Composite cross film resistant to ejection pin tearing and method of making the same

Abstract

The application provides a preparation method of a composite cross film resistant to ejector rod tearing, 1) high-density polyethylene, linear low-density polyethylene, mica powder and bentonite are uniformly mixed, then blow molding is performed, after film forming, constant temperature stretching, rotary cutting and corona treatment are sequentially performed, and a raw material film is obtained; high-density polyethylene, linear low-density polyethylene, EVA, mica powder and bentonite are uniformly mixed, then blow molding is performed to obtain a middle layer modified film; 2) the middle layer modified film is placed in the middle, two raw material films are respectively placed on two surfaces of the middle layer modified film, then adhesion is performed, then winding is performed, then aging is performed, and a composite cross film is obtained; the raw material film is used, and the heat shrinkage performance of the material is improved; the constant temperature stretching and 45-degree rotary cutting improve the strength; the middle layer modified film is used, and the ejector rod tearing strength is improved; the 110 DEG C heat shrinkage rate is reduced to less than 1%, the tensile strength is greater than 120 MPa, and the ejector rod tearing strength is greater than 60 MPa.

Description

Technical Field

[0001] This invention belongs to the field of polyethylene cross-linked film production technology, specifically relating to a composite cross-linked film resistant to top rod tearing and its preparation method. Background Technology

[0002] High-strength cross-laminated self-adhesive waterproof membrane is a high-performance, cold-applied self-adhesive composite waterproof membrane made of specially formulated cross-laminated high-density polyethylene (HDPE) high-strength cross-laminated membrane and high-quality polymer self-adhesive rubber asphalt through a special process. It has excellent dimensional stability, thermal stability, UV resistance and bidirectional tear resistance.

[0003] Polyethylene (PE) is one of the main raw materials among the five major general-purpose plastics, but it has poor high-temperature resistance. The advantages of polyethylene cross-linked films are their softness, high elongation, smooth and aesthetically pleasing roll appearance, high dry silica content, low risk of peeling difficulty, recyclability, and environmental friendliness. However, their drawbacks include poor aging resistance, especially during the hot summer months with strong sunlight. Prolonged storage or outdoor exposure during construction can cause the film surface to yellow easily and the asphalt viscosity to decrease rapidly or even be completely lost.

[0004] Because polyethylene has poor high-temperature heat shrinkage resistance, the asphalt temperature needs to be lowered for bonding, which makes the process of self-adhesive asphalt waterproof membrane more complicated and increases costs. Therefore, it is very important to improve the high-temperature shrinkage resistance of polyethylene cross-laminated film. At the same time, because polyethylene cross-laminated film has poor resistance to top bar tearing, it is prone to damage and tearing, resulting in losses.

[0005] Therefore, how to reduce the thermal shrinkage rate of cross-laminated membranes, improve their tensile strength, and enhance their resistance to top bar tearing are technical problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0006] The objective of this invention is to provide a method for preparing a composite cross-linked membrane resistant to top rod tearing. Another objective of this invention is to provide a composite cross-linked membrane resistant to top rod tearing.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for preparing a composite cross-linked membrane resistant to top bar tearing includes the following steps performed sequentially:

[0009] 1) Mix high-density polyethylene, linear low-density polyethylene, mica powder and bentonite evenly, then blow mold the mixture, and after forming the film, perform constant temperature stretching, rotary cutting and corona treatment in sequence to obtain the raw material film.

[0010] High-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, mica powder and bentonite are mixed evenly, and then blow molding is used to obtain the intermediate layer modified film.

[0011] 2) Place the intermediate layer modified film in the middle, place at least one raw material film on each of the two surfaces of the intermediate layer modified film, clamp the intermediate layer modified film with the raw material film, then bond it with adhesive, then roll it up, and then put it into the curing chamber for curing. After completion, a composite cross-laminated film is obtained.

[0012] Preferably, the raw materials for the raw material membrane include 2-8 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of high-density polyethylene 6888, 1-5 parts by weight of linear low-density polyethylene 7042, 1-3 parts by weight of nano mica powder, and 3-6 parts by weight of 2000 mesh bentonite.

