Organosilicon modified high-temperature cooking grade laminating adhesive capable of being cured at low temperature and preparation method thereof

Abstract

The invention discloses an organosilicon modified high-temperature cooking grade laminating adhesive capable of being cured at low temperature and a preparation method thereof, and belongs to the field of polyurethane adhesives, the laminating adhesive is composed of a main agent and a curing agent according to a mass ratio of 20: 2-3, wherein the main agent is hydroxyl-terminated polyol resin prepared by reacting polyester polyol, isocyanate, an organic silicon monomer containing an isocyanate group, an organic silicon monomer containing a tertiary amine group and ethyl acetate; the solid content of the hydroxyl-terminated polyol resin is 48-52 wt%, and the rotary viscosity of the hydroxyl-terminated polyol resin at the temperature of 25 DEG C is 500-2000 mPa.s; and the curing agent is a tripolymer prepolymer of aromatic isocyanate. The low-temperature curing performance of the laminating adhesive is remarkably improved, and the high-temperature cooking performance is more excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane adhesives, and in particular to an organosilicon-modified high-temperature cooking-grade laminating adhesive capable of being cured at low temperature and a preparation method thereof. Background Art

[0002] In areas such as food and pharmaceutical packaging, packaging materials must possess excellent adhesive properties and high-temperature retort resistance to ensure product safety and stability during storage and transportation. However, traditional high-temperature retort adhesives have numerous limitations. Curing typically requires temperatures above 50°C and specialized curing chambers.

[0003] In parts of Southeast Asia, the Middle East, and Africa, due to relatively high temperatures, local operating practices, and economic conditions, most packaging manufacturers lack aging rooms and other equipment. Using traditional high-temperature retort adhesives not only results in lengthy aging times, making it difficult to meet production efficiency requirements, but also inadequate crosslinking and curing of some adhesives at low temperatures, failing to meet the performance requirements of high-temperature retort applications. This results in lower product yields and severely impacts production efficiency and business profitability.

[0004] Therefore, the packaging industry in these regions is in urgent need of adhesives that can rapidly cure at low temperatures of 30-45°C. However, traditional high-temperature retort adhesives currently on the market struggle to achieve both rapid low-temperature curing and excellent high-temperature retort performance. Therefore, developing a laminating adhesive that can cure at low temperatures of 30-45°C while also exhibiting excellent high-temperature retort performance is of great practical significance and market value, filling the market gap in these regions and boosting the development of the packaging industry.

[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 low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive and a preparation method thereof, which can meet the packaging industry's demand for low-temperature curing and can be quickly cured even in a low-temperature environment of 30-45°C. At the same time, the composite film product has high bonding strength and good heat resistance, and can meet the cooking requirements of 121°C and 135°C, thereby solving the above-mentioned technical problems existing in the prior art.

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

[0008] A low-temperature curable organic silicon modified high-temperature cooking grade laminating adhesive, the laminating adhesive is composed of a main agent and a curing agent in a mass ratio of 20:2-3; wherein,

[0009] The main agent is a hydroxyl-terminated polyol resin prepared by reacting polyester polyol, isocyanate, an isocyanate-containing silicone monomer, a tertiary amine-containing silicone monomer, and ethyl acetate; the hydroxyl-terminated polyol resin has a solid content of 48-52 wt% and a rotational viscosity of 500-2000 mPa·s at 25°C;

[0010] The curing agent is a trimer prepolymer of aromatic isocyanate.

[0011] Preferably, in the above-mentioned laminating adhesive, the amounts of the components in the main agent are as follows by mass: 45-49 parts of polyester polyol, 1-3 parts of isocyanate, 0.1-0.3 parts of isocyanate-containing silicone monomer, 0.1-0.3 parts of tertiary amine-containing silicone monomer, and 48-52 parts of ethyl acetate.

[0012] Preferably, in the above-mentioned laminating adhesive, the polyester polyol in the main agent is formed by condensation polymerization of aromatic dibasic acid, aliphatic dibasic acid, branched diol, linear diol, alicyclic diol, fluorine-containing diol, catalyst and antioxidant, and has an average molecular weight of 6000-7500 and a hydroxyl value of 15-18 mgKOH / g.

