Alkoxy-terminated polydimethylsiloxane and preparation method thereof

Abstract

The invention discloses an alkoxy-terminated polydimethylsiloxane and a preparation method thereof. The molecular formula of the alkoxy-terminated polydimethylsiloxane is as follows, and the preparation method comprises the following steps: adding an alkoxy-terminated agent and a formic acid catalyst to a hydroxy-terminated polydimethylsiloxane to obtain a mixed solution; heating the mixed solution and maintaining a constant temperature to react; adding an organic amine for neutralization to obtain the alkoxy-terminated polydimethylsiloxane. In the technical scheme, due to the high catalytic activity of formic acid, the amount of formic acid added is very small, and the alkoxy-terminated polydimethylsiloxane finally obtained has a transparent appearance and good storage stability; and the preparation method is simple and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic silicone adhesives, and in particular relates to curable alkoxy-terminated polydimethylsiloxane and a preparation method thereof. Background Art

[0002] Alkoxy-terminated polydimethylsiloxane is mainly used as the basic raw material for preparing one-component and two-component alcohol-type silicone adhesives. Since most one-component alcohol-type silicone adhesives are catalyzed by titanate systems, viscosity peaks are prone to occur during the production process, affecting production. When alkoxy-terminated polydimethylsiloxane is used in one-component alcohol-type silicone adhesives, the viscosity peak caused by titanate catalysts can be effectively suppressed. However, the alkoxy-terminated polydimethylsiloxane currently produced has a relatively complex process and poor storage stability. Summary of the invention

[0003] The main purpose of the present invention is to provide an alkoxy-terminated polydimethylsiloxane and a preparation method thereof, aiming to solve the technical problems of the current alkoxy-terminated polydimethylsiloxane having a complex production process and poor storage stability.

[0004] To achieve the above object, the present invention provides an alkoxy-terminated polydimethylsiloxane, the molecular formula of the alkoxy-terminated polydimethylsiloxane is as follows:

[0005] ,

[0006] In the formula,

[0007] R1 is methyl, vinyl, methoxy, or ethoxy;

[0008] R2 is methoxy or ethoxy;

[0009] R3 is methoxy or ethoxy.

[0010] The present invention also provides a method for preparing the above-mentioned alkoxy-terminated polydimethylsiloxane, which comprises the following steps:

[0011] S10, adding an alkoxy end-capping agent and a formic acid catalyst to a hydroxyl-terminated polydimethylsiloxane to obtain a mixed solution;

[0012] S20, heating the mixed solution and maintaining a constant temperature to react;

[0013] S30, adding an organic amine for neutralization to obtain an alkoxy-terminated polydimethylsiloxane.

[0014] Optionally, in step S10, the viscosity of the hydroxyl-terminated polydimethylsiloxane at 23° C. is 500-200000 mPa·s.

[0015] Optionally, in step S10, the alkoxy capping agent is one or more of ethyl orthosilicate, methyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0016] Optionally, in step S10, the molar number of the alkoxy end-capping agent added is 100% to 105% of the molar number of hydroxyl groups in the hydroxyl end-capped polydimethylsiloxane.

[0017] Optionally, in step S10, the added weight of formic acid is 0.1%-0.5% of the weight of the hydroxyl-terminated polydimethylsiloxane.

[0018] Optionally, in step S20, the reaction temperature is between 50 and 80°C.

[0019] Optionally, in step S20, the reaction time is 1 h to 4 h.

[0020] Optionally, in step S30, the organic amine is an organic tertiary amine.

[0021] Optionally, the added mole number of the organic tertiary amine is equal to the added mole number of the formic acid.

[0022] In the technical scheme of the present invention, the prepared alkoxy-terminated polydimethylsiloxane can suppress the viscosity peak caused by the titanate catalyst when used in a one-component alcohol-type organic silicone adhesive. In the preparation process, formic acid with high catalytic activity is used and added in a small amount, and the finally prepared alkoxy-terminated polydimethylsiloxane has a transparent appearance and good storage stability; and the preparation method is simple and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 The molecular structure formula of the alkoxy-terminated polydimethylsiloxane provided by the present invention;

[0025] Figure 2 The present invention provides a schematic flow chart of an embodiment of a method for preparing alkoxy-terminated polydimethylsiloxane.

[0026] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0028] It should be noted that, in the embodiments, those without specifying specific conditions are carried out according to normal conditions or conditions recommended by the manufacturer. Those without specifying the manufacturer of reagents or instruments used are conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, and "A and / or B" is taken as an example, including schemes A, B, or A and B that meet the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of the technical schemes is contradictory or cannot be achieved, it should be considered that the combination of such technical schemes does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work, all belong to the scope of protection of the present invention.

