FR2579609A1 - Self-adhesive sheet of high optical quality - Google Patents

Abstract

A plastic self-adhesive sheet of high optical quality. The sheet according to the invention comprises at least one layer of polyurethane and at least one adhesive layer making the sheet self-adhesive.

Description

HIGH OPTICAL SELF-ADHESIVE SHEET
IN PLASTIC MATERIAL
The present invention relates to a high optical quality plastic sheet comprising at least one layer of polyurethane, which can be used as an external sheet in laminated glazing, that is to say glazing with several layers of glass and / or plastic material and in particular glazing comprising a rigid, monolithic or laminated support of glass or plastic material coated on at least one of its faces by said sheet of plastic material.

 Plastic sheets comprising at least one layer of polyurethane, which can be used as an external sheet in laminated glazing have been described in numerous patent publications. Thus in French patent publication 2 398 606, a plastic sheet comprising two layers is described, namely, a polyurethane layer having adhesion properties and, where appropriate, energy absorber properties, and a thermosetting polyurethane layer with anti-laceration and self-healing properties. This sheet is assembled with a monolithic or laminated support, made of glass and / or plastic to form the laminated glazing, by means of the thermoplastic layer, by using heat and pressure.

 The publication of European patent 0 133 090 likewise describes a sheet with one or two layers of plastic material, the assembly of which with the glass support or the plastic material uses temperature and pressure.

 It follows that the assembly of these plastic sheets with the support to form the laminated glazing is carried out in a manufacturing center equipped with assembly means such as calenders and autoclaves.

 The invention provides a plastic sheet having the desired properties, suitable for use in laminated glazing, and which can be associated with the support without the use of heat and in places which are not necessarily those of traditional manufacture. laminated glazing. In particular, the sheet according to the invention can be associated with the support of the glazing while the latter is already in place in a building window frame or in a motor vehicle body frame for example.

 According to the invention, the sheet which comprises at least one layer of polyurethane of high optical quality as an essential element comprises on at least one of its faces an adhesive layer making the sheet self-adhesive.

 According to a characteristic of the invention, this adhesive layer is based on an acrylic resin and has a thickness of less than approximately 100 μm and preferably less than approximately 50 μm.

 The polyurethane layer constituting an essential part of the sheet according to the invention can be based on a thermoplastic polyurethane as described in the French patent publications 2,398,606 and European patent 0 133,090 already mentioned. It can also be a layer of thermosetting polyurethane as also described in the patent publications cited above, this layer having self-healing and anti-laceration properties. The sheet according to the invention can comprise one or more of these polyurethane layers depending on the properties sought. These properties are, for example, anti-splinter, energy absorber, scratch and abrasion resistance properties.

 When the sheet comprises both a layer of thermoplastic polyurethane having adhesion properties and, where appropriate, energy absorbing properties, and a layer of thermosetting polyurethane having surface properties such as resistance to scratching and to abrasion, also designated by self-healing, the adhesive layer making the self-adhesive sheet according to the invention is placed on the layer of thermoplastic polyurethane.

 The self-adhesive sheet according to the invention can also further comprise polyurethane layer (s), other layers of plastic material giving it the desired properties, for example of energy absorber, of reinforcement, such as polyterephthalate ethylene glycol.

 To manufacture the adhesive layer making the self-adhesive sheet, one starts from a liquid composition which is a solution or dispersion of the acrylic resin in water or an organic liquid, the viscosity of the solution or dispersion being at 25 "C lower to 5000 centipoise and preferably less than 2000 centipoise.

 This solution or dispersion is applied to the plastic sheet to be made self-adhesive by any means such as casting, spraying, coating with a roller or curtain.

 The liquid composition is preferably an acrylic emulsion with at least 50% solids content, of the polymer or copolymer type based on acrylate and / or methacrylate and in particular based on butylacrylate and methylacrylate.

 When the sheet according to the invention is not used at the place of its manufacture for assembly with the support in order to constitute the laminated glazing, in one aspect of the invention, the tackiness and the optical qualities are preserved of the sheet by protecting the adhesive layer rendering the sheet self-adhesive by a protective layer which is removed from the sheet just before assembly of the latter with the support. This protective layer may be paper or a plastic material comprising a non-stick coating layer such as a silicone coating so as not to alter the adhesive power of the adhesive layer making the sheet self-adhesive.

 The adhesive sheet according to the invention can be assembled with glass or plastic supports to form safety glazing which can be used as building or automobile glazing. Examples of the use of the sheet are described below together with other advantages and features of the invention.

EXAMPLE 1
A self-adhesive plastic sheet is produced based on a thermosetting polyurethane having self-healing and anti-laceration properties, usable in laminated safety glazing such as a motor vehicle windshield.

 On a movable glass support, continuously moving, coated with a separating agent which may for example be that described in French patent publication 2,383,000, namely a modified addition product of ethylene oxide, flows a homogeneous reaction mixture taken in the following proportions 1000 g of a polyester with a molecular weight of about 450 obtained by condensation of 1,2-propylene oxide with 2,2-bis (hydroxymethyl) -1butanol and having a content of free hydroxyl radicals of approximately 10.5% to 12% containing 1% by weight of a stabilizer, 0.05% by weight of a catalyst, namely dibutyltin dilaurate and 0.1% by weight of a coating agent, 1020 g of a 1,6-hexane diisocyanate biuret having a free isocyanate radical content of approximately 23.2%.

 A casting head such as that described in French patent publication 2 347 170 is used. A uniform layer is formed which, by polymerization under the effect of heat, for example about 15 minutes at 1200C, has a thickness of about 0.50 mm and self-healing properties.

 On the layer obtained, an aqueous emulsion with 70% of dry extract of a butylacrylate / methylacrylate copolymer having a viscosity at 25 "C. of 1000 centipoise is sprayed. After a drying of 5 minutes at 110 ° C., a layer is obtained. 30 µm of good optical quality, having cold adhesive properties.

 The two-layer sheet is assembled by calendering to a laminated glazing comprising two glass sheets and an intermediate layer of polyvinyl butyral. The glazing obtained can be used as a motor vehicle safety windshield, the two-layer sheet being arranged on the face of the glazing oriented towards the passenger compartment of the vehicle.

EXAMPLE 2
A self-adhesive plastic sheet is produced comprising a layer of thermosetting polyurethane having self-healing properties, and a layer of thermoplastic polyurethane having energy-absorbing properties and an adhesive layer rendering the sheet self-adhesive.

 In the same way as in Example 1, a first layer of thermosetting polyurethane with a thickness of approximately 0.2 mm is formed. On this first layer, a second layer is formed by pouring a mixture of a polyol component and an isocyanate component, the polyol component being formed of polytetramethylene glycol of molecular weight 1000, 1,4-butanediol and polycaprolactonetriol in the respective proportions of 0.35, 0.55 and 0.10 in hydroxyl equivalent for each of these polyols to which a stabilizer is added at a rate of 0.5% by weight of the total mass of the polyol component, a coating agent in an amount of 0.05% by weight and a catalyst, namely dibutyltin dilaurate in an amount of 0.02% by weight.

 The isocyanate component used is 3-isocyanatomethyl 3,5,5-trimethyl cycl ohexyl i socyanate (IPDI) having urea functions obtained by partial hydrolysis of IPDI and having a content of NCO groups of approximately 31.5% by weight.

Components are taken in quantities such as ratio
NCO / OH is 1.

 After degassing the components under vacuum, the mixture brought to about 40 "C is poured onto the layer of self-healing polyurethane previously formed. This forms a layer of about 0.50 mm d after a polymerization cycle of 25 mm at 1200C. 'thickness.

 On this layer having energy absorbing properties, the emulsion described in Example 1 is sprayed in order to form a layer 40 μm thick making the sheet self-adhesive. The three-layer sheet is removed from its formation support and it is assembled with a sheet of glass to form a safety glazing usable in particular as a windshield for a motor vehicle.

EXAMPLE 3
A self-adhesive composite sheet is produced comprising a layer of self-healing polyurethane and a film of polyethylene terephthalate.

 To this end, on a ribbon of polyethylene terephthalate 50 μm thick, held stretched horizontally by a device as described in European patent publication 0 038 760, the reaction mixture described in the example is formed by reactive casting. 1, a 200 μm thick layer of a thermosetting polyurethane having self-healing properties. After polymerization, the composite film is turned over and on the uncoated side of the polyethylene terephthalate film, an adhesive layer 40 μm thick is formed by spraying the aqueous emulsion described in Example 1, making the sheet self-adhesive. . On the adhesive sheet is placed a sheet of paper coated with a non-stick layer and the assembly can be rolled up and stored.

 The composite sheet produced can be assembled, for example, to building glazing already in place in a window frame. To this end, the sheet of protective paper is removed from the sheet just before assembly, which is carried out by applying the self-adhesive composite sheet to the glass sheet by means of the adhesive layer.

EXAMPLE 4
A self-adhesive composite sheet is produced in the same way as in Example 1. This sheet is then used to coat glazings made of rigid plastic material, for example polycarbonate or polymethyl methacrylate in order to give them properties of resistance to abrasion and scratch.

Claims (8)

 1. Sheet of high optical quality plastic material comprising at least one layer of polyurethane, suitable for use in particular as an outer sheet in laminated glazing, characterized in that it comprises on at least one of its faces a adhesive layer making the adhesive sheet.  2. Sheet according to claim 1, characterized in that the adhesive layer rendering the self-adhesive sheet is based on an acrylic resin and it has a thickness less than about 100 µm and preferably less than 50 µm.  3. Sheet according to claim 2, characterized in that the adhesive layer is obtained from an acrylic solution, dispersion or emulsion with a viscosity at 25 "C less than 5000 centipoises and preferably less than 2000 centipoises.  4. Sheet according to claim 3, characterized in that the adhesive layer is obtained from an aqueous emulsion with at least 50% of dry extract of a copolymer of butylacrylate and methyl acryl ate.  5. Sheet according to one of claims 1 to 4, characterized in that it comprises a temporary protective layer which preserves its adhesive properties.  6. Sheet according to one of claims 1 to 5, characterized in that the polyurethane layer is a thermosetting polyurethane having self-healing and anti-laceration properties.  7. Sheet according to one of claims 1 to 6, characterized in that it comprises a polyurethane layer having energy absorbing properties.  8. Sheet according to one of claims 1 to 7, characterized in that it further comprises at least one other layer of plastic material such as a layer of polyethylene terephthalate.