An encapsulation film and a preparation method thereof

Abstract

The present invention discloses an encapsulating film and a preparation method thereof. The encapsulating film of the present invention comprises the following components, by mass percentage: 86.5-99.5% of a base resin, 0.2-1% of a primary cross-linking agent, 0.2-1% of an auxiliary cross-linking agent, 0.05-0.5% of a titanate coupling agent, 0.05-0.3% of an isocyanate coupling agent, 0.05-0.3% of a silane coupling agent, 0.05-0.5% of an initiator, 0.05-0.5% of a filler, 0.05-0.5% of a light stabilizer, and 0-0.5% of an ultraviolet light absorber. The encapsulating film prepared by the present invention has good mechanical properties and good bonding properties, and in particular, can maintain high adhesion to glass for a long time after electron beam irradiation.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive films, and in particular to an encapsulating adhesive film and a preparation method thereof, and in particular to an encapsulating adhesive film capable of maintaining high adhesion to glass for a long time after electron beam irradiation and a preparation method thereof. Background Art

[0002] Solar cell encapsulation film uses EVA (ethylene-vinyl acetate copolymer) and POE (ethylene-octene copolymer) as main materials; EVA and POE are transparent, soft, have hot-melt adhesive properties, low melting temperature and good melt fluidity, etc. These characteristics meet the needs of film manufacturing and solar cell encapsulation.

[0003] White EVA film is widely used in single-glass panels due to its high reflectivity, which improves the efficiency of solar modules. However, to prevent it from melting and flowing onto the front of the solar cells during use at temperatures around 145°C, affecting the appearance of the module, the white film is often treated with electron beam irradiation to create a certain degree of pre-crosslinking. This pre-crosslinking prevents flow at 145°C, thus maintaining the module's appearance. However, the high energy of the electron beam breaks down small molecules, including the silanes that contribute to the adhesive bond. This results in unstable adhesion between the white film and the glass. After one month of storage, the film loses significant strength and becomes virtually incompatible with the glass. Especially after PCT (high-voltage accelerated aging), it can completely delaminate from the glass. Therefore, white film is rarely used in double-glass panels. However, with the increasing use of these films, such as in coastal areas with high humidity and heat, double-glass panels with high-reflectivity black film require the use of electron beam irradiated films with glass.

[0004] CN113444249A discloses an electron beam-cured silicone encapsulant, made from the following raw materials, calculated by mass: 100 parts dimethoxysilane, 30-120 parts trimethoxysilane, 20-80 parts silane coupling agent, 0.2-2 parts acid catalyst, 40-80 parts alcohol solvent, and 0.5-1.5 parts base catalyst; the silane coupling agent is a mixture of γ-methacryloxypropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane. This electron beam-cured silicone encapsulant, which requires no photoinitiator and can be cured by electron beam irradiation, significantly reduces energy consumption and production costs, significantly improves production efficiency and product thermal stability, and significantly enhances the encapsulant's bonding strength by introducing polar groups, resulting in significantly improved encapsulation performance. The cured encapsulant film exhibits a light transmittance exceeding 97%, a tensile strength exceeding 4 MPa, and an adhesive strength exceeding 6 MPa. It also exhibits no yellowing after aging at 180°C for one hour. However, the encapsulation adhesive prepared by this invention is not suitable for encapsulation of solar cells.

[0005] Therefore, it is very necessary to develop an encapsulation film with good bonding properties, especially one that can maintain good bonding strength after electron beam irradiation, and a preparation method thereof. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a packaging film and a preparation method thereof. The prepared packaging film has good mechanical properties and good bonding properties, especially after electron beam irradiation, it can maintain high adhesion with glass for a long time.

[0007] One of the objectives of the present invention is to provide a packaging film. To achieve this objective, the present invention adopts the following technical solutions:

[0008] A packaging film, comprising the following components by mass percentage:

[0009]

[0010]

[0011] The encapsulating adhesive film of the present invention grafts a titanate coupling agent onto a base resin, thereby preventing the coupling agent from being destroyed by high-intensity electrons during an irradiation reaction. The addition of an isocyanate coupling agent also prevents the coupling agent from being destroyed by high-intensity electrons during an irradiation reaction. Isocyanate has good adhesion to glass and can maintain long-term good adhesion to glass. After aging for 24 hours, the adhesion of the PCT to the glass still reaches more than 60N, and after aging for 48 hours, the adhesion of the PCT to the glass still reaches more than 40N. The adhesive film itself also has good impact resistance.

[0012] Specifically, the encapsulation film comprises the following components by mass percentage:

[0013] The mass percentage of the matrix resin is 86.5-99.5%, for example, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, etc.

[0014] The mass percentage of the main cross-linking agent is 0.2-1%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0015] The mass percentage of the auxiliary cross-linking agent is 0.2-1%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0016] The mass percentage of the titanate coupling agent is 0.05-0.5%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc.

