CN113637252B - A strong cross-membrane, its preparation method, and its application - Google Patents

Abstract

The invention discloses a strong crossed membrane and a preparation method and application thereof, wherein the preparation method comprises the following steps: blowing film to obtain film; performing secondary stretching and heat setting on the film to obtain a base film, and performing stretching test on the obtained base film on a universal testing machine along the traction direction to obtain a stress sigma-strain epsilon curve, wherein the maximum stress is sigma _max Maximum strain of ε _max Performing first-order derivation on the stress sigma-strain epsilon curve to obtain dsigma/depsilon, wherein 45MPa is less than or equal to sigma _max ≤150MPa，150％≤ε _max Less than or equal to 800 percent, dsigma/depsilon meets dsigma/depsilon not less than 0; and (3) carrying out cross compounding on the base film after spiral cutting to obtain the strong cross film. The base film meets the tensile property, so that yield damage of a common strong crossed film cannot occur when the finally obtained strong crossed film is in service in a small deformation area, and a new microcosmic bearing unit is formed under a certain strain condition; and meanwhile, the strong crossed film has excellent tensile strength and elongation at break due to the maximum stress and strain in a specific range.

Description

A strong cross-membrane, its preparation method, and its application

technical field

The invention relates to the technical field of polymer film processing, in particular to a strong cross film, a preparation method thereof, and an application thereof.

Background technique

The strong cross film is composed of two or more uniaxially oriented films. Compared with ordinary blown film products, biaxially oriented films have higher strength, toughness, tear resistance and dimensional stability. It is widely used in the fields of label film, packaging film and waterproof membrane.

At present, when paying attention to the mechanical properties of the strong cross membrane, especially the tensile strength of the strong cross membrane, it is usually from the perspective of the maximum tensile force when the strong cross membrane is damaged and the elongation at the maximum tensile force. Performance evaluation and improvement. Among them, the maximum tensile force when the strong cross membrane is damaged is one of the important indicators for evaluating the mechanical properties of the strong cross membrane. However, even if the strong cross membrane has a high tensile strength, wrinkles, hollowing, Bubbles and other service defects, the occurrence of these defects is usually not accompanied by the stretching and tearing of the strong cross-membrane. The damage occurs under the condition of small deformation of the strong cross-membrane, but seriously affects the performance of the strong cross-membrane.

Contents of the invention

The main purpose of the present invention is to propose a strong cross-membrane and its preparation method, as well as its application, aiming to solve the problem that the strong cross-membrane will be damaged under the condition of small deformation and affect its performance.

In order to achieve the above object, the present invention proposes a preparation method of a strong cross membrane, the preparation method comprising the following steps:

The raw material is processed by blown film to obtain a film, wherein the raw material includes a polyethylene mixture, and the polyethylene mixture includes high-density polyethylene and linear low-density polyethylene, and the melt flow rate of the high-density polyethylene is 0.015- 0.45g/10min, the melting temperature of the high-density polyethylene is Tm, the melt flow rate of the linear low-density polyethylene is 0.5～0.8g/10min, the air ring cooling air in the blown film processing step The temperature is 0-28°C, the die temperature is Tm+100°C-Tm+150°C, and the traction ratio is 2.8-15.0;

The film is subjected to secondary stretching and heat setting to obtain a base film, and the obtained base film is subjected to a tensile test along the traction direction on a universal testing machine to obtain a stress σ-strain ε curve, and the maximum stress is σ _max , The maximum strain is ε _max , and the first-order derivation of the stress σ-strain ε curve is performed to obtain dσ/dε, wherein, 45MPa≤σ _max ≤150MPa, 150%≤ε _max ≤800%, and dσ/dε satisfies dσ/dε ≥0;

After the basement membrane is helically cut, it is cross compounded to obtain a strong cross membrane.

Optionally, the film produced by the blown film processing is subjected to a tensile test along the traction direction on a universal testing machine to obtain a stress σ'-strain ε' curve, the maximum stress is _σ'max , and the maximum strain is _ε'max , Perform first-order derivation on the stress σ'-strain ε' curve to obtain dσ'/dε', wherein there are at least two yield behaviors in the stress σ'-strain ε' curve, 35MPa≤σ' _max ≤120MPa , 300%≤ε' _max ≤1400%, dσ'/dε' satisfies dσ'/dε'≥-0.1.

Optionally, the stretch ratio of the secondary stretching is 1.8-4.5, and the heat-setting temperature is Tm-35°C-Tm-5°C.

