JPH0428032B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to an adhesive primer used to increase the adhesive strength when bonding a metal and a fluororesin, and the invention relates to an adhesive primer that is used to increase the adhesive strength when bonding a metal and a fluororesin. The present invention relates to an improvement in a primer for adhesion between a metal and a fluororesin, which is difficult to separate from the base resin. [Prior Art] Conventionally, in copying machines and the like, a heating roller type fixing device is widely used to fix an unfixed toner image onto a sheet of paper. In other words, this fixing device is
As shown in the figure, a heating roller d consisting of a metal cylindrical body b equipped with a heater a inside, a heat-resistant fluororesin layer c adhered to the outer peripheral surface of the metal cylindrical body b, and a heating roller d placed in pressure contact with the heating roller d. A sheet f on which an unfixed toner image has been formed is inserted between these rollers d and e to heat and fix it. By the way, when manufacturing the heating roller d, the metal cylindrical body b is used because fluororesin has poor adhesive properties.
If only the fluororesin was applied to the outer peripheral surface and baked, the fluororesin layer c would easily peel off from the cylindrical body b, making it unusable as a heating roller d. Therefore, conventionally, the metal cylindrical body b
In order to improve the adhesion between the resin and the fluororesin,
As described in Publication No. 177067, a polyimide precursor obtained by the reaction of pyromellitic anhydride and diaminodiphenyl ether or diaminodiphenyl meta, etc., and a 4-fluorinated ethylene/perfluoroalkoxyethylene copolymer resin A method has been adopted in which the cylindrical body b and the fluororesin are bonded via an adhesive primer containing the following. [Problems to be Solved by the Invention] By the way, when the metal cylindrical body b and the fluororesin are bonded via the adhesive primer described above,
Although the adhesion between the two improves and good results are obtained in the initial stage, the adhesive primer deteriorates over time and the cylindrical body b and the fluororesin tend to separate over time. There was a problem that it could not withstand long-term use. That is, the heating roller d is repeatedly heated to a high temperature of 200° C. when the device is in motion, and cooled down to room temperature when the device is stationary.
In addition, the pressure roller e is placed in pressure contact and stress is constantly applied to the fluororesin layer c, and the outer peripheral surface is constantly moistened by being supplied with silicone oil to prevent the toner offset phenomenon of unfixed toner. Moreover, it is exposed to severe conditions such as the peeling claw g that prevents the paper f from being wrapped around the heating roller d, which is constantly in pressure contact with the paper f. Therefore, the adhesive primer described above tends to deteriorate over time, and stress is constantly applied to the fluororesin layer c, making it easy for the metal cylindrical body b and the fluororesin layer c to separate over time. There was a problem that it could not withstand long-term use. [Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and its problem is that even when exposed to harsh conditions, the fluorocarbon resin, including the heating roller, An object of the present invention is to provide a primer for adhesion between metal and fluororesin that is difficult to peel off. That is, the adhesive primer of the present invention is an aromatic polyimide precursor obtained by reacting pyromellitic anhydride and 4,4'-diaminodiphenylsulfone as main components in a mixed solvent of a water-soluble organic solvent and water. Alternatively, it is characterized by containing a free carboxylic acid thereof neutralized with an amine, and a 4-fluorinated ethylene/perfluoroalkoxyethylene copolymer resin. In such technical means, the aromatic polyimide precursor is the following pyromellitic anhydride ()
and 4,4'-diaminodiphenyl sulfone (), preferably dimethyl sulfoxide (DMSO).
