CN117511291A - An alkali-regulated high-temperature-resistant modified cyclopropene, fresh-keeping varnish and fresh-keeping packaging products - Google Patents

Abstract

The invention discloses an alkali-regulated high-temperature-resistant modified cyclopropene, a fresh-keeping varnish and a fresh-keeping packaging product. The modified cyclopropene is in a solid state and includes an active ingredient cyclopropene compound, a solidifying inclusion agent, and a high-temperature-resistant modified cyclopropene. agent; the high temperature resistant modifier is an organic silicon compound. This application uses an organic silicon compound together with a curing inclusion agent to modify cyclopropene compounds, which can significantly enhance its thermal stability and anti-oxidation stability, and can meet the 180°C high temperature conditions required for corrugated cardboard production; and it has alkali properties Controlled release characteristics, it can be stored stably in a neutral system with a pH of 6.5 to 8.5, and is activated to release cyclopropene gas in an alkaline system with a pH > 8.5. Therefore, the modified MCP and the modified MCP can be stored for a long time in a conventional environment. Other products prepared by MCP, such as fresh-keeping varnish, fresh-keeping cartons, etc.

Description

An alkali-regulated high-temperature-resistant modified cyclopropene, fresh-keeping varnish and fresh-keeping packaging products

Technical field

The invention belongs to the technical field of preservation, and specifically relates to an alkali-controlled high-temperature-resistant modified cyclopropene, preservation varnish and preservation packaging products.

Background technique

In the prior art, desiccants or preservatives used in fruits, vegetables and other fresh foods are usually packaged in single-sided water-locking breathable paper-plastic materials and put into fresh food packaging boxes. The contact area is small and the freshness preservation effect is limited. Although respiratory inhibitory preservatives for fruits and vegetables have good preservation effects, they are usually used in the form of fumigation to preserve fruits and vegetables in cold storage, and there are no cases of application in fresh food transportation.

Existing technical research is mostly focused on antibacterial preservation, anti-mildew preservation coatings, or adsorption coatings. Some technical operations are cumbersome and cannot be applied on a large scale, and some technical effects are limited and cannot deal with perishable fruits such as cherries, bananas, and kiwis.

1-Methylcyclopropene (abbreviated as 1-MCP) is a cyclopropene compound. It exists in a gaseous state under normal temperature conditions. It is non-toxic and has no odor. Its boiling point is about 10°C. It is unstable in the liquid state because it interacts with The molecular structure of ethylene is similar. 1-MCP can competitively bind to these receptors and inhibit various biochemical reactions related to post-ripening. In reality, it is mostly used for warehouse fumigation and preservation.

In the prior art, in order to solve the storage and transportation problems of cyclopropene liquid preservatives, inclusion agents such as dextrin are generally used for solidification. When used, 1-MCP gas can be released by absorbing only a small amount of moisture.

The most commonly used packaging material during the transportation of fruits and vegetables is cartons. In specific applications, the cured MCP inclusions can be made into bagged preservatives and directly put into cartons for use. However, this method has a contact area as mentioned above. Small and limited preservation effect.

Another method is to prepare MCP inclusions as coatings as described in patent CN201610637567.9, and then apply it on the surface of the base paper layer by coating, and then dry it at 40-60°C to obtain fresh-keeping paper, and then use the fresh-keeping paper Paper is used as a carton. Before the fruits and vegetables are put in, the moisture in the air is not enough to cause the release of MCP gas. After the fruits and vegetables are placed directly into the carton, the water vapor generated by the respiration of the fruits and vegetables will induce the slow release of MCP gas. Or as described in patent CN201710283918.5, the cyclodextrin-coated MCP is added to monomers, porogens, cross-linking agents, initiators, etc. to make a premix. After drying, it is used in the printing ink of packaging cartons. , after adding fruits and vegetables, the water vapor breathed by the fruits and vegetables can be used to slowly release the gas MCP. Although this method is easy to use, it has a good preservation effect. However, these two patents also have certain problems: 1. Although under normal conditions, the moisture in the air is not enough to cause the cured MCP to release MCP gas, but when the carton is stored unused for a long time, the storage environment is complex and changeable, and in a humid environment It is still easy to cause the release of gas MCP, affecting the preservation effect. 2. The carton obtained by the patent CN201610637567.9 is directly coated and dried. The coating has poor bonding force and is easy to fall off. The carton obtained by the patent CN201710283918.5 is printed. During the ink printing process, a high temperature of more than 120°C can be generated instantaneously. This leads to a large amount of release of gaseous MCP, especially as the existing carton pre-printing process becomes more and more popular. After pre-printing, corrugated board is produced on a flatbed line at 160 to 180°C. Therefore, the cured MCP is required to withstand high temperatures above 180°C. These two Patented products are not satisfactory.

