JPH0222336A - Production of fiber-reinforced thermoplastic polyamide-imide resin prepreg - Google Patents

Abstract

PURPOSE:To obtain a prepreg capable of readily removing a residual solvent without forming voids and deteriorating physical properties even at high temperatures by washing an intermediate prepreg with water or/and methanol and drying the washed prepreg. CONSTITUTION:An intermediate prepreg prepared by impregnating a reinforcing fiber with a resin composition consisting of a thermoplastic polyamide-imide resin and a solvent is washed with water or/and methanol and dried. The amount of the water or/and methanol may be 30-50 times based on that of the solvent.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention enables easy removal of the solvent remaining in the fiber-reinforced thermoplastic polyamide-imide resin intermediate prepreg, and manufactures the fiber-reinforced thermoplastic polyamide-imide resin prepreg. It is about the method.

[Conventional technology]

In recent years, fiber-reinforced plastics (hereinafter referred to as FRP), represented by carbon fiber-reinforced plastics, have been used as advanced composite materials, taking advantage of their excellent properties of high specific strength and high specific modulus. It has been put into practical use in the leisure field, automobiles, and general industrial fields.

Conventionally, matrix resins used in FRP are generally thermosetting resins such as epoxy resins, but they have drawbacks such as brittleness, poor impact resistance, and long curing time. For this reason, in recent years thermoplastic resins have become popular due to their high toughness and
It is attracting attention as a matrix resin for FRP because it has advantages such as a short molding cycle and repairability.

Heat-resistant thermoplastic resins, so-called super engineering plastics, are used particularly in applications in the aerospace field that require heat resistance and high toughness. Among these, thermoplastic polyamide-imide resin is attracting attention as an important matrix resin due to its excellent heat resistance, chemical resistance, mechanical properties, etc.

Conventionally, methods for producing fiber-reinforced thermoplastic polyamide-imide resin prepregs made of thermoplastic polyamide-imide resin and reinforcing fibers have been difficult to produce, such as by film stacking or real-melt methods, because the melt viscosity of polyamide-imide resin is extremely high. At present, it is difficult to use the so-called dry method, in which the resin is molten and impregnated into reinforcing fiber bundles under pressure, and a complicated wet method must be used. In other words, the fiber-reinforced thermoplastic polyamide-imide resin prepreg produced by the wet method is produced by dissolving the thermoplastic polyamide-imide resin in a suitable and compatible solvent at a ratio of about 10 to 30% by weight, and then adding this solution with a lower viscosity to the fibers. It has been produced by applying the solution to textiles or by dipping the textile into the solution and subsequently heating to remove the solvent.

For example, JP-A-59-202819 discloses that 50 to 97% by weight of thermoplastic polyamideimide resin and 50% by weight of organic solvent are used.
A first step in which a composition consisting of ~3% by weight and a fiber fabric are laminated and heated and pressurized to form a sheet.The organic solvent is removed from the sheet-like laminate obtained in the first step to less than 3% by weight. A method for manufacturing a fiber-reinforced thermoplastic polyamide-imide resin molded article is described, which comprises a second step of applying a solvent and a third step of shaping the desolventized sheet material obtained in the second step into a desired shape. Alternatively, JP-A-61-69841 describes laminates of thermally stable continuous fibers, such as glass, alumina, steel, graphite or carbon fibers, impregnated with a solution of an amide-imide polymer; The fibers are coated with a size composition of an amide-imide copolymer, an amide-imide copolymer/amide-imide-phthalamide copolymer blend, or a polyamide-imide/polyetherimide blend, thereby improving the fluidity of the polyamide-imide resin. It is stated that it has improved.

[Problem to be solved by the invention]

However, in JP-A No. 59-202819, although the amount of solvent is small compared to the conventional method, heating in the air or under reduced pressure is used as a method for removing the solvent, which requires a large amount of time in the desolvation process. It takes time and money,
In addition, fiber fabrics or unidirectionally aligned fiber bundles impregnated with a low viscosity solution are extremely flexible and have poor shape retention.
There is a problem that fibers are misaligned or disordered during the solvent removal process, and a sufficient composite effect is not achieved. Also, JP-A-61-
Since JP-A-69841 uses a large amount of solvent, it has the same problem as JP-A-59-202819.

