CN108641665A - A kind of polyimides adhesive and preparation method thereof - Google Patents

Abstract

The present invention relates to a kind of polyimides adhesives and preparation method thereof, belong to adhesive technical field, solve the problem of polyimides adhesive resistance to thermally labile when temperature is higher than 350 DEG C in the prior art, adhesive property declines.A kind of polyimides adhesive is obtained using polyimides adhesive prepolymer cures, and the raw material for preparing of polyimides adhesive prepolymer is the aromatic diamines of biphenyl contenting structure, the aromatic diamines of silicone-containing structure, aromatic dianhydride and end-capping reagent.Polyimides adhesive prepolymer is dissolved in organic solvent, obtains homogeneous phase solution by the preparation method of polyimides adhesive；Homogeneous phase solution is coated on bonded object surface, removes organic solvent, solidification obtains polyimides adhesive, completes the bonding of bonded object.The polyimides adhesive of the present invention can be applied to the bonding of the high temperature resistant component in the fields such as Aeronautics and Astronautics, precision machinery, petrochemical industry.

Description

A kind of polyimide adhesive and preparation method thereof

technical field

The invention relates to the technical field of adhesives, in particular to a polyimide adhesive and a preparation method thereof.

Background technique

With the rapid development of aerospace technology, organic heat-resistant adhesives have been widely used in various aircraft manufacturing.

Polyimide adhesives are more and more popular because of their excellent heat resistance and high temperature bonding properties. Generally, polyimide adhesives are classified according to processing and synthesis methods: condensation type, thermoplastic type and addition type. For condensation-type polyimide adhesives, the curing process is the dehydration and cyclization process of polyamic acid, and the formation of water in the middle is easy to form pore defects, which is not suitable for large-scale bonding. For thermoplastic polyimide adhesives, although the material can be bonded by direct hot melting to avoid the generation of pores, the heat resistance of this type of adhesive is insufficient, and its glass transition temperature (T _g ) generally does not exceed 250°C. Addition-type polyimide adhesives are usually used in the form of prepolymers with reactive end-capping agents. During heating and molding, the resin prepolymers melt and infiltrate the bonding material first, and then solidify to form a three-dimensional network structure. Therefore, this type Polyimide adhesives have higher heat resistance and bonding properties than the first two. Among them, the addition-type polyimide adhesive terminated with phenylethynyl groups is the most widely used because of its rigid main chain structure, strong inter-molecular chain interaction and high cross-linking density, outstanding heat resistance. However, the rigid main chain structure and strong molecular chain interaction will increase the melt viscosity of the polyimide adhesive prepolymer, which cannot better infiltrate the surface of the bonded material, thus reducing its bonding performance. . At the same time, the high crosslink density in the structure will also bring obvious curing shrinkage stress, which will affect the bonding performance. In order to obtain a phenylethynyl-terminated addition-type polyimide adhesive with both thermal stability and adhesive performance, researchers have carried out a series of research work. PETI-5 is an addition-type polyimide adhesive developed earlier, which is composed of 3,3',4,4'-biphenyltetraacid dianhydride (s-BPDA) and 15% of 1, 3-bis(3-aminophenoxy)benzene (1,3,3-APB) and 85% of 3,4'-diaminodiphenyl ether (3,4'-ODA) were polymerized, and 4-benzene The polyimide adhesive prepolymer prepared by capping ethynyl phthalic anhydride (PEPA) has a designed molecular weight of 5000 g/mol. The glass transition temperature of the cured product is 270°C, and the titanium alloy after adhesive film bonding is made with E-112 fiberglass cloth as the carrier. The shear strength at room temperature is 49.0MPa and 29.7MPa at 177°C, but this adhesive The melt viscosity of the adhesive is relatively high, and the minimum melt viscosity is 10000Pa·s. The researchers further increased the degree of branching of the PETI-5 structure by introducing triamine monomers, and the minimum melt viscosity of the modified PETI-5 was 60Pa·s. The shear strengths of titanium alloy bonded by it at room temperature and 177°C are 41MPa and 36MPa respectively. Domestic researchers have also conducted a lot of research on the high-temperature bonding properties of polyimide adhesives. For example, the glass transition temperature of PEPA-capped thermosetting polyimide adhesives developed by the Institute of Chemistry, Chinese Academy of Sciences exceeds 310°C. The shear strength of stainless steel sheet bonding is 13MPa at room temperature, and exceeds 10MPa at 316°C, but there is still a problem of high melt viscosity (>300Pa·s), which is prone to bonding defects.

