阅读说明：本技术 一种硅树脂侧链接枝的固化交联方法 (Curing and crosslinking method for silicone side chain grafting ) 是由 刘丽 姜警 黄玉东 于 2019-11-13 设计创作，主要内容包括：本发明公开了一种硅树脂侧链接枝的固化交联方法,所述方法包括如下步骤：步骤一、将有机硅树脂溶于乙醇中,配制成混合溶液A；步骤二、向混合溶液A中加入异氰酸酯类,混合均匀,得到混合溶液B；步骤三、将混合溶液B放进烘箱,在150~300℃的温度下梯度固化2~10h。本发明制成的硅树脂可用作基体树脂制备耐高温复合材料及耐高温粘接剂。本发明采用的操作步骤适用于大规模生产,利用大型搅拌设备使硅树脂与异氰酸酯间混合充分,制备出来的复合材料耐热性能优异。(The invention discloses a curing and crosslinking method for silicone side chain grafting, which comprises the following steps: dissolving organic silicon resin in ethanol to prepare a mixed solution A; adding isocyanate into the mixed solution A, and uniformly mixing to obtain a mixed solution B; and step three, placing the mixed solution B into an oven, and curing at 150-300 ℃ for 2-10 h in a gradient manner. The silicone resin prepared by the invention can be used as matrix resin to prepare high-temperature-resistant composite materials and high-temperature-resistant adhesives. The operation steps adopted by the invention are suitable for large-scale production, the silicone resin and the isocyanate are fully mixed by using large-scale stirring equipment, and the prepared composite material has excellent heat resistance.)

1. A method for curing and crosslinking silicone side-chain grafts, characterized in that the method comprises the following steps:

step one, dissolving organic silicon resin in ethanol to prepare a mixed solution A:

adding isocyanate into the mixed solution A, and uniformly mixing to obtain a mixed solution B;

and step three, placing the mixed solution B into an oven, and curing at 150-300 ℃ for 2-10 h in a gradient manner.

2. The method for curing and crosslinking silicone resin with side chain grafting of claim 1, wherein the mixed solution A contains 10 to 50% by mass of ethanol.

3. The method of claim 3, wherein the mixed solution A contains 20-40% by weight of ethanol.

4. The method of claim 1, wherein the silicone resin has an R/Si atomic ratio of 1.0 to 1.5, and the content of phenyl groups is 0 to 50% of the total content of alkyl groups.

5. The method of claim 4, wherein the phenyl content is 15-35% of the total alkyl content.

6. The method of claim 1, wherein the silicone resin is of the structure (R)₂SiO_2/2)_x(RSiO_3/2)_y(S)_zIn the formula, R₂SiO_2/2、RSiO_3/2Respectively represent D unit siloxane and T unit siloxane, and x, y and z respectively represent R₂SiO_2/2、RSiO_3/2And the number of structural units of S, wherein x is 0 or a positive integer, y and z are positive integers, R independently represents methyl or phenyl, S is derived from siloxane group-Si (OH)₃、-RSi（OH）₂、-R₂Si（OH）、-R₂SiOR、-RSiOR₂、-SiOR₃One kind of (1).

7. The method for curing and crosslinking by grafting the silicone resin side chain according to claim 1, wherein the molar ratio of the silicone resin to the isocyanate is 100:1 to 1: 10.

8. The method for curing and crosslinking by grafting the silicone resin side chain according to claim 7, wherein the molar ratio of the silicone resin to the isocyanate is 50:1 to 1: 2.

9. The method of claim 1, 7 or 8, wherein the isocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate.

10. The method of claim 9, wherein the isocyanate is one of toluene diisocyanate and diphenylmethane diisocyanate.

Technical Field

The invention relates to a side chain grafting and curing method, in particular to a curing and crosslinking method for silicone side chain grafting.

Background

The organic silicon resin has a stable structure and bonding energy, and is a hot point for researching high-temperature and high-performance resin in recent years. The bond energy of Si-O bond in the main chain Si-O-Si structure is about 456 kJ/mol, while in general organic resin, the bond energy of C-C bond is about 332 kJ/mol, and the bond energy of Si-O bond is far greater than that of C-C bond, so that the Si-O bond structure in the organic silicon resin is more stable, is not easy to damage, has excellent thermal stability, and is widely used in the fields of aerospace composite materials, electric protective sleeves and the like.

