JP2010195944A - Method for recovering polyurethane resin and method for producing polyurethane resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method and a production method of a polyurethane resin in which an acidic liquid is added to an aqueous polyurethane emulsion to adjust the pH to 5.0 to 7.0, and a polyurethane resin is suitably obtained by aggregation and separation. And
SOLUTION: An acidic liquid (b) is added to an aqueous polyurethane emulsion (a) to adjust the hydrogen ion index (pH) of the aqueous polyurethane emulsion (a) to 5.0 to 7.0, and agglomeration and separation are performed. This is a method for recovering or producing a polyurethane resin to obtain a polyurethane resin, and solves the above problems by using a specific one as the aqueous polyurethane emulsion (A).
[Selection figure] None

Description

  In the present invention, an acidic liquid (b) is added to an aqueous polyurethane emulsion (a) to adjust the hydrogen ion index (hereinafter abbreviated as “pH”) to 5.0 to 7.0, and the polyurethane is formed by aggregation and separation. The present invention relates to a method for recovering and producing a polyurethane resin to obtain a resin.

Aqueous polyurethane emulsions are excellent in adhesion to substrates, abrasion resistance, impact resistance, solvent resistance, etc., so paper, plastics, films, metals, paints, inks, adhesives, and various coating agents Widely used in textile products, etc., and various production methods have been studied. For example, acetone, methyl ethyl ketone, N-methyl pyrrolidone, aromatic organic solvent, etc. are used alone or mixed with a solvent to produce a urethane resin solution, followed by water dispersion and desolvation process, and then aqueous such as emulsion, colloidal dispersion, aqueous solution, etc. Polyurethane resins have been developed.

Allophanate-modified polyisocyanates generally have low viscosity compared to other urethane-modified polyisocyanates and isocyanurate-modified polyisocyanates, and various side chain groups are introduced into the isocyanate skeleton depending on the choice of the modifier. be able to. For example, if a polyoxyethylene group is introduced, a hydrophilic polyisocyanate can be obtained. If a hydrocarbon group having a large number of carbon atoms is introduced, a poor solvent-soluble polyisocyanate can be obtained.

Patent Document 1 discloses an aqueous polyurethane emulsion in which an allophanate-modified polyisocyanate having a polyoxyethylene group introduced into a side chain is used as an isocyanate component of a polyurethane resin. However, in Patent Document 1, an organic diisocyanate (asymmetric diisocyanate) having two isocyanate groups having different reactivities such as 2,4-tolylene diisocyanate and isophorone diisocyanate is used as a raw material for allophanate-modified polyisocyanate. Since general asymmetric organic diisocyanates usually have a ring structure (a kind of ladder structure), the flexibility of the molecular skeleton is low and the viscosity tends to be high.

Patent Document 2 proposes a method that does not use an organic solvent when producing an aqueous polyurethane resin dispersion. However, in the production method of Patent Document 2, since the viscosity of the isocyanate group-terminated prepolymer is very high, water dispersion does not proceed unless a homomixer, homogenizer, or microfluidizer having a strong shearing force is used. In many cases, it is necessary to modify the manufacturing equipment.

  On the other hand, by adding an acidic liquid to the aqueous polyurethane emulsion, the polyurethane dispersion uniformly dispersed in the aqueous polyurethane emulsion has a property of agglomerating. However, such a property does not appear unless the acid value (acid value in terms of solid content of the polyurethane resin) is remarkably high, for example, 50 mgKOH / g or more. In addition, the aqueous polyurethane emulsion comprising such a polyurethane dispersion having a remarkably high acid value may be difficult to handle due to its high viscosity, and has a low solid content and a small amount of polyurethane resin component obtained by aggregation. Thus, it has not been practical to obtain a polyurethane resin by aggregation and separation by adding an acidic liquid. In addition, the coating film and film obtained using the aqueous polyurethane emulsion which consists of a polyurethane dispersion which has such a remarkably high acid value also produce the malfunction that water resistance is inferior.

  In addition, it is difficult to agglomerate a polyurethane dispersion that is uniformly dispersed in an aqueous polyurethane emulsion by adding an acidic liquid to the aqueous polyurethane emulsion unless it is prepared until the pH exhibits a strong acidity of 4.0, for example. there were. This is another reason why it is not practical to obtain a polyurethane resin by aggregation and separation by adding an acidic liquid.

JP-A-1-104612 Japanese Patent Laid-Open No. 10-265539

  In the present invention, in view of the series of backgrounds described above, an acidic liquid is added to an aqueous polyurethane emulsion having a relatively low acid value, specifically, an acid value of about 10 to 20 mgKOH / g, and the pH is adjusted to 5. The main purpose is to establish a polyurethane resin recovery method and production method for obtaining a polyurethane resin by preparing, agglomerating and separating from 0 to 7.0.

  The present invention also provides a polyurethane resin by agglomeration and separation even when an acidic liquid is added to an aqueous polyurethane emulsion, even when the pH is adjusted to 5.0 to 7.0, which is weakly acidic (or neutral). The main object is to establish a method for recovering and producing a polyurethane resin capable of suitably obtaining the above.

  As a result of intensive studies, the present inventors have solved the above problem by using an aqueous polyurethane emulsion having a specific structure and a relatively low acid value (specifically, an acid value of 10 to 20 mgKOH / g). The present inventors have found that it is possible to solve the problem and have completed the present invention.

That is, this invention is shown by the following (1)-(4).

(1) An acidic liquid (b) is added to an aqueous polyurethane emulsion (a) having a hydrogen ion index (pH) of 7.1 to 9.0, and the hydrogen ion index (pH) of the aqueous polyurethane emulsion (a) is determined. A method of recovering a polyurethane resin by preparing 5.0 to 7.0, and aggregating and separating the polyurethane resin, wherein the aqueous polyurethane emulsion (a) contains 50 mol% or more of oxyethylene groups in the repeating unit Organic polyisocyanate (A) containing allophanate-modified polyisocyanate (A1) obtained from alkoxy poly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2), active hydrogen group-containing compound (B) An anionic polar group and active hydrogen group-containing compound (C), and a neutralizing agent (D). A polyurethane resin recovery method, wherein the polyurethane dispersion is obtained by uniformly dispersing and emulsifying a polyurethane dispersion having an acid value of 10 to 20 mgKOH / g in water.
(2) The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). The method for recovering a polyurethane resin according to (1).

