1. A modified acrylic resin is characterized in that the structural formula is as follows:

(ii) a Wherein

R₁、R₂、R₃Are respectively one of alkyl or alkoxy, and R₁、R₂、R₃At least one of which is an alkoxy group;

the values of x, y, z, w and i are respectively that x is more than or equal to 20 and less than or equal to 100, y is more than or equal to 20 and less than or equal to 100, z is more than or equal to 20 and less than or equal to 100, w is more than or equal to 20 and less than or equal to 100, and i is more than or equal to 10 and less than or equal to 50.

2. The method for preparing a modified acrylic resin according to claim 1, comprising the steps of:

mixing an acrylic resin composition, an alkoxysilane compound containing vinyl and a chain transfer agent, and adding the mixture into a first dropping container to prepare a first dropping liquid;

adding an initiator into a second dripping container to prepare second dripping liquid;

adding a reaction solvent into a reaction container, and dropwise adding a first drop of liquid into the reaction container to obtain a reaction mixed liquid;

and heating the reaction mixed solution, preserving heat, cooling, adding a second dropping liquid, performing reflux reaction, and cooling to obtain the modified acrylic resin.

3. The method according to claim 2,

the acrylic resin composition comprises the following components in parts by mass:

methyl methacrylate: 1-35 parts;

acrylic acid: 1-25 parts;

butyl methacrylate: 1-40 parts; and

hydroxypropyl methacrylate: 1-15 parts.

4. The method according to claim 2,

the vinyl-containing alkoxysilane compound includes: at least one of vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, and vinyltris (2-methoxyethoxy) silane and oligomers thereof.

5. The method according to claim 2,

the chain transfer agent is mercaptoethanol.

6. The method according to claim 2,

the reaction solvent comprises one or more of dimethylbenzene, methylbenzene and butyl acetate.

7. Use of the modified acrylic resin as claimed in claim 1 in a solar cell back sheet.

Background

Fluoropolymer films have been considered important components in photovoltaic modules in recent years due to their weatherability, UV resistance and moisture resistance. When a fluoropolymer such as PVF is used as the backsheet for the module, its properties significantly improve the module lifetime, allowing the module warranty period to be up to 25 years. Fluoropolymer backsheets are often used in the form of a laminate with a polyethylene terephthalate (PET) film, typically PET sandwiched between two fluoropolymer films.

However, laminates of preformed fluoropolymer films on polymer substrates having a bond that does not delaminate after years of outdoor exposure are difficult to prepare. At least one adhesive layer or both a primer and an adhesive layer is required to be applied prior to the actual lamination step, which requires the application of heat and pressure to form the laminate. Thus, prior art laminates using preformed fluoropolymer films are expensive to manufacture and costly.

Disclosure of Invention

The invention provides a modified acrylic resin, a preparation method and application thereof.

In order to solve the above technical problems, the present invention provides a modified acrylic resin comprising: an alkoxysilane group located on a side chain of the modified acrylic resin; and a reactive group comprising at least one of a hydroxyl group, a carboxyl group, or an amine group.

In a second aspect, the present invention also provides a method for preparing a modified acrylic resin, comprising the following steps: step S1, uniformly mixing the acrylic resin composition, the vinyl-containing alkoxysilane compound and mercaptoethanol, and adding the mixture into a first addition container to prepare a first addition liquid; adding an initiator into a second dripping container to prepare second dripping liquid; step S2, adding xylene, toluene and butyl acetate into a reaction container, and dropwise adding a first drop of liquid into the reaction container to obtain a reaction mixed liquid; and step S3, heating the reaction mixed solution, preserving heat, cooling, adding a second dropping liquid, performing reflux reaction, and cooling to obtain the modified acrylic resin.

In a third aspect, the invention also provides the application of the modified acrylic resin in the solar cell back sheet.

