Medium-resistant two-component solvent-free polyurethane adhesive and preparation method thereof

Abstract

The invention discloses a medium-resistant double-component solvent-free polyurethane adhesive and a preparation method thereof, a component A of the adhesive is a polyurethane prepolymer, and the component A is prepared from the following components in parts by mass: 20-50 parts of graphene oxide modified polyester polyol and 25-60 parts of isocyanate; the component B is prepared from the following components in parts by mass: 30 to 60 parts of graphene oxide modified polyester polyol, 20 to 50 parts of maleic structure special polyester polyol, 5 to 20 parts of nano silicon dioxide modified polyether polyol, 5 to 20 parts of isocyanate, 2 to 10 parts of micromolecular polyol and 0.3 to 5 parts of a silane coupling agent. The adhesive disclosed by the invention has outstanding barrier property, boiling resistance and steaming and boiling resistance, has relatively high bonding strength, and can be used as a polyurethane material for a film layer in the packaging field.

Description

Technical Field

[0001] The present invention relates to the field of polymer material preparation, in particular to a medium-resistant solvent-free polyurethane adhesive for flexible packaging and a preparation method thereof. Background Art

[0002] Solvent-free polyurethane adhesives are polyurethane materials that do not contain any solvents. They are safe, environmentally friendly, low-cost, and stable in production. With the rapid development of solvent-free polyurethane adhesives in recent years, they have been widely used in various packaging applications, including food, daily necessities, pharmaceuticals, agricultural products, industrial products, cosmetics, and electronic products.

[0003] As the application scope of solvent-free polyurethane adhesives in the packaging field becomes wider and wider, the market requirements for solvent-free polyurethane are also getting higher and higher. Faced with complex and diverse contents, the bonding performance and resistance of adhesives used for flexible packaging and lamination play a vital role. This includes the requirements for resistance to different foods (various complex food additives), daily chemicals (alcohol wipes, facial masks), and pharmaceuticals (chemical substances with different ingredients). In addition, many contents are acidic and alkaline, so the adhesive is also required to have excellent acid and alkali resistance. The bonding performance of adhesives used for packaging and lamination has a crucial impact. Small molecular compounds or acidic and alkaline substances in the contents can penetrate the heat seal layer and reach the adhesive layer, destroying the bonding performance of the adhesive, leading to delamination of the composite flexible packaging and the storage and scrapping of the contents.

[0004] Currently, the composite packaging industry primarily addresses the resistance requirements for different contents by modifying film materials, increasing the number of composite layers, and using high-barrier, dielectric-resistant films. However, this also increases the number of composite layers, raising composite costs and hindering recycling. Furthermore, the flexible packaging market currently primarily utilizes high-molecular-weight solvent-based adhesives to achieve resistance requirements for different contents. However, solvent-based adhesives contain large amounts of volatile solvents, which not only increases manufacturing costs but also leads to significant solvent volatilization, increasing VOC emissions and adversely affecting environmental protection.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a medium-resistant two-component solvent-free polyurethane adhesive and a preparation method thereof. The two-component solvent-free polyurethane adhesive does not contain solvents, is safe and environmentally friendly, can enhance the medium resistance and composite strength of the composite film, and improve the anti-attenuation performance of the composite film, thereby improving the resistance to different contents and acid and alkaline substances, increasing the scope of application of the adhesive, and solving the problems existing in the prior art.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A media-resistant two-component solvent-free polyurethane adhesive comprising:

[0009] Component A and component B, wherein component A is an isocyanate component and component B is a hydroxyl value component, the weight ratio of component A to component B is 100:60-80, and the functional group molar ratio of component A to component B is: -NCO:-OH=1.2:1-2.0:1;

[0010] The A component is a polyurethane prepolymer made from the following components in parts by mass:

[0011] Polyetherester polyol, used in an amount of 20 to 60 parts;

[0012] Isocyanate, used in an amount of 40 to 80 parts;

[0013] The B component is made from the following components in parts by mass:

[0014] Graphene oxide modified polyester polyol, used in an amount of 15 to 40 parts;

[0015] Special polyester polyol with cis-butylene structure, dosage is 25-50 parts

[0016] Polyether polyol, used in an amount of 10 to 25 parts;

[0017] Isocyanate, used in an amount of 5 to 10 parts;

[0018] Silane coupling agent, dosage is 0.3 to 5 parts.

