HUT52534A - Ellipsoide particles - Google Patents

Abstract

The present invention relates to a process for producing ellipsoidal particles from mono-disperse latices and the particles so produced. The process involves (a) preparing a homogenous dispersion of the polymer particles in a matrix capable of affine deformation and having a higher softening temperature that the softening temperature of the dispersed polymer; (b) deforming into ellipsoids the dispersed polymer in the matrix at a temperature which is at or above the softening temperature of the polymer; (c) quenching the ellipsoids to a temperature below the softening temperature of the dispersed polymer to fix the ellipsoid into a rigid shape, and (d) recovering the rigid polymer particles.

Description

The process relates to brittle, non-spherical ellipsoidal polymer particles and their preparation. The size, weight and axis ratio of the non-spherical ellipsoids produced by the process may be varied as desired. The ellipsoidal particles thus produced are widely applicable in the field of colloidal research.

525 34-

EUO.PÍST INTERNATIONAL WORKING PARTY

PATENT OFFICE 'I N.IÁZ U 1 0 1533-7 3

Published. COPIES

6189

48 647 / BE

Elliptic particles

Miklós József Nagy, Budapest,

Date of application: 10.10.1988. 12th

My invention relates to a process for the preparation of ellipsoidal particles from monodisperse lattices, and to such particles.

Spherical particles, either original or latex, are used in many applications. The use of such particles is particularly widespread in chromatography, immunology, and as a standard for screening or electron microscopy as a standard for light scattering and the like. The use of particles in this direction represents a very significant part of today's colloidal research and application.

It is also known that such spherical particles can be converted to ellipsoidal particles; the field of application of the particles can be extended to many other areas due to the increase in the axial ratio of the ellipsoidal particles to the spherical ore.

• · · · · · · · · · · · · · · · · ·

Some publications have been published on non-spherical ellipsoidal particles produced from naturally occurring materials such as disk-shaped bentonite crystals, tobacco mosaic virus, human red blood cells, and inorganic materials such as iron oxide, barium sulfate, titanium oxide. A method for preparing such ellipsoids is described in J. Colloid and Interface Sci., Vol. 63, pp 509 (1978) by Schneider, P. et al., And J. Colloid and Interface Sci., Vol. 73, pp 295 (1980) by Boylan, C.W. et al.

Briefly, these methods produce ellipsoids by either splitting larger portions and forming the appropriate particles after nucleation using a growth-regulating process, or by using a difficult-to-handle aging process. The grain thus formed is rather narrow. A Boylan, C.W. et al., for example, subject human red blood cells to shear deformation and chemically solidify the resulting particles. Only one particle size (about 14 µm) and one axis ratio (about 4.6) are described in this specification, and there is no reference to the possibility of changing the particle size or axis ratio.

Another disadvantage of these prior methods is that neither the axis ratio nor the mass of the ellipsoid can be varied or controlled at the same time. In addition, the ellipsoids thus formed are presumably chemically and morphologically unstable, especially when post-treatment is used. It would be desirable to control these parameters so that they are designed to meet end-use requirements.

In my work I have found that the above parameters can be controlled if non-spherical, ellipsoidal, organic polymer particles are prepared by a suitable process.

The process of the present invention relates to the preparation of rigid non-spherical ellipsoidal particles from polymeric particles.

a) forming a homogeneous dispersion of particulate polymer particles in a matrix having a similar deformation and having a softening temperature greater than the softening temperature of the dispersed polymer;

b) deforming the matrix material containing the dispersed polymer under similar deformation conditions at or above the softening point of the dispersed polymer to form ellipsoidal particles of the dispersed polymer;

c) washing the thus formed ellipsoids, washing at a temperature below the softening point of the dispersed polymer to solidify the ellipsoids;

d) separating and recovering the polymeric particles having a volume distribution of dispersed, brittle, ellipsoidal and substantially the same as the starting polymer particles from the matrix material.

Ζ ·· * · ♦ · ·· * ·· ······

As used herein, the term polymer refers to both homo- and copolymers.

The term softening temperature as used herein refers to the higher of the glass transition temperature and melting point of the polymer.

The term similar deformation used in my description refers to a deformation that is independent of size and is uniform throughout the deformed region. The deformation can be elastic, ductile or can be induced by flow. Generally, the flow of liquid forced into solid boundaries will depend on the distance of the boundaries, producing a shear deformation that is not considered to be similar to the deformation described herein.

Prior to dispersing in the deformable matrix, the starting polymer particles are preferably spherical.

Materials suitable for use as polymer particles are those having a softening temperature of 50-200 ° C, preferably 70-100 ° C.

