POSS (polyhedral oligomeric silsesquioxane) modified polyamide acid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polymer materials, and particularly relates to POSS (Polyhedral Oligomeric Silsesquioxane) modified polyamide acid as well as a preparation method and application thereof. The preparation method of the POSS modified polyamide acid comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, and uniformly stirring and dispersing to obtain a diamine monomer mixed solution; and (2) continuously stirring, adding the dianhydride monomer into the diamine monomer mixed solution in batches, reacting for 3-5 hours, adding the polyamino POSS monomer again, and continuously reacting for 3-6 hours to obtain the POSS modified polyamide acid. A small amount of polyamino POSS is added in the initial feeding part, and the POSS is mainly used for introducing a cage structure on a polyamide acid main chain, so that the compatibility and the stability of polyimide are improved. After the reaction is carried out for a period of time, more polyamino POSS monomers are added again, so that the formation of a net structure of polyamide acid can be promoted, and the adhesive property can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a POSS modified polyamic acid and a preparation method and application thereof. Background Art

[0002] Epoxy resins are a general term for compounds containing two or more epoxy groups within a single molecule, capable of forming three-dimensional crosslinked, cured compounds under appropriate chemical reagents and conditions. Epoxy resins come in many varieties, and their molecular weights are classified as oligomers (or oligomers). Sometimes, to distinguish them from cured epoxy resins, they are also referred to as epoxy resin oligomers.

[0003] There are many types of epoxy resins, with bisphenol A epoxy resin being the primary type used as an adhesive, accounting for 90% of total epoxy resin production. Bisphenol A epoxy resin was synthesized in the early 1940s, and the cured resin exhibits excellent bonding properties for materials such as glass, ceramics, and metals. Since production practices at the time did not require specialized bonding techniques and the concept of solvent-free synthetic adhesives had not yet been established, the significance of this experimental discovery was not fully appreciated. The development of the aircraft manufacturing industry placed new demands on bonding technology, sparking interest in epoxy resin adhesives. By the 1950s, the application and research of epoxy resin adhesives had experienced a significant leap forward. With the synthesis of new epoxy resin adhesives and curing agents, epoxy adhesives with a wide range of properties could be formulated. Epoxy resins are widely used in bonding metals and various other materials, particularly in the aviation industry, where high-strength and high-temperature-resistant epoxy adhesives demonstrate their unique advantages.

[0004] The widespread use of bisphenol A epoxy resin stems from its numerous advantages in producing adhesives. First, the bisphenol A epoxy resin used in adhesives is typically a viscous liquid, easily mixed with other reagents, and easily adjusted during application and use. Second, it is suitable for bonding a wide variety of substrates with high strength. For example, ideal bond strength can be achieved on various metals, stone, ceramics, glass, rubber, and paper. Furthermore, the curing process involves the resin directly participating in the reaction, an addition reaction that produces no byproducts and minimizes shrinkage.

[0005] Epoxy resins are classified by their primary composition into pure epoxy resin adhesives (or unmodified epoxy resin adhesives) and modified epoxy resin adhesives (also known as composite epoxy resin adhesives). Commercially available modified epoxy resin adhesives include phenolic-epoxy resin adhesives, nylon-epoxy resin adhesives, nitrile-epoxy resin adhesives, acrylic-epoxy resin adhesives, polysulfide-epoxy resin adhesives, and polyurethane-epoxy resin adhesives. Modified epoxy resin adhesives have completely replaced pure epoxy resin adhesives and are widely used in various sectors. However, the low mechanical strength of currently prepared modified epoxy resin adhesives limits their application. Summary of the Invention

[0006] The invention provides a POSS modified polyamic acid and a preparation method and application thereof. The preparation process is simple, low in cost, easy to operate, and the source of reaction raw materials is convenient, which is conducive to industrial production. In addition, the epoxy resin modified with the POSS modified polyamic acid has excellent mechanical properties and broad application prospects.

