HK1213846B - Composite system with high impact strength and a high softening point - Google Patents

Description

Composite system with high impact resistance and heat distortion resistance

Technical Field

The present invention relates to composite systems, preferably multilayer films, having high impact resistance and heat distortion resistance, to a process for their preparation and to their use.

Background

Composite systems, preferably multilayer films, are used in display front panels, mobile displays, for example in portable telephones, smart phones and input terminals, and in display panels. Furthermore, composite systems, preferably multilayer films, are used as automotive glazing, automotive bodies, in games and carports.

Various embodiments of composite systems formed from various polymer types are known. Important requirements here are good impact resistance, high optical transparency and good surface hardness. Furthermore, there should be a high scratch resistance. In the case of the use of composite systems, preferably multilayer films, low warpage of the multilayer film at high temperatures and high air humidity is also an important property.

When the composite system or multilayer film is used as a front panel in a display, the composite system or multilayer film is positioned in front of an actual display unit, such as an OLED (organic light emitting diode) or LCD panel (liquid crystal display). The composite system or multilayer film should be laid flat on the display units. Deformation of the composite system or multilayer film by environmental influences is therefore undesirable, since pressure is subsequently applied to the underlying LCD cell, which results in a strong color structure.

Deformation or warpage of the composite system or multilayer film during use can be attributed to, inter alia, excessively high operating or ambient temperatures.

In order to increase the impact resistance of the composite material/film, one layer of the composite material/film may for example consist of Polycarbonate (PC). The polycarbonate layer or film has high impact resistance and high heat distortion resistance. However, polycarbonate has the disadvantage of its low surface hardness and scratch resistance. To improve scratch resistance and surface hardness, PC may be laminated with polymethyl methacrylate (PMMA).

Polymethyl methacrylate (PMMA), which generally has a higher surface hardness than polycarbonate and is known to have a very good weathering stability, can also be used as a protection for polycarbonate.

By laminating PC with polymethyl methacrylate, the resulting multilayer film or composite has high impact resistance and high surface hardness on the PMMA side. However, PMMA is often much less resistant to thermal deformation than PC, causing warping of the film/composite at higher temperatures.

It is known in the art to counteract this warpage by increasing the heat distortion resistance of the PMMA layer, for example JP 2009196125 a.

For example, JP 2009196125a describes a multilayer film composed of a polymethacrylate copolymer layer and a polycarbonate layer for display use. In order to increase the heat distortion resistance of polymethacrylates, specific polymethacrylate copolymers are described. The polymethacrylate copolymer is a copolymer of (meth) acrylate and a cyclic vinyl monomer. In the examples of JP 2009196125A vinylcyclohexane is mentioned.

The preparation of polymethacrylates as described in JP 2009196125A is also known to be very complicated, since the claimed cyclic vinyl monomers do not polymerize well free-radically with other (meth) acrylates.

The free-radical copolymerization of free-radically polymerizable monomers, such as (meth) acrylates, is a simple, known and inexpensive process for preparing, for example, polymethacrylates.

EP 1680276B 1 describes multilayer films composed of polycarbonate and polymethacrylates with cyclohexyl methacrylate as comonomer in the polymethacrylate. Due to the cyclic ester group, the cyclohexyl methacrylate-containing polymethacrylates have better compatibility with PC than standard PMMA. However, cyclohexyl methacrylate does not significantly improve the heat distortion resistance of polymethacrylates.

Furthermore, it is known from DE 4440219A 1 that copolymers obtained by copolymerization of methyl methacrylate and styrene and maleic anhydride improve the heat distortion resistance. The methyl methacrylate-styrene-maleic anhydride copolymers known from DE 4440219 a1, although exhibiting a high resistance to thermal deformation, achieve a high warpage in the case of lamination to PC.

Disclosure of Invention

Problem and solution

In view of the prior art cited and discussed herein, the problem addressed by the present invention was therefore to develop a composite system, preferably a multilayer film, which can be easily produced, exhibits good impact resistance and lower warpage at higher temperatures than multilayer films formed from polycarbonate and standard PMMA known in the prior art, but at the same time achieves high heat distortion resistance as known from DE 4440219 a 1.

A further problem is to provide a composite system or multilayer film according to the above requirements which likewise has good adhesion, i.e. between the individual layers, within the composite system or multilayer film.

Another problem is to construct the composite system or multilayer film such that the outer sides or layers of the composite system or multilayer film can each be coated with a functional coating.

