JP2016169327A - Water absorbing polymer and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water absorbing polymer having a suppressed change in swelling properties with the passage of time, and a method for producing the water absorbing polymer.SOLUTION: A method for producing a water absorbing polymer includes the steps of: (I) mixing a phosphate group-containing (meth)acrylic monomer (A), a monomer (B) having one (meth)acrylic group in the molecule other than the component (A), an organopolysiloxane (C) having (meth)acrylic groups at both terminals, and water (D) to obtain an aqueous solution; (II) adding a radical polymerization initiator to the aqueous solution and radical-polymerizing the components (A)-(C) to obtain a water-containing gel-like water absorbing polymer; (III) after the radical polymerization reaction, washing and drying the water-containing gel-like water absorbing polymer to obtain a water absorbing polymer. Before or after the step (II), or both before and after the step (II), a basic compound (E) is added in an amount to make the pH 7 or more when the water absorbing polymer absorbs water to be swollen.SELECTED DRAWING: None

Description

  The present invention relates to a water-absorbing polymer and a method for producing the same.

  In the field of skin external preparations such as cosmetics (water-based cosmetics) and skin external medicines (water-based skin external medicines), water-absorbing polymers are widely used as thickening / gelling agents that keep the system stable. However, as a drawback of the water-absorbing polymer, there is an uncomfortable feeling of slimming during use. This is because polymers form a gel network structure and the system is stabilized, so that the gel network is not easily broken during use. There are cases in which the use is interrupted due to unpleasant feeling during use, and the solution is desired, but the use of a non-silicone water-absorbing polymer is insufficient (Patent Document 1).

  In order to solve the drawbacks of the aqueous skin external composition using the water-absorbing polymer, a water-absorbing polymer having a silicone skeleton and a cosmetic composition using the same have been proposed (Patent Documents 2 and 3). ). However, the water-absorbing polymer obtained by this method has problems in that it is difficult to control the three-dimensional structure by cross-linking of epoxy groups, and that the water absorption changes with time due to residual.

JP 2000-327516 A International Publication No. WO2007 / 130412 Pamphlet International Publication No. WO2007 / 130460 Pamphlet

  The water-absorbing polymer having the silicone skeleton introduced therein has a problem that the swellability is lowered due to excessive heating during the drying process, and the water-absorbing property changes with time when stored at a high temperature in summer. This is considered to be caused by the fact that an acid derived from an acidic component contained in the water-absorbing polymer serves as a catalyst and promotes cracking of the polyether.

  This invention is made | formed in view of the said problem, Comprising: It aims at providing the water absorbing polymer which suppressed the temporal change of swelling property, and its manufacturing method.

（一般式（１）中、Ｒ^１はそれぞれ同一または異なる、脂肪族不飽和基を有しない炭素原子数１〜８の一価炭化水素基であり、Ｒ^２は一般式（２）で示されるポリオキシアルキレン基を含有する基（一般式（２）中、Ｒ^４はそれぞれ同一または異なる炭素数２〜１５の２価有機基であり、ｘ、ｙは０〜３０の整数であり、かつ１≦（ｘ＋ｙ）≦５０を満たす整数である。）であり、Ｒ^３は（メタ）アクリル基を有する置換基であり、ａ≧０、ｂ≧１の整数である。） In order to achieve the above object, in the present invention, (I) (A): a phosphate group-containing (meth) acryl monomer, (B): one (meth) acryl group other than the component (A) is included in the molecule. A monomer having (C): an organopolysiloxane having (meth) acryl groups at both ends represented by the following general formula (1), (D) a step of mixing water to obtain an aqueous solution;
(II) adding a radical polymerization initiator to the aqueous solution and radically polymerizing the component (A), the component (B) and the component (C) to obtain a hydrous gel-like water-absorbing polymer;
(III) after the radical polymerization reaction, washing and drying the water-containing gel-like water-absorbing polymer to obtain a water-absorbing polymer,
Before the step (II), after the step (II), or both before and after the step (II), the pH of the basic compound (E) when the water-absorbing polymer is absorbed and swollen is 7 Provided is a method for producing a water-absorbing polymer, which is added in such an amount as described above.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)

  With such a method for producing a water-absorbing polymer, it is possible to stably produce a water-absorbing polymer with suppressed change in swelling over time.

  Moreover, when adding the said (E) component only before the said process (II), it is preferable that pH of the aqueous solution after the said (E) component addition and before the said process (II) shall be 7 or more.