A polyamic acid obtained by reacting DMSO in a single solvent or in a mixed solvent of DMSO and N-methyl-2-pyrrolidone or NN'-dimethylacetamide, etc. Polyimide ( ), it has excellent adhesion to metals, heat resistance, cold and hot cycle resistance, etc., and is resistant to deterioration even by organic solvents such as silicone oil, and is useful for improving adhesive strength with metals. It is something that contributes. In addition, the above pyromellitic anhydride () and 4,4'-
The reaction with diaminodiphenylsulfone ()
Preferably in dimethyl sulfoxide (DMSO) alone or in combination with DMSO and N-methyl-
The reason why the reaction is carried out in a mixed solvent with 2-pyrrolidone or NN'-dimethylacetamide is that the polymerization reaction occurs more easily than when the reaction is carried out in other solvents. Furthermore, in order to prevent hydrolysis of the polyamic acid which is the aromatic polyimide precursor, it is desirable to stabilize the free carboxylic acid by neutralizing it with an amine such as trimethylamine, triethylamine, or methylethanolamine. On the other hand, the above-mentioned 4-fluoroethylene/perfluoroalkoxyethylene copolymer resin (hereinafter referred to as PFA resin) is a resin obtained by copolymerizing 4-fluoroethylene and perfluoroalkoxyethylene, and has a high heat resistance. This contributes to improving the adhesive strength with the fluororesin. Then, the aromatic polyimide precursor was mixed with furfuryl alcohol, butanol, isopropanol,
An adhesive primer is prepared by mixing a solution dissolved in a water-soluble organic solvent such as ethanol with an aqueous solution in which the PFA resin is uniformly dispersed. The mixing ratio of the aromatic polyimide precursor and PFA resin is 10:90 to 90:90 by weight.
10, preferably 30:70 to 70:30. Also,
A surfactant such as polyoxyethylene-nonyl phenyl ether may be added for the purpose of improving the dispersibility of the PFA resin. In order to bond a metal and a fluororesin using this adhesive primer, the metal surface is first degreased and roughened as in the conventional method. Next, the above-mentioned adhesive primer is applied uniformly, and a fluororesin powder such as PFA resin or this dispersion is applied on the adhesive primer under dry or wet conditions, and then baked to remove the aroma in the above-mentioned adhesive primer. In addition to dehydrating and cyclizing the group polyimide precursor to form polyimide,
The PFA resin and the applied fluororesin are melted to bond the metal and the fluororesin. The target metals include iron, aluminum,
There are alloys such as copper, nickel, and stainless steel, as well as silver alloys and nickel alloys, while fluororesins include PFA resin, PTFE resin (polytetrafluoroethylene resin), and FEP resin (both tetrafluoroethylene and hexafluoropropylene). polymer resin),
PCTFE resin (polychlorotrifluoroethylene resin), ETFE resin (ethylene/tetrafluoroethylene copolymer resin), ECTFE resin (ethylene/chlorotrifluoroethylene copolymer resin),
Examples include PVF resin (vinyl fluoride resin) and PVdF resin (vinylidene fluoride resin). The adhesive primer of the present invention can be used not only as a primer for manufacturing heating rollers that are used even under harsh conditions, but also as a primer for adhesives between metals and fluororesins that are exposed to harsh conditions like heating rollers. can be used. [Function] According to the above-mentioned technical means, this adhesive primer contains pyromellitic anhydride and 4,4'-
Because it contains an aromatic polyimide precursor obtained by reacting with diaminodiphenyl sulfone and PFA resin, it can be obtained by reacting conventional pyromellitic anhydride with diaminodiphenyl ether or diaminodiphenyl methane. Compared to adhesive primers containing polyimide precursors and PFA resins, they have better adhesion to metals and fluororesins, heat resistance, cold/hot cycle resistance, silicone oil resistance,
It has excellent stress resistance, is resistant to deterioration over time even when exposed to harsh conditions, and has the effect of preventing metal and fluororesin from peeling off over a long period of time. [Examples] Examples of the present invention will be described in detail below. ◎First Example 120.0 g of DMSO was charged into a 500 ml four-necked separable flask equipped with a stirrer, thermometer, cooling tube, and hopper for charging materials, and 4,4'-
Diaminodiphenylsulfone 24.8g (0.100mol)
Add and dissolve. Then in the flask,
While cooling with ice to prevent the temperature of the outside bath from rising above 30℃,
21.8 g (0.100 mol) of pyromellitic anhydride powder is added over about 2 minutes. At this time, the stirring device was operated at a rotation speed of 250 to 270 rpm. After adding the pyromellitic anhydride, the heat generation will stop in about 5 minutes, so remove the external bath, wash away the pyromellitic anhydride that has adhered to the inner wall of the flask with 40g of DMSO, and after 30 minutes, add more water.
