Ultrathin PU adhesive tape resistant to low-temperature bending and preparation method thereof

Abstract

The invention relates to the technical field of adhesive tape production, in particular to a low-temperature-bending-resistant ultrathin PU adhesive tape and a preparation method thereof. According to the invention, 10-15 [mu] m ultrathin high-shading low-temperature-bending-resistant PU is used as a base material, the PU base material has high tensile property and elastic deformation at the low temperature of-25 DEG C, the tensile strength at the low temperature of-25 DEG C is greater than 30 MPa, the elongation at break is greater than 600%, and the elastic deformation is 0-200%. The low-temperature bending-resistant ultrathin PU adhesive tape is prepared by adhering the acrylate pressure-sensitive adhesive layer with the thickness of 5-10 microns to one side or two sides of the PU base material, and the acrylate pressure-sensitive adhesive layer has high bending resistance and high creep recovery rate under the low-temperature condition, so that the material is not broken when being bent under the low-temperature condition and has good deformation recovery. The acrylate pressure-sensitive adhesive layer is prepared from an acrylate polymer with high flexibility and low shrinkage, tackifying resin and a curing agent. The ultra-thin PU adhesive tape resistant to low-temperature bending prepared by the preparation method disclosed by the invention is respectively bent for 300,000 times under the conditions of low temperature of-25 DEG C, normal temperature and high temperature of 65 DEG C in sequence, the surface of a material is free from cracks and glue failure, and no damage is caused to parts.

Description

Technical Field

[0001] The invention relates to the technical field of adhesive tape production, and in particular to an ultra-thin PU adhesive tape resistant to low-temperature bending and a preparation method thereof. Background Art

[0002] With the continuous development of display technology, foldable flexible displays have a large display area and excellent visual experience when in use. When folded, they have a small volume, making them easy to carry and store. They are increasingly used and have become the current mainstream development trend. They are applied to electronic products such as mobile phones, tablets, and computers.

[0003] This application field requires that the folding screen not only has the characteristics of bending resistance, but also has to be light, thin, and have excellent impact resistance and drop resistance. In order to achieve the lightness and thinness of the entire product, tape will be used when combining the layers of the internal module components of the above-mentioned folding screen. PU substrate tape has been used in this field because of its good flexibility, bending resistance and ductility. However, the temperature at which display devices are used is not the same, and the tape material is required to have good folding resistance and high viscosity under low temperature, normal temperature and high temperature conditions. The bending resistance, ductility and viscosity of ordinary PU substrate tapes are sharply reduced under low temperature conditions. At low temperatures, the surface will bend and crack, separate from the back sticker, and the adhesive layer and the PU substrate layer will separate (debonding), which will affect customer use.

[0004] Therefore, providing a tape product with a wide range of applications, resistance to low-temperature folding, high viscosity, light weight and thinness, good bonding between the substrate and the adhesive layer at low temperatures, and the ability to be widely used in the field of foldable flexible display screens has become a technical problem that needs to be urgently solved by technicians in this field. Summary of the invention

[0005] The purpose of the present invention is to provide an ultra-thin PU tape resistant to low temperature bending and a preparation method thereof, so as to solve the problems raised in the above background technology. The present invention uses ultra-thin PU resistant to low temperature bending as a substrate, and uses a high-flexibility, low-shrinkage acrylate polymer to prepare an acrylate pressure-sensitive adhesive to achieve a low shrinkage rate (<1%) and high flexibility of the adhesive layer at a low temperature of -25°C, ensuring that the shrinkage rate of the adhesive layer and the substrate layer is the same at low temperatures, and no delamination or debonding will occur during bending. Thus, even if the product thickness is very thin (15-20μm), it has good folding resistance, high viscosity and extremely high elastic deformation performance under low temperature (-25°C), normal temperature and high temperature (65°C) conditions. The ultra-thin PU tape resistant to low temperature bending prepared by the present invention is bent 300,000 times (a total of 900,000 times) at low temperature of -25°C, normal temperature and high temperature of 65°C, respectively, with no cracking on the surface, no debonding, and no damage to parts.

[0006] The present invention provides the following technical solutions:

[0007] A low-temperature-resistant ultra-thin PU tape and a preparation method thereof. The PU tape comprises a substrate, which is a 10-15 μm ultra-thin, high-light-shielding, low-temperature-resistant, and bendable PU substrate; a 5-10 μm thick acrylic pressure-sensitive adhesive layer is adhered to one side or both sides of the substrate; and a release film is adhered to the outer side of the acrylic pressure-sensitive adhesive layer.

