NL8900201A - Bonding fibrous material to solid thermoplastic surface - by contact in presence of solvent or swelling agent for thermoplast, embedding fibres partly in thermoplast - Google Patents

Abstract

In bonding a fibrous material with a solid thermoplastic surface, the fibrous material and (part of) the surface are contacted in presence of a solvent or swelling agent for the thermoplast, in such a way that after drying, part of the fibrous material is embedded and firmly anchored in the thermoplast, whilst another part of the fibrous material extends free above the surface of the thermoplast. The fibrous material is pref. a sheet or strip comprising coherent fibres or threads. The solvent or swelling agent is applied to the sheet or strip, which is then contacted, opt. under pressure, with the surface of the thermoplast. Supplementary materials or units may be bonded to the thermoplast by way of the projecting parts of the fibrous material, and the strip or sheet of fibrous material may be used as a bridge and bond between thermoplastic surfaces of separate parts placed more or less close together. Supplementary material may be placed on the sheet or strip, esp. a material which strengthens the bond. The solid thermoplast is esp. a (modified) polycarbonate.

Description

Title: Method for joining a fibrous material with a solid thermoplastic material.

The invention relates to a method for joining a fibrous material to a surface of a solid thermoplastic material.

It is known from numerous literature references to combine fibrous materials, such as glass fibers, with resin materials, often to strengthen the latter. In addition, it is known to fasten objects together of resin materials which may have been reinforced in the manner indicated above, to obtain a firm connection. For this, reference may be made, for example, to U.S. Patents 4,552,281 and 4,630,846.

According to U.S. Patent 4,552,281, two halves of storage tanks are thus joined together. Both halves consist of an outer wall of a corrosion-sensitive resin and an inner lining of a corrosion-resistant resin. From a place near the edge where the connection is to be made, the inner liner also takes the place of the outer wall and thus extends over the total thickness of the material. The two halves are then connected to each other by means of a support plate of a corrosion-resistant resin, which bridges the place of assembly, and possibly a coating of a corrosion-sensitive resin over it. The support plate and the latter covering are provided with glass fibers or glass fiber mats which are usual for reinforcement. This known construction, and in particular the manner in which the connection is formed, is complicated and expensive and requires great skill.

The technique known from US patent 4,630,846 is intended to connect pipes or tubes of, for example, a thermoplastic resin. To this end, a type of barbed wire is wound around the tubular ends, which are heated to a suitable temperature, so that spikes of the barbed wire penetrate into the resin material. Then, a fiber sheet-reinforced resin sleeve is formed by lamination around the tubular ends thus joined together. This technique is also cumbersome and is in fact limited to a specific application, namely the joining of pipes or tubes.

A very simple and efficient method has now been found to securely anchor or embed fibrous material into the surface of a solid thermoplastic material, the fibrous material serving to attach individual elements or parts having such a surface and / or to connect other elements or layers to the thermoplastic surface via that fibrous material, in particular reinforcing, protective and / or finishing layers.

The invention is therefore characterized in that when carrying out the method described in the opening paragraph, the fibrous material and that surface or a part thereof are brought into contact with each other in the presence of a solvent or a swelling agent for the thermoplastic material, all this in such a manner that after drying, a portion of the fibrous material is embedded in the thermoplastic material and is firmly anchored therewith, while another portion of the fibrous material projects freely above the surface of the thermoplastic material.

It is essential that according to the invention a part of the fibrous material protrudes freely above the thermoplastic surface and thus forms a new type of base or substrate on which further construction can be carried out.

The invention will be explained in more detail below, partly with reference to the figures of the drawing, which relate to a preferred embodiment and of which - figure 1 is a detail side view of a connecting joint between two canoe halves, and - figure 2 is an enlarged cross-section along the line II-II in figure 1.

The solid thermoplastic surface for use according to the invention can consist of any solid thermoplastic resin material / such as polyester, polycarbonate, polystyrene, polyamide, polyacrylate, polyetherimide, polyolefin, polyvinyl chloride, etc. Also copolymers or copolyesters or modified products of the just said polycondensates or polymers are used, provided that they are solid thermoplastic materials.

The solid thermoplastic material can be a plate or any molded part and can also be part of a composite material, for example a laminate, but at least one free surface must always consist of the solid thermoplastic material. The solid thermoplastic material can also contain internal reinforcement, for example in the form of inlaid fiber webs or fiber mats.

The fibrous material, which according to the invention is connected to the thermoplastic surface, can consist of loose, preferably fairly long fibers or fiber wires with a length of at least 1 cm, but preferably use is made of more or less cohesive, e.g. fibers or fiber threads stitched together or woven into a braid. Thus, the fibrous material can be used in the form of a fabric or knit. Preferably, use is therefore made of so-called fiber mats or fiber webs, which are generally known in the art and whose density, strength and thickness are chosen depending on the intended application.

The nature of the fibrous material can be very diverse. Glass fibers can be used, but also fibers or threads of various other materials, such as carbon, nylon, aramid, acrylic resin, etc. The nature of the fibrous material to be used in a specific case depends, among other things, on the nature of the solid thermoplastic surface, but also depends to a great extent on the function of the applied fibrous material, whether the latter is intended as a new basis for further construction or to fix or join two thermoplastic surfaces together or also to combine both as a basis for further construction.

As the solvent or swelling agent, which is present at the contact between the fibrous material and the thermoplastic surface, an organic liquid is chosen which on the one hand at least slightly dissolves or softens the respective thermoplastic surface, and on the other hand does not dissolve the fibrous material in order to effect that the fibrous material, after evaporation of the solvent or swelling agent, is partly firmly embedded or anchored in the thermoplastic surface and partly protrudes as free fibrous material above that surface. It is known to a person skilled in the art which solvent or swelling agent can be used in a specific case. The connection of a glass fiber web with a surface of an optionally modified polycarbonate can for instance take place in the presence of methylene chloride.

To carry out the present process, the thermoplastic surface to be coated can be wetted with any chosen solvent or swelling agent by any suitable technique, for example spraying, after which the fibrous material is also applied by any suitable technique. Optionally, the fibrous material can be partially embedded in the slightly dissolved or softened surface by pressing, for example with a roller. After a short time, usually in about 20 seconds to about 3 minutes, the solvent or swelling agent has evaporated and the intended anchorage has been obtained. In a preferred alternative embodiment, a web or strip of the fibrous material is wetted, for example by application or soaking, with the selected solvent or swelling agent, while that web or strip is on the solid thermoplastic surface. Shortly after that, pressing pressure can still be applied, in this case too the intended anchoring is obtained after the solvent or swelling agent has evaporated. Of course, according to the invention, it is also possible to wet the solid thermoplastic surface and the fibrous material with the selected solvent or swelling agent and then to contact them.

By applying the method according to the invention, the thermoplastic surface is in fact provided with a novel type surface, consisting of the fibrous material protruding above the original surface.

This offers the opportunity for further build-up on the new surface. Thus, by means of a suitable adhesive, further construction elements of all kinds of materials can be attached to the original thermoplastic surface via the fibrous material. Reinforcing layers and / or finishing layers such as decorative layers can also be applied. For example, a reinforcing layer can be formed by applying a curable polyester resin in liquid form or in solution and then curing, which can be accelerated if desired by heating or irradiation depending on the type of resin used.

According to a preferred embodiment, the present method is used to establish a durable connection between two thermoplastic surfaces. This is often a major problem in the manufacture and in particular in the assembly of objects from thermoplastic synthetic resin. This problem manifests itself very clearly in the assembly of the top and bottom half of canoes from possibly dopr reinforced inlay material, possibly modified polycarbonate.

For example, the top and bottom halves of a canoe are formed by evenly heating a polycarbonate flat sheet while it is stretched on a die. During that heating, the plate is supported by an air cushion. When the plate is sufficiently plastic, it is sucked into the mold and, after it has cooled, taken out of the mold again.

However, it is no easy matter to merge a top and bottom half of a canoe thus manufactured in a durable manner. For this purpose, large industry uses very expensive equipment, which fuses the contact edges, while the aim is not to damage the strength in other parts of the canoe body, or to do so as little as possible.

If one simply wants to weld the two canoe halves together, too many stresses will occur, which will cause deformation, and the material will become brittle in the vicinity of the weld seam.

Another possible embodiment consists in that the two canoe halves are manufactured in such a way that they fit together in the opposite direction. The surfaces lying against each other can then be joined together by gluing. In practice, however, a smooth and durable connection cannot be obtained in this way.

The present invention now provides a simple, efficient and inexpensive method of fastening two canoe halves together, after which a durable, strong and watertight connection can be obtained by applying a suitable reinforcement material. This preferred embodiment of the invention will be explained below with reference to Figures 1 and 2, which respectively. a detailed view of a connecting joint between two canoe halves and an enlarged section thereof,

In figures 1 and 2 an upper half 1 and a lower half 2 of a canoe are placed against each other via a joint 3. A fiber web 4 consisting of glass fibers 5, which has been soaked in a solvent or a swelling agent for the thermoplastic resin of the two canoe halves, is laid on a part of the two canoe halves in the manner shown, so that the joint 3 is bridged thereby. The fiber web 4 thus arranged is pressed against the two canoe halves by means of a roller. Due to this and the dissolving action of the solvent or swelling agent, some of the glass fibers 5 are partially embedded in the surface of the thermoplastic resin of the two canoe halves, while part of the glass fibers protrude above the surface of the thermoplastic resin, as clearly can be seen in figure 2. After a drying time of usually only 0.3-1 minute, a firm and reliable connection between the two canoe halves 1,2 is thus obtained.

