Multilayer UV curable adhesive film
阅读说明：本技术 多层uv可固化胶膜 (Multilayer UV curable adhesive film ) 是由 张恩重 孙新欣 任璞 于 2019-04-28 设计创作，主要内容包括：本发明提供多层UV可固化胶膜,其包括中间胶膜层以及分别位于所述中间胶膜层两侧上的两个表面胶膜层,其中用于形成中间胶膜层的UV可固化组合物I和用于形成两个表面胶膜层的UV可固化组合物II分别包含特定含量的乙烯-醋酸乙烯共聚物、环氧树脂化合物、含羟基化合物、光引发剂和抗氧化剂。本发明提供的多层UV可固化胶膜展现出良好的在初粘性、固化后的较高结构强度、耐冲击性、无气味或低气味以及长的保存时间方面的平衡性能。(The invention provides a multi-layer UV curable adhesive film, which comprises an intermediate adhesive film layer and two surface adhesive film layers respectively positioned on two sides of the intermediate adhesive film layer, wherein a UV curable composition I for forming the intermediate adhesive film layer and a UV curable composition II for forming the two surface adhesive film layers respectively comprise ethylene-vinyl acetate copolymer, epoxy resin compound, hydroxyl compound, photoinitiator and antioxidant with specific content. The multilayer UV curable adhesive film provided by the invention exhibits a good balance of properties in terms of initial tack, higher structural strength after curing, impact resistance, no or low odor, and long shelf life.)
1. A multi-layered UV-curable adhesive film comprising an intermediate adhesive film layer and two surface adhesive film layers respectively located on both sides of the intermediate adhesive film layer, the intermediate adhesive film layer being formed of a UV-curable composition I and the surface adhesive film layers being formed of a UV-curable composition II,
wherein the UV curable composition I comprises, based on its total weight:
a) 70-85% by weight of an ethylene-vinyl acetate copolymer;
b) 15-30% by weight of an epoxy resin compound;
c)0.3 to 8 wt% of a hydroxyl group-containing compound;
d)0.5 to 5 weight percent of a photoinitiator; and
e) 0.5-2% by weight of an antioxidant,
and wherein the UV curable composition II comprises, based on its total weight:
a) 30-70% by weight of an ethylene-vinyl acetate copolymer:
b) 30-70% by weight of an epoxy resin compound;
c)0.3 to 8 wt% of a hydroxyl group-containing compound;
d)0.5 to 5 weight percent of a photoinitiator; and
e)0.5-2 wt.% of an antioxidant.
2. The multilayer UV-curable adhesive film according to claim 1, wherein the vinyl acetate unit content in the ethylene-vinyl acetate copolymers of UV-curable compositions I and II is 60 to 90% by weight.
3. The multilayer UV curable glue film according to claim 1 or 2, characterized in that the ethylene-vinyl acetate copolymer is a pre-crosslinked polymer or a non-crosslinked linear polymer and the ethylene-vinyl acetate copolymers in the UV curable compositions I and II are the same or different.
4. The multilayer UV curable adhesive film according to claim 1, wherein the epoxy resin compound in the UV curable compositions I and II is one or more selected from aromatic epoxy resins or epoxidized polyolefins.
5. The multilayer UV-curable adhesive film according to claim 1, wherein the UV-curable composition I comprises 20 to 30 wt% of the epoxy resin compound based on the total weight thereof, and the UV-curable composition II comprises 30 to 50 wt% of the epoxy resin compound based on the total weight thereof.
6. The multilayer UV-curable adhesive film according to claim 1 or 5, wherein the epoxy resin compounds of the UV-curable compositions I and II have an epoxy equivalent weight of 150 to 600.
7. The multilayer UV-curable adhesive film according to claim 1 or 5, wherein the epoxy resin compounds in the UV-curable compositions I and II are the same or different in kind and/or epoxy equivalent.
8. The multilayer UV curable adhesive film according to claim 1, wherein the hydroxyl group containing compound in the UV curable compositions I and II is a polyol or an ester or ether of a polyol.
