Microgel

Details Microgel Microgel

1997-11-21

1999-11-02

Niland, Patrick D.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

524306, 524457, C08F 800, C08J 300, C08K 320, C08L 6706

Patent

active

059772581

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a new kind of microgels, to a process of manufacturing the same and to their use.
Microgels are crosslinked polymeric microparticles in a liquid medium, said particles having an average particle diameter of from 0.01 to 10 .mu.m and are produced by emulsion polymerisation of vinyl monomers with divinyl monomers in the presence of emulsifiers. Water-based microgels of the kind are used as rheology adjuvants or as auxiliary agents in the motorcar industry for producing a good metallic effect.
A main disadvantage of the so-obtained microgels consists in that the emulsifier remains in the finished microgel and, for example, because of the sulfur-containing groups (sulfonic acid groups), one has to put up with considerable disadvantages when using said microgels in a plurality of applications. Thus, in view of the emulsifier contained therein, these microgels have disadvantageous properties, for example in connection with their use in water-based coatings in the motorcar industry, in particular because of the humidity resistance.
Microgels obtained by emulsion polymerization can also be used after modification in conventional coatings, i.e. solvent-based coatings. To this end, it is necessary to convert the aqueous microgel into a solvent-containing form.
This is done by the coagulation process, which is often applied industrially, as described, for example, in WO-91/00895 and EP-A-029 637. To this end, n-butanol is added to the aqueous microgel dispersion resulting in a coagulation of the microgel. Thereafter, the lower phase, containing n-butanol, water and parts of the emulsifier, is separated and the upper phase, containing the microgel, n-butanol and residual water, is azeotropically -freed from residual water in vacuo by adding a solvent and/or a carrier resin solution. This method is disadvantageous in that the coagulation and thus the separation of the water does not, or unsatisfactorily, takes place if the solids content of the aqueous microgel dispersion is above 20% by weight. For this reason, great amounts of n-butanol-saturated water result which have to be adequately disposed at considerable expenditure.
Besides, significant amounts of emulsifier remain in the microgel present in the solvent-containing phase, which again entails the disadvantages indicated above.
The object of the invention is to provide, on the one hand, a microgel and, on the other hand, a process of manufacturing the same which does not exhibit the above-mentioned disadvantages.
This problem is solved according to the present invention by producing an emulsifier-free microgel comprising polymerizing in aqueous phase a monomer blend consisting of at least one ethylenic monofuntional compound and at least one ethylenic di- or multifunctional compound in the presence of a polyester.
The polyester functions here as carrier resin and, for example, as binder if the finished microgel is used in a base coat for the motorcar industry. Consequently, the microgel of the present invention does not contain any components (emulsifiers) which might impair a later use. An ethylenic mono-, di- or multifunctional compound includes all compounds which have one, two or several vinylic and/or allylic carbon-carbon double bond(s)).
In a particular embodiment of the present invention, the ethylenic monofunctional compound is selected from the group consisting of alkyl esters of acrylic and methacrylic acid, such as, e.g., methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate as well as isomers thereof; vinylic aromatic compounds, such as styrene, .alpha.-methylstyrene, vinyl toluene, vinyl naphthalene, vinyl ester, such as, e.g., vinyl acetate, vinyl ester of synthetic fatty acids, such as, e.g., VeoVa.RTM. 9, VeoVa.RTM. 10 of the Shell-Chemie company.
The expression "(meth)acrylic" as used in the following includes derivatives of acrylic and methacr

REFERENCES:
patent: 4090991 (1978-05-01), Fukusaki et al.
patent: 4563372 (1986-01-01), Kurauchi et al.

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