Polyolefin adhesive as well as preparation method and application thereof

Abstract

The invention relates to the technical field of organic synthesis, in particular to a polyolefin adhesive as well as a preparation method and application thereof. The method comprises the following steps: mixing first polyolefin, second polyolefin and unsaturated acid or anhydride thereof, and carrying out grafting reaction to obtain the polyolefin adhesive, the melting temperature of the first olefin is 90-110 DEG C; the first olefin is a copolymer of propylene and alpha-olefin; the melting temperature of the second olefin is 70-80 DEG C; the second olefin is a copolymer of propylene and alpha-olefin; the mass ratio of the first polyolefin to the second polyolefin is (0.2-0.9): 1. The polyolefin adhesive disclosed by the invention has excellent high-temperature peel strength, good high-temperature electrolyte corrosion resistance and good deep drawing performance, and can meet the application performance requirements of a lithium battery aluminum-plastic film on an inner-layer adhesive.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and particularly relates to a polyolefin-based adhesive, a preparation method thereof, and an application thereof. Background Art

[0002] Polyolefin materials such as polyethylene (PE) and polypropylene (PP) have the characteristics of high mechanical strength, good chemical stability and heat resistance, and low price. They are widely used in various industrial fields of the national economy, such as medical and health, transportation, building materials, etc. They are currently the synthetic resin varieties with the largest production and the widest use in the world. Due to the inert chemical structure and high crystallinity of such materials, the plastic products made from them have the characteristics of low surface energy, non-polarity and weak interfacial layer, belonging to a kind of difficult-to-bond materials, which has become a major problem in the processing and application of the plastic manufacturing industry.

[0003] Graft-modified polyolefin-based adhesives are to graft-modify polyolefin materials such as PE and PP with maleic anhydride, acrylate, etc. to make them carry polar groups. Since polar molecules such as maleic anhydride can penetrate adjacent layers to form stronger bonds, the adhesiveness of polyolefin materials is improved, and the polyolefin-based adhesive has excellent adhesive properties for low-polarity and difficult-to-bond materials, and can be used for the bonding of materials such as plastic wallpapers, floor coverings, polyethylene and polypropylene plastic films, and aluminum foils.

[0004] When polyolefin-based adhesives are used, some products will have a relatively high use temperature. For example, the inner layer adhesive used in lithium battery packaging requires the adhesive to have relatively excellent high-temperature resistance. In the existing domestic synthesis technologies, the publicly available patents for specifically preparing high-temperature-resistant polyolefin adhesives are limited, and there is still a large room for improvement in high-temperature resistance performance.

[0005] Therefore, there is an urgent need to develop a preparation method for polyolefin-based adhesives. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. For this reason, the present invention provides a polyolefin-based adhesive, a preparation method thereof, and an application thereof, and the obtained polyolefin-based adhesive has excellent high-temperature peel strength.

[0007] For this reason, in the first aspect of the present invention, a preparation method for a polyolefin-based adhesive is provided, including the following steps:

[0008] Mix a first polyolefin, a second polyolefin and an unsaturated acid or its anhydride, and carry out a graft reaction to obtain a polyolefin-based adhesive;

[0009] The melting temperature of the first olefin is 90-110°C; the first olefin is a copolymer of propylene and an α-olefin;

[0010] The melting temperature of the second olefin is 70 - 80 °C; the second olefin is a copolymer of propylene and α-olefin;

[0011] The mass ratio of the first polyolefin to the second polyolefin is (0.2 - 0.9):1;

[0012] The mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the unsaturated acid or its anhydride is 1:(0.15 - 0.25).

[0013] In the present invention, the first polyolefin, the second polyolefin and the unsaturated acid or its anhydride are mixed and subjected to a graft reaction, and the obtained polyolefin-based adhesive has excellent high-temperature peel strength, good high-temperature electrolyte corrosion resistance and good deep drawing performance, and can meet the application performance requirements of the inner layer adhesive of the lithium battery aluminum-plastic film.

[0014] In some embodiments of the present invention, in the first olefin, the molar ratio of propylene to α-olefin is (5 - 9):1.

[0015] In some embodiments of the present invention, in the second olefin, the molar ratio of propylene to α-olefin is (3 - 7):1.

[0016] In some embodiments of the present invention, the first olefin includes a copolymer of propylene and 1-butene.