9. The multilayer UV-curable glue film according to claim 1, characterized in that the photoinitiator in the UV-curable compositions I and II is a cationic photoinitiator.
10. The multilayer UV curable adhesive film according to claim 9, wherein the cationic photoinitiator is one or more selected from diazonium salts, iodonium salts, sulfonium salts, stibonium salts and iron arene salts.
11. The multilayer UV-curable adhesive film according to claim 1, wherein each of the UV-curable compositions I and II independently further comprises one or more selected from the group consisting of an electrically conductive agent, a thermally conductive agent, a flame retardant agent and a filler.
12. The multilayer UV curable adhesive film according to claim 11, wherein the electrically conductive agent is electrically conductive particles or fibers, the thermally conductive agent is thermally conductive particles or fibers, and the filler is fumed silica.
13. The multilayer UV-curable adhesive film according to claim 2 or 5, wherein neither of UV-curable compositions I and II contains a solvent.
14. The multi-layer UV curable adhesive film according to claim 1, wherein the thickness of the intermediate adhesive film layer is 300 to 800 μm.
15. The multilayer UV curable adhesive film according to claim 1, wherein the thickness of each of the two surface adhesive film layers is 50 to 100 μm.
16. The multilayer UV curable adhesive film according to claim 1, wherein the intermediate adhesive film layer and the two surface adhesive film layers are formed by hot melt extrusion.
17. The multilayer UV-curable adhesive film according to claim 1, further comprising a release paper or a release film disposed on one or both of the two surface adhesive film layers.
Technical Field
The present invention relates to the field of pressure sensitive adhesive technology, and more particularly, to a multilayer UV curable adhesive film.
Background
At present, household electrical appliances (such as televisions, refrigerators, washing machines, range hoods and the like) and automobile products and the like have higher and higher requirements on appearance design, and tend to use adhesive tapes or adhesive films to replace bolts, and meanwhile, the products have high requirements on the smell of used materials. In addition, the current electronic products such as notebook computers, handheld mobile terminals, etc. have a tendency to be miniaturized, lightened, thinned and have high production efficiency, and this tendency requires that such products increasingly use polymer materials (such as plastics, rubbers, etc.). Therefore, there is a need to use a bonding product having a high bonding strength for these materials so as to achieve a firm bonding with a small bonding area while having a low odor characteristic.
In addition, many of the adhesive parts in the above products are subjected to strong impact during transportation or use, and therefore these materials require not only a strong adhesive property but also a good impact resistance of the adhesive film.
Traditionally, one-component or two-component structural adhesives have been able to meet the bonding task of these products. However, structural glues suffer from a number of disadvantages such as: the adhesive surface is not beautiful due to uncontrollable adhesive area because the adhesive surface is not removable or reworkable (namely, the adhesive surface is reassembled after being dismantled); moreover, some structural glues contain a large amount of solvents, long time is required for curing (low efficiency) or curing is required at high temperature (plastic materials which cannot resist temperature cannot be bonded), and the structural glues often have very high modulus, so that the structural glues do not have good impact resistance; all of these aspects greatly restrict the use of structured glues in large quantities in these aforementioned products.
Pressure sensitive adhesive tapes are also a product for bonding. The pressure-sensitive adhesive tape is extremely convenient to use, can realize bonding by applying slight pressure, and does not need to be cured for a long time or at a temperature higher than 160 ℃; can be directly bonded after being die-cut and formed, and can realize continuous production, so the bonding efficiency is extremely high. However, a critical disadvantage of pressure-sensitive adhesive tapes is their poor adhesive strength, generally not exceeding 1MPa, and are therefore unsuitable for small-area bonding.
Another traditional mass-used foam tape is similar to pressure-sensitive adhesive, and can realize bonding only by applying small pressure without long-time or high-temperature curing at a temperature of more than 160 ℃; the foam adhesive tape can be directly bonded after being molded by die cutting, can realize continuous production, has extremely high bonding efficiency and higher bonding strength than a pressure-sensitive adhesive, but has the biggest defect of strong smell, and is not suitable for being used in household appliances or automobile interiors.
