Preparation method of low-temperature-resistant heat-sealing emulsion

Abstract

The invention discloses a preparation method of a low-temperature-resistant heat-sealing emulsion, and belongs to the technical field of food packaging heat-sealing emulsions. The emulsion is composed of polyol, isocyanate, polydimethylsiloxane glycol, a micromolecule chain extender, a low-temperature-resistant bio-based adhesive, a cross-linking agent, an emulsifying dispersant and an antioxidant. The preparation method comprises the following steps: carrying out a reaction on polyol and isocyanate to generate a prepolymer, adding polydimethylsiloxane glycol and a micromolecular chain extender for continuous reaction, and then adding the low-temperature-resistant bio-based adhesive, the cross-linking agent, the emulsifying dispersant and the antioxidant to finally form an emulsion. The emulsion can still keep good heat sealing performance and stability in a low-temperature environment, is suitable for the field of food packaging, and meets the sealing performance requirement in the low-temperature storage and transportation process.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging heat-sealing emulsions, and in particular relates to a method for preparing a low-temperature-resistant heat-sealing emulsion. Background Art

[0002] Low-temperature resistant heat-sealing emulsions and coating materials are currently mainly used in aerospace, electronic components, cryogenic engineering and other fields. Their outstanding advantage is that they can still maintain high mechanical strength in low-temperature environments. In the food packaging industry, related research on low-temperature resistant heat-sealing emulsions is still in its infancy, so conducting performance research on such materials is of great practical significance. In reality, many food packages need to be stored under freezing, but traditional heat-sealing emulsions are prone to brittle fracture in low-temperature environments, resulting in microcracks in the sealing layer, which in turn causes problems such as heat-sealing strength attenuation and seal failure, making it difficult to meet the packaging requirements during low-temperature storage and transportation of food. Taking cold chain logistics as an example, when packaging materials are exposed to extreme low-temperature environments of -25°C and below for a long time, conventional heat-sealing emulsions will experience a decrease in viscoelasticity and weakened interfacial bonding strength, resulting in loss of packaging sealing, causing quality and safety risks such as food deterioration due to moisture and microbial contamination. Summary of the Invention

[0003] In response to the above technical problems, the present invention proposes a method for preparing a low-temperature resistant heat-sealing emulsion, which can maintain good heat-sealing performance and stability in a low-temperature environment, ensure the sealing and safety of food packaging, and meet the hygiene standards of food packaging.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a low-temperature resistant heat-sealing emulsion, comprising the following raw materials in parts by mass: 45-80 parts of polyol, 2-30 parts of isocyanate, 3-10 parts of polydimethylsiloxane (PDMS) diol, 4-10 parts of a small molecule chain extender, 10-20 parts of a low-temperature resistant bio-based adhesive, 2-5 parts of a cross-linking agent, 1-5 parts of an emulsifying dispersant, and 0.5-1 part of an antioxidant.

[0006] The low-temperature-resistant bio-based adhesive is prepared by mixing sodium polyglutamate (γ-PGA) and polylysine hydrochloride (ε-PLL) as raw materials.

[0007] As a soft segment component, polyols impart flexibility to the molecular chains, improving the material's low-temperature toughness and effectively preventing embrittlement. By introducing a specific crosslinking component, melamine formaldehyde resin, along with flexible molecules such as polyglutamic acid and polylysine hydrochloride, the formulation system synergistically optimizes interactions between the molecular chains, enhancing the material's mechanical toughness and interfacial adhesion properties at low temperatures. Both sodium polyglutamate and polylysine hydrochloride contain dual reactive groups, amino and carboxyl groups, in their molecular structures. The amino groups in sodium polyglutamate, due to their strong positive charge, readily react with isocyanate groups to form crosslinked bonds, thereby enhancing the adhesive's cohesive strength and building a reversible network, imparting low-temperature flexibility to the material. The amino group activity of polylysine hydrochloride is significantly higher than that of the urethane bond formed by isocyanate and alcoholic hydroxyl groups. Its nitrogen atom can attack the CO bond of the urethane bond, ultimately converting it into a urea bond, creating a high-crosslink density hard segment network that effectively enhances the mechanical strength and low-temperature resistance of the adhesive layer. The strong polarity of amino groups can also strengthen the van der Waals force and hydrogen bond interaction between the adhesive and the substrate surface, thereby improving the interfacial adhesion strength.

[0008] Furthermore, the structural formula of the polyol is in,

[0009] R is and One of the following;

[0010] n = 2 to 136;

[0011] The relative molecular weight is 200 to 6000.

[0012] Furthermore, the isocyanate is one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.

[0013] Furthermore, the small molecule chain extender is one or more of 1,4-butanediol (BDO), 1,3-butanediol, neopentyl glycol and 1,6-hexanediol.