[0017] In some embodiments of the present invention, the second olefin includes a copolymer of propylene and 1-octene.

[0018] In some embodiments of the present invention, the unsaturated acid includes α,β-unsaturated carboxylic acid; the anhydride of the unsaturated acid includes the anhydride of α,β-unsaturated carboxylic acid.

[0019] In some embodiments of the present invention, the unsaturated acid includes one or more of maleic acid, itaconic acid, citraconic acid; the anhydride of the unsaturated acid includes one or more of maleic anhydride, itaconic anhydride, citraconic anhydride.

[0020] In some embodiments of the present invention, the graft reaction specifically includes:

[0021] At 90 - 110 °C, the solvent, the initiator, the first polyolefin, the second polyolefin and the unsaturated acid or its anhydride are reacted for 6 - 9 h.

[0022] In some embodiments of the present invention, the solvent includes one or more of toluene, xylene, benzene, cyclohexane, methylcyclohexane, cyclopentane, cycloheptane.

[0023] In some embodiments of the present invention, the initiator includes organic peroxide.

[0024] The second aspect of the present invention provides a polyolefin-based adhesive prepared by the preparation method of the above polyolefin-based adhesive.

[0025] The third aspect of the present invention provides the application of the polyolefin-based adhesive prepared by the preparation method of the above polyolefin-based adhesive and / or the above polyolefin-based adhesive in a high-temperature resistant adhesive.

[0026] The additional aspects and advantages of the present invention will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present invention. Detailed Embodiments

[0027] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0028] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0029] The first aspect of the present invention provides a preparation method of a polyolefin-based adhesive, comprising the following steps:

[0030] Mix a first polyolefin, a second polyolefin and an unsaturated acid or its anhydride, and carry out a graft reaction to obtain a polyolefin-based adhesive;

[0031] The melting temperature of the first olefin is 90 - 110 °C; the first olefin is a copolymer of propylene and an α-olefin;

[0032] The melting temperature of the second olefin is 70 - 80 °C; the second olefin is a copolymer of propylene and an α-olefin;

[0033] The mass ratio of the first polyolefin to the second polyolefin is (0.2 - 0.9):1;

[0034] The mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the unsaturated acid or its anhydride is 1:(0.15 - 0.25).

[0035] The present invention mixes a first polyolefin, a second polyolefin and an unsaturated acid or its anhydride, and carries out a graft reaction. The obtained polyolefin-based adhesive has excellent high-temperature peel strength, good high-temperature resistance to electrolyte corrosion performance, and good deep drawing performance, and can meet the application performance requirements of the inner layer adhesive of the lithium battery aluminum-plastic film.

[0036] In some embodiments of the present invention, an α-olefin refers to a monoolefin with a double bond at the end of the molecular chain, and its molecular formula is R-CH=CH2, where R is an alkyl group. According to the different R groups, α-olefins can be divided into linear α-olefins and branched α-olefins.

[0037] In some embodiments of the present invention, the α-olefin includes one or more of ethylene, propylene, 1-butene, 1-heptene, and 1-octene.

[0038] In some embodiments of the present invention, by way of example, the melting temperature of the first olefin can be 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 °C. The polyolefin at this melting temperature can improve the cohesion of the adhesive at high temperatures and enhance the high-temperature resistance.

[0039] In some embodiments of the present invention, in the first olefin, the molar ratio of propylene to α-olefin is (5-9):1. By way of example, in the first olefin, the molar ratio of propylene to α-olefin can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1.

[0040] In some embodiments of the present invention, the first olefin includes a copolymer of propylene and 1-butene; the molar ratio of propylene to 1-butene is 9:1.

[0041] In some embodiments of the present invention, by way of example, the melting temperature of the second olefin can be 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 °C. The polyolefin at this melting temperature can increase the grafting rate of the main agent of the adhesive and improve the bonding effect of the adhesive on non-polar materials.

[0042] In some embodiments of the present invention, in the second olefin, the molar ratio of propylene to α-olefin is (3-7):1. By way of example, in the second olefin, the molar ratio of propylene to α-olefin can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1.

[0043] In some embodiments of the present invention, the second olefin includes a copolymer of propylene and 1-octene; the molar ratio of propylene to 1-octene is 3:1.

[0044] In some embodiments of the present invention, by way of example, the mass ratio of the first polyolefin to the second polyolefin may be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1 or 0.9:1. The above mass ratio can improve the cohesive strength of the material, thereby improving the high-temperature bonding strength of the adhesive.