Patent US2002/182955a1(Weglewski) discloses an adhesive tape with a single-layer structure reinforced with fibres. However, this structural adhesive tape requires that the adhesive film must be reinforced with specific fibers to achieve good shape retention and adhesive strength, which makes the manufacturing process significantly more complicated and costly; in addition, the production process of the structural adhesive tape can achieve a good attaching effect only by vacuum hot pressing, so that the production process is high in cost, harsh in conditions and difficult to industrialize.
Accordingly, there is still a need in the art to develop a film or tape that can exhibit good initial tack, higher structural strength after curing, impact resistance, no or low odor, and long shelf life, while solving the common problem of glue overflow.
Disclosure of Invention
In view of the foregoing, it is an object of the present invention to provide a novel Ultraviolet (UV) curable adhesive film that can exhibit a good balance of initial tack, higher structural strength after curing, impact resistance, no or low odor, and long shelf life.
Accordingly, the present invention provides a multi-layered UV-curable adhesive film comprising an intermediate adhesive film layer and two surface adhesive film layers respectively located on both sides of the intermediate adhesive film layer, the intermediate adhesive film layer being formed of a UV-curable composition I and the surface adhesive film layers being formed of a UV-curable composition II,
wherein the UV curable composition I comprises, based on its total weight:
a) 70-85% by weight of an ethylene-vinyl acetate copolymer;
b) 15-30% by weight of an epoxy resin compound;
c)0.3 to 8 wt% of a hydroxyl group-containing compound;
d)0.5 to 5 weight percent of a photoinitiator; and
e) 0.5-2% by weight of an antioxidant,
and wherein the UV curable composition II comprises, based on its total weight:
a) 30-70% by weight of an ethylene-vinyl acetate copolymer:
b) 30-70% by weight of an epoxy resin compound;
c)0.3 to 8 wt% of a hydroxyl group-containing compound;
d)0.5 to 5 weight percent of a photoinitiator; and
e)0.5-2 wt.% of an antioxidant.
In a preferred embodiment, the content of vinyl acetate units in the ethylene-vinyl acetate copolymers of the UV curable compositions I and II is 60 to 90% by weight.
In a preferred embodiment, the ethylene-vinyl acetate copolymer is a pre-crosslinked polymer or a non-crosslinked linear polymer, and the ethylene-vinyl acetate copolymers in the UV curable compositions I and II are the same or different.
In a preferred embodiment, the epoxy resin compound in the UV curable compositions I and II is one or more selected from aromatic epoxy resins or epoxidized polyolefins.
In a preferred embodiment, the UV curable composition I comprises 20 to 30 wt% of epoxy resin compound based on its total weight and the UV curable composition II comprises 30 to 50 wt% of epoxy resin compound based on its total weight.
In a preferred embodiment, the epoxy resin compound of the UV curable compositions I and II has an epoxy equivalent weight of between 150 and 600.
In a preferred embodiment, the epoxy resin compounds in the UV curable compositions I and II are the same or different in kind and/or epoxy equivalent.
In a preferred embodiment, the hydroxyl containing compound in the UV curable compositions I and II is a polyol or an ester or ether of a polyol.
In a preferred embodiment, the photoinitiator in the UV curable compositions I and II is a cationic photoinitiator.
In a further preferred embodiment, the cationic photoinitiator is one or more selected from diazonium salts, iodonium salts, sulfonium salts, antimonium salts and iron arene salts.
In a preferred embodiment, the UV curable compositions I and II each independently further comprise one or more selected from the group consisting of an electrically conductive agent, a thermally conductive agent, a flame retardant, and a filler.
In a further preferred embodiment, the electrically conductive agent is electrically conductive particles or fibers, the thermally conductive agent is thermally conductive particles or fibers, and the filler is fumed silica.
In a preferred embodiment, both the UV curable compositions I and II are solvent free.
In a preferred embodiment, the thickness of the intermediate adhesive film layer is 300 to 800 μm.
In a preferred embodiment, the thicknesses of the two surface adhesive film layers are respectively 50-100 μm.
