Colored interlayer for laminated glass with improved optical properties

Abstract

The present invention relates to an intermediate film for laminated glass, in particular for vehicle windows, comprising four or more layers, said layers comprising colored layers with improved optical properties.

Description

[0001] The present invention relates to an interlayer for laminated glass, in particular for vehicle side windows, comprising four or more layers, said layers comprising a colored layer with improved optical properties.

[0002] Glass laminates comprising two sheets of glass bonded to each other with an interlayer containing a thermoplastic resin are well known for example for windows used in vehicles.

[0003] In order to improve the comfort of passengers inside a vehicle, so-called acoustic insulating glass is used. It typically comprises three layers of an acoustic insulating interlayer comprising a softer acoustic insulating layer and two protective layers on either side of the acoustic insulating layer. The acoustic insulating layer typically contains a polyvinyl acetal resin which is highly compatible with the plasticizer used, making it softer and thus providing good acoustic insulating properties. The protective layers prevent the exudation of the large amount of plasticizer in the acoustic insulating layer and provide stability and ease of use.

[0004] It is also known to use tinted windows for rear side windows, sunroofs and back windows in passenger vehicles in order to provide privacy and sun protection for passengers in the back seat.

[0005] Such tinted windows providing simultaneously acoustic damping are especially used in high-end cars. However, it has been previously reported that stacking a colored layer with an acoustically damping three-layer interlayer can lead to undesirable optical properties in the final glass laminate as a pattern of brighter and darker stripes can be seen. However, such poor appearance is not acceptable in the high-end vehicle market.

[0006] The appearance of these patterns, also called mottling, is generally explained by the fact that the surface of the interlayer for laminated glass is usually embossed to form recesses, allowing good degassing properties during the lamination process.

[0007] In common production of laminated glass, the laminate comprising at least one interlayer for laminated glass between two glass sheets is passed through a press roll to degas, or is put in a rubber bag under vacuum for pressure bonding, while removing the air remaining between the glass sheets and the interlayer.

[0008] Then, when the surface of the interlayer is pressed between the glass sheets at high temperature and pressure, the recesses on the surface of the interlayer are removed during the lamination step. However, when the surface of the interlayer is pressed against another interlayer, the recesses can create a pattern in the colored layer and / or the acoustically damping layer which is rather soft, and this pattern is not completely removed during the lamination step, leading to the mottling effect. Several approaches have been taken to mitigate mottling, including increasing the distance between the recesses and the colored layer. However, the inventors have found that a particular design of the roughness pattern of the colored layer itself plays a decisive role in preventing the mottling effect.

[0009] Typically, colored interlayers with acoustic properties are prepared by adding colorants to the bulk of the acoustic three-ply itself. However, such products are difficult to recycle, as the colored three-ply can only be fed into other colored laminated applications, which are rather limited.

[0010] On the other hand, in order to provide sustainable products, recycling of interlayers for laminated glass is becoming more and more important in the glass industry. One advantage of the present invention is to provide color in an additional colored ply which can be separated from the bulk acoustic part of the interlayer, for example by cutting the colored ply from the bulk interlayer according to the method disclosed in EP 3808558 A1. Thus, only a part of the interlayer needs to be recycled into colored applications and the bulk of the interlayer can be recycled into all standard colorless applications.

[0011] The present invention thus relates to an interfilm for laminated glass comprising four or more layers each containing a polyvinyl acetal and a plasticizer, said four or more layers being stacked on top of each other in the following order:

[0012] - a colored ply comprising a polyvinyl acetal, a plasticizer and at least one colorant,

[0013] - a first protective ply comprising a polyvinyl acetal and a plasticizer,

[0014] - an acoustic damping ply comprising a polyvinyl acetal and a plasticizer, and

[0015] - a second protective ply comprising a polyvinyl acetal and a plasticizer,

[0016] wherein the colored ply has on at least one of its surfaces a roughness of a ten-point average roughness Rz measured according to DIN EN ISO 4287 of between 5 pm and 30 pm and an average width Rsm measured according to DIN EN ISO 4287 of between 10 pm and 1000 pm.