[0029] In the prior art, most of the one-component alcohol-based silicone adhesives are catalyzed by a titanate system, which easily causes a viscosity peak during the production process, affecting production. However, when alkoxy-terminated polydimethylsiloxane is used in a one-component alcohol-based silicone adhesive, the viscosity peak caused by the titanate catalyst can be effectively suppressed.

[0030] In view of this, the present invention provides an alkoxy-terminated polydimethylsiloxane, combined with Figure 1 The molecular structure of the powder treatment agent is as follows:

[0031] ,

[0032] In the formula,

[0033] R1 is methyl, vinyl, methoxy, or ethoxy;

[0034] R2 is methoxy or ethoxy;

[0035] R3 is methoxy or ethoxy.

[0036] The alkoxy-terminated polydimethylsiloxane has a transparent appearance and good storage stability. When used in the preparation of a single-component alcohol-type organic silicone adhesive, it can effectively suppress the viscosity peak caused by a titanate catalyst.

[0037] The present invention also provides a method for preparing the alkoxy-terminated polydimethylsiloxane. Figure 2A schematic flow chart of an embodiment of a method for preparing alkoxy-terminated polydimethylsiloxane is provided, and the steps of the preparation method are as follows.

[0038] Step S10, adding an alkoxy end-capping agent and a formic acid catalyst to the hydroxyl end-capped polydimethylsiloxane to obtain a mixed solution.

[0039] In the specific implementation, a certain weight of hydroxyl-terminated polydimethylsiloxane is placed in a container, and then an alkoxyl-terminated agent and a formic acid catalyst are added respectively to obtain a mixed solution. The molecular structure of the hydroxyl-terminated polydimethylsiloxane is , and the viscosity of the hydroxyl-terminated polydimethylsiloxane at 23°C is 500-200000 mPa·s. The alkoxy end-capping agent is a mixture of one or more of ethyl orthosilicate, methyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane; and the added molar number of the alkoxy end-capping agent is 100%-105% of the molar number of hydroxyl groups in the hydroxyl-terminated polydimethylsiloxane, that is, the alkoxy end-capping agent is excessive relative to the hydroxyl group to make the reaction more complete. The added weight of formic acid is 0.1%-0.5% of the weight of the hydroxyl-terminated polydimethylsiloxane.

[0040] Step S20, heating the mixed solution and maintaining a constant temperature to carry out a reaction.

[0041] In the specific implementation, the mixed solution in the container is stirred, and the solution is heated to 50-80°C, and then kept at a constant temperature for reaction. At a certain temperature, formic acid catalyzes the alkoxy group of the alkoxy end-capping agent to condense with the silanol group, and the alkoxy end-capping agent reacts to cap one end of 107 glue (that is, hydroxyl-terminated polydimethylsiloxane) and produces corresponding methanol or ethanol. In general, the higher the temperature, the higher the activity of the catalytic reaction.

[0042] The reaction time is 1~4h.

[0043] Step S30, adding an organic amine for neutralization to obtain alkoxy-terminated polydimethylsiloxane.

[0044] In the specific implementation, organic amine is continuously added to the reaction-completed mixed solution, and a neutralization reaction is carried out under stirring. Among them, the organic amine used to neutralize formic acid is preferably an organic tertiary amine with high reaction activity, and the number of moles of the organic tertiary amine added is equal to the number of moles of the formic acid added. After complete neutralization, extremely tiny white salt particles are generated and evenly dispersed in the system, so that the reaction system is finally neutral, that is, the treated alkoxy-terminated polydimethylsiloxane is obtained.

[0045] In the technical scheme of the present invention, the prepared alkoxy-terminated polydimethylsiloxane can effectively suppress the viscosity peak caused by the titanate catalyst when used in a single-component alcohol-type organic silicone adhesive. In the preparation process, formic acid with high catalytic activity is used, and the addition amount is very small. After formic acid neutralization treatment, extremely small white salt particles are generated, which are evenly dispersed in the system and have no effect on the color of the system. The alkoxy-terminated polydimethylsiloxane finally obtained has a transparent appearance and good storage stability; and the preparation method is simple and suitable for industrial production.

