Low-temperature-brittleness-resistant BOPP (biaxially-oriented polypropylene) film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of BOPP film materials, and particularly relates to a low-temperature-brittleness-resistant BOPP film, a preparation method and application. The film comprises an anti-adhesion layer, a corona treatment layer and a core layer, wherein the core layer is prepared from the following raw materials in parts by weight: 60-80 parts of homo-polypropylene, 18-39 parts of TPU elastomer and 1-2 parts of an antistatic agent; the anti-adhesion layer is prepared from the following raw materials in parts by weight: 68-85 parts of homo-polypropylene, 12-25 parts of modified polypropylene resin and 3-7 parts of an anti-adhesion agent; and the corona treatment layer is prepared from the following raw materials in parts by weight: 96-98 parts of homo-polypropylene and 2-4 parts of an anti-sticking agent.

Description

Technical Field

[0001] The invention belongs to the technical field of BOPP film materials, and in particular relates to a low-temperature brittleness-resistant BOPP film, a preparation method and an application thereof. Background Art

[0002] BOPP film (biaxially oriented polypropylene film) is a widely used flexible packaging material, which has the advantages of being colorless, odorless, non-toxic, easy to process, and has good comprehensive performance. Nowadays, people's pace of life is accelerating, and the fast food industry is booming, which requires more BOPP film to wrap fast food boxes for protection. However, the current BOPP film also has some disadvantages, such as being brittle in low temperature environments, which will greatly limit the application of BOPP film, especially when used in winter environments, where the brittleness will make it difficult to protect the product well.

[0003] In the face of market demand, improving the low-temperature brittleness resistance of BOPP film has become a technical problem that needs to be solved urgently. At present, polypropylene can be blended and modified to make it less prone to breakage. However, when polypropylene is blended with thermoplastic elastomers or rubber, although the outstanding performance of each component can be combined, the low-temperature brittleness and aging resistance of the blended and modified polypropylene composite material are not ideal due to the inappropriate selection of plasticizers. Therefore, only by selecting a suitable toughening agent can the shear force generated by the polypropylene composite material cause the macromolecular chain to be cut off to form free radicals, thereby forming grafted or block copolymers. These new copolymers will effectively increase the capacity of polypropylene, thereby improving its low-temperature brittleness resistance. TPU (polyurethane elastomer) as an elastomer is a material between rubber and plastic. From its rigidity, the rigidity of TPU can be measured by the elastic modulus. The elastic modulus of rubber is usually 1-10MPa, and that of TPU is 10-1000MPa. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a BOPP film resistant to low-temperature brittleness, a preparation method and an application thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A BOPP film resistant to low temperature brittleness, the film comprising an anti-adhesion layer, a corona treatment layer and a core layer, wherein the raw materials for preparing the core layer include, by weight: 60-80 parts of homopolypropylene, 18-39 parts of TPU elastomer, and 1-2 parts of antistatic agent;

[0007] The raw materials for preparing the anti-adhesive layer include, by weight: 68-85 parts of homopolymerized polypropylene, 12-25 parts of modified polypropylene resin, and 3-7 parts of anti-adhesive agent;

[0008] The raw materials for preparing the corona treatment layer include, by weight: 96-98 parts of homopolypropylene and 2-4 parts of anti-sticking agent.

[0009] Furthermore, the modified polypropylene resin is a polypropylene block copolymer, wherein the ethylene content is 10-25wt%.

[0010] Furthermore, the thickness of the anti-adhesion layer and the corona treatment layer are both 4-6 μm, and the thickness of the core layer is 3-5 μm.

[0011] Furthermore, the antistatic agent is a non-ionic antistatic agent.

[0012] Furthermore, the anti-sticking agent is a wax powder anti-sticking agent.

[0013] A method for preparing a low-temperature brittle BOPP film, the preparation method comprising the following preparation steps:

[0014] S1, adding homopolypropylene, TPU elastomer and antistatic agent into a main extruder, and preparing a core layer melt by melt blending and extrusion; adding homopolypropylene, polypropylene block copolymer and anti-sticking agent into an auxiliary extruder, and preparing an anti-adhesive layer melt by melt blending and extrusion; adding homopolypropylene and anti-sticking agent into another auxiliary extruder, and preparing a corona treatment layer melt by melt blending and extrusion; filtering the core layer melt, the anti-adhesive layer melt and the corona treatment layer melt through a filter respectively, and converging and extruding them in an extruder with a three-layer structure die to obtain a thick film sheet;

[0015] S2, using compressed air to attach the air knife patch to the chill roller through the thick film sheet, and rapidly cool it to form a casting sheet;

[0016] S3, first longitudinally stretching the obtained cast sheet to obtain a thick sheet, and then transversely stretching the thick sheet to obtain a film;

[0017] S4, flattening the film with a guide roller, and performing surface corona treatment on the inner surface layer with a corona treatment device, and finally winding up to obtain a parent roll film;

[0018] S5. After the mother roll film passes the quality inspection, it is transported to the slitting machine via a crane and a lift for slitting and winding of different widths and lengths, and finally made into a BOPP film that is resistant to low-temperature brittleness.

[0019] Furthermore, in the step S1, the die head temperature of the extruder is 230-240°C; and in the step S2, the temperature of the chilled roller is 20-30°C.

[0020] Furthermore, the preheating temperature during the longitudinal stretching is set to 110-130°C, the stretching temperature is 120-140°C, and the stretching ratio is 4.0-4.5 times; the preheating temperature during the transverse stretching is 160-175°C, the stretching temperature is 145-150°C, the stretching ratio is 6.0-7.0 times, and the heat setting temperature is 160-180°C.

[0021] The above-mentioned low-temperature brittle resistant BOPP film is used as a raw material in the preparation of fast food packaging box products.

[0022] Beneficial effects of the present invention: The BOPP film resistant to low temperature brittleness proposed by the present invention has a core layer formed by melt-blending TPU elastomer (polyurethane elastomer), antistatic agent and homopolypropylene in a certain ratio at a certain temperature, so that the finally prepared film has good low temperature brittleness resistance, aging resistance and good toughness; the anti-adhesion layer is formed by melt-blending modified polypropylene (polypropylene block copolymer), anti-adhesion agent and homopolypropylene in a certain ratio at a certain temperature, so that the mother roll film has good anti-adhesion properties and low temperature brittleness resistance; the corona treatment layer is composed of homopolypropylene and anti-adhesion agent, and then formed into a film after biaxial stretching, and then subjected to corona treatment by a corona instrument, so that the mother roll film has good low temperature brittleness resistance and anti-adhesion: the three-layer structure of the core layer, the anti-adhesion layer and the corona treatment layer is co-extruded to form a BOPP film mother roll resistant to low temperature brittleness, which has the advantages of low temperature brittleness resistance (brittleness temperature can reach -30°C) and good toughness. The low-temperature resistant and brittle BOPP film master roll prepared by the present invention can effectively broaden the application field of BOPP film under cold temperature conditions and improve the market competitiveness of the product. DETAILED DESCRIPTION

[0023] The following will be combined with several embodiments of the present invention to clearly and completely describe the technical solutions proposed by the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A low-temperature brittle BOPP film, the film comprising an anti-blocking layer, a corona treatment layer and a core layer;

[0026] The core layer is composed of 60 parts of homopolymer polypropylene, 39 parts of TPU elastomer, and 1 part of antistatic agent (Clariant HS1);

[0027] The anti-adhesive layer is composed of 68 parts of homopolymer polypropylene, 27 parts of modified polypropylene resin (polypropylene block copolymer), and 5 parts of anti-adhesive agent (Clariant wax powder 9610F);

[0028] The corona treatment layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-sticking agent (Clariant wax powder 9610F).