[0014] Furthermore, the preparation method of the low-temperature resistant bio-based adhesive comprises the following steps:

[0015] Weigh sodium polyglutamate and add it to 4-hydroxyethylpiperazineethanesulfonic acid (HEPES) buffer solution to obtain a sodium polyglutamate solution;

[0016] Weighing polylysine hydrochloride and adding it to 4-hydroxyethylpiperazineethanesulfonic acid buffer solution to obtain a polylysine hydrochloride solution;

[0017] The pH values ​​of the sodium polyglutamate solution and the polylysine hydrochloride solution are adjusted to neutral, and then the two solutions are mixed in equal volumes, centrifuged, and the precipitate phase is separated to obtain a white emulsion colloidal adhesive.

[0018] Furthermore, the cross-linking agent is one or more of benzoyl peroxide, melamine formaldehyde resin and divinylbenzene.

[0019] Furthermore, the emulsifying dispersant is one or more of castor oil polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether (only as a dispersant).

[0020] Furthermore, the antioxidant is one or more of butylated hydroxyanisole (BHA), propyl gallate (PG), calcium stearate and DL-α-tocopherol.

[0021] The present invention also discloses a method for preparing a low-temperature resistant heat-sealing emulsion, comprising the following steps:

[0022] 1) Adding polyol and isocyanate into a reaction kettle, heating and stirring under nitrogen protection, mixing and continuing the reaction to form a prepolymer;

[0023] 2) heating and stirring the prepolymer, adding polydimethylsiloxane diol and a small molecule chain extender, continuing to stir and react, and then adding a low-temperature resistant bio-based adhesive, and continuing to react under the same conditions;

[0024] 3) adding a crosslinking agent in step 2), heating for reaction, cooling the reactor after the reaction is complete, adding an emulsifying dispersant, and stirring to form an emulsion system;

[0025] 4) Keep the temperature of the reactor constant, add antioxidant and stir;

[0026] 5) filtering the product obtained in step 4) to obtain a low-temperature resistant heat-sealing emulsion.

[0027] Furthermore, in the entire reaction system, unless otherwise specified, the stirring speed of the stirring device is controlled at 300-500 rpm. Specifically:

[0028] In step 1), the heating and stirring is: stirring at 50-70° C. for 5 minutes to preliminarily mix the raw materials, and continuing stirring for 5 minutes; the reaction time is 1-2 hours;

[0029] In step 2), the heating and stirring is: stirring at 50-70°C for 1-3 hours; the continued stirring reaction is: reacting at 80-100°C for 2-4 hours; the continued reaction time is 0.5-2.5 hours;

[0030] In step 3), the heating reaction is: reacting at 80-120°C for 1-3 hours; the cooling is to 50-70°C; the stirring speed is increased to 800-1200 rpm, stirring for 1-3 hours to initially disperse the reaction system, and stirring is continued for 0.5-2.5 hours to form an emulsion system;

[0031] In step 4), stirring for 0.5-1.5 hours to uniformly disperse the antioxidant in the emulsion;

[0032] In step 5), the product in the reactor is filtered through a filtering device to remove unreacted impurities and possible solid particles to obtain a pure low-temperature heat-sealing emulsion.

[0033] The invention also discloses application of a low-temperature resistant heat-sealing emulsion in the field of food packaging.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] The present invention optimizes the low-temperature compliance of the material through molecular structure design, improves the mechanical properties of the material in an extremely low-temperature environment, and develops a heat-sealing emulsion system with wide temperature adaptability to meet food packaging needs.

[0036] The coacervate of sodium polyglutamate and polylysine hydrochloride is a low-temperature resistant bio-based adhesive with high adhesion strength and average shear adhesion strength. It can maintain good bonding properties in the extreme temperature range of -150 to 300°C, showing excellent low-temperature resistance. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] The embodiment of the present invention provides a low-temperature resistant heat-sealing emulsion, comprising the following raw materials in parts by weight: 45-80 parts of polyol (as an example, 45 parts, 52.5 parts, 60 parts, 62.5 parts, 65 parts, 66 parts or 70 parts can be selected), 2-30 parts of isocyanate (as an example, 2 parts, 3 parts, 4 parts, 5 parts, 11 parts or 30 parts can be selected), 3-10 parts of polydimethylsiloxane diol (as an example, 3 parts, 4 parts, 5 parts, 6 parts, 9 parts or 10 parts can be selected), a small molecule chain extender 4-10 parts (as an example, 4 parts, 5 parts, 6 parts, 7 parts, 7.5 parts or 8 parts can be selected), 10-20 parts of low-temperature resistant bio-based adhesive (as an example, 10 parts, 12 parts, 15 parts or 20 parts can be selected), 2-5 parts of cross-linking agent (as an example, 2 parts, 3.5 parts or 5 parts can be selected), 1-5 parts of emulsifying dispersant (as an example, 1 part, 2 parts or 3 parts can be selected) and 0.5-1 part of antioxidant (as an example, 0.5 part, 0.6 part, 0.75 part or 1 part can be selected);

[0043] The low-temperature-resistant bio-based adhesive is prepared by mixing raw materials sodium polyglutamate (γ-PGA) and polylysine hydrochloride (ε-PLL) in a mass ratio of 1:1.

