CN114106535A

CN114106535A - Degradable pearlized film and preparation method thereof

Info

Publication number: CN114106535A
Application number: CN202111466094.8A
Authority: CN
Inventors: 冯羽风; 陈志平; 彭文理; 陆春立; 黄静; 戴展鹏
Original assignee: Guilin Grace Technology Co ltd
Current assignee: Guilin Grace Technology Co ltd
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2022-03-01

Abstract

The invention discloses a degradable pearlized film and a preparation method thereof, wherein the degradable pearlized film comprises a core layer, and the core layer contains the following components: 100 parts of degradable resin, which consists of 50-80 parts of PLA and the balance of PBAT; 0-10 parts of titanium dioxide; 0-1.5 parts of an antioxidant; 0-1.5 parts of a nucleating agent; 0-2.0 parts of a chain extender; during preparation, firstly obtaining a single-layer thick sheet or a multi-layer co-extruded thick sheet including a core layer, and then stretching the obtained thick sheet to prepare the degradable pearlized film, wherein the stretching is carried out at the temperature of 60-90 ℃, and the total stretching ratio is more than 6 times. The pearlized film disclosed by the invention has a pearlized effect, is biodegradable, has good tensile strength and elongation at break, and is simple in preparation method.

Description

Degradable pearlized film and preparation method thereof

Technical Field

The invention relates to a pearlized film, in particular to a degradable pearlized film and a preparation method thereof.

Background

The pearlized film on the market at present is mainly formed by taking polypropylene (PP) resin as a raw material, adding inorganic fillers such as calcium carbonate and pearlescent pigment, mixing and then carrying out biaxial stretching, countless uniform cavities can be formed by stretching, when light enters the cavities, interference occurs, and multi-level interference light finally forms a pearlized effect. In the production process, various additives and carrier PP are usually prepared into pearly-luster master batch, and then the pearly-luster master batch is added into a production line in the form of master batch to prepare the BOPP pearly-luster film. The white and opaque BOPP pearlized film has the texture like silk, soft and beautiful pearl luster, good light shading property and excellent smoothness and gas barrier property, and is widely applied to the direct packaging of dry fruits, ice cream, candies, high-grade soaps, gifts and the like; it is also a good printing substrate, and it is not necessary to perform full-page priming when performing surface printing, so it is very popular. The pearl film produced at home and abroad mostly adopts a three-layer extrusion process and a five-layer process, wherein the three-layer film structure is ABC (single-sided heat sealing type) or ABA (double-sided heat sealing type), and the five-layer film structure is ABCBD type or ABCBA type. Each layer is composed of polypropylene resin and different additives, and the function of each layer is determined by the type of polypropylene and the type of additives.

Since PP is a non-degradable material, its use poses serious environmental problems and does not meet the requirements of sustainable development. In recent years, with the attention of people on environmental protection, biodegradable materials have been rapidly developed, and especially polylactic acid (PLA) is the most important. PLA is a bio-based polymer, is derived from renewable natural resources, has good biocompatibility, mechanical strength and transparency, has the outstanding characteristics of sufficient renewable raw material sources and the like, is considered as biodegradable plastic with the greatest development prospect, and is mainly applied to the fields of biological medicines and food packaging at present. Such as: the invention patent with publication number CN102453319A provides a polylactic acid biaxially oriented frosted film, which comprises the following blended components: 100 parts of polylactic resin and 0.2-10 parts of modified auxiliary agent; the components are melted, blended, granulated, cast and tableted, and then are stretched in two directions at a higher temperature to prepare the polylactic acid two-way stretching frosted film. The film has pearl luster and frosted texture, the light transmittance is more than or equal to 93 percent, the haze is more than or equal to 70 percent, the surface glossiness is less than or equal to 10, and the film can be used for packaging and film pasting. However, the modification auxiliary agents added in the formula are all oily substances with low molecular weight, are easy to precipitate from the interior of the film to the surface of the film, and have the hidden danger of polluting the contacted articles in the use process of the film.

Although PLA has high mechanical strength, it is brittle and has low impact strength and melt strength, which limits its application and development. In order to avoid these disadvantages and to take advantage of them, many researchers have conducted toughening modification studies on polylactic acid. The poly (terephthalic acid) -butylene adipate (PBAT) is completely biodegradable aliphatic-aromatic copolyester, has higher elongation at break of more than 700 percent, good flexibility and processability, is widely applied to plastic flexible packaging at present, but the source of the PBAT is still petrochemical engineering, consumes petroleum resources in the production and processing processes and generates more carbon dioxide emission. The film for packaging prepared by compounding the PBAT and the PLA not only can combine the advantages of the flexibility of the PBAT and the strength of the PLA, but also can improve the biomass source of the composite material and reduce the use of petroleum resources. However, the solubility parameters of PBAT and PLA are very different, and directly blending the two materials can cause phase separation of the prepared composite material, so that the cost and compatibility problems need to be solved firstly when the PBAT and PLA are compounded to prepare the film for packaging at present.

