Heat-resistant degradable film and preparation method thereof

Abstract

The invention relates to the technical field of degradable films, and discloses a heat-resistant degradable film and a preparation method thereof.The degradable film sequentially comprises a PBAT film layer, a PBAT / hollow glass bead composite film layer, a PBAT / PBS composite film layer and a PBAT / bamboo powder composite film layer, and all the layers are subjected to film blowing and hot press molding. According to the invention, a multi-layer film compounding form is adopted, the bamboo powder increases the strength modulus and heat resistance of the film, the glass beads can enhance the heat insulation property of the material, the PBS and PBAT are mixed to increase the heat deformation temperature of the material, and after the four layers of films are compounded, the mechanical property is enhanced, the flexibility of the material is maintained, and the heat resistance temperature of the material is also increased. Therefore, the thin film can serve as a package for containing high-temperature food.

Description

Technical Field

[0001] The invention relates to the technical field of degradable films, and in particular to a heat-resistant degradable film and a preparation method thereof. Background Art

[0002] The current take-out industry is developing rapidly, and the demand for take-out packaging is also increasing. With the implementation and promotion of plastic bans in various places, the market for degradable take-out packaging has also become hot. In the field of degradable materials, the only resin that can currently be used to produce degradable film bags on a large scale is PBAT. However, although PBAT has good ductility and processability, its heat resistance temperature is around 50°C, which is far from enough for soups, stews, and water mixtures that have just come out of the pot.

[0003] At present, the main means of modifying PBAT film bags is to blend resins with higher heat deformation temperatures or add other fillers. As a degradable material, there are not many resins that can be used for blending, and polylactic acid is generally chosen. However, polylactic acid itself is very brittle, so adding a large amount to PBAT to increase the heat deformation temperature will cause the material to become brittle and unable to be blown into film. At the same time, the melting points of polylactic acid and PBAT are quite different, and the processing conditions are not very good.

[0004] Another way is to add fillers, usually calcium carbonate powder or starch. However, due to the requirements of the film blowing process, the filling amount can only be up to 30-40%, and the heat resistance temperature can reach up to 75-80℃.

[0005] CN112251002 A discloses a PBS degradable packaging material with excellent toughness and heat resistance and a preparation method thereof. The PBS degradable packaging material with excellent toughness and heat resistance comprises raw materials including PBS, PBST, PBAT, a compatibilizer, a nucleating agent, a heat-resistant agent, a plasticizer, and an inorganic filler. The raw materials are mixed evenly, granulated, and blown into a film to obtain the PBS degradable packaging material with excellent toughness and heat resistance. The product made from the inexpensive PBS has excellent toughness and heat resistance, is completely biodegradable, and is a good substitute for existing non-degradable packaging bags. The preparation method of the PBS degradable packaging material with excellent toughness and heat resistance is simple, the production process is easy to implement, and it is environmentally friendly and economical. However, the above method has a complex formula, and the mechanical strength of the product has also been publicly discussed.

[0006] CN 208199305 U discloses a degradable high-mineral express bag, comprising an upper film and a lower film heat-sealed with the upper film, wherein the upper film or the lower film comprises a PBAT plastic layer, a PLA plastic layer, and a high-mineral PE plastic layer from the outside to the inside. The express bag film is composited with a plurality of degradable plastics, and the degradation speed is increased as much as possible while providing degradable performance, thereby improving the environmental protection of the express bag. The outermost PBAT layer has good toughness, heat resistance, and impact resistance, and protects the contents from being affected by the external environment. The PLA layer is made of renewable plant resources and has better environmental protection performance. The high-mineral PE layer has light-biodegradable performance, but the PE layer is a non-degradable material, and the heat resistance of the film has not been verified. Summary of the invention

[0007] In view of the problem that the heat resistance of degradable film bag materials is poor, the present invention provides a heat-resistant degradable film, which is a combination of four layers of film by hot pressing to achieve the effects of strengthening, toughening and effectively improving the heat-resistant temperature, and has excellent biodegradability.

[0008] To achieve the above object, the technical solution adopted by the present invention is: A heat-resistant and degradable film comprises a PBAT film layer, a PBAT / hollow glass microbead composite film layer, a PBAT / PBS composite film layer and a PBAT / bamboo powder composite film layer in sequence.

[0009] According to the weight percentage, the PBAT / hollow glass microsphere composite film layer includes 90-97 parts of PBAT resin, 3-8 parts of hollow glass microspheres, and 1-3 parts of maleic anhydride grafted PBAT as raw material components. Preferably, the PBAT / hollow glass microsphere composite film layer includes 93 parts of PBAT resin, 5 parts of hollow glass microspheres, and 2 parts of maleic anhydride grafted PBAT as raw material components.

