UV high-shear blue film adhesive for lithium battery cell insulation protection and preparation method of UV high-shear blue film adhesive

Abstract

The invention discloses a UV high-shear blue film adhesive for lithium battery cell insulation protection and a preparation method of the UV high-shear blue film adhesive in the technical field of lithium battery blue film adhesives, and the UV high-shear blue film adhesive for lithium battery cell insulation protection comprises modified polyacrylate main adhesive, saturated polyester resin, epoxy resin, a silane coupling agent, a photoinitiator composition and a solvent, the modified polyacrylate main adhesive comprises ethyl acetate, acrylic acid, butyl acrylate, 2-ethylhexyl acrylate, a special modified monomer, azodiisobutyronitrile and ethyl acetate, the acrylic acid pressure-sensitive adhesive is used as a main body and is matched with the UV cation curing component to prepare the high-shear blue film adhesive, and the high-shear blue film adhesive has the characteristic that the pressure-sensitive adhesive is easy to construct and the mechanical strength of a structural adhesive; the high-shear blue film adhesive provided by the invention can meet the use requirements of a lithium battery in a complex environment, and compared with a traditional lithium battery blue film using a pressure-sensitive adhesive, the high-shear blue film adhesive provided by the scheme has relatively high viscosity and mechanical properties, and can better protect the lithium battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery blue film adhesive, in particular to UV high shear blue film adhesive for lithium battery cell insulation protection and a preparation method thereof. Background Art

[0002] With the continuous development of lithium battery technology, lithium battery blue film, as an important component of lithium batteries, is used for the insulation and protection of lithium batteries. Traditional lithium battery blue film uses pressure-sensitive adhesive for bonding, which has the advantages of easy construction and low cost, but has disadvantages such as low bonding force and insufficient strength. With the structural changes of the new generation of power batteries, the battery cells can be directly bonded to the PACK cover or the chassis of the vehicle body, and the bonding shear force requirements are further increased, while the bonding performance of the blue film PSA back glue is limited. Therefore, the research and development of a high-shear blue film adhesive with good mechanical properties has become an urgent problem that needs to be solved.

[0003] Although there are already some solutions for high shear blue film adhesives that can be used for lithium battery blue films in the prior art, such as the use of structural adhesives such as epoxy resins and polyurethanes for bonding. These adhesives have high viscosity and mechanical properties, which can meet the use requirements of lithium batteries in complex environments. However, these adhesives have problems such as difficulty in use, long curing time, low adhesion, and insufficient strength, which cannot meet the requirements of industrial production. Therefore, it is necessary to develop a high shear blue film adhesive that has the easy construction characteristics of pressure-sensitive adhesives and the mechanical strength of structural adhesives to meet the use requirements of lithium batteries in complex environments. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] Therefore, the purpose of the present invention is to provide a UV high shear blue film adhesive for insulation protection of lithium battery cells and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0006] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions: UV high shear blue film adhesive for lithium battery cell insulation protection, comprising by weight: 90-110 parts of modified polyacrylate main adhesive, 10-20 parts of saturated polyester resin, 10-20 parts of epoxy resin, 0.5-1 parts of silane coupling agent, 3-5 parts of photoinitiator composition, and 30-60 parts of solvent; The modified polyacrylate main glue includes 100-150 parts of ethyl acetate, 4-10 parts of acrylic acid, 20-60 parts of butyl acrylate, 20-60 parts of isooctyl acrylate, 10-20 parts of special modified monomer, 0.1-0.4 parts of azobisisobutyronitrile, and 10-20 parts of ethyl acetate.

[0007] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the saturated polyester resin is one or more of ES-120, ES-210, ES-360M, ES-910, SGR-2400, and SGR-2600.

[0008] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the epoxy resin is one or more of E12, E20, E44, and E51.

[0009] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the silane coupling agent is one or more of KBM303, KBM402, KBM-403, KBE-402, and KBE-403.

[0010] As a preferred embodiment of the UV high shear blue film adhesive for lithium battery cell insulation protection of the present invention, the photoinitiator composition comprises a cationic photoinitiator and a sensitizer; Wherein, the photoinitiator is one or more of PAG-201, PAG-201S, PAG-202, PAG-202S, PAG-20101, and PAG-20102P; The sensitizer is one or more of PSS-002, PSS-303, PSS-306, PSS-402, and PSS-510.

