JPS6028289B2 - Method for producing polyurethane emulsion with crosslinking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyurethane emulsions.

More specifically, the present invention relates to a method for producing a polyurethane emulsion having crosslinking bonds that can maintain a stable dispersion state even in a dimethylformamide solution of other types of polyurethane.
Recently, it has been reported that the green coagulation property of a polymer solution can be improved by the presence of polymer fine particles in the polymer solution.
For example, the samurai era 51-7 private shout and the feudal lord 52-27464.
proposed by No.

These proposed methods involve adding polymer latexes having different solubility or solvent insolubility into a solution of a certain polymer, and according to the method, the wet coagulation property of the polymer solution is improved. Although improved, it has now been discovered that there is one major problem in implementing the best practice of this method. That is, according to the research of the present inventors, in order to improve the wet coagulation property by the presence of fine particles of polymer (B) in a polymer solution, chemical or physical It has been found that very similar properties are required, and this presents an irreconcilable technical problem: the combination of polymer wind and polymer [BI] with very similar chemical or physical properties. If polymers with significantly different values are selected, it is possible to produce an emulsion with a polymer curve that exists relatively stably in a polymer-like solution. When chemical or physical properties are similar, it is difficult to stably disperse the polymer in a polymer solution because the solvent solubility (or solubility parameter) of the polymer and the polymer are similar. It has been completely impossible to satisfy the above objectives with conventionally known polyurethane emulsions.For example, the basic patent for polyurethane emulsion, Hakama Kosho No. 33-11141, has patents 750-4.
polytetramethylene ether glycol having a molecular weight of 0.000 is reacted with an aromatic diisocyanate,
The molar ratio of glycol and diisocyanate is 1:1.2~
1:2 and the reaction product is mixed with an organic acid having at least 12 carbon atoms, the resulting product containing an alkali metal hydroxide and suitably an aromatic primary diamine. Although a method is disclosed in which the polyurethane is injected into at least an equivalent amount of water, the polyurethane obtained by this method is generally soluble in dimethylformamide (hereinafter abbreviated as OM), which is a good solvent for polyurethane, or swells greatly. It has this characteristic and is not liked.

Polyurethane latexes with improved solvent resistance are also known for use in finishes such as various paints.

For example, Samurai Ko No. 45-110957 has 1.5:1 to 3:
consisting of an aqueous dispersion of a chain-enhanced prepolymer of an organic diisocyanate and a polyol in an NCO/OH equivalent ratio of 1, the polyol having functional groups greater than 2 (3 or more) and having a molecular weight of at least 1500 Disclosed is a polyurethane latex made from a polyalkylene ether polyol, the polyol being an alkylene oxide having at least 3 carbon atoms, or a mixture of alkylene oxides having at least 3 carbon atoms. has been done. Since a polyol having three or more functional groups is used in this method, the solvent resistance is increased, and depending on the conditions, the chemical or physical properties desired in the present invention are similar to that of polyurethane in special cases. Polyurethane emulsions that do not dissolve in DMF, which is a good solvent, may be obtained in some cases, but these polyurethane emulsions generally have poor stability, and in particular, when the emulsions are dispersed in DMF solutions, the dispersion stability is extremely low. Furthermore, the state of the emulsion (for example, particle size) changes significantly over time, making it difficult to achieve the object of the present invention on an industrial scale. Also, in a similar concept to the above, the molecular weight is 1500 to 5000.
Polypropylene triol with a molecular weight of 500-3000
Cross-linked emulsions with specified proportions of polypropylene diol and glycol are also available, for example, in Japanese Patent Publication No. 48-417.
No. 18.

However, similar to the above, although the mechanical strength and solvent resistance after film formation can be improved, this has the drawback of poor dispersion stability in emulsions, particularly in polyurethane DMF solutions. The use of special surfactants has also been proposed as a way to improve the stability of aqueous emulsions.

For example, according to Japanese Patent Publication No. 986 of 1972, the conventional method using only a commercially available surfactant is not satisfactory for forming a stable emulsion of polyurethane, and therefore, a method using only a commercially available surfactant is not satisfactory for forming a stable emulsion of polyurethane. It is proposed to use a special compound and a sulfosuccinic acid type surfactant (both are anionic type surfactants). However, this proposed method has the drawback that very special compounds must be used and only linear polyurethane emulsions that are soluble in DM can be obtained; There is an inconvenience that it cannot be left until later. In view of the above object of the present invention, the present inventors have produced an emulsion that is stable itself and can be stably dispersed even when mixed with a DMF solution of polyurethane having similar chemical or physical properties. As a result of intensive research, it was surprisingly discovered that when manufacturing polyurethane, low molecular weight tri- or tetraols are used as one of the starting materials, and in addition, nonionic surfactants and specific anionic surfactants are used as surfactants. It has been found that the above-mentioned problems can be significantly improved by using these agents together.

