Preparation method of phosphate-based polyalkoxysilane and its application in silicone rubber

Abstract

The invention discloses a preparation method of phosphate-based polyalkoxysilane and application thereof in silicone rubber, belonging to the technical field of silicone rubber bonding and sealing materials and preparation thereof. The invention uses acrylic acid phosphate, a catalyst, hydrogen-containing siloxane and an aminosilane coupling agent as raw materials and prepares the phosphate-based polyalkoxysilane through a temperature-raising reaction. The phosphate-based polyalkoxysilane prepared by the invention is used as a tackifier for silicone rubber and has excellent bonding performance, can be suitable for bonding substrates such as peeling, metal and plastic, has good compatibility with silicone rubber and does not affect the mechanical properties of liquid silicone rubber.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of organosilicon materials, and in particular relates to a preparation method of phosphate-based polyalkoxysilane and application of the same in silicone rubber. Background Art

[0002] Silicone rubber has the advantages of high and low temperature resistance, corrosion resistance, radiation resistance, and weather resistance. As a sealant, it is widely used in the fields of construction, electronics, mechanical processing, automobile manufacturing, medicine, etc., and is used for bonding with metals, plastics, glass, etc. However, silicone rubber itself has low cohesive strength and weak adhesion, and usually needs to be strengthened by adding adhesion promoters. The commonly used adhesion promoter in silicone rubber is silane coupling agent, because it contains epoxy groups, amino groups, acryloxy groups, isocyanate groups, etc., which show certain bonding properties to various substrates.

[0003] Silane coupling agents containing epoxy groups and acryloxy groups have weak adhesion to glass, metal, plastic, etc., while amino groups, isocyanate groups, etc. easily cause yellowing of silicone rubber. Therefore, the development of special tackifiers with polyalkoxy groups has become a hot topic in the research of the silicone industry. For example, the invention patent (CN201310729125.3) announced that alkoxysilanes with different functionalities were used as monomers, and the colorless and transparent siloxane oligomers were obtained by co-hydrolysis and condensation at 40 to 100°C in the presence of a catalyst, and then reacted with boric acid derivatives to prepare a borate-modified polyalkoxy silicone tackifier suitable for the hydrosilane addition system; the invention patent (CN201611227643.5) announced that dimethyldialkoxysilane, diphenyldialkoxysilane, methylvinyldialkoxysilane, glycidol Etheroxypropyl trialkoxysilane and (methacryloyloxy)propyl trialkoxysilane are used as raw materials. The polyalkoxy oligomers obtained by hydrolysis reaction and equilibrium reaction can improve the bonding performance of silicone rubber to metals and organic synthetic materials; the invention patent (CN201711175147.4) announced the polyalkoxy polyisocyanate obtained by reacting trimethoxyhydrogensilane, triethoxyhydrogensilane, tripropoxyhydrogensilane, catalyst and triallyl isocyanurate, which not only has strong adhesion and thermal stability, but also is compatible with most hot melt adhesive resins. Therefore, polyalkoxy silane compounds have a promoting effect on the bonding of silicone rubber. Phosphorus-containing acrylates, as polymerization monomers, have good bonding effects on a variety of substrates. The invention patent (CN201510173674.6) discloses a water-based adhesive made by emulsion polymerization of diacrylic phosphate, acrylic monomer, styrene, emulsifier, initiator, inhibitor, pH adjuster, aqueous wetting agent, aqueous defoamer and deionized water, which has extremely strong adhesion between low surface tension materials.

[0004] However, the development of polyalkoxysilane thickeners with multifunctional groups still faces many difficulties in terms of structure control synthesis, compatibility with silicone rubber, and controllable thickening performance.

