Cross film and preparation method and application thereof

Abstract

The invention provides a cross film as well as a preparation method and application thereof, and belongs to the technical field of polymer films. The cross film is formed by compounding at least two layers of sheet films in a cross manner; wherein the sheet film is prepared by rotationally cutting and rolling a base film at 46-47 degrees, and the orientation degree of the base film is 0.70-0.85. By controlling the orientation degree and the rotary cutting angle of the base film, the problems of warping and edge curling of the crossed film can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer films, and in particular to a cross film and a preparation method and application thereof. Background Art

[0002] Cross-film is usually a composite film made of polyethylene blown into a blank, then unidirectionally stretched and then 45° peeled and cross-laminated. It is often used in building waterproofing, packaging film and other fields. In the actual production and application process, cross-film often has problems such as warping and deformation. Summary of the invention

[0003] In view of this, the present invention provides a cross membrane and a preparation method and application thereof.

[0004] According to an embodiment of one aspect of the present invention, a cross film is provided, wherein the cross film is cross-compounded by at least two layers of sheet film; wherein the sheet film is made by rotary cutting and rolling a base film at 46°~47°, and the orientation degree of the base film is 0.70~0.85.

[0005] According to an embodiment of the present invention, the film comprises high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of the low-density polyethylene is 0.915~0.935g / cm 3 .

[0006] According to an embodiment of the present invention, the mass percentage of high-density polyethylene in the above-mentioned film is 40% to 70%, and the mass percentage of low-density polyethylene is 30% to 60%.

[0007] According to an embodiment of the present invention, the melt index of the high-density polyethylene is 0.01-5 g·(10 min) -1 .

[0008] According to an embodiment of the present invention, the melt index of the low-density polyethylene is 0.3-20 g·(10min) -1 .

[0009] According to an embodiment of another aspect of the present invention, a method for preparing a cross film is provided, comprising: rotary cutting and rolling a base film at 46°~47° to obtain a sheet film; cross-compounding at least two layers of the above sheet films to obtain a cross film; wherein the above base film is obtained by film blowing, secondary stretching, and heat setting.

[0010] According to an embodiment of the present invention, the secondary stretching is longitudinal stretching, and the stretching ratio is 1-2.

[0011] According to an embodiment of the present invention, the temperature of the secondary stretching is 100-150°C.

[0012] According to an embodiment of the present invention, the raw materials of the base film include high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of low-density polyethylene is 0.915~0.935g / cm 3 .

[0013] According to an embodiment of the present invention, the die temperature of the above-mentioned film blowing process is 150-300° C., and the draw ratio is 1-3.

[0014] According to an embodiment of the present invention, the temperature of the heat setting is 70-120° C. and the time is 30-300 seconds.

[0015] According to an embodiment of another aspect of the present invention, there is provided application of the above cross film or the cross film prepared by the above preparation method in the field of building waterproofing and packaging film.

[0016] According to an embodiment of the present invention, by controlling the orientation degree of the base film to 0.70-0.85 and adjusting the rotary cutting angle of the base film to 46°-47°, the warping and deformation of the cross film can be effectively improved.

[0017] According to an embodiment of the present invention, a sheet film is obtained by rotary cutting and rolling the base film at 46°~47°, and at least two layers of the sheet film are cross-laminated to obtain a cross film. Only the slitting angle needs to be adjusted from 45° to 46°~47° to effectively alleviate the warping and curling of the cross film. The process is simple and has strong operability. It can be adapted to the original process and original equipment, and is convenient for large-scale application. DETAILED DESCRIPTION

[0018] Below, embodiments of the present invention will be described. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0019] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0020] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0021] The preparation method of the cross film usually includes: subjecting polyethylene to film blowing, secondary stretching, and heat setting in sequence to obtain a base film; then the base film is peeled and rolled at 45 degrees to obtain a sheet film; and the two layers of sheet film are cross-laminated to obtain a cross film. Among them, the 45° slitting angle makes the tension and elongation of the cross film tend to be consistent in the horizontal and vertical directions. In the actual production and application process, it is found that the cross film often has warping, curling and other phenomena.

[0022] In order to solve the above-mentioned problems of cross film warping and curling, a lot of research has been conducted and it has been found that the cross film warping and curling can be effectively improved by adjusting the slitting angle of the base film and the orientation degree of the base film.

[0023] Specifically, according to an embodiment of one aspect of the present invention, a cross film is provided, which is formed by cross-compounding at least two layers of sheet film; wherein the sheet film is made by rotary cutting and rolling a base film at 46°~47°, and the orientation degree of the base film is 0.70~0.85.