(3) An acidic liquid (b) is added to the aqueous polyurethane emulsion (a) having a hydrogen ion index (pH) of 7.1 to 9.0, and the hydrogen ion index (pH) of the aqueous polyurethane emulsion (a) is determined. A method for producing a polyurethane resin, which is prepared to 5.0 to 7.0 to obtain a polyurethane resin by aggregation and separation, wherein the aqueous polyurethane emulsion (a) contains 50 mol% or more of oxyethylene groups in the repeating unit Organic polyisocyanate (A) containing allophanate-modified polyisocyanate (A1) obtained from alkoxy poly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2), active hydrogen group-containing compound (B) An anionic polar group and active hydrogen group-containing compound (C), and a neutralizing agent (D). And a polyurethane dispersion having an acid value of 10 to 20 mg KOH / g obtained by uniformly dispersing and emulsifying in water.
(4) The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). The method for producing a polyurethane resin according to (3).

  According to the production method of the present invention, an aqueous polyurethane emulsion in which a polyurethane dispersion is uniformly dispersed can be easily prepared by preparing a weakly acidic (or neutral) pH of about 5.0 to 7.0. It became possible to collect and produce the polyurethane resin through aggregation and separation.

  The aqueous polyurethane emulsion used in the recovery method and the production method of the present invention is excellent in water resistance in the coating film obtained by itself, and uses of the aqueous polyurethane emulsion other than the production method of the present invention (known (Use form) is also useful.

<Water-based polyurethane emulsion (I)>
The aqueous polyurethane emulsion (a) used in the present invention is obtained from alkoxypoly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit. An organic polyisocyanate (A) containing an allophanate-modified polyisocyanate (A1) substantially free of isocyanurate groups, an active hydrogen group-containing compound (B), an anionic polar group and an active hydrogen group-containing compound (C), and It is a polyurethane emulsion in which a polyurethane dispersion having an acid value of 10 to 20 mg KOH / g, which is obtained by reacting a neutralizing agent (D), is uniformly dispersed in water. The aqueous polyurethane emulsion (A) used in the present invention has a pH in the range of 7.1 to 9.0 (exhibits weak alkalinity).

<Organic polyisocyanate (A)>
The organic polyisocyanate (A) used in the present invention is abbreviated as alkoxy poly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (hereinafter referred to as “HDI”) containing 50 mol% or more of oxyethylene groups in the repeating unit. ) It contains the allophanate-modified polyisocyanate (A1) obtained from (A1-2) and substantially does not contain an isocyanurate group in the molecule. When the isocyanurate group is substantially contained, the viscosity of the organic polyisocyanate (A) increases, and it is necessary to reduce the viscosity such as dilution with an organic solvent during the production of the aqueous polyurethane emulsion.

<Allophanate-modified polyisocyanate (A1)>
The allophanate-modified polyisocyanate (A1) used in the present invention comprises an alkoxypoly (oxyalkylene) glycol (A1-1) and HDI containing 50 mol% or more (preferably 70 mol% or more) of oxyethylene groups in the repeating unit. Obtained from (A1-2). Here, when the oxyethylene group in the repeating unit in the alkoxypoly (oxyalkylene) glycol is less than 50 mol%, the water dispersibility of the resulting polyurethane dispersion (uniform dispersion stability in the aqueous polyurethane emulsion (I)) is It becomes insufficient. In addition, when an organic diisocyanate other than HDI, such as toluene diisocyanate (hereinafter abbreviated as “TDI”) or isophorone diisocyanate (hereinafter abbreviated as “IPDI”) is used, it has a ring structure (a kind of ladder structure). Therefore, the flexibility of the molecular skeleton is low and the viscosity in the aqueous polyurethane emulsion (a) tends to be high. For this reason, since an organic solvent is needed when manufacturing such an allophanate modified polyisocyanate, it is not preferable in this invention.

In the present invention, the isocyanate group content of the allophanate-modified polyisocyanate (A1) is preferably in the range of 5 to 15% by mass, and particularly preferably in the range of 8 to 13% by mass. The viscosity of the allophanate-modified polyisocyanate (A1) at 25 ° C. is preferably 1,000 mPa · s or less, and particularly preferably in the range of 100 to 800 mPa · s. When the isocyanate group content is less than 5% by mass or when the viscosity exceeds 1,000 mPa · s, the viscosity of the intermediate reactant during the reaction becomes high, and a large load is imposed on the production apparatus (of the production apparatus). Failure may occur). Moreover, when isocyanate group content exceeds 15 mass%, or when viscosity is too low, for example, less than 800 mPa * s, there is a possibility that the degree of allophanate modification in allophanate-modified polyisocyanate (A1) is insufficient. In many cases, the dispersibility (uniform dispersion stability in the aqueous polyurethane emulsion (i)) of the obtained polyurethane dispersion tends to be insufficient.

The method for producing the allophanate-modified polyisocyanate (A1) is as follows. An excess amount of HDI (alkoxy poly (oxyalkylene) glycol / HDI = 1/5 to 1/20 (molar ratio) is preferred) is added to the alkoxy poly (oxyalkylene) glycol, and a urethanization reaction is performed. Next, an allophanatization catalyst such as a metal salt of a carboxylic acid is charged and an allophanatization reaction is performed. A reaction terminator such as phosphoric acid is charged to stop the allophanatization reaction, and unreacted HDI is removed by thin film distillation or the like to obtain the desired allophanate-modified polyisocyanate.

