PREPARING SAME

TECHNICAL FIELD

The present invention relates to a modified phytic acid derivative resin, a liquid flame-retardant resin, and a flame-retardant film, and specifically relates to a light-curable liquid flame -retardant resin, a flame-retardant film, and a method for preparing the same.

BACKGROUND

Flame-retardant materials play an important role in maintaining safety in society. In recent years, the state has promulgated a number of industry standards to strengthen the application of

flame-retardant materials in various fields. Halogen-containing flame retardants, which were widely used before, have been gradually restricted due to environmental reasons. Therefore, halogen-free flame retardants are more popular among users. However, most halogen-free flame retardants are less efficient than halogen-containing flame retardants. Furthermore, products with small thickness, such as thin films and adhesive tapes, have stronger combustibility. It is difficult to achieve UL-94 VTMO-rating flame retardancy by using halogen-free flame retardants. If excessive flame retardants are added, the properties of materials themselves, such as strength and viscosity, will be greatly affected.

Most organophosphorus flame retardants have the advantages of low smoke emission, non-toxicity, low halogen, and no halogen which accord with the development direction of flame retardants, and have excellent prospects for development.

There are many kinds of organophosphorus flame retardants, which can be sub-divided, according to use methods, into additive flame retardants and reactive flame retardants. Chinese patent application No. CN 2010123312.3 (XIA, Yuzheng et al.) has disclosed a method for preparing a combined phosphorus type flame-retardant acrylate pressure-sensitive adhesive. The method is as follows: the flame-retardant pressure-sensitive adhesive is prepared by using a commonly available, inexpensive, and environmentally-friendly flame retardant and flame retardant system; an intrinsic flame-retardant macromolecular pressure-sensitive adhesive is prepared by means of

copolymerization of a phosphorus-containing acrylate monomer and a conventional acrylate monomer by introducing phosphate groups to provide the acrylate pressure-sensitive adhesive with flame retardancy, and then a small amount of the flame retardant is added to obtain the pressure-sensitive adhesive with excellent pressure sensitivity and flame retardancy. Phytic acid has a high phosphorus content, and some people therefore use it or its derivatives in halogen-free flame -retardant products. US 2006234044 (NAKANISHI TORU et al.) has disclosed a bicomponent flame -retardant adhesive consisting of (A) a non-halogen epoxy resin, (B) a thermoplastic resin and/or synthetic rubber, (C) a hardening agent, (D) a phytate compound and (E) a hardening accelerator. The adhesive can be used for bonding thin sheets, covering fdms and flexible copper laminates.

JP 5311380 (TAGUCHI KAZUHIRO et al.) has disclosed a flame-retardant epoxy resin and a method for preparing the same. The phosphorus-containing flame-retardant epoxy resin contains an epoxy compound, an alcohol and phosphorus-containing phytic acid. Cationic polymerization of the epoxy compound and phytic acid occurs under the catalysis of an acid.

SUMMARY

The present invention is intended to provide a modified phytic acid derivative resin and a light-curable liquid flame-retardant resin prepared by using the same. A flame-retardant film obtained through light curing of the liquid flame -retardant resin is halogen-free, and the flame retardancy rating thereof can reach UU-94 V-0.

According to one aspect of the present invention, the present invention provides a modified phytic acid derivative resin, which comprises reaction products of the following components: 35-65 wt. % of phytic acid, 20-65 wt. % of an epoxy compound containing a double bond, and 0-35 wt. % of a bifunctional epoxy compound, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

According to some specific embodiments of the present invention, the epoxy compound containing a double bond is one or more selected from the group consisting of glycidyl methacrylate, glycidyl acrylate and allyl glycidyl ester.

According to some specific embodiments of the present invention, the content of the phytic acid is 45-55 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

According to some specific embodiments of the present invention, the content of the epoxy compound containing a double bond is 30-40 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

According to some specific embodiments of the present invention, the content of the bifunctional epoxy compound is 10-20 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %. According to another aspect of the present invention, the present invention provides a light-curable liquid flame -retardant resin, which comprises, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %, 79-99.9 wt. % of the modified phytic acid derivative resin according to claims 1 to 5, 0-20 wt. % of a polyurethane acrylate resin, and 0.1-5 wt. % of a photoinitiator.

