Anti-extrusion, cross-linking aid polyolefin grafting material, its preparation method and application

Abstract

The present application relates to the field of polymerization aids, and aims at the problem of easy precipitation of crosslinking aids for photovoltaic adhesive films, and provides a precipitation-preventing crosslinking aid polyolefin grafting material and a preparation method and application thereof.The precipitation-preventing crosslinking aid polyolefin grafting material comprises the following components: a polyolefin elastomer, a first monomer and a second monomer; the first monomer is at least one selected from triallyl isocyanurate, triallyl cyanurate and an acrylate compound containing 2-4 carbon-carbon double bonds; and the second monomer is a dialkoxy silane or trialkoxy silane compound containing a carbon-carbon double bond.The present application uses a polyolefin elastomer as a base, adds the first monomer and the second monomer to obtain a high grafting rate, low crosslinking photovoltaic crosslinking aid grafting material, the crosslinking aid grafting material is free of crystal point impurities, has good transparency, high effective grafting rate, small melt index drop, high volume resistivity and high transparency, and is suitable for photovoltaic adhesive films.

Description

Technical Field

[0001] This invention relates to the field of polymerization aids, and in particular to polyolefin grafting materials that prevent precipitation and promote crosslinking, as well as their preparation methods and applications. Background Technology

[0002] In recent years, the market share of TOPCon cells has been expanding, with more and more industry leaders shifting from PERC cell technology to TOPCon cells. This has led to changes in cell structure and encapsulation films. The PID (Potential Injury Point) of N-type TOPCon cells mainly occurs on the front side, thus requiring POE or EPE encapsulation films. However, POE itself is a non-polar material with poor absorption of additives. After prolonged storage, liquid additives may migrate to the surface of the encapsulation film (POE film) or the EVA layer (EPE film). This can cause slippage between the encapsulation film and the cell / glass during use (POE film), or insufficient cross-linking of the encapsulation film and low interlayer peel strength of the E and P layers (EPE film), thereby affecting the yield of module manufacturing.

[0003] Patent CN117925142A describes a method that uses a hydrophobic cyclodextrin cavity to absorb oily liquid additives (such as initiators, crosslinking agents, and thickeners). After vacuum drying the cyclodextrin hydrogel, external moisture is removed, while the internal oily additives are retained. This hydrogel is then used as a raw material for preparing POE resin to create POE films, preventing the precipitation of liquid additives. However, the preparation and vacuum drying process of cyclodextrin hydrogels is relatively complex and time-consuming. Furthermore, the cost of cyclodextrin materials and the equipment and time required for vacuum drying are high, increasing the overall production cost.

[0004] Patent CN116948560A encapsulates organic additives using polymer microcapsules to prevent leaching. However, microcapsules may rupture during processing, leading to additive leakage, and the application cost of microcapsule technology is relatively high, which may not be suitable for large-scale production.

[0005] Patent CN117186781A uses a longer alkane structure to increase the compatibility of silanes with polyolefin elastomer resins and reduce the risk of silane additive precipitation. However, this method only applies to silane additives and fails to prevent the precipitation of other additives (such as crosslinking agents). Patent CN115895532A uses a solution grafting method to graft anti-potential-induced decay monomers onto the polyolefin elastomer molecular chain, avoiding the precipitation problem of direct blending. However, the solution grafting process is quite complex and difficult to implement in continuous production.

[0006] Therefore, an economical and effective solution is needed to address the precipitation problem of photovoltaic crosslinking agents such as ethoxylated trimethylolpropane triacrylate and triallyl cyanurate in POE and EPE films. Summary of the Invention

