JPH01306680A - Production of bundled reinforcing fiber and short fiber chip - Google Patents

Abstract

PURPOSE:To obtain the subject bundled fiber, having coherency and excellent uniform dispersibility suitable as a reinforcing material for fiber-reinforced molding materials, by preapplying fine resin particles having a specific particle diameter to a fiber bundle and then applying a binder. CONSTITUTION:A bundled reinforcing fiber strand and short fiber chips are produced. In the process, fine particles of a thermoplastic and/or solvent-soluble resin (e.g. polyethylene terephthalate or nylons) having <=20mum average diameter of primary particles in an amount of 0.1-10wt.% based on the weight of fibers are preapplied thereto by a method for spraying the particles, etc. A resin of the same kind as that used in molding materials, e.g. polyolefin or polyester, in an amount of 0.1-50wt.% based on the weight of the fibers as a binder is then applied to afford a fiber bundle excellent in coherency. The above- mentioned bundled fibers are cut to readily provide short fiber chips. The resultant chips are excellent in coherency without causing opening thereof in molding the chips to afford uniform dispersibility in matrix resins and the operating efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing bundled reinforcing fibers and staple fiber chips. More specifically, the present invention relates to a method for producing bundled reinforcing fibers and short fiber chips that have a suitable bundling property and excellent uniform dispersibility as a reinforcing agent for fiber-reinforced molding materials.

(Prior Art) In recent years, fiber-reinforced molding materials made by mixing and dispersing reinforcing fibers such as glass fibers, carbon fibers, and aramid fibers in various matrix resins have been attracting attention as industrially important materials. In particular, aramid fibers, especially para-oriented aromatic polyamide fibers represented by poly-paraphenylene terephthalamide, have excellent properties such as high strength, high modulus, high impact resistance, and high abrasion resistance. Therefore, it is expected to have a wide range of applications as fiber-reinforced molding materials.

Generally, in order to obtain a fiber-reinforced molding material by mixing and dispersing reinforcing fibers in various thermoplastic resins, the fibers are bundled in advance with a glue, etc., and then cut into 1 to 10 pieces to form short fiber chips. A method has been adopted in which this is melt-kneaded together with thermoplastic resin pellets or powder in an extruder.

However, in this case, if the short fiber chips have insufficient convergence, they cannot be uniformly dispersed in the thermoplastic resin, and workability also decreases.

Therefore, such short fiber chips are required to have sufficient bundling properties, and in order to improve the bundling properties of the fibers, a method is usually used in which the fiber bundle is treated with a bundling agent. For example, resins of the same type as the matrix resins normally used as sizing agents in fiber-reinforced molding materials, such as polyolefins, polyesters, polyamides, acrylic resins, epoxy resins,
A method using phenol resin etc. and dissolving these resins in a solvent and attaching them to fiber bundles (Japanese Patent Laid-Open No. 53-10675)
2 Publication) 1 or a method of focusing with polyamide resin granules surface-treated with a surfactant (Japanese Patent Application Laid-open No. 6!
-254629) has been adopted.

However, depending on the method described above, it is difficult to uniformly attach enough resin to the fiber bundle for convergence.
Short fiber chips with excellent cohesion and workability cannot be obtained. In particular, when the fiber bundle is made of para-oriented aromatic polyamide fiber, it is difficult to adhere uniformly, and the fiber itself is a high-strength fiber with excellent flexibility. In the process of cutting and forming into shapes, fiber opening of the chips occurs. When such short fiber chips are fed into a matrix resin using, for example, a screw feeder, hopper feeder, table feeder, etc., the short fiber chips are subjected to mechanical mixing or agitation during the feeding process, so that the chips are The fiber opening progresses further, impeding smooth supply and causing clogging in the supply process. In this way, in the conventional method, it is not possible to control the amount of fiber in the fiber-reinforced molding material constant and uniformly, and the short fiber chips and matrix resin are continuously kneaded in an extruder. When attempting to extrude a strand-shaped molding material, a constant extrusion speed cannot be obtained, resulting in frequent breakage of the strand, resulting in a significant drop in productivity.

(Problems to be Solved by the Invention) The present invention solves the disadvantages that occur when producing fiber-reinforced molding materials using conventional methods, namely troubles in the supply process caused by opening of short fiber chips and poor workability. To provide a method for efficiently producing bundled fibers that do not cause the chips to open during short fiber chip molding, and to overcome troubles in uniform dispersion in a matrix resin, and to overcome troubles in the supply process. To provide a method for producing short fiber chips that have excellent convergence and uniform dispersibility in a matrix resin so as not to cause fibers to form, thereby producing a fiber-reinforced molding material having high physical properties. The purpose is to

(Means for Solving the Problems) In order to overcome the above-mentioned problems and achieve the object of the present invention, the present inventor has conducted extensive research on a method for applying a sizing agent to reinforcing fibers. As a result, the sizing agent can be efficiently and uniformly applied between the single yarns of reinforcing fibers by adhering specific fine particles in advance before applying the sizing agent, and the resulting reinforcing fibers and short fiber chips It was discovered that this compound has extremely excellent dispersibility in a matrix resin, and the present invention was completed.

