JPS6030277B2 - Manufacturing method of capsule dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a microcapsule dispersion, and in particular to a method for producing a microcapsule dispersion, and in particular to prevent abnormalities observed when pulp powder is added to a capsule dispersion prepared using polyvinyl alcohol as an emulsifier for capsule core material. The present invention relates to a method for improving viscosity increase, and provides a microcapsule dispersion that is extremely useful for use in pressure-sensitive copying paper.

Pressure-sensitive copying paper and heat-sensitive recording paper are widely used as recording materials that utilize the principle that an electron-donating organic coloring agent and an electron-accepting coloring agent come into contact to form a color.

In pressure-sensitive copying paper, at least one of the organic coloring agent and the coloring agent is contained in microcapsules and the two are isolated.
The structure is such that when the microcapsules are destroyed by applying pressure, the two components come into contact and a colored image appears. In the most common type of pressure sensitive copying paper, microcapsules contain an organic color former dissolved or dispersed in a suitable oily substance. Examples of oily substances include animal oils such as fish oil and lard oil, vegetable oils such as castor oil and soybean oil, mineral oils such as kerosene and naphtha, alkylated naphthalenes, alkylated biphenyls, hydrogenated terphenyls, and alkylated diphenylmethanes. Synthetic oils are used alone or in combination.

Examples of organic color formers include crystal violet lactone, 3.3-bis(P-dimethylaminophenyl) phthalide, 3-(P-dimethylaminophenyl)-3-(
Triarylmethane compounds such as 1.2-dimethylindol-3-yl) phthalide, 4.4-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2.4.5-trichlorophenyl Diphenylmethane compounds such as leukoolamine, rhodamine B-anilinolactam, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6.8-dimethylfluorane, 3.7-diethylaminofluorane, 3-diethylamino-7 -xanthene compounds such as chloroethylmethylaminofluorane, thiazine compounds such as benzylleucomethylene blue, P-nitrobenzylleucomethylene blue, 3-methyl-spirodinaphthopyran, 3-ethyl-spirodinaphthopyran , 3-propyl-spiro dibenzopyran, and other spiro compounds are used alone or in combination.

On the other hand, coloring agents that can develop color upon contact with organic coloring agents include:
Inorganic acidic substances such as acid clay, activated clay, attapulgide, silica, and aluminum silicate, and organic acidic substances such as phenolic compounds, phenol polymers, aromatic carboxylic acids and their polyvalent metal salts are known. (For example, Japanese Patent Publication No. 49-10850, Japanese Patent Publication No. 51-25174, etc.) Methods for encapsulating a core material such as an oily substance in which an organic coloring agent is dissolved or dispersed include, for example, a coacervation method, an interfacial vehicle condensation method, Various methods such as in-situ polycondensation methods have been used. Generally, these capsule manufacturing methods require an emulsification process in which the capsule core material is emulsified and dispersed in an aqueous medium. An activator or the like is used as an emulsifier. In particular, since polyvinyl alcohol easily produces a homogeneous and stable emulsion, for example, a capsule manufacturing method (Japanese Patent Publication No. 42-771, Japanese Patent Publication No. 52) by polymerizing polyvalent isocyanates, water, polyvalent amines, and polyhydroxy compounds is used. -13508, etc.) and a capsule manufacturing method by condensation of a polyvalent amine with an acid chloride compound (U.S. Patent No. 34)
No. 29827, etc.), it is preferably used as an emulsifier for capsule core materials. On the other hand, pressure-sensitive copy paper can be used for computer output recording paper, office slips, etc.
It is used in a wide variety of applications, such as copying forms, and is required to have various quality characteristics depending on its use.

Therefore, when preparing a microcapsule dispersion, various auxiliary agents are added to the dispersion in order to meet various quality characteristics.

Among them, pulp powder is one of the most commonly used auxiliaries, especially for preventing agglomeration of capsule dispersions, - preventing streaks when coating dispersions, protecting capsules in capsule-coated papers, and even for capsule-coated papers. It has been widely used in the industry for the purpose of preventing ink stains, and is highly effective. However, as mentioned above, when pulp powder is added as an auxiliary agent to a capsule dispersion prepared using polyvinyl alcohol as an emulsifier for the capsule core material and continues to be used, the viscosity of the dispersion gradually increases and In some cases, pulp powder may form a core or capsules may aggregate, resulting in a dispersion that cannot be coated uniformly. Despite its excellent effectiveness as an auxiliary agent, At present, pulp powder cannot be used in a satisfactory manner.