The invention patent with publication number CN112976735A discloses a multilayer composite full-biodegradable plastic film, which comprises at least one reinforcing layer, at least one substrate layer, and a transition compatible layer between the adjacent reinforcing layer and the substrate layer, wherein the substrate layer comprises the following components: 100 parts of full-biodegradable resin and 10-30 parts of auxiliary agent, wherein the reinforced layer comprises the following components: 100 parts of full-biodegradable resin, 10-30 parts of an auxiliary agent and 80-100 parts of modified calcium carbonate; the components of the transition compatible layer include: 50 parts of full biodegradable resin of the enhancement layer and 50 parts of full biodegradable resin of the matrix layer, wherein the full biodegradable resin of the enhancement layer and the full biodegradable resin of the matrix layer are the same or different. The biodegradable resin comprises one or more of polybutylene succinate (PBS), polylactic acid (PLA), Polyhydroxyalkanoate (PHA) and polybutylene adipate-terephthalate (PBAT); the auxiliary agent comprises one or a combination of a plasticizer, a nucleating agent, a chain extender, an opening agent, a lubricant, an anti-blocking agent, an antistatic agent, a light absorber and an antioxidant. On one hand, the invention fully utilizes the performance of different biodegradable resins with larger performance difference to compound and form a film, and improves the mechanical performance of the composite film through the improvement of the compatibility of the transition compatible layer and the adjacent layer; on the other hand, the modified calcium carbonate has better compatibility with biodegradable resin, especially PBAT resin, and the treated calcium carbonate powder is chemically bonded with the resin, so that the modified calcium carbonate has good interface binding force, and the mechanical property of the biodegradable film is greatly improved. Therefore, the film disclosed by the invention has biodegradability, high tear strength, high tensile strength and high elongation at break, and can be widely applied to the fields of various food packages, medical products, environment-friendly labels, advertisements, various environment-friendly products and the like. However, the modification treatment step of the calcium carbonate of the present invention is complicated, and the obtained film does not have a pearl effect.

Through retrieval, no report related to the preparation of the pearlized film by directly compounding PBAT and PLA is found at present.

Disclosure of Invention

The invention aims to provide a degradable pearlized film with pearlized effect and good tensile strength and elongation at break and a preparation method thereof.

In order to solve the technical problems, the invention adopts the following technical scheme:

a degradable pearlescent film, comprising a core layer, the core layer comprising the following components:

100 parts of degradable resin, which consists of 50-80 parts of PLA and the balance of PBAT;

0-10 parts of titanium dioxide;

0-1.5 parts of an antioxidant;

0-1.5 parts of a nucleating agent;

0-2.0 parts of a chain extender;

during preparation, firstly obtaining a single-layer thick sheet or a multi-layer co-extruded thick sheet including a core layer, and then stretching the obtained thick sheet to prepare the degradable pearlized film, wherein the stretching is carried out at the temperature of 60-90 ℃, and the total stretching ratio is more than 6 times.

The degradable pearlized film can be of a one-layer structure or a three-layer structure. When the structure is a layer, the pearlized film only comprises the core layer; when having a three-layer structure, the pearlescent film includes a core layer, an upper surface layer disposed on an upper surface of the core layer, and a lower surface layer disposed on a lower surface of the core layer.

In the core layer, the components of titanium dioxide, antioxidant, nucleating agent and chain extender can be added or not added according to the performance requirement of the obtained film, wherein the titanium dioxide is added to facilitate the reduction of the light transmittance of the obtained film, the antioxidant and the chain extender are added to facilitate the stability of the obtained film, the nucleating agent is added to facilitate the crystallization of PLA, and the strength of the obtained film is improved.

Optionally, the core layer contains the following components:

3-10 parts of titanium dioxide;

0-1.5 parts of an antioxidant;

0-1.5 parts of a nucleating agent;

0-2.0 parts of a chain extender.

It is further preferred that the core layer contains the following components:

3-10 parts of titanium dioxide;

0.5-1.5 parts of antioxidant;

0.3-1.5 parts of nucleating agent;

0.5-2.0 parts of a chain extender.

