EP0819189B1 - Method for making a glass mat and resulting product - Google Patents

Abstract

A method for making a glass yarn mat, wherein a binder is continuously deposited on a mat of glass yarns spread over a moving conveyor, and the mat is baked and optionally calendered. For this purpose, a liquid binder with a viscosity on deposition of less than around 40 millipascals per second is deposited on the yarn mat, and said binder consists of an aqueous solution of one or more polyvinyl alcohols.

Description

The present invention relates to a method of manufacturing a mat consisting of glass threads and the resulting product. By mat is meant glass a product formed of glass strands (cut or continuous) whose filaments components remain linked together, thus distinguishing themselves from glass veils formed by the association of dispersed glass filaments.

When manufacturing a glass strand mat, among the main problems to be resolved include the choice of the nature of the binder which will allow give the mat its cohesion, the form in which the binder will be used and the process which will ensure the contact of the binder with the mat.

There are many solutions to these problems.

Thus the nature of the binder chosen is most often a function of its chemical compatibility with the resin system that the mat should reinforce.

The binder can be used in the form of powder, suspension, emulsion or solution. When the binder is used under a other than dry powder, the liquid with which it is associated is, increasingly more often water to avoid the difficulties that always presents the job organic solvents.

The application methods are also very varied.

If the deposit of the binder in the form of a dry powder avoids the use of a liquid that will need to be removed later, it is difficult to remove distribute evenly within the mass of the mat. In addition, the grains of binder sometimes remains in the composite reinforced by the mat, which gives an irregular surface finish.

The deposition of a binder in the form of an emulsion or solution in water or in an organic solvent gives a good cohesion to the mat because, the more often it at least partially sticks the glass strands. However this advantage can be less interesting when the mast must be associated with a product that it must strengthen, whether organic or mineral. When the binder remains on the glass strands during this association phase, it can constitute an obstacle to the good wetting of said wires by said product. It is especially the case when the mat must be combined with a resin which found in the form of a dispersion or suspension in water or with a mixture of cement and water. This results in a decrease in mechanical properties and poor surface condition of the composite part final.

The present invention relates to a manufacturing process allowing to obtain a mat of glass strands which has good cohesion and which is easily wetted by resins, in particular by resins in an aqueous medium, especially in aqueous solution, dispersion or suspension or by a mixture based on cement and water.

The present invention relates to a manufacturing process which allows distribute the binder evenly throughout the thickness of the mat.

The present invention also relates to a method of manufacturing a glass fiber mat which allows continuous recycling of the binder used.

These aims are achieved by a manufacturing process which consists in continuously deposit on a sheet of glass threads, distributed on a conveyor in motion, a binder whose viscosity during deposition is less than approximately 40 mPa.s, said binder being formed from an aqueous solution of alcohol (s) polyvinyl (s).

The polyvinyl alcohol (s) used in the context of the invention preferably have a degree of polymerization of less than about 1,000.

The binder is deposited on the sheet of glass strands in the form of a liquid tablecloth or curtain of liquid nets which fall transversely over the entire width of said layer of wires. The binder thus deposited, and thanks to its relatively low viscosity, penetrates and crosses the entire ply of yarns distributing throughout the volume of said sheet. The binder is retained for the essential on a large part of the contact points of the crossing wires. The binder is deposited when its temperature is higher than approximately 10 ° C and most generally between 20 and 60 ° C.

The flow rate of binder thus deposited is in particular a function of the speed of the conveyor and the quantity of glass deposited per square meter on said conveyor. This binder flow rate is determined so as to obtain between approximately 3 and 15% by weight of binder in the dry matter state relative to the weight of glass.

Alternatively, the binder may be deposited, in part, on the surface of the sheet of yarn, upstream of the area where it is deposited in the form of nets or of a liquid tablecloth. The binder can be, for example, sprayed upstream, this which has the effect of compacting the layer of thread slightly and moistening its layer surface, thus promoting the penetration of the binder deposited downstream.

A fraction of the binder thus deposited completely crosses the sheet of yarns and can be collected under the conveyor. One of the advantages of the binder used is that it is stable over time even after being heated to a temperature above about 30 ° C, unlike binders whose composition contains at least one constituent which promotes its crosslinking. The binder used in the context of the invention can thus be directly recycled, this which constitutes an economic advantage.

Once the binder has been deposited, the layer of wires passes through an oven of in a manner known per se, then possibly in a grille.

The method according to the invention applies to the glass son mats obtained by all known means, whether continuous or indirect processes.