[0007] This object of the invention is achieved through the following technical solutions: A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the monomers to obtain a diamine monomer mixed solution; the number of amino groups on the polyamino POSS monomer is 6-8; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3-5 hours, add the polyamino POSS monomer again and continue reacting for 3-6 hours to obtain POSS-modified polyamic acid. By adjusting the initial reaction time, the molecular weight can be fully increased while preventing premature cross-linking of the polyamic acid due to excessive reaction time, thereby improving the stability of the polymer. In particular, the reaction time is 3.2-4.5 hours or 3.5-4 hours.

[0008] Normally, polyimide cannot be directly fused with epoxy resin, while the precursor of polyimide, polyamic acid, is a liquid substance with a certain viscosity that can be evenly mixed in epoxy resin, and the operation method is extremely simple. The carboxyl group on polyamic acid mainly reacts with the epoxy group. Each unit has two active hydrogens in different positions, which may react simultaneously, thus forming a complex macromolecular ester graft copolymer with an interpenetrating network structure. When the temperature reaches 200-300°C, the carboxyl group that does not react with the epoxy and the amino group on the adjacent benzene ring will undergo a condensation reaction to form a five-membered ring group. The formation of this stable five-membered ring further improves the stability of the system and is particularly beneficial for improving heat resistance. Due to the presence of the imide group, the use of polyamide acid to modify epoxy resin adhesives can improve the heat resistance of the system, but its mechanical properties are limited. In order to further improve its bonding strength, the present invention uses polyamino POSS to modify polyamic acid. The introduction of polyamino POSS groups can improve the wetting properties of the adhesive with materials such as metals and improve the bonding strength.

[0009] Preferably, the non-POSS diamine monomer in step (1) is selected from p-phenylenediamine, m-phenylenediamine, 2-trifluoromethyl-1,4-diaminobenzene, 5-methyl-1,3-diaminobenzene, 5-trifluoromethyl-1,3-diaminobenzene, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-bis(trifluoromethyl)diphenylmethane, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorodiphenylmethane, One or more of benzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 4,4'-bis(4-aminophenoxy)benzene, 4,4'-bis(3-aminophenoxy)benzene, 4,4'-diaminodiphenyl sulfone, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-bis(trifluoromethyl)biphenyl or 4,4'-bis(4-aminophenoxy)biphenyl.

[0010] Preferably, the polyamino POSS monomer in step (1) is selected from one or more of hexaaminopropyl silsesquioxane, hexaaminophenyl silsesquioxane, octaaminophenyl cage silsesquioxane, and octaaminopropyl cage silsesquioxane.

[0011] Preferably, the organic solvent in step (1) is one or more of N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone; and the stirring rate is 100-300 rpm. The amount of organic solvent used is not particularly limited. Specifically, the mass-to-volume ratio of the sum of the mass of the non-POSS diamine monomer, the twice-added polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:(10-15) g / mL.

[0012] Preferably, the dianhydride monomer in step (2) is selected from pyromellitic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxylic)hexafluoropropane dianhydride, 4,4'-hexafluoroisopropylphthalic anhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) One or more of alkane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, and 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride; the dianhydride monomer is added to the diamine monomer mixed solution in 2-6 times, with an interval of 2-6 minutes between each addition.

[0013] Preferably, the reaction temperature in step (2) is 25-35°C.

[0014] Preferably, the molar ratio of the dianhydride monomer to the sum of all diamine monomers of the non-POSS diamine monomer and the twice-added polyamino POSS monomer in step (2) is (1-1.05):1.

[0015] Particularly preferably, the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer in step (1) is (0.01-1):100; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer added again in step (2) is (2-5):100. In order to improve the performance of polyamic acid and the dispersibility of polyamino POSS in the matrix and improve the epoxy resin bonding performance, the present invention adopts a step-by-step feeding method to prepare POSS modified polyamic acid. First, a small amount of polyamino POSS is added in the initial feeding part. This part of POSS is mainly for introducing a cage structure on the polyamic acid main chain, which can improve the compatibility of polyimide and epoxy resin on the one hand and improve the stability of polyamic acid on the other hand. The amount of polyamino POSS in the initial part should not be too much, otherwise it will affect the growth of the molecular chain and be unfavorable for the improvement of mechanical properties. After a period of reaction, more polyamino POSS monomer is added. This monomer acts as both a chain extender and a crosslinker, forming a network structure for the polyamic acid, promoting the formation of an interpenetrating network with the epoxy resin and improving adhesion. Adding an appropriate amount of polyamino POSS monomer further improves the performance of the polyamic acid while preventing excessive crosslinking that can increase the brittleness of the adhesive. Furthermore, the molar ratio of the added polyamino POSS monomer to the non-POSS diamine monomer is (2.5-4):100.

