Isocyanate modified silane coupling agent and preparation method thereof

Abstract

The invention discloses an isocyanate modified silane coupling agent and a preparation method thereof. The content of acid in the chlorine-based modified silane coupling agent serving as the raw material is controlled to be greater than 0 and less than or equal to 150ppm through the pretreatment step; and carrying out phase transfer reaction on the pretreated chlorine-based modified silane coupling agent to obtain the isocyanate modified silane coupling agent. According to the method disclosed by the invention, the generation of byproducts in the phase transfer reaction process can be reduced, so that the yield and the stability of the product isocyanate modified silane coupling agent can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silane coupling agent modification, and in particular relates to an isocyanate-modified silane coupling agent and a preparation method thereof. Background Art

[0002] Isocyanate-modified silane coupling agents have the properties of both aliphatic isocyanates and silane coupling agents. They have been used as raw materials for coatings and adhesives in various industrial products, especially in adhesives. Xylylene diisocyanate can be obtained by reacting a chlorine-modified silane coupling agent with a cyanate (for example, see patent application DE 3524215A).

[0003] The cyanate route has a simple process and low cost. However, for isocyanate-modified silane coupling agents, excellent discoloration resistance and coupling performance are required according to the purpose and use. However, the conventional cyanate route (for example, see patent application CN 110437273A) sometimes ignores discoloration resistance and final yield.

[0004] Therefore, the art urgently needs to provide a method for preparing an isocyanate-modified silane coupling agent that can improve product yield and color change resistance. Summary of the invention

[0005] The purpose of the present invention is to provide an isocyanate-modified silane coupling agent (TSPI) and a preparation method thereof in view of the problems existing in the existing isocyanate-modified silane coupling agent synthesis method. A chlorine-modified silane coupling agent (TSPC) as a raw material is pretreated and separated through a pretreatment process, and the acid content therein is controlled within a reasonable range, thereby reducing the amount of by-products generated during the isocyanate synthesis process, improving the yield and application stability of the final product isocyanate-modified silane coupling agent, and prolonging the storage period.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing an isocyanate-modified silane coupling agent comprises the following steps: controlling the acid content (in the form of molecules or combinations) in a chlorine-modified silane coupling agent as a raw material to be greater than 0 and less than or equal to 150 ppm (for example, 1 ppm, 5 ppm, 50 ppm, 100 ppm, 150 ppm) through a pretreatment step of reduced pressure separation and / or gas stripping separation; and obtaining an isocyanate-modified silane coupling agent by subjecting the pretreated chlorine-modified silane coupling agent to a phase transfer reaction.

[0008] According to the preparation method provided by the present invention, in some embodiments, the structural formula of the isocyanate-modified silane coupling agent (TSPI) is as shown in formula (I):

[0009]

[0010] The structural formula of the chlorine-modified silane coupling agent (TSPC) is shown in formula (V):

[0011]

[0012] In formula (I) and formula (V), R2, R3, and R4 are the same or different, and are independently saturated alkyl and / or saturated alkoxy groups, and at least one of R2, R3, and R4 is a saturated alkoxy group (for example, R2 is a saturated alkoxy group, or R3 is a saturated alkoxy group, or R4 is a saturated alkoxy group, R2 and R3 are both saturated alkoxy groups, or R2 and R3 are both saturated alkoxy groups); preferably, the saturated alkyl group is a saturated alkyl group of C1 to C6; the general formula of the saturated alkoxy group is R5O—, in which R5 is preferably a saturated alkyl group of C1 to C6;

[0013] R1 is a branched or straight-chain alkylene or cycloalkylene, arylene or aralkylene, preferably the branched or straight-chain alkylene or cycloalkylene contains 1-12 carbon atoms, preferably the arylene contains 6-10 carbon atoms, preferably the aralkylene contains 7-10 carbon atoms, and R1 is more preferably a branched or straight-chain alkylene containing 1-6 carbon atoms.

[0014] In the present invention, the C1-C6 saturated alkyl group may be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or an n-pentyl group.

[0015] The branched or straight chain alkylene or cycloalkylene group containing 1 to 12 carbon atoms may be, for example, methylene, ethylene, n-propylene, isopropylene, n-butylene, n-pentylene, hexylene, heptylene, octylene. The aralkylene group containing 7 to 10 carbon atoms may be, for example, methylenephenyl, ethylenephenyl.