[0007] To overcome the problem of easy precipitation of crosslinking agents in photovoltaic films, this invention provides a polyolefin grafting material that prevents precipitation and promotes crosslinking, as well as its preparation method and application. Using a polyolefin elastomer as a matrix, a first monomer and a second monomer are added to react and obtain a photovoltaic crosslinking agent grafting material with high grafting rate and low crosslinking. The crosslinking agent grafting material is free of crystalline impurities, has good transparency, high effective grafting rate, and minimal decrease in melt index. At the same time, it also has the characteristics of high volume resistivity and high transparency, which are suitable for photovoltaic films.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An anti-exudation and crosslinking-aiding polyolefin grafting material comprises the following components: a polyolefin elastomer, a first monomer, and a second monomer; the first monomer is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and acrylate compounds containing 2-4 carbon-carbon double bonds; the second monomer is a dialkoxysilane or trialkoxysilane compound containing carbon-carbon double bonds; the mass sum of the first monomer and the second monomer is 1-10% of the polyolefin elastomer, and the mass ratio of the first monomer to the second monomer is (0.1-50):1.

[0010] Preferably, the polyolefin elastomer is one or more polymers generated by copolymerization of ethylene with any C3-C8 olefin (propylene, butene, pentene, hexene, octene), and the melt index of the polyolefin elastomer is 0.5-45 g / 10 min.

[0011] Preferably, the acrylate compounds containing 2-4 carbon-carbon double bonds are selected from the following compounds: trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, propionylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propionylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, bis(trimethylolpropane tetraacrylate), bis(trimethylolpropane tetramethacrylate), propionylated pentaerythritol tetraacrylate, tricyclodecanediethanol diacrylate, propionylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate.

[0012] Preferably, the second monomer is selected from at least one of the following compounds: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentoxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethyldioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, vinyltricarboxylsilane, or vinyl silanes such as γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, etc. (meth)acryloyloxysilane.

[0013] Preferably, the first monomer and the second monomer have one electron-withdrawing and the other electron-donating; the conjugation effect Q value of the second monomer is ≥0.2, more preferably 0.2-1; the Q values ​​of the first monomer and the second monomer differ by more than 0.2, more preferably by more than 0.8.

[0014] As a further preferred option, the first monomer is triallyl isocyanurate, and the second monomer is γ-methacryloyloxypropylmethyldimethoxysilane.

[0015] Melt grafting is a suitable method due to its advantages such as simple process and continuous production capability. Anti-precipitation grafted materials are prepared by grafting a crosslinking agent into a matrix resin via melt grafting. However, the crosslinking agent (the first monomer of this invention) contains multiple double bonds that can participate in the reaction, easily initiating crosslinking during the grafting process, weakening the flowability and crosslinking effect in subsequent processing. Therefore, a method to inhibit crosslinking during the grafting process is needed. This invention selects a second monomer with opposite electron-withdrawing (or electron-donating) properties based on the Q and e values ​​of the first monomer. Under the action of an initiator, the second monomer forms a more stable free radical with the first monomer, inhibiting the crosslinking reaction of the first monomer.

[0016] Preferably, the mass ratio of the first monomer to the second monomer is (0.25-10):1.

[0017] Preferably, the polyolefin grafting material for preventing exudation and promoting crosslinking is composed of the following components: 91.0-97.5 wt% polyolefin elastomer, 1.0-5.0 wt% first monomer, 0.5-4.0 wt% second monomer, 0.08-0.2 wt% initiator, and 0-0.2 wt% antioxidant; the sum of the amounts of each component is equal to 100%.

[0018] Preferably, the initiator is a peroxide initiator, and more preferably at least one of the following compounds: tert-butyl peroxycarbonate isopropyl ester, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxycarbonate of 2-ethylhexyl carbonate, tert-pentyl peroxycarbonate, and tert-butyl peroxycarbonate of 3,3,5-trimethylhexanoate.

[0019] Preferably, the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants. More preferably, the antioxidant is selected from at least one of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 101), tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), tris(nonylphenyl) phosphite, and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; more preferably, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0020] The present invention also provides a method for preparing the polyolefin graft material that prevents precipitation and promotes cross-linking, comprising the following steps: mixing the components of the raw materials, extruding and granulating at 85-220°C to obtain granules; homogenizing and drying the granules to obtain the polyolefin graft material.