The modified acrylic resin has the beneficial effects that the side chain of the modified acrylic resin contains an alkoxysilane group, so that the weather resistance and the acid resistance of the solar cell back plate can be improved, the binding force between the solar cell back plate and a photovoltaic adhesive film is further improved, the modified acrylic resin has high weather resistance, and the modified acrylic resin can be used for a long time.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a H1-NMR hydrogen nuclear magnetic resonance spectrum of the modified acrylic resin obtained in the present invention.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Although the fluorine material can improve the weather resistance of the back plate, due to the characteristics of the fluorine material, the use of a large amount of fluorine material can cause high surface energy and hydrophobic surface, which leads to poor adhesive property, so that the adhesive property between the back plate and the EVA is reduced, especially the adhesive force with a high-reflection white EVA adhesive film is extremely poor, which leads to the reduction of the peeling strength between the back plate and the EVA adhesive film, the delamination phenomenon occurs, and the service life of the assembly is influenced.

In order to solve the above technical problems, the present invention provides a modified acrylic resin for improving adhesive strength of a back sheet, the modified acrylic resin comprising: an alkoxysilane group located on a side chain of the modified acrylic resin; and a reactive group comprising at least one of a hydroxyl group, a carboxyl group, or an amine group.

Specifically, the alkoxysilane groups are hydrolyzable groups, and the alkoxysilane groups are partially hydrolyzed during a short baking and curing process during preparation of the back sheet to generate silicon hydroxyl groups, and a condensation reaction is generated among the silicon hydroxyl groups to generate a siloxane structure of silicon-oxygen-silicon, so that the weather resistance and acid resistance of the bonded fluoropolymer layer can be improved; in the lamination process of the back plate, the alkoxy silane groups which are not hydrolyzed can form hydrogen bonds with hydroxyl on the surface of titanium dioxide in the white EVA adhesive film, so that the high-adhesion fluoropolymer layer has high adhesion to white EVA.

Optionally, the hydroxyl value of the modified acrylic resin can be but is not limited to 10-30, and the acid value is not more than 4.

Optionally, the glass transition temperature of the modified acrylic resin is not lower than 30 ℃, and the weight average molecular weight can be, but is not limited to, 20000-50000 g/mol.

Alternatively, when the solid content is not less than 60wt%, the viscosity of the modified acrylic resin at 25 ℃ may be, but is not limited to, 2000 to 4000 mPa · s.

Optionally, the structural formula of the modified acrylic resin is as follows:

(ii) a Wherein R is₁、R₂、R₃Are respectively one of alkyl or alkoxy, and R₁、R₂、R₃At least one of which is an alkoxy group; the values of x, y, z, w and i are respectively that x is more than or equal to 20 and less than or equal to 100, y is more than or equal to 20 and less than or equal to 100, z is more than or equal to 20 and less than or equal to 100, w is more than or equal to 20 and less than or equal to 100, and i is more than or equal to 10 and less than or equal to.

Further, the invention also provides a preparation method of the modified acrylic resin, which comprises the following steps: s1, uniformly mixing the acrylic resin composition, the vinyl-containing alkoxysilane compound and mercaptoethanol, and adding into a dropping container to obtain a first dropping solution; adding an initiator into a second dripping container to prepare second dripping liquid; s2, adding xylene, toluene and butyl acetate into a reaction container, and dropwise adding the first drop of liquid into the reaction container to obtain a reaction mixed liquid; and S3, heating the reaction mixed solution, preserving heat, cooling, adding an initiator, performing reflux reaction, and cooling to obtain the modified acrylic resin.

Specifically, the acrylic resin composition, the vinyl-containing alkoxysilane compound and mercaptoethanol are uniformly mixed and added into a first titration funnel; adding an initiator to a second titration funnel; and (2) filling xylene, toluene and butyl acetate into a glass reaction flask with a stirring reflux condenser, heating to 140 ℃ under a stirring state, preserving heat for 0.5h, then slowly dropwise adding the first addition liquid in the first titration funnel, controlling the dropwise adding time to be 3h, preserving heat for 0.5h after dropwise adding is finished, cooling to 80 ℃, dropwise adding an initiator in the second titration funnel, and carrying out reflux reaction for 2 h.

Wherein the completion of the reaction can be determined by measuring the hydroxyl number, acid number, molecular weight, viscosity or glass transition temperature.

