Ultra-thin PTFE film anti-adhesive tape and preparation method and use thereof

Abstract

The present invention belongs to the technical field of new tape materials, and provides an ultra-thin PTFE film anti-adhesive tape, and a preparation method and use thereof. The preparation method of the ultra-thin PTFE film anti-adhesive tape provided by the present invention comprises: compounding a backing film on the ultra-thin PTFE film, then performing chemical treatment, coating, compounding a release film, and then removing the backing film. Since the ultra-thin PTFE film is too thin and is very easy to curl and deform, the use of a backing film helps to increase its stiffness to a certain extent, which can effectively improve or solve this problem. The present invention also provides an ultra-thin PTFE film anti-adhesive tape prepared by the above method and its use in PCB substrate and / or FPC circuit protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of new adhesive tape materials, and relates to a method for preparing a PTFE (polytetrafluoroethylene) adhesive tape, in particular to a method for preparing an ultra-thin PTFE film anti-adhesive tape. The present invention also relates to the application of the ultra-thin PTFE film anti-adhesive tape in PCB substrate and / or FPC circuit protection. Background Art

[0002] With the rapid development of electronic products, electronic products are increasingly demanding complete functions and exquisite appearance, prompting developers to continuously innovate their products. Their structures are becoming more and more complex, and their volumes are becoming thinner and lighter, making the internal space narrower and narrower, resulting in higher and higher requirements for the volume of various components and their performance. Therefore, in order to meet this trend, it is necessary to design thinner structural components to be suitable for today's thin and light electronic devices.

[0003] At present, PTFE film is generally processed by special machine tools. A prefabricated PTFE cylinder is peeled off layer by layer through a special turning process. The thinner the PTFE film, the more difficult it is to make. Films with a thickness of less than 0.02mm are too thin and very soft, and often deform or curl, increasing the difficulty of operation.

[0004] After the PTFE film is made, it needs to be glued. This production process is also very difficult. Since the PTFE material has extremely low surface energy and extremely low adhesion, it is difficult to glue it using general methods. Therefore, the surface of the PTFE film must be activated to combine with the glue to form an adhesive layer and finally complete the production of Teflon tape. There are many methods for surface treatment of PTFE film. Chemical methods and plasma treatment are commonly used, but if the PTFE film is too thin, these treatment methods will be difficult to carry out. Summary of the invention

[0005] On the one hand, the present invention provides a method for preparing an ultra-thin PTFE film release tape, comprising:

[0006] 1) coating one side of the first backing film with glue, and drying the coated film to form a first adhesive layer (3) on the first backing film;

[0007] 2) compounding the first base film with one surface of the PTFE film through the first adhesive layer to form a PTFE composite film;

[0008] 3) treating the other surface of the PTFE film in the PTFE composite membrane with a chemical treatment agent to destroy the surface energy of the PTFE film, introduce active groups, and form a chemical treatment layer, thereby improving the adhesion and wettability of the other surface of the PTFE film;

[0009] 4) applying glue on the chemical treatment layer to form a second adhesive layer;

[0010] 5) compounding a second base film on the second adhesive layer; and

[0011] 6) peeling off the first base film and the first adhesive layer from the PTFE composite film to obtain the ultra-thin PTFE film anti-adhesive tape.

[0012] In some embodiments, the first backing film is a PET (polyethylene terephthalate) film with a thickness of 0.002-0.05 mm, and the second backing film is a PET release film with a thickness of 0.005-0.008 mm.

[0013] In some embodiments, the PTFE film has a thickness of 0.009-0.05 mm.

[0014] In some embodiments, the first adhesive layer is formed by silicone pressure-sensitive adhesive or acrylic adhesive.

[0015] In some embodiments, the second adhesive layer is formed by using acrylic glue, silicone glue, epoxy resin glue or polyurethane glue.

[0016] In some embodiments, the chemical treatment agent is a sodium naphthalene treatment agent.

[0017] In some embodiments, the chemical treatment agent is a sodium naphthalene treatment agent comprising: 0.2-0.4 M sodium naphthalene complex, 0.1-0.3 M sodium borohydride and 0.005-0.01 M HEDTA (hydroxyethylethylenediaminetriacetic acid), and the solvent is tetrahydrofuran.