These objects and others which may be inferred or derived from the context discussed herein, although not explicitly mentioned, are surprisingly solved by a composite system comprising:

a) a polymer blend layer comprising or consisting of A) and B)

A) (meth) acrylate (co) polymer or mixture of (meth) acrylate (co) polymers

B) Styrene-maleic anhydride (co) polymer,

wherein the proportion of maleic anhydride recurring units in the styrene-maleic anhydride (co) polymer B) is from 10 to 30% by weight, preferably from 15 to 28% by weight, more preferably from 20 to 26% by weight, based in each case on the total weight of the styrene-maleic anhydride (co) polymer B), and

wherein the proportion of maleic anhydride recurring units in the polymer blend layer a) is from 1 to 27% by weight, preferably from 1.5 to 25% by weight, more preferably from 2 to 23% by weight, based in each case on the total weight of the polymer blend layer a), and

wherein the styrene-maleic anhydride (co) polymer B) is made from a monomer mixture comprising styrene, maleic anhydride and from 0 to 50% by weight, based on the total weight of maleic anhydride in the styrene-maleic anhydride (co) polymer B), of a vinyl monomer copolymerizable with styrene and/or maleic anhydride,

-b) optionally one or more adhesive layers, glass layers and/or optical films, preferably one or more adhesive layers, more preferably at least one adhesive layer of an Optically Clear Adhesive (OCA) or a Pressure Sensitive Adhesive (PSA), and

-c) a glass or plastic layer, preferably a plastic layer, more preferably a polycarbonate layer,

wherein a) and c) are bonded to each other or the one or more layers b) bond two layers a) and c) to each other.

The monomer mixture used for the preparation of the styrene-maleic anhydride (co) polymer B) may contain further constituents, for example additives, in addition to styrene, maleic anhydride and from 0 to 50% by weight, based on the total weight of maleic anhydride in the styrene-maleic anhydride (co) polymer B), of vinyl monomers copolymerizable with styrene and/or maleic anhydride.

For a particular embodiment of the invention, the monomer mixture used for the preparation of the styrene-maleic anhydride (co) polymer B) consists of styrene, maleic anhydride and from 0 to 50% by weight, based on the total weight of maleic anhydride in the styrene-maleic anhydride (co) polymer B), of a vinyl monomer copolymerizable with styrene and/or maleic anhydride.

It has surprisingly been found that by preparing a blend from a (meth) acrylate (co) polymer or a mixture of (meth) acrylate (co) polymers a) and a styrene-maleic anhydride (co) polymer B) and subsequently applying, preferably laminating, onto a glass or plastic layer, preferably a polycarbonate layer, according to the above details, firstly the heat distortion resistance of PMMA is increased to a comparable extent to a copolymer made from Methyl Methacrylate (MMA) and maleic anhydride and styrene, and secondly the requirement for good compatibility with the plastic or glass layer, preferably polycarbonate layer is met, and also a lower warpage of the composite, preferably laminate, is achieved than is known and predictable from the prior art using known composite systems or laminates.

(meth) acrylate (co) polymers or mixtures of (meth) acrylate (co) polymers A) ═ polymers A)

The polymers described under A) are generally obtained by free-radical polymerization of mixtures comprising methyl methacrylate. In general, these mixtures comprise at least 30% by weight, preferably at least 50% by weight, more preferably at least 80% by weight, more preferably at least 90% by weight, very particularly preferably at least 95% by weight, based on the weight of the monomers, of methyl methacrylate. Polymers consisting essentially of polymethyl methacrylate exhibit particularly high quality.

Furthermore, these mixtures for obtaining the polymers A) may comprise further (meth) acrylates copolymerizable with methyl methacrylate. The term "(meth) acrylate" encompasses methacrylates and acrylates and mixtures of the two.

According to the invention, the composition to be polymerized may comprise, in addition to the above-mentioned (meth) acrylic esters, further unsaturated monomers copolymerizable with methyl methacrylate and the above-mentioned (meth) acrylic esters. These include, in particular, alkyl (meth) acrylates, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl (meth) acrylate, norbornyl (meth) acrylate, styrene, substituted styrenes, vinylcyclohexane, vinyl acetate, (meth) acrylic acid, glutaric anhydride, maleic anhydride, n-isopropyl (meth) acrylamide, (meth) acrylamide and acrylonitrile. Preferably, in the mixture used to obtain polymer a), the comonomers (meth) acrylic acid, glutaric anhydride, maleic anhydride, n-isopropyl (meth) acrylamide, (meth) acrylamide and acrylonitrile are present, among other monomers described above, only in a total weight proportion of up to 8% by weight, based on the weight proportion of the styrene-maleic anhydride (co) polymer B) in the polymer blend layer a). The vinylcyclohexane repeating units in the polymers A) can also be obtained by hydrogenating the benzene ring of the methyl methacrylate-styrene copolymers, since vinylcyclohexane is only poorly free-radically copolymerized with methyl methacrylate. All monomers listed are preferably used in high purity.

Furthermore, the polymer A) may be a blend of various polymers of type A).

