High-barrier polyester and preparation method thereof

Abstract

The invention relates to high-barrier polyester and a preparation method thereof, and belongs to the field of polymers. The method comprises the following steps: soaking sodium-based MMT in mixed fatty acid, stirring, mixing with a conventional water bottle grade slice at a high speed, and finally melting and granulating the blended material by using double screws to obtain the high-barrier master batch. A known polyester product is mixed with the prepared high-barrier master batch, and the high-barrier polyester bottle is produced on an injection molding machine.

Description

Technical Field

[0001] The invention belongs to the field of polyester, and particularly relates to a high-barrier polyester and a preparation method thereof. Background Art

[0002] In recent years, with the continuous development of PET in the non-fiber field, the application of polyethylene terephthalate (PET) in the medical equipment and packaging industries has grown rapidly. It has stable chemical properties, is not easy to react chemically with the substances in the packaging, and is light, transparent, has excellent barrier properties, is non-toxic and not easy to break.

[0003] In order to extend the shelf life of PET packaging products and maintain the freshness of food to the greatest extent, high-barrier packaging materials are required. For example, pharmaceutical packaging has very high requirements for packaging materials: (1) blocking air, water vapor, microorganisms and other substances in the environment from invading the drug from the outside; (2) blocking volatile components, fat-soluble components in the drug, water vapor in the drug solution and other substances from escaping from the drug from the inside. Therefore, the barrier properties of pharmaceutical packaging materials play an important role in protecting the quality of the drugs in the package. Packaging with barrier properties that do not meet the requirements is likely to shorten the shelf life of the drug. For example: the compound amino acid injection packaged in an ordinary multi-layer co-extruded infusion bag changes color and deteriorates in a short period of time, due to the low ability of the packaging material to block oxygen; the biochemical freeze-dried preparation sealed with a halogenated butyl rubber plug (referred to as a freeze plug) for freeze drying for injection absorbs moisture and deliquesces in less than a year, due to the insufficient ability of the freeze plug to block water vapor.

[0004] The methods for preparing high barrier polyester mainly include copolymerization modification, blending modification, multi-layer composite modification, surface coating modification, nano-composite modification, etc. From the barrier mechanism, there are two types: passive barrier and active barrier. For example: PET is composited with montmorillonite, and there is a strong interaction between the two. The PET molecular chain can be intercalated between the montmorillonite layers, so that the movement of the molecular chain is restricted, and the lamellar structure of montmorillonite makes it difficult for gas to pass through, thereby improving the gas barrier of the composite material. It is a passive barrier, which is effective for both gas and water vapor. The other type is to add active oxygen absorbing additives to react with the oxygen entering the material to prevent the oxygen in the environment from acting on the sample. This method is only effective for oxygen.

[0005] In terms of passive barrier, the existing technology mainly uses PEG, quaternary ammonium salt or quaternary phosphonium salt to modify montmorillonite, and prepares PET composite materials through extruder blending to improve the mechanical properties and barrier properties of polyester. There are defects: quaternary ammonium salt modified montmorillonite, quaternary ammonium salt has poor thermal stability, high temperature and long time conditions will lead to poor product quality; PEG will reduce the heat resistance of PET. In terms of active barrier, unsaturated olefins such as polybutadiene and transition metal catalysts are introduced into PET materials and mixed in a physical way. The transition metal catalyst is added in the form of chloride, acetate, stearate or cyclopentaneate. This type of oxygen absorber uses the principle that olefins can be catalytically oxidized into epoxides to achieve the effect of oxygen absorption. The oxygen absorption effect is good, however, there are also some obvious defects: first, polybutadiene has low polarity, low solubility in the terephthalic acid-ethylene glycol system, poor compatibility, and is not easy to distribute evenly, thus affecting the oxygen absorption effect; second, the transition metal catalyst is added to the organic monomer in the form of a small molecule inorganic salt, and there are also problems of poor compatibility and uneven distribution. In addition, the dosage is large, the catalytic efficiency is not high, the metal ions are easy to migrate, and at the same time, excessive metal ion content will make the color value of the polymer high. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of insufficient barrier properties of existing PET, and to propose a high barrier polyester and its preparation method, using known polyester (including but not limited to: water bottle slices, oil bottles, PETG slices, etc., but requiring the above products to use Co2+ as a toner) and self-made high barrier masterbatch to produce high barrier polyester bottles. In addition to polyester bottles, this product is also suitable for films, sheets and other fields.