  With such a method for producing a water-absorbing polymer, it is possible to more reliably produce a water-absorbing polymer having a pH of 7 or more when absorbed and swollen.

  Further, when the component (E) is added both before and after the step (II), the pH of the aqueous solution after the addition of the component (E) and before the step (II) is 5.5 to 6.5. It is preferable that

  If it is the manufacturing method of such a water absorbing polymer, it can partially neutralize before process (II).

  In the step (III) of obtaining the water-absorbing polymer, it is preferable that the water-absorbing polymer is further pulverized after the drying.

  With such a method for producing a water-absorbing polymer, it is possible to more reliably produce a water-absorbing polymer in which the swellability change with time is suppressed.

  Moreover, it is preferable that the ratio of the number of moles of the acid of the acidic component contained in the water-absorbing polymer to the number of moles of the base of the component (E) (number of moles of base / number of moles of acid) is 1 or more.

  If it is a manufacturing method of such a water absorbing polymer, the neutralization degree of the water absorbing polymer obtained can be made appropriate.

  In the step (III) of obtaining the water-absorbing polymer, it is preferable to further add (F): an antioxidant after the washing.

  If it is the manufacturing method of such a water absorbing polymer, the oxidative degradation of the polyether in a water absorbing polymer can be suppressed.

  The present invention also provides a water-absorbing polymer obtained by the method for producing a water-absorbing polymer of the present invention.

  With such a water-absorbing polymer, the swellability can be maintained for a long time.

（一般式（１）中、Ｒ^１はそれぞれ同一または異なる、脂肪族不飽和基を有しない炭素原子数１〜８の一価炭化水素基であり、Ｒ^２は一般式（２）で示されるポリオキシアルキレン基を含有する基（一般式（２）中、Ｒ^４はそれぞれ同一または異なる炭素数２〜１５の２価有機基であり、ｘ、ｙは０〜３０の整数であり、かつ１≦（ｘ＋ｙ）≦５０を満たす整数である。）であり、Ｒ^３は（メタ）アクリル基を有する置換基であり、ａ≧０、ｂ≧１の整数である。） Furthermore, in the present invention, (A): a phosphate group-containing (meth) acrylic monomer, (B): a monomer having one (meth) acrylic group in the molecule other than the component (A), (C): A water-absorbing polymer composed of an organopolysiloxane having (meth) acrylic groups at both ends represented by the formula (1), wherein the acid group in the water-absorbing polymer is neutralized with a basic compound And providing a water-absorbing polymer having a pH of 7 or more when the water-absorbing polymer is absorbed and swollen.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)

  With such a water-absorbing polymer, the swellability can be maintained for a long time.

  In the method for producing a water-absorbing polymer according to the present invention, by neutralizing the acidic component contained in the water-absorbing polymer, the acid derived from the acidic component contained in the water-absorbing polymer becomes a catalyst, and the cracking of the polyether is promoted. Can be prevented. As a result, it is possible to produce a water-absorbing polymer that suppresses the change in swellability with time while eliminating an unpleasant sliminess during use. Moreover, if it is the water absorbing polymer of this invention, a swelling property can be maintained for a long period of time.

Hereinafter, the present invention will be described in more detail.
As described above, there is a need for a water-absorbing polymer and a method for producing the same that suppress the change in swellability with time.

  As a result of diligent studies to achieve the above object, the present inventors have completely neutralized the acidic component contained in the water-absorbing polymer, thereby suppressing the water-absorbing property that suppresses the change over time due to the cracking of the polyether. The present inventors have found that a functional polymer can be produced and have completed the present invention.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

（一般式（１）中、Ｒ^１はそれぞれ同一または異なる、脂肪族不飽和基を有しない炭素原子数１〜８の一価炭化水素基であり、Ｒ^２は一般式（２）で示されるポリオキシアルキレン基を含有する基（一般式（２）中、Ｒ^４はそれぞれ同一または異なる炭素数２〜１５の２価有機基であり、ｘ、ｙは０〜３０の整数であり、かつ１≦（ｘ＋ｙ）≦５０を満たす整数である。）であり、Ｒ^３は（メタ）アクリル基を有する置換基であり、ａ≧０、ｂ≧１の整数である。） [Water-absorbing polymer]
The water-absorbing polymer of the present invention includes (A): a phosphate group-containing (meth) acrylic monomer, (B): a monomer having one (meth) acrylic group other than the component (A) in the molecule, (C): A water-absorbing polymer composed of an organopolysiloxane having (meth) acrylic groups at both ends represented by the following general formula (1), wherein the acid group in the water-absorbing polymer is neutralized by a basic compound The pH when the water-absorbing polymer is absorbed and swollen is 7 or more.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)