Preferred polymers that are well convertible to non-spherical ellipsoidal particles are, for example, polystyrene and poly (methyl methacrylate).

The deformable bedding material is a solid, preferably a polymer. The stretching ratio of the bedding material is at least twice, preferably 4-5 times that of the dispersed starting polymer at operating temperature.

The local deformation in a solid bed material is a stretching scar and may be a function of the stretch ratio. The polymer particles convertible into an ellipsoid are dispersed in a non-soluble matrix material. The concentration of the dispersed polymer is less than 50%, preferably 10% and more preferably 2% by volume of the dispersion. If a high concentration of polymer is dispersed in the matrix material within the above concentration range, it is necessary to ensure that the viscosity of the softened polymer and the matrix material is maintained during the deformation operation.

Prior to association with the matrix, the surface of the polymer particles may be modified to form a homogeneous and stable dispersion.

Conversion of the matrix material containing the dispersed polymer into non-spherical ellipsoids can be accomplished, for example, by axial stretching or by axial compression. The deformation is preferably carried out at a temperature above the softening point of the dispersed polymer but below the polymer softening point of the matrix.

In order to solidify the dispersed polymer in the bedding material, the dispersion must be washed rapidly at temperatures below the softening point of the dispersed polymer.

The resulting solid, non-spherical, dispersed polymer may be separated from the matrix by any of the methods well known in the art. The separation is preferably carried out with a solvent which selectively dissolves the matrix material, such as a solid, non-spherical, dispersed polymer particles in the form of an ellipse, for example by simple filtration or by filtration. centrifugation.

The surface of the non-spherical ellipsoids thus formed can be modified. Physical adsorption, chemical reaction or a combination thereof may be used as surface modifying process. Such modifying techniques may, for example, control the hydrophobic properties of the particles or promote the attachment of a functional material such as an enzyme, cell or metal coating to the surface of the particle.

In addition, the present invention relates to a process for making rigid, non-spherical ellipsoids from spherical polymer particles by:

a) forming a homogeneous dispersion of spherical polymer particles in a bulk material having a similar deformation and having a softening temperature greater than the softening temperature of the dispersed polymer;

b) axially deforming the matrix material containing the dispersed polymer under similar deformation conditions at or below the softening point of the dispersed polymer so as to form ellipsoidal particles of the dispersed polymer;

c) washing the thus formed ellipsoids, washing at a temperature below the softening point of the dispersed polymer to solidify the ellipsoids;

d) separating and recovering the dispersed, brittle, lipidoid, and substantially polymeric particles having a volume distribution corresponding to the volume distribution of the starting polymer particles from the matrix material.

The significance of the method of the present invention is that the size, weight and axis ratio of non-spherical ellipsoids can be varied and controlled as desired. In addition, the mass or volume distribution of the ellipsoids is the same, so long as the standard deviation in the ratio of the ratio of polymer to polydispersed material is less than 20% of the arithmetic mean of the ratio.

Not a sphere produced by the process of the present invention

The volume of the ellipsoids -213 -123 varies from 10 m to 10 m and has a constant shape. The axis ratio of the particles (ratio of the longest and shortest axes of the ellipsoids) is 1-12 if the stretch ratio is not greater than 5.

Accordingly, my invention relates to brittle, non-spherical, substantially uniform volume and stable ellipsoidal particles having a volume of 10 ^{2 to} 10 ¹² m ³ , a standard mass or volume difference of about 3%, and an axis ratio of up to 12.

Thus, for example, particles with an axial ratio greater than 6 can be obtained at 4 stretch ratios.

The process of the present invention makes it possible to produce non-spherical polymeric ellipsoids which have substantially the same volume distribution as the parent polymer particles and whose axis ratio can be varied as desired, provided the particles have a constant volume distribution.

The following examples illustrate the process of the invention in more detail.

EXAMPLES

Solid polyvinyl alcohol (PVA, softening point)

Above 200 ° C) a polystyrene (PS) dispersion was prepared by pouring a film of aqueous PVA solutions containing PS particles.

150 g of a 4.79 wt.% Fully hydrolyzed PVA sample (BDH 125) and 1.2 g of PS latex (Sigma Chemical Co., LB-5, solids content 9.0 wt.%) Were weighed into a beaker and with a magnetic stirrer for 15 minutes. The average particle diameter was 0.46 µm (standard deviation 0.0048 µm).

cm of homogeneous dispersion was poured into a 14x21 cm perspex film casting frame fixed on a horizontal table and allowed to dry for four days. To prevent the ingress of dust and other chemical contaminants, the film frame is covered with a cardboard box. The air-dried film was easily removed from the surface of the frame. The solid dispersion thus obtained had a particle concentration of 1.5% by weight.