[0045] In some embodiments of the present invention, by way of example, the mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the unsaturated acid or its anhydride may be 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24 or 1:0.25. The above mass ratio can obtain a modified polyolefin suitable for the weight-average molecular weight and grafting rate, improve the polarity of the polyolefin and the wettability of the adhesive, thereby improving the high-temperature bonding strength of the adhesive.

[0046] In some embodiments of the present invention, the unsaturated acid includes α,β-unsaturated carboxylic acid; the anhydride of the unsaturated acid includes the anhydride of α,β-unsaturated carboxylic acid; further, the unsaturated acid includes one or more of maleic acid, itaconic acid, citraconic acid; the anhydride of the unsaturated acid includes one or more of maleic anhydride, itaconic anhydride, citraconic anhydride; further, the anhydride of the unsaturated acid includes maleic anhydride. The amount of maleic anhydride affects the grafting rate of the modified polyolefin resin. If within the above range, a modified polyolefin with a suitable grafting rate can be obtained, and the application performance is good. If less than the above range, the concentration of maleic anhydride is small, the collision probability with the polyolefin macromolecular free radicals is small, and the grafting rate is low; if exceeding the above range, the collision frequency of maleic anhydride with the primary free radicals increases, the generated polyolefin macromolecular free radicals are less, maleic anhydride produces a shielding effect, and the grafting rate is low, reducing the bonding performance and high-temperature peel strength of the adhesive.

[0047] In some embodiments of the present invention, α,β-unsaturated carboxylic acid refers to a compound containing a carboxyl group (-COOH) and an olefinic bond (C=C) in the molecule, and the olefinic bond is directly connected to the carboxyl group. The structural feature of this kind of compound is that the carboxyl group and the olefinic bond are located on adjacent carbon atoms, forming a conjugated system, and having a certain stability.

[0048] In some embodiments of the present invention, the grafting reaction specifically includes: reacting a solvent, an initiator, a first polyolefin, a second polyolefin and an unsaturated acid or its anhydride at 90-110 °C for 6-9 h.

[0049] In some embodiments of the present invention, the grafting reaction is carried out in an inert atmosphere; further, the inert atmosphere is provided by nitrogen.

[0050] In some embodiments of the present invention, the grafting reaction specifically includes: heating a first solvent, an initiator, a first polyolefin, a second polyolefin, and an unsaturated acid or its anhydride to 90°C under nitrogen, and then heating to 110°C at a rate of 30 - 40°C / h for reaction.

[0051] In some embodiments of the present invention, the solvent includes one or more of toluene, xylene, benzene, cyclohexane, methylcyclohexane, cyclopentane, and cycloheptane.

[0052] The present invention has no special requirements for the usage amount of the solvent, and the commonly used amount in the art can be adopted.

[0053] In some embodiments of the present invention, the initiator includes an organic peroxide; the organic peroxide includes one or more of methyl ethyl ketone peroxide, benzoyl peroxide, diisopropylbenzene peroxide, tert-butyl peroxybenzoate, and tert-butyl peroxide; further, the organic peroxide includes benzoyl peroxide.

[0054] In some embodiments of the present invention, the mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the organic peroxide is 100:(0.5 - 5), and further, the mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the organic peroxide is 100:(1 - 3). If within the said range, a modified polyolefin resin with a certain range of weight-average molecular weight and a certain range of grafting rate can be obtained; if less than the said range, the number of polyolefin macromolecular free radicals generated due to fewer initial free radicals is too low, resulting in too large a weight-average molecular weight of the modified polyolefin. If exceeding the said range, the number of initial free radicals generated by the initiator is too large, thus the number of polyolefin macromolecular free radicals formed is too large, leading to an increased probability of crosslinking between macromolecular free radicals, making the weight-average molecular weight of the modified polyolefin resin too large, and the adhesive has poor solution stability, reduced fluidity, is not easy to operate and use, thereby reducing the high-temperature peel strength and electrolyte corrosion resistance of the adhesive.

[0055] In some embodiments of the present invention, the preparation method of the polyolefin-based adhesive further includes: removing impurities from the product obtained by the grafting reaction; further, using an organic solvent and / or centrifugation to remove impurities from the product obtained by the grafting reaction; the organic solvent includes one or more of acetone, butanone, and ethyl acetate; the rotation speed of the centrifugation is 3000 - 4000 rpm.