[0017] The feature "in the following order" is intended to mean that the four layers necessary for the invention are present in the order required by the claim. However, additional layers can be present above, below or between these four layers.

[0018] Preferably, the colored ply has on both of its surfaces a roughness of a ten-point average roughness Rz measured according to DIN EN ISO 4287 of between 5 pm and 30 pm and an average width Rsm measured according to DIN EN ISO 4287 of between 10 pm and 1000 pm.

[0019] More preferably, Rz is 10 pm to 20 pm, more preferably 12.5 pm to 17.5 pm.

[0020] It is also preferred that Rsm is from 700 pm to 900 pm or from 500 pm to 800 pm, more preferably from 850 pm to 950 pm.

[0021] In another embodiment, the first protective layer can also have an embossed pattern, wherein the values of Rz and / or Rsm are in the same range as the values given by the colored layer.

[0022] When polyvinyl acetal film is recycled, for example, from offcuts obtained during production of glass laminates, the recycled polyvinyl acetal material can have problems with higher haze values or yellowness due to repeated extrusion steps carried out at high temperatures and high pressures, potentially leading to partial degradation of the polyvinyl acetal. However, when such recycled material is used for colored glass laminates, the color of the colored layer masks this slight optical defect, thus mitigating the problem of this increased haze and yellowness.

[0023] Thus, in another embodiment of the present application, the polyvinyl acetal in the colored layer comprises at least 75% by weight of recycled polyvinyl acetal, preferably at least 90% by weight, most preferably at least 95% by weight. Most preferably, all polyvinyl acetal in the colored layer is from recycled material.

[0024] It is also preferred that the polyvinyl acetal in each of the four or more layers comprises at least 75% by weight of recycled polyvinyl acetal, more preferably at least 90% by weight, most preferably at least 95% by weight. In particular, all polyvinyl acetal in each of the four or more layers is from recycled material.

[0025] Preferably, the colored layer covers the entire surface area of the intermediate film. In other words, the entire intermediate layer appears colored, preferably presenting a predetermined gray tone.

[0026] The individual films used according to the present application can each be used in almost any thickness, provided that the sound insulation properties are not adversely changed and the colored layer provides a sufficiently colored appearance. The individual films can all, for example, have the same thickness; however, combinations of individual films of different thicknesses are also possible.

[0027] Preferably, the thickness of the colored layer is from 150 pm to 500 pm, more preferably from 250 pm to 350 pm.

[0028] It is also preferred that the total thickness of the first protective layer and the second protective layer together with the acoustic layer is from 450 pm to 750 pm, more preferably from 550 pm to 650 pm.

[0029] The various membranes according to the invention comprise plasticizer-containing polyvinyl acetal obtained by acetalizing fully or partially saponified polyvinyl alcohol with aldehydes. The acoustic damping layer preferably comprises 17-22% by weight, more preferably 18-21% by weight, and even more preferably 19.5-20.5% by weight of polyvinyl acetal containing polyvinyl alcohol groups. Preferably, the protective layer and the colored layer each comprise less than 14% by weight, more preferably 11-13.5% by weight, and even more preferably less than 11.5-13% by weight of polyvinyl acetal containing polyvinyl alcohol groups.

[0030] The polyvinyl alcohol content and polyvinyl acetate content of polyvinyl acetal were determined according to ASTM D 1396-92.

[0031] The compatibility of plasticizers with partially acetalized polyvinyl alcohol (PVA) generally decreases as the polarity of the plasticizer decreases. Therefore, plasticizers with higher polarity are more compatible with PVA acetal compared to those with lower polarity. Alternatively, the compatibility of lower polarity plasticizers increases with increasing degree of acetalization, i.e., with a decrease in the number of hydroxyl groups in PVA acetal and a corresponding decrease in polarity.

[0032] Each membrane may contain the same or different plasticizers. It is preferred to use the same plasticizer; the composition of the plasticizer blend in each membrane may vary slightly due to migration.