According to some specific embodiments of the present invention, the content of the modified phytic acid derivative resin is 82-87 wt. %, based on the total weight percentage of the liquid

flame-retardant resin as 100 wt. %.

According to some specific embodiments of the present invention, the content of the polyurethane acrylate resin is 12-17 wt. %, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %.

According to some specific embodiments of the present invention, the content of the photoinitiator is 0.1-1 wt. %, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %.

According to some specific embodiments of the present invention, the liquid flame-retardant resin further comprises 0-30 wt. % of expansible graphite, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %.

According to some specific embodiments of the present invention, the content of the expansible graphite is 5-10 wt. %, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %.

According to another aspect of the present invention, the present invention provides a

flame-retardant film, which is a flame-retardant film formed through light curing of the liquid film prepared from the liquid flame -retardant resin.

According to another aspect of the present invention, the present invention provides a

flame-retardant adhesive tape, which is a flame -retardant adhesive tape formed by bonding the flame-retardant film as a substrate to an adhesive film.

According to some specific embodiments of the present invention, the adhesive film bonded to the substrate is a pressure-sensitive adhesive film, a heat-sensitive adhesive film, a light-curable adhesive film, or a moisture-curable adhesive film.

DETAILED DESCRIPTION

It is to be understood that, those of skill in the art can envisage other various embodiments according to teachings in this description and can make modifications thereto, without departing from the scope or spirit of the present invention. Therefore, the following particular embodiments have no limiting meaning.

All figures for denoting quantities and physicochemical properties used in the description and claims are to be understood as modified by a term“about” in all situations, unless indicated otherwise. Therefore, unless stated conversely, parameters in numerical values listed in the above specification and the claims are all approximate values. Those skilled in the art are capable of seeking to obtain desired properties by taking advantage of contents of the teachings disclosed herein, and changing these approximate values as needed. The use of a numerical range represented by end points includes all figures within the range and any range within the range, for example, 1, 2, 3, 4 and 5 include 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, 5, and the like.

Modified Phytic Acid Derivative Resin

A modified phytic acid derivative resin provided by the present invention comprises reaction products of the following components: 35-65 wt. % of phytic acid, 20-65 wt. % of an epoxy compound containing a double bond, and 0-35 wt. % of a bifunctional epoxy compound, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %. The phytic acid used is an aqueous solution with a concentration greater than or equal to 30 wt. %, preferably greater than or equal to 50 wt. %. The weight percentage of the phytic acid in the modified phytic acid derivative resin is calculated based on the weight of pure phytic acid. When the content of the phytic acid is lower than 35 wt. %, the flame-retardant effect of a prepared flame-retardant film is not optimal; when the content of the phytic acid is greater than 65 wt. %, light curing of a

flame-retardant resin is incomplete. The content of the phytic acid is preferably 45-55 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %. In this range, the prepared flame -retardant film has excellent flame retardancy, as well as desirable mechanical properties of the obtained flame-retardant film. The epoxy compound containing a double bond is preferably glycidyl methacrylate, glycidyl acrylate and/or allyl glycidyl ester, more preferably glycidyl methacrylate. The content of the epoxy compound containing a double bond is 20-65 wt. %, preferably 30-40 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %. When the content of the epoxy compound containing a double bond is smaller than 20 wt. %, the obtained liquid flame-retardant resin cannot be completely cured; when the content of the epoxy compound containing a double bond is greater than 65 wt. %, the flame-retardant effect of the prepared flame-retardant film is poor.

Light-Curable Liquid Flame -Retardant Resin

A light-curable liquid flame-retardant resin provided by the present invention comprises reaction products of the following components: 79-99.9 wt. % of the modified phytic acid derivative resin, 0-20 wt. % of a polyurethane acrylate resin, and 0.1-5 wt. % of a photoinitiator, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %.

