CN114276554A - High-thixotropy and high-dispersion resin and silver paste, and preparation method and application thereof - Google Patents
High-thixotropy and high-dispersion resin and silver paste, and preparation method and application thereof Download PDFInfo
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- CN114276554A CN114276554A CN202111584657.3A CN202111584657A CN114276554A CN 114276554 A CN114276554 A CN 114276554A CN 202111584657 A CN202111584657 A CN 202111584657A CN 114276554 A CN114276554 A CN 114276554A
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- 229920005989 resin Polymers 0.000 title claims abstract description 136
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- 239000004332 silver Substances 0.000 title claims abstract description 98
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 98
- 239000006185 dispersion Substances 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 239000013008 thixotropic agent Substances 0.000 claims abstract description 50
- 230000009974 thixotropic effect Effects 0.000 claims abstract description 49
- 239000000080 wetting agent Substances 0.000 claims abstract description 48
- 230000008719 thickening Effects 0.000 claims abstract description 39
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims description 38
- 229920000587 hyperbranched polymer Polymers 0.000 claims description 33
- 230000008569 process Effects 0.000 claims description 28
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 21
- -1 fatty acid salt Chemical class 0.000 claims description 21
- 125000000217 alkyl group Chemical group 0.000 claims description 18
- 229920000058 polyacrylate Polymers 0.000 claims description 18
- 239000002904 solvent Substances 0.000 claims description 17
- 239000011521 glass Substances 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 15
- 125000001931 aliphatic group Chemical group 0.000 claims description 14
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- 229920002635 polyurethane Polymers 0.000 claims description 14
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- ZEMPKEQAKRGZGQ-XOQCFJPHSA-N glycerol triricinoleate Natural products CCCCCC[C@@H](O)CC=CCCCCCCCC(=O)OC[C@@H](COC(=O)CCCCCCCC=CC[C@@H](O)CCCCCC)OC(=O)CCCCCCCC=CC[C@H](O)CCCCCC ZEMPKEQAKRGZGQ-XOQCFJPHSA-N 0.000 claims description 4
- 229910019142 PO4 Inorganic materials 0.000 claims description 3
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- IUVCFHHAEHNCFT-INIZCTEOSA-N 2-[(1s)-1-[4-amino-3-(3-fluoro-4-propan-2-yloxyphenyl)pyrazolo[3,4-d]pyrimidin-1-yl]ethyl]-6-fluoro-3-(3-fluorophenyl)chromen-4-one Chemical compound C1=C(F)C(OC(C)C)=CC=C1C(C1=C(N)N=CN=C11)=NN1[C@@H](C)C1=C(C=2C=C(F)C=CC=2)C(=O)C2=CC(F)=CC=C2O1 IUVCFHHAEHNCFT-INIZCTEOSA-N 0.000 description 7
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Images
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- Compositions Of Macromolecular Compounds (AREA)
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Abstract
A high thixotropic and high dispersive resin, silver paste and its preparation method and use, connect multiple side chains on the backbone of its resin, the end section of the side chain has hyperbranched structures; silver paste using the above highly thixotropic and highly dispersed resin; the preparation method is used for preparing the resin and the silver paste; the scheme provides a resin with high thixotropy and high dispersion, and the tail end of a side chain grafted on the main chain of the resin has a hyperbranched structure to form a molecular structure with telechelics, so that the resin has double functions of a thixotropic agent and a dispersing agent. The modified resin used by the silver paste has the effects of dispersing wetting and thickening thixotropy, the problem of mutual interference caused by an additional dispersing wetting agent and a thickening thixotropic agent can be avoided, and the negative effect caused by direct addition of an auxiliary agent for improving thixotropy is effectively solved.
Description
Technical Field
The invention relates to the technical field of silver paste resin, in particular to high-thixotropy and high-dispersion resin, silver paste, a preparation method and application.
Background
The high-temperature silver paste mainly comprises easily-decomposed resin, silver powder, glass powder, a solvent and various auxiliaries, and is widely applied to the fields of photovoltaics, filters, inductors, resistors, capacitors and the like. Generally, a part composed of resin, solvent and auxiliary agent is called as an organic carrier, and the organic carrier is mainly used for endowing the silver paste with various construction properties, such as meeting the process requirements of silk-screen printing, pad printing, spraying, dip coating and the like. The resin used therein needs to be easily thermally (oxygen) decomposed and has a small amount of carbon residue. The silver powder provides a conductive function, while the glass frit provides an adhesive property and assists sintering of the silver powder.
Meanwhile, in the fields of photovoltaic and filter, the thixotropic requirement on the carrier is higher due to the process requirement. For example, photovoltaic silver requires printing of fine lines with high aspect ratio, so that thixotropic requirements on the carrier are high, namely, the carrier needs to be shaped immediately after printing to maintain the aspect ratio. The majority of the processes used in silver on filters are dip coating and spray coating processes. The 2 processes all need to keep the viscosity of the silver paste low, the viscosity of the silver paste is controlled within the range of 1000-10000cps in dip coating, and the viscosity of the silver paste is controlled within the range of <3000cps in spray coating. The low viscosity state causes serious problems of sagging, flowing, feathering and the like, and particularly, the feathering can seriously affect the insertion loss performance of the filter. In this case, it is also required that the silver paste has a very high thixotropic effect.
At present, various thickening agents, thixotropic agents and the like are mainly used for improving the thixotropy of the silver paste, and the thixotropic agents include modified polyethylene waxes, castor oil and derivatives thereof, modified polyamide waxes, modified polyurethanes, modified polyureas, fumed silica, modified clays and the like (since the silver paste is generally a non-aqueous system, all the silver paste is an oily system adaptive auxiliary agent).
Disclosure of Invention
The invention aims to provide a resin with high thixotropy and high dispersion, wherein the tail end of a side chain grafted on the main chain of the resin has a hyperbranched structure to form a molecular structure with telechelic, so that the resin has the double functions of a thixotropic agent and a dispersing agent.
