JPS62119255A - Aqueous dispersion of substituted succinic anhydride - Google Patents

Abstract

PURPOSE:An aqueous dispersion of a substituted succinic anhydride, containing a specific water-soluble copolymer and having improved sizing effect and good dilution stability in use as a sizing agent utilized in a paper making process. CONSTITUTION:An aqueous dispersion obtained by adding (B) a mixture prepared by additionally premixing a substituted succinic anhydride with an oil-in- water type surfactant to (A) (A1) a water-soluble copolymer containing 50-98.5mol% (meth)acrylamide, 1-49.5mol% N,N-dialkylaminoalkyl (meth) acrylamide and 0.5-20mol% (meth)acrylic acid as monomer components or (A2) a water-soluble copolymer consisting of >=70wt% mixed monomer components of the component (A1) and another monomer copolymerizable monomer or an aqueous solution containing both components (A1) and (A2) and preparing a dispersion in a mixer. The aimed stable dispersion with 0.01-25wt% content of the component (B) is obtained by using 0.2-2pts.wt., based on 1pt.wt. component (B), component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an aqueous dispersion of substituted succinic anhydride, which has excellent sizing effects and good properties, particularly when used as a sizing agent used in paper manufacturing processes. The present invention provides an aqueous dispersion of substituted succinic anhydride which has excellent operability and excellent dilution stability.

[Conventional technology]

It is well known that an aqueous dispersion of substituted succinic anhydride is used as a sizing agent, and there are various proposals regarding the type of aqueous dispersion.

For example, an aqueous solution of cationic starch and a substituted succinic anhydride are mixed and homogenized under strong mechanical stirring (Japanese Patent Publication No. 39-2305), and a substituted succinic anhydride and a specific interface are used. A premix prepared by mixing an activator in advance and dispersing it in water or an aqueous solution of a specific water-soluble polymer substance (
For example, Japanese Patent Publication No. 53-36044, Japanese Patent Application Publication No. 58-
45731, JP-A-59-47498, etc.)
, furthermore, a substituted alkyl succinic anhydride, a substituted alkenyl succinic anhydride, or a mixture of these succinic anhydrides [a) 70 to 99.9 mi%, and polyoxyethylene alkyl ether phosphate or polyoxyethylene alkyl Aryl ether phosphate ester or mixture of these phosphate esters [b] 0.
There is one in which a mixture of 1 to 30% by weight is dispersed in an aqueous solution of a water-soluble polymer compound (Japanese Unexamined Patent Publication No. 60-28598).

[Problem that the invention seeks to solve]

By the way, among the aqueous dispersions of substituted succinic anhydride, the former one that utilizes cationic starch not only requires large-scale equipment for dispersing the substituted succinic anhydride in water, but also Since it is difficult to sufficiently reduce the dispersed particle size of the liquid, it has the disadvantage that a slight decrease in size performance cannot be avoided.

However, for those that use the latter premix, this premix has poor stability during storage, and as time passes after preparing the premix, the dispersibility of the premix in water disappears and the size increases. Substituted succinic anhydrides, including substituted succinic anhydrides with an internal olefin structure that are particularly suitable as sizing agents, have serious drawbacks such as reduced performance or no performance at all. It has the disadvantage of poor dispersion performance in water. In addition, in the method of obtaining an aqueous dispersion using this premix, when preparing an aqueous dispersion from the premix, the premix is dispersed in an aqueous solution in which cationic starch is dissolved in advance. For example, it is possible to make an aqueous dispersion with good dilution stability, but since the aqueous solution of cationic starch itself is unstable over time, it is necessary to dissolve the cationic starch in water immediately before using the aqueous dispersion as a sizing agent. In addition, because the dispersibility of cationic starch in water for substituted succinic anhydride is low, it has negative factors such as the need for a powerful (large-scale) emulsifying device to prepare the aqueous dispersion. are doing.