Optionally, said linear low density polyethylene comprises metallocene linear low density polyethylene; and/or,

In the polyethylene mixture, the mass percentage of the high-density polyethylene is not less than 75%.

Optionally, the weight-average molecular weight of the high-density polyethylene is 160000-360000 g/mol, and the molecular weight distribution is 3.2-9.0; and/or,

The weight-average molecular weight of the low-density polyethylene is 80000-250000 g/mol.

Optionally, the temperature of the air ring cooling air is 5-25° C., and the traction ratio is 3.0-12.0.

Optionally, the stretch ratio of the secondary stretching is 1.8-4.5, and the heat-setting temperature is Tm-35°C-Tm-5°C.

Optionally, the maximum stress is σ _max , the maximum strain is ε _max , and dσ/dε obtained by first-order derivation of the stress σ-strain ε curve satisfies the following conditions:

60MPa≤σ _max <150MPa, 200%≤ε _max ≤700%, dσ/dε satisfies dσ/dε>0.

Furthermore, the present invention also proposes a strong crossing membrane, which is prepared by the method for preparing the strong crossing membrane as described above.

In addition, the present invention also proposes a waterproof roll material, which includes the above-mentioned strong cross membrane.

The present invention also proposes a label film, which includes the strong cross film as described above.

In the technical solution provided by the present invention, through the design of the raw materials and the process parameters of the blown film processing steps, the base film made by blown film processing, secondary stretching, and heat setting is stretched along the traction direction on a universal testing machine. The stress σ-strain ε curve is obtained by testing, the maximum stress _is σ _max , and the maximum strain is ε _max , and the first-order derivation is performed on the stress σ-strain ε curve to obtain dσ/dε, wherein, 45MPa≤σmax≤150MPa, 150 % ≤ ε _max ≤ 800%, dσ/dε satisfies dσ/dε ≥ 0, so that the strong cross membrane obtained by cross-compositing of the basement membrane will not appear the yield failure of ordinary strong cross membrane when it serves in the small deformation area, Instead, a new microscopic load-bearing unit is formed under certain strain conditions; at the same time, a specific range of maximum stress and strain also makes the strong cross membrane have excellent tensile strength and elongation at break.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only For some embodiments of the present invention, those skilled in the art can also obtain other related drawings according to these drawings without any creative effort.

Fig. 1 is the stress-strain curve that the film that blown film processing makes in the embodiment of the present invention 1 carries out tensile test and obtains;

Fig. 2 is the first-order derivative curve corresponding to the stress-strain curve in Fig. 1;

3 is a schematic structural view of the base film prepared in Example 1 of the present invention;

Fig. 4 is the stress-strain curve that the base film that makes in the embodiment 1 of the present invention carries out tensile test and obtains;

Fig. 5 is the first-order derivative curve corresponding to the stress-strain curve in Fig. 4;

Figure 6 is a schematic structural view of the strong cross membrane prepared in Example 1 of the present invention;

Fig. 7 is the stress-strain curve that the film that blown film processing makes in comparative example 1 of the present invention carries out tensile test and obtains;

Fig. 8 is the first-order derivative curve corresponding to the stress-strain curve in Fig. 7;

Fig. 9 is the stress-strain curve obtained by tensile test of the base film prepared in Comparative Example 1 of the present invention;

FIG. 10 is a first-order derivative curve corresponding to the stress-strain curve in FIG. 9 .

The realization of the purpose of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

In addition, the meaning of "and/or" appearing in the whole text includes three parallel schemes, taking "A and/or B" as an example, including scheme A, scheme B, or schemes that both A and B satisfy. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , nor within the scope of protection required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The maximum tensile force when the strong cross-membrane is broken is one of the important indicators for evaluating the mechanical properties of the strong cross-membrane. However, even if the strong cross-membrane has a high tensile strength, wrinkles, hollows, bubbles, etc. will still appear during actual use Service defects, the occurrence of these defects is usually not accompanied by the stretching and tearing of the strong cross-membrane. The damage occurs under the condition of small deformation of the strong cross-membrane, but seriously affects the performance of the strong cross-membrane.

In view of this, the present invention proposes a kind of preparation method of strong cross membrane, and described preparation method comprises the following steps:

Step S10, blowing the raw material to obtain a film, wherein the raw material includes a polyethylene mixture, the polyethylene mixture includes high-density polyethylene and linear low-density polyethylene, and the melt flow rate of the high-density polyethylene is 0.015～0.45g/10min, the melting temperature of the high-density polyethylene is Tm, the melt flow rate of the linear low-density polyethylene is 0.5～0.8g/10min, the air ring in the blown film processing step The temperature of the cooling air is 0-28°C, the die temperature is Tm+100°C-Tm+150°C, and the traction ratio is 2.8-15.0;

Step S20, performing secondary stretching and heat setting on the film to obtain a base film;

In step S30, the basement membrane is helically cut and then cross-composited to obtain a strong cross-membrane.