[0018] In some embodiments, the total thickness of the ultra-thin PTFE film anti-adhesive tape is between 0.016-0.019 mm, and the longitudinal and transverse tensile strengths are between 35-80 PMa.

[0019] In another aspect, the present invention provides an ultra-thin PTFE film release tape prepared by the above method.

[0020] On the other hand, the present invention provides the use of the above-mentioned ultra-thin PTFE film anti-adhesive tape in PCB substrate and / or FPC circuit protection.

[0021] The beneficial effects of the present invention are that the preparation method improves the operability of the ultra-thin PTFE film by means of the first supporting film, and overcomes the problem that the ultra-thin PTFE film is easily deformed or curled during processing; and the surface chemical treatment can be performed without substantially damaging the ultra-thin PTFE film by improving the sodium naphthalene treatment agent, so as to improve the adhesion and wettability of the surface of the PTFE film. In addition, the preparation method of the present invention is easy to operate, low in cost, and suitable for large-scale production of ultra-thin PTFE film anti-adhesive tape in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of an intermediate product with a first backing film that appears during the process of preparing the ultra-thin PTFE film anti-adhesive tape of the present invention.

[0023] Figure 2 Schematic diagram of removing the first backing film to obtain the ultra-thin PTFE film release tape of the present invention. DETAILED DESCRIPTION

[0024] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0025] In this document, the term "and / or" should be understood to mean either one or both of the alternatives.

[0026] Herein, the term "comprising" generally means including the elements explicitly specified but not excluding other elements, and also includes the case consisting of these elements.

[0027] As used herein, the term "about" generally refers to variations within a range of 0.5%-10% above or below a specified value, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% above or below a specified value.

[0028] The present invention provides a method for preparing an ultra-thin PTFE film anti-adhesive tape, comprising the following steps (see Figure 1 and Figure 2 ).

[0029] 1. Material selection

[0030] 1.1 PTFE film selection

[0031] The PTFE film 1 is preferably a skived film, and the thickness range is 0.009-0.05 mm, which can be selected according to the requirements but is not limited to it. For example, the selected PTFE film 1 is a skived film with a thickness of 0.01 mm.

[0032] The specific preparation method of the PTFE film can be: adding the PTFE suspension powder according to the expected amount into a circular mold, using a hydraulic press to perform production pressing (similar to the powder metallurgy process), with a unit pressure of 18-40MPa, to obtain a cylindrical green blank, leaving the green blank at room temperature for more than 24 hours, and then sintering it in a high-temperature sintering furnace, maintaining the sintering temperature at 360-385°C, cooling it, and then machining it with a high-precision CNC lathe to turn it into a film of the required thickness, and finally rolling it up to obtain a PTFE film coil of the required thickness (such as 0.01mm).

[0033] 1.2 Selection of reinforcement layer film (first base film 2)

[0034] According to the operation requirements, films with good rigidity, high stiffness, folding resistance and high tensile strength are preferred.

[0035] Preferably, a PET film is used. Since PET has high strength, high hardness, good wear resistance, good rigidity, good toughness, and good dimensional stability, a PET film with a thickness range of 0.002-0.05 mm can be selected according to demand but is not limited to a PET film with a thickness of 0.002 mm. The PET film used herein preferably has a shrinkage rate of < 1% after cooling at 180° C. for 5 minutes, and a tensile strength of > 50 MPa, preferably > 100 MPa.

[0036] 2. Preparation process

[0037] 2.1 Gluing the bottom film

[0038] The first support film 2 is coated with glue on one side by a transfer coating method (or a glue coating machine), and the glue type is silicone pressure-sensitive adhesive or acrylic adhesive. After coating, the PET film is dried in an oven to form a first adhesive layer 3 on the first support film 2.

[0039] 2.2 PTFE film and base film composite

[0040] The PTFE film 1 and the first adhesive-coated backing film 2 are laminated on one side by a film laminating machine, and the laminated side is the protective side. The so-called laminating means that the equipment has at least two rollers, and the PTFE film 1 and the first adhesive-coated backing film 2 with one side are pressed together by the roller surface, and the PTFE film 1 is adhered to the surface of the first adhesive layer 3 on the first backing film 2, and the other side of the PTFE film 1 is the non-laminated side, that is, the surface to be chemically treated later. The PTFE film 1 laminated with the first backing film 2 and the first adhesive layer 3 is referred to as a PTFE composite film in this article, and the first backing film 2 is also referred to as a first protective film in this article.