[0019] A method for preparing the medium-resistant two-component solvent-free polyurethane adhesive of the present invention comprises:

[0020] Prepare component A and component B separately, wherein,

[0021] Preparation of Component A: According to the medium-resistant two-component solvent-free polyurethane adhesive formulation of the present invention, the raw materials of Component A are taken, and the polyether ester polyol in Component A is reacted with the isocyanate at 50-60° C. for 1 hour, and then the temperature is raised to 80-90° C. and reacted for 3 hours. The obtained product is Component A;

[0022] Preparation of component B: According to the formulation of the medium-resistant two-component solvent-free polyurethane adhesive of the present invention, the raw materials of component A are taken, the graphene oxide-modified polyester polyol, the special polyester polyol with a cis-butylene structure, and the polyether polyol in component B are vacuum dehydrated at a temperature of 110-120° C. for 1-2 hours, reacted with isocyanate at 50-60° C. for 1 hour, then heated to 80-90° C. for reaction for 3 hours, and a silane coupling agent is added to obtain the product, which is component B;

[0023] The prepared component A and component B are combined in a functional group molar ratio of -NCO:-OH=1.1:1 to 2.0:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive;

[0024] Compared with the prior art, the medium-resistant two-component solvent-free polyurethane adhesive and its preparation method provided by the present invention have the following beneficial effects:

[0025] By using graphene oxide-modified polyester polyols and cis-butene-structured specialty polyester polyols in component B, graphene, with its high barrier properties, and cis-butene, with its high chemical resistance, are introduced into the adhesive system, thereby improving the adhesive's inherent resistance. Simultaneously, the use of polyetherester polyols in component A, leveraging their combined properties of polyester and polyether, ensures the adhesive possesses high leveling properties while also ensuring excellent heat and decay resistance, broadening its application range. This improves the adhesive's media resistance and reduces the risk of food packaging waste due to glue delamination caused by the migration of small molecule compounds from the contents. This can extend food shelf life and improve food safety, making this adhesive more suitable for the lamination of flexible packaging bags. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the specific content of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments, and do not constitute a limitation of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] First, the following terms may be used in this article:

[0028] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y includes both “X” or “Y” and “X and Y”.

[0029] The terms "include," "comprises," "contains," "has," or other similar expressions should be interpreted as non-exclusive. For example, "including certain technical features (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products, or manufactured articles, etc.) should be interpreted as including not only the technical features explicitly listed, but also other technical features known in the art that are not explicitly listed.

[0030] The term "consisting of" excludes any technical features not explicitly listed. If used in a claim, this term renders the claim closed, excluding any technical features other than those explicitly listed, except for conventional impurities associated with them. If this term appears only in a clause of a claim, it limits only the elements explicitly listed in that clause; elements listed in other clauses are not excluded from the claim as a whole.

[0031] The term "parts by mass" refers to the mass ratio of multiple components. For example, if component X is x parts by mass and component Y is y parts by mass, then the mass ratio of component X to component Y is x:y. One part by mass can represent any mass, for example, 1 kg or 3.1415926 kg. The sum of the parts by mass of all components is not necessarily 100 parts; it can be greater than, less than, or equal to 100 parts. Unless otherwise specified, parts, ratios, and percentages herein are by mass.

[0032] When concentration, temperature, pressure, size or other parameters are expressed in the form of a numerical range, the numerical range should be understood to specifically disclose all ranges formed by the pairing of any upper limit, lower limit, or preferred value within the numerical range, regardless of whether the range is explicitly stated. For example, if a numerical range of "2 to 8" is stated, the numerical range should be interpreted as including ranges of "2 to 7," "2 to 6," "5 to 7," "3 to 4 and 6 to 7," "3 to 5 and 7," "2 and 5 to 7," etc. Unless otherwise specified, the numerical ranges stated herein include both their endpoints and all integers and fractions within the numerical range.

[0033] The following describes in detail the media-resistant, two-component, solvent-free polyurethane adhesive and its preparation method provided by the present invention. Any information not described in detail in the examples herein is prior art known to those skilled in the art. Where specific conditions are not specified in the examples herein, the procedures were carried out in accordance with conventional conditions in the art or the conditions recommended by the manufacturer. Reagents or instruments used in the examples herein, where the manufacturer is not specified, are commercially available conventional products.

