Patent Application
20050090604
The invention relates to suspension copolymers composed of methyl methacrylate and of other monomers copolymerizable therewith, which have a high and not previously achieved content of residual peroxides. The beads of the invention with increased residual peroxide content may be used for example in construction chemistry as a polymerization initiator in or redox-curing binders.
EP 581 387 (Bristol-Myers Squibb Company) describes a bone cement composed of polymer particles, where the polymer particles are composed of two or more layers, which may comprise a very wide variety of additives. Besides X-ray contrast agents, dyes, antibiotics, bone growth factors, these layers may also comprise polymerization initiators. The polymer particles always have a layer structure. Various polymerization kinetics are achieved by distributing the polymerization initiator over various compartments (see FIG. 7 of EP 581 387) having a shell-type structure.
An object was therefore to; provide polymer beads with varying composition of the starting monomers and with maximum contents of homogeneously distributed polymerization initiator, which can be produced without the complicated shell-type structure and can therefore be produced more simply and at lower cost. The beads are also intended to have a wide processing spectrum in monomer-containing reactive resin systems which can be cured by a free-radical route, the intended result being maximum pot life.
The object has been achieved by way of a depot polymerization initiator bead according to the claims.
The bead of the invention has the following advantages:
1. from 1-99% by weight of a derivative of an unsaturated carboxylic acid of the formula (I),
where:
By way of example, copolymerizable monomers used are styrene or styrene derivatives, such as methyl styrene or maleic acid or maleic anhydride.
The average diameter of the beads is from 50 to 200 μm. The diameter was determined by means of laser diffraction spectroscopy, using a Malvern Mastersizer Microplus (measurement range: from 0.05 to 555 μm).
Residual monomer content was measured by means of gas-chromatographic head-space analysis, a method for determining vaporizable constituents in liquids, and solids (inter alia of monomers in thermoplastics).
The viscosity number VN (or Staudinger function) is the relative change in viscosity, divided by concentration, of a 0.5% strength solution of the copolymer in chloroform, based on the solvent, the flow times being determined in a suspended-globe Ubbelohde viscometer, Schott No. 53203 and capillary 0c to D/N 51562 at 25° C. Chloroform was used as solvent.
where:
The production of the copolymers to be used according to the invention is known per se. They may be produced by bulk polymerization or suspension polymerization. Useful information on bulk polymerization is found in Houben-Weyl, Volume E20, Part 2 (1987), page 1145 et seq. The suspension polymerization technique is also described there on page 1149 et seq.
Production specification for depot peroxide bead:
37.75 g of aluminum sulfate×14 H2O are dissolved in 3 750 g of demineralized water and heated to 40° C. in a 5 1 polymerization vessel equipped with stirrer, reflux condenser and thermometer. To generate the suspension stabilizer, 166.25 g of a 10% strength aqueous sodium carbonate solution, 0.28 g of sodium C15-paraffin sulfonate and 0.272 g of polyethylene glycol (molecular weight from 5 000 to 6 000) are added, with stirring. 1 250 g of a mixture composed of 43.1 parts by weight of methyl methacrylate, 43.1 parts by weight of n-butyl methacrylate, 0.013 part by weight of 2-ethylhexyl thioglycolate and 13.7 parts by weight of 75% strength aqueous dibenzoyl peroxide were then added, with continued stirring. The mixture was then heated to 70° C., polymerized for 40 minutes at 70° C. and for 60 minutes at 77° C. and then cooled to 50° C. At this temperature 36 g of 50% strength sulfuric acid were added to disperse the suspension stabilizer. After further cooling to room temperature, the polymerization beads were filtered off, thoroughly rinsed with demineralized water, and dried in a fluidized-bed dryer at 40° C.
1 391 g of clear polymer beads were obtained with a residual dibenzoyl peroxide content of 10% by weight, determined iodometrically.
Curing experiment with a reactive resin based on high-boiling (meth)acrylate (HB):
The peroxide bead described in example 1 with a content of 10% of dibenzoyl peroxide was introduced within a period of 2 minutes, with stirring, as reaction initator in a reactive resin based on high-boiling (meth)acrylates at a concentration of 10% (=1% of active dibenzoyl peroxide). The activated reactive resin was then poured, at a layer thickness of about 2 mm, onto a concrete substrate. It cured tack-free within about 30 minutes and had a pot life of from 15 to 18 minutes.
Comparative experiment with phlegmatized dibenzoyl peroxide:
The experiment of example 2 was repeated, but the initiator used comprised 2% of dibenzoyl peroxide phlegmatized at 50% strength in dicyclohexyl phthalate (BP-50-FT, Interox). The reactive resin likewise cured within about 30 minutes. However, the pot life was only about 8-10 minutes.
Degadur 523 (DGD 523) is marketed by Röhm GmbH & Co. KG and is a reactive resin produced from low-boiling monomers. The monomer phase of Degadur 523 is composed of methyl methacrylate, 2-ethylhexyl acrylate and polyfunctional methacrylates. NGB52 is a reactive resin based on moderate-boiling-point monomers (e.g. butyl methacrylate). GFG 330 HS is a reactive resin based on high-boiling monomers, e.g. tetrahydrofurfuryl methacrylate.
The table gives the pot life first and secondly the curing time. Pot life should be from 50 to 20 minutes, and curing time should be from 25 to 60 minutes. The coating composition is a homogeneous mixture which is easy to apply.
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 37 968.4 | Aug 2001 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10485253 | Feb 2004 | US |
| Child | 10988706 | Nov 2004 | US |