[0041] The composite equipment used includes two rollers, the rollers have a rubber surface and a large compression ratio. The composite machine has multiple unwinding shafts, each of which has a servo motor to provide resistance tension and can adjust the tension.

[0042] 2.3 Surface treatment

[0043] The PTFE composite membrane is surface treated by a transfer coating method, the principle of which is to apply a chemical reagent that can chemically react with PTFE to the surface of the PTFE film 1, thereby chemically corroding the surface of the PTFE film 1, destroying the surface energy of the PTFE film 1, forming a large number of free radicals, and introducing a large number of active groups to form a chemical treatment layer 4 on the surface of the PTFE film 1, thereby improving the adhesion and wettability of the PTFE material.

[0044] The so-called transfer coating method here is different from the transfer coating method in the container. It is a method of transferring the glue carried on the surface of the roller to the surface of the PTFE composite membrane by rotating the roller (also known as the roller transfer coating method). The specific operation is to put the chemical reagent in the tank body, suspend the roller axially horizontally, and immerse the lower edge of the roller in the reagent. When the roller keeps rotating, the entire roller surface will carry the chemical reagent. Then the PTFE composite membrane is pulled around the upper surface of the roller and the two are effectively contacted. The contact surface is selected as a non-composite surface. As the roller rotates, the PTFE composite membrane also begins to move under the traction. The control of its moving speed can be synchronized with the linear speed generated by the rotation of the roller surface. This process completes the migration of the chemical reagent from the roller surface to the surface of the PTFE composite membrane. After a certain distance (time), the chemical reagent can complete the chemical reaction with the PTFE surface, and then the PTFE composite membrane is cleaned (using acetone and water in turn), dried and rolled up, realizing the surface treatment of the PTFE composite membrane.

[0045] 2.4 PTFE composite membrane coating

[0046] The PTFE composite film that has been surface treated is coated with glue on the treated surface by the above-mentioned roller coating method or a glue coating machine to form a second adhesive layer 5. The glue (or adhesive) used includes acrylic glue, silicone glue, epoxy resin glue or polyurethane glue commonly used in the art. This step is preferably performed within 24 hours after the surface treatment of the PTFE film is completed.

[0047] 2.5 Re-support

[0048] The second backing film 6 (release protective film, also referred to as the second protective film in this article) is compounded on the adhesive surface of the PTFE composite film by a compounding device, and then rolled up to obtain the tape mother roll. The second backing film 6 is used for the convenience of winding and protection during the process, and can be easily peeled off during use, preferably a PET release film.

[0049] 2.6 Cutting

[0050] The first backing film 2 (and the first adhesive layer 3) is peeled off from the tape mother roll after backing again to expose the PTFE release surface, i.e., the non-stick surface (see Figure 2 ). Then use a slitting machine to cut it according to the needs, and then roll it into a roll to obtain the anti-sticking PTFE film tape.

[0051] 2.7 When in use, peel off the second base film 6 to expose the second adhesive layer 5, and this surface can be used for pasting.

[0052] The above process involves unwinding and rewinding, which can be achieved by an unwinding and rewinding device.

[0053] Since then, an ultra-thin PTFE film anti-sticking tape has been produced, with the adhesive surface being the adhesive surface and the other side being the anti-sticking surface.

[0054] Ultra-thin PTFE film is too thin and too soft to curl and deform easily. During the surface treatment and gluing process, the film is too easy to curl, so it is difficult and uneven to apply chemical reagents and glue. It is also likely that the film will stick together due to curling, which is difficult to operate. This preparation method adopts a method of enhancing the skeleton bottom support, using a film (first bottom support film) with good rigidity and high flatness such as PET film as support, which successfully solves this problem. At the same time, the bottom support film can also provide protection for the non-treated surface during subsequent single-sided treatment, preventing the non-treated surface from being accidentally contaminated with reagents and corroded, and acting as an isolation layer.

