Process for the preparation of colloidal polymerized particles

Abstract

The present invention relates to a process for the preparation of dispersions of colloidal polymerized particles and to the colloidal polymerized particles obtained and/or obtainable by the process as well as to their use.

Claims

1. A process for the preparation of colloidal polymerized particles (CPP) in the absence of emulsifier or other dispersing aid comprising the steps of: (a) forming a photopolymerizable aqueous colloidal dispersion (ACD) comprising: (i) at least one self-water dispersible compound (SW), (ii) at least one photoinitiator (PI), and (iii) optionally at least one photopolymerizable compound (B), (b) polymerizing the photopolymerizable aqueous colloidal dispersion (ACD) by photoinduced polymerization to form a dispersion of colloidal polymerized particles (DCPP), and (c) optionally isolating the particles obtained at step (b) from the aqueous phase to obtain isolated colloidal polymerized particles (ICPP), wherein the dispersion (ACD) comprises: (a) from 35 to 99.5 wt % of water calculated based on the total weight of the dispersion (ACD), and (b) from 0.5 to 65 wt % of dry content calculated based on the total weight of the dispersion (ACD), wherein the dry content comprises: (i) from 26 to 99.9 wt % of compound (SW), (ii) from 0.1 to 14 wt % of photoinitiator (PI), and (iii) from 0 to 60 wt % of compound (B), wherein the amounts of compound (SW), photoinitiator (PI) and compound (B) are calculated based on the dry content of the dispersion (ACD), and wherein the self-water dispersible compound (SW) comprises at least one photopolymerizable self-water dispersible compound (SW1), the self-water dispersible compound (SW) comprises at least one non photopolymerizable self-water dispersible compound (SW2) and at least one photopolymerizable compound (B) is present, or the self-water dispersible compound (SW) comprises at least one photopolymerizable self-water dispersible compound (SW1) and at least one non photopolymerizable self-water dispersible compound (SW2).

2. The process according to claim 1, wherein compound (SW1) is selected from the group consisting of (meth)acrylated self-water dispersible polyurethanes, (meth)acrylated self-water dispersible poly(meth)acrylates, (meth)acrylated self-water dispersible polyesters, (meth)acrylated self-water dispersible polyethers, (meth)acrylated self-water dispersible polycarbonates, (meth)acrylated self-water dispersible polyepoxys and mixtures thereof.

3. The process according to claim 1, wherein compound (SW2) is selected from the group consisting of self-water dispersible polyurethanes, self-water dispersible poly(meth)acrylics, self-water dispersible polyepoxys, self-water dispersible polyesters, self-water dispersible alkyd polymers, self-water dispersible phenolic resins and mixtures thereof.

4. The process according to claim 1, wherein compound (B) is selected from the group consisting of (meth)acrylated compounds.

5. The process according to claim 1, wherein compound (SW) and/or compound (B) are compounds bearing at least one functional group selected from the group consisting of epoxide, hydroxyl, amine, isocyanate, and carboxylic acid.

6. The according to claim 1, wherein the dispersion (ACD) further comprises at least one additive (C) selected from solid and/or liquid non reactive additives that are not soluble in water.

7. The according to claim 6, wherein additive (C) is selected from the group consisting of dyes, organic and/or inorganic corrosion inhibitors, catalysts, UV-absorbers, crosslinkers, anti-fouling agents, biocides, hydrophobicity modifiers, antiscaling agents, freezing depressors, phase change compounds and mixtures thereof.

8. The process according to claim 1, wherein the dispersion (ACD) further comprises at least one non self water dispersible compound (D).

9. Dispersion of colloidal polymerized particles (DCPP) obtained by a process according to claim 1.

10. A method comprising adding the dispersion of colloidal polymerized particles (DCPP) according to claim 9 as fillers to compositions suitable for the preparation of composite materials.

11. Isolated colloidal polymerized particles (ICPP) obtained by a process according to claim 1.

12. A method comprising adding isolated colloidal polymerized particles (ICPP) according to claim 11 as fillers to compositions suitable for the preparation of composite materials.