Contents of the invention

The purpose of the present invention is to provide an alkali-regulated high-temperature-resistant modified cyclopropene, fresh-keeping varnish and fresh-keeping packaging products to solve the deficiencies of the existing technology.

The purpose of the present invention is achieved by the following technical solutions:

A kind of alkali-regulated high-temperature-resistant modified cyclopropene, which is in a solid state and includes an active ingredient cyclopropene compound, a curing inclusion agent, and a high-temperature-resistant modifier; the high-temperature resistant modifier is an organic silicon compound; The content of the organosilicon compound is 1 to 50% by mass of the cyclopropene compound.

Preferably, the modified cyclopropene can withstand high temperatures of ≥180°C and can be stably stored in a neutral system with a pH of 6.5 to 8.5 without releasing cyclopropene gas, and can be activated to release cyclopropene in an alkaline system with a pH of >8.5. Gas-like.

Preferably, the cyclopropene compound is 1-methylcyclopropene;

Preferably, the organosilicon compound is selected from ethyl orthosilicate and/or silicate hydrogel obtained by hydrolysis of ethyl orthosilicate;

Preferably, the curing inclusion agent is one or more combinations selected from β-cyclodextrin, yellow dextrin, and white dextrin.

Preferably, in the modified cyclopropene, the content of the curing inclusion agent is 8 to 12 times the mass of the cyclopropene compound.

The preparation method of alkali-regulated high-temperature-resistant modified cyclopropene as described above includes the following steps:

S1. First, mix the cyclopropene compound stock solution and the organosilicon compound in proportions evenly to obtain the first mixture; mix the curing inclusion agent and the quantitative water evenly to obtain the second mixture;

S2. Then mix and react the first mixture and the second mixture;

S3. Separate the solid-liquid mixture after the reaction to obtain the modified cyclopropene;

Step S1 and step S2 are performed at a temperature lower than the boiling point of the cyclopropene compound.

A kind of fresh-keeping varnish, the pH of the fresh-keeping varnish is 6.5-8.5, including water-based resin and modified cyclopropene as mentioned above; the mass percentage of the modified cyclopropene in the fresh-keeping varnish is 0.1 ~5%;

The types of resins in the water-based resin system are selected from resins that can withstand high temperatures of ≥180°C without decomposing and are stable at pH ≥6.5.

Preferably, the resin is one or more combinations selected from styrene-acrylic emulsion, sulfonated polyester, and sulfonic acid-type water-based polyurethane.

Preferably, the resin is a mixture selected from the group consisting of high hardness styrene acrylic emulsion, medium hardness styrene acrylic emulsion and low hardness styrene acrylic soft emulsion; the high hardness styrene acrylic emulsion, the medium hardness styrene acrylic emulsion, the low hardness styrene acrylic emulsion The dosages of styrene-acrylic soft emulsion are respectively 10-35%, 30-70% and 10-35% of the total mass of the resin.

Preferably, the fresh-keeping varnish also includes a defoaming agent and water;

The mass percentage of water in the fresh-keeping varnish is 0.5-12%, the mass percentage of the defoaming agent is 0.3-0.5%, and the rest is the resin.

A fresh-keeping packaging product, including a packaging material body layer and a fresh-keeping varnish layer located on at least one side surface of the packaging material body layer;

The fresh-keeping varnish layer is solidified by adding alkali to the fresh-keeping varnish mentioned above; the amount of alkali is 2 to 6% of the mass of the fresh-keeping varnish.

Preferably, the packaging material is paper; the fresh-keeping packaging product is prepared by any of the following processes:

A. Pre-printing process: First, mix neutral fresh-keeping varnish and alkali evenly as printing ink, and immediately print it through a pre-printing machine to obtain a fresh-keeping varnish paper roll, and then prepare it through a flat line to obtain a cardboard containing a fresh-keeping varnish layer;

B. Ordinary process: first use ordinary base paper to obtain ordinary cardboard through a flat line, then use the ordinary cardboard as the base, mix neutral fresh-keeping varnish and alkali as printing ink, and immediately print it with a watermark printer to obtain a layer containing fresh-keeping varnish cardboard.

This application uses an organic silicon compound together with a curing inclusion agent to modify cyclopropene compounds, which can significantly enhance its thermal stability and anti-oxidation stability, and can meet the conditions of 180°C high temperature required for printing (pre-printing); and It has alkali-controlled release characteristics and can be stored stably in a neutral system with a pH of 6.5 to 8.5. It is activated to release cyclopropene gas in an alkaline system with a pH > 8.5. Therefore, the modified MCP and its components can be stored for a long time in a conventional environment. Other products prepared by modified MCP, such as fresh-keeping varnish, fresh-keeping cartons, etc.