The antioxidant, nucleating agent and chain extender are all conventional choices in the prior art. Specifically, the antioxidant can be a phosphite antioxidant and/or a hindered phenol antioxidant, wherein the phosphite antioxidant can be one or a combination of more than two selected from antioxidant 168, antioxidant 618, antioxidant 626 and the like, and the hindered phenol antioxidant can be one or a combination of more than two selected from antioxidant 1010, antioxidant 1076 and antioxidant 1098; the nucleating agent can be one or the combination of more than two of hydrazide compounds, talcum powder, silicon dioxide and calcium carbonate; the chain extender is an epoxy functional group type chain extender, such as ADR4300, ADR4400, ADR4468C or ADR-4370S and the like.

The upper surface layer at least comprises the following components: the degradable resin is 100 parts, the degradable resin is composed of 50-80 parts of PLA and the balance of PBAT, whether some components which are conventional in the field, such as an antioxidant and/or a chain extender, are added or not can be determined according to the performance requirements of the obtained film, and the specific selection of the antioxidant and the chain extender is as described above. The addition amounts of the antioxidant and the chain extender may be 0 to 1.5 parts and 0 to 2.0 parts, respectively, based on 100 parts of the degradable resin.

The lower surface layer contains the following components: 100 parts of degradable resin, which consists of 50-80 parts of PLA and the balance of PBAT, and whether some components which are conventional in the field, such as an antioxidant and/or a chain extender, are added or not can be determined according to the performance requirements of the obtained film, wherein the specific selection of the antioxidant and the chain extender is as described above. The addition amounts of the antioxidant and the chain extender may be 0 to 1.5 parts and 0 to 2.0 parts, respectively, based on 100 parts of the degradable resin.

When the degradable pearlized film is of a three-layer structure, the proportions of the degradable resins in the core layer, the upper surface layer and the lower surface layer can be the same or different.

In experiments, the applicant finds that the composition and the matching of the degradable resin and the stretching process during preparation have important influence on whether the obtained film has the pearlescent effect. In a PLA/PBAT system, the proportion of PBAT is only modified to be more than 50 percent of the total amount of the resin, and the prepared film has no pearlescent effect; and modifying the proportion of PBAT to less than 50% of the total resin does not have a pearl effect; the film prepared by the same stretching process of other degradable material blending systems such as PLA/PHA (polyhydroxylated fatty acid), PLA/PPC (polypropylene carbonate), PBAT/PHA, PBAT/PPC, PHA/PPC, PLA/PBS (polybutylene succinate), PBAT/PBS and the like has no pearlescent effect. Therefore, the film has a pearly luster effect only when the degradable resin consists of 50-80 parts of PLA and 20-50 parts of PBAT, the stretching is carried out at 60-90 ℃ and the total stretching magnification is more than 6 times, and the pearly luster effect is not achieved when the composition and the proportion of the degradable resin are not adopted or the stretching process is not in the limited range.

When the degradable pearlized film is prepared, the stretching can be single longitudinal stretching or single transverse stretching, and can also be longitudinal and transverse sequential stretching or longitudinal and transverse synchronous stretching. The total stretching ratio is preferably controlled to be 6 to 20 times, and more preferably 2 × 3 to 4 × 5 times by sequential longitudinal and transverse stretching or simultaneous longitudinal and transverse stretching. When the stretching is carried out in a single longitudinal direction or a single transverse direction, the total stretching ratio is preferably controlled to be 6 to 8.

The preparation method of the degradable pearlized film comprises the following steps: the components are blended according to a formula to obtain a single-layer thick sheet or a multi-layer co-extruded thick sheet including a core layer, and the obtained thick sheet is stretched to prepare the degradable pearlized film, wherein the stretching is carried out at the temperature of 60-90 ℃, and the total stretching ratio is more than 6 times.

The operation of obtaining the single-layer thick sheet or the multi-layer co-extruded thick sheet including the core layer in the preparation method is the same as that of the prior art, and specifically, the components of the single-layer thick sheet or the multi-layer co-extruded thick sheet including the core layer can be respectively fed into respective mixing hoppers according to the formula of each layer to be uniformly mixed, then respectively fed into respective screw extruders, melted and plasticized at 175-200 ℃, then fed into respective independent flow channels of a die head, and cast sheet at 5-40 ℃ to obtain the single-layer thick sheet or the multi-layer co-extruded thick sheet including the core layer. The resulting slabs were subjected to the stretching process as described previously. After stretching, conventional post-treatment is required, such as heat setting operation, and particularly, the stretching can be carried out for 2-20 s at 100-120 ℃.

Compared with the prior art, the degradable pearlized film with pearlized effect and good tensile strength and elongation at break is obtained by adopting a PLA/PBAT system with a specific ratio and combining a specific stretching process, and the preparation method is simple and easy to operate.

Detailed Description

In order to better explain the technical solution of the present invention, the present invention is further described in detail with reference to the following examples, but the embodiments of the present invention are not limited thereto.