Based on the existing research results, polyimide adhesives still have the problems of unstable heat resistance and reduced adhesive performance when used at high temperatures, which cannot meet the future demand for higher temperature-resistant adhesives in the aerospace field.

Contents of the invention

In view of the above analysis, the present invention aims to provide a polyimide adhesive and a preparation method thereof to solve the problem of thermal instability of the polyimide adhesive and decreased bonding performance when the temperature is higher than 350°C. question.

The purpose of the present invention is mainly achieved through the following technical solutions:

The invention provides a polyimide adhesive, which is obtained by curing a polyimide adhesive prepolymer, and the preparation raw material of the polyimide adhesive prepolymer is an aromatic diamine containing a biphenyl structure , Aromatic diamines, aromatic dianhydrides and end-capping agents containing siloxane structures.

Polyimide adhesive beneficial effect of the present invention is as follows:

On the one hand, the present invention selects aromatic diamine with siloxane structure as the raw material for the preparation of polyimide adhesive prepolymer, because a flexible siloxane structure is introduced into the polyimide rigid main chain structure, thereby The melt viscosity of the prepolymer is greatly reduced, so that it can better infiltrate the surface of the bonded material and improve the bonding performance; on the other hand, due to the solidification of the polyimide adhesive prepolymer to form a three-dimensional network structure, The glass transition temperature of the cured adhesive increases, and the adhesive has excellent bonding performance and heat resistance at room temperature and high temperature.

On the basis of the foregoing scheme, the present invention has also made the following improvements:

Further, polyimide adhesive prepolymer has the structure of general formula I:

Wherein, Ar is selected from any one of the following aromatic structures:

R ₁ is a biphenyl structure, R ₂ is a siloxane structure, the ratio of x to y is (9:1)-(7:3), and n is 1-3.

Considering that the rigid main chain structure and strong molecular chain interaction will increase the melt viscosity of the polyimide adhesive prepolymer, it will not be able to better infiltrate the surface of the bonded material, thus reducing its bonding performance . So the present invention selects the polyimide adhesive prepolymer with general formula I structure, because introduces the siloxane structure with flexibility in the rigid main chain structure, thereby greatly reduces the melt viscosity of prepolymer, makes its It can better wet the surface of the bonded material to improve the bonding performance.

When the ratio of x to y is (9:1)-(7:3) and n is 1-3, the number average molecular weight (M _n ) of the polyimide adhesive prepolymer is 1100-2900g/mol between. Appropriate polyimide adhesive prepolymer molecular weight contributes to the compatibility of adhesive performance and heat resistance. The above prepolymer molecular weight can ensure good melt viscosity and suitable crosslink density.

Further, the aromatic diamine containing siloxane structure is bis(4-aminophenoxy)tetramethyldisiloxane and/or bis(4-(4-aminophenylcarboxylate)benzene)tetramethyldisiloxane oxane.

The above two aromatic diamines containing siloxane structure endow the polyimide adhesive with excellent melt fluidity and heat resistance due to the long-chain segment disiloxane and aromatic structure in the structure, so the present invention prefers the above-mentioned Two aromatic diamines containing siloxane structure are used as raw materials for the preparation of polyimide adhesive prepolymer.

R ₂ is selected from any one of the following structures:

Further, the aromatic diamine of biphenyl structure is 4,4'-diamino-2,2'-dimethylbiphenyl and/or 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl benzene.

Considering that methyl substitution and trifluoromethyl substitution in the biphenyl structure can effectively reduce the stacking between molecular chains, thereby improving the wettability of the adhesive and the material to be bonded, and improving the bonding performance and heat resistance, the present invention preferably prefers the above-mentioned Two aromatic diamines with biphenyl structures are used as raw materials for the preparation of polyimide adhesive prepolymers.

R ₁ is selected from any one of the following structures:

Further, the aromatic dianhydride is pyromellitic dianhydride, 3,3',4,4'-biphenyltetraic dianhydride or 3,3',4,4'-benzophenone tetraacid dianhydride One or more; the end-capping agent is 4-phenylethynyl phthalic anhydride.

It was found in experiments that dianhydrides with rigid symmetrical structures can endow polyimide adhesives with outstanding heat resistance, while pyromellitic dianhydride, 3,3',4,4'-biphenyltetraic dianhydride and 3,3',4,4'-benzophenone tetraacid dianhydride have a rigid symmetrical structure, so the present invention preferably uses the above-mentioned aromatic dianhydride as the raw material for the preparation of the adhesive prepolymer, and the prepared polyimide When the amine adhesive is used above 350°C, it not only has good heat resistance stability, but also has excellent bonding performance.