[0005] The main difficulty in the development of polyalkoxysilane tackifiers is to effectively chemically graft alkoxysilanes with multifunctional groups such as acrylic acid, phosphoric acid, boric acid, and polyurethane. Usually, alkoxysilanes are chemically grafted with various tackifying resin polymers (such as polyalkoxy polyisocyanates, polyalkoxy polyacrylates, and polyalkoxy oligomers), but this will cause the problem of uneven dispersion of alkoxysilanes in carbon-based resins. In addition, silicone-modified tackifying resin oligomers are mainly carbon-based molecular chains, which are incompatible with the siloxy molecular chains of silicone rubber, resulting in the disadvantage of decreased adhesion during actual use. In functional group-modified silicone resins, the alkoxy groups have been hydrolyzed to form silanol groups, which will cause the disadvantage of decreased storage stability of silicone rubber. Summary of the invention

[0006] In view of the above problems existing in the prior art, the present invention provides a method for preparing phosphate-based polyalkoxysilane and application of the phosphate-based polyalkoxysilane in silicone rubber.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] In one aspect, the present invention provides a method for preparing a phosphate-based polyalkoxysilane, characterized in that the method comprises the following steps:

[0009] 1) Add phosphate and catalyst into a container and stir to form a mixture, heat the mixture to T1, drop hydrogen-containing siloxane to react for a reaction time of H1; then drop amino-functional silane to react for a reaction time of H2;

[0010] 2) Raise the temperature to T2 and perform vacuum treatment until there is no fraction to obtain the product.

[0011] The process principle of the present invention is as follows: firstly, trialkoxysilane is grafted onto the acrylic acid structure of acrylic acid phosphate by means of hydrosilylation to form a stable chemical bond; then, the phosphorus hydroxyl bond in acrylic acid phosphate is chemically reacted with the amino group of the aminosilane coupling agent to further graft the amino coupling agent onto the acrylic acid phosphate.

[0012] Furthermore, the phosphate ester is selected from at least one of 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate (PM-1), hydroxyethyl methacrylate phosphate (PM-2), and 10-methacryloyloxydecane dihydrogen phosphate (10-MDP).

[0013] Furthermore, the hydrogen-containing siloxane is selected from at least one of trimethoxysilane and triethoxysilane.

[0014] Furthermore, the amino-functional silane is selected from at least one of 3-aminopropyltrimethoxysilane (APS), 3-aminopropyltriethoxysilane (KH-550), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792), and diethylaminomethyltriethoxysilane.

[0015] Furthermore, the molar ratio of the phosphate ester, hydrogen-containing siloxane and amino-functional silane is 1:(0.5-1.5):(1.5-3).

[0016] Furthermore, the catalyst is a platinum catalyst, preferably chloroplatinic acid, with a concentration of 5000 ppm.

[0017] Furthermore, the added amount of the catalyst is 0.1-1‰ of the total mass of the phosphate ester and the hydrogen-containing siloxane.

[0018] Furthermore, in step 1), the reaction temperature T1 is 30-60°C, H1 is 2-6h, and H2 is 4-8h; preferably, the reaction temperature T1 is 50-60°C, H1 is 3-4h, and H2 is 5-7h.

[0019] Furthermore, in step 2), the reaction temperature T2 is 70-100°C, preferably 80-90°C.

[0020] On the other hand, the present invention provides a use of the above-mentioned phosphate-based polyalkoxysilane in silicone rubber, characterized in that the phosphate-based polyalkoxysilane is used as a viscosity-enhancing aid for silicone rubber.

[0021] The phosphate groups in the product have good adhesion to metal substrates, and the presence of multiple alkoxy groups and silane groups further enhances the bonding strength to various substrates. The product is used as an adhesive additive for silicone rubber and has a significant adhesion-enhancing effect.