Further, the substituted alkyl succinic anhydride or substituted alkenyl succinic anhydride or a mixture of these succinic anhydrides (a) 70 to 99.9 weight pot, and polyoxyethylene alkyl ether phosphate ester or ? Lyoxyethylene alkylaryl ether phosphate ester or mixture of these phosphate esters [b) 0.
A mixture of 1 to 30 f'it% has excellent properties in terms of storage stability, which is a drawback of the above-mentioned premixture of substituted succinic anhydride and surfactant. It was proposed as a premix that exhibits good dispersibility in water even for substituted succinic anhydride having an internal olefin structure, which is excellent as a sizing agent. When using the aqueous dispersion as a sizing agent on an industrial scale,
It turned out that there were some problems. That is, the aqueous dispersion of substituted succinic anhydride obtained from the premix proposed in JP-A-60-28598 is as follows:
When the continuous aqueous phase contains dissolved cationic starch, the dilution stability of the aqueous dispersion is good; however, in other cases, the dilution stability is insufficient. When this aqueous dispersion is applied as a sizing agent in the papermaking process for commercial use, it may cause staining of the wires, rolls, blankets, etc. of the paper machine, making continuous operation for long periods of time impossible. have.

For this reason, the present inventors proposed that (meth)acrylamide and N
, N-sialkylaminoalkyl (meth)acrylamide and a specific water-soluble copolymer obtained as an essential monomer component. The authors discovered that the various problems mentioned above can be solved, and proposed an aqueous dispersion of substituted succinic anhydride containing the specific water-soluble copolymer. When the liquid is used as a sizing agent for paper manufacturing, the sizing effect is not necessarily satisfactory in the low addition range of the sizing agent, and it is difficult to use an acidic papermaking process that does not use calcium carbonate filler or uses calcium carbonate filler. In addition, when applied to the neutral paper making process of medium-quality paper, which is often carried out by adding a small amount of sulfuric acid, peeling between the wet paper and the roll at the press section becomes difficult. However, it has been found that there is an operational problem in that paper breaks easily occur.

In contrast, the present invention provides a specific water-soluble copolymer obtained from the above-mentioned (meth)acrylamide and N,N-dialkylaminoalkyl (meth)acrylamide as essential monomer components, which was previously proposed by the present inventors. The aqueous dispersion of substituted succinic anhydride containing It exhibits a fully satisfactory size effect even in the addition range, and is completely effective in acidic papermaking processes that do not use calcium carbonate filler and in neutral papermaking processes, including cases using sulfuric acid band. Similarly, it was possible to provide an aqueous dispersion of substituted succinic anhydride that exhibits excellent operability.

[Failure to solve the problem]

The present invention comprises 50 to 98.5 mol% of (meth)acrylamide (a), 1 to 49.5 mol% of N,N-dialkylaminoalkyl (meth)acrylamide (b), and 0.5 to 98.5 mol% of (meth)acrylamide (b).
Water-soluble copolymer [A,] containing 20 mol% of (meth)acrylic acid (c) as a monomer component or 50 to 98°5
Mol% of (meth)acrylamide (a) and 1 to 49.5
mol % of N,N-sialkylaminoalkyl (meth)acrylamide (b) and 0.5-20 mol % of (meth)acrylic acid (c),! : Mixed monomer component 70 consisting of
A water-soluble copolymer [A2] containing at least % by weight and another copolymerizable monomer (d) as a monomer component, or the water-soluble copolymer [A2] similar to the water-soluble copolymer [AI].
A2], i.e., 50 to 98.5 mol% of (meth)acrylamide (a) and 1 to 49.5 mol% of N,N-sialkyl Water-soluble copolymer obtained by copolymerizing aminoalkyl (meth)acrylamide (b) and (meth)acrylic acid (c) with a molar ratio of 0.5 to 20 [:Al1, 50 to 98.5 molar ratio] Mol% (meth)acrylamide (a)
70% by weight of a mixed monomer component consisting of 1 to 49.5 mol % of N,N-sialkylaminoalkyl (meth)acrylamide (b) and 0.5 to 20 mol of (meth)acrylic m (c) The above and other copolymerizable monomers (d
) a water-soluble copolymer [A2] obtained by copolymerizing less than 30% by weight, or both the water-soluble copolymer [AI] and the water-soluble copolymer [A2], and a substituted amber It is an aqueous dispersion containing acid anhydride CB) as an essential component.

As the substituted succinic anhydride CB in the aqueous dispersion of substituted succinic anhydride of the present invention having the above structure, any substituted succinic anhydride known as a conventional sizing agent can be used.

Specifically, a hydrophobic hydrocarbon group having 8 or more carbon atoms, preferably 12 to 36 carbon atoms (for example, an alkyl group or an alkenyl group)
A substituted succinic anhydride having the following is used. This substituted succinic anhydride is generally easily produced by an addition reaction between maleic anhydride and olefins such as α-olefins, internal olefins, or mixtures thereof having the corresponding number of carbon atoms. It's something you get. In particular, substituted succinic anhydrides such as octadecene-9, tetradecene-7
, hexadecene-7, eicosene-11, or mixtures thereof, or linear internal olefin mixtures obtained by dehydrogenation of linear paraffins, in which double bonds are almost evenly distributed at all positions except the α-position. , the double bond obtained by subjecting a linear α-olefin to an isomerization reaction in the presence of a catalyst is 2-. When it is an addition reaction product of maleic anhydride and an internal olefin selected from a linear internal olefin mixture in which the total amount of internal olefins at the 3- and 4-positions is 70% or more,
That is, when the substituted succinic anhydride is an alkenyl succinic anhydride having a succinyl anhydride group inside the substituent, the aqueous dispersion of the substituted succinic anhydride of the present invention can be applied to the paper manufacturing process as a paper sizing agent. By doing so, the size effect produced will be even better.

A water-soluble copolymer (A
, ) or [A2] are acrylamide, methacrylamide, or both, that is, (meth)acrylamide (a) and N
, N-dialkylamino alkylacrylamide,
N,N-dialkylamino-alkylmethacrylamide, or both of these, i.e., N,N-dialkylamino-alkyl(meth)acrylamide (b);
Acryno C acid, methacrylic acid, or both, ie (meth)acrylic acid (c). Furthermore, the above N
, N-sialkylamine alkyl (meth)acrylamide (b) is a basic tertiary amino group-containing monomer represented by the general formula.

The water-soluble copolymer [A1] contains 50 to 98.5 mol% of the (meth)acrylamide (a) and 1 to 98.5 mol% of the N,N-sialkylaminoalkyl (meth)acrylamide (b).
49.5 mol% and (meth)acrylic acid (c) 0.5~
This copolymer [A1] can be easily obtained by subjecting a monomer mixture adjusted to the above composition ratio to a normal polymerization operation. ) Acrylamide (a) 75-94 mol% and N,N-sialkylaminoalkyl(meth)acrylamide (b)
5-20 mol% and (meth)acrylic acid (c) 1-1
The copolymer [A1] with 0 mol% of the substituted succinic anhydride of the present invention has a size effect in the low addition range of the sizing agent, which is a characteristic when the aqueous dispersion of the substituted succinic anhydride of the present invention is used as a sizing agent, and the acidic paper making process. It has been confirmed that this method brings about more favorable results due to better operability in the neutral papermaking process. Further, as the copolymerization method, it is preferable to use aqueous solution polymerization, and the molecular weight of the water-soluble copolymer [A1] is about 5,000.
0 or more, preferably 20,000 or more are effectively used.

In addition, the water-soluble copolymer [A2] comprises 50 to 98.5 mol% of the above (meth)acrylamide (a) and 1 to 98.5 mol% of the N,N-dialkylaminoalkyl (meth)acrylamide (b).
49.5 mol% and (meth)acrylic acid (c) 0.5-2
In the case of the above-mentioned water-soluble copolymer [A1], it is a copolymer whose monomer components are 70% by weight or more of a mixed monomer component consisting of 0 mol% and less than 30% by weight of other copolymerizable monomers (d). It can be easily obtained in the same way. In the case of this water-soluble copolymer [A2], as well as the water-soluble copolymer [A1], (meth)acrylamide (a)
and N,N-dialkylaminoalkyl (meth)acrylamide p (b) and (meth)acrylic acid (c), (meth)acrylamide (a) 75 to 94 mol%
N,N-dialkylaminoalkyl (meth)acrylamide (b) 5-20 mol%.

When the water-soluble copolymer [A2] in the case of 1-10 mol% of (meth)acrylic acid (c) is used as a sizing agent, the aqueous dispersion of the substituted succinic anhydride of the present invention is used as the sizing agent. The above-mentioned attributes of are more preferred. Furthermore, in the case of water-soluble copolymer [A2], the molecular weight is 5000 or more,
Preferably, 20,000 or more are effectively used.

In addition, in the water-soluble copolymer [A2], the copolymer [A
), examples of other copolymerizable monomer components that make up less than 30% by weight include aromatic vinyl monomers such as styrene and alkylstyrene, alkyl esters of α,β-unsaturated carboxylic acids, hydroxyalkyl esters, amino α,β-unsaturated carboxylic acid esters such as alkyl esters, vinyl acetate and other fatty acid vinyl esters, other vinyl compounds such as vinyl ethers and vinylamides,
Allyl compounds such as allyl alcohol, allyl ether, allyl amine, diallyl amine, and their quaternary ammonium salts, the N,N-dialkylaminoalkyl (meth)acrylamide, aminoalkyl (meth)acrylate, vinyl pyridine, etc. Polymerizable quaternary ammonium compounds and other polymerizable unsaturated compounds may be mentioned.

Although the content of substituted succinic anhydride in the aqueous dispersion of substituted succinic anhydride of the present invention can be arbitrarily selected, it is generally stable within the range of 0.01 to 25% by weight. An aqueous dispersion is obtained. In particular, the aqueous dispersion of the present invention is particularly useful due to its excellent stability upon dilution, and therefore, at a concentration of 1% by weight or less, the effect brought about by the dilution stability is It becomes even clearer.

1. The total content of the water-soluble copolymer [A1] and the water-soluble copolymer [A2] contained in the aqueous dispersion of the present invention is preferably approximately 0.05 to 20% by weight, and the substitution It is preferable that the total amount of water-soluble copolymer [A1] and water-soluble copolymer [A2] be selected within the range of about 0.2 to 2 parts by weight per 1 part by weight of succinic anhydride. .

Furthermore, it goes without saying that the aqueous dispersion of substituted succinic anhydride of the present invention may additionally contain other surfactants and water-soluble polymeric substances. In particular, if a small amount of an oil-in-water surfactant consisting of, for example, a polyoxyalkylene alkyl (aryl) ether and its sulfuric acid half-ester or phosphoric acid ester is additionally included, the substituted surfactants in the aqueous dispersion may be The aqueous dispersion of substituted succinic anhydride additionally contains a small amount of such an oil-in-water surfactant because the dispersed particle size of the acid anhydride can be made very fine. The most preferred form is an aqueous dispersion. still.

In the aqueous dispersion containing the oil-in-water surfactant, it is usually preferable to use the oil-in-water surfactant in an amount of about 0.1 to 10% by weight relative to the substituted succinic anhydride.

Aqueous dispersions of uninvented substituted succinic anhydrides.

The aforementioned water-soluble copolymer [A1] or water-soluble copolymer [
It can be easily obtained by adding substituted succinic anhydride [B] to an aqueous solution containing A2] or both, and mechanically emulsifying and dispersing it using various homogenizers or mixers. If small amounts of oil-in-water surfactants are used together, it is preferred to use a premix of oil-in-water surfactants and substituted succinic anhydride CB). As the oil-in-water surfactant used in the premix, any surfactant that is compatible with the substituted succinic anhydride [B) can be used. It is desirable to select and use a surfactant that provides dispersibility in water and has little negative impact on the size effect; for example, polyoxyalkylphalkyl (aryl) ether and its sulfuric acid half ester or phosphoric acid ester, etc. The content of the oil-in-water surfactant in the premix is preferably about 0.1 to 10% by weight.

Particularly preferred oil-in-water surfactants are polyoxyalkylene/alkyl(aryl)ether phosphates represented by the general formula, which have extremely good compatibility with substituted succinic anhydrides. Moreover, it provides substituted succinic anhydride with particularly excellent dispersibility in water.

Furthermore, an oil-in-water surfactant in which R3 in the general formula is an alkyl group or alkylaryl group having 10 to 2 carbon atoms, X is an ethylene group, and m is an integer of 5 or more. When an agent is used, a premix of substituted succinic anhydride and oil-in-water surfactant is added to the water-soluble copolymer [A1] or the water-soluble copolymer [A2] or these. An aqueous dispersion of substituted succinic anhydride obtained by dispersing it in an aqueous solution containing both of the above is used as a sizing agent for paper manufacturing because the particles dispersed in water of the aqueous dispersion become very small. When used, the size effect produced is even more excellent, resulting in a particularly preferred aqueous dispersion of substituted succinic anhydride. Further, in order to obtain the aqueous dispersion of the substituted succinic anhydride of the present invention using the premix of the substituted succinic anhydride [B] and the oil-in-water surfactant, 1 part by weight of the premix should be added to the premix. On the other hand, using an aqueous solution containing the water-soluble copolymer [A+] and the water-soluble copolymer [A2] in a total amount of about 0.1 to 2 parts by weight,
It is preferable to mix and stir by any procedure, and mixing can be carried out using a stirring device such as an ordinary propeller-type stirrer or various other homogenizers or mixers.

The aqueous dispersion of substituted succinic anhydride of the present invention having the above structure is mainly used as a sizing agent for paper manufacturing, but it can also be used as a sizing agent in various textile industries, for example. be. In addition, in the case of use as a sizing agent for paper manufacturing, the aqueous dispersion of the substituted cono-monolyric acid anhydride is arbitrarily adjusted to a desired concentration and added to pulp slurry, which is a raw material for paper making, for internal sizing. Alternatively, it can be used for surface sizing applied by any means to a wet or dry sheet after sheet formation, and can be applied to all papermaking processes, such as acid papermaking that uses sulfuric acid band or neutral papermaking that does not use sulfuric acid band. be.

[For production]

In the aqueous dispersion of substituted succinic anhydride of the present invention,
The above-mentioned water-soluble copolymer [AI] and water-soluble copolymer [A2] added and contained in the dispersion exhibit high adsorption to the pulp, and due to this action, the dispersion It exhibits the effect of efficiently fixing the fine particulate substituted succinic anhydride in the liquid to the pulp fiber surface.

In addition, the water-soluble copolymer [A+) and the water-soluble copolymer [A2] contained in the aqueous dispersion of the substituted succinic anhydride of the present invention bring about the dispersion in water in the substituted succinic anhydride CB). The performance is far superior to that of the copolymer of (meth)acrylamide (a) and N,N-dialkylaminoalkyl (meth)acrylamide (b),
This action of the water-soluble copolymer [A1] and the water-soluble copolymer [A2] provides the aqueous dispersion of the substituted succinic anhydride of the present invention with extremely high dilution stability.

Furthermore, the water-soluble copolymer [A,] contained in the aqueous dispersion of the present invention? In the water-soluble copolymer [A2], the carboxyl group based on the (meth)acrylic acid monomer component contained in the copolymer [A1] or [A2] is bonded to the aluminum polyvalent cation in the sulfate band. Therefore, when the aqueous dispersion of the substituted succinic anhydride is applied as a paper sizing agent in a paper manufacturing process containing sulfuric acid, it is necessary to use the above-mentioned carboxyl group and aluminum polyvalent sizing agent. The interaction with cations results in a better fixing effect, which not only provides excellent size effects, but also avoids various troubles such as contaminating paper machine wires, rolls, blankets, etc. during the paper making process. It is something that will be done.

〔Example〕

The specific composition of the aqueous dispersion of substituted succinic anhydride and the method for producing the same of the present invention will be explained below in Examples, and the properties of the aqueous dispersion of substituted succinic anhydride prepared for comparison will also be explained. Compare and explain their properties.

Examples and Comparative Examples Each part by weight of the surfactant shown in the specified column of Table 1 was added to 100 parts by weight of alkenylsuccinic anhydride, and the mixture was stirred and mixed at room temperature to obtain the composition of alkenylsuccinic anhydride. I got something. The alkenylsuccinic anhydride is obtained by reacting maleic anhydride with an internal olefin containing 90% by weight of an olefin having 15 to 18 carbon atoms and having a double bond at the 2 to 4 positions in a conventional manner.

Next, the composition of each of the alkenylsuccinic anhydrides,
Similarly, it was mixed into each part by weight of a 10% by weight solution of a water-soluble polymer compound shown in the specified column of Table 1 above, and mixed using a homomixer [manufactured by Tokushu Kika Kogyo ■: HV: M type]. , 50V for 1 minute to prepare each aqueous dispersion of substituted succinic anhydride.

Experiment 1 Each of the aqueous dispersions obtained in the above Examples and Comparative Examples was mixed with 20% by weight of heavy calcium carbonate filler (manufactured by Sankyo Seifun ■: Escalon@aOO) based on the pulp weight. pulp slurry (L-BKP, c, s,
f, 400 cc), the composition of the substituted succinic anhydride and surfactant in the aqueous dispersion was added to 0.0 cc of the pulp weight.
Add it to make it 15%, and follow the usual method below.
TAPPI Standard She
After preparing hand-made paper equivalent to 80 P/m using a 110° C. rotary dryer for 120 seconds, hand-made paper was obtained.

Table 2 shows the Steckigt sizing degree (seconds) measured after humidity conditioning the obtained handmade paper according to JIS.

In addition, Table 2 shows the emulsion average particle diameter (μm) of each aqueous dispersion, the emulsion average particle diameter (μm) after leaving each dispersion for 10 hours, and the average emulsion particle diameter (μm) after each dispersion was soaked in tap water with a total hardness of 100. , the stability of a diluted dispersion in which the composition of alkenylsuccinic anhydride and surfactant was diluted to 0.05% is also listed.

Table 2 Experiment 2 Each of the aqueous dispersions obtained in the above Examples and Comparative Examples was treated with talc in an amount of 20% by weight based on the weight of the pulp and sulfuric acid band at a rate of 0.5% by weight based on the weight of the pulp. [Al2
(SO4)3.16-18H20] and 2% by weight of Parzosura IJ-(L-BKP, c, g, f, 4
00CC), the composition of substituted succinic anhydride and surfactant in the aqueous dispersion was 0.1% by weight of the pulp weight.
The following procedure was repeated in the same manner as in Experiment 1 to obtain handmade paper. Table 3 shows the Steckigt size degree (seconds) obtained by temporarily measuring the humidity of the obtained handmade paper according to JIS.

Experiment 3゜To a valve slurry having the same composition as that used in Experiment 2, each of the aqueous dispersions obtained in the above Examples and Comparative Examples was added to the substituted succinic anhydride in the aqueous dispersion and the surfactant. The composition with the agent was added so as to be 1% by weight of the pulp weight, and paper was made in the same manner as in Experiment 1 to prepare a wet sheet. The obtained wet sheet was mixed with chrome methoxylate.
After holding the wet sheet between sheets of paper and pressing for 5 minutes at a pressure of 3.5 Ky/Cm, remove the wet sheet from the plate and visually observe the stains on the plate surface (presence of deposits such as fine grains). Shida. The results are shown in Table 4.

〔Effect of the invention〕

The aqueous dispersion of substituted succinic anhydride of the present invention has a specific structure, and the aqueous dispersion of substituted succinic anhydride has the following properties: Due to the stabilizing effect of the water-soluble copolymer [A2], it has the same dilution stability as a conventional aqueous dispersion of substituted succinic anhydride using cationic starch, and Since the aqueous dispersion of the substituted succinic anhydride using the emulsion particle size is even finer than the emulsion particle size in the aqueous dispersion of the substituted succinic anhydride, the aqueous dispersion of the substituted succinic anhydride can be used as a sizing agent in the paper manufacturing process. When a liquid is used, a sufficiently satisfactory size effect can be obtained even when the amount of substituted succinic anhydride added is low, for example, 0.15% by weight or less relative to the pulp weight. It is something that can be done.

Furthermore, since the aqueous dispersion of substituted succinic anhydride of the present invention has a better fixing effect on Palreso fibers in the presence of sulfuric acid band, the aqueous dispersion of substituted succinic anhydride can be used for paper manufacturing. When used as a sizing agent,
Not only can excellent sizing effects be obtained in all papermaking processes, including papermaking processes that use sulfuric acid, it also allows paper to be made without inducing contamination of paper machine wires, rolls, blankets, etc., and provides excellent operability. It is something that brings.

Claims (5)

[Claims] (1) 50 to 98.5 mol% (meth)acrylamide (a), 1 to 49.5 mol% N,N-dialkylaminoalkyl (meth)acrylamide (b), and 0.5 to 2 mol%
Water-soluble copolymer [A_1] containing 0 mol% of (meth)acrylic acid (c) as a monomer component, or 50 to 98.
5 mol% of (meth)acrylamide (a) and 1-49.
5 mol% N,N-dialkylaminoalkyl(meth)
Acrylamide (b) and 0.5-20 mol% (meth)
A water-soluble copolymer [A_2] containing 70% by weight or more of a mixed monomer component consisting of acrylic acid (c) and another copolymerizable monomer (d) [A_2], or the above-mentioned water-soluble copolymer [A_1] Similarly, the water-soluble copolymer [
A_2] and a substituted succinic anhydride [B]. (2) The water-soluble copolymer [A_1] or [A_2] is
75-94 mol% of (meth)acrylamide (a) and 5
~20 mol% N,N-dialkylaminoalkyl(meth)acrylamide (b) and 1-10 mol% (meth)
The aqueous dispersion of substituted succinic anhydride according to claim 1, which is a water-soluble copolymer containing acrylic acid (c) as a monomer component. (3) The aqueous dispersion of substituted succinic anhydride according to claim 1 or 2, wherein the substituted succinic anhydride is an alkenylsuccinic anhydride. (4) The aqueous dispersion of substituted succinic anhydride according to claim 1, 2 or 3, which contains an oil-in-water surfactant as a dispersion aid. (5) The aqueous dispersion of substituted succinic anhydride according to claim 4, wherein the oil-in-water surfactant is a polyoxyalkylene alkyl (aryl) ether phosphate.