NL9400413A - Highly filled, foamed polymer material based on polymethacrylate. - Google Patents

Description

Highly filled, foamed polymer material based on polyvinyl chloride.

The invention relates to a highly filled, foamed polymer material based on polymethacrylate.

Highly filled casting resins, for example on a PMMA basis, have long been successfully available on the market (compare EP-218,866; US-A-3,8if7,865; US-A-4,221,697, US-A-4,251,576, US-A-4,826,901; US-A-if,786,660). Polymeric materials enriched with mineral fillers in such a manner, which can be used, for example, for rinsing in the kitchen, sanitary area, as well as generally as sheet material in the building sector, do generally come close in particular in modern implementation techniques. of the requirements of the technique with regard to appearance, shelf life, machinability, etc., but are comparatively heavy materials. For example, PMMA can be based on a filler content of 60-70% by weight of silicon dioxide or aluminum hydroxide with a density of 1.8 g / cm3. Tests for recovering foamed polymer material have been conducted fairly early.

German Pat. No. 1,017,784 describes a process for the preparation of porous, predominantly PMMA, shaped bodies, wherein in the polymer and monomer mixture, at least for partial enrichment at the prescribed low temperatures, at the same time to achieve a porous structure of the carbon dioxide snow formed during the polymerization is incorporated. The same patent states that dyes, pigments and, respectively, fillers can be added to the mass which is capable of polymerization. A generally applicable method for the production of porous shaped bodies consists, according to French patent specification Ι.Ι55Ό58, in that thermoplastic plastics, which contain gases dissolved, are heated above their softening point, whereby the plastic matrix is expanded by the expanding gases are foamed. Further protection rights concern foamed polymeric material, whereby the propellant is produced by incorporating a water-containing polymeric component into a calcium carbide-containing polymeric component (South African patent 68.08312) or polymeric materials which are foamed up using peroxidic compounds (Japan-Kokai 78.105 -565; Chem. Abstr. 90, 39 662a; Japan Kokai75.i5i.278, Chem. Abstr. £ 4.151 530h).

It is known from European patent publication 0.503 * 156 to emulsify the preparation of casting resins in a filled suspension of methyl methacrylate to 50% by weight of water. After curing, the water portion is expelled from the casting by heating. A foam-like, highly filled material remains.

The preparation of highly filled, foamed polymethyl methacrylate, i.e. of a material with at least 40 to 80% by weight content of an inorganic filler, the technique presents qualitatively different problems than, for example, the production of "porous shaped bodies mainly consisting of polyacrylic acid methyl ester" according to German patent specification 1,017 * 784. This is a variant of the chamber polymerization process, in which the prepolymer containing the usual initiator is mixed with carbon dioxide snow in a homogeneous distribution while stirring, and this mixture is filled into the shaping chamber. heating it gels to a solid mass. Therefore, the prior art does not open an immediately accessible path for the preparation of foamed, highly filled polymer material based on PMMA. It was therefore an object to provide a process which allows the preparation of highly filled, foamed polymer materials based on polymethyl methacrylate while retaining the properties required of casting resins using well proven technologies.

It has now been found that the method according to the invention is well suited for solving the stated objective.

The invention relates to a process for the preparation of highly filled, foamed polymer materials based on polymethyl methacrylate in a suitable form using solid carbon dioxide, comprising a pre-solution prepared from 70 to 95 parts by weight of methyl methacrylate and 5 to 30 parts by weight parts of polymethyl methacrylate prepolymer and 0 to 5, if desired, 0.05 to 5 parts by weight of a divalent cross-linking agent and 0 to 5, optionally 0.5 to 5, preferably 0.5 to 1.5 parts by weight of a silane lilac SI-M goes out. To this pre-solution are introduced under high-speed stirring of the particulate inorganic filler in amounts of 30 to 80% by weight (based on the foamed material as the end product) and carbon dioxide in the form of carbon dioxide snow or carbon dioxide ice (reduced / ground) therein in amounts of 0.5 to 30% by weight, based on the slurry formed, distributed evenly as gaseous carbonic acid, and then by external heating or by the heat of reaction due to the polymerization process, preferably using a redox initiator system expels the carbon dioxide as the polymerization proceeds and performs demoulding after the polymerization is completed. The introduction of the carbon dioxide can occur in the pre-solution or in the suspension formed.

Suitable prepolymers are, for example, the commonly used PMMA polymers, which may contain minor amounts, up to about 15% by weight, of preferably selected comonomers, such as, for example, methyl acrylate. The prepolymers usually have molar mass in the range 2 x 104 to * t x 105 Daltons [determined size exclusion chromatography (SEC)]. Optionally, a cross-linking agent, for example in the form of the (meth) -acrylic acid ester of polyhydric alcohols, in amounts of 0.1 to 1.5% by weight, based on the monomers, can also be added to the pre-solution.

