SE461593B - FIBER CONTAINING REINFORCEMENT MATERIAL, PROCEDURES FOR PREPARING THEREOF AND USING THE REINFORCEMENT MATERIAL IN A COMPOSITION MATERIAL - Google Patents

Description

461 10 15 20 25 30 35 593 bonds between them.

One problem in this context is that it is a lot difficult to split carbon fiber bundles, which are cut in very short lengths (approx. 0.5-6.0 mm) for individuals carbon fiber threads.

The same problem exists with glass wires of the type roving, which are cut into relatively short wire lengths and which are connected in parallel bundles of wires.

Absolutely crucial for the effect of the reinforcement material are, among other things, the length and diameter of the threads and their chemical and physical surface structure. To good reinforcement effect to be achieved, the length / diameter ratio should be as follows as large as possible. When this ratio, (L / D ratio) ie the slenderness of the trees, increases, so the possibilities decrease to vigorously process the mixture of fibers in the composite material. rialets matrix. Glass wires of the rovíng type normally have a diameter between 10 and 20 μm, while the wire length can vary from a few millimeters up to several centimeters meter. The limitation of roving is its diameter, which in the manufacturing process can not be reduced as far as preferably. The limit is at about 8-10 μm. This means that if you want to increase the L / D ratio, it is basically the only one the ability to increase the wire length. As the length increases, it becomes however, it is becoming increasingly difficult to the distributors in the matrix are evenly distributed, and the the percentage of roving must therefore be kept low. Wishes a higher percentage of rovíng in the composite material, the length of the wire should be kept at a not too high value, which of course has a negative effect on the reinforcement effect.

To achieve the desired reinforcement effect, you get in instead join several threads into even larger bundles, s k flak. This in turn has a negative impact on the mixture with carbon fibers, since one only obtains a mechanical interaction in the matrix without any chemical or physical adhesion fiber to fiber. The result is that any significant improvements in terms of strength the values cannot be achieved. 10 15 20 25 30 35 461 593 3 The object of the present invention is to try provide a solution to the problem of defibrating carbon fiber bundles in individual carbon fibers and that in addition try to solve the problem of achieving a homogeneous mixture of carbon fibers and glass fibers, which mixture years useful as reinforcement material in manufacture of composite material.

The above objects are achieved by the invention provides a fiber-containing reinforcing material, characterized in that it consists of an essential homogeneous distribution of carbon fibers, glass fibers, fob, anionic, colloidal silica and cationic talc, wherein the weight ratio between carbon fibers and glass fibers is from 1: 99 to 99: 1, the silica constitutes about 5-20% by weight of the total amount of fiber, and the talc constitutes about 5-20% by weight of the total amount of fiber.

According to the invention there is also provided a method for production of a fiber-containing reinforcing material, which way is characterized by it, a) adding hydrophobic, anionic carbon fiber bundles, colloidal silica in an amount of about 5-20% by weight, calculated on the final reinforcement material total amount of fiber, and is divided into individual fibers by mixing under shear in dry conditions stand; b) that glass fibers are added to the mixture of fibers and silica in such an amount as to the ratio between carbon fibers and glass fibers is from 1:99 to 99: 1; and c) that about 5-20% by weight, calculated on the total fiber the amount, of cationic talc is distributed in the mixture of carbon fibers, silica and glass fibers. ,, Finally, the invention also encompasses use of the above fiber-containing reinforcement material material for the production of fiber-reinforced composite materials rial.

These and other characteristics are apparent from the the following description and of the claims. 461 10 15 20 25 30 35 593 4 In the following, the invention will be explained more in detail.

The fiber-containing reinforcement material according to the invention contains four essential components, namely carbon fibers, glass fibers, hydrophobic, anionic, colloidal silica, as well as cationic talc. These components and the limitations imposed on them by the invention explained in more detail below.

The carbon fibers used in the invention are of a conventional nature and originally exists as carbon fiber bundles. Both this raw material and its preparation are well known and need not be described closer here. Both the carbon fiber bundles and the individual ones the dimensions of carbon fibers can vary widely.