The first type of process is used to make masts of continuous glass. It consists, most often, of stretching a multiplicity of filaments from molten glass flowing from the orifices of several dies, combine these filaments at the rate of at least one thread per die and distribute mechanically the wires thus obtained on a conveyor moving below said channels.

The second type of process is generally used to manufacture the chopped glass strands. It consists in extracting from a multiplicity of continuous wire windings, to cut them simultaneously and to distribute them on a moving conveyor.

The second type of process can also be used to manufacture continuous yarn mats when the extraction of the yarns from their winding is immediately followed by their distribution on the conveyor.

For some applications, the mat used can be reinforced with continuous glass strands arranged longitudinally over at least part of its width. This is particularly the case when the mat is intended to be associated with a cement-based mixture.

This mat is obtained, for example, by distributing simultaneously over the moving conveyor cut and continuous wires, the latter being extracts from a series of windings.

Whatever the process used, the average diameter of the filaments constituting the wires is between approximately 9 and 30 micrometers. when these are chopped strands the length of the said strands is generally greater than 20 millimeters.

One of the advantages of this mat is that, put in contact with a resin in an aqueous medium, the binder disappears almost entirely, which promotes the wetting of the glass with resin.

The advantages presented by the invention will be better perceived through the description, detailed below of an exemplary embodiment which is in no way limitative of said invention.

We deposit on a conveyor moving at a speed of 13 meters by minute, a sheet of cut wire 50 millimeters long, at a rate total glass of 250 kilograms per hour. This tablecloth is obtained by the simultaneous cutting of a multiplicity of threads extracted from a multiplicity of windings. These glass threads, with a title of 30 tex, consist of a multiplicity of filaments with an average diameter of 12 micrometers; they were coated, during their manufacture, with a conventional size based on acetate of polyvinyl and coupling agents such as silanes.

An aqueous solution of polyvinyl alcohol at a concentration of 8%, maintained at 30 ° C and whose viscosity at this temperature is 15 millipascals / second, is deposited over the entire width of the layer of wires under the form of a curtain of liquid nets. This solution was obtained by dissolution in water brought to 80 ° C of a polyvinyl alcohol characterized by a degree of polymerization of 530 and a hydrolysis rate of 88%. This polyvinyl alcohol is sold under the reference F 105 by the Company Lamberti. This solution is poured onto the sheet of wires at a rate schedule of 3 cubic meters. The excess solution is sucked under the conveyor and recycled.

The layer of wires thus treated then passes into a hot air oven at the interior of which it is subjected to a temperature of the order of 200 ° C. for about 50 seconds. At the exit of the oven, the layer of wires is calendered and cooled before being wound on a rotary mandrel.

The mat obtained has a binder content of 8% and has a mass area of 250 grams per square meter. Its cohesion is good as the shows its tensile strength which, measured according to ISO 3342 method, is on average 40 decanewtons. In comparison, a mat that has the same characteristics, but the binder rate is 4.5%, this binder being plasticized polyvinyl acetate, has a tensile strength, measured by the same method, less than 20 decanewtons.

The binder used in the present invention also offers the advantage to be partially dissolved in the presence of water. The following test allows you to note: a series of samples of 100 x 125 millimeters are cut in the mat whose manufacturing process has been described previously. These samples are immersed in water at 20 ° C and subjected to a load of 100 grams. Partial elimination of the binder in water and the effect of the filler cause the mat to tear in two parts after an average time of 25 seconds. This time is very short for this kind of test. Indeed, the tearing of the mat bound with plasticized polyvinyl acetate, cited previously, intervenes, under the same conditions, only after a average time greater than 5 minutes.

This rapid removal of the binder allows the mat obtained according to the invention to be very easily associated with all kinds of products mixed with water, whether it is a mixture of cement or resins in the form of dispersion or suspension in an aqueous medium, and obtaining by molding composite parts whose mechanical properties and surface condition are particularly satisfactory. The comparative example described below makes it possible to show it.

Cement sheets are made using on the one hand a mixture based on cement and cut glass yarns called premix, other part of mast according to the invention or, for comparison, of a known mast.

• ciment portland artificiel CEMI   100 parties en poids
• sable siliceux   100 parties en poids
• eau   40 parties en poids
• fluidifiant   1,8 parties en poids

The mixture itself is classic and its composition is as follows:

• CEMI artificial Portland cement 100 parts by weight
• silica sand 100 parts by weight
• water 40 parts by weight
• thinner 1.8 parts by weight

4.8 parts are incorporated into this mixture in a manner known per se. weight of cut glass yarn with an average length of 12 millimeters.

