HK1008881B - Transparent glass laminate - Google Patents

Description

Field of invention

The invention relates to a transparent composite system of polymethyl methacrylate (PMMA) discs with an intermediate layer of an acrylate-based elastomeric resin between two PMMA discs to be joined.

State of the art

Polymethyl methacrylate and its copolymers are known to have a high degree of the desired properties for glazing materials, in particular high transparency and relative weather resistance and, compared to silicate glass, a lower weight.

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For example, DE-A 29 14 223 recommends a clear synthetic resin bonding board consisting of a clear plastic base sheet of at least 1 mm thickness with parallel surfaces, at least one clear plastic film with a scratch resistance not lower than that of the base sheet and at least one clear adhesive resin layer placed between the base sheet and the plastic film, which adheres to the film insolubly and is detachable from the base sheet.

JP-A 61 132 343 (Chem. abstract 105, 154387e) is known as an acrylic glass laminate consisting of two hard plastic outer discs and an intermediate layer of soft plastic with an electrically conductive layer on or near the surface.

DE-A 31 28 985 provides for laminated thermoplastic articles, which are obtained by attaching at least one PMMA film with at least one impact-resistant methacrylate polymer to the calender.

EP 419 166 describes coextruded multi-layer pathways with a complex configuration of individual layers of allyl methacrylate, each 0.3-6 mm thick. The first outer layer is to be composed of a blend of polyvinylidene fluoride with Mn < 250 000, 30-60% by weight of C1-C8 alkyl methacrylate with Mn ≤ 150 000 and possibly 10-30% by weight of a Pfropfelastomer of C1-C8 alkyl methacrylate grafted and interlaced with allyl methacrylate, and at least a second layer of an alkyl methacrylate homopolymer or -C polymer. The coextrusion is to be carried out via a multi-layer extrusion process. The first two layers are to be composed of polymers composed of various polymers of different types of glass.

Task and solution

The problem of remedying the abovementioned disadvantages of polymethyl methacrylate as a material, particularly in the field of glazing technology, while maintaining its advantageous properties, particularly its optical properties, was further examined: it was now found that a transparent sheet composite system consisting of (a) two sheets of glass at least 2 mm thick, preferably with transparent acrylic glass outer sheets S and S' with parallel surfaces, and (b) an intermediate layer containing a thermoplastic, which is a workable elastomer, satisfies the technical requirements very well.The thickness of the acrylic panels S and S' can be any thickness, but from a practical point of view they will rarely exceed 50 mm, preferably 30 mm. The layer thickness of the intermediate layer Z is also mainly limited from a practical point of view. It is generally in the range of 0.05 to 5 mm, preferably 0.1 to 3 mm. The other dimensions of the transparent glass-interconnect system are also mainly based on practical considerations. The S/S' panels are produced in dimensions up to 10 m.However, it may be advantageous to assume predetermined dimensions for certain applications. The acrylic glass panes S and S' are preferably made of commercial PMMA or of known transparent copolymers of methyl methacrylate, which may be modified according to their properties, e.g. cross-linked, equipped with known stabilizers or other additives, e.g. flame retardant or antistatic. The acrylic glass panes may also be coloured in a known way. They may also be coated, usually on exposed surfaces, with a scratch-resistant coating (see Ullmann's Encyclopedia of Industrial Chemistry 5th Ed., Vol. A20, 459 - 507, VCH 1992). For the acrylic glass pane S or S' comes so-called cast material,The use of a polymer is not recommended for the production of polymers, but for the production of polymers. The intermediate layer Z consists wholly or partly of elastomer E. The elastomers E are 60 to 100% by weight of polymers of CP from 50 to 5% by weight of polymethyl methacrylate macronomers of formula I and 50 to 95% by weight of alkylacrylate of formula II. Such polymers are described, for example, in DE-A 39 02 653 or DE-A 41 21 811 or US-A 5 028 677.