[0021] The aforementioned anti-exudation and crosslinking-aiding polyolefin grafting material is used in photovoltaic films, wherein the photovoltaic film is a POE film or an EPE film, and the POE layer of the photovoltaic film contains the following components: 1-25 wt% of the aforementioned polyolefin grafting material, 70-98 wt% of polyolefin elastomer, and 1-5 wt% of additives; the additives include at least one of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers, and pigments.

[0022] Preferably, the photovoltaic encapsulant film is an EPE encapsulant film, which is composed of an EVA layer, the POE layer, and an EVA layer. The EVA layer contains the following components: 95-99.0 wt% EVA resin and 1.0-5.0 wt% additives. The additives include at least one of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers, or pigments.

[0023] Therefore, the beneficial effects of the present invention are: (1) The present invention uses polyolefin elastomer as the matrix, adds a first monomer and a second monomer, selects a suitable initiator, and controls the ratio of each raw material to obtain a photovoltaic crosslinking agent graft material with high grafting rate and low crosslinking. The crosslinking agent graft material has no crystal point impurities, good transparency, high effective grafting rate, and low melt index decrease. At the same time, it also has the characteristics of high volume resistivity and high transparency, which are suitable for photovoltaic films.

[0024] (2) The anti-precipitation and cross-linking adhesive film prepared by the present invention has fast vulcanization, high cross-linking degree, high volume resistivity, high light transmittance, and low yellowing value after PCT aging. The adhesive film does not precipitate the additives after long-term storage and the peeling force does not decrease. It has significant benefits for the long-term preservation of the adhesive film, the anti-slip of POE adhesive film and the interlayer peeling of EPE adhesive film. Detailed Implementation

[0025] The technical solution of the present invention will be further described below through specific embodiments.

[0026] In this invention, unless otherwise specified, the raw materials and equipment used are commercially available or commonly used in the art. The methods in the embodiments, unless otherwise specified, are conventional methods in the art. Unless otherwise specified, all parts are parts by weight, temperatures are expressed in °C or at ambient temperature, and pressures are at or near atmospheric pressure. Various variations and combinations of reaction conditions (e.g., component concentrations, required solvents, solvent mixtures, temperature, pressure, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method exist, and only reasonable routine experiments are needed to optimize such method conditions.

[0027] Example

[0028] I. The polyolefin grafting material for preventing exudation and promoting cross-linking is composed of the following components: 91.0-97.5 wt% polyolefin elastomer, 1.0-5.0 wt% first monomer, 0.5-4.0 wt% second monomer, 0.08-0.2 wt% initiator, and 0-0.2 wt% antioxidant; the sum of the amounts of each component is equal to 100%.

[0029] (1) The polyolefin elastomer is one or more polymers generated by copolymerization of ethylene with any C3-C8 olefin (more preferably propylene, butene, pentene, hexene, octene) and the melt index of the polyolefin elastomer is 0.5-45 g / 10 min.

[0030] (2) The first monomer is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and acrylate compounds containing 2-4 carbon-carbon double bonds, and is more preferably triallyl isocyanurate. Specifically, acrylate compounds containing 2-4 carbon-carbon double bonds are selected from the following compounds: trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, propionylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propionylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, bis(trimethylolpropane tetraacrylate), bis(trimethylolpropane tetramethacrylate), propionylated pentaerythritol tetraacrylate, tricyclodecanediethanol diacrylate, propionylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate.

[0031] (3) The second monomer is a trialkoxysilane compound containing a carbon-carbon double bond. Specifically, it is selected from at least one of the following compounds: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentoxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethyldioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, vinyltricarboxylsilane, or vinyl silanes such as γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, etc. (meth)acryloyloxysilanes.

[0032] (4) The initiator is a peroxide initiator. Specifically, it is selected from at least one of the following compounds: tert-butyl peroxycarbonate isopropyl ester, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxycarbonate of 2-ethylhexyl carbonate, tert-pentyl peroxycarbonate, and tert-butyl peroxycarbonate of 3,3,5-trimethylhexanoate.