[0034] An embodiment of the present invention provides a medium-resistant two-component solvent-free polyurethane adhesive, comprising:

[0035] Component A and component B, wherein component A is an isocyanate component, component B is a hydroxyl component, and the functional group molar ratio of component A to component B is: n(NCO):n(OH)=1.2:1-2.0:1;

[0036] The A component is a polyurethane prepolymer made from the following components in parts by mass:

[0037] Polyetherester polyol, used in an amount of 20 to 60 parts;

[0038] Isocyanate, used in an amount of 40 to 80 parts;

[0039] The B component is made from the following components in parts by mass:

[0040] Graphene oxide modified polyester polyol, used in an amount of 15 to 40 parts;

[0041] Special polyester polyol with cis-butylene structure, dosage is 25-50 parts

[0042] Polyether polyol, used in an amount of 10 to 25 parts;

[0043] Isocyanate, used in an amount of 5 to 10 parts;

[0044] Silane coupling agent, dosage is 0.3 to 5 parts.

[0045] Preferably, in the above adhesive, the molecular weight of the polyetherester polyol is 500 to 2000 and the functionality is 2 to 3;

[0046] The polyetherester polyol in the polyurethane prepolymer of component A is currently widely used in the adhesive field. It is a material that combines the flexibility of polyether with the heat resistance and attenuation resistance of polyester and is more suitable for solvent-free adhesives.

[0047] Preferably, in the above adhesive, the graphene oxide-modified polyester polyol in the B component is a graphene oxide-modified polyester polyol obtained by introducing graphene into polyester in the form of characteristic functional groups of graphene oxide, wherein the proportion of graphene oxide is 0.05 to 1 part.

[0048] Preferably, in the above adhesive, the graphene oxide-modified polyester polyol is prepared in the following manner, including:

[0049] Graphene oxide is obtained by oxidizing graphite powder through the Hummers method, and the obtained graphene oxide is evenly dispersed in a small molecule polyol by ultrasonic dispersion for 5 to 10 minutes to obtain a graphene oxide alcohol dispersion. The graphene oxide alcohol dispersion is then esterified and polycondensed with a small molecule dibasic acid to obtain a graphene oxide-modified polyester polyol.

[0050] Preferably, in the above adhesive, the small molecule dibasic acid used in the graphene oxide modified polyester polyol is composed of an aromatic dibasic acid and an aliphatic dibasic acid, wherein the aromatic dibasic acid accounts for 50 to 100% of the total mass of the small molecule dibasic acid;

[0051] The aromatic dibasic acid is at least one of terephthalic acid, isophthalic acid and phthalic anhydride;

[0052] The aliphatic dibasic acid is at least one of adipic acid, sebacic acid and azelaic acid.

[0053] Preferably, in the above-mentioned adhesive, the special polyester polyol with a butene structure used in the B component is prepared in the following manner, including: synthesizing polyester from maleic anhydride, a small molecule dibasic acid and a small molecule polyol, setting the molar ratio of alkyd to acid to 1.1 to 1.6, esterifying and polycondensing to obtain a polyester polyol with a certain molecular weight; placing nano-silica and the polyester polyol obtained above into a high-speed disperser for dispersion, dispersing at speeds of 1000 rpm and 2000 rpm for 5 to 10 minutes respectively, until uniformly dispersed, and stopping to obtain the special polyester polyol with a butene structure.

[0054] Preferably, in the above adhesive, the amount of maleic anhydride used in the maleic butene structure special polyester polyol is 5 to 15% of the total mass of the maleic butene structure special polyester polyol raw material;

[0055] The amount of nano-silica used in the special polyester polyol with maleic butene structure is 0.5-3% of the total mass of the raw material of the special polyester polyol with maleic butene structure; the nano-silica is hydrophobic fumed silica; preferably, the hydrophobic fumed silica is: Evonik AEROSIL R972, Cabot Corporation and Wacker H15;

[0056] The small molecule dibasic acid used in the special polyester polyol with maleic structure is at least one of adipic acid, sebacic acid and azelaic acid;

[0057] The small molecule polyol used in the special polyester polyol with cis-butene structure is at least one of diethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propylene glycol, and 2-methyl-1,3-propylene glycol; and at least one of glycerol and trimethylolpropane.

[0058] Preferably, in the above-mentioned adhesive, the isocyanate in component A and component B is the same, and both are at least one of: diphenylmethane-4,4'-diisocyanate (4,4'-MDI), a mixture of diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate, polyether-modified MDI, HMDI, carbonized diimide-modified MDI, and polymethylene polyphenyl polyisocyanate; wherein the weight proportion of 2,4' isomers in the mixture of diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate is greater than 35%.