It is worth noting that the phenylethynyl end-capping agent can endow the polyimide adhesive with a wider molding temperature window, and it does not generate small molecule volatiles during the curing molding process. Therefore, the present invention preferably uses 4-phenylethynylphthalic anhydride as the end-capping agent.

The present invention also provides a kind of preparation method of polyimide adhesive, and this preparation method comprises the following steps:

Step 1: dissolving the polyimide adhesive prepolymer in an organic solvent to obtain a homogeneous solution;

Step 2: Coating the homogeneous solution on the surface of the adherend, removing the organic solvent, curing to obtain a polyimide adhesive, and completing the bonding of the adherend.

In the preparation method of the above polyimide adhesive, the removal of the organic solvent is stepwise temperature removal, and the specific process is: 60-80°C, 1-4 hours; 120-150°C, 0.5-4 hours; 180-200°C, 0.5-4 hours.

The organic solvent used in the preparation method of the above-mentioned polyimide adhesive is N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide ( One or more of DMF), dimethyl sulfoxide (DMSO) and cyclopentanone.

The beneficial effect of the preparation method of polyimide adhesive of the present invention is as follows:

On the one hand, due to the introduction of a flexible siloxane structure into the polyimide rigid main chain structure, the melt viscosity of the prepolymer is greatly reduced, so that it can better wet the surface of the bonded material and improve the adhesion. On the other hand, because siloxane has the organic-inorganic transformation characteristic of oxidative crosslinking at high temperature, during the curing process, the polyimide adhesive produces a silica-like inorganic structure, which further improves the Heat resistance of polyimide adhesives. The polyimide adhesive prepared by the above method still has excellent heat resistance stability and outstanding bonding performance at a high temperature above 350°C. The preparation method has simple process and easy operation.

Further, the solid content of the homogeneous solution in the above preparation method is 40wt.%-65wt.%.

It is found in the experiment that if the solid content of the homogeneous solution is too low in the above preparation method, the solvent will easily remain, which will affect its bonding performance; if the solid content is too high, it will not be easy to preserve. The invention controls the solid content of the homogeneous solution to be 40wt.%-65wt.%.

Further, the curing in step 2 of the above preparation method is temperature-rising curing. The temperature-rising curing process is as follows: the temperature is raised to 350-400° C. at a heating rate of 2-6° C./min, and the curing reaction time is 1-6 hours.

A heating rate of 2-6°C/min is conducive to better solvent removal and avoids solvent residues affecting the adhesive performance of the adhesive.

The temperature range of 350-400°C is the reaction temperature of thermal curing of the phenylethynyl group in the end-capping agent. If the temperature is too low, it will cause incomplete curing, and if the temperature is too high, it may cause decomposition, which is not conducive to the bonding performance of the adhesive. Therefore, the preferred curing temperature of the present invention is 350-400°C.

It is found in the experiment that the curing reaction is incomplete if the reaction time is less than 1 hour; when the reaction time is 6 hours, the curing reaction has been completed, so the curing reaction time is controlled to be 1-6 hours in the above preparation method.

Further, the polyimide adhesive prepolymer is prepared by the following method:

Dissolve aromatic diamine containing biphenyl structure and aromatic diamine containing siloxane structure in an organic solvent, and dissolve completely under the protection of inert gas to obtain a mixed solution; add aromatic dianhydride and end-capping agent to the mixed solution in sequence , under the protection of an inert gas until completely dissolved, stirring and reacting to obtain a homogeneous solution of prepolymer raw materials; adding a dehydrating agent to the homogeneous solution of prepolymer raw materials, an azeotropic reaction occurs, removing the dehydrating agent, cooling, precipitation and separation to obtain poly Imide adhesive prepolymer.

In the preparation method of the polyimide adhesive prepolymer, the organic solvent used is the same as that used in the preparation method of the polyimide adhesive.

In the preparation method of the above-mentioned polyimide adhesive prepolymer, the stirring reaction is carried out at room temperature, the stirring reaction time is 6-24 hours, and the solid content of the homogeneous solution of the obtained prepolymer raw material is 25wt.%. -40 wt.%.

When considering this solid content range, it is beneficial to obtain the polyimide adhesive prepolymer with the expected structure and designed molecular weight, and the appropriate molecular weight of the polyimide adhesive prepolymer contributes to the bonding performance and resistance thermally compatible. Therefore, in the preparation method of the polyimide adhesive prepolymer of the present invention, the solid content of the homogeneous solution of the prepolymer raw material is controlled to be 25wt.%-40wt.%.