[0044] In the following optional embodiments of the present invention, the structural formula of the polyol is in,

[0045] R is and As an example, in the following preferred embodiments of the present invention, the polyol is

[0046] n = 2 to 136;

[0047] The relative molecular weight is 200 to 6000, such as 200, 1000, 2000, 3000, 4000 or 6000.

[0048] In the following optional embodiments of the present invention, the isocyanate is one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate. As an example, in the following preferred embodiments of the present invention, the isocyanate is 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate, or 2,6-toluene diisocyanate.

[0049] In the following optional embodiments of the present invention, the small molecule chain extender is one or more of 1,4-butanediol (BDO), 1,3-butanediol, neopentyl glycol, and 1,6-hexanediol. As an example, in the following preferred embodiments of the present invention, the small molecule chain extender is neopentyl glycol, 1,4-butanediol, 1,3-butanediol, or 1,6-hexanediol.

[0050] The preparation method of the low-temperature resistant bio-based adhesive comprises the following steps:

[0051] S1. Weigh 5-10 parts of sodium polyglutamate and add them to 100 parts of HEPES (4-hydroxyethylpiperazineethanesulfonic acid) buffer solution (wherein the amount of HEPES is 0.1-0.3 parts) to obtain a sodium polyglutamate solution;

[0052] S2. Weigh 5-10 parts of polylysine hydrochloride and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.15-0.35 parts) to obtain a polylysine hydrochloride solution;

[0053] S3. Adjust the pH of both solutions to neutral with 0.1-2 parts of NaOH. Thoroughly mix equal volumes of sodium polyglutamate solution and polylysine hydrochloride solution for 1 minute. Let it settle for 30 seconds. The transparent mixture will turn into a white emulsion. Centrifuge at 1000-1600 rpm for 5-15 minutes to separate the precipitate phase to obtain a white emulsion colloidal adhesive.

[0054] In the following optional embodiments of the present invention, the cross-linking agent is one or more of benzoyl peroxide, melamine formaldehyde resin and divinylbenzene. As an example, in the following preferred embodiments of the present invention, the cross-linking agent is melamine formaldehyde resin, benzoyl peroxide or divinylbenzene.

[0055] In the following optional embodiments of the present invention, the emulsifying dispersant is one or more of castor oil polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether (used only as a dispersant). As an example, in the following preferred embodiments of the present invention, the emulsifying dispersant is octylphenol polyoxyethylene ether, castor oil polyoxyethylene ether, nonylphenol polyoxyethylene ether, or lauryl alcohol polyoxyethylene ether.

[0056] In the following optional embodiments of the present invention, the antioxidant is one or more of butylated hydroxyanisole (BHA), propyl gallate (PG), calcium stearate and DL-α-tocopherol. As an example, in the following preferred embodiments of the present invention, the antioxidant is propyl gallate, butylated hydroxyanisole or DL-α-tocopherol.

[0057] The present invention provides a method for preparing a low-temperature resistant heat-sealing emulsion, comprising the following steps:

[0058] 1) Add polyol and isocyanate to a reactor, start a stirring device under nitrogen protection, control the stirring speed at 300-500 rpm (as an example, 300 rpm, 400 rpm or 500 rpm can be selected), slowly raise the temperature to 50-70° C. (as an example, 50° C., 60° C. or 70° C. can be selected), stir for 5 minutes to preliminarily mix the raw materials, continue stirring for 5 minutes, mix evenly, and react for 1-2 hours (as an example, 1 hour, 1.5 hours or 2 hours can be selected) to produce a prepolymer;

[0059] 2) After the prepolymer is stirred and reacted at 50-70° C. (as an example, 50° C., 60° C., or 70° C. can be selected), polydimethylsiloxane (PDMS) diol is added, and then a small molecule chain extender is added to the reactor. The stirring reaction is continued, and the temperature is raised to 80-100° C. (as an example, 80° C., 90° C., or 100° C. can be selected) and the reaction is carried out for 2-4 hours (as an example, 2 hours, 3 hours, or 4 hours can be selected);

[0060] 3) Adding the low-temperature resistant bio-based adhesive to the reactor, maintaining the stirring speed and reaction temperature constant, and continuing the reaction for 0.5-2.5 hours (as an example, 0.5 hours, 1.5 hours, or 2.5 hours can be selected);

[0061] 4) adding a cross-linking agent to a reaction vessel, and reacting at 80-120° C. (for example, 80° C., 100° C., or 120° C.) for 1-3 hours (for example, 1 hour, 2 hours, or 3 hours);

[0062] 5) After the above reaction is completed, the temperature of the reactor is lowered to 50-70°C (as an example, 50°C, 60°C or 70°C can be selected), an emulsifying dispersant is added, the stirring speed is increased to 800-1200 rpm (as an example, 800 rpm, 1000 rpm or 1200 rpm can be selected), and stirring is carried out for 1-3 hours (as an example, 1 hour, 2 hours or 3 hours can be selected) to initially disperse the reaction system, and stirring is continued for 0.5-2.5 hours (as an example, 0.5 hour, 1.5 hours or 2.5 hours can be selected) to form an emulsion system;

[0063] 6) Maintaining the product temperature in the reactor at 50-70° C. (for example, 50° C., 60° C., or 70° C.) adding an antioxidant, adjusting the stirring speed to 300-500 rpm (for example, 300 rpm, 400 rpm, or 500 rpm) and stirring for 0.5-1.5 hours (for example, 0.5 hour, 1 hour, or 1.5 hours) to uniformly disperse the antioxidant in the emulsion;

[0064] 7) Post-treatment: The product in the reactor is filtered through a filter device to remove unreacted impurities and possible solid particles to obtain a pure low-temperature heat-sealing emulsion.