[0016] In the present invention, the acid content mainly comes from the raw materials and auxiliary materials and / or acidic catalyst residues in the synthesis process of the raw material TSPC, such as Bronsted acid and / or compounds that can release Bronsted acid (such as compounds that can release Bronsted acid at room temperature).

[0017] According to the preparation method provided by the present invention, in some embodiments, the pretreatment step is: controlling the acid content in the chlorine-modified silane coupling agent (TSPC) as a raw material to be greater than 0 and less than or equal to 150 ppm by reduced pressure separation and / or gas stripping separation.

[0018] If acid is removed by pretreatment with acid-base neutralization, the reaction is difficult to proceed completely, and acidic or alkaline substances are likely to remain, resulting in an increase in subsequent side reactions, affecting the yield and stability of the product. At the same time, the salt substances produced by acid-base neutralization are difficult to handle in an organic system. If water and / or alcohol phases are introduced into the system, acid-base neutralization can be promoted, but the isocyanate-modified silane coupling agent is very easy to react with water or alcohol phases, which is not conducive to the next reaction, affecting the yield and product stability; and the present invention can effectively avoid the above-mentioned disadvantages brought about by the traditional treatment method through decompression separation and / or gas stripping separation.

[0019] The vacuum separation is preferably distillation and / or rectification separation. According to the present invention, the temperature range in the vacuum separation process is selected. The separation temperature should be higher than the boiling point of the acid substances that may exist in the system to improve the separation effect of the acid. At the same time, too high a treatment temperature may cause the polymerization of TPSC, so a suitable treatment temperature has an impact on the improvement of the product yield in the subsequent steps. In some embodiments, it can be found that the separation temperature is a key factor affecting the treatment effect.

[0020] According to the present invention, the separation pressure of the reaction liquid in the reduced pressure separation treatment needs to be controlled. Too low a separation pressure will lead to system boiling and poor separation effect; too high a separation pressure requires a higher separation temperature, which is not conducive to temperature control. At the same time, the preferred treatment time is kept at 30 to 120 minutes.

[0021] According to the present invention, the reduced pressure separation is preferably distillation separation or rectification separation, and the process conditions are: the distillation and / or rectification treatment temperature is 60°C to 180°C, preferably 85°C to 135°C; the distillation and / or rectification treatment pressure is 1 to 100 kPa, preferably 5 to 50 kPa.

[0022] The distillation and / or rectification operation of the present invention can be carried out in a reaction device such as a kettle reactor, a tower reactor, a fixed bed reactor, a tubular reactor, etc., preferably in a tower reactor. The aspect ratio of the reaction device is not particularly limited, for example, it is greater than 10, preferably greater than 15, for example, it is less than 50, preferably less than 35. There is no particular limitation on the filler inside the reaction device, and there may be no filler, preferably a non-metallic filler, such as a ceramic filler, a plastic filler such as polypropylene (PP), polyethylene (PE) and polyvinyl chloride (PVC), etc.

[0023] According to the present invention, the gas stripping separation is preferably nitrogen gas stripping separation, and preheating is performed under continuous nitrogen purge; the inventors found that before the phase transfer reaction, preheating under nitrogen purge can remove a small amount of acidic substances that may remain in the system, which is beneficial to improve the reaction yield of the phase transfer reaction. Preferably, the chlorine-modified silane coupling agent is heated to 60°C to 180°C for the pretreatment. When the temperature is too low, the effect of gas stripping separation cannot be fully achieved. When the temperature is too high, the reaction result of the phase transfer reaction cannot be significantly improved, but energy consumption and heavy components are increased. Preferably, the nitrogen purge flux of the continuous nitrogen purge is 20 to 300 times the volume of the gas stripping separator / h (under normal temperature and pressure conditions), and the pretreatment is performed under the preferred temperature and nitrogen purge flux conditions, which is beneficial to improve the removal effect of a small amount of acidic substances that may remain, and is beneficial to further improve the yield of the target isocyanate. Preferably, it is retained for 30 to 120 minutes after reaching the target temperature.