Description

EXAMPLE 1

(1) An acrylated self-water dispersible polyurethane UA1 (compound (SW1)) was dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 35.9 wt % and an average particle size of 54 nm (commercialized by Cytec as Ucecoat 7655). 98.5 wt % of this dispersion was mixed with 1.5 wt % of a liquid photoinitiator (PI) (Irgacure 500: 1:1 mixture of 1-hydroxy cyclohexyl phenyl ketone and benzophenone) to form a dispersion (ACD) according to the present invention. Subsequent photopolymerizations were conducted at three dry contents of the dispersion (ACD), i.e., 9.0, 20.0 and 35.9 wt % obtained by addition of the required amount of water.

(2) The dispersions (ACD) were exposed to UV-light following method (i) to form the colloidal dispersions of polymerized particles (DCPP). Table 1 reports the exposure time, the evolution of the T.sub.g and average size of the particles upon photoinduced polymerization.

(3) The visual appearance of the dispersions during photoinduced polymerization is typically milky white due to intense light scattering.

(4) TABLE-US-00001 TABLE 1 Dry content (wt %) UV-exposure time (min) T.sub.g ( C.) d.sub.DLS (nm) 20 0 0 54 9 5 55 10 58 15 84 55 20 5 10 48 15 56 60 35.9 5 5 10 2 69 15 18 78

(5) The results in Table 1 clearly show that the particles of the dispersions (ACD) preserve their colloidal nature after exposure to UV-light. The marked increase in T.sub.g demonstrates that the particles polymerize and transform from viscous to solid-like. It is also shown that the average T.sub.g can be adjusted by the irradiation conditions. The experiment further shows that the process is not limited to the photoinduced polymerization of translucent dispersions. It is also suitable for systems with a high degree of opacity.

COMPARATIVE EXAMPLE 1

(6) A qualitative assessment of the degree of cross-linking of the particles can be obtained by coating a thin film (60 m) of the dispersion (ACD) onto a corona-treated bioriented polypropylene (OPP) substrate using a bar coater followed by drying the film in an oven at 60 C. for 10 min.

(7) Prior to UV-exposure, the dispersion (ACD) of Example 1 forms a uniform non-tacky film after evaporation of the water. When the dried film is subsequently UV-cured, a solvent resistant, uniformly cross-linked coating is obtained with a T.sub.g of about 60 C. Contrarily, a dry film of the (CDPP) prepared in Example 1 is not uniform. A brittle and pearly-looking material lacking any cohesion is obtained which shows that the CPP were cross-linked before film application.

EXAMPLE 2

(8) An acrylated self-water dispersible polyurethane UA1 (compound (SW1)) was dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 35.9 wt % and an average particle size of 54 nm (commercialized by Cytec as Ucecoat 7655). 98.6 wt % of this dispersion was mixed with 1.4 wt % of a liquid photoinitiator (PI) (composed of EDB/BDK/BZP/TPO.sup.(1) in the ratio 30:30:20:20) to form a dispersion (ACD) according to the present invention. The dispersion (ACD) was next diluted with water to a dry content of 20 wt %.

(9) After 30 min of UV-exposure following method (i), the final average T.sub.g value of the polymerized particles (CPP) was 55 C. .sup.(1)EDB: Ethyl-4-dimethylamino benzoate BDK: 2,2-Dimethoxy-1,2-diphenylethan-1-one BZP: Benzophenone TPO: 2,4,6-Trimethylbenzoyldiphenylphosphine oxide

EXAMPLE 3

(10) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)) was dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 40.1 wt % and an average particle size of 121 nm (commercialized by Cytec as Ucecoat 7719). 98.5 wt % of this dispersion was mixed with 1.5 wt % of a liquid photoinitiator (PI) (Irgacure 500: 1:1 mixture of 1-hydroxy cyclohexyl phenyl ketone and benzophenone) to form a dispersion (ACD) according to the present invention. Subsequent photopolymerizations were conducted at two dry contents of the dispersion (ACD), i.e., 10.0 and 20.0 wt % obtained by addition of the required amount of water.

(11) The dispersions (ACD) were exposed to UV-light following method (i) to form the colloidal dispersions of polymerized particles (DCPP). Table 2 reports the exposure time, the evolution of the T.sub.g and average size of the particles upon photoinduced polymerization.