[0017] The mass percentage of the isocyanate coupling agent is 0.05-0.3%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0018] The mass percentage of the silane coupling agent is 0.05-0.3%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0019] The mass percentage of the initiator is 0.05-0.5%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc.

[0020] The mass percentage of the filler is 0-10%, for example, 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0021] The mass percentage of the light stabilizer is 0.05-0.5%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc.

[0022] The mass percentage of the ultraviolet light absorber is 0-0.5%, for example, 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0023] In the present invention, the titanate coupling agent comprises any one of isopropyl triisostearoyl titanate (TTS), isopropyl tri(dioctyl pyrophosphoryl) titanate (KR-38S), bis(dioctyl pyrophosphoryl) titanium oxyacetate (KR-138S) or bis(dioctyl pyrophosphoryl) ethylene titanate (KR-238S) or a mixture of at least two thereof.

[0024] In the present invention, the isocyanate coupling agent comprises any one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and lysine diisocyanate (LDI), or a mixture of at least two thereof, and the isocyanate of the isocyanate coupling agent is end-capped and protected by DMP or MEKO.

[0025] In the present invention, the silane coupling agent comprises any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, N-(2-aminoethyl-3-aminopropyl)trimethoxysilane, 3-(2,3-epoxypropyloxy)propylmethyldiethoxysilane, 3-(methacryloyl chloride)propyltrimethoxysilane, methylpropylaminopropyloxypropyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane, or a mixture of at least two thereof.

[0026] In the present invention, the matrix resin is EVA and / or POE.

[0027] In the present invention, the initiator and the main cross-linking agent are independently selected from any one of diisopropylbenzene peroxide, tert-butyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, tert-butylperoxy-2-ethylhexyl carbonate, n-butyl-4,4-di(tert-butylperoxy)valerate, diisopropylbenzene peroxide, α,α′-bis(tert-butylperoxy)-1,3-diisopropylbenzene and 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, or a mixture of at least two thereof.

[0028] In the present invention, the auxiliary cross-linking agent comprises any one of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate or ethoxylated pentaerythritol tetraacrylate, or a mixture of at least two thereof.

[0029] In the present invention, the filler comprises any one of carbon black, titanium dioxide, calcium carbonate, barium sulfate or perylene black, or a mixture of at least two thereof.

[0030] In the present invention, the light stabilizer comprises any one of hindered phenol antioxidants, aromatic amine antioxidants, phosphite antioxidants, thioether antioxidants or metal passivator antioxidants, or a mixture of at least two thereof.

[0031] In the present invention, the ultraviolet absorber comprises any one of a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber or a triazine ultraviolet absorber, or a mixture of at least two thereof.

[0032] A second object of the present invention is to provide a method for preparing the encapsulating film described in the first object, comprising the following steps:

[0033] The matrix resin, titanate coupling agent and initiator are mixed according to a proportion, grafted and granulated, and a main cross-linking agent, an auxiliary cross-linking agent, an isocyanate coupling agent, a silane coupling agent, a filler, a light stabilizer and an ultraviolet absorber are added to the grafted particles, mixed and cast into a film, and irradiated to obtain the encapsulating film.

[0034] In the present invention, the temperature of the grafting granulation is 140-250°C, for example, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0035] In the present invention, the temperature of the film casting is 90-120°C, for example, 90°C, 100°C, 110°C, 120°C, etc.

[0036] In the present invention, the irradiation voltage is 300-500kV, for example, 300kV, 350kV, 400kV, 450kV, 500kV, etc.; the irradiation dose is 5-50KGY, for example, 5KGY, 10KGY, 15KGY, 20KGY, 25KGY, 30KGY, 35KGY, 40KGY, 45KGY, 50KGY, etc.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The encapsulating film of the present invention has good mechanical properties and good adhesion to glass after PCT aging. Specifically, the initial adhesion between the encapsulating film and the glass is 98-178 N. After 24 hours of PCT aging, the adhesion to the glass still reaches 60 N or more, specifically 62-78 N. After 48 hours of PCT aging, the adhesion to the glass still reaches 40 N or more, specifically 44-68 N. After storage for 6 months, the initial adhesion to the glass is 68-116 N, the tensile strength is 21.5-28.9 MPa, and the elongation at break is 558-624%. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0040] Unless otherwise specified, various raw materials of the present invention can be purchased commercially or prepared according to conventional methods in the art.