[0024] According to an embodiment of the present invention, by controlling the orientation degree of the base film to 0.70-0.85 and adjusting the rotary cutting angle of the base film to 46°-47°, the warping and deformation of the cross film can be effectively improved.

[0025] According to an embodiment of the present invention, the peeling angle may be any angle between 46° and 47°, specifically, the peeling angle may be 46°, 46.3°, 46.5°, 46.7° or 47°. The peeling angle may be selected according to the preparation process of the cross film.

[0026] According to the embodiments of the present invention, the present invention does not limit the raw materials of the cross film, and a cross film made of any raw materials can be prepared into the above-mentioned cross film to alleviate the warping and curling of the cross film.

[0027] According to the embodiment of the present invention, the present invention does not limit the number of layers of the sheet film in the cross film, and is preferably an even number of layers, for example, 2 layers, 4 layers, 6 layers or 8 layers.

[0028] According to an embodiment of the present invention, the orientation degree of the base film is 0.70-0.85, preferably 0.75-0.80. Specifically, the orientation degree of the base film is 0.70, 0.75, 0.78, 0.80 or 0.85.

[0029] The embodiments of the present invention can effectively improve the warping and curling of the cross film by controlling the orientation degree and the rotary cutting angle of the base film.

[0030] According to an embodiment of the present invention, the film comprises high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of low-density polyethylene is 0.915~0.935g / cm 3 .

[0031] According to an embodiment of the present invention, the mass percentage of high-density polyethylene in the film is 40% to 70%, and the mass percentage of low-density polyethylene is 30% to 60%.

[0032] According to the embodiments of the present invention, suitable raw materials and raw material ratios can further alleviate the warping and curling of the cross film.

[0033] According to an embodiment of the present invention, the melt index of high-density polyethylene is 0.01~5g·(10min) -1 .

[0034] According to an embodiment of the present invention, the melt index of the low-density polyethylene is 0.3-20 g·(10 min) -1 .

[0035] According to the embodiments of the present invention, a suitable melt index can enable the material to have better processing performance while ensuring the performance of the base film.

[0036] According to another embodiment of the present invention, there is provided a method for preparing the above-mentioned cross membrane, comprising:

[0037] The base film is rotary cut and rolled at 46° to 47° to obtain a sheet film;

[0038] Cross-compounding at least two layers of sheet membranes to obtain a cross-membrane;

[0039] The base film is obtained by film blowing, secondary stretching and heat setting.

[0040] According to an embodiment of the present invention, a sheet film is obtained by rotary cutting and rolling the base film at 46°~47°, and at least two layers of the sheet film are cross-laminated to obtain a cross film. Only the slitting angle needs to be adjusted from 45° to 46°~47° to effectively alleviate the warping and curling of the cross film. The process is simple and has strong operability. It can be adapted to the original process and original equipment, and is convenient for large-scale application.

[0041] According to an embodiment of the present invention, the secondary stretching is longitudinal stretching, and the stretching ratio is 1 to 2, preferably 1.5 to 2.0. Specifically, the stretching ratio can be 1.0, 1.2, 1.5, 1.8 or 2.0.

[0042] According to the embodiments of the present invention, a suitable stretching ratio can maintain the orientation degree of the base film at a low level, further alleviating the problems of cross film warping and curling.

[0043] According to the embodiments of the present invention, as the stretch ratio increases, the orientation degree of the base film increases, and the tensile strength of the cross film increases. However, the higher the stretch ratio, the more difficult it is to eliminate the residual internal stress, and the risk of warping and curling of the cross film increases. Therefore, it is necessary to select an appropriate stretch ratio to further alleviate the problem of warping and curling of the cross film.

[0044] According to an embodiment of the present invention, the temperature of the secondary stretching is 100-150° C., preferably 120-140° C. Specifically, the temperature of the secondary stretching may be 100° C., 110° C., 120° C., 130° C., 140° C. or 150° C.

[0045] According to an embodiment of the present invention, the raw materials of the base film include high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of low-density polyethylene is 0.915~0.935g / cm 3 .

[0046] According to an embodiment of the present invention, the die temperature of the film blowing process is 150-300°C, preferably 200-250°C, specifically, the die temperature is 150°C, 170°C, 200°C, 220°C, 250°C, 270°C or 300°C.

[0047] According to an embodiment of the present invention, the draw ratio of the blown film process is 1-3, preferably 1.5-2.5, specifically, the draw ratio is 1, 1.2, 1.5, 1.7, 2.0, 2.5 or 3.