[0024] According to the present invention, the decompression separation and the gas stripping separation can be used alone or simultaneously. In some embodiments, using both can better separate the acid content in the system.

[0025] Preferably, the reaction process of the phase transfer reaction step of the present invention can be understood as firstly contacting the chlorine-modified silane coupling agent TSPC represented by formula (V) with a phase transfer reagent and reacting in the presence of a catalyst to obtain an isocyanate-modified silane coupling agent (TSPI) represented by formula (I), and the reaction formula is as follows:

[0026]

[0027] If TSPC is not pretreated, the acidic substances in the system enter the phase transfer reaction and are likely to react with the chlorine element in the system to produce a side reaction to generate the compound shown in formula (II);

[0028]

[0029] The reaction formula is as follows:

[0030]

[0031] According to the residual acid content in the TSPC system, the isocyanate-modified silane coupling agent product may also contain compounds represented by formula (III) and / or (IV);

[0032]

[0033] In some embodiments, it is found that when the content of formula (II) in the product system exceeds 200ppm, the storage period of the product TSPI system will be shortened and obvious yellowing will occur. When the content of formula (III) and / or (IV) in the product system exceeds 50ppm, similar results will occur. The contents of formula (II), (III) and (IV) are all affected by the acid content in TSPC. When the acid content in TSPC exceeds 150ppm, it is very easy to cause a high content of substances of formula (II), (III) and (IV) in the product TSPI system. However, due to economic efficiency and raw material yield, it is difficult to reduce the acid content in TSPC to a lower level through pretreatment. At the same time, the presence of appropriate acid content and formula (II), (III) and (IV) can improve the polymerization phenomenon of TSPI and reduce the probability of turbidity of TSPI products. Therefore, the acid content of TSPC can be within an appropriate range.

[0034] As a preferred solution, the isocyanate-modified silane coupling agent product prepared by the method of the present invention contains 0.2-200 ppm of the compound represented by formula (II);

[0035]

[0036] As a preferred solution, the isocyanate-modified silane coupling agent product prepared by the method of the present invention further comprises a compound represented by formula (III) and / or (IV);

[0037]

[0038] The total content of the compounds represented by formula (III) and / or (IV) is 0.5-50 ppm.

[0039] In some embodiments, the phase transfer agent is selected from one or more alkaline metal cyanates, and the alkaline metal can be selected from alkali metals such as Ca, K, Na, Mg and / or alkaline earth metals.

[0040] In some embodiments, in the phase transfer reaction step, the molar amount of the phase transfer agent is 0.9-4.0 times (eg, 1 times, 1.5 times, 2.5 times, 3 times, 4 times) of the chlorine-modified silane coupling agent, preferably 1.0-2.0 times.

[0041] The catalyst is selected from one or more of chain polyethylene glycol, chain polyethylene glycol dialkyl ether, cyclic crown ether, quaternary ammonium salt, tertiary amine, quaternary ammonium base, quaternary phosphonium salt, and metal chloride, preferably one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, 18-crown ether, zinc chloride, and pyridine.

[0042] Isocyanate groups are generated during the phase transfer reaction. Isocyanate groups are at risk of polymerization at high temperatures, and lower temperatures require longer reaction times. Therefore, the reaction temperature needs to be within an appropriate range to avoid self-polymerization of isocyanate groups. At the same time, in the presence of a phase transfer catalyst, a lower temperature can meet the reaction requirements. On the other hand, too high a catalyst amount will promote the self-polymerization of isocyanates. Therefore, the amount of catalyst used should be coordinated with the reaction temperature to increase the reaction rate while ensuring the product yield.

[0043] In some embodiments, the molar amount of the catalyst is 0.001-0.05 times (eg, 0.001 times, 0.005 times, 0.01 times, 0.02 times, 0.04 times) of the chlorine-modified silane coupling agent, preferably 0.005-0.01 times.

[0044] The reaction temperature of the phase transfer reaction is 60-150°C, for example, 40°C, 60°C, 80°C, 100°C), preferably 85-125°C.