[0041] Example 1

[0042] The encapsulation film of this embodiment is prepared by the following method:

[0043] By mass percentage, 99.3% of the matrix resin EVA282 was mixed with 0.2% of 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane and 0.5% of isopropyl tri(dioctyl pyrophosphoryl) titanate, and grafted and granulated at 180°C to obtain a granulated material. By mass percentage, 90.3% of the granulated material, 8% of Panhua titanium dioxide 2588, and 0.5% of tert-butyl peroxycarbonate-2-ethylhexyl were taken. , 0.5% of triallyl isocyanurate, 0.3% of trimethylolpropane triacrylate, 0.2% of 3-isocyanatepropyltriethoxysilane terminated with DMP, 0.1% of KH570 silane coupling agent, and 0.1% of light stabilizer 770 are mixed and cast at 100°C to form a film. The cast film is irradiated with an electron beam at an irradiation voltage of 400kV and an irradiation dose of 13KGY to obtain an encapsulation film.

[0044] Example 2

[0045] By mass percentage, 98.7% of the base resin POE 38669 was mixed with 0.5% of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane and 0.8% of isopropyl tri(dioctyl pyrophosphoryl) titanate, and the mixture was grafted and granulated at 180°C to obtain a granulated material. By mass percentage, 98% of the granulated material, 0.8% of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.7% of triallyl isocyanurate, 0.2% of 3-isocyanate propyl triethoxysilane capped with DMP, 0.2% of KH570 silane coupling agent, and 0.1% of light stabilizer 770 were mixed and cast at 100°C to form a film. The cast film was irradiated by electron beam with an irradiation voltage of 400kV and an irradiation dose of 40KGY to obtain an encapsulating film.

[0046] Example 3

[0047] By mass percentage, 99.75% of the matrix resin EVA 282 was mixed with 0.05% of 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane and 0.2% of isopropyl tri(dioctyl pyrophosphoryl) titanate, and the mixture was grafted and granulated at 180° C. to obtain a granulated material. By mass percentage, 93.75% of the granulated material, 5% of perylene black L0086, 0.4% of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.2% of triallyl isocyanurate, and 0.2% of Ethoxylated pentaerythritol tetraacrylate, 0.05% of 3-isocyanatepropyltriethoxysilane terminated with DMP, 0.05% of KH570 silane coupling agent, 0.05% of light stabilizer 770, and 0.5% of UV-531 were mixed and cast at 100°C to form a film. The cast film was irradiated with an electron beam at an irradiation voltage of 400kV and an irradiation dose of 15KGY to obtain an encapsulating film.

[0048] Example 4

[0049] By mass percentage, 99.3% of the matrix resin EVA 282 is mixed with 0.2% of 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane and 0.5% of isopropyl tri(dioctyl pyrophosphoryl) titanate, and grafted and granulated at 180°C to obtain a granulated material. 86.9% of the granulated material, 10% of Panhua titanium dioxide 2588, 1% of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.6% of triallyl isocyanurate, 0.4% of ethoxylated pentaerythritol tetraacrylate, 0.3% of 3-isocyanatepropyltriethoxysilane capped with DMP, 0.3% of KH570 silane coupling agent, and 0.5% of 770 are mixed and cast at 100°C to form a film. The cast film is irradiated by electron beam at a voltage of 400kV and a dose of 15KGY to obtain an encapsulating film.

[0050] Example 5

[0051] The difference between this embodiment and embodiment 1 is that the titanate coupling agent is replaced by di(dioctylpyrophosphoryl)ethylene titanate, and the other aspects are the same as those of embodiment 1.

[0052] Example 6

[0053] The difference between this embodiment and embodiment 1 is that the titanate coupling agent is replaced by isopropyl tris(n-ethylamino-ethylamino) titanate (KB-44), and the other aspects are the same as those of embodiment 1.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that granulation is not performed, that is, the titanate coupling agent is not grafted onto the base resin in advance. The preparation method of this comparative example is as follows: by mass percentage, 89.8% of base resin 282, 0.2% of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, 0.5% of isopropyl tri(dioctyl pyrophosphoryl) titanate, 8% of Panhua titanium dioxide 2588, 0.5% of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.5% of triallyl isocyanurate, 0.3% of trimethylolpropane triacrylate, 0.1% KH570 silane coupling agent, and 0.1% of light stabilizer 770 are mixed, and the mixture is cast at 100° C. to form a film. The cast film is irradiated by electron beam at an irradiation voltage of 400 kV and an irradiation dose of 30 kGY to obtain an encapsulating film.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the amount of titanate coupling agent used is 0.03%, and the reduced amount is added to other components on average to ensure that the total amount remains unchanged. The rest are the same as in Example 1.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that the dosage of the titanate coupling agent is 1, and the increased dosage of the titanate coupling agent is deducted from the other components on average to ensure that the total dosage remains unchanged. The other parameters are the same as those in Example 1.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the titanate coupling agent is replaced by KH171, and the other components are the same as those in Example 1.

[0062] The performance of the encapsulating films prepared in Examples 1-6 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1.

[0063] Among them, the test of adhesion is carried out in accordance with GB / T29848-2018 standard, and the tests of mechanical properties tensile strength and elongation at break are carried out in accordance with GB / T29848-2018.