(12) TABLE-US-00002 TABLE 2 Dry content (wt %) UV-exposure time (min) T.sub.g ( C.) d.sub.DLS (nm) 20 0 29 121 10 5 1 10 40 15 50 146 20 5 10 22 15 5 129

(13) Table 2 shows that the particles of the dispersions (ACD) preserve their colloidal nature after exposure to UV-light. The increase in T.sub.g demonstrates that the particles polymerize and transform from viscous to solid-like upon UV-irradiation. The average T.sub.g can be tuned by the irradiation conditions.

COMPARATIVE EXAMPLE 2

(14) A qualitative assessment of the degree of cross-linking of the particles can be obtained by coating a thin film (60 m) of the ACD onto a corona-treated bioriented polypropylene (OPP) substrate using a bar coater followed by drying the film in an oven at 60 C. for 10 min.

(15) Prior to UV-exposure, the dispersion (ACD) of Example 3 forms a tacky liquid-like film after water evaporation. When the dried film is subsequently UV-cured, a solvent resistant, uniformly cross-linked coating is obtained with a T.sub.g of about 40 C. However, a dry film of the CDPP prepared in Example 3 appears as a film-forming, but non-tacky, material after water evaporation. An acetone rub test reveals that the film has no cohesion and is easily removed from the OPP substrate which indicates that the CPP were cross-linked prior to film application.

EXAMPLES 4 AND 5

(16) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)) and trimethylolpropanetriacrylate (TMPTA) (compound (B)) were blended in a ratio 80:20 and codispersed in water resulting in an aqueous colloidal dispersion with a dry content of 40.0 wt % and an average particle size of 65 nm.

(17) Two different approaches were followed to incorporate the (PI) (Irgacure 500) in order to obtain the dispersion (ACD). In Example 4, the (PI) was dissolved in the acrylated urethane oligomer UA2 prior to the dispersion step in water (pre-addition). In Example 5, the (PI) was added by simple mixing into the aqueous dispersion (post-addition). The amount of (PI) in examples 4 and 5 was 3.7 wt % with respect to the dry content of the dispersion and the dispersion (ACD) was diluted to a dry content of 20 wt %.

(18) The dispersion (ACD) was exposed to UV-light following method (i) to form the colloidal dispersion of polymerized particles (DCPP).

(19) Table 3 shows the average T.sub.g of the particles of the dispersions (ACD) as a function of the exposure time. In Example 4 where the (PI) is incorporated by pre-addition, the T.sub.g value raises by 60 C. in about 3 min reaching a plateau. In Example 5 where the (PI) is added by post-addition, the T.sub.g increase is delayed by a few minutes. Despite the kinetics difference, the final T.sub.g obtained in Examples 4 and 5 are close.

(20) TABLE-US-00003 TABLE 3 T.sub.g ( C.) UV-exposure time (min) Pre-addition Post-addition 0 29 29 1 24.4 28.7 2 12.1 24.7 3 26.9 22.2 4 33.3 11.1 5 32.6 26.1 7 30.9 21.2 10 33.2 25.6 15 29.6 28.3 20 34.2 35.7 30 35.6 38.3

(21) This result shows clearly that when the PI is introduced differently in the dispersion, the polymerization kinetics of the particles is affected accordingly. When the PI is mixed with the resin before dispersion, the polymerization proceeds faster. Introduction of the PI in post-addition still results in the photo-initiated curing of the resin in the particles, which suggests that the PI penetrates into the particles, or at least partially.

EXAMPLES 6 AND 7

(22) In Examples 6 and 7, Example 1 is reproduced, but UA1 is replaced by an acrylated self-water dispersible polyacrylic (AA1) (compound (SW1)) in Example 6 and by an acrylated self-water dispersible polyepoxy (EA1) (compound (SW1)) in Example 7. Table 4 reports the exposure time, the evolution of the T.sub.g and the average particle size upon photoinduced polymerization.

(23) TABLE-US-00004 TABLE 4 Dry content (wt %) UV-exposure time (min) T.sub.g ( C.) d.sub.DLS (nm) AA1 20 0 7 104 15 22 30 28 109 EA1 20 0 13 381 30 41 361

EXAMPLE 8

(24) A hydroxyl-terminated self-water dispersible polyurethane, UA3 (compound (SW2)), was blended with acrylated ethoxylated trimethylolpropane (TMPOETA) (compound (B)) in a ratio 66.6:33.3 and codispersed into water resulting in an aqueous colloidal dispersion with a dry content of 45.1 wt % and an average particle size of 97 nm. The dispersion (ACD) was next obtained by addition of the liquid photoinitiator Irgacure 500 (PI) in an amount of 4.4 wt % on dry content.

