Process to produce polyvinyl-ester compositions with low residual monomer and the use thereof

Abstract

A process for reducing the amount of residual monomer in aqueous polymerization emulsion by using a sequential polymerization steps, The first step consists in adding an emulsion, of vinyl ester of alkyl of C1 to C18 carboxylic acids, to water containing a radical initiator, the second step consists in adding further an emulsion of alkyl acrylate and/or methacrylate, and the third step consists in c) adding to polymeric emulsion, resulting of the steps a) and b), pure liquid acrylate or methacrylate with alkyl chain of C.sub.1 to C.sub.12.

Claims

1. A process for reducing the amount of residual vinyl ester monomer in a vinyl ester-acrylate co-polymeric emulsion by using sequential polymerization steps consisting essentially of: a) adding a pre-emulsion consisting essentially of monomers of vinyl ester of alkyl of C1 to C18 carboxylic acids to water containing a radical initiator; b) adding to a) a pre-emulsion consisting essentially of monomers of alkyl acrylate, an emulsion consisting essentially of monomers of alkyl methacrylate, or a combination thereof to form a polymeric emulsion; and c) adding to the polymeric emulsion one or more monomers of liquid acrylates, methacrylates, or combinations thereof, wherein each of the one or more liquid acrylates or methacrylates monomers comprise an alkyl chain of C1 to C16, and forming the vinyl ester-acrylate co-polymeric emulsion, wherein the vinyl ester-acrylate co-polymer is a co-polymer of vinyl ester monomers and acrylate monomers, methacrylate monomers, or combinations thereof.

2. The process of claim 1, wherein the vinyl ester of alkyl of C1 to C18 carboxylic acids consists of a linear alkyl chain, from 3 carbon atoms as a branched alkyl chain, from 5 carbon atoms as a branched tertiary alkyl chain, or a mixture thereof.

3. The process of claim 2, wherein the vinyl ester of alkyl of C1 to C18 carboxylic acids is vinyl propionate, vinyl n-butyrate, vinyl laurate, vinyl ester of 2-ethyl hexanoic acid, vinyl caprate, and vinyl stearate, vinyl neodecanoates, vinyl pivalate or a mixture thereof.

4. The process of claim 1, wherein the monomers of alkyl acrylate or alkyl methacrylate are reaction products of ethylenically unsaturated carboxylic acids and C1 to C20 alcohols.

5. The process of claim 4, wherein the monomers of alkyl acrylate or alkyl methacrylate are selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, 2-propyl heptyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, 4-tertbutylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate or a mixture thereof.

6. The process of claim 1, wherein the monomers of alkyl acrylate or the alkyl methacrylate of c) is selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate or a mixture thereof.

7. The process of claim 3, wherein the vinyl ester of alkyl of C1 to C18 carboxylic acids is a vinyl ester of neodecanoic acids.

Description

EXAMPLES

Latex Preparation See Table 1 for the Intake of Composition of Example 2

(1) The reactor is charged with water and potassium per-sulfate and heated to 85 C. A 10% seed from the pre-emulsion 1 (PE 1) (containing all of the VeoVa-10) is added and reacted for 10 minutes before the remainder of the PE 1 is fed for 1 h. At the end of the addition, the PE 2 containing the acrylic monomers is added for 2 hours. At the end of this addition, a shot of pure monomer (acrylate or a vinyl ester) is added and reacted for 0.5 h whereas the initiator solution is fed in parallel for a total of 3.5 h. After a 1 h cooking period, the latex is cooled down to 60 C. The agitation is slowed down to about 100 rpm, to avoid to any funnel into the latex. A 10% solution of sodium carbonate and sodium hydrogenocarbonate (1/1) is added to adjust the pH to 4. A first addition of BruggoliteFF6 M solution is added in one shot. After 5 minutes, the remainder of BruggoliteFF6 M and the tBHP are added via two separate lines during 90 minutes.

(2) Finally, the reactor is cooled down to room temperature and a biocide is added. The product is finally filtered over a 130 filter. The final latex has a solid content of 53%.

(3) A way to determine the residual level of VeoVa-10 and other residual monomers, is to perform a Gas Chromatography (GC) analysis. The GC method and sampling procedure is described in above section. The level of residual monomer was followed with time. A small amount (+10 g) of latex is taken out from the reactor each 30 minutes, mixed with 10 mg of hydroquinone and immediately place in the ice. The samples are then analyzed by GC.