[0033] (5) The antioxidant is at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants. Specifically, it is selected from at least one of the following compounds: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 101), tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), tris(nonylphenyl) phosphite, and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; more preferably, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0034] Preferably, the first monomer and the second monomer have opposite electron-withdrawing and electron-donating properties, i.e., their e values ​​are opposite; the conjugation effect Q value of the second monomer is ≥0.2, more preferably 0.2-1; the Q values ​​of the first monomer and the second monomer differ by more than 0.2, more preferably by more than 0.8.

[0035] II. Preparation method of the aforementioned anti-exudation and cross-linking-aiding polyolefin graft material

[0036] Includes the following steps:

[0037] (1) Preparation of polyolefin modified resin granules: Polyolefin elastomer, initiator, first monomer, second monomer and antioxidant are added into a high-speed mixing equipment in proportion and mixed evenly. Then, the granules are obtained by granulation in a twin-screw extruder at 85-220℃.

[0038] (2) The extruded granules are homogenized and dehumidified in a homogenizing tank to obtain polyolefin graft material.

[0039] III. Application of the aforementioned anti-exudation and cross-linking-aiding polyolefin grafting material in photovoltaic modules

[0040] (1) Used in POE photovoltaic films. POE photovoltaic films comprise the following components: 1-25 wt% of the aforementioned polyolefin grafting material, 70-98 wt% of polyolefin elastomer, and 1-5 wt% additives; the sum of the amounts of each component equals 100%. Additives include at least one of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers, and pigments.

[0041] (2) Used for EPE photovoltaic film, the EPE film is composed of EVA layer, POE layer and EVA layer from top to bottom. The POE layer is the same as the POE photovoltaic film in (1). The EVA layer contains the following components: 95-99.0 wt% EVA resin, 1.0-5.0 wt% additives; the sum of the amounts of each component is equal to 100%. The additives include at least one of crosslinking agent, co-crosslinking agent, silane coupling agent, antioxidant, ultraviolet absorber, light stabilizer, tackifier or pigment. The POE layer and EVA layer are added to the co-extrusion equipment for melt co-extrusion, cooled and shaped by the casting equipment, and then the edges are cut and wound to obtain the EPE photovoltaic film.

[0042] Example 1

[0043] An anti-exudation and cross-linking polyolefin grafting material is composed of the following components in parts by weight: 94.8 parts of polyolefin elastomer, ethylene-1-butene copolymer (grade LF675) with a melt index of 14 g / 10 min;

[0044] 3 parts of the first monomer, triallyl isocyanurate;

[0045] Two portions of the second monomer, γ-methacryloyloxypropylmethyldimethoxysilane;

[0046] 0.1 parts initiator, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane;

[0047] 0.1 part antioxidant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0048] The preparation method of polyolefin graft material with anti-precipitation and cross-linking properties is as follows: the above raw material components are put into a high-speed mixing equipment in proportion and mixed evenly. The processing temperature is set to 210℃, and the granules are obtained by twin-screw extruder. The extruded granules are homogenized and dried by homogenizing tank to obtain polyolefin graft material.

[0049] A method for preparing a POE photovoltaic film includes the following steps: 13 wt% of the above-mentioned polyolefin grafting material, 84 wt% of polyolefin elastomer (brand name LF675) and 3 wt% of other additives, the other additives being 0.8 wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5 wt% of triallyl isocyanurate, 0.5 wt% of trimethylolpropane trimethacrylate, 0.7 wt% of vinyltrimethoxysilane, 0.1 wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1 wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3 wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain the POE photovoltaic film.

[0050] A method for preparing an EPE photovoltaic encapsulant film, comprising the following steps:

[0051] (1) Preparation of POE resin layer: 13wt% of the above-mentioned polyolefin graft material, 84wt% of polyolefin elastomer (brand name LF675) and 3wt% of other additives, the other additives being 0.8wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5wt% of triallyl isocyanurate, 0.5wt% of trimethylolpropane trimethacrylate, 0.7wt% of vinyltrimethoxysilane, 0.1wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain POE resin layer.

