Copolymerized polypropylene biaxially oriented film and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a co-polypropylene biaxially oriented film and a preparation method thereof, the co-polypropylene biaxially oriented film comprises an upper surface layer, a lower surface layer and three core layers; each of the upper surface layer and the lower surface layer independently comprises the following components in parts by weight: 80-90 parts of propylene copolymer; 6-8 parts of an anti-adhesion agent; 2-6 parts of a slipping agent; 2-6 parts of a hot slipping agent; the three core layers comprise the following components in parts by weight: 94-98 parts of a propylene copolymer; and 2-6 parts of a slipping agent. The co-polypropylene biaxially oriented film provided by the invention has excellent tensile strength, tear resistance and shrinkage effect, and solves the problem of film breakage caused by too high speed during packaging of the biaxially oriented film. Meanwhile, the surface of the film has a relatively low friction coefficient, so that the biaxially oriented film is endowed with relatively good thermal smoothness.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a copolymer polypropylene biaxially stretched film and a preparation method thereof. Background Art

[0002] Polyolefin heat shrinkable film (POF) is generally made of PP and PE co-extrusion composite, which contains the advantages of polyethylene and polypropylene, and its performance is better than polyethylene film and polypropylene film, such as high transparency, low temperature resistance, high strength, and rubbing resistance. POF film is widely used in various industrial and retail products such as food, cosmetics, medicine, and electronic products for bundling and packaging applications. POF film is generally a 3-5 layer co-extrusion structure, and the biaxial stretching process mainly consists of the following steps: mixing ingredients, extrusion by extruder, extrusion through the co-extrusion die head to form a tube billet, the tube billet is quenched, preheated by pulling into a long heating cylinder, inflated in a large heating cylinder, heat-set, cooling, winding, slitting and storage.

[0003] In the guidelines for film packaging materials formulated by CEFLEX, the European Flexible Packaging Recycling Economic Organization, the definition of overall flexible packaging materials is: a single material (including copolymers based on raw materials) must reach more than 90wt%, and the weight of each other non-single material must be less than 5% to be called a single-material packaging material (Mono-material Packaging). At present, with the continuous development of the market, higher requirements are put forward for single-material film packaging materials, such as better shrinkage, higher elongation and thermal slip performance. Summary of the invention

[0004] In view of this, the present invention proposes a copolymer polypropylene biaxially oriented film and a preparation method thereof, aiming to solve the problem of poor shrinkage and stretching rate of film packaging materials in the current technology.

[0005] On the one hand, the present invention provides a copolymer polypropylene biaxially oriented film, comprising: an upper surface layer, a lower surface layer and three core layers;

[0006] The upper surface layer and the lower surface layer each independently include the following components in parts by weight:

[0007]

[0008] Each of the three core layers includes the following components in parts by weight:

[0009] 94-98 parts of propylene copolymer;

[0010] 2-6 parts of lubricant.

[0011] Preferably, the anti-blocking agent includes a silica anti-blocking agent or an organic anti-blocking agent.

[0012] Preferably, the lubricant is oleamide and / or erucamide lubricant.

[0013] Preferably, the thermal lubricant includes one or more of silicone oil, silicone grease and zinc stearate.

[0014] Preferably, the silicone oil includes one or more of methyl silicone oil, amino silicone oil and phenyl silicone oil.

[0015] Preferably, the silicone grease includes methyl silicone grease or methylphenyl silicone oil.

[0016] Preferably, the surface friction coefficient of the copolymerized polypropylene biaxially stretched film at 25° C. is 0.07-0.35.

[0017] Preferably, the total thickness of the copolymerized polypropylene biaxially oriented film is 10-35 um.

[0018] On the other hand, the present invention also provides a method for preparing the copolymerized polypropylene biaxially stretched film, comprising the following steps:

[0019] (1) putting the components of the upper surface layer, the three-layer core layer, and the lower surface layer into respective extruders according to the above weight percentages for extrusion to obtain corresponding extrudates;

[0020] (2) stretching the extrudate obtained in step (1) to obtain a copolymer polypropylene biaxially stretched film.