Weight average molecular weight M of Polymer A)_wPreferably 50000 to 500000g/mol, more preferably 60000 to 300000g/mol, particularly preferably 80000 to 200000 g/mol, without thereby being intended to be limiting.

Styrene-maleic anhydride (co) polymer B) ═ polymer B)

The composite systems of the invention are preferably characterized in that the styrene-maleic anhydride (co) polymers B) have a proportion of styrene repeating units of from 55 to 90% by weight, preferably from 58 to 85% by weight, more preferably from 61 to 80% by weight, based in each case on the total weight of the styrene-maleic anhydride (co) polymers B).

If the styrene-maleic anhydride (co) polymer B) in the composite system of the invention is prepared from a monomer mixture comprising up to 50% by weight, based on the total weight of maleic anhydride in the styrene-maleic anhydride (co) polymer B), of vinyl monomers copolymerizable with styrene and/or maleic anhydride, these vinyl monomers are preferably selected from the group consisting of methyl (meth) acrylate, alkyl (meth) acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl (meth) acrylate, norbornyl (meth) acrylate, vinylcyclohexane.

The weight-average molecular weight M of the styrene-maleic anhydride (co) polymers B) used according to the invention_wCan vary over a wide range, with the molecular weight generally being matched to the end use and processing method. However, in general, it is at 40000 and 500000g/mol, preferably 50000 to 300000g/mol, more preferably 70000 to 150000 g/mol, without thereby being intended to be limiting.

In a preferred embodiment of the composite system of the invention, the styrene-maleic anhydride (co) polymer B) has at least M_wAverage molecular weight 70000 g/mol.

The styrene-maleic anhydride (co) polymers B) of the invention are preferably prepared by the process explained below in the description of the examples according to the invention.

Polymer blend layer a)

The polymer blends a) used for producing the composite systems produced according to the invention are preferably polymer mixtures of (meth) acrylate (co) polymers or mixtures a of (meth) acrylate (co) polymers (═ polymer a)) and styrene-maleic anhydride (co) polymers B) (═ polymer B)), the thermoplastic main component of the (meth) acrylate (co) polymers or mixtures a of (meth) acrylate (co) polymers (═ polymer a)) being composed of at least 30% by weight, preferably at least 50% by weight, of methyl methacrylate repeat units. More preferably, the thermoplastic main component of the (meth) acrylate (co) polymer or of the mixture a of (meth) acrylate (co) polymers) (═ polymer a)) consists of at least 80% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, of methyl methacrylate repeat units.

The preferred polymer blend layer a) is in some cases also referred to as "modified PMMA of the present invention" in the present invention.

In a preferred composite system according to the invention, the composition constituting the polymer blend layer a) has a vicat softening temperature VET (ISO 306-B50) of at least 110 ℃, preferably at least 112 ℃, more preferably at least 115 ℃.

Another embodiment of the invention of the composite system is characterized in that the polymer blend layer a) has a thickness of 10 to 2000 micrometers, preferably 20 to 1500 micrometers, more preferably 30 to 1000 micrometers, more preferably 40 to 500 micrometers, very particularly preferably 50 to 300 micrometers.

Another embodiment of the present invention is a composite system, preferably according to one of the above preferred embodiments, wherein the polymer blend layer a) comprises customary additives or additives. These include, inter alia, UV stabilizers, UV absorbers, lubricants, antistatics, flame retardants, additives for increasing the scratch resistance, antioxidants, light stabilizers, organophosphorus compounds, weathering stabilizers and/or plasticizers.

It is also preferred that these additives or additives present in the polymer blend layer a) of the composite system of the invention are each present in a proportion of from 0.001 to 5% by weight, preferably in a proportion of from 0.001 to 1% by weight, more preferably in a proportion of from 0.002 to 0.5% by weight, in particular preferably in a proportion of from 0.005 to 0.2% by weight, based in each case on the total weight of the polymer blend layer a). The amount of additive or additives should be determined according to the end use. Preferably, the polymer blend layer a) of the composite system of the present invention comprises a total of up to 5 wt. -%, preferably up to 2 wt. -%, based on the total weight of the polymer blend layer a), of additives.

The UV stabilizers are preferably sterically hindered amines (hindered amine light stabilizers; HALS) and methyl salicylate.

The UV absorber is preferably a sterically hindered phenol, especially a benzotriazole, for example a hydroxyphenylbenzotriazole and/or a triazine. However, substituted benzophenones, salicylates, cinnamates, oxanilides, benzophenones, may also be usedA ketone or a benzylidene malonate.

Preferred lubricants are fatty acids, fatty acid esters or fatty alcohols, such as stearic acid, palmitic acid, stearyl alcohol, cetyl alcohol and technical mixtures thereof.

Preferred antistatic agents are, for example, laurylamine ethoxylate and glycerol monostearate.

