JP2006037252A - Method for producing fiber structure for resin reinforcement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a fiber structure, with which adhesiveness to a matrix resin, especially low water absorption properties of a composite material in the case of resin reinforcement is remarkably improved without impairing properties that an aromatic polyamide fiber essentially has and to obtain a fiber-reinforced composite material. <P>SOLUTION: The fiber structure composed of an aromatic polyamide fiber is coated with a treatment liquid that contains 0.01-10 wt.% of an adhesive component and mainly comprises a fiber-swelling organic solvent and then heat-treated at a temperature of the boiling point of the organic solvent minus ≥50°C. Preferably the aromatic polyamide fiber is a para-type aromatic polyamide fiber, the adhesive component is a silane coupling agent or a thermosetting resin and the fiber-swelling organic solvent comprises one or more kinds selected from the group consisting of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and sulfolane. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a fiber structure that significantly improves the adhesion to a resin without impairing the inherent properties of the fiber when used as a composite material, and a fiber-reinforced composite material using the same.

  Aromatic polyamide fiber is an organic polymer material with high strength, high elastic modulus, and excellent heat resistance. Therefore, this fiber is used as a reinforcing material, and fiber reinforcement using a matrix as thermosetting and thermoplastic resin. Composite materials are used in various fields such as automobiles, architecture, civil engineering, and electricity, and their utilization is desired in other fields.

  However, aromatic polyamide fibers are known to have a lower affinity with resins than glass fibers and carbon fibers, which are reinforcing fibers for other general-purpose resins. The current situation is that development is difficult.

  For example, chemical surface treatment by chemical treatment or plasma treatment has been attempted in order to improve the affinity with the matrix. However, these treatments have a problem in that the fiber is deteriorated due to excessive reaction. Even when the surface treatment method using plasma discharge (for example, Patent Document 1) or excimer laser (for example, Patent Document 2) is employed as a method for etching only the surface of the aromatic polyamide fiber, the surface morphology is changed. This causes a decrease in surface crystallinity, and there is a problem that the fibrillation phenomenon of the fiber becomes conspicuous with a remarkable decrease in crystallinity near the surface. When such fibrillation occurs, it is known that although the adhesiveness at the interface is improved in order to cause fiber breakage, the fiber material embrittlement leads to deterioration of the composite material characteristics.

  Further, for example, Patent Document 3 discloses a method of treating fibers in advance with an aqueous treatment agent containing an adhesive component and a surfactant. However, an aqueous adhesive has a weaker adhesive strength than a solvent-based adhesive, and further has a fragrance. The group polyamide fibers (aramid fibers) have a problem that they easily absorb moisture. Organic aramid fibers may be more hygroscopic than inorganic glass fibers and carbon fibers, and fiber-reinforced composites using fibers that have been treated in this way are at the interface between the fibers and the matrix resin. There was a problem that moisture was absorbed, resulting in deterioration of physical properties and microscopic destruction of the matrix resin.

Japanese Patent Publication No. 1-1867 JP-A-4-136267 JP 2002-194669 A

  The object of the present invention is to solve the problems in the prior art described above, and to reduce the water absorption of the composite when the resin is reinforced, particularly the adhesiveness to the matrix resin without impairing the inherent properties of the aromatic polyamide fiber. An object of the present invention is to provide a method for producing a fiber structure that can be remarkably improved, and a fiber-reinforced composite material that is excellent in mechanical properties.

  In the method for producing a fiber structure for resin reinforcement of the present invention, a treatment liquid mainly containing a fiber swellable organic solvent containing 0.01 to 10% by weight of an adhesive component is added to a fiber structure made of aromatic polyamide fibers. It is characterized by being coated and then heat-treated at a temperature of the boiling point of the organic solvent minus 50 ° C. or higher.

  Further, the aromatic polyamide fiber is a para-type aromatic polyamide fiber, the adhesive component is a silane coupling agent or a thermosetting resin, and the fiber swellable organic solvent is N- It is preferable to include one or more selected from the group consisting of methyl-2-pyrrolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, and sulfolane. Moreover, it is preferable that the fiber structure after heat treatment is impregnated with a matrix resin, and the adhesive component is the same as one component of the matrix resin.

  The fiber-reinforced composite material of the present invention is characterized in that it is formed from the fiber structure obtained by the above production method and a thermosetting resin or a thermoplastic resin.