[0065] The low-temperature resistant heat-sealing emulsion of the present invention can be used in the field of food packaging.

[0066] Unless otherwise specified, the "normal temperature" mentioned in the present invention refers to 25±2°C.

[0067] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0068] The raw materials used in the present invention are all purchased from the market.

[0069] The technical solution of the present invention is further illustrated by the following examples.

[0070] Example 1

[0071] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0072] 1) Preparation of low-temperature resistant bio-based adhesive:

[0073] S1. Weigh 5 parts of sodium polyglutamate and add them to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.15 parts) to obtain a sodium polyglutamate solution;

[0074] S2. Weigh 5 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.15 parts) to obtain a polylysine hydrochloride solution;

[0075] S3. The pH values ​​of both solutions were adjusted to neutral with 0.1 parts of NaOH. Equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution were thoroughly mixed for 1 minute and allowed to settle for 30 seconds. The transparent mixture turned into a white emulsion. The mixture was centrifuged at 1000 rpm for 5 minutes to separate the precipitate phase, thereby obtaining a white emulsion colloidal adhesive.

[0076] 2) Under nitrogen protection, 45 parts of polyol with a relative molecular weight of 200 and 30 parts of 4,4-diisocyanate dicyclohexylmethane were added to the reactor, the stirring device was turned on, the mixture was stirred at a speed of 300 rpm, the temperature was slowly raised to 50°C, and the mixture was stirred for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1 hour to perform a prepolymerization reaction to generate a prepolymer; the prepolymer was continued to be stirred and reacted at 50°C for 1 hour, and then 4 parts of polydimethylsiloxane (PDMS) diol were gradually added; then 4 parts of neopentyl glycol were added to the reactor, and the temperature was raised to 80°C at the same time, and the stirring reaction was continued for 2 hours to ensure sufficient reaction; then 10 parts of low-temperature resistant bio-based adhesive were added, the stirring speed and reaction temperature were kept unchanged, and the reaction was continued for 0.5 hours to make it fully mixed. The steps of: combining the two components to participate in the reaction to enhance the low-temperature resistance of the final product; adding 5 parts of melamine formaldehyde resin and reacting at 80°C for 1 hour; after the above reaction is completed, lowering the temperature of the reactor to 50°C, adding 1 part of octylphenol polyoxyethylene ether and increasing the stirring speed to 800 rpm, stirring for 1 hour to preliminarily disperse the reaction system, and continuing stirring for 0.5 hour to form an emulsion system; then maintaining the emulsion temperature at 50°C, adding 0.5 parts of propyl gallate, adjusting the stirring speed to 300 rpm, stirring for 30 minutes, and stopping heating and stirring after stirring is completed; and finally filtering through a filtration device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-sealing emulsion.

[0077] Example 2

[0078] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0079] 1) Preparation of low-temperature resistant bio-based adhesive:

[0080] S1. Weigh 10 parts of sodium polyglutamate and add them to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a sodium polyglutamate solution;

[0081] S2. Weigh 10 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a polylysine hydrochloride solution;

[0082] S3. The pH values ​​of both solutions were adjusted to neutral with 0.5 parts of NaOH. Equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution were thoroughly mixed for 1 minute and allowed to settle for 30 seconds. The transparent mixture turned into a white emulsion. The mixture was centrifuged at 1300 rpm for 10 minutes to separate the precipitate phase, thereby obtaining a white emulsion colloidal adhesive.

[0083] 2) Under nitrogen protection, 52.5 parts of polyol with a relative molecular weight of 6000 and 2 parts of isophorone diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 300 rpm, the temperature was slowly raised to 60 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to generate a prepolymer. The prepolymer was stirred and reacted at 50 ° C for 1 hour, and then 9 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 8 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 80 ° C, and the stirring reaction was continued for 2 hours to ensure sufficient reaction; then, 20 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 1.5 hours to fully mix and participate in the reaction. and react to enhance the low-temperature resistance of the final product; add 5 parts of melamine formaldehyde resin and react at 100°C for 2 hours; after the above reaction is completed, reduce the temperature of the reactor to 50°C, add 3 parts of castor oil polyoxyethylene ether and increase the stirring speed to 1000 rpm, stir for 1 hour to make the reaction system initially dispersed, and continue stirring for 1.5 hours to form an emulsion system; then continue to maintain the emulsion temperature at 50°C, add 1 part of butylated hydroxyanisole (BHA), adjust the stirring speed to 300 rpm, stir for 30 minutes, and stop heating and stirring after stirring is completed; finally, filter through a filtration device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-sealing emulsion.