[0011] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the solvent is one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, toluene, and dimethyl carbonate.

[0012] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the modified polyacrylate main adhesive includes 120 parts of ethyl acetate, 8 parts of acrylic acid, 30 parts of butyl acrylate, 30 parts of isooctyl acrylate, 15 parts of special modified monomers, 0.15 parts of azobisisobutyronitrile and 20 parts of ethyl acetate.

[0013] As a preferred embodiment of the UV high shear blue film adhesive for insulation protection of lithium battery cells described in the present invention, the special modified monomer is any one or more of glycidyl methacrylate, 3,4-epoxycyclohexyl methyl methacrylate, 3,4-epoxycyclohexyl methacrylate, 1,2-epoxy-4-vinylcyclohexane, 3-ethyl-3-(methacryloyloxymethyl)oxetane, 3-ethyl-3-(acryloyloxymethyl)oxetane, and cyclotrimethylolpropane methyl acrylate.

[0014] A method for preparing UV high shear blue film adhesive for lithium battery cell insulation protection, the specific steps are as follows: S1. Add 100-150 parts of ethyl acetate, 4-10 parts of acrylic acid, 20-60 parts of butyl acrylate, 20-60 parts of isooctyl acrylate, 10-20 parts of special modified monomers, and 0.05-0.2 parts of azobisisobutyronitrile into a reaction kettle, introduce nitrogen and stir for 20-60 minutes, and react at 65-75°C for 2-4 hours; S2, dissolving 0.05-0.2 parts of azobisisobutyronitrile in 10-20 parts of ethyl acetate, adding the mixture into the reaction kettle in 2-5 times, each time with an interval of 30-60 minutes, to obtain a modified acrylate main glue; S3, dissolving 10-20 parts of saturated polyester resin, 10-20 parts of epoxy resin, and 0.5-1 part of silane coupling agent in 30-60 parts of solvent to prepare a pre-solution; S4, stirring and mixing the modified acrylate main glue obtained in step S2, 3-5 parts of the photoinitiator composition and the pre-solution prepared in step S3 in a light-proof condition to obtain a blue film glue.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The modified polyacrylate main adhesive of the present invention provides basic pressure-sensitive adhesive properties and serves as the main body of the structure to ensure construction performance. The modified part participates in cationic light curing and connects the overall structure in series. The saturated polyester resin assists in bonding and improves the bonding strength. At the same time, it serves as the high Tg part to ensure the bonding strength at high temperatures. The epoxy resin serves as a cationic light curing component. The silane coupling agent increases the bonding strength of the metal surface.

[0016] 2. The present invention uses acrylic pressure-sensitive adhesive as the main body and cooperates with UV cationic curing components to prepare high shear blue film adhesive. It has the easy construction characteristics of pressure-sensitive adhesive and the mechanical strength of structural adhesive, and can meet the use requirements of lithium batteries in complex environments. Compared with the traditional lithium battery blue film using pressure-sensitive adhesive, the high shear blue film adhesive of this scheme has higher viscosity and mechanical properties, can better protect lithium batteries, and has the advantages of easy construction, high mechanical strength, and short curing time compared to the existing technology.

[0017] 3. The key technical points of the present invention are: 1. The modification of the main glue, the introduction of cationic photocurable groups, and different from most modification methods that only use glycidyl methacrylate, other monomers with higher cationic reaction activity are used, including but not limited to epoxy monomers and oxygen heterocyclic monomers; 2. Saturated polyester is used to improve the bonding performance, and acrylic modified polyester is preferred, which has better compatibility; 3. Silane coupling agents with epoxy groups are used to participate in the photocuring reaction to reduce free silanes; 4. The use of initiator combinations can achieve good curing in all wavelength bands and has a wider adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in combination with the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them: Figure 1 This is a flow chart of a method for preparing a UV high shear blue film adhesive for insulation protection of lithium battery cells according to the present invention; Figure 2 This is a schematic diagram of the shear strength and peel strength of the samples prepared in Examples 1 to 8 provided by the present invention. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0020] The invention provides a UV high shear blue film adhesive for lithium battery cell insulation protection. The UV high shear blue film adhesive comprises, by weight, 90-110 parts of modified polyacrylate main adhesive, 10-20 parts of saturated polyester resin, 10-20 parts of epoxy resin, 0.5-1 parts of silane coupling agent, 3-5 parts of photoinitiator composition, and 30-60 parts of solvent. The modified polyacrylate main adhesive comprises 100-150 parts of ethyl acetate, 4-10 parts of acrylic acid, 20-60 parts of butyl acrylate, 20-60 parts of isooctyl acrylate, 10-20 parts of special modified monomer, 0.1-0.4 parts of azobisisobutyronitrile, and 10-20 parts of ethyl acetate.

