MXPA00010689A - Eliminating adhesion difference due to glass orientation in laminated safety glass - Google Patents

Abstract

A laminar structure comprised of at least two layers (16, 20) of glass and a sheet (18) of plasticized PVB containing an adhesion control additive is provided wherein the difference in adhesion between the PVB interlayer and the glass due to glass orientation is minimized by including a leveling agent in the bulk or on the surface of the sheet of plasticized PVB or by coating the leveling agent onto the glass prior to laminating.

Description

ELIMINATION OF THE DIFFERENCE OF ACCESSION DUE TO THE ORIENTATION OF THE GLASS IN A LAMINATED SAFETY GLASS BACKGROUND OF THE INVENTION The adhesion between glass and the inner layer is the most critical and controllable parameter related to the penetration resistance of laminated safety glass. If the adhesion is very high, with the impact the laminate fails as a monolithic unit, and therefore does not offer much protection to the occupant of a motor vehicle. If the adhesion is very low, the sharp pieces could be separated from the laminate at the moment of impact, and then they could cause injuries to the occupant.

Currently, laminated safety glasses are mainly made of float glass. For example, the windshield of the automobile is manufactured from two pieces of float glass which have been warped by warping with heat or by heating followed by pressure molding. The warped glass pieces are joined by an inner layer of plasticized polyvinyl butyral (PVB). In the manufacture of float glass, the glass is melted and transported on top of a molten tin bath. While one of the surfaces is in contact with Ref. 123635 tin (the tinned side), the other is usually in contact with an inert atmosphere such as nitrogen (the air side). Consequently, the chemistry of the two surfaces of the same sheet of glass can be very different. Sometimes, the difference in the chemistry of the surfaces manifests itself in the adhesion between the glass and the inner layer of PVB. One of them acquires greater or lesser adhesion depending on whether the "tinned" side or the "air" side of the glass is in contact with the inner layer of PVB, among other factors such as PVB moisture, inherent adhesiveness of the inner layer , chemistry of the glass mass. The difference in adhesion, often referred to as asymmetric adhesion, can be such that a laminate is considered to be used as a windshield in one orientation of the glass, but not in another. Some mills are frustrated by having to identify and keep track of the orientation of the glass, or when they have to install extra equipment to rotate the glass to achieve some prescribed orientation.

It is therefore an object of the present invention to provide a laminar structure which can be used as windshields and side windows in automobiles in such a way as to reduce the difference in adhesion between the inner layer of PVB and the tinned side and that of the PVB and the air side of the glass. The present invention also applies to other laminar structures of glass sheets / adhesive in which asymmetric adhesion is experienced.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention there is provided a laminar structure of glass / adhesive sheets comprising at least two layers of glass and a laminated polyvinyl butyral (PVB) sheet, said polyvinyl butyral containing a mixture of a metal salt capable of being ionized as an additive. of adhesion control to provide a preselected level of adhesion between said glass layers and said polyvinyl butyral sheet which is suitable for use as automotive windshields and side windows and body glasses, and incorporating another metal salt capable of ionizing the which provides a cation different from that provided by the adhesion control additive such that the cation content that is provided by leveling agent is between 0.03 and 1.35, and preferably 0.07 to 1.1 milliequivalents / kg (meq / kg) of the laminate. The second metal salt may be a salt of an alkaline earth metal such as magnesium or calcium or of a transition metal such as zinc, copper, or a Group IV metal such as tin. Surprisingly, this small amount of salt or leveling agent is suitable for reduction, and in some cases, essentially for the removal of asymmetric adhesion without other harmful effects on the overall operation of the laminate such as fogging. In addition, the level of adhesion of the PVB layers can be controlled through conventional means by adjusting the amount of adhesion control additive.

BRIEF DESCRIPTION OF THE DRAWINGS In the description of the invention, reference should be made to the accompanying drawing in which Figure 1 illustrates in diagrammatic form a pattern used to determine the compressive shear stress of a laminate.

