PROCESS FOR THE PRODUCTION OF AN ELASTOMER AGGLOMERATE COMPOSITION

Abstract

A process for the production of an elastomer agglomerate composition wherein the process comprises the steps in this order: (a) providing a slurry comprising elastomeric particles having an average particle size of 150 nm in water; and (b) forcing the slurry from (a) through an aperture at a flow velocity of at least 500 m/s. The elastomer agglomerate compositions produced via such process demonstrate a particularly desirable high average particle size.

Claims

1. A process for the production of an elastomer agglomerate composition wherein the process comprises the steps in this order: (a) providing a slurry comprising elastomeric particles having an average particle size of 150 nm in water; and (b) forcing the slurry from (a) through an aperture at a flow velocity of at least 500 m/s.

2. The process according to claim 1, wherein the material flow through the aperture is confined by a flat first surface and a flat second surface together forming a channel.

3. The process according to claim 1, wherein the slurry is introduced at a pressure of 40 and 60 MPa.

4. The process according to claim 1, wherein the slurry comprises 20.0 wt % of elastomeric particles with regard to the total weight of the slurry.

5. The process according to claim 1, wherein the elastomeric particles are selected from polybutadiene particles, poly(styrene-butadiene) particles, poly(acrylonitrile butadiene) particles or polybutylacrylate particles.

6. The process according to claim 1, wherein the process is performed using a valve assembly comprising the aperture, the valve assembly further comprising a seat, a flow channel through which the slurry flows at a certain pressure towards the aperture, and a valve subjected to a pressure in the direction opposite the flow direction of the slurry, wherein the seat comprises a central opening forming the flow channel, and wherein the valve pressure and the pressure of the slurry are arranged such that the slurry is forced through the aperture at a flow velocity of at least 500 m/s.

7. The process according to claim 6, wherein the seat is a circular seat comprising a circular opening.

8. The process according to claim 1, wherein the slurry is forced through the aperture at a flow velocity of at least 700 m/s and at most 1000 m/s.

9. The process according to claim 1, wherein the elastomeric particles account for at least 98.0 wt % of the total weight of solid ingredients in the slurry.

10. An elastomer agglomerate composition produced according to the process of claim 1, wherein the elastomer agglomerate composition comprises less than 0.02 wt %, with regard to the total weight of the elastomer agglomerates in the elastomer composition, of agglomerates having a particle size of >3000 nm.

11. The elastomer agglomerate composition according to claim 10, wherein the elastomer agglomerate composition comprises <30 wt % of elastomer agglomerates having a particle size of <200 nm, with regard to the total weight of the elastomer agglomerates.

12. The elastomer agglomerate composition according to claim 10, wherein the elastomer agglomerate composition comprises 60 wt % with regard to the total weight of the elastomer agglomerates, of agglomerates having a particle size of >200 nm and 1000 nm.

13. The elastomer agglomerate composition according to claim 10, wherein the elastomer agglomerate composition comprises 10.0 wt % of elastomer agglomerates having a particle size of >1000 nm, with regard to the total weight of the elastomer agglomerates.

14. The elastomer agglomerate composition according to claim 10, wherein the elastomer agglomerate composition comprises 1.0 wt % of elastomer agglomerates having a particle size of >1500 nm, with regard to the total weight of the elastomer agglomerates.

15. Acrylonitrile-butadiene-styrene copolymer produced using the elastomer agglomerate composition according to claim 10.

16. The process according to claim 1, wherein the material flow through the aperture is confined by a flat first surface and a flat second surface together forming a channel; wherein the slurry is introduced at a pressure of 40 and 60 MPa; wherein the slurry comprises 20.0 wt % of elastomeric particles with regard to the total weight of the slurry; wherein the elastomeric particles are selected from polybutadiene particles, poly(styrene-butadiene) particles, poly(acrylonitrile butadiene) particles or polybutylacrylate particles;

17. The process according to claim 16, wherein the process is performed using a valve assembly comprising the aperture, the valve assembly further comprising a seat, a flow channel through which the slurry flows at a certain pressure towards the aperture, and a valve subjected to a pressure in the direction opposite the flow direction of the slurry, wherein the seat comprises a central opening forming the flow channel, and wherein the valve pressure and the pressure of the slurry are arranged such that the slurry is forced through the aperture at a flow velocity of at least 700 m/s and at most 1000 m/s.

18. The process according to claim 16, wherein the elastomeric particles account for at least 98.0 wt % of the total weight of solid ingredients in the slurry.

Description

[0036] Such slurry composition particularly allows for formation of elastomeric agglomerates according to the process of the present invention having a desired high average particle size, in particular having a particle size distribution as according to example 2 below, exemplified in FIG. 3, having, when considering increase of particle size, first a shoulder at a particle size which is lower than the average particle size of the elastomeric agglomerates, and a highest peak at a particle size which is higher than the average particle size.

[0037] The step (b) of the present invention, involving forcing the slurry comprising the elastomer particles through an aperture, may be performed using a valve assembly.

[0038] An exemplary embodiment of a valve assembly that may be used in certain embodiments of the present invention is presented in FIG. 1. FIG. 1 shows a cross-section of a valve assembly comprising an aperture (1), a seat (2), a flow channel (3) and a valve (4). The seat (2) comprises a central opening that forms the flow channel (3). In a particular embodiment of the process, the slurry is introduced to the valve via the flow channel (3) and flows towards the aperture (1). The slurry is introduced at a certain pressure. For example, the slurry may be introduced at a pressure of 40 MPa, preferably 50 MPa. The slurry may for example be introduced at a pressure or 80 MPa, preferably 70 MPa, more preferably 60 MPa. For example, the slurry may be introduced at a pressure of 40 and 80 MPa, preferably 40 and 70 MPa, more preferably 40 and 60 MPa, even more preferably 50 and 60 MPa.

[0039] The slurry may be an aqueous dispersion. In order to ensure a certain desired flow velocity when the slurry passed the aperture (1), the valve must be subjected to a certain pressure to achieve a certain desired flow velocity of the slurry in the aperture (1).

[0040] In the process according to the invention, the material flow through the aperture may be confined by a flat first surface and a flat second surface together forming a channel.

[0041] A front view of the seat (2) is presented in FIG. 2. FIG. 2 shows a seat (2) being a circular seat comprising a circular aperture forming the flow channel (3). It is preferred that the seat is a circular seat comprising a circular opening.

[0042] In a particular embodiment of the invention, the process is performed using a valve assembly comprising the aperture (1), the valve assembly further comprising a seat (2), a flow channel (3) through which the slurry flows at a certain pressure towards the aperture (1), and a valve (4) subjected to a pressure in the direction opposite the flow direction of the slurry, wherein the seat (2) comprises a central opening forming the flow channel (3), and wherein the valve pressure and the pressure of the slurry are arranged such that the slurry is forced through the aperture (1) at a flow velocity of at least 500 m/s, preferably of at least 600 m/s, more preferably at least 700 m/s, such as at least 700 m/s and at most 1000 m/s. For example, the slurry may be forced through the aperture (1) at a flow velocity of at least 500 m/s and at most 1000 m/s, preferably at least 500 m/s and at most 800 m/s.

[0043] The present invention in one of its embodiments also relates to the use of the elastomer agglomerate composition in the production of acrylonitrile-butadiene-styrene copolymers, methacrylate butadiene styrene copolymers, acrylonitrile styrene butylacrylate copolymers, or styrene butylacrylate copolymers.

[0044] The present invention further also relates to an acrylonitrile-butadiene-styrene copolymer produced using the elastomer agglomerate composition according to the invention.

[0045] The invention will now be illustrated by the following non-limiting examples.

[0046] In an emulsion polymerisation process, a polybutadiene slurry was prepared by polymerisation of 1,3-butadiene via a free-radical polymerisation process in an aqueous environment. The polybutadiene particles in the slurry had an average particle size of about 80 nm. The slurry comprised 39.0 wt % of polybutadiene particles and 0.7 wt % of oleic acid.

[0047] The slurry was subjected to homogenisation at a temperature of 35 C. according to the process of the present invention. A flow of 2375 litres per hour of the slurry were supplied to a homogeniser. In example 1, the homogenisation was conducted at a velocity of 775 m/s in the aperture. In example 2, included for comparative purposes, the homogenisation was conducted at a velocity of 392 m/s. The pressure drop in both examples was 52 MPa.

[0048] The homogeniser valve was a valve as in FIG. 1.

[0049] The particle size distribution of the polybutadiene particles in the slurry obtained from the homogenisations was determined using a Beckman Coulter multi-wavelength laser diffraction particle size analyser type LS12 320.

[0050] The results of the particle size determination are presented in table II below. In FIG. 3, the values on the x axis represent the particle size in m, and the values on the y axis represent the volume fraction of particles with regard to the total particle volume having a corresponding particle size in vol %.

TABLE-US-00001 TABLE II Average Ve- particle locity size Fraction Fraction Fraction Fraction Example (m/s) (m) <0.2 m 0.2-1.0 m >1.0 m >1.5 m 1 775 0.31 21.7 73.7 4.6 0.7 2 392 0.31 18.0 58.5 23.5 16.4

[0051] The fractions as presented in table II represent volume fractions in vol % of the polybutadiene particles in the slurry obtained from homogenisation. The velocity is the velocity of the slurry in the aperture 1 of the valve of FIG. 1.

[0052] The particle size distribution data as presented in table II demonstrates the process according to the present invention to result in a homogenised elastomer agglomerate composition having a more narrow particle size increased fraction of particles in the range of 0.2-1.0 m. In particular, the homogenised elastomer agglomerate composition of example 1 comprised a far lower content of particles having a large particle size, as demonstrate by the low fraction of particles having a particle size of 1.5 m.

[0053] FIG. 3 presents the particle size distributions of the polybutadiene particles in the homogenised slurries of examples 1 and 2. Both homogenised elastomer agglomerates demonstrated a bimodal particle size distribution. However, the particle size distribution of the homogenised elastomer agglomerate of example 1 showed a bimodal distribution having a shoulder corresponding to a first modus of the bimodal distribution at lower particle sizes and a peak corresponding to a second modus of the bimodal distribution at a higher particle size than the shoulder.

[0054] For example 2, this is the opposite. The peak is present at a lower particle size than the shoulder. From this it may be concluded that the homogenised elastomer agglomerate obtained in example 2, the comparative example, contains a larger fraction of polybutadiene particles that have not formed agglomerates. Further, there is a larger fraction of agglomerates in example 2 that have a larger particle size, as demonstrated by the presence of particles above 2 m in FIG. 3.