[0021] Specifically, the saturated polyester resin is one or more of ES-120, ES-210, ES-360M, ES-910, SGR-2400, and SGR-2600.

[0022] The epoxy resin is one or more of E12, E20, E44 and E51.

[0023] The silane coupling agent is one or more of KBM303, KBM402, KBM-403, KBE-402, and KBE-403.

[0024] The photoinitiator composition includes a cationic photoinitiator and a sensitizer; wherein the photoinitiator is one or more of PAG-201, PAG-201S, PAG-202, PAG-202S, PAG-20101, and PAG-20102P, and the sensitizer is one or more of PSS-002, PSS-303, PSS-306, PSS-402, and PSS-510.

[0025] The solvent is one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, toluene, and dimethyl carbonate.

[0026] The modified polyacrylate main adhesive includes 120 parts of ethyl acetate, 8 parts of acrylic acid, 30 parts of butyl acrylate, 30 parts of isooctyl acrylate, 15 parts of special modified monomer, 0.15 parts of azobisisobutyronitrile and 20 parts of ethyl acetate.

[0027] The special modified monomer is any one or more of glycidyl methacrylate, 3,4-epoxycyclohexyl methyl methacrylate, 3,4-epoxycyclohexyl methacrylate, 1,2-epoxy-4-vinylcyclohexane, 3-ethyl-3-(methacryloyloxymethyl)oxetane, 3-ethyl-3-(acryloyloxymethyl)oxetane, and cyclotrimethylolpropane formal acrylate.

[0028] In order to verify the performance of the UV high shear blue film adhesive for insulation protection of lithium battery cells of the present invention, the following Examples 1-8 are provided. Example 1

[0029] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir for 30min under nitrogen, and react at 68°C for 2-4h; S2, take 0.5g of azobisisobutyronitrile and dissolve it in 100g of ethyl acetate, add it into the reactor three times, each time with an interval of 40min, to obtain a modified acrylate main glue; S3, dissolving 15g of saturated polyester resin SGR-2600, 15g of epoxy resin E20, and 0.5g of silane coupling agent KBM403 in 25g of ethyl acetate and 25g of toluene to prepare a pre-solution; S4. Take 100 g of modified polyacrylate main glue, 3 g of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue. Example 2

[0030] S1, add 600g ethyl acetate, 40g acrylic acid, 175g butyl acrylate, 150g isooctyl acrylate, 50g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir under nitrogen for 30min, and react at 68°C for 2-4h; S2, take 0.5g of azobisisobutyronitrile and dissolve it in 100g of ethyl acetate, add it into the reactor three times, each time with an interval of 40min, to obtain a modified acrylate main glue; S3. Dissolve 15 g of saturated polyester resin SGR-2600, 15 g of epoxy resin E20, and 0.5 g of silane coupling agent KBM403 in 25 g of ethyl acetate and 25 g of toluene to prepare a pre-solution.

[0031] S4. Take 100 g of modified polyacrylate main glue, 3 g of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue. Example 3

[0032] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexylmethyl methacrylate, and 0.25g azobisisobutyronitrile into a reaction kettle, stir under nitrogen for 30min, and react at 68°C for 2-4h; S2, take 0.5g of azobisisobutyronitrile and dissolve it in 100g of ethyl acetate, add it into the reactor three times, each time with an interval of 40min, to obtain a modified acrylate main glue; S3, dissolving 15g of saturated polyester resin ES-910, 15g of epoxy resin E20, and 0.5g of silane coupling agent KBM403 in 25g of ethyl acetate and 25g of toluene to prepare a pre-solution; S4. Take 100 g of modified polyacrylate main glue, 3 g of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue. Example 4

[0033] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir for 30min under nitrogen, and react at 68°C for 2-4h; S2. Take 0.5 g of azobisisobutyronitrile and dissolve it in 100 g of ethyl acetate, and add it into the reactor three times, each time with an interval of 40 minutes, to obtain a modified acrylate main glue.