The invention also provides a preparation method of the high-thixotropy and high-dispersion resin, which is used for preparing the high-thixotropy and high-dispersion resin.
The invention also provides application of the resin in preparation of high-thixotropy and high-dispersion silver paste.
The invention also provides a high-thixotropy and high-dispersion silver paste, which can endow the paste with good dispersion wetting and thickening thixotropy effects by using the modified resin, does not generate the problem of mutual interference caused by an additional dispersion wetting agent and an additional thickening thixotropic agent, and effectively solves the negative effect caused by the direct addition of an auxiliary agent for improving the thixotropy.
The invention also provides a preparation method of the silver paste with high thixotropy and high dispersion, which is used for preparing the silver paste.
In order to achieve the purpose, the invention adopts the following technical scheme:
a highly thixotropic and highly dispersible resin having a plurality of side chains attached to a main chain;
the structure of the side chain is as follows:
wherein-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
a represents the terminal group of the hyperbranched polymer and is an active group.
Preferably, the backbone comprises: at least one of cellulose chain segment, polyvinyl acetal chain segment and polyacrylate chain segment, or the combination of two or more of them, or derivatives.
More preferably, the cellulose segments comprise the following segments:
any one of X is aliphatic hydrocarbon group, aromatic hydrocarbon group, HOOCR2-、R1CO-or-H; n is the degree of polymerization; r1And R2Is an alkyl group;
or the polyvinyl acetal chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Y is-COOH or-OH; any one R is aliphatic hydrocarbon group or aromatic hydrocarbon group; p and q are the degree of polymerization;
or the polyacrylate chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Z is-H, -COOH or-OH; any one of R1And/or R2Is aliphatic hydrocarbon group, aromatic hydrocarbon group and-H; p and q are the degree of polymerization.
More preferably, said-M-and/or said-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2At least one of-O-and-NHCOO-.
A method for preparing a highly thixotropic and highly dispersed resin comprising the steps of:
s1: dissolving a main chain resin containing a first active group in a solvent, and heating;
s2: adding side chain resin with at least two terminal groups having second active groups, and carrying out heat preservation reaction; the second active group at one end of the side chain resin reacts with the first active group to graft the side chain resin to the main chain resin; the side chain resin comprises the following chain segments:
-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
s3: adding the hyperbranched polymer with the third active group at the tail end, and carrying out heat preservation reaction; the third active group reacts with the second active group to graft the hyperbranched polymer to the other end of the side chain resin;
the hyperbranched polymer has a structural formula as follows:
a represents the end of the hyperbranched polymer and is a third active group.
More preferably, -M-and/or-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2-at least one of-O-and-NHCOO-; the polymerization degree n is 50 to 200.
Further optimally, the first active group, the second active group and the third active group are-OH, -COOH and-NH2One of epoxy group and-NCO.
Use of a resin in the preparation of a highly thixotropic and highly dispersed silver paste, wherein the resin is one of the highly thixotropic and highly dispersed resins.
A high thixotropic and high dispersion silver paste comprises the following components in parts by weight: 20-100 parts of silver powder, less than 10 parts of glass powder, less than 5 parts of auxiliary agent, less than 10 parts of resin and solvent;
the resin is a highly thixotropic and highly dispersed resin as described above.
More preferably, the auxiliary agent comprises: at least one of a dispersing wetting agent, a thickening thixotropic agent, an inorganic filler and/or an organic filler;
the dispersing wetting agent comprises: at least one of polyacrylate dispersing wetting agent or its derivative, fatty acid salt dispersing wetting agent or its derivative, organic phosphate dispersing wetting agent or its derivative, polyurethane dispersing wetting agent or its derivative and polyester dispersing wetting agent or its derivative;
the thickened thixotropic agent comprises: at least one of castor oil thickening thixotropic agent or derivatives thereof, modified polyamide thickening thixotropic agent or derivatives thereof and modified polyurethane thickening thixotropic agent or derivatives thereof.
A preparation method of high thixotropic and high dispersion silver paste is used for preparing the high thixotropic and high dispersion silver paste, and comprises the following steps:
1) dissolving resin in solvent in proportion, heating to 60-120 deg.C, dissolving, and cooling to room temperature;
2) adding glass powder, silver powder and an auxiliary agent in proportion, and stirring at a low speed of 60-300 rpm; then continuously stirring at medium-high speed of 300-;
3) rolling the silver paste obtained in the step 2) by using a rolling mill;
4) uniformly mixing the silver paste obtained in the step 3) by using a dispersion machine, wherein the rotating speed is 60-600rpm at medium and low speeds, so as to prepare the electrode silver paste;
performing step 5) and step 6) as required
5) Filtering;
6) and synchronously adding a diluent in the slurry homogenizing process for dilution treatment.
The technical scheme provided by the invention can have the following beneficial effects:
1. the scheme provides a resin with high thixotropy and high dispersion, the tail segment grafted by the main chain of the resin has a long chain with a hyperbranched structure, a molecular structure with a telechelic is formed, the resin has double functions of a thixotropic agent and a dispersing agent, and the resin is used for preparing silver paste with high thixotropy and high dispersion, for example, the resin can be applied to special scenes such as front silver paste and filter silver paste, and the use process requirements of the resin are met.
2. The silver paste of the scheme can have good dispersion wetting and thickening thixotropic effects by adopting the modified resin, the problem of mutual interference caused by an additional dispersion wetting agent and an additional thickening thixotropic agent can not be generated, and the negative effect caused by the direct addition of an auxiliary agent for improving the thixotropy is effectively solved.
Drawings
FIG. 1 is a schematic structural view of a highly thixotropic and highly dispersed resin.
FIG. 2 is a schematic diagram showing the reaction of a main chain with a side chain;
FIG. 3 is a schematic representation of a side-chain grafted hyperbranched polymer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, 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.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The technical solution of the present solution is further explained by the following embodiments with reference to the accompanying drawings.