[0013] Preferably, in the above-mentioned laminating adhesive, the amount of each component in the polyester polyol in the main agent is as follows by mass: 30-35 parts of aromatic dibasic acid, 12-14 parts of aliphatic dibasic acid, 13-15 parts of branched diol, 22-24 parts of linear diol, 10-12 parts of alicyclic diol, 6-8 parts of fluorine-containing diol, 0.03-0.06 parts of catalyst and 0.02-0.05 parts of antioxidant.

[0014] Preferably, in the above-mentioned laminating adhesive, the aromatic dibasic acid is one or both of isophthalic acid and terephthalic acid;

[0015] The aliphatic dibasic acid is adipic acid;

[0016] The branched diol is one of 2,2-dimethyl-1,3-propylene glycol, 2,5-dimethyl-2,5-hexanediol, and 2,4-diethyl-1,5-pentanediol;

[0017] The linear diol is one or two of ethylene glycol, diethylene glycol, and 1,4-butanediol;

[0018] The alicyclic diol is tricyclodecane dimethanol;

[0019] The fluorinated diol is 2-fluoro-2-methylpropane-1,3-diol;

[0020] The catalyst is one of Guangzhou Yourun's AUCAT-ES01 and AUCAT-ES02 hydrolysis-resistant environmentally friendly titanium metal catalysts;

[0021] The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0022] Preferably, in the above-mentioned laminating adhesive, the polyester polyol in the main agent is prepared by condensation polymerization in the following manner, including:

[0023] Esterification reaction: Add linear diols, branched diols, alicyclic diols, fluorinated diols, aliphatic dibasic acids, aromatic dibasic acids and catalysts into a reactor and carry out esterification reaction. Heat to 150°C to start dehydration, then increase the temperature by 10°C every hour until it reaches 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the system should be ≤10mgKOH / g.

[0024] Polycondensation reaction: After the esterification and dehydration reaction is completed, an antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 230-245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5-1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 8-10 hours, until the hydroxyl value of the product reaches 15-18mgKOH / and the acid value of the product is ≤1.0mgKOH / g. The obtained product is polyester polyol.

[0025] Preferably, in the main agent of the above-mentioned laminating adhesive, the isocyanate is one of 2,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate;

[0026] The isocyanate group-containing organic silicon monomer is one of 3-isocyanate propyltrimethoxysilane, 3-isocyanate propyltriethoxysilane and isocyanate methyltrimethylsilane.

[0027] The tertiary amino group-containing organic silicon monomer is 3-(N,N-dimethylamino)propyltrimethoxysilane.

[0028] Preferably, in the above-mentioned laminating adhesive, the aromatic isocyanate trimer prepolymer of the curing agent is L75 from Covestro.

[0029] A method for preparing the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of the present invention comprises:

[0030] Preparation of a main agent: taking the raw materials of the main agent according to the formula of claims 1 to 8, adding the polyester polyol and isocyanate in the raw materials into a reaction kettle and mixing them evenly, heating the temperature to 80-85° C. and reacting for 2 hours to obtain a polyurethane prepolymer; then lowering the system temperature to 50° C., adding an isocyanate group-containing silicone monomer, heating the temperature to 85° C. and continuing the reaction for 2-3 hours, cooling the temperature to below 55° C., adding a tertiary amine group-containing silicone monomer and ethyl acetate, and during the stirring process, using ultrasonic wave with a frequency of 20-40 kHz to assist in dispersion so that the components are more evenly dispersed to obtain a main agent with a solid content of 48-52 wt% and a rotational viscosity of 500-2000 mPa·s at 25° C.;

[0031] Curing agent: trimer prepolymer of aromatic isocyanate;

[0032] Preparation of laminating adhesive: the main agent and curing agent prepared above are mixed uniformly at a mass ratio of 20:2-3 to obtain the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to any one of claims 1-8.

