WO2002077050A1

WO2002077050A1 - Discrete microcavity particles having a flexible wall structure

Info

Publication number: WO2002077050A1
Application number: PCT/EP2002/002079
Authority: WO
Inventors: Rudolf Nastke; Gerald Rafler
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2001-03-08
Filing date: 2002-02-27
Publication date: 2002-10-03
Also published as: EP1370594A1; DE10111094A1

Abstract

The invention relates to discrete microcavity particles having a flexible polymer wall structure, a method for the production of said particles and the use of the same as compounding materials for thermoplastic polymers, additives for paints and varnishes, latex, dispersions, emulsions or suspensions of prepolymers.

Description

Discrete micro hollow particles with a flexible wall structure

The present invention relates to discrete micro hollow particles with a flexible polymeric wall structure, a process for their production and their use as compounding materials for thermoplastic polymers, additives for paints and varnishes, latexes, dispersions, emulsions or suspensions of prepolymers.

Hollow microspheres are generally made from inorganic substances, and here primarily from glass or ceramic materials, as taught in US Pat. No. 5,217,928. A main field of application of these materials is the compounding of thermoplastics (US 5,017,629) or the use for silicone rubber (JP 58057462). Another area of application of hollow microspheres extends to the catalytic field, with microporous materials in particular as particularly light carriers serve for catalysts (US 4,820,503) or metallic or metallized polymer-based hollow particles, for example used as conductive components in paints and adhesives, in particular in the electronics industry (US 5,024,695). In medicine, gas- or air-filled particles are already used as ultrasound reflectors in clinical examination methods (WO 92/05806). In polymer compounding, hollow particles are also used to a considerable extent, which are based on organic starting materials or which are expandable particles as blowing, blowing and nucleating agents (EP 0 998 521). Mineral hollow particles are also used for the production of decorative foils, furniture panels, decorative papers and the like. The synthesis and use of hollow particles in latexes is also known from the prior art, the hollow particles serving as extenders, pigmenting elements, carriers for auxiliaries and color additives (US Pat. No. 5,521,253). The use of organosilicon compounds as wall-forming materials for hollow spheres is also known, for example, from EP 0 820 807.

The disadvantages of the processes mentioned here are in particular the properties of the hollow particles produced in this way, which severely restrict their use in many fields of application. Above all, these include such negative properties as brittleness, insufficient flexibility, high bulk densities (as is the case with glass and ceramics), insufficient temperature stability, plasticization behavior under extrusion conditions, thermolytic degradation and the associated discoloration of the Materials, compatibility problems, or quality degradation, for example due to process additives. It was therefore the object of the present invention to eliminate the disadvantages of the prior art described and to produce discrete hollow microparticles with a defined surface structure, wall morphology and particle size and to dispense with the addition of quality-reducing additives.

The object is achieved in relation to the hollow microparticles by the features of claim 1 and in relation to the method for production by the features of claim 13. The use of the hollow microparticles is described in claims 41 to 44. The further subclaims show advantageous developments of the invention.

According to the invention, the discrete micro hollow particles have a flexible polymeric wall structure which encloses at least one cavity. The polymeric wall structure consists of an aminoplast, the ratio between the wall thickness and the particle outside diameter being at least 1:10. The structure of these micro-hollow particles corresponds to the core-shell type, the core being the cavity or a cavity-containing matrix and the shell being formed by the aminoplast wall structure.

The aminoplasts used are preferably those based on a precondensate composed of melamine, urea, benzoganamine, acrylamide and / or a mixture thereof and an aldehyde. The aldehyde is preferably selected from the group of the mono- and dialdehydes, formaldehyde, glyoxal, glutaraldehyde and mixtures thereof being particularly preferred.

In a preferred variant, the hollow microparticles can also be incorporated by incorporating organosilanes hydrophobic and / or flame retardant properties.

The micro hollow particles preferably have a particle outside diameter between 500 nm and 200 μm, particularly preferably between 1 μm and 50 μm. The particular advantage here is that the particle size and the particle size distribution can be set specifically for the different fields of application.

The hollow microparticles advantageously also have a very low bulk density. In the dried state, this is preferably between 30 and 200 g / l, particularly preferably between 30 and 90 g / l.

The micro hollow particles preferably have a spherical shape. The wall structure of these hollow microparticles can preferably also have micropores. This wall structure can not only have a single cavity, but also a cavity matrix, e.g. a porous material.

The process for producing discrete micro hollow particles with a flexible polymer wall structure with at least one cavity with a ratio between wall thickness and particle outer diameter of at least 1:10 is based on the following steps:

a) an aminoplast precondensate is introduced into a dispersion of two essentially immiscible phases,

b) the wall structures are formed by polymerizing an aminoplast precondensate at the phase interfaces in the dispersion, c) the particles thus formed are separated from the dispersion and

d) the particles are dried to form the cavities.