[0029] The ethylene content in the polypropylene block copolymer is 10-25wt%;

[0030] The thickness of the anti-blocking layer and the corona treatment layer are both 3-6 μm.

[0031] A method for preparing a low-temperature brittle BOPP film comprises the following steps:

[0032] S1, homopolypropylene, TPU elastomer and antistatic agent are added to the main extruder according to a certain ratio, and a core layer melt is made by melt blending and extrusion; homopolypropylene, polypropylene block copolymer and anti-sticking agent are added to an auxiliary extruder according to a certain ratio, and an anti-adhesive layer melt is made by melt blending and extrusion; homopolypropylene and anti-sticking agent are added to another auxiliary extruder according to a certain ratio, and a corona treatment layer melt is made by melt blending and extrusion; finally, the core layer melt, the anti-adhesive layer melt and the corona treatment layer melt are filtered through a filter respectively, and the thick film sheet is extruded in an extruder with a three-layer structure die head, and the die head temperature of the extruder is 230°C;

[0033] S2. Use compressed air to attach the air knife patch to the chill roller through the thick film sheet, and quickly cool it to form a casting sheet. The temperature of the chill roller is 20°C.

[0034] S3, the obtained cast sheet is first longitudinally stretched into a thick sheet, the preheating temperature is set to 110-130°C, the stretching temperature is 120-140°C, and the stretching ratio is 4.0-4.5 times; then the thick sheet is transversely stretched, the preheating temperature is 160-175°C, the stretching temperature is 145-150°C, the stretching ratio is 6.0-7.0 times, and the heat setting temperature is 160-180°C;

[0035] S4, flattening the film obtained in step S3 with a guide roller, performing surface corona treatment on the inner surface layer with a corona treatment device, and finally winding up to obtain a parent roll film;

[0036] S5. After the mother roll film passes the quality inspection, it is transported to the slitting machine via a crane and a lift for slitting and winding into different widths and lengths, and finally made into finished film.

[0037] Example 2

[0038] A low-temperature brittle BOPP film, the film comprising an anti-blocking layer, a corona treatment layer and a core layer;

[0039] The core layer is composed of 70 parts of homopolymer polypropylene, 29 parts of TPU elastomer, and 1 part of antistatic agent (Clariant HS1);

[0040] The anti-adhesive layer is composed of 73 parts of homopolymer polypropylene, 23 parts of modified polypropylene resin (polypropylene block copolymer), and 4 parts of anti-adhesive agent (Clariant wax powder 9610F);

[0041] The corona treatment layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-sticking agent (Clariant wax powder 9610F).

[0042] The ethylene content in the polypropylene block copolymer is 10-25wt%;

[0043] The thickness of the anti-blocking layer and the corona treatment layer are both 3-6 μm.

[0044] The preparation method is the same as that of Example 1.

[0045] Example 3

[0046] A low-temperature brittle BOPP film, the film comprising an anti-blocking layer, a corona treatment layer and a core layer;

[0047] The core layer is composed of 80 parts of homopolymer polypropylene, 18 parts of TPU elastomer, and 2 parts of antistatic agent (Clariant HS1);

[0048] The anti-adhesive layer is composed of 78 parts of homopolymer polypropylene, 18 parts of modified polypropylene resin (polypropylene block copolymer), and 4 parts of anti-adhesive agent (Clariant wax powder 9610F);

[0049] The corona treatment layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-sticking agent (Clariant wax powder 9610F).

[0050] The ethylene content in the polypropylene block copolymer is 10-25wt%;

[0051] The thickness of the anti-blocking layer and the corona treatment layer are both 3-6 μm.

[0052] The preparation method is the same as that of Example 1.

[0053] Example 4

[0054] A low-temperature brittle BOPP film, the film comprising an anti-blocking layer, a corona treatment layer and a core layer;

[0055] The core layer is composed of 80 parts of homopolymer polypropylene, 19 parts of TPU elastomer, and 1 part of antistatic agent (Clariant HS1);

[0056] The anti-adhesive layer is composed of 85 parts of homopolymer polypropylene, 12 parts of modified polypropylene resin (polypropylene block copolymer), and 3 parts of anti-adhesive agent (Clariant wax powder 9610F);

[0057] The corona treatment layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-sticking agent (Clariant wax powder 9610F).

[0058] The ethylene content in the polypropylene block copolymer is 10-25wt%;

[0059] The thickness of the anti-blocking layer and the corona treatment layer are both 3-6 μm.

[0060] The preparation method is the same as that of Example 1.

[0061] Comparative Example 1

[0062] The core layer is composed of 99 parts of homopolymer polypropylene and 1 part of antistatic agent (Clariant HS1);

[0063] The anti-adhesive layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-adhesive agent (Clariant wax powder 9610F);

[0064] The corona treatment layer is composed of 97 parts of homopolymer polypropylene and 3 parts of anti-sticking agent (Clariant wax powder 9610F).

[0065] The thickness of the anti-blocking layer and the corona treatment layer are both 3-6 μm.

[0066] The preparation method is as follows:

[0067] a. Adding homopolypropylene and antistatic agent to a main extruder according to a certain ratio, and preparing a core layer melt through melt blending and extrusion; adding homopolypropylene and anti-adhesive agent to an auxiliary extruder according to a certain ratio, and preparing an anti-adhesive layer melt through melt blending and extrusion; adding homopolypropylene and anti-adhesive agent to another auxiliary extruder according to a certain ratio, and preparing a corona treatment layer melt through melt blending and extrusion; finally filtering the core layer melt, anti-adhesive layer melt and corona treatment layer melt through filter screens respectively, and merging them in an extruder with a three-layer structure die head to extrude a thick film sheet;

[0068] b. Using compressed air to attach the air knife patch to the chill roll through the thick film sheet, and rapidly cool it to form a casting sheet;

[0069] c. The obtained cast sheet is first longitudinally stretched into a thick sheet, the preheating temperature is set to 110-130° C., the stretching temperature is 120-140° C., and the stretching ratio is 4.0-4.5 times;

[0070] d. Then the thick sheet is stretched transversely, with a preheating temperature of 160-175°C, a stretching temperature of 145-150°C, a stretching ratio of 6.0-7.0 times, and a heat setting temperature of 160-180°C;

[0071] e. Flattening the film obtained in step S3 with a guide roller, performing surface corona treatment on the inner surface layer with a corona treatment apparatus, and finally winding up to obtain a parent roll film;

[0072] f. After the mother roll film passes the quality inspection, it is transported to the slitting machine via a crane and a lift for slitting and winding into different widths and lengths, and finally made into finished film.

[0073] The die head temperature of the extruder is 230-240°C, and the temperature of the chilled roller in step b is 20-30°C.

[0074] Performance Test:

[0075] In order to verify the effect of the present invention, the samples prepared in the above embodiments 1-4 and the comparative examples were tested respectively according to corresponding standards for comparative experiments, and the results are shown in Table 1.

[0076] The test method is: prepare the finished BOPP film into a sample of a certain size (MD: 200mm*TD: 100mm), evenly spread a layer of talcum powder on both surfaces of the sample and a stainless steel plate with a length of 300mm and a width of 200mm, place the sample on the stainless steel plate, and then fold it in half longitudinally so that the two ends overlap to form a flat ring, keep this state for 5 minutes, and use a ruler with an accuracy of 1mm to measure the maximum height of the two sides of the sample relative to the plate. The height of the folded flat ring can characterize the low-temperature brittleness resistance of the film. The higher the height, the worse the low-temperature brittleness resistance of the film. The obtained flat ring height data is shown in Table 1.

