CN112226193B

CN112226193B - Preparation method and application of water-based high-strength bi-component adhesive

Info

Publication number: CN112226193B
Application number: CN202011119296.0A
Authority: CN
Inventors: 罗惠超; 罗锐光; 杨浩文
Original assignee: Huizhou Logos Packaging Material Co ltd
Current assignee: Huizhou Logos Packaging Material Co ltd
Priority date: 2020-10-19
Filing date: 2020-10-19
Publication date: 2021-10-15
Anticipated expiration: 2040-10-19
Also published as: CN112226193A

Abstract

The invention discloses a preparation method and application of a water-based high-strength bi-component adhesive for plastic packaging composition, which comprises the following steps: the preparation method of the aqueous polyurethane dispersion comprises the following steps: preparing a compound containing acetoacetyl groups, a compound containing two isocyanate groups, a polyoxyethylene polyoxypropylene ether polymer and a carboxyl compound containing two hydroxyl groups, which are shown in a formula 1, to obtain an aqueous polyurethane dispersion containing the acetoacetyl groups; blending: the water-based polyurethane dispersion containing the acetoacetyl group and a water-soluble compound which is shown as a formula 3 and has three or four acrylate groups shown as a formula 4 are mixed and coated on a plastic packaging material for compounding. The packaging material of the invention can achieve excellent bonding strength and boiling resistance. Meanwhile, the method has better environmental protection and safety.

Description

Preparation method and application of water-based high-strength bi-component adhesive

Technical Field

The invention relates to the field of adhesive preparation, in particular to a preparation method and application of a water-based high-strength bi-component adhesive for plastic packaging compounding.

Background

In the packaging industry, due to the portability, rapidness and low cost of plastic flexible packages and the convenience in design, the plastic flexible packages are rapidly developed. This is because plastic packaging can be printed, compounded, rolled, cut at very high speeds and is easy to mass produce. In addition, plastic packaging is low in cost, convenient to transport and convenient to apply, and gradually replaces traditional packaging in many industries. Particularly in food packaging, under the condition of high product diversification and individual requirements, the plastic packaging is a more suitable material, can meet the iterative requirement of the existing rapid product, and can meet the required performance requirement by carrying out different structural designs.

In the process of plastic package preparation, the film is often compounded from multiple layers of films to achieve desired appearance and performance effects. Such as BOPP/CPP, CPP/aluminum/BOPP, BOPP/PET, etc. In these structures, it is necessary to use a chemical component, a compounding adhesive, which is critical to the overall multilayer structure. The proper adhesive is selected, so that the multilayer films can be bonded together, and the effects of increasing the tearing strength, boiling resistance, aging resistance, oxygen resistance, water resistance and the like can be achieved. Therefore, the preparation of high-performance composite packages and the used composite adhesives are inseparable.

The adhesive for packaging and compounding mainly comprises a solvent type, a solvent-free type and a water-based type. The solvent-based composite adhesive has been applied to plastic flexible packaging for many years, can basically meet most of performance requirements of flexible packaging application, and has the advantages of high drying speed, high mechanical speed, high strength, good appearance effect and the like. But a large amount of solvent is needed in the using process, which causes great pollution to the environment and also causes serious health injury to operators in construction workshop. Although the harm to the environment and people caused by solvent volatilization can be reduced by additionally arranging the solvent recovery device, the solvent cannot be completely volatilized, and a certain amount of solvent is volatilized in the operation process to cause harm. And the solvents used are organic compounds with low flash points, not only are the solvents belonging to dangerous chemicals and needing to be carried out in certain working environments, but also fire or explosion can be caused if the operation is not proper. With the stricter environmental protection standards and laws, the cost is greatly increased by using solvent adhesives, and the more serious risks of elimination and production halt can be caused. In addition to the strong market demand for flexible packaging, products that can replace solvent-based adhesives are needed. Solvent-free and aqueous adhesives are produced at the same time, and through a large number of applications and adjustments, some performance requirements of basic composite packaging can be basically met.

