EP-4736999-A1 - DEVICE FOR PREPARATION OF EXPANDED MICROSPHERES

EP4736999A1EP 4736999 A1EP4736999 A1EP 4736999A1EP-4736999-A1

Abstract

The present disclosure relates to a method and a device for producing expanded microspheres.

Inventors

AJDÉN, Per Erik
HOLMLUND, Ulf Thomas
SVENSSON, Per Olov Fredrik

Assignees

Nouryon Chemicals International B.V.

Dates

Publication Date: 20260506
Application Date: 20251016

Claims (15)

A device for expanding unexpanded, thermally expandable microspheres comprising: - a heating zone having an inlet and an outlet, wherein the inlet is configured to receive a slurry of unexpanded, thermally expandable microspheres; - a first pump upstream of and in fluid communication with the heating zone inlet; - an expansion zone with an inlet and an outlet, said inlet of the expansion zone being connected to the outlet of the heating zone, wherein the expansion zone is configured to be at a lower pressure than the heating zone; - a flow control device downstream of and in fluid communication with the outlet of the expansion zone; - a fluid inlet disposed between the outlet of the expansion zone and the flow control device; - a fluid metering device configured to control an addition rate of a dilution liquid introduced at the fluid inlet; and - a controller, wherein at least one of the first pump, the flow control device, and the fluid metering device is operatively linked to the controller, and wherein the controller is programmed to: receive at least a first flow rate signal related to a first flow rate generated by the first pump, a second flow rate signal related to a second flow rate generated by the flow control device, and a third flow rate signal related to a third flow rate of the dilution liquid, calculate the density of expanded microspheres in response to at least the first flow rate, the second flow rate, and the third flow rate, and control the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.
The device of claim 1, wherein the device further comprises a first flow sensor disposed between the first pump and the inlet of the heating zone and communicatively linked to the controller, the first flow sensor configured to provide the first flow rate signal to the controller.
The device of claims 1 or 2, wherein the device further comprises a second flow sensor disposed downstream of the flow control device and communicatively linked to the controller, the second flow sensor configured to provide the second flow rate signal to the controller.
The device of any one of claims 1-3, wherein the device further comprises a third flow sensor communicatively linked to the fluid metering device and the controller, the third flow sensor configured to provide the third flow rate signal to the controller.
The device of any one of claims 1-4, wherein the flow control device is a second pump or a flow adjuster, preferably a second pump.
The device of any one of claims 1-5, wherein the fluid metering device is a third pump.
The device of any one of claims 1-6, wherein the device further comprises a static mixer disposed downstream of the flow control device.
The device of any one of claims 1-7, wherein the flow control device is operatively linked to the controller, and wherein the controller is programmed to control the density of the expanded microspheres by controlling the second flow rate.
The device of claim 8, wherein the fluid metering device is operatively linked to the controller, and wherein the controller is programmed to control the density of the expanded microspheres by controlling the second flow rate and the third flow rate.
A process for expanding unexpanded, thermally expandable microspheres comprising a polymer encapsulating a blowing agent, wherein said blowing agent is a liquid having a boiling temperature not higher than the softening temperature of the polymer shell, the process comprising: - feeding a slurry of unexpanded, thermally expandable microspheres into a heating zone using a first pump operating at a first pump speed to generate a first flow rate, - heating the microspheres to a temperature above their softening temperature, while under a pressure sufficiently high to ensure they do not fully expand; - passing the so-heated microspheres from the heating zone to an expansion zone, such that a pressure drop is created, resulting in a pressure in the expansion zone sufficiently low for the microspheres to expand, - removing the expanded microspheres from the expansion zone and diluting the expanded microspheres with a dilution liquid introduced at a fluid inlet by a fluid metering device operating at a third flow rate to obtain a final slurry solid content value, and - transporting the diluted expanded microspheres to a flow control device operating at a second flow rate; wherein a controller operatively linked to at least one of the first pump, the flow control device, and the fluid metering device, calculates the density of expanded microspheres in response to at least the first flow rate, the second flow rate, and the third flow rate, and controls the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.
The process of claim 10, wherein the first flow rate is determined by a first flow sensor disposed between the first pump and the inlet of the heating zone and communicatively linked to the controller, wherein the second flow rate is determined by a second flow sensor disposed downstream of the flow control device and communicatively linked to the controller, and wherein the third flow rate is determined by a third flow sensor communicatively linked to the fluid metering device and the controller.
The process of claims 10 or 11, wherein the flow control device is a second pump operating at a second pump speed to generate the second flow rate.
The process of any one of claims 10-12, wherein the dilution liquid is water or an aqueous composition.
The process of any one of claims 10-13, wherein the controller controls the density of the expanded microspheres by controlling at least the second flow rate.
The device of any one of claims 1-9 or the process of any one of claims 10-14, wherein the controller is further programmed to receive an initial density value and/or an initial solid content value for the slurry of unexpanded, thermally expandable microspheres, and to calculate the density of expanded microspheres in response to at least the first flow rate, the second flow rate, the third flow rate, and one or both of the initial density value or the initial solid content value.

Description

TECHNICAL FIELD The present disclosure relates to a method of producing expanded microspheres and a device therefore. BACKGROUND Thermally expandable microspheres are known in the art and described in detail in, for example, US Patent No. 3615972. Various grades of expandable microsphere, having different expansion temperature, are commercially available from Nouryon under the trademark Expancel™, both as dry free flowing microspheres and as an aqueous slurry of microspheres. Such expandable microspheres comprise a blowing agent encapsulated within a thermoplastic shell. Upon heating, the blowing agent evaporates to increase the internal pressure, at the same time as the shell softens, resulting in significant expansion of the microspheres, normally from 2 to 5 times their diameter. Thermoplastic microspheres can be used in various applications in both unexpanded or pre-expanded states. Examples of products where dry (essentially water free) pre-expanded microspheres are used are as sensitizer in emulsion explosives and as light weight filler in solvent based paints and various thermosetting materials such as cultured marble, polyester putty and artificial wood. In many products, such as water based paints and coatings, thermal printing papers, porous ceramics and emulsion explosives, wet pre-expanded microspheres are used. Transporting pre-expanded microspheres requires significant space, for which reason the unexpanded microspheres often are transported to the end user wishing to use expanded microspheres and are then expanded on-site. The microspheres may then be expanded close to or directly into a process for producing the final product, e.g. any of those mentioned above. Various methods and devices have been developed for expanding thermoplastic microspheres. US 5484815 and US 7192989 disclose methods and devices suitable for expanding dry microspheres. US 4513106 discloses a method and a device suitable for expanding microspheres in an aqueous slurry by introducing steam to the slurry in a pressure zone in an amount sufficient for heating the microspheres and at least partially expand them, followed by allowing the partially expanded microspheres to leave the pressure zone under a pressure drop whereby the microspheres are further expanded and accelerated into a stream with a velocity of at least 1 m/s. In WO2014198532 an expander for non-expanded thermally expandable microspheres is described, wherein a slurry of the microspheres in a suitable carrier is brought into a pressure zone and heated without contacting the slurry directly with the heating medium. The heating zone may for example be a heat exchanger. The advantage of the indirect heating, over steam expansion, is that there is no need to introduce (extra) water into the slurry. The indirect heating also allows for other heating- and slurry media than steam and water, and thus creates a wider flexibility in temperature ranges. The apparatus disclosed in WO2014198532 comprises a heating zone which is capable of withstanding a pressure of at least 4 bars. The apparatus comprises a pump for feeding a slurry of thermally expandable thermoplastic microspheres into the heating zone. The pump is capable of generating a pressure of at least 4 bars in the heating zone. The pressure within the heating zone is maintained such that the thermally expandable thermoplastic microspheres do not fully expand. The apparatus comprises a means for heating the slurry of thermally expandable thermoplastic microspheres in the heating zone to a temperature of at least 60 °C without any direct contact of the slurry to any fluid heat transfer medium. After the microspheres are heated in the heating zone, the slurry is withdrawn from the heating zone and experiences a pressure drop, into a zone with a pressure sufficiently low for the microspheres to start expanding. A further improvement of an expansion device is described in WO2016091847. To reduce potential agglomeration of expanded particles, the slurry is withdrawn from the heating zone through an outlet pipe, and the microparticles start to expand in the outlet pipe, after they have left the heating zone where they were heated under pressure. in WO2016091847 it is described that the outlet pipe (where the microparticles start to expand) may be attached to a downstream distribution pipe (also referred to as "mixing zone"). The distribution pipe has an inlet for a cooling medium, and the outlet pipe is attached downstream of this inlet to the distribution pipe (or "mixing zone") between the inlet and an outlet of the distribution pipe. As an additional measure, to keep the pressure in the heating zone sufficiently high, it is thought in WO2016091739 to put a back pressure generator in fluid communication with the heating zone, said back pressure generator being capable of increasing pressure in the heating zone, after which the particles experience a pressure drop and begin to expand (e.g in the "expansion zone" th