[0052] (2) Preparation of EVA resin layer: 97wt% EVA resin and 3wt% other additives, including at least one or more of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers or pigments, are mixed evenly, melted and extruded, cooled, shaped and wound to obtain EVA resin layer.

[0053] (3) Composite: The POE resin layer obtained in step (1) and the EVA resin layer obtained in step (2) are added to the co-extrusion equipment for melt co-extrusion. After cooling and shaping by the casting equipment, the edges are cut and rolled up to obtain a three-layer EPE photovoltaic film with a layered structure. From top to bottom, the layers are a 100μm thick EVA resin layer, a 250μm thick POE resin layer, and a 100μm thick EVA resin layer.

[0054] Example 2

[0055] An anti-exudation and cross-linking-promoting polyolefin grafting material, comprising the following components in parts by weight:

[0056] 91 parts of polyolefin elastomer, ethylene-1-butene copolymer (grade LF675) with a melt index of 14 g / 10 min;

[0057] 4.72 parts of the first monomer, triallyl isocyanurate;

[0058] 4 parts of the second monomer, γ-methacryloyloxypropylmethyldimethoxysilane;

[0059] 0.08 parts initiator, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane;

[0060] 0.2 parts antioxidant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0061] The preparation method of polyolefin graft material with anti-precipitation and cross-linking properties is as follows: the above raw material components are put into a high-speed mixing equipment in proportion and mixed evenly. The processing temperature is set to 210℃, and the granules are obtained by twin-screw extruder. The extruded granules are homogenized and dried by homogenizing tank to obtain polyolefin graft material.

[0062] A method for preparing a POE photovoltaic film includes the following steps: 13 wt% of the above-mentioned polyolefin grafting material, 84 wt% of polyolefin elastomer (brand name LF675) and 3 wt% of other additives, the other additives being 0.8 wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5 wt% of triallyl isocyanurate, 0.5 wt% of trimethylolpropane trimethacrylate, 0.7 wt% of vinyltrimethoxysilane, 0.1 wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1 wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3 wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain the POE photovoltaic film.

[0063] A method for preparing an EPE photovoltaic encapsulant film, comprising the following steps:

[0064] (1) Preparation of POE resin layer: 13wt% of the above-mentioned polyolefin graft material, 84wt% of polyolefin elastomer (brand name LF675) and 3wt% of other additives, the other additives being 0.8wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5wt% of triallyl isocyanurate, 0.5wt% of trimethylolpropane trimethacrylate, 0.7wt% of vinyltrimethoxysilane, 0.1wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain POE resin layer.

[0065] (2) Preparation of EVA resin layer: 97wt% EVA resin and 3wt% other additives, including at least one or more of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers or pigments, are mixed evenly, melted and extruded, cooled, shaped and wound to obtain EVA resin layer.

[0066] (3) Composite: The POE resin layer obtained in step (1) and the EVA resin layer obtained in step (2) are added to the co-extrusion equipment for melt co-extrusion. After cooling and shaping by the casting equipment, the edges are cut and rolled up to obtain a three-layer EPE photovoltaic film with a layered structure. From top to bottom, the layers are a 100μm thick EVA resin layer, a 250μm thick POE resin layer, and a 100μm thick EVA resin layer.

[0067] Example 3

[0068] An anti-exudation and cross-linking polyolefin grafting material is composed of the following components in parts by weight: 97.5 parts polyolefin elastomer and ethylene-1-butene copolymer (grade LF675) with a melt index of 14 g / 10 min.

[0069] 1.5 parts of the first monomer, triallyl isocyanurate;

[0070] 0.8 parts of the second monomer, γ-methacryloyloxypropylmethyldimethoxysilane;

[0071] 0.2 parts initiator, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane.