The parts referred to in the following examples and comparative examples are parts by weight.

Examples 1 to 12 and comparative example

The raw materials of the components of each layer are respectively sent into respective mixing hoppers according to the formula shown in the table 1 to be uniformly mixed according to the set proportion, then the raw materials are respectively sent into respective screw extruders, the raw materials are melted and plasticized at 175-200 ℃, then the raw materials enter into respective independent flow channels of a die head, casting sheets are cast at 5-40 ℃ to obtain single-layer thick sheets or multi-layer co-extruded thick sheets comprising a core layer, the obtained thick sheets are stretched and heat-set to obtain the pearlized film with the thickness of 25 mu m, the stretching and heat-set process and the thickness of the ABC three-layer film are shown in the table 2, and the stretching and heat-set process and the thickness of the ABC three-layer film of the comparative examples 3-9 are the same as the example 4.

TABLE 1 example and comparative example formulations

TABLE 2 stretch film-making Process and film thickness of each layer

The films obtained in the above examples and comparative examples were observed for their appearance having pearl effect and their properties were examined, and the results are shown in Table 3.

TABLE 3 film Properties

The films obtained in the embodiments 1 to 12 have the pearlescent effect, wherein the films obtained in the embodiments 1 to 7 have small light transmittance and large haze, the films have excellent pearlescent effect and high film surface gloss, and the films obtained in the embodiments 8 to 9 have high longitudinal strength and low transverse strength due to the fact that only longitudinal stretching is performed, the transverse and longitudinal performance difference is large, and the surface gloss is low. While example 11 has high gloss and a pearlescent effect, but also has high light transmittance; example 12 had low gloss despite low light transmittance. Comparative example 1 was prepared by blow molding and had no pearlescent effect, and comparative example 2 had a 5.5-fold uniaxial stretch and no pearlescent effect. In comparative example 3, the PLA content was 45 parts, the PBAT content was 55 parts, and the PBAT in the blend system had a dominant effect on performance, and since the PBAT molecular chain had very good flexibility, the strength of the prepared film was low, the surface gloss was also significantly low, and the film did not have a pearlescent effect. Comparative examples 4 and 7 could not be prepared by the stretching method, and comparative examples 5 and 6 and comparative examples 8 and 9 could be prepared by the biaxial stretching, but the prepared films did not have the pearl effect.

Claims

1. The degradable pearlized film is characterized by comprising a core layer, wherein the core layer contains the following components:

0-10 parts of titanium dioxide;

0-1.5 parts of an antioxidant;

0-1.5 parts of a nucleating agent;

0-2.0 parts of a chain extender;

2. The degradable pearlescent film of claim 1, further comprising an upper surface layer disposed on the upper surface of the core layer and a lower surface layer disposed on the lower surface of the core layer, wherein:

the upper surface layer contains the following components: 100 parts of degradable resin, which consists of 50-80 parts of PLA and the balance of PBAT;

the lower surface layer contains the following components: 100 parts of degradable resin, which consists of 50-80 parts of PLA and the balance of PBAT.

3. The degradable pearlescent film according to claim 1 or 2, wherein the total stretching magnification is 6 to 20 times.

4. The degradable pearlescent film according to claim 1 or 2, wherein the core layer comprises the following components:

3-10 parts of titanium dioxide;

0-1.5 parts of an antioxidant;

0-1.5 parts of a nucleating agent;

0-2.0 parts of a chain extender.

5. The degradable pearlescent film according to claim 1 or 2, wherein the core layer comprises the following components:

3-10 parts of titanium dioxide;

0.5-1.5 parts of antioxidant;

0.3-1.5 parts of nucleating agent;

0.5-2.0 parts of a chain extender.

6. The degradable pearlescent film according to claim 1 or 2, wherein the antioxidant is a phosphite antioxidant and/or a hindered phenol antioxidant.

7. The degradable pearlescent film according to claim 1 or 2, wherein the nucleating agent is one or a combination of two or more selected from the group consisting of hydrazide compounds, talc, silica and calcium carbonate.

8. The degradable pearlescent film according to claim 1 or 2, wherein the chain extender is an epoxy functional group type chain extender.

9. The method for preparing the degradable pearlized film as claimed in claim 1, which is characterized in that the components are blended according to a formula to obtain a single-layer thick sheet or a multi-layer co-extruded thick sheet including a core layer, and the obtained thick sheet is stretched to obtain the degradable pearlized film, wherein the stretching is carried out at the temperature of 60-90 ℃, and the total stretching ratio is more than 6 times.

10. The method according to claim 9, wherein the total draw ratio is 6 to 20 times.