  With such a water-absorbing polymer, the swellability can be maintained for a long time. The silicone crosslinked water-absorbing polymer of the present invention is characterized in that the pH when absorbed and swollen is 7 or more. When the pH is less than 7, an acid derived from an acidic component contained in the water-absorbing polymer serves as a catalyst, which may cause a decrease in swellability by promoting cracking of the polyether moiety.

  The silicone crosslinked water-absorbing polymer of the present invention has an action of gelling an aqueous solvent. The gelation described here is a state in which a low-viscosity liquid exhibits little or no fluidity due to the silicone crosslinked water-absorbing polymer. The aqueous solvent may be water alone or a mixture of water and another organic solvent. The organic solvent to be mixed is not particularly limited, but an amphiphilic solvent is preferable. Examples of the amphiphilic solvent include alcohols such as methanol, ethanol, propanol, and 2-propanol, ketones such as acetone, and ethers such as tetrahydrofuran and dioxane.

  Hereinafter, each component of the water-absorbing polymer of the present invention will be described in detail.

[(A) component]
(A): In the phosphoric acid group-containing (meth) acrylic monomer, the phosphoric acid group-containing (meth) acrylic monomer only needs to have a phosphoric acid group and a (meth) acrylic group. The linking group structure to be bonded is not particularly limited, but examples thereof include alkylene groups such as methylene group, ethylene group and propylene group, polyoxyalkylene groups composed of ethylene oxide units, propylene oxide units, butylene oxide units, pentamethylene oxide units, and the like. Is done. A polyoxyalkylene group is preferable, and a polypropylene oxide group is particularly preferable. Examples of the product name include Rhomer's SIPOMER PAM-200.

[Component (B)]
(B): (Meth) acrylic monomers other than component (A) include (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, 2- (meth) acrylamide-2-methylpropane Sulfonic acid, (meth) acryloxyalkanesulfonic acid, N-vinyl-2-pyrrolidone, N-vinylylacetamide, (meth) acrylamide, N-isopropyl (meth) acrylate, N, N-dimethyl (meth) acrylamide, 2- Examples thereof include hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, stearyl acrylate and the like. Moreover, as (B) component, you may use the salt obtained by adding alkaline aqueous solution to said (meth) acryl monomer, and performing a neutralization reaction. Furthermore, in this invention, you may use combining the salt obtained by performing (meth) acryl monomer other than said (A) component, and said neutralization reaction as (B) component.

[Component (C)]
In the organopolysiloxane having (meth) acryl groups at both ends of the organopolysiloxane represented by the following general formula (1) of the component (C), R ^{1 s} are the same or different, and are carbon atoms not having an aliphatic unsaturated group. A monovalent hydrocarbon group of 1 to 8, wherein R ² is a group containing a polyoxyalkylene group represented by the general formula (2) (in the general formula (2), each R ⁴ is the same or different carbon number 2 To 15 divalent organic groups, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ has a (meth) acrylic group. It is a substituent and is an integer of a ≧ 0 and b ≧ 1.

As the substituent R ^{1 in} the general formula (1), an alkyl group such as a methyl group, an ethyl group or a butyl group, a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, an aryl group such as a phenyl group or a tolyl group, a benzyl group, An aralkyl group such as a phenethyl group is exemplified. Preferably it is a C1-C4 alkyl group or a phenyl group, More preferably, it is a methyl group.

R ⁴ in the general formula (2) is the same or different divalent organic group having 2 to 15 carbon atoms, and R ⁴ is not particularly limited, but — (CH ₂ ) ₂ —, — (CH ₂ ) _3— , — (CH ₂ ) ₄ —, —CH ₂ CH (CH ₃ ) CH ₂ —, — (CH ₂ ) ₈ —, — (CH ₂ ) ₁₁ — are exemplified, preferably — (CH ₂ ) _{2. -, - (CH 2) 3} -, - (CH 2) 4 - a.

  x and y are integers of 0 to 30 and are integers satisfying 1 ≦ (x + y) ≦ 50, preferably both x and y are integers of 5 to 25, more preferably 10 to 20, and , (X + y) is 10 to 45, more preferably 20 to 40.