[0072] The preparation method of polyolefin graft material with anti-precipitation and cross-linking properties is as follows: the above raw material components are put into a high-speed mixing equipment in proportion and mixed evenly. The processing temperature is set to 210℃, and the granules are obtained by twin-screw extruder. The extruded granules are homogenized and dried by homogenizing tank to obtain polyolefin graft material.

[0073] A method for preparing a POE photovoltaic film includes the following steps: 13 wt% of the above-mentioned polyolefin grafting material, 84 wt% of polyolefin elastomer (brand name LF675) and 3 wt% of other additives, the other additives being 0.8 wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5 wt% of triallyl isocyanurate, 0.5 wt% of trimethylolpropane trimethacrylate, 0.7 wt% of vinyltrimethoxysilane, 0.1 wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1 wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3 wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain the POE photovoltaic film.

[0074] A method for preparing an EPE photovoltaic encapsulant film, comprising the following steps:

[0075] (1) Preparation of POE resin layer: 13wt% of the above-mentioned polyolefin graft material, 84wt% of polyolefin elastomer (brand name LF675) and 3wt% of other additives, the other additives being 0.8wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5wt% of triallyl isocyanurate, 0.5wt% of trimethylolpropane trimethacrylate, 0.7wt% of vinyltrimethoxysilane, 0.1wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain POE resin layer.

[0076] (2) Preparation of EVA resin layer: 97wt% EVA resin and 3wt% other additives, including at least one or more of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers or pigments, are mixed evenly, melted and extruded, cooled, shaped and wound to obtain EVA resin layer.

[0077] (3) Composite: The POE resin layer obtained in step (1) and the EVA resin layer obtained in step (2) are added to the co-extrusion equipment for melt co-extrusion. After cooling and shaping by the casting equipment, the edges are cut and rolled up to obtain a three-layer EPE photovoltaic film with a layered structure. From top to bottom, the layers are a 100μm thick EVA resin layer, a 250μm thick POE resin layer, and a 100μm thick EVA resin layer.

[0078] Example 4

[0079] The difference from Example 1 is that the first monomer is propionyl oxypentaerythritol tetraacrylate.

[0080] Example 5

[0081] The difference from Example 1 is that the second monomer is vinyltrimethylenedioxysilane.

[0082] Example 6

[0083] The difference from Example 1 is that the first monomer is propoxylated trimethylolpropane triacrylate.

[0084] Example 7

[0085] The difference from Example 1 is that the second monomer is vinyltributoxysilane.

[0086] Example 8

[0087] The difference from Example 1 is that the first monomer is trimethylolpropane tetraacrylate.

[0088] Example 9

[0089] The difference from Example 1 is that the second monomer is vinyltriethylenedioxysilane.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that no second monomer was added, and the missing amount was made up with polyolefin elastomer. Specifically:

[0092] An anti-exudation and cross-linking polyolefin grafting material is composed of the following components in parts by weight: 96.8 parts of polyolefin elastomer, ethylene-1-butene copolymer (grade LF675) with a melt index of 14 g / 10 min;

[0093] 3 parts of the first monomer, triallyl isocyanurate;

[0094] 0.1 parts initiator, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane;

[0095] 0.1 part antioxidant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0096] The preparation method of polyolefin graft material with anti-precipitation and cross-linking properties is as follows: the above raw material components are put into a high-speed mixing equipment in proportion and mixed evenly. The processing temperature is set to 210℃, and the granules are obtained by twin-screw extruder. The extruded granules are homogenized and dried by homogenizing tank to obtain polyolefin graft material.

[0097] A method for preparing a POE photovoltaic film includes the following steps: 13 wt% of the above-mentioned polyolefin grafting material, 84 wt% of polyolefin elastomer (brand name LF675) and 3 wt% of other additives, the other additives being 0.8 wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5 wt% of triallyl isocyanurate, 0.5 wt% of trimethylolpropane trimethacrylate, 0.7 wt% of vinyltrimethoxysilane, 0.1 wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1 wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3 wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain the POE photovoltaic film.

