阅读说明：本技术 一种聚乳酸薄膜表面食品级阻氧涂层及其制备方法 (Food-grade oxygen-barrier coating on surface of polylactic acid film and preparation method thereof ) 是由 张涛 方兰兰 王家俊 于 2020-06-29 设计创作，主要内容包括：本发明公开了一种聚乳酸薄膜表面食品级阻氧涂层及其制备方法。在聚乳酸薄膜两个表面覆有至少一层由魔芋葡甘聚糖层和植酸层形成的组合涂层,魔芋葡甘聚糖层和植酸层分别为内层和外层；清洗聚乳酸薄膜,烘干、剪切后备用；将聚乳酸薄膜在氢氧化钠和无水乙醇混合溶液中浸泡,漂洗,烘干,得到碱化处理的聚乳酸薄膜；制备魔芋葡甘聚糖溶液；制备植酸溶液；将碱化处理的聚乳酸薄膜在魔芋葡甘聚糖溶液中浸泡,漂洗,烘干,在植酸溶液中浸泡,漂洗,烘干,重复若干次,得到聚乳酸薄膜表面食品级阻氧涂层。本发明的制备方法简便快捷,所得的涂层具有阻氧功能,在食品包装薄膜领域具有广阔的应用前景。(The invention discloses a food-grade oxygen-barrier coating on the surface of a polylactic acid film and a preparation method thereof. At least one combined coating layer formed by a konjac glucomannan layer and a phytic acid layer is coated on the two surfaces of the polylactic acid film, and the konjac glucomannan layer and the phytic acid layer are respectively an inner layer and an outer layer; cleaning the polylactic acid film, drying and shearing for later use; soaking the polylactic acid film in a mixed solution of sodium hydroxide and absolute ethyl alcohol, rinsing and drying to obtain an alkalized polylactic acid film; preparing konjac glucomannan solution; preparing a phytic acid solution; soaking the alkalized polylactic acid film in konjac glucomannan solution, rinsing, drying, soaking in phytic acid solution, rinsing, drying, and repeating for several times to obtain the food-grade oxygen barrier coating on the surface of the polylactic acid film. The preparation method is simple, convenient and quick, and the obtained coating has an oxygen barrier function and has wide application prospect in the field of food packaging films.)

1. A polylactic acid film surface food level hinders oxygen coating which characterized in that: at least one combined coating layer formed by a konjac glucomannan layer and a phytic acid layer is covered on the two surfaces of the polylactic acid film, and the konjac glucomannan layer and the phytic acid layer in the combined coating layer are respectively used as an inner layer and an outer layer.

2. The polylactic acid film surface food grade oxygen barrier coating according to claim 1, characterized in that: the combined coating is only composed of a konjac glucomannan layer and a phytic acid layer, and the konjac glucomannan layer and the phytic acid layer are respectively formed by adhesion of a konjac glucomannan solution and a phytic acid solution.

3. A preparation method of a food-grade oxygen barrier coating on the surface of a polylactic acid film is characterized by comprising the following steps:

(1) washing the polylactic acid film with deionized water and absolute ethyl alcohol, drying and shearing for later use;

(2) fully soaking the standby polylactic acid film obtained in the step (1) in a mixed solution of sodium hydroxide and absolute ethyl alcohol, rinsing and drying to obtain an alkalized polylactic acid film;

(3) adding konjac glucomannan into deionized water, and stirring until the konjac glucomannan is completely dissolved to obtain a konjac glucomannan solution;

(4) adding phytic acid into deionized water, and stirring until the phytic acid is completely dissolved to obtain a phytic acid solution;

(5) fully soaking the alkalized polylactic acid film obtained in the step (2) in a sufficient amount of konjac glucomannan solution, rinsing in deionized water, and drying; then fully soaking in sufficient phytic acid solution, rinsing in deionized water, and drying;

(6) and (5) repeating the step (5) for a plurality of times to obtain the food-grade oxygen barrier coating on the surface of the polylactic acid film.

4. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: the mixed solution of sodium hydroxide and absolute ethyl alcohol in the step (2) is a solution in which a 1 wt% sodium hydroxide solution and absolute ethyl alcohol are mixed according to the same volume.

5. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: the time for fully soaking in the step (2) is 1-2 h.

6. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: the concentration of the konjac glucomannan solution in the step (3) is 0.5 wt%.

7. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: the concentration of the phytic acid solution in the step (4) is 0.5 wt%.

8. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: the time for fully soaking in the step (5) is at least 1 min.

