Preparation method of polyurethane modified organosilicon tackifier and its application in silicone rubber

Abstract

The present invention discloses a preparation method of a polyurethane modified organic silicon tackifier and its application in silicone rubber, belonging to the technical field of organic silicon materials. The technical scheme includes the following steps: 1) uniformly mixing enediol and a catalyst, heating up, and dripping hydrogen-containing siloxane for reaction; 2) dripping dimethyl carbonate for further reaction; 3) heating up, dripping aminosilane, and continuing the reaction. After the reaction is completed, the low-boiling substances are removed by decompression to obtain the organic silicon tackifier. The polyurethane modified organic silicon tackifier prepared by the present invention has excellent performance and stable structure. While improving the bonding performance, it does not affect the mechanical properties of liquid silicone rubber, and has a good application prospect in silicone rubber.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of organosilicon materials, and in particular to a preparation method of a polyurethane modified organosilicon tackifier and application of the polyurethane modified organosilicon tackifier in silicone rubber. Background Art

[0002] Silicone rubber has outstanding characteristics such as excellent temperature resistance, corrosion resistance, radiation resistance, weather resistance, physiological inertness, and does not cause coagulation. It is widely used in the fields of construction, electronics and electrical fields, mechanical processing, automobile manufacturing, and medical fields, and is often used for bonding metals, plastics, glass and other substrates. However, silicone rubber itself has low cohesive strength and poor adhesion, and it is necessary to add a tackifier to enhance its bonding properties. The commonly used tackifier is a silane coupling agent. Different types of silane coupling agents contain different organic functional groups, such as epoxy, amino, acryloxy, vinyl chloropropyl, mercapto, isocyanate and other groups, which can have certain bonding properties to various substrates.

[0003] Different organic functional groups in silane coupling agents play different roles. Silane coupling agents containing epoxy groups and acryloxy groups have weak adhesion to glass, metal, plastic, etc. Vinyl chloropropyl silane coupling agents are prone to produce hydrochloric acid, and mercapto groups will affect the deep curing of sealants. Although amino groups and isocyanate groups have strong adhesion to the substrate, they are easy to cause yellowing of silicone rubber. Therefore, the development of special tackifiers with non-isocyanate polyalkoxy groups has become a hot topic in the research of the silicone industry. For example, the invention patent (CN201810984717.2) first mixes pentaerythritol allyl ether, solvent, and catalyst, and heats and stirs; then, under heating and stirring conditions, slowly drips the hydrogen-containing silane coupling agent, and after the dripping is completed, stir the reaction for 0.5-2h; finally, evaporate the solvent in the system to obtain a polyallyl silane coupling agent. The prepared coupling agent has good coupling properties. The invention patent (CN202110570423.7) discloses that aminosilane and solvent A are mixed and heated, an inhibitor is added at 50-60°C, chloromethylstyrene is added dropwise at 60-70°C, the dropping speed is controlled to be 1d / s, and the reaction is kept at 90-100°C for 2h after the dropping is completed; after the reaction is completed, the temperature is lowered and organic amines are added, the mixture is stirred evenly and filtered, and the filtrate is distilled under reduced pressure to obtain a pure product, which improves the material's adhesion, durability, mechanical strength and electrical properties, and can be used in electronic-grade glass fiber yarn and cloth. The invention patent (CN202011621317.9) discloses that allyl chloride and allyl alcohol are used to synthesize diallyl ether in the presence of a catalyst and a base, and allyloxypropyl chlorosilane is obtained by a hydrosilylation reaction under the action of a platinum catalyst. The allyloxypropyl chlorosilane is esterified with a saturated alcohol to obtain allyloxyalkoxysilane, and the allyloxyalkoxysilane is epoxidized with an oxidant to obtain (glycidoxypropyl)alkoxysilane. The invention patent (CN202011614981.0) announced that the isocyanate silane coupling agent and the compound containing both hydroxyl and vinyl in the molecular structure, under the action of organic metal or tertiary amine catalyst, the isocyanate and hydroxyl undergo addition reaction, and the silicone thickener is prepared in one step. The double bond that can participate in the curing of silicone also has a strong polar carbamate group, which significantly promotes the bonding effect between silicone and the substrate, and does not affect the curing effect of silicone. It can work at room temperature. The development of polyalkoxysilane thickeners with polyurethane groups is of great help in improving the bonding performance of silicone rubber. However, there are still many difficulties in the control synthesis of the structure, compatibility with silicone rubber, and improvement of thickening performance of the product. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for preparing a polyurethane modified silicone tackifier and the application of the polyurethane modified silicone tackifier in silicone rubber. The prepared polyurethane modified silicone tackifier has excellent performance and a stable structure. While improving the bonding performance, it does not affect the mechanical properties of liquid silicone rubber and has a good application prospect in silicone rubber.

