JPS58127753A - Reversible thermowhitening composition - Google Patents

Abstract

PURPOSE:To provide a reversible thermowhitening compsn. in which light transmissibility can be reversibly changed at a specified temperature, by dissolving a polymer contg. dimethylaminoethyl methacrylate as a polymeric component in water. CONSTITUTION:Dimethylaminoethyl methacrylate homopolymer or a copolymer contg. the same as a copolymeric component is dissolved in water. A water-soluble whitening temperature modifier may be added to the reversible thermowhitening compsn. prepd. by dissolving said homopolymer or copolymer in water so that the whitening temp. can be raised or lowered. Pref. said modifier is added in an amount of 0.1-30pts.wt. per 100pts.wt. said compsn. The thermowhitening of said compsn. is thought to be due to the fact that since the formation of iceberg by water molecule surrounding said polymer or said copolymer is reduced with the rise in temperature, said polymer or said copolymer becomes insoluble in water, and if hydrophilic and hydrophobic moieties are present in a suitable proportion, the solubility in water is lowered with the rise in temperature and the aq. soln. becomes cloudy suddenly at a temp. above a clouding point.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reversible whitening composition that can reversibly change its optical properties, ie, light transmittance, at a specific temperature.

Traditionally, it has been used to perform reversible whitening phenomenon.

As described in Japanese Patent Publication No. 55-23590, there is a temperature-sensitive light-shielding composition in which a nonionic surfactant is encapsulated in a gel-like substance such as an acrylamide polymer.
This is because when a nonionic surfactant is in an aqueous solution state, it undergoes phase separation at the cloud point and cannot maintain a stable white cloudy width, so it must be encapsulated in a gel-like substance, and preparation for practical use is difficult. requires an extra step.

The present invention is a reversible whitening composition that can be used in the form of an aqueous solution. In addition, the reversible whitening composition of the present invention is stable in the form of an aqueous solution and is transparent at low temperatures, but when heated, whitening with good light shielding properties can be obtained at a specific temperature, and the transparency and whitening are sharp. It is characterized by reversibly occurring repeatedly. In other words, one aspect of the present invention is.

A reversible whitening composition prepared by dissolving in water a homopolymer of dimethaminoethyl methacrylate or a copolymer in which at least dimethylaminoethyl methacrylate is a copolymerization component, and a homopolymer of dimethaminoethyl methacrylate or a small amount thereof. Tomodimethylaminoethyl methacrylate is dissolved in copolymer 2 water, which is a copolymerization component, and whitening temperature A
This is a reversible whitening composition containing an I\i'i agent.

The thermal whitening mechanism in the present invention is that the formation of ice barbs by water molecules surrounding the polymer or copolymer decreases as the temperature rises, so the polymer or copolymer becomes insoluble in water and the hydrophilic portion If the proportion of the polymer and the hydrophobic part is appropriate, the dispersibility of the polymer or copolymer into water will decrease as the temperature increases.5. This is thought to be because the aqueous solution suddenly becomes cloudy at IW temperatures above the chain point.

The present inventor discovered that when dimethylaminoethyl methacrylate or a copolymer thereof is dissolved in water at a specific ratio, the solution suddenly turns white at a certain temperature, and the clearing and whitening occur repeatedly. I discovered it for the first time. They also discovered for the first time that the whitening temperature can be freely adjusted by adding specific additives.

Heat-whitening materials having such properties are very useful.

The copolymer in which dimethylamine ethyl methacrylate is a copolymerization component as used in the present invention is prepared as follows. Take dimethylamine ethyl methacrylate and at least one of styrene monomers, acrylic monomers, olefins, vinyl acetate, etc., and add 100 parts by weight.

200 to 5,000 parts by weight of water or an organic solvent such as methanol, benzene, or ethyl acetate, or a mixture thereof, and 0.00 parts by weight of a polymerization initiator such as a peroxide, azo photoresist, or persulfate.
01 to 1 part by weight is added, and polymerization is carried out at 20 to 80 tZ' according to a conventional method.