[0056] In some embodiments of the present invention, the preparation method of the polyolefin-based adhesive further includes: drying the product after the grafting reaction; further, the drying temperature is 30 - 50°C and the time is 5 - 6 h.

[0057] The second aspect of the present invention provides a polyolefin-based adhesive prepared by the preparation method of the above polyolefin-based adhesive.

[0058] In some embodiments of the present invention, the molecular weight of the polyolefin-based adhesive is 100,000 - 150,000 g / mol; further, the molecular weight of the polyolefin-based adhesive is 100,000 - 120,000 g / mol. If within this range, the stability and fluidity of the adhesive solution are good, the compatibility with the curing agent is good, the gluing process is easy to implement, and the adhesive can spread and wet on the surfaces of aluminum foil and transparent polypropylene (cpp) better, thereby improving the high-temperature peel strength and high-temperature electrolyte corrosion resistance of the adhesive. If less than this range, the cohesive force of the modified polyolefin becomes weak and the heat resistance of the adhesive is poor. If exceeding this range, the modified polyolefin is not easily soluble, the solution stability and fluidity decrease, and the adhesive is not easily spread on the surface of the bonding layer, thus reducing the high-temperature resistance of the adhesive.

[0059] In some embodiments of the present invention, the grafting rate of the polyolefin-based adhesive is 1% - 2%. If within this range, the content of the anhydride is appropriate, the bonding effect of the adhesive on non-polar materials such as polyolefin is good, and the high-temperature resistance is good. If lower than this range, the polarity of the polyolefin is insufficient and the bonding property of the adhesive is poor.

[0060] The third aspect of the present invention provides the application of the polyolefin-based adhesive prepared by the preparation method of the above polyolefin-based adhesive and / or the above polyolefin-based adhesive in high-temperature-resistant adhesives.

[0061] In some embodiments of the present invention, before use, the polyolefin-based adhesive and the curing agent are mixed. Isocyanate can crosslink the carboxylic acid or anhydride groups on the modified polyolefin resin to form a dense three-dimensional adhesive layer.

[0062] In some embodiments of the present invention, the molar ratio of the acid value of the polyolefin-based adhesive to the isocyanate group is 1:(1 - 2).

[0063] In some embodiments of the present invention, the curing agent includes isocyanate. Through the crosslinking of carboxylic acid or anhydride groups with isocyanate groups, a dense three-dimensional adhesive layer is obtained, enabling the adhesive to have excellent high-temperature peel strength and electrolyte corrosion resistance.

[0064] The following will explain the solution of the present disclosure in combination with examples. Those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. For those not specified in the examples regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0065] In the examples and comparative examples of the present invention, polyolefin A used is a copolymer of propylene and 1-butene, and the melting temperature (T m ) is 105 °C, and the molar ratio of propylene / 1-butene is 90 / 10; polyolefin B is a copolymer of propylene and 1-octene, and the melting temperature (T m ) is 80 °C, and the molar ratio of propylene / 1-octene is 75 / 25.

[0066] Example 1

[0067] For the polyolefin-based adhesive of this example, the preparation method includes the following steps:

[0068] (1) Add polyolefin A (30 parts by mass), polyolefin B (70 parts by mass), xylene (300 parts by mass), maleic anhydride (20 parts by mass), and benzoyl peroxide (2 parts by mass) to the reaction flask. After replacing the air in the reaction system with nitrogen, heat it to 90 °C under nitrogen protection. After the solid materials are completely dissolved, raise the temperature to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and carry out heat preservation reaction for 6 h. Cool the reaction solution to 70 °C, add xylene (50 parts by mass) preheated to 45 °C, then cool to 50 °C, and drop acetone (300 parts by mass) into the reaction solution to precipitate the product.

[0069] (2) Put the product of step (1) into acetone (500 parts by mass) under high-speed stirring, continue stirring for 1 h, then carry out centrifugal separation of the solution at a rotation speed of 4000 rpm to separate low-molecular-weight products and poly maleic anhydride in the copolymer, and repeat this operation twice for purification. After purification, dry it at 30 °C under reduced pressure for 6 h to obtain a polyolefin-based adhesive. The molecular weight of the adhesive is 120,000 g / mol, and the melt flow index under the conditions of 190 °C and a load of 2.16 kg is 3.5 g / 10 min.