[0033] Each membrane may contain at least one of the following plasticizers known for PVB membranes, or a plasticizer blend:

[0034] Esters of polyvalent aliphatic or aromatic acids, such as dialkyl adipates like dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, heptyl adipate and nonyl adipate mixtures, diisononyl adipate, heptylnonyl adipate and esters of adipate with alicyclic ester alcohols or ether-bonded ester alcohols, dialkyl sebacate like dibutyl sebacate and esters of sebacate with alicyclic ester alcohols or ether-bonded ester alcohols, esters of phthalic acid like butyl benzyl phthalate or bis-2-butoxyethyl phthalate, and esters of cyclohexanedicarboxylic acid like diisononyl 1,2-cyclohexanedicarboxylic acid;

[0035] Esters or ethers of polyvalent aliphatic or aromatic alcohols or oligoether diols having one or more unbranched or branched aliphatic or aromatic substituents, such as esters of di-, tri-, or tetra-diols with straight-chain or branched aliphatic or alicyclic carboxylic acids; diethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), tetraethylene glycol bis(n-heptanoate), triethylene glycol bis(n-heptanoate), triethylene glycol bis(n-heptanoate), tetraethylene glycol dimethyl ether and / or dipropylene glycol benzoate, may be used as examples of the latter group of phosphate esters having aliphatic or aromatic ester alcohols, said phosphate esters being, for example, tri(2-ethylhexyl) phosphate (TOF) of citric acid, succinic acid and / or fumaric acid, triethyl phosphate, diphenyl-2-ethylhexyl phosphate and / or tricresyl phosphate.

[0036] Particularly preferred is the use of one or more of the following plasticizers:

[0037] Di(2-ethylhexyl) sebacate (DOS), Di(2-ethylhexyl) adipate (DOA), Dihexyl adipate (DHA), Dibutyl sebacate (DBS), Triethylene glycol di-n-heptanoate (3G7), Tetraethylene glycol di-n-heptanoate (4G7), Triethylene glycol bis(2-ethylhexanoate) (3GO or 3G8), Tetraethylene glycol bis(n-2-ethylhexanoate) (4GO or 4G8), Di(2-butoxyethyl) adipate (DBE) A) Di(2-butoxyethoxyethyl) adipate (DBEEA), Di(2-butoxyethyl) sebacic acid ester (DBES), Di(2-ethylhexyl) phthalate (DOP), Diisononyl phthalate (DINP), Triethylene glycol bis(isononyl) ester, Triethylene glycol bis(2-propylhexanoate), Diisononyl 1,2-cyclohexanedicarboxylate (DINCH), Tri(2-ethylhexyl) phosphate (TOF), and Dipropylene glycol benzoate.

[0038] Furthermore, the various membranes according to the invention may further contain additives known to those skilled in the art, such as residual water, UV absorbers, antioxidants, adhesion modifiers, optical brighteners, stabilizers, colorants, processing aids, organic or inorganic nanoparticles, fumed silica and / or surfactants.

[0039] The film based on polyvinyl acetal containing plasticizer preferably contains polyvinyl butyral (PVB) obtained by acetalizing polyvinyl alcohol with butyraldehyde.

[0040] The polyvinyl acetal in the acoustic damping layer preferably contains 5-8 mol% polyvinyl acetate groups, while the protective layer and the colored layer contain 0.1-11 mol% polyvinyl acetate groups, preferably 0.1-4 mol%, more preferably 0.1-2 mol% polyvinyl acetal, which is particularly preferred.

[0041] Preferably, the colorant is at least one dye and / or pigment. They can be any suitable coloring material, inorganic or organic, which should not dissolve in the polymer matrix and therefore resist migration from the colored layer to other layers.

[0042] Carbon black, iron oxide, titanium dioxide, or spinel pigments are preferred as pigments. The pigment can be dispersed in the masterbatch prior to extrusion, using the same polyvinyl acetal and / or the same plasticizer as used to produce the colored layer. Preferably, the colorant is added to the colored layer during extrusion in an amount that provides a predetermined gray tone in the final laminate.

[0043] In another aspect, the present invention relates to a laminate comprising an intermediate layer according to the invention between two pieces of glass, for example, each having a thickness of 1.0 mm to 2.5 mm, preferably 1.5 mm to 2.0 mm.

