SI9400451A - Method for making of considerably filled plastic slab-products - Google Patents

Abstract

The invention relates to a process for the preparation of highly filled plastic sheet (board) material by the chamber polymerisation process using a customary, monomer-containing presolution and fillers and auxiliaries customary per se, where the monomer-containing presolution VL is transferred into the filler-containing suspension, and the casting resin formed in this way, which contains at least one free-radical initiator, is introduced into the polymerisation chamber, the polymerisation is carried out, and the product is subsequently demoulded, where the casting resin contains pyrogenic or thermally produced, highly disperse silicon dioxide in amounts of from 0.1 to 5% by weight.

Description

A process for the preparation of a highly filled plastic sheet material

FIELD OF THE INVENTION

The invention relates to a process for the preparation of a highly charged plastic sheet material based on a polymethylmethacrylate base prepared by polymerisation in a chamber.

The state of the art

Plastic sheets on polymethylmethacrylate (PMMA) -based material have been prepared for decades, in a proven manner, by a casting process using a chamber consisting of glass plates and sealing rings, respectively. made of polished metal sheets (chamber polymerization: cf. H. Rauch-Putingam, Th. Volker, Acryl- und Methacrylverbindungen, pp. 274-292, Springer-Verlag 1967).

In the past, a number of processes for the preparation of polyacrylate-based plastics have already been provided, to which an inorganic particulate filler has been added. JP-Kokai 62, 197 346 (Chem. Abstr. 107, 2189346y) describes e.g. marble-like PMMA sheet material, which has been mixed with crushed Al-silicate particles with a diameter of 1 -30 μτη by conventional polymer prep.

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and an acrylic resin containing red dye and polymerized (solidified) into glass.

Simultaneous use of powdered cristobalite (10 - 40 μτη diameter) or. quartz and A1 (OH) ₃ (2 - 5 μτη in diameter) for the preparation of marble-like decorative panels is described in JP-Kokai 60, 231 729 (Chem. Abstr. 104,150191t).

Molded acrylic glass sheets with a smooth surface were prepared according to JP-Kokai 76,40 108 (Chem, Abstr. 88, 90641d) using SiO ₂ with a diameter of <44 μπι.

The use of surface-oxidized aluminum plates for the preparation of a PMMA-plate material filled with powdered quartz (made compatible with -γ-methacryloxypropyltrimethoxysilane) is described in JP-Kokai 61 271 302 (Chem. Abstr. 106, 215075w).

Rough-surface filled PMMA plates containing at least 20% by weight % A1 (OH) ₃ in the size range 20 - 80 μτη are described in JP-Kokai 61 108 536 (Chem. Abstr. 105, 227922η).

Further printed documents address the use of silanized SiO ₂ particles with an average particle diameter of 0.05 - 50 μτη (cf. JP-Kokai 61 69 867, (Chem, Abstr. 105, 173745m) or calcium carbonate in the form of particles (1 - 20 μτη diameter) [compare JP-Kokai 57 155 145 (Chem. Abstr. 98, 90499v); Ind. Pat. 146 892 (Chem. Abstr. 93 47799c)].

Task and solution

Preparation of Highly Filled Plastics, i. E. material with a content of at least 40 and up to about 80 wt. % of one or more inorganic fillers on a PMMA base, using PMMA prepolymerizate, still poses problems in the art. First, the particulate filler must be suspended in the organic phase.

Due to the extended standstill time of the suspension prior to polymerization in the chamber, partial sedimentation of the filler particles on the inner surface of the polymerization chamber must be accounted for.

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This partial sedimentation of the filler particles prior to polymerization is observed after polymerization and decomposition in the form of bent plates. Thus, the task was to prevent the sedimentation of the filler particles or to reduce it at least so that the bending of the cast plates would no longer occur.

It has now been found that the relatively small addition of pyrogenic or thermally obtained, highly dispersed silica to the suspension of filler particles in prepolymerized polymethyl methacrylate and methyl methacrylate, which may contain further constituents prepared according to the state of the art, prevents sedimentation of the particles prior to polymerization. Upon completion of the polymerization, non-bent plates are obtained. Thus, the invention relates to a process for the preparation of a highly charged plastic sheet based on polymethylmethacrylate based on a polymerisation process in a chamber, starting from a prior VL solution preferably containing M monomers, in particular methyl methacrylate and polymethylmethacrylate prepolymerate (PM), preferably polymethylmethacrylate. and, optionally, a two-functional cross-linking monomer and known silanizing agent, prepare a particulate filler suspension with such a suspension containing at least one radical initiator, fill the polymerization chamber, polymerize upon heating, and after the polymerization is completed, adding pyrogen or thermally obtained highly dispersed silica to the suspension.