9. The preparation method of the polylactic acid film surface food grade oxygen barrier coating according to claim 3, characterized in that: in the step (6), the number of times of repeating the step (5) is at least 1, and the drying is carried out again after each time.

Technical Field

The invention relates to a coating and a preparation method thereof, in particular to a food-grade oxygen-barrier coating on the surface of a polylactic acid film and a preparation method thereof.

Background

Compared with the traditional high-barrier packaging film, the polylactic acid film has lower oxygen barrier property, and the application of the polylactic acid film in products such as food or medicines with higher requirements on the oxygen barrier property is limited. One effective approach to solving such problems is to build oxygen barrier coatings based on a layer-by-layer assembly process. However, the affinity of the surface of the polylactic acid film to the coating raw material is weak, which is not favorable for coating deposition, and more assembly layers are often required to achieve better oxygen barrier effect. Moreover, most coating materials do not address safety concerns when in contact with food. If an effective polylactic acid film surface treatment method and a coating construction material which is easy to deposit are adopted, the number of layers assembled layer by layer is reduced, and the safety of the coating raw material is considered, so that the polylactic acid film is valuable for prolonging the shelf life of food or medicines and industrial application.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention aims to provide a food-grade oxygen barrier coating on the surface of a polylactic acid film and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention for solving the technical problems is as follows:

a food-grade oxygen barrier coating on the surface of a polylactic acid film: at least one combined coating layer formed by a konjac glucomannan layer and a phytic acid layer is covered on the two surfaces of the polylactic acid film, and the konjac glucomannan layer and the phytic acid layer in the combined coating layer are respectively used as an inner layer and an outer layer.

The combined coating is only composed of a konjac glucomannan layer and a phytic acid layer, and the konjac glucomannan layer and the phytic acid layer are respectively formed by adhesion of a konjac glucomannan solution and a phytic acid solution.

Secondly, a preparation method of the food-grade oxygen barrier coating on the surface of the polylactic acid film comprises the following steps:

(1) washing the polylactic acid film with deionized water and absolute ethyl alcohol, drying and shearing for later use;

(2) fully soaking the standby polylactic acid film obtained in the step (1) in a mixed solution of sodium hydroxide and absolute ethyl alcohol, rinsing and drying to obtain an alkalized polylactic acid film;

(3) adding konjac glucomannan into deionized water, and stirring until the konjac glucomannan is completely dissolved to obtain a konjac glucomannan solution;

(4) adding phytic acid into deionized water, and stirring until the phytic acid is completely dissolved to obtain a phytic acid solution;

(5) fully soaking the alkalized polylactic acid film obtained in the step (2) in a sufficient amount of konjac glucomannan solution, rinsing in deionized water, and drying; then fully soaking in sufficient phytic acid solution, rinsing in deionized water, and drying;

(6) and (5) repeating the step (5) for a plurality of times to obtain the food-grade oxygen barrier coating on the surface of the polylactic acid film.

The mixed solution of sodium hydroxide and absolute ethyl alcohol in the step (2) is a solution in which a 1 wt% sodium hydroxide solution and absolute ethyl alcohol are mixed according to the same volume.

The time for fully soaking in the step (2) is 1-2 h.

The concentration of the konjac glucomannan solution in the step (3) is 0.5 wt%.

The concentration of the phytic acid solution in the step (4) is 0.5 wt%.

The time for fully soaking in the step (5) is at least 1 min.

In the step (6), the number of times of repeating the step (5) is at least 1, and drying is required to be carried out again after each time.

The invention has the beneficial effects that:

the preparation method is simple, convenient and quick, and the surface of the polylactic acid film is soaked in a mixed solution of sodium hydroxide and absolute ethyl alcohol; the coating raw material has good affinity with the surface of the polylactic acid film, is a food-grade material and has good safety when contacting with food.

The coating obtained by the invention has excellent oxygen barrier function under the condition of less layers, and has wide application prospect in the field of food packaging films. The method of the invention is also suitable for polyethylene terephthalate films, polypropylene films, polyethylene films or paper, and the obtained coating has an anti-oxidation function under the condition of less layers.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

In the embodiment of the invention, the polylactic acid film, the konjac glucomannan (not less than 95 percent) and the phytic acid (aqueous solution with the concentration of 50 weight percent) are commercially available materials.

The oxygen barrier performance test method comprises the following steps: a MOCON OX-tran 2/21 gas permeameter was used, temperature 23 ℃, humidity 50% RH.