[0033] Preferably, in the above method for preparing the main agent, the polyester polyol used is prepared by condensation polymerization in the following manner, including:

[0034] Esterification reaction: 22-24 parts by mass of linear diol, 13-15 parts by mass of branched diol, 10-12 parts by mass of alicyclic diol, 6-8 parts by mass of fluorinated diol, 12-14 parts by mass of aliphatic dibasic acid, 30-35 parts by mass of aromatic dibasic acid and 0.03-0.06 parts by mass of catalyst are added to a reactor and esterification reaction is carried out. The temperature is raised to 150°C to start dehydration, and then the temperature is raised by 10°C every hour to gradually increase to 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the detection system is ≤10mgKOH / g;

[0035] Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.02 to 0.05 parts by mass of an antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 230 to 245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02 MPA, -0.04 MPA, -0.06 MPA, and -0.08 MPA, and each vacuuming period is 0.5 to 1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1 MPA. The long vacuuming time is 8 to 10 hours, until the hydroxyl value of the product reaches 15 to 18 mgKOH / , and the acid value of the product is ≤1.0 mgKOH / g. The obtained product is polyester polyol.

[0036] Compared with the prior art, the present invention provides a low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive and a preparation method thereof, which has the following beneficial effects:

[0037] (1) Significantly improved low-temperature curing performance: The laminating adhesive provided by the present invention has a unique raw material formula and system design, especially the introduction of tertiary amine groups and the application of ultrasonic-assisted dispersion technology. The introduction of tertiary amine groups can reduce the activation energy of the reaction, promote the rapid progress of the main reaction, and inhibit side reactions. The high-temperature and high-pressure environment generated by the cavitation effect of ultrasound also helps to initiate the polymerization reaction, reduce the activation energy of the reaction, and make the reaction easier to proceed; on the other hand, the uniform monomer dispersion and enhanced mass transfer effect are also conducive to the effective collision between the reactant molecules, thereby accelerating the reaction rate. This enables the composite product to achieve faster and more uniform curing at a low temperature of 30-45°C. There is no need for special equipment such as curing rooms, which greatly reduces the dependence on equipment and energy, and meets the packaging production needs of some foreign regions that lack curing rooms due to high temperature climates and special usage habits.

[0038] (2) Better high-temperature cooking performance: The laminating adhesive provided by the present invention exhibits higher peel strength and a smoother cooking appearance after being steamed at 121°C or 135°C. In food packaging with a PETink / AL / RCPP composite structure, the peel strength is not less than 7N / 15mm after steaming at 121°C for 40 minutes; and the peel strength is not less than 6N / 15mm after steaming at 135°C for 30 minutes. This is mainly due to the introduction of special structural compounds into the raw materials, such as tricyclic rigid structure tricyclodecane dimethanol, fluorinated diols, and isocyanate-containing silicone monomers. Their synergistic effect enhances the interaction between polyurethane molecular chains and the adhesion to the surface of the packaging material. The modification of the silicone monomer improves the weather resistance and heat resistance of the polyurethane laminating adhesive, effectively preventing problems such as delamination and debonding during high-temperature steaming. DETAILED DESCRIPTION

[0039] 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.

[0040] First, the following terms may be used in this article:

[0041] 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”.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The scheme provided by the present invention is described in detail below. The contents not described in detail in the examples of the present invention belong to the prior art known to professionals in this field. If specific conditions are not specified in the examples of the present invention, they are carried out according to conventional conditions in the field or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used in the examples of the present invention is not specified, they are all conventional products that can be purchased commercially.

[0047] The embodiment of the present invention provides a low-temperature curable organic silicon modified high-temperature cooking grade laminating adhesive, which is composed of a main agent and a curing agent, and the mass ratio of the main agent to the curing agent is 20:2-3; wherein,

[0048] The main agent is a hydroxyl-terminated polyol resin prepared by reacting polyester polyol, isocyanate, an isocyanate-containing organic silicon monomer and ethyl acetate; the hydroxyl-terminated polyol resin has a solid content of 48-52 wt% and a rotational viscosity of 500-2000 mPa·s at 25°C;

[0049] The curing agent is a trimer prepolymer of aromatic isocyanate.

[0050] Preferably, in the above-mentioned laminating adhesive, the amounts of the components in the main agent are as follows by mass: 45-49 parts of polyester polyol, 1-3 parts of isocyanate, 0.1-0.3 parts of isocyanate-containing silicone monomer, 0.1-0.3 parts of tertiary amine-containing silicone monomer and 48-52 parts of ethyl acetate.