For example, the KP comb polymers can be produced from the macronomers of formula I where R is a radically polymerizable end group and n is measured to be in the range of 500-100 000 Daltons by copolymerization with at least one alkylacrylate monomer of formula II. R is preferably a group of formula III after DE-A 39 02 653 wherein R1 for hydrogen, methyl and wherein Q for a bifunctional residue selected from the group where R2 is hydrogen or an alkyl residue with 1 to 24 carbon atoms,preferably 1 to 6 carbon atoms, means and X is an alkyl residue with 2 to 24 carbon atoms, preferably an alkyl residue containing at least one oxygen, sulphur or nitrogen atom, preferably next to the polymer chain. Alternatively, R may also be the group of formula IV after US-A 5 028 677 where R3 stands for an alkyl residue with preferably methyl. Particular preference shall be given to groups X selected from the formulae -CH2CH2-S-; in formula III. The alkylacrylate monomers in the comb polymers KP correspond to formula II where R4 stands for C2-C20 alkyl, especially for ethyl, butyl, iso-butyl, 2-ethylhexyl and particularly preferably for butyl. The molecular weight of the KP comb polymers is in the range of 50 000 to 2 000 000The maximum level of protection is 100 000 to 800 000 Daltons. The determination of the molecular weights Mw is performed by SEC (Size Exclusion Chromatography; see H.F. Mark et al. Encyclopedia of Polymer Science and Engineering, 2nd Ed. Vol. 10, pp. 1 - 19, J. Wiley & Sons 1967).

In so far as elastomers E contain, in addition to the combustion polymers KP, a further polymer component in proportions of 0-40% by weight, they are, on the one hand, unrecycled residual macronomers of formula I and, on the other hand, I-derived polymethyl methacrylate, which does not have a vinyl group, and is therefore not a macronomer. This polymer component can be present on a technical scale as a by-product of macromonomer synthesis, for example in proportions of 0.1 to 40%, in particular 0.5 to 20% by weight, and is thus represented in elastomer E with these proportions.

A preferred method for the production of KP comb polymers is the radical initiated polymerization of the macronomers of formula I with the alkylacrylates of formula II, preferably in a weight ratio of 20-50 to 80-50. Polymerization is carried out as substance polymerization or preferably as solution polymerization, e.g. in an ester such as butylacetate or in toluene and under an inert protective gas such as argon in a reactor equipped with a protective gas inlet and a stirring resistance measuring device, using radical initiators such as a per compound such as a perester, e.g. tert-butyl perneodecanoate in amounts of 0,005 to 0,5% by weight, in particular about 0,1% by weight.For example, dissolved in an aliphatic solvent or in the monomers themselves. Initially, something can be heated, say to about 50°C, then a portion of the dissolved initiator is added and after a few hours, say 3 1/2 hours, another initiator is added. The reaction is continued for a few hours, for example for a total of 12 hours, and a stabilizer, for example a flame retardant from the HALS class, such as a phosphorus based product in the usual quantities (see Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. Vol. A20 loc.cit.), can be added to the reaction.The polymer has the characteristics of an elastomer and the advanced techniques are used to produce the macronomers of formula I.

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The transparent interconnected system

The transparent discs can be produced by various methods, for example by pressing the PMMA discs S and S' between which a layer of elastomer E is placed. The quantity of elastomer is usually measured to give a thickness of the intermediate layer Z of 0.05 to 5 mm. The pressing may be carried out by means of a suitable pressing device, e.g. a hydraulic press, usually initiated by heating, e.g. at 180°C. The heating time is preferably in the range of over one hour, e.g. 75 minutes.

Subject to the rheological conditions - alignment of the rheology of the elastomer E and the PMMA form mass - the disc-joint system of the invention can also be produced by extrusion.

The composite panels obtained according to the invention can be processed in the same way as PMMA, in particular by sawing and, if appropriate parameters are met, also by thermal processing.

Beneficial features

The transparent glass-joint systems of the invention fully meet the requirements for transparent glazing. They can be used in a familiar way, e.g. in brackets, frames, etc. From the safety point of view, they represent a considerable advance compared with the state of the art. Such joints can be shattered by a blow or a shock with sufficient force, but the fragments are not shattered. The resulting fragments remain attached to the intermediate layer Z. Therefore, the glass composite systems of the invention can be used, in part, with advantage as safety glazing with a surface equipped with scratch resistance, e.g. in buildings and parts of buildings as windows, shop windows, doors, room dividers, display cases, railing glazing, switchgear and in furniture, in all types of vehicles, cranes, windows, instrument glazing, etc., in industry as safety covers, in glazing, optical applications, etc. The application is particularly interesting for glazing in public areas, in particular where there is a risk of damage from traffic or noise, e.g. in swimming pools, heating towers, telephone towers, as a ventilation system, as a radiator.

The following examples illustrate the invention: The viscosity J (ml/g) is determined according to ISO 1628-6.