In the preparation method of above-mentioned polyimide adhesive prepolymer, in order to realize the dehydration cyclization of polyamic acid completely, the dehydrating agent used is toluene or xylene, and the mass ratio of dehydrating agent and organic solvent is (0.5-1.5 ): 10. The azeotropic reaction is carried out at a temperature of 120-190° C. under nitrogen protection, and the azeotropic reaction time is 6-18 hours. After removing the dehydrating agent, the reaction solution was cooled to 80-120°C.

In the preparation method of the above-mentioned polyimide adhesive prepolymer, the precipitant used in the precipitation separation is any one or several arbitrary proportions of water, methanol, ethanol, propanol, isopropanol or butanol. mixture. Resin precipitates are obtained after precipitation separation, repeated washing, filtration, and drying to obtain polyimide adhesive prepolymers. The washing of resin precipitation can use hot water, methanol, ethanol or other low-boiling point alcoholic solvents in any one or a mixture of several random proportions.

When using the polyimide adhesive of the present invention to bond objects, the polyimide resin prepolymer is first dissolved in an organic solvent to prepare a homogeneous solution with a certain solid content; this homogeneous solution is evenly coated On the surface of the object to be bonded, the solvent is removed through a stepwise temperature rise, and then a firm bonded body is obtained through a temperature rise curing process.

The adherend in the present invention can be common metals such as stainless steel, aluminum alloy, titanium alloy, and high temperature resistant resin-based composite materials.

In the present invention, the above technical solutions can also be combined with each other to realize more preferred combination solutions. Additional features and advantages of the invention will be set forth in the description which follows, and some of the advantages will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by what is particularly pointed out in the written description, claims as well as the appended drawings.

Description of drawings

The drawings are only for the purpose of illustrating specific embodiments and are not to be considered as limiting the invention.

Fig. 1 is the rheological curve of the polyimide adhesive prepolymer prepared in Example 1.

Fig. 2 is the DMA curve of the polyimide adhesive prepared in Example 1.

Fig. 3 is a TEM image of the polyimide adhesive prepared in Example 1 after a single lap shear test at a high temperature of 380°C.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The following examples select representative monomer raw materials such as diamines, dianhydrides, and end-capping agents to prepare addition-type polyimide adhesives with different structures, and select representative stainless steel as the adherend for bonding performance. Test, replace the raw material monomer or adherend in the embodiment with other raw material monomers or other types of adherends described in the content of the present invention, adopt the preparation method and conditions described in the content of the present invention, the prepared polyimide The amine adhesive has the same effect as this embodiment.

The percentage content and percentage concentration in the present invention are all mass percentage content and mass percentage concentration unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.

Example 1

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 28.82 grams (0.09 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 3.49 g (0.01 mol) of bis(4-aminophenoxy)tetramethyldisiloxane and 110 g of N-methylpyrrolidone were stirred under nitrogen protection until completely dissolved. After that, 16.11 g (0.05 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 24.82 g (0.10 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 12 hours to obtain a homogeneous solution with a solid content of 40 wt.%.

(2) Add 16 grams of toluene to the above homogeneous solution, raise the temperature of the reaction system to 175° C., react for 12 hours under nitrogen protection, then raise the temperature to 200° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into ethanol to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer Solid powder with a yield of 97% (prepolymer structure x:y=9:1, n=1.0, M _n =1410 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N-methylpyrrolidone to obtain a resin solution with a solid content of 65wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80°C/2 hours , 120°C/1 hour, 200°C/1.5 hours stepwise heating process to remove the solvent, then increase the temperature to 370°C at a heating rate of 2°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 2

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 25.62 grams (0.08 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 6.97 g (0.02 mol) of bis(4-aminophenoxy)tetramethyldisiloxane and 215 g of N,N-dimethylacetamide were stirred under nitrogen protection until completely dissolved. After that, 19.33 g (0.06 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 19.86 g (0.08 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 12 hours to obtain a homogeneous solution with a solid content of 25 wt.%.

(2) 11 grams of xylene was added to the above homogeneous solution, the temperature of the reaction system was raised to 150° C., and the reaction was carried out under nitrogen protection for 12 hours, and then the temperature was raised to 166° C. to evaporate the xylene and stop heating.