[0008] Preferably, the acrylic pressure-sensitive adhesive layer comprises the following components: by weight:

[0009] 100 parts of highly flexible, low shrinkage acrylic polymer;

[0010] 5-30 parts of tackifying resin;

[0011] Curing agent 0.1-5 parts;

[0012] 200-500 parts of solvent;

[0013] The glass transition temperature of the acrylic pressure-sensitive adhesive layer is between -45 and -5°C, the storage modulus G′ of the acrylic pressure-sensitive adhesive at -25°C is between 300 and 700 KPa, and the loss factor tanδ is between 0.65 and 0.80; the storage modulus G′ of the acrylic pressure-sensitive adhesive at 23°C is between 80 and 200 KPa, and the loss factor tanδ is between 0.45 and 0.60; the storage modulus G′ of the acrylic pressure-sensitive adhesive at 65°C is between 35 and 60 KPa, and the loss factor tanδ is between 0.3 and 0.45; the creep recovery rate of the acrylic pressure-sensitive adhesive is greater than 50% after the temperature drops from 65°C to 25°C under a high creep state of 400%; the shrinkage rate of the acrylic pressure-sensitive adhesive at a low temperature of -25°C is less than 1%.

[0014] The highly flexible, low shrinkage acrylic polymer comprises the following components: by weight,

[0015] 60-95 parts of high-flexibility acrylic monomer;

[0016] 10-40 parts of acrylate hard segment monomer;

[0017] Functional monomer 0.5-5 parts

[0018] Thermal initiator 0.1-0.5 parts;

[0019] 80-150 parts of solvent.

[0020] More optimally, the high-flexibility acrylic ester monomer is any one or more of 2-[[butylamino)carbonyl]oxy]ethyl acrylate, isodecyl acrylate, eicosyl acrylate, docosyl acrylate, isodecyl methacrylate, and lauric methacrylate; the acrylic ester hard segment monomer is any one or more of isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl methacrylate, isobornyl acrylate, tetrahydrofurfuryl methacrylate, propoxylated nonylphenol acrylate, tetrahydrofurfuryl acrylate, and cyclohexyl methacrylate; the functional monomer is any one or more of acrylic acid, acrylamide, 2-hydroxyethyl methacrylate, methacrylic acid, and 2-hydroxyethyl acrylate; the thermal initiator is any one or more of azobisisobutyronitrile, dodecyl peroxide, dibenzoyl peroxide, azobisisoheptylonitrile, benzoyl peroxide, lauroyl peroxide, and tert-butyl perbenzoate.

[0021] More optimally, the tackifying resin is any one or more of rosin resin, modified rosin resin, terpene resin, rosin terpene phenol resin and petroleum resin; the curing agent is any one or more of polyisocyanate, epoxy curing agent and metal salt curing agent; and the solvent is ethyl acetate and / or butyl acetate.

[0022] More optimally, the thickness of the PU substrate is a polyurethane film of 10-15 μm; the tensile strength of the PU substrate at a low temperature of -25°C is >30 MPa, the elongation at break is >600%, and the low-temperature elastic deformation is 0-200%; the Young's modulus of the PU substrate at room temperature is <3 MPa, the storage and loss moduli are <5 MPa, the loss factor tanδ is 0.9-1.2, and the glass transition temperature is -30 to -20°C;

[0023] The thickness of the pressure-sensitive adhesive layer is 5-10 μm;

[0024] The release film has a thickness of 20-100 μm;

[0025] A method for preparing an ultra-thin PU tape resistant to low temperature bending, characterized in that it comprises the following steps:

[0026] Step 1: Take high-flexibility acrylate monomer, acrylate hard segment monomer, functional monomer, thermal initiator, and solvent, mix them evenly, and react at 60-90° C. for 5-9 hours to obtain a high-flexibility, low-shrinkage acrylate polymer;

[0027] Step 2: Take a high-flexibility, low-shrinkage acrylic polymer, a tackifying resin, a curing agent, and a solvent, mix them evenly, and ultrasonically disperse them to obtain an acrylic pressure-sensitive adhesive;

[0028] Step three: coating an acrylic pressure-sensitive adhesive on the release surface of the release film, and drying the coating to obtain an acrylic pressure-sensitive adhesive layer; and laminating the acrylic pressure-sensitive adhesive layer on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0029] Preferably, the coating method is any one of micro-concave coating, slit extrusion coating, and comma blade coating.