In a preferred variant, the dispersion is prepared in step a) from an aqueous solvent and a gas. Preferred gases are preferred

Nitrogen and / or carbon dioxide used. Carbon dioxide can also be used under supercritical conditions. If the gases are dispersed in the reaction medium, small amounts of a protective colloid, such as e.g. Polyethylene glycol or cellulose ether is used to avoid the coalescence of the gas bubbles.

In a further variant, a dispersion is formed from an aqueous solvent and an organic solvent which is essentially immiscible therewith. Aliphatic, cycloaliphatic and / or aromatic hydrocarbons, also in substituted form, can preferably be used as organic solvents. Solvents from the group of pentane, hexane, heptane, cyclohexane, methylcyclohexane, decalin, benzene, toluene, xylene, diethyl ether, dibutyl ether and petroleum ether are particularly preferred.

In a further preferred variant, the dispersion is prepared in step a) from an aqueous solvent and a solid. For example, a salt that decomposes under acidic conditions with the formation of gas, such as finely divided calcium carbonate, is used as the solid. IV) t) oo cπ cπ

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not primarily for absorption and adsorption purposes, but preferably for compounding plastics, e.g. in their extrusion, injection molding, pressing, blowing. The hollow microparticles can also be used for the production of closed-cell foams by gluing the individual particles in shape-forming processes. The hollow microparticles can be used as additives for latices, paints, varnishes and pastes, e.g. in primers as a force-absorbing component for stone chip protection or as a sound absorber in anti-drone pastes or similar products. For example, stone chip protection is improved compared to the usual use of hollow glass spheres in the base coats by e.g. segregation due to the much lower bulk density of the hollow polymeric body can be prevented, and that due to the good flexibility of the hollow plastic spheres in the event of a stone impact there is generally no destruction of the hollow sphere with the formation of micro-cracked structures. These micro-cracked structures could then contribute to corrosion damage when exposed to moisture and temperature. Due to the flexibility of the wall structures, these impact forces can be absorbed, however, only deformations could be demonstrated.

The subject according to the invention is intended to be explained in more detail with reference to the following examples, without restricting it to these examples.

Example 1:

Production of a pre-condensate based on melamine

1 mol of melamine is stirred in 3.5 mol of a 30th

% By weight formalin solution. After setting the pH with 1 N aqueous sodium hydroxide solution to pH 8-9, the solution is heated to 80 ° C. and stirred at this temperature for 20 to 120 minutes, preferably 30 to 60 minutes. Then you cool down to room temperature.

Example 2:

Production of a pre-condensate based on melamine

1 mol of melamine is dissolved in 800 g of 25% by weight aqueous glutardialdehyde solution (2 mol) with stirring. The pH is then adjusted to 6 to 7 with 1N aqueous sodium hydroxide solution and the solution is heated to a temperature of 50 ° C. and stirred at this temperature for 10 to 60 minutes, preferably 20 to 30 minutes. The precondensate is added directly to the dispersion medium.

Example 3: Partially etherified melamine resin precondensate

4450 ml of 30% formalin are adjusted to pH 9 at 80 ° C. with 1N NaOH. 1000 g of melamine are added and the melamine is dissolved after about 2 minutes with an increase in temperature. Shortly before boiling begins, the resin solution is cooled to 60 ° C. 4300 ml of methanol and 45 ml of dilute HCl (1: 1) are added to the precipitated methylolmelamines. The reaction temperature must not exceed 60 ° C. After etherification is complete, 100 g of triethanola in are added and about 2500 ml of a methanol-water mixture are distilled off in vacuo, the temperature not exceeding 60.degree. 166 g of urea are added to the resin solution and the mixture is stirred for a further 60 min with cooling. Example 4:

Production of a pre-condensate based on urea

60 g of urea are introduced into 300 ml of 30% strength by weight aldehyde solution with stirring, the pH is adjusted to 7 to 8 with 1N aqueous sodium hydroxide solution and at 70 ° C. for a time of 10 to 60 minutes, preferably 20 to 40 Minutes reacted. The pre-condensates can then be cooled to room temperature or they are transferred directly to the dispersion.