DETAILED DESCRIPTION OF THE INVENTION The laminated PVB laminate is prepared by processes well known in the art. The preparation of plasticized PVB is described by Phillips, in US Pat. No. 4,276,351 which is incorporated herein by reference. A wide variety of additives can be used for adhesion control with polyvinyl butyral laminate. In the present invention a PVB sheet is plasticized with a compatible amount of glycol ester selected from the group consisting of triethylene glycol di-n-heptanoate and tetraethylene glycol di-n-heptanoate, or with a compatible amount of branched or non-branched diols glycols branched such as triethylene glycol di-2-ethylbutyrate triethylene glycol di-2-ethylhexanoate, and contains as an adhesion control additive an alkali metal carboxylate such as potassium formate, acetate and the like. A process for the preparation of such a laminate is described by Moynihan, in US Pat. No. 4,292,372 which is incorporated herein by reference.

In the examples of the present invention, 100 parts of dry PVB lamellae with 23% nominal weight of non-butylated vinyl alcohol groups are mixed with 36-40 parts of tetraethylene glycol di-n-heptanoate plasticizer containing a light stabilizer (Tinuvin-P or other suitable compounds) and an antioxidant which are previously mixed continuously in the plasticizer in a twin screw extruder. The melt exiting the extruder is at 200-220 ° C. This passes through a gear pump and a melt filter, and then through a slotted die and forms a laminate with a nominal thickness of 0.76 mm. The adhesion control additive is added as an aqueous side stream directly into the melt. The leveling agent, if soluble in water, is added either as a direct aqueous side stream in the melt, or preferably as a solution combined with the adhesion control additive. If the leveling agent is not readily soluble in water it may be added as a solution in an organic solvent directly in the melt as a solution in the plasticizer which is fed to the extruder.

As used herein, the term, inorganic acids, include sulfuric acid, nitric acid, and hydrochloric acid. Organic monobasic acids include formic acid, acetic acid, as well as linear carboxylic acids having from 1-12 carbon atoms and branched carboxylic acids having from 3-12 carbon atoms. Polybasic organic acids refer to acids with two or more carboxylic acid groups, and include oxalic acid, succinic acid, oxaloacetic acid, citric acid, and ethylenediamine tetra acetic acid.

In addition to an adhesion control additive and a leveling agent, common adjuvants such as antioxidants, colorants and ultraviolet absorbers that do not adversely affect the performance of the adhesion control additive can be included in the PVB composition. In addition, to reduce the defect relative to air, surface energy modifying agents can be added consisting of silicones, hydrolyzed silanes, fluorine-containing eurfactants, carboxylic acid salts of a chain extender or combinations thereof. Defects in relation to the air in the laminate include air bubbles and worm-like defects that are formed as a result of the confinement of the air and the air absorbed in the inner layer of the PVB during the process in the autoclave.

The manufacture of the lamellar structures is well known in the art. It is also known that in order to remove most of the air from between the surfaces in the laminar structure, the surface of the PVB laminate should be roughened. This can be done mechanically by embossing or by melt fracture during the extrusion of the PVB sheet. The retention of the roughness of the surface is essential to facilitate the effective deaeration of trapped air during the preparation of the laminate. (The surface roughness, Rz, is expressed in microns by an average roughness of 10 points in accordance with ISO-R468 of the International Organization for Standardization). For laminates that have a thickness greater than about 0.030 inches (0.76 mm), 10 points of average roughness, Rz, of up to 60 microns is enough to prevent air from being trapped. To prevent blockage a minimum roughness of about 20 microns is needed if the laminate is going to be rolled on a roller without internal debris or without antiblocking agents. The surface roughness of the thermoplastic resin laminate and the methods of characterization and quantification of surface roughness are described in ANSI / ASME B46.1 (1995).

Adhesion Test The adhesion of the laminate, that is, of the inner layer of PVB with the glass, is determined using the compression shear test using the pattern 10, 12 shown in Figure 1. The laminates for the determination of the adhesion are first prepared by conditioning the inner layer of polyvinyl butyral a -. 23S í 2e C in a run of relative humidity of 23 ± 3% throughout the night before rolling. With reference to Figure 1, the inner layer 18 is subsequently placed between two pieces of heated float glass 16 and 20 with dimensions of 12"xl2" (305 mm x 305 mm) and 2.3 mm nominal thickness which has been washed and rinsed in demineralized water. Two laminates are produced from each internal layer of PVB: one with the inner layer with both tin sides of the glass pieces (ATTA); another with the inner layer in contact with both sides to the air of the pieces of glass. Subsequently, the glass / PVB / glass assemblies are heated in an oven set at a temperature of 90-100 ° C for 30 minutes. Subsequently, each is passed through the strait of a roller assembly in such a way that the air in the empty spaces between the glass and the inner layer can be removed by pressure, and the edge of the assembly sealed. In this stage, the assembly is called pre-pressed. The pre-pressing is then placed in an air autoclave where the temperature rises to 135 ° C and the pressure to 200 psig (14.3 bar). These conditions are maintained for 20 minutes, after which the air is cooled, while the air that is added to the autoclave is suspended. After 20 minutes of cooling when the temperature of the air in the autoclave is less than 50 ° C, the excess air is vented.