[0059] Preferably, in the above adhesive, the silane silane coupling agent used in the B component is at least one of an aminosilane silane coupling agent, an epoxysilane silane coupling agent, a phenylsilane silane coupling agent, and a titanate silane coupling agent; preferably, any one of KH-540, KH-550, KH-560, and KH-570 is used.

[0060] The present invention also provides a method for preparing the above-mentioned medium-resistant two-component solvent-free polyurethane adhesive, comprising:

[0061] Prepare component A and component B separately, wherein,

[0062] Preparation of Component A: According to the above-mentioned medium-resistant two-component solvent-free polyurethane adhesive formula, take the raw materials of Component A, react the polyetherester polyol in Component A with the isocyanate at 50-60°C for 1 hour, then raise the temperature to 80-90°C and react for 3 hours. The resulting product is Component A;

[0063] Preparation of component B: According to the above-mentioned medium-resistant two-component solvent-free polyurethane adhesive formula, the raw materials of component A are taken, and the graphene oxide-modified polyester polyol, the special polyester polyol with a cis-butylene structure, and the polyether polyol in component B are vacuum dehydrated at a temperature of 110-120° C. for 1-2 hours, reacted with isocyanate at 50-60° C. for 1 hour, then heated to 80-90° C. for reaction for 3 hours, and a silane coupling agent is added to obtain the product, which is component B;

[0064] The prepared component A and component B are combined in a functional group molar ratio of -NCO:-OH=1.1:1 to 2.0:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive;

[0065] Preferably, in the above preparation method, the graphene oxide-modified polyester polyol used in the preparation of component B is prepared as follows: graphite powder is oxidized to obtain graphene oxide by the Hummers method, the obtained graphene oxide is uniformly dispersed in a small molecule polyol by ultrasonic dispersion for 5 to 10 minutes to obtain a graphene oxide alcohol dispersion, and the graphene oxide alcohol dispersion is then subjected to esterification and polycondensation reaction with a small molecule dibasic acid to obtain the graphene oxide-modified polyester polyol;

[0066] The maleic anhydride used in the preparation of component B is prepared as follows: maleic anhydride accounting for 5-15% of the total weight of the raw materials is synthesized with a small molecule dibasic acid and a small molecule polyol, with the molar ratio of the alcohol to the acid being set at 1.1-1.6, and esterification and polycondensation are performed to obtain a polyester polyol with a certain molecular weight;

[0067] Nano-silicon dioxide accounting for 0.5-3% of the total mass of the raw materials and the polyester polyol obtained above are placed into a high-speed disperser for dispersion, and dispersed at a speed of 1000 rpm and 2000 rpm for 5-10 minutes respectively until uniformly dispersed. After stopping, a special polyester polyol with a butene structure is obtained.

[0068] The adhesive of the embodiment of the present invention adopts a special polyester polyol with a butene structure in component B. By utilizing the unsaturated double bonds contained in the butene structure, these double bonds may be partially retained in the polyester molecular chain during polyester synthesis. The retained unsaturated double bonds can participate in the subsequent cross-linking reaction, increase the cross-linking density of the polyurethane adhesive, and thus improve the hardness, heat resistance and chemical resistance of the adhesive; the nanostructure introduced in the special polyester polyol with a butene structure can also effectively improve the heat resistance and medium resistance of the adhesive; and graphene oxide-modified polyester polyol is added to component B to make the graphene oxide-modified polyester polyol have a high chemical resistance. Graphene, introduced into adhesives due to its unique structure and excellent barrier properties, reduces or prolongs the transport pathways of small molecules while enhancing the adhesive's reactivity to small-molecule chemicals, reducing damage to the adhesive layer and improving the adhesive's resistance and barrier properties to small-molecule compounds in the adhesive. This imparts outstanding barrier properties to polyurethane adhesives, along with excellent heat and hydrolysis resistance. It also mitigates the poor hydrolysis resistance of the cis-butylene structure, resulting in excellent media resistance and barrier properties. Introducing a novel material, polyetherester polyol, in component A, combines the characteristics of polyester and polyether. This structure in the adhesive enhances the solvent-free adhesive's leveling properties while ensuring excellent heat and decay resistance, broadening its application range. This improved media resistance reduces the risk of food packaging waste caused by adhesive delamination due to migration of small-molecule compounds from the adhesive, extending the shelf life and improving food safety.

