JP3311837B2 - Thermosensitive gelling emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to heat-sensitive gelled emulsions. More specifically, the present invention relates to a heat-sensitive gelling emulzine used for a coating material, a coating material for paper, a fiber impregnation process, and the like.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a heat-sensitive gelled emulsion which remains as an emulsion at room temperature but gels when heated and remains in a gelled state even when cooled to room temperature. It is necessary to use an acrylic emulsion from the viewpoint that the performance of the film to be formed is good for the thermosensitive gelation emulsion.
Conventionally, it has been known in the technical field of rubber-based latex to use a heat-sensitive gelling agent to cause gelation. For example, JP-A-63-19390, JP-B-3-64337, JP-A-4-261453, and the like.

Although several types of gelling agents have been known, these gelling agents can gel a rubber latex, but can thermally gel a synthetic resin emulsion, especially an acrylic emulsion. Did not. This is because rubber latex has an unstable factor as apparent from the fact that it is susceptible to salting out, and it is easy to impart heat-sensitive gelling property, but acrylic emulsion has salt mixing stability, storage stability, This is because the mechanical stability is good and the thermosensitive gelling property is hardly imparted. Recently, some techniques for studying the thermal gelation properties of acrylic emulsions have been observed. For example, Japanese Patent Application Laid-Open No. Hei 2-308844 and the like.

[0004]

The conventional proposals have problems that, when actually used, they do not have a thermosensitive gelling property, have poor storage stability, and change the thermosensitive gelling property depending on pH. The present invention provides an excellent heat-sensitive gelling emulsion that solves all of these problems.

[0005]

According to the present invention, (A) (a) an acetoacetyl group-containing monomer 0.5 to 5
0% by weight; (b) 50 to 99% by weight of one or more monomers selected from acrylates and methacrylates; and (c) other copolymerizable α, β-ethylenically unsaturated monomers. The present invention provides a thermosensitive gelling emulsion comprising: a synthetic resin emulsion obtained by emulsion polymerization of a monomer comprising 0 to 49.0% by weight of a body; and (B) a thermosensitive gelling agent. According to a preferred embodiment of the present invention, the aqueous synthetic resin emulsion (A) comprises: (a) 0.5 to 30% by weight of an acetoacetyl group-containing monomer (b) acrylic acid ester and methacrylic acid ester (C) another copolymerizable α, β-ethylenically unsaturated monomer is 0 to 48.5% by weight, and (d) copolymerization. It is preferably an aqueous synthetic resin emulsion obtained by emulsion polymerization of a monomer comprising 0.5 to 20% by weight of a possible functional group-containing α, β-ethylenically unsaturated monomer. According to a further preferred aspect of the present invention, the copolymerizable functional group-containing monomer (d) is selected from the group consisting of an amide group or a derivative thereof, a hydroxyl group, a glycidyl group and a carboxyl group. Having a solubility in water of 10 at 100 g of water at 25 ° C.
It is a functional group-containing monomer of 0 g or less. According to another preferred embodiment of the present invention, the heat-sensitive gelling agent (B) is an organopolysiloxane-based heat-sensitive gelling agent, a nonionic surfactant-based heat-sensitive gelling agent, or a nonionic surfactant and an inorganic material. It is a thermosensitive gelling agent consisting of a salt. According to a preferred embodiment of the present invention, the heat-sensitive gelling agent (B) is added to the aqueous synthetic resin emulsion in a solid content of 0.5 to 5%.
A thermosensitive gelling emulsion blended by weight% is preferred.
Further, according to still another preferred embodiment of the present invention, the monomer of the component (A) (c) is (c-1) an amide group or a derivative thereof, a hydroxyl group, a glycidyl group, or a carboxyl group. Any one
Functional group-containing monomer having two functional groups and having a solubility in water of not more than 100 g per 100 g of water at 25 ° C.
(C-2) a copolymerizable α other than the components (a), (b) and (c-1); , Β-ethylenically unsaturated monomer in an amount of 0 to 48.5% by weight (based on the total amount of the monomer of component (A)).

[0006]

DETAILED DESCRIPTION OF THE INVENTION The thermosensitive gelling emulsion has the following properties.