According to the microstructure analysis of the strong cross membrane and the research on the structural transformation process under the real service conditions, the inventors found that: the service defects of the strong cross membrane when there is no stretching or tearing failure are mainly related to the crystal structure and the small deformation area. It is related to the non-uniformity of the microstructure. Specifically, the structural evolution near the yield point during the stretching process directly affects the non-uniform wrinkles and hollows that appear during use.

In the present invention, through the design of raw materials, process parameters of blown film processing, and preparation steps, the base film prepared in step S20 is tensile tested along the traction direction on a universal testing machine to obtain a stress σ-strain ε curve, and the maximum stress is σ _max , the maximum strain is ε _max , and the stress σ-strain ε curve is first-order derived to obtain dσ/dε, where, 45MPa≤σ _max ≤150MPa, 150%≤ε _max ≤800%, dσ/dε satisfies dσ /dε≥0, in this way, when the strong cross-membrane made of basement membrane composited by cross-membrane serves in the small deformation area, it will not appear the yield failure that will occur in the ordinary strong cross-membrane, but will form a new microscopic Load-bearing unit; at the same time, the maximum stress and strain in a specific range also make the strong cross membrane have excellent tensile strength and elongation at break. In a preferred embodiment, _{60MPa≤σmax} <150MPa, 200% _{≤εmax≤700} %, and dσ/dε satisfies dσ/dε>0.

In order to obtain the above-mentioned base film, the stretchability of the film obtained by blown film processing in step S10 is the key to obtain the above-mentioned base film. Further, in this embodiment, by adjusting and controlling the specific formula of raw materials and the specific process parameters of blown film processing, the tensile test is carried out on the film universal testing machine made by the blown film processing along the traction direction to obtain the stress σ For the '-strain ε' curve, the maximum stress is σ' _max and the maximum strain is ε' _max , and the first-order derivation is performed on the stress σ'-strain ε' curve to obtain dσ'/dε', wherein the stress σ There are at least two yield behaviors in the '-strain ε' curve, 35MPa≤σ' _max ≤120MPa, 300%≤ε' _max ≤1400%, dσ'/dε' satisfy dσ'/dε'≥-0.1, so blowing The film obtained by film processing can be stretched twice and heat-set to obtain the above-mentioned base film.

In the technical solution provided by the present invention, the ratio of raw materials, the die temperature of the film blowing process, the cooling air temperature of the air ring and the traction ratio, these four have a linkage effect. When one of the parameters changes, the remaining three parameters Corresponding changes are also required, and the four cooperate with each other to obtain a film with the above-mentioned tensile properties. That is, by defining the tensile properties of the film produced by the blown film process, the relationship between the raw material, the die temperature of the blown film process, the cooling air temperature of the air ring and the draw ratio can be determined.

In order to facilitate the preparation of a film with the above-mentioned tensile properties, in a specific embodiment, the linear low-density polyethylene includes metal linear low-density polyethylene; and/or, in the polyethylene mixture, the high-density polyethylene The mass percentage of ethylene is not less than 75%.

Further, the melt flow rate of polyethylene is affected by multiple parameters such as polyethylene weight-average molecular weight, molecular weight distribution, and branching. In this embodiment, the weight-average molecular weight of the high-density polyethylene is 160,000 to 360,000 g/ mol (i.e. 1.6×10 ⁵ ~3.6×10 ⁵ g/mol), the molecular weight distribution is 3.2~9.0; and/or, the weight average molecular weight of the low density polyethylene is 80000~250000 g/mol (i.e. 0.8×10 ⁵ ~2.5×10 ⁵ g/mol). In another embodiment, the comonomer of the metallocene LLDPE is hexene, and its branched chain content is 1.2-1.5 mol%. In this way, high-density polyethylene and metallocene linear low-density polyethylene containing specific molecular parameters are used as raw materials, and by controlling the key process parameters such as die temperature, air ring cooling air temperature, and traction ratio in the film blowing process, it is possible to obtain the above film.