[0045] The reaction between chlorine-modified silane coupling agent TSPC and phase transfer agent is a strong exothermic reaction. Too high a reaction temperature will increase the content of by-products and affect the reaction yield. At the same time, if the addition ratio of the phase transfer agent is appropriately increased, the generation of polymerized heavy components in the synthesis process of isocyanate-modified silane coupling agent TSPI can be reduced.

[0046] In the phase transfer reaction step, an inert organic solvent may be optionally used to dilute the reaction system to reduce the polymerization reactivity of the raw materials. The inert organic solvent may be selected from aromatic hydrocarbons, halogenated aromatic hydrocarbons, halogenated aliphatic hydrocarbons, aliphatic ester compounds or aromatic ester compounds, aliphatic hydrocarbons or aromatic hydrocarbon organic solvents, such as but not limited to benzene, toluene, xylene, octane, decane, cyclohexane, methylcyclohexane, ethylcyclohexane, chlorotoluene, chlorobenzene, dichlorobenzene, dibromobenzene, trichlorobenzene, nitrobenzene, N,N-dimethylformamide, N,N-dimethylacetamide, N,N'-dimethylimidazolidinone, heptanone, diisobutyl ketone, methyl isobutyl ketone, methyl ethyl ketone, ethyl acetate, butyl acetate, amyl acetate, ethoxyethyl acetate, methyl salicylate, dimethyl phthalate, dibutyl phthalate, methyl benzoate, etc. The inventors have found through research that when the acid content of the raw material TSPC is controlled to be less than 150 ppm after pretreatment, a high product yield can still be guaranteed without using a solvent.

[0047] After the phase transfer reaction is complete, the solids and / or salts are separated by filtration or centrifugation, preferably filtering or centrifuging the product stream from the phase transfer to separate the solids, preferably at 30-100° C., more preferably at 50-80° C. The filtration can be carried out through a membrane, adsorber / adsorbent or fiber pad, by vacuum filtration or pressure filtration.

[0048] If a solvent is used, the inactive solvent is distilled off from the reaction solution using a known distillation tower after the solid phase separation step to recover the inert organic solvent: the reaction solution obtained by the phase transfer reaction is distilled, and the inert organic solvent and unreacted TSPC are collected to obtain a crude isocyanate-modified silane coupling agent TSPI. Preferably, the crude TSPI is further distilled to remove the heavy component tar in the system to obtain a pure TSPI product for entering the purification process.

[0049] The purification treatment is vacuum distillation and / or rectification, and the obtained isocyanate product stream containing the isocyanate represented by formula (IV) with higher purity is purified by distillation and / or rectification process.

[0050] When purification is performed by distillation, the distillation tower may be a plate tower or a packed tower. Specifically, the number of theoretical plates of the distillation tower (packed tower) is, for example, 2 or more, preferably 5 or more, for example, 60 or less, preferably 40 or less. In addition, the top pressure of the distillation tower is, for example, 0.1 kPa or more, preferably 0.15 kPa or more, for example, 4 kPa or less, preferably 2.5 kPa or less. In addition, the top reflux ratio of the distillation tower is, for example, 0.01 or more, preferably 0.1 or more, for example, 60 or less, preferably 40 or less.

[0051] According to the preparation method of TPSI of the present invention, the yield of TPSI of formula (IV) after purification can reach more than 90%.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) In the present invention, the acid content in the raw material is controlled to be greater than 0 and less than or equal to 150 ppm; at the same time, the appropriate phase transfer reaction and separation process are combined to effectively improve the yield of the target product, reduce the processing cost of the by-products, and increase the storage period; under optimal conditions, the yield of the product TPSI can reach more than 90%, and the conversion rate of the raw material TPSC can reach more than 98%;

[0054] (2) The method provided by the present invention does not use highly toxic chemicals, the reaction conditions are mild, and all solvents and raw materials can be recycled, which meets environmental protection requirements; conventional equipment is used for combination, the equipment is simple, and it is easy to realize industrialization. DETAILED DESCRIPTION

[0055] In order to understand the technical features and contents of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described here.

[0056] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0057] TSPI products can be qualitatively and quantitatively analyzed by liquid chromatography; instrument: Agilent 1260; chromatographic column: Agilent Extend C18 RRHD 2.1×100mm 1.8μm; column temperature: 40℃; flow rate: 0.2ml / min; mobile phase: A: pure water, B: pure acetonitrile; injection volume: 20μL; detection wavelength: 210nm.