[0070] Comparative Example 1

[0071] The polyolefin-based adhesive of this comparative example is only different from that of Example 1 in that: in this comparative example, polyolefin A is replaced by polyolefin B, and the preparation method specifically includes the following steps:

[0072] (1) Add polyolefin B (100 parts by mass), xylene (300 parts by mass), maleic anhydride (20 parts by mass), and benzoyl peroxide (2 parts by mass) to the reaction flask. After replacing the air in the reaction system with nitrogen, heat it to 90 °C under nitrogen protection. After the solid materials are completely dissolved, raise the temperature to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and carry out heat preservation reaction for 6 h. Cool the reaction solution to 70 °C, add xylene (50 parts by mass) preheated to 45 °C, then cool to 50 °C, and drop acetone (300 parts by mass) into the reaction solution to precipitate the product.

[0073] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate the low-molecular-weight products and poly maleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain a polyolefin-based adhesive.

[0074] Comparative Example 2

[0075] The polyolefin-based adhesive of this comparative example is different from that of Example 1 only in that: in this comparative example, polyolefin B is replaced by polyolefin A, and the preparation method specifically includes the following steps:

[0076] (1) Add polyolefin A (100 parts by mass), xylene (300 parts by mass), maleic anhydride (20 parts by mass), and benzoyl peroxide (2 parts by mass) to a reaction flask. After replacing the air in the reaction system with nitrogen, the temperature is raised to 90 °C under nitrogen protection. After the solid materials are completely dissolved, the temperature is raised to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, xylene (50 parts by mass) preheated to 45 °C is added, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0077] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate the low-molecular-weight products and poly maleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain a polyolefin-based adhesive.

[0078] Comparative Example 3

[0079] The polyolefin-based adhesive of this comparative example is different from that of Example 1 only in that: in this comparative example, maleic anhydride is omitted; the preparation method specifically includes the following steps:

[0080] (1) Add polyolefin A (30 parts by mass), polyolefin B (70 parts by mass), xylene (300 parts by mass), and benzoyl peroxide (2 parts by mass) to a reaction flask. After replacing the air in the reaction system with nitrogen, the temperature is raised to 90 °C under nitrogen protection. After the solid materials are completely dissolved, the temperature is raised to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, xylene (50 parts by mass) preheated to 45 °C is added, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0081] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate the low-molecular-weight products and poly(maleic anhydride) in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain the polyolefin-based adhesive.

[0082] Comparative Example 4

[0083] The polyolefin-based adhesive of this comparative example is different from that of Example 1 only in that: the mass ratio of polyolefin A and polyolefin B used in this comparative example is 1:9; the preparation method specifically includes the following steps:

[0084] (1) Polyolefin A (10 parts by mass), polyolefin B (90 parts by mass), xylene (300 parts by mass), and benzoyl peroxide (2 parts by mass) are added to a reaction flask. After replacing the air in the reaction system with nitrogen, it is heated to 90 °C under nitrogen protection. After the solid materials are completely dissolved, it is heated to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, xylene (50 parts by mass) preheated to 45 °C is added, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0085] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate the low-molecular-weight products and poly(maleic anhydride) in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain the polyolefin-based adhesive.

[0086] Comparative Example 5

[0087] The polyolefin-based adhesive of this comparative example is different from that of Example 1 only in that: the mass ratio of polyolefin A and polyolefin B used in this comparative example is 1:1; the preparation method specifically includes the following steps:

[0088] (1) Polyolefin A (50 parts by mass), polyolefin B (50 parts by mass), xylene (300 parts by mass), and benzoyl peroxide (2 parts by mass) are added to a reaction flask. After replacing the air in the reaction system with nitrogen, it is heated to 90 °C under nitrogen protection. After the solid materials are completely dissolved, it is heated to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, xylene (50 parts by mass) preheated to 45 °C is added, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0089] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate low-molecular-weight products and maleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain the polyolefin-based adhesive.