[0005] The technical solution of the present invention is:

[0006] The first aspect discloses a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0007] 1) Ethylenediol and catalyst are mixed evenly, heated, and hydrogen-containing siloxane is added dropwise to react;

[0008] 2) adding dimethyl carbonate dropwise for further reaction;

[0009] 3) Raise the temperature, add aminosilane dropwise, and continue the reaction. After the reaction is completed, remove the low-boiling substances under reduced pressure to obtain an organosilicon thickener.

[0010] Preferably, the enediol is one or more of 3,4-dihydroxy-1-butene, 2-methyl-2,4-pentenediol, butenediol and hexenediol.

[0011] Preferably, the hydrogen-containing siloxane is trimethoxysilane or triethoxysilane.

[0012] Preferably, the aminosilane is one or more of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane.

[0013] Preferably, the catalyst is chloroplatinic acid with a concentration of 3000ppm to 5000ppm.

[0014] Preferably, the molar ratio of the ethylene glycol, hydrogen-containing siloxane, dimethyl carbonate and aminosilane is 1:(0.5-1.5):(0.5-1.5):(1-2).

[0015] Preferably, the added amount of the catalyst is 3‰ of the total mass of enediol and hydrogen-containing siloxane.

[0016] Preferably, in step 1), the reaction temperature is 40-80° C. and the reaction time is 2-5 h; in step 2), the reaction time is 4-6 h.

[0017] Preferably, in step 3), the reaction temperature is 60-100° C. and the reaction time is 5-8 h.

[0018] On the other hand, disclosed is the use of the organosilicon tackifier prepared by the preparation method in the preparation of silicone rubber.

[0019] The present invention firstly utilizes hydrosilylation to graft trialkoxysilane onto the double bond of enediol to form a stable chemical bond. Then, a five-membered cyclic carbonate is obtained by transesterification of diols, and the cyclic carbonate is chemically reacted with the amino group of an aminosilane coupling agent, and the amino coupling agent is further subjected to ring-opening addition to the cyclic carbonate to form a polyurethane-modified organic silicon material. The amide group in the organic silicon tackifier prepared by the method of the present invention has good adhesion to glass, metal, plastic, etc., and the presence of the polyalkoxy silane group further enhances the bonding strength to various substrates. As an adhesive auxiliary agent for silicone rubber, the tackifier has an obvious adhesion effect.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The polyurethane modified silicone tackifier prepared by the present invention adopts a non-isocyanate method, thus avoiding the environmental problems caused by isocyanate. The preparation process is simple, safe and environmentally friendly, and suitable for industrial production.

[0022] (2) The product of the present invention is easy to construct, has good compatibility with liquid silicone rubber, and has a significant viscosity-increasing effect;

[0023] (3) The tackifier prepared by the present invention has excellent performance and stable structure. It improves the bonding performance without affecting the mechanical properties of the liquid silicone rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the infrared spectrum of product 1 of Example 1 of the present invention.

[0025] Figure 2 It is the infrared spectrum of product 2 of Example 1 of the present invention.

[0026] Figure 3 This is the infrared spectrum of the organosilicon tackifier of Example 1 of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment provides a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0029] 1) 1 mol of 3,4-dihydroxy-1-butene and 0.2 g of 5000 ppm chloroplatinic acid were added into a three-necked flask in sequence and stirred evenly. The temperature was raised to 40°C, and 1 mol of trimethoxysilane was added dropwise. The reaction was continued for 5 hours to obtain product 1.

[0030] 2) Add 1 mol of dimethyl carbonate dropwise and react for 6 hours to obtain product 2;

[0031] 3) Raise the temperature to 60°C, add 1.5 mol of 3-aminopropyltriethoxysilane dropwise, and react for 8 hours. After the reaction is completed, remove low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer.