  According to the present invention, while maintaining the properties inherent to aromatic polyamide fibers, the method for producing a fiber structure that significantly improves the adhesiveness to the matrix resin, particularly the low water absorption of the composite when the resin is reinforced, And a fiber-reinforced composite material using the same and having excellent mechanical properties.

Hereinafter, embodiments of the present invention will be described in detail.
The production method of the present invention is a method of applying a treatment liquid mainly containing a fiber swellable organic solvent and containing an adhesive component to a fiber structure composed of aromatic polyamide fibers, followed by heat treatment.

  The aromatic polyamide fiber used in the present invention is a short fiber in which 80 mol% or more, preferably 90 mol% or more of the repeating units constituting the polyamide are composed of aromatic homopolyamide or aromatic copolyamide. Here, the aromatic groups to be fibers may be the same or different aromatic groups. The hydrogen atom of the aromatic group may be substituted with a halogen atom, a lower alkyl group, a phenyl group, or the like.

  With respect to the production method and fiber characteristics of such aromatic polyamide fibers, for example, conventionally known methods such as JP-A-49-100322, JP-A-47-10863, JP-A-58-144152, JP-A-Hei. What is described in 4-65513 gazette etc. can be used.

  Among the aromatic polyamide fibers, para-type aromatic polyamide fibers are preferable because they are excellent in heat resistance and strength. The para-type aromatic polyamide fiber is a fiber made of polyamide in which the chain bond of the aromatic polyamide is coaxial or parallel and faces in the opposite direction.

  Specifically, polyparaphenylene terephthalamide fiber (for example, “Twaron” manufactured by Teijin Towalon BV) or copolyparaphenylene • 3,4′-oxydiphenylene which is a copolymer type aromatic polyamide fiber. -A terephthalamide fiber (for example, "Technola" manufactured by Teijin Techno Products Co., Ltd.) is exemplified, and the latter, which is a copolymer type, is particularly preferable because of its high swellability with respect to the organic solvent.

  The aromatic polyamide fiber used in the present invention is preferably used as a long fiber filament in order to utilize its strength, and more preferably as a non-twisted multifilament, but depending on the form of reinforcement, it may be used as a short fiber. Is also preferable.

  Further, the fiber structure made of the aromatic polyamide of the present invention is not particularly limited as long as it is a form used for resin reinforcement, but a woven fabric, a nonwoven fabric, a knitted fabric having an aromatic polyamide fiber as a main component, A mesh shape, a unidirectionally aligned sheet shape, and a honeycomb sheet material are preferable, and it is also preferable that one or a combination of two or more materials thereof is used.

  The production method of the present invention is such that a fiber assembly composed of aromatic polyamide fibers is mainly subjected to a heat treatment by attaching a treatment liquid containing an adhesive component mainly containing a fiber swellable organic solvent. A swellable organic solvent is an organic solvent that has the effect of swelling fibers to lower the crystallinity and loosening the crystal orientation. For example, preferred examples include N-methyl-2-pyrrolidone, dimethyl sulfoxide (hereinafter referred to as DMSO), N, N-dimethylformamide, N, N-dimethylacetamide, sulfolane (tetramethylene sulfone) and the like. I can do it. DMSO is particularly preferable because of its high fiber swelling effect. In addition to the fiber-swellable organic solvent, a normal organic solvent that dissolves the adhesive component may be added to the treatment liquid. Preferably, the fiber-swellable organic solvent is 50% by weight in the treatment liquid. % Or more is preferable. By using such an organic solvent as a solvent for the treatment liquid, in the composite material finally obtained, not only the adhesion between the fiber and the resin used in the subsequent process, but also the adhesion is increased, so that the fiber / resin of the composite material Moisture absorption into the water can be significantly reduced.

  The adhesive component used in the present invention is preferably a silane coupling agent or a thermosetting resin.

  As the silane coupling agent, conventionally known silane coupling agents can be used, but epoxy silane, amino silane, and imidazole silane are preferable from the viewpoint of affinity with the aromatic polyamide fiber.

  More specifically, examples of the thermosetting resin include phenol resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, polyimide resin, bismaleimide-triazine resin, and the like.

  These adhesive components may be appropriately selected according to the type of matrix resin impregnated into the fiber structure to form a fiber reinforced composite material, the use of the final fiber reinforced composite material, and the required characteristics. It is preferably the same as one component of the matrix resin.