In general, however, the carbon fiber bundles have an average diameter of about 10-15 μm and includes about 10-20 individual fibers in each bundle. The average diameter of each individual carbon fiber preferably amounts to at most approx. l um. The carbon fiber bundles are generally made in relatively large lengths, which are cut into smaller ones lengths of about 1 cm or less. In the invention carbon fiber bundles (and thus carbon fibers) are preferred with an average length of about 0.5-6.0 mm. the reason in addition, below about 0.5 mm the carbon fiber deteriorates reinforcing effect, while carbon fibers with a length of more than about 6.0 mm are difficult to homogeneously mix and distribute in a matrix of a composite material. Within the specified, preferred limits (maximum approx. 1 μm average diameter and about 0.5-6.0 mm average length) should be the L / D ratio of the fiber, i.e. the slenderness number, is chosen so that optimal properties obtained with respect to reinforcement effect and homogeneous distribution in the matrix. , In addition to carbon fibers, the reinforcement material includes according to the invention also glass fibers. Also for fiberglass that both they and their presentation are so known that no further description here is necessary you. In the invention, glass fibers are used, as already 10 15 2_o 25 30 35 461 593 5 from the beginning exist as individual fibers, in contrast from, for example, roving, at which the threads are hard interconnected and therefore difficult to separate. It is desirable It is worth noting that the glass fibers of the invention are relatively thin and they preferably have an average diameter of about 0.5-6.0 μm, most preferably about 0.8-3.0 μm. It is further preferred that the average fiber length is about 0.5-15 mm, most preferably about 0.8-3 mm. Within these ranges of diameter and length, desirably high slenderness rates can be achieved, such as allows an optimal balance between good reinforcement effect and easy incorporation and distribution in the matrix material.

The invention is not limited to use of glass fibers of a particular type or composition but in principle all kinds of glass fibers, which are suitable as reinforcing fibers, useful. A particular preferred type of glass fibers are glass fibers of so-called C-glass.

Both the amount of carbon fibers and the amount of glass fibers in the fiber-containing reinforcement material according to the finding can be varied within wide limits. General applies that the weight ratio of carbon fibers: glass fibers can vary from about 1:99 to about 99: 1, preferably from about 10:90 to about 40:60. It is preferred to use a smaller one carbon fibers, among other things due to their high price fiberglass.

The third component in the fiber-containing the reinforcing material according to the invention is hydrophobic, anionic, colloidal silica. The main uptake of silica poison in the invention is to constitute a dispersant to divide the carbon fiber bundles into individual fibers.

Without being bound by any particular theory presumed that the silica penetrates into the fiber bundles and is distributed on the surface of the individual carbon fibers and thereby imparts these a negative charge, which acts repellent and thereby helping to separate the fibers.

Colloidal silica comes in several different forms, whereby can be mentioned: 461 593 10 15 20 25 30 35 6 1) Silica airgel, which is a colloidal silica, which is produced by replacing the water of a silica hydrogel with a low boiling point, water-miscible liquid, heated in an autoclave above the critical temperature of the liquid and thereafter ventilate the autoclave, 2) So-called fumed silica, which is a colloidal silicon dioxide, which is obtained by burning silicon tetra- chloride and collect the resulting silica fume, 3) Precipitated silica, produced by destabilizing water-soluble silica under conditions which does not allow the formation of a gel structure, but which instead causes flocculation of silica xid particles to cohesive aggregates, such as by adding sodium ions to a sodium silicate solution, as well as aluminosilicate, copper silicate, magnesium silicate and zinc silicate.

Colloidal silica is generally present as an aggregate, which are made up of extremely small primary particles .a size in the range about 5-20 nm. The extremely small primary the particle size causes colloidal silica to exhibit a large surface area of about 50-400 m2 / g or higher.

Colloidal silica is generally hydrophilic, but man has found in the invention that it should be hydrophobic to give satisfactory results in the division and the separation of the carbon fiber bundles. To the extent silica is not initially hydrophobic, it can be made hydrophobic by special surface treatment, which is known per se.

In the invention, colloidal silica of so-called pyrogen type and a particularly preferred silica is it marketed by Degussa under the trade name Aerosil R 972. This is a hydrophobic, anionic, colloidal silica having the following properties: Surface area according to BET (m3 / g) l20i30 Average particle size (nm) 16 pH value (according to DIN 53200) in 4% aqueous dispersion 3.5-4.1 10 15 20 25 30 35 461 593 7 SiO2> 93 | 3 Ä1203 (US) Fe2O3 <0.0l TiO2 <0.03 HCl <0.05 Among other types of silica can be mentioned the one that marketed by Cabot Corporation under the trade name ning Cab-O-Sil.