[0058] The acid content in TSPC is qualitatively and quantitatively analyzed by titration. The specific parameters are as follows:

[0059] Accurately weigh the Mg sample to an accuracy of 0.1 mg (when the sample acidity is less than 0.0050%, the sample size M is 10 g; when the sample acidity is greater than 0.0050%, the sample size M is 5 g), and place it in two clean and dry 250 ml conical flasks.

[0060] Use 50ml and 100ml measuring cylinders to add appropriate amount of toluene (when the sample weight is 5g, add 10ml toluene; when the sample weight is 10g, add 20ml toluene) and appropriate amount of methanol (when the sample weight is 5g, add 50ml methanol; when the sample weight is 10g, add 100ml methanol) to each conical flask respectively, and then add the magnetic rotor to the flask. (When adding methanol, rinse the mouth and inner wall of the conical flask, and flush the sample splashed on the wall of the cup to the bottom of the flask).

[0061] Connect the conical flask to the reflux condenser, tighten the ground mouth by rotating it, cover the upper end with a ground mouth stopper, and turn on the condensing water.

[0062] Place the flask in an oil bath, set the oil bath temperature to 80°C, turn on the magnetic stirring and adjust the speed. Start timing when droplets drip from the condenser and reflux for 1 hour.

[0063] After the sample reflux reaction is completed, cool to room temperature, remove the ground-mouth stopper on the condenser, rinse the inner wall of the reflux condenser with 20 ml of methanol, and then remove the conical flask.

[0064] Transfer the liquid in the conical flask to a 300ml beaker three times with 50ml of methanol. Perform potentiometric titration with potassium hydroxide-ethanol standard titration solution, and take the maximum jump as the titration end point.

[0065] The acid content (calculated as HCl) is expressed as mass fraction W1, and the value is expressed in %:

[0066]

[0067] Where:

[0068] V1—the volume of potassium hydroxide-ethanol standard titration solution consumed by the titration sample, ml;

[0069] V0—the volume of potassium hydroxide-ethanol standard titration solution consumed in the titration blank, ml;

[0070] C—concentration of potassium hydroxide-ethanol standard titration solution, mol / L;

[0071] m—sample mass g;

[0072] 3.646—Constant.

[0073] The yield of TSPI products is calculated as product molar amount / raw material molar amount η, and the value is expressed in %:

[0074]

[0075] Where:

[0076] m1—product TSPI mass, g;

[0077] m2—mass of raw material TSPC, g;

[0078] n1—product TSPI molar mass fraction, g / mol;

[0079] n2—molar mass fraction of raw material TSPC, g / mol;

[0080] Example 1

[0081] The preparation method of an isocyanate-modified silane coupling agent comprises the following steps:

[0082] (A) Pretreatment process

[0083] A tubular separator with an inner diameter of 20 mm and a length of 500 mm filled with regular fillers was used as a decompression separation device; the separation temperature was 100°C, the separation pressure was 5 kPa, the light component tail gas obtained by pretreatment was absorbed by alkali solution, the treatment time was 80 minutes, and the raw material stream containing chlorine-modified silane coupling agent entered the phase transfer reaction process. The acid content values ​​before and after pretreatment are shown in Table 1.

[0084] (B) Phase transfer reaction step

[0085] Use a 500ml glass reactor as a phase transfer reactor, prepare 120g of pretreated 3-chloropropyltrimethoxysilane (TMSPC), first place 60g of TMSPC in the phase transfer reactor, add 0.97g of tetrabutylammonium bromide catalyst and 41.5g of sodium cyanate, and then heat to 80°C. Then add the remaining 60g of TMSPC at 5ml / min through a peristaltic pump, and react for 120min under normal pressure. Obtain a reaction solution containing TMSPI product. The reaction formula is as follows:

[0086]

[0087] (C) Solid-Liquid and Distillation Separation Process

[0088] The reaction liquid obtained by the phase transfer reaction is filtered under reduced pressure to remove the solid salts that are insoluble in the system. The distillation device first controls the distillation conditions to 150°C and 3kPa to remove the unreacted raw materials and light components contained in the reaction liquid; then the distillation conditions are changed to 150°C and 100Pa to further remove the heavy components generated during the synthesis process.