The reversible whitening composition of the present invention is prepared by dissolving 3 to 30 parts by weight of the homopolymer or copolymer in 1 part of 100 parts of water. When the homopolymer or copolymer exceeds 30 parts by weight, the color changes from transparent before and after heating to pure white, =!
Or, the sensitivity of the whitening phenomenon from pure white to transparent becomes dull, and if it is less than 3 parts by weight, the light-shielding property when pure white is reduced.

In the present invention, a water-soluble whitening temperature regulator can be added to a reversible whitening composition prepared by dissolving the above homopolymer or copolymer in water to increase or lower the whitening temperature. It is preferable to add 0.1 to 30 parts by weight of the whitening temperature regulator to 100 parts by weight of the heat whitening composition. Whitening temperature regulators include salts such as sodium sulfate, potassium chloride, sodium chloride, sodium hydroxide, and potassium hydroxide.

PH regulators such as triethanolamine, hydrochloric acid, and sulfuric acid can be used. The whitening temperature of the hot whitening composition is lowered by the addition of the above-mentioned compounds, and the whitening temperature is lowered by the addition of sodium hydroxide, potassium hydroxide, and triethanolamine among the pH regulators until the pH of the aqueous solution reaches about 9.5. is falling.

When it exceeds about 9.5, the whitening temperature increases, and the addition of hydrochloric acid and sulfuric acid increases the whitening temperature. It is believed that the change in whitening temperature is due to the change in the chain point of the thermal whitening composition due to the addition of the whitening temperature regulator.

Thermal whitening compositions can be used for various purposes. for example,
When injecting into a container and using it, it is preferable to add an antifoaming agent to eliminate air bubbles during injection, a coloring agent when still coloring, a water-soluble polymer compound when increasing viscosity, etc. can be added depending on the purpose.

Next, nine examples of the present invention will be shown.

Example 1 20 parts of dimethylaminoethyl methacrylate and 180 parts of water
ammonium persulfate as a polymerization catalyst dissolved in 9 parts.
Polydimethylaminoethyl methacrylate was synthesized by a conventional method. This transparent 10% aqueous solution was sealed in a transparent glass cell with one gap, and when the temperature of the cell was gradually raised, the aqueous solution sharply turned white with no light-shielding properties at 43.0 C.
gave birth to When the cell was cooled below 43.0 C, the aqueous solution became clear. I was able to go from transparent to white and from white to transparent again and again.

Example 2 Azobis-2 using 59.7 parts of dimethylamine ethyl methacrylate and 2 parts of methyl methacrylate as a polymerization initiator
A copolymer of dimethylaminoethyl methacrylate and methyl methacrylate in a copolymerization ratio of 95:5 was synthesized by a conventional method using 0.5 parts of ,4-dimethylvaleronitrile.

This transparent 5% aqueous solution was sealed in the cell of Example 1, and when the cell was gradually heated, the aqueous solution sharply turned white with no light-shielding property at 35 OC. When the cell was cooled below 35.0 C, the aqueous solution became clear.

I was able to repeat this process from transparent to white and from white to transparent many times.

Example 3 Using dimethylamine ethyl methacrylate and 2-hydroxypropyl methacrylate as a single polymerization initiator and azobis-2,4-dimethylvaleronitrile, the copolymerization ratio of dimethylaminoethyl methacrylate and 2-hydroxypropyl methacrylate was - r Saki → Tome 4-
Copolymers of 98/2, 9 s/s, and 90/10 were synthesized. When these transparent 5% aqueous solutions were sealed in the cell of Example 1 and the temperature of the cell was gradually raised, the aqueous solutions sharply turned white without light-shielding properties at the temperatures shown in the table below.

The aqueous solution became clear when the cell was brought to a temperature below the temperature shown in the table below.

I was able to go from transparent to white and then from white to transparent over and over again.

Aqueous solution ゛ Whitening temperature (C)': Copolymerization ratio 9
8/2, 30.0/l 95/
2' 29.0/I 90/10
□ 26.0 'Example 4 Clear 7% aqueous solution of polydimethylaminoethyl methacrylate of Example 1 5? and sodium sulfate 0. When OO5g, 0.011i', 0.02g, and 0052 added were sealed in the cell of Example 1 and the cell was gradually heated, the aqueous solution sharply turned white without light shielding at the temperature shown in the table below. . The aqueous solution became clear when the cell was brought to a temperature below the temperature shown in the table below. I was able to go from transparent to white and then from white to transparent over and over again.