Preferred allophanatization catalysts are zirconium carboxylate, zirconyl carboxylate, and tin (divalent) carboxylate. Other allophanatization catalysts have a high degree of side reaction such as isocyanurate reaction and a low content of the desired allophanate-modified polyisocyanate. The polyisocyanate obtained by such a method has a large average number of functional groups, and gelation tends to occur during the production of a polyurethane resin. Specific products of the allophanate catalyst include Nikka Octix Zircon (manufactured by Nippon Chemical Industry Co., Ltd.).

When an allophanate-modified polyisocyanate is produced using the above-mentioned zirconium-based catalyst using an organic diisocyanate that is widely distributed in markets other than HDI, the allophanate-forming polyisocyanate is insufficient. It is difficult to obtain.

The alkoxypoly (oxyalkylene) glycol (A1-1) used for the allophanate-modified polyisocyanate (A1) is generally a compound having one hydroxyl group having 1 to 10 carbon atoms and 50 mol of ethylene oxide. % Or more of alkylene oxide is contained by ring-opening addition.

Here, examples of the initiator include saturated aliphatic alcohol compounds such as methanol, ethanol, propanol (including various isomers), butanol (including various isomers), pentanol (including various isomers), and allyl alcohol. Unsaturated fatty alcohol compounds such as phenol, phenolic compounds such as phenol, and araliphatic alcohols such as benzyl alcohol. In the present invention, an aliphatic alcohol having 5 or less carbon atoms is preferable, and a saturated aliphatic alcohol having 2 or less carbon atoms is particularly preferable in order to enhance the effect of imparting hydrophilicity. Further, the ethylene oxide content of the alkylene oxide is more preferably 70 mol% or more in consideration of the water dispersibility (uniform dispersion stability in the aqueous polyurethane emulsion (i)) in the obtained polyurethane dispersion.

The number average molecular weight of the alkoxy poly (oxyalkylene) glycol (A1-1) is preferably in the range of 200 to 2,000, particularly preferably in the range of 300 to 1,000. When the number average molecular weight of the alkoxy poly (oxyalkylene) glycol (A1-1) is less than 200, the effect of imparting hydrophilicity in the allophanate-modified polyisocyanate (A1) is small, and the water dispersibility (aqueous) of the polyurethane dispersion using the same The uniform dispersion stability in the polyurethane emulsion (a) is insufficient. Further, when the number average molecular weight exceeds 2,000, the viscosity of the obtained allophanate-modified polyisocyanate (A1) is increased or solidified due to crystallization of the polyoxyethylene chain, and it is water-free without using a solvent. It becomes difficult to produce a polyurethane emulsion.

<Organic polyisocyanate (A)>
The organic polyisocyanate (A) used in the present invention contains the allophanate-modified polyisocyanate (A1), and an organic polyisocyanate other than the allophanate-modified polyisocyanate (A1) can be used in combination. For example, 2,4-TDI, 2,6-TDI, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, diphenyldimethylmethane diisocyanate, dibenzyl diisocyanate, naphthylene diisocyanate Aromatic diisocyanates such as phenylene diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, tetramethylene diisocyanate, HDI, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, 2,2,4-trimethylhexahylene-1,6-diisocyanate, 2,4,4-trimethylhexahylene-1,6-diisocyanate Aliphatic diisocyanates such as sulfonate, IPDI, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, is alicyclic diisocyanates such as hydrogenated trimethyl xylylene diisocyanate. These organic diisocyanates can be used alone or in a mixture. Furthermore, modified products such as these adduct-modified products, carbodiimide-modified products, allophanate-modified products (excluding those described above), burette-modified products, uretdione-modified products, uretoimine-modified products, and isocyanurate-modified products can also be used. In this case, it is preferable that the allophanate-modified polyisocyanate (A1) is 25% by mass or more based on the entire organic polyisocyanate (A). When there is too much organic polyisocyanate other than (A1), the intermolecular force of the resulting polyurethane dispersion becomes too large, so that the aqueous polyurethane emulsion itself aggregates before being subjected to the recovery method or production method of the present invention. It becomes easy to do. This makes it difficult to use as the aqueous polyurethane emulsion (i) in the production method of the present invention.

<Active hydrogen group-containing compound (B)>
The active hydrogen group-containing compound used in the present invention preferably contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). This is to obtain a resin by the prepolymer method described later. In the prepolymer method, the urethane group imparting adhesiveness and adhesion and the urea group effective in heat resistance and strength development are balanced with a polyurethane resin skeleton. This is because the viscosity during the reaction can be lowered.

The number average molecular weight of the polymer polyol (B1) is 500 or more, preferably in the range of 1,000 to 5,000. Moreover, it is preferable that the average functional group number of this (A) polyol exists in the range of 2-4, and it is still more preferable that it exists in the range of 2-3 among these. When the number average molecular weight of the polymer polyol is less than 500, the film obtained using the aqueous polyurethane emulsion (A) is likely to be broken. Further, when the number average molecular weight of the polymer polyol exceeds 5,000, the film obtained using the aqueous polyurethane emulsion (a) may not have sufficient physical properties. The number average molecular weight of the polymer polyol is calculated from the average number of functional groups and the end group amount determined by the end group determination method.

Specific examples of the polymer polyol (B1) include polyester polyols, polyamide ester polyols, polyether polyols, polyether ester polyols, polycarbonate polyols, polyolefin polyols, and animal and plant polyols.

In the present invention, the preferred polymer polyol (B1) for obtaining the aqueous polyurethane emulsion (I) is a polyester polyol when adhesion is important in the film obtained using the aqueous polyurethane emulsion (I). When water resistance is important, polyether polyol or polycarbonate polyol is used.