The content of the modified phytic acid derivative resin is preferably 82-87 wt. %, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %. When the content of the modified phytic acid derivative resin is smaller than 79 wt. %, the flame retardant properties of the prepared flame-retardant film are poor; when the content of the modified phytic acid derivative resin is greater than 99.9 wt. %, a sufficient amount of the photoinitiator cannot be added, such that a light-cured liquid flame -retardant resin cannot be obtained; when the content of the modified phytic acid derivative resin is 82-87 wt. %, the obtained flame -retardant film has better flame -retardant properties and also has optimal mechanical properties. The polyurethane acrylate resin can be any polyurethane resin containing an acryloyl functional group. When the content of the polyurethane acrylate resin is preferably 12-17 wt. %, the mechanical properties of the prepared flame-retardant film are better. The photoinitiator is any compound that generates free radicals and initiates monomer polymerization after light irradiation. The photoinitiator may be selected from UV photoinitiators or visible photoinitiators. The content of the photoinitiator is preferably 0.1-1 wt. %, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %. In this range, the prepared flame-retardant film is cured more completely.

The liquid flame-retardant resin may further comprise 0-30 wt. % of expansible graphite, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %, which can further improve the flame -retardant properties of the prepared flame -retardant film. The content of the expansible graphite is preferably 5-10 wt. %, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %. When the content of the expansible graphite is greater than 30 wt. %, the prepared flame -retardant film has poor mechanical properties. The mesh number of the expandable graphite is preferably 50-500 meshes.

Flame-Retardant Film Flame-Retardant Adhesive Tape and Method For Preparing Same

The“light-curable liquid flame-retardant resin” is applied to a substrate, and is then light-cured in an environment isolated from oxygen, to form a flame-retardant film. Herein, the“light-curable liquid flame-retardant resin” may be applied in the middle of two layers of release films, and the flame-retardant film can be obtained by tearing off the release films on the two sides after light curing; or, the“light-curable liquid flame -retardant resin” is applied to one layer of release film, and is then light-cured in an environment isolated from oxygen. The application method may be coating. The coating method may be preferably one or more of the following group: roll coating, flow coating, dip coating, spin coating, spray coating, scrape coating and die coating. The thickness of the flame-retardant film may be 100-5000 microns, preferably 200-2000 microns, more preferably 500-1000 microns. Light used for curing may an UV lamp, visible light, etc., and the energy density thereof may be gre ater than 10 mJ/cm ² , preferably 300-1000 mJ/cm ² .

A flame -retardant adhesive tape is formed by bonding the“flame-retardant film” as a substrate to an adhesive film. The adhesive film bonded to the substrate may be a pressure-sensitive adhesive film, a heat-sensitive adhesive film, a light-curable adhesive film, a moisture-curable adhesive film etc. The adhesive film bonded to the substrate may be a pressure-sensitive adhesive film, a heat-sensitive adhesive film, a light-curable adhesive film, a moisture-curable adhesive film, etc. The adhesive film is made of any material, such as a polyacrylate, rubber, a polyurethane, or silica gel. In addition, in practical application the thickness of the adhesive film bonded to the substrate needs to be adjusted according to requirements on flame retardancy and adhesiveness, as well as the flame retardancy and thickness of the compounded flame-retardant film provided by the present invention. The bonding mode of the substrate and the adhesive film may be single-sided or double-sided bonding, and correspondingly a single-sided flame -retardant adhesive tape and a double-sided flame-retardant adhesive tape can be prepared.

The flame -retardant adhesive film and the flame-retardant adhesive tape have optimal

flame-retardant properties, and the formula may be adjusted according to needs to provide both optimal flame -retardant properties and optimal mechanical properties.

The present invention provides a plurality of preferred embodiments of the liquid flame-retardant resin, the flame-retardant film and the flame -retardant adhesive tape.

Preferred embodiment 1 is a modified phytic acid derivative resin, comprising reaction products of the following components: 35-65 wt. % of phytic acid, 20-65 wt. % of an epoxy compound containing a double bond, and 0-35 wt. % of a bifunctional epoxy compound, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

Preferred embodiment 2 is the modified phytic acid derivative resin according to preferred embodiment 1, and the epoxy compound containing a double bond is one or more selected from the group consisting of glycidyl methacrylate, glycidyl acrylate and allyl glycidyl ester.

Preferred embodiment 3 is the modified phytic acid derivative resin according to preferred embodiment 1, and the content of the phytic acid is 45-55 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

Preferred embodiment 4 is the modified phytic acid derivative resin according to preferred embodiment 1, and the content of the epoxy compound containing a double bond is 30-40 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %. Preferred embodiment 5 is the modified phytic acid derivative resin according to preferred embodiment 1, and the content of the bifunctional epoxy compound is 10-20 wt. %, based on the total weight percentage of the modified phytic acid derivative resin as 100 wt. %.