Solvent-free composite adhesives generally consist of two-component modified polyurethane adhesives, one component containing an isocyanate-terminated polyurethane polymer and the other component containing a compound or polymer having groups capable of reacting with isocyanates, primarily hydroxyl-containing compounds or polymers. When in use, the two components are premixed and then coated and compounded. A boiling resistant, solvent free type polyurethane adhesive as disclosed in patent CN107022059, uses an a-component of a urethane polymer in pre-acid ester powder stage and a B-component comprising castor oil and/or castor oil derivatives and/or castor oil urethane polymers and/or specific roaming derivatives urethane polymers as a first component and a polyether polyol having a weight average molecular weight of less than 1000 as a second component. The adhesive for compounding plastic packages can be used under the sterilization condition of water boiling at 80-100 ℃. The bond strength and the workable time of such adhesives are not given by the present invention. According to the structure and the reaction activity of the solvent-free double-component polyurethane, several defects in the compounding process mainly exist, one is that the usable time is short, after the isocyanate and the polyether polyol containing hydroxyl or other components containing hydroxyl are mixed, the isocyanate and the polyether polyol containing hydroxyl react at room temperature, the two components are pre-cured within 30 minutes to 2 hours, the viscosity of the glue is greatly improved, the gluing is difficult, the bonding strength is extremely reduced, as the gluing and compounding are extremely fast, more loss is caused, and the glue after pre-curing is difficult to clean; the other is that the initial bonding strength is low, and the actual required strength can be achieved only by a later curing process, so that rolling sliding is easy to occur in the rolling process, and the material waste and loss of the whole roll are caused; the third is that the viscosity of the bi-component polyurethane is usually larger, and the bi-component polyurethane can not be adjusted by adding a solvent and water like a solvent-based or water-based adhesive, so that the gluing amount is high, the thickness is influenced, the surface effect of a composite finished product is poor, and the apparent effect is one of the most important performance factors in plastic packaging; the fourth is that isocyanates are sensitive to moisture, require strict humidity control during storage and handling, and are environmentally more demanding during storage and use. The fifth is that the amounts of the two components are controlled more strictly, and if one of the components is excessive, the bonding strength is greatly reduced. Due to the low initial composite strength and the apparent effect of the solvent-free polyurethane adhesive and the various influences, the application of the solvent-free polyurethane adhesive in high-end fields, particularly in food packaging with higher requirements on water boiling resistance, steam boiling resistance and the like is limited. And the isocyanate groups have a certain sensitization, which may present a risk of causing health hazards to the operators.

Compared with solvent-free composite adhesives, the aqueous composite adhesive is more environment-friendly and easy to operate, generally the aqueous composite adhesive is divided into single component and double component, and the chemical composition mainly comprises aqueous polyacrylate and aqueous polyurethane dispersoid. The aqueous adhesive is in a form that organic polymer particles are suspended in water, has larger molecular weight ratio and higher initial bonding strength, can achieve better strength after being put off a machine after being compounded on site, does not need to be cured for a long time like a solvent-free system to obtain the required strength, can greatly improve the production efficiency and reduce the energy consumption; the water-based composite adhesive has no harmful substances and almost no VOC. The other is more important to the appearance after compounding, the appearance can be judged in the running and rolling process by using the water-based compound adhesive, and the composite film of a solvent-free system can be judged after being cured, so the risk of appearance defects of a finished product can be greatly reduced by using the water-based compound adhesive. However, the adhesive strength of the aqueous polyacrylic acid and aqueous polyurethane dispersions using a single component is usually only 0.5-1.5N/15mm, and the aqueous polyacrylic acid and aqueous polyurethane dispersions can only be used as common food packages, and cannot meet the requirement of the adhesive strength when used as foods requiring heating and boiling. Although the strength is further improved by adding water-dispersed isocyanate, a cohesive strength of only 2.0N is basically achieved, and the addition of such a water-dispersed isocyanate curing agent results in a very poor surface performance, which can be used for only 30 minutes to 2 hours, and does not meet the requirements of high-end food packaging.