[0090] Comparative Example 6

[0091] The polyolefin-based adhesive of this comparative example is only different from that of Example 1 in that: the mass ratio of polyolefin A and polyolefin B used in this comparative example is 9:1; the preparation method specifically includes the following steps:

[0092] (1) Add polyolefin A (90 parts by mass), polyolefin B (10 parts by mass), xylene (300 parts by mass), and benzoyl peroxide (2 parts by mass) to the reaction flask. After purging the air in the reaction system with nitrogen, it is heated to 90 °C under nitrogen protection. After the solid materials are completely dissolved, it is heated to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, add xylene (50 parts by mass) preheated to 45 °C, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0093] (2) The product from step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate low-molecular-weight products and maleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain the polyolefin-based adhesive.

[0094] Comparative Example 7

[0095] The polyolefin-based adhesive of this comparative example is only different from that of Example 1 in that: the mass ratio of the total mass of polyolefin A and polyolefin B and maleic anhydride used in this comparative example is 10:1; the preparation method specifically includes the following steps:

[0096] (1) Add polyolefin A (30 parts by mass), polyolefin B (70 parts by mass), xylene (300 parts by mass), maleic anhydride (10 parts by mass), and benzoyl peroxide (2 parts by mass) to the reaction flask. After purging the air in the reaction system with nitrogen, it is heated to 90 °C under nitrogen protection. After the solid materials are completely dissolved, it is heated to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, add xylene (50 parts by mass) preheated to 45 °C, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0097] (2) The product of step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate low-molecular-weight products and polymaleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain a polyolefin-based adhesive.

[0098] Comparative Example 8

[0099] The polyolefin-based adhesive of this comparative example is only different from that of Example 1 in that: the mass ratio of the total mass of polyolefin A and polyolefin B used in this comparative example to maleic anhydride is 10:3; the preparation method specifically includes the following steps:

[0100] (1) Polyolefin A (30 parts by mass), polyolefin B (70 parts by mass), xylene (300 parts by mass), maleic anhydride (30 parts by mass), and benzoyl peroxide (2 parts by mass) are added to a reaction flask. After replacing the air in the reaction system with nitrogen, the temperature is raised to 90 °C under nitrogen protection. After the solid materials are completely dissolved, the temperature is raised to 110 °C at a rate of 30 °C / h for solution grafting modification reaction, and the heat preservation reaction is carried out for 6 h. The reaction solution is cooled to 70 °C, xylene (50 parts by mass) preheated to 45 °C is added, and then cooled to 50 °C. Acetone (300 parts by mass) is added dropwise to the reaction solution to precipitate the product.

[0101] (2) The product of step (1) is put into acetone (500 parts by mass) under high-speed stirring. After continuing to stir for 1 h, the solution is centrifuged at a speed of 4000 rpm to separate low-molecular-weight products and polymaleic anhydride in the copolymer. This operation is repeated twice for purification. After purification, it is dried at 30 °C under reduced pressure for 6 h to obtain a polyolefin-based adhesive.

[0102] Test Example

[0103] The polyolefin-based adhesives obtained in Example 1 and Comparative Examples 1-8 above are mixed with an isocyanate curing agent at a molar ratio of the acid value of the solute to isocyanate (NCO) of 1:2, coated on the surface of an aluminum foil to form an inner layer film, and then heat lamination bonding operation of the polyolefin layer, adhesion and curing of the inner layer film, etc. are carried out. Finally, application performance tests such as deep drawing and peeling are carried out. The test data are shown in Table 1.

[0104] 1. Peel Strength Test: Referring to the standard of "GB-T2791-1995 Adhesives - T Peel Strength Test Method - Flexible Material to Flexible Material", cut the aluminum-plastic film sample into strips with a size of 15mm×20cm. Symmetrically clamp the unbonded ends of the nylon layer and the aluminum foil layer on the upper and lower holders of a universal testing machine respectively, and ensure that the clamped parts do not slip, so as to ensure that the applied tensile force is evenly distributed across the width of the specimen. Start the testing machine and separate the upper and lower holders at a rate of 100±10mm / min. The peeling length of the specimen should be at least 125mm.

[0105] 2. High Temperature Resistance Test: Referring to the peel strength test method, place the sample strips under the conditions of 25℃, 80℃ and 120℃ for testing respectively.

[0106] 3. Deep Drawing Performance Test: Use a double-pit deep drawing die with a pit depth of 5mm and a distance of 1mm between the two pits. Check whether there are abnormal phenomena such as delamination and whitening at the corners of the inner layer film after deep drawing.

