Linear easy-to-tear film and preparation method thereof

Abstract

The invention belongs to the field of polyethylene films, and particularly relates to a linear easy-to-tear film and a preparation method thereof.The linear easy-to-tear film is formed by laminating the following material layers layer by layer: an outer surface layer, a core layer and an inner surface layer, and the mass part ratio of the outer surface layer to the core layer to the inner surface layer is (30-35): (50-55): (15-20); the raw material of the outer surface layer is linear branched chain type polyethylene; the raw material of the core layer is high-density polyethylene; and the inner surface layer is made of polypropylene. Through cooperation of raw material parameters, proportion and process parameters, the effect that a conventional polyethylene material is adopted to achieve the effect of adding an easy-to-tear material to form a linear easy-to-tear film is achieved, tearing with the width of 1 cm is achieved, tearing is conducted along the middle straight line of a tearing opening, and the effects of no deflection and no turning are achieved.

Description

Technical Field

[0001] The invention belongs to the field of polyethylene films, and in particular relates to a linear easy-tear film and a preparation method thereof. Background Art

[0002] Straight-line easy-tear film means that after a notch is created in the film, it can be torn apart with just a slight pulling force, and the tearing direction of the film is a straight line without any deviation or turn.

[0003] At present, conventional straight-line easy-tear film products are usually produced using special easy-tear materials. The easy-tear material is a non-crystalline polyethylene. This polyethylene is a linear polymer compound and generally has no active groups. When heated, it will not undergo intermolecular cross-linking and will not generate intermolecular forces. Based on this property, the film produced using the easy-tear material can achieve a straight-line easy-tear effect.

[0004] However, the mechanical properties of non-crystalline polyethylene materials are poor, resulting in the resulting film having low performance indicators such as strength, toughness, and ductility, which does not meet the performance requirements of some easy-tear film application fields. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a straight easy-tear film and a preparation method thereof. By coordinating the raw material parameters, proportions and process parameters, the conventional polyethylene material is used to achieve the effect of adding easy-tear materials to form a straight easy-tear film, and a tearing width of 1 cm is achieved. The tearing mouth is torn along the middle straight line, achieving the effect of no deviation and no turning.

[0006] The specific technical solution adopted by the present invention is:

[0007] A straight easy-tear film, which is formed by laminating the following material layers layer by layer: outer layer / core layer / inner layer, and the outer layer / core layer / inner layer have a mass fraction of 30-35 / 50-55 / 15-20 respectively;

[0008] The raw material of the outer layer is linear branched polyethylene with a melt index of 7-9 g / 10 min and a density of 0.900-0.910 g / cm 2 ;

[0009] The core layer is made of high-density polyethylene with a melt index of 2.5-3.5 g / 10 min and a density of 0.940-0.950 g / cm 2 ;

[0010] The raw material of the inner surface layer is polypropylene, with a melt index of 2.5-3.5g / 10min and a density of 0.905-0..915g / cm 2 .

[0011] Furthermore, the outer layer / core layer / inner layer have a mass fraction of 30 / 55 / 15 respectively;

[0012] The raw material of the outer layer is linear branched polyethylene with a melt index of 8g / 10min and a density of 0.900g / cm 2 ;

[0013] The core layer is made of high-density polyethylene with a melt index of 3g / 10min and a density of 0.945g / cm 2 ;

[0014] The raw material of the inner surface layer is polypropylene, with a melt index of 3g / 10min and a density of 0.910g / cm 2 .

[0015] A method for preparing a straight easy-tear film comprises the following steps:

[0016] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0017] Furthermore, the barrel temperature of the extruder is 150-250°C, and the die temperature is 240-250°C.

[0018] Furthermore, the linear speed ratio of the extruder is shaping:winding=1.000-1.100.