, Aqueous solution:' Whitening temperature (tZ') Addition amount of sodium sulfate (y) o, o
os l 38. s//
0.01 1 37.01/
0. 0 2 35. 5
11 0.05'
32.0 → □
□ □ □The whitening temperature of the aqueous solution to which sodium sulfate was not added was 430C.

Example 5 To 5f of the transparent aqueous solution of polydimethylaminoethyl methacrylate of Example 1, 0.11. o2g, 0.3F.

When the aqueous solution containing 042 was sealed in the cell of Example 1 and the cell was gradually heated, the aqueous solution sharply turned white without light-shielding properties at the temperatures shown in the table below. The aqueous solution became clear when the cell was brought to a temperature below the temperature shown in the table below. I was able to go from transparent to white and from white to transparent again and again.

:I/O,2(//9.1)・315
11 tt O, 3 (tt 9.5)
132.0 '□ // 0.4 (1110,9) 1 33.0
Note that the whitening temperature of the aqueous solution to which sodium hydroxide was not added was 43.0C.

Example 6 (9) Azobis-2,4 using 89 parts of dimethylamine ethyl methacrylate and 2 parts of ethyl methacrylate as polymerization initiators
- Using 0.5 parts of dimethylvaleronitrile, a copolymer of dimethylaminoethyl methacrylate and ethyl methacrylate in a copolymerization ratio of 97:3 was synthesized by a conventional method.

Sodium chloride 0.0 in this transparent 70% aqueous solution g151
05ii', 0.01fF, 0.02? , 0.0
When the aqueous solution containing 5 f/ was sealed in the cell of Example 1 and the cell was gradually heated, the aqueous solution sharply turned white without light-shielding properties at the temperatures shown in the table below. When the cell temperature was lowered to below the temperature shown in the table below, the aqueous solution became crystal clear. I was able to go from transparent to white and then from white to transparent over and over again.

Addition amount (10,005・27.5 '□ // Q,., ・26.5
'1/ 0.02 25.8//
0.05 2'4.6' (10
) The whitening temperature of the aqueous solution to which no sodium chloride was added was 29.5 U.

Triethanolamine 0.05 ii', 0.1 f
.

0.2? , 0.3? When the aqueous solution was sealed in the cell of Example 1 and the cell was gradually heated, the aqueous solution sharply turned white without g-light at the temperatures shown in the table below.

The aqueous solution became clear when the cell was brought to a temperature below the temperature shown in the table below.

I was able to go from transparent to white and then from white to transparent over and over again.

Aqueous solution, whitening temperature (C) i□□□ヰ〃0.1:27.6 tt O,2127,8 p O,3,28,2 In addition, whitening temperature of aqueous solution without adding triethanolamine was 295C.

Next, an example of how the composition of the present invention is used will be shown.

(1) An aqueous solution that turns white at a temperature similar to body temperature is placed inside a transparent glass cell with an image on the back glass (for example, Example 3).
) and the image is visible under normal conditions, but when you touch the glass, the aqueous solution turns white and the image disappears. Make it a visible and hidden display.

(2) An aqueous solution that whitens at room temperature or higher (for example, Example 6) is sealed in a large transparent plastic panel, and the panel is attached to a window glass.

On hot days, use heat-sensitive blackout windows to block direct sunlight.

(3) A certain temperature range is divided into several parts, and an aqueous solution that whitens at that temperature is sealed in a transparent hollow plastic sheet with a harmonica structure in which the inside is partially partitioned in the order of whitening temperature.
It will be a temperature display panel.

In addition, the reversible whitening composition of the present invention can be applied to industrial materials and toys that require color change depending on temperature.

Useful for household goods, packaging materials, etc.

35F

Claims (2)

[Claims] (1) A reversible whitening composition prepared by dissolving in water a homopolymer of dimethylamine ethyl methacrylate or a copolymer containing at least dimethylaminoethyl methacrylate as a copolymerization component. (2) A reversible whitening composition prepared by dissolving a homopolymer of dimethylaminoethyl methacrylate or a copolymer having at least dimethylaminoethyl methacrylate as a copolymerization component in water, and adding a whitening temperature 1 change regulator.