[0021] Preferably, the extrusion temperatures of the upper surface layer, the three-layer core layer and the lower surface layer are independently 240-280°C, the longitudinal stretching ratio of the stretching is 4.5-5.5, the preheating temperature is 116-140°C; the transverse stretching ratio is 4.5-7, the preheating temperature is 165-180°C, and the setting temperature is 165-180°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a copolymer polypropylene biaxially stretched film, comprising: an upper surface layer, a lower surface layer and a three-layer core layer; the upper surface layer and the lower surface layer each independently comprise the following components in parts by weight: 80-90 parts of propylene copolymer; 6-8 parts of anti-adhesion agent; 2-6 parts of lubricant; 2-6 parts of thermal lubricant; the three-layer core layer comprises the following components in parts by weight: 94-98 parts of propylene copolymer; 2-6 parts of lubricant. The copolymer polypropylene biaxially stretched film provided by the present invention has excellent tensile strength, tear resistance and shrinkage effect, and solves the problem of film rupture caused by excessive speed during packaging of the biaxially stretched film. At the same time, the film surface has a low friction coefficient, which gives the biaxially stretched film better thermal lubricity.

[0024] The copolymerized polypropylene biaxially stretched film provided by the present invention includes an anti-blocking agent, and further defines that the anti-blocking agent includes a silicon dioxide anti-blocking agent or an organic anti-blocking agent, thereby preventing adhesion between film layers and the processing performance of the film, thereby improving the stretching and shrinking effects of the film.

[0025] The copolymer polypropylene biaxially stretched film provided by the present invention comprises a lubricant, and the lubricant is further limited to oleamide and / or erucamide lubricants, which reduces the friction coefficient of the surface of the biaxially stretched film, thereby improving the thermal lubricity and making the film easier to stretch and shrink during processing.

[0026] The thermal lubricant in the present invention includes one or more of silicone oil, silicone grease and zinc stearate. The thermal lubricant works at high temperatures and helps to improve the fluidity of the film during thermal processing, thereby improving the stretching and shrinking effects. In addition, silicone oil and silicone grease can reduce the viscosity of the film at high temperatures, making it easier to stretch. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0028] The present invention provides a copolymer polypropylene biaxially stretched film, the copolymer polypropylene biaxially stretched film comprising: an upper surface layer, a lower surface layer and three core layers;

[0029] The upper surface layer and the lower surface layer each independently include the following components in parts by weight:

[0030]

[0031] The three-layer core layer comprises the following components in parts by weight:

[0032] 94-98 parts of propylene copolymer;

[0033] 2-6 parts of lubricant.

[0034] In some embodiments of the present invention, the upper surface layer includes the following components in weight fractions: 80-90 parts of propylene copolymer, 6-8 parts of anti-blocking agent; 2-6 parts of lubricant; 2-6 parts of thermal lubricant; wherein the propylene copolymer can specifically be 80 parts, 84 parts, 86 parts, 90 parts, the anti-blocking agent can specifically be 6 parts, 7 parts, 8 parts, the lubricant can specifically be 2 parts, 4 parts, 6 parts, 8 parts, and the thermal lubricant can specifically be 2 parts, 4 parts, 6 parts, 8 parts.

[0035] In some embodiments of the present invention, the lower surface layer includes the following components in weight fractions: 80-90 parts of propylene copolymer, 6-8 parts of anti-blocking agent; 2-6 parts of lubricant; 2-6 parts of thermal lubricant; wherein the propylene copolymer can be specifically 80 parts, 84 parts, 86 parts, 90 parts, the anti-blocking agent can be specifically 6 parts, 7 parts, 8 parts, the lubricant can be specifically 2 parts, 4 parts, 6 parts, 8 parts, and the thermal lubricant can be specifically 2 parts, 4 parts, 6 parts, 8 parts.

[0036] In some embodiments of the present invention, the three-layer core layer includes the following components in parts by weight: 94-98 parts of propylene copolymer; 2-6 parts of lubricant, wherein the propylene copolymer can be specifically 94 parts, 95 parts, 97 parts, and 98 parts, and the lubricant can be specifically 2 parts, 4 parts, 5 parts, and 6 parts.

[0037] In some embodiments of the present invention, the propylene copolymer of the upper surface layer, the lower surface layer and the three-layer core layer is Exonmobil 3980FL elastomer.

[0038] In some embodiments of the present invention, the anti-blocking agent includes a silica anti-blocking agent or an organic anti-blocking agent.

[0039] In some embodiments of the present invention, the lubricant is oleamide and / or erucamide lubricant.

[0040] In some embodiments of the present invention, the thermal lubricant includes one or more of silicone oil, silicone grease and zinc stearate.