[0044] In another aspect, the present invention relates to the use of such laminates as side windows, sunroofs and / or rear windows of vehicles, particularly rear side windows.

[0045] Preferably, the colored film is produced by extrusion separately from the other layers, while the acoustic damping layer is co-extruded with the two protective layers. These layers are then stacked and laminated between two glass plates.

[0046] For the purpose of stacking layers, methods familiar to those skilled in the art can be used with or without pre-produced pre-stacked bodies.

[0047] The so-called "autoclave process" is carried out under pressure of about 10 to 15 bar and at a temperature of 100 to 150°C for about 2 hours. For example, it works at about 200 mbar and 130 to 145°C according to the vacuum bag or vacuum ring method according to EP 1 235 683 B1.

[0048] Vacuum laminators can also be used. These consist of heated and evacuated chambers in which laminated glass can be laminated within 30-60 minutes. Reduced pressures of 0.01-300 mbar and temperatures of 100-200°C, particularly 130-160°C, have proven worthwhile in practice.

[0049] Therefore, the present invention also relates to a method for producing an intermediate layer according to the present invention, comprising the following steps:

[0050] - At least a portion of the polyvinyl acetal for the colored layer is provided by shredding the pre-extruded polyvinyl acetal film.

[0051] - The shredded polyvinyl acetal from the previous step is extruded together with a colorant to form a colored layer.

[0052] - Provides a stack of layers comprising, in sequence, a colored layer, a first protective layer, an acoustic damping layer, and a second protective layer, and

[0053] - The resulting intermediate layer is then stacked between the two pieces of glass. Example

[0054] method

[0055] Measurement of L*a*b and TL

[0056] The color space values ​​L*a*b of the intermediate layer were measured using a HunterLab ColorQuest XE spectrophotometer (available from Hunter Associates Laboratory, Inc.) according to ASTM E 313 (Illuminant C, observer angle 2°).

[0057] Measurement of Rz and Rsm

[0058] The surface properties Rz and Rsm of the membrane are measured according to DIN EN ISO 4287.

[0059] Photographs of stacked bodies

[0060] In the darkroom, a 30cm x 30cm stack was placed horizontally on a light platform with an illumination area of ​​65cm x 45cm. An opaque black template was placed around the stack to prevent light that had not previously passed through it from entering the camera lens. The LED light type was 2-CB-D65, using D65 standard light with a color temperature of 6500K and a brightness of 5000lx.

[0061] Mount the camera on a support above the stacked structure, with the lens 50cm away from the structure. For the photograph, use an aperture of f / 5.6 and an exposure time between 1 / 160 and 1 / 40 of a second, as shown below.

[0062] The photograph measures 6000px × 4000px, corresponding to an area of ​​approximately 69cm × 46cm around the stacked body. To better display the observed optical indentations, a portion of approximately 434px × 434px, corresponding to 5cm × 5cm, was cropped from the photograph at the top center of the stacked body. This portion was edited using a standard image editing program (Microsoft PowerPoint) to increase brightness and contrast, as shown below.

[0063] Membrane preparation

[0064] Preparation of transparent single layer

[0065] Use commercially available Trosifol® Clear 0.76mm.

[0066] Preparation of transparent three layers

[0067] Use commercially available Trosifol® SC Multilayer 0.50mm.

[0068] Preparation of colored monolayers

[0069] Colored single-layer films are produced by film extrusion using a single-screw extruder. Recycled PVB scraps are extruded together with colored PVB masterbatch as feedstock. Both materials are ground into flakes of approximately 5 mm in a water-cooled mill, then transferred to a water-cooled mixing tank, and from there to the extruder hopper. The film is extruded through a flat-slit die and cooled in a water bath. The film thickness is adjusted by the roller speed, with a target of 380 μm. Film surface roughness is controlled by the die slit size and die lip temperature.

[0070] Preparation of laminates

[0071] Program 1

[0072] A standard test laminate of 30cm × 30cm was produced using conventional clear glass (Planiclear® 2.1mm) cleaned with <5μS deionized water on a flat glass washer, along with membranes A and B, in the following layup sequence: bottom glass - membrane A - membrane B - top glass. Membrane A was used as the original membrane, either with its original surface roughness or after the surface roughness had been modified as described in Procedure 2.