By the use of the invention, pyrogenic or thermally obtained, highly dispersed silica is understood in the art such silica products which are prepared by flame hydrolysis or. by arc method (cf. Ullmanns Encyclopadie der Technischen Chemie, 4th ed., vol. 18, pp. 652-653 Verlag Chemie; Kirk-Othmer, Encyclopedia of Chemical Technologie, 3rd ed. Vol. 20, 768773, J.Wiley 1982). In general, highly dispersed pyrogen silica contains> 99.7% SiO ₂ . It is made up of amorphous bead-shaped particles with, as a rule, a particle diameter of 5-50, especially up to 20 nm. The primary particle size of the silica prepared by the arc process lies at 5-500 nm. For both product types, the density is approx. 2.2 g / cm ³ . The use of pyrogenic silica obtained by flame hydrolysis is preferred.

Particularly preferred are products commercially available as AEROSIL® or

CABO-SIL®, especially under the code AEROSIL® 200.

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The proportion of pyrogenic or thermally obtained highly dispersed silica in the suspension in the range of 0.1 to 5.0% by weight is reasonable, with 0.5% by weight of support.

Furthermore, further known additives and auxiliaries, in particular pigments and / or pigments, may be added to the casting resins before being filled into the polymerization chamber. dyes, light protectants and stabilizers, lubricants and disintegrators in conventional quantities (cf. Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed. Vol. A20, pp. 459 to 507, VCH 1992).

The process of the invention further relates mainly to chamber polymerization processes of the prior art (cf. H. Rauch-Puntigam, Th. Volker Acryl- und Methacrylverbnidungen loc. Cit. Vieweg-Esser, Kunststoff-Handbuch Bd. IX, Polymethacrylate, C. Hanser Munchen 1975; EP 218 866; US-A 3 847 865;

US-A 4,221,697; US-A 4,251,576; US-A 4,826,901; US-A 4 786 660).

M or M monomers are suitable as liquid polymer precursors. monomer mixtures such as e.g. described in EP-PS 218 866. M monomers containing preferably one or more PM prepolymerizates - in particular MMA and PMMA are polymerized preferably radical to form a polymer that is solid at room temperature. This is related to the state of the art (e.g., DE-PS 24 49 656, EP-PS 0 214 551 or EP-PS 0 218 866), whereby liquid polymer precursors at a design temperature have a viscosity of less than 5 Pa. .s, preferably less than 0.5 Pa.s. Vinyl monomers or vinylidene monomers (cf. Ullmanns Enzyklopadie der Technischen Chemie, 3rd ed. Bd. 14, pages 108 to 110; Urban & Schwarzenberg 1963), such as e.g. vinyl esters and -ethers, as well as vinyl compounds, vinyl carbonyl compounds, vinyl aromatics, heterocyclic vinyl compounds, macromonomeric compounds such as e.g. unsaturated polyesters or polyurethanes, and in particular acrylic and methacrylic acid derivatives. Preferably we use the monomers of formula I:

Ri O

I II ch ₂ = ccor ₂ i

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wherein R 1 is hydrogen or methyl, R _{2 is} optionally branched or optionally substituted alkyl radical of 1 to 18 carbon atoms, optionally substituted cycloalkyl radical of 5 to 12 carbon atoms or optionally substituted an aryl radical having from 6 to 10 carbon atoms. Known substituents are e.g. halogen, hydroxy, alkoxy, dialkylamino substituents with C-alkyl residues, preferably with C1-C-alkyl residues.

o

In particular, the monomers M are those of formula I, wherein R ₂ stands for alkyl radicals having 1 to 8 carbon atoms, such as e.g. ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, or. isomers, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate), benzyl (meth) acrylate, and especially methyl methacrylate. Further, the polymer precursors may contain known crosslinking monomers, e.g. such with at least two polymerisable vinyl groups in the molecule (cf. H. Rauch-Puntigam, Th. Volker, Acryl- und Methacrylverbindungen, page 184, Springer-Verlag, 1967), citing ethylene glycol dimethacrylate, 1,4- butanediol methacrylate, triglycoldimethacrylate, trimethylolpropantrimetacrylate, allyl compounds such as allylmethacrylate or triethylcyanurate. The content of crosslinking monomers generally lies at 0.01 to 10 wt.%, Preferably at 0.1 to 5 wt.% Relative to the liquid polymer precipitates.