[0016] On the other hand, the present invention also provides a POSS modified polyamic acid and its application. The POSS modified polyamic acid is used in the field of epoxy resin adhesives. The epoxy resin adhesive comprises epoxy resin and POSS modified polyamic acid, which can greatly improve the mechanical properties of the epoxy resin adhesive.

[0017] Specifically, the epoxy resin adhesive contains 100 parts of epoxy resin, 10-150 parts of POSS modified polyamic acid, and 5-10 parts of curing agent. After the epoxy resin and modified polyamic acid are evenly mixed, the curing agent is added, and the mixture is heated and stirred evenly to obtain the epoxy resin adhesive. The heating temperature is not particularly limited, and is generally between 60-80°C, and stirred for 2.5-4 hours. The specific curing conditions are curing at 110-130°C for 0.5-1.5 hours, curing at 140-160°C for 0.5-1.5 hours, curing at 160-180°C for 1-2 hours, curing at 190-210°C for 1-2 hours, and curing at 240-270°C for 1-2 hours; the curing pressure is 0.1-0.3MPa. The high-temperature curing process not only promotes the curing process, but also promotes the amidation process of polyamic acid, thereby improving the adhesive properties of the adhesive. The type of curing agent is not particularly limited, and common amines, acid anhydrides, and other types in the field can be used.

[0018] Beneficial effect: the present invention adopts step-by-step feeding mode to prepare POSS modified polyamic acid.First, a small amount of polyamino POSS is added in the initial feeding part. This part POSS is mainly for introducing cage structure on the polyamic acid main chain, can improve the compatibility of polyimide and epoxy resin on the one hand, improves the stability of polyamic acid on the other hand. After reacting for a period of time, more polyamino POSS monomers are added again. This part monomer can play the function of chain extender, has the effect of cross-linking agent again, can form the network structure of polyamic acid, promotes to form interpenetrating network structure with epoxy resin, improves adhesion. Adding an amount of polyamino POSS monomer again can improve polyamic acid performance, can avoid excessive cross-linking again and cause adhesive brittleness to increase. DETAILED DESCRIPTION

[0019] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0020] Unless otherwise specified, the raw material types and specific process parameters of the following examples and comparative examples are consistent. Among them, the product performance test method is: under the same conditions, the effect of the POSS modified polyamic acid prepared in Examples 1-10 and Comparative Example 1 on the performance of the epoxy resin adhesive is tested. The epoxy resin adhesive comprises: 100 parts of E-51 epoxy resin, 50 parts of POSS modified polyamic acid, and 6 parts of 4,4'-diaminodiphenyl sulfone. After the epoxy resin and modified polyamic acid are evenly mixed, the curing agent 4,4'-diaminodiphenyl sulfone is added and stirred at 75°C for 3h to obtain the epoxy resin adhesive. The epoxy resin adhesive is evenly coated on the treated aluminum alloy surface and cured at 120°C for 0.8h, 150°C for 1h, 170°C for 1.8h, 210°C for 1.8h, and 250°C for 1.8h; the curing pressure is 0.2MPa. The shear strength is tested with reference to GB7124-86.

[0021] Example 1 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.3:100; the non-POSS diamine monomer is selected from a mixture of 2-trifluoromethyl-1,4-diaminobenzene and 4,4'-diaminodiphenyl ether in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3 hours, add the polyamino POSS monomer again and continue reacting for 6 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 2.5:100; the dianhydride monomer is selected from pyromellitic dianhydride; the dianhydride monomer is added to the diamine monomer mixed solution in 3 times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:14 g / mL; the reaction temperature is 28°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.01:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 27.8 MPa.

[0022] Example 2 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 1:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diamino-3,3'-dimethyldiphenylmethane in a molar ratio of 2:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N-methylpyrrolidone; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 4 hours, add the polyamino POSS monomer again and continue reacting for 3 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 4:100; the dianhydride monomer is selected from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride; the dianhydride monomer is added to the diamine monomer mixed solution in 3 times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 33°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.05:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 30.1 MPa.

[0023] Example 3 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing them uniformly to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 27.2 MPa.

[0024] Example 4 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.3:100; the non-POSS diamine monomer is selected from 4,4'-diamino-3,3'-dimethyldiphenylmethane; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After the reaction lasts for 3.2 hours, add the polyamino POSS monomer again and continue the reaction for 5.6 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3.8:100; the dianhydride monomer is selected from a mixture of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 2,3,3',4'-benzophenonetetracarboxylic acid dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:14.5 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.02:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 29.4MPa.

[0025] Example 5 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing them uniformly to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 2:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 27.5 MPa.

[0026] Example 6 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.5:100; the non-POSS diamine monomer is selected from a mixture of 3,3'-diaminobenzophenone and 4,4'-diaminodiphenyl sulfone in a molar ratio of 2:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N-methylpyrrolidone; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.3 hours, add the polyamino POSS monomer again and continue reacting for 3.8 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 2.8:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer and the dianhydride monomer to the organic solvent is 1:14.2 g / mL; the reaction temperature is 28°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.02:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 28.3 MPa.

[0027] Example 7 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing them uniformly to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 5:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 28.2 MPa.

[0028] Example 8 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.8:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenyl ether and 4,4'-diaminobenzophenone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.9 hours, add the polyamino POSS monomer again and continue reacting for 5 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3.6:100; the dianhydride monomer is selected from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer and the dianhydride monomer to the organic solvent is 1:14.6 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.04:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 28.7 MPa.

[0029] Example 9 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 3:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 0.6:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 25.8 MPa.

[0030] Example 10 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing them uniformly to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 3,3'-diaminobenzophenone in a molar ratio of 1:2; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.8 hours, add the polyamino POSS monomer again and continue reacting for 3.8 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3.4:100; the dianhydride monomer is selected from a mixture of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:14.5 g / mL; the reaction temperature is 30°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 28.8MPa.

[0031] Example 11 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing them uniformly to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 0.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 30.5 MPa.

[0032] Comparative Example 1 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer to an organic solvent, stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer is 3.6:100; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone in a molar ratio of 1:1; the polyamino POSS monomer is selected from octaaminophenyl cage silsesquioxane; the organic solvent is N,N-dimethylacetamide; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 7.5 hours, POSS modified polyamic acid is obtained; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in three times, with an interval of 5 minutes each time; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer and the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 15.8 MPa.

[0033] Comparative Example 2 A preparation method of POSS modified polyamic acid, characterized in that, comprises the following steps: (1) adding a non-POSS diamine monomer to an organic solvent and stirring and dispersing the mixture to obtain a diamine monomer mixed solution; the non-POSS diamine monomer is selected from a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylsulfone in a molar ratio of 1:1; the organic solvent is N,N-dimethylacetamide; and the stirring rate is 200 rpm; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3.5 hours, add the polyamino POSS monomer again and continue reacting for 4 hours to obtain POSS modified polyamic acid; the polyamino POSS monomer is selected from octaaminophenyl cage-type silsesquioxane; the molar ratio of the polyamino POSS monomer added again to the non-POSS diamine monomer is 3.6:100; the dianhydride monomer is selected from a mixture of pyromellitic dianhydride and 3,3',4,4'-diphenylether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixed solution in 3 times, each time with an interval of 5 minutes; the mass volume ratio of the sum of the mass of the non-POSS diamine monomer, the polyamino POSS monomer, and the dianhydride monomer to the organic solvent is 1:15 g / mL; the reaction temperature is 31°C; the molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer is 1.03:1. After testing, the shear strength of the polyamic acid modified epoxy resin adhesive is 16.7MPa.

