SK156894A3 - Method of production of high filling plastic materials - 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

Method for producing high-filled plastic materials

Technical field

The invention relates to a process for the production of sheet material of high-filled polymethylmethacrylate-based plastic produced by chamber polymerization technology.

BACKGROUND OF THE INVENTION

Plastic sheets based on polymethyl methacrylate (PMMA) have been produced for decades in a reputable way by casting into a chamber consisting of sheet glass and gaskets or polished metal plates (chamber polymerization: compare H.Rauch-Puntigam, Th.Volker: Acrylate and methacrylate compounds, pp. 274-292, Springer Verlag 1967).

Recently, several processes for the production of polyacrylate-based plastic sheet material with the addition of particulate inorganic filler have been described. So eg. JP-Kokai 62, 197 346 (Chem. Abstr.107, 2189345y) discloses a marble-like PMMA sheet material in the manufacture of which mixes crushed acrylic resin containing Al-silicate particles with a diameter of 1 to 30 gm and a red colorant, with a conventional colorant. polymerization precursor and allowed to co-polymerize (cure) in glass form. JP-Kokai 60,231,729 (Chem. Abstr. 104. 150191t) also discloses the simultaneous use of powdered cristobalite (10 to 40 µm diameter) or silica and Al 2 OH 5 (diameter 2 to 5 gm) for the production of decorative marble slabs.

Smooth surface acrylic glass cast plates are manufactured according to JP-Kokai 76.40 108 (Chem. Abstr. 88., 90641d) with the addition of SiCl 2 with a diameter of less than 44 µπι. The use of surface oxidized aluminum plates for the production of PMMA sheet material filled with powdered silica (which has been compatible with gamma-methacryloxypropyltrimethoxysilane) is disclosed in JP-Kokai 61 271 302 (Chem. Abstr. 106, 215075w).

Rough surface PMMA filled plates containing at least 20% by weight of Α1 (ΟΗ) β particles in the 20 to 80 µm particle size range are described in JP-Kokai 61 108 536 (Chem Abstr. 105, 227922η).

Further literature relates to the use of silanized SiO 2 particles with an average particle diameter of 0.05 to 50 µm (compare JP-Kokai 61 69 867, Chem. Abstr. 105. 173745m) or calcium carbonate particles (diameter 1 to 20 µm) [compare JP- Kokai 57 155 145 (Chem. Abstr. 98, 90499v): Ind. U.S. Pat. No. 1,492,892 (Chem. Abstr. 93, 47799c)].

SUMMARY OF THE INVENTION

Production of plastic sheet materials based on high-filled PMMA, i. Materials which contain at least 40% and at most about 80% by weight of one or more inorganic fillers, of PMMA prepolymer, continue to present problems with the technique. In particular, the particulate filler must be suspended in the organic phase.

Due to the longer residence time of the suspension in the chamber prior to polymerization, partial sedimentation of the filler particles towards the bottom of the polymerization chamber has to be considered.

This partial sedimentation of the filler particles, which occurs prior to polymerization, is manifested as a deflection of the plates after polymerization and removal from the mold. The object is therefore to prevent sedimentation of the filler particles, or at least to reduce it to such an extent that no deflection occurs on the poured plates.

It has been found that the relatively small addition of pyrogenic or thermally produced highly disperse silica to a suspension of filler particles in a prepolymer of polymer-methyl methacrylate and methyl methacrylate prepared in accordance with the prior art, which may also contain other components, prevents sedimentation of the particles prior to polymerization. After polymerization we get boards that are not bent. Thus, the invention relates to a process for the production of a high-filled polymeric sheet material based on methylene methacrylate by chamber polymerization.

starting from a prime solution PR which contains predominantly monomers M, in particular methyl methacrylate and prepolymerizate of polymeric acrylamide PM, in particular polymethylmethacrylate and optionally also a two-function polymerizing monomer and a known silanizing agent, from which a particulate filler suspension is formed. The suspension thus prepared, which contains at least one radical initiator, is charged into the polymerization chamber, where polymerization takes place under heating. After completion of the polymerization, it is removed from the mold. Typically, pyrogenic or thermally produced highly disperse silica is added to the suspension.