Latex Preparation of Composition of Example 3

(4) The reactor is charged with water and potassium per-sulfate and heated to 85 C. A 10% seed from the pre-emulsion 1 (PE 1) (containing all of the VeoVa-10) is added and reacted for 10 minutes before the remainder of the PE 1 is fed for 1 h 30 minutes. At the end of the addition, the reaction mixture is kept at 85 C. for 30 minutes after that period the PE 2 containing the acrylic monomers is added for 2 hours 30 minutes. At the end of this addition, the reaction medium was kept at 85 C. for 30 minutes, then the latex is cooled down to 60 C. The agitation is slowed down to about 100 rpm, to avoid any funnel into the latex. A 10% solution of sodium carbonate and sodium hydrogenocarbonate (1/1) is added to adjust the pH to 4. A first addition of BruggoliteFF6 M solution is added in one shot. After 5 minutes, the remainder of BruggoliteFF6 M and the tBHP are added via two separate lines during 60 minutes.

(5) Finally, the reactor is cooled down to room temperature and a biocide is added. The product is finally filtered over a 130 filter. The final latex has a solid content of 60%.

(6) TABLE-US-00002 TABLE 1 Intake for Ex 2 Product: Example 2 Intake (g) Initial reactor content Demineralised Water 380.25 Potassium persulfate 1.05 Na2CO3 1.98 Monomer pre-emulsion 1 (1 h addition) Demineralised Water 79.81 DisponilA3065 (65%) 7.77 Rhodacal DS10 1.51 VeoVa-10 200 AA 3.09 MAA 10.1 nDDCM 2.02 Initiator solution (3 h 30 addition) Demi Water 115.82 Potassium persulfate 4.76 Monomer pre-emulsion 2 (2 h addition) Demineralised Water 270.26 REASOAP 30.86 Rhodacal DS10 16.24 BA 639.79 EA 50.04 MA 50.46 AA 7.13 MAA 20.8 MMA 10.22 BA Shot (30) 25.36 Post cooking 60 Iron shot Iron II - Fe(SO.sub.4) 0.02 water 5.12 Conversion booster Shot Demineralised water 12.49 Bruggolite FF6 0.78 Addition in parallel with Shot Demineralised water 33.42 Bruggolite FF6 2.86 Demineralised water 33.71 tBHP (70%) 4.07

(7) TABLE-US-00003 TABLE 2 Residual Monomer Levels Exam- Exam- Exam- Compar. 1 Compar. 2 ple 1 ple 2 ple 3 PE-1 + (h) 2.5 (VV/A) 1 (VV) 1 (VV) 1 (VV) 1.5 (VV) Init + (h) 3 3.5 (A) 3.5 (A) 3.5 (A) 4.5 Cooking 0.5 (+KPS) 0.5 PE-2 + (h) 2 2 2 2.5 Shot (h) 0.5 0.5 0.5 0.5 Cooking 1 1 1 1 0.5 (h) Booster 1.5 1.5 1.5 1.5 1.0 (h) No shot x x Shot Vinyl x Acetate Shot x Methyl Acrylate Shot Butyl x Acrylate Residual 2100 380 360 200 224 VV 10 (ppm) Residual 40 60 120 22 BA (ppm) Residual 340 VAM (ppm) Sum 2100 760 420 320 246 Residuals

(8) From the table 2 above, it appears that the new sequential process where all of the VeoVa is placed in the first pre-emulsion 1 and kept separated from the acrylic monomers has a profound effect on the total monomer conversion. Shots of various monomers were tested at the end of the addition of the second pre-emulsion. It is clearly demonstrate that the monomer conversion is higher, as the total residual level of below 500 ppm is reached. However a similar effect on the residual monomer can be reach by changing the sequence and the reaction time period (as for example 3).

(9) PSA Properties

(10) Upon applications and drying, the lattices prepared with the new core/shell approach, are defect free and show good clarity.

(11) PSA films were prepared by direct coating on 23 micron Polyester Facestock at 20 gsm coat-weight.

(12) The basic PSA properties were evaluated and various substrates (Stainless Steel and High Density Polyethylene) after different dwell times.

(13) The results given in Table 3 below shows slightly lower adhesion level, slightly higher loop tack and equal shear resistance. Overall it can be stated that the new process used to obtain residual monomer levels below 500 ppm does not affect significantly the PSA properties of the polymers.

(14) TABLE-US-00004 TABLE 3 Comp 1 EX 1 EX 3 PL SS 20 N/inch 7.2 5.7 5.6 PL SS 24 h N/inch 9.7 8.6 7.4 PL PE 24 h N/inch 5.4 3.3 5.4 LT SS N/inch 3.1 4.9 5.6 Shear (0.5 inch.sup.2 1 kg) min >10000 >10000 >10000

(15) The dry films based on the composition of the present invention provide enhanced water whitening resistance. Moreover these polymer compositions could also formulated with nonpolar tackifiers and other additives without compatibility issues.