A highly thixotropic and highly dispersible resin having a plurality of side chains attached to a main chain;
the structure of the side chain is as follows:
wherein-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
m-may be as practical; for example R1Is CH2CH2when-M-is-OR1-or-O-CH2CH2-CO-; it is also possible to combine two different-M-groups, for example combination 1 having the formula-O-CH2CH2-CO-with the formula of combination 2 being-OR1-, combination 2 and combination 1 constitute-O-CH2CH2COOR1-; here, the term "derivative" means that other hetero groups such as an alkyl group, a halogen group, an epoxy group, a hydroxyl group, a carboxyl group, a siloxy group and the like are added to the group-M-via a chemical bond. Meanwhile, the polymerization degree of the side chain can be selected according to the actual choice, but is preferably selected from 10 to 1000, more preferably from 50 to 200, and most preferably from 50 to 100. The molecular chain is too short, at which point the short arm length is not conducive to improved or less favorable interaction probability at low resin concentrations. The molecular chain is too long, so that the problems of low reactivity, preferential internal interaction and the like can be caused;
preferably, the intermediate branched arm may be at least one of a polyoxyethylene segment, a polyoxypropylene segment, a polyurethane segment, a polyester segment, a polyacrylate segment, or a combination of two or more thereof, or a derivative;
a represents the terminal group of the hyperbranched polymer and is an active group. Reactive groups such as-OH, -COOH, -NH2And the like. The hyperbranched polymer selected may be of polyoxyethylene, polyoxypropylene, polyurethane, polyester or even polyacrylate construction, but from the viewpoint of the need to decompose residual carbon, hyperbranched polymers of polyoxyethylene, polyoxypropylene, polyester and polyacrylate construction are preferred. From the viewpoint of the terminal functional group of the hyperbranched polymer, hydroxyl group, carboxyl group and amino group are all of the types that can be selected, but from the viewpoint of decreasing hydrophilicity, it may be preferable to block a part of the functional group at the terminal.
The scheme provides a resin with high thixotropy and high dispersion, the end of a side chain grafted on the main chain of the resin has a hyperbranched structure, a molecular structure with a telechelic is formed, the resin has double functions of a thixotropic agent and a dispersing agent, and the resin is used for preparing silver paste with high thixotropy and high dispersion, for example, the resin can be applied to special scenes such as front silver paste and filter silver paste, and the use process requirements of the resin are met.
Specifically, in order to solve the problem of negative effects caused by direct addition of an auxiliary agent for improving thixotropy and limit application in special fields such as photovoltaic positive silver and filter silver paste, the scheme grafts a long chain with a hyperbranched structure at the tail section on the resin containing a specific functional group to form a molecular structure with telechelics, so that high thixotropy of the resin under extremely low concentration is realized.
Generally, resins dissolved in organic solvents form a thixotropic structure, relying on the interaction between the resins: the intensity of the interaction and the density of the interaction points; the interaction is strong enough to be gelled when the interaction point density is higher than 2 (see the polymer gel theory in polymer physics), and the conductive paste cannot be used in the conductive paste, so that the fluidity required by use cannot be met. When the interaction is not strong enough, the interaction between the molecular chains brings about a stronger thixotropic effect. When the resin concentration is extremely low, the interaction points between the molecular chains are relatively sparse (see the polymer gel theory in polymer physics), which is not favorable for obtaining strong thixotropic effect. In application scenes such as front silver and filter silver paste, the resin consumption is not large, and some resin consumption is even as low as 0.1%.
To solve such problems, we improve the interaction probability between resins by designing long side chains with telechelic structures; meanwhile, the modified polyvinyl chloride resin is used as a dispersing agent of the inorganic filler, the probability of interaction is improved by using the inorganic filler as a bridge, and the thixotropic effect is further improved, as shown in the figure. In FIG. 1, a is the main chain, b is the side chain, and c is the hyperbranched structure; d is a particle, such as glass frit, silver powder, or an additive; the terminal of the hyperbranched structure is provided with functional groups such as-NH 2, -COOH, -OH and the like, the whole side chain is of a telechelic structure, and the collision probability of the telechelic structure under low concentration can be improved.
And in the prior art, small molecule type dispersants are widely used, however, due to lack of long-range linkage of hyperbranched structures, there is no effect on thixotropic enhancement. The long side chain with the telechelic structure in the patent connects the small molecules, so that the double effects are achieved, the use of auxiliaries can be reduced, and a larger operation space is provided for the formula.
Preferably, the backbone comprises: at least one of cellulose chain segment, polyvinyl acetal chain segment and polyacrylate chain segment, or the combination of two or more of them, or derivatives.
The cellulose mainly comprises beta-D-glucopyranosyl with a simple molecular formula of (C)6H10O5)nThe cellulose chain segment of the scheme is based on the cellulose structure, and a part of groups such as aliphatic hydrocarbon group, aromatic hydrocarbon group, -H, -OH, -COOH and the like are used for replacing-H or-OH of the cellulose structure to form a modified cellulose chain segment。
The main chain of the scheme preferably uses a cellulose chain segment, a polyvinyl acetal chain segment and a polyacrylate chain segment, which have active groups, such as hydroxyl, carboxyl functional groups and the like, are also suitable for high-temperature silver paste, and are not easy to accumulate residual carbon during decomposition. Although such resins are gel or gel-like structures that can form interactions in solvents, the presence of a large number of hydrogen bonds results in polymers that are strongly hydrophilic, and their storage and use properties are disadvantageous.
More preferably, the cellulose segments comprise the following segments:
any one of X is aliphatic hydrocarbon group, aromatic hydrocarbon group, HOOCR2-、R1CO-or-H; n is the degree of polymerization; r1And R2Is an alkyl group;
when X is aliphatic hydrocarbon group, aromatic hydrocarbon group, it has aliphatic hydrocarbon group or aromatic hydrocarbon group, or chain group of derivative; preferably, X may be ethyl, (iso) propyl, (iso) butyl; x is-OH or HOOCR2When-is-it is possible to provide sites for side chain attachment.