Additives for improving the scratch resistance are, for example, polyorganosiloxanes.

In the composite systems particularly preferred according to the invention, a weight ratio of (meth) acrylate (co) polymer or mixture a of (meth) acrylate (co) polymers) (═ polymer a)) to styrene-maleic anhydride (co) polymer B) (═ polymer B) of from 10:90 to 90:10, preferably from 15:85 to 85:15, more preferably from 20:80 to 80:20, very preferably from 70:30 to 30:70 is present.

The polymer blend layer a) of the composite system of the invention may optionally be impact-modified. Suitable impact modifiers which can be used in the present invention are, for example, rubber particles containing crosslinked butadiene and/or styrene and/or crosslinked longer chain alkyl (meth) acrylates. However, it may also be preferred in the context of the present invention that neither the polymer blend layer a) nor all the other constituents of the composite system of the present invention comprise any impact modifier. Impact modifiers may interfere with optical performance in one of the preferred uses of the composite systems of the present invention, for example as plastic glazing for displays.

Glass or plastic layer c)

It has been found to be advantageous in the present invention to use thermoplastics as layer c).

In a particularly preferred embodiment, the composite system according to the invention is characterized in that layer c) is a polycarbonate layer.

Preferably, according to the invention, the polycarbonate component used is obtained from Bayer Materials2607 (having an MVR of 12ml/10min (300 ℃/1.2kg according to ISO 1133) and a Vicat temperature B50 of 143 ℃ according to ISO 306). However, it is also conceivable that other polycarbonate types from Bayer Materials are used as polycarbonate layers. From Styron CorpOf Sabic corporationIdemitsu corporationOf Tejin Kasei CorpPolycarbonate of the type and other polycarbonates of other polycarbonate manufacturers are likewise possible as polycarbonate layers.

Particularly preferred embodiments of the composite system of the invention in which layer c) is a polycarbonate layer yield particularly good results in terms of warpage reducing properties and in providing impact-modified composites having a high resistance to thermal deformation in combination. It should be mentioned in particular here that the polycarbonate layer is generally comparatively soft and that good impact resistance in combination with good surface hardness is achieved only by the composite material. However, the combination of these properties is important for many desired applications, such as in display applications.

An especially preferred embodiment of the composite system of the invention is one in which the outer polycarbonate layer c) and/or the outer polymer blend layer a) is provided with a functional coating.

According to the invention, it is further preferred that the composite system, preferably according to one of the above embodiments, is characterized in that layer c), which is more preferably a polycarbonate layer, has a thickness of 20 to 3000 micrometers, preferably 50 to 2000 micrometers, more preferably 200 to 1500 micrometers, more preferably 300 to 1200 micrometers.

Composite material

More preferred in the present invention is that in the composite system of the invention, especially where layer c) is a polycarbonate layer, the polymer blend layer a) is applied to layer c), preferably by lamination.

Lamination can be achieved in the present invention by coextrusion, i.e. by joining the two layers a) and c), in the present invention preferably a layer comprising PMMA and a polycarbonate layer. However, the lamination is not limited to coextrusion. Other known methods for joining the two layers a) and c), preferably a layer comprising PMMA, and a polycarbonate layer are also suitable in the present invention.

It is preferred according to the invention that the composite system, preferably according to one of the above-described preferred embodiments, is a laminate, i.e. is present in the form of a laminate.

Furthermore, the composite system according to the invention is particularly preferably a multilayer film, i.e. in the form of a multilayer film.

The composite systems of the invention may preferably be characterized in that a) and/or c) have a functional coating, preferably a scratch-resistant coating, an antireflection coating and/or an antistatic coating, on one or both sides. According to the teaching of the invention, these coatings can either each be identical or can each be different from one another (for example a) and c) are embodiments in which the single-sided or double-sided coatings are scratch-resistant coatings, or a) and c) each have only one coating and these coatings are different from one another, for example one embodiment in which one is a scratch-resistant coating and one is an antistatic coating). All possible combinations resulting from the fact that a) and/or c) may have a functional coating on one or both sides according to the above list are included according to the invention.

Particularly preferred according to the invention are embodiments in which the composite system has at least one scratch-resistant coating in a) or c), more preferably in a) and c). It is particularly preferred in the present invention when a) and c) each have a scratch-resistant coating on their respective outer layer side (i.e. the side not facing the interior of the composite).

Scratch-resistant coatings in the form of thermally or UV-crosslinked coatings based on (meth) acrylates or silicones are preferably used according to the invention. These coatings may further comprise nanoparticles that improve scratch resistance, such as those based on silicon oxide. They often also contain silicate spheres to achieve an anti-glare effect. However, in the choice of the additional particles, it should be very important to note that these are so small that no light refraction occurs or that these particles have the same refractive index as the coating used. The coating is preferably applied as dip coating, spray coating, spin coating, or the like.