[0013] The particle size of the nano mica powder is 12,000-12,500 mesh;

[0014] The raw material film is obtained by three-layer co-extrusion blow molding, and the film thickness is 0.04-0.1mm.

[0015] Preferably, in step 1), the isothermal stretching temperature is 40℃-70℃; and a 45-degree rotary cut is used.

[0016] Preferably, the raw materials for the intermediate layer modified membrane include 4-5 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of linear low-density polyethylene 7042, 3-8 parts by weight of ethylene-vinyl acetate copolymer, 1-3 parts by weight of nano mica powder, and 3-6 parts by weight of 2000 mesh bentonite.

[0017] The thickness of the intermediate modified film is 0.04-0.1 mm.

[0018] Preferably, in step 2), the adhesive is a polyurethane adhesive, and the amount of polyurethane adhesive used is 1-3 grams per square meter.

[0019] Preferably, in step 2), the food is placed in a curing chamber for curing for 24-36 hours, and the curing temperature is 35℃-60℃.

[0020] The composite cross-linked membrane resistant to top rod tearing prepared by any one of the above methods.

[0021] Compared with the prior art, the present invention achieves the following beneficial technical effects:

[0022] The present invention uses a mixture of nano-mica powder, bentonite and high-density polyethylene, and prepares a raw material film by three-layer co-extrusion blow molding, which has the advantage of improving the thermal shrinkage performance of the material.

[0023] This application employs constant temperature stretching and 45-degree rotary cutting, which has the advantage of improving the strength of the composite film.

[0024] This application uses a modified intermediate layer film made by blow molding a mixture of high-density polyethylene 7000F, linear low-density polyethylene 7042, EVA ethylene-vinyl acetate copolymer, nano mica powder, and bentonite, which has the advantage of being resistant to top rod tearing.

[0025] The composite cross-linked membrane prepared in this application has a heat shrinkage rate of less than 1% at 110°C, a tensile strength greater than 120 MPa, and a top bar tear resistance greater than 60 MPa. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] This application provides a method for preparing a composite cross-linked membrane resistant to top bar tearing, comprising the following steps performed sequentially:

[0028] 1) Mix high-density polyethylene, linear low-density polyethylene, mica powder and bentonite evenly, then blow mold the mixture, and after forming the film, perform constant temperature stretching, rotary cutting and corona treatment in sequence to obtain the raw material film.

[0029] High-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, mica powder and bentonite are mixed evenly, and then blow molding is used to obtain the intermediate layer modified film.

[0030] 2) Place the intermediate layer modified film in the middle, place at least one raw material film on each of the two surfaces of the intermediate layer modified film, clamp the intermediate layer modified film with the raw material film, then bond it with adhesive, then roll it up, and then put it into the curing chamber for curing. After completion, a composite cross-laminated film is obtained.

[0031] In one embodiment of this application, the raw materials for the raw material membrane include 2-8 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of high-density polyethylene 6888, 1-5 parts by weight of linear low-density polyethylene 7042, 1-3 parts by weight of nano-mica powder, and 3-6 parts by weight of 2000-mesh bentonite.

[0032] The particle size of the nano mica powder is 12,000-12,500 mesh;

[0033] The raw material film is obtained by three-layer co-extrusion blow molding, and the film thickness is 0.04-0.1mm.

[0034] In one embodiment of this application, in step 1), the isothermal stretching temperature is 40°C-70°C; and 45° rotary cutting is used.

[0035] In one embodiment of this application, the raw materials for the intermediate layer modified film include 4-5 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of linear low-density polyethylene 7042, 3-8 parts by weight of ethylene-vinyl acetate copolymer, 1-3 parts by weight of nano mica powder, and 3-6 parts by weight of 2000 mesh bentonite.

[0036] The thickness of the intermediate modified film is 0.04-0.1 mm.

[0037] In one embodiment of this application, in step 2), the adhesive is a polyurethane adhesive, and the amount of polyurethane adhesive used is 1-3 grams per square meter.

[0038] In one embodiment of this application, in step 2), the food is placed in a curing chamber for curing for 24-36 hours, and the curing temperature is 35℃-60℃.