As a result of repeated research on various capsule dispersions, the inventors of the present invention have found that polyvinyl alcohol, which is used as an emulsifier for capsule core materials, interacts with pulp powder, resulting in a phenomenon in which the viscosity of capsule dispersions increases significantly. We discovered that this was causing an abnormal increase in viscosity, and tried to improve it by using polyvinyl alcohol with a low molecular weight as an emulsifier. was insufficient, and no satisfactory results were obtained.

Therefore, an object of the present invention is to improve the abnormal increase in viscosity observed when pulp powder is added to a capsule dispersion prepared using polyvinyl alcohol as an emulsifier for capsule core material.

This object of the invention is achieved by adding pulp powder in the presence of carboxymethyl cellulose into a capsule dispersion prepared using polyvinyl alcohol as an emulsifier for the capsule core material.

In the method of the present invention, carboxymethyl cellulose (hereinafter simply abbreviated as CMC) is added to the capsule dispersion as described above.

), but the pulp powder is added in the presence of CM
C needs to be added and blended into the capsule dispersion before adding the pulp powder. However, considering the influence of CMC on the capsule dispersion system and the most effective way for CMC to act on the pulp powder, CMC should be added and blended into the capsule dispersion immediately before the capsule manufacturing process is completed and the pulp powder is added. is preferable. As the CMC used in the method of the present invention, CMC with a relatively small molecular weight is preferably used in order to prevent an increase in viscosity when CMC is added to the capsule dispersion. The viscosity of the dispersion varies significantly depending on the type and proportion of the various materials used.
CMC is selected depending on the properties of the capsule dispersion liquid to which MC is added, but in general, a 2% concentration aqueous solution of 25 qo is measured with a B-type viscometer (6 pm, Nolo meter) and has a value of 2 to 2. Preferably, a CMC of 500 centipoise is used.

Further, the addition ratio of CMC to the capsule dispersion liquid is appropriately adjusted according to the molecular weight of CMC used, etc., and is not particularly limited, but is generally 0.01 to the total amount of the capsule dispersion liquid. It is added in an amount of at least 0.03% by weight, more preferably about 0.03 to 1% by weight.

In the method of the present invention, pulp powder is added to the capsule dispersion containing CMC.

There are no particular limitations on the pulp powder used in this step, and any pulp powder conventionally blended into capsule dispersions can be used as is. For example, even if ordinary pulp powder, which has been subjected to oxidized moisture scale treatment and has a weight average fiber length of 85 to 95 microns, is added and mixed, the abnormal viscosity increase phenomenon of the capsule dispersion liquid is suppressed by the action of CMC, and the viscosity is extremely high. A capsule dispersion liquid with good stability can be obtained. Thus, according to the method of the present invention, a capsule dispersion with extremely good viscosity stability can be obtained even though pulp powder is added and mixed into a capsule dispersion using polyvinyl alcohol as an emulsifier for the capsule core material.

Therefore, due to significant fluctuations in viscosity conditions, dilution of coating fluids,
Capsule coating liquid, which had previously been difficult to coat uniformly by adjusting various coating conditions, can now be coated uniformly over a long period of time, making it possible to efficiently produce high-quality capsule coated paper. be. The reason for such excellent effects is not clear, but CM
It is speculated that this is because in the presence of C, the negative charge density on the surface of the pulp powder increases, and the dispersion state of the pulp powders is maintained more stably.

In addition, in the method of the present invention, the polyvinyl alcohol used as an emulsifier for the capsule core material includes, of course, various modified polyvinyl alcohols, and capsule dispersions using such polyvinyl alcohol as an emulsifier are also included. There are no particular limitations on the manufacturing method, and they can be manufactured by various known methods such as those described above.

However, in the method of forming capsules by the interfacial disarmament method, not only the viscosity stability of the capsule dispersion liquid is excellent, but also capsules having extremely excellent abrasion stain resistance, printability, etc. can be obtained. The present invention will be explained in more detail with reference to Examples below, but it is of course not limited thereto.

Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively. Example 1 Trimethylol group of tolylene diisocyanate.