(25) The dispersion (ACD) was exposed to UV-light following method (i) to form the colloidal dispersion of polymerized particles (DCPP).

(26) After 7 min of UV-exposure, the average T.sub.g value of the particles jumped from 37 to 26 C. without altering the colloidal nature of the dispersion. After 30 min, the ultimate T.sub.g value was 32 C. and the final particle size was 109 nm, compared to 97 nm before polymerization. The resulting particles bear residual hydroxyl functions.

(27) The particles obtained from Examples 1 to 8 do not swell in contact with acetone. Acetone is a good solvent of the starting resins UA1, UA2, UA3, AA1 and EA1 before photoinduced polymerization.

EXAMPLE 9

(28) An acrylated self-water dispersible polyurethane UA4 (compound (SW1)) was dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 35.0 wt % and an average particle size of 35 nm. UA4 is based on a long chain polyester, a carboxylic diol moiety, an aliphatic diisocyanate and hydroxyethyl acrylate.

(29) The dispersion (ACD) was obtained by adding 4 wt % of Irgacure 500 with respect to the dry content of the dispersion. The dispersion (ACD) was diluted to a dry content of 20 wt % prior to photopolymerization.

(30) The dispersion (ACD) was exposed to UV-light following method (ii) to form the colloidal dispersion of polymerized particles (DCPP).

(31) Dilution of the (DCPP) in acetone shows that the (CPP) particles do not dissolve but, in contrast to the former examples, they swell from an initial size d.sub.DLS of 35 nm to about 70 nm corresponding to an eightfold increase in volume. Before photopolymerization, the T.sub.g value of the particles is about 30 C. After photopolymerization, two glass transitions are evidenced reflecting the soft segments of the polymer (T.sub.g=30 C.) and the hard domains formed after reaction of the acrylate double bonds (T.sub.g=85 C.).

EXAMPLE 10

(32) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)) and Neozapon Blue 807 (blue dye commercialized by BASF, additive (C)) were blended in a ratio 98:2 and codispersed in water resulting in an aqueous colloidal dispersion with a dry content of 40.0 wt % and an average particle size of 68 nm. 1.5 wt % of Irgacure 500 (PI) was subsequently blended to 98.5 wt % of the previous dispersion to obtain the dispersion (ACD).

(33) In order to produce a colloidal dispersion of polymerized particles (DCPP), the dispersion (ACD) was exposed to UV-light according to method (i). Experiments were performed at a dry content of 13.3 wt %.

(34) The particles were separated from the aqueous phase by addition of a few drops of concentrated HCl to coagulate the colloids followed by centrifugation at 24000 rpm during 30 min. The supernatant was uncolored and nearly transparent showing that the dye was completely incorporated into the particles.

(35) Table 5 reports the exposure time, the evolution of the T.sub.g and average size of the particles upon photoinduced polymerization. The results in Table 5 show that the particles preserve their colloidal nature after exposure to UV-light. Starting from a T.sub.g=30 C. for the particles of the non-exposed dispersion (ACD), the T.sub.g raises significantly upon UV-exposure showing that the particles gradually transform from viscous to solid-like upon UV-irradiation. The average T.sub.g can be tuned by the irradiation conditions.

(36) TABLE-US-00005 TABLE 5 UV-exposure time T.sub.g d.sub.DLS (s) ( C.) (nm) 0 30 68 30 21 101 45 30 101 75 33 101 135 46 101

EXAMPLE 11

(37) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)), TMPTA (compound (B)) and Irgarol 1051 (biocide commercialized by BASF, additive (C)) were blended in a ratio 78:19.5:2.5 and codispersed in water resulting in an aqueous colloidal dispersion with a dry content of 40.4 wt % and an average particle size of 88 nm. 1.6 wt % of Irgacure 500 (PI) was subsequently blended to 98.4 wt % of the previous dispersion to obtain the dispersion (ACD).