[0010] The PBAT / bamboo powder composite film layer comprises 70-95 parts of PBAT resin and 5-30 parts of bamboo powder as raw material components by weight. Preferably, the PBAT / bamboo powder composite film layer comprises 80-90 parts of PBAT resin and 10-20 parts of bamboo powder as raw material components.

[0011] The mass ratio of PBAT to PBS in the raw material components of the PBAT / PBS composite film layer is 90:10-80:20.

[0012] The present invention adopts a multi-layer film composite form, bamboo powder increases the film strength modulus and heat resistance, glass microspheres can enhance the thermal insulation of the material, PBS and PBAT are mixed to increase the thermal deformation temperature of the material, and the four-layer film composite not only enhances the mechanical properties but also maintains the flexibility of the material, and also improves the heat resistance temperature of the material, so that the film can be used as a food packaging for high temperature.

[0013] The PBAT melt index is 3-5g / 10min (190°C, 2.16kg), the PBAT film thickness is 50-100μm, the PBAT / hollow glass microsphere composite film thickness is 50-100μm, the PBAT / bamboo powder composite film thickness is 50-100μm, and the PBAT / PBS composite film thickness is 50-100μm. The four film layers are formed by hot pressing to obtain the heat-resistant and degradable film, and the hot pressing temperature is 140-170°C.

[0014] The mesh number of the glass micro beads is 500-1500 meshes.

[0015] The bamboo powder has a size of 100-500 meshes and an aspect ratio of 20-100. Preferably, the bamboo powder has a size of 300-500 meshes and an aspect ratio of 40-80, and the corresponding product has stronger mechanical properties.

[0016] The present invention also provides a method for preparing the heat-resistant and degradable film, comprising the steps of: Step 1, preparing a PBAT film layer by blowing a PBAT resin; The PBAT resin, hollow glass microspheres and maleic anhydride grafted PBAT are melt blended and then blown to prepare a PBAT / hollow glass microsphere composite film layer; The PBAT resin and bamboo powder are melt-blended and then blown into a film to obtain the PBAT / bamboo powder composite film layer; The PBAT resin and the PBS resin are melt-blended and then blown into a film to obtain the PBAT / PBS composite film layer; Step 2, stacking the layers in the order of PBAT film layer, PBAT / hollow glass microsphere composite film layer, PBAT / PBS composite film layer and PBAT / bamboo powder composite film layer from the outside to the inside, and hot pressing to obtain the heat-resistant and degradable film.

[0017] The temperature of the melt blending is 135-150°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, a multi-layer degradation film is stacked, PBAT / hollow glass microspheres are used to increase the thermal insulation performance of the material, PBAT / PBS are blended to increase the thermal deformation temperature of the material, PBAT / bamboo powder is mixed, the strength modulus of the material is increased while the thermal deformation temperature of the material is increased, and finally the joint hot pressing is performed, which not only maintains the flexibility of the material but also improves the heat resistance temperature of the material. The composite method is simple and can be achieved by ordinary hot pressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of hot pressing molding of each degradation film layer in the present invention.

[0020] Among them, a is a PBAT film layer, b is a PBAT / hollow glass microsphere composite film layer, c is a PBAT / PBS composite film layer, and d is a PBAT / bamboo powder composite film layer. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0022] The raw materials used in the following specific embodiments were purchased from the market, PBAT was Blue Mountain Tunhe TH801, bamboo powder was purchased from Changxing Tianhe Building Materials Co., Ltd., PBS was Blue Mountain Tunhe TH803S, glass beads were purchased from Zhejiang Zhongteng Environmental Protection Technology Co., Ltd., and maleic anhydride grafted PBAT was purchased from Shenzhen Xinyi Plastic Chemical Co., Ltd.

[0023] Example 1

[0024] Step 1, blow the PBAT film at 135°C to obtain a PBAT film layer a with a thickness of 50 μm.

[0025] Step 2, 5 parts of 500 mesh hollow glass microspheres, 2 parts of maleic anhydride grafted PBAT, and 93 parts of PBAT are blended at 150° C. by a screw, and a film blowing machine is used to form a PBAT / hollow glass microsphere composite film layer b with a thickness of 50 μm; Step 3, 90 parts of PBAT and 10 parts of PBS are blended by a screw at 150° C., and a film blowing machine is used to form a PBAT / PBS composite film layer c with a thickness of 50 μm; Step 4, 10 parts of bamboo powder (100 mesh, aspect ratio 20) and 90 parts of PBAT are blended by a screw at 135° C., and a film blowing machine is used to form a PBAT / bamboo powder composite film layer d with a thickness of 50 μm; Step 5, such as Figure 1 As shown, the film layers prepared in steps 1-4 are stacked in the order of abcd, and then subjected to roller hot pressing at 140° C. to obtain a heat-resistant and degradable film.