Description of drawings

Figure 1 is the heated gas release curve of the modified MCP solid powder obtained in Example 1 and conventional dextrin-modified MCP;

Figure 2 is a diagram of the stability test results of the neutral fresh-keeping varnish obtained in Example 1 and the fresh-keeping varnish with a pH of 11 after adding sodium hydroxide;

Figure 3 is a diagram of the fresh-keeping test process of fresh-keeping cartons;

Figure 4 is a graph showing the change in hardness of kiwi fruits stored in fresh-keeping cartons and ordinary cartons;

Figure 5 is a graph showing the weight changes of kiwi fruits stored in fresh-keeping cartons and ordinary cartons.

Detailed ways

This application provides an alkali-regulated high-temperature-resistant modified cyclopropene, which is in a solid state and includes an active ingredient cyclopropene compound, a curing inclusion agent, and a high-temperature-resistant modifier; the high-temperature resistant modifier is an organic silicon compound ; The content of the organosilicon compound is 1 to 50% of the mass of the cyclopropene compound.

In the existing technology, MCP that has been coated and solidified with dextrin and other substances can release gaseous MCP in a neutral system. Therefore, subsequent applications "such as patent 201710283918.5 and patent 201610637567.9 to make fresh-keeping cartons" may absorb too much during normal storage. Moisture will release MCP prematurely, limiting the application of cured MCP. In addition, conventional encapsulated and cured MCP has poor high temperature resistance and cannot withstand the high temperatures of conventional printing such as watermark printing and pre-printing.

Through in-depth research, this application found that by using an organic silicon compound together with a curing inclusion agent to modify cyclopropene compounds (such as 1-MCP), the silicone has strong thermal stability and oxidation stability in the organic silicon molecule. On the basis of -oxygen bond, its thermal stability and anti-oxidation stability can be significantly enhanced. According to the thermal release curve, the modified gas MCP is almost not released at 180°C, and the large release temperature is between 250 and 350°C. It can meet the 180°C high temperature conditions required for corrugated cardboard production; it also has alkali controlled release characteristics and can be stably stored in a neutral system with pH 6.5 to 8.5. It is activated to release cyclopropene gas in an alkaline system with pH > 8.5. Therefore, Modified MCP and other products prepared from modified MCP, such as fresh-keeping varnish, fresh-keeping cartons, etc., can be stored for a long time under normal conditions. Regarding the alkali-controlled release mechanism, the applicant speculates that the modified cyclopropene has certain characteristics of Lewis base, and strong alkali can destroy this structural characteristic, resulting in the release of the coated gas. However, in the absence of water vapor, the strong base is solid and has limited destructive power on the coating structure. Therefore, it is relatively stable in a dry state and does not release cyclopropene gas.

By adjusting the amount of organosilicon compound, the heat release curve can be adjusted. Generally, within a limited range, when the amount of organosilicon compound is large, the heat release temperature is relatively high.

Preferably, the cyclopropene compound is 1-methylcyclopropene, which is widely used, or a cyclopropene derivative with properties similar to 1-methylcyclopropene.

Preferably, the organosilicon compound is selected from ethyl orthosilicate and/or silicic acid hydrogel obtained by hydrolysis of ethyl orthosilicate.

Preferably, the curing inclusion agent is one or more combinations selected from β-cyclodextrin, yellow dextrin, and white dextrin, and is further preferably the most common and widely used β-cyclodextrin.

Preferably, in the modified cyclopropene, the content of the curing inclusion agent is 8 to 12 times the mass of the cyclopropene compound.

The preparation method of alkali-regulated high-temperature-resistant modified cyclopropene as described above includes the following steps:

S1. First, mix the cyclopropene compound stock solution and the organosilicon compound in proportions evenly to obtain the first mixture; mix the curing inclusion agent and the quantitative water evenly to obtain the second mixture;

S2. Then mix the first mixture and the second mixture for reaction;

S3. Separate the solid-liquid mixture of the reaction mixture to obtain modified cyclopropene.

The proportioning amount is: the amount of organic silicon compound is 1 to 50% of the mass of the cyclopropene compound, and the amount of curing inclusion agent is 8 to 12 times the mass of the cyclopropene compound.

Steps S1 and S2 are performed at a temperature lower than the boiling point of the cyclopropene compound to prevent premature release of the preservation gas under higher temperature conditions.