The compressive shear stress of the laminate prepared as prescribed above is determined using the method that here- Six pieces of l "xl" (25 mm x 25 mm) are cut from the laminate. The pieces are conditioned in a controlled room at 23 ° C ± 2 ° C and 50% ± 1% relative humidity for one hour before the test. The shear stress of compression of the piece is determined using a pattern 12 shown in Figure 1. The piece, 16, 18, 20, is placed in the cut in the lower half of the pattern 12, and the upper half is then placed over the piece. A transverse load is lowered at a rate of 0.1 inches per minute (2.5 mm per minute) until it contacts the top piece of the device. As the downward movement of the transverse load continues, a piece of glass of the piece begins to slide relative to the other. The shear stress of compression of the piece is the shear required to cause a failure of the adhesive. The accuracy of this test is such that one standard deviation is typically 6% of the average result of six chunks. A glass / PVB / glass laminate tested in this way for adhesion that has a compressive shear force of 1500 psi to about 2700 psi (1050 N / cm2 to 1850 N / cm2) is considered the most appropriate for use in windshields of cars and side windows.

Accelerated Measurements of the Haze A laminate is made of each internal layer of PVB tested. The TAAT orientation is used. The laminate is assembled and deaerated as discussed in the adhesion section, except that a warmer and longer autoclave cycle is employed. The time is maintained in 90 minutes at 150 ° C and 225 psig (15.3 bar) of pressure. The mist is measured following the procedure described in the ASTM D-1003 method using a Hazegard Haze gauge from Gardner. Mist levels greater than 0.4% are considered undesirable for use in windshields.

EXAMPLES The present invention is further illustrated by the following examples of which parts and percentages are by weight unless otherwise specified.

Comparative Examples Cl and C2 The plasticized polyvinylbutyral laminate (commercially available from E.l. duPont de Nemours &Co. as Butacite®) in which the plasticizer was tetraethylene glycol di-heptanoate, was used to prepare laminates in the method described above. Laminates with two levels of adhesiveness were used. The adhesion of the laminates made with two orientations of the glass (TAAT and ATTA) was measured. The results are shown in Table 1.

Comparative Example C3 100 parts by weight of polyvinylbutyral were mixed in an extruder with 38.5 parts of plasticizer doped with antioxidants (octylphenol) and ultraviolet light stabilizers (Tinuvin P). This composition is the same as in Comparative Example 1. The potassium formate was added to the melt in the extruder as an adhesion control additive in such a way that the concentration of potassium in the laminate was 250 parts per million by weight of the sheet. plasticized The adhesion results in both TAAT and ATTA orientations are shown in Table 1.

Example 1 The inner layer of polyvinyl butyral in this example was similar to that of Example C3, except that, a leveling agent, magnesium sulfate was added in such a way that the magnesium concentration was 0.40 meq / kg. The adhesion and haze results are shown in Table 1.

Example 2 The inner layer of polyvinyl butyral in this example is similar to that of Example 1, except that the laminate was made by feeding the adhesion control additive, potassium format, and the leveling agent, magnesium sulfate, as a mixed solution. The resulting level of potassium in the laminate was 381 ppm, and the magnesium level was 0.11 meq / kg. Adhesion and haze data are shown in Table 1.

Example 3 The inner layer of polyvinyl butyral in this example was similar to that used in Example 1, except that the potassium level of the adhesion control additive was 300 ppm, and magnesium neodecanoate was added to the melt as a leveling agent in the Extruder as a solution in mineral essences and plasticizer in such a way that the concentration of magnesium in the mass of the PVB laminate was 0.50 meq / kg. The adhesion and haze results are shown in Table 1.