[0089] (D) Distillation process

[0090] The material flow entering the distillation process is separated by a Weiss distillation column at a pressure of 100 Pa and a bottom temperature of 140° C. to separate the products. The distillate is distilled to obtain a TMSPI product with a content of 98.9% and a yield of 92.3%. The finished product is a colorless liquid.

[0091] The conditions and experimental results of each process are shown in Table 1.

[0092] Example 2-3

[0093] Referring to the operation steps of Example 1, the differences between Examples 2-3 and Example 1 are: changing the temperature, pretreatment time, pretreatment pressure of the pretreatment step and the process conditions of the phase transfer reaction. Specific experimental parameters are shown in Table 1.

[0094] Example 4

[0095]

[0096] Referring to the operation steps of Example 1, the difference from Example 1 is that the raw material used is replaced with 3-chloropropylmethyldiethoxysilane and the amount thereof is changed. Specific experimental parameters are shown in Table 1.

[0097] Example 5

[0098] Referring to the operation steps of Example 1, the difference from Example 1 is that the raw material used is replaced with 3-chloropropyltriethoxysilane and its amount is changed. Specific experimental parameters are shown in Table 1.

[0099]

[0100] Embodiment 6-7

[0101] Referring to the operation steps of Example 1, the differences between Example 6 and Example 1 are as follows: a gas stripping separation process is used, a 500 ml glass kettle is used as a gas stripping separator, the amount of raw materials used is 300 g, the gas stripping separation temperature is 75 ° C, the nitrogen flow rate is 100 L / h, and the gas stripping time is 100 min. Example 7 adjusts the process conditions of the pretreatment pressure, nitrogen flow rate and phase transfer reaction. Specific experimental parameters are shown in Table 1.

[0102] Example 8

[0103] Referring to the operation steps of Example 1, the difference from Example 1 is that: two process modes of vacuum separation and gas stripping separation are used simultaneously, that is, the raw material sample after vacuum separation is separated by gas stripping, wherein the vacuum separation is carried out in a tubular separator with an inner diameter of 20 mm and a length of 500 mm and filled with regular fillers, the vacuum separation time is 80 min, and the vacuum separation temperature is 100° C. The gas stripping separation is carried out in a 500 ml glass kettle, the gas stripping separation time is 30 min, the gas stripping separation temperature is 100° C., and the nitrogen flow rate is 50 L / h.

[0104] Comparative Example 1

[0105] The operation steps of Example 1 are referred to, except that: in step (A), the neutralized raw material TMSPC is used to separate the acid content, that is, alkaline substances are added to the system, and the acid content values ​​are shown in Table 1.

[0106] Comparative Example 2

[0107] The operating steps of Example 1 are referred to, except that: in step (A), the raw material TMSPC is deacidified by adsorption, that is, 25 g of KIP211 resin is added to 500 g of TMSPC and mixed and stirred at 30° C. for 60 min, and the deacidified TMSPC is obtained by filtration; the acid content values ​​are shown in Table 1.

[0108] Comparative Example 3

[0109] Referring to the operating steps of Example 1, the acid removal pretreatment process of step (A) is not performed; the water content values ​​are shown in Table 1.

[0110] The experimental conditions and experimental results of each embodiment, and the experimental conditions and experimental results of each comparative example are shown in Figure 1.

[0111] Table 1 Conditions and results of examples and comparative examples

[0112]

[0113]

[0114] As can be seen from Table 1, the method of the present invention can effectively reduce the generation of by-products, and the yield of the prepared isocyanate-modified silane coupling agent product is greatly improved. In some embodiments, the purity of the final product is >95%, and the overall yield is >90%, which effectively avoids the generation of by-products, improves the yield, extends the storage period, and reduces the cost.

[0115] The results of the examples show that in the pretreatment process, temperature plays a major role and the three factors of temperature, pretreatment process and pretreatment time work together to control the acid content in the pretreated raw material at a very low level.

