Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-08-27
2003-05-06
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S240000, C526S304000, C526S303100, C524S558000, C524S376000, C524S458000, C524S460000, C524S556000, C524S560000, C524S522000, C524S523000
Reexamination Certificate
active
06559259
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to crosslinkable protective colloids, processes for the polymerization of ethylenically unsaturated monomers using the crosslinkable protective colloids, and polymers and polymer dispersions obtainable with these, and their use.
The stabilization of polymer dispersions with protective colloids and surfactants is known. An overview of the customary stabilizers is to be found, for example, in G. Schulz “Die Kunststoffe”[Plastics], C. Hanser Verlag, 1964, or in J. C. Jonson “Emulsifiers and Emulsifying Techniques” Noyes Data Corp., Park Ridge, N.J., 1979, and in Ullmann, “Encyklopädie der technischen Chemie”[Encyclopedia of Industrial Chemistry], 4th edition, Volume 10, Verlag Weinheim, 1980.
These compounds are distinguished by a hydrophilic and a hydrophobic part in the molecule, the latter serving for anchoring in the polymer resin. It is generally assumed that these surface-active substances are chiefly located at the interface between the polymer particles and the aqueous liquor. These stabilizers thus greatly influence the total surface area of the system and therefore in the end also the profile of properties of a polymer dispersion. The choice of suitable emulsifying auxiliary thus ultimately determines the desired final properties of a polymer dispersion.
The use of surface-active polymers as protective colloids is also often descried in the more recent patent literature. In a departure from the conventional polymeric protective colloids, such as polyvinyl alcohol, cellulose derivatives or gelatin, new synthesis routes are taken here, and water-soluble polymers with ionic groups, so-called polyelectrolytes, are employed as protective colloids.
An unsaturated polyester of maleic or fumaric acid polyethylene glycol ester which is used for stabilizing emulsion polymers is known from DE 4212768 (U.S. Pat. No. 5,385,971). The polymer dispersions prepared with these are distinguished by good stability to frost and electrolytes. DE-A 4304014 (WO-A 94/18249) describes a process for the continuous polymerization of acrylic polymers with a low degree of polymerization in an aqueous medium. The polymers thus obtained are suitable as dispersing auxiliaries for pigments and of binders. However, a disadvantage of these products is a certain thickener action, which is undesirable for many applications.
The stabilization of dispersions with polyelectrolytes is also known form DE 2540468 (GB-A 1551126), in which a good stability in respect of exposure to salts and shear is attributed to the resulting dispersions. WO-A 92/03482 describes oligomeric carboxylic acids as stabilizers for emulsion polymerization of monomers which can be polymerized by free radicals, which are said to be particularly suitable for the preparation of binders for printing inks. Binder dispersions for textile uses are claimed in U.S. Pat. No. 5,314,943. The polymer dispersions described therein are stabilized by means of a protective colloid containing carboxylic acids groups. Fast setting properties are attributed to them.
Aqueous polymer dispersions of crosslinkable polymers are often employed for the preparation of binders which lead to very stable polymer films, for example in the use as adhesives or coating compositions. Crosslinkable polymers with N-methylol-functional comonomer units as crosslinker groups are widely used. Such crosslinkable polymers are known, for example, from DE-C 2512589 (U.S. Pat. No. 4,044,197). However, the strength of the polymer films obtainable with these cannot be increased without problems by increasing the content of N-methylol-functional units in the polymer. It is therefore proposed in the prior art to increase the crosslinking action of such polymers by special preparation processes (EP-3 205862) or to polymerize comonomers with a blocked N-methylol function (EP-A 261373).
Against this prior art, there was therefore the object of providing polymers or aqueous polymer dispersions which form polymer films of high mechanical strength and high resistance to water and solvents.
The object has been achieved by providing a water-soluble, crosslinkable polymer with protective colloid properties which has functional groups which are capable of auto-crosslinking, in particular N-methylol groups, incorporated into the molecular chain.
Water-soluble polymers of high NMA content tend to have high molecular weights with a correspondingly high viscosity of the aqueous solution. Water-soluble acrylic compounds, such as acrylic acid or N-methylol-acrylamide, which is customary as a crosslinking agent, in fact tend towards very high degrees of polymerization, which severely impedes widespread use because of the resulting high viscosities. For example, EP-3 94898 (U.S. Pat. No. 4,736,005) describes the preparation of very high molecular weight (MW>1,000,000) terpolymers of 30 to 95% of dimethylacrylamide (DMA), 0.1 to 10% of N-methylolacrylamide (NMA) and 4 to 50% of acrylamido-methylpropanesulphonate (AMPS) and their use as rheological additives in crude oil production.
Another disadvantage of polyalectrolytes based on water-soluble monomers is that such polyelectrolytes are often incompatible with a polymer dispersion and the aqueous polyelectrolyte solution separates out from the polymer dispersion as a serum.
BRIEF SUMMARY OF THE INVENTION
Surprisingly, it has been found that by copolymerization of N-methylolacrylamide with acrylic compounds containing sulphonic acid or sulphonate groups, significantly lower molecular weights can be achieved. It has furthermore been found, surprisingly, that significantly lower surface tensions and lower viscosities already result by copolymerization of only small amounts of hydrophobic comonomers.
The invention relates to water-soluble, crosslinkable protective colloids having a molecular weight of ±500,000 comprising
a) at least 20% by weight of monomer units containing sulphonic acid or sulphonate groups,
b) 4 to 80% by weight of monomer units containing N-methylol or N-alkoxymethyl groups,
c) 0.1 to 20% by weight of hydrophobic monomer units from the group consisting of water-insoluble, ethylenically unsaturated compounds and the hydrophobic end groups of initiator radicals or regulator molecules, the contents in % by weight being based on the total weight of the copolymer, and
it being possible, where appropriate, for up to 50% by weight, based on the weight content of monomer units a), of the content of monomer units containing sulphonic acid/sulphonate groups to be replaced by monomer units d) containing carboxyl groups or monomer units e) containing amide groups.
Water-soluble, crosslinkable protective colloids having a molecular weight of ±500,000 comprising
a) 30 to 37% by weight of monomer units containing sulfonic acid or sulphonate groups,
b) 12 to 60% by weight of monomer units containing N-methylol or N-alkoxymethyl groups,
c) 0.1 to 10% by weight of hydrophobic monomer units from the group consisting of water-insoluble, ethylenically unsaturated compounds and the hydrophobic end groups of initiator radicals or regulator molecules,
the contents in % by weight being based on the total weight of the copolymer, are preferred.
Water-soluble, crosslinkable protective colloids having a molecular weight of ±500,000 comprising
a) 70 to 87% by weight of monomer units containing sulphonic acid or sulphonate groups,
b) 12 to 25% by weight of monomer units containing N-methylol or N-alkoxymethyl groups,
c) 1 to 5% by weight of hydrophobic monomer units from the group consisting of water-insoluble, ethylenically unsaturated compounds and the hydrophobic end groups of initiator radicals or regulator molecules,
the contents in % by weight being based on the total weight of the copolymer, are particularly preferred.
Suitable monomer units a) are, for example, water-soluble, ethylenically unsaturated compounds which can be polymerized by free radicals and contain sulphonic acid or sulphonate groups —SO
3
M, where M=H or alkali metal, ammonium or alkaline earth
Dobler Walter
Koegler Gerhard
Kohlhammer Klaus
Rockinger Monika
Brooks & Kushman P.C.
Choi Ling-Siu
Wacker-Chemie GmbH
Wu David W.
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