[0051] Preferably, in the above-mentioned laminating adhesive, the polyester polyol in the main agent is prepared by condensation polymerization of aromatic dibasic acid, aliphatic dibasic acid, branched diol, linear diol, alicyclic diol, fluorine-containing diol, catalyst and antioxidant, and has an average molecular weight of 6000-7500 and a hydroxyl value of 15-18 mgKOH / g.

[0052] Preferably, in the above-mentioned laminating adhesive, the amount of each component in the polyester polyol in the main agent is as follows by mass: 30-35 parts of aromatic dibasic acid, 12-14 parts of aliphatic dibasic acid, 13-15 parts of branched diol, 22-24 parts of linear diol, 10-12 parts of alicyclic diol, 6-8 parts of fluorine-containing diol, 0.03-0.06 parts of catalyst and 0.02-0.05 parts of antioxidant.

[0053] Preferably, in the polyester polyol, the aromatic dibasic acid is one or both of isophthalic acid and terephthalic acid;

[0054] The aliphatic dibasic acid is adipic acid;

[0055] The branched diol is one of 2,2-dimethyl-1,3-propylene glycol, 2,5-dimethyl-2,5-hexanediol, and 2,4-diethyl-1,5-pentanediol;

[0056] The linear diol is one or two of ethylene glycol, diethylene glycol, and 1,4-butanediol;

[0057] The alicyclic diol is tricyclodecane dimethanol, and the three-ring rigid structure in its molecular structure can improve the heat resistance of the laminating adhesive;

[0058] The fluorinated diol is 2-fluoro-2-methylpropane-1,3-diol. The strong electronegativity of the fluorine atoms in its structure and the steric hindrance of the methyl group increase the interaction force between the molecular chains, hinder the movement of the chain segments, and lead to an increase in the Tg of the polyester, which can improve the water resistance and chemical resistance of the laminating adhesive.

[0059] The catalyst is selected from one of Guangzhou Yourun's AUCAT-ES01 and AUCAT-ES02 hydrolysis-resistant and environmentally friendly titanium metal catalysts. Compared with the organic titanium catalysts commonly used in the synthesis of polyester polyols, this type of catalyst is perfectly compatible with the polyurethane system, is stable and does not hydrolyze, has good high-temperature stability, and can maintain the catalytic effect for a long time during the reaction without the need for supplementation, ensuring efficient and stable synthesis of polyester polyols.

[0060] The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0061] Preferably, in the above-mentioned laminating adhesive, the polyester polyol in the main agent is prepared by condensation polymerization in the following manner, including:

[0062] Esterification reaction: Add linear diols, branched diols, alicyclic diols, fluorinated diols, aliphatic dibasic acids, aromatic dibasic acids and catalysts into a reactor and carry out esterification reaction. Heat to 150°C to start dehydration, then increase the temperature by 10°C every hour until it reaches 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the system should be ≤10mgKOH / g.

[0063] Polycondensation reaction: After the esterification and dehydration reaction is completed, an antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 230-245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5-1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 8-10 hours, until the hydroxyl value of the product reaches 15-18mgKOH / and the acid value of the product is ≤1.0mgKOH / g, thereby obtaining polyester polyol.

[0064] Preferably, in the above-mentioned laminating adhesive, the isocyanate in the main agent is one of 2,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

[0065] Preferably, in the above-mentioned laminating adhesive, the isocyanate group-containing silicone monomer in the main agent is one of 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane and isocyanatemethyltrimethylsilane.

[0066] Preferably, in the above-mentioned laminating adhesive, the tertiary amino group-containing organosilicon monomer in the main agent is 3-(N,N-dimethylamino)propyltrimethoxysilane.

[0067] Preferably, in the above-mentioned laminating adhesive, the trimer prepolymer of aromatic isocyanate used as the curing agent is L75 from Covestro.