[0032] The obtained product 1, product 2 and organosilicon tackifier were subjected to infrared spectroscopy respectively to obtain infrared spectra as shown in FIG. Figure 1-3 As shown, Figure 1 As shown, there are no Si-H (2250-2100cm-1) characteristic peaks and C=C (1665-1635cm-1) characteristic peaks in the infrared spectrum, indicating that trialkoxysilane is grafted onto 3,4-dihydroxy-1-butene; Figure 2 As shown in the figure, the infrared spectrum contains five-membered ring carbonate (1752cm -1 ) characteristic peak, indicating that product 1 reacts with dimethyl carbonate to form a five-membered ring; Figure 3 As shown, at (1704cm -1 )、(1755cm -1 ), indicating that product II undergoes a ring-opening addition reaction with amino-functional silane to generate CONH groups.

[0033] Example 2

[0034] This embodiment provides a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0035] 1) 1 mol of 3,4-dihydroxy-1-butene and 0.2 g of 5000 ppm chloroplatinic acid were added into a three-necked flask in sequence and stirred evenly. The temperature was raised to 50°C, and 1.2 mol of trimethoxysilane was added dropwise. The reaction was continued for 5 hours to obtain product 1.

[0036] 2) Add 1.2 mol of dimethyl carbonate dropwise and react for 5 hours to obtain product 2;

[0037] 3) Raise the temperature to 70°C, add 1.5 mol of 3-aminopropyltriethoxysilane dropwise, and react for 7 hours. After the reaction is completed, remove low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer.

[0038] Example 3

[0039] This embodiment provides a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0040] 1) 1 mol of 3,4-dihydroxy-1-butene and 0.2 g of 5000 ppm chloroplatinic acid were added into a three-necked flask in sequence and stirred evenly. The temperature was raised to 60°C, and 1 mol of trimethoxysilane was added dropwise. The reaction was continued for 4 hours to obtain product 1.

[0041] 2) Add 1.3 mol of dimethyl carbonate dropwise and react for 5 hours to obtain product 2;

[0042] 3) Raise the temperature to 80°C, add 1.6 mol of 3-aminopropyltriethoxysilane dropwise, and react for 7 hours. After the reaction is completed, remove low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer.

[0043] Example 4

[0044] This embodiment provides a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0045] 1) 1 mol of 3,4-dihydroxy-1-butene and 0.2 g of 5000 ppm chloroplatinic acid were added into a three-necked flask in sequence and stirred evenly. The temperature was raised to 70°C, and 1.1 mol of trimethoxysilane was added dropwise. The reaction was continued for 3 hours to obtain product 1.

[0046] 2) Add 1.3 mol of dimethyl carbonate dropwise and react for 4 hours to obtain product 2;

[0047] 3) Raise the temperature to 90°C, add 1.7 mol of 3-aminopropyltriethoxysilane dropwise, and react for 6 hours. After the reaction is completed, remove low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer.

[0048] Example 5

[0049] This embodiment provides a method for preparing a polyurethane modified silicone tackifier, comprising the following steps:

[0050] 1) 1 mol of 3,4-dihydroxy-1-butene and 0.2 g of 5000 ppm chloroplatinic acid were added into a three-necked flask in sequence and stirred evenly. The temperature was raised to 80°C, and 1 mol of trimethoxysilane was added dropwise. The reaction was continued for 2 h to obtain product 1.

[0051] 2) Add 1.4 mol of dimethyl carbonate dropwise and react for 4 hours to obtain product 2;

[0052] 3) Raise the temperature to 100°C, add 2 mol of 3-aminopropyltriethoxysilane dropwise, and react for 5 hours. After the reaction is completed, remove low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer.

[0053] Embodiment 6-10

[0054] 5g of the organosilicon tackifier prepared in Examples 1-5 was added to 90g of 107 glue, and then 5g of methyltrimethoxysilane and 0.1g of chelated tin were added and stirred evenly, and then applied on an acrylic plate to prepare a peeling specimen. The test method was based on GB / T2790-1995 "Adhesive 180° Peel Strength Test Method Flexible Material to Rigid Material". The 180° peel strength test results are shown in Table 1.