Preferably, when the cyclopropene compound is 1-MCP, in step S1, the cyclopropene compound stock solution and the organosilicon compound are stirred and mixed at -5°C to -10°C for 60 to 90 minutes, and the solidification inclusion agent and quantitative water are mixed at 1 to 10°C. Grind and mix at 5°C. The amount of water used is 1.5 to 2.5 times the mass of the cured inclusion agent; in step S2, pour the first mixture into the second mixture and continue grinding and mixing for 90 to 120 minutes.

Step S3: Suction filter the ground solid mixture, rinse the filter cake with ethanol more than two times, put it into a vacuum drying oven at 40-60°C and vacuum-dry it for 18-30 hours, and then take it out and grind it to obtain modified cyclopropene.

The modified cyclopropene can be used in the same way as conventional cyclopropene preservatives. For example, it can be made into a fresh-keeping bag. Benefiting from the excellent high-temperature resistance of the modified cyclopropene, it can be stored for a long time in a high-temperature dry environment and can be placed directly during application. Put it in a fruit and vegetable transport box and then moisten it with alkali solution to release cyclopropene gas. Of course, the modified cyclopropene plus solid alkali powder can also be mixed evenly to make a fresh-keeping bag, which can be directly placed in a fruit and vegetable transport box during use, and then moistened with water.

In order to make full use of the advantages of high temperature resistance and alkali-controlled release of the modified cyclopropene of the present application, the present application provides a fresh-keeping varnish that is stable under neutral conditions and can withstand high temperatures above 180°C. This fresh-keeping varnish can be used as Ink is directly printed to produce fruit and vegetable packaging boxes. Specifically, the pH of the fresh-keeping varnish is 6.5-8.5, and includes water-based resin and modified cyclopropene as mentioned above; the mass percentage of modified cyclopropene in the fresh-keeping varnish is 0.1-5%. When the amount of modified cyclopropene in the varnish is too small, the corresponding preservation effect will not be achieved. When the amount is too much, the cost will be higher.

This preservation glossy oleoresin system can use conventional water-based resin systems and water-based coatings. It not only has high safety performance and is suitable for the preservation of fresh fruits and vegetables, but also helps absorb moisture and release preservation gases during subsequent applications. However, it is required that the resin can withstand high temperatures of ≥180°C without decomposing, and be stable under neutral and alkaline conditions with a pH of ≥6.5. Preferably, the resin is selected from the group consisting of styrene-acrylic emulsion, sulfonated polyester, and sulfonic acid-type water-based polyurethane. Various combinations of species. Further preferred is a styrene-acrylic emulsion that is cheap and suitable for large-scale production.

There are many styrene-acrylic emulsion products in the prior art. By adjusting the ratio of styrene and other acrylic functional monomers, styrene-acrylic emulsions with different hardnesses can be obtained. In this application, the styrene-acrylic emulsion is preferably high-hardness styrene-acrylic emulsion and medium-hardness styrene-acrylic emulsion. Mixing of emulsion and low-hardness styrene-acrylic soft emulsion, in which the dosages of high-hardness styrene-acrylic emulsion, medium-hardness styrene-acrylic emulsion, and low-hardness styrene-acrylic soft emulsion are respectively 10% to 35%, 30% to 70%, and 10% of the total resin mass. 35%. The technical characteristics of high hardness styrene acrylic emulsion, medium hardness styrene acrylic emulsion, and low hardness styrene acrylic soft emulsion in this application are shown in Table 1 (hardness mainly refers to the Tg value, the higher the Tg value, the greater the emulsion hardness).

Table 1

The higher the hardness of styrene-acrylic emulsion, the worse the film-forming properties. After printing and curing, tiny cracks will occur, which will help the entry of water vapor and the release of preservation gas. However, the printing process has certain requirements for the hardness of the ink. If the hardness is too high, printing Therefore, on the basis of taking into account the printability, stability and release properties, this application preferably uses a mixture of styrene-acrylic emulsions with different hardnesses, which has better technical effects than using styrene-acrylic emulsions with a single hardness.

As those skilled in the art can understand, when using other resin systems, the principle is similar to that of styrene-acrylic emulsion, and it is also preferred to use resins with different hardnesses mixed for use.

Preferably, the fresh-keeping varnish also includes a defoaming agent and water; the mass percentage of water in the fresh-keeping varnish is 0.5-12%, the mass percentage of the defoaming agent is 0.3-0.5%, and the rest is resin. The defoaming agent is preferably BYK-019 defoaming agent. The amount of water can be adjusted accordingly according to the water content in the resin to keep the viscosity of the fresh-keeping varnish within a range suitable for printing. Generally, the total water content in the varnish is kept between 30 and 60%.

