Preparation method of low-odor hydrogen-containing polysiloxane

Abstract

The invention discloses a preparation method of low-odor hydrogen-containing polysiloxane, which comprises the following steps: adding hydrogen-containing silicone oil, toluene and a platinum catalyst into a four-neck flask, slowly heating to 80 DEG C, dropwise adding DS-300, heating to 85 DEG C after dropwise adding, reacting for 2 hours, adding baked activated carbon into the four-neck flask in two times, reacting for 2 hours after the reaction is finished, and cooling to room temperature to obtain the low-odor hydrogen-containing polysiloxane. Adding activated carbon for the first time, reacting for 3 hours, filtering the activated carbon, adding activated carbon for the second time, reacting for 3 hours, filtering the activated carbon by a sand core funnel, adding the residual filtrate into a clean reaction kettle, carrying out rotary distillation to obtain a solvent, adding a low-boiling-point solvent after distillation, and carrying out secondary reduced pressure distillation to obtain the low-odor hydrogen-containing polysiloxane. According to the technical scheme, after most of low-boiling-point substances (such as unreacted D4 / D5) are removed through primary distillation, a low-boiling-point solvent (such as methyl cyclohexane) is added, and residual trace low-molecular substances (such as cyclic siloxane D3-D6) are azeotrope-brought out through secondary reduced pressure distillation, so that the odor of the product is further reduced.

Description

Technical Field

[0001] The present invention relates to a method for preparing a low-odor hydrogen-containing polysiloxane. Background Art

[0002] The existing method for preparing hydrogen-containing polysiloxane is as follows: Put hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heat up to 80 °C, dropwise add DS-300. After the addition is complete, heat up to 85 °C and react for 2 h, then distill out the low-boiling substances to obtain the synthetic product. However, for the hydrogen-containing polysiloxane produced by this preparation method, the residual low-molecular cyclic siloxanes (D3-D6) in the product cause a strong odor. Since it is the odor inherent in the raw materials themselves, it is rather difficult to completely remove it. Previously, only by increasing the reaction ratio to make the raw materials react completely, this method is also a bit difficult because of the chemical bond steric hindrance. Whether increasing the temperature or increasing the amount of catalyst cannot achieve a 100% reaction efficiency; traditional purification methods (such as single distillation or activated carbon treatment) cannot completely remove the odor substances, which limits its application in fields such as food packaging and medical devices. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for preparing a low-odor hydrogen-containing polysiloxane.

[0004] To solve the above-mentioned existing technical problems, the present invention adopts the following technical solutions:

[0005] A method for preparing a low-odor hydrogen-containing polysiloxane, comprising the following steps: Put hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heat up to 80 °C, dropwise add DS-300. After the addition is complete, heat up to 85 °C and react for 2 h. Add the baked activated carbon into the four-necked flask in two portions. After the first addition of activated carbon and reaction for 3 h, filter the activated carbon. The second time, add activated carbon and react for 3 h, and filter the activated carbon with a sintered glass funnel. Add the remaining filtrate into a clean reaction kettle, rotate to distill out the solvent, and after distillation, add a low-boiling solvent for secondary vacuum distillation to obtain a low-odor hydrogen-containing polysiloxane.

[0006] Preferably, the baked activated carbon and arbutin are added into the four-necked flask together, and the arbutin forms an ester bond with the carboxyl group on the surface of the activated carbon through a phenolic hydroxyl group.

[0007] Preferably, the baked activated carbon and photoglucosamine are added into the four-necked flask together.

[0008] Preferably, the low-boiling solvent is methylcyclohexane.

[0009] Preferably, the activated carbon is composed of macroporous activated carbon with a pore diameter > 5 nm and microporous activated carbon with a pore diameter < 2 nm.

[0010] Preferably, the activated carbon is coconut shell, and the iodine value of the coconut shell is < 800 mg / g.