Diisopropylnaphthalene (trade name K-11) is prepared by dissolving 25 parts of bread adduct (trade name Coronate L, manufactured by Nippon Polyurethane Industries, Ltd.) and 4 parts of crystal violet lactone.
3 (manufactured by Kureha Kagaku Co., Ltd.) in 10 ounces, and this was emulsified in a 5% aqueous solution of polyvinyl alcohol (trade name PVA-117, manufactured by Kuraray Co., Ltd.) in 40 Togeto using a homomixer. The average particle diameter of the emulsified oil droplets was 7.8 mm as measured by a Coulter counter. The temperature of the obtained emulsified dispersion was raised to 80 qo while stirring with a propeller mixer, and the reaction was allowed to continue for 3 hours while stirring, and then the temperature was lowered to room temperature to complete the encapsulation. CMC [substitution degree 0.75, viscosity primary PS (25 qo,
Add 10 parts of a 2% aqueous solution of [2% aqueous solution)] and 140 parts of water, and add pulp powder (trade name: KC Flock W-3) while holding a light.
00, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) was added to prepare a capsule coating liquid. The viscosity of the capsule coating solution immediately after preparation at 20:00 was measured using a Brockfield viscometer and found to be 1&PS. In order to confirm the viscosity stability of the coating liquid, a 500-hour sample of this coating liquid was taken, and the viscosity was measured in the same way after 10 hours of continuous mixing at a rotation speed of 80 pm using a paddle mixer. As a result, it was confirmed that the viscosity stability was extremely excellent at 3 saps. Example 2 CM was added to the capsule dispersion obtained in the same manner as in Example 1.
Add 3 parts of a 2% aqueous solution of C [degree of substitution 0.70, viscosity aps (25°C, 2% aqueous solution)] and 12 parts of water, and add pulp powder (trade name: KC Flock W-250, Sanyo) while bowing. (manufactured by Kokusaku Pulp Co., Ltd.) was added to prepare a capsule coating liquid.

The viscosity measured in the same manner as in Example 1 was 14c.
ps and 29 pS. Example 3 CMC [degree of substitution 1.0] was added to the capsule dispersion obtained in the same manner as in Example 1.
0, viscosity 48&ps (2500, 2% aqueous solution)] 1%
1 part of aqueous solution and 14 parts of water were added, and 3 parts of pulp powder (trade name: KC Flock W-300) were added while stirring to prepare a capsule coating solution.

The viscosities measured in the same manner as in Example 1 were 2 ps and 31 cps, respectively. Example 4 A solution obtained by heating and dissolving 4 parts of crystal violet lactone in 6 parts of diisopropylnaphthalene and a solution obtained by dissolving 1 part of terephthaloyl chloride in 4 parts of diisopropylnaphthalene was mixed. The mixture was emulsified into 25 parts of a 2% aqueous solution of polypynyl alcohol (trade name: PVA-224, manufactured by Kuraray Co., Ltd.) using a homomixer so that the average particle size was 5.3 mm.

5.5 parts of diethylenetetramine, 3.6 parts of soda carbonate, and 5 parts of water were added to the emulsified dispersion, and Nadazusa was continued at room temperature. The reaction was continued for about 2 hours until the pH of the system reached 8.0 to obtain a capsule dispersion. CMC to the obtained capsule dispersion
Add 60 parts of a 2% aqueous solution with a degree of substitution of 0.70, viscosity ps (25 qo, 2% aqueous solution) and 120 parts of water, and add 3 anchors of pulp powder (trade name KC Flock W300) while stirring. A capsule coating solution was prepared. The viscosities measured in the same manner as in Example 1 were 1 EU ps and 3 $ps, respectively. Comparative Example 1 A capsule coating liquid was prepared in the same manner as in Example 1 except that CMC was not added.

The viscosity of the coating liquid immediately after preparation was 1 ps. However, when the viscosity stability was confirmed in the same manner as in Example 1, the viscosity increased to 10 specific ps after 5 wind hours and to 21 specific ps after 10 g hours. Comparative Example 2 A capsule coating liquid was prepared in the same manner as in Example 4 except that CMC was not added.

Claims (1)

[Scope of Claims] 1. A method for producing a capsule dispersion, which comprises adding pulp powder in the presence of carboxymethyl cellulose to a capsule dispersion prepared using polyvinyl alcohol as an emulsifier for a capsule core material. 2 Carboxymethyl cellulose has a viscosity of 2 to 500 centipoise [2% concentration aqueous solution at 25°C was measured with a B-type viscometer (6
2. The method according to claim 1, wherein the carboxymethylcellulose is carboxymethyl cellulose having a 100% carbon chloride (measured at 0 rpm, N01 rotor).