Example 4 The inner layer of polyvinyl butyral in this example was similar to that used in Example 2, except that the potassium concentration of the adhesion control additive, potassium format, was 405 ppm, and an ethylidene leveling agent was added. Disodium magnesium tetraacetate in such a way that the magnesium concentration was 0.14 meq / kg in the laminate. The laminates were prepared and the adhesion was measured. The results are shown in Table 1.

Example 5 The inner layer of polyvinyl butyral in this example is the same as in Example 1 in which the potassium level of the potassium formate adhesion control additive was 350 ppm, but the leveling agent was magnesium acetate magnesium. The magnesium level in the laminate was 0.58 meq / kg. The adhesion data are shown in Table 1.

Example 6 The inner layer of polyvinyl butyral in this example was similar to that used in Example 3, except that the potassium level of the adhesion control additive was 400 ppm, and 0.007 parts of glycoxypropyltrimethoxy silane were added and also 0.07 parts of silicone oil modified with polyoxyethylene were added as surface energy modifiers, and the magnesium concentration in the PVB laminate mass was 1.0 meq / kg. The adhesion and haze results are shown in Table 1.

Example 7 The inner layer of polyvinyl butyral in this example was similar to that used in Example 1, except that the potassium level in the laminate mass due to the adhesion control additive was 300 ppm, and calcium acetate was added as the leveling agent in such a way that the concentration of calcium in the mass of the PVB laminate was 1.0 meq / kg. The adhesion and haze results are shown in Table 1.

Example 8 The inner layer of polyvinyl butyral in this example was similar to that used in Example 7, except that zinc acetate was used as a leveling agent. It was added in such a way that the concentration of zinc in the mass of the PVB laminate was 0.83 meq / kg. The adhesion and haze results are shown in Table 1.

Example 9 The internal layer of polyvinyl butyral in this example (material commercially available under the registered trademark Butacite®) was similar to that used in the Comparative Example Cl, except that the inner layer was precoated by immersion in a bath containing a 0.012% aqueous solution of magnesium sulfate at 25 feet / minute (7.6 m / minute). The resulting laminate was analyzed by ion chromatography and found to contain 0.17 meq / kg of magnesium based on the entire mass. The resulting laminate was dried and conditioned in an environment with a relative humidity of 23 ± 2% before rolling. The adhesion results are shown in Table 1.

Example 10 The inner layer of polyvinyl butyral in this example was similar to that used in Comparative Example Cl. However, the glass was immersed in a solution of magnesium sulfate in demineralized water and dried before rolling. The concentration of the magnesium ions in the solution was 10 mg / liter. The adhesion of the laminates was measured in the TAAT and ATTA orientations. The data is shown in Table 1. It was surprising that such a low concentration of magnesium ions of 10 parts per million in the solution was able to substantially reduce the difference in adhesions between the two orientations of the glass.

Comparative Example C4 The inner layer of polyvinyl butyral in this example was similar to that used in Example 1, except that the potassium level of the adhesion control additive was 300 ppm and the level of magnesium of the leveling agent is 1.5 meq / kg. The adhesion and haze results are shown in Table 1. Also the level of haze was sufficiently high that such a laminate is not preferred as automobile windshields.

Comparative Example C5 The inner layer of polyvinyl butyral in this example was similar to that used in Comparative Example C3, except that magnesium was used in the form of magnesium format as the sole adhesion control additive. The magnesium level was 4.2 meq / kg. No other leveling agent was used. The adhesion and haze results are shown in Table 1. Adherence in the ATTA orientation was greater than in the TAAT orientation. This shows that the use of magnesium alone does not have the desired leveling effect.

Comparative Example C6 The inner layer of polyvinyl butyral in this example was similar to that used in Example 2, except that no leveling agent was added. The potassium level of the adhesion control additive, potassium format, was 385 ppm. The adhesion in this example is lower than in Example 2 despite the fact that the adhesion control additive concentrations in both were very identical. This shows that the magnesium in the inner layer of PVB in Example 2 does not act as an adhesion control additive, but rather as an agent for tempering the effect due to the orientation of the glass in the laminate.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the aforementioned invention as above, the content of the following is claimed as property.

Claims (1)

CLAIMS A laminate of glass / adhesive layers comprising at least two layers of glass and a laminated polyvinyl butyral sheet, said polyvinyl butyral having an alkali metal salt incorporated as an adhesion control additive to provide a selected level of adhesion between said layers of glass and said polyvinyl butyral sheet, characterized in that between the layers and the joining surfaces of the polyvinyl butyral sheet an asymmetric adhesion, and a different metal salt as a leveling agent in an amount to provide a different metal salt cation concentration is presented. in the PVB inner layer of 0.03-1.35 meq / kg, said amount being sufficient to reduce the asymmetric adhesion between the plasticized inner layer and the glass joining surfaces. A laminar structure according to Claim 1, characterized in that said leveling agent is an alkaline earth metal of an inorganic acid or an organic acid. A laminar structure according to Claim 1, characterized in that said leveling agent is a salt of a transition metal or a tin salt of an inorganic acid or an organic acid. A laminar structure according to Claim 1, characterized in that said adhesion control additive is a potassium salt of an inorganic acid or potassium salts of organic acids. A laminar structure according to Claim 1, characterized in that the leveling agent is a salt of alkaline earth metal, transition metal, or tin of a monobasic organic acid. A laminar structure according to Claim 1, characterized in that the leveling agent is a salt of alkaline earth metal or transition metal of a polybasic organic acid. A laminar structure according to Claim 1, characterized in that the plasticizer is a glycol ester. A plasticized polyvinyl butyral laminate in a laminar structure according to claim 1, having a glycol ester incorporated as a plasticizer, an alkali or an alkali metal salt as an adhesion control additive to provide a preselected level of adhesion between said layers of glass and said polyvinyl butyral sheet, characterized in that an asymmetric adhesion between the glass layers and the joining surfaces of the polyvinyl butyral sheet is presented, and as a leveling agent an alkali metal salt in an amount to provide a concentration of the cation of the different metal salt in the PVB inner layer from 0.03 to 1.35 meq / kg, said amount being sufficient to reduce the asymmetric adhesion between the plasticized inner layer and the glass joining surfaces. The polyvinyl butyral inner layer according to claim 8, characterized in that the leveling agent is an alkaline earth metal or transition salt of an inorganic acid or an organic acid. A process for minimizing asymmetric adhesion between an inner layer of polyvinyl butyral and glass in a laminate of glass / adhesive layers comprising at least two layers of glass and a sheet of plasticized polyvinyl butyral adhesive, characterized in that it comprises the steps of preparing a polyvinyl butyral mass composition containing an alkali metal salt as an adhesion control additive which provides a preselected level of adhesion between said glass and said sheet, incorporating a second metal salt different from said adhesion control additive as a leveling agent in an amount to provide a cation concentration of the different metal salt in the polyvinylbutyral sheet from 0.03 to

1.35 meq / kg, forming a laminar structure by adhesion of said sheet to the glass plate, the deaeration of the structure and the sealing of said sheet and glass plate by the application in them of heat and pressure. The process according to claim 10, characterized in that the leveling agent is a salt of alkali metal or transition metal or tin of an organic acid or an organic acid. The process according to claim 10, characterized in that said adhesion control additive is selected from the group consisting of potassium formate, potassium acetate and other potassium salts. A process for minimizing asymmetric adhesion between an inner layer of polyvinyl butyral and glass in a laminate of glass / adhesive layers comprising at least two layers of glass and a sheet of plasticized polyvinyl butyral adhesive, characterized in that it comprises the steps of preparing a polyvinyl butyral mass composition containing an alkali metal salt as an adhesion control additive which provides a preselected level of adhesion between said glass and said sheet, and the glass being precoated with a leveling agent which is dissolved in a solution which It contains 2 parts per million by weight of metal ions, forming a laminar structure by adhering said sheet to said glass plate, deaerating the structure and sealing said sheet and glass plate by applying heat and pressure. The process according to claim 13, characterized in that the cation of the leveling agent of magnesium, calcium, zinc, or tin, and anions are portions of monobasic or polybasic organic acids. The process according to claim 13, characterized in that two or more leveling agents with different cations are used in combination.