阅读说明：本技术 一种导电海绵及其制备方法和应用 (Conductive sponge and preparation method and application thereof ) 是由 袁平 朱宗玉 谢涛 丁杰 梅志亮 陈秀忠 于 2020-07-17 设计创作，主要内容包括：本发明涉及压敏胶技术领域,具体涉及一种导电海绵及其制备方法和应用,导电海绵包括如下原料：丙烯酸酯共聚物、活性单体、增粘树脂、发泡剂、光引发剂和第一热引发剂；本发明的压敏胶为光热固化压敏胶,光固化的特性在于越容易被照射到的区域越容易反应,没有照射到的阴影区域不反应,因此利用光固化的特性并通过控制固化条件使得压敏胶的表面先行固化,具备一定的硬度后在进行热固化,热固化的同时进行发泡,使得在压敏胶内部形成气泡,从而制得内部具有海绵结构、表面具有完整粘结面的压敏胶,兼具导电、弹性和粘性的功能。(The invention relates to the technical field of pressure-sensitive adhesives, in particular to a conductive sponge and a preparation method and application thereof, wherein the conductive sponge comprises the following raw materials: the adhesive comprises an acrylate copolymer, a reactive monomer, tackifying resin, a foaming agent, a photoinitiator and a first thermal initiator; the pressure-sensitive adhesive is photo-thermal curing pressure-sensitive adhesive, and the photo-curing characteristic is that the more easily irradiated area is reacted, and the non-irradiated shadow area is not reacted, so that the surface of the pressure-sensitive adhesive is cured in advance by utilizing the photo-curing characteristic and controlling the curing condition, and the pressure-sensitive adhesive is subjected to thermosetting after having certain hardness and foaming while being subjected to thermosetting, so that bubbles are formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive with a sponge structure in the pressure-sensitive adhesive and a complete bonding surface on the surface is prepared, and has the functions of conductivity, elasticity and viscosity.)

1. An electrically conductive sponge, characterized in that: the feed comprises the following raw materials in parts by weight:

the acrylate copolymer is prepared from the following raw materials:

2. the conductive sponge according to claim 1, wherein: the active monomer consists of isooctyl acrylate, glycidyl methacrylate and butyl acrylate in the weight ratio of 10-20 to 20-30 to 50-70.

3. The conductive sponge according to claim 1, wherein: the tackifying resin is terpene-phenolic resin.

4. The conductive sponge according to claim 1, wherein: the foaming agent is sodium bicarbonate.

5. The conductive sponge according to claim 1, wherein: the photoinitiator is at least one of 907 photoinitiator, 1173 photoinitiator and TPO photoinitiator.

6. The conductive sponge according to claim 1, wherein: the first thermal initiator is BPO or/and LPO, and the second thermal initiator is BPO or/and LPO.

7. The conductive sponge according to claim 1, wherein: the particle size of the nano conductive carbon black is 20-30 nm.

8. The conductive sponge according to claim 1, wherein: the preparation method of the acrylate copolymer comprises the following steps: mixing 7.5-12.5 parts by weight of butyl acrylate, 3-5 parts by weight of methyl acrylate, 10-20 parts by weight of nano conductive carbon black and 0.05-0.1 part by weight of second thermal initiator, heating to 65-75 ℃, reacting for 1-2h, then gradually dropwise adding 7.5-12.5 parts by weight of butyl acrylate, 3-5 parts by weight of methyl acrylate, 1-3 parts by weight of acrylic acid and 0.05-0.1 part by weight of second thermal initiator, continuing the dropwise adding process for 1-1.4h, and continuing to react for 2-3h to obtain the acrylic copolymer.

9. A method of making a conductive sponge according to any one of claims 1 to 8, comprising: mixing acrylic copolymer, active monomer, tackifying resin, foaming agent, photoinitiator and first thermal initiator according to parts by weight, coating the mixture on the surface of a release film, and then carrying out UV surface curing, wherein the illumination energy of the UV surface curing is 400-²And (3) curing for 30-60s, and finally transferring to a thermal curing furnace for thermal curing at the temperature of 80-90 ℃ for 2-3h to obtain the conductive sponge.

10. Use of an electrically conductive sponge according to any one of claims 1 to 8, wherein: the adhesive is applied to the adhesion of accessories of the front shell of the mobile phone.

Technical Field

The invention relates to the technical field of pressure-sensitive adhesives, in particular to a conductive sponge and a preparation method and application thereof.

Background

The foam adhesive tape is manufactured by coating a solvent type (or hot melt type) pressure-sensitive adhesive on one surface or two surfaces of EVA (ethylene vinyl acetate) or PE (polyethylene) foam which is taken as a base material and then compounding release paper. Has sealing and shock absorbing effects. Has excellent sealing property, compression deformation resistance, flame retardancy, wetting property and the like. The product is widely applied to electronic and electric products, mechanical parts, various small household appliances, mobile phone accessories, industrial instruments, computers and peripheral equipment, automobile accessories, audio and video equipment, toys, cosmetics and the like.

The foam substrate occupies a larger thickness, generally more than 150 μm, and is easily bonded with the pressure-sensitive adhesive, so that the material stripping phenomenon is easily caused in the automatic material taking process.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a conductive sponge and a preparation method and application thereof, wherein the conductive sponge combines the elasticity and pressure-sensitive viscosity of foam; the invention also aims to provide a preparation method of the conductive sponge, which comprises the steps of firstly curing the surface through UV surface curing to avoid through holes generated on the surface by foaming to reduce viscosity, and then forming the conductive sponge through thermal curing foaming; the invention also aims to provide the application of the conductive sponge, which replaces the traditional foam adhesive tape to be applied to the bonding of the auxiliary materials of the front shell of the mobile phone.

The purpose of the invention is realized by the following technical scheme:

the conductive sponge comprises the following raw materials in parts by weight:

the acrylate copolymer is prepared from the following raw materials:

the conductive sponge of the present invention needs to fulfill 3 functions: conductive, elastic, and adhesive. The combination of these three functions presents a number of technical difficulties that need to be overcome: firstly, the foaming can cause the surface of the pressure-sensitive adhesive to generate cavities, thereby greatly reducing the viscosity and being incapable of meeting the use requirement; secondly, the conductive particles are often inorganic particles, the added reinforcing material of the conductive particles is brittle, and cracking easily occurs in the foaming process, and the conductive particles are often attached to the foam wall, and the conductive particles fall off along with expansion of the foam and shrinkage of the cured resin, so that a conductive path is difficult to form.

In the invention, firstly, the nano conductive carbon black is added in the forming process of the acrylate copolymer, and the foaming agent is added in the curing and crosslinking process of the acrylate copolymer and the active monomer, so that a certain separation effect can be achieved on the acrylate copolymer and the active monomer, more bubbles are formed in the bridge structure of the acrylate copolymer and the active monomer, and the nano conductive carbon black is bonded with the acrylic monomer through the surface hydroxyl and the acrylic monomer, so that the phenomenon that conductive particles are attached to the walls of the bubbles is avoided, conductive particles are facilitated to form a conductive path, and the conductivity of the pressure-sensitive adhesive is improved; then, the pressure-sensitive adhesive is photo-thermal curing pressure-sensitive adhesive, and the photo-curing characteristic is that the more easily irradiated area is reacted, and the non-irradiated shadow area is not reacted, so that the surface of the pressure-sensitive adhesive is cured in advance by utilizing the photo-curing characteristic and controlling the curing condition, and the pressure-sensitive adhesive is subjected to thermosetting after having certain hardness and foaming while being subjected to thermosetting, so that bubbles are formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive with a sponge structure inside and a complete bonding surface on the surface is prepared, and has the functions of conductivity, elasticity and viscosity.

Wherein the active monomer consists of isooctyl acrylate, glycidyl methacrylate and butyl acrylate according to the weight ratio of 10-20:20-30: 50-70.

In the preferable active monomer combination, the wetting capacity of the pressure-sensitive adhesive can be improved by utilizing the property that the isooctyl acrylate molecular chain is more flexible, so that the peeling strength of the pressure-sensitive adhesive is improved; the addition of the glycidyl methacrylate can improve the thermosetting speed and further improve the flexibility of the pressure-sensitive adhesive, thereby being beneficial to the formation of uniform bubbles inside; and the cohesion of the pressure-sensitive adhesive can be improved by adding a small amount of butyl acrylate, so that the permanent adhesion capability of the pressure-sensitive adhesive is improved. According to the invention, by compounding the isooctyl acrylate, the glycidyl methacrylate and the butyl acrylate in reasonable amounts, the advantages and the disadvantages are made up, and the foaming degree, the peel strength and the adhesion maintaining capability of the pressure-sensitive adhesive layer are improved in a balanced manner.

Wherein the tackifying resin is terpene-phenolic resin. The wetting capacity of the pressure-sensitive adhesive can be improved by adding the tackifying resin, so that the peel strength of the pressure-sensitive adhesive is improved; while unsuitable tackifying resins are also more destructive to the cross-linked structure of the acrylate, the preferred terpene-phenolic resins of the present invention have a lower UV cure blocking effect on the acrylate of the present invention and an overall improved effect on the peel strength of the pressure sensitive adhesive layer due to less cohesive failure on the copolymer.

Wherein the foaming agent is sodium bicarbonate. The sodium bicarbonate starts to decompose at 50 ℃, although the decomposition peak can be reached only at 100 ℃, the invention can complete the decomposition at the curing temperature of 80-90 ℃ by prolonging the heat curing time, and the decomposed water can be evaporated and discharged through air holes formed by foaming.

Wherein the photoinitiator is at least one of 907 photoinitiator, 1173 photoinitiator and TPO photoinitiator. Preferably, the photoinitiator consists of 907 photoinitiator, 1173 photoinitiator and TPO photoinitiator according to the weight ratio of 1:1:1, and the UV surface curing efficiency is higher.

Wherein the first thermal initiator is BPO or/and LPO, and the second thermal initiator is BPO or/and LPO. The decomposition time of the BPO at 80 ℃ is 1/2 h, the decomposition time of the LPO at 79 ℃ is 1/2 h, the LPO with lower decomposition temperature is not suitable for avoiding excessive polymerization of the acrylate copolymer, and therefore the second thermal initiator is preferably BPO; the curing temperature of the invention is 80-90 ℃, the thermosetting efficiency can be obviously accelerated by adding a proper amount of LPO, the pore wall can have certain strength when the pore wall is foamed to a certain size, and through practice, the first thermal initiator preferably consists of BPO and LPO according to the weight ratio of 3: 1.

Wherein the particle size of the nano conductive carbon black is 20-30 nm. The particle size of the nano conductive carbon black is less than 20nm, and the nano conductive carbon black is easy to agglomerate and settle due to overlarge surface energy and is not beneficial to the dispersion of the nano conductive carbon black; the grain diameter is higher than 30nm, the connection efficiency of the nanometer conductive carbon black is low, and the difficulty of forming a conductive path is high.

The preparation method of the acrylate copolymer comprises the following steps: mixing 7.5-12.5 parts by weight of butyl acrylate, 3-5 parts by weight of methyl acrylate, 10-20 parts by weight of nano conductive carbon black and 0.05-0.1 part by weight of second thermal initiator, heating to 65-75 ℃, reacting for 1-2h, then gradually dropwise adding 7.5-12.5 parts by weight of butyl acrylate, 3-5 parts by weight of methyl acrylate, 1-3 parts by weight of acrylic acid and 0.05-0.1 part by weight of second thermal initiator, continuing the dropwise adding process for 1-1.4h, and continuing to react for 2-3h to obtain the acrylic copolymer.

The preparation method of the conductive sponge comprises the following steps: mixing acrylic copolymer, active monomer and tackifying resinThe foaming agent, the photoinitiator and the first thermal initiator are mixed according to the parts by weight, and then coated on the surface of the release film, and then UV surface curing is carried out, wherein the illumination energy of the UV surface curing is 400-500 mJ/cm-²And (3) curing for 30-60s, and finally transferring to a thermal curing furnace for thermal curing at the temperature of 80-90 ℃ for 2-3h to obtain the conductive sponge.

Use of a conductive sponge as described above: the adhesive is applied to the adhesion of accessories of the front shell of the mobile phone.

The invention has the beneficial effects that: in the invention, firstly, the nano conductive carbon black is added in the forming process of the acrylate copolymer, and the foaming agent is added in the curing and crosslinking process of the acrylate copolymer and the active monomer, so that a certain separation effect can be achieved on the acrylate copolymer and the active monomer, more bubbles are formed in the bridge structure of the acrylate copolymer and the active monomer, and the nano conductive carbon black is bonded with the acrylic monomer through the surface hydroxyl and the acrylic monomer, so that the phenomenon that conductive particles are attached to the walls of the bubbles is avoided, conductive particles are facilitated to form a conductive path, and the conductivity of the pressure-sensitive adhesive is improved; then, the pressure-sensitive adhesive is photo-thermal curing pressure-sensitive adhesive, and the photo-curing characteristic is that the more easily irradiated area is reacted, and the non-irradiated shadow area is not reacted, so that the surface of the pressure-sensitive adhesive is cured in advance by utilizing the photo-curing characteristic and controlling the curing condition, and the pressure-sensitive adhesive is subjected to thermosetting after having certain hardness and foaming while being subjected to thermosetting, so that bubbles are formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive with a sponge structure inside and a complete bonding surface on the surface is prepared, and has the functions of conductivity, elasticity and viscosity. .

Detailed Description

The present invention will be further described with reference to the following examples for facilitating understanding of those skilled in the art, and the description of the embodiments is not intended to limit the present invention.