Example 5:

Manufacture of discrete hollow particles

200 ml of water, 100 ml of hexane and 15 ml of an acid mixture of 35% strength by weight aqueous acetic acid and 2 N citric acid in a volume ratio of 1: 1 are placed in a stirred vessel and mixed vigorously with a dispersion stirrer. 100 ml of the precondensate produced in Example 1 are then quickly introduced, with the stirring intensity remaining the same. After approx. 15 minutes, the precondensate has deposited on the surface of the dispersed phase with the formation of spherical particles. A suspension of microparticles containing hexane is obtained. After separation of the continuous phase and evaporation of the hexane by suction or pressure filtration and drying, these particles form hollow spheres with a diameter of 1 to 30 μm, which are fed directly to the application. The bulk weight is 45 g / 1.

Example 6: Production of hydrophobized hollow spheres The procedure is as in Example 5, with 10% by weight poly (dimethylsiloxane) partially having hydroxyl end groups being added to the hexane phase. The hollow particles obtained in the final phase are hydrophobic and have a flame-retardant effect.

Example 7:

Hollow particle synthesis using gases

In a vertical tube reactor, which is equipped with a mammoth pump and a membrane part, water as the continuous phase, the precondensate and the catalyst acid are introduced and a protective colloid based on cellulose or polyethylene glycol is added. Subsequently, nitrogen is dispersed in this solution over the membrane in a laminar flow and enveloped by the condensation process of the resin component. After about 60 minutes at a temperature of 50 ° C this process is complete and the hollow particles are separated by filtration and dried gently.

Example 8:

Hollow particle synthesis using salts

20 1 of water, 8 1 of precondensate according to Example 3 and 1.2 1 2 N aqueous citric acid as an acid catalyst are placed in a reactor vessel and heated to 60.degree. After a pre-condensation time of 8 minutes, a mixture of 2 1 pre-condensate according to Example 3, 500 ml of poly (dimethylsiloxane) and 5 kg of finely divided calcium carbonate is stirred therein with high agitation (eg 3000 rpm with Polytron PT80F-600 from Kinematika) Dispersed solution. The process is complete after 60 minutes, the solid constituents are separated off, washed with acid and gently dried. Example 9:

Synthesis of hollow spheres using polystyrene particles

The hollow particles are synthesized and prepared analogously to Example 8. Polystyrene particles obtained by cryomilling are used, which were also treated with a poly (dimethylsiloxane) before they were used. The coated and separated particles are treated with acetone in a washing process and then dried. The polystyrene-containing acetone solution is then processed in a suitable manner.

Example 10: Synthesis of hollow spheres using polyacrylic acid gels

In a suitable reactor, equipped with appropriate stirring technology, water, pre-condensate solution e.g. according to Example 4 and the acid catalyst based on citric acid and ascorbic acid, heated to 60 ° C and carried out for a maximum of 10 minutes, but at least 3 minutes, the precondensation. Then you give e.g. a ground swollen superabsorbent based on polyacrylic acid (DOW). If hydrophobic and / or flame-retardant finish is desired, the use of silicone compounds analogous to Examples 8 and 9 is required.

Claims

claims

1. discrete micro hollow particle with a flexible polymeric wall structure which encloses at least one cavity,

characterized ,

that the wall structure consists of an aminoplast and the ratio between wall thickness and particle outer diameter is at least 1:10.

2. Discrete hollow microparticles according to claim 1, characterized in that the aminoplast is based on a pre-condensate of melamine, urea, benoguananamine, acrylamide and / or a mixture thereof and an aldehyde.

3. Discrete micro hollow particles according to claim 2, characterized in that the aldehyde is selected from the group of mono- and dialdehydes.

4. Discrete micro hollow particles according to claim 2 or 3, characterized in that the aldehyde is selected from the group formaldehyde, glyoxal, glutaraldehyde and mixtures thereof.

5. Discrete hollow microparticles according to at least one of claims 1 to 4, characterized in that the hollow microparticles have hydrophobic and / or flame-retardant properties by incorporating organosilanes.

6. Discrete micro hollow particles according to at least one of claims 1 to 5, characterized in that the particle outer diameter is between 500 n and 200 microns.

7. Discrete micro hollow particles according to claim 6, characterized in that the particle outer diameter is between 1 μm and 50 μm.

8. Discrete hollow microparticles according to at least one of claims 1 to 7, characterized in that the hollow microparticles have a bulk density of between 30 and 200 g / L in the dried state.

9. Discrete hollow microparticles according to claim 8, characterized in that the hollow microparticles have a bulk density of between 30 and 90 g / L in the dried state.

10. Discrete hollow microparticles according to at least one of claims 1 to 9, characterized in that the hollow microparticles have a spherical shape.

11. Discrete hollow microparticles according to at least one of claims 1 to 10, characterized in that the wall structure has micropores.

12. Discrete micro hollow particles according to at least one of claims 1 to 11, characterized in that the wall structure surrounds a cavity matrix.