[0055] Since the PTFE film 1 used is too thin (such as 0.005 mm), it is easy to damage the PTFE film 1 when using conventional sodium naphthalene treatment agent for PTFE surface chemical treatment, resulting in a decrease in shear strength. For this reason, we have improved the sodium naphthalene treatment agent. On the one hand, the sodium naphthalene concentration is reduced to 0.2-0.4 M, and on the other hand, sodium borohydride (0.1-0.3 M) and a small amount of HEDTA (0.005-0.01M) are added. The activity of the improved sodium naphthalene treatment agent is weakened and will not cause damage to the PTFE film. Due to the weakened activity, in order to achieve the desired surface treatment effect, it can be overcome by extending the treatment time, such as delaying the acetone cleaning time by 5-10 minutes (depending on the concentration of the sodium naphthalene treatment agent, the surface to be treated contacts the sodium naphthalene treatment agent for a total of about 7-12 minutes). The surface of the PTFE film treated in this way was detected by INCA-X-ray energy spectrometer, and the C element content was about 31%, and the F element content was about 55%, which still met the chemical treatment requirements. In addition, we unexpectedly found that the improved sodium naphthalene treatment agent has good stability in the air, and there is no significant change in activity after 48 hours, while the conventional sodium naphthalene treatment agent (such as 2M concentration sodium naphthalene) has a significant decrease in activity after 12 hours. Therefore, the improved sodium naphthalene treatment agent can also greatly reduce the overall workload of the production process (omitting inert gas protection or frequent replacement of sodium naphthalene treatment agent), ensuring the process stability between batches.

[0056] The preparation method of the present invention is easy to operate, the equipment cost is not high, and the overall cost is relatively economical.

[0057] The present invention is further illustrated by the following specific examples.

[0058] Embodiment 1: Conventional sodium naphthalene treatment agent can damage the PTFE membrane when processing thinner PTFE membrane. We have studied the sodium naphthalene treatment agent and found that reducing the sodium naphthalene use concentration and adding sodium borohydride and HEDTA can reduce membrane damage when reaching the required treatment effect.

[0059] Treatment agent grouping (solvents are all tetrahydrofuran):

[0060] #1: 2M Sodium Naphthalene

[0061] #2: 0.5 M sodium naphthalene

[0062] #3: 0.2 M sodium naphthalene

[0063] #4: 0.2 M sodium naphthalene, 0.1 M sodium borohydride

[0064] #5: 0.2 M sodium naphthalene, 0.1 M sodium borohydride, 0.01 M HEDTA

[0065] #6: THF only, as a control

[0066] After soaking the 0.008 mm thick PTFE membrane in the above treatment agent for different time periods (2 min or 8 min), it was immediately washed with acetone and water in turn, and its relative shear strength (relative to the untreated control PTFE membrane) and surface C element content were tested. The representative results are shown in Table 1.

[0067] Table 1 Relative shear strength and surface C content of PTFE membrane treated with sodium naphthalene treatment agent

[0068]

[0069] From the results in Table 1, it can be seen that reducing the concentration of sodium naphthalene can reduce membrane damage, but the treatment effect is also poor (comparing the surface C element content results of groups #1, #2 and #3). The addition of 0.1M sodium borohydride helps to reduce membrane damage, but the surface C element content is also low (comparing the results of groups #3 and #4). After adding 0.1M sodium borohydride and 0.01M HEDTA, a better treatment effect (surface C element content 31.8%) can be obtained at a lower sodium naphthalene complex concentration (0.2 M), and the membrane damage is reduced to a minimum (relative shear strength 98.9%).

[0070] Embodiment 2: A method for preparing an ultra-thin high-strength PTFE anti-adhesive tape, comprising:

[0071] 1. Use a glue coating machine to coat one side of a 0.002 mm thick PET film with acrylic glue. After coating, use an oven to dry the PET film.

[0072] 2. Use a thin film laminating machine to laminate the 0.01 mm thick PTFE film and the above-mentioned glue-coated PET film (as the first base film) on one side;

[0073] 3. Use chemical treatment agent to treat the surface of PTFE composite membrane by transfer coating method. The chemical treatment agent used includes: 0.3 M sodium naphthalene complex, 0.1 M sodium borohydride, 0.005 M HEDTA, and the solvent is tetrahydrofuran. After coating, wash with acetone and water in turn 8 minutes, and dry;

[0074] 4. Use a glue coating machine to coat the surface-treated PTFE composite membrane with acrylic glue on the treated surface to form an adhesive layer;

[0075] 5. Use a composite device to composite a PET release protective film (0.005 mm thick, as a second protective film) on the adhesive coated surface of the PTFE composite film, and reel it up to obtain a tape mother roll;

[0076] 6. Remove the first backing film from the tape mother roll to expose the PTFE release surface, i.e. the non-stick surface. Use a slitting machine to cut it as required, and then roll it into a roll to obtain the anti-stick PTFE film tape.

