Titanate catalysts, processes for their preparation and use

Abstract

This invention provides a titanate catalyst, its preparation method, and its application. The titanate catalyst of this invention, through organic synthesis, introduces silicon-based groups onto the titanate catalyst, enabling it to exhibit good compatibility with the dealcoholized silicone sealant matrix. In dealcoholized silicone sealants, the catalyst is less likely to migrate to the surface, leading to yellowing. Furthermore, this invention selects a titanate with a specific molecular structure, in which at least two alkoxy groups are chemically covalently coupled with titanium atoms to form a cyclic spatial structure. This, in conjunction with organosilicon molecules, alters the performance of the titanate catalyst at the molecular structure level, significantly improving its catalytic activity, reducing the amount of catalyst required, and preventing the prepared sealant from darkening in color at higher temperatures.

Description

Technical Field

[0001] This invention relates to the field of catalyst materials technology, and in particular to a titanate catalyst, its preparation method, and its application. Background Technology

[0002] Sealants are widely used in the electronics, LED lighting, aerospace, and automotive industries. Among them, silicone sealants are the most widely used. Based on their curing mechanism, they can be divided into de-alcohol type, de-acid type, and de-ketoxime type silicone sealants. De-alcohol type silicone sealants release small molecule alcohols as byproducts during the curing process. They are environmentally friendly, non-corrosive to various substrates, have good adhesion to glass, metal and plastic, and have a fast curing speed, making them the preferred sealant.

[0003] Currently, most dealcohol-based silicone sealants use titanate esters or their complexes as catalysts. However, this approach presents several problems during production and use. For instance, titanate esters are prone to crystallization, especially at low temperatures in winter. Furthermore, most commercially available titanate catalysts are yellow or even reddish-brown, which can cause the sealant to yellow when introduced into the sealant system, making it unusable in certain applications (such as LED lighting). Current research attempts to address this by compounding multiple titanate esters or adding stabilizers. However, these compounded or stabilized products often have poor compatibility with the silicone matrix, easily migrating to the sealant surface and causing yellowing, thus affecting product usability.

[0004] Therefore, further improvements are needed to the catalysts used in sealants, which can be used to prepare durable, stable, and yellowing-resistant silicone sealants. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of poor yellowing resistance of existing silicone sealants by improving the catalyst used in sealants and providing a new titanate catalyst.

[0006] Another object of the present invention is to provide a method for preparing the titanate catalyst.

[0007] Another object of the present invention is to provide the application of the titanate catalyst in the preparation of silicone sealants.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A titanate catalyst, comprising

[0010]

[0011] In the formula, R1 is R3 is methylene or n1 is a natural number between 1 and 12;

[0012] R2 is H and / or —(CH2) n —, n2 is a natural number between 1 and 12.

[0013] This invention introduces silicon-based groups onto a titanate catalyst through organic synthesis, enabling it to be highly compatible with the matrix of dealcoholized silicone sealant. In dealcoholized silicone sealant, the catalyst is less likely to migrate to the surface, causing yellowing. Furthermore, this invention uses titanate with a specific molecular structure. The alkoxy groups in the titanate and the hydroxyl groups in the intermediate are chemically covalently coupled to form a cyclic spatial structure with titanium atoms. This, in conjunction with organosilicon molecules, alters the performance of the titanate catalyst at the molecular structure level, significantly improving its catalytic activity and reducing the amount of catalyst required. This makes the prepared sealant less prone to color deepening at higher temperatures. Moreover, the introduction of silicon-based groups into the chain body ensures good compatibility with the sealant matrix and prevents migration to the surface, thus reducing the likelihood of yellowing.

[0014] Preferably, in the titanate catalyst shown in Formula I, R1 is:

[0015]

[0016] n1 is a natural number between 1 and 6.

[0017] Preferably, in the titanate catalyst shown in Formula I, R1 is:

[0018]

[0019] n1 is a natural number between 1 and 12.

[0020] Preferably, in the titanate catalyst shown in Formula I, n2 is a natural number between 1 and 6.

[0021] The preparation method of the titanate catalyst includes the following steps:

[0022] S1 Raw Material Preparation

[0023] In an inert atmosphere, tetraisopropyl titanate and ethyl acetoacetate undergo transesterification to yield diisopropoxydiacetoacetate titanium (also known as primary titanium).

[0024] In an inert atmosphere, unsaturated oxygen-containing compounds and heptamethyltrisiloxane undergo hydrosilylation reactions in the presence of a catalyst to yield intermediates.

[0025] The titanium diisopropoxybisacetoacetate prepared in step S1 is reacted with the intermediate in a solvent to obtain the titanium ester catalyst.

[0026] By selecting different unsaturated alkyl alcohols, the corresponding products can be prepared:

[0027] 1) To prepare the titanate catalyst of Formula I, the unsaturated oxygen-containing compound is selected from terminal enols or terminal allyl polyethers with the structural formula CH2=CHR3OH;

[0028] 2) To prepare the titanate catalyst of Formula II, the unsaturated oxygen-containing compound is selected from alkynyl diols with the structural formula HOR2C≡CR2OH.

