JPH075645B2 - Surfactant for emulsion polymerization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surfactant for emulsion polymerization of unsaturated monomers.

More specifically, the present invention is used in emulsion polymerization of an ethylenically unsaturated monomer or a conjugated diene unsaturated monomer, or a mixture of these monomers, and has an extremely low foaming property and an appropriate emulsion polymerization rate. The present invention relates to a surfactant for emulsion polymerization, which can provide an emulsion having good water resistance and adhesion of a film.

[Conventional technology and its problems]

Emulsions, which are so-called emulsions of various polymeric substances, use water as a solvent, so they are more advantageous than solvent-type products in terms of safety for the environment and human body, and they are used for paints, fiber processing agents, adhesives, and paper. It is currently widely used as a processing agent.

In the production of emulsion, it provides a place for polymerization,
Anionic surfactants such as alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, alkyl sulfate ester salts and higher fatty acid salts, and nonionic surfactants such as polyoxyethylene alkyl phenyl ethers are generally used for stabilizing the produced emulsion. 0.5 to 5% by weight based on the raw material monomers, either alone or as a mixture
It is used.

However, the emulsion produced using these surfactants has a large foaming property and a low surface tension, and has some problems as follows in production or use.

That is, since these surfactants have a large foaming property, the charging capacity becomes large at the time of emulsion production, and the observation of the reaction state becomes insufficient.

Bubbles can also cause pinholes when coating emulsions.

When the surface tension is low, the adhesive strength tends to weaken when the emulsion is used as an adhesive, and when it is used as a fiber processing agent, the emulsion has too high permeability to the fiber and the characteristics of the fiber itself are utilized. It gets harder.

Furthermore, it is pointed out that the surfactant is non-volatile and therefore remains in the film prepared from the emulsion, which causes deterioration of water resistance, adhesion, tensile strength, heat resistance, weather resistance, etc. of the film. Has been done.

Various methods have been studied in order to improve the adverse effects caused by these surfactants, so-called reactive surfactants having an ethylenically unsaturated bond in the molecule, carboxyl groups or sulfonic acid groups having an alkylmercapto group at the terminal. Copolymer of contained monomers (JP-B-47-34832, JP-A-54-214)
No. 85) or a copolymer of a carboxyl group- or sulfonic acid group-containing monomer and various unsaturated monomers (Japanese Patent Publication No. 47-6).
06, JP-B-51-31280, JP-A-53-18490, JP-A-57
-30703) and the like, a method using an oligomer type surfactant, an emulsion polymerization method in the absence of an active agent, and the like are known.

However, even in the method using these reactive type and oligomer type activators, since it is dependent on the micelle forming ability of the activator to provide a place for the polymerization, which is the basic performance required for the surfactant in emulsion polymerization, it is appropriate. Those that give a high emulsion polymerization rate have a large foaming property and cannot exert a sufficient effect even with respect to the reduction of the water resistance of the film. On the other hand, those having a low foaming property by lowering the micelle forming ability have drawbacks such as a slow emulsion polymerization rate and needing an addition amount more than the usual amount used, and these conflicting performances can be satisfied at the same time. Absent.

In addition, emulsion polymerization in the absence of an activator is not practical because there are problems with various stability of the obtained emulsion.

[Means for Solving the Problems] In the actual conditions, the present inventors have an emulsion polymerization that has an excessive emulsion polymerization rate despite having a low foaming property and does not adversely affect the water resistance of the film. As a result of earnest research on the surfactant for use, a surfactant composed of a copolymer of an unsaturated monomer containing a carboxyl group, a sulfonic acid group or a polyalkylene oxide group and a specific monomer copolymerizable therewith is extremely effective. This has led to the completion of the present invention.

That is, the present invention comprises 7 to 35 parts by weight of a polar unsaturated monomer (hereinafter referred to as a polar monomer) containing a carboxyl group, a sulfonic acid group or a polyalkylene oxide group, and 70% by weight or more of which can be copolymerized therewith. , 93 to 65 parts by weight of one or more hydrophobic unsaturated monomers (hereinafter referred to as hydrophobic monomers) consisting of hydrophobic unsaturated monomers having a glass transition temperature (hereinafter referred to as Tg) of 0 ° C. or less. The present invention relates to a surfactant for emulsion polymerization, which comprises a salt of a copolymer having a number average molecular weight of 700 to 10,000 obtained by polymerization.