Preferred embodiment 6 is a light-curable liquid flame-retardant resin, comprising the following components based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %:

79-99.9 wt. % of the modified phytic acid derivative resin;

0-20 wt. % of a polyurethane acrylate resin; and

0.1-5 wt. % of a photoinitiator.

Preferred embodiment 7 is the liquid flame-retardant resin according to preferred embodiment 6, and the content of the modified phytic acid derivative resin is 82-87 wt. %, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %.

Preferred embodiment 8 is the liquid flame-retardant resin according to preferred embodiment 6, and the content of the polyurethane acrylate resin is 12-17 wt. %, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %.

Preferred embodiment 9 is the liquid flame-retardant resin according to preferred embodiment 6, and the content of the photoinitiator is 0.1-1 wt. %.

Preferred embodiment 10 is the liquid flame-retardant resin according to preferred embodiment 6, and the liquid flame-retardant resin further comprises 0-30 wt. % of expansible graphite, based on the total weight percentage of the liquid flame -retardant resin as 100 wt. %.

Preferred embodiment 11 is the liquid flame-retardant resin according to preferred embodiment 6, and the content of the expansible graphite is 5-10 wt. %, based on the total weight percentage of the liquid flame-retardant resin as 100 wt. %.

Preferred embodiment 12 is a flame-retardant fdm, which is a flame -retardant film formed through light curing of a liquid film prepared from the liquid flame-retardant resin according to any one of preferred embodiments 6-11.

Preferred embodiment 13 is a flame-retardant adhesive tape, which is a flame-retardant adhesive tape formed by bonding the flame-retardant film according to preferred embodiment 11 as a substrate to an adhesive film.

Preferred embodiment 14 is the flame -retardant adhesive tape according to preferred embodiment 13, wherein the adhesive film bonded to the substrate is a pressure -sensitive adhesive film, a heat-sensitive adhesive film, a light-curable adhesive film, or a moisture-curable adhesive film. EXAMPLES

Examples and comparative examples provided hereinafter facilitate understanding of the present invention, and should not be understood to limit the scope of the present invention. Unless otherwise indicated, all parts and percentages used herein are by weight.

Raw materials employed in examples and comparative examples of the present invention are shown in the following Table 1.

Table 1: Raw Materials Used in Examples and Comparative Examples

The present invention evaluates the adhesiveness of the flame-retardant adhesive tapes provided in the examples and comparative examples by testing 180-degree peeling force, evaluates the flame-retardant properties of the flame -retardant films and the flame-retardant adhesive tapes provided in the examples and comparative examples by testing flame retardancy, and further evaluates the mechanical properties of the flame-retardant films and the flame -retardant adhesive tapes provided in the examples and comparative examples by testing tensile stress and elongation at break. 180-Degree Peeling Force Test

The procedure to test 180-degree room-temperature peeling force is described in ASTM

International Standard D3330. The test was completed on an Instron tension tester, at a peeling speed of 304.8 mm/min. The used bonded substrate was a standard steel plate. The method for preparing a sample was rolling a 25.4 mm ^c 200 mm adhesive tape sample back and forth once with a 1 kg rubber roller to adhere it to the surface of the steel plate, placing the prepared sample for 20 min in an environment with a temperature of 23 °C and relative humidity of 60 %, and then performing testing. The number of samples representing the same property should not be less than five. The test results were expressed by the arithmetic average of peeling strength in unit of N/mm. The test results of the adhesiveness can provide a reference for users to choose suitable flame-retardant resins according to their application needs.

The test results of the 180-degree room -temperature peeling force of the flame-retardant adhesive tapes provided in the examples and comparative examples of the present invention are listed in Table 4.

Flame Retardancv Test

According to UL-94 (a standard developed by U.S. Underwriters' Laboratories Inc.) vertical combustion tests, the flame was placed under the sample for 10 seconds, and then removed; the time taken for the sample to stop burning was measured. Two groups of samples were evaluated; each group consisted of five samples (a total of 10 burning durations were measured). The following were evaluated: the maximum among the 10 burning durations, the sum of the 10 burning durations, and whether droplets were present during burning. The classification of flame retardancy will be given below. Other details are in accordance with UL-94 standard.