A liquid polyester resin 6 can then be poured onto the fiber web 4, which after curing results in a durable, strong and watertight connection between the two canoe halves.

In the figures, the fiber web 4 and the covering polyester resin 6 are arranged on one surface of the canoe halves 1,2 placed against one another. This is then preferably the inner surface, but it can also be the outer surface. Preferably, however, both the inner and outer surfaces are treated in this way.

It goes without saying that further elements or coatings can be applied to the polyester resin 6, such as a finishing layer, an ornamental strip, etc.

To illustrate the invention, there is now another example in which the manufacture and assembly of two canoe halves is described in detail.

Example

A sheet of Impax 7006 (a thermoplastic resin of the polycarbonate type of General Electric Plastics) of 3200 by 680 mm and with a thickness of 3 mm was airtightly clamped on a die for the bottom half of a canoe, using a clamping frame. The mold was provided with openings for the supply and exhaust of air.

The plate thus clamped was heated uniformly at a temperature of around 200 ° C in about 3 minutes by means of ceramic heating elements placed above the free surface. During this treatment, the plate was supported by an air cushion formed between the plate and the mold.

When the said temperature was reached, the air was sucked out of the space between the plate and the mold, whereby the plasticized sheet formed to the surface of the mold. After a cooling time of about 1 minute, the molding was taken out of the mold and sawed out to obtain a bottom half of a canoe.

Analogously as described above, a top half of a canoe fitting to the bottom half was manufactured.

The top and bottom halves were then placed one on top of the other and fastened together with strips of tape (applied every 5 cm).

2

Then, a 300 g / m glass fabric tape 6 cm wide was placed inside the joint (as shown in the figures) along the entire circumference of the attached canoe halves. The glass fabric tape was brushed with methylene chloride and then quickly pressed with a roller. After about 30 seconds, the two canoe halves were firmly joined together and the strips of tape could be peeled off on the outside. The product thus obtained can be transported, etc., without the damaged connection being damaged.

In an analogous way as described above, the same type of glass fiber tape, but with a width of only 3 cm, was applied on the outside, whereby the two canoe halves were also joined together there.

Both inside and outside, the fiberglass tape was partially embedded in the sheet surface and partially protruded above it.

Finally, the established connection, both inside and outside, was strengthened and finished by applying a polyester resin on and over the fiberglass tapes. A thermosetting polyester resin type BE from Voss-Chemie was used for this. Just before use, 2% of a MEK (methyl ethyl ketone) peroxide hardener was added to that resin and mixed with it. The resulting mixture was applied with a brush. After about 45 minutes at ordinary temperature, the polyester resin applied was hard.

In this way, a strong canoe was obtained in a simple and inexpensive manner, which is excellently suitable for use under many circumstances.

Claims (8)

A method for joining a fibrous material to a surface of a solid thermoplastic material, characterized in that the fibrous material and that surface or part thereof are brought into contact in the presence of a solvent or a swelling agent for thermoplastic material, such that after drying, a portion of the fibrous material is embedded in the thermoplastic material and is firmly anchored therewith, while another portion of the fibrous material projects freely above the surface of the thermoplastic material. A method according to claim 1, characterized in that the fibrous material is in the form of a web or strip consisting of coherent fibers or fiber threads. A method according to claim 2, characterized in that the solvent or swelling agent is applied to the web or strip of the fibrous material and then, if necessary under pressure, is brought into contact with the surface of thermoplastic material, Method according to claims 1-3, characterized in that additional materials or elements are connected to the solid thermoplastic material via the projecting part of the fibrous material. A method according to claim 2 or 3, characterized in that the web or strip of the fibrous material is used as a bridging between thermoplastic surfaces of separate, more or less closely placed parts, in order to connect them together. A method according to claim 5, characterized in that an additional material is applied to the web or strip of the fibrous material, in particular a material to strengthen the effected connection. Method according to claim 5 or 6, characterized in that the method is used to connect the top and bottom half of a canoe. A method according to claims 1-7, characterized in that the solid thermoplastic material is an optionally modified polycarbonate.