[0068] The present invention also provides a method for preparing the aforementioned low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive, comprising:

[0069] ① Preparation of the main agent: Take the raw materials according to the formula of the main agent of the above-mentioned laminating adhesive, add 45-49 parts by mass of polyester polyol and 1-3 parts by mass of isocyanate from the raw materials into a reactor and mix evenly, heat to 80-85°C and react for 2 hours to obtain a polyurethane prepolymer. Then reduce the system temperature to 50°C, add 0.1-0.3 parts by mass of an isocyanate-containing silicone monomer, heat to 85°C and continue to react for 2-3 hours. Cool to below 55°C, add 0.1-0.3 parts by mass of a tertiary amine-containing silicone monomer and 48-52 parts by mass of ethyl acetate. During the stirring process, use ultrasonic assisted dispersion technology with a frequency of 20-40kHz to make the components more evenly dispersed, and obtain a main agent with a solid content of 48-52wt% and a rotational viscosity of 500-2000mPa·s at 25°C;

[0070] ②Curing agent: Aromatic isocyanate trimer prepolymer is selected as the curing agent;

[0071] ③ Preparation of laminating adhesive: the main agent and the curing agent are mixed uniformly in a mass ratio of 20:2-3 to obtain the above-mentioned low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive.

[0072] Preferably, in the above-mentioned laminating adhesive, the polyester polyol used in the main agent is prepared by condensation polymerization in the following manner, including:

[0073] Esterification reaction: 22-24 parts of linear diol, 13-15 parts of branched diol, 10-12 parts of alicyclic diol, 6-8 parts of fluorinated diol, 12-14 parts of aliphatic dibasic acid, 30-35 parts of aromatic dibasic acid and 0.03-0.06 parts of catalyst are added to a reactor and esterification reaction is carried out. The temperature is raised to 150°C to start dehydration, and then the temperature is raised by 10°C every hour to gradually increase to 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the system is tested to be ≤10mgKOH / g.

[0074] Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.02 to 0.05 parts of an antioxidant are added to the reactor, the reactor is evacuated, the temperature is controlled at 230 to 245° C., and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02 MPA, -0.04 MPA, -0.06 MPA, and -0.08 MPA. Each vacuuming period is 0.5 to 1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1 MPA. The long vacuuming time is 8 to 10 hours, until the hydroxyl value of the product reaches 15 to 18 mgKOH / and the acid value of the product is ≤1.0 mgKOH / g, thereby obtaining polyester polyol.

[0075] In summary, the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive provided by the embodiments of the present invention can be used in food packaging, pharmaceutical packaging, electronic packaging and other fields. The composite products can be cured at low temperatures of 30 to 45°C and have excellent high-temperature cooking performance. This has extremely important practical significance and market value in filling market gaps in relevant foreign regions and promoting the development of the packaging industry.

[0076] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the solution provided by the embodiment of the present invention is described in detail with reference to specific embodiments below.

[0077] Example 1

[0078] This embodiment provides a low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive, the preparation method of which may include (all raw materials are in parts by mass):

[0079] (1) First prepare polyester polyol:

[0080] Esterification reaction: 22 parts of diethylene glycol, 14 parts of 2,2-dimethyl-1,3-propylene glycol, 10 parts of tricyclodecane dimethanol, 7 parts of 2-fluoro-2-methylpropane-1,3-diol, 14 parts of adipic acid, 32 parts of isophthalic acid, and 0.04 parts of AUCAT-ES01 were added to a reactor for esterification reaction. The temperature was raised to 150°C to begin dehydration, and then the temperature was raised by 10°C every hour until it reached 240°C. After 10 hours of esterification and dehydration, the acid value of the system was detected to be 8 mgKOH / g.

[0081] Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.03 parts of antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 240°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 10 hours, until the hydroxyl value of the product reaches 15mgKOH / , and the acid value of the product is 0.51mgKOH / g, thereby obtaining polyester polyol.

[0082] (2) Preparation of the main agent: 48 parts by mass of the above-mentioned polyester polyol and 1.5 parts by mass of isophorone diisocyanate were added to a reactor and mixed evenly, and the temperature was raised to 85°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then the system temperature was lowered to 50°C, 0.2 parts by mass of 3-isocyanatepropyltrimethoxysilane was added, and the temperature was raised to 85°C and the reaction was continued for 3 hours. The temperature was lowered to below 55°C, 0.3 parts by mass of 3-(N,N-dimethylamino)propyltrimethoxysilane and 50 parts by mass of ethyl acetate were added, and during the stirring process, ultrasonic assisted dispersion technology was used at a frequency of 30kHz to make the components more evenly dispersed, and a main agent with a solid content of 50wt% and a rotational viscosity of 1200mPa·s at 25°C was obtained;

[0083] (3) Selection of curing agent: Covestro's L75, a trimer prepolymer of aromatic isocyanate, was selected as the curing agent;

[0084] (4) Preparation of laminating adhesive: The main agent and the curing agent are mixed uniformly in a mass ratio of 20:2.5 to obtain the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of this embodiment.