[0069] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the medium-resistant two-component solvent-free polyurethane adhesive and the preparation method thereof provided by the embodiments of the present invention are described in detail below with reference to specific embodiments.

[0070] Example 1

[0071] This embodiment provides a medium-resistant two-component solvent-free polyurethane adhesive. The preparation method of the adhesive is as follows (the amount of each component is based on mass):

[0072] Step 1: According to the formula of component A and component B, take the raw materials of component A and component B respectively;

[0073] Step 2: preparing a graphite oxide polyol dispersion: first, graphite powder is oxidized to obtain graphene oxide by the Hummers method, and the obtained graphene oxide is ultrasonically dispersed in ethylene glycol for 5 minutes to uniformly disperse the graphene oxide to obtain a diethylene glycol graphene oxide dispersion;

[0074] Step 3, preparing graphene oxide modified polyester polyol: adding 30 parts of adipic acid, 10 parts of isophthalic acid, 35 parts of diethylene glycol graphene oxide dispersion, 15 parts of 2-methyl-1,3-propanediol, and 10 parts of glycerol into a synthesis kettle to generate graphene oxide modified polyester polyol after esterification and polycondensation reaction;

[0075] Step 4, preparing a special polyester polyol intermediate with a maleic butene structure: adding 40 parts of diethylene glycol, 10 parts of ethylene glycol, 5 parts of 2-methyl-1,3-propylene glycol, 10 parts of maleic anhydride, and 35 parts of adipic acid into a synthesis kettle, and subjecting the mixture to an esterification and polycondensation reaction to generate a special polyester polyol intermediate with a maleic butene structure;

[0076] Step 5: Preparation of special polyester polyol with cis-butylene structure: 2 parts of Cabot Corporation The hydrophobic fumed silica and the prepared special polyester polyol intermediate with a cis-butene structure were mixed and placed in a high-speed disperser for dispersion. The dispersion was carried out at a speed of 1000 rpm for 10 minutes, and then the speed was adjusted to 2000 rpm for further dispersion for 5 minutes to obtain a special polyester polyol with a cis-butene structure.

[0077] Step 6, preparing component A: adding 40 parts of polyether ester polyol to 60 parts of diphenylmethane-4,4'-diisocyanate solution, reacting at 50-60°C for 1 hour, raising the temperature to 80-90°C and continuing the reaction for 3 hours to obtain component A;

[0078] Step 7, preparing component B: First, 38 parts of the graphene oxide-modified polyester polyol prepared above, 35 parts of the special polyester polyol with a cis-butylene structure, and 20 parts of the polyether polyol are mixed uniformly, then dehydrated under vacuum at 110-120°C for 1 hour, cooled to 50°C, and 5 parts of diphenylmethane-4,4'-diisocyanate are added and reacted for 1 hour. The temperature is then raised to 80-90°C and reacted for 3 hours. Subsequently, the temperature is lowered to below 50°C and maintained at this temperature, and 2 parts of KH-560 silane coupling agent are added and stirred uniformly to obtain component B;

[0079] The prepared component A and component B are combined and used at a functional group molar ratio of -NCO:-OH=1.5:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive.

[0080] Example 2

[0081] This embodiment provides a medium-resistant two-component solvent-free polyurethane adhesive. The preparation method of the adhesive is as follows (the amount of each component is based on mass):

[0082] Step 1: preparing a graphite oxide polyol dispersion: first, graphite powder is oxidized to obtain graphene oxide by the Hummers method, and the obtained graphene oxide is ultrasonically dispersed in diethylene glycol for 5 minutes to uniformly disperse the graphene oxide to obtain a diethylene glycol graphene oxide dispersion;

[0083] Step 3, preparing graphene oxide modified polyester polyol: adding 35 parts of sebacic acid, 5 parts of terephthalic acid, 40 parts of diethylene glycol graphene oxide dispersion, 10 parts of ethylene glycol, and 10 parts of trimethylolpropane into a synthesis kettle to generate graphene oxide modified polyester polyol after esterification and polycondensation reaction;

[0084] Step 4, preparing a special polyester polyol intermediate with a butene structure: adding 35 parts of ethylene glycol, 10 parts of 1,4-butanediol, 10 parts of 2-methyl-1,3-propanediol, 8 parts of maleic anhydride, and 37 parts of sebacic acid into a synthesis kettle to generate a special polyester polyol intermediate with a butene structure after esterification and polycondensation reaction.