[0084] Example 3

[0085] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0086] 1) Low temperature resistant bio-based adhesive:

[0087] S1. Weigh 7.5 parts of sodium polyglutamate and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.35 parts) to obtain a sodium polyglutamate solution;

[0088] S2. Weigh 7.5 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.35 parts) to obtain a polylysine hydrochloride solution;

[0089] S3. The pH values ​​of both solutions were adjusted to neutral with 0.5 parts of NaOH. Equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution were thoroughly mixed for 1 minute and allowed to settle for 30 seconds. The transparent mixture turned into a white emulsion. The mixture was centrifuged at 1600 rpm for 15 minutes to separate the precipitate phase, thereby obtaining a white emulsion colloidal adhesive.

[0090] 2) Under nitrogen protection, 62.5 parts of polyol with a relative molecular weight of 1000 and 11 parts of hexamethylene diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 400 rpm, the temperature was slowly raised to 60 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to form a prepolymer. The prepolymer was stirred and reacted at 50 ° C for 1 hour, and then 3 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 5 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 80 ° C, and the stirring reaction was continued for 2 hours to ensure sufficient reaction; then, 15 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 1.5 hours to fully mix and The invention relates to a method for preparing an emulsion comprising: participating in the reaction to enhance the low-temperature resistance of the final product; adding 2 parts of melamine formaldehyde resin and reacting at 100°C for 2 hours; after the above reaction is completed, lowering the temperature of the reactor to 50°C, adding 1 part of nonylphenol polyoxyethylene ether and increasing the stirring speed to 1000 rpm, stirring for 1 hour to preliminarily disperse the reaction system, and continuing stirring for 1.5 hours to form an emulsion system; then maintaining the emulsion temperature at 50°C, adding 1 part of butylated hydroxyanisole (BHA), adjusting the stirring speed to 300 rpm, stirring for 30 minutes, and stopping heating and stirring after stirring is completed; finally, filtering through a filter device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-sealing emulsion.

[0091] Example 4

[0092] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0093] 1) Low temperature resistant bio-based adhesive:

[0094] S1. Weigh 6 parts of sodium polyglutamate and add them to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a sodium polyglutamate solution;

[0095] S2. Weigh 6 parts of polylysine hydrochloride (ε-PLL) and add them to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a polylysine hydrochloride solution;

[0096] S3. Adjust the pH of both solutions to neutral with 1 part NaOH, thoroughly mix equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution for 1 minute, and allow to settle for 30 seconds. The transparent mixture turns into a white emulsion, which is then centrifuged at 1600 rpm for 10 minutes to separate the precipitate phase, yielding a white emulsion colloidal adhesive.

[0097] 2) Under nitrogen protection, 66 parts of polyol with a relative molecular weight of 4000 and 3 parts of toluene diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 400 rpm, the temperature was slowly raised to 60 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to generate a prepolymer. The prepolymer was stirred and reacted at 60 ° C for 2 hours, and then 6 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 6 parts of 1,3-butanediol were added to the reactor, and the temperature was raised to 90 ° C, and the stirring reaction was continued for 3 hours to ensure sufficient reaction; then, 12 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 1.5 hours to ensure that it was fully mixed and involved The invention relates to a method for preparing an emulsion system comprising: performing a reaction to enhance the low-temperature resistance of the final product; adding 5 parts of benzoyl peroxide and reacting at 100° C. for 2 hours; after the reaction is completed, lowering the temperature of the reactor to 60° C., adding 2 parts of castor oil polyoxyethylene ether and increasing the stirring speed to 1000 rpm, stirring for 2 hours to achieve preliminary dispersion of the reaction system, and continuing stirring for 1.5 hours to form an emulsion system; then maintaining the emulsion temperature at 60° C., adding 0.75 parts of DL-α-tocopherol, adjusting the stirring speed to 400 rpm, stirring for 1 hour, and stopping heating and stirring after stirring is completed; and finally filtering through a filtration device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-seal emulsion.

[0098] Example 5

[0099] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0100] 1) Low temperature resistant bio-based adhesive:

[0101] S1. Weigh 7.5 parts of sodium polyglutamate and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.15 parts) to obtain a sodium polyglutamate solution;

[0102] S2. Weigh 7.5 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.15 parts) to obtain a polylysine hydrochloride solution;

[0103] S3. The pH values ​​of both solutions were adjusted to neutral with 1.5 parts of NaOH. Equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution were thoroughly mixed for 1 minute and allowed to settle for 30 seconds. The transparent mixture turned into a white emulsion. The mixture was centrifuged at 1000 rpm for 15 minutes to separate the precipitate phase, thereby obtaining a white emulsion colloidal adhesive.

[0104] 2) Under nitrogen protection, 65 parts of polyol with a relative molecular weight of 4000 and 4 parts of 1,5-naphthalene diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 500 rpm, the temperature was slowly raised to 70 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 2 hours to perform a prepolymerization reaction to generate a prepolymer. The prepolymer was stirred and reacted at 70 ° C for 3 hours, and then 4 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 7.5 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 100 ° C, and the stirring reaction was continued for 4 hours to ensure sufficient reaction; then, 15 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 2.5 hours to ensure that it was fully mixed and involved. The invention relates to a method for preparing an emulsion comprising: performing a reaction to enhance the low-temperature resistance of the final product; adding 3.5 parts of melamine formaldehyde resin and reacting at 120° C. for 3 hours; after the above reaction is completed, lowering the temperature of the reactor to 70° C., adding 2 parts of castor oil polyoxyethylene ether and increasing the stirring speed to 1200 rpm, stirring for 3 hours to achieve preliminary dispersion of the reaction system, and continuing stirring for 2.5 hours to form an emulsion system; then maintaining the emulsion temperature at 70° C., adding 0.5 parts of butylated hydroxyanisole (BHA), adjusting the stirring speed to 500 rpm, stirring for 1.5 hours, and stopping heating and stirring after stirring is completed; and finally filtering through a filtration device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-seal emulsion.

[0105] Example 6

[0106] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0107] 1) Low temperature resistant bio-based adhesive:

[0108] S1. Weigh 7.5 parts of sodium polyglutamate and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a sodium polyglutamate solution;

[0109] S2. Weigh 7.5 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a polylysine hydrochloride solution;

[0110] S3. Adjust the pH of both solutions to neutral with 2 parts of NaOH. Mix equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution thoroughly for 1 minute. Allow to settle for 30 seconds until the transparent mixture turns into a white emulsion. Centrifuge at 1300 rpm for 10 minutes to separate the precipitate phase, obtaining a white emulsion colloidal adhesive.

[0111] 2) Under nitrogen protection, 70 parts of polyol with a relative molecular weight of 3000 and 4 parts of 2,4-toluene diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 400 rpm, the temperature was slowly raised to 60 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1 hour to perform a prepolymerization reaction to generate a prepolymer. The prepolymer was stirred and reacted at 50 ° C for 3 hours, and then 5 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 4 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 90 ° C, and the stirring reaction was continued for 3 hours to ensure sufficient reaction; then, 15 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 0.5 hours to make it fully mixed and The invention relates to a method for preparing an emulsion system comprising: preparing an emulsion comprising: a first step of preparing an emulsion ...

[0112] Example 7

[0113] A method for preparing a low-temperature resistant heat-sealing emulsion comprises the following steps:

[0114] 1) Low temperature resistant bio-based adhesive:

[0115] S1. Weigh 5 parts of sodium polyglutamate and add them to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.35 parts) to obtain a sodium polyglutamate solution;

[0116] S2. Weigh 5 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.35 parts) to obtain a polylysine hydrochloride solution;

[0117] S3. Adjust the pH of both solutions to neutral with 1 part NaOH, thoroughly mix equal volumes of the sodium polyglutamate solution and the polylysine hydrochloride solution for 1 minute, and allow to settle for 30 seconds. The transparent mixture turns into a white emulsion, which is then centrifuged at 1300 rpm for 10 minutes to separate the precipitate phase, yielding a white emulsion colloidal adhesive.

[0118] 2) Under nitrogen protection, 60 parts of polyol with a relative molecular weight of 2000 and 5 parts of 2,6-toluene diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 500 rpm, the temperature was slowly raised to 70 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 2 hours to carry out prepolymerization to generate a prepolymer. The prepolymer was stirred and reacted at 70 ° C for 2 hours, and then 10 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 7 parts of 1,6-hexanediol were added to the reactor, and the temperature was raised to 100 ° C at the same time, and the stirring reaction was continued for 4 hours to ensure sufficient reaction; then, 10 parts of low-temperature resistant bio-based adhesive were added, and the stirring speed and reaction temperature were kept constant, and the reaction was continued for 2.5 hours to ensure that it was fully mixed and participated in the reaction. The low-temperature resistance of the final product should be enhanced; 5 parts of melamine formaldehyde resin are added and reacted at 120°C for 3 hours; after the above reaction is completed, the temperature of the reactor is lowered to 70°C, 3 parts of lauryl alcohol polyoxyethylene ether are added and the stirring speed is increased to 1200 rpm, and stirring is carried out for 3 hours to initially disperse the reaction system, and stirring is continued for 0.5 hours to form an emulsion system; then the emulsion temperature is continued to be maintained at 70°C, 0.5 parts of butylated hydroxyanisole (BHA) are added, the stirring speed is adjusted to 500 rpm, and stirring is carried out for 1 hour. After stirring is completed, heating and stirring are stopped; finally, the mixture is filtered through a filtration device to remove impurities and solid particles to obtain a pure low-temperature resistant heat-sealing emulsion.