[0055] Embodiment 11

[0056] 50 g of 107 glue, 20 g of silicone oil and 10 g of the organosilicon tackifier prepared in Example 1 were placed in a container, rotated evenly with a three-dimensional high-speed mixer, filled with nitrogen and sealed with plastic wrap, left to stand for 24 hours, and no stratification was observed.

[0057] Comparative Example 1

[0058] 5g of 3-aminopropyltriethoxysilane was added to 90g of 107 glue, and then 5g of methyltrimethoxysilane and 0.1g of chelated tin were added and stirred evenly, and then applied on an acrylic plate to prepare a peeling specimen. The 180° peel strength test results are shown in Table 1.

[0059] Comparative Example 2

[0060] 5g of γ-methacryloxypropyltrimethoxysilane was added to 90g of 107 glue, and then 5g of methyltrimethoxysilane and 0.1g of chelated tin were added and stirred evenly, and then applied on an acrylic plate to prepare a peeling specimen. The 180° peel strength test results are shown in Table 1.

[0061] Comparative Example 3

[0062] 50g of 107 glue, 20g of silicone oil and 10g of polyurethane silane were placed in a container, rotated evenly with a three-dimensional high-speed mixer, filled with nitrogen and sealed with plastic wrap. After standing for 24 hours, stratification was observed.

[0063] Table 1

[0064]

[0065] As can be seen from Table 1, the polyurethane modified silicone tackifiers prepared in Examples 6-10 of the present application have a more obvious tackifying effect than those in Comparative Examples 1-2, mainly because (1) the product structure contains more alkoxy groups than conventional silane coupling agents, which can more effectively promote adhesion; the hydroxyl groups generated by the hydrolysis of the alkoxy groups react with the hydroxyl hydrogen atoms on the surface of the substrate to form chemical bonds; (2) the product structure contains urethane bonds and urea bonds with high cohesive energy, which can aggregate on the bonding surface under certain conditions to form a high surface tension adhesive layer. The greater the surface tension, the tougher the adhesive, which can be well matched with substrates such as metals, and the bonding strength is generally higher; (3) the active groups in the product structure diffuse on the surface of the substrate and form strong chemical bonds with the carbonyl groups on the surface of the substrate, thereby strengthening the weak interface layer, so that the composite film has very good peel strength.

[0066] By comparing Example 11 with Comparative Example 3, it can be found that the polyurethane modified silicone tackifier prepared by the present invention has good compatibility with silicone rubber.

[0067] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a polyurethane-modified silicone tackifier, characterized in that: The following steps are involved: 1) Ethylenediol and catalyst are mixed evenly, heated, and hydrogen-containing siloxane is added dropwise to react; 2) adding dimethyl carbonate dropwise for further reaction; 3) Raise the temperature, add aminosilane dropwise, and continue the reaction. After the reaction is completed, remove the low-boiling substances under reduced pressure to obtain an organosilicon viscosity enhancer; The enediol is one or more of 2-methyl-2,4-pentenediol, butenediol and hexenediol; The hydrogen-containing siloxane is trimethoxysilane or triethoxysilane; The aminosilane is one or more of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; The molar ratio of the ethylene glycol, hydrogen-containing siloxane, dimethyl carbonate and aminosilane is 1:(0.5-1.5):(0.5-1.5):(1-2).

2. The method for preparing the polyurethane modified silicone tackifier according to claim 1, characterized in that: The catalyst is chloroplatinic acid, and the concentration is 3000ppm-5000ppm.

3. The method for preparing the polyurethane modified silicone tackifier according to claim 1, characterized in that: The added amount of the catalyst is 3‰ of the total mass of enediol and hydrogen-containing siloxane.

4. The method for preparing the polyurethane modified silicone tackifier according to claim 1, characterized in that: In step 1), the reaction temperature is 40-80°C and the reaction time is 2-5h; in step 2), the reaction time is 4-6h.

5. The method for preparing the polyurethane modified silicone tackifier according to claim 1, characterized in that: In step 3), the reaction temperature is 60-100°C and the reaction time is 5-8h.

6. Use of the organosilicon tackifier prepared by the preparation method according to any one of claims 1 to 5 in the preparation of silicone rubber.

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