[0030] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0031] 1. The present invention prepares a high-flexibility, low-shrinkage acrylate polymer by free radical polymerization of a high-flexibility acrylate monomer and an acrylate hard monomer in a specific weight ratio, and reasonably combines the acrylate polymer and a curing agent to prepare an acrylate pressure-sensitive adhesive layer with a low shrinkage rate (<1%) and high flexibility at -25°C, and prepares a PU tape with an ultra-thin PU substrate resistant to low-temperature bending. The PU tape can have good folding resistance and high elastic deformation under low temperature (-25°C), normal temperature and high temperature (65°C) conditions at an ultra-thin thickness of 15-20μm, and the pressure-sensitive adhesive layer and the PU substrate layer have the same shrinkage rate at low temperature, so that the pressure-sensitive adhesive layer and the PU substrate layer will not be delaminated or debonded when bent at low temperature.

[0032] 2. The high-flexibility, low-shrinkage acrylic pressure-sensitive adhesive layer prepared by the present invention has high flexibility and high creep recovery under low temperature conditions, and has high viscosity under low temperature (-25°C), room temperature and high temperature (65°C) conditions.

[0033] 3. The ultra-thin PU tape provided by the present invention is bent 300,000 times at -25°C, room temperature and 65°C (a total of 900,000 times), with no cracks or debonding on the surface. Because it has low-temperature bendability, high viscosity, excellent tensile strength and elongation at break, it can be used on folding screens under different environmental conditions. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The following table shows the purchase channels of the chemical reagents used in the present invention:

[0036]

[0037] Example 1

[0038] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0039] 50 g of ethyl 2-[[butylamino)carbonyl]oxy]acrylate, 35 g of isodecyl acrylate, 15 g of isobornyl acrylate, 5 g of acrylic acid, 0.15 g of benzoyl peroxide, 0.3 g of azobisisoheptanenitrile and 120 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85° C. and subjected to free radical polymerization reaction for 8 hours to obtain an acrylic ester polymer A with high flexibility and low shrinkage.

[0040] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0041] a. Mix 100 parts of highly flexible, low-shrinkage acrylic polymer A, 15 parts of tackifying resin, 1.5 parts of curing agent, and 125 parts of solvent by weight, and perform ultrasonic dispersion to obtain acrylic pressure-sensitive adhesive A;

[0042] The tackifying resin is a rosin terpene phenol resin with a softening point of 150°C, specifically T-803L produced by Arakawa Chemical; the curing agent is a polyisocyanate and a metal salt curing agent, with a mass ratio of 1:1; the solvent is butyl acetate;

[0043] Acrylic pressure-sensitive adhesive A, glass transition temperature is -25 ° C, the storage modulus G' of the acrylic pressure-sensitive adhesive at -25 ° C is 600 KPa, and the loss factor tanδ is 0.77; the storage modulus G' of the acrylic pressure-sensitive adhesive at 23 ° C is 130 KPa, and the loss factor tanδ is 0.52; the storage modulus G' of the acrylic pressure-sensitive adhesive at 65 ° C is 58 KPa, and the loss factor tanδ is 0.36; the acrylic pressure-sensitive adhesive is in a 400% high creep state, and after dropping from 65 ° C to 25 ° C, the creep recovery rate is 58%, and the shrinkage rate at a low temperature of -25 ° C is 0.6%;

[0044] b. Coat an acrylate pressure-sensitive adhesive A with a thickness of 8 μm on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 minutes to obtain an acrylate pressure-sensitive adhesive layer A; and laminate the acrylate pressure-sensitive adhesive layer A on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0045] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0046] Example 2

[0047] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0048] 50 g of ethyl 2-[[butylamino)carbonyl]oxy]acrylate, 30 g of eicosyl acrylate, 25 g of tetrahydrofurfuryl methacrylate, 4 g of 2-hydroxyethyl methacrylate, 0.15 g of benzoyl peroxide, 0.2 g of azobisisoheptonitrile and 125 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization for 7 hours to obtain an acrylic polymer B with high flexibility and low shrinkage.

[0049] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0050] a. Mix 100 parts of highly flexible, low-shrinkage acrylate polymer B, 20 parts of tackifying resin, 1.0 part of curing agent, and 125 parts of solvent by weight, and perform ultrasonic dispersion to obtain acrylate pressure-sensitive adhesive B;

[0051] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is polyisocyanate; the solvent is butyl acetate;

[0052] Acrylic pressure-sensitive adhesive B, glass transition temperature is -20°C, storage modulus G' of the acrylic pressure-sensitive adhesive at -25°C is 650KPa, loss factor tanδ is 0.77; storage modulus G' of the acrylic pressure-sensitive adhesive at 23°C is 150KPa, loss factor tanδ is 0.55; storage modulus G' of the acrylic pressure-sensitive adhesive at 65°C is 55KPa, loss factor tanδ is 0.40; the acrylic pressure-sensitive adhesive has a creep recovery rate of 63% after dropping from 65°C to 25°C under a high creep state of 400%; shrinkage rate at a low temperature of -25°C is 0.4%;

[0053] b. Coat an acrylate pressure-sensitive adhesive B with a thickness of 8 μm on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 minutes to obtain an acrylate pressure-sensitive adhesive layer B; and laminate the acrylate pressure-sensitive adhesive layer B on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0054] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0055] Example 3

[0056] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0057] 90 g of lauric acid methacrylate, 25 g of tetrahydrofurfuryl acrylate, 3.5 g of 2-hydroxyethyl methacrylate, 0.4 g of azobisisoheptanenitrile and 140 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization reaction for 8 hours to obtain an acrylic polymer C with high flexibility and low shrinkage.

[0058] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0059] a. Mix 100 parts of highly flexible, low-shrinkage acrylic polymer C, 25 parts of tackifying resin, 1 part of curing agent, and 125 parts of solvent by weight, stir, and ultrasonically disperse to obtain acrylic pressure-sensitive adhesive C;

[0060] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is a polyisocyanate and an epoxy curing agent, with a mass ratio of 1:1; the solvent is ethyl acetate;

[0061] Acrylic pressure-sensitive adhesive C, glass transition temperature is -18 ° C, the storage modulus G' of the acrylic pressure-sensitive adhesive at -25 ° C is 650 KPa, and the loss factor tanδ is 0.75; the storage modulus G' of the acrylic pressure-sensitive adhesive at 23 ° C is 150 KPa, and the loss factor tanδ is 0.53; the storage modulus G' of the acrylic pressure-sensitive adhesive at 65 ° C is 57 KPa, and the loss factor tanδ is 0.40; the acrylic pressure-sensitive adhesive is in a 400% high creep state, and after dropping from 65 ° C to 25 ° C, the creep recovery rate is 65%, and the shrinkage rate at a low temperature of -25 ° C is 0.3%;

[0062] b. Coat an acrylate pressure-sensitive adhesive C with a thickness of 8 μm on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 min to obtain an acrylate pressure-sensitive adhesive layer C; and laminate the acrylate pressure-sensitive adhesive layer C on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0063] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0064] Comparative Example 1

[0065] Example 1 was used as a control group, but no acrylic polymer containing high flexibility and low shrinkage was used, specifically 149H of Shimei Chemical, which was recorded as acrylic polymer A1;

[0066] a. Mix 100 parts of acrylate polymer A1, 15 parts of tackifying resin, 1.5 parts of curing agent and 125 parts of solvent by weight, stir and ultrasonically disperse to obtain acrylate pressure-sensitive adhesive A1;

[0067] The tackifying resin is a rosin terpene phenol resin with a softening point of 150°C, specifically T-803L produced by Arakawa Chemical; the curing agent is a polyisocyanate and a metal salt curing agent, with a mass ratio of 1:1; the solvent is butyl acetate;

[0068] Acrylic pressure-sensitive adhesive A1, glass transition temperature is -25°C, storage modulus G' of the acrylic pressure-sensitive adhesive at -25°C is 340000KPa, loss factor tanδ is 0.21; storage modulus G' of the acrylic pressure-sensitive adhesive at 23°C is 76KPa, loss factor tanδ is 0.60; storage modulus G' of the acrylic pressure-sensitive adhesive at 65°C is 43KPa, loss factor tanδ is 0.14; the acrylic pressure-sensitive adhesive is in a 400% high creep state, after dropping from 65°C to 25°C, the creep recovery rate is 12.6%, and the shrinkage rate at a low temperature of -25°C is 1.9%;

[0069] b. Coat 8 μm thick acrylic pressure-sensitive adhesive A1 on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110° C. for 5 min to obtain an acrylic pressure-sensitive adhesive layer A1; and laminate the acrylic pressure-sensitive adhesive layer A1 on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0070] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0071] Comparative Example 2

[0072] Using Example 2 as a control group, the ratio of high-flexibility acrylate monomer to acrylate hard segment monomer was changed during the preparation of high-flexibility, low-shrinkage acrylate polymer;

[0073] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0074] 25 g of ethyl 2-[[butylamino)carbonyl]oxy]acrylate, 30 g of eicosyl acrylate, 50 g of tetrahydrofurfuryl methacrylate, 4 g of 2-hydroxyethyl methacrylate, 0.15 g of benzoyl peroxide, 0.2 g of azobisisoheptonitrile and 125 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization for 7 hours to obtain a highly flexible, low shrinkage acrylate polymer B1.

[0075] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0076] a. Mix 100 parts of highly flexible, low-shrinkage acrylic polymer B1, 20 parts of tackifying resin, 1.0 part of curing agent, and 125 parts of solvent, and perform ultrasonic dispersion to obtain acrylic pressure-sensitive adhesive B1.

[0077] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is polyisocyanate; the solvent is butyl acetate;

[0078] Acrylic pressure-sensitive adhesive B1, glass transition temperature is -25°C, storage modulus G' of the acrylic pressure-sensitive adhesive at -25°C is 450KPa, loss factor tanδ is 0.68; storage modulus G' of the acrylic pressure-sensitive adhesive at 23°C is 120KPa, loss factor tanδ is 0.42; storage modulus G' of the acrylic pressure-sensitive adhesive at 65°C is 62KPa, loss factor tanδδ is 0.47; the acrylic pressure-sensitive adhesive is in a 400% high creep state, after dropping from 65°C to 25°C, the creep recovery rate is 48%, and the shrinkage rate at a low temperature of -25°C is 0.9%;

[0079] b. Coat 8 μm thick acrylic pressure-sensitive adhesive B1 on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 min to obtain an acrylic pressure-sensitive adhesive layer B1; and laminate the acrylic pressure-sensitive adhesive layer B1 onto a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0080] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0081] Comparative Example 3:

[0082] Using Example 2 as a control group, the ratio of high-flexibility acrylate monomer to acrylate hard segment monomer was changed during the preparation of high-flexibility, low-shrinkage acrylate polymer;

[0083] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0084] 50 g of 2-[[butylamino)carbonyl]oxy]ethyl acrylate, 50 g of eicosyl acrylate, 5 g of tetrahydrofurfuryl methacrylate, 4 g of 2-hydroxyethyl methacrylate, 0.15 g of benzoyl peroxide, 0.2 g of azobisisoheptanenitrile and 125 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization for 7 hours to obtain a highly flexible, low shrinkage acrylate polymer B2.

[0085] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0086] a. Mix 100 parts of highly flexible, low-shrinkage acrylic polymer B2, 20 parts of tackifying resin, 1.0 part of curing agent, and 125 parts of solvent, and perform ultrasonic dispersion to obtain acrylic pressure-sensitive adhesive B2.

[0087] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is polyisocyanate; the solvent is butyl acetate;

[0088] Acrylic pressure-sensitive adhesive B2, glass transition temperature is -30 ° C, the storage modulus G' of the acrylic pressure-sensitive adhesive at -25 ° C is 320 KPa, and the loss factor tanδ is 0.58; the storage modulus G' of the acrylic pressure-sensitive adhesive at 23 ° C is 75 KPa, and the loss factor tanδ is 0.41; the storage modulus G' of the acrylic pressure-sensitive adhesive at 65 ° C is 40 KPa, and the loss factor tanδ is 0.41; the acrylic pressure-sensitive adhesive is in a 400% high creep state, and after dropping from 65 ° C to 25 ° C, the creep recovery rate is 48%, and the shrinkage rate at a low temperature of -25 ° C is 1.1%;

[0089] b. Coat 8 μm thick acrylic pressure-sensitive adhesive B2 on the release surface of a 50 μm thick release film with an aged release force of 10 gl / in and a residual rate of 87%, and dry at 110°C for 5 min to obtain an acrylic pressure-sensitive adhesive layer B2; and laminate the acrylic pressure-sensitive adhesive layer B2 onto a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0090] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0091] Comparative Example 4

[0092] Using Example 3 as a control group, the ratio of the high-flexibility, low-shrinkage acrylic polymer and the tackifying resin in the acrylic pressure-sensitive adhesive layer was changed.