Furthermore, in these techniques, a good solvent is used for the thermoplastic polyamide-imide resin, and the solvent is removed by heating, but since the good solvent has a strong affinity with the thermoplastic polyamide-imide resin, Remains in the resin longer than necessary. Therefore, when molded using these materials, there are problems such as generation of voids or deterioration of physical properties at high temperatures.

An object of the present invention is to provide a method for producing a fiber-reinforced thermoplastic polyamide-imide resin prepreg that solves these problems.

Another object of the present invention is to provide a fiber-reinforced thermoplastic polyamide-imide resin prepreg that does not generate voids when molded and does not deteriorate its physical properties at high temperatures.

[Means to solve the problem]

In view of these circumstances, the inventors of the present invention have conducted intensive studies on the above-mentioned problems, and have discovered that a prepreg can be produced by removing the residual solvent from an intermediate prepreg using easy-to-handle water and/or methanol and with a simple operation. The invention was completed.

That is, the present invention provides a method for producing a prepreg by removing the solvent from an intermediate prepreg produced by impregnating reinforcing fibers with a resin composition consisting of a thermoplastic polyamide-imide resin and a solvent. The present invention provides a method for producing a fiber-reinforced thermoplastic polyamide-imide resin prepreg, which comprises washing with methanol and drying.

The present invention will be explained in detail below.

The intermediate prepreg in the present invention refers to a resin composition consisting of a thermoplastic polyamideimide resin and a solvent reinforced with MIi.
It refers to the product impregnated with M, and the solvent has not been removed. On the other hand, prepreg refers to intermediate prepreg from which unnecessary solvent remaining is removed, and this prepreg is used for molding. That is, the fiber-reinforced thermoplastic polyamideimide resin prepreg in the present invention is produced by removing unnecessary solvent from an intermediate prepreg.

The thermoplastic polyamideimide resin used in the present invention is -a
The repeating unit represented by 2 (1) is mainly represented by the above general formula (1
) and (If), Ar.

is a heterocycle or a trivalent aromatic residue that may have an inert substituent such as alkyl, alkoxy, allyloxy, or halogen introduced, and two of the three carbonyl groups are adjacent carbon atoms. It is connected with.

Specific examples of Ar include the following groups.

30 to 100 mol% as essential structure, preferably 50-1
00 mol%, remaining less than 70 mol%, preferably 5
It has less than 0 mol% of repeating units represented by the following general formula (n).

Further, Ar and Ar= are divalent aromatic residues different from each other, and specific examples include the following groups.
As described in Japanese Patent No. 80532, in a method of subjecting an aromatic tricarboxylic acid and/or an aromatic tricarboxylic acid anhydride to an aromatic diamine in the presence of a dehydration catalyst through a heating polycondensation reaction, a solvent containing sulfolane is used as a solvent. can be manufactured.

The solvent used in the present invention refers to a good organic solvent that has good affinity with the thermoplastic polyamide-imide resin, and the solvent used in the present invention is not particularly limited as long as it is a good solvent. Examples include N-methyl-2-pyrrolidone, N, todimethylformamide, N, todimethylacetamide, N, N-diethylformamide, dimethyl sulfoxide, tetramethylurea, and --cresol.

More preferably N,N-dimethylformamide and N.

N-dimethylacetamide.

The amount of the solvent used in the present invention is not particularly limited as long as a uniform solution state of the thermoplastic polyamideimide resin is obtained, and can be appropriately selected depending on the resin content in the prepreg, but is preferably 50% by weight to 97% by weight. % by weight, more preferably 65% to 85% by weight. If it is less than 50% by weight, it is difficult to obtain a uniform solution state;
If it is used in excess of this weight percent, the resin concentration will be too low to be of practical use, which is not preferable.