The high temperature resistance of silicone resin has many factors, including increasing its molecular weight, doping hetero atoms in the main chain, grafting high temperature resistant groups onto the side chains, etc. Most people select high-temperature-resistant cyclic molecules in the side-linked branches, the side-chain grafting introduced by the method is low, the steric hindrance effect is too obvious, the treatment time is long, and the improvement on the heat-resistant stability and the mechanical property of the silicone resin is limited. Therefore, the introduction of a method with excellent heat resistance and enhanced curing degree is particularly important for the application of silicone resin in the high-temperature field.

Disclosure of Invention

Aiming at the existing silicone resin curing technology, the invention provides a novel silicone resin side chain grafting curing and crosslinking method, so that the curing and crosslinking degree of the resin is greatly improved.

The purpose of the invention is realized by the following technical scheme:

a method for curing and crosslinking silicone side chain grafting comprises the following steps:

step one, dissolving organic silicon resin in ethanol to prepare a mixed solution A, wherein:

in the mixed solution A, the mass fraction of ethanol is 10-50%, preferably 20-40%;

the R/Si ratio of the organic silicon resin is 1.0-1.5 (atomic ratio), and the phenyl content accounts for 0-50% of the total alkyl content, preferably 15-35%;

the organic silicon resin has the structure of (R)₂SiO_2/2)_x(RSiO_3/2)_y(S)_zIn the formula, R₂SiO_2/2、RSiO_3/2Respectively represent D unit siloxane and T unit siloxane, and x, y and z respectively represent R₂SiO_2/2、RSiO_3/2And the number of structural units of S, wherein x is 0 or a positive integer, y and z are positive integers, R independently represents methyl or phenyl, S is derived from siloxane group-Si (OH)₃、-RSi（OH）₂、-R₂Si（OH）、-R₂SiOR、-RSiOR₂、-SiOR₃One of (1);

step two, adding isocyanate into the mixed solution A, and uniformly mixing to obtain a mixed solution B, wherein:

the molar ratio of the organic silicon resin to the isocyanate is 100: 1-1: 10, preferably 50: 1-1: 2;

the isocyanate includes but is not limited to one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and the like, preferably one of toluene diisocyanate and diphenylmethane diisocyanate;

and step three, placing the mixed solution B into an oven, and curing at 150-300 ℃ for 2-10 h in a gradient manner.

The invention adopts isocyanate side chain grafted silicone resin to promote curing crosslinking, and the reasons are as follows:

(1) the isocyanate can react with the hydroxyl of the silicone side chain;

(2) the isocyanate is selected to have two isocyanate groups, so that self-polymerization reaction can be carried out in the curing process to form triazine ring or carbon chain isomerization, so that a silicone resin chain and a chain directly form a covalent bond and are converted into a more compact three-dimensional structure;

(3) the isocyanates themselves are very resistant to high temperatures.

The existing silicone resin curing technology mainly comprises thermal curing and light curing. Both of these curing techniques tend to produce significant intermolecular dehydration upon curing of the silicone resin. Because the viscosity of the silicon resin is high during curing, the generated water molecules are not easy to discharge, so that air bubbles are formed to cause air holes in the silicon resin, and the thermal property and the mechanical property of the silicon resin are influenced. The invention adopts a novel silicone side chain grafting, curing and crosslinking method, which can effectively solve the problem, the adopted difunctional isocyanate can be added with the side chain hydroxyl of the silicone, no water is generated, the self isocyanate group can be subjected to self-addition or ring formation reaction, the generation of water molecules in the system is very little, and the phenomenon of air holes generated by curing the silicone can be greatly reduced.

Compared with the prior art, the invention has the following advantages:

1. the silicone resin prepared by the invention can be used as matrix resin to prepare high-temperature-resistant composite materials and high-temperature-resistant adhesives.

2. The operation steps adopted by the invention are suitable for large-scale production, the silicone resin and the isocyanate are fully mixed by using large-scale stirring equipment, and the prepared composite material has excellent heat resistance.

3. The invention can effectively reduce the dehydration phenomenon generated by the thermal curing of the silicon resin and greatly reduce the bubble and air hole phenomenon generated by the curing of the silicon resin.

4. The invention can reduce the thermosetting time of the silicone resin, and can save the energy consumption of the curing process because the reaction of the side chain hydroxyl of the silicone resin and the isocyanate group can release a large amount of heat.

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.