[0085] Step 5. Preparation of a special polyester polyol with a butene structure: Mix 2 parts of Evonik AEROSIL R972 hydrophobic fumed silica with the special polyester polyol intermediate with a butene structure prepared above, and then put them into a high-speed disperser for dispersion. Disperse them at a machine speed of 1000 rpm for 5 minutes, then adjust the machine speed to 2000 rpm and continue dispersing for 5 minutes to obtain a special polyester polyol with a butene structure.

[0086] Step 6, preparing component A: adding 35 parts of polyetherester polyol to 65 parts of a mixture of 4,4'-MDI and 2,4'-MDI, reacting at 50-60°C for 1 hour, raising the temperature to 80-90°C and continuing the reaction for 3 hours to obtain component A;

[0087] Step 7, preparing component B: First, 40 parts of the graphene oxide-modified polyester polyol prepared above, 35 parts of the special polyester polyol with a cis-butylene structure, and 19 parts of the polyether polyol were mixed uniformly, and then dehydrated under vacuum at 110-120°C for 1 hour. The mixture was cooled to 50°C, and 5 parts of carbonized diimide-modified isocyanate were added and reacted for 1 hour. The mixture was heated to 80-90°C and reacted for 3 hours. The mixture was then cooled to below 50°C and kept warm. 1 part of KH-560 silane coupling agent was added and stirred uniformly to obtain component B.

[0088] The prepared component A and component B are combined and used at a functional group molar ratio of -NCO:-OH=1.6:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive.

[0089] Example 3

[0090] This embodiment provides a medium-resistant two-component solvent-free polyurethane adhesive. The preparation method of the adhesive is as follows (the amount of each component is based on mass):

[0091] Step 1: preparing a graphite oxide polyol dispersion: first, graphite powder is oxidized to obtain graphene oxide by the Hummers method, and the obtained graphene oxide is ultrasonically dispersed in 1,6-hexanediol for 5 minutes to uniformly disperse the graphene oxide to obtain a 1,6-hexanediol graphene oxide dispersion;

[0092] Step 3, preparing graphene oxide modified polyester polyol: adding 40 parts of adipic acid, 10 parts of terephthalic acid, 25 parts of 1,6-hexanediol graphene oxide dispersion, 15 parts of diethylene glycol, and 10 parts of glycerol into a synthesis kettle to generate graphene oxide modified polyester polyol after esterification and polycondensation reaction;

[0093] Step 4, preparing a special polyester polyol intermediate with a butene structure: adding 35 parts of diethylene glycol, 15 parts of ethylene glycol, 5 parts of 1,6-hexanediol, 10 parts of maleic anhydride, and 35 parts of adipic acid into a synthesis kettle to generate a special polyester polyol intermediate with a butene structure after esterification and polycondensation reaction.

[0094] Step 5. Preparation of special polyester polyol with butene structure: Mix 2 parts of Wacker H15 hydrophobic fumed silica with the special polyester polyol intermediate with butene structure prepared above and put them into a high-speed disperser for dispersion. Disperse for 5 minutes at a machine speed of 1000 rpm, then adjust the machine speed to 2000 rpm and continue dispersing for 5 minutes to obtain special polyester polyol with butene structure.

[0095] Step 6, preparing component A: adding 40 parts of polyether ester polyol to 60 parts of polyether modified MDI, reacting at 50-60°C for 1 hour, raising the temperature to 80-90°C and continuing the reaction for 3 hours to obtain component A;

[0096] Step 7, preparing component B: First, mix 35 parts of the graphene oxide-modified polyester polyol prepared above, 35 parts of the special polyester polyol with a cis-butylene structure, and 20 parts of the polyether polyol, then dehydrate under vacuum at 110-120°C for 1 hour, cool to 50°C, add 8 parts of diphenylmethane-4,4'-diisocyanate, and react for 1 hour, then heat to 80-90°C and react for 3 hours. Then, cool to below 50°C and keep warm, add 2 parts of KH-560 silane coupling agent and stir evenly to obtain component B;

[0097] The prepared component A and component B are combined and used at a functional group molar ratio of -NCO:-OH=1.65:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive.

[0098] The two-component solvent-free polyurethane adhesives synthesized in Examples 1 to 3 were mixed in predetermined proportions to form composite structures such as PET / AL / PA / CPP and PET / AL / CPP. The resistance of the composite film to contents such as daily chemicals (alcohol wipes) at room temperature was tested; the performance of the composite film to food contents under high-temperature cooking (125 degrees, 40 minutes of cooking) and attenuation performance were tested; and the solvent resistance of the composite film in solutions such as ethanol solution and ethyl acetate was tested.