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

[0008] A high barrier polyester having an oxygen permeability of 5 to 9 ml / (pkg·day) and a water vapor permeability of 10 to 13 g / (m 2 ·day).

[0009] In the above-mentioned high-barrier polyester: the high-barrier polyester contains 1-10% of high-barrier masterbatch, and the preparation method of the high-barrier masterbatch is: soaking sodium-based MMT in mixed fatty acids, stirring for 1-3 hours at 40-60°C to obtain a mixture; mixing the mixture with conventional water bottle-grade chips at high speed, and finally using a twin-screw to melt and re-granulate the blended material to obtain a high-barrier masterbatch.

[0010] In the above-mentioned high barrier polyester, the mass ratio of sodium-based MMT to mixed fatty acids is 1:8-12.

[0011] In the above-mentioned high barrier polyester, the mixed fatty acid is a C20-C24 mixed fatty acid containing unsaturated C=C bonds; preferably, the mixed fatty acid is one or more of oleic acid, palmitoleic acid and linolenic acid.

[0012] A method for preparing the above-mentioned high barrier polyester comprises the following steps:

[0013] (1) Soaking sodium-based MMT in mixed fatty acids, stirring at 40 to 60° C. for 1 to 3 hours to obtain a mixture; mixing the mixture with conventional water bottle-grade chips at high speed, and finally melt-granulating the blended materials using a twin-screw extruder to obtain a high-barrier masterbatch;

[0014] (2) The polyester product is mixed with the high barrier masterbatch prepared in step (1) to produce a high barrier polyester bottle on an injection molding machine.

[0015] In the above preparation method: the content of high barrier masterbatch in the high barrier polyester bottle in step (2) is 1 to 10 wt%.

[0016] In the above preparation method, the mass ratio of sodium-based MMT to mixed fatty acids is 1:8-12.

[0017] In the above preparation method, the mixed fatty acid is a C20-C24 mixed fatty acid containing unsaturated C=C bonds; preferably, the mixed fatty acid is one or more of oleic acid, palmitoleic acid and linolenic acid.

[0018] In the technical solution of the present invention, the high barrier polyester is used in the preparation of polyester bottles, films and sheets.

[0019] Oxygen barrier performance test: The prepared product is tested for oxygen permeability using an isobaric oxygen permeability tester. The test conditions are: temperature 23°C, humidity: 50%.

[0020] Water vapor barrier performance test: Add the indicated volume of purified water to the sample, place it in a constant temperature and humidity chamber with a temperature accuracy of ±0.6°C and a test temperature of 38°C; set the relative humidity to 100% and the humidity accuracy of the constant temperature and humidity chamber to ±2%, place it for 24 hours, and test the volatility.

[0021] Barrier mechanism description: C containing unsaturated C=C bonds 20 -C 24 There are a lot of carboxyl groups in the molecular chain structure of mixed fatty acids, which can react with the alkali metal Na+ in the sodium montmorillonite silicate layer, so that the fatty acid molecular chain can effectively enter the MMT layer and increase the interlayer spacing, which makes it easier for the PET macromolecular chain to be inserted into the MMT layer structure. It was unexpectedly found during the experiment that the C 20 -C 24The interlayer spacing of MMT is greatly improved compared with conventional intercalating agents such as PTMEG and palmitic acid, thereby improving the passive barrier properties of the composite material. 20 -C 24 The mixed fatty acids are in a stable state in the masterbatch. When the bottle is made, the unsaturated C=C bonds can be used by the Co 2+ Catalyzes and consumes oxygen molecules that enter the bottle, playing an active barrier role.