That is, the present invention provides a method for producing reinforcing fiber strands and short fiber chips by applying a sizing agent to a fiber bundle, and prior to applying the sizing agent, the fiber bundle is preliminarily treated with primary particles having an average diameter of 20 μm or less. This is a method for producing bundled reinforcing fibers and short fiber chips, characterized in that a sizing agent is applied after fine particles made of a thermoplastic and/or solvent-soluble resin are attached.

The reinforcing fibers used in the present invention include glass fibers, carbon fibers obtained by firing polyacrylonitrile fibers, pinch carbon fibers, ceramic fibers made of alumina, boron nitride, silicon nitride, etc., and para-oriented aromatic polyamide fibers. It is.

In particular, para-oriented aromatic polyamide fibers are high-strength fibers with great flexibility, and are inferior in uniform application of sizing agents and uniform dispersion into matrix resins. It exhibits particularly excellent effects on polyamide fibers.

Here, the para-oriented aromatic polyamide fiber refers to poly-paraphenylene terephthalamide and its -NH+NH- position or/and other aromatic diamino residues or/and other aromatic dicarboxyl residues. It refers to fibers made of copolyamides made of substituted copolyamide units and mixtures of two or more of these, and specifically includes poly-varabenzamide, poly-vara phenylene terephthalamide, poly-4,4'-
Diaminobenzanilide terephthalamide, poly-varaphenylene-2,6-natalic amide, copoly-varaphenylene/4.4'(3,3'-dimethylbiphenylene) terephthalamide, copoly-varaphenylene/
Examples include fibers made of 3.4' (oxydiphenylene) terephthalamide and the like.

In the present invention, prior to applying a sizing agent to the above-mentioned fiber bundle, it is important to previously attach fine particles made of a thermoplastic and/or solvent-soluble resin with an average primary particle diameter of 20 μm or less.

In order to obtain a fiber-reinforced molding material, a method is used in which short fiber chips bundled together with thermoplastic resin pellets or powder are melt-kneaded in an extruder. At that time, if the sizing agent is not uniformly contained between each single yarn in the short fiber chip, cracking, unraveling, etc. will occur in the extruder, and workability will be significantly reduced, and the thermoplastic matrix It cannot be uniformly dispersed in the resin. In order to prevent this, it is important to uniformly contain the sizing agent between the single yarns of the reinforcing fibers. In the present invention, prior to applying the sizing agent, fine particles made of thermoplastic and/or solvent-soluble resin are attached to the fiber bundle to form voids between the single yarns, so the sizing agent is applied between each single yarn. As a result of being able to contain it uniformly, it exhibits extremely excellent convergence, and furthermore, it becomes possible to uniformly disperse it in the resin that is the matrix.

In the present invention, thermoplastic and/or solvent-soluble resins include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyoxybenzoate, and aliphatic or aromatic groups such as nylon-6 and nylon-66. , polyolefins such as polyethylene, polypropylene, polyacrylonitrile, and polystyrene, polyvinyl alcohol, polyether sulfone, polyether ether ketone, and polyarylene sulfide.

In some cases, fiber bundles or short fiber knobs with good cohesiveness and uniform dispersibility can be obtained by using fine particles made of thermosetting resin in the method of the present invention, but generally the cohesiveness and uniform dispersibility are poor. It's not a good idea because there are too many things. Moreover, the physical properties of the fiber-reinforced molding material often deteriorate in the end.

In the present invention, the diameter of the particles attached to the fiber bundle is
- It is necessary that the average diameter of the particles is 20 μm or less. If excessively large particles are used, although it becomes easier to contain the sizing agent, the performance of the resulting fiber-reinforced molding material may be lowered, which is not preferable. On the other hand, if the particle size is too small, the content of the sizing agent will decrease, but this does not pose any particular problem in terms of sizing properties, and particles of several tens of μm can usually be used. . Workability,
.

From the point of view of the content efficiency of focusing property, etc., those having a diameter in the range of 0.1 to 15 μm are most preferably used.

Such particles can be produced by commonly used methods and equipment, such as freeze-pulverization, mechanical pulverization using a grinder mill, hammer mill, etc., or a method in which a dilute solution of the resin is first introduced into a precipitant and reprecipitated. etc., obtained by
If necessary, the particles may be sieved to a predetermined particle size by other treatments.

