoallyl polyether as raw materials under the action of boron trifluoride diethyl ether. The drawbacks of this method are: numerous byproducts, high cost of the raw material glycidyl ether, and the inability to completely remove the raw material, which affects the subsequent silane reaction.

[0007] Chinese patent CN 101885839A discloses a method for preparing end-capped allyl polyethers, which utilizes an organic solvent for azeotropic dehydration, followed by alkali-based alkali alkali oxidation of the polyether, and then the addition of allyl chloride or allyl bromide. However, this method uses a solid alkali. In the end-capping reaction of high molecular weight polyethers, due to the high viscosity, the solid alkali is unevenly distributed in the material system, resulting in poor reactivity. The preparation reaction requires a large feed volume, a long reaction time, and high production costs. Moreover, in the purification stage, this method uses vacuum distillation, followed by filtration and desalting, and finally purification, which is not suitable for high-viscosity materials. The filtration speed of high molecular weight products is extremely slow, making it impossible to remove the salts generated in the reaction by filtration.

[0008] Chinese patent CN 104448284A discloses a method for preparing allyl-terminated polyethers. The method involves pre-reaction, vacuum degassing, dehydration, and then adding a capping agent to achieve the synthesis of dielyl-terminated polyethers. However, this method still uses a solid alkali, so it is not suitable for preparing high-molecular-weight capped polyethers.

[0009] Chinese patent CN 105001408A discloses a method for preparing high molecular weight diallyl-terminated polyethers. Using allyl polyether as a raw material, it reacts with 1,2-dichloroethane in the presence of an alkoxide reagent to obtain diallyl-terminated polyethers with doubled molecular weight. This method suffers from harsh reaction conditions, the use of excessive amounts of the toxic reagent 1,2-dichloroethane, and is harmful to the environment.

[0010] Eiichi Okuno et al. (One-component silicone-modified sealant [J]. Journal of the Japanese Society for Continuing Science, 1993, 29(3):30) obtained allyl alcohol polyethers of suitable molecular weight by chain extension of low molecular weight allyl polyoxypropylene ether with polypropylene glycol (PPG), and finally obtained dielyl-terminated polyethers by allyl end-capping. This method requires multiple reactions with PPG, resulting in increased solid waste, reduced yield, cumbersome process steps, and more byproducts. Moreover, due to incomplete polymerization in each step, the final product has an excessively wide molecular weight distribution, and the performance of the prepared MS sealant product is limited.

[0011] The Jinling Petrochemical Research Institute (Research on Refining Process of Crude Polyether Polyols, Polyurethane Industry, Vol. 18, No. 3, 2003) disclosed a polyether refining process using direct adsorption. An appropriate amount of water is added to crude polyether polyol ZS-2801 (hydroxyl value 55 mg KOH / g, functionality 2, relative molecular weight 2040), and the mixture is heated to a specified temperature. A measured amount of adsorbent is then added, and adsorption is carried out at a constant temperature for several minutes. Dehydration is then performed under vacuum at approximately 120°C for 1 hour, followed by filtration at 90–100°C to obtain the final product. This method is mainly used to remove potassium and sodium ions, as well as polyethers with a molecular weight below 3000. However, it is not suitable for high molecular weight, high viscosity products due to the long filtration time and the inability to completely remove potassium and sodium ions.

[0012] Chinese patent CN 111499858A discloses a method for refining crude viscous polymers. The method involves washing with saturated brine, adsorption with a refining agent, azeotropic dehydration, and recrystallization to remove inorganic salts. The refined product is then obtained after filtration and solvent removal. However, this method uses saturated salt added to the crude polyether to achieve stratification. This method is not suitable for high molecular weight dielyl-terminated polypropylene glycol due to its poor stratification effect.

[0013] Based on this, the present invention patent is proposed. Summary of the Invention

[0014] The purpose of this invention is to solve the problems in the existing technology of preparing high molecular weight dielyl-terminated polypropylene glycol for MS adhesive, such as excessive alkali and allyl chloride feeding ratio, low product end-capping rate, slow filtration speed, dark and opaque product color, and high potassium and sodium ion content.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] A method for synthesizing and purifying high molecular weight dielyl-terminated polypropylene glycol for MS adhesives includes the following steps:

[0017] S1. Add the prescribed amounts of polypropylene glycol, alkaline catalyst aqueous solution, toluene, and phase transfer catalyst to the reaction vessel;

[0018] S2. The polypropylene glycol reacts with the alkaline catalyst to produce water and potassium polypropylene glycol. During the reaction, water is continuously removed, driving the reaction forward until the reaction is complete.