With the improvement of the requirements of safety and environmental factors, the water-based composite adhesive has more advantages, and because water is used as a carrier, the volatilization of water can not cause environmental pollution after drying. In addition, the viscosity can be conveniently adjusted by adding water, which is a type compared with the solvent-type viscosity adjustability, only uses pollution-free water as a diluent, and has better operability compared with a solvent-free adhesive. According to the advantages of the aqueous composite adhesive, a plurality of companies and organizations carry out a great deal of research and product development, and a plurality of documents and patents are also available to research the synthesis and application of the aqueous composite adhesive, and a research patent CN104263292 discloses an aqueous film-covering adhesive and a preparation method thereof, wherein a self-crosslinking system containing diacetone acrylamide and ADH is prepared by adopting an emulsion polymerization method, the solid content is 48-50%, and the viscosity is 100-500 mPa.s. The disclosed technology can not meet the requirements under the dry compounding condition of tolling operation, the composite bonding strength can be reduced due to the fact that the diacetone acrylamide component of the adhesive prepared in the drying process is crosslinked with the ADH component, and the gluing uniformity of a gluing roller is poor under the viscosity of 100-500mPa.s, so that the appearance of a coated strip can not meet the requirement of smooth surface. US patent US6190767 discloses a process for the preparation of an emulsion adhesive wherein more than 50% of a long chain alkyl acrylate is used, and a polymerisable emulsifier is employed to produce an emulsion with good resistance to water and moisture, with good adhesion to non-polar substrates. The bonding strength of the composite adhesive is greatly related to the crosslinking of the adhesive, and the thermoplastic polyacrylic acid adhesive used as a single component is difficult to meet the strength and heat resistance requirements required by boiling resistance. Patent CN104745139 discloses a preparation process of a waterborne polyurethane composite adhesive, which is prepared by taking polybutylene adipate, polyglycol, diisocyanate, dimethylolbutyric acid and the like as main raw materials. Although this patent states that 100 ℃ boil resistance can be achieved for 40 minutes, no specific bond strength and experimental data are given, and it is proved by long-term experience and extensive experiments in the field of aqueous polyurethane by the present inventors that only bond strengths of less than 1.5N/15mm can be achieved with such aqueous polyester polyurethane dispersions, and that no bond strength of more than 2.5N/15mm can be achieved with a boil resistance retention of more than 85%.

In summary, there are two main types of adhesives for packaging compositions that do not contain solvent:

one type is a water-based polyacrylate dispersion adhesive or a water-based polyurethane dispersion, the adhesive can be used independently and does not contain VOC basically, but the packaging strength can only reach 0.6-1.2N, and the requirements of water boiling resistance and boiling resistance required by high-end packaging materials cannot be met.

For the adhesive, the strength can be improved to 1.2-2.5N/15mm by adding an isocyanate curing agent and matching with a curing process.

However, this approach has serious drawbacks:

firstly, the isocyanate curing agent is not easy to disperse in water, and can obtain a better dispersing effect only by high-speed stirring, and in addition, the isocyanate can slowly react with the water, so that the usable time of the mixed adhesive is only 1-2 hours, and the application field and the application effect are greatly limited;

secondly, the isocyanate curing agent is only dispersed in water, which can have a relatively large effect on the appearance. Although the composite strength can be further improved by using the water-dispersed PUD, the appearance problem still remains, and the conventional PUD production process requires a large amount of acetone as a diluent, and there is a risk in the acetone recovery and use process. And in the curing process, because the moisture is not completely volatilized, the water can further react with isocyanate groups to generate bubbles, thereby causing serious appearance problems.