[0093] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0094] 90 g of lauric acid methacrylate, 25 g of tetrahydrofurfuryl acrylate, 3.5 g of 2-hydroxyethyl methacrylate, 0.4 g of azobisisoheptanenitrile and 140 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization reaction for 8 hours to obtain an acrylic polymer C with high flexibility and low shrinkage.

[0095] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0096] a. Mix 90 parts of high-flexibility, low-shrinkage acrylic polymer C, 35 parts of tackifying resin, 1 part of curing agent, and 125 parts of solvent, by weight, and perform ultrasonic dispersion to obtain acrylic pressure-sensitive adhesive C1;

[0097] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is a polyisocyanate and an epoxy curing agent, with a mass ratio of 1:1; the solvent is ethyl acetate;

[0098] Acrylic pressure-sensitive adhesive C1, glass transition temperature is -10°C, storage modulus G' of the acrylic pressure-sensitive adhesive at -25°C is 670KPa, loss factor tanδ is 0.60; storage modulus G' of the acrylic pressure-sensitive adhesive at 23°C is 160KPa, loss factor tanδ is 0.43; storage modulus G' of the acrylic pressure-sensitive adhesive at 65°C is 62KPa, loss factor tanδ is 0.40; the acrylic pressure-sensitive adhesive is in a 400% high creep state, after dropping from 65°C to 25°C, the creep recovery rate is 59%, and the shrinkage rate at a low temperature of -25°C is 1.3%;

[0099] b. Coat an acrylate pressure-sensitive adhesive C1 with a thickness of 8 μm on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 min to obtain an acrylate pressure-sensitive adhesive layer C1; and laminate the acrylate pressure-sensitive adhesive layer C1 on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0100] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0101] Comparative Example 5

[0102] Using Example 3 as a control group, the ratio of the high-flexibility, low-shrinkage acrylic polymer and the tackifying resin in the acrylic pressure-sensitive adhesive layer was changed.

[0103] S1. Preparation of highly flexible, low shrinkage acrylic polymers:

[0104] 90 g of lauric acid methacrylate, 25 g of tetrahydrofurfuryl acrylate, 3.5 g of 2-hydroxyethyl methacrylate, 0.4 g of azobisisoheptanenitrile and 140 g of ethyl acetate were uniformly mixed to obtain a mixed solution. The mixed solution was placed in a constant temperature oil bath at 85°C and subjected to free radical polymerization reaction for 8 hours to obtain an acrylic polymer C with high flexibility and low shrinkage.

[0105] S2. Preparation of an ultra-thin PU tape resistant to low temperature bending:

[0106] a. Mix 120 parts of high-flexibility, low-shrinkage acrylic polymer C, 5 parts of tackifying resin, 1 part of curing agent, and 125 parts of solvent, and perform ultrasonic dispersion to obtain acrylic pressure-sensitive adhesive C2;

[0107] The tackifying resin is a rosin resin with a softening point of 100°C, specifically GB100 produced by Arakawa Chemical; the curing agent is a polyisocyanate and an epoxy curing agent, with a mass ratio of 1:1; the solvent is ethyl acetate;

[0108] Acrylic pressure-sensitive adhesive C2, glass transition temperature is -35 ° C, the storage modulus G' of the acrylic pressure-sensitive adhesive at -25 ° C is 590 KPa, and the loss factor tanδ is 0.61; the storage modulus G' of the acrylic pressure-sensitive adhesive at 23 ° C is 79 KPa, and the loss factor tanδ is 0.41; the storage modulus G' of the acrylic pressure-sensitive adhesive at 65 ° C is 39 KPa, and the loss factor tanδ is 0.48; the acrylic pressure-sensitive adhesive is in a 400% high creep state, and the creep recovery rate is 61% after the temperature drops from 65 ° C to 25 ° C; the shrinkage rate at a low temperature of -25 ° C is 1.3%;