V-0: Maximum burning duration: 10 seconds or less; total burning duration: 50 seconds or less; no presence of droplets.

V-l : Maximum burning duration: 30 seconds or less; total burning duration: 250 seconds or less; no presence of droplets.

V-2: Maximum burning duration: 30 seconds or less; total burning duration: 250 seconds or less; presence of droplets.

Burning: The above-mentioned conditions are not satisfied.

In the present invention, general flame retardancy requirements are considered to be met if a sample passes the UL-94 V-2 test. Higher flame retardancy requirements are considered to be met if a sample passes the UL-94 V-0 test. The test results of the flame retardancy of the flame -retardant fdms provided by the examples and comparative examples of the present invention are listed in Table 3, and the test results of the flame-retardant adhesive tapes provided by the examples and comparative examples of the present invention are listed in Table 4.

Tensile Stress and Elongation at Break Test

The test was completed on an Instron tension tester, at a drawing speed of 12.7 mm/min, and the distance between upper and lower fixtures was 100 mm, The method for preparing a sample was cutting a sample to a size of 25.4 mm ^c 200 mm, placing the prepared sample to be tested for 20 min in an environment with a temperature of 23 °C and relative humidity of 60 %, and then performing testing. The number of samples representing the same property should not be less than five. The ratio of a maximum stress to the cross-sectional area of a sample is tensile stress in unit of MPa, and elongation at which the sample is broken is elongation at break. Test results of tensile stress and elongation at break can provide a reference for users to choose suitable flame-retardant resins according to their application needs.

The test results of the tensile stress and elongation at break of the flame -retardant films provided in the examples and comparative examples of the present invention are listed in Table 3.

Preparation of Modified Phytic Acid Derivative Resin

Examples El-1 to El-8 and Comparative Examples CEl-9

In a 0°C ice water bath, an epoxy compound containing a double bond and a bifunctional epoxy compound were slowly added to phytic acid (50 % aqueous solution) while stirring. The reaction produced a lot of heat, and the reaction temperature should be maintained at 60°C by controlling the adding speed. After the reaction of epoxy groups was completed, the temperature gradually returned to room temperature, and the solution viscosity increased to obtain the modified phytic acid derivative resin. For the amounts of the added phytic acid (50 % aqueous solution), the epoxy compound containing a double bond and the bifunctional epoxy compound, refer to Table 2.

Table 2 Formulas of Modified Phytic Acid Derivative Resins in

Examples and Comparative Examples

Preparation and properties testing of light-curable liquid flame -retardant resin and flame -retardant film

Examples E2-1 to E2-13, and Comparative Examples CE2-14 and CE2-15

Polyurethane acrylate and a photoinitiator Ingracure 184 were added to the modified phytic acid derivative resin, and a light-curable liquid flame -retardant resin was obtained after stirring uniformly. The resin was coated by using a comma roller in the middle of two layers of release films, a slit was set to 500 microns, and curing was performed under a UV lamp (energy density: 500 mJ/cm ² , 10 seconds). A light-curable flame-retardant film was obtained by tearing off the release films on two sides. For the amounts of the added modified phytic acid derivative resin, the polyurethane acrylate and the photoinitiator Ingracure 184, refer to Table 3.

Comparative Examples CE2-16

In 80 g of phytic acid, 20 g of polyurethane acrylate and 0.3 g of a photoinitiator Ingracure 184 were added, stirred and then stood for 5 min. The mixture had been layered and a light-curable liquid flame-retardant resin could not be obtained. Table 3 Formulas Of Liquid Flame-Retardant Resins And Property Parameters Of Corresponding Flame-Retardant Films Obtained By Curing In Examples And Comparative Examples