Preferably, the polymer precipitates contain more than 50% by weight, in particular from 80 to 100% by weight of methyl methacrylate. Comonomers may be used as further monomers that can be copolymerized with methacrylic esters of formula I, such as e.g. the aforementioned vinyl aromatics and heterocyclic vinyl compounds, e.g. styrene, ring-substituted styrene, α-methylstyrene, divinylbenzene, vinylpyrrolidone or vinylpyridine, acrylonitrile and methacrylonitrile, vinyl esters such as vinyl acetate or vinylpropionate, vinyl chloride or vinylidene chloride. In general, an even proportion of the (meth) acrylic acid esters of formula I and crosslinking monomers (> 50% by weight), which may preferably be up to 100% by weight of the polymer precipitate, is predominant. A mixture of methyl methacrylate monomer and one of the crosslinking monomers, such as e.g. of glycoldimethacrylate, the weight ratio being preferably between 95: 5 and 99.9: 0.1. Preferably, the liquid, organic polymerizable pre-polymer PMs are generally constructed of the same M monomers as the polymeric pre-polymerisers, but the PM polymerisations do not contain any functionalized monomers. In general, the same relationships as those for M monomers apply. The monomer components of PM prepolymerizates may be identical or different from M monomers. Pred24499-1 l / 94-D6-Re.

However, PM prepolymerizates are dissolved in M monomers and may be dispersed in them. As a rule, PM polymer molecules of medium molecular weight M _{w have} a range between 2 χ 10 ⁴ and 4 χ 10 ⁵ daltons. (determination by gel permeable chromatography, cf. HF Mark et al., Encyclopedia of Polymer Science and Technology, Vol. 10, pages 1 to 19, J. Wiley, 1987). The proportion of PM prepolymerizates in the liquid polymer precursors lies in the range of 0 to 20% by weight, preferably 0 to 10% by weight. For example, PM polymer may be a copolymer of methylmethacrylate and methyl acrylate in a 9: 1 weight ratio with a mean molecular weight M _{w of} about 2.5 χ 10 ⁵ Dalton.

Silanizing agent C)

Organosilicon component C) serves in a known manner as a promoter of adhesion between the filler and the organic phase of the casting resin, using organosilicon compounds known in the art. It is primarily a functional organosilicon compound with at least one ethylene unsaturated group in the molecule. The functional residue bearing the ethylene unsaturated group is generally bonded to the central silicon atom via a carbon atom. The remaining ligands on silicon are typically alkoxy residues of 1 to 6 carbon atoms, with ether bridges in the alkyl residue. Trialkoxysilanes are known, such as vinyltrialkoxysilanes ah organosilicon compounds, in which CC double bonding with the Si atom is linked via one or more carbon atoms, such as allyltrialkoxysilanes or γ-methacryloyloxypropyltriloxysilanes. Further, dialkoxysilanes can be used, wherein a further functional residue with a CC double bond, mostly of the same type, or an alkyl residue with preferably 1 to 6 carbon atoms, is attached to the Si atom. Examples of organosilicon components include: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltris (methoxyethoxy) silane, divinyldimethoxysilane, vinylmethyldimethoxysilane, vinyltrichlorosilane, • γ-methacryloyloxypropyltrimethyloxypropyltrimethyloxypropyltrimethoxysilane Preferably, organosilicon compounds are used together with catalysts of the amine type, especially the alkylamines of 3 to 6 carbon atoms, especially n-butylamine. The amine catalyst is generally used in amounts of 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the organosilicon compound. In general, the weight ratio of inorganic filler A) to organosilicon compound C) is between 500: 1 to 20: 1, preferably (50 ± 25): 1.

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The present process is suitable for use with conventional fine-grained inorganic fillers such as those described e.g. in US-A 4,221,697. A grain size not exceeding 200, especially 100 gm, is considered appropriate. Particles with a size <0.1 gm should preferably not exceed 20% of the total number of particles. The particle size can be determined by the usual procedure [cf. B. Scarlett v Filtration & Separation p. 215, (1965)], whereby the maximum particle dimensions are taken to determine the particle size.

Particularly preferred particulate filler is the alumina hydroxide used in question. aluminum oxide hydrate.

The proportion of filler in the casting resins (containing commonly used ingredients) lies before the casting at least 40% by weight and up to 80% by weight, preferably at 66% by weight.

We also use conventional initiators as radical initiators, e.g. peroxy- oz. peroxybicarbonate or azo-initiators such as azodiisobutyronitrile (AIBN) or diacylperoxides in conventional amounts, e.g. 0.02 to approx. 1% by weight of existing monomers or in this case, the redox initiators used.