Wherein, optionally, the acrylic resin composition can include, but is not limited to, the following components in parts by mass: methyl methacrylate: 1-35 parts; acrylic acid: 1-25 parts; butyl methacrylate: 1-40 parts; and hydroxypropyl methacrylate: 1-15 parts.

Alternatively, the vinyl group-containing alkoxysilane compound may include, but is not limited to: at least one of vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, and vinyltris (2-methoxyethoxy) silane and oligomers thereof.

Specifically, the reaction formula for preparing the modified acrylic resin is

。

Example 1

Uniformly mixing 30 parts by mass of methyl methacrylate, 15 parts by mass of acrylic acid, 20 parts by mass of butyl methacrylate, 12 parts by mass of hydroxypropyl methacrylate, 8 parts by mass of vinyl methyl dimethoxysilane and mercaptoethanol, and adding the mixture into a first sizing funnel; adding an initiator to a second titration funnel; placing dimethylbenzene, methylbenzene and butyl acetate into a glass reaction flask with a stirring reflux condenser, heating to 140 ℃ under a stirring state, preserving heat for 0.5h, then slowly dropwise adding a first addition liquid in a first dropping funnel, controlling the dropwise adding time to be 3h, preserving heat for 0.5h after dropwise adding is finished, cooling to 80 ℃, adding azobisisobutyronitrile, and continuing to carry out reflux reaction for 2 h; when the indexes of the reaction solution to be detected reach a hydroxyl value of 25, an acid value of 3, a molecular weight of 25000g/mol, a viscosity of 3500 mPa.s and a glass transition temperature of 32 ℃, the reaction is finished, and the modified acrylic resin is prepared.

As shown in FIG. 1, the modified acrylic resin obtained in example 1 had a spectral intensity a at 10.5ppm to 10.7ppm in the H1-NMR hydrogen nuclear magnetic resonance spectrum, which is derived from the 1H characteristic peak of-COOH in the modified acrylic resin; a 1H characteristic peak originating from R-OH in the modified acrylic resin having a spectral intensity b at 5.2ppm to 5.4 ppm; has a spectral intensity c at 3.3ppm to 3.8ppm, which is derived from the 1H characteristic peak of the modified acrylic resin in which alkane protons are bonded to O atoms.

Example 2

Uniformly mixing 5 parts by mass of methyl methacrylate, 20 parts by mass of acrylic acid, 35 parts by mass of butyl methacrylate, 15 parts by mass of hydroxypropyl methacrylate, 15 parts by mass of vinyl methyl dimethoxy silane and mercaptoethanol, and adding the mixture into a first sizing funnel; adding an initiator to a second titration funnel; placing dimethylbenzene, methylbenzene and butyl acetate into a glass reaction flask with a stirring reflux condenser, heating to 140 ℃ under a stirring state, preserving heat for 0.5h, then slowly dropwise adding a first addition liquid in a first dropping funnel, controlling the dropwise adding time to be 3h, preserving heat for 0.5h after dropwise adding is finished, cooling to 80 ℃, adding azobisisobutyronitrile, and continuing to carry out reflux reaction for 2 h; when the indexes of the reaction solution to be detected reach a hydroxyl value of 25, an acid value of 3, a molecular weight of 25000g/mol, a viscosity of 3500 mPa.s and a glass transition temperature of 32 ℃, the reaction is finished, and the modified acrylic resin is prepared.

Example 3

Uniformly mixing 18 parts by mass of methyl methacrylate, 25 parts by mass of acrylic acid, 15 parts by mass of butyl methacrylate, 10 parts by mass of hydroxypropyl methacrylate, 5 parts by mass of vinyl methyl dimethoxysilane and mercaptoethanol, and adding the mixture into a first sizing funnel; adding an initiator to a second titration funnel; placing dimethylbenzene, methylbenzene and butyl acetate into a glass reaction flask with a stirring reflux condenser, heating to 140 ℃ under a stirring state, preserving heat for 0.5h, then slowly dropwise adding a first addition liquid in a first dropping funnel, controlling the dropwise adding time to be 3h, preserving heat for 0.5h after dropwise adding is finished, cooling to 80 ℃, adding azobisisobutyronitrile, and continuing to carry out reflux reaction for 2 h; when the indexes of the reaction solution to be detected reach a hydroxyl value of 25, an acid value of 3, a molecular weight of 25000g/mol, a viscosity of 3500 mPa.s and a glass transition temperature of 32 ℃, the reaction is finished, and the modified acrylic resin is prepared.