[0022] The innovation of the solution of the present invention lies in:

[0023] (1) C containing unsaturated C=C bonds 20 -C 24 The mixed fatty acids can intercalate with sodium-based MMT, promoting the easier insertion of PET macromolecular chains into the MMT sheet structure, thereby improving the passive barrier properties of the composite material.

[0024] (2) Existing deoxidizers contain both deoxidizing active structures and autocatalysts, and require vacuum packaging to maintain stability. The high-barrier masterbatch of the present invention only contains C=C bond active groups that can be oxidized and is in a stable state before use; only after being prepared into packaging bottles with known polyester products, will the autocatalytic reaction occur.

[0025] (3) The C of the unsaturated C=C bond in the high barrier product 20 -C 24 The mixed fatty acid content of the polyester accounts for 0.25-0.5% of the total amount of the polyester; the Si element content accounts for 0.005-0.01% of the total amount of the polyester; and the aluminum element content accounts for 0.001-0.003% of the total amount of the polyester.

[0026] The invention uses a known polyester product and a self-made high-barrier masterbatch to prepare a high-barrier polyester bottle, which solves the problem of insufficient barrier performance of conventional polyester bottles in the prior art. After the known polyester product is added with the high-barrier masterbatch, the oxygen barrier performance is improved by more than 5 times; the water vapor transmission rate is reduced by 50%, meeting the demand for high-barrier polyester products. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0028] (1) Preparation of sodium-based MMT / PET masterbatch

[0029] Sodium-based MMT is mixed at a weight ratio of 0.5% with conventional water bottle-grade chips at high speed, and finally the blended materials are melt-granulated by a twin-screw extruder to obtain sodium-based MMT / PET masterbatch, which is recorded as M masterbatch.

[0030] (2) Preparation of high barrier masterbatch

[0031] Sodium-based MMT was soaked in mixed fatty acids (oleic acid accounted for 35% of the mass ratio of the mixed acid, and palmitic acid accounted for 65% of the mass ratio of the mixed acid) at a weight ratio of 5%, stirred at 50°C for 2 hours, and the mixture of sodium-based MMT and mixed fatty acids was mixed at a ratio of 10% with conventional water bottle-grade chips (required to use red / blue coloring agent) at high speed, and finally the blended materials were melted and regranulated using a twin screw to obtain a high barrier masterbatch, recorded as G masterbatch. The interlayer spacing of the prepared intercalated MMT was tested by X-diffraction, and the test values ​​are shown in Table 1.

[0032] Table 1 Interlayer spacing of intercalated MMT prepared by different intercalation agents

[0033] Intercalant D(nm) Sodium MMT 1.54 PTMEG-MMT 2.18 Palmitic acid-MMT 2.14 C20-C24-MMT with C=C bond 4.26

[0034] Preparation of high barrier polyester bottles

[0035] Comparative Example 1: Yihua water bottle material BG80, carbonated bottle material BG85 and PETG product BG804 were dried at 160°C for 4 hours, and then injection molded and blown to produce 1.25L conventional polyester bottles. The oxygen permeability and water vapor permeability of different polyester bottles were tested.

[0036] Comparative Example 2: First, Yihua water bottle material BG80 was dried at 160℃ for 4 hours, and then M masterbatch was added at a ratio of 5%, mixed evenly, and fed into the screw of the injection molding machine to make a 40g bottle blank; then the bottle flakes were blown into high-barrier bottles. The oxygen permeability and water vapor permeability were tested.

[0037] Embodiment 1:

[0038] First, Yihua BG80 water bottle material (http: / / hgxs.sinopec.com / ) was dried at 160℃ for 4 hours, and then G masterbatch was added at a ratio of 3%. After mixing evenly, the mixture was fed into the screw of the injection molding machine to form a 40g bottle blank; the bottle flakes were then blown into high-barrier bottles. The oxygen permeability and water vapor permeability were tested.