As can be seen from Table 3, the flame retardancy ratings of the flame-retardant films obtained after curing in Examples E2-1 to E2-13 can all reach above UL-94 V-l, thus having optimal flame-retardant properties. The flame-retardant films obtained after curing in Examples E2-4 to E2-13 have better tensile stress and elongation at break. Examples E2-1 and E2-3 are flame-retardant films obtained from pure modified phytic acid derivative resins, thereby having optimal flame-retardant properties, but tensile stress and elongation at break thereof are relatively poor. Examples E2-4 to E2-13 are flame-retardant films obtained through curing after adding a certain amount of polyurethane acrylic resin into a modified phytic acid derivative resin, and tensile stress and elongation at break thereof are improved. The greater the increase of the amount of added polyurethane acrylic resin, the greater the increase of the tensile stress and elongation at break thereof. However, when the excessive amount of polyurethane acrylic resin is added, such as in Comparative Examples CE2-15, the mass percentage of the total phosphorus (P %) in the resin is excessively low, resulting in poor flame-retardant properties of the obtained flame-retardant film. In Examples E2-4 to E2-13, the flame-retardant films obtained after curing have optimal flame-retardant properties, as well as optimal mechanical properties such as tensile stress and elongation at break. In Examples E2-4, E2-6, and E2-8 to E2-13, when the mass percentage of the total phosphorus (P %) in the resin reaches about 6.0 % or more, the flame-retardant film obtained after curing has better flame-retardant properties.

Examples E3-1 to E3-6

A light-curable liquid flame-retardant resin was prepared according to Examples E2-9. After further addition of expansible graphite according to Table 4 and uniform stirring, the resin was coated by using a comma roller in the middle of two layers of release films, the width of a slit was set to 500 microns and curing was performed under a UV lamp (energy density: 500 mJ/cm ² , 10 seconds). A light-curable flame-retardant film was obtained by tearing off the release films on two sides. The flame-retardant films were coated on both sides with 3M pressure-sensitive films of different thickness and product numbers, and the flame Oretardant double-sided adhesive tapes were obtained. For thickness and product number of the 3M pressure-sensitive adhesive films, refer to Table 4.

Examples E3-7 and E3-8

A light-curable liquid flame-retardant resin was prepared according to Examples E2-9. After further addition of 5 wt. % of expansible graphite according to Table 4 and uniform stirring, the resin was foamed by using nitrogen gas and then coated by using a comma roll in the middle of two layers of release films, the width of a slit was set to 500 microns and curing was performed under a UV lamp (energy density: 500 mJ/cm ² , 10 seconds). A light-curable flame-retardant film with thickness of 500 microns was obtained by tearing off the release films on two sides. The flame-retardant films were coated on both sides with 3M pressure-sensitive films of different thickness and product numbers, and the flame retardant double-sided adhesive tapes were obtained. For the thickness and product numbers of the 3M pressure-sensitive adhesive films, refer to Table 4.

Table 4 Formulas of Flame-Retardant Adhesive Tapes And Corresponding Property Parameters in

Examples and Comparative Examples

Note: EG in Table 4 represents expansible graphite.

From Table 4, it can be seen that, Examples E3-1 and E3-3 are flame-retardant double-sided adhesive tapes obtained by bonding pressure-sensitive films with certain thickness on both sides of the flame-retardant films. The flame retardancy ratings thereof are UL-94 V-l, which are lower than those of the corresponding flame-retardant films, but they still have desirable flame-retardant properties. From Table 4, it can also be seen that the 180-degree peeling force of each of the flame-retardant adhesive tapes prepared in Examples E3-1 to E3-8 is no less than or equal to 0.5 N/mm, and their adhesiveness is therefore optimal. Examples E3-2 and E3-4 to E3-8 are double-sided adhesive tapes prepared by further adding 5 wt. % of expandable graphite to the liquid flame-retardant resin. When the thickness of the pressure-sensitive film is not more than about 30 microns, the flame retardancy rating of the double-sided adhesive tape can be improved to UL-94 V-0. Furthermore, the prepared double-sided adhesive tapes have optimal adhesiveness.

Though the above particular examples comprise a great many concrete details for the purpose of illustration through specific examples, it is to be understand by those of ordinary skill in the art that, many variations, modifications, replacements and changes to these details shall all fall within the scope of the present invention as claimed in the claims. Therefore, the disclosure as described in the specific examples does not pose any limitation to the present invention as claimed in the claims. The proper scope of the present invention should be defined by the claims and proper legal equivalents thereof. All references referred to are incorporated herein by reference in their entireties.