Polymers, their preparation and their use

Details Polymers, their preparation and their use Polymers, their preparation and their use

1997-12-11

2003-08-12

Metzmaier, Daniel S. (Department: 1712)

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Treatment with particular chemical

C162S078000, C252S186270, C252S186290, C008S111000, C526S229000, C526S292950, C526S238200, C526S238220, C526S238230, C524S401000, C524S845000

Reexamination Certificate

active

06605182

ABSTRACT:

In peroxide bleaching of fibrous material, in particular of cellulosic fibrous material, for increasing the bleaching yield, i.e. in order to avoid a premature decomposition of the peroxide bleaching agent—before all hydrogen peroxide—there are employed stabilizers, which may be formulated as stock solutions and before all for continuous bleaching processes, also as reinforcing liquors. Depending on the process the reinforcing liquors may be of a different alkalinity and may also be very strongly alkaline, e.g. of an alkalinity that corresponds to 0.2N to 8N NaOH. For the employed stabilizer it is desired that they be stable also at high alkalinities. Since the stabilizers are employed only as adjuvants, i.e. shall not build up or shall build up only in a labile way on the substrate and are finally present in the backwater, it is thus desired that these adjuvants be biologically degradable.
From U.S. Pat. No. 4,363,699 it is known to bleach textile material or paper with hydrogen peroxide under alkaline conditions in the presence of certain sodium polya-hydroxyacrylates. In U.S. Pat. No. 4,916,699 there are described poly-&agr;-hydroxyacrylates of high stability to alkali, which may also be formulated in alkaline stock solutions and reinforcing liquors. In DE-A43 44 029 there are described copolymers that derive from certain mono- or disaccharides and certain unsaturated sulphonic acids or dicarboxylic acids and monoethylenically unsaturated C
3-10
-carboxylic acids (there are named acrylic acid and methacrylic acid) or from certain mono- or disaccharides and acrylic acid, as dispersants and cobuilders or sequestrants. These copolymers do not have a sufficient stabilizing activity on peroxy bleaching agents (this means that in the course of the bleaching process the peroxide decomposition provoked by the alkali cannot be sufficiently hemmed by them, so that a substantial proportion of the peroxide is decomposed prematurely, i.e. long before completion of the bleaching process, and thus cannot display its bleaching activity), and thus for the peroxide bleaching it is recommended to combine the copolymer with stabilizers for percompounds. However, it is also possible to bleach with a peroxide without using a stabilizer, but the use of a stabilizer increases significantly the yield by avoiding premature decomposition of the peroxide, which is of particular importance in alkaline peroxide bleaching liquors, especially in more concentrated alkaline peroxide bleaching liquors, such as those used in padding processes.
It has now been found, that the below defined polymers (P), which contain the monomer units (a) and (s), while the presence of costly sulphogroup-containing monomer units is not necessary, meet surprisingly well the above requirements, namely not only with reference to biological degradability but also as for stability, especially under strongly alkaline conditions, e.g. at ≧0.2N NaOH, or even ≧0.5N NaOH, principally ≧2N NaOH, and efficiency for the stabilizing of peroxy compounds in the alkaline peroxide bleaching (in particular in padding liquors and in stock solutions), namely also without the presence of additional sequestrants or other stabilizers.
The invention relates to the polymers (P), their production and use, as well as to the corresponding (P)-containing compositions and alkaline stock solutions as are suitable for bleaching liquors, and to the corresponding (P)-containing bleaching liquors.
A first object of the invention is, thus, a (co)poly-&agr;-hydroxyacrylic-acid-based polymer (P), optionally in lactonized form or in salt form, which is characterized by a content in
(s) at least one carbohydrate unit and
(a) at least one 2-hydroxy-2-carboxyethylene-1,2-unit,
or a mixture of such polymers (P).
The polymers (P) of the invention are obtainable by polymerisation of at least one vinyl monomer (A), which provides the monomer units (a) and which is principally an a-halogenacrylic acid or a salt thereof, and optionally at least one further vinyl monomer (B), in the presence of at least one optionally modified carbohydrate (S), which provides the unit (s), and optionally reaction of the polymerisation product with at least one base for salt formation.
The units (a) correspond in the non-lactonized acid form to the formula
as occur e.g. in poly-&agr;-hydroxyacrylic acids (and therefore are also called “&agr;-hydroxyacrylic acid units”). Optionally a carboxylic group in (a) may be lactonized with a suitable hydroxy group or it may be present in salt form.
As vinyl monomers (A) there may be employed monomers which in their polymerisation lead to corresponding 2-hydroxy-2-carboxyethylene-1,2 units, principally &agr;-Hal-acrylic acid, wherein Hal signifies chlorine or bromine, i.e. &agr;-chloroacrylic acid or &agr;-bromoacrylic acid, or a hydrosoluble salt thereof. Preferably as (A) there is employed (A
1
), i.e. &agr;-chloroacrylic acid optionally in salt form. If desired there may be employed a precursor of (A
1
), e.g. &agr;,&bgr;-dichloropropionic acid or a functional derivative thereof (e.g. methylester or chloride), which before the polymerisation to (A
1
) is dehydrochlorinated and, if required, saponified.
As further vinyl monomers (B), come into consideration mainly low molecular anionic or non-ionic monomers, in particular (B
1
), i.e. &agr;,&bgr;-ethylenically unsaturated aliphatic carboxylic acids containing preferably 3 to 6 carbon atoms, e.g. acrylic acid, methacrylic acid, maleic acid, itaconic acid, aconitic acid, fumaric acid or citraconic acid.
The monomers (A) and (B), in particular (A
1
) and (B
1
), may be employed in the form of the free acids or, preferably, at least in part in the form of a hydrosoluble salt, and if they are employed as salts, these are transformed to the acid form in the acidic reaction medium. There may e.g. be employed ammonium salts or preferably alkali metal salts (e.g. Li-, Na- or K-salts), with particular preference sodium salts of the mentioned monomers. The monomers (A) and (B), in particular (A
1
) and (B
1
) are advantageously employed in such quantitative ratios that (A) amounts to at least 50 mol-%, i.e. to 50 to 100 mol-% of [(A)+(B)], respectively so that (a) amounts to 50 to 100 mol-% of [(a)+(b)], in which (b) are the monomer units introduced by reaction with (B). Advantageously the proportion of (A) is 80 to 100 mol-%, with particular preference 100 mol-% of [(A)+(B)], respectively the proportion of (a) amounts advantageously to 80 to 100 mol-%, preferably 100 mol-% of [(a)+(b)], i.e. preferably there is employed no (B).
As optionally modified carbohydrates (S) come into consideration any such compounds containing at least three carbon atoms and having polyol character, i.e. containing at least three hydroxy groups per carbon chain or ring, and which are soluble, suspendable or swellable in water. As (S) there are principally meant natural saccharides or modification products thereof, i.e. saccharides that are obtained from animal or vegetable products (e.g. from the processing of milk, honey or parts of plants) or simple modification products thereof, e.g. enzymatically or chemically modified products (e.g. by hydrolysis, by hydrogenation, by oxidation, by partial etherification or esterification and/or by derivatisation), so long as the essential polyol character of the saccharide is maintained. However, it is also possible to employ synthetic saccharides, principally polymerisation products of mono- or/and disaccharides as are producible by polymerisation in aqueous solution, but preferably the saccharides (S) are natural saccharides or simple modification products thereof.
As carbohydrates (S) come advantageously into consideration mono-, oligo- or polysaccharides, whose monomer units contain 4 to 7, preferably 5 or 6 carbon atoms. As modified carbohydrates (S) come principally into consideration those carbohydrates in which one ot two functional groups have been chemically modified, e.g. by reduction to polyols or desoxysugars, by o

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