[0109] b. Coat an acrylate pressure-sensitive adhesive C2 with a thickness of 8 μm on the release surface of a 50 μm thick release film with an aged release force of 10 gf / in and a residual rate of 87%, and dry at 110°C for 5 min to obtain an acrylate pressure-sensitive adhesive layer C2; and laminate the acrylate pressure-sensitive adhesive layer C2 onto a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

[0110] The PU substrate (Ningbo Clariant SBU-100-12) is a polyurethane film with a thickness of 12μm, a tensile strength of 32MPa at a low temperature of -25℃, an elongation at break of 628%, and a low-temperature elastic deformation of 175%; the Young's modulus at room temperature is 2.5MPa, the storage and loss moduli are 4.1MPa and 4.3MPa respectively, the loss factor tanδ is 1.05, and the glass transition temperature is -25℃.

[0111] experiment

[0112] The normal temperature, low temperature and high temperature peel strength and bending resistance of the adhesive tapes prepared in Examples 1-3 and Comparative Examples 1-5 were tested, and the test results are shown in the following table;

[0113] The peel strength of the prepared tape was measured with reference to the method of GB / T2792-2014: the adhered object was a SUS steel plate with a bright surface and a roughness (GB / T2523-2008) of 50 nm. The tape was cut into a size of 25 mm × 300 mm, pressed back and forth 3 times with a 2 kg roller, and left for 20 minutes. The normal temperature test environment was 23 ° C / 50% RH, the low temperature test environment was -25 ° C, and the high temperature test environment was 65 ° C. The 180 ° peeling was performed at a speed of 300 mm / min.

[0114] Bending resistance: The prepared tape was cut into 40 mm × 300 cm strips and pasted in the middle of the PI substrate of a sample with a thickness of 50 μm and a size of 200 mm × 300 cm. It was pressed back and forth 3 times with a 2 kg roller and placed in an environment with a temperature of 23 ± 1 ° C and a relative humidity of 50 ± 5% RH for 24 hours. The above components that need to be bent are placed in -25℃, 23℃ and 65℃ bending equipment in turn, and subjected to 300,000 bending tests with a bending radius of 3mm and a bending angle of 180° (i.e., the sample is first subjected to 300,000 bending tests at -25℃. If the sample meets the bending resistance requirements, i.e., there is no cracking, orange peel texture or creases, the sample is then subjected to 300,000 bending tests at 23℃. If the sample meets the bending resistance requirements, the sample is then subjected to 300,000 bending tests at 65℃. A total of 900,000 bendings are performed in three tests). Take out the tape and restore it to room temperature to observe whether there are cracks, orange peel texture or creases on the surface of the tape.

[0115] The performance comparison of the adhesive tapes prepared in Examples 1-3 and Comparative Examples 1-3 is shown in the following table:

[0116]

[0117] Conclusion: By comparing the examples with the comparative examples, it can be seen that the ultra-thin PU tape prepared by the method provided by the present invention has good folding resistance and extremely high elastic deformation performance under low temperature (-25°C), room temperature and high temperature (65°C), and is bent 300,000 times (a total of 900,000 times) at low temperature of -25°C, room temperature and high temperature of 65°C, respectively, without cracking or debonding on the surface, unlike ordinary PU substrate tapes, which have a sharp decrease in bending resistance, ductility and viscosity under low temperature conditions, and bending and cracking on the surface at low temperatures. The ultra-thin PU tape of the present invention has high flexibility and high creep recovery under low temperature conditions, and has high viscosity under low temperature to high temperature conditions.

[0118] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-thin PU tape resistant to low temperature bending, characterized by: The ultra-thin PU tape includes a substrate, which is a 10-15μm ultra-thin, high-light-shielding, low-temperature-resistant and bendable PU substrate, a 5-10μm thick acrylic pressure-sensitive adhesive layer is adhered to one side or both sides of the substrate, and a release film is adhered to the outer side of the acrylic pressure-sensitive adhesive layer; the ultra-thin PU tape is bent 300,000 times under low temperature of -25°C, room temperature and high temperature of 65°C respectively, and there are no cracks or debonding on the surface of the material.

2. The ultra-thin PU tape resistant to low temperature bending according to claim 1, characterized in that: The acrylic pressure-sensitive adhesive layer comprises the following components: by weight: 100 parts of highly flexible, low shrinkage acrylic polymer; 5-30 parts of tackifying resin; Curing agent 0.1-5 parts; 200-500 parts of solvent.