[0029] Furthermore, in the above method for preparing titanate catalysts:

[0030] Optionally, the inert atmosphere is an atmosphere formed by at least one gas selected from nitrogen, helium, and argon.

[0031] Preferably, the solvent includes at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0032] Preferably, the catalyst comprises at least one of Karstedt's catalyst and chloroplatinic acid solution (Speier catalyst). The amount of catalyst added is 5-20 ppm based on the total mass of the unsaturated oxygen-containing compounds.

[0033] Preferably, the temperature of the transesterification reaction is 50-70°C.

[0034] Preferably, the transesterification reaction takes 4-6 hours.

[0035] Preferably, in the transesterification reaction, the molar ratio of tetraisopropyl titanate and ethyl acetoacetate is 1:(2-2.1).

[0036] Preferably, the temperature of the hydrosilylation reaction is 80-90°C.

[0037] Preferably, the hydrosilylation reaction takes 2-4 hours.

[0038] Preferably, in the hydrosilylation reaction, the molar ratio of the unsaturated oxygen-containing compound and heptamethyltrisiloxane is (1.1-1.3):1.

[0039] Preferably, the temperature of the substitution reaction is 15-30°C.

[0040] Preferably, in the substitution reaction, the molar ratio of the hydroxyl group in the intermediate to the titanium atoms in the ethyl diisopropoxybisacetoacetate titanium is n. (—OH) :n [Ti] =(2-2.4):1.

[0041] The application of the above-mentioned titanate catalyst in the preparation of organosilicon sealants is also within the scope of protection of this invention.

[0042] The silicone sealant comprises the following components in parts by weight: 100 parts alkoxy polydimethylsiloxane, 8-10 parts dimethyl silicone oil, 80-100 parts filler, 5-10 parts silane coupling agent, and 0.1-2 parts titanate catalyst according to any one of claims 1-4.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] This invention modifies the molecular structure of titanate catalysts through organic synthesis, thereby improving their catalytic activity and dispersion and migration in the organosilicon matrix, making the prepared sealant less prone to color darkening. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0046] Example 1

[0047] This embodiment provides a titanate catalyst, the preparation method of which includes the following steps:

[0048] S1. Raw Material Preparation

[0049] (1) Under a nitrogen atmosphere at room temperature (25℃), 260g of ethyl acetoacetate (2mol) was slowly added dropwise to 284g of tetraisopropyl titanate (1mol). After stirring at 50℃ for 3h, the temperature was raised to 90℃ to remove the byproduct—isopropanol—under reduced pressure. When the distillate was small, the temperature was raised to 120℃ and the residual isopropanol was removed under a vacuum of 680mmHg. After releasing the vacuum, the temperature was lowered to room temperature to obtain the primary titanium product (diisopropoxydiacetoacetate titanium) for later use. The reaction equation is as follows:

[0050]

[0051] (2) At room temperature (25℃) and under a nitrogen atmosphere, 112.2 g of allyl hydroxyethyl ether (1.3 mol) was dissolved in 100 mL of toluene. After stirring evenly, 10 ppm of Karstedt's catalyst (based on allyl hydroxyethyl ether) was added, followed by the dropwise addition of 222 g of heptamethyltrisiloxane (1 mol). After the addition was complete, the temperature was raised to 80℃ and the reaction was carried out for 4 h. After the reaction was completed, the solvent and excess raw materials were removed by rotary evaporation at 80℃ and 1.33 kPa to obtain the intermediate for later use. The reaction equation is as follows:

[0052]

[0053] S2. Preparation of titanate catalyst

[0054] The above 224g intermediate was quickly added to 212g of primary titanium, and the reaction was stirred for 3h at room temperature (25℃) under a nitrogen atmosphere. Then the temperature was raised to 70℃ and the isopropanol generated in the reaction was removed by vacuum evaporation to obtain the above silicon-modified titanate catalyst.

[0055]

[0056] Example 2

[0057] This embodiment provides a titanate catalyst, prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of polyethylene glycol vinyl ether (degree of polymerization 6). The structural formula of the prepared titanate catalyst is as follows:

[0058]

[0059] Example 3

[0060] This embodiment provides a titanate catalyst, prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of allyl alcohol. The structural formula of the prepared titanate catalyst is as follows:

[0061]

[0062] Example 4

[0063] This embodiment provides a titanate catalyst, prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of 11-dodecenol. The structural formula of the prepared titanate catalyst is as follows:

[0064]

[0065] Example 5

[0066] This embodiment provides a titanate catalyst, prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of butynediol. The structural formula of the prepared titanate catalyst is as follows:

[0067]

[0068] Example 6

[0069] This embodiment provides a titanate catalyst, prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of 2,5,8,11-dimethyl-6-dodecyne-5,8-diol. The structural formula of the prepared titanate catalyst is as follows:

[0070]

[0071] Comparative Example 1

[0072] This comparative example provides a titanate catalyst, prepared according to the method of Example 1, except that: in step S1, titanium is prepared only once; and in step S2, the intermediate is replaced with an equimolar amount of propylene glycol to prepare an unmodified titanate coupling agent, the structural formula of which is as follows:

[0073]

[0074] Comparative Example 2

[0075] This comparative example provides a titanate catalyst, prepared according to the method of Example 1, except that: in step S1, no preparation was performed; in step S2, the intermediate was replaced with an equimolar amount of propylene glycol, and tetraisopropyl titanate was used to prepare an unmodified titanate coupling agent, with the following structural formula:

[0076]

[0077] Comparative Example 3

[0078] This comparative example provides a titanate catalyst prepared according to the method of Example 1, except that allyl hydroxyethyl ether is replaced with an equimolar amount of propylene glycol.