80 g of DMSO was added and the reaction was continued for 6 hours. After the reaction was completed, 24.2 g of triethylamine was added and stirred uniformly to neutralize the free carboxylic acid and obtain an aromatic polyimide precursor. The physical properties of this product were as follows. Viscosity: 900 cps (25℃) Intrinsic viscosity [η] inh: 1.12 Next, prepare liquid A of this aromatic polyimide precursor with the following composition and liquid B of PFA resin dispersion with the following composition, and keep both liquids at 10℃ or less. While maintaining the temperature and stirring the B solution slowly, the A solution was added evenly to the B solution over 15 minutes to obtain an adhesive primer. This primer is a slightly brownish emulsion, and when it was thinly applied on a glass plate and observed, no coarse particles were observed, indicating that the PFA resin dispersion particles were stably dispersed. confirmed. ●Liquid A [Parts by weight] Aromatic polyimide precursor 20 Furfuryl alcohol 2 2% nonionic surfactant aqueous solution (trade name NS-210, manufactured by NOF Corporation) 10 Water 39 ●Liquid B [Parts by weight] PFA resin dispersion (Solid content ratio Ts = 50%)
12 2% nonionic surfactant aqueous solution (product name NS-210, manufactured by NOF Corporation) 15 ◎Second Example 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were mixed in DMSO/N-methyl-2-
An adhesive primer was obtained in the same manner as in Example 1, except that the reaction was carried out in a mixed solvent of pyrrolidone (50/50 weight ratio). The aromatic polyimide precursor obtained by this reaction had an intrinsic viscosity [η]inh of 0.54. ◎Third Example Same as the first example except that 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were reacted in a mixed solvent of DMSO/NN'-dimethylacetamide (50/50 weight ratio). An adhesive primer was obtained in the same manner. The aromatic polyimide precursor obtained by this reaction had an intrinsic viscosity [η]inh of 0.51. ◎Fourth Example An adhesive primer was obtained in the same manner as in the first example except that 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were reacted in the sole solvent of NN'-dimethylacetamide. Ta. The aromatic polyimide precursor obtained in this reaction had an intrinsic viscosity [η]inh of 0.29. ◎Fifth Example 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were mixed into N-methyl-2-pyrrolidone/NN'-dimethylacetamide (weight ratio 83/
An adhesive primer was obtained in the same manner as in Example 1 except that the reaction was carried out in the mixed solvent of 17). The aromatic polyimide precursor obtained by this reaction had an intrinsic viscosity [η]inh of 0.19. ◎Sixth Example 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were mixed into N-methyl-2-pyrrolidone/NN'-dimethylformamide (weight ratio 83/
An adhesive primer was obtained in the same manner as in Example 1 except that the reaction was carried out in the mixed solvent of 17). The aromatic polyimide precursor obtained by this reaction had an intrinsic viscosity [η]inh of 0.12. ◎ Seventh Example An adhesive primer was prepared in the same manner as in the first example, except that 4,4'-diaminodiphenylsulfone and pyromellitic anhydride were reacted in the sole solvent of N-methyl-2-pyrrolidone. I got it. The aromatic polyimide precursor obtained by this reaction had an intrinsic viscosity [η]inh of 0.17. Comparative Example An adhesive primer was obtained in the same manner as in Example 1, except that diaminodiphenyl ether and pyromellitic anhydride were reacted in the sole solvent of N-methyl-2-pyrrolidone. The intrinsic viscosity [η]inh of the aromatic polyimide precursor obtained by this reaction is
It was 0.43. However, here the intrinsic viscosity [η]inh
The measurements were made using the solvent composition of the aromatic polyimide precursor, at a concentration of 0.5 g/100 ml and a temperature of 30
℃. Note that this value may be regarded as the intrinsic viscosity [η]inh of the aromatic polyimide precursor. [Efficacy Confirmation Test] Among the adhesive primers obtained in the above Examples and Comparative Examples, the primers of the First Example and Comparative Example were selected, and these primers were used to conduct the thermal cycle test described below. I went there. ◎First test Prepare multiple 3mm thick steel plates (STKM material) cut into 100 x 100mm pieces, degrease each with Triclean, sandblast the surface, and then apply each primer uniformly to these steel plates with a spray gun. It was applied to. These primers were dried at 60°C for 30 minutes, then PFA resin powder paint was sprinkled from above to completely cover the surface, and paper was pressed over this to make the surface dense.