Specifically, the die temperature set by the present invention is higher than the blown film temperature of conventional polyethylene, and the temperature of the air ring cooling air is lower than the set temperature of conventional blown film, and the polyethylene with a specific structure can obtain the above-mentioned under the condition of high supercooling degree. Stretchable film. Therefore, when the film blowing temperature is set lower, the temperature of the air ring cooling air should also be set lower, so that the temperature difference is larger. In a preferred embodiment, the temperature of the air ring cooling air is 5-25° C., and the traction ratio is 3.0-12.0.

During specific implementation, the polyethylene mixture is added into a blown film machine to obtain a film through blown film processing. Wherein, the film blowing machine may be a single-layer film blowing machine, or a multi-layer co-extrusion film blowing machine. In addition, the melting point temperature Tm of high-density polyethylene refers to the peak temperature of the melting curve of high-density polyethylene.

In order to improve the performance of the prepared strong cross film and facilitate its use according to different needs, in this embodiment, the raw materials also include processing aids and color masterbatches. Among them, the color masterbatch refers to a plastic colorant that is well dispersed with a high proportion of pigments or additives and thermoplastic resins. Through the addition of color masterbatches, the strong cross film can be made into different colors according to actual needs. . The present invention does not limit the specific type of the processing aid, and it may be a conventional aid in the field of strong cross-membrane. In a specific embodiment, the processing aids include antioxidants and UV absorbers. Further, the total mass of the ultraviolet absorber, antioxidant and color masterbatch is 1 to 3% of the total mass of the polyethylene mixture (ie high-density polyethylene and metallocene linear low-density polyethylene), preferably 1.5%.

The present invention does not limit how to obtain the base film with the above-mentioned stretching properties through the secondary stretching and heat-setting processing technology of the film containing the above-mentioned stretching properties obtained by blown film processing. In this embodiment, the secondary The stretching ratio of stretching is 1.8-4.5, and the heat setting temperature is Tm-35°C-Tm-5°C.

Wherein, the secondary stretching and heat setting process can be carried out in the form of a tubular film, a flat film method, or a multi-roller longitudinal stretching method.

In one embodiment, the step S30 specifically includes: cutting the base film helically to obtain a plurality of membrane sheets; then performing cross compounding on at least two of the film sheets to obtain a strong cross membrane. In another embodiment, the base film is first subjected to post-treatments such as coating and modification, and then spirally cut to obtain multiple membranes; then at least two of the membranes are cross-composited to obtain a strong cross membrane.

It should be noted that the tensile curves of the above-mentioned film and the above-mentioned base film provided in the present invention are obtained by testing with reference to GB/T1040.3-2006, wherein the tensile rate is 50-200mm/min, preferably 50mm /min.

In the technical solution provided by the present invention, through the design of raw materials and process parameters of blown film processing, a film that meets the following tensile properties can be produced: the film is tensile tested along the traction direction on a universal testing machine to obtain the stress σ'- Strain ε' curve, the maximum stress is σ' _max , the maximum strain is ε' _max , the stress σ'-strain ε' curve is first-order derived to obtain dσ'/dε', wherein, 35MPa≤σ' _max ≤ 120MPa, 300%≤ε' _max ≤1400%, dσ'/dε' satisfies dσ'/dε'≥-0.1, there are at least two yield behaviors in the stress σ'-strain ε'curve; The design of stretching and heat setting parameters can produce the base film that meets the following tensile properties: the base film is tensile tested on a universal testing machine along the traction direction to obtain a stress σ-strain ε curve, the maximum stress is σ _max , and the maximum The strain is ε _max , and the first-order derivation of the stress σ-strain ε curve is performed to obtain dσ/dε, wherein, 45MPa≤σ _max ≤150MPa, 150%≤ε _max ≤800%, and dσ/dε satisfies dσ/dε≥ 0. In this way, when the strong cross-membrane obtained by cross-compositing the base film is in service in a small deformation area, it will not appear the yield failure that will occur in the ordinary strong cross-membrane, but will form a new microscopic load-bearing unit under a certain strain condition; at the same time, a specific range The maximum stress and strain also make the strong cross film have excellent tensile strength and elongation at break.

Furthermore, the present invention also proposes a strong crossing membrane, which is prepared by the above-mentioned strong crossing membrane preparation method. The specific preparation method of the strong cross-membrane refers to the above-mentioned embodiments. Since the waterproof roll material adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments. I won't repeat them one by one.

In addition, the present invention also proposes a waterproof coiled material, which includes a strong cross membrane, and the strong cross membrane is obtained by the method for preparing a strong cross membrane as described above. Specifically, the polyethylene strong cross-membrane is used as one layer of the waterproof roll material, and it is combined with other functional layers such as asphalt layer to obtain a waterproof roll material. The specific preparation method of the strong cross-membrane refers to the above-mentioned embodiments. Since the waterproof roll material adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments. I won't repeat them one by one.

The present invention also proposes a label film or packaging film, which includes the strong cross film as described above. The strong cross film can be directly used as a label film or a packaging film, and can also be compounded with other functional substances according to actual needs to obtain a label film or packaging film with required functions. Specifically, special coatings, such as heat-sensitive coatings, writing ink coatings, etc., can be coated on the surface of polyethylene strong cross film, and some special materials can also be compounded to make it resistant to high temperature, easy to print, and anti-corrosion. The specific components and the ratio between the components of the strong cross film refer to the above-mentioned examples. Since the label film or packaging film adopts all the technical solutions of all the above-mentioned examples, it has at least the technical solutions of the above-mentioned examples. All the beneficial effects brought about will not be described one by one here.

The technical solutions of the present invention will be described in further detail below in conjunction with specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

Example 1

(1) 90wt% high-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.055g/10min, the weight-average molecular weight is 1.85×10 ⁵ g/mol, the molecular weight distribution is 4.2, and the melting point is 129.4°C) and 10wt% metallocene linear low density polyethylene (wherein, the melt flow rate of metallocene linear low density polyethylene is 0.6g/10min, comonomer is hexene, branched chain content is 1.5mol%, weight average molecular weight is 1.1×10 ⁵ g/mol) after mixing evenly, then add 0.3wt% antioxidant (specifically antioxidant 1010), 0.7wt% UV absorber (specifically UV-0 and UV -944 obtained by compounding in equal proportions) and 0.5wt% color masterbatch, and then mix uniformly to obtain raw materials, which are processed by film blowing to obtain films, wherein the die temperature is set at 250° C. during the film blowing process (i.e. Tm+120.6°C), the cooling air temperature of the air ring is 15°C by installing refrigerant between the air ring and the fan, and the traction ratio is 10. The film was subjected to a tensile test to obtain a tensile curve as shown in Figure 1. It can be seen from Figure 1 that there are two yield behaviors in the tensile curve, the maximum stress is 50.8MPa, and the maximum strain is 994.8%. The first-order derivation is performed on the extension curve, and the curve shown in Figure 2 is obtained. It can be seen from Figure 2 that dσ/dε>-0.1.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 3.5, and the heat setting temperature is 100° C. (ie Tm-29.4° C.), the base film The structure of the film is shown in Figure 3. The horizontal line in Figure 3 represents the orientation direction of the molecular chain, which is consistent with the traction direction of the blown film process, and the sample is prepared along this direction during the tensile performance test. The base film was subjected to a tensile test to obtain the tensile curve shown in Figure 4. It can be seen from Figure 4 that the maximum stress is 100.4MPa and the maximum strain is 427.0%, and the first-order derivative of the tensile curve is obtained. From the curve shown in Figure 5, it can be seen from Figure 5 that dσ/dε≥0.

(3) After the basement membrane is helically cut, a plurality of membrane sheets are obtained, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane, and the structure of the strong-cross membrane is shown in FIG. 6 .

Example 2

(1) 80wt% high-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.055g/10min, the weight-average molecular weight is 1.85×10 ⁵ g/mol, the molecular weight distribution is 4.2, and the melting point is 129.4°C) And 20wt% metallocene linear low density polyethylene (wherein, the melt flow rate of metallocene linear low density polyethylene is 0.6g/10min, and comonomer is hexene, branch content is 1.5mol%, weight average molecular weight is 1.1×10 ⁵ g/mol) after mixing evenly, then add 0.4wt% antioxidant (specifically antioxidant 1010), 0.6wt% UV absorber (specifically UV-0) and 0.6wt% color masterbatch, and then mix uniformly to obtain raw materials, which are processed by blown film to obtain a film, wherein, the die temperature is set at 245°C (ie Tm+115.6°C) during the blown film process, and the Refrigerant is installed between the ring and the fan so that the temperature of the air ring cooling air is 13°C and the traction ratio is 12. The tensile curve obtained by carrying out the tensile test on the film, there are two yield behaviors in the tensile curve, the maximum stress is 50.8MPa, and the maximum strain is 994.8%, and the first-order derivative of the tensile curve is obtained to obtain the first-order Conductive curve, where dσ/dε≥-0.1.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 3.5, and the heat setting temperature is 98° C. (ie Tm-31.4° C.). The tensile test of the film is carried out to obtain the tensile curve. The maximum stress in the tensile curve is 98.7MPa, and the maximum strain is 444.1%. The tensile curve is first-order derivation. In the first-order derivation curve, dσ/dε≥0 .