[0007] In line coating of paint, if a film is formed on the surface quickly during heating and drying, moisture in the film cannot evaporate and internal drying is difficult to proceed. If the drying temperature is increased, blisters called thermal blisters are formed on the coating film. There are problems that occur. By imparting the thermosensitive gelling property to the emulsion, it is possible to prevent the formation of a continuous film on the surface, to accelerate the drying of the inside to facilitate the evaporation of water, and to prevent the thermal blister.

In the pigment coating of paper, if the binder of the emulsion is gelled during coating and heating and drying, excessive penetration can be prevented and thermal blistering can be prevented.

In the process of impregnating paper and fiber, the emulsion is thermally gelled at the time of heating and drying after impregnation, whereby transfer of the impregnated resin to the surface layer can be prevented, and uniform application of the resin can be performed. Properties required for the thermogelling emulsion include a thermogelation temperature of 50 to 95 ° C., a high thermogelation rate, a high gel strength, and a good storage stability. Can be

A first feature of the present invention is that thermal gelation occurs in a wide pH range. Conventionally known thermosensitive gelling emulsions needed to keep the pH near neutrality. Therefore, it is not possible to freely select the monomer composition and additives constituting the emulsion to exhibit the required film performance, and the performance and application of the thermosensitive gelling emulsion are limited to a narrow range. was there. In particular, in the case of a paint or paper pigment coat, the pH of the emulsion is 7 to 10 due to the stability of the emulsion itself and the dispersion stability of pigments and fillers.
9 is used on the neutral to alkaline side, but the emulsion stabilized on the alkaline side has a problem in that it becomes difficult to form a thermal gel even when a thermal gelling agent is added. In addition, in the impregnation of paper or fiber, an acidic catalyst is used in combination, so that it is often used in an acidic region. The heat-sensitive gelling emulsion of the present invention has an advantage that it can be used in a wide pH range without affecting the pH range depending on the application since the influence of pH is small.

A second feature of the present invention is that thermal gelation occurs even at a low concentration of about 20% by weight of solids. Conventionally, it was thought that thermal gelation would not occur at a low concentration of solid content of 35% by weight or less, but the present invention has broken this common sense. In the impregnation of paper or fiber, the emulsion is diluted with water for uniform impregnation and the amount of impregnation is adjusted. However, in the conventional thermosensitive gelling emulsion, the solid content concentration is 35%. Since it is not less than the weight%, it hardly penetrates into the base material and is difficult to use for impregnation. Since the heat-sensitive gelling emulsion of the present invention can cause heat-sensitive gelation even at a low concentration, it can be effectively used for these applications. In paints as well, the emulsion concentration in the paint decreases in high PVC paints that use a large amount of pigments and fillers, and thermal gelation does not occur in conventional thermal gelling emulsions.
There is a disadvantage that the amount of the pigment / filler used is limited.

A third feature of the present invention is that the gelation when the gelation temperature is reached is sharp. It does not gradually gel. Such a characteristic action of the present invention is that a copolymer emulsion of a specific monomer composition to be used is used, and an organopolysiloxane-based thermal gelling agent or a nonionic surfactant-based thermal gelling agent which is a thermal gelling agent. It is played by the combination of. Organopolysiloxane itself is widely used as a heat-sensitive gelling agent, and forms a heat-sensitive gel alone without using inorganic compounds such as zinc oxide, potassium sulfate, and sodium sulfate, and its behavior is sharp and miscible. The properties are also good. Also, there are many types with different cloud points in the market, which are easily available. Even a thermosensitive gelling agent that is effective alone, such as polymethyl vinyl ether, has poor miscibility with synthetic resin emulsions,
Although it cannot be used because water is separated over time, organopolysiloxane is easy to use without water separation over time. However, ordinary acrylic synthetic resin emulsions have strong selectivity, and it has been difficult to form a thermosensitive gel.

Examples of the organopolysiloxane include Japanese Patent Publication No. 40-21427 and Japanese Patent Publication No. 47-19604.
No. JP-A-50-24336, U.S. Pat.
No. 3, US Pat. No. 3,255,140, British Patent No. 114
The compounds described in No. 1867 can be used.