  The treatment liquid to be attached to the fiber structure is mainly composed of a fiber swellable organic solvent and contains an adhesive component in an amount of 0.01 to 10% by weight. The proportion of the adhesive component is preferably 5% by weight or less, more preferably 4% by weight or less. Moreover, as a minimum, it is preferable that it is 0.01 weight% or more, Furthermore, it is 0.1 weight% or more. When the adhesive component exceeds 10% by weight, the effect of the organic solvent is reduced, and the organic solvent in the treatment liquid in the subsequent heating process may not be completely removed. In such a case, the viscosity of the treatment liquid may increase. In the subsequent process, a matrix resin is impregnated to create a fiber-reinforced composite material. Is likely to occur, which is not preferable. When the adhesive component is too small, the viscosity is insufficient and the treatment liquid tends not to adhere uniformly around the fiber.

  In order to apply the treatment liquid to the fiber structure, for example, the fiber structure may be passed through a dip bath of the treatment liquid and impregnated. Here, “pass” means not to immerse in a solvent and leave it to react in a bath, but to immerse it in a processing solution and then immediately pull it up to make contact for a short time. To tell. The impregnation time in the treatment liquid depends on the temperature of the treatment liquid, but is preferably 0.1 to 60 seconds, and more preferably 1 to 5 seconds. The temperature of the treatment liquid is preferably in the range of 0 to 60 ° C, more preferably 10 to 50 ° C, and particularly preferably 15 to 30 ° C. It is preferable from the viewpoint of work efficiency that the temperature of the treatment liquid is around room temperature.

  The adhesive component in the treatment liquid applied in this manner preferably has a solid content adhesion amount of 0.01 to 10% by weight based on the fiber weight after drying. Furthermore, it is preferable that it is 1 weight% or less. In order to increase the adhesion amount of the adhesive component, it is necessary to increase the content of the adhesive component in the treatment liquid, which tends to hinder the effects of the present invention.

  The fiber structure to which the treatment liquid has been applied is subsequently subjected to heat treatment. As the processing temperature, it is essential that the boiling point of the organic solvent in the processing liquid is minus 50 ° C. or higher. Further, the boiling point is preferably minus 40 ° C. or higher. The upper limit may be any processing condition or temperature condition in which the resin as the adhesive component is not completely cured, but is preferably 30 ° C. or less from the boiling point. Here, when a plurality of organic solvents are used as the solvent, the boiling point of the organic solvent having the highest boiling point is used as a reference. When the heat treatment is performed at a temperature lower than the boiling point minus 50 ° C., even if the drying time is extended, the excess organic solvent cannot be removed, causing adhesion spots, which is a defect in adhesion. Even if it can be removed, since the heat treatment for a long time is required, the treatment agent is completely cured or altered, and then peels off at the interface with the matrix resin layer to be impregnated, or cohesive failure occurs in the treatment agent layer. This is undesirable because the performance of the composite material is reduced.

  As the heat treatment time, it is necessary to adjust the time appropriately according to the type of resin and the degree of curing, and the treatment agent attached to the fiber surface after this heat treatment is preferably in a semi-cured state. Accordingly, the heat treatment time is preferably 1 to 60 minutes, more preferably 3 to 20 minutes. Here, the semi-curing means a state in which a part of the solvent is removed and the adhesive component is solidified but not yet completely crosslinked.

  Moreover, it is preferable that the fiber structure of the present invention is further impregnated with a matrix resin after the heat treatment. Several prepreg sheets made of such fibers and matrix resin can be stacked to form a fiber-reinforced composite material. At this time, the adhesive component used in the treatment liquid is preferably the same as one component of the matrix resin. By performing heat treatment in the process of forming a composite material using such a prepreg sheet, the crosslinking reaction with the matrix resin of the adhesive component proceeds, and the adhesive component applied to the fiber structure is finally completely cured. It becomes a state. In other words, by impregnating the matrix resin in a semi-cured state and then heat forming, it is combined with the matrix resin with the adhesive component embedded in the fiber, and as a result, the adhesion between the fiber and the matrix resin is improved. The

  Another fiber-reinforced composite material of the present invention is formed from a fiber structure for resin reinforcement obtained by the above production method and a thermosetting resin or a thermoplastic resin. In order to further secure the thickness, a method of stacking several resin reinforcing fiber composites is preferable.