Or the polyvinyl acetal chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Y is-COOH or-OH; any one R is aliphatic hydrocarbon group or aromatic hydrocarbon group; p and q are the degree of polymerization;
when R is an aliphatic or aromatic hydrocarbon group, it has an aliphatic or aromatic hydrocarbon group or a chain group of a derivative, for example, a methyl group, an ethyl group, an (iso) butyl group, a benzene ring, etc.; preferably, R is-CH2CH2CH3At this time, the masterThe chain is polyvinyl butyral, is convenient to prepare and can be prepared by condensing polyvinyl alcohol and butyraldehyde under the catalysis of acid; y is-OOCCH3or-OH, a site for side chain attachment may be provided.
Or the polyacrylate chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Z is-H, -COOH or-OH; any one of R1And/or R2Is aliphatic hydrocarbon group, aromatic hydrocarbon group and-H; p and q are the degree of polymerization.
When Z is-COOH or-OH, it may provide a site for attachment of a side chain. R1When the alkyl group is aliphatic alkyl or aromatic alkyl, the alkyl group has aliphatic alkyl or aromatic alkyl or chain group of derivative; preferably, R1Examples thereof include methyl, ethyl, (iso) butyl, (iso) pentyl and (iso) hexyl, and benzene rings.
More preferably, said-M-and/or said-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2At least one of-O-and-NHCOO-.
the-M-segment and the hyperbranched polymer-N-of the straight chain segment in the side chain can be at least one of a polyoxyethylene segment, a polyoxypropylene segment, a polyurethane segment, a polyester segment and a polyacrylate segment, or the combination of more than two of the polyoxyethylene segment, the polyoxypropylene segment, the polyurethane segment, the polyester segment and the polyacrylate segment, or derivatives; the segments chosen for-M-and-N-may be different or identical, for example-M-is a polyoxyethylene segment, -N-is a polyurethane segment; or-M-is a polyoxypropylene segment and-N-is a polyacrylate segment.
Preferably, the-M-segment and the-N-segment adopt the same chain segment, and the overall regularity of the molecular chain is good, so as to further improve the thixotropy and the dispersity.
A method for preparing a highly thixotropic and highly dispersed resin comprising the steps of:
s1: dissolving a main chain resin containing a first active group in a solvent, and heating;
s2: adding side chain resin with at least two terminal groups having second active groups, and carrying out heat preservation reaction; the second active group at one end of the side chain resin reacts with the first active group to graft the side chain resin to the main chain resin; the side chain resin comprises the following chain segments:
-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
s3: adding the hyperbranched polymer with the third active group at the tail end, and carrying out heat preservation reaction; the third active group reacts with the second active group to graft the hyperbranched polymer to the other end of the side chain resin; the hyperbranched polymer selected may be of polyoxyethylene, polyoxypropylene, polyurethane, polyester or even polyacrylate construction, but from the viewpoint of the need to decompose residual carbon, hyperbranched polymers of polyoxyethylene, polyoxypropylene, polyester and polyacrylate construction are preferred. From the viewpoint of the terminal functional group of the hyperbranched polymer, hydroxyl group, carboxyl group and amino group are all of the types that can be selected, but from the viewpoint of decreasing hydrophilicity, a part of the functional group may be blocked at the terminal.
The hyperbranched polymer has a structural formula as follows:
a represents the end of the hyperbranched polymer and is a third active group.
More preferably, -M-and/or-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2-at least one of-O-and-NHCOO-; the polymerization degree n is 50 to 200.
The polymerization degree can be determined according to actual conditions, the polymerization degree n is 50-200, the main chain and the hyperbranched structure are effectively separated by the side chain, the steric hindrance of the molecular chain is moderate, and the final thixotropy and the dispersibility of the product are optimal.
More preferably, the first, second and third active groups are-OH, -COOH, -NH2One of epoxy group and-NCO.
The second active groups are respectively positioned at two ends of the side chain and are used for reacting with the first active groups, and the side chain is connected to the main chain; meanwhile, the second active group also needs to react with the third active group to connect the side chain with the hyperbranched polymer, and further connect the main chain with the hyperbranched polymer. The epoxy group is preferably selected, and the epoxy group has better reaction capability and is easy to control, so that the reaction process of the side chain can be controlled.
Use of a resin in the preparation of a highly thixotropic and highly dispersed silver paste, wherein the resin is one of the highly thixotropic and highly dispersed resins.
A high thixotropic and high dispersion silver paste comprises the following components in parts by weight: 20-100 parts of silver powder, less than 10 parts of glass powder, less than 5 parts of auxiliary agent, less than 10 parts of resin and solvent;
the resin is a highly thixotropic and highly dispersed resin as described above.
The content of the solvent may be determined in accordance with the actual application, and is preferably within 30 parts, more preferably within 20 parts.
The resin of the scheme has dispersibility and thixotropy, and an auxiliary agent with a dispersing wetting agent is preferably used, so that the resin can be effectively matched with the scheme, and the dispersion wettability is improved; meanwhile, an auxiliary agent with a thickening thixotropic agent is preferably used, so that the resin can be effectively matched to improve the thixotropy. The dispersing wetting agent and the thickening thixotropic agent are added under the modified resin, so that the problem of mutual interference between the silver powder and the dispersing wetting agent is avoided, the using effect of the added dispersing wetting agent is not influenced, and the negative effect caused by the direct addition of the thixotropic additive is effectively solved.
More preferably, the auxiliary agent comprises: at least one of a dispersing wetting agent, a thickening thixotropic agent, an inorganic filler and/or an organic filler;
the dispersing wetting agent comprises: at least one of polyacrylate dispersing wetting agent or its derivative, fatty acid salt dispersing wetting agent or its derivative, organic phosphate dispersing wetting agent or its derivative, polyurethane dispersing wetting agent or its derivative and polyester dispersing wetting agent or its derivative;
of course, the auxiliaries mentioned above can also be used as dispersing wetting agents which are not mentioned, for example modified polyamide waxes, modified polyurethanes, modified polyureas. However, since many of these thixotropic agents are in a gel state, large particles may be present in the paste, which may interfere with fine line printing, and the effect is poor relative to the preferred dispersing wetting agent of the present scheme.
The thickened thixotropic agent comprises: at least one of castor oil thickening thixotropic agent or derivatives thereof, modified polyamide thickening thixotropic agent or derivatives thereof and modified polyurethane thickening thixotropic agent or derivatives thereof.
Of course, the additives may also be used as thickening thixotropic agents not mentioned above, such as fumed silica, thixotropic agents of modified clay type, etc., but since such inorganic substances are not decomposable at high temperatures, they remain to easily interact with the glass at high temperatures, interfere with the glass, and affect the electromagnetic properties of the silver layer to some extent, the effect being inferior to that of the thickening thixotropic agents preferred in the present embodiment.
The resin has dispersibility and thixotropy, and an auxiliary agent with a dispersing wetting agent is preferably used, so that the resin can be effectively matched with the scheme, and the dispersing wettability is improved; meanwhile, an auxiliary agent with a thickening thixotropic agent is preferably used, so that the resin can be effectively matched to improve the thixotropy.
The auxiliary agent can also comprise other components which can be added by silver paste, such as defoaming agent, silicone oil, wax powder and the like.
A preparation method of high thixotropic and high dispersion silver paste is used for preparing the high thixotropic and high dispersion silver paste, and comprises the following steps:
1) dissolving resin in a solvent according to a proportion, heating to 60-120 ℃, dissolving for 4-12h, and then cooling to room temperature for later use;
2) adding glass powder, silver powder and an auxiliary agent according to a proportion, and stirring at a low speed of 60-300 rpm; stirring at medium-high speed of 300 and 1500 rpm;
3) rolling the silver paste obtained in the step 2) by using a rolling mill; the specific process usually comprises 1-3 times of large-gap rolling, 1-3 times of middle-gap rolling and 1-3 times of small-gap rolling;
4) uniformly mixing the silver paste obtained in the step 3) by using a dispersion machine, wherein the rotating speed is 60-600rpm at medium and low speeds, so as to prepare the electrode silver paste;
performing step 5) and step 6) as required
5) Filtering;
6) and synchronously adding a diluent in the slurry homogenizing process for dilution treatment. The diluent is complemented according to the solvent proportion requirement of the final product.
And (3) performance testing:
when the embodiment is the silver paste of the dip-coating type filter, the performance test steps of the thixotropic index are as follows:
the test adopts an MCR-102 type rheometer, selects a CP-25 type rotor, and sets the temperature at 25 ℃; placing a sample to be tested on a testing platform of a rheometer according to requirements, and carrying out measurement according to program operation; for dip-coated filter silver paste, shear rate 20-sIs a very effective reference value for the use of the process. Thus, we set shear rate 2 using a constant shear rate test procedure-sOr 20-sThe shearing time is 300s, and the value is read after the shearing viscosity is stable. For dip-coated filter silver paste, shear rate 2 is used for thixotropic index-sViscosity and shear rate of 20-sThe ratio of viscosity of (a).
When the embodiment is spraying type filter silver paste, the performance test steps of the thixotropic index are as follows:
the test adopts an MCR-102 type rheometer, selects a CP-25 type rotor, and sets the temperature at 25 ℃; placing a sample to be tested on a testing platform of a rheometer according to requirements, and carrying out measurement according to program operation; for dip-coated filter silver paste, shear rate 10-sIs a very effective reference value for the use of the process. Thus, we set shear rate 1 using a constant shear rate test procedure-sOr 10-sThe shearing time is 300s, and the value is read after the shearing viscosity is stable. For dip-coated filter silver paste, shear rate for thixotropic index of 1-sViscosity and shear rate of 10-sThe ratio of viscosity of (a).
For positive silver pastes, the test procedure for the ultimate width of the fine line print is:
a printing sample preparation process: the printing machine is a BACCINI solar cell printing system, and the printing test screen parameters are as follows: 520 meshes/11 wire diameter-17N tension-14/18/22 micron fine grid wire width-6 micron film thickness-PI film without net knot. After drying, the line width was measured using a 3D optical microscope.
Example A:
1) dissolving ethyl cellulose containing aliphatic hydroxyl in diethylene glycol butyl ether acetate, terpineol and Solvesso200, and heating to 100 ℃;
2) the selected grafted side chain has the following structure: epoxy groups are contained at two ends, and the middle chain segment is selected
n is 200. The dosage of the grafting side chain is 1: 10; adding grafted side chains into the solution obtained in the step 1) in proportion, keeping the temperature at 100 ℃, and reacting for 24 hours;
3) adding hyperbranched polymer with the same amount as that of the grafted side chain, wherein the tail segment of the hyperbranched polymer contains-COOH groups, and the middle branched arm is selected
n is 50; keeping the temperature at 100 ℃ after adding, and reacting for 15h to obtain the resin with high thixotropy and high dispersion.
After the modified resin is obtained, silver paste can be prepared according to the following process:
1) dissolving the modified resin in diethylene glycol monobutyl ether acetate, terpineol and Solvesso200 according to a certain proportion, adding the modified resin, heating to 100 ℃, dissolving for 10 hours, and then cooling to room temperature for later use;
2) then adding the glass powder, the silver powder and the auxiliary agent in proportion one by one, specifically as shown in the table, stirring for 60min at low speed (the rotating speed is set at 250rpm) by a planetary stirrer, and then stirring for 180min at medium-high speed (800 rpm); at this time, the method can be used in the next process. The auxiliary agent comprises a dispersing wetting agent, a thickening thixotropic agent and other auxiliary agents;
3) rolling the silver paste obtained in the step 2) by using a three-roll mill, wherein the specific process comprises 3 times of large-gap rolling, 3 times of middle-gap rolling and 3 times of small-gap rolling;
4) uniformly mixing the silver paste obtained in the step 3) by using a planetary disperser again, wherein the rotating speed is medium-low speed (300 rpm);
5) and synchronously adding a diluent in the process of homogenizing the silver paste to dilute the silver paste to prepare the dip-coated filter silver paste. The diluent is complemented according to the solvent proportion requirement of the final product.
Example a was tested for performance as in table 1.
TABLE 1 formulation and Performance comparison of example A
Description of the drawings:
1. as can be seen from the comparison of example A1 with comparative example A1, comparative example A1 uses an ethyl cellulose resin which is unmodified; although the dispersion wetting agent and the thickening thixotropic agent are also added when the ethyl cellulose is applied to the silver paste, the added dispersion wetting agent and the thickening thixotropic agent cannot form a stable thixotropic network in a medium-low viscosity system due to the small molecules or the aggregates thereof, and the use effect is limited; the final result shows that although the viscosity of the silver paste can be controlled to be 1000-10000cps in dip coating, the thixotropic effect of the silver paste is low and is only 3.3. The embodiment A1 modifies the ethyl cellulose, introduces a side chain into the ethyl cellulose, and connects the hyperbranched polymer through the side chain to form a molecular structure with a telechelic, so that the modified ethyl cellulose has double functions of a thixotropic agent and a dispersing agent, meets the viscosity requirement and has high thixotropy, and the resin modification method in the scheme is feasible for solving the problem that the effect of using a small molecular thixotropic agent in a medium-low viscosity system is poor.
2. As can be seen by comparing example A2 with comparative example A1, example A2 does not contain a dispersing wetting agent and a thickening thixotropic agent; the comparative example A1 is added with a dispersing wetting agent and a thickening thixotropic agent, and although the comparative example A1 has a viscosity similar to that of the example A2, the thixotropic index of the example A2 is higher than that of the comparative example A1 under the condition that the dispersing wetting agent and the thickening thixotropic agent are not added in the example A2, which shows that the modified resin of the scheme can be independently used under the condition that the dispersing wetting agent and the thickening thixotropic agent are not added, and the double functions of enabling the silver paste to have high thixotropy and high dispersibility under the condition that the dispersing wetting agent and the thickening thixotropic agent are not added can be realized.
3. Comparing example A2 with example A3 and example A4, it can be seen that example A3 adds the thickening thixotropic agent, and no dispersing wetting agent is added, so that the thixotropy of the resin becomes thick, the thixotropy is improved, and the viscosity is still in a better range, which indicates that the modified resin of the scheme can be matched with the thickening thixotropic agent, and further indicates that the addition of the thickening thixotropic agent with the modified resin does not cause the problem that the silver powder and the thixotropic agent interfere with each other, and the use effect of the added thickening thixotropic agent is not influenced.
In the embodiment a4, the dispersing wetting agent is added, and the thickening thixotropic agent is not added, so that the dispersibility of the resin is improved, the viscosity is reduced, but the silver paste still has high thixotropy, which indicates that the modified resin of the scheme can be matched with the dispersing wetting agent, and further indicates that the problem of mutual interference between the silver powder and the dispersing wetting agent is not caused by adding the dispersing wetting agent in the presence of the modified resin, and the use effect of the added dispersing wetting agent is not affected.
Example B:
1) dissolving polyvinyl acetal resin containing aliphatic hydroxyl in terpineol, diethylene glycol ethyl ether acetate and diethylene glycol butyl ether acetate, and heating to 100 ℃; the polyvinyl acetal resin is prepared by randomly copolymerizing a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
r is-C3H7Part of Y is hydroxyl and part of Y is-OOCCH3。
2) The selected grafted side chain has the following structure: epoxy groups are contained at two ends, and the middle chain segment is selected
Group (2)And n is 50. The dosage of the grafting side chain is respectively added into 1: 8, or more; adding grafted side chains into the solution obtained in the step 1) in proportion, and reacting for 10 hours at 100 ℃;
3) adding hyperbranched polymer with the same amount as that of the grafted side chain, wherein the tail segment of the hyperbranched polymer contains-OH, and the intermediate branched arm is selected from (-OCR)1COO-R2-O-)nN is 100; keeping the temperature at 100 ℃ after adding, and reacting for 4 hours to obtain the resin with high thixotropy and high dispersion.
After the modified resin is obtained, silver paste can be prepared according to the following process:
1) dissolving the modified resin in diethylene glycol ethyl ether acetate, terpineol and diethylene glycol butyl ether acetate according to a certain proportion, adding the modified resin, heating to 100 ℃, dissolving for 4 hours, and then cooling to room temperature for later use;
2) then adding the glass powder, the silver powder and the auxiliary agent in proportion one by one, specifically as shown in Table 2, stirring for 30min at low speed (the rotating speed is set at 60rpm) by a planetary stirrer, and then stirring for 60min at medium-high speed (300 rpm); at this time, the method can be used in the next process. The auxiliary agent comprises a dispersing wetting agent, a thickening thixotropic agent and fumed silica;
3) rolling the silver paste obtained in the step 2) by using a three-roll mill, wherein the specific process is 2 times of large-gap rolling, 2 times of middle-gap rolling and 2 times of small-gap rolling;
4) uniformly mixing the silver paste obtained in the step 3) by using a planetary disperser again, wherein the rotating speed is medium-low speed (400 rpm);
5) and synchronously adding a diluent in the process of homogenizing the slurry to dilute, thereby preparing the spraying type filter silver slurry. The diluent is complemented according to the solvent proportion requirement of the final product.
Example B was tested for performance as in table 2.
TABLE 2 formulation and Performance comparison of example B
Description of the drawings:
1. as can be seen from the comparison of example B1 with comparative example B1, the resin used in comparative example B1 is a polyvinyl acetal resin which is not modified, and the silver paste finally obtained has low thixotropy and a thixotropy index of 1.5, although the viscosity can be kept low. The resin used in example B1 is a modified polyvinyl acetal resin, and the thixotropic index thereof can reach 6.7, which indicates that the modification of the polyvinyl acetal resin can effectively maintain low viscosity and high thixotropy of the silver paste.