Polyester polyols include known phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelaic acid, sebacin Acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α, β-diethylsuccin At least one kind of dicarboxylic acid or anhydride such as acid, maleic acid, fumaric acid and the like, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butane Diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanedio 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol , Cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, ethylene oxide and propylene oxide adducts of bisphenol A, bis (β-hydroxyethyl) benzene, xylylene glycol, glycerin, trimethylol It can be obtained from a polycondensation reaction with one or more low molecular polyols such as propane and pentaerythritol. Furthermore, there are lactone polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Further, a part of the low molecular polyol may be replaced with a low molecular polyamine such as ethylenediamine, hexamethylenediamine, and isophoronediamine, or a low molecular amino alcohol such as monoethanolamine. In this case, a polyester-amide polyol is obtained.

As the polyether polyol, active hydrogen groups such as low molecular polyols used in the above-mentioned polyester polyol, low molecular polyamines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, xylylenediamine, etc. Starting from a compound having 2 or more, preferably 2 to 3, alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide, alkyl glycidyl ethers such as methyl glycidyl ether, and aryl glycidyl such as phenyl glycidyl ether It can be obtained by addition polymerization by a known method from a single or mixture of cyclic ether monomers such as ethers and tetrahydrofuran.

The polycarbonate polyol is obtained from a dealcoholization reaction or a dephenol reaction between one or more low molecular diols or low molecular triols from the above-mentioned polyester polyol source and ethylene carbonate, diethyl carbonate, or diphenyl carbonate. In addition, the transesterification product of the above-mentioned polycarbonate polyol and polyester polyol can also be used suitably.

Examples of polyether ester polyols include copolyols obtained from the aforementioned polyether polyols and the aforementioned dicarboxylic acids. Further, there are those obtained by reacting the aforementioned polyester or polycarbonate with epoxide or cyclic ether.

Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

Examples of animal and plant-based polyols include castor oil-based polyols and silk fibroin.

In addition, if the number average molecular weight is 500 or more (preferably in the range of 1,000 to 5,000) and one molecule has an average of one or more active hydrogen groups, dimer acid-based polyol, hydrogen In addition to added dimer acid-based polyols, active hydrogen group-containing resins such as epoxy resins, polyamide resins, polyester resins, acrylic resins, rosin resins, urea resins, melamine resins, phenol resins, coumarone resins, and polyvinyl alcohols are also used as polymer polyols. it can.

Examples of the low molecular weight polyamine (B2) include ethylenediamine, tetramethylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethanediamine, diphenylmethanediamine, and diethylenetriamine. In the present invention, when considering the physical properties and durability of the coating obtained using the aqueous polyurethane emulsion (a) as the low molecular weight polyamine (B2), both water and hexamethylenediamine are used. Isophoronediamine is preferred.

<Anionic polar group and active hydrogen group-containing compound (C)>
Examples of the anionic polar group and the active hydrogen group-containing compound (C) used in the present invention include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphinic acid group, and a phosphonic acid group. Here, specific examples of the anionic polar group include a sulfonate group, a phosphate group, a phosphinate group, and a phosphonate group. In this invention, the carboxyl group from which the change of a film state from an emulsion state becomes irreversible in aqueous | water-based polyurethane emulsion (a) by the selection of the neutralizing agent (D) mentioned later is preferable.

Examples of the carboxyl group and active hydrogen group-containing compound include 2,2-dimethylolpropionic acid (hereinafter abbreviated as “DMPA”), 2,2-dimethylolbutanoic acid (hereinafter abbreviated as “DMBA”), polyamine and acid anhydride. And lactone adducts using dimethylolpropionic acid and dimethylolbutanoic acid as initiators. Preferred in the present invention are DMPA and DMBA.

<Neutralizing agent (D)>
Examples of the neutralizing agent (D) used in the present invention include ammonia, ethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethylethanolamine. Organic amines such as diethylethanolamine, morpholine, N-methylmorpholine and 2-amino-2-ethyl-1-propanol, alkali metals such as lithium, potassium and sodium, inorganic alkalis such as sodium hydroxide and potassium hydroxide For example, in order to improve the weather resistance and water resistance after drying in a film obtained using the aqueous polyurethane emulsion (a), a highly volatile material that is easily dissociated by heat is preferable. Properly, ammonia, trimethylamine, triethylamine is preferred. These neutralizing agents can be used alone or in a mixture of two or more.

<Optional components used in obtaining the aqueous polyurethane emulsion (I)>
In the present invention, a low molecular polyol having a number average molecular weight of less than 500 can be used as a component constituting the aqueous polyurethane emulsion (A) in consideration of the physical properties of the polyurethane resin obtained by the production method of the present invention. As this low molecular polyol, the low molecular polyol which comprises the above-mentioned polyester polyol is mentioned.

In the present invention, when synthesizing a polyurethane dispersion that is uniformly dispersed in the aqueous polyurethane emulsion (i), a reaction terminator can be used as necessary, such as adjustment of molecular weight. Examples of the reaction terminator include monoalcohols and monoamines. In some cases, aminoalcohols can also serve as the reaction terminator. Monoisocyanates such as phenyl isocyanate, butyl isocyanate, cyclohexyl isocyanate and the like can also be used as a reaction terminator.

Specific monoalcohols used as the reaction terminator include methanol, ethanol, propanol, isopropanol, 2-ethylhexanol and the like. Monoamines include primary amines such as ethylamine, propylamine, and butylamine, and secondary amines such as diethylamine and dibutylamine. Examples of amino alcohols include monoethanolamine and diethanolamine.

<Method for producing aqueous polyurethane emulsion (I)>
Examples of the method for producing the aqueous polyurethane emulsion (a) used in the present invention mainly include the methods described below.
A polyurethane dispersion is synthesized by reacting the organic polyisocyanate (A), the active hydrogen group-containing compound (B), and the anionic polar group and the active hydrogen group-containing compound (C) in an atmosphere having an excess of active hydrogen groups, A one-shot method in which it is neutralized with a neutralizing agent (D) as necessary and dispersed in water.
-An organic polyisocyanate (A), a low molecular weight polyamine and / or an active hydrogen group-containing compound (B) other than water (B2), and an anionic polar group and active hydrogen group-containing compound (C), in an isocyanate group-excess atmosphere A prepolymer method in which an isocyanate group-terminated prepolymer is synthesized by reacting under the following conditions, then neutralized with a neutralizing agent (D), then dispersed in water, and subjected to a chain extension reaction with a low molecular weight polyamine and / or water (B2). .