[(D) component]
The component (D) is water, and specific examples include ion exchange water.

[(E) component]
(E): The basic substance to be used (basic compound) is, for example, alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, etc. Examples thereof include alkaline earth metal hydroxides, ammonium, ammonium such as primary alkyl ammonium, secondary alkyl ammonium, and tertiary alkyl ammonium. Of these, sodium hydroxide is the most common and preferred.

  A preferred temperature for carrying out the neutralization reaction is 10 to 80 ° C, more preferably 20 to 50 ° C. The salt formation by the neutralization reaction can be performed before radical polymerization, after radical polymerization, and further in multiple stages (both before and after radical polymerization). In any case, the obtained water-absorbing polymer may be a water-absorbing polymer in which the acidic component is completely neutralized, that is, a water-absorbing polymer having a pH of 7 or more when absorbed and swollen. The neutralization degree of the water-absorbing polymer of the present invention is preferably based on the number of moles of acid groups in the water-absorbent polymer, and the ratio of moles of base / moles of acid groups is 1 or more, more preferably 1 to 1.2, particularly preferably 1 to 1.1.

[(F) component]
The antioxidant of (F) can be added to the water-absorbing polymer of the present invention as necessary. The antioxidant (F) has a function of suppressing the oxidative deterioration of the polyether, and the addition of the antioxidant can suppress a decrease in swellability over time. Examples of such antioxidants include phenolic, amine-based, sulfur-based, phosphorus-based, waxes, and metal complexes thereof, vitamin C (L-ascorbic acid), vitamin E (α-tocopherol), kojic acid, and the like. Natural product-derived compounds and derivatives thereof. Most of these are commercially available, and usually commercially available antioxidants may be used.

  In the water-absorbing polymer of the present invention, the mass% (blending amount) of the (A) phosphate group-containing (meth) acrylic monomer is preferably 30 to 95 mass%. If the amount is 30% by mass or more, sufficient water absorption is obtained. If it is 95 mass% or less, a paste-like substance will be obtained after water absorption. (A) The compounding quantity of a component becomes like this. More preferably, it is 40-95 mass%, More preferably, it is 50-80 mass%. The blending amount of the monomer having one (meth) acryl group other than the component (B), that is, the component (A) and / or a salt thereof is 4 to 50% by mass, and (C), that is, the (meth) acryl at both ends. The blending amount of the organopolysiloxane having a group is preferably 0.01 to 20% by mass, more preferably (B) is 15 to 50% by mass, and (C) is 2 to 20% by mass.

[Radical polymerization initiator]
The polymerization initiator that can be used in the synthesis of the water-absorbing polymer of the present invention is appropriately selected depending on the polymerization form. Examples of such polymerization initiators include photodecomposition polymerization initiators, thermal decomposition polymerization initiators, and redox polymerization initiators. The amount of the polymerization initiator used is not particularly limited, but is usually 0.001 to 10 mol%, preferably 0.001 based on the monomer (component (A), component (B) and component (C)). Used in an amount of ˜5 mol%. If it is such an amount, coloring and off-flavor will not be caused, and the residual monomer will not increase.

  Examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, and azo compounds. Examples of the thermal decomposition type polymerization initiator include persulfates (sodium persulfate, potassium persulfate, ammonium persulfate, etc.), peroxides (hydrogen peroxide, t-butyl peroxide, methyl ethyl ketone peroxide, etc.), Azo compounds (2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, etc.), perchlorates (perchloric acid) Examples thereof include potassium and sodium perchlorate.

  Examples of the redox polymerization initiator include a system in which a reducing compound such as sulfite, L-ascorbic acid, and ferrous salt is used in combination with the persulfate and peroxide. Moreover, a photodegradable initiator and a thermal decomposable polymerization initiator can be used in combination. Among these, a peroxide salt is preferable for achieving the object of the present invention.