[0073] The sandwich structure is routinely pre-laminated industrially in a vacuum bag, followed by (1) 20 minutes at room temperature and 0.1 bar and (2) 20 minutes at 90°C and 0.1 bar. The final laminate is routinely produced industrially from the pre-laminated structure in an autoclave at up to 140°C and up to 12 bar.

[0074] Program 2

[0075] To modify the surface roughness of membrane A, including parameters Rz and Rsm, a 30cm × 30cm laminate was produced using conventional clear glass (Planiclear® 2.1mm) cleaned with <5μS deionized water on a flat glass washer and a commercially available PET (polyethylene terephthalate) film with a thickness of approximately 0.18mm and low adhesion to both PVB and glass, in the following layup sequence: bottom glass - PET - membrane A - PET - top glass.

[0076] The sandwich structure is routinely pre-laminated industrially in a vacuum bag, followed by (1) 20 minutes at room temperature and 0.1 bar and (2) 20 minutes at 90°C and 0.1 bar. The final laminate is routinely produced industrially from the pre-laminated structure in an autoclave at up to 140°C and up to 12 bar.

[0077] A film A with altered surface roughness is obtained by removing two glass layers and two PET layers from the sandwich structure after final lamination. The film A with altered surface roughness is then used to produce conventional test laminates as described in Procedure 1.

[0078] The films used, with roughness parameters Rz and Rsm and color space parameters, are shown in Table 1. Film #2 was prepared from film #1 according to laminate preparation procedure 2. The Rsm value of film #2 is not shown because the Rsm value under the measurement method used is meaningless for such a low Rz value. Films #1, #3, and #4 were produced as described in the film preparation section.

[0079] Explanation of the photo

[0080] Example 1

[0081] To illustrate the effect of Rz and Rsm of the colored film on the visibility of mottles, the laminate was produced according to laminate preparation procedure 1. The films used with roughness parameters Rz and Rsm and color space parameters are shown in Table 1. Films #1, #2, #3, #4 and #5 were produced as described in the film preparation procedure.

[0082] Table 1. Films used for co-lamination and subsequent optical evaluation via photographic images.

[0083]

[0084] Figure 1 Photographs of a laminate produced according to laminate preparation procedure 1 are shown, wherein membrane A = membrane #1 and membrane B = membrane #5. Figure 1 a), where membrane A = membrane #2 and membrane B = membrane #5 ( Figure 1 b), where membrane A = membrane #3 and membrane B = membrane #5 ( Figure 1 c), where membrane A = membrane #4 and membrane B = membrane #5 ( Figure 1 d). The photograph was taken with an exposure time of 1 / 80 second. The image shows a 5cm x 5cm section with a +10% change in brightness and a +80% change in contrast, as described in the photograph of the overlay. Figure 1 a (film #1 with high Rz and high Rsm) shows a distinct wavy pattern of repeating bright and dark stripes.

[0085] Figure 1 b and Figure 1c (films #2 and #3 with high Rz and low Rsm) showed a coarse pattern of brighter and darker spots; however, compared to Figure 1 Conversely, repeating patterns caused by lower Rsm cannot be observed. Figure 1 d (film #4 with low Rz and low Rsm) shows a smooth pattern without obvious bright and dark spots or repeating patterns (caused by low Rz and low Rsm, respectively).

[0086] Example 2

[0087] To further illustrate the effect of the Rz value of the colored film on the visibility of mottles, a laminate was produced according to laminate preparation procedure 1. The films used, with roughness parameters Rz and Rsm and color space parameters, are shown in Table 2. Film #7 was produced from film #6 according to laminate preparation procedure 2. The Rsm value of film #2 is not shown because the Rsm value under the measurement method used is meaningless when the Rz value is so low. Films #6, #8, and #9 were produced as described in the film preparation section.

[0088] Table 2. Films used for co-lamination and subsequent optical evaluation via photographic images.