[0034] S3, dissolving 15g of saturated polyester resin SGR-2600, 15g of epoxy resin E20, and 0.5g of silane coupling agent KBM303 in 25g of ethyl acetate and 25g of toluene to prepare a pre-solution; S4. Stir and mix 100 g of modified polyacrylate main glue, 3 g of photoinitiator composition and the prepared pre-solution in a light-proof condition to obtain a blue film glue. Example 5

[0035] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir for 30min under nitrogen, and react at 68°C for 2-4h; S2. Take 0.5 g of azobisisobutyronitrile and dissolve it in 100 g of ethyl acetate, and add it into the reactor three times, each time with an interval of 40 minutes, to obtain a modified acrylate main glue.

[0036] S3, dissolving 10 g of saturated polyester resin SGR-2600, 15 g of epoxy resin E20, and 0.5 g of silane coupling agent KBM403 in 25 g of ethyl acetate and 25 g of toluene to prepare a pre-solution; S4. Stir and mix 100 g of modified polyacrylate main glue, 3 parts of photoinitiator composition and the prepared pre-solution in a light-proof condition to obtain a blue film glue. Example 6

[0037] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir for 30min under nitrogen, and react at 68°C for 2-4h; S2. Take 0.5 g of azobisisobutyronitrile and dissolve it in 100 g of ethyl acetate, and add it into the reactor three times, each time with an interval of 40 minutes, to obtain a modified acrylate main glue.

[0038] S3, dissolving 15g of saturated polyester resin SGR-2600, 15g of epoxy resin E20, and 0.2g of silane coupling agent KBM403 in 25g of ethyl acetate and 25g of toluene to prepare a pre-solution; S4. Take 100 g of modified polyacrylate main glue, 3 parts of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue. Example 7

[0039] S1, add 600g ethyl acetate, 40g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir for 30min under nitrogen, and react at 68°C for 2-4h; S2. Take 0.5 g of azobisisobutyronitrile and dissolve it in 100 g of ethyl acetate, and add it into the reactor three times, each time with an interval of 40 minutes, to obtain a modified acrylate main glue.

[0040] S3, dissolving 15 g of saturated polyester resin SGR-2400, 15 g of epoxy resin E44, and 0.5 g of silane coupling agent KBM403 in 25 g of ethyl acetate and 25 g of toluene to prepare a pre-solution; S4. Take 100 g of modified polyacrylate main glue, 3 parts of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue. Example 8

[0041] S1, add 600g ethyl acetate, 20g acrylic acid, 150g butyl acrylate, 150g isooctyl acrylate, 75g 3,4-epoxycyclohexyl methacrylate, 0.25g azobisisobutyronitrile into a reaction kettle, stir under nitrogen for 30min, and react at 68°C for 2-4h; S2. Take 0.5 g of azobisisobutyronitrile and dissolve it in 100 g of ethyl acetate, and add it into the reactor three times, each time with an interval of 40 minutes, to obtain a modified acrylate main glue.

[0042] S3. Dissolve 15 g of saturated polyester resin SGR-2400, 15 g of epoxy resin E20, and 0.5 g of silane coupling agent KBM403 in 25 g of ethyl acetate and 25 g of toluene to prepare a pre-solution.

[0043] S4. Take 100 g of modified polyacrylate main glue, 3 parts of photoinitiator composition and the prepared pre-solution, stir and mix them evenly under light-proof conditions to obtain a blue film glue.

[0044] Figure 2 Shown is a schematic diagram of the shear strength and peel strength of the samples prepared in Example 1 to Example 8. It can be seen from the figure that the blue film adhesive of the present invention has the easy construction characteristics of pressure-sensitive adhesive and the mechanical strength of structural adhesive, and can meet the use requirements of lithium batteries in complex environments. Compared with the traditional lithium battery blue film using pressure-sensitive adhesive, the high shear blue film adhesive of this scheme has higher viscosity and mechanical properties, can better protect lithium batteries, and has advantages over the prior art such as easy construction, high mechanical strength and short curing time.