In particular, the cloud point of a 15% by weight aqueous solution of an organopolysiloxane-based thermosensitive gelling agent is preferably 50 ° C. or less. If the cloud point exceeds 50 ° C., the gelation temperature becomes too high, and the heat-sensitive gelation becomes insensitive, which is not preferable. The compounding amount of the organopolysiloxane is 0.5 to 5% by weight based on the solid content of the emulsion. If it is less than this range, the thermosensitive gelling effect cannot be obtained, and if it is too large,
The stability of the emulsion becomes poor, and the water resistance of a film obtained from the emulsion is lowered. It is preferable to use the necessary minimum amount for obtaining the thermosensitive gelling effect.

Examples of the nonionic surfactant-based thermosensitive gelling agent include polyoxyethylene alkyl ether having a cloud point of 30 to 80 ° C., polyoxyethylene alkyl allyl ether, polyoxyethylene-polyoxypropylene block polymer, and polyoxyethylene sorbitan. Fatty acid esters, polyoxyethylene acyl esters, polyoxyethylene polyaryl ethers and the like are used. An alkylene oxide adduct of an alkylphenol-formalin condensate can also be used. An alkylene oxide adduct of an alkylphenol-formalin condensate is particularly preferred because it reacts sharply with temperature.

The amount of the surfactant to be used is 0.5 to 5% by weight in solid content with respect to the synthetic resin emulsion. If it is less than this range, the thermosensitive gelling effect cannot be obtained, and if it is too large,
The stability of the emulsion becomes poor, and the water resistance of a film obtained from the emulsion is lowered. It is preferable to use the necessary minimum amount for obtaining the thermosensitive gelling effect.

It is necessary to use acrylic acid ester or methacrylic acid ester as a main component of the monomer constituting the emulsion copolymer from the viewpoint of film performance. As described above, acrylic acid ester or methacrylic acid ester polymer emulsions do not gelate with a thermal gelling agent such as an organopolysiloxane. In order to cause thermal gelation, it is necessary to introduce 0.5 to 50% by weight of an acetoacetyl group-containing monomer into the copolymer. Other monomers can be used for the remainder, but the amount used is 49% by weight.
The above cannot be used because it has an adverse effect on the thermal gelation property. That is, the main components are an acrylate monomer and a monomer having an acetoacetyl group.

The copolymerizable α, β-ethylenic monomer having a functional group can be used in an amount of 0.5 to 20% by weight. Amide groups, such functional group-containing monomers,
Or a derivative thereof, a functional group-containing monomer having any one of a hydroxyl group, a glycidyl group, and a carboxyl group, and having a solubility in water of 100 g or less per 100 g of water at 25 ° C. The amount of the functional group-containing monomer must be 0.5 to 20% by weight. 0.5
When the amount is less than 20% by weight, a crosslinking effect cannot be obtained. When the amount exceeds 20% by weight, it is difficult to obtain a stable aqueous synthetic resin emulsion at the time of emulsion polymerization. It is not preferable because it decreases.

The acrylate or methacrylate used in the present invention includes methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate,
2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylonitrile, methacrylonitrile and the like. The acetoacetyl group-containing monomer reacts diketene with a functional group-containing monomer such as a hydroxyl group, an amide group, a urethane group, an amino group, a carboxyl group, or transesterifies an acetoacetic ester with the monomer. It can be obtained by: Particularly, allyl acetoacetate, vinyl acetoacetate, 2-acetoacetoxyethyl (meth) acrylate, and 2-acetoacetoxypropyl (meth) acrylate are preferred.

As other copolymerizable monomers, vinyl esters such as vinyl acetate and vinyl versatate, styrene, methylstyrene, vinyl chloride, ethylene and the like are used. Among monomers having a functional group, a monomer having a monomer having an amide group or a derivative thereof includes methacrylamide (31), N-methylol methacrylamide (90), and a monomer having a hydroxyl group. Is
2-hydroxypropyl methacrylate (13.4) 2
-Hydroxybutyl methacrylate (10 or less) and monomers having a glycidyl group include glycidyl methacrylate (10 or less) and allyl glycidyl ether (1
3) and so on. The numbers in parentheses indicate the solubility in 100 g of water at 25 ° C.