[0089]

[0090] Figure 2 Photographs of a laminate produced according to laminate preparation procedure 1 are shown, where membrane A = membrane #6 and membrane B = membrane #8 (left image), and membrane A = membrane #7 and membrane B = membrane #8 (right image). The photographs were taken with an exposure time of 1 / 80 second. The images show a 5cm × 5cm portion, with a +10% change in brightness and a +90% change in contrast for the left image, and a +14% change in brightness and a +90% change in contrast for the right image, as described in the photographs of the laminate.

[0091] Figure 3 Photographs of the laminate produced according to laminate preparation procedure 1 are shown, where membrane A = membrane #6 and membrane B = membrane #9 (left image), and membrane A = membrane #7 and membrane B = membrane #9 (right image). The images show a 5cm × 5cm portion, with a +14% change in brightness and a +90% change in contrast for both images, as described in the photographs of the laminate.

[0092] Figure 2 and Figure 3 Both show a distinct wavy pattern of brighter and darker repeating stripes in the laminate using membrane #6 (left image, higher Rz) and the absence of this pattern in the laminate using membrane #7 (right image, lower Rz).

Claims

1. An interlayer for laminated glass comprising four or more layers each comprising a polyvinyl acetal and a plasticizer, the four or more layers being stacked on top of each other in the following order: - a colored layer comprising a polyvinyl acetal, a plasticizer and at least one colorant, - a first protective layer comprising a polyvinyl acetal and a plasticizer, - an acoustically damping layer comprising a polyvinyl acetal and a plasticizer, and - a second protective layer comprising a polyvinyl acetal and a plasticizer, wherein the colored layer has on at least one of its surfaces a roughness of a ten-point average roughness Rz measured according to DIN EN ISO 4287 of between 5 pm and 30 pm and an average width Rsm measured according to DIN EN ISO 4287 of between 10 pm and 1000 pm.

2. The interlayer according to claim 1, wherein the colored layer has on both of its surfaces a roughness of a ten-point average roughness Rz measured according to DIN EN ISO 4287 of between 5 pm and 30 pm and an average width Rsm measured according to DIN EN ISO 4287 of between 10 pm and 1000 pm.

3. The interlayer according to claim 1 or 2, wherein Rz is between 10 pm and 20 pm.

4. The interlayer according to any one of the preceding claims, wherein Rsm is between 700 pm and 900 pm.

5. The interlayer according to any one of the preceding claims, wherein the polyvinyl acetal in the colored layer comprises at least 75 wt% of a recycled polyvinyl acetal.

6. The interlayer according to any one of the preceding claims, wherein the polyvinyl acetal in each of the four or more layers comprises at least 75 wt% of a recycled polyvinyl acetal.

7. The interlayer according to any one of the preceding claims, wherein the colored layer covers the entire surface area of the interlayer.

8. The interlayer according to any one of the preceding claims, wherein the thickness of the colored layer is between 150 pm and 500 pm.

9. The interlayer according to any one of the preceding claims, wherein the total thickness of the first protective layer and the second protective layer together with the acoustically damping layer is between 450 pm and 750 pm.

10. The interlayer according to any one of the preceding claims, wherein the colorant is at least one dye and / or pigment.

11. The interlayer according to any one of the preceding claims, wherein the colorant is added to the colored layer during extrusion in an amount to provide a predetermined shade of gray in the final stack.

12. The interlayer according to any one of the preceding claims, wherein the polyvinyl acetal is polyvinyl butyral.

13. A stack comprising the interlayer according to any one of claims 1 to 12 interposed between two sheets of glass.

14. Use of the stack according to claim 11 as a side window, sunroof and / or rear window of a vehicle.

15. A method of producing the interlayer according to claim 12, comprising the steps of: - providing at least part of a polyvinyl acetal for a colored layer by shredding a pre-extruded polyvinyl acetal film, - extruding the shredded polyvinyl acetal from the previous step together with a polyvinyl acetal masterbatch comprising a colorant to form the colored layer, - providing a stack of layers comprising in sequence the colored layer, a first protective layer, an acoustically damping layer, and a second protective layer, and - laminating the intermediate layer thus formed between two pieces of glass.

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