(3) The reaction solution is cooled to 80°C, poured into methanol to obtain a resin precipitate, washed repeatedly with ethanol, filtered, pulverized and dried in an oven to obtain a polyimide adhesive prepolymer solid powder, The yield was 98% (prepolymer structure x:y=8:2, n=1.5, _Mn =1721 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylacetamide to obtain a resin solution with a solid content of 50wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80 °C/2 hours, 150°C/2 hours, 200°C/1.5 hours stepwise heating process to remove the solvent, then increase the temperature to 350°C at a heating rate of 3°C/min, and obtain a firm bonded body after curing for 6 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 3

(1) In a three-neck flask equipped with a mechanical stirrer, a water separator, a nitrogen inlet and outlet, and a thermometer, add 22.42 grams (0.07 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 10.46 g (0.03 mol) of bis(4-aminophenoxy)tetramethyldisiloxane and 165 g of N,N-dimethylformamide were stirred under nitrogen protection until completely dissolved. After that, 21.49 g (0.067 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 16.56 g (0.067 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 8 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) 8 grams of toluene was added to the above homogeneous solution, the temperature of the reaction system was raised to 140° C., and the reaction was carried out under nitrogen protection for 12 hours, and then the temperature was raised to 153° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 120°C, pour it into propanol to obtain a resin precipitate, wash it repeatedly with methanol, filter, pulverize and dry it in an oven to obtain a solid powder of polyimide adhesive prepolymer , the yield was 96% (prepolymer structure x:y=7:3, n=2.0, M _n =2034 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylformamide to obtain a resin solution with a solid content of 40wt.%, and apply the homogeneous solution evenly on the surface of the stainless steel sheet, and first pass through 60 °C/2 hours, 120°C/4 hours, 200°C/2 hours stepwise heating process to remove the solvent, then increase the temperature to 400°C at a heating rate of 5°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 4

(1) In a three-neck flask equipped with a mechanical stirrer, a water separator, a nitrogen inlet and outlet, and a thermometer, add 22.42 grams (0.07 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 10.46 g (0.03 mol) of bis(4-aminophenoxy)tetramethyldisiloxane and 162 g of N-methylpyrrolidone were stirred under nitrogen protection until completely dissolved. After that, 24.17 g (0.075 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 12.41 g (0.05 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 8 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) 16 grams of toluene was added to the above homogeneous solution, the temperature of the reaction system was raised to 180° C., and the reaction was carried out under nitrogen protection for 12 hours, then the temperature was raised to 200° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 120°C, pour it into propanol to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a prepolymerized polyimide adhesive The product was solid powder with a yield of 96% (prepolymer structure x:y=7:3, n=3.0, M _n =2649 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylformamide to obtain a resin solution with a solid content of 40wt.%, and apply the homogeneous solution evenly on the surface of the stainless steel sheet, and first pass through 60 °C/4 hours, 120°C/3 hours, 200°C/1 hour stepwise heating process to remove the solvent, then increase the temperature to 400°C at a heating rate of 6°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 5

(1) In a three-neck flask equipped with a mechanical stirrer, a water separator, a nitrogen inlet and outlet, and a thermometer, add 22.42 grams (0.07 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 16.70 g (0.03 mol) of bis(4-(4-aminophenylcarboxylate) phenyl) tetramethyldisiloxane and 176 g of dimethyl sulfoxide were stirred under nitrogen protection until completely dissolved. After that, 24.17 g (0.075 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 12.41 g (0.05 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 6 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) Add 18 grams of toluene to the above-mentioned homogeneous solution, raise the temperature of the reaction system to 160° C., react for 18 hours under the protection of nitrogen, then raise the temperature to 177° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 80°C, pour it into ethanol to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer Solid powder with a yield of 97% (prepolymer structure x:y=7:3, n=3.0, M _n =2867 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in dimethyl sulfoxide to obtain a resin solution with a solid content of 50wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80°C/4 hours , 150°C/2 hours, 200°C/4 hours stepwise heating process to remove the solvent, then increase the temperature to 400°C at a heating rate of 2°C/min, and obtain a firm bonded body after curing for 1 hour.