[0019] The beneficial effects of the present invention are:

[0020] 1. In the present invention, by coordinating the raw material parameters, the ratio and the process parameters, the conventional polyethylene material is used to achieve the effect of adding easy-tear material to form a straight easy-tear film, and a tearing width of 1 cm is achieved, and the tearing opening is torn along the middle straight line, achieving the effect of no deflection and no turning.

[0021] 2. The present invention can achieve the effect of a straight-line easy-tear film by using common raw materials, without the need for special raw materials, thereby achieving the purpose of simplifying the production process and controlling the production cost. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 1. Specific embodiments

[0024] Among them, linear branched polyethylene is linear branched polyethylene, high-density polyethylene is high-density polyethylene, and polypropylene is polypropylene.

[0025] Example 1

[0026]

[0027] The linear branched polyethylene has a melt index of 7g / 10min and a density of 0.905g / cm 2 ;

[0028] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0029] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0030] Preparation steps:

[0031] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0032] The barrel temperatures of zones 1 to 5 of the extruder are 150°C, 180°C, 210°C, 230°C, and 250°C, respectively, and the die temperature is 250°C;

[0033] The linear speed ratio of the extruder is setting:winding=1.020.

[0034] The straight easy-tear film produced in Example 1 has a better effect, but there is a deviation when tearing.

[0035] Example 2

[0036]

[0037]

[0038] The linear branched polyethylene has a melt index of 7g / 10min and a density of 0.905g / cm 2 ;

[0039] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0040] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0041] Preparation steps:

[0042] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0043] The barrel temperatures of zones 1 to 5 of the extruder are 150°C, 180°C, 210°C, 230°C, and 250°C, respectively, and the die temperature is 250°C;

[0044] The linear speed ratio of the extruder is setting:winding=1.020.

[0045] Compared with Example 1, Example 2 changes the formula, reduces the proportion of high-density polyethylene, and increases the proportion of polypropylene. The produced straight easy-tear film has obvious longitudinal lines and uneven thickness. After 24 hours, the film becomes brittle and stiff, and the tearing effect is poor. Therefore, it is necessary to ensure that the proportion of PP is ≤15%.

[0046] Example 3

[0047]

[0048] The linear branched polyethylene has a melt index of 7g / 10min and a density of 0.905g / cm 2 ;

[0049] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0050] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0051] Preparation steps:

[0052] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0053] The barrel temperatures of zones 1 to 5 of the extruder are 150°C, 180°C, 210°C, 230°C, and 250°C, respectively, and the die temperature is 250°C;

[0054] The linear speed ratio of the extruder is setting:winding=1.100.

[0055] Compared with Example 1, Example 3 improves the line speed ratio, and the tearing performance of the produced straight easy-tear film is improved, and no longitudinal deviation occurs, but bumping occurs during the tearing process;

[0056] Increasing the linear speed ratio means increasing the shaping stretching, so that the molecular chain can be longitudinally oriented during the curling process, thereby avoiding longitudinal deviation.

[0057] Example 4

[0058]

[0059] The linear branched polyethylene has a melt index of 8g / 10min and a density of 0.900g / cm 2 ;

[0060] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0061] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0062] Preparation steps:

[0063] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0064] The barrel temperatures of zones 1 to 5 of the extruder are 140°C, 170°C, 200°C, 220°C, and 240°C, respectively, and the die temperature is 240°C;

[0065] The linear speed ratio of the extruder is setting:winding=1.100.

[0066] Compared with Example 1, Example 4 uses a linear branched polyethylene material with a higher degree of branching and reduces the process temperature. The straight easy-tear film produced has a better straight easy-tear effect without deflection or turning.

[0067] Example 5

[0068]

[0069] The linear branched polyethylene has a melt index of 8g / 10min and a density of 0.900g / cm 2 ;

[0070] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0071] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0072] Preparation steps:

[0073] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0074] The barrel temperatures of zones 1 to 5 of the extruder are 140°C, 170°C, 200°C, 220°C, and 240°C, respectively, and the die temperature is 240°C;

[0075] The linear speed ratio of the extruder is setting:winding=1.100.