In a preferred embodiment, the intermediate adhesive film layer and the two surface adhesive film layers are formed by hot-melt extrusion.
In a preferred embodiment, the multi-layered UV-curable adhesive film further comprises a release paper or a release film disposed on one or both of the two surface adhesive film layers.
Advantages of the invention include, but are not limited to, the following:
the invention designs a multi-layer (usually three-layer) UV curable adhesive film structure by utilizing UV curable compositions respectively having specific components and specific contents, wherein an ethylene-vinyl acetate copolymer with rubber elasticity performance is used as a base material for a middle adhesive film layer and two surface adhesive film layers on two sides of the middle adhesive film layer, and an epoxy resin compound is used as a curable material; and the ethylene-vinyl acetate copolymer content of the intermediate layer is not less than and preferably higher than the ethylene-vinyl acetate copolymer content in the surface layers on both sides, while the epoxy resin content of the intermediate layer is not greater than and preferably lower than the epoxy resin content of the surface layers. The higher epoxy content of superficial layer can provide stronger interfacial action to reach higher initial and solidification back bonding strength, and the lower epoxy content of intermediate level makes the glued membrane have fine energy absorption and buffering effect, makes the multilayer glued membrane structure that obtains not only can have good initial viscidity from this, can ensure that the glued membrane that obtains has good impact resistance moreover, and has excellent structural strength after the solidification, does not have the characteristics of excessive gluey problem simultaneously.
In addition, the multi-layer UV curable adhesive film structure obtained by the present invention can be stored for a long period of time by including a specific content of an antioxidant in the UV curable composition I or II of the adhesive film. For example, the multi-layer adhesive film UV curable adhesive film can be stored at room temperature for a long time, the storage time can be more than 24 months under the condition of light-proof storage, and the transportation and storage cost is greatly reduced compared with the prior art that most of the adhesive films are required to be stored at low temperature for refrigeration.
In addition, the compositions I and II for forming the multi-layer UV curable adhesive film structure adopt the EVA copolymer with large molecular weight, and the use of organic solvent is avoided in the process of preparing the multi-layer adhesive film, so that the multi-layer UV curable adhesive film obtained by the invention has the characteristics of low odor or no odor.
Further, with the adhesive film UV curable composition of the present invention, the intermediate adhesive film layer and the surface adhesive film layer can be formed by, for example, hot melt extrusion, so that a desired multi-layer adhesive film structure can be easily and conveniently produced. Preferably, the intermediate layer prepared by the hot-melt extrusion method has a larger thickness with respect to the surface layers on both sides, which can ensure that the resulting adhesive film structure can be sufficiently cured by ultraviolet rays.
In addition, the multilayer UV curable adhesive film can be conveniently prepared at normal temperature through a simple process, and industrial production can be realized.
In addition, the multi-layer UV curable adhesive film provided by the invention shows the characteristics of a common pressure-sensitive adhesive tape in the initial stage of bonding, namely has initial viscosity, can bond an adherend by applying slight pressure, and can be molded by die cutting; the multi-layer adhesive film can be solidified into an adhesive tape with a half structural strength to a structural strength at room temperature after being initiated by UV, so that plastic products which are not high in temperature resistance, such as PC, PMMA, ABS and the like, can be adhered.
Drawings
Fig. 1 is a schematic structural view of a multilayer UV curable adhesive film according to an embodiment of the present invention.
Detailed Description
Through intensive research of the inventor of the invention, the following results are unexpectedly found: by using the UV curable composition having a specific composition and a specific content for forming the middle layer and both side surface layers of the multi-layered UV curable adhesive film, respectively, a multi-layered (typically three-layered) UV curable adhesive film structure having an excellent balance of properties can be provided. Herein, the terms adhesive film and tape are used interchangeably.
In the multi-layer UV curable adhesive film structure provided by the invention, the intermediate adhesive film layer and the two surface adhesive film layers on the two sides (or the upper surface and the lower surface) of the intermediate adhesive film layer are respectively formed by using a UV-induced curable composition of an ethylene-vinyl acetate copolymer/epoxy resin hybrid system with a specific composition.