The mat according to the invention has a surface mass of 120 grams per square meter, it consists of cut wires 50 millimeters in length, including the title is 38 tex and which consist of a multiplicity of filaments of a average diameter of 14 micrometers. Its binder rate is 10%.

The mat used for comparison has the same characteristics, apart from the binder rate, which is 4.5% and the binder itself, which is plasticized polyvinyl acetate.

The glass used to obtain these mats is an alkali-resistant glass marketed under the CEMFIL brand.

A first layer of mat is deposited at the bottom of a mold and covered with a layer of premix uniformly distributed by subjecting said mold to vibrations.

A second mat layer identical to the first is deposited on the premix, then applied against the premix using a roller to impregnate. The plate thus formed is maintained for 24 hours in the mold, then stored in an enclosure maintained at 20 ° C in a atmosphere at 50% relative humidity.

Samples are taken from the plates thus obtained and some of their mechanical properties in flexion were measured after 7 days and 28 days of storage. the results of these measurements, carried out according to the draft standard pr.EN 1170-5 of March 1995, are collated in the following table.

The symbols MOR, LOP and EPS respectively denote the module of rupture, the limit of proportionality or elasticity and the deformation at the rupture during the bending test.

The percentage of reinforcement in the premix is 2% by weight per compared to the composite for the two kinds of plates, the percentage of reinforcement due to the mat itself being 1.4% for the plate reinforced by the mat according to the invention and for the plate reinforced with known mat.

These results show that the mat according to the invention gives the composite with excellent mechanical properties, including deformation remarkable in view of the relatively low reinforcement content.

The examples illustrating the invention are not limiting and the association of the mat according to the invention with a cement-based mixture can be produced in many ways, for example deposited in situ on all or part of a slab or fixed on a wall and covered by spraying a layer of cement.

The association with resins in an aqueous medium can also be carried out by all means known to those skilled in the art.

Claims (13)

1. Process for the manufacture of a mat of glass threads according to which a binder is deposited continuously on a sheet of glass threads distributed on a moving conveyor, then the sheet is subjected to oven-drying and optionally calendering, which process consists in depositing on the sheet of threads a liquid binder, the viscosity of which during deposition is lower than approximately 40 millipascals.second, the binder being formed from an aqueous solution of polyvinyl alcohol(s).
2. Process according to claim 1, characterised in that the binder is deposited in the form of a liquid sheet or in the form of a curtain of thin liquid streams which fall onto the entire width of the sheet of threads.
3. Process according to claim 2, characterised in that a portion of the binder is deposited upstream of the region where it is deposited in the form of a liquid sheet or in the form of a curtain of thin liquid streams.
4. Process according to claim 3, characterised in that the binder is deposited upstream by spraying.
5. Process according to any one of the preceding claims, characterised in that the fraction of binder that has passed through the sheet of threads is recovered beneath the conveyor and recycled directly.
6. Sheet of glass threads that is coated with a binder, characterised in that the sheet is formed from glass threads, the constituent filaments of which remain bound to one another, and in that the binder is a liquid binder, the viscosity of which during deposition on the sheet of glass threads is lower than approximately 40 millipascals.second, the binder being formed from an aqueous solution of polyvinyl alcohol(s).
7. Sheet of glass threads according to claim 6, characterised in that its content of binder is approximately from 3 to 15% by weight relative to the weight of the glass.
8. Mat of glass threads that is obtained after oven-drying and optionally calendering a sheet of glass threads according to either claim 6 or claim 7, characterised in that it is formed from threads constituted by glass filaments that remain bound to one another and the average diameter of which is from 9 to 30 micrometres.
9. Mat of glass threads according to claim 8, characterised in that it is formed from cut threads, the length of which is greater than approximately 20 millimetres.
10. Mat of glass threads according to claim 9, characterised in that it is reinforced by continuous glass threads arranged longitudinally on at least a portion of the width of the mat.
11. Mat of glass threads according to claim 8, characterised in that it is formed from continuous threads.
12. Application of the mat of glass threads according to any one of claims 8 to 11, characterised in that it is associated with a mixture based on cement and water and optionally comprises glass threads in order subsequently to form a composite.
13. Application of the mat of glass threads according to claims 8 to 11, characterised in that it is associated with a resin in aqueous medium in order subsequently to form a composite by moulding.