The second type is to use a solvent-free hydroxyl reaction polyether-containing component and an isocyanate-containing component after on-site mixing, and although the scheme avoids the use of VOC, the initial composite strength is low (<0.5N/15mm), dislocation is easily caused in curing and rolling processes, and the requirement on the use environment is high, and if the humidity is high, the gel is pre-cured, so that the later curing viscosity cannot be improved, and a serious waste proportion is caused.

Although the aqueous composite adhesive has been greatly developed, especially the adhesive strength of the two-component aqueous composite adhesive is greatly improved. However, the used curing is usually the curing of isocyanate groups, the isocyanate groups are sensitive to water, the service life is short, the dispersibility in water is checked, the surface effect is poor, and the boiling-resistant requirement of high-end packaging is difficult to achieve. There is therefore a need and great interest in products and techniques that overcome these deficiencies.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a preparation method of a water-based high-strength two-component adhesive for plastic packaging composite and a product.

The adhesive of the polyurethane aqueous dispersion has higher bonding strength and heat resistance than the aqueous polyacrylate due to the hydrogen bonding action of polyurethane groups contained in the molecular chains. If further improvements in cohesive strength and heat resistance are desired, it is necessary to increase the molecular weight of the main molecular chains of the polyurethane dispersion to achieve this. This requires a chain extension reaction in the synthetic preparation process to increase the molecular weight, which requires the use of a large amount of solvent such as acetone, N-methylpyrrolidone, etc., which not only increases the risk of using a large amount of solvent in the production process, but also causes solvent residue due to incomplete removal in the later period, which has a great influence on the application of food packaging, especially on the flavor of food. If the polyurethane dispersion is not subjected to chain extension, the initial adhesion, the bonding strength and the heat resistance can not meet the requirements of packaging composite performance. The inventor surprisingly found in the process of product development that when the system contains acetoacetyl groups, the initial adhesion is greatly improved. And the acetoacetyl group can be used as a nucleophilic group to perform Michael addition reaction with an acrylate group, so that an aqueous polyurethane dispersion can be prepared by using a compound containing the acetoacetyl group to provide excellent initial adhesion, and then the reaction of the acetoacetyl group and the acrylate group is utilized to provide crosslinking so as to improve the bonding strength and the heat resistance, so that the high-strength boiling and boiling resistance of high-end food plastic packaging can be achieved. The compounds having a polyacrylate reactive with an acetoacetyl group used are all water-soluble, have an excellent surface appearance after compounding, and do not have white spots or fogging like the aqueous isocyanate dispersant.

In order to realize the purpose of the invention, the adopted technical scheme is as follows:

a preparation method of an aqueous high-strength bi-component adhesive for plastic packaging compounding comprises the following steps:

the preparation method of the aqueous polyurethane dispersion comprises the following steps:

preparing a compound containing acetoacetyl groups, a compound containing two isocyanate groups, polyoxyethylene polyoxypropylene ether and a carboxyl compound containing two hydroxyl groups, which are shown in a formula 1, to obtain an aqueous polyurethane dispersion containing acetoacetyl groups;

wherein the compound of two isocyanate groups comprises any one or more of 4,4' -dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDA) or Hexamethylene Diisocyanate (HDI);

the carboxyl compound containing two hydroxyl groups is one or more of dimethylolpropionic acid, dimethylolbutyric acid and dimethylolcaproic acid

Blending:

blending the aqueous polyurethane dispersion containing the acetoacetyl groups with any one or two of water-soluble compounds with three or four acrylate groups shown in formula 4 shown in formula 3, and coating the mixture on a plastic packaging material for compounding, wherein the mass ratio of the blending is 1: 0.9-1: 1.15.

in a preferred embodiment of the present invention, the polyoxyethylene polyoxypropylene ether has a molecular weight of 500-3000.

In a preferred embodiment of the invention, the temperature of the sizing drying is 70-90 ℃, and the speed of the sizing compounding machine is 180-350 m/min.