As used herein in the description of adhesive films, compositions I and/or II, the term "curable" means that the adhesive film or composition in question is cured under induction of UV light by a photoinitiator therein which can initiate a chemical reaction of the epoxy resin component in the adhesive film or composition. In the present invention, after the UV light irradiation or induction, even after the UV source is removed, the reaction of the epoxy group can be continuously initiated at room temperature, thereby completing the curing process (so-called living polymerization process). In addition, each layer of the multi-layer adhesive film is produced by a hot melting method, so that the use of a solvent is avoided, the effect of low odor is achieved, and meanwhile, the middle layer of the multi-layer adhesive film has lower modulus, so that the cured adhesive film has good impact resistance.
The low-odor multilayer UV curable adhesive film provided by the invention shows the characteristics of a common pressure-sensitive adhesive tape (namely has initial viscosity) at the initial stage of bonding, can be bonded with an adherend by applying tiny pressure, and can be molded by die cutting; after the adhesive film is induced by UV, the adhesive film can be solidified into an adhesive tape with a half structural strength to a structural strength at room temperature, so that some plastic products which are not high in temperature resistance can be bonded, such as: PC, PMMA, ABS, etc. Meanwhile, the UV curable composition I or II does not contain a solvent, and the adhesive film is produced in a solvent-free hot melting extrusion mode, so that the requirement of low odor or no odor can be met, and the UV curable composition I or II is particularly suitable for bonding plastic parts in household appliances and automobile internal parts and hand-held mobile terminals of electronic products or between the plastic parts and the metal parts. In addition, the UV-induced curable high temperature resistant pressure sensitive adhesive tape of the present invention has a room temperature shelf life of up to 24 months or more under light-shielding conditions.
As used herein, the term "structural adhesive" refers to an adhesive having a shear strength between the tape and the adhesive of greater than 1000psi (where 1MPa is about equal to 145 psi); the term "structural strength" means that the shear strength of the adhesive member formed by the tape and the adhesive is greater than 1000 psi; the term "half structural strength" means that the shear strength of the adhesive member formed by the tape and the adhesive is greater than 100psi but less than 1000 psi.
Unless otherwise indicated, all numbers expressing feature sizes, quantities, and physical and chemical characteristics used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can be suitably varied by those skilled in the art in seeking to obtain the desired properties utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range and any range within that range. For example, a range of "1 to 5" is intended to include 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, and so forth.
In an embodiment of the present invention, the present invention provides a multi-layered UV-curable adhesive film comprising an intermediate adhesive film layer and two surface adhesive film layers respectively located on both sides of the intermediate adhesive film layer, the intermediate adhesive film layer being formed of a UV-curable composition I and the surface adhesive film layers being formed of a UV-curable composition II,
Wherein the UV curable composition I comprises, based on its total weight: a) 70-85% by weight of an ethylene-vinyl acetate copolymer; b) 15-30% by weight of an epoxy resin compound; c)0.3 to 8 wt% of a hydroxyl group-containing compound; d)0.5 to 5 weight percent of a photoinitiator; and e)0.5 to 2% by weight of an antioxidant,
and wherein the UV curable composition II comprises, based on its total weight: a) 30-70% by weight of an ethylene-vinyl acetate copolymer: b) 30-70% by weight of an epoxy resin compound; c)0.3 to 8 wt% of a hydroxyl group-containing compound; d)0.5 to 5 weight percent of a photoinitiator; and e)0.5 to 2% by weight of an antioxidant.
a) Ethylene-vinyl acetate copolymer
In the multi-layer UV curable adhesive film structure of the present invention, the intermediate adhesive film layer and both surface adhesive film layers on both sides or upper and lower surfaces thereof use an ethylene-vinyl acetate copolymer having rubber elastomer properties as a base material. The ethylene-vinyl acetate copolymer (abbreviated as "EVA") used in the present invention may be a non-crosslinked or non-crosslinked linear copolymer, or may be a pre-crosslinked ethylene-vinyl acetate copolymer having a certain degree of crosslinking. In a preferred embodiment, the ethylene-vinyl acetate copolymers in the UV curable compositions I and II used in the present invention may be the same or different, and the ethylene-vinyl acetate copolymers in the UV curable compositions I and II are not simultaneously pre-crosslinked polymers.