[0116] Compared with Example 1, since the acid removal method used in Comparative Examples 1-2 cannot achieve the acid content of the raw material being controlled below 150 ppm, the yield of the obtained product is not high. Since Comparative Example 3 does not perform a pretreatment step for acid removal, it will also have an adverse effect on the improvement of the yield of the obtained product.

[0117] The above describes some embodiments of the present invention, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An isocyanate-modified silane coupling agent, having a structural formula as shown in formula (I), comprising 0.2-200 ppm of a compound as shown in formula (II); In formula (I) and formula (II), R2, R3, and R4 are the same or different, and are independently saturated alkyl groups and / or saturated alkoxy groups, and at least one of R2, R3, and R4 is a saturated alkoxy group; preferably, the saturated alkyl group is a saturated alkyl group of C1 to C6; the general formula of the saturated alkoxy group is R5O—, in which R5 is preferably a saturated alkyl group of C1 to C6; R1 is a branched or straight-chain alkylene or cycloalkylene, arylene or aralkylene, preferably the branched or straight-chain alkylene or cycloalkylene contains 1-12 carbon atoms, preferably the arylene contains 6-10 carbon atoms, preferably the aralkylene contains 7-10 carbon atoms, and R1 is more preferably a branched or straight-chain alkylene containing 1-6 carbon atoms.

2. The isocyanate-modified silane coupling agent according to claim 1, characterized in that: Also includes compounds represented by formula (III) and / or (IV); The total content of the compounds represented by formula (III) and / or (IV) is 0.5-50 ppm.

3. A method for preparing the isocyanate-modified silane coupling agent according to claim 1 or 2, comprising the following steps: The acid content in the chlorine-modified silane coupling agent as a raw material is controlled to be greater than 0 and less than or equal to 150 ppm by a pretreatment step of reduced pressure separation and / or gas stripping separation; the pretreated chlorine-modified silane coupling agent is subjected to a phase transfer reaction to obtain an isocyanate-modified silane coupling agent; The structural formula of the chlorine-modified silane coupling agent is shown in formula (V): In formula (V), R2, R3, and R4 are the same or different, and are independently saturated alkyl and / or saturated alkoxy groups, and at least one of R2, R3, and R4 is a saturated alkoxy group; preferably, the saturated alkyl group is a saturated alkyl group of C1 to C6; the general formula of the saturated alkoxy group is R5O—, in which R5 is preferably a saturated alkyl group of C1 to C6; R1 is a branched or straight-chain alkylene or cycloalkylene, arylene or aralkylene, preferably the branched or straight-chain alkylene or cycloalkylene contains 1-12 carbon atoms, preferably the arylene contains 6-10 carbon atoms, preferably the aralkylene contains 7-10 carbon atoms, and R1 is more preferably a branched or straight-chain alkylene containing 1-6 carbon atoms.

4. The method according to claim 3, characterized in that The reduced pressure separation adopts distillation separation and / or rectification separation, and the process conditions are: the distillation and / or rectification treatment temperature is 60°C to 180°C, preferably 85°C to 135°C; the distillation and / or rectification treatment pressure is 1 to 100 kPa, preferably 5 to 50 kPa.

5. The method according to claim 3, characterized in that: The gas stripping uses nitrogen, and the chlorine-modified silane coupling agent is maintained at 60° C. to 180° C.

6. The method according to claim 3, characterized in that The phase transfer agent is selected from one or more of alkaline metal cyanates, and the alkaline metal is selected from one or more of Ca, K, Na, and Mg.

7. The method according to claim 3, characterized in that The catalyst is selected from one or more of chain polyethylene glycol, chain polyethylene glycol dialkyl ether, cyclic crown ether, quaternary ammonium salt, tertiary amine, quaternary ammonium base, quaternary phosphonium salt, and metal chloride, preferably one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, 18-crown ether, zinc chloride, and pyridine.

8. The method according to claim 3, characterized in that The molar amount of the catalyst is 0.001-0.05 times that of the chlorine-modified silane coupling agent.

9. The method according to claim 3, characterized in that: The reaction temperature of the phase transfer reaction is 60-150°C, preferably 85-125°C.

10. The method according to claim 3, characterized in that In the phase transfer reaction step, the molar amount of the phase transfer agent is 0.9-4.0 times that of the chlorine-modified silane coupling agent.

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