[0039] This application provides a composite cross-linked membrane resistant to top rod tearing prepared by a method for preparing a top rod tear-resistant composite cross-linked membrane as described in any one of the above-mentioned methods.

[0040] In this application, for example, high-density polyethylene 7000F, high-density polyethylene 6888, etc., where the numbers 7000F and 6888 are grades, equivalent to models.

[0041] In this application, the constant temperature stretching is specifically as follows: the longitudinal stretching roller group is divided into two parts: the first part of the roller group is a slow roller group, which guides the film to be stretched to move forward and is heated by the roller surface at a certain temperature; the second part of the roller group is a fast roller group, in which the film to be stretched is stretched between the fast and slow rollers. The difference in speed between the two rollers is the longitudinal stretching multiple of the film to be stretched. This method of stretching the film can also be called point stretching, the purpose of which is to make the film obtain higher tensile strength and mechanical properties.

[0042] In this application, the rotary cutting specifically refers to using a rotary cutting machine to perform rotary cutting at a 45-degree angle to the central axis, with the aim of obtaining strong transverse and longitudinal tensile forces after double-sided composite.

[0043] In this application, the corona treatment specifically refers to the use of a corona machine, which is an electrical discharge treatment that improves the adhesion of the substrate surface. Most plastic films (such as polycarbonate films) are non-polar polymers with low surface tension, and known inks and adhesives cannot adhere firmly to them. Therefore, corona treatment is performed on their surfaces to break the chemical bonds of the plastic molecules and degrade them. During the discharge, a large amount of ozone is also generated. Ozone is a strong oxidant that can oxidize plastic molecules and produce highly polar groups such as carbonyl groups and peroxides, thereby increasing their surface energy.

[0044] In this application, the thickness of the composite cross-linked membrane is 0.08-0.3 mm.

[0045] The functions and roles of each raw material in the formulation of the raw material membrane in this application are as follows:

[0046] Functions and roles of high-density polyethylene 7000F: One of the main raw materials for blown film, providing the main strength of the film;

[0047] Functions and uses of high-density polyethylene 6888: One of the main raw materials for blown film, improving blown film forming processability and facilitating film formation;

[0048] Functions and applications of linear low-density polyethylene 7042: Increases membrane flexibility and improves elongation at break;

[0049] Functions and effects of nano mica powder: improves membrane rigidity, reduces membrane thermal shrinkage rate. Mica powder has a unique flaky structure, silky luster and smooth texture. Mica powder has good elasticity, toughness, insulation, high temperature resistance, acid and alkali resistance, corrosion resistance and strong adhesion. It is an excellent additive. Nano mica powder has excellent dispersibility and has a significant effect on improving the temperature resistance of membrane.

[0050] The functions and uses of bentonite: to improve the rigidity of membranes, reduce the thermal shrinkage of membranes, and have the advantages of high rigidity, resistance to thermal shrinkage, low price, and reduced cost.

[0051] The functions and roles of each raw material in the formulation of the intermediate layer modified membrane of this application are as follows:

[0052] Functions and roles of high-density polyethylene 7000F: One of the main raw materials for blown film, providing the main strength of the film;

[0053] Functions and applications of linear low-density polyethylene 7042: Increases membrane flexibility and improves elongation at break;

[0054] The function and role of EVA-ethylene-vinyl acetate copolymer: to improve the ejector bar tear resistance of the film, specifically EVA268, which has excellent ejector bar tear resistance, flexibility, and ductility, making it suitable for blow molding;

[0055] The functions and uses of nano mica powder are the same as described above.

[0056] The reason or working principle of this application for reducing the thermal shrinkage rate of the composite cross-linked film is as follows: the nano-mica powder and bentonite are uniformly distributed in the middle of the polymer chain segments. Due to their own rigidity, when heated, the polymer chain segments undergo thermal motion. The rigid mica powder and bentonite absorb the surrounding heat, effectively reducing the kinetic energy of the polymer chain segments. At the same time, as rigid materials, they effectively block the displacement of the polymer chain segments, thereby achieving the purpose of reducing the thermal shrinkage rate.