That is, the present invention uses an organic diisocyanate with a molecular weight of 500
3000 PM of a dry film from an emulsion obtained by dispersing a polymer diol with a molecular weight of ~3000 and a low molecular weight tri- or tetraol with a molecular weight of 1000 or less in water or a liquid mainly composed of water.
A terminal isocyanate group prepolymer having a swelling degree in the range of 3 to 9 is prepared, and the prepolymer is selected from at least one nonionic surfactant and a sulfate ester type, a sulfonic acid type, and a phosphate ester type. A crosslinked polyurethane characterized by carrying out a chain extension reaction at the same time or after dispersion when dispersed in the form of fine particles with water or a water-based liquid containing at least one anionic surfactant. This is a method for producing emulsions. The organic diisocyanate used in the present invention is one commonly used in the synthesis of polyurethane, such as tolylene diisocyanate, xylylene diisocyanate,
In addition to aromatic diisocyanates such as 4,4'-difhenylmethane diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate and decamethylene diisocyanate are used.

The polymer diols used in the present invention are also polymer glycols commonly used in the synthesis of polyurethane elastomers, such as polyether glycols such as polytetramethylene glycol and polypropylene glycol, polyethylene adipate glycol, and polypropylene adipate glycol. and polyester glycols such as polytetramethylene adibate glycol, and mixtures or cocondensates thereof.

However, in the present invention, the average molecular weight of these polymer glycols should be 3000 or less, preferably 500 to 1500, which is a low molecular weight characteristic. When the average molecular weight of this polymer glycol becomes large, the viscosity in the DMF solution tends to change over time, and especially when it becomes larger than 3000, the dispersion stability in the DMF solution is good no matter how much the composition of the starting material is changed. You can't get emulsion. Furthermore, if the average molecular weight is less than 500, the resulting polyurethane becomes hard, and it becomes difficult to obtain an emulsion with a small particle size that contributes to dispersion stability, and therefore it is generally difficult to obtain a stable emulsion. It is also possible to use an organic low-molecular tri- or tetraol with a molecular weight of 1000 or less,
This is characteristic in the present invention.

For the first time, the use of low-molecular-weight tri- or tetraols has made it possible to produce emulsions that are self-stable and stably dispersed even in solutions. The stability of this emulsion increases as the molecular weight of the triol decreases, especially when the average molecular weight is 50.
It is preferable that it is 0 or less. Specific examples include trimethylolpropane, glycerin, hexanetriol, bentaerythritol, and ethylene oxide or salt at the hydroxyl group end of these. It is a low molecular weight tri- or tetraol synthesized by adding pyrene oxide. Note that the use of triol is preferred because the particle size and swelling degree of the emulsion can be easily controlled. In the present invention, a prepolymer having isocyanate groups at the terminals is produced by mixing and reacting the above three components in a desired ratio.

In this case, it is preferable that the NCO/OH ratio be at least 1.2 or more in order to produce a fine particle emulsion.
Generally, the NCO/OH ratio is preferably in the range of 1.3 to 2.5. The individual proportions of the polymer diol, low-molecular triol, and organic diisocyanate should be adjusted to give the desired hardness of the polyurethane of the target polyurethane emulsion. It is preferable that the degree of swelling of the IJ urethane emulsion in a DMF solution is adjusted to fall within the range of 3 to 9. The stability of a crosslinked polyurethane elastomer in a polyurethane elastomer solution having similar chemical or physical properties is determined by the particle size of the emulsion described below and the weight basis of the crosslinked polyurethane constituting the emulsion in a DMF solution. The present inventors have found that the degree of swelling is greatly affected, and have proposed the following. In this case, the degree of swelling is more preferably 4-8. Here, the degree of swelling is calculated by casting polyurethane emulsion on a glass plate to make a dry film with a thickness of 0.5 ribs, and immersing the film in 48-hour MF at 30 qC. It is expressed as a weight ratio before bonding.

The prepolymer may be synthesized either in the absence of a solvent or in a solvent, but an organic solvent (sometimes abbreviated as organic solvent [1]) that is incompatible with water is added during emulsion production.

Aromatic hydrocarbons such as benzene, toluene, and xylene are often used as organic solvents that are incompatible with water, but there are also comparatively Chlorinated hydrocarbons with low boiling points are used. When organic solvent [1] is added, the weight ratio of organic solvent [1] and prepolymer is 10
:100 to 200:100 is suitable for preparing fine particulate emulsions.

To form a fine particulate emulsion, a liquid that is miscible with both the organic solvent [1] and water and inert to isocyanate groups, such as ketones such as acetone and methyl ethyl ketone, is added to the prepolymer solution. Good for making.

The viscosity of the prepolymer solution thus obtained is preferably relatively low, preferably 50 poise or less at 30 qo.

When the viscosity of the solution becomes high, it becomes difficult to obtain a fine-grained emulsion even if the Taiazusa conditions are strengthened. The viscosity of the solution can be lowered by using various additives or the solvent used, and it is also possible to adjust the above-mentioned three components, especially the NCO/OH ratio and the amount of triol used. In the present invention, the organic solvent solution of the polyurethane prepolymer obtained above is dispersed into fine particles in accordance with a conventional method together with water containing a specific surfactant or a liquid mainly composed of water.

Here, in the present invention, it is essential that the type of surfactant is limited. That is, in the present invention, the surfactant is essentially a combination of a nonionic surfactant and a specific anionic surfactant. The anionic surfactant used in the present invention is a surfactant selected from sulfate ester type, sulfonic acid type, and phosphate ester type, and even among the same anionic surfactants, fatty acid salt type surfactants are hardly effective. There is no.

The surfactant used in the present invention is described, for example, in pages 68 to 664 of Oil and Fat Chemistry Handbook, Second Revised Edition (published November 30, 1972), published by Maruzen Co., Ltd.

A preferred example of a nonionic surfactant has an HLB value of 8 to 2.
0, especially a relatively large HLB of 13 to 20.
It is something that has value.

Higher fatty acid esters or ethers of polyoxyethylene glycol or polyoxyethylene-polyoxypropylene glycol, alkyl phenyl or alkyl naphthyl ethers of polyoxyethylene glycol or polyoxyethylene-polyoxypropylene glycol, polyoxyethylene-poly Typical examples include oxypropylene glycol. As anionic surfactants, sulfonic acid type or sulfate ester type surfactants are better than phosphate type surfactants, such as sulfate ester type surfactants such as funnel oil and polyoxyethylene alkyl sulfate ester sodium salt, alkylbenzene or naphthalene. A sulfonic acid type surfactant such as sodium sulfonate is preferable.

The proportion of the emulsifier to be used is not particularly limited, but the present invention has the characteristic that the amount used is small, and generally 2 to Bait HR (parts by weight per 100 parts by weight of polyurethane) is used.

The preferred mixing ratio of nonionic activator and anionic activator is 20:80 by weight, 90 to 10, especially 45:55.
The ratio is none, 7 and 30. In the present invention, a chain elongation reaction is carried out in the above-mentioned emulsifier composition liquid at the same time as emulsification or after emulsification. However, in the present invention, since water in the emulsifier composition liquid is used as a chain extender, in particular, another extender is used. Although it is not necessary to add it, it may be added separately.

The particle size of the emulsion thus emulsified is preferably controlled to be within a range of about 0.1 to 3 µm on average (according to microscopic observation).

If the particle size is large, the stability of the polyurethane emulsion itself is poor, or especially when the emulsion is present in a polyurethane DM solution, the fine particles exhibit sedimentation and the dispersion stabilizer deteriorates. If the particle size is 0.1 puyo and smaller, it is not preferred in the present invention because the wet coagulation property of the polyurethane solution, which is the intended objective of the present invention, cannot be sufficiently improved. The preferred particle size is 0.1 to 1 micron, particularly 0.3 to 0.8 micron. The emulsion can be prepared by any known conventional method.

The polyurethane emulsion obtained in the present invention is stable by itself, and is particularly stable even when added to a DMF solution of a polyurethane having a similar nitrogen percentage based on isocyanate groups in the soft segment constituting the polyurethane. Polyurethane DMF
It is suitable for making films, synthetic leather, etc. by adding it to a solution and performing wet coagulation, but it can also be used alone for paints with excellent solvent resistance, bond products, paper processing agents, fiber processing agents, etc. It is possible.

The present invention will be described below with reference to Examples, where all parts in the Examples refer to weight unless otherwise specified.

Example 1 Toluene 27, polypropylene glycol with an average molecular weight of 700, 62 parts, and trimethylolpropane 35 parts were dissolved, and then 32 parts of tolylene diisocyanate were added to the bottom of the tank, and then at 95 qo for 4 hours. By reacting, a prepolymer solution containing terminal isocyanate groups was obtained.