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

Example 3

(1) 75wt% high-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.015g/10min, the weight-average molecular weight is 1.6×10 ⁵ g/mol, the molecular weight distribution is 3.2, and the melting point is 129.9°C) and 25wt% metallocene linear low density polyethylene (wherein, the melt flow rate of metallocene linear low density polyethylene is 0.8g/10min, comonomer is hexene, branched chain content is 1.5mol%, weight average molecular weight is 1.1×10 ⁵ g/mol) after mixing evenly, then add 0.5wt% of the antioxidant (antioxidant 1010 and antioxidant 168 are compounded in equal proportions), 0.4wt% of the ultraviolet absorber ( UV-531 and UV-622 are compounded in equal proportions) and 0.6wt% color masterbatch, and then mixed evenly to obtain raw materials, which are processed by film blowing to obtain films, wherein the die temperature is set during the film blowing process The temperature is 230°C (ie Tm+100.1°C). By installing refrigerant between the air ring and the fan, the temperature of the cooling air in the air ring is 0°C, and the traction ratio is 15. The tensile curve obtained from the tensile test of the film shows that there are two yield behaviors in the tensile curve, the maximum stress is 36.7MPa, and the maximum strain is 1200.5%, and the first-order derivative of the tensile curve is obtained to obtain the first-order Conductive curve, where dσ/dε≥-0.1.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 4.5, and the heat setting temperature is 95° C. (ie Tm-34.9° C.). The tensile test of the film is carried out to obtain the tensile curve. The maximum stress in the tensile curve is 85.5MPa, the maximum strain is 554.3%, and the tensile curve is first-order derivation. In the first-order derivation curve, dσ/dε≥0 .

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

Example 4

(1) 85wt% high-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.45g/10min, the weight-average molecular weight is 3.6×10 ⁵ g/mol, the molecular weight distribution is 9, and the melting point is 130.2°C) and 15wt% metallocene linear low density polyethylene (wherein, the melt flow rate of metallocene linear low density polyethylene is 0.5g/10min, comonomer is hexene, branched chain content is 1.2mol%, weight average molecular weight is 2.5×10 ⁵ g/mol) after mixing evenly, the raw material is obtained, and the raw material is processed by film blowing to obtain a film, wherein, the die temperature is set at 280°C (ie Tm+149.8°C) during the film blowing process, and the Refrigerant is installed between the ring and the fan so that the temperature of the air ring cooling air is 28°C and the traction ratio is 2.8. The tensile curve obtained from the tensile test of the film shows that there are two yield behaviors in the tensile curve, the maximum stress is 81.4MPa, and the maximum strain is 606.5%. The first-order derivative of the tensile curve is obtained to obtain Conductive curve, where dσ/dε≥-0.1.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 1.8, and the heat setting temperature is 115° C. (ie Tm-15.2° C.). The tensile test of the film is carried out to obtain the tensile curve. The maximum stress in the tensile curve is 101.6MPa, and the maximum strain is 321.5%. The tensile curve is first-order derivation. In the first-order derivation curve, dσ/dε≥0 .

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

Comparative example 1

(1) The raw material used is a strong cross film with a proportion of 88% of high-density polyethylene, and the remaining 12% is an auxiliary agent. Among them, the melting point of high-density polyethylene is 130.2 ° C. The raw material is processed by blown film to obtain a film, wherein In the film blowing process, the die temperature is set to 210°C (ie Tm+79.8°C), and the cooling air temperature of the air ring is 30°C by installing a refrigerant between the air ring and the fan, and the traction ratio is 15. The film was subjected to a tensile test to obtain the tensile curve shown in Figure 7. It can be seen from Figure 7 that there is a yield behavior in the tensile curve, the maximum stress is 30.9MPa, and the maximum strain is 951.6%. The first-order derivative of the curve is obtained to obtain the curve shown in Figure 8. It can be seen from Figure 8 that dσ/dε is less than -0.1.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 3.5, and the heat setting temperature is 100° C. (ie Tm-30.2° C.). The tensile test of the film was carried out to obtain the tensile curve shown in Figure 9. It can be seen from Figure 9 that the maximum stress is 71.0MPa and the maximum strain is 348.2%, and the first-order derivative of the tensile curve is obtained to obtain the tensile curve shown in Figure 5. It can be seen from the curve shown in Figure 5 that dσ/dε is less than 0.