Such fine particles can be attached to the fiber bundle by spraying the dried fiber bundle, by introducing the fiber bundle into a fine particle layer deposited in a tank, or by dispersing the fine particles in a dispersion medium such as water. Any method may be used, such as introducing the fiber bundle into a bath and then drying it.

The amount of adhesion to the fiber bundle is 0.1 to 1 based on the fiber weight.
Preferably it is 0% by weight. If the amount of adhesion is too small, the effect of subsequent impregnation with a sizing agent will be reduced. On the other hand, if the amount is too large, the physical properties of the resulting molding material may be deteriorated, which is not preferable.

In the present invention, a sizing agent is applied to the fiber bundle to which fine particles are attached as described above. The sizing agent is not particularly limited, but it is usually the same type of resin used for the molding material, such as polyolefin, polyester, polyamide, acrylic resin, epoxy resin, phenolic resin, or highly heat resistant resin. aromatic polyetheretherketone, polyphenylene sulfide, aromatic polyetherketone,
Examples include aromatic polyetherimide.

Such a sizing agent is usually applied as a solution or dispersion dissolved in a solvent, but it can also be applied as a melt, for example. The amount of sizing agent applied to the fibers is often in the range of 0.1 to 50% by weight, preferably 0.5 to 30% by weight, based on the weight of the dry fibers, but is particularly limited to this range. It is not a matter of specificity, but may be determined as appropriate.

The specific method of applying the sizing agent is not particularly limited, and may be any commonly used method. For example, a method of applying a solution or dispersion of a sizing agent with a roll coater, dipping, spraying, squeezing roll, etc.
Examples include a method of adjusting the sizing agent through a diaphragm nozzle or the like. The bundled fiber bundle obtained by such a method may be subjected to removal of the solvent or dispersion medium, or heating of the applied sizing agent to improve the sizing property, as necessary.

Further, short fiber chips can be easily obtained by cutting the bundled fibers obtained as described above into a suitable length by known means.

The fiber-reinforced molding material can be produced by, for example, supplying the short fiber chips obtained by the method of the present invention and the matrix resin to an extruder either alone or in the form of a tri-blend, melting and kneading them, and then forming them into strands. It is obtained by cooling the extruded kneaded material with water and cutting it into lengths of 2 to 8 mm.

As a filler, for example, a powder or flake additive such as glass, calcium carbonate, mica, metal oxide, carbon black, etc. can be used in combination with this molding material as necessary.

The matrix resin used in the fiber-reinforced molding material may be a known resin, such as a thermoplastic saturated polyester resin such as polybutylene terephthalate resin or polyethylene terephthalate resin, polyolefin resin, polyamide resin, polyacetal resin, or polysulfone resin. , thermoplastic resins such as styrene resins and vinyl chloride resins, thermosetting resins such as epoxy resins, acrylic resins, phenolic resins, and unsaturated polyester resins, and aromatic polyetheretherketones as highly heat-resistant thermoplastic resins. , polyphenylene sulfide, aromatic polyether ketone, aromatic polyetherimide and the like.

In addition, the bundled fibers of the present invention are useful as they are, without being made into short fiber chips, for example, as reinforcing machines for concrete, cables, tension members for optical fibers, etc., and have high strength, It exhibits great properties such as dimensional stability.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A fiber bundle consisting of 3000 fibers with a single filament fineness of 1.42 denier made of poly-paraphenylene terephthalamide (
Kevlar 49) (manufactured by DuPont) was pulled out from the pan cage, wound 15 times on a pair of Nelson rolls with a 19 mm pinch, and then rolled up with a wine goo at a speed of 50 m/min. At this time, on the Nelson roll, the average particle size was 15
Fine particles made of nylon 66 of μm were sprayed. Fine particles were attached to the obtained fiber bundle in an amount of 1.8% by weight based on the weight of the fibers.

The thus wound fiber bundle is treated with epoxy resin (Araldite Standard, manufactured by Ciba Geigy), which is a condensation product of bisphenol A and epichlorohydrin.
After passing through the liquid, it was taken out through a 1.2φ aperture nozzle and heated at 130° C. for 2 minutes to obtain a bundle of fibers. The obtained fiber bundle was provided with 22.4 weight percent of epoxy resin based on the weight of the fibers.

As a result of cross-sectional observation of this fiber bundle, it was found that the spaces between each single yarn were well filled with epoxy resin.

This fiber bundle was cut into lengths of 5 mm using a chip cutter.
Short fiber chips were obtained. 15% by weight of the short fiber chips and 85 parts by weight of nylon 66 resin pellets were triblended using a type mixer.