Example 4

Uniformly mixing 35 parts by mass of methyl methacrylate, 8 parts by mass of acrylic acid, 40 parts by mass of butyl methacrylate, 3 parts by mass of hydroxypropyl methacrylate, 13 parts by mass of vinyl methyl dimethoxysilane and mercaptoethanol, and adding the mixture into a first sizing funnel; adding an initiator to a second titration funnel; placing dimethylbenzene, methylbenzene and butyl acetate into a glass reaction flask with a stirring reflux condenser, heating to 140 ℃ under a stirring state, preserving heat for 0.5h, then slowly dropwise adding a first addition liquid in a first dropping funnel, controlling the dropwise adding time to be 3h, preserving heat for 0.5h after dropwise adding is finished, cooling to 80 ℃, adding azobisisobutyronitrile, and continuing to carry out reflux reaction for 2 h; when the indexes of the reaction solution to be detected reach a hydroxyl value of 25, an acid value of 3, a molecular weight of 25000g/mol, a viscosity of 3500 mPa.s and a glass transition temperature of 32 ℃, the reaction is finished, and the modified acrylic resin is prepared.

Example 5

40 parts by mass of a fluorine-containing resin GK570 (Japan Dajin), 30 parts by mass of the modified acrylic resin obtained in example 1, 3 parts by mass of a dispersant BYK111 (Germany Bikk chemical), 30 parts by mass of butyl acetate and 5 parts by mass of xylene were stirred in a vessel and predispersed for 10 minutes, adding 20 parts by mass of titanium dioxide R960 (DuPont, USA), grinding for 3h with a sand mill until the particle fineness is less than or equal to 2 μm, adding 3 parts by mass of adhesion promoting resin ADK (Hamming modesty), 1 part by mass of coupling agent KH560 (Baker Nanjing Ouchui, Germany), 0.5 part by mass of catalyst dibutyltin dilaurate (Allatin reagent), 0.1 part by mass of matting powder TSA250 (Ling, Guangzhou), dispersing and stirring at 3000rpm, adding 5 parts by mass of curing agent Z4470 (German Bayer), dispersing at 1000rpm, filtering to obtain high-adhesion fluoropolymer layer coating liquid, and storing in a dry sealed container for later use.

And (3) selecting a 275-micron-thick PET film, carrying out corona treatment on one surface of the PET film to 50-60 dyne/cm by adopting a corona device, coating the prepared high-adhesion fluorine-containing polymer on the corona-treated surface of the PET base film, drying the PET base film for 2min at 170 ℃ by using a circulating oven, primarily drying and curing to form a 5-micron high-adhesion fluorine-containing polymer layer, and thus obtaining the finished product of the solar backboard. And finally, curing for 48 hours by using a 50 ℃ oven to obtain the solar backboard.

Example 6

25 parts by mass of fluorine-containing resin ZHM-2 (Shanghai Dongfeng fluorine), 40 parts by mass of the modified acrylic resin prepared in example 2, 3 parts by mass of dispersant BYK163 (Germany Bike chemical), 45 parts by mass of butyl acetate are stirred and pre-dispersed in a container for 10min, 15 parts by mass of titanium pigment CR506 (Jinzhou titanium industry) are added, the mixture is ground for 3h by a sand mill until the particle fineness is less than or equal to 2 mu m, 5 parts by mass of adhesion promoting resin ADK (Hamming modernit), 0.5 part by mass of coupling agent KH550 (Nanjing Aureox), 0.3 part by mass of catalyst dioctyltin dilaurate (Allantin reagent) and 0.2 part by mass of extinction powder TSA230 (Guangzhou Ling), dispersing and stirring at a high speed of 3000rpm, finally adding 5 parts by mass of curing agent N3390 (Germany Bayer), dispersing at a high speed of 1000rpm, filtering to obtain a high-adhesion fluoropolymer layer coating liquid, and storing in a dry sealed container for later use.

