Ternary random copolymer, preparation method thereof and high-barrier packaging material

Abstract

The invention discloses a ternary random copolymer, a preparation method thereof and a high-barrier packaging material, and belongs to the technical field of polymer synthesis and packaging materials. The structural unit of the ternary random copolymer is composed of an ethylene monomer, a carbon monoxide monomer and a third monomer; wherein the molar content of the ethylene monomer is 40-48%, the molar content of the carbon monoxide monomer is 50%, and the molar content of the third monomer is 2-10%. The third monomer is selected from vinyl acetate or vinyl ether as shown in a formula 1 (CH2 = CH-OR); wherein R is selected from C1-C4 alkyl groups. The ternary random copolymer has excellent gas barrier property, good water resistance and considerable mechanical strength, and is suitable for the field of food and medicine packaging requiring high barrier and high moisture resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and packaging materials technology, and in particular to a ternary random copolymer, its preparation method, and a high-barrier packaging material. Background Technology

[0002] In the food and pharmaceutical packaging industry, high-barrier polymer materials are crucial for extending product shelf life and ensuring product quality. Currently, mainstream high-barrier materials on the market, such as polyvinylidene chloride (PVDC) and polyvinyl alcohol (PVOH), both have significant drawbacks. PVDC materials offer excellent barrier properties at a low price, and possess superior freshness preservation, aroma retention, corrosion resistance, and heat resistance. However, the presence of chlorine in its molecular chain poses potential environmental problems during processing and handling, leading to increasing limitations on its application. While PVOH materials exhibit excellent oxygen barrier properties, their strong hydrophilicity causes a sharp decline in barrier performance and even dissolution in high-humidity environments, severely restricting their use in many applications requiring moisture protection or water resistance.

[0003] Known ethylene-carbon monoxide alternating copolymers (polyketides) possess good mechanical properties and certain barrier properties. However, their barrier properties, especially against oxygen, are insufficient to completely replace PVDC or PVOH. Therefore, it is crucial to research and develop a novel copolymer with excellent gas barrier properties and good water resistance. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a ternary random copolymer, a method for preparing the same, and a high-barrier packaging material. The ternary random copolymer possesses excellent gas barrier properties, good water resistance, and considerable mechanical strength.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a ternary random copolymer whose structural units are composed of ethylene monomer, carbon monoxide monomer and a third monomer;

[0007] The molar content of ethylene monomer is 40%-48%, the molar content of carbon monoxide monomer is 50%, and the molar content of the third monomer is 2%-10%.

[0008] The third monomer is selected from vinyl acetate or the vinyl ether shown in Formula 1;

[0009] CH2=CH-OR Equation 1;

[0010] R is selected from C1-C4 alkyl groups.

[0011] The C1-C4 alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, etc.

[0012] Preferably, the third monomer is selected from vinyl acetate, vinyl methyl ether, or vinyl ethyl ether.

[0013] More preferably, the structural unit of the ternary random copolymer is composed of 44% ethylene, 50% carbon monoxide and 6% vinyl methyl ether.

[0014] More preferably, the structural unit of the ternary random copolymer is composed of 42% ethylene, 50% carbon monoxide and 8% vinyl methyl ether.

[0015] More preferably, the structural unit of the ternary random copolymer is composed of 45% ethylene, 50% carbon monoxide and 5% vinyl acetate.

[0016] The ternary random copolymer described in this invention significantly improves its oxygen barrier properties through the synergistic effect of three monomers, bringing it to a level similar to that of PVOH; at the same time, it also has excellent water resistance, successfully overcoming the application limitations of existing PVDC and PVOH materials.

[0017] The present invention also provides a method for preparing the above-mentioned ternary random copolymer, comprising the following steps:

[0018] The tertiary random copolymer is obtained by mixing ethylene monomer, carbon monoxide monomer, and third monomer with a complexing catalyst and performing a copolymerization reaction.

[0019] The complexing catalyst is selected from palladium-based or nickel-based catalysts.

[0020] Preferably, the palladium catalyst of the present invention is selected from complex catalysts formed by Pd(II) salts, bidentate phosphine ligands and acid compounds.

[0021] The Pd(II) salts include, but are not limited to, palladium acetate (Pd(OAc)2) and palladium trifluoromethanesulfonate.

[0022] The bidentate phosphine ligands include, but are not limited to, 1,3-bis(diphenylphosphine)propane (dppp), 2,2-dimethyl-1,3-bis(diphenylphosphine)propane, etc.

[0023] The acid compounds include, but are not limited to, trifluoroacetic acid and p-toluenesulfonic acid.

[0024] Preferably, the nickel-based catalytic system is selected from complex catalysts formed by Ni(II) salts, bidentate phosphine ligands, and acid compounds.

[0025] The Ni(II) salts include, but are not limited to, nickel acetate, nickel dichloride, etc.

[0026] The bidentate phosphine ligands and acid compounds mentioned above are within the same range as those in the palladium-based catalysts described above, and will not be repeated here.