This fresh-keeping varnish can be directly coated on the surface of packaging materials like patent 201610637567.9. Since the modified MCP in the fresh-keeping varnish of this application is an alkali-controlled release of fresh-keeping gas, a certain amount of fresh-keeping varnish needs to be added to the fresh-keeping varnish before coating. In order to reduce the excessive release of preservation gas during the coating and drying process, the alkali must be applied immediately after mixing evenly and dried quickly. The packaging material needs to be able to quickly absorb the moisture in the paint and enable the paint to cure quickly, such as paper, foam, etc.

Therefore, this application also provides a fresh-keeping packaging product, including a packaging material body layer and a fresh-keeping varnish layer located on at least one side surface of the packaging material body layer;

The fresh-keeping varnish layer is solidified by adding alkali to the fresh-keeping varnish mentioned above; the amount of alkali is 2 to 6% of the mass of the fresh-keeping varnish.

Cartons are the most widely used fruit and vegetable packaging boxes. They are cheap and have excellent water absorption properties. Therefore, the preferred packaging material is paper. This application proposes for the first time to manually add a small amount of alkali before printing, preferably sodium hydroxide/potassium hydroxide, and then use it immediately For printing, when the carton is dry at room temperature, the active ingredient 1-MCP releases slowly and can be stored stably for several months. During use, you only need to spray the coating with a sprayer, and then the fruits and vegetables can be packaged to activate 1-MCP and start releasing it. Specifically, any of the following processes can be used to prepare fresh-keeping cartons:

A. Pre-printing process: First, mix neutral fresh-keeping varnish and alkali evenly as printing ink, and immediately print it through a pre-printing machine to obtain a fresh-keeping varnish paper roll, and then prepare it through a flat line to obtain a cardboard containing a fresh-keeping varnish layer; as shown in this field Technical personnel can understand that the fresh-keeping varnish layer is located on the inner layer of the cardboard, and conventional surface layer printing can also be performed on the outside of the cardboard using a watermark printer.

B. Ordinary process: first use ordinary base paper through a flat line to obtain ordinary cardboard, then use ordinary cardboard as the base, mix neutral preservation varnish and alkali as printing ink, and immediately print it with a watermark printer to obtain a cardboard containing a preservation varnish layer . As those skilled in the art can understand, the fresh-keeping varnish layer is located on the inner layer of the cardboard, and the base can be ordinary cardboard printed with an ordinary surface layer.

In order to fully mix the fresh-keeping varnish and alkali, the solid alkali can be diluted with a small amount of water, and then added to the fresh-keeping varnish. To reduce the release of MCP gas, printing should be done immediately after mixing.

The pre-printing process has high production efficiency and uniform printing; the ordinary process has a simple process and slightly poor uniformity, but due to cumbersome steps, low efficiency and relatively high cost, the process can be selected according to the actual production situation for printing production. The pre-printing process and the ordinary process can use conventional corrugated cardboard production and printing processes, and will not be described in detail in this application.

Dry fresh-keeping cartons can be stored for a long time in a dry room temperature environment. When using, spray the inside of the carton with water and put fruits and vegetables to get the fresh-keeping effect. The length of the fresh-keeping period can be adjusted by adjusting the alkali content and the amount of paint printing. In addition, fresh-keeping The period is also related to the ambient temperature and air humidity of the carton.

Example 1

(1) Preparation of modified MCP solid

(a) Set the low-temperature reactor temperature to -10°C, pour 10g of 1-MCP stock solution and 0.5g of ethyl orthosilicate into the split four-neck flask, and stir at low temperature for 60 minutes at 360r/min.

(b) Set the temperature of the low-temperature dispersing device to 3°C. After the dispersing device is fully cooled, add 100g β-cyclodextrin and 200g distilled water to grind into a paste, then add the mixed solution obtained in step (1) and continue grinding for 120 minutes.

(c) Filter the ground solid mixture, rinse the filter cake three times with 30 ml of ethanol, put it into a 50°C vacuum drying oven (vacuum degree -0.09Mpa), take it out after 24 hours and grind it to obtain modified MCP solid powder.

(2) Preparation of fresh-keeping varnish

At room temperature, add 15g of high-hardness styrene-acrylic emulsion, 60g of medium-hardness styrene-acrylic emulsion, 15g of low-hardness styrene-acrylic soft emulsion, 9.5g of deionized water, 0.1g of modified MCP, and BYK-019 defoaming into the high-speed disperser. Add 0.4g of the agent and disperse at high speed for 60 minutes to obtain fresh-keeping varnish. The pH of the varnish is 7.8. (Among them, 0590 emulsion and 1207 emulsion are from Tianlong Ink, and BYK-019 is from BYK Chemical).