[0026] Example 2

[0027] Step 1, blow the PBAT film at 140° C. to obtain a PBAT film layer a with a thickness of 100 μm.

[0028] Step 2, 5 parts of 500 mesh hollow glass microspheres, 2 parts of maleic anhydride grafted PBAT, and 93 parts of PBAT are blended at 135° C. by a screw, and a film blowing machine is used to form a PBAT / hollow glass microsphere composite film layer b with a thickness of 100 μm; Step 3, 80 parts of PBAT and 20 parts of PBS are blended by a screw at 140° C., and a film blowing machine is used to form a PBAT / PBS composite film layer c with a thickness of 100 μm; Step 4, 20 parts of bamboo powder (500 mesh, aspect ratio 100) and 80 parts of PBAT are blended by a screw at 140° C., and a film blowing machine is used to form a PBAT / bamboo powder composite film layer d with a thickness of 100 μm; Step 5, stacking the film layers prepared in steps 1-4 in the order of abcd, and subjecting them to roller hot pressing at 170° C. to obtain a heat-resistant and degradable film.

[0029] Example 3 Step 1, blow the PBAT film at 145°C to obtain a PBAT film layer a with a thickness of 75 μm.

[0030] Step 2, 5 parts of 1000 mesh hollow glass microspheres, 2 parts of maleic anhydride grafted PBAT, and 93 parts of PBAT are blended at 140° C. by a screw, and a film blowing machine is used to form a PBAT / hollow glass microsphere composite film layer b with a thickness of 75 μm; Step 3, 85 parts of PBAT and 15 parts of PBS are blended by a screw at 135° C., and a film blowing machine is used to form a PBAT / PBS composite film layer c with a thickness of 75 μm; Step 4, 15 parts of bamboo powder (300 mesh, aspect ratio 60) and 85 parts of PBAT are blended by a screw at 150° C., and a film blowing machine is used to form a PBAT / bamboo powder composite film layer d with a thickness of 75 μm; Step 5, stacking the film layers prepared in steps 1-4 in the order of abcd, and subjecting them to roller hot pressing at 160° C. to obtain a heat-resistant and degradable film.

[0031] Example 4 Step 1, blow the PBAT film at 145°C to obtain a PBAT film layer a with a thickness of 50.

[0032] Step 2, 5 parts of 800 mesh hollow glass microspheres, 2 parts of maleic anhydride grafted PBAT, and 93 parts of PBAT are blended at 150° C. by a screw, and a film blowing machine is used to form a PBAT / hollow glass microsphere composite film layer b with a thickness of 60 μm; Step 3, 80 parts of PBAT and 20 parts of PBS are blended by a screw at 135° C., and a film blowing machine is used to form a PBAT / PBS composite film layer c with a thickness of 80 μm; Step 4, 10 parts of bamboo powder (400 mesh, aspect ratio 80) and 90 parts of PBAT are blended by a screw at 145° C., and a film blowing machine is used to form a PBAT / bamboo powder composite film layer d with a thickness of 60 μm; Step 5, stacking the film layers prepared in steps 1-4 in the order of abcd, and subjecting them to roller hot pressing at 160° C. to obtain a heat-resistant and degradable film.

[0033] Example 5 Step 1, blow the PBAT film at 150° C. to obtain a PBAT film layer a with a thickness of 70 μm.

[0034] Step 2, 5 parts of 1200 mesh hollow glass microspheres, 2 parts of maleic anhydride grafted PBAT, and 93 parts of PBAT are blended by a screw at 135° C., and a film blowing machine is used to form a PBAT / hollow glass microsphere composite film layer b with a thickness of 90 μm; Step 3, 90 parts of PBAT and 10 parts of PBS are blended by a screw at 140° C., and a film blowing machine is used to form a PBAT / PBS composite film layer c with a thickness of 70 μm; Step 4, 20 parts of bamboo powder (500 mesh, aspect ratio 80) and 90 parts of PBAT are blended by a screw at 135° C., and a film blowing machine is used to form a PBAT / bamboo powder composite film layer d with a thickness of 50 μm; Step 5, stacking the film layers prepared in steps 1-4 in the order of abcd, and subjecting them to roller hot pressing at 160° C. to obtain a heat-resistant and degradable film.