In the case of the one-shot method, the isocyanate group / active hydrogen group molar ratio is 0.5 to less than 1, preferably 0.8 to less than 1. When the molecular weight is less than 0.5, the molecular weight of the polyurethane polymer is too small, so that, for example, the film obtained using the aqueous polyurethane emulsion (A) lacks durability. In the case of 1 or more, gelation tends to occur when a polymer is synthesized.

After urethanization, it is neutralized with a neutralizing agent (D) as necessary, and then water is added to disperse the resin, thereby obtaining a desired aqueous polyurethane emulsion. The faster the stirring speed at this time, the better.

In the case of the prepolymer method, the molar ratio of isocyanate group / active hydrogen group during prepolymer synthesis is in the range of 1.1 to 5.0, preferably in the range of 1.2 to 4.0. If it is less than 1.1, the molecular weight of the prepolymer becomes too large and it becomes difficult to proceed to the subsequent reaction step. On the other hand, if it exceeds 5.0, for example, the film obtained using the aqueous polyurethane emulsion (A) has poor adhesion.

After prepolymerization, neutralize with neutralizer (D), add water to disperse the prepolymer, and add low molecular weight polyamine and / or water (B2) and reaction terminator as necessary to extend amine. By carrying out the reaction, the desired aqueous polyurethane emulsion is obtained. The reaction temperature of the amine extension reaction is preferably 30 to 50 ° C. After the prepolymer is dispersed, the faster the stirring speed, the better.

The aqueous polyurethane emulsion of the present invention is characterized by using an allophanate-modified polyisocyanate (A1) that is effective in reducing the viscosity of the resin. However, in the one-shot method, even when the allophanate-modified polyisocyanate (A1) effective for reducing the viscosity is used, the number average molecular weight of the polyurethane dispersion immediately before water dispersion is often 10,000 or more. , The viscosity becomes reasonably high (eg, 100,000 mPa · s or more at 75 ° C.), and water dispersion tends to be difficult. For this reason, a prepolymer method in which water dispersion is performed at the stage of a prepolymer having a low number average molecular weight (low viscosity) is preferable because solvent-free production can be achieved.

In the urethanization reaction or prepolymerization reaction, a known so-called urethanization catalyst can be used as a reaction catalyst. Specific examples include organic metal compounds such as dioctyltin dilaurate, organic amines such as triethylenediamine, and salts thereof. The reaction temperature during urethanization is 10 to 100 ° C, preferably 30 to 80 ° C.

<Characteristics of Aqueous Polyurethane Emulsion (I)>
The acid value of the polyurethane resin in the aqueous polyurethane emulsion (a) used in the present invention (the acid value in terms of solid content of the polyurethane dispersion interposed in a uniformly dispersed state in the aqueous polyurethane emulsion (a)) is 10 to 20 mgKOH / Within the range of g. When the acid value is less than 10 mgKOH / g, the mechanical strength of the polyurethane resin obtained by the production method of the present invention may be inferior. Further, when the acid value exceeds 20 mgKOH / g, the viscosity of the aqueous polyurethane emulsion (a) used in the present invention is increased and the solid content becomes low, so the amount of polyurethane resin obtained by the recovery method or the production method of the present invention In some cases, there is a problem that the polyurethane resin obtained by the decrease or the water resistance of the polyurethane resin obtained by the recovery method or the production method of the present invention is lowered. The acid value is measured by, for example, a method disclosed in Japanese Industrial Standard JIS K5400.

The number average molecular weight of the polyurethane dispersion in the aqueous polyurethane emulsion (a) used in the present invention is preferably 5,000 or more, particularly preferably 10,000 or more. When the number average molecular weight of the polyurethane dispersion is less than 5,000, for example, the durability of the film obtained using the aqueous polyurethane emulsion (A) becomes poor. In the present invention, the number average molecular weight is measured by a gel permeation chromatography (GPC) method using a polyethylene glycol calibration curve.

The average particle size of the polyurethane dispersion in the aqueous polyurethane emulsion (a) used in the present invention is 150 nm or less, preferably 135 nm or less. When the average particle size exceeds 150 nm, the polyurethane dispersion may precipitate in the aqueous polyurethane emulsion (i) over time (it becomes difficult to be used in the recovery method or production method of the present invention). The average particle diameter is a value obtained by analyzing a value measured by a dynamic light scattering method by a cumulant method.

The viscosity at 25 ° C. of the polyurethane dispersion in the aqueous polyurethane emulsion (i) used in the present invention is 2,000 mPa · s or less, preferably in the range of 50 to 1,000 mPa · s, at a solid content of 30% by mass. Is within. When the viscosity exceeds 2,000 mPa · s, for example, it is difficult to make a coating using an aqueous polyurethane emulsion (I).

The anionic polar group content of the polyurethane dispersion in the aqueous polyurethane emulsion (i) used in the present invention is preferably 0.5 mmol / g or less, particularly preferably 0.3 mmol / g or less. When the anionic polar group content exceeds 0.5 mmol / g, the viscosity of the dispersion or prepolymer immediately before water dispersion becomes too high, making it difficult to disperse the polyurethane dispersion in the aqueous polyurethane emulsion (a). Become.

The nonionic hydrophilic group (polyoxyethylene group) content of the polyurethane dispersion in the aqueous polyurethane emulsion (i) used in the present invention is preferably in the range of 10 to 50% by mass, more preferably 15 to 40% by mass. It is particularly preferable that the value falls within the range. When the nonionic hydrophilic group content exceeds 50% by mass, the water resistance of the polyurethane resin obtained by the recovery method or the production method of the present invention may be easily lowered. On the other hand, when the amount is less than 10% by mass, it is difficult to disperse the dispersion or prepolymer in water immediately before water dispersion during the production of the aqueous polyurethane emulsion (a).