3. The ultra-thin PU tape resistant to low temperature bending according to claim 2, characterized in that: The glass transition temperature of the acrylic pressure-sensitive adhesive layer is between -45 and -5°C, the storage modulus G′ of the acrylic pressure-sensitive adhesive at -25°C is between 300 and 700 KPa, and the loss factor tanδ is between 0.65 and 0.80; the storage modulus G′ of the acrylic pressure-sensitive adhesive at 23°C is between 80 and 200 KPa, and the loss factor tanδ is between 0.45 and 0.60; the storage modulus G′ of the acrylic pressure-sensitive adhesive at 65°C is between 35 and 60 KPa, and the loss factor tanδ is between 0.3 and 0.45; the creep recovery rate of the acrylic pressure-sensitive adhesive is greater than 50% after the temperature drops from 65°C to 25°C under a high creep state of 400%; the shrinkage rate of the acrylic pressure-sensitive adhesive at a low temperature of -25°C is less than 1%.

4. The ultra-thin PU tape resistant to low temperature bending according to claim 2, characterized in that: The highly flexible, low shrinkage acrylic polymer comprises the following components: by weight, 60-95 parts of high-flexibility acrylic monomer; 10-40 parts of acrylate hard segment monomer; 0.5-5 parts of functional monomer; Thermal initiator 0.1-0.5 parts; 80-150 parts of solvent.

5. The ultra-thin PU tape resistant to low temperature bending according to claim 4, characterized in that: The high-flexibility acrylic ester monomer is any one or more of 2-[[butylamino)carbonyl]oxy]ethyl acrylate, isodecyl acrylate, eicosyl acrylate, docosyl acrylate, isodecyl methacrylate, and lauric methacrylate; the acrylic ester hard segment monomer is any one or more of isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl methacrylate, isobornyl acrylate, tetrahydrofurfuryl methacrylate, propoxylated nonylphenol acrylate, tetrahydrofurfuryl acrylate, and cyclohexyl methacrylate; the functional monomer is any one or more of acrylic acid, acrylamide, 2-hydroxyethyl methacrylate, methacrylic acid, and 2-hydroxyethyl acrylate; the thermal initiator is any one or more of azobisisobutyronitrile, dodecyl peroxide, dibenzoyl peroxide, azobisisoheptylonitrile, benzoyl peroxide, lauroyl peroxide, and tert-butyl perbenzoate.

6. The ultra-thin PU tape resistant to low temperature bending according to claim 2, characterized in that: The tackifying resin is any one or more of rosin resin, modified rosin resin, terpene resin, rosin terpene phenol resin and petroleum resin.

7. The ultra-thin PU tape resistant to low temperature bending according to claim 2, characterized in that: The curing agent is any one or more of polyisocyanate, epoxy curing agent and metal salt curing agent.

8. The ultra-thin PU tape resistant to low temperature bending according to claim 2, characterized in that: The solvent is ethyl acetate and / or butyl acetate.

9. The ultra-thin PU tape resistant to low temperature bending according to claim 1, characterized in that: The PU substrate has a tensile strength of >30MPa at a low temperature of -25°C, an elongation at break of >600%, and a low-temperature elastic deformation of 0-200%; the PU substrate has a Young's modulus of <3MPa at room temperature, a storage and loss modulus of <5MPa, a loss factor tanδ of 0.9-1.2, and a glass transition temperature of -30 to -20°C.

10. A method for preparing the ultra-thin PU tape resistant to low temperature bending according to any one of claims 1 to 9, characterized in that: The following steps are included: Step 1: Take high-flexibility acrylate monomer, acrylate hard segment monomer, functional monomer, thermal initiator, and solvent, mix them evenly, and react at 60-90° C. for 5-9 hours to obtain a high-flexibility, low-shrinkage acrylate polymer; Step 2: Take a high-flexibility, low-shrinkage acrylic polymer, a tackifying resin, a curing agent, and a solvent, mix them evenly, and ultrasonically disperse them to obtain an acrylic pressure-sensitive adhesive; Step three: coating an acrylic pressure-sensitive adhesive on the release surface of the release film, and drying the coating to obtain an acrylic pressure-sensitive adhesive layer; and laminating the acrylic pressure-sensitive adhesive layer on a PU substrate to obtain an ultra-thin PU tape that is resistant to low-temperature bending.

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