[0035] Comparative Example 1 Take ordinary degradable film bags purchased on the market as control, Mingli Packaging, PBAT degradable bags, purchased from Alibaba.

[0036] Comparative Examples 2-5 According to the process of Example 2, in step 5, layer a, layer b, layer c or layer d is reduced respectively to obtain three-layer degradable films.

[0037] Since the film material cannot be tested for polymer heat deformation temperature (HDT), a PP lunch box was placed on top of the film, and hot water at 70°C, 80°C, and 90°C was poured into the lunch box respectively. The film was lifted up to observe the deformation of the film to determine whether the composite film is heat-resistant.

[0038] Table 1 Heat resistance of the degradable films of the embodiments and comparative examples

[0039] The heat resistance of the materials of the present invention is better than that of the products purchased on the market. Compared with comparative examples 2-5, when any layer is missing, the materials show adverse reactions. The films of examples 1-5 are subjected to tensile tests, and the results are shown in Table 2. It can be seen that the mechanical properties of the examples are better than those of the products purchased on the market.

[0040] Table 2 Mechanical properties of Examples 1-5 and Comparative Example 1

[0041] The film bags of Examples 1-5 and Comparative Example 1 were placed in compost soil, the ambient air temperature was controlled at 20°C, the soil moisture was 60%-70%, and the materials were taken out and weighed after 60 days to observe the degradability of the materials. The results are shown in Table 3, which shows that the degradation effect of the heat-resistant degradable films prepared in Examples 1-5 is comparable to that of the PBAT degradable material films on the market.

[0042] Table 3 Degradation of the films of Examples 1-5 and Comparative Example 1

Claims

1. A heat-resistant and degradable film, characterized in that: The composite film layers include a PBAT film layer, a PBAT / hollow glass microsphere composite film layer, a PBAT / PBS composite film layer and a PBAT / bamboo powder composite film layer.

2. The heat-resistant and degradable film according to claim 1, characterized in that: Calculated by weight, the PBAT / hollow glass microsphere composite film layer includes raw material components of 90-97 parts of PBAT resin, 3-8 parts of hollow glass microspheres, and 1-3 parts of maleic anhydride grafted PBAT.

3. The heat-resistant and degradable film according to claim 1, characterized in that: Calculated by weight, the PBAT / bamboo powder composite film layer includes raw material components of 70-95 parts of PBAT resin and 5-30 parts of bamboo powder.

4. The heat-resistant and degradable film according to claim 1, characterized in that: The mass ratio of PBAT to PBS in the raw material components of the PBAT / PBS composite film layer is 90:10-80:

20.

5. The heat-resistant and degradable film according to claim 1, characterized in that: The thickness of the PBAT film layer is 50-100 μm; the thickness of the PBAT / hollow glass microsphere composite film layer is 50-100 μm, the thickness of the PBAT / bamboo powder composite film layer is 50-100 μm, and the thickness of the PBAT / PBS composite film layer is 50-100 μm.

6. The heat-resistant and degradable film according to claim 1, characterized in that: The four film layers are formed by hot pressing to obtain the heat-resistant and degradable film, and the hot pressing temperature is 140-170°C.

7. The heat-resistant and degradable film according to claim 1, characterized in that: The mesh number of the glass micro beads is 500-1500 meshes.

8. The heat-resistant and degradable film according to claim 1, characterized in that: The bamboo powder has a size of 100-500 meshes and an aspect ratio of 20-100.

9. The method for preparing a heat-resistant and degradable film according to any one of claims 1 to 8, characterized in that: Includes steps: Step 1, preparing a PBAT film layer by blowing a PBAT resin; The PBAT resin, hollow glass microspheres and maleic anhydride grafted PBAT are melt blended and then blown to prepare a PBAT / hollow glass microsphere composite film layer; The PBAT resin and bamboo powder are melt-blended and then blown into a film to obtain the PBAT / bamboo powder composite film layer; The PBAT resin and the PBS resin are melt-blended and then blown into a film to obtain the PBAT / PBS composite film layer; Step 2, stacking the layers in the order of PBAT film layer, PBAT / hollow glass microsphere composite film layer, PBAT / PBS composite film layer and PBAT / bamboo powder composite film layer from the outside to the inside, and hot pressing to obtain the heat-resistant and degradable film.

10. The method for preparing a heat-resistant and degradable film according to claim 9, characterized in that: The temperature of the melt blending is 135-155°C.

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