13. A process for producing discrete micro hollow particles with a flexible polymeric wall structure which encloses at least one cavity, the ratio between wall thickness and particle outer diameter being at least

Is 1:10, with the following steps:

b) the wall structures are formed by polymerizing an aminoplast precondensate at the phase interfaces in the dispersion,

c) the particles thus formed are separated from the dispersion and

d) the particles are dried to form the cavities.

14. The method according to claim 13, characterized in that in a) the dispersion of an aqueous solvent and a

Gas is produced.

15. The method according to claim 14, characterized in that nitrogen and / or carbon dioxide is used as the gas.

16. The method according to at least one of claims 13 or 15, characterized in that the dispersion is additionally a protective colloid, such as polyethylene glycol or cellulose ether, to avoid the coalescence of the gas bubbles.

17. The method according to claim 13, characterized in that in a) the dispersion is prepared from an aqueous solvent and a substantially immiscible organic solvent.

18. The method according to claim 17, characterized in that aliphatic, cycloaliphatic and / or aromatic hydrocarbons, also in substituted form, are used as organic solvents.

19. The method according to claim 18, characterized in that the organic solvent is selected from the group pentane, hexane, heptane, cyclohexane, methylcyclohexane, decalin, benzene, toluene, xylene, diethyl ether, dibutyl ether and petroleum ether.

20. The method according to claim 13, characterized in that in a) the dispersion is prepared from an aqueous solvent and a solid.

21. The method according to claim 20, characterized in that a solid which is a decomposable gas-forming salt, e.g. a carbonate is used.

22. The method according to claim 20, characterized in that a salt and / or polymer which is soluble in organic solvents is used as the solid.

23. The method according to claim 20, characterized in that as a solid

Gel, for example based on polyacrylic acid, cellulose or amino resin, is used.

24. The method according to at least one of claims 13 to 23, characterized in that organosilanes are added to the dispersion in a).

25. The method according to claim 24, characterized in that in a) polydimethylsiloxane is added to the dispersion.

26. The method according to claim 25, characterized in that the polydimethylsiloxane has hydroxyl end groups.

27. The method according to at least one of claims 13 to 26, characterized in that in a) an organic acid is additionally added as a catalyst for the polymerization in the dispersion.

28. The method according to claim 27, characterized in that the organic acid is selected from the group formic acid, acetic acid, citric acid, ascorbic acid and polymethacrylic acid.

29. The method according to at least one of claims 13 to 28, characterized in that for b) the aminoplast precondensate is produced from melamine, urea, benzoguanamine, acrylamide and / or a mixture thereof and an aldehyde.

30. The method according to claim 29, characterized in that a mono- and / or dialdehyde is used to produce the amine plastic precondensate.

31. The method according to at least one of claims 27 or 30, characterized in that formaldehyde, glyoxal, glutaraldehyde and / or a mixture thereof is used to prepare the aminoplast precondensate.

32. The method according to at least one of claims 29 to 31, characterized in that the aminoplast precondensate of melamine and a monoaldehyde in

Molar ratio between 1: 2.5 and 1: 6 is produced.

33. The method according to at least one of claims 29 to 31, characterized in that the aminoplast precondensate is made from melamine and a dialdehyde in a molar ratio between 1: 2 and 1: 4.5.

34. The method according to at least one of claims 13 to 33, characterized in that in step c) the separation by a solid / liquid separation, e.g. with a Nutsche filter, a band filter, a centrifuge or a membrane filter apparatus.

35. The method according to at least one of claims 13 to 34, characterized in that in step d) drying is carried out by circulating air dryer, belt filter dryer and / or filter dryer.

36. The method according to claim 35, characterized in that the drying temperature is between room temperature and 60 ° C.

37. The method according to at least one of claims 13 to 36, characterized in that the size of the microparticles can be controlled via the stirring speed, the stirring head dimensions and / or the container dimensions.

38. The method according to at least one of claims 13 to 37, characterized in that the wall thickness can be controlled via the volume ratio of the two essentially immiscible phases.

39. The method according to at least one of claims 13 to 38, characterized in that hollow microparticles are produced with a spherical shape.

40. The method according to at least one of claims 13 to 39, characterized in that hollow microparticles are produced with a microporous wall structure.

41. Use of the hollow microparticles according to at least one of claims 1 to 12 as a compounding agent for thermoplastics in the processing thereof.

42. Use of the hollow microparticles according to at least one of claims 1 to 12 as an additive for plastics, paints, lacquers, pastes, casting compounds, carriers for active substances and / or sorbents.

43. Use of the hollow microparticles according to at least one of claims 1 to 12 in primers as a force-absorbing component for stone chip protection.

44. Use of the hollow microparticles according to at least one of claims 1 to 12 as sound absorbers in anti-drone pastes.