In a preferred embodiment of the invention, the initial strength after said compounding is between 0.5N and 1.2N/15 mm.

In a preferred embodiment of the invention, the compounding is followed by a curing operation, wherein the curing temperature is 50 ℃, the curing time is 48 hours, and the strength after curing is 2.5-5N/15 mm. The boiling test is carried out, the glue-opening phenomenon is avoided, and the strength is maintained to be more than 80%.

The aqueous high-strength two-component adhesive for plastic packaging compounding is prepared by the method.

The invention has the beneficial effects that:

the present invention can effectively improve adhesive strength and ensure superior surface effects by using an addition crosslinking reaction of a polymer of polyurethane containing an acetoacetic ester group with a water-soluble compound containing a plurality of acrylate functional groups. Therefore, the low-molecular-weight polyurethane aqueous dispersion prepared by using solvents such as acetone, N-methyl pyrrolidone and the like is not applicable, the prepared polyurethane aqueous dispersion contains acetoacetamide groups, the adhesion and initial adhesion to a base material are greatly improved, the polyurethane aqueous dispersion can be subjected to addition crosslinking with a compound containing a plurality of acrylate groups in the later curing process, the adhesive strength and the heat resistance are greatly improved, and the excellent flexibility and the flexibility are kept.

The compound glue for plastic packaging is prepared by mixing a water-soluble compound containing three or four acrylate groups with the prepared PUD. In the compounding process, not only the initial binding power is ensured, but also the apparent effect is excellent, white spots and fogging of water-dispersible isocyanate curing agents can not occur, the binding strength is greatly improved after curing, and the high strength of 2.5-5N/15mm is achieved. The composite adhesive prepared by the method can be stored for a long time, the service life is more than 3 months, and the service life of the curing agent using isocyanate and carbodiimide is only 1-10 hours.

The high-strength bi-component packaging composite adhesive provided by the invention overcomes the defects that the existing bi-component system needs to be prepared on site, has too short service life and has great influence on appearance, and no side reaction is generated. Meanwhile, the requirements of high bonding strength and excellent appearance on boiling-resistant packaging can be met, and the phenomena of degumming and serious reduction of strength can not occur under the conditions of boiling and boiling after bag-making packaging.

Detailed Description

The raw materials used in the examples and comparative examples are abbreviated as shown in table 1 below:

TABLE 1

The specific embodiment is as follows:

preparation of bishydroxyacetoacetamide:

a dry 2 l reaction flask was charged with 730.8 g of acetoacetyl methyl ester and 630 g of diethanolamine under nitrogen and equipped with a distillation apparatus. Then heating to 80 ℃, adding 1.5 g of tetraisopropyloxytitanium, and then heating to 85-90 ℃ for reaction. The distillation temperature is controlled between 64 and 66 ℃. When the distilled methanol is close to the theoretical amount, reduced pressure distillation is adopted, and the excessive methyl acetoacetate is distilled under reduced pressure to obtain the dihydroxyacetoacetamide which is light yellow oil.

Example 1:

a1 l reaction flask was charged with 41 g of bisacetoacetamide, 100 g of polyoxypropylene ether (molecular weight 1000) and heated to 105 ℃ to remove water under reduced pressure for 2.5 hours. Then cooling to 60 ℃, adding 1.5 g of tin dioctoate and 64 g of HDI under the protection of nitrogen, uniformly stirring, heating to 80 ℃ for reaction for 3 hours, cooling to 60 ℃ when the content of the isocyanate is not changed by infrared monitoring, then adding 10.5 g of DMPA, heating to 80 ℃ for reaction for 4 hours, and monitoring the complete reaction of the isocyanate by infrared. The temperature was initially reduced to 50 deg.C, 7.8 g triethylamine was added, then the temperature was increased to 75 deg.C, and 330 g deionized water at 70-80 deg.C was slowly added. The stirring speed was increased to maintain fluidity during the reverse phase, deionized water was added dropwise to obtain a milky aqueous dispersion, and 70 g of trimethylolpropane ethoxylate triacrylate (formula 3, average n: 3) was added to the dispersion, the solids content was 46.5%, and the pH was 7.5.