（一般式（１）中、Ｒ^１はそれぞれ同一または異なる、脂肪族不飽和基を有しない炭素原子数１〜８の一価炭化水素基であり、Ｒ^２は一般式（２）で示されるポリオキシアルキレン基を含有する基（一般式（２）中、Ｒ^４はそれぞれ同一または異なる炭素数２〜１５の２価有機基であり、ｘ、ｙは０〜３０の整数であり、かつ１≦（ｘ＋ｙ）≦５０を満たす整数である。）であり、Ｒ^３は（メタ）アクリル基を有する置換基であり、ａ≧０、ｂ≧１の整数である。） [Method for producing water-absorbing polymer]
The method for producing a water-absorbing polymer of the present invention has (I) (A): a phosphate group-containing (meth) acrylic monomer and (B): one (meth) acrylic group other than the component (A) in the molecule. Monomer, (C): an organopolysiloxane having (meth) acrylic groups at both ends represented by the following general formula (1), and (D) mixing water to obtain an aqueous solution;
(II) adding a radical polymerization initiator to the aqueous solution and radically polymerizing the component (A), the component (B) and the component (C) to obtain a hydrous gel-like water-absorbing polymer;
(III) after the radical polymerization reaction, washing and drying the water-containing gel-like water-absorbing polymer to obtain a water-absorbing polymer,
Before the step (II), after the step (II), or both before and after the step (II), the pH of the basic compound (E) when the water-absorbing polymer is absorbed and swollen is 7 This is the production method to be added in such an amount.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)

  With such a method for producing a water-absorbing polymer, it is possible to stably produce a water-absorbing polymer with suppressed change in swelling over time.

  Hereinafter, the manufacturing method of the water absorbing polymer of this invention is demonstrated in detail.

[Step (I)]
Step (I) is a step of mixing the components (A) to (D) described above to obtain an aqueous solution. The state of each component in the obtained aqueous solution is not particularly limited, but it is preferable that each component is uniformly dissolved.

[Step (II)]
Step (II) is a step of obtaining a water-containing gel-like water-absorbing polymer by adding a radical polymerization initiator to the aqueous solution and radically polymerizing the component (A), the component (B) and the component (C). The method for producing a water-absorbing polymer of the present invention comprises the above-described (E) basic compound obtained before or after step (II) or before and after step (II). The polymer is added in such an amount that the pH becomes 7 or more when the polymer is absorbed and swollen.

  As described above, the salt formation by the neutralization reaction can be performed before radical polymerization, after radical polymerization, and further in multiple stages, that is, before and after radical polymerization. For example, when adding the component (E) before the step (II), first, in the step (I), the monomers (A) and (B) are diluted in a solvent (water of the component (D)), After adding the basic compound (E), the siloxane (C) is added to obtain an aqueous solution in which the components (A) to (E) are mixed. Next, the above-mentioned radical initiator (radical polymerization initiator) is added to this aqueous solution, and a water-containing gel-like water-absorbing polymer is obtained by performing a radical polymerization reaction. Thereafter, the post-treatment (treatment such as washing, drying, and further pulverization as necessary) shown below is performed to obtain a water-absorbing polymer.

  Here, when adding (E) component only before process (II), it is preferable to make pH of the aqueous solution 7 or more after (E) component addition and before process (II). If the pH is 7 or more, the acid group (acidic component) in the monomer is neutralized before step (II), so that the water absorption is more reliably 7 or more when absorbed and swollen. A polymer can be produced.

  In addition, when the component (E) is added both before and after the step (II), the pH of the aqueous solution after the addition of the component (E) and before the step (II) is set to 5.5 to 6.5. preferable. If the pH is in the range of 5.5 to 6.5, the aqueous solution can be partially neutralized before step (II). In this case, after the step (II), the component (E) is further added to the obtained water-containing gel-like water-absorbing polymer. Thereby, the acidic component contained in the water-containing gel-like water-absorbing polymer can be completely neutralized.

  Moreover, (E) component can also be added only after process (II). In this case, after obtaining the water-containing gel-like water-absorbing polymer, the acid group in the polymer is neutralized by adding the component (E) to the water-containing gel-like water-absorbing polymer.

  The water-absorbing polymer of the present invention can be produced by a general radical polymerization reaction, and the polymerization method is not particularly limited. Specifically, precipitation polymerization, reverse phase suspension polymerization, spray polymerization, drop polymerization, solution polymerization and the like are possible. From the viewpoint of performance and ease of polymerization control, reverse phase suspension polymerization, spray or drop polymerization, and aqueous solution polymerization are preferred.

  In carrying out the polymerization, a dispersant can be used. Examples of the dispersant include cationic and amphoteric surfactants such as sorbitan fatty acid ester and carboxymethyldimethylcetylammonium, anionic surfactants such as polyoxyethylene dodecyl ether sulfate sodium salt, cellulose ester, and maleic acid. Examples thereof include polymeric dispersants such as modified polybutadiene and isopropyl methacrylate-dimethylaminoethyl methacrylate quaternary salt. One or more of these dispersants can be used. The amount of the dispersant used is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the monomer (component (A), component (B) and component (C)). In particular, when reverse phase suspension polymerization is performed, it is preferable to use an ionic surfactant as a monomer dispersant in terms of preventing aggregation of the superabsorbent resin particles.