The amount of silica in the invention is about 5-20% by weight. preferably about 5-15% by weight, based on the total fiber content. the amount. In general it can be said that the amount of silica should be sufficient for coating the surface of the carbon fibers and preferably the silica should be present in some excess to at least stone also partially coat the surface of the glass fibers and therein by providing a more even charge distribution at the fibers.

The fourth component of the fiber-containing the reinforcing material according to the invention is cationic talc and preferably the variant known as soapstone. Soapstone is gray-greenish, while talc is almost white.

The general term "talc" usually includes wise (a) the mineral talc, (b) steatite, which is a compact variant of talc, and (c) the rock soapstone.

The mineral talc is a hydrated magnesium silicate with the ideal composition Mg3Si4O10 (OH) 2. Talc- the content of commercial talc is high and usually is at about 97% by weight. In the production of commercial talc crushed and ground talc mineral and then undergoes purification by flotation to produce a talc product with high talc content and whiteness. ' Soapstone is a natural product, which is mineralogical consists of talc mixed with a high content of chlorite and minor amounts of carbonate and amphibole. For example, has soapstone from Handöl in Sweden the following mineral setting: 461 593 10 15 20 25 30 35 8 talc about 67% by weight p merit ca 18 vikta; _ i carbonate about 8% by weight amphibole about 3% by weight ß ore material about 4% by weight An example of mineral talc is the one that held under the name Finntalk P40 from Outokumpu Oy, Finland. This talc has an average diameter of about 10-20 μm, a talc content of about 97% by weight, a loss on ignition of 7% by weight and an oil absorption value of 32 g oil / 100 g talc.

Melting point is 135 ° C.

As an example of a suitable soapstone in the invention can be mentioned soapstone of type H340 from Handöl, Sweden.

This soapstone is micronized and has a medium diameter of 5-10 um. The talc content is about 67% by weight and the loss on ignition about 8% by weight. The oil absorption value is 55 g oil / 100 g soapstone and melting point is 1500 ° C.

It is also possible to use in the invention mixtures of talc minerals and soapstone. The proportions between talc and soapstone can vary widely limits, preferably from a weight ratio of approx 30:70 to about 70:30, more preferably from about 40:60 to about 60:40, and preferably about 50:50.

The particle size of the talc is not critical in the invention. but is usually in the range of about 5-10 μm.

As mentioned above, the talc is cationic, and yet the goal of incorporating talc into the fiber-containing the reinforcing material according to the invention is that it acts as a cationic additive to the anionic carbon fibers and glass fibers, but also to matrix material, which is preferably selected from anionic polymers. materials such as polyolefins (polyethylene, polypropylene), polyvinyl chloride, polyesters, polyacrylates and polymethacetates crylates, polyesters, polyurethanes, bitumen products, and more.

The amount of talc in the fiber-containing reinforcement material the material according to the invention can vary within wide limits S 10 15 20 25 30 35 461 593 9 and is generally about 5-20% by weight, based on the total the amount of fiber.

Since the constituent components of the fiber the reinforcing material described, a provision is made for the production of this material in in accordance with the invention.

The first step in the method according to the invention for the production of fiber-containing reinforcing materials is the opening of carbon fiber bundles for splitting these in individual carbon fibers and separation of the fibers from eachother. This look-up and separation takes place by mixing the carbon fiber bundles under the shear action in dry condition. This treatment comes in the following that for simplicity is called dry dispersion.

It has been noted in the invention that in the case of dry perging is not sufficient to the carbon fiber bundles mixed under the influence of shear forces in order to satisfactory separation of the carbon fibers shall be obtained.

However, it has surprisingly been discovered that a lot satisfactory dry dispersion with efficient separation tion of the carbon fibers is achieved if the mixture during shear adds hydrophobic, anionic, colloidal silica, as defined above. The function of silica in dry dis- the perging is not completely clear, but without binding invention in any particular theory it is believed that the extremely small primary particles of the negatively charged the silica penetrates into the carbon fiber bundles and is distributed over their surfaces, leaving a uniform, repellent negative surface charge is obtained on the fiber surface. This repellent surface charge on the surfaces of the carbon fibers is highly presumed contribute to the efficient separation of the carbon fibers.