Therefore, the amount of thermoplastic polyamideimide resin used in the present invention is 3% to 50% by weight, more preferably 15% to 35% by weight.

The effect of the solvent used in the present invention is to dissolve the thermoplastic polyamide-imide resin with a good solvent with strong affinity, create a uniform solution state with low viscosity, and improve impregnation into reinforcing fibers.

In the present invention, water, methanol, or a mixture thereof is used to remove the solvent. It is not necessary to use pure water, and the water may contain impurities that do not adversely affect the prepreg.

Similarly, methanol does not need to be pure methanol, and may contain impurities that do not adversely affect the prepreg. Furthermore, the same applies to mixtures thereof.

The amount of water and/or methanol to be used is not limited as long as it is sufficiently larger than the amount of solvent, and it is sufficient if the amount is about 30 to 50 times the amount of solvent.

By washing the intermediate prepreg with water and/or methanol, residual solvent in the prepreg can be easily removed.
0% by weight, and then the unnecessary solvent is removed in a shorter time than conventionally by a conventional drying method, such as a heating method or a vacuum method. Further, the specific drying temperature may be any temperature higher than the boiling point of the solvent used, and the drying equipment may be an open air dryer, a hot air dryer, a far-infrared oven, etc. Among them, an oven is preferable because it is simple.

When the intermediate prepreg is washed with water or/and methanol, a uniform porous film of thermoplastic polyamideimide resin is formed in the prepreg, and unnecessary solvent is easily removed from the film in the next drying process. It is presumed that.

Examples of the method of cleaning with water and/or methanol include a method of cleaning the intermediate prepreg by immersing it in water or/and methanol, and a method of cleaning by spraying the intermediate prepreg with water and/or methanol.

Further, the amount of residual solvent in the prepreg can be appropriately adjusted by adjusting the degree of washing with water and/or methanol, and the drying temperature and time. Furthermore, the residual content of the solvent in the prepreg is preferably less than 3% by weight, more preferably less than 1% by weight. Solvent residual content is 3% by weight
If it exceeds this value, voids will occur during molding, which is undesirable.

The method of mixing the solvent and thermoplastic polyamideimide resin is as follows:
Specific examples of the mixing method include a magnetic cooler,
Examples include a stirrer and a mixer, and among them, a stirrer is preferred because it can be applied in a wide range of solution viscosities.

The reinforcing fibers used in the present invention are not particularly limited, and include inorganic fibers such as glass fibers, carbon fibers, alumina fibers and silicon carbide fibers, and organic fibers such as aramid fibers, aromatic polyester fibers, nylon fibers, and polyethylene fibers. ,
Further examples include those used as reinforcing fibers for FRP, such as metal fibers. In addition, the form of the fiber is preferably a long fiber form in order to fully express the effects of the present invention.
Specific examples include continuous fiber rovings or tows, and further include fiber fabrics such as plain weave, satin weave, and twill weave.

It is important that the fiber bundle is impregnated with the resin composition consisting of a thermoplastic polyamide-imide resin and a solvent such that the resin composition is uniformly impregnated into the fiber bundle. A uniform prepreg in such a state is preferable because voids are less likely to occur after molding. According to the present invention, the fiber bundle is opened using a conventional opening means such as a series of bars or rollers, and is impregnated with a resin composition consisting of a thermoplastic polyamide-imide resin and a solvent under such conditions. A prepreg in which the fiber bundle is uniformly impregnated with the resin composition can be obtained.

〔Effect of the invention〕

As detailed above, the present invention allows the solvent to be easily removed by washing the intermediate prepreg with water and/or methanol, and furthermore, the residual amount of solvent in the intermediate prepreg can be controlled by drying in a short time. Therefore, it is a useful method for manufacturing prepreg.

Furthermore, the fiber-reinforced thermoplastic polyamide-imide resin prepreg obtained by the present invention does not generate voids when molded and its physical properties at high temperatures do not deteriorate, so its industrial value is extremely large.

〔Example〕

The present invention will be further explained by examples, but the present invention is not limited thereto.