  As the polymerization initiator, those described above can be used. The polymerization initiator may be added all at once or dissolved in a solvent and added dropwise. Moreover, you may add suitably in the middle of reaction.

[Step (III)]
Step (III) is a step of obtaining a water-absorbing polymer by washing and drying the water-containing gel-like water-absorbing polymer after the radical polymerization reaction. The water-containing gel-like water-absorbing polymer obtained by polymerization can be obtained as a desired water-absorbing resin by post-treatment, that is, washing and drying for the purpose of removing residual monomers and residual initiator after polymerization.

  In the case of performing washing, the solvent is not particularly limited, and examples thereof include water, acetone, alcohols, isoparaffin, and volatile silicone. These may be used alone, or may be washed in combination or stepwise.

  The drying method is not particularly limited as long as it is a normal method, but heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, freeze drying, dehydration by azeotropy with a hydrophobic organic solvent, high-temperature steam was used. A drying method such as high humidity drying is preferred. More preferred is hot air drying. The drying temperature and time are not particularly limited, but it is preferable to perform drying at a temperature of 150 ° C. or less for 5 hours or less. In this case, there is no possibility of causing deterioration of the resin, reduction in water absorption ratio, and coloring.

  In the step (III) of obtaining a water-absorbing polymer, it is preferable to further pulverize the water-absorbing polymer after drying and adjust the particle size of the water-absorbing polymer obtained. Further, the particle diameter may be uniformized by surface crosslinking. The particle size can be appropriately adjusted by polymerization, pulverization, classification, granulation, fine powder recovery and the like.

  When surface crosslinking is performed, various organic or inorganic crosslinking agents can be used as the surface crosslinking agent, but organic surface crosslinking agents are preferred. Examples include polyhydric alcohols, epoxy compounds, polyvalent amine compounds or their condensates with haloepoxy compounds, dehydrated ester reactive crosslinking agents consisting of oxazoline compounds, (mono, di, or poly) oxazolidinone compounds.

  The shape of the resulting silicone crosslinked water-absorbing polymer is not particularly limited. Any of a spherical shape, a lump shape, a scale shape, a plate shape, an egg shape, a fiber shape, an indefinite shape, and a granulated particle in which particles are hardened may be used.

  Further, the average particle size of the obtained silicone crosslinked water-absorbing polymer is not particularly limited, but the average particle size in an unabsorbed state (less than 5% loss of heating after 150 ° C./3 hours) is preferably 100 nm or more and 1 mm or less. More preferably 500 nm or more and 500 μm or less.

  In the step (III) for obtaining a water-absorbing polymer, it is preferable to add (F): an antioxidant after washing. If it is the manufacturing method of such a water absorbing polymer, the oxidative degradation of the polyether in a water absorbing polymer can be suppressed. As a method for adding the component (F), for example, in the case of 2,6-di-t-butyl-4-methylphenol, a method of adding it by dissolving in isopropyl alcohol can be mentioned.

  Moreover, it is preferable that the ratio of the number of moles of the acid of the acidic component contained in the water-absorbing polymer to the number of moles of the base of the component (E) (number of moles of base / number of moles of acid) is 1 or more. If it is a manufacturing method of such a water absorbing polymer, the neutralization degree of the water absorbing polymer obtained can be made appropriate.

  Hereinafter, the present invention will be described in more detail with reference to synthesis examples and synthesis comparative examples of the water-absorbing polymer of the present invention, but the present invention is not limited thereto.

[Synthesis Example 1]
Into a 1-liter stirring bar equipped with a stirring rod, methacrylic acid (24 g), Sipomer PMA-200 (manufactured by Rhodia) (60 g) and 180 g of ion-exchanged water are added and 43 g of 50% aqueous sodium hydroxide solution is stirred at 20-30 ° C. It was dripped at. Thereto, methacrylic group-containing siloxane (12 g) represented by the following structural formula (3) was added (the pH of the aqueous solution was about 8), and nitrogen bubbling was performed for 30 minutes with stirring, followed by 4% potassium peroxodisulfate. An aqueous solution (60 g) was added at 25 ° C. Thereafter, the mixture was heated to 80 ° C. and reacted for 5 hours. The obtained gel is washed with an excess acetone / water mixture, the powder obtained by filtration is dried in a vacuum dryer for 10 hours, and then pulverized in a pulverizer to obtain the desired water-absorbent polymer particles in the form of white powder. Got.

[Synthesis Example 2]
Into a 1-liter stirring bar equipped with a stirring rod, methacrylic acid (24 g), Sipomer PMA-200 (manufactured by Rhodia) (60 g) and 180 g of ion-exchanged water are added and 43 g of 50% aqueous sodium hydroxide solution is stirred at 20-30 ° C. It was dripped at. Then, methacrylic group-containing siloxane having both terminals represented by the structural formula (3) (6 g) was added, and nitrogen bubbling was performed for 30 minutes with stirring (the pH of this aqueous solution was about 8). 4% peroxodisulfuric acid An aqueous potassium solution (60 g) and a 4% aqueous sodium bisulfite solution (25 g) were added at 25 ° C. Thereafter, the mixture was heated to 60 ° C. and reacted for 5 hours. The obtained gel was washed three times with excess acetone / water mixture, and the powder obtained by filtration was dried in a vacuum dryer for 10 hours, and then pulverized with a pulverizer to obtain the desired white powder water absorption. Polymer particles were obtained.

[Synthesis Example 3]
Into a 1-liter stirring bar equipped with a stirring rod, methacrylic acid (24 g), Sipomer PMA-200 (manufactured by Rhodia) (60 g) and 180 g of ion-exchanged water are added, and 25 g of 50% aqueous sodium hydroxide solution is stirred at 20 to 30 ° C. It was dripped at. Thereto, methacrylic group-containing siloxane (12 g) represented by the above structural formula (3) was added (the pH of this aqueous solution was about 6), and nitrogen bubbling was performed for 30 minutes with stirring, followed by 4% peroxodisulfuric acid. A potassium aqueous solution (60 g) was added at 25 ° C. Thereafter, the mixture was heated to 80 ° C. and reacted for 5 hours. After completion of the reaction, 18 g of 50% aqueous sodium hydroxide solution was added and stirred (pH at this time was about 8). The obtained gel is washed with an excess acetone / water mixture, the powder obtained by filtration is dried in a vacuum dryer for 10 hours, and then pulverized in a pulverizer to obtain the desired water-absorbent polymer particles in the form of white powder. Got.

[Synthesis Example 4]
Into a 1-liter stirring bar equipped with a stirring rod, methacrylic acid (24 g), Sipomer PMA-200 (manufactured by Rhodia) (60 g) and 180 g of ion-exchanged water are added, and 25 g of 50% aqueous sodium hydroxide solution is stirred at 20 to 30 ° C. It was dripped at. Then, methacryl group-containing siloxane having both terminals represented by the above structural formula (3) (6 g) was added and nitrogen bubbling was performed for 30 minutes with stirring (the pH of this aqueous solution was about 6). 4% peroxodisulfuric acid An aqueous potassium solution (60 g) and a 4% aqueous sodium bisulfite solution (25 g) were added at 25 ° C. Thereafter, the mixture was heated to 60 ° C. and reacted for 5 hours. After completion of the reaction, 18 g of 50% aqueous sodium hydroxide solution was added and stirred (pH at this time was about 8). The obtained gel was washed with excess acetone / water mixture three times, and 2,6-di-t-butyl-4-methylphenol was dissolved in isopropyl alcohol and added, and then the powder obtained by filtration was filtered. It was dried for 10 hours with a vacuum dryer, and then pulverized with a pulverizer to obtain the desired white powdery water-absorbing polymer particles.

[Comparative Comparative Example]
Into a 1-liter stir bar equipped with a stir bar, methacrylic acid (24 g), Sipomer PMA-200 (manufactured by Rhodia) (60 g) and 180 g of ion-exchanged water are added and 54 g of 25% aqueous sodium hydroxide solution is stirred at 20-30 ° C. It was dripped at. Then, methacrylic group-containing siloxane (12 g) represented by the above structural formula (3) was added, and nitrogen bubbling was performed for 30 minutes with stirring (the pH of this aqueous solution was about 6). 4% peroxodisulfuric acid A potassium aqueous solution (100 g) was added at 25 ° C. Thereafter, the mixture was heated to 60 ° C. and reacted for 10 hours. The obtained gel is washed with an excess acetone / water mixture, the powder obtained by filtration is dried in a vacuum dryer for 10 hours, and then pulverized in a pulverizer to obtain the desired water-absorbent polymer particles in the form of white powder. Got.