Each of these monomers having a functional group has a solubility in 100 g of water at 25 ° C. of 100 g.
It is as follows. Why 100 g water solubility
Although it is not clear why the functional group-containing monomer cannot be used, the present inventors have found that if the solubility of the functional group-containing monomer in water is large, a heterogeneous reaction system such as emulsion polymerization may be used. Since the copolymerization with the main monomer is not sufficiently performed, and a homopolymer of the functional group-containing monomer is also generated, the homopolymer is adsorbed on the emulsion particle surface to enhance the stability. It is considered that the effect of thermal gelation cannot be obtained.

Further, a functional group-containing monomer other than the above-mentioned functional group-containing monomer can be used for other purposes as long as the effect of the thermal gelation is not impaired. Examples of the functional group-containing monomer other than the above include divinylbenzene, diallyl phthalate, 1,6 hexanediol, ethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocyanurate, and tetraallyl for improving solvent resistance. Monomers having two or more unsaturated groups such as oxyethane, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itacone for improving stability such as mechanical stability and pigment mixing stability And unsaturated carboxylic acids such as acids.

When a nonionic surfactant-based gelling agent is used as the heat-sensitive gelling agent, an inorganic salt can be used in combination. When an inorganic salt is added, thermal gelation occurs in a lower temperature range, and the thermal gelation is quick and sharp. The inorganic salts used are ammonium chloride, ammonium nitrate, ammonium sulfate, potassium sulfate, sodium sulfate, calcium chloride, calcium sulfate, ammonium carbonate, sodium nitrate and the like.

When a thermosensitive gelling emulsion is prepared by adding an aqueous solution of a thermogelling agent to an emulsion, temporary shock may destroy the stability of the emulsion and cause partial gelation. Gelation due to such a shock occurs only when the heat-sensitive gelling agent aqueous solution is added, and is stable after the heat-sensitive emulsion is formed.
In order to reduce the temporary shock of the emulsion at the time of mixing, it is effective to add a surfactant to the emulsion within a range not affecting the thermal gelation. As the surfactant, a nonionic surfactant having an HLB of 10 to 16 is used in an amount of 2 parts by weight or less based on 100 parts by weight of the emulsion.

[0025]

【Example】

Production Example A Production of Synthetic Resin Emulsion In a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a dropping funnel, 73 parts by weight of deionized water and 0.6 part by weight of a surfactant (sodium lauryl sulfate) were charged. Then, the inside temperature is adjusted to 50 ° C. by passing nitrogen gas through. Emulsion polymerization is carried out by dropping a monomer emulsion and a polymerization catalyst into which a nitrogen gas having the following composition has been passed through from a dropping funnel over 4 hours. Monomer emulsion butyl acrylate 94 parts by weight 2-acetoacetoxyethyl methacrylate 6 parts by weight Surfactant (sodium lauryl sulfate) 1.8 parts by weight Deionized water 55 parts by weight Polymerization catalyst 10% by weight ammonium persulfate aqueous solution 5 parts by weight 5% by weight of a 10% by weight aqueous solution of sodium hydrogen sulfite After completion of the dropwise addition, stirring is continued at an internal temperature of 50 ° C. for 2 hours to complete emulsion polymerization, and the mixture is cooled to room temperature. Then with ammonia water
Adjusted to H4, a synthetic resin emulsion having a concentration of 43% by weight and a viscosity of 12 centipoise was produced.

Production Examples B to D Production of Synthetic Resin Emulsion A synthetic resin emulsion was produced in the same manner as in Production Example A except that the monomers in the monomer emulsion were changed as shown in Table 1.

[0027]

[Table 1]

(Note) 100 g of water at 25 ° C.
Is the solubility in

Production Example A Production of Synthetic Resin Emulsion Used for Comparative Example Production Example A was the same as Production Example A except that 6 parts by weight of 2-acetoacetoxyethyl methacrylate was not used and 100 parts by weight of butyl acrylate was used. Thus, a synthetic resin emulsion was produced.

Production Examples B, C, D Production of Synthetic Resin Emulsion Used in Comparative Example A synthetic resin emulsion was prepared in the same manner as in Production Example A except that the monomer composition used in Production Example A was used as shown in Table 2. Manufactured.

[0031]

[Table 2]

Examples 1 to 4 Alkylene oxide adduct of alkylphenol-folimarin condensate (Latemul NP-5150 manufactured by Kao Corporation) was added to the synthetic resin emulsions obtained in Production Examples A to D.
A 0% by weight aqueous solution and a 10% by weight aqueous solution of ammonium sulfate were added as shown in Table 3 to obtain a thermosensitive gelled emulsion (I). Separately, a 10% by weight aqueous solution of Coagulant WS (manufactured by Bayer Co., cloud point 31 ° C.) as an organopolysiloxane-based thermosensitive gelling agent was added to the synthetic resin emulsion as shown in Table 3 to obtain a thermosensitive gelled emulsion (II).

[0033]

[Table 3]

Comparative Examples 1 to 4 The synthetic resin emulsions obtained in Production Examples 1 to 2 were added in the same manner as in Example 1 as shown in Table 3 to obtain emulsion compositions.

Test Method (Emulsion Stability) The heat-sensitive gelled emulsion obtained in Examples 1 to 4 and the emulsion composition obtained in Comparative Examples 1 to 4 were placed in a closed container and placed in a thermostat adjusted to 40 ° C. After standing for 2 weeks, the stability of the emulsion was tested. Table 3 shows the test results. …: The emulsion was stable with neither thickening nor water separation. ×: The emulsion was remarkably water-separated or thickened, and could not be used.

(Thermogelability) The thermogelling emulsions obtained in Examples 1 to 4 and the emulsion compositions obtained in Comparative Examples 1 to 4 were adjusted to have a pH of about 8.5 (alkaline) and about 7.5.
(Neutral) and about 4.5 (acidic), 5 g of the sample was taken in a test tube having an inner diameter of 15 mm, and immersed in a water bath adjusted to 80 ° C. for 5 minutes to determine the thermosensitive gelling property at 80 ° C. Tested. A: The whole emulsion gelled. …: The viscosity of the emulsion increased remarkably. Δ: The viscosity of the emulsion increased, but was insufficient. ×: No change was observed in the viscosity of the emulsion.

[0037]

The thermosensitive gelled emulsion of the present invention can be thermogelled in a wide pH range, and has the advantage of causing thermogelation even at a low concentration. In addition, when the gelling temperature is set to a predetermined value, an effect of sharply gelling is exerted.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08L 33/04-33/22

Claims (6)

(57) [Claims] (A) (a) 0.5 to 50% by weight of an acetoacetyl group-containing monomer, and (b) 50 to 99% by weight of one or more monomers selected from acrylates and methacrylates. (C) another copolymerizable α, β-ethylenically unsaturated monomer, a synthetic resin emulsion obtained by emulsion polymerization of a monomer comprising 0 to 49.0% by weight; A) a heat-sensitive gelling emulsion comprising a heat-sensitive gelling agent; 2. The monomer of component (A) (c) is selected from the group consisting of (c-1) one of an amide group or a derivative thereof, a hydroxyl group, a glycidyl group, and a carboxyl group.
A functional group-containing monomer having two functional groups and having a solubility in water of not more than 100 g per 100 g of water at 25 ° C. 0.5 to 20% by weight (based on the total amount of the monomer of component (A)); (C-2) 0 to 48.5% by weight of a copolymerizable α, β-ethylenically unsaturated monomer other than the components (a), (b) and (c-1) (component (A) The thermosensitive gelling emulsion according to claim 1, which is based on the total amount of the monomers). 3. The heat-sensitive gelling agent of component (B) is an organopolysiloxane-based heat-sensitive gelling agent.
2. The heat-sensitive gelling emulsion according to 1.). 4. The heat-sensitive gelling emulsion according to claim 1, wherein the heat-sensitive gelling agent of the component (B) is a nonionic surfactant-based heat-sensitive gelling agent. 5. The heat-sensitive gelling emulsion according to claim 1, wherein the heat-sensitive gelling agent of the component (B) is a heat-sensitive gelling agent comprising a nonionic surfactant and an inorganic salt. 6. The heat-sensitive gel according to any one of claims 1 to 5, wherein the heat-sensitive gelling agent of the component (B) is mixed with the synthetic resin emulsion at a solid content of 0.5 to 5% by weight. Gelling emulsion.