[0019] S3. After dehydration, cool to 70-75℃ and add the formula amount of allyl chloride dropwise over 1-2 hours. After the addition is complete, keep warm at 70-75℃ for 2-7 hours.

[0020] S4. Refining process: After maturation, add a certain amount of deionized water, wash with water, and remove the aqueous phase;

[0021] S5. After washing with water, add a certain amount of CaCl2 to the organic layer, stir for 2 hours, and allow to stand to separate into layers to obtain the organic phase; add adsorbent to the organic phase, stir and adsorb for 2 hours, filter, and distill the organic phase under reduced pressure to remove toluene to obtain the final product.

[0022] The specific principles behind the above synthesis and purification methods are as follows:

[0023] Synthesis stage: To reduce the viscosity of the materials and facilitate mixing, toluene is used as a solvent. Toluene also acts as a dehydrating agent, participating in the azeotropic dehydration reaction. A transfer catalyst is added during the reaction to further promote the reaction between KOH aqueous solution and polypropylene glycol, producing potassium alkoxide and water. The generated water and the water in the KOH solution are removed by a water separator via toluene dehydration. In the latter half of the dehydration process, a certain amount of CaCl2 is added to the water separator to completely remove the water. After the potassium alkoxide is generated, allyl chloride is added dropwise for end capping. After aging at a constant temperature, crude dielyl-terminated polypropylene glycol is obtained.

[0024] Purification stage: Potassium chloride and other substances produced in the reaction are removed by washing with water, dissolving in the aqueous phase. After washing, a certain amount of CaCl2 is added to the organic phase, and the mixture is allowed to stand and separate into layers to remove all moisture. Then, adsorbent and filter aid are added, and the mixture is stirred for adsorption before filtration to obtain a transparent dielyl-terminated polypropylene glycol toluene solution. The presence of toluene significantly reduces the product viscosity, thus shortening the filtration time. Finally, toluene is removed under reduced pressure (it can be recycled and reused) to obtain high molecular weight dielyl-terminated polypropylene glycol for MS adhesives that is transparent, light in color, has a high end-capping rate, and low potassium and sodium ion content.

[0025] Since the synthesis stage of this invention involves reacting a basic catalyst with polyether to generate potassium alkoxide and water as a byproduct, and then removing the water byproduct with toluene to promote the reaction, the basic catalyst can be KOH, NaOH, etc.

[0026] Because organic solvents have very low viscosity (toluene's dynamic viscosity is 0.6 mPa·s) and high molecular weight polyethers (polypropylene glycol) have high viscosity (dynamic viscosity can reach 3000-20000 mPa·s), mixing them significantly reduces the viscosity of the reactants, which is beneficial for mixing and stirring. From the perspective of reducing reactant viscosity, other solvents besides toluene can also achieve the same result. However, as mentioned above, the embodiments of this invention use toluene. On the one hand, toluene acts as a solvent to reduce viscosity; on the other hand, toluene also needs to act as a dehydrating agent to remove the water byproduct generated in the reaction. If other solvents, such as xylene, are used, the concentration of the reaction system can also be reduced. However, as described in S8, the final product needs to be desolventized. Since xylene has a higher boiling point than toluene and is more difficult to remove completely, the final effect is slightly worse than with toluene.

[0027] In a preferred embodiment of the present invention, the molecular weight of the polypropylene glycol in S1 is 6000-20000. All molecular weights mentioned in all embodiments of the present invention are peak molecular weights (Mp).

[0028] In a preferred embodiment of the present invention, the mass fraction of the alkaline catalyst aqueous solution in S1 is 50%, and the molar ratio of polypropylene glycol to potassium hydroxide is 1:2.2-2.5.

[0029] In a preferred embodiment of the present invention, the mass ratio of toluene to polypropylene glycol added in S1 is 0.3-1:1.

[0030] In a preferred embodiment of the present invention, the phase transfer catalyst described in S1 is tetrabutylammonium bromide, dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide, and the mass ratio of the amount added to polypropylene glycol is 0.5‰-1‰:1.

[0031] The S2 process specifically includes: slowly heating to 120-140℃, refluxing for 4-8 hours, removing the separated water using a water separator, and then adding a certain amount of CaCl2 to the water separator and continuing reflux to remove water for another 2 hours.