The average thickness of the air-dried film was 0.07 mm.

The resulting film was then stripped of about 12 x 60 mm foils and immersed in a hot silicone oil bath for 10 seconds before deformation to remove residual water and dissolved air. The temperature of the oil bath was 200 ± 3 ° C. This treatment is used to prevent bubble formation. Otherwise, the resulting bubble blues may cause local deformation of the microparticles. This heat treatment results in 10-15% near isotropic shrinkage of the strips.

The cured ribbons are mounted side by side on a stretching frame so that they have an approximately 11x40 mm area for deformation.

The bands were then immersed in an oil bath of 200 + -3 ° C and stretched by hand to a predetermined stretch ratio. The stretching speed was adjusted to an average of 3-5 cm / s. The film was kept in hot oil for about 10 seconds. After deformation, the tapes were quickly cooled to room temperature and excess oil was removed with tissue paper. In a series of measurements, 20 to 30 strips were stretched to a specific stretch ratio. Three stretch ratios were selected, namely 1.5, 2.0 and 3.0.

In order to avoid non-homogeneous deformation of the particle shapes (e.g., around the strip holding tweezers), the middle portion of the strips stretched in parallel were cut out and used for the remainder of the experiment. The remaining oil layer adhered to the strips surface was washed with n-propanol and the deformed strips were placed in distilled water or a 30:70 volume mixture of n-propanol and distilled water to swell the strips overnight (10 hours). A 50 cm ³ swelling mixture was used for 1 g of the extended film composition. After swelling, the mixture • ·

The temperature of 10 was slowly raised to 80-85 ° C to begin the dissolution temperature of the tapes. After complete dissolution, the mixture was cooled to room temperature and the particles separated by a low speed (about 3000 rpm) slope centrifuge. This purification was repeated twice using distilled water or a 30:70 by volume mixture of n-propanol and distilled water as the dispersion medium. The hyg suspension of the eluted particles was kept in sealed bottles at room temperature. No sedimentation or other instability occurred during the few weeks of the study period.

Standard electron microscopy was used to determine the shape of the particles. The study clearly showed that the particles were elliptical, and that the average axis ratio and distribution of the particles could be detected by measurement. For each series of measurements, the usual carbon film method and a 9200x magnification were used. Additional four-fold photographs were taken to determine size and shape. For the three stretch ratios given above, axial ratios of 2.1, 3.1 and 6.0 were obtained, respectively. The percentage deviation in the arithmetic mean of the axis ratio was about 4 to 15-20%. The overall experimental error for the whole procedure was 10-20%.

Application of the above-described process can be extended from 0.2 to 0.3 microns is also _close deforming diameter spherical polystyrene particles. The high molecular weight poly (with vinyl) ·························································· ·

Copolymers can be used to reduce the stretching temperature instead of 11 cans. If necessary, a plasticizer such as glycerol or ethylene glycol may be added to the polymer.

Claims

Claims (3)

A process for the preparation of rigid, non-spherical ellipsoids from polymeric particles, characterized in that: a) forming a homogeneous dispersion of particulate polymer particles in a matrix having a similar deformation that has a softening temperature greater than the softening temperature of the dispersed polymer; b) deforming the matrix material containing the dispersed polymer under similar deformation conditions at or below the softening point of the dispersed polymer to form ellipsoidal particles of the dispersed polymer; c) washing the ellipsoids thus formed, washing at a temperature below the softening point of the dispersed polymer to solidify the ellipsoids; d) separating and recovering the polymeric particles having a volume distribution of dispersed, brittle, ellipsoidal and substantially the same as the starting polymer particles from the matrix material. 2. A process for producing rigid, non-spherical ellipsoidal spherical polymer particles, characterized in that: a) forming a homogeneous dispersion of spherical polymer particles in a bulk material having a similar deformation and having a softening temperature greater than the softening temperature of the dispersed polymer; b) deforming the matrix material containing the dispersed polymer in an axial direction under similar deformation conditions at or below the softening point of the dispersed polymer to form ellipsoidal particles of the dispersed polymer; c) washing the thus formed ellipsoids, washing at a temperature below the softening point of the dispersed polymer to solidify the ellipsoids; d) separating and recovering the polymeric particles having dispersed, brittle, ellipsoidal and substantially volume distribution of the parent polymer particles from the matrix material. 3. Rigid, non-spherical, ellipsoidal and substantially uniform volume stable polymer particles characterized by: