Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-08-17
2002-09-03
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...
C526S079000, C526S080000, C526S081000, C526S271000, C526S318200
Reexamination Certificate
active
06444771
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to: an acrylic acid-maleic acid copolymer (or its salt) which is excellent in performances such as metal ion scavengeability, clay dispersibility, and scale inhibitability, and has a high random degree; a production process therefor; and uses of this copolymer (or its salt) for such as detergent builders.
The present invention further relates to a production process for an aqueous maleic salt solution with a low impurity content which has the advantage of giving the above copolymer (or its salt) more excellent performance.
B. Background Art
Generally, copolymers (or their salts), as used for detergent builders, water-treating agents, various chelating agents, and so on, are required to be high both in the metal ion scavengeability and the clay dispersibility in the presence of metal ions. Thus, various maleic acid copolymers (or their salts) have been developed to satisfy these performances. Furthermore, in water-treating processes, the alkaline earth metal ion scale inhibitability is demanded as an important performance, and the use of conventionally known maleic acid copolymers (or their salts) have been recognized to improve the scale inhibitability upon calcium ion that is the main component of the scale. However, in the case where such polymers (or their salts) as improved in the metal ion scavengeability, the clay dispersibility, and the scale inhibitability upon calcium are used for detergent builders, excellent deterging effects are exhibited according to expectation in some regions, while the hygroscopicity and touch of washed clothes are bad in other regions. In addition, there are problems in that the performances, such as the detergency or the softness of fibers after washing, vary with regions where the above polymers (or their salts) are used.
The present inventors diligently studied to pursue causes of the above problems. As a result, the present inventors have found that the cause is the formation of scale due to the generation of an inactive salt (magnesium hydroxide) from magnesium ion. That is to say, they have found that the generation and deposition of magnesium hydroxide scale have a bad influence upon the hygroscopicity and touch of clothes especially in regions where the magnesium ion content in water is high. Thus, the present inventors have further found out a copolymer (or its salt) which does not only maintain conventional performance levels of the metal ion scavengeability, the clay dispersibility, and the scale inhibitability upon calcium ion, but is also at high level in the scale inhibitability upon magnesium ion as has never been studied.
By the way, the production of the maleic acid copolymer (or its salt) involves the production of an aqueous maleic salt solution which is an aqueous solution of a monomer of the maleic acid copolymer (or its salt), but the production process for the aqueous maleic salt solution has never been studied.
The present inventors considered the production process for the aqueous maleic salt solution to be particularly important, and thus studied it. As a result, the present inventors found that a specific production process can give an aqueous maleic salt solution which contains only a small amount of formed impurities such as malic acid and therefore has high purity, and further that the resultant maleic acid copolymer (or its salt) from such an aqueous maleic salt solution also contains only a small amount of impurities such as malic acid and is therefore a copolymer (or its salt) which exhibits high calcium ion scavengeability and high clay dispersibility.
SUMMARY OF THE INVENTION
A. Objects of the Invention
Thus, a first object of the present invention is to provide: an acrylic acid-maleic acid copolymer (or its salt) which is excellent with good balance in performances such as metal ion scavengeability, clay dispersibility, calcium carbonate scale inhibitability, and magnesium hydroxide scale inhibitability; a production process therefor; and uses of this copolymer (or its salt) for such as detergent builders.
A second object of the present invention is to provide a production process for an aqueous maleic salt solution which contains only a small amount of formed impurities such as malic acid and therefore has high purity.
B. Disclosure of the Invention
An acrylic acid-maleic acid copolymer (or its salt), according to the present invention, is characterized by having a magnesium ion scavengeability of 210 mg (in terms of Mg(OH)
2
)/g or more and a magnesium hydroxide scale inhibitability of 30% or more. Preferably, this copolymer (or its salt) further has a clay dispersibility of 60% or more in the presence of magnesium ion.
Another acrylic acid-maleic acid copolymer (or its salt), according to the present invention, has a magnesium ion scavengeability of 210 mg (in terms of Mg(OH)
2
)/g or more, a molecular weight distribution of 3.5 or less, and low-molecular fractions with a molecular weight of 1,000 or less in the ratio of 9 wt % or less to the total of the copolymer (or its salt).
A production process for an acrylic acid-maleic acid copolymer (or its salt), according to the present invention, comprises the step of copolymerizing ethylenically unsaturated monomers including acrylic acid and maleic acid in the presence of a polymerization initiator, and is characterized in that: 50 wt % or more of the maleic acid is initially charged; the maleic acid has a neutralization degree of 70~95 mol % before the polymerization initiator is charged; and the resultant acrylic acid-maleic acid copolymer (or its salt) has a neutralization degree of 50~70 mol % and a solid component concentration of 45 wt % or more at the end of the polymerization.
A detergent composition, according to the present invention, comprises the above present invention acrylic acid-maleic acid copolymer (or its salt) and a surfactant.
A detergent builder, according to the present invention, comprises the above present invention acrylic acid-maleic acid copolymer (or its salt).
A production process for an aqueous maleic salt solution, according to the present invention, is characterized by comprising the steps of: charging 80% or less of the required amount of a basic substance to produce the aqueous maleic salt solution and 80% or less of the required amount of maleic acid (or its salt) and/or maleic anhydride to produce the aqueous maleic salt solution into a reaction vessel; and then adding thereto the respective balances of water, the basic substance, and the maleic acid (or its salt) and/or maleic anhydride under conditions where the highest value of the reaction temperature will be 80° C. or higher; and this process can give an aqueous maleic salt solution with a formed malic acid content of not more than 10,000 ppm.
The present invention can provide a maleic acid/acrylic acid copolymer (or its salt), which comprises maleic acid (or its salt) of 30~70 mol % and acrylic acid (or its salt) of 70~30 mol %, and has a weight-average molecular weight of 2,000~50,000, a calcium ion scavengeability of 400 mg CaCO
3
/g or more, a clay dispersibility of 0.6 or more, and a malic acid content of not more than 9 wt % in the solid content of the copolymer (or its salt).
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
Part I
In this part I, detailed descriptions are given on the present invention acrylic acid-maleic acid copolymer (or its salt) and its production process and use.
(Acrylic acid-maleic acid copolymer (or its salt):
The magnesium ion scavengeability of the present invention acrylic acid-maleic acid copolymer (or its salt) is defined as the mg number, in terms of magnesium hydroxide (Mg(OH)
2
), of magnesium ion as scavenged by 1 g of the copolymer (or its salt), and, for example, can be measured by the method as described in the below-mentioned examples of some preferred embodiments. The magnesium ion scavengeability is an index to show how
Ishida Tamao
Maeda Yoshihiro
Yamaguchi Shigeru
Haugen Law Firm PLLP
Nippon Shokubai Co. , Ltd.
Wu David W.
Zalukaeva Tanya
LandOfFree
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