[0022] The beneficial effects of the present invention are:

[0023] (1) The phosphate-based polyalkoxysilane prepared by the present invention has a simple process, is safe and environmentally friendly, and has excellent adhesion-enhancing properties;

[0024] (2) The present invention is easy to construct, and only needs to add phosphate polyalkoxy silane to liquid silicone rubber and stir evenly;

[0025] (3) The tackifier prepared by the present invention has excellent performance and good compatibility with silicone rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared spectrum of the phosphate-based polyalkoxysilane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] Example 1

[0029] The preparation method of the phosphate-based polyalkoxysilane of the present embodiment comprises the following steps:

[0030] 1) 1 mol of 2-methyl-2-acrylic acid-2-hydroxyethyl phosphate (PM-1) and 0.2 g of chloroplatinic acid were added to a three-necked flask in sequence and stirred to form a mixture. The mixture was heated to 60°C, 1 mol of trimethoxysilane was added dropwise, and the reaction was continued for 3 h; 2 mol of 3-aminopropyltriethoxysilane (KH-550) was added dropwise, and the reaction was continued for 6 h.

[0031] 2) Raise the temperature to 80°C and degas in vacuum until there is no fraction to obtain the product.

[0032] Example 2

[0033] 1) 1 mol of hydroxyethyl methacrylate phosphate (PM-2) and 0.35 g of chloroplatinic acid were added to a three-necked flask in sequence and stirred to form a mixture. The mixture was heated to 30°C, 1.2 mol of trimethoxysilane was added dropwise, and the reaction was continued for 5 h; 1.8 mol of 3-aminopropyltriethoxysilane (KH-550) was added dropwise, and the reaction was continued for 5 h;

[0034] 2) Raise the temperature to 80°C and degas in vacuum until there is no fraction to obtain the product.

[0035] Example 3

[0036] 1) 1 mol of 10-methacryloyloxydecane dihydrogen phosphate (10-MDP) and 0.3 g of chloroplatinic acid were added to a three-necked flask in sequence and stirred to form a mixture, the mixture was heated to 50° C., 0.8 mol of trimethoxysilane was added dropwise, and the mixture was reacted for 2 h; 2.5 mol of 3-aminopropyltrimethoxysilane (APS) was added dropwise, and the mixture was reacted for 7 h;

[0037] 2) Raise the temperature to 80°C and degas in vacuum until there is no fraction to obtain the product.

[0038] Example 4

[0039] 1) 1 mol of 2-methyl-2-acrylic acid-2-hydroxyethyl phosphate (PM-1) and 0.25 g of chloroplatinic acid were added to a three-necked flask in sequence and stirred to form a mixture, the mixture was heated to 30°C, 0.5 mol of triethoxysilane was added dropwise, and the reaction was continued for 2 h; 1.5 mol of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792) was added dropwise, and the reaction was continued for 4 h;

[0040] 2) Raise the temperature to 90°C and degas in vacuum until there is no fraction to obtain the product.

[0041] Example 5

[0042] 1) 1 mol of 2-methyl-2-acrylic acid-2-hydroxyethyl phosphate (PM-1) and 0.4 g of chloroplatinic acid were sequentially added into a three-necked flask and stirred to form a mixture, the mixture was heated to 50° C., 1.5 mol of triethoxysilane was added dropwise, and the mixture was reacted for 4 h; 2 mol of diethylaminomethyltriethoxysilane was added dropwise, and the mixture was reacted for 8 h;

[0043] 2) Raise the temperature to 100°C and degas in vacuum until there is no fraction to obtain the product.

[0044] Example 6

[0045] 1) 1 mol of 2-methyl-2-acrylic acid-2-hydroxyethyl phosphate (PM-1) and 0.35 g of chloroplatinic acid were added to a three-necked flask in sequence and stirred to form a mixture, the mixture was heated to 40°C, 1.5 mol of trimethoxysilane was added dropwise, and the reaction was continued for 6 h; 3 mol of 3-aminopropyltriethoxysilane (KH-550) was added dropwise, and the reaction was continued for 6 h;

[0046] 2) Raise the temperature to 70°C and degas in vacuum until there is no fraction to obtain the product.

[0047] Comparative Example 1

[0048] This comparative example uses untreated 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate (PM-1) to replace the product prepared in the example.

[0049] Comparative Example 2

[0050] This comparative example uses untreated hydroxyethyl methacrylate phosphate (PM-2) to replace the product prepared in the example.

