Grafted polymer and its production process and use

Details Grafted polymer and its production process and use Grafted polymer and its production process and use

2000-07-18

2002-09-10

Dawson, Robert (Department: 1712)

Compositions

Water-softening or purifying or scale-inhibiting agents

Plant or organic material containing

C528S403000, C525S404000, C548S543000, C510S276000

Reexamination Certificate

active

06447696

ABSTRACT:

BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a novel grafted polymer which is favorable as a scale inhibitor or detergent additive.
B. Background Art
It is generally considered that a scale inhibitor inhibits the formation of scale such as calcium carbonate in water by adsorbing and dispersing crystal nuclei of the scale (threshold effects). However, for sufficiently exhibiting such effects in water, it is important that the scale inhibitor has good hydrophilicity along with the adsorbency and the dispersibility.
On the other hand, in recent years, as laundry detergents become more and more compact, they generally contain not only surfactants, but also synthetic polymers such as acrylic acid polymers and acrylic acid/maleic acid copolymers as detergent additives. However, in the present circumstances, such conventional synthetic polymers cannot inhibit the migration of dyes from dyed cloth to other cloth which occurs in the processes of washing and rinsing.
In uses for such as scale inhibitors and detergent additives, conventionally, polymers obtained by polymerizing unsaturated carboxylic monomers such as acrylic acid or copolymers of these monomers with other monomers are widely used because of their properties such as chelatability and dispersibility. In addition, grafted polymers obtained by graft-polymerizing unsaturated carboxylic monomers (e.g. acrylic acid), vinyl acetate, or (meth)acrylate esters onto polyether compounds are used because of their properties such as dispersibility and solubility.
In addition, attempts are also made to graft-polymerize N-vinylpyrrolidone to further improve the above grafted polymers. For example, in JP-A-260995/1988 there is reported a grafted polymer as a graying inhibitor for laundry obtained by graft-polymerizing, in a specific ratio, (b) N-vinylpyrrolidone and (c) at least one vinyl ester, as derived from a saturated monocarboxylic acid with 1~6 carbon atoms, and/or a methyl or ethyl ester of acrylic or methacrylic acid onto (a) a poly(alkylene oxide) based on ethylene oxide, propylene oxide, or butylene oxide. However, this grafted polymer merely exhibits low hydrophilicity, because the ratio of the poly(alkylene oxide) (a) (which is the base of grafting) to the graft components (b) and (c) is low, and because only up to 15 mol % of the whole ester (c) is hydrolyzed.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide: a novel grafted polymer which has good hydrophilicity and is excellent in the adsorbency and the dispersibility; and a scale inhibitor and a detergent additive, both of which involve the use of this grafted polymer.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above problems. As a result, they completed the present invention by finding that if an oxyethylene chain and a pyrrolidone group were allowed to coexist and if the ratio of the oxyethylene chain which was the base of grafting was set at not smaller than a certain quantity, then good hydrophilicity could be retained, and the dispersibility and the adsorbency could be enhanced.
That is to say, a grafted polymer, according to the present invention, is a product by a process including the step of graft-polymerizing a graft component (B) onto a polyether compound (A) in a ratio such that the graft component (B) is in the range of 0.1~1.2 weight parts per 1 weight part of the polyether compound (A), wherein the polyether compound (A) is a product by a process including the step of polymerizing an alkylene oxide component with an ethylene oxide content of at least 50 mol % and has a number-average molecular weight of not lower than 200, and wherein the graft component (B) includes N-vinylpyrrolidone (b1) as an essential component and might further include a monoethylenically unsaturated monomer (b2), wherein the monomer (b2) includes a carboxyl-group-containing monoethylenically unsaturated monomer (b2-1) and/or a cationic monoethylenically unsaturated monomer (b2-2), with the proviso that the monomer (b2-1) may be a monomer having a structure formable into a carboxylic acid (or salt) by hydrolysis, wherein when the monomer (b2-1) includes the monomer having the structure formable into a carboxylic acid (or salt) by hydrolysis, not less than 50 mol % of all structural units as derived from the monomer (b2-1) have a carboxyl group, inclusive of a carboxyl group formable by the hydrolysis of the monomer having the above structure, with the proviso that when the carboxylic salt is formed by the hydrolysis, this carboxylic salt is also taken as the carboxyl group.
A production process for a grafted polymer, according to the present invention, comprises the steps of: polymerizing an alkylene oxide component with an ethylene oxide content of at least 50 mol % to obtain a polyether compound (A) having a number-average molecular weight of not lower than 200; and graft-polymerizing a graft component (B) onto the resultant polyether compound (A) in a ratio such that the graft component (B) is in the range of 0.1~1.2 weight parts per 1 weight part of the polyether compound (A), wherein the graft component (B) includes N-vinylpyrrolidone (b1) as an essential component and might further include a monoethylenically unsaturated monomer (b2), wherein the monomer (b2) includes a carboxyl-group-containing monoethylenically unsaturated monomer (b2-1) and/or a cationic monoethylenically unsaturated monomer (b2-2), with the proviso that the monomer (b2-1) may be a monomer having a structure formable into a carboxylic acid (or salt) by hydrolysis,
and this production process further comprises the step of hydrolyzing the resultant grafted polymer when the monomer (b2-1) includes the monomer having the structure formable into a carboxylic acid (or salt) by hydrolysis, wherein the hydrolyzing step is carried out such that not less than 50 mol % of all structural units as derived from the monomer (b2-1) can have a carboxyl group, inclusive of a carboxyl group formable by the hydrolysis of the monomer having the above structure, with the proviso that when the carboxylic salt is formed by the hydrolysis, this carboxylic salt is also taken as the carboxyl group.
A scale inhibitor, according to the present invention, comprises the above grafted polymer according to the present invention as an essential component.
A detergent additive, according to the present invention, comprises the above grafted polymer according to the present invention as an essential component.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
The grafted polymer, according to the present invention, is a product by a process including the step of graft-polymerizing a graft component (B) onto a polyether compound (A), wherein the polyether compound (A) is a product by a process including the step of polymerizing an alkylene oxide component including ethylene oxide.
In the present invention, it is important that the graft polymerization is carried out in a ratio such that the graft component (B) is in the range of 0.1~1.2 weight parts per 1 weight part of the polyether compound (A). In the case where the ratio of the graft component (B) is smaller than 0.1 weight parts per 1 weight part of the polyether compound (A), the amount of N-vinylpyrrolidone (b1) which is included as an essential component in the graft component (B) is too small, therefore adsorption effects by the pyrrolidone group cannot sufficiently be exhibited. On the other hand, in the case where the ratio of the graft component (B) is larger than 1.2 weight parts per 1 weight part of the polyether compound (A), the ratio of the polyether compound (A) is so small that the dispersibility or hydrophilicity of the oxyethylene chain cannot sufficiently be exhibited, and further, the number of the graft sites is so small that the graft polymerization reaction itself is difficult to run. Incidentally, when the below-mentione

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