Suitable fillers are the finely divided inorganic or organic materials commonly used for casting resins. Preferably, a grain size of 200 µm in diameter, preferably 50 µm, is not exceeded. When using cristoballite as a filler, preferably at least 95% of the particles must be <10 µm in size. Particles with a size of 0,1 0.1 µm should, if possible, not exceed 10% of the total number of particles. The particle size is determined according to the usual methods (compare B. Scarlett in "Filtration & Separation" pp. 215, 1965). For the determination of the particle size, the largest dimensions of the particles are always taken. Preference is given to granular particles. Sometimes it can be advantageous to free the particles of adsorptively bound moisture by heating, for example at 150 ° C. The fillers can be natural products or synthetically prepared. The mechanical properties, such as hardness, elastic shear modulus, are measured according to the intended application purpose of the casting resins. In addition, setting an elastic shear module of at least 5 GNm 2 may be advantageous. Suitable are, for example, mineral substances, such as aluminum oxides, aluminum hydroxides and derivatives, for example, alkali and alkaline earth metal double oxides and alkaline earth metal hydroxides, clays, silicon dioxide in the most various modifications thereof, silicates, aluminosilicates, carbonates, phosphates, sulfates, sulfides, oxides, carbons, metals and metal alloys. Furthermore, synthetic materials, such as glass flour, ceramic, porcelain, slag, finely divided synthetic SiO2, are mentioned. Silicic acid modifications, such as quartz are mentioned. (quartz flour), tridymite and cristoballite, as well as kaolin, talc, mica, feldspar, apatite, barite, gypsum, chalk, limestone, dolomite. Mixtures of fillers may also be used. The filler content in the casting resins is preferably at least 40 wt. In general, a content of 80% by weight is not exceeded A guide filler content of the casting resins> 50 and up to 80% by weight is indicated as a guide value. The preparation of the fillers in the preferred grain sizes can be carried out according to the known methods, for example by crushing and grinding. Particular preference is given to cristoballite in addition to aluminum hydroxide.

In a preferred embodiment type, the average particle size is in the range 60-0.5 µm. Preferably, the hardness (according to Mohs: compare Römpp's Chemie-Lexikon, 9th edition, p. 1700, Georg Thieme Verlag 1990) of the fillers in the case of the crystallite is at * 6, in the case of aluminum hydroxide at 2, 5-3.5. The silanizing agents SI-M serve in a manner known per se as an adhesion promoter between filler and organic phase. Therefore, the organosilicon compounds known from the prior art can be used [compare D. Skudelny, Kunststoffe 22. 1153, H56 (1987)? Plastics 68 (1978); the company brochure DynasilanR, adhesion aids from DynamitNobel, Chemistry]. Firstly, these are functional organosilicon compounds with at least one ethylenically unsaturated group in the molecule. The functional residue bearing the ethylenically unsaturated group is generally connected via a C atom to the central silicon atom. The remaining ligands on the silicon are as control alkoxy radicals with 1 to 6 carbon atoms (where ether bridges may still be present in dealkyl radicals). Mention is made, for example, of the vinyl trialkoxy silanes. The double CC bond may also be linked to the Si atom via one or more carbon atoms, for example in the form of deallyltrialkoxy silanes or the α-methacryloyloxypropyltrialkoxy silanes. Dialkoxysilanes can also be used, wherein a further functional radical with a double CC bond, usually of the same type, or an alkyl radical with preferably 1 to 6 carbon atoms is attached to the Si atom. Different types of organosilicon compounds may also be present in the organosilicon component. Mentioned are, for example, the vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tris (methoxyethoxy) silane, divinyldimethoxysilane, vinyl methyl dimethoxysilane, vinyl trichlorosilane, α-methacryloyloxypropyltrimethoxysilane or α-metha-cryloyloxyethyl-propyl. The organosilicon compounds are advantageously used together with catalysts of the amine type, in particular of the type of the alkyl amines of 3 to 6 carbon atoms, especially with n-butylamine. 0.05 to 10% by weight, preferably 1 to 5% by weight, of the organosilicon component can be used as a guide value for the use of the amine catalyst.

Generally, the weight ratio of inorganic fillers to organosilicon compound is 500: 1 to 20: 1, preferably 50 ± 25: 1.

The method can be carried out in accordance with technical methods known per se. The method according to the invention first comprises the preparation of the pre-solution in a manner known per se. The pre-solution preferably contains the amine component and the silanizing agent SI-M. Then, with the aid of a dissolving device, the filler is introduced into the pre-solution and subsequently the suspension obtained in this way is dispersed in the dissolving device. After termination of the silanization reaction, part of the redox component of the redox initiator (compare H. Rauch-Puntigam, Th. Völker, Acryl- und Methacrylverbindungen, Springer-Verlag 1967) is preferably added to the suspension and of a paddle stirrer. A polymerization inhibitor, such as, for example, a sterically hindered phenol (5th edition, vol. 20A. pp. 459-507.VCH 1992), may also be used in accordance with customary practices. and / or add a lubricant, such as a phthalic acid diester or stearic acid. Carbon dioxide is then added. Carbon dioxide can be added as carbon dioxide snow, as crushed CO2 ice or as gas, whereby value must be attached to an even distribution. The most favorable quantity must be determined when gas is supplied. A decision regarding solid CO2 with respect to the amount of gas cannot be made directly, since with the use of solid CO2 a not insignificant part emerges gaseous from the suspension in the air space.