[0011] The beneficial effects of the present invention are as follows:

[0012] In the technical solution of this application, after most of the low-boiling substances (such as unreacted D4 / D5) are removed by the first distillation, a low-boiling solvent (such as methylcyclohexane) is added, and the residual trace low-molecular substances (such as cyclic siloxanes D3-D6) are azeotropically carried out by the second vacuum distillation, further reducing the product odor and impurity content.

[0013] In the present invention, through the "gradient adsorption - solvent supplementary extraction" synergistic process, the residual cyclic siloxanes in the hydrogen-containing polysiloxane are reduced to less than 50 ppm. The gradient adsorption (physical sieving + chemical bonding) and solvent supplementary extraction (azeotropic carrying out) form a complementarity; the phenolic hydroxyl group (-OH) of arbutin can form hydrogen bonds or coordination bonds with the Si-O bond of the siloxane, improving the adsorption selectivity. The arbutin molecule can partially block the macropores of the activated carbon, forming a denser microporous structure, preferentially adsorbing small-molecule siloxanes (such as D3-D6); the antioxidant property of arbutin can reduce the oxidative degradation on the surface of the activated carbon and extend its service life. Detailed Embodiments

[0014] Reference will now be provided in detail to embodiments of the present invention, one or more examples of which are described below. Each example is provided by way of explanation and not limitation of the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the present invention. For example, features illustrated or described as part of one embodiment can be used in another embodiment to yield a still further embodiment.

[0015] Accordingly, it is intended that the present invention cover such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description or are apparent therefrom. Those of ordinary skill in the art should understand that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0017] Except as otherwise indicated or shown in the operating examples, all numbers used in the specification and claims to indicate amounts of ingredients, physical and chemical properties, etc. are understood to be adjusted by the term "about" in all cases. For example, thus, unless otherwise stated, the numerical parameters listed in the above specification and the appended claims are approximate values, and those skilled in the art can appropriately change these approximate values to obtain the desired characteristics by using the teachings disclosed herein. The use of numerical ranges expressed with endpoints includes all numbers within the range and any range within that range. For example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0018] A preparation method of a low-odor hydrogen-containing polysiloxane, comprising the following steps: putting hydrogen-containing silicone oil, toluene and a platinum catalyst into a four-necked flask, slowly heating to 80 °C, dropping DS-300 (terminal hydroxyl polydimethylsiloxane), after dropping, heating to 85 °C and reacting for 2 h, adding the baked activated carbon into the four-necked flask in two portions, filtering the activated carbon after reacting for 3 h for the first addition of activated carbon, adding the activated carbon for the second time and reacting for 3 h, filtering the activated carbon with a sintered glass funnel, adding the remaining filtrate into a clean reaction kettle, rotary distilling out the solvent, and performing secondary vacuum distillation after distillation by adding a low-boiling solvent to obtain the low-odor hydrogen-containing polysiloxane.

[0019] Further, the baked activated carbon and arbutin are added into the four-necked flask together, and the arbutin forms an ester bond with the carboxyl group on the surface of the activated carbon through a phenolic hydroxyl group.

[0020] Further, the baked activated carbon and glufosinate are added into the four-necked flask together.

[0021] Further, the low-boiling solvent is methylcyclohexane.

[0022] Further, the activated carbon is composed of macroporous activated carbon with a pore diameter > 5 nm and microporous activated carbon with a pore diameter < 2 nm.

[0023] Control group 1

[0024] Put hydrogen-containing silicone oil, toluene and a platinum catalyst into a four-necked flask, slowly heat to 80 °C, drop DS-300, after dropping, heat to 85 °C and react for 2 h, distill out the low-boiling substances to obtain the synthetic product.

[0025] Control group 2

[0026] Put hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heat up to 80 °C, dropwise add DS-300. After the addition is complete, heat up to 85 °C and react for 2 h. After the reaction is completed, cool down to room temperature, add a certain amount of activated carbon (physical method, need to be baked before use) in proportion and treat for 3 h, filter off the activated carbon; add activated carbon for the second time, treat for 3 h, filter off the activated carbon with a sintered glass funnel, add the filtrate into a clean reaction kettle, and rotary distill the solvent to obtain the synthetic product;

[0027] Control group 3

[0028] Put hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heat up to 80 °C, dropwise add DS-300. After the addition is complete, heat up to 85 °C and react for 2 h, distill off the low-boiling substances. After distillation, add a low-boiling solvent (methylcyclohexane) for secondary extraction to bring out the low-molecular substances in the material and reduce the product odor.

[0029] Control group 4

[0030] Put hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heat up to 80 °C, dropwise add DS-300. After the addition is complete, heat up to 85 °C and react for 2 h. After the reaction is completed, cool down to room temperature, add a certain amount of activated carbon (physical method, need to be baked before use) in proportion and treat for 3 h, filter off the activated carbon; add activated carbon for the second time, treat for 3 h, filter off the activated carbon with a sintered glass funnel, add the filtrate into a clean reaction kettle, and rotary distill the solvent. After distillation, add a low-boiling solvent (methylcyclohexane) for secondary extraction to bring out the low-molecular substances in the material and reduce the product odor.

[0031]

[0032] It can be proved by the above data that in the above technical solution, the technical solution of the present application (i.e., control group 4) removes most of the low-boiling substances (such as unreacted D4 / D5) by primary distillation, then adds a low-boiling solvent (such as methylcyclohexane), and azeotropically distills out the residual trace low-molecular substances (such as cyclic siloxanes D3-D6) by secondary vacuum distillation, further reducing the product odor and impurity content; the improvement of this process can solve the problem that it is difficult to separate the boiling point of conventional distillation from the main product in one step.

[0033] Control group 5

[0034] Reaction stage: Add hydrogen-containing silicone oil (Si-H content 1.5%), toluene and platinum catalyst (10 ppm) into a four-necked flask, dropwise add DS-300 (hydroxyl silicone oil, Mn = 2000) at 80 °C, and react at 85 °C for 2 h.

[0035] Gradient adsorption: First time: Add macroporous activated carbon (pore diameter > 5 nm) baked at 150 °C with a content of 5 wt%, stir at room temperature for 3 h, and filter; Second time: Add amino-functionalized microporous activated carbon (modified with KH-550, pore diameter < 2 nm) with a content of 3 wt%, stir at 40 °C for 3 h, and filter through a sintered glass funnel.

[0036] Solvent supplementary extraction: After removing most of the low-boiling substances by rotary evaporation, cool down to 60 - 80 °C, and add n-hexane according to the volume ratio of solvent:material = 1:5.

[0037] Secondary vacuum distillation: Vacuum the system to -0.08 to -0.095 MPa; Slowly heat up to 50 - 60 °C, collect the azeotrope until the distillate is clear without oil droplets (about 1 - 2 h).

[0038] Comparison with the traditional process

[0039]

[0040] By introducing the secondary supplementary extraction process of low-boiling solvents and forming a synergistic purification system with gradient activated carbon adsorption, it was unexpectedly found that the residue of cyclic siloxanes could be reduced to less than 1 / 10 of the traditional method without affecting the Si-H activity.

[0041] Detection results: The residue of D4 is 42 ppm, and the odor grade is 1.

[0042] Control group 6

[0043] Based on Example 1, during the second adsorption, activated carbon and 1 wt% arbutin were added together.

[0044] Effect: The residue of D4 was reduced to 28 ppm, and the regeneration efficiency of activated carbon was increased to 90%.

[0045] Arbutin (a natural phenolic glycoside with a structure containing a hydroquinone group) improves the adsorption performance of activated carbon in the following ways: The phenolic hydroxyl group (-OH) of arbutin can form hydrogen bonds or coordination bonds with the Si-O bond of siloxanes, improving the adsorption selectivity; The arbutin molecule can partially block the macropores of activated carbon, forming a denser microporous structure, preferentially adsorbing small molecule siloxanes (such as D3 - D6); The antioxidant property of arbutin can reduce the oxidative degradation on the surface of activated carbon and extend its service life.

[0046] Different from traditional modification methods (most existing technologies use strong acid / alkali treatment or metal loading, while arbutin is a natural and non-toxic modifier, in line with the trend of green chemistry). For the first time, arbutin was combined with silicone oil purification to solve the problems of low adsorption capacity and poor selectivity of activated carbon for siloxanes.