Example 2:

61.5 g of bisacetoacetamide and 180 g of polyoxyethylene polyoxypropylene ether (a block copolymer having a molecular weight of 3000 and a terminal group of polyoxyethylene ether, the content of polyoxyethylene ether being 15%) were added to a 1-liter reaction flask, and the mixture was heated to 105 ℃ to remove water under reduced pressure for 2.5 hours. Then cooling to 60 ℃, adding 1.5 g of tin dioctoate and 115 g of HMDI under the protection of nitrogen, uniformly stirring, heating to 80 ℃ for reaction for 3 hours, cooling to 60 ℃ when the content of the isocyanate is monitored by infrared, then adding 10.5 g of DMPA, heating to 80 ℃ for reaction for 4 hours, and monitoring the isocyanate to be completely reacted by infrared. The temperature is reduced to 65 ℃, then a solution containing 6.0 g of 25 percent ammonia water dissolved in 500 g of water is slowly added dropwise, and the temperature is controlled between 65 and 85 ℃. The pH was adjusted to 8.3 to give a milky white aqueous dispersion, and then 23 g of trimethylolpropane polyoxyethylene ether triacrylate (formula 3, average n ═ 3) and 35 g of pentaerythritol polyoxyethylene tetraacrylate (formula 4, average n ═ 2) were added, the solid content was 44.5%, and the pH was 8.0.

Example 3:

a1 liter reaction flask is added with 105 g of dihydroxyacetoacetamide and 150 g of polyoxyethylene polyoxypropylene ether (molecular weight 500, block copolymer with polyoxyethylene ether as a terminal group and polyoxyethylene ether content 10 percent), heated to 105 ℃ and decompressed to remove water for 2.5 hours. Then cooling to 60 ℃, adding 1.5 g of tin dioctoate and 122 g of IPDI under the protection of nitrogen, uniformly stirring, heating to 85 ℃ for reaction for 3 hours, cooling to 60 ℃ when the content of the isocyanate is monitored by infrared, then adding 29.8 g of DMPA, heating to 85 ℃ for reaction for 4 hours, and monitoring the complete reaction of the isocyanate by infrared. The temperature was initially lowered to 65 ℃ and then a solution of 14.5 g of 25% strength ammonia dissolved in 460 g of water was slowly added dropwise, the temperature being controlled between 65 and 85 ℃. The pH was adjusted to 8.7 to give a translucent aqueous dispersion, and 48 g of pentaerythritol polyoxyethylene tetraacrylate (formula 4, average n 2), 42% solids, pH 8.6, were added.

Example 4:

a2-liter reaction flask was charged with 95 g of bisacetoacetamide and 120 g of polyoxyethylene polyoxypropylene ether (molecular weight 2000, block copolymer having terminal group of polyoxyethylene ether, polyoxyethylene ether content 15%) and heated to 105 ℃ to remove water under reduced pressure for 2.5 hours. Then cooling to 60 ℃, adding 1.5 g of tin dioctoate and 142 g of IPDI under the protection of nitrogen, uniformly stirring, heating to 80 ℃ for reaction for 3 hours, cooling to 60 ℃ when the content of the isocyanate is monitored by infrared, then adding 13.5 g of DMPA, heating to 80 ℃ for reaction for 4 hours, and monitoring the complete reaction of the isocyanate by infrared. The temperature was initially lowered to 65 ℃ and then a solution of 5.5 g of 25% strength ammonia dissolved in 550 g of water was slowly added dropwise, the temperature being controlled between 65 and 85 ℃. The pH was adjusted to 8.3 to give a milky white aqueous dispersion, 163 g of pentaerythritol polyoxyethylene tetraacrylate (formula 4, average n: 6) was added, the solids content was 48.5%, and the pH was 8.0.