[0041] In some embodiments of the present invention, the silicone oil includes one or more of methyl silicone oil, amino silicone oil and phenyl silicone oil.

[0042] In some embodiments of the present invention, the silicone grease includes methyl silicone grease or methylphenyl silicone oil.

[0043] In some embodiments of the present invention, the surface friction coefficient of the copolymerized polypropylene biaxially oriented film at 25° C. is 0.07-0.35.

[0044] In some embodiments of the present invention, the total thickness of the copolymerized polypropylene biaxially oriented film is 15-35 um.

[0045] The present invention also provides a method for preparing the copolymerized polypropylene biaxially stretched film, comprising the following steps:

[0046] (1) putting the components of the upper surface layer, the three-layer core layer, and the lower surface layer into respective extruders according to the above weight percentages for extrusion to obtain corresponding extrudates;

[0047] (2) stretching the extrudate obtained in step (1) to obtain a copolymer polypropylene biaxially stretched film.

[0048] In some embodiments of the present invention, the extrusion temperatures of the upper surface layer, the three-layer core layer and the lower surface layer are independently 240-280°C, the longitudinal stretching ratio of the stretching is 4.5-5.5, and the preheating temperature is 116-140°C; the transverse stretching ratio is 4.5-7, the preheating temperature is 165-180°C, and the setting temperature is 165-180°C.

[0049] Specifically, the upper and lower surface layers of the propylene copolymer, the anti-blocking agent, the lubricant, and the thermal lubricant are pre-mixed, and the core layer of the propylene copolymer is mixed, and the materials of each layer are uniformly dispersed;

[0050] The upper surface layer, two outer core layers, inner core layer and lower surface layer are respectively passed through five extruders and extruded through a five-layer co-extrusion die to form a tube billet, and the tube billet is cooled and formed, wherein the temperature of the extruders corresponding to the upper surface layer and the lower surface layer is 185-195°C, and the temperature of the extruders corresponding to the three inner core layers is 180-200°C; preferably, 185°C, 190°C, and 195°C are the preferred values ​​of the extruder temperatures corresponding to the upper surface layer and the lower surface layer. 180°C, 190°C, and 200°C are the preferred values ​​of the extruder temperatures corresponding to the three inner core layers. The temperature of the above-mentioned co-extrusion die head is 179°C.

[0051] After cooling and shaping, the tube is pulled to the long heating tube, and the long heating tube preheats the tube. The preheating temperature of the tube is 200-400℃. Preferably, 200℃, 300℃, and 400℃ are all preferred values ​​of the preheating temperature. The set temperature requirement can be achieved by preheating the tube. Specifically, after cooling, the tube is pulled into the heating tube. The temperature of the long heating tube can be divided into 1-4 zones, and the corresponding temperatures are: 250℃, 260℃, 270℃, and 280℃.

[0052] The preheated tube blank is inflated and subjected to biaxial stretching to form a bubble film, wherein the temperature of the biaxial stretching treatment is 108-110°C, and the stretching can be divided into transverse stretching and longitudinal stretching, and the stretching multiples are both 4-7 times; in this step, the temperature of the preheated tube blank is relatively high, and it can be inflated after being properly cooled, and then when the temperature of the long heating tube is 108-110°C, the inflated tube blank can be subjected to transverse and longitudinal stretching to form a bubble film, and the transverse and longitudinal stretching multiples are preferably 4, 5.5, and 7 times.

[0053] The bubble film is forcedly cooled and split to obtain a copolymer polypropylene biaxially stretched film. In this step, the split copolymer polypropylene biaxially stretched film can be cut into finished products after being rolled and cured.

[0054] The extrusion temperature will affect the fluidity of the film material. If the extrusion temperature is too low, the melt viscosity will increase, the flow will be poor, and the film uniformity will deteriorate; if the extrusion temperature is too high, it will affect the surface smoothness and gloss of the film.

[0055] In the present invention, the propylene copolymer needs to be melted at a certain temperature and have good fluidity, so as to be extruded through an extruder and form a uniform film. The present invention limits the extrusion temperature to a range of 240-280°C, which can ensure that the material reaches an appropriate molten state, and within this temperature range, the melt has good stability, which helps to maintain the physical and chemical properties of the material and ensure the quality of the final film. In addition, within this range, the material has good fluidity during the extrusion process, which reduces downtime and waste generation and improves production efficiency.