In some preferred embodiments, the content of the vinyl acetate unit in the ethylene-vinyl acetate copolymer is between 60 and 90 wt%, preferably between 70 and 80 wt%, because the higher the content of vinyl acetate, the higher the Tg of the copolymer, the higher the modulus of the cured adhesive film, and thus the higher the shear strength of the adhesive film or tape obtained.
Ethylene-vinyl acetate copolymers useful in the present invention are commercially available, examples of which are exemplified by LEVAPREN 600, LEVAPREN 700, LEVAPREN 800, LEVAPREN 900, LEVAPREN 700XL, LEVAPREN 800XL, and the like available from langerhans.
In the present invention, in order for the adhesive film structure obtained in the present invention to have a good balance of properties such as initial tackiness, impact resistance and structural strength after curing, in particular, good impact resistance, it is required that the ethylene-vinyl acetate copolymer content in the UV curable composition I for forming the intermediate adhesive film layer is not lower than and preferably higher than the ethylene-vinyl acetate copolymer content in the UV curable composition II for the both-side surface adhesive film layers.
b) Epoxy resin compound
In the two-component adhesive film UV curable composition of the present invention, in addition to the ethylene-vinyl acetate copolymer as a base material, an epoxy resin compound is also used as a base material and also as a curing component.
The epoxy resin compound that can be used in the present invention may be an epoxy resin compound known in the art. For example, in some embodiments, the epoxy resin compound used may contain one or more than two epoxy groups in the molecule, and preferably has an epoxy equivalent of 150 to 600. Preferably, aromatic epoxy resins such as glycidyl ethers or esters obtained by reacting polyhydric phenols such as bisphenol a, bisphenol F, bisphenol S, hexahydrobisphenol a, tetramethylbisphenol a, diarylbisphenol a, tetramethylbisphenol F, etc. with epichlorohydrin, and derivatives thereof; in addition, epoxidized polyolefins and the like are also known epoxy resin compounds that can be used.
The epoxy resin compound usable in the present invention is commercially available, and examples thereof are YD 128 (having an epoxy equivalent of about 187) and KD212 (having an epoxy equivalent of 535) available from kunko (kudko) chemistry (korea).
In the present invention, in order for the adhesive film structure obtained in the present invention to have a good balance of properties of initial tackiness, impact resistance and structural strength after curing, in particular, good initial tackiness and structural strength before curing, it is required in the present invention that the epoxy resin compound content in the UV curable composition I for forming the intermediate adhesive film layer is not higher than and preferably lower than the epoxy resin compound content in the UV curable composition II for the both-side surface adhesive film layers. More specifically, the content of the epoxy resin compound in the UV curable composition II for the adhesive film layers on both sides is generally between 30% and 70%, more preferably between 35% and 60%, and more preferably between 40% and 50%, and the higher epoxy content of the surface layer can provide a stronger interfacial action, so that the initial adhesiveness of the formed adhesive film can be ensured and the cured adhesive tape has sufficient strength; the content of the epoxy resin compound in the UV curable composition I for forming the intermediate adhesive film layer is generally 15-30%, and more preferably 20-30%, so that the intermediate adhesive film layer is ensured to have certain structural strength, and the curing speed of the adhesive film is ensured to meet the actual requirement.
Without being bound by a particular theory, it is believed that, as described above, the relatively low ethylene-vinyl acetate copolymer content in the surface glue layer, along with the relatively high epoxy content, provides a stronger interfacial effect, thereby achieving higher initial and post-cure bond strengths; the middle adhesive film layer has relatively low epoxy content and relatively high ethylene-vinyl acetate copolymer content, so that the adhesive film has good energy absorption and buffering effects, a three-layer structure with different moduli of the surface adhesive film layer/the middle adhesive film layer/the surface adhesive film layer is formed, and the cured adhesive film has good impact resistance.
c) Hydroxyl group-containing compound
The UV curable composition for forming a multilayer UV curable adhesive film of the present invention contains a hydroxyl group-containing compound which functions as a chain transfer agent when the epoxy group in the epoxy resin compound reacts in a cationic mechanism.
The hydroxyl group-containing compound useful in the present invention includes ether or ester derivatives of such hydroxyl group-containing compounds. In some preferred embodiments, the hydroxyl containing compound may be a polyol compound. Examples of polyols that may be used include, but are not limited to, polyether polyols such as polyether diols; polyester polyols such as polyester diols; bisphenol a polyols, and the like. One of the above polyols, or a mixture of a plurality thereof, may be used.
Hydroxyl-containing compounds useful in the present invention are commercially available, and examples thereof are TONE 0230 Polyol, VORANOL 230-238, VORANOL 2070; dianol 285 from J4T Seppic company (France) and the like. In some embodiments, VORANOL 2070, a polyether diol with a molecular weight of 700, available from dow chemical, usa, is used.
In the present invention, the hydroxyl group-containing compound is contained in the UV curable compositions I and II in an amount ranging from 0.3 to 8.0% by weight, more preferably from 1.0 to 6.0% by weight, and still more preferably from 2.0 to 4.0% by weight, based on the total weight of the UV curable composition I or II, respectively. The inventors of the present invention have found that the adhesive film or tape obtained when the hydroxyl group-containing compound is present in the UV curable compositions I and II of the present invention in the above-mentioned ranges, respectively, has the above-mentioned balance of properties. Also, if the content of the polyol compound is too low, the UV-induced pressure sensitive adhesive tape is slow in curing speed after UV-induction, and the cured tape may be brittle; if the polyol content is too high, the cured tape will be too soft, affecting shear strength.
d) Photoinitiator
The UV curable composition for forming a multi-layer UV curable adhesive film of the present invention contains a photoinitiator, and although the amount of the photoinitiator in the adhesive film UV curable composition is small, the photoinitiator has a great influence on the curing speed and the storage stability of the adhesive film UV curable composition.
The photoinitiator usable in the present invention may be at least one selected from cationic photoinitiators. Cationic photoinitiators that may be used include, but are not limited to, diazonium salts, iodonium salts, sulfonium salts, antimonate salts, and iron arene salts, and specific examples thereof include diaryliodonium salts, diarylsulfonium salts, alkylsulfonium salts, iron arene salts, sulfonyloxy ketones, and diarylsiloxy ethers. In some embodiments, diarylsulfonium hexafluorophosphate or hexafluoroantimonate salts are used. Such photoinitiators are commercially available, an example of which is, for example, DOUBLECURE 1176 available from taiwan chemical company for double bonds.
In the present invention, the photoinitiator, e.g., a cationic photoinitiator, is present in the UV curable compositions I and II described above in an amount ranging from 0.5 to 5%, and more preferably from 0.75 to 2.5%, respectively (based on the total weight of the UV curable composition I or II, respectively). In general, as the content of a photoinitiator such as a cationic photoinitiator increases, the curing speed of the adhesive film UV-curable composition increases, but if the content is too high, it results in too high a curing speed, and even curing under sunlight or daylight lamp light (containing a small amount of UV), thereby causing deterioration of some properties of the cured adhesive film or tape, such as poor storage stability at room temperature; if the amount of the cationic photoinitiator is too small, the requirements on ultraviolet radiation energy during curing are high, the curing speed is slow, and partial performances of the cured adhesive film or the adhesive tape are damaged.
e) Antioxidant agent
The UV curable composition I and/or II for forming a multilayer UV curable adhesive film of the present invention contains an antioxidant. The antioxidant used serves to prevent the polymer from being oxidized during the hot-melt extrusion of the adhesive film UV curable composition I and/or II of the present invention.
Antioxidants useful in the present invention include, but are not limited to, phenolic antioxidants such as alkyl monophenols, alkyl polyphenols, thio polyphenols, and the like. Such antioxidants are known in the art and are commercially available, examples of which are, for example, antioxidants 264, IRGANOX 1076, IRGANOX 2246 and IRGANOX 1010, etc. available from basf, germany.
