FI57068C - ANVAENDANDE AV EXPANDERADE MIKROSFAERER INNEHAOLLANDE FIBERBANA SOM ARMERINGSMEDEL - Google Patents

Description

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Patent · och reglstentyrelaen Amikin utitgd och utUkrUtm publkmd 29.02.80 (32) (33) (31) PjT4 «ty • tuolkuui — BujW prleritut 20.07.73

Netherlands-Nederland (NL) 7310138 _ (71) Firet BV, Verlaat 22, Veenendaal, Netherlands-Nederland (NL) (72) Adam Paul Geel, Doorwerth, Nederland (NL) (7 * 0 Berggren Oy Ab (5l +) Use of a fibrous web containing expanded microspheres as a reinforcing material - Användande av expandexade microspheres innehällande fiberbana som armeringsmedel

It is known to reinforce plastics such as unsaturated polyesters and epoxy resins by incorporating a fibrous web such as bonded or unbonded glass fiber mat or glass cloth, bonded nonwoven web or fabric based on linear polymers such as polyesters, polyamides, polyolefins, etc. in such processes. with a liquid and uncured polymer containing a curing agent or crosslinking component, after which the fibrous web is brought into the desired shape and cured.

In order to achieve weight savings when using a certain thickness of material, attempts have previously been made to provide a foam-like structure in the polymer by incorporating expanded microspheres.

Such microspheres are marketed in both expanded and unexpanded form. The microspheres may be formed by a vinylidene chloride polymer or a copolymer thereof, for example, together with acrylonitrile or, if desired, other monomers, and the core portions of the microspheres 57068 contain a certain amount of blowing agent, such as iso-butane. In the unexpanded state, the microspheres have a diameter of, for example, 4-20 microns and a bulk weight of 0.65-0.75 g / cm 2. At room temperature, they are very stable, but when heated to the softening temperature of the polymer formed by the copolymer, the blowing agent in them expands them several times in volume. In commercial materials, this expansion temperature is usually about 90-120 ° C. When heated to even higher temperatures, there is a risk that the spheres will disintegrate due to internal pressure, after which the soft polymer will coagulate, which is not desirable. The expanded spheres have a diameter of, for example, 10 to 100 microns and a bulk weight of, for example, 0.01 to 0.02 g / cm 2.

Attempts to mix such microspheres in an expanded state with liquid unsaturated polyester appear to be very difficult to obtain a homogeneous mixture due to the large difference in apparent density between the polyester and the expanded spheres, while said spheres tend to disintegrate and are very harmful if ingested.

On the other hand there is no risk of confusion of MIA-expanded beads with a liquid polymer as the spheres can be expanded only by heating, and a rule that is incompatible with polymer treatment, as in this case the cross-coupling starts.

As a result, there is a considerable need to be able to combine the expanded microspheres with the liquid polymer in an easy and well-controlled manner.

This is achieved according to the invention by using a binder-bonded fibrous web which binds to the web 10 to 60% by volume, based on the volume of the bonded web, of expanded microspheres, most preferably a copolymer of vinylidene chloride and acrylonitrile. resin.

These microspheres can be made by any known method and from any of the materials conventional 3,57068 for this purpose. The most suitable are microspheres having an diameter in the expanded state of 10 to 100 microns. The material from which said microspheres are made must, of course, withstand the action of the resin used in the uncured state. Spheres formed by a copolymer of vinylidene chloride and acrylonitrile are very suitable.

Such a bonded fibrous web containing microspheres is described in U.S. Patent 3,676,288, which proposes a nonwoven fabric containing such spheres. To achieve this, according to this patent, a staple fiber web is first formed and a solution of a conventional curable binder is then sprayed on this web in a weaving tower on fabrics, and at the same time the microspheres are dispersed in this solution in an unexpanded state.

After the formed sheet of fibers, such as tekosilkkikuitujen, is wetted in this manner is introduced into it through an oven and dried and is then heated at a temperature which on the other side is sufficiently high to cure the binder and also to provide the micro-spheres to expand, while the temperature should not be . so high that it breaks up the spheres due to internal pressure. According to this patent, a temperature of 88-120 ° C is suitable.

According to this patent, said method provides a highly porous nonwoven fabric having a high water absorption capacity, so that this product can be used, for example, as an insulating material and as a wiping and cleaning cloth. In addition, this patent mentions that the presence of spheres reduces the transparency of the nonwoven fabric and also the permeability of the air.

Such nonwoven fabrics containing microspheres are very suitable for use in accordance with the present invention. Instead of rayon fibers, other fibers such as glass fibers, polyester fibers, nylon fibers, etc. can also be used, while instead of a nonwoven fabric, it is also possible to use a fabric to which the microspheres are analogously connected.

Of course, it is also possible to previously separately separate the microspheres into the fibrous web in the form of an aqueous dispersion, or the microspheres can be dispersed in the desired amount in advance or after impregnation into the web. In either case, they are then attached to the like 57068 by means of a binder during the crosslinking of said binder.

When expanding the spheres during drying and crosslinking of the binder, care must be taken that the temperature of the spheres in the web does not rise to a significant fraction of microspheres, after which the coagulated wall material has only a small volume so that the desired goal of reducing the required amount of impregnating resin is not achieved. When commercially available spheres are used, this maximum temperature is usually about 120 ° C and the binder must therefore be selected so that it is sufficiently crosslinked at or below this temperature.

This is very feasible when using conventional binders.

The number of microspheres can, of course, vary greatly.

However, this amount is preferably selected so that, after expansion, it does not exceed about 50% by volume. the volume of the expanded fiber web. If the number of balls is greater than 60? the volume of the expanded fibrous web usually decreases the strength of the final product. During the expansion of the spheres, the apparent volume of the fibrous web usually also increases. An amount of 10-60 volume -? And preferably 30-50 volume -? Based on the volume of the expanded fibrous web seems very suitable. As a result, for certain types of microspheres, it may be easy to calculate the number of volumes of unexpanded spheres to be added.

The nature of the fibrous web can vary greatly. For example, glass fabrics, fiberglass mats, fibrous webs based on all kinds of natural or synthetic fibers, knitted felt, or fabrics based on natural or synthetic fibers can be used.

As the binder, all conventional binders can be used, which can be crosslinked or cured at the temperature allowed for the expansion of the microspheres.

An example of a suitable binder is a polyacrylonitrile latex.

Such a binder latex contains particles with a diameter of, for example, 2 microns. The fibrous webs used in accordance with the present invention, which contain expanded microspheres, can be used to reinforce crosslinkable polymers in exactly the same manner as fibrous webs conventional for this purpose.

However, the final molded products are preferred over those which have been made using conventional fibrous webs, as they are on one side of the lighter, cheaper and on the other side they have a high impact strength, and these products in forming's a need for any further treatment in comparison with previous methods of treatment.

Example 2 An unbonded fibrous web with a weight of 60 g / m 3 is used, which consists of polyester fibers with a dtex value of 1.5.

It is impregnated with polyacrylonitrile latex in which unexpanded microspheres are dispersed.

This latex contains 20 weight? solid materials, namely 6 weight? polyacrylonitrile and 14 weight? Microspheres. A certain amount of 2 is combined with the fibrous web so that it contains 18 g of polyacrylonitrile and 42 g of microspheres per m 2. The impregnated web is then dried and then heated to a maximum temperature of 118 ° C. During drying, the water evaporates, the polyacrylonitrile cross-links and the microspheres expand.

The resulting fibrous web is very suitable for treatment with unsaturated polyester, for example by impregnating it with 9 times its own weight of polyester containing a curing agent, bringing the impregnated web into the desired shape, in this case a flat sheet, and curing the polyester at room temperature.

The resulting plate contains the following ingredients in various amounts:

Polyester fiber 5 weight? 2.7 volume?

Polyacrylonitrile 1.5 "0.8"

Microspheres 3 * 5 "48.3"

Unsaturated polyester 90_11 48.2 _ "_ • 100.0 weight? 100.0 volume?