[0034] As can be seen from the foregoing description and comparative example, the present invention adopts the step-by-step feeding mode to prepare the POSS modified polyamic acid.First, a small amount of polyamino POSS is added in the initial feeding part, this part POSS is mainly for introducing cage structure on the polyamic acid main chain, can improve the compatibility of polyimide and epoxy resin on the one hand, improves the stability of polyamic acid on the other hand. After reacting for a period of time, again add more polyamino POSS monomer, this part monomer can play the function of chain extender, has the effect of cross-linking agent again, can form the network structure of polyamic acid, promotes to form interpenetrating network structure with epoxy resin, improves adhesiveness. Again add appropriate amount of polyamino POSS monomer, both can improve polyamic acid performance, can avoid excessive cross-linking again and cause adhesive fragility to increase. Compared with Example 11, Comparative Example 1 and Comparative Example 2 only add polyamino POSS in step (1) or step (2), respectively. Adding polyamino POSS only in step (1) will affect the growth of the molecular chain, and adding polyamino POSS only in step (2) will cause excessive cross-linking of the polyamic acid. The prepared polyamic acid has poor performance and cannot effectively improve the bonding strength of the epoxy resin.

[0035] The above description is only a preferred embodiment of the invention and is not intended to limit the scope of the invention. That is, any equivalent changes and modifications made according to the content of the patent application of the present invention should fall within the technical scope of the present invention.

Claims

1. A method for preparing a POSS modified polyamic acid, characterized in that, The following steps are involved: (1) adding a non-POSS diamine monomer and a polyamino POSS monomer into an organic solvent, stirring and dispersing the monomers to obtain a diamine monomer mixed solution; the number of amino groups on the polyamino POSS monomer is 6-8; (2) Continue stirring and add the dianhydride monomer to the diamine monomer mixed solution in batches. After reacting for 3-5 hours, add the polyamino POSS monomer again and continue reacting for 3-6 hours to obtain POSS modified polyamic acid.

2. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The non-POSS diamine monomer in step (1) is selected from p-phenylenediamine, m-phenylenediamine, 2-trifluoromethyl-1,4-diaminobenzene, 5-methyl-1,3-diaminobenzene, 5-trifluoromethyl-1,3-diaminobenzene, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-bis(trifluoromethyl)diphenylmethane, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorodiphenylmethane One or more of ketone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 4,4'-bis(4-aminophenoxy)benzene, 4,4'-bis(3-aminophenoxy)benzene, 4,4'-diaminodiphenyl sulfone, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-bis(trifluoromethyl)biphenyl or 4,4'-bis(4-aminophenoxy)biphenyl.

3. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The polyamino POSS monomer in step (1) is selected from one or more of hexaaminopropyl silsesquioxane, hexaaminophenyl silsesquioxane, octaaminophenyl cage silsesquioxane, and octaaminopropyl cage silsesquioxane.

4. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The organic solvent in step (1) is one or more of N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone; and the stirring rate is 100-300 rpm.

5. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The dianhydride monomer in step (2) is selected from pyromellitic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxylic)hexafluoropropane dianhydride, 4,4'-hexafluoroisopropylphthalic anhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dicarboxylic anhydride, Anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride or more thereof; the dianhydride monomer is added to the diamine monomer mixed solution in 2-6 times, with an interval of 2-6 minutes between each addition.

6. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The reaction temperature in step (2) is 25-35°C.

7. the preparation method of a kind of POSS modified polyamic acid as claimed in claim 1, is characterized in that, The molar ratio of the dianhydride monomer to the sum of the non-POSS diamine monomer and the polyamino POSS monomer in step (2) is (1-1.05):1; the molar ratio of the polyamino POSS monomer to the non-POSS diamine monomer in step (1) is (0.01-1):100; and the molar ratio of the polyamino POSS monomer added again in step (2) to the non-POSS diamine monomer is (2-5):

100.

8. A POSS modified polyamic acid, characterized in that, The polyamide is prepared by the preparation method of the POSS modified polyamide acid described in claims 1-7.

9. An application of a POSS modified polyamic acid as claimed in claim 8, characterized in that, POSS modified polyamic acid is used in the field of epoxy resin adhesives.

10. An epoxy resin adhesive, characterized in that: The invention comprises epoxy resin and POSS modified polyamic acid, wherein the POSS modified polyamic acid is the POSS modified polyamic acid according to claims 1-10.