[0047] Experimental data

[0048]

[0049] The adsorption capacity of activated carbon with arbutin increased by 2.3 times, and the regeneration performance was excellent. The selectivity for cyclic siloxane (D3 / D4) was significantly improved, making it suitable for the production of high-purity silicone oil.

[0050] Control group 7 (glabridin-assisted)

[0051] During the second adsorption, the activated carbon was loaded with 0.5 wt % zinc phthalocyanine (glabridin) and irradiated with ultraviolet light (365 nm) for 30 min after adsorption.

[0052] Experimental group Adsorption capacity (mg / g) <![CDATA[Adsorption rate (min -1 )]]> Unmodified activated carbon 120 0.05 Glyphosine-modified activated carbon 300 0.20

[0053] The adsorption capacity of glabridin-modified activated carbon increased by 2.5 times.

[0054] Effect: D4 residue is 22ppm, and the adsorption capacity remains 95% after light regeneration.

[0055] The present invention reduces the residual cyclic siloxane in hydrogen-containing polysiloxane to below 50 ppm through the "gradient adsorption-solvent supplementary extraction" synergistic process, and the gradient adsorption (physical screening + chemical bonding) and the solvent supplementary extraction (azeotropic removal) complement each other; the phenolic hydroxyl group (-OH) of arbutin can form a hydrogen bond or a coordination bond with the Si-O bond of siloxane to improve the adsorption selectivity; the arbutin molecules can partially block the macropores of the activated carbon to form a denser microporous structure, and preferentially adsorb small molecular siloxanes (such as D3-D6); the antioxidant property of arbutin can reduce the oxidative degradation of the surface of the activated carbon and extend its service life.

[0056] The activated carbon used is coconut shell with an iodine value of <800 mg / g.

[0057] Although the present invention is described in detail with reference to the above embodiments, it is obvious to those skilled in the art through this disclosure that various changes or modifications may be made to the present invention without departing from the principle and spirit of the present invention defined by the claims. Therefore, the detailed description of the embodiments of the present disclosure is only used to explain, not to limit the present invention, but the scope of protection is limited by the content of the claims.

Claims

1. A method for preparing a low-odor hydrogen-containing polysiloxane, characterized in that: The method comprises the following steps: putting hydrogen-containing silicone oil, toluene and platinum catalyst into a four-necked flask, slowly heating up to 80 degrees, dropping DS-300, and after the dropping is completed, heating up to 85 degrees for reaction for 2 hours, adding the baked activated carbon into the four-necked flask twice, filtering the activated carbon after the first addition for reaction for 3 hours, adding the activated carbon for the second time for reaction for 3 hours, filtering the activated carbon with a sand core funnel, adding the remaining filtrate into a clean reactor, rotating to distill out the solvent, adding a low boiling point solvent after distillation for secondary reduced pressure distillation, and obtaining low-odor hydrogen-containing polysiloxane.

2. The method for preparing a low-odor hydrogen-containing polysiloxane according to claim 1, characterized in that: The baked activated carbon and arbutin are added into a four-necked flask, and the arbutin forms an ester bond with the carboxyl group on the surface of the activated carbon through the phenolic hydroxyl group.

3. The method for preparing a low-odor hydrogen-containing polysiloxane according to claim 1, characterized in that: The baked activated carbon and glabridin are added into a four-necked flask.

4. The method for preparing a low-odor hydrogen-containing polysiloxane according to claim 1, characterized in that: The low boiling point solvent is methylcyclohexane.

5. The method for preparing a low-odor hydrogen-containing polysiloxane according to claim 1, characterized in that: The activated carbon consists of macroporous activated carbon with a pore size of more than 5 nm and microporous activated carbon with a pore size of less than 2 nm.

6. The method for preparing a low-odor hydrogen-containing polysiloxane according to claim 1, characterized in that: The activated carbon is coconut shell, and the iodine value of the coconut shell is less than 800 mg / g.

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