[0046] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention. Example 1

[0047] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s was placed in a container, and then 8.66 g of ethyl orthosilicate and 5 g of formic acid were added. The container was heated and kept at a constant temperature of 50° C. and stirred for reaction. After reacting for 1 hour, 10.99 g of triethylamine was added for neutralization to obtain triethoxy-terminated polydimethylsiloxane. Example 2

[0048] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 10000 mPa·s was placed in a container, and then 6.21 g of methyl orthosilicate and 3 g of formic acid were added. The container was heated and kept at a constant temperature of 55° C. and stirred for reaction. After reacting for 1.5 hours, 6.595 g of triethylamine was added for neutralization to obtain trimethoxy-terminated polydimethylsiloxane. Example 3

[0049] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 20000 mPa·s was placed in a container, and then 3.3 g of methyltrimethoxysilane and 2.5 g of formic acid were added. The container was heated and kept at a constant temperature of 60° C. and stirred for reaction. After reacting for 2 hours, 5.5 g of triethylamine was added for neutralization to obtain dimethoxy-terminated polydimethylsiloxane. Example 4

[0050] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 80000 mPa·s was placed in a container, and then 2.75 g of methyltriethoxysilane and 4 g of formic acid were added. The container was heated and kept at a constant temperature of 65° C. and stirred for reaction. After reacting for 2.5 hours, 8.79 g of triethylamine was added for neutralization to obtain diethoxy-terminated polydimethylsiloxane. Example 5

[0051] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 200000 mPa·s was placed in a container, and then 1.63 g of vinyltrimethoxysilane and 2 g of formic acid were added. The container was heated and kept at a constant temperature of 70°C and stirred for reaction. After reacting for 3 hours, 4.4 g of triethylamine was added for neutralization to obtain dimethoxy-terminated polydimethylsiloxane. Example 6

[0052]

Quantitative analysis

[0053] 1000 g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 500 mPa·s was placed in a container, and then 807.1 g of vinyltriethoxysilane and 4.5 g of formic acid were added. The container was heated and kept at a constant temperature of 75° C. and stirred for reaction. After reacting for 4 hours, 9.893 g of triethylamine was added for neutralization to obtain low-viscosity diethoxy-terminated polydimethylsiloxane.

[0054] After sampling, sample pretreatment, and sample determination, the yields of each embodiment were calculated as follows:

[0055]

[0056] The above control experiment shows that the reaction activity of methoxysilane end-capping agent is higher than that of ethoxy, and generally, the reaction yield is also higher. Under the same type of alkoxy end-capping agent conditions, the extension of reaction time and the increase of temperature will help to improve the yield of the product.

[0057]

Performance evaluation

[0058] The samples of Examples 1-6 were subjected to high temperature storage experiments, and the viscosity changes are shown in the following table:

[0059]

[0060] The above control experiment shows that after high-temperature accelerated storage, the viscosity changes are relatively small.

[0061] The samples of Examples 1-6 were taken for curing experiments. The basic formulas of Examples 1, 4 and 6 are as follows:

[0062] Component A ;

[0063] Component B ;

[0064] Component A and component B are mixed in a volume ratio of 1:1. The curing speed is shown in the following table:

[0065]

[0066] The above control experiment shows that after high-temperature accelerated storage, the system has little effect on the curing speed, indicating that the storage stability is good.

[0067] The basic formula of Examples 2, 3 and 5 is as follows:

[0068]

[0069] The curing time is shown in the table below:

[0070]

[0071] The above control experiment shows that after high-temperature accelerated storage, the system has little effect on the curing speed, indicating that the storage stability is good.

[0072] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preparing an alkoxy-terminated polydimethylsiloxane, characterized in that: The preparation method comprises the following steps: S10, adding an alkoxy end-capping agent and a formic acid catalyst to a hydroxyl-terminated polydimethylsiloxane to obtain a mixed solution; S20, heating the mixed solution and maintaining a constant temperature to react; S30, adding an organic amine for neutralization to obtain an alkoxy-terminated polydimethylsiloxane; Wherein, in the step S30, the organic amine is an organic tertiary amine, and the number of moles of the organic tertiary amine added is equal to the number of moles of the formic acid added; The molecular formula of the alkoxy-terminated polydimethylsiloxane is as follows: ， In the formula, R1 is methyl, vinyl, methoxy, or ethoxy; R2 is methoxy or ethoxy; R3 is methoxy or ethoxy; In the step S10, the molar number of the alkoxy end-capping agent added is 100% to 105% of the molar number of hydroxyl groups in the hydroxyl end-capped polydimethylsiloxane, and the weight portion of formic acid added is 0.1% to 0.5% of the weight portion of the hydroxyl end-capped polydimethylsiloxane.

2. The method for preparing the alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that: In the step S10, the viscosity of the hydroxyl-terminated polydimethylsiloxane at 23° C. is 500-200000 mPa·s.

3. The method for preparing the alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that: In the step S10, the alkoxy end-capping agent is one or more of ethyl orthosilicate, methyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

4. The method for preparing the alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that: In the step S20, the reaction temperature is 50-80°C.

5. The method for preparing the alkoxy-terminated polydimethylsiloxane according to claim 1, characterized in that: In the step S20, the reaction time is 1 h to 4 h.

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