[0119] Comparative Example 1 (without adding low-temperature resistant bio-based adhesive)

[0120] Under nitrogen protection, 65 parts of polyol with a relative molecular weight of 2000 were added and 7 parts of isophorone diisocyanate were added to the reactor, the stirring device was turned on, the stirring was carried out at a speed of 300 rpm, the temperature was slowly raised to 60 ° C, and the stirring was carried out for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to form a prepolymer. The prepolymer was continued to react at 50 ° C with stirring for 1 hour, and then 9 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 10 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 80 ° C. The stirring reaction was continued for 2 hours to ensure sufficient reaction; then, 5 parts of melamine formaldehyde resin were added, and the mixture was stirred at 80 ° C. The mixture was reacted at 100° C. for 2 hours. After the reaction was completed, the temperature of the reactor was lowered to 50° C., 3 parts of castor oil polyoxyethylene ether were added, the stirring speed was increased to 1000 rpm, and the mixture was stirred for 1 hour to achieve preliminary dispersion of the reaction system. The stirring was continued for 1.5 hours to form an emulsion system. The emulsion temperature was then maintained at 50° C., 1 part of butylated hydroxyanisole (BHA) was added, the stirring speed was adjusted to 300 rpm, and the mixture was stirred for 30 minutes. After the stirring was completed, heating and stirring were stopped. Finally, the mixture was filtered through a filtration device to remove impurities and solid particles to obtain a pure low-temperature heat-sealable emulsion.

[0121] Comparative Example 2 (low-temperature resistant bio-based adhesive with only sodium polyglutamate added)

[0122] 1) Sodium polyglutamate solution: 10 parts of sodium polyglutamate were weighed and added to 100 parts of HEPES buffer solution (wherein the amount of HEPES was 0.25 parts) to obtain a sodium polyglutamate solution;

[0123] 2) Under nitrogen protection, 60 parts of polyol with a relative molecular weight of 3000 1,4-Butanediol (BDO) and 5 parts of isophorone diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 300 rpm, the temperature was slowly raised to 60 ° C, and the stirring speed was kept constant for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to form a prepolymer. The prepolymer was stirred and reacted at 50 ° C for 1 hour, and then 6 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 4 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 80 ° C. The stirring reaction was continued for 2 hours to ensure sufficient reaction; then, 20 parts of sodium polyglutamate solution were added, the stirring speed and reaction temperature were kept constant, and the reaction was continued for 1.5 hours to make it fully mixed. The reaction was combined to enhance the low-temperature resistance of the final product; thereafter, 2 parts of melamine formaldehyde resin were added; after the above reaction was completed, the temperature of the reactor was lowered to 50°C, 3 parts of castor oil polyoxyethylene ether were added and the stirring speed was increased to 1000 rpm, and the reaction system was stirred for 1 hour to initially disperse the reaction system, and the stirring was continued for 1.5 hours to form an emulsion system; then the emulsion temperature was continued to be maintained at 50°C, 0.5 parts of butylated hydroxyanisole (BHA) was added, the stirring speed was adjusted to 300 rpm, and the mixture was stirred for 30 minutes. After the stirring was completed, heating and stirring were stopped; finally, the mixture was filtered through a filter to remove impurities and solid particles to obtain a pure low-temperature resistant heat-sealing emulsion.

[0124] Comparative Example 3 (only polylysine hydrochloride (ε-PLL) was added to the low-temperature-resistant bio-based adhesive.)

[0125] 1) Polylysine hydrochloride solution: Weigh 12 parts of polylysine hydrochloride (ε-PLL) and add it to 100 parts of HEPES buffer solution (wherein the amount of HEPES is 0.25 parts) to obtain a polylysine hydrochloride solution;

[0126] 2) Under nitrogen protection, 60 parts of polyol with a relative molecular weight of 1000 and 13 parts of isophorone diisocyanate were added to the reactor, the stirring device was turned on, the stirring speed was 300 rpm, the temperature was slowly raised to 60 ° C, and the stirring was performed for 5 minutes to make the raw materials preliminarily mixed and then reacted for 1.5 hours to perform a prepolymerization reaction to generate a prepolymer. The prepolymer was continued to stir and react at 50 ° C for 1 hour, and then 6 parts of polydimethylsiloxane (PDMS) diol were gradually added; then, 4 parts of 1,4-butanediol (BDO) were added to the reactor, and the temperature was raised to 80 ° C. The stirring reaction was continued for 2 hours to ensure sufficient reaction; then, 12 parts of ε-poly L-lysine hydrochloride (ε-PLL) solution was added, the stirring speed and reaction temperature were kept unchanged, and the reaction was continued for 1.5 hours. , so that it is fully mixed and participates in the reaction to enhance the low-temperature resistance of the final product; then, 2 parts of melamine formaldehyde resin are added; after the above reaction is completed, the temperature of the reactor is lowered to 50°C, 3 parts of castor oil polyoxyethylene ether are added and the stirring speed is increased to 1000 rpm, and the reaction system is stirred for 1 hour to initially disperse the reaction system, and the stirring is continued for 1.5 hours to form an emulsion system; then the emulsion temperature is continued to be maintained at 50°C, 0.5 parts of butylated hydroxyanisole (BHA) are added, the stirring speed is adjusted to 300 rpm, and the mixture is stirred for 30 minutes. After the stirring is completed, heating and stirring are stopped; finally, impurities and solid particles are removed by filtering through a filtering device to obtain a pure low-temperature resistant heat-sealing emulsion.