Example 1 25% by weight of thermoplastic polyamide-imide resin (Sumika FAI injection molding grade manufactured by Sumikagaku Kogyo ■) was used, and 75% by weight of N,N-dimethylformamide was used as a solvent.

A uniform solution state was obtained by mixing the resin and N,N-dimethylformamide using a stirrer.

Carbon fiber tow (Magnamite@AS-4 manufactured by Sumika Vercules ■, number of filaments = 12 kf) was used as the reinforcing fiber.

By passing the carbon fiber tow through two bars immersed in the solution, the fiber bundle was impregnated with the solution, and a unidirectionally aligned intermediate prepreg was produced by a drum winding method. As a result of spraying industrial water on the intermediate prepreg wound on a drum to remove the solvent, the intermediate prepreg showed a state in which the thermoplastic polyamide-imide resin and the fibers were strongly bonded and had extremely good shape retention. Furthermore, the residual content of N,N-dimethylformamide was 5.6% by weight.

Subsequently, the intermediate prepreg is cut in the axial direction of the drum,
As a result of heating for 1 hour in an oven set at a temperature of 200°C, there was no residual amount of N,N-dimethylformamide.
A prepreg uniformly impregnated with 5% by weight of the resin was obtained.

The 16 sheets of prepreg were laminated into a mold of 100 x 100 m size and hot press molded under the molding conditions of 380"C 160 kg/cd. As a result, 10 sheets with no voids were formed.
A good laminate measuring 0 m x 100 mm x 2 m thick was obtained. The fiber volume content in the laminate was 60% by volume.

The physical properties of the laminate are shown in Table 1.

Example 2 A unidirectionally aligned intermediate prepreg was produced by the drum winding method in the same manner as in Example 1 except that methanol was used to remove the solvent from the intermediate prepreg.

After cleaning with methanol 3 iV, N in the intermediate prepreg,
The residual content of N-dimethylformamide was 6.2% by weight.

Next, cut the intermediate prepreg in the axial direction of the drum.1.
As a result of heating for 1 hour in an oven set at a temperature of 200°C, there was no residual N,N-dimethylacetamide.
．． A prepreg uniformly impregnated with 6% by weight of the resin was obtained.

As a result of molding the prepreg in the same manner as in Example 1, a good laminate without voids was obtained. The fiber volume content in the laminate was 60% by volume.

The physical properties of the laminate are shown in Table 1.

Example 3 A unidirectionally aligned intermediate prepreg was produced by the drum winding method in the same manner as in Example 1 except that N,N-dimethylacetamide was used as the medium.

Water 3! After washing, the residual amount of N,N-dimethylacetamide in the intermediate prepreg was 3.6% by weight.

Next, cut the intermediate prepreg in the axial direction of the drum, and
As a result of heating for 1 hour in an open air set at a temperature of 00°C, the residual amount of N,N-dimethylacetamide was 0.2
A prepreg was obtained which was uniformly impregnated with the resin in the same amount by weight.

As a result of molding the prepreg in the same manner as in Example 1, a good laminate without voids was obtained. The fiber volume content in the laminate was 60% by volume.

The physical properties of the laminate are shown in Table 1.

Comparative Example 1 A unidirectionally aligned intermediate prepreg was produced in the same manner as in Example 1 by the drum winding method.

With the intermediate prepreg wound on the drum, 200
When heated for 12 hours in an open air set at °C,
The residual content of N,N-dimethylformamide is 3.8% by weight.
A prepreg was obtained.

As a result of molding the prepreg in the same manner as in Example 1, a laminate with many voids was obtained. The fiber volume content in the laminate was 60% by volume.

The physical properties of the A-layer plate are shown in Table 1.

Claims (1)

[Claims] In a method for producing a prepreg by removing the solvent from an intermediate prepreg produced by impregnating reinforcing fibers with a resin composition consisting of a thermoplastic polyamide-imide resin and a solvent,
A method for producing a fiber-reinforced thermoplastic polyamide-imide resin prepreg, which comprises washing the intermediate prepreg with water or/and methanol and drying it.