Optionally, the polymer blend layer a) and the glass or plastic layer c), each independently of the other, optionally functionally coated on one or both sides, are joined to each other via one or more adhesive layers, glass layers and/or optical films, preferably one or more adhesive layers, more preferably at least one adhesive layer of an Optically Clear Adhesive (OCA) or a Pressure Sensitive Adhesive (PSA).

Preferred composite systems according to the invention have haze values (according to ISO 13803) of < 10%, preferably < 5%.

As already explained above, the composite system of the present invention is preferably a multilayer film. It is furthermore particularly preferred that such a multilayer film is present in the form of a housing, preferably a display housing or touch screen or glazing, preferably an automotive glazing, or in the form of a part of a display, a housing (preferably a display housing) or a display front panel or touch screen or glazing, preferably an automotive glazing. "display" is understood in the present invention to mean a device for displaying information that is variable over time.

Thus, in addition to the composite system of the present invention, the present invention also provides a display comprising a composite system according to the present invention as described above, in particular according to one of the preferred embodiments.

In the present invention, such displays comprising the composite system of the present invention are more preferably LCD, OLED or electrophoretic displays.

In the displays of the invention, the polymer blend layer a) is preferably joined to the underlying layer c) by means of an Optically Clear Adhesive (OCA) or a Pressure Sensitive Adhesive (PSA). The selection of a suitable OCA or PSA is generally familiar to those skilled in the art herein. Such an adhesive layer improves the mechanical stability of the entire display and reduces the light reflection at the layer interfaces.

The invention also includes the use of a styrene-maleic anhydride (co) polymer for reducing warpage of a display, display housing, touch screen or glazing, preferably an automotive glazing,

wherein the proportion of maleic anhydride repeating units in the styrene-maleic anhydride (co) polymer is from 10 to 30% by weight, preferably from 15 to 28% by weight, more preferably from 20 to 26% by weight, based in each case on the total weight of the styrene-maleic anhydride (co) polymer,

and is

-wherein the styrene-maleic anhydride (co) polymer is made from a monomer mixture comprising styrene, maleic anhydride and 0 to 50 wt% of a vinyl monomer copolymerizable with styrene and/or maleic anhydride, based on the total weight of maleic anhydride in the styrene-maleic anhydride (co) polymer.

In the use according to the invention for reducing the warpage of a display, display housing, touch screen or glazing, preferably an automotive glazing, the display, display housing, touch screen or glazing, preferably an automotive glazing, comprises a plastic or glass layer, preferably a thermoplastic layer, more preferably a polycarbonate layer.

Another embodiment encompassed by the present invention relates to the use of the composite system according to the invention as described above as or in an optical display element.

Description of the drawings:

FIG. 1: after storage in a climate of 85 deg.c/85% relative humidity/72 h according to an embodiment of the invention,

FIG. 2: comparative example 1 after storage in a climate of 85 c/85% relative humidity/72 h,

FIG. 3: comparative example 2 was stored in a climate of 85 ℃/85% relative humidity/72 h.

The measuring method comprises the following steps:

average molecular weight M_w(weight average) and average molecular weight M_n(number average):

average molecular weight M_w(weight average) and average molecular weight M_n(number average) is determined in the present invention via size exclusion chromatography (GPC) under the following conditions:

column: PSS 5 SDV columns (Mainz)

Agilent 1100 series, UV Detector G1314A

Agilent 1100 series, RI detector G1362A

Column furnace T35 deg.C

Eluent tetrahydrofuran for Polymer A) and comparative example II

Tetrahydrofuran + 0.2% by volume of trifluoroacetic acid for Polymer B) and comparative example I

Flow rate 1ml/min

Injection volume 100. mu.l

Detecting RI, adjusting temperature to 35 deg.C

Concentration of sample solution 2g/l (at Mw)>10⁶In the case of (1.. 0.25g/l)

Standard PMMA (e.g. PSS (Mainz) Co.), for Polymer A) and

comparative examples I + II

Polystyrene (e.g. PSS (Mainz) Corp.) for Polymer B)

Concentration of the standard solution 1g/l (in Mw)>10⁶In case of 0.5g/l)

Internal standard o-dichlorobenzene → 1 drop/1.5 ml automatic sampling bottle

Warpage 85 ℃, 85% relative humidity, 72h (maximum curvature measured with a vernier caliper, 100X 100mm sample)

The warpage is measured in the present invention for a sample cut from the coextruded sheet to a size of 100X 100 mm. The approximately planar and flat samples after production were laid on a grid and stored for 72 hours in a climate-controlled cabinet at 85 ℃ and 85% relative humidity, with the polymer blend layer a) or the layer corresponding to the polymer blend layer a) according to the comparative experiments carried out being placed on top. After removal from the climatic chamber and complete cooling of the samples at 23 ℃ for 24 hours, the curvature of the highest point (distance of the highest point in mm from the flat bottom) is determined with a vernier caliper. To obtain a potent value, at least a double determination is performed.