For the practical implementation of the process, a pre-solution may be prepared which may contain e.g. as an auxiliary substance for silanizing one amino component, as well as silanizing agent. The filler and, if appropriate, the pigments, dyes and other auxiliaries, as well as pyrogen or thermally obtained, highly dispersible silica, preferably in the form of the AEROSIL® 200 product, are then introduced into the pre-solution using the disolver. The suspension thus obtained contains one or more initiators, after complete dispersion of all ingredients, e.g. by means of a disolver (high-speed intensive mixer), it is filled into a conventional polymerization chamber, which preferably consists of silicate-glass panels, which are provided with spacer seals, and claim e.g. approx. 4-5 hours at 40 ° C. For the final polymerization, the polymerization chambers are held for a certain period of time, e.g. 1-2 hours at elevated temperature, e.g. 110 ° C in a warm cabinet. After cooling down, decompose. The thickness of the panels is usually in the range of 5 to 20 mm.

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Preferred effects

The process of the invention, in a surprising manner, produces a very well-filled plate of very good quality in a surprising manner, with no bending observed. A further advantage resulting from the addition of pyrogenic or. of thermally obtained highly dispersed silica, in that the viscosity of the suspension shear is much lower than in the quiescent state, where a thixotropic network can be formed. During an important chamber filling process, when low viscosity is desired, it is actually tuned, while a thixotropic mesh is formed immediately after completion of the filling process, effectively preventing sedimentation of existing particles.

The following examples serve only to illustrate the invention.

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EXAMPLES

A. Preparation of a heavily charged suspension

Example A-1

In 296.99 g of MMA and 0.03 g of 2,4-dimethyl-6-tert-butylphenol over 5 hours at approx. Dissolve 40 g of PMMA prepolymerate (r | _{spec / c} = 130-140, M _w approx. 400,000) (Plexigum M920®) and then cool to room temperature. Dissolve 5.0 g of stearic acid and 3.0 g of glycoldimethacrylate in this syrup. In a disolver, 5 g of Aerosil 200®, 330.0 g of aluminum hydroxide with a medium particle size of 45 μτη (ALCOA C33®, product of ALCOA, USA) are then introduced into the syrup with moderate mixing, followed by 330.0 g of medium hydroxide of aluminum. 8 μτη particles (ALCOA C333®). The suspension was then dispersed with a disolver (HD 7.5 type from Getzman, ZRN) at 20.0 m / sec. about 10 minutes. After cooling to room temperature, 1 g of bis- (4-tert-butylcyclohexyl) -peroxycarbonate and 1 g of tert-butylperpivalate are dissolved in the suspension on a wing mixer, and the included air bubbles, under vacuum, are removed from the suspension in a very short time.

B. Preparation of Highly Filled Plate Material

From two silicate glass panels (6 mm thick), a chamber is constructed using a round PVC twine (3.2 mm diameter). Pour a suspension of A-1 into the space between the silicate glass chambers and close the chamber. Place the filled chamber horizontally in a 40 ° C water bath. The polymerization time is 260 minutes. It is then finally polymerized in a drying cabinet for 30 minutes at 105 ° C. Next, open the chamber and remove the solid mold. The flat cast has a high gloss finish on both sides and does not bend.

Comparative example

Prepare the suspension as described in Example 1, replacing 5 g of Aerosil 200® with 2.5 g of ALCOA C33® and 2.5 g of ALCOA C333®.

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Prepare plate castings as described in Example 1.

The non-Aerosil 200® non-Aerosil 200 molded cast mold has a high gloss surface on both sides and is clearly bent.

For

Rohm GmbH Chemische Fabrik:

Claims (6)

1. A process for the preparation of a highly charged plastic plate material by polymerisation in a chamber using a conventional pre-solution containing monomers and conventional fillers and excipients, wherein the monomers-containing pre-solution VL is converted into a suspension containing the fillers and thus formed a casting resin containing at least one radical initiator is filled into a polymerization chamber, polymerized and then decomposed, characterized in that the casting resin contains pyrogen or thermally obtained highly dispersed silica in amounts of 0.1 to 5% by weight. Method according to claim 1, characterized in that the plastic sheet material consists entirely or predominantly of polymethylmethacrylate. Process according to claim 1, characterized in that aluminum hydroxide or aluminum oxyhydrate is used as the filler. Process according to claims 1 to 3, characterized in that the filler content in the casting resin is at least 40 and up to 80% by weight. Process according to claims 1 to 4, characterized in that the VL pre-solution is formed of polymethylmethacrylate prepolymerate and methyl methacrylate in a ratio of 5 to 30 wt. parts against 95 to 70 wt. parts. Process according to claim 5, characterized in that the polymethylmethacrylate has a molar mass of 2 χ 10 ⁴ to 4 χ 10 ⁵ daltons. For Rohm GmbH Chemische Fabrik: