JPH0362180B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses polyetherimide (hereinafter referred to as "PEI")
) is dissolved in a solvent and cast, thereby producing a PEI film. PEI is known as an engineering plastic with excellent heat resistance, and is suitable for printed wiring boards, storage media base materials, electrical insulation materials, etc. and,
Melt extrusion is generally considered to be a method for producing such films, but it is difficult to obtain films with high thickness accuracy using melt extrusion. Therefore, the casting method can be considered as a method to obtain a film with good thickness accuracy, but engineering plastics such as PEI generally have excellent heat resistance and solvent resistance, so it is difficult to select an appropriate solvent, and it is difficult to obtain high-quality films. Selection of this solvent is important in order to obtain a film. In the present invention, as a result of various studies on solvents for dissolving and casting PEI, it was discovered that a specific mixed solvent is particularly preferable, and its characteristics include 1,1,2-trichloroethane, 1 ,1,1
- A mixed solution of trichloroethane and 1,2-dichloroethylene is used as a solvent. The present invention will be explained in detail below. The PEI referred to in the present invention is A typical example is one having the following structure. Solvents for dissolving this PEI include (1) 1,1,2-trichloroethane (ClCH ₂ CHCl ₂ , boiling point 114°C) 50 to 95% by weight (2) 1,1,1-trichloroethane (CH ₃ CCl ₃ ,
A mixed solvent of 3-30% by weight (3) 1,2-dichloroethane (ClCH ₂ CH ₂ Cl, boiling point 84°C) 2-20% by weight is used. 1,1,2-trichloroethane has some
It has the ability to dissolve PEI and has a high boiling point, so it is suitable as a solvent for PEI casting, but it is not sufficient to use it alone as a solvent for high concentrations.
PEI cannot be completely dissolved, and the boiling point is too high, which slows down the solvent removal rate after casting. However, when 1,2-dichloroethane was added to this
Mixing more than % by weight greatly improves PEI dissolving ability. However, since 1,2-dichloroethane has a low boiling point, if it exceeds 20% by weight, the mixed liquid will scatter quickly, making it difficult to control conditions when removing the solvent and forming a film. Moreover, if the amount of 1,2-dichloroethane is too large, it tends to become difficult to peel off the film from the casting support (such as a steel belt), so the amount should be within 20% by weight. Furthermore, when 3% by weight or more of 1,1,1-trichloroethane is mixed, the membrane can be easily peeled from the casting support, and the range of conditions for removing the solvent from the membrane can be expanded, making control easier. A phenomenon can be seen. However, if it exceeds 30% by weight, the mixed solvent
Since the PEI dissolving ability is significantly reduced and only a cloudy film is obtained, it is necessary to keep the amount below 30% by weight. A mixed solvent of the above three types of solvents has sufficient PEI dissolving ability for practical purposes, and this mixed solvent has appropriate scattering properties, and the film can be easily peeled off from the casting support, so it is especially suitable for thin films. Ideal for film production. In this case, it is preferable to set the concentration of the PEI solution such that the viscosity at 25° C. is about 8000 CPS or more, so that a film with a uniform thickness can be obtained when cast. In the method of the present invention, the above three types of solvents are first mixed, and PEI is dissolved in the mixed solvent. When one or two solvents and PEI are mixed and then the remaining solvent is added, the solution often becomes cloudy and does not return to a clear state even after stirring. The method of casting the PEI solution obtained in this way is usually to discharge the PEI solution in a film form from a die onto a support such as a metal belt, glass plate, or polyester film. Alternatively, the PEI solution may be coated onto the support in a film form using a roll coater or the like. Next, the method of the present invention will be explained in more detail with reference to Examples. [Example] 100 g of PEI was added to 400 g of a mixed solvent prepared by mixing three types of solvents in various ratios shown in Table 1, and the mixture was stirred at 70° C. for 50 hours to obtain a PEI solution. Each solution was then applied onto a glass plate using an applicator, and then heated at 60°C.
The film was dried by heating for 30 seconds to remove approximately 97% of the solvent, and the formed film was annealed on a glass plate to completely remove the solvent and then peeled off to obtain a 15 μm thick film. . For each film, evaluate the film appearance, peelability from the support, and annealing condition range,
The results are also listed in Table 1. The range of annealing conditions is one in which the solvent is completely removed at a higher temperature (or longer time) than 140°C for 5 minutes (○), and one in which the solvent is completely removed at 180°C for 10 minutes or more severe conditions. The items were marked with an (x).

【table】

[Table] As is clear from the results in Table 1, Nos. 3, 5 to 6, and 8 in which the mixing ratio of the solvent is within the range of the present invention.
is excellent in all properties. Comparative Example 1 30% by weight of methylene chloride as a solvent, 1,1,2
A film was obtained in the same manner as in Example except that a mixed solvent consisting of 70% by weight of trichloroethane was used, but when the atmosphere was humid, the appearance of the film became opaque and a good film could not be obtained. This is thought to be because the methylene chloride scatters quickly and takes away the latent heat of vaporization, so that moisture in the atmosphere condenses on the film surface, and the film surface becomes engulfed with fine water droplets. Comparative example 2 200g of 1,1,2-trichloroethane and 1,2
- Add PEI100 to a solution of 80g of dichloroethane.
g was added and stirred at 70°C for 50 hours to obtain a clear solution. When 120 g of 1,1,1-trichloroethane heated to 70°C was added to this, the mixture became cloudy, so although the mixture was stirred at 70°C for 1 hour, no clear solution was obtained. Comparative Example 3 200g of 1,1,2-trichloroethane and 1,1,
PEI was dissolved in a mixed solvent of 120 g of 1-trichloroethane, then 80 g of 1,2-dichloroethane was added, and the same operation as in Comparative Example 2 was carried out, but only a cloudy solution was obtained.

Claims (1)

[Claims] 1. When producing a polyetherimide film by a casting method, 1,1,2-trichloroethane 50-95% by weight, 1,1,1-trichloroethane 3-30% by weight, and 1,2-dichloroethane 2-95% by weight are used as solvents. A method characterized by mixing 20% by weight of polyetherimide, dissolving the polyetherimide in the mixed solvent, and casting the solution.