[0085] Example 2

[0086] This embodiment provides a low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive, the preparation method of which may include (all raw materials are in parts by mass):

[0087] (1) Preparation of polyester polyol:

[0088] Esterification reaction: 18 parts of diethylene glycol, 6 parts of 1,4-butanediol, 13 parts of 2,2-dimethyl-1,3-propylene glycol, 11 parts of tricyclodecane dimethanol, 6 parts of 2-fluoro-2-methylpropane-1,3-diol, 12 parts of adipic acid, 15 parts of terephthalic acid, 20 parts of isophthalic acid, and 0.04 parts of AUCAT-ES01 were added to a reactor and esterification reaction was carried out. The temperature was raised to 150°C to begin dehydration, and then the temperature was raised by 10°C every hour until it reached 245°C. After 11 hours of esterification and dehydration, the acid value of the system was detected to be 6 mgKOH / g.

[0089] Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.05 parts of antioxidant are added to the reactor, the reactor is evacuated, the temperature is controlled at 245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5 hours. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 9 hours, until the hydroxyl value of the product reaches 17mgKOH / and the acid value of the product is 0.46mgKOH / g, thereby obtaining polyester polyol.

[0090] (2) Preparation of the main agent: 49 parts by mass of the above polyester polyol and 2 parts by mass of hexamethylene diisocyanate were added to a reactor and mixed evenly, and the temperature was raised to 85°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then the system temperature was lowered to 50°C, 0.3 parts by mass of 3-isocyanatepropyltrimethoxysilane was added, and the temperature was raised to 85°C and the reaction was continued for 3 hours. The temperature was lowered to below 55°C, 0.2 parts by mass of 3-(N,N-dimethylamino)propyltrimethoxysilane and 49 parts by mass of ethyl acetate were added, and during the stirring process, ultrasonic assisted dispersion technology was used at a frequency of 30kHz to make the components more evenly dispersed, and a main agent with a solid content of 50wt% and a rotational viscosity of 1500mPa·s at 25°C was obtained;

[0091] (3) Selection of curing agent: Covestro's L75, a trimer prepolymer of aromatic isocyanate, was selected as the curing agent;

[0092] (4) Preparation of laminating adhesive: The main agent and the curing agent are mixed uniformly in a mass ratio of 20:2 to obtain the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of this embodiment.

[0093] Example 3

[0094] This embodiment provides a low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive and a preparation method thereof. The preparation method may include (all raw materials are in parts by mass):

[0095] (1) Preparation of polyester polyol:

[0096] Esterification reaction: 18 parts of diethylene glycol, 5 parts of ethylene glycol, 13 parts of 2,5-dimethyl-2,5-hexanediol, 11 parts of tricyclodecane dimethanol, 8 parts of 2-fluoro-2-methylpropane-1,3-diol, 13 parts of adipic acid, 34 parts of isophthalic acid, and 0.05 parts of AUCAT-ES02 were added to a reactor and esterification reaction was carried out. The temperature was raised to 150°C to begin dehydration, and then the temperature was increased by 10°C every hour until it reached 240°C. After 8 hours of esterification and dehydration, the acid value of the system was tested to be ≤7mgKOH / g.

[0097] Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.03 parts of antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5 hours. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 9 hours, until the hydroxyl value of the product reaches 16mgKOH / and the acid value of the product is 0.6mgKOH / g, thereby obtaining polyester polyol.