[0045] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A UV high shear blue film adhesive for lithium battery cell insulation protection, characterized in that: The composition comprises, by weight: 90-110 parts of modified polyacrylate main glue, 10-20 parts of saturated polyester resin, 10-20 parts of epoxy resin, 0.5-1 parts of silane coupling agent, 3-5 parts of photoinitiator composition, and 30-60 parts of solvent; The modified polyacrylate main glue includes 100-150 parts of ethyl acetate, 4-10 parts of acrylic acid, 20-60 parts of butyl acrylate, 20-60 parts of isooctyl acrylate, 10-20 parts of special modified monomer, 0.1-0.4 parts of azobisisobutyronitrile, and 10-20 parts of ethyl acetate.

2. The UV high shear blue film adhesive for lithium battery cell insulation protection according to claim 1, characterized in that: The saturated polyester resin is one or more of ES-120, ES-210, ES-360M, ES-910, SGR-2400, and SGR-2600.

3. The UV high shear blue film adhesive for lithium battery cell insulation protection according to claim 1, characterized in that: The epoxy resin is one or more of E12, E20, E44 and E51.

4. The UV high shear blue film adhesive for insulation protection of lithium battery cells according to claim 1, characterized in that: The silane coupling agent is one or more of KBM303, KBM402, KBM-403, KBE-402, and KBE-403.

5. The UV high shear blue film adhesive for insulation protection of lithium battery cells according to claim 1, characterized in that: The photoinitiator composition comprises a cationic photoinitiator and a sensitizer; Wherein, the photoinitiator is one or more of PAG-201, PAG-201S, PAG-202, PAG-202S, PAG-20101, and PAG-20102P; The sensitizer is one or more of PSS-002, PSS-303, PSS-306, PSS-402, and PSS-510.

6. The UV high shear blue film adhesive for insulation protection of lithium battery cells according to claim 1, characterized in that: The solvent is one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, toluene, and dimethyl carbonate.

7. The UV high shear blue film adhesive for lithium battery cell insulation protection according to claim 1, characterized in that: The modified polyacrylate main adhesive includes 120 parts of ethyl acetate, 8 parts of acrylic acid, 30 parts of butyl acrylate, 30 parts of isooctyl acrylate, 15 parts of special modified monomer, 0.15 parts of azobisisobutyronitrile and 20 parts of ethyl acetate.

8. The UV high shear blue film adhesive for lithium battery cell insulation protection according to claim 1, characterized in that: The special modified monomer is any one or more of glycidyl methacrylate, 3,4-epoxycyclohexyl methyl methacrylate, 3,4-epoxycyclohexyl methacrylate, 1,2-epoxy-4-vinylcyclohexane, 3-ethyl-3-(methacryloyloxymethyl)oxetane, 3-ethyl-3-(acryloyloxymethyl)oxetane, and cyclotrimethylolpropane formal acrylate.

9. A method for preparing the UV high shear blue film adhesive for lithium battery cell insulation protection as claimed in claim 1, characterized in that: The specific steps are as follows: S1. Add 100-150 parts of ethyl acetate, 4-10 parts of acrylic acid, 20-60 parts of butyl acrylate, 20-60 parts of isooctyl acrylate, 10-20 parts of special modified monomers, and 0.05-0.2 parts of azobisisobutyronitrile into a reaction kettle, introduce nitrogen and stir for 20-60 minutes, and react at 65-75°C for 2-4 hours; S2, dissolving 0.05-0.2 parts of azobisisobutyronitrile in 10-20 parts of ethyl acetate, adding the mixture into the reaction kettle in 2-5 times, each time with an interval of 30-60 minutes, to obtain a modified acrylate main glue; S3, dissolving 10-20 parts of saturated polyester resin, 10-20 parts of epoxy resin, and 0.5-1 part of silane coupling agent in 30-60 parts of solvent to prepare a pre-solution; S4, stirring and mixing the modified acrylate main glue obtained in step S2, 3-5 parts of the photoinitiator composition and the pre-solution prepared in step S3 in a light-proof condition to obtain a blue film glue.

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