A plurality of two types of sample pieces each were prepared by baking at 390°C for 10 minutes and bonding a steel plate and PFA resin. In addition, at this time, the thickness of the above primer is
The thickness was adjusted to 10 to 15 μm. Further, the thickness of the PFA resin powder was 100 to 200 μm. Next, these sample pieces were immersed in heat-resistant dimethyl silicone oil maintained at 230°C for 18 hours.
The sample was then taken out and placed in the same oil maintained at -5°C, immersed for 10 minutes, and then taken out for one cycle of the heat-cool cycle test.
Then, each of the above two types of sample pieces was subjected to one cycle ~
After repeating 16 cycles and preparing sample pieces for the heat-cooling cycle test for each number of cycles, after washing these sample pieces with toluene and acetone,
A 90 degree peel strength test was conducted. This measurement test was conducted at room temperature at a peeling rate of 50 mm/min. Figure 1 plots these measurement results, and shows that even after 16 cycles, the primer did not easily deteriorate over time, and the peel strength of the sample piece () using the primer of Example 1 was low. It also shows that it has not decreased. On the other hand, regarding the sample piece () using the primer according to the comparative example, the primer deteriorated significantly over time, and the peel strength of the sample piece after 10 cycles was 0.5 kg from 1.5 kg/cm width compared to the initial one. It was confirmed that the width decreased to /cm width. The present inventors have also conducted similar effect confirmation tests on the primers according to the second to seventh examples, and have confirmed that the same results as in the first example were obtained. . ◎Second test A rolled steel pipe was used instead of the steel plate used in the first test, and the primer () of the first example was placed on the steel pipe.
A plurality of two types of sample tubes were prepared by adhering PFA resin using the same method as in the first test using the primer () of the comparative example. However, the application method of PFA powder paint shall be electrostatic coating method and the film thickness shall be 30μm.
And so. Then, as in the first test, these two types of sample tubes were alternately immersed in heat-resistant dimethyl silicone oil held at 230°C and in the same oil held at -5°C, and 0 to 25 cycles were repeated for each. Sample tubes for the heat/cool cycle test were prepared for each number of cycles, and the same peel strength test as in the first test was conducted on these sample tubes.

[Table] However, ○ means that the steel pipe and PFA resin will not peel off, and △ means that peeling will occur in a part of the sample tube.
Also, × indicates that peeling occurs in all sample tubes. From this result, it was confirmed that the use of the primer according to the first example made it difficult for the steel pipe and the PFA resin to separate over a long period of time. Incidentally, the present inventors have conducted similar effect confirmation tests on the primers according to the second to seventh examples, and have confirmed that the same results as in the first example were obtained. [Effects of the Invention] As described above, the adhesive primer of the present invention has superior adhesion to metals and fluororesins compared to conventional primers, and has excellent heat resistance, cold and hot cycle resistance, silicone oil resistance, and Because it has excellent stress resistance, the primer is unlikely to deteriorate over time even when exposed to harsh conditions, and the metal and fluororesin will not peel off over a long period of time. Therefore, by applying this primer to, for example, the heating roller of a fixing device, it has the effect of significantly extending the life of the heating roller and maintaining the adhesion between metal and fluororesin over a long period of time.

[Brief explanation of drawings]

Figure 1 compares the adhesion effects of primers according to examples of the present invention and comparative examples, and is a diagram showing the relationship between the number of heating and cooling cycles and peel strength. A schematic cross-sectional view is shown in each case.

Claims (1)

[Scope of Claims] 1. An aromatic polyimide precursor obtained by reacting pyromellitic anhydride and 4,4'-diaminodiphenylsulfone as main components in a mixed solvent of a water-soluble organic solvent and water, or its release. A primer for adhesion between a metal and a fluororesin, comprising a carboxylic acid neutralized with an amine and a 4-fluoroethylene/perfluoroalkoxyethylene copolymer resin. 2 The aromatic polyimide precursor is characterized in that it is obtained by reacting pyromellitic anhydride and 4,4'-diaminodiphenylsulfone in dimethyl sulfoxide alone or in a mixed solvent containing dimethyl sulfoxide. A primer for adhesion between a metal and a fluororesin according to claim 1.