Comparative example 1: aqueous polyurethane dispersions without added hardener component

The procedure was the same as in example 2, except that trimethylolpropane polyoxyethylene ether triacrylate (formula 3, average n ═ 3) and pentaerythritol polyoxyethylene tetraacrylate were not added.

Comparative example 2: single-component aqueous polyurethane dispersions

The aqueous polyurethane dispersions prepared according to the preparation process of the examples of patent CN104745139 have a solids content of 40% and a pH of 7.5.

Comparative example 3: two-component polyacrylic acid emulsion and water-based isocyanate curing agent

360 g of deionized water was added to a 2-liter reaction flask under nitrogen and heating to 85 ℃ was started. 180 g of deionized water, 10 g of dioctyl sodium sulfosuccinate (20% solution), 486 g of butyl acrylate, 100 g of styrene and 102 g of methyl methacrylate are mixed and stirred uniformly to obtain a stable white monomer emulsion. 7.1 g of acrylic acid was weighed into a glass bottle, and 20 g of deionized water was added to obtain an aqueous solution. When the temperature of the reaction flask reached 85 ℃, the following raw materials were added in succession: a solution of 10 grams of deionized water containing 1.2 grams of sodium carbonate, 18 grams of the monomer emulsion and 3 grams of acrylic acid in water, and a solution of 2.0 grams of ammonium persulfate dissolved in 15 grams of deionized water. And (3) releasing heat, and adding the monomer emulsion within 3 hours, dropwise adding an acrylic acid aqueous solution within 2.5 hours, and dropwise adding a solution of 2.0 g of ammonium persulfate dissolved in 80 g of deionized water within 3 hours under the condition that the temperature is not increased and then the temperature of the reaction bottle is maintained at 85 ℃. After the addition, the temperature is kept for 2 hours, then the temperature is reduced to 80 ℃, 5.0 g of 0.1 percent ferrous sulfate aqueous solution is added, then 0.8 g of solution of 70 percent tert-butyl hydroperoxide dissolved in 30 g of deionized water and 0.5 g of solution of sodium bisulfite dissolved in 30 g of deionized water are added, and the temperature is kept for 1 hour. The temperature is reduced to 40 ℃, and then 6.8 g of ammonia (28%) is added to adjust the pH value to 6.5-7.5. Stirring evenly, cooling to room temperature, and filtering by a 300-mesh sun screen to obtain the water-based acrylic emulsion adhesive.

200 g of the acrylic emulsion adhesive is taken, 30 g of modified water-dispersible HDI curing agent 2655 is added, and the mixture is used after being uniformly stirred.

Comparative example 4: solvent-free bi-component polyurethane adhesive

Component A, 100 g of liquefied MDI, 100 g of polyoxypropylene ether with the molecular weight of 1000 and 15 g of polyether triol with the molecular weight of 500, 0.02 g of phosphoric acid are mixed uniformly, and the mixture is kept at 60 ℃ for 2 hours.

Then the

When the temperature is increased to 85 ℃ and the reaction is carried out for 4 hours, the isocyanate groups are not changed any more by infrared detection. Detecting NCO content to 13-15% to obtain A component of solvent-free polyurethane component.

And (B) component:

100 g of polyether triol with the molecular weight of 500 and 20 g of carbodiimide modified MDI are uniformly mixed, heated to 60 ℃, kept warm for 2 hours, then heated to 85 ℃ for reaction for 4 hours, and the mixture is the component B without solvent when the tested hydroxyl value is 200-220 mgKOH/g.

The components A and B were mixed at an NCO/OH ratio of 1.5/1 and subjected to compounding test.