The main properties of the polyimide adhesive prepared in this embodiment are shown in Table 1

Example 6

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 28.82 grams (0.09 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 5.5676 g (0.01 mole) of bis(4-(4-aminophenylcarboxylate) phenyl) tetramethyldisiloxane and 172 g of N-methylpyrrolidone were stirred under nitrogen protection until completely dissolved. After that, 14.71 g (0.05 mol) of 3,3',4,4'-biphenyltetralic dianhydride and 24.82 g (0.10 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. , stirred at room temperature for 12 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) Add 9 grams of toluene to the above homogeneous solution, raise the temperature of the reaction system to 190° C., and react for 6 hours under nitrogen protection, then raise the temperature to 200° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into isopropanol to obtain a resin precipitate, wash it repeatedly with methanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive preprecipitate. Polymer solid powder with a yield of 98% (prepolymer structure x:y=9:1, n=1.0, M _n =1400 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylacetamide to obtain a resin solution with a solid content of 50wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80 °C/1 hour, 150°C/4 hours, 200°C/1 hour stepwise heating process to remove the solvent, then increase the temperature to 350°C at a heating rate of 2°C/min, and obtain a firm bonded body after curing for 3 hours.

The main properties of the polyimide adhesive prepared in this embodiment are shown in Table 1

Example 7

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 25.62 grams (0.08 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 6.97 g (0.02 mol) of bis(4-aminophenoxy)tetramethyldisiloxane and 130 g of N,N-dimethylacetamide were stirred under nitrogen protection until completely dissolved. After that, 17.65 g (0.06 mol) of 3,3',4,4'-biphenyltetralic dianhydride and 19.86 g (0.08 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 10 hours to obtain a homogeneous solution with a solid content of 35 wt.%.

(2) Add 7 grams of xylene to the above homogeneous solution, raise the temperature of the reaction system to 150° C., react for 10 hours under nitrogen protection, then raise the temperature to 166° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 80°C, pour it into butanol to obtain a resin precipitate, wash it repeatedly with hot water, filter, pulverize and dry it in an oven to obtain a solid polyimide adhesive prepolymer Powder with a yield of 96% (prepolymer structure x:y=8:2, n=1.5, M _n =1665 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylacetamide to obtain a resin solution with a solid content of 50wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80 °C/4 hours, 150°C/2 hours, 200°C/2 hours stepwise heating process to remove the solvent, then increase the temperature to 370°C at a heating rate of 3°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this embodiment are shown in Table 1

Example 8

(1) In a three-neck flask equipped with a mechanical stirrer, a water separator, a nitrogen inlet and outlet, and a thermometer, add 22.42 grams (0.07 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 16.70 g (0.03 mole) of bis(4-(4-aminophenylcarboxylate) phenyl) tetramethyldisiloxane and 112 g of N-methylpyrrolidone were stirred under nitrogen protection until completely dissolved. After that, 19.62 g (0.067 mol) of 3,3',4,4'-biphenyltetraacid dianhydride and 16.56 g (0.067 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 10 hours to obtain a homogeneous solution with a solid content of 40 wt.%.

(2) Add 17 grams of toluene to the above-mentioned homogeneous solution, raise the temperature of the reaction system to 175° C., and react for 8 hours under nitrogen protection, then raise the temperature to 200° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into hot water to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer The product was solid powder with a yield of 97% (prepolymer structure x:y=7:3, n=2.0, M _n =2120 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N,N-dimethylacetamide to obtain a resin solution with a solid content of 50wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80 °C/4 hours, 150°C/0.5 hours, 200°C/2 hours stepwise heating process to remove the solvent, then increase the temperature to 390°C at a heating rate of 3°C/min, and obtain a firm bonded body after curing for 4 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 9

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 19.11 grams (0.09 moles) of 4,4'-diamino-2,2'-dimethylbiphenyl, 3.49 grams (0.01 mol) bis(4-aminophenoxy)tetramethyldisiloxane and 136 grams of cyclopentanone were stirred under nitrogen protection until completely dissolved. Then, 10.91 g (0.05 mol) of phthalic dianhydride and 24.82 g (0.10 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 24 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) Add 6.8 g of toluene to the above-mentioned homogeneous solution, raise the temperature of the reaction system to 120° C., react for 6 hours under the protection of nitrogen, then raise the temperature to 130° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into ethanol to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer Solid powder with a yield of 95% (prepolymer structure x:y=9:1, n=1.0, M _n =1116 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in cyclopentanone to obtain a resin solution with a solid content of 40wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 60°C/4 hours, 150 °C/4 hours, 200 °C/0.5 hours stepwise heating process to remove the solvent, then increase the temperature to 400 °C at a heating rate of 6 °C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 10

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 16.98 grams (0.08 moles) of 4,4'-diamino-2,2'-dimethylbiphenyl, 6.97 grams (0.02 mol) bis(4-aminophenoxy)tetramethyldisiloxane and 128 g of N,N-dimethylacetamide were stirred under nitrogen protection until completely dissolved. After that, 14.55 g (0.067 mol) of pyromellitic dianhydride and 16.56 g (0.067 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 10 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) Add 13 grams of toluene to the above homogeneous solution, raise the temperature of the reaction system to 145° C., react for 8 hours under nitrogen protection, then raise the temperature to 166° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 120°C, pour it into hot water to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer The product was solid powder with a yield of 97% (prepolymer structure x:y=8:2, n=2.0, M _n =1550 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N-methylpyrrolidone to obtain a resin solution with a solid content of 60wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass 60°C/4 hours , 150°C/2 hours, 180°C/4 hours stepwise heating process to remove the solvent, then increase the temperature to 400°C at a heating rate of 2°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Example 11

(1) In a three-necked flask equipped with a mechanical stirrer, water separator, nitrogen inlet and outlet, and a thermometer, add 16.98 grams (0.08 moles) of 4,4'-diamino-2,2'-dimethylbiphenyl, 11.14 grams (0.02 mol) of bis(4-(4-aminophenylcarboxylate)phenyl)tetramethyldisiloxane and 138 g of N,N-dimethylacetamide were stirred under nitrogen protection until completely dissolved. After that, 14.55 g (0.067 mol) of pyromellitic dianhydride and 16.56 g (0.067 mol) of 4-phenylethynylphthalic anhydride were added, and stirred under a nitrogen atmosphere until completely dissolved. Stir at room temperature for 12 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) 14 grams of toluene was added to the above homogeneous solution, the temperature of the reaction system was raised to 145° C., and the reaction was carried out under nitrogen protection for 10 hours, and then the temperature was raised to 166° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into hot water to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer The product was solid powder with a yield of 97% (prepolymer structure x:y=8:2, n=2.0, M _n =1655 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N-methylpyrrolidone to obtain a resin solution with a solid content of 65wt.%, and apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass 60°C/4 hours , 150°C/2 hours, 200°C/4 hours stepwise heating process to remove the solvent, then increase the temperature to 370°C at a heating rate of 4°C/min, and obtain a firm bonded body after curing for 3 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

Comparative example 1

(1) In a three-necked flask equipped with a mechanical stirrer, a water separator, a nitrogen inlet and outlet, and a thermometer, add 12.81 grams (0.04 moles) of 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl and 64 grams of N-methylpyrrolidone was stirred under nitrogen protection until completely dissolved. Then add 9.67 g (0.03 mol) of 3,3',4,4'-benzophenone tetraacid dianhydride and 4.96 g (0.02 mol) of 4-phenylethynylphthalic anhydride, and stir until completely dissolved under nitrogen atmosphere. Stir at room temperature for 12 hours to obtain a homogeneous solution with a solid content of 30 wt.%.

(2) Add 6 grams of toluene to the above homogeneous solution, raise the temperature of the reaction system to 180° C., and react for 12 hours under nitrogen protection, then raise the temperature to 200° C. to evaporate the toluene and stop heating.

(3) Cool the reaction solution to 100°C, pour it into ethanol to obtain a resin precipitate, wash it repeatedly with ethanol and hot water, filter, pulverize and dry it in an oven to obtain a polyimide adhesive prepolymer Solid powder with a yield of 97% (prepolymer structure x:y=10:0, n=3.0, M _n =2619 g/mol).

Bonding experiment of polyimide adhesive and stainless steel sheet:

Dissolve the solid powder of the above polyimide adhesive in N-methylpyrrolidone to obtain a resin solution with a solid content of 65wt.%. Apply this homogeneous solution evenly on the surface of a stainless steel sheet, and first pass through 80°C/2 hours , 120°C/1 hour, 200°C/1.5 hours stepwise heating process to remove the solvent, then increase the temperature to 370°C at a heating rate of 2°C/min, and obtain a firm bonded body after curing for 2 hours.

The main properties of the polyimide adhesive prepared in this example are shown in Table 1.

The main properties of the prepared polyimide adhesive of table 1 embodiment 1-11 and comparative example 1

Table 1 has listed the melt fluidity, heat resistance and bonding performance etc. of the polyimide adhesive prepared by embodiment 1-11 and comparative example 1, specifically include: polyimide adhesive pre-prepared The number average molecular weight and melt fluidity of the polymer and the heat resistance and bonding performance of the cured polyimide adhesive. It can be seen from Table 1 that the number average molecular weight of the polyimide adhesive prepolymer prepared by the method provided by the present invention is 1100-2900g/mol, and the minimum melt viscosity at 353-375°C is 1.7-18.5Pa·s, The glass transition temperature (T _g ) of the adhesive after curing is ≥360°C. The shear strength of the adhesive for bonding stainless steel is 18-25MPa at room temperature, 15-18MPa and 7-10MPa at 350°C and 380°C respectively. Compared with Comparative Example 1 without adding diamine containing siloxane structure, the melt viscosity of the polyimide adhesive prepared in Examples 1-11 is greatly reduced, and the shear strength after bonding with stainless steel is greatly improved. The excellent high-temperature adhesive performance of the adhesive is closely related to the organic-inorganic transformation characteristics of siloxane oxidative crosslinking at high temperature, and the appearance of the inorganic phase in the adhesive structure at high temperature improves its heat resistance stability. The above data show that the polyimide adhesive prepared by the method provided by the present invention has excellent melt fluidity, heat resistance and high-temperature bonding performance, and can be applied to high-temperature resistant adhesives in fields such as aviation, aerospace, precision machinery, and petrochemical industry. Bonding of components.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention.

Claims (10)

1. a kind of polyimides adhesive, which is characterized in that obtained using polyimides adhesive prepolymer cures, the polyamides The raw material for preparing of imines adhesive prepolymer is the aromatic diamines of biphenyl contenting structure, the aromatic diamines of silicone-containing structure, fragrance Dianhydride and end-capping reagent.

2. polyimides adhesive according to claim 1, which is characterized in that the polyimides adhesive prepolymer tool There is the structure of general formula I：

Wherein, any one of Ar in following aromatic structures：

R₁For biphenyl structural, R₂For siloxane structure, the ratio of x and y are (9:1)-(7:3), n 1-3.

3. polyimides adhesive according to claim 2, which is characterized in that the aromatic diamines of the silicone-containing structure For bis- (4- amino-benzene oxygens) tetramethyl disiloxanes and/or bis- (4- (4- amino carbobenzoxy) benzene) tetramethyl disiloxanes；

R₂Any one in following structures：

。

4. polyimides adhesive according to claim 2, which is characterized in that the aromatic diamines of the biphenyl structural are 4, 4 '-diamino -2,2 '-dimethyl diphenyl and/or 4,4 '-diamino -2,2 '-bis trifluoromethyl biphenyl；

R₁Any one in following structures：

5. polyimides adhesive according to claim 2, which is characterized in that the aromatic dianhydride is pyromellitic acid two Acid anhydride, 3,3 ', 4,4 '-biphenyltetracarboxylic dianhydride or 3,3 ', one or more of 4,4 '-benzophenone tetracarboxylic dianhydrides；

The end-capping reagent is 4- phenylacetylene base phthalic anhydrides.

6. a kind of preparation method of polyimides adhesive, which is characterized in that be used to prepare poly- as described in claim 1 to 5 Acid imide adhesive, the preparation method comprises the following steps：

Step 1：Polyimides adhesive prepolymer is dissolved in organic solvent, obtains homogeneous phase solution；

Step 2：The homogeneous phase solution is coated on bonded object surface, removes organic solvent, solidification obtains polyimides gluing The bonding of bonded object is completed in agent.

7. the preparation method of polyimides adhesive according to claim 6, which is characterized in that the homogeneous phase solution is consolidated Content is 40wt.%-65wt.%.

8. the preparation method of polyimides adhesive according to claim 6, which is characterized in that consolidating in the step 2 Elevated cure is turned to, the elevated cure process is：With the heating rate of 2-6 DEG C/min, it is warming up to 350-400 DEG C, solidification is anti- It is 1-6 hours between seasonable.

9. the preparation method of polyimides adhesive according to claim 6, which is characterized in that the polyimides gluing Agent prepolymer is prepared by the following method to obtain：

The aromatic diamines of the aromatic diamines of biphenyl contenting structure and silicone-containing structure are dissolved in organic solvent, in inert gas shielding Down toward being completely dissolved, mixed solution is obtained；Aromatic dianhydride and end-capping reagent are sequentially added into mixed solution, in inert gas shielding It down toward being completely dissolved, is stirred to react, obtains pre-polymerization raw material homogeneous phase solution；Dehydration is added into pre-polymerization raw material homogeneous phase solution Azeotropic reaction occurs for agent, removes dehydrating agent, cooling, precipitates isolated polyimides adhesive prepolymer.

10. the preparation method of polyimides adhesive according to claim 9, which is characterized in that the pre-polymerization raw material The solid content of homogeneous phase solution is 25wt.%-40wt.%.