The term pyrogenic or thermally produced silicon dioxide as used herein means silicic acid products which are produced by flame hydrolysis or arc technology (cf. Ullmann's Encyclopedia of Technical Chemistry, 4th Edition, Vol. 18, p. 652). -653, Verlag Chemistry: Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Vol 20, 768-773, J.Viley 1982). Typically, the highly dispersed pyrogenic silica contains more than 99.7% SiC4. It consists of amorphous bead particles, generally having a diameter of 5 to 50 nm, in particular 20 nm. The primary particle size of the silica produced by arc technology is between 5 and 500 nm. Both products have a density of about 2.2 g / cm 2. Preference is given to using pyrogenic silicic acid and flame hydrolysis.

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Priority is given to products under the trade name AEROSIL or CABO-SIL ^, especially AEROSIL ^ 200. A suitable proportion of pyrogenic or thermally produced highly disperse silica in the suspension is in the range of 0.1 to 5.0% by weight, preferably 0.5% weight.

Further, in principle known additives and auxiliaries, in particular pigments and / or colorants, light-protective agents and stabilizers, lubricants and release aids, can be added to the casting resins before they are filled into the polymerization chamber, in amounts which are appropriate for the casting resin. common purpose (cf. Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Vol. A20, pp. 459-507, VCH 1992).

The process object of the invention adheres as much as possible to the prior art chamber polymerization technology (cf. H. Rauch-Puntigam, Th. Volker: Acrylate and Methacrylate Compounds, cited by Vieweg-Esser; Handbook of Plastics, Vol. IX, Polymethacrylates, C. Hanser Munich 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).

Monomers M or monomer mixtures as described in EP-PS 218 866 are suitable as the liquid polymerization precursors. M monomers which contain, in particular, one or more prepolymers M - in particular MMA and PMMA - are preferably polymerized radically to form a polymerizate which is at room temperature in the solid state. In accordance with the state of the art, for example DE-PS 24 49 656, EP-PS 0 214 551 or EP-PS 0 218 866, which requires a viscosity of less than 5 Pa.s from the polymerization precursors, a viscosity below 0 is recommended. 5 Pa.s. As monomers M, vinyl monomers or vinylidene monomers are recommended (see Ullmann's Encyclopedia of Technical Chemistry, 3rd Edition, Vol.14, p.108-110, Urban & Schwarzenberg, 1963), such as vinyl ester and vinyl ether, as well as vinyl compounds, carbonyl vinyl compounds, vinylaromates, heterocyclic vinyl compounds, macromonomer compounds such as unsaturated polyesters or polyurethanes, preferably acrylic and methacrylic acid derivatives. Preferred are monomers of formula I:

R ^{10 is} ₂ = c - c - O - R ² (I) wherein R is hydrogen or methyl, R is optionally branched and optionally substituted C 1 -C 18 alkyl, optionally substituted C 5 -C 12 cycloalkyl; optionally substituted aryl of 6 to 10 carbon atoms. Known substituents are, for example, halogens, hydroxy-, alkoxy-, dialkylamino- substituents having up to C 1-2 alkyl radicals, preferably C 1 -C 6 alkyl radicals.

Particularly suitable as monomers M are compounds of formula 9

Wherein R is C 1 -C 8 alkyl radicals such as ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate or isomers of 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, preferably methyl methacrylate. In addition, the polymerization precursors may also contain known polymerizing monomers, for example those having at least two vinyl-capable polymers in the molecule (see H. Rauch-Puntigam, Th. Volker: Acrylic and Methacrylic Compounds, p. 184,

Springer-Verlag, 1967), mentioning for example ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, triglycol dimethacrylate, trimethylolpropane trimethacrylate, allyl compounds such as allyl methacrylate or trialyl cyanurate. The content of polymerizable monomers is in principle 0.01 to 10% by weight, preferably 0.1 to 5% by weight, relative to the liquid polymerization precursors.

The polymerization precursors preferably contain more than 50% by weight, in particular 80 to 100% by weight, of methyl methacrylate. Other co-monomers which copolymerize with methacrylates of formula I, such as the aforementioned vinylaromates and heterocyclic vinyl compounds, such as styrene, core-substituted styrene, α-methylstyrene, divinylbenzene, vinylpyrrole don or vinylpyridine, acrylonitrile and methacrylonitrile may be used as co-monomers. vinyl esters such as vinyl acetate or vinyl propionate, vinyl chloride or vinylidene chloride. In general, the addition of equal amounts of (meth) acrylic acid ester of formula I and polymerizing monomers (over 50% by weight) predominates, which may advantageously constitute up to 100% by weight of the polymerization precursor. Particular preference is given to a mixture of a methyl methacrylate monomer and a polymerizing monomer, for example glycol dimethacrylate, the preferred weight ratio of the components being between 95: 5 and 99.9:

0.1. Preferably, the liquid organic polymerizable precursor comprises PM prepolymerisates which are essentially composed of the same monomers as the polymerizable precursor, but the PM prepolymerizates contain no functionalized monomers. For the proportion of constituents five, in principle, what for monomers M. The monomer components of the prepolymerizates PM may be identical to, but different from, the monomers M. Preferably, the PM prepolymers will be dissolved in M monomers, but may also be dispersed therein. As a rule, PM prepolymers have an average molecular weight M _w in the range of 2 x 10 4 to 4 x 10 ⁵ Daltons (determined by gel permeation chromatography; see also HFMark et al., Encyclopedia of Polymer Science and Techniques, Vol. 10, pp. 1-19). (J.Viley, 1987). The proportion of PM prepolymers in the liquid polymerization precursors ranges from 0 to 20% by weight, preferably 0 to 10% by weight. For example, the PM prepolymer may be a 9: 1 methyl methacrylate / methyl acrylate copolymerizate with an average molecular weight M, of about 2.5 x 10 6 Dalton.

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Silanizing agent C)

The organic silicon component C) serves in a known manner as a coupling agent between the filler and the organic phase of the casting resin, using organic silicon compounds known in the art. First of all, these are functional organic silicon compounds with at least one ethylene unsaturated group per molecule. The functional moiety on which the ethylene unsaturated group is attached is generally linked to the central silicon atom through a carbon atom. The other ligands on silicon are generally C 1 -C 6 alkoxy radicals, and the ether radicals may also be present in the alkyl radical. Trialkoxysilanes, for example vinyl rialkoxysilanes or organic silicon compounds in which the carbon-carbon double bonds are linked via one or more carbon atoms, for example allyltrialkoxysilanes or gamma-methacryloxyloxypropyltrialkoxysilanes, are mentioned. In addition, dialkoxysilanes may be used, wherein an additional functional moiety with one carbon-carbon double bond, mostly of the same type, or an alkyl moiety with preferably 1 to 6 carbon aromas, is attached to the Si atom. Organic silicon compounds which may be used are, for example: vinyltrimethoxysilane, vinylrrieroxysilane, vinyltriaceroxysilane, vinyltris (methoxyethoxy) silane, divinyldimethoxysilane, vinylmethyldimethoxysilane, vinylrrichlorosilane, gamma-methacryloyloxypropyltrimethoxysilane-propyltrimethoxysilane-propyltrimethoxysilane-propyltrimethoxysilane). Preferably, organic silicon compounds are used together with amine-type catalysts, in particular C 3 -C 6 -alkylamine type, especially n-butylamine. The amine catalyst is in principle added in amounts of 0.5 to 10% by weight, preferably 1 to 5% by weight, relative to the organic silicon compound. In principle, the weight ratio of the inorganic filler A) to the organic silicon compound C) is between 50: 1 to 20: 1, preferably (50 ± 25): 1.

Said process is suitable for use with conventional fine-grained inorganic fillers such as those described in US-A. It is not suitable to exceed a grain size of 200, preferably 100 gm. Particles less than 0.1 µm in size should preferably not comprise more than 20% of the total amount of particles. Particle size can be determined by conventional methods (see B.Scarlett in Filtration and Separation, p. 215 (1965)), whereby the largest particle size is always taken as the particle size value.

Particularly preferred particulate filler is alumina or alumina hydrate, respectively. The proportion of filler in the casting resin (which contains all necessary components) before casting is at least 40% by weight to 80% by weight, preferably about 66% by weight.

Conventional initiators such as peroxy or peroxydicarbonate and / or azo initiators such as azodiisobutyronitrile (AIBN) or diacyl peroxides are also used as radical initiators, in conventional amounts, for example 0.02 to about 1% by weight relative to the monomers. Redox initiators are also used accordingly. In practice, we first prepare a solution which may contain, for example, an amine component as an auxiliary silanizing agent and a strong strength component. The filler and optionally pigments, dyes and other excipients are then mixed with the dissolvator together with the pyrogenic or thermally produced highly disperse silica, preferably in the form of AEROSIL® 200. The suspension thus prepared, which contains one or more initiators, after dispersion all components, for example by means of a dissolvator (high-speed intensive stirrer), and filled into a conventional polymerization chamber, preferably consisting of silicate glass plates provided with spacer gaskets, and allowed to cure, for example about 4 to 5 hours at 40 ° C . Due to the final polymerization, it is left in the polymerization chamber for a period of time, for example 1-2 hours at elevated temperature, for example 110 ° C, in a thermostatic chamber. After cooling, the product is removed from the mold. The plates are generally adjusted to a thickness of between 5 and 20 mm.

