JPH0546859B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature-sensitive polymer emulsion;
More specifically, the present invention relates to a polymer emulsion whose light transmittance increases above a certain temperature and decreases below that temperature.

[Conventional technology]

Water-soluble polymers with cloud points are already known. For example, hydroxypropyl cellulose, polyvinyl methyl ether, some acrylamide derivatives. All of these are water-soluble at relatively low temperatures, and when the temperature is raised, the solubility decreases and polymer particles precipitate and become cloudy (light becomes difficult to transmit). For example, light blocking materials for greenhouse greenhouses and photosensitive emulsifier coatings for photographic film (Japanese Patent Laid-Open No. 59-1999)
187010), etc.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a polymer emulsion that has the property of increasing light transmittance as the temperature increases and decreasing the light transmittance as the temperature decreases, which was hitherto unknown.

[Means for solving problems]

As a result of various studies to find an emulsion with properties opposite to those previously known, the present inventors discovered a certain type of N-substituted (meth)acrylamide derivative and a hydrophobic emulsion with low solubility in water. The present invention was completed after discovering that emulsions obtained by copolymerizing monomers have special properties.

That is, the present invention uses N-substituted (meth)acrylamide derivatives having cloud points as homopolymers from 5 to 50
part by weight and 95 to 50 parts by weight of a monomer having an unsaturated double bond copolymerizable with the monomer, the light transmittance increases above a certain temperature and decreases below the temperature. It is a temperature-sensitive polymer emulsion.

Examples of the N-substituted (meth)acrylamide having a cloud point as a homopolymer in the present invention include compounds represented by the following general formulas (1) and (2).

[In the formula, R ₁ is a hydrogen atom or a methyl group, and A is (-
CH ₂ ) _o -- (n is an integer from 4 to 6) or (-CH ₂ ) ₂ --
―
O-(-CH ₂ ) ₂ represents] [In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a hydrogen atom, a methyl group or an ethyl group, R ₃ is a methyl group,
Ethyl group or propyl group (except when R ₂ is a hydrogen atom and R ₃ is a methyl group, and R ₂ is a methyl or ethyl group and R ₃ is a propyl group; if R ₃ is a propyl group, R ₂ is a hydrogen atom)] The monomer represented by the general formula (1) is N-
Preferred compounds include acryloylpyrrolidine, N-acryloylpiperidine, N-methacryloylpyrrolidine, N-methacryloylpiperidine, N-acryloylhexahydroazepine, and N-acryloylmorpholine, and examples of the monomer represented by general formula (2) include N-ethyl Acrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N-cyclopropylacrylamide, N-isopropylmethacrylamide, N-cyclopropylmethacrylamide,
Preferred compounds include N,N-diethylacrylamide and N,N-ethylmethylacrylamide.

Preferred monomers having unsaturated double bonds copolymerizable with N-substituted (meth)acrylamide are hydrophobic or lipophilic monomers, such as N-n-hexylacrylamide, N-n
-hexyl methacrylamide, N-n-octyl methacrylamide, N-tert.-octylacrylamide, N-n-dodecyl acrylamide, N
N-alkyl (meth)acrylamide derivatives such as -n-dodecyl methacrylamide; N,N-diglycidyl acrylamide, N,N-diglycidyl methacrylamide, N-(4-glycidoxybutyl)acrylamide, N-(4 N- such as -glycidoxybutyl)methacrylamide, N-(5-glycidoxypentyl)acrylamide, N-(6-glycidoxyhexyl)acrylamide, etc.
(ω-glycidoxyalkyl) (meth)acrylamide derivatives; (meth)acrylate derivatives such as ethyl acrylate, methyl methacrylate, butyl methacrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate; acrylonitrile, methacrylonitrile, Vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, propylene,
Olefins such as butene; styrene, α-methylstyrene, butadiene, isoprene, etc. can be mentioned.

The proportion of the N-substituted (meth)acrylamide used in the copolymerization with a monomer having a double bond copolymerizable with the amide is 5 to 50 parts by weight, preferably 7 to 30 parts by weight of the N-substituted (meth)acrylamide. The latter is 95 to 50 parts by weight, preferably 93 to 70 parts by weight.
If the proportion is outside this range, the above-mentioned specificity of light transmittance with respect to temperature will not occur.

As other copolymerization components, hydrophilic monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, hydroxyethyl methacrylate, and hydroxyethyl acrylate can be used for purposes such as stabilizing emulsion particles. The amount used is 0 to 20% by weight (based on the total amount of main component monomers).

Any known method can be used to produce a polymer emulsion from the above monomers. In the polymerization, common surfactants such as alkyl sulfates, alkylaryl sulfonates, fatty acid soaps, etc. may be used as necessary. As a polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate, N,N'-azobisamidinopropane hydrochloride,
It is also possible to use azo compounds such as 2,2'-azobis-2,4 dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleic acid and its salts, and also redox initiators. Examples of reducing agents used in combination with the above-mentioned oxidizing agents as redox initiators include sulfites, hydrogen sulfites, iron,
Examples include salts with low ionic valences such as copper and cobalt, organic amines such as aniline, and reducing sugars such as aldose and ketose.

In addition to the water-soluble radical polymerization initiators described above, oil-soluble initiators such as azobisisobutyronitrile and butyl peroxide can also be used. The amount of initiator used is 0.5 to 5% by weight based on the total amount of monomers. The polymerization temperature varies depending on the polymerization initiator used, but is usually in the range of 0 to 100°C, preferably 5 to 90°C. The polymer concentration is not particularly limited, but is approximately 5 to 60% by weight.

In the polymer emulsion of the present invention, the N
Substituted (meth)acrylamide is generally found to be rich on the surface of the emulsion particles, and lipophilic monomers are found to be rich in the portion forming the emulsion core.

The emulsion of the present invention can be used as a temperature sensor because its light transmittance changes rapidly after reaching a certain temperature, and this change is reversible.
This change in light transmittance is caused by the emulsion particles coagulating and partially forming water masses at high temperatures, which reduces the number of particles blocking the passage of light, reduces light scattering, and allows light to pass freely. This occurs when the proportion of the available area increases. It has also been revealed that the above specific temperature is within the range of ±10° C. of the clouding point of the homopolymer of N-substituted (meth)acrylamide, which is one of the components forming the copolymer.

The present invention will be described in more detail below with reference to Examples.

〔Example〕

Example 1 10 parts by weight of N-acryloylpyrrolidine, 90 parts by weight of styrene, and 1.6 parts by weight of N,N'-azobisamidinopropane hydrochloride as a polymerization initiator were dissolved or dispersed in 600 parts by weight of distilled water, and the mixture was heated at 50°C for 24 hours. The emulsion of the present invention was obtained by polymerization by stirring for a period of time. The particle size at 25°C was 0.83μ, and the particles were of core-shell type as shown in Figure 2A. Further, dilute this emulsion with water to make the polymer concentration 0.1% by weight, take 3 ml of this, and add 2 ml of 5M saline solution.
The mixture was left at each temperature for 2 hours, and further diluted 10 times with water at the same temperature to obtain a transmittance T of light at λ = 700 nm.
% was measured and the results shown in FIG. 1 were obtained. The change point of the light transmittance was 50 to 57°C, and was within ±10°C of the cloud point of 51°C of the emulsion of N-acryloylpyrrolidine homopolymer, which was separately adjusted and measured.

Example 2 An emulsion of the present invention was obtained in the same manner as in Example 1, except that 20 parts by weight of N-acryloylpyrrolidine and 80 parts by weight of styrene were used. The particle size at 25° C. was 0.70 μm, which was a core-shell type, and the same temperature change curve of light transmittance as in Example 1 was obtained.

Example 3 An emulsion of the present invention was obtained in the same manner as in Example 1, except that 40 parts by weight of N-acryloylpyrrolidine and 60 parts by weight of styrene were used. The grain size at 25° C. was 0.90 μm, and it had an irregular structure as shown in FIG. 2B, but the temperature change curve of light transmittance was the same as in Example 1.

As described above, according to Examples 1 to 3, the emulsion of the present invention has a light transmittance that is large at higher temperatures and significantly smaller at lower temperatures within the range of ±10°C of the cloud point of the homopolymer of N-acryloylpyrrolidine. It was clearly shown that there was a change in

The particle size of the emulsion of the present invention shifts from a core-shell type to an irregularly shaped structure as the proportion of hydrophilic monomer used increases, but this shape itself does not affect specific changes in light transmittance. do not have.

Example 4 Using 20 parts by weight of N-isopropylmethacrylamide, 80 parts by weight of styrene, and 1.5 parts by weight of N,N'-azobisamidinopropane hydrochloride, the polymerization temperature was adjusted.
An emulsion of the present invention was obtained in the same manner as in Example 1 except that the temperature was 40°C. Particle size at 25℃ is 0.63μ
It is a core-shell type, and the changing point of light transmittance is
At 35° to 45°C, it was within ±10°C of the cloud point of the homopolymer of N-isopropylmethacrylamide, 43°C.

Example 5 The same procedure as in Example 1 was carried out, except that 20 parts by weight of N,N-diethylacrylamide, 80 parts by weight of styrene, and 1.0 parts by weight of N,N'-azobisamidinopropane hydrochloride were used, and the polymerization temperature was set at 40°C. An emulsion of the invention was obtained. The particle size at 25°C is 0.55μ and it is a core-shell type, and the changing point of light transmittance is between 25° and 35°.
The cloud point of the homopolymer of N,N-diethylacrylamide was within ±10°C of 32°C.

Comparative Example 1 N-acryloylpyrrolidine without styrene
Same as Example 1 except that 100 parts by weight was used,
An emulsion of a homopolymer of N-acryloylpyrrolidine was obtained. This emulsion became solubilized when the temperature was lowered.

Comparative Example 2 Styrene was emulsion polymerized by a conventional method and the light transmittance was measured in the same manner as in Example 1, but no difference due to temperature was observed.

Comparative Example 3 A copolymer emulsion was obtained in the same manner as in Example 1, except that 80 parts by weight of N-acryloylpyrrolidine and 20 parts by weight of styrene were used and the polymerization temperature was 65°C. When the temperature of this emulsion was lowered below 50°C, it became solubilized and the liquid became transparent, and when the temperature was raised again, it became cloudy, and the light transmittance exhibited characteristics opposite to those of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the light transmittance and temperature of the emulsion of the present invention, and FIG. 2 is a diagram showing the shape of the particles of the emulsion of the present invention, with A representing a core-shell type and B representing a modified structure. 1... N-substituted (meth)acrylamide derivative rich region, 2... Lipophilic monomer rich region.

Claims (1)

[Scope of Claims] 1. 5 to 50 parts by weight of an N-substituted (meth)acrylamide derivative having a cloud point as a homopolymer, and 95 to 50 parts by weight of a monomer having an unsaturated double bond that can be copolymerized with the monomer. A temperature-sensitive polymer emulsion whose light transmittance increases above a certain temperature and decreases below that temperature. 2 N-substituted (meth)acrylamide has the general formula [In the formula, R ₁ is a hydrogen atom or a methyl group, A is (CH ₂ ) _o -- (n is an integer from 4 to 6) or (-CH ₂ ) ₂
---
The polymer emulsion according to claim 1, which is represented by O-(CH ₂ ) ₂ --. Claim 2, wherein the 3N-substituted (meth)acrylamide is N-acryloylpyrrolidine, N-acryloylpiperidine, N-methacryloylpyrrolidine, N-methacryloylpiperidine, N-acryloylhexahydroazepine, or N-acryloylmorpholine. Polymer emulsion. 4 N-substituted (meth)acrylamide has the general formula [In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a hydrogen atom, a methyl group or an ethyl group, R ₃ is a methyl group,
Ethyl group or propyl group (except when R ₂ is a hydrogen atom and R ₃ is a methyl group, and R ₂ is a methyl or ethyl group and R ₃ is a propyl group; if R ₃ is a propyl group, 2. The polymer emulsion according to claim 1, wherein R ₂ is a hydrogen atom. 5 N-substituted (meth)acrylamide is N-ethylacrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N-cyclopropylacrylamide, N-isopropylmethacrylamide, N-cyclopropylmethacrylamide, N,N-diethylacrylamide ,
The emulsion according to claim 4, which is N,N-ethylmethylacrylamide.