It will be appreciated that the dry dispersion of the carbon fiber bundles can be performed in any machine which performs mixing of the carbon fiber bundles during the application of shear forces. Suitable machines for carrying out the dry dispersion at the invention are high-speed mixers of the Lödige type, Drais or Cowles-Dissolver. The mixer is adjusted to 461 595 10 15 20 25 30 35 10 suitable operating speed, such as preferably 1000-3000 rpm, and the dry dispersion is carried out for an additional sufficient time for the fibers to be satisfactory they separated. This can be very easily ascertained by a routine test, in which the dry-dispersed fiber mixture combined with matrix material and commissioned on a glass plate. If the fibers on drawing up show isotropic distribution in the matrix is the dry dispersion satisfactory. Usually the dry dispersion amounts to time to about 10-30 min.

The second step in the method according to the invention is that glass fibers are added to the carbon fiber mixture. Pair- the meters of the glass fibers are as previously stated, and the glass fibers are added to the dry dispersing machine.

The time for adding the glass fibers can be after the dry dispersion of the carbon fiber bundles finished, but usually the glass fibers are added in the final stage of the dry dispersion of the carbon fiber bundles (eg after about 10-12 min dry dispersion). In both cases the operation of the mixer is continued to achieve a substantially homogeneous distribution of the glass fibers among the carbon fibers. Unlike carbon fibers exist the glass fibers from the beginning as individual, a lot thin fibers with negative surface charge. With respect to that the level of surface charge can vary between the carbon fibers and the glass fibers it is convenient to when adding of the silica add this in any excess so that the amount of silica is sufficient even for partial coating of the surfaces of the glass fibers. In this way a uniform is achieved distribution of the surface charge between carbon fibers and glass fibers and when the glass fiber is added to the carbon fiber system and colloidal silica, the glass fiber is distributed very evenly in the further dispersion and mix into one completely homogeneous system with carbon fiber and silica. Among- the processing time after the addition of the glass fibers is preferably to about 5-15 minutes.

The third step in the method according to the invention \ '\ (J 10 15 20 25 30 35 461 593 ll is the addition of cationic talc, preferably stone, as defined above, to the dry dispersed the mixture of carbon fibers, glass fibers and silica. MAN' has in fact found in the invention that talc, and then in particular soapstone, acts as an adhesive between the fibers and the matrix of the composite material. The cause to the good effect of talc as an adhesive is not complete clarified, but is probably due to the fact that talc is a material with cationic, hydrophobic surface and through its positive surface charging, the talc achieves excellent adhesion to them negatively charged fibers and at the same time also a good one adhesion to the matrix material, which is preferably is anionic, such as anionic polymeric materials of the type specified earlier. Through the collaboration of the talk between the carbon fibers and the glass fibers is achieved according to the invention a unique fiber-containing reinforcement mate-H material for the production of completely new types of composites.

In the reinforcing material according to the invention, the carbon fibers give mainly improved impact resistance of the composite material, while the other ingredients also provide a significant increased rigidity and dimensional stability at higher temperatures.

The mixing of the talc in the method according to the invention takes place by means of dry dispersion, as in the case of other parts, and this dry dispersion is carried out until the talc distributed substantially homogeneously in the mixture. This is generally achieved within about 5 min.

Until now, it has not been possible to reinforcement materials maintain strength and oxidation stability of composite materials at higher temperatures tours. Through the new fiber-containing reinforcement material according to the invention, which is hydrophobic and where one has a chemical and physical interaction between carbon fibers and glass fibers and also with the matrix material, are obtained a good adhesion between the composite material components and it has surprisingly been shown that can largely maintain the strength values and stability the quality of the composite material to more than 90% also 461 10 15 20 25 30 35 593 12 at elevated temperatures, such as at a temperature of 120 ° C for 200 hours. Corresponding values after similar heat treatment is for roving and fiberglass only and carbon fiber alone about 60-70%. U Another important aspect is the fiber materials orientation in the matrix of the composite material. In order to get a uniform strength in all directions should the fibers be isotropically oriented, i.e. uniformly distributed in all directions. In conventional technology is oriented the fibers, however, more or less perpendicular to the direction of flow during the shaping process, which gives a anisotropic distribution and strength. With the fiber content holding the reinforcing material according to the invention has it turned out that one surprisingly obtains an isotropic orientation of the fibers, which means a uniform distributed strength of the material. It is believed that this isotropy arises through the constituents of the constituents charges and the interaction achieved between carbon fibers and glass fibers and also between carbon fibers, fiberglass and matrix materials.