(3) Printing of fresh-keeping cartons

Add 2wt% sodium hydroxide solid powder to the fresh-keeping varnish (can be diluted with a small amount of water and mixed evenly with the fresh-keeping varnish), mix thoroughly, pour into a preprinting machine for printing, and wind up to obtain a fresh-keeping varnish layer paper roll. The fresh-keeping varnish layer paper roll passes through a 180°C flat line to obtain a cardboard containing a fresh-keeping varnish layer in the inner layer (the printing amount of the fresh-keeping varnish layer is 3g/m ² ). The cardboard is printed on the surface layer through a watermark printing machine to obtain a fresh-keeping carton.

Example 2

(1) Preparation of modified MCP solid

(a) Set the low-temperature reactor temperature to -5°C, pour 10g of 1-MCP liquid and 5g of silicate hydrogel into the split four-neck flask, and stir at low temperature for 90 minutes at 800r/min.

(b) Set the temperature of the low-temperature dispersing device to 3°C. After the dispersing device is fully cooled, add 80g yellow dextrin and 160g distilled water to grind into a paste, then add the mixed solution obtained in step (1) and continue grinding for 90 minutes.

(c) Filter the ground solid mixture, rinse the filter cake three times with 30 ml of ethanol, put it into a 50°C vacuum drying oven (vacuum degree -0.09Mpa), take it out after 24 hours and grind it to obtain modified MCP solid powder.

(2) Preparation of fresh-keeping varnish

At room temperature, add 30g each of high-hardness styrene-acrylic emulsion, medium-hardness styrene-acrylic emulsion, and styrene-acrylic soft emulsion, 9.3g deionized water, 0.3g modified MCP, and 0.4g BYK-019 defoaming agent into the high-speed disperser. , high-speed dispersion for 90 minutes, you can get fresh-keeping varnish, the pH of the varnish is 7.6.

(3) Printing of fresh-keeping cartons:

(a) Use ordinary base paper to make ordinary corrugated cardboard through a 180°C flatbed line, and print the surface layer through a watermark printing machine.

(b) Add 3wt% sodium hydroxide solid powder to the fresh-keeping varnish and stir thoroughly.

(c) Pour into a watermark printing machine, use the back of the cardboard that has completed surface layer printing as the base, and print the inner layer of fresh-keeping varnish to obtain a fresh-keeping carton (the printing amount of the fresh-keeping varnish is 3g/m ² ).

Example 3

(1) Preparation of modified MCP solid

(a) Set the low-temperature reactor temperature to -3°C, pour 10g of 1-MCP stock solution and 0.1g of ethyl orthosilicate into the split four-neck flask in sequence, and stir at low temperature at 720r/min for 30min.

(b) Set the temperature of the low-temperature dispersing device to 3°C. After the dispersing device is fully cooled, add 100g of dextrin and 200g of distilled water to grind into a paste, then add the mixed solution obtained in step (1) and continue grinding for 120 minutes.

(c) Filter the ground solid mixture, rinse the filter cake three times with 30 ml of ethanol, put it into a 50°C vacuum drying oven (vacuum degree -0.09Mpa), take it out after 24 hours and grind it to obtain modified MCP solid powder.

(2) Preparation of fresh-keeping varnish

At room temperature, add 10g of high-hardness styrene-acrylic emulsion, 60g of medium-hardness styrene-acrylic emulsion, 20g of low-hardness styrene-acrylic soft emulsion, 9.1g of deionized water, 0.5g of modified MCP, and BYK-019 defoaming into the high-speed disperser. Add 0.4g of the agent and disperse at high speed for 120 minutes to obtain fresh-keeping varnish with a pH of 7.9. (Among them, 0590 emulsion and 1207 emulsion are from Tianlong Ink, and BYK-019 is from BYK Chemical).

(3) Printing of fresh-keeping cartons

Add 2wt% sodium hydroxide solid powder to the fresh-keeping varnish and mix thoroughly, pour it into a preprinting machine for printing, and wind it up to obtain a fresh-keeping varnish layer paper roll. The fresh-keeping varnish layer paper roll passes through a 180°C flat line to obtain a cardboard containing a fresh-keeping varnish layer in the inner layer (the printing amount of the fresh-keeping varnish layer is 3g/m ² ). The cardboard is printed on the surface layer through a watermark printing machine to obtain a fresh-keeping carton.