2. As can be seen from the comparison of example B1 with example B2, example B2 has no fumed silica added, whereas example B1 has fumed silica added. The polyvinyl acetal resin effectively bridges and thickens fumed silica through a side chain grafted hyperbranched structure, and further improves the thixotropic effect; therefore, the modified resin can be selectively added with the inorganic filler, and the inorganic filler is used for bridging, so that the thixotropy can be effectively improved.
Example C:
1) dissolving ethyl cellulose containing aliphatic carboxyl in terpineol, diethylene glycol butyl ether acetate and Solvesso200, and heating to 60 ℃;
2) the selected grafted side chain has the following structure: both ends contain hydroxyl, and the middle chain segment is-CH2CHCOOR1-, R1 is-CH2CH3And n is 100. The dosage of the grafting side chain is 1: 7; adding grafted side chains into the solution obtained in the step 1) in proportion, and reacting for 24 hours while keeping the temperature at 120 ℃;
3) adding hyperbranched polymer with the same mass as that of the grafted side chain, wherein the tail end of the hyperbranched polymer contains carboxyl, and the middle branched arm is (-O-RCO-) n, wherein n is 100; keeping the temperature at 120 ℃ after adding, and reacting for 20 hours to obtain the resin with high thixotropy and high dispersion.
After the modified resin is obtained, silver paste can be prepared according to the following process:
1) dissolving the modified resin in terpineol, diethylene glycol monobutyl ether acetate and Solvesso200 in proportion, adding the modified resin, heating to 80 ℃, dissolving for 5 hours, and then cooling to room temperature for later use;
2) then adding the glass powder, the silver powder and the auxiliary agent in proportion one by one, specifically as shown in Table 3, stirring for 30min at low speed (the rotating speed is set at 200rpm) by a planetary stirrer, and then stirring for 120min at medium-high speed (500 rpm); at this time, the method can be used in the next process. The auxiliary agent comprises a dispersing wetting agent, a thickening thixotropic agent and other auxiliary agents;
3) rolling the silver paste obtained in the step 2) by using a three-roll mill, wherein the specific process is usually 1 large-gap rolling, 2 middle-gap rolling and 3 small-gap rolling;
4) uniformly mixing the silver paste obtained in the step 3) by using a planetary disperser again, wherein the rotating speed is medium-low speed (300 rpm);
5) and further filtering to obtain the photovoltaic positive silver paste.
The above example C was tested for performance as shown in table 3;
table 3 formulation and Performance comparison of example C
Description of the drawings:
as can be seen from the comparison of example C1 with comparative example C1, the resin used in comparative example C1 is not modified and is only a single ethyl cellulose, resulting in a larger fine line printing limit width; compared with the silver paste of the filter, the silver paste of the front electrode of the crystalline silicon solar cell is provided by the embodiment, the thixotropy and the printing fluidity of the front silver are really embodied by the limit width of fine line printing in use, and the comprehensive performance is embodied. In order to pursue higher battery conversion efficiency, the smaller the width of the photovoltaic positive silver fine grid, the larger the light receiving area of the battery is, and therefore the conversion efficiency of the battery is improved. The fine line ultimate print width of comparative example C1 was 24-26 μm. And the embodiment C1 modifies the ethyl cellulose, so that the width of 18-20 mu m can be kept, the comprehensive performance is good and is superior to that of unmodified ethyl cellulose, and the fine line printing performance of the positive silver paste can be improved by modifying the ethyl cellulose.
Example D:
1) dissolving amino-containing polyacrylate resin in diethylene glycol monobutyl ether acetate, terpineol and Solvesso200, and heating to 100 ℃; the polyacrylate resin is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 is
The chain 2 is
Z is-OH, R1Is methyl, R2Is ethyl.
2) The selected grafted side chain has the following structure: the two ends contain carboxyl, the middle chain is selected from (CH)3)CH2O) n, n is 100. The dosage of the grafting side chain is 1: 6 or more; adding grafted side chains into the solution obtained in the step 1) in proportion, keeping the temperature at 100 ℃, and reacting for 17 hours;
3) adding hyperbranched polymer with the same amount of grafted side chain and the end containing-NH2The group, the middle branch arm, is selected from (CH)3)CH2O) n, n is 50; keeping the temperature at 100 ℃ after adding, and reacting for 4 hours to obtain the resin with high thixotropy and high dispersion.
Example E:
1) dissolving hydroxyl-containing ethyl cellulose resin and polyacrylate resin in diethylene glycol butyl ether acetate, terpineol and Solvesso200, and heating to 100 ℃;
the polyacrylate resin is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 is
The chain 2 is
Z is-OH, R1Is methyl, R2Is propyl.
2) Selected graftsThe side chain has the following structure: two ends contain carboxyl, and the middle chain segment is selected
n is 50. The dosage of the grafting side chain is 1: 8, or more; adding grafted side chains into the solution obtained in the step 1) in proportion, keeping the temperature at 100 ℃, and reacting for 17 hours;
3) adding hyperbranched polymer with the same amount as that of the grafted side chain, wherein the tail end contains hydroxyl, and the middle branched arm is selected
n is 100; keeping the temperature at 100 ℃ after adding, and reacting for 4 hours to obtain the resin with high thixotropy and high dispersion.
After the modified resins of examples D and E are obtained, silver paste can be prepared according to the following process:
1) dissolving the modified resin in diethylene glycol monobutyl ether acetate, terpineol and Solvesso200 according to a certain proportion, adding the modified resin, heating to 100 ℃, dissolving for 10 hours, and then cooling to room temperature for later use;
2) then adding the glass powder, the silver powder and the auxiliary agent in proportion one by one, specifically as shown in Table 4, stirring for 50min at low speed (the rotating speed is set at 200rpm) by a planetary stirrer, and then stirring for 120min at medium-high speed (600 rpm); at this time, the method can be used in the next process. The auxiliary agent comprises a dispersing wetting agent, a thickening thixotropic agent and other auxiliary agents;
3) rolling the silver paste obtained in the step 2) by using a three-roll mill, wherein the specific process is usually 1 large-gap rolling, 2 middle-gap rolling and 2 small-gap rolling;
4) uniformly mixing the silver paste obtained in the step 3) by using a planetary disperser again, wherein the rotating speed is medium-low speed (500 rpm);
5) and synchronously adding a diluent in the process of homogenizing the silver paste to dilute the silver paste to prepare the dip-coated filter silver paste. The diluent is complemented according to the solvent proportion requirement of the final product.