[0057] The reason or working principle of this application for improving the tensile strength of composite cross-linked films is that the polymer chain segments are oriented through isothermal stretching, thereby improving the tensile strength.

[0058] By performing 45-degree rotary cutting followed by double-sided composite processing, the tensile strength in both the transverse and longitudinal directions is improved.

[0059] The overall strength is improved by using a three-layer composite structure.

[0060] The reason or working principle for improving the jacking tear resistance of the composite cross-laminated film in this application is as follows: Because EVA has excellent elongation at break and flexibility, it has good jacking tear resistance. Therefore, adding EVA-ethylene-vinyl acetate copolymer to the middle layer can effectively improve its jacking tear resistance.

[0061] The methods and apparatus not described in detail in this invention are all prior art and will not be elaborated further.

[0062] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0063] Example 1

[0064] A method for preparing a composite cross-linked membrane resistant to top bar tearing includes the following steps performed sequentially:

[0065] 1) Mix 8 parts by weight of high-density polyethylene 7000F, 5 parts by weight of high-density polyethylene 6888, 4 parts by weight of linear low-density polyethylene 7042, 3 parts by weight of nano mica powder and 3 parts by weight of 2000 mesh bentonite evenly, and then form a film with a thickness of 0.04-0.1 mm by three-layer co-extrusion blow molding. Then, it is subjected to constant temperature stretching (temperature 70℃), 45-degree rotary cutting and corona treatment in sequence to obtain the raw material film.

[0066] Five parts by weight of high-density polyethylene 7000F, five parts by weight of linear low-density polyethylene 7042, four parts by weight of EVA (V2510J), two parts by weight of nano mica powder and three parts by weight of 2000 mesh bentonite were mixed evenly and then blow-molded to obtain an intermediate layer modified film with a film thickness of 0.05 mm.

[0067] 2) Place the intermediate modified membrane in the middle, place a raw material membrane on each of the two surfaces of the intermediate modified membrane, sandwich the intermediate modified membrane with the two raw material membranes, and bond them with polyurethane adhesive (3 grams / square meter). Roll it up and put it into the curing chamber for curing for 24 hours at a curing temperature of 60°C. After completion, a composite cross-laminated membrane is obtained.

[0068] The composite cross-linked membrane prepared in Example 1 has a heat shrinkage rate of 0.62% at 110°C, a tensile strength of 129 MPa, and a top rod tear strength greater than 68 MPa.

[0069] Example 2

[0070] A method for preparing a composite cross-linked membrane resistant to top bar tearing includes the following steps performed sequentially:

[0071] 1) Mix 5 parts by weight of high-density polyethylene 7000F, 6 parts by weight of high-density polyethylene 6888, 3 parts by weight of linear low-density polyethylene 7042, 2 parts by weight of nano mica powder and 4 parts by weight of 2000 mesh bentonite evenly, and then form a film with a thickness of 0.04-0.1 mm by three-layer co-extrusion blow molding. Then, it is subjected to constant temperature stretching (temperature 60℃), 45-degree rotary cutting and corona treatment in sequence to obtain the raw material film.

[0072] Four parts by weight of high-density polyethylene 7000F, eight parts by weight of linear low-density polyethylene 7042, seven parts by weight of EVA (V2510J), two parts by weight of nano mica powder and four parts by weight of 2000 mesh bentonite were mixed evenly and then blow-molded to obtain an intermediate layer modified film with a film thickness of 0.08 mm.

[0073] 2) Place the intermediate modified membrane in the middle, place a raw material membrane on each of the two surfaces of the intermediate modified membrane, sandwich the intermediate modified membrane with the two raw material membranes, and bond them with polyurethane adhesive (2 grams / square meter). Roll it up and put it into the curing chamber for curing at 48°C and 50°C. After completion, a composite cross-laminated membrane is obtained.

[0074] The composite cross-linked membrane prepared in Example 2 had a heat shrinkage rate of 0.73% at 110°C, a tensile strength of 146 MPa, and a top rod tear strength of 77 MPa.