[0079] Comparative Example 4

[0080] This comparative example provides a titanate catalyst, prepared according to the method of Comparative Example 1. The difference is that 4 mol of heptamethyltrisiloxane was added to the final product of Comparative Example 1, the reaction was stirred for 3 hours, and then the temperature was raised to 70°C to remove byproducts under vacuum. The structure of the resulting titanate coupling agent is as follows:

[0081]

[0082] Performance testing

[0083] The performance of the titanate catalysts obtained in the above examples and comparative examples was characterized as follows:

[0084] (I) Appearance of Titanate Catalysts

[0085] The appearance of the titanate catalyst was characterized according to the method in GB / T 35493-2017 standard, and the results are shown in Table 1:

[0086] Table 1

[0087]

[0088] (II) Properties of the prepared silicone sealant

[0089] The titanate catalysts prepared in the above examples and comparative examples were added to silicone sealants (unless otherwise specified, all "parts" are parts by weight) for curing:

[0090] (1) Dehydration of base adhesive

[0091] Add 100 parts of alkoxy polydimethylsiloxane (dynamic viscosity of 20000 mPa·s at 25℃), 8 parts of dimethyl silicone oil (dynamic viscosity of 100 mPa·s at 25℃), and 100 parts of nano calcium carbonate (brand name CCS-25i, manufacturer: Guangxi Huana New Material Co., Ltd.) to a mixer, vacuum stir and heat to 120℃ for 4 hours to dehydrate, and cool to room temperature (below 30℃) to obtain the base adhesive;

[0092] (2) In the mixer, add 100 parts of the base adhesive prepared in step (1), then add 8 parts of methyltrimethoxysilane (brand name JH-N311, manufacturer Jianghan New Materials) and 1 part of the titanate catalyst prepared in the above example or comparative example (the amount of titanate catalyst added is calculated according to its titanium content). After each addition of raw materials, vacuum mix for 30 minutes. After all the raw materials are added and mixed evenly, discharge the mixture to obtain the silicone sealant mixture.

[0093] The high-temperature stability and curing performance (surface drying time, tested according to GB / T13477.5-2002 standard) of the cured sealant were tested, and the test results are shown in Table 2.

[0094]

[0095] The results above show that:

[0096] The titanate catalyst prepared by this invention has excellent stability at high temperatures and can remain unchanged in color after being placed at 70°C for 5 days; it also has good catalytic activity, with a surface drying time of less than 15 minutes.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A titanate catalyst, characterized in that, The molecular structure of the titanate catalyst is shown below: or .

2. The method for preparing the titanate catalyst according to claim 1, characterized in that, Includes the following steps: S1 Raw Material Preparation In an inert atmosphere, tetraisopropyl titanate and ethyl acetoacetate undergo transesterification to yield diisopropoxydiacetoacetate titanium. In an inert atmosphere, unsaturated oxygen-containing compounds and heptamethyltrisiloxane undergo hydrosilylation reactions in the presence of a catalyst to yield intermediates. The titanium diisopropoxybisacetoacetate prepared in step S1 is reacted with the intermediate in a solvent to obtain the titanium ester catalyst.

3. The method for preparing the titanate catalyst according to claim 2, characterized in that, The unsaturated oxygen-containing compound is an alkynyl alcohol, which is butynediol or 2,5,8,11-dimethyl-6-dodecyn-5,8-diol.

4. The method for preparing the titanate catalyst according to claim 2, characterized in that, Satisfying at least one of the following characteristics: a. The inert atmosphere is an atmosphere formed by at least one gas selected from nitrogen, helium, and argon; b. The catalyst includes at least one of cassette catalyst and chloroplatinic acid; c. The solvent includes at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide; d. The molar ratio of the hydroxyl group in the intermediate to the titanium atoms in the ethyl diisopropoxybisacetoacetate titanium is n. （—OH） :n [Ti] =(2-2.4):

1.

5. The method for preparing the titanate catalyst according to claim 2, characterized in that, The temperature for the transesterification reaction is 50-70℃; the temperature for the addition reaction is 80-90℃; and the temperature for the substitution reaction is 15-30℃.

6. The application of the titanate catalyst according to claim 1, characterized in that, The titanate catalyst is used to prepare an organosilicon sealant, which comprises the following components in parts by weight: 100 parts alkoxy polydimethylsiloxane, 8-10 parts dimethyl silicone oil, 80-100 parts filler, 5-10 parts silane coupling agent, and 0.1-2 parts titanate catalyst as described in claim 1.

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