In order that the invention and its advantages may be go clearer, it will be described in the following by some non-limiting embodiments.

Examples 1-6 In a high-speed mixer with high shear type Lödige, which was operated at about 2000 rpm, was invested materials for producing the fibrous content the reinforcing material according to the invention in the concentrations given in the following table. The carbon fiber bundles had a length of about 3 mm and a diameter of about 10-15 μm.

Each bundle contained about 10-20 individual carbon fibers a diameter of about 0.7 μm. The L / D ratio of carbon fibers was 4280- ' The glass fibers consisted of C-glass and had a medium length of about 2.7 mm and an average diameter of about 0.8 μm.

The L / D ratio of glass fibers was about 3375. The hydrophobic, anionic collodial silica consisted of Aerosilß R 972 from Degussa. The talc consisted of soapstone H-340 from Handöl.

/IN 10 15 20 25 30 35 461 595 13 For testing the fiber-containing reinforcement properties of the material, it was mixed into a matrix standing of Crastine S 600, which is a polyester plastic from Ciba-Geigy. The amount of reinforcement material involved amounted to 20% by weight in all cases. In the production of the reinforcing material, the carbon fiber bundles were dry dispersed first for about 10 minutes together with the silica, after which the glass fibers were added and the dry dispersion was continued for about 15 min. Then the soapstone was added and the dry dispersion was continued for another 5 minutes.

Table I Ingredient / Ex 1 2 3 4 5 6 Unit =% Fiberglass 100 50 30 - 80 - Carbon fiber - 30 50 100 * - 80 Silica - 8 8 - 8 8 Soapstone - 12 12 - 12 12 Bending test to crime, N 560 970 825 730 590 750 Traction strength N / mm, 1350 1980 1670 1585 1420 1610 Pressure resistance N / mm, 600 1410 1180 900 630 950 * The carbon fiber bundles were not dispersed. The distribution was anisotropic.

Table I shows that only glass fibers or carbon fibers alone (Examples 1 and 4, respectively) give unsatisfactory the results and that also only fiberglass or only carbon fibers in combination with silica and soapstone (examples 5 and 6, respectively, provide minimal improvements in the result.

However, it provides a combination of fiberglass and carbon fiber together with silica and soapstone in accordance with the finding (examples 2 and 3) exceptionally good results.

The reinforcing material according to the invention is useful 461 593 14 in a variety of areas and for a large number various products, such as reinforcement materials in protective helmets, earmuffs for hearing aids, car parts, and many other articles, in which there is a need Of a, preferably isotropic fiber reinforcement.

Claims (7)

10 15 20 25 30 461 593 15 CLAIMS 1. Fiber-containing reinforcement material, characterized in that it consists of a substantially homogeneous distribution of carbon fibers, glass fibers, hydrophobic anionic, colloidal silica and cationic talc, the weight ratio of carbon fibers to glass fibers from 1:99 to 99: 1, the silica constitutes about 5-20% by weight of the total amount of fiber and the talc constitutes about 5-20% by weight of the total amount of fiber. Fiber-containing reinforcement material according to claim 1, characterized in that the carbon fibers have an average length of about 0.5-6.0 mm. Fiber-containing reinforcement material according to claim 1 or 2, the different carbon fibers have an average diameter of at most about 1 μm. k ä n n e t e c k n a t by the fact that they Fiber-containing reinforcement material according to any one of claims 1-3, characterized in that the glass fibers have an average length of about 0.5-15 mm. Fiber-containing reinforcing material according to any one of claims 1-4, characterized in that the glass fibers have an average diameter of about 0.5-6.0 μm. 6. A process for the preparation of a fiber-containing reinforcing material, characterized in that: a) the addition of hydrophobic, anionic, colloidal silica to carbon fiber bundles, in an amount of about 5-20% by weight, based on the total amount of fiber of the final reinforcement material, and divided into individual fibers by blending under shear in the dry state; b) adding glass fibers to the mixture of carbon fibers and silica in such an amount that the weight ratio of carbon fibers to glass fibers is from 1:99 to 99: 1; and c) that about 5-20% by weight, based on the total amount of fiber, of cationic talc be distributed in the mixture of carbon fibers, silica and glass fibers. 461 593 16 Use of the fiber-containing reinforcing material according to any one of claims 1-5 for the production of fiber-reinforced composite materials.