As soon as no gas emerging from the slurry is observed, the remaining redox components of the slurry can be added with stirring. During the now-starting, exothermic redox polymerization or - if only working with peroxidic initiators (see Rauch-Puntigam, loc. Cit) - as a result of external heat supply, the suspension foams during the curing. Finally, the shaping can then be carried out. In particular, with continuous preparation of the foamed polymer material, the carbon dioxide can also be added to the pre-solution.

The suspension is prepared in the appropriate mixing units. Suitable types are, for example, the devices of the companies Respecta / Düsseldorf / BRD or Coudenhove & Hübner / Vienna. The initiators can be added prior to the mixing unit leaving.

According to the process of the invention, a PMMA foamed as a rule with closed pores is recovered. Judging by the results obtained so far, the density of the foamed plastic compared to non-foamed PMMA at an equal filler content is significantly lower, optionally at half.

With the aid of the method according to the invention, a highly filled, foamed PMMA material can be obtained in a relatively simple manner and in connection with the proven technology.

Due to the lower density of this material, numerous interesting applications also appear.

The following examples further illustrate the invention.

EXAMPLES

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

In 266.97 g of methyl methacrylate (MMA) and 0.03 g of 2,4-dimethyl-6-tert-butylphenol, 60 g of an MMA polymer (η5ρεε. / Ε = 130-140, Mw approximately 400,000, product PLEXIGUM ® M 920 from Röhm GmbH) dissolved at about 50 ° C in 5 hours and then cooled to room temperature. 5.0 g of stearic acid and 3.0 g of glycol dimethacrylate are dissolved in the syrup obtained. In a dissolver (product Dispermat® from VMAGetzmann / BRD), with moderate stirring, 332.5 g of aluminum hydroxide with an average particle size of 45 µm (product ALCOA® C33 from ALC0A / USA) and then 332.5 g of aluminum hydroxide with an average particle size of 8 µm (product ALCOA® C333) brought into the syrup. The suspension is then dispersed in a dissolver at 12.5 m / s for about 10 minutes.

B. Preparation of the Foamed Polymer Material Example B-1

700 g of the strongly filled suspension according to Example A-1 are weighed into a beaker of polyethylene (0 = 9 cm, H = 15 cm). Immediately stirring with a paddle stirrer at about 25 ° C, 7 g of dibenzoyl peroxide, 502's in di-butyl phthalate (product INTER0J® BP-50-FT from the company Peroxid Chemie

GmbH) and 3.5 g azo-bis-isobutyronitrile (product INTEROJ® NN IBN) added and dissolved. 7.0 g of CO2 snow is then added to the suspension with stirring. The temperature of the suspension is measured after a stirring time of 5 minutes. Then 7.0 g.N.N-dimethyl-p-toluidine as a solution in MMA is added to the suspension with stirring. The stirrer is removed after a stirring time of 1 minute. A polymeric foam is obtained, which is characterized in Table A.

Example B-2

Method analogous to B-1. Instead of 7.0 g CO2 snow, 35.0 g CO2 snow is added to the suspension.

Example Β-λ

Method analogous to B-1. Instead of 7.0 g CO2 snow, 70.0 g CO2 snow is added to the suspension.

Example B-4

Method analogous to B-1. Instead of 7.0 g CO2 snow, 140 g CO2 snow is added to the suspension.

TABLE A

Data Relating to Examples B-1 through B-4

Properties of the Foamed Polymeric Materials: According to the process of the invention, predominantly closed-pore foams are obtained.

As figures 1-3 show (Fig. 1: with 5 wt% CO2 snow; Fig. 2: with 5 wt% CO2 CO2, ground; Fig. 3: with 10 wt% CO2 snow) rises the average pore size with increasing CO2 content. Fig. 4 shows the dependence of the foam density on the addition of CO2.

Claims (5)

1. Process for the preparation of highly filled, foamed polymer materials based on polymethyl methacrylate in a suitable form using carbon dioxide, characterized in that a pre-solution of 5-70 parts by weight of methyl methacrylate and 1-15% by wt. Prepare parts of polymethyl methacrylate prepolymer, into which the particulate inorganic filler in amounts of 30-80% by weight, based on the suspension formed, is introduced, with stirring at high speed, under the formation of a suspension, provided that in the pre-solution or in the slurry of gaseous or solid carbon dioxide is evenly introduced in a fine distribution, after which the carbon dioxide is expelled by external heating or by the reaction heat of the polymerization step initiated by a redox initiator, while the polymerization proceeds and, after the polymerization has been completed, takes the form. Process according to claim 1, characterized in that solid carbon dioxide is added as carbon dioxide snow or as crushed carbon dioxide ice in amounts of Q, 5, 30% by weight, based on the suspension formed. Method according to claims 1 and 2, characterized in that aluminum hydroxide is used as the filler. Method according to claims 1 and 2, characterized in that crystallallite is used as filler. Molded article, consisting wholly or partly of a process material according to one or more of the preceding claims, polymer material obtained.