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from Table 1, the encapsulating film of the present invention has excellent mechanical properties and exhibits good adhesion to glass after PCT aging. Specifically, the initial adhesion between the encapsulating film and glass is 98-178 N. After 24 hours of PCT aging, the adhesion to the glass still reaches over 60 N, specifically 62-78 N. After 48 hours of PCT aging, the adhesion to the glass still reaches over 40 N, specifically 44-68 N. After 6 months of storage, the initial adhesion to the glass is 68-116 N, the tensile strength is 21.5-28.9 MPa, and the elongation at break is 558-624%.

[0068] In Example 6, if other titanate coupling agents than those specified in this application are used, the tensile strength will not meet the standard, and the adhesion after PCT will not achieve the expected effect.

[0069] In Comparative Example 1, no grafting and granulation was performed, ie, the titanate coupling agent was not grafted onto the matrix resin in advance, which would cause the adhesion of the film PCT to the glass to be significantly reduced after aging.

[0070] In Comparative Example 2, the amount of titanate coupling agent used is too small, which will prevent the coupling agent from being grafted onto the resin, resulting in the adhesion failing to achieve the desired effect.

[0071] In Comparative Example 3, the amount of titanate coupling agent used is too much, which will result in excessive use of additives during granulation, causing screw slippage and difficulty in processing. In addition, the excess additives cannot be grafted onto the resin, resulting in great waste.

[0072] In comparative example 4, replacing the titanate coupling agent with the silane coupling agent KH171 will result in unqualified adhesion after PCT.

[0073] While the present invention uses the above-described embodiments to illustrate the detailed process equipment and process flow of the present invention, the present invention is not limited to the above-described detailed process equipment and process flow, and does not necessarily rely on the above-described detailed process equipment and process flow for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for raw materials in the products of the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

[0074] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0075] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0076] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A packaging film, characterized in that: Calculated by mass percentage, it contains the following components: The titanate coupling agent is any one of isopropyl tris(dioctyl pyrophosphoryl) titanate or di(dioctyl pyrophosphoryl) ethylene titanate or a mixture of the two; The silane coupling agent is any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane or 3-(methacryloyl chloride)propyltrimethyloxysilane or a mixture of two thereof; The isocyanate coupling agent is 3-isocyanatepropyltrimethoxysilane and / or 3-isocyanatepropyltriethoxysilane, and the isocyanate of the isocyanate coupling agent is blocked and protected by DMP or MEKO; The matrix resin is EVA and / or POE; The encapsulating film is prepared by the following method, which comprises the following steps: The matrix resin, titanate coupling agent and initiator are mixed according to a proportion, grafted and granulated, and a main cross-linking agent, an auxiliary cross-linking agent, an isocyanate coupling agent, a silane coupling agent, a filler, a light stabilizer and an ultraviolet absorber are added to the grafted particles, mixed and cast into a film, and irradiated to obtain the encapsulating film.

2. The packaging film according to claim 1, wherein The initiator and the primary cross-linking agent are independently selected from any one of diisopropylbenzene peroxide, tert-amyl peroxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, tert-butylperoxy-2-ethylhexyl carbonate, n-butyl-4,4-di(tert-butylperoxy)valerate, α,α′-bis(tert-butylperoxy)-1,3-diisopropylbenzene and 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, or a mixture of at least two thereof.

3. The packaging film according to claim 1, wherein The auxiliary cross-linking agent comprises any one of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate or ethoxylated pentaerythritol tetraacrylate, or a mixture of at least two thereof.

4. The packaging film according to claim 1, wherein The filler comprises any one of carbon black, titanium dioxide, calcium carbonate, barium sulfate or perylene black, or a mixture of at least two thereof.

5. The packaging film according to claim 1, wherein The light stabilizer is light stabilizer 770.

6. The packaging film according to claim 1, characterized in that The ultraviolet absorber comprises any one of a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber or a triazine ultraviolet absorber, or a mixture of at least two thereof.

7. A method for preparing a packaging film according to any one of claims 1 to 6, characterized in that: The following steps are included: The matrix resin, titanate coupling agent and initiator are mixed according to a proportion, grafted and granulated, and a main cross-linking agent, an auxiliary cross-linking agent, an isocyanate coupling agent, a silane coupling agent, a filler, a light stabilizer and an ultraviolet absorber are added to the grafted particles, mixed and cast into a film, and irradiated to obtain the encapsulating film.

8. The preparation method according to claim 7, characterized in that The temperature of the grafting granulation is 140-250°C.

9. The preparation method according to claim 7, characterized in that The temperature of the film casting is 90-120°C.

10. The preparation method according to claim 7, characterized in that The voltage of the irradiation is 300-500 kV, and the dose of the irradiation is 5-50 kGY.

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