[0051] Comparative Example 3

[0052] In this comparative example, untreated 10-methacryloyloxydecane dihydrogen phosphate (10-MDP) was used to replace the product prepared in the example.

[0053] Comparative Example 4

[0054] The tackifier of this comparative example adopts liquid terpene resin (Guangzhou Songbao Chemical Co., Ltd., model T-30).

[0055] Figure 1 The infrared spectrum of the phosphate polyalkoxysilane prepared in Example 1 is shown in FIG. Figure 1As shown, there is no Si-H (2250-2100cm -1 ) characteristic peak and C=C (1665-1635cm-1) characteristic peak, indicating that trialkoxysilane is grafted onto the acrylic structure of acrylic phosphate; 1071.62cm-1 is the PNC characteristic peak, indicating that the phosphorus hydroxyl group on the phosphate reacts with the amino group on the amino-functional silane.

[0056] In addition, the infrared spectra of the products obtained in Examples 2-6 all showed characteristic peaks similar to those in Example 1, indicating that the trialkoxysilane was grafted onto the acrylic acid structure of acrylic phosphate, and the phosphorus hydroxyl group on the phosphate reacted with the amino group on the amino-functional silane, which will not be described in detail here.

[0057] The products obtained in the above examples and comparative examples were used as tackifiers for silicone rubber, and the peel strength of the silicone rubber after adding the tackifier was tested. The specific method is as follows: 5g of the product of each example / comparative example was added to 90g of 107 glue, and then 5g of methyltrimethoxysilane and 0.1g of organotin were added and stirred evenly, and then applied on different substrates to prepare peeling specimens. The test method was based on GB / T 2790-1995. The peel strength test results are shown in Table 1.

[0058] Table 1 Peel strength (N / mm) data of each embodiment and comparative example

[0059]

[0060] Among them, when the comparative examples 1-3 are mixed with silicone rubber, the peel strength is close to 0, which may be due to the poor compatibility with silicone rubber, resulting in a decrease in the bonding force during actual use.

[0061] Compared with Comparative Example 4, when the tackifier prepared in the present invention is applied to silicone rubber, it has a good tackifying effect on various substrates such as stainless steel plates, glass, aluminum plates, PC plates (polycarbonate), etc.

Claims

1. A method for preparing a phosphate-based polyalkoxysilane, characterized in that: The following steps are involved: 1) Add phosphate ester and catalyst into a container and stir to form a mixture, heat the mixture to T1, drop hydrogen-containing siloxane to react; then drop amino-functional silane to react; 2) Raise the temperature to T2 and perform vacuum treatment until no fraction is left to obtain the product; The phosphate ester is selected from at least one of 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate, hydroxyethyl methacrylate phosphate, and 10-methacryloyloxydecane dihydrogen phosphate; The hydrogen-containing siloxane is selected from at least one of trimethoxysilane and triethoxysilane; The amino-functional silane is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and diethylaminomethyltriethoxysilane; The molar ratio of the phosphate ester, hydrogen-containing siloxane and amino-functional silane is 1:(0.5-1.5):(1.5-3).

2. The method for preparing phosphate-based polyalkoxysilane according to claim 1, characterized in that: The catalyst is a platinum catalyst.

3. The method for preparing the phosphate-based polyalkoxysilane according to claim 1 or 2, characterized in that: The added amount of the catalyst is 0.1-1‰ of the total mass of the phosphate ester and the hydrogen-containing siloxane.

4. The method for preparing phosphate-based polyalkoxysilane according to claim 1, characterized in that: In step 1), the reaction temperature T1 is 30-60°C.

5. The method for preparing phosphate-based polyalkoxysilane according to claim 1, characterized in that: In step 2), the reaction temperature T2 is 70-100°C.

6. The use of phosphate polyalkoxysilane in silicone rubber according to claim 1, characterized in that: Phosphate-based polyalkoxysilanes are used as adhesion promoters for silicone rubber.

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