(38) In order to produce a colloidal dispersion of polymerized particles (DCPP), the dispersion (ACD) was exposed to UV-light according to method (i). Experiments were performed at a dry content of 20 wt %.

(39) After 30 min, the average T.sub.g value of the dispersed particles raised from 25 to 36 C.

EXAMPLE 12

(40) Example 11 is reproduced, but using 8-hydroxyquinoline (corrosion inhibitor for aluminum, additive (C)) instead of the biocide. UA2 (compound (SW1)), TMPTA (compound (B)) and 8-hydroxyquinoline were blended in a ratio 78.8:19.7:1.5 and codispersed in water resulting in an aqueous colloidal dispersion with a dry content of 39.6 wt % and an average particle size of 70 nm. 1.6 wt % of Irgacure 500 (PI) was subsequently blended to 98.4 wt % of the previous dispersion to obtain the dispersion (ACD).

(41) In order to produce a colloidal dispersion of polymerized particles (DCPP), the dispersion (ACD) was exposed to UV-light according to method (i). Experiments were performed at a dry content of 20 wt %.

(42) The T.sub.g of the particles increased from 25 to 4 C. over the course of a 30 min UV-exposure.

EXAMPLE 13

(43) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)) and hexadecane (phase change material, additive (C)) were blended in a ratio 80:20 and codispersed in water resulting in an aqueous colloidal dispersion with a dry content of 35.3 wt % and an average particle size of 161 nm. 1.5 wt % of Irgacure 500 (PI) was subsequently mixed to 98.5 wt % of the previous dispersion to obtain the dispersion (ACD).

(44) The dispersion (ACD) was diluted to a dry content of 20 wt % prior to photopolymerization.

(45) The dispersion (ACD) was exposed to UV-light following method (ii) to form the colloidal dispersion of polymerized particles (DCPP).

(46) Dilution of the DCPP in acetone shows that the particles (CPP) do not dissolve anymore after a UV-exposure of 1 min due to the cross-linking of UA2. As hexadecane is not miscible with UA2, it is believed that encapsulation of the phase-change material took place in this case.

EXAMPLE 14

(47) An acrylated self-water dispersible polyurethane UA1 (compound (SW1)) was dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 35.9 wt % and an average particle size of 51 nm (commercialized by Cytec as Ucecoat 7655). 98.5 wt % of this dispersion was mixed with 1.5 wt % of a liquid photoinitiator (PI) (Irgacure 500: 1:1 mixture of 1-hydroxy cyclohexyl phenyl ketone and benzophenone) to form a dispersion (ACD) according to the present invention. The dispersion (ACD) was diluted to a dry content of 20 wt % prior to photopolymerization.

(48) The dispersion (ACD) was exposed to UV-light following method (iii) to form the colloidal dispersion of polymerized particles (DCPP). The exposure time was varied by changing the flow rate of the aqueous dispersion in the continuous flow reactor.

(49) After photoinduced polymerization, the (CPP) particles could not be dissolved anymore upon dilution of the (DCPP) in acetone. However, significant swelling could be established from a comparison of the particle size d.sub.DLS in water and acetone at different flow rates (Table 6). By increasing the length of the reactor to 2.3 m, swelling was suppressed.

(50) TABLE-US-00006 TABLE 6 d.sub.DLS Flow rate (nm) (L/h) Water Acetone 0.71 51 73 1.18 52 92 1.78 52 106

EXAMPLE 15

(51) An acrylated self-water dispersible polyurethane UA2 (compound (SW1)) and ReofosBAPP (Chemtura, flame retardant additive (C)) were blended in a ratio 70:30 and co-dispersed in water resulting in an aqueous colloidal dispersion with a dry content of 40.0 wt % and an average particle size of 129 nm. 1.0 wt % of Irgacure 500 (PI) was subsequently mixed to 99.0 wt % of the previous dispersion to obtain the dispersion (ACD). The dispersion (ACD) was not diluted prior to photopolymerization. The dispersion (ACD) was exposed to UV-light following method (iii) to form the colloidal dispersion of polymerized particles (DCPP). The flow rate was 0.4 L/h. Dilution of the DCPP in acetone shows that the particles (CPP) do not dissolve anymore after a UV-exposure due to the cross-linking of UA2. The crosslinked particles act as sub-micron sized containers for the flame retardant agent.