The Commission A. Manufacture of elastomers E A-1:

In a stirring reactor with a protective gas inlet, coolant and stirring resistance measurement are performed under argon. 96 g macronomer of formula I-A (example A-2) 224 g butylacrylate 480 g butylacetate and heated to 51 °C. After about 3 1/2 hours, a further 0.2 g of initiator is added. The temperature in the reactor is kept below 60°C by cooling. After a total of 8 hours of polymerization, the polymerization is completed by adding 0.1 g of TINUVIN R 770 to 500 g of butylacetate and the polymer is isolated by precipitation in 15 l of methanol. Alternatively, the polymer can be isolated by degassing by extruder. The polymer has a tensile stress δR = 11.5 MPa (stretch test according to DIN 53 455) and a tensile strength εR of 433% (according to DIN 53 455).

A-2:

Manufacture of the macromonomers of formula I-A (compound of formula I, where R is the

Equipment used:

2 l quadruple cylinder pumps with stirrer, thermometer, return cooler with water separator, boiler capillaries for introducing dried air.

Implementation of the programme:

In the above apparatus, 140 g of hydroxy terminated polymethyl methacrylate (J = 11.3 ml/g) from A-3 is dissolved with 1 g of 4-methyl-2,6-di-tert-butyl phenol in 1 000 g of methyl methacrylate and heated to boil until no water is left, 12 ml of isopropyl titanate is added, heated for another 3 hours, cooled to 88 °C and 20 ml of water is added. The completely cooled residue is removed from the precipitation by filtration through a pressure filter (filter layer S 500). The clear, colourless filtrate is reduced to dry by means of a rotary evaporator. The resulting residue is dissolved in 700 ml of acetone and the macronomer of formula I-A is precipitated by dripping in 4 l of water. The precipitated material is filtered and dried in the air dryer at 60°C.

A-3:

Manufacture of hydroxyl terminated polymethylamine acrylate.

200 g of methyl methacrylate is heated to 90 °C in a 2 l reactor with cooling mantle, stirrer, return cooler, drip funnel and thermometer. When the internal temperature reaches 90°C, add 4 g of mercaptoethanol, after which polymerisation is started by adding 0,04 g of butylperneodecanoate (75 per cent in aliphate) dissolved in 10 g of methyl methacrylate. Polymerization begins immediately, with the temperature in the reaction vessel rising to about 95°C to 98°C within 5 minutes when the internal temperature drops back, dosing is done simultaneously from 2 different drip tubes within 4 hours: 0,4 g butylperneodecanoate dissolved in 780,0 g methyl methacrylate drip funnel 116,0 g mercaptoethanol drip funnel 2

The temperature in the reactor is maintained in the range of 94 to 98°C. After that, it is maintained at about 96 to 98°C for 20 minutes. Then, a solution of 0.5 g of butylperoxyneodecanoate is dosed in 250 g of toluene at 96 to 98 °C for 4 hours (final polymerization). Finally, 0.02 g of Tinuvin® 770 is added to 250 g of toluene for stabilisation, cooled to room temperature and obtained as a solid by precipitation in methanol. J = 11.3 ml/g. The total volume of the solution is approximately

B. Manufacture of the interconnected system B-1:

By blackmail 60 g of the elastomer E from example A-1 are placed between two transparent PMMA discs (5 mm thick, 120 mm in diameter) and heated on a hydraulic press for about 75 min at 180 °C. Then they are pressed at 50 bar and cooled to room temperature for about 1 hour. You get a bonding disc with very good transparency and good adhesion at the intermediate layer Z. When the glass is broken by hammer blows, the adhesion between the acrylic glass and the interlayer, i.e. the cohesion of the system, is maintained, so that the movement of glass fragments is safely avoided.

Claims (2)

1. Transparent laminated sheet systems comprising a) at least two outer acrylic glass sheets S, S' at least 2 mm thick having parallel surfaces and b) an intermediate layer Z containing a thermoplastically workable elastomer, characterised in that the elastomer E is made up of 60 - 100 wt.% of a copolymer synthesised from a comb polymer KP consisting of 50 to 5 wt.% of polymethyl methacrylate macromonomers of formula I wherein R denotes a radically polymerisable terminal group and n is such that the molecular weight of the macromonomers is in the range from 500 to 100,000 Daltons, and 95 to 50 wt.% of alkyl acrylates of formula II wherein R₄ denotes an alkyl group having 2 - 20 carbon atoms.
2. Transparent laminated sheet systems according to claim 1, characterised in that the intermediate layer Z has a thickness in the range from 0.05 to 5 mm.