[0099] (1) Tolerance test of contents:

[0100] Table 1 shows the resistance of the adhesive composite product to different contents

[0101]

[0102] (2) High-temperature cooking and attenuation performance evaluation: The composite film was loaded with specific contents and cooked at 125°C for 40 minutes to evaluate the resistance of the adhesive to cooking with different contents. The adhesive was then placed at room temperature for 60 days to evaluate the resistance to attenuation of the adhesive. The different composite structures did not show delamination or adhesive layer shedding after cooking for 40 minutes and after attenuation at room temperature for 60 days after cooking, and had good peel strength. The high-temperature cooking and attenuation performance results of the composite structures of Examples 1-3 are shown in Table 2:

[0103] Table 2 is the evaluation of high temperature cooking and attenuation performance of different composite structures

[0104]

[0105] (3) Immersion test of composite film in organic solvent: The composite film was immersed in different organic solvents to evaluate the peel strength and composite appearance of the composite film, thereby evaluating the resistance of the glue to organic solvents. The specific results are shown in Table 3:

[0106] Table 3 shows the resistance of the composite film to immersion in different organic solvents

[0107]

[0108]

[0109] By comparison, it can be found that the medium-resistant two-component solvent-free polyurethane adhesive of the present invention has excellent resistance to different contents and organic solvents, and also has excellent temperature resistance. Compared with ordinary products, the resistance to different contents, cooking performance, attenuation performance and immersion performance in organic solvents are significantly improved: when the content is 75% alcohol wipes, the composite appearance is qualified and the composite strength meets the standard after being placed at room temperature for 60 days; for food contents, its cooking performance and resistance after cooking are both up to standard; in addition, after soaking in different organic solvents for different times, there is no delamination of the composite film and the peeling strength and appearance of the composite film are both qualified.

[0110] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A medium-resistant two-component solvent-free polyurethane adhesive, characterized in that: include: Component A and component B, wherein component A is an isocyanate component, component B is a hydroxyl component, and the functional group molar ratio of component A to component B is: -NCO:-OH=1.2:1-2.0:1; The A component is a polyurethane prepolymer made from the following components in parts by mass: Polyether ester polyol, used in an amount of 20 to 60 parts; Isocyanate, used in an amount of 40 to 80 parts; The B component is made of the following components by mass: Graphene oxide modified polyester polyol, used in an amount of 15 to 40 parts; Cis-butylene structure special polyester polyol, dosage is 25-50 parts Polyether polyol, used in an amount of 10 to 25 parts; Isocyanate, used in an amount of 5 to 10 parts; Silane coupling agent, dosage is 0.3 to 5 parts.

2. According to the medium-resistant two-component solvent-free polyurethane adhesive of claim 1, the molecular weight of the polyether ester polyol is 500-2000 and the functionality is 2-3.

3. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 1 or 2, characterized in that: The graphene oxide modified polyester polyol in the B component is a graphene oxide modified polyester polyol obtained by introducing graphene into polyester in the form of characteristic functional groups of graphene oxide, wherein the weight proportion of graphene oxide is 0.05% to 1%.

4. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 3, characterized in that: The graphene oxide modified polyester polyol is prepared in the following manner, comprising: Graphene oxide is obtained by oxidizing graphite powder through the Hummers method, and the obtained graphene oxide is evenly dispersed in a small molecule polyol by ultrasonic dispersion for 5 to 10 minutes to obtain a graphene oxide alcohol dispersion, and then the graphene oxide alcohol dispersion is esterified and polycondensed with a small molecule dibasic acid to obtain a graphene oxide-modified polyester polyol.

5. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 4, characterized in that: The small molecule dibasic acid used in the graphene oxide modified polyester polyol is composed of aromatic dibasic acid and aliphatic dibasic acid, wherein the aromatic dibasic acid accounts for 50-100% of the total mass of the small molecule dibasic acid; The aromatic dibasic acid is at least one of terephthalic acid, isophthalic acid and phthalic anhydride; The aliphatic dibasic acid is at least one of adipic acid, sebacic acid and azelaic acid.

6. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 1 or 2, characterized in that: The special polyester polyol with butene structure used in the B component is prepared in the following manner, including: synthesizing polyester from maleic anhydride, small molecule dibasic acid and small molecule polyol, setting the molar ratio of alcohol to acid to 1.1-1.6, performing esterification and polycondensation to obtain a polyester polyol with a certain molecular weight; placing nano-silicon dioxide and the obtained polyester polyol in a high-speed disperser for dispersion, dispersing at a rotation speed of 1000 rpm and 2000 rpm for 5-10 minutes respectively, until the dispersion is uniform, and stopping to obtain the special polyester polyol with butene structure.

7. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 6, characterized in that: The amount of maleic anhydride used in the maleic butene structure special polyester polyol is 5-15% of the total mass of the maleic butene structure special polyester polyol raw material; The amount of nano silicon dioxide used in the special polyester polyol with cis-butene structure is 0.5-3% of the total mass of the raw material of the special polyester polyol with cis-butene structure; the nano silicon dioxide is hydrophobic fumed silicon dioxide; The small molecule dibasic acid used in the special polyester polyol with maleic structure is at least one of adipic acid, sebacic acid and azelaic acid; The small molecule polyol used in the special polyester polyol with cis-butene structure is at least one of diethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, 2,2-dimethyl-1,3-propylene glycol, and 2-methyl-1,3-propylene glycol; and at least one of glycerol and trimethylolpropane.

8. The medium-resistant two-component solvent-free polyurethane adhesive according to claim 6, characterized in that: The isocyanate in the A component and the B component is the same, and both are at least one of diphenylmethane-4,4'-diisocyanate (4,4'-MDI), a mixture of diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate, polyether-modified MDI, HMDI, carbonized diimide-modified MDI, and polymethylene polyphenyl polyisocyanate; wherein the weight proportion of 2,4' isomers in the mixture of diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate is greater than 35%; The silane coupling agent in the B component is at least one of an aminosilane coupling agent, an epoxysilane coupling agent, a phenylsilane coupling agent, and a titanate silane coupling agent.

9. A method for preparing the medium-resistant two-component solvent-free polyurethane adhesive according to any one of claims 1 to 8, characterized in that: include: Prepare component A and component B separately, wherein: Preparation of component A: taking the raw materials of component A according to the medium-resistant two-component solvent-free polyurethane adhesive formula of any one of claims 1 to 8, reacting the polyether ester polyol in component A with isocyanate at 50-60° C. for 1 hour, then heating to 80-90° C. for 3 hours, and the obtained product is component A; Preparation of component B: taking the raw materials of component A according to the medium-resistant two-component solvent-free polyurethane adhesive formula of any one of claims 1 to 8, vacuum dehydrating the graphene oxide-modified polyester polyol, the special polyester polyol with butene structure and the polyether polyol in component B at a temperature of 110 to 120° C. for 1 to 2 hours, reacting with isocyanate at 50 to 60° C. for 1 hour, then heating to 80 to 90° C. for reaction for 3 hours, and adding a silane coupling agent to obtain a product, which is component B; The prepared component A and component B are used in combination according to the functional group molar ratio of -NCO:-OH=1.1:1-2.0:1 to obtain a medium-resistant two-component solvent-free polyurethane adhesive.

10. The method for preparing the medium-resistant two-component solvent-free polyurethane adhesive according to claim 9, characterized in that: The graphene oxide modified polyester polyol used in the preparation of component B is prepared in the following manner: graphene oxide is obtained by oxidizing graphite powder by the Hummers method, the obtained graphene oxide is uniformly dispersed in a small molecule polyol by ultrasonic dispersion for 5 to 10 minutes to obtain a graphene oxide alcohol dispersion, and then the graphene oxide alcohol dispersion is subjected to esterification and polycondensation reaction with a small molecule dibasic acid to obtain a graphene oxide modified polyester polyol; The maleic anhydride used in the preparation of component B is prepared in the following manner: maleic anhydride accounting for 5 to 15% of the total mass of the raw materials is synthesized with a small molecular dibasic acid and a small molecular polyol, the molar ratio of the alcohol and the acid is set to 1.1 to 1.6, and esterification and polycondensation are performed to obtain a polyester polyol with a certain molecular weight; Put 0.5-3% of the total mass of the raw materials into a high-speed disperser with the polyester polyol obtained above for dispersion, and disperse at 1000 rpm and 2000 rpm for 5-10 minutes respectively until the dispersion is uniform. After stopping, the special polyester polyol with butene structure is obtained.

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