[0056] Example 1

[0057] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0058] 80 parts of propylene copolymer, 6 parts of anti-blocking agent, 2 parts of lubricant, 2 parts of thermal lubricant;

[0059] The lower surface layer includes the following components in parts by weight:

[0060] 80 parts of propylene copolymer, 6 parts of anti-blocking agent, 2 parts of lubricant, 2 parts of thermal lubricant;

[0061] The three-layer core layer includes the following components in parts by weight:

[0062] 94 parts of propylene copolymer and 2 parts of lubricant.

[0063] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0064] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 245° C., the extrusion temperature of the lower surface layer is 245° C., and the extrusion temperature of the three-layer core layer is 250° C., to obtain corresponding extrudates;

[0065] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 4.5, the preheating temperature was 116°C, the transverse stretching ratio was 5.5, the preheating temperature was 165°C, and the setting temperature was 170°C.

[0066] Example 2

[0067] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0068] 84 parts of propylene copolymer, 7 parts of anti-blocking agent, 4 parts of lubricant, 6 parts of thermal lubricant;

[0069] The lower surface layer includes the following components in parts by weight:

[0070] 86 parts of propylene copolymer, 6 parts of anti-blocking agent, 4 parts of lubricant, 2 parts of thermal lubricant;

[0071] The three-layer core layer includes the following components in parts by weight:

[0072] 94 parts of propylene copolymer and 4 parts of lubricant.

[0073] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0074] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 255° C., the extrusion temperature of the lower surface layer is 245° C., and the extrusion temperature of the three-layer core layer is 250° C., to obtain corresponding extrudates;

[0075] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 5.0, the preheating temperature was 125°C, the transverse stretching ratio was 5.0, the preheating temperature was 170°C, and the setting temperature was 175°C.

[0076] Example 3

[0077] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0078] 86 parts of propylene copolymer, 7 parts of anti-blocking agent, 6 parts of lubricant, 6 parts of thermal lubricant;

[0079] The lower surface layer includes the following components in parts by weight:

[0080] 84 parts of propylene copolymer, 6 parts of anti-blocking agent, 4 parts of lubricant, 4 parts of thermal lubricant;

[0081] The three-layer core layer includes the following components in parts by weight:

[0082] 95 parts of propylene copolymer and 4 parts of lubricant.

[0083] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0084] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 260° C., the extrusion temperature of the lower surface layer is 255° C., and the extrusion temperature of the three-layer core layer is 265° C., to obtain corresponding extrudates;

[0085] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 5.5, the preheating temperature was 135°C, the transverse stretching ratio was 6.5, the preheating temperature was 170°C, and the setting temperature was 175°C.

[0086] Example 4

[0087] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0088] 90 parts of propylene copolymer, 8 parts of anti-blocking agent, 4 parts of lubricant, 8 parts of thermal lubricant;

[0089] The lower surface layer includes the following components in parts by weight:

[0090] 80 parts of propylene copolymer, 6 parts of anti-blocking agent, 4 parts of lubricant, 6 parts of thermal lubricant;

[0091] The three-layer core layer includes the following components in parts by weight:

[0092] 98 parts of propylene copolymer and 4 parts of lubricant.

[0093] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0094] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 265° C., the extrusion temperature of the lower surface layer is 265° C., and the extrusion temperature of the three-layer core layer is 255° C., to obtain corresponding extrudates;

[0095] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 5.5, the preheating temperature was 140°C, the transverse stretching ratio was 7, the preheating temperature was 170°C, and the setting temperature was 180°C.

[0096] Example 5

[0097] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0098] 84 parts of propylene copolymer, 8 parts of anti-blocking agent, 6 parts of lubricant, 8 parts of thermal lubricant;

[0099] The lower surface layer includes the following components in parts by weight:

[0100] 90 parts of propylene copolymer, 2 parts of anti-blocking agent, 8 parts of lubricant, 2 parts of thermal lubricant;

[0101] The three-layer core layer includes the following components in parts by weight:

[0102] 97 parts of propylene copolymer and 4 parts of lubricant.

[0103] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0104] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 270° C., the extrusion temperature of the lower surface layer is 275° C., and the extrusion temperature of the three-layer core layer is 270° C., to obtain corresponding extrudates;

[0105] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 5.5, the preheating temperature was 135°C, the transverse stretching ratio was 7.0, the preheating temperature was 170°C, and the setting temperature was 175°C.