Example 4

(1) Preparation of modified MCP solid

(a) Set the low-temperature reactor temperature to -5°C, pour 10g of 1-MCP liquid and 1g of silicate hydrogel into the split four-neck flask in sequence, and stir at 800r/min at low temperature for 90min.

(b) Set the temperature of the low-temperature dispersing device to 3°C. After the dispersing device is fully cooled, add 120g β-cyclodextrin and 200g distilled water to grind into a paste, then add the mixed solution obtained in step (1) and continue grinding for 90 minutes.

(c) Filter the ground solid mixture, rinse the filter cake three times with 30 ml of ethanol, put it into a 50°C vacuum drying oven (vacuum degree -0.09Mpa), take it out after 24 hours and grind it to obtain modified MCP solid powder.

(2) Preparation of fresh-keeping varnish

At room temperature, add 30g of high-hardness styrene-acrylic emulsion, 40g of medium-hardness styrene-acrylic emulsion, 20g of styrene-acrylic soft emulsion, 8.6g of deionized water, 1g of modified MCP, and 0.4g of BYK-019 defoaming agent into the high-speed disperser. Disperse at high speed for 90 minutes to obtain fresh-keeping varnish with a pH of 8.2.

(3) Printing of fresh-keeping cartons:

(a) Use ordinary base paper to make ordinary corrugated cardboard through a 180°C flatbed line, and print the surface layer through a watermark printing machine.

(b) Add 6wt% sodium hydroxide solid powder to the fresh-keeping varnish and stir thoroughly.

(c) Pour into a watermark printing machine, use the back of the cardboard that has completed surface layer printing as the base, and print the inner layer of fresh-keeping varnish to obtain a fresh-keeping carton (the printing amount of the fresh-keeping varnish is 3g/m ² ).

Experimental example

1. Modified MCP solid thermal stability test

Take the modified MCP solid powder obtained in Example 1, and use the conventional dextrin-modified MCP solid powder (without silicone modification) as a control, and test its heated gas release curve under the following test conditions. The results are shown in Figure 1 As shown (x-axis is temperature in °C; y-axis is weight residual percentage).

Test conditions: Thermal weight loss test, sampling 5mg, 30~800℃, _N2 atmosphere, heating rate 10℃/min.

As can be seen from Figure 1, when the temperature reaches 200°C, conventional dextrin-modified MCP has more than 10% gas release, while the gas release of modified cyclopropene in this application is less than 5%, and the gas release reaches the maximum level at about 250°C. 10%, therefore it can be proved that the modified MCP obtained in this application can fully withstand the printing high temperature of 180°C.

2. Stability test of fresh-keeping varnish

Multiple cans of 100g neutral fresh-keeping varnish obtained in Example 1 (in order to improve the test accuracy, the preservative addition amount was increased from 0.1wt% to 5wt%, and the water consumption was reduced accordingly) and the fresh-keeping varnish added with 2wt% sodium hydroxide. (pH is 11), put them into metal cans and seal them separately. Place the sealed jars into a 60°C oven for thermal storage. Take out one jar every 24 hours and let it cool. Open the seal, stir slightly and then weigh. Record the mass change. The results are shown in Figure 2.

It can be seen from Figure 2 that the preservation varnish produced by this application can be stored stably under neutral conditions with almost no quality loss, and slowly releases preservation gas under alkaline conditions.

3.Fresh-keeping carton test

Test conditions: Use cartons with a fresh-keeping varnish layer (fresh-keeping cartons obtained in Example 1) and cartons without a fresh-keeping varnish layer (ordinary cartons obtained without printing a fresh-keeping varnish layer under the same production process conditions) to store kiwi fruits picked in the same batch with the same weight. After being stored for 6 days at 25°C and 70% RH, a comparative test was conducted on the hardness changes and weight changes of the two kiwi fruits. The test process pictures are shown in Figure 3, and the results are shown in Figures 4 and 5.

As can be seen from Figure 4, the hardness of kiwi fruits stored in cartons with a fresh-keeping glossy oil layer was higher than that in uncoated cartons during the test period. Therefore, cartons with a fresh-keeping glossy oil layer can delay the ripening of kiwi fruits and play a role in preserving freshness.

It can be seen from Figure 5 that when stored for 4 to 5 days, the weight loss of kiwi fruits in cartons with a preservation varnish layer begins to approach that of uncoated cartons. During this time period, the preservation varnish begins to fail, and the kiwi fruit consumes organic matter at a faster rate. . Therefore, the ethylene-inhibiting water-based coating can inhibit the respiration of kiwi fruit for about 4 to 5 days, and the carton can preserve the freshness of kiwi fruit for about 4 to 5 days.