In the present invention, the Tg of the unsaturated monomer means the value of Tg of the homopolymer obtained by homopolymerizing the monomer.

When the above-mentioned surfactant for emulsion polymerization of the present invention is used, the micelle forming ability is very weak, and although the foamability is low, an excessive emulsion polymerization rate is obtained and a stable emulsion is produced. The reason is considered as follows.

That is, since the hydrophobic monomer is randomly copolymerized in the surfactant for emulsion polymerization of the present invention, the number of polar groups is large even though it has a molecular structure that does not easily form a micellar structure in which hydrophobic groups gather together. Since the amount of water is less than that of ordinary surfactants and the water solubility of the molecule is reduced, it is easy for the molecule to become entangled in water and form a thread-like shape. It is presumed that emulsion polymerization has occurred and emulsion polymerization is in progress. It should be noted that the molecular weight should be increased to simply promote the entanglement of the molecule,
With this, the movement of molecules is suppressed, and when polymer particles grow and grow, they efficiently move to the particle surface and cannot contribute to stabilization of particles, and at the same time a function as a flocculating agent occurs, so the molecular weight (number average molecular weight) ), 700 to 10,000 is suitable, and more preferably 800 to 7,000. Further, by using as the hydrophobic copolymerizable monomer, one containing 70% by weight or more of a monomer having Tg of 0 ° C. or less,
The performance is further improved, but it is considered that this is because when the emulsion particles grow and grow, they can more efficiently move and coordinate to the particle surface and contribute to the stabilization of the emulsion.

The polar group-containing unsaturated monomer that is a polar monomer that can be used in the present invention is acrylic acid, methacrylic acid, itaconic acid, or the like, and the sulfonic acid group-containing monomer is acrylamide alkyl such as 2-acrylamido-2-methylpropanesulfonic acid. (C ₁ ~C ₄₎ sulfonic acid, alkylsulfonyl, such as sulfoethyl acrylate (C ₁ ~C ₄₎
Examples thereof include acrylate, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid and the like. Among these, acrylamidoalkyl (C _1-
C ₄ ) Sulfonic acid is more preferable because it has excellent copolymerizability with a hydrophobic monomer to be copolymerized and solubility in a reaction solvent.

Further, examples of the polyalkylene oxide group-containing monomer include esters of an unsaturated carboxylic acid monomer and a polyoxyalkylene oxide adduct of polyoxyalkylene glycol or a lower alcohol.

Among the monomers constituting the hydrophobic monomer, the monomers having Tg of 0 ° C. or lower include ethyl acrylate, butyl acrylate, octyl acrylate, octyl methacrylate,
Dodecyl methacrylate and the like can be mentioned, and one or more of these may be used in combination.

The content of the polar monomer in the copolymer constituting the surfactant of the present invention is 7 to 35% by weight. When the content of the polar monomer is less than 7% by weight, the hydrophilic group is insufficient and the polar group is separated from the aqueous layer. Or the stability of the produced emulsion decreases. On the other hand, when the content of the polar monomer exceeds 35% by weight, the hydrophilicity of the molecule is too strong, the entanglement of the polymer is decreased and the emulsion polymerization rate is decreased, and the electric double layer is compressed due to the increase of ionic strength. Occurs, the resulting emulsion becomes unstable, and the water resistance of the film also decreases.

Acrylamide alkyl as a polar monomer (C ₁ ~C ₄₎
When using sulfonic acid, its content is 15-35% by weight
Is more preferable, and when used as a surfactant for emulsion polymerization, an emulsion having good emulsion polymerization properties and excellent film physical properties can be obtained.

The content of the monomer having a Tg of 0 ° C or less in the hydrophobic monomer needs to be 70% by weight or more. As described above, if it is less than this, the emulsion becomes unstable and aggregates are easily generated in the latter half of the emulsion polymerization reaction. Therefore, the higher the content, the better.

However, since the types of monomers having Tg of 0 ° C or lower are limited, when only the above-mentioned monomers are used, the compatibility with the monomers to be emulsion-polymerized is poor, the monomers are hard to be solubilized, and the physical properties of the resin are deteriorated. Therefore, a suitable monomer may be contained within a range not exceeding 30% by weight.

Examples of this type of monomer include aromatic vinyl monomers such as styrene, (meth) acrylic acid esters such as methyl methacrylate, vinyl esters such as vinyl acetate, acrylonitrile, 2-hydroxyethyl, methacrylate and the like, or 2 You can choose from more than one species.

The number average molecular weight of the copolymer of the present invention is 70
0 to 10000, more preferably 800 to 7000 is required, and in order to obtain a molecular weight in this range, it is generally necessary to use a molecular weight regulator, for example, lower alkyl mercaptan, a chain transfer agent such as a halide, methyl ethyl ketone, isopropyl alcohol. It is conceivable to use a solvent having chain transfer ability such as carbon tetrachloride.

Incidentally, when the number average molecular weight of the copolymer exceeds 10,000, as described above, aggregates are likely to occur in the latter half of the emulsion polymerization, and when the number average molecular weight is 700 or less, foamability appears, or due to the remaining chain transfer agent. The emulsion polymerization reaction may not proceed.

The copolymer to be the surfactant for emulsion polymerization of the present invention may be synthesized by any method such as solution polymerization, bulk polymerization, etc., but a lower alcohol type having a large chain transfer constant, a ketone type or a mixture thereof with a water mixed solvent. It is desirable that the compound is synthesized by the solution polymerization method in consideration of the adjustment of the molecular weight of the produced copolymer. Regarding the addition method of each monomer to the polymerization reaction system,
Either of divided addition and continuous addition may be used, but it is preferable to obtain a copolymer as homogeneous as possible, and when copolymerizing monomers having different copolymerizability ratios, the residual monomer ratio in the reaction system is as high as possible. It is preferable to control the dropping rate of the monomer so that it is kept constant.

After the completion of the copolymerization reaction, an appropriate amount of basic substance is added, and then water is added to adjust the pH to 6 to 8, and the solvent is removed by topping or the like to obtain an aqueous solution of the copolymer salt. it can. Examples of the basic substance include alkali metal hydroxides and carbonates, ammonia, organic amines such as triethylamine and triethanolamine, and the like.

It is convenient to use the surfactant of the present invention comprising the copolymer salt as an aqueous solution having a concentration of 10 to 50% for emulsion polymerization reaction.

The emulsion polymerization reaction using the surfactant for emulsion polymerization of the present invention can be carried out by a known method. For example, 80 to 200 parts by weight of water to 100 parts by weight of the monomer, 0.5 to 10 parts by weight of the surfactant for emulsion polymerization of the present invention, a proper amount of a polymerization initiator, and further an inorganic salt and a chain transfer agent if necessary. And the like are added, and a suitable temperature is set in a nitrogen atmosphere to carry out a polymerization reaction. The monomers used in this emulsion polymerization include styrene and α
-Aromatic vinyl monomers such as methylstyrene, methyl acrylate, butyl acrylate, acrylic acid or methacrylic acid esters such as methyl methacrylate, vinyl chloride, vinyl halides such as vinylidene chloride or vinylidene,
Examples thereof include vinyl esters such as vinyl acetate, and conjugated dienes such as butadiene and isobrene. These monomers may be used alone or as a mixture of two or more kinds.

〔Example〕

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. All parts in the examples are based on weight.

<Synthesis of Copolymer Salt> Synthetic Examples 1 to 12 and Synthetic Comparative Examples 1 to 6 Copolymers were synthesized using the monomer mixtures and reagents shown in Table 1, and neutralized with triethylamine to give a copolymer. An aqueous solution of the combined salt was obtained. The number average molecular weight (Mn) of the copolymer is also shown in Table 1, but the molecular weight was obtained by applying gel permeation chromatography to the unneutralized product of the copolymer with polystyrene having a known molecular weight as the standard substance. is there.

The copolymerization reaction was carried out by mixing and dissolving the monomer mixture, the solvent and the initiator, and stirring the mixture at the reflux temperature for 8 hours in a nitrogen gas atmosphere. In each case, the polymerization rate was almost 100%.

After the completion of the copolymerization reaction, triethylamine in an amount equal to that of the acidic group was added, 400 parts of ion-exchanged water was added, and the solvent was removed by topping to obtain an aqueous solution having a solid content of about 30%.

Acrylamide alkyl as a polar monomer (C ₁ ~C ₄₎
When using sulfonic acid, its content is 15-35% by weight
Is more preferable, and when used as a surfactant for emulsion polymerization, an emulsion having good emulsion polymerization properties and excellent film physical properties can be obtained.

The abbreviations in Table 1 have the following meanings.

Hydrophobic monomer Polar monomer Solvent, initiator, etc. Synthesis Examples 13 and 14 Synthesis was performed in the same manner as in Synthesis Example 8 except that ammonia (Synthesis Example 13) or sodium hydroxide (Synthesis Example 14) was used instead of neutralizing AMPS with triethylamine.

Examples 1 to 14 and Comparative Examples 1 to 9 Emulsion Polymerization Performance Evaluation Part 1 The copolymer salts obtained in Synthesis Examples 1 to 14 and Synthetic Comparative Examples 1 to 6 and dodecylbenzene which is a commercially available anionic surfactant. Sodium sulfonate (NeoPerex F-25),
Using sodium lauryl sulfate (Emal 2F) and sodium polyoxyethylene nonylphenyl ether sulfate (Rebenol WZ) as activators for emulsion polymerization, emulsion polymerization performance was evaluated according to the following prescription.

500 parts by weight of ion-exchanged water, 3 parts by weight of various activators shown in Table 2, styrene / methyl methacrylate in a four-necked separable flask equipped with a reflux condenser, a stirrer, and a nitrogen introduction tube.
100 parts by weight of a mixture of / n-butyl acrylate = 1/1/2 was added, and the atmosphere was replaced with nitrogen at room temperature.

Then, the liquid temperature was adjusted to 30 ° C., 5 parts of a 2% potassium persulfate aqueous solution was added, and the reactor was immersed in an 80 ° C. oil bath to start polymerization.

After a certain period of time, a part of the reaction solution was sampled and the solid content thereof was measured (150 ° C., 3 hours drying) to determine the polymerization rate. After further polymerizing for 2 hours, the surface tension, foaming, and water resistance of the dried film of the obtained emulsion were measured by the methods described below.

The following results are summarized in Table 2.

<Surface tension> Measured at room temperature using CBVP Surface tension meter 3A manufactured by Kyowa Chemical Co., Ltd.

<Bubbling> 10 ml of the emulsion was put into a 30 ml test tube, shaken vigorously for 30 seconds, the total volume including bubbles was measured, and the increased volume amount was shown in%.

<Water resistance> The emulsion was coated on a glass plate and dried overnight at 70 ° C, and the coating film obtained was set in tap water for one sunset, and the degree of blushing and blistering was visually determined according to the following criteria. .

Examples 15 to 22 and Comparative Examples 10 to 14 Emulsion Polymerization Performance Evaluation No. 2 Emulsions were obtained in the same manner as described above except that the activator and the monomer mixture for emulsion polymerization shown in Table 3 were used, and the surface tension of the emulsions. , Foaming power, etc. were measured by the above-mentioned methods.

The abbreviations of the monomers in Table 3 have the same meanings as described above.

Claims (3)

[Claims] 1. A polar unsaturated monomer 7 containing a carboxyl group, a sulfonic acid group or a polyalkylene oxide group.
To 35 parts by weight and 70% by weight or more of which are copolymerizable with one or more hydrophobic unsaturated monomers having a glass transition temperature (Tg) of 0 ° C or less. A surfactant for emulsion polymerization, which comprises a salt of a copolymer having a number average molecular weight of 700 to 10000 obtained by copolymerizing with about 65 parts by weight. 2. The surfactant for emulsion polymerization according to claim 1, wherein the polar unsaturated monomer is an unsaturated monomer containing a sulfonic acid group or a polyalkylene oxide group. 3. The surfactant for emulsion polymerization according to claim 1, wherein the unsaturated monomer having a sulfonic acid group is acrylamidoalkylsulfonic acid.