This Drablend product was kneaded and extruded using a twin-screw extruder equipped with a screw feeder, and the resulting strands were pelletized to produce a PPT^ fiber-reinforced molding material. In this example, the twin-screw extruder was operated continuously for 6 hours, but no troubles such as supply stoppage due to fiber opening in the screw feeder or breakage of extruded strands occurred.

The tensile strength of a dumbbell-shaped test piece obtained by injection molding the fiber-reinforced molding material thus obtained was 1137 kg/
cJ, the bending strength was 1835 kg/cal, and the Izod impact value was 4.8 kg-cm/am. Comparative Example 1 All of the fiber bundles were the same as Example 1 except that fine particles made of nylon 66 were not attached to the fiber bundle. A focused fiber bundle was obtained in the same manner.

When this fiber bundle was cut into 511 pieces with a chip cutter,
Cracking of short fiber chips occurred.

A PPTA fiber-reinforced molding material was produced in the same manner as in Example 1, but at that time, a bridge was formed in the supply hopper of the screw feeder, making the supply unstable. Although there was no breakage of the extruded strand, the extrusion condition was unstable and a strand of constant thickness could not be obtained. This strand was pelletized and injection molded with the same fiber ratio as in Example 1. The tensile strength of the test piece obtained was 89.
0kg/c++! .

Bending strength: 1630kg/c, Izod impact value: 3.5k
g-cm/Cll1, which were all inferior to those using short fiber chips according to the method of the present invention.

Example 2 In exactly the same manner as in Example 1, polyether sulfone (Pictrex manufactured by Sumitomo Chemical was pulverized by the freeze-pulverization method) having an average particle diameter of 10 μm was sprayed, and the fiber weight was 2.5 μm.
A polyvara phenylene terephthalamide fiber bundle having 4% by weight of polyether sulfone fine particles attached thereto was obtained. Next, this fiber bundle was passed through a solution in which polyether sulfone was dissolved at a concentration of 35% by weight in N-methyl-2-pyrrolidone, and then taken out through a 1.2φ aperture nozzle in the same manner as in Example 1. N-methyl-2-pyrrolidone was evaporated in a hot air dryer with a residence time of 10 minutes at 180"C to obtain a fiber bundle.

Next, this fiber bundle was cut through a chip cutter so that it had a length of 6.5 fins to obtain short fiber chips. At this time, the cutting was carried out smoothly without generating fluff or cracking, and the cut surface was extremely clean short fiber chips.

Example 3 Polybutylene terephthalate was pulverized by freeze pulverization to obtain particles with an average particle size of 8.5 μm. These particles were dispersed in acetone to prepare a dispersion having a particle concentration of 5.4% by weight. Next, the same polyvalent phenylene terephthalamide fibers used in Example 1 were immersed in this dispersion, and then pulled up and the acetone was removed in a dryer at 80°C to remove the polybutylene terephthalate i particles. A fiber bundle was obtained. This fiber bundle has a fiber weight of 0.
8% by weight of fine particles were attached. Next, the epoxy resin used in Example 1 was applied to this fiber bundle in the same manner as in Example 1 to obtain a bundled fiber bundle. This fiber bundle was cut into 411 lengths to produce short fiber chips, mixed with polybutylene terephthalate chips so that the fiber weight was 15% by weight, and the strands were drawn out through an extruder and cut into 31 lengths using a chip cutter. A chip for molding was obtained by cutting it into pieces.

At this time, there were no operational troubles and good chips were obtained.

A test piece for measuring physical properties was molded from the obtained molding chip and the physical properties were measured. As a result, the tensile strength was 1065 kg/c+
+! The bending strength was 1440 kg/cnl, and the isot impact was 4.1 kg-cm/cm, which were extremely excellent.

(Effect of the invention) According to the method of the present invention, when obtaining bundled reinforcing fibers,
Since the sizing agent is evenly filled between each single yarn, the sizing property is extremely excellent, and a high-quality fiber bundle without cracking or fuzzing can be obtained. In addition, the short fiber chips obtained by the method of the present invention have excellent flowability as chips as well as bundling properties, and when producing fiber reinforced molding materials, they have excellent flowability in a supply hopper such as an extruder. As a result, productivity can be greatly improved because continuous and stable production is possible. Further, by having excellent uniform dispersibility in the matrix resin, a molded article having excellent mechanical properties can be obtained.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] In a method for producing reinforcing fiber strands and short fiber chips by applying a sizing agent to a fiber bundle, prior to applying the sizing agent, the average diameter of primary particles is preliminarily set to 20 μm in the fiber bundle.
A method for producing bundled reinforcing fibers and short fiber chips, which comprises adhering fine particles made of the following thermoplastic and/or solvent-soluble resin and then applying a binding agent.