[0032] In a preferred embodiment of the present invention, the mass ratio of CaCl2 added in S2 to the polypropylene glycol is 1‰-2‰:1.

[0033] In a preferred embodiment of the present invention, the molar ratio of allyl chloride added in S3 to the polypropylene glycol is 2.1-2.5:1;

[0034] In a preferred embodiment of the present invention, the mass ratio of deionized water to polypropylene glycol in S4 is 0.1-0.2:1.

[0035] In a preferred embodiment of the present invention, the mass ratio of deionized water to polypropylene glycol in S5 is 0.1-0.2:1; the mass ratio of CaCl2 to polypropylene glycol is 1%-2%:1; the adsorbent is composed of magnesium silicate and diatomaceous earth, and the mass ratio of the adsorbent to polypropylene glycol is 0.5%-1%:1; the vacuum distillation temperature is 100-130℃, and the vacuum degree is less than 20mbar.

[0036] The reaction principle of this invention:

[0037] Taking potassium hydroxide as an alkaline catalyst as an example, polypropylene glycol reacts with potassium hydroxide in an aqueous solution to produce potassium polypropylene glycol:

[0038]

[0039] Note: 103 ≤ n ≤ 344

[0040] The generated potassium polypropylene glycol reacts with allyl chloride to produce allyl-terminated polypropylene glycol:

[0041]

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] In the synthesis stage, toluene is used as a solvent, which significantly reduces the viscosity of the materials and facilitates mixing of the alkaline catalyst and polypropylene glycol, making stirring easier. The use of an aqueous solution of the alkaline catalyst, compared to a solid catalyst, makes it easier to mix with the materials, resulting in a more complete reaction. Toluene also acts as a dehydrating agent; when the catalyst reacts with the polyether, water is generated as a byproduct, which can be removed by toluene. The combined participation of toluene and the aqueous solution of the alkaline catalyst in the reaction not only reduces the viscosity of the materials but also removes the byproduct water, exhibiting a synergistic effect and enhancing the overall efficiency.

[0044] During the refining stage, the crude polyether (containing polyether and byproducts—salt) dissolves in toluene solvent and easily separates into layers with water. Therefore, after washing with water, the salt in the crude product can be removed by water washing. A small portion of the salt is removed by filtration through adsorption with an adsorbent. Due to the presence of toluene, the material viscosity is low, which speeds up the filtration process and saves filtration time. As a result, the final product is transparent, light in color, has a capping rate of over 95%, potassium and sodium ions are below 10 ppm, and the reactivity is high.

[0045] Furthermore, since this invention relates to an aqueous phase (an aqueous solution of an alkaline catalyst) and an organic phase (a toluene solution of polyether), adding an appropriate amount of phase transfer catalyst can accelerate the reaction. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to specific embodiments.

[0047] Example:

[0048] 1000g of polypropylene glycol (molecular weight X), Ag of KOH solution (mass fraction 50%), and B g of phase transfer catalyst Y were added to a glass reactor. Nitrogen was added three times, followed by the addition of C g of toluene. The mixture was slowly heated to D℃ and refluxed for E h. Water was removed using a water separator. F g of CaCl2 was added to the water separator, and reflux was continued for another 2 h to remove water. After water removal, the mixture was cooled to 70-75℃, and G g of allyl chloride was added dropwise over H h. After the addition, the mixture was aged at 70-75℃ for 1 h. Purification: After aging, J g of deionized water was added, and the mixture was washed to remove the aqueous phase. This washing was repeated three times. After washing, K g of CaCl2 was added to the organic layer, and the mixture was stirred for 2 h. The mixture was allowed to stand and separate into layers to obtain the organic layer. L g of magnesium silicate and L g of diatomaceous earth were added to the organic layer, and the mixture was adsorbed and stirred for 2 h before filtration. The organic layer is subjected to vacuum distillation at 100-130℃ and a vacuum degree of less than 20mbar to remove toluene (toluene can be recycled) and obtain the final product.