MVR ISO 133 part 1; 230 ℃/3.8kg

Heat distortion resistance, Vicat temperature; ISO 306-B50

Transmittance ISO 13468

Haze ISO 13803

IR method for determining the proportion of maleic anhydride repeating units in a styrene-maleic anhydride (co) polymer:

IR measurement of a chloroform solution of 15 mg of a styrene-maleic anhydride (co) polymer in 1ml of chloroform.

The following examples are presented to further illustrate and better understand the present invention, but are not intended to limit the invention or its scope in any way.

Detailed Description

Examples

Preparation of Polymer blend a) (for Polymer blend layer a)) or of a comparative composition

Examples (invention)

The modified PMMA of the present invention (polymer blend for polymer blend layer a) is prepared from:

50.00% by weight of standard PMMA (corresponding to Polymer A)

50.00% by weight of a styrene-maleic anhydride (co) polymer (corresponding to Polymer B))

Standard PMMA (═ polymer a) consists of 96% methyl methacrylate and 4% methyl acrylate. This PMMA was prepared on the basis of DE 4440219A 1:

the reactants were weighed into polyester bags, polymerized in a water bath and then heat treated in a tempering furnace. Subsequently, the polymer is ground and devolatilized by means of an extruder.

Temperature profile for polymerization in water bath:

24h 60℃

temperature distribution in a tempering furnace:

at 110 ℃ for 6 hours

The resulting molecular weight of PMMA, determined by GPC method, is M_w＝149 000g/mol。

The PMMA has a Vicat softening temperature VET of 105 ℃ (ISO 306-B50).

The styrene-maleic anhydride (co) polymer (═ polymer B) was prepared by continuous polymerization of styrene and maleic anhydride with dibenzoyl peroxide in methyl ethyl ketone at 120 ℃ by means of an anchor stirrer in a continuously operated stirred tank reactor of 100 liters with good back-mixing. Backmixing stirred tanks of this type are known from the prior art (for example: Chemische Reaktiontechnik [ chemical reaction technology ], Georg Thieme Verlag 1987, pages 237 to 241).

The partially converted polymer slurry with styrene and maleic anhydride at the stirred tank reactor outlet was continuously degassed via a twin screw extruder with vent holes and then pelletized in a pelletizer, followed by analysis of the polymer composition of the product by IR spectroscopy. In the preparation of styrene-maleic anhydride (co) polymers, it was noted that the polymer content in the polymer slurry at the reactor outlet was about 28%, which means a total mass (Massen) conversion of about 40% of the styrene and maleic anhydride used.

Specifically, a mixture of 9.2kg/h methyl ethyl ketone, 2.3kg/h maleic anhydride and 18.8kg/h styrene was continuously fed into the reactor at 23 ℃. Dibenzoyl peroxide was additionally continuously fed into the reactor as a polymerization initiator. The necessary amount of flow of dibenzoyl peroxide was derived from the measured reactor temperature, which was maintained at a constant reactor temperature of 110 ℃ using a regulating system to vary the stroke length of a metering pump feeding dibenzoyl peroxide. In order to obtain a maleic anhydride repeating unit proportion of 23% by weight in the styrene-maleic anhydride (co) polymer, pellet samples were taken periodically and the composition was determined by means of IR spectroscopy. The maleic anhydride proportion in the feed mixture was slightly varied based on IR analysis to obtain a maleic anhydride repeating unit proportion of 23 wt% in the styrene-maleic anhydride (co) polymer.

IR spectroscopic analysis of the styrene-maleic anhydride (co) polymer used for preparing the polymer blend layer a) gave a proportion of maleic anhydride repeating units of 23% by weight and a proportion of styrene repeating units of 77% by weight in the styrene-maleic anhydride (co) polymer and M determined by means of GPC_w86500 g/mol and M_n48000 g/mol of the molecular weight of the styrene-maleic anhydride (co) polymer. The Vicat softening temperature VET (ISO 306-B50) of the styrene-maleic anhydride (co) polymer was 146 ℃.

The ingredients (polymer a and polymer B) were mixed with each other in a twin-screw extruder to prepare polymer blend a).

The measured proportion of maleic anhydride repeating units in the polymer blend a) was 11.5% by weight, based on the total weight of the polymer blend a).