[0098] (2) Preparation of the main agent: 47 parts by mass of the above-mentioned polyester polyol and 1 part by mass of 2,4'-diphenylmethane diisocyanate were added to a reactor and mixed evenly, and the temperature was raised to 85°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then the system temperature was lowered to 50°C, 0.2 parts by mass of 3-isocyanatepropyltriethoxysilane was added, and the temperature was raised to 85°C and the reaction was continued for 3 hours. The temperature was lowered to below 55°C, and 0.2 parts by mass of 3-(N,N-dimethylamino)propyltrimethoxysilane and 51 parts by mass of ethyl acetate were added. During the stirring process, ultrasonic assisted dispersion technology was used at a frequency of 35kHz to make the components more evenly dispersed, and a main agent with a solid content of 51wt% and a rotational viscosity of 1900mPa·s at 25°C was obtained;

[0099] (3) Selection of curing agent: Covestro's L75, a trimer prepolymer of aromatic isocyanate, was selected as the curing agent;

[0100] (4) Preparation of laminating adhesive: The main agent and the curing agent are mixed uniformly in a mass ratio of 20:2 to obtain the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of this embodiment.

[0101] Performance testing

[0102] The use and performance testing methods of the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesives of Examples 1, 2, and 3 of the present invention are as follows:

[0103] Dry basis glue amount: 3.5-4g / m 2 ;

[0104] Composite structure: PETink / AL / RCPP, PETink / AL / PA / RCPP;

[0105] Curing conditions: 35-40℃×72h;

[0106] Cooking conditions: 121°C × 40 min, 135°C × 30 min;

[0107] The peel strength comparison test of the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of the present invention before and after cooking was conducted. The results are shown in Table 1 below:

[0108] Table 1 is the comparative test results of the peeling strength of the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive before and after cooking.

[0109]

[0110] As can be seen from Table 1, the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive of the present invention exhibits significant advantages in both low-temperature curing speed and high-temperature cooking performance. It can effectively meet the stringent adhesive requirements of the domestic and international food and pharmaceutical packaging industries, and in particular, provides a high-quality solution for packaging production in areas abroad that lack curing rooms.

[0111] 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 low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive, characterized in that: The laminating adhesive is composed of a main agent and a curing agent in a mass ratio of 20:2-3; wherein, The main agent is a hydroxyl-terminated polyol resin prepared by reacting polyester polyol, isocyanate, an isocyanate-containing silicone monomer, a tertiary amine-containing silicone monomer, and ethyl acetate; the hydroxyl-terminated polyol resin has a solid content of 48-52 wt% and a rotational viscosity of 500-2000 mPa·s at 25°C; The curing agent is a trimer prepolymer of aromatic isocyanate.

2. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 1, characterized in that: The amounts of the components in the main agent are as follows by mass: 45-49 parts of polyester polyol, 1-3 parts of isocyanate, 0.1-0.3 parts of isocyanate group-containing silicone monomer, 0.1-0.3 parts of tertiary amine group-containing silicone monomer, and 48-52 parts of ethyl acetate.

3. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 1 or 2, characterized in that: The polyester polyol in the main agent is prepared by condensation polymerization of aromatic dibasic acid, aliphatic dibasic acid, branched diol, linear diol, alicyclic diol, fluorine-containing diol, catalyst and antioxidant, and has an average molecular weight of 6000-7500 and a hydroxyl value of 15-18 mgKOH / g.

4. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 3, characterized in that: The amounts of the components of the polyester polyol in the main agent are as follows by mass: 30 to 35 parts of aromatic dibasic acid, 12 to 14 parts of aliphatic dibasic acid, 13 to 15 parts of branched diol, 22 to 24 parts of linear diol, 10 to 12 parts of alicyclic diol, 6 to 8 parts of fluorine-containing diol, 0.03 to 0.06 parts of catalyst and 0.02 to 0.05 parts of antioxidant.

5. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 4, characterized in that: The aromatic dibasic acid is one or both of isophthalic acid and terephthalic acid; The aliphatic dibasic acid is adipic acid; The branched diol is one of 2,2-dimethyl-1,3-propylene glycol, 2,5-dimethyl-2,5-hexanediol, and 2,4-diethyl-1,5-pentanediol; The linear diol is one or two of ethylene glycol, diethylene glycol, and 1,4-butanediol; The alicyclic diol is tricyclodecane dimethanol; The fluorinated diol is 2-fluoro-2-methylpropane-1,3-diol; The catalyst is one of Guangzhou Yourun's AUCAT-ES01 and AUCAT-ES02 hydrolysis-resistant environmentally friendly titanium metal catalysts; The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

6. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 3, characterized in that: The polyester polyol in the main agent is prepared by condensation polymerization in the following manner, including: Esterification reaction: Add linear diols, branched diols, alicyclic diols, fluorinated diols, aliphatic dibasic acids, aromatic dibasic acids and catalysts into a reactor and carry out esterification reaction. Heat to 150°C to start dehydration, then increase the temperature by 10°C every hour until it reaches 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the system should be ≤10mgKOH / g. Polycondensation reaction: After the esterification and dehydration reaction is completed, an antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 230-245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02MPA, -0.04MPA, -0.06MPA, and -0.08MPA, and each vacuuming period is 0.5-1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1MPA. The long vacuuming time is 8-10 hours, until the hydroxyl value of the product reaches 15-18mgKOH / and the acid value of the product is ≤1.0mgKOH / g. The obtained product is polyester polyol.

7. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 1 or 2, characterized in that: In the main agent, the isocyanate is one of 2,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; The isocyanate group-containing organic silicon monomer is one of 3-isocyanate propyltrimethoxysilane, 3-isocyanate propyltriethoxysilane and isocyanate methyltrimethylsilane. The tertiary amino group-containing organic silicon monomer is 3-(N,N-dimethylamino)propyltrimethoxysilane.

8. The low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 1 or 2, characterized in that: The aromatic isocyanate trimer prepolymer of the curing agent is Covestro's L75.

9. A method for preparing the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to any one of claims 1 to 8, characterized in that: include: Preparation of a main agent: taking the raw materials of the main agent according to the formula of claims 1 to 8, adding the polyester polyol and isocyanate in the raw materials into a reaction kettle and mixing them evenly, heating the temperature to 80-85° C. and reacting for 2 hours to obtain a polyurethane prepolymer; then lowering the system temperature to 50° C., adding an isocyanate group-containing silicone monomer, heating the temperature to 85° C. and continuing the reaction for 2-3 hours, cooling the temperature to below 55° C., adding a tertiary amine group-containing silicone monomer and ethyl acetate, and during the stirring process, using ultrasonic wave with a frequency of 20-40 kHz to assist in dispersion so that the components are more evenly dispersed to obtain a main agent with a solid content of 48-52 wt% and a rotational viscosity of 500-2000 mPa·s at 25° C.; Curing agent: trimer prepolymer of aromatic isocyanate; Preparation of laminating adhesive: the main agent and curing agent prepared above are mixed uniformly at a mass ratio of 20:2-3 to obtain the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to any one of claims 1-8.

10. The method for preparing the low-temperature curable organosilicon-modified high-temperature cooking-grade laminating adhesive according to claim 9, characterized in that: In the method for preparing the main agent, the polyester polyol used is prepared by condensation polymerization in the following manner, including: Esterification reaction: 22-24 parts by mass of linear diol, 13-15 parts by mass of branched diol, 10-12 parts by mass of alicyclic diol, 6-8 parts by mass of fluorinated diol, 12-14 parts by mass of aliphatic dibasic acid, 30-35 parts by mass of aromatic dibasic acid and 0.03-0.06 parts by mass of catalyst are added to a reactor and esterification reaction is carried out. The temperature is raised to 150°C to start dehydration, and then the temperature is raised by 10°C every hour to gradually increase to 230-245°C. After 8-12 hours of esterification and dehydration, the acid value of the detection system is ≤10mgKOH / g; Polycondensation reaction: After the esterification and dehydration reaction is completed, 0.02 to 0.05 parts by mass of an antioxidant is added to the reactor, the reactor is evacuated, the temperature is controlled at 230 to 245°C, and the polycondensation reaction is carried out. The negative pressure is gradually increased by -0.02 MPA, -0.04 MPA, -0.06 MPA, and -0.08 MPA, and each vacuuming period is 0.5 to 1 hour. After that, a long vacuuming operation is performed, and the vacuum degree reaches 0.1 MPA. The long vacuuming time is 8 to 10 hours, until the hydroxyl value of the product reaches 15 to 18 mgKOH / , and the acid value of the product is ≤1.0 mgKOH / g. The obtained product is polyester polyol.

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