And (3) selecting a 275-micron-thick PET film, carrying out corona treatment on one surface of the PET film to 50-60 dyne/cm by adopting a corona device, coating the prepared high-adhesion fluorine-containing polymer on the corona-treated surface of the PET base film, drying the PET base film for 2min at 170 ℃ by using a circulating oven, primarily drying and curing to form a 5-micron high-adhesion fluorine-containing polymer layer, and thus obtaining the finished product of the solar backboard. And finally, curing for 48 hours by using a 50 ℃ oven to obtain the solar backboard.

Example 7

30 parts by mass of fluorine-containing resin ZHM-5 (Shanghai Dongfeng), 25 parts by mass of the modified acrylic resin prepared in example 3, 2.5 parts by mass of dispersant BYK163 (Germany Bikko), 45 parts by mass of butyl acetate and 10 parts by mass of propylene glycol methyl ether acetate are stirred and pre-dispersed in a container for 10min, 10 parts by mass of titanium dioxide R-5566 (Oriental titanium industry) are added, then the mixture is ground by a sand mill for 3h until the particle fineness is less than or equal to 2 μm, 5 parts by mass of adhesion promoting resin ADK (Hamming Sode), 1 part by mass of coupling agent KH560 (Germany Bikko Nanjing Auchi), 0.1 part by mass of curing agent promoter dibutyltin dilaurate (Allantin reagent) and 0.15 parts by mass of extinction powder OK412 (Creutzfeldt-Guc), after high-speed dispersion at 3000rpm, 5 parts by mass of curing agent D120N (Japan Triwell) are added, and after high-speed dispersion at 1000rpm, high-adhesion fluoropolymer layer coating liquid is obtained by filtration, storing in a dry sealed container for later use.

And (3) selecting a 275-micron-thick PET film, carrying out corona treatment on one surface of the PET film to 50-60 dyne/cm by adopting a corona device, coating the prepared high-adhesion fluorine-containing polymer on the corona-treated surface of the PET base film, drying the PET base film for 2min at 170 ℃ by using a circulating oven, primarily drying and curing to form a 5-micron high-adhesion fluorine-containing polymer layer, and thus obtaining the finished product of the solar backboard. And finally, curing for 48 hours by using a 50 ℃ oven to obtain the solar backboard.

Example 8

30 parts by mass of fluorine-containing resin ZHM-5 (Shanghai Dongfeng), 25 parts by mass of the modified acrylic resin obtained in example 4, 2.5 parts by mass of dispersant BYK163 (Germany Bikko), 45 parts by mass of butyl acetate and 10 parts by mass of propylene glycol methyl ether acetate are stirred and pre-dispersed in a container for 10min, 10 parts by mass of titanium dioxide R-5566 (Oriental titanium industry) are added, then the mixture is ground by a sand mill for 3h until the particle fineness is less than or equal to 2 μm, 5 parts by mass of adhesion promoting resin ADK (Hamming Sode), 1 part by mass of coupling agent KH560 (Germany Bikko Nanjing Aumi), 0.1 part by mass of curing agent dibutyltin dilaurate (Latin reagent) and 0.15 parts of extinction powder OK412 (Windgehead), after high-speed stirring at 3000rpm, 5 parts by mass of curing agent D120N (Japan Triwell) are added, high-viscosity fluoropolymer coating liquid is obtained by filtering after high-speed dispersion at 1000rpm, storing in a dry sealed container for later use.

And (3) selecting a 275-micron-thick PET film, carrying out corona treatment on one surface of the PET film to 50-60 dyne/cm by adopting a corona device, coating the prepared high-adhesion fluorine-containing polymer on the corona-treated surface of the PET base film, drying the PET base film for 2min at 170 ℃ by using a circulating oven, primarily drying and curing to form a 5-micron high-adhesion fluorine-containing polymer layer, and thus obtaining the finished product of the solar backboard. And finally, curing for 48 hours by using a 50 ℃ oven to obtain the solar backboard.

Comparative example

Referring to example 8, a PET base film having a thickness of 275 μm was used in comparative example 1, and the modified acrylic resin was replaced with a conventional acrylic resin in the formulation of the high adhesion fluoropolymer layer, with the other parameters being unchanged;

(1) preparation of high-adhesion fluoropolymer layer coating liquid

40 parts by mass of a fluorine-containing resin GK570 (Japan gold), 30 parts by mass of an acrylic resin (Allantin reagent), 3 parts by mass of a dispersant BYK111 (Germany Bikk chemical), 30 parts by mass of butyl acetate and 5 parts by mass of xylene were stirred in a vessel and predispersed for 10 minutes, adding 20 parts by mass of titanium dioxide R960 (DuPont, USA), grinding for 3h with a sand mill until the particle fineness is less than or equal to 2 μm, adding 3 parts by mass of adhesion promoting resin ADK (Hamming modesty), 1 part by mass of coupling agent KH560 (Nanjing Ouchi, Beike, Germany), 0.5 part by mass of catalyst dibutyltin dilaurate (Allatin reagent), 0.1 part by mass of matting powder TSA250 (Ling, Guangzhou), dispersing and stirring at a high speed of 3000rpm, finally adding 5 parts by mass of a curing agent Z4470 (German Bayer), dispersing at a high speed of 1000rpm, filtering to obtain a high-adhesion fluoropolymer layer coating liquid, and storing in a dry sealed container for later use.

(2) Making a backing plate

And (3) selecting a 275-micron-thick PET film, carrying out corona treatment on one surface of the PET film to 50-60 dyne/cm by adopting a corona device, coating the prepared high-adhesion fluorine-containing polymer on the corona-treated surface of the PET base film, drying the PET base film for 2min at 170 ℃ by using a circulating oven, primarily drying and curing to form a 5-micron high-adhesion fluorine-containing polymer layer, and thus obtaining the finished product of the solar backboard. And finally, curing for 48 hours by using a 50 ℃ oven to obtain the solar backboard.

And (3) performance testing:

the solar back sheets prepared in the above examples 5 to 8 and comparative example were tested for yellowness index, peeling strength with EVA, and various indexes of wet heat test, and the results are shown in table 1, wherein

Yellowing index: detection was carried out according to GB 2409-80.

Peel strength from EVA: the peel strength test was carried out according to GB/T2790.

And (3) damp-heat experiment: the method is carried out according to the specification of IEC 61215-. The yellowing index (. DELTA.YI) and peel strength of the samples after 1000h of aging were recorded.

Thermal cycling experiments: according to the IEC 61215-2005 regulations, a spiral welding strip twisted by a photovoltaic flat welding strip with the length of 10cm and the length of 0.35 multiplied by 2.0mm is placed between two layers of EVA during lamination, the bulge caused by welding of the welding strip during actual packaging of a photovoltaic module is simulated, and accelerated aging is carried out in a test box circulating between the temperature of minus 40 ℃ plus or minus 2 ℃ and the temperature of plus 85 ℃ plus or minus 2 ℃. The yellowing index (Δ YI) and appearance of the samples after 600 cycles of aging were recorded.

Table 1 each backplane performance test data

As can be seen from the test data of table 1, the high adhesion coating type back sheet provided by each example of the present invention has excellent adhesion property with EVA, and excellent aging resistance. In the comparative example, the adhesion with white EVA was significantly reduced and the adhesion was poor without the addition of modified acrylic resin.

In conclusion, the side chain of the modified acrylic resin disclosed by the invention contains an alkoxysilane group, so that the weather resistance and the acid resistance of the solar cell back plate can be improved, the binding force between the solar cell back plate and a photovoltaic adhesive film is further improved, and the modified acrylic resin has high weather resistance and can be used for a long time.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.