Positive effects

The method object of the invention provides a high, filled sheet material of surprisingly good quality, without detectable sag. A further advantage resulting from the addition _{to the} pyrogenic or thermally produced highly disperse silica is that when shearing the suspension, the viscosity is substantially lower than at rest, when a thixotropic network can be formed. Indeed, during an important filling step of the chamber, when a low viscosity is required, this is indeed achieved, and upon completion of the filling, a thixotropic network is immediately formed which effectively prevents sedimentation of the particles present.

Lady peak of the invention

A. Preparation of a Highly Filled Suspension Example A-1

40 g of MMA prepolymer (^ specific / c ⁼ up to 140, M _w about 400,000) (Plexigum M920 ^R ) were dissolved in 299.99 g of MMA and 0.03 g of 2,4-dimethyl-6-tert-butylphenol at a temperature of about 40 ° C over 5 hours, then the mixture is cooled to room temperature. 5.0 g of stearic acid and 3.0 g of glycol dimethacrylate are dissolved in this syrup. Add to the dissolver

D syrup under gentle stirring, 5 g of Aerosil 200, 330.0 grams of aluminum hydroxide having a mean particle size of 45 μ m (ALCOA ^R C33, manufactured by ALCOA, USA) and 330.0 grams of aluminum hydroxide _Λ a mean particle size of 8 gm ( ALCOA C333 ^R ). Then disperse the suspension with a dissoLver (type HD 7.5 from Getzmann, Germany) at a speed of 20.0 m / s for 10 minutes.

After cooling to room temperature, 1 g of bis- (4-tert-butylcyclohexyl) peroxide dicarbonate and 1 g of tert.-butylperpivalate are dissolved in the suspension using a vortex mixer and the trapped air bubbles are quickly removed by vacuum.

B. Preparation of high-filled sheet material

A chamber made of two plates of silicate glass (6 mm thick) and a strand of PVC round cross-section (diameter _t 3.2 mm) are built. The suspension prepared as in Al is poured into the space between the glass plates and the chamber is closed. The filled chamber is placed vertically in a 40 ° C water bath. The polymerization time was 260 minutes. It is then allowed to dopolymerize in an oven for 30 minutes at 105 ° C. The mold is removed and the cured cast is removed. The plate casting has a high gloss surface on both sides and is not bent.

Comparative example

The suspension was prepared as in Example 1, but with Aerosil 200 ^R replaced by 2.5 g ALCOA C33 ^R and 2.5 g ALCOA C333 ^R.

Plate casting was prepared as in Example 1.

The plate cast from this suspension without Aerosil at 200 ^R has a high gloss surface on both sides and is clearly folded.

Claims (6)

A process for the production of a high-filled plastic sheet material by the chamber polymerization method and using a conventional initial monomer solution, conventional fillers and auxiliaries, wherein a monomer-containing suspension PR is prepared from the initial PR-containing monomer solution and the cast resin thus prepared containing at least one The radical initiator is poured into the polymerization chamber, allowed to polymerize and subsequently removed from the mold, characterized in that the casting resin contains pyrogenic or thermally produced highly disperse silica in an amount of 0.1 to 5% by weight. Method according to claim 1, characterized in that the sheet plastic material consists wholly or predominantly of polymethyl methacrylate. Method according to claim 1, characterized in that aluminum hydroxide or alumina hydrate is used as the filler. Method according to one of Claims 1 to 3, characterized in that the filler content in the casting resin is at least 40 to 80% by weight. Method according to claims 1 to 4, characterized in that the initial PR solution is composed of a prepolymer of polymethyl methacrylate and methyl methacrylate in a ratio of 5 to 30 parts by weight to 95 to 70 parts by weight. The method of claim 5, wherein the polymethyl methacrylate has a molecular weight of 2.10 4 to 4.10 Dalton.