In the present invention, the antioxidant is contained in the above UV curable compositions I and II in an amount ranging from 0.5 to 2%, respectively (based on the total weight of the UV curable composition I or II, respectively). If the amount of the antioxidant added is too small, for example, less than 0.5%, a good antioxidant effect cannot be obtained; on the other hand, if the amount of the antioxidant added is too large, for example, more than 2%, other properties are impaired.
Other ingredients
As known to those skilled in the art, the adhesive film UV curable compositions I and II of the present invention may contain other ingredients or additive auxiliaries well known in the art according to the requirements of practical application. There is no particular limitation on the kind and content of these other ingredients as long as the properties required for the adhesive film UV curable composition of the present invention are not affected. In a preferred embodiment, the UV curable compositions I and II of the present invention may comprise, independently of each other, one or more selected from the group consisting of an electrically conductive agent, a thermally conductive agent, a flame retardant and a filler. In a further preferred embodiment, the electrically conductive agent may be, for example, electrically conductive particles or fibers (e.g., 2 to 45 wt%), the thermally conductive agent may be thermally conductive particles or fibers (e.g., 2 to 45 wt%), and the flame retardant may be, for example, zinc borate (e.g., 2 to 30 wt%); the filler may be fumed silica (e.g., 0.5 to 8 wt.%), wherein the content of each component is based on 100 wt.% of the total weight of the corresponding UV-curable composition I or II.
In a preferred embodiment, both UV-curable compositions I and II used according to the invention are free of solvents, in particular organic solvents. In such cases, the UV curable compositions I and II of the present invention may be, for example, in the form of a powder or a mixture of particles. Such UV curable compositions I and II may be prepared, for example, by simply mixing the individual components in a mixing vessel or machine.
Adhesive film/tape
In the present invention, the adhesive film/tape may be formed using the UV curable compositions I and II of the present invention, for example, or preferably may be formed by hot extrusion or melt extrusion, which includes an intermediate adhesive film layer and a surface adhesive film layer formed from the UV curable composition I and the UV curable composition II, respectively. More specifically, the UV curable composition I may be first heat extruded or melt extruded onto flexible and non-flexible substrates (including release films or release papers) to form an intermediate adhesive film layer; the UV curable composition II is then formed into two surface adhesive film layers by thermal extrusion or melt extrusion onto both sides of the intermediate adhesive film layer, thereby forming the adhesive film required in the present invention. As an example, fig. 1 is a schematic diagram of a double-sided tape of a multilayer UV curable adhesive film/tape structure (excluding a substrate) obtained according to an embodiment of the present invention. As shown in fig. 1, the adhesive film/tape comprises an intermediate layer or intermediate
Further, the present invention can provide a single-sided adhesive tape by replacing the above-described release paper or release film on the adhesive film side with an adhesive substrate, such substrates being known in the art, examples of which include, but are not limited to, polymer films, woven or nonwoven fabrics, metal foils, foams, and combinations thereof, in addition to the above-described double-sided adhesive tape.
In a preferred embodiment, the thickness of the intermediate adhesive film layer formed using the UV curable composition I may be 300 to 800 μm, and the thicknesses of the two surface adhesive film layers respectively positioned on both sides of the intermediate adhesive film layer may be each independently 50 to 100 μm. The adhesive film structure with the thicker middle layer and the thinner surface layers can ensure the curing speed and the impact resistance of the formed adhesive tape.
The multilayer UV curable adhesive film provided by the invention shows the characteristics of a common pressure-sensitive adhesive tape in the initial stage of bonding, namely has initial viscosity, can bond an adherend by applying slight pressure, and can be molded by die cutting; the adhesive film can be solidified into an adhesive tape with the structural strength from the semi-structural strength to the structural strength at room temperature after being initiated by UV, so that plastic products which are not high in temperature resistance, such as PC, PMMA, ABS and the like, can be adhered.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：LED模压封装胶片的使用方法