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

Comparative example 2

(1) 90wt% high-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.055g/10min, the weight-average molecular weight is 1.85×10 ⁵ g/mol, the molecular weight distribution is 4.2, and the melting point is 129.4°C) and 10wt% metallocene linear low density polyethylene (wherein, the melt flow rate of metallocene linear low density polyethylene is 0.6g/10min, comonomer is hexene, branched chain content is 1.5mol%, weight average molecular weight is 1.1×10 ⁵ g/mol) after mixing evenly, then add 0.3wt% antioxidant (specifically antioxidant 1010), 0.7wt% UV absorber (specifically UV-0 and UV -944 obtained by compounding in equal proportions) and 0.5wt% color masterbatch, and then mix uniformly to obtain raw materials, which are processed by film blowing to obtain films, wherein the die temperature is set at 220° C. during the film blowing process (i.e. Tm+109.4°C), the cooling air temperature of the air ring is 30°C by installing refrigerant between the air ring and the fan, and the traction ratio is 10.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 3.5, and the heat setting temperature is 100° C. (ie Tm-29.4° C.). The tensile test of the film is carried out to obtain the tensile curve. The maximum stress in the tensile curve is 80.6MPa, and the maximum strain is 336.4%. The tensile curve is first-order derivation. In the first-order derivation curve, dσ/dε exists less than 0 case.

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

Comparative example 3

(1) High-density polyethylene (wherein, the melt flow rate of high-density polyethylene is 0.01g/10min, the weight average molecular weight is 1.93×10 ⁵ g/mol, the molecular weight distribution is 3.1, and the melting point is 130.1°C), and then Add 0.3wt% of antioxidant (specifically antioxidant 1010), 0.7wt% of UV absorber (specifically obtained by compounding UV-0 and UV-944 in equal proportions) and 0.5wt% of the total amount of Color masterbatch, and then mixed evenly to obtain raw materials, which are processed by film blowing to obtain films, wherein the die temperature is set at 220°C (ie Tm+89.9°C) during the film blowing process, and the temperature is passed between the air ring and the fan Refrigerant is installed in the room so that the temperature of the cooling air in the air ring is 30°C and the traction ratio is 12.

(2) The film is subjected to secondary stretching and heat setting to obtain a base film, wherein the stretching ratio of the secondary stretching is 3.5, and the heat setting temperature is 100° C. (ie Tm-30.1° C.). The tensile test of the film is carried out to obtain the tensile curve. The maximum stress in the tensile curve is 78.4MPa, the maximum strain is 294.1%, and the first-order derivation of the tensile curve is performed. In the first-order derivation curve, dσ/dε exists less than 0 case.

(3) The basement membrane is spirally cut to obtain a plurality of membrane sheets, and two of the membrane sheets are cross-composited to obtain a strong cross-membrane.

The base film prepared in the embodiment and the comparative example is prepared into a strong cross film after rotary cutting, lamination and cross compounding (that is, one more lamination step than the strong cross film of the preparation of the above examples and comparative examples) and Self-adhesive rubber asphalt composite (that is, made of waterproof membrane), and the actual construction test was carried out, and the test results shown in Table 1 were obtained. It should be noted that, for the convenience of comparison, the correlation of the tensile curve of the base film The parameters are also placed in Table 1, where:

○: During the construction process, there are no wrinkles or bubbling defects in the strong cross-membrane;

△: During the construction process, a small amount of wrinkles and bubbling defects appear in the strong cross-membrane;

×: During the construction process, a large number of wrinkles and bubbling defects appeared in the strong cross-membrane.

Table 1 tensile curve and performance test results

As can be seen from Figures 1 to 10 and Table 1, the base films prepared in Examples 1 to 4 exhibit high strength and high toughness, and in the small deformation region (≤100%), the stress does not drop ( dσ/dε≥0), indicating that the basement membrane has no serious microstructural damage under the action of external force, thus preventing the service defects of the strong cross-membrane under the condition of small deformation. As can be seen from Comparative Example 1, the film obtained in the film blowing stage on the ordinary strong cross film production line has a typical polyethylene tensile yield phenomenon in the stretching process, that is, the stress is significantly reduced, and the base film finally obtained is There is also a phenomenon of stress drop in the small deformation area, indicating that the base film has structural damage during the stretching process, and the plateau area of stress after yielding represents the expansion of the narrow neck caused by inhomogeneous deformation of the material. These phenomena are macroscopically It will lead to service defects such as folds and hollowing in the strong cross-membrane. From Comparative Example 2 and Comparative Example 3, it can be seen that when one of the parameters such as the raw material formula, the die temperature of the blown film processing process, and the air ring cooling air temperature are not within the scope provided by the present invention, the present invention cannot obtain A film within the defined range of tensile properties cannot obtain a base film within the defined range of tensile properties of the present invention. Simultaneously from Comparative Examples 1 to 3, it can also be seen that when the tensile properties of the base film are not within the scope provided by the present invention, defects such as bubbling are prone to occur in the strong cross film that it finally makes during use, that is, The parameters of the tensile curve of the base film are directly related to the occurrence of defects such as bubbles.