[0127] Performance testing:

[0128] The performance testing methods of the emulsions of Examples 1-7 and Comparative Examples 1-3 are as follows:

[0129] Heat seal strength: QB / T 2358-1998 Test method for heat seal strength of plastic film packaging bags, tested using a tensile testing machine.

[0130] Peel strength: A 200 mm × 15 mm specimen was prepared according to the national standard GB / T 8808-1998 peel strength test method, and the peel strength was tested using a tensile testing machine.

[0131] Low-temperature resistance test method: Based on the shear strength test method, the prepared adhesive of the same thickness was applied to a film and placed in an oven at 110°C for 2 minutes. Two control conditions were set: room temperature (25±2°C) and low temperature (-25±2°C). Samples were taken for testing at 5, 10, 15, 20, 25, and 30 days. The peel strength of the adhesive was measured using a universal materials testing machine.

[0132] Thickness test: Tested in accordance with GB / 14057-2019 cling film using a thickness gauge. The adhesive was applied with reference to the literature "Synthesis and Performance Study of UV-Curable Trifunctional PUA Adhesives."

[0133] The results are shown in Table 1.

[0134] Table 1 Performance parameters of Examples 1-7 and Comparative Examples 1-3

[0135]

[0136]

[0137] The performance comparison between the examples and comparative examples in Table 1 clearly demonstrates that the low-temperature-resistant heat-seal emulsion of the present invention, through innovative raw material formulations and optimized preparation processes, achieves a breakthrough improvement in mechanical properties under both ambient and low-temperature environments, demonstrating remarkable results. At -25°C, the key performance retention rates of the examples reached 98.2-99.8% (e.g., in the optimal example 5, the heat seal strength decreased from 58.02 N / 15 mm to 57.89 N / 15 mm, with a decay rate of only 0.22%; the peel strength decreased from 84.71 N / 15 mm to 83.21 N / 15 mm, with a decay rate of 1.78%). This significantly surpasses the decay rate of 5.43-7.82% in the comparative example 5. This demonstrates that the emulsion can meet the stringent requirements of food packaging in low-temperature environments and has promising application prospects.

[0138] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A low temperature resistant heat sealing emulsion, characterized in that: The invention comprises the following raw materials in parts by weight: 45-80 parts of polyol, 2-30 parts of isocyanate, 3-10 parts of polydimethylsiloxane diol, 4-10 parts of small molecule chain extender, 10-20 parts of low-temperature resistant bio-based adhesive, 2-5 parts of cross-linking agent, 1-5 parts of emulsifying dispersant and 0.5-1 part of antioxidant; The low-temperature-resistant bio-based adhesive is prepared by mixing sodium polyglutamate and polylysine hydrochloride as raw materials.

2. The low-temperature resistant heat-sealing emulsion according to claim 1, characterized in that: The structural formula of the polyol is in, R is One of the following; n＝2～136。 3. The low temperature resistant heat sealing emulsion according to claim 1, characterized in that: The isocyanate is one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.

4. The low-temperature resistant heat-sealing emulsion according to claim 1, characterized in that: The small molecule chain extender is one or more of 1,4-butanediol, 1,3-butanediol, neopentyl glycol and 1,6-hexanediol.

5. The low temperature resistant heat sealing emulsion according to claim 1, characterized in that: The preparation method of the low-temperature resistant bio-based adhesive comprises the following steps: Weigh sodium polyglutamate and add it to 4-hydroxyethylpiperazineethanesulfonic acid buffer solution to obtain a sodium polyglutamate solution; Weighing polylysine hydrochloride and adding it to 4-hydroxyethylpiperazineethanesulfonic acid buffer solution to obtain a polylysine hydrochloride solution; The pH values ​​of the sodium polyglutamate solution and the polylysine hydrochloride solution are adjusted to neutral, and then the two solutions are mixed in equal volumes, centrifuged, and the precipitate phase is separated to obtain a white emulsion colloidal adhesive.

6. The low temperature resistant heat sealing emulsion according to claim 1, characterized in that: The cross-linking agent is one or more of benzoyl peroxide, melamine formaldehyde resin and divinylbenzene.

7. The low-temperature resistant heat-sealing emulsion according to claim 1, characterized in that: The emulsifying dispersant is one or more of castor oil polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether.

8. The low temperature resistant heat sealing emulsion according to claim 1, characterized in that: The antioxidant is one or more of butylated hydroxyanisole, propyl gallate, calcium stearate and DL-α-tocopherol.

9. A method for preparing the low-temperature resistant heat-sealing emulsion according to any one of claims 1 to 8, characterized in that: The following steps are involved: The polyol and isocyanate are mixed and reacted to form a prepolymer; adding polydimethylsiloxane diol and a small molecule chain extender to the prepolymer and continuing the reaction; Then, a low-temperature-resistant bio-based adhesive, a cross-linking agent, and an emulsifying dispersant are added to form an emulsion system; Finally, an antioxidant is added and the mixture is filtered to obtain a low-temperature resistant heat-sealing emulsion.

10. Use of the low-temperature resistant heat-sealing emulsion according to any one of claims 1 to 8 in the field of food packaging.

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