The polymer blend a) has a Vicat softening temperature VET (ISO 306-B50) of 123 ℃. Comparative example 1

Copolymers of methyl methacrylate, styrene and maleic anhydride are chosen as modified PMMA having a higher resistance to thermal deformation than standard PMMA. This copolymer was prepared according to DE 4440219 a 1:

the reactants were weighed into polyester bags, polymerized in a water bath and then heat treated in a tempering furnace. Subsequently, the polymer is ground and devolatilized by means of an extruder.

Temperature profile for polymerization in water bath:

12h 52℃

16h 44℃

temperature distribution in a tempering furnace:

at 110 ℃ for 6 hours

The resulting molecular weight of the modified PMMA, as measured by GPC, is M_w＝145 000g/mol。

The modified PMMA has a Vicat softening temperature VET (ISO 306-B50) of 122 ℃. Comparative example 2

For further comparison, a standard PMMA was chosen which consisted of 99% methyl methacrylate and 1% methyl acrylate. This PMMA has high heat distortion resistance. The copolymer was prepared according to DE 4440219 a 1:

the reactants were weighed into polyester bags, polymerized in a water bath and then heat treated in a tempering furnace. Subsequently, the polymer is ground and devolatilized by means of an extruder.

Temperature profile for polymerization in water bath:

24h 60℃

temperature distribution in a tempering furnace:

at 110 ℃ for 6 hours

The resulting molecular weight of the standard PMMA, determined by GPC, is M_w＝152 000g/mol。

The standard PMMA has a Vicat softening temperature VET of 109 ℃ (ISO 306-B50).

Preparation of composite materials

Polymer blend a) (examples according to the invention) or modified PMMA (comparative example 1) or standard PMMA with high heat distortion resistance (comparative example 2) was laminated on one side via the die of a co-extruder2607 (polycarbonate layer, corresponding to layer c)). The lamination step was carried out by coextrusion through an adapter die. The polycarbonate layer was 900 microns thick, while the polymer blend layer a) (according to the examples of the invention) or modified PMMA (comparative example 1) or standard PMMA with high heat distortion resistance (comparative example 2) was 120 microns thick.

Parameters of the coextrusion experiments (except for the mentioned variations, the conditions remain the same in all examples):

extruder manufacturer:

main extruder, twin-screw extruder Breyer (Singen)

Coextruder, single screw extruder Stork (R) ((R))-Walldorf)

Screw diameter:

60mm main extruder

Co-extruder 35mm

Screw revolution:

main extruder 47rpm

A co-extruder:

according to an embodiment of the invention, 82rpm

Comparative example 1:70rpm

Comparative example 2:55rpm

Polymer throughput:

60kg/h main extruder

Coextrusion machine 7.2kg/h

Discharge speed of sheet 1.9m/min

Vacuum 200 mbar +/-20 mbar in devolatilization in the two extruders

Temperature (kept the same in all examples):

barrel temperature:

	main extruder (polycarbonate)	Co-extruder (PMMA)
			Heating zone 1	225	200
Heating zone 2	280	250
			Heating zone 3	260	265
Heating zone 4	259	265
			Heating zone 5	260	275
Heating zone 6	260	275
			Heating zone 7	262	275
Heating zone 8	260	275
			Heating zone 9	265	---

Die temperature:

as a result:

the results of the examples according to the invention and of the comparative examples are compiled in the table below. A significantly lower warpage of only 1.1 mm can be seen for the composites of the present invention relative to 3.8 or 3.7 mm in the comparative examples (fig. 1-3; where fig. 1 is after storage at 85 ℃/85% relative humidity/72 h climate for the examples according to the present invention, fig. 2 is after storage at 85 ℃/85% relative humidity/72 h climate for comparative example 1, and fig. 3 is after storage at 85 ℃/85% relative humidity/72 h climate for comparative example 2). More particularly, comparative example 1 also shows that the resulting methyl methacrylate-styrene-maleic anhydride copolymer, although having a higher heat distortion resistance than standard PMMA which itself already has a high heat distortion resistance, cannot solve the problem of low warpage of the laminate using this copolymer.

The results further show that the values of the transmission and haze of the composite system according to the invention or of the multilayer film according to the invention are not negatively influenced within the measurement accuracy compared to the values of comparative examples 1 and 2 associated therewith.

TABLE 1 Property profiles of Polymer blend a) and corresponding comparative example compositions

TABLE 2 Properties of composite System/multilayer film

Claims (22)

1. A composite system in the form of a laminate comprising:

a) a polymer blend layer comprising or consisting of A) and B)

A) (meth) acrylate polymers or mixtures of (meth) acrylate polymers,

B) a styrene-maleic anhydride polymer,

wherein the proportion of maleic anhydride repeating units in the styrene-maleic anhydride polymer B) is from 10 to 30% by weight, based on the total weight of the styrene-maleic anhydride polymer B), and

wherein the proportion of maleic anhydride recurring units in the polymer blend layer a) is from 1 to 27% by weight, based on the total weight of the polymer blend layer a), and

wherein the styrene-maleic anhydride polymer B) is made from a monomer mixture comprising styrene, maleic anhydride and 0 to 50 wt% of alkyl (meth) acrylate based on the total weight of maleic anhydride in the styrene-maleic anhydride polymer B);

-b) optionally one or more adhesive layers, glass layers and/or optical films, and

-c) a glass or plastic layer,

wherein a) and c) are bonded to each other or the one or more layers b) bond two layers a) and c) to each other.

2. A composite system as set forth in claim 1 wherein said composite system comprises one or more of said adhesive layers.

3. A composite system as set forth in claim 1 wherein said composite system comprises said plastic layer.

4. A composite system as set forth in claim 1 wherein a) is composed of methyl methacrylate repeat units to an extent of at least 30 percent by weight based on a total weight of a).

5. A composite system as claimed in any of claims 1 to 4, characterized in that the composition to be polymerized for preparing A) comprises one or more of the following monomers copolymerizable with methyl methacrylate and/or (meth) acrylates: alkyl (meth) acrylates, (meth) acrylic acid, glutaric anhydride, styrene, maleic anhydride, n-isopropyl (meth) acrylamide, vinylcyclohexane, acrylonitrile, vinyl acetate, and substituted styrenes.

6. A composite system as claimed in any of claims 1 to 4, characterized in that the composition to be polymerized for preparing A) comprises one or more of the following monomers copolymerizable with methyl methacrylate and/or (meth) acrylates: methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl (meth) acrylate and norbornyl (meth) acrylate.

7. Composite system according to any of claims 1 to 4, characterized in that the styrene-maleic anhydride polymer B) has a proportion of styrene repeating units of from 55 to 90% by weight, based on the total weight of the styrene-maleic anhydride polymer B).

8. Composite system according to any of claims 1 to 4, characterised in that A) has at least M_wAn average molecular weight of 50000 g/mol and/or B) has at least M_wAverage molecular weight 40000 g/mol.

9. A composite system as claimed in any one of claims 1 to 4, characterized in that the composition constituting the polymer blend layer a) has a Vicat softening temperature VET of at least 110 ℃.

10. A composite system as claimed in any of claims 1 to 4, characterized in that the polymer blend layer a) comprises UV stabilizers, UV absorbers, lubricants, antistatics, flame retardants, additives for increasing the scratch resistance, antioxidants, light stabilizers, organic phosphorus compounds, weathering stabilizers and/or plasticizers, each in a proportion of from 0.001 to 5% by weight, in each case based on the total weight of the polymer blend layer a).

11. Composite system according to any one of claims 1 to 4, characterized in that the weight ratio of A) to B) is from 10:90 to 90: 10.

12. A composite system as claimed in any one of claims 1 to 4, characterized in that the glass or plastic layer c) is a polycarbonate layer.

13. Composite system as claimed in any of claims 1 to 4, characterized in that the glass or plastic layer c) has a thickness of 20 to 3000 μm

And/or

The polymer blend layer a) has a thickness of 10 to 2000 microns.

14. A composite system as claimed in any one of claims 1 to 4, characterized in that the polymer blend layer a) is applied to a glass or plastic layer c).

15. A composite system as claimed in claim 14, characterized in that the polymer blend layer a) is applied to the glass or plastic layer c) by lamination.

16. A composite system as claimed in any one of claims 1 to 4, characterized in that the polymer blend layer a) and/or the glass or plastic layer c) have a functional coating on one or both sides.

17. A composite system as claimed in claim 16, characterized in that the polymer blend layer a) and/or the glass or plastic layer c) have a scratch-resistant coating, an antireflection coating and/or an antistatic coating on one or both sides.

18. Composite system according to claim 16, characterized in that the scratch-resistant coating is a thermally or UV-crosslinked coating based on (meth) acrylates or silicones.

19. Composite system as claimed in any of claims 1 to 4, characterized in that it is a multilayer film in the form of a housing or glazing or in the form of a part of a display, housing, touch screen or glazing.

20. Display, characterized in that the display comprises a composite system as claimed in at least one of claims 1 to 19.

21. Use of a styrene-maleic anhydride polymer for reducing warpage of a display, display housing, touch screen or glazing,

wherein the proportion of maleic anhydride repeating units in the styrene-maleic anhydride polymer B) is from 10 to 30% by weight, based on the total weight of the styrene-maleic anhydride polymer B),

and is

Wherein the styrene-maleic anhydride polymer B) is made from a monomer mixture comprising styrene, maleic anhydride and 0 to 50 wt% of an alkyl (meth) acrylate based on the total weight of maleic anhydride in the styrene-maleic anhydride polymer.

22. Use of a composite system as claimed in any one of claims 1 to 19 as or in an optical display element.