[0098] A method for preparing an EPE photovoltaic encapsulant film, comprising the following steps:

[0099] (1) Preparation of POE resin layer: 13wt% of the above-mentioned polyolefin graft material, 84wt% of polyolefin elastomer (brand name LF675) and 3wt% of other additives, the other additives being 0.8wt% of tert-amyl peroxide-2-ethylhexyl carbonate, 0.5wt% of triallyl isocyanurate, 0.5wt% of trimethylolpropane trimethacrylate, 0.7wt% of vinyltrimethoxysilane, 0.1wt% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 0.1wt% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV absorber 770) and 0.3wt% of 2-hydroxy-4-n-octyloxybenzophenone, are mixed evenly, melt-extruded, cooled, shaped and wound to obtain POE resin layer.

[0100] (2) Preparation of EVA resin layer: 97wt% EVA resin and 3wt% other additives, including at least one or more of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers or pigments, are mixed evenly, melted and extruded, cooled, shaped and wound to obtain EVA resin layer.

[0101] (3) Composite: The POE resin layer obtained in step (1) and the EVA resin layer obtained in step (2) are added to the co-extrusion equipment for melt co-extrusion. After cooling and shaping by the casting equipment, the edges are cut and rolled up to obtain a three-layer EPE photovoltaic film with a layered structure. From top to bottom, the layers are a 100μm thick EVA resin layer, a 250μm thick POE resin layer, and a 100μm thick EVA resin layer.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that no polyolefin grafting material is added.

[0104] Comparative Example 3

[0105] The difference from Example 1 is that the amounts of the first monomer and the second monomer are 0.5 wt% and 5.0 wt%, respectively.

[0106] Performance testing

[0107] The maximum static friction coefficient of the POE photovoltaic films prepared in each embodiment and comparative example was tested according to GB / T 10006-2021 standard, and the results are shown in Table 1.

[0108] Table 1.

[0109]

[0110] The performance of the EPE photovoltaic films prepared in each embodiment and comparative example was tested, and the results are shown in Table 2. The test methods are as follows: ① Light transmittance: tested according to the method described in GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation"; ② Crosslinking degree: tested according to the method described in GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation"; ③ Peel strength test: tested according to the method described in GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation".

[0111] Table 2.

[0112]

[0113] As can be seen from Tables 1 and 2, compared with Comparative Example 2, the photovoltaic films prepared by adding the polyolefin grafting material of the present invention during the preparation of the films in each embodiment have excellent light transmittance and anti-exudation performance.

[0114] The composition of the polyolefin grafting material is crucial. Compared to Example 1:

[0115] (1) No second monomer was added in Comparative Example 1 because the first monomer contains multiple double bonds that can participate in the reaction, which can easily trigger cross-linking during the grafting process, thus weakening the fluidity and cross-linking effect in subsequent processing. Therefore, a second monomer was added in Example 1 to form a more stable free radical with the first monomer, thereby inhibiting the cross-linking reaction of the first monomer.

[0116] (2) The amounts of the first and second monomers in Comparative Example 3 were not within the preferred range, resulting in the crosslinking degree and grafting rate of the obtained polyolefin grafting material being outside the ideal range, ultimately manifesting as poor anti-exudation effect of the film.