  The white powders of Synthesis Examples 1, 2, 3, 4 and Synthesis Comparative Example are each put into a dryer at 120 ° C., taken out at each time, and the powder and water are mixed at a ratio of 5:95 (weight ratio). After being used well, mix with a high shear mixer manufactured by SILVERSON for 15 minutes using a square hole type high shear screen at a rotational speed of 3300 rpm and let stand in an atmosphere of 25 ° C. for 1 day. The viscosity was measured.

  Table 1 shows the pH measurement results of Synthesis Examples 1, 2, 3, 4, and Synthesis Comparative Example.

[Viscosity measurement]
The viscosity measurement conditions are as follows.
Apparatus: Brook Field viscometer RVDV-II +
Condition: Spindle TC, 5rpm
Procedure: Spindle TC was immersed in the sample, and the value 1 minute after the start of rotation was measured.

  The results of viscosity measurement are shown in Table 2 below.

  As shown in Table 2, Synthesis Examples 1, 2, 3, and 4 satisfying the requirements of the present invention are such that the pH when the obtained water-absorbing polymer is absorbed and swollen becomes 7 or more (E ) It can be seen that the lowering of the swelling property can be suppressed as compared with the comparative example to which the basic compound is not added.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Claims (8)

(I) (A): Phosphoric acid group-containing (meth) acrylic monomer, (B): Monomer having one (meth) acrylic group in the molecule other than component (A), (C): General formula (1) ) An organopolysiloxane having a (meth) acrylic group at both ends thereof, and (D) a step of mixing water to obtain an aqueous solution;
(II) adding a radical polymerization initiator to the aqueous solution and radically polymerizing the component (A), the component (B) and the component (C) to obtain a hydrous gel-like water-absorbing polymer;
(III) after the radical polymerization reaction, washing and drying the water-containing gel-like water-absorbing polymer to obtain a water-absorbing polymer,
Before the step (II), after the step (II), or both before and after the step (II), the pH of the basic compound (E) when the water-absorbing polymer is absorbed and swollen is 7 A method for producing a water-absorbing polymer, which is added in such an amount as described above.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)   When the component (E) is added only before the step (II), the pH of the aqueous solution after the addition of the component (E) and before the step (II) is 7 or more. Item 2. A method for producing a water-absorbing polymer according to Item 1.   When the component (E) is added both before and after the step (II), the pH of the aqueous solution is 5.5 to 6.5 after the addition of the component (E) and before the step (II). The method for producing a water-absorbing polymer according to claim 1.   The method for producing a water-absorbing polymer according to any one of claims 1 to 3, wherein in the step (III) of obtaining the water-absorbing polymer, the water-absorbing polymer is further pulverized after the drying. .   The ratio of the number of moles of acid of the acidic component contained in the water-absorbing polymer to the number of moles of base of the component (E) (number of moles of base / number of moles of acid) is 1 or more. The method for producing a water-absorbing polymer according to any one of claims 1 to 4.   The water-absorbing polymer according to any one of claims 1 to 5, wherein in the step (III) of obtaining the water-absorbing polymer, (F): an antioxidant is further added after the washing. Manufacturing method.   A water absorbent polymer obtained by the method for producing a water absorbent polymer according to any one of claims 1 to 6. (A): Phosphoric acid group-containing (meth) acrylic monomer, (B): monomer having one (meth) acrylic group other than the component (A) in the molecule, (C): represented by the following general formula (1) A water-absorbing polymer composed of an organopolysiloxane having (meth) acrylic groups at both ends thereof, wherein the acid group in the water-absorbing polymer is neutralized with a basic compound, A water-absorbing polymer having a pH of 7 or more when the polymer is absorbed and swollen.

(In the general formula (1), R ¹ is the same or different monovalent hydrocarbon group having 1 to 8 carbon atoms not having an aliphatic unsaturated group, and R ² is represented by the general formula (2). A group containing a polyoxyalkylene group (in the general formula (2), R ⁴ is the same or different divalent organic group having 2 to 15 carbon atoms, x and y are integers of 0 to 30 and 1 ≦ (x + y) ≦ 50), and R ³ is a substituent having a (meth) acryl group, and is an integer of a ≧ 0 and b ≧ 1.)