The sum of the urethane group concentration and the urea group concentration of the polyurethane dispersion in the aqueous polyurethane emulsion (a) used in the present invention is in the range of 1.0 to 3.0 mmol / g, preferably 1.3 to 2.7 mmol / g. Is within the range. When no urea group is present in the polymer, the urethane group concentration is in the range of 1.0 to 3.0 mmol / g, preferably in the range of 1.3 to 2.7 mmol / g. When the sum of the urethane group concentration and the urea group concentration is less than 1.0 mmol / g, the mechanical strength of the polyurethane resin obtained by the recovery method or the production method of the present invention tends to be insufficient. In addition, when the sum of the urethane group concentration and the urea group concentration exceeds 3.0 mmol / g, for example, when adhesion is desired in a film obtained using the aqueous polyurethane emulsion (a), this adhesion performance is insufficient. It is easy to become.

<Optional additional components that can be introduced into the aqueous polyurethane emulsion (a)>
In the aqueous polyurethane emulsion (a) used in the present invention, additives and auxiliaries commonly used in aqueous systems can be used as necessary. For example, curing agents, pigments, dyes, antiblocking agents, dispersion stabilizers, leveling agents, antigelling agents, light stabilizers, antioxidants, ultraviolet absorbers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents Agents, reinforcing materials, catalysts, etc. can be added.

  In addition, the aqueous polyurethane emulsion (a) used in the present invention has, as necessary, a viscosity reducing agent having an effect of promoting dispersion in water (the solubility in water is 0.1 to 40% by mass and the flash point is 50 ° C. or higher) can be added. Specific examples of the viscosity reducing agent include dipropylene glycol dimethyl ether (trade name: dimethylpropylene diglycol (abbreviation: DMFDG, solubility in water: 37.0 mass%, flash point: 65 ° C.), diethylene glycol dibutyl ether (commercial product). Name: Dibutyldiglycol, Abbreviation: DBDG, Solubility in water: 0.3 mass%, Flash point: 122 ° C., N-methylpyrrolidone (abbreviation: NMP, Solubility in water: (optional) mass%, flash point) : 91 ° C).

Furthermore, the aqueous polyurethane emulsion (a) used in the present invention can be blended with other resin emulsions depending on the purpose of having the desired performance of the polyurethane resin obtained by the production method of the present invention. . For example, acrylic emulsion, polyester emulsion, polyolefin emulsion, latex and the like.

<Acid liquid (b)>
Examples of the acidic liquid (b) used in the present invention include formic acid, acetic acid, propionic acid, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, citric acid, gluconic acid, and succinic acid. A liquid whose pH is in the range of 4.0 or more and less than 7.0 with an aqueous solution of an organic acid such as acid, tartaric acid, lactic acid, fumaric acid, malic acid, or, for example, phosphoric acid, phosphorous acid, hydrochloric acid, sulfuric acid, Examples thereof include an aqueous solution of an inorganic acid such as sulfite hydrochloric acid and the like having a pH in the range of 4.0 or more and less than 7.0.

  In the present invention, from the viewpoints of adverse effects on the environment caused by the remaining free acid and consideration of safety in the operator, a naturally-derived acid substance is dissolved in water and the pH is 4.0. It is preferable to use an acidic liquid prepared so as to be in the range of less than 7.0. Among them, a substance that is a dibasic acid among these naturally-derived acid substances is dissolved in water, and the pH is It is particularly preferable to use an acidic liquid prepared so as to be within a range of 4.0 or more and less than 7.0.

<Recovery method or production method of polyurethane resin>
In the present invention, the pH of the aqueous polyurethane emulsion (I) is adjusted to 5.0 to 7.0 by adding the acidic liquid (B) to the aqueous polyurethane emulsion (I) having a pH of 7.1 to 9.0. And a method for recovering or producing a polyurethane resin to obtain a polyurethane resin by aggregation and separation. In the recovery method or the production method of the present invention, an acidic liquid (B) is added to an aqueous polyurethane emulsion (A) having a pH of 7.1 to 9.0 to adjust the pH to 5.0 to 7.0. A polyurethane resin can be easily and instantly obtained by aggregation. Furthermore, the aqueous polyurethane emulsion (i) and the acidic liquid (b) having a pH of 7.1 to 9.0 are simultaneously charged into a predetermined container and the like, and after undergoing a process of aggregation and drying as necessary, the shape of the predetermined container It is also possible to obtain a polyurethane resin corresponding to the above. In addition, after adding an acidic liquid (b) to the aqueous polyurethane emulsion (i) having a pH of 7.1 to 9.0 as necessary, the mixture is uniformly mixed by a conventionally known method to obtain a liquid mixture Alternatively, a method of allowing the polyurethane resin to stand by agglomeration to obtain a polyurethane resin by aggregation is also possible.

Next, although the Example and comparative example of this invention are demonstrated in detail, this invention is limited to these Examples and is not interpreted. Unless otherwise specified, “%” in the following examples means “% by mass”.