Although the preferred embodiments of the present invention have been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once the basic inventive concepts are apparent. Therefore, it is intended that the appended claims be construed to include the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims (10)

1. The alkali-controlled high-temperature-resistant modified cyclopropene is characterized by being in a solid state and comprising an active ingredient cyclopropene compound, a curing inclusion agent and a high-temperature-resistant modifier; the high-temperature resistant modifier is an organic silicon compound; the content of the organosilicon compound is 1-50% of the mass of the cyclopropene compound.

2. The alkali-controlled high-temperature-resistant modified cyclopropene as claimed in claim 1, wherein the modified cyclopropene can resist high temperature of more than or equal to 180 ℃ and stably store in a neutral system with pH of 6.5-8.5 without releasing cyclopropene gas, and activate and release cyclopropene gas in an alkaline system with pH of more than 8.5.

3. The alkali-controlled high temperature-resistant modified cyclopropene of claim 1, wherein the cyclopropene compound is 1-methylcyclopropene;

preferably, the organosilicon compound is selected from ethyl orthosilicate and/or silicic acid hydrogel obtained by hydrolysis of ethyl orthosilicate;

preferably, the curing inclusion agent is one or more selected from beta-cyclodextrin, yellow dextrin and white dextrin.

4. The alkali-controlled high temperature-resistant modified cyclopropene of claim 1,

in the modified cyclopropene, the content of the curing inclusion agent is 8-12 times of the mass of the cyclopropene compound.

5. The method for preparing the alkali-controlled high-temperature-resistant modified cyclopropene as claimed in any one of claims 1 to 4, comprising the steps of:

s1, uniformly mixing a cyclopropene compound stock solution with a certain proportion with an organosilicon compound to obtain a first mixture; uniformly mixing the curing inclusion compound and quantitative water to obtain a second mixture;

s2, mixing the first mixture and the second mixture for reaction;

s3, carrying out solid-liquid separation on the reacted mixture to obtain the modified cyclopropene;

step S1 and step S2 are performed at a temperature less than the boiling point of the cyclopropene compound.

6. A preservative gloss oil characterized in that the preservative gloss oil has a pH of 6.5 to 8.5 and comprises an aqueous resin and the modified cyclopropene of any one of claims 1 to 4; the mass percentage of the modified cyclopropene in the fresh-keeping gloss oil is 0.1-5%;

the resin type in the aqueous resin system is selected from resins which can resist high temperature of more than or equal to 180 ℃ and are not decomposed and are stable under the condition that the pH is more than or equal to 6.5.

7. The fresh-keeping gloss oil according to claim 6, wherein,

the resin is one or a combination of more selected from styrene-acrylic emulsion, sulfonated polyester and sulfonic acid type aqueous polyurethane.

Preferably, the resin is a mixture selected from the group consisting of high hardness styrene-acrylic emulsion, medium hardness styrene-acrylic emulsion and low hardness styrene-acrylic soft emulsion; the dosages of the high-hardness styrene-acrylic emulsion, the medium-hardness styrene-acrylic emulsion and the low-hardness styrene-acrylic soft emulsion are respectively 10-35%, 30-70% and 10-35% of the total mass of the resin.

8. The fresh-keeping gloss oil according to claim 6, wherein,

the fresh-keeping gloss oil also comprises a defoaming agent and water;

the fresh-keeping gloss oil comprises, by mass, 0.5-12% of water, 0.3-0.5% of defoamer and the balance of resin.

9. A freshness package product, characterized by: comprises a packaging material body layer and a fresh-keeping gloss oil layer positioned on at least one side surface of the packaging material body layer;

the fresh-keeping gloss oil layer is formed by curing the fresh-keeping gloss oil according to any one of claims 6 to 8 with alkali; the consumption of the alkali is 2-6% of the mass of the fresh-keeping gloss oil.

10. The freshness package product of claim 9, wherein: the packaging material is paper; the fresh-keeping packaging product is prepared by any one of the following processes:

A. preprinting process: firstly, uniformly mixing neutral fresh-keeping gloss oil with alkali to be used as printing ink, immediately printing by a preprinting machine to obtain a fresh-keeping gloss oil paper roll, and preparing a paperboard containing a fresh-keeping gloss oil layer by a flat line;

B. the common process comprises the following steps: firstly, common base paper is used to obtain a common paperboard through a flat line, then the common paperboard is used as a substrate, neutral fresh-keeping gloss oil and alkali are uniformly mixed to be used as printing ink, and the paperboard containing a fresh-keeping gloss oil layer is immediately printed by a watermark printer.