[0027] Preferably, the temperature of the copolymerization reaction is 50℃-90℃; more preferably 60℃-80℃; and even more preferably 70℃-75℃.

[0028] Preferably, the pressure of the copolymerization reaction is 4-15 MPa; more preferably, it is 6-10 MPa.

[0029] In the copolymerization reaction described in this invention, the pressure of the carbon monoxide monomer is preferably 2-8 MPa; more preferably 3-6 MPa.

[0030] The copolymerization reaction is preferably carried out for 1-10 h; more preferably for 3-5 h.

[0031] The copolymerization reaction is preferably carried out in a polar organic solvent.

[0032] The present invention does not specifically limit the polar organic solvent, and it can be any polar organic solvent well known to those skilled in the art.

[0033] The polar organic solvents include, but are not limited to, methanol, ethanol, or acetone.

[0034] In some specific embodiments of the present invention, the polar organic solvent is preferably methanol.

[0035] The present invention does not specifically limit the container for the copolymerization reaction. In some embodiments of the present invention, it is a reaction vessel.

[0036] After the copolymerization reaction is completed, post-processing steps such as precipitation, filtration, washing, and drying are performed sequentially.

[0037] The precipitant used for precipitation is selected from methanol containing hydrochloric acid.

[0038] The present invention does not impose any particular limitation on the filtration method and the washing solvent, and can use any filtration method and washing solvent known to those skilled in the art.

[0039] The present invention does not specifically limit the drying method, and can be any method known to those skilled in the art, such as vacuum drying, freeze drying, etc.

[0040] In some specific embodiments of the present invention, vacuum drying is employed.

[0041] In some specific embodiments of the present invention, the method for preparing the ternary random copolymer preferably includes the following steps:

[0042] (1) A polar organic solvent, ethylene monomer, carbon monoxide monomer and a third monomer are mixed to obtain a mixed system S1;

[0043] (2) The complexing catalyst is added to the above mixed system S1 to carry out a copolymerization reaction to obtain the ternary random copolymer.

[0044] The present invention also provides a high-barrier packaging material, comprising the above-mentioned ternary random copolymer or the ternary random copolymer prepared by the above-mentioned preparation method;

[0045] Preferably, the oxygen permeability of the high-barrier packaging material is less than 10 cm³·mm / (m²·day·atm); more preferably, the oxygen permeability of the high-barrier packaging material is less than 5.5 cm³·mm / (m²·day·atm).

[0046] Preferably, the water contact angle of the high-barrier packaging material is greater than 75°; more preferably, the water contact angle of the high-barrier packaging material is greater than 78°.

[0047] The high-barrier packaging material can be further processed into films, sheets, or containers.

[0048] The processing methods include, but are not limited to, melt extrusion, blow molding, or solution casting.

[0049] The present invention also provides the application of the above-mentioned high-barrier packaging materials in food packaging or pharmaceutical packaging.

[0050] Compared with existing technologies, the structural unit of the ternary random copolymer provided by this invention is composed of ethylene monomer, carbon monoxide monomer, and a third monomer; wherein the molar content of ethylene monomer is 40%-48%, the molar content of carbon monoxide monomer is 50%, and the molar content of the third monomer is 2%-10%. The third monomer is selected from vinyl acetate or vinyl ether of formula 1 (CH2=CH-OR); wherein R is selected from C1-C4 alkyl groups. The ternary random copolymer has excellent gas barrier properties, good water resistance, and considerable mechanical strength, making it suitable for food and pharmaceutical packaging applications requiring high barrier properties and high moisture resistance. Detailed Implementation

[0051] To further illustrate the present invention, the following detailed description of the ternary random copolymer, its preparation method, and the high-barrier packaging material provided by the present invention is provided in conjunction with embodiments.

[0052] Example 1

[0053] Preparation of ethylene / carbon monoxide / vinyl methyl ether terpolymer

[0054] 400 mL of methanol was added as solvent to a 1-liter high-pressure reactor. Ethylene (initial partial pressure 1.5 MPa), vinyl methyl ether (20 mL), and carbon monoxide (initial partial pressure 4.0 MPa) were added sequentially. Then, the catalytic system was added: Pd(OAc)₂ (0.05 mmol), dppp (0.055 mmol), and trifluoroacetic acid (0.11 mmol). The reactor was heated to 75°C, and the total pressure was increased to approximately 6 MPa. The reaction was stirred for 4 hours under these conditions. After the reaction was complete, the reactor was cooled and the pressure was released. The reaction solution was poured into a methanol solution containing 5% hydrochloric acid to precipitate the precipitate. The precipitate was filtered, washed thoroughly with methanol, and dried under vacuum at 50°C to constant weight, yielding a white fibrous polymer, which is the ethylene / carbon monoxide / vinyl methyl ether terpolymer. ¹H NMR spectroscopy showed that the molar content of ethylene was 44%, the molar content of carbon monoxide was 50%, and the molar content of vinyl methyl ether was 6%.