[0076] Compared with Example 4, Example 5 has a different ratio, increasing the proportion of linear branched polyethylene and reducing the proportion of high-density polyethylene. The produced straight easy-tear film feels softer and has lower stiffness, and cannot achieve the application form of the coating.

[0077] Example 6

[0078]

[0079] The linear branched polyethylene has a melt index of 8g / 10min and a density of 0.900g / cm 2 ;

[0080] The melt index of high-density polyethylene is 3.5g / 10min and the density is 0.940g / cm2;

[0081] The melt index of polypropylene is 3.5g / 10min and the density is 0.905g / cm 2 .

[0082] Preparation steps:

[0083] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0084] The barrel temperatures of zones 1 to 5 of the extruder are 140°C, 170°C, 200°C, 220°C, and 240°C, respectively, and the die temperature is 240°C;

[0085] The linear speed ratio of the extruder is setting:winding=1.100.

[0086] In Example 6, compared with Example 4, the raw materials are adjusted. The melt index of high-density polyethylene and polypropylene is increased and the density is reduced. The fluidity in the process of producing straight easy-tear films is good, but the necking is unstable and stable production cannot be achieved.

[0087] Example 7

[0088]

[0089] The linear branched polyethylene has a melt index of 8g / 10min and a density of 0.900g / cm 2 ;

[0090] The melt index of high-density polyethylene is 3g / 10min and the density is 0.945g / cm2;

[0091] The melt index of polypropylene is 3g / 10min and the density is 0.910g / cm 2 .

[0092] Preparation steps:

[0093] Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

[0094] The barrel temperatures of zones 1 to 5 of the extruder are 140°C, 170°C, 200°C, 220°C, and 240°C, respectively, and the die temperature is 240°C;

[0095] The linear speed ratio of the extruder is setting:winding=1.180.

[0096] In Example 7, the line speed ratio is increased compared with Example 4, and the straight tearable film produced is stretched and deformed, and the product morphology is poor. This is because the line speed ratio is too large, which puts the film in a state of greater tension during curling and shaping.

Claims

1. A straight tear film, formed by laminating the following material layers layer by layer: outer layer / core layer / inner layer, characterized in that: The mass proportions of the outer layer / core layer / inner layer are 30-35 / 50-55 / 15-20 respectively; The raw material of the outer layer is linear branched polyethylene with a melt index of 7-9 g / 10 min and a density of 0.900-0.910 g / cm 2 ; The core layer is made of high-density polyethylene with a melt index of 2.5-3.5 g / 10 min and a density of 0.940-0.950 g / cm 2 ; The raw material of the inner surface layer is polypropylene, with a melt index of 2.5-3.5g / 10min and a density of 0.905-0..915g / cm 2 .

2. A straight tear film according to claim 1, characterized in that: The outer layer / core layer / inner layer are in proportions of 30 / 55 / 15 by mass respectively; The raw material of the outer layer is linear branched polyethylene with a melt index of 8g / 10min and a density of 0.900g / cm 2 ; The core layer is made of high-density polyethylene with a melt index of 3g / 10min and a density of 0.945g / cm 2 ; The raw material of the inner surface layer is polypropylene, with a melt index of 3g / 10min and a density of 0.910g / cm 2 .

3. A method for preparing a straight easy-tear film according to claim 1, characterized in that: The following steps are involved: Linear branched polyethylene, high-density polyethylene and polypropylene are blended in proportion and added to the extruder, and extruded through a T-type cast film head to form a linear easy-tear film product.

4. The method for preparing a straight easy-tear film according to claim 3, characterized in that: The barrel temperature of the extruder is 150-250°C, and the die temperature is 240-250°C.

5. The method for preparing a straight easy-tear film according to claim 3, characterized in that: The linear speed ratio of the extruder is shaping:winding=1.000-1.100.

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