[0039] Embodiment 2:

[0040] First, Yihua BG80 water bottle material was dried at 160℃ for 4 hours, then G masterbatch was added at a ratio of 5%, mixed evenly and fed into the injection molding machine screw to make 40g bottle blanks; then the bottle pieces were blown into high-barrier bottles. The oxygen permeability and water vapor permeability were tested.

[0041] Embodiment 3:

[0042] First, Yihua BG85 water bottle material was dried at 160℃ for 4 hours, then G masterbatch was added at a ratio of 5%, mixed evenly and fed into the screw of the injection molding machine to make a 40g bottle blank; then the bottle flakes were blown into high-barrier bottles. The oxygen permeability and water vapor permeability were tested.

[0043] Embodiment 4:

[0044] First, Yihua BG804 product was dried at 160℃ for 4 hours, then G masterbatch was added at a ratio of 5%, mixed evenly and fed into the screw of the injection molding machine to make a 40g bottle blank; then the bottle flakes were blown into high-barrier bottles. The oxygen permeability and water vapor permeability were tested.

[0045] Table 2 Oxygen and water vapor transmission rates of different polyester bottles

[0046] Sample bottles Oxygen permeability, ml / (pkg·day) <![CDATA[Water vapor transmission rate, g / (m 2 ·day)]]> Comparative Example 1-BG80 68 27.2 Comparative Example 1-BG85 55 24.2 Comparative Example 1-BG804 60 25.2 Comparative Example 2 48 12.8 Example 1 8.9 11.8 Example 2 7.6 10.5 Example 3 8.2 11.6 Example 4 9.0 12.5

Claims

1. A high barrier polyester, characterized in that: The oxygen permeability of the high barrier polyester is 5-9 ml / (pkg·day), and the water vapor permeability is 10-13 g / (m 2 ·day).

2. The high barrier polyester according to claim 1, characterized in that: The high-barrier polyester contains 1-10% of high-barrier masterbatch. The preparation method of the high-barrier masterbatch is as follows: soaking sodium-based MMT in mixed fatty acids, stirring for 1-3 hours at 40-60° C. to obtain a mixture; mixing the mixture with conventional water bottle-grade chips at high speed, and finally using a twin-screw extruder to melt and re-granulate the blended materials to obtain the high-barrier masterbatch.

3. The high barrier polyester according to claim 2, characterized in that: The mass ratio of sodium-based MMT to mixed fatty acids is 1:8-12.

4. The high barrier polyester according to claim 3, characterized in that: The mixed fatty acid is a C20-C24 mixed fatty acid containing unsaturated C=C bonds; preferably, the mixed fatty acid is one or more of oleic acid, palmitoleic acid and linolenic acid.

5. A method for preparing the high barrier polyester according to claim 1, characterized in that: The method comprises the following steps: (1) Soaking sodium-based MMT in mixed fatty acids and stirring at 40 to 60° C. for 1 to 3 hours to obtain a mixture; mixing the mixture with conventional water bottle-grade chips at high speed, and finally melt-granulating the blended materials using a twin-screw extruder to obtain a high-barrier masterbatch; (2) The polyester product is mixed with the high barrier masterbatch prepared in step (1) to produce a high barrier polyester bottle on an injection molding machine.

6. The method according to claim 5, characterized in that: The content of high barrier masterbatch in the high barrier polyester bottle in step (2) is 1 to 10 wt%.

7. The method according to claim 5, characterized in that: The mass ratio of sodium-based MMT to mixed fatty acids is 1:8-12.

8. The method according to claim 5, characterized in that: The mixed fatty acid is a C20-C24 mixed fatty acid containing unsaturated C=C bonds; preferably, the mixed fatty acid is one or more of oleic acid, palmitoleic acid and linolenic acid.

9. Use of the high barrier polyester according to claim 1 in the preparation of polyester bottles, films and sheets.