[0048] According to the embodiments of the present invention, the appropriate mouth film temperature and pulling ratio can further alleviate the problems of cross film warping and curling.

[0049] According to an embodiment of the present invention, the heat setting temperature is 70-120°C, preferably 80-100°C, specifically, the heat setting temperature is 70°C, 80°C, 90°C, 100°C, 110°C or 120°C.

[0050] According to an embodiment of the present invention, the heat setting time is 30 to 300 s, preferably 50 to 100 s, specifically, the heat setting time is 30 s, 50 s, 70 s, 80 s, 100 s, 120 s, 150 s, 180 s, 200 s, 250 s, 280 s or 300 s.

[0051] According to an embodiment of another aspect of the present invention, there is provided application of the above cross film or the cross film prepared by the above preparation method in the field of building waterproofing and packaging film.

[0052] The following lists a number of specific embodiments to illustrate the technical solution of the present invention in detail. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0053] Example 1

[0054] This embodiment 1 provides a cross film, which is formed by cross-compounding two layers of film with a slitting angle of 46 degrees.

[0055] This embodiment 1 also provides a method for preparing the above-mentioned cross membrane, comprising the following steps:

[0056] (1) A mixed material containing 40 wt% high-density polyethylene and 60 wt% low-density polyethylene was subjected to film blowing, with a die temperature of 230°C and a draw ratio of 2. Then, secondary stretching was performed, with a longitudinal stretching ratio of 1.5 and a temperature of 125°C. Finally, after heat setting at 90°C for 60 seconds, a base film was obtained.

[0057] (2) The base film is rotary cut at 46° and rolled up to obtain a sheet film.

[0058] (3) Take two layers of sheet membrane and cross-compound them to obtain a cross membrane.

[0059] Example 2

[0060] This embodiment 2 provides a cross film, which is formed by cross-compounding two layers of film with a slitting angle of 47 degrees.

[0061] This embodiment 2 also provides a method for preparing the above-mentioned cross membrane, comprising the following steps:

[0062] (1) A mixed material containing 60 wt% high-density polyethylene and 40 wt% low-density polyethylene was subjected to film blowing, with a die temperature of 240°C and a draw ratio of 2.5. Then, a secondary stretching was performed, and the secondary stretching was longitudinal stretching with a stretching ratio of 1.5 and a temperature of 140°C. Finally, after heat setting at 110°C for 45 seconds, a base film was obtained.

[0063] (2) The base film is rotary cut at 47° and rolled up to obtain a sheet film.

[0064] (3) Take two layers of sheet membrane and cross-compound them to obtain a cross membrane.

[0065] Example 3

[0066] This embodiment 3 provides a cross film, which is formed by cross-compounding two layers of film with a slitting angle of 46 degrees.

[0067] This embodiment 3 also provides a method for preparing the above-mentioned cross membrane, comprising the following steps:

[0068] (1) High-density polyethylene was subjected to film blowing, with a die temperature of 240°C and a draw ratio of 2.5. Then, secondary stretching was performed, with a longitudinal stretching ratio of 1.5 and a temperature of 140°C. Finally, after heat setting at 110°C for 45 seconds, a base film was obtained.

[0069] (2) The base film is rotary cut at 46° and rolled up to obtain a sheet film.

[0070] (3) Take two layers of sheet membrane and cross-compound them to obtain a cross membrane.

[0071] Example 4

[0072] This embodiment 4 provides a cross-film and a preparation method thereof, referring to embodiment 1, except that in step (1) of the preparation method of the cross-film, the stretching ratio is 2.

[0073] Comparative Example 1

[0074] This comparative example 1 provides a cross film, which is formed by cross-compounding two layers of film with a slitting angle of 45°.

[0075] This comparative example 1 also provides a method for preparing the above-mentioned cross-film, referring to Example 1, except that in step (2) of the method for preparing the cross-film, the base film is rotary cut and rolled at 45° to obtain a sheet film.

[0076] Comparative Example 2

[0077] This comparative example 1 provides a cross film, which is formed by cross-compounding two layers of film with a slitting angle of 48°.

[0078] This comparative example 1 also provides a method for preparing the above-mentioned cross-film, referring to Example 1, except that in step (2) of the method for preparing the cross-film, the base film is rotary cut and rolled at 48° to obtain a sheet film.

[0079] Comparative Example 3

[0080] This comparative example 3 provides a cross film and a preparation method thereof, referring to Example 1, except that in step (1) of the preparation method of the cross film, the stretching ratio is 2.5.