[0075] Example 3

[0076] A method for preparing a composite cross-linked membrane resistant to top bar tearing includes the following steps performed sequentially:

[0077] 1) Mix 2 parts by weight of high-density polyethylene 7000F, 8 parts by weight of high-density polyethylene 6888, 2 parts by weight of linear low-density polyethylene 7042, 1 part by weight of nano mica powder and 5 parts by weight of 2000 mesh bentonite evenly, and then form a film with a thickness of 0.1 mm by three-layer co-extrusion blow molding. Then, it is subjected to constant temperature stretching (temperature 50℃), 45-degree rotary cutting and corona treatment in sequence to obtain the raw material film.

[0078] Four parts by weight of high-density polyethylene 7000F, eight parts by weight of linear low-density polyethylene 7042, four parts by weight of EVA (V2510J), one part by weight of nano mica powder and five parts by weight of 2000 mesh bentonite were mixed evenly and then blow-molded to obtain an intermediate layer modified film with a film thickness of 0.1 mm.

[0079] 2) Place the intermediate modified membrane in the middle, place a raw material membrane on each of the two surfaces of the intermediate modified membrane, sandwich the intermediate modified membrane with the two raw material membranes, and bond them with polyurethane adhesive (1 gram / square meter). Roll it up and place it in a curing chamber for 36 hours at a curing temperature of 40°C. After completion, a composite cross-laminated membrane is obtained.

[0080] The composite cross-linked membrane prepared in Example 3 had a heat shrinkage rate of 0.93% at 110°C, a tensile strength of 162 MPa, and a top rod tear strength of 89 MPa.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite cross-linked membrane resistant to top rod tearing, characterized in that, The following steps are performed sequentially: 1) Mix high-density polyethylene, linear low-density polyethylene, mica powder and bentonite evenly, then blow mold the mixture, and after forming the film, perform constant temperature stretching, rotary cutting and corona treatment in sequence to obtain the raw material film. High-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, mica powder and bentonite are mixed evenly, and then blow molding is used to obtain the intermediate layer modified film. 2) Place the intermediate layer modified film in the middle, place at least one raw material film on each of the two surfaces of the intermediate layer modified film, clamp the intermediate layer modified film with the raw material film, then bond it with adhesive, then roll it up, and then put it into the curing chamber for curing. After completion, a composite cross-laminated film is obtained.

2. The method for preparing a composite cross-linked membrane resistant to top rod tearing according to claim 1, characterized in that: The raw materials for the membrane include 2-8 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of high-density polyethylene 6888, 1-5 parts by weight of linear low-density polyethylene 7042, 1-3 parts by weight of nano mica powder, and 3-6 parts by weight of 2000 mesh bentonite. The particle size of the nano mica powder is 12,000-12,500 mesh; The raw material film is obtained by three-layer co-extrusion blow molding, and the film thickness is 0.04-0.1mm.

3. The method for preparing a composite cross-linked membrane resistant to top rod tearing according to claim 1, characterized in that: In step 1), the isothermal stretching temperature is 40℃-70℃; 45-degree rotary cutting is used.

4. The method for preparing a composite cross-linked membrane resistant to top rod tearing according to claim 1, characterized in that: The raw materials for the intermediate layer modified membrane include 4-5 parts by weight of high-density polyethylene 7000F, 5-8 parts by weight of linear low-density polyethylene 7042, 3-8 parts by weight of ethylene-vinyl acetate copolymer, 1-3 parts by weight of nano mica powder, and 3-6 parts by weight of 2000 mesh bentonite. The thickness of the intermediate modified film is 0.04-0.1 mm.

5. The method for preparing a composite cross-linked membrane resistant to top rod tearing according to claim 1, characterized in that: In step 2), the adhesive is polyurethane adhesive, and the amount of polyurethane adhesive used is 1-3 grams per square meter.

6. The method for preparing a composite cross-linked membrane resistant to top rod tearing according to claim 1, characterized in that: In step 2), place it in the maturation chamber for maturation for 24-36 hours, with the maturation temperature being 35℃-60℃.

7. A composite cross-laminated membrane resistant to top rod tearing prepared by a method for preparing a composite cross-laminated membrane resistant to top rod tearing as described in any one of claims 1-6.