[0117] (3) The first and second monomers selected in Examples 4-9 did not exhibit the same anti-precipitation effect as those in Example 1 because the Q and e values ​​of the first and second monomers in Example 1 differed the most in these examples, with a difference of more than 0.8 in Q value. The triallyl structure of the first monomer, triallyl isocyanurate, in Example 1 has high reactivity and can react effectively with the active sites in the polymer at lower temperatures, thereby increasing the crosslinking rate and degree of crosslinking. The second monomer, γ-methacryloyloxypropylmethyldimethoxysilane, has a stronger conjugation effect and is more likely to form stable free radicals. Furthermore, its electron-withdrawing effect makes it easier to copolymerize with the electron-donating first monomer. The Q and e values ​​of the monomers can be inferred from their chemical structures. In triallyl isocyanurate, the group directly connected to the carbon-carbon double bond is -CH2-N, which has a more obvious electron-donating property and a smaller e value. In contrast, the group directly connected to the carbon-carbon double bond in γ-methacryloyloxypropylmethyldimethoxysilane is an ester group, which has conjugation characteristics and exhibits electron-withdrawing properties. Therefore, its Q and e values ​​are both larger. In Example 8, the first monomer was an acrylate monomer, and the second monomer, γ-methacryloyloxypropylmethyldimethoxysilane, had Q and e values ​​close to those of the acrylate monomer, with a Q value difference of 0.2-0.8. Therefore, its anti-precipitation effect was not as good as that of Example 1.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polyolefin grafting material that prevents exudation and promotes cross-linking, characterized in that, It is composed of the following components: 91.0-97.5 wt% polyolefin elastomer, 1.0-5.0 wt% first monomer, 0.5-4.0 wt% second monomer, 0.08-0.2 wt% initiator, and 0-0.2 wt% antioxidant, with the sum of the amounts of all components equal to 100%; the first monomer is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and acrylate compounds containing 2-4 carbon-carbon double bonds; the second monomer is a dialkoxysilane or trialkoxysilane compound containing carbon-carbon double bonds; the mass sum of the first and second monomers is 1-10% of the polyolefin elastomer, and the mass ratio of the first and second monomers is (0.25-10):1; one of the first and second monomers is electron-withdrawing and the other is electron-donating, i.e., their e values ​​are opposite; the conjugation effect Q value of the second monomer is ≥0.2, and the difference in Q values ​​between the first and second monomers is ≥0.

8.

2. The anti-exudation and cross-linking-aiding polyolefin grafting material according to claim 1, characterized in that, Polyolefin elastomers are one or more polymers produced by copolymerization of ethylene with any C3-C8 olefin, and the melt index of polyolefin elastomers is 0.5-45 g / 10min.

3. The polyolefin grafting material for preventing exudation and promoting cross-linking according to claim 1, characterized in that, Acrylates containing 2-4 carbon-carbon double bonds are selected from the following compounds: trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, propionylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propionylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, bis(trimethylolpropane tetraacrylate), bis(trimethylolpropane tetramethacrylate), propionylated pentaerythritol tetraacrylate, tricyclodecanediethanol diacrylate, propionylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate.

4. The anti-exudation and cross-linking-aiding polyolefin grafting material according to claim 1, 2, or 3, characterized in that, The second monomer is selected from at least one of the following compounds: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentoxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethyldioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, vinyltricarboxylic acid silane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and γ-acryloyloxypropyltrimethoxysilane.

5. The polyolefin grafting material for preventing exudation and promoting cross-linking according to claim 1, characterized in that, The initiator is a peroxide initiator; the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants.

6. A method for preparing the anti-precipitation and crosslinking-aiding polyolefin graft material according to any one of claims 1-5, characterized in that, The process includes the following steps: mixing the raw material components, extruding and granulating at 85-220 ℃ to obtain granules; homogenizing and drying the granules to obtain polyolefin grafted material.

7. The application of the anti-exudation and cross-linking polyolefin graft material according to any one of claims 1-5 in photovoltaic films, characterized in that, The POE layer of the photovoltaic film comprises the following components: 1-13 wt% polyolefin grafting material, 84-98 wt% polyolefin elastomer, and 1-5 wt% additives; the additives include at least one of crosslinking agent, co-crosslinking agent, silane coupling agent, antioxidant, ultraviolet absorber, light stabilizer, tackifier, and pigment.

8. The application according to claim 7, characterized in that, The photovoltaic encapsulant film is an EPE encapsulant film, which is composed of an EVA layer, the POE layer, and an EVA layer. The EVA layer contains the following components: 95-99.0 wt% EVA resin and 1.0-5.0 wt% additives. The additives include at least one of crosslinking agents, co-crosslinking agents, silane coupling agents, antioxidants, ultraviolet absorbers, light stabilizers, tackifiers, or pigments.

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