1. And (3) apparent test after compounding:

based on the BOPP/CPP structure and the PET/aluminum foil/CPP, the coating weight of 2.0 to 3.0 grams of dry weight is coated, the machine speed is 240 meters per minute, the drying channel is dried at 15 meters and 75 ℃, and then the composite winding is carried out. And cutting off the machine to see whether bubbles, white spots, blooming and fogging phenomena exist.

Then, the mixture was aged at 50 ℃ for 48 hours to see whether or not bubbles were formed on the surface, and white spots, fogging, and the like were observed.

2. And (3) testing the adhesive force:

t-type peel strength, as tested in GB/T2791-1995 using a universal tensile machine, at a tensile speed of 100 mm/min.

3. Hot-pressing flowability:

and (3) carrying out heat sealing on the compounded composite film at the heat sealing temperature of 150 ℃ for 5 seconds to see whether glue flows and the strength is reduced.

4. Boiling resistance test:

and (3) after the compounded film is made into a bag, boiling the bag in hot water at 100 ℃ for 40 minutes, cooling the bag to room temperature to see whether the glue is in a glue-opening state or not, and then testing the peel strength.

5. And (3) steaming resistance test:

and (3) after the compounded film is made into a bag, steaming and boiling the bag for 30 minutes at 110 ℃, and then cooling the bag to room temperature to see whether the film is affected by glue failure and appearance.

The test results of the above composite test are shown in table 2 below:

TABLE 2

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement and the like made within the principle of the present invention shall be included in the present invention.

Claims

1. The preparation method of the water-based high-strength bi-component adhesive for plastic packaging compounding is characterized by comprising the following steps of:

preparing acetoacetamide, a compound containing two isocyanate groups, a polyoxyethylene polyoxypropylene ether polymer and a carboxyl compound containing two hydroxyl groups to obtain an acetoacetyl group-containing aqueous polyurethane dispersion;

wherein the compound of the two isocyanate groups comprises any one or more of 4,4' -dicyclohexylmethane diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate;

the carboxyl compound containing two hydroxyl groups is one or more of dimethylolpropionic acid, dimethylolbutyric acid and dimethylolcaproic acid;

blending:

the waterborne polyurethane dispersoid containing the acetoacetyl group and any one or two of trihydroxy methyl propane polyoxyethylene ether triacrylate or four water-soluble compounds of acrylate groups shown in the formula 4 are mixed and coated on a plastic packaging material for compounding,

the mass ratio of the blending is 1 according to the molar ratio of the acetoacetic acid group in the aqueous polyurethane dispersion to the trihydroxymethyl propane polyoxyethylene ether triacrylate or the acrylate group with the structure shown in the formula 4: 0.9-1: 1.15;

formula 4(n = 1-8);

the molecular weight of the polyoxyethylene polyoxypropylene ether is 500-3000.

2. The method for preparing the waterborne high-strength bi-component adhesive for plastic packaging compounding as claimed in claim 1, wherein the compounding is dry compounding, the water adhesive is coated on the plastic substrate to be compounded by means of a sizing roller, the plastic substrate is dried at 70-90 ℃, and then the plastic substrate is compounded, bonded and wound with the plastic on the surface layer, and the speed of the sizing compounding machine is 180-350 m/min.

3. The method for preparing the water-based high-strength two-component adhesive for plastic packaging composite according to claim 1, wherein the initial strength after the composite is 0.5N-1.2N/15 mm.

4. A method for preparing the waterborne high-strength two-component adhesive for plastic packaging composite according to any one of claims 1 to 3, wherein the composite packaging material is rolled and then cured, the curing temperature is 50 ℃, the curing time is 24 to 48 hours, and the strength after curing is 2.5 to 5N/15 mm;

after the cured plastic packaging material is subjected to bag making and packaging, a boiling test is carried out, the glue failure phenomenon is avoided, and the strength is maintained to be more than 85%.

5. An aqueous high-strength two-component adhesive for plastic packaging composite, wherein the aqueous high-strength two-component adhesive is prepared by the method of any one of claims 1 to 4.