<Synthesis of Allophanate Modified Polyisocyanate (Part 1)>
Production Example 1:
863 g of “HDI (corresponding to (A1-2) of the present invention)” and “MPEG-1 (of (A1 of the present invention)) were added to a 1 L reactor equipped with a stirrer, thermometer, cooler and nitrogen gas introduction tube -1)) ”and 0.2 g of“ 2-ethylhexanoic acid zirconium ”were charged, and the reaction was performed at 90 ° C. for 2 hours in a nitrogen atmosphere. Next, 0.1 g of phosphoric acid ester “JP-508 (manufactured by Johoku Chemical Co., Ltd.)” was charged, and a stop reaction was performed at 50 ° C. for 1 hour. The isocyanate group content in the reaction product after the termination reaction was 40.2%. This reaction product was subjected to thin film distillation at 130 ° C. × 0.04 kPa to obtain an allophanate-modified polyisocyanate isocyanate “ALP-1” corresponding to (A1) of the present invention. The isocyanate content of “ALP-1” was 11.4%, the viscosity at 25 ° C. was 140 mPa · s, and the content of free diisocyanate (ie, “HDI”) was 0.1%. Further, when “ALP-1” was analyzed by FT-IR and ¹³ C-NMR, urethane groups and isocyanurate groups were hardly confirmed, and the presence of allophanate groups was confirmed.

<Synthesis of Allophanate-modified Polyisocyanate (Part 2)>
Production Example 2:
950 g of “HDI”, 50 g of “isopropanol”, and 0.006 g of “zirconium 2-ethylhexanoate” were charged in a 1 L reactor equipped with a stirrer, a thermometer, a cooler, and a nitrogen gas introduction tube, and a nitrogen atmosphere The reaction was carried out at 110 ° C. for 3 hours. Next, 0.1 g of phosphoric acid ester “JP-508 (manufactured by Johoku Chemical Co., Ltd.)” was charged, and a stop reaction was performed at 50 ° C. for 1 hour. This reaction product was subjected to thin-film distillation at 150 ° C. × 0.7 kPa to obtain allophanate-modified polyisocyanate isocyanate “ALP-2” as a component constituting (A) of the present invention. The isocyanate content of “ALP-2” was 19.3%, the viscosity at 25 ° C. was 100 mPa · s, and the content of free diisocyanate (ie, “HDI”) was 0.1%. Moreover, when "ALP-2" was analyzed by FT-IR and ¹³ C-NMR, urethane groups and isocyanurate groups were hardly confirmed, and the presence of allophanate groups was confirmed.

The details of the abbreviations in Production Example 1 and Production Example 2 are as follows.
"HDI": Hexamethylene diisocyanate.
“MPEG-1”: Methoxypolyethylene glycol (number average molecular weight = 400).

<Synthesis of aqueous polyurethane emulsion>
Synthesis example 1:
Capacity with stirrer, thermometer, nitrogen seal tube, and cooler: In a 3 L reactor, 200 g of “Polyol-1” (molar ratio = 1.00 equivalent) and 9.4 g of “DMPA” (molar ratio = 0.70 equivalent) and charged uniformly at 100 ° C. Thereafter, 14.7 g of the above-mentioned “ALP-1” (corresponding to a molar ratio = 0.40), 32.7 g of the above-mentioned “ALP-2” (corresponding to a molar ratio = 1.50), and 27. 1 g (corresponding to a molar ratio = 1.22) was charged, and 0.05 g of “DOTDL” was charged and reacted at 80 ° C. for 3 hours. Next, 70.0 g of “NMP” was added as an optional component for lowering the viscosity (corresponding to 10% with respect to the obtained aqueous polyurethane emulsion: the same in the following synthesis examples), and further stirred for 1 hour. After stirring, 3.2 g (corresponding to a molar ratio = 0.70) of “TEA” was charged to neutralize the carboxyl group to obtain an isocyanate group-terminated prepolymer. This prepolymer had an isocyanate group content of 3.19% and a viscosity at 75 ° C. of 1,350 mPa · s. Thereafter, 600 g of water was charged and emulsified. When emulsified, a chain extension reaction was performed by adding amine water in which 100 g of water and 3.2 g of “TEA” (molar ratio = 0.70 equivalent) were previously added. The reaction was terminated when the presence of isocyanate groups was no longer confirmed by FT-IR, and an aqueous polyurethane emulsion “PUE-1” corresponding to (A) of the present invention was obtained. “PUE-1” had a solid content of 35%, a viscosity at 25 ° C. of 32 mPa · s, a pH of 7.5, and an average particle size of 100 nm.
The “molar ratio” in the description is the molar ratio to the polyol component (“polyol-1” in Synthesis Example 1), and water other than “solid content” (all are the same in the following synthesis examples). .

Synthesis Examples 2-9:
According to the composition (molar ratio, content) shown in Table 1, “PUE-2” to “PUE-9”, which are aqueous polyurethane emulsions, were obtained based on the same method as in Synthesis Example 1.

The details of the abbreviations in Synthesis Examples 1 to 9 in Table 1 are as follows.
“Polyol-1” (corresponding to (B) of the present invention): Polycarbonate polyol obtained from 1,6-hexanediol and diethyl carbonate (average functional group number = 2, number average molecular weight = 2,000).
“Polyol-2” (corresponding to (B) of the present invention): Polycarbonate polyol obtained from 1,6-hexanediol and diethyl carbonate (average functional group number = 2, number average molecular weight = 1,000).
“Polyol-3” (corresponding to (B) of the present invention): Polycarbonate polyol obtained by using 3-methyl-1,5-pentanediol, 1,6-hexanediol, and diethyl carbonate as raw materials (average number of functional groups = 2, number average molecular weight = 2,000).
"Polyol-4" (corresponding to (B) of the present invention): Aromatic ring-containing polycarbonate polyol obtained using ethylene glycol, neopentyl glycol, adipic acid, and isophthalic acid as raw materials (average functional group number = 2, number average molecular weight) = 2,000).
"DMPA" (corresponding to (C) of the present invention): 2,2-dimethylolpropionic acid.
"IPDI" (component constituting (A) of the present invention): isophorone diisocyanate.
"H12MDI" (component constituting (A) of the present invention): Hydrogenated diphenylmethane diisocyanate.
"DOTDL": Dioctyltin dilaurate.
“TEA” (corresponding to (D) of the present invention): Triethylamine.
“KOH” (corresponding to (D) of the present invention): potassium hydroxide (33% aqueous solution).
"NMP": N-methylpyrrolidone.
"DMDPG": Dipropylene glycol dimethyl ether.