20 parts of acetone was added to this prepolymer solution to adjust the viscosity to about 100 centipoise. 20 parts of ethylene oxide-propylene oxide block copolymer (HLB-18) with a molecular weight of 15,500 as an emulsifier composition;
A composition containing 18 parts of polyoxyethylene (20) nonyphenyether sulfate ester salt and 76 parts of water was mixed with the prepolymer solution prepared above, kept at 360°C, and emulsified for 5 minutes in a homomixer. Then, the chain is elongated by tying with a paddle type toadusa wing for 5 hours, and the average diameter is about 0.
A stable polyurethane emulsion with fine particles of No. 8 was obtained.

The degree of swelling of this polyurethane emulsion in DMF immersion was 5.5.

Polycaprolactone glycol is converted into soft zegmethane and diphenylmethane-4 is used as an organic diisocyanate.
A polyurethane elastomer base part prepared by using 4'-diisocyanate and ethylene glycol as a chain extender to adjust the weight percentage of nitrogen based on the isocyanate group to approximately 4.5% was dissolved in 100 parts of DM. When this polyurethane emulsion was added in various amounts and mixed with Touzuka, a stable dispersion state was maintained even after being left for several days.

Comparative Examples 1 to 2 The emulsion of Comparative Example 1 was prepared by using a propylene glycol adduct of trimethylolpropane (average molecular weight 3000) in place of the trimethylolpropane of Example 1, and the polypropylene glycol of Example 1 with a molecular weight of 700 was used. Instead, an emulsion of Comparative Example 2 was prepared using polypropylene glycol with a molecular weight of 4000,
The properties of the emulsion are shown in Table 1 in comparison with the emulsion of Example 1.

Table 1 shows wet films produced by casting a composition solution of polyurethane dispersed in a DMF solution into a polyethylene film with a thickness of 0.5 mm, and then coagulating it in a 30% aqueous solution of DMF. The physical properties of are also shown. Table 1
*The viscosity of the emulsion changes over time.

Example 2 85 parts of polypropylene glycol having an average molecular weight of 850 based on 29 toluene, 30 parts of trimethylolpropane, and 348 parts of tolylene diisocyanate were added to the solution, and then reacted at 95q0 for 4 hours. A prebolimer solution of terminal isocyanate groups was obtained.

After adjusting the viscosity by adding methyl ethyl ketone 22 to this prepolymer solution, todecylbenzenesulfonate 33
parts, 22 parts of ethylene oxide propylene oxide block copolymer (HLB=18) with a molecular weight of 10,400, and 85 parts of water.
dapisonic) and then subjected to chain elongation reaction in the same manner as in Example 1 to obtain a stable emulsion with an average particle diameter of 0.5 μm and a DMF swelling degree of 6.9. This emulsion maintained a stable dispersion state in both DMF solutions of polyester-based and polyether-based polyurethanes, and the wet coagulation properties of the composition were also good.

Comparative Example 3 Dodecylbenzenesulfonate 55 as emulsifier composition
Emulsification was carried out in exactly the same manner as in Example 2, except that a composition consisting of 85 parts and 85 parts of water was used, and the swelling degree was almost the same as in Example 2, but the particle size was slightly smaller (average particle size of about 0).
．． 4) emulsion was obtained.

This emulsion had poor stability, and if left undisturbed, some of the emulsion would settle down and form an okara-like appearance. Comparative Example 4 Example 2 was carried out in exactly the same manner as in Example 2, except that a composition consisting of 55 parts of ethylene oxide propylene oxide block copolymer (HLB: 18) having a molecular weight of 10,400 and 85 parts of water was used as the emulsifier composition. When emulsified, the particle size of the obtained emulsion was as large as about one peak, and the stability was inferior to that of the emulsion of Example 2.

Claims (1)

[Claims] 1 Organic diisocyanate, average molecular weight 500-300
A dry film from an emulsion obtained by dispersing a polymer diol of 0 and a low molecular weight tri- or tetraol with a molecular weight of 1000 or less in water or a water-based liquid at 30°C in dimethylformamide.
A terminal isocyanate group prepolymer having a swelling degree in the range of 3 to 9 is prepared, and the prepolymer is mixed with at least one nonionic surfactant selected from sulfuric acid ester type, sulfonic acid type, and phosphoric acid ester type. When dispersed in the form of fine particles with an average particle size of 0.1 to 3 μm together with water or a water-based liquid containing at least one anionic surfactant, a chain elongation reaction is carried out at the same time or after dispersion. A method for producing a polyurethane emulsion having a characteristic crosslinking bond.