[0055] Example 2

[0056] Preparation of ethylene / carbon monoxide / vinyl methyl ether terpolymer

[0057] Using a similar procedure to Example 1, the third monomer, vinyl methyl ether, was increased to 30 mL, the reaction temperature and pressure were kept constant, and the reaction time was 4.5 hours to obtain the target terpolymer. The 1H NMR spectrum showed that the ethylene molar content was 42%, the carbon monoxide molar content was 50%, and the vinyl methyl ether molar content was 8%.

[0058] Example 3

[0059] Preparation of ethylene / carbon monoxide / vinyl acetate terpolymer

[0060] Using a similar procedure to Example 1, the third monomer was replaced with 25 mL of vinyl acetate, the reaction temperature was adjusted to 70°C, and the reaction time was 5 hours to obtain the target terpolymer. The 1H NMR spectrum showed that the molar content of ethylene was 45%, the molar content of carbon monoxide was 50%, and the molar content of vinyl acetate was 5%.

[0061] Comparative Example 1

[0062] Commercially available ethylene / carbon monoxide (ECO) films were used as a performance comparison reference.

[0063] Comparative Example 2

[0064] Commercially available PVOH films were used as a performance comparison reference.

[0065] Performance testing

[0066] The polymers obtained in Examples 1 and 2 and the materials in Comparative Examples 1 and 2 were used to make films with a thickness of about 50 μm. Their oxygen permeability (ASTM D3985) and water contact angle (ASTM D724) were tested, and the results are shown in Table 1.

[0067] Table 1 Performance Test Results

[0068] Material Oxygen transmission rate (cm³·mm / (m²·day·atm)) Water contact angle (°) Example 1 (E / CO / VME) 3.8 88 Example 2 (E / CO / VAc) 5.5 80 Comparative Example 1 (ECO binary copolymer) 25.0 78 Comparative Example 2 (PVOH film) 1.5 30 (easily swells)

[0069] The above test results show that the terpolymer described in this invention significantly improves oxygen barrier performance compared to traditional ECO binary copolymers. Although its oxygen barrier performance is slightly inferior to that of PVOH, the terpolymer described in this invention maintains good hydrophobic properties, overcoming the fatal flaw of poor water resistance of PVOH. Therefore, compared to traditional ECO binary copolymers and PVOH films, the terpolymer described in this invention combines good oxygen barrier performance with excellent water resistance.

[0070] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A ternary random copolymer, characterized in that, Its structural units consist of ethylene monomer, carbon monoxide monomer, and a third monomer; The molar content of ethylene monomer is 40%-48%, the molar content of carbon monoxide monomer is 50%, and the molar content of the third monomer is 2%-10%. The third monomer is selected from vinyl acetate or the vinyl ether shown in Formula 1; CH2=CH-OR Equation 1; R is selected from C1-C4 alkyl groups.

2. The ternary random copolymer according to claim 1, characterized in that, The third monomer is selected from vinyl acetate, vinyl methyl ether, or vinyl ethyl ether.

3. The ternary random copolymer according to claim 1 or 2, characterized in that, The structural units of the ternary random copolymer consist of 44% ethylene, 50% carbon monoxide and 6% vinyl methyl ether.

4. The ternary random copolymer according to claim 1 or 2, characterized in that, The structural units of the ternary random copolymer consist of 42% ethylene, 50% carbon monoxide and 8% vinyl methyl ether.

5. The ternary random copolymer according to claim 1 or 2, characterized in that, The structural units of the ternary random copolymer consist of 45% ethylene, 50% carbon monoxide and 5% vinyl acetate.

6. The method for preparing the ternary random copolymer according to any one of claims 1-5, characterized in that, Includes the following steps: The tertiary random copolymer is obtained by mixing ethylene monomer, carbon monoxide monomer, and third monomer with a complexing catalyst and performing a copolymerization reaction. The complexing catalyst is selected from palladium-based or nickel-based catalysts.

7. The preparation method according to claim 6, characterized in that, The palladium-based catalyst is selected from complex catalysts formed by Pd(II) salts, bidentate phosphine ligands, and acid compounds; The nickel-based catalytic system is selected from complex catalysts formed by Ni(II) salts, bidentate phosphine ligands, and acid compounds.

8. The preparation method according to claim 6 or 7, characterized in that, The copolymerization reaction is carried out at a temperature of 50℃-90℃; The copolymerization reaction is carried out at a pressure of 4-15 MPa.

9. A high-barrier packaging material, characterized in that, This includes the ternary random copolymer according to any one of claims 1-5 or the ternary random copolymer prepared by the preparation method according to any one of claims 6-8; The oxygen permeability of the high-barrier packaging material is less than 10 cm³·mm / (m²·day·atm); The water contact angle of the high-barrier packaging material is greater than 75°.

10. The application of the high-barrier packaging material according to claim 9 in food packaging or pharmaceutical packaging.