[0077] Table 1. Flat ring height data of each embodiment and comparative example are as follows

[0078]

[0079] It can be seen from the folded flat ring height data in Table 1 that the BOPP film prepared in the present invention has significantly better low-temperature brittleness resistance than the sample prepared in the comparative example at low temperatures of -30°C to 0°C, and its shape can be better maintained at relatively low temperatures, so it can be used for low-temperature packaging storage, transportation and special low-temperature occasions.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A BOPP film resistant to low temperature brittleness, comprising an anti-blocking layer, a corona treatment layer and a core layer, characterized in that: The raw materials for preparing the core layer include, by weight: 60-80 parts of homopolypropylene, 18-39 parts of TPU elastomer, and 1-2 parts of antistatic agent; The raw materials for preparing the anti-adhesive layer include, by weight: 68-85 parts of homopolymerized polypropylene, 12-25 parts of modified polypropylene resin, and 3-7 parts of anti-adhesive agent; The raw materials for preparing the corona treatment layer include, by weight: 96-98 parts of homopolypropylene and 2-4 parts of anti-sticking agent.

2. The low-temperature brittleness-resistant BOPP film according to claim 1, characterized in that: The modified polypropylene resin is a polypropylene block copolymer, wherein the ethylene content is 10-25wt%.

3. The low-temperature brittleness-resistant BOPP film according to claim 1, characterized in that: The thickness of the anti-blocking layer and the corona treatment layer are both 4-6 μm, and the thickness of the core layer is 3-5 μm.

4. The low-temperature brittleness-resistant BOPP film according to claim 1, characterized in that: The antistatic agent is a nonionic antistatic agent.

5. The low-temperature brittleness-resistant BOPP film according to claim 1, characterized in that: The anti-sticking agent is a wax powder anti-sticking agent.

6. A method for preparing a low-temperature brittle BOPP film, characterized in that: The preparation method comprises the following preparation steps: S1, adding homopolypropylene, TPU elastomer and antistatic agent into a main extruder, and preparing a core layer melt by melt blending and extrusion; adding homopolypropylene, polypropylene block copolymer and anti-sticking agent into an auxiliary extruder, and preparing an anti-adhesive layer melt by melt blending and extrusion; adding homopolypropylene and anti-sticking agent into another auxiliary extruder, and preparing a corona treatment layer melt by melt blending and extrusion; filtering the core layer melt, the anti-adhesive layer melt and the corona treatment layer melt through a filter respectively, and converging and extruding them in an extruder with a three-layer structure die to obtain a thick film sheet; S2, using compressed air to attach the air knife patch to the chill roller through the thick film sheet, and rapidly cool it to form a casting sheet; S3, first longitudinally stretching the obtained cast sheet to obtain a thick sheet, and then transversely stretching the thick sheet to obtain a film; S4, flattening the film with a guide roller, and performing surface corona treatment on the inner surface layer with a corona treatment device, and finally winding up to obtain a parent roll film; S5. After the mother roll film passes the quality inspection, it is transported to the slitting machine via a crane and a lift for slitting and winding into different widths and lengths, and finally made into a BOPP film that is resistant to low-temperature brittleness.

7. The method for preparing a low-temperature brittle BOPP film according to claim 6, characterized in that: In the step S1, the die head temperature of the extruder is 230-240°C; and in the step S2, the temperature of the chilled roller is 20-30°C.

8. The method for preparing a low-temperature brittle BOPP film according to claim 6, characterized in that: The preheating temperature during longitudinal stretching is set to 110-130°C, the stretching temperature is 120-140°C, and the stretching ratio is 4.0-4.5 times; the preheating temperature during transverse stretching is 160-175°C, the stretching temperature is 145-150°C, the stretching ratio is 6.0-7.0 times, and the heat setting temperature is 160-180°C.

9. Use of a low-temperature brittle BOPP film as claimed in any one of claims 1 to 5 as a raw material in the preparation of fast food packaging products.

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