[0049] The results of each embodiment are as follows (in the table, the feed ratio is the molar ratio of polypropylene glycol, KOH, and allyl chloride):

[0050]

[0051]

[0052] Comparative example:

[0053] 1000g of polypropylene glycol (molecular weight X) and Ag of solid KOH were added to a glass reactor. Nitrogen was added three times, and the temperature was slowly raised to D℃. Degassing was carried out for E h. The reactor was cooled to 70-75℃, and G g of allyl chloride was added dropwise over H h. After the addition was complete, the reactor was kept at 70-75℃ for 1 h for ripening. Purification: After ripening, J g of deionized water and K g of phosphoric acid were added for neutralization. Then, L g of magnesium silicate and L g of diatomaceous earth were added for adsorption. The temperature was slowly raised to 100℃, and the reactor was dehydrated and filtered to obtain the final product.

[0054]

[0055]

[0056] In the table above, the feeding ratio is the molar ratio of polypropylene glycol, KOH, and allyl chloride.

[0057] Comparison of effects between the examples and comparative examples:

[0058]

[0059] Note: The color testing method is GB / T 9282.1-2008; the hydroxyl value testing method is GB / T 7383-2007.

[0060]

[0061] As can be seen from the table above, the high molecular weight dielyl-terminated polypropylene glycol for MS adhesive obtained by the method of the present invention is transparent, light in color, has a termination rate of over 95%, and has potassium and sodium ions below 10 ppm, exhibiting good reactivity.

[0062] The above description, in conjunction with preferred embodiments of the present invention, provides a further detailed explanation of the technical solution. It should not be construed that the specific embodiments of the present invention are limited to the above-described examples. Simple deductions and substitutions made to the present invention without departing from its conceptual framework are all considered to be within the scope of protection of the present invention.

Claims

1. A method for synthesizing and purifying high molecular weight dielyl-terminated polypropylene glycol for MS adhesives, characterized in that, Includes the following steps: S1. Add the prescribed amounts of polypropylene glycol, alkaline catalyst aqueous solution, toluene, and phase transfer catalyst to the reaction vessel; S2. The polypropylene glycol reacts with the alkaline catalyst to produce water and potassium polypropylene glycol. During the reaction, water is continuously removed, driving the reaction forward until the reaction is complete. S3. After dehydration, cool to 70-75℃ and add the formula amount of allyl chloride dropwise over 1-2 hours. After the addition is complete, keep warm at 70-75℃ for 2-7 hours. S4. Refining process: After maturation, add a certain amount of deionized water, wash with water, and remove the aqueous phase; S5. After washing with water, add a certain amount of CaCl2 to the organic layer, stir for 2 hours, and let stand to separate into layers to obtain the organic phase; add adsorbent to the organic phase, stir and adsorb for 2 hours, filter, and distill the organic phase under reduced pressure to remove toluene and obtain the final product. The polypropylene glycol in S1 has a molecular weight of 6000-20000 and a dynamic viscosity of 3000-20000 mPa·s; The mass ratio of toluene to polypropylene glycol added in S1 is 0.3-1:

1.

2. The method according to claim 1, characterized in that, The alkaline catalyst aqueous solution in S1 has a mass fraction of 50%, the alkaline catalyst is potassium hydroxide, and the molar ratio of polypropylene glycol to potassium hydroxide is 1:2.2-2.

5.

3. The method according to claim 2, characterized in that, The molar ratio of allyl chloride added in S3 to polypropylene glycol is 2.1-2.5:

1.

4. The method according to claim 1, characterized in that, The phase transfer catalyst mentioned in S1 is tetrabutylammonium bromide, dodecyltrimethylammonium bromide, or hexadecyltrimethylammonium bromide, and the mass ratio of the amount added to polypropylene glycol is 0.5‰-1‰:

1.

5. The method according to claim 1, characterized in that, The S2 process specifically includes: slowly heating to 120-140℃, refluxing for 4-8 hours, removing the separated water using a water separator, and then adding a certain amount of CaCl2 to the water separator and continuing reflux to remove water for another 2 hours.

6. The method according to claim 5, characterized in that, The mass ratio of CaCl2 added in S2 to the polypropylene glycol is 1‰-2‰:

1.

7. The method according to any one of claims 1 to 5, characterized in that, The mass ratio of deionized water to polypropylene glycol in S4 is 0.1-0.2:

1.

8. The method according to any one of claims 1 to 6, characterized in that, In step S5, the mass ratio of CaCl2 to polypropylene glycol is 1%-2%:1; the adsorbent is composed of magnesium silicate and diatomaceous earth, and the mass ratio of the adsorbent to polypropylene glycol is 0.5%-1%:1; the vacuum distillation temperature is 100-130℃, and the vacuum degree is less than 20mbar.

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