[0106] Example 6

[0107] A copolymer polypropylene biaxially stretched film, the upper surface layer of which comprises the following components in parts by weight:

[0108] 84 parts of propylene copolymer, 2 parts of anti-blocking agent, 8 parts of lubricant, 4 parts of thermal lubricant;

[0109] The lower surface layer includes the following components in parts by weight:

[0110] 86 parts of propylene copolymer, 4 parts of anti-blocking agent, 8 parts of lubricant, 6 parts of thermal lubricant;

[0111] The three-layer core layer includes the following components in parts by weight:

[0112] 95 parts of propylene copolymer and 4 parts of lubricant.

[0113] The preparation method of the above copolymer polypropylene biaxially stretched film:

[0114] The components of the upper surface layer, the three-layer core layer, and the lower surface layer are respectively put into respective extruders for extrusion according to the above weight percentages, wherein the extrusion temperature of the upper surface layer is 265° C., the extrusion temperature of the lower surface layer is 260° C., and the extrusion temperature of the three-layer core layer is 245° C., to obtain corresponding extrudates;

[0115] The extrudate obtained above was stretched to obtain a copolymer polypropylene biaxially stretched film, wherein the longitudinal stretching ratio was 5.0, the preheating temperature was 116°C, the transverse stretching ratio was 6.5, the preheating temperature was 165°C, and the setting temperature was 175°C.

[0116] Test Case

[0117] The performance of the copolymerized polypropylene biaxially oriented films obtained in Examples 1-6 was tested, and the results are shown in Table 1.

[0118] Table 1 Performance test results of the copolymerized polypropylene biaxially stretched films obtained in Examples 1-6

[0119]

[0120] It can be seen from Table 1 that the copolymerized polypropylene biaxially oriented film provided by the present invention has excellent tensile strength, thermal shrinkage and friction coefficient.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A copolymer polypropylene biaxially stretched film, characterized in that: The copolymerized polypropylene biaxially stretched film comprises: an upper surface layer, a lower surface layer and three core layers; The upper surface layer and the lower surface layer each independently include the following components in parts by weight: Each of the three core layers includes the following components in parts by weight: 94-98 parts of propylene copolymer; 2-6 parts of lubricant.

2. A copolymer polypropylene biaxially oriented film according to claim 1, characterized in that: The anti-blocking agent includes a silicon dioxide anti-blocking agent or an organic anti-blocking agent.

3. A copolymer polypropylene biaxially oriented film according to claim 1, characterized in that: The lubricant is oleamide and / or erucamide lubricant.

4. A copolymer polypropylene biaxially oriented film according to claim 1, characterized in that: The thermal lubricant includes one or more of silicone oil, silicone grease and zinc stearate.

5. A copolymer polypropylene biaxially oriented film according to claim 4, characterized in that: The silicone oil includes one or more of methyl silicone oil, amino silicone oil and phenyl silicone oil.

6. A copolymer polypropylene biaxially oriented film according to claim 4, characterized in that: The silicone grease includes methyl silicone grease or methylphenyl silicone oil.

7. A copolymer polypropylene biaxially oriented film according to claim 1, characterized in that: The surface friction coefficient of the copolymerized polypropylene biaxially stretched film at 25° C. is 0.07-0.

35.

8. The biaxially oriented copolymer polypropylene film according to claim 1, characterized in that: The total thickness of the copolymerized polypropylene biaxially stretched film is 10-35 μm.

9. The method for preparing a biaxially oriented copolymer polypropylene film according to any one of claims 1 to 8, characterized in that: The steps include: (1) putting the components of the upper surface layer, the three-layer core layer, and the lower surface layer into respective extruders according to the above weight percentages for extrusion to obtain corresponding extrudates; (2) stretching the extrudate obtained in step (1) to obtain a copolymer polypropylene biaxially stretched film.

10. The method for preparing a biaxially oriented copolymer polypropylene film according to claim 9, characterized in that: The extrusion temperatures of the upper surface layer, the three-layer core layer and the lower surface layer are independently 240-280°C, the longitudinal stretching ratio of the stretching is 4.5-5.5, the preheating temperature is 116-140°C; the transverse stretching ratio is 4.5-7, the preheating temperature is 165-180°C, and the setting temperature is 165-180°C.

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