In summary, the present invention can obtain a film that satisfies the tensile properties through the design of parameters such as the raw material formula, the die temperature in the film blowing process, the cooling air temperature of the air ring, and the traction ratio, and then through secondary stretching and By heat setting, a base film with a specific tensile curve can be obtained, so that compared with the ordinary strong cross film, the final strong cross film can reduce its yield damage in the small deformation area, avoiding wrinkles, hollowing, etc. The emergence of service defects, while having excellent tensile strength and elongation at break.

The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the patent protection scope of the present invention.

Claims (8)

1. A preparation method for strong cross membrane, is characterized in that, comprises the following steps: The raw material is processed by blown film to obtain a film, wherein the raw material includes a polyethylene mixture, and the polyethylene mixture includes high-density polyethylene and linear low-density polyethylene, and the melt flow rate of the high-density polyethylene is 0.015- 0.45g/10min, the melting temperature of the high-density polyethylene is Tm, the melt flow rate of the linear low-density polyethylene is 0.5～0.8g/10min, the air ring cooling air in the blown film processing step The temperature is 0-28°C, the die temperature is Tm+100°C-Tm+150°C, and the traction ratio is 2.8-15.0; The film is subjected to secondary stretching and heat setting to obtain a base film, and the obtained base film is subjected to a tensile test along the traction direction on a universal testing machine to obtain a stress σ-strain ε curve, and the maximum stress is σ _max , The maximum strain is ε _max , and the first-order derivation of the stress σ-strain ε curve is performed to obtain dσ/dε, wherein, 45MPa≤σ _max ≤150MPa, 150%≤ε _max ≤800%, and dσ/dε satisfies dσ/dε ≥0; Cross compounding the basement membrane after helical cutting to obtain a strong cross membrane; Wherein, the film produced by the blown film processing is tensile tested on a universal testing machine along the traction direction to obtain a stress σ'-strain ε' curve, the maximum stress is _σ'max , and the maximum strain is _ε'max . The stress σ'-strain ε' curve is first-order derived to obtain dσ'/dε', wherein, there are at least two yield behaviors in the stress σ'-strain ε' curve, 35MPa≤σ' _max ≤120MPa, 300 %≤ε' _max ≤1400%, dσ'/dε' satisfies dσ'/dε'≥-0.1; The linear low density polyethylene comprises metallocene linear low density polyethylene; In the polyethylene mixture, the mass percentage of the high-density polyethylene is not less than 75%. 2. The preparation method of the strong cross film as claimed in claim 1, characterized in that, the draw ratio of the secondary stretching is 1.8 to 4.5, and the heat setting temperature is Tm-35°C to Tm-5°C . 3. The preparation method of strong cross membrane as claimed in claim 1, characterized in that, the weight-average molecular weight of the high-density polyethylene is 160000～360000g/mol, and the molecular weight distribution is 3.2～9.0; And/or, The weight average molecular weight of the linear low density polyethylene is 80000-250000 g/mol. 4. The method for preparing a strong cross membrane according to claim 1, characterized in that the temperature of the air ring cooling air is 5-25°C, and the traction ratio is 3.0-12.0. 5. The method for preparing a strong cross membrane as claimed in claim 1, wherein the maximum stress is σ _max , the maximum strain is ε _max , and the dσ/ dε satisfies the following conditions: 60MPa≤σ _max <150MPa, 200%≤ε _max ≤700%, dσ/dε satisfies dσ/dε>0. 6. A strong cross-membrane, characterized in that the strong cross-membrane is prepared by the preparation method of the strong cross-membrane according to any one of claims 1 to 5. 7. A waterproof coiled material, characterized in that the waterproof coiled material comprises the strong cross membrane according to claim 6. 8. A label film, characterized in that the label film comprises the strong cross film according to claim 6.

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