  There is no particular limitation on the method for producing the fiber-reinforced composite material of the present invention, but in general, in order to completely cure the semi-cured treatment agent and matrix resin adhering to the fiber surface, heating is performed at a temperature corresponding to the impregnated resin. While molding.

  Specific examples include hand lay-up method, resin injection method, BMC method, SMC method, compression molding method, etc., depending on the target shape and the type of matrix resin made of thermosetting resin or thermoplastic resin. The most suitable molding method may be applied, but the compression molding method is particularly preferred, promoting chemical bonding with the adhesive component adhering to the fiber surface, and more effective in improving the adhesion between the fiber structure and the matrix resin. Can be expressed.

  The fiber-reinforced composite material of the present invention has improved adhesion between the fiber and the matrix resin without impairing the original properties of the fiber. Therefore, it is excellent in mechanical characteristics and durability, and can be suitably used for housings such as automobiles and ships, electrical insulating materials such as printed circuit boards, and other various fields. Furthermore, the effect of the organic solvent in the treatment liquid increases the adhesion between the fiber and the matrix resin, lowers the water absorption, and excels in heat stability during moisture absorption, making it ideal for electrical insulating materials such as printed circuit boards. It is.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the preparation method of the test piece used in the Example and its evaluation method are as follows.

(1) Water Absorption Rate of Fiber Reinforced Composite Material Weight M ₁ after measuring the fiber reinforced composite material in a pressure cooker at a temperature of 121 ° C., humidity of 100% RH and pressure of 2 atm for 200 hours is measured, and then the temperature is 105 ° C. The value calculated by the following formula from the weight M ₀ after drying for 2 hours and slowly cooling in a desiccator for 30 minutes is defined as the water absorption rate.
(Water absorption) = (M ₁ −M ₀ ) × 100 / M ₀ (%)

(2) Land strength In a laminated board which is a fiber reinforced composite material, a 7 mm long pin is placed by soldering on a 2 mm square land formed by etching a surface copper foil, and the direction in which the pin is tilted down A force was applied to a position 4 mm from the bottom, and the maximum load when the land was peeled and the pin was tilted was measured. The unit was N.

(3) Bending strength and elastic modulus The fiber reinforced composite material was measured in accordance with 5.8 of JIS C-6481.

[Example 1]
As a fiber structure made of an aromatic polyamide, the basis weight is 61 g / m ² , the thickness is 0.11 mm, and untwisted fibers with a fineness of 220 dtex / 133 filaments are 34 / 2.54 cm (1 inch) both vertically and horizontally. A plain woven fabric made of copolyparaphenylene 3,4′-oxydiphenylene terephthalamide was prepared.

  Separately, a treatment solution was prepared. That is, by using an epoxy resin composition comprising a high purity brominated bisphenol A type epoxy resin and an orthocresol novolac type epoxy resin as adhesive components, this methyl ethyl ketone solution (resin composition content: 80% by weight) is used. DMSO (dimethyl sulfoxide, boiling point 189 ° C.), which is an organic solvent that swells aromatic polyamide fibers, is mixed and diluted so that the content of the adhesive composition in the processing liquid is 2% by weight. It was created.

  Next, the plain fabric prepared previously, which is a fiber structure made of aromatic polyamide, was immersed in a treatment solution at 23 ° C. for 5 seconds. After sufficiently squeezing the excessively attached treatment solution, heat treatment was performed at 150 ° C. for 10 minutes to produce a fiber structure for resin reinforcement composed of aromatic polyamide fibers to which an epoxy resin was adhered. The adhesion amount of the adhesive component after this was completely dried was 1.0% by weight. The production conditions of the fiber structure are shown in Table 1.

[Example 2]
The fiber structure for resin reinforcement obtained in Example 1 was used as a base material, and high purity brominated bisphenol A type epoxy resin and orthocresol novolac type epoxy resin were used as the base material for the base material, and dicyandiamide as a curing accelerator. After impregnating a compound varnish obtained by dissolving an epoxy resin composition containing 2-ethyl-4-methylimidazole in a mixed solution of methyl ethyl ketone and methyl cellosolve, it was dried at a temperature of 120 ° C. for 15 minutes, A semi-cured (B stage) prepreg sheet having a thickness of 0.17 mm was prepared.