[0081] Comparative Example 4

[0082] This comparative example 4 provides a cross film and a preparation method thereof, referring to Example 1, except that in step (1) of the preparation method of the cross film, the stretching ratio is 3.

[0083] The base film and cross film provided in the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 4 were tested, and the specific testing method was as follows:

[0084] 1. Wide-angle test: Use a horizontal wide-angle X-ray diffractometer to measure the orientation of the base film.

[0085] 2. Mechanical properties test: According to GB / T 1040.3-2006 test, the specimen is type 2, with a length of 150 mm, a width of 15 mm, a test speed of 500 mm / min, and three data are tested for each cross membrane to calculate the average value.

[0086] 3. 110°C oven dimensional change rate test: Cut the provided cross film into 10*10cm square samples and put them into a 110℃ oven for 30min. After the samples are cooled, accurately measure and record the dimensional changes. Measure each sample 3-6 times and calculate the average value.

[0087] 4. Determine the warping and curling of the cross film by visual inspection.

[0088] The test results are shown in Table 1. It can be seen from Table 1 that compared with Comparative Examples 1 to 4, Examples 1 to 4 effectively improve the warping and curling of the cross film by adjusting the peeling angle of the base film to 46°~47° and controlling the orientation of the base film to 0.7~0.85. Further, from the analysis of the test data of Examples 1, 4 and Comparative Examples 3, 4, it can be seen that with the increase of the stretching ratio, the orientation of the base film increases, the tensile strength of the cross film increases, but the elongation at break decreases, and the dimensional change rate of the 110°C oven increases. It shows that under the action of unidirectional stretching, the polyethylene molecular chains produce orientation arrangement and recrystallization to form a highly ordered crystalline morphology; increasing the stretching ratio can significantly increase the orientation of the lamellae; the highly ordered crystalline morphology formed during the stretching process is beneficial to improve the mechanical strength of the cross film. At the same time, the higher the stretching ratio, the more difficult it is to eliminate the residual internal stress, and its temperature resistance will deteriorate. Therefore, if you want to obtain a high-performance cross film, you need to select appropriate process parameters such as the stretching ratio. However, even if the same process parameters are used in different machines, the performance may be different. In view of this situation, the present invention takes the orientation of polyethylene as the research object, finds the law of cross film performance changes under different orientations, and obtains the optimal orientation of cross films with high dimensional stability and the corresponding production process. By controlling the orientation of the base film and the peeling angle within the appropriate range, the warping and curling of the cross film can be effectively improved.

[0089] Table 1

[0090]

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made to the technical method by any technician familiar with the art within the spirit and principle of the present invention is still included in the protection scope of the technical solution of the present invention.

Claims

1. A cross membrane, characterized in that, The cross film is formed by cross-compounding at least two layers of sheet film; wherein the sheet film is made by rotary cutting and rolling a base film at 46°~47°, and the orientation degree of the base film is 0.70~0.

85.

2. The cross membrane according to claim 1, characterized in that The film comprises high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of the low-density polyethylene is 0.915-0.935 g / cm 3 .

3. The cross membrane according to claim 2, characterized in that The mass percentage of the high-density polyethylene in the film is 40% to 70%, and the mass percentage of the low-density polyethylene is 30% to 60%.

4. The cross membrane according to claim 2 or 3, characterized in that The high-density polyethylene has a melt index of 0.01 to 5 g·(10 min) -1 ; The melt index of the low-density polyethylene is 0.3-20 g·(10 min) -1 .

5. The method for preparing a cross-film according to any one of claims 1 to 4, characterized in that: The preparation method comprises: The base film is rotary cut and rolled at 46° to 47° to obtain a sheet film; Cross-compounding at least two layers of the sheet films to obtain a cross-film; The base film is prepared by film blowing, secondary stretching and heat setting.

6. The preparation method according to claim 5, characterized in that: The secondary stretching is longitudinal stretching, and the stretching ratio is 1-2.

7. The preparation method according to claim 5, characterized in that: The secondary stretching temperature is 100-150°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that The raw materials of the base film include high-density polyethylene and low-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 The density of the low-density polyethylene is 0.915-0.935 g / cm 3 .

9. The preparation method according to any one of claims 5 to 7, characterized in that The die temperature of the film blowing process is 150-300°C, and the draw ratio is 1-3; The heat setting temperature is 70-120° C. and the time is 30-300 seconds.

10. Application of the cross film described in any one of claims 1 to 4 or the cross film prepared by the preparation method described in any one of claims 5 to 9 in the field of building waterproofing and packaging film.

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