<Recovery and production of polyurethane resin by aggregation>
Example 1:
50 g of the aqueous polyurethane emulsion “PUE-1” obtained in Synthesis Example 1 was divided into 0.1 L size glass sample bottles. To this, "formic acid (1N aqueous solution of formic acid (manufactured by Kishida Chemical Co., Ltd.): the same applies hereinafter)" was added as an acidic liquid (corresponding to (b) of the present invention) to adjust the pH of the aqueous polyurethane emulsion to 7. It prepared to 0 and the presence or absence of aggregation of a polyurethane resin was evaluated.
By the same method (addition of “formic acid”), a plurality of 0.1 L glass sample bottles charged with the same amount of “PUE-1” were prepared, and the pH of the aqueous polyurethane emulsion was adjusted to 6.0. In this case, when the pH was adjusted to 5.0, the same evaluation was performed for the presence or absence of aggregation of the polyurethane resin in each case where the pH was adjusted to 4.0 as a reference.
Furthermore, instead of “formic acid”, as hydrochloric acid (corresponding to (b) of the present invention) “hydrochloric acid (1N aqueous solution of hydrochloric acid (manufactured by Kishida Chemical Co., Ltd.): the same shall apply hereinafter)”, “acetic acid (1N of acetic acid) Aqueous solution (manufactured by Kishida Chemical Co., Ltd .: the same shall apply hereinafter) "and" citric acid (1N aqueous solution of citric acid (manufactured by Kishida Chemical Co., Ltd.): hereinafter the same shall apply) " The same evaluation was performed for the presence or absence of resin aggregation. The results are shown in Table 2.

Examples 2-4, Comparative Examples 1-5:
Evaluation similar to Example 1 was performed using “PUE-2” to “PUE-9”, which are aqueous polyurethane emulsions, in the same manner as in Example 1. The results are shown in Table 2.

Evaluation criteria for presence or absence of aggregation of polyurethane resin:
“◯”: Immediately after the addition of the acidic liquid, the polyurethane resin is significantly aggregated, and the remaining liquid other than the aggregated resin is transparent (clear).
“Δ”: When the acidic liquid was added and allowed to stand for 1 minute, the polyurethane resin agglomerated, but the remaining liquid other than the agglomerated resin was not transparent.
-"X": It left still for 1 minute after adding an acidic liquid, but aggregation of a polyurethane resin is not seen.
The aqueous polyurethane emulsions “PUE-1” to “PUE-9” before the addition of the acidic liquid all have “x” evaluation.

<Reference: Film evaluation of aqueous polyurethane emulsion>
Reference Examples 1-9:
About each of the aqueous polyurethane emulsions “PUE-1” to “PUE-9” used in each example and each comparative example, an aqueous polyurethane dispersion was cast on a plate glass and dried at 25 ° C. for 5 days to obtain a film thickness of 20 μm. A dry film having These films were immersed in warm water at 50 ° C., and the hot water resistance as a reference was evaluated by a method of observing the appearance of the film after 72 hours. The evaluation results are shown in Table 3.

Evaluation criteria for hot water resistance of film:
-“Good”: Good (no change is seen).
-"△": Although the original shape is not changed, a whitening phenomenon in the film is observed.
-"X": The original form is not fastened (a part or all of the film is dissolved).

The water-based polyurethane emulsion used in the present invention can be suitably used for paints, adhesives, fiber treatment agents, synthetic / artificial leathers, etc., but in addition to this, waste liquid treatment that occurs during the production of these series of products can be used. The resin can be easily recovered by the recovery method or the production method (that is, aggregation) of the present invention.

Claims (4)

An acidic liquid (B) is added to the aqueous polyurethane emulsion (I) having a hydrogen ion index (pH) of 7.1 to 9.0, and the hydrogen ion index (pH) of the aqueous polyurethane emulsion (I) is set to 5.0. A method of recovering a polyurethane resin by preparing a polyurethane resin by agglomeration and separation, which is prepared to ˜7.0,
Allophanate-modified polyisocyanate (A) obtained from an aqueous polyurethane emulsion (a) obtained from alkoxypoly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit. An acid obtained by reacting an organic polyisocyanate (A) containing A1), an active hydrogen group-containing compound (B), an anionic polar group and active hydrogen group-containing compound (C), and a neutralizing agent (D) A method for recovering a polyurethane resin, which is an aqueous polyurethane emulsion in which a polyurethane dispersion having a value of 10 to 20 mg KOH / g is uniformly dispersed and emulsified in water. The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). Item 2. A method for recovering a polyurethane resin according to Item 1. An acidic liquid (B) is added to the aqueous polyurethane emulsion (I) having a hydrogen ion index (pH) of 7.1 to 9.0, and the hydrogen ion index (pH) of the aqueous polyurethane emulsion (I) is set to 5.0. A method for producing a polyurethane resin by preparing a polyurethane resin by agglomeration and separation, which is prepared to ˜7.0,
Allophanate-modified polyisocyanate (A) obtained from an aqueous polyurethane emulsion (a) obtained from alkoxypoly (oxyalkylene) glycol (A1-1) and hexamethylene diisocyanate (A1-2) containing 50 mol% or more of oxyethylene groups in the repeating unit. An acid obtained by reacting an organic polyisocyanate (A) containing A1), an active hydrogen group-containing compound (B), an anionic polar group and active hydrogen group-containing compound (C), and a neutralizing agent (D) A method for producing a polyurethane resin, which is an aqueous polyurethane emulsion in which a polyurethane dispersion having a value of 10 to 20 mg KOH / g is uniformly dispersed and emulsified in water. The active hydrogen group-containing compound (B) contains at least a polymer polyol (B1) having a number average molecular weight of 500 or more, a low molecular polyamine having a number average molecular weight of less than 500, and / or water (B2). Item 4. A method for producing a polyurethane resin according to Item 3.