[0107] 4. Electrolyte Resistance Performance: Cut the aluminum-plastic film sample into a size of 100mm×15mm, soak it in the electrolyte [ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1 / 1 / 1 (volume ratio), 100g with 13g of lithium hexafluorophosphate added] at 85℃ for 24h. Then take out the aluminum-plastic film strip, wash it with deionized water, wipe off the water with a wiping paper to make the moisture dry thoroughly, and evaluate the electrolyte resistance performance by using the T-peel test.

[0108] Table 1

[0109]

[0110]

[0111] As can be seen from Table 1, in the embodiments of the present invention, polyolefin A and polyolefin B are used as main agents, and after being blended with a curing agent, they show good high temperature resistance with polyolefin resin substrates and metal substrates, and can meet the performance requirements of the inner layer glue of lithium battery aluminum-plastic films for use in high temperature fields.

[0112] Furthermore, as can be seen from Comparative Example 1, only using polyolefin B as the raw material to prepare the adhesive shows poor peel strength at high temperatures; as can be seen from Comparative Example 2, only using polyolefin A as the raw material to prepare the adhesive shows poor peel strength at both normal temperature and high temperatures; as can be seen from Comparative Example 3, after omitting the maleic anhydride raw material, the adhesive breaks during the preparation process; as can be seen from Comparative Examples 4-6, when the mass ratio of polyolefin A and polyolefin B is outside the range of (0.2-0.9):1, the peel strength of the prepared adhesive is poor at high temperatures; as can be seen from Comparative Examples 7 and 8, when the mass ratio of the total mass of polyolefin A and polyolefin B and maleic anhydride is outside the range of 1:(0.15-0.25), the peel strength of the prepared adhesive is poor at high temperatures.

[0113] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", "some implementation manners" or "some examples", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0114] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation method of a polyolefin-based adhesive, characterized in that, It includes the following steps: Mix the first polyolefin, the second polyolefin and the unsaturated acid or its anhydride, and carry out a graft reaction to obtain a polyolefin-based adhesive; The melting temperature of the first olefin is 90 - 110 °C; the first olefin is a copolymer of propylene and an α-olefin; The melting temperature of the second olefin is 70 - 80 °C; the second olefin is a copolymer of propylene and an α-olefin; The mass ratio of the first polyolefin to the second polyolefin is (0.2 - 0.9):1; The mass ratio of the total mass of the first polyolefin and the second polyolefin to the mass of the unsaturated acid or its anhydride is 1:(0.15 - 0.25).

2. The preparation method of the polyolefin-based adhesive according to claim 1, wherein, In the first olefin, the molar ratio of propylene to the α-olefin is (5 - 9):1; And / or, in the second olefin, the molar ratio of propylene to the α-olefin is (3 - 7):

1.

3. The preparation method of the polyolefin-based adhesive according to claim 1, wherein, The first olefin includes a copolymer of propylene and 1-butene; And / or, the second olefin includes a copolymer of propylene and 1-octene.

4. The preparation method of the polyolefin-based adhesive according to claim 1, characterized in that, The unsaturated acid includes α,β-unsaturated carboxylic acid; the anhydride of the unsaturated acid includes the anhydride of α,β-unsaturated carboxylic acid.

5. The preparation method of the polyolefin-based adhesive according to claim 4, characterized in that, The unsaturated acid includes one or more of maleic acid, itaconic acid, citraconic acid; The anhydride of the unsaturated acid includes one or more of maleic anhydride, itaconic anhydride, citraconic anhydride.

6. The preparation method of the polyolefin-based adhesive according to claim 1, characterized in that, The graft reaction specifically includes: At 90 - 110 °C, react the solvent, initiator, first polyolefin, second polyolefin and unsaturated acid or its anhydride for 6 - 9 h.

7. The preparation method of the polyolefin-based adhesive according to claim 6, wherein, The solvent includes one or more of toluene, xylene, benzene, cyclohexane, methylcyclohexane, cyclopentane, cycloheptane.

8. The preparation method of the polyolefin-based adhesive according to claim 6, characterized in that, The initiator includes organic peroxide.

9. The polyolefin-based adhesive prepared by the method for preparing a polyolefin-based adhesive according to any one of claims 1 - 8.

10. The polyolefin-based adhesive prepared by the method for preparing a polyolefin-based adhesive according to any one of claims 1 - 8, and / or, the application of the polyolefin-based adhesive according to claim 9 in a high-temperature resistant adhesive.

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