[0077] Embodiment 3: A method for preparing an ultra-thin high-strength PTFE anti-adhesive tape, comprising:

[0078] 1. Use a glue coating machine to coat one side of a 0.005 mm thick PET film with acrylic glue. After coating, use an oven to dry the PET film.

[0079] 2. Use a thin film laminating machine to laminate the 0.01 mm thick PTFE film and the above-mentioned glue-coated PET film (as the first base film) on one side;

[0080] 3. Use chemical treatment agent to treat the surface of PTFE composite membrane by transfer coating method. The chemical treatment agent used includes: 0.4 M sodium naphthalene complex, 0.2 M sodium borohydride, 0.01 M HEDTA, and the solvent is tetrahydrofuran. After coating, wash with acetone and water in turn 8 minutes, and dry;

[0081] 4. Use a glue coating machine to coat the surface-treated PTFE composite membrane with epoxy resin glue on the treated surface to form an adhesive layer;

[0082] 5. Use a composite device to composite a PET release protective film (0.008 mm thick, as a second protective film) on the adhesive coated surface of the PTFE composite film, and reel it up to obtain a tape mother roll;

[0083] 6. Remove the first backing film from the tape mother roll to expose the PTFE release surface, i.e. the non-stick surface. Use a slitting machine to cut it as required, and then roll it into a roll to obtain the anti-stick PTFE film tape.

[0084] It was determined that the total thickness of the ultra-thin PTFE film anti-adhesive tapes prepared in Examples 2 and 3 was between 0.016 and 0.019 mm, and the longitudinal and transverse strengths were between 35 and 80 PMa.

Claims

1. A method for preparing an ultra-thin PTFE film anti-adhesive tape, comprising: 1) coating a first backing film (2) with glue on one side, and drying the coated film to form a first adhesive layer (3) on the first backing film (2); 2) compounding the first base film (2) with one surface of the PTFE film (1) through the first adhesive layer (3) to form a PTFE composite film; 3) treating the other surface of the PTFE film (1) in the PTFE composite membrane with a chemical treatment agent to destroy the surface energy of the PTFE film (1), introduce active groups, and form a chemical treatment layer (4), thereby improving the adhesion and wettability of the other surface of the PTFE film; 4) applying glue on the chemically treated layer to form a second adhesive layer (5); 5) Compounding a second base film (6) on the second adhesive layer (5); as well as 6) peeling off the first base film (2) and the first adhesive layer (3) from the PTFE composite film to obtain the ultra-thin PTFE film anti-adhesive tape, The chemical treatment agent is a sodium naphthalene treatment agent, comprising: 0.2-0.4 M sodium naphthalene complex, 0.1-0.3 M sodium borohydride and 0.005-0.01 M HEDTA, and the solvent is tetrahydrofuran; the thickness of the PTFE film (1) is 0.009-0.05 mm.

2. The preparation method according to claim 1, wherein the first base film (2) is a PET film with a thickness of 0.002-0.05 mm, and the second base film (6) is a PET release film with a thickness of 0.005-0.008 mm.

3. The preparation method according to claim 1, wherein the first adhesive layer (3) is formed by silicone pressure-sensitive adhesive or acrylic adhesive.

4. The preparation method according to claim 1, wherein the second adhesive layer (5) is formed by acrylic glue, silicone glue, epoxy resin glue or polyurethane glue.

5. preparation method as claimed in claim 1, wherein the total thickness of the ultra-thin PTFE film anti-adhesive tape is between 0.016-0.019mm, and the longitudinal and transverse tensile strength is between 35-80MPa.

6. An ultra-thin PTFE film anti-adhesive tape, characterized in that: The preparation method is as described in any one of claims 1 to 5.

7. Application of the ultra-thin PTFE film anti-adhesive tape as claimed in claim 6 in PCB substrate and / or FPC circuit protection.

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