Furthermore, 16 sheets of the above prepreg sheets were stacked to a thickness of 1.6 mm, and an electrolytic copper foil with a thickness of 18 μm was stacked on both sides, and the pressure was 20 to 50 kg / cm ² , and the lamination temperature was 170 ° C. for 50 minutes. A thermocompression treatment was carried out, and further a curing treatment was carried out in a hot air dryer at 200 ° C. for about 20 minutes. Further, the copper foil on the surface was entirely etched, washed with water and air-dried to produce a fiber-reinforced composite material composed of aromatic polyamide fibers. . The ratio of the thermosetting resin (including the adhesive component) in the total weight was a composite material of 60% by weight, and was optimal as a printed circuit board. The various properties evaluated are shown in Table 2.

[Example 3]
In Example 1, a fiber structure for resin reinforcement was produced in the same manner as in Example 1 except that the heat treatment temperature at 150 ° C. was changed to 170 ° C. Further, a composite material was prepared in the same manner as in Example 2 using this fiber structure.
Manufacturing conditions are shown in Table 1, and various characteristics are shown in Table 2.

[Example 4]
In Example 1, the organic solvent for swelling the aromatic polyamide fiber in the treatment liquid was changed from DMSO to N, N-dimethylacetamide (DMAc, boiling point 165.5 ° C.), and the heat treatment temperature at 150 ° C. was changed to 130 ° C. Except having changed, it carried out like Example 1 and manufactured the fiber structure for resin reinforcement. Further, a composite material was prepared in the same manner as in Example 2 using this fiber structure.
Manufacturing conditions are shown in Table 1, and various characteristics are shown in Table 2.

[Comparative Example 1]
In Example 1, a resin reinforcing fiber structure was produced in the same manner as in Example 1 except that the concentration of the epoxy resin composition as the adhesive component in the treatment liquid was changed from 2% by weight to 15% by weight. Further, a composite material was prepared in the same manner as in Example 2 using this fiber structure.
Manufacturing conditions are shown in Table 1, and various characteristics are shown in Table 2.

[Comparative Example 2]
In Example 1, it carried out similarly to Example 1 except not being immersed in the process liquid, ie, the untreated plain fabric was made into the fiber structure for resin reinforcement. Further, a composite material was prepared in the same manner as in Example 2 using this plain fabric as a fiber structure.
Manufacturing conditions are shown in Table 1, and various characteristics are shown in Table 2.

[Comparative Example 3]
The untreated plain fabric prepared in Example 1 was washed with water and dried, then treated in DMSO heated to 80 ° C. for 30 minutes, then washed with hot water for 30 minutes, washed with water and dried. A composite material was prepared in the same manner as in Example 2 using this plain fabric as a fiber structure.
Manufacturing conditions are shown in Table 1, and various characteristics are shown in Table 2.

Claims (9)

  A treatment liquid containing 0.01 to 10% by weight of an adhesive component and mainly a fiber swellable organic solvent is applied to a fiber structure composed of aromatic polyamide fibers, and then the boiling point of the organic solvent is not lower than 50 ° C. A method for producing a fiber structure for resin reinforcement, characterized by heat treatment at a temperature.   The method for producing a fiber structure for resin reinforcement according to claim 1, wherein the aromatic polyamide fiber is a para-type aromatic polyamide fiber.   The method for producing a fiber structure for resin reinforcement according to claim 1 or 2, wherein the fiber structure is any one of woven fabric, nonwoven fabric, paper, knitted fabric, mesh, unidirectionally aligned sheet, and honeycomb sheet.   The method for producing a fiber structure for resin reinforcement according to any one of claims 1 to 3, wherein the adhesive component is a silane coupling agent or a thermosetting resin.   The fiber-swellable organic solvent contains at least one selected from the group consisting of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, and sulfolane. Item 5. A method for producing a fiber structure for resin reinforcement according to any one of Items 1 to 4.   The method for producing a fiber structure for resin reinforcement according to any one of claims 1 to 5, wherein the adhesive amount of the adhesive component relative to the fiber weight is 0.01 to 10% by weight.   The method for producing a fiber structure for resin reinforcement according to any one of claims 1 to 6, wherein the fiber structure after heat treatment is impregnated with a matrix resin.   The method for producing a fiber structure for resin reinforcement according to claim 7, wherein the adhesive component is the same as one component of the matrix resin.   A fiber reinforced composite material formed from the fiber structure produced by the method according to any one of claims 1 to 8, and a thermosetting resin or a thermoplastic resin.