Examples E and D were tested for performance as in Table 4.
TABLE 4 formulation and comparison of Properties for examples D and E
The technical principle of the present solution is described above with reference to specific embodiments. These descriptions are only used to explain the principles of the present solution and should not be interpreted in any way as limiting the scope of the present solution. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present solution without any inventive effort, which would fall within the scope of the present solution.
Claims (11)
1. A highly thixotropic and highly dispersed resin characterized by having a plurality of side chains attached to a main chain;
the structure of the side chain is as follows:
wherein-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
a represents the terminal group of the hyperbranched polymer and is an active group.
2. A highly thixotropic and highly dispersed resin according to claim 1 wherein the backbone comprises: at least one of cellulose chain segment, polyvinyl acetal chain segment and polyacrylate chain segment, or the combination of two or more of them, or derivatives.
3. A highly thixotropic and highly dispersed resin according to claim 2 wherein the cellulose segments comprise the following segments:
any one of X is aliphatic hydrocarbon group, aromatic hydrocarbon group, HOOCR2-、R1CO-or-H; n is the degree of polymerization; r1And R2Is an alkyl group;
or the polyvinyl acetal chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Y is-COOH or-OH; any one R is aliphatic hydrocarbon group or aromatic hydrocarbon group; p and q are the degree of polymerization;
or the polyacrylate chain segment is prepared by random copolymerization of a chain 1 and a chain 2;
the chain 1 comprises:
the chain 2 comprises:
any one Z is-H, -COOH or-OH; any one of R1And/or R2Is aliphatic hydrocarbon group, aromatic hydrocarbon group and-H; p and q are the degree of polymerization.
4. A highly thixotropic and highly dispersed resin according to any one of claims 1 to 3 wherein the-M-and/or the-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2At least one of-O-and-NHCOO-.
5. A method for preparing a highly thixotropic and highly dispersed resin, comprising the steps of:
s1: dissolving a main chain resin containing a first active group in a solvent, and heating;
s2: adding side chain resin with at least two terminal groups having second active groups, and carrying out heat preservation reaction; the second active group at one end of the side chain resin reacts with the first active group to graft the side chain resin to the main chain resin; the side chain resin comprises the following chain segments:
-M-comprises-OR1-、-R1OR2-、-CO-、-R1At least one of CO-, -COO-, -NHCOO-, or a combination of two or more of the same, or a derivative structure of-M-; n is the degree of polymerization; r1And R2Is an alkyl group;
s3: adding the hyperbranched polymer with the third active group at the tail end, and carrying out heat preservation reaction; the third active group reacts with the second active group to graft the hyperbranched polymer to the other end of the side chain resin;
the hyperbranched polymer has a structural formula as follows:
a represents the end of the hyperbranched polymer and is a third active group.
6. The method of claim 5, wherein-M-and/or-N-is-OCH2CH2-、-OCH(CH3)CH2-、-CH(CH3)CH2O-、-CH2CHCOOR1-、-CH2C(CH3)COOR-、-O-RCO-、-OCR1CO-O-R2-at least one of-O-and-NHCOO-; the polymerization degree n is 50 to 200.
7. The method of claim 5, wherein the first reactive group, the second reactive group, and the third reactive group are selected from the group consisting ofThe three active groups are-OH, -COOH and-NH2One of epoxy group and-NCO.
8. Use of a resin in the preparation of a highly thixotropic and highly dispersed silver paste, wherein the resin is a highly thixotropic and highly dispersed resin according to any one of claims 1 to 4.
9. The silver paste with high thixotropy and high dispersion is characterized by comprising the following components in parts by weight: 20-100 parts of silver powder, less than 10 parts of glass powder, less than 5 parts of auxiliary agent, less than 10 parts of resin and solvent;
the resin is a highly thixotropic and highly dispersed resin according to any one of claims 1 to 4.
10. The highly thixotropic and highly dispersible silver paste of claim 9, wherein the additive comprises: at least one of a dispersing wetting agent, a thickening thixotropic agent, an inorganic filler and/or an organic filler;
the dispersing wetting agent comprises: at least one of polyacrylate dispersing wetting agent or its derivative, fatty acid salt dispersing wetting agent or its derivative, organic phosphate dispersing wetting agent or its derivative, polyurethane dispersing wetting agent or its derivative and polyester dispersing wetting agent or its derivative;
the thickened thixotropic agent comprises: at least one of castor oil thickening thixotropic agent or derivatives thereof, modified polyamide thickening thixotropic agent or derivatives thereof and modified polyurethane thickening thixotropic agent or derivatives thereof.
11. A method for preparing a highly thixotropic and highly dispersed silver paste, which is used for preparing the highly thixotropic and highly dispersed silver paste of any one of claims 9 to 10, and comprises the following steps:
1) dissolving resin in solvent in proportion, heating to 60-120 deg.C, dissolving, and cooling to room temperature;
2) adding glass powder, silver powder and an auxiliary agent in proportion, and stirring at a low speed of 60-300 rpm; then continuously stirring at medium-high speed of 300-;
3) rolling the silver paste obtained in the step 2) by using a rolling mill;
4) uniformly mixing the silver paste obtained in the step 3) by using a dispersion machine, wherein the rotating speed is 60-600rpm at medium and low speeds, so as to prepare the electrode silver paste;
performing step 5) and step 6) as required
5) Filtering;
6) and synchronously adding a diluent in the slurry homogenizing process for dilution treatment.
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